testing ethernet device with external loopback

[Sebastien Fauris <titelive72@gmail.com>]

Hi,

for hardware testing purposes, I would like to perform an external 
loopback on my ethernet interface. For this, I wrote 2 little 
executables, one  sending a raw ethernet packet (using 'sendto') on a 
socket opened with the  parameters PF_PACKET, SOCK_RAW, 
htons(ETH_P_ALL), the other one doing a recvfrom from a raw socket.
The problem is that on the reception side, I always receive what I send, 
even when
 the external RJ45 stub is not plugged !
Is there a way to tell to the kernel on the reception side that I want 
to get only packets coming from the external world ?

Thanks,

Sebastien.