pkt_sched: Add peek emulation for non-work-conserving qdiscs.

This patch adds qdisc_peek_dequeued() wrapper to emulate peek method
with qdisc->dequeue() and storing "peeked" skb in qdisc->gso_skb until
dequeuing. This is mainly for compatibility reasons not to break some
strange configs because peeking is expected for non-work-conserving
parent qdiscs to query work-conserving child qdiscs.

This implementation requires using qdisc_dequeue_peeked() wrapper
instead of directly calling qdisc->dequeue() for all qdiscs ever
querried with qdisc->ops->peek() or qdisc_peek_dequeued().

Signed-off-by: Jarek Poplawski <jarkao2@gmail.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

1 files changed, 3 insertions, 2 deletions

diff --git a/net/sched/sch_netem.c b/net/sched/sch_netem.c
index 74fbdb52baed..3080bd6ee332 100644
--- a/net/sched/sch_netem.c
+++ b/net/sched/sch_netem.c
@@ -290,8 +290,8 @@ static struct sk_buff *netem_dequeue(struct Qdisc *sch)
 
                 /* if more time remaining? */
                 if (cb->time_to_send <= now) {
-                        skb = q->qdisc->dequeue(q->qdisc);
-                        if (!skb)
+                        skb = qdisc_dequeue_peeked(q->qdisc);
+                        if (unlikely(!skb))
                                 return NULL;
 
                         pr_debug("netem_dequeue: return skb=%p\n", skb);
@@ -714,6 +714,7 @@ static struct Qdisc_ops netem_qdisc_ops __read_mostly = {
         .priv_size      =       sizeof(struct netem_sched_data),
         .enqueue        =       netem_enqueue,
         .dequeue        =       netem_dequeue,
+        .peek           =       qdisc_peek_dequeued,
         .requeue        =       netem_requeue,
         .drop           =       netem_drop,
         .init           =       netem_init,