Whether to allow setting time in NTP mode

[Lei Yu]

On Mon, Sep 19, 2022 at 5:06 PM George Liu <liuxiwei1013 at gmail.com> wrote:
>
> Hey, everyone:
>
>   This email would like to discuss whether to allow the requirement to
> set the time when NTP is enabled.
>
>   In the phosphor-time-manager, The current design logic is:
>   1. The timeManager will listen to the TimeSyncMethod property of the
> xyz.openbmc_project.Time.Synchronization interface to set the SetNTP
> method of timedate1 and update the current Time mode. [1]
>   2. When the user changes the time using OOB, the timeManager does
> not verify the current Time mode, and directly calls the settime
> method to change the time. If the current is in NTP mode, setting the
> time will throw an exception. [2]

For the record, the exception is thrown due to the DBus call to
`org.freedesktop.timedate1` service failure.

>
>   But there is a potential problem here:
>   When the user sets the mode from NTP to manual by way of OOB, then
> the time is set immediately. At this time, there will be an error in
> setting the time because the NTP service is not completely stopped,
> but we do not want to throw this error to the user, because for the
> user layer, the mode has been switched to manual (TimeSyncMethod =
> Manual)[3]
>
>   I have a patch that determines whether the current NTP service is
> completely stopped (a timeout mechanism is added) when setting the
> time [4]. But @Lei suggested that this mechanism should not be
> implemented on the timeManager server side, but should be handled on
> the client side.

The reason is that the time-manager will have to "wait" until the time
could be set and it effectively blocks the event loop in the patch
mentioned above.
It could be resolved by making time-manager async, but it's off-topic.

>
>   Also, @Lei also has a different idea downstream, using settimeofday
> instead of timedate1

We have a requirement from the users that the "set-time" should be
successful even if the BMC is in NTP mode. (Be noted that the time
will be updated by NTP after a short while).
To set the time, use `settimeofday` instead of making DBus call to
`org.freedesktop.timedate1` service solves the above issue, and it
meets our internal requirement.
If we all agree that this is the expected behavior, I could send the
patch upstream.

>
>   I would like to hear everyone's suggestions, and I would like to
> optimize this function if appropriate.
>
> Thanks
>
> [1]: https://github.com/openbmc/phosphor-time-manager/blob/master/manager.cpp#L28-L31
> [2]: https://github.com/openbmc/phosphor-time-manager/blob/43dfeeb1e22d6d7fcec9f1d4be81f3e9d6857e62/bmc_epoch.cpp#L120-L139
> [3]: https://github.com/openbmc/bmcweb/blob/07c8c20d371aae85611738ca61015fc6a8caa16a/redfish-core/lib/network_protocol.hpp#L215-L240
> [4]: https://gerrit.openbmc.org/c/openbmc/phosphor-time-manager/+/56584
>
>
> George Liu



-- 
BRs,
Lei YU