net/netfilter/xt_time.c

   1 /*
   2  *      xt_time
   3  *      Copyright © CC Computer Consultants GmbH, 2007
   4  *      Contact: <jengelh@computergmbh.de>
   5  *
   6  *      based on ipt_time by Fabrice MARIE <fabrice@netfilter.org>
   7  *      This is a module which is used for time matching
   8  *      It is using some modified code from dietlibc (localtime() function)
   9  *      that you can find at http://www.fefe.de/dietlibc/
  10  *      This file is distributed under the terms of the GNU General Public
  11  *      License (GPL). Copies of the GPL can be obtained from gnu.org/gpl.
  12  */
  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
  20 struct xtm {
  21         u_int8_t month;    /* (1-12) */
  22         u_int8_t monthday; /* (1-31) */
  23         u_int8_t weekday;  /* (1-7) */
  24         u_int8_t hour;     /* (0-23) */
  25         u_int8_t minute;   /* (0-59) */
  26         u_int8_t second;   /* (0-59) */
  27         unsigned int dse;
  28 };
  29
  30 extern struct timezone sys_tz; /* ouch */
  31
  32 static const u_int16_t days_since_year[] = {
  33         0, 31, 59, 90, 120, 151, 181, 212, 243, 273, 304, 334,
  34 };
  35
  36 static const u_int16_t days_since_leapyear[] = {
  37         0, 31, 60, 91, 121, 152, 182, 213, 244, 274, 305, 335,
  38 };
  39
  40 /*
  41  * Since time progresses forward, it is best to organize this array in reverse,
  42  * to minimize lookup time.
  43  */
  44 enum {
  45         DSE_FIRST = 2039,
  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 % 86400;
  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         /* 1970-01-01 (w=0) was a Thursday (4). */
  99         r->weekday = (4 + r->dse) % 7;
 100 }
 101
 102 static void localtime_3(struct xtm *r, time_t time)
 103 {
 104         unsigned int year, i, w = r->dse;
 105
 106         /*
 107          * In each year, a certain number of days-since-the-epoch have passed.
 108          * Find the year that is closest to said days.
 109          *
 110          * Consider, for example, w=21612 (2029-03-04). Loop will abort on
 111          * dse[i] <= w, which happens when dse[i] == 21550. This implies
 112          * year == 2009. w will then be 62.
 113          */
 114         for (i = 0, year = DSE_FIRST; days_since_epoch[i] > w;
 115             ++i, --year)
 116                 /* just loop */;
 117
 118         w -= days_since_epoch[i];
 119
 120         /*
 121          * By now we have the current year, and the day of the year.
 122          * r->yearday = w;
 123          *
 124          * On to finding the month (like above). In each month, a certain
 125          * number of days-since-New Year have passed, and find the closest
 126          * one.
 127          *
 128          * Consider w=62 (in a non-leap year). Loop will abort on
 129          * dsy[i] < w, which happens when dsy[i] == 31+28 (i == 2).
 130          * Concludes i == 2, i.e. 3rd month => March.
 131          *
 132          * (A different approach to use would be to subtract a monthlength
 133          * from w repeatedly while counting.)
 134          */
 135         if (is_leap(year)) {
 136                 for (i = ARRAY_SIZE(days_since_leapyear) - 1;
 137                     i > 0 && days_since_year[i] > w; --i)
 138                         /* just loop */;
 139         } else {
 140                 for (i = ARRAY_SIZE(days_since_year) - 1;
 141                     i > 0 && days_since_year[i] > w; --i)
 142                         /* just loop */;
 143         }
 144
 145         r->month    = i + 1;
 146         r->monthday = w - days_since_year[i] + 1;
 147         return;
 148 }
 149
 150 static bool
 151 time_mt(const struct sk_buff *skb, const struct net_device *in,
 152         const struct net_device *out, const struct xt_match *match,
 153         const void *matchinfo, 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 = ktime_to_ns(skb->tstamp);
 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
 219 time_mt_check(const char *tablename, const void *ip,
 220               const struct xt_match *match, void *matchinfo,
 221               unsigned int hook_mask)
 222 {
 223         struct xt_time_info *info = matchinfo;
 224
 225         if (info->daytime_start > XT_TIME_MAX_DAYTIME ||
 226             info->daytime_stop > XT_TIME_MAX_DAYTIME) {
 227                 printk(KERN_WARNING "xt_time: invalid argument - start or "
 228                        "stop time greater than 23:59:59\n");
 229                 return false;
 230         }
 231
 232         return true;
 233 }
 234
 235 static struct xt_match time_mt_reg[] __read_mostly = {
 236         {
 237                 .name       = "time",
 238                 .family     = AF_INET,
 239                 .match      = time_mt,
 240                 .matchsize  = sizeof(struct xt_time_info),
 241                 .checkentry = time_mt_check,
 242                 .me         = THIS_MODULE,
 243         },
 244         {
 245                 .name       = "time",
 246                 .family     = AF_INET6,
 247                 .match      = time_mt,
 248                 .matchsize  = sizeof(struct xt_time_info),
 249                 .checkentry = time_mt_check,
 250                 .me         = THIS_MODULE,
 251         },
 252 };
 253
 254 static int __init time_mt_init(void)
 255 {
 256         return xt_register_matches(time_mt_reg, ARRAY_SIZE(time_mt_reg));
 257 }
 258
 259 static void __exit time_mt_exit(void)
 260 {
 261         xt_unregister_matches(time_mt_reg, ARRAY_SIZE(time_mt_reg));
 262 }
 263
 264 module_init(time_mt_init);
 265 module_exit(time_mt_exit);
 266 MODULE_AUTHOR("Jan Engelhardt <jengelh@computergmbh.de>");
 267 MODULE_DESCRIPTION("netfilter time match");
 268 MODULE_LICENSE("GPL");
 269 MODULE_ALIAS("ipt_time");
 270 MODULE_ALIAS("ip6t_time");