[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/include/linux/icmpv6.h b/include/linux/icmpv6.h
index 0cf6c8b..c771a7d 100644
--- a/include/linux/icmpv6.h
+++ b/include/linux/icmpv6.h
@@ -40,14 +40,16 @@
                 struct icmpv6_nd_ra {
 			__u8		hop_limit;
 #if defined(__LITTLE_ENDIAN_BITFIELD)
-			__u8		reserved:6,
+			__u8		reserved:4,
+					router_pref:2,
 					other:1,
 					managed:1;
 
 #elif defined(__BIG_ENDIAN_BITFIELD)
 			__u8		managed:1,
 					other:1,
-					reserved:6;
+					router_pref:2,
+					reserved:4;
 #else
 #error	"Please fix <asm/byteorder.h>"
 #endif
@@ -70,8 +72,13 @@
 #define icmp6_addrconf_managed	icmp6_dataun.u_nd_ra.managed
 #define icmp6_addrconf_other	icmp6_dataun.u_nd_ra.other
 #define icmp6_rt_lifetime	icmp6_dataun.u_nd_ra.rt_lifetime
+#define icmp6_router_pref	icmp6_dataun.u_nd_ra.router_pref
 };
 
+#define ICMPV6_ROUTER_PREF_LOW		0x3
+#define ICMPV6_ROUTER_PREF_MEDIUM	0x0
+#define ICMPV6_ROUTER_PREF_HIGH		0x1
+#define ICMPV6_ROUTER_PREF_INVALID	0x2
 
 #define ICMPV6_DEST_UNREACH		1
 #define ICMPV6_PKT_TOOBIG		2