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|
<?xml version="1.0" encoding="utf-8" ?>
<!DOCTYPE erlref SYSTEM "erlref.dtd">
<erlref>
<header>
<copyright>
<year>2007</year><year>2020</year>
<holder>Ericsson AB. All Rights Reserved.</holder>
</copyright>
<legalnotice>
Licensed under the Apache License, Version 2.0 (the "License");
you may not use this file except in compliance with the License.
You may obtain a copy of the License at
http://www.apache.org/licenses/LICENSE-2.0
Unless required by applicable law or agreed to in writing, software
distributed under the License is distributed on an "AS IS" BASIS,
WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
See the License for the specific language governing permissions and
limitations under the License.
</legalnotice>
<title>gen_sctp</title>
<prepared>raimo@erix.ericsson.se</prepared>
<responsible></responsible>
<docno>1</docno>
<approved></approved>
<checked></checked>
<date>2007-03-21</date>
<rev>A</rev>
<file>gen_sctp.xml</file>
</header>
<module since="">gen_sctp</module>
<modulesummary>Functions for communicating with sockets using the SCTP
protocol.</modulesummary>
<description>
<p>This module provides functions for communicating with
sockets using the SCTP protocol. The implementation assumes that
the OS kernel supports SCTP
<url href="http://www.rfc-archive.org/getrfc.php?rfc=2960">(RFC 2960)</url>
through the user-level
<url href="http://tools.ietf.org/html/draft-ietf-tsvwg-sctpsocket-13">Sockets API Extensions</url>.</p>
<p>During development, this implementation was tested on:</p>
<list type="bulleted">
<item>Linux Fedora Core 5.0 (kernel 2.6.15-2054 or later is needed)</item>
<item>Solaris 10, 11</item>
</list>
<p>During OTP adaptation it was tested on:</p>
<list type="bulleted">
<item>SUSE Linux Enterprise Server 10 (x86_64) kernel 2.6.16.27-0.6-smp,
with lksctp-tools-1.0.6</item>
<item>Briefly on Solaris 10</item>
<item>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</item>
<item>FreeBSD 8.2</item>
</list>
<p>This module was written for one-to-many style sockets
(type <c>seqpacket</c>). With the addition of
<seemfa marker="#peeloff/2"><c>peeloff/2</c></seemfa>,
one-to-one style sockets (type <c>stream</c>) were introduced.</p>
<p>Record definitions for this module can be found using:</p>
<pre>
-include_lib("kernel/include/inet_sctp.hrl").</pre>
<p>These record definitions use the "new" spelling 'adaptation',
not the deprecated 'adaption', regardless of which
spelling the underlying C API uses.</p>
</description>
<datatypes>
<datatype>
<name>assoc_id()</name>
<desc>
<p>An opaque term returned in, for example, <c>#sctp_paddr_change{}</c>,
which identifies an association for an SCTP socket. The term
is opaque except for the special value <c>0</c>, which has a
meaning such as "the whole endpoint" or "all future associations".</p>
</desc>
</datatype>
<datatype>
<name name="option"/>
<desc>
<p>One of the
<seeerl marker="#options">SCTP Socket Options</seeerl>.</p>
</desc>
</datatype>
<datatype>
<name name="option_name"/>
</datatype>
<datatype>
<name>sctp_socket()</name>
<desc>
<p>Socket identifier returned from
<seemfa marker="#open/0"><c>open/*</c></seemfa>.</p>
<marker id="exports"></marker>
</desc>
</datatype>
</datatypes>
<funcs>
<func>
<name name="abort" arity="2" since=""/>
<fsummary>Abnormally terminate the association specified by
<c>Assoc</c>, without flushing of unsent data.</fsummary>
<desc>
<p>Abnormally terminates the association specified by
<c><anno>Assoc</anno></c>, 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.</p>
</desc>
</func>
<func>
<name name="close" arity="1" since=""/>
<fsummary>Close the socket and all associations on it.</fsummary>
<desc>
<p>Closes the socket and all associations on it. The unsent
data is flushed as in <seemfa marker="#eof/2"><c>eof/2</c></seemfa>.
The <c>close/1</c> call
is blocking or otherwise depending of the value of
the <seeerl marker="inet#option-linger"><c>linger</c></seeerl>
socket <seeerl marker="#options">option</seeerl>.
If <c>close</c> does not linger or linger time-out expires,
the call returns and the data is flushed in the background.</p>
</desc>
</func>
<func>
<name name="connect" arity="4" since=""/>
<fsummary>Same as <c>connect(Socket, Addr, Port, Opts, infinity)</c>.</fsummary>
<desc>
<p>Same as <c>connect(<anno>Socket</anno>, <anno>Addr</anno>,
<anno>Port</anno>, <anno>Opts</anno>, infinity)</c>.</p>
</desc>
</func>
<func>
<name name="connect" arity="5" since=""/>
<fsummary>Establish a new association for socket <c>Socket</c>, with a
peer (SCTP server socket).</fsummary>
<desc>
<p>Establishes a new association for socket <c><anno>Socket</anno></c>,
with the peer (SCTP server socket) specified by
<c><anno>Addr</anno></c> and <c><anno>Port</anno></c>.
<c><anno>Timeout</anno></c>, is expressed in milliseconds.
A socket can be associated with multiple peers.</p>
<warning><p>Using a value of <c><anno>Timeout</anno></c> less than
the maximum time taken by the OS to establish an association (around
4.5 minutes if the default values from
<url href="https://tools.ietf.org/html/rfc4960">RFC 4960</url>
are used), can result
in inconsistent or incorrect return values. This is especially
relevant for associations sharing the same <c><anno>Socket</anno></c>
(that is, source address and port), as the controlling process
blocks until <c>connect/*</c> returns.
<seemfa marker="#connect_init/4"><c>connect_init/*</c></seemfa>
provides an alternative without this limitation.</p>
</warning>
<p><marker id="record-sctp_assoc_change"></marker>
The result of <c>connect/*</c> is an <c>#sctp_assoc_change{}</c>
event that contains, in particular, the new
<seetype marker="#assoc_id">Association ID</seetype>:</p>
<pre>
#sctp_assoc_change{
state = atom(),
error = integer(),
outbound_streams = integer(),
inbound_streams = integer(),
assoc_id = assoc_id()
}</pre>
<p>The number of outbound and inbound streams can be set by
giving an <c>sctp_initmsg</c> option to <c>connect</c> as in:</p>
<pre>
connect(Socket, Ip, Port>,
[{sctp_initmsg,#sctp_initmsg{num_ostreams=OutStreams,
max_instreams=MaxInStreams}}])</pre>
<p>All options <c><anno>Opt</anno></c> 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, <c><anno>Opt</anno></c> option records
only define field values to change before connecting.</p>
<p>The returned <c>outbound_streams</c> and <c>inbound_streams</c>
are the stream numbers on the socket. These can be different
from the requested values (<c>OutStreams</c> and <c>MaxInStreams</c>,
respectively) if the peer requires lower values.</p>
<p><c>state</c> can have the following values:</p>
<taglist>
<tag><c>comm_up</c></tag>
<item><p>Association is successfully established. This
indicates a successful completion of <c>connect</c>.</p></item>
<tag><c>cant_assoc</c></tag>
<item><p>The association cannot be established
(<c>connect/*</c> failure).</p></item>
</taglist>
<p>Other states do not normally occur in the output from
<c>connect/*</c>. Rather, they can occur in
<c>#sctp_assoc_change{}</c> events received instead of data in
<seemfa marker="#recv/1"><c>recv/*</c></seemfa> calls.
All of them indicate losing the association because of various error
conditions, and are listed here for the sake of completeness:</p>
<taglist>
<tag><c>comm_lost</c></tag>
<item></item>
<tag><c>restart</c></tag>
<item></item>
<tag><c>shutdown_comp</c></tag>
<item></item>
</taglist>
<p>Field <c>error</c> can provide more detailed diagnostics.
The <c>error</c> field value can be converted into a string using
<seemfa marker="#error_string/1"><c>error_string/1</c></seemfa>.</p>
</desc>
</func>
<func>
<name name="connect_init" arity="4" since="OTP R13B04"/>
<fsummary>Same as <c>connect_init(Socket, Addr, Port, Opts, infinity)</c>..</fsummary>
<desc>
<p>Same as <c>connect_init(<anno>Socket</anno>, <anno>Addr</anno>,
<anno>Port</anno>, <anno>Opts</anno>, infinity)</c>.</p>
</desc>
</func>
<func>
<name name="connect_init" arity="5" since="OTP R13B04"/>
<fsummary>Initiate a new association for socket <c>Socket</c>, with a
peer (SCTP server socket).</fsummary>
<desc>
<p>Initiates a new association for socket <c><anno>Socket</anno></c>,
with the peer (SCTP server socket) specified by
<c><anno>Addr</anno></c> and <c><anno>Port</anno></c>.</p>
<p>The fundamental difference between this API
and <c>connect/*</c> is that the return value is that of the
underlying OS <c>connect(2)</c> system call. If <c>ok</c> is returned,
the result of the association establishment is received
by the calling process as an
<seeerl marker="#record-sctp_assoc_change"><c>#sctp_assoc_change{}</c></seeerl>
event. The calling process must be prepared to receive this, or
poll for it using
<seemfa marker="#recv/1"><c>recv/*</c></seemfa>,
depending on the value of the active option.</p>
<p>The parameters are as described in
<seemfa marker="#connect/5"><c>connect/*</c></seemfa>,
except the <c><anno>Timeout</anno></c> value.</p>
<p>The timer associated with <c><anno>Timeout</anno></c> only supervises
IP resolution of <c><anno>Addr</anno></c>.</p>
</desc>
</func>
<func>
<name name="controlling_process" arity="2" since=""/>
<fsummary>Assign a new controlling process pid to the socket.</fsummary>
<desc>
<p>Assigns a new controlling process <c><anno>Pid</anno></c> to
<c><anno>Socket</anno></c>. Same implementation as
<seemfa marker="gen_udp#controlling_process/2"><c>gen_udp:controlling_process/2</c></seemfa>.
</p>
</desc>
</func>
<func>
<name name="eof" arity="2" since=""/>
<fsummary>Gracefully terminate the association specified by <c>Assoc</c>,
with flushing of all unsent data.</fsummary>
<desc>
<p>Gracefully terminates the association specified by
<c><anno>Assoc</anno></c>, 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.</p>
</desc>
</func>
<func>
<name name="error_string" arity="1" since=""/>
<fsummary>Translate an SCTP error number into a string.</fsummary>
<desc>
<p>Translates an SCTP error number from, for example,
<c>#sctp_remote_error{}</c> or <c>#sctp_send_failed{}</c> into
an explanatory string, or one of the atoms <c>ok</c> for no
error or <c>undefined</c> for an unrecognized error.</p>
</desc>
</func>
<func>
<name name="listen" arity="2" clause_i="1" since=""/>
<name name="listen" arity="2" clause_i="2" since="OTP R15B"/>
<fsummary>Set up a socket to listen.</fsummary>
<desc>
<p>Sets up a socket to listen on the IP address and port number
it is bound to.</p>
<p>For type <c>seqpacket</c>, sockets (the default)
<c><anno>IsServer</anno></c> must be <c>true</c> or <c>false</c>.
In contrast to TCP, there is no listening queue length in SCTP.
If <c><anno>IsServer</anno></c> is <c>true</c>, the socket accepts
new associations, that is, it becomes an SCTP server socket.</p>
<p>For type <c>stream</c>, sockets <anno>Backlog</anno> define
the backlog queue length just like in TCP.</p>
</desc>
</func>
<func>
<name name="open" arity="0" since=""/>
<name name="open" arity="1" clause_i="1" since=""/>
<name name="open" arity="1" clause_i="2" since=""/>
<name name="open" arity="2" since=""/>
<fsummary>Create an SCTP socket and binds it to local addresses.</fsummary>
<desc>
<p>Creates an SCTP socket and binds it to the local addresses
specified by all <c>{ip,<anno>IP</anno>}</c> (or synonymously
<c>{ifaddr,<anno>IP</anno>}</c>)
options (this feature is called SCTP multi-homing). The default
<c><anno>IP</anno></c> and <c><anno>Port</anno></c> are <c>any</c>
and <c>0</c>, meaning bind to all local addresses on any
free port.</p>
<p>Other options:</p>
<taglist>
<tag><c>inet6</c></tag>
<item>
<p>Sets up the socket for IPv6.</p>
</item>
<tag><c>inet</c></tag>
<item>
<p>Sets up the socket for IPv4. This is the default.</p>
</item>
</taglist>
<p>A default set of socket <seeerl marker="#options">options</seeerl>
is used. In particular, the socket is opened in
<seeerl marker="#option-binary">binary</seeerl> and
<seeerl marker="#option-active">passive</seeerl> mode,
with <anno>SockType</anno> <c>seqpacket</c>, and with reasonably large
<seeerl marker="inet#option-sndbuf">kernel</seeerl> and driver
<seeerl marker="inet#option-buffer">buffers</seeerl>.</p>
<p>
If the socket is in
<seeerl marker="#option-active">passive</seeerl>
mode data can be received through the
<seemfa marker="#recv/1"><c>recv/1,2</c></seemfa>
calls.
</p>
<p>
If the socket is in
<seeerl marker="#option-active">active</seeerl>
mode data received data is delivered to the controlling process
as messages:
</p>
<code type="none">
{sctp, <anno>Socket</anno>, FromIP, FromPort, {AncData, Data}}
</code>
<p>
See
<seemfa marker="#recv/1"><c>recv/1,2</c></seemfa>
for a description of the message fields.
</p>
<note>
<p>
This message format unfortunately differs slightly from the
<seemfa marker="gen_udp#open/1"><c>gen_udp</c></seemfa>
message format with ancillary data,
and from the
<seemfa marker="#recv/1"><c>recv/1,2</c></seemfa>
return tuple format.
</p>
</note>
</desc>
</func>
<func>
<name name="peeloff" arity="2" since="OTP R15B"/>
<fsummary>Peel off a type <c>stream</c> socket from a type
<c>seqpacket</c> one.</fsummary>
<desc>
<p>Branches off an existing association <c><anno>Assoc</anno></c>
in a socket <c><anno>Socket</anno></c> of type <c>seqpacket</c>
(one-to-many style) into
a new socket <c><anno>NewSocket</anno></c> of type <c>stream</c>
(one-to-one style).</p>
<p>The existing association argument <c><anno>Assoc</anno></c>
can be either a
<seeerl marker="#record-sctp_assoc_change"><c>#sctp_assoc_change{}</c></seeerl>
record as returned from, for example,
<seemfa marker="#recv/2"><c>recv/*</c></seemfa>,
<seemfa marker="#connect/5"><c>connect/*</c></seemfa>, or
from a listening socket in active mode. It can also be just
the field <c>assoc_id</c> integer from such a record.</p>
</desc>
</func>
<func>
<name name="recv" arity="1" since=""/>
<name name="recv" arity="2" since=""/>
<fsummary>Receive a message from a socket.</fsummary>
<desc>
<p>Receives the <c><anno>Data</anno></c> message from any association
of the socket.
If the receive times out, <c>{error,timeout}</c> is returned.
The default time-out is <c>infinity</c>. <c><anno>FromIP</anno></c>
and <c><anno>FromPort</anno></c> indicate the address of the
sender.</p>
<p><c><anno>AncData</anno></c> is a list of ancillary data items that
can be received along with the main <c><anno>Data</anno></c>.
This list can be empty, or contain a single
<seeerl marker="#record-sctp_sndrcvinfo"><c>#sctp_sndrcvinfo{}</c></seeerl>
record if receiving of such ancillary data is enabled (see option
<seeerl marker="#option-sctp_events"><c>sctp_events</c></seeerl>).
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
<c><anno>FromIP</anno></c> and <c><anno>FromPort</anno></c> using
socket option
<seeerl marker="#option-sctp_get_peer_addr_info"><c>sctp_get_peer_addr_info</c></seeerl>,
but this does still not produce the stream number).</p>
<p>
<c><anno>AncData</anno></c> may also contain
<seetype marker="inet#ancillary_data">
ancillary data
</seetype>
from the socket
<seetype marker="#option">options</seetype>
<seeerl marker="inet#option-recvtos"><c>recvtos</c></seeerl>,
<seeerl marker="inet#option-recvtclass"><c>recvtclass</c></seeerl>
or
<seeerl marker="inet#option-recvttl"><c>recvttl</c></seeerl>,
if that is supported by the platform for the socket.
</p>
<p>The <c><anno>Data</anno></c> received can be a <c>binary()</c>
or a <c>list()</c> of bytes (integers in the range 0 through 255)
depending on the socket mode, or an SCTP event.</p>
<marker id="sctp_events"></marker>
<p>Possible SCTP events:</p>
<list type="bulleted">
<item>
<seeerl marker="#record-sctp_sndrcvinfo"><c>#sctp_sndrcvinfo{}</c></seeerl>
</item>
<item>
<seeerl marker="#record-sctp_assoc_change"><c>#sctp_assoc_change{}</c></seeerl>
</item>
<item>
<pre>
#sctp_paddr_change{
addr = {ip_address(),port()},
state = atom(),
error = integer(),
assoc_id = assoc_id()
}</pre>
<p>Indicates change of the status of the IP address of the peer
specified by
<c>addr</c> within association <c>assoc_id</c>. Possible
values of <c>state</c> (mostly self-explanatory) include:</p>
<taglist>
<tag><c>addr_unreachable</c></tag>
<item></item>
<tag><c>addr_available</c></tag>
<item></item>
<tag><c>addr_removed</c></tag>
<item></item>
<tag><c>addr_added</c></tag>
<item></item>
<tag><c>addr_made_prim</c></tag>
<item></item>
<tag><c>addr_confirmed</c></tag>
<item></item>
</taglist>
<p>In case of an error (for example, <c>addr_unreachable</c>),
field <c>error</c> provides more diagnostics. In such cases,
event <c>#sctp_paddr_change{}</c> is automatically
converted into an <c>error</c> term returned by
<seemfa marker="#recv/1"><c>recv</c></seemfa>.
The <c>error</c> field value can be converted into a string using
<seemfa marker="#error_string/1"><c>error_string/1</c></seemfa>.
</p>
</item>
<item>
<pre>
#sctp_send_failed{
flags = true | false,
error = integer(),
info = #sctp_sndrcvinfo{},
assoc_id = assoc_id()
data = binary()
}</pre>
<p>The sender can receive this event if a send operation fails.</p>
<taglist>
<tag><c>flags</c></tag>
<item><p>A Boolean specifying if the data has been transmitted
over the wire.</p></item>
<tag><c>error</c></tag>
<item><p>Provides extended diagnostics, use
<seemfa marker="#error_string/1"><c>error_string/1</c>.</seemfa></p>
</item>
<tag><c>info</c></tag>
<item><p>The original
<seeerl marker="#record-sctp_sndrcvinfo"><c>#sctp_sndrcvinfo{}</c></seeerl>
record used in the failed
<seemfa marker="#send/3"><c>send/*</c>.</seemfa></p>
</item>
<tag><c>data</c></tag>
<item><p>The whole original data chunk attempted to be sent.</p>
</item>
</taglist>
<p>In the current implementation of the Erlang/SCTP binding,
this event is internally converted into an <c>error</c> term
returned by
<seemfa marker="#recv/1"><c>recv/*</c></seemfa>.</p>
</item>
<item>
<pre>
#sctp_adaptation_event{
adaptation_ind = integer(),
assoc_id = assoc_id()
}</pre>
<p>Delivered when a peer sends an adaptation layer indication
parameter (configured through option
<seeerl marker="#option-sctp_adaptation_layer"><c>sctp_adaptation_layer</c></seeerl>).
Notice that with the current implementation of
the Erlang/SCTP binding, this event is disabled by default.</p>
</item>
<item>
<pre>
#sctp_pdapi_event{
indication = sctp_partial_delivery_aborted,
assoc_id = assoc_id()
}</pre>
<p>A partial delivery failure. In the current implementation of
the Erlang/SCTP binding, this event is internally converted
into an <c>error</c> term returned by
<seemfa marker="#recv/1"><c>recv/*</c></seemfa>.</p>
</item>
</list>
</desc>
</func>
<func>
<name name="send" arity="3" since=""/>
<fsummary>Send a message using an <c>#sctp_sndrcvinfo{}</c>record.</fsummary>
<desc>
<p>Sends the <c><anno>Data</anno></c> message with all sending
parameters from a
<seeerl marker="#record-sctp_sndrcvinfo"><c>#sctp_sndrcvinfo{}</c></seeerl>
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 <c>send/4</c> is sufficient for most applications.</p>
</desc>
</func>
<func>
<name name="send" arity="4" since=""/>
<fsummary>Send a message over an existing association and specified
stream.</fsummary>
<desc>
<p>Sends a <c><anno>Data</anno></c> message over an existing association
and specified stream.</p>
</desc>
</func>
</funcs>
<section>
<marker id="options"></marker>
<title>SCTP Socket Options</title>
<p>The set of admissible SCTP socket options is by construction
orthogonal to the sets of TCP, UDP, and generic <c>inet</c> options.
Only options listed here are allowed
for SCTP sockets. Options can be set on the socket using
<seemfa marker="#open/1"><c>open/1,2</c></seemfa> or
<seemfa marker="inet#setopts/2"><c>inet:setopts/2</c></seemfa>,
retrieved using
<seemfa marker="inet#getopts/2"><c>inet:getopts/2</c></seemfa>.
Options can be changed when calling
<seemfa marker="#connect/4"><c>connect/4,5</c></seemfa>.</p>
<marker id="option-binary"></marker>
<marker id="option-list"></marker>
<taglist>
<tag><c>{mode, list|binary}</c> or just <c>list</c> or <c>binary</c></tag>
<item>
<p>Determines the type of data returned from
<seemfa marker="#recv/1"><c>recv/1,2</c></seemfa>.</p>
<marker id="option-active"></marker>
</item>
<tag><c>{active, true|false|once|N}</c></tag>
<item>
<list type="bulleted">
<item>
<p>If <c>false</c> (passive mode, the default),
the caller must do an explicit
<seemfa marker="#recv/1"><c>recv</c></seemfa> call
to retrieve the available data from the socket.</p>
</item>
<item>
<p>
If <c>true|once|N</c> (active modes)
received data or events are sent to the owning process.
See <seemfa marker="#open/0"><c>open/0..2</c></seemfa>
for the message format.
</p>
</item>
<item>
<p>
If <c>true</c> (full active mode) there is no flow control.
</p>
<note>
<p>
Note that this can cause the message queue to overflow
causing for example the virtual machine
to run out of memory and crash.
</p>
</note>
</item>
<item>
<p>If <c>once</c>, 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.</p>
</item>
<item>
<p>If <c>active</c> is specified as an integer <c>N</c> 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 to <c>0</c>. Once the
count reaches <c>0</c>, either through the delivery of messages
or by being explicitly set with
<seemfa marker="inet#setopts/2"><c>inet:setopts/2</c></seemfa>,
the socket mode is automatically reset to passive (<c>{active,
false}</c>). When a socket in this active mode transitions to
passive mode, the message <c>{sctp_passive, Socket}</c> is sent
to the controlling process to notify it that if it wants to
receive more data messages from the socket, it must call
<seemfa marker="inet#setopts/2"><c>inet:setopts/2</c></seemfa>
to set the socket back into an active mode.</p>
</item>
</list>
</item>
<tag><c>{tos, integer()}</c></tag>
<item>
<p>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.</p>
</item>
<tag><c>{priority, integer()}</c></tag>
<item>
<p>A protocol-independent equivalent of <c>tos</c> above. Setting
priority implies setting <c>tos</c> as well.</p>
</item>
<tag><c>{dontroute, true|false}</c></tag>
<item>
<p>Defaults to <c>false</c>. If <c>true</c>, the kernel does not
send packets through any gateway, only sends them to directly
connected hosts.</p>
</item>
<tag><c>{reuseaddr, true|false}</c></tag>
<item>
<p>Defaults to <c>false</c>. If true, the local binding address
<c>{IP,Port}</c> of the socket can be reused immediately.
No waiting in state <c>CLOSE_WAIT</c> is performed (can be
required for high-throughput servers).</p>
</item>
<tag><c>{sndbuf, integer()}</c></tag>
<item>
<p>The size, in bytes, of the OS kernel send buffer for this socket.
Sending errors would occur for datagrams larger than
<c>val(sndbuf)</c>. Setting this option also adjusts
the size of the driver buffer (see <c>buffer</c> above).</p>
</item>
<tag><c>{recbuf, integer()}</c></tag>
<item>
<p>The size, in bytes, of the OS kernel receive buffer for this socket.
Sending errors would occur for datagrams larger than
<c>val(recbuf)</c>. Setting this option also adjusts
the size of the driver buffer (see <c>buffer</c> above).</p>
</item>
<tag><c>{sctp_module, module()}</c></tag>
<item>
<p>Overrides which callback module is used. Defaults to
<c>inet_sctp</c> for IPv4 and <c>inet6_sctp</c> for IPv6.</p>
</item>
<tag><c>{sctp_rtoinfo, #sctp_rtoinfo{}}</c></tag>
<item>
<pre>
#sctp_rtoinfo{
assoc_id = assoc_id(),
initial = integer(),
max = integer(),
min = integer()
}</pre>
<p>Determines retransmission time-out parameters, in milliseconds,
for the association(s) specified by <c>assoc_id</c>.</p>
<p><c>assoc_id = 0</c> (default) indicates the whole endpoint. See
<url href="http://www.rfc-archive.org/getrfc.php?rfc=2960">RFC
2960</url> and
<url href="http://tools.ietf.org/html/draft-ietf-tsvwg-sctpsocket-13">Sockets
API Extensions for SCTP</url>
for the exact semantics of the field values.</p>
</item>
<tag><c>{sctp_associnfo, #sctp_assocparams{}}</c></tag>
<item>
<pre>
#sctp_assocparams{
assoc_id = assoc_id(),
asocmaxrxt = integer(),
number_peer_destinations = integer(),
peer_rwnd = integer(),
local_rwnd = integer(),
cookie_life = integer()
}</pre>
<p>Determines association parameters for the association(s) specified by
<c>assoc_id</c>.</p>
<p><c>assoc_id = 0</c> (default) indicates the whole endpoint. See
<url href="http://tools.ietf.org/html/draft-ietf-tsvwg-sctpsocket-13">Sockets API Extensions for SCTP</url>
for the discussion of their semantics. Rarely used.</p>
</item>
<tag><c>{sctp_initmsg, #sctp_initmsg{}}</c></tag>
<item>
<pre>
#sctp_initmsg{
num_ostreams = integer(),
max_instreams = integer(),
max_attempts = integer(),
max_init_timeo = integer()
}</pre>
<p>Determines the default parameters that this socket tries
to negotiate with its peer while establishing an association with it.
Is to be set after
<seemfa marker="#open/1"><c>open/*</c></seemfa>
but before the first
<seemfa marker="#connect/4"><c>connect/*</c></seemfa>.
<c>#sctp_initmsg{}</c> can also be used
as ancillary data with the first call of
<seemfa marker="#send/3"><c>send/*</c></seemfa> to
a new peer (when a new association is created).</p>
<taglist>
<tag><c>num_ostreams</c></tag>
<item>Number of outbound streams</item>
<tag><c>max_instreams</c></tag>
<item>Maximum number of inbound streams</item>
<tag><c>max_attempts</c></tag>
<item>Maximum retransmissions while establishing an association</item>
<tag><c>max_init_timeo</c></tag>
<item>Time-out, in milliseconds, for establishing an association</item>
</taglist>
</item>
<tag><c>{sctp_autoclose, integer() >= 0}</c></tag>
<item>
<p>Determines the time, in seconds, after which an idle association is
automatically closed. <c>0</c> means that the association is
never automatically closed.</p>
</item>
<tag><c>{sctp_nodelay, true|false}</c></tag>
<item>
<p>Turns on|off the Nagle algorithm for merging small packets
into larger ones. This improves throughput at the expense
of latency.</p>
</item>
<tag><c>{sctp_disable_fragments, true|false}</c></tag>
<item>
<p>If <c>true</c>, 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.</p>
</item>
<tag><c>{sctp_i_want_mapped_v4_addr, true|false}</c></tag>
<item>
<p>Turns on|off automatic mapping of IPv4 addresses into IPv6 ones
(if the socket address family is <c>AF_INET6</c>).</p>
</item>
<tag><c>{sctp_maxseg, integer()}</c></tag>
<item>
<p>Determines the maximum chunk size if message fragmentation is used.
If <c>0</c>, the chunk size is limited by the Path MTU only.</p>
</item>
<tag><c>{sctp_primary_addr, #sctp_prim{}}</c></tag>
<item>
<pre>
#sctp_prim{
assoc_id = assoc_id(),
addr = {IP, Port}
}
IP = ip_address()
Port = port_number()</pre>
<p>For the association specified by <c>assoc_id</c>,
<c>{IP,Port}</c> 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.</p>
</item>
<tag><c>{sctp_set_peer_primary_addr, #sctp_setpeerprim{}}</c></tag>
<item>
<pre>
#sctp_setpeerprim{
assoc_id = assoc_id(),
addr = {IP, Port}
}
IP = ip_address()
Port = port_number()</pre>
<p>When set, informs the peer to use <c>{IP, Port}</c>
as the primary address of the local endpoint for the association
specified by <c>assoc_id</c>.</p>
<marker id="option-sctp_adaptation_layer"></marker>
</item>
<tag><c>{sctp_adaptation_layer, #sctp_setadaptation{}}</c></tag>
<item>
<marker id="record-sctp_setadaptation"></marker>
<pre>
#sctp_setadaptation{
adaptation_ind = integer()
}</pre>
<p>When set, requests that the local endpoint uses the value specified
by <c>adaptation_ind</c> as the Adaptation Indication parameter for
establishing new associations. For details, see
<url href="http://www.rfc-archive.org/getrfc.php?rfc=2960">RFC 2960</url>
and
<url href="http://tools.ietf.org/html/draft-ietf-tsvwg-sctpsocket-13">Sockets
API Extenstions for SCTP</url>.</p>
</item>
<tag><c>{sctp_peer_addr_params, #sctp_paddrparams{}}</c></tag>
<item>
<pre>
#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()</pre>
<p>Determines various per-address parameters for
the association specified by <c>assoc_id</c> and the peer address
<c>address</c> (the SCTP protocol supports multi-homing, so
more than one address can correspond to a specified association).</p>
<taglist>
<tag><c>hbinterval</c></tag>
<item><p>Heartbeat interval, in milliseconds</p></item>
<tag><c>pathmaxrxt</c></tag>
<item><p>Maximum number of retransmissions before this address is
considered unreachable (and an alternative address is selected)</p>
</item>
<tag><c>pathmtu</c></tag>
<item><p>Fixed Path MTU, if automatic discovery is disabled (see
<c>flags</c> below)</p></item>
<tag><c>sackdelay</c></tag>
<item><p>Delay, in milliseconds, for SAC messages (if the delay is
enabled, see <c>flags</c> below)</p></item>
<tag><c>flags</c></tag>
<item><p>The following flags are available:</p>
<taglist>
<tag><c>hb_enable</c></tag>
<item>Enables heartbeat</item>
<tag><c>hb_disable</c></tag>
<item>Disables heartbeat</item>
<tag><c>hb_demand</c></tag>
<item>Initiates heartbeat immediately</item>
<tag><c>pmtud_enable</c></tag>
<item>Enables automatic Path MTU discovery</item>
<tag><c>pmtud_disable</c></tag>
<item>Disables automatic Path MTU discovery</item>
<tag><c>sackdelay_enable</c></tag>
<item>Enables SAC delay</item>
<tag><c>sackdelay_disable</c></tag>
<item>Disables SAC delay</item>
</taglist></item>
</taglist>
</item>
<tag><c>{sctp_default_send_param, #sctp_sndrcvinfo{}}</c></tag>
<item>
<marker id="record-sctp_sndrcvinfo"></marker>
<pre>
#sctp_sndrcvinfo{
stream = integer(),
ssn = integer(),
flags = list(),
ppid = integer(),
context = integer(),
timetolive = integer(),
tsn = integer(),
cumtsn = integer(),
assoc_id = assoc_id()
}</pre>
<p><c>#sctp_sndrcvinfo{}</c> 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 subsequent
<seemfa marker="#send/3"><c>send</c></seemfa>
calls on the association specified by
<c>assoc_id</c>.</p>
<p><c>assoc_id = 0</c> (default) indicates
the whole endpoint.</p>
<p>The following fields typically must be specified by the sender:</p>
<taglist>
<tag><c>sinfo_stream</c></tag>
<item><p>Stream number (0-base) within the association
to send the messages through;</p></item>
<tag><c>sinfo_flags</c></tag>
<item><p>The following flags are recognised:</p>
<taglist>
<tag><c>unordered</c></tag>
<item>The message is to be sent unordered</item>
<tag><c>addr_over</c></tag>
<item>The address specified in
<seemfa marker="#send/3"><c>send</c></seemfa>
overwrites the primary peer address</item>
<tag><c>abort</c></tag>
<item>Aborts the current association without flushing any unsent
data</item>
<tag><c>eof</c></tag>
<item>Gracefully shuts down the current association, with
flushing of unsent data</item>
</taglist>
<p>Other fields are rarely used. For complete information, see
<url href="http://www.rfc-archive.org/getrfc.php?rfc=2960">RFC 2960</url>
and
<url href="http://tools.ietf.org/html/draft-ietf-tsvwg-sctpsocket-13">Sockets
API Extensions for SCTP</url>.</p></item>
</taglist>
<marker id="option-sctp_events"></marker>
</item>
<tag><c>{sctp_events, #sctp_event_subscribe{}}</c></tag>
<item>
<marker id="record-sctp_event_subscribe"></marker>
<pre>
#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
}</pre>
<p>This option determines which
<seeerl marker="#sctp_events">SCTP Events</seeerl> are to be
received (through
<seemfa marker="#recv/1"><c>recv/*</c></seemfa>)
along with the data. The only exception is <c>data_io_event</c>,
which enables or disables receiving of
<seeerl marker="#record-sctp_sndrcvinfo"><c>#sctp_sndrcvinfo{}</c></seeerl>
ancillary data, not events.
By default, all flags except <c>adaptation_layer_event</c> are
enabled, although <c>sctp_data_io_event</c> and
<c>association_event</c> are used by the driver itself and not
exported to the user level.</p>
</item>
<tag><c>{sctp_delayed_ack_time, #sctp_assoc_value{}}</c></tag>
<item>
<pre>
#sctp_assoc_value{
assoc_id = assoc_id(),
assoc_value = integer()
}</pre>
<p>Rarely used. Determines the ACK time
(specified by <c>assoc_value</c>, in milliseconds) for
the specified association or the whole endpoint
if <c>assoc_value = 0</c> (default).</p>
</item>
<tag><c>{sctp_status, #sctp_status{}}</c></tag>
<item>
<pre>
#sctp_status{
assoc_id = assoc_id(),
state = atom(),
rwnd = integer(),
unackdata = integer(),
penddata = integer(),
instrms = integer(),
outstrms = integer(),
fragmentation_point = integer(),
primary = #sctp_paddrinfo{}
}</pre>
<p>This option is read-only. It determines the status of
the SCTP association specified by <c>assoc_id</c>.
The following are the
possible values of <c>state</c> (the state designations are mostly
self-explanatory):</p>
<taglist>
<tag><c>sctp_state_empty</c></tag>
<item>Default. Means that no other state is active.</item>
<tag><c>sctp_state_closed</c></tag>
<item></item>
<tag><c>sctp_state_cookie_wait</c></tag>
<item></item>
<tag><c>sctp_state_cookie_echoed</c></tag>
<item></item>
<tag><c>sctp_state_established</c></tag>
<item></item>
<tag><c>sctp_state_shutdown_pending</c></tag>
<item></item>
<tag><c>sctp_state_shutdown_sent</c></tag>
<item></item>
<tag><c>sctp_state_shutdown_received</c></tag>
<item></item>
<tag><c>sctp_state_shutdown_ack_sent</c></tag>
<item></item>
</taglist>
<p>Semantics of the other fields:</p>
<taglist>
<tag><c>sstat_rwnd</c></tag>
<item>Current receiver window size of the association</item>
<tag><c>sstat_unackdata</c></tag>
<item>Number of unacked data chunks</item>
<tag><c>sstat_penddata</c></tag>
<item>Number of data chunks pending receipt</item>
<tag><c>sstat_instrms</c></tag>
<item>Number of inbound streams</item>
<tag><c>sstat_outstrms</c></tag>
<item>Number of outbound streams</item>
<tag><c>sstat_fragmentation_point</c></tag>
<item>Message size at which SCTP fragmentation occurs</item>
<tag><c>sstat_primary</c></tag>
<item>Information on the current primary peer address (see below for
the format of <c>#sctp_paddrinfo{}</c>)</item>
</taglist>
<marker id="option-sctp_get_peer_addr_info"></marker>
</item>
<tag><c>{sctp_get_peer_addr_info, #sctp_paddrinfo{}}</c></tag>
<item>
<marker id="record-sctp_paddrinfo"></marker>
<pre>
#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()</pre>
<p>This option is read-only. It determines the parameters specific to
the peer address specified by <c>address</c> within the association
specified by <c>assoc_id</c>. Field <c>address</c> fmust be set by the
caller; all other fields are filled in on return.
If <c>assoc_id = 0</c> (default), the <c>address</c>
is automatically translated into the corresponding
association ID. This option is rarely used.
For the semantics of all fields, see
<url href="http://www.rfc-archive.org/getrfc.php?rfc=2960">RFC 2960</url>
and
<url href="http://tools.ietf.org/html/draft-ietf-tsvwg-sctpsocket-13">Sockets
API Extensions for SCTP</url>.</p>
</item>
</taglist>
</section>
<section>
<marker id="examples"></marker>
<title>SCTP Examples</title>
<p>Example of an Erlang SCTP server that receives SCTP messages and
prints them on the standard output:</p>
<pre>
-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).</pre>
<p>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
<c>"Test 0"</c> over stream 0 succeeds, but sending of <c>"Test 5"</c>
over stream 5 fails. The client then <c>abort</c>s the association,
which results in that the corresponding event is received on
the server side.</p>
<pre>
-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).</pre>
<p>A simple Erlang SCTP client that uses the <c>connect_init</c> API:</p>
<pre>
-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.</pre>
</section>
<section>
<marker id="seealso"></marker>
<title>See Also</title>
<p><seeerl marker="gen_tcp"><c>gen_tcp(3)</c></seeerl>,
<seeerl marker="gen_udp"><c>gen_udp(3)</c></seeerl>,
<seeerl marker="inet"><c>inet(3)</c></seeerl>,
<url href="http://www.rfc-archive.org/getrfc.php?rfc=2960">RFC 2960</url>
(Stream Control Transmission Protocol),
<url href="http://tools.ietf.org/html/draft-ietf-tsvwg-sctpsocket-13">Sockets
API Extensions for SCTP</url></p>
</section>
</erlref>
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