[OpenSIPS-Users] To tag in the CANCEL issue

[Bogdan-Andrei Iancu]

Hi all,

Just to add some info about the OpenSIPS internals, when comes to 
building the CANCEL request. It will use exactly the same TO/FROM hdrs 
as the ones sent into the INVITE request.

The CANCEL request works at transactional level - it shares the same VIA 
branch and stuff as the INVITE branch it cancels. So the tag info (which 
is at dialog level) is irrelevant, as again, the canceling happens at 
transactional level.

Even more, if we consider the proxy may do parallel forking - in this 
case the UAC may receive multiple 1xx replies, with different to-tags... 
So, following the CISCO approach, which tag the UAC should use in order 
to cancel the call ??

Regards,

Bogdan-Andrei Iancu

OpenSIPS Founder and Developer
   https://www.opensips-solutions.com
   https://www.siphub.com

On 17.11.2024 23:20, nz deals wrote:
>
> Hi Community
>
> I’m encountering a strange issue with |CANCEL| requests in my opensips 
> 3.4.2 setup. Here’s the scenario:
>
>  1. My carrier sends the initial |INVITE| without a |tag| in the |To|
>     header, which I forward to a Cisco phone.
>  2. The Cisco phone responds with a |180 Ringing| message, which
>     includes a |tag| in the |To| header.
>  3. When I send a |CANCEL| request, my carrier does not include the
>     |tag| in the |To| header, and as a result, OpenSIPS also forwards
>     the |CANCEL| to the Cisco phone without the |tag|.
>
> Because of this, the Cisco phone responds with a |481 Call/Transaction 
> Does Not Exist| error, and the call remains active on the phone 
> without being canceled.
>
> I’ve tried modifying the |CANCEL| request to include the |tag| in the 
> |To| header, but I wasn’t able to modify because the initial |INVITE| 
> doesn’t have a |tag| in the |To| header.
>
> Has anyone experienced a similar issue or found a way to fix this? Any 
> guidance would be greatly appreciated.
>
>
> Thanks
>
> Regards,
> Jason
>
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