netem: add prng attribute to netem_sched_data

Add prng attribute to struct netem_sched_data and
allows setting the seed of the PRNG through netlink
using the new TCA_NETEM_PRNG_SEED attribute.
The PRNG attribute is not actually used yet.

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/20230815092348.1449179-2-francois.michel@uclouvain.be
Signed-off-by: Jakub Kicinski <kuba@kernel.org>

diff --git a/include/uapi/linux/pkt_sched.h b/include/uapi/linux/pkt_sched.h
index 00f6ff0..3f85ae5 100644 (file)
--- a/include/uapi/linux/pkt_sched.h
+++ b/include/uapi/linux/pkt_sched.h
@@ -603,6 +603,7 @@ enum {
        TCA_NETEM_JITTER64,
        TCA_NETEM_SLOT,
        TCA_NETEM_SLOT_DIST,
+       TCA_NETEM_PRNG_SEED,
        __TCA_NETEM_MAX,
 };
 

diff --git a/net/sched/sch_netem.c b/net/sched/sch_netem.c
index 38d9aa0..621c6ac 100644 (file)
--- a/net/sched/sch_netem.c
+++ b/net/sched/sch_netem.c
@@ -105,6 +105,11 @@ struct netem_sched_data {
                u32 rho;
        } delay_cor, loss_cor, dup_cor, reorder_cor, corrupt_cor;
 
+       struct prng  {
+               u64 seed;
+               struct rnd_state prng_state;
+       } prng;
+
        struct disttable *delay_dist;
 
        enum  {
@@ -922,6 +927,7 @@ static const struct nla_policy netem_policy[TCA_NETEM_MAX + 1] = {
        [TCA_NETEM_LATENCY64]   = { .type = NLA_S64 },
        [TCA_NETEM_JITTER64]    = { .type = NLA_S64 },
        [TCA_NETEM_SLOT]        = { .len = sizeof(struct tc_netem_slot) },
+       [TCA_NETEM_PRNG_SEED]   = { .type = NLA_U64 },
 };
 
 static int parse_attr(struct nlattr *tb[], int maxtype, struct nlattr *nla,
@@ -1040,6 +1046,12 @@ 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])
+               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);
+
 unlock:
        sch_tree_unlock(sch);
 
@@ -1203,6 +1215,10 @@ static int netem_dump(struct Qdisc *sch, struct sk_buff *skb)
                        goto nla_put_failure;
        }
 
+       if (nla_put_u64_64bit(skb, TCA_NETEM_PRNG_SEED, q->prng.seed,
+                             TCA_NETEM_PAD))
+               goto nla_put_failure;
+
        return nla_nest_end(skb, nla);
 
 nla_put_failure: