[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'

[Michael Maier]

On 06/11/2017 at 01:29 PM Joshua Colp wrote:
> On Sun, Jun 11, 2017, at 08:16 AM, Michael Maier wrote:
> 
> <snip>
>  
>> 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?

Update of t38modem from 3.13 to 3.15

>> 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 195.185.37.60:5060 for the
>> fax client (extension 91):
> 
> <snip>
> 
>>
>> 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.

That's the *expected* behavior ... . I rechecked again and again. All
existing tcpdumps. The "resent" package isn't part of any tcpdump
(wireshark doesn't show it) - and during tcpdump no package was dropped.

> 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...

But even if this package would have really been sent (as retransmission)
- shouldn't there be another response? T.38 has been successfully
enabled before and the faxclient has already sent a valid 200 ok
including complete SDP information to asterisk.

All in all it looks really odd to me.


Thanks,
regards,
Michael