route: fix ICMP redirect validation

The commit f39925dbde7788cfb96419c0f092b086aa325c0f
(ipv4: Cache learned redirect information in inetpeer.)
removed some ICMP packet validations which are required by
RFC 1122, section 3.2.2.2:
...
  A Redirect message SHOULD be silently discarded if the new
  gateway address it specifies is not on the same connected
  (sub-) net through which the Redirect arrived [INTRO:2,
  Appendix A], or if the source of the Redirect is not the
  current first-hop gateway for the specified destination (see
  Section 3.3.1).

Signed-off-by: Flavio Leitner <fbl@redhat.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

diff --git a/net/ipv4/route.c b/net/ipv4/route.c
index 075212e..41557e2 100644 (file)
--- a/net/ipv4/route.c
+++ b/net/ipv4/route.c
@@ -1309,7 +1309,12 @@ static void rt_del(unsigned hash, struct rtable *rt)
 void ip_rt_redirect(__be32 old_gw, __be32 daddr, __be32 new_gw,
                    __be32 saddr, struct net_device *dev)
 {
+       int s, i;
        struct in_device *in_dev = __in_dev_get_rcu(dev);
+       struct rtable *rt;
+       __be32 skeys[2] = { saddr, 0 };
+       int    ikeys[2] = { dev->ifindex, 0 };
+       struct flowi4 fl4;
        struct inet_peer *peer;
        struct net *net;
 
@@ -1332,13 +1337,34 @@ void ip_rt_redirect(__be32 old_gw, __be32 daddr, __be32 new_gw,
                        goto reject_redirect;
        }
 
-       peer = inet_getpeer_v4(daddr, 1);
-       if (peer) {
-               peer->redirect_learned.a4 = new_gw;
+       memset(&fl4, 0, sizeof(fl4));
+       fl4.daddr = daddr;
+       for (s = 0; s < 2; s++) {
+               for (i = 0; i < 2; i++) {
+                       fl4.flowi4_oif = ikeys[i];
+                       fl4.saddr = skeys[s];
+                       rt = __ip_route_output_key(net, &fl4);
+                       if (IS_ERR(rt))
+                               continue;
 
-               inet_putpeer(peer);
+                       if (rt->dst.error || rt->dst.dev != dev ||
+                           rt->rt_gateway != old_gw) {
+                               ip_rt_put(rt);
+                               continue;
+                       }
 
-               atomic_inc(&__rt_peer_genid);
+                       if (!rt->peer)
+                               rt_bind_peer(rt, rt->rt_dst, 1);
+
+                       peer = rt->peer;
+                       if (peer) {
+                               peer->redirect_learned.a4 = new_gw;
+                               atomic_inc(&__rt_peer_genid);
+                       }
+
+                       ip_rt_put(rt);
+                       return;
+               }
        }
        return;