View Source diameter_transport behaviour (diameter v2.4)
Diameter transport interface.
A module specified as a transport_module
to diameter:add_transport/2
must
implement the interface documented here. The interface consists of a function
with which diameter starts a transport process and a message interface with
which the transport process communicates with the process that starts it (aka
its parent).
DATA TYPES
message() = binary() |
diameter_codec:packet()
- A Diameter message as passed over the transport interface.For an inbound message from a transport process, a diameter_codec:packet() must contain the received message in its
bin
field. In the case of an inbound request, any value set in thetransport_data
field will passed back to the transport module in the corresponding answer message, unless the sender supplies another value.For an outbound message to a transport process, a diameter_codec:packet() has a value other than
undefined
in itstransport_data
field and has the binary() to send in itsbin
field.
MESSAGES
All messages sent over the transport interface are of the form
{diameter, term()}
.
A transport process can expect messages of the following types from its parent.
{diameter, {send,
message()
| false}}
- An outbound Diameter message. The atomfalse
can only be received when request acknowledgements have been requests: see theack
message below.{diameter, {close, Pid}}
- A request to terminate the transport process after having received DPA in response to DPR. The transport process should exit.Pid
is the pid() of the parent process.{diameter, {tls, Ref, Type, Bool}}
- Indication of whether or not capabilities exchange has selected inband security using TLS.Ref
is a reference() that must be included in the{diameter, {tls, Ref}}
reply message to the transport's parent process (see below).Type
is eitherconnect
oraccept
depending on whether the process has been started for a connecting or listening transport respectively.Bool
is a boolean() indicating whether or not the transport connection should be upgraded to TLS.If TLS is requested (
Bool=true
) then a connecting process should initiate a TLS handshake with the peer and an accepting process should prepare to accept a handshake. A successful handshake should be followed by a{diameter, {tls, Ref}}
message to the parent process. A failed handshake should cause the process to exit.This message is only sent to a transport process over whose
Inband-Security-Id
configuration has indicated support for TLS.
A transport process should send messages of the following types to its parent.
{diameter, {self(), connected}}
- Inform the parent that the transport process withType=accept
has established a connection with the peer. Not sent if the transport process hasType=connect
.{diameter, {self(), connected, Remote}}
{diameter, {self(), connected, Remote, [LocalAddr]}}
- Inform the parent that the transport process withType=connect
has established a connection with a peer. Not sent if the transport process hasType=accept
.Remote
is an arbitrary term that uniquely identifies the remote endpoint to which the transport has connected. ALocalAddr
list has the same semantics as one returned fromstart/3
.{diameter, ack}
- Request acknowledgements of unanswered requests. A transport process should send this once before passing incoming Diameter messages into diameter. As a result, every Diameter request passed into diameter with arecv
message (below) will be answered with asend
message (above), either a message() for the transport process to send or the atomfalse
if the request has been discarded or otherwise not answered.This is to allow a transport process to keep count of the number of incoming request messages that have not yet been answered or discarded, to allow it to regulate the amount of incoming traffic. Both diameter_tcp and diameter_sctp request acknowledgements when a
message_cb
is configured, turning send/recv message into callbacks that can be used to regulate traffic.{diameter, {recv,
message()
}}
- An inbound Diameter message.{diameter, {tls, Ref}}
- Acknowledgment of a successful TLS handshake.Ref
is the reference() received in the{diameter, {tls, Ref, Type, Bool}}
message in response to which the reply is sent. A transport must exit if a handshake is not successful.
SEE ALSO
Summary
Callbacks
Start a transport process. Called by diameter as a consequence of a call to
diameter:add_transport/2
in order to establish or accept a transport
connection respectively. A transport process maintains a connection with a
single remote peer.
Callbacks
-callback start({Type, Ref}, Svc, Config) -> {ok, Pid} | {ok, Pid, LAddrs} | {error, Reason} when Type :: connect | accept, Ref :: diameter:transport_ref(), Svc :: #diameter_service{pid :: term(), capabilities :: term(), applications :: term()}, Config :: term(), Pid :: pid(), LAddrs :: [inet:ip_address()], Reason :: term().
Start a transport process. Called by diameter as a consequence of a call to
diameter:add_transport/2
in order to establish or accept a transport
connection respectively. A transport process maintains a connection with a
single remote peer.
Type
indicates whether the transport process in question is being started for
a connecting (Type=connect
) or listening (Type=accept
) transport. In the
latter case, transport processes are started as required to accept connections
from multiple peers.
Ref is the value that was returned from the call to diameter:add_transport/2
that has lead to starting of a transport process.
Svc
contains capabilities passed to diameter:start_service/2
and
diameter:add_transport/2
, values passed to the latter overriding those passed
to the former.
Config
is as passed in transport_config
tuple in the
diameter:transport_opt() list passed to
diameter:add_transport/2
.
The start function should use the Host-IP-Address
list in Svc
and/or
Config
to select and return an appropriate list of local IP addresses. In the
connecting case, the local address list can instead be communicated in a
connected
message (see MESSAGES below)
following connection establishment. In either case, the local address list is
used to populate Host-IP-Address
AVPs in outgoing capabilities exchange
messages if Host-IP-Address
is unspecified.
A transport process must implement the message interface documented below. It should retain the pid of its parent, monitor the parent and terminate if it dies. It should not link to the parent. It should exit if its transport connection with its peer is lost.