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Chapter 18. Network policy

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18.1. About network policy

As a developer, you can define network policies that restrict traffic to pods in your cluster.

18.1.1. About network policy

In a cluster using a network plugin that supports Kubernetes network policy, network isolation is controlled entirely by NetworkPolicy objects. In OpenShift Container Platform 4.12, OpenShift SDN supports using network policy in its default network isolation mode.

Warning

Network policy does not apply to the host network namespace. Pods with host networking enabled are unaffected by network policy rules. However, pods connecting to the host-networked pods might be affected by the network policy rules.

Network policies cannot block traffic from localhost or from their resident nodes.

By default, all pods in a project are accessible from other pods and network endpoints. To isolate one or more pods in a project, you can create NetworkPolicy objects in that project to indicate the allowed incoming connections. Project administrators can create and delete NetworkPolicy objects within their own project.

If a pod is matched by selectors in one or more NetworkPolicy objects, then the pod will accept only connections that are allowed by at least one of those NetworkPolicy objects. A pod that is not selected by any NetworkPolicy objects is fully accessible.

A network policy applies to only the TCP, UDP, ICMP, and SCTP protocols. Other protocols are not affected.

The following example NetworkPolicy objects demonstrate supporting different scenarios:

  • Deny all traffic:

    To make a project deny by default, add a NetworkPolicy object that matches all pods but accepts no traffic:

    kind: NetworkPolicy
    apiVersion: networking.k8s.io/v1
    metadata:
      name: deny-by-default
    spec:
      podSelector: {}
      ingress: []
  • Only allow connections from the OpenShift Container Platform Ingress Controller:

    To make a project allow only connections from the OpenShift Container Platform Ingress Controller, add the following NetworkPolicy object.

    apiVersion: networking.k8s.io/v1
    kind: NetworkPolicy
    metadata:
      name: allow-from-openshift-ingress
    spec:
      ingress:
      - from:
        - namespaceSelector:
            matchLabels:
              network.openshift.io/policy-group: ingress
      podSelector: {}
      policyTypes:
      - Ingress
  • Only accept connections from pods within a project:

    Important

    To allow ingress connections from hostNetwork pods in the same namespace, you need to apply the allow-from-hostnetwork policy together with the allow-same-namespace policy.

    To make pods accept connections from other pods in the same project, but reject all other connections from pods in other projects, add the following NetworkPolicy object:

    kind: NetworkPolicy
    apiVersion: networking.k8s.io/v1
    metadata:
      name: allow-same-namespace
    spec:
      podSelector: {}
      ingress:
      - from:
        - podSelector: {}
  • Only allow HTTP and HTTPS traffic based on pod labels:

    To enable only HTTP and HTTPS access to the pods with a specific label (role=frontend in following example), add a NetworkPolicy object similar to the following:

    kind: NetworkPolicy
    apiVersion: networking.k8s.io/v1
    metadata:
      name: allow-http-and-https
    spec:
      podSelector:
        matchLabels:
          role: frontend
      ingress:
      - ports:
        - protocol: TCP
          port: 80
        - protocol: TCP
          port: 443
  • Accept connections by using both namespace and pod selectors:

    To match network traffic by combining namespace and pod selectors, you can use a NetworkPolicy object similar to the following:

    kind: NetworkPolicy
    apiVersion: networking.k8s.io/v1
    metadata:
      name: allow-pod-and-namespace-both
    spec:
      podSelector:
        matchLabels:
          name: test-pods
      ingress:
        - from:
          - namespaceSelector:
              matchLabels:
                project: project_name
            podSelector:
              matchLabels:
                name: test-pods

NetworkPolicy objects are additive, which means you can combine multiple NetworkPolicy objects together to satisfy complex network requirements.

For example, for the NetworkPolicy objects defined in previous samples, you can define both allow-same-namespace and allow-http-and-https policies within the same project. Thus allowing the pods with the label role=frontend, to accept any connection allowed by each policy. That is, connections on any port from pods in the same namespace, and connections on ports 80 and 443 from pods in any namespace.

18.1.1.1. Using the allow-from-router network policy

Use the following NetworkPolicy to allow external traffic regardless of the router configuration:

apiVersion: networking.k8s.io/v1
kind: NetworkPolicy
metadata:
  name: allow-from-router
spec:
  ingress:
  - from:
    - namespaceSelector:
        matchLabels:
          policy-group.network.openshift.io/ingress: ""1
  podSelector: {}
  policyTypes:
  - Ingress
1
policy-group.network.openshift.io/ingress:"" label supports both OpenShift-SDN and OVN-Kubernetes.

18.1.1.2. Using the allow-from-hostnetwork network policy

Add the following allow-from-hostnetwork NetworkPolicy object to direct traffic from the host network pods.

apiVersion: networking.k8s.io/v1
kind: NetworkPolicy
metadata:
  name: allow-from-hostnetwork
spec:
  ingress:
  - from:
    - namespaceSelector:
        matchLabels:
          policy-group.network.openshift.io/host-network: ""
  podSelector: {}
  policyTypes:
  - Ingress

18.1.2. Optimizations for network policy with OpenShift SDN

Use a network policy to isolate pods that are differentiated from one another by labels within a namespace.

It is inefficient to apply NetworkPolicy objects to large numbers of individual pods in a single namespace. Pod labels do not exist at the IP address level, so a network policy generates a separate Open vSwitch (OVS) flow rule for every possible link between every pod selected with a podSelector.

For example, if the spec podSelector and the ingress podSelector within a NetworkPolicy object each match 200 pods, then 40,000 (200*200) OVS flow rules are generated. This might slow down a node.

When designing your network policy, refer to the following guidelines:

  • Reduce the number of OVS flow rules by using namespaces to contain groups of pods that need to be isolated.

    NetworkPolicy objects that select a whole namespace, by using the namespaceSelector or an empty podSelector, generate only a single OVS flow rule that matches the VXLAN virtual network ID (VNID) of the namespace.

  • Keep the pods that do not need to be isolated in their original namespace, and move the pods that require isolation into one or more different namespaces.
  • Create additional targeted cross-namespace network policies to allow the specific traffic that you do want to allow from the isolated pods.

18.1.3. Optimizations for network policy with OVN-Kubernetes network plugin

When designing your network policy, refer to the following guidelines:

  • For network policies with the same spec.podSelector spec, it is more efficient to use one network policy with multiple ingress or egress rules, than multiple network policies with subsets of ingress or egress rules.
  • Every ingress or egress rule based on the podSelector or namespaceSelector spec generates the number of OVS flows proportional to number of pods selected by network policy + number of pods selected by ingress or egress rule. Therefore, it is preferable to use the podSelector or namespaceSelector spec that can select as many pods as you need in one rule, instead of creating individual rules for every pod.

    For example, the following policy contains two rules:

    apiVersion: networking.k8s.io/v1
    kind: NetworkPolicy
    metadata:
      name: test-network-policy
    spec:
      podSelector: {}
      ingress:
      - from:
        - podSelector:
            matchLabels:
              role: frontend
      - from:
        - podSelector:
            matchLabels:
              role: backend

    The following policy expresses those same two rules as one:

    apiVersion: networking.k8s.io/v1
    kind: NetworkPolicy
    metadata:
      name: test-network-policy
    spec:
      podSelector: {}
      ingress:
      - from:
        - podSelector:
            matchExpressions:
            - {key: role, operator: In, values: [frontend, backend]}

    The same guideline applies to the spec.podSelector spec. If you have the same ingress or egress rules for different network policies, it might be more efficient to create one network policy with a common spec.podSelector spec. For example, the following two policies have different rules:

    apiVersion: networking.k8s.io/v1
    kind: NetworkPolicy
    metadata:
      name: policy1
    spec:
      podSelector:
        matchLabels:
          role: db
      ingress:
      - from:
        - podSelector:
            matchLabels:
              role: frontend
    ---
    apiVersion: networking.k8s.io/v1
    kind: NetworkPolicy
    metadata:
      name: policy2
    spec:
      podSelector:
        matchLabels:
          role: client
      ingress:
      - from:
        - podSelector:
            matchLabels:
              role: frontend

    The following network policy expresses those same two rules as one:

    apiVersion: networking.k8s.io/v1
    kind: NetworkPolicy
    metadata:
      name: policy3
    spec:
      podSelector:
        matchExpressions:
        - {key: role, operator: In, values: [db, client]}
      ingress:
      - from:
        - podSelector:
            matchLabels:
              role: frontend

    You can apply this optimization when only multiple selectors are expressed as one. In cases where selectors are based on different labels, it may not be possible to apply this optimization. In those cases, consider applying some new labels for network policy optimization specifically.

18.1.4. Next steps

18.1.5. Additional resources

18.2. Creating a network policy

As a user with the admin role, you can create a network policy for a namespace.

18.2.1. Example NetworkPolicy object

The following annotates an example NetworkPolicy object:

kind: NetworkPolicy
apiVersion: networking.k8s.io/v1
metadata:
  name: allow-27107 1
spec:
  podSelector: 2
    matchLabels:
      app: mongodb
  ingress:
  - from:
    - podSelector: 3
        matchLabels:
          app: app
    ports: 4
    - protocol: TCP
      port: 27017
1
The name of the NetworkPolicy object.
2
A selector that describes the pods to which the policy applies. The policy object can only select pods in the project that defines the NetworkPolicy object.
3
A selector that matches the pods from which the policy object allows ingress traffic. The selector matches pods in the same namespace as the NetworkPolicy.
4
A list of one or more destination ports on which to accept traffic.

18.2.2. Creating a network policy using the CLI

To define granular rules describing ingress or egress network traffic allowed for namespaces in your cluster, you can create a network policy.

Note

If you log in with a user with the cluster-admin role, then you can create a network policy in any namespace in the cluster.

Prerequisites

  • Your cluster uses a network plugin that supports NetworkPolicy objects, such as the OpenShift SDN network provider with mode: NetworkPolicy set. This mode is the default for OpenShift SDN.
  • You installed the OpenShift CLI (oc).
  • You are logged in to the cluster with a user with admin privileges.
  • You are working in the namespace that the network policy applies to.

Procedure

  1. Create a policy rule:

    1. Create a <policy_name>.yaml file:

      $ touch <policy_name>.yaml

      where:

      <policy_name>
      Specifies the network policy file name.
    2. Define a network policy in the file that you just created, such as in the following examples:

      Deny ingress from all pods in all namespaces

      This is a fundamental policy, blocking all cross-pod networking other than cross-pod traffic allowed by the configuration of other Network Policies.

      kind: NetworkPolicy
      apiVersion: networking.k8s.io/v1
      metadata:
        name: deny-by-default
      spec:
        podSelector:
        ingress: []

      Allow ingress from all pods in the same namespace

      kind: NetworkPolicy
      apiVersion: networking.k8s.io/v1
      metadata:
        name: allow-same-namespace
      spec:
        podSelector:
        ingress:
        - from:
          - podSelector: {}

      Allow ingress traffic to one pod from a particular namespace

      This policy allows traffic to pods labelled pod-a from pods running in namespace-y.

      kind: NetworkPolicy
      apiVersion: networking.k8s.io/v1
      metadata:
        name: allow-traffic-pod
      spec:
        podSelector:
         matchLabels:
            pod: pod-a
        policyTypes:
        - Ingress
        ingress:
        - from:
          - namespaceSelector:
              matchLabels:
                 kubernetes.io/metadata.name: namespace-y
  2. To create the network policy object, enter the following command:

    $ oc apply -f <policy_name>.yaml -n <namespace>

    where:

    <policy_name>
    Specifies the network policy file name.
    <namespace>
    Optional: Specifies the namespace if the object is defined in a different namespace than the current namespace.

    Example output

    networkpolicy.networking.k8s.io/deny-by-default created

Note

If you log in to the web console with cluster-admin privileges, you have a choice of creating a network policy in any namespace in the cluster directly in YAML or from a form in the web console.

18.2.3. Creating a default deny all network policy

This is a fundamental policy, blocking all cross-pod networking other than network traffic allowed by the configuration of other deployed network policies. This procedure enforces a default deny-by-default policy.

Note

If you log in with a user with the cluster-admin role, then you can create a network policy in any namespace in the cluster.

Prerequisites

  • Your cluster uses a network plugin that supports NetworkPolicy objects, such as the OpenShift SDN network provider with mode: NetworkPolicy set. This mode is the default for OpenShift SDN.
  • You installed the OpenShift CLI (oc).
  • You are logged in to the cluster with a user with admin privileges.
  • You are working in the namespace that the network policy applies to.

Procedure

  1. Create the following YAML that defines a deny-by-default policy to deny ingress from all pods in all namespaces. Save the YAML in the deny-by-default.yaml file:

    kind: NetworkPolicy
    apiVersion: networking.k8s.io/v1
    metadata:
      name: deny-by-default
      namespace: default 1
    spec:
      podSelector: {} 2
      ingress: [] 3
    1
    namespace: default deploys this policy to the default namespace.
    2
    podSelector: is empty, this means it matches all the pods. Therefore, the policy applies to all pods in the default namespace.
    3
    There are no ingress rules specified. This causes incoming traffic to be dropped to all pods.
  2. Apply the policy by entering the following command:

    $ oc apply -f deny-by-default.yaml

    Example output

    networkpolicy.networking.k8s.io/deny-by-default created

18.2.4. Creating a network policy to allow traffic from external clients

With the deny-by-default policy in place you can proceed to configure a policy that allows traffic from external clients to a pod with the label app=web.

Note

If you log in with a user with the cluster-admin role, then you can create a network policy in any namespace in the cluster.

Follow this procedure to configure a policy that allows external service from the public Internet directly or by using a Load Balancer to access the pod. Traffic is only allowed to a pod with the label app=web.

Prerequisites

  • Your cluster uses a network plugin that supports NetworkPolicy objects, such as the OpenShift SDN network provider with mode: NetworkPolicy set. This mode is the default for OpenShift SDN.
  • You installed the OpenShift CLI (oc).
  • You are logged in to the cluster with a user with admin privileges.
  • You are working in the namespace that the network policy applies to.

Procedure

  1. Create a policy that allows traffic from the public Internet directly or by using a load balancer to access the pod. Save the YAML in the web-allow-external.yaml file:

    kind: NetworkPolicy
    apiVersion: networking.k8s.io/v1
    metadata:
      name: web-allow-external
      namespace: default
    spec:
      policyTypes:
      - Ingress
      podSelector:
        matchLabels:
          app: web
      ingress:
        - {}
  2. Apply the policy by entering the following command:

    $ oc apply -f web-allow-external.yaml

    Example output

    networkpolicy.networking.k8s.io/web-allow-external created

This policy allows traffic from all resources, including external traffic as illustrated in the following diagram:

Allow traffic from external clients

18.2.5. Creating a network policy allowing traffic to an application from all namespaces

Note

If you log in with a user with the cluster-admin role, then you can create a network policy in any namespace in the cluster.

Follow this procedure to configure a policy that allows traffic from all pods in all namespaces to a particular application.

Prerequisites

  • Your cluster uses a network plugin that supports NetworkPolicy objects, such as the OpenShift SDN network provider with mode: NetworkPolicy set. This mode is the default for OpenShift SDN.
  • You installed the OpenShift CLI (oc).
  • You are logged in to the cluster with a user with admin privileges.
  • You are working in the namespace that the network policy applies to.

Procedure

  1. Create a policy that allows traffic from all pods in all namespaces to a particular application. Save the YAML in the web-allow-all-namespaces.yaml file:

    kind: NetworkPolicy
    apiVersion: networking.k8s.io/v1
    metadata:
      name: web-allow-all-namespaces
      namespace: default
    spec:
      podSelector:
        matchLabels:
          app: web 1
      policyTypes:
      - Ingress
      ingress:
      - from:
        - namespaceSelector: {} 2
    1
    Applies the policy only to app:web pods in default namespace.
    2
    Selects all pods in all namespaces.
    Note

    By default, if you omit specifying a namespaceSelector it does not select any namespaces, which means the policy allows traffic only from the namespace the network policy is deployed to.

  2. Apply the policy by entering the following command:

    $ oc apply -f web-allow-all-namespaces.yaml

    Example output

    networkpolicy.networking.k8s.io/web-allow-all-namespaces created

Verification

  1. Start a web service in the default namespace by entering the following command:

    $ oc run web --namespace=default --image=nginx --labels="app=web" --expose --port=80
  2. Run the following command to deploy an alpine image in the secondary namespace and to start a shell:

    $ oc run test-$RANDOM --namespace=secondary --rm -i -t --image=alpine -- sh
  3. Run the following command in the shell and observe that the request is allowed:

    # wget -qO- --timeout=2 http://web.default

    Expected output

    <!DOCTYPE html>
    <html>
    <head>
    <title>Welcome to nginx!</title>
    <style>
    html { color-scheme: light dark; }
    body { width: 35em; margin: 0 auto;
    font-family: Tahoma, Verdana, Arial, sans-serif; }
    </style>
    </head>
    <body>
    <h1>Welcome to nginx!</h1>
    <p>If you see this page, the nginx web server is successfully installed and
    working. Further configuration is required.</p>
    
    <p>For online documentation and support please refer to
    <a href="http://nginx.org/">nginx.org</a>.<br/>
    Commercial support is available at
    <a href="http://nginx.com/">nginx.com</a>.</p>
    
    <p><em>Thank you for using nginx.</em></p>
    </body>
    </html>

18.2.6. Creating a network policy allowing traffic to an application from a namespace

Note

If you log in with a user with the cluster-admin role, then you can create a network policy in any namespace in the cluster.

Follow this procedure to configure a policy that allows traffic to a pod with the label app=web from a particular namespace. You might want to do this to:

  • Restrict traffic to a production database only to namespaces where production workloads are deployed.
  • Enable monitoring tools deployed to a particular namespace to scrape metrics from the current namespace.

Prerequisites

  • Your cluster uses a network plugin that supports NetworkPolicy objects, such as the OpenShift SDN network provider with mode: NetworkPolicy set. This mode is the default for OpenShift SDN.
  • You installed the OpenShift CLI (oc).
  • You are logged in to the cluster with a user with admin privileges.
  • You are working in the namespace that the network policy applies to.

Procedure

  1. Create a policy that allows traffic from all pods in a particular namespaces with a label purpose=production. Save the YAML in the web-allow-prod.yaml file:

    kind: NetworkPolicy
    apiVersion: networking.k8s.io/v1
    metadata:
      name: web-allow-prod
      namespace: default
    spec:
      podSelector:
        matchLabels:
          app: web 1
      policyTypes:
      - Ingress
      ingress:
      - from:
        - namespaceSelector:
            matchLabels:
              purpose: production 2
    1
    Applies the policy only to app:web pods in the default namespace.
    2
    Restricts traffic to only pods in namespaces that have the label purpose=production.
  2. Apply the policy by entering the following command:

    $ oc apply -f web-allow-prod.yaml

    Example output

    networkpolicy.networking.k8s.io/web-allow-prod created

Verification

  1. Start a web service in the default namespace by entering the following command:

    $ oc run web --namespace=default --image=nginx --labels="app=web" --expose --port=80
  2. Run the following command to create the prod namespace:

    $ oc create namespace prod
  3. Run the following command to label the prod namespace:

    $ oc label namespace/prod purpose=production
  4. Run the following command to create the dev namespace:

    $ oc create namespace dev
  5. Run the following command to label the dev namespace:

    $ oc label namespace/dev purpose=testing
  6. Run the following command to deploy an alpine image in the dev namespace and to start a shell:

    $ oc run test-$RANDOM --namespace=dev --rm -i -t --image=alpine -- sh
  7. Run the following command in the shell and observe that the request is blocked:

    # wget -qO- --timeout=2 http://web.default

    Expected output

    wget: download timed out

  8. Run the following command to deploy an alpine image in the prod namespace and start a shell:

    $ oc run test-$RANDOM --namespace=prod --rm -i -t --image=alpine -- sh
  9. Run the following command in the shell and observe that the request is allowed:

    # wget -qO- --timeout=2 http://web.default

    Expected output

    <!DOCTYPE html>
    <html>
    <head>
    <title>Welcome to nginx!</title>
    <style>
    html { color-scheme: light dark; }
    body { width: 35em; margin: 0 auto;
    font-family: Tahoma, Verdana, Arial, sans-serif; }
    </style>
    </head>
    <body>
    <h1>Welcome to nginx!</h1>
    <p>If you see this page, the nginx web server is successfully installed and
    working. Further configuration is required.</p>
    
    <p>For online documentation and support please refer to
    <a href="http://nginx.org/">nginx.org</a>.<br/>
    Commercial support is available at
    <a href="http://nginx.com/">nginx.com</a>.</p>
    
    <p><em>Thank you for using nginx.</em></p>
    </body>
    </html>

18.2.7. Additional resources

18.3. Viewing a network policy

As a user with the admin role, you can view a network policy for a namespace.

18.3.1. Example NetworkPolicy object

The following annotates an example NetworkPolicy object:

kind: NetworkPolicy
apiVersion: networking.k8s.io/v1
metadata:
  name: allow-27107 1
spec:
  podSelector: 2
    matchLabels:
      app: mongodb
  ingress:
  - from:
    - podSelector: 3
        matchLabels:
          app: app
    ports: 4
    - protocol: TCP
      port: 27017
1
The name of the NetworkPolicy object.
2
A selector that describes the pods to which the policy applies. The policy object can only select pods in the project that defines the NetworkPolicy object.
3
A selector that matches the pods from which the policy object allows ingress traffic. The selector matches pods in the same namespace as the NetworkPolicy.
4
A list of one or more destination ports on which to accept traffic.

18.3.2. Viewing network policies using the CLI

You can examine the network policies in a namespace.

Note

If you log in with a user with the cluster-admin role, then you can view any network policy in the cluster.

Prerequisites

  • You installed the OpenShift CLI (oc).
  • You are logged in to the cluster with a user with admin privileges.
  • You are working in the namespace where the network policy exists.

Procedure

  • List network policies in a namespace:

    • To view network policy objects defined in a namespace, enter the following command:

      $ oc get networkpolicy
    • Optional: To examine a specific network policy, enter the following command:

      $ oc describe networkpolicy <policy_name> -n <namespace>

      where:

      <policy_name>
      Specifies the name of the network policy to inspect.
      <namespace>
      Optional: Specifies the namespace if the object is defined in a different namespace than the current namespace.

      For example:

      $ oc describe networkpolicy allow-same-namespace

      Output for oc describe command

      Name:         allow-same-namespace
      Namespace:    ns1
      Created on:   2021-05-24 22:28:56 -0400 EDT
      Labels:       <none>
      Annotations:  <none>
      Spec:
        PodSelector:     <none> (Allowing the specific traffic to all pods in this namespace)
        Allowing ingress traffic:
          To Port: <any> (traffic allowed to all ports)
          From:
            PodSelector: <none>
        Not affecting egress traffic
        Policy Types: Ingress

Note

If you log in to the web console with cluster-admin privileges, you have a choice of viewing a network policy in any namespace in the cluster directly in YAML or from a form in the web console.

18.4. Editing a network policy

As a user with the admin role, you can edit an existing network policy for a namespace.

18.4.1. Editing a network policy

You can edit a network policy in a namespace.

Note

If you log in with a user with the cluster-admin role, then you can edit a network policy in any namespace in the cluster.

Prerequisites

  • Your cluster uses a network plugin that supports NetworkPolicy objects, such as the OpenShift SDN network provider with mode: NetworkPolicy set. This mode is the default for OpenShift SDN.
  • You installed the OpenShift CLI (oc).
  • You are logged in to the cluster with a user with admin privileges.
  • You are working in the namespace where the network policy exists.

Procedure

  1. Optional: To list the network policy objects in a namespace, enter the following command:

    $ oc get networkpolicy

    where:

    <namespace>
    Optional: Specifies the namespace if the object is defined in a different namespace than the current namespace.
  2. Edit the network policy object.

    • If you saved the network policy definition in a file, edit the file and make any necessary changes, and then enter the following command.

      $ oc apply -n <namespace> -f <policy_file>.yaml

      where:

      <namespace>
      Optional: Specifies the namespace if the object is defined in a different namespace than the current namespace.
      <policy_file>
      Specifies the name of the file containing the network policy.
    • If you need to update the network policy object directly, enter the following command:

      $ oc edit networkpolicy <policy_name> -n <namespace>

      where:

      <policy_name>
      Specifies the name of the network policy.
      <namespace>
      Optional: Specifies the namespace if the object is defined in a different namespace than the current namespace.
  3. Confirm that the network policy object is updated.

    $ oc describe networkpolicy <policy_name> -n <namespace>

    where:

    <policy_name>
    Specifies the name of the network policy.
    <namespace>
    Optional: Specifies the namespace if the object is defined in a different namespace than the current namespace.
Note

If you log in to the web console with cluster-admin privileges, you have a choice of editing a network policy in any namespace in the cluster directly in YAML or from the policy in the web console through the Actions menu.

18.4.2. Example NetworkPolicy object

The following annotates an example NetworkPolicy object:

kind: NetworkPolicy
apiVersion: networking.k8s.io/v1
metadata:
  name: allow-27107 1
spec:
  podSelector: 2
    matchLabels:
      app: mongodb
  ingress:
  - from:
    - podSelector: 3
        matchLabels:
          app: app
    ports: 4
    - protocol: TCP
      port: 27017
1
The name of the NetworkPolicy object.
2
A selector that describes the pods to which the policy applies. The policy object can only select pods in the project that defines the NetworkPolicy object.
3
A selector that matches the pods from which the policy object allows ingress traffic. The selector matches pods in the same namespace as the NetworkPolicy.
4
A list of one or more destination ports on which to accept traffic.

18.4.3. Additional resources

18.5. Deleting a network policy

As a user with the admin role, you can delete a network policy from a namespace.

18.5.1. Deleting a network policy using the CLI

You can delete a network policy in a namespace.

Note

If you log in with a user with the cluster-admin role, then you can delete any network policy in the cluster.

Prerequisites

  • Your cluster uses a network plugin that supports NetworkPolicy objects, such as the OpenShift SDN network provider with mode: NetworkPolicy set. This mode is the default for OpenShift SDN.
  • You installed the OpenShift CLI (oc).
  • You are logged in to the cluster with a user with admin privileges.
  • You are working in the namespace where the network policy exists.

Procedure

  • To delete a network policy object, enter the following command:

    $ oc delete networkpolicy <policy_name> -n <namespace>

    where:

    <policy_name>
    Specifies the name of the network policy.
    <namespace>
    Optional: Specifies the namespace if the object is defined in a different namespace than the current namespace.

    Example output

    networkpolicy.networking.k8s.io/default-deny deleted

Note

If you log in to the web console with cluster-admin privileges, you have a choice of deleting a network policy in any namespace in the cluster directly in YAML or from the policy in the web console through the Actions menu.

18.6. Defining a default network policy for projects

As a cluster administrator, you can modify the new project template to automatically include network policies when you create a new project. If you do not yet have a customized template for new projects, you must first create one.

18.6.1. Modifying the template for new projects

As a cluster administrator, you can modify the default project template so that new projects are created using your custom requirements.

To create your own custom project template:

Procedure

  1. Log in as a user with cluster-admin privileges.
  2. Generate the default project template:

    $ oc adm create-bootstrap-project-template -o yaml > template.yaml
  3. Use a text editor to modify the generated template.yaml file by adding objects or modifying existing objects.
  4. The project template must be created in the openshift-config namespace. Load your modified template:

    $ oc create -f template.yaml -n openshift-config
  5. Edit the project configuration resource using the web console or CLI.

    • Using the web console:

      1. Navigate to the Administration Cluster Settings page.
      2. Click Configuration to view all configuration resources.
      3. Find the entry for Project and click Edit YAML.
    • Using the CLI:

      1. Edit the project.config.openshift.io/cluster resource:

        $ oc edit project.config.openshift.io/cluster
  6. Update the spec section to include the projectRequestTemplate and name parameters, and set the name of your uploaded project template. The default name is project-request.

    Project configuration resource with custom project template

    apiVersion: config.openshift.io/v1
    kind: Project
    metadata:
    # ...
    spec:
      projectRequestTemplate:
        name: <template_name>
    # ...

  7. After you save your changes, create a new project to verify that your changes were successfully applied.

18.6.2. Adding network policies to the new project template

As a cluster administrator, you can add network policies to the default template for new projects. OpenShift Container Platform will automatically create all the NetworkPolicy objects specified in the template in the project.

Prerequisites

  • Your cluster uses a default CNI network provider that supports NetworkPolicy objects, such as the OpenShift SDN network provider with mode: NetworkPolicy set. This mode is the default for OpenShift SDN.
  • You installed the OpenShift CLI (oc).
  • You must log in to the cluster with a user with cluster-admin privileges.
  • You must have created a custom default project template for new projects.

Procedure

  1. Edit the default template for a new project by running the following command:

    $ oc edit template <project_template> -n openshift-config

    Replace <project_template> with the name of the default template that you configured for your cluster. The default template name is project-request.

  2. In the template, add each NetworkPolicy object as an element to the objects parameter. The objects parameter accepts a collection of one or more objects.

    In the following example, the objects parameter collection includes several NetworkPolicy objects.

    objects:
    - apiVersion: networking.k8s.io/v1
      kind: NetworkPolicy
      metadata:
        name: allow-from-same-namespace
      spec:
        podSelector: {}
        ingress:
        - from:
          - podSelector: {}
    - apiVersion: networking.k8s.io/v1
      kind: NetworkPolicy
      metadata:
        name: allow-from-openshift-ingress
      spec:
        ingress:
        - from:
          - namespaceSelector:
              matchLabels:
                network.openshift.io/policy-group: ingress
        podSelector: {}
        policyTypes:
        - Ingress
    - apiVersion: networking.k8s.io/v1
      kind: NetworkPolicy
      metadata:
        name: allow-from-kube-apiserver-operator
      spec:
        ingress:
        - from:
          - namespaceSelector:
              matchLabels:
                kubernetes.io/metadata.name: openshift-kube-apiserver-operator
            podSelector:
              matchLabels:
                app: kube-apiserver-operator
        policyTypes:
        - Ingress
    ...
  3. Optional: Create a new project to confirm that your network policy objects are created successfully by running the following commands:

    1. Create a new project:

      $ oc new-project <project> 1
      1
      Replace <project> with the name for the project you are creating.
    2. Confirm that the network policy objects in the new project template exist in the new project:

      $ oc get networkpolicy
      NAME                           POD-SELECTOR   AGE
      allow-from-openshift-ingress   <none>         7s
      allow-from-same-namespace      <none>         7s

18.7. Configuring multitenant isolation with network policy

As a cluster administrator, you can configure your network policies to provide multitenant network isolation.

Note

If you are using the OpenShift SDN network plugin, configuring network policies as described in this section provides network isolation similar to multitenant mode but with network policy mode set.

18.7.1. Configuring multitenant isolation by using network policy

You can configure your project to isolate it from pods and services in other project namespaces.

Prerequisites

  • Your cluster uses a network plugin that supports NetworkPolicy objects, such as the OpenShift SDN network provider with mode: NetworkPolicy set. This mode is the default for OpenShift SDN.
  • You installed the OpenShift CLI (oc).
  • You are logged in to the cluster with a user with admin privileges.

Procedure

  1. Create the following NetworkPolicy objects:

    1. A policy named allow-from-openshift-ingress.

      $ cat << EOF| oc create -f -
      apiVersion: networking.k8s.io/v1
      kind: NetworkPolicy
      metadata:
        name: allow-from-openshift-ingress
      spec:
        ingress:
        - from:
          - namespaceSelector:
              matchLabels:
                policy-group.network.openshift.io/ingress: ""
        podSelector: {}
        policyTypes:
        - Ingress
      EOF
      Note

      policy-group.network.openshift.io/ingress: "" is the preferred namespace selector label for OpenShift SDN. You can use the network.openshift.io/policy-group: ingress namespace selector label, but this is a legacy label.

    2. A policy named allow-from-openshift-monitoring:

      $ cat << EOF| oc create -f -
      apiVersion: networking.k8s.io/v1
      kind: NetworkPolicy
      metadata:
        name: allow-from-openshift-monitoring
      spec:
        ingress:
        - from:
          - namespaceSelector:
              matchLabels:
                network.openshift.io/policy-group: monitoring
        podSelector: {}
        policyTypes:
        - Ingress
      EOF
    3. A policy named allow-same-namespace:

      $ cat << EOF| oc create -f -
      kind: NetworkPolicy
      apiVersion: networking.k8s.io/v1
      metadata:
        name: allow-same-namespace
      spec:
        podSelector:
        ingress:
        - from:
          - podSelector: {}
      EOF
    4. A policy named allow-from-kube-apiserver-operator:

      $ cat << EOF| oc create -f -
      apiVersion: networking.k8s.io/v1
      kind: NetworkPolicy
      metadata:
        name: allow-from-kube-apiserver-operator
      spec:
        ingress:
        - from:
          - namespaceSelector:
              matchLabels:
                kubernetes.io/metadata.name: openshift-kube-apiserver-operator
            podSelector:
              matchLabels:
                app: kube-apiserver-operator
        policyTypes:
        - Ingress
      EOF

      For more details, see New kube-apiserver-operator webhook controller validating health of webhook.

  2. Optional: To confirm that the network policies exist in your current project, enter the following command:

    $ oc describe networkpolicy

    Example output

    Name:         allow-from-openshift-ingress
    Namespace:    example1
    Created on:   2020-06-09 00:28:17 -0400 EDT
    Labels:       <none>
    Annotations:  <none>
    Spec:
      PodSelector:     <none> (Allowing the specific traffic to all pods in this namespace)
      Allowing ingress traffic:
        To Port: <any> (traffic allowed to all ports)
        From:
          NamespaceSelector: network.openshift.io/policy-group: ingress
      Not affecting egress traffic
      Policy Types: Ingress
    
    
    Name:         allow-from-openshift-monitoring
    Namespace:    example1
    Created on:   2020-06-09 00:29:57 -0400 EDT
    Labels:       <none>
    Annotations:  <none>
    Spec:
      PodSelector:     <none> (Allowing the specific traffic to all pods in this namespace)
      Allowing ingress traffic:
        To Port: <any> (traffic allowed to all ports)
        From:
          NamespaceSelector: network.openshift.io/policy-group: monitoring
      Not affecting egress traffic
      Policy Types: Ingress

18.7.2. Next steps

18.7.3. Additional resources

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