NetworkPolicy

NetworkPolicy is a Kubernetes object used to restrict pod access. In CCE, by setting network policies, you can define ingress rules specifying the addresses to access pods or egress rules specifying the addresses pods can access. This is equivalent to setting up a firewall at the application layer to further ensure network security.

Network policies depend on the networking add-on of the cluster to which the policies apply.

By default, if a namespace does not have any policy, pods in the namespace accept traffic from any source and send traffic to any destination.

NetworkPolicy rules are classified into the following types:

namespaceSelector: This selects particular namespaces for which all pods should be allowed as ingress sources or egress destinations.
podSelector: This selects particular pods in the same namespace as the NetworkPolicy which should be allowed as ingress sources or egress destinations.
ipBlock: This selects particular IP CIDR ranges to allow as ingress sources or egress destinations.

Using Ingress Rules

Using podSelector to specify the access scope

apiVersion: networking.k8s.io/v1
kind: NetworkPolicy
metadata:
  name: test-network-policy
  namespace: default
spec:
  podSelector:                  # The rule takes effect for pods with the role=db label.
    matchLabels:
      role: db
  ingress:                      # This is an ingress rule.
  - from:
    - podSelector:              # Only traffic from the pods with the "role=frontend" label is allowed.
        matchLabels:
          role: frontend
    ports:                      # Only TCP can be used to access port 6379.
    - protocol: TCP
      port: 6379

The following figure shows how podSelector works.

Figure 1 podSelector

Using namespaceSelector to specify the access scope

apiVersion: networking.k8s.io/v1
kind: NetworkPolicy
metadata:
  name: test-network-policy
spec:
  podSelector:                  # The rule takes effect for pods with the role=db label.
    matchLabels:
      role: db
  ingress:                      # This is an ingress rule.
  - from:
    - namespaceSelector:        # Only traffic from the pods in the namespace with the "project=myproject" label is allowed.
        matchLabels:
          project: myproject
    ports:                      # Only TCP can be used to access port 6379.
    - protocol: TCP
      port: 6379

The following figure shows how namespaceSelector works.

Figure 2 namespaceSelector