`hostPort` is ignored within VPC CNI plugin

[nabeelpaytrix]

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What happened: I am using the Datadog Agent helm chart and I wish to configure it to expose a hostPort on each of the pods from the Datadog DaemonSet. The port number is 8126, therefore I expect each node in my cluster to be listening on this port.

The port config within the DaemonSet is:

containers:
 - name: trace-agent
    ports:
    - containerPort: 8126
      hostPort: 8126
      name: traceport
      protocol: TCP

The Pods do indeed have this port listening within them, running netstat -tln within the pod shows the following:

Proto Recv-Q Send-Q Local Address           Foreign Address         State 
tcp6       0      0 :::8126                 :::*                    LISTEN 

However the host is not exposing this same port, running netstat -tln within the Host does not show 8126 is listening.

What you expected to happen: Both Pods and Host should be exposing this port.

How to reproduce it (as minimally and precisely as possible):

Enable a version v1.18.3-eksbuild.2 VPC CNI plugin within an version v1.29 AWS EKS cluster.

deploy the following nginx-pod.yml

apiVersion: v1
kind: Pod
metadata:
  name: nginx-hostport
  namespace: default
  labels:
    app: nginx
spec:
  containers:
  - name: nginx
    image: nginx
    ports:
    - containerPort: 8126
      hostPort: 8126
      protocol: TCP
    command: ["/bin/sh", "-c"]
    args:
    - |
      echo 'server {
              listen 8126;
              location / {
                  return 200 "Hello from Nginx running on port 8126!\n";
              }
            }' > /etc/nginx/conf.d/default.conf && nginx -g 'daemon off;'
  restartPolicy: Always

Observe that the host is not listening on port 8126, but the pod is.

Anything else we need to know?:

The aws-node DaemonSet pods do not display any errors related to the hostPort.

Environment:

• Kubernetes version (use kubectl version): 1.29
• CNI Version: v1.18.3-eksbuild.2
• OS (e.g: cat /etc/os-release): Amazon Linux 2
• Kernel (e.g. uname -a): Linux ip-x-x-x-x.eu-west-2.compute.internal 5.10.217-205.860.amzn2.x86_64 #1 SMP Tue May 21 16:52:24 UTC 2024 x86_64 x86_64 x86_64 GNU/Linux