path: root/include/meta.h
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authorAnder Juaristi <>2019-08-29 16:09:02 +0200
committerFlorian Westphal <>2019-09-06 16:25:57 +0200
commitf8f32deda31df597614d9f1f64ffb0c0320f4d54 (patch)
tree7e59bf617b39e30936521f000d9202b816472e04 /include/meta.h
parentf521033afc41876173e6430cdd45fc07a1b76654 (diff)
meta: Introduce new conditions 'time', 'day' and 'hour'
These keywords introduce new checks for a timestamp, an absolute date (which is converted to a timestamp), an hour in the day (which is converted to the number of seconds since midnight) and a day of week. When converting an ISO date (eg. 2019-06-06 17:00) to a timestamp, we need to substract it the GMT difference in seconds, that is, the value of the 'tm_gmtoff' field in the tm structure. This is because the kernel doesn't know about time zones. And hence the kernel manages different timestamps than those that are advertised in userspace when running, for instance, date +%s. The same conversion needs to be done when converting hours (e.g 17:00) to seconds since midnight as well. The result needs to be computed modulo 86400 in case GMT offset (difference in seconds from UTC) is negative. We also introduce a new command line option (-t, --seconds) to show the actual timestamps when printing the values, rather than the ISO dates, or the hour. Some usage examples: time < "2019-06-06 17:00" drop; time < "2019-06-06 17:20:20" drop; time < 12341234 drop; day "Saturday" drop; day 6 drop; hour >= 17:00 drop; hour >= "17:00:01" drop; hour >= 63000 drop; We need to convert an ISO date to a timestamp without taking into account the time zone offset, since comparison will be done in kernel space and there is no time zone information there. Overwriting TZ is portable, but will cause problems when parsing a ruleset that has 'time' and 'hour' rules. Parsing an 'hour' type must not do time zone conversion, but that will be automatically done if TZ has been overwritten to UTC. Hence, we use timegm() to parse the 'time' type, even though it's not portable. Overwriting TZ seems to be a much worse solution. Finally, be aware that timestamps are converted to nanoseconds when transferring to the kernel (as comparison is done with nanosecond precision), and back to seconds when retrieving them for printing. We swap left and right values in a range to properly handle cross-day hour ranges (e.g. 23:15-03:22). Signed-off-by: Ander Juaristi <> Reviewed-by: Florian Westphal <>
Diffstat (limited to 'include/meta.h')
1 files changed, 3 insertions, 0 deletions
diff --git a/include/meta.h b/include/meta.h
index 0fe95fd6..1478902e 100644
--- a/include/meta.h
+++ b/include/meta.h
@@ -41,5 +41,8 @@ extern const struct datatype uid_type;
extern const struct datatype devgroup_type;
extern const struct datatype pkttype_type;
extern const struct datatype ifname_type;
+extern const struct datatype date_type;
+extern const struct datatype hour_type;
+extern const struct datatype day_type;
#endif /* NFTABLES_META_H */