kind cross cluster

init.sh

#!/bin/bash
 
set -eux
 
SUBNET_A="10.10.0.0/16"
SUBNET_B="10.20.0.0/16"
 
CONFIG_A=$(cat <<EOF
kind: Cluster
apiVersion: kind.x-k8s.io/v1alpha4
networking:
  podSubnet: ${SUBNET_A}
  serviceSubnet: 10.96.0.0/12
kubeadmConfigPatches:
- |
  apiVersion: kubeadm.k8s.io/v1beta2
  kind: ClusterConfiguration
  networking:
    dnsDomain: "cluster1.com"
EOF
)
CONFIG_B=$(cat <<EOF
kind: Cluster
apiVersion: kind.x-k8s.io/v1alpha4
networking:
  podSubnet: ${SUBNET_B}
  serviceSubnet: 10.96.0.0/12
kubeadmConfigPatches:
- |
  apiVersion: kubeadm.k8s.io/v1beta2
  kind: ClusterConfiguration
  networking:
    dnsDomain: "cluster2.com"
EOF
)
kind create cluster --name a --config <(echo "${CONFIG_A}") --wait 60s
kind create cluster --name b --config <(echo "${CONFIG_B}") --wait 60s
 
DOCKER_IP_A=$(docker inspect -f "{{ .NetworkSettings.Networks.kind.IPAddress }}" a-control-plane)
DOCKER_IP_B=$(docker inspect -f "{{ .NetworkSettings.Networks.kind.IPAddress }}" b-control-plane)
 
POD_CIDR_A=$(KUBECONFIG="$(kind export kubeconfig --name a)" kubectl get node -ojsonpath='{.items[0].spec.podCIDR}')
POD_CIDR_B=$(KUBECONFIG="$(kind export kubeconfig --name b)" kubectl get node -ojsonpath='{.items[0].spec.podCIDR}')
 
docker exec a-control-plane ip route add ${POD_CIDR_B} via ${DOCKER_IP_B}
docker exec b-control-plane ip route add ${POD_CIDR_A} via ${DOCKER_IP_A}

cat << EOF | kubectl apply --context=kind-a -f -
apiVersion: v1
kind: Service
metadata:
  name: coredns-service
  namespace: kube-system
spec:
  type: NodePort
  selector:
    k8s-app: kube-dns
  ports:
    - name: dns
      port: 53
      protocol: UDP
      targetPort: 53
    - name: dns-tcp
      port: 53
      protocol: TCP
      targetPort: 53
    - name: metrics
      port: 9153
      protocol: TCP
      targetPort: 9153
EOF

cat << EOF | kubectl apply --context=kind-b -f -
apiVersion: v1
kind: Service
metadata:
  name: coredns-service
  namespace: kube-system
spec:
  type: NodePort
  selector:
    k8s-app: kube-dns
  ports:
    - name: dns
      port: 53
      protocol: UDP
      targetPort: 53
    - name: dns-tcp
      port: 53
      protocol: TCP
      targetPort: 53
    - name: metrics
      port: 9153
      protocol: TCP
      targetPort: 9153
EOF