If the minimum delay is known (in a static network configuration), it
can replace the measured minimum from the register. This should improve
the stability of corrections for asymmetric jitter, sample weighting and
maxdelay* tests.
In order to stabilize the weights of refclock samples which have only
slightly different distances, don't allow the stddev value used in the
weight calculation to be smaller than the precision and also assign
weight of 1 to all samples which have distance < minimum + precision.
Source selection uses the last event time as current time. If it was
called from a refclock which generates a sample in its poll function
(e.g. PHC), the sample time may be later than the event time. This
gives a negative elapsed time in SST_GetSelectionData() and possibly
also a negative root distance, which causes the source to be rejected as
a falseticker.
Use absolute value of the difference in order to always get a positive
root distance.
It was never used for anything and messages in debug output already
include filenames, which can be easily grepped if there is a need
to see log messages only from a particular file.
This reduces leak of sample times (and receive timestamps which are
related to sample times), which could be useful in off-path attacks on
unauthenticated symmetric interleaved mode.
Replace struct timeval with struct timespec as the main data type for
timestamps. This will allow the NTP code to work with timestamps in
nanosecond resolution.
Estimate asymmetry of network jitter on the path to the source as a
slope of offset against network delay in multiple linear regression. If
the asymmetry is significant and its sign doesn't change frequently, the
measured offsets (which are used later to estimate the offset and
frequency of the clock) are corrected to correspond to the minimum
network delay. This can significantly improve the accuracy and stability
of the estimated offset and frequency.
The minsamples and maxsamples directives now set the default value,
which can be overriden for individual sources in the server/peer/pool
and refclock directives.
Add new functions to change source's reference ID/address and reset the
instance. Use that instead of destroying and creating a new instance
when the NTP address is changed.
Reachability is no longer a requirement for selection. An unreachable
source can remain selected if its newest sample is not older than the
oldest sample from all reachable sources.
This is useful to prevent reselection when an accurate source uses a
very short polling interval (e.g. refclock) and is occasionally
unreachable for short periods of time.
If the newly accumulated sample is not newer than than the last one,
discard the source history and start from scratch. This can happen after
loading an invalid dump or when the system clock was stepped.
With iburst and very jittery sources the source skew can reach very high
values which makes the NTP test4 fail even with relatively small delays.
Limit the skew to 2000 ppm to avoid getting state where a source is unable
to accept more than first three iburst samples.
