WIP: containerd: Support for kubenet-style networking modes

[justinsb]

By configuration conf_template, we can continue to support these
networking modes.

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[k8s-ci-robot]

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[hakman]

@justinsb I removed something similar in c02e5a2.
The problem with it isn't that it wouldn't work at all, but that is just unsupported and should not be used as default or in production.

[justinsb]

@hakman that's surprising; this is how all the CNI plugins work :-) Do you have a link to what's deprecated?

I can imagine that maybe conf_template is deprecated, in which case each provider (e.g. kopeio networking) might have to implement this behaviour.

We can also change the default to a different CNI provider, though then we'd have to agree what the new default should be, which will be tricky...

[justinsb]

Ah - I bet the confusion is passing --networking=kubenet to kubelet, vs using CNI in a kubenet-style. By kubenet-style I mean that nodes are configured externally with routes (either by the cloudprovider or by a CNI provider), and that we don't need to do anything per-pod.

Maybe we should come up with a better name for "kubenet-style" to avoid the confusion!

The reason I pursued this was because otherwise we have to figure out a migration strategy for clusters using kubenet/kopeio/gce-networking.

[hakman]

Yes, I meant the template from containerd conf and what it does behind the scenes.
Let's make this the main topic of today's call

[hakman]

@justinsb I added #10651 back to the master branch and cherry-picked for 1.19.
I see kopeio networking tests working again:
https://testgrid.k8s.io/kops-network-plugins#kops-aws-cni-kopeio

[k8s-ci-robot]

@justinsb: PR needs rebase.

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[justinsb]

Thanks for fixing @hakman - this is now unneeded

/close

[k8s-ci-robot]

@justinsb: Closed this PR.

In response to this:

Thanks for fixing @hakman - this is now unneeded

/close

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