[asterisk-dev] 'sip unregister devicename' device unavaiable 25/3600 seconds

[Alec Davis]

The 3600 in the subject assumes a sip registration period of 60 minutes.
 
refer https://issues.asterisk.org/view.php?id=15118
 
The testing and reporting of the bug was done with a Grandstream BT100, but
it is no way a reflection on Grandstream.
 
The reported 25 seconds of available time is a combination of the 10 seconds
chan_sip adds to the requested expiry period, and the 15 seconds that
Grandstream re-Registers before the expire time.
 
For testing, I used a register expire period of 60 seconds. Configured
either in sip.conf as maxexpiry=60 in the [general] section or set the
phone's parameter.
 
The fault is that a stale expire_register schedule is left in the scheduler,
and expires 25 seconds after the device adds a new fresh expire schedule,
due to expire in 70 seconds...
 
If a device has a re-register time of 3600 seconds, the phone is unavailable
for 3575 seconds in every 3600.!!!
 
There are 2 patches:
1st targets the sip_unregister problem directly, its removes the current
active expire_register callback scheduled event.
 
The 2nd is more general and may be over kill, it removes if present the
event that called expire_register, most of the time it's already gone.
 
A last thought, sure the cause was buggy sip_unregister, but what about the
concept of instead of using ast_sched_add when the phone registers, use
ast_sched_replace, where it would replace an existing expire_register id, or
if not found, would add a new event.
 
Alec Davis.
 
 
 
 
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