Troubleshoot GKE on VMware NFS and DataPlane v2 issues

This document details a manual procedure for GKE on VMware if you have issues with NFS mounts with a stuck volume or pod and you created your cluster with DataPlane v2 enabled. You might encounter issues if you have workloads using ReadWriteMany volumes powered by storage drivers that are susceptible to this issue, such as (but not limited to):

Robin.io
Portworx (sharedv4 service volumes)
csi-nfs

NFS mounts on some storage architectures might become stuck when they're connected to an endpoint using a Kubernetes Service (ClusterIP) and DataPlane v2. This behavior is because of the limitations in how Linux kernel socket code interacts with Cillium's eBPF program. Containers might become blocked on I/O or even be unkillable, as the defunct NFS mount can't be unmounted.

You might experience this issue if you use RWX storage hosted on NFS servers that run on a Kubernetes node, including software-defined or hyperconverged storage solutions like as Ondat, Robin.io, or Portworx.

If you need additional assistance, reach out to Cloud Customer Care.

Review existing cluster configuration

Get some existing configuration values from your cluster. You use the values from these steps to create a kube-proxy manifest in the next section.

Get the ClusterCIDR from cm/cilium-config:

kubectl get cm -n kube-system cilium-config -o yaml | grep native-routing-cidr

The following example output shows that you would use 192.168.0.0/16 as the ClusterCIDR:

ipv4-native-routing-cidr: 192.168.0.0/16
native-routing-cidr: 192.168.0.0/16

Get the APIServerAdvertiseAddress and APIServerPort from the anetd DaemonSet:
```
kubectl get ds -n kube-system  anetd -o yaml | grep KUBERNETES -A 1
```
The following example output show that you would use 21.1.4.119 as the APIServerAdvertiseAddress and 443 as the APIServerPort:
```
- name: KUBERNETES_SERVICE_HOST
  value: 21.1.4.119
- name: KUBERNETES_SERVICE_PORT
  value: "443"
```
Get the RegistryCredentialsSecretName from the anetd DaemonSet:
```
kubectl get ds -n kube-system  anetd -o yaml | grep imagePullSecrets -A 1
```
The following example output shows that you would use private-registry-creds as the RegistryCredentialsSecretName:
```
imagePullSecrets:
  - name: private-registry-creds
```

Get the Registry from the anetd DameonSet:

kubectl get ds -n kube-system  anetd -o yaml | grep image

The following example output shows that you would use gcr.io/gke-on-prem-release as the Registry:

image: gcr.io/gke-on-prem-release/cilium/cilium:v1.12.6-anthos1.15-gke4.2.7

Get the KubernetesVersion from the image tag for kube-apiserver in the cluster namespace of the admin cluster:
```
KUBECONFIG=ADMIN_KUBECONFIG
kubectl get sts -n CLUSTER_NAME kube-apiserver -o yaml | grep image
```
Replace ADMIN_KUBECONFIG with the kubeconfig file for your admin cluster and CLUSTER_NAME with the name of your user cluster.

The following example output shows that you would use v1.26.2-gke.1001 as the KubernetesVersion:
```
image: gcr.io/gke-on-prem-release/kube-apiserver-amd64:v1.26.2-gke.1001
imagePullPolicy: IfNotPresent
```

Prepare `kube-proxy` manifests

Use the values obtained in the previous section to create and apply a YAML manifest that will deploy kube-proxy to your cluster.

Create a manifest named kube-proxy.yaml in the editor of your choice:
```
nano kube-proxy.yaml
```

Copy and paste the following YAML definition:

apiVersion: apps/v1
kind: DaemonSet
metadata:
  labels:
    k8s-app: kube-proxy
  name: kube-proxy
  namespace: kube-system
spec:
  selector:
    matchLabels:
      k8s-app: kube-proxy
  template:
    metadata:
      annotations:
        scheduler.alpha.kubernetes.io/critical-pod: ""
      labels:
        k8s-app: kube-proxy
    spec:
      containers:
      - command:
        - kube-proxy
        - --v=2
        - --profiling=false
        - --iptables-min-sync-period=10s
        - --iptables-sync-period=1m
        - --oom-score-adj=-998
        - --ipvs-sync-period=1m
        - --ipvs-min-sync-period=10s
        - --cluster-cidr=ClusterCIDR
        env:
        - name: KUBERNETES_SERVICE_HOST
          value:APIServerAdvertiseAddress
        - name: KUBERNETES_SERVICE_PORT
          value: "APIServerPort"
        image: Registry/kube-proxy-amd64:KubernetesVersion
        imagePullPolicy: IfNotPresent
        name: kube-proxy
        resources:
          requests:
            cpu: 100m
            memory: 15Mi
        securityContext:
          privileged: true
        volumeMounts:
        - mountPath: /run/xtables.lock
          name: xtables-lock
        - mountPath: /lib/modules
          name: lib-modules
      imagePullSecrets:
      - name: RegistryCredentialsSecretName
      nodeSelector:
        kubernetes.io/os: linux
      hostNetwork: true
      priorityClassName: system-node-critical
      serviceAccount: kube-proxy
      serviceAccountName: kube-proxy
      tolerations:
      - effect: NoExecute
        operator: Exists
      - effect: NoSchedule
        operator: Exists
      volumes:
      - hostPath:
          path: /run/xtables.lock
          type: FileOrCreate
        name: xtables-lock
      - hostPath:
          path: /lib/modules
          type: DirectoryOrCreate
        name: lib-modules
  ---
  apiVersion: rbac.authorization.k8s.io/v1
  kind: ClusterRoleBinding
  metadata:
    name: system:kube-proxy
  roleRef:
    apiGroup: rbac.authorization.k8s.io
    kind: ClusterRole
    name: system:node-proxier
  subjects:
    - kind: ServiceAccount
      name: kube-proxy
      namespace: kube-system
  ---
  apiVersion: v1
  kind: ServiceAccount
  metadata:
    name: kube-proxy
    namespace: kube-system

In this YAML manifest, set the following values:

APIServerAdvertiseAddress: the value of KUBERNETES_SERVICE_HOST, such as 21.1.4.119.
APIServerPort: the value of KUBERNETES_SERVICE_PORT, such as 443.
Registry: the prefix of the Cilium image, such as gcr.io/gke-on-prem-release.
RegistryCredentialsSecretName: the image pull secret name, such as private-registry-creds.

Save and close the manifest file in your editor.

Prepare `anetd` patch

Create and prepare an update for anetd:

Create a manifest named cilium-config-patch.yaml in the editor of your choice:
```
nano cilium-config-patch.yaml
```

Copy and paste the following YAML definition:

data:
  kube-proxy-replacement: "disabled"
  kube-proxy-replacement-healthz-bind-address: ""
  retry-kube-proxy-healthz-binding: "false"
  enable-host-reachable-services: "false"

Save and close the manifest file in your editor.

Deploy `kube-proxy` and reconfigure `anetd`

Apply your configuration changes to your cluster. Create backups of your existing configuration before you apply the changes.

Back up your current anetd and cilium-config configuration:

kubectl get ds -n kube-system anetd > anetd-original.yaml
kubectl get cm -n kube-system cilium-config > cilium-config-original.yaml

Apply kube-proxy.yaml using kubectl:
```
kubectl apply -f kube-proxy.yaml
```

Check that the Pods are Running:

kubectl get pods -n kube-system -o wide | grep kube-proxy

The following example condensed output shows that the Pods are running correctly:

kube-proxy-f8mp9    1/1    Running   1 (4m ago)    [...]
kube-proxy-kndhv    1/1    Running   1 (5m ago)    [...]
kube-proxy-sjnwl    1/1    Running   1 (4m ago)    [...]

Patch the cilium-config ConfigMap using kubectl:

kubectl patch cm -n kube-system cilium-config --patch-file cilium-config-patch.yaml

Edit anetd using kubectl:

kubectl edit ds -n kube-system anetd

In the editor that opens up, edit the spec of anetd. Insert the following as the first item under initContainers:

- name: check-kube-proxy-rules
  image: Image
  imagePullPolicy: IfNotPresent
  command:
  - sh
  - -ec
  - |
    if [ "$KUBE_PROXY_REPLACEMENT" != "strict" ]; then
      kube_proxy_forward() { iptables -L KUBE-FORWARD; }
      until kube_proxy_forward; do sleep 2; done
    fi;
  env:
  - name: KUBE_PROXY_REPLACEMENT
    valueFrom:
      configMapKeyRef:
        key: kube-proxy-replacement
        name: cilium-config
        optional: true
  securityContext:
    privileged: true

Replace Image with the same image used in the other Cilium containers in the anetd DaemonSet, such as gcr.io/gke-on-prem-release/cilium/cilium:v1.12.6-anthos1.15-gke4.2.7.

Save and close the manifest file in your editor.
To apply these changes, reboot of all nodes in your cluster. To minimize disruption, you can attempt to drain each node prior to the reboot. However, Pods using RWX volumes may be stuck in a Terminating state due to broken NFS mounts that block the drain process.

You can force delete blocked Pods and allow the Node to correctly drain:
```
kubectl delete pods -–force -–grace-period=0 --namespace POD_NAMESPACE POD_NAME
```
Replace POD_NAME with the Pod you are trying to delete and POD_NAMESPACE with its namespace.

What's next