netfilter: xt_time: add support to ignore day transition

Currently, if you want to do something like:
"match Monday, starting 23:00, for two hours"
You need two rules, one for Mon 23:00 to 0:00 and one for Tue 0:00-1:00.

The rule: --weekdays Mo --timestart 23:00  --timestop 01:00

looks correct, but it will first match on monday from midnight to 1 a.m.
and then again for another hour from 23:00 onwards.

This permits userspace to explicitly ignore the day transition and
match for a single, continuous time period instead.

Signed-off-by: Florian Westphal <fw@strlen.de>
Signed-off-by: Pablo Neira Ayuso <pablo@netfilter.org>

diff --git a/include/linux/netfilter/xt_time.h b/include/linux/netfilter/xt_time.h
index 7c37fac..0958860 100644 (file)
--- a/include/linux/netfilter/xt_time.h
+++ b/include/linux/netfilter/xt_time.h
@@ -17,6 +17,9 @@ enum {
        /* Match against local time (instead of UTC) */
        XT_TIME_LOCAL_TZ = 1 << 0,
 
+       /* treat timestart > timestop (e.g. 23:00-01:00) as single period */
+       XT_TIME_CONTIGUOUS = 1 << 1,
+
        /* Shortcuts */
        XT_TIME_ALL_MONTHDAYS = 0xFFFFFFFE,
        XT_TIME_ALL_WEEKDAYS  = 0xFE,
@@ -24,4 +27,6 @@ enum {
        XT_TIME_MAX_DAYTIME   = 24 * 60 * 60 - 1,
 };
 
+#define XT_TIME_ALL_FLAGS (XT_TIME_LOCAL_TZ|XT_TIME_CONTIGUOUS)
+
 #endif /* _XT_TIME_H */

diff --git a/net/netfilter/xt_time.c b/net/netfilter/xt_time.c
index c48975f..0ae55a3 100644 (file)
--- a/net/netfilter/xt_time.c
+++ b/net/netfilter/xt_time.c
@@ -42,6 +42,7 @@ static const u_int16_t days_since_leapyear[] = {
  */
 enum {
        DSE_FIRST = 2039,
+       SECONDS_PER_DAY = 86400,
 };
 static const u_int16_t days_since_epoch[] = {
        /* 2039 - 2030 */
@@ -78,7 +79,7 @@ static inline unsigned int localtime_1(struct xtm *r, time_t time)
        unsigned int v, w;
 
        /* Each day has 86400s, so finding the hour/minute is actually easy. */
-       v         = time % 86400;
+       v         = time % SECONDS_PER_DAY;
        r->second = v % 60;
        w         = v / 60;
        r->minute = w % 60;
@@ -199,6 +200,18 @@ time_mt(const struct sk_buff *skb, struct xt_action_param *par)
                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(&current_time, stamp);
@@ -227,6 +240,15 @@ static int time_mt_check(const struct xt_mtchk_param *par)
                return -EDOM;
        }
 
+       if (info->flags & ~XT_TIME_ALL_FLAGS) {
+               pr_info("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;
 }