View Source gen_sctp (kernel v10.1.2)
Interface to SCTP sockets.
This module provides functions for communicating over SCTP sockets. The implementation assumes that the OS kernel supports SCTP (RFC 2960) through the user-level Sockets API Extensions.
During development, this implementation was tested on:
- Linux Fedora Core 5.0 (kernel 2.6.15-2054 or later is needed)
- Solaris 10, 11
During OTP adaptation it was tested on:
- SUSE Linux Enterprise Server 10 (x86_64) kernel 2.6.16.27-0.6-smp, with lksctp-tools-1.0.6
- Briefly on Solaris 10
- SUSE Linux Enterprise Server 10 Service Pack 1 (x86_64) kernel 2.6.16.54-0.2.3-smp with lksctp-tools-1.0.7
- FreeBSD 8.2
This module was written for one-to-many style sockets (type seqpacket
).
With the addition of peeloff/2
, one-to-one style sockets (type stream
)
were introduced.
Record definitions for this module can be found using:
-include_lib("kernel/include/inet_sctp.hrl").
These record definitions use the "new" spelling 'adaptation', not the deprecated 'adaption', regardless of which spelling the underlying C API uses.
SCTP Socket Options
The set of admissible SCTP socket options is by construction orthogonal
to the sets of TCP, UDP, and generic inet
options. Here are only
options listed that are allowed for SCTP sockets.
Options can be set on the socket when calling open/1,2
,
and changed when calling connect/4,5
or
by calling inet:setopts/2
. They can be retrieved using inet:getopts/2
.
{mode, list|binary} | list | binary
- Determines the type of data returned fromrecv/1,2
or in active mode data messages.If
false
(passive mode, the default), the caller must do an explicitrecv
call to retrieve the available data from the socket.If
true|once|N
(active modes) received data or events are sent to the owning process. Seeopen/0..2
for the message format.If
true
(fully active mode) there is no flow control.Note
Note that this can cause the message queue to overflow causing for example the virtual machine to run out of memory and crash.
If
once
, only one message is automatically placed in the message queue, and the mode resets to passive. This provides flow control and the possibility for the receiver to listen for incoming SCTP data interleaved with other inter-process messages.If
active
is specified as an integerN
in the range -32768 to 32767 (inclusive), that number is added to the socket's data messages counter. If the result of the addition is negative, the counter is set to0
. Once the counter reaches0
, either through the delivery of messages or by being explicitly set withinet:setopts/2
, the socket mode resets to passive ({active, false}
). When a socket in{active, N}
mode transitions to passive mode, the message{sctp_passive, Socket}
is sent to the controlling process to notify that if it wants to receive more data messages from the socket, it must callinet:setopts/2
to set the socket back into an active mode.
{tos, integer()}
- Sets the Type-Of-Service field on the IP datagrams that are sent, to the specified value. This effectively determines a prioritization policy for the outbound packets. The acceptable values are system-dependent.{priority, integer()}
- A protocol-independent equivalent oftos
above. Setting priority implies settingtos
as well.{dontroute, true|false}
- Defaults tofalse
. Iftrue
, the kernel does not send packets through any gateway, but only sends them to directly connected hosts.{reuseaddr, true|false}
- Defaults tofalse
. Iftrue
, the local binding address{IP,Port}
of the socket can be reused immediately. No waiting in stateCLOSE_WAIT
is performed (can be required for some types of servers).{sndbuf, integer()}
- The size, in bytes, of the OS kernel send buffer for this socket. Sending errors would occur for datagrams larger thanval(sndbuf)
. Setting this option also adjusts the size of the driver buffer (seebuffer
above).{recbuf, integer()}
- The size, in bytes, of the OS kernel receive buffer for this socket. Sending errors would occur for datagrams larger thanval(recbuf)
. Setting this option also adjusts the size of the driver buffer (seebuffer
above).
{non_block_send, boolean()}
- A send call that would otherwise block (hang), will instead immediately return with e.g.{error, eagain}
if this option has been set totrue
. Defaults tofalse
.{sctp_module, module()}
- Overrides which callback module is used. Defaults toinet_sctp
for IPv4 andinet6_sctp
for IPv6.{sctp_rtoinfo, #sctp_rtoinfo{}}
#sctp_rtoinfo{ assoc_id = assoc_id(), initial = integer(), max = integer(), min = integer() }
Determines retransmission time-out parameters, in milliseconds, for the association(s) specified by
assoc_id
.assoc_id = 0
(default) indicates the whole endpoint. See RFC 2960 and Sockets API Extensions for SCTP for the exact semantics of the field values.{sctp_associnfo, #sctp_assocparams{}}
#sctp_assocparams{ assoc_id = assoc_id(), asocmaxrxt = integer(), number_peer_destinations = integer(), peer_rwnd = integer(), local_rwnd = integer(), cookie_life = integer() }
Determines association parameters for the association(s) specified by
assoc_id
.assoc_id = 0
(default) indicates the whole endpoint. See Sockets API Extensions for SCTP for the discussion of their semantics. Rarely used.{sctp_initmsg, #sctp_initmsg{}}
#sctp_initmsg{ num_ostreams = integer(), max_instreams = integer(), max_attempts = integer(), max_init_timeo = integer() }
Determines the default parameters that this socket tries to negotiate with its peer while establishing an association with it. Is to be set after
open/*
but before the firstconnect/*
.#sctp_initmsg{}
can also be used as ancillary data with the first call ofsend/*
to a new peer (when a new association is created).num_ostreams
- Number of outbound streamsmax_instreams
- Maximum number of inbound streamsmax_attempts
- Maximum retransmissions while establishing an associationmax_init_timeo
- Time-out, in milliseconds, for establishing an association
{sctp_autoclose, integer() >= 0}
- Determines the time, in seconds, after which an idle association is automatically closed.0
means that the association is never automatically closed.{sctp_nodelay, true|false}
- Turns on|off the Nagle algorithm for merging small packets into larger ones. This improves throughput at the expense of latency.{sctp_disable_fragments, true|false}
- Iftrue
, induces an error on an attempt to send a message larger than the current PMTU size (which would require fragmentation/reassembling). Notice that message fragmentation does not affect the logical atomicity of its delivery; this option is provided for performance reasons only.{sctp_i_want_mapped_v4_addr, true|false}
- Turns on|off automatic mapping of IPv4 addresses into IPv6 ones (if the socket address family isAF_INET6
).{sctp_maxseg, integer()}
- Determines the maximum chunk size if message fragmentation is used. If0
, the chunk size is limited by the Path MTU only.{sctp_primary_addr, #sctp_prim{}}
#sctp_prim{ assoc_id = assoc_id(), addr = {IP, Port} } IP = ip_address() Port = port_number()
For the association specified by
assoc_id
,{IP,Port}
must be one of the peer addresses. This option determines that the specified address is treated by the local SCTP stack as the primary address of the peer.{sctp_set_peer_primary_addr, #sctp_setpeerprim{}}
#sctp_setpeerprim{ assoc_id = assoc_id(), addr = {IP, Port} } IP = ip_address() Port = port_number()
When set, informs the peer to use
{IP, Port}
as the primary address of the local endpoint for the association specified byassoc_id
.{sctp_adaptation_layer, #sctp_setadaptation{}}
#sctp_setadaptation{ adaptation_ind = integer() }
When set, requests that the local endpoint uses the value specified by
adaptation_ind
as the Adaptation Indication parameter for establishing new associations. For details, see RFC 2960 and Sockets API Extensions for SCTP.{sctp_peer_addr_params, #sctp_paddrparams{}}
#sctp_paddrparams{ assoc_id = assoc_id(), address = {IP, Port}, hbinterval = integer(), pathmaxrxt = integer(), pathmtu = integer(), sackdelay = integer(), flags = list() } IP = ip_address() Port = port_number()
Determines various per-address parameters for the association specified by
assoc_id
and the peer addressaddress
(the SCTP protocol supports multi-homing, so more than one address can correspond to a specified association).hbinterval
- Heartbeat interval, in millisecondspathmaxrxt
- Maximum number of retransmissions before this address is considered unreachable (and an alternative address is selected)pathmtu
- Fixed Path MTU, if automatic discovery is disabled (seeflags
below)sackdelay
- Delay, in milliseconds, for SAC messages (if the delay is enabled, seeflags
below)flags
- The following flags are available:hb_enable
- Enables heartbeathb_disable
- Disables heartbeathb_demand
- Initiates heartbeat immediatelypmtud_enable
- Enables automatic Path MTU discoverypmtud_disable
- Disables automatic Path MTU discoverysackdelay_enable
- Enables SAC delaysackdelay_disable
- Disables SAC delay
{sctp_default_send_param, #sctp_sndrcvinfo{}}
#sctp_sndrcvinfo{ stream = integer(), ssn = integer(), flags = list(), ppid = integer(), context = integer(), timetolive = integer(), tsn = integer(), cumtsn = integer(), assoc_id = assoc_id() }
#sctp_sndrcvinfo{}
is used both in this socket option, and as ancillary data while sending or receiving SCTP messages. When set as an option, it provides default values for subsequentsend
calls on the association specified byassoc_id
.assoc_id = 0
(default) indicates the whole endpoint.The following fields typically must be specified by the sender:
sinfo_stream
- Stream number (0-base) within the association to send the messages through;sinfo_flags
- The following flags are recognised:unordered
- The message is to be sent unorderedaddr_over
- The address specified insend
overwrites the primary peer addressabort
- Aborts the current association without flushing any unsent dataeof
- Gracefully shuts down the current association, with flushing of unsent data
Other fields are rarely used. For complete information, see RFC 2960 and Sockets API Extensions for SCTP.
{sctp_events, #sctp_event_subscribe{}}
#sctp_event_subscribe{ data_io_event = true | false, association_event = true | false, address_event = true | false, send_failure_event = true | false, peer_error_event = true | false, shutdown_event = true | false, partial_delivery_event = true | false, adaptation_layer_event = true | false }
This option determines which SCTP Events that are to be received (through
recv/*
) along with the data. The only exception isdata_io_event
, which enables or disables receiving of#sctp_sndrcvinfo{}
ancillary data, not events. By default, all flags exceptadaptation_layer_event
are enabled, althoughsctp_data_io_event
andassociation_event
are used by the driver itself and not exported to the user level.{sctp_delayed_ack_time, #sctp_assoc_value{}}
#sctp_assoc_value{ assoc_id = assoc_id(), assoc_value = integer() }
Rarely used. Determines the ACK time (specified by
assoc_value
, in milliseconds) for the specified association or the whole endpoint ifassoc_value = 0
(default).{sctp_status, #sctp_status{}}
#sctp_status{ assoc_id = assoc_id(), state = atom(), rwnd = integer(), unackdata = integer(), penddata = integer(), instrms = integer(), outstrms = integer(), fragmentation_point = integer(), primary = #sctp_paddrinfo{} }
This option is read-only. It determines the status of the SCTP association specified by
assoc_id
. The following are the possible values ofstate
(the state designations are mostly self-explanatory):sctp_state_empty
- Default. Means that no other state is active.sctp_state_closed
sctp_state_cookie_wait
sctp_state_cookie_echoed
sctp_state_established
sctp_state_shutdown_pending
sctp_state_shutdown_sent
sctp_state_shutdown_received
sctp_state_shutdown_ack_sent
Semantics of the other fields:
sstat_rwnd
- Current receiver window size of the associationsstat_unackdata
- Number of unacked data chunkssstat_penddata
- Number of data chunks pending receiptsstat_instrms
- Number of inbound streamssstat_outstrms
- Number of outbound streamssstat_fragmentation_point
- Message size at which SCTP fragmentation occurssstat_primary
- Information on the current primary peer address (see below for the format of#sctp_paddrinfo{}
)
{sctp_get_peer_addr_info, #sctp_paddrinfo{}}
#sctp_paddrinfo{ assoc_id = assoc_id(), address = {IP, Port}, state = inactive | active | unconfirmed, cwnd = integer(), srtt = integer(), rto = integer(), mtu = integer() } IP = ip_address() Port = port_number()
This option is read-only. It determines the parameters specific to the peer address specified by
address
within the association specified byassoc_id
. Fieldaddress
fmust be set by the caller; all other fields are filled in on return. Ifassoc_id = 0
(default), theaddress
is automatically translated into the corresponding association ID. This option is rarely used. For the semantics of all fields, see RFC 2960 and Sockets API Extensions for SCTP.
SCTP Examples
Example of an Erlang SCTP server that receives SCTP messages and prints them on the standard output:
-module(sctp_server).
-export([server/0,server/1,server/2]).
-include_lib("kernel/include/inet.hrl").
-include_lib("kernel/include/inet_sctp.hrl").
server() ->
server(any, 2006).
server([Host,Port]) when is_list(Host), is_list(Port) ->
{ok, #hostent{h_addr_list = [IP|_]}} = inet:gethostbyname(Host),
io:format("~w -> ~w~n", [Host, IP]),
server([IP, list_to_integer(Port)]).
server(IP, Port) when is_tuple(IP) orelse IP == any orelse IP == loopback,
is_integer(Port) ->
{ok,S} = gen_sctp:open(Port, [{recbuf,65536}, {ip,IP}]),
io:format("Listening on ~w:~w. ~w~n", [IP,Port,S]),
ok = gen_sctp:listen(S, true),
server_loop(S).
server_loop(S) ->
case gen_sctp:recv(S) of
{error, Error} ->
io:format("SCTP RECV ERROR: ~p~n", [Error]);
Data ->
io:format("Received: ~p~n", [Data])
end,
server_loop(S).
Example of an Erlang SCTP client interacting with the above server.
Note that in this example the client creates an association with
the server with 5 outbound streams. Therefore, sending of "Test 0"
over stream 0 succeeds, but sending of "Test 5"
over stream 5 fails.
The client then abort
s the association, which results in that
the corresponding event is received on the server side.
-module(sctp_client).
-export([client/0, client/1, client/2]).
-include_lib("kernel/include/inet.hrl").
-include_lib("kernel/include/inet_sctp.hrl").
client() ->
client([localhost]).
client([Host]) ->
client(Host, 2006);
client([Host, Port]) when is_list(Host), is_list(Port) ->
client(Host,list_to_integer(Port)),
init:stop().
client(Host, Port) when is_integer(Port) ->
{ok,S} = gen_sctp:open(),
{ok,Assoc} = gen_sctp:connect
(S, Host, Port, [{sctp_initmsg,#sctp_initmsg{num_ostreams=5}}]),
io:format("Connection Successful, Assoc=~p~n", [Assoc]),
io:write(gen_sctp:send(S, Assoc, 0, <<"Test 0">>)),
io:nl(),
timer:sleep(10000),
io:write(gen_sctp:send(S, Assoc, 5, <<"Test 5">>)),
io:nl(),
timer:sleep(10000),
io:write(gen_sctp:abort(S, Assoc)),
io:nl(),
timer:sleep(1000),
gen_sctp:close(S).
A simple Erlang SCTP client that uses the connect_init
API:
-module(ex3).
-export([client/4]).
-include_lib("kernel/include/inet.hrl").
-include_lib("kernel/include/inet_sctp.hrl").
client(Peer1, Port1, Peer2, Port2)
when is_tuple(Peer1), is_integer(Port1), is_tuple(Peer2), is_integer(Port2) ->
{ok,S} = gen_sctp:open(),
SctpInitMsgOpt = {sctp_initmsg,#sctp_initmsg{num_ostreams=5}},
ActiveOpt = {active, true},
Opts = [SctpInitMsgOpt, ActiveOpt],
ok = gen_sctp:connect(S, Peer1, Port1, Opts),
ok = gen_sctp:connect(S, Peer2, Port2, Opts),
io:format("Connections initiated~n", []),
client_loop(S, Peer1, Port1, undefined, Peer2, Port2, undefined).
client_loop(S, Peer1, Port1, AssocId1, Peer2, Port2, AssocId2) ->
receive
{sctp, S, Peer1, Port1, {_Anc, SAC}}
when is_record(SAC, sctp_assoc_change), AssocId1 == undefined ->
io:format("Association 1 connect result: ~p. AssocId: ~p~n",
[SAC#sctp_assoc_change.state,
SAC#sctp_assoc_change.assoc_id]),
client_loop(S, Peer1, Port1, SAC#sctp_assoc_change.assoc_id,
Peer2, Port2, AssocId2);
{sctp, S, Peer2, Port2, {_Anc, SAC}}
when is_record(SAC, sctp_assoc_change), AssocId2 == undefined ->
io:format("Association 2 connect result: ~p. AssocId: ~p~n",
[SAC#sctp_assoc_change.state, SAC#sctp_assoc_change.assoc_id]),
client_loop(S, Peer1, Port1, AssocId1, Peer2, Port2,
SAC#sctp_assoc_change.assoc_id);
{sctp, S, Peer1, Port1, Data} ->
io:format("Association 1: received ~p~n", [Data]),
client_loop(S, Peer1, Port1, AssocId1,
Peer2, Port2, AssocId2);
{sctp, S, Peer2, Port2, Data} ->
io:format("Association 2: received ~p~n", [Data]),
client_loop(S, Peer1, Port1, AssocId1,
Peer2, Port2, AssocId2);
Other ->
io:format("Other ~p~n", [Other]),
client_loop(S, Peer1, Port1, AssocId1,
Peer2, Port2, AssocId2)
after 5000 ->
ok
end.
See Also
gen_tcp
, gen_udp
, inet
,
RFC 2960 (Stream Control
Transmission Protocol),
Sockets API Extensions for SCTP
Summary
Types: Exported data types
Association ID.
SCTP Socket Option name and value, to set.
SCTP Socket Option name, to get.
SCTP Socket Option name and value, what you get.
Socket identifier returned from open/*
.
Functions
Abort an association.
Close an SCTP socket.
Establish an association with a peer.
Establish an association with a peer.
Start establishing an association with a peer.
Start establishing an association with a peer.
Start establishing an association with a peer (multiple addresses).
Equivalent to connectx_init(Socket, Addrs, Port, Opts, infinity)
.
Start establishing an association with a peer (multiple addresses).
Change the controlling process (owner) of a socket.
Terminate an association gracefully.
Translate an error number into a string or atom.
Make an SCTP socket listen to incoming associations.
Create an SCTP socket.
Equivalent to open([{port, Port} | Opts])
.
Branch off an association into a new socket of type stream
.
Equivalent to recv(Socket, infinity)
.
Receive a Data
message.
Send a Data
message, full-featured.
Send a data message.
Types: Exported data types
-type assoc_id() :: term().
Association ID.
An opaque term returned in, for example, #sctp_paddr_change{}
, which
identifies an association for an SCTP socket. The term is opaque except for the
special value 0
, which has a meaning such as "the whole endpoint" or "all
future associations".
-type option() :: elementary_option() | record_option().
SCTP Socket Option name and value, to set.
-type option_name() :: elementary_option_name() | record_option() | ro_option().
SCTP Socket Option name, to get.
-type option_value() :: elementary_option() | record_option() | ro_option().
SCTP Socket Option name and value, what you get.
-type sctp_socket() :: port().
Socket identifier returned from open/*
.
Types: Internal data types
-type elementary_option() :: {active, true | false | once | -32768..32767} | {buffer, non_neg_integer()} | {non_block_send, boolean()} | {debug, boolean()} | {dontroute, boolean()} | {exclusiveaddruse, boolean()} | {high_msgq_watermark, pos_integer()} | {linger, {boolean(), non_neg_integer()}} | {low_msgq_watermark, pos_integer()} | {mode, list | binary} | list | binary | {priority, non_neg_integer()} | {recbuf, non_neg_integer()} | {reuseaddr, boolean()} | {reuseport, boolean()} | {reuseport_lb, boolean()} | {ipv6_v6only, boolean()} | {sndbuf, non_neg_integer()} | {sctp_autoclose, non_neg_integer()} | {sctp_disable_fragments, boolean()} | {sctp_i_want_mapped_v4_addr, boolean()} | {sctp_maxseg, non_neg_integer()} | {sctp_nodelay, boolean()} | {tos, non_neg_integer()} | {tclass, non_neg_integer()} | {ttl, non_neg_integer()} | {recvtos, boolean()} | {recvtclass, boolean()} | {recvttl, boolean()}.
-type elementary_option_name() ::
active | buffer | non_block_send | debug | dontroute | exclusiveaddruse |
high_msgq_watermark | linger | low_msgq_watermark | mode | priority | recbuf | reuseaddr |
reuseport | reuseport_lb | ipv6_v6only | sctp_autoclose | sctp_disable_fragments |
sctp_i_want_mapped_v4_addr | sctp_maxseg | sctp_nodelay | sndbuf | tos | tclass | ttl |
recvtos | recvtclass | recvttl.
-type record_option() :: {sctp_adaptation_layer, #sctp_setadaptation{adaptation_ind :: term()}} | {sctp_associnfo, #sctp_assocparams{assoc_id :: term(), asocmaxrxt :: term(), number_peer_destinations :: term(), peer_rwnd :: term(), local_rwnd :: term(), cookie_life :: term()}} | {sctp_default_send_param, #sctp_sndrcvinfo{stream :: term(), ssn :: term(), flags :: term(), ppid :: term(), context :: term(), timetolive :: term(), tsn :: term(), cumtsn :: term(), assoc_id :: term()}} | {sctp_delayed_ack_time, #sctp_assoc_value{assoc_id :: term(), assoc_value :: term()}} | {sctp_events, #sctp_event_subscribe{data_io_event :: term(), association_event :: term(), address_event :: term(), send_failure_event :: term(), peer_error_event :: term(), shutdown_event :: term(), partial_delivery_event :: term(), adaptation_layer_event :: term(), authentication_event :: term()}} | {sctp_initmsg, #sctp_initmsg{num_ostreams :: term(), max_instreams :: term(), max_attempts :: term(), max_init_timeo :: term()}} | {sctp_peer_addr_params, #sctp_paddrparams{assoc_id :: term(), address :: term(), hbinterval :: term(), pathmaxrxt :: term(), pathmtu :: term(), sackdelay :: term(), flags :: term()}} | {sctp_primary_addr, #sctp_prim{assoc_id :: term(), addr :: term()}} | {sctp_rtoinfo, #sctp_rtoinfo{assoc_id :: term(), initial :: term(), max :: term(), min :: term()}} | {sctp_set_peer_primary_addr, #sctp_setpeerprim{assoc_id :: term(), addr :: term()}}.
-type ro_option() :: {sctp_get_peer_addr_info, #sctp_paddrinfo{assoc_id :: term(), address :: term(), state :: term(), cwnd :: term(), srtt :: term(), rto :: term(), mtu :: term()}} | {sctp_status, #sctp_status{assoc_id :: term(), state :: term(), rwnd :: term(), unackdata :: term(), penddata :: term(), instrms :: term(), outstrms :: term(), fragmentation_point :: term(), primary :: term()}}.
Functions
-spec abort(Socket, Assoc) -> ok | {error, inet:posix()} when Socket :: sctp_socket(), Assoc :: #sctp_assoc_change{state :: term(), error :: term(), outbound_streams :: term(), inbound_streams :: term(), assoc_id :: term()}.
Abort an association.
Abnormally terminates the association specified by Assoc
,
without flushing unsent data. The socket itself remains open.
Other associations opened on this socket are still valid,
and the socket can be used in new associations.
-spec close(Socket) -> ok | {error, inet:posix()} when Socket :: sctp_socket().
Close an SCTP socket.
Closes the socket and all associations on it. The unsent data is flushed
as for eof/2
. The close/1
call is blocking
depending of the value of the linger
socket [option]. If it is false
or the linger time-out expires,
the call returns and unsent data is flushed in the background.
-spec connect(Socket, SockAddr, Opts) -> {ok, #sctp_assoc_change{state :: comm_up, error :: term(), outbound_streams :: term(), inbound_streams :: term(), assoc_id :: term()}} | {error, #sctp_assoc_change{state :: cant_assoc, error :: term(), outbound_streams :: term(), inbound_streams :: term(), assoc_id :: term()}} | {error, inet:posix()} when Socket :: sctp_socket(), SockAddr :: socket:sockaddr_in() | socket:sockaddr_in6(), Opts :: [Opt :: option()].
Equivalent to connect(Socket, SockAddr, Opts, infinity)
.
-spec connect(Socket, SockAddr, Opts, Timeout) -> {ok, #sctp_assoc_change{state :: comm_up, error :: term(), outbound_streams :: term(), inbound_streams :: term(), assoc_id :: term()}} | {error, #sctp_assoc_change{state :: cant_assoc, error :: term(), outbound_streams :: term(), inbound_streams :: term(), assoc_id :: term()}} | {error, inet:posix()} when Socket :: sctp_socket(), SockAddr :: socket:sockaddr_in() | socket:sockaddr_in6(), Opts :: [Opt :: option()], Timeout :: timeout(); (Socket, Addr, Port, Opts) -> {ok, #sctp_assoc_change{state :: comm_up, error :: term(), outbound_streams :: term(), inbound_streams :: term(), assoc_id :: term()}} | {error, #sctp_assoc_change{state :: cant_assoc, error :: term(), outbound_streams :: term(), inbound_streams :: term(), assoc_id :: term()}} | {error, inet:posix()} when Socket :: sctp_socket(), Addr :: inet:ip_address() | inet:hostname(), Port :: inet:port_number(), Opts :: [Opt :: option()].
Establish an association with a peer.
With arguments Addr
and Port
, equivalent to
connect(Socket, Addr, Port, Opts, infinity)
.
With arguments SockAddr
and Opts
(since OTP 24.3), equivalent to
connect(Socket, Addr, Port, Opts, Timeout)
where Addr
and Port
are extracted from SockAddr
.
-spec connect(Socket, Addr, Port, Opts, Timeout) -> {ok, #sctp_assoc_change{state :: comm_up, error :: term(), outbound_streams :: term(), inbound_streams :: term(), assoc_id :: term()}} | {error, #sctp_assoc_change{state :: cant_assoc, error :: term(), outbound_streams :: term(), inbound_streams :: term(), assoc_id :: term()}} | {error, inet:posix()} when Socket :: sctp_socket(), Addr :: inet:ip_address() | inet:hostname(), Port :: inet:port_number(), Opts :: [Opt :: option()], Timeout :: timeout().
Establish an association with a peer.
Establishes a new association for socket Socket
, with the peer
(SCTP server socket) specified by Addr
and Port
.
Timeout
, is expressed in milliseconds.
A socket can be associated with multiple peers.
The socket has to be of type seqpacket
.
Warning
Using a value of
Timeout
less than the maximum time taken by the OS to establish an association (around 4.5 minutes if the default values from RFC 4960 are used), can result in inconsistent or incorrect return values. This is especially relevant for associations sharing the sameSocket
(that is, source address and port), as the controlling process blocks untilconnect/*
returns.connect_init/*
provides an alternative without this limitation.
#sctp_assoc_change{}
The result of connect/*
is an #sctp_assoc_change{}
event that contains,
in particular, the new Association ID:
l
#sctp_assoc_change{
state = atom(),
error = integer(),
outbound_streams = integer(),
inbound_streams = integer(),
assoc_id = assoc_id()
}
The number of outbound and inbound streams for the association
can be set by giving an sctp_initmsg
option to connect
as in:
connect(Socket, Ip, Port>,
[{sctp_initmsg,#sctp_initmsg{num_ostreams=OutStreams,
max_instreams=MaxInStreams}}])
All options Opt
are set on the socket before the association is attempted.
If an option record has undefined field values, the options record
is first read from the socket for those values. In effect,
Opt
option records only need to define field values to change
before connecting.
The returned outbound_streams
and inbound_streams
are the number of
stream on the socket. These can be different from the requested values
(OutStreams
and MaxInStreams
, respectively), if the peer
requires lower values.
state
can have the following values:
comm_up
- Association is successfully established. This indicates a successful completion ofconnect
.cant_assoc
- The association cannot be established (connect/*
failure).
Other states do not normally occur in the output from connect/*
.
Rather, they can occur in #sctp_assoc_change{}
events received
instead of data from recv/*
calls or socket messages.
All of them indicate losing the association because of various
error conditions, and are listed here for the sake of completeness:
comm_lost
restart
shutdown_comp
The field error
can provide more detailed diagnostics. Its value
can be converted into a string using error_string/1
.
-spec connect_init(Socket, SockAddr, Opts) -> ok | {error, inet:posix()} when Socket :: sctp_socket(), SockAddr :: socket:sockaddr_in() | socket:sockaddr_in6(), Opts :: [option()].
Equivalent to connect_init(Socket, SockAddr, Opts, infinity)
.
-spec connect_init(Socket, SockAddr, Opts, Timeout) -> ok | {error, inet:posix()} when Socket :: sctp_socket(), SockAddr :: socket:sockaddr_in() | socket:sockaddr_in6(), Opts :: [option()], Timeout :: timeout(); (Socket, Addr, Port, Opts) -> ok | {error, inet:posix()} when Socket :: sctp_socket(), Addr :: inet:ip_address() | inet:hostname(), Port :: inet:port_number(), Opts :: [option()].
Start establishing an association with a peer.
With arguments Addr
and Port
, equivalent to
connect_init(Socket, Addr, Port, Opts, infinity)
.
With arguments SockAddr
and Opts
(since OTP 24.3), equivalent to
connect_init(Socket, Addr, Port, Opts, Timeout)
where Addr
and Port
are extracted from SockAddr
.
connect_init(Socket, Addr, Port, Opts, Timeout)
View Source (since OTP R13B04)-spec connect_init(Socket, Addr, Port, Opts, Timeout) -> ok | {error, inet:posix()} when Socket :: sctp_socket(), Addr :: inet:ip_address() | inet:hostname(), Port :: inet:port_number(), Opts :: [option()], Timeout :: timeout().
Start establishing an association with a peer.
Initiates a new association for socket Socket
, with the peer
(SCTP server socket) specified by Addr
and Port
.
The fundamental difference between this API and connect/*
is that
the return value is that of the underlying OS connect(2)
system call.
If ok
is returned, the operation has been succesfully initiated,
and the final result result of the association establishment
is sent to the socket owner (controlling process) as an
#sctp_assoc_change{}
event.
The socket owner must be prepared to receive this, the
recv/*
call has to be polled, depending on the value
of the active option.
The parameters are as described for connect/*
,
except the Timeout
value since for this function, the time-out only
applies to the name resolving of Addr
when it is a inet:hostname/0
.
-spec connectx_init(Socket, SockAddrs, Opts) -> {ok, assoc_id()} | {error, inet:posix()} when Socket :: sctp_socket(), SockAddrs :: [{inet:ip_address(), inet:port_number()} | inet:family_address() | socket:sockaddr_in() | socket:sockaddr_in6()], Opts :: [option()].
Start establishing an association with a peer (multiple addresses).
Similar to connectx_init/5
except using socket addresses, and not having a
Timeout
. Since the addresses do not need lookup and the connect is
non-blocking this call returns immediately.
The value of each socket address port
must be the same or zero.
At least one socket address must have a non-zero port
-spec connectx_init(Socket, Addrs, Port, Opts) -> {ok, assoc_id()} | {error, inet:posix()} when Socket :: sctp_socket(), Addrs :: [inet:ip_address() | inet:hostname()], Port :: inet:port_number() | atom(), Opts :: [option()].
Equivalent to connectx_init(Socket, Addrs, Port, Opts, infinity)
.
connectx_init(Socket, Addrs, Port, Opts, Timeout)
View Source (since OTP 25.0)-spec connectx_init(Socket, Addrs, Port, Opts, Timeout) -> {ok, assoc_id()} | {error, inet:posix()} when Socket :: sctp_socket(), Addrs :: [inet:ip_address() | inet:hostname()], Port :: inet:port_number() | atom(), Opts :: [option()], Timeout :: timeout().
Start establishing an association with a peer (multiple addresses).
Initiates a new association for socket Socket
, with the peer
(SCTP server socket) specified by Addrs
and Port
.
This API is similar to connect_init/*
except the underlying OS
sctp_connectx(3)
system call is used, that accepts multiple
destination addresses.
If successful, the association ID is returned which will be received in a
subsequent #sctp_assoc_change{}
event.
The parameters are as described in connect_init/5
Note
This API allows the OS to use all Addrs when establishing an association, but does not guarantee it will. Therefore, if the connection fails, the user may want to rotate the order of addresses for a subsequent call.
-spec controlling_process(Socket, Pid) -> ok | {error, Reason} when Socket :: sctp_socket(), Pid :: pid(), Reason :: closed | not_owner | badarg | inet:posix().
Change the controlling process (owner) of a socket.
Assigns a new controlling process Pid
to Socket
.
See gen_udp:controlling_process/2
.
-spec eof(Socket, Assoc) -> ok | {error, Reason} when Socket :: sctp_socket(), Assoc :: #sctp_assoc_change{state :: term(), error :: term(), outbound_streams :: term(), inbound_streams :: term(), assoc_id :: term()}, Reason :: term().
Terminate an association gracefully.
Gracefully terminates the association specified by Assoc
, flushing
all unsent data. The socket itself remains open. Other associations
opened on this socket are still valid. The socket can be used
in new associations.
Translate an error number into a string or atom.
Translates an SCTP error number from, for example, #sctp_remote_error{}
or #sctp_send_failed{}
into an explanatory string, or into
one of the atoms ok
for no error, or unknown_error
for an unrecognized integer.
-spec listen(Socket, IsServer) -> ok | {error, Reason} when Socket :: sctp_socket(), IsServer :: boolean(), Reason :: term(); (Socket, Backlog) -> ok | {error, Reason} when Socket :: sctp_socket(), Backlog :: integer(), Reason :: term().
Make an SCTP socket listen to incoming associations.
The socket will listen on the IP address(es) and port number it is bound to.
For type seqpacket
, sockets (the default), the argumentIsServer
must be a boolean/0
. In contrast to stream
sockets, there is
no listening queue length. If IsServer
is true
, the socket accepts
new associations, that is, it becomes an SCTP server socket.
For type stream
sockets, the argument Backlog
sets
the backlog queue length just like for TCP.
-spec open() -> {ok, Socket} | {error, inet:posix()} when Socket :: sctp_socket().
Equivalent to open([])
.
-spec open(Port) -> {ok, Socket} | {error, inet:posix()} when Port :: inet:port_number(), Socket :: sctp_socket(); (Opts) -> {ok, Socket} | {error, inet:posix()} when Opts :: [Opt], Opt :: {ifaddr, IP | SockAddr} | {ip, IP} | {port, Port} | inet:address_family() | {type, SockType} | {netns, file:filename_all()} | {bind_to_device, binary()} | option(), IP :: inet:ip_address() | any | loopback, SockAddr :: socket:sockaddr_in() | socket:sockaddr_in6(), Port :: inet:port_number(), SockType :: seqpacket | stream, Socket :: sctp_socket().
Create an SCTP socket.
With argument Port
,
equivalent toopen([{port, Port}]
.
Creates an SCTP socket and binds it to the local addresses specified by all
{ip,IP}
(or synonymously {ifaddr,IP}
) options (this feature is called
SCTP multi-homing). The default IP
and Port
are any
and 0
,
meaning bind to all local addresses on any free port.
It is also possible to use {ifaddr, SockAddr}
, in which case it takes
precedence over the ip
and port
options. These options can however
be used to update the address and port of ifaddr (if they occur
after ifaddr in the options list), although this is not recommended.
Other options:
inet6
- Sets up the socket for IPv6.inet
- Sets up the socket for IPv4. This is the default.
A default set of socket options is used.
In particular, the socket is opened in binary
and passive mode, with SockType seqpacket
,
and with reasonably large kernel and driver
buffers.
When the socket is in passive mode,
data can be received through the recv/1,2
calls.
When the socket is in active mode, data received data is delivered to the controlling process as messages:
{sctp, Socket, FromIP, FromPort, {AncData, Data}}
See recv/1,2
for a description of the message fields.
Note
This message format unfortunately differs slightly from the
gen_udp
message format with ancillary data, and from therecv/1,2
return tuple format.
Equivalent to open([{port, Port} | Opts])
.
-spec peeloff(Socket, Assoc) -> {ok, NewSocket} | {error, Reason} when Socket :: sctp_socket(), Assoc :: #sctp_assoc_change{state :: term(), error :: term(), outbound_streams :: term(), inbound_streams :: term(), assoc_id :: term()} | assoc_id(), NewSocket :: sctp_socket(), Reason :: term().
Branch off an association into a new socket of type stream
.
The existing association Assoc
in the socket Socket
(that has to
be of type seqpacket
; one-to-many style) is branched off into
a new socket NewSocket
of type stream
(one-to-one style).
The existing association argument Assoc
can be a
#sctp_assoc_change{}
record as
returned from, for example, recv/*
, connect/*
,
or from a listening socket in active mode.
It can also be just the field assoc_id
integer/0
from such a record.
-spec recv(Socket) -> {ok, {FromIP, FromPort, AncData, Data}} | {error, Reason} when Socket :: sctp_socket(), FromIP :: inet:ip_address(), FromPort :: inet:port_number(), AncData :: [#sctp_sndrcvinfo{stream :: term(), ssn :: term(), flags :: term(), ppid :: term(), context :: term(), timetolive :: term(), tsn :: term(), cumtsn :: term(), assoc_id :: term()} | inet:ancillary_data()], Data :: binary() | string() | #sctp_sndrcvinfo{stream :: term(), ssn :: term(), flags :: term(), ppid :: term(), context :: term(), timetolive :: term(), tsn :: term(), cumtsn :: term(), assoc_id :: term()} | #sctp_assoc_change{state :: term(), error :: term(), outbound_streams :: term(), inbound_streams :: term(), assoc_id :: term()} | #sctp_paddr_change{addr :: term(), state :: term(), error :: term(), assoc_id :: term()} | #sctp_adaptation_event{adaptation_ind :: term(), assoc_id :: term()}, Reason :: inet:posix() | #sctp_send_failed{flags :: term(), error :: term(), info :: term(), assoc_id :: term(), data :: term()} | #sctp_paddr_change{addr :: term(), state :: term(), error :: term(), assoc_id :: term()} | #sctp_pdapi_event{indication :: term(), assoc_id :: term()} | #sctp_remote_error{error :: term(), assoc_id :: term(), data :: term()} | #sctp_shutdown_event{assoc_id :: term()}.
Equivalent to recv(Socket, infinity)
.
-spec recv(Socket, Timeout) -> {ok, {FromIP, FromPort, AncData, Data}} | {error, Reason} when Socket :: sctp_socket(), Timeout :: timeout(), FromIP :: inet:ip_address(), FromPort :: inet:port_number(), AncData :: [#sctp_sndrcvinfo{stream :: term(), ssn :: term(), flags :: term(), ppid :: term(), context :: term(), timetolive :: term(), tsn :: term(), cumtsn :: term(), assoc_id :: term()} | inet:ancillary_data()], Data :: binary() | string() | #sctp_sndrcvinfo{stream :: term(), ssn :: term(), flags :: term(), ppid :: term(), context :: term(), timetolive :: term(), tsn :: term(), cumtsn :: term(), assoc_id :: term()} | #sctp_assoc_change{state :: term(), error :: term(), outbound_streams :: term(), inbound_streams :: term(), assoc_id :: term()} | #sctp_paddr_change{addr :: term(), state :: term(), error :: term(), assoc_id :: term()} | #sctp_adaptation_event{adaptation_ind :: term(), assoc_id :: term()}, Reason :: inet:posix() | #sctp_send_failed{flags :: term(), error :: term(), info :: term(), assoc_id :: term(), data :: term()} | #sctp_paddr_change{addr :: term(), state :: term(), error :: term(), assoc_id :: term()} | #sctp_pdapi_event{indication :: term(), assoc_id :: term()} | #sctp_remote_error{error :: term(), assoc_id :: term(), data :: term()} | #sctp_shutdown_event{assoc_id :: term()}.
Receive a Data
message.
Receives the Data
message from any association of the socket.
If the receive times out, {error,timeout}
is returned. The default
time-out is infinity
. FromIP
and FromPort
indicate the address
of the sender.
AncData
is a list of ancillary data items received with the main Data
.
This list can be empty, or contain a single
#sctp_sndrcvinfo{}
record,
if receiving ancillary data is enabled
(see option sctp_events
).
Per default, it is enabled, as such ancillary data provides an easy way
to determine the association and stream over which the message was received.
(An alternative way is to get the association ID from FromIP
and FromPort
using socket option
sctp_get_peer_addr_info
,
but this does still not give the stream number).
AncData
may also contain ancillary data
from the socket options
recvtos
,
recvtclass
or
recvttl
, if that is supported for the socket
by the platform.
The Data
received can, depending on the socket mode
be a binary/0
or a list/0
of bytes (integers in the range
0
through 255
), or it can be an SCTP event.
Possible SCTP events
#sctp_paddr_change{ addr = {ip_address(),port()}, state = atom(), error = integer(), assoc_id = assoc_id() }
Indicates change of the status of the IP address of the peer specified by
addr
within associationassoc_id
. Possible values ofstate
(mostly self-explanatory) include:addr_unreachable
addr_available
addr_removed
addr_added
addr_made_prim
addr_confirmed
In case of an error (for example,
addr_unreachable
), the fielderror
provides more diagnostics. In such cases, event#sctp_paddr_change{}
is automatically converted into anerror
term returned byrecv
. Theerror
field value can be converted into a string usingerror_string/1
.#sctp_send_failed{ flags = true | false, error = integer(), info = #sctp_sndrcvinfo{}, assoc_id = assoc_id() data = binary() }
The sender can receive this event if a send operation fails.
flags
- A Boolean specifying if the data has been transmitted over the wire.error
- Provides extended diagnostics, useerror_string/1
.info
- The original#sctp_sndrcvinfo{}
record used in the failedsend/*
.data
- The whole original data chunk attempted to be sent.
In the current implementation of the Erlang/SCTP binding, this event is internally converted into an
error
term returned byrecv/*
.#sctp_adaptation_event{ adaptation_ind = integer(), assoc_id = assoc_id() }
Delivered when a peer sends an adaptation layer indication parameter (configured through option
sctp_adaptation_layer
). Notie that with the current implementation of the Erlang/SCTP binding, this event is disabled by default.#sctp_pdapi_event{ indication = sctp_partial_delivery_aborted, assoc_id = assoc_id() }
A partial delivery failure. In the current implementation of the Erlang/SCTP binding, this event is internally converted into an
error
term returned byrecv/*
.
-spec send(Socket, SndRcvInfo, Data) -> ok | {error, Reason} when Socket :: sctp_socket(), SndRcvInfo :: #sctp_sndrcvinfo{stream :: term(), ssn :: term(), flags :: term(), ppid :: term(), context :: term(), timetolive :: term(), tsn :: term(), cumtsn :: term(), assoc_id :: term()}, Data :: binary() | iolist(), Reason :: term().
Send a Data
message, full-featured.
Sends the Data
message with all sending parameters from a
#sctp_sndrcvinfo{}
record.
This way, the user can specify the PPID (passed to the remote end)
and context (passed to the local SCTP layer), which can be used,
for example, for error identification. However, such a fine grained
user control is rarely required. The function send/4
is sufficient for most applications.
Note
Send is normally blocking, but if the socket option
non_block_send
is set to true, the function will return with e.g. {error, eagain} in the case when the function would otherwise block. It is then up to the user to try again later.
-spec send(Socket, Assoc, Stream, Data) -> ok | {error, Reason} when Socket :: sctp_socket(), Assoc :: #sctp_assoc_change{state :: term(), error :: term(), outbound_streams :: term(), inbound_streams :: term(), assoc_id :: term()} | assoc_id(), Stream :: integer(), Data :: binary() | iolist(), Reason :: term().
Send a data message.
Sends a Data
message on the association Assoc
and Stream
.
Assoc
can be specified with a
#sctp_assoc_change{}
record
from an association establishment, or as the assoc_id/0
integer/0
field value.
Note
Send is normally blocking, but if the socket option
non_block_send
is set to true, the function will return with e.g. {error, eagain} in the case when the function would otherwise block. It is then up to the user to try again later.