Fixing Kubernetes NetworkPolicy 'endPort' Validation Errors

#Kubernetes #NetworkPolicy #API Validation #Cloud Native #Troubleshooting #Kubernetes Networking

What's the problem?

Learn how to resolve misleading Kubernetes API validation errors when configuring NetworkPolicy port ranges. Improve your cluster debugging and configuration.

Why does this happen?

The error occurs because the Kubernetes API server’s validation logic incorrectly references the starting 'port' value when reporting an 'endPort' violation. This mismatch between the field path and the reported value generates confusing 422 Unprocessable Entity errors during resource creation.

Code Example

apiVersion: networking.k8s.io/v1
kind: NetworkPolicy
metadata:
  name: example-policy
spec:
  ingress:
  - ports:
    - port: 81
      endPort: 80  # INCORRECT: endPort must be >= port
      protocol: TCP

How to fix it

To resolve this, ensure your NetworkPolicy configuration adheres strictly to valid range logic where 'endPort' is greater than or equal to the base 'port'. If you are encountering this error despite correct configuration, verify your Kubernetes API server version. This bug was addressed by updating the validation logic in 'pkg/apis/networking/validation/validation.go' to correctly map the 'endPort' value to the 'field.Invalid' error response, ensuring precise feedback for invalid port ranges.