netdev - Re: [PATCH v2 net-next 0/3] netem: use a seeded PRNG for loss and corruption events

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Message-ID: <ZNyYnLrA7bLMpM4O@vergenet.net>
Date: Wed, 16 Aug 2023 11:36:28 +0200
From: Simon Horman <horms@...nel.org>
To: Francois Michel <francois.michel@...ouvain.be>
Cc: Jamal Hadi Salim <jhs@...atatu.com>,
	Cong Wang <xiyou.wangcong@...il.com>, Jiri Pirko <jiri@...nulli.us>,
	Stephen Hemminger <stephen@...workplumber.org>,
	"David S. Miller" <davem@...emloft.net>,
	Eric Dumazet <edumazet@...gle.com>,
	Jakub Kicinski <kuba@...nel.org>, Paolo Abeni <pabeni@...hat.com>,
	netdev@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH v2 net-next 0/3] netem: use a seeded PRNG for loss and
 corruption events

On Tue, Aug 15, 2023 at 11:23:37AM +0200, Francois Michel wrote:
> From: François Michel <francois.michel@...ouvain.be>
> 
> In order to reproduce bugs or performance evaluation of
> network protocols and applications, it is useful to have
> reproducible test suites and tools. This patch adds
> a way to specify a PRNG seed through the
> TCA_NETEM_PRNG_SEED attribute for generating netem
> loss and corruption events. Initializing the qdisc
> with the same seed leads to the exact same loss
> and corruption patterns. If no seed is explicitly
> specified, the qdisc generates a random seed using
> get_random_u64().
> 
> This patch can be and has been tested using tc from
> the following iproute2-next fork:
> https://github.com/francoismichel/iproute2-next
> 
> For instance, setting the seed 42424242 on the loopback
> with a loss rate of 10% will systematically drop the 5th,
> 12th and 24th packet when sending 25 packets.
> 
> v1 -> v2: Address comments and directly use
> prandom_u32_state() instead of get_random_u32() for
> generating loss and corruption events. Generates a random
> seed using get_random_u64() if none was provided explicitly.
> 
> François Michel (3):
>   netem: add prng attribute to netem_sched_data
>   netem: use a seeded PRNG for generating random losses
>   netem: use seeded PRNG for correlated loss events
> 
>  include/uapi/linux/pkt_sched.h |  1 +
>  net/sched/sch_netem.c          | 49 +++++++++++++++++++++++-----------
>  2 files changed, 35 insertions(+), 15 deletions(-)

For series,

Reviewed-by: Simon Horman <horms@...nel.org>