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Network Policies

• Prerequisites
• Configuring Namespace Isolation Policy
• The NetworkPolicy Resource

A network policy is a specification of how selections of pods are allowed to communicate with each other and other network endpoints.

NetworkPolicy resources use labels to select pods and define whitelist rules which allow traffic to the selected pods in addition to what is allowed by the isolation policy for a given namespace.

Prerequisites

You must enable the extensions/v1beta1/networkpolicies runtime config in your apiserver to enable this resource.

You must also be using a networking solution which supports NetworkPolicy - simply creating the resource without a controller to implement it will have no effect.

Configuring Namespace Isolation Policy

Isolation can be configured on a per-namespace basis. Once isolation is configured on a namespace it will be applied to all pods in that namespace. Currently, only isolation policy on inbound traffic (ingress) can be defined.

The following ingress isolation types being supported:

• DefaultDeny: Pods in the namespace will be inaccessible from any source except the pod’s local node.

Ingress isolation can be enabled using an annotation on the Namespace.

kind: Namespace
apiVersion: v1
metadata:
  annotations:
    net.beta.kubernetes.io/network-policy: |
      {
        "ingress": {
          "isolation": "DefaultDeny"
        }
      }

To configure the annotation via kubectl:

kubectl annotate ns <namespace> "net.beta.kubernetes.io/network-policy={\"ingress\": {\"isolation\": \"DefaultDeny\"}}"

The NetworkPolicy Resource

See the api-reference for a full definition of the resource.

A minimal NetworkPolicy might look like this:

apiVersion: extensions/v1beta1
kind: NetworkPolicy
metadata:
 name: test-network-policy
spec:
 podSelector:
  matchLabels:
    role: db
 ingress:
  - from:
     - podSelector:
        matchLabels:
         role: frontend
    ports:
     - protocol: tcp
       port: 6379

POSTing this to the API server will have no effect unless your chosen networking solution supports network policy.

Mandatory Fields: As with all other Kubernetes config, a NetworkPolicy needs apiVersion, kind, and metadata fields. For general information about working with config files, see here, here, and here.

spec: NetworkPolicy spec has all the information needed to define a network isolation policy in the deployed controller.

podSelector: Each NetworkPolicy includes a podSelector which selects the grouping of pods to which the ingress rules in the policy apply.

ingress: Each NetworkPolicy includes a list of whitelist ingress rules. Each rule allows traffic which matches both the from and ports sections.