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_check_sysfs_name(const char *name, unsigned int size)
 118 {
 119         int ret;
 120
 121         ret = xt_check_proc_name(name, size);
 122         if (ret < 0)
 123                 return ret;
 124
 125         if (!strcmp(name, "power") ||
 126             !strcmp(name, "subsystem") ||
 127             !strcmp(name, "uevent"))
 128                 return -EINVAL;
 129
 130         return 0;
 131 }
 132
 133 static int idletimer_tg_create(struct idletimer_tg_info *info)
 134 {
 135         int ret;
 136
 137         info->timer = kmalloc(sizeof(*info->timer), GFP_KERNEL);
 138         if (!info->timer) {
 139                 ret = -ENOMEM;
 140                 goto out;
 141         }
 142
 143         ret = idletimer_check_sysfs_name(info->label, sizeof(info->label));
 144         if (ret < 0)
 145                 goto out_free_timer;
 146
 147         sysfs_attr_init(&info->timer->attr.attr);
 148         info->timer->attr.attr.name = kstrdup(info->label, GFP_KERNEL);
 149         if (!info->timer->attr.attr.name) {
 150                 ret = -ENOMEM;
 151                 goto out_free_timer;
 152         }
 153         info->timer->attr.attr.mode = 0444;
 154         info->timer->attr.show = idletimer_tg_show;
 155
 156         ret = sysfs_create_file(idletimer_tg_kobj, &info->timer->attr.attr);
 157         if (ret < 0) {
 158                 pr_debug("couldn't add file to sysfs");
 159                 goto out_free_attr;
 160         }
 161
 162         list_add(&info->timer->entry, &idletimer_tg_list);
 163
 164         timer_setup(&info->timer->timer, idletimer_tg_expired, 0);
 165         info->timer->refcnt = 1;
 166
 167         INIT_WORK(&info->timer->work, idletimer_tg_work);
 168
 169         mod_timer(&info->timer->timer,
 170                   msecs_to_jiffies(info->timeout * 1000) + jiffies);
 171
 172         return 0;
 173
 174 out_free_attr:
 175         kfree(info->timer->attr.attr.name);
 176 out_free_timer:
 177         kfree(info->timer);
 178 out:
 179         return ret;
 180 }
 181
 182 /*
 183  * The actual xt_tables plugin.
 184  */
 185 static unsigned int idletimer_tg_target(struct sk_buff *skb,
 186                                          const struct xt_action_param *par)
 187 {
 188         const struct idletimer_tg_info *info = par->targinfo;
 189
 190         pr_debug("resetting timer %s, timeout period %u\n",
 191                  info->label, info->timeout);
 192
 193         mod_timer(&info->timer->timer,
 194                   msecs_to_jiffies(info->timeout * 1000) + jiffies);
 195
 196         return XT_CONTINUE;
 197 }
 198
 199 static int idletimer_tg_checkentry(const struct xt_tgchk_param *par)
 200 {
 201         struct idletimer_tg_info *info = par->targinfo;
 202         int ret;
 203
 204         pr_debug("checkentry targinfo%s\n", info->label);
 205
 206         if (info->timeout == 0) {
 207                 pr_debug("timeout value is zero\n");
 208                 return -EINVAL;
 209         }
 210         if (info->timeout >= INT_MAX / 1000) {
 211                 pr_debug("timeout value is too big\n");
 212                 return -EINVAL;
 213         }
 214         if (info->label[0] == '\0' ||
 215             strnlen(info->label,
 216                     MAX_IDLETIMER_LABEL_SIZE) == MAX_IDLETIMER_LABEL_SIZE) {
 217                 pr_debug("label is empty or not nul-terminated\n");
 218                 return -EINVAL;
 219         }
 220
 221         mutex_lock(&list_mutex);
 222
 223         info->timer = __idletimer_tg_find_by_label(info->label);
 224         if (info->timer) {
 225                 info->timer->refcnt++;
 226                 mod_timer(&info->timer->timer,
 227                           msecs_to_jiffies(info->timeout * 1000) + jiffies);
 228
 229                 pr_debug("increased refcnt of timer %s to %u\n",
 230                          info->label, info->timer->refcnt);
 231         } else {
 232                 ret = idletimer_tg_create(info);
 233                 if (ret < 0) {
 234                         pr_debug("failed to create timer\n");
 235                         mutex_unlock(&list_mutex);
 236                         return ret;
 237                 }
 238         }
 239
 240         mutex_unlock(&list_mutex);
 241         return 0;
 242 }
 243
 244 static void idletimer_tg_destroy(const struct xt_tgdtor_param *par)
 245 {
 246         const struct idletimer_tg_info *info = par->targinfo;
 247
 248         pr_debug("destroy targinfo %s\n", info->label);
 249
 250         mutex_lock(&list_mutex);
 251
 252         if (--info->timer->refcnt == 0) {
 253                 pr_debug("deleting timer %s\n", info->label);
 254
 255                 list_del(&info->timer->entry);
 256                 del_timer_sync(&info->timer->timer);
 257                 cancel_work_sync(&info->timer->work);
 258                 sysfs_remove_file(idletimer_tg_kobj, &info->timer->attr.attr);
 259                 kfree(info->timer->attr.attr.name);
 260                 kfree(info->timer);
 261         } else {
 262                 pr_debug("decreased refcnt of timer %s to %u\n",
 263                          info->label, info->timer->refcnt);
 264         }
 265
 266         mutex_unlock(&list_mutex);
 267 }
 268
 269 static struct xt_target idletimer_tg __read_mostly = {
 270         .name           = "IDLETIMER",
 271         .family         = NFPROTO_UNSPEC,
 272         .target         = idletimer_tg_target,
 273         .targetsize     = sizeof(struct idletimer_tg_info),
 274         .usersize       = offsetof(struct idletimer_tg_info, timer),
 275         .checkentry     = idletimer_tg_checkentry,
 276         .destroy        = idletimer_tg_destroy,
 277         .me             = THIS_MODULE,
 278 };
 279
 280 static struct class *idletimer_tg_class;
 281
 282 static struct device *idletimer_tg_device;
 283
 284 static int __init idletimer_tg_init(void)
 285 {
 286         int err;
 287
 288         idletimer_tg_class = class_create(THIS_MODULE, "xt_idletimer");
 289         err = PTR_ERR(idletimer_tg_class);
 290         if (IS_ERR(idletimer_tg_class)) {
 291                 pr_debug("couldn't register device class\n");
 292                 goto out;
 293         }
 294
 295         idletimer_tg_device = device_create(idletimer_tg_class, NULL,
 296                                             MKDEV(0, 0), NULL, "timers");
 297         err = PTR_ERR(idletimer_tg_device);
 298         if (IS_ERR(idletimer_tg_device)) {
 299                 pr_debug("couldn't register system device\n");
 300                 goto out_class;
 301         }
 302
 303         idletimer_tg_kobj = &idletimer_tg_device->kobj;
 304
 305         err =  xt_register_target(&idletimer_tg);
 306         if (err < 0) {
 307                 pr_debug("couldn't register xt target\n");
 308                 goto out_dev;
 309         }
 310
 311         return 0;
 312 out_dev:
 313         device_destroy(idletimer_tg_class, MKDEV(0, 0));
 314 out_class:
 315         class_destroy(idletimer_tg_class);
 316 out:
 317         return err;
 318 }
 319
 320 static void __exit idletimer_tg_exit(void)
 321 {
 322         xt_unregister_target(&idletimer_tg);
 323
 324         device_destroy(idletimer_tg_class, MKDEV(0, 0));
 325         class_destroy(idletimer_tg_class);
 326 }
 327
 328 module_init(idletimer_tg_init);
 329 module_exit(idletimer_tg_exit);
 330
 331 MODULE_AUTHOR("Timo Teras <ext-timo.teras@nokia.com>");
 332 MODULE_AUTHOR("Luciano Coelho <luciano.coelho@nokia.com>");
 333 MODULE_DESCRIPTION("Xtables: idle time monitor");
 334 MODULE_LICENSE("GPL v2");
 335 MODULE_ALIAS("ipt_IDLETIMER");
 336 MODULE_ALIAS("ip6t_IDLETIMER");