[asterisk-dev] Dialog Subscriptions, Bug 6728 and snom dialog; purpose=call-completion

[Martin Koenig]

Kevin p. Fleming wrote:

> 
> Martin Koenig wrote:
> 
> > In specific cases of call forwarding via a function key, the dialog
> state
> > subscriptions to specific hints get unsubscribed because the call
> completion
> > mechanism subscribes to the same hint with a shorter expires time
> than the
> > original subscription.
> >
> > The original subscription is
> > Event: dialog, Expires: 3600
> >
> > The call-completion subscription is
> > Event: dialog;purpose=call-completion, Expires: 60
> 
> [...]
>
> If the RFC that describes the dialog event package says that these
> should be considered distinct package names because of the parameter
> added to the second one, then the parser in chan_sip should be improved
> to treat them as such (and it's a bug if it treats them as the same
> package).

I believe relevant in this case is RFC3265, 7.2.1.

<snip>
"Event" header

   Event is added to the definition of the element "message-header" in
   the SIP message grammar.

   For the purposes of matching responses and NOTIFY messages with
   SUBSCRIBE messages, the event-type portion of the "Event" header is
   compared byte-by-byte, and the "id" parameter token (if present) is
   compared byte-by-byte.  An "Event" header containing an "id"
   parameter never matches an "Event" header without an "id" parameter.
   No other parameters are considered when performing a comparison.

      Note that the forgoing text means that "Event: foo; id=1234" would
      match "Event: foo; param=abcd; id=1234", but not "Event: foo" (id
      does not match) or "Event: Foo; id=1234" (event portion does not
      match).

   This document does not define values for event-types.  These values
   will be defined by individual event packages, and MUST be registered
   with the IANA.

   There MUST be exactly one event type listed per event header.
   Multiple events per message are disallowed.
</snip>