net: Add netdev_alloc_skb_ip_align() helper

Instead of hardcoding NET_IP_ALIGN stuff in various network drivers,
we can add a helper around netdev_alloc_skb()
Signed-off-by: NEric Dumazet <eric.dumazet@gmail.com>
Signed-off-by: NDavid S. Miller <davem@davemloft.net>

include/linux/skbuff.h

@@ -1491,6 +1491,16 @@ static inline struct sk_buff *netdev_alloc_skb(struct net_device *dev,
 	return __netdev_alloc_skb(dev, length, GFP_ATOMIC);
 }
 
+static inline struct sk_buff *netdev_alloc_skb_ip_align(struct net_device *dev,
+		unsigned int length)
+{
+	struct sk_buff *skb = netdev_alloc_skb(dev, length + NET_IP_ALIGN);
+
+	if (NET_IP_ALIGN && skb)
+		skb_reserve(skb, NET_IP_ALIGN);
+	return skb;
+}
+
 extern struct page *__netdev_alloc_page(struct net_device *dev, gfp_t gfp_mask);
 
 /**