ip6_vti: support IP6IP tunnel processing

For IP6IP tunnel processing, the functions called will be the
same as that for IP6IP6 tunnel's. So reuse it and register it
with family == AF_INET.

Signed-off-by: Xin Long <lucien.xin@gmail.com>
Signed-off-by: Steffen Klassert <steffen.klassert@secunet.com>

net/ipv6/ip6_vti.c

@@ -1267,7 +1267,10 @@ static int __init vti6_tunnel_init(void)
 	msg = "ipv6 tunnel";
 	err = xfrm6_tunnel_register(&vti_ipv6_handler, AF_INET6);
 	if (err < 0)
-		goto vti_tunnel_failed;
+		goto vti_tunnel_ipv6_failed;
+	err = xfrm6_tunnel_register(&vti_ipv6_handler, AF_INET);
+	if (err < 0)
+		goto vti_tunnel_ip6ip_failed;
 #endif
 
 	msg = "netlink interface";
@@ -1279,8 +1282,10 @@ static int __init vti6_tunnel_init(void)
 
 rtnl_link_failed:
 #if IS_ENABLED(CONFIG_INET6_XFRM_TUNNEL)
+	err = xfrm6_tunnel_deregister(&vti_ipv6_handler, AF_INET);
+vti_tunnel_ip6ip_failed:
 	err = xfrm6_tunnel_deregister(&vti_ipv6_handler, AF_INET6);
-vti_tunnel_failed:
+vti_tunnel_ipv6_failed:
 #endif
 	xfrm6_protocol_deregister(&vti_ipcomp6_protocol, IPPROTO_COMP);
 xfrm_proto_comp_failed:
@@ -1301,6 +1306,7 @@ static void __exit vti6_tunnel_cleanup(void)
 {
 	rtnl_link_unregister(&vti6_link_ops);
 #if IS_ENABLED(CONFIG_INET6_XFRM_TUNNEL)
+	xfrm6_tunnel_deregister(&vti_ipv6_handler, AF_INET);
 	xfrm6_tunnel_deregister(&vti_ipv6_handler, AF_INET6);
 #endif
 	xfrm6_protocol_deregister(&vti_ipcomp6_protocol, IPPROTO_COMP);