Client can connect via tcp

[robberphex]

In main branch, if caller pass address tcp://1.1.1.1:8090 to client.New, will get err.

In this PR, if caller pass tcp://1.1.1.1:8090, the client will try to connect via tcp.

[k8s-ci-robot]

Hi @robberphex. Thanks for your PR.

I'm waiting for a containerd member to verify that this patch is reasonable to test. If it is, they should reply with /ok-to-test on its own line. Until that is done, I will not automatically test new commits in this PR, but the usual testing commands by org members will still work. Regular contributors should join the org to skip this step.

Once the patch is verified, the new status will be reflected by the ok-to-test label.

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[theopenlab-ci]

Build succeeded.

• containerd-build-arm64 : SUCCESS in 4m 55s (non-voting)
• containerd-test-arm64 : SUCCESS in 6m 08s (non-voting)
• containerd-integration-test-arm64 : FAILURE in 14m 35s (non-voting)

[AkihiroSuda]

mTLS support is necessary for TCP.
Also, please explain the motivation of this.
Most APIs don’t work when the daemon and the client don’t share the same filesystem.
containerd/nerdctl#473 (comment)

[theopenlab-ci]

Build succeeded.

• containerd-build-arm64 : SUCCESS in 4m 44s (non-voting)
• containerd-test-arm64 : SUCCESS in 5m 57s (non-voting)
• containerd-integration-test-arm64 : SUCCESS in 27m 18s (non-voting)

[dmcgowan]

See #1324

If you have an issue with an existing use case, please open an issue describing the problem and solutions can be discussed there. This is intentionally not allowed today, so closing this for now.

Some higher level APIs such as CRI can support TCP today and we are looking to more higher level APIs which may be exposed via TCP. However, we do not plan to support the existing containerd APIs over TCP.