net/netfilter/xt_IDLETIMER.c

   1 /*
   2  * linux/net/netfilter/xt_IDLETIMER.c
   3  *
   4  * Netfilter module to trigger a timer when packet matches.
   5  * After timer expires a kevent will be sent.
   6  *
   7  * Copyright (C) 2004, 2010 Nokia Corporation
   8  * Written by Timo Teras <ext-timo.teras@nokia.com>
   9  *
  10  * Converted to x_tables and reworked for upstream inclusion
  11  * by Luciano Coelho <luciano.coelho@nokia.com>
  12  *
  13  * Contact: Luciano Coelho <luciano.coelho@nokia.com>
  14  *
  15  * This program is free software; you can redistribute it and/or
  16  * modify it under the terms of the GNU General Public License
  17  * version 2 as published by the Free Software Foundation.
  18  *
  19  * This program is distributed in the hope that it will be useful, but
  20  * WITHOUT ANY WARRANTY; without even the implied warranty of
  21  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
  22  * General Public License for more details.
  23  *
  24  * You should have received a copy of the GNU General Public License
  25  * along with this program; if not, write to the Free Software
  26  * Foundation, Inc., 51 Franklin St, Fifth Floor, Boston, MA
  27  * 02110-1301 USA
  28  */
  29
  30 #define pr_fmt(fmt) KBUILD_MODNAME ": " fmt
  31
  32 #include <linux/module.h>
  33 #include <linux/timer.h>
  34 #include <linux/list.h>
  35 #include <linux/mutex.h>
  36 #include <linux/netfilter.h>
  37 #include <linux/netfilter/x_tables.h>
  38 #include <linux/netfilter/xt_IDLETIMER.h>
  39 #include <linux/kdev_t.h>
  40 #include <linux/kobject.h>
  41 #include <linux/workqueue.h>
  42 #include <linux/sysfs.h>
  43
  44 struct idletimer_tg_attr {
  45         struct attribute attr;
  46         ssize_t (*show)(struct kobject *kobj,
  47                         struct attribute *attr, char *buf);
  48 };
  49
  50 struct idletimer_tg {
  51         struct list_head entry;
  52         struct timer_list timer;
  53         struct work_struct work;
  54
  55         struct kobject *kobj;
  56         struct idletimer_tg_attr attr;
  57
  58         unsigned int refcnt;
  59 };
  60
  61 static LIST_HEAD(idletimer_tg_list);
  62 static DEFINE_MUTEX(list_mutex);
  63
  64 static struct kobject *idletimer_tg_kobj;
  65
  66 static
  67 struct idletimer_tg *__idletimer_tg_find_by_label(const char *label)
  68 {
  69         struct idletimer_tg *entry;
  70
  71         list_for_each_entry(entry, &idletimer_tg_list, entry) {
  72                 if (!strcmp(label, entry->attr.attr.name))
  73                         return entry;
  74         }
  75
  76         return NULL;
  77 }
  78
  79 static ssize_t idletimer_tg_show(struct kobject *kobj, struct attribute *attr,
  80                                  char *buf)
  81 {
  82         struct idletimer_tg *timer;
  83         unsigned long expires = 0;
  84
  85         mutex_lock(&list_mutex);
  86
  87         timer = __idletimer_tg_find_by_label(attr->name);
  88         if (timer)
  89                 expires = timer->timer.expires;
  90
  91         mutex_unlock(&list_mutex);
  92
  93         if (time_after(expires, jiffies))
  94                 return sprintf(buf, "%u\n",
  95                                jiffies_to_msecs(expires - jiffies) / 1000);
  96
  97         return sprintf(buf, "0\n");
  98 }
  99
 100 static void idletimer_tg_work(struct work_struct *work)
 101 {
 102         struct idletimer_tg *timer = container_of(work, struct idletimer_tg,
 103                                                   work);
 104
 105         sysfs_notify(idletimer_tg_kobj, NULL, timer->attr.attr.name);
 106 }
 107
 108 static void idletimer_tg_expired(struct timer_list *t)
 109 {
 110         struct idletimer_tg *timer = from_timer(timer, t, timer);
 111
 112         pr_debug("timer %s expired\n", timer->attr.attr.name);
 113
 114         schedule_work(&timer->work);
 115 }
 116
 117 static int idletimer_tg_create(struct idletimer_tg_info *info)
 118 {
 119         int ret;
 120
 121         info->timer = kmalloc(sizeof(*info->timer), GFP_KERNEL);
 122         if (!info->timer) {
 123                 ret = -ENOMEM;
 124                 goto out;
 125         }
 126
 127         sysfs_attr_init(&info->timer->attr.attr);
 128         info->timer->attr.attr.name = kstrdup(info->label, GFP_KERNEL);
 129         if (!info->timer->attr.attr.name) {
 130                 ret = -ENOMEM;
 131                 goto out_free_timer;
 132         }
 133         info->timer->attr.attr.mode = 0444;
 134         info->timer->attr.show = idletimer_tg_show;
 135
 136         ret = sysfs_create_file(idletimer_tg_kobj, &info->timer->attr.attr);
 137         if (ret < 0) {
 138                 pr_debug("couldn't add file to sysfs");
 139                 goto out_free_attr;
 140         }
 141
 142         list_add(&info->timer->entry, &idletimer_tg_list);
 143
 144         timer_setup(&info->timer->timer, idletimer_tg_expired, 0);
 145         info->timer->refcnt = 1;
 146
 147         INIT_WORK(&info->timer->work, idletimer_tg_work);
 148
 149         mod_timer(&info->timer->timer,
 150                   msecs_to_jiffies(info->timeout * 1000) + jiffies);
 151
 152         return 0;
 153
 154 out_free_attr:
 155         kfree(info->timer->attr.attr.name);
 156 out_free_timer:
 157         kfree(info->timer);
 158 out:
 159         return ret;
 160 }
 161
 162 /*
 163  * The actual xt_tables plugin.
 164  */
 165 static unsigned int idletimer_tg_target(struct sk_buff *skb,
 166                                          const struct xt_action_param *par)
 167 {
 168         const struct idletimer_tg_info *info = par->targinfo;
 169
 170         pr_debug("resetting timer %s, timeout period %u\n",
 171                  info->label, info->timeout);
 172
 173         mod_timer(&info->timer->timer,
 174                   msecs_to_jiffies(info->timeout * 1000) + jiffies);
 175
 176         return XT_CONTINUE;
 177 }
 178
 179 static int idletimer_tg_checkentry(const struct xt_tgchk_param *par)
 180 {
 181         struct idletimer_tg_info *info = par->targinfo;
 182         int ret;
 183
 184         pr_debug("checkentry targinfo%s\n", info->label);
 185
 186         if (info->timeout == 0) {
 187                 pr_debug("timeout value is zero\n");
 188                 return -EINVAL;
 189         }
 190         if (info->timeout >= INT_MAX / 1000) {
 191                 pr_debug("timeout value is too big\n");
 192                 return -EINVAL;
 193         }
 194         if (info->label[0] == '\0' ||
 195             strnlen(info->label,
 196                     MAX_IDLETIMER_LABEL_SIZE) == MAX_IDLETIMER_LABEL_SIZE) {
 197                 pr_debug("label is empty or not nul-terminated\n");
 198                 return -EINVAL;
 199         }
 200
 201         mutex_lock(&list_mutex);
 202
 203         info->timer = __idletimer_tg_find_by_label(info->label);
 204         if (info->timer) {
 205                 info->timer->refcnt++;
 206                 mod_timer(&info->timer->timer,
 207                           msecs_to_jiffies(info->timeout * 1000) + jiffies);
 208
 209                 pr_debug("increased refcnt of timer %s to %u\n",
 210                          info->label, info->timer->refcnt);
 211         } else {
 212                 ret = idletimer_tg_create(info);
 213                 if (ret < 0) {
 214                         pr_debug("failed to create timer\n");
 215                         mutex_unlock(&list_mutex);
 216                         return ret;
 217                 }
 218         }
 219
 220         mutex_unlock(&list_mutex);
 221         return 0;
 222 }
 223
 224 static void idletimer_tg_destroy(const struct xt_tgdtor_param *par)
 225 {
 226         const struct idletimer_tg_info *info = par->targinfo;
 227
 228         pr_debug("destroy targinfo %s\n", info->label);
 229
 230         mutex_lock(&list_mutex);
 231
 232         if (--info->timer->refcnt == 0) {
 233                 pr_debug("deleting timer %s\n", info->label);
 234
 235                 list_del(&info->timer->entry);
 236                 del_timer_sync(&info->timer->timer);
 237                 cancel_work_sync(&info->timer->work);
 238                 sysfs_remove_file(idletimer_tg_kobj, &info->timer->attr.attr);
 239                 kfree(info->timer->attr.attr.name);
 240                 kfree(info->timer);
 241         } else {
 242                 pr_debug("decreased refcnt of timer %s to %u\n",
 243                          info->label, info->timer->refcnt);
 244         }
 245
 246         mutex_unlock(&list_mutex);
 247 }
 248
 249 static struct xt_target idletimer_tg __read_mostly = {
 250         .name           = "IDLETIMER",
 251         .family         = NFPROTO_UNSPEC,
 252         .target         = idletimer_tg_target,
 253         .targetsize     = sizeof(struct idletimer_tg_info),
 254         .usersize       = offsetof(struct idletimer_tg_info, timer),
 255         .checkentry     = idletimer_tg_checkentry,
 256         .destroy        = idletimer_tg_destroy,
 257         .me             = THIS_MODULE,
 258 };
 259
 260 static struct class *idletimer_tg_class;
 261
 262 static struct device *idletimer_tg_device;
 263
 264 static int __init idletimer_tg_init(void)
 265 {
 266         int err;
 267
 268         idletimer_tg_class = class_create(THIS_MODULE, "xt_idletimer");
 269         err = PTR_ERR(idletimer_tg_class);
 270         if (IS_ERR(idletimer_tg_class)) {
 271                 pr_debug("couldn't register device class\n");
 272                 goto out;
 273         }
 274
 275         idletimer_tg_device = device_create(idletimer_tg_class, NULL,
 276                                             MKDEV(0, 0), NULL, "timers");
 277         err = PTR_ERR(idletimer_tg_device);
 278         if (IS_ERR(idletimer_tg_device)) {
 279                 pr_debug("couldn't register system device\n");
 280                 goto out_class;
 281         }
 282
 283         idletimer_tg_kobj = &idletimer_tg_device->kobj;
 284
 285         err =  xt_register_target(&idletimer_tg);
 286         if (err < 0) {
 287                 pr_debug("couldn't register xt target\n");
 288                 goto out_dev;
 289         }
 290
 291         return 0;
 292 out_dev:
 293         device_destroy(idletimer_tg_class, MKDEV(0, 0));
 294 out_class:
 295         class_destroy(idletimer_tg_class);
 296 out:
 297         return err;
 298 }
 299
 300 static void __exit idletimer_tg_exit(void)
 301 {
 302         xt_unregister_target(&idletimer_tg);
 303
 304         device_destroy(idletimer_tg_class, MKDEV(0, 0));
 305         class_destroy(idletimer_tg_class);
 306 }
 307
 308 module_init(idletimer_tg_init);
 309 module_exit(idletimer_tg_exit);
 310
 311 MODULE_AUTHOR("Timo Teras <ext-timo.teras@nokia.com>");
 312 MODULE_AUTHOR("Luciano Coelho <luciano.coelho@nokia.com>");
 313 MODULE_DESCRIPTION("Xtables: idle time monitor");
 314 MODULE_LICENSE("GPL v2");
 315 MODULE_ALIAS("ipt_IDLETIMER");
 316 MODULE_ALIAS("ip6t_IDLETIMER");