[SR-Users] Problem with CANCEL handling

[Mordechay Kaganer]

B.H.

Hello, all!

I'm trying to set up kamailio as a simple load balancer proxy between PSTN
gateway and a cluster of asterisk servers - rather common use case IMHO.
I'm completely new to kamailio.

I have started with the default kamailio.cfg that comes with Ubuntu package
and added the dispatcher module as described in the docs (
http://www.kamailio.org/docs/modules/4.0.x/modules/dispatcher.html).

At the end, i got this up and running, but with one exception: if incoming
call is not answered by the asterisk end (i.e. it is in ringing state), and
then the gateway sends CANCEL request, kamailio is unable to recognize the
transaction and is not forwarding the request to asterisk. The result is:
the call is left "dangling" in the PBX and is not properly hang up.

When the gateway sends CANCEL to kamailio, i get the following log messages:
 4(25442) DEBUG: tm [t_lookup.c:769]: t_lookupOriginalT(): DEBUG:
t_lookupOriginalT: searching on hash entry 31287
 4(25442) DEBUG: tm [t_lookup.c:492]: matching_3261(): DEBUG: RFC3261
transaction matching failed
 4(25442) DEBUG: tm [t_lookup.c:859]: t_lookupOriginalT(): DEBUG:
t_lookupOriginalT: no CANCEL matching found!
 4(25442) DEBUG: tm [t_lookup.c:861]: t_lookupOriginalT(): DEBUG:
t_lookupOriginalT completed
 4(25442) DEBUG: tm [tm.c:1039]: w_t_lookup_cancel(): lookup_original:
t_lookupOriginalT returned: (nil)
 4(25442) ERROR: *** cfgtrace: c=[/etc/kamailio/kamailio.cfg] l=485 a=25
n=xdbg
 4(25442) DEBUG: <script>: is_method(CANCEL): t_check_trans()==false
4(25442) ERROR: *** cfgtrace: c=[/etc/kamailio/kamailio.cfg] l=487 a=2
n=exit

The relevant script snippet is standard from the distro package:
        # CANCEL processing
        if (is_method("CANCEL"))
        {
                xdbg("is_method(CANCEL): entry");
                if (t_check_trans()) {
                        xdbg("is_method(CANCEL): t_check_trans()==true");
                        route(RELAY);
                } else {
                        xdbg("is_method(CANCEL): t_check_trans()==false");
                }
                exit;
        }

How can i fix this?

Thanks!

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