[OpenSIPS-Users] nat_traversal fails on loose_route ACK

[Robert Dyck]

Maybe before fiddling with the contact make sure you are not being hit by a 
bug in some versions of asterisk. The re-invite arrived OK but not the ACK. 
Was the route set present in the ACK. In-dialog messages should not alter the 
route set. The UAS is not required to send a route header in the reply while 
in-dialog. The UAC should not interpret this as a null route set and must use 
the route set already established. Private addresses can be reached this way.

On Friday 10 July 2009, Jeff Pyle wrote:
> ¡Easy indeed!  I didn't have any NAT intelligence in the reply route.
>
> Here's what I tried first:
>
> onreply_route[1] {
>         if (client_nat_test("3")) {
>                 xlog("L_INFO", "NAT Reply\n");
>                 fix_contact();
>         } else {
>                 xlog("L_INFO", "Reply\n");
>         }
> }
>
> This appeared to work a bit "too" well.  The client_nat_test returned true
> even for non-NAT'd hosts.  I changed the test from "3" to "1" and it seems
> to be behaving as expected.
>
> None of the examples seem to use the number 4 "private IP address in the
> top Via field" test.  Is there any particular reason for that?  In my
> searches I haven't come across a discussion on the pros and cons of the
> various tests.
>
>
> - Jeff
>
> On 7/10/09 5:03 PM, "Iñaki Baz Castillo" <ibc at aliax.net> wrote:
> > Easy: you must ensure that the proxy performs NAT detection for reply
> > routes (onreply_route) for in-dialog requests, and fix the Contact
> > (fix_contact()) in onreply_route.
> >
> > This is:
> >
> > - The UA sends INVITE behind NAT.
> > - OpenSIPS fixed Contact and routes it to Asterisk.
> > - Asterisk replies 200 => proxy => UA.
> > - UA sends ACK => proxy => Asterisk.
> > - Now Asterisk sends re-INVITE (in-dialog request) to the proxy.
> > - The proxy routes it to UA.
> > - UA replies 200.
> > - Proxy *fixes Contact* for the 200 and routes to Asterisk.
> > - Asterisk now will send ACK to proxy with RURI containing the fixed
> > Contact address (UA's public IP:port).
>
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