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/net/netfilter/xt_time.c

http://github.com/mirrors/linux
C | 300 lines | 158 code | 40 blank | 102 comment | 29 complexity | 44b1f7464b159158ce3251e2b9616398 MD5 | raw file
  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
 22struct 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
 32extern struct timezone sys_tz; /* ouch */
 33
 34static const u_int16_t days_since_year[] = {
 35	0, 31, 59, 90, 120, 151, 181, 212, 243, 273, 304, 334,
 36};
 37
 38static 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 */
 46enum {
 47	DSE_FIRST = 2039,
 48	SECONDS_PER_DAY = 86400,
 49};
 50static 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
 67static 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 */
 80static inline unsigned int localtime_1(struct xtm *r, time64_t time)
 81{
 82	unsigned int v, w;
 83
 84	/* Each day has 86400s, so finding the hour/minute is actually easy. */
 85	div_u64_rem(time, SECONDS_PER_DAY, &v);
 86	r->second = v % 60;
 87	w         = v / 60;
 88	r->minute = w % 60;
 89	r->hour   = w / 60;
 90	return v;
 91}
 92
 93static inline void localtime_2(struct xtm *r, time64_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 = div_u64(time, SECONDS_PER_DAY);
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
108static void localtime_3(struct xtm *r, time64_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
157static bool
158time_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	time64_t 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 (ktime_get_real_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 = ktime_get_real_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	 * note: info->date_start/stop are unsigned 32-bit values that
198	 *	 can hold values beyond y2038, but not after y2106.
199	 */
200
201	if (stamp < info->date_start || stamp > info->date_stop)
202		return false;
203
204	packet_time = localtime_1(&current_time, stamp);
205
206	if (info->daytime_start < info->daytime_stop) {
207		if (packet_time < info->daytime_start ||
208		    packet_time > info->daytime_stop)
209			return false;
210	} else {
211		if (packet_time < info->daytime_start &&
212		    packet_time > info->daytime_stop)
213			return false;
214
215		/** if user asked to ignore 'next day', then e.g.
216		 *  '1 PM Wed, August 1st' should be treated
217		 *  like 'Tue 1 PM July 31st'.
218		 *
219		 * This also causes
220		 * 'Monday, "23:00 to 01:00", to match for 2 hours, starting
221		 * Monday 23:00 to Tuesday 01:00.
222		 */
223		if ((info->flags & XT_TIME_CONTIGUOUS) &&
224		     packet_time <= info->daytime_stop)
225			stamp -= SECONDS_PER_DAY;
226	}
227
228	localtime_2(&current_time, stamp);
229
230	if (!(info->weekdays_match & (1 << current_time.weekday)))
231		return false;
232
233	/* Do not spend time computing monthday if all days match anyway */
234	if (info->monthdays_match != XT_TIME_ALL_MONTHDAYS) {
235		localtime_3(&current_time, stamp);
236		if (!(info->monthdays_match & (1 << current_time.monthday)))
237			return false;
238	}
239
240	return true;
241}
242
243static int time_mt_check(const struct xt_mtchk_param *par)
244{
245	const struct xt_time_info *info = par->matchinfo;
246
247	if (info->daytime_start > XT_TIME_MAX_DAYTIME ||
248	    info->daytime_stop > XT_TIME_MAX_DAYTIME) {
249		pr_info_ratelimited("invalid argument - start or stop time greater than 23:59:59\n");
250		return -EDOM;
251	}
252
253	if (info->flags & ~XT_TIME_ALL_FLAGS) {
254		pr_info_ratelimited("unknown flags 0x%x\n",
255				    info->flags & ~XT_TIME_ALL_FLAGS);
256		return -EINVAL;
257	}
258
259	if ((info->flags & XT_TIME_CONTIGUOUS) &&
260	     info->daytime_start < info->daytime_stop)
261		return -EINVAL;
262
263	return 0;
264}
265
266static struct xt_match xt_time_mt_reg __read_mostly = {
267	.name       = "time",
268	.family     = NFPROTO_UNSPEC,
269	.match      = time_mt,
270	.checkentry = time_mt_check,
271	.matchsize  = sizeof(struct xt_time_info),
272	.me         = THIS_MODULE,
273};
274
275static int __init time_mt_init(void)
276{
277	int minutes = sys_tz.tz_minuteswest;
278
279	if (minutes < 0) /* east of Greenwich */
280		pr_info("kernel timezone is +%02d%02d\n",
281			-minutes / 60, -minutes % 60);
282	else /* west of Greenwich */
283		pr_info("kernel timezone is -%02d%02d\n",
284			minutes / 60, minutes % 60);
285
286	return xt_register_match(&xt_time_mt_reg);
287}
288
289static void __exit time_mt_exit(void)
290{
291	xt_unregister_match(&xt_time_mt_reg);
292}
293
294module_init(time_mt_init);
295module_exit(time_mt_exit);
296MODULE_AUTHOR("Jan Engelhardt <jengelh@medozas.de>");
297MODULE_DESCRIPTION("Xtables: time-based matching");
298MODULE_LICENSE("GPL");
299MODULE_ALIAS("ipt_time");
300MODULE_ALIAS("ip6t_time");