diff options
| author | Stephen Hemminger <stephen@networkplumber.org> | 2026-04-18 06:19:41 +0300 |
|---|---|---|
| committer | Jakub Kicinski <kuba@kernel.org> | 2026-04-28 03:30:28 +0300 |
| commit | 986afaf809940577224a99c3a08d97a15eb37e93 (patch) | |
| tree | f3bc0d5484637545f472122a2894a7062c131d41 | |
| parent | 4185701fcce6b426b6c3630b25330dddd9c47b0d (diff) | |
| download | linux-986afaf809940577224a99c3a08d97a15eb37e93.tar.xz | |
net/sched: netem: only reseed PRNG when seed is explicitly provided
netem_change() unconditionally reseeds the PRNG on every tc change
command. If TCA_NETEM_PRNG_SEED is not specified, a new random seed
is generated, destroying reproducibility for users who set a
deterministic seed on a previous change.
Move the initial random seed generation to netem_init() and only
reseed in netem_change() when TCA_NETEM_PRNG_SEED is explicitly
provided by the user.
Fixes: 4072d97ddc44 ("netem: add prng attribute to netem_sched_data")
Signed-off-by: Stephen Hemminger <stephen@networkplumber.org>
Reviewed-by: Simon Horman <horms@kernel.org>
Link: https://patch.msgid.link/20260418032027.900913-4-stephen@networkplumber.org
Signed-off-by: Jakub Kicinski <kuba@kernel.org>
| -rw-r--r-- | net/sched/sch_netem.c | 10 |
1 files changed, 6 insertions, 4 deletions
diff --git a/net/sched/sch_netem.c b/net/sched/sch_netem.c index d400a730eadd..556f9747f0e7 100644 --- a/net/sched/sch_netem.c +++ b/net/sched/sch_netem.c @@ -1112,11 +1112,10 @@ static int netem_change(struct Qdisc *sch, struct nlattr *opt, /* capping jitter to the range acceptable by tabledist() */ q->jitter = min_t(s64, abs(q->jitter), INT_MAX); - if (tb[TCA_NETEM_PRNG_SEED]) + if (tb[TCA_NETEM_PRNG_SEED]) { q->prng.seed = nla_get_u64(tb[TCA_NETEM_PRNG_SEED]); - else - q->prng.seed = get_random_u64(); - prandom_seed_state(&q->prng.prng_state, q->prng.seed); + prandom_seed_state(&q->prng.prng_state, q->prng.seed); + } unlock: sch_tree_unlock(sch); @@ -1139,6 +1138,9 @@ static int netem_init(struct Qdisc *sch, struct nlattr *opt, return -EINVAL; q->loss_model = CLG_RANDOM; + q->prng.seed = get_random_u64(); + prandom_seed_state(&q->prng.prng_state, q->prng.seed); + ret = netem_change(sch, opt, extack); if (ret) pr_info("netem: change failed\n"); |