From: Thomas Monjalon <thomas@monjalon.net>
To: Stephen Hemminger <stephen@networkplumber.org>
Cc: Dmitry Kozlyuk <dmitry.kozliuk@gmail.com>,
dev@dpdk.org, leyi.rong@intel.com,
Yipeng Wang <yipeng1.wang@intel.com>,
Sameh Gobriel <sameh.gobriel@intel.com>,
Alan Liu <zaoxingliu@gmail.com>
Subject: Re: [PATCH] member: fix PRNG seed reset in NitroSketch mode
Date: Thu, 06 Jul 2023 18:20:19 +0200 [thread overview]
Message-ID: <4969062.ejJDZkT8p0@thomas> (raw)
In-Reply-To: <20230703085458.23c383e6@hermes.local>
03/07/2023 17:54, Stephen Hemminger:
> On Wed, 21 Jun 2023 00:17:20 +0300
> Dmitry Kozlyuk <dmitry.kozliuk@gmail.com> wrote:
>
> > Seeding the global PRNG at sketch creation
> > does not make the sketch operation deterministic:
> > it uses rte_rand() later, the PRNG may be seeded again by that point.
> > On the other hand, seeding the global PRNG with a hash seed,
> > is likely undesired, because it may be low-entropy or even constant.
> > Deterministic operation can be achieved by seeding the PRNG externally.
> >
> > Remove the call to rte_srand() at sketch creation.
> > Document that hash seeds are not used by SKETCH set summary type.
> >
> > Fixes: db354bd2e1f8 ("member: add NitroSketch mode")
> > Cc: leyi.rong@intel.com
> >
> > Signed-off-by: Dmitry Kozlyuk <dmitry.kozliuk@gmail.com>
>
> This raises a more global issue.
> rte_srand() overrides the system seed which is set during startup.
> This is a bad thing, it reduces the entropy in the random number generator.
>
> There are two possible solutions to this:
> 1. Remove all all calls to rte_srand() and deprecate it.
> 2. Make rte_srand() add a fixed value to existing entropy. This is what the
> kernel PRNG does. It adds any user supplied additional entropy to original
> state.
>
> Looking at current source.
> - code in tests seeding PRNG with TSC. This is unnecessary and can be removed.
> - this code in member library. Should be removed.
>
> Acked-by: Stephen Hemminger <stephen@networkplumber.org>
Applied, thanks.
What's next regarding rte_srand?
next prev parent reply other threads:[~2023-07-06 16:20 UTC|newest]
Thread overview: 5+ messages / expand[flat|nested] mbox.gz Atom feed top
2023-06-20 21:17 [PATCH] member: fix PRNG seed reset in NitroSketch mode Dmitry Kozlyuk
2023-07-03 15:00 ` Thomas Monjalon
2023-07-03 15:54 ` Stephen Hemminger
2023-07-06 16:20 ` Thomas Monjalon [this message]
2023-07-06 17:22 ` Stephen Hemminger
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