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 {
  45         struct list_head entry;
  46         struct timer_list timer;
  47         struct work_struct work;
  48
  49         struct kobject *kobj;
  50         struct device_attribute attr;
  51
  52         unsigned int refcnt;
  53 };
  54
  55 static LIST_HEAD(idletimer_tg_list);
  56 static DEFINE_MUTEX(list_mutex);
  57
  58 static struct kobject *idletimer_tg_kobj;
  59
  60 static
  61 struct idletimer_tg *__idletimer_tg_find_by_label(const char *label)
  62 {
  63         struct idletimer_tg *entry;
  64
  65         list_for_each_entry(entry, &idletimer_tg_list, entry) {
  66                 if (!strcmp(label, entry->attr.attr.name))
  67                         return entry;
  68         }
  69
  70         return NULL;
  71 }
  72
  73 static ssize_t idletimer_tg_show(struct device *dev,
  74                                  struct device_attribute *attr, char *buf)
  75 {
  76         struct idletimer_tg *timer;
  77         unsigned long expires = 0;
  78
  79         mutex_lock(&list_mutex);
  80
  81         timer = __idletimer_tg_find_by_label(attr->attr.name);
  82         if (timer)
  83                 expires = timer->timer.expires;
  84
  85         mutex_unlock(&list_mutex);
  86
  87         if (time_after(expires, jiffies))
  88                 return sprintf(buf, "%u\n",
  89                                jiffies_to_msecs(expires - jiffies) / 1000);
  90
  91         return sprintf(buf, "0\n");
  92 }
  93
  94 static void idletimer_tg_work(struct work_struct *work)
  95 {
  96         struct idletimer_tg *timer = container_of(work, struct idletimer_tg,
  97                                                   work);
  98
  99         sysfs_notify(idletimer_tg_kobj, NULL, timer->attr.attr.name);
 100 }
 101
 102 static void idletimer_tg_expired(struct timer_list *t)
 103 {
 104         struct idletimer_tg *timer = from_timer(timer, t, timer);
 105
 106         pr_debug("timer %s expired\n", timer->attr.attr.name);
 107
 108         schedule_work(&timer->work);
 109 }
 110
 111 static int idletimer_check_sysfs_name(const char *name, unsigned int size)
 112 {
 113         int ret;
 114
 115         ret = xt_check_proc_name(name, size);
 116         if (ret < 0)
 117                 return ret;
 118
 119         if (!strcmp(name, "power") ||
 120             !strcmp(name, "subsystem") ||
 121             !strcmp(name, "uevent"))
 122                 return -EINVAL;
 123
 124         return 0;
 125 }
 126
 127 static int idletimer_tg_create(struct idletimer_tg_info *info)
 128 {
 129         int ret;
 130
 131         info->timer = kmalloc(sizeof(*info->timer), GFP_KERNEL);
 132         if (!info->timer) {
 133                 ret = -ENOMEM;
 134                 goto out;
 135         }
 136
 137         ret = idletimer_check_sysfs_name(info->label, sizeof(info->label));
 138         if (ret < 0)
 139                 goto out_free_timer;
 140
 141         sysfs_attr_init(&info->timer->attr.attr);
 142         info->timer->attr.attr.name = kstrdup(info->label, GFP_KERNEL);
 143         if (!info->timer->attr.attr.name) {
 144                 ret = -ENOMEM;
 145                 goto out_free_timer;
 146         }
 147         info->timer->attr.attr.mode = 0444;
 148         info->timer->attr.show = idletimer_tg_show;
 149
 150         ret = sysfs_create_file(idletimer_tg_kobj, &info->timer->attr.attr);
 151         if (ret < 0) {
 152                 pr_debug("couldn't add file to sysfs");
 153                 goto out_free_attr;
 154         }
 155
 156         list_add(&info->timer->entry, &idletimer_tg_list);
 157
 158         timer_setup(&info->timer->timer, idletimer_tg_expired, 0);
 159         info->timer->refcnt = 1;
 160
 161         INIT_WORK(&info->timer->work, idletimer_tg_work);
 162
 163         mod_timer(&info->timer->timer,
 164                   msecs_to_jiffies(info->timeout * 1000) + jiffies);
 165
 166         return 0;
 167
 168 out_free_attr:
 169         kfree(info->timer->attr.attr.name);
 170 out_free_timer:
 171         kfree(info->timer);
 172 out:
 173         return ret;
 174 }
 175
 176 /*
 177  * The actual xt_tables plugin.
 178  */
 179 static unsigned int idletimer_tg_target(struct sk_buff *skb,
 180                                          const struct xt_action_param *par)
 181 {
 182         const struct idletimer_tg_info *info = par->targinfo;
 183
 184         pr_debug("resetting timer %s, timeout period %u\n",
 185                  info->label, info->timeout);
 186
 187         mod_timer(&info->timer->timer,
 188                   msecs_to_jiffies(info->timeout * 1000) + jiffies);
 189
 190         return XT_CONTINUE;
 191 }
 192
 193 static int idletimer_tg_checkentry(const struct xt_tgchk_param *par)
 194 {
 195         struct idletimer_tg_info *info = par->targinfo;
 196         int ret;
 197
 198         pr_debug("checkentry targinfo%s\n", info->label);
 199
 200         if (info->timeout == 0) {
 201                 pr_debug("timeout value is zero\n");
 202                 return -EINVAL;
 203         }
 204         if (info->timeout >= INT_MAX / 1000) {
 205                 pr_debug("timeout value is too big\n");
 206                 return -EINVAL;
 207         }
 208         if (info->label[0] == '\0' ||
 209             strnlen(info->label,
 210                     MAX_IDLETIMER_LABEL_SIZE) == MAX_IDLETIMER_LABEL_SIZE) {
 211                 pr_debug("label is empty or not nul-terminated\n");
 212                 return -EINVAL;
 213         }
 214
 215         mutex_lock(&list_mutex);
 216
 217         info->timer = __idletimer_tg_find_by_label(info->label);
 218         if (info->timer) {
 219                 info->timer->refcnt++;
 220                 mod_timer(&info->timer->timer,
 221                           msecs_to_jiffies(info->timeout * 1000) + jiffies);
 222
 223                 pr_debug("increased refcnt of timer %s to %u\n",
 224                          info->label, info->timer->refcnt);
 225         } else {
 226                 ret = idletimer_tg_create(info);
 227                 if (ret < 0) {
 228                         pr_debug("failed to create timer\n");
 229                         mutex_unlock(&list_mutex);
 230                         return ret;
 231                 }
 232         }
 233
 234         mutex_unlock(&list_mutex);
 235         return 0;
 236 }
 237
 238 static void idletimer_tg_destroy(const struct xt_tgdtor_param *par)
 239 {
 240         const struct idletimer_tg_info *info = par->targinfo;
 241
 242         pr_debug("destroy targinfo %s\n", info->label);
 243
 244         mutex_lock(&list_mutex);
 245
 246         if (--info->timer->refcnt == 0) {
 247                 pr_debug("deleting timer %s\n", info->label);
 248
 249                 list_del(&info->timer->entry);
 250                 del_timer_sync(&info->timer->timer);
 251                 cancel_work_sync(&info->timer->work);
 252                 sysfs_remove_file(idletimer_tg_kobj, &info->timer->attr.attr);
 253                 kfree(info->timer->attr.attr.name);
 254                 kfree(info->timer);
 255         } else {
 256                 pr_debug("decreased refcnt of timer %s to %u\n",
 257                          info->label, info->timer->refcnt);
 258         }
 259
 260         mutex_unlock(&list_mutex);
 261 }
 262
 263 static struct xt_target idletimer_tg __read_mostly = {
 264         .name           = "IDLETIMER",
 265         .family         = NFPROTO_UNSPEC,
 266         .target         = idletimer_tg_target,
 267         .targetsize     = sizeof(struct idletimer_tg_info),
 268         .usersize       = offsetof(struct idletimer_tg_info, timer),
 269         .checkentry     = idletimer_tg_checkentry,
 270         .destroy        = idletimer_tg_destroy,
 271         .me             = THIS_MODULE,
 272 };
 273
 274 static struct class *idletimer_tg_class;
 275
 276 static struct device *idletimer_tg_device;
 277
 278 static int __init idletimer_tg_init(void)
 279 {
 280         int err;
 281
 282         idletimer_tg_class = class_create(THIS_MODULE, "xt_idletimer");
 283         err = PTR_ERR(idletimer_tg_class);
 284         if (IS_ERR(idletimer_tg_class)) {
 285                 pr_debug("couldn't register device class\n");
 286                 goto out;
 287         }
 288
 289         idletimer_tg_device = device_create(idletimer_tg_class, NULL,
 290                                             MKDEV(0, 0), NULL, "timers");
 291         err = PTR_ERR(idletimer_tg_device);
 292         if (IS_ERR(idletimer_tg_device)) {
 293                 pr_debug("couldn't register system device\n");
 294                 goto out_class;
 295         }
 296
 297         idletimer_tg_kobj = &idletimer_tg_device->kobj;
 298
 299         err =  xt_register_target(&idletimer_tg);
 300         if (err < 0) {
 301                 pr_debug("couldn't register xt target\n");
 302                 goto out_dev;
 303         }
 304
 305         return 0;
 306 out_dev:
 307         device_destroy(idletimer_tg_class, MKDEV(0, 0));
 308 out_class:
 309         class_destroy(idletimer_tg_class);
 310 out:
 311         return err;
 312 }
 313
 314 static void __exit idletimer_tg_exit(void)
 315 {
 316         xt_unregister_target(&idletimer_tg);
 317
 318         device_destroy(idletimer_tg_class, MKDEV(0, 0));
 319         class_destroy(idletimer_tg_class);
 320 }
 321
 322 module_init(idletimer_tg_init);
 323 module_exit(idletimer_tg_exit);
 324
 325 MODULE_AUTHOR("Timo Teras <ext-timo.teras@nokia.com>");
 326 MODULE_AUTHOR("Luciano Coelho <luciano.coelho@nokia.com>");
 327 MODULE_DESCRIPTION("Xtables: idle time monitor");
 328 MODULE_LICENSE("GPL v2");
 329 MODULE_ALIAS("ipt_IDLETIMER");
 330 MODULE_ALIAS("ip6t_IDLETIMER");