net: fix napi_reuse_skb() skb reserve

BugLink: http://bugs.launchpad.net/bugs/971808

[ Upstream commit 2a2a459eeeff48640dc557548ce576d666ab06ed ]

napi->skb is allocated in napi_get_frags() using
netdev_alloc_skb_ip_align(), with a reserve of NET_SKB_PAD +
NET_IP_ALIGN bytes.

However, when such skb is recycled in napi_reuse_skb(), it ends with a
reserve of NET_IP_ALIGN which is suboptimal.

Signed-off-by: Eric Dumazet <eric.dumazet@gmail.com>
Cc: Herbert Xu <herbert@gondor.apana.org.au>
Signed-off-by: David S. Miller <davem@davemloft.net>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

1 files changed, 2 insertions, 1 deletions

diff --git a/net/core/dev.c b/net/core/dev.c
index 17fdbf8d478..f134f88606e 100644
--- a/net/core/dev.c
+++ b/net/core/dev.c
@@ -3504,7 +3504,8 @@ EXPORT_SYMBOL(napi_gro_receive);
 static void napi_reuse_skb(struct napi_struct *napi, struct sk_buff *skb)
 {
         __skb_pull(skb, skb_headlen(skb));
-        skb_reserve(skb, NET_IP_ALIGN - skb_headroom(skb));
+        /* restore the reserve we had after netdev_alloc_skb_ip_align() */
+        skb_reserve(skb, NET_SKB_PAD + NET_IP_ALIGN - skb_headroom(skb));
         skb->vlan_tci = 0;
         skb->dev = napi->dev;
         skb->skb_iif = 0;