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Re: ip_vs_lblcr logic error causing table flushing

To: Simon Kirby <sim@xxxxxxxxxx>
Subject: Re: ip_vs_lblcr logic error causing table flushing
Cc: lvs-devel@xxxxxxxxxxxxxxx, Wensong Zhang <wensong@xxxxxxxxxxxx>
From: Simon Horman <horms@xxxxxxxxxxxx>
Date: Thu, 5 Nov 2009 12:35:13 +1100
On Wed, Nov 04, 2009 at 04:38:01PM -0800, Simon Kirby wrote:
> [ Resent with a reasonable subject and to lvs-devel :) ]
> 
> Hello!
> 
> I was noticing a significant amount of what seems/seemed to be
> destination lists with multiple entries with the lblcr LVS algorithm. 
> While tracking it down, I think I stumbled over a mistake.  In
> ip_vs_lblcr_full_check(), it appears the time check logic is reversed:
> 
>         for (i=0, j=tbl->rover; i<IP_VS_LBLCR_TAB_SIZE; i++) {
>                 j = (j + 1) & IP_VS_LBLCR_TAB_MASK;
> 
>                 write_lock(&svc->sched_lock);
>                 list_for_each_entry_safe(en, nxt, &tbl->bucket[j], list) {
>                         if 
> (time_after(en->lastuse+sysctl_ip_vs_lblcr_expiration,
>                                        now))
>                                 continue;
>                         
>                         ip_vs_lblcr_free(en);
>                         atomic_dec(&tbl->entries);
>                 }
>                 write_unlock(&svc->sched_lock);
>         }
> 
> Shouldn't this be "time_before"?  It seems that it currently nukes all
> recently-used entries every time this function is called, which seems to
> be every 30 minutes, rather than removing the not-recently-used ones.
> 
> If my reading is correct, this patch should fix it.  Am I missing
> something?
> 
> Cheers,
> 
> Simon-
> 
> diff --git a/net/netfilter/ipvs/ip_vs_lblcr.c 
> b/net/netfilter/ipvs/ip_vs_lblcr.c
> index 715b57f..937743f 100644
> --- a/net/netfilter/ipvs/ip_vs_lblcr.c
> +++ b/net/netfilter/ipvs/ip_vs_lblcr.c
> @@ -432,7 +432,7 @@ static inline void ip_vs_lblcr_full_check(struct 
> ip_vs_service *svc)
>  
>               write_lock(&svc->sched_lock);
>               list_for_each_entry_safe(en, nxt, &tbl->bucket[j], list) {
> -                     if 
> (time_after(en->lastuse+sysctl_ip_vs_lblcr_expiration,
> +                     if 
> (time_before(en->lastuse+sysctl_ip_vs_lblcr_expiration,
>                                      now))
>                               continue;
>  

Hi Simon,

your analysis seems correct to me. Could you supply a Signed-off-line
with the patch and I'll see about getting it merged.

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