[SR-Dev] [Fwd: [Kamailio-Devel] race condition]

[Daniel-Constantin Mierla]

Hello,

On 04/23/2009 11:51 AM, Klaus Darilion wrote:
> Hi guys!
>
> In Kamilio we had (have?) the problem described here. Maybe the problem 
> still applies to ser-tm too, then it needs this fix too.
>   
this was discussed some months ago, also with SR. SR has a completely 
different locking/synchronization system and the issue does not apply.

Cheers,
Daniel

> regards
> klaus
>
> -------- Original-Nachricht --------
> Betreff: [Kamailio-Devel] race condition
> Datum: Thu, 23 Apr 2009 10:34:26 +0200
> Von: Zappasodi Daniele <Daniele.Zappasodi at seltatel.it>
> An: <devel at lists.kamailio.org>
> Referenzen: <mailman.9.1240394401.8388.devel at lists.kamailio.org>
>
>
> Hello,
> I have a problem with a race condition with the reply and retransmission.
> Sometimes Openser (I'm still working with 1.3.x version) ignores the 
> provisional reply and tears down the call after the fr_timer.
> This happens only in a particulary conditions:
> I have a short value for fr_timer (5 sec);
> the reply arrives very fast (I have gateway and proxy on the same box).
>
> In this situation can happen that a child sends the INVITE (SEND_BUFFER 
> in t_forward_nonack) and it is suspended by the scheduler before it can 
> execute start_retr.
> Another child get the reply.
> When the first child executes start_retr it sends immediately a 
> retransmission for the INVITE and after 5 seconds (the fr_timer) it 
> tears down the call with CANCEL, because it ignores the reply.
>
> I know that this is a very improbable condition (even if I encountered 
> it), but if you want to fix it, it should be easy to solve: in 
> t_forward_nonack, before start_retr, it should be tested if another 
> child has already received a reply.
> Something like this (t_fwd.c on head):
>
> @@ -719,7 +719,10 @@
>                                          -p_msg->REQ_METHOD);
>                          }
>
> -                       start_retr( &t->uac[i].request );
> +                       if(p_msg->REQ_METHOD==METHOD_INVITE && 
> t->uac[i].last_received>=100)
> +                               LM_DBG("Last received 
> %d\n",t->uac[i].last_received);
> +                       else
> +                               start_retr( &t->uac[i].request );
>                          set_kr(REQ_FWDED);
>                  }
>          }
>
>
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>   

-- 
Daniel-Constantin Mierla
http://www.asipto.com/