10 Dec
2014
10 Dec
'14
11:31 p.m.
Hello,
On 12/10/2014 03:57 PM, Heenan, Timothy Steven wrote:
I’ve recently run into a rather strange issue where,
in response to an
INVITE sent by Kamailio, I’m receiving a 183 Session Progress and SIP
200 OK response about .000050 seconds apart (.05 miliseconds) .
Kamailio is choosing to forward the SIP 200 OK ahead of the 183, as if
they had arrived at the same time and is prioritizing the 200.
This is likely because these replies are being handled by distinct
(parallel) Kamailio SIP worker processes. The kernel chooses which child
process handles which incoming packets semi-randomly, and there is no
means of forcing replies belonging to the same transaction, message
flow, Call-ID, etc. to be handled serially by one process. 0.05 msec
sounds like it could be within the timing tolerance that would create
such a race condition.
There's not much you can do here. You can probably rig up something with
locking, but any such strategy will end up blocking a whole child
process, and it's risky--it might not get unblocked if there is abnormal
messaging behaviour. Your best bet is to figure out why the 183 and the
200 are coming in near-simultaneously, as that is abnormal--if not
exactly proscribed--behaviour.
--
Alex Balashov - Principal
Evariste Systems LLC
235 E Ponce de Leon Ave
Suite 106
Decatur, GA 30030
United States
Tel: +1-678-954-0670
Web: http://www.evaristesys.com/, http://www.alexbalashov.com/