[asterisk-bugs] [Asterisk 0017849]: Asterisk does not properly align SDP "m=" lines when answering an SDP offer (provoking a T.38 negociation issue)

[Asterisk Bug Tracker]

The following issue has been SUBMITTED. 
====================================================================== 
https://issues.asterisk.org/view.php?id=17849 
====================================================================== 
Reported By:                frawd
Assigned To:                
====================================================================== 
Project:                    Asterisk
Issue ID:                   17849
Category:                   Channels/chan_sip/General
Reproducibility:            always
Severity:                   major
Priority:                   normal
Status:                     new
Asterisk Version:           1.6.2.11 
JIRA:                        
Regression:                 No 
Reviewboard Link:            
SVN Branch (only for SVN checkouts, not tarball releases): N/A 
SVN Revision (number only!):  
Request Review:              
====================================================================== 
Date Submitted:             2010-08-12 10:23 CDT
Last Modified:              2010-08-12 10:23 CDT
====================================================================== 
Summary:                    Asterisk does not properly align SDP "m=" lines when
answering an SDP offer (provoking a T.38 negociation issue)
Description: 
It appears that Asterisk generates SDP replies with "m=" lines always
aligned in the same order:
1. m=audio
2. m=video
3. m=text
4. m=image

When it should reply with the same order that was in the initial offer per
RFC-3264 (page 8):

[QUOTE]For each "m=" line in the offer, there MUST be a corresponding "m="
line in the answer. The answer MUST contain exactly the same number of "m="
lines as the offer. This allows for streams to be matched up based on their
order. This implies that if the offer contained zero "m=" lines, the answer
MUST contain zero "m=" lines.[/QUOTE]

This could potentially provoke many interoperability issues, one of which
is presented below.
====================================================================== 

Issue History 
Date Modified    Username       Field                    Change               
====================================================================== 
2010-08-12 10:23 frawd          New Issue                                    
2010-08-12 10:23 frawd          Asterisk Version          => 1.6.2.11        
2010-08-12 10:23 frawd          Regression                => No              
2010-08-12 10:23 frawd          SVN Branch (only for SVN checkouts, not tarball
releases) => N/A             
======================================================================