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<img alt="Erlang logo" src="../../../../doc/erlang-logo.png"><br><small><a href="users_guide.html">User's Guide</a><br><a href="index.html">Reference Manual</a><br><a href="release_notes.html">Release Notes</a><br><a href="../pdf/diameter-1.3.pdf">PDF</a><br><a href="../../../../doc/index.html">Top</a></small><p><strong>Diameter</strong><br><strong>Reference Manual</strong><br><small>Version 1.3</small></p>
<br><a href="javascript:openAllFlips()">Expand All</a><br><a href="javascript:closeAllFlips()">Contract All</a><p><small><strong>Table of Contents</strong></small></p>
<ul class="flipMenu">
<li id="loadscrollpos" title="diameter " expanded="true">diameter<ul>
<li><a href="diameter.html">
Top of manual page
</a></li>
<li title="add_transport-2"><a href="diameter.html#add_transport-2">add_transport/2</a></li>
<li title="call-4"><a href="diameter.html#call-4">call/4</a></li>
<li title="origin_state_id-0"><a href="diameter.html#origin_state_id-0">origin_state_id/0</a></li>
<li title="remove_transport-2"><a href="diameter.html#remove_transport-2">remove_transport/2</a></li>
<li title="service_info-2"><a href="diameter.html#service_info-2">service_info/2</a></li>
<li title="services-0"><a href="diameter.html#services-0">services/0</a></li>
<li title="session_id-1"><a href="diameter.html#session_id-1">session_id/1</a></li>
<li title="start-0"><a href="diameter.html#start-0">start/0</a></li>
<li title="start_service-2"><a href="diameter.html#start_service-2">start_service/2</a></li>
<li title="stop-0"><a href="diameter.html#stop-0">stop/0</a></li>
<li title="stop_service-1"><a href="diameter.html#stop_service-1">stop_service/1</a></li>
<li title="subscribe-1"><a href="diameter.html#subscribe-1">subscribe/1</a></li>
<li title="unsubscribe-1"><a href="diameter.html#unsubscribe-1">unsubscribe/1</a></li>
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</li>
<li title="diameterc"><a href="diameterc.html">diameterc</a></li>
<li id="no" title="diameter_app " expanded="false">diameter_app<ul>
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</a></li>
<li title="Mod:peer_up-3"><a href="diameter_app.html#Mod:peer_up-3">Mod:peer_up/3</a></li>
<li title="Mod:peer_down-3"><a href="diameter_app.html#Mod:peer_down-3">Mod:peer_down/3</a></li>
<li title="Mod:pick_peer-4"><a href="diameter_app.html#Mod:pick_peer-4">Mod:pick_peer/4</a></li>
<li title="Mod:prepare_request-3"><a href="diameter_app.html#Mod:prepare_request-3">Mod:prepare_request/3</a></li>
<li title="Mod:prepare_retransmit-3"><a href="diameter_app.html#Mod:prepare_retransmit-3">Mod:prepare_retransmit/3</a></li>
<li title="Mod:handle_answer-4"><a href="diameter_app.html#Mod:handle_answer-4">Mod:handle_answer/4</a></li>
<li title="Mod:handle_error-4"><a href="diameter_app.html#Mod:handle_error-4">Mod:handle_error/4</a></li>
<li title="Mod:handle_request-3"><a href="diameter_app.html#Mod:handle_request-3">Mod:handle_request/3</a></li>
</ul>
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<li id="no" title="diameter_codec " expanded="false">diameter_codec<ul>
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Top of manual page
</a></li>
<li title="decode-2"><a href="diameter_codec.html#decode-2">decode/2</a></li>
<li title="encode-2"><a href="diameter_codec.html#encode-2">encode/2</a></li>
</ul>
</li>
<li title="diameter_dict"><a href="diameter_dict.html">diameter_dict</a></li>
<li id="no" title="diameter_make " expanded="false">diameter_make<ul>
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</a></li>
<li title="codec-2"><a href="diameter_make.html#codec-2">codec/2</a></li>
</ul>
</li>
<li id="no" title="diameter_transport " expanded="false">diameter_transport<ul>
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</a></li>
<li title="Mod:start-3"><a href="diameter_transport.html#Mod:start-3">Mod:start/3</a></li>
</ul>
</li>
<li id="no" title="diameter_tcp " expanded="false">diameter_tcp<ul>
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</a></li>
<li title="start-3"><a href="diameter_tcp.html#start-3">start/3</a></li>
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<li id="no" title="diameter_sctp " expanded="false">diameter_sctp<ul>
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<li title="start-3"><a href="diameter_sctp.html#start-3">start/3</a></li>
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<div id="content">
<div class="innertube">
<!-- refpage --><center><h1>diameter</h1></center>
<h3>MODULE</h3>
<div class="REFBODY">diameter</div>
<h3>MODULE SUMMARY</h3>
<div class="REFBODY">Main API of the diameter application.</div>
<h3>DESCRIPTION</h3>
<div class="REFBODY"><p>
<p>
This module provides the interface with which a user can
implement a Diameter node that sends and receives messages using the
Diameter protocol as defined in RFC 6733.</p>
<p>
Basic usage consists of creating a representation of a
locally implemented Diameter node and its capabilities with
<span class="bold_code"><a href="#start_service-2">start_service/2</a></span>, adding transport capability using
<span class="bold_code"><a href="#add_transport-2">add_transport/2</a></span> and sending Diameter
requests and receiving Diameter answers with <span class="bold_code"><a href="#call-4">call/4</a></span>.
Incoming Diameter requests are communicated as callbacks to a
<span class="bold_code"><a href="diameter_app.html">diameter_app(3)</a></span> callback modules as
specified in the service configuration.</p>
<p>
Beware the difference between <strong>diameter</strong> (not capitalised) and
<strong>Diameter</strong> (capitalised).
The former refers to the Erlang application named diameter whose main
api is defined here, the latter to Diameter protocol in the sense of
RFC 6733.</p>
<p>
The diameter application must be started before calling most functions
in this module.</p>
</p></div>
<h3><a name="id64675">DATA TYPES</a></h3>
<div class="REFBODY">
<dl>
<dt><strong><span class="code">Address()</span></strong></dt>
<dt><strong><span class="code">DiameterIdentity()</span></strong></dt>
<dt><strong><span class="code">Grouped()</span></strong></dt>
<dt><strong><span class="code">OctetString()</span></strong></dt>
<dt><strong><span class="code">Time()</span></strong></dt>
<dt><strong><span class="code">Unsigned32()</span></strong></dt>
<dt><strong><span class="code">UTF8String()</span></strong></dt>
<dd>
<p>
Types corresponding to RFC 6733 AVP Data Formats.
Defined in <span class="bold_code"><a href="diameter_dict.html#DATA_TYPES">diameter_dict(4)</a></span>.</p>
<a name="application_alias"></a>
</dd>
<dt><strong><span class="code">application_alias() = term()</span></strong></dt>
<dd>
<p>
A name identifying a Diameter application in
service configuration.
Passed to <span class="bold_code"><a href="#call-4">call/4</a></span> when sending requests
defined by the application.</p>
<a name="application_module"></a>
</dd>
<dt><strong><span class="code">application_module() = Mod
| [Mod | ExtraArgs]
| #diameter_callback{}</span></strong></dt>
<dd>
<div class="example"><pre>
Mod = atom()
ExtraArgs = list()
</pre></div>
<p>
A module implementing the callback interface defined in <span class="bold_code"><a href="diameter_app.html">diameter_app(3)</a></span>,
along with any
extra arguments to be appended to those documented for the interface.
Note that extra arguments specific to an outgoing request can be
specified to <span class="bold_code"><a href="#call-4">call/4</a></span>, in which case
those are are appended to any module-specific extra arguments.</p>
<p>
Specifying a <span class="code">#diameter_callback{}</span> record allows individual
functions to be configured in place of the usual <span class="bold_code"><a href="diameter_app.html">diameter_app(3)</a></span> callbacks.
See that module for details.</p>
<a name="application_opt"></a>
</dd>
<dt><strong><span class="code">application_opt()</span></strong></dt>
<dd>
<p>
Options defining a Diameter application.
Has one the following types.</p>
<dl>
<dt><strong><span class="code">{alias, <span class="bold_code"><a href="#application_alias">application_alias()</a></span>}</span></strong></dt>
<dd>
<p>
An unique identifier for the application in the scope of the
service.
Defaults to the value of the <span class="code">dictionary</span> option if
unspecified.</p>
</dd>
<dt><strong><span class="code">{dictionary, atom()}</span></strong></dt>
<dd>
<p>
The name of an encode/decode module for the Diameter
messages defined by the application.
These modules are generated from a specification file whose format is
documented in <span class="bold_code"><a href="diameter_dict.html">diameter_dict(4)</a></span>.</p>
</dd>
<dt><strong><span class="code">{module, <span class="bold_code"><a href="#application_module">application_module()</a></span>}</span></strong></dt>
<dd>
<p>
The callback module with which messages of the Diameter application are
handled.
See <span class="bold_code"><a href="diameter_app.html">diameter_app(3)</a></span> for the required interface and semantics.</p>
</dd>
<dt><strong><span class="code">{state, term()}</span></strong></dt>
<dd>
<p>
The initial callback state.
The prevailing state is passed to some
<span class="bold_code"><a href="diameter_app.html">diameter_app(3)</a></span>
callbacks, which can then return a new state.
Defaults to the value of the <span class="code">alias</span> option if unspecified.</p>
</dd>
<dt><strong><span class="code">{call_mutates_state, true|false}</span></strong></dt>
<dd>
<p>
Specifies whether or not the <span class="bold_code"><a href="diameter_app.html#Mod:pick_peer-4">pick_peer/4</a></span>
application callback can modify the application state,
Defaults to <span class="code">false</span> if unspecified.</p>
<div class="note">
<div class="label">Note</div>
<div class="content"><p>
<p>
<span class="bold_code"><a href="diameter_app.html#Mod:pick_peer-4">pick_peer/4</a></span> callbacks
are serialized when these are allowed to modify state, which is a
potential performance bottleneck.
A simple Diameter client may suffer no ill effects from using mutable
state but a server or agent that responds to incoming request should
probably avoid it.</p>
</p></div>
</div>
</dd>
<dt><strong><span class="code">{answer_errors, callback|report|discard}</span></strong></dt>
<dd>
<p>
Determines the manner in which incoming answer messages containing
decode errors are handled.
If <span class="code">callback</span> then errors result in a <span class="bold_code"><a href="diameter_app.html#Mod:handle_answer-4">handle_answer/4</a></span>
callback in the same fashion as for <span class="bold_code"><a href="diameter_app.html#Mod:handle_request-3">handle_request/3</a></span>, with
errors communicated in the <span class="code">errors</span> field of the
<span class="code">#diameter_packet{}</span> record passed to the callback.
If <span class="code">report</span> then an answer containing errors is discarded
without a callback and a warning report is written to the log.
If <span class="code">discard</span> then an answer containing errors is silently
discarded without a callback.
In both the <span class="code">report</span> and <span class="code">discard</span> cases the return value
for the <span class="bold_code"><a href="#call-4">call/4</a></span> invocation in
question is as if a callback had taken place and returned
<span class="code">{error, failure}</span>.</p>
<p>
Defaults to <span class="code">report</span> if unspecified.</p>
</dd>
</dl>
<a name="call_opt"></a>
</dd>
<dt><strong><span class="code">call_opt()</span></strong></dt>
<dd>
<p>
Options available to <span class="bold_code"><a href="#call-4">call/4</a></span> when
sending an outgoing Diameter request.
Has one of the following types.</p>
<dl>
<dt><strong><span class="code">{extra, list()}</span></strong></dt>
<dd>
<p>
Extra arguments to append to callbacks to the callback
module in question.
These are appended to any extra arguments configured on the callback
itself.
Multiple options append to the argument list.</p>
</dd>
<dt><strong><span class="code">{filter, <span class="bold_code"><a href="#peer_filter">peer_filter()</a></span>}</span></strong></dt>
<dd>
<p>
A filter to apply to the list of available peers before passing them to
the <span class="bold_code"><a href="diameter_app.html#Mod:pick_peer-4">pick_peer/4</a></span>
callback for the application in question.
Multiple options are equivalent a single <span class="code">all</span> filter on the
corresponding list of filters.
Defaults to <span class="code">none</span>.</p>
</dd>
<dt><strong><span class="code">{timeout, <span class="bold_code"><a href="diameter_dict.html#DATA_TYPES">Unsigned32()</a></span>}</span></strong></dt>
<dd>
<p>
The number of milliseconds after which the request should
timeout.
Defaults to 5000.</p>
</dd>
<dt><strong><span class="code">detach</span></strong></dt>
<dd>
<p>
Causes <span class="bold_code"><a href="#call-4">call/4</a></span> to return <span class="code">ok</span> as
soon as the request in
question has been encoded instead of waiting for and returning
the result from a subsequent <span class="bold_code"><a href="diameter_app.html#Mod:handle_answer-4">handle_answer/4</a></span> or
<span class="bold_code"><a href="diameter_app.html#Mod:handle_error-4">handle_error/4</a></span> callback.</p>
</dd>
</dl>
<p>
An invalid option will cause <span class="bold_code"><a href="#call-4">call/4</a></span> to fail.</p>
<a name="capability"></a>
</dd>
<dt><strong><span class="code">capability()</span></strong></dt>
<dd>
<p>
AVP values sent in outgoing CER or CEA messages during capabilities
exchange.
Can be configured both on a service and a transport, values specified
on the latter taking precedence over any specified on the former.
Has one of the following types.</p>
<dl>
<dt><strong><span class="code">{'Origin-Host', <span class="bold_code"><a href="diameter_dict.html#DATA_TYPES">DiameterIdentity()</a></span>}</span></strong></dt>
<dt><strong><span class="code">{'Origin-Realm', <span class="bold_code"><a href="diameter_dict.html#DATA_TYPES">DiameterIdentity()</a></span>}</span></strong></dt>
<dt><strong><span class="code">{'Host-IP-Address', [<span class="bold_code"><a href="diameter_dict.html#DATA_TYPES">Address()</a></span>]}</span></strong></dt>
<dd>
<p>
An address list is available to the start function of a
<span class="bold_code"><a href="diameter_transport.html">transport module</a></span>, which
can return a new list for use in the subsequent CER or CEA.
Host-IP-Address need not be specified if the transport start function
returns an address list.</p>
</dd>
<dt><strong><span class="code">{'Vendor-Id', <span class="bold_code"><a href="diameter_dict.html#DATA_TYPES">Unsigned32()</a></span>}</span></strong></dt>
<dt><strong><span class="code">{'Product-Name', <span class="bold_code"><a href="diameter_dict.html#DATA_TYPES">UTF8String()</a></span>}</span></strong></dt>
<dt><strong><span class="code">{'Origin-State-Id', <span class="bold_code"><a href="diameter_dict.html#DATA_TYPES">Unsigned32()</a></span>}</span></strong></dt>
<dd>
<p>
Origin-State-Id is optional but will be included in outgoing messages
sent by diameter itself: CER/CEA, DWR/DWA and DPR/DPA.
Setting a value of <span class="code">0</span> (zero) is equivalent to not setting a
value as documented in RFC 6733.
The function <span class="bold_code"><a href="#origin_state_id-0">origin_state_id/0</a></span>
can be used as to retrieve a value that is computed when the diameter
application is started.</p>
</dd>
<dt><strong><span class="code">{'Supported-Vendor-Id', [<span class="bold_code"><a href="diameter_dict.html#DATA_TYPES">Unsigned32()</a></span>]}</span></strong></dt>
<dt><strong><span class="code">{'Auth-Application-Id', [<span class="bold_code"><a href="diameter_dict.html#DATA_TYPES">Unsigned32()</a></span>]}</span></strong></dt>
<dt><strong><span class="code">{'Inband-Security-Id', [<span class="bold_code"><a href="diameter_dict.html#DATA_TYPES">Unsigned32()</a></span>]}</span></strong></dt>
<dd>
<p>
Inband-Security-Id defaults to the empty list, which is equivalent to a
list containing only 0 (= NO_INBAND_SECURITY).
If 1 (= TLS) is specified then TLS is selected if the CER/CEA received
from the peer offers it.</p>
</dd>
<dt><strong><span class="code">{'Acct-Application-Id', [<span class="bold_code"><a href="diameter_dict.html#DATA_TYPES">Unsigned32()</a></span>]}</span></strong></dt>
<dt><strong><span class="code">{'Vendor-Specific-Application-Id', [<span class="bold_code"><a href="diameter_dict.html#DATA_TYPES">Grouped()</a></span>]}</span></strong></dt>
<dt><strong><span class="code">{'Firmware-Revision', <span class="bold_code"><a href="diameter_dict.html#DATA_TYPES">Unsigned32()</a></span>}</span></strong></dt>
</dl>
<p>
Note that each tuple communicates one or more AVP values.
It is an error to specify duplicate tuples.</p>
<a name="evaluable"></a>
</dd>
<dt><strong><span class="code">evaluable() = {M,F,A} | fun() | [evaluable() | A]</span></strong></dt>
<dd>
<p>
An expression that can be evaluated as a function in the following
sense.</p>
<div class="example"><pre>
eval([{M,F,A} | T]) ->
apply(M, F, T ++ A);
eval([[F|A] | T]) ->
eval([F | T ++ A]);
eval([F|A]) ->
apply(F, A);
eval(F) ->
eval([F]).
</pre></div>
<p>
Applying an <span class="code"><span class="bold_code"><a href="#evaluable">evaluable()</a></span></span>
<span class="code">E</span> to an argument list <span class="code">A</span>
is meant in the sense of <span class="code">eval([E|A])</span>.</p>
<div class="warning">
<div class="label">Warning</div>
<div class="content"><p>
<p>
Beware of using fun expressions of the form <span class="code">fun Name/Arity</span> in
situations in which the fun is not short-lived
and code is to be upgraded at runtime since any processes retaining
such a fun will have a reference to old code.
In particular, such a value is typically inappropriate in
configuration passed to <span class="bold_code"><a href="#start_service-2">start_service/2</a></span> or <span class="bold_code"><a href="#add_transport-2">add_transport/2</a></span>.</p>
</p></div>
</div>
<a name="peer_filter"></a>
</dd>
<dt><strong><span class="code">peer_filter() = term()</span></strong></dt>
<dd>
<p>
A filter passed to <span class="bold_code"><a href="#call-4">call/4</a></span> in order to select candidate peers for a
<span class="bold_code"><a href="diameter_app.html#Mod:pick_peer-4">pick_peer/4</a></span> callback.
Has one of the following types.</p>
<dl>
<dt><strong><span class="code">none</span></strong></dt>
<dd>
<p>
Matches any peer.
This is a convenience that provides a filter equivalent to no
filter at all.</p>
</dd>
<dt><strong><span class="code">host</span></strong></dt>
<dd>
<p>
Matches only those peers whose <span class="code">Origin-Host</span> has the same value
as <span class="code">Destination-Host</span> in the outgoing request in question,
or any peer if the request does not contain
a <span class="code">Destination-Host</span> AVP.</p>
</dd>
<dt><strong><span class="code">realm</span></strong></dt>
<dd>
<p>
Matches only those peers whose <span class="code">Origin-Realm</span> has the same value
as <span class="code">Destination-Realm</span> in the outgoing request in question,
or any peer if the request does not contain
a <span class="code">Destination-Realm</span> AVP.</p>
</dd>
<dt><strong><span class="code">{host, any|<span class="bold_code"><a href="diameter_dict.html#DATA_TYPES">DiameterIdentity()</a></span>}</span></strong></dt>
<dd>
<p>
Matches only those peers whose <span class="code">Origin-Host</span> has the
specified value, or all peers if the atom <span class="code">any</span>.</p>
</dd>
<dt><strong><span class="code">{realm, any|<span class="bold_code"><a href="diameter_dict.html#DATA_TYPES">DiameterIdentity()</a></span></span></strong></dt>
<dd>
<p>
Matches only those peers whose <span class="code">Origin-Realm</span> has the
specified value, or all peers if the atom <span class="code">any</span>.</p>
</dd>
<dt><strong><span class="code">{eval, <span class="bold_code"><a href="#evaluable">evaluable()</a></span>}</span></strong></dt>
<dd>
<p>
Matches only those peers for which the specified
<span class="code"><span class="bold_code"><a href="#evaluable">evaluable()</a></span></span> returns
<span class="code">true</span> on the connection's <span class="code">diameter_caps</span> record.
Any other return value or exception is equivalent to <span class="code">false</span>.</p>
</dd>
<dt><strong><span class="code">{neg, <span class="bold_code"><a href="#peer_filter">peer_filter()</a></span>}</span></strong></dt>
<dd>
<p>
Matches only those peers not matched by the specified filter.</p>
</dd>
<dt><strong><span class="code">{all, [<span class="bold_code"><a href="#peer_filter">peer_filter()</a></span>]}</span></strong></dt>
<dd>
<p>
Matches only those peers matched by each filter in the specified list.</p>
</dd>
<dt><strong><span class="code">{any, [<span class="bold_code"><a href="#peer_filter">peer_filter()</a></span>]}</span></strong></dt>
<dd>
<p>
Matches only those peers matched by at least one filter in the
specified list.</p>
</dd>
</dl>
<p>
An invalid filter is equivalent to <span class="code">{any,[]}</span>, a filter
that matches no peer.</p>
<div class="note">
<div class="label">Note</div>
<div class="content"><p>
<p>
The <span class="code">host</span> and <span class="code">realm</span> filters examine the
outgoing request as passed to <span class="bold_code"><a href="#call-4">call/4</a></span>,
assuming that this is a record- or list-valued <span class="code"><span class="bold_code"><a href="diameter_codec.html#message">diameter_codec:message()</a></span></span>,
and that the message contains at most one of each AVP.
If this is not the case then the <span class="code">{host|realm, <span class="bold_code"><a href="diameter_dict.html#DATA_TYPES">DiameterIdentity()</a></span>}</span>
filters must be used to achieve the desired result.
An empty <span class="code"><span class="bold_code"><a href="diameter_dict.html#DATA_TYPES">DiameterIdentity()</a></span></span>
(which should not be typical)
matches all hosts/realms for the purposes of filtering.</p>
</p></div>
</div>
<div class="warning">
<div class="label">Warning</div>
<div class="content"><p>
<p>
A <span class="code">host</span> filter is not typically desirable when setting
Destination-Host since it will remove peer agents from the
candidates list.</p>
</p></div>
</div>
<a name="service_event"></a>
</dd>
<dt><strong><span class="code">service_event() = #diameter_event{}</span></strong></dt>
<dd>
<p>
An event message sent to processes that have subscribed to these using
<span class="bold_code"><a href="#subscribe-1">subscribe/1</a></span>.</p>
<p>
The <span class="code">info</span> field of the event record can have one of the
following types.</p>
<dl>
<dt><strong><span class="code">start</span></strong></dt>
<dt><strong><span class="code">stop</span></strong></dt>
<dd>
<p>
The service is being started or stopped.
No event precedes a <span class="code">start</span> event.
No event follows a <span class="code">stop</span> event and this event
implies the termination of all transport processes.</p>
</dd>
<dt><strong><span class="code">{up, Ref, Peer, Config, Pkt}</span></strong></dt>
<dt><strong><span class="code">{up, Ref, Peer, Config}</span></strong></dt>
<dt><strong><span class="code">{down, Ref, Peer, Config}</span></strong></dt>
<dd>
<div class="example"><pre>
Ref = <span class="bold_code"><a href="#transport_ref">transport_ref()</a></span>
Peer = <span class="bold_code"><a href="diameter_app.html#peer">diameter_app:peer()</a></span>
Config = {connect|listen, [<span class="bold_code"><a href="#transport_opt">transport_opt()</a></span>]}
Pkt = #diameter_packet{}
</pre></div>
<p>
The RFC 3539 watchdog state machine has
transitioned into (<span class="code">up</span>) or out of (<span class="code">down</span>) the OKAY
state.
If a <span class="code">#diameter_packet{}</span> record is present in an <span class="code">up</span> event
then there has been a capabilties exchange on a newly established
transport connection and the record contains the received CER or CEA.
Otherwise a connection has reestablished without the loss or
connectivity.</p>
<p>
Note that a single <span class="code">up</span>/<span class="code">down</span> event for a given peer
corresponds to one <span class="bold_code"><a href="diameter_app.html#Mod:peer_up-3">peer_up/3</a></span>/<span class="bold_code"><a href="diameter_app.html#Mod:peer_down-3">peer_up/3</a></span>
callback for each of the Diameter applications negotiated during
capablilities exchange.
That is, the event communicates connectivity with the
peer as a whole while the callbacks communicate connectivity with
respect to individual Diameter applications.</p>
</dd>
<dt><strong><span class="code">{reconnect, Ref, Opts}</span></strong></dt>
<dd>
<div class="example"><pre>
Ref = <span class="bold_code"><a href="#transport_ref">transport_ref()</a></span>
Opts = [<span class="bold_code"><a href="#transport_opt">transport_opt()</a></span>]
</pre></div>
<p>
A connecting transport is attempting to establish/reestablish a
transport connection with a peer following <span class="bold_code"><a href="#reconnect_timer">reconnect_timer</a></span> or
<span class="bold_code"><a href="#watchdog_timer">watchdog_timer</a></span> expiry.</p>
</dd>
<dt><strong><span class="code">{closed, Ref, Reason, Config}</span></strong></dt>
<dd>
<div class="example"><pre>
Ref = <span class="bold_code"><a href="#transport_ref">transport_ref()</a></span>
Config = {connect|listen, [<span class="bold_code"><a href="#transport_opt">transport_opt()</a></span>]}
</pre></div>
<p>
Capabilities exchange has failed.
<span class="code">Reason</span> can have one of the following types.</p>
<dl>
<dt><strong><span class="code">{'CER', Result, Caps, Pkt}</span></strong></dt>
<dd>
<div class="example"><pre>
Result = ResultCode | {capabilities_cb, CB, ResultCode|discard}
Caps = #diameter_caps{}
Pkt = #diameter_packet{}
ResultCode = integer()
CB = <span class="bold_code"><a href="#evaluable">evaluable()</a></span>
</pre></div>
<p>
An incoming CER has been answered with the indicated result code or
discarded.
<span class="code">Caps</span> contains pairs of values for the the local node and remote
peer.
<span class="code">Pkt</span> contains the CER in question.
In the case of rejection by a capabilities callback, the tuple
contains the rejecting callback.</p>
</dd>
<dt><strong><span class="code">{'CER', Caps, {ResultCode, Pkt}}</span></strong></dt>
<dd>
<div class="example"><pre>
ResultCode = integer()
Caps = #diameter_caps{}
Pkt = #diameter_packet{}
</pre></div>
<p>
An incoming CER contained errors and has been answered with the
indicated result code.
<span class="code">Caps</span> contains only values for the the local node.
<span class="code">Pkt</span> contains the CER in question.</p>
</dd>
<dt><strong><span class="code">{'CER', timeout}</span></strong></dt>
<dd>
<p>
An expected CER was not received within <span class="bold_code"><a href="#capx_timeout">capx_timeout</a></span> of
connection establishment.</p>
</dd>
<dt><strong><span class="code">{'CEA', Result, Caps, Pkt}</span></strong></dt>
<dd>
<div class="example"><pre>
Result = integer() | atom() | {capabilities_cb, CB, ResultCode|discard}
Caps = #diameter_caps{}
Pkt = #diameter_packet{}
ResultCode = integer()
</pre></div>
<p>
An incoming CEA has been rejected for the indicated reason.
An integer-valued <span class="code">Result</span> indicates the result code sent
by the peer.
<span class="code">Caps</span> contains pairs of values for the the local node and remote
peer.
<span class="code">Pkt</span> contains the CEA in question.
In the case of rejection by a capabilities callback, the tuple
contains the rejecting callback.</p>
</dd>
<dt><strong><span class="code">{'CEA', Caps, Pkt}</span></strong></dt>
<dd>
<div class="example"><pre>
Caps = #diameter_caps{}
Pkt = #diameter_packet{}
</pre></div>
<p>
An incoming CEA contained errors and has been rejected.
<span class="code">Caps</span> contains only values for the the local node.
<span class="code">Pkt</span> contains the CEA in question.</p>
</dd>
<dt><strong><span class="code">{'CEA', timeout}</span></strong></dt>
<dd>
<p>
An expected CEA was not received within <span class="bold_code"><a href="#capx_timeout">capx_timeout</a></span>
of connection establishment.</p>
</dd>
</dl>
</dd>
<dt><strong><span class="code">{watchdog, Ref, PeerRef, {From, To}, Config}</span></strong></dt>
<dd>
<div class="example"><pre>
Ref = <span class="bold_code"><a href="#transport_ref">transport_ref()</a></span>
PeerRef = <span class="bold_code"><a href="diameter_app.html#peer_ref">diameter_app:peer_ref()</a></span>
From, To = initial | okay | suspect | down | reopen
Config = {connect|listen, [transport_opt()]}
</pre></div>
<p>
An RFC 3539 watchdog state machine has changed state.</p>
</dd>
</dl>
<p>
For forward compatibility, a subscriber should be prepared to receive
info fields of forms other than the above.</p>
<a name="service_name"></a>
</dd>
<dt><strong><span class="code">service_name() = term()</span></strong></dt>
<dd>
<p>
The name of a service as passed to <span class="bold_code"><a href="#start_service-2">start_service/2</a></span> and with which the
service is identified.
There can be at most one service with a given name on a given node.
Note that <span class="bold_code"><a href="javascript:erlhref('../../../../doc/../','erts','erlang.html#make_ref-0');">erlang:make_ref/0</a></span>
can be used to generate a service name that is somewhat unique.</p>
<a name="service_opt"></a>
</dd>
<dt><strong><span class="code">service_opt()</span></strong></dt>
<dd>
<p>
An option passed to <span class="bold_code"><a href="#start_service-2">start_service/2</a></span>.
Can be any <span class="code"><span class="bold_code"><a href="#capability">capability()</a></span></span> as well as the following.</p>
<dl>
<dt><strong><span class="code">{application, [<span class="bold_code"><a href="#application_opt">application_opt()</a></span>]}</span></strong></dt>
<dd>
<p>
Defines a Diameter application supported by the service.</p>
<p>
A service must configure one tuple for each Diameter
application it intends to support.
For an outgoing Diameter request, the relevant <span class="code"><span class="bold_code"><a href="#application_alias">application_alias()</a></span></span> is
passed to <span class="bold_code"><a href="#call-4">call/4</a></span>, while for an
incoming request the application identifier in the message
header determines the application, the identifier being specified in
the application's <span class="bold_code"><a href="diameter_dict.html">dictionary</a></span> file.</p>
</dd>
<dt><strong><span class="code">{restrict_connections, false
| node
| nodes
| [node()]
| evaluable()}</span></strong></dt>
<dd>
<p>
Specifies the degree to which multiple transport connections to the
same peer are accepted by the service.</p>
<p>
If type <span class="code">[node()]</span> then a connection is rejected if another already
exists on any of the specified nodes.
Values of type <span class="code">false</span>, <span class="code">node</span>, <span class="code">nodes</span> or
<span class="bold_code"><a href="#evaluable">evaluable()</a></span> are equivalent to
values <span class="code">[]</span>, <span class="code">[node()]</span>, <span class="code">[node()|nodes()]</span> and the
evaluated value, respectively, evaluation of each expression taking
place whenever a new connection is to be established.
Note that <span class="code">false</span> allows an unlimited number of connections to be
established with the same peer.</p>
<p>
Multiple connections are independent and governed
by their own peer and watchdog state machines.</p>
<p>
Defaults to <span class="code">nodes</span>.</p>
</dd>
<dt><strong><span class="code">{sequence, {H,N} | <span class="bold_code"><a href="#evaluable">evaluable()</a></span>}</span></strong></dt>
<dd>
<p>
Specifies a constant value <span class="code">H</span> for the topmost <span class="code">32-N</span> bits of
of 32-bit End-to-End and Hop-by-Hop identifiers generated
by the service, either explicity or as a return value of a function
to be evaluated at <span class="bold_code"><a href="#start_service-2">start_service/2</a></span>.
In particular, an identifier <span class="code">Id</span> is mapped to a new identifier
as follows.</p>
<div class="example"><pre>
(H bsl N) bor (Id band ((1 bsl N) - 1))
</pre></div>
<p>
Note that RFC 6733 requires that End-to-End identifiers remain unique
for a period of at least 4 minutes and that this and the call rate
places a lower bound on the appropriate values of <span class="code">N</span>:
at a rate of <span class="code">R</span> requests per second an <span class="code">N</span>-bit counter
traverses all of its values in <span class="code">(1 bsl N) div (R*60)</span> minutes so
the bound is <span class="code">4*R*60 =< 1 bsl N</span>.</p>
<p><span class="code">N</span> must lie in the range <span class="code">0..32</span> and <span class="code">H</span> must be a
non-negative integer less than <span class="code">1 bsl (32-N)</span>.</p>
<p>
Defaults to <span class="code">{0,32}</span>.</p>
</dd>
</dl>
<a name="transport_opt"></a>
</dd>
<dt><strong><span class="code">transport_opt()</span></strong></dt>
<dd>
<p>
An option passed to <span class="bold_code"><a href="#add_transport-2">add_transport/2</a></span>.
Has one of the following types.</p>
<dl>
<a name="applications"></a>
<dt><strong><span class="code">{applications, [<span class="bold_code"><a href="#application_alias">application_alias()</a></span>]}</span></strong></dt>
<dd>
<p>
The list of Diameter applications to which the transport should be
restricted.
Defaults to all applications configured on the service in question.
Applications not configured on the service in question are ignored.</p>
</dd>
<a name="capabilities"></a>
<dt><strong><span class="code">{capabilities, [<span class="bold_code"><a href="#capability">capability()</a></span>]}</span></strong></dt>
<dd>
<p>
AVP's used to construct outgoing CER/CEA messages.
Values take precedence over any specified on the service in
question.</p>
<p>
Specifying a capability as a transport option
may be particularly appropriate for Inband-Security-Id, in case
TLS is desired over TCP as implemented by <span class="bold_code"><a href="diameter_tcp.html">diameter_tcp(3)</a></span>.</p>
</dd>
<a name="capabilities_cb"></a>
<dt><strong><span class="code">{capabilities_cb, <span class="bold_code"><a href="#evaluable">evaluable()</a></span>}</span></strong></dt>
<dd>
<p>
A callback invoked upon reception of CER/CEA during capabilities
exchange in order to ask whether or not the connection should
be accepted.
Applied to the <span class="code"><span class="bold_code"><a href="#transport_ref">transport_ref()</a></span></span> and
<span class="code">#diameter_caps{}</span> record of the connection.</p>
<p>
The return value can have one of the following types.</p>
<dl>
<dt><strong><span class="code">ok</span></strong></dt>
<dd>
<p>
Accept the connection.</p>
</dd>
<dt><strong><span class="code">integer()</span></strong></dt>
<dd>
<p>
Causes an incoming CER to be answered with the specified Result-Code.</p>
</dd>
<dt><strong><span class="code">discard</span></strong></dt>
<dd>
<p>
Causes an incoming CER to be discarded without CEA being sent.</p>
</dd>
<dt><strong><span class="code">unknown</span></strong></dt>
<dd>
<p>
Equivalent to returning <span class="code">3010</span>, DIAMETER_UNKNOWN_PEER.</p>
</dd>
</dl>
<p>
Returning anything but <span class="code">ok</span> or a 2xxx series result
code causes the transport connection to be broken.
Multiple <span class="bold_code"><a href="#capabilities_cb">capabilities_cb</a></span>
options can be specified, in which
case the corresponding callbacks are applied until either all return
<span class="code">ok</span> or one does not.</p>
</dd>
<a name="capx_timeout"></a>
<dt><strong><span class="code">{capx_timeout, <span class="bold_code"><a href="diameter_dict.html#DATA_TYPES">Unsigned32()</a></span>}</span></strong></dt>
<dd>
<p>
The number of milliseconds after which a transport process having an
established transport connection will be terminated if the expected
capabilities exchange message (CER or CEA) is not received from the peer.
For a connecting transport, the timing reconnection attempts is
governed by <span class="bold_code"><a href="#watchdog_timer">watchdog_timer</a></span> or
<span class="bold_code"><a href="#reconnect_timer">reconnect_timer</a></span> expiry.
For a listening transport, the peer determines the timing.</p>
<p>
Defaults to 10000.</p>
</dd>
<a name="disconnect_cb"></a>
<dt><strong><span class="code">{disconnect_cb, <span class="bold_code"><a href="#evaluable">evaluable()</a></span>}</span></strong></dt>
<dd>
<p>
A callback invoked prior to terminating the transport process of a
transport connection having watchdog state <span class="code">OKAY</span>.
Applied to <span class="code">Reason=transport|service|application</span> and the
<span class="code"><span class="bold_code"><a href="#transport_ref">transport_ref()</a></span></span> and
<span class="code"><span class="bold_code"><a href="diameter_app.html#peer">diameter_app:peer()</a></span></span>
in question, <span class="code">Reason</span> indicating whether the the diameter
application is being stopped, the service in question is being stopped
at <span class="bold_code"><a href="#stop_service-1">stop_service/1</a></span> or
the transport in question is being removed at <span class="bold_code"><a href="#remove_transport-2">remove_transport/2</a></span>,
respectively.</p>
<p>
The return value can have one of the following types.</p>
<dl>
<dt><strong><span class="code">{dpr, [option()]}</span></strong></dt>
<dd>
<p>
Causes Disconnect-Peer-Request to be sent to the peer, the transport
process being terminated following reception of
Disconnect-Peer-Answer or timeout.
An <span class="code">option()</span> can be one of the following.</p>
<dl>
<dt><strong><span class="code">{cause, 0|rebooting|1|busy|2|goaway}</span></strong></dt>
<dd>
<p>
The Disconnect-Cause to send, <span class="code">REBOOTING</span>, <span class="code">BUSY</span> and
<span class="code">DO_NOT_WANT_TO_TALK_TO_YOU</span> respectively.
Defaults to <span class="code">rebooting</span> for <span class="code">Reason=service|application</span> and
<span class="code">goaway</span> for <span class="code">Reason=transport</span>.</p>
</dd>
<dt><strong><span class="code">{timeout, <span class="bold_code"><a href="diameter_dict.html#DATA_TYPES">Unsigned32()</a></span>}</span></strong></dt>
<dd>
<p>
The number of milliseconds after which the transport process is
terminated if DPA has not been received.
Defaults to 1000.</p>
</dd>
</dl>
</dd>
<dt><strong><span class="code">dpr</span></strong></dt>
<dd>
<p>
Equivalent to <span class="code">{dpr, []}</span>.</p>
</dd>
<dt><strong><span class="code">close</span></strong></dt>
<dd>
<p>
Causes the transport process to be terminated without
Disconnect-Peer-Request being sent to the peer.</p>
</dd>
<dt><strong><span class="code">ignore</span></strong></dt>
<dd>
<p>
Equivalent to not having configured the callback.</p>
</dd>
</dl>
<p>
Multiple <span class="bold_code"><a href="#disconnect_cb">disconnect_cb</a></span>
options can be specified, in which
case the corresponding callbacks are applied until one of them returns
a value other than <span class="code">ignore</span>.
All callbacks returning <span class="code">ignore</span> is equivalent to not having
configured them.</p>
<p>
Defaults to a single callback returning <span class="code">dpr</span>.</p>
</dd>
<a name="reconnect_timer"></a>
<dt><strong><span class="code">{reconnect_timer, Tc}</span></strong></dt>
<dd>
<div class="example"><pre>
Tc = <span class="bold_code"><a href="diameter_dict.html#DATA_TYPES">Unsigned32()</a></span>
</pre></div>
<p>
For a connecting transport, the RFC 6733 Tc timer, in milliseconds.
Note that this timer determines the frequency with which a transport
will attempt to establish a connection with its peer only <strong>before</strong>
an initial connection is established: once there is an initial
connection it's <span class="bold_code"><a href="#watchdog_timer">watchdog_timer</a></span> that determines the
frequency of reconnection attempts, as required by RFC 3539.</p>
<p>
For a listening transport, the timer specifies the time after which a
previously connected peer will be forgotten: a connection after this time is
regarded as an initial connection rather than a reestablishment,
causing the RFC 3539 state machine to pass to state OKAY rather than
REOPEN.
Note that these semantics are not governed by the RFC and
that a listening transport's <span class="bold_code"><a href="#reconnect_timer">reconnect_timer</a></span> should be greater
than its peer's Tw plus jitter.</p>
<p>
Defaults to 30000 for a connecting transport and 60000 for a listening
transport.</p>
</dd>
<a name="transport_config"></a>
<dt><strong><span class="code">{transport_config, term()}</span></strong></dt>
<dt><strong><span class="code">{transport_config, term(), <span class="bold_code"><a href="diameter_dict.html#DATA_TYPES">Unsigned32()</a></span>}</span></strong></dt>
<dd>
<p>
A term passed as the third argument to the <span class="bold_code"><a href="diameter_transport.html#Mod:start-3">start/3</a></span> function of
the relevant <span class="bold_code"><a href="diameter_transport.html">transport module</a></span> in order to
start a transport process.
Defaults to the empty list if unspecified.</p>
<p>
The 3-tuple form additionally specifies an interval, in milliseconds,
after which a started transport process should be terminated if it has
not yet established a connection.
For example, the following options on a connecting transport
request a connection with one peer over SCTP or another
(typically the same) over TCP.</p>
<div class="example"><pre>
{transport_module, diameter_sctp}
{transport_config, SctpOpts, 5000}
{transport_module, diameter_tcp}
{transport_config, TcpOpts}
</pre></div>
<p>
To listen on both SCTP and TCP, define one transport for each.</p>
</dd>
<a name="transport_module"></a>
<dt><strong><span class="code">{transport_module, atom()}</span></strong></dt>
<dd>
<p>
A module implementing a transport process as defined in <span class="bold_code"><a href="diameter_transport.html">diameter_transport(3)</a></span>.
Defaults to <span class="code">diameter_tcp</span> if unspecified.</p>
<p>
Multiple <span class="code">transport_module</span> and <span class="bold_code"><a href="#transport_config">transport_config</a></span>
options are allowed.
The order of these is significant in this case (and only in this case),
a <span class="code">transport_module</span> being paired with the first
<span class="bold_code"><a href="#transport_config">transport_config</a></span>
following it in the options list, or the default value for trailing
modules.
Transport starts will be attempted with each of the
modules in order until one establishes a connection within the
corresponding timeout (see below) or all fail.</p>
</dd>
<a name="watchdog_timer"></a>
<dt><strong><span class="code">{watchdog_timer, TwInit}</span></strong></dt>
<dd>
<div class="example"><pre>
TwInit = <span class="bold_code"><a href="diameter_dict.html#DATA_TYPES">Unsigned32()</a></span>
| {M,F,A}
</pre></div>
<p>
The RFC 3539 watchdog timer.
An integer value is interpreted as the RFC's TwInit in milliseconds,
a jitter of ± 2 seconds being added at each rearming of the
timer to compute the RFC's Tw.
An MFA is expected to return the RFC's Tw directly, with jitter
applied, allowing the jitter calculation to be performed by
the callback.</p>
<p>
An integer value must be at least 6000 as required by RFC 3539.
Defaults to 30000 if unspecified.</p>
</dd>
</dl>
<p>
Unrecognized options are silently ignored but are returned unmodified
by <span class="bold_code"><a href="#service_info-2">service_info/2</a></span> and can be referred to
in predicate functions passed to <span class="bold_code"><a href="#remove_transport-2">remove_transport/2</a></span>.</p>
<a name="transport_ref"></a>
</dd>
<dt><strong><span class="code">transport_ref() = reference()</span></strong></dt>
<dd>
<p>
An reference returned by <span class="bold_code"><a href="#add_transport-2">add_transport/2</a></span> that
identifies the configuration.</p>
</dd>
</dl>
</div>
<h3>EXPORTS</h3>
<p><a name="add_transport-2"><span class="bold_code">add_transport(SvcName, {connect|listen, [Opt]})
-> {ok, Ref} | {error, Reason}</span></a><br></p>
<div class="REFBODY">
<p>Types:</p>
<div class="REFTYPES">
<span class="bold_code">SvcName = <span class="bold_code"><a href="#service_name">service_name()</a></span></span><br>
</div>
<div class="REFTYPES">
<span class="bold_code">Opt = <span class="bold_code"><a href="#transport_opt">transport_opt()</a></span></span><br>
</div>
<div class="REFTYPES">
<span class="bold_code">Ref = <span class="bold_code"><a href="#transport_ref">transport_ref()</a></span></span><br>
</div>
<div class="REFTYPES">
<span class="bold_code">Reason = term()</span><br>
</div>
</div>
<div class="REFBODY"><p>
<p>
Add transport capability to a service.</p>
<p>
The service will start transport processes as required in order to
establish a connection with the peer, either by connecting to the peer
(<span class="code">connect</span>) or by accepting incoming connection requests
(<span class="code">listen</span>).
A connecting transport establishes transport connections with at most
one peer, an listening transport potentially with many.</p>
<p>
The diameter application takes responsibility for exchanging
CER/CEA with the peer.
Upon successful completion of capabilities exchange the service
calls each relevant application module's <span class="bold_code"><a href="diameter_app.html#Mod:peer_up-3">peer_up/3</a></span> callback
after which the caller can exchange Diameter messages with the peer over
the transport.
In addition to CER/CEA, the service takes responsibility for the
handling of DWR/DWA and required by RFC 3539, as well as for DPR/DPA.</p>
<p>
The returned reference uniquely identifies the transport within the
scope of the service.
Note that the function returns before a transport connection has been
established.</p>
<div class="note">
<div class="label">Note</div>
<div class="content"><p>
<p>
It is not an error to add a transport to a service that has not yet
been configured: a service can be started after configuring
its transports.</p>
</p></div>
</div>
</p></div>
<p><a name="call-4"><span class="bold_code">call(SvcName, App, Request, [Opt]) -> Answer | ok | {error, Reason}</span></a><br></p>
<div class="REFBODY">
<p>Types:</p>
<div class="REFTYPES">
<span class="bold_code">SvcName = <span class="bold_code"><a href="#service_name">service_name()</a></span></span><br>
</div>
<div class="REFTYPES">
<span class="bold_code">App = <span class="bold_code"><a href="#application_alias">application_alias()</a></span></span><br>
</div>
<div class="REFTYPES">
<span class="bold_code">Request = <span class="bold_code"><a href="diameter_codec.html#message">diameter_codec:message()</a></span></span><br>
</div>
<div class="REFTYPES">
<span class="bold_code">Answer = term()</span><br>
</div>
<div class="REFTYPES">
<span class="bold_code">Opt = <span class="bold_code"><a href="#call_opt">call_opt()</a></span></span><br>
</div>
</div>
<div class="REFBODY"><p>
<p>
Send a Diameter request message.</p>
<p>
<span class="code">App</span> specifies the Diameter application in which the request is
defined and callbacks to the corresponding callback module
will follow as described below and in <span class="bold_code"><a href="diameter_app.html">diameter_app(3)</a></span>.
Unless the <span class="code">detach</span> option is specified, the call returns either
when an answer message is received from the peer or an error occurs.
In the answer case, the return value is as returned by a
<span class="bold_code"><a href="diameter_app.html#Mod:handle_answer-4">handle_answer/4</a></span> callback.
In the error case, whether or not the error is returned directly
by diameter or from a <span class="bold_code"><a href="diameter_app.html#Mod:handle_error-4">handle_error/4</a></span>
callback depends on whether or not the outgoing request is
successfully encoded for transmission to the peer, the cases being
documented below.</p>
<p>
If there are no suitable peers, or if
<span class="bold_code"><a href="diameter_app.html#Mod:pick_peer-4">pick_peer/4</a></span>
rejects them by returning <span class="code">false</span>, then <span class="code">{error,no_connection}</span>
is returned.
Otherwise <span class="bold_code"><a href="diameter_app.html#Mod:pick_peer-4">pick_peer/4</a></span> is followed by a
<span class="bold_code"><a href="diameter_app.html#Mod:prepare_request-3">prepare_request/3</a></span> callback, the message is encoded and then sent.</p>
<p>
There are several error cases which may prevent an
answer from being received and passed to a
<span class="bold_code"><a href="diameter_app.html#Mod:handle_answer-4">handle_answer/4</a></span> callback:</p>
<ul>
<li>
<p>
If the initial encode of the outgoing request
fails, then the request process fails and <span class="code">{error,encode}</span>
is returned.</p>
</li>
<li>
<p>
If the request is successfully encoded and sent but
the answer times out then a
<span class="bold_code"><a href="diameter_app.html#Mod:handle_error-4">handle_error/4</a></span> callback takes place with <span class="code">Reason = timeout</span>.</p>
</li>
<li>
<p>
If the request is successfully encoded and sent but the service in
question is stopped before an answer is received then a
<span class="bold_code"><a href="diameter_app.html#Mod:handle_error-4">handle_error/4</a></span> callback takes place with <span class="code">Reason = cancel</span>.</p>
</li>
<li>
<p>
If the transport connection with the peer goes down after the request
has been sent but before an answer has been received then an attempt
is made to resend the request to an alternate peer.
If no such peer is available, or if the subsequent
<span class="bold_code"><a href="diameter_app.html#Mod:pick_peer-4">pick_peer/4</a></span> callback rejects the candidates, then a
<span class="bold_code"><a href="diameter_app.html#Mod:handle_error-4">handle_error/4</a></span> callback takes place with <span class="code">Reason = failover</span>.
If a peer is selected then a <span class="bold_code"><a href="diameter_app.html#Mod:prepare_retransmit-3">prepare_retransmit/3</a></span>
callback takes place, after which the semantics are the same as
following an initial <span class="bold_code"><a href="diameter_app.html#Mod:prepare_request-3">prepare_request/3</a></span> callback.</p>
</li>
<li>
<p>
If an encode error takes place during
retransmission then the request process fails and
<span class="code">{error,failure}</span> is returned.</p>
</li>
<li>
<p>
If an application callback made in processing the request fails
(pick_peer, prepare_request, prepare_retransmit,
handle_answer or handle_error) then either
<span class="code">{error,encode}</span> or <span class="code">{error,failure}</span>
is returned depending on whether or not there has been an
attempt to send the request over the transport.</p>
</li>
</ul>
<p>
Note that <span class="code">{error,encode}</span> is the only return value which
guarantees that the request has <strong>not</strong> been sent over the
transport connection.</p>
</p></div>
<p><a name="origin_state_id-0"><span class="bold_code">origin_state_id() -> Unsigned32()</span></a><br></p>
<div class="REFBODY"><p>
<p>
Return a reasonable value for use as Origin-State-Id in
outgoing messages.</p>
<p>
The value returned is the number of seconds since 19680120T031408Z,
the first value that can be encoded as a Diameter <span class="code"><span class="bold_code"><a href="diameter_dict.html#DATA_TYPES">Time()</a></span></span>,
at the time the diameter application was started.</p>
</p></div>
<p><a name="remove_transport-2"><span class="bold_code">remove_transport(SvcName, Pred) -> ok | {error, Reason}</span></a><br></p>
<div class="REFBODY">
<p>Types:</p>
<div class="REFTYPES">
<span class="bold_code">SvcName = <span class="bold_code"><a href="#service_name">service_name()</a></span></span><br>
</div>
<div class="REFTYPES">
<span class="bold_code">Pred = Fun | MFA | <span class="bold_code"><a href="#transport_ref">transport_ref()</a></span> | list() | true | false</span><br>
</div>
<div class="REFTYPES">
<span class="bold_code"></span><br>
</div>
<div class="REFTYPES">
<span class="bold_code">Fun = fun((<span class="bold_code"><a href="#transport_ref">transport_ref()</a></span>, connect|listen, list()) -> boolean())</span><br>
</div>
<div class="REFTYPES">
<span class="bold_code"> | fun((<span class="bold_code"><a href="#transport_ref">transport_ref()</a></span>, list()) -> boolean())</span><br>
</div>
<div class="REFTYPES">
<span class="bold_code"> | fun((list()) -> boolean())</span><br>
</div>
<div class="REFTYPES">
<span class="bold_code">MFA = {atom(), atom(), list()}</span><br>
</div>
<div class="REFTYPES">
<span class="bold_code">Reason = term()</span><br>
</div>
</div>
<div class="REFBODY"><p>
<p>
Remove previously added transports.</p>
<p>
<span class="code">Pred</span> determines which transports to remove.
An arity-3-valued <span class="code">Pred</span> removes all transports for which
<span class="code">Pred(Ref, Type, Opts)</span> returns <span class="code">true</span>, where <span class="code">Type</span> and
<span class="code">Opts</span> are as passed to <span class="bold_code"><a href="#add_transport-2">add_transport/2</a></span> and <span class="code">Ref</span> is
as returned by it.
The remaining forms are equivalent to an arity-3 fun as follows.</p>
<div class="example"><pre>
Pred = fun(transport_ref(), list()): fun(Ref, _, Opts) -> Pred(Ref, Opts) end
Pred = fun(list()): fun(_, _, Opts) -> Pred(Opts) end
Pred = transport_ref(): fun(Ref, _, _) -> Pred == Ref end
Pred = list(): fun(_, _, Opts) -> [] == Pred -- Opts end
Pred = true: fun(_, _, _) -> true end
Pred = false: fun(_, _, _) -> false end
Pred = {M,F,A}: fun(Ref, Type, Opts) -> apply(M, F, [Ref, Type, Opts | A]) end
</pre></div>
<p>
Removing a transport causes the corresponding transport processes to
be terminated.
Whether or not a DPR message is sent to a peer is
controlled by value of <span class="bold_code"><a href="#disconnect_cb">disconnect_cb</a></span>
configured on the transport.</p>
</p></div>
<p><a name="service_info-2"><span class="bold_code">service_info(SvcName, Info) -> term()</span></a><br></p>
<div class="REFBODY">
<p>Types:</p>
<div class="REFTYPES">
<span class="bold_code">SvcName = <span class="bold_code"><a href="#service_name">service_name()</a></span></span><br>
</div>
<div class="REFTYPES">
<span class="bold_code">Info = Item | [Info]</span><br>
</div>
<div class="REFTYPES">
<span class="bold_code">Item = atom()</span><br>
</div>
</div>
<div class="REFBODY"><p>
<p>
Return information about a started service.
Requesting info for an unknown service causes <span class="code">undefined</span> to be
returned.
Requesting a list of items causes a tagged list to be
returned.</p>
<p>
<span class="code">Item</span> can be one of the following.</p>
<dl>
<dt><strong><span class="code">'Origin-Host'</span></strong></dt>
<dt><strong><span class="code">'Origin-Realm'</span></strong></dt>
<dt><strong><span class="code">'Vendor-Id'</span></strong></dt>
<dt><strong><span class="code">'Product-Name'</span></strong></dt>
<dt><strong><span class="code">'Origin-State-Id'</span></strong></dt>
<dt><strong><span class="code">'Host-IP-Address'</span></strong></dt>
<dt><strong><span class="code">'Supported-Vendor'</span></strong></dt>
<dt><strong><span class="code">'Auth-Application-Id'</span></strong></dt>
<dt><strong><span class="code">'Inband-Security-Id'</span></strong></dt>
<dt><strong><span class="code">'Acct-Application-Id'</span></strong></dt>
<dt><strong><span class="code">'Vendor-Specific-Application-Id'</span></strong></dt>
<dt><strong><span class="code">'Firmware-Revision'</span></strong></dt>
<dd>
<p>
Return a capability value as configured with <span class="bold_code"><a href="#start_service-2">start_service/2</a></span>.</p>
</dd>
<dt><strong><span class="code">applications</span></strong></dt>
<dd>
<p>
Return the list of applications as configured with <span class="bold_code"><a href="#start_service-2">start_service/2</a></span>.
</p>
</dd>
<dt><strong><span class="code">capabilities</span></strong></dt>
<dd>
<p>
Return a tagged list of all capabilities values as configured with
<span class="bold_code"><a href="#start_service-2">start_service/2</a></span>.</p>
</dd>
<dt><strong><span class="code">transport</span></strong></dt>
<dd>
<p>
Return a list containing one entry for each of the service's transport
as configured with <span class="bold_code"><a href="#add_transport-2">add_transport/2</a></span>.
Each entry is a tagged list containing both configuration and
information about established peer connections.
An example return value with for a client service with Origin-Host
"client.example.com" configured with a single transport connected to
"server.example.com" might look as follows.</p>
<div class="example"><pre>
[[{ref,#Ref<0.0.0.93>},
{type,connect},
{options,[{transport_module,diameter_tcp},
{transport_config,[{ip,{127,0,0,1}},
{raddr,{127,0,0,1}},
{rport,3868},
{reuseaddr,true}]}]},
{watchdog,{<0.66.0>,{1346,171491,996448},okay}},
{peer,{<0.67.0>,{1346,171491,999906}}},
{apps,[{0,common}]},
{caps,[{origin_host,{"client.example.com","server.example.com"}},
{origin_realm,{"example.com","example.com"}},
{host_ip_address,{[{127,0,0,1}],[{127,0,0,1}]}},
{vendor_id,{0,193}},
{product_name,{"Client","Server"}},
{origin_state_id,{[],[]}},
{supported_vendor_id,{[],[]}},
{auth_application_id,{[0],[0]}},
{inband_security_id,{[],[0]}},
{acct_application_id,{[],[]}},
{vendor_specific_application_id,{[],[]}},
{firmware_revision,{[],[]}},
{avp,{[],[]}}]},
{port,[{owner,<0.69.0>},
{module,diameter_tcp},
{socket,{{127,0,0,1},48758}},
{peer,{{127,0,0,1},3868}},
{statistics,[{recv_oct,656},
{recv_cnt,6},
{recv_max,148},
{recv_avg,109},
{recv_dvi,19},
{send_oct,836},
{send_cnt,6},
{send_max,184},
{send_avg,139},
{send_pend,0}]}]},
{statistics,[{{{0,258,0},recv},3},
{{{0,258,1},send},3},
{{{0,257,0},recv},1},
{{{0,257,1},send},1},
{{{0,258,0},recv,{'Result-Code',2001}},3},
{{{0,280,1},recv},2},
{{{0,280,0},send},2}]}]]
</pre></div>
<p>
Here <span class="code">ref</span> is a <span class="code"><span class="bold_code"><a href="#transport_ref">transport_ref()</a></span></span> and <span class="code">options</span>
the corresponding <span class="code"><span class="bold_code"><a href="#transport_opt">transport_opt()</a></span></span> list passed to
<span class="bold_code"><a href="#add_transport-2">add_transport/2</a></span>.
The <span class="code">watchdog</span> entry shows the state of a connection's RFC 3539 watchdog
state machine.
The <span class="code">peer</span> entry identifies the <span class="code"><span class="bold_code"><a href="diameter_app.html#peer_ref">diameter_app:peer_ref()</a></span></span> for
which there will have been <span class="bold_code"><a href="diameter_app.html#Mod:peer_up-3">peer_up/3</a></span> callbacks for the
Diameter applications identified by the <span class="code">apps</span> entry,
<span class="code">common</span> being the <span class="code"><span class="bold_code"><a href="#application_alias">application_alias()</a></span></span>.
The <span class="code">caps</span> entry identifies the capabilities sent by the local
node and received from the peer during capabilities exchange.
The <span class="code">port</span> entry displays socket-level information about the
transport connection.
The <span class="code">statistics</span> entry presents Diameter-level counters,
an entry like <span class="code">{{{0,280,1},recv},2}</span> saying that the client has
received 2 DWR messages: <span class="code">{0,280,1} = {Application_Id, Command_Code,
R_Flag}</span>.</p>
<p>
Note that <span class="code">watchdog</span>, <span class="code">peer</span>, <span class="code">apps</span>, <span class="code">caps</span>
and <span class="code">port</span> entries depend on connectivity
with the peer and may not be present.
Note also that the <span class="code">statistics</span> entry presents values acuumulated
during the lifetime of the transport configuration.</p>
<p>
A listening transport presents its information slightly differently
since there may be multiple accepted connections for the same
<span class="code"><span class="bold_code"><a href="#transport_ref">transport_ref()</a></span></span>.
The <span class="code">transport</span> info returned by a server with a single client
connection might look as follows.</p>
<div class="example"><pre>
[[{ref,#Ref<0.0.0.61>},
{type,listen},
{options,[{transport_module,diameter_tcp},
{transport_config,[{reuseaddr,true},
{ip,{127,0,0,1}},
{port,3868}]}]},
{accept,[[{watchdog,{<0.56.0>,{1346,171481,226895},okay}},
{peer,{<0.58.0>,{1346,171491,999511}}},
{apps,[{0,common}]},
{caps,[{origin_host,{"server.example.com","client.example.com"}},
{origin_realm,{"example.com","example.com"}},
{host_ip_address,{[{127,0,0,1}],[{127,0,0,1}]}},
{vendor_id,{193,0}},
{product_name,{"Server","Client"}},
{origin_state_id,{[],[]}},
{supported_vendor_id,{[],[]}},
{auth_application_id,{[0],[0]}},
{inband_security_id,{[],[]}},
{acct_application_id,{[],[]}},
{vendor_specific_application_id,{[],[]}},
{firmware_revision,{[],[]}},
{avp,{[],[]}}]},
{port,[{owner,<0.62.0>},
{module,diameter_tcp},
{socket,{{127,0,0,1},3868}},
{peer,{{127,0,0,1},48758}},
{statistics,[{recv_oct,1576},
{recv_cnt,16},
{recv_max,184},
{recv_avg,98},
{recv_dvi,26},
{send_oct,1396},
{send_cnt,16},
{send_max,148},
{send_avg,87},
{send_pend,0}]}]}],
[{watchdog,{<0.72.0>,{1346,171491,998404},initial}}]]},
{statistics,[{{{0,280,0},recv},7},
{{{0,280,1},send},7},
{{{0,258,0},send,{'Result-Code',2001}},3},
{{{0,258,1},recv},3},
{{{0,258,0},send},3},
{{{0,280,1},recv},5},
{{{0,280,0},send},5},
{{{0,257,1},recv},1},
{{{0,257,0},send},1}]}]]
</pre></div>
<p>
The information presented here is as in the <span class="code">connect</span> case except
that the client connections are grouped under an <span class="code">accept</span> tuple.</p>
</dd>
<dt><strong><span class="code">connections</span></strong></dt>
<dd>
<p>
Return a list containing one entry for every established transport
connection whose watchdog state machine is not in the <span class="code">down</span>
state.
This is a flat view of <span class="code">transport</span> info which lists only active
connections and for which Diameter-level statistics are accumulated
only for the lifetime of the transport connection.
A return value for the server above might look as follows.</p>
<div class="example"><pre>
[[{ref,#Ref<0.0.0.61>},
{type,accept},
{options,[{transport_module,diameter_tcp},
{transport_config,[{reuseaddr,true},
{ip,{127,0,0,1}},
{port,3868}]}]},
{watchdog,{<0.56.0>,{1346,171481,226895},okay}},
{peer,{<0.58.0>,{1346,171491,999511}}},
{apps,[{0,common}]},
{caps,[{origin_host,{"server.example.com","client.example.com"}},
{origin_realm,{"example.com","example.com"}},
{host_ip_address,{[{127,0,0,1}],[{127,0,0,1}]}},
{vendor_id,{193,0}},
{product_name,{"Server","Client"}},
{origin_state_id,{[],[]}},
{supported_vendor_id,{[],[]}},
{auth_application_id,{[0],[0]}},
{inband_security_id,{[],[]}},
{acct_application_id,{[],[]}},
{vendor_specific_application_id,{[],[]}},
{firmware_revision,{[],[]}},
{avp,{[],[]}}]},
{port,[{owner,<0.62.0>},
{module,diameter_tcp},
{socket,{{127,0,0,1},3868}},
{peer,{{127,0,0,1},48758}},
{statistics,[{recv_oct,10124},
{recv_cnt,132},
{recv_max,184},
{recv_avg,76},
{recv_dvi,9},
{send_oct,10016},
{send_cnt,132},
{send_max,148},
{send_avg,75},
{send_pend,0}]}]},
{statistics,[{{{0,280,0},recv},62},
{{{0,280,1},send},62},
{{{0,258,0},send,{'Result-Code',2001}},3},
{{{0,258,1},recv},3},
{{{0,258,0},send},3},
{{{0,280,1},recv},66},
{{{0,280,0},send},66},
{{{0,257,1},recv},1},
{{{0,257,0},send},1}]}]]
</pre></div>
<p>
Note that there may be multiple entries with the same <span class="code">ref</span>, in
contrast to <span class="code">transport</span> info.</p>
</dd>
<dt><strong><span class="code">statistics</span></strong></dt>
<dd>
<p>
Return a <span class="code">{{Counter, Ref}, non_neg_integer()}</span> list of counter values.
<span class="code">Ref</span> can be either a <span class="code"><span class="bold_code"><a href="#transport_ref">transport_ref()</a></span></span>
or a <span class="code"><span class="bold_code"><a href="diameter_app.html#peer_ref">diameter_app:peer_ref()</a></span></span>.
Entries for the latter are folded into corresponding entries for the
former as peer connections go down.
Entries for both are removed at <span class="bold_code"><a href="#remove_transport-2">remove_transport/2</a></span>.
The Diameter-level statistics returned by <span class="code">transport</span> and
<span class="code">connections</span> info are based upon these entries.</p>
</dd>
<dt><strong><span class="code"><span class="bold_code"><a href="diameter_app.html#peer_ref">diameter_app:peer_ref()</a></span></span></strong></dt>
<dd>
<p>
Return transport configuration associated with a single peer, as
passed to <span class="bold_code"><a href="#add_transport-2">add_transport/2</a></span>.
The returned list is empty if the peer is unknown.
Otherwise it contains the <span class="code">ref</span>, <span class="code">type</span> and <span class="code">options</span>
tuples as in <span class="code">transport</span> and <span class="code">connections</span> info above.
For example:</p>
<div class="example"><pre>
[{ref,#Ref<0.0.0.61>},
{type,accept},
{options,[{transport_module,diameter_tcp},
{transport_config,[{reuseaddr,true},
{ip,{127,0,0,1}},
{port,3868}]}]}]
</pre></div>
</dd>
</dl>
</p></div>
<p><a name="services-0"><span class="bold_code">services() -> [SvcName]</span></a><br></p>
<div class="REFBODY">
<p>Types:</p>
<div class="REFTYPES">
<span class="bold_code">SvcName = <span class="bold_code"><a href="#service_name">service_name()</a></span></span><br>
</div>
</div>
<div class="REFBODY"><p>
<p>
Return the list of started services.</p>
</p></div>
<p><a name="session_id-1"><span class="bold_code">session_id(Ident) -> OctetString()</span></a><br></p>
<div class="REFBODY">
<p>Types:</p>
<div class="REFTYPES">
<span class="bold_code">Ident = <span class="bold_code"><a href="diameter_dict.html#DATA_TYPES">DiameterIdentity()</a></span></span><br>
</div>
</div>
<div class="REFBODY"><p>
<p>
Return a value for a Session-Id AVP.</p>
<p>
The value has the form required by section 8.8 of RFC 6733.
Ident should be the Origin-Host of the peer from which
the message containing the returned value will be sent.</p>
</p></div>
<p><a name="start-0"><span class="bold_code">start() -> ok | {error, Reason}</span></a><br></p>
<div class="REFBODY"><p>
<p>
Start the diameter application.</p>
<p>
The diameter application must be started before starting a service.
In a production system this is typically accomplished by a boot
file, not by calling <span class="code">start/0</span> explicitly.</p>
</p></div>
<p><a name="start_service-2"><span class="bold_code">start_service(SvcName, Options) -> ok | {error, Reason}</span></a><br></p>
<div class="REFBODY">
<p>Types:</p>
<div class="REFTYPES">
<span class="bold_code">SvcName = <span class="bold_code"><a href="#service_name">service_name()</a></span></span><br>
</div>
<div class="REFTYPES">
<span class="bold_code">Options = [<span class="bold_code"><a href="#service_opt">service_opt()</a></span>]</span><br>
</div>
<div class="REFTYPES">
<span class="bold_code">Reason = term()</span><br>
</div>
</div>
<div class="REFBODY"><p>
<p>
Start a diameter service.</p>
<p>
A service defines a locally-implemented Diameter node, specifying the
capabilities to be advertised during capabilities exchange.
Transports are added to a service using <span class="bold_code"><a href="#add_transport-2">add_transport/2</a></span>.
</p>
<div class="note">
<div class="label">Note</div>
<div class="content"><p>
<p>
A transport can both override its service's
capabilities and restrict its supported Diameter applications so
"service = Diameter node as identified by Origin-Host" is not
necessarily the case.</p>
</p></div>
</div>
</p></div>
<p><a name="stop-0"><span class="bold_code">stop() -> ok | {error, Reason}</span></a><br></p>
<div class="REFBODY"><p>
<p>
Stop the diameter application.</p>
<p>
</p>
</p></div>
<p><a name="stop_service-1"><span class="bold_code">stop_service(SvcName) -> ok | {error, Reason}</span></a><br></p>
<div class="REFBODY">
<p>Types:</p>
<div class="REFTYPES">
<span class="bold_code">SvcName = <span class="bold_code"><a href="#service_name">service_name()</a></span></span><br>
</div>
<div class="REFTYPES">
<span class="bold_code">Reason = term()</span><br>
</div>
</div>
<div class="REFBODY"><p>
<p>
Stop a diameter service.</p>
<p>
Stopping a service causes all associated transport connections to be
broken.
A DPR message with be sent as in the case of <span class="bold_code"><a href="#remove_transport-2">remove_transport/2</a></span>.</p>
<div class="note">
<div class="label">Note</div>
<div class="content"><p>
<p>
Stopping a service does not remove any associated transports:
<span class="bold_code"><a href="#remove_transport-2">remove_transport/2</a></span> must
be called to remove transport configuration.</p>
</p></div>
</div>
</p></div>
<p><a name="subscribe-1"><span class="bold_code">subscribe(SvcName) -> true</span></a><br></p>
<div class="REFBODY">
<p>Types:</p>
<div class="REFTYPES">
<span class="bold_code">SvcName = <span class="bold_code"><a href="#service_name">service_name()</a></span></span><br>
</div>
</div>
<div class="REFBODY"><p>
<p>
Subscribe to <span class="code"><span class="bold_code"><a href="#service_event">service_event()</a></span></span> messages from
a service.</p>
<p>
It is not an error to subscribe to events from a service
that does not yet exist.
Doing so before adding transports is required to guarantee the
reception of all related events.</p>
</p></div>
<p><a name="unsubscribe-1"><span class="bold_code">unsubscribe(SvcName) -> true</span></a><br></p>
<div class="REFBODY">
<p>Types:</p>
<div class="REFTYPES">
<span class="bold_code">SvcName = <span class="bold_code"><a href="#service_name">service_name()</a></span></span><br>
</div>
</div>
<div class="REFBODY"><p>
<p>
Unsubscribe to event messages from a service.</p>
</p></div>
<h3><a name="id73621">SEE ALSO</a></h3>
<div class="REFBODY">
<p>
<span class="bold_code"><a href="diameter_app.html">diameter_app(3)</a></span>, <span class="bold_code"><a href="diameter_transport.html">diameter_transport(3)</a></span>, <span class="bold_code"><a href="diameter_dict.html">diameter_dict(4)</a></span></p>
</div>
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