netdev - Re: Single socket with TX_RING and RX

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Message-ID: <51938BAD.5050502@redhat.com>
Date:	Wed, 15 May 2013 15:20:45 +0200
From:	Daniel Borkmann <dborkman@...hat.com>
To:	Ricardo Tubío <rtpardavila@...il.com>
CC:	netdev@...r.kernel.org
Subject: Re: Single socket with TX_RING and RX_RING

On 05/15/2013 02:53 PM, Ricardo Tubío wrote:
> Once I tell kernel to export the TX_RING through setsockopt() (see code
> below) I always get an error (EBUSY) if i try to tell kernel to export the
> RX_RING with the same socket descriptor. Therefore, I have to open an
> additional socket for the RX_RING and I require of two sockets when I though
> that I would only require of one socket for both TX and RX using mmap()ed
> memory.
>
> Do I need both sockets or am I doing something wrong?

The second time you call init_ring() in your code e.g. with TX_RING, where
you have previously set it up for the RX_RING. The kernel will give you
-EBUSY because the packet socket is already mmap(2)'ed.
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