target/linux/generic/patches-4.4/030-7-kaweth-use-skb_cow_head-to-deal-with-cloned-skbs.patch

   1 From 39fba7835aacda65284a86e611774cbba71dac20 Mon Sep 17 00:00:00 2001
   2 From: Eric Dumazet <edumazet@google.com>
   3 Date: Wed, 19 Apr 2017 09:59:26 -0700
   4 Subject: [PATCH] kaweth: use skb_cow_head() to deal with cloned skbs
   5
   6 We can use skb_cow_head() to properly deal with clones,
   7 especially the ones coming from TCP stack that allow their head being
   8 modified. This avoids a copy.
   9
  10 Signed-off-by: Eric Dumazet <edumazet@google.com>
  11 Cc: James Hughes <james.hughes@raspberrypi.org>
  12 Signed-off-by: David S. Miller <davem@davemloft.net>
  13 ---
  14  drivers/net/usb/kaweth.c | 18 ++++++------------
  15  1 file changed, 6 insertions(+), 12 deletions(-)
  16
  17 --- a/drivers/net/usb/kaweth.c
  18 +++ b/drivers/net/usb/kaweth.c
  19 @@ -812,18 +812,12 @@ static netdev_tx_t kaweth_start_xmit(str
  20         }
  21
  22         /* We now decide whether we can put our special header into the sk_buff */
  23 -       if (skb_cloned(skb) || skb_headroom(skb) < 2) {
  24 -               /* no such luck - we make our own */
  25 -               struct sk_buff *copied_skb;
  26 -               copied_skb = skb_copy_expand(skb, 2, 0, GFP_ATOMIC);
  27 -               dev_kfree_skb_irq(skb);
  28 -               skb = copied_skb;
  29 -               if (!copied_skb) {
  30 -                       kaweth->stats.tx_errors++;
  31 -                       netif_start_queue(net);
  32 -                       spin_unlock_irq(&kaweth->device_lock);
  33 -                       return NETDEV_TX_OK;
  34 -               }
  35 +       if (skb_cow_head(skb, 2)) {
  36 +               kaweth->stats.tx_errors++;
  37 +               netif_start_queue(net);
  38 +               spin_unlock_irq(&kaweth->device_lock);
  39 +               dev_kfree_skb_any(skb);
  40 +               return NETDEV_TX_OK;
  41         }
  42
  43         private_header = (__le16 *)__skb_push(skb, 2);