--- 1/draft-ietf-shim6-multihome-shim-api-11.txt 2010-01-09 11:12:13.000000000 +0100 +++ 2/draft-ietf-shim6-multihome-shim-api-12.txt 2010-01-09 11:12:13.000000000 +0100 @@ -1,22 +1,22 @@ SHIM6 Working Group M. Komu Internet-Draft HIIT Intended status: Informational M. Bagnulo -Expires: June 10, 2010 UC3M +Expires: July 13, 2010 UC3M K. Slavov S. Sugimoto, Ed. Ericsson - December 7, 2009 + January 9, 2010 Socket Application Program Interface (API) for Multihoming Shim - draft-ietf-shim6-multihome-shim-api-11 + draft-ietf-shim6-multihome-shim-api-12 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. @@ -25,25 +25,25 @@ and may be updated, replaced, or obsoleted by other documents at any time. It is inappropriate to use Internet-Drafts as reference material or to cite them other than as "work in progress." The list of current Internet-Drafts can be accessed at http://www.ietf.org/ietf/1id-abstracts.txt. The list of Internet-Draft Shadow Directories can be accessed at http://www.ietf.org/shadow.html. - This Internet-Draft will expire on June 10, 2010. + This Internet-Draft will expire on July 13, 2010. Copyright Notice - Copyright (c) 2009 IETF Trust and the persons identified as the + 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 in effect on the date of publication of this document (http://trustee.ietf.org/license-info). Please review these documents carefully, as they describe your rights and restrictions with respect to this document. Abstract @@ -80,117 +80,102 @@ 5.14. SHIM_DEFERRED_CONTEXT_SETUP . . . . . . . . . . . . . . . 24 5.15. Applicability . . . . . . . . . . . . . . . . . . . . . . 25 5.16. Error Handling . . . . . . . . . . . . . . . . . . . . . 25 6. Ancillary Data for Multihoming Shim Sub-layer . . . . . . . . 26 6.1. Get Locator from Incoming Packet . . . . . . . . . . . . 27 6.2. Set Locator for Outgoing Packet . . . . . . . . . . . . . 27 6.3. Notification from Application to Multihoming Shim Sub-layer . . . . . . . . . . . . . . . . . . . . . . . . 27 6.4. Notification from Multihoming Shim Sub-layer to Application . . . . . . . . . . . . . . . . . . . . . . . 28 - 6.5. Applicability . . . . . . . . . . . . . . . . . . . . . . 29 + 6.5. Applicability . . . . . . . . . . . . . . . . . . . . . . 28 7. Data Structures . . . . . . . . . . . . . . . . . . . . . . . 29 7.1. Placeholder for Locator Information . . . . . . . . . . . 29 7.1.1. Handling Locator behind NAT . . . . . . . . . . . . . 30 7.2. Path Exploration Parameter . . . . . . . . . . . . . . . 31 7.3. Feedback Information . . . . . . . . . . . . . . . . . . 32 8. System Requirements . . . . . . . . . . . . . . . . . . . . . 33 - 9. Implications for Existing Socket API Extensions . . . . . . . 33 - 10. Resolving Conflicts with Preference Values . . . . . . . . . . 34 - 10.1. Implicit Forking . . . . . . . . . . . . . . . . . . . . 34 - 11. Discussion . . . . . . . . . . . . . . . . . . . . . . . . . . 35 - 11.1. Naming at Socket Layer . . . . . . . . . . . . . . . . . 35 - 11.2. Additional Requirements from Applications . . . . . . . . 35 - 11.3. Issues of Header Conversion among Different Address - Family . . . . . . . . . . . . . . . . . . . . . . . . . 36 - 11.4. Handling of Unknown Locator Provided by Application . . . 36 - 12. Changes . . . . . . . . . . . . . . . . . . . . . . . . . . . 36 - 12.1. Changes from version 00 to version 01 . . . . . . . . . . 36 - 12.2. Changes from version 01 to version 02 . . . . . . . . . . 37 - 12.3. Changes from version 02 to version 03 . . . . . . . . . . 37 - 12.4. Changes from version 03 to version 04 . . . . . . . . . . 37 - 12.5. Changes from version 04 to version 05 . . . . . . . . . . 37 - 12.6. Changes from version 05 to version 06 . . . . . . . . . . 37 - 12.7. Changes from version 06 to version 07 . . . . . . . . . . 37 - 12.8. Changes from version 07 to version 08 . . . . . . . . . . 37 - 12.9. Changes from version 08 to version 09 . . . . . . . . . . 38 - 12.10. Changes from version 09 to version 10 . . . . . . . . . . 38 - 12.11. Changes from version 10 to version 11 . . . . . . . . . . 38 - 13. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 38 - 14. Security Considerations . . . . . . . . . . . . . . . . . . . 38 - 15. Conclusion . . . . . . . . . . . . . . . . . . . . . . . . . . 38 - 16. Acknowledgments . . . . . . . . . . . . . . . . . . . . . . . 39 - 17. References . . . . . . . . . . . . . . . . . . . . . . . . . . 39 - 17.1. Normative References . . . . . . . . . . . . . . . . . . 39 - 17.2. Informative References . . . . . . . . . . . . . . . . . 40 - Appendix A. Context Forking . . . . . . . . . . . . . . . . . . . 40 - Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . . 43 + 9. Relation to Existing Sockets API Extensions . . . . . . . . . 33 + 10. Operational Considerations . . . . . . . . . . . . . . . . . . 34 + 10.1. Conflict Resolution . . . . . . . . . . . . . . . . . . . 34 + 10.2. Incompatiblility between IPv4 and IPv6 . . . . . . . . . 35 + 11. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 35 + 12. Protocol Constants and Variables . . . . . . . . . . . . . . . 35 + 13. Security Considerations . . . . . . . . . . . . . . . . . . . 35 + 13.1. Treatment of Unknown Locator . . . . . . . . . . . . . . 35 + 13.1.1. Treatment of Unknown Source Locator . . . . . . . . . 35 + 13.1.2. Treatment of Unknown Destination Locator . . . . . . . 36 + 14. Changes . . . . . . . . . . . . . . . . . . . . . . . . . . . 36 + 14.1. Changes from version 00 to version 01 . . . . . . . . . . 36 + 14.2. Changes from version 01 to version 02 . . . . . . . . . . 36 + 14.3. Changes from version 02 to version 03 . . . . . . . . . . 37 + 14.4. Changes from version 03 to version 04 . . . . . . . . . . 37 + 14.5. Changes from version 04 to version 05 . . . . . . . . . . 37 + 14.6. Changes from version 05 to version 06 . . . . . . . . . . 37 + 14.7. Changes from version 06 to version 07 . . . . . . . . . . 37 + 14.8. Changes from version 07 to version 08 . . . . . . . . . . 37 + 14.9. Changes from version 08 to version 09 . . . . . . . . . . 37 + 14.10. Changes from version 09 to version 10 . . . . . . . . . . 37 + 14.11. Changes from version 10 to version 11 . . . . . . . . . . 38 + 14.12. Changes from version 11 to version 12 . . . . . . . . . . 38 + 15. Acknowledgments . . . . . . . . . . . . . . . . . . . . . . . 38 + 16. References . . . . . . . . . . . . . . . . . . . . . . . . . . 38 + 16.1. Normative References . . . . . . . . . . . . . . . . . . 38 + 16.2. Informative References . . . . . . . . . . . . . . . . . 39 + Appendix A. Context Forking . . . . . . . . . . . . . . . . . . . 39 + Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . . 41 1. Introduction - HIP and SHIM6 have a commonality in their protocol design in the - sense that the semantic roles of an IP address, i.e., an identifier - and a locator, are distinguished. Separation of identifier and - locator is done by introducing a "shim" inside the IP layer which - maintains mapping of the identifier and associated locators. This - design principle is called "identifier/locator separation" and the - shim is referred to as a "shim sub-layer" in this document. - - The shim sub-layer provides a nice property to present a stable - communication endpoints (i.e., identifiers) to the upper layer - protocols. An on-going session can be maintained even when the - locator associated with the identifier is changed, for instance, upon - a re-homing event under a multihomed environment. Therefore, upper - layer protocols, especially connection-oriented applications are no - more annoyed by the locator change thanks to the identifier/locator - separation mechanism. + This document defines socket API extensions by which upper layer + protocols may be informed about and control the way in which a + multihoming shim sub-layer in the IP layer manages the dynamic choice + of locators. Initially it applies to SHIM6 and HIP, but it is + defined generically. - While the identifier/locator separation removes negative impact of - locator change, it does not necessarily mean that applications are - always ignorant about locators. We rather think that applications - may want to have a control of locators in some cases. For instance, - an application may want to use a specific locator to send IP packets. - Such a control of locators is referred to as "locator management" in - this document. Besides, applications may want to turn on or off the - identifier/locator separation mechanism. This document defines API - that provides locator management and additional control of shim sub- - layer for applications. + The role of the multihoming shim sub-layer (hereafter called "shim + sub-layer" in this document) is to avoid impacts to upper layer + protocols which may be caused when the endhost changes its attachment + point to the Internet, for instance, in the case of rehoming event + under the multihomed environment. The key design of the shim sub- + layer is to treat identifier and locator separately. Identifiers are + presented to upper layer protocols and used as communication + endpoints. Locators represent toplogical location of endhosts and + are used to route packet from the source to the destiantion. The + shim sub-layer maintains mapping of identifiers and locators. - This document recommends that the switching of identifier and locator - is done only once inside the TCP/IP stack of an endhost. That is, if - multiple shim sub-layers exist at the IP layer, any one of them - should be applied exclusively for a given flow. + Note that the shim sub-layer may conflict with other multihoming + mechanisms such as SCTP and multipath + TCP[I-D.ietf-shim6-applicability]. To avoid any conflict, only one + of SHIM6 and HIP should be in use. - As this document specifies sockets API extensions, it is written so - that the syntax and semantics are in line with the Posix standard - [POSIX] as much as possible. The API specified in this document - defines how to use ancillary data (aka cmsg) to access the locator - information with recvmsg() and/or sendmsg() I/O calls. The - definition of API is presented in C language and data types follow - the Posix format; intN_t means a singed integer of exactly N bits - (e.g. int16_t) and uintN_t means an unsigned integer of exactly N - bits (e.g. uint32_t). + In this document, syntax and semantics of the API are given in the + same way as the Posix standard [POSIX]. The API specifies how to use + ancillary data (aka cmsg) to access the locator information with + recvmsg() and/or sendmsg() I/O calls. The API is described in C + language and data types are defined in the Posix format; intN_t means + a singed integer of exactly N bits (e.g. int16_t) and uintN_t means + an unsigned integer of exactly N bits (e.g. uint32_t). The distinction between "connected" sockets and "unconnected" sockets is important when discussing the applicability of the socket API defined in this document. A connected socket is bound to a given peer, whereas an unconnected socket is not bound to any specific - peers. That is, the destination of the user data is not known until - the application writes data to an unconnected socket. TCP sockets - are connected, by definition. UDP sockets are unconnected, unless - the application uses the connect() system call. + peers. A TCP socket becomes a connected socket when the TCP + connection establishment is completed. UDP sockets are unconnected, + unless the application uses the connect() system call. The target readers of this document are application programmers who develop application software which may benefit greatly from multihomed environments. In addition, this document aims to provide - necessary information for developers of multihoming shim protocols to - implement API for enabling advanced locator management. + necessary information for developers of shim protocols to implement + API for enabling advanced locator management. 2. Terminology This section provides terminology used in this document. Basically most of the terms used in this document are taken from the following documents: o SHIM6 Protocol Specification[RFC5533] o HIP Architecture[RFC4423] o Reachability Protocol (REAP)[RFC5534] @@ -203,33 +188,40 @@ to specify the endpoint of a given communication. Applications may handle EIDs in various ways such as long-lived connections, callbacks, and referrals[I-D.ietf-shim6-app-refer]. * In the case of SHIM6, an identifier called a ULID serves as an EID. A ULID is chosen from locators available on the host. * In the case of HIP, an identifier called a Host Identifier serves as an EID. A Host Identifier is derived from the public key of a given host. For the sake of backward compatibility with the sockets API, the Host Identifier is represented in a form of hash of public key. + * Note that the EID appears in the standard socket API as an + address, and does not appear in the extensions defined in this + document, which only concern locators. o Locator - The IP address actually used to deliver IP packets. Locators are present in the source and destination fields of the IP header of a packet on the wire. * List of locators - A list of locators associated with an EID. There are two lists of locators stored in a given context. One is associated with the local EID and the other is associated with the remote EID. As defined in [RFC5533], the list of locators associated with an EID 'A' is denoted as Ls(A). - * Preferred locator - The (source/destination) locator currently used to send packets within a given context. As defined in [RFC5533], the preferred locator of a host 'A' is denoted as Lp(A). + * Unknown locator - Any locator that does not appear in the + locator list of the shim context associated with the socket. + When there is no shim context associated with the socket, any + source and/or destination locator requested by the application + is considered to be unknown locator. o Shim - The conceptual sub-layer inside the IP layer which maintains mappings between EIDs and locators. An EID can be associated with more than one locator at a time when the host is multihomed. The term 'shim' does not refer to a specific protocol but refers to the conceptual sub-layer inside the IP layer. o Identifier/locator adaptation - The adaptation performed at the shim sub-layer which may end up re-writing the source and/or destination addresses of an IP packet. In the outbound packet processing, the EID pair is converted to the associated locator pair. In the inbound packet processing, the locator pair is @@ -292,39 +284,49 @@ v v +------------------------------------------+ | Link Layer | +------------------------------------------+ Figure 1: System overview 4. Requirements The following is a list of requirements from applications: + o Turn on/off shim. An application should be able to request to + turn on or turn off the multihoming support by the shim layer: + * Apply shim. The application should be able to explicitly + request the shim sub-layer to apply multihoming support. + * Don't apply shim. The application should be able to request + the shim sub-layer not to apply the multihoming support but to + apply normal IP processing at the IP layer. + * Note that this function is also required by other types of + multihoming mechanisms such as SCTP and multipath TCP to avoid + potential conflict with the shim sub-layer. o Locator management. * It should be possible to set preferred source and/or destination locator within a given context: Lp(local) and/or Lp(remote). * It should be possible to get preferred source and/or destination locator within a given context: Lp(local) and/or Lp(remote). + * It should be possible to set a list of source and/or destination locators within a given context: Ls(local) and Ls(remote). - * It should be possible to get a list of source and/or destination locators within a given context: Ls(local) and Ls(remote). o Notification from applications to the shim sub-layer about the status of the communication. The notification occurs in an event- based manner. Applications and/or upper layer protocols may provide positive feedbacks or negative feedbacks to the shim sub- - layer. Note that these feedbacks are mentioned in [RFC5534]]: + layer. Note that these feedbacks are mentioned in [RFC5534]: * Applications and/or upper layer protocols (e.g., TCP) may provide positive feedbacks to the shim sub-layer informing that the communication is going well. * Applications and/or upper layer protocols (e.g., TCP) may provide negative feedbacks to the shim sub-layer informing that the communication status is not satisfactory. TCP may detect a problem when it does not receive any expected ACK message from the peer. Besides, a receipt of an ICMP error message could be a clue for the application to detect problems. The REAP module may be triggered by these negative feedbacks and invoke the @@ -349,49 +351,41 @@ should be able to obtain information about the locator pair which was actually used to send or receive the packet. * For inbound traffic, the application may be interested in the locator pair which was actually used to receive the packet. * For outbound traffic, the application may be interested in the locator pair which was actually used to transmit the packet. In this way, applications may have additional control on the locator management. For example, an application becomes able to verify if its preference for locator is actually applied to the flow or not. - o Applications should be able to specify if they want to defer the context setup, or if they want context establishment to be started immediately in the case where there is no available context. A deferred context setup means that the initiation of communication should not be blocked to wait for completion of the context establishment. - o Turn on/off shim. An application should be able to request to - turn on or turn off the multihoming support by the shim layer: - * Apply shim. The application should be able to explicitly - request the shim sub-layer to apply multihoming support. - * Don't apply shim. The application should be able to request - the shim sub-layer not to apply the multihoming support but to - apply normal IP processing at the IP layer. o An application should be able to know if the communication is now being served by the shim sub-layer or not. o An application should be able to use a common interface to access an IPv4 locator and an IPv6 locator. 5. Socket Options for Multihoming Shim Sub-layer In this section, socket options that are specific to the shim sub- layer are defined. Table 1 shows a list of the socket options that are specific to the - multihoming shim sub-layer. An application may use these socket - options for a given socket either by the getsockopt() system call or - by the setsockopt() system call. All of these socket options are - defined at level SOL_SHIM. + shim sub-layer. An application may use these socket options for a + given socket either by the getsockopt() system call or by the + setsockopt() system call. All of these socket options are defined at + level SOL_SHIM. The first column of Table 1 gives the name of the option. The second and third columns indicate whether the option can be handled by the getsockopt() system call and/or by the setsockopt() system call. The fourth column provides a brief description of the socket option. The fifth column shows the type of data structure specified along with the socket option. By default, the data structure type is an integer. +-----------------------------+-----+-----+-----------------+-------+ @@ -577,28 +571,27 @@ getsockopt(fd, SOL_SHIM, SHIM_ASSOCIATED, &optval, &optlen); 5.2. SHIM_DONTSHIM The SHIM_DONTSHIM option is used to request the shim layer not to provide the multihoming support for the communication established over the socket. The data type of the option value is an integer, and it takes 0 or 1. - An option value 0 means that the multihoming shim sub-layer is - employed if available. An option value 1 means that the application - does not want the multihoming shim sub-layer to provide the - multihoming support for the communication established over the - socket. + An option value 0 means that the shim sub-layer is employed if + available. An option value 1 means that the application does not + want the shim sub-layer to provide the multihoming support for the + communication established over the socket. - Default value is set as 0, which means that the multihoming shim sub- - layer performs identifier/locator adaptation if available. + Default value is set as 0, which means that the shim sub-layer + performs identifier/locator adaptation if available. Any attempt to disable the multihoming shim support MUST be made by the application before the socket is connected. If an application makes such an attempt for a connected-socket, an error code EOPNOTSUPP MUST be returned. For example, an application can request the system not to apply the multihoming support as follows: int optval; @@ -663,22 +657,22 @@ The option is effective only when there is a shim context associated with the socket. The data type of the option value is a pointer to the buffer where a set of information for path exploration is stored. The data structure is defined in Section 7. By default, the option value is set to NULL, meaning that the option is disabled. - An error ENOENT will be returned when there is no context associated - with the socket. + An error ENOENT is returned when there is no context associated with + the socket. For example, an application can set parameters for path exploration by using the socket option as follows. struct shim6_pathexplore pe; pe.pe_probenum = 4; /* times */ pe.pe_keepaliveto = 10; /* seconds */ pe.pe_initprobeto = 500; /* milliseconds */ pe.pe_reserved = 0; @@ -707,24 +701,24 @@ By default, the option value is set to NULL, meaning that the option is disabled. The preferred locator can be set by setsockopt(). The shim sub-layer shall verify requested locator before it updating the preferred locator. An application can get the preferred locator by getsockopt(). - An error ENOENT will be returned when there is no context associated - with the socket. + An error ENOENT is returned when there is no context associated with + the socket. - An error EINVALIDLOCATOR will be returned when the validation of the + An error EINVALIDLOCATOR is returned when the validation of the specified locator failed. For example, an application can set the preferred locator by using the socket option as follows. Note that some members of the shim_locator (lc_ifidx and lc_flags) are ignored in the set operation. struct shim_locator lc; struct in6_addr ip6; @@ -761,24 +755,24 @@ By default, the option value is set to NULL, meaning that the option is disabled. The preferred locator can be set by setsockopt(). The shim sub-layer shall verify requested locator before it updating the preferred locator. An application can get the preferred locator by getsockopt(). - An error ENOENT will be returned when there is no context associated - with the socket. + An error ENOENT is returned when there is no context associated with + the socket. - An error EINVALIDLOCATOR will be returned when the validation of the + An error EINVALIDLOCATOR is returned when the validation of the requested locator fails. The usage of the option is same as that of SHIM_LOC_LOCAL_PREF. Note that some members of the shim_locator (lc_ifidx and lc_flags) are ignored in the set operation. 5.7. SHIM_LOC_LOCAL_RECV The SHIM_LOC_LOCAL_RECV option can be used to request the shim sub- layer to store the destination locator of the received IP packet in @@ -790,22 +784,22 @@ should be binary (0 or 1). By default, the option value is set to 0, meaning that the option is disabled. An application can set the option value by setsockopt(). An application can get the option value by getsockopt(). See Section 6 for the procedure to access locator information stored in the ancillary data objects. - An error ENOENT will be returned when there is no context associated - with the socket. + An error ENOENT is returned when there is no context associated with + the socket. For example, an application can request the shim sub-layer to store destination locator by using the socket option as follows. int optval; optval = 1; setsockopt(fd, SOL_SHIM, SHIM_LOC_LOCAL_RECV, &optval, sizeof(optval)); @@ -831,22 +825,22 @@ should be binary (0 or 1). By default, the option value is set to 0, meaning that the option is disabled. The option value can be set by setsockopt(). The option value can be read by getsockopt(). See Section 6 for the procedure to access locator information stored in the ancillary data objects. - An error ENOENT will be returned when there is no context associated - with the socket. + An error ENOENT is returned when there is no context associated with + the socket. The usage of the option is same as that of SHIM_LOC_LOCAL_RECV option. 5.9. SHIM_LOC_LOCAL_SEND The SHIM_LOC_LOCAL_SEND option is used to request the shim sub-layer to use a specific locator as the source locator for the IP packets to be sent from the socket. Hence this option is effective only when there is a shim context associated with the socket. @@ -854,24 +848,24 @@ The data type of option value is pointer to shim_locator data structure. An application can set the local locator by setsockopt() providing a valid locator which is stored in a shim_locator data structure. When a zero-filled locator is specified, pre-existing setting of local locator is inactivated. An application can get the local locator by getsockopt(). - An error ENOENT will be returned when there is no context associated - with the socket. + An error ENOENT is returned when there is no context associated with + the socket. - An error EINVALIDLOCATOR will be returned when invalid locator is + An error EINVALIDLOCATOR is returned when invalid locator is specified. For example, an application can request the shim sub-layer to use a specific local locator by using the socket option as follows. struct shim_locator locator; struct in6_addr ia6; /* an IPv6 address preferred for the source locator is copied to the parameter ia6 */ @@ -910,22 +904,22 @@ The data type of the option value is a pointer to shim_locator data structure. An application can set the remote locator by setsockopt() providing a valid locator which is stored in a shim_locator data structure. When a zero-filled locator is specified, pre-existing setting of remote locator is inactivated. An application can get the specified remote locator by getsockopt(). - An error ENOENT will be returned when there is no context associated - with the socket. + An error ENOENT is returned when there is no context associated with + the socket. An error EINVALIDLOCATOR when invalid locator is specified. The usage of the option is as the same as that of SHIM_LOC_LOCAL_SEND option. 5.11. SHIM_LOCLIST_LOCAL The SHIM_LOCLIST_LOCAL option is used to get or set the locator list associated with the local EID of the shim context associated with the @@ -938,26 +932,29 @@ to NULL, meaning that the option is disabled. An application can get the locator list by getsockopt(). Note that the size of the buffer pointed by optval argument should be large enough to store an array of locator information. The number of the locator information is not known beforehand. The local locator list can be set by setsockopt(). The buffer pointed by optval argument should contain an array of locator list. - An error ENOENT will be returned when there is no context associated - with the socket. + An error ENOENT is returned when there is no context associated with + the socket. - An error EINVALIDLOCATOR will be returned when the validation of the + An error EINVALIDLOCATOR is returned when the validation of the specified locator failed. + An error ETOOMANYLOCATORS is returned when the number of locators + specified exceeds the limit (SHIM_MAX_LOCATORS). + For example, an application can set a list of locators to be associated with the local EID by using the socket option as follows: struct shim_locator locators[SHIM_MAX_LOCATORS]; struct sockaddr_in *sin; struct sockaddr_in6 *sin6; memset(locators, 0, sizeof(locators)); ... @@ -1013,47 +1010,50 @@ to NULL, meaning that the option is disabled. An application can get the locator list by getsockopt(). Note that the size of the buffer pointed by optval argument should be large enough to store an array of locator information. The number of the locator information is not known beforehand. An application can set the locator list by setsockopt(). The buffer pointed by optval argument should contain an array of locator list. - An error ENOENT will be returned when there is no context associated - with the socket. + An error ENOENT is returned when there is no context associated with + the socket. - An error EINVALIDLOCATOR will be returned when the validation of the + An error EINVALIDLOCATOR is returned when the validation of the specified locator failed. + An error ETOOMANYLOCATORS is returned when the number of locators + specified exceeds the limit (SHIM_MAX_LOCATORS). + The usage of the option is same as that of SHIM_LOCLIST_LOCAL. 5.13. SHIM_APP_TIMEOUT The SHIM_APP_TIMEOUT option is used to get or set the timeout value for application to detect failure. Hence this option is effective only when there is a shim context associated with the socket. The data type of the option value is an integer. The value indicates the period of timeout in seconds to send a REAP Keepalive message since the last outbound traffic. By default, the option value is set to 0, meaning that the option is disabled. When the option is disabled, the REAP mechanism follows its default value of Send Timeout value as specified in [RFC5534] If the timeout value specified is longer than the Send Timeout configured in the REAP component, the REAP Keepalive message should be suppressed. - An error ENOENT will be returned when there is no context associated - with the socket. + An error ENOENT is returned when there is no context associated with + the socket. For example, an application can set the timeout value by using the socket option as follows. int optval; optval = 15; /* 15 seconds */ setsockopt(fd, SOL_SHIM, SHIM_APP_TIMEOUT, &optval, sizeof(optval)); @@ -1106,29 +1106,27 @@ int optval; int len; len = sizeof(optval); getsockopt(fd, SOL_SHIM, SHIM_DEFERRED_CONTEXT_SETUP, &optval, &len); 5.15. Applicability - All the socket options for the multihoming shim sub-layer except for - SHIM_HOT_STANDBY are applicable for both connected and unconnected - sockets. - - The reason SHIM_HOT_STANDBY socket option cannot be used for an - unconnected socket is that the multihoming shim sub-layer cannot + All the socket options for the shim sub-layer except for + SHIM_HOT_STANDBY are applicable to both connected and unconnected + sockets. SHIM_HOT_STANDBY socket option is applicable only to + connected sockets. This is because the shim sub-layer cannot initiate context establishment to create a hot standby connection - because the peer's IP address is not known until the application - writes data to the unconnected socket. + when the peer's IP address is not known until the application writes + data to the unconnected socket. 5.16. Error Handling If successful, getsockopt() and setsockopt() return 0; otherwise, the functions return -1 and set errno to indicate an error. The following are new error values defined for some shim specific socket options indicating that the getsockopt() or setsockopt() finished incompletely: @@ -1137,71 +1135,67 @@ inside the shim sub-layer for the specified locator has failed. In case of SHIM6, there are two kinds of verifications required for security reasons prior to sending an IP packet to the peer's new locator; one is the return routability (check if the peer is actually willing to receive data with the specified locator) and the other one is the verification based on crypto identifier mechanisms [RFC3972], [RFC5535]. 6. Ancillary Data for Multihoming Shim Sub-layer - In this section, the definition and the usage of the ancillary data - specific to multihoming shim sub-layer are provided. + This section provides definitions of ancillary data to be used for + locator management and notification from/to the shim sub-layer to/ + from application. - As defined in the Posix standard, sendmsg() and recvmsg() input a - msghdr structure as their arguments. These system calls can handle - control information along with data. Figure 3 shows the msghdr - structure which is defined in . The member msg_control - holds a pointer to the buffer where the shim specific ancillary data - objects can be stored in addition to other ancillary data objects. + When the application performs locator management by sendmsg() or + recvmsg(), a member of the msghdr structure (given in Figure 3) + called msg_control holds a pointer to the buffer in which one ore + more shim specific ancillary data objects may be stored. An + ancillary data object can store a single locator. It should be + possible to process the shim specific ancillary data object by the + existing macros defined in the Posix standard and [RFC3542]. struct msghdr { caddr_t msg_name; /* optional address */ u_int msg_namelen; /* size of address */ struct iovec *msg_iov; /* scatter/gather array */ u_int msg_iovlen; /* # elements in msg_iov */ caddr_t msg_control; /* ancillary data, see below */ u_int msg_controllen; /* ancillary data buffer len */ int msg_flags; /* flags on received message */ }; Figure 3: msghdr structure - The buffer pointed by the member msg_control of the msghdr structure - may contain locator information which is a single locator and it - should be possible to process them with the existing macros defined - in Posix and [RFC3542]. Each cmsghdr{} should be followed by data - which stores a single locator. - - In case of non-connected socket, msg_name member stores the socket - address of the peer which should be considered as an identifier - rather than a locator. The locator of the peer node should be - retrieved by SHIM_LOC_PEER_RECV as specified below. + In the case of unconnected socket, msg_name stores the socket address + of the peer which should be considered to be an identifier rather + than a locator. SHIM_LOC_PEER_RECV should be used to get the locator + of the peer node. Table 2 is a list of the shim specific ancillary data which can be - used for recvmsg() or sendmsg(). In any case, SOL_SHIM must be set - as cmsg_level. + used for locator management by recvmsg() or sendmsg(). In any case, + the value of cmsg_level must be set as SOL_SHIM. +---------------------+-----------+-----------+-----------------+ | cmsg_type | sendmsg() | recvmsg() | cmsg_data[] | +---------------------+-----------+-----------+-----------------+ | SHIM_LOC_LOCAL_RECV | | o | *1 | | SHIM_LOC_PEER_RECV | | o | *1 | | SHIM_LOC_LOCAL_SEND | o | | *1 | | SHIM_LOC_PEER_SEND | o | | *1 | | SHIM_FEEDBACK | o | | shim_feedback{} | +---------------------+-----------+-----------+-----------------+ Table 2: Shim specific ancillary data - *1: cmsg_data[] should include padding (if necessary) and a single - sockaddr_in{}/sockaddr_in6{}. + *1: cmsg_data[] includes a single sockaddr_in{} or sockaddr_in6{} and + padding if necessary 6.1. Get Locator from Incoming Packet An application can get locator information from the received IP packet by specifying the shim specific socket options for the socket. When SHIM_LOC_LOCAL_RECV and/or SHIM_LOC_PEER_RECV socket options are set, the application can retrieve local and/or remote locator from the ancillary data. 6.2. Set Locator for Outgoing Packet @@ -1211,94 +1205,97 @@ SHIM_LOC_LOCAL_SEND and/or SHIM_LOC_PEER_SEND are specified, the application can explicitly specify the source and/or the destination locators to be used for the communication over the socket. Note that the effect is limited to the datagram transmitted by the sendmsg(). If the specified locator pair is verified, the shim sub-layer overrides the locators of the IP packet. - An error EINVALIDLOCATOR will be returned when validation of the - specified locator failed. + An error EINVALIDLOCATOR is returned when validation of the specified + locator failed. 6.3. Notification from Application to Multihoming Shim Sub-layer An application may provide feedbacks to the shim sub-layer about the communication status. Such feedbacks are particularly useful for the shim sub-layer in the absence of REAP mechanism to monitor the reachability status of the currently used locator pair in a given shim context. The notification can be made by sendmsg() specifying a new ancillary data called SHIM_FEEDBACK. The ancillary data can be handled by specifying SHIM_FEEDBACK option in cmsg_type. - An error ENOENT will be returned when there is no context associated - with the socket. + An error ENOENT is returned when there is no context associated with + the socket. See Section 7.3 for details of the data structure to be used. It is outside the scope of this document how the shim sub-layer would react when a feedback is provided by an application. 6.4. Notification from Multihoming Shim Sub-layer to Application - The multihoming shim sub-layer MAY provide notification about a - locator change within a multihome shim context to applications that - have concern with the context. Such a notification is useful, for - example, for an application which is sensitive to path - characteristics. A locator change is caused when either of local or + The shim sub-layer MAY provide notification about a locator change + within a multihome shim context to applications that have concern + with the context. Such a notification may be useful, for example, + for an application which is sensitive to the characteristics of the + current path. A locator change is caused when either of local or peer's locator (or both) is changed. Note that locators discussed here are the ones that appear in the IP packet header, and not the ones that are included in the locator list. A locator change may take place asynchronously. The notification is handled as an out-of-band data by the application. 1. Application calls the select() system call by setting non-NULL value for the fourth argument. 2. When there is a notification, the application reads out-of-band - data from the socket by calling the recvmsg() system call. + data from the socket by calling recvmsg(). 3. The application checks the flag in the msghdr (msg_flags) to see if there is any notification about locator change delivered. If - the MSG_SHIM_LOCATOR_CHANGE flag is set, application parse the + the MSG_SHIM_LOCATOR_CHANGE flag is set, application parses the chain of control message to read a pair of ancillary data objects which contains the source locator and the destination locator. Note that the direction of locator change is distinguished by the - cmsg_type; SHIM_LOC_*_RECV is used for inbound locator change, - and SHIM_LOC_*_SEND is used for outbound locator change. + value of cmsg_type; SHIM_LOC_*_RECV is used for inbound locator + change, and SHIM_LOC_*_SEND is used for outbound locator change. There is no restriction in terms of applicability of the notification - about locator change. The notification can be delivered to sockets - regardless of if it is connected or unconnected, stream-oriented or - datagram-oriented. + about locator change. The notification can be delivered to any type + of socket (connected or unconnected, stream-oriented or datagram- + oriented). 6.5. Applicability + All the ancillary data for the shim sub-layer is applicable to both + connected and unconnected sockets. + A care is needed when the SHIM_LOC_*_RECV socket option is used for stream-oriented sockets (e.g., TCP sockets) because there is no one- to-one mapping between a single send or receive operation and the data (e.g., a TCP segment) being received. In other words, there is no gurantee that the locator(s) set in the SHIM_LOC_*_RECV ancillary data is identical to the locator(s) that appear in the IP packets - received. The multihoming shim sub-layer SHOULD provide the latest - locator information to the application in response to the - SHIM_LOC_*_RECV socket option. + received. The shim sub-layer SHOULD provide the latest locator + information to the application in response to the SHIM_LOC_*_RECV + socket option. 7. Data Structures - In this section, data structures specifically defined for the - multihoming shim sub-layer are introduced. These data structures are - either used as a parameter for setsockopt()/getsockopt() (as - mentioned in Section 5) or as a parameter for ancillary data to be - processed by sendmsg()/recvmsg() (as mentioned in Section 6). + This section data structures for the shim sub-layer. These data + structures are either used as a parameter for setsockopt() or + getsockopt() (as mentioned in Section 5) or as a parameter for + ancillary data to be processed by sendmsg() or recvmsg() (as + mentioned in Section 6). 7.1. Placeholder for Locator Information As defined in Section 5, the SHIM_LOC_LOCAL_PREF, SHIM_LOC_PEER_PREF, SHIM_LOCLIST_LOCAL, and SHIM_LOCLIST_PEER socket options need to handle one or more locator information. Locator information includes not only the locator itself but also additional information about the locator which is useful for locator management. A new data structure is defined to serve as a placeholder for the locator information. @@ -1453,354 +1451,309 @@ unidirectional reachability between the locator pair in question. * 3: Satisfactory. There is satisfactory unidirectional reachability between the locator pair in question. reserved Reserved field. Must be ignored by the receiver. 8. System Requirements - As discussed in Section 5, all the socket options for multihoming - shim sub-layer except for the SHIM_HOT_STANDBY socket option are - applicable to both connected and unconnected sockets. The - implications of this design choice on system requirements should be - noted. + This section gives system requirements posed by the sockets API + defined in this document. There exist requirements for the system + (kernel) to maintain the association between sockets and shim + contexts. + + As addressed in Section 5, all the socket options and ancillary data + defined in this document except for the SHIM_HOT_STANDBY socket + option are applicable to both connected and unconnected sockets. There are less system requirements to enable support for applications - that use connected sockets. This is because the kernel can easily - maintain association between a connected socket and a multihoming - shim context. Note that the multihoming shim contexts are identified - by an EID pair. In contrast, there are more system requirements to - enable support for applications that use unconnected sockets. The - kernel needs to dynamically resolve association between an - unconnected socket and a multihoming shim context, if any, upon - packet processing. As to outbound packet processing, the kernel - needs to check if there is any multihoming shim context whose EID - pair matches with the source and destination IP addresses of the user - data originating from an unconnected socket. If a matching context - is found, the multihoming shim sub-layer performs packet processing - taking the application's preference into account. Note that the - multihoming shim sub-layer should be able to backtrack the socket - from which the user data was originated. As to inbound packet - processing, the multihoming shim sub-layer needs to check not only - the IP header but also the transport layer protocol header to resolve - the destination socket. If the destination socket is resolved and it - contains any values concerning the multihoming shim sub-layer socket - options, the multihoming shim sub-layer processes the IP packet as - requested (e.g., set locator information of received packet in the - ancillary data). + that use connected sockets. This is because the kernel can maintain + the association between a connected socket and a shim context in a + static manner because a connected socket is bound to a source and + destination IP addresses (identifiers). The kernel should be able to + identify shim context associated with a connected socket by searching + shim context keyed by the pair of source and destination identifiers. + However, this is not the case for unnconnected sockets. The kernel + needs to dynamically resolve association between an unconnected + socket and a shim context, if any, upon packet processing. As to + outbound packet processing, the kernel needs to check if there is any + shim context whose EID pair matches with the source and destination + IP addresses of the user data originating from an unconnected socket. + If a matching context is found, the shim sub-layer performs packet + processing taking the application's preference into account. Note + that the shim sub-layer should be able to backtrack the socket from + which the user data was originated. As to inbound packet processing, + the shim sub-layer needs to check not only the IP header but also the + transport layer protocol header to resolve the destination socket. + If the destination socket is resolved and it contains any values + concerning the shim sub-layer socket options, the shim sub-layer + processes the IP packet as requested (e.g., set locator information + of received packet in the ancillary data). -9. Implications for Existing Socket API Extensions +9. Relation to Existing Sockets API Extensions - Some of the socket options defined in this document are overlapping - with existing sockets API and care should be taken for the usage not - to confuse with the overlapping features. + This section explains relation between the sockets API defined in + this document and the existing sockets API extensions. - The socket options for requesting specific locators to be used for a - given transaction (SHIM_LOC_LOCAL_PREF and SHIM_LOC_PEER_PREF) are - semantically similar to the existing sockets API (IPV6_PKTINFO). The - socket options for obtaining the locator information from the - received IP packet (SHIM_LOC_LOCAL_RECV and SHIM_LOC_PEER_RECV) are - semantically similar to the existing sockets API (IP_RECVDSTADDR and - IPV6_PKTINFO). + As mentioned in Section 5, the basic assumption is that the existing + sockets API continues to work above the shim sub-layer. This means + that, the existing sockets API deals with identifiers, and the + sockets API defined in this document deals with locators. - In IPv4, application can obtain the destination IP address of the - received IP packet (IP_RECVDSTADDR). If the shim sub-layer performs - identifier/locator adaptation for the received packet, the - destination EID should be stored in the ancillary data - (IP_RECVDSTADDR). + SHIM_LOC_LOCAL_PREF and SHIM_LOC_PEER_PREF socket options are + semantically similar to the IPV6_PKTINFO socket API in the sense that + both provide a means for application to set the source IP address of + outbound IP packets. - In IPv6, [RFC3542] defines that IPV6_PKTINFO can be used to specify - source IPv6 address and the outgoing interface for outgoing packets, - and retrieve destination IPv6 address and receiving interface for - incoming packets. This information is stored in ancillary data being - IPV6_PKTINFO specified as cmsg_type. Existing sockets API should - continue to work above the shim sub-layer, that is, the IP addresses - handled in IPV6_PKTINFO should be EIDs, not the locators. + SHIM_LOC_LOCAL_RECV and SHIM_LOC_PEER_RECV socket options are + semantically similar to the IP_RECVDSTADDR and IPV6_PKTINFO socket + APIs in the sense that both provides a means for application to get + the source and/or destination IP address of inbound IP packets. - Baseline is that the above existing sockets API (IP_RECVDSTADDR and - IPV6_PKTINFO) is assumed to work above the multihoming shim sub- - layer. In other words, the IP addresses those socket options deal - with are EIDs rather than locators. + getsockname() and getpeername() enable application to get 'name' of + the communication endpoints which is represented by a pair of IP + address and port number assigned to the socket. getsockname() gives + IP address and port number assigned to the socket on the local side, + and getpeername() gives IP address and port number of the peer side. -10. Resolving Conflicts with Preference Values +10. Operational Considerations - Since the multihoming shim API allows application to specify - preference value for the context which is associated with the socket - instance, there may be a conflict with preference values specified by - different applications. For instance, application A and B may - establish communication with the same EID pair while both - applications have different preference in their choice of local - locator. + This section gives operational considerations of the sockets API + defined in this document. - SHIM6 supports a notion of context forking in which a context is - split when there is a conflict with preference values specified by - multiple applications. Thus, context forking can simply resolve the - conflicting situation which may be caused by the use of socket - options for multihoming shim sub-layer. +10.1. Conflict Resolution -10.1. Implicit Forking + There may be a conflicting situation when different applications + specify difference preference for the same shim context. For + instance, application A and B may establish communication with the + same EID pair while both applications have different preference in + their choice of local locator. The notion of context forking in + SHIM6 can resolve the conflicting situation. Socket options defined in Section 5 may cause conflicting situation when the target context is shared by multiple applications. In such - case, socket handler should inform the shim sub-layer that context - forking is required. In SHIM6, when a context is forked, an unique - identifier called Forked Instance Identifier (FII) is assigned to the - newly forked context. The forked context is then exclusively + a case, the socket handler should inform the shim sub-layer that + context forking is required. In SHIM6, when a context is forked, an + unique identifier called Forked Instance Identifier (FII) is assigned + to the newly forked context. The forked context is then exclusively associated with the socket through which non-default preference value - was specified. The forked context is maintained by the multihoming - shim sub-layer during the lifetime of associated socket instance. - When the socket is closed, the multihoming shim sub-layer SHOULD - delete associated context. In this way, garbage collection can be - carried out to cleanup unused forked contexts. Upon garbage - collection, every forked context SHOULD be checked if there is no - socket (process) associated with the context. If there is none, the - forked context should be deleted. When a forked context is torn - down, SHIM6 should notify the peer about the deletion of forked + was specified. The forked context is maintained by the shim sub- + layer during the lifetime of associated socket instance. When the + socket is closed, the shim sub-layer SHOULD delete associated + context. When a forked context is torn down, the SHIM6 + implementation should notify the peer about the deletion of forked context. - As opposed to socket options, context forking MUST NOT be triggered - by any use of ancillary data that is specific to multihoming shim - sub-layer as defined in Section 6. +10.2. Incompatiblility between IPv4 and IPv6 -11. Discussion + The shim sub-layer performs identifier/locator adaptation. + Therefore, in some cases, the whole IP header can be replaced with + new IP header of a different address family (e.g. conversion from + IPv4 to IPv6 or vice versa). Hence, there is an issue how to make + the conversion with minimum impact. Note that this issue is common + in other protocol conversion such as SIIT[RFC2765]. - In this section, open issues are introduced. + As addressed in the SIIT specification, some of the features (IPv6 + routing headers, hop-by-hop extension headers, or destination + headers) from IPv6 are not convertible to IPv4. In addition, notion + of source routing is not exactly the same in IPv4 and IPv6. This + means that an error may occur during the conversion of identifier and + locator. It is ffs exactly how the shim sub-layer should behave in + such erroneous cases. -11.1. Naming at Socket Layer +11. IANA Considerations - The getsockname() and getpeername() system calls are used to obtain - the 'name' of an endpoint which is actually a pair of IP address and - port number assigned to a given socket. getsockname() is used when an - application wants to obtain the local IP address and port number - assigned for a given socket instance. getpeername() is used when an - application obtains the remote IP address and port number. + This document contains no IANA consideration. - The above is based on a traditional system model of the sockets API - where an IP address is expected to play both the role of identifier - and the role of locator. +12. Protocol Constants and Variables - In a system model where a shim sub-layer exists inside the IP layer, - both getsockname() and getpeername() deal with identifiers, namely - EIDs. In this sense, the shim sub-layer serves to (1) hide locators - and (2) provide access to the identifier for the application over the - legacy socket APIs. + This section defines protocol constants and variables. + SHIM_MAX_LOCATORS The maximum number of the locators to be included + in a locator list. 32. -11.2. Additional Requirements from Applications +13. Security Considerations - At the moment, it is not certain if following requirements are common - in all the multihomed environments (SHIM6 and HIP). These are mainly - identified during discussions made on SHIM6 WG mailing list. + This section gives security considerations of the API defined in this + document. - o The application should be able to set preferences for the - locators, local and remote ones, and also to the preferences of - the local locators that will be passed to the peer. +13.1. Treatment of Unknown Locator -11.3. Issues of Header Conversion among Different Address Family + When sending IP packets, application may request use of unknown + locator for the source and/or destination locators. Note that + treatment of unknown locator can be a subject of security + considerations because use of invalid source and/or destination + locator may cause redirection attack. - The shim sub-layer performs identifier/locator adaptation. - Therefore, in some cases, the whole IP header can be replaced with - new IP header of a different address family (e.g. conversion from - IPv4 to IPv6 or vice versa). Hence, there is an issue how to make - the conversion with minimum impact. Note that this issue is common - in other protocol conversion such as SIIT[RFC2765]. +13.1.1. Treatment of Unknown Source Locator - As addressed in SIIT specification, some of the features (IPv6 - routing headers, hop-by-hop extension headers, or destination - headers) from IPv6 are not convertible to IPv4. In addition, notion - of source routing is not exactly the same in IPv4 and IPv6. Hence, - there is a certain limitation in protocol conversion between IPv4 and - IPv6. + The shim sub-layer checks if the requested locator is available on + any of the local interface. If not, the shim sub-layer MUST reject + the request and return an error message with the EINVALIDLOCATOR code + to the application. If the locator is confirmed to be available, the + shim sub-layer SHOULD initiate the procedure to update the locator + list. - The question is how should the shim sub-layer behave when it faces - with limitation problem of protocol conversion. Should we introduce - new error something like ENOSUITABLELOCATOR ? + Use of the following socket options and ancillary data may require + treatment of unknown source locator: + o SHIM_LOC_LOCAL_SEND + o SHIM_LOC_LOCAL_PREF + o SHIM_LOC_LIST_LOCAL -11.4. Handling of Unknown Locator Provided by Application +13.1.2. Treatment of Unknown Destination Locator - There might be a case where application provides the shim layer new - locator with the SHIM_LOC_*_PREF socket options or SHIM_LOC_*_SEND - ancillary data. Then there is a question how should the shim sub- - layer treat the new locator informed by the application. + If the shim sub-layer turns out to be SHIM6, the SHIM6 implementation + MUST reject the request for using unknown destination locator. - In principle, locator information are exchanged by the shim protocol. - However, there might be a case where application acquires information - about the locator and prefers to use it for its communication. + If the shim sub-layer turns out to be HIP, the HIP implementation MAY + accept the request for using unknown destination locator. -12. Changes + Use of the following socket options and ancillary data may require + treatment of unknown destination locator: + o SHIM_LOC_PEER_SEND + o SHIM_LOC_PEER_PREF + o SHIM_LOC_LIST_PEER -12.1. Changes from version 00 to version 01 +14. Changes + +14.1. Changes from version 00 to version 01 - The followings are changes from version 00 to version 01: o Define shim_locator{} data type which is a placeholder for locator. o Define shim_pathexplore{} data type in which a set of REAP parameters are stored. o Remove descriptions about "stickiness" of socket options. - o Deprecate SHIM_IF_RECV and SHIM_IF_SEND socket options. o Give default value and how to disable given socket option. -12.2. Changes from version 01 to version 02 +14.2. Changes from version 01 to version 02 - The followings are changes from version 01 to version 02: o Add section describing context forking. o Rephrase conclusion section. o Separate normative references from informative references. o Remove texts from discussion section that are not relevant to the contents of the document. o Add section describing change history (this section). -12.3. Changes from version 02 to version 03 +14.3. Changes from version 02 to version 03 - The followings are changes from version 02 to version 03: o Add an Appendix section describing the issue of context forking. -12.4. Changes from version 03 to version 04 +14.4. Changes from version 03 to version 04 - The followings are changes from version 03 to version 04: o Updated reference. o Correct typo and grammatical errors. -12.5. Changes from version 04 to version 05 +14.5. Changes from version 04 to version 05 - The followings are changes from version 04 to version 05: o Added definition of SHIM_FEEDBACK ancillary data. o Added an example of code using the SHIM_LOCLIST_LOCAL o Added SHIM_LOC_LOCAL_SEND and SHIM_LOC_PEER_SEND socket options. -12.6. Changes from version 05 to version 06 +14.6. Changes from version 05 to version 06 - The followings are changes from version 04 to version 05: o Updated references. -12.7. Changes from version 06 to version 07 +14.7. Changes from version 06 to version 07 - The followings are changes from version 06 to version 07: o Resolved editorial issues. -12.8. Changes from version 07 to version 08 +14.8. Changes from version 07 to version 08 No changes are made except for updates of the references. -12.9. Changes from version 08 to version 09 +14.9. Changes from version 08 to version 09 - The followings are changes from version 08 to version 09: o Updated texts for Section 1 and Section 5 according to the comments provided by Samu Varjonen. o Made it clear that downgrading the multihoming shim support (i.e., specifying value 1 with the SHIM_DONTSHIM socket option) is only allowed before the socket is connected. o Updated locator information (shim_locator{}) so that it can contain a locator behind NAT. -12.10. Changes from version 09 to version 10 +14.10. Changes from version 09 to version 10 - The followings are changes from version 09 to version 10: o Addressed applicability of socket options and ancillary data for - the multihoming shim sub-layer. + the shim sub-layer. o Addressed system requirements. o Removed unnecessary description about deprecated socket option (SHIM_IF_RECV). -12.11. Changes from version 10 to version 11 +14.11. Changes from version 10 to version 11 - The followings are changes from version 10 to version 11: o Added short descriptions about connected sockets and unconnected sockets. - o Relax applicability of the socket options. - o Relax applicability of the ancillary data. + o Relaxed applicability of the socket options. + o Relaxed applicability of the ancillary data. o Added notification about locator change. -13. IANA Considerations - - This document contains no IANA consideration. - -14. Security Considerations - - This document does not specify any security mechanism for the shim - sub-layer. Fundamentally, the shim sub-layer has a potential to - impose security threats, as it changes the source and/or destination - IP addresses of the IP packet being sent or received. Therefore, the - basic assumption is that the security mechanism defined in each - protocol of the shim sub-layer is strictly applied. - -15. Conclusion - - In this document, the Application Program Interface (API) for - multihoming shim sub-layer is specified. The sockets API allows - applications to have additional control of the locator management and - interface to the REAP mechanism inside the multihoming shim sub- - layer. - - Socket options for multihoming shim sub-layer can be used by - getsockopt() and/or setsockopt() system calls. Besides, applications - can use some ancillary data that are specific to multihoming shim - sub-layer to get locator from received packet or to set locator for - outgoing packet. +14.12. Changes from version 11 to version 12 - From an architectural point of view, the sockets API provides extends - the existing sockets API framework in the face of ID/Locator - separation. With regard to API that relate to IP address management, - it is assured that existing sockets API continue to work above the - shim sub-layer dealing with identifiers, while multihoming shim API - deals with locators. + o Reflected comments from Brian Karpenter + o Reflected comments from Michael Scharf -16. Acknowledgments +15. Acknowledgments Authors would like to thank Jari Arkko who participated in the discussion that lead to the first version of this document, and Tatuya Jinmei who thoroughly reviewed the early version of this draft and provided detailed comments on sockets API related issues. Thomas Henderson provided valuable comments especially from HIP perspectives. Authors sincerely thank to the following people for their help to improve this document: Samu Varjonen and Dmitriy Kuptsov. -17. References +16. References -17.1. Normative References +16.1. Normative References [POSIX] "IEEE Std. 1003.1-2001 Standard for Information Technology -- Portable Operating System Interface (POSIX). Open group Technical Standard: Base Specifications, Issue 6, http://www.opengroup.org/austin", December 2001. [RFC3542] Stevens, W., Thomas, M., Nordmark, E., and T. Jinmei, "Advanced Sockets Application Program Interface (API) for IPv6", RFC 3542, May 2003. [RFC4423] Moskowitz, R. and P. Nikander, "Host Identity Protocol (HIP) Architecture", RFC 4423, May 2006. [RFC5533] Bagnulo, M. and E. Nordmark, "Level 3 multihoming shim protocol", RFC 5533, June 2009. [RFC5534] Arkko, J. and I. Beijnum, "Failure Detection and Locator Pair Exploration Protocol for IPv6 Multihoming", RFC 5534, June 2009. -17.2. Informative References +16.2. Informative References [I-D.ietf-hip-nat-traversal] Komu, M., Henderson, T., Tschofenig, H., Melen, J., and A. Keranen, "Basic HIP Extensions for Traversal of Network Address Translators", Internet Draft draft-ietf-hip-nat-traversal-09, October 2009. [I-D.ietf-shim6-app-refer] Nordmark, E., "Shim6 Application Referral Issues", draft-ietf-shim6-app-refer-00 (work in progress), July 2005. + [I-D.ietf-shim6-applicability] + Abley, J., Bagnulo, M., and A. Garcia-Martinez, + "Applicability Statement for the Level 3 Multihoming Shim + Protocol (Shim6)", draft-ietf-shim6-applicability-04 (work + in progress), November 2009. + [RFC2765] Nordmark, E., "Stateless IP/ICMP Translation Algorithm (SIIT)", RFC 2765, February 2000. [RFC3972] Aura, T., "Cryptographically Generated Addresses (CGA)", RFC 3972, March 2005. [RFC4291] Hinden, R. and S. Deering, "IP Version 6 Addressing Architecture", RFC 4291, February 2006. [RFC5535] Bagnulo, M., "Hash Based Addresses (HBA)", RFC 5535, @@ -1810,39 +1763,41 @@ In this section, an issue concerning context forking and its relation to the multihoming shim API are discussed. SHIM6 supports a notion of context forking. A peer may decide to fork a context for certain reason (e.g. upper layer protocol prefers to use different locator pair than the one defined in available context). The procedure of forking context is done similar to the normal context establishment, performing the 4-way message exchange. A peer who has decided to fork a context initiates the context - establishment. Hereafter, we call this peer initiator. + establishment. Hereafter, we call this peer the "initiator". The + peer of the initiator is called the "responder". Once the forked context is established between the peers, on the initiator side, it is possible to apply forked context to the packet flow since the system maintains an association between the forked context and the socket owned by the application that has requested - the context forking. How this association is maintained is + the context forking. How this association is maintained is an implementation specific issue. However, on the responder side, there - is a question on how the outbound packet can be multiplexed by the - shim sub-layer. Since there are more than one SHIM6 contexts that - match with the ULID pair of the packet flow. There is a need to - differentiate packet flows not only by the ULID pairs but some other - information and associate a given packet flow with specific context. + is a question how the outbound packet can be multiplexed by the shim + sub-layer because there are more than one SHIM6 contexts that match + with the ULID pair of the packet flow. There is a need to + differentiate packet flows not only by the ULID pairs but by some + other information and associate a given packet flow with a specific + context. Figure 8 gives an example of a scenario where two communicating peers fork a context. Initially, there has been a single transaction between the peers, by the application 1 (App1). Accordingly, another transaction is started, by application 2 (App2). Both of the - transactions are made based the same ULID pair. The first context + transactions are made based on the same ULID pair. The first context pair (Ctx1) is established for the transaction of App1. Given the requests from App2, the shim sub-layer on Peer 1 decides to fork a context. Accordingly, a forked context (Ctx2) is established between the peers, which should be exclusively applied to the transaction of App2. Ideally, multiplexing and demultiplexing of packet flows that relate to App1 and App2 should be done as illustrated in Figure 8. However, as mentioned earlier, the responder needs to multiplex outbound flows of App1 and App2 somehow. Note that if a context forking occurs on the initiator side, a context forking needs to occur also on the responder side. @@ -1868,49 +1823,21 @@ || || || || || || || || \..............||....................../| || \.............||......................./ || || || \|...................................../| \....................................../ Figure 8: context forking - To overcome the problem mentioned above, there are some solutions. - - One viable approach is to let the system implicitly maintain an - association between the socket and the associated context by keeping - the record of inbound packet processing. That is, the system stores - the information about the context on which the inbound packet flow - was demultiplexed. The information comprises the ULID pair and FII - of the context and is stored in the socket instance. Later, the - system can use the information to identify the associated context in - outbound packet processing. This approach should be feasible as far - as there is bi-directional user traffic. - - Another viable approach is to extend SHIM6 protocol by adding - capability of exchanging additional information to identify the - packet flow from others which needs to be handled by a newly forked - context. The information exchange can be done during the context - establishment. The initiator appends 5 tuple of the packet flow to - be handled by the newly forked context. Note that the additional - information provided by the 5 tuple are source and destination port - numbers and upper layer protocol. The information is later used by - the shim sub-layer to multiplex the outbound packet flow on the - responder side. - - The socket options for multihoming shim can be used by the - application to trigger the context forking in implicit manner. The - peer becomes an initiator in the establishment of the forked context. - Once the forked context is established between the peers, application - on each end can influence the preference on context by utilizing the - multihoming shim API. + Any solution is needed to overcome the problem mentioned above. Authors' Addresses Miika Komu Helsinki Institute for Information Technology Tammasaarenkatu 3 Helsinki Finland Phone: +358503841531 @@ -1929,19 +1855,20 @@ URI: http://it.uc3m.es/marcelo Kristian Slavov Ericsson Research Nomadiclab Hirsalantie 11 Jorvas FI-02420 Finland Phone: +358 9 299 3286 Email: kristian.slavov@ericsson.com + Shinta Sugimoto (editor) Nippon Ericsson K.K. Koraku Mori Building 1-4-14, Koraku, Bunkyo-ku Tokyo 112-0004 Japan Phone: +81 3 3830 2241 - Email: shinta.sugimoto@ericsson.com + Email: shinta@sfc.wide.ad.jp