[SR-Users] Hop by hop CANCEL, wrong to header

[Vitaliy Aleksandrov]

Hello Daniel,

Thanks for the reply.

Sorry i have made a typo. If E2E_CANCEL_HOP_BY_HOP is defined then 
e2e_cancel() from t_fwd.c calls cancel_branch() function for each branch 
it found at a t_invite transaction.
Then if cfg_get(tm, tm_cfg, reparse_invite) is true cancel_branch() 
calls build_local_reparse() which returns new CANCEL request buffer 
based on outgoing INVITE, but with original To header.

I've searched a bit deeper and found that if E2E_CANCEL_HOP_BY_HOP is 
not defined e2e_cancel() calls e2e_cancel_branch(), which then calls 
build_local_reparse() like in previous description when 
E2E_CANCEL_HOP_BY_HOP was defined.

So the main question is why does kamailio take "To" field from a 
transaction cell and not from outgoing buffer like it does with other 
headers ?

I'm using kamailio-3.0.2, but i have checked 3.2.2 sources and haven't 
found any changes at the functions mentioned above.

Cheers,
Vitaliy Aleksandrov

> Hello,
>
> On 5/23/12 5:22 PM, Vitaliy Aleksandrov wrote:
>> Hi all,
>>
>> I have a question about CANCEL message processing.
>>
>> My call sceraio:
>> When an INVITE request comes I need to rewrite a domain part of the 
>> several headers(to, from, contact, SDP ip) according to the outgoing 
>> interface.
>> I can do it before t_relay(), but when destination user has more then 
>> one locations and they are reachable through different interfaces all 
>> forked INVITEs will have the same domain.
>> To avoid that problem i have tried to move rewriting part(subst from 
>> the textops module) to the branch_route.
>>
>> Unfortunately that solution didn't helped me, because "To" header of 
>> the outgoing CANCEL messages is wrong (unchanged. as it was at the 
>> moment when transaction was created by the t_relay() ).
>> As i understood from the documentation and mailing list kamailio 
>> builds CANCEL based on outgoing INVITE.
>>
>> I did a small research and found that Kamailio really takes outgoing 
>> INVITE from each branch (invite_transaction_cell -> 
>> uac[b_id].request.buffer) and builds CANCEL (build_local_reparse() 
>> from tm/t_msgbuilder.c) based on it.
>> But kamailio does an exception for the To header which is described 
>> below:
>> ***cancel_branch* function (from t_cancel.c) calls 
>> *build_local_reparse*() and fills one of the parameters with a 
>> pointer to unmodified To header.
>> *    build_local_reparse*() uses received To header to construct 
>> outgoing CANCEL.
>>
>> I have changed:
>>     cancel = build_local_reparse(t, branch, &len, CANCEL, CANCEL_LEN, 
>> &t->to, reason);
>> to:
>>     cancel = build_local_reparse(t, branch, &len, CANCEL, CANCEL_LEN, 
>> NULL, reason);
>> and it works for me now.
>>
>> It looks like if E2E_CANCEL_HOP_BY_HOP *e2e_cancel()* (t_fwd.c) will 
>> call *e2e_cancel_branch()* which works as i want instead of 
>> *cancel_branch()*, but it is just my assumption.
>
> do you mean if E2E_CANCEL_HOP_BY_HOP is defined? I quick grep at this 
> time showed it is defined in t_fwd.h...
>
> What is the version you are using?
>
> Cheers,
> Daniel
>
>>
>> Why does kamailio generate CANCEL requests in such a way ? Did i miss 
>> something from the RFC3261 or kamailio documentation ?
>>
>> Thanks in advance for any help !
>>
>>
>>
>>
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>
> -- 
> Daniel-Constantin Mierla -http://www.asipto.com
> http://twitter.com/#!/miconda  -http://www.linkedin.com/in/miconda
>
>

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