[Swan-dev] time representation in Pluto
D. Hugh Redelmeier
hugh at mimosa.com
Wed Aug 13 19:41:27 EEST 2014
Generally speaking, time should not be represented within Pluto with a
Most (not all!) times in system and library calls are time_t, which
may or may not be uint64_t (system dependent).
There are three kinds of time_t that are not the same.
So Pluto has three distinct types for these distinct purposes. The
- the compiler can detect when you are mixing up kinds of time values:
you will violate C's type system.
- the programmer has to clearly think out what kind of type is being
This is documented in linux/include/libreswan.h. Here's a comment
* realtime_t: absolute UTC time. Might be discontinuous due to clock adjustment.
* monotime_t: absolute monotonic time. No discontinuities (except for machine sleep?)
* deltatime_t: relative time between events. Presumed continuous.
I introduced these types because the uses were being mixed up and
this created at least one long-standing subtle bug.
The commit 1913dd115696793d8dc5d6b6fd3f8238408fc1d1 message says:
- Add PLUTO_ADDTIME= for use in updown script. This is an epoch time
stamp, since the IPsec SA was added to the kernel (NETKEY only)
I don't know what this means. Perhaps
- ... This is the time_t representation of the UTC time when
the IPsec SA was added ...
Wall-clock time is "the time since the Epoch (00:00:00 UTC, January 1,
1970), measured in seconds." (see time(2)).
In Pluto, the type for wall-clock time is realtime_t.
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