[asterisk-bugs] [Asterisk 0010274]: T.38 passthrough with 2 Asterisk boxes not working

[noreply at bugs.digium.com]

A NOTE has been added to this issue. 
====================================================================== 
http://bugs.digium.com/view.php?id=10274 
====================================================================== 
Reported By:                cstadlmann
Assigned To:                
====================================================================== 
Project:                    Asterisk
Issue ID:                   10274
Category:                   Channels/chan_sip/T.38
Reproducibility:            always
Severity:                   block
Priority:                   normal
Status:                     new
Asterisk Version:            SVN 
SVN Branch (only for SVN checkouts, not tarball releases):  1.4  
SVN Revision (number only!): 76410 
Disclaimer on File?:        N/A 
Request Review:              
====================================================================== 
Date Submitted:             07-23-2007 08:41 CDT
Last Modified:              07-30-2007 13:11 CDT
====================================================================== 
Summary:                    T.38 passthrough with 2 Asterisk boxes not working
Description: 
This is the configuration I'm using:

ATA 1 <-> Asterisk 1 <-> Asterisk 2 <-> ATA 2

As long ATA's are resided on the same Asterisk box, no T.38 problem. But
if ATA 1 is trying to send a fax via T.38 to ATA 2, the complete call fails
because Asterisk 1 is killing it during re-invite and Asterisk 2 gives up.

Both Asterisk boxes are: SVN-branch-1.4-r76410
======================================================================
Relationships       ID      Summary
----------------------------------------------------------------------
has duplicate       0010317 Bug 10274 seems to be SIP related, not ...
====================================================================== 

---------------------------------------------------------------------- 
 cstadlmann - 07-30-07 13:11  
---------------------------------------------------------------------- 
Puh... I really thought noone concerns about that issue...

To 1)
During the last week's testing and tracking and tracing I found out that
every  ATA or other device immediately sends a '100 Trying' after it
receives  the reinvite. After that the device responds with '200 OK'. So if
Asterisk1 would also send a 100 response immedately to Asterisk2 I think
the whole situation wouldn't go that far in the wrong direction. I tried to
figure out where to put in that code snippet, but had no luck because I'm
not familiar with chan_sip.c at all.

To 2)
As I mentioned before, Asterisk1 sends a completely senseless reinvite to
ATA1  with NO T.38 information, just plain RTP information. Please have a
look at line 3424 of 'Log Asterisk 1.txt' and below. You will see what I
mean. While ATA1 is responding with a '200 OK' for the T.38 reinvite it
receives that useless invite , reponds with '200 OK' again and 'falls back'
to plain RTP, so Asterisk 1 thinks that ATA 1 is not capable of T.38. This
is that I meant with Asterisk is not handling '100 Trying' correctly
because it sends wrong invite packets.


So again, I think that all problems are located in the '100 Trying'
message. Maybe you can implement that code segment into chan_sip.c or just
tell me where I can find it and I will try to patch by myself although I'm
not a C guru... Anyway, I would appreciate a quick solution 'cause my boss
is already on my tail... 

Issue History 
Date Modified   Username       Field                    Change               
====================================================================== 
07-30-07 13:11  cstadlmann     Note Added: 0068070                          
======================================================================