route: Per route IP tunnel metadata via lightweight tunnel

This introduces a new IP tunnel lightweight tunnel type which allows
to specify IP tunnel instructions per route. Only IPv4 is supported
at this point.

Signed-off-by: Thomas Graf <tgraf@suug.ch>
Signed-off-by: David S. Miller <davem@davemloft.net>
diff --git a/include/net/dst_metadata.h b/include/net/dst_metadata.h
index e843937..7b03068 100644
--- a/include/net/dst_metadata.h
+++ b/include/net/dst_metadata.h
@@ -23,13 +23,23 @@
 	return NULL;
 }
 
-static inline struct ip_tunnel_info *skb_tunnel_info(struct sk_buff *skb)
+static inline struct ip_tunnel_info *skb_tunnel_info(struct sk_buff *skb,
+						     int family)
 {
 	struct metadata_dst *md_dst = skb_metadata_dst(skb);
+	struct rtable *rt;
 
 	if (md_dst)
 		return &md_dst->u.tun_info;
 
+	switch (family) {
+	case AF_INET:
+		rt = (struct rtable *)skb_dst(skb);
+		if (rt && rt->rt_lwtstate)
+			return lwt_tun_info(rt->rt_lwtstate);
+		break;
+	}
+
 	return NULL;
 }