net: fix napi_reuse_skb() skb reserve

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>

diff --git a/net/core/dev.c b/net/core/dev.c
index 0f3eb7d..452db70 100644 (file)
--- a/net/core/dev.c
+++ b/net/core/dev.c
@@ -3560,7 +3560,8 @@ 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;