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>

diff --git a/net/ipv4/inetpeer.c b/net/ipv4/inetpeer.c
index 6442c35..86b1d08 100644 (file)
--- a/net/ipv4/inetpeer.c
+++ b/net/ipv4/inetpeer.c
@@ -511,6 +511,7 @@ struct inet_peer *inet_getpeer(struct inetpeer_addr *daddr, int create)
                p->rate_tokens = 0;
                p->rate_last = 0;
                p->pmtu_expires = 0;
+               p->pmtu_orig = 0;
                memset(&p->redirect_learned, 0, sizeof(p->redirect_learned));
                INIT_LIST_HEAD(&p->unused);
 

diff --git a/net/ipv4/route.c b/net/ipv4/route.c
index 5655095..209989c 100644 (file)
--- 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);
        }
 }