Tunnel.py MAC address

GNU Radio
1

When I run tunnel.py and configure the grX interface IP address I
noticedusing
ifconfigthat a seemingly random MAC address is assigned to the gr
interface.
Does ayone know if there is any logic to how the address is created?

Thanks,
Dave

2

On Thu, Mar 24, 2011 at 9:45 AM, David B.
[email protected]wrote:

When I run tunnel.py and configure the grX interface IP address I
noticed using ifconfig that a seemingly random MAC address is assigned to
the gr interface. Does ayone know if there is any logic to how the address
is created?

Thanks,
Dave

tunnel.py uses the TUN/TAP interface. From my understanding, the kernel
autogenerates a MAC address when you create a new tun/tap device. I
don’t
know the actual internals of how it is generated though.

You should be able to change the address using the SIOCSIFHWADDR option
for
ioctl(), though I haven’t tried this myself on the device.

Tom

3

the origin code in tunnel.py is

def open_tun_interface(tun_device_filename):
from fcntl import ioctl

mode = IFF_TAP | IFF_NO_PI
TUNSETIFF = 0x400454ca

tun = os.open(tun_device_filename, os.O_RDWR)
ifs = ioctl(tun, TUNSETIFF, struct.pack("16sH", "gr%d", mode))
ifname = ifs[:16].strip("\x00")
return (tun, ifnam

how to add the code:
ioctl(s, SIOCSIFHWADDR, struct.pack(“16sH6s”, ifname,
socket.AF_UNIX, hwaddr))
how can i get ifname and hwaddr?

thank you!!!

4

Here is what you need to do

 SIOCSIFHWADDR = 0x8924
 s = socket.socket(socket.AF_INET, socket.SOCK_DGRAM)
 ioctl(s, SIOCSIFHWADDR, struct.pack("16sH6s", ifname,

socket.AF_UNIX, hwaddr))

Andrew