Set up Konnectivity service

The Konnectivity service provides a TCP level proxy for the control plane to cluster communication.

Before you begin

You need to have a Kubernetes cluster, and the kubectl command-line tool must be configured to communicate with your cluster. If you do not already have a cluster, you can create one by using minikube or you can use one of these Kubernetes playgrounds:

Configure the Konnectivity service

The following steps require an egress configuration, for example:

admin/konnectivity/egress-selector-configuration.yaml Set up Konnectivity service - 图1

  1. apiVersion: apiserver.k8s.io/v1beta1
  2. kind: EgressSelectorConfiguration
  3. egressSelections:
  4. # Since we want to control the egress traffic to the cluster, we use the
  5. # "cluster" as the name. Other supported values are "etcd", and "master".
  6. - name: cluster
  7.   connection:
  8.     # This controls the protocol between the API Server and the Konnectivity
  9.     # server. Supported values are "GRPC" and "HTTPConnect". There is no
  10.     # end user visible difference between the two modes. You need to set the
  11.     # Konnectivity server to work in the same mode.
  12.     proxyProtocol: GRPC
  13.     transport:
  14.       # This controls what transport the API Server uses to communicate with the
  15.       # Konnectivity server. UDS is recommended if the Konnectivity server
  16.       # locates on the same machine as the API Server. You need to configure the
  17.       # Konnectivity server to listen on the same UDS socket.
  18.       # The other supported transport is "tcp". You will need to set up TLS 
  19.       # config to secure the TCP transport.
  20.       uds:
  21.         udsName: /etc/kubernetes/konnectivity-server/konnectivity-server.socket

You need to configure the API Server to use the Konnectivity service and direct the network traffic to the cluster nodes:

  1. Make sure that the ServiceAccountTokenVolumeProjection feature gate is enabled. You can enable service account token volume protection by providing the following flags to the kube-apiserver:

    1. --service-account-issuer=api
    2. --service-account-signing-key-file=/etc/kubernetes/pki/sa.key
    3. --api-audiences=system:konnectivity-server

  2. Create an egress configuration file such as admin/konnectivity/egress-selector-configuration.yaml.

  3. Set the --egress-selector-config-file flag of the API Server to the path of your API Server egress configuration file.

Generate or obtain a certificate and kubeconfig for konnectivity-server.
For example, you can use the OpenSSL command line tool to issue a X.509 certificate, using the cluster CA certificate /etc/kubernetes/pki/ca.crt from a control-plane host.

  1. openssl req -subj "/CN=system:konnectivity-server" -new -newkey rsa:2048 -nodes -out konnectivity.csr -keyout konnectivity.key -out konnectivity.csr
  2. openssl x509 -req -in konnectivity.csr -CA /etc/kubernetes/pki/ca.crt -CAkey /etc/kubernetes/pki/ca.key -CAcreateserial -out konnectivity.crt -days 375 -sha256
  3. SERVER=$(kubectl config view -o jsonpath='{.clusters..server}')
  4. kubectl --kubeconfig /etc/kubernetes/konnectivity-server.conf config set-credentials system:konnectivity-server --client-certificate konnectivity.crt --client-key konnectivity.key --embed-certs=true
  5. kubectl --kubeconfig /etc/kubernetes/konnectivity-server.conf config set-cluster kubernetes --server "$SERVER" --certificate-authority /etc/kubernetes/pki/ca.crt --embed-certs=true
  6. kubectl --kubeconfig /etc/kubernetes/konnectivity-server.conf config set-context system:konnectivity-server@kubernetes --cluster kubernetes --user system:konnectivity-server
  7. kubectl --kubeconfig /etc/kubernetes/konnectivity-server.conf config use-context system:konnectivity-server@kubernetes
  8. rm -f konnectivity.crt konnectivity.key konnectivity.csr

Next, you need to deploy the Konnectivity server and agents. kubernetes-sigs/apiserver-network-proxy is a reference implementation.

Deploy the Konnectivity server on your control plane node. The provided konnectivity-server.yaml manifest assumes that the Kubernetes components are deployed as a static Pod in your cluster. If not, you can deploy the Konnectivity server as a DaemonSet.

admin/konnectivity/konnectivity-server.yaml Set up Konnectivity service - 图2

  1. apiVersion: v1
  2. kind: Pod
  3. metadata:
  4.   name: konnectivity-server
  5.   namespace: kube-system
  6. spec:
  7.   priorityClassName: system-cluster-critical
  8.   hostNetwork: true
  9.   containers:
  10.   - name: konnectivity-server-container
  11.     image: us.gcr.io/k8s-artifacts-prod/kas-network-proxy/proxy-server:v0.0.12
  12.     command: ["/proxy-server"]
  13.     args: [
  14.             "--logtostderr=true",
  15.             # This needs to be consistent with the value set in egressSelectorConfiguration.
  16.             "--uds-name=/etc/kubernetes/konnectivity-server/konnectivity-server.socket",
  17.             # The following two lines assume the Konnectivity server is
  18.             # deployed on the same machine as the apiserver, and the certs and
  19.             # key of the API Server are at the specified location.
  20.             "--cluster-cert=/etc/kubernetes/pki/apiserver.crt",
  21.             "--cluster-key=/etc/kubernetes/pki/apiserver.key",
  22.             # This needs to be consistent with the value set in egressSelectorConfiguration.
  23.             "--mode=grpc",
  24.             "--server-port=0",
  25.             "--agent-port=8132",
  26.             "--admin-port=8133",
  27.             "--health-port=8134",
  28.             "--agent-namespace=kube-system",
  29.             "--agent-service-account=konnectivity-agent",
  30.             "--kubeconfig=/etc/kubernetes/konnectivity-server.conf",
  31.             "--authentication-audience=system:konnectivity-server"
  32.             ]
  33.     livenessProbe:
  34.       httpGet:
  35.         scheme: HTTP
  36.         host: 127.0.0.1
  37.         port: 8134
  38.         path: /healthz
  39.       initialDelaySeconds: 30
  40.       timeoutSeconds: 60
  41.     ports:
  42.     - name: agentport
  43.       containerPort: 8132
  44.       hostPort: 8132
  45.     - name: adminport
  46.       containerPort: 8133
  47.       hostPort: 8133
  48.     - name: healthport
  49.       containerPort: 8134
  50.       hostPort: 8134
  51.     volumeMounts:
  52.     - name: k8s-certs
  53.       mountPath: /etc/kubernetes/pki
  54.       readOnly: true
  55.     - name: kubeconfig
  56.       mountPath: /etc/kubernetes/konnectivity-server.conf
  57.       readOnly: true
  58.     - name: konnectivity-uds
  59.       mountPath: /etc/kubernetes/konnectivity-server
  60.       readOnly: false
  61.   volumes:
  62.   - name: k8s-certs
  63.     hostPath:
  64.       path: /etc/kubernetes/pki
  65.   - name: kubeconfig
  66.     hostPath:
  67.       path: /etc/kubernetes/konnectivity-server.conf
  68.       type: FileOrCreate
  69.   - name: konnectivity-uds
  70.     hostPath:
  71.       path: /etc/kubernetes/konnectivity-server
  72.       type: DirectoryOrCreate

Then deploy the Konnectivity agents in your cluster:

admin/konnectivity/konnectivity-agent.yaml Set up Konnectivity service - 图3

  1. apiVersion: apps/v1
  2. # Alternatively, you can deploy the agents as Deployments. It is not necessary
  3. # to have an agent on each node.
  4. kind: DaemonSet
  5. metadata:
  6.   labels:
  7.     addonmanager.kubernetes.io/mode: Reconcile
  8.     k8s-app: konnectivity-agent
  9.   namespace: kube-system
  10.   name: konnectivity-agent
  11. spec:
  12.   selector:
  13.     matchLabels:
  14.       k8s-app: konnectivity-agent
  15.   template:
  16.     metadata:
  17.       labels:
  18.         k8s-app: konnectivity-agent
  19.     spec:
  20.       priorityClassName: system-cluster-critical
  21.       tolerations:
  22.         - key: "CriticalAddonsOnly"
  23.           operator: "Exists"
  24.       containers:
  25.         - image: us.gcr.io/k8s-artifacts-prod/kas-network-proxy/proxy-agent:v0.0.12
  26.           name: konnectivity-agent
  27.           command: ["/proxy-agent"]
  28.           args: [
  29.                   "--logtostderr=true",
  30.                   "--ca-cert=/var/run/secrets/kubernetes.io/serviceaccount/ca.crt",
  31.                   # Since the konnectivity server runs with hostNetwork=true,
  32.                   # this is the IP address of the master machine.
  33.                   "--proxy-server-host=35.225.206.7",
  34.                   "--proxy-server-port=8132",
  35.                   "--admin-server-port=8133",
  36.                   "--health-server-port=8134",
  37.                   "--service-account-token-path=/var/run/secrets/tokens/konnectivity-agent-token"
  38.                   ]
  39.           volumeMounts:
  40.             - mountPath: /var/run/secrets/tokens
  41.               name: konnectivity-agent-token
  42.           livenessProbe:
  43.             httpGet:
  44.               port: 8134
  45.               path: /healthz
  46.             initialDelaySeconds: 15
  47.             timeoutSeconds: 15
  48.       serviceAccountName: konnectivity-agent
  49.       volumes:
  50.         - name: konnectivity-agent-token
  51.           projected:
  52.             sources:
  53.               - serviceAccountToken:
  54.                   path: konnectivity-agent-token
  55.                   audience: system:konnectivity-server

Last, if RBAC is enabled in your cluster, create the relevant RBAC rules:

admin/konnectivity/konnectivity-rbac.yaml Set up Konnectivity service - 图4

  1. apiVersion: rbac.authorization.k8s.io/v1
  2. kind: ClusterRoleBinding
  3. metadata:
  4.   name: system:konnectivity-server
  5.   labels:
  6.     kubernetes.io/cluster-service: "true"
  7.     addonmanager.kubernetes.io/mode: Reconcile
  8. roleRef:
  9.   apiGroup: rbac.authorization.k8s.io
  10.   kind: ClusterRole
  11.   name: system:auth-delegator
  12. subjects:
  13.   - apiGroup: rbac.authorization.k8s.io
  14.     kind: User
  15.     name: system:konnectivity-server
  16. ---
  17. apiVersion: v1
  18. kind: ServiceAccount
  19. metadata:
  20.   name: konnectivity-agent
  21.   namespace: kube-system
  22.   labels:
  23.     kubernetes.io/cluster-service: "true"
  24.     addonmanager.kubernetes.io/mode: Reconcile