[OpenSIPS-Users] rtpengine_answer() is silently ignored on request route handling the initial INVITE when acting as an UAS - what am I missing?

[Pavel Sindelka]

Hello again,

answering to myself, the solution is not really intuitive - instead of 
using |rtpengine_answer()| directly, one has to use |rtpengine_offer()| 
with a |force-answer| flag. Doing so makes the |rtpengine| module set 
the |command| value to |answer| when sending the request via the control 
interface:

|rtpengine_offer("force-answer to-tag=$sig_local_totag", , 
$var(new_sdp_answer), $var(orig_sdp_answer));|
|append_to_reply("Contact: $var(contact)\r\n");
append_to_reply("Content-Type: application/sdp\r\n");
t_reply_with_body(200,"OK",$var(||new_sdp_answer||));
exit;|

Pavel

Dne 08.03.2026 v 14:01 Pavel Sindelka napsal(a):
>
> Hello,
>
> https://opensips.org/docs/modules/3.6.x/rtpengine.html#func_rtpengine_answer 
> doesn't mention any restrictions on use of this function, but in 
> reality opensips does not send anything to rtpengine if 
> |rtpengine_answer()| is called on a request route handling the INVITE. 
> Nothing in the log, no UDP exchange on the rtpengine control port, 
> regardless whether |rtpengine_offer()| is called earlier on that route 
> or not. If it is, the information exchange with rtpengine related to 
> |rtpengine_offer()| can be seen both in the log and on the rtpengine 
> control port.
>
> The intended overall workflow is to call |rtpengine_offer()|, handle 
> the mangled SDP offer internally and generate the SDP answer, and get 
> it "mangled back" using |rtpengine_answer()| before using it as the 
> body of a locally generated 200 response to the INVITE. Could it be 
> that as of now, |rtpengine_manage()| not only "combines the 
> functionality ... based on message type and method ..." but the three 
> individual methods have actually become just aliases of 
> |rtpengine_manage()| for backward compatibility? Or is the actual 
> execution of |rtpengine_answer()| suppressed thanks to some 
> undocumented plausibility check?
>
> Is there any way to enforce execution of |rtpengine_answer()| on a 
> request route handling the INVITE?
>
> Thank you for advice.
>
> Pavel
>

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