Re: testing ethernet device with external loopback

[David Anders <dave123_aml@yahoo.com>]

Sebastien,

check out the snull network driver from the "Linux Device Drivers" book. it has a short explanation on how to "trick" the kernel into sending the packet even though the destination is on the local machine:

http://www.linuxdriver.co.il/ldd3/chp-17-sect-1.shtml

dave aka prpplague



--- On Sun, 7/27/08, Sebastien Fauris <titelive72@gmail.com> wrote:

> From: Sebastien Fauris <titelive72@gmail.com>
> Subject: testing ethernet device with external loopback
> To: linux-embedded@vger.kernel.org
> Date: Sunday, July 27, 2008, 3:47 AM
> 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.
> 
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