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netem: use seeded PRNG for correlated loss events
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>
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@ -184,15 +184,16 @@ static void init_crandom(struct crndstate *state, unsigned long rho)
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* Next number depends on last value.
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* rho is scaled to avoid floating point.
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*/
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static u32 get_crandom(struct crndstate *state)
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static u32 get_crandom(struct crndstate *state, struct prng *p)
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{
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u64 value, rho;
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unsigned long answer;
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struct rnd_state *s = &p->prng_state;
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if (!state || state->rho == 0) /* no correlation */
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return get_random_u32();
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return prandom_u32_state(s);
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value = get_random_u32();
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value = prandom_u32_state(s);
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rho = (u64)state->rho + 1;
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answer = (value * ((1ull<<32) - rho) + state->last * rho) >> 32;
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state->last = answer;
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@ -295,7 +296,7 @@ static bool loss_event(struct netem_sched_data *q)
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switch (q->loss_model) {
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case CLG_RANDOM:
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/* Random packet drop 0 => none, ~0 => all */
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return q->loss && q->loss >= get_crandom(&q->loss_cor);
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return q->loss && q->loss >= get_crandom(&q->loss_cor, &q->prng);
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case CLG_4_STATES:
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/* 4state loss model algorithm (used also for GI model)
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@ -324,6 +325,7 @@ static bool loss_event(struct netem_sched_data *q)
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*/
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static s64 tabledist(s64 mu, s32 sigma,
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struct crndstate *state,
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struct prng *prng,
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const struct disttable *dist)
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{
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s64 x;
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@ -333,7 +335,7 @@ static s64 tabledist(s64 mu, s32 sigma,
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if (sigma == 0)
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return mu;
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rnd = get_crandom(state);
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rnd = get_crandom(state, prng);
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/* default uniform distribution */
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if (dist == NULL)
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@ -455,7 +457,7 @@ static int netem_enqueue(struct sk_buff *skb, struct Qdisc *sch,
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skb->prev = NULL;
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/* Random duplication */
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if (q->duplicate && q->duplicate >= get_crandom(&q->dup_cor))
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if (q->duplicate && q->duplicate >= get_crandom(&q->dup_cor, &q->prng))
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++count;
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/* Drop packet? */
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@ -498,7 +500,7 @@ static int netem_enqueue(struct sk_buff *skb, struct Qdisc *sch,
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* If packet is going to be hardware checksummed, then
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* do it now in software before we mangle it.
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*/
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if (q->corrupt && q->corrupt >= get_crandom(&q->corrupt_cor)) {
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if (q->corrupt && q->corrupt >= get_crandom(&q->corrupt_cor, &q->prng)) {
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if (skb_is_gso(skb)) {
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skb = netem_segment(skb, sch, to_free);
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if (!skb)
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@ -536,12 +538,12 @@ static int netem_enqueue(struct sk_buff *skb, struct Qdisc *sch,
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cb = netem_skb_cb(skb);
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if (q->gap == 0 || /* not doing reordering */
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q->counter < q->gap - 1 || /* inside last reordering gap */
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q->reorder < get_crandom(&q->reorder_cor)) {
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q->reorder < get_crandom(&q->reorder_cor, &q->prng)) {
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u64 now;
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s64 delay;
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delay = tabledist(q->latency, q->jitter,
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&q->delay_cor, q->delay_dist);
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&q->delay_cor, &q->prng, q->delay_dist);
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now = ktime_get_ns();
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@ -645,7 +647,7 @@ static void get_slot_next(struct netem_sched_data *q, u64 now)
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else
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next_delay = tabledist(q->slot_config.dist_delay,
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(s32)(q->slot_config.dist_jitter),
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NULL, q->slot_dist);
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NULL, &q->prng, q->slot_dist);
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q->slot.slot_next = now + next_delay;
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q->slot.packets_left = q->slot_config.max_packets;
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