Date:	Tue, 26 Mar 2013 14:24:19 +0100
From:	Pablo Neira Ayuso <pablo@...filter.org>
To:	dmitry pervushin <dpervushin@...il.com>
Cc:	netfilter-devel@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: Android netfilter patches (xt_IDLETIMER) [2/3]

On Mon, Mar 25, 2013 at 11:09:16PM +0100, dmitry pervushin wrote:
> Send notifications when the label becomes active after an idle period.
> Send netlink message notifications in addition to sysfs notifications.
> Using a uevent with
>       subsystem=xt_idletimer
>       INTERFACE=...
>       STATE={active,inactive}
> 
> This is backport from common android-3.0
> commit: beb914e987cbbd368988d2b94a6661cb907c4d5a
> with uevent support instead of a new netlink message type.
> 
> Cc: netdev@...r.kernel.org
> Cc: JP Abgrall <jpa@...gle.com>
> Cc: Ashish Sharma <ashishsharma@...gle.com>
> Cc: Peter P Waskiewicz Jr <peter.p.waskiewicz.jr@...el.com>
> 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/include/uapi/linux/netfilter/xt_IDLETIMER.h b/include/uapi/linux/netfilter/xt_IDLETIMER.h
> index 208ae93..96ed520 100644
> --- a/include/uapi/linux/netfilter/xt_IDLETIMER.h
> +++ b/include/uapi/linux/netfilter/xt_IDLETIMER.h
> @@ -42,4 +42,18 @@ struct idletimer_tg_info {
>  	struct idletimer_tg *timer __attribute__((aligned(8)));
>  };
> 
> +#define NL_EVENT_TYPE_INACTIVE 0
> +#define NL_EVENT_TYPE_ACTIVE 1

This definitions above are not unused.

> +struct idletimer_tg_info_v1 {
> +	__u32 timeout;
> +
> +	char label[MAX_IDLETIMER_LABEL_SIZE];
> +
> +	/* Use netlink messages for notification in addition to sysfs */
> +	__u8 send_nl_msg;

I think it's better if you add __u32 flags here instead, and you
define XT_IDLETIMER_F_NL (1 << 0). This can be used later on to extend
IDLETIMER more easily if needed.

> +	/* for kernel module internal use only */
> +	struct idletimer_tg *timer __attribute__((aligned(8)));
> +};
>  #endif
> diff --git a/net/netfilter/xt_IDLETIMER.c b/net/netfilter/xt_IDLETIMER.c
> index 3540c04..cbf059c 100644
> --- a/net/netfilter/xt_IDLETIMER.c
> +++ b/net/netfilter/xt_IDLETIMER.c
> @@ -40,6 +40,11 @@
>  #include <linux/kobject.h>
>  #include <linux/workqueue.h>
>  #include <linux/sysfs.h>
> +#include <linux/skbuff.h>
> +#include <net/net_namespace.h>
> +#include <uapi/linux/netfilter/xt_IDLETIMER.h>
> +
> +#define NLMSG_MAX_SIZE 64

Better rename this to IDLETIME_BUFSIZ, so people grepping for NLMSG_
stuff don't hit this.

>  struct idletimer_tg_attr {
>  	struct attribute attr;
> @@ -56,6 +61,8 @@ struct idletimer_tg {
>  	struct idletimer_tg_attr attr;
> 
>  	unsigned int refcnt;
> +	bool send_nl_msg;
> +	bool active;

I think you can use timer_pending instead of this new active variable.

>  };
> 
>  static LIST_HEAD(idletimer_tg_list);
> @@ -63,6 +70,30 @@ static DEFINE_MUTEX(list_mutex);
> 
>  static struct kobject *idletimer_tg_kobj;
> 
> +static void notify_netlink_uevent(const char *iface, struct idletimer_tg *timer)
> +{
> +	char iface_msg[NLMSG_MAX_SIZE];
> +	char state_msg[NLMSG_MAX_SIZE];
> +	char *envp[] = { iface_msg, state_msg, NULL };
> +	int res;
> +
> +	res = snprintf(iface_msg, NLMSG_MAX_SIZE, "INTERFACE=%s",
> +		       iface);
> +	if (NLMSG_MAX_SIZE <= res) {
> +		pr_err("message too long (%d)", res);
> +		return;
> +	}
> +	res = snprintf(state_msg, NLMSG_MAX_SIZE, "STATE=%s",
> +		       timer->active ? "active" : "inactive");
> +	if (NLMSG_MAX_SIZE <= res) {
> +		pr_err("message too long (%d)", res);
> +		return;
> +	}
> +	pr_debug("putting nlmsg: <%s> <%s>\n", iface_msg, state_msg);
> +	kobject_uevent_env(idletimer_tg_kobj, KOBJ_CHANGE, envp);
> +	return;
> +}
> +
>  static
>  struct idletimer_tg *__idletimer_tg_find_by_label(const char *label)
>  {
> @@ -83,6 +114,7 @@ static ssize_t idletimer_tg_show(struct kobject *kobj, struct attribute *attr,
>  {
>  	struct idletimer_tg *timer;
>  	unsigned long expires = 0;
> +	unsigned long now = jiffies;
> 
>  	mutex_lock(&list_mutex);
> 
> @@ -92,11 +124,15 @@ static ssize_t idletimer_tg_show(struct kobject *kobj, struct attribute *attr,
> 
>  	mutex_unlock(&list_mutex);
> 
> -	if (time_after(expires, jiffies))
> +	if (time_after(expires, now))
>  		return sprintf(buf, "%u\n",
> -			       jiffies_to_msecs(expires - jiffies) / 1000);
> +			       jiffies_to_msecs(expires - now) / 1000);
> 
> -	return sprintf(buf, "0\n");
> +	if (timer->send_nl_msg)
> +		return sprintf(buf, "0 %d\n",
> +			jiffies_to_msecs(now - expires) / 1000);
> +	else
> +		return sprintf(buf, "0\n");
>  }
> 
>  static void idletimer_tg_work(struct work_struct *work)
> @@ -105,6 +141,9 @@ static void idletimer_tg_work(struct work_struct *work)
>  						  work);
> 
>  	sysfs_notify(idletimer_tg_kobj, NULL, timer->attr.attr.name);
> +
> +	if (timer->send_nl_msg)
> +		notify_netlink_uevent(timer->attr.attr.name, timer);
>  }
> 
>  static void idletimer_tg_expired(unsigned long data)
> @@ -113,12 +152,15 @@ static void idletimer_tg_expired(unsigned long data)
> 
>  	pr_debug("timer %s expired\n", timer->attr.attr.name);
> 
> +	timer->active = false;
>  	schedule_work(&timer->work);
>  }
> 
> -static int idletimer_tg_create(struct idletimer_tg_info *info)
> +static int idletimer_tg_create(void *pinfo, int revision)
>  {
>  	int ret;
> +	struct idletimer_tg_info *info = (struct idletimer_tg_info*)pinfo;
> +	struct idletimer_tg_info_v1 *info1 = (struct idletimer_tg_info_v1*)pinfo;
> 
>  	info->timer = kmalloc(sizeof(*info->timer), GFP_KERNEL);
>  	if (!info->timer) {
> @@ -144,6 +186,10 @@ static int idletimer_tg_create(struct idletimer_tg_info *info)
> 
>  	setup_timer(&info->timer->timer, idletimer_tg_expired,
>  		    (unsigned long) info->timer);
> +	info->timer->send_nl_msg = false;

This won't work. info->timer points to the wrong offset if revision 1
is used.

You can add add some shim code for this, eg.

static int idletimer_tg_checkentry_v0(const struct xt_tgchk_param *par)
{
        struct idletimer_tg_info *info = par->targinfo;
        struct idletimer_tg_info_v1 info_v1 = {
                .timeout = info->timeout,
        };
        memcpy(&info_v1.label, info->label, MAX_IDLETIMER_LABEL_SIZE);

        return idletimer_tg_check(par, &info_v1);
}

static int idletimer_tg_checkentry_v1(const struct xt_tgchk_param *par)
{
        return idletimer_tg_check(par, par->targinfo);
}

I know, it's ugly, but this is how our limited revision support works.

See net/netfilter/xt_CT.c in the new current linux git tree for
instance.

> +	info->timer->active = true;
> +	if (revision == 1 && info1->send_nl_msg)
> +		info->timer->send_nl_msg = true;
>  	info->timer->refcnt = 1;
> 
>  	mod_timer(&info->timer->timer,
> @@ -175,6 +221,8 @@ static unsigned int idletimer_tg_target(struct sk_buff *skb,
> 
>  	BUG_ON(!info->timer);
> 
> +	info->timer->active = true;
> +
>  	if (time_before(info->timer->timer.expires, now)) {
>  		schedule_work(&info->timer->work);
>  		pr_debug("Starting timer %s (Expired, Jiffies): %lu, %lu\n",
> @@ -188,7 +236,7 @@ static unsigned int idletimer_tg_target(struct sk_buff *skb,
>  	return XT_CONTINUE;
>  }
> 
> -static int idletimer_tg_checkentry(const struct xt_tgchk_param *par)
> +static int idletimer_tg_checkentry_rev(const struct xt_tgchk_param *par, int revision)
>  {
>  	struct idletimer_tg_info *info = par->targinfo;
>  	int ret;
> @@ -213,18 +261,21 @@ 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++;
> +		info->timer->active = true;
> +
>  		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) + now);
> 
>  		pr_debug("increased refcnt of timer %s to %u\n",
>  			 info->label, info->timer->refcnt);
>  	} else {
> -		ret = idletimer_tg_create(info);
> +		ret = idletimer_tg_create(info, revision);
>  		if (ret < 0) {
>  			pr_debug("failed to create timer\n");
>  			mutex_unlock(&list_mutex);
> @@ -236,6 +287,16 @@ static int idletimer_tg_checkentry(const struct xt_tgchk_param *par)
>  	return 0;
>  }
> 
> +static int idletimer_tg_checkentry(const struct xt_tgchk_param *par)
> +{
> +	return idletimer_tg_checkentry_rev(par, 0);
> +}
> +
> +static int idletimer_tg_checkentry_v1(const struct xt_tgchk_param *par)
> +{
> +	return idletimer_tg_checkentry_rev(par, 1);
> +}
> +
>  static void idletimer_tg_destroy(const struct xt_tgdtor_param *par)
>  {
>  	const struct idletimer_tg_info *info = par->targinfo;
> @@ -260,14 +321,27 @@ static void idletimer_tg_destroy(const struct xt_tgdtor_param *par)
>  	mutex_unlock(&list_mutex);
>  }
> 
> -static struct xt_target idletimer_tg __read_mostly = {
> +static struct xt_target idletimer_tg[] __read_mostly = {
> +{
>  	.name		= "IDLETIMER",
> +	.revision	= 0,
>  	.family		= NFPROTO_UNSPEC,
>  	.target		= idletimer_tg_target,
>  	.targetsize     = sizeof(struct idletimer_tg_info),
>  	.checkentry	= idletimer_tg_checkentry,
>  	.destroy        = idletimer_tg_destroy,
>  	.me		= THIS_MODULE,
> +},
> +{
> +	.name		= "IDLETIMER",
> +	.revision	= 1,
> +	.family		= NFPROTO_UNSPEC,
> +	.target		= idletimer_tg_target,
> +	.targetsize     = sizeof(struct idletimer_tg_info_v1),
> +	.checkentry	= idletimer_tg_checkentry_v1,
> +	.destroy        = idletimer_tg_destroy,
> +	.me		= THIS_MODULE,
> +},
>  };
> 
>  static struct class *idletimer_tg_class;
> @@ -295,7 +369,7 @@ static int __init idletimer_tg_init(void)
> 
>  	idletimer_tg_kobj = &idletimer_tg_device->kobj;
> 
> -	err =  xt_register_target(&idletimer_tg);
> +	err =  xt_register_targets(idletimer_tg, ARRAY_SIZE(idletimer_tg));
>  	if (err < 0) {
>  		pr_debug("couldn't register xt target\n");
>  		goto out_dev;
> @@ -312,7 +386,7 @@ out:
> 
>  static void __exit idletimer_tg_exit(void)
>  {
> -	xt_unregister_target(&idletimer_tg);
> +	xt_unregister_targets(idletimer_tg, ARRAY_SIZE(idletimer_tg));
> 
>  	device_destroy(idletimer_tg_class, MKDEV(0, 0));
>  	class_destroy(idletimer_tg_class);
> @@ -327,3 +401,4 @@ MODULE_DESCRIPTION("Xtables: idle time monitor");
>  MODULE_LICENSE("GPL v2");
>  MODULE_ALIAS("ipt_IDLETIMER");
>  MODULE_ALIAS("ip6t_IDLETIMER");
> +MODULE_ALIAS("arpt_IDLETIMER");

We don't currently have the userspace code in arptables to use
IDLETIMER from there. Do you have that code in your tree? Should be
good to pass it to get it mainstream.
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