diameter_transport
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).
Functions
Mod:start({Type, Ref}, Svc, Opts) -> {ok, Pid} | {ok, Pid, LAddrs} | {error, Reason}
Type = connect | accept
Ref = diameter:transport_ref()
Svc = #diameter_service{}
Opts = 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.
The first argument indicates whether the transport process in question
is being started for a connecting (connect
) or listening
(accept
) transport.
In the latter case, transport processes are started as required to
accept connections from multiple peers.
Ref is in each case the same value that was returned from the
call to diameter:add_transport/2
that has lead to starting of a transport process.
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.
The capabilities in the #diameter_service{}
record are as
passed to diameter:start_service/2 and
diameter:add_transport/2,
values passed to the latter overriding those passed to the former.
The start function should use the Host-IP-Address
list and/or
Opts
to select an appropriate list of local IP addresses,
and should return this list if different from the
#diameter_service{}
addresses.
The returned list is used to populate Host-IP-Address
AVPs in
outgoing capabilities exchange messages, the
#diameter_service{}
addresses being used otherwise.
MESSAGES
All messages sent over the transport interface are of the
form {diameter, term()}
.
A transport process can expect the following messages from diameter.
{diameter, {send, Packet}}
An outbound Diameter message.
Packet
can be either binary() (the message to be sent)
or a #diameter_packet{}
record whose transport_data
field contains a value other than undefined and whose bin
field
contains the binary to send.
{diameter, {close, Pid}}
A request to close the transport connection.
The transport process should terminate after closing the
connection.
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 either connect
or accept
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 the following messages to its parent.
{diameter, {self(), connected}}
Inform the parent that the transport process with Type=accept
has
established a connection with the peer.
Not sent if the transport process has Type=connect
.
{diameter, {self(), connected, Remote}}
Inform the parent that the transport process with Type=connect
has established a connection with a peer.
Not sent if the transport process has Type=accept
.
Remote
is an arbitrary term that uniquely identifies the remote
endpoint to which the transport has connected.
{diameter, {recv, Packet}}
An inbound Diameter message.
Packet
can be either binary() (the received message)
or a #diameter_packet{}
record
whose bin
field contains the received binary().
Any value (other than undefined
) set in
the transport_data
field will be passed back with a
corresponding answer message in the case that the inbound message is a
request unless the sender sets another value.
How transport_data
is used/interpreted is up to the
transport module.
{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.