pkt_sched: Add qdisc->ops->peek() implementation.

Add qdisc->ops->peek() implementation for work-conserving qdiscs.
With feedback from Patrick McHardy.

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

1 files changed, 29 insertions, 0 deletions

diff --git a/net/sched/sch_multiq.c b/net/sched/sch_multiq.c
index 915f3149dde2..155648d23b7c 100644
--- a/net/sched/sch_multiq.c
+++ b/net/sched/sch_multiq.c
@@ -155,6 +155,34 @@ static struct sk_buff *multiq_dequeue(struct Qdisc *sch)
 
 }
 
+static struct sk_buff *multiq_peek(struct Qdisc *sch)
+{
+        struct multiq_sched_data *q = qdisc_priv(sch);
+        unsigned int curband = q->curband;
+        struct Qdisc *qdisc;
+        struct sk_buff *skb;
+        int band;
+
+        for (band = 0; band < q->bands; band++) {
+                /* cycle through bands to ensure fairness */
+                curband++;
+                if (curband >= q->bands)
+                        curband = 0;
+
+                /* Check that target subqueue is available before
+                 * pulling an skb to avoid excessive requeues
+                 */
+                if (!__netif_subqueue_stopped(qdisc_dev(sch), curband)) {
+                        qdisc = q->queues[curband];
+                        skb = qdisc->ops->peek(qdisc);
+                        if (skb)
+                                return skb;
+                }
+        }
+        return NULL;
+
+}
+
 static unsigned int multiq_drop(struct Qdisc *sch)
 {
         struct multiq_sched_data *q = qdisc_priv(sch);
@@ -451,6 +479,7 @@ static struct Qdisc_ops multiq_qdisc_ops __read_mostly = {
         .priv_size      =       sizeof(struct multiq_sched_data),
         .enqueue        =       multiq_enqueue,
         .dequeue        =       multiq_dequeue,
+        .peek           =       multiq_peek,
         .requeue        =       multiq_requeue,
         .drop           =       multiq_drop,
         .init           =       multiq_init,