[ovs-dev] Multiple OVS vswitchd controlling same kernel path?

[William Tu]

On Wed, Mar 25, 2020 at 10:08:14AM -0400, Tim Rozet wrote:
> Hi All,
> I've run into this question several times, and several folks have different
> opinions. I was hoping we could resolve it. The question centers around

Me too. Thanks for bringing this up.

> having multiple OVS vswitchd instances in different netns on the same host
> using kernel data path. In the past several folks have told me this does
> not work, because there will be potential conflicts in the kernel data
> path, or each OVS may flush the kernel path flows without regard for
> what another OVS has programmed. In contrast, some other folks have told me
> this should work perfectly fine as each OVS has is using its own DPID and
> there should be 0 conflicts.

There is a talk about this in 2015 mentioning a couple of issues
https://www.openvswitch.org/support/ovscon2015/17/1555-benc.pdf
Maybe we could go over and test issues in this slide?

but in reality, I do see people running multiple ovs-vswitcd in multiple
containers sharing one ovs kernel datapath, without any problem.

> 
> One use case around this is being able to use Kubernetes In Docker (KIND),
> where we are running multiple Docker containers acting as "nodes" with ovs
> containers inside them, to simulate a large k8s deployment on a single
> host. Antrea has added support for using netdev mode and claims that kernel
> data path with multiple OVS will not work:
> https://github.com/vmware-tanzu/antrea/issues/14
> https://github.com/vmware-tanzu/antrea/blob/master/docs/kind.md#why-is-the-yaml-manifest-different-when-using-kind
> 
> Would appreciate if anyone has any insights on this.
> 
> Thanks,
> Tim Rozet
> Red Hat CTO Networking Team
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