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