Re: [Discuss-gnuradio] Question about how GNURadio interacts with the linux kernel

[Eric Blossom]

On Thu, Apr 27, 2006 at 12:21:47PM -0400, Naveen Manicka wrote:
> Hi everybody,
> 
> I am trying to understand how GNUradio interacts with the kernel to send and
> receive data packets using the tunnel communication example.

Have you read the README in gnuradio-examples/python/gmsk2 and the
documents that it references?  

  See /usr/src/linux/Documentation/networking/tuntap.txt and/or Google
  for "universal tun tap".  The Linux kernel includes the tun module.
  You may have to "modprobe tun" if it's not loaded by default.  If
  /dev/net/tun doesn't exist, try "modprobe tun".


> Since we don't recompile the kernel when installing gnuradio, the USRP board
> is just recognized as a USB device. 

It's *always* just recognized as a USB device.
As the README says, we use the "tun driver" to push and pull packets
into the kernel from user mode.

In the tunnel_ip_null_mac.py code, look at open_tun_interface, and
then look at all references to tun_fd.

> So, after setting up the static routes (the gr0 and gr1 in the tunnel
> example) how is the data packet handed to the gnuradio?

>From the outside use ping, tcp, udp, whatever...  It looks like a
network interface. 


> Also, If I want to implement a different MAC protocol in GNURadio. how do I
> go about it?

More on that later...
  
> Thank you,
> Naveen

Eric