[Users] Can't replace duplicate c= lines in SDP

[Bogdan-Andrei Iancu]

Hi Jerome,

this is a topic that was debated couple of times. according to the SDP 
RFC, the connection information (c=) can exists both in session 
description (s= section ) and in media description (m= section). This 
because a session may contain several media description and if the c= in 
media is not specify, the one from session is used.

It looks lie the Cisco GW sets both c= (in session and media 
description) - it is redundant, but correct (c= in media has priority 
over the one in media description). Nathelper changes only the one to be 
used - If present, the one from media, otherwise the one from session 
section.

If from some reasons, the other party  is buggy and looks for c= in 
session (even if C= is present in media part), you should try to use the 
"c" flag for force_rtp_proxy():
    http://www.openser.org/docs/modules/1.2.x/nathelper.html#AEN275

regards,
bogdan

Jerome Martin wrote:

>Hello everyone,
>
>I've already noticed a few posts on that topic, but none has been
>answered up to resolution of the problem.
>
>Here is the issue : I am receiving SDP in INVITEs from a Cisco AS5350
>(IOS 12.4) gateway that contain two identical c= lines for the same
>media.
>
>When using force_rtp_proxy, only the last one is replaced by my proxy
>IP. If I use the mangler module on top of it, then both are replaced,
>but the one already replaced by force_rtp_proxy is now a concatenation
>of twice the proxy IP address.
>
>Is there a way to deal with this so that both lines are replaced ?
>Depending on which equipement gets the REQUEST next, either the first or
>the second line is used, and this leads to RTP proxy problems.
>
>Best Regards,
>
>Jerome Martin
>
>
>
>
>
>
>
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