Allow setting vswitchd opts

[Edward Hope-Morley]

/etc/default/openvswitch allows setting OVS_CTL_OPTS but that gets applies to all daemons. If we want to set ovs-vswitchd specific options we need a way to pass them through. ovs-ctl [1] has variables like OVS_VSWITCHD_OPTIONS that get set to '' with no regard for globals so cannot currently be set in /etc/default/openvswitch. We propose the following change to [1] to allow these overrides to be set in /etc/default/openvswitch:

340c340
< OVS_VSWITCHD_OPTIONS=
---
> OVS_VSWITCHD_OPTIONS=${OVS_VSWITCHD_OPTIONS:-''}

This will allow us to do e.g.

OVS_VSWITCHD_OPTIONS="-vnetdev_offload:dbg -vnetdev_offload_tc:dbg"

in /etc/default/openvswitch.

[1] /usr/share/openvswitch/scripts/ovs-ctl

[Edward Hope-Morley (hopem)]

Also adding neutron-openvswitch charm since it currently writes the /etc/default/openvswitch and does not yet support OVS_VSWITCHD_OPTIONS.

[Frode Nordahl (fnordahl)]

Thank you for your bug report.

Extending the OVS/OVN knobs the charm can manage does indeed have merit, however the proposed approach would require the Open vSwitch instance to be restarted, with subsequent data plane interruption, in order to apply the configuration changes.

The options used in the example above can be set at runtime through calls to `ovs-appctl vlog/set`, which does not require a restart of Open vSwitch.

Most of the configuration and debug toggles Open vSwitch can either be applied through `ovs-appctl` or by manipulating the database through appropriate tools.

I wonder if it would be more appropriate if the charms grew the capability of managing OVS/OVN runtime vlog state through a charm configuration option?