diameter_codec - Decode and encode of Diameter messages.
Incoming Diameter messages are decoded from binary() before being
communicated to diameter_app(3erl) callbacks. Similarly, outgoing Diameter
messages are encoded into binary() before being passed to the appropriate
diameter_transport(3erl) module for transmission. The functions documented
here implement the default encode/decode.
Warning:
The diameter user does not need to call functions here explicitly when sending
and receiving messages using diameter:call/4 and the callback interface
documented in diameter_app(3erl): diameter itself provides encode/decode as a
consequence of configuration passed to diameter:start_service/2, 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.
- 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
diameter_dict(5).
- 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 diameterc(1) or
diameter_make:codec/2. The interface provided by a dictionary module is an
implementation detail that may change.
- The record representation of the Diameter header. Values in a packet()
returned by decode/2 are as extracted from the incoming message. Values
set in an packet() passed to encode/2 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.
Note:
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.
- message() =
record() | maybe_improper_list():
- The representation of a Diameter message as passed to diameter:call/4 or
returned from a handle_request/3 callback. The record representation is as
outlined in diameter_dict(5): 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 diameter:service_opt()
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 handle_request/3 callback. It differs
from the 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.
- 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.
Warning:
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 handle_request/3 callback in diameter_app(3erl). For
an incoming answer, the diameter: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 diameter_transport(3erl).
decode(Mod, Bin) -> Pkt
Types:
Mod = dictionary()
Bin = binary()
Pkt = packet()
Decode a Diameter message.
encode(Mod, Msg) -> Pkt
Types:
Mod = dictionary()
Msg = message() | packet()
Pkt = packet()
Encode a Diameter message.