[Discuss-gnuradio] gr-extras: tuntap : How to use ?

[Iain Young, G7III]

Hi Folks,

Finally getting around to playing with some of the stuff in gr-extras.

Having compiled 3.6.2, and the extras, I found the tuntap block, and
was hoping to use it to implement some RF Networking with the GMSK
modules.

I found the tuntap block, and noticed that it had an input and output.
I was expecting my flowgraph to take the userspace end of the network
interface, with the other end being the network device.

I found the presentation from the recent conference on a basic MAC
layer, and that seemed to imply the input could be almost anything,
but didn't leave me any the wiser as to exactly how to use it.

What I was hoping to do was essentially this (and a similiar) RX chain:

tuntap --> packet framer --> GMSK_Mod --> USRP

But the input to the tuntap block has confused me. Can I just give
it a Null source ? (With the block picking up data from the network
device ?)


Also, even when connecting it to a source, I seem to have another
issue, as I get this error at runtime:

RuntimeError: gr_make_tuntap: tun_alloc failed

Despite having the /dev/net/tun device, and it being writable by the
user running the flow graph. This happens if I specify "Automatic" or
a specific network device.

Anyone want to point me in the right direction ? Or even anyone have
an example ?


Best Regards

Iain