Basic policy demo

11 MINUTE READ

This guide provides a simple demo to illustrate basic pod-to-pod connectivity and the application of network policy in a Calico for Windows cluster. We will create client and server pods on Linux and Windows nodes, verify connectivity between the pods, and then we’ll apply a basic network policy to isolate pod traffic.

Prerequisites

To run this demo, you will need a Calico for Windows cluster with Windows Server 1809 (build 17763.1432 August 2020 update or newer). More recent versions of Windows Server can be used with a change to the demo manifests.

Note: Windows Server 1809 (build older than 17763.1432) do not support direct server return. This means that policy support is limited to only pod IP addresses.

Create pods on Linux nodes

First, create a client (busybox) and server (nginx) pod on the Linux nodes:

kubectl apply -f - <<EOF
apiVersion: v1
kind: Namespace
metadata:
  name: calico-demo

---

apiVersion: v1
kind: Pod
metadata:
  labels:
    app: busybox
  name: busybox
  namespace: calico-demo
spec:
  containers:
  - args:
    - /bin/sh
    - -c
    - sleep 360000
    image: busybox:1.28
    imagePullPolicy: Always
    name: busybox
  nodeSelector:
    beta.kubernetes.io/os: linux

---

apiVersion: v1
kind: Pod
metadata:
  labels:
    app: nginx
  name: nginx
  namespace: calico-demo
spec:
  containers:
  - name: nginx
    image: nginx:1.8
    ports:
    - containerPort: 80
  nodeSelector:
    beta.kubernetes.io/os: linux
EOF

Create pods on Window nodes

Next, we’ll create a client (powershell) and server (porter) pod on the Windows nodes. First the create the powershell pod.

Note: The powershell and porter pod manifests below use images based on mcr.microsoft.com/windows/servercore:1809. If you are using a more recent Windows Server version, update the manifests to use a servercore image that matches your Windows Server version.

kubectl apply -f - <<EOF
apiVersion: v1
kind: Pod
metadata:
  name: pwsh
  namespace: calico-demo
  labels:
    app: pwsh
spec:
  containers:
  - name: pwsh
    image: mcr.microsoft.com/windows/servercore:1809
    args:
    - powershell.exe
    - -Command
    - "Start-Sleep 360000"
    imagePullPolicy: IfNotPresent
  nodeSelector:
    kubernetes.io/os: windows
EOF

Next, we’ll create the porter server pod:

kubectl apply -f - <<EOF
apiVersion: v1
kind: Pod
metadata:
  name: porter
  namespace: calico-demo
  labels:
    app: porter
spec:
  containers:
  - name: porter
    image: calico/porter:1809
    ports:
    - containerPort: 80
    env:
    - name: SERVE_PORT_80
      value: This is a Calico for Windows demo.
    imagePullPolicy: IfNotPresent
  nodeSelector:
    kubernetes.io/os: windows
EOF

Check connectivity between pods on Linux and Windows nodes

Now that client and server pods are running on both Linux and Windows nodes, let’s verify that client pods on Linux nodes can reach server pods on Windows nodes. First, we will need the porter pod IP:

kubectl get po porter -n calico-demo -o 'jsonpath={.status.podIP}'

Then we can exec into the busybox pod and try reaching the porter pod on port 80:

kubectl exec -n calico-demo busybox -- nc -vz <porter_ip> 80

To combine both of the above steps:

kubectl exec -n calico-demo busybox -- nc -vz $(kubectl get po porter -n calico-demo -o 'jsonpath={.status.podIP}') 80

If the connection from the busybox pod to the porter pod succeeds, we will get output similar to the following:

192.168.40.166 (192.168.40.166:80) open

Now let’s verify that the powershell pod can reach the nginx pod:

kubectl exec -n calico-demo pwsh -- powershell Invoke-WebRequest -Uri http://$(kubectl get po nginx -n calico-demo -o 'jsonpath={.status.podIP}') -UseBasicParsing -TimeoutSec 5

If the connection succeeds, we will get output similar to:

StatusCode        : 200
StatusDescription : OK
Content           : <!DOCTYPE html>
                    <html>
                    <head>
                    <title>Welcome to nginx!</title>
                    <style>
                        body {
                            width: 35em;
                            margin: 0 auto;
                            font-family: Tahoma, Verdana, Arial, sans-serif;
                        }
                    </style>
                    <...
...

Finally, let’s verify that the powershell pod can reach the porter pod:

kubectl exec -n calico-demo pwsh -- powershell Invoke-WebRequest -Uri http://$(kubectl get po porter -n calico-demo -o 'jsonpath={.status.podIP}') -UseBasicParsing -TimeoutSec 5

If that succeeds, we will see something like:

StatusCode        : 200
StatusDescription : OK
Content           : This is a Calico for Windows demo.
RawContent        : HTTP/1.1 200 OK
                    Content-Length: 49
                    Content-Type: text/plain; charset=utf-8
                    Date: Fri, 21 Aug 2020 22:45:46 GMT

                    This is a Calico for Windows demo.
Forms             :
Headers           : {[Content-Length, 49], [Content-Type, text/plain;
                    charset=utf-8], [Date, Fri, 21 Aug 2020 22:45:46 GMT]}
Images            : {}
InputFields       : {}
Links             : {}
ParsedHtml        :
RawContentLength  : 49

Apply policy to the Windows client pod

Now let’s apply a basic network policy that allows only the busybox pod to reach the porter pod.

calicoctl apply -f - <<EOF
apiVersion: projectcalico.org/v3
kind: NetworkPolicy
metadata:
  name: allow-busybox
  namespace: calico-demo
spec:
  selector: app == 'porter'
  types:
  - Ingress
  ingress:
  - action: Allow
    protocol: TCP
    source:
      selector: app == 'busybox'
EOF

With the policy in place, the busybox pod should still be able to reach the porter pod:

kubectl exec -n calico-demo busybox -- nc -vz $(kubectl get po porter -n calico-demo -o 'jsonpath={.status.podIP}') 80

However, the powershell pod will not able to reach the porter pod:

kubectl exec -n calico-demo pwsh -- powershell Invoke-WebRequest -Uri http://$(kubectl get po porter -n calico-demo -o 'jsonpath={.status.podIP}') -UseBasicParsing -TimeoutSec 5

The request times out with a message like:

Invoke-WebRequest : The operation has timed out.
At line:1 char:1
+ Invoke-WebRequest -Uri http://192.168.40.166 -UseBasicParsing -Timeou ...
+ ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
    + CategoryInfo          : InvalidOperation: (System.Net.HttpWebRequest:Htt
   pWebRequest) [Invoke-WebRequest], WebException
    + FullyQualifiedErrorId : WebCmdletWebResponseException,Microsoft.PowerShe
   ll.Commands.InvokeWebRequestCommand

command terminated with exit code 1

Wrap up

In this demo we’ve brought up pods on Linux and Windows nodes, verified basic pod connectivity, and tried a basic network policy to isolate pod to pod traffic. Finally, we can clean up all of our demo resources:

kubectl delete ns calico-demo

Installing kubectl on Windows

To run the commands in this demo you need the Windows version of kubectl installed and add it to the system path. Install kubectl and move the kubectl binary to c:\k.

Add c:\k to the system path

  1. Open a PowerShell window as Administrator

     $env:Path += ";C:\k"
    
  2. Close all PowerShell windows.

Create pods on Linux nodes

First, create a client (busybox) and server (nginx) pod on the Linux nodes.

Create a YAML file policy-demo-linux.yaml using your favorite editor on Windows


apiVersion: v1
kind: Namespace
metadata:
  name: calico-demo

---

apiVersion: v1
kind: Pod
metadata:
  labels:
    app: busybox
  name: busybox
  namespace: calico-demo
spec:
  containers:
  - args:
    - /bin/sh
    - -c
    - sleep 360000
    image: busybox:1.28
    imagePullPolicy: Always
    name: busybox
  nodeSelector:
    beta.kubernetes.io/os: linux

---

apiVersion: v1
kind: Pod
metadata:
  labels:
    app: nginx
  name: nginx
  namespace: calico-demo
spec:
  containers:
  - name: nginx
    image: nginx:1.8
    ports:
    - containerPort: 80
  nodeSelector:
    beta.kubernetes.io/os: linux

Apply the policy-demo-linux.yaml file to the Kubernetes cluster

  1. Open a PowerShell window.
  2. Use kubectl to apply the policy-demo-linux.yaml configuration.
kubectl apply -f policy-demo-linux.yaml

Create pods on Window nodes

Next, we’ll create a client (pwsh) and server (porter) pod on the Windows nodes.

Note: The pwsh and porter pod manifests below use images based on mcr.microsoft.com/windows/servercore:1809. If you are using a more recent Windows Server version, update the manifests to use a servercore image that matches your Windows Server version.

Create the policy-demo-windows.yaml using your favorite editor on Windows


apiVersion: v1
kind: Pod
metadata:
  name: pwsh
  namespace: calico-demo
  labels:
    app: pwsh
spec:
  containers:
  - name: pwsh
    image: mcr.microsoft.com/windows/servercore:1809
    args:
    - powershell.exe
    - -Command
    - "Start-Sleep 360000"
    imagePullPolicy: IfNotPresent
  nodeSelector:
    kubernetes.io/os: windows
---
apiVersion: v1
kind: Pod
metadata:
  name: porter
  namespace: calico-demo
  labels:
    app: porter
spec:
  containers:
  - name: porter
    image: calico/porter:1809
    ports:
    - containerPort: 80
    env:
    - name: SERVE_PORT_80
      value: This is a Calico for Windows demo.
    imagePullPolicy: IfNotPresent
  nodeSelector:
    kubernetes.io/os: windows

Apply the policy-demo-windows.yaml file to the Kubernetes cluster

  1. Open a PowerShell window.
  2. Use kubectl to apply the policy-demo-windows.yaml configuration
kubectl apply -f policy-demo-windows.yaml

Verify four pods have been created and are running

Note: Launching the Windows pods is going to take some time depending on your network download speed.

  1. Open a powershell window.
  2. Using kubectl to list the pods in the calico-demo namespace.
kubectl get pods --namespace calico-demo

You should see something like the below

NAME      READY   STATUS              RESTARTS   AGE
busybox   1/1     Running             0          4m14s
nginx     1/1     Running             0          4m14s
porter    0/1     ContainerCreating   0          74s
pwsh      0/1     ContainerCreating   0          2m9s

Repeat the command every few minutes until the output shows all 4 pods in the Running state.

NAME      READY   STATUS    RESTARTS   AGE
busybox   1/1     Running   0          7m24s
nginx     1/1     Running   0          7m24s
porter    1/1     Running   0          4m24s
pwsh      1/1     Running   0          5m19s

Check connectivity between pods on Linux and Windows nodes

Now that client and server pods are running on both Linux and Windows nodes, let’s verify that client pods on Linux nodes can reach server pods on Windows nodes.

  1. Open a PowerShell window.
  2. Using kubectl to determine the porter pod IP address:

     kubectl get pod porter --namespace calico-demo -o 'jsonpath={.status.podIP}'
    
  3. Log into the busybox pod and try reaching the porter pod on port 80. Replace the ‘' tag with the IP address returned from the previous command.

     kubectl exec --namespace calico-demo busybox -- nc -vz <porter_ip> 80
    

    Note: You can also combine both of the above steps:

     kubectl exec --namespace calico-demo busybox -- nc -vz $(kubectl get pod porter --namespace calico-demo -o 'jsonpath={.status.podIP}') 80
    

    If the connection from the busybox pod to the porter pod succeeds, you will get output similar to the following:

     192.168.40.166 (192.168.40.166:80) open
    

    Note: The IP addresses returned will vary depending on your environment setup.

  4. Now you can verify that the pwsh pod can reach the nginx pod:

     kubectl exec --namespace calico-demo pwsh -- powershell Invoke-WebRequest -Uri http://$(kubectl get po nginx -n calico-demo -o 'jsonpath={.status.podIP}') -UseBasicParsing -TimeoutSec 5
    

    If the connection succeeds, you will see output similar to:

     StatusCode        : 200
     StatusDescription : OK
     Content           : <!DOCTYPE html>
                         <html>
                         <head>
                         <title>Welcome to nginx!</title>
                         <style>
                             body {
                                 width: 35em;
                                 margin: 0 auto;
                                 font-family: Tahoma, Verdana, Arial, sans-serif;
                             }
                         </style>
                         <...
    
  5. Verify that the pwsh pod can reach the porter pod:

     kubectl exec --namespace calico-demo pwsh -- powershell Invoke-WebRequest -Uri http://$(kubectl get po porter -n calico-demo -o 'jsonpath={.status.podIP}') -UseBasicParsing -TimeoutSec 5
    

    If that succeeds, you will see something like:

     StatusCode        : 200
     StatusDescription : OK
     Content           : This is a Calico for Windows demo.
     RawContent        : HTTP/1.1 200 OK
                         Content-Length: 49
                         Content-Type: text/plain; charset=utf-8
                         Date: Fri, 21 Aug 2020 22:45:46 GMT
        
                         This is a Calico for Windows demo.
     Forms             :
     Headers           : {[Content-Length, 49], [Content-Type, text/plain;
                         charset=utf-8], [Date, Fri, 21 Aug 2020 22:45:46 GMT]}
     Images            : {}
     InputFields       : {}
     Links             : {}
     ParsedHtml        :
     RawContentLength  : 49
    
    

You have now verified that communication is possible between all pods in the application.

Apply policy to the Windows client pod

In a real world deployment you would want to make sure only pods that are supposed to communicate with each other, are actually allowed to do so.

To achieve this you wil apply a basic network policy which allows only the busybox pod to reach the porter pod.

Create the network-policy.yaml file using your favorite editor on Windows

apiVersion: networking.k8s.io/v1
kind: NetworkPolicy
metadata:
  name: allow-busybox
  namespace: calico-demo
spec:
  podSelector:
    matchLabels:
      app: porter
  policyTypes:
  - Ingress
  ingress:
  - from:
    - podSelector:
        matchLabels:
          app: busybox
    ports:
    - protocol: TCP
      port: 80

Apply the network-policy.yaml file

  1. Open a PowerShell window.
  2. Use kubectl to apply the network-policy.yaml file.
kubectl apply -f network-policy.yaml

Verify the policy is in effect

With the policy in place, the busybox pod should still be able to reach the porter pod:

Note: We will be using the combined command line from earlier in this chapter.

kubectl exec --namespace calico-demo busybox -- nc -vz $(kubectl get po porter -n calico-demo -o 'jsonpath={.status.podIP}') 80

However, the pwsh pod will not able to reach the porter pod:

kubectl exec --namespace calico-demo pwsh -- powershell Invoke-WebRequest -Uri http://$(kubectl get po porter -n calico-demo -o 'jsonpath={.status.podIP}') -UseBasicParsing -TimeoutSec 5

The request times out with a message like the below:

Invoke-WebRequest : The operation has timed out.
At line:1 char:1
+ Invoke-WebRequest -Uri http://192.168.40.166 -UseBasicParsing -Timeout ...
+ ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
    + CategoryInfo          : InvalidOperation: (System.Net.HttpWebRequest:Htt
pWebRequest) [Invoke-WebRequest], WebException
    + FullyQualifiedErrorId : WebCmdletWebResponseException,Microsoft.PowerShell.Commands.InvokeWebRequestCommand
command terminated with exit code 1

Wrap up

In this demo we’ve configured pods on Linux and Windows nodes, verified basic pod connectivity, and tried a basic network policy to isolate pod to pod traffic. As the final step you can clean up all of the demo resources:

  1. Open a PowerShell window.
kubectl delete namespace calico-demo