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
19struct 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
29extern struct timezone sys_tz; /* ouch */
30
31static const u_int16_t days_since_year[] = {
32	0, 31, 59, 90, 120, 151, 181, 212, 243, 273, 304, 334,
33};
34
35static 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 */
43enum {
44	DSE_FIRST = 2039,
45	SECONDS_PER_DAY = 86400,
46};
47static 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
64static 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 */
77static 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
90static 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
105static 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
154static bool
155time_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.tv64 == 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(&current_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(&current_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(&current_time, stamp);
225		if (!(info->monthdays_match & (1 << current_time.monthday)))
226			return false;
227	}
228
229	return true;
230}
231
232static 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
255static 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
264static 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
280static void __exit time_mt_exit(void)
281{
282	xt_unregister_match(&xt_time_mt_reg);
283}
284
285module_init(time_mt_init);
286module_exit(time_mt_exit);
287MODULE_AUTHOR("Jan Engelhardt <jengelh@medozas.de>");
288MODULE_DESCRIPTION("Xtables: time-based matching");
289MODULE_LICENSE("GPL");
290MODULE_ALIAS("ipt_time");
291MODULE_ALIAS("ip6t_time");
292