这次我们来说先来看看K8S中负责网络隔离的组件（也可以成为类）---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（为什么使用Calico这个第三方网络插件我们之后会专门解释）。
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 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 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：
- Network Policies
- Declaring Network Policy
- Using Calico for NetworkPolicy