net: check the return value of ndo_select_queue()

Check the return value of ndo_select_queue(). If the value isn't smaller
than the real_num_tx_queues, print a warning message, and reset it to zero.

Signed-off-by: Changli Gao <xiaosuo@gmail.com>
Signed-off-by: Eric Dumazet <eric.dumazet@gmail.com>
----
Signed-off-by: David S. Miller <davem@davemloft.net>

net/core/dev.c

@@ -1848,6 +1848,20 @@ u16 skb_tx_hash(const struct net_device *dev, const struct sk_buff *skb)
 }
 EXPORT_SYMBOL(skb_tx_hash);
 
+static inline u16 dev_cap_txqueue(struct net_device *dev, u16 queue_index)
+{
+	if (unlikely(queue_index >= dev->real_num_tx_queues)) {
+		if (net_ratelimit()) {
+			WARN(1, "%s selects TX queue %d, but "
+			     "real number of TX queues is %d\n",
+			     dev->name, queue_index,
+			     dev->real_num_tx_queues);
+		}
+		return 0;
+	}
+	return queue_index;
+}
+
 static struct netdev_queue *dev_pick_tx(struct net_device *dev,
 					struct sk_buff *skb)
 {
@@ -1861,6 +1875,7 @@ static struct netdev_queue *dev_pick_tx(struct net_device *dev,
 
 		if (ops->ndo_select_queue) {
 			queue_index = ops->ndo_select_queue(dev, skb);
+			queue_index = dev_cap_txqueue(dev, queue_index);
 		} else {
 			queue_index = 0;
 			if (dev->real_num_tx_queues > 1)