[1]Summary of the problem:
On IA32 system, If jiffies - b > 0x7fffffff, router can not send
redirect packet.unsigned long b = rt->u.dst.rate_last
+(ip_rt_redirect_load << rt->u.dst.rate_tokens)
[2]Full description of the problem:
In linux kernel, if time_after(jiffies, (rt->u.dst.rate_last
+(ip_rt_redirect_load << rt->u.dst.rate_tokens)) == false,
router will not send redirect packet. Here define b = rt-
>u.dst.rate_last +(ip_rt_redirect_load << rt->u.dst.rate_tokens):
1. If (jiffies - b <= 0x7fffffff), time_after(jiffies, b) == true,
router will send redirect packet.
2. If (jiffies - b > 0x7fffffff), time_after(jiffies, b) == false,
router will not send redirect packet. For example: when I add a router
after system boot, jiffies = (unsigned long)(-300000),
rt->u.dst.rate_last = 0, rt->u.dst.rate_tokens = 0, b = 20,
time_after((unsigned long)(-300000), 20) == false, send redirect packet
can not be send even if router is used in the first time.
When router send a redirect packet in time b, and before jiffies
increased to 0x7fffffff + b, router can send redirect packet.
But if a redirect packet must be send in 0x80000000+ b,
time_after(jiffies, b) == false, redirect packet will not be send also.
So between time (0x80000000+ b) to time b, router do not send redirect
packet. That is to say, in a circle of jiffies, router has 24.9 days can
not send redirect packet (0x80000000/1000/60/60/24=24.9).
jiffies b
------|------------------------------|----------------------|---->time
0x80000000+b b 0x7fffffff+b
|<--jiffies - b < 0x7fffffff-->|
Following is my patch.
Signed-off-by: Li Yewang <[EMAIL PROTECTED]>
--- linux-2.6.9/net/ipv4/route.c.org 2006-11-16 08:49:48.000000000 +0800
+++ linux-2.6.9/net/ipv4/route.c 2006-11-16 08:51:30.000000000 +0800
@@ -1196,7 +1196,8 @@ void ip_rt_send_redirect(struct sk_buff
/* No redirected packets during ip_rt_redirect_silence;
* reset the algorithm.
*/
- if (time_after(jiffies, rt->u.dst.rate_last + ip_rt_redirect_silence)
+ if (time_after(jiffies, rt->u.dst.rate_last + ip_rt_redirect_silence) ||
+ time_after(rt->u.dst.rate_last, jiffies))
rt->u.dst.rate_tokens = 0;
/* Too many ignored redirects; do not send anything
@@ -1212,7 +1213,8 @@ void ip_rt_send_redirect(struct sk_buff
*/
if (time_after(jiffies,
(rt->u.dst.rate_last +
- (ip_rt_redirect_load << rt->u.dst.rate_tokens)))) {
+ (ip_rt_redirect_load << rt->u.dst.rate_tokens))) ||
+ time_after(rt->u.dst.rate_last, jiffies)) {
icmp_send(skb, ICMP_REDIRECT, ICMP_REDIR_HOST, rt->rt_gateway);
rt->u.dst.rate_last = jiffies;
++rt->u.dst.rate_tokens;
-
To unsubscribe from this list: send the line "unsubscribe netdev" in
the body of a message to [EMAIL PROTECTED]
More majordomo info at http://vger.kernel.org/majordomo-info.html
