ipv4: Fix PMTU update.

On current net-next-2.6, when Linux receives ICMP Type: 3, Code: 4
(Destination unreachable (Fragmentation needed)),

  icmp_unreach
    -> ip_rt_frag_needed
         (peer->pmtu_expires is set here)
    -> tcp_v4_err
         -> do_pmtu_discovery
              -> ip_rt_update_pmtu
                   (peer->pmtu_expires is already set,
                    so check_peer_pmtu is skipped.)
                   -> check_peer_pmtu

check_peer_pmtu is skipped and MTU is not updated.

To fix this, let check_peer_pmtu execute unconditionally.
And some minor fixes
1) Avoid potential peer->pmtu_expires set to be zero.
2) In check_peer_pmtu, argument of time_before is reversed.
3) check_peer_pmtu expects peer->pmtu_orig is initialized as zero,
   but not initialized.

Signed-off-by: Hiroaki SHIMODA <shimoda.hiroaki@gmail.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

1 files changed, 17 insertions, 5 deletions

diff --git a/net/ipv4/route.c b/net/ipv4/route.c
index 5655095a89e0..209989cf7d1b 100644
--- a/net/ipv4/route.c
+++ b/net/ipv4/route.c
@@ -1533,9 +1533,15 @@ unsigned short ip_rt_frag_needed(struct net *net, struct iphdr *iph,
                 if (mtu < ip_rt_min_pmtu)
                         mtu = ip_rt_min_pmtu;
                 if (!peer->pmtu_expires || mtu < peer->pmtu_learned) {
+                        unsigned long pmtu_expires;
+
+                        pmtu_expires = jiffies + ip_rt_mtu_expires;
+                        if (!pmtu_expires)
+                                pmtu_expires = 1UL;
+
                         est_mtu = mtu;
                         peer->pmtu_learned = mtu;
-                        peer->pmtu_expires = jiffies + ip_rt_mtu_expires;
+                        peer->pmtu_expires = pmtu_expires;
                 }
 
                 inet_putpeer(peer);
@@ -1549,7 +1555,7 @@ static void check_peer_pmtu(struct dst_entry *dst, struct inet_peer *peer)
 {
         unsigned long expires = peer->pmtu_expires;
 
-        if (time_before(expires, jiffies)) {
+        if (time_before(jiffies, expires)) {
                 u32 orig_dst_mtu = dst_mtu(dst);
                 if (peer->pmtu_learned < orig_dst_mtu) {
                         if (!peer->pmtu_orig)
@@ -1574,14 +1580,20 @@ static void ip_rt_update_pmtu(struct dst_entry *dst, u32 mtu)
                 if (mtu < ip_rt_min_pmtu)
                         mtu = ip_rt_min_pmtu;
                 if (!peer->pmtu_expires || mtu < peer->pmtu_learned) {
+                        unsigned long pmtu_expires;
+
+                        pmtu_expires = jiffies + ip_rt_mtu_expires;
+                        if (!pmtu_expires)
+                                pmtu_expires = 1UL;
+
                         peer->pmtu_learned = mtu;
-                        peer->pmtu_expires = jiffies + ip_rt_mtu_expires;
+                        peer->pmtu_expires = pmtu_expires;
 
                         atomic_inc(&__rt_peer_genid);
                         rt->rt_peer_genid = rt_peer_genid();
-
-                        check_peer_pmtu(dst, peer);
                 }
+                check_peer_pmtu(dst, peer);
+
                 inet_putpeer(peer);
         }
 }