[asterisk-bugs] [Asterisk 0013849]: problem handling race condition - reINVITE before ACK

[Asterisk Bug Tracker]

The following issue is now READY FOR TESTING. 
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http://bugs.digium.com/view.php?id=13849 
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Reported By:                klaus3000
Assigned To:                mmichelson
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Project:                    Asterisk
Issue ID:                   13849
Category:                   Channels/chan_sip/General
Reproducibility:            have not tried
Severity:                   minor
Priority:                   normal
Status:                     ready for testing
Asterisk Version:           SVN 
Regression:                 No 
SVN Branch (only for SVN checkouts, not tarball releases):  trunk 
SVN Revision (number only!): 154926 
Request Review:              
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Date Submitted:             2008-11-06 11:35 CST
Last Modified:              2009-03-31 13:50 CDT
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Summary:                    problem handling race condition - reINVITE before
ACK
Description: 
Hi! 

Asterisk has problems handling incoming reINVITE if the ACK of the
incoming INVITE is still missing. Although this a pssobile scenario, e.g:

client   proxy     Asterisk
  --INV--->
           ----INV----->
           <---200 ok---
  <-200 ok-
  --ACK--->
  -reINV-->
            --reINV----->
            --ACK------->

This is a scearion which can really happen, e.g. as the processing of the
ACK in the proxy may takes more time. It can also happen without proxy (an
packet can overtake another packet).

The problem is:
1. Asterisk does not accept the reINVITE but sends 491 request pending
Sending 491 is only allowed if the request is in a pending state. But as
the request is finished (200 is already sent) there can not be 491. The
proper solution would be to accept the reINVITE - as this reINVITE is an
implicit ACK to the previous INVITE. Receiving the reINVITE means, that the
caller has received the 200 ok.

2. Asterisk does not accept the ACK to the 491, it goes on resending the
491.

3. My client then tries to reINVITE again, which is accepted by Asterisk.
But then, if the call is hang up from the other side (in this case DHADI),
Asterisk does not send BYE

It happends with pedantic= yes and no.
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---------------------------------------------------------------------- 
 (0102493) mmichelson (administrator) - 2009-03-31 13:50
 http://bugs.digium.com/view.php?id=13849#c102493 
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I sat down to work on this and after an hour of analyzing everything and
trying to make sense of it all, it seems like a simple 3-line change is all
that may be necessary to handle this correctly. I've uploaded a patch
(13849.patch) which I believe will handle this problem. Right now it has a
bunch of comments so that if things don't work, I can follow what my
previous logic was and potentially figure out what went wrong.

I'm optimistic that this patch will work; however, if it does not, please
post a sip debug as well as core debug output from a failure so that I may
see what went wrong. 

Issue History 
Date Modified    Username       Field                    Change               
====================================================================== 
2009-03-31 13:50 mmichelson     Note Added: 0102493                          
2009-03-31 13:50 mmichelson     Status                   acknowledged => ready
for testing
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