Revise on account registration Contact update rule

[bennylp]

Handle But in NAT Router

Some firewall such as Microsoft Forefront Threat Management Gateway may leave rport parameter with wrong port number, causing us to update our registration Contact with wrong URI.

For example, when we're behind NAT and we're registering to server in public Internet:

• our original Via header in the request:

Via: SIP/2.0/UDP 10.0.0.1;rport;branch=xyz

• Via value in the response, after the server's response passes through the firewall:

Via: SIP/2.0/UDP 10.0.0.1;rport=56284;branch=xyz

Probably we don't need to do registration update when only the port number changes.

Always Update Via Address

While the Contact address is updated by acc_check_nat_addr() function, the Via (i.e. transport address) is only updated if the transport is UDP and STUN is enabled.

For TCP/TLS, this is a bug, as the Via address should always be updated.

For UDP, probably it's better to always update it too, as some server will still think that we're behind NAT (while probably true, we want the server to think otherwise).

[bennylp]

Fixed in r3001:

• don't switch if only port number is different and the Via received address is private
• always update the transport (i.e. Via) address as well