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

From: Francois Michel
Date: Tue Aug 15 2023 - 05:26:14 EST


From: François Michel <francois.michel@xxxxxxxxxxxx>

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@xxxxxxxxxxxx>
---
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