[PATCH net-next 4/4] netem: add per-impairment extended statistics
From: Stephen Hemminger <stephen@networkplumber.org>
Date: 2026-05-02 00:18:53
Also in:
netdev
Subsystem:
netem network emulator, networking [general], tc subsystem, the rest · Maintainers:
Stephen Hemminger, "David S. Miller", Eric Dumazet, Jakub Kicinski, Paolo Abeni, Jamal Hadi Salim, Jiri Pirko, Linus Torvalds
Adds new counters that keep track of when netem applied impairments (delay, loss, corruption, duplication, reordering). Add a struct tc_netem_xstats reported via TCA_STATS_APP so that userspace (tc -s qdisc show) can display per-impairment counters. Use the WRITE_ONCE/READ_ONCE pattern to allow for lockless qdisc usage. Accompanying iproute2 change is submitted separately. Signed-off-by: Stephen Hemminger <stephen@networkplumber.org> --- include/uapi/linux/pkt_sched.h | 9 ++++++++ net/sched/sch_netem.c | 40 +++++++++++++++++++++++++++++++--- 2 files changed, 46 insertions(+), 3 deletions(-)
diff --git a/include/uapi/linux/pkt_sched.h b/include/uapi/linux/pkt_sched.h
index 66e8072f44df..1c84c8076e22 100644
--- a/include/uapi/linux/pkt_sched.h
+++ b/include/uapi/linux/pkt_sched.h@@ -569,6 +569,15 @@ struct tc_netem_gemodel { #define NETEM_DIST_SCALE 8192 #define NETEM_DIST_MAX 16384 +struct tc_netem_xstats { + __u64 delayed; /* packets delayed */ + __u64 dropped; /* packets dropped by loss model */ + __u64 corrupted; /* packets with bit errors injected */ + __u64 duplicated; /* duplicate packets generated */ + __u64 reordered; /* packets sent out of order */ + __u64 ecn_marked; /* packets ECN CE-marked (not dropped)*/ +}; + /* DRR */ enum {
diff --git a/net/sched/sch_netem.c b/net/sched/sch_netem.c
index 116e96d79ddf..c871c7a3b117 100644
--- a/net/sched/sch_netem.c
+++ b/net/sched/sch_netem.c@@ -152,6 +152,14 @@ struct netem_sched_data { } slot; struct disttable *slot_dist; + + /* Per-impairment counters */ + __u64 delayed; + __u64 dropped; + __u64 corrupted; + __u64 duplicated; + __u64 reordered; + __u64 ecn_marked; }; /* Time stamp put into socket buffer control block
@@ -459,17 +467,23 @@ 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, &q->prng)) + if (q->duplicate && q->duplicate >= get_crandom(&q->dup_cor, &q->prng)) { ++count; + WRITE_ONCE(q->duplicated, q->duplicated + 1); + } /* Drop packet? */ if (loss_event(q)) { - if (q->ecn && INET_ECN_set_ce(skb)) + if (q->ecn && INET_ECN_set_ce(skb)) { qdisc_qstats_drop(sch); /* mark packet */ - else + WRITE_ONCE(q->ecn_marked, q->ecn_marked + 1); + } else { --count; + } } + if (count == 0) { + WRITE_ONCE(q->dropped, q->dropped + 1); qdisc_qstats_drop(sch); __qdisc_drop(skb, to_free); return NET_XMIT_SUCCESS | __NET_XMIT_BYPASS;
@@ -495,6 +509,7 @@ static int netem_enqueue(struct sk_buff *skb, struct Qdisc *sch, * do it now in software before we mangle it. */ if (q->corrupt && q->corrupt >= get_crandom(&q->corrupt_cor, &q->prng)) { + WRITE_ONCE(q->corrupted, q->corrupted + 1); if (skb_is_gso(skb)) { skb = netem_segment(skb, sch, to_free); if (!skb)
@@ -600,12 +615,15 @@ static int netem_enqueue(struct sk_buff *skb, struct Qdisc *sch, cb->time_to_send = now + delay; ++q->counter; + WRITE_ONCE(q->delayed, q->delayed + 1); + tfifo_enqueue(skb, sch); } else { /* * Do re-ordering by putting one out of N packets at the front * of the queue. */ + WRITE_ONCE(q->reordered, q->reordered + 1); cb->time_to_send = ktime_get_ns(); q->counter = 0;
@@ -1344,6 +1362,21 @@ static int netem_dump(struct Qdisc *sch, struct sk_buff *skb) return -1; } +static int netem_dump_stats(struct Qdisc *sch, struct gnet_dump *d) +{ + struct netem_sched_data *q = qdisc_priv(sch); + struct tc_netem_xstats st = { + .delayed = READ_ONCE(q->delayed), + .dropped = READ_ONCE(q->dropped), + .corrupted = READ_ONCE(q->corrupted), + .duplicated = READ_ONCE(q->duplicated), + .reordered = READ_ONCE(q->reordered), + .ecn_marked = READ_ONCE(q->ecn_marked), + }; + + return gnet_stats_copy_app(d, &st, sizeof(st)); +} + static int netem_dump_class(struct Qdisc *sch, unsigned long cl, struct sk_buff *skb, struct tcmsg *tcm) {
@@ -1406,6 +1439,7 @@ static struct Qdisc_ops netem_qdisc_ops __read_mostly = { .destroy = netem_destroy, .change = netem_change, .dump = netem_dump, + .dump_stats = netem_dump_stats, .owner = THIS_MODULE, }; MODULE_ALIAS_NET_SCH("netem");
--
2.53.0