GKE networking known issues

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• 1.30.10-gke.1070000 and later
• 1.31.5-gke.1068000 and later
• 1.32.1-gke.1002000 and later

Newly created nodes are not added to the layer 4 internal load balancers

Google Cloud load balancers that are created for internal LoadBalancer Services might miss newly created nodes in the backend instance group.

The issue will be most visible on a cluster that was scaled to zero nodes and then scaled back to one or more nodes.

Workarounds:

• Turn on GKE subsetting and recreate the Service.

  Note: GKE subsetting can't be turned off after it is turned on.

• Create another internal LoadBalancing Service. When it syncs, the instance group will also be fixed for the affected Service. The new Service can be removed after the sync.
• Add and then remove the node.kubernetes.io/exclude-from-external-load-balancers label from one of the nodes.
• Add a node to the cluster. You can remove the node after the Service starts functioning.

NEG Controller stops managing endpoints when port removed from Service

When the NEG controller is configured to create a Standalone NEG for a Service and one of the configured ports is later removed from the Service, the NEG controller will eventually stop managing endpoints for the NEG. In addition to Services where the user creates a Standalone NEG annotation, this also affects Services which are referenced by GKE Gateway, MCI, and GKE Multi Cluster Gateway.

Workaround:

When removing a port from a Service with a Standalone NEG annotation, the annotation needs to also be updated to remove the port in question.

Gateway TLS configuration error

We've identified an issue with configuring TLS for Gateways in clusters running GKE version 1.28.4-gke.1083000. This affects TLS configurations using either an SSLCertificate or a CertificateMap. If you're upgrading a cluster with existing Gateways, updates made to the Gateway will fail. For new Gateways, the load balancers won't be provisioned. This issue will be fixed in an upcoming GKE 1.28 patch version.

• 1.26.13-gke.1052000 and later
• 1.27.10-gke.1055000 and later
• 1.28.6-gke.1095000 and later
• 1.29.1-gke.1016000 and later

Intermittent connection establishment failures

Clusters on control plane versions 1.26.6-gke.1900 and later might encounter intermittent connection establishment failures.

The chances of failures are low and it doesn't affect all clusters. The failures should stop completely after a few days since the symptom onset.

• 1.27.11-gke.1118000 or later
• 1.28.7-gke.1100000 or later
• 1.29.2-gke.1217000 or later

DNS resolution issues with Container-Optimized OS

Workloads running on GKE clusters with Container-Optimized OS-based nodes might experience DNS resolution issues.

Network Policy drops a connection due to incorrect connection tracking lookup

For clusters with GKE Dataplane V2 enabled, when a client Pod connects to itself using a Service or the virtual IP address of an internal passthrough Network Load Balancer, the reply packet is not identified as a part of an existing connection due to incorrect conntrack lookup in the dataplane. This means that a Network Policy that restricts ingress traffic for the Pod is incorrectly enforced on the packet.

The impact of this issue depends on the number of configured Pods for the Service. For example, if the Service has 1 backend Pod, the connection always fails. If the Service has 2 backend Pods, the connection fails 50% of the time.

Workaround:

You can mitigate this issue by configuring the port and containerPort in the Service manifest to be the same value.

• 1.28.3-gke.1090000 or later
• 1.27.11-gke.1097000 or later

Packet drops for hairpin connection flows

For clusters with GKE Dataplane V2 enabled, when a Pod creates a TCP connection to itself using a Service, such that the Pod is both the source and destination of the connection, GKE Dataplane V2 eBPF connection tracking incorrectly tracks the connection states, leading to leaked conntrack entries.

When a connection tuple (protocol, source/destination IP, and source/destination port) has been leaked, new connections using the same connection tuple might result in return packets being dropped.

Workaround:

Use one of the following workarounds:

• Enable TCP reuse (keep-alives) for an application running in a Pod that might communicate with itself using a Service. This prevents the TCP FIN flag from being issued and avoids leaking the conntrack entry.
• When using short-lived connections, expose the Pod using a proxy load balancer, such as Gateway, to expose the Service. This results in the destination of the connection request being set to the load balancer IP address, preventing GKE Dataplane V2 from performing SNAT to the loopback IP address.

Device typed network in GKE multi-network fails with long network names

Cluster creation fails with the following error:

error starting very-long-string-that-exceeds-character-limit-gpu-nic0 device plugin endpoint: listen unix /var/lib/kubelet/plugins_registry/networking.gke.io.networks_very-long-string-that-exceeds-character-limit-gpu-nic0.sock: bind: invalid argument

Workaround:

Limit the length of device-typed network object names to 41 characters or less. The full path of each UNIX domain socket is composed, including the corresponding network name. Linux has a limitation on socket path lengths (under 107 bytes). After accounting for the directory, filename prefix, and the .sock extension, the network name is limited to a maximum of 41 characters.

• 1.30.4-gke.1282000 or later
• 1.29.8-gke.1157000 or later
• 1.28.13-gke.1078000 or later
• 1.27.16-gke.1342000 or later

Connectivity issues for hostPort Pods after control plane upgrade

Clusters with network policy enabled might experience connectivity issues with hostPort Pods. Additionally, newly created Pods might take an additional 30 to 60 seconds to be ready.

The issue is triggered when the GKE control plane of a cluster is upgraded to one of the following GKE versions

• 1.30 to 1.30.4-gke.1281999
• 1.29.1-gke.1545000 to 1.29.8-gke.1156999
• 1.28.7-gke.1042000 to 1.28.13-gke.1077999
• 1.27.12-gke.1107000 to 1.27.16-gke.1341999

Workaround:

Upgrade or recreate nodes immediately after the GKE control plane upgrade.

• 1.32.1-gke.1729000 or later
• 1.31.6-gke.1020000 or later

Broken UDP traffic between Pods that run on the same node

Clusters with intra-node visibility enabled might experience broken UDP traffic between Pods that run on the same node.

The issue is triggered when the GKE cluster node is upgraded to or created with one of the following GKE versions:

• 1.32.1-gke.1729000 or later
• 1.31.6-gke.1020000 or later

The impacted path is Pod-to-Pod UDP traffic on the same node through Hostport or Service.

Workaround

Until a fix is rolled out, select one of the following options:

• Apply the mitigation DaemonSet to the cluster:

  apiVersion: apps/v1
  kind: DaemonSet
  metadata:
    name: mitigation-skip-udp
    namespace: kube-system
  spec:
    selector:
      matchLabels:
        k8s-app: mitigation-skip-udp
    template:
      metadata:
        labels:
          k8s-app: mitigation-skip-udp
      spec:
        hostNetwork: true
        initContainers:
        - name: mitigation-skip-udp
          image: gke.gcr.io/cilium/cilium:v1.16.6-gke.31@sha256:4b0b21b6c1ba5c4d28284e6d6027ceb5b243856c236b642d0ff8624c0c57716a
          command: ["/bin/bash", "-c", "--"]
          args:
          - |
            echo "Installing an IP rule to skip UDP traffic for intra-node visibility. No-op if it already exists."
            ip rule add from all ipproto udp lookup main prio 29998 || true
          securityContext:
            privileged: false
            capabilities:
              drop: ["ALL"]
              add: ["NET_ADMIN", "NET_RAW"]
            allowPrivilegeEscalation: false
            seccompProfile:
              type: RuntimeDefault
        containers:
        - image: gke.gcr.io/pause:3.8@sha256:880e63f94b145e46f1b1082bb71b85e21f16b99b180b9996407d61240ceb9830
          name: pause
          securityContext:
            privileged: false
            capabilities:
              drop: ["ALL"]
            allowPrivilegeEscalation: false
            readOnlyRootFilesystem: true
            runAsUser: 1000
            runAsGroup: 1000
            seccompProfile:
              type: RuntimeDefault
        tolerations:
        - effect: NoSchedule
          operator: Exists
        - effect: NoExecute
          operator: Exists
        - key: "CriticalAddonsOnly"
          operator: "Exists"

• Disable intranode-visibility for the cluster.

Calico Pods not healthy on clusters with less than 3 total nodes and insufficient vCPU

Calico-typha and calico-node Pods can't be scheduled on clusters meeting all of the following conditions: fewer than 3 nodes total, each node having 1 or fewer allocatable vCPUs, and network policy enabled enabled. This is due to insufficient CPU resources.

Workarounds:

• Scale to a minimum of 3 node pools with 1 node using 1 allocatable vCPU.
• Resize a single node pool to a minimum of 3 nodes with 1 allocatable vCPU.
• Use a machine-type with at least 2 allocatable vCPU on a node pool with a single node.