[SR-Users] Send 200 OK response with body to INVITE requests

[Alex Balashov]

Again, the SIP standards forbid this, because proxies just don’t do that!

—
Sent from mobile, with due apologies for brevity and errors.

> On Apr 16, 2019, at 3:57 AM, David Dean <just_bytesize at yahoo.co.uk> wrote:
> 
> As you say, the rtpengine SDP mangling is turn-key with rtpengine_answer(). It's working perfectly.
> 
> But I'm surprised to find I cannot generate a 200 OK and attach the SDP inside Kamailio.
> 
> sl_send_reply() would be perfect but it doesn't allow a body to be attached (unless I missed something in the docs?)
> 
> uac_req() allows the headers and body to be created but doesn't allow a status code to be set (as far as I know?)
> 
> So frustrating because I've been able to script everything else I need within Kamailio. The missing piece is being able to create this response then everything works.
> 
> Dave.
> 
> 
> 
> 
> 
> On Tuesday, 16 April 2019, 00:21:07 BST, Alex Balashov <abalashov at evaristesys.com> wrote:
> 
> 
> Kamailio will substitute RTPEngine-mangled SDP upon your invocation of rtpengine_answer(). You’re working about a thousand times too hard on this issue; it’s already turn-key. :-)
> 
> —
> Sent from mobile, with due apologies for brevity and errors.
> 
>> On Apr 15, 2019, at 6:03 PM, David Dean <just_bytesize at yahoo.co.uk> wrote:
>> 
>> Hi Alex,
>> 
>> Thanks for the tip re: rtpengine routing, that's really useful.
>> 
>> The flow I'm trying to create is like this:
>> 
>> [ Test Client ] ------> INVITE ------> [ Kamailio ]
>>           ^                                                   |
>>           |-------------- 200 OK + SDP --------|
>> 
>> The goal is for the test client to think a remote client accepted the call, when actually it's just Kamailio faking the 200 response.
>> 
>> There must be some way (even if it's hacky!) to get a 200 response back to the client with the rtpengine SDP included?
>> 
>> I got very close with $uac_req but it doesn't seem to be able to set the "200" status so the Test Client thought it was a brand new call. If I could set the 200 status with $uac_req (or something similar) then this will be working.
>> 
>> Thanks.
>> 
>> 
>> 
>> On Monday, 15 April 2019, 20:50:18 BST, Alex Balashov <abalashov at evaristesys.com> wrote:
>> 
>> 
>> Hi David,
>> 
>> Kamailio is a proxy, so it cannot endogenously originate either requests
>> or most replies. A 200 OK to an INVITE transaction can only come from a
>> user agent (endpoint), and Kamailio's sole job is to forward it. So, the
>> 200 OK is going to come from the auto-answering callee. 
>> 
>> To engage RTPEngine in both directions, you need to intercept the 200 OK
>> that is generated from the callee and call rtpengine_answer() /
>> rtpengine_manage() on it:
>> 
>> ---
>> route {
>>   ...
>> 
>>   if(is_method("INVITE")) {
>>       ...
>> 
>>       rtpengine_offer("...");
>> 
>>       t_on_reply("REPLY");
>> 
>>       if(!t_relay())
>>         sl_reply_error();
>> 
>>       exit;
>>   }
>> 
>>   ...
>> }
>> 
>> onreply_route[REPLY] {
>>   if(is_method("INVITE") && sdp_content()) 
>>       rtpengine_answer("...");
>> }
>> ---
>> 
>> -- Alex
>> 
>> On Mon, Apr 15, 2019 at 07:41:22PM +0000, David Dean wrote:
>> 
>> > Hi all,
>> > I'm building an automated load testing system for an rtp media server with TURN that uses Kamailio for SIP.
>> > When a client sends an INVITE to Kamailio, I need Kamailio to respond with "200 OK" and the SDP generated by rtpengine.
>> > I've enabled auto-answer in the client, so as soon as it receives the response from Kamailio it will start sending RTP packets.
>> > Right now I'm using send_reply("200", "OK"); which is sending the right 200 response back to the client, but it doesn't include any body.
>> > How can I get Kamailio to send a "200 OK" and add the rtpengine_answer into the body?
>> > Appreciate any help, I've been struggling with this for three days.
>> > Cheers.
>> > 
>> > rtpengine_offer("SIP-source-address ICE=force-relay RTP");send_reply("200", "OK");
>> 
>> > 
>> 
>> > _______________________________________________
>> > Kamailio (SER) - Users Mailing List
>> > sr-users at lists.kamailio.org
>> > https://lists.kamailio.org/cgi-bin/mailman/listinfo/sr-users
>> 
>> 
>> -- 
>> Alex Balashov | Principal | Evariste Systems LLC
>> 
>> Tel: +1-706-510-6800 / +1-800-250-5920 (toll-free) 
>> Web: http://www.evaristesys.com/, http://www.csrpswitch.com/
>> 
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