add example of linkerd integration

Signed-off-by: Nikita Skrynnik <[email protected]>

examples/interdomain/linkerd/README.md

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+# NSM + linkerd interdomain example over kind clusters
+
+This diagram shows that we have 2 clusters with NSM and also linkerd deployed on the Cluster-2.
+
+In this example, we deploy an http-server (**Workload-2**) on the Cluster-2 and show how it can be reached from Cluster-1.
+
+The client will be `alpine` (**Workload-1**), we will use curl.
+
+## Requires
+
+- [Load balancer](../../loadbalancer)
+- [Interdomain DNS](../../dns)
+- [Interdomain spire](../../spire)
+- [Interdomain nsm](../../nsm)
+
+
+## Run
+
+```bash
+export KUBECONFIG=$KUBECONFIG2
+linkerd check --pre
+linkerd install --crds | kubectl apply -f -
+linkerd install | kubectl apply -f -
+linkerd check
+```
+
+Install networkservice for the second cluster:
+```bash
+kubectl create ns ns-nsm-linkerd
+kubectl apply -f ./networkservice.yaml
+```
+
+Start `alpine` with networkservicemesh client on the first cluster:
+
+```bash
+kubectl --kubeconfig=$KUBECONFIG1 apply -f ./greeting/client.yaml
+```
+
+Start `auto-scale` networkservicemesh endpoint:
+```bash
+kubectl --kubeconfig=$KUBECONFIG2 apply -k ./nse-auto-scale
+```
+
+Install http-server for the second cluster:
+```bash
+export KUBECONFIG=$KUBECONFIG2
+kubectl apply -f ./greeting/server.yaml
+kubectl get deploy greeting -o yaml | linkerd inject - | kubectl apply -f -
+```
+
+
+Wait for the `alpine` client to be ready:
+```bash
+kubectl --kubeconfig=$KUBECONFIG1 wait --timeout=2m --for=condition=ready pod -l app=alpine
+```
+
+Install everything for client:
+```bash
+kubectl --kubeconfig=$KUBECONFIG1 exec deploy/alpine -c alpine -- apk add curl
+kubectl --kubeconfig=$KUBECONFIG1 exec deploy/alpine -c alpine -- apk add iproute2
+kubectl --kubeconfig=$KUBECONFIG1 exec deploy/alpine -c alpine -- apk add iptables
+```
+
+```bash
+kubectl --kubeconfig=$KUBECONFIG1 exec deploy/alpine -c alpine -- iptables -t mangle -A OUTPUT -p tcp -d 199.0.0.0/8 -j MARK --set-mark 8
+kubectl --kubeconfig=$KUBECONFIG1 exec deploy/alpine -c alpine -- iptables -t nat -A OUTPUT -m mark --mark 8 -j NETMAP --to 10.0.0.0/8
+kubectl --kubeconfig=$KUBECONFIG1 exec deploy/alpine -c alpine -- iptables -t nat -A POSTROUTING -m mark --mark 8 -j SNAT --to 172.16.1.3
+```
+
+```bash
+kubectl --kubeconfig=$KUBECONFIG1 exec deploy/alpine -c alpine -- echo 201 nsm_table >> /etc/iproute2/rt_tables
+kubectl --kubeconfig=$KUBECONFIG1 exec deploy/alpine -c alpine -- ip ru add fwmark 8 lookup nsm_table pref 3333
+kubectl --kubeconfig=$KUBECONFIG1 exec deploy/alpine -c alpine -- ip ro add default via 172.16.1.3 table nsm_table
+```
+
+Verify connectivity:
+```bash
+kubectl --kubeconfig=$KUBECONFIG1 exec deploy/alpine -c alpine -- curl -s greeting.default:9080 | grep -o "hello world from linkerd"
+```
+**Expected output** is "hello world from linkerd"
+
+Congratulations! 
+You have made a interdomain connection between two clusters via NSM + linkerd!
+
+## Cleanup
+
+```bash
+export KUBECONFIG=$KUBECONFIG2
+kubectl delete deployment greeting
+kubectl delete ns ns-nsm-linkerd
+linkerd uninstall | kubectl delete -f -
+```
+
+```bash
+kubectl --kubeconfig=$KUBECONFIG1 delete deployment alpine
+```

examples/interdomain/linkerd/greeting/client.yaml

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+---
+apiVersion: apps/v1
+kind: Deployment
+metadata:
+  name: alpine
+  labels:
+    app: alpine
+spec:
+  replicas: 1
+  selector:
+    matchLabels:
+      app: alpine
+  template:
+    metadata:
+      labels:
+        app: alpine
+      annotations:
+        networkservicemesh.io: kernel://[email protected]/nsm-1?app=greeting
+    spec:
+      containers:
+        - name: alpine
+          image: alpine:3.15.0
+          imagePullPolicy: IfNotPresent
+          stdin: true
+          tty: true
+          securityContext:
+            privileged: true
+        - name: server
+          image: hashicorp/http-echo:alpine
+          args:
+            - -text="hello world from greeting.cluster1"
+            - -listen=:9081
+          ports:
+            - containerPort: 9081
+              name: http

examples/interdomain/linkerd/greeting/server.yaml

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+---
+apiVersion: v1
+kind: Service
+metadata:
+  name: greeting
+  labels:
+    app: greeting
+    service: greeting
+spec:
+  ports:
+  - port: 9080
+    name: http
+  selector:
+    app: greeting
+---
+apiVersion: v1
+kind: ServiceAccount
+metadata:
+  name: greeting-sa
+  labels:
+    account: greeting
+---
+apiVersion: apps/v1
+kind: Deployment
+metadata:
+  name: greeting
+  labels:
+    app: greeting
+  annotations:
+    linkerd.io/inject: enabled
+spec:
+  replicas: 1
+  selector:
+    matchLabels:
+      app: greeting
+  template:
+    metadata:
+      labels:
+        app: greeting
+    spec:
+      serviceAccountName: greeting-sa
+      containers:
+      - name: server
+        image: hashicorp/http-echo:alpine
+        args:
+          - -text="hello world from linkerd"
+          - -listen=:9080
+        ports:
+          - containerPort: 9080
+            name: http
+---

examples/interdomain/linkerd/networkservice.yaml

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+---
+apiVersion: networkservicemesh.io/v1
+kind: NetworkService
+metadata:
+  name: nsm-linkerd
+  namespace: nsm-system
+spec:
+  payload: IP
+  matches:
+    - source_selector:
+      fallthrough: true
+      routes:
+        - destination_selector:
+            podName: "{{ .podName }}"
+    - source_selector:
+      routes:
+        - destination_selector:
+            any: "true"

examples/interdomain/linkerd/nse-auto-scale/iptables-map.yaml

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+---
+- -t nat -I PREROUTING 1 -p tcp -i {{ .NsmInterfaceName }} -j DNAT --to-destination 127.0.0.1:4140

examples/interdomain/linkerd/nse-auto-scale/kustomization.yaml

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+---
+apiVersion: kustomize.config.k8s.io/v1beta1
+kind: Kustomization
+
+namespace: ns-nsm-linkerd
+bases:
+- https://github.com/networkservicemesh/deployments-k8s/apps/nse-supplier-k8s?ref=5278bf09564d36b701e8434d9f1d4be912e6c266
+
+patchesStrategicMerge:
+- patch-supplier.yaml
+
+configMapGenerator:
+  - name: supplier-pod-template-configmap
+    files:
+      - pod-template.yaml
+  - name: iptables-map
+    files:
+      - iptables-map.yaml
+
+generatorOptions:
+  disableNameSuffixHash: true

examples/interdomain/linkerd/nse-auto-scale/patch-supplier.yaml

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+---
+apiVersion: apps/v1
+kind: Deployment
+metadata:
+  name: nse-supplier-k8s
+spec:
+  template:
+    spec:
+      containers:
+        - name: nse-supplier
+          env:
+            - name: NSM_SERVICE_NAME
+              value: nsm-linkerd
+            - name: NSM_LABELS
+              value: any:true
+            - name: NSM_NAMESPACE
+              valueFrom:
+                fieldRef:
+                  fieldPath: metadata.namespace
+            - name: NSM_POD_DESCRIPTION_FILE
+              value: /run/supplier/pod-template.yaml
+          volumeMounts:
+            - name: pod-file
+              mountPath: /run/supplier
+              readOnly: true
+      volumes:
+        - name: pod-file
+          configMap:
+            name: supplier-pod-template-configmap

examples/interdomain/linkerd/nse-auto-scale/pod-template.yaml

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+---
+apiVersion: apps/v1
+kind: Pod
+metadata:
+  name: proxy-{{ index .Labels "podName" }}
+  labels:
+    "spiffe.io/spiffe-id": "true"
+  annotations:
+    linkerd.io/inject: enabled
+    config.linkerd.io/enable-debug-sidecar: "false"
+spec:
+  restartPolicy: Never
+  containers:
+    - name: nse
+      image: nikitaxored/cmd-nse-l7-proxy:custom-subnet
+      imagePullPolicy: IfNotPresent
+      securityContext:
+        privileged: true
+      env:
+        - name: SPIFFE_ENDPOINT_SOCKET
+          value: unix:///run/spire/sockets/agent.sock
+        - name: NSM_NAME
+          valueFrom:
+            fieldRef:
+              fieldPath: metadata.name
+        - name: POD_NAME
+          value: {{ index .Labels "podName" }}
+        - name: NSM_CONNECT_TO
+          value: unix:///var/lib/networkservicemesh/nsm.io.sock
+        - name: NSM_CIDR_PREFIX
+          value: 172.16.1.2/31
+        - name: NSM_SERVICE_NAMES
+          value: nsm-linkerd
+        - name: NSM_LABELS
+          value: app:{{ index .Labels "app" }}
+        - name: NSM_IDLE_TIMEOUT
+          value: 240s
+        - name: NSM_LOG_LEVEL
+          value: TRACE
+        - name: NSM_REWRITEIP
+          value: "false"
+        - name: NSM_POD_IP
+          valueFrom:
+            fieldRef:
+              fieldPath: status.podIP
+        - name: NSM_RULES_CONFIG_PATH
+          value: iptables-map/iptables-map.yaml
+        - name: NSM_REGISTRY_CLIENT_POLICIES
+          value: ""
+      volumeMounts:
+        - name: spire-agent-socket
+          mountPath: /run/spire/sockets
+          readOnly: true
+        - name: nsm-socket
+          mountPath: /var/lib/networkservicemesh
+          readOnly: true
+        - name: iptables-config-map
+          mountPath: /iptables-map
+      resources:
+        limits:
+          memory: 40Mi
+          cpu: 150m
+  volumes:
+    - name: spire-agent-socket
+      hostPath:
+        path: /run/spire/sockets
+        type: Directory
+    - name: nsm-socket
+      hostPath:
+        path: /var/lib/networkservicemesh
+        type: DirectoryOrCreate
+    - name: iptables-config-map
+      configMap:
+        name: iptables-map