packet: Add pre-defragmentation support for ipv4 fanouts.

The skb->rxhash cannot be properly computed if the
packet is a fragment.  To alleviate this, allow the
AF_PACKET client to ask for defragmentation to be
done at demux time.

Signed-off-by: David S. Miller <davem@davemloft.net>

include/linux/if_packet.h

@@ -53,6 +53,7 @@ struct sockaddr_ll {
 
 #define PACKET_FANOUT_HASH		0
 #define PACKET_FANOUT_LB		1
+#define PACKET_FANOUT_FLAG_DEFRAG	0x8000
 
 struct tpacket_stats {
 	unsigned int	tp_packets;