During inserted leap second the time is invalid, reply with
unsynchronized status to avoid confusing clients that are not smart
enough to ignore measurements close to leap second.
In addition to the system driver handling add new modes to slew or step
the system clock for leap second, or ignore it completely. This can be
configured with leapsecmode directive.
This will be used to set the kernel adjtimex() variables to allow other
applications running on the system to know if the system clock is
synchronized and the estimated error and the maximum error.
The second form configures the automatic stepping, similarly to the
makestep directive. It has two parameters, stepping threshold (in
seconds) and number of future clock updates for which will be the
threshold active. This can be used with the burst command to quickly
make a new measurement and correct the clock by stepping if needed,
without waiting for chronyd to complete the measurement and update the
clock.
When current time is within 5 seconds of a leap second, don't accumulate
new samples or update the leap second status to increase the chances of
getting through safely.
Rework makestep to cancel accumulated offset and step with the new
offset instead of accumulating new offset first, canceling all
accumulated offset and making the step.
This avoids two large frequency changes to initiate and cancel a slew
before making the step.
This is a partial revert of 8aa9eb19c8.
With the new generic driver cooking is cheap and it should be slighly
more accurate than reusing offset correction from the scheduler
timestamps.
Add a new change type and use it when an unexpected time jump is
detected in the scheduler to reset reference times, offset and slewing,
NCR instances (with their polling interval), synchronization status, and
drop all sourcestats, manual, refclock and RTC samples.
This should make the recovery more graceful if the estimated jump has a
large error (e.g. select didn't timeout, or after system suspend).
The initstepslew code has its own minimal NTP implementation. Drop the
code, add a new initstepslew mode to the reference updating code and
use regular NTP sources with iburst flag for initstepslew addresses
instead. When an update is made or a source is found unreachable, log a
message, remove the initstepslew sources and switch to normal mode.
This reduces code duplication and makes initstepslew use features
implemented only in the main code like source combining or SO_TIMESTAMP
support.
leapsectz directive is used to set the name of the timezone in the
system tz database which chronyd can use to find out when will the next
leap second occur. It will periodically check if dates Jun 30 23:59:60
and Dec 31 23:59:60 are valid in that timezone. This is mainly useful
with reference clocks which don't provide the leap second information.
It is not necessary to restart chronyd if the tz database is updated
with a new leap second at least 12 hours before the event.
This directive sets the maximum allowed offset corrected on a clock
update. The check is performed only after the specified number of
updates to allow a large initial adjustment of the system clock. When
an offset larger than the specified maximum occurs, it will be ignored
for the specified number of times and then chronyd will give up
and exit (a negative value can be used to never exit). In both cases
a message is sent to syslog.
The corrtimeratio directive controls the ratio between the
duration in which the clock is slewed for an average correction
according to the source history and the interval in which the
corrections are done (usually the NTP polling interval). Corrections
larger than the average take less time and smaller corrections take
more time, the amount of the correction and the correction time are
inversely proportional.
Increasing corrtimeratio makes the overall frequency error of
the system clock smaller, but increases the overall time error as
the corrections will take longer.
By default, the ratio is 1, which means the duration of an average
correction will be close to the update interval.
