Re: non-random IP IDs

From: Kris Kennaway (kris@obsecurity.org)
Date: 04/16/01 

Date: Mon, 16 Apr 2001 13:08:14 -0700
From: Kris Kennaway <kris@obsecurity.org>
To: Darren Reed <avalon@coombs.anu.edu.au>

On Tue, Apr 17, 2001 at 06:02:42AM +1000, Darren Reed wrote:

> > > You should optimize it for mod being 2^n-1 (or make that a requirement).
> >
> > I'm afraid I don't have time to look at this right now. Perhaps it
> > can be revisited (the sysctl defaults to off for now), or Niels Provos
> > may be interested in the idea.
>
> Basically it means '% mod' -> '& mod' and call it with a 2^n-1 number.

Oh, okay.

> > Well, it still has wrapping properties like a network-order counter,
> > i.e. the algorithm attempts to order the output so that it doesn't
> > wrap within the segment lifetime. That would be lost without using
> > HTONS.
>
> You're confusing properties of the local number and some opaque bits in
> a packet being sent over the 'net.

Quite likely.

Kris

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