xref: /openbmc/linux/net/netfilter/xt_IDLETIMER.c (revision ba61bb17) 
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 = 0444;
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");
321