[OpenSER-Users] How to expose the expires value in REGISTER

[Robert Dyck]

On Wednesday 31 October 2007, Christian Schlatter wrote:
> Robert Dyck wrote:
> > I am wondering how to expose and test the value of the expires parameter
> > in a REGISTER request.
> >
> > I am experimenting with openser as the basis for a home phone network. I
> > use multiple devices with the same user ID. They register locally ( with
> > no reply ) and with an external service provider. The contacts are
> > mangled to show the public address of openser. Multiple registrations
> > result in a single AOR at the external registrar. Incoming calls from the
> > outside are forked and ring the local phones. Local phones can also call
> > each other without the hairpin problem associated with STUN enabled
> > phones.
> >
> > The problem is that a softphone will deregister when it is closed or its
> > profile changes. This would deregister the AOR at the external registrar.
> > The remaining phones could not receive calls from the outside until they
> > refreshed their registrations.
> >
> > I would like to prevent deregistration at the external registrar unless
> > the phone that was deregistering was the only remaining one. The first
> > step would be to identify REGISTER messages where the expires value is
> > equal to zero.
>
> Both 'Expires' header and 'expires' contact uri parameter have to be
> checked like e.g.
>
> if ((is_present_hf("Expires") && $(hdr(Expires){s.int}) == 0) ||
>      ($(ct{param.value,expires}) == '0'))
> {
> 	# someone tries to unregister
> }
>
> Have a look at
> http://www.openser.org/dokuwiki/doku.php/transformations:1.2.x if you're
> not familiar with the PV transformations introduced with 1.2.

I am indeed unfamiliar with PV transformations. I will have a look it. I was 
afraid I might have to do something ugly with regular expressions. I probably 
should not put off upgrading any longer.

Thanks, Rob