自己动手写 Docker 系列 -- 6.2 创建网络
作者：萧
- 2022 年 4 月 16 日
本文字数：7460 字
阅读完需：约 24 分钟
简介
在前面的文章中，我们完成了一个 IP 管理和分配的工具类，能自动分配和回收子网的 IP，本篇将继续上篇，开始网络的创建部分
源码说明
同时放到了 Gitee 和 Github 上，都可进行获取
本章节对应的版本标签是：6.2，防止后面代码过多，不好查看，可切换到标签版本进行查看
代码实现
主要是实现思路如下：
创建网络：读取用户输入的子网，如何取第一个作为网关 ip，创建虚拟网络（或者网卡）；创建成功后，将网络信息序列化成 JSON 保存到本地，便于后序读取
删除网络：根据输入的虚拟网络名，删除对应的网络
下面是具体的实现：
network 命令新增
首先增加相关的命令操作：
新增 network 命令操作
func main() { ...... app.Commands = []cli.Command{ command.InitCommand, command.RunCommand, command.CommitCommand, command.ListCommand, command.LogCommand, command.ExecCommand, command.StopCommand, command.RemoveCommand, command.NetworkCommand, } ......}
复制代码
network 相关详细命令
var NetworkCommand = cli.Command{ Name: "network", Usage: "container network commands", Subcommands: []cli.Command{ { Name: "create", Usage: "create a container network", Flags: []cli.Flag{ cli.StringFlag{ Name: "driver", Usage: "network driver", }, cli.StringFlag{ Name: "subnet", Usage: "subnet cidr", }, }, Action: func(context *cli.Context) error { if len(context.Args()) < 1 { return fmt.Errorf("missing network name") }
err := network.Init() if err != nil { return err }
driver := context.String("driver") subnet := context.String("subnet") name := context.Args()[0] if err := network.CreateNetwork(driver, subnet, name); err != nil { return err } return nil }, },
{ Name: "list", Usage: "list container network", Action: func(context *cli.Context) error { if err := network.Init(); err != nil { return err } return network.ListNetwork() }, },
{ Name: "remove", Usage: "remove container network", Action: func(context *cli.Context) error { if len(context.Args()) < 1 { return fmt.Errorf("missing network name") } if err := network.Init(); err != nil { return err } if err := network.DeleteNetwork(context.Args()[0]); err != nil { return err } return nil }, }, },}
复制代码
如上，新增了创建新的网络、查看网络列表和删除网络的操作
创建新网络
在命令启动的时候，传入子网和虚拟网络名，我们根据这些去创建虚拟网络
func CreateNetwork(driver, subnet, name string) error { nw, err := drivers[driver].Create(subnet, name) if err != nil { return err } log.Infof("create network success") return nw.dump(defaultNetworkPath)}
复制代码
下面的网络信息：Network，做了一些小改造，增加了 GatewayIP（网关 IP）和 Subnet（子网网段信息），保存了下来，因为使用 IpRange 字段，无法正常使用我们的 IP 回收操作
func (b *BridgeNetworkDriver) Create(subnet string, name string) (*NetWork, error) { _, ipRange, _ := net.ParseCIDR(subnet) // 得到网段的第一个IP作为网关IP ip, err := ipAllocator.Allocate(ipRange) if err != nil { return nil, err } ipRange.IP = ip n := &NetWork{ Name: name, IpRange: ipRange, Driver: b.Name(), GatewayIP: ip, Subnet: subnet, } log.Infof("BridgeNetworkDriver creat network subnet: %s, gateway ip: %s", ipRange.String(), ip.String()) // 初始化虚拟网络 return n, b.initBridge(n)}
复制代码
下面是具体的虚拟化网络创建，基本是都是使用系统函数（博主目前还不是太懂这个，说不出东西了，先照抄吧......）
func (b *BridgeNetworkDriver) initBridge(n *NetWork) error { // try to get bridge by name, if it already exists then just exit bridgeName := n.Name if err := createBridgeInterface(bridgeName); err != nil { return err } log.Infof("createBridgeInterface success")
// set bridge ip gatewayIp := *n.IpRange gatewayIp.IP = n.IpRange.IP
if err := setInterfaceIp(bridgeName, gatewayIp.String()); err != nil { return err } log.Infof("setInterfaceIp success")
if err := setInterfaceUp(bridgeName); err != nil { return err } log.Infof("crsetInterfaceUp success")
if err := setupIpTables(bridgeName, n.IpRange); err != nil { return err } log.Infof("setInterfaceUp success") return nil}
复制代码
func createBridgeInterface(bridgeName string) error { _, err := net.InterfaceByName(bridgeName) if err == nil || !strings.Contains(err.Error(), "no such network interface") { return err }
// create *netlink.Bridge object la := netlink.NewLinkAttrs() la.Name = bridgeName
br := &netlink.Bridge{LinkAttrs: la} if err := netlink.LinkAdd(br); err != nil { return fmt.Errorf("bridge creating failed for bridge %s, err: %w", bridgeName, err) } return nil}
func setInterfaceUp(interfaceName string) error { iface, err := netlink.LinkByName(interfaceName) if err != nil { return fmt.Errorf("error retrieving a link named [ %s ], err: %w", iface.Attrs().Name, err) }
if err := netlink.LinkSetUp(iface); err != nil { return fmt.Errorf("error enabling interface for %s, err: %w", interfaceName, err) } return nil}
func setInterfaceIp(name string, rawIp string) error { retries := 2 var iface netlink.Link var err error for i := 0; i < retries; i++ { iface, err = netlink.LinkByName(name) if err == nil { break } log.Debugf("error retrieving new bridge netlink link [ %s ]... retrying", name) time.Sleep(2 * time.Second) } if err != nil { return fmt.Errorf("abandoning retrieving the new bridge ink from netlink, run [ip link] to troubleshoot the err: %w", err) }
ipNet, err := netlink.ParseIPNet(rawIp) if err != nil { return fmt.Errorf("netlink.ParseIPNet err: %w", err) }
addr := &netlink.Addr{ IPNet: ipNet, Peer: ipNet, Label: "", Flags: 0, Scope: 0, Broadcast: nil, } return netlink.AddrAdd(iface, addr)}
func setupIpTables(bridgeName string, subnet *net.IPNet) error { iptablesCmd := fmt.Sprintf("-t nat -A POSTROUTING -s %s ! -o %s -j MASQUERADE", subnet.String(), bridgeName) cmd := exec.Command("iptables", strings.Split(iptablesCmd, " ")...) output, err := cmd.Output() if err != nil { return fmt.Errorf("iptablse err %v, %w", output, err) } return nil}
复制代码
上面就是虚拟网络的创建相关代码
查看已存在的虚拟网络
在查看的时候，需要初始化网络配置信息，及 Init 函数
我们写了一个网络配置信息的固定位置，所有的网络配置文件都会以其名称，存放到下面,网络驱动和配置也会加载到内存中
var ( // 网络配置的默认存放位置 defaultNetworkPath = "/var/run/mydocker/network/network/" // 不同网络的网络驱动 drivers = map[string]NetworkDriver{} // 不同网络的网络配置 networks = map[string]*NetWork{})
复制代码
网络信息初始化的基本原理就是读取网络配置默认存放文件夹，加载所有的网络配置即可：
func Init() error { var bridgeDriver = BridgeNetworkDriver{} drivers[bridgeDriver.Name()] = &bridgeDriver
if _, err := os.Stat(defaultNetworkPath); err != nil { if os.IsNotExist(err) { _ = os.MkdirAll(defaultNetworkPath, 0644) } else { return err } }
_ = filepath.Walk(defaultNetworkPath, func(nwPath string, info os.FileInfo, err error) error { if strings.HasSuffix(nwPath, "/") { return nil } _, nwName := path.Split(nwPath) nw := &NetWork{ Name: nwName, }
if err := nw.load(nwPath); err != nil { log.Errorf("error load network: %v", err) }
networks[nwName] = nw return nil }) return nil}
复制代码
查看网络配置就比较简单了，遍历打印即可：
func ListNetwork() error { w := tabwriter.NewWriter(os.Stdout, 12, 1, 3, ' ', 0) _, _ = fmt.Fprint(w, "NAME\tIpRange\tDriver\n") for _, nw := range networks { fmt.Fprintf(w, "%s\t%s\t\t%s\n", nw.Name, nw.IpRange.String(), nw.Driver, ) } if err := w.Flush(); err != nil { return fmt.Errorf("flush error: %w", err) } return nil}
复制代码
删除网络
删除网络就是删除相关虚拟网络和配置文件
func DeleteNetwork(networkName string) error { nw, ok := networks[networkName] if !ok { return fmt.Errorf("no such network: %s", networkName) }
// 将网关IP进行释放 _, ipNet, _ := net.ParseCIDR(nw.Subnet) if err := ipAllocator.Release(ipNet, &nw.GatewayIP); err != nil { return fmt.Errorf("remove network gateway ip err: %w", err) }
// 删除虚拟网络 if err := drivers[nw.Driver].Delete(*nw); err != nil { return fmt.Errorf("remove network driver err: %w", err) }
// 删除配置文件 return nw.remove(defaultNetworkPath)}
复制代码
网络配置使用系统函数删除即可
func (b *BridgeNetworkDriver) Delete(network NetWork) error { bridgeName := network.Name br, err := netlink.LinkByName(bridgeName) if err != nil { return err } return netlink.LinkDel(br)}
复制代码
网络配置文件的删除：
func (nw *NetWork) remove(dumpPath string) error { if _, err := os.Stat(path.Join(dumpPath, nw.Name)); err != nil { if os.IsNotExist(err) { return nil } else { return fmt.Errorf("remvove path err: %w", err) } } else { return os.Remove(path.Join(dumpPath, nw.Name)) }}
复制代码
运行测试
如下命令所示，创建和查看对应的网络
编译程序，创建网络
查看网络情况
删除网络并确认
root@lw-Code-01-Series-PF5NU1G ~/code/go/dockerDemo go build mydocker/main.go ✔ ⚡ 651 11:00:01root@lw-Code-01-Series-PF5NU1G ~/code/go/dockerDemo ./main network create --driver bridge --subnet 192.168.10.1/24 testbridge ✔ ⚡ 652 11:00:06{"level":"info","msg":"load ipam file from: /var/run/mydocker/network/ipam/subnet.json","time":"2022-04-16T11:00:11+08:00"}{"level":"info","msg":"allocate subnet: 192.168.10.1/24, ip: 192.168.10.1","time":"2022-04-16T11:00:11+08:00"}{"level":"info","msg":"dump ipam file from: /var/run/mydocker/network/ipam/","time":"2022-04-16T11:00:11+08:00"}{"level":"info","msg":"BridgeNetworkDriver creat network subnet: 192.168.10.1/24, gateway ip: 192.168.10.1","time":"2022-04-16T11:00:11+08:00"}{"level":"info","msg":"createBridgeInterface success","time":"2022-04-16T11:00:11+08:00"}{"level":"info","msg":"setInterfaceIp success","time":"2022-04-16T11:00:11+08:00"}{"level":"info","msg":"crsetInterfaceUp success","time":"2022-04-16T11:00:11+08:00"}{"level":"info","msg":"setInterfaceUp success","time":"2022-04-16T11:00:11+08:00"}{"level":"info","msg":"create network success","time":"2022-04-16T11:00:11+08:00"}
root@lw-Code-01-Series-PF5NU1G ~/code/go/dockerDemo ./main network list ✔ ⚡ 653 11:00:16NAME IpRange Drivertestbridge 192.168.10.1/24 bridge
root@lw-Code-01-Series-PF5NU1G ~/code/go/dockerDemo ip link show dev testbridge ✔ ⚡ 654 11:00:197: testbridge: <BROADCAST,MULTICAST,UP,LOWER_UP> mtu 1500 qdisc noqueue state UNKNOWN mode DEFAULT group default qlen 1000 link/ether 6a:a8:a1:a4:74:b4 brd ff:ff:ff:ff:ff:ff root@lw-Code-01-Series-PF5NU1G ~/code/go/dockerDemo ip addr show dev testbridge ✔ ⚡ 655 11:00:247: testbridge: <BROADCAST,MULTICAST,UP,LOWER_UP> mtu 1500 qdisc noqueue state UNKNOWN group default qlen 1000 link/ether 6a:a8:a1:a4:74:b4 brd ff:ff:ff:ff:ff:ff inet 192.168.10.1/24 brd 192.168.10.255 scope global testbridge valid_lft forever preferred_lft forever inet6 fe80::68a8:a1ff:fea4:74b4/64 scope link valid_lft forever preferred_lft forever root@lw-Code-01-Series-PF5NU1G ~/code/go/dockerDemo iptables -t nat -vnL POSTROUTING ✔ ⚡ 656 11:00:29Chain POSTROUTING (policy ACCEPT 44 packets, 4188 bytes) pkts bytes target prot opt in out source destination 0 0 MASQUERADE all -- * !docker0 172.17.0.0/16 0.0.0.0/0 0 0 MASQUERADE all -- * !testbridge 192.168.10.0/24 0.0.0.0/0 0 0 MASQUERADE all -- * !testbridge 192.168.10.0/24 0.0.0.0/0 0 0 MASQUERADE all -- * !testbridge 192.168.10.0/24 0.0.0.0/0 0 0 MASQUERADE all -- * !testbridge 192.168.10.0/24 0.0.0.0/0 0 0 MASQUERADE all -- * !testbridge 192.168.10.0/24 0.0.0.0/0 root@lw-Code-01-Series-PF5NU1G ~/code/go/dockerDemo ./main network remove testbridge ✔ ⚡ 657 11:00:35{"level":"info","msg":"release subnet: 192.168.10.0/24, ip: 192.168.10.1","time":"2022-04-16T11:00:40+08:00"}{"level":"info","msg":"load ipam file from: /var/run/mydocker/network/ipam/subnet.json","time":"2022-04-16T11:00:40+08:00"}{"level":"info","msg":"release index: 0","time":"2022-04-16T11:00:40+08:00"}{"level":"info","msg":"dump ipam file from: /var/run/mydocker/network/ipam/","time":"2022-04-16T11:00:40+08:00"}
root@lw-Code-01-Series-PF5NU1G ~/code/go/dockerDemo ./main network list ✔ ⚡ 658 11:00:42NAME IpRange Driver
root@lw-Code-01-Series-PF5NU1G ~/code/go/dockerDemo ip addr show dev testbridge ✔ ⚡ 659 11:00:47Device "testbridge" does not exist.
复制代码
总体感觉下来好像是创建桥接网卡？和使用 VMware 的时候，会生成虚拟网卡，如果在没删除的时候，使用下面的命令查看，会得到
root@lw-Code-01-Series-PF5NU1G ~/code/go/dockerDemo ifconfig ✔ ⚡ 661 11:04:37testbridge: flags=4163<UP,BROADCAST,RUNNING,MULTICAST> mtu 1500 inet 192.168.10.1 netmask 255.255.255.0 broadcast 192.168.10.255 inet6 fe80::fc2b:95ff:fe8d:5c98 prefixlen 64 scopeid 0x20<link> ether fe:2b:95:8d:5c:98 txqueuelen 1000 (以太网) RX packets 0 bytes 0 (0.0 B) RX errors 0 dropped 0 overruns 0 frame 0 TX packets 33 bytes 4700 (4.7 KB) TX errors 0 dropped 0 overruns 0 carrier 0 collisions 0
复制代码
总体来说，书上的代码有点乱，抄下来，运行不起来，主要还是 ip 的分配和释放问题，所以本篇中进行了一些小的改造，初步达到预期
划线
评论
复制
发布于: 刚刚阅读数: 3
版权声明: 本文为 InfoQ 作者【萧】的原创文章。
原文链接:【http://xie.infoq.cn/article/ed21f70063e4987cecfebd4c4】。
本文遵守【CC-BY 4.0】协议，转载请保留原文出处及本版权声明。
萧
关注
还未添加个人签名 2018.09.09 加入
代码是门手艺活，也是门艺术活
评论