text: /*
   * linux/net/netfilter/xt_IDLETIMER.c
   *
   * Netfilter module to trigger a timer when packet matches.
   * After timer expires a kevent will be sent.
   *
   * Copyright (C) 2004, 2010 Nokia Corporation
   *
   * Written by Timo Teras <ext-timo.teras@nokia.com>
   *
   * Converted to x_tables and reworked for upstream inclusion
   * by Luciano Coelho <luciano.coelho@nokia.com>
   *
   * Contact: Luciano Coelho <luciano.coelho@nokia.com>
   *
   * This program is free software; you can redistribute it and/or
   * modify it under the terms of the GNU General Public License
   * version 2 as published by the Free Software Foundation.
   *
   * This program is distributed in the hope that it will be useful, but
   * WITHOUT ANY WARRANTY; without even the implied warranty of
   * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
   * General Public License for more details.
   *
   * You should have received a copy of the GNU General Public License
   * along with this program; if not, write to the Free Software
   * Foundation, Inc., 51 Franklin St, Fifth Floor, Boston, MA
   * 02110-1301 USA
   */
  
  #define pr_fmt(fmt) KBUILD_MODNAME ": " fmt
  
  #include <linux/module.h>
  #include <linux/timer.h>
  #include <linux/list.h>
  #include <linux/mutex.h>
  #include <linux/netfilter.h>
  #include <linux/netfilter/x_tables.h>
  #include <linux/netfilter/xt_IDLETIMER.h>
  #include <linux/kdev_t.h>
  #include <linux/kobject.h>
  #include <linux/skbuff.h>
  #include <linux/workqueue.h>
  #include <linux/sysfs.h>
  #include <net/net_namespace.h>
  
  struct idletimer_tg_attr {
  	struct attribute attr;
  	ssize_t	(*show)(struct kobject *kobj,
  			struct attribute *attr, char *buf);
  };
  
  struct idletimer_tg {
  	struct list_head entry;
  	struct timer_list timer;
  	struct work_struct work;
  
  	struct kobject *kobj;
  	struct idletimer_tg_attr attr;
  
  	unsigned int refcnt;
  	bool send_nl_msg;
  	bool active;
  };
  
  static LIST_HEAD(idletimer_tg_list);
  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)
  {
  	struct idletimer_tg *entry;
  
  	BUG_ON(!label);
  
  	list_for_each_entry(entry, &idletimer_tg_list, entry) {
  		if (!strcmp(label, entry->attr.attr.name))
  			return entry;
  	}
  
  	return NULL;
  }
  
  static ssize_t idletimer_tg_show(struct kobject *kobj, struct attribute *attr,
  				 char *buf)
  {
  	struct idletimer_tg *timer;
  	unsigned long expires = 0;
  	unsigned long now = jiffies;
  
  	mutex_lock(&list_mutex);
  
  	timer =	__idletimer_tg_find_by_label(attr->name);
  	if (timer)
  		expires = timer->timer.expires;
  
  	mutex_unlock(&list_mutex);
  
  	if (time_after(expires, now))
  		return sprintf(buf, "%u\n",
  			       jiffies_to_msecs(expires - now) / 1000);
  
  	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)
  {
  	struct idletimer_tg *timer = container_of(work, struct idletimer_tg,
  						  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)
  {
  	struct idletimer_tg *timer = (struct idletimer_tg *) 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)
  {
  	int ret;
  
  	info->timer = kmalloc(sizeof(*info->timer), GFP_KERNEL);
  	if (!info->timer) {
  		ret = -ENOMEM;
  		goto out;
  	}
  
  	info->timer->attr.attr.name = kstrdup(info->label, GFP_KERNEL);
  	if (!info->timer->attr.attr.name) {
  		ret = -ENOMEM;
  		goto out_free_timer;
  	}
  	info->timer->attr.attr.mode = S_IRUGO;
  	info->timer->attr.show = idletimer_tg_show;
  
  	ret = sysfs_create_file(idletimer_tg_kobj, &info->timer->attr.attr);
  	if (ret < 0) {
  		pr_debug("couldn't add file to sysfs");
  		goto out_free_attr;
  	}
  
  	list_add(&info->timer->entry, &idletimer_tg_list);
  
  	setup_timer(&info->timer->timer, idletimer_tg_expired,
  		    (unsigned long) info->timer);
  	info->timer->refcnt = 1;
  	info->timer->send_nl_msg = (info->send_nl_msg == 0) ? false : true;
  	info->timer->active = true;
  
  	mod_timer(&info->timer->timer,
  		  msecs_to_jiffies(info->timeout * 1000) + jiffies);
  
  	INIT_WORK(&info->timer->work, idletimer_tg_work);
  
  	return 0;
  
  out_free_attr:
  	kfree(info->timer->attr.attr.name);
  out_free_timer:
  	kfree(info->timer);
  out:
  	return ret;
  }
  
  /*
   * The actual xt_tables plugin.
   */
  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);
  
  	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",
  			 info->label, info->timer->timer.expires, now);
  	}
  
  	/* TODO: Avoid modifying timers on each packet */
  	mod_timer(&info->timer->timer,
  		  msecs_to_jiffies(info->timeout * 1000) + now);
  
  	return XT_CONTINUE;
  }
  
  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);
  
  	if (info->timeout == 0) {
  		pr_debug("timeout value is zero\n");
  		return -EINVAL;
  	}
  
  	if (info->label[0] == '\0' ||
  	    strnlen(info->label,
  		    MAX_IDLETIMER_LABEL_SIZE) == MAX_IDLETIMER_LABEL_SIZE) {
  		pr_debug("label is empty or not nul-terminated\n");
  		return -EINVAL;
  	}
  
  	mutex_lock(&list_mutex);
  
  	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);
  		if (ret < 0) {
  			pr_debug("failed to create timer\n");
  			mutex_unlock(&list_mutex);
  			return ret;
  		}
  	}
  
  	mutex_unlock(&list_mutex);
  
  	return 0;
  }
  
  static void idletimer_tg_destroy(const struct xt_tgdtor_param *par)
  {
  	const struct idletimer_tg_info *info = par->targinfo;
  
  	pr_debug("destroy targinfo %s\n", info->label);
  
  	mutex_lock(&list_mutex);
  
  	if (--info->timer->refcnt == 0) {
  		pr_debug("deleting timer %s\n", info->label);
  
  		list_del(&info->timer->entry);
  		del_timer_sync(&info->timer->timer);
  		sysfs_remove_file(idletimer_tg_kobj, &info->timer->attr.attr);
  		kfree(info->timer->attr.attr.name);
  		kfree(info->timer);
  	} else {
  		pr_debug("decreased refcnt of timer %s to %u\n",
  		info->label, info->timer->refcnt);
  	}
  
  	mutex_unlock(&list_mutex);
  }
  
  static struct xt_target idletimer_tg __read_mostly = {
  	.name		= "IDLETIMER",
  	.revision	= 1,
  	.family		= NFPROTO_UNSPEC,
  	.target		= idletimer_tg_target,
  	.targetsize     = sizeof(struct idletimer_tg_info),
  	.checkentry	= idletimer_tg_checkentry,
  	.destroy        = idletimer_tg_destroy,
  	.me		= THIS_MODULE,
  };
  
  static struct class *idletimer_tg_class;
  
  static struct device *idletimer_tg_device;
  
  static int __init idletimer_tg_init(void)
  {
  	int err;
  
  	idletimer_tg_class = class_create(THIS_MODULE, "xt_idletimer");
  	err = PTR_ERR(idletimer_tg_class);
  	if (IS_ERR(idletimer_tg_class)) {
  		pr_debug("couldn't register device class\n");
  		goto out;
  	}
  
  	idletimer_tg_device = device_create(idletimer_tg_class, NULL,
  					    MKDEV(0, 0), NULL, "timers");
  	err = PTR_ERR(idletimer_tg_device);
  	if (IS_ERR(idletimer_tg_device)) {
  		pr_debug("couldn't register system device\n");
  		goto out_class;
  	}
  
  	idletimer_tg_kobj = &idletimer_tg_device->kobj;
  
  	err =  xt_register_target(&idletimer_tg);
  	if (err < 0) {
  		pr_debug("couldn't register xt target\n");
  		goto out_dev;
  	}
  
  	return 0;
  out_dev:
  	device_destroy(idletimer_tg_class, MKDEV(0, 0));
  out_class:
  	class_destroy(idletimer_tg_class);
  out:
  	return err;
  }
  
  static void __exit idletimer_tg_exit(void)
  {
  	xt_unregister_target(&idletimer_tg);
  
  	device_destroy(idletimer_tg_class, MKDEV(0, 0));
  	class_destroy(idletimer_tg_class);
  }
  
  module_init(idletimer_tg_init);
  module_exit(idletimer_tg_exit);
  
  MODULE_AUTHOR("Timo Teras <ext-timo.teras@nokia.com>");
  MODULE_AUTHOR("Luciano Coelho <luciano.coelho@nokia.com>");
  MODULE_DESCRIPTION("Xtables: idle time monitor");
  MODULE_LICENSE("GPL v2");
  MODULE_ALIAS("ipt_IDLETIMER");
  MODULE_ALIAS("ip6t_IDLETIMER");
  MODULE_ALIAS("arpt_IDLETIMER");
  