[PKT_SCHED]: Qdisc drop operation is optional

The drop operation is optional and qdiscs must check if childs support it.

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

1 files changed, 2 insertions, 2 deletions

diff --git a/net/sched/sch_tbf.c b/net/sched/sch_tbf.c
index cb9711ea8c6c..e9e473457361 100644
--- a/net/sched/sch_tbf.c
+++ b/net/sched/sch_tbf.c
@@ -177,9 +177,9 @@ static int tbf_requeue(struct sk_buff *skb, struct Qdisc* sch)
 static unsigned int tbf_drop(struct Qdisc* sch)
 {
         struct tbf_sched_data *q = qdisc_priv(sch);
-        unsigned int len;
+        unsigned int len = 0;
 
-        if ((len = q->qdisc->ops->drop(q->qdisc)) != 0) {
+        if (q->qdisc->ops->drop && (len = q->qdisc->ops->drop(q->qdisc)) != 0) {
                 sch->q.qlen--;
                 sch->qstats.drops++;
         }