Re: [PATCH] drivers/net: remove network drivers' last few usesofIRQF_SAMPLE_RANDOM

From: Adrian Bunk
Date: Sun May 18 2008 - 10:46:24 EST

On Sun, May 18, 2008 at 08:24:10AM -0400, Theodore Tso wrote:
> On Sun, May 18, 2008 at 03:02:36PM +0300, Adrian Bunk wrote:
> > > Yes that's the whole point.
> > > Why remove IRQF_SAMPLE_RANDOM if "it cannot make the RNG output worse."
> > > We should not care if network traffic can be sniffed in some configurations
> > > (plus sniffing could be very unlikely in some others).
> > >...
> > > Are network drivers better without SAMPLE_RANDOM?
> > > My understanding of openssl developper answer is same as yours :
> > > "it cannot make the RNG output worse."
> >
> > The "it cannot make the RNG output worse." only applies to the OpenSSL
> > case (one could argue whether it makes sense, but it can't do harm).
> Actually, it applies here too. Or it can be made to apply here. If
> people are concerned that for certain cards the entropy could
> potentially be guessed by someone on the local network (although I
> suspect it's still useful for protecting against someone who doesn't
> have local network access), we could still sample the entropy, and
> just not increment the entropy credit for /dev/random's sake.

The latter is exactly the difference between the two cases.

But Gilles was implying using IRQF_SAMPLE_RANDOM for gathering entropy
was as harmless as OpenSSL mixing uninitialized memory into their RNG.

> It will
> still put something into the entropy pool which is also used by
> /dev/urandom.
> > The replacement solution ready on all Linux machines today is for
> > userspace to use /dev/urandom instead of /dev/random if feasible.
> Sampling interrupt entropy will definitely not hurt /dev/urandon, and
> may help, especially in the freshly installed server case. Especially
> if it's using kickstart-style install, where there is no keyboard
> entropy, sampling the interrupts as it pulls RPM's from the network
> and/or the CD-ROM drive may be all that we have.

No disagreement on this.

> - Ted



"Is there not promise of rain?" Ling Tan asked suddenly out
of the darkness. There had been need of rain for many days.
"Only a promise," Lao Er said.
Pearl S. Buck - Dragon Seed

To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@xxxxxxxxxxxxxxx
More majordomo info at
Please read the FAQ at