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