I think you need to use 
t_on_branch_failure() 
If I got you correctly

Regards, Igor
On Sep 6, 2018, 10:06 PM +0300, Henning Westerholt <hw@kamailio.org>, wrote:
Am Mittwoch, 5. September 2018, 14:03:10 CEST schrieb Володимир Іванець:
I wanted to ask those who know if Kamailio's behavior I'm facing is
expected or I should make some improvements to the configuration. Kamailio
version is 5.1.0.

I have a route where RTPEngine parameters are being collected and
*rtpengine_offer()* is called. After that *t_on_reply("REPLY_SIP_TO_SIP");*
followed by the *t_on_failure("FAILURE_SIP_TO_SIP");* are used. The idea is
to process all responces except 415 or 488 from UAC as usual in
*onreply_route[REPLY_SIP_TO_SIP]* and use
*failure_route[FAILURE_SIP_TO_SIP]* to update SDP with *rtpengine_offer()*
if necessary.

*onreply_route[REPLY_SIP_TO_SIP]* just goes to *exit;* if *$rs* equals 415
or 488. This works fine with Htek phone which sends 100, 180 and then 488.
But I can not see *failure_route[FAILURE_SIP_TO_SIP]* execution for calls
to Zoiper which replies with 100 and immediately 415.

t_on_failure(failure_route) documentation says: "Sets failure routing
block, to which control is passed after a transaction completed with a
negative result but before sending a final reply." and to be honest I don't
really understand how lacking of responce prevents failure_route from
executing.

Hello,

I did not understand you completely here. Did you receive a 415 and the
failure route is not entered, or you did not receive a response as stated in
the last sentence?

If the failure_route is entered for the 488, then it should be also entered
for the 415. I am not aware of a special handling of this code in tm. (Only
that 415 is one of the replies that get a priority comparing to normal 4xx.)

I would suggest to try with debugging enabled and compare the logs for a
working, and for a non-working call. You could also try to concentrate on one
problem first, like the failure_route topic, and then combining this with the
reply_route.

Best regards,

Henning

--
Henning Westerholt
https://skalatan.de/blog/

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