[Asterisk-Dev] IAX2 Native Transfer + NAT

[Steven Sokol]

Over the weekend I discovered that IAX2 calls are not able to establish
native audio bridging when two clients are behind the same NAT screen.  It
seems that my Linksys router is not smart enough to "pinwheel" packets
between two clients behind the screen, so all traffic has to go out through
the router, to the cable provider's router, back to the Asterisk box (on a
separate routable IP address but on the same cable modem) then back the same
path to the router and to the destination client.

Would it be possible for chan_iax2 to discern that both parties to a call
are behind the same NAT screen and using inside IP addresses 192.168.1.X and
192.168.1.Y, then direct the clients to communicate on the appropriate ports
on their "inside" addresses?  Or to try (TXCNT/TXREJ) before forcing the
conversation to pass through several additional switching/routing points
(most of which are not TOS-aware)?

Anybody have a guess as to how hard that would be?

Thanks,

Steve