From owner-freebsd-security  Mon Apr 16 11:36:54 2001
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From: Darren Reed <avalon@coombs.anu.edu.au>
Message-Id: <200104161836.EAA03291@caligula.anu.edu.au>
Subject: Re: non-random IP IDs
To: kris@obsecurity.org (Kris Kennaway)
Date: Tue, 17 Apr 2001 04:36:15 +1000 (Australia/ACT)
Cc: kris@obsecurity.org (Kris Kennaway),
	silby@silby.com (Mike Silbersack),
	newsletter@marktroberts.com (Mark T Roberts),
	freebsd-security@FreeBSD.ORG, net@FreeBSD.ORG
In-Reply-To: <20010416024805.A688@xor.obsecurity.org> from "Kris Kennaway" at Apr 16, 2001 02:48:05 AM
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In some mail from Kris Kennaway, sie said:
> 
> 
> --rwEMma7ioTxnRzrJ
> Content-Type: text/plain; charset=us-ascii
> Content-Disposition: inline
> Content-Transfer-Encoding: quoted-printable
> 
> On Mon, Apr 16, 2001 at 02:03:11AM -0700, Kris Kennaway wrote:
> 
> > Here's a patch ported from OpenBSD which randomizes this (supposedly
> > such that it respects the constraint of not wrapping within the
> > prescribed time period).  I should wrap it in a sysctl, I guess.
> >=20
> >   http://www.freebsd.org/~kris/ipid.patch
> 
> Okay, I did this and updated the patch, with the sysctl defaulting to
> off since the random algorithm does add some amount of overhead.
> 
> > Comments?

You should optimize it for mod being 2^n-1 (or make that a requirement).

Also, drop the HTONS statements, they no longer make sense.  Before ip_id
was a counter and so it made sense (sorta) to change its byte ordering to
network.  Now it's just a random number so there is no longer any need.

Darren

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