func main() {
if len(os.Args) != 3 {
fmt.Println("syntax:", os.Args[0], "tun|tap", "<device name>")
return
}
var typ tuntap.DevKind
switch os.Args[1] {
case "tun":
typ = tuntap.DevTun
case "tap":
typ = tuntap.DevTap
default:
fmt.Println("Unknown device type", os.Args[1])
return
}
tun, err := tuntap.Open(os.Args[2], typ)
if err != nil {
fmt.Println("Error opening tun/tap device:", err)
return
}
fmt.Println("Listening on", string(tun.Name()))
buf := make([]byte, 1522)
for {
n, err := tun.Read(buf)
if err != nil {
fmt.Println("Read error:", err)
} else {
if util.IsIPv4(buf) {
fmt.Printf("%d bytes from iface, IHL:%02X, TTL:%d\n", n, buf[0], buf[8])
fmt.Printf("from %s to %s\n", util.IPv4Source(buf).String(), util.IPv4Destination(buf).String())
fmt.Printf("protocol %02x checksum %02x\n", util.IPv4Protocol(buf), binary.BigEndian.Uint16(buf[22:24]))
if util.IPv4Protocol(buf) == util.ICMP {
srcip := make([]byte, 4)
copy(srcip, buf[12:16])
copy(buf[12:16], buf[16:20])
copy(buf[16:20], srcip)
buf[20] = 0x00
buf[21] = 0x00
buf[22] = 0x00
buf[23] = 0x00
cksum := util.Checksum(buf[20:n])
fmt.Printf("my checksum:%02x\n", uint16(cksum))
buf[22] = byte((cksum & 0xff00) >> 8)
buf[23] = byte(cksum & 0xff)
fmt.Printf("rsp: from %s to %s\n", util.IPv4Source(buf).String(), util.IPv4Destination(buf).String())
_, err = tun.Write(buf)
if err != nil {
fmt.Println(err)
}
}
}
}
}
}
func main() {
lip := flag.String("l", "192.168.102.32", "client local ip")
rip := flag.String("r", "192.168.102.31", "server remote ip")
flag.Parse()
tun, err := tuntap.Open("tun0", tuntap.DevTun)
checkError(err)
switch runtime.GOOS {
case "linux":
setTunLinux()
case "darwin":
setTunDarwin()
default:
fmt.Println("OS NOT supported")
os.Exit(1)
}
laddr, err := net.ResolveUDPAddr("udp", *lip+":0")
checkError(err)
raddr, err := net.ResolveUDPAddr("udp", *rip+":9826")
checkError(err)
conn, err := net.DialUDP("udp", laddr, raddr)
checkError(err)
defer conn.Close()
fmt.Println("Waiting IP Packet from tun interface")
go func() {
buf := make([]byte, 10000)
for {
n, err := tun.Read(buf)
if err != nil {
fmt.Println("tun Read error:", err)
continue
}
fmt.Printf("receive %d bytes, from %s to %s, \n", n, util.IPv4Source(buf).String(), util.IPv4Destination(buf).String())
n, err = conn.Write(buf[:n])
if err != nil {
fmt.Println("udp write error:", err)
continue
}
fmt.Printf("write %d bytes to udp network\n", n)
}
}()
buf := make([]byte, 10000)
for {
n, _, err := conn.ReadFromUDP(buf)
if err != nil {
fmt.Println("udp Read error:", err)
continue
}
fmt.Sprintf("receive %d bytes, from %s to %s, \n", n, util.IPv4Source(buf).String(), util.IPv4Destination(buf).String())
n, err = tun.Write(buf[:n])
if err != nil {
fmt.Println("udp write error:", err)
continue
}
fmt.Printf("write %d bytes to tun interface\n", n)
}
}