[OpenSIPS-Users] CANCEL with a To tag.

[Alex Balashov]

It sounds like the CANCEL with the To-tag should have a Route header as 
well in order for it to be processed like any other sequential/in-dialog 
request -- that is to say, under loose_route().

Or, the CANCEL is intended for OpenSIPS itself, in which case it should 
not have a To-tag.

I would not try to accommodate this broken UA if I were you.  When 
breakage is so fundamental, this way lies madness.

Chris Maciejewski wrote:

> You can see a SIP flow before I added "CANCEL" to a lose routing
> section of my Opensips config here:
> 
> http://wima.co.uk/sip/2009-05-11_10-18-39-test-call_index.html
> 
> Note: F23 is rejected by OpenSIPs as it got "tag" in a To: header.
> 
> And after I added:
> 
>   if (is_method("CANCEL"))
>   {
>     t_relay();
>     exit;
>   }
> 
> to my lose routing logic, OpenSIPs generates CANCEL and sends it to
> the next hop:
> 
> http://wima.co.uk/sip/2009-05-11_10-46-46-test-call_index.html
> 
> 
> 2009/5/11 Iñaki Baz Castillo <ibc at aliax.net>:
>> 2009/5/11 Chris Maciejewski <chris at wima.co.uk>:
>>> Hi,
>>>
>>> I would like to ask what would be the best way to handle CANCEL
>>> request with a To tag. I know such a CANCEL request is not RFC
>>> compatible
>> CANCEL is hop-by-hop. This means that when OpenSIPS receives a CANCEL,
>> it *doesn't* route it, but it generates a new one (this occurs when
>> you do "t_relay()" for a CANCEL).
>> It's impossible to add "To tag" to a CANCEL generated by OpenSIPS
>> (expect if the CANCEL occurs for a re-INVITE being into an already
>> established dialog, so arriving CANCEL has To tag and OpenSIPS routes
>> it as any other in-dialog request).
>>
>>
>>>  but unfortunately I came across some buggy UAs doing this.
>> What do you mean with it? what does this UAS?
>>
>>
>> --
>> Iñaki Baz Castillo
>> <ibc at aliax.net>
>>
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>>
> 
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-- 
Alex Balashov
Evariste Systems
Web     : http://www.evaristesys.com/
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Direct  : (+1) (678) 954-0671