HCloudMachineTemplate and ipv6 not working

[erkules]

/kind bug

What steps did you take and what happened:
I was trying to deploy ipv6 only machines.

apiVersion: infrastructure.cluster.x-k8s.io/v1beta1
kind: HCloudMachineTemplate
metadata:
  name: name-md-0
spec:
  template:
    spec:
      publicNetwork:
        enableIPv4:   false
        enableIPv6:   true

What did you expect to happen:
I was expecting ipv6 only machines

Anything else you would like to add:
nothing

Environment:

• cluster-api-provider-hetzner version: caph:v1.0.0
• Kubernetes version: 1.30.1
• OS (e.g. from /etc/os-release):

[janiskemper]

We use the hcloud-go provider for this:

cluster-api-provider-hetzner/pkg/services/hcloud/server/server.go

Line 379 in c6cab3c

EnableIPv6: s.scope.HCloudMachine.Spec.PublicNetwork.EnableIPv6,

There is no more logic involved in CAPH to control this. Maybe you can explain a bit more what happens, so that the root cause of your problem is easier to find?

[erkules]

I use the setting you see above. The machines are created but also with a ipv4 interface.
That's all. I had the impression this is sufficient to tell hetzner to create machines without ipv4.
Or do I need to fulfill more requirements?

[janiskemper]

@apricote do you know?

[apricote]

This IPv4 is always enabled if the cluster does not use private networks, maybe thats the cause?

cluster-api-provider-hetzner/pkg/services/hcloud/server/server.go

Lines 463 to 466 in c6cab3c

	// if no private network exists, there must be an IPv4 for the load balancer
	if !s.scope.HetznerCluster.Spec.HCloudNetwork.Enabled {
	opts.PublicNet.EnableIPv4 = true
	}