Module implementing the callback interface defined in diameter_app(3), along with any extra arguments to be appended to those documented. Note that extra arguments specific to an outgoing request can be specified to call/4, in which case those 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 diameter_callback.erl for details.

{alias, application_alias()}:

Unique identifier for the application in the scope of the service. Defaults to the value of the dictionary option.

{dictionary, atom()}:

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).

{module, application_module()}:

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

{state, term()}:

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.

{call_mutates_state, true|false}:

Whether or not the pick_peer/4 application callback can modify the application state. Defaults to false.

{answer_errors, callback|report|discard}:

Manner in which incoming answer messages containing decode errors are handled.

{request_errors, answer_3xxx|answer|callback}:

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.

{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()}:

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.

{peer, diameter_app:peer_ref()}:

Peer to which the request in question can be sent, preempting the selection of peers having advertised support for the Diameter application in question. Multiple options can be specified, and their order is respected in the candidate lists passed to a subsequent pick_peer/4 callback.

{timeout, Unsigned32()}:

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

detach:

Cause 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.

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

{'Vendor-Id', Unsigned32()}:

{'Product-Name', UTF8String()}:

{'Origin-State-Id', Unsigned32()}:

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.

{'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.

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

none:

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

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, eval()}:

Matches only those peers for which the specified eval() returns true when applied to 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. The resulting list will be in match order, peers matching the first filter of the list sorting before those matched by the second, and so on.

{first, [peer_filter()]}:

Like any, but stops at the first filter for which there are matches, which can be much more efficient when there are many peers. For example, the following filter causes only peers best matching both the host and realm filters to be presented.

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

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

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{}

{reconnect, Ref, Opts}:

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

{closed, Ref, Reason, Config}:

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

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

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

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

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

{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()]}

any():

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

{application, [application_opt()]}:

A Diameter application supported by the service.

{decode_format, record | list | map | none}:

The format of decoded messages and grouped AVPs in the msg field of diameter_packet records and value field of diameter_avp records respectively. If record then a record whose definition is generated from the dictionary file in question. If list or map then a [Name | Avps] pair where Avps is a list of AVP name/values pairs or a map keyed on AVP names respectively. If none then the atom-value message name, or undefined for a Grouped AVP. See also diameter_codec:message().

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

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

{sequence, {H,N} | eval()}:

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))

{share_peers, boolean() | [node()] | eval()}:

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.

{strict_arities, boolean() | encode | decode}:

Whether or not to require that the number of AVPs in a message or grouped AVP agree with those specified in the dictionary in question when passing messages to diameter_app(3) callbacks. If true then mismatches in an outgoing messages cause message encoding to fail, while mismatches in an incoming message are reported as 5005/5009 errors in the errors field of the diameter_packet record passed to handle_request/3 or handle_answer/4 callbacks. If false then neither error is enforced/detected. If encode or decode then errors are only enforced/detected on outgoing or incoming messages respectively.

{string_decode, boolean()}:

Whether or not to decode AVPs of type OctetString() and its derived types DiameterIdentity(), DiameterURI(), IPFilterRule(), QoSFilterRule(), and UTF8String(). If true then AVPs of these types are decoded to string(). If false then values are retained as binary().

{traffic_counters, boolean()}:

Whether or not to count application-specific messages; those for which diameter_app(3) callbacks take place. If false then only messages handled by diameter itself are counted: CER/CEA, DWR/DWA, DPR/DPA.

{use_shared_peers, boolean() | [node()] | eval()}:

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

transport_opt():

Any transport option except applications, capabilities, transport_config, and transport_module. Used as defaults for transport configuration, values passed to add_transport/2 overriding values configured on the service.

{applications, [application_alias()]}:

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.

{avp_dictionaries, [module()]}:

A list of alternate dictionary modules with which to encode/decode AVPs that are not defined by the dictionary of the application in question. At decode, such AVPs are represented as diameter_avp records in the 'AVP' field of a decoded message or Grouped AVP, the first alternate that succeeds in decoding the AVP setting the record's value field. At encode, values in an 'AVP' list can be passed as AVP name/value 2-tuples, and it is an encode error for no alternate to define the AVP of such a tuple.

{capabilities, [capability()]}:

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

{capabilities_cb, eval()}:

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.

{capx_timeout, Unsigned32()}:

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.

{connect_timer, Tc}:

Tc = Unsigned32()

{disconnect_cb, eval()}:

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.

{dpa_timeout, Unsigned32()}:

Number of milliseconds after which a transport connection is terminated following an outgoing DPR if DPA is not received.

{dpr_timeout, Unsigned32()}:

Number of milliseconds after which a transport connection is terminated following an incoming DPR if the peer does not close the connection.

{incoming_maxlen, 0..16777215}:

Bound on the expected size of incoming Diameter messages. Messages larger than the specified number of bytes are discarded.

{length_errors, exit|handle|discard}:

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).

{pool_size, pos_integer()}:

Number of transport processes to start. For a listening transport, determines the size of the pool of accepting transport processes, a larger number being desirable for processing multiple concurrent peer connection attempts. For a connecting transport, determines the number of connections to the peer in question that will be attempted to be establshed: the service_opt(): restrict_connections should also be configured on the service in question to allow multiple connections to the same peer.

{spawn_opt, [term()] | {M,F,A}}:

An options list passed to erlang:spawn_opt/2 to spawn a handler process for an incoming Diameter request on the local node, or an MFA that returns the pid of a handler process.

{strict_capx, boolean()]}:

Whether or not to enforce the RFC 6733 requirement that any message before capabilities exchange should close the peer connection. If false then unexpected messages are discarded.

{strict_mbit, boolean()}:

Whether or not to regard an AVP setting the M-bit as erroneous when the command grammar in question does not explicitly allow the AVP. If true then such AVPs are regarded as 5001 errors, DIAMETER_AVP_UNSUPPORTED. If false then the M-bit is ignored and policing it becomes the receiver's responsibility.

The reason for the latter is presumably interoperability: allowing arbitrary AVPs setting the M-bit in a command makes its interpretation implementation-dependent, since there's no guarantee that all implementations will understand the same set of arbitrary AVPs in the context of a given command. However, interpreting AVP in a command grammar as any AVP, regardless of M-bit, renders 1.3.4 meaningless, since the receiver can simply ignore any AVP it thinks isn't relevant, regardless of the sender's intent.

Beware of confusing mandatory in the sense of the M-bit with mandatory in the sense of the command grammar. The former is a semantic requirement: that the receiver understand the semantics of the AVP in the context in question. The latter is a syntactic requirement: whether or not the AVP must occur in the message in question.

{transport_config, term()}:

{transport_config, term(), Unsigned32() | infinity}:

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.

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

{transport_module, atom()}:

Module implementing a transport process as defined in diameter_transport(3). Defaults to diameter_tcp.

{watchdog_config, [{okay|suspect, non_neg_integer()}]}:

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.

{watchdog_timer, TwInit}:

TwInit = Unsigned32()
       | {M,F,A}

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.

*

If the initial encode of the outgoing request fails, then the request process fails and {error,encode} is returned.

*

If the request is successfully encoded and sent but the answer times out then a handle_error/4 callback takes place with Reason = timeout.

*

If the request is successfully encoded and sent but the service in question is stopped before an answer is received then a handle_error/4 callback takes place with Reason = cancel.

*

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 pick_peer/4 callback rejects the candidates, then a handle_error/4 callback takes place with Reason = failover. If a peer is selected then a prepare_retransmit/3 callback takes place, after which the semantics are the same as following an initial prepare_request/3 callback.

*

If an encode error takes place during retransmission then the request process fails and {error,failure} is returned.

*

If an application callback made in processing the request fails (pick_peer, prepare_request, prepare_retransmit, handle_answer or handle_error) then either {error,encode} or {error,failure} is returned depending on whether or not there has been an attempt to send the request over the transport.

Fun = fun((transport_ref(), connect|listen, list()) -> boolean()) | fun((transport_ref(), list()) -> boolean()) | fun((list()) -> boolean())
MFA = {atom(), atom(), list()}
Reason = term()

'Origin-Host':

'Origin-Realm':

'Vendor-Id':

'Product-Name':

'Origin-State-Id':

'Host-IP-Address':

'Supported-Vendor':

'Auth-Application-Id':

'Inband-Security-Id':

'Acct-Application-Id':

'Vendor-Specific-Application-Id':

'Firmware-Revision':

Return a capability value as configured with start_service/2.

applications:

Return the list of applications as configured with start_service/2.

capabilities:

Return a tagged list of all capabilities values as configured with start_service/2.

transport:

Return a list containing one entry for each of the service's transport as configured with add_transport/2. 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.

[[{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>,-576460736368485571,okay}},
  {peer,{<0.67.0>,-576460736357885808}},
  {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},
               {{{0,258,0},recv,{'Result-Code',2001}},3},
               {{{0,257,0},recv},1},
               {{{0,257,1},send},1},
               {{{0,257,0},recv,{'Result-Code',2001}},1},
               {{{0,280,1},recv},2},
               {{{0,280,0},send},2},
               {{{0,280,0},send,{'Result-Code',2001}},2}]}]]

[[{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>,-576460739249514012,okay}},
            {peer,{<0.58.0>,-576460638229179167}},
            {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>,-576460638229717546,initial}}]]},
  {statistics,[{{{0,280,0},recv},7},
               {{{0,280,1},send},7},
               {{{0,280,0},recv,{'Result-Code',2001}},7},
               {{{0,258,1},recv},3},
               {{{0,258,0},send},3},
               {{{0,258,0},send,{'Result-Code',2001}},3},
               {{{0,280,1},recv},5},
               {{{0,280,0},send},5},
               {{{0,280,0},send,{'Result-Code',2001}},5},
               {{{0,257,1},recv},1},
               {{{0,257,0},send},1},
               {{{0,257,0},send,{'Result-Code',2001}},1}]}]]

connections:

Return a list containing one entry for every established transport connection whose watchdog state machine is not in the down state. This is a flat view of transport 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.

[[{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>,-576460739249514012,okay}},
  {peer,{<0.58.0>,-576460638229179167}},
  {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},
               {{{0,280,0},recv,{'Result-Code',2001}},62},
               {{{0,258,1},recv},3},
               {{{0,258,0},send},3},
               {{{0,258,0},send,{'Result-Code',2001}},3},
               {{{0,280,1},recv},66},
               {{{0,280,0},send},66},
               {{{0,280,0},send,{'Result-Code',2001}},66},
               {{{0,257,1},recv},1},
               {{{0,257,0},send},1},
               {{{0,257,0},send,{'Result-Code',2001}},1}]}]]

statistics:

Return a {{Counter, Ref}, non_neg_integer()} list of counter values. Ref can be either a transport_ref() or a diameter_app:peer_ref(). Entries for the latter are folded into corresponding entries for the former as peer connections go down. Entries for both are removed at remove_transport/2. The Diameter-level statistics returned by transport and connections info are based upon these entries.

diameter_app:peer_ref():

Return transport configuration associated with a single peer, as passed to add_transport/2. The returned list is empty if the peer is unknown. Otherwise it contains the ref, type and options tuples as in transport and connections info above. For example:

[{ref,#Ref<0.0.0.61>},
 {type,accept},
 {options,[{transport_module,diameter_tcp},
           {transport_config,[{reuseaddr,true},
                              {ip,{127,0,0,1}},
                              {port,3868}]}]}]