[asterisk-users] asterisk 13.16 / pjsip / t.38: res_pjsip_t38.c:207 t38_automatic_reject: Automatically rejecting T.38 request on channel 'PJSIP/91-00000007'

Joshua Colp jcolp at digium.com
Sun Jun 11 06:29:44 CDT 2017

On Sun, Jun 11, 2017, at 08:16 AM, Michael Maier wrote:

> I did some further investigations and fixed a local problem. Now,
> asterisk is able to successfully activate T.38 - unfortunately just for
> very shot time because of a phantom package it receives!

What was the local problem?
> Let's go into details:
> I'm starting at the point where asterisk / fax client receives the T.38
> reininvite from the server from the provider for the
> fax client (extension 91):


> But now, something strange happens: Asterisk "receives" a T.38 reinvite
> package from provider!
> Why is it strange? Because *this package doesn't exist at all* ! It
> can't be seen in tcpdump. I did 4 tests - always the same! Where does
> this package come from? It's exactly the same package which can be seen
> at the beginning of the trace excerpted here! Isn't it been deleted
> after it has been processed the first time?

PJSIP uses a dispatch model. The request is queued up, acted on, and
then that's it. The act of acting on it removes it from the queue. The
only reason I'd expect to see it again is if there was a retransmission
or something somehow requeued it up - but I don't think we do that
anywhere. Not quite sure why it would be happening...

Joshua Colp
Digium, Inc. | Senior Software Developer
445 Jan Davis Drive NW - Huntsville, AL 35806 - US
Check us out at: www.digium.com & www.asterisk.org

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