Creating a network policy

Standard

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This page explains how to configure the enforcement of network policies in Google Kubernetes Engine (GKE). For general information about GKE networking, visit the Network overview.

Overview

You can use GKE's network policy enforcement to control the communication between your cluster's Pods and Services. You define a network policy by using the Kubernetes Network Policy API to create Pod-level firewall rules. These firewall rules determine which Pods and Services can access one another inside your cluster.

Defining network policy helps you enable things like defense in depth when your cluster is serving a multi-level application. For example, you can create a network policy to ensure that a compromised front-end service in your application cannot communicate directly with a billing or accounting service several levels down.

Network policy can also make it easier for your application to host data from multiple users simultaneously. For example, you can provide secure multi-tenancy by defining a tenant-per-namespace model. In such a model, network policy rules can ensure that Pods and Services in a given namespace cannot access other Pods or Services in a different namespace.

Note: Network policy enforcement is only available for clusters running Kubernetes version 1.7.6 or later.

Before you begin

Before you start, make sure you have performed the following tasks:

• Ensure that you have enabled the Google Kubernetes Engine API.
Enable Google Kubernetes Engine API
• Ensure that you have installed the Cloud SDK.
• Set up default gcloud command-line tool settings for your project by using one of the following methods:
• Use gcloud init, if you want to be walked through setting project defaults.
• Use gcloud config, to individually set your project ID, zone, and region.

gcloud init

1. Run gcloud init and follow the directions:

   gcloud init

   If you are using SSH on a remote server, use the --console-only flag to prevent the command from launching a browser:

   gcloud init --console-only

2. Follow the instructions to authorize the gcloud tool to use your Google Cloud account.
3. Create a new configuration or select an existing one.
4. Choose a Google Cloud project.
5. Choose a default Compute Engine zone.
6. Choose a default Compute Engine region.

Note: You can override these default settings in the gcloud tool by using the --project, --zone, and --region flags.

gcloud config

1. Set your default project ID:

   gcloud config set project PROJECT_ID

2. Set your default Compute Engine region (for example, us-central1):

   gcloud config set compute/region COMPUTE_REGION

3. Set your default Compute Engine zone (for example, us-central1-c):

   gcloud config set compute/zone COMPUTE_ZONE

4. Update gcloud to the latest version:

   gcloud components update

Note: You can override these default settings in the gcloud tool by using the --project, --zone, and --region flags.

By setting default locations, you can avoid errors in gcloud tool like the following: One of [--zone, --region] must be supplied: Please specify location.

Using network policy enforcement

You can enable network policy enforcement when you create a GKE cluster or enable it for an existing cluster. You can also disable network policy for an existing cluster.

Once you have enabled network policy in your cluster, you can create a network policy by using the Kubernetes Network Policy API.

Note: If you enable or disable network policy enforcement for an existing cluster, GKE is required to manually recreate all of your cluster's node pools to ensure that the nodes are configured to run the network policy process.

Enabling network policy enforcement

Network policy enforcement is built into GKE Dataplane V2. You do not need to enable network policy enforcement in clusters that use GKE Dataplane V2.

When you enable network policy enforcement in a GKE cluster that doesn't use GKE Dataplane V2, GKE manages and enforces network policies within that cluster.

Caution: By default, enabling network policy enforcement for your cluster also enables enforcement for the cluster's nodes.

You can enable network policy enforcement in GKE by using the gcloud tool, the Google Cloud Console, or the GKE API.

gcloud

To enable network policy enforcement when creating a new cluster, run the following command:

gcloud container clusters create CLUSTER_NAME --enable-network-policy

Replace CLUSTER_NAME with the name of the new cluster.

To enable network policy enforcement for an existing cluster, perform the following tasks:

1. Run the following command to enable the add-on:

   gcloud container clusters update CLUSTER_NAME --update-addons=NetworkPolicy=ENABLED
   

   Replace CLUSTER_NAME with the name of the cluster.

2. Run the following command to enable network policy enforcement on your cluster, which in turn recreates your cluster's node pools with network policy enforcement enabled:

   gcloud container clusters update CLUSTER_NAME --enable-network-policy
   

Console

To enable network policy enforcement when creating a new cluster:

1. Go to the Google Kubernetes Engine page in the Cloud Console.

   Go to Google Kubernetes Engine

2. Click Create.

3. Configure your cluster as desired.

4. From the navigation pane, under Cluster, click Networking.

5. Select the Enable network policy checkbox.

6. Click Create.

To enable network policy enforcement for an existing cluster:

1. Go to the Google Kubernetes Engine page in Cloud Console.

   Go to Google Kubernetes Engine

2. In the cluster list, click the name of the cluster you want to modify.

3. Under Networking, in the Network policy field, click Edit network policy.

4. Select the Enable network policy for master checkbox and click Save Changes.

5. Wait for your changes to apply, and then click Edit network policy again.

6. Select the Enable network policy for nodes checkbox.

7. Click Save Changes.

Note: For network policy to work, you must enable it on both your control plane and nodes. When you update an existing cluster, you must enable network policy on control planes and nodes. GKE enables network policy on control planes and nodes automatically when you create a new cluster.

API

To enable network policy enforcement, perform the following:

1. Specify the networkPolicy object inside the cluster object that you provide to projects.zones.clusters.create or projects.zones.clusters.update.

2. The networkPolicy object requires an enum that specifies which network policy provider to use, and a boolean value that specifies whether to enable network policy. If you enable network policy but do not set the provider, the create and update commands return an error.

Disabling network policy enforcement

You can disable network policy enforcement by using the gcloud tool, the Google Cloud Console, or the GKE API. Network policy enforcement can't be disabled in clusters that use GKE Dataplane V2.

gcloud

To disable network policy enforcement for an existing cluster, run the following command:

gcloud container clusters update CLUSTER_NAME --no-enable-network-policy

Replace CLUSTER_NAME with the name of the cluster.

Console

To disable network policy enforcement for an existing cluster, perform the following:

1. Go to the Google Kubernetes Engine page in Cloud Console.

   Go to Google Kubernetes Engine

2. In the cluster list, click the name of the cluster you want to modify.

3. Under Networking, in the Network policy field, click Edit network policy.

4. Clear the Enable network policy for nodes checkbox and click Save Changes.

5. Wait for your changes to apply, and then click Edit network policy again.

6. Clear the Enable network policy for master checkbox.

7. Click Save Changes.

API

To disable network policy enforcement for an existing cluster, perform the following:

1. Specify the networkPolicy object inside your cluster object you provide to projects.zones.clusters.update.
2. Inside the networkPolicy object, set the boolean enabled value to false.

If you disable network policy enforcement, make sure to also update any add-ons (for example, Calico DaemonSet) to indicate the network policy is disabled for the add-ons:

gcloud container clusters update CLUSTER_NAME --update-addons=NetworkPolicy=DISABLED

Replace CLUSTER_NAME with the name of the cluster.

Creating a network policy

Once you have enabled network policy enforcement for your cluster, you'll need to define the actual network policy. You define the network policy using the Kubernetes Network Policy API.

For further details on creating a network policy, see the following topics in the Kubernetes documentation:

• Network Policy Overview
• Declare Network Policy

Working with PodSecurityPolicy

Warning: Kubernetes has officially deprecated PodSecurityPolicy in version 1.21. PodSecurityPolicy will be shut down in version 1.25. For information about alternatives, refer to PodSecurityPolicy deprecation.

If you are using a NetworkPolicy, and you have a Pod that is subject to a PodSecurityPolicy, create an RBAC Role or ClusterRole that has permission to use the PodSecurityPolicy. Then bind the Role or ClusterRole to the Pod's service account. When using NetworkPolicy and PodSecurityPolicy together, granting permissions to user accounts is not sufficient. You must bind the role to the service account. For more information, see Authorizing policies.

Overhead, limitations, and caveats

• Enabling network policy enforcement consumes additional resources in nodes. Specifically, it increases the memory footprint of the kube-system process by approximately 128 MB, and requires approximately 300 millicores of CPU.

  Note: If you're enabling network policies for an existing cluster, you might need to increase the cluster's size to continue running your scheduled workloads.

• Enabling network policy enforcement requires that your nodes be recreated. If your cluster has an active maintenance window, your nodes are not automatically recreated until the next maintenance window. If you prefer, you can manually upgrade your cluster at any time.

Limitations and requirements

• Your cluster must have at least 2 nodes of type e2-medium or higher. The recommended minimum size cluster to run network policy enforcement is 3 e2-medium instances.
• Network policy is not supported for clusters whose nodes are f1-micro or g1-small instances, as the resource requirements are too high for instances of that size.
• If you use network policy with GKE Workload Identity, you must allow egress to the following IP addresses and port numbers so your Pods can communicate with the GKE metadata server. For clusters running GKE version 1.21.0-gke.1000 and later, allow egress to 169.254.169.252/32 on port 988. For clusters running GKE versions prior to 1.21.0-gke.1000, allow egress to 127.0.0.1/32 on port 988. To avoid disruptions during auto-upgrades, allow egress to all of these IP addresses and ports.

For more information about node machine types and allocatable resources, see Standard cluster architecture - Nodes.

Migrating from Calico to GKE Dataplane V2

If you migrate your network policies from Calico to GKE Dataplane V2, consider the following limitations:

• You cannot use a Pod or Service IP address in the ipBlock.cidr field of a NetworkPolicy manifest. You must reference workloads using labels. For example, the following configuration is invalid:

  - ipBlock:
      cidr: 10.8.0.6/32
  

• You cannot specify an empty ports.port field in a NetworkPolicy manifest. If you specify a port, you must also specify a protocol. For example, the following configuration is invalid:

  ingress:
  - ports:
    - protocol: TCP
  

Working with HTTP(S) Load Balancing

When an Ingress is applied to a Service to build an HTTP(S) load balancer, you must configure the network policy applied to Pods behind that Service to allow the appropriate HTTP(S) load balancer health check IP ranges. If you are using an internal HTTP(S) load balancer, you must also configure the network policy to allow the proxy-only subnet.

If you are not using container-native load balancing with network endpoint groups, node ports for a Service might forward connections to Pods on other nodes unless they are prevented from doing so by setting externalTrafficPolicy to Local in the Service definition. If externalTrafficPolicy is not set to Local, the network policy must also allow connections from other node IPs in the cluster.

Known issues

StatefulSet pod termination with Calico

GKE clusters with Calico network policy enabled might experience an issue where a StatefulSet pod drops existing connections when the pod is deleted. After a pod enters the Terminating state, the terminationGracePeriodSeconds configuration in the pod spec is not honored and causes disruptions for other applications that have an existing connection with the StatefulSet pod. For more information about this issue, see Calico issue #4710.

This issue affects the following GKE versions:

• 1.18
• 1.19 to 1.19.16-gke.99
• 1.20 to 1.20.11-gke.1299
• 1.21 to 1.21.4-gke.1499

To mitigate this issue, upgrade your GKE control plane to one of the following versions:

• 1.19.16-gke.100 or later
• 1.20.11-gke.1300 or later
• 1.21.4-gke.1500 or later

What's next

• Follow the Network Policies tutorial.
• Read the Kubernetes documentation about network policies.
• Implement common approaches to restrict traffic using network policies.
• Using network policy logging.
• Use security insights to explore other ways to harden your infrastructure