ipv6: Add support for IPsec virtual tunnel interfaces

This patch adds IPv6  support for IPsec virtual tunnel interfaces
(vti). IPsec virtual tunnel interfaces provide a routable interface
for IPsec tunnel endpoints.

Signed-off-by: Steffen Klassert <steffen.klassert@secunet.com>
diff --git a/net/ipv6/Makefile b/net/ipv6/Makefile
index 470a9c0..17bb830 100644
--- a/net/ipv6/Makefile
+++ b/net/ipv6/Makefile
@@ -36,6 +36,7 @@
 obj-$(CONFIG_IPV6_MIP6) += mip6.o
 obj-$(CONFIG_NETFILTER)	+= netfilter/
 
+obj-$(CONFIG_IPV6_VTI) += ip6_vti.o
 obj-$(CONFIG_IPV6_SIT) += sit.o
 obj-$(CONFIG_IPV6_TUNNEL) += ip6_tunnel.o
 obj-$(CONFIG_IPV6_GRE) += ip6_gre.o