[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>

3 files changed, 30 insertions, 4 deletions

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;