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NFSv4                                                         J. Lentini
Internet-Draft                                                 M. Eisler
Intended status: Standards Track                                 R. Iyer
Expires: July 11, 2010                                    D. Kenchammana
                                                                  NetApp
                                                                A. Madan
                                              Carnegie Mellon University
                                                         January 7, 2010


                          NFS Server-side Copy
              draft-lentini-nfsv4-server-side-copy-04.txt

Abstract

   This document describes a set of NFS operations for offloading a file
   copy to a file server or between two file servers.

Status of this Memo

   This Internet-Draft is submitted to IETF in full conformance with the
   provisions of BCP 78 and BCP 79.

   Internet-Drafts are working documents of the Internet Engineering
   Task Force (IETF), its areas, and its working groups.  Note that
   other groups may also distribute working documents as Internet-
   Drafts.

   Internet-Drafts are draft documents valid for a maximum of six months
   and may be updated, replaced, or obsoleted by other documents at any
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   This Internet-Draft will expire on July 11, 2010.

Copyright Notice

   Copyright (c) 2010 IETF Trust and the persons identified as the
   document authors.  All rights reserved.

   This document is subject to BCP 78 and the IETF Trust's Legal
   Provisions Relating to IETF Documents



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   (http://trustee.ietf.org/license-info) in effect on the date of
   publication of this document.  Please review these documents
   carefully, as they describe your rights and restrictions with respect
   to this document.  Code Components extracted from this document must
   include Simplified BSD License text as described in Section 4.e of
   the Trust Legal Provisions and are provided without warranty as
   described in the BSD License.


Table of Contents

   1.  Requirements notation  . . . . . . . . . . . . . . . . . . . .  3
   2.  Introduction . . . . . . . . . . . . . . . . . . . . . . . . .  3
   3.  Protocol Overview  . . . . . . . . . . . . . . . . . . . . . .  3
     3.1.  Intra-Server Copy  . . . . . . . . . . . . . . . . . . . .  5
     3.2.  Inter-Server Copy  . . . . . . . . . . . . . . . . . . . .  6
     3.3.  Server-to-Server Copy Protocol . . . . . . . . . . . . . .  9
       3.3.1.  Using NFSv4.x as a Server-to-Server Copy Protocol  . .  9
       3.3.2.  Using an alternative Server-to-Server Copy Protocol  . 10
   4.  Operations . . . . . . . . . . . . . . . . . . . . . . . . . . 11
     4.1.  netloc4 - Network Locations  . . . . . . . . . . . . . . . 11
     4.2.  Operation U: COPY_NOTIFY - Notify a source server of a
           future copy  . . . . . . . . . . . . . . . . . . . . . . . 12
     4.3.  Operation V: COPY_REVOKE - Revoke a destination
           server's copy privileges . . . . . . . . . . . . . . . . . 14
     4.4.  Operation W: COPY - Initiate a server-side copy  . . . . . 15
     4.5.  Operation X: COPY_ABORT - Cancel a server-side copy  . . . 20
     4.6.  Operation Y: COPY_STATUS - Poll for status of a
           server-side copy . . . . . . . . . . . . . . . . . . . . . 21
     4.7.  Operation Z: CB_COPY - Report results of a server-side
           copy . . . . . . . . . . . . . . . . . . . . . . . . . . . 22
     4.8.  Copy Offload Stateids  . . . . . . . . . . . . . . . . . . 23
   5.  Security Considerations  . . . . . . . . . . . . . . . . . . . 24
     5.1.  Inter-Server Copy Security . . . . . . . . . . . . . . . . 24
       5.1.1.  Requirements for Secure Inter-Server Copy  . . . . . . 24
       5.1.2.  Inter-Server Copy with RPCSEC_GSSv3  . . . . . . . . . 25
       5.1.3.  Inter-Server Copy via ONC RPC but without
               RPCSEC_GSSv3 . . . . . . . . . . . . . . . . . . . . . 31
       5.1.4.  Inter-Server Copy without ONC RPC and RPCSEC_GSSv3 . . 32
   6.  IANA Considerations  . . . . . . . . . . . . . . . . . . . . . 32
   7.  References . . . . . . . . . . . . . . . . . . . . . . . . . . 32
     7.1.  Normative References . . . . . . . . . . . . . . . . . . . 32
     7.2.  Informational References . . . . . . . . . . . . . . . . . 32
   Appendix A.  Acknowledgments . . . . . . . . . . . . . . . . . . . 33
   Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . . 33






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1.  Requirements notation

   The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
   "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this
   document are to be interpreted as described in [RFC2119].


2.  Introduction

   This document describes a server-side copy feature for the NFS
   protocol.

   The server-side copy feature provides a mechanism for the NFS client
   to perform a file copy on the server without the data being
   transmitted back and forth over the network.

   Without this feature, an NFS client copies data from one location to
   another by reading the data from the server over the network, and
   then writing the data back over the network to the server.  Using
   this server-side copy operation, the client is able to instruct the
   server to copy the data locally without the data being sent back and
   forth over the network unnecessarily.

   In general, this feature is useful whenever data is copied from one
   location to another on the server.  It is particularly useful when
   copying the contents of a file from a snapshot.  Snapshot-versions of
   a file are copied for a number of reasons, including restoring and
   cloning data.

   If the source object and destination object are on different file
   servers, the file servers will communicate with one another to
   perform the copy operation.  The server-to-server protocol by which
   this is accomplished is not defined in this document.


3.  Protocol Overview

   The server-side copy offload operations support both intra-server and
   inter-server file copies.  An intra-server copy is a copy in which
   the source file and destination file reside on the same server.  In
   an inter-server copy, the source file and destination file are on
   different servers.  In both cases, the copy may be performed
   synchronously or asynchronously.

   Throughout the rest of this document, we refer to the NFS server
   containing the source file as the "source server" and the NFS server
   to which the file is transferred as the "destination server".  In the
   case of an intra-server copy, the source server and destination



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   server are the same server.  Therefore in the context of an intra-
   server copy, the terms source server and destination server refer to
   the single server performing the copy.

   The operations described below are designed to copy files.  Other
   file system objects can be copied by building on these operations or
   using other techniques.  For example if the user wishes to copy a
   directory, the client can synthesize a directory copy by first
   creating the destination directory and then copying the source
   directory's files to the new destination directory.  If the user
   wishes to copy a namespace junction [FEDFS-NSDB] [FEDFS-ADMIN], the
   client can use the ONC RPC Federated Filesystem protocol
   [FEDFS-ADMIN] to perform the copy.  Specifically the client can
   determine the source junction's attributes using the FEDFS_LOOKUP_FSN
   procedure and create a duplicate junction using the
   FEDFS_CREATE_JUNCTION procedure.

   For the inter-server copy protocol, the operations are defined to be
   compatible with a server-to-server copy protocol in which the
   destination server reads the file data from the source server.  This
   model in which the file data is pulled from the source by the
   destination has a number of advantages over a model in which the
   source pushes the file data to the destination.  The advantages of
   the pull model include:

   o  The pull model only requires a remote server (i.e. the destination
      server) to be granted read access.  A push model requires a remote
      server (i.e. the source server) to be granted write access, which
      is more privileged.

   o  The pull model allows the destination server to stop reading if it
      has run out of space.  In a push model, the destination server
      must flow control the source server in this situation.

   o  The pull model allows the destination server to easily flow
      control the data stream by adjusting the size of its read
      operations.  In a push model, the destination server does not have
      this ability.  The source server in a push model is capable of
      writing chunks larger than the destination server has requested in
      attributes and session parameters.  In theory, the destination
      server could perform a "short" write in this situation, but this
      approach is known to behave poorly in practice.

   The following operations are provided to support server-side copy:







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   COPY_NOTIFY:  For inter-server copies, the client sends this
      operation to the source server to notify it of a future file copy
      from a given destination server for the given user.

   COPY_REVOKE:  Also for inter-server copies, the client sends this
      operation to the source server to revoke permission to copy a file
      for the given user.

   COPY:  Used by the client to request a file copy.

   COPY_ABORT:  Used by the client to abort an asynchronous file copy.

   COPY_STATUS:  Used by the client to poll the status of an
      asynchronous file copy.

   CB_COPY:  Used by the destination server to report the results of an
      asynchronous file copy to the client.

   These operations are described in detail in Section 4.  This section
   provides an overview of how these operations are used to perform
   server-side copies.

3.1.  Intra-Server Copy

   To copy a file on a single server, the client uses a COPY operation.
   The server may respond to the copy operation with the final results
   of the copy or it may perform the copy asynchronously and deliver the
   results using a CB_COPY operation callback.  If the copy is performed
   asynchronously, the client may poll the status of the copy using
   COPY_STATUS or cancel the copy using COPY_ABORT.

   A synchronous intra-server copy is shown in Figure 1.  In this
   example, the NFS server chooses to perform the copy synchronously.
   The copy operation is completed, either successfully or
   unsuccessfully, before the server replies to the client's request.
   The server's reply contains the final result of the operation.

     Client                                  Server
        +                                      +
        |                                      |
        |--- COPY ---------------------------->| Client requests
        |<------------------------------------/| a file copy
        |                                      |
        |                                      |

                Figure 1: A synchronous intra-server copy.

   An asynchronous intra-server copy is shown in Figure 2.  In this



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   example, the NFS server performs the copy asynchronously.  The
   server's reply to the copy request indicates that the copy operation
   was initiated and the final result will be delivered at a later time.
   The server's reply also contains a copy stateid.  The client may use
   this copy stateid to poll for status information (as shown) or to
   cancel the copy using a COPY_ABORT.  When the server completes the
   copy, the server performs a callback to the client and reports the
   results.


     Client                                  Server
        +                                      +
        |                                      |
        |--- COPY ---------------------------->| Client requests
        |<------------------------------------/| a file copy
        |                                      |
        |                                      |
        |--- COPY_STATUS --------------------->| Client may poll
        |<------------------------------------/| for status
        |                                      |
        |                  .                   | Multiple COPY_STATUS
        |                  .                   | operations may be sent.
        |                  .                   |
        |                                      |
        |<-- CB_COPY --------------------------| Server reports results
        |\------------------------------------>|
        |                                      |

               Figure 2: An asynchronous intra-server copy.

3.2.  Inter-Server Copy

   A copy may also be performed between two servers.  The copy protocol
   is designed to accommodate a variety of network topologies.  As shown
   in Figure 3, the client and servers may be connected by multiple
   networks.  In particular, the servers may be connected by a
   specialized, high speed network (network 192.168.33.0/24 in the
   diagram) that does not include the client.  The protocol allows the
   client to setup the copy between the servers (over network
   10.11.78.0/24 in the diagram) and for the servers to communicate on
   the high speed network if they choose to do so.










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                             192.168.33.0/24
                 +-------------------------------------+
                 |                                     |
                 |                                     |
                 | 192.168.33.18                       | 192.168.33.56
         +-------+------+                       +------+------+
         |     Source   |                       | Destination |
         +-------+------+                       +------+------+
                 | 10.11.78.18                         | 10.11.78.56
                 |                                     |
                 |                                     |
                 |             10.11.78.0/24           |
                 +------------------+------------------+
                                    |
                                    |
                                    | 10.11.78.243
                              +-----+-----+
                              |   Client  |
                              +-----------+

            Figure 3: An example inter-server network topology.

   For an inter-server copy, the client notifies the source server that
   a file will be copied by the destination server using a COPY_NOTIFY
   operation.  The client then initiates the copy by sending the COPY
   operation to the destination server.  The destination server may
   perform the copy synchronously or asynchronously.

   A synchronous inter-server copy is shown in Figure 4.  In this case,
   the destination server chooses to perform the copy before responding
   to the client's COPY request.

   An asynchronous copy is shown in Figure 5.  In this case, the
   destination server chooses to respond to the client's COPY request
   immediately and then perform the copy asynchronously.
















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     Client                Source         Destination
        +                    +                 +
        |                    |                 |
        |--- COPY_NOTIFY --->|                 |
        |<------------------/|                 |
        |                    |                 |
        |                    |                 |
        |--- COPY ---------------------------->|
        |                    |                 |
        |                    |                 |
        |                    |<----- read -----|
        |                    |\--------------->|
        |                    |                 |
        |                    |        .        | Multiple reads may
        |                    |        .        | be necessary
        |                    |        .        |
        |                    |                 |
        |                    |                 |
        |<------------------------------------/| Destination replies
        |                    |                 | to COPY

                Figure 4: A synchronous inter-server copy.





























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     Client                Source         Destination
        +                    +                 +
        |                    |                 |
        |--- COPY_NOTIFY --->|                 |
        |<------------------/|                 |
        |                    |                 |
        |                    |                 |
        |--- COPY ---------------------------->|
        |<------------------------------------/|
        |                    |                 |
        |                    |                 |
        |                    |<----- read -----|
        |                    |\--------------->|
        |                    |                 |
        |                    |        .        | Multiple reads may
        |                    |        .        | be necessary
        |                    |        .        |
        |                    |                 |
        |                    |                 |
        |--- COPY_STATUS --------------------->| Client may poll
        |<------------------------------------/| for status
        |                    |                 |
        |                    |        .        | Multiple COPY_STATUS
        |                    |        .        | operations may be sent
        |                    |        .        |
        |                    |                 |
        |                    |                 |
        |                    |                 |
        |<-- CB_COPY --------------------------| Destination reports
        |\------------------------------------>| results
        |                    |                 |

               Figure 5: An asynchronous inter-server copy.

3.3.  Server-to-Server Copy Protocol

   During an inter-server copy, the destination server reads the file
   data from the source server.  The source server and destination
   server are not required to use a specific protocol to transfer the
   file data.  The choice of what protocol to use is ultimately the
   destination server's decision.

3.3.1.  Using NFSv4.x as a Server-to-Server Copy Protocol

   The destination server MAY use standard NFSv4.x (where x >= 1) to
   read the data from the source server.  If NFSv4.x is used for the
   server-to-server copy protocol, the destination server can use the
   filehandle contained in the COPY request with standard NFSv4.x



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   operations to read data from the source server.  Specifically, the
   destination server may use the NFSv4.x OPEN operation's CLAIM_FH
   facility to open the file being copied and obtain an open stateid.
   Using the stateid, the destination server may then use NFSv4.x READ
   operations to read the file.

3.3.2.  Using an alternative Server-to-Server Copy Protocol

   In a homogeneous environment, the source and destination servers
   might be able to perform the file copy extremely efficiently using
   specialized protocols.  For example the source and destination
   servers might be two nodes sharing a common file system format for
   the source and destination file systems.  Thus the source and
   destination are in an ideal position to efficiently render the image
   of the source file to the destination file by replicating the file
   system formats at the block level.  Another possibility is that the
   source and destination might be two nodes sharing a common storage
   area network, and thus there is no need to copy any data at all, and
   instead ownership of the file and its contents might simply be re-
   assigned to the destination.  To allow for these possibilities, the
   destination server is allowed to use a server-to-server copy protocol
   of its choice.

   In a heterogeneous environment, using a protocol other than NFSv4.x
   (e.g.  HTTP [RFC2616] and FTP [RFC0959]) presents some challenges.
   In particular, the destination server is presented with the challenge
   of accessing the source file given only an NFSv4.x filehandle.

   One option for protocols that identify source files with path names
   is to use an ASCII hexadecimal representation of the source
   filehandle as the file name.

   Another option for the source server is to use URLs to direct the
   destination server to a specialized service.  For example, the
   response to COPY_NOTIFY could include the URL
   ftp://s1.example.com:9999/_FH/0x12345, where 0x12345 is the ASCII
   hexadecimal representation of the source filehandle.  When the
   destination server receives the source server's URL, it would use
   "_FH/0x12345" as the file name to pass to the FTP server listening on
   port 9999 of s1.example.com.  On port 9999 there would be a special
   instance of the FTP service that understands how to convert NFS
   filehandles to an open file descriptor (in many operating systems,
   this would require a new system call, one which is the inverse of the
   makefh() function that the pre-NFSv4 MOUNT service needs).

   Authenticating and identifying the destination server to the source
   server is also a challenge.  Recommendations for how to accomplish
   this are given in Section 5.1.2.4 and Section 5.1.4.



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4.  Operations

   In the sections that follow, several operations are defined that
   together provide the server-side copy feature.  These operations are
   intended to be OPTIONAL operations as defined in section 17 of
   [NFSv4.1].  The COPY_NOTIFY, COPY_REVOKE, COPY, COPY_ABORT, and
   COPY_STATUS operations are designed to be sent within an NFSv4
   COMPOUND procedure.  The CB_COPY operation is designed to be sent
   within an NFSv4 CB_COMPOUND procedure.

   Each operation is performed in the context of the user identified by
   the ONC RPC credential of its containing COMPOUND or CB_COMPOUND
   request.  For example, a COPY_ABORT operation issued by a given user
   indicates that a specified COPY operation initiated by the same user
   be canceled.  Therefore a COPY_ABORT MUST NOT interfere with a copy
   of the same file initiated by another user.

   An NFS server MAY allow an administrative user to monitor or cancel
   copy operations using an implementation specific interface.

4.1.  netloc4 - Network Locations

   The server-side copy operations specify network locations using the
   netloc4 data type shown below:

                   enum netloc_type4 {
                           NL4_NAME      = 0,
                           NL4_URL       = 1,
                           NL4_NETADDR   = 2
                   };

                   union netloc4 switch (netloc_type4 nl_type) {
                           case NL4_NAME:    utf8str_cis nl_name;
                           case NL4_URL:     utf8str_cis nl_url;
                           case NL4_NETADDR: netaddr4    nl_addr;
                   };

   If the netloc4 is of type NL4_NAME, the nl_name field MUST be
   specified as a UTF-8 string.  The nl_name is expected to be resolved
   to a network address via DNS, LDAP, NIS, /etc/hosts, or some other
   means.  If the netloc4 is of type NL4_URL, a server URL [RFC3986]
   appropriate for the server-to-server copy operation is specified as a
   UTF-8 string.  If the netloc4 is of type NL4_NETADDR, the nl_addr
   field MUST contain a valid netaddr4 as defined in Section 3.3.9 of
   [NFSv4.1].

   When netloc4 values are used for an inter-server copy as shown in
   Figure 3, their values may be evaluated on the source server,



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   destination server, and client.  The network environment in which
   these systems operate should be configured so that the netloc4 values
   are interpreted as intended on each system.

4.2.  Operation U: COPY_NOTIFY - Notify a source server of a future copy

   ARGUMENTS

                   struct COPY_NOTIFY4args {
                           /* CURRENT_FH: source file */
                           netloc4         cna_destination_server;
                   };

   RESULTS

                   union COPY_NOTIFY4res switch (nfsstat4 cnr_status) {
                   case NFS4_OK:
                           nfstime4        cnr_lease_time;
                           netloc4         cnr_source_server<>;
                   default:
                           void;
                   };

   DESCRIPTION

   This operation is used for an inter-server copy.  A client sends this
   operation in a COMPOUND request to the source server to authorize a
   destination server identified by cna_destination_server to read the
   file specified by CURRENT_FH on behalf of the given user.

   The cna_destination_server MUST be specified using the netloc4
   network location format.  The server is not required to resolve the
   cna_destination_server address before completing this operation.

   If this operation succeeds, the source server will allow the
   cna_destination_server to copy the specified file on behalf of the
   given user.  If COPY_NOTIFY succeeds, the destination server is
   granted permission to read the file as long as both of the following
   conditions are met:

   o  The destination server begins reading the source file before the
      cnr_lease_time expires.  If the cnr_lease_time expires while the
      destination server is still reading the source file, the
      destination server is allowed to finish reading the file.

   o  The client has not issued a COPY_REVOKE for the same combination
      of user, filehandle, and destination server.




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   The cnr_lease_time is chosen by the source server.  A cnr_lease_time
   of 0 (zero) indicates an infinite lease.  To renew the copy lease
   time the client should resend the same copy notification request to
   the source server.

   To avoid the need for synchronized clocks, copy lease times are
   granted by the server as a time delta.  However, there is a
   requirement that the client and server clocks do not drift
   excessively over the duration of the lease.  There is also the issue
   of propagation delay across the network which could easily be several
   hundred milliseconds as well as the possibility that requests will be
   lost and need to be retransmitted.

   To take propagation delay into account, the client should subtract it
   from copy lease times (e.g. if the client estimates the one-way
   propagation delay as 200 milliseconds, then it can assume that the
   lease is already 200 milliseconds old when it gets it).  In addition,
   it will take another 200 milliseconds to get a response back to the
   server.  So the client must send a lease renewal or send the copy
   offload request to the cna_destination_server at least 400
   milliseconds before the copy lease would expire.  If the propagation
   delay varies over the life of the lease (e.g. the client is on a
   mobile host), the client will need to continuously subtract the
   increase in propagation delay from the copy lease times.

   The server's copy lease period configuration should take into account
   the network distance of the clients that will be accessing the
   server's resources.  It is expected that the lease period will take
   into account the network propagation delays and other network delay
   factors for the client population.  Since the protocol does not allow
   for an automatic method to determine an appropriate copy lease
   period, the server's administrator may have to tune the copy lease
   period.

   A successful response will also contain a list of names, addresses,
   and URLs called cnr_source_server, on which the source is willing to
   accept connections from the destination.  These might not be
   reachable from the client and might be located on networks to which
   the client has no connection.

   If the client wishes to perform an inter-server copy, the client MUST
   send a COPY_NOTIFY to the source server.  Therefore, the source
   server MUST support COPY_NOTIFY.

   For a copy only involving one server (the source and destination are
   on the same server), this operation is unnecessary.

   The COPY_NOTIFY operation may fail for the following reasons (this is



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   a partial list):

   NFS4ERR_MOVED:  The file system which contains the source file is not
      present on the source server.  The client can determine the
      correct location and reissue the operation with the correct
      location.

   NFS4ERR_NOTSUPP:  The copy offload operation is not supported by the
      NFS server receiving this request.

   NFS4ERR_WRONGSEC:  The security mechanism being used by the client
      does not match the server's security policy.

4.3.  Operation V: COPY_REVOKE - Revoke a destination server's copy
      privileges

   ARGUMENTS

                   struct COPY_REVOKE4args {
                           /* CURRENT_FH: source file */
                           netloc4         cra_destination_server;
                   };

   RESULTS

                   struct COPY_REVOKE4res {
                           nfsstat4        crr_status;
                   };

   DESCRIPTION

   This operation is used for an inter-server copy.  A client sends this
   operation in a COMPOUND request to the source server to revoke the
   authorization of a destination server identified by
   cra_destination_server from reading the file specified by CURRENT_FH
   on behalf of given user.  If the cra_destination_server has already
   begun copying the file, a successful return from this operation
   indicates that further access will be prevented.

   The cra_destination_server MUST be specified using the netloc4
   network location format.  The server is not required to resolve the
   cra_destination_server address before completing this operation.

   The COPY_REVOKE operation is useful in situations in which the source
   server granted a very long or infinite lease on the destination
   server's ability to read the source file and all copy operations on
   the source file have been completed.




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   For a copy only involving one server (the source and destination are
   on the same server), this operation is unnecessary.

   If the server supports COPY_NOTIFY, the server is REQUIRED to support
   the COPY_REVOKE operation.

   The COPY_REVOKE operation may fail for the following reasons (this is
   a partial list):

   NFS4ERR_MOVED:  The file system which contains the source file is not
      present on the source server.  The client can determine the
      correct location and reissue the operation with the correct
      location.

   NFS4ERR_NOTSUPP:  The copy offload operation is not supported by the
      NFS server receiving this request.

4.4.  Operation W: COPY - Initiate a server-side copy

   ARGUMENTS

                   #define COPY4_GUARDED           = 0x00000001;
                   #define COPY4_METADATA          = 0x00000002;
                   #define COPY4_SPACE_RESERVED    = 0x00000004;

                   struct COPY4args {
                           /* SAVED_FH: source file */
                           /* CURRENT_FH: destination file or */
                           /*             directory           */
                           offset4           ca_src_offset;
                           offset4           ca_dst_offset;
                           length4           ca_count;
                           uint32_t          ca_flags;
                           component4        ca_destination;
                           netloc4           ca_source_server<>;
                   };

   RESULTS

                   union COPY4res switch (nfsstat4 cr_status) {
                           /* CURRENT_FH: destination file */
                   case NFS4_OK:
                           stateid4        cr_callback_id<1>;
                   default:
                           length4         cr_bytes_copied;
                   };

   DESCRIPTION



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   The COPY operation is used for both intra- and inter-server copies.
   In both cases, the COPY is always sent from the client to the
   destination server of the file copy.  The COPY operation requests
   that a file be copied from the location specified by the SAVED_FH
   value to the location specified by the combination of CURRENT_FH and
   ca_destination.

   The SAVED_FH must be a regular file.  If SAVED_FH is not a regular
   file, the operation MUST fail and return NFS4ERR_WRONG_TYPE.

   In order to set SAVED_FH to the source file handle, the compound
   procedure requesting the COPY will include a sub-sequence of
   operations such as

                           PUTFH source-fh
                           SAVEFH

   If the request is for a server-to-server copy, the source-fh is a
   filehandle from the source server and the compound procedure is being
   executed on the destination server.  In this case, the source-fh is a
   foreign filehandle on the server receiving the COPY request.  If
   either PUTFH or SAVEFH checked the validity of the filehandle, the
   operation would likely fail and return NFS4ERR_STALE.

   In order to avoid this problem, the minor version incorporating the
   COPY operations will need to make a few small changes in the handling
   of existing operations.  If a server supports the server-to-server
   COPY feature, a PUTFH followed by a SAVEFH MUST NOT return
   NFS4ERR_STALE for either operation.  These restrictions do not pose
   substantial difficulties for servers.  The CURRENT_FH and SAVED_FH
   may be validated in the context of the operation referencing them and
   an NFS4ERR_STALE error returned for an invalid file handle at that
   point.

   The CURRENT_FH and ca_destination together specify the destination of
   the copy operation.  If ca_destination is of 0 (zero) length, then
   CURRENT_FH specifies the target file.  In this case, CURRENT_FH MUST
   be a file and not a directory.  If ca_destination is not of 0 (zero)
   length, the ca_destination argument specifies the file name to which
   the data will be copied within the directory identified by
   CURRENT_FH.  In this case, CURRENT_FH MUST be a directory and not a
   file.

   If the file named by ca_destination does not exist and the operation
   completes successfully, the file will be visible in the file system
   namespace.  If the file does not exist and the operation fails, the
   file MAY be visible in the file system namespace depending on when
   the failure occurs and on the implementation of the NFS server



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   receiving the COPY operation.  If the ca_destination name cannot be
   created in the destination file system (due to file name
   restrictions, such as case or length), the operation MUST fail.

   The ca_src_offset is the offset within the source file from which the
   data will be read, the ca_dst_offset is the offset within the
   destination file to which the data will be written, and the ca_count
   is the number of bytes that will be copied.  An offset of 0 (zero)
   specifies the start of the file.  A count of 0 (zero) requests that
   all bytes from ca_src_offset through EOF be copied to the
   destination.  If concurrent modifications to the source file overlap
   with the source file region being copied, the data copied may include
   all, some, or none of the modifications.  If the source file's end of
   file is being modified in parallel with a copy that specifies a count
   of 0 (zero) bytes, the amount of data copied is implementation
   dependent (clients may guard against this case by specifying a non-
   zero count value).

   If the source offset or the source offset plus count is greater than
   or equal to the size of the source file, the operation will fail with
   NFS4ERR_INVAL.  The destination offset or destination offset plus
   count may be greater than the size of the destination file.  This
   allows for the client to issue parallel copies to implement
   operations such as "cat file1 file2 file3 file4 > dest".

   If the destination file is created as a result of this command, the
   destination file's size will be equal to the number of bytes
   successfully copied.  If the destination file already existed, the
   destination file's size may increase as a result of this operation
   (e.g. if ca_dst_offset plus ca_count is greater than the
   destination's initial size).

   If the ca_source_server list is specified, then this is an inter-
   server copy operation and the source file is on a remote server.  The
   client is expected to have previously issued a successful COPY_NOTIFY
   request to the remote source server.  The ca_source_server list
   SHOULD be the same as the COPY_NOTIFY response's cnr_source_server
   list.  If the client includes the entries from the COPY_NOTIFY
   response's cnr_source_server list in the ca_source_server_list, the
   source server can indicate a specific copy protocol for the
   destination server to use by returning a URL, which specifies both a
   protocol service and server name.  Server-to-server copy protocol
   considerations are described in Section 3.3 and Section 5.1.

   The ca_flags argument allows the copy operation to be customized in
   the following ways using the guarded flag (COPY4_GUARDED), the
   metadata flag (COPY4_METADATA), and the space reserved flag
   (COPY4_SPACE_RESERVED).



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   If the guarded flag is set and the destination exists on the server,
   this operation will fail with NFS4ERR_EXIST.

   If the guarded flag is not set and the destination exists on the
   server, the behavior is implementation dependent.

   If the metadata flag is set, the REQUIRED and RECOMMENDED attributes
   of the destination file MUST be the same as the source file's
   corresponding REQUIRED and RECOMMENDED attributes.  The set of
   REQUIRED and RECOMMENDED attributes are defined by the NFS protocol
   version over which the copy is being performed (i.e., if the COPY is
   being sent over NFSv4.X then these are the REQUIRED and RECOMMENDED
   attributes defined by NFSv4.X).  By definition the source server and
   destination server will support the same set of REQUIRED attributes
   but might not support the same set of RECOMMENDED attributes.  The
   destination server MUST return NFS4ERR_ATTRNOTSUPP if the source file
   has a RECOMMENDED attribute that cannot be set on the destination
   file.  Any attribute supported by the destination server that is not
   set on the source file SHOULD be left unset.  The destination file's
   named attributes are not duplicated from the source file.  After the
   copy process completes, the client MAY attempt to duplicate named
   attributes using standard NFSv4 operations.  However, the destination
   server's named attribute capabilities MAY be different from the
   source server's named attribute capabilities.

   If the metadata flag is not set, the destination's metadata is
   implementation dependent.

   If the space reserved flag is set, the operation will only succeed if
   the file server can guarantee that all future non-extending writes to
   the copied file will not fail due to insufficient space.

   If space_reserved is not set, the space reservation state of the new
   file is implementation dependent.

   If the operation does not result in an immediate failure, the server
   will return NFS4_OK, and the CURRENT_FH will be set to the
   destination's filehandle.

   If an immediate failure does occur, cr_bytes_copied will be set to
   the number of bytes copied to the destination file before the error
   occurred.  The cr_bytes_copied value indicates what percentage of the
   copy was performed before the error occurred, but not which specific
   bytes were copied.

   A return of NFS4_OK indicates that either the operation is complete
   or the operation was initiated and a callback will be used to deliver
   the final status of the operation.



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   If the cr_callback_id is returned, this indicates that the operation
   was initiated and a CB_COPY callback will deliver the final results
   of the operation.  The cr_callback_id stateid is termed a copy
   stateid in this context.  The server is given the option of returning
   the results in a callback because the data may require a relatively
   long period of time to copy.

   If no cr_callback_id is returned, the operation completed
   synchronously and no callback will be issued by the server.  The
   completion status of the operation is indicated by cr_status.

   In the event of a failure the state of the destination file is
   implementation dependent.The COPY operation may fail for the
   following reasons (this is a partial list).

   NFS4ERR_MOVED:  The file system which contains the source file, or
      the destination file or directory is not present.  The client can
      determine the correct location and reissue the operation with the
      correct location.

   NFS4ERR_NOTSUPP:  The copy offload operation is not supported by the
      NFS server receiving this request.

   NFS4ERR_PARTNER_NOTSUPP:  The remote server does not support the
      server-to-server copy offload protocol.

   NFS4ERR_PARTNER_NO_AUTH:  The remote server does not authorize a
      server-to-server copy offload operation.  This may be due to the
      client's failure to send the COPY_NOTIFY operation to the remote
      server, the remote server receiving a server-to-server copy
      offload request after the copy lease time expired, or for some
      other permission problem.

   NFS4ERR_FBIG:  The copy operation would have caused the file to grow
      beyond the server's limit.

   NFS4ERR_NOTDIR:  The CURRENT_FH is a file and ca_destination has non-
      zero length.

   NFS4ERR_WRONG_TYPE:  The SAVED_FH is not a regular file.

   NFS4ERR_ISDIR:  The CURRENT_FH is a directory and ca_destination has
      zero length.

   NFS4ERR_INVAL:  The source offset or offset plus count are greater
      than or equal to the size of the source file.





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   NFS4ERR_DELAY:  The server does not have the resources to perform the
      copy operation at the current time.  The client should retry the
      operation sometime in the future.

   NFS4ERR_METADATA_NOTSUPP:  The destination file cannot support the
      same metadata as the source file.

   NFS4ERR_WRONGSEC:  The security mechanism being used by the client
      does not match the server's security policy.

4.5.  Operation X: COPY_ABORT - Cancel a server-side copy

   ARGUMENTS

                   struct COPY_ABORT4args {
                           /* CURRENT_FH: destination file */
                           stateid4        caa_stateid;
                   };

   RESULTS

                   struct COPY_ABORT4res {
                           nfsstat4        car_status;
                   };

   DESCRIPTION

   COPY_ABORT is used for both intra- and inter-server asynchronous
   copies.  The COPY_ABORT operation allows the client to cancel a
   server-side copy operation that it initiated.  This operation is sent
   in a COMPOUND request from the client to the destination server.
   This operation may be used to cancel a copy when the application that
   requested the copy exits before the operation is completed or for
   some other reason.

   The request contains the filehandle and copy stateid cookies that act
   as the context for the previously initiated copy operation.

   The result's car_status field indicates whether the cancel was
   successful or not.  A value of NFS4_OK indicates that the copy
   operation was canceled and no callback will be issued by the server.
   A copy operation that is successfully canceled may result in none,
   some, or all of the data copied.

   If the server supports asynchronous copies, the server is REQUIRED to
   support the COPY_ABORT operation.

   The COPY_ABORT operation may fail for the following reasons (this is



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   a partial list):

   NFS4ERR_NOTSUPP:  The abort operation is not supported by the NFS
      server receiving this request.

   NFS4ERR_RETRY:  The abort failed, but a retry at some time in the
      future MAY succeed.

   NFS4ERR_COMPLETE_ALREADY:  The abort failed, and a callback will
      deliver the results of the copy operation.

   NFS4ERR_SERVERFAULT:  An error occurred on the server that does not
      map to a specific error code.

4.6.  Operation Y: COPY_STATUS - Poll for status of a server-side copy

   ARGUMENTS

                   struct COPY_STATUS4args {
                           /* CURRENT_FH: destination file */
                           stateid4        csa_stateid;
                   };

   RESULTS

                   union COPY_STATUS4res switch (nfsstat4 cr_status) {
                   case NFS4_OK:
                           length4         csr_bytes_copied;
                           nfsstat4        csr_complete<1>;
                   default:
                           void;
                   };

   DESCRIPTION

   COPY_STATUS is used for both intra- and inter-server asynchronous
   copies.  The COPY_STATUS operation allows the client to poll the
   server to determine the status of an asynchronous copy operation.
   This operation is sent by the client to the destination server.

   If this operation is successful, the number of bytes copied are
   returned to the client in the csr_bytes_copied field.  The
   csr_bytes_copied value indicates what percentage of the copy has been
   performed but not which specific bytes have been copied.

   If the optional csr_complete field is present, the copy has
   completed.  In this case the status value indicates the result of the
   asynchronous copy operation.  In all cases, the server will also



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   deliver the final results of the asynchronous copy in a CB_COPY
   operation.

   The failure of this operation does not indicate the result of the
   asynchronous copy in any way.

   If the server supports asynchronous copies, the server is REQUIRED to
   support the COPY_STATUS operation.

   The COPY_STATUS operation may fail for the following reasons (this is
   a partial list):

   NFS4ERR_NOTSUPP:  The copy status operation is not supported by the
      NFS server receiving this request.

   NFS4ERR_BAD_STATEID:  The stateid is not valid (see Section 4.8
      below).

   NFS4ERR_EXPIRED:  The stateid has expired (see Copy Offload Stateid
      section below).

4.7.  Operation Z: CB_COPY - Report results of a server-side copy

   ARGUMENTS

                   union copy_info4 switch (nfsstat4 cca_status) {
                   case NFS4_OK:
                           void;
                   default:
                           length4       cca_bytes_copied;
                   };

                   struct CB_COPY4args {
                           nfs_fh4       cca_fh;
                           stateid4      cca_stateid;
                           copy_info4    cca_copy_info;
                   };

   RESULTS

                   struct CB_COPY4res {
                           nfsstat4      ccr_status;
                   };

   DESCRIPTION

   CB_COPY is used for both intra- and inter-server asynchronous copies.
   The CB_COPY callback informs the client of the result of an



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   asynchronous server-side copy.  This operation is sent by the
   destination server to the client in a CB_COMPOUND request.  The copy
   is identified by the filehandle and stateid arguments.  The result is
   indicated by the status field.  If the copy failed, cca_bytes_copied
   contains the number of bytes copied before the failure occurred.  The
   cca_bytes_copied value indicates what percentage of the copy was
   performed before the error occurred but not which specific bytes were
   copied.

   In the absence of an established backchannel, the server cannot
   signal the completion of the COPY via a CB_COPY callback.  The loss
   of a callback channel would be indicated by the server setting the
   SEQ4_STATUS_CB_PATH_DOWN flag in the sr_status_flags field of the
   SEQUENCE operation.  The client must re-establish the callback
   channel to receive the status of the COPY operation.  Prolonged loss
   of the callback channel could result in the server dropping the COPY
   operation state and invalidating the copy stateid.

   If the client supports the COPY operation, the client is REQUIRED to
   support the CB_COPY operation.

   The CB_COPY operation may fail for the following reasons (this is a
   partial list):

   NFS4ERR_NOTSUPP:  The copy offload operation is not supported by the
      NFS client receiving this request.

4.8.  Copy Offload Stateids

   A server may perform a copy offload operation asynchronously.  An
   asynchronous copy is tracked using a copy offload stateid.  Copy
   offload stateids are include in the COPY, COPY_ABORT, COPY_STATUS,
   and CB_COPY operations.

   Section 8.2.4 of [NFSv4.1] specifies that stateids are valid until
   either (A) the client or server restart or (B) the client returns the
   resource.

   A copy offload stateid will be valid until either (A) the client or
   server restart or (B) the client returns the resource by issuing a
   COPY_ABORT operation or the client replies to a CB_COPY operation.

   A copy offload stateid's seqid MUST NOT be 0 (zero).  In the context
   of a copy offload operation, it is ambiguous to indicate the most
   recent copy offload operation using a stateid with seqid of 0 (zero).
   Therefore a copy offload stateid with seqid of 0 (zero) MUST be
   considered invalid.




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5.  Security Considerations

   The security considerations pertaining to NFSv4 [RFC3530] apply to
   this document.

   The standard security mechanisms provide by NFSv4 [RFC3530] may be
   used to secure the protocol described in this document.

   NFSv4 clients and servers supporting the the inter-server copy
   operations described in this document are REQUIRED to implement
   [RPCSEC_GSSv3], including the RPCSEC_GSSv3 privileges copy_from_auth
   and copy_to_auth.  If the server-to-server copy protocol is ONC RPC
   based, the servers are also REQUIRED to implement the RPCSEC_GSSv3
   privilege copy_confirm_auth.  These requirements to implement are not
   requirements to use.  NFSv4 clients and servers are RECOMMENDED to
   use [RPCSEC_GSSv3] to secure server-side copy operations.

5.1.  Inter-Server Copy Security

5.1.1.  Requirements for Secure Inter-Server Copy

   Inter-server copy is driven by several requirements:

   o  The specification MUST NOT mandate an inter-server copy protocol.
      There are many ways to copy data.  Some will be more optimal than
      others depending on the situation that exists between a source and
      destination server.  For example the source and destination
      servers might be two nodes sharing a common file system format for
      the source and destination file systems.  Thus the source and
      destination are in an ideal position to efficiently render the
      image of the source file to the destination file by replicating
      the file system formats at the block level.  For example, the
      source and destination might be two nodes sharing a common storage
      area network, and thus there is no need to copy any data at all,
      and instead ownership of the file and its contents simply gets re-
      assigned to the destination.

   o  The specification MUST provide guidance for using NFSv4.x as a
      copy protocol.  For those source and destination servers willing
      to use NFSv4.x there are specific security considerations that
      this specification can and does address.

   o  The specification MUST NOT mandate pre-configuration between the
      source and destination server.  Requiring that the source and
      destination first have a "copying relationship" increases the
      administrative burden.  However the specification MUST NOT
      preclude implementations that require pre-configuration.




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   o  The specification MUST NOT mandate a trust relationship between
      the source and destination server.  The NFSv4 security model
      requires mutual authentication between a principal on an NFS
      client and a principal on an NFS server.  This model MUST continue
      with the introduction of COPY.

5.1.2.  Inter-Server Copy with RPCSEC_GSSv3

   When the client sends a COPY_NOTIFY to the source server to expect
   the destination to attempt to copy data from the source server, it is
   expected that this copy is being done on behalf of the principal
   (called the "user principal") that sent the RPC request that encloses
   the COMPOUND procedure that contains the COPY_NOTIFY operations.  The
   user principal is identified by the RPC credentials.  The problem is
   how can the user principal provide an authorization that directs the
   source to allow the destination to perform the copy in a manner that
   lets the source properly authenticate the destination's copy, and
   without allowing the destination to exceed its authorization?

   One way would be to send delegated credentials of the client's user
   principal to the destination server.  The destination would then
   authenticate as the user principal.  If the destination were using
   the NFSv4 protocol to perform the copy, then the source server would
   authenticate the destination server as the user principal, and the
   file copy could securely proceed.  However, this approach would allow
   the destination server to copy other files.  The user principal would
   have to trust the destination server to not do so.  This is counter
   to the requirements, and so is not presented here.  Instead an
   approach using RPCSEC_GSSv3 [RPCSEC_GSSv3] privileges is proposed.

   One of the stated applications of the proposed RPCSEC_GSSv3 protocol
   is compound client host and user authentication [+ privilege
   assertion].  For inter-server file copy, we require compound NFS
   server host and user authentication [+ privilege assertion].  The
   distinction between the two is one without meaning.

   RPCSEC_GSSv3 introduces the notion of privileges.  We define three
   privileges:

   copy_from_auth:  A user principal is authorizing a source principal
      ("nfs@<source>") to allow a destination principal ("nfs@
      <destination>") to copy a file from the source to the destination.
      This privilege is established on the source server before the user
      principal sends a COPY_NOTIFY operation to the source server.







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           typedef string secret4<>;

           struct copy_from_auth_priv {
               secret4             cfap_shared_secret;
               netloc4             cfap_destination;
               /* the NFSv4 user name that the user principal maps to */
               utf8str_mixed       cfap_username;
               /* equal to seq_num of rpc_gss_cred_vers_3_t */
               unsigned int        cfap_seq_num;
           };


      cap_shared_secret is a secret value the user principal generates.

   copy_to_auth:  A user principal is authorizing a destination
      principal ("nfs@<destination>") to allow it to copy a file from
      the source to the destination.  This privilege is established on
      the destination server before the user principal sends a COPY
      operation to the destination server.


           struct copy_to_auth_priv {
              /* equal to cfap_shared_secret */
              secret4              ctap_shared_secret;
              netloc4              ctap_source;
              /* the NFSv4 user name that the user principal maps to */
              utf8str_mixed        ctap_username;
              /* equal to seq_num of rpc_gss_cred_vers_3_t */
              unsigned int         ctap_seq_num;
           };


      ctap_shared_secret is a secret value the user principal generated
      and was used to establish the copy_from_auth privilege with the
      source principal.

   copy_confirm_auth:  A destination principal is confirming with the
      source principal that it is authorized to copy data from the
      source on behalf of the user principal.  When the inter-server
      copy protocol is NFSv4, or for that matter, any protocol capable
      of being secured via RPCSEC_GSSv3 (i.e. any ONC RPC protocol),
      this privilege is established before the file is copied from the
      source to the destination.








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           struct copy_confirm_auth_priv {
               /* equal to GSS_GetMIC() of cfap_shared_secret */
               opaque              ccap_shared_secret_mic<>;
               /* the NFSv4 user name that the user principal maps to */
               utf8str_mixed       ccap_username;
               /* equal to seq_num of rpc_gss_cred_vers_3_t */
               unsigned int        ccap_seq_num;
           };

5.1.2.1.  Establishing a Security Context

   When the user principal wants to COPY a file between two servers, if
   it has not established copy_from_auth and copy_to_auth privileges on
   the servers, it establishes them:

   o  The user principal generates a secret it will share with the two
      servers.  This shared secret will be placed in the
      cfap_shared_secret and ctap_shared_secret of the appropriate
      privilege data types, copy_from_auth_priv, and copy_to_auth_priv.

   o  An instance of copy_from_auth_priv is filled in with the shared
      secret, the destination server, and the NFSv4 user id of the user
      principal.  It will be sent with an RPCSEC_GSS3_CREATE procedure,
      and so cfap_seq_num it set to the seq_num of the credential of the
      RPCSEC_GSS3_CREATE procedure.  Because cfap_shared_secret is a
      secret, after XDR encoding copy_from_auth_priv, GSS_Wrap() (with
      privacy) is invoked on copy_from_auth_priv.  The
      RPCSEC_GSS3_CREATE procedure's arguments are:


           struct {
               rpc_gss3_gss_binding    *compound_binding;
               rpc_gss3_chan_binding   *chan_binding_mic;
               rpc_gss3_assertion      assertions<>;
               rpc_gss3_extension      extensions<>;
           } rpc_gss3_create_args;


      The string "copy_from_auth" is placed in assertions[0].privs.  The
      output of GSS_Wrap() is placed in extensions[0].data.  The field
      extensions[0].critical is set to TRUE.  The source server calls
      GSS_Unwrap() on the privilege, and verifies that the seq_num
      matches the credential.  It then verifies that the NFSv4 user id
      being asserted matches the source server's mapping of the user
      principal.  If it does, the privilege is established on the source
      server as: <"copy_from_auth", user id, destination>.  The
      successful reply to RPCSEC_GSS3_CREATE has:




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           struct {
               opaque                  handle<>;
               rpc_gss3_chan_binding   *chan_binding_mic;
               rpc_gss3_assertion      granted_assertions<>;
               rpc_gss3_assertion      server_assertions<>;
               rpc_gss3_extension      extensions<>;
           } rpc_gss3_create_res;


      The field "handle" is the RPCSEC_GSSv3 handle that the client will
      use on COPY_NOTIFY requests involving the source and destination
      server. granted_assertions[0].privs will be equal to
      "copy_from_auth".  The server will return a GSS_Wrap() of
      copy_to_auth_priv.

   o  An instance of copy_to_auth_priv is filled in with the shared
      secret, the source server, and the NFSv4 user id.  It will be sent
      with an RPCSEC_GSS3_CREATE procedure, and so ctap_seq_num it set
      to the seq_num of the credential of the RPCSEC_GSS3_CREATE
      procedure.  Because ctap_shared_secret is a secret, after XDR
      encoding copy_to_auth_priv, GSS_Wrap() is invoked on
      copy_to_auth_priv.  The RPCSEC_GSS3_CREATE procedure's arguments
      are:


           struct {
               rpc_gss3_gss_binding    *compound_binding;
               rpc_gss3_chan_binding   *chan_binding_mic;
               rpc_gss3_assertion      assertions<>;
               rpc_gss3_extension      extensions<>;
           } rpc_gss3_create_args;


      The string "copy_to_auth" is placed in assertions[0].privs.  The
      output of GSS_Wrap() is placed in extensions[0].data.  The field
      extensions[0].critical is set to TRUE.  After unwrapping,
      verifying the seq_num, and the user principal to NFSv4 user ID
      mapping, the destination establishes a privilege of
      <"copy_to_auth", user id, source>.  The successful reply to
      RPCSEC_GSS3_CREATE has:


           struct {
               opaque                  handle<>;
               rpc_gss3_chan_binding   *chan_binding_mic;
               rpc_gss3_assertion      granted_assertions<>;
               rpc_gss3_assertion      server_assertions<>;
               rpc_gss3_extension      extensions<>;



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           } rpc_gss3_create_res;


      The field "handle" is the RPCSEC_GSSv3 handle that the client will
      use on COPY requests involving the source and destination server.
      The field granted_assertions[0].privs will be equal to
      "copy_to_auth".  The server will return a GSS_Wrap() of
      copy_to_auth_priv.

5.1.2.2.  Starting a Secure Inter-Server Copy

   When the client sends a COPY_NOTIFY request to the source server, it
   uses the privileged "copy_from_auth" RPCSEC_GSSv3 handle.
   cna_destination_server in COPY_NOTIFY MUST be the same as the name of
   the destination server specified in copy_from_auth_priv.  Otherwise,
   COPY_NOTIFY will fail with NFS4ERR_ACCESS.  The source server
   verifies that the privilege <"copy_from_auth", user id, destination>
   exists, and annotates it with the source filehandle, if the user
   principal has read access to the source file, and if administrative
   policies give the user principal and the NFS client read access to
   the source file (i.e. if the ACCESS operation would grant read
   access).  Otherwise, COPY_NOTIFY will fail with NFS4ERR_ACCESS.

   When the client sends a COPY request to the destination server, it
   uses the privileged "copy_to_auth" RPCSEC_GSSv3 handle.
   ca_source_server in COPY MUST be the same as the name of the source
   server specified in copy_to_auth_priv.  Otherwise, COPY will fail
   with NFS4ERR_ACCESS.  The destination server verifies that the
   privilege <"copy_to_auth", user id, source> exists, and annotates it
   with the source and destination filehandles.  If the client has
   failed to establish the "copy_to_auth" policy it will reject the
   request with NFS4ERR_PARTNER_NO_AUTH.

   If the client sends a COPY_REVOKE to the source server to rescind the
   destination server's copy privilege, it uses the privileged
   "copy_from_auth" RPCSEC_GSSv3 handle and the cra_destination_server
   in COPY_REVOKE MUST be the same as the name of the destination server
   specified in copy_from_auth_priv.  The source server will then delete
   the <"copy_from_auth", user id, destination> privilege and fail any
   subsequent copy requests sent under the auspices of this privilege
   from the destination server.

5.1.2.3.  Securing ONC RPC Server-to-Server Copy Protocols

   After a destination server has a "copy_to_auth" privilege established
   on it, and it receives a COPY request, if it knows it will use an ONC
   RPC protocol to copy data, it will establish a "copy_confirm_auth"
   privilege on the source server, using nfs@<destination> as the



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   initiator principal, and nfs@<source> as the target principal.

   The value of the field ccap_shared_secret_mic is a GSS_VerifyMIC() of
   the shared secret passed in the copy_to_auth privilege.  The field
   ccap_username is the mapping of the user principal to an NFSv4 user
   name ("user"@"domain" form), and MUST be the same as ctap_username
   and cfap_username.  The field ccap_seq_num is the seq_num of the
   RPCSEC_GSSv3 credential used for the RPCSEC_GSS3_CREATE procedure the
   destination will send to the source server to establish the
   privilege.

   The source server verifies the privilege, and establishes a
   <"copy_confirm_auth", user id, destination> privilege.  If the source
   server fails to verify the privilege, the COPY operation will be
   rejected with NFS4ERR_PARTNER_NO_AUTH.  All subsequent ONC RPC
   requests sent from the destination to copy data from the source to
   the destination will use the RPCSEC_GSSv3 handle returned by the
   source's RPCSEC_GSS3_CREATE response.

   Note that the use of the "copy_confirm_auth" privilege accomplishes
   the following:

   o  if a protocol like NFS is being used, with export policies, export
      policies can be overridden in case the destination server as-an-
      NFS-client is not authorized

   o  manual configuration to allow a copy relationship between the
      source and destination is not needed.

   If the attempt to establish a "copy_confirm_auth" privilege fails,
   then when the user principal sends a COPY request to destination, the
   destination server will reject it with NFS4ERR_PARTNER_NO_AUTH.

5.1.2.4.  Securing Non ONC RPC Server-to-Server Copy Protocols

   If the destination won't be using ONC RPC to copy the data, then the
   source and destination are using an unspecified copy protocol.  The
   destination could use the shared secret and the NFSv4 user id to
   prove to the source server that the user principal has authorized the
   copy.

   For protocols that authenticate user names with passwords (e.g.  HTTP
   [RFC2616] and FTP [RFC0959]), the nfsv4 user id could be used as the
   user name, and an ASCII hexadecimal representation of the
   RPCSEC_GSSv3 shared secret could be used as the user password or as
   input into non-password authentication methods like CHAP [RFC1994].





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5.1.3.  Inter-Server Copy via ONC RPC but without RPCSEC_GSSv3

   ONC RPC security flavors other than RPCSEC_GSSv3 MAY be used with the
   server-side copy offload operations described in this document.  In
   particular, host-based ONC RPC security flavors such as AUTH_NONE and
   AUTH_SYS MAY be used.  If a host-based security flavor is used, a
   minimal level of protection for the server-to-server copy protocol is
   possible.

   In the absence of strong security mechanisms such as RPCSEC_GSSv3,
   the challenge is how the source server and destination server
   identify themselves to each other, especially in the presence of
   multi-homed source and destination servers.  In a multi-homed
   environment, the destination server might not contact the source
   server from the same network address specified by the client in the
   COPY_NOTIFY.  This can be overcome using the procedure described
   below.

   When the client sends the source server the COPY_NOTIFY operation,
   the source server may reply to the client with a list of target
   addresses, names, and/or URLs and assign them to the unique triple:
   <source fh, user ID, destination address Y>.  If the destination uses
   one of these target netlocs to contact the source server, the source
   server will be able to uniquely identify the destination server, even
   if the destination server does not connect from the address specified
   by the client in COPY_NOTIFY.

   For example, suppose the network topology is as shown in Figure 3.
   If the source filehandle is 0x12345, the source server may respond to
   a COPY_NOTIFY for destination 10.11.78.56 with the URLs:

      nfs://10.11.78.18//_COPY/10.11.78.56/_FH/0x12345

      nfs://192.168.33.18//_COPY/10.11.78.56/_FH/0x12345

   The client will then send these URLs to the destination server in the
   COPY operation.  Suppose that the 192.168.33.0/24 network is a high
   speed network and the destination server decides to transfer the file
   over this network.  If the destination contacts the source server
   from 192.168.33.56 over this network using NFSv4.1, it does the
   following:

   COMPOUND  { PUTROOTFH, LOOKUP "_COPY" ; LOOKUP "10.11.78.56"; LOOKUP
      "_FH" ; OPEN "0x12345" ; GETFH }

   The source server will therefore know that these NFSv4.1 operations
   are being issued by the destination server identified in the
   COPY_NOTIFY.



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5.1.4.  Inter-Server Copy without ONC RPC and RPCSEC_GSSv3

   The same techniques as Section 5.1.3, using unique URLs for each
   destination server, can be used for other protocols (e.g.  HTTP
   [RFC2616] and FTP [RFC0959]) as well.


6.  IANA Considerations

   This document has no actions for IANA.


7.  References

7.1.  Normative References

   [NFSv4.1]  Shepler, S., Eisler, M., and D. Noveck, "NFS Version 4
              Minor Version 1", draft-ietf-nfsv4-minorversion1-29 (work
              in progress), December 2008.

   [RFC2119]  Bradner, S., "Key words for use in RFCs to Indicate
              Requirement Levels", BCP 14, RFC 2119, March 1997.

   [RFC3530]  Shepler, S., Callaghan, B., Robinson, D., Thurlow, R.,
              Beame, C., Eisler, M., and D. Noveck, "Network File System
              (NFS) version 4 Protocol", RFC 3530, April 2003.

   [RFC3986]  Berners-Lee, T., Fielding, R., and L. Masinter, "Uniform
              Resource Identifier (URI): Generic Syntax", STD 66,
              RFC 3986, January 2005.

   [RPCSEC_GSSv3]
              Williams, N., "Remote Procedure Call (RPC) Security
              Version 3", draft-williams-rpcsecgssv3 (work in progress),
              2008.

7.2.  Informational References

   [FEDFS-ADMIN]
              Lentini, J., Everhart, C., Ellard, D., Tewari, R., and M.
              Naik, "Administration Protocol for Federated Filesystems",
              draft-ietf-nfsv4-federated-fs-admin (Work In Progress),
              2009.

   [FEDFS-NSDB]
              Lentini, J., Everhart, C., Ellard, D., Tewari, R., and M.
              Naik, "NSDB Protocol for Federated Filesystems",
              draft-ietf-nfsv4-federated-fs-protocol (Work In Progress),



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              2009.

   [RFC0959]  Postel, J. and J. Reynolds, "File Transfer Protocol",
              STD 9, RFC 959, October 1985.

   [RFC1994]  Simpson, W., "PPP Challenge Handshake Authentication
              Protocol (CHAP)", RFC 1994, August 1996.

   [RFC2616]  Fielding, R., Gettys, J., Mogul, J., Frystyk, H.,
              Masinter, L., Leach, P., and T. Berners-Lee, "Hypertext
              Transfer Protocol -- HTTP/1.1", RFC 2616, June 1999.


Appendix A.  Acknowledgments

   Tom Talpey co-authored an unpublished version of this document.  We
   thank Tom for his contributions, especially with regards to the
   asynchronous completion callback mechanism.

   This document was reviewed by a number of individuals.  We would like
   to thank Pranoop Erasani, Tom Haynes, Arthur Lent, Trond Myklebust,
   Dave Noveck, Theresa Lingutla-Raj, Manjunath Shankararao, Satyam
   Vaghani, and Nico Williams for their input and advice.


Authors' Addresses

   James Lentini
   NetApp
   1601 Trapelo Rd, Suite 16
   Waltham, MA  02451
   USA

   Phone: +1 781-768-5359
   Email: jlentini@netapp.com


   Mike Eisler
   NetApp
   5765 Chase Point Circle
   Colorado Springs, CO  80919
   USA

   Phone: +1 719-599-9026
   Email: mike@eisler.com
   URI:   http://www.eisler.com





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   Rahul Iyer
   NetApp
   475 East Java Drive
   Sunnyvale, CA  94089
   USA

   Phone: +1 408-822-3980
   Email: iyer@netapp.com


   Deepak Kenchammana
   NetApp
   475 East Java Drive
   Sunnyvale, CA  94089
   USA

   Phone: +1 408-822-4765
   Email: kencham@netapp.com


   Anshul Madan
   Carnegie Mellon University
   The Institute for Software Research, Wean Hall
   5000 Forbes Avenue
   Pittsburgh, PA  15213
   USA

   Email: amadan@andrew.cmu.edu























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