diameter

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

The name of an encode/decode module for the Diameter messages defined by the application. These modules are generated from files whose format is documented in diameter_dict(4).

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

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.

Specifies whether or not the pick_peer/4 application callback can modify the application state. Defaults to false if unspecified.

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{} 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 discard if unspecified.

Determines the manner in which incoming requests are handled when an error other than 3007 (DIAMETER_APPLICATION_UNSUPPORTED, which cannot be associated with an application callback module), is detected.

If answer_3xxx then requests are answered without a handle_request/3 callback taking place. If answer then even 5xxx errors are answered without a callback unless the connection in question has configured the RFC 3588 common dictionary as noted below. If callback then a handle_request/3 callback always takes place and its return value determines the answer sent to the peer, if any.

Defaults to answer_3xxx if unspecified.

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.

A filter to apply to the list of available peers before passing it 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.

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

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 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 module in question communicates an address list as described in diameter_transport(3)

Origin-State-Id is optional but, if configured, will be included in outgoing CER/CEA and DWR/DWA messages. Setting a value of 0 (zero) is equivalent to not setting a value, as documented in RFC 6733. The function origin_state_id/0 can be used as to retrieve a value that is computed when the diameter application is started.

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.

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

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.

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.

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

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

Matches only those peers for which the specified evaluable() returns true when applied to the connection's diameter_caps record. Any other return value or exception is equivalent to false.

Matches only those peers not matched by the specified filter.

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

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

The resulting peer list will be in match order, peers matching the first filter of the list sorting before those matched by the second, and so on. For example, the following filter causes peers matching both the host and realm filters to be presented before those matching only the realm filter.

{any, [{all, [host, realm]}, realm]}

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.

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{} is present in an up event then there has been a capabilities exchange on a newly established transport connection and the record contains the received CER or CEA.

Note that a single up or down event for a given peer corresponds to multiple peer_up/3 or peer_up/3 callbacks, one for each of the Diameter applications negotiated during capabilities exchange. That is, the event communicates connectivity with the peer as a whole while the callbacks communicate connectivity with respect to individual Diameter applications.

Ref  = transport_ref()
Opts = [transport_opt()]

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

Ref = transport_ref()
Config = {connect|listen, [transport_opt()]}

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

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

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

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

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

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.

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 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.

Specifies the degree to which the service allows multiple transport connections to the same peer, as identified by its Origin-Host at capabilities exchange.

If [node()] then a connection is rejected if another already exists on any of the specified nodes. Types false, node, nodes and evaluable() are equivalent to [], [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.

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 explicitly 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 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 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}.

Specifies nodes to which peer connections established on the local Erlang node are communicated. Shared peers become available in the remote candidates list passed to pick_peer/4 callbacks on remote nodes whose services are configured to use them: see use_shared_peers below.

If false then peers are not shared. If [node()] then peers are shared with the specified list of nodes. If evaluable() then peers are shared with the nodes returned by the specified function, evaluated whenever a peer connection becomes available or a remote service requests information about local connections. The value true is equivalent to fun erlang:nodes/0. The value node() in a list is ignored, so a collection of services can all be configured to share with the same list of nodes.

Defaults to false.

An options list passed to erlang:spawn_opt/2 when spawning a process for an incoming Diameter request, unless the transport in question specifies another value. Options monitor and link are ignored.

Defaults to the empty list.

Specifies nodes from which communicated peers are made available in the remote candidates list of pick_peer/4 callbacks.

If false then remote peers are not used. If [node()] then only peers from the specified list of nodes are used. If evaluable() then only peers returned by the specified function are used, evaluated whenever a remote service communicates information about an available peer connection. The value true is equivalent to fun erlang:nodes/0. The value node() in a list is ignored.

Defaults to false.

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.

AVPs 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).

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.

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.

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 connection attempts is governed by connect_timer or watchdog_timer expiry. For a listening transport, the peer determines the timing.

Defaults to 10000.

Tc = Unsigned32()

For a connecting transport, the RFC 6733 Tc timer, in milliseconds. This timer determines the frequency with which a transport attempts to establish an initial connection with its peer following transport configuration. Once an initial connection has been established, watchdog_timer 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 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 connect_timer should be greater than its peer's Tw plus jitter.

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

A callback invoked prior to terminating the transport process of a transport connection having watchdog state OKAY. Applied to application|service|transport and the transport_ref() and diameter_app:peer() in question: application indicates that the diameter application is being stopped, service that the service in question is being stopped by stop_service/1, and transport that the transport in question is being removed by remove_transport/2.

The return value can have one of the following types.

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.

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 diameter_transport(3).

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 diameter_transport(3). If handle then the message is processed as usual, a resulting handle_request/3 or handle_answer/4 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.

An options list passed to erlang:spawn_opt/2 when spawning a process for an incoming Diameter request. Options monitor and link are ignored.

Defaults to the list configured on the service if not specified.

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.

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.

Specifies configuration that alters the behaviour of the watchdog state machine. On key okay, the non-negative number of answered DWR messages before transitioning from REOPEN to OKAY. On key suspect, the number of watchdog timeouts before transitioning from OKAY to SUSPECT when DWR is unanswered, or 0 to not make the transition.

Defaults to [{okay, 3}, {suspect, 1}]. Not specifying a key is equivalent to specifying the default value for that key.

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.