[net/chrony] makestep parameter configurable

[iqt4]

Problem situation
We are running OPNsense (HA) in a virtualised environments with chrony as ntp client. The OPNsense clock is getting synchronised after starting the VM (a. the VM internal clock is synched to the host, and b. kept in sync with chrony). So far so good. But during weekly backups of the VMs (initiated by the host), the VM with OPNsense is stopped and resumed for a few seconds and the clock is getting out of sync. The normal slewing process from chrony takes too long to correct the clock again.

With this patch #2350, the makestep 1 3 option was introduced with fixed values of threshold (1) and limit (3). Thus, instead of slewing the clock is stepped but only if there were no more clock updates since chronyd was started than the specified limit.

Suggested solution
I suggest to make threshold and limit parameters configurable in the WebGUI as they depend on the environment (see also
https://chrony-project.org/faq.html#_is_chronyd_allowed_to_step_the_system_clock
For VMs makestep 1 -1 would be an option.

A workaround would be to set up a cron job with chronyc makestep to set the clock manually, however we don't know when the backup ends and there might be other cases where the VM is getting suspended.

Additional context
N.b. We observed a flickering of traffic graph (as described here https://forum.opnsense.org/index.php?topic=41755.msg205207#msg205207) if the clock is out of sync. As soon as we correct the clock the flickering is gone.

[OPNsense-bot]

Thank you for creating an issue.
Since the ticket doesn't seem to be using one of our templates, we're marking this issue as low priority until further notice.

For more information about the policies for this repository,
please read https://github.com/opnsense/plugins/blob/master/CONTRIBUTING.md for further details.

The easiest option to gain traction is to close this ticket and open a new one using one of our templates.