lxd/device: unix-hotplug ownership fix

[kadinsayani]

Fixes the second bug raised in #14266.

This PR adds a setting, ownership.inherit for unix-hotplug devices and a function unixDeviceOwnership() which returns device ownership.

New behaviour:

• The default setting for ownership.inherit is false;
• When ownership.inherit is set to true, the device ownership is inherited from the host;
• ownership.inherit cannot be set to true when gid or uid are set.

Existing behaviour (unchanged):

• When gid and uid are set, they are used for device ownership;
• If gid and uid are not present in the config, root (0) ownership is used.

[tomponline]

@kadinsayani please can you update the PR description to explain the change of behaviour in this PR and what, if any, will change for existing users?

[kadinsayani]

@kadinsayani please can you update the PR description to explain the change of behaviour in this PR and what, if any, will change for existing users?

Sure thing!

[github-actions]

Heads up @mionaalex - the "Documentation" label was applied to this issue.

[kadinsayani]

I noticed some wording inconsistencies in the documentation for unix-hotplug and the other unix device types. I've opened #14451 to track the issue and engage @minaelee for feedback. I'll open up a separate PR to update the docs and resolve the issue.

[kadinsayani]

@tomponline, do we need an API extension for the new setting even if we're not adding tests?

[tomponline]

@tomponline, do we need an API extension for the new setting even if we're not adding tests?

yes new settings require API extensions in order for clients to be able to ascertain whether the server supports the setting.

[kadinsayani]

@tomponline, do we need an API extension for the new setting even if we're not adding tests?

yes new settings require API extensions in order for clients to be able to ascertain whether the server supports the setting.

Gotcha, makes sense.

[kadinsayani]

I've added the API extension :)