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

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, 12 insertions, 0 deletions

diff --git a/net/sched/sch_api.c b/net/sched/sch_api.c
index b16ad2972c6b..e5646614e88d 100644
--- a/net/sched/sch_api.c
+++ b/net/sched/sch_api.c
@@ -102,6 +102,10 @@ static int tclass_notify(struct sk_buff *oskb, struct nlmsghdr *n,
    requeues once dequeued packet. It is used for non-standard or
    just buggy devices, which can defer output even if netif_queue_stopped()=0.
 
+   ---peek
+
+   like dequeue but without removing a packet from the queue
+
    ---reset
 
    returns qdisc to initial state: purge all buffers, clear all
@@ -149,6 +153,14 @@ int register_qdisc(struct Qdisc_ops *qops)
                 qops->enqueue = noop_qdisc_ops.enqueue;
         if (qops->requeue == NULL)
                 qops->requeue = noop_qdisc_ops.requeue;
+        if (qops->peek == NULL) {
+                if (qops->dequeue == NULL) {
+                        qops->peek = noop_qdisc_ops.peek;
+                } else {
+                        rc = -EINVAL;
+                        goto out;
+                }
+        }
         if (qops->dequeue == NULL)
                 qops->dequeue = noop_qdisc_ops.dequeue;