Support Docker Desktop port forwarding for talosctl kubeconfig

[PhilipSchmid]

Hi there 👋,

When setting up a Talos-in-Docker cluster using talosctl like this:

talos-local-cluster-patch.yaml:

cluster:
  allowSchedulingOnControlPlanes: true # required if only a single node cluster
  network:
    cni:
      name: none
  proxy:
    disabled: false
    mode: iptables

talosctl cluster create \
  --controlplanes 1 \
  --workers 0 \
  --kubernetes-version 1.31.0 \
  --image ghcr.io/siderolabs/talos:v1.8.0 \
  --install-image ghcr.io/siderolabs/installer:v1.8.0 \
  --config-patch-control-plane @talos-local-cluster-patch.yaml \
  --config-patch-control-plane '[{"op": "remove", "path": "/cluster/apiServer/admissionControl"}]' \
  --docker-disable-ipv6 \
  --skip-k8s-node-readiness-check

It automatically patches the kubeconfig (by default ~/.kube/config), pointing to the Docker Desktop port forwarded KAPI (e.g., https://127.0.0.1:59886). However, when trying to manually get the kubeconfig using something like talosctl kubeconfig ./talos-kubeconfig -n 10.5.0.2 -f, the server points to, for example, https://10.5.0.2:6443. This doesn't work, as 10.5.0.2:6443 is not reachable from, for example, macOS.

Potential workaround I've been using for far:

# Kubectl
talosctl kubeconfig ./talos-kubeconfig -n 10.5.0.2 -f
# Change server to Docker Desktop port forwarding:
sed -i "s/10.5.0.2:6443/127.0.0.1:$(docker inspect talos-default-controlplane-1 -f json | jq -r '.[].NetworkSettings.Ports["6443/tcp"][].HostPort')/g" ./talos-kubeconfig

However, it would be highly appreciated if there was a specific talosctl kubeconfig flag that would either automatically write the proper Docker port forward information into the kubeconfig or provide a manual flag to override it (not only the IP but also the port). I'd assume the first option wouldn't even be too complicated, as talosctl already has this knowledge from the setup:

PROVISIONER           docker
NAME                  talos-default
NETWORK NAME          talos-default
NETWORK CIDR          10.5.0.0/24
NETWORK GATEWAY       10.5.0.1
NETWORK MTU           1500
KUBERNETES ENDPOINT   https://127.0.0.1:59886