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Network Policy

Official documentation: About network policy

Basics

  1. Based on labeling or annotations
  2. Empty label selector match all
  3. Rules for allowing
    • Ingress -> who can connect to this POD
    • Egress -> where can this POD connect to
  4. Rules
    • traffic is allowed unless a Network Policy selecting the POD
    • traffic is denied if pod is selected in policie but none of them have any rules allowing it
    • => You can only write rules that allow traffic!
    • Scope: Namespace

Demo Network Policies

Tested on OpenShift 4.6.8 with OpenShift SDN network plugin

demo overview

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oc new-project bouvier
oc new-app quay.io/rbo/demo-http:master --name patty
oc expose svc/patty
oc scale deployment/patty --replicas=2
oc new-app quay.io/rbo/demo-http:master --name selma
oc scale deployment/selma --replicas=2
oc expose svc/selma

oc new-project simpson
oc new-app quay.io/rbo/demo-http:master --name homer
oc expose svc/homer
oc scale deployment/homer --replicas=2
oc new-app quay.io/rbo/demo-http:master --name marge
oc scale deployment/marge --replicas=2
oc expose svc/marge

Let's start with the Network Policy demonstration

Every one can connect to each other

Clean

Case 1 - Simpson - default-deny

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oc create -n simpson  -f - <<EOF
kind: NetworkPolicy
apiVersion: networking.k8s.io/v1
metadata:
  name: default-deny
spec:
  podSelector: {}
EOF

Case 1

2) Simpson allow from openshift-ingress namespaces, because of router

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cat << EOF| oc create -f -
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
EOF

Because of HostNetwork access of the OpenShift Ingress you have to apply a label to the default namespace: 

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oc label namespace default 'network.openshift.io/policy-group=ingress'
Documentation: 2. If the default Ingress Controller configuration has the...

Case 2

3) Simpson allow internal communcation

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

Case 3

4) Selma and Patty want's to talk with Marge!

1) First label the namespace bouvier: 

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oc label namespace/bouvier name=bouvier

2) Apply Network Policy 

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oc create -n simpson -f - <<EOF
apiVersion: networking.k8s.io/v1
kind: NetworkPolicy
metadata:
  name: allow-from-bouviers-to-marge
spec:
  podSelector:
    matchLabels:
      deployment: marge
  ingress:
  - from:
    - namespaceSelector:
        matchLabels:
          name: bouvier
EOF

Case 4

Destroy demo env

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oc delete project simpson bouvier
Last update: December 29, 2020
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