[Serusers] [Serdev] loose_route behaviour, detecting single Route with myself

[Nils Ohlmeier]

On Friday 13 July 2007 14:12:52 Martin Hoffmann wrote:
> Nils Ohlmeier wrote:
> > An non-2xx ACK with a preloaded route looks exactly the same then a 2xx
> > ACK. A preloaded_route() function thus has no chance to distinguish them.
> > And I will not make the rr module depending on the tm module, just to
> > query tm all the time if it knows something about this transaction or
> > not.
> > IMHO the only way to distinguish these two is the RURI. Because in a
> > normal loose route case the 2xx ACK should have non-local URI (the remote
> > Contact) as RURI. But the non-2xx ACK should have a local RURI.
>
> Indeed. But doesn't that point towards the old behaviour? Only return
> true if forwarding can be done based on a Route, otherwise the script
> needs to decide what to do based on the Request-URI? Apparently, having
> a Route header pointing to the proxy doesn't mean a thing.
>
> BTW: What does loose_route() do if the topmost route doesn't point to
> this proxy?

loose_route should return false for this, because the message can not be 
handled/routed by simply forwarding the request. This was the thing which 
Dragos complained about earlier on the mailing lists already.
I chose this return code, because otherwise people would rely on the 
loose_route return value true, and forward the message without further 
inspection assuming it is in-dialog. And uuuppss you have an open proxy 
without knowing ;-)

> > But with this theory we are back to the original topic: is a TEL URI a
> > local URI or not.
>
> I though that was solved. Only SIP and SIPS URI are allowed in Contact.
> Your 2xx ACK will never have a TEL URI (unless the UA is broken in which
> case someone should have sent a 400 back).

No. That is not true. Because you could receive a non-2xx ACK with a TEL RURI 
and preloaded route. What now?

> > Is just came to my mind that a possible solution could be to add some
> > kind of secret information to our Record-Route headers.
>
> /me not like. Sounds like magic plus vendor specific extensions are
> frowned upon in SIP.

Sure, they are. But I currently do not really see any option for this problem. 
Except we would consider removing strict route support. Then would not have 
to look at the RURI at all any more. But I'm not in favor of that.

  Nils