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netem: use seeded PRNG for correlated loss events

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Use prandom_u32_state() instead of get_random_u32() to generate
the correlated loss events of netem.

Signed-off-by: François Michel <francois.michel@uclouvain.be>
Reviewed-by: Simon Horman <horms@kernel.org>
Acked-by: Stephen Hemminger <stephen@networkplumber.org>
Link: https://lore.kernel.org/r/20230815092348.1449179-4-francois.michel@uclouvain.be
Signed-off-by: Jakub Kicinski <kuba@kernel.org>
This commit is contained in:
François Michel 2023-08-15 11:23:40 +02:00 committed by Jakub Kicinski
parent 9c87b2aecc
commit 3cad70bc74
1 changed files with 12 additions and 10 deletions
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22
net/sched/sch_netem.c
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@ -184,15 +184,16 @@ static void init_crandom(struct crndstate *state, unsigned long rho)
* Next number depends on last value. * Next number depends on last value.
* rho is scaled to avoid floating point. * 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; u64 value, rho;
unsigned long answer; unsigned long answer;
struct rnd_state *s = &p->prng_state;
if (!state || state->rho == 0) /* no correlation */ 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; rho = (u64)state->rho + 1;
answer = (value * ((1ull<<32) - rho) + state->last * rho) >> 32; answer = (value * ((1ull<<32) - rho) + state->last * rho) >> 32;
state->last = answer; state->last = answer;
@ -295,7 +296,7 @@ static bool loss_event(struct netem_sched_data *q)
switch (q->loss_model) { switch (q->loss_model) {
case CLG_RANDOM: case CLG_RANDOM:
/* Random packet drop 0 => none, ~0 => all */ /* 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: case CLG_4_STATES:
/* 4state loss model algorithm (used also for GI model) /* 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, static s64 tabledist(s64 mu, s32 sigma,
struct crndstate *state, struct crndstate *state,
struct prng *prng,
const struct disttable *dist) const struct disttable *dist)
{ {
s64 x; s64 x;
@ -333,7 +335,7 @@ static s64 tabledist(s64 mu, s32 sigma,
if (sigma == 0) if (sigma == 0)
return mu; return mu;
rnd = get_crandom(state); rnd = get_crandom(state, prng);
/* default uniform distribution */ /* default uniform distribution */
if (dist == NULL) if (dist == NULL)
@ -455,7 +457,7 @@ static int netem_enqueue(struct sk_buff *skb, struct Qdisc *sch,
skb->prev = NULL; skb->prev = NULL;
/* Random duplication */ /* 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; ++count;
/* Drop packet? */ /* 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 * If packet is going to be hardware checksummed, then
* do it now in software before we mangle it. * 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)) { if (skb_is_gso(skb)) {
skb = netem_segment(skb, sch, to_free); skb = netem_segment(skb, sch, to_free);
if (!skb) if (!skb)
@ -536,12 +538,12 @@ static int netem_enqueue(struct sk_buff *skb, struct Qdisc *sch,
cb = netem_skb_cb(skb); cb = netem_skb_cb(skb);
if (q->gap == 0 || /* not doing reordering */ if (q->gap == 0 || /* not doing reordering */
q->counter < q->gap - 1 || /* inside last reordering gap */ 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; u64 now;
s64 delay; s64 delay;
delay = tabledist(q->latency, q->jitter, delay = tabledist(q->latency, q->jitter,
&q->delay_cor, q->delay_dist); &q->delay_cor, &q->prng, q->delay_dist);
now = ktime_get_ns(); now = ktime_get_ns();
@ -645,7 +647,7 @@ static void get_slot_next(struct netem_sched_data *q, u64 now)
else else
next_delay = tabledist(q->slot_config.dist_delay, next_delay = tabledist(q->slot_config.dist_delay,
(s32)(q->slot_config.dist_jitter), (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.slot_next = now + next_delay;
q->slot.packets_left = q->slot_config.max_packets; q->slot.packets_left = q->slot_config.max_packets;