零入门kubernetes网络实战-20-＞golang编程syscall操作tun设备介绍

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本篇文章主要是使用golang自带的syscall包来创建tun类型的虚拟网络设备。

注意：

目前只能使用syscall包来创建tun类型的虚拟设备。

tun虚拟网卡设备的启动，IP配置，路由配置可能需要其他方式实现。

比方说通过netlink包方式来实现。

1、golang代码

package mainimport ("bytes""fmt""github.com/vishvananda/netlink""net""os""syscall""unsafe"
)const (tunDevice  = "/dev/net/tun"ifnameSize = 16
)type ifreqFlags struct {IfrnName  [ifnameSize]byteIfruFlags uint16
}func ioctl(fd int, request, argp uintptr) error {_, _, errno := syscall.Syscall(syscall.SYS_IOCTL, uintptr(fd), request, argp)if errno != 0 {return fmt.Errorf("ioctl failed with '%s'", errno)}return nil
}func fromZeroTerm(s []byte) string {return string(bytes.TrimRight(s, "\000"))
}func OpenTun(name string) (*os.File, string, error) {tun, err := os.OpenFile(tunDevice, os.O_RDWR, 0)if err != nil {fmt.Printf("----OpenTun----err:%v\n", err.Error())return nil, "", err}var ifr ifreqFlagscopy(ifr.IfrnName[:len(ifr.IfrnName)-1], []byte(name+"\000"))ifr.IfruFlags = syscall.IFF_TUN | syscall.IFF_NO_PIerr = ioctl(int(tun.Fd()), syscall.TUNSETIFF, uintptr(unsafe.Pointer(&ifr)))if err != nil {fmt.Printf("----OpenTun---ioctl----err:%v\n", err.Error())return nil, "", err}// 1，表示，程序结束后，创建的tun设备依旧在。// 默认为0，程序结束后，创建的tun设备就自动删除了err = ioctl(int(tun.Fd()), syscall.TUNSETPERSIST, 1)if err != nil {fmt.Printf("----OpenTun---ioctl---persist---err:%v\n", err.Error())return nil, "", err}ifname := fromZeroTerm(ifr.IfrnName[:ifnameSize])return tun, ifname, nil
}func configureIface(ifname string, ipn *net.IPNet, mtu int) error {iface, err := netlink.LinkByName(ifname)if err != nil {return fmt.Errorf("failed to lookup interface %v", ifname)}err = netlink.AddrAdd(iface, &netlink.Addr{IPNet: ipn, Label: ""})if err != nil {return fmt.Errorf("failed to add IP address %v to %v: %v", ipn.String(), ifname, err)}err = netlink.LinkSetMTU(iface, mtu)if err != nil {return fmt.Errorf("failed to set MTU for %v: %v", ifname, err)}err = netlink.LinkSetUp(iface)if err != nil {return fmt.Errorf("failed to set interface %v to UP state: %v", ifname, err)}err = netlink.RouteAdd(&netlink.Route{LinkIndex: iface.Attrs().Index,Scope:     netlink.SCOPE_UNIVERSE,Dst:       ipn,})if err != nil && err != syscall.EEXIST {return fmt.Errorf("failed to add route (%v -> %v): %v", ipn.String(), ifname, err)}return nil
}func main() {tun, fname, err := OpenTun("flannel-test")if err != nil {fmt.Printf("----Create--Tun------err:%v\n", err.Error())return}fmt.Printf("-----create---tun---name:%v\tfname:%v\n", tun.Name(), fname)_, ipn, _ := net.ParseCIDR("10.244.1.0/24")configureIface(fname, ipn, 1500)//time.Sleep(time.Hour)
}

2、本地编译

Makefile

build:CGO_ENABLED=0 GOOS=linux GOARCH=amd64 go build main.goscp:scp main root@10.211.55.122:/rootall:make build && make scp

3、远程服务器测试

route -n
å
ip a s | grep 10.211ip link sh flannel-test./main ip link sh flannel-testip a sh flannel-testroute -n

ip tuntap listethtool -i flannel-testethtool -i eth0

4、测试虚拟网卡flannel-test的连通性

5、/dev/net/tun: not pollable

read /dev/net/tun: not pollable

其实，曾经还出现过，此代码存在的情况下，也会报上面的错误。

可惜，已经不知道如何恢复异常场景了。

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