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

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Date: Tue, 15 Aug 2023 11:23:37 +0200
From: Francois Michel <francois.michel@...ouvain.be>
To:
Cc: Francois Michel <francois.michel@...ouvain.be>,
	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: [PATCH v2 net-next 0/3] netem: use a seeded PRNG for loss and corruption events

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(-)

base-commit: f614a29d6ca6962139b0eb36b985e3dda80258a6
-- 
2.41.0