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

[Asterisk Bug Tracker]

A NOTE has been added to this issue. 
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http://bugs.digium.com/view.php?id=13849 
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Reported By:                klaus3000
Assigned To:                putnopvut
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Project:                    Asterisk
Issue ID:                   13849
Category:                   Channels/chan_sip/General
Reproducibility:            have not tried
Severity:                   minor
Priority:                   normal
Status:                     acknowledged
Asterisk Version:           SVN 
SVN Branch (only for SVN checkouts, not tarball releases):  trunk 
SVN Revision (number only!): 154926 
Disclaimer on File?:        N/A 
Request Review:              
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Date Submitted:             2008-11-06 11:35 CST
Last Modified:              2008-12-02 17:08 CST
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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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---------------------------------------------------------------------- 
 (0095694) putnopvut (administrator) - 2008-12-02 17:08
 http://bugs.digium.com/view.php?id=13849#c95694 
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Ah, you are quite right. I did not notice that difference. This makes
things a bit more complicated.

Ok, Asterisk should send a 200 OK to the reINVITE. That part would
probably be easy enough to handle. There are two tricky parts to handle for
this situation. One is similar to what I stated in my previous message.
Asterisk is not equipped to be able to recognize ACKs for multiple INVITEs
in a single dialog. Change needs to be made with regards to how the
'pendinginvite' field is handled. The other tricky part is that I'm not
sure of the proper way to tell if an SDP offer has been answered on the
dialog at the time the reINVITE is handled. I'll do some searching and see
what I can find. 

Issue History 
Date Modified    Username       Field                    Change               
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2008-12-02 17:08 putnopvut      Note Added: 0095694                          
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