Re: [Iaxclient-devel] Registration process losing REGACK packet

[<mar...@op...>]

Hi,

Continuing with my investigations, I have identified an issue with
registrations that immediately follow a call hangup. There may also be other
scenarios which may cause similar problems, when the session pointer address
is being reused (read on for my explanation).

If a hangup is made on a call and the session is destroyed by calling the
destroy_session method of iax.c, frames still in the schedq associated with
the session being destroyed are marked as being sent by setting the retries
value to -1. In my case, not so long after, a registration sequence is
begun, which just happens to calloc the same address as the session pointer
used in the session for the call above (it is common to see addresses being
reused soon after being free'd). When the schedq is being processed in the
iax_get_event method of iax.c, a HANGUP frame from the previous call is
found, with frame->retries set to -1, frame->final set to 1 and
frame->session containing the same pointer address as the one we have been
allocated for use as the registration session. The frame processing decides
it's a good idea to destroy this session (again), which unfortunately
destroys the session being used for the registration, and we have a
registration failure as a result.

My fix was to add a curs->frame->session = NULL; in destroy_session, for all
scheduled events with the same session in the queue, thus preventing the
session from being destroyed later on in iax_get_event of iax.c when the
HANGUP frame is scheduled. We know that this session is the one being
destroyed and is now invalid. Another possibility is to set
curs->frame->final = 0; but I felt that setting the session to NULL was more
"correct" (note to self: make sure that the rest of the code can handle
this). Those more experienced with the library code make like to offer
another solution.

HTH
Mark

-----Original Message-----
From: Andrea Suisani [mailto:si...@op...] 
Sent: Monday, 21 April 2008 11:53 PM
To: mar...@op...
Cc: Iax...@li...
Subject: Re: [Iaxclient-devel] Registration process losing REGACK packet

Hi,


I really don't  know if it is related but the last registration known bugs
that I'm aware of was fixed in 2.0.1 release

if you are interested the thread with subject
[Iaxclient-devel] [announce] iaxclient-2.0.0 (final) released
contains info regarding bug's details

andrea


mar...@op... wrote:
> Hi,
> 
> My build is a DLL on Windows XP, with the IAX v2.1beta2 tag from source
> forge.
> 
> I have been testing the registration process with an Asterisk server
(v1.4,
> v1.6) using unit tests, and found that regularly (not always) the REGACK
> packet is not processed by my client. Using Wireshark, I see the REGREQ
from
> the client, the ACK from the server, and then the REGACK from the server,
> but this packet is not processed by the client. I would expect the
> iaxc_handle_regreply function in iax.c to be called, but this never
happens
> when the error occurs. Additionally, if the server requires authentication
> from the client and there is a REGAUTH packet sent from the server, the
> registration process always completes successfully.
> 
> Does anyone else have this problem, or already addressed the issue in
code?
> Is there a problem with identifying the session?
> 
> regards,
> Mark
> 
> 
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