[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>

1 files changed, 14 insertions, 7 deletions

diff --git a/net/ipv4/route.c b/net/ipv4/route.c
index 9fcbb1b0a8d6..726ea5e8180a 100644
--- 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