net/netfilter/xt_time.c

   1 /*
   2  *      xt_time
   3  *      Copyright © Jan Engelhardt <jengelh@computergmbh.de>, 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 };
  46 static const u_int16_t days_since_epoch[] = {
  47         /* 2039 - 2030 */
  48         25202, 24837, 24472, 24106, 23741, 23376, 23011, 22645, 22280, 21915,
  49         /* 2029 - 2020 */
  50         21550, 21184, 20819, 20454, 20089, 19723, 19358, 18993, 18628, 18262,
  51         /* 2019 - 2010 */
  52         17897, 17532, 17167, 16801, 16436, 16071, 15706, 15340, 14975, 14610,
  53         /* 2009 - 2000 */
  54         14245, 13879, 13514, 13149, 12784, 12418, 12053, 11688, 11323, 10957,
  55         /* 1999 - 1990 */
  56         10592, 10227, 9862, 9496, 9131, 8766, 8401, 8035, 7670, 7305,
  57         /* 1989 - 1980 */
  58         6940, 6574, 6209, 5844, 5479, 5113, 4748, 4383, 4018, 3652,
  59         /* 1979 - 1970 */
  60         3287, 2922, 2557, 2191, 1826, 1461, 1096, 730, 365, 0,
  61 };
  62
  63 static inline bool is_leap(unsigned int y)
  64 {
  65         return y % 4 == 0 && (y % 100 != 0 || y % 400 == 0);
  66 }
  67
  68 /*
  69  * Each network packet has a (nano)seconds-since-the-epoch (SSTE) timestamp.
  70  * Since we match against days and daytime, the SSTE value needs to be
  71  * computed back into human-readable dates.
  72  *
  73  * This is done in three separate functions so that the most expensive
  74  * calculations are done last, in case a "simple match" can be found earlier.
  75  */
  76 static inline unsigned int localtime_1(struct xtm *r, time_t time)
  77 {
  78         unsigned int v, w;
  79
  80         /* Each day has 86400s, so finding the hour/minute is actually easy. */
  81         v         = time % 86400;
  82         r->second = v % 60;
  83         w         = v / 60;
  84         r->minute = w % 60;
  85         r->hour   = w / 60;
  86         return v;
  87 }
  88
  89 static inline void localtime_2(struct xtm *r, time_t time)
  90 {
  91         /*
  92          * Here comes the rest (weekday, monthday). First, divide the SSTE
  93          * by seconds-per-day to get the number of _days_ since the epoch.
  94          */
  95         r->dse = time / 86400;
  96
  97         /* 1970-01-01 (w=0) was a Thursday (4). */
  98         r->weekday = (4 + r->dse) % 7;
  99 }
 100
 101 static void localtime_3(struct xtm *r, time_t time)
 102 {
 103         unsigned int year, i, w = r->dse;
 104
 105         /*
 106          * In each year, a certain number of days-since-the-epoch have passed.
 107          * Find the year that is closest to said days.
 108          *
 109          * Consider, for example, w=21612 (2029-03-04). Loop will abort on
 110          * dse[i] <= w, which happens when dse[i] == 21550. This implies
 111          * year == 2009. w will then be 62.
 112          */
 113         for (i = 0, year = DSE_FIRST; days_since_epoch[i] > w;
 114             ++i, --year)
 115                 /* just loop */;
 116
 117         w -= days_since_epoch[i];
 118
 119         /*
 120          * By now we have the current year, and the day of the year.
 121          * r->yearday = w;
 122          *
 123          * On to finding the month (like above). In each month, a certain
 124          * number of days-since-New Year have passed, and find the closest
 125          * one.
 126          *
 127          * Consider w=62 (in a non-leap year). Loop will abort on
 128          * dsy[i] < w, which happens when dsy[i] == 31+28 (i == 2).
 129          * Concludes i == 2, i.e. 3rd month => March.
 130          *
 131          * (A different approach to use would be to subtract a monthlength
 132          * from w repeatedly while counting.)
 133          */
 134         if (is_leap(year)) {
 135                 for (i = ARRAY_SIZE(days_since_leapyear) - 1;
 136                     i > 0 && days_since_year[i] > w; --i)
 137                         /* just loop */;
 138         } else {
 139                 for (i = ARRAY_SIZE(days_since_year) - 1;
 140                     i > 0 && days_since_year[i] > w; --i)
 141                         /* just loop */;
 142         }
 143
 144         r->month    = i + 1;
 145         r->monthday = w - days_since_year[i] + 1;
 146         return;
 147 }
 148
 149 static bool xt_time_match(const struct sk_buff *skb,
 150                           const struct net_device *in,
 151                           const struct net_device *out,
 152                           const struct xt_match *match, const void *matchinfo,
 153                           int offset, unsigned int protoff, bool *hotdrop)
 154 {
 155         const struct xt_time_info *info = matchinfo;
 156         unsigned int packet_time;
 157         struct xtm current_time;
 158         s64 stamp;
 159
 160         /*
 161          * We cannot use get_seconds() instead of __net_timestamp() here.
 162          * Suppose you have two rules:
 163          *      1. match before 13:00
 164          *      2. match after 13:00
 165          * If you match against processing time (get_seconds) it
 166          * may happen that the same packet matches both rules if
 167          * it arrived at the right moment before 13:00.
 168          */
 169         if (skb->tstamp.tv64 == 0)
 170                 __net_timestamp((struct sk_buff *)skb);
 171
 172         stamp = skb->tstamp.tv64;
 173         do_div(stamp, NSEC_PER_SEC);
 174
 175         if (info->flags & XT_TIME_LOCAL_TZ)
 176                 /* Adjust for local timezone */
 177                 stamp -= 60 * sys_tz.tz_minuteswest;
 178
 179         /*
 180          * xt_time will match when _all_ of the following hold:
 181          *   - 'now' is in the global time range date_start..date_end
 182          *   - 'now' is in the monthday mask
 183          *   - 'now' is in the weekday mask
 184          *   - 'now' is in the daytime range time_start..time_end
 185          * (and by default, libxt_time will set these so as to match)
 186          */
 187
 188         if (stamp < info->date_start || stamp > info->date_stop)
 189                 return false;
 190
 191         packet_time = localtime_1(&current_time, stamp);
 192
 193         if (info->daytime_start < info->daytime_stop) {
 194                 if (packet_time < info->daytime_start ||
 195                     packet_time > info->daytime_stop)
 196                         return false;
 197         } else {
 198                 if (packet_time < info->daytime_start &&
 199                     packet_time > info->daytime_stop)
 200                         return false;
 201         }
 202
 203         localtime_2(&current_time, stamp);
 204
 205         if (!(info->weekdays_match & (1 << current_time.weekday)))
 206                 return false;
 207
 208         /* Do not spend time computing monthday if all days match anyway */
 209         if (info->monthdays_match != XT_TIME_ALL_MONTHDAYS) {
 210                 localtime_3(&current_time, stamp);
 211                 if (!(info->monthdays_match & (1 << current_time.monthday)))
 212                         return false;
 213         }
 214
 215         return true;
 216 }
 217
 218 static bool xt_time_check(const char *tablename, const void *ip,
 219                           const struct xt_match *match, void *matchinfo,
 220                           unsigned int hook_mask)
 221 {
 222         struct xt_time_info *info = matchinfo;
 223
 224         if (info->daytime_start > XT_TIME_MAX_DAYTIME ||
 225             info->daytime_stop > XT_TIME_MAX_DAYTIME) {
 226                 printk(KERN_WARNING "xt_time: invalid argument - start or "
 227                        "stop time greater than 23:59:59\n");
 228                 return false;
 229         }
 230
 231         return true;
 232 }
 233
 234 static struct xt_match xt_time_reg[] __read_mostly = {
 235         {
 236                 .name       = "time",
 237                 .family     = AF_INET,
 238                 .match      = xt_time_match,
 239                 .matchsize  = sizeof(struct xt_time_info),
 240                 .checkentry = xt_time_check,
 241                 .me         = THIS_MODULE,
 242         },
 243         {
 244                 .name       = "time",
 245                 .family     = AF_INET6,
 246                 .match      = xt_time_match,
 247                 .matchsize  = sizeof(struct xt_time_info),
 248                 .checkentry = xt_time_check,
 249                 .me         = THIS_MODULE,
 250         },
 251 };
 252
 253 static int __init xt_time_init(void)
 254 {
 255         return xt_register_matches(xt_time_reg, ARRAY_SIZE(xt_time_reg));
 256 }
 257
 258 static void __exit xt_time_exit(void)
 259 {
 260         xt_unregister_matches(xt_time_reg, ARRAY_SIZE(xt_time_reg));
 261 }
 262
 263 module_init(xt_time_init);
 264 module_exit(xt_time_exit);
 265 MODULE_AUTHOR("Jan Engelhardt <jengelh@computergmbh.de>");
 266 MODULE_DESCRIPTION("netfilter time match");
 267 MODULE_LICENSE("GPL");
 268 MODULE_ALIAS("ipt_time");
 269 MODULE_ALIAS("ip6t_time");