There are inputs to mktime() where the behavior is not specified and there's
also no single obviously correct behavior. In particular, this affects how
auto-detection of whether DST is in effect is done when tm_isdst = -1 is set
and the time specified does not exist at all or exists twice on that day.
If different implementations are used within an Icinga 2 cluster, that can lead
to inconsistent behavior because different nodes may interpret the same
TimePeriod differently.
This commit introduces a wrapper to mktime(), namely Utility::NormalizeTm()
that implements the behavior provided by glibc. The choice for glibc's behavior
is pretty arbitrary, it was simply picked because most systems that are
officially/fully supported use it (with the only exception being Windows), so
this should give the least possible amount of user-visible changes.
As part of this commit, the closely related helper function mktime_const() is
also moved to Utility::TmToTimestamp() and made a wrapper around the newly
introduced NormalizeTm().
for (const T& needle : haystack) creates the illusion that haystack is a
container of T and we're just borrowing needle. In these cases that's not true.
A day specification like "monday -1" refers to the last Monday of the month.
However, there was an off by one if the first day of the next month is the same
day of the week, i.e. a Monday in this example.
LegacyTimePeriod::FindNthWeekday() picks a day to start the search for the day
in question. When given a negative n to search for the n-th last day, it
wrongly used the first day of the following month as the start and counted it
as if it was within the current month. This resulted in a 1/7 chance that the
result was one week too late.
This is fixed by using the last day of the current month instead.
This change fixes two problems:
* The internal functions used by ScriptFunc more or less expect to operate on
full days, but ScriptFunc may have called them with some random timestamp
during the day. This is fixed by always using midnight of the day as
reference time.
* Previously, the code advanced a timestamp to the next day by adding 24 hours.
On days with DST changes, this could either still be on the same day (a day
may have 25 hours) or skip an entire day (a day may have 23 hours). This is
fixed by using a struct tm to advance the time to the next day.
Many functions of LegacyTimePeriod take a tm pointer as an input parameter and
then pass it to mktime() which actually modifies it. This causes problems if
tm_isdst was intentionally set to -1 (to automatically detect whether DST is
active at some time) and then a function is called that implicitly sets
tm_isdst and then the values of tm are modified in a way that crosses a DST
change. This resulted in 1 hour offsets with ScheduledDowntimes on days with
DST changes.
If Icinga2 was restarted with a newly configured downtime that should
be in effect at the time of restart, the should-be-running segment of
it was not put into effect.
Add new LegacyTimePeriod::FindRunningSegment() and
ScheduledDowntime::FindRunningSegment() functions, call the latter in
ScheduledDowntime::CreateNextDowntime() before trying the old
ScheduledDowntime::FindNextSegment().
What does this change?
* Remove use of spaces for formatting
These could be found by using `grep -r -l -P '^\t+ +[^*]'
* Removal of training whitespaces
* A few lines longer than 120 chars
