Hi,

 

I am using Kamailio as a gateway for inbound calls to a group of Asterisk servers.

 

One particular call scenario involves matching pairs of calls. Originally I was just sending the calls through to Asterisk for processing (including the ‘matching up’), but there is a further requirement that the first received call must not be answered until its matching call arrives – and this is a little awkward in Asterisk, especially if there will be many calls.

 

I thought of t_suspend/t_continue functionality in Kamailio.  I have implemented this:

 

CallA arrives.

Send 180-ringing

Use ds_select_dst() to choose an Asterisk to handle the paired calls

Store destination and other data in an htable so that I can match the call later.

Invoke t_suspend() for CallA.

 

What I have implemented when the matching call arrives is this:

 

CallB arrives (and some logic matches it to the suspended CallA).

Invoke t_continue(‘id’,’label’,’CONTINUE_CALL’); so that CallA is now released and the route ends in t_relay() to send it on to Asterisk.

Set $du on CallB to match the destination, then t_relay() this call to send it on to the same Asterisk.

 

The solution almost works, but there is a problem.

 

The t_relay() for CallA is fine, and the call is forwarded.

 

When the script runs the t_relay() for CallB, I get this logged:
ERROR: tm [t_fwd.c:1728]: t_forward_nonack(): no branches for forwarding

ERROR: sl [sl_funcs.c:362]: sl_reply_error(): stateless error reply used: I'm terribly sorry, server error occurred (6/SL)

 

AND after each call I notice an extra transaction stuck in Kamailio (when I use kamctl rpc tm.list).

Can anyone point out where my Kamailio/SIP understanding has let me down?

Many Thanks,

Mark Hall

 

 

 

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