draft-ietf-tsvwg-sctpsocket-06.txt   draft-ietf-tsvwg-sctpsocket-07.txt 
Network Working Group R. Stewart Network Working Group R. Stewart
Internet-Draft Cisco Systems, Inc. Internet-Draft Cisco Systems, Inc.
Expires: August 27, 2003 Q. Xie Expires: February 20, 2004 Q. Xie
L. Yarroll
Motorola, Inc. Motorola, Inc.
L. Yarroll
USACE ERDC-CERL.
J. Wood J. Wood
DoCoMo USA Labs DoCoMo USA Labs
K. Poon K. Poon
Consultant Consultant
K. Fujita K. Fujita
NEC USA, Inc. NEC USA, Inc.
M. Tuexen M. Tuexen
February 26, 2003 Univ. of Applied Sciences Muenster
August 22, 2003
Sockets API Extensions for Stream Control Transmission Protocol Sockets API Extensions for Stream Control Transmission Protocol
(SCTP) (SCTP)
draft-ietf-tsvwg-sctpsocket-06.txt draft-ietf-tsvwg-sctpsocket-07.txt
Status of this Memo Status of this Memo
This document is an Internet-Draft and is in full conformance with This document is an Internet-Draft and is in full conformance with
all provisions of Section 10 of RFC2026. all provisions of Section 10 of RFC2026.
Internet-Drafts are working documents of the Internet Engineering Internet-Drafts are working documents of the Internet Engineering
Task Force (IETF), its areas, and its working groups. Note that Task Force (IETF), its areas, and its working groups. Note that other
other groups may also distribute working documents as groups may also distribute working documents as Internet-Drafts.
Internet-Drafts.
Internet-Drafts are draft documents valid for a maximum of six months Internet-Drafts are draft documents valid for a maximum of six months
and may be updated, replaced, or obsoleted by other documents at any and may be updated, replaced, or obsoleted by other documents at any
time. It is inappropriate to use Internet-Drafts as reference time. It is inappropriate to use Internet-Drafts as reference
material or to cite them other than as "work in progress." material or to cite them other than as "work in progress."
The list of current Internet-Drafts can be accessed at http:// The list of current Internet-Drafts can be accessed at http://
www.ietf.org/ietf/1id-abstracts.txt. www.ietf.org/ietf/1id-abstracts.txt.
The list of Internet-Draft Shadow Directories can be accessed at The list of Internet-Draft Shadow Directories can be accessed at
http://www.ietf.org/shadow.html. http://www.ietf.org/shadow.html.
This Internet-Draft will expire on August 27, 2003. This Internet-Draft will expire on February 20, 2004.
Copyright Notice Copyright Notice
Copyright (C) The Internet Society (2003). All Rights Reserved. Copyright (C) The Internet Society (2003). All Rights Reserved.
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 . . . . . . . . . . . . . . . . . . . . . . . 4 1. Introduction . . . . . . . . . . . . . . . . . . . . . . . 4
2. Conventions . . . . . . . . . . . . . . . . . . . . . . . 6 2. Conventions . . . . . . . . . . . . . . . . . . . . . . . 6
2.1 Data Types . . . . . . . . . . . . . . . . . . . . . . . . 6 2.1 Data Types . . . . . . . . . . . . . . . . . . . . . . . . 6
skipping to change at page 2, line 13 skipping to change at page 2, line 14
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 . . . . . . . . . . . . . . . . . . . . . . . 4 1. Introduction . . . . . . . . . . . . . . . . . . . . . . . 4
2. Conventions . . . . . . . . . . . . . . . . . . . . . . . 6 2. Conventions . . . . . . . . . . . . . . . . . . . . . . . 6
2.1 Data Types . . . . . . . . . . . . . . . . . . . . . . . . 6 2.1 Data Types . . . . . . . . . . . . . . . . . . . . . . . . 6
3. UDP-style Interface . . . . . . . . . . . . . . . . . . . 7 3. one-to-many style Interface . . . . . . . . . . . . . . . 7
3.1 3.1 Basic Operation . . . . . . . . . . . . . . . . . . . 7 3.1 Basic Operation . . . . . . . . . . . . . . . . . . . . . 7
3.1.1 socket() - UDP Style Syntax . . . . . . . . . . . . . . . 8 3.1.1 socket() - one-to-many style socket . . . . . . . . . . . 8
3.1.2 bind() - UDP Style Syntax . . . . . . . . . . . . . . . . 8 3.1.2 bind() - one-to-many style socket . . . . . . . . . . . . 8
3.1.3 listen() - UDP Style Syntax . . . . . . . . . . . . . . . 9 3.1.3 listen() - One-to-many style socket . . . . . . . . . . . 9
3.1.4 sendmsg() and recvmsg() - UDP Style Syntax . . . . . . . . 10 3.1.4 sendmsg() and recvmsg() - one-to-many style socket . . . . 10
3.1.5 close() - UDP Style Syntax . . . . . . . . . . . . . . . . 11 3.1.5 close() - one-to-many style socket . . . . . . . . . . . . 11
3.1.6 connect() - UDP Style Syntax . . . . . . . . . . . . . . . 12 3.1.6 connect() - one-to-many style socket . . . . . . . . . . . 12
3.2 Implicit Association Setup . . . . . . . . . . . . . . . . 12 3.2 Implicit Association Setup . . . . . . . . . . . . . . . . 12
3.3 Non-blocking mode . . . . . . . . . . . . . . . . . . . . 13 3.3 Non-blocking mode . . . . . . . . . . . . . . . . . . . . 13
3.4 Special considerations . . . . . . . . . . . . . . . . . . 13 3.4 Special considerations . . . . . . . . . . . . . . . . . . 14
4. TCP-style Interface . . . . . . . . . . . . . . . . . . . 16 4. one-to-one style Interface . . . . . . . . . . . . . . . . 16
4.1 Basic Operation . . . . . . . . . . . . . . . . . . . . . 16 4.1 Basic Operation . . . . . . . . . . . . . . . . . . . . . 16
4.1.1 socket() - TCP Style Syntax . . . . . . . . . . . . . . . 17 4.1.1 socket() - one-to-one style socket . . . . . . . . . . . . 17
4.1.2 bind() - TCP Style Syntax . . . . . . . . . . . . . . . . 17 4.1.2 bind() - one-to-one style socket . . . . . . . . . . . . . 17
4.1.3 listen() - TCP Style Syntax . . . . . . . . . . . . . . . 18 4.1.3 listen() - one-to-one style socket . . . . . . . . . . . . 18
4.1.4 accept() - TCP Style Syntax . . . . . . . . . . . . . . . 19 4.1.4 accept() - one-to-one style socket . . . . . . . . . . . . 19
4.1.5 connect() - TCP Style Syntax . . . . . . . . . . . . . . . 19 4.1.5 connect() - one-to-one style socket . . . . . . . . . . . 19
4.1.6 close() - TCP Style Syntax . . . . . . . . . . . . . . . . 20 4.1.6 close() - one-to-one style socket . . . . . . . . . . . . 20
4.1.7 shutdown() - TCP Style Syntax . . . . . . . . . . . . . . 20 4.1.7 shutdown() - one-to-one style socket . . . . . . . . . . . 20
4.1.8 sendmsg() and recvmsg() - TCP Style Syntax . . . . . . . . 21 4.1.8 sendmsg() and recvmsg() - one-to-one style socket . . . . 21
4.1.9 getpeername() . . . . . . . . . . . . . . . . . . . . . . 22 4.1.9 getpeername() . . . . . . . . . . . . . . . . . . . . . . 22
5. Data Structures . . . . . . . . . . . . . . . . . . . . . 23 5. Data Structures . . . . . . . . . . . . . . . . . . . . . 23
5.1 The msghdr and cmsghdr Structures . . . . . . . . . . . . 23 5.1 The msghdr and cmsghdr Structures . . . . . . . . . . . . 23
5.2 SCTP msg_control Structures . . . . . . . . . . . . . . . 24 5.2 SCTP msg_control Structures . . . . . . . . . . . . . . . 24
5.2.1 SCTP Initiation Structure (SCTP_INIT) . . . . . . . . . . 25 5.2.1 SCTP Initiation Structure (SCTP_INIT) . . . . . . . . . . 25
5.2.2 SCTP Header Information Structure (SCTP_SNDRCV) . . . . . 26 5.2.2 SCTP Header Information Structure (SCTP_SNDRCV) . . . . . 26
5.3 SCTP Events and Notifications . . . . . . . . . . . . . . 29 5.3 SCTP Events and Notifications . . . . . . . . . . . . . . 28
5.3.1 SCTP Notification Structure . . . . . . . . . . . . . . . 29 5.3.1 SCTP Notification Structure . . . . . . . . . . . . . . . 29
5.4 Ancillary Data Considerations and Semantics . . . . . . . 39 5.4 Ancillary Data Considerations and Semantics . . . . . . . 38
5.4.1 Multiple Items and Ordering . . . . . . . . . . . . . . . 39 5.4.1 Multiple Items and Ordering . . . . . . . . . . . . . . . 38
5.4.2 Accessing and Manipulating Ancillary Data . . . . . . . . 39 5.4.2 Accessing and Manipulating Ancillary Data . . . . . . . . 39
5.4.3 Control Message Buffer Sizing . . . . . . . . . . . . . . 40 5.4.3 Control Message Buffer Sizing . . . . . . . . . . . . . . 39
6. Common Operations for Both Styles . . . . . . . . . . . . 42 6. Common Operations for Both Styles . . . . . . . . . . . . 41
6.1 send(), recv(), sendto(), recvfrom() . . . . . . . . . . . 42 6.1 send(), recv(), sendto(), recvfrom() . . . . . . . . . . . 41
6.2 setsockopt(), getsockopt() . . . . . . . . . . . . . . . . 43 6.2 setsockopt(), getsockopt() . . . . . . . . . . . . . . . . 42
6.3 read() and write() . . . . . . . . . . . . . . . . . . . . 43 6.3 read() and write() . . . . . . . . . . . . . . . . . . . . 42
6.4 getsockname() . . . . . . . . . . . . . . . . . . . . . . 43 6.4 getsockname() . . . . . . . . . . . . . . . . . . . . . . 42
7. Socket Options . . . . . . . . . . . . . . . . . . . . . . 45 7. Socket Options . . . . . . . . . . . . . . . . . . . . . . 44
7.1 Read / Write Options . . . . . . . . . . . . . . . . . . . 46 7.1 Read / Write Options . . . . . . . . . . . . . . . . . . . 45
7.1.1 Retransmission Timeout Parameters (SCTP_RTOINFO) . . . . . 46 7.1.1 Retransmission Timeout Parameters (SCTP_RTOINFO) . . . . . 45
7.1.2 Association Parameters (SCTP_ASSOCINFO) . . . . . . . . . 47 7.1.2 Association Parameters (SCTP_ASSOCINFO) . . . . . . . . . 46
7.1.3 Initialization Parameters (SCTP_INITMSG) . . . . . . . . . 49 7.1.3 Initialization Parameters (SCTP_INITMSG) . . . . . . . . . 47
7.1.4 SO_LINGER . . . . . . . . . . . . . . . . . . . . . . . . 49 7.1.4 SO_LINGER . . . . . . . . . . . . . . . . . . . . . . . . 48
7.1.5 SCTP_NODELAY . . . . . . . . . . . . . . . . . . . . . . . 49 7.1.5 SCTP_NODELAY . . . . . . . . . . . . . . . . . . . . . . . 48
7.1.6 SO_RCVBUF . . . . . . . . . . . . . . . . . . . . . . . . 50 7.1.6 SO_RCVBUF . . . . . . . . . . . . . . . . . . . . . . . . 48
7.1.7 SO_SNDBUF . . . . . . . . . . . . . . . . . . . . . . . . 50 7.1.7 SO_SNDBUF . . . . . . . . . . . . . . . . . . . . . . . . 48
7.1.8 Automatic Close of associations (SCTP_AUTOCLOSE) . . . . . 50 7.1.8 Automatic Close of associations (SCTP_AUTOCLOSE) . . . . . 49
7.1.9 Set Primary Address (SCTP_SET_PRIMARY_ADDR) . . . . . . . 50 7.1.9 Set Peer Primary Address (SCTP_SET_PEER_PRIMARY_ADDR) . . 49
7.1.10 Set Peer Primary Address (SCTP_SET_PEER_PRIMARY_ADDR) . . 51 7.1.10 Set Primary Address (SCTP_PRIMARY_ADDR) . . . . . . . . . 49
7.1.11 Set Adaption Layer Indicator (SCTP_SET_ADAPTION_LAYER) . . 51 7.1.11 Set Adaption Layer Indicator (SCTP_ADAPTION_LAYER) . . . . 50
7.1.12 Enable/Disable message fragmentation 7.1.12 Enable/Disable message fragmentation
(SCTP_DISABLE_FRAGMENTS) . . . . . . . . . . . . . . . . . 51 (SCTP_DISABLE_FRAGMENTS) . . . . . . . . . . . . . . . . . 50
7.1.13 Peer Address Parameters (SCTP_SET_PEER_ADDR_PARAMS) . . . 51 7.1.13 Peer Address Parameters (SCTP_PEER_ADDR_PARAMS) . . . . . 50
7.1.14 Set default send parameters (SET_DEFAULT_SEND_PARAM) . . . 52 7.1.14 Set default send parameters (SCTP_DEFAULT_SEND_PARAM) . . 51
7.1.15 Set notification and ancillary events (SCTP_SET_EVENTS) . 52 7.1.15 Set notification and ancillary events (SCTP_EVENTS) . . . 51
7.1.16 Set/clear IPv4 mapped addresses 7.1.16 Set/clear IPv4 mapped addresses
(SCTP_I_WANT_MAPPED_V4_ADDR) . . . . . . . . . . . . . . . 53 (SCTP_I_WANT_MAPPED_V4_ADDR) . . . . . . . . . . . . . . . 51
7.1.17 Set the maximum fragrmentation size (SCTP_MAXSEG) . . . . 53 7.1.17 Set the maximum fragmentation size (SCTP_MAXSEG) . . . . . 52
7.2 Read-Only Options . . . . . . . . . . . . . . . . . . . . 53 7.2 Read-Only Options . . . . . . . . . . . . . . . . . . . . 52
7.2.1 Association Status (SCTP_STATUS) . . . . . . . . . . . . . 53 7.2.1 Association Status (SCTP_STATUS) . . . . . . . . . . . . . 52
7.2.2 Peer Address Information (SCTP_GET_PEER_ADDR_INFO) . . . . 54 7.2.2 Peer Address Information (SCTP_GET_PEER_ADDR_INFO) . . . . 53
7.3 Ancillary Data and Notification Interest Options . . . . . 55 7.3 Ancillary Data and Notification Interest Options . . . . . 54
8. New Interfaces . . . . . . . . . . . . . . . . . . . . . . 58 8. New Interfaces . . . . . . . . . . . . . . . . . . . . . . 57
8.1 sctp_bindx() . . . . . . . . . . . . . . . . . . . . . . . 58 8.1 sctp_bindx() . . . . . . . . . . . . . . . . . . . . . . . 57
8.2 Branched-off Association . . . . . . . . . . . . . . . . . 59 8.2 Branched-off Association . . . . . . . . . . . . . . . . . 58
8.3 sctp_getpaddrs() . . . . . . . . . . . . . . . . . . . . . 59 8.3 sctp_getpaddrs() . . . . . . . . . . . . . . . . . . . . . 58
8.4 sctp_freepaddrs() . . . . . . . . . . . . . . . . . . . . 60 8.4 sctp_freepaddrs() . . . . . . . . . . . . . . . . . . . . 59
8.5 sctp_getladdrs() . . . . . . . . . . . . . . . . . . . . . 60 8.5 sctp_getladdrs() . . . . . . . . . . . . . . . . . . . . . 59
8.6 sctp_freeladdrs() . . . . . . . . . . . . . . . . . . . . 61 8.6 sctp_freeladdrs() . . . . . . . . . . . . . . . . . . . . 60
8.7 sctp_sndmsg() . . . . . . . . . . . . . . . . . . . . . . 61 8.7 sctp_sendmsg() . . . . . . . . . . . . . . . . . . . . . . 60
9. Preprocessor Constants . . . . . . . . . . . . . . . . . . 62 8.8 sctp_recvmsg() . . . . . . . . . . . . . . . . . . . . . . 61
10. Security Considerations . . . . . . . . . . . . . . . . . 63 8.9 sctp_connectx() . . . . . . . . . . . . . . . . . . . . . 61
11. Acknowledgments . . . . . . . . . . . . . . . . . . . . . 64 9. Preprocessor Constants . . . . . . . . . . . . . . . . . . 63
References . . . . . . . . . . . . . . . . . . . . . . . . 65 10. Security Considerations . . . . . . . . . . . . . . . . . 64
Authors' Addresses . . . . . . . . . . . . . . . . . . . . 65 11. Acknowledgments . . . . . . . . . . . . . . . . . . . . . 65
A. TCP-style Code Example . . . . . . . . . . . . . . . . . . 68 References . . . . . . . . . . . . . . . . . . . . . . . . 66
B. UDP-style Code Example . . . . . . . . . . . . . . . . . . 74 Authors' Addresses . . . . . . . . . . . . . . . . . . . . 66
Intellectual Property and Copyright Statements . . . . . . 76 A. one-to-one style Code Example . . . . . . . . . . . . . . 69
B. one-to-many style Code Example . . . . . . . . . . . . . . 75
Intellectual Property and Copyright Statements . . . . . . 77
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
UDP RFC768 [2] have benefited from this standard representation and 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
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 UDP-style interface 2) Support a one-to-many style interface
This set of semantics is similar to that defined for connection This set of semantics is similar to that defined for connection
less protocols, such as UDP. It is more efficient than a TCP-like less protocols, such as UDP. It is more efficient than a TCP-like
connection-oriented interface in terms of exploring the new connection-oriented (the one-to-one style) interface in terms of
features of SCTP. exploring the new features of SCTP. But the one-to-one style
interface can also make use of most new SCTP features.
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 TCP-style interface 3) Support a one-to-one style interface
This interface supports the same basic semantics as sockets for This interface supports a similar semantics as sockets for
connection-oriented protocols, such as TCP. connection-oriented protocols, such as TCP.
The purpose of defining this interface is to allow existing The purpose of defining this interface is to allow existing
applications built on connection-oriented protocols be ported to applications built on connection-oriented protocols be ported to
use SCTP with very little effort, and developers familiar with use SCTP with very little effort, and developers familiar with
those semantics can easily adapt to SCTP. those semantics can easily adapt to SCTP.
Extensions will be 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 UDP-style mapping and the TCP-style modes of mapping, namely the one-to-many style mapping and the
mapping. These two modes share some common data structures and one-to-one style mapping. These two modes share some common data
operations, but will require the use of two different application structures and operations, but will require the use of two different
programming models. application programming styles.
A mechanism is defined to convert a UDP-style SCTP association into a A mechanism is defined to extract a one-to-many style SCTP
TCP-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. This document also interface instead of using existing socket calls. This document also
describes those new interface. 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. UDP-style Interface 3. one-to-many style Interface
The UDP-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 3.1 Basic Operation 3.1 Basic Operation
A typical server in this model 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()
skipping to change at page 7, line 44 skipping to change at page 7, line 44
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 model, 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. endpoint are represented with a single socket.
If the server or client wishes to branch an existing association off If the server or client wishes to branch an existing association off
to a separate socket, it is required to call sctp_peeloff() and in to a separate socket, it is required to call sctp_peeloff() and in
the parameter specifies one of the transport addresses of the the parameter specifies the association identification. The
association. The sctp_peeloff() call will return a new socket which sctp_peeloff() call will return a new socket which can then be used
can then be used with recv() and send() functions for message with recv() and send() functions for message passing. See Section 8.2
passing. See Section Section 8.2 for more on branched-off for more on branched-off associations.
associations.
Once an association is branched off to a separate socket, it becomes Once an association is branched off to a separate socket, it becomes
completely separated from the original socket. All subsequent completely separated from the original socket. All subsequent
control and data operations to that association must be done through control and data operations to that association must be done through
the new socket. For example, the close operation on the original the new socket. For example, the close operation on the original
socket will not terminate any associations that have been branched socket will not terminate any associations that have been branched
off to a different socket. off to a different socket.
We will discuss the UDP-style socket calls in more details in the We will discuss the one-to-many style socket calls in more details in
following subsections. the following subsections.
3.1.1 socket() - UDP Style Syntax 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 UDP-style socket. Here, SOCK_SEQPACKET indicates the creation of a one-to-many style
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() - UDP Style Syntax 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
skipping to change at page 9, line 36 skipping to change at page 9, line 36
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() or sctp_bindx() is not called prior to a sendmsg() call If a bind() or sctp_bindx() is not called prior to a sendmsg() call
that initiates a new association, the system picks an ephemeral port that initiates a new association, the system picks an ephemeral port
and will choose an address set equivalent to binding with a wildcard and will choose an address set equivalent to binding with a wildcard
address. One of those addresses will be the primary address for the address. One of those addresses will be the primary address for the
association. This automatically enables the multi-homing capability association. This automatically enables the multi-homing capability
of SCTP. of SCTP.
3.1.3 listen() - UDP Style Syntax 3.1.3 listen() - One-to-many style socket
By default, new associations are not accepted for UDP style sockets. By default, new associations are not accepted for one-to-many style
An application uses listen() to mark a socket as being able to accept sockets. An application uses listen() to mark a socket as being able
new associations. The syntax is, to accept new associations. The syntax is,
int listen(int socket, int backlog); int listen(int socket, int backlog);
socket - the socket descriptor of the endpoint. socket - the socket descriptor of the endpoint.
backlog - ignored for UDP-style sockets. backlog - if backlog is non-zero, enable listening else
disable listening.
Note that UDP-style socket consumers do not need to call accept to Note that one-to-many style socket consumers do not need to call
retrieve new associations. Calling accept() on a UDP-style socket accept to retrieve new associations. Calling accept() on a
should return EOPNOTSUPP. Rather, new associations are accepted one-to-many style socket should return EOPNOTSUPP. Rather, new
automatically, and notifications of the new associations are associations are accepted automatically, and notifications of the new
delivered via recvmsg() with the SCTP_ASSOC_CHANGE event (if these associations are delivered via recvmsg() with the SCTP_ASSOC_CHANGE
notifications are enabled). Clients will typically not call listen, event (if these notifications are enabled). Clients will typically
so that they can be assured that the only associations on the socket not call listen(), so that they can be assured that the only
will be ones they actively initiated. Server or peer-to-peer associations on the socket will be ones they actively initiated.
sockets, on the other hand, will always accept new associations, so a Server or peer-to-peer sockets, on the other hand, will always accept
well-written application using server UDP-style sockets must be new associations, so a well-written application using server
prepared to handle new associations from unwanted peers. one-to-many style sockets must be prepared to handle new associations
from unwanted peers.
Also note that the SCTP_ASSOC_CHANGE event provides the association Also note that the SCTP_ASSOC_CHANGE event provides the association
ID for a new association, so if applications wish to use the ID for a new association, so if applications wish to use the
association ID as input to other socket calls, they should ensure association ID as input to other socket calls, they should ensure
that the SCTP_ASSOC_CHANGE event is enabled (it is enabled by that the SCTP_ASSOC_CHANGE event is enabled (it is enabled by
default). default).
3.1.4 sendmsg() and recvmsg() - UDP Style Syntax 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 socket, const struct msghdr *message, int flags); ssize_t sendmsg(int socket, const struct msghdr *message, int flags);
ssize_t recvmsg(int socket, struct msghdr *message, int flags); ssize_t recvmsg(int socket, struct msghdr *message, int flags);
socket: the socket descriptor of the endpoint. socket: 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
5 for SCTP-specific flags used in the msghdr structure. 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.
When sending user data with sendmsg(), the msg_name field in msghdr When sending user data with sendmsg(), the msg_name field in msghdr
skipping to change at page 11, line 31 skipping to change at page 11, line 33
receive a data message, MSG_EOR will not be set in msg_flags. receive a data message, MSG_EOR will not be set in msg_flags.
Successive reads will consume more of the same message until the Successive reads will consume more of the same message until the
entire message has been delivered, and MSG_EOR will be set. entire message has been delivered, and MSG_EOR will be set.
If the SCTP stack is running low on buffers, it may partially deliver If the SCTP stack is running low on buffers, it may partially deliver
a message. In this case, MSG_EOR will not be set, and more calls to a message. In this case, MSG_EOR will not be set, and more calls to
recvmsg() will be necessary to completely consume the message. Only recvmsg() will be necessary to completely consume the message. Only
one message at a time can be partially delivered. 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 is not used when association (see Section 3.1), the msg_name field can be used to
sending data (i.e., ignored by the SCTP stack). override the primary address when sending data.
3.1.5 close() - UDP Style Syntax 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 UDP-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
UDP-style socket, an application should use the sendmsg() call, one-to-many style socket, an application should use the sendmsg()
possibly passing a user specified abort code in the data field, and call, and including the MSG_EOF flag. A user may optionally terminate
including the MSG_EOF flag in the ancillary data (see Section 5.2.2). an association non-gracefully by sending with the MSG_ABORT flag and
possibly passing a user specified abort code in the data field. Both
flags MSG_EOF and MSG_ABORT are passwd with ancillary data (see
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() - UDP Style Syntax 3.1.6 connect() - one-to-many style socket
An application may use the connect() call in the UDP model 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 associations. This is different from the semantics of
connect() on a UDP socket.
3.2 Implicit Association Setup 3.2 Implicit Association Setup
Once all bind() calls are complete on a UDP-style socket, the Once all bind() calls are complete on a one-to-many style socket, the
application can begin sending and receiving data using the sendmsg()/ application can begin sending and receiving data using the sendmsg()/
recvmsg() or sendto()/recvfrom() calls, without going through any recvmsg() or sendto()/recvfrom() calls, without going through any
explicit association setup procedures (i.e., no connect() calls explicit association setup procedures (i.e., no connect() calls
required). required).
Whenever sendmsg() or sendto() is called and the SCTP stack at the Whenever sendmsg() or sendto() is called and the SCTP stack at the
sender finds that there is no association existing between the sender sender finds that there is no association existing between the sender
and the intended receiver (identified by the address passed either in and the intended receiver (identified by the address passed either in
the msg_name field of msghdr structure in the sendmsg() call or the the msg_name field of msghdr structure in the sendmsg() call or the
dest_addr field in the sendto() call), the SCTP stack will dest_addr field in the sendto() call), the SCTP stack will
automatically setup an association to the intended receiver. automatically setup an association to the intended receiver.
Upon the successful association setup a SCTP_COMM_UP notification Upon the successful association setup a SCTP_COMM_UP notification
will be dispatched to the socket at both the sender and receiver will be dispatched to the socket at both the sender and receiver
side. This notification can be read by the recvmsg() system call side. This notification can be read by the recvmsg() system call (see
(see Section 3.1.3). Section 3.1.3).
Note, if the SCTP stack at the sender side supports bundling, the Note, if the SCTP stack at the sender side supports bundling, the
first user message may be bundled with the COOKIE ECHO message first user message may be bundled with the COOKIE ECHO message
RFC2960 [8]. RFC2960 [8].
When the SCTP stack sets up a new association implicitly, it first When the SCTP stack sets up a new association implicitly, it first
consults the sctp_initmsg structure, which is passed along within the consults the sctp_initmsg structure, which is passed along within the
ancillary data in the sendmsg() call (see Section 5.2.1 for details ancillary data in the sendmsg() call (see Section 5.2.1 for details
of the data structures), for any special options to be used on the of the data structures), for any special options to be used on the
new association. new association.
skipping to change at page 13, line 21 skipping to change at page 13, line 31
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.
Whenever the user which want to avoid blocking must call select() Whenever the user which want to avoid blocking must call select()
before calling sendmsg()/sendto() and recvmsg()/recvfrom(), and check before calling sendmsg()/sendto() and recvmsg()/recvfrom(), and check
the socket status is writable or readable. If the socket status the socket status is writable or readable. If the socket status is
isn't writeable or readable, the user should not call sendmsg()/ not writable sendmsg() and sendto() return EAGAIN and do not transmit
sendto() and recvmsg()/recvfrom(). the message. Similarly, if the status is not readable, recvmsg() and
recvfrom() return EAGAIN.
Once all bind() calls are complete on a UDP-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 MSG_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). SHUTDOWN_COMPLETE (see Section 5.3.1.1).
3.4 Special considerations 3.4 Special considerations
The fact that a UDP-style socket can provide access to many SCTP The fact that a one-to-many style socket can provide access to many
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
directly affects how application programmers must write their code to affects how application programmers must write their code to ensure
ensure correct operation and portability, this section provides some correct operation and portability, this section provides some
guidance to both implementors and application programmers. guidance to both implementors and application programmers.
An important feature that SCTP shares with TCP is flow control: An important feature that SCTP shares with TCP is flow control:
specifically, a sender may not send data faster than the receiver can specifically, a sender may not send data faster than the receiver can
consume it. consume it.
For TCP, flow control is typically provided for in the sockets API as For TCP, flow control is typically provided for in the sockets API as
follows. If the reader stops reading, the sender queues messages in follows. If the reader stops reading, the sender queues messages in
the socket layer until it uses all of its socket buffer space the socket layer until it uses all of its socket buffer space
allocation creating a "stalled connection". Further attempts to allocation creating a "stalled connection". Further attempts to
write to the socket will block or return the error EAGAIN (for a write to the socket will block or return the error EAGAIN (for a
non-blocking socket). At some point, either the connection is non-blocking socket). At some point, either the connection is
closed, or the receiver begins to read again freeing space in the closed, or the receiver begins to read again freeing space in the
output queue. output queue.
For TCP-style SCTP sockets (this includes sockets descriptors that For one-to-one style SCTP sockets (this includes sockets descriptors
were separated from a UDP style socket with sctp_peeloff()) the that were separated from a one-to-many style socket with
behavior is identical. For UDP-style SCTP sockets, the fact that we sctp_peeloff()) the behavior is identical. For one-to-many style
have multiple associations on a single socket makes the situation SCTP sockets, the fact that we have multiple associations on a single
more complicated. If the implementation uses a single buffer space socket makes the situation more complicated. If the implementation
allocation shared by all associations, a single stalled association uses a single buffer space allocation shared by all associations, a
can prevent the further sending of data on all associations active on single stalled association can prevent the further sending of data on
a particular UDP-style socket. all associations active on a particular one-to-many style socket.
For a blocking socket, it should be clear that a single stalled For a blocking socket, it should be clear that a single stalled
association can block the entire socket. For this reason, association can block the entire socket. For this reason,
application programmers may want to use non-blocking UDP-style application programmers may want to use non-blocking one-to-many
sockets. The application should at least be able to send messages to style sockets. The application should at least be able to send
the non-stalled associations. messages to the non-stalled associations.
But a non-blocking socket is not sufficient if the API implementor But a non-blocking socket is not sufficient if the API implementor
has chosen a single shared buffer allocation for the socket. A has chosen a single shared buffer allocation for the socket. A single
single stalled association would eventually cause the shared stalled association would eventually cause the shared allocation to
allocation to fill, and it would become impossible to send even to fill, and it would become impossible to send even to non-stalled
non-stalled associations. associations.
The API implementor can solve this problem by providing each The API implementor can solve this problem by providing each
association with its own allocation of outbound buffer space. Each association with its own allocation of outbound buffer space. Each
association should conceptually have as much buffer space as it would association should conceptually have as much buffer space as it would
have if it had its own socket. As a bonus, this simplifies the have if it had its own socket. As a bonus, this simplifies the
implementation of sctp_peeloff(). implementation of sctp_peeloff().
To ensure that a given stalled association will not prevent other To ensure that a given stalled association will not prevent other
non-stalled associations from being writable, application programmers non-stalled associations from being writable, application programmers
should either: should either:
(a) demand that the underlying implementation dedicates independent (a) demand that the underlying implementation dedicates independent
buffer space allotments to each association (as suggested above), buffer space allotments to each association (as suggested above),
or or
(b) verify that their application layer protocol does not permit (b) verify that their application layer protocol does not permit
large amounts of unread data at the receiver (this is true of some large amounts of unread data at the receiver (this is true of some
request-response protocols, for example), or request-response protocols, for example), or
(c) use TCP-style sockets for association which may potentially stall (c) use one-to-one style sockets for association which may
(either from the beginning, or by using sctp_peeloff before potentially stall (either from the beginning, or by using
sending large amounts of data that may cause a stalled condition). sctp_peeloff before sending large amounts of data that may cause a
stalled condition).
4. TCP-style Interface An implemenation which dedicates independent buffer space for each
association should define HAVE_SCTP_MULTIBUF to 1.
The goal of this model is to follow as closely as possible the 4. one-to-one style Interface
The goal of this style is to follow as closely as possible the
current practice of using the sockets interface for a connection current practice of using the sockets interface for a connection
oriented protocol, such as TCP. This model 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. 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
this interface style.
4.1 Basic Operation 4.1 Basic Operation
A typical server in TCP-style model 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()
4. accept() 4. accept()
skipping to change at page 17, line 4 skipping to change at page 17, line 6
association with a server to request services: association with a server to request services:
1. socket() 1. socket()
2. connect() 2. connect()
After returning from connect(), the client uses send() and recv() After returning from connect(), the client uses send() and recv()
calls to send out requests and receive responses from the server. calls to send out requests and receive responses from the server.
The client calls The client calls
3. close() 3. close()
to terminate this association when done. to terminate this association when done.
4.1.1 socket() - TCP Style Syntax 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 TCP-style socket. Here, SOCK_STREAM indicates the creation of a one-to-one style
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() - TCP Style Syntax 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 job of associating multiple addresses. 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
skipping to change at page 18, line 32 skipping to change at page 18, line 35
set equivalent to binding with a wildcard address. One of those set equivalent to binding with a wildcard address. One of those
addresses will be the primary address for the association. This addresses will be the primary address for the association. This
automatically enables the multi-homing capability of SCTP. automatically enables the 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() - TCP Style Syntax 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() - TCP Style Syntax 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);
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() - TCP Style Syntax 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.
skipping to change at page 20, line 12 skipping to change at page 20, line 12
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.
Note that SCTP allows data exchange, similar to T/TCP RFC1644 [3], Note that SCTP allows data exchange, similar to T/TCP RFC1644 [3],
during the association set up phase. If an application wants to do during the association set up phase. If an application wants to do
this, it cannot use connect() call. Instead, it should use sendto() this, it cannot use connect() call. Instead, it should use sendto()
or sendmsg() to initiate an association. If it uses sendto() and it or sendmsg() to initiate an association. If it uses sendto() and it
wants to change initialization behavior, it needs to use the wants to change initialization behavior, it needs to use the
SCTP_INITMSG socket option before calling sendto(). Or it can use SCTP_INITMSG socket option before calling sendto(). Or it can use
SCTP_INIT type sendmsg() to initiate an association without doing the SCTP_INIT type sendmsg() to initiate an association without doing the
setsockopt(). setsockopt(). Note that some sockets implementations may not support
the sending of data to initiate an assocation with the one-to-one
style (implementations that do not support T/TCP normally have this
restriction). Implementations which allow sending of data to
initiate an association without calling connect() define the
preprocessor constant HAVE_SCTP_NOCONNECT to 1.
SCTP does not support half close semantics. This means that unlike SCTP does not support half close semantics. This means that unlike
T/TCP, MSG_EOF should not be set in the flags parameter when calling T/TCP, MSG_EOF should not be set in the flags parameter when calling
sendto() or sendmsg() when the call is used to initiate a connection. sendto() or sendmsg() when the call is used to initiate a connection.
MSG_EOF is not an acceptable flag with SCTP socket. MSG_EOF is not an acceptable flag with SCTP socket.
4.1.6 close() - TCP Style Syntax 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() - TCP Style Syntax 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-compatibility is not provided, so developers porting TCP TCP-compatibility is not provided, so developers porting TCP
applications to SCTP may need to recode sections that use shutdown(). applications to SCTP may need to recode sections that use shutdown().
(Note that it is possible to achieve the same results as half close (Note that it is possible to achieve the same results as half close
in SCTP using SCTP streams.) in SCTP using SCTP streams.)
The syntax is: The syntax is:
skipping to change at page 21, line 27 skipping to change at page 21, line 23
Disables further send operations, and initiates Disables further send operations, and initiates
the SCTP shutdown sequence. the SCTP shutdown sequence.
SHUT_RDWR SHUT_RDWR
Disables further send and receive operations Disables further send and receive operations
and initiates the SCTP shutdown sequence. and initiates the SCTP shutdown sequence.
The major difference between SCTP and TCP shutdown() is that SCTP The major difference between SCTP and TCP shutdown() is that SCTP
SHUT_WR initiates immediate and full protocol shutdown, whereas TCP SHUT_WR initiates immediate and full protocol shutdown, whereas TCP
SHUT_WR causes TCP to go into the half closed state. SHUT_RD behaves SHUT_WR causes TCP to go into the half closed state. SHUT_RD behaves
the same for SCTP as TCP. The purpose of SCTP SHUT_WR is to close the same for SCTP as TCP. The purpose of SCTP SHUT_WR is to close the
the SCTP association while still leaving the socket descriptor open, SCTP association while still leaving the socket descriptor open, so
so that the caller can receive back any data SCTP was unable to that the caller can receive back any data SCTP was unable to deliver
deliver (see Section 5.3.1.4 for more information). (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() - TCP Style Syntax 4.1.8 sendmsg() and recvmsg() - one-to-one style socket
With a TCP-style socket, the application can also use sendmsg() and With a one-to-one style socket, the application can also use
recvmsg() to transmit data to and receive data from its peer. The sendmsg() and recvmsg() to transmit data to and receive data from its
semantics is similar to those used in the UDP-style model (section peer. The semantics is similar to those used in the one-to-many style
Section 3.1.3), with the following differences: (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
different peer address if the sender does not want to send the preferred peer address if the sender wishes to discourage the stack
message over the primary address of the receiver. If the transport from sending the message to the primary address of the receiver. If
address given is not part of the current association, the data will the transport address given is not part of the current association,
not be sent and a SCTP_SEND_FAILED event will be delivered to the the data will not be sent and a SCTP_SEND_FAILED event will be
application if send failure events are enabled. delivered to the application if send failure events are enabled.
2) An application must use close() to gracefully shutdown an 2) An application must use close() to gracefully shutdown an
association, or use SO_LINGER option with close() to abort an association, or use SO_LINGER option with close() to abort an
association. It must not use the MSG_ABORT or MSG_EOF flag in association. It must not use the MSG_ABORT or MSG_EOF flag in
sendmsg(). The system returns an error if an application tries to do sendmsg(). The system returns an error if an application tries to do
so. so.
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-homed. It does not work with UDP-style sockets. See Section multi-homed. It does not work with one-to-many style sockets. See
8.3 for a multi-homed/UDP-sockets 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 socket, struct sockaddr *address, int getpeername(int socket, 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
skipping to change at page 24, line 27 skipping to change at page 24, line 27
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
(UDP-style only) sets protocol parameters for new associations. (one-to-many style only) sets protocol parameters for new
Section 5.2.1 provides more details. Header information can set or associations. Section 5.2.1 provides more details. Header information
report parameters on individual messages in a stream. See Section can set or report parameters on individual messages in a stream. See
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 TCP-style socket, SCTP will pass no ancillary data; By default on a one-to-one style socket, SCTP will pass no ancillary
on a UDP-style socket, SCTP will only pass SCTP_SNDRCV and data; on a one-to-many style socket, SCTP will only pass SCTP_SNDRCV
SCTP_ASSOC_CHANGE information. Specific ancillary data items can be and SCTP_ASSOC_CHANGE information. Specific ancillary data items can
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.
Other protocols may also provide ancillary data to the socket layer Other protocols may also provide ancillary data to the socket layer
consumer. These ancillary data items from other protocols may consumer. These ancillary data items from other protocols may
intermingle with SCTP data. For example, the IPv6 socket API intermingle with SCTP data. For example, the IPv6 socket API
definitions (RFC2292 [6] and RFC2553 [7]) define a number of definitions (RFC2292 [6] and RFC2553 [7]) define a number of
skipping to change at page 25, line 40 skipping to change at page 25, line 40
in the SCTP_COMM_UP notification and must be verified since it is a in the SCTP_COMM_UP notification and must be verified since it is a
negotiated number with the remote endpoint. The default value of 0 negotiated number with the remote endpoint. The default value of 0
indicates to use the endpoint default value. indicates to use the endpoint default value.
sinit_max_instreams: 16 bits (unsigned integer) sinit_max_instreams: 16 bits (unsigned integer)
This value represents the maximum number of inbound streams the This value represents the maximum number of inbound streams the
application is prepared to support. This value is bounded by the application is prepared to support. This value is bounded by the
actual implementation. In other words the user MAY be able to actual implementation. In other words the user MAY be able to
support more streams than the Operating System. In such a case, the support more streams than the Operating System. In such a case, the
Operating System limit overrides the value requested by the user. Operating System limit overrides the value requested by the user. The
The default value of 0 indicates to use the endpoint's default value. default value of 0 indicates to use the endpoint's default value.
sinit_max_attempts: 16 bits (unsigned integer) sinit_max_attempts: 16 bits (unsigned integer)
This integer specifies how many attempts the SCTP endpoint should This integer specifies how many attempts the SCTP endpoint should
make at resending the INIT. This value overrides the system SCTP make at resending the INIT. This value overrides the system SCTP
'Max.Init.Retransmits' value. The default value of 0 indicates to 'Max.Init.Retransmits' value. The default value of 0 indicates to
use the endpoint's default value. This is normally set to the use the endpoint's default value. This is normally set to the
system's default 'Max.Init.Retransmit' value. system's default 'Max.Init.Retransmit' value.
sinit_max_init_timeo: 16 bits (unsigned integer) sinit_max_init_timeo: 16 bits (unsigned integer)
skipping to change at page 26, line 40 skipping to change at page 26, line 40
uint32_t sinfo_context; uint32_t sinfo_context;
uint32_t sinfo_timetolive; uint32_t sinfo_timetolive;
uint32_t sinfo_tsn; uint32_t sinfo_tsn;
uint32_t sinfo_cumtsn; uint32_t sinfo_cumtsn;
sctp_assoc_t sinfo_assoc_id; sctp_assoc_t sinfo_assoc_id;
}; };
sinfo_stream: 16 bits (unsigned integer) sinfo_stream: 16 bits (unsigned integer)
For recvmsg() the SCTP stack places the message's stream number in For recvmsg() the SCTP stack places the message's stream number in
this value. For sendmsg() this value holds the stream number that this value. For sendmsg() this value holds the stream number that the
the application wishes to send this message to. If a sender application wishes to send this message to. If a sender specifies an
specifies an invalid stream number an error indication is returned invalid stream number an error indication is returned and the call
and the call fails. fails.
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)
skipping to change at page 28, line 16 skipping to change at page 27, line 40
MSG_UNORDERED - This flag is present when the message was sent MSG_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 MSG_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 UDP model, requests the SCTP MSG_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 MSG_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
(UDP-style only). The ABORT chunk will contain an (one-to-many style only). The ABORT chunk will contain an
error cause 'User Initiated Abort' with cause code 12. error cause 'User Initiated Abort' with cause code 12.
The cause specific information of this error cause is The cause specific information of this error cause is
provided in msg_iov. provided in msg_iov.
MSG_EOF - Setting this flag invokes the SCTP graceful shutdown MSG_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 (UDP-style only). the association (one-to-many style only).
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
set using any socket option. Also note that the value of 0 is set using any socket option. Also note that the value of 0 is special
special in that it indicates no timeout should occur on this message. in that it indicates no timeout should occur on this message.
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. MSG_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 TCP-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.
skipping to change at page 30, line 12 skipping to change at page 29, line 31
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_padr_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_rcv_pdapi_event sn_rcv_pdapi_event; struct sctp_pdapi_event sn_pdapi_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.
skipping to change at page 31, line 10 skipping to change at page 30, line 27
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
All standard values for sn_type flags are greater than 2^15. Values All standard values for sn_type are greater than 2^15. Values from
from 2^15 and down are reserved. 2^15 and down are reserved.
sn_flags: 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.
skipping to change at page 32, line 50 skipping to change at page 32, line 20
sac_inbound_streams: 16 bits (unsigned integer) sac_inbound_streams: 16 bits (unsigned integer)
The maximum number of streams allowed in each direction are available The maximum number of streams allowed in each direction are available
in sac_outbound_streams and sac_inbound streams. in sac_outbound_streams and sac_inbound streams.
sac_assoc_id: sizeof (sctp_assoc_t) sac_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 TCP style socket, this field is ignored. identifier. For one-to-one style socket, this field is ignored.
sac_info: variable
sac_data: 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_data[] 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;
skipping to change at page 34, line 9 skipping to change at page 33, line 24
spc_state: 32 bits (signed integer) spc_state: 32 bits (signed integer)
This field holds one of a number of values that communicate the event This field holds one of a number of values that communicate the event
that happened to the address. They include: that happened to the address. They include:
Event Name Description Event Name Description
---------------- --------------- ---------------- ---------------
SCTP_ADDR_AVAILABLE This address is now reachable. SCTP_ADDR_AVAILABLE This address is now reachable.
SCTP_ADDR_UNREACHABL The address specified can no SCTP_ADDR_UNREACHABLE The address specified can no
longer be reached. Any data sent longer be reached. Any data sent
to this address is rerouted to an to this address is rerouted to an
alternate until this address becomes alternate until this address becomes
reachable. reachable.
SCTP_ADDR_REMOVED The address is no longer part of SCTP_ADDR_REMOVED The address is no longer part of
the association. the association.
SCTP_ADDR_ADDED The address is now part of the SCTP_ADDR_ADDED The address is now part of the
association. association.
SCTP_ADDR_MADE_PRIM This address has now been made SCTP_ADDR_MADE_PRIM This address has now been made
to be the primary destination address. to be the primary destination address.
spc_error: 32 bits (signed integer) spc_error: 32 bits (signed integer)
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_UNREACHABL) 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 TCP 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
This message indicates a variety of error conditions on an message indicates a variety of error conditions on an association.
association. The entire ERROR chunk as it appears on the wire is The entire ERROR chunk as it appears on the wire is included in a
included in a SCTP_REMOTE_ERROR event. Please refer to the SCTP SCTP_REMOTE_ERROR event. Please refer to the SCTP specification
specification RFC2960 [8] and any extensions for a list of possible RFC2960 [8] and any extensions for a list of possible error formats.
error formats. SCTP error notifications have the format: SCTP error notifications have the format:
struct sctp_remote_error { struct sctp_remote_error {
uint16_t sre_type; uint16_t sre_type;
uint16_t sre_flags; uint16_t sre_flags;
uint32_t sre_length; uint32_t sre_length;
uint16_t sre_error; uint16_t sre_error;
sctp_assoc_t sre_assoc_id; sctp_assoc_t sre_assoc_id;
uint8_t sre_data[0]; uint8_t sre_data[0];
}; };
skipping to change at page 35, line 36 skipping to change at page 34, line 45
sre_error: 16 bits (unsigned integer) sre_error: 16 bits (unsigned integer)
This value represents one of the Operational Error causes defined in This value represents one of the Operational Error causes defined in
the SCTP specification, in network byte order. the SCTP specification, in network byte order.
sre_assoc_id: sizeof (sctp_assoc_t) sre_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 TCP 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.
skipping to change at page 36, line 48 skipping to change at page 36, line 9
ssf_info: sizeof (struct sctp_sndrcvinfo) ssf_info: sizeof (struct sctp_sndrcvinfo)
The original send information associated with the undelivered The original send information associated with the undelivered
message. message.
ssf_assoc_id: sizeof (sctp_assoc_t) ssf_assoc_id: sizeof (sctp_assoc_t)
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 TCP style socket, this field is ignored. association identifier. For one-to-one style socket, this field is
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.
skipping to change at page 37, line 44 skipping to change at page 36, line 51
sctp_shutdown_event). sctp_shutdown_event).
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 TCP 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_adaptation_bits; uint32_t sai_adaption_ind;
sctp_assoc_t sai_assoc_id; sctp_assoc_t sai_assoc_id;
}; };
sai_type sai_type
It should be SCTP_ADAPTION_INDICATION It should be SCTP_ADAPTION_INDICATION
sai_flags: 16 bits (unsigned integer) sai_flags: 16 bits (unsigned integer)
Currently unused. Currently unused.
sai_length: 32 bits (unsigned integer) sai_length: 32 bits (unsigned integer)
This field is the total length of the notification data, including This field is the total length of the notification data, including
the notification header. It will generally be sizeof (struct the notification header. It will generally be sizeof (struct
sctp_adaption_event). sctp_adaption_event).
sai_adaption_bits: 32 bits (unsigned integer) sai_adaption_ind: 32 bits (unsigned integer)
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 TCP 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_rcv_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;
}; };
pdapi_type pdapi_type
It should be SCTP_PARTIAL_DELIVERY_EVENT It should be SCTP_PARTIAL_DELIVERY_EVENT
pdapi_flags: 16 bits (unsigned integer) pdapi_flags: 16 bits (unsigned integer)
Currently unused. Currently unused.
pdapi_length: 32 bits (unsigned integer) pdapi_length: 32 bits (unsigned integer)
This field is the total length of the notification data, including This field is the total length of the notification data, including
the notification header. It will generally be sizeof (struct the notification header. It will generally be sizeof (struct
skipping to change at page 39, line 14 skipping to change at page 38, line 20
It should be SCTP_PARTIAL_DELIVERY_EVENT It should be SCTP_PARTIAL_DELIVERY_EVENT
pdapi_flags: 16 bits (unsigned integer) pdapi_flags: 16 bits (unsigned integer)
Currently unused. Currently unused.
pdapi_length: 32 bits (unsigned integer) pdapi_length: 32 bits (unsigned integer)
This field is the total length of the notification data, including This field is the total length of the notification data, including
the notification header. It will generally be sizeof (struct the notification header. It will generally be sizeof (struct
sctp_rcv_pdapi_event). sctp_pdapi_event).
pdapi_indication: 32 bits (unsigned integer) pdapi_indication: 32 bits (unsigned integer)
This field holds the indication being sent to the application This field holds the indication being sent to the application
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 TCP style socket, this field is ignored. identifier. For one-to-one style socket, this field is ignored.
5.4 Ancillary Data Considerations and Semantics 5.4 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
skipping to change at page 40, line 10 skipping to change at page 39, line 16
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], demonstrating
demonstrating the use of these macros to access ancillary data: the use of these macros to access ancillary data:
struct msghdr msg; struct msghdr msg;
struct cmsghdr *cmsgptr; struct cmsghdr *cmsgptr;
/* fill in msg */ /* fill in msg */
/* call recvmsg() */ /* call recvmsg() */
for (cmsgptr = CMSG_FIRSTHDR(&msg); cmsgptr != NULL; for (cmsgptr = CMSG_FIRSTHDR(&msg); cmsgptr != NULL;
cmsgptr = CMSG_NXTHDR(&msg, cmsgptr)) { cmsgptr = CMSG_NXTHDR(&msg, cmsgptr)) {
skipping to change at page 40, line 34 skipping to change at page 39, line 40
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 UDP semantics, but application. This is particularly true of the one-to-many semantics,
also of the TCP semantics. For example, if an application needs to but also of the one-ton-one semantics. For example, if an application
send and receive data on different SCTP streams, SCTP_SNDRCV events needs to send and receive data on different SCTP streams, SCTP_SNDRCV
are indispensable. 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
carefully written to always provide a large enough buffer to contain carefully written to always provide a large enough buffer to contain
all possible ancillary data that can be presented by recvmsg(). If all possible ancillary data that can be presented by recvmsg(). If
the buffer is too small, and crucial data is truncated, it may pose a the buffer is too small, and crucial data is truncated, it may pose a
fatal error condition. fatal error condition.
Thus it is essential that applications be able to deterministically Thus it is essential that applications be able to deterministically
calculate the maximum required buffer size to pass to recvmsg(). One calculate the maximum required buffer size to pass to recvmsg(). One
constraint imposed on this specification that makes this possible is constraint imposed on this specification that makes this possible is
that all ancillary data definitions are of a fixed length. One way that all ancillary data definitions are of a fixed length. One way to
to calculate the maximum required buffer size might be to take the calculate the maximum required buffer size might be to take the sum
sum the sizes of all enabled ancillary data item structures, as the sizes of all enabled ancillary data item structures, as
calculated by CMSG_SPACE. For example, if we enabled calculated by CMSG_SPACE. For example, if we enabled SCTP_SNDRCV_INFO
SCTP_SNDRCV_INFO and IPV6_RECVPKTINFO RFC2292 [6], we would calculate and IPV6_RECVPKTINFO RFC2292 [6], we would calculate and allocate the
and allocate the buffer size as follows: buffer size as follows:
size_t total; size_t total;
void *buf; void *buf;
total = CMSG_SPACE(sizeof (struct sctp_sndrcvinfo)) + total = CMSG_SPACE(sizeof (struct sctp_sndrcvinfo)) +
CMSG_SPACE(sizeof (struct in6_pktinfo)); CMSG_SPACE(sizeof (struct in6_pktinfo));
buf = malloc(total); buf = malloc(total);
We could then use this buffer for msg_control on each call to We could then use this buffer for msg_control on each call to
skipping to change at page 42, line 15 skipping to change at page 41, line 15
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, connst 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, int tolen); const struct sockaddr *to, socklen_t tolen);
ssize_t recv(int sd, void *buf, size_t len, int flags); ssize_t recv(int sd, void *buf, size_t len, int flags);
ssize_t recvfrom(int sd, void *buf, size_t len, int flags, ssize_t recvfrom(int sd, void *buf, size_t len, int flags,
struct sockaddr *from, int *fromlen); struct sockaddr *from, socklen_t *fromlen);
sd - the socket descriptor of an SCTP endpoint. sd - the socket descriptor of an SCTP endpoint.
msg - the message to be sent. msg - the message to be sent.
len - the size of the message or the size of buffer. len - the size of the message or the size of buffer.
to - one of the peer addresses of the association to be to - one of the peer addresses of the association to be
used to send the message. used to send the message.
tolen - the size of the address. tolen - the size of the address.
buf - the buffer to store a received message. buf - the buffer to store a received message.
from - the buffer to store the peer address used to send the from - the buffer to store the peer address used to send the
received message. received message.
skipping to change at page 43, line 11 skipping to change at page 42, line 11
wants to send a message which is composed by several buffers, the wants to send a message which is composed by several buffers, the
caller needs to combine them before calling send() or sendto(). caller needs to combine them before calling send() or sendto().
Alternately, the caller can use sendmsg() to do that without Alternately, the caller can use sendmsg() to do that without
combining them. recv() and recvfrom() cannot distinguish message combining them. recv() and recvfrom() cannot distinguish message
boundaries. boundaries.
In receiving, if the buffer supplied is not large enough to hold a In receiving, if the buffer supplied is not large enough to hold a
complete message, the receive call acts like a stream socket and complete message, the receive call acts like a stream socket and
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, when used in the UDP-style model, may Note, the send() and recv() calls may not be used for a one-to-many
only be used with branched off socket descriptors (see Section 8.2). 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,
size_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,
size_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 UDP-style model, may only be used Note, these calls, when used in the one-to-many style, may only be
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:
skipping to change at page 45, line 8 skipping to change at page 44, line 8
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 models. SCTP associations can be that are common to both styles. SCTP associations can be
multi-homed. Therefore, certain option parameters include a multi-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 UDP-style sockets, an sctp_assoc_t structure (association ID) For the one-to-many style sockets, an sctp_assoc_t structure
is used to identify the the association instance that the operation (association ID) is used to identify the the association instance
affects. So it must be set when using this model. that the operation affects. So it must be set when using this style.
For the TCP-style sockets and branched off UDP-style sockets (see
Section 8.2) this association ID parameter is ignored. In the cases
noted below where the parameter is ignored, an application can pass
to the system a corresponding option structure similar to those
described below but without the association ID parameter, which
should be the last field of the option structure. This can make the
option setting/getting operation more efficient. If an application
does this, it should also specify an appropriate optlen value (i.e.
sizeof (option parameter) - sizeof (struct sctp_assoc_t)).
Note that socket or IP level options is set or retrieved per socket. For the one-to-one style sockets and branched off one-to-many style
This means that for UDP-style sockets, those options will be applied sockets (see Section 8.2) this association ID parameter is ignored.
to all associations belonging to the socket. And for TCP-style
model, those options will be applied to all peer addresses of the
association controlled by the socket. Applications should be very
careful in setting those options.
sctp_opt_info() 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
applied to all associations belonging to the socket. And for
one-to-one style, those options will be applied to all peer addresses
of the association controlled by the socket. Applications should be
very careful in setting those options.
For some implementations getsockopt() is read-only, so a new For some IP stacks getsockopt() is read-only, so a new interface will
interface will be needed when information must be passed both in to be needed when information must be passed both in to and out of the
and out of the SCTP stack. The syntax for scpt_opt_info() is, SCTP stack. The syntax for scpt_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,
size_t *size); socklen_t *size);
For UDP-style sockets, id specifies the association to query. For For one-to-many style sockets, id specifies the association to query.
TCP-style sockets, id is ignored. For one-to-one style sockets, id is ignored.
opt specifies which SCTP socket option to get. It can any socket opt specifies which SCTP socket option to get. It can any socket
option currently supported that requests information (either read/ option currently supported that requests information (either read/
write options or read only) such as: write options or read only) such as:
SCTP_RTOINFO SCTP_RTOINFO
SCTP_ASSOCINFO SCTP_ASSOCINFO
SCTP_SET_PRIMARY_ADDR SCTP_DEFAULT_SEND_PARAM
SCTP_SET_PEER_PRIMARY_ADDR
SCTP_SET_PEER_ADDR_PARAMS
SCTP_STATUS
SCTP_GET_PEER_ADDR_INFO SCTP_GET_PEER_ADDR_INFO
SCTP_PRIMARY_ADDR
SCTP_PEER_ADDR_PARAMS
SCTP_STATUS
arg is an option-specific structure buffer provided by the caller. arg is an option-specific structure buffer provided by the caller.
See Section 8.5) subsections for more information on these options See Section 8.5) subsections for more information on these options
and option-specific structures. and option-specific structures.
sctp_opt_info() returns 0 on success, or on failure returns -1 and sctp_opt_info() returns 0 on success, or on failure returns -1 and
sets errno to the appropriate error code. sets errno to the appropriate error code.
All options that support specific settings on an association by All options that support specific settings on an association by
filling in either an association id variable or a sockaddr_storage filling in either an association id variable or a sockaddr_storage
SHOULD also support setting of the same value for the entire endpoint SHOULD also support setting of the same value for the entire endpoint
(i.e. future associations). To accomplish this the following logic (i.e. future associations). To accomplish this the following logic is
is used when setting one of these options: 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 and in the structure the address is used to lookup the association and
the settings are applied to the specific address (if appropriate) the settings are applied to the specific address (if appropriate)
or to the entire association. 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 specified). the entire association (since a specific address is not
Note this also applies to options that hold an association specified). Note this also applies to options that hold an
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 sockadd_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. The peer address how these parameters are used in RTO calculation.
parameter is ignored for TCP style socket.
The following structure is used to access and modify these The following structure is used to access and modify these
parameters: parameters:
struct sctp_rtoinfo { struct sctp_rtoinfo {
sctp_assoc_t srto_assoc_id; sctp_assoc_t srto_assoc_id;
uint32_t srto_initial; uint32_t srto_initial;
uint32_t srto_max; uint32_t srto_max;
uint32_t srto_min; uint32_t srto_min;
}; };
srto_initial - This contains the initial RTO value. srto_initial - This contains the initial RTO value.
srto_max and srto_min - These contain the maximum and minimum bounds srto_max and srto_min - These contain the maximum and minimum bounds
for all RTOs. for all RTOs.
srto_assoc_id - (UDP style socket) This is filled in the application, srto_assoc_id - (one-to-many style socket) This is filled in the application,
and identifies the association for this query. If and identifies the association for this query. If
this parameter is missing (on a UDP style socket), this parameter is '0' (on a one-to-many style socket),
then the change effects the entire endpoint. then the change 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 TCP 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 {
sctp_assoc_t sasoc_assoc_id; sctp_assoc_t sasoc_assoc_id;
uint16_t sasoc_asocmaxrxt; uint16_t sasoc_asocmaxrxt;
uint16_t sasoc_number_peer_destinations; uint16_t sasoc_number_peer_destinations;
uint32_t sasoc_peer_rwnd; uint32_t sasoc_peer_rwnd;
uint32_t sasoc_local_rwnd; uint32_t sasoc_local_rwnd;
uint32_t sasoc_cookie_life; uint32_t sasoc_cookie_life;
}; };
sasoc_asocmaxrxt - This contains the maximum retransmission attempts sasoc_asocmaxrxt - This contains the maximum retransmission attempts
to make for the association. to make for the association.
sasoc_number_peer_destinations - This is the number of destination sasoc_number_peer_destinations - This is the number of destination
address that the peer considers addresses that the peer has.
valid.
sasoc_peer_rwnd - This holds the current value of the peers sasoc_peer_rwnd - This holds the current value of the peers
rwnd (reported in the last SACK) minus any rwnd (reported in the last SACK) minus any
outstanding data (i.e. data inflight). outstanding data (i.e. data inflight).
sasoc_local_rwnd - This holds the last reported rwnd that was sasoc_local_rwnd - This holds the last reported rwnd that was
sent to the peer. sent to the peer.
sasoc_cookie_life - This is the associations cookie life value sasoc_cookie_life - This is the associations cookie life value
used when issuing cookies. used when issuing cookies.
sasoc_assoc_id - (UDP style socket) This is filled in the application, sasoc_assoc_id - (one-to-many style socket) This is filled in the application,
and identifies the association for this query. and identifies the association for this query.
This information may be examined for either the endpoint or a This information may be examined for either the endpoint or a
specific association. To examine a endpoints default parameters the specific association. To examine a endpoints default parameters the
association id (sasoc_assoc_id) should must be set to the value '0'. association id (sasoc_assoc_id) should must be set to the value '0'.
The values of the sasoc_peer_rwnd is meaningless when examining The values of the sasoc_peer_rwnd is meaningless when examining
endpoint information. endpoint information.
All parameters are time values, in milliseconds. A value of 0, when
modifying the parameters, indicates that the current value should not
be changed.
The values of the sasoc_asocmaxrxt and sasoc_cookie_life may be set The values of the sasoc_asocmaxrxt and sasoc_cookie_life may be set
on either an endpoint or association basis. The rwnd and destination on either an endpoint or association basis. The rwnd and destination
counts (sasoc_number_peer_destinations, counts (sasoc_number_peer_destinations,
sasoc_peer_rwnd,sasoc_local_rwnd) are NOT settable and any value sasoc_peer_rwnd,sasoc_local_rwnd) are NOT settable and any value
placed in these is ignored. placed in these is ignored.
To access or modify these parameters, the application should call To access or modify these parameters, the application should call
getsockopt or setsockopt() respectively with the option name getsockopt or setsockopt() respectively with the option name
SCTP_ASSOCINFO. SCTP_ASSOCINFO.
skipping to change at page 49, line 20 skipping to change at page 47, line 48
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 UDP-style sockets only future associations are effected socket (for one-to-many style sockets only future associations are
by the change). With TCP-style sockets, this option is inherited by effected by the change). With one-to-one style sockets, this option
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 TCP-style socket can use this option to An application using the one-to-one style socket can use this option
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
to 0, calling close() is the same as the ABORT primitive. If the to 0, calling close() is the same as the ABORT primitive. If the
value is set to a negative value, the setsockopt() call will return value is set to a negative value, the setsockopt() call will return
an error. If the value is set to a positive value linger_time, the an error. If the value is set to a positive value linger_time, the
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
when setting SO_LINGER you must specify a level of SOL_SOCKET in the 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. For SCTP TCP-style sockets, this controls Sets receive buffer size in octets. For SCTP one-to-one style
the receiver window size. For UDP-style sockets, this controls the sockets, this controls the receiver window size. For one-to-many
receiver window size for all associations bound to the socket style sockets the meaning depends on the constant HAVE_SCTP_MULTIBUF
descriptor used in the setsockopt() or getsockopt() call. The option (see Section 3.4). If the implementation defines HAVE_SCTP_MULTIBUF
applies to each association's window size separately. Expects an as 1, this controls the receiver window size for each association
integer. bound to the socket descriptor. If the implementation defines
HAVE_SCTP_MULTIBUF as 0, this controls the size of the single receive
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 TCP-style sockets, this controls the Sets send buffer size. For SCTP one-to-one style sockets, this
amount of data SCTP may have waiting in internal buffers to be sent. controls the amount of data SCTP may have waiting in internal buffers
This option therefore bounds the maximum size of data that can be to be sent. This option therefore bounds the maximum size of data
sent in a single send call. For UDP-style sockets, the effect is the that can be sent in a single send call. For one-to-many style
same, except that it applies to all associations bound to the socket sockets, the effect is the same, except that it applies to one or all
descriptor used in the setsockopt() or getsockopt() call. The option associations (see Section 3.4) bound to the socket descriptor
applies to each association's window size separately. Expects an used in the setsockopt() or getsockopt() call. The option applies to
each 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 UDP-style socket only. When This socket option is applicable to the one-to-many style socket
set it will cause associations that are idle for more than the only. When set it will cause associations that are idle for more than
specified number of seconds to automatically close. An association the specified number of seconds to automatically close. An
being idle is defined an association that has NOT sent or received association being idle is defined an association that has NOT sent or
user data. The special value of '0' indicates that no automatic received user data. The special value of '0' indicates that no
close of any associations should be performed. The option expects an automatic close of any associations should be performed. The option
integer defining the number of seconds of idle time before an expects an integer defining the number of seconds of idle time before
association is closed. an association is closed.
7.1.9 Set Primary Address (SCTP_SET_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_setprim { struct sctp_setpeerprim {
sctp_assoc_t ssp_assoc_id; sctp_assoc_t sspp_assoc_id;
struct sockaddr_storage ssp_addr; struct sockaddr_storage sspp_addr;
}; };
ssp_addr The address to set as primary
ssp_assoc_id (UDP style socket) This is filled in by the sspp_addr The address to set as primary
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 Peer Primary Address (SCTP_SET_PEER_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
make a set peer primary request: a set peer primary request:
struct sctp_setpeerprim { struct sctp_setprim {
sctp_assoc_t sspp_assoc_id; sctp_assoc_t ssp_assoc_id;
struct sockaddr_storage sspp_addr; struct sockaddr_storage ssp_addr;
}; };
ssp_addr The address to set as primary
sspp_addr The address to set as primary ssp_assoc_id (one-to-many style socket) This is filled in by the
sspp_assoc_id (UDP 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_SET_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 {
u_int32_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. If enabled no SCTP message This option is a on/off flag and is passed an integer where a
non-zero is on and a zero is off. If enabled no SCTP message
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_SET_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;
struct sockaddr_storage spp_address; struct sockaddr_storage spp_address;
uint32_t spp_hbinterval; uint32_t spp_hbinterval;
uint16_t spp_pathmaxrxt; uint16_t spp_pathmaxrxt;
}; };
spp_assoc_id - (UDP style socket) This is filled in the application, spp_assoc_id - (one-to-many style socket) This is filled in the application,
and identifies the association for this query. and identifies the association for this query.
spp_address - This specifies which address is of interest. spp_address - This specifies which address is of interest.
spp_hbinterval - This contains the value of the heartbeat interval, spp_hbinterval - This contains the value of the heartbeat interval,
in milliseconds. A value of 0, when modifying the in milliseconds. A value of 0, when modifying the
parameter, specifies that the heartbeat on this parameter, specifies that the heartbeat on this
address should be disabled. A value of UINT32_MAX address should be disabled. A value of UINT32_MAX
(4294967295), when modifying the parameter, (4294967295), when modifying the parameter,
specifies that a heartbeat should be sent specifies that a heartbeat should be sent
immediately to the peer address, and the current immediately to the peer address, and the current
interval should remain unchanged. interval should remain unchanged.
spp_pathmaxrxt - This contains the maximum number of spp_pathmaxrxt - This contains the maximum number of
retransmissions before this address shall be retransmissions before this address shall be
considered unreachable. considered unreachable. If a value of zero
is present in this field then no changes are to
be made to this parameter.
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_SET_PEER_ADDR_PARAMS option. sctp_opt_info() with the SCTP_PEER_ADDR_PARAMS option.
7.1.14 Set default send parameters (SET_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
The application that wishes to use this socket option simply passes application that wishes to use this socket option simply passes in to
in to this call the sctp_sndrcvinfo structure defined in Section this call the sctp_sndrcvinfo structure defined in Section 5.2.2) The
5.2.2) The input parameters accepted by this call include input parameters accepted by this call include sinfo_stream,
sinfo_stream, sinfo_flags, sinfo_ppid, sinfo_context, sinfo_flags, sinfo_ppid, sinfo_context, sinfo_timetolive. The user
sinfo_timetolive. The user must provide the sinfo_assoc_id field in must set the sinfo_assoc_id field to identify the association to
to this call if the caller is using the UDP model. affect if the caller is using the one-to-many style.
7.1.15 Set notification and ancillary events (SCTP_SET_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
If this option is turned off, then no mapping will be done of V4 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. 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
option.
7.1.17 Set the maximum fragrmentation 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 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 user. The option expects an integer.
The default value for this option is '0' which indicates the user is
NOT limiting fragmentation and only the PMTU will effect SCTP's
choice of DATA chunk size.
7.2 Read-Only Options 7.2 Read-Only Options
7.2.1 Association Status (SCTP_STATUS) 7.2.1 Association Status (SCTP_STATUS)
Applications can retrieve current status information about an Applications can retrieve current status information about an
association, including association state, peer receiver window size, association, including association state, peer receiver window size,
number of unacked data chunks, and number of data chunks pending number of unacked data chunks, and number of data chunks pending
receipt. This information is read-only. The following structure is receipt. This information is read-only. The following structure is
used to access this information: used to access this information:
skipping to change at page 54, line 11 skipping to change at page 53, line 4
SCTP_CLOSED SCTP_CLOSED
SCTP_BOUND SCTP_BOUND
SCTP_LISTEN SCTP_LISTEN
SCTP_COOKIE_WAIT SCTP_COOKIE_WAIT
SCTP_COOKIE_ECHOED SCTP_COOKIE_ECHOED
SCTP_ESTABLISHED SCTP_ESTABLISHED
SCTP_SHUTDOWN_PENDING SCTP_SHUTDOWN_PENDING
SCTP_SHUTDOWN_SENT SCTP_SHUTDOWN_SENT
SCTP_SHUTDOWN_RECEIVED SCTP_SHUTDOWN_RECEIVED
SCTP_SHUTDOWN_ACK_SENT SCTP_SHUTDOWN_ACK_SENT
sstat_rwnd - This contains the association peer's current sstat_rwnd - This contains the association peer's current
receiver window size. receiver window size.
sstat_unackdata - This is the number of unacked data chunks. sstat_unackdata - This is the number of unacked data chunks.
sstat_penddata - This is the number of data chunks pending receipt. sstat_penddata - This is the number of data chunks pending receipt.
sstat_primary - This is information on the current primary peer sstat_primary - This is information on the current primary peer
address. address.
sstat_assoc_id - (UDP style socket) This holds the an identifier for the sstat_assoc_id - (one-to-many style socket) This holds the an identifier for the
association. All notifications for a given association association. All notifications for a given association
have the same association identifier. have the same association identifier.
sstat_instrms - The number of streams that the peer will sstat_instrms - The number of streams that the peer will
be using inbound. be using inbound.
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 TCP 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-only. The following structure is used to access this read-only. The following structure is used to access this
information: information:
struct sctp_paddrinfo { struct sctp_paddrinfo {
skipping to change at page 55, line 21 skipping to change at page 54, line 6
uint32_t spinfo_rto; uint32_t spinfo_rto;
uint32_t spinfo_mtu; uint32_t spinfo_mtu;
}; };
spinfo_address - This is filled in the application, and contains spinfo_address - This is filled in the application, and contains
the peer address of interest. the peer address of interest.
On return from getsockopt(): On return from getsockopt():
spinfo_state - This contains the peer addresses's state (either spinfo_state - This contains the peer addresses's state (either
SCTP_ACTIVE or SCTP_INACTIVE). SCTP_ACTIVE or SCTP_INACTIVE and possibly the modifer
SCTP_UNCONFIRMED)
spinfo_cwnd - This contains the peer addresses's current congestion spinfo_cwnd - This contains the peer addresses's current congestion
window. window.
spinfo_srtt - This contains the peer addresses's current smoothed spinfo_srtt - This contains the peer addresses's current smoothed
round-trip time calculation in milliseconds. round-trip time calculation in milliseconds.
spinfo_rto - This contains the peer addresses's current spinfo_rto - This contains the peer addresses's current
retransmission timeout value in milliseconds. retransmission timeout value in milliseconds.
spinfo_mtu - The current P-MTU of this address. spinfo_mtu - The current P-MTU of this address.
spinfo_assoc_id - (UDP style socket) This is filled in the application, spinfo_assoc_id - (one-to-many style socket) This is filled in the application,
and identifies the association for this query. and identifies the 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: Per-message information (i.e. stream number, TSN, 1. SCTP_SNDRCV (sctp_data_io_event): Per-message information (i.e.
SSN, etc. described in Section 5.2.2) stream number, TSN, SSN, etc. described in Section 5.2.2)
2. SCTP_ASSOC_CHANGE: (described in Section 5.3.1.1) 2. SCTP_ASSOC_CHANGE (sctp_association_event): (described in Section
5.3.1.1)
3. SCTP_PEER_ADDR_CHANGE: (described in Section 5.3.1.2) 3. SCTP_PEER_ADDR_CHANGE (sctp_address_event): (described in Section
5.3.1.2)
4. SCTP_REMOTE_ERROR: (described in Section 5.3.1.3) 4. SCTP_SEND_FAILED (sctp_send_failure_event): (described in Section
5.3.1.4)
5. SCTP_SEND_FAILED: (described in Section 5.3.1.4) 5. SCTP_REMOTE_ERROR (sctp_peer_error_event): (described in Section
6. SCTP_SHUTDOWN_EVENT: (described in Section 5.3.1.5) 5.3.1.3)
7. SCTP_ADAPTION_INDICATION: (described in Section 5.3.1.6) 6. SCTP_SHUTDOWN_EVENT (sctp_shtudown_event): (described in Section
5.3.1.5)
8. SCTP_PARTIAL_DELIVERY_EVENT: (described in Section 5.3.1.7) 7. SCTP_PARTIAL_DELIVERY_EVENT (sctp_partial_delivery_event):
(described in Section 5.3.1.7)
8. SCTP_ADAPTION_INDICATION (sctp_adaption_layer_event): (described
in Section 5.3.1.6)
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_SET_EVENTS setsockopt() registers it's interest by calling the SCTP_EVENTS setsockopt() with
with the following structure. the following structure.
struct sctp_event_subscribe{ struct sctp_event_subscribe{
u_int8_t sctp_data_io_event; u_int8_t sctp_data_io_event;
u_int8_t sctp_association_event; u_int8_t sctp_association_event;
u_int8_t sctp_address_event; u_int8_t sctp_address_event;
u_int8_t sctp_send_failure_event; u_int8_t sctp_send_failure_event;
u_int8_t sctp_peer_error_event; u_int8_t sctp_peer_error_event;
u_int8_t sctp_shutdown_event; u_int8_t sctp_shutdown_event;
u_int8_t sctp_partial_delivery_event; u_int8_t sctp_partial_delivery_event;
u_int8_t sctp_adaption_layer_event; u_int8_t sctp_adaption_layer_event;
skipping to change at page 56, line 34 skipping to change at page 55, line 28
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
reception of association event notifications. Setting the flag to 0 reception of association event notifications. Setting the flag to 0
will disable association event notifications. For more information will disable association event notifications. For more information on
on event notifications please see Section 5.3. event notifications please see Section 5.3.
sctp_address_event - Setting this flag to 1 will enable the reception sctp_address_event - Setting this flag to 1 will enable the reception
of address event notifications. Setting the flag to 0 will disable of address event notifications. Setting the flag to 0 will disable
address event notifications. For more information on event address event notifications. For more information on event
notifications please see Section 5.3. notifications please see Section 5.3.
sctp_send_failure_event - Setting this flag to 1 will enable the sctp_send_failure_event - Setting this flag to 1 will enable the
reception of send failure event notifications. Setting the flag to 0 reception of send failure event notifications. Setting the flag to 0
will disable send failure event notifications. For more information will disable send failure event notifications. For more information
on event notifications please see Section 5.3. on event notifications please see Section 5.3.
sctp_peer_error_event - Setting this flag to 1 will enable the sctp_peer_error_event - Setting this flag to 1 will enable the
reception of peer error event notifications. Setting the flag to 0 reception of peer error event notifications. Setting the flag to 0
will disable peer error event notifications. For more information on will disable peer error event notifications. For more information on
event notifications please see Section 5.3. event notifications please see Section 5.3.
sctp_shutdown_event - Setting this flag to 1 will enable the sctp_shutdown_event - Setting this flag to 1 will enable the
reception of shutdown event notifications. Setting the flag to 0 reception of shutdown event notifications. Setting the flag to 0 will
will disable shutdown event notifications. For more information on disable shutdown event notifications. For more information on event
event notifications please see Section 5.3. notifications please see Section 5.3.
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
will disable adaption layer event notifications. For more disable adaption layer event notifications. For more information on
information on event notifications please see Section 5.3. event notifications 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_SET_EVENT, &event, sizeof(event)); setsockopt(fd, IPPROTO_SCTP, SCTP_EVENT, &event, sizeof(event));
} }
Note that for UDP-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 TCP-style SCTP sockets, the caller to the file descriptor. For one-to-one style SCTP sockets, the
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 a UDP-style socket has sctp_data_io_event and By default both the one-to-one style and one-to-many style socket has
sctp_association_event on and all other 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_storage *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.
A single address may be specified as INADDR_ANY or IN6ADDR_ANY, see A single address may be specified as INADDR_ANY or IN6ADDR_ANY, see
Section 3.1.2 for this usage. Section 3.1.2 for this usage.
addrs is a pointer to an array of one or more socket addresses. Each addrs is a pointer to an array of one or more socket addresses. Each
address is contained in a struct sockaddr_storage, so each address is address is contained in its appropriate structure (i.e. struct
a fixed length. The caller specifies the number of addresses in the sockaddr_in or struct sockaddr_in6) the family of the address type
array with addrcnt. must be used to distengish the address length (note that this
representation is termed a "packed array" of addresses). The caller
specifies the number of addresses in the array with addrcnt.
On success, sctp_bindx() returns 0. On failure, sctp_bindx() returns On success, sctp_bindx() returns 0. On failure, sctp_bindx() returns
-1, and sets errno to the appropriate error code. -1, and sets errno to the appropriate error code.
For SCTP, the port given in each socket address must be the same, or For SCTP, the port given in each socket address must be the same, or
sctp_bindx() will fail, setting errno to EINVAL. sctp_bindx() will fail, setting errno to EINVAL.
The flags parameter is formed from the bitwise OR of zero or more of The flags parameter is formed from the bitwise OR of zero or more of
the following currently defined flags: the following currently defined flags:
SCTP_BINDX_ADD_ADDR SCTP_BINDX_ADD_ADDR
SCTP_BINDX_REM_ADDR SCTP_BINDX_REM_ADDR
SCTP_BINDX_ADD_ADDR directs SCTP to add the given addresses to the SCTP_BINDX_ADD_ADDR directs SCTP to add the given addresses to the
association, and SCTP_BINDX_REM_ADDR directs SCTP to remove the given association, and SCTP_BINDX_REM_ADDR directs SCTP to remove the given
addresses from the association. The two flags are mutually addresses from the association. The two flags are mutually exclusive;
exclusive; if both are given, sctp_bindx() will fail with EINVAL. A if both are given, sctp_bindx() will fail with EINVAL. A caller may
caller may not remove all addresses from an association; sctp_bindx() not remove all addresses from an association; sctp_bindx() will
will reject such an attempt with EINVAL. reject such an attempt with EINVAL.
An application can use sctp_bindx(SCTP_BINDX_ADD_ADDR) to associate An application can use sctp_bindx(SCTP_BINDX_ADD_ADDR) to associate
additional addresses with an endpoint after calling bind(). Or use additional addresses with an endpoint after calling bind(). Or use
sctp_bindx(SCTP_BINDX_REM_ADDR) to remove some addresses a listening sctp_bindx(SCTP_BINDX_REM_ADDR) to remove some addresses a listening
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 UDP-style socket, the After an association is established on a one-to-many style socket,
application may wish to branch off the association into a separate the application may wish to branch off the association into a
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 UDP-style socket but branch off those associations under the original one-to-many style socket but branch off those
carrying high volume data traffic into their own separate socket associations carrying high volume data traffic into their own
descriptors. separate socket descriptors.
The application uses sctp_peeloff() call to branch off an association The application uses sctp_peeloff() call to branch off an association
into a separate socket (Note the semantics are somewhat changed from into a separate socket (Note the semantics are somewhat changed from
the traditional TCP-style accept() call). 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
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 UDP-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
TCP-style accept() call, this would be an out parameter, but for one-to-one style accept() call, this would be an out parameter,
the UDP-style call, this is an in parameter). but for 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_storage **addrs); struct sockaddr **addrs);
On return, addrs will point to a dynamically allocated array of
struct sockaddr_storages, one for each peer address. The caller On return, addrs will point to a dynamically allocated packed array
should use sctp_freepaddrs() to free the memory. addrs must not be of sockaddr structures of the appropriate type for each address. The
NULL. caller should use sctp_freepaddrs() to free the memory. Note that the
in/out parameter addrs must not be NULL.
If sd is an IPv4 socket, the addresses returned will be all IPv4 If sd is an IPv4 socket, the addresses returned will be all IPv4
addresses. If sd is an IPv6 socket, the addresses returned can be a addresses. If sd is an IPv6 socket, the addresses returned can be a
mix of IPv4 or IPv6 addresses. mix of IPv4 or IPv6 addresses.
For UDP-style sockets, id specifies the association to query. For For one-to-many style sockets, id specifies the association to query.
TCP-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_storage *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 on a socket. The sctp_getladdrs() returns all locally bound address(es) on a socket.
syntax is, The syntax is,
int sctp_getladdrs(int sock, sctp_assoc_t id, int sctp_getladdrs(int sock, sctp_assoc_t id,
struct sockaddr_storage **ss); struct sockaddr **ss);
On return, addrs will point to a dynamically allocated array of On return, addrs will point to a dynamically allocated packed array
struct sockaddr_storages, one for each local address. The caller of sockaddr structures of the appropriate type for each local
should use sctp_freeladdrs() to free the memory. addrs must not be address. The caller should use sctp_freeladdrs() to free the memory.
NULL. Note that the in/out parameter addrs must not be NULL.
If sd is an IPv4 socket, the addresses returned will be all IPv4 If sd is an IPv4 socket, the addresses returned will be all IPv4
addresses. If sd is an IPv6 socket, the addresses returned can be a addresses. If sd is an IPv6 socket, the addresses returned can be a
mix of IPv4 or IPv6 addresses. mix of IPv4 or IPv6 addresses.
For UDP-style sockets, id specifies the association to query. For For one-to-many style sockets, id specifies the association to query.
TCP-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_storage *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_sndmsg() 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,
void sctp_sendmsg(int s, const void *msg, size_t len, ssize_t sctp_sendmsg(int s,
const void *msg,
size_t len,
struct sockaddr *to,
socklen_t tolen,
uint32_t ppid, uint32_t ppid,
uint32_t flags, uint32_t flags,
uint16_t stream_no, uint16_t stream_no,
uint32_t timetolive, uint32_t timetolive,
uint32_t context) uint32_t context)
s - is the socket descriptor s - is the socket descriptor
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.
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()
An implementation may provide a library function (or possibly system
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
sctp_recvmsg() the caller must enable the sctp_data_io_events with
the SCTP_EVENTS option.
sctp_recvmsg(). Its syntax is,
ssize_t sctp_recvmsg(int s,
void *msg,
size_t *len,
struct sockaddr *from,
socklen_t *fromlen
struct sctp_sndrcvinfo *sinfo
int *msg_flags)
s - is the socket descriptor
msg - is a message buffer to be filled.
len - is the length of the message buffer.
from - is a pointer to a address to be filled with
the sender of this messages address.
fromlen - is the from length.
sinfo - A pointer to a sctp_sndrcvinfo structure
to be filled upon receipt of the message.
msg_flags - A pointer to a integer to be filled with
any message flags (e.g. MSG_NOTIFICATION).
8.9 sctp_connectx()
An implementation may provide a library function (or possibly system
call) to assist the user with associating to an endpoint that is
multi-homed. Much like sctp_bindx() this call allows a caller to
specify multiple addresses at which a peer can be reached.
sctp_connectx(). Its syntax is,
int sctp_connectx(int s,
struct sockaddr *addrs,
int addrcnt)
s - is the socket descriptor
addrs - is an array of addresses.
addrcnt - is the number of addresses in the array.
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.
skipping to change at page 63, line 5 skipping to change at page 63, line 33
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
implementation dedicates separate buffer space to each association
on a one-to-many socket. If this constant is defined to 0, then
the implementation provides a single block of shared buffer space
for a one-to-many socket.
HAVE_SCTP_NOCONNECT - If this constant is defined to 1, then the SCTP
implementation supports initiating an association on a one-to-one
style socket without the use of connect(), as outlined in 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
sctp_bindx() on these port numbers to privileged users. sctp_bindx() on these port numbers to privileged users.
Similarly unprevledged users should not be able to set protocol Similarly unpriviledged users should not be able to set protocol
parameters which could result in the congestion control algorithm parameters which could result in the congestion control algorithm
being more aggressive than permitted on the public Internet. These being more aggressive than permitted on the public Internet. These
parameters are: parameters are:
struct sctp_rtoinfo struct sctp_rtoinfo
If an unprivileged user inherits a UDP-style socket with open If an unprivileged user inherits a one-to-many style socket with open
associations on a privileged port, it MAY be permitted to accept new associations on a privileged port, it MAY be permitted to accept new
associations, but it SHOULD NOT be permitted to open new associations, but it SHOULD NOT be permitted to open new
associations. This could be relevant for the r* family of protocols. associations. This could be relevant for the r* family of protocols.
11. Acknowledgments 11. Acknowledgments
The authors wish to thank Kavitha Baratakke, Mike Bartlett, Jon The authors wish to thank Kavitha Baratakke, Mike Bartlett, Jon
Berger, Scott Kimble, Renee Revis, and many others on the TSVWG Berger, Scott Kimble, Renee Revis, and many others on the TSVWG
mailing list for contributing valuable comments. mailing list for contributing valuable comments.
skipping to change at page 65, line 43 skipping to change at page 67, line 4
Randall R. Stewart Randall R. Stewart
Cisco Systems, Inc. Cisco Systems, Inc.
8725 West Higgins Road 8725 West Higgins Road
Suite 300 Suite 300
Chicago, IL 60631 Chicago, IL 60631
USA USA
Phone: Phone:
EMail: rrs@cisco.com EMail: rrs@cisco.com
Qiaobing Xie Qiaobing Xie
Motorola, Inc. Motorola, Inc.
1501 W. Shure Drive, #2309 1501 W. Shure Drive, #2309
Arlington Heights, IL 60004 Arlington Heights, IL 60004
USA USA
Phone: Phone:
EMail: qxie1@email.mot.com EMail: qxie1@email.mot.com
La Monte H.P. Yarroll La Monte H.P. Yarroll
Motorola, Inc. USACE ERDC-CERL.
1501 W. Shure Drive, IL-2315 2902 Newmark Drive
Arlington Heights, IL 60004 Champaign, IL 6182-1076
USA USA
Phone: Phone:
EMail: piggy@acm.org EMail: piggy@acm.org
Jonathan Wood Jonathan Wood
DoCoMo USA Labs DoCoMo USA Labs
181 Metro Drive, Suite 300 181 Metro Drive, Suite 300
San Jose, CA 95110 San Jose, CA 95110
USA USA
skipping to change at page 66, line 41 skipping to change at page 68, line 4
EMail: kcpoon@yahoo.com EMail: kcpoon@yahoo.com
Ken Fujita Ken Fujita
NEC USA, Inc. NEC USA, Inc.
10080 Wolfe Road, Suite SW3-350 10080 Wolfe Road, Suite SW3-350
Cupertino, CA 95014 Cupertino, CA 95014
USA USA
Phone: Phone:
EMail: fken@ccrl.sj.nec.com EMail: fken@ccrl.sj.nec.com
Michael Tuexen Michael Tuexen
Univ. of Applied Sciences Muenster
Stegerwaldstr. 39
48565 Steinfurt
Germany Germany
Phone:
EMail: tuexen@fh-muenster.de EMail: tuexen@fh-muenster.de
Appendix A. TCP-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 TCP-style IPv4 SCTP. The example shows how to use some features of one-to-one style
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
skipping to change at page 69, line 17 skipping to change at page 70, line 17
"outstr=%hu\n", sac->sac_state, sac->sac_error, "outstr=%hu\n", sac->sac_state, sac->sac_error,
sac->sac_inbound_streams, sac->sac_outbound_streams); sac->sac_inbound_streams, sac->sac_outbound_streams);
break; break;
case SCTP_SEND_FAILED: case SCTP_SEND_FAILED:
ssf = &snp->sn_send_failed; ssf = &snp->sn_send_failed;
printf("^^^ sendfailed: len=%hu err=%d\n", ssf->ssf_length, printf("^^^ sendfailed: len=%hu err=%d\n", ssf->ssf_length,
ssf->ssf_error); ssf->ssf_error);
break; break;
case SCTP_PEER_ADDR_CHANGE: case SCTP_PEER_ADDR_CHANGE:
spc = &snp->sn_paddr_change; /* mt changed */ spc = &snp->sn_paddr_change;
if (spc->spc_aaddr.ss_family == AF_INET) { if (spc->spc_aaddr.ss_family == AF_INET) {
sin = (struct sockaddr_in *)&spc->spc_aaddr; sin = (struct sockaddr_in *)&spc->spc_aaddr;
ap = inet_ntop(AF_INET, &sin->sin_addr, ap = inet_ntop(AF_INET, &sin->sin_addr,
addrbuf, INET6_ADDRSTRLEN); addrbuf, INET6_ADDRSTRLEN);
} else { } else {
sin6 = (struct sockaddr_in6 *)&spc->spc_aaddr; sin6 = (struct sockaddr_in6 *)&spc->spc_aaddr;
ap = inet_ntop(AF_INET6, &sin6->sin6_addr, ap = inet_ntop(AF_INET6, &sin6->sin6_addr,
addrbuf, INET6_ADDRSTRLEN); addrbuf, INET6_ADDRSTRLEN);
} }
printf("^^^ intf_change: %s state=%d, error=%d\n", ap, printf("^^^ intf_change: %s state=%d, error=%d\n", ap,
spc->spc_state, spc->spc_error); spc->spc_state, spc->spc_error);
break; break;
case SCTP_REMOTE_ERROR: case SCTP_REMOTE_ERROR:
sre = &snp->sn_remote_error; sre = &snp->sn_remote_error;
printf("^^^ remote_error: err=%hu len=%hu\n", printf("^^^ remote_error: err=%hu len=%hu\n",
ntohs(sre->sre_error), ntohs(sre->sre_len)); ntohs(sre->sre_error), ntohs(sre->sre_length));
break; break;
case SCTP_SHUTDOWN_EVENT: case SCTP_SHUTDOWN_EVENT:
printf("^^^ shutdown event\n"); printf("^^^ shutdown event\n");
break; break;
default: default:
printf("unknown type: %hu\n", snp->sn_header.sn_type); printf("unknown type: %hu\n", snp->sn_header.sn_type);
break; break;
} }
} }
static void * static void *
sctp_recvmsg(int fd, struct msghdr *msg, void *buf, size_t *buflen, mysctp_recvmsg(int fd, struct msghdr *msg, void *buf, size_t *buflen,
ssize_t *nrp, size_t cmsglen) ssize_t *nrp, size_t cmsglen)
{ {
ssize_t nr = 0, nnr = 0; ssize_t nr = 0, nnr = 0;
struct iovec iov[1]; struct iovec iov[1];
*nrp = 0; *nrp = 0;
iov->iov_base = buf; iov->iov_base = buf;
iov->iov_len = *buflen; iov->iov_len = *buflen;
msg->msg_iov = iov; msg->msg_iov = iov;
msg->msg_iovlen = 1; msg->msg_iovlen = 1;
skipping to change at page 70, line 29 skipping to change at page 71, line 29
return (NULL); return (NULL);
} }
nr += nnr; nr += nnr;
if ((msg->msg_flags & MSG_EOR) != 0) { if ((msg->msg_flags & MSG_EOR) != 0) {
*nrp = nr; *nrp = nr;
return (buf); return (buf);
} }
/* Realloc the buffer? */ /* Realloc the buffer? */
if (*buflen == nr) { if (*buflen == (size_t)nr) {
buf = realloc(buf, *buflen * 2); buf = realloc(buf, *buflen * 2);
if (buf == 0) { if (buf == 0) {
fprintf(stderr, "out of memory\n"); fprintf(stderr, "out of memory\n");
exit(1); exit(1);
} }
*buflen *= 2; *buflen *= 2;
} }
/* Set the next read offset */ /* Set the next read offset */
iov->iov_base = (char *)buf + nr; iov->iov_base = (char *)buf + nr;
iov->iov_len = *buflen - nr; iov->iov_len = *buflen - nr;
} }
} }
static void static void
echo(int fd, int socketModeUDP) echo(int fd, int socketModeone_to_many)
{ {
ssize_t nr; ssize_t nr;
struct sctp_sndrcvinfo *sri; struct sctp_sndrcvinfo *sri;
struct msghdr msg[1]; struct msghdr msg[1];
struct cmsghdr *cmsg; struct cmsghdr *cmsg;
char cbuf[sizeof (*cmsg) + sizeof (*sri)]; char cbuf[sizeof (*cmsg) + sizeof (*sri)];
char *buf; char *buf;
size_t buflen; size_t buflen;
struct iovec iov[1]; struct iovec iov[1];
size_t cmsglen = sizeof (*cmsg) + sizeof (*sri); size_t cmsglen = sizeof (*cmsg) + sizeof (*sri);
skipping to change at page 71, line 27 skipping to change at page 72, line 27
/* Set up the msghdr structure for receiving */ /* Set up the msghdr structure for receiving */
memset(msg, 0, sizeof (*msg)); memset(msg, 0, sizeof (*msg));
msg->msg_control = cbuf; msg->msg_control = cbuf;
msg->msg_controllen = cmsglen; msg->msg_controllen = cmsglen;
msg->msg_flags = 0; msg->msg_flags = 0;
cmsg = (struct cmsghdr *)cbuf; cmsg = (struct cmsghdr *)cbuf;
sri = (struct sctp_sndrcvinfo *)(cmsg + 1); sri = (struct sctp_sndrcvinfo *)(cmsg + 1);
/* Wait for something to echo */ /* Wait for something to echo */
while (buf = sctp_recvmsg(fd, msg, buf, &buflen, &nr, cmsglen)) { while (buf = mysctp_recvmsg(fd, msg, buf, &buflen, &nr, cmsglen)) {
/* Intercept notifications here */ /* Intercept notifications here */
if (msg->msg_flags & MSG_NOTIFICATION) { if (msg->msg_flags & MSG_NOTIFICATION) {
handle_event(buf); handle_event(buf);
continue; continue;
} }
iov->iov_base = buf; iov->iov_base = buf;
iov->iov_len = nr; iov->iov_len = nr;
msg->msg_iov = iov; msg->msg_iov = iov;
skipping to change at page 72, line 7 skipping to change at page 73, line 7
/* Echo it back */ /* Echo it back */
msg->msg_flags = MSG_XPG4_2; msg->msg_flags = MSG_XPG4_2;
if (sendmsg(fd, msg, 0) < 0) { if (sendmsg(fd, msg, 0) < 0) {
perror("sendmsg"); perror("sendmsg");
exit(1); exit(1);
} }
} }
if (nr < 0) { if (nr < 0) {
perror("recvmsg"); perror("recvmsg");
} }
if(socketModeUDP == 0) if(socketModeone_to_many == 0)
close(fd); close(fd);
} }
int main() int main()
{ {
struct sctp_event_subscribe event;
int lfd, cfd; int lfd, cfd;
int onoff = 1; int onoff = 1;
struct sockaddr_in sin[1]; struct sockaddr_in sin[1];
if ((lfd = socket(AF_INET, SOCK_STREAM, IPPROTO_SCTP)) == -1) { if ((lfd = socket(AF_INET, SOCK_STREAM, IPPROTO_SCTP)) == -1) {
perror("socket"); perror("socket");
exit(1); exit(1);
} }
sin->sin_family = AF_INET; sin->sin_family = AF_INET;
skipping to change at page 72, line 37 skipping to change at page 73, line 38
exit(1); exit(1);
} }
if (listen(lfd, 1) == -1) { if (listen(lfd, 1) == -1) {
perror("listen"); perror("listen");
exit(1); exit(1);
} }
/* Wait for new associations */ /* Wait for new associations */
for (;;) { for (;;) {
struct sctp_event_subscribe event;
if ((cfd = accept(lfd, NULL, 0)) == -1) { if ((cfd = accept(lfd, NULL, 0)) == -1) {
perror("accept"); perror("accept");
exit(1); exit(1);
} }
/* Enable all events */ /* Enable all events */
event.sctp_data_io_event = 1; event.sctp_data_io_event = 1;
event.sctp_association_event = 1; event.sctp_association_event = 1;
event.sctp_address_event = 1; event.sctp_address_event = 1;
event.sctp_send_failure_event = 1; event.sctp_send_failure_event = 1;
event.sctp_peer_error_event = 1; event.sctp_peer_error_event = 1;
event.sctp_shutdown_event = 1; event.sctp_shutdown_event = 1;
event.sctp_partial_delivery_event = 1; event.sctp_partial_delivery_event = 1;
event.sctp_adaption_layer_event = 1; event.sctp_adaption_layer_event = 1;
if (setsockopt(cfd, IPPROTO_SCTP, if (setsockopt(cfd, IPPROTO_SCTP,
SCTP_SET_EVENTS, &event, SCTP_EVENTS, &event,
sizeof(event)) != 0) { sizeof(event)) != 0) {
perror("setevent failed"); perror("setevent failed");
exit(1); exit(1);
} }
/* Echo back any and all data */ /* Echo back any and all data */
echo(cfd,0); echo(cfd,0);
} }
} }
Appendix B. UDP-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 UDP-style IPv4 SCTP. The example shows how to use some features of one-to-many style
SCTP sockets, including: IPv4 SCTP sockets, including:
o Opening and binding of a socket; o Opening and binding of a socket;
o Enabling ancillary data o Enabling ancillary data
o Enabling notifications o Enabling notifications
o Using ancillary data with sendmsg() and recvmsg() o Using ancillary data with sendmsg() and recvmsg()
o Using MSG_EOR to determine if an entire message has been read o Using MSG_EOR to determine if an entire message has been read
o Handling notifications o Handling notifications
Note most functions defined in Appendix A are reused in this example. Note most functions defined in Appendix A are reused in this example.
int main() int main()
{ {
int fd; int fd;
int onoff = 1;
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");
exit(1); exit(1);
} }
sin->sin_family = AF_INET; sin->sin_family = AF_INET;
skipping to change at page 75, line 7 skipping to change at page 76, line 6
/* Enable all notifications and events */ /* Enable all notifications and events */
event.sctp_data_io_event = 1; event.sctp_data_io_event = 1;
event.sctp_association_event = 1; event.sctp_association_event = 1;
event.sctp_address_event = 1; event.sctp_address_event = 1;
event.sctp_send_failure_event = 1; event.sctp_send_failure_event = 1;
event.sctp_peer_error_event = 1; event.sctp_peer_error_event = 1;
event.sctp_shutdown_event = 1; event.sctp_shutdown_event = 1;
event.sctp_partial_delivery_event = 1; event.sctp_partial_delivery_event = 1;
event.sctp_adaption_layer_event = 1; event.sctp_adaption_layer_event = 1;
if (setsockopt(fd, IPPROTO_SCTP, if (setsockopt(fd, IPPROTO_SCTP,
SCTP_SET_EVENTS, &event, SCTP_EVENTS, &event,
sizeof(event)) != 0) { sizeof(event)) != 0) {
perror("setevent failed"); perror("setevent failed");
exit(1); exit(1);
} }
/* Set associations to auto-close in 2 seconds of /* Set associations to auto-close in 2 seconds of
* inactivity * inactivity
*/ */
if (setsockopt(fd, IPPROTO_SCTP, SCTP_AUTOCLOSE, if (setsockopt(fd, IPPROTO_SCTP, SCTP_AUTOCLOSE,
&idleTime, 4) < 0) { &idleTime, 4) < 0) {
perror("setsockopt SCTP_AUTOCLOSE"); perror("setsockopt SCTP_AUTOCLOSE");
exit(1); exit(1);
} }
/* Allow new associations to be accepted */ /* Allow new associations to be accepted */
if (listen(fd, 0) < 0) { if (listen(fd, 1) < 0) {
perror("listen"); perror("listen");
exit(1); exit(1);
} }
/* Wait for new associations */ /* Wait for new associations */
while(1){ while(1){
/* Echo back any and all data */ /* Echo back any and all data */
echo(fd,1); echo(fd,1);
} }
} }
 End of changes. 

This html diff was produced by rfcdiff 1.23, available from http://www.levkowetz.com/ietf/tools/rfcdiff/