/* * xt_time * Copyright © CC Computer Consultants GmbH, 2007 * * based on ipt_time by Fabrice MARIE * This is a module which is used for time matching * It is using some modified code from dietlibc (localtime() function) * that you can find at http://www.fefe.de/dietlibc/ * This file is distributed under the terms of the GNU General Public * License (GPL). Copies of the GPL can be obtained from gnu.org/gpl. */ #include #include #include #include #include #include struct xtm { u_int8_t month; /* (1-12) */ u_int8_t monthday; /* (1-31) */ u_int8_t weekday; /* (1-7) */ u_int8_t hour; /* (0-23) */ u_int8_t minute; /* (0-59) */ u_int8_t second; /* (0-59) */ unsigned int dse; }; extern struct timezone sys_tz; /* ouch */ static const u_int16_t days_since_year[] = { 0, 31, 59, 90, 120, 151, 181, 212, 243, 273, 304, 334, }; static const u_int16_t days_since_leapyear[] = { 0, 31, 60, 91, 121, 152, 182, 213, 244, 274, 305, 335, }; /* * Since time progresses forward, it is best to organize this array in reverse, * to minimize lookup time. */ enum { DSE_FIRST = 2039, SECONDS_PER_DAY = 86400, }; static const u_int16_t days_since_epoch[] = { /* 2039 - 2030 */ 25202, 24837, 24472, 24106, 23741, 23376, 23011, 22645, 22280, 21915, /* 2029 - 2020 */ 21550, 21184, 20819, 20454, 20089, 19723, 19358, 18993, 18628, 18262, /* 2019 - 2010 */ 17897, 17532, 17167, 16801, 16436, 16071, 15706, 15340, 14975, 14610, /* 2009 - 2000 */ 14245, 13879, 13514, 13149, 12784, 12418, 12053, 11688, 11323, 10957, /* 1999 - 1990 */ 10592, 10227, 9862, 9496, 9131, 8766, 8401, 8035, 7670, 7305, /* 1989 - 1980 */ 6940, 6574, 6209, 5844, 5479, 5113, 4748, 4383, 4018, 3652, /* 1979 - 1970 */ 3287, 2922, 2557, 2191, 1826, 1461, 1096, 730, 365, 0, }; static inline bool is_leap(unsigned int y) { return y % 4 == 0 && (y % 100 != 0 || y % 400 == 0); } /* * Each network packet has a (nano)seconds-since-the-epoch (SSTE) timestamp. * Since we match against days and daytime, the SSTE value needs to be * computed back into human-readable dates. * * This is done in three separate functions so that the most expensive * calculations are done last, in case a "simple match" can be found earlier. */ static inline unsigned int localtime_1(struct xtm *r, time_t time) { unsigned int v, w; /* Each day has 86400s, so finding the hour/minute is actually easy. */ v = time % SECONDS_PER_DAY; r->second = v % 60; w = v / 60; r->minute = w % 60; r->hour = w / 60; return v; } static inline void localtime_2(struct xtm *r, time_t time) { /* * Here comes the rest (weekday, monthday). First, divide the SSTE * by seconds-per-day to get the number of _days_ since the epoch. */ r->dse = time / 86400; /* * 1970-01-01 (w=0) was a Thursday (4). * -1 and +1 map Sunday properly onto 7. */ r->weekday = (4 + r->dse - 1) % 7 + 1; } static void localtime_3(struct xtm *r, time_t time) { unsigned int year, i, w = r->dse; /* * In each year, a certain number of days-since-the-epoch have passed. * Find the year that is closest to said days. * * Consider, for example, w=21612 (2029-03-04). Loop will abort on * dse[i] <= w, which happens when dse[i] == 21550. This implies * year == 2009. w will then be 62. */ for (i = 0, year = DSE_FIRST; days_since_epoch[i] > w; ++i, --year) /* just loop */; w -= days_since_epoch[i]; /* * By now we have the current year, and the day of the year. * r->yearday = w; * * On to finding the month (like above). In each month, a certain * number of days-since-New Year have passed, and find the closest * one. * * Consider w=62 (in a non-leap year). Loop will abort on * dsy[i] < w, which happens when dsy[i] == 31+28 (i == 2). * Concludes i == 2, i.e. 3rd month => March. * * (A different approach to use would be to subtract a monthlength * from w repeatedly while counting.) */ if (is_leap(year)) { /* use days_since_leapyear[] in a leap year */ for (i = ARRAY_SIZE(days_since_leapyear) - 1; i > 0 && days_since_leapyear[i] > w; --i) /* just loop */; r->monthday = w - days_since_leapyear[i] + 1; } else { for (i = ARRAY_SIZE(days_since_year) - 1; i > 0 && days_since_year[i] > w; --i) /* just loop */; r->monthday = w - days_since_year[i] + 1; } r->month = i + 1; } static bool time_mt(const struct sk_buff *skb, struct xt_action_param *par) { const struct xt_time_info *info = par->matchinfo; unsigned int packet_time; struct xtm current_time; s64 stamp; /* * We cannot use get_seconds() instead of __net_timestamp() here. * Suppose you have two rules: * 1. match before 13:00 * 2. match after 13:00 * If you match against processing time (get_seconds) it * may happen that the same packet matches both rules if * it arrived at the right moment before 13:00. */ if (skb->tstamp.tv64 == 0) __net_timestamp((struct sk_buff *)skb); stamp = ktime_to_ns(skb->tstamp); stamp = div_s64(stamp, NSEC_PER_SEC); if (info->flags & XT_TIME_LOCAL_TZ) /* Adjust for local timezone */ stamp -= 60 * sys_tz.tz_minuteswest; /* * xt_time will match when _all_ of the following hold: * - 'now' is in the global time range date_start..date_end * - 'now' is in the monthday mask * - 'now' is in the weekday mask * - 'now' is in the daytime range time_start..time_end * (and by default, libxt_time will set these so as to match) */ if (stamp < info->date_start || stamp > info->date_stop) return false; packet_time = localtime_1(¤t_time, stamp); if (info->daytime_start < info->daytime_stop) { if (packet_time < info->daytime_start || packet_time > info->daytime_stop) return false; } else { if (packet_time < info->daytime_start && packet_time > info->daytime_stop) return false; /** if user asked to ignore 'next day', then e.g. * '1 PM Wed, August 1st' should be treated * like 'Tue 1 PM July 31st'. * * This also causes * 'Monday, "23:00 to 01:00", to match for 2 hours, starting * Monday 23:00 to Tuesday 01:00. */ if ((info->flags & XT_TIME_CONTIGUOUS) && packet_time <= info->daytime_stop) stamp -= SECONDS_PER_DAY; } localtime_2(¤t_time, stamp); if (!(info->weekdays_match & (1 << current_time.weekday))) return false; /* Do not spend time computing monthday if all days match anyway */ if (info->monthdays_match != XT_TIME_ALL_MONTHDAYS) { localtime_3(¤t_time, stamp); if (!(info->monthdays_match & (1 << current_time.monthday))) return false; } return true; } static int time_mt_check(const struct xt_mtchk_param *par) { const struct xt_time_info *info = par->matchinfo; if (info->daytime_start > XT_TIME_MAX_DAYTIME || info->daytime_stop > XT_TIME_MAX_DAYTIME) { pr_info("invalid argument - start or " "stop time greater than 23:59:59\n"); return -EDOM; } if (info->flags & ~XT_TIME_ALL_FLAGS) { pr_info("unknown flags 0x%x\n", info->flags & ~XT_TIME_ALL_FLAGS); return -EINVAL; } if ((info->flags & XT_TIME_CONTIGUOUS) && info->daytime_start < info->daytime_stop) return -EINVAL; return 0; } static struct xt_match xt_time_mt_reg __read_mostly = { .name = "time", .family = NFPROTO_UNSPEC, .match = time_mt, .checkentry = time_mt_check, .matchsize = sizeof(struct xt_time_info), .me = THIS_MODULE, }; static int __init time_mt_init(void) { int minutes = sys_tz.tz_minuteswest; if (minutes < 0) /* east of Greenwich */ printk(KERN_INFO KBUILD_MODNAME ": kernel timezone is +%02d%02d\n", -minutes / 60, -minutes % 60); else /* west of Greenwich */ printk(KERN_INFO KBUILD_MODNAME ": kernel timezone is -%02d%02d\n", minutes / 60, minutes % 60); return xt_register_match(&xt_time_mt_reg); } static void __exit time_mt_exit(void) { xt_unregister_match(&xt_time_mt_reg); } module_init(time_mt_init); module_exit(time_mt_exit); MODULE_AUTHOR("Jan Engelhardt "); MODULE_DESCRIPTION("Xtables: time-based matching"); MODULE_LICENSE("GPL"); MODULE_ALIAS("ipt_time"); MODULE_ALIAS("ip6t_time");