Container Service for Kubernetes：Use network policies in ACK clusters

Use the ACK console

1. Log on to the ACK console. In the left-side navigation pane, click Clusters.

2. On the Clusters page, click the name of the cluster that you want to manage and choose Workloads > Deployments in the left-side navigation pane.

3. On the Deployments tab, click Create from Image. On the Create page, create an application named nginx and expose the application by using a Service. After you complete the application configuration, click Create.

   You can configure the following parameters based on the description in the following table and use default settings for other parameters. For more information, see Create a Deployment from an image.

   Parameter		Description	Example
   Basic Information	Name	Specify a custom application name.	nginx
   	Replicas	Specify the value based on your business requirements.	1
   Container	Image Name	Specify the name of the container image.	nginx:latest
   Advanced	Services	Click Create to the right of Services. In the Create Service dialog box, set the parameters.	Name: nginx
   			Type: Server Load Balancer Public Access Create SLB Instance
   			Port Mapping: Name: nginx Service Port: 80 Container Port: 80 Protocol: TCP

4. Return to the Deployments page and click Create from Image. On the Create page, create a client application named busybox to test the accessibility of the nginx Service created in the preceding step.

   You can configure the following parameters for the busybox client application based on the description in the following table and use default settings for other parameters. For more information, see Create a Deployment from an image.

   Parameter		Description	Example
   Basic Information	Name	Specify a custom application name.	busybox
   	Replicas	Specify a value based on your business requirements.	1
   Container Start Parameter	Image Name	Specify the name of the container image.	busybox:latest
   	Container Start Parameter	None.	Select stdin and tty.

5. 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

1. 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

   View the Service:

   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

2. 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.
   / #
   / #

   Obtain the nginx Service:

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

Use the ACK console

1. Create a network policy for the nginx Service. For more information, see Allow only applications with specific labels to access a Service.

2. On the Services page, find the nginx Service and copy its IP address (47.xxx.xx.x) in the External Endpoint column. Access the IP address in your browser.

   The nginx Service cannot be accessed due to the preconfigured network policy.

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

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

   2. 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 for Server Load Balancer (SLB) 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

      

   3. Click Next, and then click OK.

   4. On the Services page, find the nginx Service and click the IP address (47.xxx.xx.x:80) in the External Endpoint column.

      

      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

1. 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.

   vim nginx-service.yaml

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

   # Copy the following YAML content to the nginx-service.yaml file: 
   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

   Run the following command to create a network policy by using the nginx-service.yaml file:

   kubectl apply -f nginx-service.yaml 

   Expected output:

   service/nginx-slb created

   Check whether the application is exposed by using the nginx Service:

   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

2. 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.

3. 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.

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

   vim policy.yaml

   Example of the policy.yaml file:

   # The following content is an example of the YAML file. 
   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.

   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 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.

5. Run the following command to create the resources that are provisioned for the nginx Service:

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

   Access the nginx Service:

   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

   If the output shows 100%, this indicates that the nginx Service can be accessed.

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.

1. Use the Ping command to query the IP address (120.55.XXX.XXX) to which the registry.aliyuncs.com domain name is resolved.

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

   1. 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	Description	Example
   Parameter	Specify a custom network policy name.	busybox-policy
   Pod Selectors	Click + Specify workload type and labels and specify pod selectors for the network policy. Note If you do not set the pod selector, the network policy applies to all pods in the specified namespace.	In this example, the following settings are used: Type: Deployment Workload: busybox Label: app=busybox
   Destination	Click + Add to the right of Destination. Then, click + Add to the right of Rule. Select ipBlock and add the IP address to which registry.aliyuncs.com is resolved. In this example, the IP address is 120.55.XXX.XXX/32.	Selector: ipBlock CIDR: 120.55.XXX.XXX/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. Click + Add to the right of Port. Add UDP port 53 to ensure that the application can perform DNS lookups.	Rules: Selector: namespaceSelector Namespace: All Port: Protocol: UDP Port: 53

   2. Click Next, and then click OK.

   3. 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

1. 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

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

   vim busybox-policy.yaml

   Example of the busybox-policy file:

   # The following content is a sample 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 limit outbound access from the application. You must allow the application to access UDP port 53. Otherwise, Domain Name System (DNS) resolution does not work.

3. 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

4. Run the following command to create the busybox application:

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

   Access a website other than www.aliyun.com, such as www.taobao.com:

   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.

5. 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.

Use the ACK console

1. 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
   Parameter	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.

2. Click Next, and then click OK.

3. On the Basic Information tab of the cluster details page, obtain the private IP address and port.

   

4. Run the following command on the terminal of the busybox pod to test whether the pod can access the Internet and the internal network:

   nc -vz -w 1 www.aliyunc.com 443

   nc -vz -w 1 10.xx.xx.xx:<IP port> # Specify the private IP address.

   The output shows that the pod can access the internal network but not the Internet.

Use the CLI

1. 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

2. 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

   Example of the default-deny.yaml file:

   # The following content is a sample 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

   Check whether a network policy is created by using the default-deny.yaml file.

   kubectl apply -f default-deny.yaml

   Expected output:

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

   View the network policy:

   kubectl get networkpolicy -n test-np

   Expected output:

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

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

   vim allow-specify-label.yaml

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

   # The following content is a sample 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

   Run the following command to create the network policy:

   kubectl apply -f allow-specify-label.yaml

   Expected output:

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

   View the network policy:

   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

4. 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.

5. 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.