bionic (3) diameter_tcp.3erl.gz
NAME
diameter_tcp - Diameter transport over TCP.
DESCRIPTION
This module implements diameter transport over TCP using gen_tcp(3erl). It can be specified as the value of a transport_module option to diameter:add_transport/2 and implements the behaviour documented in diameter_transport(3erl). TLS security is supported, either as an upgrade following capabilities exchange or at connection establishment. Note that the ssl application is required for TLS and must be started before configuring TLS capability on diameter transports.
EXPORTS
start({Type, Ref}, Svc, [Opt]) -> {ok, Pid} | {ok, Pid, [LAddr]} | {error, Reason}
Types:
Type = connect | accept
Ref = diameter:transport_ref()
Svc = #diameter_service{}
Opt = OwnOpt | SslOpt | TcpOpt
Pid = pid()
LAddr = inet:ip_address()
Reason = term()
OwnOpt = {raddr, inet:ip_address()} | {rport, integer()} | {accept, Match} | {port, integer()}
| {fragment_timer, infinity | 0..16#FFFFFFFF} | {message_cb, diameter:eval()} | {sender,
boolean()}
SslOpt = {ssl_options, true | list()}
TcpOpt = term()
Match = inet:ip_address() | string() | [Match]
The start function required by diameter_transport(3erl).
Options raddr and rport specify the remote address and port for a connecting transport and are not
valid for a listening transport.
Option accept specifies remote addresses for a listening transport and is not valid for a
connecting transport. If specified, a remote address that does not match one of the specified
addresses causes the connection to be aborted. Multiple accept options can be specified. A string-
valued Match that does not parse as an address is interpreted as a regular expression.
Option ssl_options must be specified for a transport that should support TLS: a value of true
results in a TLS handshake immediately upon connection establishment while list() specifies
options to be passed to ssl:connect/2 or ssl:ssl_accept/2 after capabilities exchange if TLS is
negotiated.
Option fragment_timer specifies the timeout, in milliseconds, of a timer used to flush messages
from the incoming byte stream even if the number of bytes indicated in the Message Length field of
its Diameter Header have not yet been accumulated: such a message is received over the transport
interface after two successive timeouts without the reception of additional bytes. Defaults to
1000.
Option sender specifies whether or not to use a dedicated process for sending outgoing messages,
which avoids the possibility of send blocking reception. Defaults to false. If set to true then a
message_cb that avoids the possibility of messages being queued in the sender process without
bound should be configured.
Option message_cb specifies a callback that is invoked on incoming and outgoing messages, that can
be used to implement flow control. It is applied to two arguments: an atom indicating the reason
for the callback (send, recv, or ack after a completed send), and the message in question
(binary() on recv, binary() or diameter_packet record on send or ack, or false on ack when an
incoming request has been discarded). It should return a list of actions and a new callback as
tail; eg. [fun cb/3, State]. Valid actions are the atoms send or recv, to cause a following
message-valued action to be sent/received, a message to send/receive (binary() or diameter_packet
record), or a boolean() to enable/disable reading on the socket. More than one send/recv/message
sequence can be returned from the same callback, and an initial send/recv can be omitted if the
same as the value passed as the callback's first argument. Reading is initially enabled, and
returning false does not imply there cannot be subsequent recv callbacks since messages may
already have been read. An empty tail is equivalent to the prevailing callback. Defaults to a
callback equivalent to fun(ack, _) -> []; (_, Msg) -> [Msg] end.
Remaining options are any accepted by ssl:connect/3 or gen_tcp:connect/3 for a connecting
transport, or ssl:listen/2 or gen_tcp:listen/2 for a listening transport, depending on whether or
not {ssl_options, true} has been specified. Options binary, packet and active cannot be specified.
Also, option port can be specified for a listening transport to specify the local listening port,
the default being the standardized 3868. Note that the option ip specifies the local address.
An ssl_options list must be specified if and only if the transport in question has set Inband-
Security-Id to 1 (TLS), as specified to either diameter:start_service/2 or
diameter:add_transport/2, so that the transport process will receive notification of whether or
not to commence with a TLS handshake following capabilities exchange. Failing to specify an
options list on a TLS-capable transport for which TLS is negotiated will cause TLS handshake to
fail. Failing to specify TLS capability when ssl_options has been specified will cause the
transport process to wait for a notification that will not be forthcoming, which will eventually
cause the RFC 3539 watchdog to take down the connection.
The first element of a non-empty Host-IP-Address list in Svc provides the local IP address if an
ip option is not specified. The local address is either returned fromstart/3 or passed in a
connected message over the transport interface.
SEE ALSO
diameter(3erl), diameter_transport(3erl), gen_tcp(3erl), inet(3erl), ssl(3erl)