容器编排之Kubernetes网络隔离NetworkPolicy

Kubernetes的一个重要特性就是要把不同node节点的pod(container)连接起来,无视物理节点的限制。但是在某些应用环境中,比如公有云,不同租户的pod不应该互通,这个时候就需要网络隔离。幸好,Kubernetes提供了NetworkPolicy,支持按Namespace级别的网络隔离,这篇文章就带你去了解如何使用NetworkPolicy。

需要注意的是,使用NetworkPolicy需要特定的网络解决方案,如果不启用,即使配置了NetworkPolicy也无济于事。我们这里使用Calico解决网络隔离问题。

互通测试

在使用NetworkPolicy之前,我们先验证不使用的情况下,pod是否互通。这里我们的测试环境是这样的:

Namespace:ns-calico1,ns-calico2

Deployment: ns-calico1/calico1-nginx, ns-calico2/busybox

Service: ns-calico1/calico1-nginx

先创建Namespace:

apiVersion: v1
kind: Namespace
metadata:
  name: ns-calico1
  labels:
    user: calico1
---
apiVersion: v1
kind: Namespace
metadata:
  name: ns-calico2
# kubectl create -f namespace.yaml
namespace "ns-calico1" created
namespace "ns-calico2" created
# kubectl get ns
NAME          STATUS    AGE
default       Active    9d
kube-public   Active    9d
kube-system   Active    9d
ns-calico1    Active    12s
ns-calico2    Active    8s

接着创建ns-calico1/calico1-nginx:

apiVersion: extensions/v1beta1
kind: Deployment
metadata:
  name: calico1-nginx
  namespace: ns-calico1
spec:
  replicas: 1
  template:
    metadata:
      labels:
        user: calico1
        app: nginx
    spec:
      containers:
      - name: nginx
        image: nginx
        ports:
        - containerPort: 80
---
apiVersion: v1
kind: Service
metadata:
  name: calico1-nginx
  namespace: ns-calico1
  labels: 
    user: calico1
spec:
  selector:
    app: nginx
  ports:
  - port: 80
# kubectl create -f calico1-nginx.yaml
deployment "calico1-nginx" created
service "calico1-nginx" created
# kubectl get svc -n ns-calico1
NAME            CLUSTER-IP      EXTERNAL-IP   PORT(S)   AGE
calico1-nginx   192.168.3.141   <none>        80/TCP    26s
# kubectl get deploy -n ns-calico1
NAME            DESIRED   CURRENT   UP-TO-DATE   AVAILABLE   AGE
calico1-nginx   1         1         1            1           34s

最后创建ns-calico2/calico2-busybox:

apiVersion: v1
kind: Pod
metadata:
  name: calico2-busybox
  namespace: ns-calico2
spec:
  containers:
  - name: busybox
    image: busybox
    command:
      - sleep
      - "3600"
# kubectl create -f calico2-busybox.yaml
pod "calico2-busybox" created
# kubectl get pod -n ns-calico2
NAME              READY     STATUS    RESTARTS   AGE
calico2-busybox   1/1       Running   0          40s

测试服务已经安装完成,现在我们登进calico2-busybox里,看是否能够连通calico1-nginx

# kubectl exec -it calico2-busybox -n ns-calico2 -- wget --spider --timeout=1 calico1-nginx.ns-calico1
Connecting to calico1-nginx.ns-calico1 (192.168.3.141:80)

由此可以看出,在没有设置网络隔离的时候,两个不同Namespace下的Pod是可以互通的。接下来我们使用Calico进行网络隔离。

网络隔离

先决条件

要想在Kubernetes集群中使用Calico进行网络隔离,必须满足以下条件:

  1. kube-apiserver必须开启运行时extensions/v1beta1/networkpolicies,即设置启动参数:–runtime-config=extensions/v1beta1/networkpolicies=true
  2. kubelet必须启用cni网络插件,即设置启动参数:–network-plugin=cni
  3. kube-proxy必须启用iptables代理模式,这是默认模式,可以不用设置
  4. kube-proxy不得启用–masquerade-all,这会跟calico冲突

注意:配置Calico之后,之前在集群中运行的Pod都要重新启动

安装calico

首先需要安装Calico网络插件,我们直接在Kubernetes集群中安装,便于管理。

# Calico Version v2.1.4
# http://docs.projectcalico.org/v2.1/releases#v2.1.4
# This manifest includes the following component versions:
#   calico/node:v1.1.3
#   calico/cni:v1.7.0
#   calico/kube-policy-controller:v0.5.4

# This ConfigMap is used to configure a self-hosted Calico installation.
kind: ConfigMap
apiVersion: v1
metadata:
  name: calico-config
  namespace: kube-system
data:
  # Configure this with the location of your etcd cluster.
  etcd_endpoints: "https://10.1.2.154:2379,https://10.1.2.147:2379"

  # Configure the Calico backend to use.
  calico_backend: "bird"

  # The CNI network configuration to install on each node.
  cni_network_config: |-
    {
        "name": "k8s-pod-network",
        "type": "calico",
        "etcd_endpoints": "__ETCD_ENDPOINTS__",
        "etcd_key_file": "__ETCD_KEY_FILE__",
        "etcd_cert_file": "__ETCD_CERT_FILE__",
        "etcd_ca_cert_file": "__ETCD_CA_CERT_FILE__",
        "log_level": "info",
        "ipam": {
            "type": "calico-ipam"
        },
        "policy": {
            "type": "k8s",
            "k8s_api_root": "https://__KUBERNETES_SERVICE_HOST__:__KUBERNETES_SERVICE_PORT__",
            "k8s_auth_token": "__SERVICEACCOUNT_TOKEN__"
        },
        "kubernetes": {
            "kubeconfig": "__KUBECONFIG_FILEPATH__"
        }
    }

  # If you're using TLS enabled etcd uncomment the following.
  # You must also populate the Secret below with these files.
  etcd_ca: "/calico-secrets/etcd-ca"   # "/calico-secrets/etcd-ca"
  etcd_cert: "/calico-secrets/etcd-cert" # "/calico-secrets/etcd-cert"
  etcd_key: "/calico-secrets/etcd-key"  # "/calico-secrets/etcd-key"

---

# The following contains k8s Secrets for use with a TLS enabled etcd cluster.
# For information on populating Secrets, see http://kubernetes.io/docs/user-guide/secrets/
apiVersion: v1
kind: Secret
type: Opaque
metadata:
  name: calico-etcd-secrets
  namespace: kube-system
data:
  # Populate the following files with etcd TLS configuration if desired, but leave blank if
  # not using TLS for etcd.
  # This self-hosted install expects three files with the following names.  The values
  # should be base64 encoded strings of the entire contents of each file.
  etcd-key: base64 key.pem
  etcd-cert: base64 cert.pem
  etcd-ca: base64 ca.pem

---

# This manifest installs the calico/node container, as well
# as the Calico CNI plugins and network config on
# each master and worker node in a Kubernetes cluster.
apiVersion: extensions/v1beta1
kind: DaemonSet
metadata:
  name: calico-node
  namespace: kube-system
  labels:
    k8s-app: calico-node
spec:
  selector:
    matchLabels:
      k8s-app: calico-node
  template:
    metadata:
      labels:
        k8s-app: calico-node
      annotations:
        scheduler.alpha.kubernetes.io/critical-pod: ''
        scheduler.alpha.kubernetes.io/tolerations: |
          [{"key": "dedicated", "value": "master", "effect": "NoSchedule" },
           {"key":"CriticalAddonsOnly", "operator":"Exists"}]
    spec:
      hostNetwork: true
      containers:
        # Runs calico/node container on each Kubernetes node.  This
        # container programs network policy and routes on each
        # host.
        - name: calico-node
          image: quay.io/calico/node:v1.1.3
          env:
            # The location of the Calico etcd cluster.
            - name: ETCD_ENDPOINTS
              valueFrom:
                configMapKeyRef:
                  name: calico-config
                  key: etcd_endpoints
            # Choose the backend to use.
            - name: CALICO_NETWORKING_BACKEND
              valueFrom:
                configMapKeyRef:
                  name: calico-config
                  key: calico_backend
            # Disable file logging so `kubectl logs` works.
            - name: CALICO_DISABLE_FILE_LOGGING
              value: "true"
            # Set Felix endpoint to host default action to ACCEPT.
            - name: FELIX_DEFAULTENDPOINTTOHOSTACTION
              value: "ACCEPT"
            # Configure the IP Pool from which Pod IPs will be chosen.
            - name: CALICO_IPV4POOL_CIDR
              value: "192.168.0.0/16"
            - name: CALICO_IPV4POOL_IPIP
              value: "always"
            # Disable IPv6 on Kubernetes.
            - name: FELIX_IPV6SUPPORT
              value: "false"
            # Set Felix logging to "info"
            - name: FELIX_LOGSEVERITYSCREEN
              value: "info"
            # Location of the CA certificate for etcd.
            - name: ETCD_CA_CERT_FILE
              valueFrom:
                configMapKeyRef:
                  name: calico-config
                  key: etcd_ca
            # Location of the client key for etcd.
            - name: ETCD_KEY_FILE
              valueFrom:
                configMapKeyRef:
                  name: calico-config
                  key: etcd_key
            # Location of the client certificate for etcd.
            - name: ETCD_CERT_FILE
              valueFrom:
                configMapKeyRef:
                  name: calico-config
                  key: etcd_cert
            # Auto-detect the BGP IP address.
            - name: IP
              value: ""
          securityContext:
            privileged: true
          #resources:
            #requests:
              #cpu: 250m
          volumeMounts:
            - mountPath: /lib/modules
              name: lib-modules
              readOnly: true
            - mountPath: /var/run/calico
              name: var-run-calico
              readOnly: false
            - mountPath: /calico-secrets
              name: etcd-certs
        # This container installs the Calico CNI binaries
        # and CNI network config file on each node.
        - name: install-cni
          image: quay.io/calico/cni:v1.7.0
          command: ["/install-cni.sh"]
          env:
            # The location of the Calico etcd cluster.
            - name: ETCD_ENDPOINTS
              valueFrom:
                configMapKeyRef:
                  name: calico-config
                  key: etcd_endpoints
            # The CNI network config to install on each node.
            - name: CNI_NETWORK_CONFIG
              valueFrom:
                configMapKeyRef:
                  name: calico-config
                  key: cni_network_config
          volumeMounts:
            - mountPath: /host/opt/cni/bin
              name: cni-bin-dir
            - mountPath: /host/etc/cni/net.d
              name: cni-net-dir
            - mountPath: /calico-secrets
              name: etcd-certs
      volumes:
        # Used by calico/node.
        - name: lib-modules
          hostPath:
            path: /lib/modules
        - name: var-run-calico
          hostPath:
            path: /var/run/calico
        # Used to install CNI.
        - name: cni-bin-dir
          hostPath:
            path: /opt/cni/bin
        - name: cni-net-dir
          hostPath:
            path: /etc/cni/net.d
        # Mount in the etcd TLS secrets.
        - name: etcd-certs
          secret:
            secretName: calico-etcd-secrets

---

# This manifest deploys the Calico policy controller on Kubernetes.
# See https://github.com/projectcalico/k8s-policy
apiVersion: extensions/v1beta1
kind: Deployment
metadata:
  name: calico-policy-controller
  namespace: kube-system
  labels:
    k8s-app: calico-policy
  annotations:
    scheduler.alpha.kubernetes.io/critical-pod: ''
    scheduler.alpha.kubernetes.io/tolerations: |
      [{"key": "dedicated", "value": "master", "effect": "NoSchedule" },
       {"key":"CriticalAddonsOnly", "operator":"Exists"}]
spec:
  # The policy controller can only have a single active instance.
  replicas: 1
  strategy:
    type: Recreate
  template:
    metadata:
      name: calico-policy-controller
      namespace: kube-system
      labels:
        k8s-app: calico-policy
    spec:
      # The policy controller must run in the host network namespace so that
      # it isn't governed by policy that would prevent it from working.
      hostNetwork: true
      containers:
        - name: calico-policy-controller
          image: quay.io/calico/kube-policy-controller:v0.5.4
          env:
            # The location of the Calico etcd cluster.
            - name: ETCD_ENDPOINTS
              valueFrom:
                configMapKeyRef:
                  name: calico-config
                  key: etcd_endpoints
            # Location of the CA certificate for etcd.
            - name: ETCD_CA_CERT_FILE
              valueFrom:
                configMapKeyRef:
                  name: calico-config
                  key: etcd_ca
            # Location of the client key for etcd.
            - name: ETCD_KEY_FILE
              valueFrom:
                configMapKeyRef:
                  name: calico-config
                  key: etcd_key
            # Location of the client certificate for etcd.
            - name: ETCD_CERT_FILE
              valueFrom:
                configMapKeyRef:
                  name: calico-config
                  key: etcd_cert
            # The location of the Kubernetes API.  Use the default Kubernetes
            # service for API access.
            - name: K8S_API
              value: "https://kubernetes.default:443"
            # Since we're running in the host namespace and might not have KubeDNS
            # access, configure the container's /etc/hosts to resolve
            # kubernetes.default to the correct service clusterIP.
            - name: CONFIGURE_ETC_HOSTS
              value: "true"
          volumeMounts:
            # Mount in the etcd TLS secrets.
            - mountPath: /calico-secrets
              name: etcd-certs
      volumes:
        # Mount in the etcd TLS secrets.
        - name: etcd-certs
          secret:
            secretName: calico-etcd-secrets
# kubectl create -f calico.yaml
configmap "calico-config" created
secret "calico-etcd-secrets" created
daemonset "calico-node" created
deployment "calico-policy-controller" created
# kubectl get ds -n kube-system                                     
NAME          DESIRED   CURRENT   READY     UP-TO-DATE   AVAILABLE   NODE-SELECTOR                              AGE
calico-node   1         1         1         1            1           <none>                                     52s
 # kubectl get deploy -n kube-system
NAME                       DESIRED   CURRENT   UP-TO-DATE   AVAILABLE   AGE
calico-policy-controller   1         1         1            1           6m

这样就搭建了Calico网络,接下来就可以配置NetworkPolicy了。

配置NetworkPolicy

首先,修改ns-calico1的配置:

apiVersion: v1
kind: Namespace
metadata:
  name: ns-calico1
  labels:
    user: calico1
  annotations:
    net.beta.kubernetes.io/network-policy: |
      {
        "ingress": {
          "isolation": "DefaultDeny"
        }
      }
# kubectl apply -f ns-calico1.yaml
namespace "ns-calico1" configured

如果这个时候再测试两个pod是否连通,一定会不通:

# kubectl exec -it calico2-busybox -n ns-calico2 -- wget --spider --timeout=1 calico1-nginx.ns-calico1
Connecting to calico1-nginx.ns-calico1 (192.168.3.71:80)
wget: download timed out

这就是我们想要的效果,不同Namespace之间的pod不能互通,当然这只是最简单的情况,如果这时候ns-calico1的pod去连接ns-calico2的pod,还是互通的。因为ns-calico2没有设置Namespace annotations。

而且,这时候的ns-calico1会拒绝任何pod的通讯请求。因为,Namespace的annotations只是指定了拒绝所有的通讯请求,还未规定何时接受其他pod的通讯请求。在这里,我们指定只有拥有user=calico1标签的pod可以互联。

apiVersion: extensions/v1beta1
kind: NetworkPolicy
metadata:
 name: calico1-network-policy
 namespace: ns-calico1
spec:
 podSelector:
  matchLabels:
    user: calico1
 ingress:
  - from:
     - namespaceSelector:
        matchLabels:
         user: calico1
     - podSelector:
        matchLabels:
         user: calico1
--- 
apiVersion: v1
kind: Pod
metadata:
  name: calico1-busybox
  namespace: ns-calico1
  labels:
    user: calico1
spec:
  containers:
  - name: busybox
    image: busybox
    command:
      - sleep
      - "3600"
# kubectl create -f calico1-network-policy.yaml
networkpolicy "calico1-network-policy" created
# kubectl create -f calico1-busybox.yaml
pod "calico1-busybox" created

这时候,如果我通过calico1-busybox连接calico1-nginx,则可以连通。

# kubectl exec -it calico1-busybox -n ns-calico1 -- wget --spider --timeout=1 calico1-nginx.ns-calico1     
Connecting to calico1-nginx.ns-calico1 (192.168.3.71:80)

这样我们就实现了Kubernetes的网络隔离。基于NetworkPolicy,可以实现公有云安全组策略。更多的NetworkPolicy参数,请参考 api-reference

参考资料:

  1. Network Policies
  2. Declaring Network Policy
  3. Using Calico for NetworkPolicy
  4. Calico for Kubernetes