linux-kernel - Re: [PATCH] drivers/net: remove network drivers' last few uses of IRQF_SAMPLE

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Message-ID: <87a5b0800805160659j1e8482efjea2fb8167f755e05@mail.gmail.com>
Date:	Fri, 16 May 2008 14:59:03 +0100
From:	"Will Newton" <will.newton@...il.com>
To:	"Jeff Garzik" <jeff@...zik.org>
Cc:	"Lennart Sorensen" <lsorense@...lub.uwaterloo.ca>,
	"Kok, Auke" <auke-jan.h.kok@...el.com>,
	"Rick Jones" <rick.jones2@...com>,
	"Brandeburg, Jesse" <jesse.brandeburg@...el.com>,
	"Alan Cox" <alan@...rguk.ukuu.org.uk>,
	"Chris Peterson" <cpeterso@...terso.com>, netdev@...r.kernel.org,
	linux-kernel@...r.kernel.org
Subject: Re: [PATCH] drivers/net: remove network drivers' last few uses of IRQF_SAMPLE_RANDOM

On Fri, May 16, 2008 at 2:40 PM, Jeff Garzik <jeff@...zik.org> wrote:
> Lennart Sorensen wrote:
>>
>> On Thu, May 15, 2008 at 03:21:49PM -0400, Jeff Garzik wrote:
>>>
>>> "no other form of entropy"?   See examples in this thread.
>>
>> So where does one get entropy if not the ethernet adapter on many
>> embedded systems?  If you have no mouse, no keyboard, no hardware number
>> generator, just ethernet ports and a serial console that usually
>> receives no input.  While ethernet might not be preferable if you have
>> something else, sometimes you really don't have anything else.
>
> Already answered in this thread...  EGD illustrates how many sources of
> entropy remain, even in the example you just gave.
>
> Further, you do not want to rely on entropy from a source that declines just
> as network traffic increases.

I don't know egd that well, but from a cursory look it gets data from
such things as w or last (wtmp) which is static on most embedded
boxes. It also uses netstat and snmp - surely this is at least as easy
to manipulate as interrupt timings? I'm not a cryptographer by any
means but it looks as if it works by magic. Last changed 2002, written
in perl. No, I don't think I'll be shipping this on any systems any
time soon.
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