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Commit e488eafc authored Nov 29, 2006 by Patrick McHardy Committed by David S. Miller Dec 02, 2006

[NET_SCHED]: Fix endless loops (part 5): netem/tbf/hfsc ->requeue failures

When peeking at the next packet in a child qdisc by calling dequeue/requeue,
the upper qdisc qlen counter may get out of sync in case the requeue fails.
The qdisc and the child qdisc both have their counter decremented, but since
no packet is given to the upper qdisc it won't decrement its counter itself.

requeue should not fail, so this is mostly for "correctness".

Signed-off-by: Patrick McHardy <kaber@trash.net>
Signed-off-by: David S. Miller <davem@davemloft.net>

parent 256d61b8

net/sched/sch_hfsc.c

+1 −0

Original line number	Diff line number	Diff line
		@@ -946,6 +946,7 @@ qdisc_peek_len(struct Qdisc *sch)
		if (unlikely(sch->ops->requeue(skb, sch) != NET_XMIT_SUCCESS)) {
		if (net_ratelimit())
		printk("qdisc_peek_len: failed to requeue\n");
		qdisc_tree_decrease_qlen(sch, 1);
		return 0;
		}
		return len;

net/sched/sch_netem.c

+1 −4

Original line number	Diff line number	Diff line
		@@ -287,13 +287,10 @@ static struct sk_buff netem_dequeue(struct Qdisc sch)
		psched_tdiff_t delay = PSCHED_TDIFF(cb->time_to_send, now);

		if (q->qdisc->ops->requeue(skb, q->qdisc) != NET_XMIT_SUCCESS) {
		qdisc_tree_decrease_qlen(q->qdisc, 1);
		sch->qstats.drops++;

		/* After this qlen is confused */
		printk(KERN_ERR "netem: queue discpline %s could not requeue\n",
		q->qdisc->ops->id);

		sch->q.qlen--;
		}

		mod_timer(&q->timer, jiffies + PSCHED_US2JIFFIE(delay));

net/sched/sch_tbf.c

+1 −1

Original line number	Diff line number	Diff line
		@@ -250,7 +250,7 @@ static struct sk_buff tbf_dequeue(struct Qdisc sch)

		if (q->qdisc->ops->requeue(skb, q->qdisc) != NET_XMIT_SUCCESS) {
		/* When requeue fails skb is dropped */
		sch->q.qlen--;
		qdisc_tree_decrease_qlen(q->qdisc, 1);
		sch->qstats.drops++;
		}