[Users] How to handle "302 Moved temporarily" with TCP transport and changing port

[Ingmar Kliche]

 Hi all,

I'm very new to OpenSER and I would like to ask for your advice to find a
solution for my problem:

I have a SIP gateway (A) which uses UDP transport and a SIP endpoint (B)
which only supports TCP. I'd like to use OpenSER to convert UDP to TCP. The
second issue is that the TCP endpoint (B) will redirect the incoming INVITE
to itself to another TCP port using a "302 Moved temporarily" containing a
CONTACT header.

Here is my approach:
My current understanding is that I would have to add something to the
routing block to select the traffic for my TCP endpoint. Then I would have
to add route where I would have to handle the TCP forwarding, something
like:

if (uri=~"...") {
t_relay_to_tcp("<ip>", "5060");
}

This looks very straight forward and should solve the UDP to TCP issue as I
understand it. Is this approach correct?

For the second issue I don't have a solution right now. As described above
the TCP endpoint (B) will answer something like

SIP/2.0 302 Moved Temporarily
FROM: <sip:tel at HOST_A>;tag=1c552078080
TO: <sip:tel at HOST_B>;tag=7189e7deae
CSEQ: 1 INVITE
CALL-ID: 552077216117200615500 at HOST_A
MAX-FORWARDS: 70
VIA: SIP/2.0/TCP HOST_A;branch=z9hG4bKac552089789;alias
CONTENT-LENGTH: 0
SERVER: RTCC/2.0.6011.0
CONTACT: <sip:tel at HOST_B:1223;transport=tcp;maddr=HOST_B;x-mss-call-id=552077216117200615500%40HOST_B>


I want OpenSER now to send out another INVITE via TCP to HOST_B Port 1223
(but the port changes for each call). In principle I would need a possiblity
to extract the host and the port out of the CONTACT header of the message to
send another t_relay_to_tcp("<host>", "<port>"). But how to do that?

Or is there another possibility to tell OpenSER to take the target info out
of the CONTACT header?

Thanks in advance!
 Ingmar
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