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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