Cilium fails to start with IPv4 disabled

[ken-letter]

Bug report

General Information

• Cilium version 1.9.3
• Kernel version 5.10.12-200.fc33.x86_64
• Orchestration system version in use kubectl version

Client Version: version.Info{Major:"1", Minor:"20", GitVersion:"v1.20.4", GitCommit:"e87da0bd6e03ec3fea7933c4b5263d151aafd07c", GitTreeState:"clean", BuildDate:"2021-02-18T16:12:00Z", GoVersion:"go1.15.8", Compiler:"gc", Platform:"linux/amd64"}

• Link to relevant artifacts: (similar to) kubeadm configuration
• Generate and upload a system zip: -

How to reproduce the issue

1. Setup kubernetes with kubeadm, using only IPv6 subnets
2. install cilium with helm as follows: helm install cilium cilium/cilium --version 1.9.4 --namespace kube-system --set ipv4.enabled=false --set ipv6.enabled=true
3. observe cilium pods fail to start successfully:

$ kubectl get pods --all-namespaces
NAMESPACE     NAME                                                                     READY   STATUS              RESTARTS   AGE
kube-system   cilium-operator-5cdf66574-4hq7n                                          1/1     Running             0          55s
kube-system   cilium-operator-5cdf66574-j4sl2                                          0/1     Pending             0          55s
kube-system   cilium-xwg4g                                                             0/1     Error               2          55s
...

$ kubectl logs --namespace kube-system cilium-xwg4g
...
level=info msg="  --enable-ipv4='false'" subsys=daemon
level=info msg="  --ipv4-node='auto'" subsys=daemon
...
level=fatal msg="postinit failed" error="external IPv4 node address could not be derived, please configure via --ipv4-node" subsys=daemon

[nebril]

By looking at the code: https://github.com/cilium/cilium/blob/v1.9.3/pkg/node/address.go#L305 it seems like we do not support IPv6 only when tunneling is enabled (tunneling is enabled by default). Can you run with tunneling disabled (--set tunnel=disabled)?

[pchaigno]

@tgraf changed this condition in 0c22956, maybe he has more info on why this is unsupported.

[ken-letter]

Disabling does allow cilium to proceed launching, but this leaves the networking in a fairly useless state.

[stale]

This issue has been automatically marked as stale because it has not had recent activity. It will be closed if no further activity occurs.

[stale]

This issue has not seen any activity since it was marked stale. Closing.

[notpeelz]

Can this issue be reopened? Why is the ipv4 stack required for --routing-mode tunnel?