[Serusers] TCP endpoints behind NAT

[Klaus Darilion]

NAT traversal with TCP is only possible, if you configure port 
forwarding at the NAT boxes, and configure your endpoints to use the 
configured ports and the public IP in the contact header.

Maybe another solution would be to establish the TCP session always from 
the endpoint to the SIP proxy. The problem is, as soon as the sip proxy 
finishes the TCP session, the endpoint has to re-connect again, to be 
able to receive SIP messages.  This also depends on the way ser re-uses 
existing sessions.

regards
klaus

Martin Rusnak wrote:
> Hello
> 
> I have following use case:
> 
> Endpoint1 <------> NAT <------> SER <------> NAT <------> Endpoint2
> 10.0.0.10    TCP                                   TCP    192.168.0.4
> 
> Both enpoints are behind a NAT, connected via TCP transport to SER.
> The problem is that no message can be routed between them. It looks
> like SER connot find open tcp connection. Here are the error
> messages copied from the log:
> 
> 11(13977) build_req_from_req: id added: <;i=e71>, rcv proto=2
> 11(13977) parse_headers: flags=2048
> 11(13977) parse_headers: flags=2048
> 11(13977) parse_headers: flags=-1
> 11(13977) clen_builder: content-length: 281 (281)
> 11(13977) check_via_address(63.64.165.70, 10.0.0.10, 0)
> 11(13977) tcp_send: no open tcp connection found, opening new one
> 11(13977) ERROR: tcp_blocking_connect: SO_ERROR (113) No route to host
> 11(13977) ERROR: tcpconn_connect: tcp_blocking_connect failed
> 11(13977) ERROR: tcp_send: connect failed
> 11(13977) msg_send: ERROR: tcp_send failed
> 11(13977) ERROR: t_forward_nonack: sending request failed
> 
> The records for TCP subscribers behind a NAT contains local address
> like:
> Contact: 'sip:10.0.0.10:12451;transport=tcp'
> even if the function fix_contact() is called in registration.
> 
> So, how to configure SER for serving the TCP endpoints behind a NAT?
> 
> Martin
> 
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