Chapter 17. Configuring system controls and interface attributes using the tuning plugin

Procedure

1. Create a network attachment definition, such as tuning-example.yaml, with the following content:

   apiVersion: "k8s.cni.cncf.io/v1"
   kind: NetworkAttachmentDefinition
   metadata:
     name: <name> 

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     namespace: default 

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   spec:
     config: '{
       "cniVersion": "0.4.0", 

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       "name": "<name>", 

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       "plugins": [{
          "type": "<main_CNI_plugin>" 

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         },
         {
          "type": "tuning", 

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          "sysctl": {
               "net.ipv4.conf.IFNAME.accept_redirects": "1" 

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           }
         }
        ]
   }

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   1

   Specifies the name for the additional network attachment to create. The name must be unique within the specified namespace.

   2

   Specifies the namespace that the object is associated with.

   3

   Specifies the CNI specification version.

   4

   Specifies the name for the configuration. It is recommended to match the configuration name to the name value of the network attachment definition.

   5

   Specifies the name of the main CNI plugin to configure.

   6

   Specifies the name of the CNI meta plugin.

   7

   Specifies the sysctl to set. The interface name is represented by the IFNAME token and is replaced with the actual name of the interface at runtime.

   An example YAML file is shown here:

   apiVersion: "k8s.cni.cncf.io/v1"
   kind: NetworkAttachmentDefinition
   metadata:
     name: tuningnad
     namespace: default
   spec:
     config: '{
       "cniVersion": "0.4.0",
       "name": "tuningnad",
       "plugins": [{
         "type": "bridge"
         },
         {
         "type": "tuning",
         "sysctl": {
            "net.ipv4.conf.IFNAME.accept_redirects": "1"
           }
       }
     ]
   }'

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2. Apply the YAML by running the following command:

   $ oc apply -f tuning-example.yaml

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   Example output

   networkattachmentdefinition.k8.cni.cncf.io/tuningnad created

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3. Create a pod such as examplepod.yaml with the network attachment definition similar to the following:

   apiVersion: v1
   kind: Pod
   metadata:
     name: tunepod
     namespace: default
     annotations:
       k8s.v1.cni.cncf.io/networks: tuningnad 

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   spec:
     containers:
     - name: podexample
       image: centos
       command: ["/bin/bash", "-c", "sleep INF"]
       securityContext:
         runAsUser: 2000 

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         runAsGroup: 3000 

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         allowPrivilegeEscalation: false 

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         capabilities: 

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           drop: ["ALL"]
     securityContext:
       runAsNonRoot: true 

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       seccompProfile: 

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         type: RuntimeDefault

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   1

   Specify the name of the configured NetworkAttachmentDefinition.

   2

   runAsUser controls which user ID the container is run with.

   3

   runAsGroup controls which primary group ID the containers is run with.

   4

   allowPrivilegeEscalation determines if a pod can request to allow privilege escalation. If unspecified, it defaults to true. This boolean directly controls whether the no_new_privs flag gets set on the container process.

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   capabilities permit privileged actions without giving full root access. This policy ensures all capabilities are dropped from the pod.

   6

   runAsNonRoot: true requires that the container will run with a user with any UID other than 0.

   7

   RuntimeDefault enables the default seccomp profile for a pod or container workload.

4. Apply the yaml by running the following command:

   $ oc apply -f examplepod.yaml

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5. Verify that the pod is created by running the following command:

   $ oc get pod

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   Example output

   NAME      READY   STATUS    RESTARTS   AGE
   tunepod   1/1     Running   0          47s

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6. Log in to the pod by running the following command:

   $ oc rsh tunepod

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7. Verify the values of the configured sysctl flags. For example, find the value net.ipv4.conf.net1.accept_redirects by running the following command:

   sh-4.4# sysctl net.ipv4.conf.net1.accept_redirects

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   Expected output

   net.ipv4.conf.net1.accept_redirects = 1

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Procedure

1. Create a network attachment definition, such as tuning-example.yaml, with the following content:

   apiVersion: "k8s.cni.cncf.io/v1"
   kind: NetworkAttachmentDefinition
   metadata:
     name: <name> 

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     namespace: default 

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   spec:
     config: '{
       "cniVersion": "0.4.0", 

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       "name": "<name>", 

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       "plugins": [{
          "type": "<main_CNI_plugin>" 

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         },
         {
          "type": "tuning", 

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          "allmulti": true 

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           }
         }
        ]
   }

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   1

   Specifies the name for the additional network attachment to create. The name must be unique within the specified namespace.

   2

   Specifies the namespace that the object is associated with.

   3

   Specifies the CNI specification version.

   4

   Specifies the name for the configuration. Match the configuration name to the name value of the network attachment definition.

   5

   Specifies the name of the main CNI plugin to configure.

   6

   Specifies the name of the CNI meta plugin.

   7

   Changes the all-multicast mode of interface. If enabled, all multicast packets on the network will be received by the interface.

   An example YAML file is shown here:

   apiVersion: "k8s.cni.cncf.io/v1"
   kind: NetworkAttachmentDefinition
   metadata:
     name: setallmulti
     namespace: default
   spec:
     config: '{
       "cniVersion": "0.4.0",
       "name": "setallmulti",
       "plugins": [
         {
           "type": "bridge"
         },
         {
           "type": "tuning",
           "allmulti": true
         }
       ]
     }'

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2. Apply the settings specified in the YAML file by running the following command:

   $ oc apply -f tuning-allmulti.yaml

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   Example output

   networkattachmentdefinition.k8s.cni.cncf.io/setallmulti created

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3. Create a pod with a network attachment definition similar to that specified in the following examplepod.yaml sample file:

   apiVersion: v1
   kind: Pod
   metadata:
     name: allmultipod
     namespace: default
     annotations:
       k8s.v1.cni.cncf.io/networks: setallmulti 

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   spec:
     containers:
     - name: podexample
       image: centos
       command: ["/bin/bash", "-c", "sleep INF"]
       securityContext:
         runAsUser: 2000 

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         runAsGroup: 3000 

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         allowPrivilegeEscalation: false 

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         capabilities: 

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           drop: ["ALL"]
     securityContext:
       runAsNonRoot: true 

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       seccompProfile: 

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         type: RuntimeDefault

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   1

   Specifies the name of the configured NetworkAttachmentDefinition.

   2

   Specifies the user ID the container is run with.

   3

   Specifies which primary group ID the containers is run with.

   4

   Specifies if a pod can request privilege escalation. If unspecified, it defaults to true. This boolean directly controls whether the no_new_privs flag gets set on the container process.

   5

   Specifies the container capabilities. The drop: ["ALL"] statement indicates that all Linux capabilities are dropped from the pod, providing a more restrictive security profile.

   6

   Specifies that the container will run with a user with any UID other than 0.

   7

   Specifies the container’s seccomp profile. In this case, the type is set to RuntimeDefault. Seccomp is a Linux kernel feature that restricts the system calls available to a process, enhancing security by minimizing the attack surface.

4. Apply the settings specified in the YAML file by running the following command:

   $ oc apply -f examplepod.yaml

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5. Verify that the pod is created by running the following command:

   $ oc get pod

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   Example output

   NAME          READY   STATUS    RESTARTS   AGE
   allmultipod   1/1     Running   0          23s

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6. Log in to the pod by running the following command:

   $ oc rsh allmultipod

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7. List all the interfaces associated with the pod by running the following command:

   sh-4.4# ip link

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   Example output

   1: lo: <LOOPBACK,UP,LOWER_UP> mtu 65536 qdisc noqueue state UNKNOWN mode DEFAULT group default qlen 1000
       link/loopback 00:00:00:00:00:00 brd 00:00:00:00:00:00
   2: eth0@if22: <BROADCAST,MULTICAST,UP,LOWER_UP> mtu 8901 qdisc noqueue state UP mode DEFAULT group default
       link/ether 0a:58:0a:83:00:10 brd ff:ff:ff:ff:ff:ff link-netnsid 0 

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   3: net1@if24: <BROADCAST,MULTICAST,ALLMULTI,UP,LOWER_UP> mtu 1500 qdisc noqueue state UP mode DEFAULT group default
       link/ether ee:9b:66:a4:ec:1d brd ff:ff:ff:ff:ff:ff link-netnsid 0 

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   1

   eth0@if22 is the primary interface

   2

   net1@if24 is the secondary interface configured with the network-attachment-definition that supports the all-multicast mode (ALLMULTI flag)