[OpenSIPS-Users] [OpenSIPS-Devel] Problem with presence, if event header has id.

[Andrew Pogrebennyk]

Anca,
I spotted this bug before. Note that there are some peculiarities that 
are easy to get wrong.

E.g. the package name in the "Event" header of NOTIFY must match the 
"Event" header in the corresponding SUBSCRIBE message, including "id". 
If an "id" parameter was present in the SUBSCRIBE message, that "id" 
parameter must also be present in the corresponding NOTIFY messages.

Next, each subscription request by UA should be processed with separate 
SIP request, even if it is requested from the same agent and for the 
same Event but with different Event ID. There probably should be some 
kind of check in presence that if the same UA generates a SUBSCRIBE 
request with a new Event ID, but mistakenly does not generate a new From 
tag etc, presence does not change the state of the matching subscription 
which differs by the Event ID.

anca at voice-sistem.ro wrote:
> Hi,
> 
> You are right. I have now looked through the RFC's and it seems that even
> presence event might contain an id parameter.
> The mistake came from bad interpretation of RFC3856 which says:
> 
> The SIP event framework allows event packages to define additional
>    parameters carried in the Event header field.  This package,
>    presence, does not define any additional parameters.
> 
> However, RFC3265 says:
>    Subscribers MUST include exactly one "Event" header in SUBSCRIBE
>    requests, indicating to which event or class of events they are
>    subscribing.  The "Event" header will contain a token which indicates
>    the type of state for which a subscription is being requested.  This
>    token will be registered with the IANA and will correspond to an
>    event package which further describes the semantics of the event or
>    event class.  The "Event" header MAY also contain an "id" parameter.
>    This "id" parameter, if present, contains an opaque token which
>    identifies the specific subscription within a dialog.  An "id"
>    parameter is only valid within the scope of a single dialog.
> 
> I will fix this.
> 
> Thanks,
> Anca

-- 
Sincerely,
Andrew Pogrebennyk