[ntp:questions] Falseticker determination

A C agcarver+ntp at acarver.net
Thu Apr 5 04:37:25 UTC 2012

On 4/4/2012 18:52, E-Mail Sent to this address will be added to the 
BlackLists wrote:
> Dave Hart wrote:
>> A C<agcarver+ntp at acarver.net>  wrote:
>>> Where in the code of 4.2.7p270 is the determination that
>>>   a peer is a falseticker?  I'm looking through ntp_proto.c
>>>   but I don't think I'm fully grasping how the determination
>>>   is made and the peer marked.
>>> I want to put some debug lines in the area of the code
>>>   where the falseticker is determined so I can figure out
>>>   what conditions are causing the PPS to be marked as a
>>>   false ticker.
>> Line 2519 of ntp_proto.c (in clock_select):
>> 		peer->new_status = CTL_PST_SEL_SANE;
>> All survivors to that point in the code get the x, fleetingly.  Those
>> that keep it fail to survive to line 2688:
>> 		peers[i].peer->new_status = CTL_PST_SEL_SELCAND;
> I would have thought 2835 - 2855 might be where he would
>   want to take a closer look.

Well that was a fun exercise.  The end result is that the PPS is no 
longer a false ticker and I don't need a prefer peer either. :)

Believe it or not, it's actually working better this way.  For starters, 
the offset is staying within +/- 10 us of the PPS pulse.  Additionally, 
allowing the system to select the rest of the clocks using the normal 
clock selection instead of a prefer peer has actually quieted the 
sys_fuzz messages.  Usually I was seeing a sys_fuzz message perhaps once 
every couple minutes.  Now I see one maybe once in a few hours or more. 
  Plus if any of the peers explodes for whatever reason it doesn't wipe 
out my clock because the averaged time doesn't move much.

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