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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         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, "\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(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 
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         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 
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 
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 
225 static 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 
249 static 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 
259 static struct class *idletimer_tg_class;
260 
261 static struct device *idletimer_tg_device;
262 
263 static 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;
291 out_dev:
292         device_destroy(idletimer_tg_class, MKDEV(0, 0));
293 out_class:
294         class_destroy(idletimer_tg_class);
295 out:
296         return err;
297 }
298 
299 static 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 
307 module_init(idletimer_tg_init);
308 module_exit(idletimer_tg_exit);
309 
310 MODULE_AUTHOR("Timo Teras <ext-timo.teras@nokia.com>");
311 MODULE_AUTHOR("Luciano Coelho <luciano.coelho@nokia.com>");
312 MODULE_DESCRIPTION("Xtables: idle time monitor");
313 MODULE_LICENSE("GPL v2");
314 MODULE_ALIAS("ipt_IDLETIMER");
315 MODULE_ALIAS("ip6t_IDLETIMER");
316 

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