[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>

6 files changed, 49 insertions, 7 deletions

diff --git a/include/linux/icmpv6.h b/include/linux/icmpv6.h
index 0cf6c8b12caf..c771a7db9871 100644
--- a/include/linux/icmpv6.h
+++ b/include/linux/icmpv6.h
@@ -40,14 +40,16 @@ struct icmp6hdr {
                 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 @@ struct icmp6hdr {
 #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
diff --git a/include/linux/ipv6_route.h b/include/linux/ipv6_route.h
index d7c41d1d706a..f4b085c91608 100644
--- a/include/linux/ipv6_route.h
+++ b/include/linux/ipv6_route.h
@@ -27,8 +27,16 @@
 #define RTF_FLOW        0x02000000      /* flow significant route       */
 #define RTF_POLICY      0x04000000      /* policy route                 */
 
+#define RTF_PREF(pref)  ((pref) << 27)
+#define RTF_PREF_MASK   0x18000000
+
 #define RTF_LOCAL       0x80000000
 
+#ifdef __KERNEL__
+#define IPV6_EXTRACT_PREF(flag) (((flag) & RTF_PREF_MASK) >> 27)
+#define IPV6_DECODE_PREF(pref)  ((pref) ^ 2)    /* 1:low,2:med,3:high */
+#endif
+
 struct in6_rtmsg {
         struct in6_addr         rtmsg_dst;
         struct in6_addr         rtmsg_src;
diff --git a/include/net/ip6_route.h b/include/net/ip6_route.h
index 01acca06d6dd..50161322b828 100644
--- a/include/net/ip6_route.h
+++ b/include/net/ip6_route.h
@@ -87,7 +87,8 @@ extern struct rt6_info *addrconf_dst_alloc(struct inet6_dev *idev,
 extern struct rt6_info *        rt6_get_dflt_router(struct in6_addr *addr,
                                                     struct net_device *dev);
 extern struct rt6_info *        rt6_add_dflt_router(struct in6_addr *gwaddr,
-                                                    struct net_device *dev);
+                                                    struct net_device *dev,
+                                                    unsigned int pref);
 
 extern void                     rt6_purge_dflt_routers(void);
 
diff --git a/net/ipv6/Kconfig b/net/ipv6/Kconfig
index f925f206d8ff..c456ead8a4a3 100644
--- a/net/ipv6/Kconfig
+++ b/net/ipv6/Kconfig
@@ -38,6 +38,17 @@ config IPV6_PRIVACY
 
           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
diff --git a/net/ipv6/ndisc.c b/net/ipv6/ndisc.c
index 3b56be85234e..966ab6b3022e 100644
--- a/net/ipv6/ndisc.c
+++ b/net/ipv6/ndisc.c
@@ -1023,6 +1023,7 @@ static void ndisc_router_discovery(struct sk_buff *skb)
         int lifetime;
         struct ndisc_options ndopts;
         int optlen;
+        unsigned int pref = 0;
 
         __u8 * opt = (__u8 *)(ra_msg + 1);
 
@@ -1086,6 +1087,13 @@ static void ndisc_router_discovery(struct sk_buff *skb)
 
         lifetime = ntohs(ra_msg->icmph.icmp6_rt_lifetime);
 
+#ifdef CONFIG_IPV6_ROUTER_PREF
+        pref = ra_msg->icmph.icmp6_router_pref;
+        /* 10b is handled as if it were 00b (medium) */
+        if (pref == ICMPV6_ROUTER_PREF_INVALID)
+                pref = ICMPV6_ROUTER_PREF_MEDIUM;
+#endif
+
         rt = rt6_get_dflt_router(&skb->nh.ipv6h->saddr, skb->dev);
 
         if (rt)
@@ -1101,7 +1109,7 @@ static void ndisc_router_discovery(struct sk_buff *skb)
                 ND_PRINTK3(KERN_DEBUG
                            "ICMPv6 RA: adding default router.\n");
 
-                rt = rt6_add_dflt_router(&skb->nh.ipv6h->saddr, skb->dev);
+                rt = rt6_add_dflt_router(&skb->nh.ipv6h->saddr, skb->dev, pref);
                 if (rt == NULL) {
                         ND_PRINTK0(KERN_ERR
                                    "ICMPv6 RA: %s() failed to add default route.\n",
@@ -1120,6 +1128,8 @@ static void ndisc_router_discovery(struct sk_buff *skb)
                         return;
                 }
                 neigh->flags |= NTF_ROUTER;
+        } else if (rt) {
+                rt->rt6i_flags |= (rt->rt6i_flags & ~RTF_PREF_MASK) | RTF_PREF(pref);
         }
 
         if (rt)
diff --git a/net/ipv6/route.c b/net/ipv6/route.c
index 6a068e7f81f1..a7030fed1a18 100644
--- a/net/ipv6/route.c
+++ b/net/ipv6/route.c
@@ -251,8 +251,11 @@ static int rt6_score_route(struct rt6_info *rt, int oif,
         int m = rt6_check_dev(rt, oif);
         if (!m && (strict & RT6_SELECT_F_IFACE))
                 return -1;
+#ifdef CONFIG_IPV6_ROUTER_PREF
+        m |= IPV6_DECODE_PREF(IPV6_EXTRACT_PREF(rt->rt6i_flags)) << 2;
+#endif
         if (rt6_check_neigh(rt))
-                m |= 4;
+                m |= 16;
         else if (strict & RT6_SELECT_F_REACHABLE)
                 return -1;
         return m;
@@ -1256,7 +1259,8 @@ struct rt6_info *rt6_get_dflt_router(struct in6_addr *addr, struct net_device *d
 }
 
 struct rt6_info *rt6_add_dflt_router(struct in6_addr *gwaddr,
-                                     struct net_device *dev)
+                                     struct net_device *dev,
+                                     unsigned int pref)
 {
         struct in6_rtmsg rtmsg;
 
@@ -1264,7 +1268,8 @@ struct rt6_info *rt6_add_dflt_router(struct in6_addr *gwaddr,
         rtmsg.rtmsg_type = RTMSG_NEWROUTE;
         ipv6_addr_copy(&rtmsg.rtmsg_gateway, gwaddr);
         rtmsg.rtmsg_metric = 1024;
-        rtmsg.rtmsg_flags = RTF_GATEWAY | RTF_ADDRCONF | RTF_DEFAULT | RTF_UP | RTF_EXPIRES;
+        rtmsg.rtmsg_flags = RTF_GATEWAY | RTF_ADDRCONF | RTF_DEFAULT | RTF_UP | RTF_EXPIRES |
+                            RTF_PREF(pref);
 
         rtmsg.rtmsg_ifindex = dev->ifindex;