net/ipv6/udp: UDP encapsulation: introduce encap_rcv hook into IPv6

Now that the sematics of udpv6_queue_rcv_skb() match IPv4's
udp_queue_rcv_skb(), introduce the UDP encap_rcv() hook for IPv6.

Signed-off-by: Benjamin LaHaise <bcrl@kvack.org>
Signed-off-by: David S. Miller <davem@davemloft.net>
diff --git a/include/net/udp.h b/include/net/udp.h
index e66fc29..065f379 100644
--- a/include/net/udp.h
+++ b/include/net/udp.h
@@ -268,4 +268,7 @@
 extern struct sk_buff *udp4_ufo_fragment(struct sk_buff *skb,
 	netdev_features_t features);
 extern void udp_encap_enable(void);
+#if IS_ENABLED(CONFIG_IPV6)
+extern void udpv6_encap_enable(void);
+#endif
 #endif	/* _UDP_H */