networking flannel
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@ -19,6 +19,7 @@
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- [CRI - Container Runtime Interface(容器运行时接口)](concepts/cri.md)
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- [CNI - Container Network Interface(容器网络接口)](concepts/cni.md)
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- [CSI - Container Storage Interface(容器存储接口)](concepts/csi.md)
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- [Kubernetes中的网络解析——以flannel为例](concepts/networking.md)
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- [资源对象与基本概念解析](concepts/objects.md)
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- [基本概念](concepts/basic.md)
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- [Pod概览](concepts/pod-overview.md)
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@ -0,0 +1,381 @@
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### Kubernetes中的网络解析——以flannel为例
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我们当初使用[kubernetes-vagrant-centos-cluster](https://github.com/rootsongjc/kubernetes-vagrant-centos-cluster)安装了拥有三个节点的kubernetes集群,节点的状态如下所述。
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```bash
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[root@node1 ~]# kubectl get nodes -o wide
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NAME STATUS ROLES AGE VERSION EXTERNAL-IP OS-IMAGE KERNEL-VERSION CONTAINER-RUNTIME
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node1 Ready <none> 2d v1.9.1 <none> CentOS Linux 7 (Core) 3.10.0-693.11.6.el7.x86_64 docker://1.12.6
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node2 Ready <none> 2d v1.9.1 <none> CentOS Linux 7 (Core) 3.10.0-693.11.6.el7.x86_64 docker://1.12.6
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node3 Ready <none> 2d v1.9.1 <none> CentOS Linux 7 (Core) 3.10.0-693.11.6.el7.x86_64 docker://1.12.6
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```
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当前Kubernetes集群中运行的所有Pod信息:
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```bash
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[root@node1 ~]# kubectl get pods --all-namespaces -o wide
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NAMESPACE NAME READY STATUS RESTARTS AGE IP NODE
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kube-system coredns-5984fb8cbb-sjqv9 1/1 Running 0 1h 172.33.68.2 node1
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kube-system coredns-5984fb8cbb-tkfrc 1/1 Running 1 1h 172.33.96.3 node3
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kube-system heapster-v1.5.0-684c7f9488-z6sdz 4/4 Running 0 1h 172.33.31.3 node2
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kube-system kubernetes-dashboard-6b66b8b96c-mnm2c 1/1 Running 0 1h 172.33.31.2 node2
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kube-system monitoring-influxdb-grafana-v4-54b7854697-tw9cd 2/2 Running 2 1h 172.33.96.2 node3
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```
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当前etcd中的注册的宿主机的pod地址网段信息:
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```bash
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[root@node1 ~]# etcdctl ls /kube-centos/network/subnets
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/kube-centos/network/subnets/172.33.68.0-24
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/kube-centos/network/subnets/172.33.31.0-24
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/kube-centos/network/subnets/172.33.96.0-24
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```
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而每个node上的Pod子网是根据我们在安装flannel时配置来划分的,在etcd中查看该配置:
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```bash
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[root@node1 ~]# etcdctl get /kube-centos/network/config
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{"Network":"172.33.0.0/16","SubnetLen":24,"Backend":{"Type":"host-gw"}}
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```
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我们知道Kubernetes集群内部存在三类IP,分别是:
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- Node IP:宿主机的IP地址
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- Pod IP:使用网络插件创建的IP(如flannel),使夸主机的Pod可以互通
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- Service IP:虚拟IP,通过iptabes转发访问服务
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在安装node节点的时候,节点上的进程是按照flannel -> docker -> kubelet -> kube-proxy的顺序启动的,我们下面也会按照该顺序来讲解,flannel的网络划分和如何与docker交互,如何通过iptables访问service。
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### Flannel
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Node1上的flannel配置如下:
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```bash
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[root@node1 ~]# cat /usr/lib/systemd/system/flanneld.service
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[Unit]
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Description=Flanneld overlay address etcd agent
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After=network.target
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After=network-online.target
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Wants=network-online.target
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After=etcd.service
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Before=docker.service
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[Service]
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Type=notify
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EnvironmentFile=/etc/sysconfig/flanneld
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EnvironmentFile=-/etc/sysconfig/docker-network
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ExecStart=/usr/bin/flanneld-start $FLANNEL_OPTIONS
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ExecStartPost=/usr/libexec/flannel/mk-docker-opts.sh -k DOCKER_NETWORK_OPTIONS -d /run/flannel/docker
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Restart=on-failure
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[Install]
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WantedBy=multi-user.target
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RequiredBy=docker.service
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```
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其中有两个环境变量文件的配置如下:
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```bash
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[root@node1 ~]# cat /etc/sysconfig/flanneld
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# Flanneld configuration options
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FLANNEL_ETCD_ENDPOINTS="http://172.17.8.101:2379"
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FLANNEL_ETCD_PREFIX="/kube-centos/network"
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FLANNEL_OPTIONS="-iface=eth2"
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```
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上面的配置文件仅供flanneld使用。
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```bash
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[root@node1 ~]# cat /etc/sysconfig/docker-network
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# /etc/sysconfig/docker-network
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DOCKER_NETWORK_OPTIONS=
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```
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还有一个`ExecStartPost=/usr/libexec/flannel/mk-docker-opts.sh -k DOCKER_NETWORK_OPTIONS -d /run/flannel/docker`,其中的`/usr/libexec/flannel/mk-docker-opts.sh`脚本是在flanneld启动后运行,将会生成两个环境变量配置文件:
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- /run/flannel/docker
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- /run/flannel/subnet.env
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我们再来看下`/run/flannel/docker`的配置。
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```bash
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[root@node1 ~]# cat /run/flannel/docker
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DOCKER_OPT_BIP="--bip=172.33.68.1/24"
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DOCKER_OPT_IPMASQ="--ip-masq=true"
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DOCKER_OPT_MTU="--mtu=1500"
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DOCKER_NETWORK_OPTIONS=" --bip=172.33.68.1/24 --ip-masq=true --mtu=1500"
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```
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如果你使用`systemctl`命令先启动flannel后启动docker的话,docker讲会读取以上环境变量。
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我们再来看下`/run/flannel/subnet.env`的配置。
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```bash
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[root@node1 ~]# cat /run/flannel/subnet.env
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FLANNEL_NETWORK=172.33.0.0/16
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FLANNEL_SUBNET=172.33.68.1/24
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FLANNEL_MTU=1500
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FLANNEL_IPMASQ=false
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```
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以上环境变量是flannel向etcd中注册的。
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### Docker
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Node1的docker配置如下:
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```bash
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[root@node1 ~]# cat /usr/lib/systemd/system/docker.service
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[Unit]
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Description=Docker Application Container Engine
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Documentation=http://docs.docker.com
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After=network.target rhel-push-plugin.socket registries.service
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Wants=docker-storage-setup.service
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Requires=docker-cleanup.timer
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[Service]
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Type=notify
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NotifyAccess=all
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EnvironmentFile=-/run/containers/registries.conf
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EnvironmentFile=-/etc/sysconfig/docker
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EnvironmentFile=-/etc/sysconfig/docker-storage
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EnvironmentFile=-/etc/sysconfig/docker-network
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Environment=GOTRACEBACK=crash
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Environment=DOCKER_HTTP_HOST_COMPAT=1
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Environment=PATH=/usr/libexec/docker:/usr/bin:/usr/sbin
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ExecStart=/usr/bin/dockerd-current \
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--add-runtime docker-runc=/usr/libexec/docker/docker-runc-current \
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--default-runtime=docker-runc \
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--exec-opt native.cgroupdriver=systemd \
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--userland-proxy-path=/usr/libexec/docker/docker-proxy-current \
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$OPTIONS \
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$DOCKER_STORAGE_OPTIONS \
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$DOCKER_NETWORK_OPTIONS \
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$ADD_REGISTRY \
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$BLOCK_REGISTRY \
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$INSECURE_REGISTRY\
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$REGISTRIES
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ExecReload=/bin/kill -s HUP $MAINPID
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LimitNOFILE=1048576
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LimitNPROC=1048576
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LimitCORE=infinity
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TimeoutStartSec=0
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Restart=on-abnormal
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MountFlags=slave
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KillMode=process
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[Install]
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WantedBy=multi-user.target
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```
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查看Node1上的docker启动参数:
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```bash
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[root@node1 ~]# systemctl status -l docker
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● docker.service - Docker Application Container Engine
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Loaded: loaded (/usr/lib/systemd/system/docker.service; enabled; vendor preset: disabled)
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Drop-In: /usr/lib/systemd/system/docker.service.d
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└─flannel.conf
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Active: active (running) since Fri 2018-02-02 22:52:43 CST; 2h 28min ago
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Docs: http://docs.docker.com
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Main PID: 4334 (dockerd-current)
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CGroup: /system.slice/docker.service
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‣ 4334 /usr/bin/dockerd-current --add-runtime docker-runc=/usr/libexec/docker/docker-runc-current --default-runtime=docker-runc --exec-opt native.cgroupdriver=systemd --userland-proxy-path=/usr/libexec/docker/docker-proxy-current --selinux-enabled --log-driver=journald --signature-verification=false --bip=172.33.68.1/24 --ip-masq=true --mtu=1500
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```
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我们可以看到在docker在启动时有如下参数:`--bip=172.33.68.1/24 --ip-masq=true --mtu=1500`。上述参数flannel启动时运行的脚本生成的,通过环境变量传递过来的。
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我们查看下node1宿主机上的网络接口:
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```bash
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[root@node1 ~]# ip addr
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1: lo: <LOOPBACK,UP,LOWER_UP> mtu 65536 qdisc noqueue state UNKNOWN qlen 1
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link/loopback 00:00:00:00:00:00 brd 00:00:00:00:00:00
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inet 127.0.0.1/8 scope host lo
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valid_lft forever preferred_lft forever
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inet6 ::1/128 scope host
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valid_lft forever preferred_lft forever
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2: eth0: <BROADCAST,MULTICAST,UP,LOWER_UP> mtu 1500 qdisc pfifo_fast state UP qlen 1000
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link/ether 52:54:00:00:57:32 brd ff:ff:ff:ff:ff:ff
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inet 10.0.2.15/24 brd 10.0.2.255 scope global dynamic eth0
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valid_lft 85095sec preferred_lft 85095sec
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inet6 fe80::5054:ff:fe00:5732/64 scope link
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valid_lft forever preferred_lft forever
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3: eth1: <BROADCAST,MULTICAST,UP,LOWER_UP> mtu 1500 qdisc pfifo_fast state UP qlen 1000
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link/ether 08:00:27:7b:0f:b1 brd ff:ff:ff:ff:ff:ff
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inet 172.17.8.101/24 brd 172.17.8.255 scope global eth1
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valid_lft forever preferred_lft forever
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4: eth2: <BROADCAST,MULTICAST,UP,LOWER_UP> mtu 1500 qdisc pfifo_fast state UP qlen 1000
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link/ether 08:00:27:ef:25:06 brd ff:ff:ff:ff:ff:ff
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inet 172.30.113.231/21 brd 172.30.119.255 scope global dynamic eth2
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valid_lft 85096sec preferred_lft 85096sec
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inet6 fe80::a00:27ff:feef:2506/64 scope link
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valid_lft forever preferred_lft forever
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5: docker0: <BROADCAST,MULTICAST,UP,LOWER_UP> mtu 1500 qdisc noqueue state UP
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link/ether 02:42:d0:ae:80:ea brd ff:ff:ff:ff:ff:ff
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inet 172.33.68.1/24 scope global docker0
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valid_lft forever preferred_lft forever
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inet6 fe80::42:d0ff:feae:80ea/64 scope link
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valid_lft forever preferred_lft forever
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7: veth295bef2@if6: <BROADCAST,MULTICAST,UP,LOWER_UP> mtu 1500 qdisc noqueue master docker0 state UP
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link/ether 6a:72:d7:9f:29:19 brd ff:ff:ff:ff:ff:ff link-netnsid 0
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inet6 fe80::6872:d7ff:fe9f:2919/64 scope link
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valid_lft forever preferred_lft forever
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```
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我们分类来解释下该虚拟机中的网络接口。
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- lo:回环网络,127.0.0.1
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- eth0:NAT网络,虚拟机创建时自动分配,仅可以在几台虚拟机之间访问
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- eth1:bridge网络,使用vagrant分配给虚拟机的地址,虚拟机之间和本地电脑都可以访问
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- eth2:bridge网络,使用DHCP分配,用于访问互联网的网卡
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- docker0:bridge网络,docker默认使用的网卡,作为该节点上所有容器的虚拟交换机
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- veth295bef2@if6:veth pair,连接docker0和Pod中的容器。veth pair可以理解为使用网线连接好的两个接口,把两个端口放到两个namespace中,那么这两个namespace就能打通。参考[linux 网络虚拟化: network namespace 简介](http://cizixs.com/2017/02/10/network-virtualization-network-namespace)。
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我们再看下该节点的docker上有哪些网络。
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```bash
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[root@node1 ~]# docker network ls
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NETWORK ID NAME DRIVER SCOPE
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940bb75e653b bridge bridge local
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d94c046e105d host host local
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2db7597fd546 none null local
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```
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再检查下bridge网络`940bb75e653b`的信息。
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```bash
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[root@node1 ~]# docker network inspect 940bb75e653b
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[
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{
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"Name": "bridge",
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"Id": "940bb75e653bfa10dab4cce8813c2b3ce17501e4e4935f7dc13805a61b732d2c",
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"Scope": "local",
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"Driver": "bridge",
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"EnableIPv6": false,
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"IPAM": {
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"Driver": "default",
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"Options": null,
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"Config": [
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{
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"Subnet": "172.33.68.1/24",
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"Gateway": "172.33.68.1"
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}
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]
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},
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"Internal": false,
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"Containers": {
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"944d4aa660e30e1be9a18d30c9dcfa3b0504d1e5dbd00f3004b76582f1c9a85b": {
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"Name": "k8s_POD_coredns-5984fb8cbb-sjqv9_kube-system_c5a2e959-082a-11e8-b4cd-525400005732_0",
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"EndpointID": "7397d7282e464fc4ec5756d6b328df889cdf46134dbbe3753517e175d3844a85",
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"MacAddress": "02:42:ac:21:44:02",
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"IPv4Address": "172.33.68.2/24",
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"IPv6Address": ""
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}
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},
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"Options": {
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"com.docker.network.bridge.default_bridge": "true",
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"com.docker.network.bridge.enable_icc": "true",
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"com.docker.network.bridge.enable_ip_masquerade": "true",
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"com.docker.network.bridge.host_binding_ipv4": "0.0.0.0",
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"com.docker.network.bridge.name": "docker0",
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"com.docker.network.driver.mtu": "1500"
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},
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"Labels": {}
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}
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]
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```
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我们可以看到该网络中的`Config`与docker的启动配置相符。
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Node1上运行的容器:
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```bash
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[root@node1 ~]# docker ps
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CONTAINER ID IMAGE COMMAND CREATED STATUS PORTS NAMES
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a37407a234dd docker.io/coredns/coredns@sha256:adf2e5b4504ef9ffa43f16010bd064273338759e92f6f616dd159115748799bc "/coredns -conf /etc/" About an hour ago Up About an hour k8s_coredns_coredns-5984fb8cbb-sjqv9_kube-system_c5a2e959-082a-11e8-b4cd-525400005732_0
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944d4aa660e3 docker.io/openshift/origin-pod "/usr/bin/pod" About an hour ago Up About an hour k8s_POD_coredns-5984fb8cbb-sjqv9_kube-system_c5a2e959-082a-11e8-b4cd-525400005732_0
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```
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我们可以看到当前已经有2个容器在运行。
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Node1上的路由信息:
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```bash
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[root@node1 ~]# route -n
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Kernel IP routing table
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Destination Gateway Genmask Flags Metric Ref Use Iface
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0.0.0.0 10.0.2.2 0.0.0.0 UG 100 0 0 eth0
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0.0.0.0 172.30.116.1 0.0.0.0 UG 101 0 0 eth2
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10.0.2.0 0.0.0.0 255.255.255.0 U 100 0 0 eth0
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172.17.8.0 0.0.0.0 255.255.255.0 U 100 0 0 eth1
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172.30.112.0 0.0.0.0 255.255.248.0 U 100 0 0 eth2
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172.33.68.0 0.0.0.0 255.255.255.0 U 0 0 0 docker0
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172.33.96.0 172.30.118.65 255.255.255.0 UG 0 0 0 eth2
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```
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以上路由信息是由flannel添加的,当有新的节点加入到Kubernetes集群中后,每个节点上的路由表都将增加。
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我们在node上来`traceroute`下node3上的`coredns-5984fb8cbb-tkfrc`容器,其IP地址是`172.33.96.3`,看看其路由信息。
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```bash
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[root@node1 ~]# traceroute 172.33.96.3
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traceroute to 172.33.96.3 (172.33.96.3), 30 hops max, 60 byte packets
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1 172.30.118.65 (172.30.118.65) 0.518 ms 0.367 ms 0.398 ms
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2 172.33.96.3 (172.33.96.3) 0.451 ms 0.352 ms 0.223 ms
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```
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我们看到路由直接经过node3的公网IP后就到达了node3节点上的Pod。
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Node1的iptables信息:
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```bash
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[root@node1 ~]# iptables -L
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Chain INPUT (policy ACCEPT)
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target prot opt source destination
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KUBE-FIREWALL all -- anywhere anywhere
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KUBE-SERVICES all -- anywhere anywhere /* kubernetes service portals */
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Chain FORWARD (policy ACCEPT)
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target prot opt source destination
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KUBE-FORWARD all -- anywhere anywhere /* kubernetes forward rules */
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DOCKER-ISOLATION all -- anywhere anywhere
|
||||
DOCKER all -- anywhere anywhere
|
||||
ACCEPT all -- anywhere anywhere ctstate RELATED,ESTABLISHED
|
||||
ACCEPT all -- anywhere anywhere
|
||||
ACCEPT all -- anywhere anywhere
|
||||
|
||||
Chain OUTPUT (policy ACCEPT)
|
||||
target prot opt source destination
|
||||
KUBE-FIREWALL all -- anywhere anywhere
|
||||
KUBE-SERVICES all -- anywhere anywhere /* kubernetes service portals */
|
||||
|
||||
Chain DOCKER (1 references)
|
||||
target prot opt source destination
|
||||
|
||||
Chain DOCKER-ISOLATION (1 references)
|
||||
target prot opt source destination
|
||||
RETURN all -- anywhere anywhere
|
||||
|
||||
Chain KUBE-FIREWALL (2 references)
|
||||
target prot opt source destination
|
||||
DROP all -- anywhere anywhere /* kubernetes firewall for dropping marked packets */ mark match 0x8000/0x8000
|
||||
|
||||
Chain KUBE-FORWARD (1 references)
|
||||
target prot opt source destination
|
||||
ACCEPT all -- anywhere anywhere /* kubernetes forwarding rules */ mark match 0x4000/0x4000
|
||||
ACCEPT all -- 10.254.0.0/16 anywhere /* kubernetes forwarding conntrack pod source rule */ ctstate RELATED,ESTABLISHED
|
||||
ACCEPT all -- anywhere 10.254.0.0/16 /* kubernetes forwarding conntrack pod destination rule */ ctstate RELATED,ESTABLISHED
|
||||
|
||||
Chain KUBE-SERVICES (2 references)
|
||||
target prot opt source destination
|
||||
```
|
||||
|
||||
从上面的iptables中可以看到注入了很多Kuberentes service的规则,请参考[iptables 规则](https://www.cnyunwei.cc/archives/393)获取更多详细信息。
|
||||
|
||||
## 参考
|
||||
|
||||
- [linux 网络虚拟化: network namespace 简介](http://cizixs.com/2017/02/10/network-virtualization-network-namespace)
|
||||
- [Linux虚拟网络设备之veth](https://segmentfault.com/a/1190000009251098)
|
||||
- [iptables 规则](https://www.cnyunwei.cc/archives/393)
|
||||
- [flannel host-gw network](http://hustcat.github.io/flannel-host-gw-network/)
|
Loading…
Reference in New Issue