[Buildroot] [PATCH] package/rng-tools: make jitterentropy conditional

[Thomas Petazzoni]

Hello Matt,

On Thu, 13 Feb 2020 11:07:36 -0600
Matthew Weber <matthew.weber at rockwellcollins.com> wrote:

> > We had similar issue today with am335x (kernel 5.4.x). Bumping
> > rng-tools to v6.9 helped.
> 
> Thank you for that feedback, I'll make this patch is superseded as the
> bump resolved the bug.  I'll add a note with this patchwork thread in
> the bug report as well.

As I was going through open bug reports, I looked again at
https://bugs.busybox.net/show_bug.cgi?id=12511, and I disagree with the
conclusion of discarding this patch "package/rng-tools: make
jitterentropy conditional".

If I understand correctly:

 - If you have a hardware RNG, the jitterentropy library is not
   necessary.

 - If you don't have a hardware RNG, rng-tools will error out, unless
   jitterentropy support is enabled.

So, we really want to make the jitterentropy support in rng-tools
optional, and leave it up to the user to enable it if (s)he has no
hardware RNG available. And if there's no hardware RNG and no
jitterentropy support, rng-tools will error out, the service will fail
to start, and that's good. So the trick with the special 66 return code
is not necessary.

Do you agree ?

Best regards,

Thomas
-- 
Thomas Petazzoni, CTO, Bootlin
Embedded Linux and Kernel engineering
https://bootlin.com