draft-ietf-tsvwg-sctpsocket-10.txt   draft-ietf-tsvwg-sctpsocket-11.txt 
Network Working Group R. Stewart Network Working Group R. Stewart
Internet-Draft Cisco Systems, Inc. Internet-Draft Cisco Systems, Inc.
Expires: August 25, 2005 Q. Xie Expires: March 11, 2006 Q. Xie
Motorola, Inc. Motorola, Inc.
L. Yarroll L. Yarroll
TimeSys Corp TimeSys Corp
J. Wood J. Wood
DoCoMo USA Labs DoCoMo USA Labs
K. Poon K. Poon
Sun Microsystems, Inc. Sun Microsystems, Inc.
M. Tuexen M. Tuexen
Univ. of Applied Sciences Muenster Univ. of Applied Sciences Muenster
February 21, 2005 September 7, 2005
Sockets API Extensions for Stream Control Transmission Protocol Sockets API Extensions for Stream Control Transmission Protocol (SCTP)
(SCTP) draft-ietf-tsvwg-sctpsocket-11.txt
draft-ietf-tsvwg-sctpsocket-10.txt
Status of this Memo Status of this Memo
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Copyright Notice Copyright Notice
Copyright (C) The Internet Society (2005). Copyright (C) The Internet Society (2005).
Abstract Abstract
This document describes a mapping of the Stream Control Transmission This document describes a mapping of the Stream Control Transmission
Protocol SCTP RFC2960 [8] into a sockets API. The benefits of this Protocol SCTP RFC2960 [8] into a sockets API. The benefits of this
mapping include compatibility for TCP applications, access to new mapping include compatibility for TCP applications, access to new
SCTP features and a consolidated error and event notification scheme. SCTP features and a consolidated error and event notification scheme.
Table of Contents Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 5 1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . 5
2. Conventions . . . . . . . . . . . . . . . . . . . . . . . . 7 2. Conventions . . . . . . . . . . . . . . . . . . . . . . . . . 7
2.1 Data Types . . . . . . . . . . . . . . . . . . . . . . . . 7 2.1. Data Types . . . . . . . . . . . . . . . . . . . . . . . . 7
3. one-to-many style Interface . . . . . . . . . . . . . . . . 8 3. one-to-many style Interface . . . . . . . . . . . . . . . . . 8
3.1 Basic Operation . . . . . . . . . . . . . . . . . . . . . 8 3.1. Basic Operation . . . . . . . . . . . . . . . . . . . . . 8
3.1.1 socket() - one-to-many style socket . . . . . . . . . 9 3.1.1. socket() - one-to-many style socket . . . . . . . . . 9
3.1.2 bind() - one-to-many style socket . . . . . . . . . . 9 3.1.2. bind() - one-to-many style socket . . . . . . . . . . 10
3.1.3 listen() - One-to-many style socket . . . . . . . . . 10 3.1.3. listen() - One-to-many style socket . . . . . . . . . 11
3.1.4 sendmsg() and recvmsg() - one-to-many style socket . . 11 3.1.4. sendmsg() and recvmsg() - one-to-many style socket . . 11
3.1.5 close() - one-to-many style socket . . . . . . . . . . 12 3.1.5. close() - one-to-many style socket . . . . . . . . . . 13
3.1.6 connect() - one-to-many style socket . . . . . . . . . 13 3.1.6. connect() - one-to-many style socket . . . . . . . . . 13
3.2 Implicit Association Setup . . . . . . . . . . . . . . . . 13 3.2. Implicit Association Setup . . . . . . . . . . . . . . . . 14
3.3 Non-blocking mode . . . . . . . . . . . . . . . . . . . . 14 3.3. Non-blocking mode . . . . . . . . . . . . . . . . . . . . 14
3.4 Special considerations . . . . . . . . . . . . . . . . . . 15 3.4. Special considerations . . . . . . . . . . . . . . . . . . 15
4. one-to-one style Interface . . . . . . . . . . . . . . . . . 17 4. one-to-one style Interface . . . . . . . . . . . . . . . . . . 18
4.1 Basic Operation . . . . . . . . . . . . . . . . . . . . . 17 4.1. Basic Operation . . . . . . . . . . . . . . . . . . . . . 18
4.1.1 socket() - one-to-one style socket . . . . . . . . . . 18 4.1.1. socket() - one-to-one style socket . . . . . . . . . . 19
4.1.2 bind() - one-to-one style socket . . . . . . . . . . . 18 4.1.2. bind() - one-to-one style socket . . . . . . . . . . . 19
4.1.3 listen() - one-to-one style socket . . . . . . . . . . 19 4.1.3. listen() - one-to-one style socket . . . . . . . . . . 20
4.1.4 accept() - one-to-one style socket . . . . . . . . . . 20 4.1.4. accept() - one-to-one style socket . . . . . . . . . . 21
4.1.5 connect() - one-to-one style socket . . . . . . . . . 20 4.1.5. connect() - one-to-one style socket . . . . . . . . . 21
4.1.6 close() - one-to-one style socket . . . . . . . . . . 21 4.1.6. close() - one-to-one style socket . . . . . . . . . . 22
4.1.7 shutdown() - one-to-one style socket . . . . . . . . . 21 4.1.7. shutdown() - one-to-one style socket . . . . . . . . . 22
4.1.8 sendmsg() and recvmsg() - one-to-one style socket . . 22 4.1.8. sendmsg() and recvmsg() - one-to-one style socket . . 23
4.1.9 getpeername() . . . . . . . . . . . . . . . . . . . . 23 4.1.9. getpeername() . . . . . . . . . . . . . . . . . . . . 24
5. Data Structures . . . . . . . . . . . . . . . . . . . . . . 24 5. Data Structures . . . . . . . . . . . . . . . . . . . . . . . 25
5.1 The msghdr and cmsghdr Structures . . . . . . . . . . . . 24 5.1. The msghdr and cmsghdr Structures . . . . . . . . . . . . 25
5.2 SCTP msg_control Structures . . . . . . . . . . . . . . . 25 5.2. SCTP msg_control Structures . . . . . . . . . . . . . . . 26
5.2.1 SCTP Initiation Structure (SCTP_INIT) . . . . . . . . 26 5.2.1. SCTP Initiation Structure (SCTP_INIT) . . . . . . . . 27
5.2.2 SCTP Header Information Structure (SCTP_SNDRCV) . . . 27 5.2.2. SCTP Header Information Structure (SCTP_SNDRCV) . . . 28
5.3 SCTP Events and Notifications . . . . . . . . . . . . . . 30 5.3. SCTP Events and Notifications . . . . . . . . . . . . . . 31
5.3.1 SCTP Notification Structure . . . . . . . . . . . . . 30 5.3.1. SCTP Notification Structure . . . . . . . . . . . . . 31
5.4 Ancillary Data Considerations and Semantics . . . . . . . 40 5.4. Ancillary Data Considerations and Semantics . . . . . . . 42
5.4.1 Multiple Items and Ordering . . . . . . . . . . . . . 40 5.4.1. Multiple Items and Ordering . . . . . . . . . . . . . 43
5.4.2 Accessing and Manipulating Ancillary Data . . . . . . 40 5.4.2. Accessing and Manipulating Ancillary Data . . . . . . 43
5.4.3 Control Message Buffer Sizing . . . . . . . . . . . . 41 5.4.3. Control Message Buffer Sizing . . . . . . . . . . . . 43
6. Common Operations for Both Styles . . . . . . . . . . . . . 43 6. Common Operations for Both Styles . . . . . . . . . . . . . . 45
6.1 send(), recv(), sendto(), recvfrom() . . . . . . . . . . . 43 6.1. send(), recv(), sendto(), recvfrom() . . . . . . . . . . . 45
6.2 setsockopt(), getsockopt() . . . . . . . . . . . . . . . . 44 6.2. setsockopt(), getsockopt() . . . . . . . . . . . . . . . . 46
6.3 read() and write() . . . . . . . . . . . . . . . . . . . . 44 6.3. read() and write() . . . . . . . . . . . . . . . . . . . . 46
6.4 getsockname() . . . . . . . . . . . . . . . . . . . . . . 44 6.4. getsockname() . . . . . . . . . . . . . . . . . . . . . . 46
7. Socket Options . . . . . . . . . . . . . . . . . . . . . . . 46 7. Socket Options . . . . . . . . . . . . . . . . . . . . . . . . 48
7.1 Read / Write Options . . . . . . . . . . . . . . . . . . . 47 7.1. Read / Write Options . . . . . . . . . . . . . . . . . . . 49
7.1.1 Retransmission Timeout Parameters (SCTP_RTOINFO) . . . 47 7.1.1. Retransmission Timeout Parameters (SCTP_RTOINFO) . . . 49
7.1.2 Association Parameters (SCTP_ASSOCINFO) . . . . . . . 48 7.1.2. Association Parameters (SCTP_ASSOCINFO) . . . . . . . 50
7.1.3 Initialization Parameters (SCTP_INITMSG) . . . . . . . 50 7.1.3. Initialization Parameters (SCTP_INITMSG) . . . . . . . 52
7.1.4 SO_LINGER . . . . . . . . . . . . . . . . . . . . . . 50 7.1.4. SO_LINGER . . . . . . . . . . . . . . . . . . . . . . 52
7.1.5 SCTP_NODELAY . . . . . . . . . . . . . . . . . . . . . 50 7.1.5. SCTP_NODELAY . . . . . . . . . . . . . . . . . . . . . 52
7.1.6 SO_RCVBUF . . . . . . . . . . . . . . . . . . . . . . 51 7.1.6. SO_RCVBUF . . . . . . . . . . . . . . . . . . . . . . 53
7.1.7 SO_SNDBUF . . . . . . . . . . . . . . . . . . . . . . 51 7.1.7. SO_SNDBUF . . . . . . . . . . . . . . . . . . . . . . 53
7.1.8 Automatic Close of associations (SCTP_AUTOCLOSE) . . . 51 7.1.8. Automatic Close of associations (SCTP_AUTOCLOSE) . . . 53
7.1.9 Set Peer Primary Address 7.1.9. Set Peer Primary Address
(SCTP_SET_PEER_PRIMARY_ADDR) . . . . . . . . . . . . . 51 (SCTP_SET_PEER_PRIMARY_ADDR) . . . . . . . . . . . . . 53
7.1.10 Set Primary Address (SCTP_PRIMARY_ADDR) . . . . . . 52 7.1.10. Set Primary Address (SCTP_PRIMARY_ADDR) . . . . . . . 54
7.1.11 Set Adaption Layer Indicator (SCTP_ADAPTION_LAYER) . 52 7.1.11. Set Adaption Layer Indicator (SCTP_ADAPTION_LAYER) . . 54
7.1.12 Enable/Disable message fragmentation 7.1.12. Enable/Disable message fragmentation
(SCTP_DISABLE_FRAGMENTS) . . . . . . . . . . . . . . 53 (SCTP_DISABLE_FRAGMENTS) . . . . . . . . . . . . . . . 55
7.1.13 Peer Address Parameters (SCTP_PEER_ADDR_PARAMS) . . 53 7.1.13. Peer Address Parameters (SCTP_PEER_ADDR_PARAMS) . . . 55
7.1.14 Set default send parameters 7.1.14. Set default send parameters
(SCTP_DEFAULT_SEND_PARAM) . . . . . . . . . . . . . 55 (SCTP_DEFAULT_SEND_PARAM) . . . . . . . . . . . . . . 57
7.1.15 Set notification and ancillary events 7.1.15. Set notification and ancillary events (SCTP_EVENTS) . 57
(SCTP_EVENTS) . . . . . . . . . . . . . . . . . . . 55 7.1.16. Set/clear IPv4 mapped addresses
7.1.16 Set/clear IPv4 mapped addresses (SCTP_I_WANT_MAPPED_V4_ADDR) . . . . . . . . . . . . . 57
(SCTP_I_WANT_MAPPED_V4_ADDR) . . . . . . . . . . . . 55 7.1.17. Set the maximum fragmentation size (SCTP_MAXSEG) . . . 57
7.1.17 Set the maximum fragmentation size (SCTP_MAXSEG) . . 55 7.1.18. Add a chunk that must be authenticated
7.1.18 Set/Get the list of chunks that must be (SCTP_AUTH_CHUNK) . . . . . . . . . . . . . . . . . . 58
authenticated (SCTP_AUTH_CHUNKS) . . . . . . . . . . 56 7.1.19. Set the endpoint pair shared key (SCTP_AUTH_KEY) . . . 58
7.1.19 Set/Get the current authentication shared secret 7.1.20. Get the list of chunks the peer requires to be
(SCTP_AUTH_SECRET) . . . . . . . . . . . . . . . . . 56 authenticated (SCTP_PEER_AUTH_CHUNKS) . . . . . . . . 59
7.1.20 Get the list of chunks that peer requires to be 7.1.21. Get the list of chunks the local endpoint requires
authenticated (SCTP_PEER_AUTH_CHUNKS) . . . . . . . 57 to be authenticated (SCTP_LOCAL_AUTH_CHUNKS) . . . . 60
7.2 Read-Only Options . . . . . . . . . . . . . . . . . . . . 57 7.1.22. Set the list of supported HMAC Identifiers
7.2.1 Association Status (SCTP_STATUS) . . . . . . . . . . . 57 (SCTP_HMAC_IDENT) . . . . . . . . . . . . . . . . . . 60
7.2.2 Peer Address Information (SCTP_GET_PEER_ADDR_INFO) . . 58 7.1.23. Get or set the active key
7.3 Ancillary Data and Notification Interest Options . . . . . 59 (SCTP_AUTH_SETKEY_ACTIVE) . . . . . . . . . . . . . . 61
8. New Interfaces . . . . . . . . . . . . . . . . . . . . . . . 62 7.1.24. Get or set delayed ack timer
8.1 sctp_bindx() . . . . . . . . . . . . . . . . . . . . . . . 62 (SCTP_DELAYED_ACK_TIME) . . . . . . . . . . . . . . . 63
8.2 Branched-off Association . . . . . . . . . . . . . . . . . 63 7.2. Read-Only Options . . . . . . . . . . . . . . . . . . . . 63
8.3 sctp_getpaddrs() . . . . . . . . . . . . . . . . . . . . . 63 7.2.1. Association Status (SCTP_STATUS) . . . . . . . . . . . 63
8.4 sctp_freepaddrs() . . . . . . . . . . . . . . . . . . . . 64 7.2.2. Peer Address Information (SCTP_GET_PEER_ADDR_INFO) . . 65
8.5 sctp_getladdrs() . . . . . . . . . . . . . . . . . . . . . 64 7.3. Ancillary Data and Notification Interest Options . . . . . 65
8.6 sctp_freeladdrs() . . . . . . . . . . . . . . . . . . . . 65 8. New Interfaces . . . . . . . . . . . . . . . . . . . . . . . . 69
8.7 sctp_sendmsg() . . . . . . . . . . . . . . . . . . . . . . 65 8.1. sctp_bindx() . . . . . . . . . . . . . . . . . . . . . . . 69
8.8 sctp_recvmsg() . . . . . . . . . . . . . . . . . . . . . . 66 8.2. Branched-off Association . . . . . . . . . . . . . . . . . 70
8.9 sctp_connectx() . . . . . . . . . . . . . . . . . . . . . 67 8.3. sctp_getpaddrs() . . . . . . . . . . . . . . . . . . . . . 71
8.10 sctp_send() . . . . . . . . . . . . . . . . . . . . . . 68 8.4. sctp_freepaddrs() . . . . . . . . . . . . . . . . . . . . 71
8.11 sctp_sendx() . . . . . . . . . . . . . . . . . . . . . . 68 8.5. sctp_getladdrs() . . . . . . . . . . . . . . . . . . . . . 71
9. Preprocessor Constants . . . . . . . . . . . . . . . . . . . 70 8.6. sctp_freeladdrs() . . . . . . . . . . . . . . . . . . . . 72
10. Security Considerations . . . . . . . . . . . . . . . . . . 71 8.7. sctp_sendmsg() . . . . . . . . . . . . . . . . . . . . . . 72
11. Acknowledgments . . . . . . . . . . . . . . . . . . . . . . 72 8.8. sctp_recvmsg() . . . . . . . . . . . . . . . . . . . . . . 73
12. References . . . . . . . . . . . . . . . . . . . . . . . . . 72 8.9. sctp_connectx() . . . . . . . . . . . . . . . . . . . . . 74
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . 73 8.10. sctp_send() . . . . . . . . . . . . . . . . . . . . . . . 75
A. one-to-one style Code Example . . . . . . . . . . . . . . . 75 8.11. sctp_sendx() . . . . . . . . . . . . . . . . . . . . . . . 75
B. one-to-many style Code Example . . . . . . . . . . . . . . . 81 9. Preprocessor Constants . . . . . . . . . . . . . . . . . . . . 77
Intellectual Property and Copyright Statements . . . . . . . 83 10. Security Considerations . . . . . . . . . . . . . . . . . . . 78
11. Acknowledgments . . . . . . . . . . . . . . . . . . . . . . . 79
12. References . . . . . . . . . . . . . . . . . . . . . . . . . . 79
Appendix A. one-to-one style Code Example . . . . . . . . . . . . 80
Appendix B. one-to-many style Code Example . . . . . . . . . . . 86
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . . 88
Intellectual Property and Copyright Statements . . . . . . . . . . 90
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 RFC793 [1] and Protocol suite to many operating systems. Both TCP RFC793 [1] and
UDP RFC768 [2] have benefited from this standard representation and UDP RFC768 [2] have benefited from this standard representation and
access method across many diverse platforms. SCTP is a new protocol access method across many diverse platforms. SCTP is a new protocol
that provides many of the characteristics of TCP but also that provides many of the characteristics of TCP but also
incorporates semantics more akin to UDP. This document defines a incorporates semantics more akin to UDP. This document defines a
method to map the existing sockets API for use with SCTP, providing method to map the existing sockets API for use with SCTP, providing
skipping to change at page 5, line 21 skipping to change at page 5, line 21
that provides many of the characteristics of TCP but also that provides many of the characteristics of TCP but also
incorporates semantics more akin to UDP. This document defines a incorporates semantics more akin to UDP. This document defines a
method to map the existing sockets API for use with SCTP, providing method to map the existing sockets API for use with SCTP, providing
both a base for access to new features and compatibility so that most both a base for access to new features and compatibility so that most
existing TCP applications can be migrated to SCTP with few (if any) existing TCP applications can be migrated to SCTP with few (if any)
changes. changes.
There are three basic design objectives: There are three basic design objectives:
1) Maintain consistency with existing sockets APIs: 1) Maintain consistency with existing sockets APIs:
We define a sockets mapping for SCTP that is consistent with other We define a sockets mapping for SCTP that is consistent with other
sockets API protocol mappings (for instance, UDP, TCP, IPv4, and sockets API protocol mappings (for instance, UDP, TCP, IPv4, and
IPv6). IPv6).
2) Support a one-to-many style interface 2) Support a one-to-many style interface
This set of semantics is similar to that defined for
connection-less protocols, such as UDP. A one-to-many style SCTP This set of semantics is similar to that defined for connection-
socket should be able to control multiple SCTP associations. This less protocols, such as UDP. A one-to-many style SCTP socket
is similar to an UDP socket, which can communicate with many peer should be able to control multiple SCTP associations. This is
end points. Each of these associations is assigned an association similar to an UDP socket, which can communicate with many peer end
ID so that an applications can use the ID to differentiate them. points. Each of these associations is assigned an association ID
so that an applications can use the ID to differentiate them.
Note that SCTP is connection-oriented in nature, and it does not Note that SCTP is connection-oriented in nature, and it does not
support broadcast or multicast communications, as UDP does. support broadcast or multicast communications, as UDP does.
3) Support a one-to-one style interface 3) Support a one-to-one style interface
This interface supports a similar semantics as sockets for This interface supports a similar semantics as sockets for
connection-oriented protocols, such as TCP. A one-to-one style connection-oriented protocols, such as TCP. A one-to-one style
SCTP socket should only control one SCTP association. SCTP socket should only control one SCTP association.
One purpose of defining this interface is to allow existing One purpose of defining this interface is to allow existing
applications built on other connection-oriented protocols be applications built on other connection-oriented protocols be
ported to use SCTP with very little effort. And developers ported to use SCTP with very little effort. And developers
familiar with those semantics can easily adapt to SCTP. Another familiar with those semantics can easily adapt to SCTP. Another
purpose is to make sure that existing mechanisms in most OSes to purpose is to make sure that existing mechanisms in most OSes to
deal with socket, such as select(), should continue to work with deal with socket, such as select(), should continue to work with
this style of socket. this style of socket.
Extensions are added to this mapping to provide mechanisms to Extensions are added to this mapping to provide mechanisms to
exploit new features of SCTP. exploit new features of SCTP.
Goals 2 and 3 are not compatible, so in this document we define two Goals 2 and 3 are not compatible, so in this document we define two
modes of mapping, namely the one-to-many style mapping and the modes of mapping, namely the one-to-many style mapping and the one-
one-to-one style mapping. These two modes share some common data to-one style mapping. These two modes share some common data
structures and operations, but will require the use of two different structures and operations, but will require the use of two different
application programming styles. Note that all new SCTP features can application programming styles. Note that all new SCTP features can
be used with both styles of socket. The decision on which one to use be used with both styles of socket. The decision on which one to use
depends mainly on the nature of applications. depends mainly on the nature of applications.
A mechanism is defined to extract a one-to-many style SCTP A mechanism is defined to extract a one-to-many style SCTP
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 8 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. Conventions
2.1 Data Types 2.1. 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.
3. 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:
A) Outbound association setup is implicit. A) Outbound association setup is implicit.
B) Messages are delivered in complete messages (with one notable B) Messages are delivered in complete messages (with one notable
exception). exception).
C) There is a 1 to MANY relationship between socket and association. C) There is a 1 to MANY relationship between socket and association.
3.1 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:
1. socket() 1. socket()
2. bind() 2. bind()
3. listen() 3. listen()
4. recvmsg() 4. recvmsg()
5. sendmsg() 5. sendmsg()
6. close() 6. close()
A typical client uses the following calls in sequence to setup an A typical client uses the following calls in sequence to setup an
association with a server to request services: association with a server to request services:
1. socket() 1. socket()
2. sendmsg() 2. sendmsg()
3. recvmsg() 3. recvmsg()
4. close() 4. close()
In this style, by default, all the associations connected to the In this style, by default, all the associations connected to the
endpoint are represented with a single socket. Each associations is endpoint are represented with a single socket. Each associations is
assigned an association ID (type is sctp_assoc_t) so that an assigned an association ID (type is sctp_assoc_t) so that an
application can use it to differentiate between them. In some application can use it to differentiate between them. In some
implementations, the peer end point's addresses can also be used for implementations, the peer end point's 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
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Once an association is branched off to a separate socket, it becomes Once an association is branched off to a separate socket, it becomes
completely separated from the original socket. All subsequent completely separated from the original socket. All subsequent
control and data operations to that association must be done through control and data operations to that association must be done through
the new socket. For example, the close operation on the original the new socket. For example, the close operation on the original
socket will not terminate any associations that have been branched socket will not terminate any associations that have been branched
off to a different socket. off to a different socket.
We will discuss the one-to-many style socket calls in more details in We will discuss the one-to-many style socket calls in more details in
the following subsections. the following subsections.
3.1.1 socket() - one-to-many style socket 3.1.1. socket() - one-to-many style socket
Applications use socket() to create a socket descriptor to represent Applications use socket() to create a socket descriptor to represent
an SCTP endpoint. an SCTP endpoint.
The syntax is, The syntax is,
sd = socket(PF_INET, SOCK_SEQPACKET, IPPROTO_SCTP); sd = socket(PF_INET, SOCK_SEQPACKET, IPPROTO_SCTP);
or, or,
sd = socket(PF_INET6, SOCK_SEQPACKET, IPPROTO_SCTP); sd = socket(PF_INET6, SOCK_SEQPACKET, IPPROTO_SCTP);
Here, SOCK_SEQPACKET indicates the creation of a one-to-many style Here, SOCK_SEQPACKET indicates the creation of a one-to-many style
socket. socket.
The first form creates an endpoint which can use only IPv4 addresses, The first form creates an endpoint which can use only IPv4 addresses,
while, the second form creates an endpoint which can use both IPv6 while, the second form creates an endpoint which can use both IPv6
and IPv4 addresses. and IPv4 addresses.
3.1.2 bind() - one-to-many style socket 3.1.2. bind() - one-to-many style socket
Applications use bind() to specify which local address the SCTP Applications use bind() to specify which local address the SCTP
endpoint should associate itself with. endpoint should associate itself with.
An SCTP endpoint can be associated with multiple addresses. To do An SCTP endpoint can be associated with multiple addresses. To do
this, sctp_bindx() is introduced in section Section 8.1 to help this, sctp_bindx() is introduced in section Section 8.1 to help
applications do the job of associating multiple addresses. applications 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
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If addr is specified as a wildcard (INADDR_ANY for an IPv4 address, If addr is specified as a wildcard (INADDR_ANY for an IPv4 address,
or as IN6ADDR_ANY_INIT or in6addr_any for an IPv6 address), the or as IN6ADDR_ANY_INIT or in6addr_any for an IPv6 address), the
operating system will associate the endpoint with an optimal address operating system will associate the endpoint with an optimal address
set of the available interfaces. set of the available interfaces.
If a bind() is not called prior to a sendmsg() call that initiates a If a bind() is not called prior to a sendmsg() call that initiates a
new association, the system picks an ephemeral port and will choose new association, the system picks an ephemeral port and will choose
an address set equivalent to binding with a wildcard address. One of an address set equivalent to binding with a wildcard address. One of
those addresses will be the primary address for the association. those addresses will be the primary address for the association.
This automatically enables the multi-homing capability of SCTP. This automatically enables the multi-homing capability of SCTP.
3.1.3 listen() - One-to-many style socket 3.1.3. listen() - One-to-many style socket
By default, new associations are not accepted for one-to-many style By default, new associations are not accepted for one-to-many style
sockets. An application uses listen() to mark a socket as being able sockets. An application uses listen() to mark a socket as being able
to accept new associations. The syntax is, to accept new associations. The syntax is,
int listen(int sd, int backlog); int listen(int sd, int backlog);
sd - the socket descriptor of the endpoint. sd - the socket descriptor of the endpoint.
backlog - if backlog is non-zero, enable listening else backlog - if backlog is non-zero, enable listening else
disable listening. disable listening.
Note that one-to-many style socket consumers do not need to call Note that one-to-many style socket consumers do not need to call
accept to retrieve new associations. Calling accept() on a accept to retrieve new associations. Calling accept() on a one-to-
one-to-many style socket should return EOPNOTSUPP. Rather, new many style socket should return EOPNOTSUPP. Rather, new associations
associations are accepted automatically, and notifications of the new are accepted automatically, and notifications of the new associations
associations are delivered via recvmsg() with the SCTP_ASSOC_CHANGE are delivered via recvmsg() with the SCTP_ASSOC_CHANGE event (if
event (if these notifications are enabled). Clients will typically these notifications are enabled). Clients will typically not call
not call listen(), so that they can be assured that the only listen(), so that they can be assured that the only associations on
associations on the socket will be ones they actively initiated. the socket will be ones they actively initiated. Server or peer-to-
Server or peer-to-peer sockets, on the other hand, will always accept peer sockets, on the other hand, will always accept new associations,
new associations, so a well-written application using server so a well-written application using server one-to-many style sockets
one-to-many style sockets must be prepared to handle new associations must be prepared to handle new associations from unwanted peers.
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 (it is enabled by that the SCTP_ASSOC_CHANGE event is enabled.
default).
3.1.4 sendmsg() and recvmsg() - one-to-many style socket 3.1.4. sendmsg() and recvmsg() - one-to-many style socket
An application uses sendmsg() and recvmsg() call to transmit data to An application uses sendmsg() and recvmsg() call to transmit data to
and receive data from its peer. and receive data from its peer.
ssize_t sendmsg(int sd, const struct msghdr *message, int flags); ssize_t sendmsg(int sd, const struct msghdr *message, int flags);
ssize_t recvmsg(int sd, struct msghdr *message, int flags); ssize_t recvmsg(int sd, struct msghdr *message, int flags);
sd: the socket descriptor of the endpoint. sd: the socket descriptor of the endpoint.
message: pointer to the msghdr structure which contains a single user message: pointer to the msghdr structure which contains a single user
message and possibly some ancillary data. See Section 5 for 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 Section flags: No new flags are defined for SCTP at this level. See Section
5 for SCTP-specific flags used in the msghdr structure. 5 for SCTP-specific flags used in the msghdr structure.
As we will see in Section 5, 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.
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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. one message at a time can be partially delivered.
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 3.1), 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.
3.1.5 close() - one-to-many style socket 3.1.5. close() - one-to-many style socket
Applications use close() to perform graceful shutdown (as described Applications use close() to perform graceful shutdown (as described
in Section 10.1 of RFC2960 [8]) on ALL the associations currently in Section 10.1 of RFC2960 [8]) on ALL the associations currently
represented by a one-to-many style socket. represented by a one-to-many style socket.
The syntax is: The syntax is:
ret = close(int sd); ret = close(int sd);
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 To gracefully shutdown a specific association represented by the one-
one-to-many style socket, an application should use the sendmsg() to-many style socket, an application should use the sendmsg() call,
call, and including the MSG_EOF flag. A user may optionally and including the SCTP_EOF flag. A user may optionally terminate an
terminate an association non-gracefully by sending with the MSG_ABORT association non-gracefully by sending with the SCTP_ABORT flag and
flag and possibly passing a user specified abort code in the data possibly passing a user specified abort code in the data field. Both
field. Both flags MSG_EOF and MSG_ABORT are passwd with ancillary flags SCTP_EOF and SCTP_ABORT are passed with ancillary data (see
data (see Section 5.2.2) 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.
3.1.6 connect() - one-to-many style socket 3.1.6. connect() - one-to-many style socket
An application may use the connect() call in the one-to-many style to An application may use the connect() call in the one-to-many style to
initiate an association without sending data. initiate an association without sending data.
The syntax is: The syntax is:
ret = connect(int sd, const struct sockaddr *nam, socklen_t len); ret = connect(int sd, const struct sockaddr *nam, socklen_t len);
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 RFC2553 [7]). sockaddr_in6 defined in RFC2553 [7]).
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.
3.2 Implicit Association Setup 3.2. Implicit Association Setup
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 application can begin sending and receiving data using the sendmsg()/
sendmsg()/recvmsg() or sendto()/recvfrom() calls, without going recvmsg() or sendto()/recvfrom() calls, without going through any
through any explicit association setup procedures (i.e., no connect() explicit association setup procedures (i.e., no connect() calls
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
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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.
3.3 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
be sent (due to a CANT_START_ASSOC), the sender will also receive a be sent (due to a CANT_START_ASSOC), the sender will also receive a
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 MSG_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 5.3.1.1). Note that this can also be SHUTDOWN_COMPLETE (see Section 5.3.1.1). Note that this can also be
done using the sctp_send() call described in Section 8.10. 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 interpretation of select on write is implementation specific.
Generally a positive return on a select on write would only indicate Generally a positive return on a select on write would only indicate
that one of the associations represented by the one-to-many socket is that one of the associations represented by the one-to-many socket is
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destination association of the write call. Likewise select (or destination association of the write call. Likewise select (or
poll()) for reading from a one-to-many socket will only return an 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_peelloff() (see Section 8.2) function to seperate the or use the sctp_peelloff() (see Section 8.2) function to seperate the
association of interest from the one-to-many socket. association of interest from the one-to-many socket.
3.4 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 implementors and application programmers. guidance to both implementors and application programmers.
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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 4.1.8. 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.
4.1 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:
1. socket() 1. socket()
2. bind() 2. bind()
3. listen() 3. listen()
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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
3. close() 3. close()
to terminate this association when done. to terminate this association when done.
4.1.1 socket() - one-to-one style socket 4.1.1. socket() - one-to-one style socket
Applications calls socket() to create a socket descriptor to Applications calls socket() to create a socket descriptor to
represent an SCTP endpoint. represent an SCTP endpoint.
The syntax is: The syntax is:
int socket(PF_INET, SOCK_STREAM, IPPROTO_SCTP); int socket(PF_INET, SOCK_STREAM, IPPROTO_SCTP);
or, or,
int socket(PF_INET6, SOCK_STREAM, IPPROTO_SCTP); int socket(PF_INET6, SOCK_STREAM, IPPROTO_SCTP);
Here, SOCK_STREAM indicates the creation of a one-to-one style Here, SOCK_STREAM indicates the creation of a one-to-one style
socket. socket.
The first form creates an endpoint which can use only IPv4 addresses, The first form creates an endpoint which can use only IPv4 addresses,
while the second form creates an endpoint which can use both IPv6 and while the second form creates an endpoint which can use both IPv6 and
IPv4 addresses. IPv4 addresses.
4.1.2 bind() - one-to-one style socket 4.1.2. bind() - one-to-one style socket
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 8.1 to help applications do sctp_bindx() is introduced in Section 8.1 to help applications do the
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 RFC2960 [8]. initialization process, see RFC2960 [8].
The syntax is: The syntax is:
int bind(int sd, struct sockaddr *addr, socklen_t addrlen); int bind(int sd, struct sockaddr *addr, socklen_t addrlen);
sd: the socket descriptor returned by socket() call. sd: the socket descriptor returned by socket() call.
addr: the address structure (either struct sockaddr_in or struct addr: the address structure (either struct sockaddr_in or struct
sockaddr_in6 defined in RFC2553 [7]). sockaddr_in6 defined in RFC2553 [7]).
addrlen: the size of the address structure. addrlen: the size of the address structure.
If sd is an IPv4 socket, the address passed must be an IPv4 address. If sd is an IPv4 socket, the address passed must be an IPv4 address.
Otherwise, i.e., the sd is an IPv6 socket, the address passed can Otherwise, i.e., the sd is an IPv6 socket, the address passed can
either be an IPv4 or an IPv6 address. either be an IPv4 or an IPv6 address.
Applications cannot call bind() multiple times to associate multiple Applications cannot call bind() multiple times to associate multiple
addresses to the endpoint. After the first call to bind(), all addresses to the endpoint. After the first call to bind(), all
subsequent calls will return an error. subsequent calls will return an error.
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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.
4.1.3 listen() - one-to-one style socket 4.1.3. listen() - one-to-one style socket
Applications use listen() to ready the SCTP endpoint for accepting Applications use listen() to ready the SCTP endpoint for accepting
inbound associations. inbound associations.
The syntax is: The syntax is:
int listen(int sd, int backlog); int listen(int sd, int backlog);
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 RFC2960 [8]) and are in the ESTABLISHED state. Note, a 5 of RFC2960 [8]) and are in the ESTABLISHED state. Note, a
backlog of '0' indicates that the caller no longer wishes to backlog of '0' indicates that the caller no longer wishes to
receive new associations. receive new associations.
4.1.4 accept() - one-to-one style socket 4.1.4. accept() - one-to-one style socket
Applications use accept() call to remove an established SCTP Applications use accept() call to remove an established SCTP
association from the accept queue of the endpoint. A new socket association from the accept queue of the endpoint. A new socket
descriptor will be returned from accept() to represent the newly descriptor will be returned from accept() to represent the newly
formed association. formed association.
The syntax is: The syntax is:
new_sd = accept(int sd, struct sockaddr *addr, socklen_t *addrlen); new_sd = accept(int sd, struct sockaddr *addr, socklen_t *addrlen);
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Applications use accept() call to remove an established SCTP Applications use accept() call to remove an established SCTP
association from the accept queue of the endpoint. A new socket association from the accept queue of the endpoint. A new socket
descriptor will be returned from accept() to represent the newly descriptor will be returned from accept() to represent the newly
formed association. formed association.
The syntax is: The syntax is:
new_sd = accept(int sd, struct sockaddr *addr, socklen_t *addrlen); new_sd = accept(int sd, struct sockaddr *addr, socklen_t *addrlen);
new_sd: the socket descriptor for the newly formed association. new_sd: the socket descriptor for the newly formed association.
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.
4.1.5 connect() - one-to-one style socket 4.1.5. connect() - one-to-one style socket
Applications use connect() to initiate an association to a peer. Applications use connect() to initiate an association to a peer.
The syntax is: The syntax is:
int connect(int sd, const struct sockaddr *addr, socklen_t addrlen); int connect(int sd, const struct sockaddr *addr, socklen_t addrlen);
sd: the socket descriptor of the endpoint. 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 RFC2960 [8]. section 10.1 of RFC2960 [8].
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 7.1.3 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
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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 assocation with the one-to-one the sending of data to initiate an assocation with the one-to-one
style (implementations that do not support T/TCP normally have this style (implementations that do not support T/TCP normally have this
restriction). Implementations which allow sending of data to restriction). Implementations which allow sending of data to
initiate an association without calling connect() define the initiate an association without calling connect() define the
preprocessor constant HAVE_SCTP_NOCONNECT to 1. preprocessor constant HAVE_SCTP_NOCONNECT to 1.
SCTP does not support half close semantics. This means that unlike SCTP does not support half close semantics. This means that unlike
T/TCP, MSG_EOF should not be set in the flags parameter when calling T/TCP, SCTP_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. SCTP_EOF is not an acceptable flag with SCTP socket.
4.1.6 close() - one-to-one style socket 4.1.6. close() - one-to-one style socket
Applications use close() to gracefully close down an association. Applications use close() to gracefully close down an association.
The syntax is: The syntax is:
int close(int sd); int close(int sd);
sd - the socket descriptor of the association to be closed. sd - the socket descriptor of the association 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.
4.1.7 shutdown() - one-to-one style socket 4.1.7. shutdown() - one-to-one style socket
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 shutdown() call, and solves some different problems. Full TCP-
TCP-compatibility is not provided, so developers porting TCP compatibility is not provided, so developers porting TCP applications
applications to SCTP may need to recode sections that use shutdown(). to SCTP may need to recode sections that use shutdown(). (Note that
(Note that it is possible to achieve the same results as half close it is possible to achieve the same results as half close in SCTP
in SCTP using SCTP streams.) using SCTP streams.)
The syntax is: The syntax is:
int shutdown(int sd, int how); int shutdown(int sd, int how);
sd - the socket descriptor of the association to be closed. sd - the socket descriptor of the association to be closed.
how - Specifies the type of shutdown. The values are how - Specifies the type of shutdown. The values are
as follows: as follows:
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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 5.3.1.4 for more information). deliver (see Section 5.3.1.4 for more information).
To perform the ABORT operation described in RFC2960 [8] section 10.1, To perform the ABORT operation described in RFC2960 [8] 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 7.1.4. in Section 7.1.4.
4.1.8 sendmsg() and recvmsg() - one-to-one style socket 4.1.8. sendmsg() and recvmsg() - one-to-one style socket
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 3.1.3), 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 stack preferred peer address if the sender wishes to discourage the stack
from sending the message to the primary address of the receiver. If from sending the message to the primary address of the receiver. If
the transport address given is not part of the current association, the transport address given is not part of the current association,
the data will not be sent and a SCTP_SEND_FAILED event will be the data will not be sent and a SCTP_SEND_FAILED event will be
delivered to the application if send failure events are enabled. delivered to the application if send failure events are enabled.
4.1.9 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 of the peer. This call is for TCP compatibility, and is not multi-
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 8.3 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 syntax is: The syntax is:
int getpeername(int sd, struct sockaddr *address, int getpeername(int sd, struct sockaddr *address,
socklen_t *len); socklen_t *len);
sd - the socket descriptor to be queried. sd - the socket descriptor to be queried.
address - On return, the peer primary address is stored in address - On return, the peer primary address is stored in
this buffer. If the socket is an IPv4 socket, the this buffer. If the socket is an IPv4 socket, the
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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.
5. 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.
5.1 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 RFC2292 [6]. Here we will cite their discussed in details in RFC2292 [6]. Here we will cite their
definitions from RFC2292 [6]. definitions from RFC2292 [6].
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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 5.3 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.
5.2 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 5.1), 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 data, and, header information (SNDRCV). Initialization data (one-to-
(one-to-many style only) sets protocol parameters for new many style only) sets protocol parameters for new associations.
associations. Section 5.2.1 provides more details. Header Section 5.2.1 provides more details. Header information can set or
information can set or report parameters on individual messages in a report parameters on individual messages in a stream. See
stream. See Section 5.2.2 for how to use SNDRCV ancillary data. Section 5.2.2 for how to use SNDRCV ancillary data.
By default on a one-to-one style socket, SCTP will pass no ancillary By default on a one-to-one style socket, SCTP will pass no ancillary
data; on a one-to-many style socket, SCTP will only pass SCTP_SNDRCV data; on a one-to-many style socket, SCTP will only pass SCTP_SNDRCV
and SCTP_ASSOC_CHANGE information. Specific ancillary data items can and SCTP_ASSOC_CHANGE information. Specific ancillary data items can
be enabled with socket options defined for SCTP; see Section 7.3. be enabled with socket options defined for SCTP; see Section 7.3.
Note that all ancillary types are fixed length; see Section 5.4 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 RFC2553 [7]) as a portable, fixed length sockaddr_storage (defined in RFC2553 [7]) as a portable, fixed length
address format. address format.
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ancillary data items. If a socket API consumer enables delivery of ancillary data items. If a socket API consumer enables delivery of
both SCTP and IPv6 ancillary data, they both may appear in the same both SCTP and IPv6 ancillary data, they both may appear in the same
msg_control buffer in any order. An application may thus need to msg_control buffer in any order. An application may thus need to
handle other types of ancillary data besides that passed by SCTP. handle other 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.
5.2.1 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
Here is the definition of the sctp_initmsg structure: Here is the definition of the sctp_initmsg structure:
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sinit_max_init_timeo: 16 bits (unsigned integer) sinit_max_init_timeo: 16 bits (unsigned integer)
This value represents the largest Time-Out or RTO value (in This value represents the largest Time-Out or RTO value (in
milliseconds) to use inattempting a INIT. Normally the 'RTO.Max' is milliseconds) to use inattempting a INIT. Normally the 'RTO.Max' is
used to limit the doubling of the RTO upon timeout. For the INIT used to limit the doubling of the RTO upon timeout. For the INIT
message this value MAY override 'RTO.Max'. This value MUST NOT message this value MAY override 'RTO.Max'. This value MUST NOT
influence 'RTO.Max' during data transmission and is only used to influence 'RTO.Max' during data transmission and is only used to
bound the initial setup time. A default value of 0 indicates to use bound the initial setup time. A default value of 0 indicates to use
the endpoint's default value. This is normally set to the system's the endpoint's default value. This is normally set to the system's
'RTO.Max' value (60 seconds). 'RTO.Max' value (60 seconds).
5.2.2 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:
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sinfo_ssn: 16 bits (unsigned integer) sinfo_ssn: 16 bits (unsigned integer)
For recvmsg() this value contains the stream sequence number that the For recvmsg() this value contains the stream sequence number that the
remote endpoint placed in the DATA chunk. For fragmented messages remote endpoint placed in the DATA chunk. For fragmented messages
this is the same number for all deliveries of the message (if more this is the same number for all deliveries of the message (if more
than one recvmsg() is needed to read the message). The sendmsg() than one recvmsg() is needed to read the message). The sendmsg()
call will ignore this parameter. call will ignore this parameter.
sinfo_ppid: 32 bits (unsigned integer) sinfo_ppid: 32 bits (unsigned integer)
This value in sendmsg() is an opaque unsigned value that is passed to This value in sendmsg() is an unsigned integer that is passed to the
the remote end in each user message. In recvmsg() this value is the remote end in each user message. In recvmsg() this value is the same
same information that was passed by the upper layer in the peer information that was passed by the upper layer in the peer
application. Please note that byte order issues are NOT accounted application. Please note that the SCTP stack performs no byte order
for and this information is passed opaquely by the SCTP stack from modification of this field. For example, if the DATA chunk has to
one end to the other. contain a given value in network byte order, the SCTP user has to
perform the htonl() computation.
sinfo_context: 32 bits (unsigned integer) sinfo_context: 32 bits (unsigned integer)
This value is an opaque 32 bit context datum that is used in the 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 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 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 undelivered message (Note: if a endpoint has done multiple sends, all
of which fail, multiple different sinfo_context values will be of which fail, multiple different sinfo_context values will be
returned. One with each user data message). returned. One with each user data message).
sinfo_flags: 16 bits (unsigned integer) sinfo_flags: 16 bits (unsigned integer)
This field may contain any of the following flags and is composed of This field may contain any of the following flags and is composed of
a bitwise OR of these values. a bitwise OR of these values.
recvmsg() flags: recvmsg() flags:
MSG_UNORDERED - This flag is present when the message was sent SCTP_UNORDERED - This flag is present when the message was sent
non-ordered. non-ordered.
sendmsg() flags: sendmsg() flags:
MSG_UNORDERED - This flag requests the un-ordered delivery of the SCTP_UNORDERED - This flag requests the un-ordered delivery of the
message. If this flag is clear the datagram is message. If this flag is clear the datagram is
considered an ordered send. considered an ordered send.
MSG_ADDR_OVER - This flag, in the one-to-many style, requests the SCTP SCTP_ADDR_OVER - This flag, in the one-to-many style, requests the SCTP
stack to override the primary destination address stack to override the primary destination address
with the address found with the sendto/sendmsg with the address found with the sendto/sendmsg
call. call.
MSG_ABORT - Setting this flag causes the specified association SCTP_ABORT - Setting this flag causes the specified association
to abort by sending an ABORT message to the peer to abort by sending an ABORT message to the peer
(one-to-many style only). The ABORT chunk (one-to-many style only). The ABORT chunk
will contain an error cause 'User Initiated Abort' will contain an error cause 'User Initiated Abort'
with cause code 12.The cause specific with cause code 12.The cause specific
information of this error cause is provided in msg_iov. information of this error cause is provided in msg_iov.
MSG_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 procedures on the specified association. Graceful
shutdown assures that all data enqueued by both shutdown assures that all data enqueued by both
endpoints is successfully transmitted before closing endpoints is successfully transmitted before closing
the association (one-to-many style only). the association (one-to-many style only).
MSG_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 socket to send the message to all associations
that are currently established on this socket. For that are currently established on this socket. For
the one-to-one socket, this flag has no effect. the one-to-one socket, this flag has no effect.
sinfo_timetolive: 32 bit (unsigned integer) sinfo_timetolive: 32 bit (unsigned integer)
For the sending side, this field contains the message time to live in For the sending side, this field contains the message time to live in
milliseconds. The sending side will expire the message within the milliseconds. The sending side will expire the message within the
specified time period if the message as not been sent to the peer specified time period if the message as not been sent to the peer
within this time period. This value will override any default value within this time period. This value will override any default value
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sinfo_tsn: 32 bit (unsigned integer) sinfo_tsn: 32 bit (unsigned integer)
For the receiving side, this field holds a TSN that was assigned to For the receiving side, this field holds a TSN that was assigned to
one of the SCTP Data Chunks. one of the SCTP Data Chunks.
sinfo_cumtsn: 32 bit (unsigned integer) sinfo_cumtsn: 32 bit (unsigned integer)
This field will hold the current cumulative TSN as known by the This field will hold the current cumulative TSN as known by the
underlying SCTP layer. Note this field is ignored when sending and underlying SCTP layer. Note this field is ignored when sending and
only valid for a receive operation when sinfo_flags are set to only valid for a receive operation when sinfo_flags are set to
MSG_UNORDERED. SCTP_UNORDERED.
sinfo_assoc_id: sizeof (sctp_assoc_t) sinfo_assoc_id: sizeof (sctp_assoc_t)
The association handle field, sinfo_assoc_id, holds the identifier The association handle field, sinfo_assoc_id, holds the identifier
for the association announced in the SCTP_COMM_UP notification. All for the association announced in the SCTP_COMM_UP notification. All
notifications for a given association have the same identifier. notifications for a given association have the same identifier.
Ignored for one-to-one style sockets. 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.
5.3 SCTP Events and Notifications 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
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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.
5.3.1 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 {
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_adaption_event sn_adaption_event; struct sctp_adaption_event sn_adaption_event;
struct sctp_pdapi_event sn_pdapi_event; struct sctp_pdapi_event sn_pdapi_event;
struct sctp_authkey_event sn_auth_event;
}; };
sn_type: 16 bits (unsigned integer) sn_type: 16 bits (unsigned integer)
The following list describes the SCTP notification and event types The following list describes the SCTP notification and event types
for the field sn_type. for the field sn_type.
SCTP_ASSOC_CHANGE: This tag indicates that an association has either SCTP_ASSOC_CHANGE: This tag indicates that an association has either
been opened or closed. Refer to Section 5.3.1.1 for details. been opened or closed. Refer to Section 5.3.1.1 for details.
SCTP_PEER_ADDR_CHANGE: This tag indicates that an address that is SCTP_PEER_ADDR_CHANGE: This tag indicates that an address that is
part of an existing association has experienced a change of state part of an existing association has experienced a change of state
(e.g. a failure or return to service of the reachability of a (e.g. a failure or return to service of the reachability of a
endpoint via a specific transport address). Please see endpoint via a specific transport address). Please see
Section 5.3.1.2 for data structure details. Section 5.3.1.2 for data structure details.
SCTP_REMOTE_ERROR: The attached error message is an Operational Error SCTP_REMOTE_ERROR: The attached error message is an Operational Error
received from the remote peer. It includes the complete TLV sent received from the remote peer. It includes the complete TLV sent
by the remote endpoint. See Section 5.3.1.3 for the detailed by the remote endpoint. See Section 5.3.1.3 for the detailed
format. 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 5.3.1.4. structure uses the sctp_sndrecvinfo per Section 5.3.1.4.
SCTP_SHUTDOWN_EVENT: The peer has sent a SHUTDOWN. No further data SCTP_SHUTDOWN_EVENT: The peer has sent a SHUTDOWN. No further data
should be sent on this socket. should be sent on this socket.
SCTP_ADAPTION_INDICATION: This notification holds the peers indicated SCTP_ADAPTION_INDICATION: This notification holds the peers indicated
adaption layer. Please see Section 5.3.1.6. adaption layer. Please see Section 5.3.1.6.
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 5.3.1.7 Section 5.3.1.7
SCTP_AUTHENTICATION_EVENT: This notification is used to tell a
receiver that either an error occured on authentication, or a new
key was made active. Section 5.3.1.8
All standard values for sn_type are greater than 2^15. Values from All standard values for sn_type are greater than 2^15. Values from
2^15 and down are reserved. 2^15 and down are reserved.
sn_flags: 16 bits (unsigned integer) sn_flags: 16 bits (unsigned integer)
These are notification-specific flags. These are notification-specific flags.
sn_length: 32 bits (unsigned integer) sn_length: 32 bits (unsigned integer)
This is the length of the whole sctp_notification structure including This is the length of the whole sctp_notification structure including
the sn_type, sn_flags, and sn_length fields. the sn_type, sn_flags, and sn_length fields.
5.3.1.1 SCTP_ASSOC_CHANGE 5.3.1.1. 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;
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The association id field, holds the identifier for the association. The association id field, holds the identifier for the association.
All notifications for a given association have the same association All notifications for a given association have the same association
identifier. For one-to-one style socket, this field is ignored. identifier. For one-to-one style socket, this field is ignored.
sac_info: variable sac_info: variable
If the sac_state is SCTP_COMM_LOST and an ABORT chunk was received If the sac_state is SCTP_COMM_LOST and an ABORT chunk was received
for this association, sac_info[] contains the complete ABORT chunk as for this association, sac_info[] contains the complete ABORT chunk as
defined in the SCTP specification RFC2960 [8] section 3.3.7. defined in the SCTP specification RFC2960 [8] section 3.3.7.
5.3.1.2 SCTP_PEER_ADDR_CHANGE 5.3.1.2. 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;
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If the state was reached due to any error condition (e.g. If the state was reached due to any error condition (e.g.
SCTP_ADDR_UNREACHABLE) any relevant error information is available in SCTP_ADDR_UNREACHABLE) any relevant error information is available in
this field. this field.
spc_assoc_id: sizeof (sctp_assoc_t) spc_assoc_id: sizeof (sctp_assoc_t)
The association id field, holds the identifier for the association. The association id field, holds the identifier for the association.
All notifications for a given association have the same association All notifications for a given association have the same association
identifier. For one-to-one style socket, this field is ignored. identifier. For one-to-one style socket, this field is ignored.
5.3.1.3 SCTP_REMOTE_ERROR 5.3.1.3. 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 RFC2960 [8] and any extensions for a list of possible specification RFC2960 [8] 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;
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The association id field, holds the identifier for the association. The association id field, holds the identifier for the association.
All notifications for a given association have the same association All notifications for a given association have the same association
identifier. For one-to-one style socket, this field is ignored. identifier. For one-to-one style socket, this field is ignored.
sre_data: variable sre_data: variable
This contains the ERROR chunk as defined in the SCTP specification This contains the ERROR chunk as defined in the SCTP specification
RFC2960 [8] section 3.3.10. RFC2960 [8] section 3.3.10.
5.3.1.4 SCTP_SEND_FAILED 5.3.1.4. 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;
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The association id field, sf_assoc_id, holds the identifier for the The association id field, sf_assoc_id, holds the identifier for the
association. All notifications for a given association have the same association. All notifications for a given association have the same
association identifier. For one-to-one style socket, this field is association identifier. For one-to-one style socket, this field is
ignored. ignored.
ssf_data: variable length ssf_data: variable length
The undelivered message, exactly as delivered by the caller to the The undelivered message, exactly as delivered by the caller to the
original send*() call. original send*() call.
5.3.1.5 SCTP_SHUTDOWN_EVENT 5.3.1.5. 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 38, line 36 skipping to change at page 39, line 47
sse_flags: 16 bits (unsigned integer) sse_flags: 16 bits (unsigned integer)
Currently unused. Currently unused.
sse_assoc_id: sizeof (sctp_assoc_t) sse_assoc_id: sizeof (sctp_assoc_t)
The association id field, holds the identifier for the association. The association id field, holds the identifier for the association.
All notifications for a given association have the same association All notifications for a given association have the same association
identifier. For one-to-one style socket, this field is ignored. identifier. For one-to-one style socket, this field is ignored.
5.3.1.6 SCTP_ADAPTION_INDICATION 5.3.1.6. SCTP_ADAPTION_INDICATION
When a peer sends a Adaption Layer Indication parameter , SCTP When a peer sends a Adaption 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 adaption layer. peers requested adaption layer.
struct sctp_adaption_event { struct sctp_adaption_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_adaption_ind; uint32_t sai_adaption_ind;
skipping to change at page 39, line 25 skipping to change at page 40, line 38
This field holds the bit array sent by the peer in the adaption layer This field holds the bit array sent by the peer in the adaption layer
indication parameter. The bits are in network byte order. indication parameter. The bits are in network byte order.
sai_assoc_id: sizeof (sctp_assoc_t) sai_assoc_id: sizeof (sctp_assoc_t)
The association id field, holds the identifier for the association. The association id field, holds the identifier for the association.
All notifications for a given association have the same association All notifications for a given association have the same association
identifier. For one-to-one style socket, this field is ignored. identifier. For one-to-one style socket, this field is ignored.
5.3.1.7 SCTP_PARTIAL_DELIVERY_EVENT 5.3.1.7. SCTP_PARTIAL_DELIVERY_EVENT
When a receiver is engaged in a partial delivery of a message this When a receiver is engaged in a partial delivery of a message this
notification will be used to indicate various events. notification will be used to indicate various events.
struct sctp_pdapi_event { struct sctp_pdapi_event {
uint16_t pdapi_type; uint16_t pdapi_type;
uint16_t pdapi_flags; uint16_t pdapi_flags;
uint32_t pdapi_length; uint32_t pdapi_length;
uint32_t pdapi_indication; uint32_t pdapi_indication;
sctp_assoc_t pdapi_assoc_id; sctp_assoc_t pdapi_assoc_id;
skipping to change at page 40, line 18 skipping to change at page 41, line 29
possible values include: possible values include:
SCTP_PARTIAL_DELIVERY_ABORTED SCTP_PARTIAL_DELIVERY_ABORTED
pdapi_assoc_id: sizeof (sctp_assoc_t) pdapi_assoc_id: sizeof (sctp_assoc_t)
The association id field, holds the identifier for the association. The association id field, holds the identifier for the association.
All notifications for a given association have the same association All notifications for a given association have the same association
identifier. For one-to-one style socket, this field is ignored. identifier. For one-to-one style socket, this field is ignored.
5.4 Ancillary Data Considerations and Semantics 5.3.1.8. SCTP_AUTHENTICATION_EVENT
When a receiver is using authentication this message will provide
notifications regarding new keys being made active as well as errors.
struct sctp_authkey_event {
uint16_t auth_type;
uint16_t auth_flags;
uint32_t auth_length;
uint32_t auth_keynumber;
uint32_t auth_altkeynumber;
uint32_t auth_indication;
sctp_assoc_t auth_assoc_id;
};
auth_type
It should be SCTP_AUTHENTICATION_EVENT
auth_flags: 16 bits (unsigned integer)
Currently unused.
auth_length: 32 bits (unsigned integer)
This field is the total length of the notification data, including
the notification header. It will generally be sizeof (struct
sctp_authkey_event).
auth_keynumber: 32 bits (unsigned integer)
This field holds the keynumber set by the user for the effected key.
If more than one key is involved, this will contain one of the keys
involved in the notification.
auth_altkeynumber: 32 bits (unsigned integer)
This field holds an alternate keynumber which is used by some
notifications.
auth_indication: 32 bits (unsigned integer)
This field hold the error or indication being reported. The
following values are currently defined:
1) - SCTP_AUTH_NEWKEY, this report indicates that a new key has been
made active (used for the first time by the peer) and is now the
active key. The auth_keynumber field holds the user specified key
number.
2) - SCTP_KEY_CONFLICT, this report indicates that an association was
attempting to be formed and that two seperate keys were discovered
for the same peer endpoint. In other words, two distinct keys
would have been active for the same association due to multi-
homing. The field auth_keynumber contains one of the conflicting
keys and the field auth_altkeynumber contains one of the other
keys. Note that more than two key COULD be in conflict.
auth_assoc_id: sizeof (sctp_assoc_t)
The association id field, holds the identifier for the association.
All notifications for a given association have the same association
identifier.
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.
5.4.1 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.
5.4.2 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
RFC2292 [6] and your SCTP implementation's documentation for more RFC2292 [6] and your SCTP implementation's documentation for more
information. Following is an example, from RFC2292 [6], information. Following is an example, from RFC2292 [6],
skipping to change at page 41, line 22 skipping to change at page 43, line 49
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 */
} }
} }
5.4.3 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 43, line 7 skipping to change at page 45, line 7
CMSG_SPACE(sizeof (struct in6_pktinfo)); CMSG_SPACE(sizeof (struct in6_pktinfo));
buf = malloc(total); buf = malloc(total);
We could then use this buffer for msg_control on each call to We could then use this buffer for msg_control on each call to
recvmsg() and be assured that we would not lose any ancillary data to recvmsg() and be assured that we would not lose any ancillary data to
truncation. truncation.
6. Common Operations for Both Styles 6. Common Operations for Both Styles
6.1 send(), recv(), sendto(), recvfrom() 6.1. send(), recv(), sendto(), recvfrom()
Applications can use send() and sendto() to transmit data to the peer Applications can use send() and sendto() to transmit data to the peer
of an SCTP endpoint. recv() and recvfrom() can be used to receive of an SCTP endpoint. recv() and recvfrom() can be used to receive
data from the peer. data from the peer.
The syntax is: The syntax is:
ssize_t send(int sd, const void *msg, size_t len, int flags); ssize_t send(int sd, const void *msg, size_t len, int flags);
ssize_t sendto(int sd, const void *msg, size_t len, int flags, ssize_t sendto(int sd, const void *msg, size_t len, int flags,
const struct sockaddr *to, socklen_t tolen); const struct sockaddr *to, socklen_t tolen);
skipping to change at page 44, line 19 skipping to change at page 46, line 19
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 RFC2960 [8]. to send a Data chunk with no user data RFC2960 [8].
6.2 setsockopt(), getsockopt() 6.2. setsockopt(), 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 7 behavior of sockets calls. They are described in Section 7
The syntax is: The syntax is:
ret = getsockopt(int sd, int level, int optname, void *optval, ret = getsockopt(int sd, int level, int optname, void *optval,
socklen_t *optlen); socklen_t *optlen);
ret = setsockopt(int sd, int level, int optname, const void *optval, ret = setsockopt(int sd, int level, int optname, const void *optval,
socklen_t optlen); socklen_t optlen);
sd - the socket descript. sd - the socket descript.
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).
6.3 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, may only be
used with branched off socket descriptors (see Section 8.2). used with branched off socket descriptors (see Section 8.2).
6.4 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 8.5 for a multi-homed version of the call. sockets. See Section 8.5 for a multi-homed version of the call.
The syntax is: The syntax is:
int getsockname(int sd, struct sockaddr *address, int getsockname(int sd, struct sockaddr *address,
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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.
7. 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 that are common to both styles. SCTP associations can be multi-
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 the association instance (association ID) is used to identify the the association instance
that the operation affects. So it must be set when using this style. that 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 8.2) 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 applied to all associations belonging to the socket. And for one-to-
one-to-one style, those options will be applied to all peer addresses one style, those options will be applied to all peer addresses of the
of the association controlled by the socket. Applications should be association controlled by the socket. Applications should be very
very careful in setting those options. careful in setting those options.
For some IP stacks getsockopt() is read-only; so a new interface will For some IP stacks getsockopt() is read-only; so a new interface will
be needed when information must be passed both in to and out of the be needed when information must be passed both in to and out of the
SCTP stack. The syntax for sctp_opt_info() is, SCTP stack. The syntax for sctp_opt_info() is,
int sctp_opt_info(int sd, int sctp_opt_info(int sd,
sctp_assoc_t id, sctp_assoc_t id,
int opt, int opt,
void *arg, void *arg,
socklen_t *size); socklen_t *size);
The sctp_opt_info() call is a replacement for getsockopt() only and The sctp_opt_info() call is a replacement for getsockopt() only and
will not set any options associated with the specified socket. A will not set any options associated with the specified socket. A
setsockopt() must be used to set any writeable option. setsockopt() must be used to set any writeable option.
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 opt specifies which SCTP socket option to get. It can get any socket
option currently supported that requests information (either option currently supported that requests information (either read/
read/write options or read only) such as: 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_AUTH_CHUNKS SCTP_AUTH_CHUNKS
SCTP_AUTH_SECRET SCTP_AUTH_SECRET
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All options that support specific settings on an association by All options that support specific settings on an association by
filling in either an association id variable or a sockaddr_storage filling in either an association id variable or a sockaddr_storage
SHOULD also support setting of the same value for the entire endpoint SHOULD also support setting of the same value for the entire endpoint
(i.e. future associations). To accomplish this the following logic (i.e. future associations). To accomplish this the following logic
is used when setting one of these options: is used when setting one of these options:
a) If an address is specified via a sockaddr_storage that is included a) If an address is specified via a sockaddr_storage that is included
in the structure, the address is used to lookup the association in the structure, the address is used to lookup the association
and the settings are applied to the specific address (if and the settings are applied to the specific address (if
appropriate) or to the entire association. appropriate) or to the entire association.
b) If an association identification is filled in but not a b) If an association identification is filled in but not a
sockaddr_storage (if present), the association is found using the sockaddr_storage (if present), the association is found using the
association identification and the settings should be applied to association identification and the settings should be applied to
the entire association (since a specific address is not the entire association (since a specific address is not
specified). Note this also applies to options that hold an specified). Note this also applies to options that hold an
association identification in their structure but do not have a association identification in their structure but do not have a
sockaddr_storage field. sockaddr_storage field.
c) If neither the sockaddr_storage or association identification is c) If neither the sockaddr_storage or association identification is
set i.e. the sockaddr_storage is set to all 0's (INADDR_ANY) and set, i.e. the sockaddr_storage is set to all 0's (INADDR_ANY) and
the association identification is 0, the settings are a default the association identification is 0, the settings are a default
and to be applied to the endpoint (all future associations). and to be applied to the endpoint (all future associations).
7.1 Read / Write Options 7.1. Read / Write Options
7.1.1 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 RFC2960 [8] for more information on timeout (RTO) are tunable. See RFC2960 [8] for more information on
how these parameters are used in RTO calculation. how 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;
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effects the entire endpoint. effects the entire endpoint.
All parameters are time values, in milliseconds. A value of 0, when All parameters are time values, in milliseconds. A value of 0, when
modifying the parameters, indicates that the current value should not modifying the parameters, indicates that the current value should not
be changed. be changed.
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.
7.1.2 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. endpoint parameters.
See RFC2960 [8] for more information on how this parameter is used. See RFC2960 [8] for more information on how this parameter is used.
The peer address parameter is ignored for one-to-one style socket. The peer address parameter is ignored for one-to-one style socket.
The following structure is used to access and modify this parameters: The following structure is used to access and modify this parameters:
struct sctp_assocparams { struct sctp_assocparams {
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shall return an error. The reason for this, from RFC2960 [8] section shall return an error. The reason for this, from RFC2960 [8] 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.
7.1.3 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 5.2.1). 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.
7.1.4 SO_LINGER 7.1.4. SO_LINGER
An application using the one-to-one style socket can use this option An application using the one-to-one style socket can use this option
to perform the SCTP ABORT primitive. The linger option structure is: to perform the SCTP ABORT primitive. The linger option structure is:
struct linger { struct linger {
int l_onoff; /* option on/off */ int l_onoff; /* option on/off */
int l_linger; /* linger time */ int l_linger; /* linger time */
}; };
To enable the option, set l_onoff to 1. If the l_linger value is set To enable the option, set l_onoff to 1. If the l_linger value is set
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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.
7.1.5 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.
7.1.6 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 depends on the constant HAVE_SCTP_MULTIBUF style sockets the meaning depends on the constant HAVE_SCTP_MULTIBUF
(see Section 3.4). If the implementation defines HAVE_SCTP_MULTIBUF (see Section 3.4). If the implementation defines HAVE_SCTP_MULTIBUF
as 1, this controls the receiver window size for each association as 1, this controls the receiver window size for each association
bound to the socket descriptor. If the implementation defines bound to the socket descriptor. If the implementation defines
HAVE_SCTP_MULTIBUF as 0, this controls the size of the single receive HAVE_SCTP_MULTIBUF as 0, this controls the size of the single receive
buffer for the whole socket. The call expects an integer. buffer for the whole socket. The call expects an integer.
7.1.7 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 3.4) bound to the socket descriptor associations (see Section 3.4) bound to the socket descriptor used in
used in the setsockopt() or getsockopt() call. The option applies to the setsockopt() or getsockopt() call. The option applies to each
each association's window size separately. The call expects an association's window size separately. The call expects an integer.
integer.
7.1.8 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. An than the specified number of seconds to automatically close. An
association being idle is defined as an association that has NOT sent association being idle is defined as an association that has NOT sent
or received user data. The special value of '0' indicates that no or received user data. The special value of '0' indicates that no
automatic close of any associations should be performed, this is the automatic close of any associations should be performed, this is the
default value. The option expects an integer defining the number of default value. The option expects an integer defining the number of
seconds of idle time before an association is closed. seconds of idle time before an 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.
7.1.9 Set Peer Primary Address (SCTP_SET_PEER_PRIMARY_ADDR) 7.1.9. 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. The following structure is used to make a locally bound addresses. The following structure is used to make a
set primary request: set 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 (one-to-many style socket) This is filled in by the sspp_assoc_id (one-to-many style socket) This is filled in by the
application, and identifies the association application, and identifies the association
for this request. for this request.
This functionality is optional. Implementations that do not support This functionality is optional. Implementations that do not support
this functionality should return EOPNOTSUPP. this functionality should return EOPNOTSUPP.
7.1.10 Set Primary Address (SCTP_PRIMARY_ADDR) 7.1.10. Set Primary Address (SCTP_PRIMARY_ADDR)
Requests that the local SCTP stack use the enclosed peer address as Requests that the local SCTP stack use the enclosed peer address as
the association primary. The enclosed address must be one of the the association primary. The enclosed address must be one of the
association peer's addresses. The following structure is used to association peer's addresses. The following structure is used to
make a set peer primary request: 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 (one-to-many style socket) This is filled in by the ssp_assoc_id (one-to-many style socket) This is filled in by the
application, and identifies the association application, and identifies the association
for this request. for this request.
7.1.11 Set Adaption Layer Indicator (SCTP_ADAPTION_LAYER) 7.1.11. Set Adaption Layer Indicator (SCTP_ADAPTION_LAYER)
Requests that the local endpoint set the specified Adaption Layer Requests that the local endpoint set the specified Adaption Layer
Indication parameter for all future INIT and INIT-ACK exchanges. Indication parameter for all future INIT and INIT-ACK exchanges.
struct sctp_setadaption { struct sctp_setadaption {
uint32_t ssb_adaption_ind; uint32_t ssb_adaption_ind;
}; };
ssb_adaption_ind The adaption layer indicator that will be included ssb_adaption_ind The adaption layer indicator that will be included
in any outgoing Adaption Layer Indication in any outgoing Adaption Layer Indication
parameter. parameter.
7.1.12 Enable/Disable message fragmentation (SCTP_DISABLE_FRAGMENTS) 7.1.12. Enable/Disable message fragmentation (SCTP_DISABLE_FRAGMENTS)
This option is a on/off flag and is passed an integer where a This option is a on/off flag and is passed an integer where a non-
non-zero is on and a zero is off. If enabled no SCTP message zero is on and a zero is off. If enabled no SCTP message
fragmentation will be performed. Instead if a message being sent fragmentation will be performed. Instead if a message being sent
exceeds the current PMTU size, the message will NOT be sent and exceeds the current PMTU size, the message will NOT be sent and
instead a error will be indicated to the user. instead a error will be indicated to the user.
7.1.13 Peer Address Parameters (SCTP_PEER_ADDR_PARAMS) 7.1.13. Peer Address Parameters (SCTP_PEER_ADDR_PARAMS)
Applications can enable or disable heartbeats for any peer address of Applications can enable or disable heartbeats for any peer address of
an association, modify an address's heartbeat interval, force a an association, modify an address's heartbeat interval, force a
heartbeat to be sent immediately, and adjust the address's maximum heartbeat to be sent immediately, and adjust the address's maximum
number of retransmissions sent before an address is considered number of retransmissions sent before an address is considered
unreachable. The following structure is used to access and modify an unreachable. The following structure is used to access and modify an
address's parameters: address's parameters:
struct sctp_paddrparams { struct sctp_paddrparams {
sctp_assoc_t spp_assoc_id; sctp_assoc_t spp_assoc_id;
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for. This value will apply to all addresses of an for. This value will apply to all addresses of an
association if the spp_address field is empty. Note association if the spp_address field is empty. Note
also, that if delayed sack is enabled and this also, that if delayed sack is enabled and this
value is set to 0, no change is made to the last value is set to 0, no change is made to the last
recorded delayed sack timer value. recorded delayed sack timer value.
spp_flags - These flags are used to control various features spp_flags - These flags are used to control various features
on an association. The flag field may contain on an association. The flag field may contain
zero or more of the following options. zero or more of the following options.
SPP_HB_ENABLED - Enable heartbeats on the SPP_HB_ENABLE - Enable heartbeats on the
specified address. Note that if the address specified address. Note that if the address
field is empty all addresses for the association field is empty all addresses for the association
have heartbeats enabled upon them. have heartbeats enabled upon them.
SPP_HB_DISABLED - Disable heartbeats on the SPP_HB_DISABLE - Disable heartbeats on the
speicifed address. Note that if the address speicifed address. Note that if the address
field is empty all addresses for the association field is empty all addresses for the association
will have their heartbeats disabled. Note also will have their heartbeats disabled. Note also
that SPP_HB_ENABLED and SPP_HB_DISABLED are that SPP_HB_ENABLE and SPP_HB_DISABLE are
mutually exclusive, only one of these two should mutually exclusive, only one of these two should
be specified. Enabling both fields will have be specified. Enabling both fields will have
undetermined results. undetermined results.
SPP_PMTUD_ENABLED - This field will enable PMTU SPP_HB_DEMAND - Request a user initiated heartbeat
to be made immediately.
SPP_PMTUD_ENABLE - This field will enable PMTU
discovery upon the specified address. Note that discovery upon the specified address. Note that
if the address feild is empty then all addresses if the address feild is empty then all addresses
on the association are effected. on the association are effected.
SPP_PMTUD_DISABLED - This field will disable PMTU SPP_PMTUD_DISABLE - This field will disable PMTU
discovery upon the specified address. Note that discovery upon the specified address. Note that
if the address feild is empty then all addresses if the address feild is empty then all addresses
on the association are effected. Not also that on the association are effected. Not also that
SPP_PMTUD_ENABLE and SPP_PMTUD_DISABLE are mutually SPP_PMTUD_ENABLE and SPP_PMTUD_DISABLE are mutually
exclusive. Enabling both will have undetermined exclusive. Enabling both will have undetermined
results. results.
SPP_SACKDELAY_ENABLED - Setting this flag turns SPP_SACKDELAY_ENABLE - Setting this flag turns
on delayed sack. The time specified in spp_sackdelay on delayed sack. The time specified in spp_sackdelay
is used to specify the sack delay for this address. Note is used to specify the sack delay for this address. Note
that if spp_address is empty then all addresses will that if spp_address is empty then all addresses will
enable delayed sack and take on the sack delay enable delayed sack and take on the sack delay
value specified in spp_sackdelay. value specified in spp_sackdelay.
SPP_SACKDELAY_DISABLED - Setting this flag turns SPP_SACKDELAY_DISABLE - Setting this flag turns
off delayed sack. If the spp_address field is blank then off delayed sack. If the spp_address field is blank then
delayed sack is disabled for the entire association. Note delayed sack is disabled for the entire association. Note
also that this field is mutually exclusive to also that this field is mutually exclusive to
SPP_SACKDELAY_ENABLED, setting both will have undefined SPP_SACKDELAY_ENABLE, setting both will have undefined
results. results.
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.
7.1.14 Set default send parameters (SCTP_DEFAULT_SEND_PARAM) 7.1.14. 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 5.2.2) 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_stream, sinfo_flags, sinfo_ppid, sinfo_context,
sinfo_timetolive. The user must set the sinfo_assoc_id field to sinfo_timetolive. The user must set the sinfo_assoc_id field to
identify the association to affect if the caller is using the identify the association to affect if the caller is using the one-to-
one-to-many style. many style.
7.1.15 Set notification and ancillary events (SCTP_EVENTS) 7.1.15. 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 7.3) ancillary data the user wishes to receive. Please see Section 7.3)
for a full description of this option and its usage. for a full description of this option and its usage.
7.1.16 Set/clear IPv4 mapped addresses (SCTP_I_WANT_MAPPED_V4_ADDR) 7.1.16. 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 on and expects an integer to be By default this option is turned on 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.
7.1.17 Set the maximum fragmentation size (SCTP_MAXSEG) 7.1.17. Set the maximum fragmentation size (SCTP_MAXSEG)
This socket option specifies the maximum size to put in any outgoing This socket option specifies 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 option expects an integer. the user. The option expects an integer.
The default value for this option is '0' which indicates the user is The default value for this option is '0' which indicates the user is
NOT limiting fragmentation and only the PMTU will effect SCTP's NOT limiting fragmentation and only the PMTU will effect SCTP's
choice of DATA chunk size. choice of DATA chunk size.
7.1.18 Set/Get the list of chunks that must be authenticated 7.1.18. Add a chunk that must be authenticated (SCTP_AUTH_CHUNK)
(SCTP_AUTH_CHUNKS)
This options gets or sets a list of chunks that the user is This option adds a chunk type that the user is requesting to be
requesting to be received only in an authenticated way. Changes to received only in an authenticated way. Changes to the list of chunks
this list will only effect associations that have not been formed. will only effect associations that have not been formed.
struct sctp_authchunks { struct sctp_authchunks {
uint8_t sauth_chunks[]; uint8_t sauth_chunk;
}; };
sauth_chunks - This parameter contains an array of chunks sauth_chunks - This parameter contains a chunk type
that the user is requesting to be authenticated. that the user is requesting to be authenticated.
7.1.19 Set/Get the current authentication shared secret The chunk types for INIT, INIT-ACK, COOKIE-ECHO, COOKIE-ACK,
(SCTP_AUTH_SECRET) SHUTDOWN-COMPLETE, and AUTH chunks MUST not be used. If they are
used an error MUST be returned. The usage of this option enables
SCTP-AUTH in cases where it is not required by other means (for
example the use of ADD-IP).
This option will get or set the shared secret to be used with any 7.1.19. Set the endpoint pair shared key (SCTP_AUTH_KEY)
authentication parameters.
struct sctp_authsecrets { This option will set the endpoint pair shared key which is used to
build the association shared key.
struct sctp_authkey {
sctp_assoc_t sca_assoc_id; sctp_assoc_t sca_assoc_id;
uint8_t sca_secret[]; uint32_t sca_keynumber;
struct sockaddr_storage sca_address;
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 secret is being set association that the shared key is being set
upon. Note that if this element contains zero, then upon. Note that if this element contains zero, then
the secret is set upon the endpoint and all future the secret is set upon the endpoint and all future
associations will use this secret (if not changed by associations will use this secret (if not changed by
subsequent calls to SCTP_AUTH_SECRET). subsequent calls to SCTP_AUTH_KEY).
sca_secret - This parameter contains an array of bytes sca_address - this parameter contains either a zero filled address,
in which case it has no effect on the call. Or this
parameter may contain an existing association.
An address may also be specified for a future association
including the IP layer address and the transport port, or
just the IP layer address. Note that if multiple keys
are defined for addresses of the same endpoint (for a
multihomed endpoint) then an error will be returned and
NO association will be formed on recipt of the INIT
or INIT-ACK.
sca_keynumber - this parameter is the key index by which the application
will refer to this key. If a key of the specified
index already exists, then this new key will replace
the old key.
sca_key - This parameter contains an array of bytes
that is to be used by the endpoint (or association) that is to be used by the endpoint (or association)
as the shared secret. as the shared secret.
7.1.20 Get the list of chunks that peer requires to be authenticated 7.1.20. Get the list of chunks the peer requires to be authenticated
(SCTP_PEER_AUTH_CHUNKS) (SCTP_PEER_AUTH_CHUNKS)
This options 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 authenticated. The requesting to be received the peer requires to be received authenticated only.
only in an authenticated way. Changes to this list will only effect
associations that have not been formed.
struct sctp_authchunks { struct sctp_authchunks {
sctp_assoc_t gpauth_assoc_id; sctp_assoc_t gauth_assoc_id;
uint8_t gpauth_chunks[]; uint8_t gauth_chunks[];
}; };
sca_assoc_id - This parameter, indicates for which association the gauth_assoc_id - This parameter, indicates for which association the
user is requesting the list of peer authenticated user is requesting the list of peer authenticated
chunks. chunks.
gputh_chunks - This parameter contains an array of chunks gauth_chunks - This parameter contains an array of chunks
that the peer is requesting to be authenticated. that the peer is requesting to be authenticated.
7.2 Read-Only Options 7.1.21. Get the list of chunks the local endpoint requires to be
authenticated (SCTP_LOCAL_AUTH_CHUNKS)
7.2.1 Association Status (SCTP_STATUS) This option gets a list of chunks for a specified association that
the local endpoint requires to be received authenticated only.
struct sctp_authchunks {
sctp_assoc_t gauth_assoc_id;
uint8_t gauth_chunks[];
};
gauth_assoc_id - This parameter, indicates for which association the
user is requesting the list of local authenticated
chunks.
gauth_chunks - This parameter contains an array of chunks
that the local endpoint is requesting to be authenticated.
7.1.22. Set the list of supported HMAC Identifiers (SCTP_HMAC_IDENT)
This option sets a list of algorithms for a specified association
that the local endpoint requires the peer to use.
struct sctp_hmacalgo {
sctp_assoc_t shmac_assoc_id;
uint32_t shmac_idents[];
};
shmac_assoc_id - This parameter, indicates for which association the
user is setting the list of HMAC Identifiers.
shmac_idents - This parameter contains an array of HMAC Identifiers
that the local endpoint is requesting the peer to use.
7.1.23. Get or set the active key (SCTP_AUTH_SETKEY_ACTIVE)
This options will get or set the active key.
struct sctp_authkey {
sctp_assoc_t scact_assoc_id;
uint32_t scact_keynumber;
uint32_t scact_sec_old;
uint32_t scact_sec_new;
struct sockaddr_storage scact_address;
};
scact_assoc_id - This parameter, if non-zero, indicates what
association that the shared key is being set
upon. Note that if this element contains zero, then
the secret activation applys to the endpoint and
all future associations will use this secret (if not changed by
subsequent calls).
scact_address - this parameter contains either a zero filled address,
in which case it has no effect on the call. Or this
parameter may contain an existing association address.
An address may also be specified for a future association
including the IP layer address and the transport port, or
just the IP layer address. Note that if multiple keys
are defined for addresses of the same endpoint (for a
multihomed endpoint) then an error will be returned and
NO association will be formed on recipt of the INIT
or INIT-ACK.
scact_keynumber - this parameter is the key index by which the application
will refer to this key. If a key of the specified
index already exists, then this new key will replace
the old key.
scact_sec_old this parameter list the number of seconds for which
both keys will be accepted. If this value is 0, then
the new key is made active immediately and packets
with the old key will be discarded. If this value
is non-zero, then for the specified time in seconds
both keys will be accepted.
scact_sec_new this parameter indicates the number of seconds until
the new key will start being used as the active key.
If this value is '0' then the new key will start
being used immediately. If this value is non-zero then
the specified number of seconds will be delayed until
new chunks being transmitted begin using the new
key.
7.1.24. Get or set delayed ack timer (SCTP_DELAYED_ACK_TIME)
This options will get or set the delayed ack timer. The time is set
in milliseconds. If the assoc_id is 0, then this sets or gets the
endpoints default delayed ack timer value. If the assoc_id field is
non-zero, then the set or get effects the specified association.
struct sctp_assoc_value {
sctp_assoc_t assoc_id;
uint32_t assoc_value;
};
assoc_id - This parameter, indicates which association the
user is preforming an action upon. Note that if
this field's value is zero then the endpoints
default value is changed (effecting future
associations only).
assoc_value - This parameter contains the number of milliseconds
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 milliseconds.
7.2. Read-Only Options
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. The following structure is receipt. This information is read-only. The following structure is
used to access this information: used to access this information:
struct sctp_status { struct sctp_status {
sctp_assoc_t sstat_assoc_id; sctp_assoc_t sstat_assoc_id;
int32_t sstat_state; int32_t sstat_state;
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sstat_outstrms - The number of streams that the endpoint is sstat_outstrms - The number of streams that the endpoint is
allowed to use outbound. allowed to use outbound.
sstat_fragmentation_point - The size at which SCTP fragmentation sstat_fragmentation_point - The size at which SCTP fragmentation
will occur. will occur.
To access these status values, the application calls getsockopt() To access these status values, the application calls getsockopt()
with the option name SCTP_STATUS. The sstat_assoc_id parameter is with the option name SCTP_STATUS. The sstat_assoc_id parameter is
ignored for one-to-one style socket. ignored for one-to-one style socket.
7.2.2 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 window, and retransmission timer values. This information is read-
read-only. The following structure is used to access this only. The following structure is used to access this information:
information:
struct sctp_paddrinfo { struct sctp_paddrinfo {
sctp_assoc_t spinfo_assoc_id; sctp_assoc_t spinfo_assoc_id;
struct sockaddr_storage spinfo_address; struct sockaddr_storage spinfo_address;
int32_t spinfo_state; int32_t spinfo_state;
uint32_t spinfo_cwnd; uint32_t spinfo_cwnd;
uint32_t spinfo_srtt; uint32_t spinfo_srtt;
uint32_t spinfo_rto; uint32_t spinfo_rto;
uint32_t spinfo_mtu; uint32_t spinfo_mtu;
}; };
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spinfo_rto - This contains the peer addresses's current spinfo_rto - This contains the peer addresses's current
retransmission timeout value in milliseconds. retransmission timeout value in milliseconds.
spinfo_mtu - The current P-MTU of this address. spinfo_mtu - The current P-MTU of this address.
spinfo_assoc_id - (one-to-many style socket) This is filled in spinfo_assoc_id - (one-to-many style socket) This is filled in
the application, and identifies the the application, and identifies the
association for this query. association for this query.
To retrieve this information, use sctp_opt_info() with the To retrieve this information, use sctp_opt_info() with the
SCTP_GET_PEER_ADDR_INFO options. SCTP_GET_PEER_ADDR_INFO options.
7.3 Ancillary Data and Notification Interest Options 7.3. 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:
1. SCTP_SNDRCV (sctp_data_io_event): Per-message information (i.e. 1. SCTP_SNDRCV (sctp_data_io_event): Per-message information (i.e.
stream number, TSN, SSN, etc. described in Section 5.2.2) stream number, TSN, SSN, etc. described in Section 5.2.2)
2. SCTP_ASSOC_CHANGE (sctp_association_event): (described in 2. SCTP_ASSOC_CHANGE (sctp_association_event): (described in
Section 5.3.1.1) Section 5.3.1.1)
3. SCTP_PEER_ADDR_CHANGE (sctp_address_event): (described in 3. SCTP_PEER_ADDR_CHANGE (sctp_address_event): (described in
Section 5.3.1.2) Section 5.3.1.2)
4. SCTP_SEND_FAILED (sctp_send_failure_event): (described in 4. SCTP_SEND_FAILED (sctp_send_failure_event): (described in
Section 5.3.1.4) Section 5.3.1.4)
5. SCTP_REMOTE_ERROR (sctp_peer_error_event): (described in 5. SCTP_REMOTE_ERROR (sctp_peer_error_event): (described in
Section 5.3.1.3) Section 5.3.1.3)
6. SCTP_SHUTDOWN_EVENT (sctp_shtudown_event): (described in 6. SCTP_SHUTDOWN_EVENT (sctp_shtudown_event): (described in
Section 5.3.1.5) Section 5.3.1.5)
7. SCTP_PARTIAL_DELIVERY_EVENT (sctp_partial_delivery_event): 7. SCTP_PARTIAL_DELIVERY_EVENT (sctp_partial_delivery_event):
(described in Section 5.3.1.7) (described in Section 5.3.1.7)
8. SCTP_ADAPTION_INDICATION (sctp_adaption_layer_event): (described 8. SCTP_ADAPTION_INDICATION (sctp_adaption_layer_event): (described
in Section 5.3.1.6) in Section 5.3.1.6)
9. SCTP_AUTHENTICATION_INDICATION (sctp_authentication_event):
(described in Section 5.3.1.8)
To receive any ancillary data or notifications, first the application To receive any ancillary data or notifications, first the application
registers it's interest by calling the SCTP_EVENTS setsockopt() with registers it's interest by calling the SCTP_EVENTS setsockopt() with
the following structure. the following structure.
struct sctp_event_subscribe{ struct sctp_event_subscribe{
uint8_t sctp_data_io_event; uint8_t sctp_data_io_event;
uint8_t sctp_association_event; uint8_t sctp_association_event;
uint8_t sctp_address_event; uint8_t sctp_address_event;
uint8_t sctp_send_failure_event; uint8_t sctp_send_failure_event;
uint8_t sctp_peer_error_event; uint8_t sctp_peer_error_event;
uint8_t sctp_shutdown_event; uint8_t sctp_shutdown_event;
uint8_t sctp_partial_delivery_event; uint8_t sctp_partial_delivery_event;
uint8_t sctp_adaption_layer_event; uint8_t sctp_adaption_layer_event;
uint8_t sctp_authentication_event;
}; };
sctp_data_io_event - Setting this flag to 1 will cause the reception sctp_data_io_event - Setting this flag to 1 will cause the reception
of SCTP_SNDRCV information on a per message basis. The application of SCTP_SNDRCV information on a per message basis. The application
will need to use the recvmsg() interface so that it can receive the will need to use the recvmsg() interface so that it can receive the
event information contained in the msg_control field. Please see event information contained in the msg_control field. Please see
Section 5.2 for further details. Setting the flag to 0 will disable Section 5.2 for further details. Setting the flag to 0 will disable
reception of the message control information. reception of the message control information.
sctp_association_event - Setting this flag to 1 will enable the sctp_association_event - Setting this flag to 1 will enable the
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sctp_partial_delivery_event - Setting this flag to 1 will enable the sctp_partial_delivery_event - Setting this flag to 1 will enable the
reception of partial delivery notifications. Setting the flag to 0 reception of partial delivery notifications. Setting the flag to 0
will disable partial delivery event notifications. For more will disable partial delivery event notifications. For more
information on event notifications please see Section 5.3. information on event notifications please see Section 5.3.
sctp_adaption_layer_event - Setting this flag to 1 will enable the sctp_adaption_layer_event - Setting this flag to 1 will enable the
reception of adaption layer notifications. Setting the flag to 0 reception of adaption layer notifications. Setting the flag to 0
will disable adaption layer event notifications. For more will disable adaption layer event notifications. For more
information on event notifications please see Section 5.3. information on event notifications please see Section 5.3.
sctp_authentication_event - Setting this flag to 1 will enable the
receiption of authentication layer notifications. Setting the flag
to 0 will disable authentication layer event notifications. For More
information please see Section 5.3.
An example where an application would like to receive data io events An example where an application would like to receive data io events
and association events but no others would be as follows: and association events but no others would be as follows:
{ {
struct sctp_event_subscribe event; struct sctp_event_subscribe event;
memset(&event,0,sizeof(event)); memset(&event,0,sizeof(event));
event.sctp_data_io_event = 1; event.sctp_data_io_event = 1;
event.sctp_association_event = 1; event.sctp_association_event = 1;
setsockopt(fd, IPPROTO_SCTP, SCTP_EVENT, &event, sizeof(event)); setsockopt(fd, IPPROTO_SCTP, SCTP_EVENTS, &event, sizeof(event));
} }
Note that for one-to-many style SCTP sockets, the caller of recvmsg() Note that for one-to-many style SCTP sockets, the caller of recvmsg()
receives ancillary data and notifications for ALL associations bound receives ancillary data and notifications for ALL associations bound
to the file descriptor. For one-to-one style SCTP sockets, the to the file descriptor. For one-to-one style SCTP sockets, the
caller receives ancillary data and notifications for only the single caller receives ancillary data and notifications for only the single
association bound to the file descriptor. association bound to the file descriptor.
By default both the one-to-one style and one-to-many style socket has By default both the one-to-one style and one-to-many style socket has
all options off. all options off.
8. New Interfaces 8. New Interfaces
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.
8.1 sctp_bindx() 8.1. sctp_bindx()
The syntax of sctp_bindx() is, The syntax of sctp_bindx() is,
int sctp_bindx(int sd, struct sockaddr *addrs, int addrcnt, int sctp_bindx(int sd, struct sockaddr *addrs, int addrcnt,
int flags); int flags);
If sd is an IPv4 socket, the addresses passed must be IPv4 addresses. If sd is an IPv4 socket, the addresses passed must be IPv4 addresses.
If the sd is an IPv6 socket, the addresses passed can either be IPv4 If the sd is an IPv6 socket, the addresses passed can either be IPv4
or IPv6 addresses. or IPv6 addresses.
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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
optional functionality. Implementations that do not support this optional functionality. Implementations that do not support this
functionality should return EOPNOTSUPP. functionality should return EOPNOTSUPP.
8.2 Branched-off Association 8.2. Branched-off Association
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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the traditional one-to-one style accept() call). Note that the new the traditional one-to-one style accept() call). Note that the new
socket is a one-to-one style socket. Thus it will be confined to socket is a one-to-one style socket. Thus it will be confined to
operations allowed for a one-to-one style socket. operations allowed for a one-to-one style socket.
The syntax is: The syntax is:
new_sd = sctp_peeloff(int sd, sctp_assoc_t assoc_id); new_sd = sctp_peeloff(int sd, sctp_assoc_t assoc_id);
the new socket descriptor representing the branched-off the new socket descriptor representing the branched-off
association. association.
the original one-to-many style socket descriptor returned from the the original one-to-many style socket descriptor returned from the
socket() system call (see Section 3.1.1). socket() system call (see Section 3.1.1).
the specified identifier of the association that is to be branched the specified identifier of the association that is to be branched
off to a separate file descriptor (Note, in a traditional off to a separate file descriptor (Note, in a traditional one-to-
one-to-one style accept() call, this would be an out parameter, one style accept() call, this would be an out parameter, but for
but for the one-to-many style call, this is an in parameter). the one-to-many style call, this is an in parameter).
8.3 sctp_getpaddrs() 8.3. sctp_getpaddrs()
sctp_getpaddrs() returns all peer addresses in an association. The sctp_getpaddrs() returns all peer addresses in an association. The
syntax is, syntax is,
int sctp_getpaddrs(int sd, sctp_assoc_t id, int sctp_getpaddrs(int sd, sctp_assoc_t id,
struct sockaddr **addrs); struct sockaddr **addrs);
On return, addrs will point to an array dynamically allocated On return, addrs will point to an array dynamically allocated
sockaddr structures of the appropriate type for the socket type. The sockaddr structures of the appropriate type for the socket type. The
caller should use sctp_freepaddrs() to free the memory. Note that caller should use sctp_freepaddrs() to free the memory. Note that
the in/out parameter addrs must not be NULL. the in/out parameter addrs must not be NULL.
If sd is an IPv4 socket, the addresses returned will be all IPv4 If sd is an IPv4 socket, the addresses returned will be all IPv4
addresses. If sd is an IPv6 socket, the addresses returned can be a addresses. If sd is an IPv6 socket, the addresses returned can be a
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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.
8.4 sctp_freepaddrs() 8.4. sctp_freepaddrs()
sctp_freepaddrs() frees all resources allocated by sctp_freepaddrs() frees all resources allocated by
sctp_getpaddrs(). Its syntax is, sctp_getpaddrs(). Its syntax is,
void sctp_freepaddrs(struct sockaddr *addrs); void sctp_freepaddrs(struct sockaddr *addrs);
addrs is the array of peer addresses returned by sctp_getpaddrs(). addrs is the array of peer addresses returned by sctp_getpaddrs().
8.5 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 syntax is, The syntax is,
int sctp_getladdrs(int sd, sctp_assoc_t id, int sctp_getladdrs(int sd, sctp_assoc_t id,
struct sockaddr **ss); struct sockaddr **ss);
On return, addrs will point to a dynamically allocated array of On return, addrs will point to a dynamically allocated array of
sockaddr structures of the appropriate type for the socket type. The sockaddr structures of the appropriate type for the socket type. The
caller should use sctp_freeladdrs() to free the memory. Note that caller should use sctp_freeladdrs() to free the memory. Note that
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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.
8.6 sctp_freeladdrs() 8.6. sctp_freeladdrs()
sctp_freeladdrs() frees all resources allocated by sctp_freeladdrs() frees all resources allocated by
sctp_getladdrs(). Its syntax is, sctp_getladdrs(). Its syntax is,
void sctp_freeladdrs(struct sockaddr *addrs); void sctp_freeladdrs(struct sockaddr *addrs);
addrs is the array of peer addresses returned by sctp_getladdrs(). addrs is the array of peer addresses returned by sctp_getladdrs().
8.7 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.
sctp_sendmsg(). Its syntax is, sctp_sendmsg(). Its syntax 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,
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msg - is the message to be sent. msg - is the message to be sent.
len - is the length of the message. len - is the length of the message.
to - is the destination address of the message. to - is the destination address of the message.
tolen - is the length of the destination address. tolen - is the length of the destination address.
ppid - is the same as sinfo_ppid (see section 5.2.2) ppid - is the same as sinfo_ppid (see section 5.2.2)
flags - is the same as sinfo_flags (see section 5.2.2) flags - is the same as sinfo_flags (see section 5.2.2)
stream_no - is the same as sinfo_stream (see section 5.2.2) stream_no - is the same as sinfo_stream (see section 5.2.2)
timetolive - is the same as sinfo_timetolive (see section 5.2.2) timetolive - is the same as sinfo_timetolive (see section 5.2.2)
context - is the same as sinfo_context (see section 5.2.2) context - is the same as sinfo_context (see section 5.2.2)
8.8 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. the SCTP_EVENTS option.
sctp_recvmsg(). Its syntax is, sctp_recvmsg(). Its syntax is,
ssize_t sctp_recvmsg(int sd, ssize_t sctp_recvmsg(int sd,
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msg - is a message buffer to be filled. msg - is a message buffer to be filled.
len - is the length of the message buffer. len - is the length of the message buffer.
from - is a pointer to a address to be filled with from - is a pointer to a address to be filled with
the sender of this messages address. the sender of this messages address.
fromlen - is the from length. fromlen - is the from length.
sinfo - A pointer to a sctp_sndrcvinfo structure sinfo - A pointer to a sctp_sndrcvinfo structure
to be filled upon receipt of the message. to be filled upon receipt of the message.
msg_flags - A pointer to a integer to be filled with msg_flags - A pointer to a integer to be filled with
any message flags (e.g. MSG_NOTIFICATION). any message flags (e.g. MSG_NOTIFICATION).
8.9 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 dependant. This function only specifies that the is implementation dependant. 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.
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retrieve them after the association has been set up. retrieve them after the association has been set up.
sctp_connectx(). Its syntax is, sctp_connectx(). Its syntax is,
int sctp_connectx(int sd, int sctp_connectx(int sd,
struct sockaddr *addrs, struct sockaddr *addrs,
int addrcnt) int addrcnt)
sd - is the socket descriptor sd - is the socket descriptor
addrs - is an array of addresses. addrs - is an array of addresses.
addrcnt - is the number of addresses in the array. addrcnt - is the number of addresses in the array.
8.10 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. The function takes the following use of the CMSG header structures. The function takes the following
form: form:
sctp_send(). Its syntax is, sctp_send(). Its syntax is,
int sctp_send(int sd, int sctp_send(int sd,
const void *msg, const void *msg,
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sd - is the socket descriptor sd - is 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 struture used sinfo - A pointer to a sctp_sndrcvinfo struture used
as described in 5.2.2 for a sendmsg call. as described in 5.2.2 for a sendmsg call.
flags - is used in the same format as the sendmsg call flags - is used in the same format as the sendmsg call
flags (e.g. MSG_DONTROUTE). flags (e.g. MSG_DONTROUTE).
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
MSG_EOF and the sinfo.sinf_associd to the association that needs to SCTP_EOF and the sinfo.sinf_associd to the association that needs to
be terminated. In such a case the len of the message would be zero. be terminated. In such a case the len of the message would be zero.
8.11 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 8.9). Section 8.9).
sctp_sendx(). Its syntax is, sctp_sendx(). Its syntax is,
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as described in 5.2.2 for a sendmsg call. as described in 5.2.2 for a sendmsg call.
flags - is used in the same format as the sendmsg call flags - is used in the same format as the sendmsg call
flags (e.g. MSG_DONTROUTE). flags (e.g. MSG_DONTROUTE).
Note that on return from this call the sinfo structure will have Note that on return from this call the sinfo structure will have
changed in that the sinfo_assoc_id will be filled in with the new changed in that the sinfo_assoc_id will be filled in with the new
association id. association id.
This function call may also be used to terminate an association using This function call may also be used to terminate an association using
an association identification by setting the sinfo.sinfo_flags to an association identification by setting the sinfo.sinfo_flags to
MSG_EOF and the sinfo.sinf_associd to the association that needs to SCTP_EOF and the sinfo.sinfo_associd to the association that needs to
be terminated. In such a case the len of the message would be zero. be terminated. In such a case the len of the message would be zero.
9. Preprocessor Constants 9. Preprocessor Constants
For application portability it is desireable to define pre-processor For application portability it is desireable to define pre-processor
constants for determination if sctp is present and supports various constants for determination if sctp is present and supports various
features. The following pre-processor constants should be defined in features. The following pre-processor constants should be defined in
a include file, sctp.h. a include file, sctp.h.
HAVE_SCTP - If this constant is defined to 1, then an implementation HAVE_SCTP - If this constant is defined to 1, then an implementation
of SCTP is available. of SCTP is available.
HAVE_KERNEL_SCTP - If this constant is defined to 1, then a kernel HAVE_KERNEL_SCTP - If this constant is defined to 1, then a kernel
SCTP implementation is available through the sockets interface. SCTP implementation is available through the sockets interface.
HAVE_SCTP_PRSCTP - If this constant is defined to 1, then the SCTP HAVE_SCTP_PRSCTP - If this constant is defined to 1, then the SCTP
implementation supports the partial reliablility extension to implementation supports the partial reliablility extension to
SCTP. SCTP.
HAVE_SCTP_ADDIP - If this constant is defined to 1, then the SCTP HAVE_SCTP_ADDIP - If this constant is defined to 1, then the SCTP
implementation supports the dynamic address extension to SCTP. implementation supports the dynamic address extension to SCTP.
HAVE_SCTP_CANSET_PRIMARY - If this constant is defined to 1, then the HAVE_SCTP_CANSET_PRIMARY - If this constant is defined to 1, then the
SCTP implementation supports the ability to request setting of the SCTP implementation supports the ability to request setting of the
remote primary address. remote primary address.
HAVE_SCTP_SAT_NETWORK_CAPABILITY - If this constant is defined to 1, HAVE_SCTP_SAT_NETWORK_CAPABILITY - If this constant is defined to 1,
then the SCTP implementation supports the satellite network then the SCTP implementation supports the satellite network
extension to SCTP. extension to SCTP.
HAVE_SCTP_MULTIBUF - If this constant is defined to 1, then the SCTP HAVE_SCTP_MULTIBUF - If this constant is defined to 1, then the SCTP
implementation dedicates separate buffer space to each association implementation dedicates separate buffer space to each association
on a one-to-many socket. If this constant is defined to 0, then on a one-to-many socket. If this constant is defined to 0, then
the implementation provides a single block of shared buffer space the implementation provides a single block of shared buffer space
for a one-to-many socket. for a one-to-many socket.
HAVE_SCTP_NOCONNECT - If this constant is defined to 1, then the SCTP HAVE_SCTP_NOCONNECT - If this constant is defined to 1, then the SCTP
implementation supports initiating an association on a one-to-one implementation supports initiating an association on a one-to-one
style socket without the use of connect(), as outlined in style socket without the use of connect(), as outlined in
Section 4.1.5. Section 4.1.5.
10. 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
skipping to change at page 72, line 23 skipping to change at page 79, line 23
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.
12. References 12. References
[1] Postel, J., "Transmission Control Protocol", STD 7, RFC 793, [1] Postel, J., "Transmission Control Protocol", STD 7, RFC 793,
September 1981. September 1981.
[2] Postel, J., "User Datagram Protocol", STD 6, RFC 768, August [2] Postel, J., "User Datagram Protocol", STD 6, RFC 768,
1980. August 1980.
[3] Braden, B., "T/TCP -- TCP Extensions for Transactions Functional [3] Braden, B., "T/TCP -- TCP Extensions for Transactions Functional
Specification", RFC 1644, July 1994. Specification", RFC 1644, July 1994.
[4] Bradner, S., "The Internet Standards Process -- Revision 3", [4] Bradner, S., "The Internet Standards Process -- Revision 3",
BCP 9, RFC 2026, October 1996. BCP 9, RFC 2026, October 1996.
[5] Bradner, S., "Key words for use in RFCs to Indicate Requirement [5] Bradner, S., "Key words for use in RFCs to Indicate Requirement
Levels", BCP 14, RFC 2119, March 1997. Levels", BCP 14, RFC 2119, March 1997.
[6] Stevens, W. and M. Thomas, "Advanced Sockets API for IPv6", [6] Stevens, W. and M. Thomas, "Advanced Sockets API for IPv6",
RFC 2292, February 1998. RFC 2292, February 1998.
[7] Gilligan, R., Thomson, S., Bound, J. and W. Stevens, "Basic [7] Gilligan, R., Thomson, S., Bound, J., and W. Stevens, "Basic
Socket Interface Extensions for IPv6", RFC 2553, March 1999. Socket Interface Extensions for IPv6", RFC 2553, March 1999.
[8] Stewart, R., Xie, Q., Morneault, K., Sharp, C., Schwarzbauer, [8] Stewart, R., Xie, Q., Morneault, K., Sharp, C., Schwarzbauer,
H., Taylor, T., Rytina, I., Kalla, M., Zhang, L. and V. Paxson, H., Taylor, T., Rytina, I., Kalla, M., Zhang, L., and V. Paxson,
"Stream Control Transmission Protocol", RFC 2960, October 2000. "Stream Control Transmission Protocol", RFC 2960, October 2000.
Authors' Addresses
Randall R. Stewart
Cisco Systems, Inc.
4875 Forest Drive
Suite 200
Columbia, SC 29206
USA
Phone:
Email: rrs@cisco.com
Qiaobing Xie
Motorola, Inc.
1501 W. Shure Drive, #2309
Arlington Heights, IL 60004
USA
Phone:
Email: qxie1@email.mot.com
La Monte H.P. Yarroll
TimeSys Corp
925 Liberty Ave.
Pittsburgh, PA 15222
USA
Phone:
Email: piggy@acm.org
Jonathan Wood
DoCoMo USA Labs
181 Metro Drive, Suite 300
San Jose, CA 95110
USA
Phone:
Email: jonwood@speakeasy.net
Kacheong Poon
Sun Microsystems, Inc.
4150 Network Circle
Santa Clara, CA 95054
USA
Phone:
Email: kacheong.poon@sun.com
Michael Tuexen
Univ. of Applied Sciences Muenster
Stegerwaldstr. 39
48565 Steinfurt
Germany
Email: tuexen@fh-muenster.de
Appendix A. one-to-one style Code Example Appendix A. one-to-one style Code Example
The following code is a simple implementation of an echo server over The following code is a simple implementation of an echo server over
SCTP. The example shows how to use some features of one-to-one style SCTP. The example shows how to use some features of one-to-one style
IPv4 SCTP sockets, including: IPv4 SCTP sockets, including:
o Opening, binding, and listening for new associations on a socket; o Opening, binding, and listening for new associations on a socket;
o Enabling ancillary data o Enabling ancillary data
o Enabling notifications o Enabling notifications
o Using ancillary data with sendmsg() and recvmsg() o Using ancillary data with sendmsg() and recvmsg()
o Using MSG_EOR to determine if an entire message has been read o Using MSG_EOR to determine if an entire message has been read
o Handling notifications o Handling notifications
#include <stdio.h> #include <stdio.h>
#include <sys/types.h> #include <sys/types.h>
#include <sys/socket.h> #include <sys/socket.h>
#include <netinet/in.h> #include <netinet/in.h>
#include <arpa/inet.h> #include <arpa/inet.h>
#include <stdlib.h> #include <stdlib.h>
#include <unistd.h> #include <unistd.h>
#include <netinet/sctp.h> #include <netinet/sctp.h>
skipping to change at page 81, line 12 skipping to change at page 86, line 12
} }
} }
Appendix B. one-to-many style Code Example Appendix B. one-to-many style Code Example
The following code is a simple implementation of an echo server over The following code is a simple implementation of an echo server over
SCTP. The example shows how to use some features of one-to-many SCTP. The example shows how to use some features of one-to-many
style IPv4 SCTP sockets, including: style IPv4 SCTP sockets, including:
o Opening and binding of a socket; o Opening and binding of a socket;
o Enabling ancillary data o Enabling ancillary data
o Enabling notifications o Enabling notifications
o Using ancillary data with sendmsg() and recvmsg() o Using ancillary data with sendmsg() and recvmsg()
o Using MSG_EOR to determine if an entire message has been read o Using MSG_EOR to determine if an entire message has been read
o Handling notifications o Handling notifications
Note most functions defined in Appendix A are reused in thi Note most functions defined in Appendix A are reused in this example.
s example.
int main() int main()
{ {
int fd; int fd;
int idleTime = 2; int idleTime = 2;
struct sockaddr_in sin[1]; struct sockaddr_in sin[1];
struct sctp_event_subscribe event; struct sctp_event_subscribe event;
if ((fd = socket(AF_INET, SOCK_SEQPACKET, IPPROTO_SCTP)) == -1) { if ((fd = socket(AF_INET, SOCK_SEQPACKET, IPPROTO_SCTP)) == -1) {
perror("socket"); perror("socket");
skipping to change at page 83, line 5 skipping to change at page 88, line 5
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);
} }
} }
Authors' Addresses
Randall R. Stewart
Cisco Systems, Inc.
4875 Forest Drive
Suite 200
Columbia, SC 29206
USA
Phone:
Email: rrs@cisco.com
Qiaobing Xie
Motorola, Inc.
1501 W. Shure Drive, #2309
Arlington Heights, IL 60004
USA
Phone:
Email: qxie1@email.mot.com
La Monte H.P. Yarroll
TimeSys Corp
925 Liberty Ave.
Pittsburgh, PA 15222
USA
Phone:
Email: piggy@acm.org
Jonathan Wood
DoCoMo USA Labs
181 Metro Drive, Suite 300
San Jose, CA 95110
USA
Phone:
Email: jonwood@speakeasy.net
Kacheong Poon
Sun Microsystems, Inc.
4150 Network Circle
Santa Clara, CA 95054
USA
Phone:
Email: kacheong.poon@sun.com
Michael Tuexen
Univ. of Applied Sciences Muenster
Stegerwaldstr. 39
48565 Steinfurt
Germany
Email: tuexen@fh-muenster.de
Intellectual Property Statement Intellectual Property Statement
The IETF takes no position regarding the validity or scope of any The IETF takes no position regarding the validity or scope of any
Intellectual Property Rights or other rights that might be claimed to Intellectual Property Rights or other rights that might be claimed to
pertain to the implementation or use of the technology described in pertain to the implementation or use of the technology described in
this document or the extent to which any license under such rights this document or the extent to which any license under such rights
might or might not be available; nor does it represent that it has might or might not be available; nor does it represent that it has
made any independent effort to identify any such rights. Information made any independent effort to identify any such rights. Information
on the procedures with respect to rights in RFC documents can be on the procedures with respect to rights in RFC documents can be
found in BCP 78 and BCP 79. found in BCP 78 and BCP 79.
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