netdev - Re: 2.6.21 -> 2.6.22 & 2.6.23-rc8 performance regression

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Date:	Mon, 01 Oct 2007 22:10:03 +0200
From:	Eric Dumazet <dada1@...mosbay.com>
To:	Denys <nuclearcat@...learcat.com>,
	"David S. Miller" <davem@...emloft.net>
CC:	linux-kernel@...r.kernel.org,
	Linux Netdev List <netdev@...r.kernel.org>
Subject: Re: 2.6.21 -> 2.6.22 & 2.6.23-rc8 performance regression

So maybe the following patch is necessary...

I believe IPV6 & DCCP are immune to this problem.

Thanks again Denys for spotting this.

Eric

[PATCH] TCP : secure_tcp_sequence_number() should not use a too fast clock

TCP V4 sequence numbers are 32bits, and RFC 793 assumed a 250 KHz clock.
In order to follow network speed increase, we can use a faster clock, but
we should limit this clock so that the delay between two rollovers is
greater than MSL (TCP Maximum Segment Lifetime : 2 minutes)

Choosing a 64 nsec clock should be OK, since the rollovers occur every
274 seconds.

Problem spotted by Denys Fedoryshchenko

Signed-off-by: Eric Dumazet <dada1@...mosbay.com>

View attachment "seq.patch" of type "text/plain" (990 bytes)