Fali to create/update placeholder service when k8s open IPv4/IPv6 dual-stack feature

[MIBc]

/area API

What version of Knative?

0.15.0

Expected Behavior

serving controller can create/update placeholder service without errors

Actual Behavior

If k8s open IPv4/IPv6 dual-stack feature. Knative will return error: "Service is invalid: spec.ipFamily: Required value"
We should a default ipFamily to prevent the error.

[mattmoor]

/area API
/area networking

cc @tcnghia @nak3 @ZhiminXiang

[ZhiminXiang]

We don't set ipFamily for all Knative-generated services. So we probably need to add it to all of those services.

I am thinking about reading ipFamily from a ConfigMap. the ipFamily is empty string by default, which means it will use cluster's primary IP family automatically (see doc). If users explicitly configure their cluster to use the dual-stack, they need to manually set the ipFamily of the ConfigMap, so it can be explicitly added into service spec.

WDYT?

[mattmoor]

Is this something that could be defaulted and we could be taught to preserve?

Is there a way for us to start testing this?

[MIBc]

The ipFamily config may be a better way.
In our environment, I must set the IPFamily in service spec. Otherwise, the error would happen.

[github-actions]

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[howardjohn]

Should this be re-opened?

You can test ipv6 and dual stack with the latest versions of kind

[nak3]

Yes, I think this should be opened.

[dprotaso]

/lifecycle frozen