/*
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* xt_time
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* Copyright © CC Computer Consultants GmbH, 2007
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*
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* based on ipt_time by Fabrice MARIE <fabrice@netfilter.org>
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* This is a module which is used for time matching
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* It is using some modified code from dietlibc (localtime() function)
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* that you can find at https://www.fefe.de/dietlibc/
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* This file is distributed under the terms of the GNU General Public
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* License (GPL). Copies of the GPL can be obtained from gnu.org/gpl.
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*/
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#define pr_fmt(fmt) KBUILD_MODNAME ": " fmt
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#include <linux/ktime.h>
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#include <linux/module.h>
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#include <linux/skbuff.h>
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#include <linux/types.h>
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#include <linux/netfilter/x_tables.h>
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#include <linux/netfilter/xt_time.h>
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struct xtm {
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u_int8_t month; /* (1-12) */
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u_int8_t monthday; /* (1-31) */
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u_int8_t weekday; /* (1-7) */
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u_int8_t hour; /* (0-23) */
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u_int8_t minute; /* (0-59) */
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u_int8_t second; /* (0-59) */
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unsigned int dse;
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};
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extern struct timezone sys_tz; /* ouch */
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static const u_int16_t days_since_year[] = {
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0, 31, 59, 90, 120, 151, 181, 212, 243, 273, 304, 334,
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};
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static const u_int16_t days_since_leapyear[] = {
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0, 31, 60, 91, 121, 152, 182, 213, 244, 274, 305, 335,
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};
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/*
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* Since time progresses forward, it is best to organize this array in reverse,
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* to minimize lookup time.
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*/
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enum {
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DSE_FIRST = 2039,
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SECONDS_PER_DAY = 86400,
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};
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static const u_int16_t days_since_epoch[] = {
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/* 2039 - 2030 */
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25202, 24837, 24472, 24106, 23741, 23376, 23011, 22645, 22280, 21915,
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/* 2029 - 2020 */
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21550, 21184, 20819, 20454, 20089, 19723, 19358, 18993, 18628, 18262,
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/* 2019 - 2010 */
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17897, 17532, 17167, 16801, 16436, 16071, 15706, 15340, 14975, 14610,
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/* 2009 - 2000 */
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14245, 13879, 13514, 13149, 12784, 12418, 12053, 11688, 11323, 10957,
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/* 1999 - 1990 */
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10592, 10227, 9862, 9496, 9131, 8766, 8401, 8035, 7670, 7305,
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/* 1989 - 1980 */
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6940, 6574, 6209, 5844, 5479, 5113, 4748, 4383, 4018, 3652,
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/* 1979 - 1970 */
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3287, 2922, 2557, 2191, 1826, 1461, 1096, 730, 365, 0,
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};
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static inline bool is_leap(unsigned int y)
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{
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return y % 4 == 0 && (y % 100 != 0 || y % 400 == 0);
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}
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/*
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* Each network packet has a (nano)seconds-since-the-epoch (SSTE) timestamp.
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* Since we match against days and daytime, the SSTE value needs to be
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* computed back into human-readable dates.
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*
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* This is done in three separate functions so that the most expensive
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* calculations are done last, in case a "simple match" can be found earlier.
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*/
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static inline unsigned int localtime_1(struct xtm *r, time64_t time)
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{
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unsigned int v, w;
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/* Each day has 86400s, so finding the hour/minute is actually easy. */
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div_u64_rem(time, SECONDS_PER_DAY, &v);
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r->second = v % 60;
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w = v / 60;
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r->minute = w % 60;
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r->hour = w / 60;
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return v;
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}
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static inline void localtime_2(struct xtm *r, time64_t time)
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{
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/*
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* Here comes the rest (weekday, monthday). First, divide the SSTE
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* by seconds-per-day to get the number of _days_ since the epoch.
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*/
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r->dse = div_u64(time, SECONDS_PER_DAY);
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/*
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* 1970-01-01 (w=0) was a Thursday (4).
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* -1 and +1 map Sunday properly onto 7.
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*/
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r->weekday = (4 + r->dse - 1) % 7 + 1;
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}
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static void localtime_3(struct xtm *r, time64_t time)
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{
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unsigned int year, i, w = r->dse;
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/*
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* In each year, a certain number of days-since-the-epoch have passed.
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* Find the year that is closest to said days.
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*
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* Consider, for example, w=21612 (2029-03-04). Loop will abort on
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* dse[i] <= w, which happens when dse[i] == 21550. This implies
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* year == 2009. w will then be 62.
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*/
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for (i = 0, year = DSE_FIRST; days_since_epoch[i] > w;
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++i, --year)
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/* just loop */;
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w -= days_since_epoch[i];
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/*
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* By now we have the current year, and the day of the year.
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* r->yearday = w;
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*
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* On to finding the month (like above). In each month, a certain
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* number of days-since-New Year have passed, and find the closest
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* one.
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*
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* Consider w=62 (in a non-leap year). Loop will abort on
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* dsy[i] < w, which happens when dsy[i] == 31+28 (i == 2).
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* Concludes i == 2, i.e. 3rd month => March.
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*
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* (A different approach to use would be to subtract a monthlength
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* from w repeatedly while counting.)
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*/
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if (is_leap(year)) {
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/* use days_since_leapyear[] in a leap year */
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for (i = ARRAY_SIZE(days_since_leapyear) - 1;
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i > 0 && days_since_leapyear[i] > w; --i)
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/* just loop */;
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r->monthday = w - days_since_leapyear[i] + 1;
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} else {
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for (i = ARRAY_SIZE(days_since_year) - 1;
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i > 0 && days_since_year[i] > w; --i)
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/* just loop */;
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r->monthday = w - days_since_year[i] + 1;
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}
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r->month = i + 1;
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}
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static bool
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time_mt(const struct sk_buff *skb, struct xt_action_param *par)
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{
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const struct xt_time_info *info = par->matchinfo;
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unsigned int packet_time;
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struct xtm current_time;
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time64_t stamp;
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/*
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* We need real time here, but we can neither use skb->tstamp
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* nor __net_timestamp().
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*
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* skb->tstamp and skb->skb_mstamp_ns overlap, however, they
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* use different clock types (real vs monotonic).
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*
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* Suppose you have two rules:
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* 1. match before 13:00
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* 2. match after 13:00
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*
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* If you match against processing time (ktime_get_real_seconds) it
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* may happen that the same packet matches both rules if
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* it arrived at the right moment before 13:00, so it would be
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* better to check skb->tstamp and set it via __net_timestamp()
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* if needed. This however breaks outgoing packets tx timestamp,
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* and causes them to get delayed forever by fq packet scheduler.
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*/
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stamp = ktime_get_real_seconds();
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if (info->flags & XT_TIME_LOCAL_TZ)
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/* Adjust for local timezone */
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stamp -= 60 * sys_tz.tz_minuteswest;
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/*
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* xt_time will match when _all_ of the following hold:
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* - 'now' is in the global time range date_start..date_end
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* - 'now' is in the monthday mask
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* - 'now' is in the weekday mask
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* - 'now' is in the daytime range time_start..time_end
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* (and by default, libxt_time will set these so as to match)
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*
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* note: info->date_start/stop are unsigned 32-bit values that
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* can hold values beyond y2038, but not after y2106.
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*/
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if (stamp < info->date_start || stamp > info->date_stop)
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return false;
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packet_time = localtime_1(¤t_time, stamp);
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if (info->daytime_start < info->daytime_stop) {
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if (packet_time < info->daytime_start ||
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packet_time > info->daytime_stop)
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return false;
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} else {
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if (packet_time < info->daytime_start &&
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packet_time > info->daytime_stop)
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return false;
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/** if user asked to ignore 'next day', then e.g.
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* '1 PM Wed, August 1st' should be treated
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* like 'Tue 1 PM July 31st'.
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*
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* This also causes
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* 'Monday, "23:00 to 01:00", to match for 2 hours, starting
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* Monday 23:00 to Tuesday 01:00.
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*/
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if ((info->flags & XT_TIME_CONTIGUOUS) &&
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packet_time <= info->daytime_stop)
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stamp -= SECONDS_PER_DAY;
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}
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localtime_2(¤t_time, stamp);
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if (!(info->weekdays_match & (1 << current_time.weekday)))
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return false;
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/* Do not spend time computing monthday if all days match anyway */
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if (info->monthdays_match != XT_TIME_ALL_MONTHDAYS) {
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localtime_3(¤t_time, stamp);
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if (!(info->monthdays_match & (1 << current_time.monthday)))
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return false;
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}
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return true;
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}
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static int time_mt_check(const struct xt_mtchk_param *par)
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{
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const struct xt_time_info *info = par->matchinfo;
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if (info->daytime_start > XT_TIME_MAX_DAYTIME ||
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info->daytime_stop > XT_TIME_MAX_DAYTIME) {
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pr_info_ratelimited("invalid argument - start or stop time greater than 23:59:59\n");
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return -EDOM;
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}
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if (info->flags & ~XT_TIME_ALL_FLAGS) {
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pr_info_ratelimited("unknown flags 0x%x\n",
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info->flags & ~XT_TIME_ALL_FLAGS);
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return -EINVAL;
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}
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if ((info->flags & XT_TIME_CONTIGUOUS) &&
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info->daytime_start < info->daytime_stop)
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return -EINVAL;
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return 0;
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}
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static struct xt_match xt_time_mt_reg __read_mostly = {
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.name = "time",
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.family = NFPROTO_UNSPEC,
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.match = time_mt,
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.checkentry = time_mt_check,
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.matchsize = sizeof(struct xt_time_info),
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.me = THIS_MODULE,
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};
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static int __init time_mt_init(void)
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{
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int minutes = sys_tz.tz_minuteswest;
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if (minutes < 0) /* east of Greenwich */
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pr_info("kernel timezone is +%02d%02d\n",
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-minutes / 60, -minutes % 60);
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else /* west of Greenwich */
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pr_info("kernel timezone is -%02d%02d\n",
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minutes / 60, minutes % 60);
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return xt_register_match(&xt_time_mt_reg);
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}
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static void __exit time_mt_exit(void)
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{
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xt_unregister_match(&xt_time_mt_reg);
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}
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module_init(time_mt_init);
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module_exit(time_mt_exit);
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MODULE_AUTHOR("Jan Engelhardt <jengelh@medozas.de>");
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MODULE_DESCRIPTION("Xtables: time-based matching");
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MODULE_LICENSE("GPL");
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MODULE_ALIAS("ipt_time");
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MODULE_ALIAS("ip6t_time");
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