[chrony-dev] default maxupdateskew

[Miroslav Lichvar <mlichvar@xxxxxxxxxx>]

I'm implementing an iburst option for the server directive, so it
could be used instead of initstepslew (I'm not planning to remove
initstepslew code, at least not yet). One of the advantages will be
that it won't trigger KoD RATE response from NTP servers configured
with "discard minimum 1", or that it will be possibly to use it with
delayed name resolution when it's implemented.

The problem is that the frequency on first update will be calculated
only over 4 second span (3 samples with 2 second sampling interval)
and the error can be easily be in thousands of ppm. This is not really
a problem when starting with drift file as the new frequency will be
weighted with old and new skew, but without drift file such error in
initial frequency is probably undesired.

There could be a special variable to not allow frequency update when
using iburst, but I think it would be easier and cleaner to employ the
existing maxupdateskew mechanism.

Currently maxupdateskew is set to DBL_MAX by default, i.e. effectively
disabled. I'd propose to set it by default to something like 100 or
1000 ppm.

What do you think?

-- 
Miroslav Lichvar

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