[Serusers] Max-Forwards missing in SER CANCEL during forking

Jiri Kuthan jiri at iptel.org
Thu Jan 14 10:52:44 CET 2010

Try to set parameter tm/reparse_invite to 1 -- I was not aware of the option
but the code seems to adopt more message pieces including MF than if the parameter
is set to 0.

BTW was this an esthetic thing or did actually the CANCEL result in a loop?
I could have imagined that the downstream hop absorbs the CANCEL at transaction
level and the CANCEL follows the INVITE path, therefore not looping unless INVITE
did too.


Andres wrote:
> Hi,
> We encountered an issue in 0.9.6 when SER forks requests because there 
> are several endpoints registered with the same account (ie office and 
> home phones).  When one of the endpoints answers the call, SER sends a 
> CANCEL to the other endpoints so they can stop further call processing.  
> It turns our that this SER generated CANCEL does not contain the 
> "Max-Forwards" header which apparently violates RFC3261.
> Here is an example:
> U SER IP:5060 ->
> sip:3055551234 at;rinstance=C926AD943D258534F5F62913216C50ADC9D895D2; 
>  transport=udp SIP/2.0..Via: SIP/2.0/UDP 
>  From: "9545551234" <sip:9545551234 at>;tag=as7d1243c9..
>  Call-ID: 4385c66230a310e714f020926aa2028c at
>  To: <sip:3055551234 at X.X.X.X:5065>..CSeq: 102 CANCEL..
>  User-Agent: Sip EXpress router(0.9.6 (i386/linux))..
>  Content-Length: 0....    
> Is there any fix or workaround for this?  How can we get that 
> "Max-Forwards" header in the Message if it is internally generated by 
> SER and no something that flows through the config script.
> Thanks,
> Andres
> http://www.telesip.net
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