In case systemd is used to set cgroups for the container,
it creates a scope unit dedicated to it (usually named
`runc-$ID.scope`).
This patch adds an ability to set arbitrary systemd properties
for the systemd unit via runtime spec annotations.
Initially this was developed as an ability to specify the
`TimeoutStopUSec` property, but later generalized to work with
arbitrary ones.
Example usage: add the following to runtime spec (config.json):
```
"annotations": {
"org.systemd.property.TimeoutStopUSec": "uint64 123456789",
"org.systemd.property.CollectMode":"'inactive-or-failed'"
},
```
and start the container (e.g. `runc --systemd-cgroup run $ID`).
The above will set the following systemd parameters:
* `TimeoutStopSec` to 2 minutes and 3 seconds,
* `CollectMode` to "inactive-or-failed".
The values are in the gvariant format (see [1]). To figure out
which type systemd expects for a particular parameter, see
systemd sources.
In particular, parameters with `USec` suffix require an `uint64`
typed argument, while gvariant assumes int32 for a numeric values,
therefore the explicit type is required.
NOTE that systemd receives the time-typed parameters as *USec
but shows them (in `systemctl show`) as *Sec. For example,
the stop timeout should be set as `TimeoutStopUSec` but
is shown as `TimeoutStopSec`.
[1] https://developer.gnome.org/glib/stable/gvariant-text.html
Signed-off-by: Kir Kolyshkin <kolyshkin@gmail.com>
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