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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 {
 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, "\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");
331 

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