Question

Server on kubernetes not responding to UDP calls.

Posted November 14, 2021 115 views
KubernetesDigitalOcean Managed Kubernetes

We have encountered an issue with running a relay server that processes UDP calls on DigitalOcean Kubernetes cluster. Even with fully open inbound UDP port range allowing all UDP traffic to go trough firewall, the server still doesn’t seem to respond when pinged.

The k8’s deployment is configured to use host network.

I listed the added firewall rules below.

  [...]
  inbound_rule {
    protocol         = "udp"
    port_range       = "1-65535"
    source_addresses = ["0.0.0.0/0", "::/0"]
  }

  outbound_rule {
    protocol              = "udp"
    port_range            = "1-65535"
    destination_addresses = ["0.0.0.0/0", "::/0"]
  }

  outbound_rule {
    protocol              = "tcp"
    port_range            = "1-65535"
    destination_addresses = ["0.0.0.0/0", "::/0"]
  }

  outbound_rule {
    protocol              = "icmp"
    port_range            = "1-65535"
    destination_addresses = ["0.0.0.0/0", "::/0"]
  }
  [...]

A note: The server works without issues when deployed as a simple docker container without Kubernetes, that leads us to think that the issue could be related Kubernetes, but we haven’t found a specific explanation for that yet.

2 comments
  • Could I see your service config.yaml?

  • Here is the k8’s deployment config.

    apiVersion: apps/v1
    kind: Deployment
    metadata:
      name: relay-server
    spec:
      replicas: 1
      selector:
        matchLabels:
          app: relay-server
      template:
        metadata:
          labels:
            app: relay-server
        spec:
          hostNetwork: true
          containers:
            - name: relay-server
              image: ***
              imagePullPolicy: Always
    

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