ipv6: fix route lookup in addrconf_prefix_rcv()

The route lookup to find a previously auto-configured route for a prefixes used
to use rt6_lookup(), with the prefix from the RA used as an address. However,
that kind of lookup ignores routing tables, the prefix length and route flags,
so when there were other matching routes, even in different tables and/or with
a different prefix length, the wrong route would be manipulated.

Now, a new function "addrconf_get_prefix_route()" is used for the route lookup,
which searches in RT6_TABLE_PREFIX and takes the prefix-length and route flags
into account.
Signed-off-by: Andreas Hofmeister <andi@collax.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

net/ipv6/addrconf.c

@@ -1713,6 +1713,40 @@ addrconf_prefix_route(struct in6_addr *pfx, int plen, struct net_device *dev,
 	ip6_route_add(&cfg);
 }
 
+
+static struct rt6_info *addrconf_get_prefix_route(const struct in6_addr *pfx,
+						  int plen,
+						  const struct net_device *dev,
+						  u32 flags, u32 noflags)
+{
+	struct fib6_node *fn;
+	struct rt6_info *rt = NULL;
+	struct fib6_table *table;
+
+	table = fib6_get_table(dev_net(dev), RT6_TABLE_PREFIX);
+	if (table == NULL)
+		return NULL;
+
+	write_lock_bh(&table->tb6_lock);
+	fn = fib6_locate(&table->tb6_root, pfx, plen, NULL, 0);
+	if (!fn)
+		goto out;
+	for (rt = fn->leaf; rt; rt = rt->dst.rt6_next) {
+		if (rt->rt6i_dev->ifindex != dev->ifindex)
+			continue;
+		if ((rt->rt6i_flags & flags) != flags)
+			continue;
+		if ((noflags != 0) && ((rt->rt6i_flags & flags) != 0))
+			continue;
+		dst_hold(&rt->dst);
+		break;
+	}
+out:
+	write_unlock_bh(&table->tb6_lock);
+	return rt;
+}
+
+
 /* Create "default" multicast route to the interface */
 
 static void addrconf_add_mroute(struct net_device *dev)
@@ -1842,10 +1876,13 @@ void addrconf_prefix_rcv(struct net_device *dev, u8 *opt, int len)
 		if (addrconf_finite_timeout(rt_expires))
 			rt_expires *= HZ;
 
-		rt = rt6_lookup(net, &pinfo->prefix, NULL,
-				dev->ifindex, 1);
+		rt = addrconf_get_prefix_route(&pinfo->prefix,
+					       pinfo->prefix_len,
+					       dev,
+					       RTF_ADDRCONF | RTF_PREFIX_RT,
+					       RTF_GATEWAY | RTF_DEFAULT);
 
-		if (rt && addrconf_is_prefix_route(rt)) {
+		if (rt) {
 			/* Autoconf prefix route */
 			if (valid_lft == 0) {
 				ip6_del_rt(rt);