【kubernetes/k8s源码分析】CNI flannel源码分析

Dear 丶 2022-04-13 13:54 247阅读 0赞

源码路径： [https://github.com/containernetworking/plugins][https_github.com_containernetworking_plugins]

版本： v.0.10.0

flannel cni路径： plugins/plugins/meta/flannel/flannel.go

## subnet.env文件 ##

# cat /run/flannel/subnet.env 
    FLANNEL_NETWORK=172.30.0.0/16
    FLANNEL_SUBNET=172.30.45.1/24
    FLANNEL_MTU=1500
    FLANNEL_IPMASQ=false

# cni 配置文件 #

\# cat /etc/cni/net.d/10-flannel.conf   
\{"name":"cbr0","type":"flannel","delegate": \{"bridge": "docker0", "isDefaultGateway": true, "ipMasq": false\}\}

## NetConf结构体 ##

subnetFile文件默认为：/run/flannel/subnet.env

dataDIr默认为：/var/lib/cni/flannel

type NetConf struct {
    	types.NetConf
    
    	SubnetFile string                 `json:"subnetFile"`
    	DataDir    string                 `json:"dataDir"`
    	Delegate   map[string]interface{} `json:"delegate"`
    }

# 1. cmdAdd函数 #

###   1.1 loadFlannelNetConf函数 ###

将传入的参数解析到NetConf结构体，这里设置了默认的subnetFile，与dataDir

n, err := loadFlannelNetConf(args.StdinData)
    	if err != nil {
    		return err
    	}

###   1.2 loadFlannelSubnetEnv函数 ###

从/run/flannel/subnet.env读取配置，包括：

*  FLANNEL\_NETWORK=172.30.0.0/16
 *  FLANNEL\_SUBNET=172.30.46.1/24
 *  FLANNEL\_MTU=1500
 *  FLANNEL\_IPMASQ=false

fenv, err := loadFlannelSubnetEnv(n.SubnetFile)
    	if err != nil {
    		return err
    	}

###   1.3 subnet.env验证参数合法性 ###

if n.Delegate == nil {
    		n.Delegate = make(map[string]interface{})
    	} else {
    		if hasKey(n.Delegate, "type") && !isString(n.Delegate["type"]) {
    			return fmt.Errorf("'delegate' dictionary, if present, must have (string) 'type' field")
    		}
    		if hasKey(n.Delegate, "name") {
    			return fmt.Errorf("'delegate' dictionary must not have 'name' field, it'll be set by flannel")
    		}
    		if hasKey(n.Delegate, "ipam") {
    			return fmt.Errorf("'delegate' dictionary must not have 'ipam' field, it'll be set by flannel")
    		}
    	}

###   1.4 doCmdAdd函数 ###

对于未设置的参数初始化，如果未设置ipam则使用默认host-local

func doCmdAdd(args *skel.CmdArgs, n *NetConf, fenv *subnetEnv) error {
    	n.Delegate["name"] = n.Name
    
    	if !hasKey(n.Delegate, "type") {
    		n.Delegate["type"] = "bridge"
    	}
    
    	if !hasKey(n.Delegate, "ipMasq") {
    		// if flannel is not doing ipmasq, we should
    		ipmasq := !*fenv.ipmasq
    		n.Delegate["ipMasq"] = ipmasq
    	}
    
    	if !hasKey(n.Delegate, "mtu") {
    		mtu := fenv.mtu
    		n.Delegate["mtu"] = mtu
    	}
    
    	if n.Delegate["type"].(string) == "bridge" {
    		if !hasKey(n.Delegate, "isGateway") {
    			n.Delegate["isGateway"] = true
    		}
    	}
    	if n.CNIVersion != "" {
    		n.Delegate["cniVersion"] = n.CNIVersion
    	}
    
    	n.Delegate["ipam"] = map[string]interface{}{
    		"type":   "host-local",
    		"subnet": fenv.sn.String(),
    		"routes": []types.Route{
    			{
    				Dst: *fenv.nw,
    			},
    		},
    	}
    
    	return delegateAdd(args.ContainerID, n.DataDir, n.Delegate)
    }

# 2. delegateAdd函数 #

saveScratchNetConf函数创建/var/lib/cni/flannel目录

调用DelegateAdd函数

func delegateAdd(cid, dataDir string, netconf map[string]interface{}) error {
    	netconfBytes, err := json.Marshal(netconf)
    	if err != nil {
    		return fmt.Errorf("error serializing delegate netconf: %v", err)
    	}
    
    	// save the rendered netconf for cmdDel
    	if err = saveScratchNetConf(cid, dataDir, netconfBytes); err != nil {
    		return err
    	}
    
    	result, err := invoke.DelegateAdd(netconf["type"].(string), netconfBytes, nil)
    	if err != nil {
    		return err
    	}
    
    	return result.Print()
    }

# 3. 根據設置的bridge，調用bridge cni #

參照[https://blog.csdn.net/zhonglinzhang/article/details/82733201][https_blog.csdn.net_zhonglinzhang_article_details_82733201]

###   3.1 setupBridge函数 ###

*  通过netlink.LinkAdd(br)创建网桥，相当于ip link add br-test type bridge
 *   然后通过 netlink.LinkSetUp(br)启动网桥，相当于ip link set dev br-test up

###   3.2 setupVeth函数 ###

*   调用netlink.LinkAdd(veth)创建veth，这个是一个管道，Linux的网卡对，在容器对应的namespace下创建好虚拟网络接口，相当于ip link add test-veth0 type veth peer name test-veth1
 *   调用netlink.LinkSetUp(contVeth)启动容器端网卡，相当于ip link set dev test-veth0 up
 *  调用netlink.LinkSetNsFd(hostVeth, int(hostNS.Fd()))将host端加入namespace中，相当于ip link set $link netns $ns
 *   调用netlink.LinkSetMaster(hostVeth, br)绑到bridge，相当于ip link set dev test-veth0 master br-test

### 与calico不同点： ###

calico 绑到eth0

flannel 绑到docker0 bridge上，在调用bridage cni创建一大堆网络相关

[https_github.com_containernetworking_plugins]: https://github.com/containernetworking/plugins
[https_blog.csdn.net_zhonglinzhang_article_details_82733201]: https://blog.csdn.net/zhonglinzhang/article/details/82733201