NetworkPolicy

NetworkPolicy is a Kubernetes object used to restrict pod access. By setting a NetworkPolicy, you can define ingress rules specifying what addresses can be allowed to the selected pods or egress rules specifying what addresses can be allowed from the selected pods. This is equivalent to setting up a firewall at the application layer to further ensure network security.

NetworkPolicy is implemented by the network plugin of the cluster to which NetworkPolicy will apply. Therefore, the type of rules supported by NetworkPolicy depends on the network plugin. For example, CCE clusters support only ingress rules of pods.

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. Currently, CCE does not support ipBlock.

Using podSelector to Select Ingress Sources and Egress Destinations

apiVersion: networking.k8s.io/v1
kind: NetworkPolicy
metadata:
  name: test-network-policy
  namespace: default
spec:
  podSelector:
    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

Figure 1 shows how podSelector selects ingress sources.

Figure 1 podSelector

Using namespaceSelector to Select Ingress Sources

apiVersion: networking.k8s.io/v1
kind: NetworkPolicy
metadata:
  name: test-network-policy
spec:
  podSelector:
    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

Figure 2 shows how namespaceSelector selects ingress sources.

Figure 2 namespaceSelector