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Chapter 6. Configuring network policy with OpenShift SDN

6.1. About network policy

In a cluster using a Kubernetes Container Network Interface (CNI) plug-in that supports Kubernetes network policy, network isolation is controlled entirely by NetworkPolicy Custom Resource (CR) objects. In OpenShift Container Platform 4.2, OpenShift SDN supports using NetworkPolicy in its default network isolation mode.

Note

The Kubernetes v1 NetworkPolicy features are available in OpenShift Container Platform except for egress policy types and IPBlock.

Warning

Network policy does not apply to the host network namespace. Pods with host networking enabled are unaffected by NetworkPolicy object rules.

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.

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

    If the Ingress Controller is configured with endpointPublishingStrategy: HostNetwork, then the Ingress Controller Pod runs on the host network. When running on the host network, the traffic from the Ingress Controller is assigned the netid:0 Virtual Network ID (VNID). The netid for the namespace that is associated with the Ingress Operator is different, so the matchLabel in the allow-from-openshift-ingress network policy does not match traffic from the default Ingress Controller. Because the default namespace is assigned the netid:0 VNID, you can allow traffic from the default Ingress Controller by labeling your default namespace with network.openshift.io/policy-group: ingress.

  • Only accept connections from Pods within a project:

    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.

6.2. Example NetworkPolicy object

The following annotates an example NetworkPolicy object: 

kind: NetworkPolicy
apiVersion: extensions/v1beta1
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 describing the Pods the policy applies to. The policy object can only select Pods in the project that the NetworkPolicy object is defined.
3
A selector matching the Pods that the policy object allows ingress traffic from. The selector will match Pods in any project.
4
A list of one or more destination ports to accept traffic on.

6.3. Creating a NetworkPolicy object

To define granular rules describing Ingress network traffic allowed for projects in your cluster, you can create NetworkPolicy objects.

Prerequisites

  • A cluster using the OpenShift SDN network plug-in with mode: NetworkPolicy set. This mode is the default for OpenShift SDN.
  • Install the OpenShift Command-line Interface (CLI), commonly known as oc.
  • You must log in to the cluster.

Procedure

  1. Create a policy rule:

    1. Create a <policy-name>.yaml file where <policy-name> describes the policy rule.

    2. In the file you just created define a policy object, such as in the following example: 

      kind: NetworkPolicy
apiVersion: networking.k8s.io/v1
metadata:
  name: <policy-name> 1
spec:
  podSelector:
  ingress: []
      1
      Specify a name for the policy object.

  2. Run the following command to create the policy object: 

    $ oc create -f <policy-name>.yaml -n <project>

    In the following example, a new NetworkPolicy object is created in a project named project1: 

    $ oc create -f default-deny.yaml -n project1
networkpolicy "default-deny" created

6.4. Deleting a NetworkPolicy object

You can delete a NetworkPolicy object.

Prerequisites

  • A cluster using the OpenShift SDN network plug-in with mode: NetworkPolicy set. This mode is the default for OpenShift SDN.
  • Install the OpenShift Command-line Interface (CLI), commonly known as oc.
  • You must log in to the cluster.

Procedure

  • To delete a NetworkPolicy object, run the following command: 

    $ oc delete networkpolicy -l name=<policy-name> 1
    1
    Specify the name of the NetworkPolicy object to delete.

6.5. Viewing NetworkPolicy objects

You can list the NetworkPolicy objects in your cluster.

Prerequisites

  • A cluster using the OpenShift SDN network plug-in with mode: NetworkPolicy set. This mode is the default for OpenShift SDN.
  • Install the OpenShift Command-line Interface (CLI), commonly known as oc.
  • You must log in to the cluster.

Procedure

  • To view NetworkPolicy objects defined in your cluster, run the following command: 

    $ oc get networkpolicy

6.6. Configuring multitenant isolation using NetworkPolicy

You can configure your project to isolate it from Pods and Services in other projects.

Prerequisites

  • A cluster using the OpenShift SDN network plug-in with mode: NetworkPolicy set. This mode is the default for OpenShift SDN.
  • Install the OpenShift Command-line Interface (CLI), commonly known as oc.
  • You must log in to the cluster.

Procedure

  1. Create the following files containing NetworkPolicy object definitions:

    1. A file named allow-from-openshift-ingress.yaml containing the following: 

      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

    2. A file named allow-from-openshift-monitoring.yaml containing the following: 

      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

  2. For each policy file, run the following command to create the NetworkPolicy object: 

    $ oc apply -f <policy-name>.yaml \ 1
  -n <project> 2
    1
    Replace <policy-name> with the filename of the file containing the policy.
    2
    Replace <project> with the name of the project to apply the NetworkPolicy object to.

  3. If the default Ingress Controller configuration has the spec.endpointPublishingStrategy: HostNetwork value set, you must apply a label to the default OpenShift Container Platform namespace to allow network traffic between the Ingress Controller and the project:

    1. Determine if your default Ingress Controller uses the HostNetwork endpoint publishing strategy: 

      $ oc get --namespace openshift-ingress-operator ingresscontrollers/default \
  --output jsonpath='{.status.endpointPublishingStrategy.type}'

    2. If the previous command reports the endpoint publishing strategy as HostNetwork, set a label on the default namespace: 

      $ oc label namespace default 'network.openshift.io/policy-group=ingress'

  4. Optional: Confirm that the NetworkPolicy object exists in your current project by running the following command: 

    $ oc get networkpolicy <policy-name> -o yaml

    In the following example, the allow-from-openshift-ingress NetworkPolicy object is displayed: 

    $ oc get networkpolicy allow-from-openshift-ingress -o yaml

apiVersion: networking.k8s.io/v1
kind: NetworkPolicy
metadata:
  name: allow-from-openshift-ingress
  namespace: project1
spec:
  ingress:
  - from:
    - namespaceSelector:
        matchLabels:
          network.openshift.io/policy-group: ingress
  podSelector: {}
  policyTypes:
  - Ingress

6.7. Creating default network policies for a new project

As a cluster administrator, you can modify the new project template to automatically include NetworkPolicy objects when you create a new project.

6.7.1. 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 Global 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.

6.7.2. Adding network policy objects to the new project template

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

Prerequisites

  • A cluster using the OpenShift SDN network plug-in with mode: NetworkPolicy set. This mode is the default for OpenShift SDN.
  • Install the OpenShift Command-line Interface (CLI), commonly known as 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
...

  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
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