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Linux/net/netfilter/xt_IDLETIMER.c

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  1 // SPDX-License-Identifier: GPL-2.0-only
  2 /*
  3  * linux/net/netfilter/xt_IDLETIMER.c
  4  *
  5  * Netfilter module to trigger a timer when packet matches.
  6  * After timer expires a kevent will be sent.
  7  *
  8  * Copyright (C) 2004, 2010 Nokia Corporation
  9  * Written by Timo Teras <ext-timo.teras@nokia.com>
 10  *
 11  * Converted to x_tables and reworked for upstream inclusion
 12  * by Luciano Coelho <luciano.coelho@nokia.com>
 13  *
 14  * Contact: Luciano Coelho <luciano.coelho@nokia.com>
 15  */
 16 
 17 #define pr_fmt(fmt) KBUILD_MODNAME ": " fmt
 18 
 19 #include <linux/module.h>
 20 #include <linux/timer.h>
 21 #include <linux/alarmtimer.h>
 22 #include <linux/list.h>
 23 #include <linux/mutex.h>
 24 #include <linux/netfilter.h>
 25 #include <linux/netfilter/x_tables.h>
 26 #include <linux/netfilter/xt_IDLETIMER.h>
 27 #include <linux/kdev_t.h>
 28 #include <linux/kobject.h>
 29 #include <linux/workqueue.h>
 30 #include <linux/sysfs.h>
 31 
 32 struct idletimer_tg {
 33         struct list_head entry;
 34         struct alarm alarm;
 35         struct timer_list timer;
 36         struct work_struct work;
 37 
 38         struct kobject *kobj;
 39         struct device_attribute attr;
 40 
 41         unsigned int refcnt;
 42         u8 timer_type;
 43 };
 44 
 45 static LIST_HEAD(idletimer_tg_list);
 46 static DEFINE_MUTEX(list_mutex);
 47 
 48 static struct kobject *idletimer_tg_kobj;
 49 
 50 static
 51 struct idletimer_tg *__idletimer_tg_find_by_label(const char *label)
 52 {
 53         struct idletimer_tg *entry;
 54 
 55         list_for_each_entry(entry, &idletimer_tg_list, entry) {
 56                 if (!strcmp(label, entry->attr.attr.name))
 57                         return entry;
 58         }
 59 
 60         return NULL;
 61 }
 62 
 63 static ssize_t idletimer_tg_show(struct device *dev,
 64                                  struct device_attribute *attr, char *buf)
 65 {
 66         struct idletimer_tg *timer;
 67         unsigned long expires = 0;
 68         struct timespec64 ktimespec = {};
 69         long time_diff = 0;
 70 
 71         mutex_lock(&list_mutex);
 72 
 73         timer = __idletimer_tg_find_by_label(attr->attr.name);
 74         if (timer) {
 75                 if (timer->timer_type & XT_IDLETIMER_ALARM) {
 76                         ktime_t expires_alarm = alarm_expires_remaining(&timer->alarm);
 77                         ktimespec = ktime_to_timespec64(expires_alarm);
 78                         time_diff = ktimespec.tv_sec;
 79                 } else {
 80                         expires = timer->timer.expires;
 81                         time_diff = jiffies_to_msecs(expires - jiffies) / 1000;
 82                 }
 83         }
 84 
 85         mutex_unlock(&list_mutex);
 86 
 87         if (time_after(expires, jiffies) || ktimespec.tv_sec > 0)
 88                 return snprintf(buf, PAGE_SIZE, "%ld\n", time_diff);
 89 
 90         return snprintf(buf, PAGE_SIZE, "\n");
 91 }
 92 
 93 static void idletimer_tg_work(struct work_struct *work)
 94 {
 95         struct idletimer_tg *timer = container_of(work, struct idletimer_tg,
 96                                                   work);
 97 
 98         sysfs_notify(idletimer_tg_kobj, NULL, timer->attr.attr.name);
 99 }
100 
101 static void idletimer_tg_expired(struct timer_list *t)
102 {
103         struct idletimer_tg *timer = from_timer(timer, t, timer);
104 
105         pr_debug("timer %s expired\n", timer->attr.attr.name);
106 
107         schedule_work(&timer->work);
108 }
109 
110 static enum alarmtimer_restart idletimer_tg_alarmproc(struct alarm *alarm,
111                                                           ktime_t now)
112 {
113         struct idletimer_tg *timer = alarm->data;
114 
115         pr_debug("alarm %s expired\n", timer->attr.attr.name);
116         schedule_work(&timer->work);
117         return ALARMTIMER_NORESTART;
118 }
119 
120 static int idletimer_check_sysfs_name(const char *name, unsigned int size)
121 {
122         int ret;
123 
124         ret = xt_check_proc_name(name, size);
125         if (ret < 0)
126                 return ret;
127 
128         if (!strcmp(name, "power") ||
129             !strcmp(name, "subsystem") ||
130             !strcmp(name, "uevent"))
131                 return -EINVAL;
132 
133         return 0;
134 }
135 
136 static int idletimer_tg_create(struct idletimer_tg_info *info)
137 {
138         int ret;
139 
140         info->timer = kmalloc(sizeof(*info->timer), GFP_KERNEL);
141         if (!info->timer) {
142                 ret = -ENOMEM;
143                 goto out;
144         }
145 
146         ret = idletimer_check_sysfs_name(info->label, sizeof(info->label));
147         if (ret < 0)
148                 goto out_free_timer;
149 
150         sysfs_attr_init(&info->timer->attr.attr);
151         info->timer->attr.attr.name = kstrdup(info->label, GFP_KERNEL);
152         if (!info->timer->attr.attr.name) {
153                 ret = -ENOMEM;
154                 goto out_free_timer;
155         }
156         info->timer->attr.attr.mode = 0444;
157         info->timer->attr.show = idletimer_tg_show;
158 
159         ret = sysfs_create_file(idletimer_tg_kobj, &info->timer->attr.attr);
160         if (ret < 0) {
161                 pr_debug("couldn't add file to sysfs");
162                 goto out_free_attr;
163         }
164 
165         list_add(&info->timer->entry, &idletimer_tg_list);
166 
167         timer_setup(&info->timer->timer, idletimer_tg_expired, 0);
168         info->timer->refcnt = 1;
169 
170         INIT_WORK(&info->timer->work, idletimer_tg_work);
171 
172         mod_timer(&info->timer->timer,
173                   msecs_to_jiffies(info->timeout * 1000) + jiffies);
174 
175         return 0;
176 
177 out_free_attr:
178         kfree(info->timer->attr.attr.name);
179 out_free_timer:
180         kfree(info->timer);
181 out:
182         return ret;
183 }
184 
185 static int idletimer_tg_create_v1(struct idletimer_tg_info_v1 *info)
186 {
187         int ret;
188 
189         info->timer = kmalloc(sizeof(*info->timer), GFP_KERNEL);
190         if (!info->timer) {
191                 ret = -ENOMEM;
192                 goto out;
193         }
194 
195         ret = idletimer_check_sysfs_name(info->label, sizeof(info->label));
196         if (ret < 0)
197                 goto out_free_timer;
198 
199         sysfs_attr_init(&info->timer->attr.attr);
200         info->timer->attr.attr.name = kstrdup(info->label, GFP_KERNEL);
201         if (!info->timer->attr.attr.name) {
202                 ret = -ENOMEM;
203                 goto out_free_timer;
204         }
205         info->timer->attr.attr.mode = 0444;
206         info->timer->attr.show = idletimer_tg_show;
207 
208         ret = sysfs_create_file(idletimer_tg_kobj, &info->timer->attr.attr);
209         if (ret < 0) {
210                 pr_debug("couldn't add file to sysfs");
211                 goto out_free_attr;
212         }
213 
214         /*  notify userspace  */
215         kobject_uevent(idletimer_tg_kobj,KOBJ_ADD);
216 
217         list_add(&info->timer->entry, &idletimer_tg_list);
218         pr_debug("timer type value is %u", info->timer_type);
219         info->timer->timer_type = info->timer_type;
220         info->timer->refcnt = 1;
221 
222         INIT_WORK(&info->timer->work, idletimer_tg_work);
223 
224         if (info->timer->timer_type & XT_IDLETIMER_ALARM) {
225                 ktime_t tout;
226                 alarm_init(&info->timer->alarm, ALARM_BOOTTIME,
227                            idletimer_tg_alarmproc);
228                 info->timer->alarm.data = info->timer;
229                 tout = ktime_set(info->timeout, 0);
230                 alarm_start_relative(&info->timer->alarm, tout);
231         } else {
232                 timer_setup(&info->timer->timer, idletimer_tg_expired, 0);
233                 mod_timer(&info->timer->timer,
234                                 msecs_to_jiffies(info->timeout * 1000) + jiffies);
235         }
236 
237         return 0;
238 
239 out_free_attr:
240         kfree(info->timer->attr.attr.name);
241 out_free_timer:
242         kfree(info->timer);
243 out:
244         return ret;
245 }
246 
247 /*
248  * The actual xt_tables plugin.
249  */
250 static unsigned int idletimer_tg_target(struct sk_buff *skb,
251                                          const struct xt_action_param *par)
252 {
253         const struct idletimer_tg_info *info = par->targinfo;
254 
255         pr_debug("resetting timer %s, timeout period %u\n",
256                  info->label, info->timeout);
257 
258         mod_timer(&info->timer->timer,
259                   msecs_to_jiffies(info->timeout * 1000) + jiffies);
260 
261         return XT_CONTINUE;
262 }
263 
264 /*
265  * The actual xt_tables plugin.
266  */
267 static unsigned int idletimer_tg_target_v1(struct sk_buff *skb,
268                                          const struct xt_action_param *par)
269 {
270         const struct idletimer_tg_info_v1 *info = par->targinfo;
271 
272         pr_debug("resetting timer %s, timeout period %u\n",
273                  info->label, info->timeout);
274 
275         if (info->timer->timer_type & XT_IDLETIMER_ALARM) {
276                 ktime_t tout = ktime_set(info->timeout, 0);
277                 alarm_start_relative(&info->timer->alarm, tout);
278         } else {
279                 mod_timer(&info->timer->timer,
280                                 msecs_to_jiffies(info->timeout * 1000) + jiffies);
281         }
282 
283         return XT_CONTINUE;
284 }
285 
286 static int idletimer_tg_helper(struct idletimer_tg_info *info)
287 {
288         if (info->timeout == 0) {
289                 pr_debug("timeout value is zero\n");
290                 return -EINVAL;
291         }
292         if (info->timeout >= INT_MAX / 1000) {
293                 pr_debug("timeout value is too big\n");
294                 return -EINVAL;
295         }
296         if (info->label[0] == '\0' ||
297             strnlen(info->label,
298                     MAX_IDLETIMER_LABEL_SIZE) == MAX_IDLETIMER_LABEL_SIZE) {
299                 pr_debug("label is empty or not nul-terminated\n");
300                 return -EINVAL;
301         }
302         return 0;
303 }
304 
305 
306 static int idletimer_tg_checkentry(const struct xt_tgchk_param *par)
307 {
308         struct idletimer_tg_info *info = par->targinfo;
309         int ret;
310 
311         pr_debug("checkentry targinfo%s\n", info->label);
312 
313         ret = idletimer_tg_helper(info);
314         if(ret < 0)
315         {
316                 pr_debug("checkentry helper return invalid\n");
317                 return -EINVAL;
318         }
319         mutex_lock(&list_mutex);
320 
321         info->timer = __idletimer_tg_find_by_label(info->label);
322         if (info->timer) {
323                 info->timer->refcnt++;
324                 mod_timer(&info->timer->timer,
325                           msecs_to_jiffies(info->timeout * 1000) + jiffies);
326 
327                 pr_debug("increased refcnt of timer %s to %u\n",
328                          info->label, info->timer->refcnt);
329         } else {
330                 ret = idletimer_tg_create(info);
331                 if (ret < 0) {
332                         pr_debug("failed to create timer\n");
333                         mutex_unlock(&list_mutex);
334                         return ret;
335                 }
336         }
337 
338         mutex_unlock(&list_mutex);
339         return 0;
340 }
341 
342 static int idletimer_tg_checkentry_v1(const struct xt_tgchk_param *par)
343 {
344         struct idletimer_tg_info_v1 *info = par->targinfo;
345         int ret;
346 
347         pr_debug("checkentry targinfo%s\n", info->label);
348 
349         if (info->send_nl_msg)
350                 return -EOPNOTSUPP;
351 
352         ret = idletimer_tg_helper((struct idletimer_tg_info *)info);
353         if(ret < 0)
354         {
355                 pr_debug("checkentry helper return invalid\n");
356                 return -EINVAL;
357         }
358 
359         if (info->timer_type > XT_IDLETIMER_ALARM) {
360                 pr_debug("invalid value for timer type\n");
361                 return -EINVAL;
362         }
363 
364         mutex_lock(&list_mutex);
365 
366         info->timer = __idletimer_tg_find_by_label(info->label);
367         if (info->timer) {
368                 if (info->timer->timer_type != info->timer_type) {
369                         pr_debug("Adding/Replacing rule with same label and different timer type is not allowed\n");
370                         mutex_unlock(&list_mutex);
371                         return -EINVAL;
372                 }
373 
374                 info->timer->refcnt++;
375                 if (info->timer_type & XT_IDLETIMER_ALARM) {
376                         /* calculate remaining expiry time */
377                         ktime_t tout = alarm_expires_remaining(&info->timer->alarm);
378                         struct timespec64 ktimespec = ktime_to_timespec64(tout);
379 
380                         if (ktimespec.tv_sec > 0) {
381                                 pr_debug("time_expiry_remaining %lld\n",
382                                          ktimespec.tv_sec);
383                                 alarm_start_relative(&info->timer->alarm, tout);
384                         }
385                 } else {
386                                 mod_timer(&info->timer->timer,
387                                         msecs_to_jiffies(info->timeout * 1000) + jiffies);
388                 }
389                 pr_debug("increased refcnt of timer %s to %u\n",
390                          info->label, info->timer->refcnt);
391         } else {
392                 ret = idletimer_tg_create_v1(info);
393                 if (ret < 0) {
394                         pr_debug("failed to create timer\n");
395                         mutex_unlock(&list_mutex);
396                         return ret;
397                 }
398         }
399 
400         mutex_unlock(&list_mutex);
401         return 0;
402 }
403 
404 static void idletimer_tg_destroy(const struct xt_tgdtor_param *par)
405 {
406         const struct idletimer_tg_info *info = par->targinfo;
407 
408         pr_debug("destroy targinfo %s\n", info->label);
409 
410         mutex_lock(&list_mutex);
411 
412         if (--info->timer->refcnt == 0) {
413                 pr_debug("deleting timer %s\n", info->label);
414 
415                 list_del(&info->timer->entry);
416                 del_timer_sync(&info->timer->timer);
417                 cancel_work_sync(&info->timer->work);
418                 sysfs_remove_file(idletimer_tg_kobj, &info->timer->attr.attr);
419                 kfree(info->timer->attr.attr.name);
420                 kfree(info->timer);
421         } else {
422                 pr_debug("decreased refcnt of timer %s to %u\n",
423                          info->label, info->timer->refcnt);
424         }
425 
426         mutex_unlock(&list_mutex);
427 }
428 
429 static void idletimer_tg_destroy_v1(const struct xt_tgdtor_param *par)
430 {
431         const struct idletimer_tg_info_v1 *info = par->targinfo;
432 
433         pr_debug("destroy targinfo %s\n", info->label);
434 
435         mutex_lock(&list_mutex);
436 
437         if (--info->timer->refcnt == 0) {
438                 pr_debug("deleting timer %s\n", info->label);
439 
440                 list_del(&info->timer->entry);
441                 if (info->timer->timer_type & XT_IDLETIMER_ALARM) {
442                         alarm_cancel(&info->timer->alarm);
443                 } else {
444                         del_timer_sync(&info->timer->timer);
445                 }
446                 cancel_work_sync(&info->timer->work);
447                 sysfs_remove_file(idletimer_tg_kobj, &info->timer->attr.attr);
448                 kfree(info->timer->attr.attr.name);
449                 kfree(info->timer);
450         } else {
451                 pr_debug("decreased refcnt of timer %s to %u\n",
452                          info->label, info->timer->refcnt);
453         }
454 
455         mutex_unlock(&list_mutex);
456 }
457 
458 
459 static struct xt_target idletimer_tg[] __read_mostly = {
460         {
461         .name           = "IDLETIMER",
462         .family         = NFPROTO_UNSPEC,
463         .target         = idletimer_tg_target,
464         .targetsize     = sizeof(struct idletimer_tg_info),
465         .usersize       = offsetof(struct idletimer_tg_info, timer),
466         .checkentry     = idletimer_tg_checkentry,
467         .destroy        = idletimer_tg_destroy,
468         .me             = THIS_MODULE,
469         },
470         {
471         .name           = "IDLETIMER",
472         .family         = NFPROTO_UNSPEC,
473         .revision       = 1,
474         .target         = idletimer_tg_target_v1,
475         .targetsize     = sizeof(struct idletimer_tg_info_v1),
476         .usersize       = offsetof(struct idletimer_tg_info_v1, timer),
477         .checkentry     = idletimer_tg_checkentry_v1,
478         .destroy        = idletimer_tg_destroy_v1,
479         .me             = THIS_MODULE,
480         },
481 
482 
483 };
484 
485 static struct class *idletimer_tg_class;
486 
487 static struct device *idletimer_tg_device;
488 
489 static int __init idletimer_tg_init(void)
490 {
491         int err;
492 
493         idletimer_tg_class = class_create(THIS_MODULE, "xt_idletimer");
494         err = PTR_ERR(idletimer_tg_class);
495         if (IS_ERR(idletimer_tg_class)) {
496                 pr_debug("couldn't register device class\n");
497                 goto out;
498         }
499 
500         idletimer_tg_device = device_create(idletimer_tg_class, NULL,
501                                             MKDEV(0, 0), NULL, "timers");
502         err = PTR_ERR(idletimer_tg_device);
503         if (IS_ERR(idletimer_tg_device)) {
504                 pr_debug("couldn't register system device\n");
505                 goto out_class;
506         }
507 
508         idletimer_tg_kobj = &idletimer_tg_device->kobj;
509 
510         err = xt_register_targets(idletimer_tg, ARRAY_SIZE(idletimer_tg));
511 
512         if (err < 0) {
513                 pr_debug("couldn't register xt target\n");
514                 goto out_dev;
515         }
516 
517         return 0;
518 out_dev:
519         device_destroy(idletimer_tg_class, MKDEV(0, 0));
520 out_class:
521         class_destroy(idletimer_tg_class);
522 out:
523         return err;
524 }
525 
526 static void __exit idletimer_tg_exit(void)
527 {
528         xt_unregister_targets(idletimer_tg, ARRAY_SIZE(idletimer_tg));
529 
530         device_destroy(idletimer_tg_class, MKDEV(0, 0));
531         class_destroy(idletimer_tg_class);
532 }
533 
534 module_init(idletimer_tg_init);
535 module_exit(idletimer_tg_exit);
536 
537 MODULE_AUTHOR("Timo Teras <ext-timo.teras@nokia.com>");
538 MODULE_AUTHOR("Luciano Coelho <luciano.coelho@nokia.com>");
539 MODULE_DESCRIPTION("Xtables: idle time monitor");
540 MODULE_LICENSE("GPL v2");
541 MODULE_ALIAS("ipt_IDLETIMER");
542 MODULE_ALIAS("ip6t_IDLETIMER");
543 

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