[OpenSIPS-Users] CANCEL handling

Bogdan-Andrei Iancu bogdan at opensips.org
Wed Jan 9 12:54:04 CET 2013

Hi Mariana,

If CANCEL hits opensips while the the INVITE is still under processing 
(in a different process), the INVITE transaction will not exist yet (it 
is created by t_relay), so the t_check_trans() will return false -> 
script will exit without doing anything for the CANCEL - more or less 
the CANCEL will be dropped without being replied or fwded. This will 
force retransmission of Cancel -> buying more time to finish the 
processing of the INVITE.

Hope this helped.


Bogdan-Andrei Iancu
OpenSIPS Founder and Developer

On 01/08/2013 10:49 PM, Mariana Arduini wrote:
> Hello all,
> I hope somebody can give me a kind hint on what to do here.
> We have this piece of code for CANCEL handling:
>     # CANCEL processing
>     if (is_method("CANCEL")) {
>         if (t_check_trans()) {
>             t_relay();
>         }
>         exit;
>     }
> What happens is sometimes we take too long to process the INVITE due 
> to some DB issues, and the UAC sends us a CANCEL before we relay the 
> We don´t use t_newtran() because of this big warning in docs saying 
> that "the changes on the request that are made after this function 
> call will not be saved into transaction!!!". We need to perform a lot 
> of changes in the requests and I understand this wouldn´t be possible 
> after calling t_newtran().
> So our transaction is not created untill we relay the INVITE, which 
> means that any CANCEL received before that will be dropped.
> We also tried testing the CANCEL messages we´re receiving in these 
> cases with has_totag() and loose_route(), but they won´t pass as well.
> Is there any way to verify a CANCEL message in this scenario and relay 
> it in case is belongs to a valid transaction?
> Any help will be much appreciated.
> Regards,
> Mariana.
> _______________________________________________
> Users mailing list
> Users at lists.opensips.org
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