[PATCH net-next 4/5] net/sched: netem: add per-impairment extended statistics

[Stephen Hemminger <stephen@networkplumber.org>]

netem applies several impairments (delay, loss, corruption, duplication,
reordering) but exposes no counters distinguishing which impairment
affected a given packet.

Add a struct tc_netem_xstats reported via TCA_STATS_APP so that
userspace (tc -s qdisc show) can display per-impairment counters.

Signed-off-by: Stephen Hemminger <stephen@networkplumber.org>
---
 include/uapi/linux/pkt_sched.h |  9 +++++++++
 net/sched/sch_netem.c          | 27 ++++++++++++++++++++++++---
 2 files changed, 33 insertions(+), 3 deletions(-)

diff --git a/include/uapi/linux/pkt_sched.h b/include/uapi/linux/pkt_sched.h
index 66e8072f44df..fada10cb9b7b 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 {
+	__u32	delayed;	/* packets delayed */
+	__u32	dropped;	/* packets dropped by loss model      */
+	__u32	corrupted;	/* packets with bit errors injected   */
+	__u32	duplicated;	/* duplicate packets generated        */
+	__u32	reordered;	/* packets sent out of order          */
+	__u32	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 76af9bd3ecaa..6dc1ba8e999b 100644
--- a/net/sched/sch_netem.c
+++ b/net/sched/sch_netem.c
@@ -152,6 +152,9 @@ struct netem_sched_data {
 	} slot;
 
 	struct disttable *slot_dist;
+
+	/* Per-impairment counters */
+	struct tc_netem_xstats xstats;
 };
 
 /* Time stamp put into socket buffer control block
@@ -459,17 +462,22 @@ 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;
+		q->xstats.duplicated++;
+	}
 
 	/* 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
+			q->xstats.ecn_marked++;
+		} else {
 			--count;
+		}
 	}
 	if (count == 0) {
+		q->xstats.dropped++;
 		qdisc_qstats_drop(sch);
 		__qdisc_drop(skb, to_free);
 		return NET_XMIT_SUCCESS | __NET_XMIT_BYPASS;
@@ -520,6 +528,7 @@ static int netem_enqueue(struct sk_buff *skb, struct Qdisc *sch,
 		if (skb_headlen(skb))
 			skb->data[get_random_u32_below(skb_headlen(skb))] ^=
 				1 << get_random_u32_below(8);
+		q->xstats.corrupted++;
 	}
 
 	if (unlikely(q->t_len >= sch->limit)) {
@@ -598,6 +607,9 @@ static int netem_enqueue(struct sk_buff *skb, struct Qdisc *sch,
 			delay += packet_time_ns(qdisc_pkt_len(skb), q);
 		}
 
+		if (delay > 0)
+			q->xstats.delayed++;
+
 		cb->time_to_send = now + delay;
 		++q->counter;
 		tfifo_enqueue(skb, sch);
@@ -610,6 +622,7 @@ static int netem_enqueue(struct sk_buff *skb, struct Qdisc *sch,
 		q->counter = 0;
 
 		__qdisc_enqueue_head(skb, &sch->q);
+		q->xstats.reordered++;
 		sch->qstats.requeues++;
 	}
 
@@ -1296,6 +1309,13 @@ 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);
+
+	return gnet_stats_copy_app(d, &q->xstats, sizeof(q->xstats));
+}
+
 static int netem_dump_class(struct Qdisc *sch, unsigned long cl,
 			  struct sk_buff *skb, struct tcmsg *tcm)
 {
@@ -1358,6 +1378,7 @@ 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