linux-kernel - Re: [PATCH] Add IPv6 support to TCP SYN cookies

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Message-ID: <20080205212017.5db50114@core>
Date:	Tue, 5 Feb 2008 21:20:17 +0000
From:	Alan Cox <alan@...rguk.ukuu.org.uk>
To:	Evgeniy Polyakov <johnpol@....mipt.ru>
Cc:	Andi Kleen <andi@...stfloor.org>,
	Glenn Griffin <ggriffin.kernel@...il.com>,
	netdev@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH] Add IPv6 support to TCP SYN cookies

> How does syncookies prevent windows from growing?

Enabling them doesn't.

> Most (if not all) distributions have them enabled and window growing
> works just fine. Actually I do not see any reason why connection
> establishment handshake should prevent any run-time operations at all,
> even if it was setup during handshake.

Syncookies are only triggered if the system is under a load where it
would begin to lose connections otherwise. So they merely turn a DoS into
a working if slightly slower setup (and > 64K windows don't matter for
most normal users, especially on mobile devices).

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