From: Matt Mackall <mpm@selenic.com>
To: Eric Dumazet <dada1@cosmosbay.com>
Cc: Alan Cox <alan@lxorguk.ukuu.org.uk>,
Adrian Bunk <bunk@kernel.org>,
Marc Haber <mh+linux-kernel@zugschlus.de>,
linux-kernel@vger.kernel.org,
"David S. Miller" <davem@davemloft.net>
Subject: Re: Why does reading from /dev/urandom deplete entropy so much?
Date: Thu, 6 Dec 2007 10:09:50 -0600 [thread overview]
Message-ID: <20071206160950.GX19691@waste.org> (raw)
In-Reply-To: <47579E89.6080802@cosmosbay.com>
On Thu, Dec 06, 2007 at 08:02:33AM +0100, Eric Dumazet wrote:
> Matt Mackall a ?crit :
> >On Tue, Dec 04, 2007 at 07:17:58PM +0100, Eric Dumazet wrote:
> >>Alan Cox a ?crit :
> >>>>No matter what you consider as being better, changing a 12 years old
> >>>>and widely used userspace interface like /dev/urandom is simply not an
> >>>>option.
> >>>>
> >>>Fixing it to be more efficient in its use of entropy and also fixing the
> >>>fact its not actually a good random number source would be worth looking
> >>>at however.
> >>>
> >>Yes, since current behavior on network irq is very pessimistic.
> >
> >No, it's very optimistic. The network should not be trusted.
>
> You keep saying that. I am refering to your previous attempts last year to
> remove net drivers from sources of entropy. No real changes were done.
Dave and I are both a bit stubborn on this point. I've been meaning to
respin those patches..
> If the network should not be trusted, then a patch should make sure network
> interrupts feed /dev/urandom but not /dev/random at all. (ie not calling
> credit_entropy_store() at all)
Yes. My plan is to change the interface from SA_SAMPLE_RANDOM to
add_network_entropy. The SA_SAMPLE_RANDOM interface sucks because it
doesn't tell the core what kind of source it's dealing with.
> There is a big difference on get_cycles() and jiffies. You should try to
> measure it on a typical x86_64 platform.
I'm well aware of that. We'd use get_cycles() exclusively, but it
returns zero on lots of platforms. We used to use sched_clock(), I
can't remember why that got changed.
> >Also, for future reference, patches for /dev/random go through me, not
> >through Dave.
>
> Why ? David is the network maintainer, and he was the one who rejected your
> previous patches.
Because I'm the /dev/random maintainer and it's considered the polite
thing to do, damnit.
--
Mathematics is the supreme nostalgia of our time.
next prev parent reply other threads:[~2007-12-06 16:10 UTC|newest]
Thread overview: 77+ messages / expand[flat|nested] mbox.gz Atom feed top
2007-12-04 11:41 Why does reading from /dev/urandom deplete entropy so much? Marc Haber
2007-12-04 14:16 ` Eric Dumazet
2007-12-04 16:18 ` Adrian Bunk
2007-12-04 16:47 ` Alan Cox
2007-12-04 18:17 ` Eric Dumazet
2007-12-05 21:26 ` Matt Mackall
2007-12-06 7:02 ` Eric Dumazet
2007-12-06 16:09 ` Matt Mackall [this message]
2007-12-09 12:42 ` Marc Haber
2007-12-09 16:16 ` Matt Mackall
2007-12-10 23:06 ` Marc Haber
2007-12-10 23:35 ` Matt Mackall
2007-12-11 1:34 ` Theodore Tso
2007-12-11 19:46 ` Phillip Susi
2007-12-11 20:02 ` Ray Lee
2007-12-12 5:34 ` David Schwartz
2007-12-04 16:54 ` Ray Lee
2007-12-04 16:55 ` Alan Cox
2007-12-04 18:02 ` Matt Mackall
2007-12-04 19:50 ` Theodore Tso
2007-12-04 20:36 ` Matt Mackall
2007-12-04 20:40 ` Alan Cox
2007-12-04 20:48 ` Mike McGrath
2007-12-04 21:54 ` Matt Mackall
2007-12-04 22:03 ` Theodore Tso
2007-12-04 22:12 ` Mike McGrath
2007-12-04 22:28 ` Matt Mackall
2007-12-04 21:08 ` Matt Mackall
2007-12-04 21:18 ` Mike McGrath
2007-12-04 22:15 ` Matt Mackall
2007-12-04 22:23 ` Mike McGrath
2007-12-04 22:33 ` Matt Mackall
2007-12-05 14:26 ` Mike McGrath
2007-12-05 14:49 ` Theodore Tso
2007-12-08 7:38 ` Jon Masters
2007-12-08 17:32 ` Theodore Tso
2007-12-08 17:33 ` Mike McGrath
2007-12-08 17:49 ` Theodore Tso
2007-12-08 17:54 ` Jon Masters
2007-12-08 18:15 ` Matt Mackall
2007-12-08 18:24 ` Theodore Tso
2007-12-08 19:36 ` entropy gathering (was Re: Why does reading from /dev/urandom deplete entropy so much?) Jeff Garzik
2007-12-08 19:53 ` Matt Mackall
2007-12-08 20:04 ` Jeff Garzik
2007-12-08 20:19 ` Matt Mackall
2007-12-08 21:07 ` Willy Tarreau
2007-12-08 20:31 ` Theodore Tso
2007-12-08 20:47 ` Jeff Garzik
2007-12-08 20:42 ` Willy Tarreau
2007-12-08 23:47 ` Theodore Tso
2007-12-09 1:07 ` Jon Masters
2007-12-08 18:31 ` Why does reading from /dev/urandom deplete entropy so much? Jeff Garzik
2007-12-08 20:26 ` David Schwartz
2007-12-08 17:43 ` Matt Mackall
2007-12-08 17:47 ` Jon Masters
2007-12-08 18:05 ` Theodore Tso
2007-12-08 17:45 ` Jon Masters
2007-12-10 16:37 ` Pavel Machek
2007-12-04 18:01 ` Matt Mackall
2007-12-06 20:08 ` Bill Davidsen
2007-12-05 12:23 ` Marc Haber
2007-12-05 12:29 ` Marc Haber
2007-12-05 13:33 ` Theodore Tso
2007-12-05 15:10 ` Marc Haber
2007-12-06 19:32 ` Bill Davidsen
2007-12-08 22:03 ` Adrian Bunk
2007-12-08 22:10 ` Ismail Dönmez
2007-12-08 23:46 ` Theodore Tso
2007-12-09 5:21 ` Willy Tarreau
2007-12-09 6:52 ` Jon Masters
2007-12-09 6:21 ` Ismail Dönmez
2007-12-09 12:31 ` Theodore Tso
2007-12-09 14:06 ` Ismail Dönmez
2007-12-11 15:42 ` Bill Davidsen
2007-12-20 22:27 ` Marc Haber
2007-12-26 18:27 ` Phillip Susi
2007-12-04 18:49 ` Russ Dill
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