kaweth: use skb_cow_head() to deal with cloned skbs

commit 39fba7835aacda65284a86e611774cbba71dac20 upstream.

We can use skb_cow_head() to properly deal with clones,
especially the ones coming from TCP stack that allow their head being
modified. This avoids a copy.

Signed-off-by: Eric Dumazet <edumazet@google.com>
Cc: James Hughes <james.hughes@raspberrypi.org>
Signed-off-by: David S. Miller <davem@davemloft.net>
Signed-off-by: Linus Walleij <linus.walleij@linaro.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

diff --git a/drivers/net/usb/kaweth.c b/drivers/net/usb/kaweth.c
index 66b34ddbe216dfc3578a81831b733b9463622fa7..72d9e7954b0a6167a8ae102dbab92f3ef57e6df0 100644 (file)
--- a/drivers/net/usb/kaweth.c
+++ b/drivers/net/usb/kaweth.c
@@ -803,18 +803,12 @@ static netdev_tx_t kaweth_start_xmit(struct sk_buff *skb,
        }
 
        /* We now decide whether we can put our special header into the sk_buff */
-       if (skb_cloned(skb) || skb_headroom(skb) < 2) {
-               /* no such luck - we make our own */
-               struct sk_buff *copied_skb;
-               copied_skb = skb_copy_expand(skb, 2, 0, GFP_ATOMIC);
-               dev_kfree_skb_irq(skb);
-               skb = copied_skb;
-               if (!copied_skb) {
-                       kaweth->stats.tx_errors++;
-                       netif_start_queue(net);
-                       spin_unlock_irq(&kaweth->device_lock);
-                       return NETDEV_TX_OK;
-               }
+       if (skb_cow_head(skb, 2)) {
+               kaweth->stats.tx_errors++;
+               netif_start_queue(net);
+               spin_unlock_irq(&kaweth->device_lock);
+               dev_kfree_skb_any(skb);
+               return NETDEV_TX_OK;
        }
 
        private_header = (__le16 *)__skb_push(skb, 2);