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Commit 0afb51e7 authored by Stephen Hemminger's avatar Stephen Hemminger Committed by David S. Miller
Browse files

[PKT_SCHED]: netem: reinsert for duplication 



Handle duplication of packets in netem by re-inserting at top of qdisc tree.
This avoid problems with qlen accounting with nested qdisc. This recursion
requires no additional locking but will potentially increase stack depth.

Signed-off-by: default avatarStephen Hemminger <shemminger@osdl.org>
Signed-off-by: default avatarDavid S. Miller <davem@davemloft.net>
parent cdbbde14

net/sched/sch_netem.c

+29 −24
Original line number Diff line number Diff line
@@ -203,42 +203,47 @@ static int netem_run(struct Qdisc *sch) 
	return 0;

}



/*

 * Insert one skb into qdisc.

 * Note: parent depends on return value to account for queue length.

 * 	NET_XMIT_DROP: queue length didn't change.

 *      NET_XMIT_SUCCESS: one skb was queued.

 */

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;

	int count = 1;



	pr_debug("netem_enqueue skb=%p\n", skb);



	/* Random duplication */

	if (q->duplicate && q->duplicate >= get_crandom(&q->dup_cor))

		++count;



	/* Random packet drop 0 => none, ~0 => all */

	if (q->loss && q->loss >= get_crandom(&q->loss_cor)) {

		pr_debug("netem_enqueue: random loss\n");

	if (q->loss && q->loss >= get_crandom(&q->loss_cor))

		--count;



	if (count == 0) {

		sch->qstats.drops++;

		kfree_skb(skb);

		return 0;	/* lie about loss so TCP doesn't know */

		return NET_XMIT_DROP;

	}



	/* Random duplication */

	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.

	/*

	 * If we need to duplicate packet, then re-insert at top of the

	 * qdisc tree, since parent queuer expects that only one

	 * skb will be queued.

	 */

			qp = qdisc_lookup(sch->dev, TC_H_MAJ(sch->parent));

			if (qp)

				qp->q.qlen++;

	if (count > 1 && (skb2 = skb_clone(skb, GFP_ATOMIC)) != NULL) {

		struct Qdisc *rootq = sch->dev->qdisc;

		u32 dupsave = q->duplicate; /* prevent duplicating a dup... */

		q->duplicate = 0;



			sch->q.qlen++;

			sch->bstats.bytes += skb2->len;

			sch->bstats.packets++;

		} else

			sch->qstats.drops++;

		rootq->enqueue(skb2, rootq);

		q->duplicate = dupsave;

	}



	/* If doing simple delay then gap == 0 so all packets