tunneling: Add generic Tunnel segmentation.

Adds generic tunneling offloading support for IPv4-UDP based
tunnels.
GSO type is added to request this offload for a skb.
netdev feature NETIF_F_UDP_TUNNEL is added for hardware offloaded
udp-tunnel support. Currently no device supports this feature,
software offload is used.

This can be used by tunneling protocols like VXLAN.

CC: Jesse Gross <jesse@nicira.com>
Signed-off-by: Pravin B Shelar <pshelar@nicira.com>
Acked-by: Stephen Hemminger <stephen@networkplumber.org>
Signed-off-by: David S. Miller <davem@davemloft.net>
diff --git a/include/linux/netdev_features.h b/include/linux/netdev_features.h
index 3dd3934..f5e797c0 100644
--- a/include/linux/netdev_features.h
+++ b/include/linux/netdev_features.h
@@ -42,9 +42,9 @@
 	NETIF_F_TSO6_BIT,		/* ... TCPv6 segmentation */
 	NETIF_F_FSO_BIT,		/* ... FCoE segmentation */
 	NETIF_F_GSO_GRE_BIT,		/* ... GRE with TSO */
-	/**/NETIF_F_GSO_LAST,		/* [can't be last bit, see GSO_MASK] */
-	NETIF_F_GSO_RESERVED2		/* ... free (fill GSO_MASK to 8 bits) */
-		= NETIF_F_GSO_LAST,
+	NETIF_F_GSO_UDP_TUNNEL_BIT,	/* ... UDP TUNNEL with TSO */
+	/**/NETIF_F_GSO_LAST =		/* last bit, see GSO_MASK */
+		NETIF_F_GSO_UDP_TUNNEL_BIT,
 
 	NETIF_F_FCOE_CRC_BIT,		/* FCoE CRC32 */
 	NETIF_F_SCTP_CSUM_BIT,		/* SCTP checksum offload */
@@ -103,6 +103,7 @@
 #define NETIF_F_RXFCS		__NETIF_F(RXFCS)
 #define NETIF_F_RXALL		__NETIF_F(RXALL)
 #define NETIF_F_GRE_GSO		__NETIF_F(GSO_GRE)
+#define NETIF_F_UDP_TUNNEL	__NETIF_F(UDP_TUNNEL)
 
 /* Features valid for ethtool to change */
 /* = all defined minus driver/device-class-related */
diff --git a/include/linux/skbuff.h b/include/linux/skbuff.h
index d7f96ff..eb2106f 100644
--- a/include/linux/skbuff.h
+++ b/include/linux/skbuff.h
@@ -316,6 +316,8 @@
 	SKB_GSO_FCOE = 1 << 5,
 
 	SKB_GSO_GRE = 1 << 6,
+
+	SKB_GSO_UDP_TUNNEL = 1 << 7,
 };
 
 #if BITS_PER_LONG > 32