KIND网络插件实验：使用flannel作为cni插件

前言

KIND环境介绍及启动（禁用默认的网络插件）请跳转到《KIND网络插件实验：使用bridge作为cni插件》
上文介绍了使用bridge作为KIND网络插件的方法，本文将使用flannel
KIND启动后由于没有网络插件,coredns无法被分配地址，所以没起来。禁用默认网络插件启动后的POD状况如下：

部署flannel

kubectl apply -f flannel-v0.14.0.yaml

YAML文件可以从flannel官网获得

# flannel-v0.14.0.yaml
apiVersion: policy/v1beta1
kind: PodSecurityPolicy
metadata:
  name: psp.flannel.unprivileged
  annotations:
    seccomp.security.alpha.kubernetes.io/allowedProfileNames: docker/default
    seccomp.security.alpha.kubernetes.io/defaultProfileName: docker/default
    apparmor.security.beta.kubernetes.io/allowedProfileNames: runtime/default
    apparmor.security.beta.kubernetes.io/defaultProfileName: runtime/default
spec:
  privileged: false
  volumes:
  - configMap
  - secret
  - emptyDir
  - hostPath
  allowedHostPaths:
  - pathPrefix: "/etc/cni/net.d"
  - pathPrefix: "/etc/kube-flannel"
  - pathPrefix: "/run/flannel"
  readOnlyRootFilesystem: false
  # Users and groups
  runAsUser:
    rule: RunAsAny
  supplementalGroups:
    rule: RunAsAny
  fsGroup:
    rule: RunAsAny
  # Privilege Escalation
  allowPrivilegeEscalation: false
  defaultAllowPrivilegeEscalation: false
  # Capabilities
  allowedCapabilities: ['NET_ADMIN', 'NET_RAW']
  defaultAddCapabilities: []
  requiredDropCapabilities: []
  # Host namespaces
  hostPID: false
  hostIPC: false
  hostNetwork: true
  hostPorts:
  - min: 0
    max: 65535
  # SELinux
  seLinux:
    # SELinux is unused in CaaSP
    rule: 'RunAsAny'
---
kind: ClusterRole
apiVersion: rbac.authorization.k8s.io/v1
metadata:
  name: flannel
rules:
- apiGroups: ['extensions']
  resources: ['podsecuritypolicies']
  verbs: ['use']
  resourceNames: ['psp.flannel.unprivileged']
- apiGroups:
  - ""
  resources:
  - pods
  verbs:
  - get
- apiGroups:
  - ""
  resources:
  - nodes
  verbs:
  - list
  - watch
- apiGroups:
  - ""
  resources:
  - nodes/status
  verbs:
  - patch
---
kind: ClusterRoleBinding
apiVersion: rbac.authorization.k8s.io/v1
metadata:
  name: flannel
roleRef:
  apiGroup: rbac.authorization.k8s.io
  kind: ClusterRole
  name: flannel
subjects:
- kind: ServiceAccount
  name: flannel
  namespace: kube-system
---
apiVersion: v1
kind: ServiceAccount
metadata:
  name: flannel
  namespace: kube-system
---
kind: ConfigMap
apiVersion: v1
metadata:
  name: kube-flannel-cfg
  namespace: kube-system
  labels:
    tier: node
    app: flannel
data:
  cni-conf.json: |
    {
      "name": "cbr0",
      "cniVersion": "0.3.1",
      "plugins": [
        {
          "type": "flannel",
          "delegate": {
            "hairpinMode": true,
            "isDefaultGateway": true
          }
        },
        {
          "type": "portmap",
          "capabilities": {
            "portMappings": true
          }
        }
      ]
    }
  net-conf.json: |
    {
      "Network": "10.244.0.0/16",
      "Backend": {
        "Type": "vxlan"
      }
    }
---
apiVersion: apps/v1
kind: DaemonSet
metadata:
  name: kube-flannel-ds
  namespace: kube-system
  labels:
    tier: node
    app: flannel
spec:
  selector:
    matchLabels:
      app: flannel
  template:
    metadata:
      labels:
        tier: node
        app: flannel
    spec:
      affinity:
        nodeAffinity:
          requiredDuringSchedulingIgnoredDuringExecution:
            nodeSelectorTerms:
            - matchExpressions:
              - key: kubernetes.io/os
                operator: In
                values:
                - linux
      hostNetwork: true
      priorityClassName: system-node-critical
      tolerations:
      - operator: Exists
        effect: NoSchedule
      serviceAccountName: flannel
      initContainers:
      - name: install-cni
        image: quay.io/coreos/flannel:v0.14.0
        command:
        - cp
        args:
        - -f
        - /etc/kube-flannel/cni-conf.json
        - /etc/cni/net.d/10-flannel.conflist
        volumeMounts:
        - name: cni
          mountPath: /etc/cni/net.d
        - name: flannel-cfg
          mountPath: /etc/kube-flannel/
      containers:
      - name: kube-flannel
        image: quay.io/coreos/flannel:v0.14.0
        command:
        - /opt/bin/flanneld
        args:
        - --ip-masq=false
        - --kube-subnet-mgr
        resources:
          requests:
            cpu: "100m"
            memory: "50Mi"
          limits:
            cpu: "100m"
            memory: "50Mi"
        securityContext:
          privileged: true
          capabilities:
            add: ["NET_ADMIN", "NET_RAW"]
        env:
        - name: POD_NAME
          valueFrom:
            fieldRef:
              fieldPath: metadata.name
        - name: POD_NAMESPACE
          valueFrom:
            fieldRef:
              fieldPath: metadata.namespace
        volumeMounts:
        - name: run
          mountPath: /run/flannel
        - name: flannel-cfg
          mountPath: /etc/kube-flannel/
      volumes:
      - name: run
        hostPath:
          path: /run/flannel
      - name: cni
        hostPath:
          path: /etc/cni/net.d
      - name: flannel-cfg
        configMap:
          name: kube-flannel-cfg

部署完成后会在节点的/etc/cni/net.d目录下生成flannel的配置文件

/etc/cni/net.d# cat 10-flannel.conflist 
{
    
    
  "name": "cbr0",
  "cniVersion": "0.3.1",
  "plugins": [
    {
    
    
      "type": "flannel",
      "delegate": {
    
    
        "hairpinMode": true,
        "isDefaultGateway": true
      }
    },
    {
    
    
      "type": "portmap",
      "capabilities": {
    
    
        "portMappings": true
      }
    }
  ]
}

节点subset信息生成在节点的 /run/flannel/subnet.env 文件中

root@cluster1-control-plane:/run/flannel# cat subnet.env 
FLANNEL_NETWORK=10.244.0.0/16
FLANNEL_SUBNET=10.244.0.1/24
FLANNEL_MTU=1450
FLANNEL_IPMASQ=false

部署完成后，kube-flannel以DaemonSet方式运行在master和worker节点上，但是coredns等仍旧有问题

通过kubectl describe查看:
… failed to find plugin “flannel” in path [/opt/cni/bin]

Warning FailedCreatePodSandBox 10s kubelet, cluster1-worker Failed to create pod sandbox: rpc error: code = Unknown desc = failed to setup network for sandbox “d9d1f4c592c10514313dec335bc24c6eb9c89903e59fa3db3a7f49696e1dd757”: failed to find plugin “flannel” in path [/opt/cni/bin]

需要下载CNI插件： CNI Plugins v0.8.7 （在1.0.0版本后CNI Plugins中没有flannel了，这是为什么？）
将压缩包放到master和worker的/opt/cni/bin目录下，并且解压

#将插件放到master，worker节点类似
sudo docker cp '/home/cni-plugins-linux-arm64-v0.8.7.tgz' aa7c807c9c4a:/opt/cni/bin/
sudo docker exec -it aa7c807c9c4a /bin/bash
root@cluster1-worker:/# cd /opt/cni/bin/
root@cluster1-worker:/opt/cni/bin# ls 
cni-plugins-linux-arm64-v0.8.7.tgz  host-local  loopback  portmap  ptp
root@cluster1-worker:/opt/cni/bin# tar -xzvf cni-plugins-linux-arm64-v0.8.7.tgz 
./
./macvlan
./flannel
./static
./vlan
./portmap
./host-local
./bridge
./tuning
./firewall
./host-device
./sbr
./loopback
./dhcp
./ptp
./ipvlan
./bandwidth

完成后，集群上的pod都正常运行
进入worker节点可以看到：
cni0网桥和vtep设备flannel.1 (flannel.[VNI]，默认为flannel.1) ，mtu 1450表示使用vxlan进行节点间通信

2022-06-01补充：经评论区技术大佬提醒，新版在flannel的yaml部署文件中增加了将二进制文件复制到宿主机/opt/cni/bin的操作,具体yaml文件见官网。yaml文件对应片段如下：

验证

通过上述部署操作，KIND (k8s)环境网络如下

主机	主机地址	POD子网
master node	172.18.0.3	10.244.0.0/24
worker node	172.18.0.2	10.244.1.0/24

部署测试的deployment，通过测试ip分配正常
进入master上的pod(10.244.0.2)，ping worker上的pod(10.244.1.10)

/ # ping 10.244.1.10
PING 10.244.1.10 (10.244.1.10): 56 data bytes
64 bytes from 10.244.1.10: seq=0 ttl=62 time=0.516 ms
64 bytes from 10.244.1.10: seq=1 ttl=62 time=0.480 ms
^C
--- 10.244.1.10 ping statistics ---
2 packets transmitted, 2 packets received, 0% packet loss
round-trip min/avg/max = 0.480/0.498/0.516 ms

/ # traceroute 10.244.1.10
traceroute to 10.244.1.10 (10.244.1.10), 30 hops max, 46 byte packets
 1  10.244.0.1 (10.244.0.1)  0.057 ms  0.029 ms  0.024 ms
 2  10.244.1.0 (10.244.1.0)  0.025 ms  0.021 ms  0.017 ms
 3  10.244.1.10 (10.244.1.10)  0.015 ms  0.013 ms  0.008 ms

进入worker上的pod，查看路由表：
目的地址是10.244.0.0/16(k8s网络）的包，发往网关10.244.1.1。10.244.1.1是worker节点上的网关cni0的地址。

查看worker节点上的路由表：
目的地址是10.244.0.0/24 网段(master上pod的子网）的包，发往master的vtep设备flannel.1(10.244.0.0)

master节点的flannel.1(10.244.0.0)的MAC地址已经维护在worker节点flannel.1的fdb中

上图中56:a7:fb:b4:49:b2就是master节点flannel.1的MAC地址

总结

k8s网络之Flannel网络中结尾部分讲的很好，直接拿过来引用了

总的来说，flannel更像是经典的桥接模式的扩展。我们知道，在桥接模式中，每台主机的容器都将使用一个默认的网段，容器与容器之间，主机与容器之间都能互相通信。要是，我们能手动配置每台主机的网段，使它们互不冲突。接着再想点办法，将目的地址为非本机容器的流量送到相应主机：如果集群的主机都在一个子网内，就搞一条路由转发过去；若是不在一个子网内，就搞一条隧道转发过去。这样以来，容器的跨网络通信问题就解决了。而flannel做的，其实就是将这些工作自动化了而已。

后续

查看flannel的日志

client_config.go:608] Neither --kubeconfig nor --master was specified. Using the inClusterConfig. This might not work.

貌似使用也没有什么影响
如果要增加–kubeconfig启动参数，需要如下：

# 进到master节点
# 注意：我这个集群的apiserver地址是172.18.0.3，集群name是cluster1
# 切换到需要生成配置文件的目录，比如我这里是/usr/local/flannel-wf/
kubectl config set-cluster cluster1 --kubeconfig=flannel.conf --embed-certs --server=https://172.18.0.3:6443 --certificate-authority=/etc/kubernetes/pki/ca.crt

kubectl config set-credentials flannel --kubeconfig=flannel.conf --token=$(kubectl get sa -n kube-system flannel -o jsonpath={
     
     .secrets[0].name} | xargs kubectl get secret -n kube-system  -o jsonpath={
     
     .data.token} | base64 -d)

kubectl config set-context cluster1 --kubeconfig=flannel.conf --user=flannel --cluster=cluster1

# 将生成的flannel.conf复制到其他节点
# cat flannel.conf 
apiVersion: v1
clusters:
- cluster:
    certificate-authority-data: LS0tLS1CRUdJTiBDRVJUSUZJQ0FURS0tLS0tCk1JSUM1ekNDQWMrZ0F3SUJBZ0lCQURBTkJna3Foa2lHOXcwQkFRc0ZBREFWTVJNd0VRWURWUVFERXdwcmRXSmwKY201bGRHVnpNQjRYRFRJeU1EUXlOVEEyTURjd01Wb1hEVE15TURReU1qQTJNRGN3TVZvd0ZURVRNQkVHQTFVRQpBeE1LYTNWaVpYSnVaWFJsY3pDQ0FTSXdEUVlKS29aSWh2Y05BUUVCQlFBRGdnRVBBRENDQVFvQ2dnRUJBTUFYCjNONHUzR2xya1NNdXNDZjRTZkdSQzUzSGMwRDYvb29xeTBGZnIvUURYTmpnYVdXNzVMOTlaZ1JnRG1qSTVhZ1UKMlVxOTRQWFJ5NHNjSy9xZmlNQjdjS0NhSkVJSTJ1YUowcTlKdWlSUkd1REwwZEFSbTk4dU1LMlIzcHF4MXhMMAoyQUcybk0wcnorMGpMRkZ5UkxHQmFhL1hsNzFiRy9nK3FVVUpuMFRiNjNXb1d0c3BMT1pIVDArS1A3dm41TFZNCjNzYUdjWDRxSGswOWZPZEFCYzlrZGFKRUd3dU9ZQ0NpNmUzVnM0T3I1WFNobFl1RWc0OW9oeXZZQU5JQzdCa3gKbVNveXVQM09neEhHSyttS3hRYUxnK1JEZTc3UmgydEQ5WDNZb0haaHVWMk44QWs5Z1NzWHdVZ25NOHQzQWpQNwo5d2xmcmhQZG1iYWZwN1JIYWZVQ0F3RUFBYU5DTUVBd0RnWURWUjBQQVFIL0JBUURBZ0trTUE4R0ExVWRFd0VCCi93UUZNQU1CQWY4d0hRWURWUjBPQkJZRUZKNENmNjFQOTlPY2czbEprc3JjOU1TZlp6aUlNQTBHQ1NxR1NJYjMKRFFFQkN3VUFBNElCQVFDdGFVaEpnaTRXQis4NlEyTUN3WTdRZ2pUc2hPZ2t1UWlrZmRJZ3lDTjFyZ0ZiUTUyVQo3VHBHRS9aa09HdVRLOVRQUkgvUTJNWGNJejhiZHJoL245bFcveEViNklXUnBvaWF4U25tVTkrNHlxZ0pISkdlClVTbUZhZExIQjdaRHFlNnZZdmV6aWRPOWZ1OWRtNXFKUnJOdllxc0s4MVkvM3Y4b0NYbmQ1Uk12eFRoVjlhbFAKR2dHYTk5OGFXT1B6OHFEdHFIL3NkVnJ0UmpWOWVTSVJGNVg1ZE04bDlyTkNNZE43eGt4VGY5TG82V21kQXhseApMR3FYR2hnb1BHbHdIQnhPUGtLanBqZzRTZHpCZmFVZ1J0a1ZJUERsdW1Icm94RVNtZXlQNkc4UUVVY1AzVkJRCkJ3anRzb21aYnp4RWRhUCsydXJ5a05TMXY4cmFONGFXQkRlSAotLS0tLUVORCBDRVJUSUZJQ0FURS0tLS0tCg==
    server: https://172.18.0.3:6443
  name: cluster1
contexts:
- context:
    cluster: cluster1
    user: flannel
  name: cluster1
current-context: ""
kind: Config
preferences: {
    
    }
users:
- name: flannel
  user:
    token: eyJhbGciOiJSUzI1NiIsImtpZCI6ImNPbkpfSkFlVTBWa2RfVjVqZ1d6LXNPUDk1VldSY2NVb1M0empJS3hQQ1EifQ.eyJpc3MiOiJrdWJlcm5ldGVzL3NlcnZpY2VhY2NvdW50Iiwia3ViZXJuZXRlcy5pby9zZXJ2aWNlYWNjb3VudC9uYW1lc3BhY2UiOiJrdWJlLXN5c3RlbSIsImt1YmVybmV0ZXMuaW8vc2VydmljZWFjY291bnQvc2VjcmV0Lm5hbWUiOiJmbGFubmVsLXRva2VuLXM0ajI5Iiwia3ViZXJuZXRlcy5pby9zZXJ2aWNlYWNjb3VudC9zZXJ2aWNlLWFjY291bnQubmFtZSI6ImZsYW5uZWwiLCJrdWJlcm5ldGVzLmlvL3NlcnZpY2VhY2NvdW50L3NlcnZpY2UtYWNjb3VudC51aWQiOiI2NzFmNDNiZS0zZjYzLTQwMjktOTQ4Ny1lYWZjZDhmMmQ5ZmIiLCJzdWIiOiJzeXN0ZW06c2VydmljZWFjY291bnQ6a3ViZS1zeXN0ZW06Zmxhbm5lbCJ9.kHo7v-sKNDiRtOceIcngXzpY83Tp1Fnnyo6ueaDoSffAe3dBqW_W2ExU6F99DpujM6mnmlIUXXAq0Nbv6eANagK4fwGVD20so-mM9bVsOVJP74UufQh9oYhT77BHMMfryW7n3Q-ujerSswSvq5XFCax1WAOhQXYitIETIkD3ePKf5_HteRLLjvCTC2yuFNuYK3ZwpcOdypfvm28p_K6Ly0YW1EjOcN7UJ0FGMTAqJ71jeAT2OlVNxstuhNuMNOIfgyhYZ8lppxPuqh073EjTi0Ss59fRpFJCzbaEsEiIAwiel_hVw8xkNR7zCRvKQMlL5lmF-juMCXeoHeBKPcXwLQ

修改flannel部署yaml文件，仅修改DaemonSet，增加启动参数–kubeconfig，配置文件通过宿主机目录挂载到Pod目录。
其他ClusterRole、SA、ConfigMap等都不改动

---
apiVersion: apps/v1
kind: DaemonSet
metadata:
  name: kube-flannel-ds
  namespace: kube-system
  labels:
    tier: node
    app: flannel
spec:
  selector:
    matchLabels:
      app: flannel
  template:
    metadata:
      labels:
        tier: node
        app: flannel
    spec:
      affinity:
        nodeAffinity:
          requiredDuringSchedulingIgnoredDuringExecution:
            nodeSelectorTerms:
            - matchExpressions:
              - key: kubernetes.io/os
                operator: In
                values:
                - linux
      hostNetwork: true
      priorityClassName: system-node-critical
      tolerations:
      - operator: Exists
        effect: NoSchedule
      serviceAccountName: flannel
      initContainers:
      - name: install-cni
        image: quay.io/coreos/flannel:v0.14.0
        command:
        - cp
        args:
        - -f
        - /etc/kube-flannel/cni-conf.json
        - /etc/cni/net.d/10-flannel.conflist
        volumeMounts:
        - name: cni
          mountPath: /etc/cni/net.d
        - name: flannel-cfg
          mountPath: /etc/kube-flannel/
      containers:
      - name: kube-flannel
        image: quay.io/coreos/flannel:v0.14.0
        command:
        - /opt/bin/flanneld
        args:
        - --ip-masq=false
        - --kube-subnet-mgr
        - --kubeconfig-file=/usr/local/flannel-wf/flannel.conf # 增加启动参数！
        resources:
          requests:
            cpu: "100m"
            memory: "50Mi"
          limits:
            cpu: "100m"
            memory: "50Mi"
        securityContext:
          privileged: true
          capabilities:
            add: ["NET_ADMIN", "NET_RAW"]
        env:
        - name: POD_NAME
          valueFrom:
            fieldRef:
              fieldPath: metadata.name
        - name: POD_NAMESPACE
          valueFrom:
            fieldRef:
              fieldPath: metadata.namespace
        volumeMounts:
        - name: run
          mountPath: /run/flannel
        - name: flannel-cfg
          mountPath: /etc/kube-flannel/
        - name: kube-cfg ##
          mountPath: /usr/local/flannel-wf # 从宿主机挂载
      volumes:
      - name: run
        hostPath:
          path: /run/flannel
      - name: cni
        hostPath:
          path: /etc/cni/net.d
      - name: flannel-cfg
        configMap:
          name: kube-flannel-cfg
      ### 
      - name: kube-cfg
        hostPath:
          path: /usr/local/flannel-wf # 宿主机目录

重新部署后，查看启动日志就没有这行提示了

$ sudo kubectl logs -f kube-flannel-ds-dn59l -n kube-system
I0426 07:06:52.970794 1 main.go:520] Determining IP address of default interface
I0426 07:06:52.971228 1 main.go:533] Using interface with name eth0 and address 172.18.0.3
I0426 07:06:52.971252 1 main.go:550] Defaulting external address to interface address (172.18.0.3)
I0426 07:06:53.676497 1 kube.go:116] Waiting 10m0s for node controller to sync
I0426 07:06:53.676660 1 kube.go:299] Starting kube subnet manager
I0426 07:06:54.676663 1 kube.go:123] Node controller sync successful
I0426 07:06:54.676715 1 main.go:254] Created subnet manager: Kubernetes Subnet Manager - cluster1-control-plane
I0426 07:06:54.676724 1 main.go:257] Installing signal handlers
I0426 07:06:54.676988 1 main.go:392] Found network config - Backend type: vxlan
I0426 07:06:54.677234 1 vxlan.go:123] VXLAN config: VNI=1 Port=0 GBP=false Learning=false DirectRouting=false
I0426 07:06:54.873344 1 main.go:315] Changing default FORWARD chain policy to ACCEPT
I0426 07:06:54.873695 1 main.go:323] Wrote subnet file to /run/flannel/subnet.env
I0426 07:06:54.873720 1 main.go:327] Running backend.
I0426 07:06:54.873758 1 main.go:345] Waiting for all goroutines to exit
I0426 07:06:54.873809 1 vxlan_network.go:59] watching for new subnet leases

参考：
二进制安装flannel
k8s网络之Flannel网络