draft-ietf-tsvwg-sctpsocket-19.txt   draft-ietf-tsvwg-sctpsocket-20.txt 
Network Working Group R. Stewart Network Working Group R. Stewart
Internet-Draft Researcher Internet-Draft Huawei
Intended status: Informational K. Poon Intended status: Informational K. Poon
Expires: August 20, 2009 Sun Microsystems, Inc. Expires: July 19, 2010 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.
February 16, 2009 January 19, 2010
Sockets API Extensions for Stream Control Transmission Protocol (SCTP) Sockets API Extensions for Stream Control Transmission Protocol (SCTP)
draft-ietf-tsvwg-sctpsocket-19.txt draft-ietf-tsvwg-sctpsocket-20.txt
Abstract
This document describes a mapping of the Stream Control Transmission
Protocol SCTP into a sockets API. The benefits of this mapping
include compatibility for TCP applications, access to new SCTP
features and a consolidated error and event notification scheme.
Status of this Memo Status of this Memo
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Copyright Notice Copyright Notice
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This document describes a mapping of the Stream Control Transmission This document may contain material from IETF Documents or IETF
Protocol SCTP into a sockets API. The benefits of this mapping Contributions published or made publicly available before November
include compatibility for TCP applications, access to new SCTP 10, 2008. The person(s) controlling the copyright in some of this
features and a consolidated error and event notification scheme. material may not have granted the IETF Trust the right to allow
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Table of Contents Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . 6 1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . 6
2. Conventions . . . . . . . . . . . . . . . . . . . . . . . . . 7 2. Data Types . . . . . . . . . . . . . . . . . . . . . . . . . . 7
3. Data Types . . . . . . . . . . . . . . . . . . . . . . . . . . 7 3. One-to-Many Style Interface . . . . . . . . . . . . . . . . . 7
4. One-to-Many Style Interface . . . . . . . . . . . . . . . . . 7 3.1. Basic Operation . . . . . . . . . . . . . . . . . . . . . 7
4.1. Basic Operation . . . . . . . . . . . . . . . . . . . . . 7 3.1.1. socket() . . . . . . . . . . . . . . . . . . . . . . . 8
4.1.1. socket() . . . . . . . . . . . . . . . . . . . . . . . 8 3.1.2. bind() . . . . . . . . . . . . . . . . . . . . . . . . 9
4.1.2. bind() . . . . . . . . . . . . . . . . . . . . . . . . 9 3.1.3. listen() . . . . . . . . . . . . . . . . . . . . . . . 10
4.1.3. listen() . . . . . . . . . . . . . . . . . . . . . . . 10 3.1.4. sendmsg() and recvmsg() . . . . . . . . . . . . . . . 10
4.1.4. sendmsg() and recvmsg() . . . . . . . . . . . . . . . 11 3.1.5. close() . . . . . . . . . . . . . . . . . . . . . . . 12
4.1.5. close() . . . . . . . . . . . . . . . . . . . . . . . 12 3.1.6. connect() . . . . . . . . . . . . . . . . . . . . . . 13
4.1.6. connect() . . . . . . . . . . . . . . . . . . . . . . 13 3.2. Implicit Association Setup . . . . . . . . . . . . . . . . 13
4.2. Implicit Association Setup . . . . . . . . . . . . . . . . 13 3.3. Non-blocking mode . . . . . . . . . . . . . . . . . . . . 14
4.3. Non-blocking mode . . . . . . . . . . . . . . . . . . . . 14 3.4. Special considerations . . . . . . . . . . . . . . . . . . 15
4.4. Special considerations . . . . . . . . . . . . . . . . . . 15 4. One-to-One Style Interface . . . . . . . . . . . . . . . . . . 16
5. One-to-One Style Interface . . . . . . . . . . . . . . . . . . 16 4.1. Basic Operation . . . . . . . . . . . . . . . . . . . . . 17
5.1. Basic Operation . . . . . . . . . . . . . . . . . . . . . 17 4.1.1. socket() . . . . . . . . . . . . . . . . . . . . . . . 17
5.1.1. socket() . . . . . . . . . . . . . . . . . . . . . . . 17 4.1.2. bind() . . . . . . . . . . . . . . . . . . . . . . . . 18
5.1.2. bind() . . . . . . . . . . . . . . . . . . . . . . . . 18 4.1.3. listen() . . . . . . . . . . . . . . . . . . . . . . . 19
5.1.3. listen() . . . . . . . . . . . . . . . . . . . . . . . 19 4.1.4. accept() . . . . . . . . . . . . . . . . . . . . . . . 19
5.1.4. accept() . . . . . . . . . . . . . . . . . . . . . . . 19 4.1.5. connect() . . . . . . . . . . . . . . . . . . . . . . 20
5.1.5. connect() . . . . . . . . . . . . . . . . . . . . . . 20 4.1.6. close() . . . . . . . . . . . . . . . . . . . . . . . 21
5.1.6. close() . . . . . . . . . . . . . . . . . . . . . . . 21 4.1.7. shutdown() . . . . . . . . . . . . . . . . . . . . . . 21
5.1.7. shutdown() . . . . . . . . . . . . . . . . . . . . . . 21 4.1.8. sendmsg() and recvmsg() . . . . . . . . . . . . . . . 22
5.1.8. sendmsg() and recvmsg() . . . . . . . . . . . . . . . 22 4.1.9. getpeername() . . . . . . . . . . . . . . . . . . . . 22
5.1.9. getpeername() . . . . . . . . . . . . . . . . . . . . 22 5. Data Structures . . . . . . . . . . . . . . . . . . . . . . . 23
6. Data Structures . . . . . . . . . . . . . . . . . . . . . . . 23 5.1. The msghdr and cmsghdr Structures . . . . . . . . . . . . 23
6.1. The msghdr and cmsghdr Structures . . . . . . . . . . . . 23 5.2. SCTP msg_control Structures . . . . . . . . . . . . . . . 24
6.2. SCTP msg_control Structures . . . . . . . . . . . . . . . 24 5.2.1. SCTP Initiation Structure (SCTP_INIT) . . . . . . . . 25
6.2.1. SCTP Initiation Structure (SCTP_INIT) . . . . . . . . 25 5.2.2. SCTP Header Information Structure (SCTP_SNDRCV) . . . 26
6.2.2. SCTP Header Information Structure (SCTP_SNDRCV) . . . 26 5.2.3. Extended SCTP Header Information Structure
6.2.3. Extended SCTP Header Information Structure
(SCTP_EXTRCV) . . . . . . . . . . . . . . . . . . . . 28 (SCTP_EXTRCV) . . . . . . . . . . . . . . . . . . . . 28
6.3. SCTP Events and Notifications . . . . . . . . . . . . . . 29 5.2.4. SCTP Send Information Structure (SCTP_SNDINFO) . . . . 29
6.3.1. SCTP Notification Structure . . . . . . . . . . . . . 30 5.2.5. SCTP Receive Information Structure (SCTP_RCVINFO) . . 31
6.3.2. SCTP_ASSOC_CHANGE . . . . . . . . . . . . . . . . . . 31 5.2.6. SCTP Next Receive Information Structure
6.3.3. SCTP_PEER_ADDR_CHANGE . . . . . . . . . . . . . . . . 33 (SCTP_NXTINFO) . . . . . . . . . . . . . . . . . . . . 32
6.3.4. SCTP_REMOTE_ERROR . . . . . . . . . . . . . . . . . . 34 5.2.7. SCTP PR-SCTP Information Structure (SCTP_PRINFO) . . . 32
6.3.5. SCTP_SEND_FAILED . . . . . . . . . . . . . . . . . . . 35 5.2.8. SCTP PR-SCTP Information Structure (SCTP_AUTHINFO) . . 32
6.3.6. SCTP_SHUTDOWN_EVENT . . . . . . . . . . . . . . . . . 36 5.3. SCTP Events and Notifications . . . . . . . . . . . . . . 33
6.3.7. SCTP_ADAPTATION_INDICATION . . . . . . . . . . . . . . 36 5.3.1. SCTP Notification Structure . . . . . . . . . . . . . 33
6.3.8. SCTP_PARTIAL_DELIVERY_EVENT . . . . . . . . . . . . . 37 5.3.2. SCTP_ASSOC_CHANGE . . . . . . . . . . . . . . . . . . 35
6.3.9. SCTP_AUTHENTICATION_EVENT . . . . . . . . . . . . . . 38 5.3.3. SCTP_PEER_ADDR_CHANGE . . . . . . . . . . . . . . . . 36
6.3.10. SCTP_SENDER_DRY_EVENT . . . . . . . . . . . . . . . . 38 5.3.4. SCTP_REMOTE_ERROR . . . . . . . . . . . . . . . . . . 37
6.4. Ancillary Data Considerations and Semantics . . . . . . . 39 5.3.5. SCTP_SEND_FAILED . . . . . . . . . . . . . . . . . . . 38
6.4.1. Multiple Items and Ordering . . . . . . . . . . . . . 39 5.3.6. SCTP_SHUTDOWN_EVENT . . . . . . . . . . . . . . . . . 39
6.4.2. Accessing and Manipulating Ancillary Data . . . . . . 39 5.3.7. SCTP_ADAPTATION_INDICATION . . . . . . . . . . . . . . 40
6.4.3. Control Message Buffer Sizing . . . . . . . . . . . . 40 5.3.8. SCTP_PARTIAL_DELIVERY_EVENT . . . . . . . . . . . . . 40
7. Common Operations for Both Styles . . . . . . . . . . . . . . 41 5.3.9. SCTP_AUTHENTICATION_EVENT . . . . . . . . . . . . . . 41
7.1. send(), recv(), sendto(), and recvfrom() . . . . . . . . . 41 5.3.10. SCTP_SENDER_DRY_EVENT . . . . . . . . . . . . . . . . 42
7.2. setsockopt() and getsockopt() . . . . . . . . . . . . . . 43 5.3.11. SCTP_NOTIFICATIONS_STOPPED_EVENT . . . . . . . . . . . 42
7.3. read() and write() . . . . . . . . . . . . . . . . . . . . 43 5.4. Ancillary Data Considerations and Semantics . . . . . . . 42
7.4. getsockname() . . . . . . . . . . . . . . . . . . . . . . 44 5.4.1. Multiple Items and Ordering . . . . . . . . . . . . . 43
8. Socket Options . . . . . . . . . . . . . . . . . . . . . . . . 44 5.4.2. Accessing and Manipulating Ancillary Data . . . . . . 43
8.1. Read / Write Options . . . . . . . . . . . . . . . . . . . 46 5.4.3. Control Message Buffer Sizing . . . . . . . . . . . . 44
8.1.1. Retransmission Timeout Parameters (SCTP_RTOINFO) . . . 46 6. Common Operations for Both Styles . . . . . . . . . . . . . . 44
8.1.2. Association Parameters (SCTP_ASSOCINFO) . . . . . . . 47 6.1. send(), recv(), sendto(), and recvfrom() . . . . . . . . . 44
8.1.3. Initialization Parameters (SCTP_INITMSG) . . . . . . . 48 6.2. setsockopt() and getsockopt() . . . . . . . . . . . . . . 46
8.1.4. SO_LINGER . . . . . . . . . . . . . . . . . . . . . . 48 6.3. read() and write() . . . . . . . . . . . . . . . . . . . . 47
8.1.5. SCTP_NODELAY . . . . . . . . . . . . . . . . . . . . . 49 6.4. getsockname() . . . . . . . . . . . . . . . . . . . . . . 47
8.1.6. SO_RCVBUF . . . . . . . . . . . . . . . . . . . . . . 49 7. Socket Options . . . . . . . . . . . . . . . . . . . . . . . . 48
8.1.7. SO_SNDBUF . . . . . . . . . . . . . . . . . . . . . . 49 7.1. Read / Write Options . . . . . . . . . . . . . . . . . . . 50
8.1.8. Automatic Close of Associations (SCTP_AUTOCLOSE) . . . 49 7.1.1. Retransmission Timeout Parameters (SCTP_RTOINFO) . . . 50
8.1.9. Set Primary Address (SCTP_PRIMARY_ADDR) . . . . . . . 50 7.1.2. Association Parameters (SCTP_ASSOCINFO) . . . . . . . 50
8.1.10. Set Adaptation Layer Indicator 7.1.3. Initialization Parameters (SCTP_INITMSG) . . . . . . . 52
(SCTP_ADAPTATION_LAYER) . . . . . . . . . . . . . . . 50 7.1.4. SO_LINGER . . . . . . . . . . . . . . . . . . . . . . 52
8.1.11. Enable/Disable Message Fragmentation 7.1.5. SCTP_NODELAY . . . . . . . . . . . . . . . . . . . . . 53
(SCTP_DISABLE_FRAGMENTS) . . . . . . . . . . . . . . . 50 7.1.6. SO_RCVBUF . . . . . . . . . . . . . . . . . . . . . . 53
8.1.12. Peer Address Parameters (SCTP_PEER_ADDR_PARAMS) . . . 51 7.1.7. SO_SNDBUF . . . . . . . . . . . . . . . . . . . . . . 53
8.1.13. Set Default Send Parameters 7.1.8. Automatic Close of Associations (SCTP_AUTOCLOSE) . . . 53
(SCTP_DEFAULT_SEND_PARAM) . . . . . . . . . . . . . . 53 7.1.9. Set Primary Address (SCTP_PRIMARY_ADDR) . . . . . . . 54
8.1.14. Set Notification and Ancillary Events (SCTP_EVENTS) . 53 7.1.10. Set Adaptation Layer Indicator
8.1.15. Set/Clear IPv4 Mapped Addresses (SCTP_ADAPTATION_LAYER) . . . . . . . . . . . . . . . 54
(SCTP_I_WANT_MAPPED_V4_ADDR) . . . . . . . . . . . . . 54 7.1.11. Enable/Disable Message Fragmentation
8.1.16. Get or Set the Maximum Fragmentation Size (SCTP_DISABLE_FRAGMENTS) . . . . . . . . . . . . . . . 54
(SCTP_MAXSEG) . . . . . . . . . . . . . . . . . . . . 54 7.1.12. Peer Address Parameters (SCTP_PEER_ADDR_PARAMS) . . . 54
8.1.17. Get or Set the List of Supported HMAC Identifiers 7.1.13. Set Default Send Parameters
(SCTP_HMAC_IDENT) . . . . . . . . . . . . . . . . . . 54 (SCTP_DEFAULT_SEND_PARAM) . . . . . . . . . . . . . . 57
8.1.18. Get or Set the Active Shared Key 7.1.14. Set Notification and Ancillary Events (SCTP_EVENTS) . 57
(SCTP_AUTH_ACTIVE_KEY) . . . . . . . . . . . . . . . . 55 7.1.15. Set/Clear IPv4 Mapped Addresses
8.1.19. Get or Set Delayed SACK Timer (SCTP_DELAYED_SACK) . . 56 (SCTP_I_WANT_MAPPED_V4_ADDR) . . . . . . . . . . . . . 57
8.1.20. Get or Set Fragmented Interleave 7.1.16. Get or Set the Maximum Fragmentation Size
(SCTP_FRAGMENT_INTERLEAVE) . . . . . . . . . . . . . . 57 (SCTP_MAXSEG) . . . . . . . . . . . . . . . . . . . . 58
8.1.21. Set or Get the SCTP Partial Delivery Point 7.1.17. Get or Set the List of Supported HMAC Identifiers
(SCTP_PARTIAL_DELIVERY_POINT) . . . . . . . . . . . . 58 (SCTP_HMAC_IDENT) . . . . . . . . . . . . . . . . . . 58
8.1.22. Set or Get the Use of Extended Receive Info 7.1.18. Get or Set the Active Shared Key
(SCTP_USE_EXT_RCVINFO) . . . . . . . . . . . . . . . . 58 (SCTP_AUTH_ACTIVE_KEY) . . . . . . . . . . . . . . . . 59
8.1.23. Set or Get the Auto ASCONF Flag (SCTP_AUTO_ASCONF) . . 58 7.1.19. Get or Set Delayed SACK Timer (SCTP_DELAYED_SACK) . . 60
8.1.24. Set or Get the Maximum Burst (SCTP_MAX_BURST) . . . . 59 7.1.20. Get or Set Fragmented Interleave
8.1.25. Set or Get the Default Context (SCTP_CONTEXT) . . . . 59 (SCTP_FRAGMENT_INTERLEAVE) . . . . . . . . . . . . . . 60
8.1.26. Enable or Disable Explicit EOR Marking 7.1.21. Set or Get the SCTP Partial Delivery Point
(SCTP_EXPLICIT_EOR) . . . . . . . . . . . . . . . . . 60 (SCTP_PARTIAL_DELIVERY_POINT) . . . . . . . . . . . . 62
8.1.27. Enable SCTP Port Reusage (SCTP_REUSE_PORT) . . . . . . 60 7.1.22. Set or Get the Use of Extended Receive Info
8.2. Read-Only Options . . . . . . . . . . . . . . . . . . . . 60 (SCTP_USE_EXT_RCVINFO) . . . . . . . . . . . . . . . . 62
8.2.1. Association Status (SCTP_STATUS) . . . . . . . . . . . 60 7.1.23. Set or Get the Auto ASCONF Flag (SCTP_AUTO_ASCONF) . . 62
8.2.2. Peer Address Information (SCTP_GET_PEER_ADDR_INFO) . . 61 7.1.24. Set or Get the Maximum Burst (SCTP_MAX_BURST) . . . . 63
8.2.3. Get the List of Chunks the Peer Requires to be 7.1.25. Set or Get the Default Context (SCTP_CONTEXT) . . . . 63
Authenticated (SCTP_PEER_AUTH_CHUNKS) . . . . . . . . 62 7.1.26. Enable or Disable Explicit EOR Marking
8.2.4. Get the List of Chunks the Local Endpoint Requires (SCTP_EXPLICIT_EOR) . . . . . . . . . . . . . . . . . 64
to be Authenticated (SCTP_LOCAL_AUTH_CHUNKS) . . . . . 63 7.1.27. Enable SCTP Port Reusage (SCTP_REUSE_PORT) . . . . . . 64
8.2.5. Get the Current Number of Associations 7.1.28. Set Notification Event (SCTP_EVENT) . . . . . . . . . 64
(SCTP_GET_ASSOC_NUMBER) . . . . . . . . . . . . . . . 63 7.2. Read-Only Options . . . . . . . . . . . . . . . . . . . . 64
8.2.6. Get the Current Identifiers of Associations 7.2.1. Association Status (SCTP_STATUS) . . . . . . . . . . . 64
(SCTP_GET_ASSOC_ID_LIST) . . . . . . . . . . . . . . . 63 7.2.2. Peer Address Information (SCTP_GET_PEER_ADDR_INFO) . . 66
8.3. Write-Only Options . . . . . . . . . . . . . . . . . . . . 64 7.2.3. Get the List of Chunks the Peer Requires to be
8.3.1. Set Peer Primary Address Authenticated (SCTP_PEER_AUTH_CHUNKS) . . . . . . . . 66
(SCTP_SET_PEER_PRIMARY_ADDR) . . . . . . . . . . . . . 64 7.2.4. Get the List of Chunks the Local Endpoint Requires
8.3.2. Add a Chunk That Must Be Authenticated to be Authenticated (SCTP_LOCAL_AUTH_CHUNKS) . . . . . 67
(SCTP_AUTH_CHUNK) . . . . . . . . . . . . . . . . . . 64 7.2.5. Get the Current Number of Associations
8.3.3. Set a Shared Key (SCTP_AUTH_KEY) . . . . . . . . . . . 65 (SCTP_GET_ASSOC_NUMBER) . . . . . . . . . . . . . . . 67
8.3.4. Deactivate a Shared Key (SCTP_AUTH_DEACTIVATE_KEY) . . 65 7.2.6. Get the Current Identifiers of Associations
8.3.5. Delete a Shared Key (SCTP_AUTH_DELETE_KEY) . . . . . . 66 (SCTP_GET_ASSOC_ID_LIST) . . . . . . . . . . . . . . . 68
8.4. Ancillary Data and Notification Interest Options . . . . . 67 7.3. Write-Only Options . . . . . . . . . . . . . . . . . . . . 68
9. New Functions . . . . . . . . . . . . . . . . . . . . . . . . 69 7.3.1. Set Peer Primary Address
9.1. sctp_bindx() . . . . . . . . . . . . . . . . . . . . . . . 69 (SCTP_SET_PEER_PRIMARY_ADDR) . . . . . . . . . . . . . 68
9.2. sctp_peeloff() . . . . . . . . . . . . . . . . . . . . . . 70 7.3.2. Add a Chunk That Must Be Authenticated
9.3. sctp_getpaddrs() . . . . . . . . . . . . . . . . . . . . . 71 (SCTP_AUTH_CHUNK) . . . . . . . . . . . . . . . . . . 68
9.4. sctp_freepaddrs() . . . . . . . . . . . . . . . . . . . . 72 7.3.3. Set a Shared Key (SCTP_AUTH_KEY) . . . . . . . . . . . 69
9.5. sctp_getladdrs() . . . . . . . . . . . . . . . . . . . . . 72 7.3.4. Deactivate a Shared Key (SCTP_AUTH_DEACTIVATE_KEY) . . 70
9.6. sctp_freeladdrs() . . . . . . . . . . . . . . . . . . . . 73 7.3.5. Delete a Shared Key (SCTP_AUTH_DELETE_KEY) . . . . . . 70
9.7. sctp_sendmsg() . . . . . . . . . . . . . . . . . . . . . . 73 7.4. Ancillary Data and Notification Interest Options . . . . . 71
9.8. sctp_recvmsg() . . . . . . . . . . . . . . . . . . . . . . 74 8. New Functions . . . . . . . . . . . . . . . . . . . . . . . . 74
9.9. sctp_connectx() . . . . . . . . . . . . . . . . . . . . . 74 8.1. sctp_bindx() . . . . . . . . . . . . . . . . . . . . . . . 74
9.10. sctp_send() . . . . . . . . . . . . . . . . . . . . . . . 75 8.2. sctp_peeloff() . . . . . . . . . . . . . . . . . . . . . . 75
9.11. sctp_sendx() . . . . . . . . . . . . . . . . . . . . . . . 76 8.3. sctp_getpaddrs() . . . . . . . . . . . . . . . . . . . . . 76
9.12. sctp_getaddrlen() . . . . . . . . . . . . . . . . . . . . 77 8.4. sctp_freepaddrs() . . . . . . . . . . . . . . . . . . . . 77
10. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 77 8.5. sctp_getladdrs() . . . . . . . . . . . . . . . . . . . . . 77
11. Security Considerations . . . . . . . . . . . . . . . . . . . 78 8.6. sctp_freeladdrs() . . . . . . . . . . . . . . . . . . . . 78
12. Acknowledgments . . . . . . . . . . . . . . . . . . . . . . . 78 8.7. sctp_sendmsg() . . . . . . . . . . . . . . . . . . . . . . 78
13. Normative References . . . . . . . . . . . . . . . . . . . . . 78 8.8. sctp_recvmsg() . . . . . . . . . . . . . . . . . . . . . . 79
Appendix A. One-to-One Style Code Example . . . . . . . . . . . . 79 8.9. sctp_connectx() . . . . . . . . . . . . . . . . . . . . . 79
Appendix B. One-to-Many Style Code Example . . . . . . . . . . . 84 8.10. sctp_send() . . . . . . . . . . . . . . . . . . . . . . . 80
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . . 86 8.11. sctp_sendx() . . . . . . . . . . . . . . . . . . . . . . . 81
8.12. sctp_getaddrlen() . . . . . . . . . . . . . . . . . . . . 82
9. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 82
10. Security Considerations . . . . . . . . . . . . . . . . . . . 83
11. Acknowledgments . . . . . . . . . . . . . . . . . . . . . . . 83
12. Normative References . . . . . . . . . . . . . . . . . . . . . 83
Appendix A. One-to-One Style Code Example . . . . . . . . . . . . 84
Appendix B. One-to-Many Style Code Example . . . . . . . . . . . 89
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . . 91
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: We define a
sockets mapping for SCTP that is consistent with other sockets sockets mapping for SCTP that is consistent with other sockets
API protocol mappings (for instance, UDP, TCP, IPv4, and IPv6). API protocol mappings (for instance, UDP, TCP, IPv4, and IPv6).
2. Support a one-to-many style interface This set of semantics is 2. Support a one-to-many style interface This set of semantics is
similar to that defined for connection-less protocols, such as similar to that defined for connection-less protocols, such as
UDP. A one-to-many style SCTP socket should be able to control UDP. A one-to-many style SCTP socket should be able to control
multiple SCTP associations. This is similar to an UDP socket, multiple SCTP associations. This is similar to a UDP socket,
which can communicate with many peer end points. Each of these which can communicate with many peer end points. Each of these
associations is assigned an association ID so that an associations is assigned an association ID so that an application
applications can use the ID to differentiate them. Note that can use the ID to differentiate them. Note that SCTP is
SCTP is connection-oriented in nature, and it does not support connection-oriented in nature, and it does not support broadcast
broadcast or multicast communications, as UDP does. or multicast communications, as UDP does.
3. Support a one-to-one style interface This interface supports a 3. Support a one-to-one style interface This interface supports a
similar semantics as sockets for connection-oriented protocols, similar semantics as sockets for connection-oriented protocols,
such as TCP. A one-to-one style SCTP socket should only control such as TCP. A one-to-one style SCTP socket should only control
one SCTP association. One purpose of defining this interface is one SCTP association. One purpose of defining this interface is
to allow existing applications built on other connection-oriented to allow existing applications built on other connection-oriented
protocols be ported to use SCTP with very little effort. And protocols be ported to use SCTP with very little effort. And
developers familiar with those semantics can easily adapt to developers familiar with those semantics can easily adapt to
SCTP. Another purpose is to make sure that existing mechanisms SCTP. Another purpose is to make sure that existing mechanisms
in most OSes to deal with socket, such as select(), should in most OSes to deal with socket, such as select(), should
continue to work with this style of socket. Extensions are added continue to work with this style of socket. Extensions are added
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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
association into a one-to-one style socket. association into a one-to-one style socket.
Some of the SCTP mechanisms cannot be adequately mapped to existing Some of the SCTP mechanisms cannot be adequately mapped to existing
socket interface. In some cases, it is more desirable to have new socket interface. In some cases, it is more desirable to have new
interface instead of using existing socket calls. Section 9 of this interface instead of using existing socket calls. Section 8 of this
document describes those new interface. document describes those new interface.
2. Conventions 2. Data Types
The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
"SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this
document are to be interpreted as described in [RFC2119].
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 3. 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. o Outbound association setup is implicit.
o Messages are delivered in complete messages (with one notable o Messages are delivered in complete messages (with one notable
exception). exception).
o There is a 1 to MANY relationship between socket and association. o There is a 1 to MANY relationship between socket and association.
4.1. Basic Operation 3.1. 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() o socket()
o bind() o bind()
o listen() o listen()
o recvmsg() o recvmsg()
o sendmsg() o sendmsg()
o close() o close()
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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
an established association as the association ID cannot be specified. an established association as the association ID cannot be specified.
Once as association ID is assigned to an SCTP association, that ID Once as association ID is assigned to an SCTP association, that ID
will not be reused until the application explicitly terminates the will not be reused until the application explicitly terminates the
association. The resources belonged to that association will not be association. The resources belonging to that association will not be
freed until that happens. This is similar to the close() operation freed until that happens. This is similar to the close() operation
on a normal socket. The only exception is when the SCTP_AUTOCLOSE on a normal socket. The only exception is when the SCTP_AUTOCLOSE
option (section 7.1.8) is set. In this case, after the association option (section 7.1.8) is set. In this case, after the association
is terminated gracefully automatically, the association ID assigned is terminated gracefully and automatically, the association ID
to it can be reused. All applications using this option should be assigned to it can be reused. All applications using this option
aware of this to avoid the possible problem of sending data to an should be aware of this to avoid the possible problem of sending data
incorrect peer end point. to an incorrect peer end point.
If the server or client wishes to branch an existing association off If the server or client wishes to branch an existing association off
to a separate socket, it is required to call sctp_peeloff() and in to a separate socket, it is required to call sctp_peeloff() and in
the parameter specifies the association identification. The the parameter specifies the association identification. The
sctp_peeloff() call will return a new socket which can then be used sctp_peeloff() call will return a new socket which can then be used
with recv() and send() functions for message passing. See with recv() and send() functions for message passing. See
Section 9.2 for more on branched-off associations. Section 8.2 for more on branched-off associations.
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() 3.1.1. 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 function prototype is The function prototype is
int socket(int domain, int socket(int domain,
int type, int type,
int protocol); int protocol);
and one uses PF_INET or PF_INET6 as the domain, SOCK_SEQPACKET as the and one uses PF_INET or PF_INET6 as the domain, SOCK_SEQPACKET as the
type and IPPROTO_SCTP as the protocol. 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.
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and one uses PF_INET or PF_INET6 as the domain, SOCK_SEQPACKET as the and one uses PF_INET or PF_INET6 as the domain, SOCK_SEQPACKET as the
type and IPPROTO_SCTP as the protocol. 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.
Using the PF_INET domain indicates the creation of an endpoint which Using the PF_INET domain indicates the creation of an endpoint which
can use only IPv4 addresses, while PF_INET6 creates an endpoint which can use only IPv4 addresses, while PF_INET6 creates an endpoint which
can use both IPv6 and IPv4 address. can use both IPv6 and IPv4 address.
4.1.2. bind() 3.1.2. 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 9.1 to help applications this, sctp_bindx() is introduced in Section 8.1 to help 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 associations on the socket, it must call listen() (see
Section 4.1.3). Section 3.1.3).
The function prototype of bind() is The function prototype of bind() is
int bind(int sd, int bind(int sd,
struct sockaddr *addr, struct sockaddr *addr,
socklen_t addrlen); socklen_t addrlen);
and the arguments are and the arguments are
sd: The socket descriptor returned by socket(). sd: The socket descriptor returned by socket().
addr: The address structure (struct sockaddr_in or struct addr: The address structure (struct sockaddr_in or struct
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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() 3.1.3. 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. to accept new associations.
The function prototype is The function prototype is
int listen(int sd, int listen(int sd,
int backlog); int backlog);
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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() 3.1.4. 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.
The function prototypes are The function prototypes are
ssize_t sendmsg(int sd, ssize_t sendmsg(int sd,
const struct msghdr *message, const struct msghdr *message,
int flags); int flags);
and and
ssize_t recvmsg(int sd, ssize_t recvmsg(int sd,
struct msghdr *message, struct msghdr *message,
int flags); int flags);
using the arguments: using the arguments:
sd: The socket descriptor of the endpoint. sd: The socket descriptor of the endpoint.
message: Pointer to the msghdr structure which contains a single 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 5 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 6 for SCTP-specific flags used in the msghdr structure. Section 5 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 5, 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
structure will be filled with one of the transport addresses of the structure will be filled with one of the transport addresses of the
intended receiver. If there is no association existing between the intended receiver. If there is no association existing between the
sender and the intended receiver, the sender's SCTP stack will set up sender and the intended receiver, the sender's SCTP stack will set up
a new association and then send the user data (see Section 4.2 for a new association and then send the user data (see Section 3.2 for
more on implicit association setup). If an SCTP_INIT cmsg structure more on implicit association setup). If an SCTP_INIT cmsg structure
is used with NULL data, an association will be established using the is used with NULL data, an association will be established using the
parameters from the struct sctp_initmsg structure. If no SCTP_INIT parameters from the struct sctp_initmsg structure. If no SCTP_INIT
cmsg structure is used in combination with NULL data, an association cmsg structure is used in combination with NULL data, an association
is established using the default parameters. If NULL data is used, is established using the default parameters. If NULL data is used,
no association exists and the SCTP_ABORT or SCTP_EOF -1 MUST be no association exists and the SCTP_ABORT or SCTP_EOF flags are
returned and an errno SHOULD be set to something like EDONOTBESTUPID. present then -1 must be returned and an errno should be set to
Sending a message using sendmsg() is atomic unless explicit EOR something like EDONOTBESTUPID. Sending a message using sendmsg() is
marking is enabled on the socket specified by sd. atomic unless explicit EOR marking is enabled on the socket specified
by sd.
If a peer sends a SHUTDOWN, a SCTP_SHUTDOWN_EVENT notification will If a peer sends a SHUTDOWN, a SCTP_SHUTDOWN_EVENT notification will
be delivered if that notification has been enabled, and no more data be delivered if that notification has been enabled, and no more data
can be sent to that association. Any attempt to send more data will can be sent to that association. Any attempt to send more data will
cause sendmsg() to return with an ESHUTDOWN error. Note that the cause sendmsg() to return with an ESHUTDOWN error. Note that the
socket is still open for reading at this point so it is possible to socket is still open for reading at this point so it is possible to
retrieve notifications. retrieve notifications.
When receiving a user message with recvmsg(), the msg_name field in When receiving a user message with recvmsg(), the msg_name field in
msghdr structure will be populated with the source transport address msghdr structure will be populated with the source transport address
of the user data. The caller of recvmsg() can use this address of the user data. The caller of recvmsg() can use this address
information to determine to which association the received user information to determine to which association the received user
message belongs. Note that if SCTP_ASSOC_CHANGE events are disabled, message belongs. Note that if SCTP_ASSOC_CHANGE events are disabled,
applications must use the peer transport address provided in the applications must use the peer transport address provided in the
msg_name field by recvmsg() to perform correlation to an association, msg_name field by recvmsg() to perform correlation to an association,
since they will not have the association ID. since they will not have the association ID.
If all data in a single message has been delivered, MSG_EOR will be If all data in a single message has been delivered, MSG_EOR will be
set in the msg_flags field of the msghdr structure (see section set in the msg_flags field of the msghdr structure (see section
Section 6.1). Section 5.1).
If the application does not provide enough buffer space to completely If the application does not provide enough buffer space to completely
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 8.1.20 for further one-to-many model sockets. Please consult Section 7.1.20 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 3.1), 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() 3.1.5. 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 function prototype is The function prototype is
int close(int sd); int close(int sd);
and the argument is and the argument is
sd: The socket descriptor of the associations to be closed. 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 include 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 5.2.2) 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() 3.1.6. 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 function prototype is The function prototype is
int connect(int sd, int connect(int sd,
const struct sockaddr *nam, const struct sockaddr *nam,
socklen_t len); socklen_t len);
and the arguments are and the arguments are
sd: The socket descriptor to have a new association added to. sd: The socket descriptor to have a new association added to.
nam: The address structure (either struct sockaddr_in or struct 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 3.2. 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.
Once the bind() call is complete on a one-to-many style socket, the Once the bind() call is complete on a one-to-many style socket, the
application can begin sending and receiving data using the sendmsg()/ application can begin sending and receiving data using the sendmsg()/
recvmsg() or sendto()/recvfrom() calls, without going through any recvmsg() or sendto()/recvfrom() calls, without going through any
explicit association setup procedures (i.e., no connect() calls explicit association setup procedures (i.e., no connect() calls
required). required).
Whenever sendmsg() or sendto() is called and the SCTP stack at the Whenever sendmsg() or sendto() is called and the SCTP stack at the
sender finds that there is no association existing between the sender sender finds that there is no association existing between the sender
and the intended receiver (identified by the address passed either in and the intended receiver (identified by the address passed either in
the msg_name field of msghdr structure in the sendmsg() call or the the msg_name field of msghdr structure in the sendmsg() call or the
dest_addr field in the sendto() call), the SCTP stack will dest_addr field in the sendto() call), the SCTP stack will
automatically setup an association to the intended receiver. automatically setup an association to the intended receiver.
Upon the successful association setup a SCTP_COMM_UP notification Upon the successful association setup a SCTP_COMM_UP notification
will be dispatched to the socket at both the sender and receiver will be dispatched to the socket at both the sender and receiver
side. This notification can be read by the recvmsg() system call side. This notification can be read by the recvmsg() system call
(see Section 4.1.3). (see Section 3.1.3).
Note, if the SCTP stack at the sender side supports bundling, the Note, if the SCTP stack at the sender side supports bundling, the
first user message may be bundled with the COOKIE ECHO message first user message may be bundled with the COOKIE ECHO message
[RFC4960]. [RFC4960].
When the SCTP stack sets up a new association implicitly, it first When the SCTP stack sets up a new association implicitly, it first
consults the sctp_initmsg structure, which is passed along within the consults the sctp_initmsg structure, which is passed along within the
ancillary data in the sendmsg() call (see Section 6.2.1 for details ancillary data in the sendmsg() call (see Section 5.2.1 for details
of the data structures), for any special options to be used on the of the data structures), for any special options to be used on the
new association. new association.
If this information is not present in the sendmsg() call, or if the If this information is not present in the sendmsg() call, or if the
implicit association setup is triggered by a sendto() call, the implicit association setup is triggered by a sendto() call, the
default association initialization parameters will be used. These default association initialization parameters will be used. These
default association parameters may be set with respective default association parameters may be set with respective
setsockopt() calls or be left to the system defaults. setsockopt() calls or be left to the system defaults.
Implicit association setup cannot be initiated by send()/recv() Implicit association setup cannot be initiated by send()/recv()
calls. calls.
4.3. Non-blocking mode 3.3. Non-blocking mode
Some SCTP users might want to avoid blocking when they call socket Some SCTP users might want to avoid blocking when they call socket
interface function. interface function.
Once all bind() calls are complete on a one-to-many style socket, the Once all bind() calls are complete on a one-to-many style socket, the
application must set the non-blocking option by a fcntl() (such as application must set the non-blocking option by a fcntl() (such as
O_NONBLOCK). After which the sendmsg() function returns immediately, O_NONBLOCK). After which the sendmsg() function returns immediately,
and the success or failure of the data message (and possible and the success or failure of the data message (and possible
SCTP_INITMSG parameters) will be signaled by the SCTP_ASSOC_CHANGE SCTP_INITMSG parameters) will be signaled by the SCTP_ASSOC_CHANGE
event with SCTP_COMM_UP or CANT_START_ASSOC. If user data could not event with SCTP_COMM_UP or CANT_START_ASSOC. If user data could not
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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 6.3.2). Note that this can also be SHUTDOWN_COMPLETE (see Section 5.3.2). 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 8.10.
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 the interpretation of select on write is implementation
Generally a positive return on a select on write would only indicate specific. Generally a positive return on a select on write would
that one of the associations represented by the one-to-many socket is only indicate that one of the associations represented by the one-to-
writable. An application that writes after the select return may many socket is writable. An application that writes after the select
still block since the association that was writeable is not the return may still block since the association that was writeable is
destination association of the write call. Likewise select (or not the destination association of the write call. Likewise select
poll()) for reading from a one-to-many socket will only return an (or poll()) for reading from a one-to-many socket will only return an
indication that one of the associations represented by the socket has indication that one of the associations represented by the socket has
data to be read. data to be read.
An application that wishes to know that a particular association is An application that wishes to know that a particular association is
ready for reading or writing should either use the one-to-one style ready for reading or writing should either use the one-to-one style
or use the sctp_peeloff() (see Section 9.2) function to separate the or use the sctp_peeloff() (see Section 8.2) function to separate the
association of interest from the one-to-many socket. association of interest from the one-to-many socket.
4.4. Special considerations 3.4. 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 implementers and application programmers. guidance to both implementers and application programmers.
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o demand that the underlying implementation dedicates independent o 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
o verify that their application layer protocol does not permit large o verify that their application layer protocol does not permit 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
o use one-to-one style sockets for association which may potentially o use one-to-one style sockets for association which may potentially
stall (either from the beginning, or by using sctp_peeloff before stall (either from the beginning, or by using sctp_peeloff before
sending large amounts of data that may cause a stalled condition). sending large amounts of data that may cause a stalled condition).
5. One-to-One Style Interface 4. 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 4.1.8. 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 4.1. 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() o socket()
o bind() o bind()
o listen() o listen()
o accept() o 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
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o socket() o socket()
o connect() o 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() o close()
to terminate this association when done. to terminate this association when done.
5.1.1. socket() 4.1.1. 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 function prototype is The function prototype is
int socket(int domain, int socket(int domain,
int type, int type,
int protocol); int protocol);
and one uses PF_INET or PF_INET6 as the domain, SOCK_STREAM as the and one uses PF_INET or PF_INET6 as the domain, SOCK_STREAM as the
type and IPPROTO_SCTP as the protocol. 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.
Using the PF_INET domain indicates the creation of an endpoint which Using the PF_INET domain indicates the creation of an endpoint which
can use only IPv4 addresses, while PF_INET6 creates an endpoint which can use only IPv4 addresses, while PF_INET6 creates an endpoint which
can use both IPv6 and IPv4 address. can use both IPv6 and IPv4 address.
5.1.2. bind() 4.1.2. 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 8.1 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 function prototype of bind() is The function prototype of bind() is
int bind(int sd, int bind(int sd,
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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() 4.1.3. 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 function prototype is The function prototype is
int listen(int sd, int listen(int sd,
int backlog); int backlog);
and the arguments are 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() 4.1.4. 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 function prototype is The function prototype is
int accept(int sd, int accept(int sd,
struct sockaddr *addr, struct sockaddr *addr,
socklen_t *addrlen); socklen_t *addrlen);
and the arguments are and the arguments are
sd: The listening socket descriptor. sd: The listening socket descriptor.
addr: On return, will contain the primary address of the peer 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 The functions returns the socket descriptor for the newly formed
association. association.
5.1.5. connect() 4.1.5. connect()
Applications use connect() to initiate an association to a peer. Applications use connect() to initiate an association to a peer.
The function prototype is The function prototype is
int connect(int sd, int connect(int sd,
const struct sockaddr *addr, const struct sockaddr *addr,
socklen_t addrlen); socklen_t addrlen);
and the arguments are and the arguments are
sd: The socket descriptor of the endpoint. sd: The socket descriptor of the endpoint.
addr: The peer's address. addr: The peer's address.
addrlen: The size of the 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 7.1.3 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
binding with INADDR_ANY and IN6ADDR_ANY for IPv4 and IPv6 socket binding with INADDR_ANY and IN6ADDR_ANY_INIT for IPv4 and IPv6 socket
respectively. One of those addresses will be the primary address for respectively. One of those addresses will be the primary address for
the association. This automatically enables the multi-homing the association. This automatically enables the multi-homing
capability of SCTP. capability of SCTP.
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). restriction).
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 an SCTP socket.
5.1.6. close() 4.1.6. close()
Applications use close() to gracefully close down an association. Applications use close() to gracefully close down an association.
The function prototype is The function prototype is
int close(int sd); int close(int sd);
and the argument is and the argument is
sd: The socket descriptor of the associations to be closed. 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() 4.1.7. 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 function prototype is The function prototype is
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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 6.3.5 for more information). deliver (see Section 5.3.5 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 7.1.4.
5.1.8. sendmsg() and recvmsg() 4.1.8. 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 3.1.3), 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
given is not part of the current association, the data will not given is not part of the current association, the data will not
be sent and a SCTP_SEND_FAILED event will be delivered to the be sent and a SCTP_SEND_FAILED event will be delivered to the
application if send failure events are enabled. application if send failure events are enabled.
2. Using sendmsg() on a non-connected one-to-one style socket for 2. Using sendmsg() on a non-connected one-to-one style socket for
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() 4.1.9. 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 8.3 for a multi-homed/one-to-many style version of the call.
The function prototype is The function prototype is
int getpeername(int sd, int getpeername(int sd,
struct sockaddr *address, struct sockaddr *address,
socklen_t *len); socklen_t *len);
and the arguments are: and the arguments are:
sd: The socket descriptor to be queried. sd: The socket descriptor to be queried.
address: On return, the peer primary address is stored in this address: On return, the peer primary address is stored in this
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int getpeername(int sd, int getpeername(int sd,
struct sockaddr *address, struct sockaddr *address,
socklen_t *len); socklen_t *len);
and the arguments are: and the arguments are:
sd: The socket descriptor to be queried. sd: The socket descriptor to be queried.
address: On return, the peer primary address is stored in this 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 5. 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
and notifications. and notifications.
6.1. The msghdr and cmsghdr Structures 5.1. The msghdr and cmsghdr Structures
The msghdr structure used in the sendmsg() and recvmsg() calls, as The msghdr structure used in the sendmsg() and recvmsg() calls, as
well as the ancillary data carried in the structure, is the key for well as the ancillary data carried in the structure, is the key for
the application to set and get various control information from the the application to set and get various control information from the
SCTP endpoint. SCTP endpoint.
The msghdr and the related cmsghdr structures are defined and The msghdr and the related cmsghdr structures are defined and
discussed in details in [RFC3542]. Here we will cite their discussed in details in [RFC3542]. Here we will cite their
definitions from [RFC3542]. definitions from [RFC3542].
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and 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 3.1.3 and Section 4.1.8).
The scatter/gather buffers, or I/O vectors (pointed to by the msg_iov The scatter/gather buffers, or I/O vectors (pointed to by the msg_iov
field) are treated as a single SCTP data chunk, rather than multiple field) are treated as a single SCTP data chunk, rather than multiple
chunks, for both sendmsg() and recvmsg(). chunks, for both sendmsg() and recvmsg().
The msg_flags are not used when sending a message with sendmsg(). The msg_flags are not used when sending a message with sendmsg().
If a notification has arrived, recvmsg() will return the notification If a notification has arrived, recvmsg() will return the notification
with the MSG_NOTIFICATION flag set in msg_flags. If the with the MSG_NOTIFICATION flag set in msg_flags. If the
MSG_NOTIFICATION flag is not set, recvmsg() will return data. See MSG_NOTIFICATION flag is not set, recvmsg() will return data. See
Section 6.3 for more information about notifications. Section 5.3 for more information about notifications.
If all portions of a data frame or notification have been read, If all portions of a data frame or notification have been read,
recvmsg() will return with MSG_EOR set in msg_flags. recvmsg() will return with MSG_EOR set in msg_flags.
6.2. SCTP msg_control Structures 5.2. SCTP msg_control Structures
A key element of all SCTP-specific socket extensions is the use of A key element of all SCTP-specific socket extensions is the use of
ancillary data to specify and access SCTP-specific data via the ancillary data to specify and access SCTP-specific data via the
struct msghdr's msg_control member used in sendmsg() and recvmsg(). struct msghdr's msg_control member used in sendmsg() and recvmsg().
Fine-grained control over initialization and sending parameters are Fine-grained control over initialization and sending parameters are
handled with ancillary data. handled with ancillary data.
Each ancillary data item is proceeded by a struct cmsghdr (see Each ancillary data item is proceeded by a struct cmsghdr (see
Section 6.1), which defines the function and purpose of the data Section 5.1), which defines the function and purpose of the data
contained in in the cmsg_data[] member. contained in in the cmsg_data[] member.
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 sets
many style only) sets protocol parameters for new associations. protocol parameters for new associations. Section 5.2.1 provides
Section 6.2.1 provides more details. Header information can set or more details. Header information can set or report parameters on
report parameters on individual messages in a stream. See individual messages in a stream. See Section 5.2.2 for how to use
Section 6.2.2 for how to use SNDRCV ancillary data. SNDRCV ancillary data.
By default on a one-to-one style socket, SCTP will pass no ancillary By default on either style socket, SCTP will pass no ancillary data;
data; on a one-to-many style socket, SCTP will only pass SCTP_SNDRCV Specific ancillary data items can be enabled with socket options
and SCTP_ASSOC_CHANGE information. Specific ancillary data items can defined for SCTP; see Section 7.4.
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 5.4 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
data items. If a socket API consumer enables delivery of both SCTP data items. If a socket API consumer enables delivery of both SCTP
and IPv6 ancillary data, they both may appear in the same msg_control and IPv6 ancillary data, they both may appear in the same msg_control
buffer in any order. An application may thus need to handle other buffer in any order. An application may thus need to handle other
types of ancillary data besides that passed by SCTP. types of ancillary data besides that passed by SCTP.
The sockets application must provide a buffer large enough to The sockets application must provide a buffer large enough to
accommodate all ancillary data provided via recvmsg(). If the buffer accommodate all ancillary data provided via recvmsg(). If the buffer
is not large enough, the ancillary data will be truncated and the is not large enough, the ancillary data will be truncated and the
msghdr's msg_flags will include MSG_CTRUNC. msghdr's msg_flags will include MSG_CTRUNC.
6.2.1. SCTP Initiation Structure (SCTP_INIT) 5.2.1. SCTP Initiation Structure (SCTP_INIT)
This cmsghdr structure provides information for initializing new SCTP This cmsghdr structure provides information for initializing new SCTP
associations with sendmsg(). The SCTP_INITMSG socket option uses associations with sendmsg(). The SCTP_INITMSG socket option uses
this same data structure. This structure is not used for recvmsg(). this same data structure. This structure is not used for recvmsg().
+--------------+-----------+---------------------+ +--------------+-----------+---------------------+
| cmsg_level | cmsg_type | cmsg_data[] | | cmsg_level | cmsg_type | cmsg_data[] |
+--------------+-----------+---------------------+ +--------------+-----------+---------------------+
| IPPROTO_SCTP | SCTP_INIT | struct sctp_initmsg | | IPPROTO_SCTP | SCTP_INIT | struct sctp_initmsg |
+--------------+-----------+---------------------+ +--------------+-----------+---------------------+
skipping to change at page 26, line 9 skipping to change at page 25, line 50
sinit_max_attempts: This integer specifies how many attempts the sinit_max_attempts: This integer specifies how many attempts the
SCTP endpoint should make at resending the INIT. This value SCTP endpoint should make at resending the INIT. This value
overrides the system SCTP 'Max.Init.Retransmits' value. The overrides the system SCTP 'Max.Init.Retransmits' value. The
default value of 0 indicates to use the endpoints default value. default value of 0 indicates to use the endpoints default value.
This is normally set to the system's default 'Max.Init.Retransmit' This is normally set to the system's default 'Max.Init.Retransmit'
value. value.
sinit_max_init_timeo: This value represents the largest Time-Out or sinit_max_init_timeo: This value represents the largest Time-Out or
RTO value (in milliseconds) to use in attempting an INIT. RTO value (in milliseconds) to use in attempting an INIT.
Normally the 'RTO.Max' is used to limit the doubling of the RTO Normally the 'RTO.Max' is used to limit the doubling of the RTO
upon timeout. For the INIT message this value MAY override upon timeout. For the INIT message this value MAY override
'RTO.Max'. This value MUST NOT influence 'RTO.Max' during data 'RTO.Max'. This value must not influence 'RTO.Max' during data
transmission and is only used to bound the initial setup time. A transmission and is only used to bound the initial setup time. A
default value of 0 indicates to use the endpoints default value. default value of 0 indicates to use the endpoints default value.
This is normally set to the system's 'RTO.Max' value (60 seconds). This is normally set to the system's 'RTO.Max' value (60 seconds).
6.2.2. SCTP Header Information Structure (SCTP_SNDRCV) 5.2.2. 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[] |
+--------------+-------------+------------------------+ +--------------+-------------+------------------------+
| IPPROTO_SCTP | SCTP_SNDRCV | struct sctp_sndrcvinfo | | IPPROTO_SCTP | SCTP_SNDRCV | struct sctp_sndrcvinfo |
+--------------+-------------+------------------------+ +--------------+-------------+------------------------+
Here is the definition of sctp_sndrcvinfo: Here is the definition of sctp_sndrcvinfo:
struct sctp_sndrcvinfo { struct sctp_sndrcvinfo {
uint16_t sinfo_stream; uint16_t sinfo_stream;
uint16_t sinfo_ssn; uint16_t sinfo_ssn;
uint16_t sinfo_flags; uint16_t sinfo_flags;
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: For recvmsg() the SCTP stack places the message's sinfo_stream: For recvmsg() the SCTP stack places the message's
stream number in this value. For sendmsg() this value holds the stream number in this value. For sendmsg() this value holds the
skipping to change at page 27, line 45 skipping to change at page 27, line 38
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 queued 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 SCTP_SENDALL: This flag, if set, will cause a one-to-many model
socket to send the message to all associations that are socket to send the message to all associations that are
currently established on this socket. For the one-to-one currently established on this socket. For the one-to-one
socket, this flag has no effect. 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.
sinfo_pr_value: The meaning of this field depends of the PR-SCTP sinfo_pr_value: The meaning of this field depends of the PR-SCTP
policy specified by the sinfo_pr_policy field. It is ignored when 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 SCTP_PR_SCTP_NONE is specified. In case of SCTP_PR_SCTP_TTL the
lifetime is specified. lifetime is specified.
sinfo_tsn: For the receiving side, this field holds a TSN that was sinfo_tsn: For the receiving side, this field holds a TSN that was
assigned to one of the SCTP Data Chunks. assigned to one of the SCTP Data Chunks.
sinfo_cumtsn: This field will hold the current cumulative TSN as sinfo_cumtsn: This field will hold the current cumulative TSN as
known by the underlying SCTP layer. Note this field is ignored known by the underlying SCTP layer. Note this field is ignored
when sending and only valid for a receive operation when when sending.
sinfo_flags are set to SCTP_UNORDERED.
sinfo_assoc_id: The association handle field, sinfo_assoc_id, holds sinfo_assoc_id: The association handle field, sinfo_assoc_id, holds
the identifier for the association announced in the SCTP_COMM_UP the identifier for the association announced in the SCTP_COMM_UP
notification. All notifications for a given association have the notification. All notifications for a given association have the
same identifier. Ignored for one-to-one style sockets. 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) 5.2.3. 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 5.2.2)
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
needed to receive ancillary data. Note that next message data is not needed to receive ancillary data. Note that next message data is not
valid unless the current message is completely read, i.e. the MSG_EOR valid unless the current message is completely read, i.e. the MSG_EOR
is set, in other words if you have more data to read from the current is set, in other words if you have more data to read from the current
message then no next message information will be available. message then no next message information will be available.
+--------------+-------------+------------------------+ +--------------+-------------+------------------------+
| cmsg_level | cmsg_type | cmsg_data[] | | cmsg_level | cmsg_type | cmsg_data[] |
+--------------+-------------+------------------------+ +--------------+-------------+------------------------+
| IPPROTO_SCTP | SCTP_EXTRCV | struct sctp_extrcvinfo | | IPPROTO_SCTP | SCTP_EXTRCV | struct sctp_extrcvinfo |
+--------------+-------------+------------------------+ +--------------+-------------+------------------------+
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; uint16_t sinfo_stream;
uint16_t sinfo_ssn;
uint16_t sinfo_flags;
uint16_t sinfo_pr_policy;
uint32_t sinfo_ppid;
uint32_t sinfo_context;
uint32_t sinfo_pr_value;
uint32_t sinfo_tsn;
uint32_t sinfo_cumtsn;
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;
sctp_assoc_t sinfo_assoc_id;
}; };
serinfo_sinfo: Please see Section 6.2.2 for the details for this
structure. sinfo_xxxxfieldsxxx: Please see Section 5.2.2 for the details for
these fields.
serinfo_next_flags: This bitmask will hold one or more of the serinfo_next_flags: This bitmask will hold one or more of the
following values: following values:
SCTP_NEXT_MSG_AVAIL: This bit, when set to 1, indicates that next SCTP_NEXT_MSG_AVAIL: This bit, when set to 1, indicates that next
message information is available i.e.: next_stream, message information is available i.e.: next_stream,
next_asocid, next_length and next_ppid fields all have valid next_asocid, next_length and next_ppid fields all have valid
values. If this bit is set to 0, then these fields are not values. If this bit is set to 0, then these fields are not
valid and should be ignored. valid and should be ignored.
SCTP_NEXT_MSG_ISCOMPLETE: This bit, when set, indicates that the SCTP_NEXT_MSG_ISCOMPLETE: This bit, when set, indicates that the
next message is completely in the receive buffer. The next message is completely in the receive buffer. The
next_length field thus contains the entire message size. If next_length field thus contains the entire message size. If
this flag is set to 0, then the next_length field only contains this flag is set to 0, then the next_length field only contains
part of the message size since the message is still being part of the message size since the message is still being
received (it is being partially delivered). received (it is being partially delivered).
SCTP_NEXT_MSG_IS_UNORDERED: 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 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 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 message to be read is an ordered message in the stream
skipping to change at page 29, line 42 skipping to change at page 29, line 34
subsequent call to one of the receive message functions. subsequent call to one of the receive message functions.
sreinfo_next_length: This value, when valid (see sreinfo_next_length: This value, when valid (see
sreinfo_next_flags), contains the length of the next message that sreinfo_next_flags), contains the length of the next message that
will be received on a subsequent call to one of the receive will be received on a subsequent call to one of the receive
message functions. Note that this length may be a partial length message functions. Note that this length may be a partial length
depending on the settings of next_flags. depending on the settings of next_flags.
sreinfo_next_ppid: This value, when valid (see sreinfo_next_flags), sreinfo_next_ppid: This value, when valid (see sreinfo_next_flags),
contains the ppid of the next message that will be received on a contains the ppid of the next message that will be received on a
subsequent call to one of the receive message functions. subsequent call to one of the receive message functions.
6.3. SCTP Events and Notifications 5.2.4. SCTP Send Information Structure (SCTP_SNDINFO)
This cmsghdr structure specifies SCTP options for sendmsg().
+--------------+--------------+---------------------+
| cmsg_level | cmsg_type | cmsg_data[] |
+--------------+--------------+---------------------+
| IPPROTO_SCTP | SCTP_SNDINFO | struct sctp_sndinfo |
+--------------+--------------+---------------------+
Here is the definition of the sctp_sndinfo structure:
struct sctp_sndinfo {
uint16_t snd_sid;
uint16_t snd_flags;
uint32_t snd_ppid;
uint32_t snd_context;
sctp_assoc_t snd_assoc_id;
};
snd_sid: This value holds the stream number that the application
wishes to send this message to. If a sender specifies an invalid
stream number an error indication is returned and the call fails.
snd_flags: This field may contain any of the following flags and is
composed of a bitwise OR of these values.
SCTP_UNORDERED: This flag requests the un-ordered delivery of the
message. If this flag is clear the datagram is considered an
ordered send.
SCTP_ADDR_OVER: This flag, in the one-to-many style, requests the
SCTP stack to override the primary destination address with the
address found with the sendto/sendmsg call.
SCTP_ABORT: Setting this flag causes the specified association to
abort by sending an ABORT message to the peer (one-to-many
style only). The ABORT chunk will contain an error cause 'User
Initiated Abort' with cause code 12. The cause specific
information of this error cause is provided in msg_iov.
SCTP_EOF: Setting this flag invokes the SCTP graceful shutdown
procedures on the specified association. Graceful shutdown
assures that all data queued by both endpoints is successfully
transmitted before closing the association (one-to-many style
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.
snd_ppid: This value in sendmsg() is an unsigned integer that is
passed to the remote end in each user message. 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.
snd_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).
snd_assoc_id: 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_sndvinfo item always corresponds to the data in msg_iov.
5.2.5. SCTP Receive Information Structure (SCTP_RCVINFO)
This cmsghdr structure describes SCTP header information about a
received message through recvmsg().
+--------------+--------------+---------------------+
| cmsg_level | cmsg_type | cmsg_data[] |
+--------------+--------------+---------------------+
| IPPROTO_SCTP | SCTP_RCVINFO | struct sctp_rcvinfo |
+--------------+--------------+---------------------+
Here is the definition of sctp_rcvinfo structure:
struct sctp_rcvinfo {
uint16_t rcv_sid;
uint16_t rcv_ssn;
uint16_t rcv_flags;
uint32_t rcv_ppid;
uint32_t rcv_tsn;
uint32_t rcv_cumtsn;
sctp_assoc_t rcv_assoc_id;
};
rcv_sid: The SCTP stack places the message's stream number in this
value.
rcv_ssn: 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).
rcv_flags: This field may contain any of the following flags and is
composed of a bitwise OR of these values.
SCTP_UNORDERED: This flag is present when the message was sent
non-ordered.
rcv_ppid: 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.
rcv_tsn: This field holds a TSN that was assigned to one of the SCTP
Data Chunks.
rcv_cumtsn: This field will hold the current cumulative TSN as known
by the underlying SCTP layer.
rcv_assoc_id: 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_rcvinfo item always corresponds to the data in msg_iov.
5.2.6. SCTP Next Receive Information Structure (SCTP_NXTINFO)
This cmsghdr structure describes SCTP receive information of the next
message which will be delivered through recvmsg() if this information
is available. It uses the same structure as the SCTP Receive
Information Structure.
+--------------+--------------+---------------------+
| cmsg_level | cmsg_type | cmsg_data[] |
+--------------+--------------+---------------------+
| IPPROTO_SCTP | SCTP_NXTINFO | struct sctp_rcvinfo |
+--------------+--------------+---------------------+
5.2.7. SCTP PR-SCTP Information Structure (SCTP_PRINFO)
This cmsghdr structure specifies SCTP options for sendmsg().
+--------------+-------------+--------------------+
| cmsg_level | cmsg_type | cmsg_data[] |
+--------------+-------------+--------------------+
| IPPROTO_SCTP | SCTP_PRINFO | struct sctp_prinfo |
+--------------+-------------+--------------------+
Here is the definition of the sctp_prinfo structure:
struct sctp_prinfo {
uint16_t pr_policy;
uint32_t pr_value;
};
pr_policy: 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 pr_value.
pr_value: 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 in milli seconds is specified.
A sctp_prinfo item always corresponds to the data in msg_iov.
5.2.8. SCTP PR-SCTP Information Structure (SCTP_AUTHINFO)
This cmsghdr structure specifies SCTP options for sendmsg().
+--------------+---------------+----------------------+
| cmsg_level | cmsg_type | cmsg_data[] |
+--------------+---------------+----------------------+
| IPPROTO_SCTP | SCTP_AUTHINFO | struct sctp_authinfo |
+--------------+---------------+----------------------+
Here is the definition of the sctp_authinfo structure:
struct sctp_authinfo {
uint16_t auth_keyid;
};
auth_keyid: This specifies the shared key identifier used for
sending the user message.
A sctp_authinfo item always corresponds to the data in msg_iov.
5.3. 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 8.4 for these socket options. When a it wants. See Section 7.4 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
the msg_iov buffer is not large enough. If a single read is not the msg_iov buffer is not large enough. If a single read is not
sufficient, msg_flags will have MSG_EOR clear. The user MUST finish sufficient, msg_flags will have MSG_EOR clear. The user must finish
reading the notification before subsequent data can arrive. reading the notification before subsequent data can arrive.
6.3.1. SCTP Notification Structure 5.3.1. SCTP Notification Structure
The notification structure is defined as the union of all The notification structure is defined as the union of all
notification types. notification types.
union sctp_notification { union sctp_notification {
struct { struct sctp_tlv {
uint16_t sn_type; /* Notification type. */ uint16_t sn_type; /* Notification type. */
uint16_t sn_flags; uint16_t sn_flags;
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_sender_dry_event sn_sender_dry_event; struct sctp_sender_dry_event sn_sender_dry_event;
}; };
sn_type: The following list describes the SCTP notification and sn_type: The following list describes the SCTP notification and
event types for the field sn_type. event types for the field sn_type.
SCTP_ASSOC_CHANGE: This tag indicates that an association has SCTP_ASSOC_CHANGE: This tag indicates that an association has
either been opened or closed. Refer to Section 6.3.2 for either been opened or closed. Refer to Section 5.3.2 for
details. 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 part of an existing association has experienced a change of
state (e.g. a failure or return to service of the reachability state (e.g. a failure or return to service of the reachability
of a endpoint via a specific transport address). Please see of a endpoint via a specific transport address). Please see
Section 6.3.3 for data structure details. Section 5.3.3 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 Error received from the remote peer. It includes the complete
TLV sent by the remote endpoint. See Section 6.3.4 for the TLV sent by the remote endpoint. See Section 5.3.4 for the
detailed 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 6.3.5. structure uses the sctp_sndrecvinfo per Section 5.3.5.
SCTP_SHUTDOWN_EVENT: The peer has sent a SHUTDOWN. No further SCTP_SHUTDOWN_EVENT: The peer has sent a SHUTDOWN. No further
data 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 6.3.7. indicated adaptation layer. Please see Section 5.3.7.
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 6.3.8 Section 5.3.8
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 receiver that either an error occurred on authentication, or a
new key was made active. Section 6.3.9 new key was made active. Section 5.3.9
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 6.3.10 neither for transmission or retransmission. Section 5.3.10
All standard values for sn_type are greater than 2^15. Values
from 2^15 and down are reserved.
sn_flags: These are notification-specific flags. sn_flags: These are notification-specific flags.
sn_length: This is the length of the whole sctp_notification sn_length: This is the length of the whole sctp_notification
structure including the sn_type, sn_flags, and sn_length fields. structure including the sn_type, sn_flags, and sn_length fields.
6.3.2. SCTP_ASSOC_CHANGE 5.3.2. 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;
skipping to change at page 32, line 30 skipping to change at page 35, line 44
including the notification header. including the notification header.
sac_state: This field holds one of a number of values that sac_state: This field holds one of a number of values that
communicate the event that happened to the association. They communicate the event that happened to the association. They
include: include:
SCTP_COMM_UP: A new association is now ready and data may be SCTP_COMM_UP: A new association is now ready and data may be
exchanged with this peer. When an association has been exchanged with this peer. When an association has been
established successfully, this notification should be the first established successfully, this notification should be the first
one. one.
SCTP_COMM_LOST: The association has failed. The association is SCTP_COMM_LOST: The association has failed. The association is
now in the closed state. If SEND FAILED notifications are now in the closed state. If SEND FAILED notifications are
turned on, a SCTP_COMM_LOST is followed by a series of turned on, a SCTP_COMM_LOST is accompanied by a series of
SCTP_SEND_FAILED events, one for each outstanding message. SCTP_SEND_FAILED events, one for each outstanding message.
SCTP_RESTART: SCTP has detected that the peer has restarted. SCTP_RESTART: SCTP has detected that the peer has restarted.
SCTP_SHUTDOWN_COMP: The association has gracefully closed. 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 accompanied by a series of
events, one for each outstanding message. SCTP_SEND_FAILED events, one for each outstanding message.
sac_error: If the state was reached due to a error condition (e.g. sac_error: If the state was reached due to a error condition (e.g.
SCTP_COMM_LOST) any relevant error information is available in SCTP_COMM_LOST) any relevant error information is available in
this field. This corresponds to the protocol error codes defined this field. This corresponds to the protocol error codes defined
in [RFC4960]. in [RFC4960].
sac_outbound_streams: sac_outbound_streams:
sac_inbound_streams: The maximum number of streams allowed in each sac_inbound_streams: The maximum number of streams allowed in each
direction are available in sac_outbound_streams and sac_inbound direction are available in sac_outbound_streams and sac_inbound
streams. streams.
sac_assoc_id: The association id field, holds the identifier for the sac_assoc_id: The association id field, holds the identifier for the
association. All notifications for a given association have the association. All notifications for a given association have the
skipping to change at page 33, line 21 skipping to change at page 36, line 33
SCTP_PR: The both endpoints support the protocol extension SCTP_PR: The both endpoints support the protocol extension
described in [RFC3758]. described in [RFC3758].
SCTP_AUTH: The both endpoints support the protocol extension SCTP_AUTH: The both endpoints support the protocol extension
described in [RFC4895]. described in [RFC4895].
SCTP_ASCONF: The both endpoints support the protocol extension SCTP_ASCONF: The both endpoints support the protocol extension
described in [RFC5061]. described in [RFC5061].
SCTP_MULTIBUF: For an one-to-many style socket, the local SCTP_MULTIBUF: For an one-to-many style socket, the local
endpoints uses separate send and/or receive buffers for each endpoints uses separate send and/or receive buffers for each
SCTP association. SCTP association.
6.3.3. SCTP_PEER_ADDR_CHANGE 5.3.3. 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;
skipping to change at page 34, line 20 skipping to change at page 37, line 31
SCTP_ADDR_CONFIRMED: This address has now been confirmed as a SCTP_ADDR_CONFIRMED: This address has now been confirmed as a
valid address. valid address.
spc_error: If the state was reached due to any error condition (e.g. spc_error: If the state was reached due to any error condition (e.g.
SCTP_ADDR_UNREACHABLE) any relevant error information is available SCTP_ADDR_UNREACHABLE) any relevant error information is available
in this field. in this field.
spc_assoc_id: The association id field, holds the identifier for the spc_assoc_id: The association id field, holds the identifier for the
association. All notifications for a given association have the association. All notifications for a given association have the
same association identifier. For one-to-one style socket, this same association identifier. For one-to-one style socket, this
field is ignored. field is ignored.
6.3.4. SCTP_REMOTE_ERROR 5.3.4. 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;
skipping to change at page 35, line 5 skipping to change at page 38, line 17
including the notification header and the contents of sre_data. including the notification header and the contents of sre_data.
sre_error: This value represents one of the Operational Error causes sre_error: This value represents one of the Operational Error causes
defined in the SCTP specification, in network byte order. defined in the SCTP specification, in network byte order.
sre_assoc_id: The association id field, holds the identifier for the sre_assoc_id: The association id field, holds the identifier for the
association. All notifications for a given association have the association. All notifications for a given association have the
same association identifier. For one-to-one style socket, this same association identifier. For one-to-one style socket, this
field is ignored. field is ignored.
sre_data: This contains the ERROR chunk as defined in the SCTP sre_data: This contains the ERROR chunk as defined in the SCTP
specification [RFC4960] section 3.3.10. specification [RFC4960] section 3.3.10.
6.3.5. SCTP_SEND_FAILED 5.3.5. 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;
skipping to change at page 36, line 16 skipping to change at page 39, line 29
identifier for the association. All notifications for a given identifier for the association. All notifications for a given
association have the same association identifier. For one-to-one association have the same association identifier. For one-to-one
style socket, this field is ignored. style socket, this field is ignored.
ssf_data: The undelivered message or part of the undelivered message ssf_data: The undelivered message or part of the undelivered message
will be present in the sf_data field. Note that the sinfo_flags 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 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 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 user data is present in this field, any chunk headers or SCTP
common headers must be removed by the SCTP stack. common headers must be removed by the SCTP stack.
6.3.6. SCTP_SHUTDOWN_EVENT 5.3.6. 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;
}; };
skipping to change at page 36, line 39 skipping to change at page 40, line 5
sse_flags: Currently unused. sse_flags: Currently unused.
sse_length: This field is the total length of the notification data, sse_length: This field is the total length of the notification data,
including the notification header. It will generally be sizeof including the notification header. It will generally be sizeof
(struct sctp_shutdown_event). (struct sctp_shutdown_event).
sse_flags: Currently unused. sse_flags: Currently unused.
sse_assoc_id: The association id field, holds the identifier for the sse_assoc_id: The association id field, holds the identifier for the
association. All notifications for a given association have the association. All notifications for a given association have the
same association identifier. For one-to-one style socket, this same association identifier. For one-to-one style socket, this
field is ignored. field is ignored.
6.3.7. SCTP_ADAPTATION_INDICATION 5.3.7. 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;
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including the notification header. It will generally be sizeof including the notification header. It will generally be sizeof
(struct sctp_adaptation_event). (struct sctp_adaptation_event).
sai_adaptation_ind: This field holds the bit array sent by the peer sai_adaptation_ind: This field holds the bit array sent by the peer
in the adaptation layer indication parameter. The bits are in in the adaptation layer indication parameter. The bits are in
network byte order. network byte order.
sai_assoc_id: The association id field, holds the identifier for the sai_assoc_id: The association id field, holds the identifier for the
association. All notifications for a given association have the association. All notifications for a given association have the
same association identifier. For one-to-one style socket, this same association identifier. For one-to-one style socket, this
field is ignored. field is ignored.
6.3.8. SCTP_PARTIAL_DELIVERY_EVENT 5.3.8. 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;
skipping to change at page 38, line 5 skipping to change at page 41, line 21
the partial delivery of a user message has been aborted. the partial delivery of a user message has been aborted.
pdapi_stream: This field holds the stream on which the partial pdapi_stream: This field holds the stream on which the partial
delivery event happened. delivery event happened.
pdapi_seq: This field holds the stream sequence number which was pdapi_seq: This field holds the stream sequence number which was
being partially delivered. being partially delivered.
pdapi_assoc_id: The association id field, holds the identifier for pdapi_assoc_id: The association id field, holds the identifier for
the association. All notifications for a given association have the association. All notifications for a given association have
the same association identifier. For one-to-one style socket, the same association identifier. For one-to-one style socket,
this field is ignored. this field is ignored.
6.3.9. SCTP_AUTHENTICATION_EVENT 5.3.9. 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;
skipping to change at page 38, line 36 skipping to change at page 42, line 4
the effected key. If more than one key is involved, this will the effected key. If more than one key is involved, this will
contain one of the keys involved in the notification. contain one of the keys involved in the notification.
auth_altkeynumber: This field holds an alternate keynumber which is auth_altkeynumber: This field holds an alternate keynumber which is
used by some notifications. used by some notifications.
auth_indication: This field hold the error or indication being auth_indication: This field hold the error or indication being
reported. The following values are currently defined: reported. The following values are currently defined:
SCTP_AUTH_NEWKEY: This report indicates that a new key has been 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 made active (used for the first time by the peer) and is now
the active key. The auth_keynumber field holds the user the active key. The auth_keynumber field holds the user
specified key number. specified key number.
SCTP_AUTH_NO_AUTH: This report indicates that the peer does not SCTP_AUTH_NO_AUTH: This report indicates that the peer does not
support the SCTP-AUTH. support the SCTP-AUTH.
SCTP_AUTH_FREE_KEY: This report indicates that the SCTP SCTP_AUTH_FREE_KEY: This report indicates that the SCTP
implementation will not use the key identifier specified in implementation will not use the key identifier specified in
auth_keynumber anymore. auth_keynumber anymore.
auth_assoc_id: The association id field, holds the identifier for auth_assoc_id: The association id field, holds the identifier for
the association. All notifications for a given association have the association. All notifications for a given association have
the same association identifier. the same association identifier.
6.3.10. SCTP_SENDER_DRY_EVENT 5.3.10. SCTP_SENDER_DRY_EVENT
When the SCTP implementation has no user data anymore to send or When the SCTP implementation has no user data anymore to send or
retransmit this notification is given to the user. If 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 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 user data to send or retransmit this notification is also given to
the user. 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: It should be SCTP_SENDER_DRY_EVENT. sender_dry_type: It should be SCTP_SENDER_DRY_EVENT.
sender_dry_flags: Currently unused. sender_dry_flags: Currently unused.
sender_dry_length: This field is the total length of the sender_dry_length: This field is the total length of the
notification data, including the notification header. It will notification data, including the notification header. It will
generally be sizeof (struct sctp_sender_dry_event). generally be sizeof (struct sctp_sender_dry_event).
6.4. Ancillary Data Considerations and Semantics 5.3.11. SCTP_NOTIFICATIONS_STOPPED_EVENT
Notifications, when subscribed to, are reliable. They are always
delivered as long as there is space in the socket receive buffer.
However if an implementation experiences a notification storm, it may
run out of socket buffer space. When this occurs it may wish to
disable notifications. If the implementation chooses to do this, it
will append a final notification SCTP_NOTIFICATIONS_STOPPED_EVENT.
This notification is an empty sctp_tlv (see the union above), that
mearly has this type in the sn_type field, the sn_length field set to
the sizeof a sctp_tlv structure and the sn_flags set to 0. If an
application receives this notification, it will need to resubscribe
to any notifications of interest to it.
5.4. 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 5.4.1. 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
items, or both. items, or both.
The ordering of ancillary data items (either by SCTP or another The ordering of ancillary data items (either by SCTP or another
protocol) is not significant and is implementation-dependent, so protocol) is not significant and is implementation-dependent, so
applications must not depend on any ordering. applications must not depend on any ordering.
SCTP_SNDRCV items must always correspond to the data in the msghdr's SCTP_SNDRCV items must always correspond to the data in the msghdr's
msg_iov member. There can be only a single SCTP_SNDRCV info for each msg_iov member. There can be only a single SCTP_SNDRCV info for each
sendmsg() or recvmsg() call. sendmsg() or recvmsg() call.
6.4.2. Accessing and Manipulating Ancillary Data 5.4.2. Accessing and Manipulating Ancillary Data
Applications can infer the presence of data or ancillary data by Applications can infer the presence of data or ancillary data by
examining the msg_iovlen and msg_controllen msghdr members, examining the msg_iovlen and msg_controllen msghdr members,
respectively. respectively.
Implementations may have different padding requirements for ancillary Implementations may have different padding requirements for ancillary
data, so portable applications should make use of the macros data, so portable applications should make use of the macros
CMSG_FIRSTHDR, CMSG_NXTHDR, CMSG_DATA, CMSG_SPACE, and CMSG_LEN. See CMSG_FIRSTHDR, CMSG_NXTHDR, CMSG_DATA, CMSG_SPACE, and CMSG_LEN. See
[RFC3542] and your SCTP implementation's documentation for more [RFC3542] and your SCTP implementation's documentation for more
information. Following is an example, from [RFC3542], demonstrating information. The following is an example, from [RFC3542],
the use of these macros to access ancillary data: demonstrating the use of these macros to access ancillary data:
struct msghdr msg; struct msghdr msg;
struct cmsghdr *cmsgptr; struct cmsghdr *cmsgptr;
/* fill in msg */ /* fill in msg */
/* call recvmsg() */ /* call recvmsg() */
for (cmsgptr = CMSG_FIRSTHDR(&msg); cmsgptr != NULL; for (cmsgptr = CMSG_FIRSTHDR(&msg); cmsgptr != NULL;
cmsgptr = CMSG_NXTHDR(&msg, cmsgptr)) { cmsgptr = CMSG_NXTHDR(&msg, cmsgptr)) {
if (cmsgptr->cmsg_level == ... && cmsgptr->cmsg_type == ... ) { if (cmsgptr->cmsg_level == ... && cmsgptr->cmsg_type == ... ) {
u_char *ptr; u_char *ptr;
ptr = CMSG_DATA(cmsgptr); ptr = CMSG_DATA(cmsgptr);
/* process data pointed to by ptr */ /* process data pointed to by ptr */
} }
} }
6.4.3. Control Message Buffer Sizing 5.4.3. Control Message Buffer Sizing
The information conveyed via SCTP_SNDRCV events will often be The information conveyed via SCTP_SNDRCV events will often be
fundamental to the correct and sane operation of the sockets fundamental to the correct and sane operation of the sockets
application. This is particularly true of the one-to-many semantics, application. This is particularly true of the one-to-many semantics,
but also of the one-ton-one semantics. For example, if an but also of the one-ton-one semantics. For example, if an
application needs to send and receive data on different SCTP streams, application needs to send and receive data on different SCTP streams,
SCTP_SNDRCV events are indispensable. SCTP_SNDRCV events are indispensable.
Given that some ancillary data is critical, and that multiple Given that some ancillary data is critical, and that multiple
ancillary data items may appear in any order, applications should be ancillary data items may appear in any order, applications should be
skipping to change at page 41, line 13 skipping to change at page 44, line 39
and allocate the buffer size as follows: and allocate the buffer size as follows:
size_t total; size_t total;
void *buf; void *buf;
total = CMSG_SPACE(sizeof (struct sctp_sndrcvinfo)) + total = CMSG_SPACE(sizeof (struct sctp_sndrcvinfo)) +
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 (buf) 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 6. Common Operations for Both Styles
7.1. send(), recv(), sendto(), and recvfrom() 6.1. 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 function prototypes are The function prototypes are
ssize_t send(int sd, ssize_t send(int sd,
const void *msg, const void *msg,
size_t len, size_t len,
int flags); int flags);
ssize_t sendto(int sd, ssize_t sendto(int sd,
const void *msg, const void *msg,
size_t len, size_t len,
int flags, int flags,
const struct sockaddr *to, const struct sockaddr *to,
skipping to change at page 43, line 10 skipping to change at page 46, line 34
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() and getsockopt() 6.2. 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 7.
The function prototypes are The function prototypes are
int getsockopt(int sd, int getsockopt(int sd,
int level, int level,
int optname, int optname,
void *optval, void *optval,
socklen_t *optlen); socklen_t *optlen);
and and
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socklen_t optlen); socklen_t optlen);
and the arguments are and the arguments are
sd: The socket descriptor. sd: The socket descriptor.
level: Set to IPPROTO_SCTP for all SCTP options. level: Set to IPPROTO_SCTP for all SCTP options.
optname - The option name. optname - The option name.
optval: The buffer to store the value 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 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 to
accepted sockets. All socket options set on a 1-to-many socket using all accepted sockets. For one-to-many style sockets often times a
the assoc_id 0 applies for all future associations on the socket. socket option will pass a structure that includes an assoc_id field.
This field can be filled with the association id of a particular
association and unless otherwise specified can be filled with one of
the following constants:
SCTP_FUTURE_ASSOC Specifies that only future associations created
after this socket option will be effected by this call.
SCTP_CURRENT_ASSOC Specifies that only currently existing
associations will be effected by this call, future associations
will still receive the previous default value.
SCTP_ALL_ASSOC Specifies that all current and future associations
will be effected by this call.
7.3. read() and write() 6.3. 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, should only be
used with branched off socket descriptors (see Section 9.2). used with branched off socket descriptors (see Section 8.2).
7.4. getsockname() 6.4. 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 8.5 for a multi-homed version of the call.
The function prototype is The function prototype is
int getsockname(int sd, int getsockname(int sd,
struct sockaddr *address, struct sockaddr *address,
socklen_t *len); socklen_t *len);
and the arguments are and the arguments are
sd: The socket descriptor to be queried. sd: The socket descriptor to be queried.
address: On return, one locally bound address (chosen by the SCTP 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.
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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 7. Socket Options
The following sub-section describes various SCTP level socket options The following sub-section describes various SCTP level socket options
that are common to both styles. SCTP associations can be multi- that are common to both styles. SCTP associations can be multi-
homed. Therefore, certain option parameters include a homed. Therefore, certain option parameters include a
sockaddr_storage structure to select which peer address the option sockaddr_storage structure to select which peer address the option
should be applied to. should be applied to.
For the one-to-many style sockets, an sctp_assoc_t structure For the one-to-many style sockets, an sctp_assoc_t structure
(association ID) is used to identify the association instance that (association ID) is used to identify the association instance that
the operation affects. So it must be set when using this style. the operation affects. So it must be set when using this style.
For the one-to-one style sockets and branched off one-to-many style For the one-to-one style sockets and branched off one-to-many style
sockets (see Section 9.2) this association ID parameter is ignored. sockets (see Section 8.2) this association ID parameter is ignored.
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
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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.
For one-to-many style sockets, id specifies the association to query. For one-to-many style sockets, id specifies the association to query.
For one-to-one style sockets, id is ignored. For one-to-one style sockets, id is ignored.
opt specifies which SCTP socket option to get. It can get any socket The field opt specifies which SCTP socket option to get. It can get
option currently supported that requests information (either read/ any socket option currently supported that requests information
write options or read only) such as: (either read/write options or read only) such as:
SCTP_RTOINFO SCTP_RTOINFO
SCTP_ASSOCINFO SCTP_ASSOCINFO
SCTP_DEFAULT_SEND_PARAM SCTP_DEFAULT_SEND_PARAM
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. The arg field is an option-specific structure buffer provided by the
See Section 9.5 subsections for more information on these options and caller. See Section 8.5 subsections for more information on these
option-specific structures. options and 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:
o 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.
o 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
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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 o 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 7.1. Read / Write Options
8.1.1. Retransmission Timeout Parameters (SCTP_RTOINFO) 7.1.1. 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
these parameters are used in RTO calculation. these parameters are used in RTO calculation.
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: This parameter is ignored for one-to-one style srto_assoc_id: This parameter is ignored for one-to-one style
sockets. For one-to-many style sockets the following applies: sockets. For one-to-many style sockets the application may fill
This is filled in the application, and identifies the association in an association identification or one of the predefined
for this query. If this parameter is '0', then the change affects constants.
the entire endpoint.
All times are given in milliseconds. A value of 0, when modifying All times are given in milliseconds. A value of 0, when modifying
the parameters, indicates that the current value should not be the parameters, indicates that the current value should not 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) 7.1.2. 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. See [RFC4960] for more information on how this endpoint parameters. See [RFC4960] for more information on how this
parameter is used. parameter is used.
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_assoc_id: This parameter is ignored for one-to-one style sasoc_assoc_id: This parameter is ignored for one-to-one style
sockets. For one-to-many style sockets the following applies: sockets. For one-to-many style sockets the application may fill
This information may be examined for either the endpoint or a in an association identification or one of the predefined
specific association. To examine a endpoints default parameters constants.
the association id (sasoc_assoc_id) should must be set to the
value '0'.
sasoc_asocmaxrxt: This contains the maximum retransmission attempts 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 to sasoc_local_rwnd: This holds the last reported rwnd that was sent 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
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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()
shall return an error. The reason for this, from [RFC4960] section may return an error. The reason for this, from [RFC4960] section
8.2: 8.2:
Note: When configuring the SCTP endpoint, the user should avoid Note: When configuring the SCTP endpoint, the user should avoid
having the value of 'Association.Max.Retrans' larger than the having the value of 'Association.Max.Retrans' larger than the
summation of the 'Path.Max.Retrans' of all the destination addresses summation of the 'Path.Max.Retrans' of all the destination addresses
for the remote endpoint. Otherwise, all the destination addresses for the remote endpoint. Otherwise, all the destination addresses
may become inactive while the endpoint still considers the peer may become inactive while the endpoint still considers the peer
endpoint reachable. endpoint reachable.
8.1.3. Initialization Parameters (SCTP_INITMSG) 7.1.3. Initialization Parameters (SCTP_INITMSG)
Applications can specify protocol parameters for the default Applications can specify protocol parameters for the default
association initialization. The structure used to access and modify association initialization. The structure used to access and modify
these parameters is defined in Section 6.2.1). The option name these parameters is defined in Section 5.2.1). 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 7.1.4. SO_LINGER
An application can use this option to perform the SCTP ABORT An application can use this option to perform the SCTP ABORT
primitive. This option affects all associations related to the primitive. This option affects all associations related to the
socket. socket.
The linger option structure is: 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 */
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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
close() can be blocked for at most linger_time ms. If the graceful close() can be blocked for at most linger_time ms. If the graceful
shutdown phase does not finish during this period, close() will shutdown phase does not finish during this period, close() will
return but the graceful shutdown phase continues in the system. return but the graceful shutdown phase continues in the system.
Note, this is a socket level option NOT an SCTP level option. So Note, this is a socket level option NOT an SCTP level option. So
when setting SO_LINGER you must specify a level of SOL_SOCKET in the when setting SO_LINGER you must specify a level of SOL_SOCKET in the
setsockopt() call. setsockopt() call.
8.1.5. SCTP_NODELAY 7.1.5. SCTP_NODELAY
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. Turning this option on disables any Nagle-like
algoithm.
8.1.6. SO_RCVBUF 7.1.6. 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 is implementation dependent. It might style sockets the meaning is implementation dependent. It might
control the receive buffer for each association bound to the socket control the receive buffer for each association bound to the socket
descriptor or it might control the receive buffer for the whole descriptor or it might control the receive buffer for the whole
socket. The call expects an integer. socket. The call expects an integer.
8.1.7. SO_SNDBUF 7.1.7. 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 3.4) 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) 7.1.8. 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 Primary Address (SCTP_PRIMARY_ADDR) 7.1.9. 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. association peer's addresses.
The following structure is used to 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 parameter is ignored for one-to-one style ssp_assoc_id: This parameter is ignored for one-to-one style
sockets. For one-to-many style sockets it identifies the sockets. For one-to-many style sockets it identifies the
association for this request. association for this request. Note that the predefined constants
are NOT allowed.
8.1.10. Set Adaptation Layer Indicator (SCTP_ADAPTATION_LAYER) 7.1.10. 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: 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.
8.1.11. Enable/Disable Message Fragmentation (SCTP_DISABLE_FRAGMENTS) 7.1.11. 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 has an integer where a
zero is on and a zero is off. If enabled no SCTP message non-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.
8.1.12. Peer Address Parameters (SCTP_PEER_ADDR_PARAMS) 7.1.12. 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. unreachable.
The following structure is used to access and modify an address's The following structure is used to access and modify an address's
parameters: 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 ssp_hbinterval; uint32_t spp_hbinterval;
uint16_t ssp_pathmaxrxt; uint16_t spp_pathmaxrxt;
uint32_t ssp_pathmtu; uint32_t spp_pathmtu;
uint32_t ssp_flags; uint32_t spp_flags;
uint32_t ssp_ipv6_flowlabel; uint32_t spp_ipv6_flowlabel;
uint8_t ssp_ipv4_tos; uint8_t spp_ipv4_tos;
}; };
spp_assoc_id: This parameter is ignored for one-to-one style spp_assoc_id: This parameter is ignored for one-to-one style
sockets. For one-to-many style sockets it identifies the sockets. For one-to-many style sockets it identifies the
association for this query. association for this query. Note that the predefined constants
are NOT allowed.
spp_address: This specifies which address is of interest. spp_address: This specifies which address is of interest.
ssp_hbinterval: This contains the value of the heartbeat interval, spp_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.
ssp_pathmaxrxt: This contains the maximum number of retransmissions spp_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 spp_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 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 field must include the flag SPP_PMTUD_DISABLE). Note that if the
spp_address field is empty then all destinations for this spp_address field is empty then all destinations for this
association will have this fixed path MTU set upon them. If an association will have this fixed path MTU set upon them. If an
address is specified, then only that address will be effected. address is specified, then only that address will be effected.
Note also that this option cannot be set on the endpoint, but must Note also that this option cannot be set on the endpoint, but must
be set on each individual association. Also, when disabling PMTU be set on each individual association. Also, when disabling PMTU
discovery, the implementation may disallow this behavior if the discovery, the implementation may disallow this behavior if the
"fixed" path MTU is below the constant value SCTP_SMALLEST_PMTU. "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: 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
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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.
8.1.13. Set Default Send Parameters (SCTP_DEFAULT_SEND_PARAM) 7.1.13. 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 5.2.2. 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 any of the predefined constants are also allowed in
setting the sinfo_assoc_id field to zero indicates that the users this field. The field is ignored on the one-to-one style.
wishes to set the endpoint default send parameters for all future
associations.
8.1.14. Set Notification and Ancillary Events (SCTP_EVENTS) 7.1.14. 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 8.4 ancillary data the user wishes to receive. Please see Section 7.4
for a full description of this option and its usage. for a full description of this option and its usage. Note that this
option is considered deprecated and present for backward
compatiability. New applications should use the SCTP_SET_EVENT
option see section Section 7.4 for a full description of that option
as well.
8.1.15. Set/Clear IPv4 Mapped Addresses (SCTP_I_WANT_MAPPED_V4_ADDR) 7.1.15. 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.
8.1.16. Get or Set the Maximum Fragmentation Size (SCTP_MAXSEG) 7.1.16. 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
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The following structure is used to access and modify this parameter: 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 is ignored for one-to-one style sockets. assoc_id: This parameter is ignored for one-to-one style sockets.
For one-to-many style sockets this parameter indicates which For one-to-many style sockets this parameter indicates which
association the user is performing an action upon. Note that if association the user is performing an action upon. Note that any
this field's value is zero then the endpoints default value is of the predefined constants are also allowed in this field.
changed (effecting future associations only).
assoc_value: This parameter specifies the maximum size in bytes. assoc_value: This parameter specifies the maximum size in bytes.
8.1.17. Get or Set the List of Supported HMAC Identifiers 7.1.17. 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: 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[];
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* SCTP_AUTH_HMAC_ID_SHA256 * SCTP_AUTH_HMAC_ID_SHA256
Note that the list supplied must include SCTP_AUTH_HMAC_ID_SHA1 and Note that the list supplied must include SCTP_AUTH_HMAC_ID_SHA1 and
may include any of the other values in its preferred order (lowest may include any of the other values in its preferred order (lowest
list position has the most preference in algorithm selection). Note list position has the most preference in algorithm selection). Note
also that the lack of SCTP_AUTH_HMAC_ID_SHA1, or the inclusion of an also that the lack of SCTP_AUTH_HMAC_ID_SHA1, or the inclusion of an
unknown HMAC identifier (including optional identifiers unknown to unknown HMAC identifier (including optional identifiers unknown to
the implementation) will cause the set option to fail and return an the implementation) will cause the set option to fail and return an
error. error.
8.1.18. Get or Set the Active Shared Key (SCTP_AUTH_ACTIVE_KEY) 7.1.18. 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 The following structure is used to access and modify these
parameters: 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;
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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 When used with setsockopt() the SCTP implementation must use the
indicated shared key identifier for all messages being given to an indicated shared key identifier for all messages being given to an
SCTP implementation via a send call after the setsockopt() call until SCTP implementation via a send call after the setsockopt() call until
changed again. Therefore the SCTP implementation MUST NOT bundle changed again. Therefore the SCTP implementation must not bundle
user messages which should be authenticated using different shared user messages which should be authenticated using different shared
key identifiers. key identifiers.
Initially the key with key identifier 0 is the active key. Initially the key with key identifier 0 is the active key.
8.1.19. Get or Set Delayed SACK Timer (SCTP_DELAYED_SACK) 7.1.19. 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 sack_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 sack_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
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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 is ignored for one-to-one style sack_assoc_id: This parameter is ignored for one-to-one style
sockets. For one-to-many style sockets this parameter indicates sockets. For one-to-many style sockets this parameter indicates
which association the user is performing an action upon. Note which association the user is performing an action upon. Note
that if this field's value is zero then the endpoints default that any of the predefined constants may also be used for one-to-
value is changed (effecting future associations only). many style sockets.
sack_delay: This parameter contains the number of milliseconds that 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.
8.1.20. Get or Set Fragmented Interleave (SCTP_FRAGMENT_INTERLEAVE) 7.1.20. 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.
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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 8.4). This is also why we recommend sctp_data_io_events (see Section 7.4). 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.
8.1.21. Set or Get the SCTP Partial Delivery Point For applications that have subscribed to events those events appear
in the normal socket buffer data stream. This means that unless the
user has set the fragmentation interleave level to 0, notifications
may also be interleaved with partially delivered messages.
7.1.21. 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.
8.1.22. Set or Get the Use of Extended Receive Info 7.1.22. 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. This option is present for
compatability with older applications and is deprecated. Future
applications should use SCTP_NXTINFO to retrieve this same
information via ancillary data.
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.
8.1.23. Set or Get the Auto ASCONF Flag (SCTP_AUTO_ASCONF) 7.1.23. 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.
8.1.24. Set or Get the Maximum Burst (SCTP_MAX_BURST) 7.1.24. 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 is ignored for one-to-one style sockets. assoc_id: This parameter is ignored for one-to-one style sockets.
For one-to-many style sockets this parameter indicates which For one-to-many style sockets this parameter indicates which
association the user is performing an action upon. Note that if association the user is performing an action upon. Note that any
this field's value is zero then the endpoints default value is of the predefined constants may be used for one-to-many style
changed (effecting future associations only). sockets.
assoc_value: This parameter contains the maximum burst. assoc_value: This parameter contains the maximum burst.
8.1.25. Set or Get the Default Context (SCTP_CONTEXT) 7.1.25. 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
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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 is ignored for one-to-one style sockets. assoc_id: This parameter is ignored for one-to-one style sockets.
For one-to-many style sockets this parameter indicates which For one-to-many style sockets this parameter indicates which
association the user is performing an action upon. Note that if association the user is performing an action upon. Note that any
this field's value is zero then the endpoints default value is of the predefined constants may be used for one-to-many style
changed (effecting future associations only). sockets.
assoc_value: This parameter contains the context. assoc_value: This parameter contains the context.
8.1.26. Enable or Disable Explicit EOR Marking (SCTP_EXPLICIT_EOR) 7.1.26. Enable or Disable Explicit EOR Marking (SCTP_EXPLICIT_EOR)
This boolean flag is used to enable or disable explicit end of record 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.
8.1.27. Enable SCTP Port Reusage (SCTP_REUSE_PORT) 7.1.27. 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 This setsockopt() call must not be used after calling bind() or
sctp_bindx() for a 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 is option to reuse ports and/or addresses for SCTP sockets is
unspecified. unspecified.
8.2. Read-Only Options 7.1.28. Set Notification Event (SCTP_EVENT)
This socket option is used to set a specific notification or
ancillary data option. Please see Section 7.4 for a full description
of this option and its usage.
7.2. Read-Only Options
The options defined in this subsection are read-only. Using this The options defined in this subsection are read-only. Using this
option in a setsockopt() call will result in a error indicating option in a setsockopt() call will result in a error indicating
EOPNOTSUPP. EOPNOTSUPP.
8.2.1. Association Status (SCTP_STATUS) 7.2.1. 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. receipt. This information is read-only.
The following structure is 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;
skipping to change at page 61, line 20 skipping to change at page 65, line 22
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_assoc_id: This parameter is ignored for one-to-one style sstat_assoc_id: This parameter is ignored for one-to-one style
sockets. For one-to-many style sockets it holds the identifier sockets. For one-to-many style sockets it holds the identifier
for the association. All notifications for a given association for the association. All notifications for a given association
have the same association identifier. have the same association identifier. Note that the one-to-many
predefined constants may not be used with this option.
sstat_state: This contains the association's current state one of 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
skipping to change at page 61, line 49 skipping to change at page 66, line 5
sstat_instrms: The number of streams that the peer will be using 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. with the option name SCTP_STATUS.
8.2.2. Peer Address Information (SCTP_GET_PEER_ADDR_INFO) 7.2.2. 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. only.
The following structure is used to access this information: 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;
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spinfo_assoc_id: This is parameter is ignored for one-to-one style spinfo_assoc_id: This is parameter is ignored for one-to-one style
sockets. For one-to-many style sockets the following applies: sockets. For one-to-many style sockets the following applies:
This is field may be filled in by the application, if so, this This is field may be filled in by the application, if so, this
field will have priority in looking up the association over the field will have priority in looking up the association over the
address specified in spinfo_address. Note that if the address address specified in spinfo_address. Note that if the address
does not belong to the association specified then this call will does not belong to the association specified then this call will
fail. If the application does NOT fill in the spinfo_assoc_id, fail. If the application does NOT fill in the spinfo_assoc_id,
then the address will be used to lookup the association and on then the address will be used to lookup the association and on
return this field will have the valid association id. In other return this field will have the valid association id. In other
words, this call can be used to translate a address into an words, this call can be used to translate a address into an
association id. association id. Note that the predefined constants are not
allowed on this option.
spinfo_address: This is filled in the application, and contains the 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 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.
8.2.3. Get the List of Chunks the Peer Requires to be Authenticated 7.2.3. 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: 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 user gauth_assoc_id: This parameter, indicates which association the user
is requesting the list of peer authenticated chunks. For one-to- is requesting the list of peer authenticated chunks. For one-to-
one sockets, this parameter is ignored. one sockets, this parameter is ignored. Note that the predefined
constants are not allowed with this option.
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 7.2.4. 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: 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;
skipping to change at page 63, line 41 skipping to change at page 67, line 45
}; };
gauth_assoc_id: This parameter, indicates which association the user gauth_assoc_id: This parameter, indicates which association the user
is requesting the list of local authenticated chunks. For one-to- is requesting the list of local authenticated chunks. For 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) 7.2.5. 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 7.2.6. 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 SCTP associations handled by a one-to-many style socket.
The 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. Write-Only Options 7.3. Write-Only Options
The options defined in this subsection are write-only. Using this The options defined in this subsection are write-only. Using this
option in a getsockopt() or sctp_opt_info() call will result in a option in a getsockopt() or sctp_opt_info() call will result in a
error indicating EOPNOTSUPP. error indicating EOPNOTSUPP.
8.3.1. Set Peer Primary Address (SCTP_SET_PEER_PRIMARY_ADDR) 7.3.1. Set Peer Primary Address (SCTP_SET_PEER_PRIMARY_ADDR)
Requests that the peer mark the enclosed address as the association Requests that the peer mark the enclosed address as the association
primary. The enclosed address must be one of the association's primary. The enclosed address must be one of the association's
locally bound addresses. locally bound addresses.
The following structure is used to make a set peer primary request: The following structure is used to make a set peer primary request:
struct sctp_setpeerprim { struct sctp_setpeerprim {
sctp_assoc_t sspp_assoc_id; sctp_assoc_t sspp_assoc_id;
struct sockaddr_storage sspp_addr; struct sockaddr_storage sspp_addr;
}; };
sspp_addr: The address to set as primary. sspp_addr: The address to set as primary.
sspp_assoc_id: This parameter is ignored for one-to-one style sspp_assoc_id: This parameter is ignored for one-to-one style
sockets. For one-to-many style sockets it identifies the sockets. For one-to-many style sockets it identifies the
association for this request. association for this request. Note that the predefined constants
are not allowed on this option.
8.3.2. Add a Chunk That Must Be Authenticated (SCTP_AUTH_CHUNK) 7.3.2. Add a Chunk That Must Be Authenticated (SCTP_AUTH_CHUNK)
This set option adds a chunk type that the user is requesting to be 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 received only in an authenticated way. Changes to the list of chunks
will only effect future associations on the socket. will only effect future associations on the socket.
The following structure is used to add a chunk: The following structure is used to add a chunk:
struct sctp_authchunk { struct sctp_authchunk {
uint8_t sauth_chunk; uint8_t sauth_chunk;
}; };
skipping to change at page 65, line 4 skipping to change at page 69, line 11
This set option adds a chunk type that the user is requesting to be 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 received only in an authenticated way. Changes to the list of chunks
will only effect future associations on the socket. will only effect future associations on the socket.
The following structure is used to add a chunk: The following structure is used to add a chunk:
struct sctp_authchunk { struct sctp_authchunk {
uint8_t sauth_chunk; uint8_t sauth_chunk;
}; };
sauth_chunk: This parameter contains a chunk type that the user is sauth_chunk: This parameter contains a chunk type that the user is
requesting to be authenticated. requesting to be authenticated.
The chunk types for INIT, INIT-ACK, SHUTDOWN-COMPLETE, and AUTH The chunk types for INIT, INIT-ACK, SHUTDOWN-COMPLETE, and AUTH
chunks MUST NOT be used. If they are used, an error MUST be 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 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 it is not required by other means (for example the use of dynamic
address reconfiguration). address reconfiguration).
8.3.3. Set a Shared Key (SCTP_AUTH_KEY) 7.3.3. Set a Shared Key (SCTP_AUTH_KEY)
This option will set a shared secret key which is used to build an This option will set a shared secret key which is used to build an
association shared key. association shared key.
The following structure is used to access and modify these The following structure is used to access and modify these
parameters: parameters:
struct sctp_authkey { struct sctp_authkey {
sctp_assoc_t sca_assoc_id; sctp_assoc_t sca_assoc_id;
uint16_t sca_keynumber; uint16_t sca_keynumber;
uint16_t sca_keylength; uint16_t sca_keylength;
uint8_t sca_key[]; uint8_t sca_key[];
}; };
sca_assoc_id: This parameter, if non-zero, indicates what sca_assoc_id: This parameter, if non-zero, indicates what
association that the shared key is being set upon. Note that if association that the shared key is being set upon. Note that any
this element contains zero, then the shared key is set upon the of the predefined constants can be used. For one-to-one sockets,
endpoint and all future associations will use this key (if not this parameter is ignored. Note, however, that this option will
changed by subsequent calls to SCTP_AUTH_KEY). For one-to-one set a key on the association if the socket is connected, otherwise
sockets, this parameter is ignored. Note, however, that this this will set a key on the endpoint.
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 sca_keynumber: This parameter is the shared key identifier by which
the application will refer to this key. If a key of the specified the application will refer to this key. If a key of the specified
index already exists, then this new key will replace the old index already exists, then this new key will replace the old
existing key. Note that shared key identifier '0' defaults to a existing key. Note that shared key identifier '0' defaults to a
null key. null key.
sca_keylength: This parameter is the length of the array sca_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 sca_key: This parameter contains an array of bytes that is to be
used by the endpoint (or association) as the shared secret key. 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, if the length of this field is zero, a null key is set.
8.3.4. Deactivate a Shared Key (SCTP_AUTH_DEACTIVATE_KEY) 7.3.4. Deactivate a Shared Key (SCTP_AUTH_DEACTIVATE_KEY)
This set option indicates that the application will not send user This set option indicates that the application will not send user
messages anymore requiring the usage of the indicated key identifier. messages anymore requiring the usage of the indicated key identifier.
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 deactivated. association that the shared key identifier is being deactivated.
Note that if this element contains zero, then the shared key is Note that the predefined constants may be used with this option.
deactivated for the endpoint and all associations will no longer For one-to-one sockets, this parameter is ignored. Note, however,
use the specified shared key identifier (unless otherwise set on that this option will deactivate the key from the association if
the association using SCTP_AUTH_KEY). For one-to-one sockets, the socket is connected, otherwise this will deactivate the key
this parameter is ignored. Note, however, that this option will from the endpoint.
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 scact_keynumber: This parameter is the shared key identifier which
the application is requesting to be deactivated. The key the application is requesting to be deactivated. The key
identifier MUST correspond to an existing shared key. Note if identifier must correspond to an existing shared key. Note if
this parameter is zero, use of the null key identifier '0' is this parameter is zero, use of the null key identifier '0' is
deactivated on the endpoint and/or association. deactivated on the endpoint and/or association.
The currently active key can not be deactivated. The currently active key can not be deactivated.
8.3.5. Delete a Shared Key (SCTP_AUTH_DELETE_KEY) 7.3.5. Delete a Shared Key (SCTP_AUTH_DELETE_KEY)
This set option will delete a shared secret key in the SCTP This set option will delete a shared secret key in the SCTP
implementation. implementation.
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
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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 deleted from. association that the shared key identifier is being deleted from.
Note that if this element contains zero, then the shared key is Note that if this element contains zero, then the shared key is
deleted from the endpoint and all associations will no longer use deleted from the endpoint and all associations will no longer use
the specified shared key identifier (unless otherwise set on the the specified shared key identifier (unless otherwise set on the
association using SCTP_AUTH_KEY). For one-to-one sockets, this association using SCTP_AUTH_KEY). For one-to-one sockets, this
parameter is ignored. Note, however, that this option will delete parameter is ignored. Note, however, that this option will delete
the key from the association if the socket is connected, otherwise the key from the association if the socket is connected, otherwise
this will delete the key from the endpoint. this will delete the key from the 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 be deleted. The key identifier the application is requesting to be deleted. The key identifier
MUST correspond to an existing shared key and MUST NOT be in use must correspond to an existing shared key and must not be in use
for any packet being sent by the SCTP implementation. This means for any packet being sent by the SCTP implementation. This means
in particular, that it MUST be deactivated first. Note if this in particular, that it must be deactivated first. Note if this
parameter is zero, use of the null key identifier '0' is deleted parameter is zero, use of the null key identifier '0' is deleted
from the endpoint and/or association. from the endpoint and/or association.
Only deactivated keys which are no longer used by the kernel can be Only deactivated keys which are no longer used by the kernel can be
deleted. deleted.
8.4. Ancillary Data and Notification Interest Options 7.4. 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. 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 5.2.2)
SCTP_ASSOC_CHANGE (sctp_association_event): described in SCTP_ASSOC_CHANGE (sctp_association_event): described in
Section 6.3.2 Section 5.3.2
SCTP_PEER_ADDR_CHANGE (sctp_address_event): described in SCTP_PEER_ADDR_CHANGE (sctp_address_event): described in
Section 6.3.3 Section 5.3.3
SCTP_SEND_FAILED (sctp_send_failure_event): described in SCTP_SEND_FAILED (sctp_send_failure_event): described in
Section 6.3.5 Section 5.3.5
SCTP_REMOTE_ERROR (sctp_peer_error_event): described in SCTP_REMOTE_ERROR (sctp_peer_error_event): described in
Section 6.3.4 Section 5.3.4
SCTP_SHUTDOWN_EVENT (sctp_shtudown_event): described in SCTP_SHUTDOWN_EVENT (sctp_shtudown_event): described in
Section 6.3.6 Section 5.3.6
SCTP_PARTIAL_DELIVERY_EVENT (sctp_partial_delivery_event): described SCTP_PARTIAL_DELIVERY_EVENT (sctp_partial_delivery_event): described
in Section 6.3.8 in Section 5.3.8
SCTP_ADAPTATION_INDICATION (sctp_adaptation_layer_event): described SCTP_ADAPTATION_INDICATION (sctp_adaptation_layer_event): described
in Section 6.3.7 in Section 5.3.7
SCTP_AUTHENTICATION_EVENT (sctp_authentication_event): described in SCTP_AUTHENTICATION_EVENT (sctp_authentication_event): described in
Section 6.3.9) Section 5.3.9)
SCTP_SENDER_DRY_EVENT (sctp_sender_dry_event): described in SCTP_SENDER_DRY_EVENT (sctp_sender_dry_event): described in
Section 6.3.10 Section 5.3.10
SCTP_NOTIFICATIONS_STOPPED_EVENT (sctp_tlv): described in
Section 5.3.11
To receive any ancillary data or notifications, first the application To receive any ancillary data or notifications, first the application
registers its 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;
skipping to change at page 69, line 4 skipping to change at page 73, line 16
{ {
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.
The SCTP_EVENTS socket option has one issue for future compatability.
As new features are added the structure (sctp_event_subscribe) must
be expanded. This can cause an ABI issue unless an implementation
has added padding at the end of the structure. To avoid this
problem, SCTP_EVENTS has been deprecated and a new option SCTP_EVENT
socket option has taken its place. The option is used with the
following structure:
struct sctp_event {
sctp_assoc_t se_assoc_id;
uint16_t se_type;
uint8_t se_on;
};
To use this option the user fills in this structure and then calls
the setsockopt to turn on or off an individual event. The following
is an example use of this option:
{
struct sctp_event set;
memset(&set,0,sizeof(set));
set.se_assoc_id = SCTP_FUTURE_ASSOC;
set.se_type = SCTP_SENDER_DRY_EVENT;
set.se_on = 1;
setsockopt(fd, IPPROTO_SCTP, SCTP_EVENTS, &event, sizeof(event));
}
The previous example would turn on the sender dry event. The se_type
field can be filled with any value that would show up in the
respective sn_type field (in the sctp_tlv structure of the
notification). The se_on field is set to 1 to turn on an event and
set to 0 to turn off an event. The se_assoc_id field is ignored for
one-to-one style sockets any this field can be a particular
association id or one of the defined constants.
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 Functions 8. 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() 8.1. sctp_bindx()
This function allows the user to bind a specific subset of addresses This function allows the user to bind a specific subset of addresses
or, if the SCTP extension described in [RFC5061] is supported, add or or, if the SCTP extension described in [RFC5061] is supported, add or
delete specific addresses. delete specific addresses.
The function prototype is The function prototype is
int sctp_bindx(int sd, int sctp_bindx(int sd,
struct sockaddr *addrs, struct sockaddr *addrs,
int addrcnt, 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 3.1.2 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
address is contained in its appropriate structure. For an IPv6 address is contained in its appropriate structure. For an IPv6
socket, an array of sockaddr_in6 would be returned. For a IPv4 socket, an array of sockaddr_in6 would be returned. For a IPv4
socket, an array of sockaddr_in would be returned. The caller socket, an array of sockaddr_in would be returned. The caller
specifies the number of addresses in the array with addrcnt. Note specifies the number of addresses in the array with addrcnt. Note
that the wildcard addresses cannot be used in combination with non that the wildcard addresses cannot be used in combination with non
wildcard addresses on a socket with this function, doing so will wildcard addresses on a socket with this function, doing so will
result in an error. result in an error.
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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
socket is associated with so that no new association accepted will be socket is associated with so that no new association accepted will be
associated with those addresses. If the endpoint supports dynamic associated with those addresses. If the endpoint supports dynamic
address a SCTP_BINDX_REM_ADDR or SCTP_BINDX_ADD_ADDR may cause a address a SCTP_BINDX_REM_ADDR or SCTP_BINDX_ADD_ADDR may cause a
endpoint to send the appropriate message to the peer to change the endpoint to send the appropriate message to the peer to change the
peers address lists. peers address lists.
Adding and removing addresses from a connected association is Adding and removing addresses from a connected association is an
optional functionality. Implementations that do not support this optional functionality. Implementations that do not support this
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.
sctp_bindx() is an atomic operation. Therefore the binding will be sctp_bindx() is an atomic operation. Therefore the binding will be
either successful on all addresses or fail on all addresses. If either successful on all addresses or fail on all addresses. If
multiple addresses are provided and the sctp_bindx() call fails there multiple addresses are provided and the sctp_bindx() call fails there
is no indication which address is responsible for the failure. The is no indication which address is responsible for the failure. The
only way to get an specific error indication is to call sctp_bindx() only way to get an specific error indication is to call sctp_bindx()
with only one address sequentially. with only one address sequentially.
9.2. sctp_peeloff() 8.2. 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.
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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 function prototype is The function prototype is
int sctp_peeloff(int sd, int sctp_peeloff(int sd,
sctp_assoc_t assoc_id); sctp_assoc_t assoc_id);
and the arguments are and the arguments are
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 3.1.1).
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 The function returns a non-negative file descriptor representing the
branched-off association, or -1 if an error occurred. The variable branched-off association, or -1 if an error occurred. The variable
errno is then set appropriately. errno is then set appropriately.
9.3. sctp_getpaddrs() 8.3. sctp_getpaddrs()
sctp_getpaddrs() returns all peer addresses in an association. sctp_getpaddrs() returns all peer addresses in an association.
The function protoype is: The function protoype is:
int sctp_getpaddrs(int sd, int sctp_getpaddrs(int sd,
sctp_assoc_t id, 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
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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.
For one-to-many style sockets, id specifies the association to query. For one-to-many style sockets, id specifies the association to query.
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() 8.4. sctp_freepaddrs()
sctp_freepaddrs() frees all resources allocated by sctp_getpaddrs(). sctp_freepaddrs() frees all resources allocated by sctp_getpaddrs().
The function prototype is The function prototype is
void sctp_freepaddrs(struct sockaddr *addrs); void sctp_freepaddrs(struct sockaddr *addrs);
and addrs is the array of peer addresses returned by and addrs is the array of peer addresses returned by
sctp_getpaddrs(). sctp_getpaddrs().
9.5. sctp_getladdrs() 8.5. 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 function prototype is The function prototype is
int sctp_getladdrs(int sd, int sctp_getladdrs(int sd,
sctp_assoc_t id, 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
skipping to change at page 73, line 5 skipping to change at page 78, line 5
For one-to-one style sockets, id is ignored. For one-to-one style sockets, id is ignored.
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() 8.6. sctp_freeladdrs()
sctp_freeladdrs() frees all resources allocated by sctp_getladdrs(). sctp_freeladdrs() frees all resources allocated by sctp_getladdrs().
The function prototype is The function prototype is
void sctp_freeladdrs(struct sockaddr *addrs); void sctp_freeladdrs(struct sockaddr *addrs);
and addrs is the array of peer addresses returned by and addrs is the array of peer addresses returned by
sctp_getladdrs(). sctp_getladdrs().
9.7. sctp_sendmsg() 8.7. 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.
The function prototype 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,
skipping to change at page 73, line 40 skipping to change at page 78, line 40
uint16_t stream_no, uint16_t stream_no,
uint32_t pr_value, uint32_t pr_value,
uint32_t context); uint32_t context);
and the arguments are: and the arguments are:
sd: The socket descriptor sd: The socket descriptor
msg: The message to be sent. msg: The message to be sent.
len: Yhe length of the message. len: Yhe length of the message.
to: The destination address of the message. to: The destination address of the message.
tolen: The length of the destination address. tolen: The length of the destination address.
ppid: The same as sinfo_ppid (see Section 6.2.2) ppid: The same as sinfo_ppid (see Section 5.2.2)
flags: The same as sinfo_flags (see Section 6.2.2) flags: The same as sinfo_flags (see Section 5.2.2)
stream_no: The same as sinfo_stream (see Section 6.2.2) stream_no: The same as sinfo_stream (see Section 5.2.2)
pr_value: The same as sinfo_pr_value (see Section 6.2.2). pr_value: The same as sinfo_pr_value (see Section 5.2.2).
context: The same as sinfo_context (see Section 6.2.2) context: The same as sinfo_context (see Section 5.2.2)
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. occurred. The variable errno is then set appropriately.
Sending a message using sctp_sendmsg() is atomic unless explicit EOR Sending a message using sctp_sendmsg() is atomic (unless explicit EOR
marking is enabled on the socket specified by sd. marking is enabled on the socket specified by sd).
Using sctp_sendmsg() on a non-connected one-to-one style socket for 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 implicit connection setup may or may not work depending on the SCTP
implementation. implementation.
9.8. sctp_recvmsg() 8.8. 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.
The function prototype is The function prototype is
skipping to change at page 74, line 45 skipping to change at page 79, line 45
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). Note that this field is an in-out 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 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 (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 will be different than what was sent in to the call. If
implemented via a recvmsg() call, the msg_flags should only implemented via a recvmsg() call, the msg_flags should only
contain the value of the flags from the recvmsg() call. 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() 8.9. 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.
skipping to change at page 75, line 32 skipping to change at page 80, line 32
sd: The socket descriptor. sd: The socket descriptor.
addrs: An (packed) array of addresses. addrs: An (packed) array of addresses.
addrcnt: The number of addresses in the array. addrcnt: The number of addresses in the array.
id: An output parameter that if passed in as a non-NULL will return id: An output parameter that if passed in as a non-NULL will return
the association identification for the newly created association the association identification for the newly created association
(if successful). (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() 8.10. 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. use of the CMSG header structures.
The function prototype is The function prototype is
ssize_t 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);
and the arguments are and the arguments are
sd: The socket descriptor. sd: The socket descriptor.
msg: The message to be sent. msg: The message to be sent.
len: The length of the message. len: The length of the message.
sinfo: A pointer to a sctp_sndrcvinfo structure used as described in sinfo: A pointer to a sctp_sndrcvinfo structure used as described in
Section 6.2.2 for a sendmsg call. Section 5.2.2 for a sendmsg call.
flags: The same flags as used by the sendmsg call flags (e.g. 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 The call returns the number of bytes sent, or -1 if an error
occurred. The variable errno is then set appropriately. 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. marking is enabled on the socket specified by sd.
9.11. sctp_sendx() 8.11. 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 8.9).
The function prototype is The function prototype is
ssize_t 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);
and the arguments are: and the arguments are:
sd: The socket descriptor. sd: The socket descriptor.
msg: The message to be sent. msg: The message to be sent.
len: The length of the message. len: The length of the message.
addrs: is an array of addresses. addrs: is an array of addresses.
addrcnt: The number of addresses in the array. addrcnt: The number of addresses in the array.
sinfo: A pointer to a sctp_sndrcvinfo structure used as described in sinfo: A pointer to a sctp_sndrcvinfo structure used as described in
Section 6.2.2 for a sendmsg call. Section 5.2.2 for a sendmsg call.
flags: The same flags as used by the sendmsg call flags (e.g. 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 The call returns the number of bytes sent, or -1 if an error
occurred. The variable errno is then set appropriately. 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
skipping to change at page 77, line 33 skipping to change at page 82, line 33
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. marking is enabled on the socket specified by sd.
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() 8.12. 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.
The function prototype is: The function prototype is:
int sctp_getaddrlen(sa_family_t family); int sctp_getaddrlen(sa_family_t family);
This function, when called with a valid family type returns the This function, when called with a valid family type returns the
length that the operating system uses in the specified family's length that the operating system uses in the specified family's
socket address structure. In case of an error, -1 is returned an the socket address structure. In case of an error, -1 is returned an the
variable errno is then set appropriately variable errno is then set appropriately.
10. IANA Considerations 9. IANA Considerations
This document requires no actions from IANA. This document requires no actions from IANA.
11. Security Considerations 10. 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
being more aggressive than permitted on the public Internet. These being more aggressive than permitted on the public Internet. These
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 8.1.20. described in Section 7.1.20.
12. Acknowledgments 11. 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.
13. Normative References 12. 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 86, line 7 skipping to change at page 91, line 7
} }
/* Allow new associations to be accepted */ /* Allow new associations to be accepted */
if (listen(fd, 1) < 0) { if (listen(fd, 1) < 0) {
perror("listen"); perror("listen");
exit(1); exit(1);
} }
/* Wait for new associations */ /* Wait for new associations */
while(1){ while(1){
/* Echo back any and all data */ /* Echo back any and all data */
echo(fd,1); echo(fd,1); /* from appendix a */
} }
} }
Authors' Addresses Authors' Addresses
Randall R. Stewart Randall R. Stewart
Researcher Huawei
Chapin, SC 29036 Chapin, SC 29036
USA USA
Email: randall@lakerest.net Email: rstewart@huawei.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
Email: kacheong.poon@sun.com Email: kacheong.poon@sun.com
Michael Tuexen Michael Tuexen
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