third_party/lksctp-tools/man/sctp.7 - RealtimeRoboticsGroup/test - Gitiles

 .\" (C) Copyright Sridhar Samudrala IBM Corp. 2004, 2005.
 .\"
 .\" Permission is granted to distribute possibly modified copies
 .\" of this manual provided the header is included verbatim,
 .\" and in case of nontrivial modification author and date
 .\" of the modification is added to the header.
 .\"
 .TH SCTP  7 2005-10-25 "Linux Man Page" "Linux Programmer's Manual"
 .SH NAME
 sctp \- SCTP protocol.
 .SH SYNOPSIS
 .nf
 .B #include <sys/socket.h>
 .B #include <netinet/in.h>
 .B #include <netinet/sctp.h>
 .sp
 .B sctp_socket = socket(PF_INET, SOCK_STREAM, IPPROTO_SCTP);
 .B sctp_socket = socket(PF_INET, SOCK_SEQPACKET, IPPROTO_SCTP);
 .fi
 .SH DESCRIPTION
 This is an implementation of the SCTP protocol as defined in RFC2960 and
 RFC3309. It is a message oriented, reliable transport protocol with direct
 support for multihoming that runs on top of
 .BR ip (7),
 and supports both v4 and v6 versions.
 .PP
 Like TCP, SCTP provides reliable, connection oriented data delivery with
 congestion control. Unlike TCP, SCTP also provides message boundary
 preservation, ordered and unordered message delivery, multi-streaming and
 multi-homing. Detection of data corruption, loss of data and duplication of
 data is achieved by using checksums and sequence numbers. A selective
 retransmission mechanism is applied to correct loss or corruption of data.
 .PP
 This implementation supports a mapping of SCTP into sockets API as defined
 in the draft-ietf-tsvwg-sctpsocket-10.txt(Sockets API extensions for SCTP).
 Two styles of interfaces are supported.
 .PP
 A
 .B one-to-many
 style interface with 1 to MANY relationship between socket and associations
 where the outbound association setup is implicit. The syntax of a one-to-many
 style socket() call is
 .PP
 .B     sd = socket(PF_INET, SOCK_SEQPACKET, IPPROTO_SCTP);
 .PP
 A typical server in this style uses the following socket calls in sequence
 to prepare an endpoint for servicing requests.
 .PP
      1. socket()
      2. bind()
      3. listen()
      4. recvmsg()
      5. sendmsg()
      6. close()
 .PP
 A typical client uses the following calls in sequence to setup an association
 with a server to request services.
 .PP
      1. socket()
      2. sendmsg()
      3. recvmsg()
      4. close()
 .PP
 A
 .B one-to-one style
 interface with a 1 to 1 relationship between socket and
 association which enables existing TCP applications to be ported to SCTP with
 very little effort. The syntax of a one-to-one style socket() call is
 .PP
 .B     sd = socket(PF_INET, SOCK_STREAM, IPPROTO_SCTP);
 .PP
 A typical server in one-to-one style uses the following
 system call sequence to prepare an SCTP endpoint for servicing requests:
 .PP
      1. socket()
      2. bind()
      3. listen()
      4. accept()
 .PP
 The accept() call blocks until a new association is set up. It returns with a
 new socket descriptor. The server then uses the new socket descriptor to
 communicate with the client, using recv() and send() calls to get requests and
 send back responses. Then it calls
 .PP
      5. close()
 .PP
 to terminate the association. A typical client uses the following system call
 sequence to setup an association with a server to request services:
 .PP
      1. socket()
      2. connect()
 .PP
 After returning from connect(), the client uses send() and recv() calls to
 send out requests and receive responses from the server. The client calls
 .PP
      3. close()
 .PP
 to terminate this association when done.
 .SH "ADDRESS FORMATS"
 SCTP is built on top of IP (see
 .BR ip (7)).
 The address formats defined by
 .BR ip (7)
 apply to SCTP.  SCTP only supports point-to-point communication; broadcasting
 and multicasting are not supported.
 .SH SYSCTLS
 These variables can be accessed by the
 .B /proc/sys/net/sctp/*
 files or with the
 .BR sysctl (2)
 interface.  In addition, most IP sysctls also apply to SCTP. See
 .BR ip (7).
 .TP
 Please check kernel documentation for this, at Documentation/networking/ip-sysctl.txt.
 .SH "STATISTICS"
 These variables can be accessed by the
 .B /proc/net/sctp/*
 files.
 .TP
 .B assocs
 Displays the following information about the active associations.
 assoc ptr, sock ptr, socket style, sock state, association state, hash bucket,
 association id, bytes in transmit queue, bytes in receive queue, user id,
 inode, local port, remote port, local addresses and remote addresses.
 .TP
 .B eps
 Displays the following information about the active endpoints.
 endpoint ptr, sock ptr, socket style, sock state, hash bucket, local port,
 user id, inode and local addresses.
 .TP
 .B snmp
 Displays the following statistics related to SCTP states, packets and chunks.
 .TP
 .TP
 .B SctpCurrEstab
 The number of associations for which the current state is either ESTABLISHED,
 SHUTDOWN-RECEIVED or SHUTDOWN-PENDING.
 .TP
 .B SctpActiveEstabs
 The number of times that associations have made a direct transition to the
 ESTABLISHED state from the COOKIE-ECHOED state. The upper layer initiated the
 association attempt.
 .TP
 .B SctpPassiveEstabs
 The number of times that associations have made a direct transition to the
 ESTABLISHED state from the CLOSED state. The remote endpoint initiated the
 association attempt.
 .TP
 .B SctpAborteds
 The number of times that associations have made a direct transition to the
 CLOSED state from any state using the primitive 'ABORT'. Ungraceful
 termination of the association.
 .TP
 .B SctpShutdowns
 The number of times that associations have made a direct transition to the
 CLOSED state from either the SHUTDOWN-SENT state or the SHUTDOWN-ACK-SENT
 state. Graceful termination of the association.
 .TP
 .B SctpOutOfBlues
 The number of out of the blue packets received by the host. An out of the blue
 packet is an SCTP packet correctly formed, including the proper checksum, but
 for which the receiver was unable to identify an appropriate association.
 .TP
 .B SctpChecksumErrors
 The number of SCTP packets received with an invalid checksum.
 .TP
 .B SctpOutCtrlChunks
 The number of SCTP control chunks sent (retransmissions are not included).
 Control chunks are those chunks different from DATA.
 .TP
 .B SctpOutOrderChunks
 The number of SCTP ordered data chunks sent (retransmissions are not included).
 .TP
 .B SctpOutUnorderChunks
 The number of SCTP unordered chunks(data chunks in which the U bit is set
 to 1) sent (retransmissions are not included).
 .TP
 .B SctpInCtrlChunks
 The number of SCTP control chunks received (no duplicate chunks included).
 .TP
 .B SctpInOrderChunks
 The number of SCTP ordered data chunks received (no duplicate chunks included).
 .TP
 .B SctpInUnorderChunks
 The number of SCTP unordered chunks(data chunks in which the U bit is set
 to 1) received (no duplicate chunks included).
 .TP
 .B SctpFragUsrMsgs
 The number of user messages that have to be fragmented because of the MTU.
 .TP
 .B SctpReasmUsrMsgs
 The number of user messages reassembled, after conversion into DATA chunks.
 .TP
 .B SctpOutSCTPPacks
 The number of SCTP packets sent. Retransmitted DATA chunks are included.
 .TP
 .B SctpInSCTPPacks
 The number of SCTP packets received. Duplicates are included.
 .SH "SOCKET OPTIONS"
 To set or get a SCTP socket option, call
 .BR getsockopt (2)
 to read or
 .BR setsockopt (2)
 to write the option with the option level argument set to
 .BR SOL_SCTP.
 .TP
 .BR SCTP_RTOINFO.
 This option is used to get or set the protocol parameters used to
 initialize and bound retransmission timout(RTO). The structure sctp_rtoinfo
 defined in /usr/include/netinet/sctp.h is used to access and modify these
 parameters.
 .TP
 .B SCTP_ASSOCINFO
 This option is used to both examine and set various association and endpoint
 parameters. The sturcture sctp_assocparams defined in
 /usr/include/netinet/sctp.h is used to access and modify these parameters.
 .TP
 .B SCTP_INITMSG
 This option is used to get or set the protocol parameters for the default
 association initialization. The structure sctp_initmsg defined in
 /usr/include/netinet/sctp.h is used to access and modify these parameters.

 Setting initialization parameters is effective only on an unconnected
 socket (for one-to-many style sockets only future associations are
 effected by the change). With one-to-one style sockets, this option
 is inherited by sockets derived from a listener socket.
 .TP
 .B SCTP_NODELAY
 Turn on/off any Nagle-like algorithm. This means that packets are generally
 sent as soon as possible and no unnecessary delays are introduced, at the cost
 of more packets in the network.  Expects an integer boolean flag.
 .TP
 .B SCTP_AUTOCLOSE
 This socket option is applicable to the one-to-many style socket
 only. When set it will cause associations that are idle for more than
 the specified number of seconds to automatically close. An
 association being idle is defined an association that has NOT sent or
 received user data. The special value of 0 indicates that no
 automatic close of any associations should be performed. The option
 expects an integer defining the number of seconds of idle time before
 an association is closed.
 .TP
 .B SCTP_SET_PEER_PRIMARY_ADDR
 Requests that the peer mark the enclosed address as the association
 primary. The enclosed address must be one of the association's
 locally bound addresses. The structure sctp_setpeerprim defined in
 /usr/include/netinet/sctp.h is used to make a set peer primary request.
 .TP
 .B SCTP_PRIMARY_ADDR
 Requests that the local SCTP stack use the enclosed peer address as
 the association primary. The enclosed address must be one of the
 association peer's addresses. The structure sctp_prim defined in
 /usr/include/netinet/sctp.h is used to make a get/set primary request.
 .TP
 .B SCTP_DISABLE_FRAGMENTS
 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 exceeds the current PMTU size, the message will
 NOT be sent and an error will be indicated to the user.
 .TP
 .B SCTP_PEER_ADDR_PARAMS
 Using this option, applications can enable or disable heartbeats for any peer
 address of an association, modify an address's heartbeat interval, force a
 heartbeat to be sent immediately, and adjust the address's maximum number of
 retransmissions sent before an address is considered unreachable. The structure
 sctp_paddrparams defined in /usr/include/netinet/sctp.h is used to
 access and modify an address's parameters.
 .TP
 .B SCTP_DEFAULT_SEND_PARAM
 Applications that wish to use the sendto() system call may wish to specify
 a default set of parameters that would normally be supplied through the
 inclusion of ancillary data. This socket option allows such an application to
 set the default sctp_sndrcvinfo structure. The application that wishes to use
 this socket option simply passes in to this call the sctp_sndrcvinfo structure
 defined in /usr/include/netinet/sctp.h. The input parameters accepted by this
 call include sinfo_stream, sinfo_flags, sinfo_ppid, sinfo_context,
 sinfo_timetolive. The user must set the sinfo_assoc_id field to identify the
  association to affect if the caller is using the one-to-many style.
 .TP
 .B SCTP_EVENTS
 This socket option is used to specify various notifications and ancillary data
 the user wishes to receive. The structure sctp_event_subscribe defined in
 /usr/include/netinet/sctp.h is used to access or modify the events of interest
 to the user.
 .TP
 .B SCTP_I_WANT_MAPPED_V4_ADDR
 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 PF_INET6,
 then IPv4 addresses will be mapped to V6 representation. If this option is
 turned off, then no mapping will be done of V4 addresses and a user will
 receive both PF_INET6 and PF_INET type addresses on the socket.

 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.
 .TP
 .B SCTP_MAXSEG
 This socket option specifies the maximum size to put in any outgoing
 SCTP DATA chunk. If a message is larger than this size it will be
 fragmented by SCTP into the specified size. Note that the underlying
 SCTP implementation may fragment into smaller sized chunks when the
 PMTU of the underlying association is smaller than the value set by
 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.
 .TP
 .B SCTP_STATUS
 Applications can retrieve current status information about an association,
 including association state, peer receiver window size, number of unacked
 data chunks, and number of data chunks pending receipt.  This information is
 read-only.  The structure sctp_status defined in /usr/include/netinet/sctp.h
 is used to access this information.
 .TP
 .B SCTP_GET_PEER_ADDR_INFO
 Applications can retrieve information about a specific peer address
 of an association, including its reachability state, congestion window,
 and retransmission timer values.  This information is read-only. The structure
 sctp_paddr_info defined in /usr/include/netinet/sctp.h is used to access this
 information.
 .TP
 .B SCTP_GET_ASSOC_STATS
 Applications can retrieve current statistics about an association, including
 SACKs sent and received, SCTP packets sent and received. The complete list can
 be found in /usr/include/netinet/sctp.h in struct sctp_assoc_stats.
 .SH AUTHORS
 Sridhar Samudrala <sri@us.ibm.com>
 .SH "SEE ALSO"
 .BR socket (7),
 .BR socket (2),
 .BR ip (7),
 .BR bind (2),
 .BR listen (2),
 .BR accept (2),
 .BR connect (2),
 .BR sendmsg (2),
 .BR recvmsg (2),
 .BR sysctl (2),
 .BR getsockopt (2),
 .BR sctp_bindx (3),
 .BR sctp_connectx (3),
 .BR sctp_sendmsg (3),
 .BR sctp_sendv (3),
 .BR sctp_send (3),
 .BR sctp_recvmsg (3),
 .BR sctp_recvv (3),
 .BR sctp_peeloff (3),
 .BR sctp_getladdrs (3),
 .BR sctp_getpaddrs (3),
 .BR sctp_opt_info (3).
 .sp
 RFC2960, RFC3309 for the SCTP specification.
	.\" (C) Copyright Sridhar Samudrala IBM Corp. 2004, 2005.
	.\"
	.\" Permission is granted to distribute possibly modified copies
	.\" of this manual provided the header is included verbatim,
	.\" and in case of nontrivial modification author and date
	.\" of the modification is added to the header.
	.\"
	.TH SCTP 7 2005-10-25 "Linux Man Page" "Linux Programmer's Manual"
	.SH NAME
	sctp \- SCTP protocol.
	.SH SYNOPSIS
	.nf
	.B #include <sys/socket.h>
	.B #include <netinet/in.h>
	.B #include <netinet/sctp.h>
	.sp
	.B sctp_socket = socket(PF_INET, SOCK_STREAM, IPPROTO_SCTP);
	.B sctp_socket = socket(PF_INET, SOCK_SEQPACKET, IPPROTO_SCTP);
	.fi
	.SH DESCRIPTION
	This is an implementation of the SCTP protocol as defined in RFC2960 and
	RFC3309. It is a message oriented, reliable transport protocol with direct
	support for multihoming that runs on top of
	.BR ip (7),
	and supports both v4 and v6 versions.
	.PP
	Like TCP, SCTP provides reliable, connection oriented data delivery with
	congestion control. Unlike TCP, SCTP also provides message boundary
	preservation, ordered and unordered message delivery, multi-streaming and
	multi-homing. Detection of data corruption, loss of data and duplication of
	data is achieved by using checksums and sequence numbers. A selective
	retransmission mechanism is applied to correct loss or corruption of data.
	.PP
	This implementation supports a mapping of SCTP into sockets API as defined
	in the draft-ietf-tsvwg-sctpsocket-10.txt(Sockets API extensions for SCTP).
	Two styles of interfaces are supported.
	.PP
	A
	.B one-to-many
	style interface with 1 to MANY relationship between socket and associations
	where the outbound association setup is implicit. The syntax of a one-to-many
	style socket() call is
	.PP
	.B sd = socket(PF_INET, SOCK_SEQPACKET, IPPROTO_SCTP);
	.PP
	A typical server in this style uses the following socket calls in sequence
	to prepare an endpoint for servicing requests.
	.PP
	1. socket()
	2. bind()
	3. listen()
	4. recvmsg()
	5. sendmsg()
	6. close()
	.PP
	A typical client uses the following calls in sequence to setup an association
	with a server to request services.
	.PP
	1. socket()
	2. sendmsg()
	3. recvmsg()
	4. close()
	.PP
	A
	.B one-to-one style
	interface with a 1 to 1 relationship between socket and
	association which enables existing TCP applications to be ported to SCTP with
	very little effort. The syntax of a one-to-one style socket() call is
	.PP
	.B sd = socket(PF_INET, SOCK_STREAM, IPPROTO_SCTP);
	.PP
	A typical server in one-to-one style uses the following
	system call sequence to prepare an SCTP endpoint for servicing requests:
	.PP
	1. socket()
	2. bind()
	3. listen()
	4. accept()
	.PP
	The accept() call blocks until a new association is set up. It returns with a
	new socket descriptor. The server then uses the new socket descriptor to
	communicate with the client, using recv() and send() calls to get requests and
	send back responses. Then it calls
	.PP
	5. close()
	.PP
	to terminate the association. A typical client uses the following system call
	sequence to setup an association with a server to request services:
	.PP
	1. socket()
	2. connect()
	.PP
	After returning from connect(), the client uses send() and recv() calls to
	send out requests and receive responses from the server. The client calls
	.PP
	3. close()
	.PP
	to terminate this association when done.
	.SH "ADDRESS FORMATS"
	SCTP is built on top of IP (see
	.BR ip (7)).
	The address formats defined by
	.BR ip (7)
	apply to SCTP. SCTP only supports point-to-point communication; broadcasting
	and multicasting are not supported.
	.SH SYSCTLS
	These variables can be accessed by the
	.B /proc/sys/net/sctp/*
	files or with the
	.BR sysctl (2)
	interface. In addition, most IP sysctls also apply to SCTP. See
	.BR ip (7).
	.TP
	Please check kernel documentation for this, at Documentation/networking/ip-sysctl.txt.
	.SH "STATISTICS"
	These variables can be accessed by the
	.B /proc/net/sctp/*
	files.
	.TP
	.B assocs
	Displays the following information about the active associations.
	assoc ptr, sock ptr, socket style, sock state, association state, hash bucket,
	association id, bytes in transmit queue, bytes in receive queue, user id,
	inode, local port, remote port, local addresses and remote addresses.
	.TP
	.B eps
	Displays the following information about the active endpoints.
	endpoint ptr, sock ptr, socket style, sock state, hash bucket, local port,
	user id, inode and local addresses.
	.TP
	.B snmp
	Displays the following statistics related to SCTP states, packets and chunks.
	.TP
	.TP
	.B SctpCurrEstab
	The number of associations for which the current state is either ESTABLISHED,
	SHUTDOWN-RECEIVED or SHUTDOWN-PENDING.
	.TP
	.B SctpActiveEstabs
	The number of times that associations have made a direct transition to the
	ESTABLISHED state from the COOKIE-ECHOED state. The upper layer initiated the
	association attempt.
	.TP
	.B SctpPassiveEstabs
	The number of times that associations have made a direct transition to the
	ESTABLISHED state from the CLOSED state. The remote endpoint initiated the
	association attempt.
	.TP
	.B SctpAborteds
	The number of times that associations have made a direct transition to the
	CLOSED state from any state using the primitive 'ABORT'. Ungraceful
	termination of the association.
	.TP
	.B SctpShutdowns
	The number of times that associations have made a direct transition to the
	CLOSED state from either the SHUTDOWN-SENT state or the SHUTDOWN-ACK-SENT
	state. Graceful termination of the association.
	.TP
	.B SctpOutOfBlues
	The number of out of the blue packets received by the host. An out of the blue
	packet is an SCTP packet correctly formed, including the proper checksum, but
	for which the receiver was unable to identify an appropriate association.
	.TP
	.B SctpChecksumErrors
	The number of SCTP packets received with an invalid checksum.
	.TP
	.B SctpOutCtrlChunks
	The number of SCTP control chunks sent (retransmissions are not included).
	Control chunks are those chunks different from DATA.
	.TP
	.B SctpOutOrderChunks
	The number of SCTP ordered data chunks sent (retransmissions are not included).
	.TP
	.B SctpOutUnorderChunks
	The number of SCTP unordered chunks(data chunks in which the U bit is set
	to 1) sent (retransmissions are not included).
	.TP
	.B SctpInCtrlChunks
	The number of SCTP control chunks received (no duplicate chunks included).
	.TP
	.B SctpInOrderChunks
	The number of SCTP ordered data chunks received (no duplicate chunks included).
	.TP
	.B SctpInUnorderChunks
	The number of SCTP unordered chunks(data chunks in which the U bit is set
	to 1) received (no duplicate chunks included).
	.TP
	.B SctpFragUsrMsgs
	The number of user messages that have to be fragmented because of the MTU.
	.TP
	.B SctpReasmUsrMsgs
	The number of user messages reassembled, after conversion into DATA chunks.
	.TP
	.B SctpOutSCTPPacks
	The number of SCTP packets sent. Retransmitted DATA chunks are included.
	.TP
	.B SctpInSCTPPacks
	The number of SCTP packets received. Duplicates are included.
	.SH "SOCKET OPTIONS"
	To set or get a SCTP socket option, call
	.BR getsockopt (2)
	to read or
	.BR setsockopt (2)
	to write the option with the option level argument set to
	.BR SOL_SCTP.
	.TP
	.BR SCTP_RTOINFO.
	This option is used to get or set the protocol parameters used to
	initialize and bound retransmission timout(RTO). The structure sctp_rtoinfo
	defined in /usr/include/netinet/sctp.h is used to access and modify these
	parameters.
	.TP
	.B SCTP_ASSOCINFO
	This option is used to both examine and set various association and endpoint
	parameters. The sturcture sctp_assocparams defined in
	/usr/include/netinet/sctp.h is used to access and modify these parameters.
	.TP
	.B SCTP_INITMSG
	This option is used to get or set the protocol parameters for the default
	association initialization. The structure sctp_initmsg defined in
	/usr/include/netinet/sctp.h is used to access and modify these parameters.

	Setting initialization parameters is effective only on an unconnected
	socket (for one-to-many style sockets only future associations are
	effected by the change). With one-to-one style sockets, this option
	is inherited by sockets derived from a listener socket.
	.TP
	.B SCTP_NODELAY
	Turn on/off any Nagle-like algorithm. This means that packets are generally
	sent as soon as possible and no unnecessary delays are introduced, at the cost
	of more packets in the network. Expects an integer boolean flag.
	.TP
	.B SCTP_AUTOCLOSE
	This socket option is applicable to the one-to-many style socket
	only. When set it will cause associations that are idle for more than
	the specified number of seconds to automatically close. An
	association being idle is defined an association that has NOT sent or
	received user data. The special value of 0 indicates that no
	automatic close of any associations should be performed. The option
	expects an integer defining the number of seconds of idle time before
	an association is closed.
	.TP
	.B SCTP_SET_PEER_PRIMARY_ADDR
	Requests that the peer mark the enclosed address as the association
	primary. The enclosed address must be one of the association's
	locally bound addresses. The structure sctp_setpeerprim defined in
	/usr/include/netinet/sctp.h is used to make a set peer primary request.
	.TP
	.B SCTP_PRIMARY_ADDR
	Requests that the local SCTP stack use the enclosed peer address as
	the association primary. The enclosed address must be one of the
	association peer's addresses. The structure sctp_prim defined in
	/usr/include/netinet/sctp.h is used to make a get/set primary request.
	.TP
	.B SCTP_DISABLE_FRAGMENTS
	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 exceeds the current PMTU size, the message will
	NOT be sent and an error will be indicated to the user.
	.TP
	.B SCTP_PEER_ADDR_PARAMS
	Using this option, applications can enable or disable heartbeats for any peer
	address of an association, modify an address's heartbeat interval, force a
	heartbeat to be sent immediately, and adjust the address's maximum number of
	retransmissions sent before an address is considered unreachable. The structure
	sctp_paddrparams defined in /usr/include/netinet/sctp.h is used to
	access and modify an address's parameters.
	.TP
	.B SCTP_DEFAULT_SEND_PARAM
	Applications that wish to use the sendto() system call may wish to specify
	a default set of parameters that would normally be supplied through the
	inclusion of ancillary data. This socket option allows such an application to
	set the default sctp_sndrcvinfo structure. The application that wishes to use
	this socket option simply passes in to this call the sctp_sndrcvinfo structure
	defined in /usr/include/netinet/sctp.h. The input parameters accepted by this
	call include sinfo_stream, sinfo_flags, sinfo_ppid, sinfo_context,
	sinfo_timetolive. The user must set the sinfo_assoc_id field to identify the
	association to affect if the caller is using the one-to-many style.
	.TP
	.B SCTP_EVENTS
	This socket option is used to specify various notifications and ancillary data
	the user wishes to receive. The structure sctp_event_subscribe defined in
	/usr/include/netinet/sctp.h is used to access or modify the events of interest
	to the user.
	.TP
	.B SCTP_I_WANT_MAPPED_V4_ADDR
	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 PF_INET6,
	then IPv4 addresses will be mapped to V6 representation. If this option is
	turned off, then no mapping will be done of V4 addresses and a user will
	receive both PF_INET6 and PF_INET type addresses on the socket.

	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.
	.TP
	.B SCTP_MAXSEG
	This socket option specifies the maximum size to put in any outgoing
	SCTP DATA chunk. If a message is larger than this size it will be
	fragmented by SCTP into the specified size. Note that the underlying
	SCTP implementation may fragment into smaller sized chunks when the
	PMTU of the underlying association is smaller than the value set by
	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.
	.TP
	.B SCTP_STATUS
	Applications can retrieve current status information about an association,
	including association state, peer receiver window size, number of unacked
	data chunks, and number of data chunks pending receipt. This information is
	read-only. The structure sctp_status defined in /usr/include/netinet/sctp.h
	is used to access this information.
	.TP
	.B SCTP_GET_PEER_ADDR_INFO
	Applications can retrieve information about a specific peer address
	of an association, including its reachability state, congestion window,
	and retransmission timer values. This information is read-only. The structure
	sctp_paddr_info defined in /usr/include/netinet/sctp.h is used to access this
	information.
	.TP
	.B SCTP_GET_ASSOC_STATS
	Applications can retrieve current statistics about an association, including
	SACKs sent and received, SCTP packets sent and received. The complete list can
	be found in /usr/include/netinet/sctp.h in struct sctp_assoc_stats.
	.SH AUTHORS
	Sridhar Samudrala <sri@us.ibm.com>
	.SH "SEE ALSO"
	.BR socket (7),
	.BR socket (2),
	.BR ip (7),
	.BR bind (2),
	.BR listen (2),
	.BR accept (2),
	.BR connect (2),
	.BR sendmsg (2),
	.BR recvmsg (2),
	.BR sysctl (2),
	.BR getsockopt (2),
	.BR sctp_bindx (3),
	.BR sctp_connectx (3),
	.BR sctp_sendmsg (3),
	.BR sctp_sendv (3),
	.BR sctp_send (3),
	.BR sctp_recvmsg (3),
	.BR sctp_recvv (3),
	.BR sctp_peeloff (3),
	.BR sctp_getladdrs (3),
	.BR sctp_getpaddrs (3),
	.BR sctp_opt_info (3).
	.sp
	RFC2960, RFC3309 for the SCTP specification.