[PATCH] check the return value of ndo_select_queue()

[Changli Gao <xiaosuo@gmail.com>]

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>
----
net/core/dev.c | 24 ++++++++++++++++++------
1 file changed, 18 insertions(+), 6 deletions(-)

diff --git a/net/core/dev.c b/net/core/dev.c
index b8f74cf..be081a5 100644
--- a/net/core/dev.c
+++ b/net/core/dev.c
@@ -1791,13 +1791,25 @@ EXPORT_SYMBOL(skb_tx_hash);
 static struct netdev_queue *dev_pick_tx(struct net_device *dev,
 					struct sk_buff *skb)
 {
-	const struct net_device_ops *ops = dev->netdev_ops;
-	u16 queue_index = 0;
-
-	if (ops->ndo_select_queue)
-		queue_index = ops->ndo_select_queue(dev, skb);
-	else if (dev->real_num_tx_queues > 1)
+	u16 queue_index;
+	u16 (*ndo_select_queue)(struct net_device*, struct sk_buff*);
+	unsigned int real_num_tx_queues = dev->real_num_tx_queues;
+
+	if (real_num_tx_queues == 1) {
+		queue_index = 0;
+	} else if ((ndo_select_queue = dev->netdev_ops->ndo_select_queue)) {
+		queue_index = ndo_select_queue(dev, skb);
+		if (unlikely(queue_index >= 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,
+				     real_num_tx_queues);
+			queue_index = 0;
+		}
+	} else {
 		queue_index = skb_tx_hash(dev, skb);
+	}
 
 	skb_set_queue_mapping(skb, queue_index);
 	return netdev_get_tx_queue(dev, queue_index);