[ovs-discuss] bug: Adding or deleting port results to flush of QoS policy for all bridge ports

[Andrey Korolyov]

Hello,

Assuming we have trivial case: libvirt, its QoS limits (for which
appropriate rules are executed for each port) and more than one VM
sharing the same OVS bridge. Port configurations are initially empty
and addition going through libvirt` internal command execution by
calling ovs-vsctl binary, so no QoS configuration is performed through
existing vswitchd mechanisms.

Since OVS decides to flush all disciplines every time when port added
or removed from the switch, one will not be able to keep more than one
port with externally set tc disciplines.

At least this bug affects 0fe1d7f39de9836fea01c560a6fdbfd1405096ea
(2.1.3 effectively) in Openflow mode, though probably cover area is
wider. FAQ suggests tc as a fallback method for complex
configurations, so I can guess that the bug is definitely a bug but
not an expected behavior.

Thanks!