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2012 2017 Ericsson AB. All Rights Reserved. Licensed under the Apache License, Version 2.0 (the "License"); you may not use this file except in compliance with the License. You may obtain a copy of the License at http://www.apache.org/licenses/LICENSE-2.0 Unless required by applicable law or agreed to in writing, software distributed under the License is distributed on an "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. See the License for the specific language governing permissions and limitations under the License. diameter_codec(3) Anders Svensson diameter_codec.xml
diameter_codec Decode and encode of Diameter messages.

Incoming Diameter messages are decoded from binary() before being communicated to &man_app; callbacks. Similarly, outgoing Diameter messages are encoded into binary() before being passed to the appropriate &man_transport; module for transmission. The functions documented here implement the default encode/decode.

The diameter user does not need to call functions here explicitly when sending and receiving messages using &mod_call; and the callback interface documented in &man_app;: diameter itself provides encode/decode as a consequence of configuration passed to &mod_start_service;, and the results may differ from those returned by the functions documented here, depending on configuration.

The &header; and &packet; records below are defined in diameter.hrl, which can be included as follows.

-include_lib("diameter/include/diameter.hrl").

Application-specific records are defined in the hrl files resulting from dictionary file compilation.
DATA TYPES

uint8()  = 0..255 uint24() = 0..16777215 uint32() = 0..4294967295

8-bit, 24-bit and 32-bit integers occurring in Diameter and AVP headers.

 avp() = #diameter_avp{}

The application-neutral representation of an AVP. Primarily intended for use by relay applications that need to handle arbitrary Diameter applications. A service implementing a specific Diameter application (for which it configures a dictionary) can manipulate values of type &message; instead.

Fields have the following types.

code = uint32() is_mandatory = boolean() need_encryption = boolean() vendor_id = uint32() | undefined

Values in the AVP header, corresponding to AVP Code, the M flag, P flags and Vendor-ID respectively. A Vendor-ID other than undefined implies a set V flag.

 data = iolist()

The data bytes of the AVP.

 name = atom()

The name of the AVP as defined in the dictionary file in question, or undefined if the AVP is unknown to the dictionary file in question.

 value = term()

The decoded value of an AVP. Will be undefined on decode if the data bytes could not be decoded, the AVP is unknown, or if the &decode_format; is none. The type of a decoded value is as document in &types;.

 type = atom()

The type of the AVP as specified in the dictionary file in question (or one it inherits). Possible types are undefined and the Diameter types: OctetString, Integer32, Integer64, Unsigned32, Unsigned64, Float32, Float64, Grouped, Enumerated, Address, Time, UTF8String, DiameterIdentity, DiameterURI, IPFilterRule and QoSFilterRule.

 dictionary() = module()

The name of a generated dictionary module as generated by &man_compile; or &make_codec;. The interface provided by a dictionary module is an implementation detail that may change.

 header() = #diameter_header{}

The record representation of the Diameter header. Values in a &packet; returned by &decode; are as extracted from the incoming message. Values set in an &packet; passed to &encode; are preserved in the encoded binary(), with the exception of length, cmd_code and application_id, all of which are determined by the &dictionary; in question.

It is not necessary to set header fields explicitly in outgoing messages as diameter itself will set appropriate values. Setting inappropriate values can be useful for test purposes.

Fields have the following types.

version = uint8() length = uint24() cmd_code = uint24() application_id = uint32() hop_by_hop_id = uint32() end_to_end_id = uint32()

Values of the Version, Message Length, Command-Code, Application-ID, Hop-by-Hop Identifier and End-to-End Identifier fields of the Diameter header.

 is_request = boolean() is_proxiable = boolean() is_error = boolean() is_retransmitted = boolean()

Values corresponding to the R(equest), P(roxiable), E(rror) and T(Potentially re-transmitted message) flags of the Diameter header.

 message() = record() | maybe_improper_list()

The representation of a Diameter message as passed to &mod_call; or returned from a &app_handle_request; callback. The record representation is as outlined in &records;: a message as defined in a dictionary file is encoded as a record with one field for each component AVP. Equivalently, a message can also be encoded as a list whose head is the atom-valued message name (as specified in the relevant dictionary file) and whose tail is either a list of AVP name/values pairs or a map with values keyed on AVP names. The format at decode is determined by &mod_decode_format;. Any of the formats is accepted at encode.

Another list-valued representation allows a message to be specified as a list whose head is a &header; and whose tail is an &avp; list. This representation is used by diameter itself when relaying requests as directed by the return value of a &app_handle_request; callback. It differs from the other other two in that it bypasses the checks for messages that do not agree with their definitions in the dictionary in question: messages are sent exactly as specified.

 packet() = #diameter_packet{}

A container for incoming and outgoing Diameter messages. Fields have the following types.

header = &header; | undefined

The Diameter header of the message. Can be (and typically should be) undefined for an outgoing message in a non-relay application, in which case diameter provides appropriate values.

 avps = [&avp;] | undefined

The AVPs of the message. Ignored for an outgoing message if the msg field is set to a value other than undefined.

 msg = &message; | undefined

The incoming/outgoing message. For an incoming message, a term corresponding to the configured &decode_format; if the message can be decoded in a non-relay application, undefined otherwise. For an outgoing message, setting a [&header; | &avp;] list is equivalent to setting the header and avps fields to the corresponding values.

A value in the msg field does not imply an absence of decode errors. The errors field should also be examined.

 bin = binary()

The incoming message prior to encode or the outgoing message after encode.

 errors = [5000..5999 | {5000..5999, avp()}]

Errors detected at decode of an incoming message, as identified by a corresponding 5xxx series Result-Code (Permanent Failures). For an incoming request, these should be used to formulate an appropriate answer as documented for the &app_handle_request; callback in &man_app;. For an incoming answer, the &mod_application_opt; answer_errors determines the behaviour.

 transport_data = term()

An arbitrary term of meaning only to the transport process in question, as documented in &man_transport;.
decode(Mod, Bin) -> Pkt Decode a Diameter message. Mod = &dictionary; Bin = binary() Pkt = &packet;

Decode a Diameter message.

 encode(Mod, Msg) -> Pkt Encode a Diameter message. Mod = &dictionary; Msg = &message; | &packet; Pkt = &packet;

Encode a Diameter message.

SEE ALSO

&man_compile;, &man_app;, &man_dict;, &man_make;