diameter(3)

DATA TYPES Address() DiameterIdentity() Grouped() OctetString() Time() Unsigned32() UTF8String()

Types corresponding to &the_rfc; AVP Data Formats. Defined in &dict_data_types;.

application_alias() = term()

A name identifying a Diameter application in service configuration. Passed to &call; when sending requests defined by the application.

application_module() = Mod | [Mod | ExtraArgs] | #diameter_callback{}

Mod = atom()
ExtraArgs = list()

A module implementing the callback interface defined in &man_app;, 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 &call;, in which case those are are appended to any module-specific extra arguments.

Specifying a #diameter_callback{} record allows individual functions to be configured in place of the usual &man_app; callbacks. See that module for details.

application_opt()

Options defining a Diameter application. Has one the following types.

{alias, &application_alias;}

An unique identifier for the application in the scope of the service. Defaults to the value of the dictionary option if unspecified.

{dictionary, atom()}

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 &man_dict;.

{module, &application_module;}

The callback module with which messages of the Diameter application are handled. See &man_app; for the required interface and semantics.

{state, term()}

The initial callback state. The prevailing state is passed to some &man_app; callbacks, which can then return a new state. Defaults to the value of the alias option if unspecified.

{call_mutates_state, true|false}

Specifies whether or not the &app_pick_peer; application callback can modify the application state, Defaults to false if unspecified.

&app_pick_peer; 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.

{answer_errors, callback|report|discard}

Determines the manner in which incoming answer messages containing decode errors are handled. If callback then errors result in a &app_handle_answer; callback in the same fashion as for &app_handle_request;, with errors communicated in the errors field of the #diameter_packet{} record passed to the callback. If report then an answer containing errors is discarded without a callback and a warning report is written to the log. If discard then an answer containing errors is silently discarded without a callback. In both the report and discard cases the return value for the &call; invocation in question is as if a callback had taken place and returned {error, failure}.

Defaults to report if unspecified.

call_opt()

Options available to &call; when sending an outgoing Diameter request. Has one of the following types.

{extra, list()}

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.

{filter, &peer_filter;}

A filter to apply to the list of available peers before passing them to the &app_pick_peer; callback for the application in question. Multiple options are equivalent a single all filter on the corresponding list of filters. Defaults to none.

{timeout, &dict_Unsigned32;}

The number of milliseconds after which the request should timeout. Defaults to 5000.

detach

Causes &call; to return ok as soon as the request in question has been encoded instead of waiting for and returning the result from a subsequent &app_handle_answer; or &app_handle_error; callback.

An invalid option will cause &call; to fail.

capability()

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.

{'Origin-Host', &dict_DiameterIdentity;} {'Origin-Realm', &dict_DiameterIdentity;} {'Host-IP-Address', [&dict_Address;]}

An address list is available to the start function of a &transport_module;, 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.

{'Vendor-Id', &dict_Unsigned32;} {'Product-Name', &dict_UTF8String;} {'Origin-State-Id', &dict_Unsigned32;}

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 0 (zero) is equivalent to not setting a value as documented in &the_rfc;. The function &origin_state_id; can be used as to retrieve a value that is computed when the diameter application is started.

{'Supported-Vendor-Id', [&dict_Unsigned32;]} {'Auth-Application-Id', [&dict_Unsigned32;]} {'Inband-Security-Id', [&dict_Unsigned32;]}

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.

{'Acct-Application-Id', [&dict_Unsigned32;]} {'Vendor-Specific-Application-Id', [&dict_Grouped;]} {'Firmware-Revision', &dict_Unsigned32;}

Note that each tuple communicates one or more AVP values. It is an error to specify duplicate tuples.

evaluable() = {M,F,A} | fun() | [evaluable() | A]

An expression that can be evaluated as a function in the following sense.

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]).

Applying an &evaluable; E to an argument list A is meant in the sense of eval([E|A]).

Beware of using fun expressions of the form fun Name/Arity 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 &start_service; or &add_transport;.

peer_filter() = term()

A filter passed to &call; in order to select candidate peers for a &app_pick_peer; callback. Has one of the following types.

none

Matches any peer. This is a convenience that provides a filter equivalent to no filter at all.

host

Matches only those peers whose Origin-Host has the same value as Destination-Host in the outgoing request in question, or any peer if the request does not contain a Destination-Host AVP.

realm

Matches only those peers whose Origin-Realm has the same value as Destination-Realm in the outgoing request in question, or any peer if the request does not contain a Destination-Realm AVP.

{host, any|&dict_DiameterIdentity;}

Matches only those peers whose Origin-Host has the specified value, or all peers if the atom any.

{realm, any|&dict_DiameterIdentity;

Matches only those peers whose Origin-Realm has the specified value, or all peers if the atom any.

{eval, &evaluable;}

Matches only those peers for which the specified &evaluable; returns true on the connection's diameter_caps record. Any other return value or exception is equivalent to false.

{neg, &peer_filter;}

Matches only those peers not matched by the specified filter.

{all, [&peer_filter;]}

Matches only those peers matched by each filter in the specified list.

{any, [&peer_filter;]}

Matches only those peers matched by at least one filter in the specified list.

An invalid filter is equivalent to {any,[]}, a filter that matches no peer.

The host and realm filters examine the outgoing request as passed to &call;, assuming that this is a record- or list-valued &codec_message;, and that the message contains at most one of each AVP. If this is not the case then the {host|realm, &dict_DiameterIdentity;} filters must be used to achieve the desired result. An empty &dict_DiameterIdentity; (which should not be typical) matches all hosts/realms for the purposes of filtering.

A host filter is not typically desirable when setting Destination-Host since it will remove peer agents from the candidates list.

service_event() = #diameter_event{service = &service_name;, info = &service_event_info;}

An event message sent to processes that have subscribed to these using &subscribe;.

service_event_info() = term()

The info field of a &service_event; record. Can have one of the following types.

start stop

The service is being started or stopped. No event precedes a start event. No event follows a stop event and this event implies the termination of all transport processes.

{up, Ref, Peer, Config, Pkt} {up, Ref, Peer, Config} {down, Ref, Peer, Config}

Ref    = &transport_ref;
Peer   = &app_peer;
Config = {connect|listen, [&transport_opt;]}
Pkt    = #diameter_packet{}

The RFC 3539 watchdog state machine has transitioned into (up) or out of (down) the OKAY state. If a #diameter_packet{} record is present in an up 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.

Note that a single up or down event for a given peer corresponds to multiple &app_peer_up; or &app_peer_down; callbacks, one 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.

{reconnect, Ref, Opts}

Ref  = &transport_ref;
Opts = [&transport_opt;]

A connecting transport is attempting to establish/reestablish a transport connection with a peer following &reconnect_timer; or &watchdog_timer; expiry.

{closed, Ref, Reason, Config}

Ref = &transport_ref;
Config = {connect|listen, [&transport_opt;]}

Capabilities exchange has failed. Reason can have one of the following types.

{'CER', Result, Caps, Pkt}

Result = ResultCode | {capabilities_cb, CB, ResultCode|discard}
Caps = #diameter_caps{}
Pkt  = #diameter_packet{}
ResultCode = integer()
CB = &evaluable;

An incoming CER has been answered with the indicated result code or discarded. Caps contains pairs of values for the local node and remote peer. Pkt contains the CER in question. In the case of rejection by a capabilities callback, the tuple contains the rejecting callback.

{'CER', Caps, {ResultCode, Pkt}}

ResultCode = integer()
Caps = #diameter_caps{}
Pkt  = #diameter_packet{}

An incoming CER contained errors and has been answered with the indicated result code. Caps contains only values for the local node. Pkt contains the CER in question.

{'CER', timeout}

An expected CER was not received within &capx_timeout; of connection establishment.

{'CEA', Result, Caps, Pkt}

Result = integer() | atom() | {capabilities_cb, CB, ResultCode|discard}
Caps = #diameter_caps{}
Pkt  = #diameter_packet{}
ResultCode = integer()

An incoming CEA has been rejected for the indicated reason. An integer-valued Result indicates the result code sent by the peer. Caps contains pairs of values for the local node and remote peer. Pkt contains the CEA in question. In the case of rejection by a capabilities callback, the tuple contains the rejecting callback.

{'CEA', Caps, Pkt}

Caps = #diameter_caps{}
Pkt  = #diameter_packet{}

An incoming CEA contained errors and has been rejected. Caps contains only values for the local node. Pkt contains the CEA in question.

{'CEA', timeout}

An expected CEA was not received within &capx_timeout; of connection establishment.

{watchdog, Ref, PeerRef, {From, To}, Config}

Ref = &transport_ref;
PeerRef = &app_peer_ref;
From, To = initial | okay | suspect | down | reopen
Config = {connect|listen, [transport_opt()]}

An RFC 3539 watchdog state machine has changed state.

any()

For forward compatibility, a subscriber should be prepared to receive info fields of forms other than the above.

service_name() = term()

The name of a service as passed to &start_service; and with which the service is identified. There can be at most one service with a given name on a given node. Note that &make_ref; can be used to generate a service name that is somewhat unique.

service_opt()

An option passed to &start_service;. Can be any &capability; as well as the following.

{application, [&application_opt;]}

Defines a Diameter application supported by the service.

A service must configure one tuple for each Diameter application it intends to support. For an outgoing Diameter request, the relevant &application_alias; is passed to &call;, while for an incoming request the application identifier in the message header determines the application, the identifier being specified in the application's &dictionary; file.

The capabilities advertised by a node must match its configured applications. In particular, application configuration must be matched by corresponding &capability; configuration, of Application-Id AVP's in particular.

{restrict_connections, false | node | nodes | [node()] | evaluable()}

Specifies the degree to which multiple transport connections to the same peer are accepted by the service.

If type [node()] then a connection is rejected if another already exists on any of the specified nodes. Values of type false, node, nodes or &evaluable; are equivalent to values [], [node()], [node()|nodes()] and the evaluated value, respectively, evaluation of each expression taking place whenever a new connection is to be established. Note that false allows an unlimited number of connections to be established with the same peer.

Multiple connections are independent and governed by their own peer and watchdog state machines.

Defaults to nodes.

{sequence, {H,N} | &evaluable;}

Specifies a constant value H for the topmost 32-N 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 &start_service;. In particular, an identifier Id is mapped to a new identifier as follows.

(H bsl N) bor (Id band ((1 bsl N) - 1))

Note that &the_rfc; 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 N: at a rate of R requests per second an N-bit counter traverses all of its values in (1 bsl N) div (R*60) minutes so the bound is 4*R*60 =< 1 bsl N.

N must lie in the range 0..32 and H must be a non-negative integer less than 1 bsl (32-N).

Defaults to {0,32}.

transport_opt()

An option passed to &add_transport;. Has one of the following types.

{applications, [&application_alias;]}

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.

The capabilities advertised by a node must match its configured applications. In particular, setting applications on a transport typically implies having to set matching Application-Id AVP's in a &capabilities; tuple.

{capabilities, [&capability;]}

AVP's used to construct outgoing CER/CEA messages. Values take precedence over any specified on the service in question.

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 &man_tcp;.

{capabilities_cb, &evaluable;}

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 &transport_ref; and #diameter_caps{} record of the connection.

The return value can have one of the following types.

Accept the connection.

integer()

Causes an incoming CER to be answered with the specified Result-Code.

discard

Causes an incoming CER to be discarded without CEA being sent.

unknown

Equivalent to returning 3010, DIAMETER_UNKNOWN_PEER.

Returning anything but ok or a 2xxx series result code causes the transport connection to be broken. Multiple &capabilities_cb; options can be specified, in which case the corresponding callbacks are applied until either all return ok or one does not.

{capx_timeout, &dict_Unsigned32;}

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 of reconnection attempts is governed by &watchdog_timer; or &reconnect_timer; expiry. For a listening transport, the peer determines the timing.

Defaults to 10000.

{disconnect_cb, &evaluable;}

A callback invoked prior to terminating the transport process of a transport connection having watchdog state OKAY. Applied to Reason=transport|service|application and the &transport_ref; and &app_peer; in question, Reason indicating whether the diameter application is being stopped, the service in question is being stopped at &stop_service; or the transport in question is being removed at &remove_transport;, respectively.

The return value can have one of the following types.

{dpr, [option()]}

Causes Disconnect-Peer-Request to be sent to the peer, the transport process being terminated following reception of Disconnect-Peer-Answer or timeout. An option() can be one of the following.

{cause, 0|rebooting|1|busy|2|goaway}

The Disconnect-Cause to send, REBOOTING, BUSY and DO_NOT_WANT_TO_TALK_TO_YOU respectively. Defaults to rebooting for Reason=service|application and goaway for Reason=transport.

{timeout, &dict_Unsigned32;}

The number of milliseconds after which the transport process is terminated if DPA has not been received. Defaults to 1000.

dpr

Equivalent to {dpr, []}.

Causes the transport process to be terminated without Disconnect-Peer-Request being sent to the peer.

ignore

Equivalent to not having configured the callback.

Multiple &disconnect_cb; options can be specified, in which case the corresponding callbacks are applied until one of them returns a value other than ignore. All callbacks returning ignore is equivalent to not having configured them.

Defaults to a single callback returning dpr.

{length_errors, exit|handle|discard}

Specifies how to deal with errors in the Message Length field of the Diameter Header in an incoming message. An error in this context is that the length is not at least 20 bytes (the length of a Header), is not a multiple of 4 (a valid length) or is not the length of the message in question, as received over the transport interface documented in &man_transport;.

If exit then a warning report is emitted and the parent of the transport process in question exits, which causes the transport process itself to exit as described in &man_transport;. If handle then the message is processed as usual, a resulting &app_handle_request; or &app_handle_answer; callback (if one takes place) indicating the 5015 error (DIAMETER_INVALID_MESSAGE_LENGTH). If discard then the message in question is silently discarded.

Defaults to exit.

The default value reflects the fact that a transport module for a stream-oriented transport like TCP may not be able to recover from a message length error since such a transport must use the Message Length header to divide the incoming byte stream into individual Diameter messages. An invalid length leaves it with no reliable way to rediscover message boundaries, which may result in the failure of subsequent messages. See &man_tcp; for the behaviour of that module.

{reconnect_timer, Tc}

Tc = &dict_Unsigned32;

For a connecting transport, the &the_rfc; 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 before an initial connection is established: once there is an initial connection it's &watchdog_timer; that determines the frequency of reconnection attempts, as required by RFC 3539.

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 &reconnect_timer; should be greater than its peer's Tw plus jitter.

Defaults to 30000 for a connecting transport and 60000 for a listening transport.

{transport_config, term()} {transport_config, term(), &dict_Unsigned32;}

A term passed as the third argument to the &transport_start; function of the relevant &transport_module; in order to start a transport process. Defaults to the empty list if unspecified.

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.

{transport_module, diameter_sctp}
{transport_config, SctpOpts, 5000}
{transport_module, diameter_tcp}
{transport_config, TcpOpts}

To listen on both SCTP and TCP, define one transport for each.

{transport_module, atom()}

A module implementing a transport process as defined in &man_transport;. Defaults to diameter_tcp if unspecified.

Multiple transport_module and &transport_config; options are allowed. The order of these is significant in this case (and only in this case), a transport_module being paired with the first &transport_config; 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.

{watchdog_timer, TwInit}

TwInit = &dict_Unsigned32;
       | {M,F,A}

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.

An integer value must be at least 6000 as required by RFC 3539. Defaults to 30000 if unspecified.

Unrecognized options are silently ignored but are returned unmodified by &service_info; and can be referred to in predicate functions passed to &remove_transport;.

transport_ref() = reference()

An reference returned by &add_transport; that identifies the configuration.