[Asterisk-Dev] SIP presence notification updated (#3644)

After months in the bug tracker, we've finally committed a lot of
changes to the SIP Subscribe subsystem in Asterisk cvs head.

+ It now works even if you reload the dial plan
+ It does not accept subscriptions to extensions without hints
+ It will terminate subscriptions if the hint does not exist after a dialplan reload

To get this to work properly, you
- Configure incominglimit for the device
- Add a hint to the dialplan for the extension

Now, you will see if the device is online, if it is
occupied in a call or just available for a call. This is confirmed
to work with Polycom phones, SNOM phones and Eye-Beam.

A big thank you to everyone that have been assisting me working with
this patch and to Kevin that solved the reload problem.

/O

*UPDATED EXAMPLE*

Dialplan (extensions.conf)
* Add a hint that points to the phone or phones that you want to
connect to an extension

exten => 3000,hint,SIP/olle
exten => 3000,1,dial(SIP/olle,30)
exten => 3010,hint,SIP/ssokol&IAX2/ssokol
exten => 3010,1,dial(SIP/ssokol&IAX2/ssokol,30)

SIP, IAX2 and agents support this kind of notification, so you can
use them as hints.

In sip.conf or iax.conf, add an call limit to the peer entry

[olle]
type=friend
incominglimit=2
secret=1234
host=dynamic

(This config option will soon be renamed call-limit)

Then in your phone, add a subscription for the extension. How you do
that depends on the phone. In Eye-Beam you have a buddy list. On the
Polycom, you configure an entry in the directory to be a buddy.
We support several formats for notification, and they all have different
properties and abilities. For Eye-Beam, you will get an icon and text
saying "Not online" if the phone is not registred or "On the phone" if
the phone is in a call. Polycom simply says "away" and the Snom phones
happily turns on and off LED's.

A lot of the changes done internally to the PBX core extension state
subsystem and in chan_sip also improves the status notification in the
manager for programs that connect to Asterisk over AMI and visualizes
the status of extensions, like FOP, The Flash operator's panel.

I hope this helps.

Regards,
/Olle