package nebula import ( "fmt" "io" "net" "os" "strings" "unsafe" "github.com/vishvananda/netlink" "golang.org/x/sys/unix" ) type Tun struct { io.ReadWriteCloser fd int Device string Cidr *net.IPNet MaxMTU int DefaultMTU int TXQueueLen int Routes []route } type ifReq struct { Name [16]byte Flags uint16 pad [8]byte } func ioctl(a1, a2, a3 uintptr) error { _, _, errno := unix.Syscall(unix.SYS_IOCTL, a1, a2, a3) if errno != 0 { return errno } return nil } /* func ipv4(addr string) (o [4]byte, err error) { ip := net.ParseIP(addr).To4() if ip == nil { err = fmt.Errorf("failed to parse addr %s", addr) return } for i, b := range ip { o[i] = b } return } */ const ( cIFF_TUN = 0x0001 cIFF_NO_PI = 0x1000 ) type ifreqAddr struct { Name [16]byte Addr unix.RawSockaddrInet4 pad [8]byte } type ifreqMTU struct { Name [16]byte MTU int32 pad [8]byte } type ifreqQLEN struct { Name [16]byte Value int32 pad [8]byte } func newTun(deviceName string, cidr *net.IPNet, defaultMTU int, routes []route, txQueueLen int) (ifce *Tun, err error) { fd, err := unix.Open("/dev/net/tun", os.O_RDWR, 0) if err != nil { return nil, err } var req ifReq req.Flags = uint16(cIFF_TUN | cIFF_NO_PI) copy(req.Name[:], deviceName) if err = ioctl(uintptr(fd), uintptr(unix.TUNSETIFF), uintptr(unsafe.Pointer(&req))); err != nil { return } name := strings.Trim(string(req.Name[:]), "\x00") file := os.NewFile(uintptr(fd), "/dev/net/tun") maxMTU := defaultMTU for _, r := range routes { if r.mtu > maxMTU { maxMTU = r.mtu } } ifce = &Tun{ ReadWriteCloser: file, fd: int(file.Fd()), Device: name, Cidr: cidr, MaxMTU: maxMTU, DefaultMTU: defaultMTU, TXQueueLen: txQueueLen, Routes: routes, } return } func (c *Tun) WriteRaw(b []byte) error { var nn int for { max := len(b) n, err := unix.Write(c.fd, b[nn:max]) if n > 0 { nn += n } if nn == len(b) { return err } if err != nil { return err } if n == 0 { return io.ErrUnexpectedEOF } } } func (c Tun) deviceBytes() (o [16]byte) { for i, c := range c.Device { o[i] = byte(c) } return } func (c Tun) Activate() error { devName := c.deviceBytes() var addr, mask [4]byte copy(addr[:], c.Cidr.IP.To4()) copy(mask[:], c.Cidr.Mask) s, err := unix.Socket( unix.AF_INET, unix.SOCK_DGRAM, unix.IPPROTO_IP, ) if err != nil { return err } fd := uintptr(s) ifra := ifreqAddr{ Name: devName, Addr: unix.RawSockaddrInet4{ Family: unix.AF_INET, Addr: addr, }, } // Set the device ip address if err = ioctl(fd, unix.SIOCSIFADDR, uintptr(unsafe.Pointer(&ifra))); err != nil { return fmt.Errorf("failed to set tun address: %s", err) } // Set the device network ifra.Addr.Addr = mask if err = ioctl(fd, unix.SIOCSIFNETMASK, uintptr(unsafe.Pointer(&ifra))); err != nil { return fmt.Errorf("failed to set tun netmask: %s", err) } // Set the device name ifrf := ifReq{Name: devName} if err = ioctl(fd, unix.SIOCGIFFLAGS, uintptr(unsafe.Pointer(&ifrf))); err != nil { return fmt.Errorf("failed to set tun device name: %s", err) } // Set the MTU on the device ifm := ifreqMTU{Name: devName, MTU: int32(c.MaxMTU)} if err = ioctl(fd, unix.SIOCSIFMTU, uintptr(unsafe.Pointer(&ifm))); err != nil { return fmt.Errorf("failed to set tun mtu: %s", err) } // Set the transmit queue length ifrq := ifreqQLEN{Name: devName, Value: int32(c.TXQueueLen)} if err = ioctl(fd, unix.SIOCSIFTXQLEN, uintptr(unsafe.Pointer(&ifrq))); err != nil { return fmt.Errorf("failed to set tun tx queue length: %s", err) } // Bring up the interface ifrf.Flags = ifrf.Flags | unix.IFF_UP if err = ioctl(fd, unix.SIOCSIFFLAGS, uintptr(unsafe.Pointer(&ifrf))); err != nil { return fmt.Errorf("failed to bring the tun device up: %s", err) } // Set the routes link, err := netlink.LinkByName(c.Device) if err != nil { return fmt.Errorf("failed to get tun device link: %s", err) } // Default route dr := &net.IPNet{IP: c.Cidr.IP.Mask(c.Cidr.Mask), Mask: c.Cidr.Mask} nr := netlink.Route{ LinkIndex: link.Attrs().Index, Dst: dr, MTU: c.DefaultMTU, Scope: unix.RT_SCOPE_LINK, Src: c.Cidr.IP, Protocol: unix.RTPROT_KERNEL, Table: unix.RT_TABLE_MAIN, Type: unix.RTN_UNICAST, } err = netlink.RouteReplace(&nr) if err != nil { return fmt.Errorf("failed to set mtu %v on the default route %v; %v", c.DefaultMTU, dr, err) } // Path routes for _, r := range c.Routes { nr := netlink.Route{ LinkIndex: link.Attrs().Index, Dst: r.route, MTU: r.mtu, Scope: unix.RT_SCOPE_LINK, } err = netlink.RouteAdd(&nr) if err != nil { return fmt.Errorf("failed to set mtu %v on route %v; %v", r.mtu, r.route, err) } } // Run the interface ifrf.Flags = ifrf.Flags | unix.IFF_UP | unix.IFF_RUNNING if err = ioctl(fd, unix.SIOCSIFFLAGS, uintptr(unsafe.Pointer(&ifrf))); err != nil { return fmt.Errorf("failed to run tun device: %s", err) } return nil }