[asterisk-dev] An idea: Interception macro for registering overlap dialling

[Richard Mudgett]

> Hi!
>   Thanks to Richard's help with my recent (rather stupid) question
>   regarding
> the Connected Party Number handling, I've familiarized using the
> Interception
> Macros for this purpose and I am very happy with them.
>   I think I have an idea for further usage of such a kind of macro:
>   to
> register the digits bridged in the overlap dialling process.
>   Let's assume a scenario, where an outgoing call is made to a trunk
>   allowing
> overlap dialling (say, DAHDI/PRI) from a technology allowing overlap
> receiving
> (say DAHDI/analog or PRI, IAX2, SIP with allowoverlap=dtmf etc.). The
> example
> dialplan entry would be very simple, say
> exten => 9,1,Dial(DAHDI/i2)

exten => _9!,1,Dial(DAHDI/g1/${EXTEN:1})
is a better way to do the overlap dialing for ISDN.

> so immediately after receiving the extension code, the connection is
> made
> (the caller can hear the external dial tone) and further dialling is
> then
> transferred in overlap mode.
>   In current Asterisk implementation (1.8), I don't know about a
>   method, how to
> bring the dialled digits to the Asterisk's "consciousness", they are
> just
> being bridged automatically but they don't appear anywhere (neither
> in CDR
> nor in CEL) and they cannot be retrieved even after the call is hung,
> for
> example using the "h" extension.
>   If there would be an interception macro, which would trigger for
>   every digit
> being bridged, it would be possible to populate all the necessary
> places with
> them (custom CDR fields, database entries for "Last Number Redial"
> feature etc.).
> The digit(s) could be passed to the macro by means of a special
> variable.
> How complex would it be to add such a possibility ? I've looked at
> the sources,
> but the internal code path, which is used to transfer the signalling
> including
> the overlap dialling events, is too complex for me to even find a
> good place,
> where such a feature could be inserted to the code.
>   Please note that I don't want to register any DTMF going over the
>   answered
> connection, what I want is just the overlap dialling phase (i.e.
> before the call
> is answered or the Proceeding event is received in the backward
> direction).
>   Is this idea at least partially feasible, or is this just a junk ?
>   Or am I stupid again and is this already handled somehow and just
>   I'm such an
> idiot that I don't know about it ?
>   With regards,
>     Pavel

The best place to do what you are asking is in app_dial.c since what you
are asking for is before a call is answered and the channels are bridged
together.  After a call is bridged there are frame hooks available to
modules to intercept frames passed over the bridge.  The FRAME_TRACE
application uses frame hooks to show you the control frames passing
over a bridge.

Richard