[Serusers] SIP Symmetric Response support in SER

[Maxim Sobolev]

Hi,

Are there any plans to add SIP Symmetric Response support
(http://www.iptel.org/info/players/ietf/firewall/nat/draft-ietf-sip-symmetric-response-00.txt)
into SER, so that it would be possible to use compliant UAs behind NATs
with SER being on a public IP? The idea is simple: when the SIP packet
is received from UA, the server checks if an empty `rport' parameter
is present in the first Via field, and if yes then compares IP:PORT in
the first Via header with the actual IP:PORT this request came from,
and adds `received' and `rport' parameters into the header if either
doesn't match before forwarding request further.

Then, when replying or forwarding the request, the server checks if
any of received or rport is present and uses it instead of the
UA-provided values in corresponding Via header.

Please let me know if there are work in progress on this, so that
I will not have to reinvent the wheel.

Thanks!

-Maxim