draft-ietf-nfsv4-rfc3010bis-04.txt   draft-ietf-nfsv4-rfc3010bis-05.txt 
NFS version 4 Working Group S. Shepler NFS version 4 Working Group S. Shepler
INTERNET-DRAFT Sun Microsystems, Inc. INTERNET-DRAFT Sun Microsystems, Inc.
Obsoletes: 3010 C. Beame Obsoletes: 3010 C. Beame
Document: draft-ietf-nfsv4-rfc3010bis-04.txt Hummingbird Ltd. Document: draft-ietf-nfsv4-rfc3010bis-05.txt Hummingbird Ltd.
B. Callaghan B. Callaghan
Sun Microsystems, Inc. Sun Microsystems, Inc.
M. Eisler M. Eisler
Network Appliance, Inc. Network Appliance, Inc.
D. Noveck D. Noveck
Network Appliance, Inc. Network Appliance, Inc.
D. Robinson D. Robinson
Sun Microsystems, Inc. Sun Microsystems, Inc.
R. Thurlow R. Thurlow
Sun Microsystems, Inc. Sun Microsystems, Inc.
October 2002 November 2002
NFS version 4 Protocol NFS version 4 Protocol
Status of this Memo Status of this Memo
This document is an Internet-Draft and is in full conformance with This document is an Internet-Draft and is in full conformance with
all provisions of Section 10 of RFC2026. all provisions of Section 10 of RFC2026.
Internet-Drafts are working documents of the Internet Engineering Internet-Drafts are working documents of the Internet Engineering
Task Force (IETF), its areas, and its working groups. Note that Task Force (IETF), its areas, and its working groups. Note that
skipping to change at page 2, line 5 skipping to change at page 2, line 5
http://www.ietf.org/ietf/1id-abstracts.txt http://www.ietf.org/ietf/1id-abstracts.txt
The list of Internet-Draft Shadow Directories can be accessed at The list of Internet-Draft Shadow Directories can be accessed at
http://www.ietf.org/shadow.html. http://www.ietf.org/shadow.html.
Abstract Abstract
This document replaces [RFC3010] as the definition of the NFS version This document replaces [RFC3010] as the definition of the NFS version
4 protocol. 4 protocol.
Draft Specification NFS version 4 Protocol October 2002 Draft Specification NFS version 4 Protocol November 2002
NFS version 4 is a distributed filesystem protocol which owes NFS version 4 is a distributed filesystem protocol which owes
heritage to NFS protocol versions 2 [RFC1094] and 3 [RFC1813]. heritage to NFS protocol versions 2 [RFC1094] and 3 [RFC1813].
Unlike earlier versions, the NFS version 4 protocol supports Unlike earlier versions, the NFS version 4 protocol supports
traditional file access while integrating support for file locking traditional file access while integrating support for file locking
and the mount protocol. In addition, support for strong security and the mount protocol. In addition, support for strong security
(and its negotiation), compound operations, client caching, and (and its negotiation), compound operations, client caching, and
internationalization have been added. Of course, attention has been internationalization have been added. Of course, attention has been
applied to making NFS version 4 operate well in an Internet applied to making NFS version 4 operate well in an Internet
environment. environment.
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Copyright Copyright
Copyright (C) The Internet Society (2000-2002). All Rights Reserved. Copyright (C) The Internet Society (2000-2002). All Rights Reserved.
Key Words Key Words
The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT", The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
"SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this
document are to be interpreted as described in [RFC2119]. document are to be interpreted as described in [RFC2119].
Draft Specification NFS version 4 Protocol October 2002 Draft Specification NFS version 4 Protocol November 2002
Table of Contents Table of Contents
1. Changes since RFC3010 . . . . . . . . . . . . . . . . . . . . 7 1. Changes since RFC3010 . . . . . . . . . . . . . . . . . . . . 8
1.1. Introduction . . . . . . . . . . . . . . . . . . . . . . . 8 1.1. Introduction . . . . . . . . . . . . . . . . . . . . . . . 9
1.2. Inconsistencies of this Document with Section 18 . . . . . 8 1.2. Inconsistencies of this Document with Section 18 . . . . . 9
1.3. Overview of NFS version 4 Features . . . . . . . . . . . . 9 1.3. Overview of NFS version 4 Features . . . . . . . . . . . 10
1.3.1. RPC and Security . . . . . . . . . . . . . . . . . . . . 9 1.3.1. RPC and Security . . . . . . . . . . . . . . . . . . . 10
1.3.2. Procedure and Operation Structure . . . . . . . . . . . . 9 1.3.2. Procedure and Operation Structure . . . . . . . . . . . 10
1.3.3. Filesystem Model . . . . . . . . . . . . . . . . . . . 10 1.3.3. Filesystem Model . . . . . . . . . . . . . . . . . . . 11
1.3.3.1. Filehandle Types . . . . . . . . . . . . . . . . . . 10 1.3.3.1. Filehandle Types . . . . . . . . . . . . . . . . . . 11
1.3.3.2. Attribute Types . . . . . . . . . . . . . . . . . . . 11 1.3.3.2. Attribute Types . . . . . . . . . . . . . . . . . . . 12
1.3.3.3. Filesystem Replication and Migration . . . . . . . . 11 1.3.3.3. Filesystem Replication and Migration . . . . . . . . 12
1.3.4. OPEN and CLOSE . . . . . . . . . . . . . . . . . . . . 12 1.3.4. OPEN and CLOSE . . . . . . . . . . . . . . . . . . . . 13
1.3.5. File locking . . . . . . . . . . . . . . . . . . . . . 12 1.3.5. File locking . . . . . . . . . . . . . . . . . . . . . 13
1.3.6. Client Caching and Delegation . . . . . . . . . . . . . 12 1.3.6. Client Caching and Delegation . . . . . . . . . . . . . 13
1.4. General Definitions . . . . . . . . . . . . . . . . . . . 13 1.4. General Definitions . . . . . . . . . . . . . . . . . . . 14
2. Protocol Data Types . . . . . . . . . . . . . . . . . . . . 15 2. Protocol Data Types . . . . . . . . . . . . . . . . . . . . 16
2.1. Basic Data Types . . . . . . . . . . . . . . . . . . . . 15 2.1. Basic Data Types . . . . . . . . . . . . . . . . . . . . 16
2.2. Structured Data Types . . . . . . . . . . . . . . . . . . 16 2.2. Structured Data Types . . . . . . . . . . . . . . . . . . 17
3. RPC and Security Flavor . . . . . . . . . . . . . . . . . . 22 3. RPC and Security Flavor . . . . . . . . . . . . . . . . . . 23
3.1. Ports and Transports . . . . . . . . . . . . . . . . . . 22 3.1. Ports and Transports . . . . . . . . . . . . . . . . . . 23
3.1.1. Client Retransmission Behavior . . . . . . . . . . . . 22 3.1.1. Client Retransmission Behavior . . . . . . . . . . . . 24
3.2. Security Flavors . . . . . . . . . . . . . . . . . . . . 23 3.2. Security Flavors . . . . . . . . . . . . . . . . . . . . 24
3.2.1. Security mechanisms for NFS version 4 . . . . . . . . . 23 3.2.1. Security mechanisms for NFS version 4 . . . . . . . . . 24
3.2.1.1. Kerberos V5 as a security triple . . . . . . . . . . 23 3.2.1.1. Kerberos V5 as a security triple . . . . . . . . . . 25
3.2.1.2. LIPKEY as a security triple . . . . . . . . . . . . . 24 3.2.1.2. LIPKEY as a security triple . . . . . . . . . . . . . 25
3.2.1.3. SPKM-3 as a security triple . . . . . . . . . . . . . 25 3.2.1.3. SPKM-3 as a security triple . . . . . . . . . . . . . 26
3.3. Security Negotiation . . . . . . . . . . . . . . . . . . 25 3.3. Security Negotiation . . . . . . . . . . . . . . . . . . 27
3.3.1. SECINFO . . . . . . . . . . . . . . . . . . . . . . . . 25 3.3.1. SECINFO . . . . . . . . . . . . . . . . . . . . . . . . 27
3.3.2. Security Error . . . . . . . . . . . . . . . . . . . . 26 3.3.2. Security Error . . . . . . . . . . . . . . . . . . . . 27
3.4. Callback RPC Authentication . . . . . . . . . . . . . . . 26 3.4. Callback RPC Authentication . . . . . . . . . . . . . . . 28
4. Filehandles . . . . . . . . . . . . . . . . . . . . . . . . 28 4. Filehandles . . . . . . . . . . . . . . . . . . . . . . . . 30
4.1. Obtaining the First Filehandle . . . . . . . . . . . . . 28 4.1. Obtaining the First Filehandle . . . . . . . . . . . . . 30
4.1.1. Root Filehandle . . . . . . . . . . . . . . . . . . . . 28 4.1.1. Root Filehandle . . . . . . . . . . . . . . . . . . . . 30
4.1.2. Public Filehandle . . . . . . . . . . . . . . . . . . . 28 4.1.2. Public Filehandle . . . . . . . . . . . . . . . . . . . 30
4.2. Filehandle Types . . . . . . . . . . . . . . . . . . . . 29 4.2. Filehandle Types . . . . . . . . . . . . . . . . . . . . 31
4.2.1. General Properties of a Filehandle . . . . . . . . . . 29 4.2.1. General Properties of a Filehandle . . . . . . . . . . 31
4.2.2. Persistent Filehandle . . . . . . . . . . . . . . . . . 30 4.2.2. Persistent Filehandle . . . . . . . . . . . . . . . . . 32
4.2.3. Volatile Filehandle . . . . . . . . . . . . . . . . . . 30 4.2.3. Volatile Filehandle . . . . . . . . . . . . . . . . . . 32
4.2.4. One Method of Constructing a Volatile Filehandle . . . 31 4.2.4. One Method of Constructing a Volatile Filehandle . . . 33
4.3. Client Recovery from Filehandle Expiration . . . . . . . 32 4.3. Client Recovery from Filehandle Expiration . . . . . . . 34
5. File Attributes . . . . . . . . . . . . . . . . . . . . . . 34 5. File Attributes . . . . . . . . . . . . . . . . . . . . . . 36
5.1. Mandatory Attributes . . . . . . . . . . . . . . . . . . 35 5.1. Mandatory Attributes . . . . . . . . . . . . . . . . . . 37
5.2. Recommended Attributes . . . . . . . . . . . . . . . . . 35 5.2. Recommended Attributes . . . . . . . . . . . . . . . . . 37
5.3. Named Attributes . . . . . . . . . . . . . . . . . . . . 35 5.3. Named Attributes . . . . . . . . . . . . . . . . . . . . 37
5.4. Classification of Attributes . . . . . . . . . . . . . . 36 5.4. Classification of Attributes . . . . . . . . . . . . . . 38
5.5. Mandatory Attributes - Definitions . . . . . . . . . . . 38 5.5. Mandatory Attributes - Definitions . . . . . . . . . . . 40
5.6. Recommended Attributes - Definitions . . . . . . . . . . 40 5.6. Recommended Attributes - Definitions . . . . . . . . . . 42
5.7. Time Access . . . . . . . . . . . . . . . . . . . . . . . 45 5.7. Time Access . . . . . . . . . . . . . . . . . . . . . . . 47
5.8. Interpreting owner and owner_group . . . . . . . . . . . 45 5.8. Interpreting owner and owner_group . . . . . . . . . . . 47
5.9. Character Case Attributes . . . . . . . . . . . . . . . . 47 5.9. Character Case Attributes . . . . . . . . . . . . . . . . 49
5.10. Quota Attributes . . . . . . . . . . . . . . . . . . . . 47 5.10. Quota Attributes . . . . . . . . . . . . . . . . . . . . 49
Draft Specification NFS version 4 Protocol October 2002 Draft Specification NFS version 4 Protocol November 2002
5.11. Access Control Lists . . . . . . . . . . . . . . . . . . 48 5.11. Access Control Lists . . . . . . . . . . . . . . . . . . 50
5.11.1. ACE type . . . . . . . . . . . . . . . . . . . . . . . 49 5.11.1. ACE type . . . . . . . . . . . . . . . . . . . . . . . 51
5.11.2. ACE Access Mask . . . . . . . . . . . . . . . . . . . 50 5.11.2. ACE Access Mask . . . . . . . . . . . . . . . . . . . 52
5.11.3. ACE flag . . . . . . . . . . . . . . . . . . . . . . . 52 5.11.3. ACE flag . . . . . . . . . . . . . . . . . . . . . . . 54
5.11.4. ACE who . . . . . . . . . . . . . . . . . . . . . . . 53 5.11.4. ACE who . . . . . . . . . . . . . . . . . . . . . . . 56
5.11.5. Mode Attribute . . . . . . . . . . . . . . . . . . . . 54 5.11.5. Mode Attribute . . . . . . . . . . . . . . . . . . . . 56
5.11.6. Mode and ACL Attribute . . . . . . . . . . . . . . . . 55 5.11.6. Mode and ACL Attribute . . . . . . . . . . . . . . . . 57
5.11.7. mounted_on_fileid . . . . . . . . . . . . . . . . . . 55 5.11.7. mounted_on_fileid . . . . . . . . . . . . . . . . . . 57
6. Filesystem Migration and Replication . . . . . . . . . . . 57 6. Filesystem Migration and Replication . . . . . . . . . . . 59
6.1. Replication . . . . . . . . . . . . . . . . . . . . . . . 57 6.1. Replication . . . . . . . . . . . . . . . . . . . . . . . 59
6.2. Migration . . . . . . . . . . . . . . . . . . . . . . . . 57 6.2. Migration . . . . . . . . . . . . . . . . . . . . . . . . 59
6.3. Interpretation of the fs_locations Attribute . . . . . . 58 6.3. Interpretation of the fs_locations Attribute . . . . . . 60
6.4. Filehandle Recovery for Migration or Replication . . . . 59 6.4. Filehandle Recovery for Migration or Replication . . . . 61
7. NFS Server Name Space . . . . . . . . . . . . . . . . . . . 60 7. NFS Server Name Space . . . . . . . . . . . . . . . . . . . 62
7.1. Server Exports . . . . . . . . . . . . . . . . . . . . . 60 7.1. Server Exports . . . . . . . . . . . . . . . . . . . . . 62
7.2. Browsing Exports . . . . . . . . . . . . . . . . . . . . 60 7.2. Browsing Exports . . . . . . . . . . . . . . . . . . . . 62
7.3. Server Pseudo Filesystem . . . . . . . . . . . . . . . . 60 7.3. Server Pseudo Filesystem . . . . . . . . . . . . . . . . 62
7.4. Multiple Roots . . . . . . . . . . . . . . . . . . . . . 61 7.4. Multiple Roots . . . . . . . . . . . . . . . . . . . . . 63
7.5. Filehandle Volatility . . . . . . . . . . . . . . . . . . 61 7.5. Filehandle Volatility . . . . . . . . . . . . . . . . . . 63
7.6. Exported Root . . . . . . . . . . . . . . . . . . . . . . 61 7.6. Exported Root . . . . . . . . . . . . . . . . . . . . . . 63
7.7. Mount Point Crossing . . . . . . . . . . . . . . . . . . 62 7.7. Mount Point Crossing . . . . . . . . . . . . . . . . . . 64
7.8. Security Policy and Name Space Presentation . . . . . . . 62 7.8. Security Policy and Name Space Presentation . . . . . . . 64
8. File Locking and Share Reservations . . . . . . . . . . . . 64 8. File Locking and Share Reservations . . . . . . . . . . . . 66
8.1. Locking . . . . . . . . . . . . . . . . . . . . . . . . . 64 8.1. Locking . . . . . . . . . . . . . . . . . . . . . . . . . 66
8.1.1. Client ID . . . . . . . . . . . . . . . . . . . . . . . 64 8.1.1. Client ID . . . . . . . . . . . . . . . . . . . . . . . 66
8.1.2. Server Release of Clientid . . . . . . . . . . . . . . 67 8.1.2. Server Release of Clientid . . . . . . . . . . . . . . 69
8.1.3. lock_owner and stateid Definition . . . . . . . . . . . 68 8.1.3. lock_owner and stateid Definition . . . . . . . . . . . 70
8.1.4. Use of the stateid and Locking . . . . . . . . . . . . 69 8.1.4. Use of the stateid and Locking . . . . . . . . . . . . 71
8.1.5. Sequencing of Lock Requests . . . . . . . . . . . . . . 71 8.1.5. Sequencing of Lock Requests . . . . . . . . . . . . . . 73
8.1.6. Recovery from Replayed Requests . . . . . . . . . . . . 72 8.1.6. Recovery from Replayed Requests . . . . . . . . . . . . 74
8.1.7. Releasing lock_owner State . . . . . . . . . . . . . . 73 8.1.7. Releasing lock_owner State . . . . . . . . . . . . . . 75
8.1.8. Use of Open Confirmation . . . . . . . . . . . . . . . 73 8.1.8. Use of Open Confirmation . . . . . . . . . . . . . . . 75
8.2. Lock Ranges . . . . . . . . . . . . . . . . . . . . . . . 74 8.2. Lock Ranges . . . . . . . . . . . . . . . . . . . . . . . 76
8.3. Upgrading and Downgrading Locks . . . . . . . . . . . . . 74 8.3. Upgrading and Downgrading Locks . . . . . . . . . . . . . 76
8.4. Blocking Locks . . . . . . . . . . . . . . . . . . . . . 75 8.4. Blocking Locks . . . . . . . . . . . . . . . . . . . . . 77
8.5. Lease Renewal . . . . . . . . . . . . . . . . . . . . . . 75 8.5. Lease Renewal . . . . . . . . . . . . . . . . . . . . . . 77
8.6. Crash Recovery . . . . . . . . . . . . . . . . . . . . . 76 8.6. Crash Recovery . . . . . . . . . . . . . . . . . . . . . 78
8.6.1. Client Failure and Recovery . . . . . . . . . . . . . . 77 8.6.1. Client Failure and Recovery . . . . . . . . . . . . . . 79
8.6.2. Server Failure and Recovery . . . . . . . . . . . . . . 77 8.6.2. Server Failure and Recovery . . . . . . . . . . . . . . 79
8.6.3. Network Partitions and Recovery . . . . . . . . . . . . 79 8.6.3. Network Partitions and Recovery . . . . . . . . . . . . 81
8.7. Recovery from a Lock Request Timeout or Abort . . . . . . 82 8.7. Recovery from a Lock Request Timeout or Abort . . . . . . 84
8.8. Server Revocation of Locks . . . . . . . . . . . . . . . 83 8.8. Server Revocation of Locks . . . . . . . . . . . . . . . 85
8.9. Share Reservations . . . . . . . . . . . . . . . . . . . 84 8.9. Share Reservations . . . . . . . . . . . . . . . . . . . 86
8.10. OPEN/CLOSE Operations . . . . . . . . . . . . . . . . . 84 8.10. OPEN/CLOSE Operations . . . . . . . . . . . . . . . . . 86
8.10.1. Close and Retention of State Information . . . . . . . 85 8.10.1. Close and Retention of State Information . . . . . . . 87
8.11. Open Upgrade and Downgrade . . . . . . . . . . . . . . . 86 8.11. Open Upgrade and Downgrade . . . . . . . . . . . . . . . 88
8.12. Short and Long Leases . . . . . . . . . . . . . . . . . 86 8.12. Short and Long Leases . . . . . . . . . . . . . . . . . 88
8.13. Clocks, Propagation Delay, and Calculating Lease 8.13. Clocks, Propagation Delay, and Calculating Lease
Expiration . . . . . . . . . . . . . . . . . . . . . . . 87 Expiration . . . . . . . . . . . . . . . . . . . . . . . 89
8.14. Migration, Replication and State . . . . . . . . . . . . 87 8.14. Migration, Replication and State . . . . . . . . . . . . 89
8.14.1. Migration and State . . . . . . . . . . . . . . . . . 88 8.14.1. Migration and State . . . . . . . . . . . . . . . . . 90
8.14.2. Replication and State . . . . . . . . . . . . . . . . 88 8.14.2. Replication and State . . . . . . . . . . . . . . . . 90
Draft Specification NFS version 4 Protocol October 2002 Draft Specification NFS version 4 Protocol November 2002
8.14.3. Notification of Migrated Lease . . . . . . . . . . . . 89 8.14.3. Notification of Migrated Lease . . . . . . . . . . . . 91
8.14.4. Migration and the Lease_time Attribute . . . . . . . . 89 8.14.4. Migration and the Lease_time Attribute . . . . . . . . 91
9. Client-Side Caching . . . . . . . . . . . . . . . . . . . . 91 9. Client-Side Caching . . . . . . . . . . . . . . . . . . . . 93
9.1. Performance Challenges for Client-Side Caching . . . . . 91 9.1. Performance Challenges for Client-Side Caching . . . . . 93
9.2. Delegation and Callbacks . . . . . . . . . . . . . . . . 92 9.2. Delegation and Callbacks . . . . . . . . . . . . . . . . 94
9.2.1. Delegation Recovery . . . . . . . . . . . . . . . . . . 93 9.2.1. Delegation Recovery . . . . . . . . . . . . . . . . . . 95
9.3. Data Caching . . . . . . . . . . . . . . . . . . . . . . 95 9.3. Data Caching . . . . . . . . . . . . . . . . . . . . . . 97
9.3.1. Data Caching and OPENs . . . . . . . . . . . . . . . . 95 9.3.1. Data Caching and OPENs . . . . . . . . . . . . . . . . 97
9.3.2. Data Caching and File Locking . . . . . . . . . . . . . 96 9.3.2. Data Caching and File Locking . . . . . . . . . . . . . 98
9.3.3. Data Caching and Mandatory File Locking . . . . . . . . 98 9.3.3. Data Caching and Mandatory File Locking . . . . . . . . 100
9.3.4. Data Caching and File Identity . . . . . . . . . . . . 98 9.3.4. Data Caching and File Identity . . . . . . . . . . . . 100
9.4. Open Delegation . . . . . . . . . . . . . . . . . . . . . 99 9.4. Open Delegation . . . . . . . . . . . . . . . . . . . . . 101
9.4.1. Open Delegation and Data Caching . . . . . . . . . . . 102 9.4.1. Open Delegation and Data Caching . . . . . . . . . . . 104
9.4.2. Open Delegation and File Locks . . . . . . . . . . . . 103 9.4.2. Open Delegation and File Locks . . . . . . . . . . . . 105
9.4.3. Handling of CB_GETATTR . . . . . . . . . . . . . . . . 103 9.4.3. Handling of CB_GETATTR . . . . . . . . . . . . . . . . 105
9.4.4. Recall of Open Delegation . . . . . . . . . . . . . . . 106 9.4.4. Recall of Open Delegation . . . . . . . . . . . . . . . 108
9.4.5. Clients that Fail to Honor Delegation Recalls . . . . . 108 9.4.5. Clients that Fail to Honor Delegation Recalls . . . . . 110
9.4.6. Delegation Revocation . . . . . . . . . . . . . . . . . 108 9.4.6. Delegation Revocation . . . . . . . . . . . . . . . . . 110
9.5. Data Caching and Revocation . . . . . . . . . . . . . . . 109 9.5. Data Caching and Revocation . . . . . . . . . . . . . . . 111
9.5.1. Revocation Recovery for Write Open Delegation . . . . . 109 9.5.1. Revocation Recovery for Write Open Delegation . . . . . 111
9.6. Attribute Caching . . . . . . . . . . . . . . . . . . . . 110 9.6. Attribute Caching . . . . . . . . . . . . . . . . . . . . 112
9.7. Data and Metadata Caching and Memory Mapped Files . . . . 112 9.7. Data and Metadata Caching and Memory Mapped Files . . . . 114
9.8. Name Caching . . . . . . . . . . . . . . . . . . . . . . 114 9.8. Name Caching . . . . . . . . . . . . . . . . . . . . . . 116
9.9. Directory Caching . . . . . . . . . . . . . . . . . . . . 115 9.9. Directory Caching . . . . . . . . . . . . . . . . . . . . 117
10. Minor Versioning . . . . . . . . . . . . . . . . . . . . . 117 10. Minor Versioning . . . . . . . . . . . . . . . . . . . . . 119
11. Internationalization . . . . . . . . . . . . . . . . . . . 120 11. Internationalization . . . . . . . . . . . . . . . . . . . 122
11.1. Universal Versus Local Character Sets . . . . . . . . . 120 11.1. Stringprep profile for the utf8str_cs type . . . . . . . 123
11.2. Overview of Universal Character Set Standards . . . . . 121 11.1.1. Intended applicability of the nfs4_cs_prep profile . . 123
11.3. Difficulties with UCS-4, UCS-2, Unicode . . . . . . . . 122 11.1.2. Character repertoire of nfs4_cs_prep . . . . . . . . . 123
11.4. UTF-8 and its solutions . . . . . . . . . . . . . . . . 122 11.1.3. Mapping used by nfs4_cs_prep . . . . . . . . . . . . . 123
11.5. Normalization . . . . . . . . . . . . . . . . . . . . . 123 11.1.4. Normalization used by nfs4_cs_prep . . . . . . . . . . 124
11.6. UTF-8 Related Errors . . . . . . . . . . . . . . . . . . 123 11.1.5. Prohibited output for nfs4_cs_prep . . . . . . . . . . 124
12. Error Definitions . . . . . . . . . . . . . . . . . . . . 125 11.1.6. Bidirectional output for nfs4_cs_prep . . . . . . . . 124
13. NFS version 4 Requests . . . . . . . . . . . . . . . . . . 131 11.2. Stringprep profile for the utf8str_cis type . . . . . . 124
13.1. Compound Procedure . . . . . . . . . . . . . . . . . . . 131 11.2.1. Intended applicability of the nfs4_cis_prep profile . 124
13.2. Evaluation of a Compound Request . . . . . . . . . . . . 132 11.2.2. Character repertoire of nfs4_cis_prep . . . . . . . . 124
13.3. Synchronous Modifying Operations . . . . . . . . . . . . 132 11.2.3. Mapping used by nfs4_cis_prep . . . . . . . . . . . . 124
13.4. Operation Values . . . . . . . . . . . . . . . . . . . . 133 11.2.4. Normalization used by nfs4_cis_prep . . . . . . . . . 125
14. NFS version 4 Procedures . . . . . . . . . . . . . . . . . 134 11.2.5. Prohibited output for nfs4_cis_prep . . . . . . . . . 125
14.1. Procedure 0: NULL - No Operation . . . . . . . . . . . . 134 11.2.6. Bidirectional output for nfs4_cis_prep . . . . . . . . 125
14.2. Procedure 1: COMPOUND - Compound Operations . . . . . . 135 11.3. Stringprep profile for the utf8str_mixed type . . . . . 125
14.2.1. Operation 3: ACCESS - Check Access Rights . . . . . . 138 11.3.1. Intended applicability of the nfs4_mixed_prep profile 125
14.2.2. Operation 4: CLOSE - Close File . . . . . . . . . . . 141 11.3.2. Character repertoire of nfs4_mixed_prep . . . . . . . 125
14.2.3. Operation 5: COMMIT - Commit Cached Data . . . . . . . 143 11.3.3. Mapping used by nfs4_cis_prep . . . . . . . . . . . . 125
14.2.4. Operation 6: CREATE - Create a Non-Regular File Object 146 11.3.4. Normalization used by nfs4_mixed_prep . . . . . . . . 126
14.2.5. Operation 7: DELEGPURGE - Purge Delegations Awaiting 11.3.5. Prohibited output for nfs4_mixed_prep . . . . . . . . 126
Recovery . . . . . . . . . . . . . . . . . . . . . . . 149 11.3.6. Bidirectional output for nfs4_mixed_prep . . . . . . . 126
14.2.6. Operation 8: DELEGRETURN - Return Delegation . . . . . 151 11.4. UTF-8 Related Errors . . . . . . . . . . . . . . . . . . 126
14.2.7. Operation 9: GETATTR - Get Attributes . . . . . . . . 152 12. Error Definitions . . . . . . . . . . . . . . . . . . . . 127
14.2.8. Operation 10: GETFH - Get Current Filehandle . . . . . 154 13. NFS version 4 Requests . . . . . . . . . . . . . . . . . . 133
14.2.9. Operation 11: LINK - Create Link to a File . . . . . . 156 13.1. Compound Procedure . . . . . . . . . . . . . . . . . . . 133
14.2.10. Operation 12: LOCK - Create Lock . . . . . . . . . . 158 13.2. Evaluation of a Compound Request . . . . . . . . . . . . 134
Draft Specification NFS version 4 Protocol October 2002 Draft Specification NFS version 4 Protocol November 2002
14.2.11. Operation 13: LOCKT - Test For Lock . . . . . . . . . 162 13.3. Synchronous Modifying Operations . . . . . . . . . . . . 134
14.2.12. Operation 14: LOCKU - Unlock File . . . . . . . . . . 164 13.4. Operation Values . . . . . . . . . . . . . . . . . . . . 135
14.2.13. Operation 15: LOOKUP - Lookup Filename . . . . . . . 166 14. NFS version 4 Procedures . . . . . . . . . . . . . . . . . 136
14.2.14. Operation 16: LOOKUPP - Lookup Parent Directory . . . 169 14.1. Procedure 0: NULL - No Operation . . . . . . . . . . . . 136
14.2. Procedure 1: COMPOUND - Compound Operations . . . . . . 137
14.2.1. Operation 3: ACCESS - Check Access Rights . . . . . . 140
14.2.2. Operation 4: CLOSE - Close File . . . . . . . . . . . 143
14.2.3. Operation 5: COMMIT - Commit Cached Data . . . . . . . 145
14.2.4. Operation 6: CREATE - Create a Non-Regular File Object 148
14.2.5. Operation 7: DELEGPURGE - Purge Delegations Awaiting
Recovery . . . . . . . . . . . . . . . . . . . . . . . 151
14.2.6. Operation 8: DELEGRETURN - Return Delegation . . . . . 153
14.2.7. Operation 9: GETATTR - Get Attributes . . . . . . . . 154
14.2.8. Operation 10: GETFH - Get Current Filehandle . . . . . 156
14.2.9. Operation 11: LINK - Create Link to a File . . . . . . 158
14.2.10. Operation 12: LOCK - Create Lock . . . . . . . . . . 160
14.2.11. Operation 13: LOCKT - Test For Lock . . . . . . . . . 164
14.2.12. Operation 14: LOCKU - Unlock File . . . . . . . . . . 166
14.2.13. Operation 15: LOOKUP - Lookup Filename . . . . . . . 168
14.2.14. Operation 16: LOOKUPP - Lookup Parent Directory . . . 171
14.2.15. Operation 17: NVERIFY - Verify Difference in 14.2.15. Operation 17: NVERIFY - Verify Difference in
Attributes . . . . . . . . . . . . . . . . . . . . . 170 Attributes . . . . . . . . . . . . . . . . . . . . . 172
14.2.16. Operation 18: OPEN - Open a Regular File . . . . . . 172 14.2.16. Operation 18: OPEN - Open a Regular File . . . . . . 174
14.2.17. Operation 19: OPENATTR - Open Named Attribute 14.2.17. Operation 19: OPENATTR - Open Named Attribute
Directory . . . . . . . . . . . . . . . . . . . . . . 182 Directory . . . . . . . . . . . . . . . . . . . . . . 184
14.2.18. Operation 20: OPEN_CONFIRM - Confirm Open . . . . . . 184 14.2.18. Operation 20: OPEN_CONFIRM - Confirm Open . . . . . . 186
14.2.19. Operation 21: OPEN_DOWNGRADE - Reduce Open File Access 187 14.2.19. Operation 21: OPEN_DOWNGRADE - Reduce Open File Access 189
14.2.20. Operation 22: PUTFH - Set Current Filehandle . . . . 189 14.2.20. Operation 22: PUTFH - Set Current Filehandle . . . . 191
14.2.21. Operation 23: PUTPUBFH - Set Public Filehandle . . . 190 14.2.21. Operation 23: PUTPUBFH - Set Public Filehandle . . . 192
14.2.22. Operation 24: PUTROOTFH - Set Root Filehandle . . . . 192 14.2.22. Operation 24: PUTROOTFH - Set Root Filehandle . . . . 194
14.2.23. Operation 25: READ - Read from File . . . . . . . . . 193 14.2.23. Operation 25: READ - Read from File . . . . . . . . . 195
14.2.24. Operation 26: READDIR - Read Directory . . . . . . . 196 14.2.24. Operation 26: READDIR - Read Directory . . . . . . . 198
14.2.25. Operation 27: READLINK - Read Symbolic Link . . . . . 200 14.2.25. Operation 27: READLINK - Read Symbolic Link . . . . . 202
14.2.26. Operation 28: REMOVE - Remove Filesystem Object . . . 202 14.2.26. Operation 28: REMOVE - Remove Filesystem Object . . . 204
14.2.27. Operation 29: RENAME - Rename Directory Entry . . . . 205 14.2.27. Operation 29: RENAME - Rename Directory Entry . . . . 207
14.2.28. Operation 30: RENEW - Renew a Lease . . . . . . . . . 208 14.2.28. Operation 30: RENEW - Renew a Lease . . . . . . . . . 210
14.2.29. Operation 31: RESTOREFH - Restore Saved Filehandle . 210 14.2.29. Operation 31: RESTOREFH - Restore Saved Filehandle . 212
14.2.30. Operation 32: SAVEFH - Save Current Filehandle . . . 212 14.2.30. Operation 32: SAVEFH - Save Current Filehandle . . . 214
14.2.31. Operation 33: SECINFO - Obtain Available Security . . 213 14.2.31. Operation 33: SECINFO - Obtain Available Security . . 215
14.2.32. Operation 34: SETATTR - Set Attributes . . . . . . . 217 14.2.32. Operation 34: SETATTR - Set Attributes . . . . . . . 219
14.2.33. Operation 35: SETCLIENTID - Negotiate Clientid . . . 220 14.2.33. Operation 35: SETCLIENTID - Negotiate Clientid . . . 222
14.2.34. Operation 36: SETCLIENTID_CONFIRM - Confirm Clientid 224 14.2.34. Operation 36: SETCLIENTID_CONFIRM - Confirm Clientid 226
14.2.35. Operation 37: VERIFY - Verify Same Attributes . . . . 228 14.2.35. Operation 37: VERIFY - Verify Same Attributes . . . . 230
14.2.36. Operation 38: WRITE - Write to File . . . . . . . . . 230 14.2.36. Operation 38: WRITE - Write to File . . . . . . . . . 232
14.2.37. Operation 39: RELEASE_LOCKOWNER - Release Lockowner 14.2.37. Operation 39: RELEASE_LOCKOWNER - Release Lockowner
State . . . . . . . . . . . . . . . . . . . . . . . . 235 State . . . . . . . . . . . . . . . . . . . . . . . . 237
14.2.38. Operation 10044: ILLEGAL - Illegal operation . . . . 237 14.2.38. Operation 10044: ILLEGAL - Illegal operation . . . . 239
15. NFS version 4 Callback Procedures . . . . . . . . . . . . 238 15. NFS version 4 Callback Procedures . . . . . . . . . . . . 240
15.1. Procedure 0: CB_NULL - No Operation . . . . . . . . . . 238 15.1. Procedure 0: CB_NULL - No Operation . . . . . . . . . . 240
15.2. Procedure 1: CB_COMPOUND - Compound Operations . . . . . 239 15.2. Procedure 1: CB_COMPOUND - Compound Operations . . . . . 241
15.2.1. Operation 3: CB_GETATTR - Get Attributes . . . . . . . 241 15.2.1. Operation 3: CB_GETATTR - Get Attributes . . . . . . . 243
15.2.2. Operation 4: CB_RECALL - Recall an Open Delegation . . 243 15.2.2. Operation 4: CB_RECALL - Recall an Open Delegation . . 245
Draft Specification NFS version 4 Protocol November 2002
15.2.3. Operation 10044: CB_ILLEGAL - Illegal Callback 15.2.3. Operation 10044: CB_ILLEGAL - Illegal Callback
Operation . . . . . . . . . . . . . . . . . . . . . . 245 Operation . . . . . . . . . . . . . . . . . . . . . . 247
16. Security Considerations . . . . . . . . . . . . . . . . . 246 16. Security Considerations . . . . . . . . . . . . . . . . . 248
17. IANA Considerations . . . . . . . . . . . . . . . . . . . 247 17. IANA Considerations . . . . . . . . . . . . . . . . . . . 250
17.1. Named Attribute Definition . . . . . . . . . . . . . . . 247 17.1. Named Attribute Definition . . . . . . . . . . . . . . . 250
17.2. ONC RPC Network Identifiers (netids) . . . . . . . . . . 247 17.2. ONC RPC Network Identifiers (netids) . . . . . . . . . . 250
18. RPC definition file . . . . . . . . . . . . . . . . . . . 248 18. RPC definition file . . . . . . . . . . . . . . . . . . . 252
19. Normative References . . . . . . . . . . . . . . . . . . . 280 19. Normative References . . . . . . . . . . . . . . . . . . . 284
20. Informative References . . . . . . . . . . . . . . . . . . 281 20. Informative References . . . . . . . . . . . . . . . . . . 285
21. Authors . . . . . . . . . . . . . . . . . . . . . . . . . 285 21. Authors . . . . . . . . . . . . . . . . . . . . . . . . . 289
21.1. Editor's Address . . . . . . . . . . . . . . . . . . . . 285 21.1. Editor's Address . . . . . . . . . . . . . . . . . . . . 289
21.2. Authors' Addresses . . . . . . . . . . . . . . . . . . . 285 21.2. Authors' Addresses . . . . . . . . . . . . . . . . . . . 289
21.3. Acknowledgements . . . . . . . . . . . . . . . . . . . . 286 21.3. Acknowledgements . . . . . . . . . . . . . . . . . . . . 290
22. Full Copyright Statement . . . . . . . . . . . . . . . . . 287 22. Full Copyright Statement . . . . . . . . . . . . . . . . . 291
Draft Specification NFS version 4 Protocol October 2002 Draft Specification NFS version 4 Protocol November 2002
1. Changes since RFC3010 1. Changes since RFC3010
This definition of the NFS version 4 protocol replaces or obsoletes This definition of the NFS version 4 protocol replaces or obsoletes
the definition present in [RFC3010]. While portions of the two the definition present in [RFC3010]. While portions of the two
documents have remained the same, there have been substantive changes documents have remained the same, there have been substantive changes
in others. The changes made between [RFC3010] and this document in others. The changes made between [RFC3010] and this document
represent implementation experience and further review of the represent implementation experience and further review of the
protocol. While some modifications were made for ease of protocol. While some modifications were made for ease of
implementation or clarification, most updates represent errors or implementation or clarification, most updates represent errors or
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server that a lock_owner4 will no longer be used by the client. server that a lock_owner4 will no longer be used by the client.
o RENEW operation changes to identify the client correctly and o RENEW operation changes to identify the client correctly and
allow for additional error returns. allow for additional error returns.
o Verify error return possibilities for all operations. o Verify error return possibilities for all operations.
o Remove use of the pathname4 data type from LOOKUP and OPEN in o Remove use of the pathname4 data type from LOOKUP and OPEN in
favor of having the client construct a sequence of LOOKUP favor of having the client construct a sequence of LOOKUP
Draft Specification NFS version 4 Protocol October 2002 Draft Specification NFS version 4 Protocol November 2002
operations to acheive the same effect. operations to acheive the same effect.
o Clarification of the internationalization issues and adoption of
the new stringprep profile framework.
1.1. Introduction 1.1. Introduction
The NFS version 4 protocol is a further revision of the NFS protocol The NFS version 4 protocol is a further revision of the NFS protocol
defined already by versions 2 [RFC1094] and 3 [RFC1813]. It retains defined already by versions 2 [RFC1094] and 3 [RFC1813]. It retains
the essential characteristics of previous versions: design for easy the essential characteristics of previous versions: design for easy
recovery, independent of transport protocols, operating systems and recovery, independent of transport protocols, operating systems and
filesystems, simplicity, and good performance. The NFS version 4 filesystems, simplicity, and good performance. The NFS version 4
revision has the following goals: revision has the following goals:
o Improved access and good performance on the Internet. o Improved access and good performance on the Internet.
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The protocol is designed to accept standard extensions that do The protocol is designed to accept standard extensions that do
not compromise backward compatibility. not compromise backward compatibility.
1.2. Inconsistencies of this Document with Section 18 1.2. Inconsistencies of this Document with Section 18
Section 18, RPC Definition File, contains the definitions in XDR Section 18, RPC Definition File, contains the definitions in XDR
description language of the constructs used by the protocol. Prior description language of the constructs used by the protocol. Prior
to Section 18, several of the constructs are reproduced for purposes to Section 18, several of the constructs are reproduced for purposes
of explanation. The reader is warned of the possibility of errors in of explanation. The reader is warned of the possibility of errors in
the reproduced constructs outside of Section 18. For any part of the the reproduced constructs outside of Section 18. For any part of the
Draft Specification NFS version 4 Protocol November 2002
document that is inconsistent with Section 18, Section 18 is to be document that is inconsistent with Section 18, Section 18 is to be
considered authoritative. considered authoritative.
Draft Specification NFS version 4 Protocol October 2002
1.3. Overview of NFS version 4 Features 1.3. Overview of NFS version 4 Features
To provide a reasonable context for the reader, the major features of To provide a reasonable context for the reader, the major features of
NFS version 4 protocol will be reviewed in brief. This will be done NFS version 4 protocol will be reviewed in brief. This will be done
to provide an appropriate context for both the reader who is familiar to provide an appropriate context for both the reader who is familiar
with the previous versions of the NFS protocol and the reader that is with the previous versions of the NFS protocol and the reader that is
new to the NFS protocols. For the reader new to the NFS protocols, new to the NFS protocols. For the reader new to the NFS protocols,
there is still a fundamental knowledge that is expected. The reader there is still a fundamental knowledge that is expected. The reader
should be familiar with the XDR and RPC protocols as described in should be familiar with the XDR and RPC protocols as described in
[RFC1831] and [RFC1832]. A basic knowledge of filesystems and [RFC1831] and [RFC1832]. A basic knowledge of filesystems and
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1.3.2. Procedure and Operation Structure 1.3.2. Procedure and Operation Structure
A significant departure from the previous versions of the NFS A significant departure from the previous versions of the NFS
protocol is the introduction of the COMPOUND procedure. For the NFS protocol is the introduction of the COMPOUND procedure. For the NFS
version 4 protocol, there are two RPC procedures, NULL and COMPOUND. version 4 protocol, there are two RPC procedures, NULL and COMPOUND.
The COMPOUND procedure is defined in terms of operations and these The COMPOUND procedure is defined in terms of operations and these
operations correspond more closely to the traditional NFS procedures. operations correspond more closely to the traditional NFS procedures.
With the use of the COMPOUND procedure, the client is able to build With the use of the COMPOUND procedure, the client is able to build
simple or complex requests. These COMPOUND requests allow for a simple or complex requests. These COMPOUND requests allow for a
reduction in the number of RPCs needed for logical filesystem reduction in the number of RPCs needed for logical filesystem
Draft Specification NFS version 4 Protocol November 2002
operations. For example, without previous contact with a server a operations. For example, without previous contact with a server a
client will be able to read data from a file in one request by client will be able to read data from a file in one request by
combining LOOKUP, OPEN, and READ operations in a single COMPOUND RPC. combining LOOKUP, OPEN, and READ operations in a single COMPOUND RPC.
With previous versions of the NFS protocol, this type of single With previous versions of the NFS protocol, this type of single
Draft Specification NFS version 4 Protocol October 2002
request was not possible. request was not possible.
The model used for COMPOUND is very simple. There is no logical OR The model used for COMPOUND is very simple. There is no logical OR
or ANDing of operations. The operations combined within a COMPOUND or ANDing of operations. The operations combined within a COMPOUND
request are evaluated in order by the server. Once an operation request are evaluated in order by the server. Once an operation
returns a failing result, the evaluation ends and the results of all returns a failing result, the evaluation ends and the results of all
evaluated operations are returned to the client. evaluated operations are returned to the client.
The NFS version 4 protocol continues to have the client refer to a The NFS version 4 protocol continues to have the client refer to a
file or directory at the server by a "filehandle". The COMPOUND file or directory at the server by a "filehandle". The COMPOUND
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In previous versions of the NFS protocol, the filehandle provided by In previous versions of the NFS protocol, the filehandle provided by
the server was guaranteed to be valid or persistent for the lifetime the server was guaranteed to be valid or persistent for the lifetime
of the filesystem object to which it referred. For some server of the filesystem object to which it referred. For some server
implementations, this persistence requirement has been difficult to implementations, this persistence requirement has been difficult to
meet. For the NFS version 4 protocol, this requirement has been meet. For the NFS version 4 protocol, this requirement has been
relaxed by introducing another type of filehandle, volatile. With relaxed by introducing another type of filehandle, volatile. With
persistent and volatile filehandle types, the server implementation persistent and volatile filehandle types, the server implementation
can match the abilities of the filesystem at the server along with can match the abilities of the filesystem at the server along with
the operating environment. The client will have knowledge of the the operating environment. The client will have knowledge of the
Draft Specification NFS version 4 Protocol November 2002
type of filehandle being provided by the server and can be prepared type of filehandle being provided by the server and can be prepared
to deal with the semantics of each. to deal with the semantics of each.
Draft Specification NFS version 4 Protocol October 2002
1.3.3.2. Attribute Types 1.3.3.2. Attribute Types
The NFS version 4 protocol introduces three classes of filesystem or The NFS version 4 protocol introduces three classes of filesystem or
file attributes. Like the additional filehandle type, the file attributes. Like the additional filehandle type, the
classification of file attributes has been done to ease server classification of file attributes has been done to ease server
implementations along with extending the overall functionality of the implementations along with extending the overall functionality of the
NFS protocol. This attribute model is structured to be extensible NFS protocol. This attribute model is structured to be extensible
such that new attributes can be introduced in minor revisions of the such that new attributes can be introduced in minor revisions of the
protocol without requiring significant rework. protocol without requiring significant rework.
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With the use of a special file attribute, the ability to migrate or With the use of a special file attribute, the ability to migrate or
replicate server filesystems is enabled within the protocol. The replicate server filesystems is enabled within the protocol. The
filesystem locations attribute provides a method for the client to filesystem locations attribute provides a method for the client to
probe the server about the location of a filesystem. In the event of probe the server about the location of a filesystem. In the event of
a migration of a filesystem, the client will receive an error when a migration of a filesystem, the client will receive an error when
operating on the filesystem and it can then query as to the new file operating on the filesystem and it can then query as to the new file
system location. Similar steps are used for replication, the client system location. Similar steps are used for replication, the client
is able to query the server for the multiple available locations of a is able to query the server for the multiple available locations of a
particular filesystem. From this information, the client can use its particular filesystem. From this information, the client can use its
own policies to access the appropriate filesystem location.
Draft Specification NFS version 4 Protocol October 2002 Draft Specification NFS version 4 Protocol November 2002
own policies to access the appropriate filesystem location.
1.3.4. OPEN and CLOSE 1.3.4. OPEN and CLOSE
The NFS version 4 protocol introduces OPEN and CLOSE operations. The The NFS version 4 protocol introduces OPEN and CLOSE operations. The
OPEN operation provides a single point where file lookup, creation, OPEN operation provides a single point where file lookup, creation,
and share semantics can be combined. The CLOSE operation also and share semantics can be combined. The CLOSE operation also
provides for the release of state accumulated by OPEN. provides for the release of state accumulated by OPEN.
1.3.5. File locking 1.3.5. File locking
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The major addition to NFS version 4 in the area of caching is the The major addition to NFS version 4 in the area of caching is the
ability of the server to delegate certain responsibilities to the ability of the server to delegate certain responsibilities to the
client. When the server grants a delegation for a file to a client, client. When the server grants a delegation for a file to a client,
the client is guaranteed certain semantics with respect to the the client is guaranteed certain semantics with respect to the
sharing of that file with other clients. At OPEN, the server may sharing of that file with other clients. At OPEN, the server may
provide the client either a read or write delegation for the file. provide the client either a read or write delegation for the file.
If the client is granted a read delegation, it is assured that no If the client is granted a read delegation, it is assured that no
other client has the ability to write to the file for the duration of other client has the ability to write to the file for the duration of
the delegation. If the client is granted a write delegation, the the delegation. If the client is granted a write delegation, the
Draft Specification NFS version 4 Protocol November 2002
client is assured that no other client has read or write access to client is assured that no other client has read or write access to
the file. the file.
Draft Specification NFS version 4 Protocol October 2002
Delegations can be recalled by the server. If another client Delegations can be recalled by the server. If another client
requests access to the file in such a way that the access conflicts requests access to the file in such a way that the access conflicts
with the granted delegation, the server is able to notify the initial with the granted delegation, the server is able to notify the initial
client and recall the delegation. This requires that a callback path client and recall the delegation. This requires that a callback path
exist between the server and client. If this callback path does not exist between the server and client. If this callback path does not
exist, then delegations can not be granted. The essence of a exist, then delegations can not be granted. The essence of a
delegation is that it allows the client to locally service operations delegation is that it allows the client to locally service operations
such as OPEN, CLOSE, LOCK, LOCKU, READ, WRITE without immediate such as OPEN, CLOSE, LOCK, LOCKU, READ, WRITE without immediate
interaction with the server. interaction with the server.
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All leases granted by a server have the same fixed All leases granted by a server have the same fixed
interval. Note that the fixed interval was chosen to interval. Note that the fixed interval was chosen to
alleviate the expense a server would have in maintaining alleviate the expense a server would have in maintaining
state about variable length leases across server failures. state about variable length leases across server failures.
Lock The term "lock" is used to refer to both record (byte- Lock The term "lock" is used to refer to both record (byte-
range) locks as well as share reservations unless range) locks as well as share reservations unless
specifically stated otherwise. specifically stated otherwise.
Draft Specification NFS version 4 Protocol November 2002
Server The "Server" is the entity responsible for coordinating Server The "Server" is the entity responsible for coordinating
client access to a set of filesystems. client access to a set of filesystems.
Draft Specification NFS version 4 Protocol October 2002
Stable Storage Stable Storage
NFS version 4 servers must be able to recover without data NFS version 4 servers must be able to recover without data
loss from multiple power failures (including cascading loss from multiple power failures (including cascading
power failures, that is, several power failures in quick power failures, that is, several power failures in quick
succession), operating system failures, and hardware succession), operating system failures, and hardware
failure of components other than the storage medium itself failure of components other than the storage medium itself
(for example, disk, nonvolatile RAM). (for example, disk, nonvolatile RAM).
Some examples of stable storage that are allowable for an Some examples of stable storage that are allowable for an
NFS server include: NFS server include:
skipping to change at page 15, line 5 skipping to change at page 16, line 5
defines the open and locking state provided by the server defines the open and locking state provided by the server
for a specific open or lock owner for a specific file. for a specific open or lock owner for a specific file.
Stateids composed of all bits 0 or all bits 1 have special Stateids composed of all bits 0 or all bits 1 have special
meaning and are reserved values. meaning and are reserved values.
Verifier A 64-bit quantity generated by the client that the server Verifier A 64-bit quantity generated by the client that the server
can use to determine if the client has restarted and lost can use to determine if the client has restarted and lost
all previous lock state. all previous lock state.
Draft Specification NFS version 4 Protocol October 2002 Draft Specification NFS version 4 Protocol November 2002
2. Protocol Data Types 2. Protocol Data Types
The syntax and semantics to describe the data types of the NFS The syntax and semantics to describe the data types of the NFS
version 4 protocol are defined in the XDR [RFC1832] and RPC [RFC1831] version 4 protocol are defined in the XDR [RFC1832] and RPC [RFC1831]
documents. The next sections build upon the XDR data types to define documents. The next sections build upon the XDR data types to define
types and structures specific to this protocol. types and structures specific to this protocol.
2.1. Basic Data Types 2.1. Basic Data Types
Data Type Definition Data Type Definition
_____________________________________________________________________ ____________________________________________________________________
int32_t typedef int int32_t; int32_t typedef int int32_t;
uint32_t typedef unsigned int uint32_t; uint32_t typedef unsigned int uint32_t;
int64_t typedef hyper int64_t; int64_t typedef hyper int64_t;
uint64_t typedef unsigned hyper uint64_t; uint64_t typedef unsigned hyper uint64_t;
attrlist4 typedef opaque attrlist4<>; attrlist4 typedef opaque attrlist4<>;
Used for file/directory attributes Used for file/directory attributes
bitmap4 typedef uint32_t bitmap4<>; bitmap4 typedef uint32_t bitmap4<>;
Used in attribute array encoding. Used in attribute array encoding.
changeid4 typedef uint64_t changeid4; changeid4 typedef uint64_t changeid4;
Used in definition of change_info Used in definition of change_info
clientid4 typedef uint64_t clientid4; clientid4 typedef uint64_t clientid4;
Shorthand reference to client identification Shorthand reference to client identification
component4 typedef utf8string component4; component4 typedef utf8str_cs component4;
Represents path name components Represents path name components
count4 typedef uint32_t count4; count4 typedef uint32_t count4;
Various count parameters (READ, WRITE, COMMIT) Various count parameters (READ, WRITE, COMMIT)
length4 typedef uint64_t length4; length4 typedef uint64_t length4;
Describes LOCK lengths Describes LOCK lengths
linktext4 typedef utf8string linktext4; linktext4 typedef utf8str_cs linktext4;
Symbolic link contents Symbolic link contents
mode4 typedef uint32_t mode4; mode4 typedef uint32_t mode4;
Mode attribute data type Mode attribute data type
nfs_cookie4 typedef uint64_t nfs_cookie4; nfs_cookie4 typedef uint64_t nfs_cookie4;
Opaque cookie value for READDIR Opaque cookie value for READDIR
nfs_fh4 typedef opaque nfs_fh4<NFS4_FHSIZE>; nfs_fh4 typedef opaque nfs_fh4<NFS4_FHSIZE>;
Filehandle definition; NFS4_FHSIZE is defined as 128 Filehandle definition; NFS4_FHSIZE is defined as 128
Draft Specification NFS version 4 Protocol October 2002 Draft Specification NFS version 4 Protocol November 2002
nfs_ftype4 enum nfs_ftype4; nfs_ftype4 enum nfs_ftype4;
Various defined file types Various defined file types
nfsstat4 enum nfsstat4; nfsstat4 enum nfsstat4;
Return value for operations Return value for operations
offset4 typedef uint64_t offset4; offset4 typedef uint64_t offset4;
Various offset designations (READ, WRITE, LOCK, COMMIT) Various offset designations (READ, WRITE,
LOCK, COMMIT)
pathname4 typedef component4 pathname4<>; pathname4 typedef component4 pathname4<>;
Represents path name for LOOKUP, OPEN and others Represents path name for LOOKUP, OPEN and others
qop4 typedef uint32_t qop4; qop4 typedef uint32_t qop4;
Quality of protection designation in SECINFO Quality of protection designation in SECINFO
sec_oid4 typedef opaque sec_oid4<>; sec_oid4 typedef opaque sec_oid4<>;
Security Object Identifier Security Object Identifier
The sec_oid4 data type is not really opaque. The sec_oid4 data type is not really opaque.
Instead contains an ASN.1 OBJECT IDENTIFIER as used Instead contains an ASN.1 OBJECT IDENTIFIER as used
by GSS-API in the mech_type argument to by GSS-API in the mech_type argument to
GSS_Init_sec_context. See [RFC2743] for details. GSS_Init_sec_context. See [RFC2743] for details.
seqid4 typedef uint32_t seqid4; seqid4 typedef uint32_t seqid4;
Sequence identifier used for file locking Sequence identifier used for file locking
utf8string typedef opaque utf8string<>; utf8string typedef opaque utf8string<>;
UTF-8 encoding for strings UTF-8 encoding for strings
utf8str_cis typedef opaque utf8str_cis<>;
Case-insensitive UTF-8 string
utf8str_cs typedef opaque utf8str_cs<>;
Case-sensitive UTF-8 string
utf8str_mixed typedef opaque utf8str_mixed<>;
UTF-8 strings with a case sensitive prefix and
a case insensitive suffix.
verifier4 typedef opaque verifier4[NFS4_VERIFIER_SIZE]; verifier4 typedef opaque verifier4[NFS4_VERIFIER_SIZE];
Verifier used for various operations (COMMIT, CREATE, Verifier used for various operations (COMMIT,
OPEN, READDIR, SETCLIENTID, SETCLIENTID_CONFIRM, WRITE) CREATE, OPEN, READDIR, SETCLIENTID,
NFS4_VERIFIER_SIZE is defined as 8. SETCLIENTID_CONFIRM, WRITE) NFS4_VERIFIER_SIZE is
defined as 8.
2.2. Structured Data Types 2.2. Structured Data Types
nfstime4 nfstime4
struct nfstime4 { struct nfstime4 {
Draft Specification NFS version 4 Protocol November 2002
int64_t seconds; int64_t seconds;
uint32_t nseconds; uint32_t nseconds;
} }
The nfstime4 structure gives the number of seconds and The nfstime4 structure gives the number of seconds and
nanoseconds since midnight or 0 hour January 1, 1970 Coordinated nanoseconds since midnight or 0 hour January 1, 1970 Coordinated
Universal Time (UTC). Values greater than zero for the seconds Universal Time (UTC). Values greater than zero for the seconds
field denote dates after the 0 hour January 1, 1970. Values field denote dates after the 0 hour January 1, 1970. Values
less than zero for the seconds field denote dates before the 0 less than zero for the seconds field denote dates before the 0
hour January 1, 1970. In both cases, the nseconds field is to hour January 1, 1970. In both cases, the nseconds field is to
be added to the seconds field for the final time representation. be added to the seconds field for the final time representation.
For example, if the time to be represented is one-half second For example, if the time to be represented is one-half second
Draft Specification NFS version 4 Protocol October 2002
before 0 hour January 1, 1970, the seconds field would have a before 0 hour January 1, 1970, the seconds field would have a
value of negative one (-1) and the nseconds fields would have a value of negative one (-1) and the nseconds fields would have a
value of one-half second (500000000). Values greater than value of one-half second (500000000). Values greater than
999,999,999 for nseconds are considered invalid. 999,999,999 for nseconds are considered invalid.
This data type is used to pass time and date information. A This data type is used to pass time and date information. A
server converts to and from its local representation of time server converts to and from its local representation of time
when processing time values, preserving as much accuracy as when processing time values, preserving as much accuracy as
possible. If the precision of timestamps stored for a filesystem possible. If the precision of timestamps stored for a filesystem
object is less than defined, loss of precision can occur. An object is less than defined, loss of precision can occur. An
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}; };
The above definitions are used as the attribute definitions to The above definitions are used as the attribute definitions to
set time values. If set_it is SET_TO_SERVER_TIME4, then the set time values. If set_it is SET_TO_SERVER_TIME4, then the
server uses its local representation of time for the time value. server uses its local representation of time for the time value.
specdata4 specdata4
struct specdata4 { struct specdata4 {
uint32_t specdata1; /* major device number */ uint32_t specdata1; /* major device number */
Draft Specification NFS version 4 Protocol November 2002
uint32_t specdata2; /* minor device number */ uint32_t specdata2; /* minor device number */
}; };
This data type represents additional information for the device This data type represents additional information for the device
file types NF4CHR and NF4BLK. file types NF4CHR and NF4BLK.
fsid4 fsid4
struct fsid4 { struct fsid4 {
uint64_t major; uint64_t major;
uint64_t minor; uint64_t minor;
Draft Specification NFS version 4 Protocol October 2002
}; };
This type is the filesystem identifier that is used as a This type is the filesystem identifier that is used as a
mandatory attribute. mandatory attribute.
fs_location4 fs_location4
struct fs_location4 { struct fs_location4 {
utf8string server<>; utf8str_cis server<>;
pathname4 rootpath; pathname4 rootpath;
}; };
fs_locations4 fs_locations4
struct fs_locations4 { struct fs_locations4 {
pathname4 fs_root; pathname4 fs_root;
fs_location4 locations<>; fs_location4 locations<>;
}; };
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}; };
The fattr4 structure is used to represent file and directory The fattr4 structure is used to represent file and directory
attributes. attributes.
The bitmap is a counted array of 32 bit integers used to contain The bitmap is a counted array of 32 bit integers used to contain
bit values. The position of the integer in the array that bit values. The position of the integer in the array that
contains bit n can be computed from the expression (n / 32) and contains bit n can be computed from the expression (n / 32) and
its bit within that integer is (n mod 32). its bit within that integer is (n mod 32).
Draft Specification NFS version 4 Protocol November 2002
0 1 0 1
+-----------+-----------+-----------+-- +-----------+-----------+-----------+--
| count | 31 .. 0 | 63 .. 32 | | count | 31 .. 0 | 63 .. 32 |
+-----------+-----------+-----------+-- +-----------+-----------+-----------+--
change_info4 change_info4
struct change_info4 { struct change_info4 {
bool atomic; bool atomic;
changeid4 before; changeid4 before;
Draft Specification NFS version 4 Protocol October 2002
changeid4 after; changeid4 after;
}; };
This structure is used with the CREATE, LINK, REMOVE, RENAME This structure is used with the CREATE, LINK, REMOVE, RENAME
operations to let the client know the value of the change operations to let the client know the value of the change
attribute for the directory in which the target filesystem attribute for the directory in which the target filesystem
object resides. object resides.
clientaddr4 clientaddr4
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Assuming big-endian ordering, h1, h2, h3, and h4, are Assuming big-endian ordering, h1, h2, h3, and h4, are
respectively, the first through fourth octets each converted to respectively, the first through fourth octets each converted to
ASCII-decimal. Assuming big-endian ordering, p1 and p2 are, ASCII-decimal. Assuming big-endian ordering, p1 and p2 are,
respectively, the first and second octets each converted to respectively, the first and second octets each converted to
ASCII-decimal. For example, if a host, in big-endian order, has ASCII-decimal. For example, if a host, in big-endian order, has
an address of 0x0A010307 and there is a service listening on, in an address of 0x0A010307 and there is a service listening on, in
big endian order, port 0x020F (decimal 527), then complete big endian order, port 0x020F (decimal 527), then complete
universal address is "10.1.3.7.2.15". universal address is "10.1.3.7.2.15".
For TCP over IPv4 the value of r_netid is the string "tcp". For For TCP over IPv4 the value of r_netid is the string "tcp". For
Draft Specification NFS version 4 Protocol November 2002
UDP over IPv4 the value of r_netid is the string "udp". UDP over IPv4 the value of r_netid is the string "udp".
For TCP over IPv4 and for UDP over IPv6, the format of r_addr is For TCP over IPv6 and for UDP over IPv6, the format of r_addr is
the US-ASCII string: the US-ASCII string:
x1:x2:x3:x4:x5:x6:x7:x8.p1.p2 x1:x2:x3:x4:x5:x6:x7:x8.p1.p2
The suffix "p1.p2" is the service port, and is computed the same The suffix "p1.p2" is the service port, and is computed the same
way as with universal addresses for TCP and UDP over IPv4. The way as with universal addresses for TCP and UDP over IPv4. The
prefix, "x1:x2:x3:x4:x5:x6:x7:x8", is the standard textual form prefix, "x1:x2:x3:x4:x5:x6:x7:x8", is the standard textual form
for representing an IPv6 address as defined in Section 2.2 of for representing an IPv6 address as defined in Section 2.2 of
Draft Specification NFS version 4 Protocol October 2002
[RFC1884]. Additionally, the two alternative forms specified in [RFC1884]. Additionally, the two alternative forms specified in
Section 2.2 of [RFC1884] are also acceptable. Section 2.2 of [RFC1884] are also acceptable.
For TCP over IPv6 the value of r_netid is the string "tcp6". For TCP over IPv6 the value of r_netid is the string "tcp6".
For UDP over IPv6 the value of r_netid is the string "udp6". For UDP over IPv6 the value of r_netid is the string "udp6".
cb_client4 cb_client4
struct cb_client4 { struct cb_client4 {
unsigned int cb_program; unsigned int cb_program;
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open_owner4 open_owner4
struct open_owner4 { struct open_owner4 {
clientid4 clientid; clientid4 clientid;
opaque owner<NFS4_OPAQUE_LIMIT>; opaque owner<NFS4_OPAQUE_LIMIT>;
}; };
This structure is used to identify the owner of open state. This structure is used to identify the owner of open state.
NFS4_OPAQUE_LIMIT is defined as 1024. NFS4_OPAQUE_LIMIT is defined as 1024.
Draft Specification NFS version 4 Protocol November 2002
lock_owner4 lock_owner4
struct lock_owner4 { struct lock_owner4 {
clientid4 clientid; clientid4 clientid;
opaque owner<NFS4_OPAQUE_LIMIT>; opaque owner<NFS4_OPAQUE_LIMIT>;
}; };
This structure is used to identify the owner of file locking This structure is used to identify the owner of file locking
state. NFS4_OPAQUE_LIMIT is defined as 1024. state. NFS4_OPAQUE_LIMIT is defined as 1024.
Draft Specification NFS version 4 Protocol October 2002
open_to_lock_owner4 open_to_lock_owner4
struct open_to_lock_owner4 { struct open_to_lock_owner4 {
seqid4 open_seqid; seqid4 open_seqid;
stateid4 open_stateid; stateid4 open_stateid;
seqid4 lock_seqid; seqid4 lock_seqid;
lock_owner4 lock_owner; lock_owner4 lock_owner;
}; };
This structure is used for the first LOCK operation done for an This structure is used for the first LOCK operation done for an
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This structure is used for the various state sharing mechanisms This structure is used for the various state sharing mechanisms
between the client and server. For the client, this data between the client and server. For the client, this data
structure is read-only. The starting value of the seqid field structure is read-only. The starting value of the seqid field
is undefined. The server is required to increment the seqid is undefined. The server is required to increment the seqid
field monotonically at each transition of the stateid. This is field monotonically at each transition of the stateid. This is
important since the client will inspect the seqid in OPEN important since the client will inspect the seqid in OPEN
stateids to determine the order of OPEN processing done by the stateids to determine the order of OPEN processing done by the
server. server.
Draft Specification NFS version 4 Protocol October 2002 Draft Specification NFS version 4 Protocol November 2002
3. RPC and Security Flavor 3. RPC and Security Flavor
The NFS version 4 protocol is a Remote Procedure Call (RPC) The NFS version 4 protocol is a Remote Procedure Call (RPC)
application that uses RPC version 2 and the corresponding eXternal application that uses RPC version 2 and the corresponding eXternal
Data Representation (XDR) as defined in [RFC1831] and [RFC1832]. The Data Representation (XDR) as defined in [RFC1831] and [RFC1832]. The
RPCSEC_GSS security flavor as defined in [RFC2203] MUST be used as RPCSEC_GSS security flavor as defined in [RFC2203] MUST be used as
the mechanism to deliver stronger security for the NFS version 4 the mechanism to deliver stronger security for the NFS version 4
protocol. protocol.
3.1. Ports and Transports 3.1. Ports and Transports
Historically, NFS version 2 and version 3 servers have resided on Historically, NFS version 2 and version 3 servers have resided on
port 2049. The registered port 2049 [RFC1700] for the NFS protocol port 2049. The registered port 2049 [RFC1700] for the NFS protocol
should be the default configuration. Using the registered port for should be the default configuration. Using the registered port for
NFS services means the NFS client will not need to use the RPC NFS services means the NFS client will not need to use the RPC
binding protocols as described in [RFC1833]; this will allow NFS to binding protocols as described in [RFC1833]; this will allow NFS to
transit firewalls. transit firewalls.
Where an NFS version 4 implementation supports operation over the IP Where an NFS version 4 implementation supports operation over the IP
network protocol, the supported transports between NFS and IP must be network protocol, the supported transports between NFS and IP MUST be
among the IETF-approved congestion control transport protocols, which among the IETF-approved congestion control transport protocols, which
include TCP and SCTP. To enhance the possibilities for include TCP and SCTP. To enhance the possibilities for
interoperability, an NFS version 4 implementation SHOULD support interoperability, an NFS version 4 implementation MUST support
operation over the TCP transport protocol. operation over the TCP transport protocol, at least until such time
as a standards track RFC revises this requirement to use a different
IETF-approved congestion control transport protocol.
If TCP is used as the transport, the client and server SHOULD use If TCP is used as the transport, the client and server SHOULD use
persistent connections. This will prevent the weakening of TCP's persistent connections. This will prevent the weakening of TCP's
congestion control via short lived connections and will improve congestion control via short lived connections and will improve
performance for the WAN environment by eliminating the need for SYN performance for the WAN environment by eliminating the need for SYN
handshakes. handshakes.
As noted in the Security Considerations section, the authentication
model for NFS version 4 has moved from machine-based to principal-
based. However, this modification of the authentication model does
not imply a technical requirement to move the TCP connection
management model from whole machine-based to one based on a per user
model. In particular, NFS over TCP client implementations have
traditionally multiplexed traffic for multiple users over a common
TCP connection between an NFS client and server. This has been true,
regardless whether the NFS client is using AUTH_SYS, AUTH_DH,
RPCSEC_GSS or any other flavor. Similarly, NFS over TCP server
implementations have assumed such a model and thus scale the
implementation of TCP connection management in proportion to the
number of expected client machines. It is intended that NFS version 4
will not modify this connection management model. NFS version 4
clients that violate this assumption can expect scaling issues on the
server and hence reduced service.
Note that for various timers, the client and server should avoid Note that for various timers, the client and server should avoid
inadvertent synchronization of those timers. For further discussion inadvertent synchronization of those timers. For further discussion
Draft Specification NFS version 4 Protocol November 2002
of the general issue refer to [Floyd]. of the general issue refer to [Floyd].
3.1.1. Client Retransmission Behavior 3.1.1. Client Retransmission Behavior
When processing a request received over a reliable transport such as When processing a request received over a reliable transport such as
TCP, the NFS version 4 server MUST NOT silently drop the request, TCP, the NFS version 4 server MUST NOT silently drop the request,
except if the transport connection has been broken. Given such a except if the transport connection has been broken. Given such a
contract between NFS version 4 clients and servers, clients MUST NOT contract between NFS version 4 clients and servers, clients MUST NOT
retry a request unless one or both of the following are true: retry a request unless one or both of the following are true:
o The transport connection has been broken o The transport connection has been broken
o The procedure being retried is the NULL procedure o The procedure being retried is the NULL procedure
Since reliable transports, such as TCP, do not always synchronously Since reliable transports, such as TCP, do not always synchronously
inform a peer when the other peer has broken the connection (for inform a peer when the other peer has broken the connection (for
example, when an NFS server reboots), so the NFS version 4 client may example, when an NFS server reboots), so the NFS version 4 client may
Draft Specification NFS version 4 Protocol October 2002
want to actively "probe" the connection to see if has been broken. want to actively "probe" the connection to see if has been broken.
Use of the NULL procedure is one recommended way to do so. So, when Use of the NULL procedure is one recommended way to do so. So, when
a client experiences a remote procedure call timeout (of some a client experiences a remote procedure call timeout (of some
arbitrary implementation specific amount), rather than retrying the arbitrary implementation specific amount), rather than retrying the
remote procedure call, it could instead issue a NULL procedure call remote procedure call, it could instead issue a NULL procedure call
to the server. If the server has died, the transport connection break to the server. If the server has died, the transport connection break
will eventually be indicated to the NFS version 4 client. The client will eventually be indicated to the NFS version 4 client. The client
can then reconnect, and then retry the original request. If the NULL can then reconnect, and then retry the original request. If the NULL
procedure call gets a response, the connection has not broken. The procedure call gets a response, the connection has not broken. The
client can decide to wait longer for the original request's response, client can decide to wait longer for the original request's response,
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uses the functionality of GSS-API [RFC2743]. This allows for the use uses the functionality of GSS-API [RFC2743]. This allows for the use
of various security mechanisms by the RPC layer without the of various security mechanisms by the RPC layer without the
additional implementation overhead of adding RPC security flavors. additional implementation overhead of adding RPC security flavors.
For NFS version 4, the RPCSEC_GSS security flavor MUST be used to For NFS version 4, the RPCSEC_GSS security flavor MUST be used to
enable the mandatory security mechanism. Other flavors, such as, enable the mandatory security mechanism. Other flavors, such as,
AUTH_NONE, AUTH_SYS, and AUTH_DH MAY be implemented as well. AUTH_NONE, AUTH_SYS, and AUTH_DH MAY be implemented as well.
3.2.1. Security mechanisms for NFS version 4 3.2.1. Security mechanisms for NFS version 4
The use of RPCSEC_GSS requires selection of: mechanism, quality of The use of RPCSEC_GSS requires selection of: mechanism, quality of
Draft Specification NFS version 4 Protocol November 2002
protection, and service (authentication, integrity, privacy). The protection, and service (authentication, integrity, privacy). The
remainder of this document will refer to these three parameters of remainder of this document will refer to these three parameters of
the RPCSEC_GSS security as the security triple. the RPCSEC_GSS security as the security triple.
3.2.1.1. Kerberos V5 as a security triple 3.2.1.1. Kerberos V5 as a security triple
The Kerberos V5 GSS-API mechanism as described in [RFC1964] MUST be The Kerberos V5 GSS-API mechanism as described in [RFC1964] MUST be
implemented and provide the following security triples. implemented and provide the following security triples.
column descriptions: column descriptions:
1 == number of pseudo flavor 1 == number of pseudo flavor
2 == name of pseudo flavor 2 == name of pseudo flavor
3 == mechanism's OID 3 == mechanism's OID
4 == mechanism's algorithm(s) 4 == mechanism's algorithm(s)
5 == RPCSEC_GSS service 5 == RPCSEC_GSS service
1 2 3 4 5 1 2 3 4 5
----------------------------------------------------------------------- -----------------------------------------------------------------------
Draft Specification NFS version 4 Protocol October 2002
390003 krb5 1.2.840.113554.1.2.2 DES MAC MD5 rpc_gss_svc_none 390003 krb5 1.2.840.113554.1.2.2 DES MAC MD5 rpc_gss_svc_none
390004 krb5i 1.2.840.113554.1.2.2 DES MAC MD5 rpc_gss_svc_integrity 390004 krb5i 1.2.840.113554.1.2.2 DES MAC MD5 rpc_gss_svc_integrity
390005 krb5p 1.2.840.113554.1.2.2 DES MAC MD5 rpc_gss_svc_privacy 390005 krb5p 1.2.840.113554.1.2.2 DES MAC MD5 rpc_gss_svc_privacy
for integrity, for integrity,
and 56 bit DES and 56 bit DES
for privacy. for privacy.
Note that the pseudo flavor is presented here as a mapping aid to the Note that the pseudo flavor is presented here as a mapping aid to the
implementor. Because this NFS protocol includes a method to implementor. Because this NFS protocol includes a method to
negotiate security and it understands the GSS-API mechanism, the negotiate security and it understands the GSS-API mechanism, the
pseudo flavor is not needed. The pseudo flavor is needed for NFS pseudo flavor is not needed. The pseudo flavor is needed for NFS
version 3 since the security negotiation is done via the MOUNT version 3 since the security negotiation is done via the MOUNT
protocol. protocol.
For a discussion of NFS' use of RPCSEC_GSS and Kerberos V5, please For a discussion of NFS' use of RPCSEC_GSS and Kerberos V5, please
see [RFC2623]. see [RFC2623].
Users and implementors are warned that 56 bit DES is no longer
considered state of the art in terms of resistance to brute force
attacks. Once a revision to [RFC1964] is available that adds support
for AES, implementors are urged to incorporate AES into their NFSv4
over Kerberos V5 protocol stacks, and users are similarly urged to
migrate to the use of AES.
3.2.1.2. LIPKEY as a security triple 3.2.1.2. LIPKEY as a security triple
The LIPKEY GSS-API mechanism as described in [RFC2847] MUST be The LIPKEY GSS-API mechanism as described in [RFC2847] MUST be
implemented and provide the following security triples. The implemented and provide the following security triples. The
definition of the columns matches the previous subsection "Kerberos definition of the columns matches the previous subsection "Kerberos
V5 as security triple" V5 as security triple"
1 2 3 4 5 1 2 3 4 5
Draft Specification NFS version 4 Protocol November 2002
----------------------------------------------------------------------- -----------------------------------------------------------------------
390006 lipkey 1.3.6.1.5.5.9 negotiated rpc_gss_svc_none 390006 lipkey 1.3.6.1.5.5.9 negotiated rpc_gss_svc_none
390007 lipkey-i 1.3.6.1.5.5.9 negotiated rpc_gss_svc_integrity 390007 lipkey-i 1.3.6.1.5.5.9 negotiated rpc_gss_svc_integrity
390008 lipkey-p 1.3.6.1.5.5.9 negotiated rpc_gss_svc_privacy 390008 lipkey-p 1.3.6.1.5.5.9 negotiated rpc_gss_svc_privacy
The mechanism algorithm is listed as "negotiated". This is because The mechanism algorithm is listed as "negotiated". This is because
LIPKEY is layered on SPKM-3 and in SPKM-3 [RFC2847] the LIPKEY is layered on SPKM-3 and in SPKM-3 [RFC2847] the
confidentiality and integrity algorithms are negotiated. Since confidentiality and integrity algorithms are negotiated. Since
SPKM-3 specifies HMAC-MD5 for integrity as MANDATORY, 128 bit SPKM-3 specifies HMAC-MD5 for integrity as MANDATORY, 128 bit
cast5CBC for confidentiality for privacy as MANDATORY, and further cast5CBC for confidentiality for privacy as MANDATORY, and further
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LIPKEY's GSS_Wrap() and GSS_GetMIC() by RPCSEC_GSS will use a quality LIPKEY's GSS_Wrap() and GSS_GetMIC() by RPCSEC_GSS will use a quality
of protection value of 0 (zero). See section 5.2 of [RFC2025] for an of protection value of 0 (zero). See section 5.2 of [RFC2025] for an
explanation. explanation.
LIPKEY uses SPKM-3 to create a secure channel in which to pass a user LIPKEY uses SPKM-3 to create a secure channel in which to pass a user
name and password from the client to the server. Once the user name name and password from the client to the server. Once the user name
and password have been accepted by the server, calls to the LIPKEY and password have been accepted by the server, calls to the LIPKEY
context are redirected to the SPKM-3 context. See [RFC2847] for more context are redirected to the SPKM-3 context. See [RFC2847] for more
details. details.
Draft Specification NFS version 4 Protocol October 2002
3.2.1.3. SPKM-3 as a security triple 3.2.1.3. SPKM-3 as a security triple
The SPKM-3 GSS-API mechanism as described in [RFC2847] MUST be The SPKM-3 GSS-API mechanism as described in [RFC2847] MUST be
implemented and provide the following security triples. The implemented and provide the following security triples. The
definition of the columns matches the previous subsection "Kerberos definition of the columns matches the previous subsection "Kerberos
V5 as security triple". V5 as security triple".
1 2 3 4 5 1 2 3 4 5
----------------------------------------------------------------------- -----------------------------------------------------------------------
390009 spkm3 1.3.6.1.5.5.1.3 negotiated rpc_gss_svc_none 390009 spkm3 1.3.6.1.5.5.1.3 negotiated rpc_gss_svc_none
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"negotiated", see the previous section "LIPKEY as a security triple." "negotiated", see the previous section "LIPKEY as a security triple."
Because SPKM-3 negotiates the algorithms, subsequent calls to SPKM- Because SPKM-3 negotiates the algorithms, subsequent calls to SPKM-
3's GSS_Wrap() and GSS_GetMIC() by RPCSEC_GSS will use a quality of 3's GSS_Wrap() and GSS_GetMIC() by RPCSEC_GSS will use a quality of
protection value of 0 (zero). See section 5.2 of [RFC2025] for an protection value of 0 (zero). See section 5.2 of [RFC2025] for an
explanation. explanation.
Even though LIPKEY is layered over SPKM-3, SPKM-3 is specified as a Even though LIPKEY is layered over SPKM-3, SPKM-3 is specified as a
mandatory set of triples to handle the situations where the initiator mandatory set of triples to handle the situations where the initiator
(the client) is anonymous or where the initiator has its own (the client) is anonymous or where the initiator has its own
Draft Specification NFS version 4 Protocol November 2002
certificate. If the initiator is anonymous, there will not be a user certificate. If the initiator is anonymous, there will not be a user
name and password to send to the target (the server). If the name and password to send to the target (the server). If the
initiator has its own certificate, then using passwords is initiator has its own certificate, then using passwords is
superfluous. superfluous.
3.3. Security Negotiation 3.3. Security Negotiation
With the NFS version 4 server potentially offering multiple security With the NFS version 4 server potentially offering multiple security
mechanisms, the client needs a method to determine or negotiate which mechanisms, the client needs a method to determine or negotiate which
mechanism is to be used for its communication with the server. The mechanism is to be used for its communication with the server. The
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a secure channel to eliminate the possibility of a third party a secure channel to eliminate the possibility of a third party
intercepting the negotiation sequence and forcing the client and intercepting the negotiation sequence and forcing the client and
server to choose a lower level of security than required or desired. server to choose a lower level of security than required or desired.
See the section "Security Considerations" for further discussion. See the section "Security Considerations" for further discussion.
3.3.1. SECINFO 3.3.1. SECINFO
The new SECINFO operation will allow the client to determine, on a The new SECINFO operation will allow the client to determine, on a
per filehandle basis, what security triple is to be used for server per filehandle basis, what security triple is to be used for server
access. In general, the client will not have to use the SECINFO access. In general, the client will not have to use the SECINFO
Draft Specification NFS version 4 Protocol October 2002
operation except during initial communication with the server or when operation except during initial communication with the server or when
the client crosses policy boundaries at the server. It is possible the client crosses policy boundaries at the server. It is possible
that the server's policies change during the client's interaction that the server's policies change during the client's interaction
therefore forcing the client to negotiate a new security triple. therefore forcing the client to negotiate a new security triple.
3.3.2. Security Error 3.3.2. Security Error
Based on the assumption that each NFS version 4 client and server Based on the assumption that each NFS version 4 client and server
must support a minimum set of security (i.e. LIPKEY, SPKM-3, and must support a minimum set of security (i.e. LIPKEY, SPKM-3, and
Kerberos-V5 all under RPCSEC_GSS), the NFS client will start its Kerberos-V5 all under RPCSEC_GSS), the NFS client will start its
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triples. During communication with the server, the client may triples. During communication with the server, the client may
receive an NFS error of NFS4ERR_WRONGSEC. This error allows the receive an NFS error of NFS4ERR_WRONGSEC. This error allows the
server to notify the client that the security triple currently being server to notify the client that the security triple currently being
used is not appropriate for access to the server's filesystem used is not appropriate for access to the server's filesystem
resources. The client is then responsible for determining what resources. The client is then responsible for determining what
security triples are available at the server and choose one which is security triples are available at the server and choose one which is
appropriate for the client. See the section for the "SECINFO" appropriate for the client. See the section for the "SECINFO"
operation for further discussion of how the client will respond to operation for further discussion of how the client will respond to
the NFS4ERR_WRONGSEC error and use SECINFO. the NFS4ERR_WRONGSEC error and use SECINFO.
Draft Specification NFS version 4 Protocol November 2002
3.4. Callback RPC Authentication 3.4. Callback RPC Authentication
Except as noted elsewhere in this section, the callback RPC Except as noted elsewhere in this section, the callback RPC
(described later) MUST mutually authenticate the NFS server to the (described later) MUST mutually authenticate the NFS server to the
principal that acquired the clientid (also described later), using principal that acquired the clientid (also described later), using
the security flavor the original SETCLIENTID operation used. the security flavor the original SETCLIENTID operation used.
For AUTH_NONE, there are no principals, so this is a non-issue. For AUTH_NONE, there are no principals, so this is a non-issue.
AUTH_SYS has no notions of mutual authentication or a server AUTH_SYS has no notions of mutual authentication or a server
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server host and directory services domain in which it lives such as a server host and directory services domain in which it lives such as a
Network Information System domain or a DNS domain. Network Information System domain or a DNS domain.
Because LIPKEY is layered over SPKM-3, it is permissible for the Because LIPKEY is layered over SPKM-3, it is permissible for the
server to use SPKM-3 and not LIPKEY for the callback even if the server to use SPKM-3 and not LIPKEY for the callback even if the
client used LIPKEY for SETCLIENTID. client used LIPKEY for SETCLIENTID.
Regardless of what security mechanism under RPCSEC_GSS is being used, Regardless of what security mechanism under RPCSEC_GSS is being used,
the NFS server, MUST identify itself in GSS-API via a the NFS server, MUST identify itself in GSS-API via a
GSS_C_NT_HOSTBASED_SERVICE name type. GSS_C_NT_HOSTBASED_SERVICE GSS_C_NT_HOSTBASED_SERVICE name type. GSS_C_NT_HOSTBASED_SERVICE
Draft Specification NFS version 4 Protocol October 2002
names are of the form: names are of the form:
service@hostname service@hostname
For NFS, the "service" element is For NFS, the "service" element is
nfs nfs
Implementations of security mechanisms will convert nfs@hostname to Implementations of security mechanisms will convert nfs@hostname to
various different forms. For Kerberos V5 and LIPKEY, the following various different forms. For Kerberos V5 and LIPKEY, the following
form is RECOMMENDED: form is RECOMMENDED:
nfs/hostname nfs/hostname
For Kerberos V5, nfs/hostname would be a server principal in the For Kerberos V5, nfs/hostname would be a server principal in the
Kerberos Key Distribution Center database. For LIPKEY, this would be Kerberos Key Distribution Center database. This is the same
the username passed to the target (the NFS version 4 client that principal the client acquired a GSS-API context for when it issued
receives the callback). the SETCLIENTID operation, therefore, the realm name for the server
principal must be the same for the callback as it was for the
SETCLIENTID.
For LIPKEY, this would be the username passed to the target (the NFS
version 4 client that receives the callback).
Draft Specification NFS version 4 Protocol November 2002
It should be noted that LIPKEY may not work for callbacks, since the It should be noted that LIPKEY may not work for callbacks, since the
LIPKEY client uses a user id/password. If the NFS client receiving LIPKEY client uses a user id/password. If the NFS client receiving
the callback can authenticate the NFS server's user name/password the callback can authenticate the NFS server's user name/password
pair, and if the user that the NFS server is authenticating to has a pair, and if the user that the NFS server is authenticating to has a
public key certificate, then it works. public key certificate, then it works.
In situations where the NFS client uses LIPKEY and uses a per-host In situations where the NFS client uses LIPKEY and uses a per-host
principal for the SETCLIENTID operation, instead of using LIPKEY for principal for the SETCLIENTID operation, instead of using LIPKEY for
SETCLIENTID, it is RECOMMENDED that SPKM-3 with mutual authentication SETCLIENTID, it is RECOMMENDED that SPKM-3 with mutual authentication
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requirements beyond a certificate for the target, and the requirements beyond a certificate for the target, and the
expectation is that existing password infrastructure can be expectation is that existing password infrastructure can be
leveraged for the initiator. In some environments, a per-host leveraged for the initiator. In some environments, a per-host
password does not exist yet. If certificates are used for any password does not exist yet. If certificates are used for any
per-host principals, then additional password infrastructure is per-host principals, then additional password infrastructure is
not needed. not needed.
o In cases when a host is both an NFS client and server, it can o In cases when a host is both an NFS client and server, it can
share the same per-host certificate. share the same per-host certificate.
Draft Specification NFS version 4 Protocol October 2002 Draft Specification NFS version 4 Protocol November 2002
4. Filehandles 4. Filehandles
The filehandle in the NFS protocol is a per server unique identifier The filehandle in the NFS protocol is a per server unique identifier
for a filesystem object. The contents of the filehandle are opaque for a filesystem object. The contents of the filehandle are opaque
to the client. Therefore, the server is responsible for translating to the client. Therefore, the server is responsible for translating
the filehandle to an internal representation of the filesystem the filehandle to an internal representation of the filesystem
object. object.
4.1. Obtaining the First Filehandle 4.1. Obtaining the First Filehandle
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used, the client can then traverse the entirety of the server's file used, the client can then traverse the entirety of the server's file
tree with the LOOKUP operation. A complete discussion of the server tree with the LOOKUP operation. A complete discussion of the server
name space is in the section "NFS Server Name Space". name space is in the section "NFS Server Name Space".
4.1.2. Public Filehandle 4.1.2. Public Filehandle
The second special filehandle is the PUBLIC filehandle. Unlike the The second special filehandle is the PUBLIC filehandle. Unlike the
ROOT filehandle, the PUBLIC filehandle may be bound or represent an ROOT filehandle, the PUBLIC filehandle may be bound or represent an
arbitrary filesystem object at the server. The server is responsible arbitrary filesystem object at the server. The server is responsible
Draft Specification NFS version 4 Protocol October 2002 Draft Specification NFS version 4 Protocol November 2002
for this binding. It may be that the PUBLIC filehandle and the ROOT for this binding. It may be that the PUBLIC filehandle and the ROOT
filehandle refer to the same filesystem object. However, it is up to filehandle refer to the same filesystem object. However, it is up to
the administrative software at the server and the policies of the the administrative software at the server and the policies of the
server administrator to define the binding of the PUBLIC filehandle server administrator to define the binding of the PUBLIC filehandle
and server filesystem object. The client may not make any and server filesystem object. The client may not make any
assumptions about this binding. The client uses the PUBLIC filehandle assumptions about this binding. The client uses the PUBLIC filehandle
via the PUTPUBFH operation. via the PUTPUBFH operation.
4.2. Filehandle Types 4.2. Filehandle Types
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otherwise interpret the contents of filehandles. If two filehandles otherwise interpret the contents of filehandles. If two filehandles
from the same server are equal, they MUST refer to the same file. from the same server are equal, they MUST refer to the same file.
Servers SHOULD try to maintain a one-to-one correspondence between Servers SHOULD try to maintain a one-to-one correspondence between
filehandles and files but this is not required. Clients MUST use filehandles and files but this is not required. Clients MUST use
filehandle comparisons only to improve performance, not for correct filehandle comparisons only to improve performance, not for correct
behavior. All clients need to be prepared for situations in which it behavior. All clients need to be prepared for situations in which it
cannot be determined whether two filehandles denote the same object cannot be determined whether two filehandles denote the same object
and in such cases, avoid making invalid assumptions which might cause and in such cases, avoid making invalid assumptions which might cause
incorrect behavior. Further discussion of filehandle and attribute incorrect behavior. Further discussion of filehandle and attribute
Draft Specification NFS version 4 Protocol October 2002 Draft Specification NFS version 4 Protocol November 2002
comparison in the context of data caching is presented in the section comparison in the context of data caching is presented in the section
"Data Caching and File Identity". "Data Caching and File Identity".
As an example, in the case that two different path names when As an example, in the case that two different path names when
traversed at the server terminate at the same filesystem object, the traversed at the server terminate at the same filesystem object, the
server SHOULD return the same filehandle for each path. This can server SHOULD return the same filehandle for each path. This can
occur if a hard link is used to create two file names which refer to occur if a hard link is used to create two file names which refer to
the same underlying file object and associated data. For example, if the same underlying file object and associated data. For example, if
paths /a/b/c and /a/d/c refer to the same file, the server SHOULD paths /a/b/c and /a/d/c refer to the same file, the server SHOULD
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server should return NFS4ERR_STALE to the client (as is the case for server should return NFS4ERR_STALE to the client (as is the case for
persistent filehandles). In all other cases where the server persistent filehandles). In all other cases where the server
determines that a volatile filehandle can no longer be used, it determines that a volatile filehandle can no longer be used, it
should return an error of NFS4ERR_FHEXPIRED. should return an error of NFS4ERR_FHEXPIRED.
The mandatory attribute "fh_expire_type" is used by the client to The mandatory attribute "fh_expire_type" is used by the client to
determine what type of filehandle the server is providing for a determine what type of filehandle the server is providing for a
particular filesystem. This attribute is a bitmask with the particular filesystem. This attribute is a bitmask with the
following values: following values:
Draft Specification NFS version 4 Protocol October 2002 Draft Specification NFS version 4 Protocol November 2002
FH4_PERSISTENT FH4_PERSISTENT
The value of FH4_PERSISTENT is used to indicate a persistent The value of FH4_PERSISTENT is used to indicate a persistent
filehandle, which is valid until the object is removed from the filehandle, which is valid until the object is removed from the
filesystem. The server will not return NFS4ERR_FHEXPIRED for filesystem. The server will not return NFS4ERR_FHEXPIRED for
this filehandle. FH4_PERSISTENT is defined as a value in which this filehandle. FH4_PERSISTENT is defined as a value in which
none of the bits specified below are set. none of the bits specified below are set.
FH4_VOLATILE_ANY FH4_VOLATILE_ANY
The filehandle may expire at any time, except as specifically The filehandle may expire at any time, except as specifically
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occurs, and it is likely that additional expirations will occur occurs, and it is likely that additional expirations will occur
(as a result of file CLOSE) that are separated in time from the (as a result of file CLOSE) that are separated in time from the
migration event itself. migration event itself.
4.2.4. One Method of Constructing a Volatile Filehandle 4.2.4. One Method of Constructing a Volatile Filehandle
A volatile filehandle, while opaque to the client could contain: A volatile filehandle, while opaque to the client could contain:
[volatile bit = 1 | server boot time | slot | generation number] [volatile bit = 1 | server boot time | slot | generation number]
Draft Specification NFS version 4 Protocol October 2002 Draft Specification NFS version 4 Protocol November 2002
o slot is an index in the server volatile filehandle table o slot is an index in the server volatile filehandle table
o generation number is the generation number for the table o generation number is the generation number for the table
entry/slot entry/slot
When the client presents a volatile filehandle, the server makes the When the client presents a volatile filehandle, the server makes the
following checks, which assume that the check for the volatile bit following checks, which assume that the check for the volatile bit
has passed. If the server boot time is less than the current server has passed. If the server boot time is less than the current server
boot time, return NFS4ERR_FHEXPIRED. If slot is out of range, return boot time, return NFS4ERR_FHEXPIRED. If slot is out of range, return
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processing of the rename request. The client can then regenerate the processing of the rename request. The client can then regenerate the
new filehandle based on the new path name. The client could also use new filehandle based on the new path name. The client could also use
the compound operation mechanism to construct a set of operations the compound operation mechanism to construct a set of operations
like: like:
RENAME A B RENAME A B
LOOKUP B LOOKUP B
GETFH GETFH
Note that the COMPOUND procedure does not provide atomicity. This Note that the COMPOUND procedure does not provide atomicity. This
example only reduces the overhead of recovering from an expired example only reduces the overhead of recovering from an expired
Draft Specification NFS version 4 Protocol October 2002 Draft Specification NFS version 4 Protocol November 2002
filehandle. filehandle.
Draft Specification NFS version 4 Protocol October 2002 Draft Specification NFS version 4 Protocol November 2002
5. File Attributes 5. File Attributes
To meet the requirements of extensibility and increased To meet the requirements of extensibility and increased
interoperability with non-UNIX platforms, attributes must be handled interoperability with non-UNIX platforms, attributes must be handled
in a flexible manner. The NFS version 3 fattr3 structure contains a in a flexible manner. The NFS version 3 fattr3 structure contains a
fixed list of attributes that not all clients and servers are able to fixed list of attributes that not all clients and servers are able to
support or care about. The fattr3 structure can not be extended as support or care about. The fattr3 structure can not be extended as
new needs arise and it provides no way to indicate non-support. With new needs arise and it provides no way to indicate non-support. With
the NFS version 4 protocol, the client is able query what attributes the NFS version 4 protocol, the client is able query what attributes
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encouraged to define their new attributes as recommended attributes encouraged to define their new attributes as recommended attributes
by bringing them to the IETF standards-track process. by bringing them to the IETF standards-track process.
The set of attributes which are classified as mandatory is The set of attributes which are classified as mandatory is
deliberately small since servers must do whatever it takes to support deliberately small since servers must do whatever it takes to support
them. A server should support as many of the recommended attributes them. A server should support as many of the recommended attributes
as possible but by their definition, the server is not required to as possible but by their definition, the server is not required to
support all of them. Attributes are deemed mandatory if the data is support all of them. Attributes are deemed mandatory if the data is
both needed by a large number of clients and is not otherwise both needed by a large number of clients and is not otherwise
Draft Specification NFS version 4 Protocol October 2002 Draft Specification NFS version 4 Protocol November 2002
reasonably computable by the client when support is not provided on reasonably computable by the client when support is not provided on
the server. the server.
Note that the hidden directory returned by OPENATTR is a convenience Note that the hidden directory returned by OPENATTR is a convenience
for protocol processing. The client should not make any assumptions for protocol processing. The client should not make any assumptions
about the server's implementation of named attributes and whether the about the server's implementation of named attributes and whether the
underlying filesystem at the server has a named attribute directory underlying filesystem at the server has a named attribute directory
or not. Therefore, operations such as SETATTR and GETATTR on the or not. Therefore, operations such as SETATTR and GETATTR on the
named attribute directory are undefined. named attribute directory are undefined.
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fabricate or construct an attribute or whether to do without the fabricate or construct an attribute or whether to do without the
attribute. attribute.
5.3. Named Attributes 5.3. Named Attributes
These attributes are not supported by direct encoding in the NFS These attributes are not supported by direct encoding in the NFS
Version 4 protocol but are accessed by string names rather than Version 4 protocol but are accessed by string names rather than
numbers and correspond to an uninterpreted stream of bytes which are numbers and correspond to an uninterpreted stream of bytes which are
stored with the filesystem object. The name space for these stored with the filesystem object. The name space for these
Draft Specification NFS version 4 Protocol October 2002 Draft Specification NFS version 4 Protocol November 2002
attributes may be accessed by using the OPENATTR operation. The attributes may be accessed by using the OPENATTR operation. The
OPENATTR operation returns a filehandle for a virtual "attribute OPENATTR operation returns a filehandle for a virtual "attribute
directory" and further perusal of the name space may be done using directory" and further perusal of the name space may be done using
READDIR and LOOKUP operations on this filehandle. Named attributes READDIR and LOOKUP operations on this filehandle. Named attributes
may then be examined or changed by normal READ and WRITE and CREATE may then be examined or changed by normal READ and WRITE and CREATE
operations on the filehandles returned from READDIR and LOOKUP. operations on the filehandles returned from READDIR and LOOKUP.
Named attributes may have attributes. Named attributes may have attributes.
It is recommended that servers support arbitrary named attributes. A It is recommended that servers support arbitrary named attributes. A
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maxread, maxwrite, no_trunc, space_avail, space_free, maxread, maxwrite, no_trunc, space_avail, space_free,
space_total, time_delta space_total, time_delta
o The per filesystem object attributes are: o The per filesystem object attributes are:
type, change, size, named_attr, fsid, rdattr_error, filehandle, type, change, size, named_attr, fsid, rdattr_error, filehandle,
ACL, archive, fileid, hidden, maxlink, mimetype, mode, numlinks, ACL, archive, fileid, hidden, maxlink, mimetype, mode, numlinks,
owner, owner_group, rawdev, space_used, system, time_access, owner, owner_group, rawdev, space_used, system, time_access,
time_backup, time_create, time_metadata, time_modify, time_backup, time_create, time_metadata, time_modify,
Draft Specification NFS version 4 Protocol October 2002 Draft Specification NFS version 4 Protocol November 2002
mounted_on_fileid mounted_on_fileid
For quota_avail_hard, quota_avail_soft, and quota_used see their For quota_avail_hard, quota_avail_soft, and quota_used see their
definitions below for the appropriate classification. definitions below for the appropriate classification.
Draft Specification NFS version 4 Protocol October 2002 Draft Specification NFS version 4 Protocol November 2002
5.5. Mandatory Attributes - Definitions 5.5. Mandatory Attributes - Definitions
Name # DataType Access Description Name # DataType Access Description
___________________________________________________________________ ___________________________________________________________________
supp_attr 0 bitmap READ The bit vector which supp_attr 0 bitmap READ The bit vector which
would retrieve all would retrieve all
mandatory and mandatory and
recommended attributes recommended attributes
that are supported for that are supported for
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only if the filesystem only if the filesystem
object can not be object can not be
updated more updated more
frequently than the frequently than the
resolution of resolution of
time_metadata. time_metadata.
size 4 uint64 R/W The size of the object size 4 uint64 R/W The size of the object
in bytes. in bytes.
Draft Specification NFS version 4 Protocol October 2002 Draft Specification NFS version 4 Protocol November 2002
link_support 5 bool READ True, if the object's link_support 5 bool READ True, if the object's
filesystem supports filesystem supports
hard links. hard links.
symlink_support 6 bool READ True, if the object's symlink_support 6 bool READ True, if the object's
filesystem supports filesystem supports
symbolic links. symbolic links.
named_attr 7 bool READ True, if this object named_attr 7 bool READ True, if this object
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server in seconds. server in seconds.
rdattr_error 11 enum READ Error returned from rdattr_error 11 enum READ Error returned from
getattr during getattr during
readdir. readdir.
filehandle 19 nfs_fh4 READ The filehandle of this filehandle 19 nfs_fh4 READ The filehandle of this
object (primarily for object (primarily for
readdir requests). readdir requests).
Draft Specification NFS version 4 Protocol October 2002 Draft Specification NFS version 4 Protocol November 2002
5.6. Recommended Attributes - Definitions 5.6. Recommended Attributes - Definitions
Name # Data Type Access Description Name # Data Type Access Description
______________________________________________________________________ ______________________________________________________________________
ACL 12 nfsace4<> R/W The access control ACL 12 nfsace4<> R/W The access control
list for the object. list for the object.
aclsupport 13 uint32 READ Indicates what types aclsupport 13 uint32 READ Indicates what types
of ACLs are supported of ACLs are supported
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with a file if the with a file if the
caller is not a caller is not a
privileged user (for privileged user (for
example, "root" in example, "root" in
UNIX operating UNIX operating
environments or in environments or in
Windows 2000 the Windows 2000 the
"Take Ownership" "Take Ownership"
privilege). privilege).
Draft Specification NFS version 4 Protocol October 2002 Draft Specification NFS version 4 Protocol November 2002
fileid 20 uint64 READ A number uniquely fileid 20 uint64 READ A number uniquely
identifying the file identifying the file
within the within the
filesystem. filesystem.
files_avail 21 uint64 READ File slots available files_avail 21 uint64 READ File slots available
to this user on the to this user on the
filesystem containing filesystem containing
this object - this this object - this
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are per filesystem are per filesystem
attributes the same attributes the same
for all filesystem's for all filesystem's
objects. objects.
maxfilesize 27 uint64 READ Maximum supported maxfilesize 27 uint64 READ Maximum supported
file size for the file size for the
filesystem of this filesystem of this
object. object.
Draft Specification NFS version 4 Protocol October 2002 Draft Specification NFS version 4 Protocol November 2002
maxlink 28 uint32 READ Maximum number of maxlink 28 uint32 READ Maximum number of
links for this links for this
object. object.
maxname 29 uint32 READ Maximum filename size maxname 29 uint32 READ Maximum filename size
supported for this supported for this
object. object.
maxread 30 uint64 READ Maximum read size maxread 30 uint64 READ Maximum read size
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to this object. to this object.
owner 36 utf8<> R/W The string name of owner 36 utf8<> R/W The string name of
the owner of this the owner of this
object. object.
owner_group 37 utf8<> R/W The string name of owner_group 37 utf8<> R/W The string name of
the group ownership the group ownership
of this object. of this object.
Draft Specification NFS version 4 Protocol October 2002 Draft Specification NFS version 4 Protocol November 2002
quota_avail_hard 38 uint64 READ For definition see quota_avail_hard 38 uint64 READ For definition see
"Quota Attributes" "Quota Attributes"
section below. section below.
quota_avail_soft 39 uint64 READ For definition see quota_avail_soft 39 uint64 READ For definition see
"Quota Attributes" "Quota Attributes"
section below. section below.
quota_used 40 uint64 READ For definition see quota_used 40 uint64 READ For definition see
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space_total 44 uint64 READ Total disk space in space_total 44 uint64 READ Total disk space in
bytes on the bytes on the
filesystem containing filesystem containing
this object. this object.
space_used 45 uint64 READ Number of filesystem space_used 45 uint64 READ Number of filesystem
bytes allocated to bytes allocated to
this object. this object.
Draft Specification NFS version 4 Protocol October 2002 Draft Specification NFS version 4 Protocol November 2002
system 46 bool R/W True, if this file is system 46 bool R/W True, if this file is
a "system" file with a "system" file with
respect to the respect to the
Windows API? Windows API?
time_access 47 nfstime4 READ The time of last time_access 47 nfstime4 READ The time of last
access to the object access to the object
by a read that was by a read that was
satisfied by the satisfied by the
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object. SETATTR use object. SETATTR use
only. only.
mounted_on_fileid 55 uint64 READ Like fileid, but if mounted_on_fileid 55 uint64 READ Like fileid, but if
the target filehandle the target filehandle
is the root of a is the root of a
filesystem return the filesystem return the
fileid of the fileid of the
underlying directory. underlying directory.
Draft Specification NFS version 4 Protocol October 2002 Draft Specification NFS version 4 Protocol November 2002
5.7. Time Access 5.7. Time Access
As defined above, the time_access attribute represents the time of As defined above, the time_access attribute represents the time of
last access to the object by a read that was satisfied by the server. last access to the object by a read that was satisfied by the server.
The notion of what is an "access" depends on server's operating The notion of what is an "access" depends on server's operating
environment and/or the server's filesystem semantics. For example, environment and/or the server's filesystem semantics. For example,
for servers obeying POSIX semantics, time_access would be updated for servers obeying POSIX semantics, time_access would be updated
only by the READLINK, READ, and READDIR operations and not any of the only by the READLINK, READ, and READDIR operations and not any of the
operations that modify the content of the object. Of course, setting operations that modify the content of the object. Of course, setting
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to these security principals. When these local identifiers are to these security principals. When these local identifiers are
translated to the form of the owner attribute, associated with files translated to the form of the owner attribute, associated with files
created by such principals they identify, in a common format, the created by such principals they identify, in a common format, the
users associated with each corresponding set of security principals. users associated with each corresponding set of security principals.
The translation used to interpret owner and group strings is not The translation used to interpret owner and group strings is not
specified as part of the protocol. This allows various solutions to specified as part of the protocol. This allows various solutions to
be employed. For example, a local translation table may be consulted be employed. For example, a local translation table may be consulted
that maps between a numeric id to the user@dns_domain syntax. A name that maps between a numeric id to the user@dns_domain syntax. A name
Draft Specification NFS version 4 Protocol October 2002 Draft Specification NFS version 4 Protocol November 2002
service may also be used to accomplish the translation. A server may service may also be used to accomplish the translation. A server may
provide a more general service, not limited by any particular provide a more general service, not limited by any particular
translation (which would only translate a limited set of possible translation (which would only translate a limited set of possible
strings) by storing the owner and owner_group attributes in local strings) by storing the owner and owner_group attributes in local
storage without any translation or it may augment a translation storage without any translation or it may augment a translation
method by storing the entire string for attributes for which no method by storing the entire string for attributes for which no
translation is available while using the local representation for translation is available while using the local representation for
those cases in which a translation is available. those cases in which a translation is available.
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unsigned uid's and gid's, owner and group strings that consist of unsigned uid's and gid's, owner and group strings that consist of
decimal numeric values with no leading zeros can be given a special decimal numeric values with no leading zeros can be given a special
interpretation by clients and servers which choose to provide such interpretation by clients and servers which choose to provide such
support. The receiver may treat such a user or group string as support. The receiver may treat such a user or group string as
representing the same user as would be represented by a v2/v3 uid or representing the same user as would be represented by a v2/v3 uid or
gid having the corresponding numeric value. A server is not gid having the corresponding numeric value. A server is not
obligated to accept such a string, but may return an NFS4ERR_BADOWNER obligated to accept such a string, but may return an NFS4ERR_BADOWNER
instead. To avoid this mechanism being used to subvert user and instead. To avoid this mechanism being used to subvert user and
group translation, so that a client might pass all of the owners and group translation, so that a client might pass all of the owners and
Draft Specification NFS version 4 Protocol October 2002 Draft Specification NFS version 4 Protocol November 2002
groups in numeric form, a server SHOULD return an NFS4ERR_BADOWNER groups in numeric form, a server SHOULD return an NFS4ERR_BADOWNER
error when there is a valid translation for the user or owner error when there is a valid translation for the user or owner
designated in this way. In that case, the client must use the designated in this way. In that case, the client must use the
appropriate name@domain string and not the special form for appropriate name@domain string and not the special form for
compatibility. compatibility.
The owner string "nobody" may be used to designate an anonymous user, The owner string "nobody" may be used to designate an anonymous user,
which will be associated with a file created by a security principal which will be associated with a file created by a security principal
that cannot be mapped through normal means to the owner attribute. that cannot be mapped through normal means to the owner attribute.
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allocations to other files or directories. allocations to other files or directories.
quota_used quota_used
The value in bytes which represent the amount of disc space used The value in bytes which represent the amount of disc space used
by this file or directory and possibly a number of other similar by this file or directory and possibly a number of other similar
files or directories, where the set of "similar" meets at least files or directories, where the set of "similar" meets at least
the criterion that allocating space to any file or directory in the criterion that allocating space to any file or directory in
the set will reduce the "quota_avail_hard" of every other file the set will reduce the "quota_avail_hard" of every other file
or directory in the set. or directory in the set.
Draft Specification NFS version 4 Protocol October 2002 Draft Specification NFS version 4 Protocol November 2002
Note that there may be a number of distinct but overlapping sets Note that there may be a number of distinct but overlapping sets
of files or directories for which a quota_used value is of files or directories for which a quota_used value is
maintained. E.g. "all files with a given owner", "all files with maintained. E.g. "all files with a given owner", "all files with
a given group owner". etc. a given group owner". etc.
The server is at liberty to choose any of those sets but should The server is at liberty to choose any of those sets but should
do so in a repeatable way. The rule may be configured per- do so in a repeatable way. The rule may be configured per-
filesystem or may be "choose the set with the smallest quota". filesystem or may be "choose the set with the smallest quota".
5.11. Access Control Lists 5.11. Access Control Lists
The NFS version 4 ACL attribute is an array of access control entries The NFS version 4 ACL attribute is an array of access control entries
(ACE). There are various access control entry types, as defined in (ACE). Although, the client can read and write the ACL attribute,
the Section "ACE type". The server is able to communicate which ACE the NFSv4 model is the server does all access control based on the
types are supported by returning the appropriate value within the server's interpretation of the ACL. If at any point the client wants
to check access without issuing an operation that modifies or reads
data or metadata, the client can use the OPEN and ACCESS operations
to do so. There are various access control entry types, as defined
in the Section "ACE type". The server is able to communicate which
ACE types are supported by returning the appropriate value within the
aclsupport attribute. Each ACE covers one or more operations on a aclsupport attribute. Each ACE covers one or more operations on a
file or directory as described in the Section "ACE Access Mask". It file or directory as described in the Section "ACE Access Mask". It
may also contain one or more flags that modify the semantics of the may also contain one or more flags that modify the semantics of the
ACE as defined in the Section "ACE flag". ACE as defined in the Section "ACE flag".
The NFS ACE attribute is defined as follows: The NFS ACE attribute is defined as follows:
typedef uint32_t acetype4; typedef uint32_t acetype4;
typedef uint32_t aceflag4; typedef uint32_t aceflag4;
typedef uint32_t acemask4; typedef uint32_t acemask4;
struct nfsace4 { struct nfsace4 {
acetype4 type; acetype4 type;
aceflag4 flag; aceflag4 flag;
acemask4 access_mask; acemask4 access_mask;
utf8string who; utf8str_mixed who;
}; };
To determine if a request succeeds, each nfsace4 entry is processed To determine if a request succeeds, each nfsace4 entry is processed
in order by the server. Only ACEs which have a "who" that matches in order by the server. Only ACEs which have a "who" that matches
the requester are considered. Each ACE is processed until all of the the requester are considered. Each ACE is processed until all of the
bits of the requester's access have been ALLOWED. Once a bit (see bits of the requester's access have been ALLOWED. Once a bit (see
below) has been ALLOWED by an ACCESS_ALLOWED_ACE, it is no longer below) has been ALLOWED by an ACCESS_ALLOWED_ACE, it is no longer
considered in the processing of later ACEs. If an ACCESS_DENIED_ACE considered in the processing of later ACEs. If an ACCESS_DENIED_ACE
is encountered where the requester's access still has unALLOWED bits is encountered where the requester's access still has unALLOWED bits
in common with the "access_mask" of the ACE, the request is denied. in common with the "access_mask" of the ACE, the request is denied.
However, unlike the ALLOWED and DENIED ACE types, the ALARM and AUDIT However, unlike the ALLOWED and DENIED ACE types, the ALARM and AUDIT
ACE types do not affect a requester's access, and instead are for ACE types do not affect a requester's access, and instead are for
triggering events as a result of a requester's access attempt. triggering events as a result of a requester's access attempt.
Draft Specification NFS version 4 Protocol November 2002
Therefore, all AUDIT and ALARM ACEs are processed until end of the Therefore, all AUDIT and ALARM ACEs are processed until end of the
ACL. When the ACL is fully processed, if there are bits in ACL. When the ACL is fully processed, if there are bits in
requester's mask that have not been considered whether the server requester's mask that have not been considered whether the server
allows or denies the access is undefined. If there is a mode allows or denies the access is undefined. If there is a mode
attribute on the file, then this cannot happen, since the mode's attribute on the file, then this cannot happen, since the mode's
Draft Specification NFS version 4 Protocol October 2002
MODE4_*OTH bits will map to EVERYONE@ ACEs that unambiguously specify MODE4_*OTH bits will map to EVERYONE@ ACEs that unambiguously specify
the requester's access. the requester's access.
The NFS version 4 ACL model is quite rich. Some server platforms may The NFS version 4 ACL model is quite rich. Some server platforms may
provide access control functionality that goes beyond the UNIX-style provide access control functionality that goes beyond the UNIX-style
mode attribute, but which is not as rich as the NFS ACL model. So mode attribute, but which is not as rich as the NFS ACL model. So
that users can take advantage of this more limited functionality, the that users can take advantage of this more limited functionality, the
server may indicate that it supports ACLs as long as it follows the server may indicate that it supports ACLs as long as it follows the
guidelines for mapping between its ACL model and the NFS version 4 guidelines for mapping between its ACL model and the NFS version 4
ACL model. ACL model.
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uses any of the access methods specified uses any of the access methods specified
in acemask4. in acemask4.
ALARM Generate a system ALARM (system ALARM Generate a system ALARM (system
dependent) when any access attempt is dependent) when any access attempt is
made to a file or directory for the made to a file or directory for the
access methods specified in acemask4. access methods specified in acemask4.
A server need not support all of the above ACE types. The bitmask A server need not support all of the above ACE types. The bitmask
constants used to represent the above definitions within the constants used to represent the above definitions within the
Draft Specification NFS version 4 Protocol November 2002
aclsupport attribute are as follows: aclsupport attribute are as follows:
const ACL4_SUPPORT_ALLOW_ACL = 0x00000001; const ACL4_SUPPORT_ALLOW_ACL = 0x00000001;
const ACL4_SUPPORT_DENY_ACL = 0x00000002; const ACL4_SUPPORT_DENY_ACL = 0x00000002;
Draft Specification NFS version 4 Protocol October 2002
const ACL4_SUPPORT_AUDIT_ACL = 0x00000004; const ACL4_SUPPORT_AUDIT_ACL = 0x00000004;
const ACL4_SUPPORT_ALARM_ACL = 0x00000008; const ACL4_SUPPORT_ALARM_ACL = 0x00000008;
The semantics of the "type" field follow the descriptions provided The semantics of the "type" field follow the descriptions provided
above. above.
The constants used for the type field (acetype4) are as follows: The constants used for the type field (acetype4) are as follows:
const ACE4_ACCESS_ALLOWED_ACE_TYPE = 0x00000000; const ACE4_ACCESS_ALLOWED_ACE_TYPE = 0x00000000;
const ACE4_ACCESS_DENIED_ACE_TYPE = 0x00000001; const ACE4_ACCESS_DENIED_ACE_TYPE = 0x00000001;
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_______________________________________________________________ _______________________________________________________________
READ_DATA Permission to read the data of the file READ_DATA Permission to read the data of the file
LIST_DIRECTORY Permission to list the contents of a LIST_DIRECTORY Permission to list the contents of a
directory directory
WRITE_DATA Permission to modify the file's data WRITE_DATA Permission to modify the file's data
ADD_FILE Permission to add a new file to a ADD_FILE Permission to add a new file to a
directory directory
APPEND_DATA Permission to append data to a file APPEND_DATA Permission to append data to a file
ADD_SUBDIRECTORY Permission to create a subdirectory to a ADD_SUBDIRECTORY Permission to create a subdirectory to a
directory directory
Draft Specification NFS version 4 Protocol November 2002
READ_NAMED_ATTRS Permission to read the named attributes READ_NAMED_ATTRS Permission to read the named attributes
of a file of a file
WRITE_NAMED_ATTRS Permission to write the named attributes WRITE_NAMED_ATTRS Permission to write the named attributes
of a file of a file
EXECUTE Permission to execute a file EXECUTE Permission to execute a file
Draft Specification NFS version 4 Protocol October 2002
DELETE_CHILD Permission to delete a file or directory DELETE_CHILD Permission to delete a file or directory
within a directory within a directory
READ_ATTRIBUTES The ability to read basic attributes READ_ATTRIBUTES The ability to read basic attributes
(non-acls) of a file (non-acls) of a file
WRITE_ATTRIBUTES Permission to change basic attributes WRITE_ATTRIBUTES Permission to change basic attributes
(non-acls) of a file (non-acls) of a file
DELETE Permission to Delete the file DELETE Permission to Delete the file
READ_ACL Permission to Read the ACL READ_ACL Permission to Read the ACL
WRITE_ACL Permission to Write the ACL WRITE_ACL Permission to Write the ACL
WRITE_OWNER Permission to change the owner WRITE_OWNER Permission to change the owner
SYNCHRONIZE Permission to access file locally at the SYNCHRONIZE Permission to access file locally at the
server with synchronous reads and writes server with synchronous reads and writes
The bitmask constants used for the access mask field are as follows: The bitmask constants used for the access mask field are as follows:
const ACE4_READ_DATA = 0x00000001; const ACE4_READ_DATA = 0x00000001;
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systems might not distinguish APPEND_DATA (the ability to append to a systems might not distinguish APPEND_DATA (the ability to append to a
file) from WRITE_DATA (the ability to modify existing contents); both file) from WRITE_DATA (the ability to modify existing contents); both
masks would be tied to a single ``write'' permission. When such a masks would be tied to a single ``write'' permission. When such a
server returns attributes to the client, it would show both server returns attributes to the client, it would show both
APPEND_DATA and WRITE_DATA if and only if the write permission is APPEND_DATA and WRITE_DATA if and only if the write permission is
enabled. enabled.
If a server receives a SETATTR request that it cannot accurately If a server receives a SETATTR request that it cannot accurately
implement, it should error in the direction of more restricted implement, it should error in the direction of more restricted
access. For example, suppose a server cannot distinguish overwriting access. For example, suppose a server cannot distinguish overwriting
Draft Specification NFS version 4 Protocol November 2002
data from appending new data, as described in the previous paragraph. data from appending new data, as described in the previous paragraph.
If a client submits an ACE where APPEND_DATA is set but WRITE_DATA is If a client submits an ACE where APPEND_DATA is set but WRITE_DATA is
not (or vice versa), the server should reject the request with not (or vice versa), the server should reject the request with
NFS4ERR_ATTRNOTSUPP. Nonetheless, if the ACE has type DENY, the NFS4ERR_ATTRNOTSUPP. Nonetheless, if the ACE has type DENY, the
server may silently turn on the other bit, so that both APPEND_DATA server may silently turn on the other bit, so that both APPEND_DATA
Draft Specification NFS version 4 Protocol October 2002
and WRITE_DATA are denied. and WRITE_DATA are denied.
5.11.3. ACE flag 5.11.3. ACE flag
The "flag" field contains values based on the following descriptions. The "flag" field contains values based on the following descriptions.
ACE4_FILE_INHERIT_ACE ACE4_FILE_INHERIT_ACE
Can be placed on a directory and indicates that this ACE should be Can be placed on a directory and indicates that this ACE should be
added to each new non-directory file created. added to each new non-directory file created.
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ACE4_SUCCESSFUL_ACCESS_ACE_FLAG ACE4_SUCCESSFUL_ACCESS_ACE_FLAG
ACL4_FAILED_ACCESS_ACE_FLAG ACL4_FAILED_ACCESS_ACE_FLAG
The ACE4_SUCCESSFUL_ACCESS_ACE_FLAG (SUCCESS) and The ACE4_SUCCESSFUL_ACCESS_ACE_FLAG (SUCCESS) and
ACE4_FAILED_ACCESS_ACE_FLAG (FAILED) flag bits relate only to ACE4_FAILED_ACCESS_ACE_FLAG (FAILED) flag bits relate only to
ACE4_SYSTEM_AUDIT_ACE_TYPE (AUDIT) and ACE4_SYSTEM_ALARM_ACE_TYPE ACE4_SYSTEM_AUDIT_ACE_TYPE (AUDIT) and ACE4_SYSTEM_ALARM_ACE_TYPE
(ALARM) ACE types. If during the processing of the file's ACL, the (ALARM) ACE types. If during the processing of the file's ACL, the
server encounters an AUDIT or ALARM ACE that matches the principal server encounters an AUDIT or ALARM ACE that matches the principal
Draft Specification NFS version 4 Protocol November 2002
attempting the OPEN, the server notes that fact, and the presence, if attempting the OPEN, the server notes that fact, and the presence, if
any, of the SUCCESS and FAILED flags encountered in the AUDIT or any, of the SUCCESS and FAILED flags encountered in the AUDIT or
ALARM ACE. Once the server completes the ACL processing, and the ALARM ACE. Once the server completes the ACL processing, and the
share reservation processing, and the OPEN call, it then notes if the share reservation processing, and the OPEN call, it then notes if the
OPEN succeeded or failed. If the OPEN succeeded, and if the SUCCESS OPEN succeeded or failed. If the OPEN succeeded, and if the SUCCESS
Draft Specification NFS version 4 Protocol October 2002
flag was set for a matching AUDIT or ALARM, then the appropriate flag was set for a matching AUDIT or ALARM, then the appropriate
AUDIT or ALARM event occurs. If the OPEN failed, and if the FAILED AUDIT or ALARM event occurs. If the OPEN failed, and if the FAILED
flag was set for the matching AUDIT or ALARM, then the appropriate flag was set for the matching AUDIT or ALARM, then the appropriate
AUDIT or ALARM event occurs. Clearly either or both of the SUCCESS AUDIT or ALARM event occurs. Clearly either or both of the SUCCESS
or FAILED can be set, but if neither is set, the AUDIT or ALARM ACE or FAILED can be set, but if neither is set, the AUDIT or ALARM ACE
is not useful. is not useful.
The previously described processing applies to that of the ACCESS The previously described processing applies to that of the ACCESS
operation as well. The difference being that "success" or "failure" operation as well. The difference being that "success" or "failure"
does not mean whether ACCESS returns NFS4_OK or not. Success means does not mean whether ACCESS returns NFS4_OK or not. Success means
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For example, suppose a client tries to set an ACE with For example, suppose a client tries to set an ACE with
ACE4_FILE_INHERIT_ACE set but not ACE4_DIRECTORY_INHERIT_ACE. If the ACE4_FILE_INHERIT_ACE set but not ACE4_DIRECTORY_INHERIT_ACE. If the
server does not support any form of ACL inheritance, the server server does not support any form of ACL inheritance, the server
should reject the request with NFS4ERR_ATTRNOTSUPP. If the server should reject the request with NFS4ERR_ATTRNOTSUPP. If the server
supports a single "inherit ACE" flag that applies to both files and supports a single "inherit ACE" flag that applies to both files and
directories, the server may reject the request (i.e., requiring the directories, the server may reject the request (i.e., requiring the
client to set both the file and directory inheritance flags). The client to set both the file and directory inheritance flags). The
server may also accept the request and silently turn on the server may also accept the request and silently turn on the
ACE4_DIRECTORY_INHERIT_ACE flag. ACE4_DIRECTORY_INHERIT_ACE flag.
Draft Specification NFS version 4 Protocol November 2002
5.11.4. ACE who 5.11.4. ACE who
There are several special identifiers ("who") which need to be There are several special identifiers ("who") which need to be
Draft Specification NFS version 4 Protocol October 2002
understood universally, rather than in the context of a particular understood universally, rather than in the context of a particular
DNS domain. Some of these identifiers cannot be understood when an DNS domain. Some of these identifiers cannot be understood when an
NFS client accesses the server, but have meaning when a local process NFS client accesses the server, but have meaning when a local process
accesses the file. The ability to display and modify these accesses the file. The ability to display and modify these
permissions is permitted over NFS, even if none of the access methods permissions is permitted over NFS, even if none of the access methods
on the server understands the identifiers. on the server understands the identifiers.
Who Description Who Description
_______________________________________________________________ _______________________________________________________________
"OWNER" The owner of the file. "OWNER" The owner of the file.
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const MODE4_XUSR = 0x040; /* execute permission: owner */ const MODE4_XUSR = 0x040; /* execute permission: owner */
const MODE4_RGRP = 0x020; /* read permission: group */ const MODE4_RGRP = 0x020; /* read permission: group */
const MODE4_WGRP = 0x010; /* write permission: group */ const MODE4_WGRP = 0x010; /* write permission: group */
const MODE4_XGRP = 0x008; /* execute permission: group */ const MODE4_XGRP = 0x008; /* execute permission: group */
const MODE4_ROTH = 0x004; /* read permission: other */ const MODE4_ROTH = 0x004; /* read permission: other */
const MODE4_WOTH = 0x002; /* write permission: other */ const MODE4_WOTH = 0x002; /* write permission: other */
const MODE4_XOTH = 0x001; /* execute permission: other */ const MODE4_XOTH = 0x001; /* execute permission: other */
Bits MODE4_RUSR, MODE4_WUSR, and MODE4_XUSR apply to the principal Bits MODE4_RUSR, MODE4_WUSR, and MODE4_XUSR apply to the principal
identified in the owner attribute. Bits MODE4_RGRP, MODE4_WGRP, and identified in the owner attribute. Bits MODE4_RGRP, MODE4_WGRP, and
Draft Specification NFS version 4 Protocol November 2002
MODE4_XGRP apply to the principals identified in the owner_group MODE4_XGRP apply to the principals identified in the owner_group
attribute. Bits MODE4_ROTH, MODE4_WOTH, MODE4_XOTH apply to any attribute. Bits MODE4_ROTH, MODE4_WOTH, MODE4_XOTH apply to any
principal that does not match that in the owner group, and does not principal that does not match that in the owner group, and does not
Draft Specification NFS version 4 Protocol October 2002
have a group matching that of the owner_group attribute. have a group matching that of the owner_group attribute.
The remaining bits are not defined by this protocol and MUST NOT be The remaining bits are not defined by this protocol and MUST NOT be
used. The minor version mechanism must be used to define further bit used. The minor version mechanism must be used to define further bit
usage. usage.
Note that in UNIX, if a file has the MODE4_SGID bit set and no Note that in UNIX, if a file has the MODE4_SGID bit set and no
MODE4_XGRP bit set, then READ and WRITE must use mandatory file MODE4_XGRP bit set, then READ and WRITE must use mandatory file
locking. locking.
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system call returns. The stat() system call is returning the fileid system call returns. The stat() system call is returning the fileid
of the root of the mounted filesystem, whereas readdir() is returning of the root of the mounted filesystem, whereas readdir() is returning
the fileid stat() would have returned before any filesystems were the fileid stat() would have returned before any filesystems were
mounted on the mount point. mounted on the mount point.
Unlike NFS version 3, NFS version 4 allows a client's LOOKUP request Unlike NFS version 3, NFS version 4 allows a client's LOOKUP request
to cross other filesystems. The client detects the filesystem to cross other filesystems. The client detects the filesystem
crossing whenever the filehandle argument of LOOKUP has an fsid crossing whenever the filehandle argument of LOOKUP has an fsid
attribute different from that of the filehandle returned by LOOKUP. A attribute different from that of the filehandle returned by LOOKUP. A
UNIX-based client will consider this a "mount point crossing". UNIX UNIX-based client will consider this a "mount point crossing". UNIX
Draft Specification NFS version 4 Protocol November 2002
has a legacy scheme for allowing a process to determine its current has a legacy scheme for allowing a process to determine its current
working directory. This relies on readdir() of a mount point's parent working directory. This relies on readdir() of a mount point's parent
and stat() of the mount point returning fileids as previously and stat() of the mount point returning fileids as previously
Draft Specification NFS version 4 Protocol October 2002
described. The mounted_on_fileid attribute corresponds to the fileid described. The mounted_on_fileid attribute corresponds to the fileid
that readdir() would have returned as described previously. that readdir() would have returned as described previously.
While the NFS version 4 client could simply fabricate a fileid While the NFS version 4 client could simply fabricate a fileid
corresponding to what mounted_on_fileid provides (and if the server corresponding to what mounted_on_fileid provides (and if the server
does not support mounted_on_fileid, the client has no choice), there does not support mounted_on_fileid, the client has no choice), there
is a risk that the client will generate a fileid that conflicts with is a risk that the client will generate a fileid that conflicts with
one that is already assigned to another object in the filesystem. one that is already assigned to another object in the filesystem.
Instead, if the server can provide the mounted_on_fileid, the Instead, if the server can provide the mounted_on_fileid, the
potential for client operational problems in this area is eliminated. potential for client operational problems in this area is eliminated.
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fileid of a directory entry returned by readdir(). If fileid of a directory entry returned by readdir(). If
mounted_on_fileid is requested in a GETATTR operation, the server mounted_on_fileid is requested in a GETATTR operation, the server
should obey an invariant that has it returning a value that is equal should obey an invariant that has it returning a value that is equal
to the file object's entry in the object's parent directory, i.e. to the file object's entry in the object's parent directory, i.e.
what readdir() would have returned. Some operating environments what readdir() would have returned. Some operating environments
allow a series of two or more filesystems to be mounted onto a single allow a series of two or more filesystems to be mounted onto a single
mount point. In this case, for the server to obey the aforementioned mount point. In this case, for the server to obey the aforementioned
invariant, it will need to find the base mount point, and not the invariant, it will need to find the base mount point, and not the
intermediate mount points. intermediate mount points.
Draft Specification NFS version 4 Protocol October 2002 Draft Specification NFS version 4 Protocol November 2002
6. Filesystem Migration and Replication 6. Filesystem Migration and Replication
With the use of the recommended attribute "fs_locations", the NFS With the use of the recommended attribute "fs_locations", the NFS
version 4 server has a method of providing filesystem migration or version 4 server has a method of providing filesystem migration or
replication services. For the purposes of migration and replication, replication services. For the purposes of migration and replication,
a filesystem will be defined as all files that share a given fsid a filesystem will be defined as all files that share a given fsid
(both major and minor values are the same). (both major and minor values are the same).
The fs_locations attribute provides a list of filesystem locations. The fs_locations attribute provides a list of filesystem locations.
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Once the servers participating in the migration have completed the Once the servers participating in the migration have completed the
move of the filesystem, the error NFS4ERR_MOVED will be returned for move of the filesystem, the error NFS4ERR_MOVED will be returned for
subsequent requests received by the original server. The subsequent requests received by the original server. The
NFS4ERR_MOVED error is returned for all operations except PUTFH and NFS4ERR_MOVED error is returned for all operations except PUTFH and
GETATTR. Upon receiving the NFS4ERR_MOVED error, the client will GETATTR. Upon receiving the NFS4ERR_MOVED error, the client will
obtain the value of the fs_locations attribute. The client will then obtain the value of the fs_locations attribute. The client will then
use the contents of the attribute to redirect its requests to the use the contents of the attribute to redirect its requests to the
specified server. To facilitate the use of GETATTR, operations such specified server. To facilitate the use of GETATTR, operations such
Draft Specification NFS version 4 Protocol October 2002 Draft Specification NFS version 4 Protocol November 2002
as PUTFH must also be accepted by the server for the migrated file as PUTFH must also be accepted by the server for the migrated file
system's filehandles. Note that if the server returns NFS4ERR_MOVED, system's filehandles. Note that if the server returns NFS4ERR_MOVED,
the server MUST support the fs_locations attribute. the server MUST support the fs_locations attribute.
If the client requests more attributes than just fs_locations, the If the client requests more attributes than just fs_locations, the
server may return fs_locations only. This is to be expected since server may return fs_locations only. This is to be expected since
the server has migrated the filesystem and may not have a method of the server has migrated the filesystem and may not have a method of
obtaining additional attribute data. obtaining additional attribute data.
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limited to locking/share state, delegation state, and asynchronous limited to locking/share state, delegation state, and asynchronous
file writes which are represented by WRITE and COMMIT verifiers. The file writes which are represented by WRITE and COMMIT verifiers. The
server should strive to minimize the impact on its clients during and server should strive to minimize the impact on its clients during and
after the migration process. after the migration process.
6.3. Interpretation of the fs_locations Attribute 6.3. Interpretation of the fs_locations Attribute
The fs_location attribute is structured in the following way: The fs_location attribute is structured in the following way:
struct fs_location { struct fs_location {
utf8string server<>; utf8str_cis server<>;
pathname4 rootpath; pathname4 rootpath;
}; };
struct fs_locations { struct fs_locations {
pathname4 fs_root; pathname4 fs_root;
fs_location locations<>; fs_location locations<>;
}; };
The fs_location struct is used to represent the location of a The fs_location struct is used to represent the location of a
filesystem by providing a server name and the path to the root of the filesystem by providing a server name and the path to the root of the
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The fs_locations struct and attribute then contains an array of The fs_locations struct and attribute then contains an array of
locations. Since the name space of each server may be constructed locations. Since the name space of each server may be constructed
differently, the "fs_root" field is provided. The path represented differently, the "fs_root" field is provided. The path represented
by fs_root represents the location of the filesystem in the server's by fs_root represents the location of the filesystem in the server's
name space. Therefore, the fs_root path is only associated with the name space. Therefore, the fs_root path is only associated with the
server from which the fs_locations attribute was obtained. The server from which the fs_locations attribute was obtained. The
fs_root path is meant to aid the client in locating the filesystem at fs_root path is meant to aid the client in locating the filesystem at
the various servers listed. the various servers listed.
Draft Specification NFS version 4 Protocol October 2002 Draft Specification NFS version 4 Protocol November 2002
As an example, there is a replicated filesystem located at two As an example, there is a replicated filesystem located at two
servers (servA and servB). At servA the filesystem is located at servers (servA and servB). At servA the filesystem is located at
path "/a/b/c". At servB the filesystem is located at path "/x/y/z". path "/a/b/c". At servB the filesystem is located at path "/x/y/z".
In this example the client accesses the filesystem first at servA In this example the client accesses the filesystem first at servA
with a multi-component lookup path of "/a/b/c/d". Since the client with a multi-component lookup path of "/a/b/c/d". Since the client
used a multi-component lookup to obtain the filehandle at "/a/b/c/d", used a multi-component lookup to obtain the filehandle at "/a/b/c/d",
it is unaware that the filesystem's root is located in servA's name it is unaware that the filesystem's root is located in servA's name
space at "/a/b/c". When the client switches to servB, it will need space at "/a/b/c". When the client switches to servB, it will need
to determine that the directory it first referenced at servA is now to determine that the directory it first referenced at servA is now
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of the fh_expire_type attribute, whether volatile filehandles will of the fh_expire_type attribute, whether volatile filehandles will
expire at the migration or replication event. If the bit expire at the migration or replication event. If the bit
FH4_VOL_MIGRATION is set in the fh_expire_type attribute, the client FH4_VOL_MIGRATION is set in the fh_expire_type attribute, the client
must treat the volatile filehandle as if the server had returned the must treat the volatile filehandle as if the server had returned the
NFS4ERR_FHEXPIRED error. At the migration or replication event in NFS4ERR_FHEXPIRED error. At the migration or replication event in
the presence of the FH4_VOL_MIGRATION bit, the client will not the presence of the FH4_VOL_MIGRATION bit, the client will not
present the original or old volatile filehandle to the new server. present the original or old volatile filehandle to the new server.
The client will start its communication with the new server by The client will start its communication with the new server by
recovering its filehandles using the saved file names. recovering its filehandles using the saved file names.
Draft Specification NFS version 4 Protocol October 2002 Draft Specification NFS version 4 Protocol November 2002
7. NFS Server Name Space 7. NFS Server Name Space
7.1. Server Exports 7.1. Server Exports
On a UNIX server the name space describes all the files reachable by On a UNIX server the name space describes all the files reachable by
pathnames under the root directory or "/". On a Windows NT server pathnames under the root directory or "/". On a Windows NT server
the name space constitutes all the files on disks named by mapped the name space constitutes all the files on disks named by mapped
disk letters. NFS server administrators rarely make the entire disk letters. NFS server administrators rarely make the entire
server's filesystem name space available to NFS clients. More often server's filesystem name space available to NFS clients. More often
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the server's name space on the client: it is static. If the server the server's name space on the client: it is static. If the server
administrator adds a new export the client will be unaware of it. administrator adds a new export the client will be unaware of it.
7.3. Server Pseudo Filesystem 7.3. Server Pseudo Filesystem
NFS version 4 servers avoid this name space inconsistency by NFS version 4 servers avoid this name space inconsistency by
presenting all the exports within the framework of a single server presenting all the exports within the framework of a single server
name space. An NFS version 4 client uses LOOKUP and READDIR name space. An NFS version 4 client uses LOOKUP and READDIR
operations to browse seamlessly from one export to another. Portions operations to browse seamlessly from one export to another. Portions
Draft Specification NFS version 4 Protocol October 2002 Draft Specification NFS version 4 Protocol November 2002
of the server name space that are not exported are bridged via a of the server name space that are not exported are bridged via a
"pseudo filesystem" that provides a view of exported directories "pseudo filesystem" that provides a view of exported directories
only. A pseudo filesystem has a unique fsid and behaves like a only. A pseudo filesystem has a unique fsid and behaves like a
normal, read only filesystem. normal, read only filesystem.
Based on the construction of the server's name space, it is possible Based on the construction of the server's name space, it is possible
that multiple pseudo filesystems may exist. For example, that multiple pseudo filesystems may exist. For example,
/a pseudo filesystem /a pseudo filesystem
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7.6. Exported Root 7.6. Exported Root
If the server's root filesystem is exported, one might conclude that If the server's root filesystem is exported, one might conclude that
a pseudo-filesystem is not needed. This would be wrong. Assume the a pseudo-filesystem is not needed. This would be wrong. Assume the
following filesystems on a server: following filesystems on a server:
/ disk1 (exported) / disk1 (exported)
/a disk2 (not exported) /a disk2 (not exported)
Draft Specification NFS version 4 Protocol October 2002 Draft Specification NFS version 4 Protocol November 2002
/a/b disk3 (exported) /a/b disk3 (exported)
Because disk2 is not exported, disk3 cannot be reached with simple Because disk2 is not exported, disk3 cannot be reached with simple
LOOKUPs. The server must bridge the gap with a pseudo-filesystem. LOOKUPs. The server must bridge the gap with a pseudo-filesystem.
7.7. Mount Point Crossing 7.7. Mount Point Crossing
The server filesystem environment may be constructed in such a way The server filesystem environment may be constructed in such a way
that one filesystem contains a directory which is 'covered' or that one filesystem contains a directory which is 'covered' or
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chooses to limit the contents of the pseudo filesystem, the server chooses to limit the contents of the pseudo filesystem, the server
may effectively hide filesystems from a client that may otherwise may effectively hide filesystems from a client that may otherwise
have legitimate access. have legitimate access.
As suggested practice, the server should apply the security policy of As suggested practice, the server should apply the security policy of
a shared resource in the server's namespace to the components of the a shared resource in the server's namespace to the components of the
resource's ancestors. For example: resource's ancestors. For example:
/ /
Draft Specification NFS version 4 Protocol October 2002 Draft Specification NFS version 4 Protocol November 2002
/a/b /a/b
/a/b/c /a/b/c
The /a/b/c directory is a real filesystem and is the shared resource. The /a/b/c directory is a real filesystem and is the shared resource.
The security policy for /a/b/c is Kerberos with integrity. The The security policy for /a/b/c is Kerberos with integrity. The
server should apply the same security policy to /, /a, and /a/b. server should apply the same security policy to /, /a, and /a/b.
This allows for the extension of the protection of the server's This allows for the extension of the protection of the server's
namespace to the ancestors of the real shared resource. namespace to the ancestors of the real shared resource.
For the case of the use of multiple, disjoint security mechanisms in For the case of the use of multiple, disjoint security mechanisms in
the server's resources, the security for a particular object in the the server's resources, the security for a particular object in the
server's namespace should be the union of all security mechanisms of server's namespace should be the union of all security mechanisms of
all direct descendants. all direct descendants.
Draft Specification NFS version 4 Protocol October 2002 Draft Specification NFS version 4 Protocol November 2002
8. File Locking and Share Reservations 8. File Locking and Share Reservations
Integrating locking into the NFS protocol necessarily causes it to be Integrating locking into the NFS protocol necessarily causes it to be
stateful. With the inclusion of share reservations the protocol stateful. With the inclusion of share reservations the protocol
becomes substantially more dependent on state than the traditional becomes substantially more dependent on state than the traditional
combination of NFS and NLM [XNFS]. There are three components to combination of NFS and NLM [XNFS]. There are three components to
making this state manageable: making this state manageable:
o Clear division between client and server o Clear division between client and server
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owner. owner.
The following sections describe the transition from the heavy weight The following sections describe the transition from the heavy weight
information to the eventual stateid used for most client and server information to the eventual stateid used for most client and server
locking and lease interactions. locking and lease interactions.
8.1.1. Client ID 8.1.1. Client ID
For each LOCK request, the client must identify itself to the server. For each LOCK request, the client must identify itself to the server.
Draft Specification NFS version 4 Protocol October 2002 Draft Specification NFS version 4 Protocol November 2002
This is done in such a way as to allow for correct lock This is done in such a way as to allow for correct lock
identification and crash recovery. A sequence of a SETCLIENTID identification and crash recovery. A sequence of a SETCLIENTID
operation followed by a SETCLIENTID_CONFIRM operation is required to operation followed by a SETCLIENTID_CONFIRM operation is required to
establish the identification onto the server. Establishment of establish the identification onto the server. Establishment of
identification by a new incarnation of the client also has the effect identification by a new incarnation of the client also has the effect
of immediately breaking any leased state that a previous incarnation of immediately breaking any leased state that a previous incarnation
of the client might have had on the server, as opposed to forcing the of the client might have had on the server, as opposed to forcing the
new client incarnation to wait for the leases to expire. Breaking new client incarnation to wait for the leases to expire. Breaking
the lease state amounts to the server removing all lock, share the lease state amounts to the server removing all lock, share
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Client identification is encapsulated in the following structure: Client identification is encapsulated in the following structure:
struct nfs_client_id4 { struct nfs_client_id4 {
verifier4 verifier; verifier4 verifier;
opaque id<NFS4_OPAQUE_LIMIT>; opaque id<NFS4_OPAQUE_LIMIT>;
}; };
The first field, verifier is a client incarnation verifier that is The first field, verifier is a client incarnation verifier that is
used to detect client reboots. Only if the verifier is different from used to detect client reboots. Only if the verifier is different from
that the server has previously recorded the client (as identified by that the server has previously recorded the client (as identified by
the second field f the structure, id) does the server start the the second field of the structure, id) does the server start the
process of canceling the client's leased state. process of canceling the client's leased state.
The second field, id is a variable length string that uniquely The second field, id is a variable length string that uniquely
defines the client. defines the client.
There are several considerations for how the client generates the id There are several considerations for how the client generates the id
string: string:
o The string should be unique so that multiple clients do not o The string should be unique so that multiple clients do not
present the same string. The consequences of two clients present the same string. The consequences of two clients
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this precludes the use of the implementation in an environment this precludes the use of the implementation in an environment
where there is no local disk and all file access is from an NFS where there is no local disk and all file access is from an NFS
version 4 server. version 4 server.
o The string should be different for each server network address o The string should be different for each server network address
that the client accesses, rather than common to all server that the client accesses, rather than common to all server
network addresses. The reason is that it may not be possible for network addresses. The reason is that it may not be possible for
the client to tell if same server is listening on multiple the client to tell if same server is listening on multiple
network addresses. If the client issues SETCLIENTID with the network addresses. If the client issues SETCLIENTID with the
Draft Specification NFS version 4 Protocol October 2002 Draft Specification NFS version 4 Protocol November 2002
same id string to each network address of such a server, the same id string to each network address of such a server, the
server will think it is the same client, and each successive server will think it is the same client, and each successive
SETCLIENTID will cause the server to begin the process of SETCLIENTID will cause the server to begin the process of
removing the client's previous leased state. removing the client's previous leased state.
o The algorithm for generating the string should not assume that o The algorithm for generating the string should not assume that
the client's network address won't change. This includes the client's network address won't change. This includes
changes between client incarnations and even changes while the changes between client incarnations and even changes while the
client is stilling running in its current incarnation. This client is stilling running in its current incarnation. This
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the same between client incarnations, this shares the same the same between client incarnations, this shares the same
problem as that of the using the timestamp of the software problem as that of the using the timestamp of the software
installation. installation.
As a security measure, the server MUST NOT cancel a client's leased As a security measure, the server MUST NOT cancel a client's leased
state if the principal established the state for a given id string is state if the principal established the state for a given id string is
not the same as the principal issuing the SETCLIENTID. not the same as the principal issuing the SETCLIENTID.
Note that SETCLIENTID and SETCLIENTID_CONFIRM has a secondary purpose Note that SETCLIENTID and SETCLIENTID_CONFIRM has a secondary purpose
Draft Specification NFS version 4 Protocol October 2002 Draft Specification NFS version 4 Protocol November 2002
of establishing the information the server needs to make callbacks to of establishing the information the server needs to make callbacks to
the client for purpose of supporting delegations. It is permitted to the client for purpose of supporting delegations. It is permitted to
change this information via SETCLIENTID and SETCLIENTID_CONFIRM change this information via SETCLIENTID and SETCLIENTID_CONFIRM
within the same incarnation of the client without removing the within the same incarnation of the client without removing the
client's leased state. client's leased state.
Once a SETCLIENTID and SETCLIENTID_CONFIRM sequence has successfully Once a SETCLIENTID and SETCLIENTID_CONFIRM sequence has successfully
completed, the client uses the short hand client identifier, of type completed, the client uses the short hand client identifier, of type
clientid4, instead of the longer and less compact nfs_client_id4 clientid4, instead of the longer and less compact nfs_client_id4
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there had been no activity from that client for many minutes. there had been no activity from that client for many minutes.
Note that if the id string in a SETCLIENTID request is properly Note that if the id string in a SETCLIENTID request is properly
constructed, and if the client takes care to use the same principal constructed, and if the client takes care to use the same principal
for each successive use of SETCLIENTID, then, barring an active for each successive use of SETCLIENTID, then, barring an active
denial of service attack, NFS4ERR_CLID_INUSE should never be denial of service attack, NFS4ERR_CLID_INUSE should never be
returned. returned.
However, client bugs, server bugs, or perhaps a deliberate change of However, client bugs, server bugs, or perhaps a deliberate change of
Draft Specification NFS version 4 Protocol October 2002 Draft Specification NFS version 4 Protocol November 2002
the principal owner of the id string (such as the case of a client the principal owner of the id string (such as the case of a client
that changes security flavors, and under the new flavor, there is no that changes security flavors, and under the new flavor, there is no
mapping to the previous owner) will in rare cases result in mapping to the previous owner) will in rare cases result in
NFS4ERR_CLID_INUSE. NFS4ERR_CLID_INUSE.
In that event, when the server gets a SETCLIENTID for a client id In that event, when the server gets a SETCLIENTID for a client id
that currently has no state, or it has state, but the lease has that currently has no state, or it has state, but the lease has
expired, rather than returning NFS4ERR_CLID_INUSE, the server MUST expired, rather than returning NFS4ERR_CLID_INUSE, the server MUST
allow the SETCLIENTID, and confirm the new clientid if followed by allow the SETCLIENTID, and confirm the new clientid if followed by
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o The stateid was generated by an earlier server instance (i.e. o The stateid was generated by an earlier server instance (i.e.
before a server reboot). The error NFS4ERR_STALE_STATEID should before a server reboot). The error NFS4ERR_STALE_STATEID should
be returned. be returned.
o The stateid was generated by the current server instance but the o The stateid was generated by the current server instance but the
stateid no longer designates the current locking state for the stateid no longer designates the current locking state for the
lockowner-file pair in question (i.e. one or more locking lockowner-file pair in question (i.e. one or more locking
operations has occurred). The error NFS4ERR_OLD_STATEID should operations has occurred). The error NFS4ERR_OLD_STATEID should
be returned. be returned.
Draft Specification NFS version 4 Protocol October 2002 Draft Specification NFS version 4 Protocol November 2002
This error condition will only occur when the client issues a This error condition will only occur when the client issues a
locking request which changes a stateid while an I/O request locking request which changes a stateid while an I/O request
that uses that stateid is outstanding. that uses that stateid is outstanding.
o The stateid was generated by the current server instance but the o The stateid was generated by the current server instance but the
stateid does not designate a locking state for any active stateid does not designate a locking state for any active
lockowner-file pair. The error NFS4ERR_BAD_STATEID should be lockowner-file pair. The error NFS4ERR_BAD_STATEID should be
returned. returned.
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the file by means of the SETATTR), even where SETATTR is not the file by means of the SETATTR), even where SETATTR is not
explicitly mentioned in the text. explicitly mentioned in the text.
If the lock_owner performs a READ or WRITE in a situation in which it If the lock_owner performs a READ or WRITE in a situation in which it
has established a lock or share reservation on the server (any OPEN has established a lock or share reservation on the server (any OPEN
constitutes a share reservation) the stateid (previously returned by constitutes a share reservation) the stateid (previously returned by
the server) must be used to indicate what locks, including both the server) must be used to indicate what locks, including both
record locks and share reservations, are held by the lockowner. If record locks and share reservations, are held by the lockowner. If
no state is established by the client, either record lock or share no state is established by the client, either record lock or share
Draft Specification NFS version 4 Protocol October 2002 Draft Specification NFS version 4 Protocol November 2002
reservation, a stateid of all bits 0 is used. Regardless whether a reservation, a stateid of all bits 0 is used. Regardless whether a
stateid of all bits 0, or a stateid returned by the server is used, stateid of all bits 0, or a stateid returned by the server is used,
if there is a conflicting share reservation or mandatory record lock if there is a conflicting share reservation or mandatory record lock
held on the file, the server MUST refuse to service the READ or WRITE held on the file, the server MUST refuse to service the READ or WRITE
operation. operation.
Share reservations are established by OPEN operations and by their Share reservations are established by OPEN operations and by their
nature are mandatory in that when the OPEN denies READ or WRITE nature are mandatory in that when the OPEN denies READ or WRITE
operations, that denial results in such operations being rejected operations, that denial results in such operations being rejected
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NFS4ERR_LOCKED. NFS4ERR_LOCKED.
For Windows environments, there are no advisory record locks, so the For Windows environments, there are no advisory record locks, so the
server always checks for record locks during I/O requests. server always checks for record locks during I/O requests.
Thus, the NFS version 4 LOCK operation does not need to distinguish Thus, the NFS version 4 LOCK operation does not need to distinguish
between advisory and mandatory record locks. It is the NFS version 4 between advisory and mandatory record locks. It is the NFS version 4
server's processing of the READ and WRITE operations that introduces server's processing of the READ and WRITE operations that introduces
the distinction. the distinction.
Draft Specification NFS version 4 Protocol October 2002 Draft Specification NFS version 4 Protocol November 2002
Every stateid other than the special stateid values noted in this Every stateid other than the special stateid values noted in this
section, whether returned by an OPEN-type operation (i.e. OPEN, section, whether returned by an OPEN-type operation (i.e. OPEN,
OPEN_DOWNGRADE), or by a LOCK-type operation (i.e. LOCK or LOCKU), OPEN_DOWNGRADE), or by a LOCK-type operation (i.e. LOCK or LOCKU),
defines an access mode for the file (i.e. READ, WRITE, or READ-WRITE) defines an access mode for the file (i.e. READ, WRITE, or READ-WRITE)
as established by the original OPEN which began the stateid sequence, as established by the original OPEN which began the stateid sequence,
and as modified by subsequent OPENs and OPEN_DOWNGRADEs within that and as modified by subsequent OPENs and OPEN_DOWNGRADEs within that
stateid sequence. When a READ, WRITE, or SETATTR which specifies the stateid sequence. When a READ, WRITE, or SETATTR which specifies the
size attribute, is done, the operation is subject to checking against size attribute, is done, the operation is subject to checking against
the access mode to verify that the operation is appropriate given the the access mode to verify that the operation is appropriate given the
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most-one" semantics that are not provided by ONCRPC. ONCRPC over a most-one" semantics that are not provided by ONCRPC. ONCRPC over a
reliable transport is not sufficient because a sequence of locking reliable transport is not sufficient because a sequence of locking
requests may span multiple TCP connections. In the face of requests may span multiple TCP connections. In the face of
retransmission or reordering, lock or unlock requests must have a retransmission or reordering, lock or unlock requests must have a
well defined and consistent behavior. To accomplish this, each lock well defined and consistent behavior. To accomplish this, each lock
request contains a sequence number that is a consecutively increasing request contains a sequence number that is a consecutively increasing
integer. Different lock_owners have different sequences. The server integer. Different lock_owners have different sequences. The server
maintains the last sequence number (L) received and the response that maintains the last sequence number (L) received and the response that
was returned. The first request issued for any given lock_owner is was returned. The first request issued for any given lock_owner is
Draft Specification NFS version 4 Protocol October 2002 Draft Specification NFS version 4 Protocol November 2002
issued with a sequence number of zero. issued with a sequence number of zero.
Note that for requests that contain a sequence number, for each Note that for requests that contain a sequence number, for each
lock_owner, there should be no more than one outstanding request. lock_owner, there should be no more than one outstanding request.
If a request (r) with a previous sequence number (r < L) is received, If a request (r) with a previous sequence number (r < L) is received,
it is rejected with the return of error NFS4ERR_BAD_SEQID. Given a it is rejected with the return of error NFS4ERR_BAD_SEQID. Given a
properly-functioning client, the response to (r) must have been properly-functioning client, the response to (r) must have been
received before the last request (L) was sent. If a duplicate of received before the last request (L) was sent. If a duplicate of
last request (r == L) is received, the stored response is returned. last request (r == L) is received, the stored response is returned.
If a request beyond the next sequence (r == L + 2) is received, it is If a request beyond the next sequence (r == L + 2) is received, it is
rejected with the return of error NFS4ERR_BAD_SEQID. Sequence rejected with the return of error NFS4ERR_BAD_SEQID. Sequence
history is reinitialized whenever the SETCLIENTID/SETCLIENTID_CONFIRM history is reinitialized whenever the SETCLIENTID/SETCLIENTID_CONFIRM
sequence changes the client verifier. sequence changes the client verifier.
Since the sequence number is represented with an unsigned 32-bit Since the sequence number is represented with an unsigned 32-bit
integer, the arithmetic involved with the sequence number is mod integer, the arithmetic involved with the sequence number is mod
2^32. 2^32. For an example of modulo arithetic involving sequence numbers
see [RFC793].
It is critical the server maintain the last response sent to the It is critical the server maintain the last response sent to the
client to provide a more reliable cache of duplicate non-idempotent client to provide a more reliable cache of duplicate non-idempotent
requests than that of the traditional cache described in [Juszczak]. requests than that of the traditional cache described in [Juszczak].
The traditional duplicate request cache uses a least recently used The traditional duplicate request cache uses a least recently used
algorithm for removing unneeded requests. However, the last lock algorithm for removing unneeded requests. However, the last lock
request and response on a given lock_owner must be cached as long as request and response on a given lock_owner must be cached as long as
the lock state exists on the server. the lock state exists on the server.
The client MUST monotonically increment the sequence number for the The client MUST monotonically increment the sequence number for the
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the methods described above, there are no risks of a Byzantine router the methods described above, there are no risks of a Byzantine router
re-sending old requests. The server need only maintain the re-sending old requests. The server need only maintain the
(lock_owner, sequence number) state as long as there are open files (lock_owner, sequence number) state as long as there are open files
or closed files with locks outstanding. or closed files with locks outstanding.
LOCK, LOCKU, OPEN, OPEN_DOWNGRADE, and CLOSE each contain a sequence LOCK, LOCKU, OPEN, OPEN_DOWNGRADE, and CLOSE each contain a sequence
number and therefore the risk of the replay of these operations number and therefore the risk of the replay of these operations
resulting in undesired effects is non-existent while the server resulting in undesired effects is non-existent while the server
maintains the lock_owner state. maintains the lock_owner state.
Draft Specification NFS version 4 Protocol October 2002 Draft Specification NFS version 4 Protocol November 2002
8.1.7. Releasing lock_owner State 8.1.7. Releasing lock_owner State
When a particular lock_owner no longer holds open or file locking When a particular lock_owner no longer holds open or file locking
state at the server, the server may choose to release the sequence state at the server, the server may choose to release the sequence
number state associated with the lock_owner. The server may make number state associated with the lock_owner. The server may make
this choice based on lease expiration, for the reclamation of server this choice based on lease expiration, for the reclamation of server
memory, or other implementation specific details. In any event, the memory, or other implementation specific details. In any event, the
server is able to do this safely only when the lock_owner no longer server is able to do this safely only when the lock_owner no longer
is being utilized by the client. The server may choose to hold the is being utilized by the client. The server may choose to hold the
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situations in which the server can avoid the need for confirmation situations in which the server can avoid the need for confirmation
when responding to open requests. The two constraints are: when responding to open requests. The two constraints are:
o The server must not bestow a delegation for any open which would o The server must not bestow a delegation for any open which would
require confirmation. require confirmation.
o The server MUST NOT require confirmation on a reclaim-type open o The server MUST NOT require confirmation on a reclaim-type open
(i.e. one specifying claim type CLAIM_PREVIOUS or (i.e. one specifying claim type CLAIM_PREVIOUS or
CLAIM_DELEGATE_PREV). CLAIM_DELEGATE_PREV).
Draft Specification NFS version 4 Protocol October 2002 Draft Specification NFS version 4 Protocol November 2002
These constraints are related in that reclaim-type opens are the only These constraints are related in that reclaim-type opens are the only
ones in which the server may be required to send a delegation. For ones in which the server may be required to send a delegation. For
CLAIM_NULL, sending the delegation is optional while for CLAIM_NULL, sending the delegation is optional while for
CLAIM_DELEGATE_CUR, no delegation is sent. CLAIM_DELEGATE_CUR, no delegation is sent.
Delegations being sent with an open requiring confirmation are Delegations being sent with an open requiring confirmation are
troublesome because recovering from non-confirmation adds undue troublesome because recovering from non-confirmation adds undue
complexity to the protocol while requiring confirmation on reclaim- complexity to the protocol while requiring confirmation on reclaim-
type opens poses difficulties in that the inability to resolve the type opens poses difficulties in that the inability to resolve the
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As discussed in the section "Server Failure and Recovery" below, the As discussed in the section "Server Failure and Recovery" below, the
server may employ certain optimizations during recovery that work server may employ certain optimizations during recovery that work
effectively only when the client's behavior during lock recovery is effectively only when the client's behavior during lock recovery is
similar to the client's locking behavior prior to server failure. similar to the client's locking behavior prior to server failure.
8.3. Upgrading and Downgrading Locks 8.3. Upgrading and Downgrading Locks
If a client has a write lock on a record, it can request an atomic If a client has a write lock on a record, it can request an atomic
downgrade of the lock to a read lock via the LOCK request, by setting downgrade of the lock to a read lock via the LOCK request, by setting
Draft Specification NFS version 4 Protocol October 2002 Draft Specification NFS version 4 Protocol November 2002
the type to READ_LT. If the server supports atomic downgrade, the the type to READ_LT. If the server supports atomic downgrade, the
request will succeed. If not, it will return NFS4ERR_LOCK_NOTSUPP. request will succeed. If not, it will return NFS4ERR_LOCK_NOTSUPP.
The client should be prepared to receive this error, and if The client should be prepared to receive this error, and if
appropriate, report the error to the requesting application. appropriate, report the error to the requesting application.
If a client has a read lock on a record, it can request an atomic If a client has a read lock on a record, it can request an atomic
upgrade of the lock to a write lock via the LOCK request by setting upgrade of the lock to a write lock via the LOCK request by setting
the type to WRITE_LT or WRITEW_LT. If the server does not support the type to WRITE_LT or WRITEW_LT. If the server does not support
atomic upgrade, it will return NFS4ERR_LOCK_NOTSUPP. If the upgrade atomic upgrade, it will return NFS4ERR_LOCK_NOTSUPP. If the upgrade
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avoid the burden of needlessly frequent polling for blocking locks. avoid the burden of needlessly frequent polling for blocking locks.
The server should take care in the length of delay in the event the The server should take care in the length of delay in the event the
client retransmits the request. client retransmits the request.
8.5. Lease Renewal 8.5. Lease Renewal
The purpose of a lease is to allow a server to remove stale locks The purpose of a lease is to allow a server to remove stale locks
that are held by a client that has crashed or is otherwise that are held by a client that has crashed or is otherwise
unreachable. It is not a mechanism for cache consistency and lease unreachable. It is not a mechanism for cache consistency and lease
Draft Specification NFS version 4 Protocol October 2002 Draft Specification NFS version 4 Protocol November 2002
renewals may not be denied if the lease interval has not expired. renewals may not be denied if the lease interval has not expired.
The following events cause implicit renewal of all of the leases for The following events cause implicit renewal of all of the leases for
a given client (i.e. all those sharing a given clientid). Each of a given client (i.e. all those sharing a given clientid). Each of
these is a positive indication that the client is still active and these is a positive indication that the client is still active and
that the associated state held at the server, for the client, is that the associated state held at the server, for the client, is
still valid. still valid.
o An OPEN with a valid clientid. o An OPEN with a valid clientid.
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8.6. Crash Recovery 8.6. Crash Recovery
The important requirement in crash recovery is that both the client The important requirement in crash recovery is that both the client
and the server know when the other has failed. Additionally, it is and the server know when the other has failed. Additionally, it is
required that a client sees a consistent view of data across server required that a client sees a consistent view of data across server
restarts or reboots. All READ and WRITE operations that may have restarts or reboots. All READ and WRITE operations that may have
been queued within the client or network buffers must wait until the been queued within the client or network buffers must wait until the
client has successfully recovered the locks protecting the READ and client has successfully recovered the locks protecting the READ and
WRITE operations. WRITE operations.
Draft Specification NFS version 4 Protocol October 2002 Draft Specification NFS version 4 Protocol November 2002
8.6.1. Client Failure and Recovery 8.6.1. Client Failure and Recovery
In the event that a client fails, the server may recover the client's In the event that a client fails, the server may recover the client's
locks when the associated leases have expired. Conflicting locks locks when the associated leases have expired. Conflicting locks
from another client may only be granted after this lease expiration. from another client may only be granted after this lease expiration.
If the client is able to restart or reinitialize within the lease If the client is able to restart or reinitialize within the lease
period the client may be forced to wait the remainder of the lease period the client may be forced to wait the remainder of the lease
period before obtaining new locks. period before obtaining new locks.
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A client can determine that server failure (and thus loss of locking A client can determine that server failure (and thus loss of locking
state) has occurred, when it receives one of two errors. The state) has occurred, when it receives one of two errors. The
NFS4ERR_STALE_STATEID error indicates a stateid invalidated by a NFS4ERR_STALE_STATEID error indicates a stateid invalidated by a
reboot or restart. The NFS4ERR_STALE_CLIENTID error indicates a reboot or restart. The NFS4ERR_STALE_CLIENTID error indicates a
clientid invalidated by reboot or restart. When either of these are clientid invalidated by reboot or restart. When either of these are
received, the client must establish a new clientid (See the section received, the client must establish a new clientid (See the section
"Client ID") and re-establish the locking state as discussed below. "Client ID") and re-establish the locking state as discussed below.
The period of special handling of locking and READs and WRITEs, equal The period of special handling of locking and READs and WRITEs, equal
Draft Specification NFS version 4 Protocol October 2002 Draft Specification NFS version 4 Protocol November 2002
in duration to the lease period, is referred to as the "grace in duration to the lease period, is referred to as the "grace
period". During the grace period, clients recover locks and the period". During the grace period, clients recover locks and the
associated state by reclaim-type locking requests (i.e. LOCK requests associated state by reclaim-type locking requests (i.e. LOCK requests
with reclaim set to true and OPEN operations with a claim type of with reclaim set to true and OPEN operations with a claim type of
CLAIM_PREVIOUS). During the grace period, the server must reject CLAIM_PREVIOUS). During the grace period, the server must reject
READ and WRITE operations and non-reclaim locking requests (i.e. READ and WRITE operations and non-reclaim locking requests (i.e.
other LOCK and OPEN operations) with an error of NFS4ERR_GRACE. other LOCK and OPEN operations) with an error of NFS4ERR_GRACE.
If the server can reliably determine that granting a non-reclaim If the server can reliably determine that granting a non-reclaim
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non-reclaim lock and I/O requests. In this case the client should non-reclaim lock and I/O requests. In this case the client should
employ a retry mechanism for the request. A delay (on the order of employ a retry mechanism for the request. A delay (on the order of
several seconds) between retries should be used to avoid overwhelming several seconds) between retries should be used to avoid overwhelming
the server. Further discussion of the general issue is included in the server. Further discussion of the general issue is included in
[Floyd]. The client must account for the server that is able to [Floyd]. The client must account for the server that is able to
perform I/O and non-reclaim locking requests within the grace period perform I/O and non-reclaim locking requests within the grace period
as well as those that can not do so. as well as those that can not do so.
A reclaim-type locking request outside the server's grace period can A reclaim-type locking request outside the server's grace period can
Draft Specification NFS version 4 Protocol October 2002 Draft Specification NFS version 4 Protocol November 2002
only succeed if the server can guarantee that no conflicting lock or only succeed if the server can guarantee that no conflicting lock or
I/O request has been granted since reboot or restart. I/O request has been granted since reboot or restart.
A server may, upon restart, establish a new value for the lease A server may, upon restart, establish a new value for the lease
period. Therefore, clients should, once a new clientid is period. Therefore, clients should, once a new clientid is
established, refetch the lease_time attribute and use it as the basis established, refetch the lease_time attribute and use it as the basis
for lease renewal for the lease associated with that server. However, for lease renewal for the lease associated with that server. However,
the server must establish, for this restart event, a grace period at the server must establish, for this restart event, a grace period at
least as long as the lease period for the previous server least as long as the lease period for the previous server
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2. Client A and server experience mutual network partition, 2. Client A and server experience mutual network partition,
such that client A is unable to renew its lease. such that client A is unable to renew its lease.
3. Client A's lease expires, so server releases lock. 3. Client A's lease expires, so server releases lock.
4. Client B acquires a lock that would have conflicted with 4. Client B acquires a lock that would have conflicted with
that of Client A. that of Client A.
5. Client B releases the lock 5. Client B releases the lock
Draft Specification NFS version 4 Protocol October 2002 Draft Specification NFS version 4 Protocol November 2002
6. Server reboots 6. Server reboots
7. Network partition between client A and server heals. 7. Network partition between client A and server heals.
8. Client A issues a RENEW operation, and gets back a 8. Client A issues a RENEW operation, and gets back a
NFS4ERR_STALE_CLIENTID. NFS4ERR_STALE_CLIENTID.
9. Client A reclaims its lock within the server's grace period. 9. Client A reclaims its lock within the server's grace period.
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Solving the first and second edge conditions requires that the server Solving the first and second edge conditions requires that the server
either assume after it reboots that edge condition occurs, and thus either assume after it reboots that edge condition occurs, and thus
return NFS4ERR_NO_GRACE for all reclaim attempts, or that the server return NFS4ERR_NO_GRACE for all reclaim attempts, or that the server
record some information stable storage. The amount of information record some information stable storage. The amount of information
the server records in stable storage is in inverse proportion to how the server records in stable storage is in inverse proportion to how
harsh the server wants to be whenever the edge conditions occur. The harsh the server wants to be whenever the edge conditions occur. The
server that is completely tolerant of all edge conditions will record server that is completely tolerant of all edge conditions will record
in stable storage every lock that is acquired, removing the lock in stable storage every lock that is acquired, removing the lock
Draft Specification NFS version 4 Protocol October 2002 Draft Specification NFS version 4 Protocol November 2002
record from stable storage only when the lock is unlocked by the record from stable storage only when the lock is unlocked by the
client and the lock's lockowner advances the sequence number such client and the lock's lockowner advances the sequence number such
that the lock release is not the last stateful event for the that the lock release is not the last stateful event for the
lockowner's sequence. For the two aforementioned edge conditions, the lockowner's sequence. For the two aforementioned edge conditions, the
harshest a server can be, and still support a grace period for harshest a server can be, and still support a grace period for
reclaims, requires that the server record in stable storage reclaims, requires that the server record in stable storage
information some minimal information. For example, a server information some minimal information. For example, a server
implementation could, for each client, save in stable storage a implementation could, for each client, save in stable storage a
record containing: record containing:
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1. Reject all reclaims with NFS4ERR_NO_GRACE. This is 1. Reject all reclaims with NFS4ERR_NO_GRACE. This is
superharsh, but necessary if the server does not want to superharsh, but necessary if the server does not want to
record lock state in stable storage. record lock state in stable storage.
2. Record sufficient state in stable storage such that all 2. Record sufficient state in stable storage such that all
known edge conditions involving server reboot, including the known edge conditions involving server reboot, including the
two noted in this section, are detected. False positives are two noted in this section, are detected. False positives are
acceptable. Note that at this time, it is not known if there acceptable. Note that at this time, it is not known if there
are other edge conditions. are other edge conditions.
Draft Specification NFS version 4 Protocol October 2002 Draft Specification NFS version 4 Protocol November 2002
In the event, after a server reboot, the server determines In the event, after a server reboot, the server determines
that there is unrecoverable damage or corruption to the the that there is unrecoverable damage or corruption to the the
stable storage, then for all clients and/or locks affected, stable storage, then for all clients and/or locks affected,
the server MUST return NFS4ERR_NO_GRACE. the server MUST return NFS4ERR_NO_GRACE.
A mandate for the client's handling of the NFS4ERR_NO_GRACE error is A mandate for the client's handling of the NFS4ERR_NO_GRACE error is
outside the scope of this specification, since the strategies for outside the scope of this specification, since the strategies for
such handling are very dependent on the client's operating such handling are very dependent on the client's operating
environment. However, one potential approach is described below. environment. However, one potential approach is described below.
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not receive a response. From this, the next time the client does a not receive a response. From this, the next time the client does a
lock operation for the lock_owner, it can send the cached request, if lock operation for the lock_owner, it can send the cached request, if
there is one, and if the request was one that established state (e.g. there is one, and if the request was one that established state (e.g.
a LOCK or OPEN operation), the server will return the cached result a LOCK or OPEN operation), the server will return the cached result
or if never saw the request, perform it. The client can follow up or if never saw the request, perform it. The client can follow up
with a request to remove the state (e.g. a LOCKU or CLOSE operation). with a request to remove the state (e.g. a LOCKU or CLOSE operation).
With this approach, the sequencing and stateid information on the With this approach, the sequencing and stateid information on the
client and server for the given lock_owner will re-synchronize and in client and server for the given lock_owner will re-synchronize and in
turn the lock state will re-synchronize. turn the lock state will re-synchronize.
Draft Specification NFS version 4 Protocol October 2002 Draft Specification NFS version 4 Protocol November 2002
8.8. Server Revocation of Locks 8.8. Server Revocation of Locks
At any point, the server can revoke locks held by a client and the At any point, the server can revoke locks held by a client and the
client must be prepared for this event. When the client detects that client must be prepared for this event. When the client detects that
its locks have been or may have been revoked, the client is its locks have been or may have been revoked, the client is
responsible for validating the state information between itself and responsible for validating the state information between itself and
the server. Validating locking state for the client means that it the server. Validating locking state for the client means that it
must verify or reclaim state for each lock currently held. must verify or reclaim state for each lock currently held.
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which the server may grant conflicting locks after the lease period which the server may grant conflicting locks after the lease period
has expired for a client. When it is possible that the lease period has expired for a client. When it is possible that the lease period
has expired, the client must validate each lock currently held to has expired, the client must validate each lock currently held to
ensure that a conflicting lock has not been granted. The client may ensure that a conflicting lock has not been granted. The client may
accomplish this task by issuing an I/O request, either a pending I/O accomplish this task by issuing an I/O request, either a pending I/O
or a zero-length read, specifying the stateid associated with the or a zero-length read, specifying the stateid associated with the
lock in question. If the response to the request is success, the lock in question. If the response to the request is success, the
client has validated all of the locks governed by that stateid and client has validated all of the locks governed by that stateid and
re-established the appropriate state between itself and the server. re-established the appropriate state between itself and the server.
Draft Specification NFS version 4 Protocol October 2002 Draft Specification NFS version 4 Protocol November 2002
If the I/O request is not successful, then one or more of the locks If the I/O request is not successful, then one or more of the locks
associated with the stateid was revoked by the server and the client associated with the stateid was revoked by the server and the client
must notify the owner. must notify the owner.
8.9. Share Reservations 8.9. Share Reservations
A share reservation is a mechanism to control access to a file. It A share reservation is a mechanism to control access to a file. It
is a separate and independent mechanism from record locking. When a is a separate and independent mechanism from record locking. When a
client opens a file, it issues an OPEN operation to the server client opens a file, it issues an OPEN operation to the server
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To provide correct share semantics, a client MUST use the OPEN To provide correct share semantics, a client MUST use the OPEN
operation to obtain the initial filehandle and indicate the desired operation to obtain the initial filehandle and indicate the desired
access and what if any access to deny. Even if the client intends to access and what if any access to deny. Even if the client intends to
use a stateid of all 0's or all 1's, it must still obtain the use a stateid of all 0's or all 1's, it must still obtain the
filehandle for the regular file with the OPEN operation so the filehandle for the regular file with the OPEN operation so the
appropriate share semantics can be applied. For clients that do not appropriate share semantics can be applied. For clients that do not
have a deny mode built into their open programming interfaces, deny have a deny mode built into their open programming interfaces, deny
equal to NONE should be used. equal to NONE should be used.
Draft Specification NFS version 4 Protocol October 2002 Draft Specification NFS version 4 Protocol November 2002
The OPEN operation with the CREATE flag, also subsumes the CREATE The OPEN operation with the CREATE flag, also subsumes the CREATE
operation for regular files as used in previous versions of the NFS operation for regular files as used in previous versions of the NFS
protocol. This allows a create with a share to be done atomically. protocol. This allows a create with a share to be done atomically.
The CLOSE operation removes all share reservations held by the The CLOSE operation removes all share reservations held by the
lock_owner on that file. If record locks are held, the client SHOULD lock_owner on that file. If record locks are held, the client SHOULD
release all locks before issuing a CLOSE. The server MAY free all release all locks before issuing a CLOSE. The server MAY free all
outstanding locks on CLOSE but some servers may not support the CLOSE outstanding locks on CLOSE but some servers may not support the CLOSE
of a file that still has record locks held. The server MUST return of a file that still has record locks held. The server MUST return
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o The time that a lockowner is freed by the server due to period o The time that a lockowner is freed by the server due to period
with no activity. with no activity.
o All locks for the client are freed as a result of a SETCLIENTID. o All locks for the client are freed as a result of a SETCLIENTID.
Servers may avoid this complexity, at the cost of less complete Servers may avoid this complexity, at the cost of less complete
protocol error checking, by simply responding NFS4_OK in the event of protocol error checking, by simply responding NFS4_OK in the event of
a CLOSE for a deallocated stateid, on the assumption that this case a CLOSE for a deallocated stateid, on the assumption that this case
must be caused by a retransmitted close. When adopting this must be caused by a retransmitted close. When adopting this
Draft Specification NFS version 4 Protocol October 2002 Draft Specification NFS version 4 Protocol November 2002
approach, it is desirable to at least log an error when returning a approach, it is desirable to at least log an error when returning a
no-error indication in this situation. If the server maintains a no-error indication in this situation. If the server maintains a
reply-cache mechanism, it can verify the CLOSE is indeed a reply-cache mechanism, it can verify the CLOSE is indeed a
retransmission and avoid error logging in most cases. retransmission and avoid error logging in most cases.
8.11. Open Upgrade and Downgrade 8.11. Open Upgrade and Downgrade
When an OPEN is done for a file and the lockowner for which the open When an OPEN is done for a file and the lockowner for which the open
is being done already has the file open, the result is to upgrade the is being done already has the file open, the result is to upgrade the
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recovery at a cost of increased RENEW or READ (with zero length) recovery at a cost of increased RENEW or READ (with zero length)
requests. Longer leases are certainly kinder and gentler to servers requests. Longer leases are certainly kinder and gentler to servers
trying to handle very large numbers of clients. The number of RENEW trying to handle very large numbers of clients. The number of RENEW
requests drop in proportion to the lease time. The disadvantages of requests drop in proportion to the lease time. The disadvantages of
long leases are slower recovery after server failure (the server must long leases are slower recovery after server failure (the server must
wait for the leases to expire and the grace period to elapse before wait for the leases to expire and the grace period to elapse before
granting new lock requests) and increased file contention (if client granting new lock requests) and increased file contention (if client
fails to transmit an unlock request then server must wait for lease fails to transmit an unlock request then server must wait for lease
expiration before granting new locks). expiration before granting new locks).
Draft Specification NFS version 4 Protocol October 2002 Draft Specification NFS version 4 Protocol November 2002
Long leases are usable if the server is able to store lease state in Long leases are usable if the server is able to store lease state in
non-volatile memory. Upon recovery, the server can reconstruct the non-volatile memory. Upon recovery, the server can reconstruct the
lease state from its non-volatile memory and continue operation with lease state from its non-volatile memory and continue operation with
its clients and therefore long leases would not be an issue. its clients and therefore long leases would not be an issue.
8.13. Clocks, Propagation Delay, and Calculating Lease Expiration 8.13. Clocks, Propagation Delay, and Calculating Lease Expiration
To avoid the need for synchronized clocks, lease times are granted by To avoid the need for synchronized clocks, lease times are granted by
the server as a time delta. However, there is a requirement that the the server as a time delta. However, there is a requirement that the
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Share Reservations" Share Reservations"
If server replica or a server immigrating a filesystem agrees to, or If server replica or a server immigrating a filesystem agrees to, or
is expected to, accept opaque values from the client that originated is expected to, accept opaque values from the client that originated
from another server, then it is a wise implementation practice for from another server, then it is a wise implementation practice for
the servers to encode the "opaque" values in network byte order. This the servers to encode the "opaque" values in network byte order. This
way, servers acting as replicas or immigrating filesystems will be way, servers acting as replicas or immigrating filesystems will be
able to parse values like stateids, directory cookies, filehandles, able to parse values like stateids, directory cookies, filehandles,
etc. even if their native byte order is different from other servers etc. even if their native byte order is different from other servers
Draft Specification NFS version 4 Protocol October 2002 Draft Specification NFS version 4 Protocol November 2002
cooperating in the replication and migration of the filesystem. cooperating in the replication and migration of the filesystem.
8.14.1. Migration and State 8.14.1. Migration and State
In the case of migration, the servers involved in the migration of a In the case of migration, the servers involved in the migration of a
filesystem SHOULD transfer all server state from the original to the filesystem SHOULD transfer all server state from the original to the
new server. This must be done in a way that is transparent to the new server. This must be done in a way that is transparent to the
client. This state transfer will ease the client's transition when a client. This state transfer will ease the client's transition when a
filesystem migration occurs. If the servers are successful in filesystem migration occurs. If the servers are successful in
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leases, stateids and clientids do not have validity across a leases, stateids and clientids do not have validity across a
transition from one server to another. The client must re-establish transition from one server to another. The client must re-establish
its locks on the new server. This can be compared to the re- its locks on the new server. This can be compared to the re-
establishment of locks by means of reclaim-type requests after a establishment of locks by means of reclaim-type requests after a
server reboot. The difference is that the server has no provision to server reboot. The difference is that the server has no provision to
distinguish requests reclaiming locks from those obtaining new locks distinguish requests reclaiming locks from those obtaining new locks
or to defer the latter. Thus, a client re-establishing a lock on the or to defer the latter. Thus, a client re-establishing a lock on the
new server (by means of a LOCK or OPEN request), may have the new server (by means of a LOCK or OPEN request), may have the
requests denied due to a conflicting lock. Since replication is requests denied due to a conflicting lock. Since replication is
Draft Specification NFS version 4 Protocol October 2002 Draft Specification NFS version 4 Protocol November 2002
intended for read-only use of filesystems, such denial of locks intended for read-only use of filesystems, such denial of locks
should not pose large difficulties in practice. When an attempt to should not pose large difficulties in practice. When an attempt to
re-establish a lock on a new server is denied, the client should re-establish a lock on a new server is denied, the client should
treat the situation as if his original lock had been revoked. treat the situation as if his original lock had been revoked.
8.14.3. Notification of Migrated Lease 8.14.3. Notification of Migrated Lease
In the case of lease renewal, the client may not be submitting In the case of lease renewal, the client may not be submitting
requests for a filesystem that has been migrated to another server. requests for a filesystem that has been migrated to another server.
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When state is transferred transparently, that state should include When state is transferred transparently, that state should include
the correct value of the lease_time attribute. The lease_time the correct value of the lease_time attribute. The lease_time
attribute on the destination server must never be less than that on attribute on the destination server must never be less than that on
the source since this would result in premature expiration of leases the source since this would result in premature expiration of leases
granted by the source server. Upon migration in which state is granted by the source server. Upon migration in which state is
transferred transparently, the client is under no obligation to re- transferred transparently, the client is under no obligation to re-
fetch the lease_time attribute and may continue to use the value fetch the lease_time attribute and may continue to use the value
previously fetched (on the source server). previously fetched (on the source server).
Draft Specification NFS version 4 Protocol October 2002 Draft Specification NFS version 4 Protocol November 2002
If state has not been transferred transparently (i.e. the client sees If state has not been transferred transparently (i.e. the client sees
a real or simulated server reboot), the client should fetch the value a real or simulated server reboot), the client should fetch the value
of lease_time on the new (i.e. destination) server, and use it for of lease_time on the new (i.e. destination) server, and use it for
subsequent locking requests. However the server must respect a grace subsequent locking requests. However the server must respect a grace
period at least as long as the lease_time on the source server, in period at least as long as the lease_time on the source server, in
order to ensure that clients have ample time to reclaim their locks order to ensure that clients have ample time to reclaim their locks
before potentially conflicting non-reclaimed locks are granted. The before potentially conflicting non-reclaimed locks are granted. The
means by which the new server obtains the value of lease_time on the means by which the new server obtains the value of lease_time on the
old server is left to the server implementations. It is not old server is left to the server implementations. It is not
specified by the NFS version 4 protocol. specified by the NFS version 4 protocol.
Draft Specification NFS version 4 Protocol October 2002 Draft Specification NFS version 4 Protocol November 2002
9. Client-Side Caching 9. Client-Side Caching
Client-side caching of data, of file attributes, and of file names is Client-side caching of data, of file attributes, and of file names is
essential to providing good performance with the NFS protocol. essential to providing good performance with the NFS protocol.
Providing distributed cache coherence is a difficult problem and Providing distributed cache coherence is a difficult problem and
previous versions of the NFS protocol have not attempted it. previous versions of the NFS protocol have not attempted it.
Instead, several NFS client implementation techniques have been used Instead, several NFS client implementation techniques have been used
to reduce the problems that a lack of coherence poses for users. to reduce the problems that a lack of coherence poses for users.
These techniques have not been clearly defined by earlier protocol These techniques have not been clearly defined by earlier protocol
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performance is to allow a client that repeatedly opens a file to do performance is to allow a client that repeatedly opens a file to do
so without reference to the server. This is done until potentially so without reference to the server. This is done until potentially
conflicting operations from another client actually occur. conflicting operations from another client actually occur.
A similar situation arises in connection with file locking. Sending A similar situation arises in connection with file locking. Sending
file lock and unlock requests to the server as well as the read and file lock and unlock requests to the server as well as the read and
write requests necessary to make data caching consistent with the write requests necessary to make data caching consistent with the
locking semantics (see the section "Data Caching and File Locking") locking semantics (see the section "Data Caching and File Locking")
can severely limit performance. When locking is used to provide can severely limit performance. When locking is used to provide
Draft Specification NFS version 4 Protocol October 2002 Draft Specification NFS version 4 Protocol November 2002
protection against infrequent conflicts, a large penalty is incurred. protection against infrequent conflicts, a large penalty is incurred.
This penalty may discourage the use of file locking by applications. This penalty may discourage the use of file locking by applications.
The NFS version 4 protocol provides more aggressive caching The NFS version 4 protocol provides more aggressive caching
strategies with the following design goals: strategies with the following design goals:
o Compatibility with a large range of server semantics. o Compatibility with a large range of server semantics.
o Provide the same caching benefits as previous versions of the o Provide the same caching benefits as previous versions of the
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on them. Preliminary testing of callback functionality by means of a on them. Preliminary testing of callback functionality by means of a
CB_NULL procedure determines whether callbacks can be supported. The CB_NULL procedure determines whether callbacks can be supported. The
CB_NULL procedure checks the continuity of the callback path. A CB_NULL procedure checks the continuity of the callback path. A
server makes a preliminary assessment of callback availability to a server makes a preliminary assessment of callback availability to a
given client and avoids delegating responsibilities until it has given client and avoids delegating responsibilities until it has
determined that callbacks are supported. Because the granting of a determined that callbacks are supported. Because the granting of a
delegation is always conditional upon the absence of conflicting delegation is always conditional upon the absence of conflicting
access, clients must not assume that a delegation will be granted and access, clients must not assume that a delegation will be granted and
they must always be prepared for OPENs to be processed without any they must always be prepared for OPENs to be processed without any
Draft Specification NFS version 4 Protocol October 2002 Draft Specification NFS version 4 Protocol November 2002
delegations being granted. delegations being granted.
Once granted, a delegation behaves in most ways like a lock. There Once granted, a delegation behaves in most ways like a lock. There
is an associated lease that is subject to renewal together with all is an associated lease that is subject to renewal together with all
of the other leases held by that client. of the other leases held by that client.
Unlike locks, an operation by a second client to a delegated file Unlike locks, an operation by a second client to a delegated file
will cause the server to recall a delegation through a callback. will cause the server to recall a delegation through a callback.
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There are three situations that delegation recovery must deal with: There are three situations that delegation recovery must deal with:
o Client reboot or restart o Client reboot or restart
o Server reboot or restart o Server reboot or restart
o Network partition (full or callback-only) o Network partition (full or callback-only)
In the event the client reboots or restarts, the failure to renew In the event the client reboots or restarts, the failure to renew
Draft Specification NFS version 4 Protocol October 2002 Draft Specification NFS version 4 Protocol November 2002
leases will result in the revocation of record locks and share leases will result in the revocation of record locks and share
reservations. Delegations, however, may be treated a bit reservations. Delegations, however, may be treated a bit
differently. differently.
There will be situations in which delegations will need to be There will be situations in which delegations will need to be
reestablished after a client reboots or restarts. The reason for reestablished after a client reboots or restarts. The reason for
this is the client may have file data stored locally and this data this is the client may have file data stored locally and this data
was associated with the previously held delegations. The client will was associated with the previously held delegations. The client will
need to reestablish the appropriate file state on the server. need to reestablish the appropriate file state on the server.
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process of handling delegation reclaim reconciles three principles of process of handling delegation reclaim reconciles three principles of
the NFS version 4 protocol: the NFS version 4 protocol:
o Upon reclaim, a client reporting resources assigned to it by an o Upon reclaim, a client reporting resources assigned to it by an
earlier server instance must be granted those resources. earlier server instance must be granted those resources.
o The server has unquestionable authority to determine whether o The server has unquestionable authority to determine whether
delegations are to be granted and, once granted, whether they delegations are to be granted and, once granted, whether they
are to be continued. are to be continued.
Draft Specification NFS version 4 Protocol October 2002 Draft Specification NFS version 4 Protocol November 2002
o The use of callbacks is not to be depended upon until the client o The use of callbacks is not to be depended upon until the client
has proven its ability to receive them. has proven its ability to receive them.
When a network partition occurs, delegations are subject to freeing When a network partition occurs, delegations are subject to freeing
by the server when the lease renewal period expires. This is similar by the server when the lease renewal period expires. This is similar
to the behavior for locks and share reservations. For delegations, to the behavior for locks and share reservations. For delegations,
however, the server may extend the period in which conflicting however, the server may extend the period in which conflicting
requests are held off. Eventually the occurrence of a conflicting requests are held off. Eventually the occurrence of a conflicting
request from another client will cause revocation of the delegation. request from another client will cause revocation of the delegation.
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invalidate the assumptions that those using these facilities depend invalidate the assumptions that those using these facilities depend
upon. upon.
9.3.1. Data Caching and OPENs 9.3.1. Data Caching and OPENs
In order to avoid invalidating the sharing assumptions that In order to avoid invalidating the sharing assumptions that
applications rely on, NFS version 4 clients should not provide cached applications rely on, NFS version 4 clients should not provide cached
data to applications or modify it on behalf of an application when it data to applications or modify it on behalf of an application when it
would not be valid to obtain or modify that same data via a READ or would not be valid to obtain or modify that same data via a READ or
Draft Specification NFS version 4 Protocol October 2002 Draft Specification NFS version 4 Protocol November 2002
WRITE operation. WRITE operation.
Furthermore, in the absence of open delegation (see the section "Open Furthermore, in the absence of open delegation (see the section "Open
Delegation") two additional rules apply. Note that these rules are Delegation") two additional rules apply. Note that these rules are
obeyed in practice by many NFS version 2 and version 3 clients. obeyed in practice by many NFS version 2 and version 3 clients.
o First, cached data present on a client must be revalidated after o First, cached data present on a client must be revalidated after
doing an OPEN. Revalidating means that the client fetches the doing an OPEN. Revalidating means that the client fetches the
change attribute from the server, compares it with the cached change attribute from the server, compares it with the cached
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written to the file. Hence, this requirement. written to the file. Hence, this requirement.
9.3.2. Data Caching and File Locking 9.3.2. Data Caching and File Locking
For those applications that choose to use file locking instead of For those applications that choose to use file locking instead of
share reservations to exclude inconsistent file access, there is an share reservations to exclude inconsistent file access, there is an
analogous set of constraints that apply to client side data caching. analogous set of constraints that apply to client side data caching.
These rules are effective only if the file locking is used in a way These rules are effective only if the file locking is used in a way
that matches in an equivalent way the actual READ and WRITE that matches in an equivalent way the actual READ and WRITE
Draft Specification NFS version 4 Protocol October 2002 Draft Specification NFS version 4 Protocol November 2002
operations executed. This is as opposed to file locking that is operations executed. This is as opposed to file locking that is
based on pure convention. For example, it is possible to manipulate based on pure convention. For example, it is possible to manipulate
a two-megabyte file by dividing the file into two one-megabyte a two-megabyte file by dividing the file into two one-megabyte
regions and protecting access to the two regions by file locks on regions and protecting access to the two regions by file locks on
bytes zero and one. A lock for write on byte zero of the file would bytes zero and one. A lock for write on byte zero of the file would
represent the right to do READ and WRITE operations on the first represent the right to do READ and WRITE operations on the first
region. A lock for write on byte one of the file would represent the region. A lock for write on byte one of the file would represent the
right to do READ and WRITE operations on the second region. As long right to do READ and WRITE operations on the second region. As long
as all applications manipulating the file obey this convention, they as all applications manipulating the file obey this convention, they
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The data that is written to the server as a prerequisite to the The data that is written to the server as a prerequisite to the
unlocking of a region must be written, at the server, to stable unlocking of a region must be written, at the server, to stable
storage. The client may accomplish this either with synchronous storage. The client may accomplish this either with synchronous
writes or by following asynchronous writes with a COMMIT operation. writes or by following asynchronous writes with a COMMIT operation.
This is required because retransmission of the modified data after a This is required because retransmission of the modified data after a
server reboot might conflict with a lock held by another client. server reboot might conflict with a lock held by another client.
A client implementation may choose to accommodate applications which A client implementation may choose to accommodate applications which
use record locking in non-standard ways (e.g. using a record lock as use record locking in non-standard ways (e.g. using a record lock as
Draft Specification NFS version 4 Protocol October 2002 Draft Specification NFS version 4 Protocol November 2002
a global semaphore) by flushing to the server more data upon an LOCKU a global semaphore) by flushing to the server more data upon an LOCKU
than is covered by the locked range. This may include modified data than is covered by the locked range. This may include modified data
within files other than the one for which the unlocks are being done. within files other than the one for which the unlocks are being done.
In such cases, the client must not interfere with applications whose In such cases, the client must not interfere with applications whose
READs and WRITEs are being done only within the bounds of record READs and WRITEs are being done only within the bounds of record
locks which the application holds. For example, an application locks locks which the application holds. For example, an application locks
a single byte of a file and proceeds to write that single byte. A a single byte of a file and proceeds to write that single byte. A
client that chose to handle a LOCKU by flushing all modified data to client that chose to handle a LOCKU by flushing all modified data to
the server could validly write that single byte in response to an the server could validly write that single byte in response to an
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the purpose of caching that distinct filehandles represent distinct the purpose of caching that distinct filehandles represent distinct
filesystem objects. The client then has the choice to organize and filesystem objects. The client then has the choice to organize and
maintain the data cache on this basis. maintain the data cache on this basis.
In the NFS version 4 protocol, there is now the possibility to have In the NFS version 4 protocol, there is now the possibility to have
significant deviations from a "one filehandle per object" model significant deviations from a "one filehandle per object" model
because a filehandle may be constructed on the basis of the object's because a filehandle may be constructed on the basis of the object's
pathname. Therefore, clients need a reliable method to determine if pathname. Therefore, clients need a reliable method to determine if
two filehandles designate the same filesystem object. If clients two filehandles designate the same filesystem object. If clients
Draft Specification NFS version 4 Protocol October 2002 Draft Specification NFS version 4 Protocol November 2002
were simply to assume that all distinct filehandles denote distinct were simply to assume that all distinct filehandles denote distinct
objects and proceed to do data caching on this basis, caching objects and proceed to do data caching on this basis, caching
inconsistencies would arise between the distinct client side objects inconsistencies would arise between the distinct client side objects
which mapped to the same server side object. which mapped to the same server side object.
By providing a method to differentiate filehandles, the NFS version 4 By providing a method to differentiate filehandles, the NFS version 4
protocol alleviates a potential functional regression in comparison protocol alleviates a potential functional regression in comparison
with the NFS version 3 protocol. Without this method, caching with the NFS version 3 protocol. Without this method, caching
inconsistencies within the same client could occur and this has not inconsistencies within the same client could occur and this has not
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delegation is recallable, since the circumstances that allowed for delegation is recallable, since the circumstances that allowed for
the delegation are subject to change. In particular, the server may the delegation are subject to change. In particular, the server may
receive a conflicting OPEN from another client, the server must receive a conflicting OPEN from another client, the server must
recall the delegation before deciding whether the OPEN from the other recall the delegation before deciding whether the OPEN from the other
client may be granted. Making a delegation is up to the server and client may be granted. Making a delegation is up to the server and
clients should not assume that any particular OPEN either will or clients should not assume that any particular OPEN either will or
will not result in an open delegation. The following is a typical will not result in an open delegation. The following is a typical
set of conditions that servers might use in deciding whether OPEN set of conditions that servers might use in deciding whether OPEN
should be delegated: should be delegated:
Draft Specification NFS version 4 Protocol October 2002 Draft Specification NFS version 4 Protocol November 2002
o The client must be able to respond to the server's callback o The client must be able to respond to the server's callback
requests. The server will use the CB_NULL procedure for a test requests. The server will use the CB_NULL procedure for a test
of callback ability. of callback ability.
o The client must have responded properly to previous recalls. o The client must have responded properly to previous recalls.
o There must be no current open conflicting with the requested o There must be no current open conflicting with the requested
delegation. delegation.
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When an open delegation is made, the response to the OPEN contains an When an open delegation is made, the response to the OPEN contains an
open delegation structure which specifies the following: open delegation structure which specifies the following:
o the type of delegation (read or write) o the type of delegation (read or write)
o space limitation information to control flushing of data on o space limitation information to control flushing of data on
close (write open delegation only, see the section "Open close (write open delegation only, see the section "Open
Delegation and Data Caching") Delegation and Data Caching")
Draft Specification NFS version 4 Protocol October 2002 Draft Specification NFS version 4 Protocol November 2002
o an nfsace4 specifying read and write permissions o an nfsace4 specifying read and write permissions
o a stateid to represent the delegation for READ and WRITE o a stateid to represent the delegation for READ and WRITE
The delegation stateid is separate and distinct from the stateid for The delegation stateid is separate and distinct from the stateid for
the OPEN proper. The standard stateid, unlike the delegation the OPEN proper. The standard stateid, unlike the delegation
stateid, is associated with a particular lock_owner and will continue stateid, is associated with a particular lock_owner and will continue
to be valid after the delegation is recalled and the file remains to be valid after the delegation is recalled and the file remains
open. open.
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The use of delegation together with various other forms of caching The use of delegation together with various other forms of caching
creates the possibility that no server authentication will ever be creates the possibility that no server authentication will ever be
performed for a given user since all of the user's requests might be performed for a given user since all of the user's requests might be
satisfied locally. Where the client is depending on the server for satisfied locally. Where the client is depending on the server for
authentication, the client should be sure authentication occurs for authentication, the client should be sure authentication occurs for
each user by use of the ACCESS operation. This should be the case each user by use of the ACCESS operation. This should be the case
even if an ACCESS operation would not be required otherwise. As even if an ACCESS operation would not be required otherwise. As
mentioned before, the server may enforce frequent authentication by mentioned before, the server may enforce frequent authentication by
returning an nfsace4 denying all access with every open delegation. returning an nfsace4 denying all access with every open delegation.
Draft Specification NFS version 4 Protocol October 2002 Draft Specification NFS version 4 Protocol November 2002
9.4.1. Open Delegation and Data Caching 9.4.1. Open Delegation and Data Caching
OPEN delegation allows much of the message overhead associated with OPEN delegation allows much of the message overhead associated with
the opening and closing files to be eliminated. An open when an open the opening and closing files to be eliminated. An open when an open
delegation is in effect does not require that a validation message be delegation is in effect does not require that a validation message be
sent to the server. The continued endurance of the "read open sent to the server. The continued endurance of the "read open
delegation" provides a guarantee that no OPEN for write and thus no delegation" provides a guarantee that no OPEN for write and thus no
write has occurred. Similarly, when closing a file opened for write write has occurred. Similarly, when closing a file opened for write
and if write open delegation is in effect, the data written does not and if write open delegation is in effect, the data written does not
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The server can recall delegations as a result of managing the The server can recall delegations as a result of managing the
available filesystem space. The client should abide by the server's available filesystem space. The client should abide by the server's
state space limits for delegations. If the client exceeds the stated state space limits for delegations. If the client exceeds the stated
limits for the delegation, the server's behavior is undefined. limits for the delegation, the server's behavior is undefined.
Based on server conditions, quotas or available filesystem space, the Based on server conditions, quotas or available filesystem space, the
server may grant write open delegations with very restrictive space server may grant write open delegations with very restrictive space
limitations. The limitations may be defined in a way that will limitations. The limitations may be defined in a way that will
always force modified data to be flushed to the server on close. always force modified data to be flushed to the server on close.
Draft Specification NFS version 4 Protocol October 2002 Draft Specification NFS version 4 Protocol November 2002
With respect to authentication, flushing modified data to the server With respect to authentication, flushing modified data to the server
after a CLOSE has occurred may be problematic. For example, the user after a CLOSE has occurred may be problematic. For example, the user
of the application may have logged off the client and unexpired of the application may have logged off the client and unexpired
authentication credentials may not be present. In this case, the authentication credentials may not be present. In this case, the
client may need to take special care to ensure that local unexpired client may need to take special care to ensure that local unexpired
credentials will in fact be available. This may be accomplished by credentials will in fact be available. This may be accomplished by
tracking the expiration time of credentials and flushing data well in tracking the expiration time of credentials and flushing data well in
advance of their expiration or by making private copies of advance of their expiration or by making private copies of
credentials to assure their availability when needed. credentials to assure their availability when needed.
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only needs to know about this modified state. If the server only needs to know about this modified state. If the server
determines that the file is currently modified, it will respond to determines that the file is currently modified, it will respond to
the second client's GETATTR as if the file had been modified locally the second client's GETATTR as if the file had been modified locally
at the server. at the server.
Since the form of the change attribute is determined by the server Since the form of the change attribute is determined by the server
and is opaque to the client, the client and server need to agree on a and is opaque to the client, the client and server need to agree on a
method of communicating the modified state of the file. For the size method of communicating the modified state of the file. For the size
attribute, the client will report its current view of the file size. attribute, the client will report its current view of the file size.
Draft Specification NFS version 4 Protocol October 2002 Draft Specification NFS version 4 Protocol November 2002
For the change attribute, the handling is more involved. For the change attribute, the handling is more involved.
For the client, the following steps will be taken when receiving a For the client, the following steps will be taken when receiving a
write delegation: write delegation:
o The value of the change attribute will be obtained from the o The value of the change attribute will be obtained from the
server and cached. Let this value be represented by c. server and cached. Let this value be represented by c.
o The client will create a value greater than c that will be used o The client will create a value greater than c that will be used
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the delegation. Let this value be represented by sc. the delegation. Let this value be represented by sc.
o When a second client sends a GETATTR operation on the same file o When a second client sends a GETATTR operation on the same file
to the server, the server obtains the change attribute from the to the server, the server obtains the change attribute from the
first client. Let this value be cc. first client. Let this value be cc.
o If the value cc is equal to sc, the file is not modified and the o If the value cc is equal to sc, the file is not modified and the
server returns the current values for change, time_metadata, and server returns the current values for change, time_metadata, and
time_modify (for example) to the second client. time_modify (for example) to the second client.
Draft Specification NFS version 4 Protocol October 2002 Draft Specification NFS version 4 Protocol November 2002
o If the value cc is NOT equal to sc, the file is currently o If the value cc is NOT equal to sc, the file is currently
modified at the first client and most likely will be modified at modified at the first client and most likely will be modified at
the server at a future time. The server then uses its current the server at a future time. The server then uses its current
time to construct attribute values for time_metadata and time to construct attribute values for time_metadata and
time_modify. A new value of sc, which we will call nsc, is time_modify. A new value of sc, which we will call nsc, is
computed by the server, such that nsc >= sc + 1. The server computed by the server, such that nsc >= sc + 1. The server
then returns the constructed time_metadata, time_modify, and nsc then returns the constructed time_metadata, time_modify, and nsc
values to the requester. The server replaces sc in the values to the requester. The server replaces sc in the
delegation record with nsc. To prevent the possibility of delegation record with nsc. To prevent the possibility of
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update sc, time_modify, time_metadata into file's metadata; update sc, time_modify, time_metadata into file's metadata;
} }
return to client (that sent GETATTR) the attributes return to client (that sent GETATTR) the attributes
it requested, but make sure size comes from what it requested, but make sure size comes from what
CB_GETATTR returned. Do not update the file's metadata CB_GETATTR returned. Do not update the file's metadata
with the client's modified size. with the client's modified size.
o In the case that the file attribute size is different than the o In the case that the file attribute size is different than the
Draft Specification NFS version 4 Protocol October 2002 Draft Specification NFS version 4 Protocol November 2002
server's current value, the server treats this as a modification server's current value, the server treats this as a modification
regardless of the value of the change attribute retrieved via regardless of the value of the change attribute retrieved via
CB_GETATTR and responds to the second client as in the last CB_GETATTR and responds to the second client as in the last
step. step.
This methodology resolves issues of clock differences between client This methodology resolves issues of clock differences between client
and server and other scenarios where the use of CB_GETATTR break and server and other scenarios where the use of CB_GETATTR break
down. down.
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delegation voluntarily. The following items of state need to be delegation voluntarily. The following items of state need to be
dealt with: dealt with:
o If the file associated with the delegation is no longer open and o If the file associated with the delegation is no longer open and
no previous CLOSE operation has been sent to the server, a CLOSE no previous CLOSE operation has been sent to the server, a CLOSE
operation must be sent to the server. operation must be sent to the server.
o If a file has other open references at the client, then OPEN o If a file has other open references at the client, then OPEN
operations must be sent to the server. The appropriate stateids operations must be sent to the server. The appropriate stateids
Draft Specification NFS version 4 Protocol October 2002 Draft Specification NFS version 4 Protocol November 2002
will be provided by the server for subsequent use by the client will be provided by the server for subsequent use by the client
since the delegation stateid will not longer be valid. These since the delegation stateid will not longer be valid. These
OPEN requests are done with the claim type of OPEN requests are done with the claim type of
CLAIM_DELEGATE_CUR. This will allow the presentation of the CLAIM_DELEGATE_CUR. This will allow the presentation of the
delegation stateid so that the client can establish the delegation stateid so that the client can establish the
appropriate rights to perform the OPEN. (see the section appropriate rights to perform the OPEN. (see the section
"Operation 18: OPEN" for details.) "Operation 18: OPEN" for details.)
o If there are granted file locks, the corresponding LOCK o If there are granted file locks, the corresponding LOCK
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the actual open state of the file may continue to change makes it not the actual open state of the file may continue to change makes it not
worthwhile to send information about opens and closes to the server, worthwhile to send information about opens and closes to the server,
except as part of delegation return. Only in the case of closing the except as part of delegation return. Only in the case of closing the
open that resulted in obtaining the delegation would clients be open that resulted in obtaining the delegation would clients be
likely to do this early, since, in that case, the close once done likely to do this early, since, in that case, the close once done
will not be undone. Regardless of the client's choices on scheduling will not be undone. Regardless of the client's choices on scheduling
these actions, all must be performed before the delegation is these actions, all must be performed before the delegation is
returned, including (when applicable) the close that corresponds to returned, including (when applicable) the close that corresponds to
the open that resulted in the delegation. These actions can be the open that resulted in the delegation. These actions can be
Draft Specification NFS version 4 Protocol October 2002 Draft Specification NFS version 4 Protocol November 2002
performed either in previous requests or in previous operations in performed either in previous requests or in previous operations in
the same COMPOUND request. the same COMPOUND request.
9.4.5. Clients that Fail to Honor Delegation Recalls 9.4.5. Clients that Fail to Honor Delegation Recalls
A client may fail to respond to a recall for various reasons, such as A client may fail to respond to a recall for various reasons, such as
a failure of the callback path from server to the client. The client a failure of the callback path from server to the client. The client
may be unaware of a failure in the callback path. This lack of may be unaware of a failure in the callback path. This lack of
awareness could result in the client finding out long after the awareness could result in the client finding out long after the
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except for RENEW, that take a stateid, to renew delegation leases except for RENEW, that take a stateid, to renew delegation leases
across callback path failures. The client that wants to keep across callback path failures. The client that wants to keep
delegations in force across callback path failures must use RENEW delegations in force across callback path failures must use RENEW
to do so. to do so.
9.4.6. Delegation Revocation 9.4.6. Delegation Revocation
At the point a delegation is revoked, if there are associated opens At the point a delegation is revoked, if there are associated opens
on the client, the applications holding these opens need to be on the client, the applications holding these opens need to be
Draft Specification NFS version 4 Protocol October 2002 Draft Specification NFS version 4 Protocol November 2002
notified. This notification usually occurs by returning errors for notified. This notification usually occurs by returning errors for
READ/WRITE operations or when a close is attempted for the open file. READ/WRITE operations or when a close is attempted for the open file.
If no opens exist for the file at the point the delegation is If no opens exist for the file at the point the delegation is
revoked, then notification of the revocation is unnecessary. revoked, then notification of the revocation is unnecessary.
However, if there is modified data present at the client for the However, if there is modified data present at the client for the
file, the user of the application should be notified. Unfortunately, file, the user of the application should be notified. Unfortunately,
it may not be possible to notify the user since active applications it may not be possible to notify the user since active applications
may not be present at the client. See the section "Revocation may not be present at the client. See the section "Revocation
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9.5.1. Revocation Recovery for Write Open Delegation 9.5.1. Revocation Recovery for Write Open Delegation
Revocation recovery for a write open delegation poses the special Revocation recovery for a write open delegation poses the special
issue of modified data in the client cache while the file is not issue of modified data in the client cache while the file is not
open. In this situation, any client which does not flush modified open. In this situation, any client which does not flush modified
data to the server on each close must ensure that the user receives data to the server on each close must ensure that the user receives
appropriate notification of the failure as a result of the appropriate notification of the failure as a result of the
revocation. Since such situations may require human action to revocation. Since such situations may require human action to
correct problems, notification schemes in which the appropriate user correct problems, notification schemes in which the appropriate user
Draft Specification NFS version 4 Protocol October 2002 Draft Specification NFS version 4 Protocol November 2002
or administrator is notified may be necessary. Logging and console or administrator is notified may be necessary. Logging and console
messages are typical examples. messages are typical examples.
If there is modified data on the client, it must not be flushed If there is modified data on the client, it must not be flushed
normally to the server. A client may attempt to provide a copy of normally to the server. A client may attempt to provide a copy of
the file data as modified during the delegation under a different the file data as modified during the delegation under a different
name in the filesystem name space to ease recovery. Note that when name in the filesystem name space to ease recovery. Note that when
the client can determine that the file has not been modified by any the client can determine that the file has not been modified by any
other client, or when the client has a complete cached copy of file other client, or when the client has a complete cached copy of file
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immediately reflected on the server. Normally such changes are not immediately reflected on the server. Normally such changes are not
propagated directly to the server but when the modified data is propagated directly to the server but when the modified data is
flushed to the server, analogous attribute changes are made on the flushed to the server, analogous attribute changes are made on the
server. When open delegation is in effect, the modified attributes server. When open delegation is in effect, the modified attributes
may be returned to the server in the response to a CB_RECALL call. may be returned to the server in the response to a CB_RECALL call.
The result of local caching of attributes is that the attribute The result of local caching of attributes is that the attribute
caches maintained on individual clients will not be coherent. Changes caches maintained on individual clients will not be coherent. Changes
made in one order on the server may be seen in a different order on made in one order on the server may be seen in a different order on
Draft Specification NFS version 4 Protocol October 2002 Draft Specification NFS version 4 Protocol November 2002
one client and in a third order on a different client. one client and in a third order on a different client.
The typical filesystem application programming interfaces do not The typical filesystem application programming interfaces do not
provide means to atomically modify or interrogate attributes for provide means to atomically modify or interrogate attributes for
multiple files at the same time. The following rules provide an multiple files at the same time. The following rules provide an
environment where the potential incoherences mentioned above can be environment where the potential incoherences mentioned above can be
reasonably managed. These rules are derived from the practice of reasonably managed. These rules are derived from the practice of
previous NFS protocols. previous NFS protocols.
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attribute changes are immediately sent to the server. attribute changes are immediately sent to the server.
In some operating environments, the equivalent to time_access is In some operating environments, the equivalent to time_access is
expected to be implicitly updated by each read of the content of the expected to be implicitly updated by each read of the content of the
file object. If an NFS client is caching the content of a file file object. If an NFS client is caching the content of a file
object, whether it is a regular file, directory, or symbolic link, object, whether it is a regular file, directory, or symbolic link,
the client SHOULD NOT update the time_access attribute (via SETATTR the client SHOULD NOT update the time_access attribute (via SETATTR
or a small READ or READDIR request) on the server with each read that or a small READ or READDIR request) on the server with each read that
is satisfied from cache. The reason is that this can defeat the is satisfied from cache. The reason is that this can defeat the
Draft Specification NFS version 4 Protocol October 2002 Draft Specification NFS version 4 Protocol November 2002
performance benefits of caching content, especially since an explicit performance benefits of caching content, especially since an explicit
SETATTR of time_access may alter the change attribute on the server. SETATTR of time_access may alter the change attribute on the server.
If the change attribute changes, clients that are caching the content If the change attribute changes, clients that are caching the content
will think the content has changed, and will re-read unmodified data will think the content has changed, and will re-read unmodified data
from the server. Nor is the client encouraged to maintain a modified from the server. Nor is the client encouraged to maintain a modified
version of time_access in its cache, since this would mean that the version of time_access in its cache, since this would mean that the
client will either eventually have to write the access time to the client will either eventually have to write the access time to the
server with bad performance effects, or it would never update the server with bad performance effects, or it would never update the
server's time_access, thereby resulting in a situation where an server's time_access, thereby resulting in a situation where an
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the application to always get the most up to date data and the application to always get the most up to date data and
metadata for the file. However, due to the negative performance metadata for the file. However, due to the negative performance
implications of this, such behavior is OPTIONAL. implications of this, such behavior is OPTIONAL.
o If the memory mapped file is not being modified on the server, o If the memory mapped file is not being modified on the server,
and instead is just being read by an application via the memory and instead is just being read by an application via the memory
mapped interface, the client will not see an updated time_access mapped interface, the client will not see an updated time_access
attribute. However, in many operating environments, neither attribute. However, in many operating environments, neither
will any process running on the server. Thus NFS clients are at will any process running on the server. Thus NFS clients are at
Draft Specification NFS version 4 Protocol October 2002 Draft Specification NFS version 4 Protocol November 2002
no disadvantage with respect to local processes. no disadvantage with respect to local processes.
o If there is another client that is memory mapping the file, and o If there is another client that is memory mapping the file, and
if that client is holding a write delegation, the same set of if that client is holding a write delegation, the same set of
issues as discussed in the previous two bullet items apply. So, issues as discussed in the previous two bullet items apply. So,
when a server does a CB_GETATTR to a file that the client has when a server does a CB_GETATTR to a file that the client has
modified in its cache, the response from CB_GETATTR will not modified in its cache, the response from CB_GETATTR will not
necessarily be accurate. As discussed earlier, the client's necessarily be accurate. As discussed earlier, the client's
obligation is to report that the file has been modified since obligation is to report that the file has been modified since
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write to the server that portion of the page that is locked. write to the server that portion of the page that is locked.
For example, if client A simply writes out the page, and then For example, if client A simply writes out the page, and then
client B writes out the page, client A's data is lost. client B writes out the page, client A's data is lost.
Moreover, if mandatory locking is enabled on the file, then we Moreover, if mandatory locking is enabled on the file, then we
have a different problem. When clients A and B issue the STORE have a different problem. When clients A and B issue the STORE
instructions, the resulting page faults require a record lock on instructions, the resulting page faults require a record lock on
the entire page. Each client then tries to extend their locked the entire page. Each client then tries to extend their locked
range to the entire page, which results in a deadlock. range to the entire page, which results in a deadlock.
Draft Specification NFS version 4 Protocol October 2002 Draft Specification NFS version 4 Protocol November 2002
Communicating the NFS4ERR_DEADLOCK error to a STORE instruction Communicating the NFS4ERR_DEADLOCK error to a STORE instruction
is difficult at best. is difficult at best.
If a client is locking the entire memory mapped file, there is If a client is locking the entire memory mapped file, there is
no problem with advisory or mandatory record locking, at least no problem with advisory or mandatory record locking, at least
until the client unlocks a region in the middle of the file. until the client unlocks a region in the middle of the file.
Given the above issues the following are permitted: Given the above issues the following are permitted:
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other clients. It does this by using the change attribute as other clients. It does this by using the change attribute as
reported before and after the directory operation in the associated reported before and after the directory operation in the associated
change_info4 value returned for the operation. The server is able to change_info4 value returned for the operation. The server is able to
communicate to the client whether the change_info4 data is provided communicate to the client whether the change_info4 data is provided
atomically with respect to the directory operation. If the change atomically with respect to the directory operation. If the change
values are provided atomically, the client is then able to compare values are provided atomically, the client is then able to compare
the pre-operation change value with the change value in the client's the pre-operation change value with the change value in the client's
name cache. If the comparison indicates that the directory was name cache. If the comparison indicates that the directory was
updated by another client, the name cache associated with the updated by another client, the name cache associated with the
Draft Specification NFS version 4 Protocol October 2002 Draft Specification NFS version 4 Protocol November 2002
modified directory is purged from the client. If the comparison modified directory is purged from the client. If the comparison
indicates no modification, the name cache can be updated on the indicates no modification, the name cache can be updated on the
client to reflect the directory operation and the associated timeout client to reflect the directory operation and the associated timeout
extended. The post-operation change value needs to be saved as the extended. The post-operation change value needs to be saved as the
basis for future change_info4 comparisons. basis for future change_info4 comparisons.
As demonstrated by the scenario above, name caching requires that the As demonstrated by the scenario above, name caching requires that the
client revalidate name cache data by inspecting the change attribute client revalidate name cache data by inspecting the change attribute
of a directory at the point when the name cache item was cached. of a directory at the point when the name cache item was cached.
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is adequate. The lifetime of the cache entry can be extended at is adequate. The lifetime of the cache entry can be extended at
these checkpoints. When a client is modifying the directory, the these checkpoints. When a client is modifying the directory, the
client needs to use the change_info4 data to determine whether there client needs to use the change_info4 data to determine whether there
are other clients modifying the directory. If it is determined that are other clients modifying the directory. If it is determined that
no other client modifications are occurring, the client may update no other client modifications are occurring, the client may update
its directory cache to reflect its own changes. its directory cache to reflect its own changes.
As demonstrated previously, directory caching requires that the As demonstrated previously, directory caching requires that the
client revalidate directory cache data by inspecting the change client revalidate directory cache data by inspecting the change
Draft Specification NFS version 4 Protocol October 2002 Draft Specification NFS version 4 Protocol November 2002
attribute of a directory at the point when the directory was cached. attribute of a directory at the point when the directory was cached.
This requires that the server update the change attribute for This requires that the server update the change attribute for
directories when the contents of the corresponding directory is directories when the contents of the corresponding directory is
modified. For a client to use the change_info4 information modified. For a client to use the change_info4 information
appropriately and correctly, the server must report the pre and post appropriately and correctly, the server must report the pre and post
operation change attribute values atomically. When the server is operation change attribute values atomically. When the server is
unable to report the before and after values atomically with respect unable to report the before and after values atomically with respect
to the directory operation, the server must indicate that fact in the to the directory operation, the server must indicate that fact in the
change_info4 return value. When the information is not atomically change_info4 return value. When the information is not atomically
reported, the client should not assume that other clients have not reported, the client should not assume that other clients have not
changed the directory. changed the directory.
Draft Specification NFS version 4 Protocol October 2002 Draft Specification NFS version 4 Protocol November 2002
10. Minor Versioning 10. Minor Versioning
To address the requirement of an NFS protocol that can evolve as the To address the requirement of an NFS protocol that can evolve as the
need arises, the NFS version 4 protocol contains the rules and need arises, the NFS version 4 protocol contains the rules and
framework to allow for future minor changes or versioning. framework to allow for future minor changes or versioning.
The base assumption with respect to minor versioning is that any The base assumption with respect to minor versioning is that any
future accepted minor version must follow the IETF process and be future accepted minor version must follow the IETF process and be
documented in a standards track RFC. Therefore, each minor version documented in a standards track RFC. Therefore, each minor version
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documented attribute. documented attribute.
Since attribute results are specified as an opaque array of Since attribute results are specified as an opaque array of
per-attribute XDR encoded results, the complexity of adding new per-attribute XDR encoded results, the complexity of adding new
attributes in the midst of the current definitions will be too attributes in the midst of the current definitions will be too
burdensome. burdensome.
3 Minor versions must not modify the structure of an existing 3 Minor versions must not modify the structure of an existing
operation's arguments or results. operation's arguments or results.
Draft Specification NFS version 4 Protocol October 2002 Draft Specification NFS version 4 Protocol November 2002
Again the complexity of handling multiple structure definitions Again the complexity of handling multiple structure definitions
for a single operation is too burdensome. New operations should for a single operation is too burdensome. New operations should
be added instead of modifying existing structures for a minor be added instead of modifying existing structures for a minor
version. version.
This rule does not preclude the following adaptations in a minor This rule does not preclude the following adaptations in a minor
version. version.
o adding bits to flag fields such as new attributes to o adding bits to flag fields such as new attributes to
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the request as an XDR decode error. This approach allows for the request as an XDR decode error. This approach allows for
the obsolescence of an operation while maintaining its structure the obsolescence of an operation while maintaining its structure
so that a future minor version can reintroduce the operation. so that a future minor version can reintroduce the operation.
8.1 Minor versions may declare attributes mandatory to NOT 8.1 Minor versions may declare attributes mandatory to NOT
implement. implement.
8.2 Minor versions may declare flag bits or enumeration values as 8.2 Minor versions may declare flag bits or enumeration values as
mandatory to NOT implement. mandatory to NOT implement.
Draft Specification NFS version 4 Protocol October 2002 Draft Specification NFS version 4 Protocol November 2002
9 Minor versions may downgrade features from mandatory to 9 Minor versions may downgrade features from mandatory to
recommended, or recommended to optional. recommended, or recommended to optional.
10 Minor versions may upgrade features from optional to recommended 10 Minor versions may upgrade features from optional to recommended
or recommended to mandatory. or recommended to mandatory.
11 A client and server that support minor version X must support 11 A client and server that support minor version X must support
minor versions 0 (zero) through X-1 as well. minor versions 0 (zero) through X-1 as well.
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This rule allows for the introduction of new functionality and This rule allows for the introduction of new functionality and
forces the use of implementation experience before designating a forces the use of implementation experience before designating a
feature as mandatory. feature as mandatory.
13 A client MUST NOT attempt to use a stateid, filehandle, or 13 A client MUST NOT attempt to use a stateid, filehandle, or
similar returned object from the COMPOUND procedure with minor similar returned object from the COMPOUND procedure with minor
version X for another COMPOUND procedure with minor version Y, version X for another COMPOUND procedure with minor version Y,
where X != Y. where X != Y.
Draft Specification NFS version 4 Protocol October 2002 Draft Specification NFS version 4 Protocol November 2002
11. Internationalization 11. Internationalization
The primary issue in which NFS needs to deal with The primary issue in which NFS version 4 needs to deal with
internationalization, or I18N, is with respect to file names and internationalization, or I18N, is with respect to file names and
other strings as used within the protocol. The choice of string other strings as used within the protocol. The choice of string
representation must allow reasonable name/string access to clients representation must allow reasonable name/string access to clients
which use various languages. The UTF-8 encoding of the UCS as which use various languages. The UTF-8 encoding of the UCS as
defined by [ISO10646] allows for this type of access and follows the defined by [ISO10646] allows for this type of access and follows the
policy described in "IETF Policy on Character Sets and Languages", policy described in "IETF Policy on Character Sets and Languages",
[RFC2277]. This choice is explained further in the following. [RFC2277].
11.1. Universal Versus Local Character Sets [RFC-XXX-stringprep-XXX], otherwise know as "stringprep", documents a
framework for using Unicode/UTF-8 in networking protocols, so as "to
increase the likelihood that string input and string comparison work
in ways that make sense for typical users throughout the world." A
protocol must define a profile of stringprep "in order to fully
specify the processing options." The remainder of this
Internationalization section defines the NFS version 4 stringprep
profiles. Much of terminology used for the remainder of this section
comes from stringprep.
[RFC1345] describes a table of 16 bit characters for many different There are three UTF-8 string types defined for NFS version 4:
languages (the bit encodings match Unicode, though of course utf8str_cs, utf8str_cis, and utf8str_mixed. Separate profiles are
[RFC1345] is somewhat out of date with respect to current Unicode defined for each. Each profile defines the following, as required by
assignments). Each character from each language has a unique 16 bit stringprep:
value in the 16 bit character set. Thus this table can be thought of
as a universal character set. [RFC1345] then talks about groupings
of subsets of the entire 16 bit character set into "Charset Tables".
For example one might take all the Greek characters from the 16 bit
table (which are consecutively allocated), and normalize their
offsets to a table that fits in 7 bits. Thus it is determined that
"lower case alpha" is in the same position as "upper case a" in the
US-ASCII table, and "upper case alpha" is in the same position as
"lower case a" in the US-ASCII table.
These normalized subset character sets can be thought of as "local o The intended applicability of the profile
character sets", suitable for an operating system locale.
Local character sets are not suitable for the NFS protocol. Consider o The character repertoire that is the input and output to
someone who creates a file with a name in a Swedish character set. stringprep (which is Unicode 3.2 for referenced version of
If someone else later goes to access the file with their locale set stringprep)
to the Swedish language, then there are no problems. But if someone
in say the US-ASCII locale goes to access the file, the file name
will look very different, because the Swedish characters in the 7 bit
table will now be represented in US-ASCII characters on the display.
It would be preferable to give the US-ASCII user a way to display the
file name using Swedish glyphs. In order to do that, the NFS protocol
would have to include the locale with the file name on each operation
to create a file.
However, the complexity burden of defining such locales in a way that o The mapping tables from stringprep used (as described in section
could be understood by all clients and servers, and maintaining them 3 of stringprep)
in the face of changes would be considerable. A better solution is
desirable.
If the NFS version 4 protocol used a universal 16 bit or 32 bit o Any additional mapping tables specific to the profile
character set (or an encoding of a 16 bit or 32 bit character set
into octets), then the server and client need not care if the locale
of the user accessing the file is different than the locale of the
user who created the file. The unique 16 bit or 32 bit encoding of
Draft Specification NFS version 4 Protocol October 2002 o The Unicode normalization used, if any (as described in section
4 of stringprep)
the character allows for determination of what language the character o The tables from stringprep listing of characters that are
is from and also how to display that character on the client. The prohibited as output (as described in section 5 of stringprep)
server need not know what locales are used.
11.2. Overview of Universal Character Set Standards o The bidirectional string testing used, if any (as described in
section 6 of stringprep)
The previous section makes a case for using a universal character o Any additional characters that are prohibited as output specific
set. This section makes the case for using UTF-8 as the specific to the profile
universal character set for the NFS version 4 protocol.
[RFC2279] discusses UTF-* (UTF-8 and other UTF-XXX encodings), Stringprep discusses Unicode characters, whereas NFS version 4
Unicode, and UCS-*. There are two standards bodies managing renders UTF-8 characters. Since there is a one to one mapping from
universal code sets: UTF-8 to Unicode, where ever the remainder of this document refers to
o ISO/IEC which has the standard 10646-1 Draft Specification NFS version 4 Protocol November 2002
o Unicode which has the Unicode standard to Unicode, the reader should assume UTF-8.
Both standards bodies have pledged to track each other's assignments Much of the text for the profiles comes from [RFC-XXX-nameprep-XXX].
of character codes.
The following is a brief analysis of the various standards. 11.1. Stringprep profile for the utf8str_cs type
UCS Universal Character Set. This is ISO/IEC 10646-1: "a Every use of the utf8str_cs type definition in the NFS version 4
multi-octet character set called the Universal Character protocol specification follows the profile named nfs4_cs_prep.
Set (UCS), which encompasses most of the world's writing
systems."
UCS-2 a two octet per character encoding that addresses the first 11.1.1. Intended applicability of the nfs4_cs_prep profile
2^16 characters of UCS. Currently there are no UCS
characters beyond that range.
UCS-4 a four octet per character encoding that permits the The utf8str_cs type is a case sensitive string of UTF-8 characters.
encoding of up to 2^31 characters. Its primary use in NFS Version 4 is for naming components and
pathnames. Components and pathnames are stored on the server's
filesystem. Two valid distinct UTF-8 strings might be the same after
processing via the utf8str_cs profile. If the strings are two names
inside a directory, the NFS version 4 server will need to either:
UTF UTF is an abbreviation of the term "UCS transformation o disallow the creation of a second name if it's post processed
format" and is used in the naming of various standards for form collides with that of an existing name, or
encoding of UCS characters as described below.
UTF-1 Only historical interest; it has been removed from 10646-1 o allow the creation of the second name, but arrange so that after
post processing, the second name is different than the post
processed form of the first name.
UTF-7 Encodes the entire "repertoire" of UCS "characters using 11.1.2. Character repertoire of nfs4_cs_prep
only octets with the higher order bit clear". [RFC2152]
describes UTF-7. UTF-7 accomplishes this by reserving one
of the 7bit US-ASCII characters as a "shift" character to
indicate non-US-ASCII characters.
Draft Specification NFS version 4 Protocol October 2002 The nfs4_cs_prep profile uses Unicode 3.2, as defined in stringprep's
Appendix A.1
UTF-8 Unlike UTF-7, uses all 8 bits of the octets. US-ASCII 11.1.3. Mapping used by nfs4_cs_prep
characters are encoded as before unchanged. Any octet with
the high bit cleared can only mean a US-ASCII character.
The high bit set means that a UCS character is being
encoded.
UTF-16 Encodes UCS-4 characters into UCS-2 characters using a The nfs4_cs_prep profile specifies mapping using the following tables
reserved range in UCS-2. from stringprep:
Unicode Unicode and UCS-2 are the same; [RFC2279] states: Table B.1
Up to the present time, changes in Unicode and amendments Table B.2 is normally not part of the nfs4_cs_prep profile as it is
to ISO/IEC 10646 have tracked each other, so that the primarily for dealing with case-insensitive comparisons. However, if
character repertoires and code point assignments have the NFS version 4 file server supports the case_insensitive
remained in sync. The relevant standardization committees filesystem attribute, and if case_insensitive is true, the NFS
have committed to maintain this very useful synchronism. version 4 server MUST use Table B.2 (in addition to Table B1) when
processing utf8str_cs strings, and the NFS version 4 client MUST
assume Table B.2 (in addition to Table B.1) are being used.
11.3. Difficulties with UCS-4, UCS-2, Unicode If the case_preserving attribute is present and set to false, then
the NFS version 4 server MUST use table B.2 to map case when
processing utf8str_cs strings. Whether the server maps from lower to
upper case or the upper to lower case is an implementation
dependency.
Adapting existing applications, and filesystems to multi-octet Draft Specification NFS version 4 Protocol November 2002
schemes like UCS and Unicode can be difficult. A significant amount
of code has been written to process streams of bytes. Also there are
many existing stored objects described with 7 bit or 8 bit
characters. Doubling or quadrupling the bandwidth and storage
requirements seems like an expensive way to accomplish I18N.
UCS-2 and Unicode are "only" 16 bits long. That might seem to be 11.1.4. Normalization used by nfs4_cs_prep
enough but, according to [Unicode1], 49,194 Unicode characters are
already assigned. According to [Unicode2] there are still more
languages that need to be added.
11.4. UTF-8 and its solutions The nfs4_cs_prep profile does not specify a normalization form. A
later revision of this specification may specify a particular
normalization form. Therefore, the server and client can expect that
they may receive unnormalized characters within protocol requests and
responses. If the operating environment requires normalization, then
the implementation must normalize utf8str_cs strings within the
protocol before presenting the information to an application (at the
client) or local filesystem (at the server).
UTF-8 solves problems for NFS that exist with the use of UCS and 11.1.5. Prohibited output for nfs4_cs_prep
Unicode. UTF-8 will encode 16 bit and 32 bit characters in a way
that will be compact for most users. The encoding table from UCS-4 to
UTF-8, as copied from [RFC2279]:
UCS-4 range (hex.) UTF-8 octet sequence (binary) The nfs4_cs_prep profile specifies prohibiting using the following
0000 0000-0000 007F 0xxxxxxx tables from stringprep:
0000 0080-0000 07FF 110xxxxx 10xxxxxx
0000 0800-0000 FFFF 1110xxxx 10xxxxxx 10xxxxxx
0001 0000-001F FFFF 11110xxx 10xxxxxx 10xxxxxx 10xxxxxx Table C.3
0020 0000-03FF FFFF 111110xx 10xxxxxx 10xxxxxx 10xxxxxx 10xxxxxx Table C.4
0400 0000-7FFF FFFF 1111110x 10xxxxxx 10xxxxxx 10xxxxxx 10xxxxxx Table C.5
10xxxxxx Table C.6
Table C.7
Table C.8
Table C.9
See [RFC2279] for precise encoding and decoding rules. Note because 11.1.6. Bidirectional output for nfs4_cs_prep
Draft Specification NFS version 4 Protocol October 2002 The nfs4_cs_prep profile does not specify any checking of
bidirectional strings.
of UTF-16, the algorithm from Unicode/UCS-2 to UTF-8 needs to account 11.2. Stringprep profile for the utf8str_cis type
for the reserved range between D800 and DFFF.
Note that the 16 bit UCS or Unicode characters require no more than 3 Every use of the utf8str_cis type definition in the NFS version 4
octets to encode into UTF-8 protocol specification follows the profile named nfs4_cis_prep.
Interestingly, UTF-8 has room to handle characters larger than 31 11.2.1. Intended applicability of the nfs4_cis_prep profile
bits, because the leading octet of form:
1111111x The utf8str_cis type is a case insensitive string of UTF-8
characters. Its primary use in NFS Version 4 is for naming NFS
servers.
is not defined. If needed, ISO could either use that octet to 11.2.2. Character repertoire of nfs4_cis_prep
indicate a sequence of an encoded 8 octet character, or perhaps use
11111110 to permit the next octet to indicate an even more expandable
character set.
So using UTF-8 to represent character encodings means never having to The nfs4_cis_prep profile uses Unicode 3.2, as defined in
run out of room. stringprep's Appendix A.1
11.5. Normalization 11.2.3. Mapping used by nfs4_cis_prep
The client and server operating environments may differ in their The nfs4_cis_prep profile specifies mapping using the following
policies and operational methods with respect to character tables from stringprep:
normalization (See [Unicode1] for a discussion of normalization
forms). This difference may also exist between applications on the
same client. This adds to the difficulty of providing a single
normalization policy for the protocol that allows for maximal
interoperability. This issue is similar to the character case issues
where the server may or may not support case insensitive file name
matching and may or may not preserve the character case when storing
file names. The protocol does not mandate a particular behavior but
allows for the various permutations.
The NFS version 4 protocol does not mandate the use of a particular Table B.1
normalization form at this time. A later revision of this Table B.2
specification may specify a particular normalization form.
Therefore, the server and client can expect that they may receive
unnormalized characters within protocol requests and responses. If
the operating environment requires normalization, then the
implementation must normalize the various UTF-8 encoded strings
within the protocol before presenting the information to an
application (at the client) or local filesystem (at the server).
11.6. UTF-8 Related Errors Draft Specification NFS version 4 Protocol November 2002
11.2.4. Normalization used by nfs4_cis_prep
The nfs4_cis_prep profile specifies using Unicode normalization form
KC, as described in stringprep.
11.2.5. Prohibited output for nfs4_cis_prep
The nfs4_cis_prep profile specifies prohibiting using the following
tables from stringprep:
Table C.1.2
Table C.2.2
Table C.3
Table C.4
Table C.5
Table C.6
Table C.7
Table C.8
Table C.9
11.2.6. Bidirectional output for nfs4_cis_prep
The nfs4_cis_prep profile specifies checking bidirectional strings as
described in stringprep's section 6.
11.3. Stringprep profile for the utf8str_mixed type
Every use of the utf8str_mixed type definition in the NFS version 4
protocol specification follows the profile named nfs4_mixed_prep.
11.3.1. Intended applicability of the nfs4_mixed_prep profile
The utf8str_mixed type is a string of UTF-8 characters, with a prefix
that is case sensitive, a separator equal to '@', and a suffix that
is fully qualified domain name. Its primary use in NFS Version 4 is
for naming principals identified in an Access Control Entry.
11.3.2. Character repertoire of nfs4_mixed_prep
The nfs4_mixed_prep profile uses Unicode 3.2, as defined in
stringprep's Appendix A.1
11.3.3. Mapping used by nfs4_cis_prep
For the prefix and the separator of a utf8str_mixed string, the
nfs4_mixed_prep profile specifies mapping using the following table
from stringprep:
Table B.1
For the suffix of a utf8str_mixed string, the nfs4_mixed_prep profile
Draft Specification NFS version 4 Protocol November 2002
specifies mapping using the following tables from stringprep:
Table B.1
Table B.2
11.3.4. Normalization used by nfs4_mixed_prep
The nfs4_mixed_prep profile specifies using Unicode normalization
form KC, as described in stringprep.
11.3.5. Prohibited output for nfs4_mixed_prep
The nfs4_mixed_prep profile specifies prohibiting using the following
tables from stringprep:
Table C.1.2
Table C.2.2
Table C.3
Table C.4
Table C.5
Table C.6
Table C.7
Table C.8
Table C.9
11.3.6. Bidirectional output for nfs4_mixed_prep
The nfs4_mixed_prep profile specifies checking bidirectional strings
as described in stringprep's section 6.
11.4. UTF-8 Related Errors
Where the client sends an invalid UTF-8 string, the server should Where the client sends an invalid UTF-8 string, the server should
return an NFS4ERR_INVAL error. This includes cases in which return an NFS4ERR_INVAL error. This includes cases in which
inappropriate prefixes are detected and where the count includes inappropriate prefixes are detected and where the count includes
trailing bytes that do not constitute a full UCS character. trailing bytes that do not constitute a full UCS character.
Where the client supplied string is valid UTF-8 but contains Where the client supplied string is valid UTF-8 but contains
Draft Specification NFS version 4 Protocol October 2002
characters that are not supported by the server as a value for that characters that are not supported by the server as a value for that
string (e.g. names containing characters that have more than two string (e.g. names containing characters that have more than two
octets on a filesystem that supports Unicode characters only), the octets on a filesystem that supports Unicode characters only), the
server should return an NFS4ERR_BADCHAR error. server should return an NFS4ERR_BADCHAR error.
Where a UTF-8 string is used as a file name, and the filesystem, Where a UTF-8 string is used as a file name, and the filesystem,
while supporting all of the characters within the name, does not while supporting all of the characters within the name, does not
allow that particular name to be used, the error should return the allow that particular name to be used, the server should return the
error NFS4ERR_BADNAME. This includes situations in which the server error NFS4ERR_BADNAME. This includes situations in which the server
filesystem imposes a normalization constraint on name strings, but filesystem imposes a normalization constraint on name strings, but
will also include such situations as filesystem prohibitions of "." will also include such situations as filesystem prohibitions of "."
and ".." as file names for certain operations, and other such and ".." as file names for certain operations, and other such
constraints. constraints.
Draft Specification NFS version 4 Protocol October 2002 Draft Specification NFS version 4 Protocol November 2002
12. Error Definitions 12. Error Definitions
NFS error numbers are assigned to failed operations within a compound NFS error numbers are assigned to failed operations within a compound
request. A compound request contains a number of NFS operations that request. A compound request contains a number of NFS operations that
have their results encoded in sequence in a compound reply. The have their results encoded in sequence in a compound reply. The
results of successful operations will consist of an NFS4_OK status results of successful operations will consist of an NFS4_OK status
followed by the encoded results of the operation. If an NFS followed by the encoded results of the operation. If an NFS
operation fails, an error status will be entered in the reply and the operation fails, an error status will be entered in the reply and the
compound request will be terminated. compound request will be terminated.
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valid name for current operation. valid name for current operation.
NFS4ERR_BADOWNER An owner, owner_group, or ACL attribute value NFS4ERR_BADOWNER An owner, owner_group, or ACL attribute value
can not be translated to local representation. can not be translated to local representation.
NFS4ERR_BADTYPE An attempt was made to create an object of a NFS4ERR_BADTYPE An attempt was made to create an object of a
type not supported by the server. type not supported by the server.
NFS4ERR_BAD_RANGE The range for a LOCK, LOCKT, or LOCKU operation NFS4ERR_BAD_RANGE The range for a LOCK, LOCKT, or LOCKU operation
Draft Specification NFS version 4 Protocol October 2002 Draft Specification NFS version 4 Protocol November 2002
is not appropriate to the allowable range of is not appropriate to the allowable range of
offsets for the server. offsets for the server.
NFS4ERR_BAD_SEQID The sequence number in a locking request is NFS4ERR_BAD_SEQID The sequence number in a locking request is
neither the next expected number or the last neither the next expected number or the last
number processed. number processed.
NFS4ERR_BAD_STATEID A stateid generated by the current server NFS4ERR_BAD_STATEID A stateid generated by the current server
instance, but which does not designate any instance, but which does not designate any
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exceeded. exceeded.
NFS4ERR_EXIST File exists. The file specified already exists. NFS4ERR_EXIST File exists. The file specified already exists.
NFS4ERR_EXPIRED A lease has expired that is being used in the NFS4ERR_EXPIRED A lease has expired that is being used in the
current operation. current operation.
NFS4ERR_FBIG File too large. The operation would have caused NFS4ERR_FBIG File too large. The operation would have caused
a file to grow beyond the server's limit. a file to grow beyond the server's limit.
Draft Specification NFS version 4 Protocol October 2002 Draft Specification NFS version 4 Protocol November 2002
NFS4ERR_FHEXPIRED The filehandle provided is volatile and has NFS4ERR_FHEXPIRED The filehandle provided is volatile and has
expired at the server. expired at the server.
NFS4ERR_FILE_OPEN The operation can not be successfully processed NFS4ERR_FILE_OPEN The operation can not be successfully processed
because a file involved in the operation is because a file involved in the operation is
currently open. currently open.
NFS4ERR_GRACE The server is in its recovery or grace period NFS4ERR_GRACE The server is in its recovery or grace period
which should match the lease period of the which should match the lease period of the
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The server has received a request that The server has received a request that
specifies an unsupported minor version. The specifies an unsupported minor version. The
server must return a COMPOUND4res with a zero server must return a COMPOUND4res with a zero
length operations result array. length operations result array.
NFS4ERR_MLINK Too many hard links. NFS4ERR_MLINK Too many hard links.
NFS4ERR_MOVED The filesystem which contains the current NFS4ERR_MOVED The filesystem which contains the current
filehandle object has been relocated or filehandle object has been relocated or
Draft Specification NFS version 4 Protocol October 2002 Draft Specification NFS version 4 Protocol November 2002
migrated to another server. The client may migrated to another server. The client may
obtain the new filesystem location by obtaining obtain the new filesystem location by obtaining
the "fs_locations" attribute for the current the "fs_locations" attribute for the current
filehandle. For further discussion, refer to filehandle. For further discussion, refer to
the section "Filesystem Migration or the section "Filesystem Migration or
Relocation". Relocation".
NFS4ERR_NAMETOOLONG The filename in an operation was too long. NFS4ERR_NAMETOOLONG The filename in an operation was too long.
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NFS4ERR_OLD_STATEID A stateid which designates the locking state NFS4ERR_OLD_STATEID A stateid which designates the locking state
for a lockowner-file at an earlier time was for a lockowner-file at an earlier time was
used. used.
NFS4ERR_OPENMODE The client attempted a READ, WRITE, LOCK or NFS4ERR_OPENMODE The client attempted a READ, WRITE, LOCK or
SETATTR operation not sanctioned by the stateid SETATTR operation not sanctioned by the stateid
passed (e.g. writing to a file opened only for passed (e.g. writing to a file opened only for
read). read).
Draft Specification NFS version 4 Protocol October 2002 Draft Specification NFS version 4 Protocol November 2002
NFS4ERR_OP_ILLEGAL An illegal operation value has been specified NFS4ERR_OP_ILLEGAL An illegal operation value has been specified
in the argop field of a COMPOUND or CB_COMPOUND in the argop field of a COMPOUND or CB_COMPOUND
procedure. procedure.
NFS4ERR_PERM Not owner. The operation was not allowed NFS4ERR_PERM Not owner. The operation was not allowed
because the caller is either not a privileged because the caller is either not a privileged
user (root) or not the owner of the target of user (root) or not the owner of the target of
the operation. the operation.
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NFS4ERR_SHARE_DENIED An attempt to OPEN a file with a share NFS4ERR_SHARE_DENIED An attempt to OPEN a file with a share
reservation has failed because of a share reservation has failed because of a share
conflict. conflict.
NFS4ERR_STALE Invalid filehandle. The filehandle given in the NFS4ERR_STALE Invalid filehandle. The filehandle given in the
arguments was invalid. The file referred to by arguments was invalid. The file referred to by
that filehandle no longer exists or access to that filehandle no longer exists or access to
it has been revoked. it has been revoked.
Draft Specification NFS version 4 Protocol October 2002 Draft Specification NFS version 4 Protocol November 2002
NFS4ERR_STALE_CLIENTID A clientid not recognized by the server was NFS4ERR_STALE_CLIENTID A clientid not recognized by the server was
used in a locking or SETCLIENTID_CONFIRM used in a locking or SETCLIENTID_CONFIRM
request. request.
NFS4ERR_STALE_STATEID A stateid generated by an earlier server NFS4ERR_STALE_STATEID A stateid generated by an earlier server
instance was used. instance was used.
NFS4ERR_SYMLINK The current filehandle provided for a LOOKUP is NFS4ERR_SYMLINK The current filehandle provided for a LOOKUP is
not a directory but a symbolic link. Also used not a directory but a symbolic link. Also used
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NFS4ERR_WRONGSEC The security mechanism being used by the client NFS4ERR_WRONGSEC The security mechanism being used by the client
for the operation does not match the server's for the operation does not match the server's
security policy. The client should change the security policy. The client should change the
security mechanism being used and retry the security mechanism being used and retry the
operation. operation.
NFS4ERR_XDEV Attempt to do an operation between different NFS4ERR_XDEV Attempt to do an operation between different
fsids. fsids.
Draft Specification NFS version 4 Protocol October 2002 Draft Specification NFS version 4 Protocol November 2002
13. NFS version 4 Requests 13. NFS version 4 Requests
For the NFS version 4 RPC program, there are two traditional RPC For the NFS version 4 RPC program, there are two traditional RPC
procedures: NULL and COMPOUND. All other functionality is defined as procedures: NULL and COMPOUND. All other functionality is defined as
a set of operations and these operations are defined in normal a set of operations and these operations are defined in normal
XDR/RPC syntax and semantics. However, these operations are XDR/RPC syntax and semantics. However, these operations are
encapsulated within the COMPOUND procedure. This requires that the encapsulated within the COMPOUND procedure. This requires that the
client combine one or more of the NFS version 4 operations into a client combine one or more of the NFS version 4 operations into a
single request. single request.
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+-----+--------------+--------+-----------+-----------+-----------+-- +-----+--------------+--------+-----------+-----------+-----------+--
and the reply's structure is: and the reply's structure is:
+------------+-----+--------+-----------------------+-- +------------+-----+--------+-----------------------+--
|last status | tag | numres | status + op + results | |last status | tag | numres | status + op + results |
+------------+-----+--------+-----------------------+-- +------------+-----+--------+-----------------------+--
The numops and numres fields, used in the depiction above, represent The numops and numres fields, used in the depiction above, represent
Draft Specification NFS version 4 Protocol October 2002 Draft Specification NFS version 4 Protocol November 2002
the count for the counted array encoding use to signify the number of the count for the counted array encoding use to signify the number of
arguments or results encoded in the request and response. As per the arguments or results encoded in the request and response. As per the
XDR encoding, these counts must match exactly the number of operation XDR encoding, these counts must match exactly the number of operation
arguments or results encoded. arguments or results encoded.
13.2. Evaluation of a Compound Request 13.2. Evaluation of a Compound Request
The server will process the COMPOUND procedure by evaluating each of The server will process the COMPOUND procedure by evaluating each of
the operations within the COMPOUND procedure in order. Each the operations within the COMPOUND procedure in order. Each
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13.3. Synchronous Modifying Operations 13.3. Synchronous Modifying Operations
NFS version 4 operations that modify the filesystem are synchronous. NFS version 4 operations that modify the filesystem are synchronous.
When an operation is successfully completed at the server, the client When an operation is successfully completed at the server, the client
can depend that any data associated with the request is now on stable can depend that any data associated with the request is now on stable
storage (the one exception is in the case of the file data in a WRITE storage (the one exception is in the case of the file data in a WRITE
operation with the UNSTABLE option specified). operation with the UNSTABLE option specified).
This implies that any previous operations within the same compound This implies that any previous operations within the same compound
Draft Specification NFS version 4 Protocol October 2002 Draft Specification NFS version 4 Protocol November 2002
request are also reflected in stable storage. This behavior enables request are also reflected in stable storage. This behavior enables
the client's ability to recover from a partially executed compound the client's ability to recover from a partially executed compound
request which may resulted from the failure of the server. For request which may resulted from the failure of the server. For
example, if a compound request contains operations A and B and the example, if a compound request contains operations A and B and the
server is unable to send a response to the client, depending on the server is unable to send a response to the client, depending on the
progress the server made in servicing the request the result of both progress the server made in servicing the request the result of both
operations may be reflected in stable storage or just operation A may operations may be reflected in stable storage or just operation A may
be reflected. The server must not have just the results of operation be reflected. The server must not have just the results of operation
B in stable storage. B in stable storage.
13.4. Operation Values 13.4. Operation Values
The operations encoded in the COMPOUND procedure are identified by The operations encoded in the COMPOUND procedure are identified by
operation values. To avoid overlap with the RPC procedure numbers, operation values. To avoid overlap with the RPC procedure numbers,
operations 0 (zero) and 1 are not defined. Operation 2 is not operations 0 (zero) and 1 are not defined. Operation 2 is not
defined but reserved for future use with minor versioning. defined but reserved for future use with minor versioning.
Draft Specification NFS version 4 Protocol October 2002 Draft Specification NFS version 4 Protocol November 2002
14. NFS version 4 Procedures 14. NFS version 4 Procedures
14.1. Procedure 0: NULL - No Operation 14.1. Procedure 0: NULL - No Operation
SYNOPSIS SYNOPSIS
<null> <null>
ARGUMENT ARGUMENT
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Standard NULL procedure. Void argument, void response. This Standard NULL procedure. Void argument, void response. This
procedure has no functionality associated with it. Because of this procedure has no functionality associated with it. Because of this
it is sometimes used to measure the overhead of processing a it is sometimes used to measure the overhead of processing a
service request. Therefore, the server should ensure that no service request. Therefore, the server should ensure that no
unnecessary work is done in servicing this procedure. unnecessary work is done in servicing this procedure.
ERRORS ERRORS
None. None.
Draft Specification NFS version 4 Protocol October 2002 Draft Specification NFS version 4 Protocol November 2002
14.2. Procedure 1: COMPOUND - Compound Operations 14.2. Procedure 1: COMPOUND - Compound Operations
SYNOPSIS SYNOPSIS
compoundargs -> compoundres compoundargs -> compoundres
ARGUMENT ARGUMENT
union nfs_argop4 switch (nfs_opnum4 argop) { union nfs_argop4 switch (nfs_opnum4 argop) {
case <OPCODE>: <argument>; case <OPCODE>: <argument>;
... ...
}; };
struct COMPOUND4args { struct COMPOUND4args {
utf8string tag; utf8str_cs tag;
uint32_t minorversion; uint32_t minorversion;
nfs_argop4 argarray<>; nfs_argop4 argarray<>;
}; };
RESULT RESULT
union nfs_resop4 switch (nfs_opnum4 resop){ union nfs_resop4 switch (nfs_opnum4 resop){
case <OPCODE>: <result>; case <OPCODE>: <result>;
... ...
}; };
struct COMPOUND4res { struct COMPOUND4res {
nfsstat4 status; nfsstat4 status;
utf8string tag; utf8str_cs tag;
nfs_resop4 resarray<>; nfs_resop4 resarray<>;
}; };
DESCRIPTION DESCRIPTION
The COMPOUND procedure is used to combine one or more of the NFS The COMPOUND procedure is used to combine one or more of the NFS
operations into a single RPC request. The main NFS RPC program has operations into a single RPC request. The main NFS RPC program has
two main procedures: NULL and COMPOUND. All other operations use two main procedures: NULL and COMPOUND. All other operations use
the COMPOUND procedure as a wrapper. the COMPOUND procedure as a wrapper.
The COMPOUND procedure is used to combine individual operations The COMPOUND procedure is used to combine individual operations
into a single RPC request. The server interprets each of the into a single RPC request. The server interprets each of the
operations in turn. If an operation is executed by the server and operations in turn. If an operation is executed by the server and
the status of that operation is NFS4_OK, then the next operation in the status of that operation is NFS4_OK, then the next operation in
the COMPOUND procedure is executed. The server continues this the COMPOUND procedure is executed. The server continues this
process until there are no more operations to be executed or one of process until there are no more operations to be executed or one of
the operations has a status value other than NFS4_OK. the operations has a status value other than NFS4_OK.
Draft Specification NFS version 4 Protocol October 2002 Draft Specification NFS version 4 Protocol November 2002
In the processing of the COMPOUND procedure, the server may find In the processing of the COMPOUND procedure, the server may find
that it does not have the available resources to execute any or all that it does not have the available resources to execute any or all
of the operations within the COMPOUND sequence. In this case, the of the operations within the COMPOUND sequence. In this case, the
error NFS4ERR_RESOURCE will be returned for the particular error NFS4ERR_RESOURCE will be returned for the particular
operation within the COMPOUND procedure where the resource operation within the COMPOUND procedure where the resource
exhaustion occurred. This assumes that all previous operations exhaustion occurred. This assumes that all previous operations
within the COMPOUND sequence have been evaluated successfully. The within the COMPOUND sequence have been evaluated successfully. The
results for all of the evaluated operations must be returned to the results for all of the evaluated operations must be returned to the
client. client.
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the minorversion field is non-zero and the server does not support the minorversion field is non-zero and the server does not support
the minor version, the server returns an error of the minor version, the server returns an error of
NFS4ERR_MINOR_VERS_MISMATCH. Therefore, the NFS4ERR_MINOR_VERS_MISMATCH. Therefore, the
NFS4ERR_MINOR_VERS_MISMATCH error takes precedence over all other NFS4ERR_MINOR_VERS_MISMATCH error takes precedence over all other
errors. errors.
It is possible that the server receives a request that contains an It is possible that the server receives a request that contains an
operation that is less than the first legal operation (OP_ACCESS) operation that is less than the first legal operation (OP_ACCESS)
or greater than the last legal operation (OP_RELEASE_LOCKOWNER). or greater than the last legal operation (OP_RELEASE_LOCKOWNER).
Draft Specification NFS version 4 Protocol October 2002 Draft Specification NFS version 4 Protocol November 2002
In this case, the server's response will encode the opcode In this case, the server's response will encode the opcode
OP_ILLEGAL rather than the illegal opcode of the request. The OP_ILLEGAL rather than the illegal opcode of the request. The
status field in the ILLEGAL return results will set to status field in the ILLEGAL return results will set to
NFS4ERR_OP_ILLEGAL. The COMPOUND procedure's return results will NFS4ERR_OP_ILLEGAL. The COMPOUND procedure's return results will
also be NFS4ERR_OP_ILLEGAL. also be NFS4ERR_OP_ILLEGAL.
The definition of the "tag" in the request is left to the The definition of the "tag" in the request is left to the
implementor. It may be used to summarize the content of the implementor. It may be used to summarize the content of the
compound request for the benefit of packet sniffers and engineers compound request for the benefit of packet sniffers and engineers
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recover from any failure. If the source of an NFS4ERR_RESOURCE recover from any failure. If the source of an NFS4ERR_RESOURCE
error was a complex or lengthy set of operations, it is likely that error was a complex or lengthy set of operations, it is likely that
if the number of operations were reduced the server would be able if the number of operations were reduced the server would be able
to evaluate them successfully. Therefore, the client is to evaluate them successfully. Therefore, the client is
responsible for dealing with this type of complexity in recovery. responsible for dealing with this type of complexity in recovery.
ERRORS ERRORS
All errors defined in the protocol All errors defined in the protocol
Draft Specification NFS version 4 Protocol October 2002 Draft Specification NFS version 4 Protocol November 2002
14.2.1. Operation 3: ACCESS - Check Access Rights 14.2.1. Operation 3: ACCESS - Check Access Rights
SYNOPSIS SYNOPSIS
(cfh), accessreq -> supported, accessrights (cfh), accessreq -> supported, accessrights
ARGUMENT ARGUMENT
const ACCESS4_READ = 0x00000001; const ACCESS4_READ = 0x00000001;
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system object specified by the current filehandle. The client system object specified by the current filehandle. The client
encodes the set of access rights that are to be checked in the bit encodes the set of access rights that are to be checked in the bit
mask "access". The server checks the permissions encoded in the mask "access". The server checks the permissions encoded in the
bit mask. If a status of NFS4_OK is returned, two bit masks are bit mask. If a status of NFS4_OK is returned, two bit masks are
included in the response. The first, "supported", represents the included in the response. The first, "supported", represents the
access rights for which the server can verify reliably. The access rights for which the server can verify reliably. The
second, "access", represents the access rights available to the second, "access", represents the access rights available to the
user for the filehandle provided. On success, the current user for the filehandle provided. On success, the current
filehandle retains its value. filehandle retains its value.
Draft Specification NFS version 4 Protocol October 2002 Draft Specification NFS version 4 Protocol November 2002
Note that the supported field will contain only as many values as Note that the supported field will contain only as many values as
was originally sent in the arguments. For example, if the client was originally sent in the arguments. For example, if the client
sends an ACCESS operation with only the ACCESS4_READ value set and sends an ACCESS operation with only the ACCESS4_READ value set and
the server supports this value, the server will return only the server supports this value, the server will return only
ACCESS4_READ even if it could have reliably checked other values. ACCESS4_READ even if it could have reliably checked other values.
The results of this operation are necessarily advisory in nature. The results of this operation are necessarily advisory in nature.
A return status of NFS4_OK and the appropriate bit set in the bit A return status of NFS4_OK and the appropriate bit set in the bit
mask does not imply that such access will be allowed to the file mask does not imply that such access will be allowed to the file
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In the NFS version 2 protocol, the only reliable way to determine In the NFS version 2 protocol, the only reliable way to determine
whether an operation was allowed was to try it and see if it whether an operation was allowed was to try it and see if it
succeeded or failed. Using the ACCESS operation in the NFS version succeeded or failed. Using the ACCESS operation in the NFS version
4 protocol, the client can ask the server to indicate whether or 4 protocol, the client can ask the server to indicate whether or
not one or more classes of operations are permitted. The ACCESS not one or more classes of operations are permitted. The ACCESS
operation is provided to allow clients to check before doing a operation is provided to allow clients to check before doing a
series of operations which will result in an access failure. The series of operations which will result in an access failure. The
OPEN operation provides a point where the server can verify access OPEN operation provides a point where the server can verify access
to the file object and method to return that information to the to the file object and method to return that information to the
Draft Specification NFS version 4 Protocol October 2002 Draft Specification NFS version 4 Protocol November 2002
client. The ACCESS operation is still useful for directory client. The ACCESS operation is still useful for directory
operations or for use in the case the UNIX API "access" is used on operations or for use in the case the UNIX API "access" is used on
the client. the client.
The information returned by the server in response to an ACCESS The information returned by the server in response to an ACCESS
call is not permanent. It was correct at the exact time that the call is not permanent. It was correct at the exact time that the
server performed the checks, but not necessarily afterwards. The server performed the checks, but not necessarily afterwards. The
server can revoke access permission at any time. server can revoke access permission at any time.
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NFS4ERR_DELAY NFS4ERR_DELAY
NFS4ERR_FHEXPIRED NFS4ERR_FHEXPIRED
NFS4ERR_INVAL NFS4ERR_INVAL
NFS4ERR_IO NFS4ERR_IO
NFS4ERR_MOVED NFS4ERR_MOVED
NFS4ERR_NOFILEHANDLE NFS4ERR_NOFILEHANDLE
NFS4ERR_RESOURCE NFS4ERR_RESOURCE
NFS4ERR_SERVERFAULT NFS4ERR_SERVERFAULT
NFS4ERR_STALE NFS4ERR_STALE
Draft Specification NFS version 4 Protocol October 2002 Draft Specification NFS version 4 Protocol November 2002
14.2.2. Operation 4: CLOSE - Close File 14.2.2. Operation 4: CLOSE - Close File
SYNOPSIS SYNOPSIS
(cfh), seqid, open_stateid -> open_stateid (cfh), seqid, open_stateid -> open_stateid
ARGUMENT ARGUMENT
struct CLOSE4args { struct CLOSE4args {
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locks would exist after the CLOSE. locks would exist after the CLOSE.
On success, the current filehandle retains its value. On success, the current filehandle retains its value.
IMPLEMENTATION IMPLEMENTATION
Even though CLOSE returns a stateid, this stateid is not useful to Even though CLOSE returns a stateid, this stateid is not useful to
the client and should be treated as deprecated. CLOSE "shuts down" the client and should be treated as deprecated. CLOSE "shuts down"
the state associated with all OPENs for the file by a single the state associated with all OPENs for the file by a single
Draft Specification NFS version 4 Protocol October 2002 Draft Specification NFS version 4 Protocol November 2002
open_owner. As noted above, CLOSE will either release all file open_owner. As noted above, CLOSE will either release all file
locking state or return an error. Therefore, the stateid returned locking state or return an error. Therefore, the stateid returned
by CLOSE is not useful for operations that follow. by CLOSE is not useful for operations that follow.
ERRORS ERRORS
NFS4ERR_ADMIN_REVOKED NFS4ERR_ADMIN_REVOKED
NFS4ERR_BADHANDLE NFS4ERR_BADHANDLE
NFS4ERR_BAD_SEQID NFS4ERR_BAD_SEQID
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NFS4ERR_LEASE_MOVED NFS4ERR_LEASE_MOVED
NFS4ERR_LOCKS_HELD NFS4ERR_LOCKS_HELD
NFS4ERR_MOVED NFS4ERR_MOVED
NFS4ERR_NOFILEHANDLE NFS4ERR_NOFILEHANDLE
NFS4ERR_OLD_STATEID NFS4ERR_OLD_STATEID
NFS4ERR_RESOURCE NFS4ERR_RESOURCE
NFS4ERR_SERVERFAULT NFS4ERR_SERVERFAULT
NFS4ERR_STALE NFS4ERR_STALE
NFS4ERR_STALE_STATEID NFS4ERR_STALE_STATEID
Draft Specification NFS version 4 Protocol October 2002 Draft Specification NFS version 4 Protocol November 2002
14.2.3. Operation 5: COMMIT - Commit Cached Data 14.2.3. Operation 5: COMMIT - Commit Cached Data
SYNOPSIS SYNOPSIS
(cfh), offset, count -> verifier (cfh), offset, count -> verifier
ARGUMENT ARGUMENT
struct COMMIT4args { struct COMMIT4args {
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The server returns a write verifier upon successful completion of The server returns a write verifier upon successful completion of
the COMMIT. The write verifier is used by the client to determine the COMMIT. The write verifier is used by the client to determine
if the server has restarted or rebooted between the initial if the server has restarted or rebooted between the initial
WRITE(s) and the COMMIT. The client does this by comparing the WRITE(s) and the COMMIT. The client does this by comparing the
write verifier returned from the initial writes and the verifier write verifier returned from the initial writes and the verifier
returned by the COMMIT operation. The server must vary the value returned by the COMMIT operation. The server must vary the value
of the write verifier at each server event or instantiation that of the write verifier at each server event or instantiation that
may lead to a loss of uncommitted data. Most commonly this occurs may lead to a loss of uncommitted data. Most commonly this occurs
when the server is rebooted; however, other events at the server when the server is rebooted; however, other events at the server
Draft Specification NFS version 4 Protocol October 2002 Draft Specification NFS version 4 Protocol November 2002
may result in uncommitted data loss as well. may result in uncommitted data loss as well.
On success, the current filehandle retains its value. On success, the current filehandle retains its value.
IMPLEMENTATION IMPLEMENTATION
The COMMIT operation is similar in operation and semantics to the The COMMIT operation is similar in operation and semantics to the
POSIX fsync(2) system call that synchronizes a file's state with POSIX fsync(2) system call that synchronizes a file's state with
the disk (file data and metadata is flushed to disk or stable the disk (file data and metadata is flushed to disk or stable
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close. In this case, the client would gather all of the buffers close. In this case, the client would gather all of the buffers
for this file that contain uncommitted data, do the COMMIT for this file that contain uncommitted data, do the COMMIT
operation with an offset of 0 and count of 0, and then free all of operation with an offset of 0 and count of 0, and then free all of
those buffers. Any other dirty buffers would be sent to the server those buffers. Any other dirty buffers would be sent to the server
in the normal fashion. in the normal fashion.
After a buffer is written by the client with the stable parameter After a buffer is written by the client with the stable parameter
set to UNSTABLE4, the buffer must be considered as modified by the set to UNSTABLE4, the buffer must be considered as modified by the
client until the buffer has either been flushed via a COMMIT client until the buffer has either been flushed via a COMMIT
Draft Specification NFS version 4 Protocol October 2002 Draft Specification NFS version 4 Protocol November 2002
operation or written via a WRITE operation with stable parameter operation or written via a WRITE operation with stable parameter
set to FILE_SYNC4 or DATA_SYNC4. This is done to prevent the buffer set to FILE_SYNC4 or DATA_SYNC4. This is done to prevent the buffer
from being freed and reused before the data can be flushed to from being freed and reused before the data can be flushed to
stable storage on the server. stable storage on the server.
When a response is returned from either a WRITE or a COMMIT When a response is returned from either a WRITE or a COMMIT
operation and it contains a write verifier that is different than operation and it contains a write verifier that is different than
previously returned by the server, the client will need to previously returned by the server, the client will need to
retransmit all of the buffers containing uncommitted cached data to retransmit all of the buffers containing uncommitted cached data to
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NFS4ERR_INVAL NFS4ERR_INVAL
NFS4ERR_IO NFS4ERR_IO
NFS4ERR_ISDIR NFS4ERR_ISDIR
NFS4ERR_MOVED NFS4ERR_MOVED
NFS4ERR_NOFILEHANDLE NFS4ERR_NOFILEHANDLE
NFS4ERR_RESOURCE NFS4ERR_RESOURCE
NFS4ERR_ROFS NFS4ERR_ROFS
NFS4ERR_SERVERFAULT NFS4ERR_SERVERFAULT
NFS4ERR_STALE NFS4ERR_STALE
Draft Specification NFS version 4 Protocol October 2002 Draft Specification NFS version 4 Protocol November 2002
14.2.4. Operation 6: CREATE - Create a Non-Regular File Object 14.2.4. Operation 6: CREATE - Create a Non-Regular File Object
SYNOPSIS SYNOPSIS
(cfh), name, type, attrs -> (cfh), change_info, attrs_set (cfh), name, type, attrs -> (cfh), change_info, attrs_set
ARGUMENT ARGUMENT
union createtype4 switch (nfs_ftype4 type) { union createtype4 switch (nfs_ftype4 type) {
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DESCRIPTION DESCRIPTION
The CREATE operation creates a non-regular file object in a The CREATE operation creates a non-regular file object in a
directory with a given name. The OPEN operation MUST be used to directory with a given name. The OPEN operation MUST be used to
create a regular file. create a regular file.
The objname specifies the name for the new object. The objtype The objname specifies the name for the new object. The objtype
determines the type of object to be created: directory, symlink, determines the type of object to be created: directory, symlink,
Draft Specification NFS version 4 Protocol October 2002 Draft Specification NFS version 4 Protocol November 2002
etc. etc.
If an object of the same name already exists in the directory, the If an object of the same name already exists in the directory, the
server will return the error NFS4ERR_EXIST. server will return the error NFS4ERR_EXIST.
For the directory where the new file object was created, the server For the directory where the new file object was created, the server
returns change_info4 information in cinfo. With the atomic field returns change_info4 information in cinfo. With the atomic field
of the change_info4 struct, the server will indicate if the before of the change_info4 struct, the server will indicate if the before
and after change attributes were obtained atomically with respect and after change attributes were obtained atomically with respect
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OPEN operation too. OPEN operation too.
Conversely, it is possible the client will specify in createattrs Conversely, it is possible the client will specify in createattrs
an owner attribute or group attribute or ACL that the principal an owner attribute or group attribute or ACL that the principal
indicated the RPC call's credentials does not have permissions to indicated the RPC call's credentials does not have permissions to
create files for. The error to be returned in this instance is create files for. The error to be returned in this instance is
NFS4ERR_PERM. This applies to the OPEN operation too. NFS4ERR_PERM. This applies to the OPEN operation too.
IMPLEMENTATION IMPLEMENTATION
Draft Specification NFS version 4 Protocol October 2002 Draft Specification NFS version 4 Protocol November 2002