*BSD News Article 92281


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From: Tony Griffiths <tonyg@OntheNet.com.au>
Newsgroups: comp.unix.bsd.freebsd.misc
Subject: Re: rand_irqs in sysconfig
Date: Sun, 30 Mar 1997 12:43:39 +1000
Organization: On the Net (ISP on the Gold Coast, Australia)
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To: Darren Henderson <darren@Quint.somtel.com>
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Darren Henderson wrote:
> 
> Meant to ask this a while ago but forgot all about it. In the sysconfig
> file for 2.1.5R there is a setting for rand_irqs. Comments say that its
> for generating entropy in the kernel.
> 
> Mine is current let to NO. I havent really noticed any performance
> problems anywhere. What will setting this to an appropriate value do for
> me?

For you, probably not much.  For the Universe, help increase the entropy
forwards zero, at which point "we" have ONE BIG PROBLEM!!!  ;-))

Actually, the "we" doesn't include me so I don't really care what you do
and don't intend losing any sleep worrying about increasing Universal
entropy.

On a more serious note...

The 'entropy' mentioned is for generating random number sequences (man
random
and urandom, et al).  The TCP protocol layer can use a 32-bit random
number as
the starting sequence of a TCP link for instance.  This reduces the
chances of
a SYN 'attack' being successful to almost zero.  If you don't know about
SYN
attacks then DON'T WORRY, but set the IRQs anyway which will reduce your
worry
level even further!

> 
> Thanks.
> 
> ______________________________________________________________________________
> Darren Henderson                                      darren@jasper.somtel.com
>                                                             dhenderson@bix.com

Tony