draft-ietf-tsvwg-sctpsocket-17.txt   draft-ietf-tsvwg-sctpsocket-18.txt 
Network Working Group R. Stewart Network Working Group R. Stewart
Internet-Draft The Resource Group Internet-Draft The Resource Group
Intended status: Informational K. Poon Intended status: Informational K. Poon
Expires: January 15, 2009 Sun Microsystems, Inc. Expires: May 7, 2009 Sun Microsystems, Inc.
M. Tuexen M. Tuexen
Univ. of Applied Sciences Muenster Univ. of Applied Sciences Muenster
V. Yasevich V. Yasevich
HP HP
P. Lei P. Lei
Cisco Systems, Inc. Cisco Systems, Inc.
July 14, 2008 November 3, 2008
Sockets API Extensions for Stream Control Transmission Protocol (SCTP) Sockets API Extensions for Stream Control Transmission Protocol (SCTP)
draft-ietf-tsvwg-sctpsocket-17.txt draft-ietf-tsvwg-sctpsocket-18.txt
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Abstract Abstract
This document describes a mapping of the Stream Control Transmission This document describes a mapping of the Stream Control Transmission
Protocol SCTP into a sockets API. The benefits of this mapping Protocol SCTP into a sockets API. The benefits of this mapping
include compatibility for TCP applications, access to new SCTP include compatibility for TCP applications, access to new SCTP
features and a consolidated error and event notification scheme. features and a consolidated error and event notification scheme.
Table of Contents Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . 5 1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . 5
2. Conventions . . . . . . . . . . . . . . . . . . . . . . . . . 6 2. Conventions . . . . . . . . . . . . . . . . . . . . . . . . . 6
3. Data Types . . . . . . . . . . . . . . . . . . . . . . . . . . 6 3. Data Types . . . . . . . . . . . . . . . . . . . . . . . . . . 6
4. one-to-many style Interface . . . . . . . . . . . . . . . . . 6 4. One-to-Many Style Interface . . . . . . . . . . . . . . . . . 6
4.1. Basic Operation . . . . . . . . . . . . . . . . . . . . . 6 4.1. Basic Operation . . . . . . . . . . . . . . . . . . . . . 6
4.1.1. socket() - one-to-many style socket . . . . . . . . . 8 4.1.1. socket() . . . . . . . . . . . . . . . . . . . . . . . 7
4.1.2. bind() - one-to-many style socket . . . . . . . . . . 8 4.1.2. bind() . . . . . . . . . . . . . . . . . . . . . . . . 8
4.1.3. listen() - One-to-many style socket . . . . . . . . . 9 4.1.3. listen() . . . . . . . . . . . . . . . . . . . . . . . 9
4.1.4. sendmsg() and recvmsg() - one-to-many style socket . . 10 4.1.4. sendmsg() and recvmsg() . . . . . . . . . . . . . . . 10
4.1.5. close() - one-to-many style socket . . . . . . . . . . 11 4.1.5. close() . . . . . . . . . . . . . . . . . . . . . . . 11
4.1.6. connect() - one-to-many style socket . . . . . . . . . 12 4.1.6. connect() . . . . . . . . . . . . . . . . . . . . . . 12
4.2. Implicit Association Setup . . . . . . . . . . . . . . . . 12 4.2. Implicit Association Setup . . . . . . . . . . . . . . . . 12
4.3. Non-blocking mode . . . . . . . . . . . . . . . . . . . . 13 4.3. Non-blocking mode . . . . . . . . . . . . . . . . . . . . 13
4.4. Special considerations . . . . . . . . . . . . . . . . . . 14 4.4. Special considerations . . . . . . . . . . . . . . . . . . 14
5. one-to-one style Interface . . . . . . . . . . . . . . . . . . 15 5. One-to-One Style Interface . . . . . . . . . . . . . . . . . . 15
5.1. Basic Operation . . . . . . . . . . . . . . . . . . . . . 16 5.1. Basic Operation . . . . . . . . . . . . . . . . . . . . . 16
5.1.1. socket() - one-to-one style socket . . . . . . . . . . 16 5.1.1. socket() . . . . . . . . . . . . . . . . . . . . . . . 16
5.1.2. bind() - one-to-one style socket . . . . . . . . . . . 17 5.1.2. bind() . . . . . . . . . . . . . . . . . . . . . . . . 17
5.1.3. listen() - one-to-one style socket . . . . . . . . . . 18 5.1.3. listen() . . . . . . . . . . . . . . . . . . . . . . . 18
5.1.4. accept() - one-to-one style socket . . . . . . . . . . 18 5.1.4. accept() . . . . . . . . . . . . . . . . . . . . . . . 18
5.1.5. connect() - one-to-one style socket . . . . . . . . . 19 5.1.5. connect() . . . . . . . . . . . . . . . . . . . . . . 19
5.1.6. close() - one-to-one style socket . . . . . . . . . . 20 5.1.6. close() . . . . . . . . . . . . . . . . . . . . . . . 20
5.1.7. shutdown() - one-to-one style socket . . . . . . . . . 20 5.1.7. shutdown() . . . . . . . . . . . . . . . . . . . . . . 20
5.1.8. sendmsg() and recvmsg() - one-to-one style socket . . 21 5.1.8. sendmsg() and recvmsg() . . . . . . . . . . . . . . . 21
5.1.9. getpeername() . . . . . . . . . . . . . . . . . . . . 21 5.1.9. getpeername() . . . . . . . . . . . . . . . . . . . . 21
6. Data Structures . . . . . . . . . . . . . . . . . . . . . . . 21 6. Data Structures . . . . . . . . . . . . . . . . . . . . . . . 22
6.1. The msghdr and cmsghdr Structures . . . . . . . . . . . . 22 6.1. The msghdr and cmsghdr Structures . . . . . . . . . . . . 22
6.2. SCTP msg_control Structures . . . . . . . . . . . . . . . 23 6.2. SCTP msg_control Structures . . . . . . . . . . . . . . . 23
6.2.1. SCTP Initiation Structure (SCTP_INIT) . . . . . . . . 24 6.2.1. SCTP Initiation Structure (SCTP_INIT) . . . . . . . . 24
6.2.2. SCTP Header Information Structure (SCTP_SNDRCV) . . . 25 6.2.2. SCTP Header Information Structure (SCTP_SNDRCV) . . . 25
6.2.3. Extended SCTP Header Information Structure 6.2.3. Extended SCTP Header Information Structure
(SCTP_EXTRCV) . . . . . . . . . . . . . . . . . . . . 28 (SCTP_EXTRCV) . . . . . . . . . . . . . . . . . . . . 27
6.3. SCTP Events and Notifications . . . . . . . . . . . . . . 29 6.3. SCTP Events and Notifications . . . . . . . . . . . . . . 28
6.3.1. SCTP Notification Structure . . . . . . . . . . . . . 30 6.3.1. SCTP Notification Structure . . . . . . . . . . . . . 29
6.4. Ancillary Data Considerations and Semantics . . . . . . . 42 6.3.2. SCTP_ASSOC_CHANGE . . . . . . . . . . . . . . . . . . 30
6.4.1. Multiple Items and Ordering . . . . . . . . . . . . . 42 6.3.3. SCTP_PEER_ADDR_CHANGE . . . . . . . . . . . . . . . . 32
6.4.2. Accessing and Manipulating Ancillary Data . . . . . . 43 6.3.4. SCTP_REMOTE_ERROR . . . . . . . . . . . . . . . . . . 33
6.4.3. Control Message Buffer Sizing . . . . . . . . . . . . 43 6.3.5. SCTP_SEND_FAILED . . . . . . . . . . . . . . . . . . . 33
7. Common Operations for Both Styles . . . . . . . . . . . . . . 44 6.3.6. SCTP_SHUTDOWN_EVENT . . . . . . . . . . . . . . . . . 35
7.1. send(), recv(), sendto(), recvfrom() . . . . . . . . . . . 44 6.3.7. SCTP_ADAPTATION_INDICATION . . . . . . . . . . . . . . 35
7.2. setsockopt(), getsockopt() . . . . . . . . . . . . . . . . 46 6.3.8. SCTP_PARTIAL_DELIVERY_EVENT . . . . . . . . . . . . . 36
7.3. read() and write() . . . . . . . . . . . . . . . . . . . . 46 6.3.9. SCTP_AUTHENTICATION_EVENT . . . . . . . . . . . . . . 37
7.4. getsockname() . . . . . . . . . . . . . . . . . . . . . . 46 6.3.10. SCTP_SENDER_DRY_EVENT . . . . . . . . . . . . . . . . 37
8. Socket Options . . . . . . . . . . . . . . . . . . . . . . . . 47 6.4. Ancillary Data Considerations and Semantics . . . . . . . 38
8.1. Read / Write Options . . . . . . . . . . . . . . . . . . . 49 6.4.1. Multiple Items and Ordering . . . . . . . . . . . . . 38
8.1.1. Retransmission Timeout Parameters (SCTP_RTOINFO) . . . 49 6.4.2. Accessing and Manipulating Ancillary Data . . . . . . 38
8.1.2. Association Parameters (SCTP_ASSOCINFO) . . . . . . . 49 6.4.3. Control Message Buffer Sizing . . . . . . . . . . . . 39
8.1.3. Initialization Parameters (SCTP_INITMSG) . . . . . . . 51 7. Common Operations for Both Styles . . . . . . . . . . . . . . 40
8.1.4. SO_LINGER . . . . . . . . . . . . . . . . . . . . . . 51 7.1. send(), recv(), sendto(), and recvfrom() . . . . . . . . . 40
8.1.5. SCTP_NODELAY . . . . . . . . . . . . . . . . . . . . . 51 7.2. setsockopt() and getsockopt() . . . . . . . . . . . . . . 42
8.1.6. SO_RCVBUF . . . . . . . . . . . . . . . . . . . . . . 52 7.3. read() and write() . . . . . . . . . . . . . . . . . . . . 42
8.1.7. SO_SNDBUF . . . . . . . . . . . . . . . . . . . . . . 52 7.4. getsockname() . . . . . . . . . . . . . . . . . . . . . . 43
8.1.8. Automatic Close of associations (SCTP_AUTOCLOSE) . . . 52 8. Socket Options . . . . . . . . . . . . . . . . . . . . . . . . 43
8.1.9. Set Peer Primary Address 8.1. Read / Write Options . . . . . . . . . . . . . . . . . . . 45
(SCTP_SET_PEER_PRIMARY_ADDR) . . . . . . . . . . . . . 52 8.1.1. Retransmission Timeout Parameters (SCTP_RTOINFO) . . . 45
8.1.10. Set Primary Address (SCTP_PRIMARY_ADDR) . . . . . . . 53 8.1.2. Association Parameters (SCTP_ASSOCINFO) . . . . . . . 46
8.1.11. Set Adaptation Layer Indicator 8.1.3. Initialization Parameters (SCTP_INITMSG) . . . . . . . 47
(SCTP_ADAPTATION_LAYER) . . . . . . . . . . . . . . . 53 8.1.4. SO_LINGER . . . . . . . . . . . . . . . . . . . . . . 47
8.1.12. Enable/Disable message fragmentation 8.1.5. SCTP_NODELAY . . . . . . . . . . . . . . . . . . . . . 48
(SCTP_DISABLE_FRAGMENTS) . . . . . . . . . . . . . . . 54 8.1.6. SO_RCVBUF . . . . . . . . . . . . . . . . . . . . . . 48
8.1.13. Peer Address Parameters (SCTP_PEER_ADDR_PARAMS) . . . 54 8.1.7. SO_SNDBUF . . . . . . . . . . . . . . . . . . . . . . 48
8.1.14. Set default send parameters 8.1.8. Automatic Close of Associations (SCTP_AUTOCLOSE) . . . 48
(SCTP_DEFAULT_SEND_PARAM) . . . . . . . . . . . . . . 56 8.1.9. Set Primary Address (SCTP_PRIMARY_ADDR) . . . . . . . 49
8.1.15. Set notification and ancillary events (SCTP_EVENTS) . 57 8.1.10. Set Adaptation Layer Indicator
8.1.16. Set/clear IPv4 mapped addresses (SCTP_ADAPTATION_LAYER) . . . . . . . . . . . . . . . 49
(SCTP_I_WANT_MAPPED_V4_ADDR) . . . . . . . . . . . . . 57 8.1.11. Enable/Disable Message Fragmentation
8.1.17. Get or set the maximum fragmentation size (SCTP_DISABLE_FRAGMENTS) . . . . . . . . . . . . . . . 49
(SCTP_MAXSEG) . . . . . . . . . . . . . . . . . . . . 57 8.1.12. Peer Address Parameters (SCTP_PEER_ADDR_PARAMS) . . . 50
8.1.18. Add a chunk that must be authenticated 8.1.13. Set Default Send Parameters
(SCTP_AUTH_CHUNK) . . . . . . . . . . . . . . . . . . 58 (SCTP_DEFAULT_SEND_PARAM) . . . . . . . . . . . . . . 52
8.1.19. Get or set the list of supported HMAC Identifiers 8.1.14. Set Notification and Ancillary Events (SCTP_EVENTS) . 52
(SCTP_HMAC_IDENT) . . . . . . . . . . . . . . . . . . 58 8.1.15. Set/Clear IPv4 Mapped Addresses
8.1.20. Set a shared key (SCTP_AUTH_KEY) . . . . . . . . . . . 59 (SCTP_I_WANT_MAPPED_V4_ADDR) . . . . . . . . . . . . . 53
8.1.21. Get or set the active shared key 8.1.16. Get or Set the Maximum Fragmentation Size
(SCTP_AUTH_ACTIVE_KEY) . . . . . . . . . . . . . . . . 59 (SCTP_MAXSEG) . . . . . . . . . . . . . . . . . . . . 53
8.1.22. Delete a shared key (SCTP_AUTH_DELETE_KEY) . . . . . . 60 8.1.17. Get or Set the List of Supported HMAC Identifiers
8.1.23. Delete a shared key (SCTP_AUTH_DEACTIVATE_KEY) . . . . 61 (SCTP_HMAC_IDENT) . . . . . . . . . . . . . . . . . . 53
8.1.24. Get or set delayed ack timer (SCTP_DELAYED_SACK) . . . 61 8.1.18. Get or Set the Active Shared Key
8.1.25. Get or set fragmented interleave (SCTP_AUTH_ACTIVE_KEY) . . . . . . . . . . . . . . . . 54
(SCTP_FRAGMENT_INTERLEAVE) . . . . . . . . . . . . . . 62 8.1.19. Get or Set Delayed SACK Timer (SCTP_DELAYED_SACK) . . 55
8.1.26. Set or Get the sctp partial delivery point 8.1.20. Get or Set Fragmented Interleave
(SCTP_PARTIAL_DELIVERY_POINT) . . . . . . . . . . . . 63 (SCTP_FRAGMENT_INTERLEAVE) . . . . . . . . . . . . . . 56
8.1.27. Set or Get the use of extended receive info 8.1.21. Set or Get the SCTP Partial Delivery Point
(SCTP_USE_EXT_RCVINFO) . . . . . . . . . . . . . . . . 64 (SCTP_PARTIAL_DELIVERY_POINT) . . . . . . . . . . . . 57
8.1.28. Set or Get the auto asconf flag (SCTP_AUTO_ASCONF) . . 64 8.1.22. Set or Get the Use of Extended Receive Info
8.1.29. Set or Get the maximum burst (SCTP_MAX_BURST) . . . . 64 (SCTP_USE_EXT_RCVINFO) . . . . . . . . . . . . . . . . 57
8.1.30. Set or Get the default context (SCTP_CONTEXT) . . . . 65 8.1.23. Set or Get the Auto ASCONF Flag (SCTP_AUTO_ASCONF) . . 57
8.1.31. Enable or disable explicit EOR marking 8.1.24. Set or Get the Maximum Burst (SCTP_MAX_BURST) . . . . 58
(SCTP_EXPLICIT_EOR) . . . . . . . . . . . . . . . . . 65 8.1.25. Set or Get the Default Context (SCTP_CONTEXT) . . . . 58
8.1.32. Enable SCTP port reusage (SCTP_REUSE_PORT) . . . . . . 65 8.1.26. Enable or Disable Explicit EOR Marking
8.2. Read-Only Options . . . . . . . . . . . . . . . . . . . . 66 (SCTP_EXPLICIT_EOR) . . . . . . . . . . . . . . . . . 59
8.2.1. Association Status (SCTP_STATUS) . . . . . . . . . . . 66 8.1.27. Enable SCTP Port Reusage (SCTP_REUSE_PORT) . . . . . . 59
8.2.2. Peer Address Information (SCTP_GET_PEER_ADDR_INFO) . . 67 8.2. Read-Only Options . . . . . . . . . . . . . . . . . . . . 59
8.2.3. Get the list of chunks the peer requires to be 8.2.1. Association Status (SCTP_STATUS) . . . . . . . . . . . 59
authenticated (SCTP_PEER_AUTH_CHUNKS) . . . . . . . . 68 8.2.2. Peer Address Information (SCTP_GET_PEER_ADDR_INFO) . . 60
8.2.4. Get the list of chunks the local endpoint requires 8.2.3. Get the List of Chunks the Peer Requires to be
to be authenticated (SCTP_LOCAL_AUTH_CHUNKS) . . . . . 69 Authenticated (SCTP_PEER_AUTH_CHUNKS) . . . . . . . . 61
8.2.5. Get the current number of associations 8.2.4. Get the List of Chunks the Local Endpoint Requires
(SCTP_GET_ASSOC_NUMBER) . . . . . . . . . . . . . . . 69 to be Authenticated (SCTP_LOCAL_AUTH_CHUNKS) . . . . . 62
8.2.6. Get the current identifiers of associations 8.2.5. Get the Current Number of Associations
(SCTP_GET_ASSOC_ID_LIST) . . . . . . . . . . . . . . . 69 (SCTP_GET_ASSOC_NUMBER) . . . . . . . . . . . . . . . 62
8.3. Ancillary Data and Notification Interest Options . . . . . 70 8.2.6. Get the Current Identifiers of Associations
9. New Interfaces . . . . . . . . . . . . . . . . . . . . . . . . 72 (SCTP_GET_ASSOC_ID_LIST) . . . . . . . . . . . . . . . 62
9.1. sctp_bindx() . . . . . . . . . . . . . . . . . . . . . . . 72 8.3. Write-Only Options . . . . . . . . . . . . . . . . . . . . 63
9.2. Branched-off Association . . . . . . . . . . . . . . . . . 74 8.3.1. Set Peer Primary Address
9.3. sctp_getpaddrs() . . . . . . . . . . . . . . . . . . . . . 74 (SCTP_SET_PEER_PRIMARY_ADDR) . . . . . . . . . . . . . 63
9.4. sctp_freepaddrs() . . . . . . . . . . . . . . . . . . . . 75 8.3.2. Add a Chunk That Must Be Authenticated
9.5. sctp_getladdrs() . . . . . . . . . . . . . . . . . . . . . 75 (SCTP_AUTH_CHUNK) . . . . . . . . . . . . . . . . . . 63
9.6. sctp_freeladdrs() . . . . . . . . . . . . . . . . . . . . 76 8.3.3. Set a Shared Key (SCTP_AUTH_KEY) . . . . . . . . . . . 64
9.7. sctp_sendmsg() . . . . . . . . . . . . . . . . . . . . . . 76 8.3.4. Deactivate a Shared Key (SCTP_AUTH_DEACTIVATE_KEY) . . 64
9.8. sctp_recvmsg() . . . . . . . . . . . . . . . . . . . . . . 77 8.3.5. Delete a Shared Key (SCTP_AUTH_DELETE_KEY) . . . . . . 65
9.9. sctp_connectx() . . . . . . . . . . . . . . . . . . . . . 77 8.4. Ancillary Data and Notification Interest Options . . . . . 66
9.10. sctp_send() . . . . . . . . . . . . . . . . . . . . . . . 78 9. New Functions . . . . . . . . . . . . . . . . . . . . . . . . 68
9.11. sctp_sendx() . . . . . . . . . . . . . . . . . . . . . . . 79 9.1. sctp_bindx() . . . . . . . . . . . . . . . . . . . . . . . 68
9.12. sctp_getaddrlen . . . . . . . . . . . . . . . . . . . . . 80 9.2. sctp_peeloff() . . . . . . . . . . . . . . . . . . . . . . 69
10. IANA considerations . . . . . . . . . . . . . . . . . . . . . 80 9.3. sctp_getpaddrs() . . . . . . . . . . . . . . . . . . . . . 70
11. Security Considerations . . . . . . . . . . . . . . . . . . . 80 9.4. sctp_freepaddrs() . . . . . . . . . . . . . . . . . . . . 71
12. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 81 9.5. sctp_getladdrs() . . . . . . . . . . . . . . . . . . . . . 71
13. Acknowledgments . . . . . . . . . . . . . . . . . . . . . . . 81 9.6. sctp_freeladdrs() . . . . . . . . . . . . . . . . . . . . 72
14. Normative references . . . . . . . . . . . . . . . . . . . . . 81 9.7. sctp_sendmsg() . . . . . . . . . . . . . . . . . . . . . . 72
Appendix A. one-to-one style Code Example . . . . . . . . . . . . 82 9.8. sctp_recvmsg() . . . . . . . . . . . . . . . . . . . . . . 73
Appendix B. one-to-many style Code Example . . . . . . . . . . . 87 9.9. sctp_connectx() . . . . . . . . . . . . . . . . . . . . . 73
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . . 89 9.10. sctp_send() . . . . . . . . . . . . . . . . . . . . . . . 74
Intellectual Property and Copyright Statements . . . . . . . . . . 91 9.11. sctp_sendx() . . . . . . . . . . . . . . . . . . . . . . . 75
9.12. sctp_getaddrlen() . . . . . . . . . . . . . . . . . . . . 76
10. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 76
11. Security Considerations . . . . . . . . . . . . . . . . . . . 77
12. Acknowledgments . . . . . . . . . . . . . . . . . . . . . . . 77
13. Normative References . . . . . . . . . . . . . . . . . . . . . 77
Appendix A. One-to-One Style Code Example . . . . . . . . . . . . 78
Appendix B. One-to-Many Style Code Example . . . . . . . . . . . 83
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . . 85
Intellectual Property and Copyright Statements . . . . . . . . . . 87
1. Introduction 1. Introduction
The sockets API has provided a standard mapping of the Internet The sockets API has provided a standard mapping of the Internet
Protocol suite to many operating systems. Both TCP [RFC0793] and UDP Protocol suite to many operating systems. Both TCP [RFC0793] and UDP
[RFC0768] have benefited from this standard representation and access [RFC0768] have benefited from this standard representation and access
method across many diverse platforms. SCTP is a new protocol that method across many diverse platforms. SCTP is a new protocol that
provides many of the characteristics of TCP but also incorporates provides many of the characteristics of TCP but also incorporates
semantics more akin to UDP. This document defines a method to map semantics more akin to UDP. This document defines a method to map
the existing sockets API for use with SCTP, providing both a base for the existing sockets API for use with SCTP, providing both a base for
access to new features and compatibility so that most existing TCP access to new features and compatibility so that most existing TCP
applications can be migrated to SCTP with few (if any) changes. applications can be migrated to SCTP with few (if any) changes.
There are three basic design objectives: There are three basic design objectives:
1. Maintain consistency with existing sockets APIs: We define a
1) Maintain consistency with existing sockets APIs: sockets mapping for SCTP that is consistent with other sockets
We define a sockets mapping for SCTP that is consistent with other API protocol mappings (for instance, UDP, TCP, IPv4, and IPv6).
sockets API protocol mappings (for instance, UDP, TCP, IPv4, and 2. Support a one-to-many style interface This set of semantics is
IPv6). similar to that defined for connection-less protocols, such as
2) Support a one-to-many style interface UDP. A one-to-many style SCTP socket should be able to control
This set of semantics is similar to that defined for connection- multiple SCTP associations. This is similar to an UDP socket,
less protocols, such as UDP. A one-to-many style SCTP socket which can communicate with many peer end points. Each of these
should be able to control multiple SCTP associations. This is associations is assigned an association ID so that an
similar to an UDP socket, which can communicate with many peer end applications can use the ID to differentiate them. Note that
points. Each of these associations is assigned an association ID SCTP is connection-oriented in nature, and it does not support
so that an applications can use the ID to differentiate them. broadcast or multicast communications, as UDP does.
Note that SCTP is connection-oriented in nature, and it does not 3. Support a one-to-one style interface This interface supports a
support broadcast or multicast communications, as UDP does. similar semantics as sockets for connection-oriented protocols,
3) Support a one-to-one style interface such as TCP. A one-to-one style SCTP socket should only control
This interface supports a similar semantics as sockets for one SCTP association. One purpose of defining this interface is
connection-oriented protocols, such as TCP. A one-to-one style to allow existing applications built on other connection-oriented
SCTP socket should only control one SCTP association. protocols be ported to use SCTP with very little effort. And
One purpose of defining this interface is to allow existing developers familiar with those semantics can easily adapt to
applications built on other connection-oriented protocols be SCTP. Another purpose is to make sure that existing mechanisms
ported to use SCTP with very little effort. And developers in most OSes to deal with socket, such as select(), should
familiar with those semantics can easily adapt to SCTP. Another continue to work with this style of socket. Extensions are added
purpose is to make sure that existing mechanisms in most OSes to to this mapping to provide mechanisms to exploit new features of
deal with socket, such as select(), should continue to work with SCTP.
this style of socket.
Extensions are added to this mapping to provide mechanisms to
exploit new features of SCTP.
Goals 2 and 3 are not compatible, so in this document we define two Goals 2 and 3 are not compatible, so in this document we define two
modes of mapping, namely the one-to-many style mapping and the one- modes of mapping, namely the one-to-many style mapping and the one-
to-one style mapping. These two modes share some common data to-one style mapping. These two modes share some common data
structures and operations, but will require the use of two different structures and operations, but will require the use of two different
application programming styles. Note that all new SCTP features can application programming styles. Note that all new SCTP features can
be used with both styles of socket. The decision on which one to use be used with both styles of socket. The decision on which one to use
depends mainly on the nature of applications. depends mainly on the nature of applications.
A mechanism is defined to extract a one-to-many style SCTP A mechanism is defined to extract a one-to-many style SCTP
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3. Data Types 3. Data Types
Whenever possible, data types from Draft 6.6 (March 1997) of POSIX Whenever possible, data types from Draft 6.6 (March 1997) of POSIX
1003.1g are used: uintN_t means an unsigned integer of exactly N bits 1003.1g are used: uintN_t means an unsigned integer of exactly N bits
(e.g., uint16_t). We also assume the argument data types from (e.g., uint16_t). We also assume the argument data types from
1003.1g when possible (e.g., the final argument to setsockopt() is a 1003.1g when possible (e.g., the final argument to setsockopt() is a
size_t value). Whenever buffer sizes are specified, the POSIX 1003.1 size_t value). Whenever buffer sizes are specified, the POSIX 1003.1
size_t data type is used. size_t data type is used.
4. one-to-many style Interface 4. One-to-Many Style Interface
The one-to-many style interface has the following characteristics: The one-to-many style interface has the following characteristics:
o Outbound association setup is implicit.
A) Outbound association setup is implicit. o Messages are delivered in complete messages (with one notable
B) Messages are delivered in complete messages (with one notable
exception). exception).
o There is a 1 to MANY relationship between socket and association.
C) There is a 1 to MANY relationship between socket and association.
4.1. Basic Operation 4.1. Basic Operation
A typical server in this style uses the following socket calls in A typical server in this style uses the following socket calls in
sequence to prepare an endpoint for servicing requests: sequence to prepare an endpoint for servicing requests:
o socket()
1. socket() o bind()
2. bind() o listen()
3. listen() o recvmsg()
4. recvmsg() o sendmsg()
5. sendmsg() o close()
6. close()
A typical client uses the following calls in sequence to setup an A typical client uses the following calls in sequence to setup an
association with a server to request services: association with a server to request services:
o socket()
1. socket() o sendmsg()
2. sendmsg() o recvmsg()
3. recvmsg() o close()
4. close()
In this style, by default, all the associations connected to the In this style, by default, all the associations connected to the
endpoint are represented with a single socket. Each associations is endpoint are represented with a single socket. Each associations is
assigned an association ID (type is sctp_assoc_t) so that an assigned an association ID (type is sctp_assoc_t) so that an
application can use it to differentiate between them. In some application can use it to differentiate between them. In some
implementations, the peer endpoints addresses can also be used for implementations, the peer endpoints addresses can also be used for
this purpose. But this is not required for performance reasons. If this purpose. But this is not required for performance reasons. If
an implementation does not support using addresses to differentiate an implementation does not support using addresses to differentiate
between different associations, the sendto() call can only be used to between different associations, the sendto() call can only be used to
setup an association implicitly. It cannot be used to send data to setup an association implicitly. It cannot be used to send data to
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Once an association is branched off to a separate socket, it becomes Once an association is branched off to a separate socket, it becomes
completely separated from the original socket. All subsequent completely separated from the original socket. All subsequent
control and data operations to that association must be done through control and data operations to that association must be done through
the new socket. For example, the close operation on the original the new socket. For example, the close operation on the original
socket will not terminate any associations that have been branched socket will not terminate any associations that have been branched
off to a different socket. off to a different socket.
We will discuss the one-to-many style socket calls in more details in We will discuss the one-to-many style socket calls in more details in
the following subsections. the following subsections.
4.1.1. socket() - one-to-many style socket 4.1.1. socket()
Applications use socket() to create a socket descriptor to represent Applications use socket() to create a socket descriptor to represent
an SCTP endpoint. an SCTP endpoint.
The syntax is, The function prototype is
int socket(int domain,
sd = socket(PF_INET, SOCK_SEQPACKET, IPPROTO_SCTP); int type,
int protocol);
or,
sd = socket(PF_INET6, SOCK_SEQPACKET, IPPROTO_SCTP); and one uses PF_INET or PF_INET6 as the domain, SOCK_SEQPACKET as the
type and IPPROTO_SCTP as the protocol.
Here, SOCK_SEQPACKET indicates the creation of a one-to-many style Here, SOCK_SEQPACKET indicates the creation of a one-to-many style
socket. socket.
The first form creates an endpoint which can use only IPv4 addresses, The first form creates an endpoint which can use only IPv4 addresses,
while, the second form creates an endpoint which can use both IPv6 while, the second form creates an endpoint which can use both IPv6
and IPv4 addresses. and IPv4 addresses.
4.1.2. bind() - one-to-many style socket 4.1.2. bind()
Applications use bind() to specify which local address the SCTP Applications use bind() to specify which local address the SCTP
endpoint should associate itself with. endpoint should associate itself with.
An SCTP endpoint can be associated with multiple addresses. To do An SCTP endpoint can be associated with multiple addresses. To do
this, sctp_bindx() is introduced in section Section 9.1 to help this, sctp_bindx() is introduced in Section 9.1 to help applications
applications do the job of associating multiple addresses. do the job of associating multiple addresses.
These addresses associated with a socket are the eligible transport These addresses associated with a socket are the eligible transport
addresses for the endpoint to send and receive data. The endpoint addresses for the endpoint to send and receive data. The endpoint
will also present these addresses to its peers during the association will also present these addresses to its peers during the association
initialization process, see [RFC4960]. initialization process, see [RFC4960].
After calling bind(), if the endpoint wishes to accept new After calling bind(), if the endpoint wishes to accept new
associations on the socket, it must call listen() (see section associations on the socket, it must call listen() (see
Section 4.1.3). Section 4.1.3).
The syntax of bind() is, The function prototype of bind() is
ret = bind(int sd, struct sockaddr *addr, socklen_t addrlen); int bind(int sd,
sd - the socket descriptor returned by socket(). struct sockaddr *addr,
addr - the address structure (struct sockaddr_in or struct socklen_t addrlen);
sockaddr_in6 [RFC3493]).
addrlen - the size of the address structure. and the arguments are
sd: The socket descriptor returned by socket().
addr: The address structure (struct sockaddr_in or struct
sockaddr_in6, see [RFC3493]).
addrlen: The size of the address structure.
If sd is an IPv4 socket, the address passed must be an IPv4 address. If sd is an IPv4 socket, the address passed must be an IPv4 address.
If the sd is an IPv6 socket, the address passed can either be an IPv4 If the sd is an IPv6 socket, the address passed can either be an IPv4
or an IPv6 address. or an IPv6 address.
Applications cannot call bind() multiple times to associate multiple Applications cannot call bind() multiple times to associate multiple
addresses to an endpoint. After the first call to bind(), all addresses to an endpoint. After the first call to bind(), all
subsequent calls will return an error. subsequent calls will return an error.
If addr is specified as a wildcard (INADDR_ANY for an IPv4 address, If addr is specified as a wildcard (INADDR_ANY for an IPv4 address,
or as IN6ADDR_ANY_INIT or in6addr_any for an IPv6 address), the or as IN6ADDR_ANY_INIT or in6addr_any for an IPv6 address), the
operating system will associate the endpoint with an optimal address operating system will associate the endpoint with an optimal address
set of the available interfaces. set of the available interfaces.
If a bind() is not called prior to a sendmsg() call that initiates a If a bind() is not called prior to a sendmsg() call that initiates a
new association, the system picks an ephemeral port and will choose new association, the system picks an ephemeral port and will choose
an address set equivalent to binding with a wildcard address. One of an address set equivalent to binding with a wildcard address. One of
those addresses will be the primary address for the association. those addresses will be the primary address for the association.
This automatically enables the multi-homing capability of SCTP. This automatically enables the multi-homing capability of SCTP.
4.1.3. listen() - One-to-many style socket 4.1.3. listen()
By default, new associations are not accepted for one-to-many style By default, new associations are not accepted for one-to-many style
sockets. An application uses listen() to mark a socket as being able sockets. An application uses listen() to mark a socket as being able
to accept new associations. The syntax is, to accept new associations.
int listen(int sd, int backlog); The function prototype is
sd - the socket descriptor of the endpoint. int listen(int sd,
backlog - if backlog is non-zero, enable listening else disable int backlog);
and the arguments are
sd: The socket descriptor of the endpoint.
backlog: If backlog is non-zero, enable listening else disable
listening. listening.
Note that one-to-many style socket consumers do not need to call Note that one-to-many style socket consumers do not need to call
accept to retrieve new associations. Calling accept() on a one-to- accept to retrieve new associations. Calling accept() on a one-to-
many style socket should return EOPNOTSUPP. Rather, new associations many style socket should return EOPNOTSUPP. Rather, new associations
are accepted automatically, and notifications of the new associations are accepted automatically, and notifications of the new associations
are delivered via recvmsg() with the SCTP_ASSOC_CHANGE event (if are delivered via recvmsg() with the SCTP_ASSOC_CHANGE event (if
these notifications are enabled). Clients will typically not call these notifications are enabled). Clients will typically not call
listen(), so that they can be assured that the only associations on listen(), so that they can be assured that the only associations on
the socket will be ones they actively initiated. Server or peer-to- the socket will be ones they actively initiated. Server or peer-to-
peer sockets, on the other hand, will always accept new associations, peer sockets, on the other hand, will always accept new associations,
so a well-written application using server one-to-many style sockets so a well-written application using server one-to-many style sockets
must be prepared to handle new associations from unwanted peers. must be prepared to handle new associations from unwanted peers.
Also note that the SCTP_ASSOC_CHANGE event provides the association Also note that the SCTP_ASSOC_CHANGE event provides the association
ID for a new association, so if applications wish to use the ID for a new association, so if applications wish to use the
association ID as input to other socket calls, they should ensure association ID as input to other socket calls, they should ensure
that the SCTP_ASSOC_CHANGE event is enabled. that the SCTP_ASSOC_CHANGE event is enabled.
4.1.4. sendmsg() and recvmsg() - one-to-many style socket 4.1.4. sendmsg() and recvmsg()
An application uses sendmsg() and recvmsg() call to transmit data to An application uses sendmsg() and recvmsg() call to transmit data to
and receive data from its peer. and receive data from its peer.
ssize_t sendmsg(int sd, const struct msghdr *message, int flags); The function prototypes are
ssize_t recvmsg(int sd, struct msghdr *message, int flags); ssize_t sendmsg(int sd,
const struct msghdr *message,
int flags);
sd - the socket descriptor of the endpoint. and
message: pointer to the msghdr structure which contains a single
ssize_t recvmsg(int sd,
struct msghdr *message,
int flags);
using the arguments:
sd: The socket descriptor of the endpoint.
message: Pointer to the msghdr structure which contains a single
user message and possibly some ancillary data. See Section 6 for user message and possibly some ancillary data. See Section 6 for
complete description of the data structures. complete description of the data structures.
flags - No new flags are defined for SCTP at this level. See flags: No new flags are defined for SCTP at this level. See
Section 5 for SCTP-specific flags used in the msghdr structure. Section 6 for SCTP-specific flags used in the msghdr structure.
As we will see in Section 6, along with the user data, the ancillary As we will see in Section 6, along with the user data, the ancillary
data field is used to carry the sctp_sndrcvinfo and/or the data field is used to carry the sctp_sndrcvinfo and/or the
sctp_initmsg structures to perform various SCTP functions including sctp_initmsg structures to perform various SCTP functions including
specifying options for sending each user message. Those options, specifying options for sending each user message. Those options,
depending on whether sending or receiving, include stream number, depending on whether sending or receiving, include stream number,
stream sequence number, various flags, context and payload protocol stream sequence number, various flags, context and payload protocol
Id, etc. Id, etc.
When sending user data with sendmsg(), the msg_name field in msghdr When sending user data with sendmsg(), the msg_name field in msghdr
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receive a data message, MSG_EOR will not be set in msg_flags. receive a data message, MSG_EOR will not be set in msg_flags.
Successive reads will consume more of the same message until the Successive reads will consume more of the same message until the
entire message has been delivered, and MSG_EOR will be set. entire message has been delivered, and MSG_EOR will be set.
If the SCTP stack is running low on buffers, it may partially deliver If the SCTP stack is running low on buffers, it may partially deliver
a message. In this case, MSG_EOR will not be set, and more calls to a message. In this case, MSG_EOR will not be set, and more calls to
recvmsg() will be necessary to completely consume the message. Only recvmsg() will be necessary to completely consume the message. Only
one message at a time can be partially delivered in any stream. The one message at a time can be partially delivered in any stream. The
socket option SCTP_FRAGMENT_INTERLEAVE controls various aspects of socket option SCTP_FRAGMENT_INTERLEAVE controls various aspects of
what interlacing of messages occurs for both the one-to-one and the what interlacing of messages occurs for both the one-to-one and the
one-to-many model sockets. Please consult Section 8.1.25 for further one-to-many model sockets. Please consult Section 8.1.20 for further
details on message delivery options. details on message delivery options.
Note, if the socket is a branched-off socket that only represents one Note, if the socket is a branched-off socket that only represents one
association (see Section 4.1), the msg_name field can be used to association (see Section 4.1), the msg_name field can be used to
override the primary address when sending data. override the primary address when sending data.
4.1.5. close() - one-to-many style socket 4.1.5. close()
Applications use close() to perform graceful shutdown (as described Applications use close() to perform graceful shutdown (as described
in Section 10.1 of [RFC4960]) on ALL the associations currently in Section 10.1 of [RFC4960]) on ALL the associations currently
represented by a one-to-many style socket. represented by a one-to-many style socket.
The syntax is: The function prototype is
ret = close(int sd); int close(int sd);
sd - the socket descriptor of the associations to be closed. and the argument is
sd: The socket descriptor of the associations to be closed.
To gracefully shutdown a specific association represented by the one- To gracefully shutdown a specific association represented by the one-
to-many style socket, an application should use the sendmsg() call, to-many style socket, an application should use the sendmsg() call,
and including the SCTP_EOF flag. A user may optionally terminate an and including the SCTP_EOF flag. A user may optionally terminate an
association non-gracefully by sending with the SCTP_ABORT flag and association non-gracefully by sending with the SCTP_ABORT flag and
possibly passing a user specified abort code in the data field. Both possibly passing a user specified abort code in the data field. Both
flags SCTP_EOF and SCTP_ABORT are passed with ancillary data (see flags SCTP_EOF and SCTP_ABORT are passed with ancillary data (see
Section 6.2.2) in the sendmsg call. Section 6.2.2) in the sendmsg call.
If sd in the close() call is a branched-off socket representing only If sd in the close() call is a branched-off socket representing only
one association, the shutdown is performed on that association only. one association, the shutdown is performed on that association only.
4.1.6. connect() - one-to-many style socket 4.1.6. connect()
An application may use the connect() call in the one-to-many style to An application may use the connect() call in the one-to-many style to
initiate an association without sending data. initiate an association without sending data.
The syntax is: The function prototype is
ret = connect(int sd, const struct sockaddr *nam, socklen_t len); int connect(int sd,
const struct sockaddr *nam,
socklen_t len);
sd - the socket descriptor to have a new association added to. and the arguments are
nam - the address structure (either struct sockaddr_in or struct sd: The socket descriptor to have a new association added to.
nam: The address structure (either struct sockaddr_in or struct
sockaddr_in6 defined in [RFC3493]). sockaddr_in6 defined in [RFC3493]).
len - the size of the address. len: The size of the address.
Multiple connect() calls can be made on the same socket to create Multiple connect() calls can be made on the same socket to create
multiple associations. This is different from the semantics of multiple associations. This is different from the semantics of
connect() on a UDP socket. connect() on a UDP socket.
4.2. Implicit Association Setup 4.2. Implicit Association Setup
Implicit association setup applies only to one-to-many style sockets. Implicit association setup applies only to one-to-many style sockets.
For one-to-one style sockets implicit association setup MUST NOT be For one-to-one style sockets implicit association setup MUST NOT be
used. used.
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SCTP_SEND_FAILED event. Those event(s) can be received by the user SCTP_SEND_FAILED event. Those event(s) can be received by the user
calling of recvmsg(). A server (having called listen()) is also calling of recvmsg(). A server (having called listen()) is also
notified of an association up event by the reception of a notified of an association up event by the reception of a
SCTP_ASSOC_CHANGE with SCTP_COMM_UP via the calling of recvmsg() and SCTP_ASSOC_CHANGE with SCTP_COMM_UP via the calling of recvmsg() and
possibly the reception of the first data message. possibly the reception of the first data message.
In order to shutdown the association gracefully, the user must call In order to shutdown the association gracefully, the user must call
sendmsg() with no data and with the SCTP_EOF flag set. The function sendmsg() with no data and with the SCTP_EOF flag set. The function
returns immediately, and completion of the graceful shutdown is returns immediately, and completion of the graceful shutdown is
indicated by an SCTP_ASSOC_CHANGE notification of type indicated by an SCTP_ASSOC_CHANGE notification of type
SHUTDOWN_COMPLETE (see Section 6.3.1.1). Note that this can also be SHUTDOWN_COMPLETE (see Section 6.3.2). Note that this can also be
done using the sctp_send() call described in Section 9.10. done using the sctp_send() call described in Section 9.10.
An application is recommended to use caution when using select() (or An application is recommended to use caution when using select() (or
poll()) for writing on a one-to-many style socket. The reason being poll()) for writing on a one-to-many style socket. The reason being
that interpretation of select on write is implementation specific. that interpretation of select on write is implementation specific.
Generally a positive return on a select on write would only indicate Generally a positive return on a select on write would only indicate
that one of the associations represented by the one-to-many socket is that one of the associations represented by the one-to-many socket is
writable. An application that writes after the select return may writable. An application that writes after the select return may
still block since the association that was writeable is not the still block since the association that was writeable is not the
destination association of the write call. Likewise select (or destination association of the write call. Likewise select (or
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4.4. Special considerations 4.4. Special considerations
The fact that a one-to-many style socket can provide access to many The fact that a one-to-many style socket can provide access to many
SCTP associations through a single socket descriptor has important SCTP associations through a single socket descriptor has important
implications for both application programmers and system programmers implications for both application programmers and system programmers
implementing this API. A key issue is how buffer space inside the implementing this API. A key issue is how buffer space inside the
sockets layer is managed. Because this implementation detail sockets layer is managed. Because this implementation detail
directly affects how application programmers must write their code to directly affects how application programmers must write their code to
ensure correct operation and portability, this section provides some ensure correct operation and portability, this section provides some
guidance to both implementors and application programmers. guidance to both implementers and application programmers.
An important feature that SCTP shares with TCP is flow control: An important feature that SCTP shares with TCP is flow control:
specifically, a sender may not send data faster than the receiver can specifically, a sender may not send data faster than the receiver can
consume it. consume it.
For TCP, flow control is typically provided for in the sockets API as For TCP, flow control is typically provided for in the sockets API as
follows. If the reader stops reading, the sender queues messages in follows. If the reader stops reading, the sender queues messages in
the socket layer until it uses all of its socket buffer space the socket layer until it uses all of its socket buffer space
allocation creating a "stalled connection". Further attempts to allocation creating a "stalled connection". Further attempts to
write to the socket will block or return the error EAGAIN or write to the socket will block or return the error EAGAIN or
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uses a single buffer space allocation shared by all associations, a uses a single buffer space allocation shared by all associations, a
single stalled association can prevent the further sending of data on single stalled association can prevent the further sending of data on
all associations active on a particular one-to-many style socket. all associations active on a particular one-to-many style socket.
For a blocking socket, it should be clear that a single stalled For a blocking socket, it should be clear that a single stalled
association can block the entire socket. For this reason, association can block the entire socket. For this reason,
application programmers may want to use non-blocking one-to-many application programmers may want to use non-blocking one-to-many
style sockets. The application should at least be able to send style sockets. The application should at least be able to send
messages to the non-stalled associations. messages to the non-stalled associations.
But a non-blocking socket is not sufficient if the API implementor But a non-blocking socket is not sufficient if the API implementer
has chosen a single shared buffer allocation for the socket. A has chosen a single shared buffer allocation for the socket. A
single stalled association would eventually cause the shared single stalled association would eventually cause the shared
allocation to fill, and it would become impossible to send even to allocation to fill, and it would become impossible to send even to
non-stalled associations. non-stalled associations.
The API implementor can solve this problem by providing each The API implementer can solve this problem by providing each
association with its own allocation of outbound buffer space. Each association with its own allocation of outbound buffer space. Each
association should conceptually have as much buffer space as it would association should conceptually have as much buffer space as it would
have if it had its own socket. As a bonus, this simplifies the have if it had its own socket. As a bonus, this simplifies the
implementation of sctp_peeloff(). implementation of sctp_peeloff().
To ensure that a given stalled association will not prevent other To ensure that a given stalled association will not prevent other
non-stalled associations from being writable, application programmers non-stalled associations from being writable, application programmers
should either: should either:
o demand that the underlying implementation dedicates independent
(a) demand that the underlying implementation dedicates independent
buffer space allotments to each association (as suggested above), buffer space allotments to each association (as suggested above),
or or
(b) verify that their application layer protocol does not permit o verify that their application layer protocol does not permit large
large amounts of unread data at the receiver (this is true of some amounts of unread data at the receiver (this is true of some
request-response protocols, for example), or request-response protocols, for example), or
(c) use one-to-one style sockets for association which may o use one-to-one style sockets for association which may potentially
potentially stall (either from the beginning, or by using stall (either from the beginning, or by using sctp_peeloff before
sctp_peeloff before sending large amounts of data that may cause a sending large amounts of data that may cause a stalled condition).
stalled condition).
An implementation which dedicates independent buffer space for
each association should define HAVE_SCTP_MULTIBUF to 1.
5. one-to-one style Interface 5. One-to-One Style Interface
The goal of this style is to follow as closely as possible the The goal of this style is to follow as closely as possible the
current practice of using the sockets interface for a connection current practice of using the sockets interface for a connection
oriented protocol, such as TCP. This style enables existing oriented protocol, such as TCP. This style enables existing
applications using connection oriented protocols to be ported to SCTP applications using connection oriented protocols to be ported to SCTP
with very little effort. with very little effort.
Note that some new SCTP features and some new SCTP socket options can Note that some new SCTP features and some new SCTP socket options can
only be utilized through the use of sendmsg() and recvmsg() calls, only be utilized through the use of sendmsg() and recvmsg() calls,
see Section 5.1.8. Also note that some socket interfaces may not be see Section 5.1.8. Also note that some socket interfaces may not be
able to provide data on the third leg of the association set up with able to provide data on the third leg of the association set up with
this interface style. this interface style.
5.1. Basic Operation 5.1. Basic Operation
A typical server in one-to-one style uses the following system call A typical server in one-to-one style uses the following system call
sequence to prepare an SCTP endpoint for servicing requests: sequence to prepare an SCTP endpoint for servicing requests:
o socket()
1. socket() o bind()
o listen()
2. bind() o accept()
3. listen()
4. accept()
The accept() call blocks until a new association is set up. It The accept() call blocks until a new association is set up. It
returns with a new socket descriptor. The server then uses the new returns with a new socket descriptor. The server then uses the new
socket descriptor to communicate with the client, using recv() and socket descriptor to communicate with the client, using recv() and
send() calls to get requests and send back responses. send() calls to get requests and send back responses.
Then it calls Then it calls
o close()
5. close()
to terminate the association. to terminate the association.
A typical client uses the following system call sequence to setup an A typical client uses the following system call sequence to setup an
association with a server to request services: association with a server to request services:
o socket()
1. socket() o connect()
2. connect()
After returning from connect(), the client uses send() and recv() After returning from connect(), the client uses send() and recv()
calls to send out requests and receive responses from the server. calls to send out requests and receive responses from the server.
The client calls The client calls
o close()
3. close()
to terminate this association when done. to terminate this association when done.
5.1.1. socket() - one-to-one style socket 5.1.1. socket()
Applications calls socket() to create a socket descriptor to Applications calls socket() to create a socket descriptor to
represent an SCTP endpoint. represent an SCTP endpoint.
The syntax is: The function prototype is
int socket(PF_INET, SOCK_STREAM, IPPROTO_SCTP);
or, int socket(int domain,
int type,
int protocol);
int socket(PF_INET6, SOCK_STREAM, IPPROTO_SCTP); and one uses PF_INET or PF_INET6 as the domain, SOCK_SEQPACKET as the
type and IPPROTO_SCTP as the protocol.
Here, SOCK_STREAM indicates the creation of a one-to-one style Here, SOCK_STREAM indicates the creation of a one-to-one style
socket. socket.
The first form creates an endpoint which can use only IPv4 addresses, The first form creates an endpoint which can use only IPv4 addresses,
while the second form creates an endpoint which can use both IPv6 and while the second form creates an endpoint which can use both IPv6 and
IPv4 addresses. IPv4 addresses.
5.1.2. bind() - one-to-one style socket 5.1.2. bind()
Applications use bind() to pass an address to be associated with an Applications use bind() to pass an address to be associated with an
SCTP endpoint to the system. bind() allows only either a single SCTP endpoint to the system. bind() allows only either a single
address or a IPv4 or IPv6 wildcard address to be bound. An SCTP address or a IPv4 or IPv6 wildcard address to be bound. An SCTP
endpoint can be associated with multiple addresses. To do this, endpoint can be associated with multiple addresses. To do this,
sctp_bindx() is introduced in Section 9.1 to help applications do the sctp_bindx() is introduced in Section 9.1 to help applications do the
job of associating multiple addresses. job of associating multiple addresses.
These addresses associated with a socket are the eligible transport These addresses associated with a socket are the eligible transport
addresses for the endpoint to send and receive data. The endpoint addresses for the endpoint to send and receive data. The endpoint
will also present these addresses to its peers during the association will also present these addresses to its peers during the association
initialization process, see [RFC4960]. initialization process, see [RFC4960].
The syntax is: The function prototype of bind() is
int bind(int sd, struct sockaddr *addr, socklen_t addrlen); int bind(int sd,
struct sockaddr *addr,
socklen_t addrlen);
sd: the socket descriptor returned by socket() call. and the arguments are
addr: the address structure (either struct sockaddr_in or struct sd: The socket descriptor returned by socket().
sockaddr_in6 defined in [RFC3493]). addr: The address structure (struct sockaddr_in or struct
addrlen: the size of the address structure. sockaddr_in6, see [RFC3493]).
addrlen: The size of the address structure.
If sd is an IPv4 socket, the address passed must be an IPv4 address. If sd is an IPv4 socket, the address passed must be an IPv4 address.
Otherwise, i.e., the sd is an IPv6 socket, the address passed can Otherwise, i.e., the sd is an IPv6 socket, the address passed can
either be an IPv4 or an IPv6 address. either be an IPv4 or an IPv6 address.
Applications cannot call bind() multiple times to associate multiple Applications cannot call bind() multiple times to associate multiple
addresses to the endpoint. After the first call to bind(), all addresses to the endpoint. After the first call to bind(), all
subsequent calls will return an error. subsequent calls will return an error.
If addr is specified as a wildcard (INADDR_ANY for an IPv4 address, If addr is specified as a wildcard (INADDR_ANY for an IPv4 address,
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binding with a wildcard address. One of those addresses will be the binding with a wildcard address. One of those addresses will be the
primary address for the association. This automatically enables the primary address for the association. This automatically enables the
multi-homing capability of SCTP. multi-homing capability of SCTP.
The completion of this bind() process does not ready the SCTP The completion of this bind() process does not ready the SCTP
endpoint to accept inbound SCTP association requests. Until a endpoint to accept inbound SCTP association requests. Until a
listen() system call, described below, is performed on the socket, listen() system call, described below, is performed on the socket,
the SCTP endpoint will promptly reject an inbound SCTP INIT request the SCTP endpoint will promptly reject an inbound SCTP INIT request
with an SCTP ABORT. with an SCTP ABORT.
5.1.3. listen() - one-to-one style socket 5.1.3. listen()
Applications use listen() to ready the SCTP endpoint for accepting Applications use listen() to ready the SCTP endpoint for accepting
inbound associations. inbound associations.
The syntax is: The function prototype is
int listen(int sd, int backlog); int listen(int sd,
int backlog);
and the arguments are
sd: the socket descriptor of the SCTP endpoint. sd: the socket descriptor of the SCTP endpoint.
backlog: this specifies the max number of outstanding associations backlog: this specifies the max number of outstanding associations
allowed in the socket's accept queue. These are the associations allowed in the socket's accept queue. These are the associations
that have finished the four-way initiation handshake (see Section that have finished the four-way initiation handshake (see Section
5 of [RFC4960]) and are in the ESTABLISHED state. Note, a backlog 5 of [RFC4960]) and are in the ESTABLISHED state. Note, a backlog
of '0' indicates that the caller no longer wishes to receive new of '0' indicates that the caller no longer wishes to receive new
associations. associations.
5.1.4. accept() - one-to-one style socket 5.1.4. accept()
Applications use accept() call to remove an established SCTP Applications use accept() call to remove an established SCTP
association from the accept queue of the endpoint. A new socket association from the accept queue of the endpoint. A new socket
descriptor will be returned from accept() to represent the newly descriptor will be returned from accept() to represent the newly
formed association. formed association.
The syntax is: The function prototype is
new_sd = accept(int sd, struct sockaddr *addr, socklen_t *addrlen);
new_sd - the socket descriptor for the newly formed association. int accept(int sd,
struct sockaddr *addr,
socklen_t *addrlen);
sd - the listening socket descriptor. and the arguments are
addr - on return, will contain the primary address of the peer sd: The listening socket descriptor.
addr: On return, will contain the primary address of the peer
endpoint. endpoint.
addrlen - on return, will contain the size of addr. addrlen: On return, will contain the size of addr.
The functions returns the socket descriptor for the newly formed
association.
5.1.5. connect() - one-to-one style socket 5.1.5. connect()
Applications use connect() to initiate an association to a peer. Applications use connect() to initiate an association to a peer.
The syntax is: The function prototype is
int connect(int sd, const struct sockaddr *addr, socklen_t addrlen); int connect(int sd,
const struct sockaddr *addr,
socklen_t addrlen);
sd - the socket descriptor of the endpoint. and the arguments are
addr - the peer's address. sd: The socket descriptor of the endpoint.
addrlen - the size of the address. addr: The peer's address.
addrlen: The size of the address.
This operation corresponds to the ASSOCIATE primitive described in This operation corresponds to the ASSOCIATE primitive described in
section 10.1 of [RFC4960]. section 10.1 of [RFC4960].
By default, the new association created has only one outbound stream. By default, the new association created has only one outbound stream.
The SCTP_INITMSG option described in Section 8.1.3 should be used The SCTP_INITMSG option described in Section 8.1.3 should be used
before connecting to change the number of outbound streams. before connecting to change the number of outbound streams.
If a bind() is not called prior to the connect() call, the system If a bind() is not called prior to the connect() call, the system
picks an ephemeral port and will choose an address set equivalent to picks an ephemeral port and will choose an address set equivalent to
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Note that SCTP allows data exchange, similar to T/TCP [RFC1644], Note that SCTP allows data exchange, similar to T/TCP [RFC1644],
during the association set up phase. If an application wants to do during the association set up phase. If an application wants to do
this, it cannot use connect() call. Instead, it should use sendto() this, it cannot use connect() call. Instead, it should use sendto()
or sendmsg() to initiate an association. If it uses sendto() and it or sendmsg() to initiate an association. If it uses sendto() and it
wants to change initialization behavior, it needs to use the wants to change initialization behavior, it needs to use the
SCTP_INITMSG socket option before calling sendto(). Or it can use SCTP_INITMSG socket option before calling sendto(). Or it can use
SCTP_INIT type sendmsg() to initiate an association without doing the SCTP_INIT type sendmsg() to initiate an association without doing the
setsockopt(). Note that some sockets implementations may not support setsockopt(). Note that some sockets implementations may not support
the sending of data to initiate an association with the one-to-one the sending of data to initiate an association with the one-to-one
style (implementations that do not support T/TCP normally have this style (implementations that do not support T/TCP normally have this
restriction). Implementations which allow sending of data to restriction).
initiate an association without calling connect() define the
preprocessor constant HAVE_SCTP_NOCONNECT to 1.
SCTP does not support half close semantics. This means that unlike SCTP does not support half close semantics. This means that unlike
T/TCP, MSG_EOF should not be set in the flags parameter when calling T/TCP, MSG_EOF should not be set in the flags parameter when calling
sendto() or sendmsg() when the call is used to initiate a connection. sendto() or sendmsg() when the call is used to initiate a connection.
MSG_EOF is not an acceptable flag with SCTP socket. MSG_EOF is not an acceptable flag with SCTP socket.
5.1.6. close() - one-to-one style socket 5.1.6. close()
Applications use close() to gracefully close down an association. Applications use close() to gracefully close down an association.
The syntax is: The function prototype is
int close(int sd); int close(int sd);
sd - the socket descriptor of the association to be closed. and the argument is
sd: The socket descriptor of the associations to be closed.
After an application calls close() on a socket descriptor, no further After an application calls close() on a socket descriptor, no further
socket operations will succeed on that descriptor. socket operations will succeed on that descriptor.
5.1.7. shutdown() - one-to-one style socket 5.1.7. shutdown()
SCTP differs from TCP in that it does not have half closed semantics. SCTP differs from TCP in that it does not have half closed semantics.
Hence the shutdown() call for SCTP is an approximation of the TCP Hence the shutdown() call for SCTP is an approximation of the TCP
shutdown() call, and solves some different problems. Full TCP- shutdown() call, and solves some different problems. Full TCP-
compatibility is not provided, so developers porting TCP applications compatibility is not provided, so developers porting TCP applications
to SCTP may need to recode sections that use shutdown(). (Note that to SCTP may need to recode sections that use shutdown(). (Note that
it is possible to achieve the same results as half close in SCTP it is possible to achieve the same results as half close in SCTP
using SCTP streams.) using SCTP streams.)
The syntax is: The function prototype is
int shutdown(int sd, int how); int shutdown(int sd,
int how);
sd - the socket descriptor of the association to be closed. and the arguments are
how - Specifies the type of shutdown. The values are as follows: sd: The socket descriptor of the association to be closed.
SHUT_RD - Disables further receive operations. No SCTP protocol how: Specifies the type of shutdown. The values are as follows:
SHUT_RD: Disables further receive operations. No SCTP protocol
action is taken. action is taken.
SHUT_WR - Disables further send operations, and initiates the SHUT_WR: Disables further send operations, and initiates the SCTP
SCTP shutdown sequence. shutdown sequence.
SHUT_RDWR - Disables further send and receive operations and SHUT_RDWR: Disables further send and receive operations and
initiates the SCTP shutdown sequence. initiates the SCTP shutdown sequence.
The major difference between SCTP and TCP shutdown() is that SCTP The major difference between SCTP and TCP shutdown() is that SCTP
SHUT_WR initiates immediate and full protocol shutdown, whereas TCP SHUT_WR initiates immediate and full protocol shutdown, whereas TCP
SHUT_WR causes TCP to go into the half closed state. SHUT_RD behaves SHUT_WR causes TCP to go into the half closed state. SHUT_RD behaves
the same for SCTP as TCP. The purpose of SCTP SHUT_WR is to close the same for SCTP as TCP. The purpose of SCTP SHUT_WR is to close
the SCTP association while still leaving the socket descriptor open, the SCTP association while still leaving the socket descriptor open,
so that the caller can receive back any data SCTP was unable to so that the caller can receive back any data SCTP was unable to
deliver (see Section 6.3.1.4 for more information). deliver (see Section 6.3.5 for more information).
To perform the ABORT operation described in [RFC4960] section 10.1, To perform the ABORT operation described in [RFC4960] section 10.1,
an application can use the socket option SO_LINGER. It is described an application can use the socket option SO_LINGER. It is described
in Section 8.1.4. in Section 8.1.4.
5.1.8. sendmsg() and recvmsg() - one-to-one style socket 5.1.8. sendmsg() and recvmsg()
With a one-to-one style socket, the application can also use With a one-to-one style socket, the application can also use
sendmsg() and recvmsg() to transmit data to and receive data from its sendmsg() and recvmsg() to transmit data to and receive data from its
peer. The semantics is similar to those used in the one-to-many peer. The semantics is similar to those used in the one-to-many
style (section Section 4.1.3), with the following differences: style (section Section 4.1.3), with the following differences:
1. When sending, the msg_name field in the msghdr is not used to 1. When sending, the msg_name field in the msghdr is not used to
specify the intended receiver, rather it is used to indicate a specify the intended receiver, rather it is used to indicate a
preferred peer address if the sender wishes to discourage the preferred peer address if the sender wishes to discourage the
stack from sending the message to the primary address of the stack from sending the message to the primary address of the
receiver. If the socket is connected and the transport address receiver. If the socket is connected and the transport address
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implicit connection setup may or may not work depending on the implicit connection setup may or may not work depending on the
SCTP implementation. SCTP implementation.
5.1.9. getpeername() 5.1.9. getpeername()
Applications use getpeername() to retrieve the primary socket address Applications use getpeername() to retrieve the primary socket address
of the peer. This call is for TCP compatibility, and is not multi- of the peer. This call is for TCP compatibility, and is not multi-
homed. It does not work with one-to-many style sockets. See homed. It does not work with one-to-many style sockets. See
Section 9.3 for a multi-homed/one-to-many style version of the call. Section 9.3 for a multi-homed/one-to-many style version of the call.
The syntax is: The function prototype is
int getpeername(int sd, struct sockaddr *address, int getpeername(int sd,
struct sockaddr *address,
socklen_t *len); socklen_t *len);
sd - the socket descriptor to be queried. and the arguments are:
address - On return, the peer primary address is stored in this sd: The socket descriptor to be queried.
address: On return, the peer primary address is stored in this
buffer. If the socket is an IPv4 socket, the address will be buffer. If the socket is an IPv4 socket, the address will be
IPv4. If the socket is an IPv6 socket, the address will be either IPv4. If the socket is an IPv6 socket, the address will be either
an IPv6 or IPv4 address. an IPv6 or IPv4 address.
len - The caller should set the length of address here. On return,
len: The caller should set the length of address here. On return,
this is set to the length of the returned address. this is set to the length of the returned address.
If the actual length of the address is greater than the length of the If the actual length of the address is greater than the length of the
supplied sockaddr structure, the stored address will be truncated. supplied sockaddr structure, the stored address will be truncated.
6. Data Structures 6. Data Structures
We discuss in this section important data structures which are We discuss in this section important data structures which are
specific to SCTP and are used with sendmsg() and recvmsg() calls to specific to SCTP and are used with sendmsg() and recvmsg() calls to
control SCTP endpoint operations and to access ancillary information control SCTP endpoint operations and to access ancillary information
skipping to change at page 22, line 31 skipping to change at page 22, line 41
struct msghdr { struct msghdr {
void *msg_name; /* ptr to socket address structure */ void *msg_name; /* ptr to socket address structure */
socklen_t msg_namelen; /* size of socket address structure */ socklen_t msg_namelen; /* size of socket address structure */
struct iovec *msg_iov; /* scatter/gather array */ struct iovec *msg_iov; /* scatter/gather array */
size_t msg_iovlen; /* # elements in msg_iov */ size_t msg_iovlen; /* # elements in msg_iov */
void *msg_control; /* ancillary data */ void *msg_control; /* ancillary data */
socklen_t msg_controllen; /* ancillary data buffer length */ socklen_t msg_controllen; /* ancillary data buffer length */
int msg_flags; /* flags on received message */ int msg_flags; /* flags on received message */
}; };
The cmsghdr structure: and the cmsghdr structure:
struct cmsghdr { struct cmsghdr {
socklen_t cmsg_len; /* #bytes, including this header */ socklen_t cmsg_len; /* #bytes, including this header */
int cmsg_level; /* originating protocol */ int cmsg_level; /* originating protocol */
int cmsg_type; /* protocol-specific type */ int cmsg_type; /* protocol-specific type */
/* followed by unsigned char cmsg_data[]; */ /* followed by unsigned char cmsg_data[]; */
}; };
In the msghdr structure, the usage of msg_name has been discussed in In the msghdr structure, the usage of msg_name has been discussed in
previous sections (see Section 4.1.3 and Section 5.1.8). previous sections (see Section 4.1.3 and Section 5.1.8).
skipping to change at page 23, line 31 skipping to change at page 23, line 41
There are two kinds of ancillary data used by SCTP: initialization There are two kinds of ancillary data used by SCTP: initialization
data, and, header information (SNDRCV). Initialization data (one-to- data, and, header information (SNDRCV). Initialization data (one-to-
many style only) sets protocol parameters for new associations. many style only) sets protocol parameters for new associations.
Section 6.2.1 provides more details. Header information can set or Section 6.2.1 provides more details. Header information can set or
report parameters on individual messages in a stream. See report parameters on individual messages in a stream. See
Section 6.2.2 for how to use SNDRCV ancillary data. Section 6.2.2 for how to use SNDRCV ancillary data.
By default on a one-to-one style socket, SCTP will pass no ancillary By default on a one-to-one style socket, SCTP will pass no ancillary
data; on a one-to-many style socket, SCTP will only pass SCTP_SNDRCV data; on a one-to-many style socket, SCTP will only pass SCTP_SNDRCV
and SCTP_ASSOC_CHANGE information. Specific ancillary data items can and SCTP_ASSOC_CHANGE information. Specific ancillary data items can
be enabled with socket options defined for SCTP; see Section 8.3. be enabled with socket options defined for SCTP; see Section 8.4.
Note that all ancillary types are fixed length; see Section 6.4 for Note that all ancillary types are fixed length; see Section 6.4 for
further discussion on this. These data structures use struct further discussion on this. These data structures use struct
sockaddr_storage (defined in [RFC3493]) as a portable, fixed length sockaddr_storage (defined in [RFC3493]) as a portable, fixed length
address format. address format.
Other protocols may also provide ancillary data to the socket layer Other protocols may also provide ancillary data to the socket layer
consumer. These ancillary data items from other protocols may consumer. These ancillary data items from other protocols may
intermingle with SCTP data. For example, the IPv6 socket API intermingle with SCTP data. For example, the IPv6 socket API
definitions ([RFC3542] and [RFC3493]) define a number of ancillary definitions ([RFC3542] and [RFC3493]) define a number of ancillary
skipping to change at page 24, line 26 skipping to change at page 24, line 34
Here is the definition of the sctp_initmsg structure: Here is the definition of the sctp_initmsg structure:
struct sctp_initmsg { struct sctp_initmsg {
uint16_t sinit_num_ostreams; uint16_t sinit_num_ostreams;
uint16_t sinit_max_instreams; uint16_t sinit_max_instreams;
uint16_t sinit_max_attempts; uint16_t sinit_max_attempts;
uint16_t sinit_max_init_timeo; uint16_t sinit_max_init_timeo;
}; };
sinit_num_ostreams: 16 bits (unsigned integer) sinit_num_ostreams: This is an integer number representing the
number of streams that the application wishes to be able to send
This is an integer number representing the number of streams that the to. This number is confirmed in the SCTP_COMM_UP notification and
application wishes to be able to send to. This number is confirmed must be verified since it is a negotiated number with the remote
in the SCTP_COMM_UP notification and must be verified since it is a endpoint. The default value of 0 indicates to use the endpoint
negotiated number with the remote endpoint. The default value of 0 default value.
indicates to use the endpoint default value. sinit_max_instreams: This value represents the maximum number of
inbound streams the application is prepared to support. This
sinit_max_instreams: 16 bits (unsigned integer) value is bounded by the actual implementation. In other words the
user MAY be able to support more streams than the Operating
This value represents the maximum number of inbound streams the System. In such a case, the Operating System limit overrides the
application is prepared to support. This value is bounded by the value requested by the user. The default value of 0 indicates to
actual implementation. In other words the user MAY be able to use the endpoints default value.
support more streams than the Operating System. In such a case, the sinit_max_attempts: This integer specifies how many attempts the
Operating System limit overrides the value requested by the user. SCTP endpoint should make at resending the INIT. This value
The default value of 0 indicates to use the endpoints default value. overrides the system SCTP 'Max.Init.Retransmits' value. The
default value of 0 indicates to use the endpoints default value.
sinit_max_attempts: 16 bits (unsigned integer) This is normally set to the system's default 'Max.Init.Retransmit'
value.
This integer specifies how many attempts the SCTP endpoint should sinit_max_init_timeo: This value represents the largest Time-Out or
make at resending the INIT. This value overrides the system SCTP RTO value (in milliseconds) to use in attempting an INIT.
'Max.Init.Retransmits' value. The default value of 0 indicates to Normally the 'RTO.Max' is used to limit the doubling of the RTO
use the endpoints default value. This is normally set to the upon timeout. For the INIT message this value MAY override
system's default 'Max.Init.Retransmit' value. 'RTO.Max'. This value MUST NOT influence 'RTO.Max' during data
transmission and is only used to bound the initial setup time. A
sinit_max_init_timeo: 16 bits (unsigned integer) default value of 0 indicates to use the endpoints default value.
This value represents the largest Time-Out or RTO value (in This is normally set to the system's 'RTO.Max' value (60 seconds).
milliseconds) to use in attempting an INIT. Normally the 'RTO.Max'
is used to limit the doubling of the RTO upon timeout. For the INIT
message this value MAY override 'RTO.Max'. This value MUST NOT
influence 'RTO.Max' during data transmission and is only used to
bound the initial setup time. A default value of 0 indicates to use
the endpoints default value. This is normally set to the system's
'RTO.Max' value (60 seconds).
6.2.2. SCTP Header Information Structure (SCTP_SNDRCV) 6.2.2. SCTP Header Information Structure (SCTP_SNDRCV)
This cmsghdr structure specifies SCTP options for sendmsg() and This cmsghdr structure specifies SCTP options for sendmsg() and
describes SCTP header information about a received message through describes SCTP header information about a received message through
recvmsg(). recvmsg().
+--------------+-------------+------------------------+ +--------------+-------------+------------------------+
| cmsg_level | cmsg_type | cmsg_data[] | | cmsg_level | cmsg_type | cmsg_data[] |
+--------------+-------------+------------------------+ +--------------+-------------+------------------------+
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uint16_t sinfo_flags; uint16_t sinfo_flags;
uint16_t sinfo_pr_policy; uint16_t sinfo_pr_policy;
uint32_t sinfo_ppid; uint32_t sinfo_ppid;
uint32_t sinfo_context; uint32_t sinfo_context;
uint32_t sinfo_pr_value; uint32_t sinfo_pr_value;
uint32_t sinfo_tsn; uint32_t sinfo_tsn;
uint32_t sinfo_cumtsn; uint32_t sinfo_cumtsn;
sctp_assoc_t sinfo_assoc_id; sctp_assoc_t sinfo_assoc_id;
}; };
sinfo_stream: 16 bits (unsigned integer) sinfo_stream: For recvmsg() the SCTP stack places the message's
stream number in this value. For sendmsg() this value holds the
For recvmsg() the SCTP stack places the message's stream number in stream number that the application wishes to send this message to.
this value. For sendmsg() this value holds the stream number that If a sender specifies an invalid stream number an error indication
the application wishes to send this message to. If a sender is returned and the call fails.
specifies an invalid stream number an error indication is returned sinfo_ssn: For recvmsg() this value contains the stream sequence
and the call fails. number that the remote endpoint placed in the DATA chunk. For
fragmented messages this is the same number for all deliveries of
sinfo_ssn: 16 bits (unsigned integer) the message (if more than one recvmsg() is needed to read the
message). The sendmsg() call will ignore this parameter.
For recvmsg() this value contains the stream sequence number that the
remote endpoint placed in the DATA chunk. For fragmented messages
this is the same number for all deliveries of the message (if more
than one recvmsg() is needed to read the message). The sendmsg()
call will ignore this parameter.
sinfo_ppid: 32 bits (unsigned integer)
This value in sendmsg() is an unsigned integer that is passed to the
remote end in each user message. In recvmsg() this value is the same
information that was passed by the upper layer in the peer
application. Please note that the SCTP stack performs no byte order
modification of this field. For example, if the DATA chunk has to
contain a given value in network byte order, the SCTP user has to
perform the htonl() computation.
sinfo_context: 32 bits (unsigned integer)
This value is an opaque 32 bit context datum that is used in the
sendmsg() function. This value is passed back to the upper layer if
a error occurs on the send of a message and is retrieved with each
undelivered message (Note: if a endpoint has done multiple sends, all
of which fail, multiple different sinfo_context values will be
returned. One with each user data message).
sinfo_flags: 16 bits (unsigned integer)
This field may contain any of the following flags and is composed of
a bitwise OR of these values.
sinfo_ppid: This value in sendmsg() is an unsigned integer that is
passed to the remote end in each user message. In recvmsg() this
value is the same information that was passed by the upper layer
in the peer application. Please note that the SCTP stack performs
no byte order modification of this field. For example, if the
DATA chunk has to contain a given value in network byte order, the
SCTP user has to perform the htonl() computation.
sinfo_context: This value is an opaque 32 bit context datum that is
used in the sendmsg() function. This value is passed back to the
upper layer if a error occurs on the send of a message and is
retrieved with each undelivered message (Note: if a endpoint has
done multiple sends, all of which fail, multiple different
sinfo_context values will be returned. One with each user data
message).
sinfo_flags: This field may contain any of the following flags and
is composed of a bitwise OR of these values.
recvmsg() flags: recvmsg() flags:
SCTP_UNORDERED - This flag is present when the message was sent non- SCTP_UNORDERED: This flag is present when the message was sent
ordered. non-ordered.
sendmsg() flags: sendmsg() flags:
SCTP_UNORDERED - This flag requests the un-ordered delivery of the SCTP_UNORDERED: This flag requests the un-ordered delivery of the
message. If this flag is clear the datagram is considered an message. If this flag is clear the datagram is considered an
ordered send. ordered send.
SCTP_ADDR_OVER: This flag, in the one-to-many style, requests the
SCTP_ADDR_OVER - This flag, in the one-to-many style, requests the
SCTP stack to override the primary destination address with the SCTP stack to override the primary destination address with the
address found with the sendto/sendmsg call. address found with the sendto/sendmsg call.
SCTP_ABORT: Setting this flag causes the specified association to
SCTP_ABORT - Setting this flag causes the specified association to abort by sending an ABORT message to the peer (one-to-many
abort by sending an ABORT message to the peer (one-to-many style style only). The ABORT chunk will contain an error cause 'User
only). The ABORT chunk will contain an error cause 'User
Initiated Abort' with cause code 12. The cause specific Initiated Abort' with cause code 12. The cause specific
information of this error cause is provided in msg_iov. information of this error cause is provided in msg_iov.
SCTP_EOF Setting this flag invokes the SCTP graceful shutdown
SCTP_EOF - Setting this flag invokes the SCTP graceful shutdown
procedures on the specified association. Graceful shutdown procedures on the specified association. Graceful shutdown
assures that all data enqueued by both endpoints is successfully assures that all data queued by both endpoints is successfully
transmitted before closing the association (one-to-many style transmitted before closing the association (one-to-many style
only). only).
SCTP_SENDALL: This flag, if set, will cause a one-to-many model
socket to send the message to all associations that are
currently established on this socket. For the one-to-one
socket, this flag has no effect.
sinfo_pr_policy: For the sending side, this specifies which PR-SCTP
policy is used. Using SCTP_PR_SCTP_NONE results in a reliable
transmission. When SCTP_PR_SCTP_TTL is used, the PR-SCTP policy
"timed reliability" defined in [RFC3758] is used. In this case,
the lifetime is provided in sinfo_pr_value.
SCTP_SENDALL - This flag, if set, will cause a one-to-many model sinfo_pr_value: The meaning of this field depends of the PR-SCTP
socket to send the message to all associations that are currently policy specified by the sinfo_pr_policy field. It is ignored when
established on this socket. For the one-to-one socket, this flag SCTP_PR_SCTP_NONE is specified. In case of SCTP_PR_SCTP_TTL the
has no effect. lifetime is specified.
sinfo_tsn: For the receiving side, this field holds a TSN that was
sinfo_pr_policy: 16 bits (unsigned integer) assigned to one of the SCTP Data Chunks.
sinfo_cumtsn: This field will hold the current cumulative TSN as
For the sending side, this specifies which PR-SCTP policy is used. known by the underlying SCTP layer. Note this field is ignored
Using SCTP_PR_SCTP_NONE results in a reliable transmission. When when sending and only valid for a receive operation when
SCTP_PR_SCTP_TTL is used, the PR-SCTP policy "timed reliabilility" sinfo_flags are set to SCTP_UNORDERED.
defined in [RFC3758] is used. In this case, the lifetime is provided sinfo_assoc_id: The association handle field, sinfo_assoc_id, holds
in sinfo_pr_value. the identifier for the association announced in the SCTP_COMM_UP
notification. All notifications for a given association have the
sinfo_pr_value: 32 bit (unsigned integer) same identifier. Ignored for one-to-one style sockets.
The meaning of this field depends of the PR-SCTP policy specified by
the sinfo_pr_policy field. It is ignored when SCTP_PR_SCTP_NONE is
specified. In case of SCTP_PR_SCTP_TTL the lifetime is specified.
sinfo_tsn: 32 bit (unsigned integer)
For the receiving side, this field holds a TSN that was assigned to
one of the SCTP Data Chunks.
sinfo_cumtsn: 32 bit (unsigned integer)
This field will hold the current cumulative TSN as known by the
underlying SCTP layer. Note this field is ignored when sending and
only valid for a receive operation when sinfo_flags are set to
SCTP_UNORDERED.
sinfo_assoc_id: sizeof (sctp_assoc_t)
The association handle field, sinfo_assoc_id, holds the identifier
for the association announced in the SCTP_COMM_UP notification. All
notifications for a given association have the same identifier.
Ignored for one-to-one style sockets.
A sctp_sndrcvinfo item always corresponds to the data in msg_iov. A sctp_sndrcvinfo item always corresponds to the data in msg_iov.
6.2.3. Extended SCTP Header Information Structure (SCTP_EXTRCV) 6.2.3. Extended SCTP Header Information Structure (SCTP_EXTRCV)
This cmsghdr structure specifies SCTP options for SCTP header This cmsghdr structure specifies SCTP options for SCTP header
information about a received message via recvmsg(). Note that this information about a received message via recvmsg(). Note that this
structure is an extended version of SCTP_SNDRCV (see Section 6.2.2) structure is an extended version of SCTP_SNDRCV (see Section 6.2.2)
and will only be received if the user has set the socket option and will only be received if the user has set the socket option
SCTP_USE_EXT_RCVINFO to true in addition to any event subscription SCTP_USE_EXT_RCVINFO to true in addition to any event subscription
skipping to change at page 28, line 33 skipping to change at page 28, line 4
Here is the definition of sctp_extrcvinfo structure: Here is the definition of sctp_extrcvinfo structure:
struct sctp_extrcvinfo { struct sctp_extrcvinfo {
struct sctp_sndrcvinfo serinfo_sinfo; struct sctp_sndrcvinfo serinfo_sinfo;
uint16_t serinfo_next_flags; uint16_t serinfo_next_flags;
uint16_t serinfo_next_stream; uint16_t serinfo_next_stream;
uint32_t serinfo_next_aid; uint32_t serinfo_next_aid;
uint32_t serinfo_next_length; uint32_t serinfo_next_length;
uint32_t serinfo_next_ppid; uint32_t serinfo_next_ppid;
}; };
serinfo_sinfo: Please see Section 6.2.2 for the details for this
serinfo_sinfo: structure structure.
serinfo_next_flags: This bitmask will hold one or more of the
Please see Section 6.2.2 for the details for this structure. following values:
SCTP_NEXT_MSG_AVAIL: This bit, when set to 1, indicates that next
serinfo_next_flags: 16 bit (unsigned integer) message information is available i.e.: next_stream,
next_asocid, next_length and next_ppid fields all have valid
This bitmask will hold one or more of the following values: values. If this bit is set to 0, then these fields are not
SCTP_NEXT_MSG_AVAIL - This bit, when set to 1, indicates that next valid and should be ignored.
message information is available i.e.: next_stream, next_asocid, SCTP_NEXT_MSG_ISCOMPLETE: This bit, when set, indicates that the
next_length and next_ppid fields all have valid values. If this next message is completely in the receive buffer. The
bit is set to 0, then these fields are not valid and should be next_length field thus contains the entire message size. If
ignored. this flag is set to 0, then the next_length field only contains
part of the message size since the message is still being
SCTP_NEXT_MSG_ISCOMPLETE - This bit, when set, indicates that the received (it is being partially delivered).
next message is completely in the receive buffer. The next_length SCTP_NEXT_MSG_IS_UNORDERED: This bit, when set, indicates that
field thus contains the entire message size. If this flag is set the next message to be received was sent by the peer as
to 0, then the next_length field only contains part of the message unordered. If this bit is not set (i.e the bit is 0) the next
size since the message is still being received (it is being message to be read is an ordered message in the stream
partially delivered). specified.
SCTP_NEXT_MSG_IS_NOTIFICATION: This bit, when set, indicates that
SCTP_NEXT_MSG_IS_UNORDERED - This bit, when set, indicates that the
next message to be received was sent by the peer as unordered. If
this bit is not set (i.e the bit is 0) the next message to be read
is an ordered message in the stream specified.
SCTP_NEXT_MSG_IS_NOTIFICATION - This bit, when set, indicates that
the next message to be received is not a message from the peer, the next message to be received is not a message from the peer,
but instead is a MSG_NOTIFICATION from the local SCTP stack. but instead is a MSG_NOTIFICATION from the local SCTP stack.
serinfo_next_stream This value, when valid (see sreinfo_next_flags),
serinfo_next_stream: 16 bit (unsigned integer) contains the next stream number that will be received on a
subsequent call to one of the receive message functions.
This value, when valid (see sreinfo_next_flags), contains the next serinfo_next_aid: This value, when valid (see next_flags), contains
stream number that will be received on a subsequent call to one of the next association identification that will be received on a
the receive message functions. subsequent call to one of the receive message functions.
sreinfo_next_length: This value, when valid (see
serinfo_next_aid: 32 bit (unsigned integer) sreinfo_next_flags), contains the length of the next message that
will be received on a subsequent call to one of the receive
This value, when valid (see next_flags), contains the next message functions. Note that this length may be a partial length
association identification that will be received on a subsequent call depending on the settings of next_flags.
to one of the receive message functions. sreinfo_next_ppid: This value, when valid (see sreinfo_next_flags),
contains the ppid of the next message that will be received on a
sreinfo_next_length: 32 bit (unsigned integer) subsequent call to one of the receive message functions.
This value, when valid (see sreinfo_next_flags), contains the length
of the next message that will be received on a subsequent call to one
of the receive message functions. Note that this length may be a
partial length depending on the settings of next_flags.
sreinfo_next_ppid: 32 bit (unsigned integer)
This value, when valid (see sreinfo_next_flags), contains the ppid of
the next message that will be received on a subsequent call to one of
the receive message functions.
6.3. SCTP Events and Notifications 6.3. SCTP Events and Notifications
An SCTP application may need to understand and process events and An SCTP application may need to understand and process events and
errors that happen on the SCTP stack. These events include network errors that happen on the SCTP stack. These events include network
status changes, association startups, remote operational errors and status changes, association startups, remote operational errors and
undeliverable messages. All of these can be essential for the undeliverable messages. All of these can be essential for the
application. application.
When an SCTP application layer does a recvmsg() the message read is When an SCTP application layer does a recvmsg() the message read is
normally a data message from a peer endpoint. If the application normally a data message from a peer endpoint. If the application
wishes to have the SCTP stack deliver notifications of non-data wishes to have the SCTP stack deliver notifications of non-data
events, it sets the appropriate socket option for the notifications events, it sets the appropriate socket option for the notifications
it wants. See Section 8.3 for these socket options. When a it wants. See Section 8.4 for these socket options. When a
notification arrives, recvmsg() returns the notification in the notification arrives, recvmsg() returns the notification in the
application-supplied data buffer via msg_iov, and sets application-supplied data buffer via msg_iov, and sets
MSG_NOTIFICATION in msg_flags. MSG_NOTIFICATION in msg_flags.
This section details the notification structures. Every notification This section details the notification structures. Every notification
structure carries some common fields which provides general structure carries some common fields which provides general
information. information.
A recvmsg() call will return only one notification at a time. Just A recvmsg() call will return only one notification at a time. Just
as when reading normal data, it may return part of a notification if as when reading normal data, it may return part of a notification if
skipping to change at page 30, line 37 skipping to change at page 29, line 40
uint32_t sn_length; uint32_t sn_length;
} sn_header; } sn_header;
struct sctp_assoc_change sn_assoc_change; struct sctp_assoc_change sn_assoc_change;
struct sctp_paddr_change sn_paddr_change; struct sctp_paddr_change sn_paddr_change;
struct sctp_remote_error sn_remote_error; struct sctp_remote_error sn_remote_error;
struct sctp_send_failed sn_send_failed; struct sctp_send_failed sn_send_failed;
struct sctp_shutdown_event sn_shutdown_event; struct sctp_shutdown_event sn_shutdown_event;
struct sctp_adaptation_event sn_adaptation_event; struct sctp_adaptation_event sn_adaptation_event;
struct sctp_pdapi_event sn_pdapi_event; struct sctp_pdapi_event sn_pdapi_event;
struct sctp_authkey_event sn_auth_event; struct sctp_authkey_event sn_auth_event;
struct sctp_no_auth_event sn_no_auth_event; struct sctp_sender_dry_event sn_sender_dry_event;
}; };
sn_type: 16 bits (unsigned integer) sn_type: The following list describes the SCTP notification and
event types for the field sn_type.
The following list describes the SCTP notification and event types SCTP_ASSOC_CHANGE: This tag indicates that an association has
for the field sn_type. either been opened or closed. Refer to Section 6.3.2 for
details.
SCTP_ASSOC_CHANGE: This tag indicates that an association has either
been opened or closed. Refer to Section 6.3.1.1 for details.
SCTP_PEER_ADDR_CHANGE: This tag indicates that an address that is SCTP_PEER_ADDR_CHANGE: This tag indicates that an address that is
part of an existing association has experienced a change of state part of an existing association has experienced a change of
(e.g. a failure or return to service of the reachability of a state (e.g. a failure or return to service of the reachability
endpoint via a specific transport address). Please see of a endpoint via a specific transport address). Please see
Section 6.3.1.2 for data structure details. Section 6.3.3 for data structure details.
SCTP_REMOTE_ERROR: The attached error message is an Operational SCTP_REMOTE_ERROR: The attached error message is an Operational
Error received from the remote peer. It includes the complete TLV Error received from the remote peer. It includes the complete
sent by the remote endpoint. See Section 6.3.1.3 for the detailed TLV sent by the remote endpoint. See Section 6.3.4 for the
format. detailed format.
SCTP_SEND_FAILED: The attached datagram could not be sent to the SCTP_SEND_FAILED: The attached datagram could not be sent to the
remote endpoint. This structure includes the original remote endpoint. This structure includes the original
SCTP_SNDRCVINFO that was used in sending this message i.e. this SCTP_SNDRCVINFO that was used in sending this message i.e. this
structure uses the sctp_sndrecvinfo per Section 6.3.1.4. structure uses the sctp_sndrecvinfo per Section 6.3.5.
SCTP_SHUTDOWN_EVENT: The peer has sent a SHUTDOWN. No further data SCTP_SHUTDOWN_EVENT: The peer has sent a SHUTDOWN. No further
should be sent on this socket. data should be sent on this socket.
SCTP_ADAPTATION_INDICATION: This notification holds the peers SCTP_ADAPTATION_INDICATION: This notification holds the peers
indicated adaptation layer. Please see Section 6.3.1.6. indicated adaptation layer. Please see Section 6.3.7.
SCTP_PARTIAL_DELIVERY_EVENT: This notification is used to tell a SCTP_PARTIAL_DELIVERY_EVENT: This notification is used to tell a
receiver that the partial delivery has been aborted. This may receiver that the partial delivery has been aborted. This may
indicate the association is about to be aborted. Please see indicate the association is about to be aborted. Please see
Section 6.3.1.7 Section 6.3.8
SCTP_AUTHENTICATION_EVENT: This notification is used to tell a SCTP_AUTHENTICATION_EVENT: This notification is used to tell a
receiver that either an error occurred on authentication, or a new receiver that either an error occurred on authentication, or a
key was made active. Section 6.3.1.8 new key was made active. Section 6.3.9
SCTP_NO_AUTHENTICATION_EVENT: This notification is used to tell a
receiver that the peer does not support SCTP-AUTH.
Section 6.3.1.9
SCTP_AUTHENTICATION_KEY_FREE_EVENT: This notification is used to
tell a receiver that a key is not used anymore for sending.
Section 6.3.1.11
SCTP_SENDER_DRY_EVENT: This notification is used to inform the SCTP_SENDER_DRY_EVENT: This notification is used to inform the
application that the sender has no user data queued anymore, application that the sender has no user data queued anymore,
neither for transmission or retransmission. Section 6.3.1.10 neither for transmission or retransmission. Section 6.3.10
All standard values for sn_type are greater than 2^15. Values
All standard values for sn_type are greater than 2^15. Values from from 2^15 and down are reserved.
2^15 and down are reserved. sn_flags: These are notification-specific flags.
sn_length: This is the length of the whole sctp_notification
sn_flags: 16 bits (unsigned integer) structure including the sn_type, sn_flags, and sn_length fields.
These are notification-specific flags.
sn_length: 32 bits (unsigned integer)
This is the length of the whole sctp_notification structure including
the sn_type, sn_flags, and sn_length fields.
6.3.1.1. SCTP_ASSOC_CHANGE 6.3.2. SCTP_ASSOC_CHANGE
Communication notifications inform the ULP that an SCTP association Communication notifications inform the ULP that an SCTP association
has either begun or ended. The identifier for a new association is has either begun or ended. The identifier for a new association is
provided by this notification. The notification information has the provided by this notification. The notification information has the
following format: following format:
struct sctp_assoc_change { struct sctp_assoc_change {
uint16_t sac_type; uint16_t sac_type;
uint16_t sac_flags; uint16_t sac_flags;
uint32_t sac_length; uint32_t sac_length;
uint16_t sac_state; uint16_t sac_state;
uint16_t sac_error; uint16_t sac_error;
uint16_t sac_outbound_streams; uint16_t sac_outbound_streams;
uint16_t sac_inbound_streams; uint16_t sac_inbound_streams;
sctp_assoc_t sac_assoc_id; sctp_assoc_t sac_assoc_id;
uint8_t sac_info[]; uint8_t sac_info[];
}; };
sac_type: sac_type: It should be SCTP_ASSOC_CHANGE.
sac_flags: Currently unused.
It should be SCTP_ASSOC_CHANGE. sac_length: This field is the total length of the notification data,
including the notification header.
sac_flags: 16 bits (unsigned integer) sac_state: This field holds one of a number of values that
communicate the event that happened to the association. They
Currently unused. include:
SCTP_COMM_UP: A new association is now ready and data may be
sac_length: 32 bits (unsigned integer) exchanged with this peer. When an association has been
established successfully, this notification should be the first
This field is the total length of the notification data, including one.
the notification header. SCTP_COMM_LOST: The association has failed. The association is
now in the closed state. If SEND FAILED notifications are
sac_state: 16 bits (signed integer) turned on, a SCTP_COMM_LOST is followed by a series of
SCTP_SEND_FAILED events, one for each outstanding message.
This field holds one of a number of values that communicate the event SCTP_RESTART: SCTP has detected that the peer has restarted.
that happened to the association. They include: SCTP_SHUTDOWN_COMP: The association has gracefully closed.
Event Name Description
---------------- ---------------
SCTP_COMM_UP - A new association is now ready and data may be
exchanged with this peer.
SCTP_COMM_LOST - The association has failed. The association is now
in the closed state. If SEND FAILED notifications are turned on,
a SCTP_COMM_LOST is followed by a series of SCTP_SEND_FAILED
events, one for each outstanding message.
SCTP_RESTART - SCTP has detected that the peer has restarted.
SCTP_SHUTDOWN_COMP - The association has gracefully closed.
SCTP_CANT_STR_ASSOC - The association failed to setup. If non SCTP_CANT_STR_ASSOC - The association failed to setup. If non
blocking mode is set and data was sent (in the udp mode), a blocking mode is set and data was sent (in the udp mode), a
SCTP_CANT_STR_ASSOC is followed by a series of SCTP_SEND_FAILED SCTP_CANT_STR_ASSOC is followed by a series of SCTP_SEND_FAILED
events, one for each outstanding message. events, one for each outstanding message.
sac_error: If the state was reached due to a error condition (e.g.
SCTP_COMM_LOST) any relevant error information is available in
this field. This corresponds to the protocol error codes defined
in [RFC4960].
sac_outbound_streams:
sac_inbound_streams: The maximum number of streams allowed in each
direction are available in sac_outbound_streams and sac_inbound
streams.
sac_assoc_id: The association id field, holds the identifier for the
association. All notifications for a given association have the
same association identifier. For one-to-one style socket, this
field is ignored.
sac_error: 16 bits (signed integer) sac_info: If the sac_state is SCTP_COMM_LOST and an ABORT chunk was
If the state was reached due to a error condition (e.g. received for this association, sac_info[] contains the complete
SCTP_COMM_LOST) any relevant error information is available in this ABORT chunk as defined in the SCTP specification [RFC4960] section
field. This corresponds to the protocol error codes defined in 3.3.7. If the sac_state is SCTP_COMM_UP or SCTP_RESTART, sac_info
[RFC4960]. may contain an array of features that the current association
supports. Features include
sac_outbound_streams: 16 bits (unsigned integer) SCTP_PR: The both endpoints support the protocol extension
described in [RFC3758].
sac_inbound_streams: 16 bits (unsigned integer) SCTP_AUTH: The both endpoints support the protocol extension
described in [RFC4895].
The maximum number of streams allowed in each direction are available SCTP_ASCONF: The both endpoints support the protocol extension
in sac_outbound_streams and sac_inbound streams. described in [RFC5061].
sac_assoc_id: sizeof (sctp_assoc_t)
The association id field, holds the identifier for the association.
All notifications for a given association have the same association
identifier. For one-to-one style socket, this field is ignored.
sac_info: variable
If the sac_state is SCTP_COMM_LOST and an ABORT chunk was received
for this association, sac_info[] contains the complete ABORT chunk as
defined in the SCTP specification [RFC4960] section 3.3.7.
6.3.1.2. SCTP_PEER_ADDR_CHANGE 6.3.3. SCTP_PEER_ADDR_CHANGE
When a destination address on a multi-homed peer encounters a change When a destination address on a multi-homed peer encounters a change
an interface details event is sent. The information has the an interface details event is sent. The information has the
following structure: following structure:
struct sctp_paddr_change { struct sctp_paddr_change {
uint16_t spc_type; uint16_t spc_type;
uint16_t spc_flags; uint16_t spc_flags;
uint32_t spc_length; uint32_t spc_length;
struct sockaddr_storage spc_aaddr; struct sockaddr_storage spc_aaddr;
uint32_t spc_state; uint32_t spc_state;
uint32_t spc_error; uint32_t spc_error;
sctp_assoc_t spc_assoc_id; sctp_assoc_t spc_assoc_id;
} }
spc_type: spc_type: It should be SCTP_PEER_ADDR_CHANGE.
spc_flags: Currently unused.
It should be SCTP_PEER_ADDR_CHANGE. spc_length: This field is the total length of the notification data,
including the notification header.
spc_flags: 16 bits (unsigned integer) spc_aaddr: The affected address field, holds the remote peer's
address that is encountering the change of state.
Currently unused. spc_state: This field holds one of a number of values that
communicate the event that happened to the address. They include:
spc_length: 32 bits (unsigned integer) SCTP_ADDR_AVAILABLE: This address is now reachable.
SCTP_ADDR_UNREACHABLE: The address specified can no longer be
This field is the total length of the notification data, including
the notification header.
spc_aaddr: sizeof (struct sockaddr_storage)
The affected address field, holds the remote peer's address that is
encountering the change of state.
spc_state: 32 bits (signed integer)
This field holds one of a number of values that communicate the event
that happened to the address. They include:
Event Name Description
---------------- ---------------
SCTP_ADDR_AVAILABLE - This address is now reachable.
SCTP_ADDR_UNREACHABLE - The address specified can no longer be
reached. Any data sent to this address is rerouted to an reached. Any data sent to this address is rerouted to an
alternate until this address becomes reachable. alternate until this address becomes reachable.
SCTP_ADDR_REMOVED - The address is no longer part of the SCTP_ADDR_REMOVED: The address is no longer part of the
association. association.
SCTP_ADDR_ADDED - The address is now part of the association. SCTP_ADDR_ADDED: The address is now part of the association.
SCTP_ADDR_MADE_PRIM - This address has now been made to be the
primary destination address.
SCTP_ADDR_CONFIRMED - This address has now been confirmed as a valid
address.
spc_error: 32 bits (signed integer)
If the state was reached due to any error condition (e.g.
SCTP_ADDR_UNREACHABLE) any relevant error information is available in
this field.
spc_assoc_id: sizeof (sctp_assoc_t)
The association id field, holds the identifier for the association. SCTP_ADDR_MADE_PRIM: This address has now been made to be the
All notifications for a given association have the same association primary destination address.
identifier. For one-to-one style socket, this field is ignored. SCTP_ADDR_CONFIRMED: This address has now been confirmed as a
valid address.
spc_error: If the state was reached due to any error condition (e.g.
SCTP_ADDR_UNREACHABLE) any relevant error information is available
in this field.
spc_assoc_id: The association id field, holds the identifier for the
association. All notifications for a given association have the
same association identifier. For one-to-one style socket, this
field is ignored.
6.3.1.3. SCTP_REMOTE_ERROR 6.3.4. SCTP_REMOTE_ERROR
A remote peer may send an Operational Error message to its peer. A remote peer may send an Operational Error message to its peer.
This message indicates a variety of error conditions on an This message indicates a variety of error conditions on an
association. The entire ERROR chunk as it appears on the wire is association. The entire ERROR chunk as it appears on the wire is
included in a SCTP_REMOTE_ERROR event. Please refer to the SCTP included in a SCTP_REMOTE_ERROR event. Please refer to the SCTP
specification [RFC4960] and any extensions for a list of possible specification [RFC4960] and any extensions for a list of possible
error formats. SCTP error notifications have the format: error formats. SCTP error notifications have the format:
struct sctp_remote_error { struct sctp_remote_error {
uint16_t sre_type; uint16_t sre_type;
uint16_t sre_flags; uint16_t sre_flags;
uint32_t sre_length; uint32_t sre_length;
uint16_t sre_error; uint16_t sre_error;
sctp_assoc_t sre_assoc_id; sctp_assoc_t sre_assoc_id;
uint8_t sre_data[]; uint8_t sre_data[];
}; };
sre_type: sre_type: It should be SCTP_REMOTE_ERROR.
sre_flags: Currently unused.
It should be SCTP_REMOTE_ERROR. sre_length: This field is the total length of the notification data,
including the notification header and the contents of sre_data.
sre_flags: 16 bits (unsigned integer) sre_error: This value represents one of the Operational Error causes
defined in the SCTP specification, in network byte order.
Currently unused. sre_assoc_id: The association id field, holds the identifier for the
association. All notifications for a given association have the
sre_length: 32 bits (unsigned integer) same association identifier. For one-to-one style socket, this
field is ignored.
This field is the total length of the notification data, including sre_data: This contains the ERROR chunk as defined in the SCTP
the notification header and the contents of sre_data. specification [RFC4960] section 3.3.10.
sre_error: 16 bits (unsigned integer)
This value represents one of the Operational Error causes defined in
the SCTP specification, in network byte order.
sre_assoc_id: sizeof (sctp_assoc_t)
The association id field, holds the identifier for the association.
All notifications for a given association have the same association
identifier. For one-to-one style socket, this field is ignored.
sre_data: variable
This contains the ERROR chunk as defined in the SCTP specification
[RFC4960] section 3.3.10.
6.3.1.4. SCTP_SEND_FAILED 6.3.5. SCTP_SEND_FAILED
If SCTP cannot deliver a message it may return the message as a If SCTP cannot deliver a message it may return the message as a
notification. notification.
struct sctp_send_failed { struct sctp_send_failed {
uint16_t ssf_type; uint16_t ssf_type;
uint16_t ssf_flags; uint16_t ssf_flags;
uint32_t ssf_length; uint32_t ssf_length;
uint32_t ssf_error; uint32_t ssf_error;
struct sctp_sndrcvinfo ssf_info; struct sctp_sndrcvinfo ssf_info;
sctp_assoc_t ssf_assoc_id; sctp_assoc_t ssf_assoc_id;
uint8_t ssf_data[]; uint8_t ssf_data[];
}; };
ssf_type: ssf_type: It should be SCTP_SEND_FAILED.
ssf_flags: The flag value will take one of the following values:
It should be SCTP_SEND_FAILED. SCTP_DATA_UNSENT: Indicates that the data was never put on the
ssf_flags: 16 bits (unsigned integer)
The flag value will take one of the following values:
SCTP_DATA_UNSENT - Indicates that the data was never put on the
wire. wire.
SCTP_DATA_SENT - Indicates that the data was put on the wire. Note SCTP_DATA_SENT: Indicates that the data was put on the wire.
that this does not necessarily mean that the data was (or was not) Note that this does not necessarily mean that the data was (or
successfully delivered. was not) successfully delivered.
ssf_length: This field is the total length of the notification data,
ssf_length: 32 bits (unsigned integer) including the notification header and the payload in ssf_data.
ssf_error: This value represents the reason why the send failed, and
This field is the total length of the notification data, including if set, will be a SCTP protocol error code as defined in [RFC4960]
the notification header and the payload in ssf_data. section 3.3.10.
ssf_info: The send information associated with the undelivered
ssf_error: 16 bits (unsigned integer) message. The sinfo_flags field will also contain an indication if
the beginning of the message and/or end of the message is present.
This value represents the reason why the send failed, and if set, In cases where no data has been sent on the wire, this field will
will be a SCTP protocol error code as defined in [RFC4960] section have or'ed in the value SCTP_DATA_NOT_FRAG, which is a composition
3.3.10. of both a "BEGIN" and "END" fragmentation bit. In cases where
part of the data has been sent this field will hold an indication
ssf_info: sizeof (struct sctp_sndrcvinfo) that just the part not sent is present SCTP_DATA_LAST_FRAG which
corresponds to the "END" bit. Note that the message itself may be
The original send information associated with the undelivered more than one chunk. If the sinfo_flags field holds neither of
message. these two values then a piece that has been fragmented and sent
but not acknowledged is present. This piece is from an
ssf_assoc_id: sizeof (sctp_assoc_t) unspecified position in the message and the application can make
no assumptions about the data itself. Applications wanting to
The association id field, sf_assoc_id, holds the identifier for the examine a recovered message should look for the
association. All notifications for a given association have the same SCTP_DATA_NOT_FRAG. Without this flag the application should
association identifier. For one-to-one style socket, this field is assume part of the message arrived and take appropriate steps to
ignored. audit and recover any lost or missing data. Note also that the
partial reliablity information that was sent down to the SCTP
ssf_data: variable length stack is NOT present in the sinfo_flags field since it occupies
the same bit positions as the SCTP_DATA_NOT_FRAG and the
SCTP_DATA_LAST_FRAG bits.
The undelivered message, exactly as delivered by the caller to the ssf_assoc_id: The association id field, sf_assoc_id, holds the
original send*() call. identifier for the association. All notifications for a given
association have the same association identifier. For one-to-one
style socket, this field is ignored.
ssf_data: The undelivered message or part of the undelivered message
will be present in the sf_data field. Note that the sinfo_flags
field as noted above should be used to determine if a complete
message is present or just a piece of the message. Note that only
user data is present in this field, any chunk headers or SCTP
common headers must be removed by the SCTP stack.
6.3.1.5. SCTP_SHUTDOWN_EVENT 6.3.6. SCTP_SHUTDOWN_EVENT
When a peer sends a SHUTDOWN, SCTP delivers this notification to When a peer sends a SHUTDOWN, SCTP delivers this notification to
inform the application that it should cease sending data. inform the application that it should cease sending data.
struct sctp_shutdown_event { struct sctp_shutdown_event {
uint16_t sse_type; uint16_t sse_type;
uint16_t sse_flags; uint16_t sse_flags;
uint32_t sse_length; uint32_t sse_length;
sctp_assoc_t sse_assoc_id; sctp_assoc_t sse_assoc_id;
}; };
sse_type sse_type It should be SCTP_SHUTDOWN_EVENT.
sse_flags: Currently unused.
It should be SCTP_SHUTDOWN_EVENT sse_length: This field is the total length of the notification data,
including the notification header. It will generally be sizeof
sse_flags: 16 bits (unsigned integer) (struct sctp_shutdown_event).
sse_flags: Currently unused.
Currently unused. sse_assoc_id: The association id field, holds the identifier for the
association. All notifications for a given association have the
sse_length: 32 bits (unsigned integer) same association identifier. For one-to-one style socket, this
field is ignored.
This field is the total length of the notification data, including
the notification header. It will generally be sizeof (struct
sctp_shutdown_event).
sse_flags: 16 bits (unsigned integer)
Currently unused.
sse_assoc_id: sizeof (sctp_assoc_t)
The association id field, holds the identifier for the association.
All notifications for a given association have the same association
identifier. For one-to-one style socket, this field is ignored.
6.3.1.6. SCTP_ADAPTATION_INDICATION 6.3.7. SCTP_ADAPTATION_INDICATION
When a peer sends a Adaptation Layer Indication parameter , SCTP When a peer sends a Adaptation Layer Indication parameter , SCTP
delivers this notification to inform the application that of the delivers this notification to inform the application that of the
peers requested adaptation layer. peers requested adaptation layer.
struct sctp_adaptation_event { struct sctp_adaptation_event {
uint16_t sai_type; uint16_t sai_type;
uint16_t sai_flags; uint16_t sai_flags;
uint32_t sai_length; uint32_t sai_length;
uint32_t sai_adaptation_ind; uint32_t sai_adaptation_ind;
sctp_assoc_t sai_assoc_id; sctp_assoc_t sai_assoc_id;
}; };
sai_type: It should be SCTP_ADAPTATION_INDICATION.
sai_flags: Currently unused.
sai_length: This field is the total length of the notification data,
including the notification header. It will generally be sizeof
(struct sctp_adaptation_event).
sai_adaptation_ind: This field holds the bit array sent by the peer
in the adaptation layer indication parameter. The bits are in
network byte order.
sai_assoc_id: The association id field, holds the identifier for the
association. All notifications for a given association have the
same association identifier. For one-to-one style socket, this
field is ignored.
sai_type 6.3.8. SCTP_PARTIAL_DELIVERY_EVENT
It should be SCTP_ADAPTATION_INDICATION
sai_flags: 16 bits (unsigned integer)
Currently unused.
sai_length: 32 bits (unsigned integer)
This field is the total length of the notification data, including
the notification header. It will generally be sizeof (struct
sctp_adaptation_event).
sai_adaptation_ind: 32 bits (unsigned integer)
This field holds the bit array sent by the peer in the adaptation
layer indication parameter. The bits are in network byte order.
sai_assoc_id: sizeof (sctp_assoc_t)
The association id field, holds the identifier for the association.
All notifications for a given association have the same association
identifier. For one-to-one style socket, this field is ignored.
6.3.1.7. SCTP_PARTIAL_DELIVERY_EVENT
When a receiver is engaged in a partial delivery of a message this When a receiver is engaged in a partial delivery of a message this
notification will be used to indicate various events. notification will be used to indicate various events.
struct sctp_pdapi_event { struct sctp_pdapi_event {
uint16_t pdapi_type; uint16_t pdapi_type;
uint16_t pdapi_flags; uint16_t pdapi_flags;
uint32_t pdapi_length; uint32_t pdapi_length;
uint32_t pdapi_indication; uint32_t pdapi_indication;
uint32_t pdapi_stream; uint32_t pdapi_stream;
uint32_t pdapi_seq; uint32_t pdapi_seq;
sctp_assoc_t pdapi_assoc_id; sctp_assoc_t pdapi_assoc_id;
}; };
pdapi_type
It should be SCTP_PARTIAL_DELIVERY_EVENT
pdapi_flags: 16 bits (unsigned integer)
Currently unused.
pdapi_length: 32 bits (unsigned integer)
This field is the total length of the notification data, including
the notification header. It will generally be sizeof (struct
sctp_pdapi_event).
pdapi_indication: 32 bits (unsigned integer) pdapi_type: It should be SCTP_PARTIAL_DELIVERY_EVENT.
pdapi_flags: Currently unused.
This field holds the indication being sent to the application pdapi_length: This field is the total length of the notification
possible values include: data, including the notification header. It will generally be
sizeof(struct sctp_pdapi_event).
SCTP_PARTIAL_DELIVERY_ABORTED pdapi_indication: This field holds the indication being sent to the
application possible values include:
pdapi_stream: 16 bits (unsigned integer) SCTP_PARTIAL_DELIVERY_ABORTED: This notification indicates that
the partial delivery of a user message has been aborted.
This field holds the stream on which the partial delivery event pdapi_stream: This field holds the stream on which the partial
happened. delivery event happened.
pdapi_seq: This field holds the stream sequence number which was
pdapi_seq: 16 bits (unsigned integer) being partially delivered.
pdapi_assoc_id: The association id field, holds the identifier for
This field holds the stream sequence number which was being partially the association. All notifications for a given association have
delivered. the same association identifier. For one-to-one style socket,
this field is ignored.
pdapi_assoc_id: sizeof (sctp_assoc_t)
The association id field, holds the identifier for the association.
All notifications for a given association have the same association
identifier. For one-to-one style socket, this field is ignored.
6.3.1.8. SCTP_AUTHENTICATION_EVENT 6.3.9. SCTP_AUTHENTICATION_EVENT
When a receiver is using authentication this message will provide When a receiver is using authentication this message will provide
notifications regarding new keys being made active as well as errors. notifications regarding new keys being made active as well as errors.
struct sctp_authkey_event { struct sctp_authkey_event {
uint16_t auth_type; uint16_t auth_type;
uint16_t auth_flags; uint16_t auth_flags;
uint32_t auth_length; uint32_t auth_length;
uint16_t auth_keynumber; uint16_t auth_keynumber;
uint16_t auth_altkeynumber; uint16_t auth_altkeynumber;
uint32_t auth_indication; uint32_t auth_indication;
sctp_assoc_t auth_assoc_id; sctp_assoc_t auth_assoc_id;
}; };
auth_type auth_type: It should be SCTP_AUTHENTICATION_EVENT.
auth_flags: Currently unused.
It should be SCTP_AUTHENTICATION_EVENT auth_length: This field is the total length of the notification
data, including the notification header. It will generally be
auth_flags: 16 bits (unsigned integer) sizeof (struct sctp_authkey_event).
auth_keynumber: This field holds the keynumber set by the user for
Currently unused. the effected key. If more than one key is involved, this will
contain one of the keys involved in the notification.
auth_length: 32 bits (unsigned integer) auth_altkeynumber: This field holds an alternate keynumber which is
used by some notifications.
This field is the total length of the notification data, including auth_indication: This field hold the error or indication being
the notification header. It will generally be sizeof (struct reported. The following values are currently defined:
sctp_authkey_event). SCTP_AUTH_NEWKEY: This report indicates that a new key has been
made active (used for the first time by the peer) and is now
auth_keynumber: 32 bits (unsigned integer) the active key. The auth_keynumber field holds the user
specified key number.
This field holds the keynumber set by the user for the effected key. SCTP_AUTH_NO_AUTH: This report indicates that the peer does not
If more than one key is involved, this will contain one of the keys support the SCTP-AUTH.
involved in the notification. SCTP_AUTH_FREE_KEY: This report indicates that the SCTP
implementation will not use the key identifier specified in
auth_altkeynumber: 32 bits (unsigned integer) auth_keynumber anymore.
auth_assoc_id: The association id field, holds the identifier for
This field holds an alternate keynumber which is used by some the association. All notifications for a given association have
notifications. the same association identifier.
auth_indication: 32 bits (unsigned integer)
This field hold the error or indication being reported. The
following values are currently defined:
SCTP_AUTH_NEWKEY - this report indicates that a new key has been
made active (used for the first time by the peer) and is now the
active key. The auth_keynumber field holds the user specified key
number.
auth_assoc_id: sizeof (sctp_assoc_t)
The association id field, holds the identifier for the association.
All notifications for a given association have the same association
identifier.
6.3.1.9. SCTP_AUTHENTICATION_EVENT
When an association is set up and the peer does not support SCTP-AUTH
this notification is provided by the kernel to the user.
struct sctp_no_auth_event {
uint16_t no_auth_type;
uint16_t no_auth_flags;
uint32_t no_auth_length;
sctp_assoc_t no_auth_assoc_id;
};
no_auth_type
It should be SCTP_NO_AUTHENTICATION_EVENT
no_auth_flags: 16 bits (unsigned integer)
Currently unused.
no_auth_length: 32 bits (unsigned integer)
This field is the total length of the notification data, including
the notification header. It will generally be sizeof (struct
sctp_no_auth_event).
6.3.1.10. SCTP_SENDER_DRY_EVENT 6.3.10. SCTP_SENDER_DRY_EVENT
When an association is set up and the peer does not support SCTP-AUTH When the SCTP implementation has no user data anymore to send or
this notification is provided by the kernel to the user. retransmit this notification is given to the user. If the user
subscribes to this event and the SCTP has at this point of time no
user data to send or retransmit this notification is also given to
the user.
struct sctp_sender_dry_event { struct sctp_sender_dry_event {
uint16_t sender_dry_type; uint16_t sender_dry_type;
uint16_t sender_dry_flags; uint16_t sender_dry_flags;
uint32_t sender_dry_length; uint32_t sender_dry_length;
sctp_assoc_t sender_dry_assoc_id; sctp_assoc_t sender_dry_assoc_id;
}; };
sender_dry_type: sender_dry_type: It should be SCTP_SENDER_DRY_EVENT.
sender_dry_flags: Currently unused.
It should be SCTP_SENDER_DRY_EVENT sender_dry_length: This field is the total length of the
notification data, including the notification header. It will
sender_dry_flags: 16 bits (unsigned integer) generally be sizeof (struct sctp_sender_dry_event).
Currently unused.
sender_dry_length: 32 bits (unsigned integer)
This field is the total length of the notification data, including
the notification header. It will generally be sizeof (struct
sctp_sender_dry_event).
6.3.1.11. SCTP_AUTHENTICATION_FREE_KEY_EVENT
When SCTP-AUTH wik not use a key identifier for sending packets
anymore, this notification is provided by the kernel to the user.
struct sctp_auth_free_key_event {
uint16_t type;
uint16_t flags;
uint32_t length;
uint16_t keynumber;
sctp_assoc_t assoc_id;
};
type:
It should be SCTP_AUTHENTICATION_FREE_KEY_EVENT
flags: 16 bits (unsigned integer)
Currently unused.
length: 32 bits (unsigned integer)
This field is the total length of the notification data, including
the notification header. It will generally be sizeof (struct
sctp_auth_free_key_event).
keynumber: 16 bits (unsigned integer)
This field holds the keynumber set by the user for the effected key.
6.4. Ancillary Data Considerations and Semantics 6.4. Ancillary Data Considerations and Semantics
Programming with ancillary socket data contains some subtleties and Programming with ancillary socket data contains some subtleties and
pitfalls, which are discussed below. pitfalls, which are discussed below.
6.4.1. Multiple Items and Ordering 6.4.1. Multiple Items and Ordering
Multiple ancillary data items may be included in any call to Multiple ancillary data items may be included in any call to
sendmsg() or recvmsg(); these may include multiple SCTP or non-SCTP sendmsg() or recvmsg(); these may include multiple SCTP or non-SCTP
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CMSG_SPACE(sizeof (struct in6_pktinfo)); CMSG_SPACE(sizeof (struct in6_pktinfo));
buf = malloc(total); buf = malloc(total);
We could then use this buffer for msg_control on each call to We could then use this buffer for msg_control on each call to
recvmsg() and be assured that we would not lose any ancillary data to recvmsg() and be assured that we would not lose any ancillary data to
truncation. truncation.
7. Common Operations for Both Styles 7. Common Operations for Both Styles
7.1. send(), recv(), sendto(), recvfrom() 7.1. send(), recv(), sendto(), and recvfrom()
Applications can use send() and sendto() to transmit data to the peer Applications can use send() and sendto() to transmit data to the peer
of an SCTP endpoint. recv() and recvfrom() can be used to receive of an SCTP endpoint. recv() and recvfrom() can be used to receive
data from the peer. data from the peer.
The syntax is: The function prototypes are
ssize_t send(int sd, const void *msg, size_t len, int flags); ssize_t send(int sd,
ssize_t sendto(int sd, const void *msg, size_t len, int flags, const void *msg,
const struct sockaddr *to, socklen_t tolen); size_t len,
ssize_t recv(int sd, void *buf, size_t len, int flags); int flags);
ssize_t recvfrom(int sd, void *buf, size_t len, int flags,
struct sockaddr *from, socklen_t *fromlen); ssize_t sendto(int sd,
sd - the socket descriptor of an SCTP endpoint. const void *msg,
msg - the message to be sent. size_t len,
len - the size of the message or the size of buffer. int flags,
to - one of the peer addresses of the association to be used to send const struct sockaddr *to,
socklen_t tolen);
ssize_t recv(int sd,
void *buf,
size_t len,
int flags);
ssize_t recvfrom(int sd,
void *buf,
size_t len,
int flags,
struct sockaddr *from,
socklen_t *fromlen);
and the arguments are
sd: The socket descriptor of an SCTP endpoint.
msg: The message to be sent.
len: the size of the message or the size of buffer.
to: one of the peer addresses of the association to be used to send
the message. the message.
tolen - the size of the address. tolen: The size of the address.
buf - the buffer to store a received message. buf: The buffer to store a received message.
from - the buffer to store the peer address used to send the from: The buffer to store the peer address used to send the received
received message. message.
fromlen - the size of the from address fromlen: The size of the from address.
flags - (described below). flags: (described below).
These calls give access to only basic SCTP protocol features. If These calls give access to only basic SCTP protocol features. If
either peer in the association uses multiple streams, or sends either peer in the association uses multiple streams, or sends
unordered data these calls will usually be inadequate, and may unordered data these calls will usually be inadequate, and may
deliver the data in unpredictable ways. deliver the data in unpredictable ways.
SCTP has the concept of multiple streams in one association. The SCTP has the concept of multiple streams in one association. The
above calls do not allow the caller to specify on which stream a above calls do not allow the caller to specify on which stream a
message should be sent. The system uses stream 0 as the default message should be sent. The system uses stream 0 as the default
stream for send() and sendto(). recv() and recvfrom() return data stream for send() and sendto(). recv() and recvfrom() return data
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returns as much data as will fit in the buffer. returns as much data as will fit in the buffer.
Note, the send() and recv() calls may not be used for a one-to-many Note, the send() and recv() calls may not be used for a one-to-many
style socket. style socket.
Note, if an application calls a send function with no user data and Note, if an application calls a send function with no user data and
no ancillary data the SCTP implementation should reject the request no ancillary data the SCTP implementation should reject the request
with an appropriate error message. An implementation is NOT allowed with an appropriate error message. An implementation is NOT allowed
to send a Data chunk with no user data [RFC4960]. to send a Data chunk with no user data [RFC4960].
7.2. setsockopt(), getsockopt() 7.2. setsockopt() and getsockopt()
Applications use setsockopt() and getsockopt() to set or retrieve Applications use setsockopt() and getsockopt() to set or retrieve
socket options. Socket options are used to change the default socket options. Socket options are used to change the default
behavior of sockets calls. They are described in Section 8 behavior of sockets calls. They are described in Section 8.
The syntax is: The function prototypes are
ret = getsockopt(int sd, int level, int optname, void *optval, int getsockopt(int sd,
int level,
int optname,
void *optval,
socklen_t *optlen); socklen_t *optlen);
ret = setsockopt(int sd, int level, int optname, const void *optval,
and
int setsockopt(int sd,
int level,
int optname,
const void *optval,
socklen_t optlen); socklen_t optlen);
sd - the socket descriptor. and the arguments are
level - set to IPPROTO_SCTP for all SCTP options. sd: The socket descriptor.
optname - the option name. level: Set to IPPROTO_SCTP for all SCTP options.
optval - the buffer to store the value of the option. optname - The option name.
optlen - the size of the buffer (or the length of the option optval: The buffer to store the value of the option.
optlen: The size of the buffer (or the length of the option
returned). returned).
All socket options set on a 1-to-1 listening sockets also apply all All socket options set on a 1-to-1 listening sockets also apply all
accepted sockets. All socket options set on a 1-to-many socket using accepted sockets. All socket options set on a 1-to-many socket using
the assoc_id 0 applies for all future assocs on the socket. the assoc_id 0 applies for all future associations on the socket.
7.3. read() and write() 7.3. read() and write()
Applications can use read() and write() to send and receive data to Applications can use read() and write() to send and receive data to
and from peer. They have the same semantics as send() and recv() and from peer. They have the same semantics as send() and recv()
except that the flags parameter cannot be used. except that the flags parameter cannot be used.
Note, these calls, when used in the one-to-many style, may only be Note, these calls, when used in the one-to-many style, may only be
used with branched off socket descriptors (see Section 9.2). used with branched off socket descriptors (see Section 9.2).
7.4. getsockname() 7.4. getsockname()
Applications use getsockname() to retrieve the locally-bound socket Applications use getsockname() to retrieve the locally-bound socket
address of the specified socket. This is especially useful if the address of the specified socket. This is especially useful if the
caller let SCTP chose a local port. This call is for where the caller let SCTP chose a local port. This call is for where the
endpoint is not multi-homed. It does not work well with multi-homed endpoint is not multi-homed. It does not work well with multi-homed
sockets. See Section 9.5 for a multi-homed version of the call. sockets. See Section 9.5 for a multi-homed version of the call.
The syntax is: The function prototype is
int getsockname(int sd, struct sockaddr *address, int getsockname(int sd,
struct sockaddr *address,
socklen_t *len); socklen_t *len);
sd - the socket descriptor to be queried.
address - On return, one locally bound address (chosen by the SCTP and the arguments are
sd: The socket descriptor to be queried.
address: On return, one locally bound address (chosen by the SCTP
stack) is stored in this buffer. If the socket is an IPv4 socket, stack) is stored in this buffer. If the socket is an IPv4 socket,
the address will be IPv4. If the socket is an IPv6 socket, the the address will be IPv4. If the socket is an IPv6 socket, the
address will be either an IPv6 or IPv4 address. address will be either an IPv6 or IPv4 address.
len - The caller should set the length of address here. On return, len: The caller should set the length of address here. On return,
this is set to the length of the returned address. this is set to the length of the returned address.
If the actual length of the address is greater than the length of the If the actual length of the address is greater than the length of the
supplied sockaddr structure, the stored address will be truncated. supplied sockaddr structure, the stored address will be truncated.
If the socket has not been bound to a local name, the value stored in If the socket has not been bound to a local name, the value stored in
the object pointed to by address is unspecified. the object pointed to by address is unspecified.
8. Socket Options 8. Socket Options
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Note that socket or IP level options are set or retrieved per socket. Note that socket or IP level options are set or retrieved per socket.
This means that for one-to-many style sockets, those options will be This means that for one-to-many style sockets, those options will be
applied to all associations belonging to the socket. And for one-to- applied to all associations belonging to the socket. And for one-to-
one style, those options will be applied to all peer addresses of the one style, those options will be applied to all peer addresses of the
association controlled by the socket. Applications should be very association controlled by the socket. Applications should be very
careful in setting those options. careful in setting those options.
For some IP stacks getsockopt() is read-only; so a new interface will For some IP stacks getsockopt() is read-only; so a new interface will
be needed when information must be passed both in to and out of the be needed when information must be passed both in to and out of the
SCTP stack. The syntax for sctp_opt_info() is, SCTP stack. The syntax for sctp_opt_info() is
int sctp_opt_info(int sd, int sctp_opt_info(int sd,
sctp_assoc_t id, sctp_assoc_t id,
int opt, int opt,
void *arg, void *arg,
socklen_t *size); socklen_t *size);
The sctp_opt_info() call is a replacement for getsockopt() only and The sctp_opt_info() call is a replacement for getsockopt() only and
will not set any options associated with the specified socket. A will not set any options associated with the specified socket. A
setsockopt() must be used to set any writeable option. setsockopt() must be used to set any writeable option.
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SCTP_GET_PEER_ADDR_INFO SCTP_GET_PEER_ADDR_INFO
SCTP_PRIMARY_ADDR SCTP_PRIMARY_ADDR
SCTP_PEER_ADDR_PARAMS SCTP_PEER_ADDR_PARAMS
SCTP_STATUS SCTP_STATUS
SCTP_CONTEXT SCTP_CONTEXT
SCTP_AUTH_ACTIVE_KEY SCTP_AUTH_ACTIVE_KEY
SCTP_PEER_AUTH_CHUNKS SCTP_PEER_AUTH_CHUNKS
SCTP_LOCAL_AUTH_CHUNKS SCTP_LOCAL_AUTH_CHUNKS
arg is an option-specific structure buffer provided by the caller. arg is an option-specific structure buffer provided by the caller.
See Section 9.5) subsections for more information on these options See Section 9.5 subsections for more information on these options and
and option-specific structures. option-specific structures.
sctp_opt_info() returns 0 on success, or on failure returns -1 and sctp_opt_info() returns 0 on success, or on failure returns -1 and
sets errno to the appropriate error code. sets errno to the appropriate error code.
All options that support specific settings on an association by All options that support specific settings on an association by
filling in either an association id variable or a sockaddr_storage filling in either an association id variable or a sockaddr_storage
SHOULD also support setting of the same value for the entire endpoint SHOULD also support setting of the same value for the entire endpoint
(i.e. future associations). To accomplish this the following logic (i.e. future associations). To accomplish this the following logic
is used when setting one of these options: is used when setting one of these options:
a) If an address is specified via a sockaddr_storage that is included o If an address is specified via a sockaddr_storage that is included
in the structure, the address is used to lookup the association in the structure, the address is used to lookup the association
and the settings are applied to the specific address (if and the settings are applied to the specific address (if
appropriate) or to the entire association. appropriate) or to the entire association.
b) If an association identification is filled in but not a o If an association identification is filled in but not a
sockaddr_storage (if present), the association is found using the sockaddr_storage (if present), the association is found using the
association identification and the settings should be applied to association identification and the settings should be applied to
the entire association (since a specific address is not the entire association (since a specific address is not
specified). Note this also applies to options that hold an specified). Note this also applies to options that hold an
association identification in their structure but do not have a association identification in their structure but do not have a
sockaddr_storage field. sockaddr_storage field.
o If neither the sockaddr_storage or association identification is
c) If neither the sockaddr_storage or association identification is
set, i.e. the sockaddr_storage is set to all 0's (INADDR_ANY) and set, i.e. the sockaddr_storage is set to all 0's (INADDR_ANY) and
the association identification is 0, the settings are a default the association identification is 0, the settings are a default
and to be applied to the endpoint (all future associations). and to be applied to the endpoint (all future associations).
8.1. Read / Write Options 8.1. Read / Write Options
8.1.1. Retransmission Timeout Parameters (SCTP_RTOINFO) 8.1.1. Retransmission Timeout Parameters (SCTP_RTOINFO)
The protocol parameters used to initialize and bound retransmission The protocol parameters used to initialize and bound retransmission
timeout (RTO) are tunable. See [RFC4960] for more information on how timeout (RTO) are tunable. See [RFC4960] for more information on how
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The following structure is used to access and modify these The following structure is used to access and modify these
parameters: parameters:
struct sctp_rtoinfo { struct sctp_rtoinfo {
sctp_assoc_t srto_assoc_id; sctp_assoc_t srto_assoc_id;
uint32_t srto_initial; uint32_t srto_initial;
uint32_t srto_max; uint32_t srto_max;
uint32_t srto_min; uint32_t srto_min;
}; };
srto_initial - This contains the initial RTO value. srto_initial: This contains the initial RTO value.
srto_max and srto_min - These contain the maximum and minimum bounds srto_max and srto_min: These contain the maximum and minimum bounds
for all RTOs. for all RTOs.
srto_assoc_id - (one-to-many style socket) This is filled in the srto_assoc_id: This parameter is ignored for one-to-one style
application, and identifies the association for this query. If sockets. For one-to-many style sockets the following applies:
this parameter is '0' (on a one-to-many style socket), then the This is filled in the application, and identifies the association
change effects the entire endpoint. for this query. If this parameter is '0', then the change affects
the entire endpoint.
All parameters are time values, in milliseconds. A value of 0, when All times are given in milliseconds. A value of 0, when modifying
modifying the parameters, indicates that the current value should not the parameters, indicates that the current value should not be
be changed. changed.
To access or modify these parameters, the application should call To access or modify these parameters, the application should call
getsockopt or setsockopt() respectively with the option name getsockopt or setsockopt() respectively with the option name
SCTP_RTOINFO. SCTP_RTOINFO.
8.1.2. Association Parameters (SCTP_ASSOCINFO) 8.1.2. Association Parameters (SCTP_ASSOCINFO)
This option is used to both examine and set various association and This option is used to both examine and set various association and
endpoint parameters. endpoint parameters. See [RFC4960] for more information on how this
parameter is used.
See [RFC4960] for more information on how this parameter is used.
The sasoc_assoc_id parameter is ignored for one-to-one style socket.
The following structure is used to access and modify this parameters: The following structure is used to access and modify this parameters:
struct sctp_assocparams { struct sctp_assocparams {
sctp_assoc_t sasoc_assoc_id; sctp_assoc_t sasoc_assoc_id;
uint16_t sasoc_asocmaxrxt; uint16_t sasoc_asocmaxrxt;
uint16_t sasoc_number_peer_destinations; uint16_t sasoc_number_peer_destinations;
uint32_t sasoc_peer_rwnd; uint32_t sasoc_peer_rwnd;
uint32_t sasoc_local_rwnd; uint32_t sasoc_local_rwnd;
uint32_t sasoc_cookie_life; uint32_t sasoc_cookie_life;
}; };
sasoc_asocmaxrxt - This contains the maximum retransmission attempts sasoc_assoc_id: This parameter is ignored for one-to-one style
sockets. For one-to-many style sockets the following applies:
This information may be examined for either the endpoint or a
specific association. To examine a endpoints default parameters
the association id (sasoc_assoc_id) should must be set to the
value '0'.
sasoc_asocmaxrxt: This contains the maximum retransmission attempts
to make for the association. to make for the association.
sasoc_number_peer_destinations - This is the number of destination sasoc_number_peer_destinations: This is the number of destination
addresses that the peer has. addresses that the peer has.
sasoc_peer_rwnd - This holds the current value of the peers rwnd sasoc_peer_rwnd: This holds the current value of the peers rwnd
(reported in the last SACK) minus any outstanding data (i.e. data (reported in the last SACK) minus any outstanding data (i.e. data
inflight). inflight).
sasoc_local_rwnd - This holds the last reported rwnd that was sent sasoc_local_rwnd: This holds the last reported rwnd that was sent to
to the peer. the peer.
sasoc_cookie_life - This is the associations cookie life value used sasoc_cookie_life: This is the associations cookie life value used
when issuing cookies. when issuing cookies.
sasoc_assoc_id - This is filled in the application, and identifies
the association for this query.
This information may be examined for either the endpoint or a
specific association. To examine a endpoints default parameters the
association id (sasoc_assoc_id) should must be set to the value '0'.
The values of the sasoc_peer_rwnd is meaningless when examining The values of the sasoc_peer_rwnd is meaningless when examining
endpoint information. endpoint information.
All parameters are time values, in milliseconds. A value of 0, when All time values are given in milliseconds. A value of 0, when
modifying the parameters, indicates that the current value should not modifying the parameters, indicates that the current value should not
be changed. be changed.
The values of the sasoc_asocmaxrxt and sasoc_cookie_life may be set The values of the sasoc_asocmaxrxt and sasoc_cookie_life may be set
on either an endpoint or association basis. The rwnd and destination on either an endpoint or association basis. The rwnd and destination
counts (sasoc_number_peer_destinations, counts (sasoc_number_peer_destinations, sasoc_peer_rwnd,
sasoc_peer_rwnd,sasoc_local_rwnd) are NOT settable and any value sasoc_local_rwnd) are NOT settable and any value placed in these is
placed in these is ignored. ignored.
To access or modify these parameters, the application should call To access or modify these parameters, the application should call
getsockopt or setsockopt() respectively with the option name getsockopt or setsockopt() respectively with the option name
SCTP_ASSOCINFO. SCTP_ASSOCINFO.
The maximum number of retransmissions before an address is considered The maximum number of retransmissions before an address is considered
unreachable is also tunable, but is address-specific, so it is unreachable is also tunable, but is address-specific, so it is
covered in a separate option. If an application attempts to set the covered in a separate option. If an application attempts to set the
value of the association maximum retransmission parameter to more value of the association maximum retransmission parameter to more
than the sum of all maximum retransmission parameters, setsockopt() than the sum of all maximum retransmission parameters, setsockopt()
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these parameters is defined in Section 6.2.1). The option name these parameters is defined in Section 6.2.1). The option name
argument to setsockopt() and getsockopt() is SCTP_INITMSG. argument to setsockopt() and getsockopt() is SCTP_INITMSG.
Setting initialization parameters is effective only on an unconnected Setting initialization parameters is effective only on an unconnected
socket (for one-to-many style sockets only future associations are socket (for one-to-many style sockets only future associations are
effected by the change). With one-to-one style sockets, this option effected by the change). With one-to-one style sockets, this option
is inherited by sockets derived from a listener socket. is inherited by sockets derived from a listener socket.
8.1.4. SO_LINGER 8.1.4. SO_LINGER
An application using the one-to-one style socket can use this option An application can use this option to perform the SCTP ABORT
to perform the SCTP ABORT primitive. The linger option structure is: primitive. This option affects all associations related to the
socket.
The linger option structure is:
struct linger { struct linger {
int l_onoff; /* option on/off */ int l_onoff; /* option on/off */
int l_linger; /* linger time */ int l_linger; /* linger time */
}; };
To enable the option, set l_onoff to 1. If the l_linger value is set To enable the option, set l_onoff to 1. If the l_linger value is set
to 0, calling close() is the same as the ABORT primitive. If the to 0, calling close() is the same as the ABORT primitive. If the
value is set to a negative value, the setsockopt() call will return value is set to a negative value, the setsockopt() call will return
an error. If the value is set to a positive value linger_time, the an error. If the value is set to a positive value linger_time, the
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Turn on/off any Nagle-like algorithm. This means that packets are Turn on/off any Nagle-like algorithm. This means that packets are
generally sent as soon as possible and no unnecessary delays are generally sent as soon as possible and no unnecessary delays are
introduced, at the cost of more packets in the network. Expects an introduced, at the cost of more packets in the network. Expects an
integer boolean flag. integer boolean flag.
8.1.6. SO_RCVBUF 8.1.6. SO_RCVBUF
Sets receive buffer size in octets. For SCTP one-to-one style Sets receive buffer size in octets. For SCTP one-to-one style
sockets, this controls the receiver window size. For one-to-many sockets, this controls the receiver window size. For one-to-many
style sockets the meaning depends on the constant HAVE_SCTP_MULTIBUF style sockets the meaning is implementation dependent. It might
(see Section 4.4). If the implementation defines HAVE_SCTP_MULTIBUF control the receive buffer for each association bound to the socket
as 1, this controls the receiver window size for each association descriptor or it might control the receive buffer for the whole
bound to the socket descriptor. If the implementation defines socket. The call expects an integer.
HAVE_SCTP_MULTIBUF as 0, this controls the size of the single receive
buffer for the whole socket. The call expects an integer.
8.1.7. SO_SNDBUF 8.1.7. SO_SNDBUF
Sets send buffer size. For SCTP one-to-one style sockets, this Sets send buffer size. For SCTP one-to-one style sockets, this
controls the amount of data SCTP may have waiting in internal buffers controls the amount of data SCTP may have waiting in internal buffers
to be sent. This option therefore bounds the maximum size of data to be sent. This option therefore bounds the maximum size of data
that can be sent in a single send call. For one-to-many style that can be sent in a single send call. For one-to-many style
sockets, the effect is the same, except that it applies to one or all sockets, the effect is the same, except that it applies to one or all
associations (see Section 4.4) bound to the socket descriptor used in associations (see Section 4.4) bound to the socket descriptor used in
the setsockopt() or getsockopt() call. The option applies to each the setsockopt() or getsockopt() call. The option applies to each
association's window size separately. The call expects an integer. association's window size separately. The call expects an integer.
8.1.8. Automatic Close of associations (SCTP_AUTOCLOSE) 8.1.8. Automatic Close of Associations (SCTP_AUTOCLOSE)
This socket option is applicable to the one-to-many style socket This socket option is applicable to the one-to-many style socket
only. When set it will cause associations that are idle for more only. When set it will cause associations that are idle for more
than the specified number of seconds to automatically close using the than the specified number of seconds to automatically close using the
graceful shutdown procedure. An association being idle is defined as graceful shutdown procedure. An association being idle is defined as
an association that has NOT sent or received user data. The special an association that has NOT sent or received user data. The special
value of '0' indicates that no automatic close of any associations value of '0' indicates that no automatic close of any associations
should be performed, this is the default value. The option expects should be performed, this is the default value. The option expects
an integer defining the number of seconds of idle time before an an integer defining the number of seconds of idle time before an
association is closed. association is closed.
An application using this option should enable receiving the An application using this option should enable receiving the
association change notification. This is the only mechanism an association change notification. This is the only mechanism an
application is informed about the closing of an association. After application is informed about the closing of an association. After
an association is closed, the association ID assigned to it can be an association is closed, the association ID assigned to it can be
reused. An application should be aware of this to avoid the possible reused. An application should be aware of this to avoid the possible
problem of sending data to an incorrect peer end point. problem of sending data to an incorrect peer end point.
8.1.9. Set Peer Primary Address (SCTP_SET_PEER_PRIMARY_ADDR) 8.1.9. Set Primary Address (SCTP_PRIMARY_ADDR)
Requests that the peer mark the enclosed address as the association
primary. The enclosed address must be one of the association's
locally bound addresses. The following structure is used to make a
set primary request:
struct sctp_setpeerprim {
sctp_assoc_t sspp_assoc_id;
struct sockaddr_storage sspp_addr;
};
sspp_addr - The address to set as primary
sspp_assoc_id - This is filled in by the application, and identifies
the association for this request.
Note that this option really should be considered a write only option
(not a read/write option) since it can NOT be passed to a
getsockopt() call and is only valid when used with setsockopt() if
the implementation supports this feature since this functionality is
optional. Implementations that do not support this functionality
should return EOPNOTSUPP.
8.1.10. Set Primary Address (SCTP_PRIMARY_ADDR)
Requests that the local SCTP stack use the enclosed peer address as Requests that the local SCTP stack use the enclosed peer address as
the association primary. The enclosed address must be one of the the association primary. The enclosed address must be one of the
association peer's addresses. The following structure is used to association peer's addresses.
make a set peer primary request:
The following structure is used to make a set peer primary request:
struct sctp_setprim { struct sctp_setprim {
sctp_assoc_t ssp_assoc_id; sctp_assoc_t ssp_assoc_id;
struct sockaddr_storage ssp_addr; struct sockaddr_storage ssp_addr;
}; };
ssp_addr - The address to set as primary ssp_addr: The address to set as primary.
ssp_assoc_id - This is filled in by the application, and identifies ssp_assoc_id: This parameter is ignored for one-to-one style
the association for this request. sockets. For one-to-many style sockets it identifies the
association for this request.
8.1.11. Set Adaptation Layer Indicator (SCTP_ADAPTATION_LAYER) 8.1.10. Set Adaptation Layer Indicator (SCTP_ADAPTATION_LAYER)
Requests that the local endpoint set the specified Adaptation Layer Requests that the local endpoint set the specified Adaptation Layer
Indication parameter for all future INIT and INIT-ACK exchanges. Indication parameter for all future INIT and INIT-ACK exchanges.
The following structure is used to access and modify this parameter:
struct sctp_setadaptation { struct sctp_setadaptation {
uint32_t ssb_adaptation_ind; uint32_t ssb_adaptation_ind;
}; };
ssb_adaptation_ind - The adaptation layer indicator that will be
ssb_adaptation_ind: The adaptation layer indicator that will be
included in any outgoing Adaptation Layer Indication parameter. included in any outgoing Adaptation Layer Indication parameter.
8.1.12. Enable/Disable message fragmentation (SCTP_DISABLE_FRAGMENTS) 8.1.11. Enable/Disable Message Fragmentation (SCTP_DISABLE_FRAGMENTS)
This option is a on/off flag and is passed an integer where a non- This option is a on/off flag and is passed an integer where a non-
zero is on and a zero is off. If enabled no SCTP message zero is on and a zero is off. If enabled no SCTP message
fragmentation will be performed. Instead if a message being sent fragmentation will be performed. Instead if a message being sent
exceeds the current PMTU size, the message will NOT be sent and exceeds the current PMTU size, the message will NOT be sent and
instead a error will be indicated to the user. instead a error will be indicated to the user.
8.1.13. Peer Address Parameters (SCTP_PEER_ADDR_PARAMS) 8.1.12. Peer Address Parameters (SCTP_PEER_ADDR_PARAMS)
Applications can enable or disable heartbeats for any peer address of Applications can enable or disable heartbeats for any peer address of
an association, modify an address's heartbeat interval, force a an association, modify an address's heartbeat interval, force a
heartbeat to be sent immediately, and adjust the address's maximum heartbeat to be sent immediately, and adjust the address's maximum
number of retransmissions sent before an address is considered number of retransmissions sent before an address is considered
unreachable. The following structure is used to access and modify an unreachable.
address's parameters:
The following structure is used to access and modify an address's
parameters:
struct sctp_paddrparams { struct sctp_paddrparams {
sctp_assoc_t spp_assoc_id; sctp_assoc_t spp_assoc_id;
struct sockaddr_storage spp_address; struct sockaddr_storage spp_address;
uint32_t spp_hbinterval; uint32_t ssp_hbinterval;
uint16_t spp_pathmaxrxt; uint16_t ssp_pathmaxrxt;
uint32_t spp_pathmtu; uint32_t ssp_pathmtu;
uint32_t spp_flags; uint32_t ssp_flags;
uint32_t spp_ipv6_flowlabel; uint32_t ssp_ipv6_flowlabel;
uint8_t spp_ipv4_tos; uint8_t ssp_ipv4_tos;
}; };
spp_assoc_id - (one-to-many style socket) This is filled in the spp_assoc_id: This parameter is ignored for one-to-one style
application, and identifies the association for this query. sockets. For one-to-many style sockets it identifies the
spp_address - This specifies which address is of interest. association for this query.
spp_hbinterval - This contains the value of the heartbeat interval, spp_address: This specifies which address is of interest.
ssp_hbinterval: This contains the value of the heartbeat interval,
in milliseconds. Note that unless the spp_flag is set to in milliseconds. Note that unless the spp_flag is set to
SPP_HB_ENABLE the value of this field is ignored. Note also that SPP_HB_ENABLE the value of this field is ignored. Note also that
a value of zero indicates the current setting should be left a value of zero indicates the current setting should be left
unchanged. To set an actual value of zero the use of the flag unchanged. To set an actual value of zero the use of the flag
SPP_HB_TIME_IS_ZERO should be used. SPP_HB_TIME_IS_ZERO should be used.
spp_pathmaxrxt - This contains the maximum number of retransmissions ssp_pathmaxrxt: This contains the maximum number of retransmissions
before this address shall be considered unreachable. Note that a before this address shall be considered unreachable. Note that a
value of zero indicates the current setting should be left value of zero indicates the current setting should be left
unchanged. unchanged.
ssp_pathmtu: When Path MTU discovery is disabled the value specified
here will be the "fixed" path MTU (i.e. the value of the spp_flags
field must include the flag SPP_PMTUD_DISABLE). Note that if the
spp_address field is empty then all destinations for this
association will have this fixed path MTU set upon them. If an
address is specified, then only that address will be effected.
Note also that this option cannot be set on the endpoint, but must
be set on each individual association. Also, when disabling PMTU
discovery, the implementation may disallow this behavior if the
"fixed" path MTU is below the constant value SCTP_SMALLEST_PMTU.
spp_pathmtu - When Path MTU discovery is disabled the value spp_ipv6_flowlabel: This field is used in conjunction with the
specified here will be the "fixed" path mtu (i.e. the value of the
spp_flags field must include the flag SPP_PMTUD_DISABLE for this
field to have any effect). Note that if the spp_address field is
empty then all destinations for this association will have this
fixed path mtu set upon them. If an address is specified, then
only that address will be effected. Note also that this option
cannot be set on the endpoint, but must be set on each individual
association. Also, when disabling PMTU discovery, the
implementation may disallow this behavior if the "fixed" path mtu
is below the constant value SCTP_SMALLEST_PMTU.
spp_ipv6_flowlabel- This field is used in conjunction with the
SPP_IPV6_FLOWLABEL flag. SPP_IPV6_FLOWLABEL flag.
spp_ipv4_tos- This field is used in conjunction with the spp_ipv4_tos: This field is used in conjunction with the
SPP_IPV4_TOS flag. SPP_IPV4_TOS flag.
spp_flags- These flags are used to control various features on an spp_flags: These flags are used to control various features on an
association. The flag field is a bit mask which may contain zero association. The flag field is a bit mask which may contain zero
or more of the following options: or more of the following options:
SPP_HB_ENABLE - Enable heartbeats on the specified address. Note SPP_HB_ENABLE: Enable heartbeats on the specified address. Note
that if the address field is empty all addresses for the that if the address field is empty all addresses for the
association have heartbeats enabled upon them. association have heartbeats enabled upon them.
SPP_HB_DISABLE - Disable heartbeats on the specified address. SPP_HB_DISABLE: Disable heartbeats on the specified address.
Note that if the address field is empty all addresses for the Note that if the address field is empty all addresses for the
association will have their heartbeats disabled. Note also association will have their heartbeats disabled. Note also
that SPP_HB_ENABLE and SPP_HB_DISABLE are mutually exclusive, that SPP_HB_ENABLE and SPP_HB_DISABLE are mutually exclusive,
only one of these two should be specified. Enabling both only one of these two should be specified. Enabling both
fields will have undetermined results. fields will have undetermined results.
SPP_HB_DEMAND - Request a user initiated heartbeat to be made SPP_HB_DEMAND: Request a user initiated heartbeat to be made
immediately. immediately.
SPP_HB_TIME_IS_ZERO - Specify's that the time for heartbeat delay SPP_HB_TIME_IS_ZERO: Specify's that the time for heartbeat delay
is to be set to the value of 0 milliseconds. is to be set to the value of 0 milliseconds.
SPP_PMTUD_ENABLE - This field will enable PMTU discovery upon the SPP_PMTUD_ENABLE: This field will enable PMTU discovery upon the
specified address. Note that if the address field is empty specified address. Note that if the address field is empty
then all addresses on the association are effected. then all addresses on the association are effected.
SPP_PMTUD_DISABLE - This field will disable PMTU discovery upon SPP_PMTUD_DISABLE: This field will disable PMTU discovery upon
the specified address. Note that if the address field is empty the specified address. Note that if the address field is empty
then all addresses on the association are effected. Not also then all addresses on the association are effected. Note also
that SPP_PMTUD_ENABLE and SPP_PMTUD_DISABLE are mutually that SPP_PMTUD_ENABLE and SPP_PMTUD_DISABLE are mutually
exclusive. Enabling both will have undetermined results. exclusive. Enabling both will have undetermined results.
SPP_IPV6_FLOWLABEL - Setting this flag enables setting of the SPP_IPV6_FLOWLABEL: Setting this flag enables setting of the IPV6
IPV6 flowlabel value associated with either the association or flowlabel value associated with either the association or the
the specific address. If the address field is filled in, then specific address. If the address field is filled in, then the
the specific destination address has this value set upon it. specific destination address has this value set upon it. If
If the association is specified, but not the address, then the the association is specified, but not the address, then the
flowlabel value is set for any future destination addresses flowlabel value is set for any future destination addresses
that may be added. The value is obtained in the that may be added. The value is obtained in the
spp_ipv6_flowlabel field. spp_ipv6_flowlabel field.
Upon retrieval, this flag will be set to indicate that the Upon retrieval, this flag will be set to indicate that the
spp_ipv6_flowlabel field has a valid value returned. If a spp_ipv6_flowlabel field has a valid value returned. If a
specific destination addresses is set (in the spp_address specific destination addresses is set (in the spp_address
field) when called then the value returned is that of the field) when called then the value returned is that of the
address. If just an association is specified (and no address) address. If just an association is specified (and no address)
then the association default flowlabel is returned. If neither then the association default flowlabel is returned. If neither
an association nor an destination is specified, then the an association nor an destination is specified, then the
sockets default flowlabel is returned. For non IPv6 sockets, sockets default flowlabel is returned. For non IPv6 sockets,
then this flag will be left cleared. then this flag will be left cleared.
SPP_IPV4_TOS - Setting this flag enables setting of the IPV4 tos
SPP_IPV4_TOS: Setting this flag enables setting of the IPV4 tos
value associated with either the association or specific value associated with either the association or specific
address. If the address field is filled in, then the specific address. If the address field is filled in, then the specific
destination address has this value set upon it. If the destination address has this value set upon it. If the
association is specified, but not the address, then the tos association is specified, but not the address, then the tos
value is set for any future destination addresses that may be value is set for any future destination addresses that may be
added. The value is obtained in the spp_ipv4_tos field. added. The value is obtained in the spp_ipv4_tos field.
Upon retrieval, this flag will be set to indicate that the Upon retrieval, this flag will be set to indicate that the
spp_ipv4_tos field has a valid value returned. If a specific spp_ipv4_tos field has a valid value returned. If a specific
destination addresses is set when called (in the spp_address destination addresses is set when called (in the spp_address
field) then that specific destination addresses tos value is field) then that specific destination addresses tos value is
returned. If just an association is specified then the returned. If just an association is specified then the
association default tos is returned. If neither an association association default tos is returned. If neither an association
nor an destination is specified, then the sockets default tos nor an destination is specified, then the sockets default tos
is returned. For non IPv4 sockets, then this flag will be left is returned. For non IPv4 sockets, then this flag will be left
cleared. cleared.
To read or modify these parameters, the application should call To read or modify these parameters, the application should call
sctp_opt_info() with the SCTP_PEER_ADDR_PARAMS option. sctp_opt_info() with the SCTP_PEER_ADDR_PARAMS option.
8.1.14. Set default send parameters (SCTP_DEFAULT_SEND_PARAM) 8.1.13. Set Default Send Parameters (SCTP_DEFAULT_SEND_PARAM)
Applications that wish to use the sendto() system call may wish to Applications that wish to use the sendto() system call may wish to
specify a default set of parameters that would normally be supplied specify a default set of parameters that would normally be supplied
through the inclusion of ancillary data. This socket option allows through the inclusion of ancillary data. This socket option allows
such an application to set the default sctp_sndrcvinfo structure. such an application to set the default sctp_sndrcvinfo structure.
The application that wishes to use this socket option simply passes The application that wishes to use this socket option simply passes
in to this call the sctp_sndrcvinfo structure defined in in to this call the sctp_sndrcvinfo structure defined in
Section 6.2.2. The input parameters accepted by this call include Section 6.2.2. The input parameters accepted by this call include
sinfo_stream, sinfo_flags, sinfo_ppid, sinfo_context, sinfo_pr_policy sinfo_stream, sinfo_flags, sinfo_ppid, sinfo_context, sinfo_pr_policy
and sinfo_pr_value. The sinfo_flags is composed of a bitwise OR of and sinfo_pr_value. The sinfo_flags is composed of a bitwise OR of
SCTP_UNORDERED, SCTP_EOF, and SCTP_SENDALL. The sinfo_assoc_id field SCTP_UNORDERED, SCTP_EOF, and SCTP_SENDALL. The sinfo_assoc_id field
specifies the association to apply the parameters to in a one-to-many specifies the association to apply the parameters to in a one-to-many
style sockets. It is ignored on the one-to-one style. Note that style sockets. It is ignored on the one-to-one style. Note that
setting the sinfo_assoc_id field to zero indicates that the users setting the sinfo_assoc_id field to zero indicates that the users
wishes to set the endpoint default send parameters for all future wishes to set the endpoint default send parameters for all future
associations. associations.
8.1.15. Set notification and ancillary events (SCTP_EVENTS) 8.1.14. Set Notification and Ancillary Events (SCTP_EVENTS)
This socket option is used to specify various notifications and This socket option is used to specify various notifications and
ancillary data the user wishes to receive. Please see Section 8.3) ancillary data the user wishes to receive. Please see Section 8.4
for a full description of this option and its usage. for a full description of this option and its usage.
8.1.16. Set/clear IPv4 mapped addresses (SCTP_I_WANT_MAPPED_V4_ADDR) 8.1.15. Set/Clear IPv4 Mapped Addresses (SCTP_I_WANT_MAPPED_V4_ADDR)
This socket option is a boolean flag which turns on or off mapped V4 This socket option is a boolean flag which turns on or off mapped V4
addresses. If this option is turned on and the socket is type addresses. If this option is turned on and the socket is type
PF_INET6, then IPv4 addresses will be mapped to V6 representation. PF_INET6, then IPv4 addresses will be mapped to V6 representation.
If this option is turned off, then no mapping will be done of V4 If this option is turned off, then no mapping will be done of V4
addresses and a user will receive both PF_INET6 and PF_INET type addresses and a user will receive both PF_INET6 and PF_INET type
addresses on the socket. addresses on the socket.
By default this option is turned off and expects an integer to be By default this option is turned off and expects an integer to be
passed where non-zero turns on the option and zero turns off the passed where non-zero turns on the option and zero turns off the
option. option.
8.1.17. Get or set the maximum fragmentation size (SCTP_MAXSEG) 8.1.16. Get or Set the Maximum Fragmentation Size (SCTP_MAXSEG)
This option will get or set the maximum size to put in any outgoing This option will get or set the maximum size to put in any outgoing
SCTP DATA chunk. If a message is larger than this size it will be SCTP DATA chunk. If a message is larger than this size it will be
fragmented by SCTP into the specified size. Note that the underlying fragmented by SCTP into the specified size. Note that the underlying
SCTP implementation may fragment into smaller sized chunks when the SCTP implementation may fragment into smaller sized chunks when the
PMTU of the underlying association is smaller than the value set by PMTU of the underlying association is smaller than the value set by
the user. The default value for this option is '0' which indicates the user. The default value for this option is '0' which indicates
the user is NOT limiting fragmentation and only the PMTU will effect the user is NOT limiting fragmentation and only the PMTU will effect
SCTP's choice of DATA chunk size. Note also that values set larger SCTP's choice of DATA chunk size. Note also that values set larger
than the maximum size of an IP datagram will effectively let SCTP than the maximum size of an IP datagram will effectively let SCTP
control fragmentation (i.e. the same as setting this option to 0). control fragmentation (i.e. the same as setting this option to 0).
The following structure is used to access and modify this parameter:
struct sctp_assoc_value { struct sctp_assoc_value {
sctp_assoc_t assoc_id; sctp_assoc_t assoc_id;
uint32_t assoc_value; uint32_t assoc_value;
}; };
assoc_id - This parameter, indicates which association the user is assoc_id: This parameter is ignored for one-to-one style sockets.
performing an action upon. Note that if this field's value is For one-to-many style sockets this parameter indicates which
zero then the endpoints default value is changed (effecting future association the user is performing an action upon. Note that if
associations only). this field's value is zero then the endpoints default value is
assoc_value - This parameter specifies the maximum size in bytes. changed (effecting future associations only).
assoc_value: This parameter specifies the maximum size in bytes.
8.1.18. Add a chunk that must be authenticated (SCTP_AUTH_CHUNK)
This set option adds a chunk type that the user is requesting to be
received only in an authenticated way. Changes to the list of chunks
will only effect future associations on the socket.
struct sctp_authchunk {
uint8_t sauth_chunk;
};
sauth_chunks - This parameter contains a chunk type
that the user is requesting to be authenticated.
The chunk types for INIT, INIT-ACK, SHUTDOWN-COMPLETE, and AUTH
chunks MUST NOT be used. If they are used an error MUST be returned.
The usage of this option enables SCTP-AUTH in cases where it is not
required by other means (for example the use of ADD-IP).
Note that this option is write-only. Using this option in a
getsockopt() or sctp_opt_info() call will return EOPNOTSUPP.
8.1.19. Get or set the list of supported HMAC Identifiers 8.1.17. Get or Set the List of Supported HMAC Identifiers
(SCTP_HMAC_IDENT) (SCTP_HMAC_IDENT)
This option gets or sets the list of HMAC algorithms that the local This option gets or sets the list of HMAC algorithms that the local
endpoint requires the peer to use. endpoint requires the peer to use.
The following structure is used to get or set these identifiers:
struct sctp_hmacalgo { struct sctp_hmacalgo {
uint32_t shmac_number_of_idents; uint32_t shmac_number_of_idents;
uint16_t shmac_idents[]; uint16_t shmac_idents[];
}; };
shmac_number_of_idents - This field gives the number of elements shmac_number_of_idents: This field gives the number of elements
present in the array shmac_idents. present in the array shmac_idents.
shmac_idents - This parameter contains an array of HMAC Identifiers shmac_idents: This parameter contains an array of HMAC Identifiers
that the local endpoint is requesting the peer to use, in priority that the local endpoint is requesting the peer to use, in priority
order. The following identifiers are valid: order. The following identifiers are valid:
* SCTP_AUTH_HMAC_ID_SHA1
* SCTP_AUTH_HMAC_ID_SHA256
1) SCTP_AUTH_HMAC_ID_SHA1 Note that the list supplied must include SCTP_AUTH_HMAC_ID_SHA1 and
2) SCTP_AUTH_HMAC_ID_SHA256 (optional) may include any of the other values in its preferred order (lowest
3) SCTP_AUTH_HMAC_ID_SHA224 (optional) list position has the most preference in algorithm selection). Note
4) SCTP_AUTH_HMAC_ID_SHA384 (optional) also that the lack of SCTP_AUTH_HMAC_ID_SHA1, or the inclusion of an
4) SCTP_AUTH_HMAC_ID_SHA512 (optional) unknown HMAC identifier (including optional identifiers unknown to
the implementation) will cause the set option to fail and return an
Note that the list supplied must include SHA1 and may include any error.
of the other values in its preferred order (lowest list postion
has the most preference in algorithm selection). Note also that
the lack of SHA1, or the inclusion of an unknown HMAC identifier
(including optional identifers unknown to the implementation) will
cause the set option to fail and return an error.
8.1.20. Set a shared key (SCTP_AUTH_KEY)
This option will set a shared secret key which is used to build an
association shared key.
struct sctp_authkey {
sctp_assoc_t sca_assoc_id;
uint16_t sca_keynumber;
uint16_t sca_keylength;
uint8_t sca_key[];
};
sca_assoc_id - This parameter, if non-zero, indicates what
association that the shared key is being set upon. Note that if
this element contains zero, then the shared key is set upon the
endpoint and all future associations will use this key (if not
changed by subsequent calls to SCTP_AUTH_KEY). For one-to-one
sockets, this parameter is ignored. Note, however, that this
option will set a key on the association if the socket is
connected, otherwise this will set a key on the endpoint.
sca_keynumber - this parameter is the shared key identifier by which
the application will refer to this key. If a key of the specified
index already exists, then this new key will replace the old
existing key. Note that shared key identifier '0' defaults to a
null key.
sca_keylength - this parameter is the length of the array sca_key.
sca_key - This parameter contains an array of bytes that is to be
used by the endpoint (or association) as the shared secret key.
Note, if the length of this field is zero, a null key is set.
Note that this option is write-only. Using this option in a
getsockopt() or sctp_opt_info() call will return EOPNOTSUPP.
8.1.21. Get or set the active shared key (SCTP_AUTH_ACTIVE_KEY) 8.1.18. Get or Set the Active Shared Key (SCTP_AUTH_ACTIVE_KEY)
This option will get or set the active shared key to be used to build This option will get or set the active shared key to be used to build
the association shared key. the association shared key.
The following structure is used to access and modify these
parameters:
struct sctp_authkeyid { struct sctp_authkeyid {
sctp_assoc_t scact_assoc_id; sctp_assoc_t scact_assoc_id;
uint16_t scact_keynumber; uint16_t scact_keynumber;
}; };
scact_assoc_id - This parameter, if non-zero, indicates what scact_assoc_id: This parameter, if non-zero, indicates what
association that the shared key identifier is being set active association that the shared key identifier is being set active
upon. Note that if this element contains zero, then the upon. Note that if this element contains zero, then the
activation applies to the endpoint and all future associations activation applies to the endpoint and all future associations
will use the specified shared key identifier. For one-to-one will use the specified shared key identifier. For one-to-one
sockets, this parameter is ignored. Note, however, that this sockets, this parameter is ignored. Note, however, that this
option will set the active key on the association if the socket is option will set the active key on the association if the socket is
connected, otherwise this will set the default active key for the connected, otherwise this will set the default active key for the
endpoint. endpoint.
scact_keynumber - this parameter is the shared key identifier which scact_keynumber: This parameter is the shared key identifier which
the application is requesting to become the active shared key to the application is requesting to become the active shared key to
be used for sending authenticated chunks. The key identifier MUST be used for sending authenticated chunks. The key identifier MUST
correspond to an existing shared key. Note that shared key correspond to an existing shared key. Note that shared key
identifier '0' defaults to a null key. identifier '0' defaults to a null key.
When used with setsockopt() the SCTP implementation MUST use the
indicated shared key identifier for all messages being sent after
the setsockopt() call until changed again. Therefore the SCTP
implementation MUST NOT bundle user messages which should be
authenticated using different shared key identifiers.
8.1.22. Delete a shared key (SCTP_AUTH_DELETE_KEY)
This set option will delete a shared secret key in the SCTP
implementation.
struct sctp_authkeyid {
sctp_assoc_t scact_assoc_id;
uint16_t scact_keynumber;
};
scact_assoc_id - This parameter, if non-zero, indicates what
association that the shared key identifier is being deleted from.
Note that if this element contains zero, then the shared key is
deleted from the endpoint and all associations will no longer use
the specified shared key identifier (unless otherwise set on the
association using SCTP_AUTH_KEY). For one-to-one sockets, this
parameter is ignored. Note, however, that this option will delete
the key from the association if the socket is connected, otherwise
this will delete the key from the endpoint.
scact_keynumber - this parameter is the shared key identifier which
the application is requesting to be deleted. The key identifier
MUST correspond to an existing shared key and MUST NOT be in use
for any packet being sent by the SCTP implementation. This means
in particular, that it MUST be deactivated first. Note if this
parameter is zero, use of the null key identifier '0' is deleted
from the endpoint and/or association.
Note that this option is write-only. Using this option in a
getsockopt() or sctp_opt_info() call will return EOPNOTSUPP.
8.1.23. Delete a shared key (SCTP_AUTH_DEACTIVATE_KEY)
This set option indicates that the application will not send user
messages anymore requiring the usage of the indicated key identifier.
struct sctp_authkeyid { When used with setsockopt() the SCTP implementation MUST use the
sctp_assoc_t scact_assoc_id; indicated shared key identifier for all messages being given to an
uint16_t scact_keynumber; SCTP implementation via a send call after the setsockopt() call until
}; changed again. Therefore the SCTP implementation MUST NOT bundle
user messages which should be authenticated using different shared
scact_assoc_id - This parameter, if non-zero, indicates what key identifiers.
association that the shared key identifier is being deactivated.
Note that if this element contains zero, then the shared key is
deactivated for the endpoint and all associations will no longer
use the specified shared key identifier (unless otherwise set on
the association using SCTP_AUTH_KEY). For one-to-one sockets,
this parameter is ignored. Note, however, that this option will
deactivate the key from the association if the socket is
connected, otherwise this will deactivate the key from the
endpoint.
scact_keynumber - this parameter is the shared key identifier which
the application is requesting to be deactivated. The key
identifier MUST correspond to an existing shared key. Note if
this parameter is zero, use of the null key identifier '0' is
deactivated on the endpoint and/or association.
Note that this option is write-only. Using this option in a Initially the key with key identifier 0 is the active key.
getsockopt() or sctp_opt_info() call will return EOPNOTSUPP.
8.1.24. Get or set delayed ack timer (SCTP_DELAYED_SACK) 8.1.19. Get or Set Delayed SACK Timer (SCTP_DELAYED_SACK)
This option will effect the way delayed acks are performed. This This option will effect the way delayed acks are performed. This
option allows you to get or set the delayed ack time, in option allows you to get or set the delayed ack time, in
milliseconds. It also allows changing the delayed ack frequency. milliseconds. It also allows changing the delayed ack frequency.
Changing the frequency to 1 disables the delayed sack algorithm. If Changing the frequency to 1 disables the delayed sack algorithm. If
the assoc_id is 0, then this sets or gets the endpoints default the sack_assoc_id is 0, then this sets or gets the endpoints default
values. If the assoc_id field is non-zero, then the set or get values. If the sack_assoc_id field is non-zero, then the set or get
effects the specified association for the one to many model (the effects the specified association for the one to many model (the
assoc_id field is ignored by the one to one model). Note that if assoc_id field is ignored by the one to one model). Note that if
sack_delay or sack_freq are 0 when setting this option, then the sack_delay or sack_freq are 0 when setting this option, then the
current values will remain unchanged. current values will remain unchanged.
The following structure is used to access and modify these
parameters:
struct sctp_sack_info { struct sctp_sack_info {
sctp_assoc_t sack_assoc_id; sctp_assoc_t sack_assoc_id;
uint32_t sack_delay; uint32_t sack_delay;
uint32_t sack_freq; uint32_t sack_freq;
}; };
sack_assoc_id - This parameter, indicates which association the user sack_assoc_id: This parameter is ignored for one-to-one style
is performing an action upon. Note that if this field's value is sockets. For one-to-many style sockets this parameter indicates
zero then the endpoints default value is changed (effecting future which association the user is performing an action upon. Note
associations only). that if this field's value is zero then the endpoints default
sack_delay - This parameter contains the number of milliseconds that value is changed (effecting future associations only).
sack_delay: This parameter contains the number of milliseconds that
the user is requesting the delayed ACK timer be set to. Note that the user is requesting the delayed ACK timer be set to. Note that
this value is defined in the standard to be between 200 and 500 this value is defined in the standard to be between 200 and 500
milliseconds. milliseconds.
sack_freq - This parameter contains the number of packets that must sack_freq: This parameter contains the number of packets that must
be received before a sack is sent without waiting for the delay be received before a sack is sent without waiting for the delay
timer to expire. The default value for this is 2, setting this timer to expire. The default value for this is 2, setting this
value to 1 will disable the delayed sack algorithm. value to 1 will disable the delayed sack algorithm.
8.1.25. Get or set fragmented interleave (SCTP_FRAGMENT_INTERLEAVE) 8.1.20. Get or Set Fragmented Interleave (SCTP_FRAGMENT_INTERLEAVE)
Fragmented interleave controls how the presentation of messages Fragmented interleave controls how the presentation of messages
occurs for the message receiver. There are three levels of fragment occurs for the message receiver. There are three levels of fragment
interleave defined. Two of the levels effect the one-to-one model, interleave defined. Two of the levels effect the one-to-one model,
while the one-to-many model is effected by all three levels. while the one-to-many model is effected by all three levels.
This option takes an integer value. It can be set to a value of 0, 1 This option takes an integer value. It can be set to a value of 0, 1
or 2. Attempting to set this level to other values will return an or 2. Attempting to set this level to other values will return an
error. error.
Setting the three levels provides the following receiver Setting the three levels provides the following receiver
interactions: interactions:
level 0 - Prevents the interleaving of any messages. This means level 0: Prevents the interleaving of any messages. This means that
that when a partial delivery begins, no other messages will be when a partial delivery begins, no other messages will be received
received except the message being partially delivered. If another except the message being partially delivered. If another message
message arrives on a different stream (or association) that could arrives on a different stream (or association) that could be
be delivered, it will be blocked waiting for the user to read all delivered, it will be blocked waiting for the user to read all of
of the partially delivered message. the partially delivered message.
level 1: Allows interleaving of messages that are from different
level 1 - Allows interleaving of messages that are from different
associations. For the one-to-one model, level 0 and level 1 thus associations. For the one-to-one model, level 0 and level 1 thus
have the same meaning since a one-to-one socket always receives have the same meaning since a one-to-one socket always receives
messages from the same association. Note that setting the one-to- messages from the same association. Note that setting the one-to-
many model to this level may cause multiple partial delivers from many model to this level may cause multiple partial delivers from
different associations but for any given association, only one different associations but for any given association, only one
message will be delivered until all parts of a message have been message will be delivered until all parts of a message have been
delivered. This means that one large message, being read with an delivered. This means that one large message, being read with an
association identification of "X", will block other messages from association identification of "X", will block other messages from
association "X" from being delivered. association "X" from being delivered.
level 2 - Allows complete interleaving of messages. This level level 2: Allows complete interleaving of messages. This level
requires that the sender carefully observe not only the peer requires that the sender carefully observe not only the peer
association identification (or address) but also must pay careful association identification (or address) but also must pay careful
attention to the stream number. With this option enabled a attention to the stream number. With this option enabled a
partially delivered message may begin being delivered for partially delivered message may begin being delivered for
association "X" stream "Y" and the next subsequent receive may association "X" stream "Y" and the next subsequent receive may
return a message from association "X" stream "Z". Note that no return a message from association "X" stream "Z". Note that no
other messages would be delivered for association "X" stream "Y" other messages would be delivered for association "X" stream "Y"
until all of stream "Y"'s partially delivered message was read. until all of stream "Y"'s partially delivered message was read.
Note that this option also effects the one-to-one model. Also Note that this option also effects the one-to-one model. Also
note that for the one-to-many model not only may another streams note that for the one-to-many model not only may another streams
skipping to change at page 63, line 37 skipping to change at page 57, line 8
receive, some other associations message may be delivered upon the receive, some other associations message may be delivered upon the
next receive. next receive.
An implementation should default the one-to-many model to level 1. An implementation should default the one-to-many model to level 1.
The reason for this is that otherwise it is possible that a peer The reason for this is that otherwise it is possible that a peer
could begin sending a partial message and thus block all other peers could begin sending a partial message and thus block all other peers
from sending data. However a setting of level 2 requires the from sending data. However a setting of level 2 requires the
application to not only be aware of the association (via the application to not only be aware of the association (via the
association id or peers address) but also the stream number. The association id or peers address) but also the stream number. The
stream number is NOT present unless the user has subscribed to the stream number is NOT present unless the user has subscribed to the
sctp_data_io_events (see Section 8.3). This is also why we recommend sctp_data_io_events (see Section 8.4). This is also why we recommend
that the one-to-one model be defaulted to level 0 (level 1 for the that the one-to-one model be defaulted to level 0 (level 1 for the
one-to-one model has no effect). Note that an implementation should one-to-one model has no effect). Note that an implementation should
return an error if a application attempts to set the level to 2 and return an error if a application attempts to set the level to 2 and
has NOT subscribed to the sctp_data_io_events. has NOT subscribed to the sctp_data_io_events.
8.1.26. Set or Get the sctp partial delivery point 8.1.21. Set or Get the SCTP Partial Delivery Point
(SCTP_PARTIAL_DELIVERY_POINT) (SCTP_PARTIAL_DELIVERY_POINT)
This option will set or get the SCTP partial delivery point. This This option will set or get the SCTP partial delivery point. This
point is the size of a message where the partial delivery API will be point is the size of a message where the partial delivery API will be
invoked to help free up rwnd space for the peer. Setting this to a invoked to help free up rwnd space for the peer. Setting this to a
lower value will cause partial deliveries to happen more often. The lower value will cause partial deliveries to happen more often. The
calls argument is an integer that sets or gets the partial delivery calls argument is an integer that sets or gets the partial delivery
point. Note also that the call will fail if the user attempts to set point. Note also that the call will fail if the user attempts to set
this value larger than the socket receive buffer size. this value larger than the socket receive buffer size.
Note that any single message having a length smaller than or equal to Note that any single message having a length smaller than or equal to
the SCTP partial delivery point will be delivered in one single read the SCTP partial delivery point will be delivered in one single read
call as long as the user provided buffer is large enough to hold the call as long as the user provided buffer is large enough to hold the
message. message.
8.1.27. Set or Get the use of extended receive info 8.1.22. Set or Get the Use of Extended Receive Info
(SCTP_USE_EXT_RCVINFO) (SCTP_USE_EXT_RCVINFO)
This option will enable or disable the use of the extended version of This option will enable or disable the use of the extended version of
the sctp_sndrcvinfo structure. If this option is disabled, then the the sctp_sndrcvinfo structure. If this option is disabled, then the
normal sctp_sndrcvinfo structure is returned in all receive message normal sctp_sndrcvinfo structure is returned in all receive message
calls. If this option is enabled then the sctp_extrcvinfo structure calls. If this option is enabled then the sctp_extrcvinfo structure
is returned in all receive message calls. is returned in all receive message calls.
Note that the sctp_extrcvinfo structure is never used in any send Note that the sctp_extrcvinfo structure is never used in any send
call. call.
8.1.28. Set or Get the auto asconf flag (SCTP_AUTO_ASCONF) 8.1.23. Set or Get the Auto ASCONF Flag (SCTP_AUTO_ASCONF)
This option will enable or disable the use of the automatic This option will enable or disable the use of the automatic
generation of ASCONF chunks to add and delete addresses to an generation of ASCONF chunks to add and delete addresses to an
existing association. Note that this option has two caveats namely: existing association. Note that this option has two caveats namely:
a) it only effects sockets that are bound to all addresses on the a) it only effects sockets that are bound to all addresses on the
machine, and b) the system administrator may have an overriding machine, and b) the system administrator may have an overriding
control that turns the asconf feature off no matter what setting the control that turns the ASCONF feature off no matter what setting the
socket option may have. socket option may have.
8.1.29. Set or Get the maximum burst (SCTP_MAX_BURST) 8.1.24. Set or Get the Maximum Burst (SCTP_MAX_BURST)
This option will allow a user to change the maximum burst of packets This option will allow a user to change the maximum burst of packets
that can be emitted by this association. Note that the default value that can be emitted by this association. Note that the default value
is 4, and some implementations may restrict this setting so that it is 4, and some implementations may restrict this setting so that it
can only be lowered. can only be lowered.
To set or get this option the user fills in the following structure: To set or get this option the user fills in the following structure:
struct sctp_assoc_value { struct sctp_assoc_value {
sctp_assoc_t assoc_id; sctp_assoc_t assoc_id;
uint32_t assoc_value; uint32_t assoc_value;
}; };
assoc_id - This parameter, indicates which association the user is assoc_id: This parameter is ignored for one-to-one style sockets.
performing an action upon. Note that if this field's value is For one-to-many style sockets this parameter indicates which
zero then the endpoints default value is changed (effecting future association the user is performing an action upon. Note that if
associations only). this field's value is zero then the endpoints default value is
changed (effecting future associations only).
assoc_value - This parameter contains the maximum burst. assoc_value: This parameter contains the maximum burst.
8.1.30. Set or Get the default context (SCTP_CONTEXT) 8.1.25. Set or Get the Default Context (SCTP_CONTEXT)
The context field in the sctp_sndrcvinfo structure is normally only The context field in the sctp_sndrcvinfo structure is normally only
used when a failed message is retrieved holding the value that was used when a failed message is retrieved holding the value that was
sent down on the actual send call. This option allows the setting of sent down on the actual send call. This option allows the setting of
a default context on an association basis that will be received on a default context on an association basis that will be received on
reading messages from the peer. This is especially helpful in the reading messages from the peer. This is especially helpful in the
one-2-many model for an application to keep some reference to an one-2-many model for an application to keep some reference to an
internal state machine that is processing messages on the internal state machine that is processing messages on the
association. Note that the setting of this value only effects association. Note that the setting of this value only effects
received messages from the peer and does not effect the value that is received messages from the peer and does not effect the value that is
saved with outbound messages. saved with outbound messages.
To set or get this option the user fills in the following structure: To set or get this option the user fills in the following structure:
struct sctp_assoc_value { struct sctp_assoc_value {
sctp_assoc_t assoc_id; sctp_assoc_t assoc_id;
uint32_t assoc_value; uint32_t assoc_value;
}; };
assoc_id - This parameter, indicates which association the user is assoc_id: This parameter is ignored for one-to-one style sockets.
performing an action upon. Note that if this field's value is For one-to-many style sockets this parameter indicates which
zero then the endpoints default value is changed (effecting future association the user is performing an action upon. Note that if
associations only). this field's value is zero then the endpoints default value is
assoc_value - This parameter contains the context. changed (effecting future associations only).
8.1.31. Enable or disable explicit EOR marking (SCTP_EXPLICIT_EOR) assoc_value: This parameter contains the context.
This boolean flag is used to enable or disable explict end of record 8.1.26. Enable or Disable Explicit EOR Marking (SCTP_EXPLICIT_EOR)
This boolean flag is used to enable or disable explicit end of record
(EOR) marking. When this option is enabled, a user may make multiple (EOR) marking. When this option is enabled, a user may make multiple
send system calls to send a record and must indicate that they are send system calls to send a record and must indicate that they are
finished sending a particular record by including on the send the finished sending a particular record by including on the send the
SCTP_EOR flag. If this boolean flag is disabled then each individual SCTP_EOR flag. If this boolean flag is disabled then each individual
send system call is considered to have a SCTP_EOR indicator set on it send system call is considered to have a SCTP_EOR indicator set on it
implicitly without the user having to explicitly add this flag. implicitly without the user having to explicitly add this flag.
8.1.32. Enable SCTP port reusage (SCTP_REUSE_PORT) 8.1.27. Enable SCTP Port Reusage (SCTP_REUSE_PORT)
This option only supports one-to-one style SCTP sockets. If used on This option only supports one-to-one style SCTP sockets. If used on
a one-to-many style SCTP socket an error is indicated. a one-to-many style SCTP socket an error is indicated.
The setsockopt() call MUST NOT be used after calling bind() or The setsockopt() call MUST NOT be used after calling bind() or
sctp_bindx() for an one-to-one style SCTP socket. If using bind() or sctp_bindx() for a one-to-one style SCTP socket. If using bind() or
sctp_bindx() on a socket with the SCTP_REUSE_PORT option, all other sctp_bindx() on a socket with the SCTP_REUSE_PORT option, all other
SCTP sockets bound to the same port MUST have set the SCTP sockets bound to the same port MUST have set the
SCTP_REUSE_PORT. Calling bind() or sctp_bindx() for a socket without SCTP_REUSE_PORT. Calling bind() or sctp_bindx() for a socket without
having set the SCTP_REUSE_PORT option will fail if there are other having set the SCTP_REUSE_PORT option will fail if there are other
sockets bound to the same port. At most one socket being bound to sockets bound to the same port. At most one socket being bound to
the same port may be listening. the same port may be listening.
It should be noted that the behaviour of the socket level socket It should be noted that the behaviour of the socket level socket
option to reuse ports and/or addresses for SCTP sockets in option to reuse ports and/or addresses for SCTP sockets is
unspecified. unspecified.
8.2. Read-Only Options 8.2. Read-Only Options
The options defined in this subsection are read-only. Using this
option in a setsockopt() call will result in a error indicating
EOPNOTSUPP.
8.2.1. Association Status (SCTP_STATUS) 8.2.1. Association Status (SCTP_STATUS)
Applications can retrieve current status information about an Applications can retrieve current status information about an
association, including association state, peer receiver window size, association, including association state, peer receiver window size,
number of unacked data chunks, and number of data chunks pending number of unacked data chunks, and number of data chunks pending
receipt. This information is read-only. The following structure is receipt. This information is read-only.
used to access this information:
The following structure is used to access this information:
struct sctp_status { struct sctp_status {
sctp_assoc_t sstat_assoc_id; sctp_assoc_t sstat_assoc_id;
int32_t sstat_state; int32_t sstat_state;
uint32_t sstat_rwnd; uint32_t sstat_rwnd;
uint16_t sstat_unackdata; uint16_t sstat_unackdata;
uint16_t sstat_penddata; uint16_t sstat_penddata;
uint16_t sstat_instrms; uint16_t sstat_instrms;
uint16_t sstat_outstrms; uint16_t sstat_outstrms;
uint32_t sstat_fragmentation_point; uint32_t sstat_fragmentation_point;
struct sctp_paddrinfo sstat_primary; struct sctp_paddrinfo sstat_primary;
}; };
sstat_state - This contains the association's current state one of sstat_assoc_id: This parameter is ignored for one-to-one style
sockets. For one-to-many style sockets it holds the identifier
for the association. All notifications for a given association
have the same association identifier.
sstat_state: This contains the association's current state one of
the following values: the following values:
SCTP_CLOSED * SCTP_CLOSED
SCTP_BOUND * SCTP_BOUND
SCTP_LISTEN * SCTP_LISTEN
SCTP_COOKIE_WAIT * SCTP_COOKIE_WAIT
SCTP_COOKIE_ECHOED * SCTP_COOKIE_ECHOED
SCTP_ESTABLISHED * SCTP_ESTABLISHED
SCTP_SHUTDOWN_PENDING * SCTP_SHUTDOWN_PENDING
SCTP_SHUTDOWN_SENT * SCTP_SHUTDOWN_SENT
SCTP_SHUTDOWN_RECEIVED * SCTP_SHUTDOWN_RECEIVED
SCTP_SHUTDOWN_ACK_SENT * SCTP_SHUTDOWN_ACK_SENT
sstat_rwnd - This contains the association peer's current receiver sstat_rwnd: This contains the association peer's current receiver
window size. window size.
sstat_unackdata - This is the number of unacked data chunks. sstat_unackdata: This is the number of unacked data chunks.
sstat_penddata - This is the number of data chunks pending receipt. sstat_penddata: This is the number of data chunks pending receipt.
sstat_primary - This is information on the current primary peer sstat_primary: This is information on the current primary peer
address. address.
sstat_assoc_id - (one-to-many style socket) This holds the an sstat_instrms: The number of streams that the peer will be using
identifier for the association. All notifications for a given
association have the same association identifier.
sstat_instrms - The number of streams that the peer will be using
inbound. inbound.
sstat_outstrms - The number of streams that the endpoint is allowed sstat_outstrms: The number of streams that the endpoint is allowed
to use outbound. to use outbound.
sstat_fragmentation_point - The size at which SCTP fragmentation sstat_fragmentation_point - The size at which SCTP fragmentation
will occur. will occur.
To access these status values, the application calls getsockopt() To access these status values, the application calls getsockopt()
with the option name SCTP_STATUS. The sstat_assoc_id parameter is with the option name SCTP_STATUS.
ignored for one-to-one style socket.
8.2.2. Peer Address Information (SCTP_GET_PEER_ADDR_INFO) 8.2.2. Peer Address Information (SCTP_GET_PEER_ADDR_INFO)
Applications can retrieve information about a specific peer address Applications can retrieve information about a specific peer address
of an association, including its reachability state, congestion of an association, including its reachability state, congestion
window, and retransmission timer values. This information is read- window, and retransmission timer values. This information is read-
only. The following structure is used to access this information: only.
The following structure is used to access this information:
struct sctp_paddrinfo { struct sctp_paddrinfo {
sctp_assoc_t spinfo_assoc_id; sctp_assoc_t spinfo_assoc_id;
struct sockaddr_storage spinfo_address; struct sockaddr_storage spinfo_address;
int32_t spinfo_state; int32_t spinfo_state;
uint32_t spinfo_cwnd; uint32_t spinfo_cwnd;
uint32_t spinfo_srtt; uint32_t spinfo_srtt;
uint32_t spinfo_rto; uint32_t spinfo_rto;
uint32_t spinfo_mtu; uint32_t spinfo_mtu;
}; };
spinfo_address - This is filled in the application, and contains the spinfo_assoc_id: This is parameter is ignored for one-to-one style
sockets. For one-to-many style sockets the following applies:
This is field may be filled in by the application, if so, this
field will have priority in looking up the association over the
address specified in spinfo_address. Note that if the address
does not belong to the association specified then this call will
fail. If the application does NOT fill in the spinfo_assoc_id,
then the address will be used to lookup the association and on
return this field will have the valid association id. In other
words, this call can be used to translate a address into an
association id.
spinfo_address: This is filled in the application, and contains the
peer address of interest. peer address of interest.
spinfo_state: This contains the peer addresses's state (either
On return from getsockopt():
spinfo_state - This contains the peer addresses's state (either
SCTP_ACTIVE or SCTP_INACTIVE and possibly the modifier SCTP_ACTIVE or SCTP_INACTIVE and possibly the modifier
SCTP_UNCONFIRMED) SCTP_UNCONFIRMED).
spinfo_cwnd - This contains the peer addresses's current congestion spinfo_cwnd: This contains the peer addresses's current congestion
window. window.
spinfo_srtt - This contains the peer addresses's current smoothed spinfo_srtt: This contains the peer addresses's current smoothed
round-trip time calculation in milliseconds. round-trip time calculation in milliseconds.
spinfo_rto - This contains the peer addresses's current spinfo_rto: This contains the peer addresses's current
retransmission timeout value in milliseconds. retransmission timeout value in milliseconds.
spinfo_mtu - The current P-MTU of this address. spinfo_mtu: The current P-MTU of this address.
spinfo_assoc_id - This is field may be filled in by the application,
if so, this field will have priority in looking up the association
over the address specified in spinfo_address. Note that if the
address does not belong to the association specified then this
call will fail. If the application does NOT fill in the
spinfo_assoc_id, then the address will be used to lookup the
association and on return this field will have the valid
association id. In other words, this call can be used to
translate a address into an association id.
To retrieve this information, use sctp_opt_info() with the
SCTP_GET_PEER_ADDR_INFO options.
8.2.3. Get the list of chunks the peer requires to be authenticated 8.2.3. Get the List of Chunks the Peer Requires to be Authenticated
(SCTP_PEER_AUTH_CHUNKS) (SCTP_PEER_AUTH_CHUNKS)
This option gets a list of chunks for a specified association that This option gets a list of chunks for a specified association that
the peer requires to be received authenticated only. the peer requires to be received authenticated only.
The following structure is used to access these parameters:
struct sctp_authchunks { struct sctp_authchunks {
sctp_assoc_t gauth_assoc_id; sctp_assoc_t gauth_assoc_id;
guint32_t gauth_number_of_chunks guint32_t gauth_number_of_chunks
uint8_t gauth_chunks[]; uint8_t gauth_chunks[];
}; };
gauth_assoc_id - This parameter, indicates which association the gauth_assoc_id: This parameter, indicates which association the user
user is requesting the list of peer authenticated chunks. For is requesting the list of peer authenticated chunks. For one-to-
one-to-one sockets, this parameter is ignored. one sockets, this parameter is ignored.
gauth_number_of_chunks - This parameter gives the number of elements gauth_number_of_chunks: This parameter gives the number of elements
in the array gauth_chunks. in the array gauth_chunks.
gauth_chunks - This parameter contains an array of chunks that the gauth_chunks: This parameter contains an array of chunks that the
peer is requesting to be authenticated. peer is requesting to be authenticated.
8.2.4. Get the list of chunks the local endpoint requires to be 8.2.4. Get the List of Chunks the Local Endpoint Requires to be
authenticated (SCTP_LOCAL_AUTH_CHUNKS) Authenticated (SCTP_LOCAL_AUTH_CHUNKS)
This option gets a list of chunks for a specified association that This option gets a list of chunks for a specified association that
the local endpoint requires to be received authenticated only. the local endpoint requires to be received authenticated only.
The following structure is used to access these parameters:
struct sctp_authchunks { struct sctp_authchunks {
sctp_assoc_t gauth_assoc_id; sctp_assoc_t gauth_assoc_id;
uint32_t gauth_number_of_chunks; uint32_t gauth_number_of_chunks;
uint8_t gauth_chunks[]; uint8_t gauth_chunks[];
}; };
gauth_assoc_id - This parameter, indicates which association the gauth_assoc_id: This parameter, indicates which association the user
user is requesting the list of local authenticated chunks. For is requesting the list of local authenticated chunks. For one-to-
one-to-one sockets, this parameter is ignored. one sockets, this parameter is ignored.
gauth_number_of_chunks - This parameter gives the number of elements gauth_number_of_chunks: This parameter gives the number of elements
in the array gauth_chunks. in the array gauth_chunks.
gauth_chunks - This parameter contains an array of chunks that the gauth_chunks: This parameter contains an array of chunks that the
local endpoint is requesting to be authenticated. local endpoint is requesting to be authenticated.
8.2.5. Get the current number of associations (SCTP_GET_ASSOC_NUMBER) 8.2.5. Get the Current Number of Associations (SCTP_GET_ASSOC_NUMBER)
This option gets the current number of associations that are attached This option gets the current number of associations that are attached
to a one-to-many style socket. The option value is an uint32_t. to a one-to-many style socket. The option value is an uint32_t.
8.2.6. Get the current identifiers of associations 8.2.6. Get the Current Identifiers of Associations
(SCTP_GET_ASSOC_ID_LIST) (SCTP_GET_ASSOC_ID_LIST)
This option gets the current list of SCTP association identifiers of This option gets the current list of SCTP association identifiers of
the SCTP associations handled by a one-to-many style socket. The the SCTP associations handled by a one-to-many style socket.
option value has the structure
The option value has the structure
struct sctp_assoc_ids { struct sctp_assoc_ids {
uint32_t gaids_number_of_ids; uint32_t gaids_number_of_ids;
sctp_assoc_t gaids_assoc_id[]; sctp_assoc_t gaids_assoc_id[];
}; };
The caller MUST provide a large enough buffer to hold all association The caller MUST provide a large enough buffer to hold all association
identifiers. If the buffer is too small, an error MUST be returned. identifiers. If the buffer is too small, an error MUST be returned.
The user can use the SCTP_GET_ASSOC_NUMBER socket option to get an The user can use the SCTP_GET_ASSOC_NUMBER socket option to get an
idea how large the buffer has to be. gaids_number_of_ids gives the idea how large the buffer has to be. gaids_number_of_ids gives the
number of elements in the array gaids_assoc_id. number of elements in the array gaids_assoc_id.
8.3. Ancillary Data and Notification Interest Options 8.3. Write-Only Options
The options defined in this subsection are write-only. Using this
option in a getsockopt() or sctp_opt_info() call will result in a
error indicating EOPNOTSUPP.
8.3.1. Set Peer Primary Address (SCTP_SET_PEER_PRIMARY_ADDR)
Requests that the peer mark the enclosed address as the association
primary. The enclosed address must be one of the association's
locally bound addresses.
The following structure is used to make a set peer primary request:
struct sctp_setpeerprim {
sctp_assoc_t sspp_assoc_id;
struct sockaddr_storage sspp_addr;
};
sspp_addr: The address to set as primary.
sspp_assoc_id: This parameter is ignored for one-to-one style
sockets. For one-to-many style sockets it identifies the
association for this request.
8.3.2. Add a Chunk That Must Be Authenticated (SCTP_AUTH_CHUNK)
This set option adds a chunk type that the user is requesting to be
received only in an authenticated way. Changes to the list of chunks
will only effect future associations on the socket.
The following structure is used to add a chunk:
struct sctp_authchunk {
uint8_t sauth_chunk;
};
sauth_chunk: This parameter contains a chunk type that the user is
requesting to be authenticated.
The chunk types for INIT, INIT-ACK, SHUTDOWN-COMPLETE, and AUTH
chunks MUST NOT be used. If they are used, an error MUST be
returned. The usage of this option enables SCTP-AUTH in cases where
it is not required by other means (for example the use of dynamic
address reconfiguration).
8.3.3. Set a Shared Key (SCTP_AUTH_KEY)
This option will set a shared secret key which is used to build an
association shared key.
The following structure is used to access and modify these
parameters:
struct sctp_authkey {
sctp_assoc_t sca_assoc_id;
uint16_t sca_keynumber;
uint16_t sca_keylength;
uint8_t sca_key[];
};
sca_assoc_id: This parameter, if non-zero, indicates what
association that the shared key is being set upon. Note that if
this element contains zero, then the shared key is set upon the
endpoint and all future associations will use this key (if not
changed by subsequent calls to SCTP_AUTH_KEY). For one-to-one
sockets, this parameter is ignored. Note, however, that this
option will set a key on the association if the socket is
connected, otherwise this will set a key on the endpoint.
sca_keynumber: This parameter is the shared key identifier by which
the application will refer to this key. If a key of the specified
index already exists, then this new key will replace the old
existing key. Note that shared key identifier '0' defaults to a
null key.
sca_keylength: This parameter is the length of the array sca_key.
sca_key: This parameter contains an array of bytes that is to be
used by the endpoint (or association) as the shared secret key.
Note, if the length of this field is zero, a null key is set.
8.3.4. Deactivate a Shared Key (SCTP_AUTH_DEACTIVATE_KEY)
This set option indicates that the application will not send user
messages anymore requiring the usage of the indicated key identifier.
struct sctp_authkeyid {
sctp_assoc_t scact_assoc_id;
uint16_t scact_keynumber;
};
scact_assoc_id: This parameter, if non-zero, indicates what
association that the shared key identifier is being deactivated.
Note that if this element contains zero, then the shared key is
deactivated for the endpoint and all associations will no longer
use the specified shared key identifier (unless otherwise set on
the association using SCTP_AUTH_KEY). For one-to-one sockets,
this parameter is ignored. Note, however, that this option will
deactivate the key from the association if the socket is
connected, otherwise this will deactivate the key from the
endpoint.
scact_keynumber: This parameter is the shared key identifier which
the application is requesting to be deactivated. The key
identifier MUST correspond to an existing shared key. Note if
this parameter is zero, use of the null key identifier '0' is
deactivated on the endpoint and/or association.
The currently active key can not be deactivated.
8.3.5. Delete a Shared Key (SCTP_AUTH_DELETE_KEY)
This set option will delete a shared secret key in the SCTP
implementation.
struct sctp_authkeyid {
sctp_assoc_t scact_assoc_id;
uint16_t scact_keynumber;
};
scact_assoc_id: This parameter, if non-zero, indicates what
association that the shared key identifier is being deleted from.
Note that if this element contains zero, then the shared key is
deleted from the endpoint and all associations will no longer use
the specified shared key identifier (unless otherwise set on the
association using SCTP_AUTH_KEY). For one-to-one sockets, this
parameter is ignored. Note, however, that this option will delete
the key from the association if the socket is connected, otherwise
this will delete the key from the endpoint.
scact_keynumber: This parameter is the shared key identifier which
the application is requesting to be deleted. The key identifier
MUST correspond to an existing shared key and MUST NOT be in use
for any packet being sent by the SCTP implementation. This means
in particular, that it MUST be deactivated first. Note if this
parameter is zero, use of the null key identifier '0' is deleted
from the endpoint and/or association.
Only deactivated keys which are no longer used by the kernel can be
deleted.
8.4. Ancillary Data and Notification Interest Options
Applications can receive per-message ancillary information and Applications can receive per-message ancillary information and
notifications of certain SCTP events with recvmsg(). notifications of certain SCTP events with recvmsg().
The following optional information is available to the application: The following optional information is available to the application:
SCTP_SNDRCV (sctp_data_io_event): Per-message information (i.e.
1. SCTP_SNDRCV (sctp_data_io_event): Per-message information (i.e.
stream number, TSN, SSN, etc. described in Section 6.2.2) stream number, TSN, SSN, etc. described in Section 6.2.2)
2. SCTP_ASSOC_CHANGE (sctp_association_event): (described in SCTP_ASSOC_CHANGE (sctp_association_event): described in
Section 6.3.1.1) Section 6.3.2
3. SCTP_PEER_ADDR_CHANGE (sctp_address_event): (described in SCTP_PEER_ADDR_CHANGE (sctp_address_event): described in
Section 6.3.1.2) Section 6.3.3
4. SCTP_SEND_FAILED (sctp_send_failure_event): (described in SCTP_SEND_FAILED (sctp_send_failure_event): described in
Section 6.3.1.4) Section 6.3.5
5. SCTP_REMOTE_ERROR (sctp_peer_error_event): (described in SCTP_REMOTE_ERROR (sctp_peer_error_event): described in
Section 6.3.1.3) Section 6.3.4
6. SCTP_SHUTDOWN_EVENT (sctp_shtudown_event): (described in SCTP_SHUTDOWN_EVENT (sctp_shtudown_event): described in
Section 6.3.1.5) Section 6.3.6
7. SCTP_PARTIAL_DELIVERY_EVENT (sctp_partial_delivery_event): SCTP_PARTIAL_DELIVERY_EVENT (sctp_partial_delivery_event): described
(described in Section 6.3.1.7) in Section 6.3.8
8. SCTP_ADAPTATION_INDICATION (sctp_adaptation_layer_event): SCTP_ADAPTATION_INDICATION (sctp_adaptation_layer_event): described
(described in Section 6.3.1.6) in Section 6.3.7
9. SCTP_AUTHENTICATION_INDICATION (sctp_authentication_event): SCTP_AUTHENTICATION_INDICATION (sctp_authentication_event):
(described in Section 6.3.1.8) described in Section 6.3.9)
SCTP_SENDER_DRY_EVENT (sctp_sender_dry_event): described in
Section 6.3.10
To receive any ancillary data or notifications, first the application To receive any ancillary data or notifications, first the application
registers it's interest by calling the SCTP_EVENTS setsockopt() with registers its interest by calling the SCTP_EVENTS setsockopt() with
the following structure. the following structure:
struct sctp_event_subscribe{ struct sctp_event_subscribe{
uint8_t sctp_data_io_event; uint8_t sctp_data_io_event;
uint8_t sctp_association_event; uint8_t sctp_association_event;
uint8_t sctp_address_event; uint8_t sctp_address_event;
uint8_t sctp_send_failure_event; uint8_t sctp_send_failure_event;
uint8_t sctp_peer_error_event; uint8_t sctp_peer_error_event;
uint8_t sctp_shutdown_event; uint8_t sctp_shutdown_event;
uint8_t sctp_partial_delivery_event; uint8_t sctp_partial_delivery_event;
uint8_t sctp_adaptation_layer_event; uint8_t sctp_adaptation_layer_event;
uint8_t sctp_authentication_event; uint8_t sctp_authentication_event;
uint8_t sctp_sender_dry_event;
}; };
sctp_data_io_event: Setting this flag to 1 will cause the reception
sctp_data_io_event - Setting this flag to 1 will cause the reception of SCTP_SNDRCV information on a per message basis. The
of SCTP_SNDRCV information on a per message basis. The application application will need to use the recvmsg() interface so that it
will need to use the recvmsg() interface so that it can receive the can receive the event information contained in the msg_control
event information contained in the msg_control field. Please see field. Setting the flag to 0 will disable reception of the
Section 6.2 for further details. Setting the flag to 0 will disable message control information.
reception of the message control information. sctp_association_event: Setting this flag to 1 will enable the
reception of association event notifications. Setting the flag to
sctp_association_event - Setting this flag to 1 will enable the 0 will disable association event notifications.
reception of association event notifications. Setting the flag to 0 sctp_address_event: Setting this flag to 1 will enable the reception
will disable association event notifications. For more information of address event notifications. Setting the flag to 0 will
on event notifications please see Section 6.3. disable address event notifications.
sctp_send_failure_event: Setting this flag to 1 will enable the
sctp_address_event - Setting this flag to 1 will enable the reception reception of send failure event notifications. Setting the flag
of address event notifications. Setting the flag to 0 will disable to 0 will disable send failure event notifications.
address event notifications. For more information on event sctp_peer_error_event: Setting this flag to 1 will enable the
notifications please see Section 6.3. reception of peer error event notifications. Setting the flag to
0 will disable peer error event notifications.
sctp_send_failure_event - Setting this flag to 1 will enable the sctp_shutdown_event: Setting this flag to 1 will enable the
reception of send failure event notifications. Setting the flag to 0
will disable send failure event notifications. For more information
on event notifications please see Section 6.3.
sctp_peer_error_event - Setting this flag to 1 will enable the
reception of peer error event notifications. Setting the flag to 0
will disable peer error event notifications. For more information on
event notifications please see Section 6.3.
sctp_shutdown_event - Setting this flag to 1 will enable the
reception of shutdown event notifications. Setting the flag to 0 reception of shutdown event notifications. Setting the flag to 0
will disable shutdown event notifications. For more information on will disable shutdown event notifications.
event notifications please see Section 6.3. sctp_partial_delivery_event: Setting this flag to 1 will enable the
reception of partial delivery notifications. Setting the flag to
sctp_partial_delivery_event - Setting this flag to 1 will enable the 0 will disable partial delivery event notifications.
reception of partial delivery notifications. Setting the flag to 0 sctp_adaptation_layer_event: Setting this flag to 1 will enable the
will disable partial delivery event notifications. For more reception of adaptation layer notifications. Setting the flag to
information on event notifications please see Section 6.3. 0 will disable adaptation layer event notifications.
sctp_authentication_event: Setting this flag to 1 will enable the
sctp_adaptation_layer_event - Setting this flag to 1 will enable the reception of authentication layer notifications. Setting the flag
reception of adaptation layer notifications. Setting the flag to 0 to 0 will disable authentication layer event notifications.
will disable adaptation layer event notifications. For more sctp_sender_dry_event: Setting this flag to 1 will enable the
information on event notifications please see Section 6.3. reception of sender dry notifications. Setting the flag to 0 will
disable sender dry event notifications.
sctp_authentication_event - Setting this flag to 1 will enable the
reception of authentication layer notifications. Setting the flag to
0 will disable authentication layer event notifications. For More
information please see Section 6.3.
An example where an application would like to receive data io events An example where an application would like to receive data io events
and association events but no others would be as follows: and association events but no others would be as follows:
{ {
struct sctp_event_subscribe event; struct sctp_event_subscribe event;
memset(&event,0,sizeof(event)); memset(&event,0,sizeof(event));
event.sctp_data_io_event = 1; event.sctp_data_io_event = 1;
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{ {
struct sctp_event_subscribe event; struct sctp_event_subscribe event;
memset(&event,0,sizeof(event)); memset(&event,0,sizeof(event));
event.sctp_data_io_event = 1; event.sctp_data_io_event = 1;
event.sctp_association_event = 1; event.sctp_association_event = 1;
setsockopt(fd, IPPROTO_SCTP, SCTP_EVENTS, &event, sizeof(event)); setsockopt(fd, IPPROTO_SCTP, SCTP_EVENTS, &event, sizeof(event));
} }
Note that for one-to-many style SCTP sockets, the caller of recvmsg() Note that for one-to-many style SCTP sockets, the caller of recvmsg()
receives ancillary data and notifications for ALL associations bound receives ancillary data and notifications for ALL associations bound
to the file descriptor. For one-to-one style SCTP sockets, the to the file descriptor. For one-to-one style SCTP sockets, the
caller receives ancillary data and notifications for only the single caller receives ancillary data and notifications for only the single
association bound to the file descriptor. association bound to the file descriptor.
By default both the one-to-one style and one-to-many style socket has By default both the one-to-one style and one-to-many style socket has
all options off. all options off.
9. New Interfaces 9. New Functions
Depending on the system, the following interface can be implemented Depending on the system, the following interface can be implemented
as a system call or library function. as a system call or library function.
9.1. sctp_bindx() 9.1. sctp_bindx()
The syntax of sctp_bindx() is, This function allows the user to bind a specific subset of addresses
or, if the SCTP extension described in [RFC5061] is supported, add or
delete specific addresses.
int sctp_bindx(int sd, struct sockaddr *addrs, int addrcnt, The function prototype is
int sctp_bindx(int sd,
struct sockaddr *addrs,
int addrcnt,
int flags); int flags);
If sd is an IPv4 socket, the addresses passed must be IPv4 addresses. If sd is an IPv4 socket, the addresses passed must be IPv4 addresses.
If the sd is an IPv6 socket, the addresses passed can either be IPv4 If the sd is an IPv6 socket, the addresses passed can either be IPv4
or IPv6 addresses. or IPv6 addresses.
A single address may be specified as INADDR_ANY or IN6ADDR_ANY, see A single address may be specified as INADDR_ANY or IN6ADDR_ANY, see
Section 4.1.2 for this usage. Section 4.1.2 for this usage.
addrs is a pointer to an array of one or more socket addresses. Each addrs is a pointer to an array of one or more socket addresses. Each
skipping to change at page 73, line 13 skipping to change at page 69, line 8
result in an error. result in an error.
On success, sctp_bindx() returns 0. On failure, sctp_bindx() returns On success, sctp_bindx() returns 0. On failure, sctp_bindx() returns
-1, and sets errno to the appropriate error code. -1, and sets errno to the appropriate error code.
For SCTP, the port given in each socket address must be the same, or For SCTP, the port given in each socket address must be the same, or
sctp_bindx() will fail, setting errno to EINVAL. sctp_bindx() will fail, setting errno to EINVAL.
The flags parameter is formed from the bitwise OR of zero or more of The flags parameter is formed from the bitwise OR of zero or more of
the following currently defined flags: the following currently defined flags:
o SCTP_BINDX_ADD_ADDR
SCTP_BINDX_ADD_ADDR o SCTP_BINDX_REM_ADDR
SCTP_BINDX_REM_ADDR
SCTP_BINDX_ADD_ADDR directs SCTP to add the given addresses to the SCTP_BINDX_ADD_ADDR directs SCTP to add the given addresses to the
association, and SCTP_BINDX_REM_ADDR directs SCTP to remove the given association, and SCTP_BINDX_REM_ADDR directs SCTP to remove the given
addresses from the association. The two flags are mutually addresses from the association. The two flags are mutually
exclusive; if both are given, sctp_bindx() will fail with EINVAL. A exclusive; if both are given, sctp_bindx() will fail with EINVAL. A
caller may not remove all addresses from an association; sctp_bindx() caller may not remove all addresses from an association; sctp_bindx()
will reject such an attempt with EINVAL. will reject such an attempt with EINVAL.
An application can use sctp_bindx(SCTP_BINDX_ADD_ADDR) to associate An application can use sctp_bindx(SCTP_BINDX_ADD_ADDR) to associate
additional addresses with an endpoint after calling bind(). Or use additional addresses with an endpoint after calling bind(). Or use
sctp_bindx(SCTP_BINDX_REM_ADDR) to remove some addresses a listening sctp_bindx(SCTP_BINDX_REM_ADDR) to remove some addresses a listening
skipping to change at page 73, line 46 skipping to change at page 69, line 38
functionality should return EOPNOTSUPP. functionality should return EOPNOTSUPP.
sctp_bindx() can be called on an already bound socket or on an sctp_bindx() can be called on an already bound socket or on an
unbound socket. If the socket is unbound and the first port number unbound socket. If the socket is unbound and the first port number
in the addrs is zero, the kernel will chose a port number. All port in the addrs is zero, the kernel will chose a port number. All port
numbers after the first one being 0 MUST also be zero. If the first numbers after the first one being 0 MUST also be zero. If the first
port number is not zero, the following port numbers MUST be zero or port number is not zero, the following port numbers MUST be zero or
have the same value as the first one. For an already bound socket, have the same value as the first one. For an already bound socket,
all port numbers provided MUST be the bound one or 0. all port numbers provided MUST be the bound one or 0.
bindx() is an atomic operation. Therefore the binding will be either sctp_bindx() is an atomic operation. Therefore the binding will be
successful on all addresses or fail on all addresses. If multiple either successful on all addresses or fail on all addresses. If
addresses are provided and the bindx() call fails there is no multiple addresses are provided and the sctp_bindx() call fails there
indication which address is responsable for the failure. The only is no indication which address is responsible for the failure. The
way to get an specific error indication is to call bindx() with only only way to get an specific error indication is to call sctp_bindx()
one address sequentially. with only one address sequentially.
9.2. Branched-off Association 9.2. sctp_peeloff()
After an association is established on a one-to-many style socket, After an association is established on a one-to-many style socket,
the application may wish to branch off the association into a the application may wish to branch off the association into a
separate socket/file descriptor. separate socket/file descriptor.
This is particularly desirable when, for instance, the application This is particularly desirable when, for instance, the application
wishes to have a number of sporadic message senders/receivers remain wishes to have a number of sporadic message senders/receivers remain
under the original one-to-many style socket but branch off those under the original one-to-many style socket but branch off those
associations carrying high volume data traffic into their own associations carrying high volume data traffic into their own
separate socket descriptors. separate socket descriptors.
The application uses sctp_peeloff() call to branch off an association The application uses sctp_peeloff() call to branch off an association
into a separate socket (Note the semantics are somewhat changed from into a separate socket (Note the semantics are somewhat changed from
the traditional one-to-one style accept() call). Note that the new the traditional one-to-one style accept() call). Note that the new
socket is a one-to-one style socket. Thus it will be confined to socket is a one-to-one style socket. Thus it will be confined to
operations allowed for a one-to-one style socket. operations allowed for a one-to-one style socket.
The syntax is: The function prototype is
new_sd = sctp_peeloff(int sd, sctp_assoc_t assoc_id); int sctp_peeloff(int sd,
sctp_assoc_t assoc_id);
new_sd: the new socket descriptor representing the branched-off and the arguments are
association. sd: The original one-to-many style socket descriptor returned from
sd: the original one-to-many style socket descriptor returned from
the socket() system call (see Section 4.1.1). the socket() system call (see Section 4.1.1).
assoc_id: the specified identifier of the association that is to be assoc_id: the specified identifier of the association that is to be
branched off to a separate file descriptor (Note, in a traditional branched off to a separate file descriptor (Note, in a traditional
one-to-one style accept() call, this would be an out parameter, one-to-one style accept() call, this would be an out parameter,
but for the one-to-many style call, this is an in parameter). but for the one-to-many style call, this is an in parameter).
The function returns a non-negative file descriptor representing the
branched-off association, or -1 if an error occurred. The variable
errno is then set appropriately.
9.3. sctp_getpaddrs() 9.3. sctp_getpaddrs()
sctp_getpaddrs() returns all peer addresses in an association. The sctp_getpaddrs() returns all peer addresses in an association.
syntax is,
int sctp_getpaddrs(int sd, sctp_assoc_t id, The function protoype is:
int sctp_getpaddrs(int sd,
sctp_assoc_t id,
struct sockaddr **addrs); struct sockaddr **addrs);
On return, addrs will point to an array dynamically allocated On return, addrs will point to an array dynamically allocated
sockaddr structures of the appropriate type for the socket type. The sockaddr structures of the appropriate type for the socket type. The
caller should use sctp_freepaddrs() to free the memory. Note that caller should use sctp_freepaddrs() to free the memory. Note that
the in/out parameter addrs must not be NULL. the in/out parameter addrs must not be NULL.
If sd is an IPv4 socket, the addresses returned will be all IPv4 If sd is an IPv4 socket, the addresses returned will be all IPv4
addresses. If sd is an IPv6 socket, the addresses returned can be a addresses. If sd is an IPv6 socket, the addresses returned can be a
mix of IPv4 or IPv6 addresses. mix of IPv4 or IPv6 addresses.
skipping to change at page 75, line 16 skipping to change at page 71, line 13
For one-to-one style sockets, id is ignored. For one-to-one style sockets, id is ignored.
On success, sctp_getpaddrs() returns the number of peer addresses in On success, sctp_getpaddrs() returns the number of peer addresses in
the association. If there is no association on this socket, the association. If there is no association on this socket,
sctp_getpaddrs() returns 0, and the value of *addrs is undefined. If sctp_getpaddrs() returns 0, and the value of *addrs is undefined. If
an error occurs, sctp_getpaddrs() returns -1, and the value of *addrs an error occurs, sctp_getpaddrs() returns -1, and the value of *addrs
is undefined. is undefined.
9.4. sctp_freepaddrs() 9.4. sctp_freepaddrs()
sctp_freepaddrs() frees all resources allocated by sctp_freepaddrs() frees all resources allocated by sctp_getpaddrs().
sctp_getpaddrs(). Its syntax is,
The function prototype is
void sctp_freepaddrs(struct sockaddr *addrs); void sctp_freepaddrs(struct sockaddr *addrs);
addrs is the array of peer addresses returned by sctp_getpaddrs().
and addrs is the array of peer addresses returned by
sctp_getpaddrs().
9.5. sctp_getladdrs() 9.5. sctp_getladdrs()
sctp_getladdrs() returns all locally bound address(es) on a socket. sctp_getladdrs() returns all locally bound address(es) on a socket.
The syntax is,
int sctp_getladdrs(int sd, sctp_assoc_t id, The function prototype is
int sctp_getladdrs(int sd,
sctp_assoc_t id,
struct sockaddr **ss); struct sockaddr **ss);
On return, addrs will point to a dynamically allocated array of On return, addrs will point to a dynamically allocated array of
sockaddr structures of the appropriate type for the socket type. The sockaddr structures of the appropriate type for the socket type. The
caller should use sctp_freeladdrs() to free the memory. Note that caller should use sctp_freeladdrs() to free the memory. Note that
the in/out parameter addrs must not be NULL. the in/out parameter addrs must not be NULL.
If sd is an IPv4 socket, the addresses returned will be all IPv4 If sd is an IPv4 socket, the addresses returned will be all IPv4
addresses. If sd is an IPv6 socket, the addresses returned can be a addresses. If sd is an IPv6 socket, the addresses returned can be a
mix of IPv4 or IPv6 addresses. mix of IPv4 or IPv6 addresses.
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If the id field is set to the value '0' then the locally bound If the id field is set to the value '0' then the locally bound
addresses are returned without regard to any particular association. addresses are returned without regard to any particular association.
On success, sctp_getladdrs() returns the number of local addresses On success, sctp_getladdrs() returns the number of local addresses
bound to the socket. If the socket is unbound, sctp_getladdrs() bound to the socket. If the socket is unbound, sctp_getladdrs()
returns 0, and the value of *addrs is undefined. If an error occurs, returns 0, and the value of *addrs is undefined. If an error occurs,
sctp_getladdrs() returns -1, and the value of *addrs is undefined. sctp_getladdrs() returns -1, and the value of *addrs is undefined.
9.6. sctp_freeladdrs() 9.6. sctp_freeladdrs()
sctp_freeladdrs() frees all resources allocated by sctp_freeladdrs() frees all resources allocated by sctp_getladdrs().
sctp_getladdrs(). Its syntax is,
The function prototype is
void sctp_freeladdrs(struct sockaddr *addrs); void sctp_freeladdrs(struct sockaddr *addrs);
addrs is the array of peer addresses returned by sctp_getladdrs(). and addrs is the array of peer addresses returned by
sctp_getladdrs().
9.7. sctp_sendmsg() 9.7. sctp_sendmsg()
An implementation may provide a library function (or possibly system An implementation may provide a library function (or possibly system
call) to assist the user with the advanced features of SCTP. call) to assist the user with the advanced features of SCTP.
sctp_sendmsg(). Its syntax is, The function prototype is
ssize_t sctp_sendmsg(int sd, ssize_t sctp_sendmsg(int sd,
const void *msg, const void *msg,
size_t len, size_t len,
const struct sockaddr *to, const struct sockaddr *to,
socklen_t tolen, socklen_t tolen,
uint32_t ppid, uint32_t ppid,
uint32_t flags, uint32_t flags,
uint16_t stream_no, uint16_t stream_no,
uint32_t pr_value, uint32_t pr_value,
uint32_t context) uint32_t context);
sd - is the socket descriptor and the arguments are:
msg - is the message to be sent. sd: The socket descriptor
len - is the length of the message. msg: The message to be sent.
to - is the destination address of the message. len: Yhe length of the message.
tolen - is the length of the destination address. to: The destination address of the message.
ppid - is the same as sinfo_ppid (see section 5.2.2) tolen: The length of the destination address.
flags - is the same as sinfo_flags (see section 5.2.2) ppid: The same as sinfo_ppid (see Section 6.2.2)
stream_no - is the same as sinfo_stream (see section 5.2.2) flags: The same as sinfo_flags (see Section 6.2.2)
pr_value - is the same as sinfo_pr_value (see section 5.2.2). stream_no: The same as sinfo_stream (see Section 6.2.2)
context - is the same as sinfo_context (see section 5.2.2) pr_value: The same as sinfo_pr_value (see Section 6.2.2).
context: The same as sinfo_context (see Section 6.2.2)
The call returns the number of characters sent, or -1 if an error The call returns the number of characters sent, or -1 if an error
occurred. The variable errno is then set appropriately. Sending a occurred. The variable errno is then set appropriately.
message using sctp_sendmsg() is atomic unless explicit EOR marking is
enabled on the socket specified by sd. Using sendto() on a non- Sending a message using sctp_sendmsg() is atomic unless explicit EOR
connected one-to-one style socket for implicit connection setup may marking is enabled on the socket specified by sd.
or may not work depending on the SCTP implementation.
Using sctp_sendmsg() on a non-connected one-to-one style socket for
implicit connection setup may or may not work depending on the SCTP
implementation.
9.8. sctp_recvmsg() 9.8. sctp_recvmsg()
An implementation may provide a library function (or possibly system An implementation may provide a library function (or possibly system
call) to assist the user with the advanced features of SCTP. Note call) to assist the user with the advanced features of SCTP. Note
that in order for the sctp_sndrcvinfo structure to be filled in by that in order for the sctp_sndrcvinfo structure to be filled in by
sctp_recvmsg() the caller must enable the sctp_data_io_events with sctp_recvmsg() the caller must enable the sctp_data_io_events with
the SCTP_EVENTS option. Note that the setting of the the SCTP_EVENTS option. Note that the setting of the
SCTP_USE_EXT_RCVINFO will effect this function as well, causing the SCTP_USE_EXT_RCVINFO will effect this function as well, causing the
sctp_sndrcvinfo information to be extended. sctp_sndrcvinfo information to be extended.
sctp_recvmsg(). Its syntax is, The function prototype is
ssize_t sctp_recvmsg(int sd, ssize_t sctp_recvmsg(int sd,
void *msg, void *msg,
size_t len, size_t len,
struct sockaddr *from, struct sockaddr *from,
socklen_t *fromlen socklen_t *fromlen
struct sctp_sndrcvinfo *sinfo struct sctp_sndrcvinfo *sinfo
int *msg_flags) int *msg_flags);
sd - is the socket descriptor and the arguments are
msg - is a message buffer to be filled. sd: The socket descriptor.
len - is the length of the message buffer. msg: The message buffer to be filled.
from - is a pointer to a address to be filled with the sender of len: The length of the message buffer.
this messages address. from: A pointer to a address to be filled with the sender of this
fromlen - is the from length. messages address.
sinfo - A pointer to a sctp_sndrcvinfo structure to be filled upon fromlen: An in/out parameter describing the from length.
sinfo: A pointer to a sctp_sndrcvinfo structure to be filled upon
receipt of the message. receipt of the message.
msg_flags - A pointer to a integer to be filled with any message msg_flags: A pointer to a integer to be filled with any message
flags (e.g. MSG_NOTIFICATION). flags (e.g. MSG_NOTIFICATION). Note that this field is an in-out
field. Options for the receive may also be passed into the value
(e.g. MSG_PEEK). On return from the call, the msg_flags value
will be different than what was sent in to the call. If
implemented via a recvmsg() call, the msg_flags should only
contain the value of the flags from the recvmsg() call.
The call returns the number of bytes received, or -1 if an error The call returns the number of bytes received, or -1 if an error
occurred. The variable errno is then set appropriately. occurred. The variable errno is then set appropriately.
9.9. sctp_connectx() 9.9. sctp_connectx()
An implementation may provide a library function (or possibly system An implementation may provide a library function (or possibly system
call) to assist the user with associating to an endpoint that is call) to assist the user with associating to an endpoint that is
multi-homed. Much like sctp_bindx() this call allows a caller to multi-homed. Much like sctp_bindx() this call allows a caller to
specify multiple addresses at which a peer can be reached. The way specify multiple addresses at which a peer can be reached. The way
the SCTP stack uses the list of addresses to set up the association the SCTP stack uses the list of addresses to set up the association
is implementation dependent. This function only specifies that the is implementation dependent. This function only specifies that the
stack will try to make use of all the addresses in the list when stack will try to make use of all the addresses in the list when
needed. needed.
Note that the list of addresses passed in is only used for setting up Note that the list of addresses passed in is only used for setting up
the association. It does not necessarily equal the set of addresses the association. It does not necessarily equal the set of addresses
the peer uses for the resulting association. If the caller wants to the peer uses for the resulting association. If the caller wants to
find out the set of peer addresses, it must use sctp_getpaddrs() to find out the set of peer addresses, it must use sctp_getpaddrs() to
retrieve them after the association has been set up. retrieve them after the association has been set up.
sctp_connectx(). Its syntax is, The function prototype is
int sctp_connectx(int sd, int sctp_connectx(int sd,
struct sockaddr *addrs, struct sockaddr *addrs,
int addrcnt, int addrcnt,
sctp_assoc_t *id) sctp_assoc_t *id);
sd - is the socket descriptor and the arguments are:
addrs - is an array of addresses. sd: The socket descriptor.
addrcnt - is the number of addresses in the array. addrs: An (packed) array of addresses.
id - is an output parameter that if passed in as a non-NULL will addrcnt: The number of addresses in the array.
return the association identification for the newly created id: An output parameter that if passed in as a non-NULL will return
association (if successful). the association identification for the newly created association
(if successful).
The call returns 0 on success or -1 if an error occurred. The The call returns 0 on success or -1 if an error occurred. The
variable errno is then set appropriately. variable errno is then set appropriately.
9.10. sctp_send() 9.10. sctp_send()
An implementation may provide another alternative function or system An implementation may provide another alternative function or system
call to assist an application with the sending of data without the call to assist an application with the sending of data without the
use of the CMSG header structures. The function takes the following use of the CMSG header structures.
form:
sctp_send(). Its syntax is, The function prototype is
int sctp_send(int sd, ssize_t sctp_send(int sd,
const void *msg, const void *msg,
size_t len, size_t len,
const struct sctp_sndrcvinfo *sinfo, const struct sctp_sndrcvinfo *sinfo,
int flags); int flags);
sd - is the socket descriptor and the arguments are
msg - The message to be sent sd: The socket descriptor.
len - The length of the message
sinfo - A pointer to a sctp_sndrcvinfo structure used as described
in 5.2.2 for a sendmsg call.
flags - is used in the same format as the sendmsg call flags (e.g. msg: The message to be sent.
len: The length of the message.
sinfo: A pointer to a sctp_sndrcvinfo structure used as described in
Section 6.2.2 for a sendmsg call.
flags: The same flags as used by the sendmsg call flags (e.g.
MSG_DONTROUTE). MSG_DONTROUTE).
The call returns the number of bytes sent, or -1 if an error
occurred. The variable errno is then set appropriately.
This function call may also be used to terminate an association using This function call may also be used to terminate an association using
an association identification by setting the sinfo.sinfo_flags to an association identification by setting the sinfo.sinfo_flags to
SCTP_EOF and the sinfo.sinfo_assoc_id to the association that needs SCTP_EOF and the sinfo.sinfo_assoc_id to the association that needs
to be terminated. In such a case the len of the message would be to be terminated. In such a case the len of the message would be
zero. zero.
Using sctp_send() on a non-connected one-to-one style socket for Using sctp_send() on a non-connected one-to-one style socket for
implicit connection setup may or may not work depending on the SCTP implicit connection setup may or may not work depending on the SCTP
implementation. implementation.
Sending a message using sctp_send() is atomic unless explicit EOR Sending a message using sctp_send() is atomic unless explicit EOR
marking is enabled on the socket specified by sd. The call returns marking is enabled on the socket specified by sd.
the number of characters sent, or -1 if an error occurred. The
variable errno is then set appropriately.
9.11. sctp_sendx() 9.11. sctp_sendx()
An implementation may provide another alternative function or system An implementation may provide another alternative function or system
call to assist an application with the sending of data without the call to assist an application with the sending of data without the
use of the CMSG header structures that also gives a list of use of the CMSG header structures that also gives a list of
addresses. The list of addresses is provided for implicit addresses. The list of addresses is provided for implicit
association setup. In such a case the list of addresses serves the association setup. In such a case the list of addresses serves the
same purpose as the addresses given in sctp_connectx (see same purpose as the addresses given in sctp_connectx() (see
Section 9.9). Section 9.9).
sctp_sendx(). Its syntax is, The function prototype is
int sctp_sendx(int sd, ssize_t sctp_sendx(int sd,
const void *msg, const void *msg,
size_t len, size_t len,
struct sockaddr *addrs, struct sockaddr *addrs,
int addrcnt, int addrcnt,
struct sctp_sndrcvinfo *sinfo, struct sctp_sndrcvinfo *sinfo,
int flags); int flags);
sd - is the socket descriptor and the arguments are:
msg - The message to be sent sd: The socket descriptor.
len - The length of the message
addrs - is an array of addresses.
addrcnt - is the number of addresses in the array.
sinfo - A pointer to a sctp_sndrcvinfo structure used as described msg: The message to be sent.
in 5.2.2 for a sendmsg call. len: The length of the message.
flags - is used in the same format as the sendmsg call flags (e.g. addrs: is an array of addresses.
addrcnt: The number of addresses in the array.
sinfo: A pointer to a sctp_sndrcvinfo structure used as described in
Section 6.2.2 for a sendmsg call.
flags: The same flags as used by the sendmsg call flags (e.g.
MSG_DONTROUTE). MSG_DONTROUTE).
The call returns the number of bytes sent, or -1 if an error
occurred. The variable errno is then set appropriately.
Note that on return from this call the sinfo structure will have Note that on return from this call the sinfo structure will have
changed in that the sinfo_assoc_id will be filled in with the new changed in that the sinfo_assoc_id will be filled in with the new
association id. association id.
This function call may also be used to terminate an association using This function call may also be used to terminate an association using
an association identification by setting the sinfo.sinfo_flags to an association identification by setting the sinfo.sinfo_flags to
SCTP_EOF and the sinfo.sinfo_assoc_id to the association that needs SCTP_EOF and the sinfo.sinfo_assoc_id to the association that needs
to be terminated. In such a case the len of the message would be to be terminated. In such a case the len of the message would be
zero. zero.
Sending a message using sctp_send() is atomic unless explicit EOR Sending a message using sctp_send() is atomic unless explicit EOR
marking is enabled on the socket specified by sd. The call returns marking is enabled on the socket specified by sd.
the number of characters sent, or -1 if an error occurred. The
variable errno is then set appropriately.
Using sctp_sendx() on a non-connected one-to-one style socket for Using sctp_sendx() on a non-connected one-to-one style socket for
implicit connection setup may or may not work depending on the SCTP implicit connection setup may or may not work depending on the SCTP
implementation. implementation.
9.12. sctp_getaddrlen 9.12. sctp_getaddrlen()
For application binary portability it is sometimes desirable to know For application binary portability it is sometimes desirable to know
what the kernel thinks is the length of a socket address family. what the kernel thinks is the length of a socket address family.
This function, when called with a valid family type will return the
length that the operating system uses in the specified family's The function prototype is:
socket address structure.
int sctp_getaddrlen(sa_family_t family); int sctp_getaddrlen(sa_family_t family);
10. IANA considerations This function, when called with a valid family type returns the
length that the operating system uses in the specified family's
socket address structure. In case of an error, -1 is returned an the
variable errno is then set appropriately
This document contains no IANA considerations. 10. IANA Considerations
This document requires no actions from IANA.
11. Security Considerations 11. Security Considerations
Many TCP and UDP implementations reserve port numbers below 1024 for Many TCP and UDP implementations reserve port numbers below 1024 for
privileged users. If the target platform supports privileged users, privileged users. If the target platform supports privileged users,
the SCTP implementation SHOULD restrict the ability to call bind() or the SCTP implementation SHOULD restrict the ability to call bind() or
sctp_bindx() on these port numbers to privileged users. sctp_bindx() on these port numbers to privileged users.
Similarly unprivileged users should not be able to set protocol Similarly unprivileged users should not be able to set protocol
parameters which could result in the congestion control algorithm parameters which could result in the congestion control algorithm
skipping to change at page 81, line 18 skipping to change at page 77, line 25
parameters are: parameters are:
o struct sctp_rtoinfo o struct sctp_rtoinfo
If an unprivileged user inherits a one-to-many style socket with open If an unprivileged user inherits a one-to-many style socket with open
associations on a privileged port, it MAY be permitted to accept new associations on a privileged port, it MAY be permitted to accept new
associations, but it SHOULD NOT be permitted to open new associations, but it SHOULD NOT be permitted to open new
associations. This could be relevant for the r* family of protocols. associations. This could be relevant for the r* family of protocols.
Applications using the one-to-many style sockets and using the Applications using the one-to-many style sockets and using the
interleave level if 0 are subject to denial of service attacks as interleave level if 0 are subject to denial of service attacks as
described in Section 8.1.25. described in Section 8.1.20.
12. IANA Considerations
There are no actions required from IANA.
13. Acknowledgments 12. Acknowledgments
Special acknowledgment is given to Ken Fujita, Jonathan Woods, Special acknowledgment is given to Ken Fujita, Jonathan Woods,
Qiaobing Xie, and La Monte Yarroll, who helped extensively in the Qiaobing Xie, and La Monte Yarroll, who helped extensively in the
early formation of this document. early formation of this document.
The authors also wish to thank Kavitha Baratakke, Mike Bartlett, Jon The authors also wish to thank Kavitha Baratakke, Mike Bartlett, Jon
Berger, Mark Butler, Scott Kimble, Renee Revis, Andreas Fink, Berger, Mark Butler, Scott Kimble, Renee Revis, Andreas Fink,
Jonathan Leighton and many others on the TSVWG mailing list for Jonathan Leighton, and many others on the TSVWG mailing list for
contributing valuable comments. contributing valuable comments.
A special thanks to Phillip Conrad, for his suggested text, quick and A special thanks to Phillip Conrad, for his suggested text, quick and
constructive insights, and most of all his persistent fighting to constructive insights, and most of all his persistent fighting to
keep the interface to SCTP usable for the application programmer. keep the interface to SCTP usable for the application programmer.
14. Normative references 13. Normative References
[RFC0793] Postel, J., "Transmission Control Protocol", STD 7, [RFC0793] Postel, J., "Transmission Control Protocol", STD 7,
RFC 793, September 1981. RFC 793, September 1981.
[RFC0768] Postel, J., "User Datagram Protocol", STD 6, RFC 768, [RFC0768] Postel, J., "User Datagram Protocol", STD 6, RFC 768,
August 1980. August 1980.
[RFC1644] Braden, B., "T/TCP -- TCP Extensions for Transactions [RFC1644] Braden, B., "T/TCP -- TCP Extensions for Transactions
Functional Specification", RFC 1644, July 1994. Functional Specification", RFC 1644, July 1994.
skipping to change at page 82, line 20 skipping to change at page 78, line 21
RFC 3493, February 2003. RFC 3493, February 2003.
[RFC3542] Stevens, W., Thomas, M., Nordmark, E., and T. Jinmei, [RFC3542] Stevens, W., Thomas, M., Nordmark, E., and T. Jinmei,
"Advanced Sockets Application Program Interface (API) for "Advanced Sockets Application Program Interface (API) for
IPv6", RFC 3542, May 2003. IPv6", RFC 3542, May 2003.
[RFC3758] Stewart, R., Ramalho, M., Xie, Q., Tuexen, M., and P. [RFC3758] Stewart, R., Ramalho, M., Xie, Q., Tuexen, M., and P.
Conrad, "Stream Control Transmission Protocol (SCTP) Conrad, "Stream Control Transmission Protocol (SCTP)
Partial Reliability Extension", RFC 3758, May 2004. Partial Reliability Extension", RFC 3758, May 2004.
[RFC4895] Tuexen, M., Stewart, R., Lei, P., and E. Rescorla,
"Authenticated Chunks for the Stream Control Transmission
Protocol (SCTP)", RFC 4895, August 2007.
[RFC4960] Stewart, R., "Stream Control Transmission Protocol", [RFC4960] Stewart, R., "Stream Control Transmission Protocol",
RFC 4960, September 2007. RFC 4960, September 2007.
Appendix A. one-to-one style Code Example [RFC5061] Stewart, R., Xie, Q., Tuexen, M., Maruyama, S., and M.
Kozuka, "Stream Control Transmission Protocol (SCTP)
Dynamic Address Reconfiguration", RFC 5061,
September 2007.
Appendix A. One-to-One Style Code Example
The following code is a simple implementation of an echo server over The following code is a simple implementation of an echo server over
SCTP. The example shows how to use some features of one-to-one style SCTP. The example shows how to use some features of one-to-one style
IPv4 SCTP sockets, including: IPv4 SCTP sockets, including:
o Opening, binding, and listening for new associations on a socket
o Opening, binding, and listening for new associations on a socket;
o Enabling ancillary data o Enabling ancillary data
o Enabling notifications o Enabling notifications
o Using ancillary data with sendmsg() and recvmsg() o Using ancillary data with sendmsg() and recvmsg()
o Using MSG_EOR to determine if an entire message has been read o Using MSG_EOR to determine if an entire message has been read
o Handling notifications o Handling notifications
#include <stdio.h> #include <stdio.h>
#include <sys/types.h> #include <sys/types.h>
#include <sys/socket.h> #include <sys/socket.h>
#include <netinet/in.h> #include <netinet/in.h>
skipping to change at page 87, line 24 skipping to change at page 83, line 35
SCTP_EVENTS, &event, SCTP_EVENTS, &event,
sizeof(event)) != 0) { sizeof(event)) != 0) {
perror("setevent failed"); perror("setevent failed");
exit(1); exit(1);
} }
/* Echo back any and all data */ /* Echo back any and all data */
echo(cfd,0); echo(cfd,0);
} }
} }
Appendix B. one-to-many style Code Example Appendix B. One-to-Many Style Code Example
The following code is a simple implementation of an echo server over The following code is a simple implementation of an echo server over
SCTP. The example shows how to use some features of one-to-many SCTP. The example shows how to use some features of one-to-many
style IPv4 SCTP sockets, including: style IPv4 SCTP sockets, including:
o Opening and binding of a socket
o Opening and binding of a socket;
o Enabling ancillary data o Enabling ancillary data
o Enabling notifications o Enabling notifications
o Using ancillary data with sendmsg() and recvmsg() o Using ancillary data with sendmsg() and recvmsg()
o Using MSG_EOR to determine if an entire message has been read o Using MSG_EOR to determine if an entire message has been read
o Handling notifications o Handling notifications
Note most functions defined in Appendix A are reused in this example. Note most functions defined in Appendix A are reused in this example.
int main() int main()
{ {
skipping to change at page 89, line 14 skipping to change at page 85, line 20
Authors' Addresses Authors' Addresses
Randall R. Stewart Randall R. Stewart
The Resource Group The Resource Group
1700 Pennsylvania Ave NW 1700 Pennsylvania Ave NW
Suite 56 Suite 56
Washington, DC 20006 Washington, DC 20006
USA USA
Phone:
Email: randall.stewart@trgworld.com Email: randall.stewart@trgworld.com
Kacheong Poon Kacheong Poon
Sun Microsystems, Inc. Sun Microsystems, Inc.
4150 Network Circle 4150 Network Circle
Santa Clara, CA 95054 Santa Clara, CA 95054
USA USA
Phone:
Email: kacheong.poon@sun.com Email: kacheong.poon@sun.com
Michael Tuexen Michael Tuexen
Univ. of Applied Sciences Muenster Univ. of Applied Sciences Muenster
Stegerwaldstr. 39 Stegerwaldstr. 39
48565 Steinfurt 48565 Steinfurt
Germany Germany
Email: tuexen@fh-muenster.de Email: tuexen@fh-muenster.de
skipping to change at page 90, line 11 skipping to change at page 86, line 11
USA USA
Email: vladislav.yasevich@hp.com Email: vladislav.yasevich@hp.com
Peter Lei Peter Lei
Cisco Systems, Inc. Cisco Systems, Inc.
8735 West Higgins Road 8735 West Higgins Road
Suite 300 Suite 300
Chicago, IL 60631 Chicago, IL 60631
USA USA
Phone:
Email: peterlei@cisco.com Email: peterlei@cisco.com
Full Copyright Statement Full Copyright Statement
Copyright (C) The IETF Trust (2008). Copyright (C) The IETF Trust (2008).
This document is subject to the rights, licenses and restrictions This document is subject to the rights, licenses and restrictions
contained in BCP 78, and except as set forth therein, the authors contained in BCP 78, and except as set forth therein, the authors
retain all their rights. retain all their rights.
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