diameter(3)

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

Types corresponding to RFC 3588 AVP Data Formats. Defined in diameter_dict(4).

application_alias() = term()

A name identifying a Diameter application in service configuration. Passed to call/4 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 diameter_app(3), 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/4, 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 diameter_app(3) 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 diameter_dict(4).

{module, application_module()}

The callback module with which messages of the Diameter application are handled. See diameter_app(3) for the required interface and semantics.

{state, term()}

The initial callback state. The prevailing state is passed to some diameter_app(3) 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 pick_peer/4 application callback can modify the application state, Defaults to false if unspecified.

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 handle_answer/4 callback in the same fashion as for handle_request/3, 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/4 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/4 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 pick_peer/4 callback for the application in question. Multiple options are equivalent a single all filter on the corresponding list of filters. Defaults to none.

{timeout, Unsigned32()}

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

detach

Causes call/4 to return ok as soon as the request in question has been encoded instead of waiting for and returning the result from a subsequent handle_answer/4 or handle_error/4 callback.

An invalid option will cause call/4 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', DiameterIdentity()} {'Origin-Realm', DiameterIdentity()} {'Host-IP-Address', [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', Unsigned32()} {'Product-Name', UTF8String()} {'Origin-State-Id', 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 RFC 3588. The function origin_state_id/0 can be used as to retrieve a value that is computed when the diameter application is started.

{'Supported-Vendor-Id', [Unsigned32()]} {'Auth-Application-Id', [Unsigned32()]} {'Inband-Security-Id', [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', [Unsigned32()]} {'Vendor-Specific-Application-Id', [Grouped()]} {'Firmware-Revision', 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/2 or add_transport/2.

peer_filter() = term()

A filter passed to call/4 in order to select candidate peers for a pick_peer/4 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|DiameterIdentity()}

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

{realm, any|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/4, assuming that this is a record- or list-valued diameter_app:message(), and that the message contains at most one of each AVP. If this is not the case then the {host|realm, DiameterIdentity()} filters must be used to achieve the desired result. An empty 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{}

An event message sent to processes that have subscribed to these using subscribe/1.

The info field of the 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   = diameter_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/down event for a given peer corresponds to one peer_up/peer_down 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.

{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 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 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 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 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  = diameter_app:peer_ref()
From, To = initial | okay | suspect | down | reopen
Config = {connect|listen, [transport_opt()]}

An RFC 3539 watchdog state machine has changed state.

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/2 and with which the service is identified. There can be at most one service with a given name on a given node. Note that erlang:make_ref/0 can be used to generate a service name that is somewhat unique.

service_opt()

An option passed to start_service/2. 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 application for each Diameter application it intends to support. For an outgoing Diameter request, the relevant application_alias() is passed to call/4, 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.

{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/2. 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 RFC 3588 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/2. 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.

{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 diameter_tcp(3).

{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, 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 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 diameter_app:peer() in question, Reason indicating whether the the diameter application is being stopped, the service in question is being stopped at stop_service/1 or the transport in question is being removed at remove_transport/2, 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, 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.

{reconnect_timer, Tc}


Tc = Unsigned32()

For a connecting transport, the RFC 3588 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(), Unsigned32()}

A term passed as the third argument to the start/3 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 diameter_transport(3). 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 = 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/2 and can be referred to in predicate functions passed to remove_transport/2.

transport_ref() = reference()

An reference returned by add_transport/2 that identifies the configuration.