Use network policies - User Guide for Kubernetes Clusters| Alibaba Cloud Documentation Center

Enable network policies

Note

To use network policies through the ACK console, Submit a ticket to apply to be added to a whitelist.
To use network policies through a CLI, you do not need to apply to be added to a whitelist.

You can enable network policies when you create the cluster or after the cluster is created. The cluster must use the Terway network plug-in.

To enable network policies when you create the cluster, select Support for NetworkPolicy in the Terway Mode section. For more information, see Create a professional managed Kubernetes cluster.
To enable network policies after the cluster is created, go to the CconfigMap page, select the eni-config ConfigMap in the kube-system namespace, and then set disable_network_policy to false. For more information about ConfigMaps, see Modify a ConfigMap.

After the eni-config ConfigMap is modified, you must restart Terway to enable network policies. For more information about how to restart Terway, see Recreate Terway pods.

Scenarios

This section describes how to configure network policies in the following scenarios:

Allow only applications with specific labels to access a Service
Allow only specific source IP addresses to access a Service through an Internet-facing SLB instance
Allow a pod to access a specific address
Control pod access to the Internet in specific namespaces

The preceding scenarios all use the application that is created in Create an NGINX application that allows access from other pods as an example.

Create an NGINX application that allows access from other pods

Use the ACK console

Create an application named nginx and create a Service to expose the application. For more information, see Create a Deployment from an image.

The following table describes the sample configurations.


Configuration	Parameter	Example
Basic Information	Name	nginx
Basic Information	Replicas	1
Container	Image Name	nginx
Service	Name	nginx
	Type	Server Load Balancer Public Access Create SLB Instance
	Port Mapping	Name: nginx Service Port: 80 Container Port: 80 Protocol: TCP

Create a client application named busybox to test access to the nginx Service created in the preceding step. For more information, see Create a Deployment from an image.

The following table describes the sample configurations.


Configuration	Parameter	Example
Basic Information	Name	busybox
Basic Information	Replicas	1
Container Start Parameter	Image Name	busybox
Container Start Parameter	Container Start Parameter	Select stdin and tty.

Check whether the busybox client application can access the nginx Service.
1. On the Deployments page, find the busybox application and click its name.
2. On the Pods page, select a pod named busybox-{hash value} and click Terminal in the Actions column.
3. In the terminal, run the wget nginx command to access the nginx Service.
  
  The preceding output indicates that busybox can access the nginx Service.

Use the CLI

Run the following command to create an application named nginx. Then, create a Service named nginx to expose the application.

Create an application named nginx:

kubectl run nginx --image=nginx

Expected output:

pod/nginx created

Query whether the pod of the application is started:

kubectl get pod

Expected output:

NAME                     READY   STATUS    RESTARTS   AGE
nginx                    1/1     Running   0          45s

Create a Service named nginx:

kubectl expose pod nginx --port=80

Expected output:

service/nginx exposed

kubectl get service

Expected output:

NAME         TYPE        CLUSTER-IP      EXTERNAL-IP   PORT(S)   AGE
kubernetes   ClusterIP   172.XX.XX.1     <none>        443/TCP   30m
nginx        ClusterIP   172.XX.XX.48    <none>        80/TCP    12s

Run the following command to create a pod named busybox and use the pod to access the nginx Service:

kubectl run busybox --rm -ti --image=busybox /bin/sh

Expected output:

If you don't see a command prompt, try pressing enter.
/ #

wget nginx

Expected output:

Connecting to nginx (172.XX.XX.48:80)
saving to 'index.html'
index.html           100% |****************************************************************************************************************************************************|   612  0:00:00 ETA
'index.html' saved

Allow only applications with specific labels to access a Service

Use the ACK console

Log on to the ACK console.
In the left-side navigation pane of the ACK console, click Clusters.
On the Clusters page, find the cluster that you want to manage and click the name of the cluster or click Details in the Actions column. The details page of the cluster appears.
In the left-side navigation pane of the details page, choose Network > NetworkPolicies.

In the upper-right corner of the NetworkPolicies page, click Create. In the Create panel, set the parameters.


Parameter	Description
Name	Set the name of the network policy. In this example, access-nginx is used.
Namespace	Set the namespace to which the network policy is scoped.
Pod Selectors	Set the pods to which the network policy applies. In this example, the following settings are used: Type: Deployment Workload: nginx Label: app=nginx Note If you do not set the pod selector, the network policy applies to all pods in the specified namespace.
Source	Each network policy can include a whitelist of allowed ingress rules. Each rule allows network traffic that matches both the source and port sections. Rule: podSelector: selects pods in the same namespace as the network policy and allows inbound traffic from these pods. namespaceSelector: selects pods from the specified namespaces and allows inbound traffic from these pods. ipBlock: selects the specified CIDR blocks and allows inbound traffic from these CIDR blocks. Port: TCP and UDP are supported. Note If you do not add rules, no pods are allowed to access the pods to which the network policy applies. In this example, no ingress rules are added.
Destination	Each network policy can include a whitelist of allowed egress rules. Each rule allows network traffic that matches both the destination and port sections. Rule: podSelector: selects pods in the same namespace as the network policy and allows outbound traffic to these pods. namespaceSelector: selects pods from the specified namespaces and allows outbound traffic to these pods. ipBlock: selects the specified CIDR blocks and allows outbound traffic to these CIDR blocks. Port: TCP and UDP are supported. In this example, no egress rules are added.

Go to the terminal of the busybox pod and run the wget nginx command to test access to the nginx Service. For more information, see Step 3.
The connection timed out because the network policy does not allow access from the busybox pod.

Modify the network policy to allow access from the busybox pod.

On the NetworkPolicies page, find the access-nginx network policy and click Edit in the Actions column.

Add an ingress rule.

Click + Add to the right of Source, and then perform the following steps:

Click + Add to the right of Rule. The following table describes the rule parameters.


Parameter	Example
Selector	podSelector
Type	Deployment
Workload	busybox

Click + Add to the right of Port. The following table describes the port parameters.


Parameter	Example
Protocol	TCP
Port	80

Click Next and then click OK.
Run the wget -O /dev/null nginx command to test access to the nginx Service from the busybox pod after the network policy is modified.
After the ingress rule is added to the network policy, the busybox pod can access the nginx Service.

Use the CLI

Run the vim policy.yaml command to create a file named policy.yaml with the following YAML template.

vim policy.yaml

The following code block shows the content of the YAML template:

kind: NetworkPolicy
apiVersion: networking.k8s.io/v1
metadata:
  name: access-nginx
spec:
  podSelector:
    matchLabels:
      run: nginx
  ingress:
  - from:
    - podSelector:
        matchLabels:
          access: "true"

Run the following command to create a network policy by using the preceding policy.yaml file:
```
kubectl apply -f policy.yaml 
```
Expected output:
```
networkpolicy.networking.k8s.io/access-nginx created
```

Run the following command to access the nginx Service. A connection timeout error is returned because the pod does not have the specified label.

kubectl run busybox --rm -ti --image=busybox /bin/sh

wget nginx

Expected output:

Connecting to nginx (172.19.8.48:80)
wget: can't connect to remote host (172.19.8.48): Connection timed out

Run the following command to add the specified label to the pod and test whether the pod can access the nginx Service:

kubectl run busybox --rm -ti --labels="access=true" --image=busybox /bin/sh

wget nginx

Expected output:

Connecting to nginx (172.21.x.114:80)
saving to 'index.html'
index.html           100% |****************************************************************************************************************************************************|   612  0:00:00 ETA
'index.html' saved

The output shows that the progress of the connection is 100%. This indicates that the pod can access the nginx Service as expected.

Allow only specific source IP addresses to access a Service through an Internet-facing SLB instance

Use the ACK console

Create a network policy for the nginx Service. For more information, see Allow only applications with specific labels to access a Service.
On the Services page, find the nginx Service created in Create an NGINX application that allows access from other pods and copy its IP address (47.xxx.xx.x) in the External Endpoint column. Visit the IP address in your browser.
The nginx Service cannot be accessed due to the preconfigured network policy.

Modify the network policy to allow specific IP addresses to access the Service.

Visit myip.ipip.net in your browser to obtain the IP address of your on-premises machine.

On the NetworkPolicies page, find the access-nginx network policy and click Edit in the Actions column. Add an ingress rule in the Edit panel.

Click + Add to the right of Source, and then perform the following steps:

Click + Add to the right of Rule. Add the IP address of your on-premises machine to the rule.


Parameter	Example
Selector	ipBlock
cidr	<IP address of your on-premises machine>/32 Example: 42.xx.xx.xx/32

Click + Add to the right of Rule. Add the CIDR block used by Server Load Balancer (SLB) for health checks to the rule.


Parameter	Example
Selector	ipBlock
cidr	100.0.0.0/8

Click + Add to the right of Port. The following table describes the port parameters.


Parameter	Example
Protocol	TCP
Port	80

Click Next and then click OK.
Access the nginx Service from your on-premises machine (47.xxx.xx.x).
After the network policy is modified, the nginx Service can be accessed through an Internet-facing SLB instance from an on-premises machine.

Use the CLI

Run the following command to create an SLB instance for the preceding nginx application. Set the Service type to LoadBalancer to make the application accessible over the Internet.

In this example, a file named nginx-service.yaml is used.

vim nginx-service.yaml
# The following content is an example. 

apiVersion: v1
kind: Service
metadata:
  labels:
    run: nginx
  name: nginx-slb
spec:
  externalTrafficPolicy: Local
  ports:
  - port: 80
    protocol: TCP
    targetPort: 80
  selector:
    run: nginx
  type: LoadBalancer

kubectl apply -f nginx-service.yaml

Expected output:

service/nginx-slb created

kubectl get service nginx-slb

Expected output:

NAME        TYPE           CLUSTER-IP      EXTERNAL-IP      PORT(S)        AGE
nginx-slb   LoadBalancer   172.19.xx.xxx   47.110.xxx.xxx   80:32240/TCP   8m

Run the following command to connect to the IP address of the created SLB instance: 47.110.xxx.xxx. The output shows that the connection failed.
```
wget 47.110.xxx.xxx
```
Expected output:
```
--2018-11-21 11:46:05--  http://47.110.xx.xxx/
Connecting to 47.110.XX.XX:80... failed: Connection refused.
```
Note
The connection failed due to the following reasons:

The nginx Service can be accessed only by applications that have the access=true label.

When you connect to the IP address of the SLB instance from your on-premises machine, you are accessing the nginx Service from outside the Kubernetes cluster. This is not the same as when you use a network policy to allow only applications with specified labels to access the nginx Service.
Solution: Modify the network policy to allow the source IP address to access the nginx Service.

Run the following command to query the IP address of your on-premises machine:

curl myip.ipip.net

Expected output:

IP address: 10.0.x.x. From: China Beijing Beijing        # This is an example. Use the actual IP address.

Run the following command to modify the policy.yaml file:

vim policy.yaml
# The following content provides an example. 
kind: NetworkPolicy
apiVersion: networking.k8s.io/v1
metadata:
  name: access-nginx
spec:
  podSelector:
    matchLabels:
      run: nginx
  ingress:
  - from:
    - podSelector:
        matchLabels:
          access: "true"
    - ipBlock:
        cidr: 100.64.0.0/10
    - ipBlock:
        cidr: 10.0.0.1/24      # This is an example. Use the actual IP address.

kubectl apply -f policy.yaml

Expected output:

networkpolicy.networking.k8s.io/access-nginx unchanged

Note

The request may come from different IP addresses. Therefore, specify a CIDR block with a mask length of 24.
The IP addresses used by SLB for health checks are within the 100.64.0.0/10 CIDR block. Therefore, make sure that you add 100.64.0.0/10 to the rule.

Run the following command to test access to the nginx Service:

kubectl run busybox --rm -ti --labels="access=true" --image=busybox /bin/sh

wget 47.110.XX.XX

Expected output:

Connecting to 47.110.XX.XX (47.110.XX.XX:80)
index.html           100% |***********************************************************|   612  0:00:00 ETA

The output shows that the progress of the connection is 100%. This indicates that your on-premises machine can access the nginx Service as expected.

Allow a pod to access a specific address

Use the ACK console

In this section, www.aliyun.com and registry.aliyuncs.com are used as examples. The network policy allows a pod to access only registry.aliyuncs.com.

Visit Public DNS to query the IP address that is associated with registry.aliyuncs.com. In this example, the domain name is resolved to IP address 120.55.105.209.

Create a network policy and add an egress rule to allow the busybox application to access only registry.aliyuncs.com.

In the upper-right corner of the NetworkPolicies page, click Create. In the Create panel, set the parameters.

For more information about the parameters, see Allow only applications with specific labels to access a Service. The following content provides a sample configuration.

Set Name to busybox-policy.

Set pod selectors.


Parameter	Example
Type	Deployment
Workload	busybox
Label	app=busybox

Click + Add to the right of Destination, and then perform the following steps:

Click + Add to the right of Rule. Select ipBlock and add the IP address associated with registry.aliyuncs.com to the rule. In this example, the IP address is 120.55.105.209/32.


Parameter	Example
Selector	ipBlock
cidr	120.55.105.209/32

Click + Add to the right of Destination. Select namespaceSelector and allow outbound traffic to pods in all namespaces through UDP port 53. This ensures that the application can perform DNS lookups.

Click + Add to the right of Rule. The following table describes the rule that selects all namespaces.


Parameter	Example
Selector	namespace
Namespace	All

Click + Add to the right of Port. Add UDP port 53 to ensure that the application can perform DNS lookups. The following table describes the port parameters.


Parameter	Example
Protocol	UDP
Port	53

The following figure shows the configuration of the egress rule. dns

Click Next and then click OK.
Go to the terminal of the busybox pod and run the following commands to access www.aliyun.com and registry.aliyuncs.com in sequence:
```
nc -vz -w 1 www.aliyunc.com 443
```
```
nc -vz -w 1 registry.aliyuncs.com 443
```
After the network policy is added, the busybox application can access only registry.aliyuncs.com.

Use the CLI

Run the following command to query the IP addresses to which www.aliyun.com is resolved:

dig +short www.aliyun.com

Expected output:

www-jp-de-intl-adns.aliyun.com.
www-jp-de-intl-adns.aliyun.com.gds.alibabadns.com.
v6wagbridge.aliyun.com.
v6wagbridge.aliyun.com.gds.alibabadns.com.
106.XX.XX.21
140.XX.XX.4
140.XX.XX.13
140.XX.XX.3

Run the following command to create a file named busybox-policy:

vim busybox-policy.yaml
# The following content is an example of the YAML file. 
kind: NetworkPolicy
apiVersion: networking.k8s.io/v1
metadata:
  name: busybox-policy
spec:
  podSelector:
    matchLabels:
      run: busybox
  egress:
  - to:
    - ipBlock:
        cidr: 106.XX.XX.21/32
    - ipBlock:
        cidr: 140.XX.XX.4/32
    - ipBlock:
        cidr: 140.XX.XX.13/32
    - ipBlock:
        cidr: 140.XX.XX.3/32
  - to:
    - ipBlock:
        cidr: 0.0.0.0/0
    - namespaceSelector: {}
    ports:
    - protocol: UDP
      port: 53

Note Egress rules are configured in the busybox-policy file to restrict outbound access from the application. You must allow the application to access UDP port 53. Otherwise, the domain name cannot be resolved.

Run the following command to create a network policy based on the busybox-policy file:
```
kubectl apply -f busybox-policy.yaml 
```
Expected output:
```
networkpolicy.networking.k8s.io/busybox-policy created
```
Run the following command to access a website other than www.aliyun.com, such as www.taobao.com:
```
kubectl run busybox --rm -ti --image=busybox /bin/sh
```
```
wget www.taobao.com
```
Expected output:
```
Connecting to www.taobao.com (64.13.XX.XX:80)
wget: can't connect to remote host (64.13.XX.XX): Connection timed out
```
The output shows the can't connect to remote host message. This indicates that the application failed to access the domain name.

Run the following command to access www.aliyun.com:

wget www.aliyun.com

Expected output:

Connecting to www.aliyun.com (140.205.XX.XX:80)
Connecting to www.aliyun.com (140.205.XX.XX:443)
wget: note: TLS certificate validation not implemented
index.html           100% |***********************************************************|  462k  0:00:00 ETA

The output shows that the progress of the connection is 100%. This indicates that the application can access the domain name as expected.

Control pod access to the Internet in specific namespaces

Note The operations in this section may affect services that are communicating with the Internet. We recommend that you create an empty namespace to perform the following operations.

Use the ACK console

In the upper-right corner of the NetworkPolicies page, click Create. In the Create panel, set the parameters.

For more information about the parameters, see Allow only applications with specific labels to access a Service. The following table provides a sample configuration.


Parameter	Example
Name	deny-public-net
Pod Selectors	Set Type to All.
Source	Add the following ingress rules: Set namespaceSelector to All. Set ipBlock to 0.0.0.0/0.
Destination	Add egress rules that allow the pod to access only the internal network. Set namespaceSelector to All. This allows the pod to access all other pods in the internal network. Create three rules and set ipBlock to the following CIDR blocks in sequence: 10.0.0.0/8 172.16.0.0/12 192.168.0.0/16 Note You cannot specify multiple CIDR blocks for the ipBlock parameter in one rule.

Click Next and then click OK.
Go to the terminal of the busybox pod created in Create an NGINX application that allows access from other pods and run the following command to test whether the pod can access the Internet:
```
nc -vz -w 1 www.aliyunc.com 443
```
```
nc -vz -w 1 192.168.0.120:10255
```
The output shows that the pod can access the internal network but not the Internet.

Use the CLI

Run the following command to create a namespace for testing.
Create a namespace named test-np.
```
kubectl create ns test-np
```
Expected output:
```
namespace/test-np created
```

Run the following command to create a default network policy that allows pods in the test-np namespace to access only internal services:

vim default-deny.yaml
# The following content is an example of the YAML file. 
kind: NetworkPolicy
apiVersion: networking.k8s.io/v1
metadata:
  namespace: test-np
  name: deny-public-net
spec:
  podSelector: {}
  ingress:
  - from:
    - ipBlock:
        cidr: 0.0.0.0/0
  egress:
  - to:
    - ipBlock:
        cidr: 192.168.0.0/16
    - ipBlock:
        cidr: 172.16.0.0/12
    - ipBlock:
        cidr: 10.0.0.0/8

kubectl apply -f default-deny.yaml

Expected output:

networkpolicy.networking.k8s.io/deny-public-net created

kubectl get networkpolicy -n test-np

Expected output:

NAME                              POD-SELECTOR          AGE
deny-public-net                   <none>                1m

Run the following command to allow pods with specific labels to access the Internet.

In this example, the public-network=true label is used.

vim allow-specify-label.yaml
# The following content is an example of the YAML file. 
kind: NetworkPolicy
apiVersion: networking.k8s.io/v1
metadata:
  name: allow-public-network-for-labels
  namespace: test-np
spec:
  podSelector:
    matchLabels:
      public-network: "true"
  ingress:
  - from:
    - ipBlock:
        cidr: 0.0.0.0/0
  egress:
  - to:
    - ipBlock:
        cidr: 0.0.0.0/0
    - namespaceSelector:
        matchLabels:
          ns: kube-system

kubectl apply -f allow-specify-label.yaml

Expected output:

networkpolicy.networking.k8s.io/allow-public-network-for-labels created

kubectl get networkpolicy -n test-np

Expected output:

NAME                              POD-SELECTOR          AGE
allow-public-network-for-labels   public-network=true    1m
deny-public-net                   <none>                 3m

Run the following command to verify that a pod without the specified label cannot access the Internet:
```
kubectl run -it --namespace test-np --rm --image busybox  busybox-intranet
```
```
ping aliyun.com
```
Expected output:
```
PING aliyun.com (106.11.2xx.xxx): 56 data bytes
^C
--- aliyun.com ping statistics ---
9 packets transmitted, 0 packets received, 100% packet loss
```
The output shows 0 packets received. This indicates that the pod failed to access the Internet.

Note The pod failed to access the Internet because the deny-public-net network policy does not allow pods in the test-np namespace to access the Internet. Therefore, pods with default labels cannot access the Internet.

Run the following command to verify that a pod with the public-network=true label can access the Internet:

kubectl run -it --namespace test-np --labels public-network=true --rm --image busybox  busybox-internet

ping aliyun.com

Expected output:

PING aliyun.com (106.11.1xx.xx): 56 data bytes
64 bytes from 106.11.1xx.xx: seq=0 ttl=47 time=4.235 ms
64 bytes from 106.11.1xx.xx: seq=1 ttl=47 time=4.200 ms
64 bytes from 106.11.1xx.xx: seq=2 ttl=47 time=4.182 ms
^C
--- aliyun.com ping statistics ---
3 packets transmitted, 3 packets received, 0% packet loss
round-trip min/avg/max = 4.182/4.205/4.235 ms

The output shows 0% packet loss. This indicates that the pod can access the Internet.

Note The pod can access the Internet because the allow-public-network-for-labels network policy allows pods with the public-network=true label to access the Internet. The busybox-internet pod has this label and therefore can access the Internet.

Prerequisites

Enable network policies

Scenarios

Create an NGINX application that allows access from other pods

Allow only applications with specific labels to access a Service

Allow only specific source IP addresses to access a Service through an Internet-facing SLB instance

Allow a pod to access a specific address

Control pod access to the Internet in specific namespaces