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NAME | SYNOPSIS | DESCRIPTION | ADDRESS FORMATS | SYSCTLS | STATISTICS | CONTROL MSGS | EVENTS and NOTIFICATIONS | SOCKET OPTIONS | AUTHORS | SEE ALSO | COLOPHON |
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SCTP(7) Linux Programmer's Manual SCTP(7)
sctp - SCTP protocol.
#include <sys/socket.h>
#include <netinet/in.h>
#include <netinet/sctp.h>
sctp_socket = socket(PF_INET, SOCK_STREAM, IPPROTO_SCTP);
sctp_socket = socket(PF_INET, SOCK_SEQPACKET, IPPROTO_SCTP);
This is an implementation of the SCTP protocol as defined in
RFC4960. It is a message oriented, reliable transport protocol
with direct support for multihoming that runs on top of ip(7), and
supports both v4 and v6 versions.
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.
This implementation supports a mapping of SCTP into sockets API as
defined in the RFC6458(Sockets API extensions for SCTP). Two
styles of interfaces are supported.
A 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
sd = socket(PF_INET, SOCK_SEQPACKET, IPPROTO_SCTP);
A typical server in this style uses the following socket calls in
sequence to prepare an endpoint for servicing requests.
1. socket()
2. bind()
3. listen()
4. recvmsg()
5. sendmsg()
6. close()
A typical client uses the following calls in sequence to setup an
association with a server to request services.
1. socket()
2. sendmsg()
3. recvmsg()
4. close()
A 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
sd = socket(PF_INET, SOCK_STREAM, IPPROTO_SCTP);
A typical server in one-to-one style uses the following system
call sequence to prepare an SCTP endpoint for servicing requests:
1. socket()
2. bind()
3. listen()
4. accept()
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
5. close()
to terminate the association. A typical client uses the following
system call sequence to setup an association with a server to
request services:
1. socket()
2. connect()
After returning from connect(), the client uses send() and recv()
calls to send out requests and receive responses from the server.
The client calls
3. close()
to terminate this association when done.
SCTP is built on top of IP (see ip(7)). The address formats
defined by ip(7) apply to SCTP. SCTP only supports point-to-point
communication; broadcasting and multicasting are not supported.
These variables can be accessed by the /proc/sys/net/sctp/* files
or with the sysctl(2) interface. In addition, most IP sysctls
also apply to SCTP. See ip(7).
Please check kernel documentation for this, at
Documentation/networking/ip-sysctl.rst.
These variables can be accessed by the /proc/net/sctp/* files.
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, remote
addresses, heartbeat interval, in streams, out streams, max
retransmissions, init retries, shutdown retries,
retransmitted chunks, sock transmit queue committed bytes,
sock transmit queue bytes, and sock send and receive buffer
bytes.
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.
snmp Displays the following statistics related to SCTP states,
packets and chunks.
SctpCurrEstab
The number of associations for which the current state is
either ESTABLISHED, SHUTDOWN-RECEIVED or SHUTDOWN-PENDING.
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.
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.
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.
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.
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.
SctpChecksumErrors
The number of SCTP packets received with an invalid
checksum.
SctpOutCtrlChunks
The number of SCTP control chunks sent (retransmissions are
not included). Control chunks are those chunks different
from DATA.
SctpOutOrderChunks
The number of SCTP ordered data chunks sent
(retransmissions are not included).
SctpOutUnorderChunks
The number of SCTP unordered chunks(data chunks in which
the U bit is set to 1) sent (retransmissions are not
included).
SctpInCtrlChunks
The number of SCTP control chunks received (no duplicate
chunks included).
SctpInOrderChunks
The number of SCTP ordered data chunks received (no
duplicate chunks included).
SctpInUnorderChunks
The number of SCTP unordered chunks(data chunks in which
the U bit is set to 1) received (no duplicate chunks
included).
SctpFragUsrMsgs
The number of user messages that have to be fragmented
because of the MTU.
SctpReasmUsrMsgs
The number of user messages reassembled, after conversion
into DATA chunks.
SctpOutSCTPPacks
The number of SCTP packets sent. Retransmitted DATA chunks
are included.
SctpInSCTPPacks
The number of SCTP packets received. Duplicates are
included.
SctpT1InitExpireds
The number of timer T1 INIT expired.
SctpT1CookieExpireds
The number of timer T1 COOKIE-ECHO expired.
SctpT2ShutdownExpireds
The number of timer T2 SHUTDOWN expired.
SctpT3RtxExpireds
The number of timer T3 RTX expired.
SctpT4RtoExpireds
The number of timer T4 RTO expired.
SctpT5ShutdownGuardExpireds
The number of timer T5 SHUTDOWN GUARD expired.
SctpDelaySackExpireds
The number of timer DELAY_SACK expired.
SctpAutocloseExpireds
The number of timer AUTOCLOSE expired.
SctpT3Retransmits
The number of T3 timer retransmission.
SctpPmtudRetransmits
The number of PMTUD retransmission.
SctpFastRetransmits
The number of FAST retransmission.
SctpInPktSoftirq
The number of SCTP packets received in Softirq.
SctpInPktBacklog
The number of SCTP packets received in Backlog.
SctpInPktDiscards
The number of SCTP packets discarded in receiving.
SctpInDataChunkDiscards
The number of SCTP data chunks discarded in receiving.
The ancillary data is carried in msg_control field of struct
msghdr, which is used in sendmsg(2) and recvmsg(2) call. The SCTP
stack uses the ancillary data to communicate the attributes, such
as SCTP_RCVINFO, of the message stored in msg_iov to the socket
endpoint. Each ancillary data item is preceded by a struct
cmsghdr, see cmsg(3). The different cmsg types for SCTP are
listed below, and all these related macros and structures are
defined in /usr/include/netinet/sctp.h.
SCTP_INIT
This cmsg provides information for initializing new SCTP
associations for sendmsg() with struct sctp_initmsg, which
is the same as SCTP_INITMSG socket option's data structure.
SCTP_SNDRCV
This cmsg specifies SCTP options for sendmsg() and
describes SCTP header information about a received message
through recvmsg() with struct sctp_sndrcvinfo. It mixes the
send and receive path, and SCTP_SNDINFO and SCTP_RCVINFO
split this information, so these structures should be used,
when possible, since SCTP_SNDRCV is deprecated.
sctp_sendmsg(3) and sctp_send(3) provide a simple way to
use this cmsg.
Note that an application must use the SCTP_RECVRCVINFO
socket option to enable the delivery of this information.
SCTP_EXTRCV
This cmsg specifies SCTP options for SCTP header
information about a received message via recvmsg() with
struct sctp_extrcvinfo, and this structure is an extended
version of SCTP_SNDRCV. Note that data in the next message
is not valid unless the current message is completely read,
i.e., unless the MSG_EOR is set. SCTP_NXTINFO should be
used when possible, since SCTP_EXTRCV is considered
deprecated. sctp_recvmsg(3) provides a simple way to use
this cmsg.
Note that an application must use the SCTP_RECVNXTINFO
socket option to enable the delivery of this information.
SCTP_RCVINFO, SCTP_NXTINFO
These cmsgs describe SCTP receive information about a
received message through recvmsg() with struct
sctp_rcvinfo, and SCTP receive information of the next
message that will be delivered through recvmsg() if this
information is already available when delivering the
current message with struct sctp_nxtinfo. sctp_recvv(3)
provides a simple way to use these cmsgs.
Note that an application must use the SCTP_RECVRCVINFO and
SCTP_RECVNXTINFO socket options accordingly to enable the
delivery of this information.
SCTP_SNDINFO, SCTP_PRINFO, SCTP_AUTHINFO, SCTP_DSTADDRV4,
SCTP_DSTADDRV6
These cmsgs specifie a couple of SCTP options for sendmsg()
for SEND, PRSCTP, AUTH and DSTADDR information with struct
sctp_sndinfo, sctp_prinfo, sctp_authinfo and in(6)_addr
accordingly. sctp_sendv(3) provides a simple way to use
these cmsgs.
An SCTP application may need to understand and process events and
errors that happen on the SCTP stack. These events include network
status changes, association startups, remote operational errors,
and undeliverable messages. When a notification arrives,
recvmsg() returns the notification in the application-supplied
data buffer via msg_iov, and sets MSG_NOTIFICATION in msg_flags.
See socket option SCTP_EVENT for the event enabling. The different
events are listed below, and all these related macros and
structures are defined in /usr/include/netinet/sctp.h.
SCTP_ASSOC_CHANGE
Communication notifications inform the application that an
SCTP association has either begun or ended. The
notification format is struct sctp_assoc_change.
SCTP_PEER_ADDR_CHANGE
When a destination address of a multi-homed peer encounters
a state change, a peer address change event is sent. The
notification format is struct sctp_paddr_change.
SCTP_REMOTE_ERROR
A remote peer may send an Operation Error message to its
peer. This message indicates a variety of error conditions
on an association. The notification format is struct
sctp_remote_error.
SCTP_SEND_FAILED
If SCTP cannot deliver a message, it can return back the
message as a notification if the SCTP_SEND_FAILED event is
enabled. The notification format is struct
sctp_send_failed. Please note that this notification is
deprecated. Use SCTP_SEND_FAILED_EVENT instead.
SCTP_SHUTDOWN_EVENT
When a peer sends a SHUTDOWN, SCTP delivers this
notification to inform the application that it should cease
sending data. The notification format is struct
sctp_shutdown_event.
SCTP_ADAPTATION_INDICATION
When a peer sends an Adaptation Layer Indication parameter,
SCTP delivers this notification to inform the application
about the peer's adaptation layer indication. The
notification format is struct sctp_adaptation_event.
SCTP_PARTIAL_DELIVERY_EVENT
When a receiver is engaged in a partial delivery of a
message, this notification will be used to indicate various
events. The notification format is struct sctp_pdapi_event.
SCTP_AUTHENTICATION_EVENT
This is used to report different events relating to the use
of the extension to authenticate SCTP messages. The
notification format is struct sctp_authkey_event.
SCTP_SENDER_DRY_EVENT
When the SCTP stack has no more user data to send or
retransmit, this notification is given to the user. Also,
at the time when a user app subscribes to this event, if
there is no data to be sent or retransmit, the stack will
immediately send up this notification. The notification
format is struct sctp_sender_dry_event.
SCTP_SEND_FAILED_EVENT
If SCTP cannot deliver a message, it can return back the
message as a notification if the SCTP_SEND_FAILED_EVENT
event is enabled. The notification format is struct
sctp_send_failed_event.
To set or get a SCTP socket option, call getsockopt(2) to read or
setsockopt(2) to write the option with the option level argument
set to SOL_SCTP. Note that all these macros and structures
described for parameters are defined in
/usr/include/netinet/sctp.h, and for one-to-one style sockets a
specified assoc_id works the same as SCTP_FUTURE_ASSOC.
SCTP_RTOINFO.
This option is used to get or set the protocol parameters
used to initialize and bound retransmission timeout(RTO).
The parameter type is struct sctp_rtoinfo, for reading and
writing. srto_assoc_id is a specified assoc_id or
SCTP_FUTURE_ASSOC.
Default: srto_max=sysctl_net.sctp.rto_max,
srto_min=sysctl_net.sctp.rto_min,
srto_initial=sysctl_net.sctp.rto_initial.
SCTP_ASSOCINFO
This option is used to both examine and set various
association and endpoint parameters.
The parameter type is struct sctp_assocparams, for reading
and writing. sasoc_assoc_id is a specified assoc_id or
SCTP_FUTURE_ASSOC. Note that some fields of this structure
are for reading only:
struct sctp_assocparams {
sctp_assoc_t sasoc_assoc_id;
__u16 sasoc_asocmaxrxt; (RW)
__u16 sasoc_number_peer_destinations;
(R)
__u32 sasoc_peer_rwnd; (R)
__u32 sasoc_local_rwnd; (R)
__u32 sasoc_cookie_life; (RW)
};
Default:
sasoc_asocmaxrxt=sysctl_net.sctp.association_max_retrans,
sasoc_cookie_life=sysctl_net.sctp.valid_cookie_life.
SCTP_INITMSG
This option is used to get or set the protocol parameters
for the default association initialization.
The parameter type is struct sctp_initmsg, for reading and
writing.
Default: sinit_num_ostreams=10, sinit_max_instreams=10,
sinit_max_attempts=sysctl_net.sctp.max_init_retransmits,
sinit_max_init_timeo=sysctl_net.sctp.rto_max.
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.
The parameter type is int boolean, for reading and writing.
Default: 0.
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
within a period.
The parameter type is int(seconds), for reading and
writing. 0 indicates that no automatic close of any
associations should be performed.
Default: sysctl_net.sctp.max_autoclose.
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 parameter type is struct sctp_setpeerprim, for writing
only. sspp_assoc_id is a specified assoc_id.
Default: the 1st local address added. Require:
SCTP_ASCONF_SUPPORTED.
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 parameter type is struct sctp_prim, for writing only.
ssp_assoc_id is a specified assoc_id.
Default: the 1st peer address added. Require:
SCTP_ASCONF_SUPPORTED.
SCTP_DISABLE_FRAGMENTS
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.
The parameter type is int boolean, for reading and writing.
Default: 0.
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 parameter type is struct sctp_paddrparams, for reading
and writing. spp_address is a specified transport address
or 0, spp_assoc_id is a specified assoc_id or
SCTP_FUTURE_ASSOC.
Default: hbinterval=sysctl_net.sctp.hb_interval,
pathmaxrxt=sysctl_net.sctp.path_max_retrans,
pathmtu=dev/route's,
sackdelay=sysctl_net.sctp.sack_timeout,
param_flags=HB_ENABLE|PMTUD_ENABLE|SACKDELAY_ENABLE,
flowlabel=0, dscp=0.
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 option has been obsoleted by
SCTP_DEFAULT_SNDINFO.
The parameter type is struct sctp_sndrcvinfo. For reading,
sinfo_assoc_id is a specified assoc_id or
SCTP_FUTURE_ASSOC. For writing, sinfo_assoc_id is a
specified assoc_id or SCTP_{FUTURE|CURRENT|ALL}_ASSOC.
Default: default_stream=0, default_flags=0, default_ppid=0,
default_context=0, default_timetolive=0.
SCTP_EVENTS
This socket option is used to specify various notifications
and ancillary data the user wishes to receive. This option
has been obsoleted by SCTP_EVENT.
The parameter type is struct sctp_event_subscribe, for
reading and writing.
Default: 0.
SCTP_I_WANT_MAPPED_V4_ADDR
This socket option is used to turn 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.
The parameter type is int boolean, for reading and writing.
Default: 1.
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. 0
indicates the user is NOT limiting fragmentation and only
the PMTU will effect SCTP's choice of DATA chunk size.
The parameter type is struct sctp_assoc_value, for reading
and writing. assoc_id is a specified assoc_id or
SCTP_FUTURE_ASSOC.
Default: 0(no limit).
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.
The parameter type is struct sctp_status, for reading only.
sstat_assoc_id is a specified assoc_id.
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.
The parameter type is struct sctp_paddrinfo, for reading
only. spinfo_address is a specified transport address,
sas_assoc_id is a specified assoc_id or SCTP_FUTURE_ASSOC.
SCTP_GET_ASSOC_STATS
Applications can retrieve current statistics about an
association, including SACKs sent and received, SCTP
packets sent and received.
The parameter type is struct sctp_assoc_stats, for reading
only. sas_assoc_id is a specified assoc_id.
SCTP_DELAYED_ACK, SCTP_DELAYED_ACK_TIME, SCTP_DELAYED_SACK
These options will affect the way delayed SACKs are
performed. They allow the application to get or set the
delayed SACK time, in milliseconds, and also allow changing
the delayed SACK frequency. Changing the frequency to 1
disables the delayed SACK algorithm. Note that if
sack_delay or sack_freq is 0 when setting this option, the
current values will remain unchanged.
The parameter type is struct sctp_sack_info. For reading,
sack_assoc_id is a specified assoc_id or SCTP_FUTURE_ASSOC.
For writing, sack_assoc_id is a specified assoc_id or
SCTP_{FUTURE|CURRENT|ALL}_ASSOC.
Default: sackdelay=sysctl_net.sctp.sack_timeout,sackfreq=2.
SCTP_CONTEXT
This option allows the setting, on an association basis, of
a default context that will be received on reading messages
from the peer. This is especially helpful for an
application when using one-to-many style sockets to keep
some reference to an internal state machine that is
processing messages on the association. Note that the
setting of this value only affects received messages from
the peer and does not affect the value that is saved with
outbound messages.
The parameter type is struct sctp_assoc_value. For reading,
assoc_id is a specified assoc_id or SCTP_FUTURE_ASSOC. For
writing, assoc_id is a specified assoc_id or
SCTP_{FUTURE|CURRENT|ALL}_ASSOC.
Default: 0.
SCTP_FRAGMENT_INTERLEAVE
Fragmented interleave controls how the presentation of
messages occurs for the message receiver. There are three
levels of fragment interleave defined: level 0:
SCTP_FRAGMENT_INTERLEAVE = 0; level 1:
SCTP_FRAGMENT_INTERLEAVE = 1; level 2:
SCTP_FRAGMENT_INTERLEAVE = 1 & SCTP_INTERLEAVING_SUPPORTED
= 1.
The parameter type is int boolean, for reading and writing.
Default: 0.
SCTP_PARTIAL_DELIVERY_POINT
This option will set or get the SCTP partial delivery
point. This point is the size of a message where the
partial delivery API will be invoked to help free up rwnd
space for the peer. Setting this to a lower value will
cause partial deliveries to happen more often. This option
expects an integer that sets or gets the partial delivery
point in bytes. Note also that the call will fail if the
user attempts to set this value larger than the socket
receive buffer size. Note that any single message having a
length smaller than or equal to the SCTP partial delivery
point will be delivered in a single read call as long as
the user-provided buffer is large enough to hold the
message.
The parameter type is uint32_t, for reading and writing.
Default: 0.
SCTP_MAX_BURST
This option will allow a user to change the maximum burst
of packets that can be emitted by this association.
The parameter type is struct sctp_assoc_value. For reading,
assoc_id is a specified assoc_id or SCTP_FUTURE_ASSOC. For
writing, assoc_id is a specified assoc_id or
SCTP_{FUTURE|CURRENT|ALL}_ASSOC.
Default: sysctl_net.sctp.max_burst.
SCTP_AUTH_CHUNK
This option adds a chunk type that the user is requesting
to be received only in an authenticated way, and it only
affects the future associations.
The parameter type is struct sauth_chunk, for writing only.
Default: no chunks. Require: SCTP_AUTH_SUPPORTED. RFC:
RFC4895.
SCTP_HMAC_IDENT
This option gets or sets the list of Hashed Message
Authentication Code (HMAC) algorithms that the local
endpoint requires the peer to use.
The parameter type is struct sctp_hmacalgo, for reading and
writing. shmac_idents can include
SCTP_AUTH_HMAC_ID_{SHA1|SHA256}.
Default: SCTP_AUTH_HMAC_ID_SHA1. Require:
SCTP_AUTH_SUPPORTED.
SCTP_AUTH_KEY
This option will set a shared secret key that is used to
build an association shared key.
The parameter type is struct sctp_authkey, for writing
only. sca_assoc_id is a specified assoc_id or
SCTP_{FUTURE|CURRENT|ALL}_ASSOC.
Default: null_key. Require: SCTP_AUTH_SUPPORTED.
SCTP_AUTH_ACTIVE_KEY
This option will get or set the active shared key to be
used to build the association shared key.
The parameter type is struct sctp_authkeyid, for writing
only. scact_assoc_id is a specified assoc_id or
SCTP_{FUTURE|CURRENT|ALL}_ASSOC.
Default: 0. Require: SCTP_AUTH_SUPPORTED.
SCTP_AUTH_DEACTIVATE_KEY
This set option indicates that the application will no
longer send user messages using the indicated key
identifier.
The parameter type is struct sctp_authkeyid, for writing
only. scact_assoc_id is a specified assoc_id or
SCTP_{FUTURE|CURRENT|ALL}_ASSOC.
Require: SCTP_AUTH_SUPPORTED.
SCTP_AUTH_DELETE_KEY
This set option will delete an SCTP association's shared
secret key that has been deactivated.
The parameter type is struct sctp_authkeyid, for writing
only. scact_assoc_id is a specified assoc_id or
SCTP_{FUTURE|CURRENT|ALL}_ASSOC.
Require: SCTP_AUTH_SUPPORTED.
SCTP_PEER_AUTH_CHUNKS
This option gets a list of chunk types for a specified
association that the peer requires to be received
authenticated only.
The parameter type is struct sctp_authchunks, for reading
only. gauth_assoc_id is a specified assoc_id.
Require: SCTP_AUTH_SUPPORTED.
SCTP_LOCAL_AUTH_CHUNKS
This option gets a list of chunk types for a specified
association that the local endpoint requires to be received
authenticated only.
The parameter type is struct sctp_authchunks, for reading
only. gauth_assoc_id is a specified assoc_id or
SCTP_FUTURE_ASSOC.
Require: SCTP_AUTH_SUPPORTED.
SCTP_GET_ASSOC_NUMBER
This option gets the current number of associations that
are attached to a one-to-many style socket. Note that this
number is only a snapshot. This means that the number of
associations may have changed when the caller gets back the
option result.
The parameter type is uint32_t, for reading only.
SCTP_GET_ASSOC_ID_LIST
This option gets the current list of SCTP association
identifiers of the SCTP associations handled by a one-to-
many style socket. It uses struct sctp_assoc_ids and must
provide a large enough buffer to hold all association
identifiers. If the buffer is too small, an error must be
returned. The user can use the SCTP_GET_ASSOC_NUMBER socket
option to get an idea of how large the buffer has to be.
The parameter type is struct sctp_assoc_ids, for reading
only.
SCTP_EXPOSE_POTENTIALLY_FAILED_STATE, SCTP_EXPOSE_PF_STATE
Applications can control the exposure of the PF path state
in the SCTP_PEER_ADDR_CHANGE event, and if pf_expose is not
'enabled', no notification will be sent for a transport
state change to SCTP_PF. It also affects the
SCTP_GET_PEER_ADDR_INFO socket option, and if pf_expose is
'disabled', users can not access the transport info via
SCTP_GET_PEER_ADDR_INFO option.
The parameter type is struct sctp_assoc_value, for reading
and writing. assoc_id is a specified assoc_id or
SCTP_FUTURE_ASSOC.
Default: sysctl_net.sctp.pf_expose.
SCTP_PEER_ADDR_THLDS
Applications can control the SCTP-PF behavior by getting or
setting the number of consecutive timeouts before a peer
address is considered PF or unreachable..
The parameter type is struct sctp_paddrthlds, for reading
and writing. spt_address is a specified transport address
or 0, spt_assoc_id is a specified assoc_id or
SCTP_FUTURE_ASSOC.
Default: pathmaxrxt=sysctl_net.sctp.path_max_retrans,
ps_retrans=sysctl_net.sctp.ps_retrans.
SCTP_PEER_ADDR_THLDS_V2
Similar to SCTP_PEER_ADDR_THLDS, but it can also be used by
applications to set and get the number of timeouts before
the primary path is changed automatically by the Primary
Path Switchover function.
The parameter type is struct sctp_paddrthlds_v2, for
reading and writing. spt_address is a specified transport
address or 0, spt_assoc_id is a specified assoc_id or
SCTP_FUTURE_ASSOC.
Default: pathmaxrxt=sysctl_net.sctp.path_max_retrans,
ps_retrans=sysctl_net.sctp.ps_retrans,
pf_retrans=sysctl_net.sctp.pf_retrans.
SCTP_RECVRCVINFO
Setting this option specifies that SCTP_RCVINFO (SCTP
receive information about a received message) is returned
as ancillary data by recvmsg(). See CONTROL MSGS for more
details.
The parameter type is int, for reading and writing.
Default: 0.
SCTP_RECVNXTINFO
Setting this option specifies that SCTP_NXTINFO (SCTP
receive information of the next message) is returned as
ancillary data by recvmsg(). See CONTROL MSGS for details.
The parameter type is int, for reading and writing.
Default: 0.
SCTP_DEFAULT_SNDINFO
This option obsoletes SCTP_DEFAULT_SEND_PARAM.
The parameter type is struct sctp_sndinfo. For reading,
snd_assoc_id is a specified assoc_id or SCTP_FUTURE_ASSOC.
For writing, snd_assoc_id is a specified assoc_id or
SCTP_{FUTURE|CURRENT|ALL}_ASSOC.
Default: default_stream=0, default_flags=0, default_ppid=0,
default_context=0.
SCTP_REUSE_PORT
This option is similar to the socket level option
SO_REUSEADDR, besides only supports one-to-one style SCTP
sockets and must not be used after calling bind() or
sctp_bindx().
The parameter type is int, for reading and writing.
Default: 0.
SCTP_SOCKOPT_BINDX_ADD
This option allows the user to bind a specific subset of
addresses or, if the SCTP extension ASCONF is supported
(see SCTP_ASCONF_SUPPORTED), add specific addresses. The
API sctp_bindx() is based on this.
The parameter type is struct sockaddr[], for writing only.
SCTP_SOCKOPT_BINDX_REM
Similar to SCTP_SOCKOPT_BINDX_ADD, but delete specific
addresses. The API sctp_bindx() is based on this.
The parameter type is struct sockaddr[], for writing only.
SCTP_SOCKOPT_PEELOFF
This option branches off an UDP type association into a
separate socket returned back to users. The API
sctp_peeloff() is based on this option.
The parameter type is sctp_peeloff_arg_t, for reading only.
associd is a specified assoc_id.
SCTP_SOCKOPT_PEELOFF_FLAGS
Peel off an UDP type association from a socket similar to
SCTP_SOCKOPT_PEELOFF option, but it allows the flags like
O_CLOEXEC and O_NONBLOCK to be used when creating the new
socket. The API sctp_peeloff_flags() is based on this
option.
The parameter type is sctp_peeloff_flags_arg_t, for reading
only. associd is a specified assoc_id.
SCTP_SOCKOPT_CONNECTX_OLD
This option allows a user to specify multiple addresses at
which a peer can be reached, and the kernel stack will use
the list of addresses to set up the association. The API
sctp_connectx() is based on this option.
The parameter type is struct sockaddr[], for writing only.
SCTP_SOCKOPT_CONNECTX
Similar to SCTP_SOCKOPT_CONNECTX_OLD, but it returns the
new assoc's id. The API sctp_connectx2() is based on this
option.
The parameter type is struct sockaddr[], for writing only.
The new assoc's id is passed to users by the return value.
SCTP_SOCKOPT_CONNECTX3
Similar to SCTP_SOCKOPT_CONNECTX, but it uses different
type parameter. The API sctp_connectx3() is based on this
option.
The parameter type is struct sctp_getaddrs_old, for reading
only. assoc_id is set to the new assoc's id by kernel and
passed to users.
SCTP_GET_PEER_ADDRS
This option is used to gets all peer addresses in an
association. The API sctp_getpaddrs() is based on this
option.
The parameter type is struct sctp_getaddrs, for reading
only. assoc_id is a specified assoc_id.
SCTP_GET_LOCAL_ADDRS
This option is used to get all local addresses in an
association. The API sctp_getladdrs() is based on this
option.
The parameter type is struct sctp_getaddrs, for reading
only. assoc_id is a specified assoc_id or
SCTP_FUTURE_ASSOC.
SCTP_ADAPTATION_LAYER
This option requests that the local endpoint set the
specified Adaptation Layer Indication parameter for all
future INIT and INIT-ACK exchanges.
The parameter type is struct sctp_setadaptation, for
reading and writing.
Default: 0.
SCTP_EVENT
This option obsoletes SCTP_EVENTS socket option, and it can
set or get one specific type of event for a specified
association.
The parameter type is struct sctp_event. For reading,
se_assoc_id is a specified assoc_id or SCTP_FUTURE_ASSOC.
For writing, se_assoc_id is a specified assoc_id or
SCTP_{FUTURE|CURRENT|ALL}_ASSOC. se_type can be one of enum
sctp_sn_type.
Default: 0.
SCTP_PR_SUPPORTED
This socket option allows the enabling or disabling of the
negotiation of PR-SCTP support for future associations.
The parameter type is struct sctp_assoc_value. For reading,
assoc_id is a specified assoc_id or SCTP_FUTURE_ASSOC. For
writing, assoc_id is SCTP_FUTURE_ASSOC.
Default: sysctl_net.sctp.prsctp_enable. RFC: RFC7496.
SCTP_DEFAULT_PRINFO
This option sets and gets the default parameters for PR-
SCTP.
The parameter type is struct sctp_default_prinfo. For
reading, pr_assoc_id is a specified assoc_id or
SCTP_FUTURE_ASSOC. For writing, pr_assoc_id is a specified
assoc_id or SCTP_{FUTURE|CURRENT|ALL}_ASSOC. pr_policy can
be SCTP_PR_SCTP_{NONE|TTL|RTX|PRIO}.
Default: SCTP_PR_SCTP_NONE. Require: SCTP_DEFAULT_PRINFO.
SCTP_PR_ASSOC_STATUS
This option is used to get Association-Specific PR-SCTP
Status.
The parameter type is struct sctp_prstatus, for reading
only. sprstat_assoc_id is a specified assoc_id,
sprstat_policy can be SCTP_PR_SCTP_{TTL|RTX|PRIO|ALL}.
SCTP_PR_STREAM_STATUS
This option is used to get Stream-Specific PR-SCTP Status.
The parameter type is struct sctp_prstatus, for reading
only. sprstat_assoc_id is a specified assoc_id,
sprstat_policy can be SCTP_PR_SCTP_{TTL|RTX|PRIO|ALL}.
SCTP_RECONFIG_SUPPORTED
Enable the Stream Reconfiguration(RECONF) for the future
associations. For different type of requests enabling, see
SCTP_ENABLE_STREAM_RESET option.
The parameter type is struct sctp_assoc_value. For reading,
assoc_id is a specified assoc_id or SCTP_FUTURE_ASSOC. For
writing, assoc_id is SCTP_FUTURE_ASSOC.
Default: sysctl_net.sctp.reconf_enable. RFC: RFC6525.
SCTP_ENABLE_STREAM_RESET
This option allows a user to control whether the kernel
processes or denies incoming requests in RECONF chunks.
The parameter type is struct sctp_assoc_value. For reading,
assoc_id is a specified assoc_id or SCTP_FUTURE_ASSOC. For
writing, assoc_id is a specified assoc_id or
SCTP_{FUTURE|CURRENT|ALL}_ASSOC. assoc_value can be
SCTP_ENABLE_{RESET_STREAM_REQ|RESET_ASSOC_REQ|CHANGE_ASSOC_REQ}.
Default: 0. Require: SCTP_RECONFIG_SUPPORTED.
SCTP_RESET_STREAMS
This option allows the user to request the reset of
incoming and/or outgoing streams.
The parameter type is struct sctp_reset_streams, for
writing only. srs_assoc_id is a specified assoc_id.
Require: SCTP_ENABLE_STREAM_RESET.
SCTP_RESET_ASSOC
This option allows a user to request the reset of the
SSN/TSN.
The parameter type is sctp_assoc_t, for writing only. It is
a specified assoc_id.
Require: SCTP_ENABLE_STREAM_RESET.
SCTP_ADD_STREAMS
This option allows a user to request the addition of a
number of incoming and/or outgoing streams.
The parameter type is struct sctp_add_streams, for writing
only. sas_assoc_id is a specified assoc_id.
Require: SCTP_ENABLE_STREAM_RESET.
SCTP_STREAM_SCHEDULER
This option is used to select a stream scheduler for data
sending.
The parameter type is struct sctp_assoc_value. For reading,
assoc_id is a specified assoc_id or SCTP_FUTURE_ASSOC. For
writing, assoc_id is a specified assoc_id or
SCTP_{FUTURE|CURRENT|ALL}_ASSOC. assoc_value can be
SCTP_SS_{FCFS|PRIO|RR|FC|WFQ}.
Default: SCTP_SS_FCFS. RFC: RFC8260.
SCTP_STREAM_SCHEDULER_VALUE
Some stream schedulers require additional information to be
set for individual streams.
The parameter type is struct sctp_assoc_value. For reading,
assoc_id is a specified assoc_id. For writing, assoc_id is
a specified assoc_id or SCTP_CURRENT_ASSOC.
Require: SCTP_STREAM_SCHEDULER.
SCTP_INTERLEAVING_SUPPORTED
This socket option allows the enabling or disabling of the
negotiation of user message interleaving support for future
associations.
The parameter type is struct sctp_assoc_value. For reading,
assoc_id is a specified assoc_id or SCTP_FUTURE_ASSOC. For
writing, assoc_id is SCTP_FUTURE_ASSOC.
Default: sysctl_net.sctp.intl_enable. Require:
SCTP_FRAGMENT_INTERLEAVE. RFC: RFC8260.
SCTP_ASCONF_SUPPORTED
Enable the Dynamic Address Reconfiguration(ASCONF) for the
future associations.
The parameter type is struct sctp_assoc_value. For reading,
assoc_id is a specified assoc_id or SCTP_FUTURE_ASSOC. For
writing, assoc_id is SCTP_FUTURE_ASSOC.
Default: sysctl_net.sctp.addip_enable. RFC: RFC5061.
SCTP_AUTO_ASCONF
This option will enable or disable the use of the automatic
generation of ASCONF chunks to add and delete addresses to
an existing association. Note that this option has two
caveats, namely a) it only affects sockets that are bound
to all addresses available to the SCTP stack, and b) the
system administrator may have an overriding control that
turns the ASCONF feature off no matter what setting the
socket option may have.
The parameter type is int boolean, for reading and writing.
Default: sysctl_net.sctp.default_auto_asconf.
SCTP_AUTH_SUPPORTED
Enable AUTH for the future associations.
The parameter type is struct sctp_assoc_value. For reading,
assoc_id is a specified assoc_id or SCTP_FUTURE_ASSOC. For
writing, ssoc_id is SCTP_FUTURE_ASSOC.
Default: sysctl_net.sctp.auth_enable. RFC: RFC4895.
SCTP_ECN_SUPPORTED
Enable ECN for the future associations.
The parameter type is struct sctp_assoc_value. For reading,
assoc_id is a specified assoc_id or SCTP_FUTURE_ASSOC. For
writing, assoc_id is SCTP_FUTURE_ASSOC.
Default: sysctl_net.sctp.ecn_enable.
SCTP_REMOTE_UDP_ENCAPS_PORT
This option is used to set the encapsulation port(a remote
listening or dest port) for SCTP over UDP, which allows
SCTP traffic to pass through legacy NATs that do not
provide native SCTP support.
The parameter type is struct sctp_udpencaps, for reading
and writing. sue_address is a specified transport address
or 0, sue_assoc_id is a specified assoc_id or
SCTP_FUTURE_ASSOC.
Default: sysctl_net.sctp.encap_port. RFC: RFC6951.
SCTP_PLPMTUD_PROBE_INTERVAL
This option is used to configure the PROBE_INTERVAL for the
Packetization Layer Path MTU Discovery(PLPMTUD). It can be
set to a value >= 5000 or 0(disabled).
The parameter type is struct sctp_probeinterval, for
reading and writing. spi_address is a specified transport
address or 0, spi_assoc_id is a specified assoc_id or
SCTP_FUTURE_ASSOC.
Default: 0(disabled). RFC: RFC8899.
Sridhar Samudrala <sri@us.ibm.com>
socket(7), socket(2), ip(7), bind(2), listen(2), accept(2),
connect(2), sendmsg(2), recvmsg(2), sysctl(2), getsockopt(2),
sctp_bindx(3), sctp_connectx(3), sctp_sendmsg(3), sctp_sendv(3),
sctp_send(3), sctp_recvmsg(3), sctp_recvv(3), sctp_peeloff(3),
sctp_getladdrs(3), sctp_getpaddrs(3), sctp_opt_info(3).
RFC2960, RFC3309 for the SCTP specification.
This page is part of the lksctp-tools (Linux kernel SCTP tools)
project. Information about the project can be found at [unknown
-- if you know, please contact man-pages@man7.org] If you have a
bug report for this manual page, send it to sctp@vger.kernel.org.
This page was obtained from the project's upstream Git repository
⟨https://github.com/sctp/lksctp-tools.git⟩ on 2025-08-11. (At
that time, the date of the most recent commit that was found in
the repository was 2024-09-26.) If you discover any rendering
problems in this HTML version of the page, or you believe there is
a better or more up-to-date source for the page, or you have
corrections or improvements to the information in this COLOPHON
(which is not part of the original manual page), send a mail to
man-pages@man7.org
Linux Man Page 2005-10-25 SCTP(7)
Pages that refer to this page: sctp_bindx(3), sctp_connectx(3), sctp_getladdrs(3), sctp_getpaddrs(3), sctp_opt_info(3), sctp_peeloff(3), sctp_recvmsg(3), sctp_recvv(3), sctp_send(3), sctp_sendmsg(3), sctp_sendv(3), ip(7)
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