hack: fix DNS on IPv6-only kind clusters #958
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| #!/usr/bin/env bash | ||
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There was a problem hiding this comment. Nit. remove this file, we can rely on e2e tests to provide signals |
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| # Copyright 2026 Google LLC | ||
| # | ||
| # Licensed under the Apache License, Version 2.0 (the "License"); | ||
| # you may not use this file except in compliance with the License. | ||
| # You may obtain a copy of the License at | ||
| # | ||
| # http://www.apache.org/licenses/LICENSE-2.0 | ||
| # | ||
| # Unless required by applicable law or agreed to in writing, software | ||
| # distributed under the License is distributed on an "AS IS" BASIS, | ||
| # WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. | ||
| # See the License for the specific language governing permissions and | ||
| # limitations under the License. | ||
| # | ||
| # Preconditions: | ||
| # IP_FAMILY=ipv6 hack/create-kind-cluster.sh | ||
| # | ||
| # Checks the two things the CoreDNS rewrite in create-kind-cluster.sh provides: | ||
| # a pod can resolve an external name (a GCS one -- that is where atelet pulls | ||
| # sandbox tarballs from) and reach the local registry by name. That script runs | ||
| # this last; re-run it by hand after the registry moves (#1049). | ||
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| set -o errexit -o nounset -o pipefail | ||
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| KUBECTL_CONTEXT="${KUBECTL_CONTEXT:-kind-${KIND_CLUSTER_NAME:-kind}}" | ||
| REG_NAME="${REG_NAME:-kind-registry}" | ||
| IPV6_DNS_UPSTREAM="${IPV6_DNS_UPSTREAM:-2001:4860:4860::8888 2001:4860:4860::8844}" | ||
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| if [[ $# -gt 0 ]]; then | ||
| case "$1" in | ||
| -h|--help) | ||
| echo "Usage: $0" | ||
| echo "Verifies pod DNS on the IPv6-only kind cluster '${KUBECTL_CONTEXT}'." | ||
| echo | ||
| echo "Configured through the environment:" | ||
| echo " KUBECTL_CONTEXT Context to check (default: kind-\${KIND_CLUSTER_NAME:-kind})." | ||
| echo " REG_NAME Name of the local registry container (default: kind-registry)." | ||
| echo " IPV6_DNS_UPSTREAM The resolvers CoreDNS was pointed at; reported on failure only." | ||
| exit 0 | ||
| ;; | ||
| *) | ||
| echo "error: unknown argument '$1'; see --help" >&2 | ||
| exit 1 | ||
| ;; | ||
| esac | ||
| fi | ||
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| kube() { kubectl --context="${KUBECTL_CONTEXT}" "$@"; } | ||
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| echo "Verifying DNS from a pod..." | ||
| # Probe from a pod, not the node: the node is dual-stack and passes either way. | ||
| # The registry leg fetches rather than resolves -- the hosts entry is AAAA-only, | ||
| # which fails nslookup's A query but satisfies getaddrinfo. Legs share one | ||
| # stream and only the last exit status survives, hence the markers; read the log | ||
| # after the pod terminates, because an attach drops lines. | ||
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| # Ask each replica directly as well as through the Service, so one sick replica | ||
| # is named instead of showing up as a coin flip -- and take the addresses from | ||
| # the EndpointSlice, filtered on ready, not from the pod list. A rollout leaves | ||
| # the previous generation running for its 30s grace period: still a listed pod, | ||
| # still unable to resolve, but already cut out of the Service. Querying it would | ||
| # fail a cluster that works. | ||
| legs="" | ||
| for ip in $(kube -n kube-system get endpointslices -l kubernetes.io/service-name=kube-dns \ | ||
| -o jsonpath='{range .items[*].endpoints[?(@.conditions.ready==true)]}{.addresses[0]}{" "}{end}'); do | ||
| legs="${legs} | ||
| nslookup storage.googleapis.com ${ip} >/dev/null 2>&1 || echo \"REPLICA_BAD ${ip}\"" | ||
| done | ||
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| probe_pod="coredns-probe-$$" | ||
| trap 'kube delete pod "${probe_pod}" --now --ignore-not-found --wait=false >/dev/null 2>&1 || true' EXIT | ||
| kube run "${probe_pod}" --restart=Never --image=busybox:1.36 --command -- \ | ||
| sh -c "if out=\$(nslookup storage.googleapis.com 2>&1); then | ||
| echo RESOLVE_OK | ||
| else | ||
| echo \"resolve failed: \$(echo \"\$out\" | tail -2 | tr '\n' ' ')\" | ||
| fi${legs} | ||
| if out=\$(wget -T10 -O/dev/null http://${REG_NAME}:5000/v2/ 2>&1); then | ||
| echo REGISTRY_OK | ||
| else | ||
| echo \"registry fetch failed: \$(echo \"\$out\" | tail -1)\" | ||
| fi" >/dev/null | ||
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| if ! kube wait --for=jsonpath='{.status.phase}'=Succeeded \ | ||
| "pod/${probe_pod}" --timeout=120s >/dev/null; then | ||
| echo "error: the probe pod never finished, so CoreDNS is unverified" >&2 | ||
| kube describe pod "${probe_pod}" | sed 's/^/ /' >&2 | ||
| exit 1 | ||
| fi | ||
| probe="$(kube logs "${probe_pod}")" | ||
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| # A replica that fails while the Service still answers is the case the per-replica | ||
| # legs exist to catch, so it has to fail the check too: the Service round-robins, | ||
| # so one sick replica out of two is not a warning, it is half the pods in the | ||
| # cluster unable to resolve. | ||
| bad_replicas="$(printf '%s\n' "${probe}" | sed -n 's/^REPLICA_BAD //p')" | ||
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| if [[ "${probe}" != *RESOLVE_OK* || "${probe}" != *REGISTRY_OK* || -n "${bad_replicas}" ]]; then | ||
| if [[ "${probe}" != *RESOLVE_OK* ]]; then | ||
| echo "error: a pod cannot resolve an external name" >&2 | ||
| echo " IPV6_DNS_UPSTREAM is '${IPV6_DNS_UPSTREAM}'; set it to a reachable resolver" >&2 | ||
| elif [[ "${probe}" == *REGISTRY_OK* ]]; then | ||
| echo "error: the Service resolves, but these CoreDNS replicas do not:" >&2 | ||
| while read -r ip; do | ||
| echo " ${ip}" >&2 | ||
| done <<<"${bad_replicas}" | ||
| echo " resolution is a coin flip until they are replaced" >&2 | ||
| else | ||
| # The Corefile holds a snapshot of the address; the registry may have moved | ||
| # off it (#1049), which is not the same fault as a registry that is down. | ||
| want="$(kube -n kube-system get cm coredns -o jsonpath='{.data.Corefile}' \ | ||
| | awk -v n="${REG_NAME}" '$2 == n {print $1}')" | ||
| have="$(docker inspect "${REG_NAME}" \ | ||
| --format '{{.NetworkSettings.Networks.kind.GlobalIPv6Address}}' 2>/dev/null || true)" | ||
| echo "error: DNS works but a pod cannot reach '${REG_NAME}'" >&2 | ||
| if [[ -n "${have}" && "${want}" != "${have}" ]]; then | ||
| echo " the Corefile says [${want}] but the registry is at [${have}]" >&2 | ||
| echo " re-create the cluster, or patch the hosts entry to match" >&2 | ||
| else | ||
| echo " check the registry container is up and on the 'kind' network" >&2 | ||
| fi | ||
| fi | ||
| echo " probe output was:" >&2 | ||
| printf '%s\n' "${probe}" | sed 's/^/ /' >&2 | ||
| exit 1 | ||
| fi | ||
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Nit. be more concise about the issue it tries to solve, and what the solution is