On 03/04/2011 04:56 PM, Klaus Darilion wrote:
Not so easy .....
16.4 Route Information Preprocessing
The proxy MUST inspect the Request-URI of the request. If the
Request-URI of the request contains a value this proxy previously
placed into a Record-Route header field (see Section 16.6 item 4),
the proxy MUST replace the Request-URI in the request with the last
value from the Route header field, and remove that value from the
Route header field. The proxy MUST then proceed as if it received
this modified request.
This will only happen when the element sending the request to the
proxy (which may have been an endpoint) is a strict router. This
rewrite on receive is necessary to enable backwards compatibility
with those elements. It also allows elements following this
specification to preserve the Request-URI through strict-routing
proxies (see Section 12.2.1.1).
Thus, Kamailio should somehow detect if the URI is inserted by himself
or not. This may only happen if the previous hop is a strict-router. As
Kamailio is a loose-router and always adds the ;lr parameter, the check
could be extended to check if the RURI also cotains lr parameter. If the
lr parameter is not present, this means for sure that the RURI was not
generated by Kamailio.
Hello,
I was thinking of maybe adding a new configurable RR param. A strict
router would copy this header into the RURI. But a.t.m. loose_route does
not perform any checking on tags. Maybe an exclude_uri_tag module param
that can work like this:
modparam("rr", "exclude_uri_tag", "mark=on");
Then, when the initial SUBSCRIBE (dialog setting message) comes
add_rr_param(";mark=on");
In the loose_route processing, if exclude_uri_tag is set and !(RURI =~
exclude_uri_tag), then perform loose routing on that request (the
request isn't coming from a strict router)
What do you think?
Marius
Of course this would require code changes.
A dirty hack would be to manipulate the Route headers manually and set $du.
regards
Klaus
Am 04.03.2011 15:25, schrieb marius zbihlei:
Hello list,
An UAC sends a resubscribe in the form
SUBSCRIBE sip:al...@example.com SIP/2.0
Route:<sip:sip.example.com;lr=on>
Route:<sip:sip.next-hop.example.com;lr=on>
....
The request has a to tag, from tag... Basic resubscribe(R-URI is the
same as original SUBSCRIBE) The proxy that handles it is a Kamailio (1.5
but this refers to 3.1 as well). The problem is that loose_route()
treats this request as coming from a strict routing router, not from the
UAC, so it applies the strict-to-loose rules and rewrites the request as:
SUBSCRIBE sip:sip.next-hop.example.com;lr=on SIP/2.0
Route:<sip:sip.example.com;lr=on>
....
The segment that handles this is pretty standard:
if (loose_route()) {
# sequential request withing a dialog should take the path
# determined by record-routing
if(has_totag()) {
forward();
exit;
}
It sees that message has Route set, it finds the to tag (so the routes
were not a preset), and then , the important thing, sees that the domain
from the RURI matches itself (kamailio has aliases configured for
example.com), thus considering the request as coming from a strict
router. Then it takes the bottom Route header and overwrites the RURI.
What is the best way to ensure that loose routing is applied to the
resubscribe as described above?
Cheers,
Marius
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