Add NodeInternalIP as a fallback to federation api-server nodeport service

[lukaszo]

Previously NodeLegacyHostIP was used as a fallback (see #41243) but in 1.7 it was removed (#44830)
Now clusters where nodes have not set ExternalIP can not be used by kubefed to setup federation.

cc @shashidharatd

kubefed will now configure NodeInternalIP as the federation API server endpoint when NodeExternalIP is unavailable for federation API servers exposed as NodePort services

[shashidharatd]

LGTM. In some non-cloud environment, nodes might not have NodeExternalIP and in such cases kubefed might not work.
But i want to hear from @madhusudancs, because he was opposed to fall-back to NodeInternalIP initially.

/cc @madhusudancs @kubernetes/sig-federation-pr-reviews

[lukaszo]

@madhusudancs ping

I consider it as a bugfix for 1.7.

[lukaszo]

/assign @madhusudancs

[irfanurrehman]

looks good to me too.
/assign @madhusudancs
/unassign

[marun]

Given the trivial nature of the fix I don't think an issue should be required.

@madhusudancs Bump, if this is going to make 1.7 it will need to be merged asap.

[madhusudancs]

/lgtm

[k8s-github-robot]

[APPROVALNOTIFIER] This PR is APPROVED

This pull-request has been approved by: lukaszo, madhusudancs

Associated issue: 41243

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[marun]

@lukaszo I think a release note is suggested here so that users know about the change in behavior.

[lukaszo]

@marun done

[madhusudancs]

@lukaszo I think the release note needs to be paraphrased a little bit. It sounds like a commit log targeted to developers. The target audience for this release note are kubefed users. Can you please phrase it in a way you would like your users to think about this change? Also see - #42092 (comment).

[lukaszo]

@madhusudancs what about now?

[madhusudancs]

@lukaszo How about: kubefed will now configure NodeInternalIP as the federation API server endpoint when NodeExternalIP is unavailable for federation API servers exposed as NodePort services?

[lukaszo]

@madhusudancs perfect, updated :)

[madhusudancs]

@lukaszo thanks for updating the release note. I have removed the do-not-merge label. PR should be good to go now.

[lukaszo]

@madhusudancs thank you

[lukaszo]

/retest

[k8s-github-robot]

Automatic merge from submit-queue