containerd: set override_path for registry mirrors with a path by peter-svensson · Pull Request #18819 · kubernetes/kops

peter-svensson · 2026-09-28T21:27:19Z

What this PR does / why we need it:

#18291 moved containerd.registryMirrors from the inline registry.mirrors.<name>.endpoint config to /etc/containerd/certs.d/<name>/hosts.toml. The two formats treat a path in the mirror URL differently:

Legacy registry.mirrors endpoints: a non-empty path is used as-is, /v2 is only added when the path is empty.
hosts.toml: containerd always appends /v2 to the host path unless override_path = true is set (hosts.md).

Mirrors that carry their own API path therefore stopped working in 1.36. With an ECR pull-through cache configured as

containerd:
  registryMirrors:
    docker.io:
      - https://<account>.dkr.ecr.eu-west-1.amazonaws.com/v2/docker-hub

kops 1.36 nodes request

HEAD https://<account>.dkr.ecr.eu-west-1.amazonaws.com/v2/docker-hub/v2/<repo>/manifests/<digest>: 403 Forbidden

while the correct URL .../v2/docker-hub/<repo>/manifests/<digest> returns 200 with the same credentials. containerd then falls back to the upstream registry, so the failure is easy to miss until upstream pulls fail as well.

This PR writes override_path = true for mirror endpoints whose URL has a non-root path, which matches the pre-1.36 behaviour. Endpoints without a path (https://mirror.example.com) produce the same hosts.toml as before.

Which issue(s) this PR fixes:

Special notes for your reviewer:

This is a regression from 1.35, so a cherry-pick to release-1.36 would be appreciated.

The complex containerd builder test gets an ECR-style quay.io mirror to cover the path case; the existing mirrors in that test are unchanged in the golden output.

linux-foundation-easycla · 2026-09-28T21:27:26Z

The committers listed above are authorized under a signed CLA.

✅ login: peter-svensson / name: Peter Svensson (f6821e4)

kubernetes-prow · 2026-09-28T21:27:29Z

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kubernetes-prow · 2026-09-28T21:27:30Z

Hi @peter-svensson. Thanks for your PR.

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hakman

Thanks for the fix @peter-svensson. I would suggest some small fixes and adding a test for endpointHasPath().

func TestEndpointHasPath(t *testing.T) {
	grid := []struct {
		endpoint string
		expected bool
	}{
		{endpoint: "https://mirror.example.com", expected: false},
		{endpoint: "https://mirror.example.com/", expected: false},
		{endpoint: "https://mirror.example.com//", expected: false},
		{endpoint: "http://10.0.0.5:5000", expected: false},
		{endpoint: "mirror.example.com", expected: false},
		{endpoint: "mirror.example.com:5000", expected: false},
		{endpoint: "10.0.0.5", expected: false},
		{endpoint: "https://mirror.example.com/v2", expected: true},
		{endpoint: "https://123456789012.dkr.ecr.us-east-1.amazonaws.com/v2/docker-hub", expected: true},
		{endpoint: "mirror.example.com:5000/v2/docker-hub", expected: true},
		{endpoint: "10.0.0.5:5000/v2/docker-hub", expected: true},
		{endpoint: "https://mirror.example.com/./", expected: false},
		{endpoint: "https://mirror.example.com/v2/..", expected: false},
		{endpoint: "https://mirror.example.com/prefix/./v2", expected: true},
		{endpoint: "https://mirror.example.com/v2/docker-hub/", expected: true},
		{endpoint: "[::1]:5000/v2/x", expected: true},
		{endpoint: "https://[fd00::1]:5000", expected: false},
	}

	for _, g := range grid {
		if actual := endpointHasPath(g.endpoint); actual != g.expected {
			t.Errorf("endpointHasPath(%q): got %v, expected %v", g.endpoint, actual, g.expected)
		}
	}
}

hakman · 2026-09-30T10:06:54Z

+// endpointHasPath reports whether a mirror endpoint carries its own API path, e.g.
+// https://<account>.dkr.ecr.<region>.amazonaws.com/v2/<prefix> for an ECR pull-through cache.
+// containerd appends /v2 to hosts.toml host paths unless override_path is set, whereas the
+// legacy registry.mirrors endpoint list used a non-empty path as-is. Setting override_path
+// for these endpoints keeps the behaviour of the legacy configuration.
+func endpointHasPath(endpoint string) bool {


Suggested change

// endpointHasPath reports whether a mirror endpoint carries its own API path, e.g.

// https://<account>.dkr.ecr.<region>.amazonaws.com/v2/<prefix> for an ECR pull-through cache.

// containerd appends /v2 to hosts.toml host paths unless override_path is set, whereas the

// legacy registry.mirrors endpoint list used a non-empty path as-is. Setting override_path

// for these endpoints keeps the behaviour of the legacy configuration.

func endpointHasPath(endpoint string) bool {

// endpointHasPath reports whether a mirror endpoint has a non-root path. These endpoints get

// override_path, so containerd uses the path as-is instead of appending /v2, as the legacy

// registry.mirrors config did.

func endpointHasPath(endpoint string) bool {

// Match containerd's parseHostConfig normalization so we check the same path.

if !strings.HasPrefix(endpoint, "http") {

endpoint = "https://" + endpoint

}

hakman · 2026-09-30T10:07:18Z

+	if err != nil {
+		return false
+	}
+	return strings.TrimSuffix(u.Path, "/") != ""


Suggested change

return strings.TrimSuffix(u.Path, "/") != ""

return u.Path != "" && path.Clean(u.Path) != "/"

peter-svensson · 2026-09-30T20:39:24Z

Thanks @hakman! Applied both suggestions and added TestEndpointHasPath in b9c131f.

The normalization matters beyond style: without the https:// prefix, url.Parse treats a scheme-less host like mirror.example.com:5000/v2/docker-hub as the URL scheme, so those mirrors did not get override_path at all, and plain hosts such as mirror.example.com got it by mistake. Your table covers both.

Since registry mirrors moved from the inline registry.mirrors config to certs.d/<registry>/hosts.toml, containerd appends /v2 to every mirror host URL. The legacy endpoint list used a non-empty path as-is, so mirrors that carry their own API path, such as an ECR pull-through cache at https://<account>.dkr.ecr.<region>.amazonaws.com/v2/<prefix>, now resolve to .../v2/<prefix>/v2/<repo> and fail. Emit override_path = true for endpoints with a non-root path, which restores the previous behaviour. Endpoints without a path are unchanged.

…g the path Endpoints without a scheme (mirror.example.com:5000/v2/docker-hub) were misparsed by url.Parse, and paths such as "//" or "/v2/.." counted as a path. Prefix https:// the way containerd parseHostConfig does and compare the cleaned path against "/". Add a table test for endpointHasPath.

hakman · 2026-09-30T21:04:10Z

/ok-to-test

hakman · 2026-10-01T08:53:33Z

Thanks @peter-svensson!
/lgtm
/approve

kubernetes-prow · 2026-10-01T08:53:43Z

[APPROVALNOTIFIER] This PR is APPROVED

This pull-request has been approved by: hakman

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…-upstream-release-1.37 Automated cherry pick of #18819: containerd: set override_path for registry mirrors with a path

…-upstream-release-1.36 Automated cherry pick of #18819: containerd: set override_path for registry mirrors with a path

kubernetes-prow Bot added cncf-cla: no Indicates the PR's author has not signed the CNCF CLA. size/M Denotes a PR that changes 30-99 lines, ignoring generated files. labels Sep 28, 2026

kubernetes-prow Bot added the needs-ok-to-test Indicates a PR that requires an org member to verify it is safe to test. label Sep 28, 2026

kubernetes-prow Bot requested review from olemarkus and zetaab September 28, 2026 21:27

kubernetes-prow Bot added area/nodeup cncf-cla: yes Indicates the PR's author has signed the CNCF CLA. and removed cncf-cla: no Indicates the PR's author has not signed the CNCF CLA. labels Sep 28, 2026

hakman requested changes Sep 30, 2026

View reviewed changes

kubernetes-prow Bot assigned hakman Sep 30, 2026

peter-svensson added 2 commits September 30, 2026 22:44

peter-svensson force-pushed the fix/containerd-mirror-override-path branch from 70ddb6e to b9c131f Compare September 30, 2026 20:44

kubernetes-prow Bot added ok-to-test Indicates a non-member PR verified by an org member that is safe to test. and removed needs-ok-to-test Indicates a PR that requires an org member to verify it is safe to test. labels Sep 30, 2026

kubernetes-prow Bot added the lgtm "Looks good to me", indicates that a PR is ready to be merged. label Oct 1, 2026

kubernetes-prow Bot added the approved Indicates a PR has been approved by an approver from all required OWNERS files. label Oct 1, 2026

kubernetes-prow Bot merged commit 2b56ba7 into kubernetes:master Oct 1, 2026
26 checks passed

kubernetes-prow Bot added a commit that referenced this pull request Oct 1, 2026

Merge pull request #18823 from hakman/automated-cherry-pick-of-#18819…

0a3510f

…-upstream-release-1.37 Automated cherry pick of #18819: containerd: set override_path for registry mirrors with a path

kubernetes-prow Bot added a commit that referenced this pull request Oct 1, 2026

Merge pull request #18824 from hakman/automated-cherry-pick-of-#18819…

39771a5

…-upstream-release-1.36 Automated cherry pick of #18819: containerd: set override_path for registry mirrors with a path

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	return strings.TrimSuffix(u.Path, "/") != ""
	return u.Path != "" && path.Clean(u.Path) != "/"

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