linux/net/netfilter/xt_IDLETIMER.c
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   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
  44struct idletimer_tg_attr {
  45        struct attribute attr;
  46        ssize_t (*show)(struct kobject *kobj,
  47                        struct attribute *attr, char *buf);
  48};
  49
  50struct 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
  61static LIST_HEAD(idletimer_tg_list);
  62static DEFINE_MUTEX(list_mutex);
  63
  64static struct kobject *idletimer_tg_kobj;
  65
  66static
  67struct 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
  81static 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
 102static 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
 110static void idletimer_tg_expired(unsigned long data)
 111{
 112        struct idletimer_tg *timer = (struct idletimer_tg *) data;
 113
 114        pr_debug("timer %s expired\n", timer->attr.attr.name);
 115
 116        schedule_work(&timer->work);
 117}
 118
 119static 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        info->timer->attr.attr.name = kstrdup(info->label, GFP_KERNEL);
 130        if (!info->timer->attr.attr.name) {
 131                ret = -ENOMEM;
 132                goto out_free_timer;
 133        }
 134        info->timer->attr.attr.mode = S_IRUGO;
 135        info->timer->attr.show = idletimer_tg_show;
 136
 137        ret = sysfs_create_file(idletimer_tg_kobj, &info->timer->attr.attr);
 138        if (ret < 0) {
 139                pr_debug("couldn't add file to sysfs");
 140                goto out_free_attr;
 141        }
 142
 143        list_add(&info->timer->entry, &idletimer_tg_list);
 144
 145        setup_timer(&info->timer->timer, idletimer_tg_expired,
 146                    (unsigned long) info->timer);
 147        info->timer->refcnt = 1;
 148
 149        mod_timer(&info->timer->timer,
 150                  msecs_to_jiffies(info->timeout * 1000) + jiffies);
 151
 152        INIT_WORK(&info->timer->work, idletimer_tg_work);
 153
 154        return 0;
 155
 156out_free_attr:
 157        kfree(info->timer->attr.attr.name);
 158out_free_timer:
 159        kfree(info->timer);
 160out:
 161        return ret;
 162}
 163
 164/*
 165 * The actual xt_tables plugin.
 166 */
 167static 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
 183static 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
 195        if (info->label[0] == '\0' ||
 196            strnlen(info->label,
 197                    MAX_IDLETIMER_LABEL_SIZE) == MAX_IDLETIMER_LABEL_SIZE) {
 198                pr_debug("label is empty or not nul-terminated\n");
 199                return -EINVAL;
 200        }
 201
 202        mutex_lock(&list_mutex);
 203
 204        info->timer = __idletimer_tg_find_by_label(info->label);
 205        if (info->timer) {
 206                info->timer->refcnt++;
 207                mod_timer(&info->timer->timer,
 208                          msecs_to_jiffies(info->timeout * 1000) + jiffies);
 209
 210                pr_debug("increased refcnt of timer %s to %u\n",
 211                         info->label, info->timer->refcnt);
 212        } else {
 213                ret = idletimer_tg_create(info);
 214                if (ret < 0) {
 215                        pr_debug("failed to create timer\n");
 216                        mutex_unlock(&list_mutex);
 217                        return ret;
 218                }
 219        }
 220
 221        mutex_unlock(&list_mutex);
 222        return 0;
 223}
 224
 225static void idletimer_tg_destroy(const struct xt_tgdtor_param *par)
 226{
 227        const struct idletimer_tg_info *info = par->targinfo;
 228
 229        pr_debug("destroy targinfo %s\n", info->label);
 230
 231        mutex_lock(&list_mutex);
 232
 233        if (--info->timer->refcnt == 0) {
 234                pr_debug("deleting timer %s\n", info->label);
 235
 236                list_del(&info->timer->entry);
 237                del_timer_sync(&info->timer->timer);
 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
 249static 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        .checkentry     = idletimer_tg_checkentry,
 255        .destroy        = idletimer_tg_destroy,
 256        .me             = THIS_MODULE,
 257};
 258
 259static struct class *idletimer_tg_class;
 260
 261static struct device *idletimer_tg_device;
 262
 263static int __init idletimer_tg_init(void)
 264{
 265        int err;
 266
 267        idletimer_tg_class = class_create(THIS_MODULE, "xt_idletimer");
 268        err = PTR_ERR(idletimer_tg_class);
 269        if (IS_ERR(idletimer_tg_class)) {
 270                pr_debug("couldn't register device class\n");
 271                goto out;
 272        }
 273
 274        idletimer_tg_device = device_create(idletimer_tg_class, NULL,
 275                                            MKDEV(0, 0), NULL, "timers");
 276        err = PTR_ERR(idletimer_tg_device);
 277        if (IS_ERR(idletimer_tg_device)) {
 278                pr_debug("couldn't register system device\n");
 279                goto out_class;
 280        }
 281
 282        idletimer_tg_kobj = &idletimer_tg_device->kobj;
 283
 284        err =  xt_register_target(&idletimer_tg);
 285        if (err < 0) {
 286                pr_debug("couldn't register xt target\n");
 287                goto out_dev;
 288        }
 289
 290        return 0;
 291out_dev:
 292        device_destroy(idletimer_tg_class, MKDEV(0, 0));
 293out_class:
 294        class_destroy(idletimer_tg_class);
 295out:
 296        return err;
 297}
 298
 299static void __exit idletimer_tg_exit(void)
 300{
 301        xt_unregister_target(&idletimer_tg);
 302
 303        device_destroy(idletimer_tg_class, MKDEV(0, 0));
 304        class_destroy(idletimer_tg_class);
 305}
 306
 307module_init(idletimer_tg_init);
 308module_exit(idletimer_tg_exit);
 309
 310MODULE_AUTHOR("Timo Teras <ext-timo.teras@nokia.com>");
 311MODULE_AUTHOR("Luciano Coelho <luciano.coelho@nokia.com>");
 312MODULE_DESCRIPTION("Xtables: idle time monitor");
 313MODULE_LICENSE("GPL v2");
 314MODULE_ALIAS("ipt_IDLETIMER");
 315MODULE_ALIAS("ip6t_IDLETIMER");
 316
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