kind: NetworkPolicy
apiVersion: networking.k8s.io/v1
metadata:
name: deny-by-default
spec:
podSelector: {}
ingress: []
As a developer, you can define network policies that restrict traffic to pods in your cluster.
In a cluster using a network plugin that supports Kubernetes network policy, network isolation is controlled entirely by NetworkPolicy
objects.
In OpenShift Container Platform 4.15, OpenShift SDN supports using network policy in its default network isolation mode.
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:
To allow ingress connections from |
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.
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. |
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
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.
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.