Interfacing with TUN\TAP for MAC OSX (Lion) using Python

Question

I found the following tun\tap example program and can not get it to work:

http://www.secdev.org/projects/tuntap_udp/files/tunproxy.py

I have modified the following lines:

f = os.open("/dev/tun0", os.O_RDWR)
ifs = ioctl(f, TUNSETIFF, struct.pack("16sH", "toto%d", TUNMODE))
ifname = ifs[:16].strip("\x00")

The first line was modified to reflect the real location of the driver. It was originally

f = os.open("/dev/net/tun", os.O_RDWR)

Upon running I get the following error:

 sudo ./tuntap.py -s 9000
 Password:
 Traceback (most recent call last):
   File "./tuntap.py", line 65, in <module>
     ifs = ioctl(f, TUNSETIFF, struct.pack("16sH", "toto%d", TUNMODE))
 IOError: [Errno 25] Inappropriate ioctl for device

I am using the latest tun\tap drivers installed from http://tuntaposx.sourceforge.net/download.xhtml

Epidote

Answer 1

The OSX tun/tap driver seems to work a bit different. The Linux example dynamically allocates a tun interface, which does not work in OSX, at least not in the same way.

I stripped the code to create a basic example of how tun can be used on OSX using a self-selected tun device, printing each packet to the console. I added Scapy as a dependency for pretty printing, but you can replace it by a raw packet dump if you want:

import os, sys
from select import select
from scapy.all import IP

f = os.open("/dev/tun12", os.O_RDWR)
try:
    while 1:
        r = select([f],[],[])[0][0]
        if r == f:
            packet = os.read(f, 4000)
            # print len(packet), packet
            ip = IP(packet)
            ip.show()
except KeyboardInterrupt:
    print "Stopped by user."

You will either have to run this as root, or do a sudo chown your_username /dev/tun12 to be allowed to open the device.

To configure it as a point-to-point interface, type:

$ sudo ifconfig tun12 10.12.0.2 10.12.0.1

Note that the tun12 interface will only be available while /dev/tun12 is open, i.e. while the program is running. If you interrupt the program, your tun interface will disappear, and you will need to configure it again next time you run the program.

If you now ping your endpoint, your packets will be printed to the console:

$ ping 10.12.0.1

Ping itself will print request timeouts, because there is no tunnel endpoint responding to your ping requests.

Dayledaylight

To save your scalp from excessive head scratching: if you experience SError: [Errno 2] No such file or directory: '/dev/tun12' when running the script, you probably have not installed the TUN/TAP driver yet. – Casmey

How do you do this for tap instead of tun? – Reverend

Answer 2

so about the 'No such file or directory' error when doing:

f = os.open("/dev/tun12", os.O_RDWR)

this worked for me:

brew install Caskroom/cask/tuntap

Generalship

tuntapis now deprecated... tuntaposx.sourceforge.net. There is a way to install using advice here: github.com/ntop/n2n/issues/773#issuecomment-1143051664 – Adlib