net: Add GRO support for UDP encapsulating protocols

Add GRO handlers for protocols that do UDP encapsulation, with the intent of
being able to coalesce packets which encapsulate packets belonging to
the same TCP session.

For GRO purposes, the destination UDP port takes the role of the ether type
field in the ethernet header or the next protocol in the IP header.

The UDP GRO handler will only attempt to coalesce packets whose destination
port is registered to have gro handler.

Use a mark on the skb GRO CB data to disallow (flush) running the udp gro receive
code twice on a packet. This solves the problem of udp encapsulated packets whose
inner VM packet is udp and happen to carry a port which has registered offloads.

Signed-off-by: Shlomo Pongratz <shlomop@mellanox.com>
Signed-off-by: Or Gerlitz <ogerlitz@mellanox.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
diff --git a/include/linux/netdevice.h b/include/linux/netdevice.h
index 83ce2ae..c310229 100644
--- a/include/linux/netdevice.h
+++ b/include/linux/netdevice.h
@@ -1675,7 +1675,10 @@
 	unsigned long age;
 
 	/* Used in ipv6_gro_receive() */
-	int	proto;
+	u16	proto;
+
+	/* Used in udp_gro_receive */
+	u16	udp_mark;
 
 	/* used to support CHECKSUM_COMPLETE for tunneling protocols */
 	__wsum	csum;
@@ -1714,6 +1717,11 @@
 	struct list_head	 list;
 };
 
+struct udp_offload {
+	__be16			 port;
+	struct offload_callbacks callbacks;
+};
+
 /* often modified stats are per cpu, other are shared (netdev->stats) */
 struct pcpu_sw_netstats {
 	u64     rx_packets;