rtnetlink: introduce new RTA_ENCAP_TYPE and RTA_ENCAP attributes

This patch introduces two new RTA attributes to attach encap
data to fib routes.

Example iproute2 command to attach mpls encap data to ipv4 routes

$ip route add 10.1.1.0/30 encap mpls 200 via inet 10.1.1.1 dev swp1

Signed-off-by: Roopa Prabhu <[email protected]>
Suggested-by: Eric W. Biederman <[email protected]>
Signed-off-by: David S. Miller <[email protected]>

Author: roopa-prabhu

include/uapi/linux/rtnetlink.h

@@ -308,6 +308,8 @@ enum rtattr_type_t {
 	RTA_VIA,
 	RTA_NEWDST,
 	RTA_PREF,
+	RTA_ENCAP_TYPE,
+	RTA_ENCAP,
 	__RTA_MAX
 };