容器编排系统K8s之NetworkPolicy资源

　　前文我们了解了k8s的网络插件flannel的基础工作逻辑，回顾请参考：https://www.cnblogs.com/qiuhom-1874/p/14225657.html；今天我们来聊一下k8s上的NetworkPolicy相关话题；

　　NetworkPolicy资源是做什么用的？

　　我们知道在k8s上我们可以用名称空间来隔离多个资源，在不同名称空间下我们可以创建相同名称和相同类型的资源；有些资源还必须依赖名称空间才可以被创建；但是在k8s上，名称空间不可以隔离网络，所谓隔离网络是指不管pod创建在那个名称空间下，都可以被其他名称空间下pod访问到；如果我们想要限制对应名称空间下的pod被别的名称空间或外部客户端访问，我们可以在对应名称空间下创建NetworkPolicy资源；该资源可以限制哪些pod可以被外部客户端访问，或者哪些pod不能够被哪个或哪些名称空间的pod访问；除了能够限制对应名称空间下的pod网络入站流量，它还可以限制对应名称空间下的pod出站的流量，允许或拒绝某个或某些个pod访问别的名称空间下pod或外部某服务等；我们可以简单的理解NetworkPolicy就是对应名称空间的一道防火墙；我们把NetworkPolicy资源创建在对应名称空间下，那么它就能实现对该名称空间下的pod进行流量管控；

　　NetworkPolicy基础工作逻辑

　　提示：首先networkpolicy是作用于一个名称空间下的pod资源之上而进行的流量管控；它可以通过pod选择器来选择对应名称空间下pod，满足对应选择器的条件的pod，将受到networkpolicy中定义的策略管控，默认pod选择器没有明确定义表示匹配对应名称空间下的所有pod；Egress是用来定义pod出站策略，默认显式定义的策略都是被允许出站的，没有定义表示拒绝；对于ingress也是同样的逻辑，只有显式定义的规则才被允许，没有定义就表示拒绝；对于出站流量来说，默认我们定义或不定义它都不会生效，都是允许放行的，只有显式配置对应出站规则生效，它才会生效；

　　示例：定义dev名称空间下的pod不允许任何客户端访问

[root@master01 ~]# cat denyall-ingress-dev.yaml
apiVersion: networking.k8s.io/v1
kind: NetworkPolicy
Metadata:
  name: deny-all-ingress
  namespace: dev
spec:
  podSelector: {}
  policyTypes:
  - Ingress
[root@master01 ~]#

　　提示：以上资源清单表示对dev名称空间下的pod的入站流量进行管控，拒绝所有客户端访问对应dev名称空间下的pod；这其中包含dev名称空间下的pod；

　　应用资源清单

　　在应用之前请确保你所部署的网络插件支持网络策略，默认flannel网络插件不支持网络策略，我们需要部署canel这个网络插件，该插件能够结合flannel插件，让其拥有calico的网络策略功能；

　　部署canel

[root@master01 ~]# kubectl apply -f https://docs.projectcalico.org/manifests/canal.yaml
configmap/canal-config created
customresourcedefinition.apiextensions.k8s.io/bgpconfigurations.crd.projectcalico.org created
customresourcedefinition.apiextensions.k8s.io/bgppeers.crd.projectcalico.org created
customresourcedefinition.apiextensions.k8s.io/blockaffinities.crd.projectcalico.org created
customresourcedefinition.apiextensions.k8s.io/clusterinformations.crd.projectcalico.org created
customresourcedefinition.apiextensions.k8s.io/felixconfigurations.crd.projectcalico.org created
customresourcedefinition.apiextensions.k8s.io/globalnetworkpolicies.crd.projectcalico.org created
customresourcedefinition.apiextensions.k8s.io/globalnetworksets.crd.projectcalico.org created
customresourcedefinition.apiextensions.k8s.io/hostendpoints.crd.projectcalico.org created
customresourcedefinition.apiextensions.k8s.io/ipamblocks.crd.projectcalico.org created
customresourcedefinition.apiextensions.k8s.io/ipamconfigs.crd.projectcalico.org created
customresourcedefinition.apiextensions.k8s.io/ipamhandles.crd.projectcalico.org created
customresourcedefinition.apiextensions.k8s.io/ippools.crd.projectcalico.org created
customresourcedefinition.apiextensions.k8s.io/kubecontrollersconfigurations.crd.projectcalico.org created
customresourcedefinition.apiextensions.k8s.io/networkpolicies.crd.projectcalico.org created
customresourcedefinition.apiextensions.k8s.io/networksets.crd.projectcalico.org created
clusterrole.rbac.authorization.k8s.io/calico-kube-controllers created
clusterrolebinding.rbac.authorization.k8s.io/calico-kube-controllers created
clusterrole.rbac.authorization.k8s.io/calico-node created
clusterrole.rbac.authorization.k8s.io/flannel configured
clusterrolebinding.rbac.authorization.k8s.io/canal-flannel created
clusterrolebinding.rbac.authorization.k8s.io/canal-calico created
daemonset.apps/canal created
serviceaccount/canal created
deployment.apps/calico-kube-controllers created
serviceaccount/calico-kube-controllers created
poddisruptionbudget.policy/calico-kube-controllers created
[root@master01 ~]#

　　提示：等待上述资源都正常运行以后，我们就可以应用资源清单，让其网络策略生效；

　　创建dev名称空间，并在其下创建一个deploy控制器，控制器创建3个Nginx pod

[root@master01 manifests]# cat pod-demo.yaml
apiVersion: v1
kind: Namespace
Metadata:
  name: dev
  labels:
    name: dev
---
apiVersion: apps/v1
kind: Deployment
Metadata:
  name: Nginx-dep
  namespace: dev
spec:
  replicas: 3
  selector:
    matchLabels:
      app: Nginx
      rel: stable
  template:
    Metadata:
      labels:
        app: Nginx
        rel: stable
    spec:
      containers:
      - name: Nginx
        image: Nginx:1.14-alpine
        imagePullPolicy: IfNotPresent
        ports:
        - name: http
          containerPort: 80
[root@master01 manifests]# kubectl apply -f pod-demo.yaml
namespace/dev unchanged
deployment.apps/Nginx-dep created
[root@master01 manifests]# kubectl get pods -n dev -o wide
NAME                        READY   STATUS    RESTARTS   AGE   IP           NODE             NOMINATED NODE   READINESS GATES
Nginx-dep-cb74c595f-5d9tb   1/1     Running   0          51s   10.244.4.6   node04.k8s.org   <none>           <none>
Nginx-dep-cb74c595f-ftmn9   1/1     Running   0          51s   10.244.1.5   node01.k8s.org   <none>           <none>
Nginx-dep-cb74c595f-jf9p9   1/1     Running   0          51s   10.244.3.4   node03.k8s.org   <none>           <none>
[root@master01 manifests]#

　　在没有应用上述网络策略前，用default里的pod访问对应dev名称空间下pod，看看是否可以正常访问？

[root@master01 manifests]# kubectl get pods -n dev -o wide
NAME                        READY   STATUS    RESTARTS   AGE   IP           NODE             NOMINATED NODE   READINESS GATES
Nginx-dep-cb74c595f-5d9tb   1/1     Running   0          86s   10.244.4.6   node04.k8s.org   <none>           <none>
Nginx-dep-cb74c595f-ftmn9   1/1     Running   0          86s   10.244.1.5   node01.k8s.org   <none>           <none>
Nginx-dep-cb74c595f-jf9p9   1/1     Running   0          86s   10.244.3.4   node03.k8s.org   <none>           <none>
[root@master01 manifests]# kubectl get pods 
NAME    READY   STATUS    RESTARTS   AGE
web-0   1/1     Running   6          3d16h
web-1   1/1     Running   5          3d16h
web-2   1/1     Running   6          3d16h
[root@master01 manifests]# kubectl exec web-0 -it -- /bin/sh
/ # wget -O - -q 10.244.4.6
<!DOCTYPE html>
<html>
<head>
<title>Welcome to Nginx!</title>
<style>
    body {
        width: 35em;
        margin: 0 auto;
        font-family: Tahoma,Verdana,Arial,sans-serif;
    }
</style>
</head>
<body>
<h1>Welcome to Nginx!</h1>
<p>If you see this page,the Nginx web server is successfully installed and
working. Further configuration is required.</p>

<p>For online documentation and support please refer to
<a href="http://Nginx.org/">Nginx.org</a>.<br/>
Commercial support is available at
<a href="http://Nginx.com/">Nginx.com</a>.</p>

<p><em>Thank you for using Nginx.</em></p>
</body>
</html>
/ #

　　提示：可以看到用default名称空间下的pod，是可以正常访问dev名称空间下的pod；

　　应用资源清单

[root@master01 ~]# cat denyall-ingress-dev.yaml 
apiVersion: networking.k8s.io/v1
kind: NetworkPolicy
Metadata:
  name: deny-all-ingress
  namespace: dev
spec:
  podSelector: {}
  policyTypes:
  - Ingress
[root@master01 ~]# kubectl apply -f denyall-ingress-dev.yaml
networkpolicy.networking.k8s.io/deny-all-ingress created
[root@master01 ~]# kubectl get netpol -n dev
NAME               POD-SELECTOR   AGE
deny-all-ingress   <none>         10s
[root@master01 ~]# kubectl describe netpol deny-all-ingress -n dev
Name:         deny-all-ingress
Namespace:    dev
Created on:   2021-01-04 15:34:40 +0800 CST
Labels:       <none>
Annotations:  <none>
Spec:
  PodSelector:     <none> (Allowing the specific traffic to all pods in this namespace)
  Allowing ingress traffic:
    <none> (Selected pods are isolated for ingress connectivity)
  Not affecting egress traffic
  Policy Types: Ingress
[root@master01 ~]#

　　提示：从上面的netpol资源的详细信息中可以了解到，对应netpol资源pod选择器为none表示选择对应名称空间下的所有pod，allowing ingress traffic 也是为none表示没有任何客户端允许访问该名称空间下的pod；没有出站策略，表示拒绝所有出站流量；默认只是入站规则生效，所以这里的出站规则不生效，即不限制出站流量；policyTypes表示对应的那个策略生效，默认不指定是Ingress；

　　验证：使用default名称空间下的pod访问dev名称空间下的pod，看看是否还可以正常访问？

　　提示：可以看到现在default名称空间下的pod是不能访问dev名称空间下的pod；

　　验证：dev名称空间下的pod访问同名称空间下的pod，看看是否可以允许访问?

　　提示：可以看到在dev名称空间下的pod也没法访问dev名称空间下的pod，但是自己可以访问自己，其原因是自己访问自己，流量不会出站，在lo接口就被处理了，所以自己访问自己不受限制；

　　验证：使用dev名称空间下的pod访问default名称空间下的pod，看看是否被允许？

　　提示：可以看到使用dev名称空间下的pod访问default名称空间下的pod上没有问题，说明刚才的那条规则只是限制了dev名称空间下的pod的入站流量，并没有限制其出站流量；上面访问10.244.4.5和3.3响应404，是因为对应pod上的web服务没有主页；

　　示例：限制dev名称空间下的pod的出站流量，拒绝所有pod流量出站

[root@master01 ~]# cat denyall-Egress.yaml
apiVersion: networking.k8s.io/v1
kind: NetworkPolicy
Metadata: 
  name: deny-all-egress
  namespace: dev
spec:
  podSelector: {}
  policyTypes:
  - Egress
[root@master01 ~]#

　　提示：policyTypes字段用来控制那个类型的规则生效，该字段是一个列表，默认是Ingress，表示只对入站流量做限制，如果明确手动定义为Egress表示，只限制出站流量；出站策略和入站策略的逻辑都是一样的，只要没有明且定义的，都是表示拒绝操作，只有明确定义的才表示对应允许操作；上述没有定义任何出站规则，表示拒绝所有pod访问外部服务；

　　应用资源清单

[root@master01 ~]# kubectl apply -f denyall-Egress.yaml
networkpolicy.networking.k8s.io/deny-all-egress created
[root@master01 ~]# kubectl get netpol -n dev
NAME               POD-SELECTOR   AGE
deny-all-egress    <none>         10s
deny-all-ingress   <none>         24m
[root@master01 ~]# kubectl describe netpol deny-all-egress -n dev
Name:         deny-all-egress
Namespace:    dev
Created on:   2021-01-04 15:59:16 +0800 CST
Labels:       <none>
Annotations:  <none>
Spec:
  PodSelector:     <none> (Allowing the specific traffic to all pods in this namespace)
  Not affecting ingress traffic
  Allowing egress traffic:
    <none> (Selected pods are isolated for egress connectivity)
  Policy Types: Egress
[root@master01 ~]#

　　验证：进入dev名称空间下的pod交互式接口，看看是否可以访问其他名称空间下的pod？

　　提示：可以看到现在dev名称空间下的pod访问default名称空间下的pod就不能访问了；

　　验证：删除入站限制，使用dev名称空间下的pod互相访问，看看是否可以正常访问呢？

[root@master01 ~]# kubectl get netpol -n dev
NAME               POD-SELECTOR   AGE
deny-all-egress    <none>         5m50s
deny-all-ingress   <none>         30m
[root@master01 ~]# kubectl delete netpol deny-all-ingress -n dev
networkpolicy.networking.k8s.io "deny-all-ingress" deleted
[root@master01 ~]# kubectl get netpol -n dev                    
NAME              POD-SELECTOR   AGE
deny-all-egress   <none>         6m9s
[root@master01 ~]# kubectl get pods -n dev -o wide                             
NAME                        READY   STATUS    RESTARTS   AGE   IP           NODE             NOMINATED NODE   READINESS GATES
Nginx-dep-cb74c595f-5d9tb   1/1     Running   0          34m   10.244.4.6   node04.k8s.org   <none>           <none>
Nginx-dep-cb74c595f-ftmn9   1/1     Running   0          34m   10.244.1.5   node01.k8s.org   <none>           <none>
Nginx-dep-cb74c595f-jf9p9   1/1     Running   0          34m   10.244.3.4   node03.k8s.org   <none>           <none>
[root@master01 ~]# kubectl exec -it Nginx-dep-cb74c595f-5d9tb -n dev -- /bin/sh
/ # wget -O - -q 10.244.1.5
^C
/ # wget -O - -q 10.244.3.4
^C
/ # wget -O - -q 10.244.4.6
<!DOCTYPE html>
<html>
<head>
<title>Welcome to Nginx!</title>
<style>
    body {
        width: 35em;
        margin: 0 auto;
        font-family: Tahoma,the Nginx web server is successfully installed and
working. Further configuration is required.</p>

<p>For online documentation and support please refer to
<a href="http://Nginx.org/">Nginx.org</a>.<br/>
Commercial support is available at
<a href="http://Nginx.com/">Nginx.com</a>.</p>

<p><em>Thank you for using Nginx.</em></p>
</body>
</html>
/ #

　　提示：可以看到限制了出站流量以后，在同一名称空间下的pod也是无法正常访问的；但是自己可以访问自己；

　　示例：限制dev名称空间下的pod的出站流量，允许dev名称空间下的pod互相访问

[root@master01 ~]# cat allow-dev-Egress.yaml
apiVersion: networking.k8s.io/v1
kind: NetworkPolicy
Metadata:
  name: allow-dev-egress
  namespace: dev
spec:
  podSelector: {}
  egress:
    - to:
      - podSelector:
          matchLabels:
            app: Nginx
            rel: stable
      ports:
      - port: 80
        protocol: TCP 
  policyTypes:
  - Egress
[root@master01 ~]#

　　提示：限制出站流量，可以在spec.egress中来定义允许的出站的规则；其中to字段是用来描述被访问端，其值类型是一个列表对象；podSelector字段是用来描述被访问端pod选择器，只有满足对应pod选择器的条件的pod都被允许出站；spec.egress.ports字段是用来描述被访问端点端口信息；该字段为一个列表对象；这里需要注意，默认没有在规则指定其名称空间表示匹配当前netpol所在名称空间；以上清单表示dev下的pod允许访问dev名称空间下标签为app=Nginx,rel=stable的pod的80端口；

　　删除deny-all-egress出站策略，应用其资源清单

[root@master01 ~]# kubectl get netpol -n dev
NAME              POD-SELECTOR   AGE
deny-all-egress   <none>         26m
[root@master01 ~]# kubectl delete netpol deny-all-egress -n dev
networkpolicy.networking.k8s.io "deny-all-egress" deleted
[root@master01 ~]# kubectl apply -f allow-dev-Egress.yaml
networkpolicy.networking.k8s.io/allow-dev-egress created
[root@master01 ~]# kubectl get netpol -n dev
NAME               POD-SELECTOR   AGE
allow-dev-egress   <none>         10s
[root@master01 ~]# kubectl describe netpol allow-dev-egress -n dev
Name:         allow-dev-egress
Namespace:    dev
Created on:   2021-01-04 16:34:23 +0800 CST
Labels:       <none>
Annotations:  <none>
Spec:
  PodSelector:     <none> (Allowing the specific traffic to all pods in this namespace)
  Not affecting ingress traffic
  Allowing egress traffic:
    To Port: 80/TCP
    To:
      PodSelector: app=Nginx,rel=stable
  Policy Types: Egress
[root@master01 ~]#

　　验证：进入dev名称空间下pod的里，看看是否可以正常访问dev名称空间下的pod？

[root@master01 ~]# kubectl get pods -n dev -o wide
NAME                        READY   STATUS    RESTARTS   AGE   IP           NODE             NOMINATED NODE   READINESS GATES
Nginx-dep-cb74c595f-5d9tb   1/1     Running   0          65m   10.244.4.6   node04.k8s.org   <none>           <none>
Nginx-dep-cb74c595f-ftmn9   1/1     Running   0          65m   10.244.1.5   node01.k8s.org   <none>           <none>
Nginx-dep-cb74c595f-jf9p9   1/1     Running   0          65m   10.244.3.4   node03.k8s.org   <none>           <none>
[root@master01 ~]# kubectl exec -it -n dev Nginx-dep-cb74c595f-5d9tb -- /bin/sh
/ # wget -O - -q 10.244.1.5
<!DOCTYPE html>
<html>
<head>
<title>Welcome to Nginx!</title>
<style>
    body {
        width: 35em;
        margin: 0 auto;
        font-family: Tahoma,the Nginx web server is successfully installed and
working. Further configuration is required.</p>

<p>For online documentation and support please refer to
<a href="http://Nginx.org/">Nginx.org</a>.<br/>
Commercial support is available at
<a href="http://Nginx.com/">Nginx.com</a>.</p>

<p><em>Thank you for using Nginx.</em></p>
</body>
</html>
/ # wget -O - -q 10.244.3.4
<!DOCTYPE html>
<html>
<head>
<title>Welcome to Nginx!</title>
<style>
    body {
        width: 35em;
        margin: 0 auto;
        font-family: Tahoma,the Nginx web server is successfully installed and
working. Further configuration is required.</p>

<p>For online documentation and support please refer to
<a href="http://Nginx.org/">Nginx.org</a>.<br/>
Commercial support is available at
<a href="http://Nginx.com/">Nginx.com</a>.</p>

<p><em>Thank you for using Nginx.</em></p>
</body>
</html>
/ #

　　提示：可以看到dev名称空间pod访问dev名称空间下的pod可以正常访问；

　　验证：使用dev名称空间pod访问default名称空间下，标签为app=Nginx，rel=stable的pod，看看是否可以正常访问？

[root@master01 ~]# kubectl get pods -n dev 
NAME                        READY   STATUS    RESTARTS   AGE
Nginx-dep-cb74c595f-27qjp   1/1     Running   2          88m
Nginx-dep-cb74c595f-b92s4   1/1     Running   1          88m
Nginx-dep-cb74c595f-wdqnh   1/1     Running   1          88m
[root@master01 ~]# kubectl get pods -o wide --show-labels                      
NAME                        READY   STATUS    RESTARTS   AGE     IP            NODE             NOMINATED NODE   READINESS GATES   LABELS
Nginx-dep-cb74c595f-5mwl2   1/1     Running   1          89m     10.244.4.18   node04.k8s.org   <none>           <none>            app=Nginx,pod-template-hash=cb74c595f,rel=stable
Nginx-dep-cb74c595f-vxc9z   1/1     Running   1          89m     10.244.3.12   node03.k8s.org   <none>           <none>            app=Nginx,rel=stable
Nginx-dep-cb74c595f-z265t   1/1     Running   1          89m     10.244.2.13   node02.k8s.org   <none>           <none>            app=Nginx,rel=stable
web-0                       1/1     Running   8          3d20h   10.244.2.14   node02.k8s.org   <none>           <none>            app=Nginx,controller-revision-hash=web-6db9455fdf,statefulset.kubernetes.io/pod-name=web-0
web-1                       1/1     Running   7          3d20h   10.244.4.16   node04.k8s.org   <none>           <none>            app=Nginx,statefulset.kubernetes.io/pod-name=web-1
web-2                       1/1     Running   8          3d20h   10.244.3.11   node03.k8s.org   <none>           <none>            app=Nginx,statefulset.kubernetes.io/pod-name=web-2
[root@master01 ~]# kubectl exec -it Nginx-dep-cb74c595f-27qjp -n dev -- /bin/sh
/ # wget -O - -q 10.244.4.18
^C
/ # wget -O - -q 10.244.3.12
^C
/ # wget -O - -q 10.244.2.13
^C
/ #

　　提示：可以看到dev名称空间下的pod访问default名称空间下标签为app=Nginx，rel=stable的pod也是无法正常访问，原因是我们在策略中没有指定对应访问目标的名称空间，默认就是对应netpol所在名称空间；

　　示例：允许dev名称空间下的pod访问default和dev名称空间下标签为app=Nginx，rel=stable的pod

[root@master01 ~]# cat allow-dev-def-egress.yaml
apiVersion: networking.k8s.io/v1
kind: NetworkPolicy
Metadata:
  name: allow-dev-egress
  namespace: dev
spec:
  podSelector: {} 
  egress:
    - to:
      - namespaceSelector:
          matchExpressions:
          - key: name
            operator: In
            values: ["def","dev"]
        podSelector:
          matchLabels:
            app: Nginx
            rel: stable
      ports:
      - port: 80
        protocol: TCP 
  policyTypes:
  - Egress
[root@master01 ~]#

　　提示：spec.egress.to中的namespeceSelector字段使用来描述被访问端所在名称空间；podSelector字段是用来描述被访问端的pod；如果这两个字段中只有一个字段前用了“-”，那么namespaceSelector和podSelector所指定的条件是与关系，即两个条件必须都满足；如果两个字段都用了“-”开头，则两个字段所指定的条件就是或关系，即满足其中一个字段的条件都可以被规则匹配；上述示例表示dev下的所有pod能够访问名称空间上的标签是name=def或name=dev的名称空间下的pod，并且这些pod的标签必须是app=Nginx,rel=stable；即要想被dev名称空间下的pod所访问，对应pod的应该同时满足两个条件，第一对应名称空间上有name=def或者name=dev的标签；其次pod本身要有两个标签，app=Nginx和rel=stable；这两个条件缺一不可；

　　删除原有netpol，应用新的清单

[root@master01 ~]# kubectl get netpol -n dev
NAME               POD-SELECTOR   AGE
allow-dev-egress   <none>         28m
[root@master01 ~]# kubectl delete netpol allow-dev-egress -n dev
networkpolicy.networking.k8s.io "allow-dev-egress" deleted
[root@master01 ~]# kubectl apply -f allow-dev-def-egress.yaml 
networkpolicy.networking.k8s.io/allow-dev-egress created
[root@master01 ~]# kubectl get netpol -n dev                    
NAME               POD-SELECTOR   AGE
allow-dev-egress   <none>         5s
[root@master01 ~]# kubectl describe netpol allow-dev-egress -n dev
Name:         allow-dev-egress
Namespace:    dev
Created on:   2021-01-04 19:44:32 +0800 CST
Labels:       <none>
Annotations:  <none>
Spec:
  PodSelector:     <none> (Allowing the specific traffic to all pods in this namespace)
  Not affecting ingress traffic
  Allowing egress traffic:
    To Port: 80/TCP
    To:
      NamespaceSelector: name in (def,dev)
      PodSelector: app=Nginx,rel=stable
  Policy Types: Egress
[root@master01 ~]#

　　提示：可以看到对应的出站规则就有两个条件，首先称空间必须匹配，name=def或者name=dev，即对应名称空间必须要这样的标签；其次pod必须满足有app=Nginx,rel=stable的标签；

　　给default名称空间打上name=def的标签

[root@master01 ~]# kubectl get ns --show-labels
NAME                   STATUS   AGE     LABELS
default                Active   27d     <none>
dev                    Active   4h24m   name=dev
ingress-Nginx          Active   13d     app.kubernetes.io/name=ingress-Nginx,app.kubernetes.io/part-of=ingress-Nginx
kube-node-lease        Active   27d     <none>
kube-public            Active   27d     <none>
kube-system            Active   27d     <none>
kubernetes-dashboard   Active   2d5h    <none>
prod                   Active   57m     name=prod
[root@master01 ~]# kubectl label ns default name=def
namespace/default labeled
[root@master01 ~]# kubectl get ns --show-labels     
NAME                   STATUS   AGE     LABELS
default                Active   27d     name=def
dev                    Active   4h24m   name=dev
ingress-Nginx          Active   13d     app.kubernetes.io/name=ingress-Nginx,app.kubernetes.io/part-of=ingress-Nginx
kube-node-lease        Active   27d     <none>
kube-public            Active   27d     <none>
kube-system            Active   27d     <none>
kubernetes-dashboard   Active   2d5h    <none>
prod                   Active   58m     name=prod
[root@master01 ~]#

　　验证：用dev下的pod访问default和dev名称空间下pod标签为app=Nginx,rel=stable的pod，看看对应pod是否能够被访问到？

[root@master01 ~]# kubectl get pods -n dev -o wide --show-labels
NAME                        READY   STATUS    RESTARTS   AGE    IP            NODE             NOMINATED NODE   READINESS GATES   LABELS
Nginx-dep-cb74c595f-27qjp   1/1     Running   2          116m   10.244.1.18   node01.k8s.org   <none>           <none>            app=Nginx,rel=stable
Nginx-dep-cb74c595f-b92s4   1/1     Running   1          116m   10.244.4.17   node04.k8s.org   <none>           <none>            app=Nginx,rel=stable
Nginx-dep-cb74c595f-wdqnh   1/1     Running   1          116m   10.244.1.19   node01.k8s.org   <none>           <none>            app=Nginx,rel=stable
[root@master01 ~]# kubectl get pods  -o wide --show-labels      
NAME                        READY   STATUS    RESTARTS   AGE     IP            NODE             NOMINATED NODE   READINESS GATES   LABELS
Nginx-dep-cb74c595f-5mwl2   1/1     Running   1          117m    10.244.4.18   node04.k8s.org   <none>           <none>            app=Nginx,rel=stable
Nginx-dep-cb74c595f-vxc9z   1/1     Running   1          117m    10.244.3.12   node03.k8s.org   <none>           <none>            app=Nginx,rel=stable
Nginx-dep-cb74c595f-z265t   1/1     Running   1          117m    10.244.2.13   node02.k8s.org   <none>           <none>            app=Nginx,rel=stable
web-0                       1/1     Running   8          3d21h   10.244.2.14   node02.k8s.org   <none>           <none>            app=Nginx,statefulset.kubernetes.io/pod-name=web-0
web-1                       1/1     Running   7          3d21h   10.244.4.16   node04.k8s.org   <none>           <none>            app=Nginx,statefulset.kubernetes.io/pod-name=web-1
web-2                       1/1     Running   8          3d21h   10.244.3.11   node03.k8s.org   <none>           <none>            app=Nginx,statefulset.kubernetes.io/pod-name=web-2
[root@master01 ~]# kubectl exec -it -n dev Nginx-dep-cb74c595f-27qjp -- /bin/sh
/ # wget --spider --timeout=1 10.244.4.17
Connecting to 10.244.4.17 (10.244.4.17:80)
/ # wget --spider --timeout=1 10.244.1.19 
Connecting to 10.244.1.19 (10.244.1.19:80)
/ # wget --spider --timeout=1 10.244.4.18
Connecting to 10.244.4.18 (10.244.4.18:80)
/ # wget --spider --timeout=1 10.244.3.12
Connecting to 10.244.3.12 (10.244.3.12:80)
/ # wget --spider --timeout=1 10.244.2.13
Connecting to 10.244.2.13 (10.244.2.13:80)
/ # wget --spider --timeout=1 10.244.2.14
Connecting to 10.244.2.14 (10.244.2.14:80)
wget: download timed out
/ #

　　提示：可以看到用dev名称空间的pod访问名称空间上有name=def或name=dev标签并且对应pod上有app=Nginx和rel=stable的标签的pod是能够正常访问到，如果不能满足对应名称空间和pod标签的pod就不能被访问；上面示例中最后一个podip不满足pod的标签，所以访问不到对应pod；

　　示例：允许dev名称空间下的pod访问名称空间上有name=def或name=dev标签的名称空间下的pod或者名称空间上有name=prod标签，并且对应名称空间下的pod必须有app=Nginx，rel=stable的标签；

[root@master01 ~]# cat allow-dev-def-egress.yaml
apiVersion: networking.k8s.io/v1
kind: NetworkPolicy
Metadata:
  name: allow-dev-egress
  namespace: dev
spec:
  podSelector: {} 
  egress:
    - to:
      - namespaceSelector:
          matchExpressions:
          - key: name
            operator: In
            values: ["def","dev"]
    - to:
      - namespaceSelector:
          matchLables:
            name: prod
        podSelector:
          matchLabels:
            app: Nginx
            rel: stable
      ports:
      - port: 80
        protocol: TCP 
  policyTypes:
  - Egress
[root@master01 ~]#

　　应用配置清单

[root@master01 ~]# kubectl apply -f allow-dev-def-egress.yaml
networkpolicy.networking.k8s.io/allow-dev-egress created
[root@master01 ~]# kubectl get netpol -n dev
NAME               POD-SELECTOR   AGE
allow-dev-egress   <none>         10s
[root@master01 ~]# kubectl describe netpol allow-dev-egress -n dev
Name:         allow-dev-egress
Namespace:    dev
Created on:   2021-01-04 20:44:42 +0800 CST
Labels:       <none>
Annotations:  <none>
Spec:
  PodSelector:     <none> (Allowing the specific traffic to all pods in this namespace)
  Not affecting ingress traffic
  Allowing egress traffic:
    To Port: <any> (traffic allowed to all ports)
    To:
      NamespaceSelector: name in (def,dev)
    ----------
    To Port: 80/TCP
    To:
      NamespaceSelector: name=prod
      PodSelector: app=Nginx,rel=stable
  Policy Types: Egress
[root@master01 ~]#

　　验证：用dev名称空间下的pod访问dev名称空间下的pod，看看是否可以正常访问？

[root@master01 ~]# kubectl get pods -n dev -o wide 
NAME                        READY   STATUS    RESTARTS   AGE    IP            NODE             NOMINATED NODE   READINESS GATES
Nginx-dep-cb74c595f-27qjp   1/1     Running   2          168m   10.244.1.18   node01.k8s.org   <none>           <none>
Nginx-dep-cb74c595f-b92s4   1/1     Running   1          168m   10.244.4.17   node04.k8s.org   <none>           <none>
Nginx-dep-cb74c595f-wdqnh   1/1     Running   1          168m   10.244.1.19   node01.k8s.org   <none>           <none>
[root@master01 ~]# kubectl exec -it -n dev Nginx-dep-cb74c595f-27qjp -- /bin/sh
/ # wget --spider --timeout=1 10.244.4.17
Connecting to 10.244.4.17 (10.244.4.17:80)
/ # wget --spider --timeout=1 10.244.1.19
Connecting to 10.244.1.19 (10.244.1.19:80)
/ # exit
[root@master01 ~]#

　　提示：可以看到dev名称空间下的pod相互访问没有问题；

　　验证：用dev名称空间下的pod访问default名称空间下的pod ，看看是否可以正常访问？

[root@master01 ~]# kubectl get pods -n dev -o wide
NAME                        READY   STATUS    RESTARTS   AGE    IP            NODE             NOMINATED NODE   READINESS GATES
Nginx-dep-cb74c595f-27qjp   1/1     Running   2          170m   10.244.1.18   node01.k8s.org   <none>           <none>
Nginx-dep-cb74c595f-b92s4   1/1     Running   1          170m   10.244.4.17   node04.k8s.org   <none>           <none>
Nginx-dep-cb74c595f-wdqnh   1/1     Running   1          170m   10.244.1.19   node01.k8s.org   <none>           <none>
[root@master01 ~]# kubectl get pods -o wide
NAME                        READY   STATUS    RESTARTS   AGE     IP            NODE             NOMINATED NODE   READINESS GATES
Nginx-dep-cb74c595f-5mwl2   1/1     Running   1          171m    10.244.4.18   node04.k8s.org   <none>           <none>
Nginx-dep-cb74c595f-vxc9z   1/1     Running   1          171m    10.244.3.12   node03.k8s.org   <none>           <none>
Nginx-dep-cb74c595f-z265t   1/1     Running   1          171m    10.244.2.13   node02.k8s.org   <none>           <none>
web-0                       1/1     Running   8          3d22h   10.244.2.14   node02.k8s.org   <none>           <none>
web-1                       1/1     Running   7          3d22h   10.244.4.16   node04.k8s.org   <none>           <none>
web-2                       1/1     Running   8          3d22h   10.244.3.11   node03.k8s.org   <none>           <none>
[root@master01 ~]# kubectl exec -it -n dev Nginx-dep-cb74c595f-27qjp -- /bin/sh
/ # wget --spider --timeout=1 10.244.4.18
Connecting to 10.244.4.18 (10.244.4.18:80)
/ # wget --spider --timeout=1 10.244.3.12
Connecting to 10.244.3.12 (10.244.3.12:80)
/ # wget --spider --timeout=1 10.244.2.13
Connecting to 10.244.2.13 (10.244.2.13:80)
/ # wget --spider --timeout=1 10.244.2.14
Connecting to 10.244.2.14 (10.244.2.14:80)
/ # wget --spider --timeout=1 10.244.4.16
Connecting to 10.244.4.16 (10.244.4.16:80)
wget: server returned error: HTTP/1.1 403 Forbidden
/ # wget --spider --timeout=1 10.244.3.11
Connecting to 10.244.3.11 (10.244.3.11:80)
wget: server returned error: HTTP/1.1 403 Forbidden
/ #

　　提示：可以看到default名称空间下的所有pod都能够被dev名称空间下的pod所访问；后面显示 403是因为对应web服务没有主页；

　　验证：使用dev名称空间下的pod访问prod名称空间下的pod，看看对应pod是否能够被访问？

[root@master01 ~]# kubectl get ns prod --show-labels
NAME   STATUS   AGE    LABELS
prod   Active   118m   name=prod
[root@master01 ~]# kubectl get pods -n prod -o wide --show-labels
NAME                         READY   STATUS    RESTARTS   AGE    IP            NODE             NOMINATED NODE   READINESS GATES   LABELS
Nginx-dep-cb74c595f-rzbv2    1/1     Running   0          118m   10.244.4.19   node04.k8s.org   <none>           <none>            app=Nginx,rel=stable
Nginx-dep-cb74c595f-v8ssx    1/1     Running   0          118m   10.244.3.13   node03.k8s.org   <none>           <none>            app=Nginx,rel=stable
Nginx-dep-cb74c595f-zsqcc    1/1     Running   0          118m   10.244.2.15   node02.k8s.org   <none>           <none>            app=Nginx,rel=stable
Nginx-dep1-f85fdcdbc-kdq5b   1/1     Running   0          117m   10.244.1.21   node01.k8s.org   <none>           <none>            app=Nginx,pod-template-hash=f85fdcdbc
Nginx-dep1-f85fdcdbc-n8cvs   1/1     Running   0          117m   10.244.3.14   node03.k8s.org   <none>           <none>            app=Nginx,pod-template-hash=f85fdcdbc
Nginx-dep1-f85fdcdbc-vz2mp   1/1     Running   0          117m   10.244.4.20   node04.k8s.org   <none>           <none>            app=Nginx,pod-template-hash=f85fdcdbc
[root@master01 ~]# kubectl get pods -n dev
NAME                        READY   STATUS    RESTARTS   AGE
Nginx-dep-cb74c595f-27qjp   1/1     Running   2          174m
Nginx-dep-cb74c595f-b92s4   1/1     Running   1          174m
Nginx-dep-cb74c595f-wdqnh   1/1     Running   1          174m
[root@master01 ~]# kubectl exec -it -n dev Nginx-dep-cb74c595f-27qjp -- /bin/sh
/ # wget --spider --timeout=1 10.244.4.20 
Connecting to 10.244.4.20 (10.244.4.20:80)
wget: download timed out
/ # wget --spider --timeout=1 10.244.3.14 
Connecting to 10.244.3.14 (10.244.3.14:80)
wget: download timed out
/ # wget --spider --timeout=1 10.244.1.21
Connecting to 10.244.1.21 (10.244.1.21:80)
wget: download timed out
/ # wget --spider --timeout=1 10.244.2.15
Connecting to 10.244.2.15 (10.244.2.15:80)
/ # wget --spider --timeout=1 10.244.3.13
Connecting to 10.244.3.13 (10.244.3.13:80)
/ # wget --spider --timeout=1 10.244.4.19
Connecting to 10.244.4.19 (10.244.4.19:80)
/ #

　　提示：可以看到在prod名称空间下对应pod标签为app=Nginx,rel=stable的pod都能够被dev下的pod所访问，如果对应标签不是app=Nginx,rel=stable的pod则不能被访问到；

　　从上面的示例可以总结，在k8s上网络策略是白名单机制，所谓白名单机制是指，只有明确定义的策略才会被允许放行，默认没有指定的规则就是拒绝的，即条件不匹配的都会被拒绝；其次对于ingress或egress来说，对应的from或to都是用来指定访问端或被访问端的信息；如果我们在对应的字段中没有定义namespaceSelector字段，默认ingress或egRSS会匹配当前netpol所在名称空间，即在没有明确指定namespaceSelector字段时，对应的其他条件都是针对当前netpol所在名称空间；多个条件组合使用，如果多个条件都在一个列表中，则表示多个条件间是与关系，即指定的条件需要同时满足对应策略才会放行；如果多个条件不再同一个列表中，则多个条件之间是或关系，即满足其中一个条件都会被对应策略放行；

原文链接：/kubernetes/995356.html

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