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# diameter_dict

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Dictionary interface of the diameter application.

## Description

A diameter service, as configured with `diameter:start_service/2`, specifies one or more supported Diameter applications. Each Diameter application specifies a dictionary module that knows how to encode and decode its messages and AVPs. The dictionary module is in turn generated from a file that defines these messages and AVPs. The format of such a file is defined in FILE FORMAT below. Users add support for their specific applications by creating dictionary files, compiling them to Erlang modules using either diameterc(1) or `diameter_make` and configuring the resulting dictionaries modules on a service.

Dictionary module generation also results in a hrl file that defines records for the messages and Grouped AVPs defined by the dictionary, these records being what a user of the diameter application sends and receives, modulo other possible formats as discussed in `diameter_app`. These records and the underlying Erlang data types corresponding to Diameter data formats are discussed in MESSAGE RECORDS and DATA TYPES respectively. The generated hrl also contains macro definitions for the possible values of AVPs of type Enumerated.

The diameter application includes five dictionary modules corresponding to applications defined in section 2.4 of RFC 6733: `diameter_gen_base_rfc3588` and `diameter_gen_base_rfc6733` for the Diameter Common Messages application with application identifier 0, `diameter_gen_accounting` (for RFC 3588) and `diameter_gen_acct_rfc6733` for the Diameter Base Accounting application with application identifier 3 and `diameter_gen_relay` the Relay application with application identifier 0xFFFFFFFF.

The Common Message and Relay applications are the only applications that diameter itself has any specific knowledge of. The Common Message application is used for messages that diameter itself handles: CER/CEA, DWR/DWA and DPR/DPA. The Relay application is given special treatment with regard to encode/decode since the messages and AVPs it handles are not specifically defined.

## FILE FORMAT

A dictionary file consists of distinct sections. Each section starts with a tag followed by zero or more arguments and ends at the the start of the next section or end of file. Tags consist of an ampersand character followed by a keyword and are separated from their arguments by whitespace. Whitespace separates individual tokens but is otherwise insignificant.

The tags, their arguments and the contents of each corresponding section are as follows. Each section can occur multiple times unless otherwise specified. The order in which sections are specified is unimportant.

- `@id Number` - Defines the integer Number as the Diameter Application Id of the application in question. Can occur at most once and is required if the dictionary defines `@messages`. The section has empty content.

  The Application Id is set in the Diameter Header of outgoing messages of the application, and the value in the header of an incoming message is used to identify the relevant dictionary module.

  Example:

      @id 16777231

- `@name Mod` - Defines the name of the generated dictionary module. Can occur at most once and defaults to the name of the dictionary file minus any extension. The section has empty content.

  Note that a dictionary module should have a unique name so as not collide with existing modules in the system.

  Example:

      @name etsi_e2

- `@prefix Name` - Defines Name as the prefix to be added to record and constant names (followed by a `'_'` character) in the generated dictionary module and hrl. Can occur at most once. The section has empty content.

  A prefix is optional but can be be used to disambiguate between record and constant names resulting from similarly named messages and AVPs in different Diameter applications.

  Example:

      @prefix etsi_e2

- `@vendor Number Name` - Defines the integer Number as the the default Vendor-Id of AVPs for which the V flag is set. Name documents the owner of the application but is otherwise unused. Can occur at most once and is required if an AVP sets the V flag and is not otherwise assigned a Vendor-Id. The section has empty content.

  Example:

      @vendor 13019 ETSI

- `@avp_vendor_id Number` - Defines the integer Number as the Vendor-Id of the AVPs listed in the section content, overriding the `@vendor` default. The section content consists of AVP names.

  Example:

      @avp_vendor_id 2937

      WWW-Auth
      Domain-Index
      Region-Set

- `@inherits Mod` - Defines the name of a dictionary module containing AVP definitions that should be imported into the current dictionary. The section content consists of the names of those AVPs whose definitions should be imported from the dictionary, an empty list causing all to be imported. Any listed AVPs must not be defined in the current dictionary and it is an error to inherit the same AVP from more than one dictionary.

  Note that an inherited AVP that sets the V flag takes its Vendor-Id from either `@avp_vendor_id` in the inheriting dictionary or `@vendor` in the inherited dictionary. In particular, `@avp_vendor_id` in the inherited dictionary is ignored. Inheriting from a dictionary that specifies the required `@vendor` is equivalent to using `@avp_vendor_id` with a copy of the dictionary's definitions but the former makes for easier reuse.

  All dictionaries should typically inherit RFC 6733 AVPs from `diameter_gen_base_rfc6733`.

  Example:

      @inherits diameter_gen_base_rfc6733

- `@avp_types` - Defines the name, code, type and flags of individual AVPs. The section consists of definitions of the form

  `Name Code Type Flags`

  where Code is the integer AVP code, Type identifies an AVP Data Format as defined in section DATA TYPES below, and Flags is a string of V, M and P characters indicating the flags to be set on an outgoing AVP or a single `'-'` (minus) character if none are to be set.

  Example:

      @avp_types

      Location-Information   350  Grouped     MV
      Requested-Information  353  Enumerated   V

  #### Warning

  The P flag has been deprecated by RFC 6733.

- `@custom_types Mod` - Specifies AVPs for which module Mod provides encode/decode functions. The section contents consists of AVP names. For each such name, `Mod:Name(encode|decode, Type, Data, Opts)` is expected to provide encode/decode for values of the AVP, where Name is the name of the AVP, Type is it's type as declared in the `@avp_types` section of the dictionary, Data is the value to encode/decode, and Opts is a term that is passed through encode/decode.

  Example:

      @custom_types rfc4005_avps

      Framed-IP-Address

- `@codecs Mod` - Like `@custom_types` but requires the specified module to export `Mod:Type(encode|decode, Name, Data, Opts)` rather than `Mod:Name(encode|decode, Type, Data, Opts)`.

  Example:

      @codecs rfc4005_avps

      Framed-IP-Address

- `@messages` - Defines the messages of the application. The section content consists of definitions of the form specified in section 3.2 of RFC 6733, "Command Code Format Specification".

      @messages

      RTR ::= < Diameter Header: 287, REQ, PXY >
              < Session-Id >
              { Auth-Application-Id }
              { Auth-Session-State }
              { Origin-Host }
              { Origin-Realm }
              { Destination-Host }
              { SIP-Deregistration-Reason }
              [ Destination-Realm ]
              [ User-Name ]
            * [ SIP-AOR ]
            * [ Proxy-Info ]
            * [ Route-Record ]
            * [ AVP ]

      RTA ::= < Diameter Header: 287, PXY >
              < Session-Id >
              { Auth-Application-Id }
              { Result-Code }
              { Auth-Session-State }
              { Origin-Host }
              { Origin-Realm }
              [ Authorization-Lifetime ]
              [ Auth-Grace-Period ]
              [ Redirect-Host ]
              [ Redirect-Host-Usage ]
              [ Redirect-Max-Cache-Time ]
            * [ Proxy-Info ]
            * [ Route-Record ]
            * [ AVP ]

- `@grouped` - Defines the contents of the AVPs of the application having type Grouped. The section content consists of definitions of the form specified in section 4.4 of RFC 6733, "Grouped AVP Values".

  Example:

      @grouped

      SIP-Deregistration-Reason ::= < AVP Header: 383 >
                                    { SIP-Reason-Code }
                                    [ SIP-Reason-Info ]
                                  * [ AVP ]

  Specifying a Vendor-Id in the definition of a grouped AVP is equivalent to specifying it with `@avp_vendor_id`.

- `@enum Name` - Defines values of AVP Name having type Enumerated. Section content consists of names and corresponding integer values. Integer values can be prefixed with 0x to be interpreted as hexadecimal.

  Note that the AVP in question can be defined in an inherited dictionary in order to introduce additional values to an enumeration otherwise defined in another dictionary.

  Example:

      @enum SIP-Reason-Code

      PERMANENT_TERMINATION    0
      NEW_SIP_SERVER_ASSIGNED  1
      SIP_SERVER_CHANGE        2
      REMOVE_SIP_SERVER        3

- `@end` - Causes parsing of the dictionary to terminate: any remaining content is ignored.

Comments can be included in a dictionary file using semicolon: characters from a semicolon to end of line are ignored.

## MESSAGE RECORDS

The hrl generated from a dictionary specification defines records for the messages and grouped AVPs defined in `@messages` and `@grouped` sections. For each message or grouped AVP definition, a record is defined whose name is the message or AVP name, prefixed with any dictionary prefix defined with `@prefix`, and whose fields are the names of the AVPs contained in the message or grouped AVP in the order specified in the definition in question. For example, the grouped AVP

    SIP-Deregistration-Reason ::= < AVP Header: 383 >
                                  { SIP-Reason-Code }
                                  [ SIP-Reason-Info ]
                                * [ AVP ]

will result in the following record definition given an empty prefix.

    -record('SIP-Deregistration-Reason', {'SIP-Reason-Code',
                                          'SIP-Reason-Info',
                                          'AVP'}).

The values encoded in the fields of generated records depends on the type and number of times the AVP can occur. In particular, an AVP which is specified as occurring exactly once is encoded as a value of the AVP's type while an AVP with any other specification is encoded as a list of values of the AVP's type. The AVP's type is as specified in the AVP definition, the RFC 6733 types being described below.

## DATA TYPES

The data formats defined in sections 4.2 ("Basic AVP Data Formats") and 4.3 ("Derived AVP Data Formats") of RFC 6733 are encoded as values of the types defined here. Values are passed to `diameter:call/4` in a request record when sending a request, returned in a resulting answer record and passed to a handle_request/3 callback upon reception of an incoming request.

In cases in which there is a choice between string() and binary() types for OctetString() and derived types, the representation is determined by the value of diameter:service_opt() string_decode.

Basic AVP Data Formats

    OctetString() = string() | binary()
    Integer32()   = -2147483647..2147483647
    Integer64()   = -9223372036854775807..9223372036854775807
    Unsigned32()  = 0..4294967295
    Unsigned64()  = 0..18446744073709551615
    Float32()     = '-infinity' | float() | infinity
    Float64()     = '-infinity' | float() | infinity
    Grouped()     = record()

On encode, an OctetString() can be specified as an iolist(), excessively large floats (in absolute value) are equivalent to `infinity` or `'-infinity'` and excessively large integers result in encode failure. The records for grouped AVPs are as discussed in the previous section.

Derived AVP Data Formats

    Address() = OctetString()
              | tuple()

On encode, an OctetString() IPv4 address is parsed in the usual x.x.x.x format while an IPv6 address is parsed in any of the formats specified by section 2.2 of RFC 2373, "Text Representation of Addresses". An IPv4 tuple() has length 4 and contains values of type 0..255. An IPv6 tuple() has length 8 and contains values of type 0..65535. The tuple representation is used on decode.

    Time() = {date(), time()}

    where

      date() = {Year, Month, Day}
      time() = {Hour, Minute, Second}

      Year   = integer()
      Month  = 1..12
      Day    = 1..31
      Hour   = 0..23
      Minute = 0..59
      Second = 0..59

Additionally, values that can be encoded are limited by way of their encoding as four octets as required by RFC 6733 with the required extension from RFC 2030. In particular, only values between `{{1968,1,20},{3,14,8}}` and `{{2104,2,26},{9,42,23}}` (both inclusive) can be encoded.

    UTF8String() = [integer()] | binary()

List elements are the UTF-8 encodings of the individual characters in the string. Invalid codepoints will result in encode/decode failure. On encode, a UTF8String() can be specified as a binary, or as a nested list of binaries and codepoints.

    DiameterIdentity() = OctetString()

A value must have length at least 1.

    DiameterURI() = OctetString()
                  | #diameter_URI{type = Type,
                                  fqdn = FQDN,
                                  port = Port,
                                  transport = Transport,
                                  protocol  = Protocol}

    where

      Type = aaa | aaas
      FQDN = OctetString()
      Port = integer()
      Transport = sctp | tcp
      Protocol  = diameter | radius | 'tacacs+'

On encode, fields port, transport and protocol default to 3868, sctp and diameter respectively. The grammar of an OctetString-valued DiameterURI() is as specified in section 4.3 of RFC 6733. The record representation is used on decode.

    Enumerated() = Integer32()

On encode, values can be specified using the macros defined in a dictionary's hrl file.

    IPFilterRule()  = OctetString()
    QoSFilterRule() = OctetString()

Values of these types are not currently parsed by diameter.

## SEE ALSO

diameterc(1), `diameter`, `diameter_app`, `diameter_codec`, `diameter_make`

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