linux-kernel - Re: Android netfilter patches (xt

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Date:	Tue, 26 Mar 2013 13:45:52 +0100
From:	Pablo Neira Ayuso <pablo@...filter.org>
To:	dmitry pervushin <dpervushin@...il.com>
Cc:	linux-kernel@...r.kernel.org, netfilter-devel@...r.kernel.org
Subject: Re: Android netfilter patches (xt_IDLETIMER) [1/3]

Hi Dmitry,

On Mon, Mar 25, 2013 at 11:09:06PM +0100, dmitry pervushin wrote:
> Fix the case in which timer has expired and we refresh it without
> sending the notification
>
> Signed-off-by: Ashish Sharma <ashishsharma@...gle.com>
> Signed-off-by: JP Abgrall <jpa@...gle.com>
> Signed-off-by: John Stultz <john.stultz@...aro.org>
> Signed-off-by: dmitry pervushin <dpervushin@...il.com>
>
> diff --git a/net/netfilter/xt_IDLETIMER.c b/net/netfilter/xt_IDLETIMER.c
> index f407ebc1..3540c04 100644
> --- a/net/netfilter/xt_IDLETIMER.c
> +++ b/net/netfilter/xt_IDLETIMER.c
> @@ -168,14 +168,22 @@ static unsigned int idletimer_tg_target(struct sk_buff *skb,
>  					 const struct xt_action_param *par)
>  {
>  	const struct idletimer_tg_info *info = par->targinfo;
> +	unsigned long now = jiffies;
>
>  	pr_debug("resetting timer %s, timeout period %u\n",
>  		 info->label, info->timeout);
>
>  	BUG_ON(!info->timer);
>
> +	if (time_before(info->timer->timer.expires, now)) {
> +		schedule_work(&info->timer->work);
> +		pr_debug("Starting timer %s (Expired, Jiffies): %lu, %lu\n",
> +			 info->label, info->timer->timer.expires, now);
> +	}

Hm, this seems to me like a new feature. With this change, IDLETIMER
is sending notifications once the timer becomes active again.

> +
> +	/* TODO: Avoid modifying timers on each packet */

Regarding this TODO, you can adapt this code snippet for this:

unsigned long newtime = jiffies + extra_jiffies;

/* Only update the timeout if the new timeout is at
 * least HZ jiffies from the old timeout. Need del_timer
 * for race avoidance (may already be dying).
 */
if (newtime - ct->timeout.expires >= HZ)
        mod_timer_pending(&ct->timeout, newtime);

We're using it in nf_conntrack.

This should come in a separate patch.

>  	mod_timer(&info->timer->timer,
> -		  msecs_to_jiffies(info->timeout * 1000) + jiffies);
> +		  msecs_to_jiffies(info->timeout * 1000) + now);
>
>  	return XT_CONTINUE;
>  }
> @@ -184,6 +192,7 @@ static int idletimer_tg_checkentry(const struct xt_tgchk_param *par)
>  {
>  	struct idletimer_tg_info *info = par->targinfo;
>  	int ret;
> +	unsigned long now = jiffies;
>
>  	pr_debug("checkentry targinfo%s\n", info->label);
>
> @@ -204,8 +213,13 @@ static int idletimer_tg_checkentry(const struct xt_tgchk_param *par)
>  	info->timer = __idletimer_tg_find_by_label(info->label);
>  	if (info->timer) {
>  		info->timer->refcnt++;
> +		if (time_before(info->timer->timer.expires, now)) {
> +			schedule_work(&info->timer->work);
> +			pr_debug("Starting Checkentry timer (Expired, Jiffies): %lu, %lu\n",
> +				info->timer->timer.expires, now);
> +		}
>  		mod_timer(&info->timer->timer,
> -			  msecs_to_jiffies(info->timeout * 1000) + jiffies);
> +			  msecs_to_jiffies(info->timeout * 1000) + now);
>
>  		pr_debug("increased refcnt of timer %s to %u\n",
>  			 info->label, info->timer->refcnt);
--
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