View Source gen_sctp (kernel v9.3)
Functions for communicating with sockets using the SCTP protocol.
This module provides functions for communicating with sockets using the SCTP protocol. 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. Only options listed here are
allowed for SCTP sockets. Options can be set on the socket using
open/1,2
or inet:setopts/2
, retrieved using inet:getopts/2
.
Options can be changed when calling connect/4,5
.
{mode, list|binary}
or justlist
orbinary
- Determines the type of data returned fromrecv/1,2
.{active, true|false|once|N}
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
(full 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 after that the mode is automatically reset to passive. This provides flow control and the possibility for the receiver to listen for its 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 counting of data messages to be delivered to the controlling process. If the result of the addition is negative, the count is set to0
. Once the count reaches0
, either through the delivery of messages or by being explicitly set withinet:setopts/2
, the socket mode is automatically reset to passive ({active, false}
). When a socket in this active mode transitions to passive mode, the message{sctp_passive, Socket}
is sent to the controlling process to notify it 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, only sends them to directly connected hosts.{reuseaddr, true|false}
- Defaults tofalse
. If true, the local binding address{IP,Port}
of the socket can be reused immediately. No waiting in stateCLOSE_WAIT
is performed (can be required for high-throughput 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).{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 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. Notice 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
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".
One of the SCTP Socket Options used to set an option.
An option name or one of the SCTP Socket Options used to get an option.
One of the SCTP Socket Options as returned when getting an option.
Socket identifier returned from open/*
.
Functions
Abnormally terminates the association specified by Assoc
, without flushing of
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.
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.
Initiates a new association for socket Socket
, with the peer (SCTP server
socket) specified by Addrs
and Port
.
Assigns a new controlling process Pid
to Socket
. Same implementation as
gen_udp:controlling_process/2
.
Gracefully terminates the association specified by Assoc
, with flushing of 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.
Translates an SCTP error number from, for example, #sctp_remote_error{}
or
#sctp_send_failed{}
into an explanatory string, or one of the atoms ok
for
no error or undefined
for an unrecognized error.
Sets up a socket to listen on the IP address and port number it is bound to.
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.
Branches off an existing association Assoc
in a socket Socket
of type
seqpacket
(one-to-many style) into a new socket NewSocket
of type stream
(one-to-one style).
Equivalent to recv/2
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.
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 level of user control is rarely required. The function
send/4
is sufficient for most applications.
Sends a Data
message over an existing association and specified stream.
Types: Exported data types
-type assoc_id() :: term().
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().
One of the SCTP Socket Options used to set an option.
-type option_name() :: elementary_option_name() | record_option() | ro_option().
An option name or one of the SCTP Socket Options used to get an option.
-type option_value() :: elementary_option() | record_option() | ro_option().
One of the SCTP Socket Options as returned when getting an option.
-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()} | {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 | 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()}.
Abnormally terminates the association specified by Assoc
, without flushing of
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().
Closes the socket and all associations on it. The unsent data is flushed as in
eof/2
. The close/1
call is blocking or otherwise depending of
the value of the linger
socket
option. If close
does not linger or linger time-out
expires, the call returns and the 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()].
-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()].
This is conceptually the same as connect/5
,
only with the difference that we use a socket address, socket:sockaddr_in/0
or socket:sockaddr_in6/0
instead of an address (inet:ip_address() or
inet:hostname()) and port-number.
-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().
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.
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.
The result of connect/*
is an
#sctp_assoc_change{}
event that contains, in particular, the new
Association ID:
#sctp_assoc_change{
state = atom(),
error = integer(),
outbound_streams = integer(),
inbound_streams = integer(),
assoc_id = assoc_id()
}
The number of outbound and inbound streams 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 define
field values to change before connecting.
The returned outbound_streams
and inbound_streams
are the stream numbers 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 in
recv/*
calls. 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
Field error
can provide more detailed diagnostics. The error
field 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()].
-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()].
This is conceptually the same as
connect_init/5
, only with the
difference that we use a socket address, socket:sockaddr_in/0
or
socket:sockaddr_in6/0
instead of an address (inet:ip_address() or
inet:hostname()) and port-number.
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().
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 result of the association establishment is received by the calling
process as an #sctp_assoc_change{}
event. The calling process must be prepared to receive this, or poll for it
using recv/*
, depending on the value of the active option.
The parameters are as described in connect/*
, except the
Timeout
value.
The timer associated with Timeout
only supervises IP resolution of Addr
.
-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()].
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()].
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().
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.
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().
Assigns a new controlling process Pid
to Socket
. Same implementation as
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().
Gracefully terminates the association specified by Assoc
, with flushing of 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.
Translates an SCTP error number from, for example, #sctp_remote_error{}
or
#sctp_send_failed{}
into an explanatory string, or one of the atoms ok
for
no error or undefined
for an unrecognized error.
-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().
Sets up a socket to listen on the IP address and port number it is bound to.
For type seqpacket
, sockets (the default) IsServer
must be true
or
false
. In contrast to TCP, there is no listening queue length in SCTP. If
IsServer
is true
, the socket accepts new associations, that is, it becomes
an SCTP server socket.
For type stream
, sockets Backlog define the backlog queue length just like in
TCP.
-spec open() -> {ok, Socket} | {error, inet:posix()} when Socket :: sctp_socket().
Equivalent to open/2
-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().
Equivalent to open/2
-spec open(Port, 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().
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.
If the socket is in passive mode data can be
received through the recv/1,2
calls.
If 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.
-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().
Branches off an existing association Assoc
in a socket Socket
of type
seqpacket
(one-to-many style) into a new socket NewSocket
of type stream
(one-to-one style).
The existing association argument Assoc
can be either 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 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/2
-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()}.
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 that can be received along with the
main Data
. This list can be empty, or contain a single
#sctp_sndrcvinfo{}
record if receiving
of such ancillary data is enabled (see option
sctp_events
). It is enabled by default, as
such ancillary data provides an easy way of determining the association and
stream over which the message is 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 produce the stream number).
AncData
may also contain ancillary data from the
socket options recvtos
,
recvtclass
or
recvttl
, if that is supported by the platform for
the socket.
The Data
received can be a binary/0
or a list/0
of bytes (integers in
the range 0 through 255) depending on the socket mode, or 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
), 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
). Notice 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().
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 level of user control is rarely required. The function
send/4
is sufficient for most applications.
-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().
Sends a Data
message over an existing association and specified stream.