Hardware offload is not disabled when setting "enable-hardware-offload=false" after having it on

[Trent Lloyd]

If you have enable-hardware-offload=true and then set enable-hardware-offload=false, the configuration is not reverted leaving offload enabled.

Specifically the following openvswitch settings are not reverted:
ovs-vsctl set Open_vSwitch . other_config:max-idle=30000
ovs-vsctl set Open_vSwitch . other_config:hw-offload=true

There appears to be no code to handle the inverse case.

Workaround:
ovs-vsctl remove Open_vSwitch . other_config max-idle=30000 hw-offload=true
systemctl restart openvswitch-switch

Note:
Restarting openvswitch-switch will trigger a neutron bug blocking all outbound traffic from compute hosts in DVR that is not fixed in 15.1.0 (current release), but is fixed in 15.2.0 (proposed):
https://bugs.launchpad.net/neutron/+bug/1864822

[Aurelien Lourot (aurelien-lourot)]

Hi Trent, thanks for reporting. Indeed we have a code path for enabling [0] but not for disabling and it doesn't seem to be a known limitation. So this seems like a valid bug to me.

0: https://opendev.org/openstack/charm-neutron-openvswitch/src/branch/master/hooks/neutron_ovs_utils.py#L558

[James Page (james-page)]

Kinda a tricky one - I'd suggest we only disable hardware offload in the event that nothing is actually in use, and in this case disabling is not just OVS, its also de-configuring the VF's etc..