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>

1 files changed, 31 insertions, 5 deletions

diff --git a/net/ipv4/route.c b/net/ipv4/route.c
index 075212e41b83..41557e2bb56e 100644
--- 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;