Re: [PATCH] Re: iproute2 / tbf with large burst seems broken again

[David Miller <davem@davemloft.net>]

From: Jarek Poplawski <jarkao2@gmail.com>
Date: Wed, 26 Aug 2009 23:59:56 +0200

> Denys Fedoryschenko wrote, On 08/25/2009 02:18 PM:
> ...
>> Just maybe good idea in next kernels to document this or handle overflow, that 
>> it will give warning in kernel. Otherwise user will have non-functional qdisc 
>> that will not pass traffic.
> 
> OK, if this patch works for you send your Tested-by, please.

Denys, please give Jarek's patch some testing and let us know
if it triggers properly for you.

> Thanks,
> Jarek P.
> ---------------->
> pkt_sched: Warn on tokens overflow in tbf_dequeue
> 
> After recent change of scheduling resolution some "extreme" configs
> can cause token overflows with stalls. This patch warns when tokens
> were negative before accounting for a packet length.
> 
> Reported-by: Denys Fedoryschenko <denys@visp.net.lb>
> Signed-off-by: Jarek Poplawski <jarkao2@gmail.com>
> ---
> 
>  net/sched/sch_tbf.c |    6 ++++++
>  1 files changed, 6 insertions(+), 0 deletions(-)
> 
> diff --git a/net/sched/sch_tbf.c b/net/sched/sch_tbf.c
> index e22dfe8..ef191c4 100644
> --- a/net/sched/sch_tbf.c
> +++ b/net/sched/sch_tbf.c
> @@ -191,6 +191,12 @@ static struct sk_buff *tbf_dequeue(struct Qdisc* sch)
>  			return skb;
>  		}
>  
> +		if (unlikely((long)(toks + L2T(q, len)) < 0 ||
> +			     (long)(ptoks + L2T_P(q, len) < 0)))
> +			if (net_ratelimit())
> +				pr_warning("tbf: tokens overflow;"
> +					   " fix limits.\n");
> +
>  		qdisc_watchdog_schedule(&q->watchdog,
>  					now + max_t(long, -toks, -ptoks));
>  
> --
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