Hi Carsten,

No, I didn't. It didn't occur to me that this function calibrates the dialog scope of the next call, which is the missing ingredient inside a reply handler that is armed out of a more general, global event route. Thank you for this!

-- Alex

On Nov 14, 2024, at 3:52 pm, Carsten Bock carsten@bock.info wrote:

Hi,

Did you try to lookup the dialog[1] before calling dlg_req_within()?

[1] https://kamailio.org/docs/modules/devel/modules/dialog.html#dialog.f.dlg_get

Thanks, Carsten

-- Schöne Grüße aus Hamburg, dem Tor zur Welt, Carsten Bock

Baron-Voght-Str. 128a I 22607 Hamburg I Germany T +49 179 2021244 I carsten@bock.info LinkedIn: https://www.linkedin.com/in/carstenbock/

Alex Balashov via sr-users sr-users@lists.kamailio.org schrieb am Do., 14. Nov. 2024, 21:44: Hi,

I am trying to use dlg_req_within() for a 3pcc-style call setup, to set up media via a reinvite:

1. Store original SDP offer from caller in $dlg_var()s;

2. Later, after e2e ACK is processed for initial INVITE transaction, send reinvite to callee using dlg_req_within(). I call rtpengine_offer() and feed it the original SDP offer (via read_sdp_pv modparam), and take the RTPEngine-transformed SDP and feed that to dlg_req_within():

   dlg_req_within("callee", "INVITE", "application/sdp", "$var(sdp_from_rtpengine)");

3. I have found that event_route[tm:local-response] does not allow me to capture the 200 OK / SDP answer to this reinvite; it is internally absorbed.

However, it is possible to arm an onreply_route in event_route[tm:local-request], to receive the 200 OK:

event_route[tm:local-request] { if(method == "INVITE" && has_body("application/sdp")) t_on_reply("REINVITE_REPLY"); }

4. My intent is for this reinvite reply handler to set off a reinvite to the caller side:

   onreply_route[REINVITE_REPLY] { if(method == "INVITE" && has_body("application/sdp") && t_check_status("200")) { ... $var(rtpengine_use_this_sdp) = $rb; rtpengine_answer("..."); dlg_req_within("caller", "INVITE", "application/sdp", "$var(sdp_from_rtpengine)"); }

This ensures proper relay symmetry. Otherwise, the caller will continue to send RTP to the previous upstream endpoint of the call, prior to any reinvite.

However, dlg_req_within() doesn't work in this later context, even though the documentation says it can be used from ANY_ROUTE. Kamailio doesn't complain, there is no error. It just doesn't initiate a reinvite to the caller.

I considered the possibility that this may be because the calling scope is that of a pending reinvite transaction to the callee, but there is no obvious way to defer that into the future. If I send it to an async task worker, the transaction scope required for dlg_req_within() to know which dialog it's operating on will be lost.

Any ideas appreciated, and thank you in advance!

-- Alex

-- Alex Balashov Principal Consultant Evariste Systems LLC Web: https://evaristesys.com Tel: +1-706-510-6800

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