[asterisk-dev] Asterisk 16 / pjsip: actual SDP handling in case of late offer during outbound call seems to break call

[Michael Maier]

On 17.06.19 at 20:15 Joshua C. Colp wrote:
> On Mon, Jun 17, 2019, at 3:10 PM, Michael Maier wrote:
>> Hello!
>>
>> I'm facing a problem on an outbound call which receives a reInvite w/o 
>> SDP (late / delayed offer technique) from ISP. The ISP won't provide
>> any SDP in the following received ACK and the call is broken therefore 
>> afterwards because no more media is sent after this reInvite.
>>
>>
>> Detail:
>>
>> - ISP sends ReInvite w/o SDP
>> - Asterisk sends 200 OK containing the SDP, received by the initial 200 
>> OK from the ISP before
>>   (which is a subset of the defined allowed media for this trunk).
>>   The <sess-version> in the SDP of the 200 OK as answer to the reInvite 
>> is the same as the one of
>>   the initial INVITE though the SDP is different. Shouldn't 
>> <sess-version> be increased if SDP
>>   is changed changed?
>> - ISP sends an ACK - but w/o SDP -> Call is dead from now on.
> 
> Yes, if the SDP is changed then the session version should be incremented. If this is not done then this is likely a bug in pjmedia-sdp (I don't believe we deal with the session version, it's down in the PJSIP SDP side). You can file an issue[1] with the details.

https://issues.asterisk.org/jira/browse/ASTERISK-28452