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 /*
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 return;
153 }
154
155 static bool
156 time_mt(const struct sk_buff *skb, const struct xt_match_param *par)
157 {
158 const struct xt_time_info *info = par->matchinfo;
159 unsigned int packet_time;
160 struct xtm current_time;
161 s64 stamp;
162
163 /*
164 * We cannot use get_seconds() instead of __net_timestamp() here.
165 * Suppose you have two rules:
166 * 1. match before 13:00
167 * 2. match after 13:00
168 * If you match against processing time (get_seconds) it
169 * may happen that the same packet matches both rules if
170 * it arrived at the right moment before 13:00.
171 */
172 if (skb->tstamp.tv64 == 0)
173 __net_timestamp((struct sk_buff *)skb);
174
175 stamp = ktime_to_ns(skb->tstamp);
176 stamp = div_s64(stamp, NSEC_PER_SEC);
177
178 if (info->flags & XT_TIME_LOCAL_TZ)
179 /* Adjust for local timezone */
180 stamp -= 60 * sys_tz.tz_minuteswest;
181
182 /*
183 * xt_time will match when _all_ of the following hold:
184 * - 'now' is in the global time range date_start..date_end
185 * - 'now' is in the monthday mask
186 * - 'now' is in the weekday mask
187 * - 'now' is in the daytime range time_start..time_end
188 * (and by default, libxt_time will set these so as to match)
189 */
190
191 if (stamp < info->date_start || stamp > info->date_stop)
192 return false;
193
194 packet_time = localtime_1(¤t_time, stamp);
195
196 if (info->daytime_start < info->daytime_stop) {
197 if (packet_time < info->daytime_start ||
198 packet_time > info->daytime_stop)
199 return false;
200 } else {
201 if (packet_time < info->daytime_start &&
202 packet_time > info->daytime_stop)
203 return false;
204 }
205
206 localtime_2(¤t_time, stamp);
207
208 if (!(info->weekdays_match & (1 << current_time.weekday)))
209 return false;
210
211 /* Do not spend time computing monthday if all days match anyway */
212 if (info->monthdays_match != XT_TIME_ALL_MONTHDAYS) {
213 localtime_3(¤t_time, stamp);
214 if (!(info->monthdays_match & (1 << current_time.monthday)))
215 return false;
216 }
217
218 return true;
219 }
220
221 static bool time_mt_check(const struct xt_mtchk_param *par)
222 {
223 const struct xt_time_info *info = par->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 xt_time_mt_reg __read_mostly = {
236 .name = "time",
237 .family = NFPROTO_UNSPEC,
238 .match = time_mt,
239 .checkentry = time_mt_check,
240 .matchsize = sizeof(struct xt_time_info),
241 .me = THIS_MODULE,
242 };
243
244 static int __init time_mt_init(void)
245 {
246 int minutes = sys_tz.tz_minuteswest;
247
248 if (minutes < 0) /* east of Greenwich */
249 printk(KERN_INFO KBUILD_MODNAME
250 ": kernel timezone is +%02d%02d\n",
251 -minutes / 60, -minutes % 60);
252 else /* west of Greenwich */
253 printk(KERN_INFO KBUILD_MODNAME
254 ": kernel timezone is -%02d%02d\n",
255 minutes / 60, minutes % 60);
256
257 return xt_register_match(&xt_time_mt_reg);
258 }
259
260 static void __exit time_mt_exit(void)
261 {
262 xt_unregister_match(&xt_time_mt_reg);
263 }
264
265 module_init(time_mt_init);
266 module_exit(time_mt_exit);
267 MODULE_AUTHOR("Jan Engelhardt <jengelh@computergmbh.de>");
268 MODULE_DESCRIPTION("Xtables: time-based matching");
269 MODULE_LICENSE("GPL");
270 MODULE_ALIAS("ipt_time");
271 MODULE_ALIAS("ip6t_time");
272
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