xt_time.c 8.5 KB

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  1. /*
  2. * xt_time
  3. * Copyright © CC Computer Consultants GmbH, 2007
  4. *
  5. * based on ipt_time by Fabrice MARIE <fabrice@netfilter.org>
  6. * This is a module which is used for time matching
  7. * It is using some modified code from dietlibc (localtime() function)
  8. * that you can find at https://www.fefe.de/dietlibc/
  9. * This file is distributed under the terms of the GNU General Public
  10. * License (GPL). Copies of the GPL can be obtained from gnu.org/gpl.
  11. */
  12. #define pr_fmt(fmt) KBUILD_MODNAME ": " fmt
  13. #include <linux/ktime.h>
  14. #include <linux/module.h>
  15. #include <linux/skbuff.h>
  16. #include <linux/types.h>
  17. #include <linux/netfilter/x_tables.h>
  18. #include <linux/netfilter/xt_time.h>
  19. struct xtm {
  20. u_int8_t month; /* (1-12) */
  21. u_int8_t monthday; /* (1-31) */
  22. u_int8_t weekday; /* (1-7) */
  23. u_int8_t hour; /* (0-23) */
  24. u_int8_t minute; /* (0-59) */
  25. u_int8_t second; /* (0-59) */
  26. unsigned int dse;
  27. };
  28. extern struct timezone sys_tz; /* ouch */
  29. static const u_int16_t days_since_year[] = {
  30. 0, 31, 59, 90, 120, 151, 181, 212, 243, 273, 304, 334,
  31. };
  32. static const u_int16_t days_since_leapyear[] = {
  33. 0, 31, 60, 91, 121, 152, 182, 213, 244, 274, 305, 335,
  34. };
  35. /*
  36. * Since time progresses forward, it is best to organize this array in reverse,
  37. * to minimize lookup time.
  38. */
  39. enum {
  40. DSE_FIRST = 2039,
  41. SECONDS_PER_DAY = 86400,
  42. };
  43. static const u_int16_t days_since_epoch[] = {
  44. /* 2039 - 2030 */
  45. 25202, 24837, 24472, 24106, 23741, 23376, 23011, 22645, 22280, 21915,
  46. /* 2029 - 2020 */
  47. 21550, 21184, 20819, 20454, 20089, 19723, 19358, 18993, 18628, 18262,
  48. /* 2019 - 2010 */
  49. 17897, 17532, 17167, 16801, 16436, 16071, 15706, 15340, 14975, 14610,
  50. /* 2009 - 2000 */
  51. 14245, 13879, 13514, 13149, 12784, 12418, 12053, 11688, 11323, 10957,
  52. /* 1999 - 1990 */
  53. 10592, 10227, 9862, 9496, 9131, 8766, 8401, 8035, 7670, 7305,
  54. /* 1989 - 1980 */
  55. 6940, 6574, 6209, 5844, 5479, 5113, 4748, 4383, 4018, 3652,
  56. /* 1979 - 1970 */
  57. 3287, 2922, 2557, 2191, 1826, 1461, 1096, 730, 365, 0,
  58. };
  59. static inline bool is_leap(unsigned int y)
  60. {
  61. return y % 4 == 0 && (y % 100 != 0 || y % 400 == 0);
  62. }
  63. /*
  64. * Each network packet has a (nano)seconds-since-the-epoch (SSTE) timestamp.
  65. * Since we match against days and daytime, the SSTE value needs to be
  66. * computed back into human-readable dates.
  67. *
  68. * This is done in three separate functions so that the most expensive
  69. * calculations are done last, in case a "simple match" can be found earlier.
  70. */
  71. static inline unsigned int localtime_1(struct xtm *r, time64_t time)
  72. {
  73. unsigned int v, w;
  74. /* Each day has 86400s, so finding the hour/minute is actually easy. */
  75. div_u64_rem(time, SECONDS_PER_DAY, &v);
  76. r->second = v % 60;
  77. w = v / 60;
  78. r->minute = w % 60;
  79. r->hour = w / 60;
  80. return v;
  81. }
  82. static inline void localtime_2(struct xtm *r, time64_t time)
  83. {
  84. /*
  85. * Here comes the rest (weekday, monthday). First, divide the SSTE
  86. * by seconds-per-day to get the number of _days_ since the epoch.
  87. */
  88. r->dse = div_u64(time, SECONDS_PER_DAY);
  89. /*
  90. * 1970-01-01 (w=0) was a Thursday (4).
  91. * -1 and +1 map Sunday properly onto 7.
  92. */
  93. r->weekday = (4 + r->dse - 1) % 7 + 1;
  94. }
  95. static void localtime_3(struct xtm *r, time64_t time)
  96. {
  97. unsigned int year, i, w = r->dse;
  98. /*
  99. * In each year, a certain number of days-since-the-epoch have passed.
  100. * Find the year that is closest to said days.
  101. *
  102. * Consider, for example, w=21612 (2029-03-04). Loop will abort on
  103. * dse[i] <= w, which happens when dse[i] == 21550. This implies
  104. * year == 2009. w will then be 62.
  105. */
  106. for (i = 0, year = DSE_FIRST; days_since_epoch[i] > w;
  107. ++i, --year)
  108. /* just loop */;
  109. w -= days_since_epoch[i];
  110. /*
  111. * By now we have the current year, and the day of the year.
  112. * r->yearday = w;
  113. *
  114. * On to finding the month (like above). In each month, a certain
  115. * number of days-since-New Year have passed, and find the closest
  116. * one.
  117. *
  118. * Consider w=62 (in a non-leap year). Loop will abort on
  119. * dsy[i] < w, which happens when dsy[i] == 31+28 (i == 2).
  120. * Concludes i == 2, i.e. 3rd month => March.
  121. *
  122. * (A different approach to use would be to subtract a monthlength
  123. * from w repeatedly while counting.)
  124. */
  125. if (is_leap(year)) {
  126. /* use days_since_leapyear[] in a leap year */
  127. for (i = ARRAY_SIZE(days_since_leapyear) - 1;
  128. i > 0 && days_since_leapyear[i] > w; --i)
  129. /* just loop */;
  130. r->monthday = w - days_since_leapyear[i] + 1;
  131. } else {
  132. for (i = ARRAY_SIZE(days_since_year) - 1;
  133. i > 0 && days_since_year[i] > w; --i)
  134. /* just loop */;
  135. r->monthday = w - days_since_year[i] + 1;
  136. }
  137. r->month = i + 1;
  138. }
  139. static bool
  140. time_mt(const struct sk_buff *skb, struct xt_action_param *par)
  141. {
  142. const struct xt_time_info *info = par->matchinfo;
  143. unsigned int packet_time;
  144. struct xtm current_time;
  145. time64_t stamp;
  146. /*
  147. * We need real time here, but we can neither use skb->tstamp
  148. * nor __net_timestamp().
  149. *
  150. * skb->tstamp and skb->skb_mstamp_ns overlap, however, they
  151. * use different clock types (real vs monotonic).
  152. *
  153. * Suppose you have two rules:
  154. * 1. match before 13:00
  155. * 2. match after 13:00
  156. *
  157. * If you match against processing time (ktime_get_real_seconds) it
  158. * may happen that the same packet matches both rules if
  159. * it arrived at the right moment before 13:00, so it would be
  160. * better to check skb->tstamp and set it via __net_timestamp()
  161. * if needed. This however breaks outgoing packets tx timestamp,
  162. * and causes them to get delayed forever by fq packet scheduler.
  163. */
  164. stamp = ktime_get_real_seconds();
  165. if (info->flags & XT_TIME_LOCAL_TZ)
  166. /* Adjust for local timezone */
  167. stamp -= 60 * sys_tz.tz_minuteswest;
  168. /*
  169. * xt_time will match when _all_ of the following hold:
  170. * - 'now' is in the global time range date_start..date_end
  171. * - 'now' is in the monthday mask
  172. * - 'now' is in the weekday mask
  173. * - 'now' is in the daytime range time_start..time_end
  174. * (and by default, libxt_time will set these so as to match)
  175. *
  176. * note: info->date_start/stop are unsigned 32-bit values that
  177. * can hold values beyond y2038, but not after y2106.
  178. */
  179. if (stamp < info->date_start || stamp > info->date_stop)
  180. return false;
  181. packet_time = localtime_1(&current_time, stamp);
  182. if (info->daytime_start < info->daytime_stop) {
  183. if (packet_time < info->daytime_start ||
  184. packet_time > info->daytime_stop)
  185. return false;
  186. } else {
  187. if (packet_time < info->daytime_start &&
  188. packet_time > info->daytime_stop)
  189. return false;
  190. /** if user asked to ignore 'next day', then e.g.
  191. * '1 PM Wed, August 1st' should be treated
  192. * like 'Tue 1 PM July 31st'.
  193. *
  194. * This also causes
  195. * 'Monday, "23:00 to 01:00", to match for 2 hours, starting
  196. * Monday 23:00 to Tuesday 01:00.
  197. */
  198. if ((info->flags & XT_TIME_CONTIGUOUS) &&
  199. packet_time <= info->daytime_stop)
  200. stamp -= SECONDS_PER_DAY;
  201. }
  202. localtime_2(&current_time, stamp);
  203. if (!(info->weekdays_match & (1 << current_time.weekday)))
  204. return false;
  205. /* Do not spend time computing monthday if all days match anyway */
  206. if (info->monthdays_match != XT_TIME_ALL_MONTHDAYS) {
  207. localtime_3(&current_time, stamp);
  208. if (!(info->monthdays_match & (1 << current_time.monthday)))
  209. return false;
  210. }
  211. return true;
  212. }
  213. static int time_mt_check(const struct xt_mtchk_param *par)
  214. {
  215. const struct xt_time_info *info = par->matchinfo;
  216. if (info->daytime_start > XT_TIME_MAX_DAYTIME ||
  217. info->daytime_stop > XT_TIME_MAX_DAYTIME) {
  218. pr_info_ratelimited("invalid argument - start or stop time greater than 23:59:59\n");
  219. return -EDOM;
  220. }
  221. if (info->flags & ~XT_TIME_ALL_FLAGS) {
  222. pr_info_ratelimited("unknown flags 0x%x\n",
  223. info->flags & ~XT_TIME_ALL_FLAGS);
  224. return -EINVAL;
  225. }
  226. if ((info->flags & XT_TIME_CONTIGUOUS) &&
  227. info->daytime_start < info->daytime_stop)
  228. return -EINVAL;
  229. return 0;
  230. }
  231. static struct xt_match xt_time_mt_reg __read_mostly = {
  232. .name = "time",
  233. .family = NFPROTO_UNSPEC,
  234. .match = time_mt,
  235. .checkentry = time_mt_check,
  236. .matchsize = sizeof(struct xt_time_info),
  237. .me = THIS_MODULE,
  238. };
  239. static int __init time_mt_init(void)
  240. {
  241. int minutes = sys_tz.tz_minuteswest;
  242. if (minutes < 0) /* east of Greenwich */
  243. pr_info("kernel timezone is +%02d%02d\n",
  244. -minutes / 60, -minutes % 60);
  245. else /* west of Greenwich */
  246. pr_info("kernel timezone is -%02d%02d\n",
  247. minutes / 60, minutes % 60);
  248. return xt_register_match(&xt_time_mt_reg);
  249. }
  250. static void __exit time_mt_exit(void)
  251. {
  252. xt_unregister_match(&xt_time_mt_reg);
  253. }
  254. module_init(time_mt_init);
  255. module_exit(time_mt_exit);
  256. MODULE_AUTHOR("Jan Engelhardt <jengelh@medozas.de>");
  257. MODULE_DESCRIPTION("Xtables: time-based matching");
  258. MODULE_LICENSE("GPL");
  259. MODULE_ALIAS("ipt_time");
  260. MODULE_ALIAS("ip6t_time");