# Simple linux tun/tap device example tunnel over udp
# create tap device with ip tuntap add device0 tap
# set ip address on it and run tap-linux on that device and set desitation ip
# run same on another node, changing dst ip to first node

import fcntl
import struct
import os
import socket
import threading
import sys

TUNSETIFF = 0x400454ca
TUNSETOWNER = TUNSETIFF + 2
IFF_TUN = 0x0001
IFF_TAP = 0x0002
IFF_NO_PI = 0x1000


def udp_send(dst, packet):
    print "udp_send"
    sock.sendto(packet, (dst, 40000))

def recv():
     ss = socket.socket(socket.AF_INET, socket.SOCK_DGRAM) 
     ss.bind(("0.0.0.0", 40000))
     while True:
         data, addr = ss.recvfrom(1024)
         print "udp_recv"
         os.write(tun.fileno(), data)

if __name__ == "__main__":

    if len(sys.argv) < 3:
        print "Usage: tap-linux.py <tap_interface> <dst_address_of_tunnel>"
        sys.exit(1)
    iface = sys.argv[1]
    dst = sys.argv[2]
    print "Working on %s inteface, destination address %s:40000 udp" % (iface, dst)
    tun = open('/dev/net/tun', 'r+b')
    ifr = struct.pack('16sH', iface, IFF_TAP | IFF_NO_PI)
    fcntl.ioctl(tun, TUNSETIFF, ifr)
    fcntl.ioctl(tun, TUNSETOWNER, 1000)
    sock = socket.socket(socket.AF_INET, socket.SOCK_DGRAM) # UDP
    t = threading.Thread(target=recv)
    try:
        t.start()
        while True:
            packet = os.read(tun.fileno(), 2048)
            if True:
                udp_send(dst, packet)

    except KeyboardInterrupt:
        print "Terminating ..."
        os._exit(0)