[asterisk-bugs] [Asterisk 0014943]: SIP INVITE contains external IP causing 404 Not Found on the Cisco 9740

[Asterisk Bug Tracker]

The following issue has been SUBMITTED. 
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http://bugs.digium.com/view.php?id=14943 
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Reported By:                sverre
Assigned To:                
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Project:                    Asterisk
Issue ID:                   14943
Category:                   Channels/chan_sip/General
Reproducibility:            always
Severity:                   minor
Priority:                   normal
Status:                     new
Asterisk Version:           1.4.24 
Regression:                 No 
SVN Branch (only for SVN checkouts, not tarball releases): N/A 
SVN Revision (number only!):  
Request Review:              
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Date Submitted:             2009-04-20 18:52 CDT
Last Modified:              2009-04-20 18:52 CDT
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Summary:                    SIP INVITE contains external IP causing 404 Not
Found on the Cisco 9740
Description: 
Some routers implement <a
href='http://www.voip-info.org/wiki/view/Routers+SIP+ALG'>SIP ALG</a>,
however as noted in the article only some of them modify the VIA header -
while all modify the CONTACT header.

Furthermore, some routers that do not modify the CONTACT header, also do
not modify the incoming INVITE header on an incoming call, even through
they do route the INVITE to the correct IP.

In such a scenario, the outbound REGISTER leaves the phone with VIA
192.168.0.15 and CONTACT 192.168.0.15, then arrives at the server with VIA
192.168.0.15 and CONTACT external-ip. The INVITE is therefore sent to the
external ip (correct), but with a Request-Line that ALSO contains the
external-ip.

In some SIP ALG implementations, this request-line is rewritten and all is
well, but in some it is NOT re-written, and therefore the phone replies
with a 404 Not Found. This is a particular problem when using the Cisco
7940 in combination with the Billion Bipac 7402XL, though likely affects
similar models of both phone and router.

This behavior could be avoided if Asterisk could be instructed to use the
contents of the VIA registration header in the construction of the INVITE,
rather than CONTACT registration header.

I will attach 4 pcap files containing the phone and server side of the
conversation in both a working (D-Link DSL-502T) and non-working (Billion
BiPac 7402XL) scenarios.
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Issue History 
Date Modified    Username       Field                    Change               
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2009-04-20 18:52 sverre         New Issue                                    
2009-04-20 18:52 sverre         Asterisk Version          => 1.4.24          
2009-04-20 18:52 sverre         Regression                => No              
2009-04-20 18:52 sverre         SVN Branch (only for SVN checkouts, not tarball
releases) => N/A             
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