udp: Add GRO functions to UDP socket

This patch adds GRO functions (gro_receive and gro_complete) to UDP
sockets. udp_gro_receive is changed to perform socket lookup on a
packet. If a socket is found the related GRO functions are called.

This features obsoletes using UDP offload infrastructure for GRO
(udp_offload). This has the advantage of not being limited to provide
offload on a per port basis, GRO is now applied to whatever individual
UDP sockets are bound to.  This also allows the possbility of
"application defined GRO"-- that is we can attach something like
a BPF program to a UDP socket to perfrom GRO on an application
layer protocol.

Signed-off-by: Tom Herbert <tom@herbertland.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
diff --git a/net/ipv6/udp_offload.c b/net/ipv6/udp_offload.c
index 2b0fbe6..5429f6b 100644
--- a/net/ipv6/udp_offload.c
+++ b/net/ipv6/udp_offload.c
@@ -153,7 +153,7 @@
 
 skip:
 	NAPI_GRO_CB(skb)->is_ipv6 = 1;
-	return udp_gro_receive(head, skb, uh);
+	return udp_gro_receive(head, skb, uh, udp6_lib_lookup_skb);
 
 flush:
 	NAPI_GRO_CB(skb)->flush = 1;
@@ -173,7 +173,7 @@
 		skb_shinfo(skb)->gso_type |= SKB_GSO_UDP_TUNNEL;
 	}
 
-	return udp_gro_complete(skb, nhoff);
+	return udp_gro_complete(skb, nhoff, udp6_lib_lookup_skb);
 }
 
 static const struct net_offload udpv6_offload = {
@@ -184,7 +184,12 @@
 	},
 };
 
-int __init udp_offload_init(void)
+int udpv6_offload_init(void)
 {
 	return inet6_add_offload(&udpv6_offload, IPPROTO_UDP);
 }
+
+int udpv6_offload_exit(void)
+{
+	return inet6_del_offload(&udpv6_offload, IPPROTO_UDP);
+}