Starting with Linux 4.19, the frequency of the system clock should be
updated immediately in the system call itself, which will significantly
reduce the maximum delay of the update.
Increase the assumed tick rate in order to reduce the dispersion
accumulated by the driver when it sets the frequency.
Add an option to use the median filter to reduce noise in measurements
before they are accumulated to sourcestats, similarly to reference
clocks. The option specifies how many samples are reduced to a single
sample.
The filter is intended to be used with very short polling intervals in
local networks where it is acceptable to generate a lot of NTP traffic.
Move the implementation of the median filter to a separate file to make
it useful for NTP. Replace some constants with parameters and generalize
the code to work with full NTP samples (including root dispersion/delay,
stratum, and leap).
For refclocks it should give the same results as before.
This moves the leap status of the last sample from the source instance
to the sourcestats instance in order to make them both accumulate the
same data.
The current code uses macros from inttypes.h. There is no point in
detecting and selecting between stdint.h and inttypes.h as the latter is
always needed.
In chronyc handle SIGPIPE similarly to SIGTERM. In chronyd ignore the
signal to avoid crashing when a TCP socket will be needed (e.g. for
NTS-KE) and will be unexpectedly closed from the other side.
Before dispatching a handler, check if it is still valid. This allows a
handler to remove itself when a descriptor has two different events at
the same time.
When the local polling interval is adjusted between minpoll and maxpoll
to a sub-second value, check if the source is reachable and the minimum
measured delay is 10 milliseconds or less. If it's not, ignore the
maxpoll value and set the interval to 1 second.
This should prevent clients (mis)configured with an extremely short
minpoll/maxpoll from flooding servers on the Internet.
If the polling interval is shorter than 8 seconds, set the burst
interval to the 1/4th of the polling interval instead of the 2-second
constant. This should make the burst option and command useful with
very short polling intervals.
