Comment 19 for bug 1912844

> The default `datapath_type` is 'system', so if it is not explicitly specified for a bridge it will not be visible in `ovs-vsctl show` output, but 'system' will still be the `datapath_type` used.

Great, I figured it wasn't material.

> You can query Open vSwitch at runtime for which datapath types it supports with `ovs-vsctl get open_vswitch . datapath_types` which would produce '[netdev, system]' as output.

Will `ovs-vsctl` always be available if OVS interfaces might be present on the system? Will it always be in (our systemd units') PATH?

(My _guess_ is that we can't be sure, about the latter at least: /opt/openvswitch/bin/ovs-vsctl doesn't seem like a wildly unreasonable path to install to, and cloud-init has no good way of finding that.)

> If we want to be opportunistic I guess iterating over the datapath_types list and check for /sys/class/net/ovs-$datapath_type could be a generic approach that may also work for the next datapath_type we currently do not know about.

I think this would be ideal, but we can avoid introducing a (runtime-detected, optional) dependency on `ovs-vsctl` if we hardcode the current options: as discussed above, this may even be necessary. Alternatively, we could opt into the more expensive lookup path if we find anything matching /sys/class/net/ovs-*: this may lead to some false positives (e.g. if network configuration specifying non-OVS interfaces named ovs-something is passed to an instance) but (a) such configurations will be extremely rare, and (b) we will only be less performant on such instances, not _incorrect_.

What do you think?