linux-kernel - Re: poll problem with PF_PACKET when using PACKET_RX

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Message-ID: <45336569.5040108@draigBrady.com>
Date:	Mon, 16 Oct 2006 11:56:41 +0100
From:	Pádraig Brady <P@...igBrady.com>
To:	Joan Raventos <jraventos@...oo.com>
CC:	linux-kernel@...r.kernel.org
Subject: Re: poll problem with PF_PACKET when using PACKET_RX_RING

Joan Raventos wrote:
> Hello,
>
> In order to use PF_PACKET/SOCK_RAW with PACKET_RX_RING
> one would possibly do (as described in
> Documentation/networking/packet_mmap.txt):
> 1. setup PF_PACKET socket via socket call.
> 2. use setsockopt to change the PF_PACKET socket into
> PACKET_RX_RING mode and alloc the ring.
> 3. mmap the ring.
> 4. use poll with the socket descriptor and then
> directly access the pkts from the mmaped ring.

A few years back I developed a network sniffer
on 2.4.20 using PACKET_MMAP supporting very high packet rates.
When testing with high packet rates, invariably if traffic
was present while the buffers were being setup, the buffer data
would be corrupted. I worked around it by ensuring no packets went
into the stack before the userspace process sniffing the packets was started.

Pádraig.
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