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Date:      Fri, 8 Dec 2000 00:50:09 -0800
From:      Guy Harris <gharris@flashcom.net>
To:        Alfred Perlstein <bright@wintelcom.net>
Cc:        Dragos Ruiu <dr@kyx.net>, tcpdump-workers@tcpdump.org, freebsd-hackers@FreeBSD.ORG, winpcap@netgroup-serv.polito.it
Subject:   Re: [tcpdump-workers] Re: Fwd: kyxtech: freebsd outsniffed by wintendo !!?!?
Message-ID:  <20001208005009.B352@quadrajet.flashcom.com>
In-Reply-To: <20001207215142.H16205@fw.wintelcom.net>; from bright@wintelcom.net on Thu, Dec 07, 2000 at 09:51:42PM -0800
References:  <0012072118150Q.09615@smp.kyx.net> <20001207215142.H16205@fw.wintelcom.net>

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On Thu, Dec 07, 2000 at 09:51:42PM -0800, Alfred Perlstein wrote:
> I'm very curious how they managed to run "windump" on FreeBSD.

Presumably they're referring to tcpdump there, as per the first
paragraph in "2.  Tests":

	This Section aims at giving some indications about the
	performance of the capture process on various operating
	systems.  Results obtained under the various Windows
	platforms have been compared with the ones provided by
	BPF/libpcap/TCPdump in FreeBSD 3.3 in order to determine
	the goodness of our implementation.

> Honestly, it really looks like the fault lies with the way tcpdump
> writes to disk and not with FreeBSD.

Perhaps.  However, from my stracing of windump on NT 4 SP4 and trussing
of tcpdump on FreeBSD 3.4, the only difference appears to be that
tcpdump does 8K writes and windump does 4K writes....

Currently, I suspect that it lies with the BPF kernel buffer only being
32K; that's the most you can get on FreeBSD 3.x, but you can crank it up
to 512KB on 4.x - libpcap on 4.x only sets it to 32K, though.


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