[SR-Users] Guidance building a WebRTC to Asterisk Intermediate Proxy

[M S]

The problem seems to that the kamailio is trying to route it over UDP port
using WSS transport, which will never work.

You are creating a transport bridge (UDP <-> WSS i.e. stateless transport
<-> stateful transport) as well media bridge (RTP <-> SRTP), so it is going
to be tricky. I strongly discourage it since things get messy for
sequential requests. But you can try the following,

Here are some PATH module parameters and functions, you will need to setup.

1. You will need to enable "use_received" parameter to ensure connection
tracking.
2. It seems you may have enabled "received_format", so you make sure you do
NAT detection and use "handle_ruri_alias" for initial requests.
3. You must also enabled "enable_r2", but with caution, since both ends
(i.e. UAC and UAS) can be using same kamailio (proxy) socket for in/out.
4. Make sure to use "add_path_received" instead of "add_path".
5. If using OUTBOUND module then make sure it is loaded BEFORE the PATH
module.

Thank you.

--
Muhammad Shahzad Shafi
Burraq Technologies
Tel: +49 176 99 83 10 85



On Sat, Jun 26, 2021 at 12:47 AM Peter Manley <peter.manley at kombea.com>
wrote:

> Hello,
>
>
>
> I’m working on building an RTP Proxy which will allow both regular SIP to
> SIP transactions and WebRTC to SIP transactions to an Asterisk Server.
>
>
>
> SIP UAC < ---UDP/SIP --- > Kamailio/RTPEngine Proxy < ---UDP/SIP----- >
> Asterisk Server
>
>
>
> AND
>
>
>
> WebRTC UAC < ---WSS--- > Kamailio/RTPEngine Proxy < ---UDP/SIP----- >
> Asterisk Server
>
>
>
> The Kamailio/RTPEngine Proxy is stateless (does not use the tm or
> registerer modules), and uses the Path module to replace the Route header
> with a Path header.
>
>
>
> It works grep for SIP/UDP to SIP/UDP transactions.
>
>
>
> HOWEVER… It only partially works for WSS to SIP/UDP transactions. The
> REGISTER/401(Unauthorized), REGISTER/200(OK) transaction works well.
>
>
>
> When the Asterisk server sends a SIP Options message, I get the following
> error:
>
> Jun 25 15:47:03 VRTPENGINE kamailio[4953]: INFO: <script>: => OPTIONS <
> sip:l4umfumh at 192.0.2.97;transport=ws;alias=209.141.117.212~59751~6 ->
> <null> (IP:172.16.0.48:sp)
>
> Jun 25 15:47:03 VRTPENGINE kamailio[4953]: WARNING: <core>
> [core/msg_translator.c:2815]: via_builder(): TCP/TLS connection (id: 0) for
> WebSocket could not be found
>
> Jun 25 15:47:03 VRTPENGINE kamailio[4953]: ERROR: <core>
> [core/msg_translator.c:2003]: build_req_buf_from_sip_req(): could not
> create Via header
>
> Jun 25 15:47:03 VRTPENGINE kamailio[4953]: ERROR: <core>
> [core/forward.c:550]: forward_request(): building failed
>
> Jun 25 15:47:03 VRTPENGINE kamailio[4953]: WARNING: <core>
> [core/receive.c:425]: receive_msg(): error while trying script
>
>
>
> It appears that the WebSocket corresponding to the WSS leg cannot be
> located when the request is initiated from the Asterisk Server.
>
>
>
> Any thoughts on how I can get this to work in the other direction
> (Asterisk to Kamailio)? I’ve been looking at the WebRTC to SIP Client and
> Server (https://github.com/havfo/WEBRTC-to-SIP), but that doesn’t quite
> do what I want it to do (i.e. it appears to act as a registrar server and
> doesn’t forward REGISTER requests on to another registrar).
>
>
>
>
>
> Thanks and regards,
>
>
>
> *Peter H. Manley, Ph.D.*
>
> Chief Software Architect
>
> KomBea Corporation
>
> 3400 North Ashton Blvd, Suite 470
> <https://urldefense.proofpoint.com/v2/url?u=https-3A__maps.google.com_-3Fq-3D3400-2BNorth-2BAshton-2BBlvd-2C-2BSuite-2B470-2B-250D-250A-2BLehi-2C-2BUtah-2B84043-26entry-3Dgmail-26source-3Dg&d=DwMF-g&c=aXfg9j-An5sFdflqnjAj_USiCjXm5xEBIX8lTgWEt0U&r=ykVOlDeeWPn-JjTs8avieNrFskQ3kNzjf6_Jn_wG5HLeLIRsvzCN4-dJx6BFR4el&m=MMSIepRfj2CXVMH3CH8SghyPAoonRISMH__5bcNFPLM&s=C4toC0HQ2JwHKiamawbqvdjdidlwyhCP0XVneFagwkY&e=>
>
> Lehi, Utah 84043
> <https://urldefense.proofpoint.com/v2/url?u=https-3A__maps.google.com_-3Fq-3D3400-2BNorth-2BAshton-2BBlvd-2C-2BSuite-2B470-2B-250D-250A-2BLehi-2C-2BUtah-2B84043-26entry-3Dgmail-26source-3Dg&d=DwMF-g&c=aXfg9j-An5sFdflqnjAj_USiCjXm5xEBIX8lTgWEt0U&r=ykVOlDeeWPn-JjTs8avieNrFskQ3kNzjf6_Jn_wG5HLeLIRsvzCN4-dJx6BFR4el&m=MMSIepRfj2CXVMH3CH8SghyPAoonRISMH__5bcNFPLM&s=C4toC0HQ2JwHKiamawbqvdjdidlwyhCP0XVneFagwkY&e=>
>
> www.kombea.com
> <https://urldefense.proofpoint.com/v2/url?u=http-3A__www.kombea.com_&d=DwMF-g&c=aXfg9j-An5sFdflqnjAj_USiCjXm5xEBIX8lTgWEt0U&r=ykVOlDeeWPn-JjTs8avieNrFskQ3kNzjf6_Jn_wG5HLeLIRsvzCN4-dJx6BFR4el&m=MMSIepRfj2CXVMH3CH8SghyPAoonRISMH__5bcNFPLM&s=ocueS1ZL34IN6qr14M-aItGjeJGQ2km5U2zpzO4Fyqw&e=>
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>
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