netdev - Re: [PATCH 2/2] tcp: syncookies: reduce mss table to four values

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Message-Id: <20130903.223248.1513014156693130244.davem@davemloft.net>
Date:	Tue, 03 Sep 2013 22:32:48 -0400 (EDT)
From:	David Miller <davem@...emloft.net>
To:	fw@...len.de
Cc:	netdev@...r.kernel.org
Subject: Re: [PATCH 2/2] tcp: syncookies: reduce mss table to four values

From: Florian Westphal <fw@...len.de>
Date: Sun,  1 Sep 2013 21:55:56 +0200

> Halve mss table size to make blind cookie guessing more difficult.
> This is sad since the tables were already small, but there
> is little alternative except perhaps adding more precise mss information
> in the tcp timestamp.  Timestamps are unfortunately not ubiquitous.
> 
> Guessing all possible cookie values still has 8-in 2**32 chance.
> 
> Reported-by: Jakob Lell <jakob@...oblell.com>
> Signed-off-by: Florian Westphal <fw@...len.de>
> ---
>  Changes since v1:
>  - add comment explaining mss choices

The ipv6 choices are still a complete mystery.

Why do you put a 9000 entry into the ipv6 table and have nothing
similar in the ipv4 table?  Why not mimick the ipv4 values in the ipv6
table, as this is exactly what I would expect to be done here?

You need to add a comment to the ipv6 table explaining things, at the
very least.
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