Messages in this thread Patch in this message | | | From | Francois Michel <> | Subject | [PATCH net-next 2/3] [PATCH 2/3] netem: allow using a seeded PRNG for generating random losses | Date | Mon, 14 Aug 2023 04:31:39 +0200 |
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From: François Michel <francois.michel@uclouvain.be>
Add the netem_get_random_u32 function to sch_netem.c and use it to generate the random loss events of netem.
If no seed was specified by the application through setting TCA_NETEM_PRNG_SEED, the default behaviour is the same as before, i.e. it relies on the unseeded get_random_u32() function. If a seed was provided, it relies on the seeded prng attribute of struct netem_sched_data.
Signed-off-by: François Michel <francois.michel@uclouvain.be> --- net/sched/sch_netem.c | 24 +++++++++++++++++++----- 1 file changed, 19 insertions(+), 5 deletions(-)
diff --git a/net/sched/sch_netem.c b/net/sched/sch_netem.c index d73596d0e912..1190782ef79d 100644 --- a/net/sched/sch_netem.c +++ b/net/sched/sch_netem.c @@ -154,6 +154,19 @@ struct netem_sched_data { struct disttable *slot_dist; }; +/* netem_get_random_u32 - polls a new random 32-bits integer from + * the prng. + * Uses a deterministic seeded prng if p->deterministic_rng is true. + * Uses get_random_u32() underneath if p is NULL or if p->deterministic_rng + * is false. + */ +static u32 netem_get_random_u32(struct prng *p) +{ + if (p && p->deterministic_rng) + return prandom_u32_state(&p->prng_state); + return get_random_u32(); +} + /* Time stamp put into socket buffer control block * Only valid when skbs are in our internal t(ime)fifo queue. * @@ -207,7 +220,7 @@ 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 = netem_get_random_u32(&q->prng); /* * Makes a comparison between rnd and the transition @@ -272,18 +285,19 @@ 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 prng *p = &q->prng; switch (clg->state) { case GOOD_STATE: - if (get_random_u32() < clg->a1) + if (netem_get_random_u32(p) < clg->a1) clg->state = BAD_STATE; - if (get_random_u32() < clg->a4) + if (netem_get_random_u32(p) < clg->a4) return true; break; case BAD_STATE: - if (get_random_u32() < clg->a2) + if (netem_get_random_u32(p) < clg->a2) clg->state = GOOD_STATE; - if (get_random_u32() > clg->a3) + if (netem_get_random_u32(p) > clg->a3) return true; } -- 2.41.0
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