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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 
 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, "\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");
337 

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