[PKT_SCHED]: netetm: adjust parent qlen when duplicating

Fix qlen underrun when doing duplication with netem. If netem is used
as leaf discipline, then the parent needs to be tweaked when packets
are duplicated.

Signed-off-by: Stephen Hemminger <shemminger@osdl.org>
Signed-off-by: David S. Miller <davem@davemloft.net>

net/sched/sch_api.c

@@ -1289,6 +1289,7 @@ static int __init pktsched_init(void)
 
 subsys_initcall(pktsched_init);
 
+EXPORT_SYMBOL(qdisc_lookup);
 EXPORT_SYMBOL(qdisc_get_rtab);
 EXPORT_SYMBOL(qdisc_put_rtab);
 EXPORT_SYMBOL(register_qdisc);

net/sched/sch_netem.c

@@ -206,7 +206,6 @@ static int netem_run(struct Qdisc *sch)
 static int netem_enqueue(struct sk_buff *skb, struct Qdisc *sch)
 {
 	struct netem_sched_data *q = qdisc_priv(sch);
-	struct sk_buff *skb2;
 	int ret;
 
 	pr_debug("netem_enqueue skb=%p\n", skb);
@@ -220,11 +219,21 @@ static int netem_enqueue(struct sk_buff *skb, struct Qdisc *sch)
 	}
 
 	/* Random duplication */
-	if (q->duplicate && q->duplicate >= get_crandom(&q->dup_cor)
-	    && (skb2 = skb_clone(skb, GFP_ATOMIC)) != NULL) {
-		pr_debug("netem_enqueue: dup %p\n", skb2);
+	if (q->duplicate && q->duplicate >= get_crandom(&q->dup_cor)) {
+		struct sk_buff *skb2;
+
+		skb2 = skb_clone(skb, GFP_ATOMIC);
+		if (skb2 && netem_delay(sch, skb2) == NET_XMIT_SUCCESS) {
+			struct Qdisc *qp;
+
+			/* Since one packet can generate two packets in the
+			 * queue, the parent's qlen accounting gets confused,
+			 * so fix it.
+			 */
+			qp = qdisc_lookup(sch->dev, TC_H_MAJ(sch->parent));
+			if (qp)
+				qp->q.qlen++;
 
-		if (netem_delay(sch, skb2)) {
 			sch->q.qlen++;
 			sch->bstats.bytes += skb2->len;
 			sch->bstats.packets++;
@@ -253,6 +262,7 @@ static int netem_enqueue(struct sk_buff *skb, struct Qdisc *sch)
 	} else
 		sch->qstats.drops++;
 
+	pr_debug("netem: enqueue ret %d\n", ret);
 	return ret;
 }