releases/3.2.14/net-fix-napi_reuse_skb-skb-reserve.patch

From b1e9f286f86f2c17995d0092da97998ed1a52b25 Mon Sep 17 00:00:00 2001
From: Eric Dumazet <eric.dumazet@gmail.com>
Date: Wed, 21 Mar 2012 06:58:03 +0000
Subject: net: fix napi_reuse_skb() skb reserve


From: Eric Dumazet <eric.dumazet@gmail.com>

[ 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>
---
 net/core/dev.c |    3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

--- a/net/core/dev.c
+++ b/net/core/dev.c
@@ -3634,7 +3634,8 @@ 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;