[SR-Users] Very strange reinvite behaviour

[Alex Balashov]

Daniel,

Thank you for this interpretation. I suspected this might be the cause,
but didn't know enough about how non-LR works to merit that speculation.

Strict routing mostly exists for 2543 compatibility, right?

On Wed, Aug 15, 2018 at 12:43:57PM +0200, Daniel-Constantin Mierla wrote:

> At a quick glance, it looks like a mixture of strict/loose route
> processing due to previous hop not setting proper URI.
> 
> If R-URI is local address, then it means the previous hop was a strict
> router. Kamailio tries to switch to loose routing, due to lr parameter,
> doing the logic of:
> 
>  - last Route becomes R-URI, overwriting the incoming R-URI (which was
> local address) and last Route header is deleted
>  - send to top Route header
> 
> In strict routing, R-URI is the address of next hop and the last Route
> is the far end. In loose routing, R-URI is the far end and top Route is
> next hop. Here seems to be the moment of switching from strict to loose
> routing.
> 
> The UA building the request (or the previous hop) seems to be rather
> broken, because it adds lr even to the contact address (last Route),
> even it acts as a strict router.
> 
> If you use dialog module in that instance, there is a function to push
> to R-URI the contact for that side, as saved in the dialog structure.
> You can do that before calling loose_route(), if R-URI host is your IP
> (I would avoid using myself on R-URI received from the UA, because if it
> is messing with the ports/protocols, there can be a mismatch of myself).
> 
> Cheers,
> Daniel
> 
> On 15.08.18 00:51, Alex Balashov wrote:
> > On Tue, Aug 14, 2018 at 11:40:09PM +0200, M S wrote:
> >
> >> It would be good if you can provide the full sip trace that includes the
> >> initial INVITE processing of both call legs.
> > That's not going to be (easily) possible in this case, due to one leg
> > being TLS.
> >
> >> Per SIP v2.0 RFCs (3261, 3665 & 6141), when callee needs to send a
> >> sequential request e.g. a re-invite, it should use the Contact header it
> >> received in initial INVITE as RURI. Since the RURI and top most Route
> >> header(s), all point to kamailio itself, so kamailio sees it as strict
> >> routing rather then loose routing, and as a result loop occurs.
> > Yes. My question was about the inconsistency between the apparent RURI
> > and the message attributes logged.
> >
> > -- Alex
> >
> 
> -- 
> Daniel-Constantin Mierla -- www.asipto.com
> www.twitter.com/miconda -- www.linkedin.com/in/miconda
> Kamailio World Conference -- www.kamailioworld.com
> 

-- 
Alex Balashov | Principal | Evariste Systems LLC

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