[IPV6]: ROUTE: Add Router Reachability Probing (RFC4191).

Signed-off-by: YOSHIFUJI Hideaki <yoshfuji@linux-ipv6.org>
Signed-off-by: David S. Miller <davem@davemloft.net>

net/ipv6/route.c

@@ -218,6 +218,42 @@ static __inline__ struct rt6_info *rt6_device_match(struct rt6_info *rt,
  return rt;
 }
 
+#ifdef CONFIG_IPV6_ROUTER_PREF
+static void rt6_probe(struct rt6_info *rt)
+{
+ struct neighbour *neigh = rt ? rt->rt6i_nexthop : NULL;
+ /*
+ * Okay, this does not seem to be appropriate
+ * for now, however, we need to check if it
+ * is really so; aka Router Reachability Probing.
+ *
+ * Router Reachability Probe MUST be rate-limited
+ * to no more than one per minute.
+ */
+ if (!neigh || (neigh->nud_state & NUD_VALID))
+ return;
+ read_lock_bh(&neigh->lock);
+ if (!(neigh->nud_state & NUD_VALID) &&
+ time_after(jiffies, neigh->updated + 60 * HZ)) {
+ struct in6_addr mcaddr;
+ struct in6_addr *target;
+
+ neigh->updated = jiffies;
+ read_unlock_bh(&neigh->lock);
+
+ target = (struct in6_addr *)&neigh->primary_key;
+ addrconf_addr_solict_mult(target, &mcaddr);
+ ndisc_send_ns(rt->rt6i_dev, NULL, target, &mcaddr, NULL);
+ } else
+ read_unlock_bh(&neigh->lock);
+}
+#else
+static inline void rt6_probe(struct rt6_info *rt)
+{
+ return;
+}
+#endif
+
 /*
  * Default Router Selection (RFC 2461 6.3.6)
  */
@@ -287,8 +323,11 @@ static struct rt6_info *rt6_select(struct rt6_info **head, int oif,
  continue;
 
  if (m > mpri) {
+ rt6_probe(match);
  match = rt;
  mpri = m;
+ } else {
+ rt6_probe(rt);
  }
  }