dns

Alpine requests for CoreDNS service

This example demonstrates how an external client configures DNS from the connected endpoint. Note: NSE provides DNS by itself. Also, NSE could provide configs for any other external DNS servers(that are not located as sidecar with NSE).

Requires

Make sure that you have completed steps from features

Run

Note: Admission webhook is required and should be started at this moment.

WH=$(kubectl get pods -l app=admission-webhook-k8s -n nsm-system --template '{{range .items}}{{.metadata.name}}{{"\n"}}{{end}}')
kubectl wait --for=condition=ready --timeout=1m pod ${WH} -n nsm-system

1. Create test namespace:

NAMESPACE=($(kubectl create -f https://raw.githubusercontent.com/networkservicemesh/deployments-k8s/c89573ec0f82ee02c425c43da72b026397cb52fc/examples/features/namespace.yaml)[0])
NAMESPACE=${NAMESPACE:10}

2. Get all available nodes to deploy:

NODES=($(kubectl get nodes -o go-template='{{range .items}}{{ if not .spec.taints  }}{{index .metadata.labels "kubernetes.io/hostname"}} {{end}}{{end}}'))

3. Create alpine deployment and set nodeSelector to the first node:

cat > alpine.yaml <<EOF
---
apiVersion: v1
kind: Pod
metadata:
  name: alpine
  annotations:
    networkservicemesh.io: kernel://my-coredns-service/nsm-1
  labels:
    app: alpine
    "spiffe.io/spiffe-id": "true"
spec:
  containers:
  - name: alpine
    image: alpine
    imagePullPolicy: IfNotPresent
    stdin: true
    tty: true
  nodeSelector:
    kubernetes.io/hostname: ${NODES[0]}
EOF

4. Add to nse-kernel the corends container and set nodeSelector it to the second node:

cat > patch-nse.yaml <<EOF
---
apiVersion: apps/v1
kind: Deployment
metadata:
  name: nse-kernel
spec:
  template:
    spec:
      containers:
      - name: nse
        env:
          - name: NSM_SERVICE_NAMES
            value: my-coredns-service
          - name: NSM_CIDR_PREFIX
            value: 172.16.1.100/31
          - name: NSM_DNS_CONFIGS
            value: "[{\"dns_server_ips\": [\"172.16.1.100\"], \"search_domains\": [\"my.coredns.service\"]}]"
      - name: coredns
        image: coredns/coredns:1.8.3
        imagePullPolicy: IfNotPresent
        resources:
          limits:
            memory: 170Mi
          requests:
            cpu: 100m
            memory: 70Mi
        args: [ "-conf", "/etc/coredns/Corefile" ]
        volumeMounts:
        - name: config-volume
          mountPath: /etc/coredns
          readOnly: true
        ports:
        - containerPort: 53
          name: dns
          protocol: UDP
        - containerPort: 53
          name: dns-tcp
          protocol: TCP
      nodeSelector:
        kubernetes.io/hostname: ${NODES[1]}
      volumes:
        - name: config-volume
          configMap:
            name: coredns
            items:
            - key: Corefile
              path: Corefile
EOF

5. Create kustomization file:

cat > kustomization.yaml <<EOF
---
apiVersion: kustomize.config.k8s.io/v1beta1
kind: Kustomization

namespace: ${NAMESPACE}

bases:
- https://github.com/networkservicemesh/deployments-k8s/apps/nse-kernel?ref=c89573ec0f82ee02c425c43da72b026397cb52fc

resources:
- alpine.yaml
- https://raw.githubusercontent.com/networkservicemesh/deployments-k8s/c89573ec0f82ee02c425c43da72b026397cb52fc/examples/features/dns/coredns-config-map.yaml

patchesStrategicMerge:
- patch-nse.yaml
EOF

6. Deploy alpine and nse

kubectl apply -k .

7. Wait for applications ready:

kubectl wait --for=condition=ready --timeout=5m pod alpine -n ${NAMESPACE}

kubectl wait --for=condition=ready --timeout=5m pod -l app=nse-kernel -n ${NAMESPACE}

8. Find NSC and NSE pods by labels:

NSC=$(kubectl get pods -l app=alpine -n ${NAMESPACE} --template '{{range .items}}{{.metadata.name}}{{"\n"}}{{end}}')

NSE=$(kubectl get pods -l app=nse-kernel -n ${NAMESPACE} --template '{{range .items}}{{.metadata.name}}{{"\n"}}{{end}}')

9. Install nslookup to alpine:

kubectl exec ${NSC} -c alpine -n ${NAMESPACE} -- sh -c "apk update && apk add bind-tools"

10. Ping from alpine to NSE by domain name:

kubectl exec ${NSC} -c alpine -n ${NAMESPACE} -- nslookup -nodef -norec my.coredns.service

kubectl exec ${NSC} -c alpine -n ${NAMESPACE} -- ping -c 4 my.coredns.service

11. Validate that default DNS server is working:

kubectl exec ${NSC} -c alpine -n ${NAMESPACE} -- nslookup -nodef google.com

Cleanup

Delete ns:

kubectl delete ns ${NAMESPACE}