pkt_sched: Add ->peek() methods for fifo, prio and SFQ qdiscs.

From: Patrick McHardy <kaber@trash.net>

Just as a demonstration how easy adding a peek operation to the
work-conserving qdiscs actually is. It doesn't need to keep or change
any internal state in many cases thanks to the guarantee that the
packet will either be dequeued or, if another packet arrives, the
upper qdisc will immediately ->peek again to reevaluate the state.

(This is only slightly modified Patrick's patch.)

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

1 files changed, 14 insertions, 0 deletions

diff --git a/net/sched/sch_prio.c b/net/sched/sch_prio.c
index 504a78cdb718..3651da3e2802 100644
--- a/net/sched/sch_prio.c
+++ b/net/sched/sch_prio.c
@@ -120,6 +120,19 @@ prio_requeue(struct sk_buff *skb, struct Qdisc* sch)
         return ret;
 }
 
+static struct sk_buff *prio_peek(struct Qdisc *sch)
+{
+        struct prio_sched_data *q = qdisc_priv(sch);
+        int prio;
+
+        for (prio = 0; prio < q->bands; prio++) {
+                struct Qdisc *qdisc = q->queues[prio];
+                struct sk_buff *skb = qdisc->ops->peek(qdisc);
+                if (skb)
+                        return skb;
+        }
+        return NULL;
+}
 
 static struct sk_buff *prio_dequeue(struct Qdisc* sch)
 {
@@ -421,6 +434,7 @@ static struct Qdisc_ops prio_qdisc_ops __read_mostly = {
         .priv_size      =       sizeof(struct prio_sched_data),
         .enqueue        =       prio_enqueue,
         .dequeue        =       prio_dequeue,
+        .peek           =       prio_peek,
         .requeue        =       prio_requeue,
         .drop           =       prio_drop,
         .init           =       prio_init,