linux-kernel - [PATCH v2 net-next 2/3] netem: use a seeded PRNG for generating random losses

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Date:   Tue, 15 Aug 2023 11:23:39 +0200
From:   Francois Michel <francois.michel@...ouvain.be>
To:     unlisted-recipients:; (no To-header on input)
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 2/3] netem: use a seeded PRNG for generating random losses

From: François Michel <francois.michel@...ouvain.be>

Use prandom_u32_state() instead of get_random_u32() to generate
the random loss events of netem. The state of the prng is part
of the prng attribute of struct netem_sched_data.

Signed-off-by: François Michel <francois.michel@...ouvain.be>
---
 net/sched/sch_netem.c | 11 ++++++-----
 1 file changed, 6 insertions(+), 5 deletions(-)

diff --git a/net/sched/sch_netem.c b/net/sched/sch_netem.c
index 621c6acfd644..8b54b1005a10 100644
--- a/net/sched/sch_netem.c
+++ b/net/sched/sch_netem.c
@@ -206,7 +206,7 @@ static u32 get_crandom(struct crndstate *state)
 static bool loss_4state(struct netem_sched_data *q)
 {
 	struct clgstate *clg = &q->clg;
-	u32 rnd = get_random_u32();
+	u32 rnd = prandom_u32_state(&q->prng.prng_state);
 
 	/*
 	 * Makes a comparison between rnd and the transition
@@ -271,18 +271,19 @@ static bool loss_4state(struct netem_sched_data *q)
 static bool loss_gilb_ell(struct netem_sched_data *q)
 {
 	struct clgstate *clg = &q->clg;
+	struct rnd_state *s = &q->prng.prng_state;
 
 	switch (clg->state) {
 	case GOOD_STATE:
-		if (get_random_u32() < clg->a1)
+		if (prandom_u32_state(s) < clg->a1)
 			clg->state = BAD_STATE;
-		if (get_random_u32() < clg->a4)
+		if (prandom_u32_state(s) < clg->a4)
 			return true;
 		break;
 	case BAD_STATE:
-		if (get_random_u32() < clg->a2)
+		if (prandom_u32_state(s) < clg->a2)
 			clg->state = GOOD_STATE;
-		if (get_random_u32() > clg->a3)
+		if (prandom_u32_state(s) > clg->a3)
 			return true;
 	}
 
-- 
2.41.0