[IPV4]: Bug fix in rt_check_expire()

- rt_check_expire() fixes (an overflow occured if size of the hash
  was >= 65536)

reminder of the bugfix:

The rt_check_expire() has a serious problem on machines with large
route caches, and a standard HZ value of 1000.

With default values, ie ip_rt_gc_interval = 60*HZ = 60000 ;

the loop count :

     for (t = ip_rt_gc_interval << rt_hash_log; t >= 0;

overflows (t is a 31 bit value) as soon rt_hash_log is >= 16  (65536
slots in route cache hash table).

In this case, rt_check_expire() does nothing at all

Signed-off-by: Eric Dumazet <dada1@cosmosbay.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

diff --git a/net/ipv4/route.c b/net/ipv4/route.c
index 9fcbb1b0a8d6f57f40b50699a3d17b3468fbfda1..726ea5e8180a1275e58ebc919490f24516c37d14 100644 (file)
--- a/net/ipv4/route.c
+++ b/net/ipv4/route.c
@@ -54,7 +54,7 @@
  *             Marc Boucher    :       routing by fwmark
  *     Robert Olsson           :       Added rt_cache statistics
  *     Arnaldo C. Melo         :       Convert proc stuff to seq_file
- *     Eric Dumazet            :       hashed spinlocks
+ *     Eric Dumazet            :       hashed spinlocks and rt_check_expire() fixes.
  *
  *             This program is free software; you can redistribute it and/or
  *             modify it under the terms of the GNU General Public License
@@ -606,18 +606,25 @@ static struct rtable **rt_remove_balanced_route(struct rtable **chain_head,
 /* This runs via a timer and thus is always in BH context. */
 static void rt_check_expire(unsigned long dummy)
 {
-       static int rover;
-       int i = rover, t;
+       static unsigned int rover;
+       unsigned int i = rover, goal;
        struct rtable *rth, **rthp;
        unsigned long now = jiffies;
-
-       for (t = ip_rt_gc_interval << rt_hash_log; t >= 0;
-            t -= ip_rt_gc_timeout) {
+       u64 mult;
+
+       mult = ((u64)ip_rt_gc_interval) << rt_hash_log;
+       if (ip_rt_gc_timeout > 1)
+               do_div(mult, ip_rt_gc_timeout);
+       goal = (unsigned int)mult;
+       if (goal > rt_hash_mask) goal = rt_hash_mask + 1;
+       for (; goal > 0; goal--) {
                unsigned long tmo = ip_rt_gc_timeout;
 
                i = (i + 1) & rt_hash_mask;
                rthp = &rt_hash_table[i].chain;
 
+               if (*rthp == 0)
+                       continue;
                spin_lock(rt_hash_lock_addr(i));
                while ((rth = *rthp) != NULL) {
                        if (rth->u.dst.expires) {
@@ -658,7 +665,7 @@ static void rt_check_expire(unsigned long dummy)
                        break;
        }
        rover = i;
-       mod_timer(&rt_periodic_timer, now + ip_rt_gc_interval);
+       mod_timer(&rt_periodic_timer, jiffies + ip_rt_gc_interval);
 }
 
 /* This can run from both BH and non-BH contexts, the latter