[OpenWrt-Devel] [PATCH 1/1] firewall3: add --contiguous to time-based rules where needed

Philip Prindeville philipp_subx at redfish-solutions.com
Tue May 12 12:39:34 EDT 2020

> On May 12, 2020, at 7:08 AM, Yousong Zhou <yszhou4tech at gmail.com> wrote:
> On Sat, 2 May 2020 at 03:21, Philip Prindeville
> <philipp at redfish-solutions.com> wrote:
>> From: Philip Prindeville <philipp at redfish-solutions.com>
>> If the start_time > stop_time on a rule, then the --contiguous arg
>> should be included in the rule.
> It seems that start_time >= stop_time has its defined meaning in
> xt_time module.  Better add another uci option for this --contiguous
> flag.
> Regards,
>                yousong

Sorry, not following.  What would that UCI option look like?

From iptables-extensions:

       This  matches  if the packet arrival time/date is within a given range.
       All options are optional, but are ANDed when specified. All  times  are
       interpreted as UTC by default.

       --datestart YYYY[-MM[-DD[Thh[:mm[:ss]]]]]

       --datestop YYYY[-MM[-DD[Thh[:mm[:ss]]]]]
              Only  match during the given time, which must be in ISO 8601 "T"
              notation.  The possible time  range  is  1970-01-01T00:00:00  to

              If  --datestart or --datestop are not specified, it will default
              to 1970-01-01 and 2038-01-19, respectively.

       --timestart hh:mm[:ss]

       --timestop hh:mm[:ss]
              Only match during the given daytime. The possible time range  is
              00:00:00  to 23:59:59. Leading zeroes are allowed (e.g. "06:03")
              and correctly interpreted as base-10.

       [!] --monthdays day[,day...]
              Only match on the given days of the month. Possible values are 1
              to  31.  Note  that  specifying  31  will of course not match on
              months which do not have a 31st day; the same goes  for  28-  or
              29-day February.

       [!] --weekdays day[,day...]
              Only  match on the given weekdays. Possible values are Mon, Tue,
              Wed, Thu, Fri, Sat, Sun, or values from 1  to  7,  respectively.
              You may also use two-character variants (Mo, Tu, etc.).

              When --timestop is smaller than --timestart value, match this as
              a single time period instead distinct intervals.  See EXAMPLES.

              Use the kernel timezone instead of UTC to  determine  whether  a
              packet meets the time regulations.

       About  kernel timezones: Linux keeps the system time in UTC, and always
       does so.  On boot, system time is initialized from a  referential  time
       source. Where this time source has no timezone information, such as the
       x86 CMOS RTC, UTC will be assumed. If the time source is however not in
       UTC,  userspace  should provide the correct system time and timezone to
       the kernel once it has the information.

       Local time is a feature on top of  the  (timezone  independent)  system
       time. Each process has its own idea of local time, specified via the TZ
       environment variable. The kernel also has its own timezone offset vari‐
       able. The TZ userspace environment variable specifies how the UTC-based
       system time is displayed, e.g. when you run date(1), or what you see on
       your  desktop clock.  The TZ string may resolve to different offsets at
       different dates, which is what enables the  automatic  time-jumping  in
       userspace.  when  DST changes. The kernel's timezone offset variable is
       used when it has to  convert  between  non-UTC  sources,  such  as  FAT
       filesystems,  to  UTC  (since the latter is what the rest of the system

       The caveat with the kernel timezone is  that  Linux  distributions  may
       ignore  to  set  the  kernel  timezone, and instead only set the system
       time. Even if a particular distribution does set the timezone at  boot,
       it  is usually does not keep the kernel timezone offset - which is what
       changes on DST - up to date.  ntpd will not touch the kernel  timezone,
       so  running it will not resolve the issue. As such, one may encounter a
       timezone that is always +0000, or one that is wrong half of the time of
       the year. As such, using --kerneltz is highly discouraged.

       EXAMPLES. To match on weekends, use:

              -m time --weekdays Sa,Su

       Or, to match (once) on a national holiday block:

              -m time --datestart 2007-12-24 --datestop 2007-12-27

       Since the stop time is actually inclusive, you would need the following
       stop time to not match the first second of the new day:

              -m     time     --datestart     2007-01-01T17:00      --datestop

       During lunch hour:

              -m time --timestart 12:30 --timestop 13:30

       The fourth Friday in the month:

              -m time --weekdays Fr --monthdays 22,23,24,25,26,27,28

       (Note  that  this  exploits  a certain mathematical property. It is not
       possible to say "fourth Thursday OR fourth Friday" in one rule.  It  is
       possible with multiple rules, though.)

       Matching across days might not do what is expected.  For instance,

              -m  time  --weekdays Mo --timestart 23:00  --timestop 01:00 Will
              match Monday, for one hour from midnight to  1  a.m.,  and  then
              again for another hour from 23:00 onwards.  If this is unwanted,
              e.g. if you would like 'match for two hours  from  Montay  23:00
              onwards' you need to also specify the --contiguous option in the
              example above.

This last section is the bit that I’m trying to address.

I’m in GMT-0700.

So if I want a rule granting access from 8am to 9pm… local, that’s 14:00 GMT … 03:00 GMT, but it requires the --contiguous flag for the above reason.

Are you suggesting adding an option like:

	option contiguous true | false

that would cause the argument to get appended when timestart > timestop?

Would it always be appended or just when timestart > timestop (it’s not clear what it does in the case where timestart < timestop && contiguous)?

>> Signed-off-by: Philip Prindeville <philipp at redfish-solutions.com>
>> ---
>> iptables.c | 3 +++
>> 1 file changed, 3 insertions(+)
>> diff --git a/iptables.c b/iptables.c
>> index 559fe7defef3be85c4eb2934884caf549f932bc5..5c02e6e26c93468f4ef6a7f917069bb49985aad8 100644
>> --- a/iptables.c
>> +++ b/iptables.c
>> @@ -1099,6 +1099,9 @@ fw3_ipt_rule_time(struct fw3_ipt_rule *r, struct fw3_time *time)
>>                fw3_ipt_rule_addarg(r, false, "--timestop", buf);
>>        }
>> +       if (time->timestart && time->timestop && time->timestart > time->timestop)
>> +               fw3_ipt_rule_addarg(r, false, "--contiguous", NULL);
>> +
>>        if (time->monthdays & 0xFFFFFFFE)
>>        {
>>                for (i = 1, p = buf; i < 32; i++)
>> --
>> 2.17.2

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