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From: Jamie Lokier <lk@tantalophile.demon.co.uk>
To: Andi Kleen <ak@muc.de>
Cc: Subba Rao <subba9@home.com>, linux-kernel@vger.kernel.org
Subject: Re: Half Duplex and Zero Copy IP
Date: Sat, 11 Aug 2001 00:50:37 +0100	[thread overview]
Message-ID: <20010811005037.A5591@thefinal.cern.ch> (raw)
In-Reply-To: <20010810095313.A6219@home.com> <k266bveos8.fsf@zero.aec.at>
In-Reply-To: <k266bveos8.fsf@zero.aec.at>; from ak@muc.de on Fri, Aug 10, 2001 at 08:46:31PM +0200

Andi Kleen wrote:
> The sniffer zero copy implementation as implemented in some libpcaps 
> does not depend on any special NIC support; it should work with any.

Do you mean mmap() on a packet socket?  Unless I am mistaken, the data
is still copied once to the mmap area, however only the capture length
is copied -- the rest of the packet is discarded.

This means that you cannot use mmap() on a packet socket to zero-copy
read whole packets.  In fact there is no way to zero-copy read whole
packets into user space, without modifying the kernel.

Am I mistaken (it would be nice)?

Thanks,
-- Jamie

  reply	other threads:[~2001-08-10 23:49 UTC|newest]

Thread overview: 6+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2001-08-10  9:53 Half Duplex and Zero Copy IP Subba Rao
2001-08-10 18:36 ` Andrew Morton
2001-08-11  7:59   ` Subba Rao
2001-08-10 18:46 ` Andi Kleen
2001-08-10 23:50   ` Jamie Lokier [this message]
2001-08-11  0:00     ` Andi Kleen

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