Time Conversion Bug (Was: no email notifications sent)

[Albrecht Dreß]

Hi all:

Am 01.12.08 21:59 schrieb(en) Albrecht Dreß:
> I have a self-compiled nagios 3.0.5 running on a 64-bit Xeon box with  
> Ubuntu 8.04 LTS.  Everything went perfectly (including notifications)  
> until I upgraded from 3.0.1 (iirc) to 3.0.5 during a bigger service  
> downtime (inter alia shifting the box into an other network etc).

After adding tons of debug messages, I was finally able to track down  
the problem.  The problem is that I added a german holiday in the form

         october 3       00:00-00:00

In function (all inbase/utils.c) check_time_against_period(), the start  
time was calculated by calculate_time_from_day_of_month() as 1222988400  
(Fri Oct  3 01:00:00 2008), but the end time as 1222984800 (Fri Oct  3  
00:00:00 2008), which is /before/ the start, and therefore the time  
span was expanded to a whole year, i.e. the end now was Oct 3, 2009...

Looking deeper into function calculate_time_from_day_of_month(), this  
is apparently caused by a wrong usage of the call to mktime(), as the  
field tm_isdst is /not/ initialised properly.  The observed 1 hour  
offset seems to come from an earlier call to this function which  
returned an active dst flag.

According to the IEEE Std 1003.1 [1], the field tm_isdst /is/ used in  
the time conversion, and should be set to -1 if the dst status is  
unknown (you may want to write a small test app, setting this flag to  
-1, 0 or 1 to observe the effect).  As mktime() is used frequently in  
the code without properly initialising this field, this seems to be a  
systematic bug which can trigger interesting effects in nagios.

Any opinions?

Best, Albrecht.

[1]  
<http://www.opengroup.org/onlinepubs/009695399/functions/mktime.html>
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