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[IPV4]: Bug fix in rt_check_expire()

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- 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>
This commit is contained in:
Eric Dumazet 2005-07-05 15:00:32 -07:00 committed by David S. Miller
parent 424c4b70cc
commit bb1d23b026
1 changed files with 13 additions and 6 deletions
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19
net/ipv4/route.c
View file

@ -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;
u64 mult;
for (t = ip_rt_gc_interval << rt_hash_log; t >= 0;
t -= ip_rt_gc_timeout) {
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