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.
This allows a server that will become the orphan source to initialize
its time with the initstepslew directive from the current orphan source
or its clients.
Instead of using a timer for switching the reference to the
unsynchronised state (which activates the local reference), check
if it should be active when returning the reference parameters.
If local reference is active, return normal leap, but unsynchronised
status. Update the callers of the function to work with the leap
directly and not change their behaviour.
REF_IsLocalActive() is no longer needed.
Use REF_GetReferenceParams() in the tracking command to simplify the
code and report the same values as what NTP clients of the server see.
When the local reference mode is active, this changes the leap status to
synchronised and reference time to one second behind current time. When
not synchronised, the root delay and root dispersion are now 1 second.
Since the update to NTPv4, when the clock is in the synchronised state
and the clock updates stop (e.g. sources become unreachable), it doesn't
switch to the unsynchronised state and the local reference is never
activate. This can be a problem for clients that rely on the server to
always have root distance below some value (e.g. chronyd's maxdistance).
Add a timer that will activate the local reference when the root
distance reaches a specified threshold. It can be configured with the
distance option in the local directive (by default 1.0 second).
Timeout ID of zero can be now safely used to indicate that the timer is
not running. Remove the extra timer_running variables that were
necessary to track that.
Time smoothing determines an offset that needs to be applied to the
cooked time to make it smooth for external observers. Observed offset
and frequency change slowly and there are no discontinuities. This can
be used on an NTP server to make it easier for the clients to track the
time and keep their clocks close together even when large offset or
frequency corrections are applied to the server's clock (e.g. after
being offline for longer time).
Accumulated offset and frequency are smoothed out in three stages. In
the first stage, the frequency is changed at a constant rate (wander) up
to a maximum, in the second stage the frequency stays at the maximum for
as long as needed and in the third stage the frequency is brought back
to zero.
Time smoothing is configured by the smoothtime directive. It takes two
arguments, maximum frequency offset and maximum wander. It's disabled by
default.
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.
