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
13 #define pr_fmt(fmt) KBUILD_MODNAME ": " fmt
14
15 #include <linux/ktime.h>
16 #include <linux/module.h>
17 #include <linux/skbuff.h>
18 #include <linux/types.h>
19 #include <linux/netfilter/x_tables.h>
20 #include <linux/netfilter/xt_time.h>
21
22 struct xtm {
23 u_int8_t month; /* (1-12) */
24 u_int8_t monthday; /* (1-31) */
25 u_int8_t weekday; /* (1-7) */
26 u_int8_t hour; /* (0-23) */
27 u_int8_t minute; /* (0-59) */
28 u_int8_t second; /* (0-59) */
29 unsigned int dse;
30 };
31
32 extern struct timezone sys_tz; /* ouch */
33
34 static const u_int16_t days_since_year[] = {
35 0, 31, 59, 90, 120, 151, 181, 212, 243, 273, 304, 334,
36 };
37
38 static const u_int16_t days_since_leapyear[] = {
39 0, 31, 60, 91, 121, 152, 182, 213, 244, 274, 305, 335,
40 };
41
42 /*
43 * Since time progresses forward, it is best to organize this array in reverse,
44 * to minimize lookup time.
45 */
46 enum {
47 DSE_FIRST = 2039,
48 SECONDS_PER_DAY = 86400,
49 };
50 static const u_int16_t days_since_epoch[] = {
51 /* 2039 - 2030 */
52 25202, 24837, 24472, 24106, 23741, 23376, 23011, 22645, 22280, 21915,
53 /* 2029 - 2020 */
54 21550, 21184, 20819, 20454, 20089, 19723, 19358, 18993, 18628, 18262,
55 /* 2019 - 2010 */
56 17897, 17532, 17167, 16801, 16436, 16071, 15706, 15340, 14975, 14610,
57 /* 2009 - 2000 */
58 14245, 13879, 13514, 13149, 12784, 12418, 12053, 11688, 11323, 10957,
59 /* 1999 - 1990 */
60 10592, 10227, 9862, 9496, 9131, 8766, 8401, 8035, 7670, 7305,
61 /* 1989 - 1980 */
62 6940, 6574, 6209, 5844, 5479, 5113, 4748, 4383, 4018, 3652,
63 /* 1979 - 1970 */
64 3287, 2922, 2557, 2191, 1826, 1461, 1096, 730, 365, 0,
65 };
66
67 static inline bool is_leap(unsigned int y)
68 {
69 return y % 4 == 0 && (y % 100 != 0 || y % 400 == 0);
70 }
71
72 /*
73 * Each network packet has a (nano)seconds-since-the-epoch (SSTE) timestamp.
74 * Since we match against days and daytime, the SSTE value needs to be
75 * computed back into human-readable dates.
76 *
77 * This is done in three separate functions so that the most expensive
78 * calculations are done last, in case a "simple match" can be found earlier.
79 */
80 static inline unsigned int localtime_1(struct xtm *r, time_t time)
81 {
82 unsigned int v, w;
83
84 /* Each day has 86400s, so finding the hour/minute is actually easy. */
85 v = time % SECONDS_PER_DAY;
86 r->second = v % 60;
87 w = v / 60;
88 r->minute = w % 60;
89 r->hour = w / 60;
90 return v;
91 }
92
93 static inline void localtime_2(struct xtm *r, time_t time)
94 {
95 /*
96 * Here comes the rest (weekday, monthday). First, divide the SSTE
97 * by seconds-per-day to get the number of _days_ since the epoch.
98 */
99 r->dse = time / 86400;
100
101 /*
102 * 1970-01-01 (w=0) was a Thursday (4).
103 * -1 and +1 map Sunday properly onto 7.
104 */
105 r->weekday = (4 + r->dse - 1) % 7 + 1;
106 }
107
108 static void localtime_3(struct xtm *r, time_t time)
109 {
110 unsigned int year, i, w = r->dse;
111
112 /*
113 * In each year, a certain number of days-since-the-epoch have passed.
114 * Find the year that is closest to said days.
115 *
116 * Consider, for example, w=21612 (2029-03-04). Loop will abort on
117 * dse[i] <= w, which happens when dse[i] == 21550. This implies
118 * year == 2009. w will then be 62.
119 */
120 for (i = 0, year = DSE_FIRST; days_since_epoch[i] > w;
121 ++i, --year)
122 /* just loop */;
123
124 w -= days_since_epoch[i];
125
126 /*
127 * By now we have the current year, and the day of the year.
128 * r->yearday = w;
129 *
130 * On to finding the month (like above). In each month, a certain
131 * number of days-since-New Year have passed, and find the closest
132 * one.
133 *
134 * Consider w=62 (in a non-leap year). Loop will abort on
135 * dsy[i] < w, which happens when dsy[i] == 31+28 (i == 2).
136 * Concludes i == 2, i.e. 3rd month => March.
137 *
138 * (A different approach to use would be to subtract a monthlength
139 * from w repeatedly while counting.)
140 */
141 if (is_leap(year)) {
142 /* use days_since_leapyear[] in a leap year */
143 for (i = ARRAY_SIZE(days_since_leapyear) - 1;
144 i > 0 && days_since_leapyear[i] > w; --i)
145 /* just loop */;
146 r->monthday = w - days_since_leapyear[i] + 1;
147 } else {
148 for (i = ARRAY_SIZE(days_since_year) - 1;
149 i > 0 && days_since_year[i] > w; --i)
150 /* just loop */;
151 r->monthday = w - days_since_year[i] + 1;
152 }
153
154 r->month = i + 1;
155 }
156
157 static bool
158 time_mt(const struct sk_buff *skb, struct xt_action_param *par)
159 {
160 const struct xt_time_info *info = par->matchinfo;
161 unsigned int packet_time;
162 struct xtm current_time;
163 s64 stamp;
164
165 /*
166 * We need real time here, but we can neither use skb->tstamp
167 * nor __net_timestamp().
168 *
169 * skb->tstamp and skb->skb_mstamp_ns overlap, however, they
170 * use different clock types (real vs monotonic).
171 *
172 * Suppose you have two rules:
173 * 1. match before 13:00
174 * 2. match after 13:00
175 *
176 * If you match against processing time (get_seconds) it
177 * may happen that the same packet matches both rules if
178 * it arrived at the right moment before 13:00, so it would be
179 * better to check skb->tstamp and set it via __net_timestamp()
180 * if needed. This however breaks outgoing packets tx timestamp,
181 * and causes them to get delayed forever by fq packet scheduler.
182 */
183 stamp = get_seconds();
184
185 if (info->flags & XT_TIME_LOCAL_TZ)
186 /* Adjust for local timezone */
187 stamp -= 60 * sys_tz.tz_minuteswest;
188
189 /*
190 * xt_time will match when _all_ of the following hold:
191 * - 'now' is in the global time range date_start..date_end
192 * - 'now' is in the monthday mask
193 * - 'now' is in the weekday mask
194 * - 'now' is in the daytime range time_start..time_end
195 * (and by default, libxt_time will set these so as to match)
196 */
197
198 if (stamp < info->date_start || stamp > info->date_stop)
199 return false;
200
201 packet_time = localtime_1(¤t_time, stamp);
202
203 if (info->daytime_start < info->daytime_stop) {
204 if (packet_time < info->daytime_start ||
205 packet_time > info->daytime_stop)
206 return false;
207 } else {
208 if (packet_time < info->daytime_start &&
209 packet_time > info->daytime_stop)
210 return false;
211
212 /** if user asked to ignore 'next day', then e.g.
213 * '1 PM Wed, August 1st' should be treated
214 * like 'Tue 1 PM July 31st'.
215 *
216 * This also causes
217 * 'Monday, "23:00 to 01:00", to match for 2 hours, starting
218 * Monday 23:00 to Tuesday 01:00.
219 */
220 if ((info->flags & XT_TIME_CONTIGUOUS) &&
221 packet_time <= info->daytime_stop)
222 stamp -= SECONDS_PER_DAY;
223 }
224
225 localtime_2(¤t_time, stamp);
226
227 if (!(info->weekdays_match & (1 << current_time.weekday)))
228 return false;
229
230 /* Do not spend time computing monthday if all days match anyway */
231 if (info->monthdays_match != XT_TIME_ALL_MONTHDAYS) {
232 localtime_3(¤t_time, stamp);
233 if (!(info->monthdays_match & (1 << current_time.monthday)))
234 return false;
235 }
236
237 return true;
238 }
239
240 static int time_mt_check(const struct xt_mtchk_param *par)
241 {
242 const struct xt_time_info *info = par->matchinfo;
243
244 if (info->daytime_start > XT_TIME_MAX_DAYTIME ||
245 info->daytime_stop > XT_TIME_MAX_DAYTIME) {
246 pr_info_ratelimited("invalid argument - start or stop time greater than 23:59:59\n");
247 return -EDOM;
248 }
249
250 if (info->flags & ~XT_TIME_ALL_FLAGS) {
251 pr_info_ratelimited("unknown flags 0x%x\n",
252 info->flags & ~XT_TIME_ALL_FLAGS);
253 return -EINVAL;
254 }
255
256 if ((info->flags & XT_TIME_CONTIGUOUS) &&
257 info->daytime_start < info->daytime_stop)
258 return -EINVAL;
259
260 return 0;
261 }
262
263 static struct xt_match xt_time_mt_reg __read_mostly = {
264 .name = "time",
265 .family = NFPROTO_UNSPEC,
266 .match = time_mt,
267 .checkentry = time_mt_check,
268 .matchsize = sizeof(struct xt_time_info),
269 .me = THIS_MODULE,
270 };
271
272 static int __init time_mt_init(void)
273 {
274 int minutes = sys_tz.tz_minuteswest;
275
276 if (minutes < 0) /* east of Greenwich */
277 pr_info("kernel timezone is +%02d%02d\n",
278 -minutes / 60, -minutes % 60);
279 else /* west of Greenwich */
280 pr_info("kernel timezone is -%02d%02d\n",
281 minutes / 60, minutes % 60);
282
283 return xt_register_match(&xt_time_mt_reg);
284 }
285
286 static void __exit time_mt_exit(void)
287 {
288 xt_unregister_match(&xt_time_mt_reg);
289 }
290
291 module_init(time_mt_init);
292 module_exit(time_mt_exit);
293 MODULE_AUTHOR("Jan Engelhardt <jengelh@medozas.de>");
294 MODULE_DESCRIPTION("Xtables: time-based matching");
295 MODULE_LICENSE("GPL");
296 MODULE_ALIAS("ipt_time");
297 MODULE_ALIAS("ip6t_time");