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 http://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 #include <linux/ktime.h> 13 #include <linux/module.h> 14 #include <linux/skbuff.h> 15 #include <linux/types.h> 16 #include <linux/netfilter/x_tables.h> 17 #include <linux/netfilter/xt_time.h> 18 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 29 extern struct timezone sys_tz; /* ouch */ 30 31 static const u_int16_t days_since_year[] = { 32 0, 31, 59, 90, 120, 151, 181, 212, 243, 273, 304, 334, 33 }; 34 35 static const u_int16_t days_since_leapyear[] = { 36 0, 31, 60, 91, 121, 152, 182, 213, 244, 274, 305, 335, 37 }; 38 39 /* 40 * Since time progresses forward, it is best to organize this array in reverse, 41 * to minimize lookup time. 42 */ 43 enum { 44 DSE_FIRST = 2039, 45 SECONDS_PER_DAY = 86400, 46 }; 47 static const u_int16_t days_since_epoch[] = { 48 /* 2039 - 2030 */ 49 25202, 24837, 24472, 24106, 23741, 23376, 23011, 22645, 22280, 21915, 50 /* 2029 - 2020 */ 51 21550, 21184, 20819, 20454, 20089, 19723, 19358, 18993, 18628, 18262, 52 /* 2019 - 2010 */ 53 17897, 17532, 17167, 16801, 16436, 16071, 15706, 15340, 14975, 14610, 54 /* 2009 - 2000 */ 55 14245, 13879, 13514, 13149, 12784, 12418, 12053, 11688, 11323, 10957, 56 /* 1999 - 1990 */ 57 10592, 10227, 9862, 9496, 9131, 8766, 8401, 8035, 7670, 7305, 58 /* 1989 - 1980 */ 59 6940, 6574, 6209, 5844, 5479, 5113, 4748, 4383, 4018, 3652, 60 /* 1979 - 1970 */ 61 3287, 2922, 2557, 2191, 1826, 1461, 1096, 730, 365, 0, 62 }; 63 64 static inline bool is_leap(unsigned int y) 65 { 66 return y % 4 == 0 && (y % 100 != 0 || y % 400 == 0); 67 } 68 69 /* 70 * Each network packet has a (nano)seconds-since-the-epoch (SSTE) timestamp. 71 * Since we match against days and daytime, the SSTE value needs to be 72 * computed back into human-readable dates. 73 * 74 * This is done in three separate functions so that the most expensive 75 * calculations are done last, in case a "simple match" can be found earlier. 76 */ 77 static inline unsigned int localtime_1(struct xtm *r, time_t time) 78 { 79 unsigned int v, w; 80 81 /* Each day has 86400s, so finding the hour/minute is actually easy. */ 82 v = time % SECONDS_PER_DAY; 83 r->second = v % 60; 84 w = v / 60; 85 r->minute = w % 60; 86 r->hour = w / 60; 87 return v; 88 } 89 90 static inline void localtime_2(struct xtm *r, time_t time) 91 { 92 /* 93 * Here comes the rest (weekday, monthday). First, divide the SSTE 94 * by seconds-per-day to get the number of _days_ since the epoch. 95 */ 96 r->dse = time / 86400; 97 98 /* 99 * 1970-01-01 (w=0) was a Thursday (4). 100 * -1 and +1 map Sunday properly onto 7. 101 */ 102 r->weekday = (4 + r->dse - 1) % 7 + 1; 103 } 104 105 static void localtime_3(struct xtm *r, time_t time) 106 { 107 unsigned int year, i, w = r->dse; 108 109 /* 110 * In each year, a certain number of days-since-the-epoch have passed. 111 * Find the year that is closest to said days. 112 * 113 * Consider, for example, w=21612 (2029-03-04). Loop will abort on 114 * dse[i] <= w, which happens when dse[i] == 21550. This implies 115 * year == 2009. w will then be 62. 116 */ 117 for (i = 0, year = DSE_FIRST; days_since_epoch[i] > w; 118 ++i, --year) 119 /* just loop */; 120 121 w -= days_since_epoch[i]; 122 123 /* 124 * By now we have the current year, and the day of the year. 125 * r->yearday = w; 126 * 127 * On to finding the month (like above). In each month, a certain 128 * number of days-since-New Year have passed, and find the closest 129 * one. 130 * 131 * Consider w=62 (in a non-leap year). Loop will abort on 132 * dsy[i] < w, which happens when dsy[i] == 31+28 (i == 2). 133 * Concludes i == 2, i.e. 3rd month => March. 134 * 135 * (A different approach to use would be to subtract a monthlength 136 * from w repeatedly while counting.) 137 */ 138 if (is_leap(year)) { 139 /* use days_since_leapyear[] in a leap year */ 140 for (i = ARRAY_SIZE(days_since_leapyear) - 1; 141 i > 0 && days_since_leapyear[i] > w; --i) 142 /* just loop */; 143 r->monthday = w - days_since_leapyear[i] + 1; 144 } else { 145 for (i = ARRAY_SIZE(days_since_year) - 1; 146 i > 0 && days_since_year[i] > w; --i) 147 /* just loop */; 148 r->monthday = w - days_since_year[i] + 1; 149 } 150 151 r->month = i + 1; 152 } 153 154 static bool 155 time_mt(const struct sk_buff *skb, struct xt_action_param *par) 156 { 157 const struct xt_time_info *info = par->matchinfo; 158 unsigned int packet_time; 159 struct xtm current_time; 160 s64 stamp; 161 162 /* 163 * We cannot use get_seconds() instead of __net_timestamp() here. 164 * Suppose you have two rules: 165 * 1. match before 13:00 166 * 2. match after 13:00 167 * If you match against processing time (get_seconds) it 168 * may happen that the same packet matches both rules if 169 * it arrived at the right moment before 13:00. 170 */ 171 if (skb->tstamp == 0) 172 __net_timestamp((struct sk_buff *)skb); 173 174 stamp = ktime_to_ns(skb->tstamp); 175 stamp = div_s64(stamp, NSEC_PER_SEC); 176 177 if (info->flags & XT_TIME_LOCAL_TZ) 178 /* Adjust for local timezone */ 179 stamp -= 60 * sys_tz.tz_minuteswest; 180 181 /* 182 * xt_time will match when _all_ of the following hold: 183 * - 'now' is in the global time range date_start..date_end 184 * - 'now' is in the monthday mask 185 * - 'now' is in the weekday mask 186 * - 'now' is in the daytime range time_start..time_end 187 * (and by default, libxt_time will set these so as to match) 188 */ 189 190 if (stamp < info->date_start || stamp > info->date_stop) 191 return false; 192 193 packet_time = localtime_1(¤t_time, stamp); 194 195 if (info->daytime_start < info->daytime_stop) { 196 if (packet_time < info->daytime_start || 197 packet_time > info->daytime_stop) 198 return false; 199 } else { 200 if (packet_time < info->daytime_start && 201 packet_time > info->daytime_stop) 202 return false; 203 204 /** if user asked to ignore 'next day', then e.g. 205 * '1 PM Wed, August 1st' should be treated 206 * like 'Tue 1 PM July 31st'. 207 * 208 * This also causes 209 * 'Monday, "23:00 to 01:00", to match for 2 hours, starting 210 * Monday 23:00 to Tuesday 01:00. 211 */ 212 if ((info->flags & XT_TIME_CONTIGUOUS) && 213 packet_time <= info->daytime_stop) 214 stamp -= SECONDS_PER_DAY; 215 } 216 217 localtime_2(¤t_time, stamp); 218 219 if (!(info->weekdays_match & (1 << current_time.weekday))) 220 return false; 221 222 /* Do not spend time computing monthday if all days match anyway */ 223 if (info->monthdays_match != XT_TIME_ALL_MONTHDAYS) { 224 localtime_3(¤t_time, stamp); 225 if (!(info->monthdays_match & (1 << current_time.monthday))) 226 return false; 227 } 228 229 return true; 230 } 231 232 static int time_mt_check(const struct xt_mtchk_param *par) 233 { 234 const struct xt_time_info *info = par->matchinfo; 235 236 if (info->daytime_start > XT_TIME_MAX_DAYTIME || 237 info->daytime_stop > XT_TIME_MAX_DAYTIME) { 238 pr_info("invalid argument - start or " 239 "stop time greater than 23:59:59\n"); 240 return -EDOM; 241 } 242 243 if (info->flags & ~XT_TIME_ALL_FLAGS) { 244 pr_info("unknown flags 0x%x\n", info->flags & ~XT_TIME_ALL_FLAGS); 245 return -EINVAL; 246 } 247 248 if ((info->flags & XT_TIME_CONTIGUOUS) && 249 info->daytime_start < info->daytime_stop) 250 return -EINVAL; 251 252 return 0; 253 } 254 255 static struct xt_match xt_time_mt_reg __read_mostly = { 256 .name = "time", 257 .family = NFPROTO_UNSPEC, 258 .match = time_mt, 259 .checkentry = time_mt_check, 260 .matchsize = sizeof(struct xt_time_info), 261 .me = THIS_MODULE, 262 }; 263 264 static int __init time_mt_init(void) 265 { 266 int minutes = sys_tz.tz_minuteswest; 267 268 if (minutes < 0) /* east of Greenwich */ 269 printk(KERN_INFO KBUILD_MODNAME 270 ": kernel timezone is +%02d%02d\n", 271 -minutes / 60, -minutes % 60); 272 else /* west of Greenwich */ 273 printk(KERN_INFO KBUILD_MODNAME 274 ": kernel timezone is -%02d%02d\n", 275 minutes / 60, minutes % 60); 276 277 return xt_register_match(&xt_time_mt_reg); 278 } 279 280 static void __exit time_mt_exit(void) 281 { 282 xt_unregister_match(&xt_time_mt_reg); 283 } 284 285 module_init(time_mt_init); 286 module_exit(time_mt_exit); 287 MODULE_AUTHOR("Jan Engelhardt <jengelh@medozas.de>"); 288 MODULE_DESCRIPTION("Xtables: time-based matching"); 289 MODULE_LICENSE("GPL"); 290 MODULE_ALIAS("ipt_time"); 291 MODULE_ALIAS("ip6t_time"); 292