[docker 网络][flannel] 源码简单分析

作者: nicktming | 来源:发表于2019-11-03 13:50 被阅读0次

1. 前言

转载请说明原文出处, 尊重他人劳动成果!

源码位置: https://github.com/nicktming/flannel
分支: tming-v0.10.0 (基于v0.10.0版本)

flannel
1. [docker 网络][flannel] 配置安装测试
2. [docker 网络][flannel] 背后操作
3. [docker 网络][flannel] 源码简单分析

前面两篇文章 [docker 网络][flannel] 配置安装测试和 [docker 网络][flannel] 背后操作已经测试了flannel vxlan实现跨主机容器之间的访问, 本文将从源码角度简单分析flannel是如何实现以及管理的, 主要追踪主要逻辑, 不会涉及特别多的细节.

所以将沿着Main方法主线进行分析.

2. 查找ExternalInterface

对外出口的设备

// backend/common.go
type ExternalInterface struct {
    Iface     *net.Interface
    IfaceAddr net.IP
    ExtAddr   net.IP
}

// main.go
func main() {
    ...
    var extIface *backend.ExternalInterface
    var err error
    // Check the default interface only if no interfaces are specified
    if len(opts.iface) == 0 && len(opts.ifaceRegex) == 0 {
        // 因为没有指定iface 所以直接从eth0里面找
        extIface, err = LookupExtIface("", "")
        if err != nil {
            log.Error("Failed to find any valid interface to use: ", err)
            os.Exit(1)
        }
    } else {
        // 按指定iface找
        // Check explicitly specified interfaces
        for _, iface := range opts.iface {
            extIface, err = LookupExtIface(iface, "")
            if err != nil {
                log.Infof("Could not find valid interface matching %s: %s", iface, err)
            }

            if extIface != nil {
                break
            }
        }
        ...
    }
    log.Infof("======>IfaceAddr:%v, ExtAddr:%v, Iface.Name:%s, Iface.Index:%d, Iface.MTU:%d", extIface.IfaceAddr, extIface.ExtAddr,
        extIface.Iface.Name, extIface.Iface.Index, extIface.Iface.MTU)
    ...
}

该段落的主要目的是找到该节点与外部网络通信的设备是哪个. 都是调用的同一个方法LookupExtIface.

如果没有指定iface或者ifaceRegex(通配符), 则寻找默认设备eth0.
如果指定了iface就直接按照iface名字去找到该设备, 比如eth0. 如果没有找到则尝试通过ifaceRegex(通配符)去找.

运行

[root@master flannel]# pwd
/root/go/src/github.com/coreos/flannel
[root@master flannel]# go build .
[root@master flannel]# ./flannel --etcd-endpoints="http://172.21.0.16:2379"
I1103 10:51:59.247205    6879 main.go:480] Determining IP address of default interface
I1103 10:51:59.247563    6879 main.go:493] Using interface with name eth0 and address 172.21.0.16
I1103 10:51:59.247575    6879 main.go:510] Defaulting external address to interface address (172.21.0.16)
I1103 10:51:59.247584    6879 main.go:232] ======>IfaceAddr:172.21.0.16, ExtAddr:172.21.0.16, Iface.Name:eth0, Iface.Index:2, Iface.MTU:1500
...

可以看到找到了默认设备eth0.

[root@master flannel]# ifconfig eth0
eth0: flags=4163<UP,BROADCAST,RUNNING,MULTICAST>  mtu 1500
        inet 172.21.0.16  netmask 255.255.240.0  broadcast 172.21.15.255
        inet6 fe80::5054:ff:fed5:4f7e  prefixlen 64  scopeid 0x20<link>
        ether 52:54:00:d5:4f:7e  txqueuelen 1000  (Ethernet)
        RX packets 10578209  bytes 2187448866 (2.0 GiB)
        RX errors 0  dropped 0  overruns 0  frame 0
        TX packets 10211912  bytes 2268572896 (2.1 GiB)
        TX errors 0  dropped 0 overruns 0  carrier 0  collisions 0
[root@master flannel]#

3. 子网管理

这个是已经存到etcd中的子网配置信息.

[root@master flannel]# etcdctl get /coreos.com/network/config
{"Network": "10.0.0.0/16", "SubnetLen": 24, "SubnetMin": "10.0.1.0","SubnetMax": "10.0.20.0", "Backend": {"Type": "vxlan"}}
[root@master flannel]#

创建子网管理

===> main.go
func main() {
...
sm, err := newSubnetManager()
...
}
func newSubnetManager() (subnet.Manager, error) {
    if opts.kubeSubnetMgr {
        return kube.NewSubnetManager(opts.kubeApiUrl, opts.kubeConfigFile)
    }

    cfg := &etcdv2.EtcdConfig{
        Endpoints: strings.Split(opts.etcdEndpoints, ","),
        Keyfile:   opts.etcdKeyfile,
        Certfile:  opts.etcdCertfile,
        CAFile:    opts.etcdCAFile,
        Prefix:    opts.etcdPrefix,
        Username:  opts.etcdUsername,
        Password:  opts.etcdPassword,
    }

    prevSubnet := ReadSubnetFromSubnetFile(opts.subnetFile)
    log.Infof("======>prevSubnet:%s\n", prevSubnet)
    return etcdv2.NewLocalManager(cfg, prevSubnet)
}
// 从/run/flannel/subnet.env中读子网
func ReadSubnetFromSubnetFile(path string) ip.IP4Net {
    var prevSubnet ip.IP4Net
    if _, err := os.Stat(path); !os.IsNotExist(err) {
        prevSubnetVals, err := godotenv.Read(path)
        if err != nil {
            log.Errorf("Couldn't fetch previous subnet from subnet file at %s: %s", path, err)
        } else if prevSubnetString, ok := prevSubnetVals["FLANNEL_SUBNET"]; ok {
            err = prevSubnet.UnmarshalJSON([]byte(prevSubnetString))
            if err != nil {
                log.Errorf("Couldn't parse previous subnet from subnet file at %s: %s", path, err)
            }
        }
    }
    return prevSubnet
}
===> subnet/etcdv2/local_manager.go
func NewLocalManager(config *EtcdConfig, prevSubnet ip.IP4Net) (Manager, error) {
    r, err := newEtcdSubnetRegistry(config, nil)
    if err != nil {
        return nil, err
    }
    return newLocalManager(r, prevSubnet), nil
}

func newLocalManager(r Registry, prevSubnet ip.IP4Net) Manager {
    return &LocalManager{
        registry:       r,
        previousSubnet: prevSubnet,
    }
}

可以看到LocalManager中有两个属性:

registry: 可以访问etcd数据的客户端.
previousSubnet: 该机器上上一次分配的子网信息.

运行

[root@master flannel]# ./flannel --etcd-endpoints="http://172.21.0.16:2379"
I1103 11:22:18.097587   10865 main.go:480] Determining IP address of default interface
I1103 11:22:18.097773   10865 main.go:493] Using interface with name eth0 and address 172.21.0.16
I1103 11:22:18.097783   10865 main.go:510] Defaulting external address to interface address (172.21.0.16)
I1103 11:22:18.097791   10865 main.go:232] ======>IfaceAddr:172.21.0.16, ExtAddr:172.21.0.16, Iface.Name:eth0, Iface.Index:2, Iface.MTU:1500
I1103 11:22:18.097807   10865 main.go:168] ======>prevSubnet:0.0.0.0/0
...

因为刚刚开始的时候/run/flannel/subnet.env文件可能不存在, 所以表明以前该机器上没有分配过子网, 或者该文件被删除了. 所以显示了======>prevSubnet:0.0.0.0/0.

4. 获得backend

4.1 vxlan注册信息

在flannel配置的时候需要告诉使用什么Type, 前文 [docker 网络][flannel] 配置安装测试用的vxlan, 比如还有udp等等, 这些Type在flannel这里就是一个backend, 每个backend要做的事情是一样的, 只是实现方式不一样而已.

type Backend interface {
    RegisterNetwork(ctx context.Context, config *subnet.Config) (Network, error)
}
type Network interface {
    Lease() *subnet.Lease
    MTU() int
    Run(ctx context.Context)
}
type BackendCtor func(sm subnet.Manager, ei *ExternalInterface) (Backend, error)

在程序启动的时候每个backend都会去backend manager注册自己的信息. 以vxlan为例

===> backend/vxlan/vxlan.go
func init() {
    backend.Register("vxlan", New)
}
const (
    defaultVNI = 1
)

type VXLANBackend struct {
    subnetMgr subnet.Manager
    extIface  *backend.ExternalInterface
}
func New(sm subnet.Manager, extIface *backend.ExternalInterface) (backend.Backend, error) {
    backend := &VXLANBackend{
        subnetMgr: sm,
        extIface:  extIface,
    }
    return backend, nil
}
// backend/manager.go
var constructors = make(map[string]BackendCtor)
func Register(name string, ctor BackendCtor) {
    constructors[name] = ctor
}

可以看到vxlan向backend manager中的constructors注册了自己的New方法, 告诉backend manager如何创建一个vxlan backend.

4.2 获得backend

既然所有的type在程序启动的时候都会注册自己的信息, 那如何获取一个特定的backend呢? 回头看看main方法.

func main() {
...
// Fetch the network config (i.e. what backend to use etc..).
    config, err := getConfig(ctx, sm)
    if err == errCanceled {
        wg.Wait()
        os.Exit(0)
    }

    // Create a backend manager then use it to create the backend and register the network with it.
    bm := backend.NewManager(ctx, sm, extIface)
    be, err := bm.GetBackend(config.BackendType)
    if err != nil {
        log.Errorf("Error fetching backend: %s", err)
        cancel()
        wg.Wait()
        os.Exit(1)
    }
...
}

1. config, err := getConfig(ctx, sm)就是从etcd获取如下的配置信息.

[root@master flannel]# etcdctl get /coreos.com/network/config
{"Network": "10.0.0.0/16", "SubnetLen": 24, "SubnetMin": "10.0.1.0","SubnetMax": "10.0.20.0", "Backend": {"Type": "vxlan"}}
[root@master flannel]#

2. bm := backend.NewManager(ctx, sm, extIface)生成一个backend manager, 为什么需要传入sm和extIface, 所以生成某一个具体的backend这两个参数, 这两个参数是给具体的backend来操作的. 从此定义从可以看到type BackendCtor func(sm subnet.Manager, ei *ExternalInterface) (Backend, error)其用法.

func NewManager(ctx context.Context, sm subnet.Manager, extIface *ExternalInterface) Manager {
    return &manager{
        ctx:      ctx,
        sm:       sm,
        extIface: extIface,
        active:   make(map[string]Backend),
    }
}

3. be, err := bm.GetBackend(config.BackendType)具体实现如下, 逻辑非常简单, 有该类型的backend就直接返回, 没有则用注册的New创建一个.

func (bm *manager) GetBackend(backendType string) (Backend, error) {
    bm.mux.Lock()
    defer bm.mux.Unlock()
    betype := strings.ToLower(backendType)
    // see if one is already running
    if be, ok := bm.active[betype]; ok {
        return be, nil
    }
    // first request, need to create and run it
    befunc, ok := constructors[betype]
    if !ok {
        return nil, fmt.Errorf("unknown backend type: %v", betype)
    }
    be, err := befunc(bm.sm, bm.extIface)
    if err != nil {
        return nil, err
    }
    bm.active[betype] = be
    bm.wg.Add(1)
    go func() {
        <-bm.ctx.Done()
        bm.mux.Lock()
        delete(bm.active, betype)
        bm.mux.Unlock()

        bm.wg.Done()
    }()
    return be, nil
}

很明显进行完之后可以获得一个VXLANBackend实例.

5. 注册网络

===> main.go
func main() {
...
bn, err := be.RegisterNetwork(ctx, config)
...
}
===> backend/vxlan/vxlan.go
func (be *VXLANBackend) RegisterNetwork(ctx context.Context, config *subnet.Config) (backend.Network, error) {
    // Parse our configuration
    cfg := struct {
        VNI           int
        Port          int
        GBP           bool
        DirectRouting bool
    }{
        VNI: defaultVNI,
    }

    if len(config.Backend) > 0 {
        if err := json.Unmarshal(config.Backend, &cfg); err != nil {
            return nil, fmt.Errorf("error decoding VXLAN backend config: %v", err)
        }
    }
    log.Infof("VXLAN config: VNI=%d Port=%d GBP=%v DirectRouting=%v", cfg.VNI, cfg.Port, cfg.GBP, cfg.DirectRouting)

    devAttrs := vxlanDeviceAttrs{
        vni:       uint32(cfg.VNI),
        name:      fmt.Sprintf("flannel.%v", cfg.VNI),
        vtepIndex: be.extIface.Iface.Index,
        vtepAddr:  be.extIface.IfaceAddr,
        vtepPort:  cfg.Port,
        gbp:       cfg.GBP,
    }
    // 生成flannel.1 设备
    dev, err := newVXLANDevice(&devAttrs)
    if err != nil {
        return nil, err
    }
    dev.directRouting = cfg.DirectRouting

    subnetAttrs, err := newSubnetAttrs(be.extIface.ExtAddr, dev.MACAddr())
    if err != nil {
        return nil, err
    }
    // 分配子网的时候 需要保存出口地址以及flannel.1 mac地址
    lease, err := be.subnetMgr.AcquireLease(ctx, subnetAttrs)
    switch err {
    case nil:
    case context.Canceled, context.DeadlineExceeded:
        return nil, err
    default:
        return nil, fmt.Errorf("failed to acquire lease: %v", err)
    }

    // Ensure that the device has a /32 address so that no broadcast routes are created.
    // This IP is just used as a source address for host to workload traffic (so
    // the return path for the traffic has an address on the flannel network to use as the destination)
    if err := dev.Configure(ip.IP4Net{IP: lease.Subnet.IP, PrefixLen: 32}); err != nil {
        return nil, fmt.Errorf("failed to configure interface %s: %s", dev.link.Attrs().Name, err)
    }

    return newNetwork(be.subnetMgr, be.extIface, dev, ip.IP4Net{}, lease)
}

运行:

===> 运行前
[root@master flannel]# etcdctl ls /coreos.com/network/subnets
[root@master flannel]# 
===> 运行
[root@master flannel]# ./flannel --etcd-endpoints="http://172.21.0.16:2379"
I1103 12:15:50.487232   18595 main.go:480] Determining IP address of default interface
I1103 12:15:50.487439   18595 main.go:493] Using interface with name eth0 and address 172.21.0.16
I1103 12:15:50.487449   18595 main.go:510] Defaulting external address to interface address (172.21.0.16)
I1103 12:15:50.487457   18595 main.go:232] ======>IfaceAddr:172.21.0.16, ExtAddr:172.21.0.16, Iface.Name:eth0, Iface.Index:2, Iface.MTU:1500
I1103 12:15:50.487505   18595 main.go:168] ======>prevSubnet:10.0.13.0/24
I1103 12:15:50.487570   18595 main.go:240] Created subnet manager: Etcd Local Manager with Previous Subnet: 10.0.13.0/24
I1103 12:15:50.487576   18595 main.go:243] Installing signal handlers
I1103 12:15:50.488757   18595 main.go:358] Found network config - Backend type: vxlan
I1103 12:15:50.488800   18595 vxlan.go:120] VXLAN config: VNI=1 Port=0 GBP=false DirectRouting=false
I1103 12:15:50.490867   18595 local_manager.go:201] Found previously leased subnet (10.0.13.0/24), reusing
I1103 12:15:50.491779   18595 local_manager.go:220] Allocated lease (10.0.13.0/24) to current node (172.21.0.16) 
I1103 12:15:50.491908   18595 main.go:305] Wrote subnet file to /run/flannel/subnet.env
I1103 12:15:50.491926   18595 main.go:309] Running backend.
I1103 12:15:50.492172   18595 vxlan_network.go:60] watching for new subnet leases
I1103 12:15:50.493612   18595 main.go:401] Waiting for 22h59m59.997445279s to renew lease
...
===> 运行后
[root@master ~]# ifconfig flannel.1
flannel.1: flags=4163<UP,BROADCAST,RUNNING,MULTICAST>  mtu 1450
        inet 10.0.13.0  netmask 255.255.255.255  broadcast 0.0.0.0
        inet6 fe80::d457:dcff:febb:a72e  prefixlen 64  scopeid 0x20<link>
        ether d6:57:dc:bb:a7:2e  txqueuelen 0  (Ethernet)
        RX packets 0  bytes 0 (0.0 B)
        RX errors 0  dropped 0  overruns 0  frame 0
        TX packets 0  bytes 0 (0.0 B)
        TX errors 0  dropped 8 overruns 0  carrier 0  collisions 0

[root@master ~]#

可以看到运行后多了flannel.1设备, 然后再看一下etcd里面的内容

[root@master ~]# etcdctl ls /coreos.com/network/subnets
/coreos.com/network/subnets/10.0.13.0-24
[root@master ~]# etcdctl get /coreos.com/network/subnets/10.0.13.0-24
{"PublicIP":"172.21.0.16","BackendType":"vxlan","BackendData":{"VtepMAC":"d6:57:dc:bb:a7:2e"}}

可以看到etcd给172.21.0.16机器分配了10.0.13.0/24网络, 并保存了此机器上的flannel.1的MAC地址. 这个是当别的机器加入到flannel中时会用到, 在add fdb, neighbor中用到.

另外会把分配得到的子网信息存到各自机器的/run/flannel/subnet.env中.

[root@master flannel]# cat /run/flannel/subnet.env
FLANNEL_NETWORK=10.0.0.0/16
FLANNEL_SUBNET=10.0.13.1/24
FLANNEL_MTU=1450
FLANNEL_IPMASQ=false
[root@master flannel]#

另外AcquireLease调用tryAcquireLease去申请子网. 主要分三步

1. 从etcd中寻找是否有该ip的子网网段存在.
2. 从本地/run/flannel/subnet.env中查看该主机是否有分配过子网.
3. 分配一个新的子网.

6. 监控变化

func main() {
...
log.Info("Running backend.")
    wg.Add(1)
    go func() {
        bn.Run(ctx)
        wg.Done()
    }()
...
}

bn, err := be.RegisterNetwork(ctx, config)是5. 注册网络中返回的一个Network对象, 该对象拥有分配的子网信息以及到期时间等等.

func (nw *network) Run(ctx context.Context) {
        ...
        subnet.WatchLeases(ctx, nw.subnetMgr, nw.SubnetLease, events)
        ...
    }()
    ...
    for {
        select {
        case evtBatch := <-events:
            nw.handleSubnetEvents(evtBatch)
        ...
    }
}

这里主要关注两个方法:

subnet.WatchLeases(ctx, nw.subnetMgr, nw.SubnetLease, events): 监控etcd中子网的变化情况, 一旦有机器加入/删除/更新等等, 就会把信息传到events中.
handleSubnetEvents: 一旦有变化, 就需要处理与该变化有关的操作.

    for _, event := range batch {
        ...
        switch event.Type {
        case subnet.EventAdded:
            if directRoutingOK {
                log.V(2).Infof("Adding direct route to subnet: %s PublicIP: %s", sn, attrs.PublicIP)

                if err := netlink.RouteReplace(&directRoute); err != nil {
                    log.Errorf("Error adding route to %v via %v: %v", sn, attrs.PublicIP, err)
                    continue
                }
            } else {
                log.V(2).Infof("adding subnet: %s PublicIP: %s VtepMAC: %s", sn, attrs.PublicIP, net.HardwareAddr(vxlanAttrs.VtepMAC))
                if err := nw.dev.AddARP(neighbor{IP: sn.IP, MAC: net.HardwareAddr(vxlanAttrs.VtepMAC)}); err != nil {
                    log.Error("AddARP failed: ", err)
                    continue
                }

                if err := nw.dev.AddFDB(neighbor{IP: attrs.PublicIP, MAC: net.HardwareAddr(vxlanAttrs.VtepMAC)}); err != nil {
                    log.Error("AddFDB failed: ", err)

                    // Try to clean up the ARP entry then continue
                    if err := nw.dev.DelARP(neighbor{IP: event.Lease.Subnet.IP, MAC: net.HardwareAddr(vxlanAttrs.VtepMAC)}); err != nil {
                        log.Error("DelARP failed: ", err)
                    }

                    continue
                }

                // Set the route - the kernel would ARP for the Gw IP address if it hadn't already been set above so make sure
                // this is done last.
                if err := netlink.RouteReplace(&vxlanRoute); err != nil {
                    log.Errorf("failed to add vxlanRoute (%s -> %s): %v", vxlanRoute.Dst, vxlanRoute.Gw, err)

                    // Try to clean up both the ARP and FDB entries then continue
                    if err := nw.dev.DelARP(neighbor{IP: event.Lease.Subnet.IP, MAC: net.HardwareAddr(vxlanAttrs.VtepMAC)}); err != nil {
                        log.Error("DelARP failed: ", err)
                    }

                    if err := nw.dev.DelFDB(neighbor{IP: event.Lease.Attrs.PublicIP, MAC: net.HardwareAddr(vxlanAttrs.VtepMAC)}); err != nil {
                        log.Error("DelFDB failed: ", err)
                    }

                    continue
                }
            }
        case subnet.EventRemoved:
            ...
        }
    }
}

可以看到有三个操作:
1. AddARP
2. AddFDB
3. RouteReplace 增加路由
所以说只要etcd中子网有变化, 那每台机器上的flannel都需要更新自己的arp, fdb, route表.

运行

在另外一台机器上(172.21.0.12)上启动flannel, 可以看到该机器分配的子网为10.0.10.0/24, 并且与机器(172.21.0.16)进行了flannel.1连通的相关操作.

// 在另外一台机器上(172.21.0.12)上启动flannel
[root@worker flannel]# ./flannel  --etcd-endpoints="http://172.21.0.16:2379" --ip-masq=true --v=2
...
I1103 12:53:18.445859    6246 local_manager.go:147] Found lease (10.0.10.0/24) for current IP (172.21.0.12)
...
I1103 12:53:18.449268    6246 vxlan_network.go:138] adding subnet: 10.0.13.0/24 PublicIP: 172.21.0.16 VtepMAC: d6:57:dc:bb:a7:2e
I

查看flannel.1 arp, fdb, route表

[root@worker ~]# ifconfig flannel.1
flannel.1: flags=4163<UP,BROADCAST,RUNNING,MULTICAST>  mtu 1450
        inet 10.0.10.0  netmask 255.255.255.255  broadcast 0.0.0.0
        inet6 fe80::acf0:22ff:fef1:f63d  prefixlen 64  scopeid 0x20<link>
        ether ae:f0:22:f1:f6:3d  txqueuelen 0  (Ethernet)
        RX packets 9  bytes 756 (756.0 B)
        RX errors 0  dropped 0  overruns 0  frame 0
        TX packets 8  bytes 672 (672.0 B)
        TX errors 0  dropped 8 overruns 0  carrier 0  collisions 0
[root@worker ~]# route -n
Kernel IP routing table
Destination     Gateway         Genmask         Flags Metric Ref    Use Iface
...
10.0.13.0       10.0.13.0       255.255.255.0   UG    0      0        0 flannel.1
...
[root@worker ~]# 
[root@worker ~]# bridge fdb show
...
10.0.13.0 dev flannel.1 lladdr d6:57:dc:bb:a7:2e PERMANENT
...
[root@worker ~]# ip neighbor show
...
10.0.13.0 dev flannel.1 lladdr d6:57:dc:bb:a7:2e PERMANENT
...
[root@worker ~]#

类似的可以看到172.21.0.16中flannel的日志中有了

[root@master flannel]# ./flannel --etcd-endpoints="http://172.21.0.16:2379" --ip-masq=true --v=2
...
I1103 12:53:18.446670   24228 vxlan_network.go:138] adding subnet: 10.0.10.0/24 PublicIP: 172.21.0.12 VtepMAC: ae:f0:22:f1:f6:3d

此时查看一下172.21.0.16中的flannel.1与172.21.0.12是否可以互通.

// flannel.1(172.21.0.16) ===> flannel.1(172.21.0.12)
[root@master flannel]# ping -c 1 10.0.10.0
PING 10.0.10.0 (10.0.10.0) 56(84) bytes of data.
64 bytes from 10.0.10.0: icmp_seq=1 ttl=64 time=0.402 ms

--- 10.0.10.0 ping statistics ---
1 packets transmitted, 1 received, 0% packet loss, time 0ms
rtt min/avg/max/mdev = 0.402/0.402/0.402/0.000 ms
[root@master flannel]# 

// flannel.1(172.21.0.12) ===> flannel.1(172.21.0.16)
root@worker ~]# ping -c 1 10.0.13.0
PING 10.0.13.0 (10.0.13.0) 56(84) bytes of data.
64 bytes from 10.0.13.0: icmp_seq=1 ttl=64 time=0.399 ms

--- 10.0.13.0 ping statistics ---
1 packets transmitted, 1 received, 0% packet loss, time 0ms
rtt min/avg/max/mdev = 0.399/0.399/0.399/0.000 ms

可以看到已经互相连通.

7. 总结

conclusion.png

1. 请求子网分配的时候, 按如下顺序, 原则就是尽量不让每个机器所属的子网发生变化:

1.1 从etcd中寻找是否有该ip的子网网段存在.
1.2 从本地/run/flannel/subnet.env中查看该主机是否有分配过子网.
1.3 分配一个新的子网.

2. 当有机器加入或者删除或更新等等, 都会触发每台机器去更新对应的arp fdb route表. 从而保证不影响通信.

[docker 网络][flannel] 源码简单分析

1. 前言

2. 查找ExternalInterface

运行

3. 子网管理

运行

4. 获得backend

4.1 vxlan注册信息

4.2 获得backend

5. 注册网络

6. 监控变化

运行

7. 总结

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