[IPV6]: ROUTE: Add support for Router Preference (RFC4191).

Signed-off-by: YOSHIFUJI Hideaki <yoshfuji@linux-ipv6.org>
Signed-off-by: David S. Miller <davem@davemloft.net>
diff --git a/net/ipv6/Kconfig b/net/ipv6/Kconfig
index f925f20..c456ead 100644
--- a/net/ipv6/Kconfig
+++ b/net/ipv6/Kconfig
@@ -38,6 +38,17 @@
 
 	  See <file:Documentation/networking/ip-sysctl.txt> for details.
 
+config IPV6_ROUTER_PREF
+	bool "IPv6: Router Preference (RFC 4191) support"
+	depends on IPV6
+	---help---
+	  Router Preference is an optional extension to the Router
+	  Advertisement message to improve the ability of hosts
+	  to pick more appropriate router, especially when the hosts
+	  is placed in a multi-homed network.
+
+	  If unsure, say N.
+
 config INET6_AH
 	tristate "IPv6: AH transformation"
 	depends on IPV6