How-to: Enable the Cinder Operator NetworkPolicy

This guide walks an operator through opting in to the chart-level NetworkPolicy that restricts the cinder-operator pod's egress and ingress to the minimum required for correct reconciliation.

Scope. This guide covers the NetworkPolicy that protects the operator pod itself. For the per-CR policy that protects the Cinder pods (spec.networkPolicy on a Cinder), see the Cinder CRD API Reference. That policy restricts ingress to TCP 8776 from the sources you list (at least one is required, so an empty list is refused) and derives its egress from the CR: DNS, the database, the cache, the Keystone, Glance and Barbican endpoints, the broker port, and the NFS exports, with additionalEgress appended after them. One policy covers the API pods, the scheduler, every volume service, the backup service and the Job pods, because its selector carries no component key.

---

Prerequisites

Devstack

This guide is written against the Quick Start (ControlPlane) devstack. Stand it up first:

KIND_HOST_PORT=8443 WITH_CONTROLPLANE=true WITH_NFS=true make deploy-infra

Follow that tutorial through the block-storage block of Step 4 and the Create a first volume check in Step 7, so the projected controlplane-cinder child is Ready in openstack with nfs1 and nfsbk attached. Every resource name in the examples below is one that devstack produces.

1. A CNI that enforces networking.k8s.io/v1 NetworkPolicy (required for real enforcement). Confirm with your platform team (Calico, Cilium, and Antrea enforce).

   The devstack enforces this policy

   The ControlPlane Quick Start kind devstack runs kind's default kindnet CNI. On kind v0.32 and later, kindnet enforces NetworkPolicy and evaluates a connection to a Service after the Service DNAT, so a kubeApiServer rule that misses the API server's endpoint address cuts the operator off on the devstack too. Step 2 below confirms the policy's shape and that the operator still reconciles under it. It sends no traffic outside the allow-list, so it does not prove that such traffic is dropped.

2. A running cinder-operator Helm release (namespace cinder-system).

3. The ControlPlane declares spec.services.cinder. Without it no controlplane-cinder child exists and the Step 2 verification has nothing to roll.

Step 1 — Enable the policy

The chart guards networkPolicy.enabled=true with a fail-closed check: networkPolicy.kubeApiServer.cidrs and ports must both be non-empty, or the template refuses to render. Gather the API server CIDRs and ports from the kubernetes Endpoints, which carry the real API server addresses. The 10.96.0.1 Service VIP that kubectl get service kubernetes reports is the wrong source: an enforcing CNI (Calico, Cilium, and kindnet on kind v0.32 and later) evaluates policy after the Service DNAT has rewritten a packet aimed at the VIP to one of those endpoint IPs, so a rule naming the VIP never matches:

kubectl get endpoints kubernetes -n default -o json \
  | jq -r '.subsets[] | (.addresses[].ip) as $ip | (.ports[].port) as $p | "\($ip)/32 port=\($p)"'

Record every endpoint IP the command prints, not just the first. A kind devstack reports the one control-plane node's address on the kind bridge (172.18.0.x), but an HA control plane reports one per API server replica. The rule must cover all of them, or the operator loses its leader-election lease whenever it happens to be talking to an excluded replica.

On the tutorial devstacks the cinder-operator release is owned by Flux (a HelmRelease), so set the values by patching its spec.values. A raw helm upgrade is reverted by the Flux helm-controller on its next reconcile; outside Flux, the same values go through helm upgrade --reuse-values. Substitute the CIDRs and ports from above; the single-CIDR list below stands in for the kind case of one control-plane node:

kubectl patch helmrelease cinder-operator -n cinder-system --type=merge \
  -p '{"spec":{"values":{"networkPolicy":{"enabled":true,"kubeApiServer":{"cidrs":["172.18.0.2/32"],"ports":[6443]}}}}}'

kubectl wait helmrelease/cinder-operator -n cinder-system \
  --for=condition=Ready --timeout=5m

The rendered policy allows egress to the kube-apiserver, to DNS and to the Cinder API, and ingress to the webhook port. The chart adds the Cinder API rule through the operator-library.chart.networkPolicyEgress hook, the hook a chart uses to append an egress rule of its own: TCP 8776 to every pod labelled app.kubernetes.io/name: cinder and app.kubernetes.io/managed-by: cinder-operator, in any namespace. It needs no value. The operator's health check GETs the Cinder API over the workload Service, and the CNI judges that connection after the Service DNAT, at the API pod and its port, so the rule selects the API pods by the labels the operator sets on them. One deployment shape does need more: with a Cinder placed on a registered target cluster, the operator talks to that cluster's API server too, so add its address and port to the same kubeApiServer lists.

The reverse direction needs nothing: the per-CR policy appends an ingress peer selecting the operator's namespace to every policy it renders, so a workload namespace running spec.networkPolicy already admits the probe.

Metrics ingress is opt-in and separate. networkPolicy.allowMetricsFrom is empty by default, and with the policy on, an empty list means no ingress rule for the metrics port (8080) at all, so a Prometheus that scraped the operator before stops reaching it. Name the scraping namespace when you enable both this policy and the ServiceMonitor from Enable the Cinder Operator Metrics Endpoint:

kubectl patch helmrelease cinder-operator -n cinder-system --type=merge \
  -p '{"spec":{"values":{"networkPolicy":{"allowMetricsFrom":[{"namespaceSelector":{"matchLabels":{"kubernetes.io/metadata.name":"monitoring"}}}]}}}}'

Each entry is rendered verbatim as a NetworkPolicyPeer, so a podSelector narrows it further to the Prometheus pods.

Upgrading from the hand-written probe policy

cinder-operator charts before 0.5.0 rendered no rule for the health check, and earlier versions of this guide had you apply a second policy, cinder-operator-api-probe, beside the chart's. The chart covers that traffic now, so delete the hand-written policy once the upgraded chart has rendered its own:

kubectl delete networkpolicy cinder-operator-api-probe -n cinder-system \
  --ignore-not-found

Step 2 — Verify

On the kind devstack this verifies the policy's shape and that the operator still reconciles under the enforced policy. It sends no traffic outside the allow-list (see the prerequisite above).

Restart the operator first. NetworkPolicy enforcement is stateful: a connection opened before the policy existed stays open, so a wrong kubeApiServer rule shows only after the next restart:

kubectl -n cinder-system rollout restart deploy/cinder-operator
kubectl -n cinder-system rollout status deploy/cinder-operator --timeout=5m

A rollout that does not finish within the timeout, with the new pod never Ready, means the egress rule does not admit the API server. See Reconcile timeouts / leader-election churn.

Then check the policy:

kubectl -n cinder-system get networkpolicy
kubectl -n cinder-system describe networkpolicy cinder-operator

Then confirm reconciliation still works end-to-end by driving a change through the ControlPlane CR and watching the projected block-storage API roll out. The block records the ControlPlane's current count, which is empty while the ControlPlane leaves it at the default, scales the API one replica above the size it runs at, and puts the count back:

if CUR=$(kubectl get controlplane controlplane -n openstack \
     -o jsonpath='{.spec.sizing.cinder.api.replicas}') &&
   RUN=$(kubectl get deploy/controlplane-cinder -n openstack \
     -o jsonpath='{.spec.replicas}'); then
  NEW=$((RUN + 1))

  kubectl patch controlplane controlplane -n openstack --type merge \
    -p "{\"spec\":{\"sizing\":{\"cinder\":{\"api\":{\"replicas\":$NEW}}}}}"
  kubectl wait deploy/controlplane-cinder -n openstack --timeout=5m \
    --for=jsonpath='{.spec.replicas}'="$NEW"
  kubectl rollout status deploy/controlplane-cinder -n openstack --timeout=5m

  # revert to the recorded count; null drops the override again
  kubectl patch controlplane controlplane -n openstack --type merge \
    -p "{\"spec\":{\"sizing\":{\"cinder\":{\"api\":{\"replicas\":${CUR:-null}}}}}}"
else
  echo "could not read the replica counts; nothing was patched" >&2
fi

The if stops the block before the first patch when either read fails. A failed read prints the same empty string as a ControlPlane without an override, so without the guard the revert would drop an override the ControlPlane carries, and a failed Deployment read would set NEW to 1 and shrink the API instead of growing it.

The kubectl wait is the check that proves the operator still reconciles: the patch travels from the ControlPlane to the Cinder CR to the Deployment, and the restarted operator writes nothing until it holds the leader lease. Until the cinder operator writes the new count the Deployment is still fully rolled out at its old size, so a rollout status alone would pass at once. The new count is always one above the running one, so the patch changes the Deployment whatever size the API already runs at.

spec.sizing.cinder.api.replicas sizes the API Deployment alone. The scheduler takes a count of its own under spec.sizing.cinder.scheduler, and the volume services and the backup service are pinned to one replica by the projection, so this patch rolls controlplane-cinder and leaves the storage path untouched.

Set the replica count on the ControlPlane CR, not on the projected controlplane-cinder child: the c5c3-operator re-asserts the child's spec.api.deployment.replicas on every reconcile, so a direct edit of the child is taken back.

Troubleshooting

Reconcile timeouts / leader-election churn

Symptom: operator logs show Get https://<kube-apiserver>: i/o timeout or leader-election lease renewals fail with context deadline exceeded, and the cinder-operator pod restarts.

Diagnosis: the egress allow-list does not match the API server the operator actually dials. Either kubeApiServer.cidrs is missing one or more of the current endpoint IPs (an HA control plane may have added a replica, or a control-plane node may have been replaced with a different IP), or your CNI maps the API server behind a port that is not in kubeApiServer.ports. A target cluster registered since the policy went on is the same failure with a different address.

Fix: re-run the discovery command from Step 1 and update networkPolicy.kubeApiServer.cidrs to include every IP it returns, plus every port.

Every Cinder, CinderBackend and CinderBackupBackend write is rejected

Symptom: kubectl apply on any of the three kinds fails with failed calling webhook plus connection refused or no route to host. The ControlPlane stalls too: the c5c3-operator projects controlplane-cinder and its nfs1 / nfsbk satellites through the same admission path.

Diagnosis: webhook ingress (9443) is blocked. The chart renders one MutatingWebhookConfiguration and one ValidatingWebhookConfiguration carrying six webhooks between them (mcinder.kb.io, mcinderbackend.kb.io, mcinderbackupbackend.kb.io, vcinder.kb.io, vcinderbackend.kb.io, vcinderbackupbackend.kb.io), all with failurePolicy: Fail on create and update, so an unreachable operator turns into a cluster-wide rejection of every write to all three kinds. Deletes pass: the rules list CREATE and UPDATE only, which is what keeps a down operator from blocking CR and namespace teardown. The usual cause is an API server that calls webhooks from an IP that is not in endpoints/kubernetes, for example because it sits behind a front-end proxy. networkPolicy.webhookClients.cidrs falls back to kubeApiServer.cidrs when empty, which is wrong in that topology.

Fix: discover the actual caller IP (check the API-server audit log or the kube-apiserver Pod's --advertise-address) and set networkPolicy.webhookClients.cidrs explicitly:

kubectl patch helmrelease cinder-operator -n cinder-system --type=merge \
  -p '{"spec":{"values":{"networkPolicy":{"webhookClients":{"cidrs":["10.1.0.0/24"]}}}}}'

If the wedge blocks you from recovering, set networkPolicy.enabled=false with the same patch shape. The policy object is removed on the next reconcile, and the operator reverts to unrestricted pod networking without a pod restart unless a cinder-operator-api-probe policy from an earlier version of this guide still selects the pod. That policy allows 8776 alone, so delete it as well:

kubectl delete networkpolicy cinder-operator-api-probe -n cinder-system \
  --ignore-not-found

Tested by

Every operator chart includes the same chart-level NetworkPolicy template from the shared operator-library, whose helm-unittest (operators/shared/helm/operator-library-testbed/tests/networkpolicy_test.yaml) pins the shared rules. The cinder chart's helm-unittest (operators/cinder/helm/cinder-operator/tests/networkpolicy_test.yaml) pins the egress rule the chart adds for its API health check. The keystone chart's policy is exercised end-to-end on the CI e2e kind cluster by the chainsaw suite below.

chainsaw test --test-dir tests/e2e/keystone-operator/network-policy-egress

A second suite, tests/e2e/cinder/network-policy, covers the other policy: the one the operator projects around the Cinder pods from spec.networkPolicy on a Cinder CR. That is a different subject from this guide's, and the Cinder CRD API Reference documents its field.