[sr-dev] handling failed t_relay() when multiple usr locations

[Andrei Pelinescu-Onciul]

On Mar 09, 2010 at 11:54, I??aki Baz Castillo <ibc at aliax.net> wrote:
> 2010/3/9 Andrei Pelinescu-Onciul <andrei at iptel.org>:
> > On Mar 08, 2010 at 21:55, I?aki Baz Castillo <ibc at aliax.net> wrote:
> >> El Lunes 08 Marzo 2010, Juha Heinanen escribi?:
> >> > Alex Balashov writes:
> >> > ??> But when does t_relay() itself ever fail due to endpoint reachability
> >> > ??> issues? ??I think t_relay() only fails for formal reasons, like host
> >> > ??> name lookup failure, invalid address format, etc? ??Otherwise, it
> >> > ??> returns success; ??if the endpoint is not reachable, the transaction
> >> > ??> simply times out. ??If this is the case, branch route does get called.
> >> >
> >> > my understanding is that t_relay calls a branch route always if
> >> > t_on_branch is used to set it. ??then in that branch route, you should be
> >> > able to call set_forward_no_connect().
> >>
> >> I really though that t_relay() fails (return a negative code and doesn't
> >> invoke a loaded branch_route) in case the TCP cannot be established. Am I
> >> wrong?
> >
> > You're partially right if tcp is used in non-async mode (when t_relay()
> > waits for the tcp connection to be established).
> > I said partially, because in all the cases the branch_route is _always_
> > executed before any send attempt (you can change the destination and
> > some send flags in the branch route so it cannot be executed after the
> > send).
> > The branch route execution is skipped only in special cases like out of
> > memory while trying to build the message, maximum number of branches
> > exceeded, transaction canceled (e.g. CANCEL arrives before the INVITE).
> >
> > So for your TCP example, branch_route will always be executed. If tcp is
> > in async mode (default), t_relay() won't return an error if the tcp
> > connect/send failed (unless that destination was already in the
> > blacklist from a previous attempt). If tcp is in non-async mode,
> > t_relay() will wait for the connect/send to complete and will return a
> > possible error immediately (assuming that all the other branches failed
> > ??too).
> 
> 
> Great, thanks for the explanation. just a question: so in TCP async
> mode, the first attemp to an unreachable TCP destination (cannot
> establish connection) would mean an internal 408?

Yes (after fr_timer ms).


Andrei