[PATCH net 6/6] kaweth: use skb_cow_head() to deal with cloned skbs

[Eric Dumazet]

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 <eduma...@google.com>
Cc: James Hughes <james.hug...@raspberrypi.org>
---
 drivers/net/usb/kaweth.c | 18 ++++++------------
 1 file changed, 6 insertions(+), 12 deletions(-)

diff --git a/drivers/net/usb/kaweth.c b/drivers/net/usb/kaweth.c
index 
876f02f4945eafdc2fb5cfa0f9dcb54d9b498af4..2a2c3edb6bad0b3bd257c3a101d100ad3b00cc59
 100644
--- 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);
-- 
2.12.2.816.g2cccc81164-goog