From 3cad70bc74ef8471e30a05a90798904ce8f8feb5 Mon Sep 17 00:00:00 2001 From: =?utf8?q?Fran=C3=A7ois=20Michel?= Date: Tue, 15 Aug 2023 11:23:40 +0200 Subject: [PATCH] netem: use seeded PRNG for correlated loss events MIME-Version: 1.0 Content-Type: text/plain; charset=utf8 Content-Transfer-Encoding: 8bit Use prandom_u32_state() instead of get_random_u32() to generate the correlated loss events of netem. Signed-off-by: François Michel Reviewed-by: Simon Horman Acked-by: Stephen Hemminger Link: https://lore.kernel.org/r/20230815092348.1449179-4-francois.michel@uclouvain.be Signed-off-by: Jakub Kicinski --- net/sched/sch_netem.c | 22 ++++++++++++---------- 1 file changed, 12 insertions(+), 10 deletions(-) diff --git a/net/sched/sch_netem.c b/net/sched/sch_netem.c index 8b54b10..4ad39a4a 100644 --- a/net/sched/sch_netem.c +++ b/net/sched/sch_netem.c @@ -184,15 +184,16 @@ static void init_crandom(struct crndstate *state, unsigned long rho) * Next number depends on last value. * rho is scaled to avoid floating point. */ -static u32 get_crandom(struct crndstate *state) +static u32 get_crandom(struct crndstate *state, struct prng *p) { u64 value, rho; unsigned long answer; + struct rnd_state *s = &p->prng_state; if (!state || state->rho == 0) /* no correlation */ - return get_random_u32(); + return prandom_u32_state(s); - value = get_random_u32(); + value = prandom_u32_state(s); rho = (u64)state->rho + 1; answer = (value * ((1ull<<32) - rho) + state->last * rho) >> 32; state->last = answer; @@ -295,7 +296,7 @@ static bool loss_event(struct netem_sched_data *q) switch (q->loss_model) { case CLG_RANDOM: /* Random packet drop 0 => none, ~0 => all */ - return q->loss && q->loss >= get_crandom(&q->loss_cor); + return q->loss && q->loss >= get_crandom(&q->loss_cor, &q->prng); case CLG_4_STATES: /* 4state loss model algorithm (used also for GI model) @@ -324,6 +325,7 @@ static bool loss_event(struct netem_sched_data *q) */ static s64 tabledist(s64 mu, s32 sigma, struct crndstate *state, + struct prng *prng, const struct disttable *dist) { s64 x; @@ -333,7 +335,7 @@ static s64 tabledist(s64 mu, s32 sigma, if (sigma == 0) return mu; - rnd = get_crandom(state); + rnd = get_crandom(state, prng); /* default uniform distribution */ if (dist == NULL) @@ -455,7 +457,7 @@ static int netem_enqueue(struct sk_buff *skb, struct Qdisc *sch, skb->prev = NULL; /* Random duplication */ - if (q->duplicate && q->duplicate >= get_crandom(&q->dup_cor)) + if (q->duplicate && q->duplicate >= get_crandom(&q->dup_cor, &q->prng)) ++count; /* Drop packet? */ @@ -498,7 +500,7 @@ static int netem_enqueue(struct sk_buff *skb, struct Qdisc *sch, * If packet is going to be hardware checksummed, then * do it now in software before we mangle it. */ - if (q->corrupt && q->corrupt >= get_crandom(&q->corrupt_cor)) { + if (q->corrupt && q->corrupt >= get_crandom(&q->corrupt_cor, &q->prng)) { if (skb_is_gso(skb)) { skb = netem_segment(skb, sch, to_free); if (!skb) @@ -536,12 +538,12 @@ static int netem_enqueue(struct sk_buff *skb, struct Qdisc *sch, cb = netem_skb_cb(skb); if (q->gap == 0 || /* not doing reordering */ q->counter < q->gap - 1 || /* inside last reordering gap */ - q->reorder < get_crandom(&q->reorder_cor)) { + q->reorder < get_crandom(&q->reorder_cor, &q->prng)) { u64 now; s64 delay; delay = tabledist(q->latency, q->jitter, - &q->delay_cor, q->delay_dist); + &q->delay_cor, &q->prng, q->delay_dist); now = ktime_get_ns(); @@ -645,7 +647,7 @@ static void get_slot_next(struct netem_sched_data *q, u64 now) else next_delay = tabledist(q->slot_config.dist_delay, (s32)(q->slot_config.dist_jitter), - NULL, q->slot_dist); + NULL, &q->prng, q->slot_dist); q->slot.slot_next = now + next_delay; q->slot.packets_left = q->slot_config.max_packets; -- 2.7.4