net: Use sk_tx_queue_mapping for connected sockets

For connected sockets, the first run of dev_pick_tx saves the
calculated txq in sk_tx_queue_mapping. This is not saved if
either the device has a queue select or the socket is not
connected. Next iterations of dev_pick_tx uses the cached value
of sk_tx_queue_mapping.
Signed-off-by: NKrishna Kumar <krkumar2@in.ibm.com>
Signed-off-by: NDavid S. Miller <davem@davemloft.net>

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;
+	u16 queue_index;
+	struct sock *sk = skb->sk;
+
+	if (sk_tx_queue_recorded(sk)) {
+		queue_index = sk_tx_queue_get(sk);
+	} else {
+		const struct net_device_ops *ops = dev->netdev_ops;
 
-	if (ops->ndo_select_queue)
-		queue_index = ops->ndo_select_queue(dev, skb);
-	else if (dev->real_num_tx_queues > 1)
-		queue_index = skb_tx_hash(dev, skb);
+		if (ops->ndo_select_queue) {
+			queue_index = ops->ndo_select_queue(dev, skb);
+		} else {
+			queue_index = 0;
+			if (dev->real_num_tx_queues > 1)
+				queue_index = skb_tx_hash(dev, skb);
+
+			if (sk && sk->sk_dst_cache)
+				sk_tx_queue_set(sk, queue_index);
+		}
+	}
 
 	skb_set_queue_mapping(skb, queue_index);
 	return netdev_get_tx_queue(dev, queue_index);