kernel: use skb_cow_head() to deal with cloned skbs

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

diff --git a/target/linux/generic/patches-4.4/030-7-kaweth-use-skb_cow_head-to-deal-with-cloned-skbs.patch b/target/linux/generic/patches-4.4/030-7-kaweth-use-skb_cow_head-to-deal-with-cloned-skbs.patch
new file mode 100644 (file)
index 0000000..541c694
--- /dev/null
+++ b/target/linux/generic/patches-4.4/030-7-kaweth-use-skb_cow_head-to-deal-with-cloned-skbs.patch
@@ -0,0 +1,43 @@
+From 39fba7835aacda65284a86e611774cbba71dac20 Mon Sep 17 00:00:00 2001
+From: Eric Dumazet <edumazet@google.com>
+Date: Wed, 19 Apr 2017 09:59:26 -0700
+Subject: [PATCH] kaweth: use skb_cow_head() to deal with cloned skbs
+
+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>
+---
+ drivers/net/usb/kaweth.c | 18 ++++++------------
+ 1 file changed, 6 insertions(+), 12 deletions(-)
+
+--- a/drivers/net/usb/kaweth.c
++++ b/drivers/net/usb/kaweth.c
+@@ -812,18 +812,12 @@ static netdev_tx_t kaweth_start_xmit(str
+       }
+ 
+       /* 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);