From: Stephen Hemminger <stephen@networkplumber.org>
To: Dmitry Kozlyuk <dmitry.kozliuk@gmail.com>
Cc: 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: Mon, 3 Jul 2023 08:54:58 -0700 [thread overview]
Message-ID: <20230703085458.23c383e6@hermes.local> (raw)
In-Reply-To: <20230620211720.350336-1-dmitry.kozliuk@gmail.com>
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>
next prev parent reply other threads:[~2023-07-03 15:55 UTC|newest]
Thread overview: 5+ messages / expand[flat|nested] mbox.gz Atom feed top
2023-06-20 21:17 Dmitry Kozlyuk
2023-07-03 15:00 ` Thomas Monjalon
2023-07-03 15:54 ` Stephen Hemminger [this message]
2023-07-06 16:20 ` Thomas Monjalon
2023-07-06 17:22 ` Stephen Hemminger
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