29 Feb
2012
29 Feb
'12
3:53 p.m.
On 29.02.2012 14:34, Andreas Granig wrote:
Hi,
I ran into an interesting scenario when experimenting with kamailio 3.1
as a stateless proxy (no tm module used):
There is an initial INVITE without to-tag and with pre-loaded Route
header pointing to the external address of the lb. When I call
loose_route for that, it returns false and the Route header is removed.
That's what I expected, and it's documented in
http://www.kamailio.org/docs/modules/3.1.x/modules_k/rr.html#loose-route-id.
However if a 407 is relayed back from the registrar via the lb to the
UA, it sends an ACK, again with pre-loaded Route header like in the
initial INVITE, this time with to-tag. In that case, loose_route()
returns true, but the $du is $null and the R-URI is still the same.
What else should happen? $du will not be set as there is no more Route
header. And R-URI is never changed (except with strict routers).
So
the Route is consumed, but the URI is not used. Since it's a stateless
proxy, this hop-by-hop ACK needs to be routed the same way as the
initial INVITE, so what I'm doing is something like that:
if(loose_route()) {
if($du == $null&& $ru == $ou) {
# skip loose-routing for such a request
}
}
Is this how it's supposed to work? And is there some documentation of
how loose_route() detects whether Route points to itself or not? I'm not
using auto_aliases, nor do I set any aliases manually.
It uses the aliases to detect if the Route points to itself. The listen
interfaces are automatically added to the aliases.
I think the problem is that the load balancer can not differentiate this
ACK-after-407 from an ACK-after-200. In both cases the Route header
points to the load-balancer and a to-tag is present.
Probably you need to add some additional functions which know how your
environment looks like and knows to differ the ACKs. I guess $ru == $ou
is always true, but for ACK-after-200 there is maybe a second Route
header and thus $du is set.
regards
Klaus
Does it determine
internally whether the Route points to its local ip and port? If not,
how come the $du is not set although loose_route returns true?
Andreas
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