• Network Resources Injector
  • Getting started
  • Network resources injection example
  • Vendoring
  • Security
    • Disable adding client CAs to server TLS endpoint
    • Client CAs
  • Additional features
    • Features control switches
    • Expose Hugepages via Downward API
    • Node Selector
    • User Defined Injections
  • Test
    • Unit tests
    • E2E tests using Kubernetes in Docker (KinD)
  • Contact Us

Network Resources Injector

Network Resources Injector is a Kubernetes Dynamic Admission Controller application that provides functionality of patching Kubernetes pod specifications with requests and limits of custom network resources (managed by device plugins such as k8snetworkplumbingwg/sriov-network-device-plugin).

Getting started

To quickly build and deploy admission controller run:

make image
kubectl apply -f deployments/auth.yaml \
              -f deployments/server.yaml

For full installation and troubleshooting steps please see Installation guide.

Network resources injection example

To see mutating webhook in action you're going to need to add custom resources to your Kubernetes node. In real life scenarios you're going to use network resources managed by network devices plugins, such as k8snetworkplumbingwg/sriov-network-device-plugin. There should be net-attach-def CRD already created before you start. In a terminal window start proxy, so that you can easily send HTTP requests to the Kubernetes API server:

kubectl proxy

In another terminal window, execute below command to add 4 example.com/foo resources. Remember to edit <node-name> to match your cluster environment.

curl -s --header "Content-Type: application/json-patch+json" \
     --request PATCH \
     --data '[{"op": "add", "path": "/status/capacity/example.com~1foo", "value": "4"}]' \
     http://localhost:8001/api/v1/nodes/<node-name>/status >/dev/null

Next, you need to create a net-attach-def linked to this example.com/foo resource. To achieve that execute below command:

cat <<EOF | kubectl create -f -
apiVersion: k8s.cni.cncf.io/v1
kind: NetworkAttachmentDefinition
metadata:
  annotations:
    k8s.v1.cni.cncf.io/resourceName: example.com/foo
  name: foo-network
  namespace: default
spec:
  config: |
    {
      "cniVersion": "0.3.0",
      "name": "foo-network",
      "type": "bridge",
      "bridge": "br0",
      "isGateway": true,
      "ipam":
      {
        "type": "host-local",
        "subnet": "172.36.0.0/24",
        "dataDir": "/mnt/cluster-ipam"
      }
    }
EOF

Finally, schedule a pod that will take advantage of automated network resources injection. Use below example, to attach 2 foo-network networks and inject resources accordingly.

cat <<EOF | kubectl create -f -
apiVersion: v1
kind: Pod
metadata:
  name: webhook-demo
  annotations:
    k8s.v1.cni.cncf.io/networks: foo-network, foo-network
spec:
  containers:
  - image: busybox
    resources:
    command: ["tail", "-f", "/dev/null"]
    imagePullPolicy: IfNotPresent
    name: busybox
  restartPolicy: Always
EOF

Now verify that resources requests/limits have been properly injected into the first container in the pod. If you have jq installed run this command:

kubectl get pod webhook-demo -o json | jq .spec.containers[0].resources

Expected output showing injected resources in the pod spec, depsite the fact that we have only defined k8s.v1.cni.cncf.io/networks annotation.

{
  "limits": {
    "example.com/foo": "2"
  },
  "requests": {
    "example.com/foo": "2"
  }
}

Alternatively, grep output of kubectl to get the same information.

kubectl get pod webhook-demo -o yaml | grep resources -A4
    resources:
      limits:
        example.com/foo: "2"
      requests:
        example.com/foo: "2"

As the last step perform cleanup by removing net-attach-def, pod and custom example.com/foo resources. To do that, simply run:

curl --header "Content-Type: application/json-patch+json" \
     --request PATCH \
     --data '[{"op": "remove", "path": "/status/capacity/example.com~1foo"}]' \
     http://localhost:8001/api/v1/nodes/<node-name>/status
kubectl delete net-attach-def foo-network
kubectl delete pod webhook-demo

Vendoring

To create the vendor folder invoke the following which will create a vendor folder.

make vendor

Security

Disable adding client CAs to server TLS endpoint

If you wish to not add any client CAs to the servers TLS endpoint, add --insecure flag to webhook binary arguments (See server.yaml).

Client CAs

By default, we consume the client CA from the Kubernetes service account secrets directory /var/run/secrets/kubernetes.io/serviceaccount/. If you wish to consume a client CA from a different location, please specify flag --client-ca with a valid path. If you wish to add more than one client CA, repeat this flag multiple times. If --client-ca is defined, the default client CA from the service account secrets directory will not be consumed.

Additional features

All additional Network Resource Injector features can be enabled by passing command line arguments to executable. It can be done by modification of arguments passed to webhook. Example yaml with deployment is here server.yaml

Currently supported arguments are below. If needed, detailed description is available below in sub points. ConfigMap with runtime configuration is described below in point Features control switches.

Argument	Default	Description	Can be set via ConfigMap
port	8443	The port on which to serve.	NO
bind-address	0.0.0.0	The IP address on which to listen for the --port port.	NO
tls-cert-file	cert.pem	File containing the default x509 Certificate for HTTPS.	NO
tls-private-key-file	key.pem	File containing the default x509 private key matching --tls-cert-file.	NO
insecure	false	Disable adding client CA to server TLS endpoint	NO
client-ca	""	File containing client CA. This flag is repeatable if more than one client CA needs to be added to server	NO
health-check-port	8444	The port to use for health check monitoring.	NO
injectHugepageDownApi	false	Enable hugepage requests and limits into Downward API.	YES
network-resource-name-keys	k8s.v1.cni.cncf.io/resourceName	comma separated resource name keys	YES
honor-resources	false	Honor the existing requested resources requests & limits	YES

NOTE: Network Resource Injector would not mutate pods in kube-system namespace.

Features control switches

It is possible to control some features of Network Resource Injector with runtime configuration. NRI is watching for a ConfigMap with name nri-control-switches that should be available in the same namespace as NRI (default is kube-system). Below is example with full configuration that sets all features to disable state. Not all values have to be defined. User can toggle only one feature leaving others in default state. By default state, one should understand state set during webhook initialization. Could be a state set by CLI argument, default argument embedded in code or environment variable.

apiVersion: v1
kind: ConfigMap
metadata:
  name: nri-control-switches
  namespace: kube-system
data:
  config.json: |
    {
      "features": {
        "enableHugePageDownApi": false,
        "enableHonorExistingResources": false
      }
    }

Set feature state is available as long as ConfigMap exists. Webhook checks for map update every 30 seconds. Please keep in mind that runtime configuration settings override all other settings. They have the highest priority.

Expose Hugepages via Downward API

In Kubernetes 1.20, an alpha feature was added to expose the requested hugepages to the container via the Downward API. Being alpha, this feature is disabled in Kubernetes by default. If enabled when Kubernetes is deployed via FEATURE_GATES="DownwardAPIHugePages=true", then Network Resource Injector can be used to mutate the pod spec to publish the hugepage data to the container. To enable this functionality in Network Resource Injector, add --injectHugepageDownApi flag to webhook binary arguments (See server.yaml).

NOTE: Please note that the Network Resource Injector does not add hugepage resources to the POD specification. It means that user has to explicitly add it. This feature only exposes it to Downward API. More information about hugepages can be found within Kubernetes specification. Snippet of how to request hugepage resources in pod spec:

spec:
  containers:
  - image: busybox
    resources:
      limits:
        hugepages-1Gi: 2Gi
        memory: 2Gi
      requests:
        hugepages-1Gi: 2Gi
        memory: 2Gi

Like the other Downward API provided data, hugepage information for a pod can be located by an application at the path /etc/podnetinfo/ in the container's file system. This directory will contain the request and limit information for 1Gi/2Mb.

1Gi Hugepages:

    Requests: /etc/podnetinfo/hugepages_1G_request_${CONTAINER_NAME}
    Limits: /etc/podnetinfo/hugepages_1G_limit_${CONTAINER_NAME}

2Mb: Hugepages:

    Requests: /etc/podnetinfo/hugepages_2M_request_${CONTAINER_NAME}
    Limits: /etc/podnetinfo/hugepages_2M_limit_${CONTAINER_NAME}

NOTE: To aid the application, when hugepage fields are being requested via the Downward API, Network Resource Injector also mutates the pod spec to add the environment variable CONTAINER_NAME with the container's name applied.

Node Selector

If a NetworkAttachmentDefinition CR annotation k8s.v1.cni.cncf.io/nodeSelector is present and a pod utilizes this network, Network Resources Injector will add this node selection constraint into the pod spec field nodeSelector. Injecting a single node selector label is currently supported.

Example:

apiVersion: k8s.cni.cncf.io/v1
kind: NetworkAttachmentDefinition
metadata:
  name: test-network
  annotations:
    k8s.v1.cni.cncf.io/nodeSelector: master=eno3
spec:
  config: '{
  "cniVersion": "0.3.1",
  "type": "macvlan",
  "master": "eno3",
  "mode": "bridge",
  }'
...

Pod spec after modification by Network Resources Injector:

apiVersion: v1
kind: Pod
metadata:
  name: testpod
  annotations:
    k8s.v1.cni.cncf.io/networks: test-network
spec:
 ..
 nodeSelector:
   master: eno3

User Defined Injections

User Defined injections allows user to define additional injections (besides what's supported in NRI, such as ResourceName, Downward API volumes etc) in Kubernetes ConfigMap and request additional injection for individual pod based on pod label. Currently user defined injection only support injecting pod annotations.

In order to use this feature, user needs to create the user defined injection ConfigMap with name nri-control-switches in the namespace where NRI was deployed in (kube-system namespace is used when there is no NAMESPACE environment variable passed to NRI). The ConfigMap is shared between control switches and user defined injections. The data entry in ConfigMap is in the format of key:value pair. Key is a user defined label that will be used to match with pod labels, Value is the actual injection in the format as defined by RFC6902 that will be applied to pod manifest. NRI would listen to the creation/update/deletion of this ConfigMap and update its internal data structure every 30 seconds so that subsequential creation of pods will be evaluated against the latest user defined injections.

Metadata.Annotations in Pod definition is the only supported field for customization, whose path should be "/metadata/annotations".

Below is an example of user defined injection ConfigMap:

apiVersion: v1
kind: ConfigMap
metadata:
  name: nri-control-switches
  namespace: kube-system
data:
  config.json: |
    {
      "user-defined-injections": {
        "feature.pod.kubernetes.io_sriov-network": {
          "op": "add",
          "path": "/metadata/annotations",
          "value": {
            "k8s.v1.cni.cncf.io/networks": "sriov-net-attach-def"
          }
        }
      }
    }

feature.pod.kubernetes.io/sriov-network is a user defined label to request additional networks. Every pod that contains this label with a value set to "true" will be applied with the patch that's defined in the following json string.

'{"op": "add", "path": "/metadata/annotations", "value": {"k8s.v1.cni.cncf.io/networks": "sriov-net -attach-def"}} defines how/where/what the patch shall be applied.

"op": "add" is the action for user defined injection. In above case, it requests to add the value to path in pod manifests.

"path": "/metadata/annotations" is the path in pod manifest to be updated.

"value": {"k8s.v1.cni.cncf.io/networks": "sriov-net-attach-def"}} is the value to be updated in the given path.

NOTE: Please be aware that current implementation supports only add type of JSON operation. Other types like remove, replace, copy, move are not yet supported.

For a pod to request user defined injection, one of its labels shall match with the labels defined in user defined injection ConfigMap. For example, with the below pod manifest:

apiVersion: v1
kind: Pod
metadata:
  name: testpod
  labels:
   feature.pod.kubernetes.io_sriov-network: "true"
spec:
  containers:
  - name: app
    image: centos:7
    command: [ "/bin/bash", "-c", "--" ]
    args: [ "while true; do sleep 300000; done;" ]

NRI would update pod manifest to:

apiVersion: v1
kind: Pod
metadata:
  name: testpod
  labels:
   feature.pod.kubernetes.io_sriov-network: "true"
  annotations:
    k8s.v1.cni.cncf.io/networks: sriov-net-attach-def
spec:
  containers:
  - name: app
    image: centos:7
    command: [ "/bin/bash", "-c", "--" ]
    args: [ "while true; do sleep 300000; done;" ]

NOTE: It it worth to mention that every existing network defined in annotations.k8s.v1.cni.cncf.io/networks is going to be replaced by NRI with new value.

NOTE: NRI is only able to inject one custom definition. When user will define more key/values pairs within ConfigMap (nri-user-defined-injections), only one will be injected.

Test

Unit tests

$ make test

E2E tests using Kubernetes in Docker (KinD)

Deploy KinD and run tests

$ make e2e

Note: For all tests to run you will need to provision your host with 3 Gi and 1024 Mi hugepages.

Cleanup KinD deployment

make e2e-clean

Contact Us

For any questions about Network Resources Injector, feel free to ask a question in #network-resources-injector in NPWG slack, or open up a GitHub issue. Request an invite to NPWG slack here.