[PATCH] (3/3) netem: adjust parent qlen when duplicating

[Stephen Hemminger <shemminger@xxxxxxxx>]

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@xxxxxxxx>

Index: netem-2.6.12-rc3/net/sched/sch_api.c
===================================================================
--- netem-2.6.12-rc3.orig/net/sched/sch_api.c   2005-05-03 11:19:23.000000000 
-0700
+++ netem-2.6.12-rc3/net/sched/sch_api.c        2005-05-03 15:20:59.000000000 
-0700
@@ -1289,6 +1289,7 @@
 
 subsys_initcall(pktsched_init);
 
+EXPORT_SYMBOL(qdisc_lookup);
 EXPORT_SYMBOL(qdisc_get_rtab);
 EXPORT_SYMBOL(qdisc_put_rtab);
 EXPORT_SYMBOL(register_qdisc);
Index: netem-2.6.12-rc3/net/sched/sch_netem.c
===================================================================
--- netem-2.6.12-rc3.orig/net/sched/sch_netem.c 2005-05-03 11:20:05.000000000 
-0700
+++ netem-2.6.12-rc3/net/sched/sch_netem.c      2005-05-03 15:41:14.000000000 
-0700
@@ -206,7 +206,6 @@
 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 @@
        }
 
        /* 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 @@
        } else
                sch->qstats.drops++;
 
+       pr_debug("netem: enqueue ret %d\n", ret);
        return ret;
 }