ipv4: Kill routes during PMTU/redirect updates.

Mark them obsolete so there will be a re-lookup to fetch the
FIB nexthop exception info.

Signed-off-by: David S. Miller <davem@davemloft.net>

2 files changed, 30 insertions, 12 deletions

diff --git a/include/net/dst.h b/include/net/dst.h
index 0df661a0c29..baf59789006 100644
--- a/include/net/dst.h
+++ b/include/net/dst.h
@@ -78,6 +78,7 @@ struct dst_entry {
 #define DST_OBSOLETE_NONE       0
 #define DST_OBSOLETE_DEAD       2
 #define DST_OBSOLETE_FORCE_CHK  -1
+#define DST_OBSOLETE_KILL       -2
         unsigned short          header_len;     /* more space at head required */
         unsigned short          trailer_len;    /* space to reserve at tail */
 #ifdef CONFIG_IP_ROUTE_CLASSID
diff --git a/net/ipv4/route.c b/net/ipv4/route.c
index 50d2498c928..d52f7699c2f 100644
--- a/net/ipv4/route.c
+++ b/net/ipv4/route.c
@@ -673,7 +673,8 @@ out_unlock:
         return;
 }
 
-static void __ip_do_redirect(struct rtable *rt, struct sk_buff *skb, struct flowi4 *fl4)
+static void __ip_do_redirect(struct rtable *rt, struct sk_buff *skb, struct flowi4 *fl4,
+                             bool kill_route)
 {
         __be32 new_gw = icmp_hdr(skb)->un.gateway;
         __be32 old_gw = ip_hdr(skb)->saddr;
@@ -728,8 +729,8 @@ static void __ip_do_redirect(struct rtable *rt, struct sk_buff *skb, struct flow
                                 update_or_create_fnhe(nh, fl4->daddr, new_gw,
                                                       0, 0);
                         }
-                        rt->rt_gateway = new_gw;
-                        rt->rt_flags |= RTCF_REDIRECTED;
+                        if (kill_route)
+                                rt->dst.obsolete = DST_OBSOLETE_KILL;
                         call_netevent_notifiers(NETEVENT_NEIGH_UPDATE, n);
                 }
                 neigh_release(n);
@@ -760,7 +761,7 @@ static void ip_do_redirect(struct dst_entry *dst, struct sock *sk, struct sk_buf
         rt = (struct rtable *) dst;
 
         ip_rt_build_flow_key(&fl4, sk, skb);
-        __ip_do_redirect(rt, skb, &fl4);
+        __ip_do_redirect(rt, skb, &fl4, true);
 }
 
 static struct dst_entry *ipv4_negative_advice(struct dst_entry *dst)
@@ -919,7 +920,7 @@ out:	kfree_skb(skb);
         return 0;
 }
 
-static void __ip_rt_update_pmtu(struct rtable *rt, struct flowi4 *fl4, u32 mtu)
+static u32 __ip_rt_update_pmtu(struct rtable *rt, struct flowi4 *fl4, u32 mtu)
 {
         struct fib_result res;
 
@@ -932,8 +933,7 @@ static void __ip_rt_update_pmtu(struct rtable *rt, struct flowi4 *fl4, u32 mtu)
                 update_or_create_fnhe(nh, fl4->daddr, 0, mtu,
                                       jiffies + ip_rt_mtu_expires);
         }
-        rt->rt_pmtu = mtu;
-        dst_set_expires(&rt->dst, ip_rt_mtu_expires);
+        return mtu;
 }
 
 static void ip_rt_update_pmtu(struct dst_entry *dst, struct sock *sk,
@@ -943,7 +943,14 @@ static void ip_rt_update_pmtu(struct dst_entry *dst, struct sock *sk,
         struct flowi4 fl4;
 
         ip_rt_build_flow_key(&fl4, sk, skb);
-        __ip_rt_update_pmtu(rt, &fl4, mtu);
+        mtu = __ip_rt_update_pmtu(rt, &fl4, mtu);
+
+        if (!rt->rt_pmtu) {
+                dst->obsolete = DST_OBSOLETE_KILL;
+        } else {
+                rt->rt_pmtu = mtu;
+                dst_set_expires(&rt->dst, ip_rt_mtu_expires);
+        }
 }
 
 void ipv4_update_pmtu(struct sk_buff *skb, struct net *net, u32 mtu,
@@ -989,7 +996,7 @@ void ipv4_redirect(struct sk_buff *skb, struct net *net,
                          RT_TOS(iph->tos), protocol, mark, flow_flags);
         rt = __ip_route_output_key(net, &fl4);
         if (!IS_ERR(rt)) {
-                __ip_do_redirect(rt, skb, &fl4);
+                __ip_do_redirect(rt, skb, &fl4, false);
                 ip_rt_put(rt);
         }
 }
@@ -1004,7 +1011,7 @@ void ipv4_sk_redirect(struct sk_buff *skb, struct sock *sk)
         __build_flow_key(&fl4, sk, iph, 0, 0, 0, 0, 0);
         rt = __ip_route_output_key(sock_net(sk), &fl4);
         if (!IS_ERR(rt)) {
-                __ip_do_redirect(rt, skb, &fl4);
+                __ip_do_redirect(rt, skb, &fl4, false);
                 ip_rt_put(rt);
         }
 }
@@ -1014,7 +1021,15 @@ static struct dst_entry *ipv4_dst_check(struct dst_entry *dst, u32 cookie)
 {
         struct rtable *rt = (struct rtable *) dst;
 
-        if (rt_is_expired(rt))
+        /* All IPV4 dsts are created with ->obsolete set to the value
+         * DST_OBSOLETE_FORCE_CHK which forces validation calls down
+         * into this function always.
+         *
+         * When a PMTU/redirect information update invalidates a
+         * route, this is indicated by setting obsolete to
+         * DST_OBSOLETE_KILL.
+         */
+        if (dst->obsolete == DST_OBSOLETE_KILL || rt_is_expired(rt))
                 return NULL;
         return dst;
 }
@@ -1186,8 +1201,10 @@ restart:
                                 dst_set_expires(&rt->dst, diff);
                         }
                 }
-                if (gw)
+                if (gw) {
+                        rt->rt_flags |= RTCF_REDIRECTED;
                         rt->rt_gateway = gw;
+                }
                 fnhe->fnhe_stamp = jiffies;
                 break;
         }