Add Host field to TCPSocketAction

[louyihua]

Currently, TCPSocketAction always uses Pod's IP in connection. But when a pod uses the host network, sometimes firewall rules may prevent kubelet from connecting through the Pod's IP.

This PR introduces the 'Host' field for TCPSocketAction, and if it is set to non-empty string, the probe will be performed on the configured host rather than the Pod's IP. This gives users an opportunity to explicitly specify 'localhost' as the target for the above situations.

Add Host field to TCPSocketAction

[k8s-ci-robot]

Hi @louyihua. Thanks for your PR.

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[k8s-reviewable]

This change is 

[k8s-github-robot]

[APPROVALNOTIFIER] This PR is NOT APPROVED

The following people have approved this PR: louyihua

Needs approval from an approver in each of these OWNERS Files:

• pkg/api/OWNERS
• pkg/kubelet/OWNERS

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cc @Random-Liu @smarterclayton
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[louyihua]

@k8s-bot tell me a joke

[k8s-ci-robot]

@louyihua: What do you call a fake noodle? An impasta.

In response to this comment:

@k8s-bot tell me a joke

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[louyihua]

@smarterclayton
This is a required patch to solve the openshift BUG 1405440 & 1430729.

[soltysh]

@kubernetes/sig-network-pr-reviews ptal

[nikhiljindal]

We generally recommend keeping real code changes and autogenerated changes in separate commit for easier reviewing.

This is an API change so cc @kubernetes/api-reviewers.

Assigning to @thockin to triage since this a network related API change.

[thockin]

@k8s-bot ok to test

[louyihua]

Always fail on the aws e2e with strange error :(

[jwendell]

I would also add:

diff --git a/pkg/kubectl/describe.go b/pkg/kubectl/describe.go
index 0359b9c..c63654d 100644
--- a/pkg/kubectl/describe.go
+++ b/pkg/kubectl/describe.go
@@ -1123,7 +1123,7 @@ func DescribeProbe(probe *api.Probe) string {
                url.Path = probe.HTTPGet.Path
                return fmt.Sprintf("http-get %s %s", url.String(), attrs)
        case probe.TCPSocket != nil:
-               return fmt.Sprintf("tcp-socket :%s %s", probe.TCPSocket.Port.String(), attrs)
+               return fmt.Sprintf("tcp-socket %s:%s %s", probe.TCPSocket.Host, probe.TCPSocket.Port.String(), attrs)
        }
        return fmt.Sprintf("unknown %s", attrs)
 }

[louyihua]

@jwendell
Thanks! Have added this to commit.

[jwendell]

@louyihua no problem. I was also working on that feature, for the last 3 days at least, and just saw this PR. The only difference to my work was that chunk above.

[louyihua]

@thockin
All tests are passed now.

[k8s-github-robot]

Automatic merge from submit-queue (batch tested with PRs 42998, 42902, 42959, 43020, 42948)