diameter_codec - Decode and encode of Diameter messages.
Please see following description for synopsis
diameter_codec(3) Erlang Module Definition diameter_codec(3)
NAME
diameter_codec - Decode and encode of Diameter messages.
DESCRIPTION
Incoming Diameter messages are decoded from binary() before being com-
municated to diameter_app(3) callbacks. Similarly, outgoing Diameter
messages are encoded into binary() before being passed to the appropri-
ate diameter_transport(3) module for transmission. The functions docu-
mented 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(3): diameter itself provides
encode/decode as a consequence of configuration passed to diame-
ter: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.
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 arbi-
trary 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 unde-
fined 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 ques-
tion, 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(4).
type = atom():
The type of the AVP as specified in the dictionary file in ques-
tion (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 QoS-
FilterRule.
dictionary() = module():
The name of a generated dictionary module as generated by diame-
terc(1) or diameter_make:codec/2. The interface provided by a dic-
tionary 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/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 mes-
sages as diameter itself will set appropriate values. Setting inap-
propriate 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 diame-
ter:call/4 or returned from a handle_request/3 callback. The record
representation is as outlined in diameter_dict(4): 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.
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 equiva-
lent 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 call-
back in diameter_app(3). For an incoming answer, the diame-
ter: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(3).
EXPORTS
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.
SEE ALSO
diameterc(1), diameter_app(3), diameter_dict(4), diameter_make(3)
Ericsson AB diameter 2.2.4 diameter_codec(3)