With TIME_BACKTRACK_PROTECTION defined, openvpn_gettimeofday() uses and
updates global variable "now_usec" along with "now" only if current time
is ahead of the previsouly stored, taking nanoseconds into account.
But, update_time() function updates only "now" leaving "now_usec" as
is with any previously value stored.
This breaks both update_time() and openvpn_gettimeofday() results and
leads to time jumps in the future within one second, can affect shaper
and user timers.
100.900 openvpn_gettimeofday():
now set to 100s, now_usec set to 900ns, stored time is 100.900
101.300 update_time():
now set to 101s, but now_usec is not updated and still 900ns, stored
time jumps to the future 101.900
101.600 openvpn_gettimeofday():
current time 101.600 is in the past relatively stored time 101.900,
now & now_usec variables are not updated, returned time 101.900 is
still and again incorrect
102.100 openvpn_gettimeofday():
current time 102.100 is no longer in the past relatively stored time
101.900, so now & now_usec get updated with wrong time delta from
previous openvpn_gettimeofday() call or now/now_usec math
Since update_time() and openvpn_gettimeofday() calls are mixed in runtime,
there're two ways to fix their coexistance:
* either fix update_time() to always update "now_usec" for example by
moving update_time() to gettimeofday(). Unfortunately, it may bring
performance penalty depending on Arch/OS and vuruallized/hw environmant
according the tests on various Linux, FreeBSD and MacOS versions.
* or, for now, allow update_time() to break "now_usec" value, since it's
used directly only in time ajusting and always invalidate it in
openvpn_gettimeofday() w/o checking the previous and possibly obsolete
value with no performance changes against the current implementation.
This patch implements the second way.
Signed-off-by: Vladislav Grishenko <themi...@yandex-team.ru>
---
src/openvpn/otime.c | 2 +-
1 file changed, 1 insertion(+), 1 deletion(-)
diff --git a/src/openvpn/otime.c b/src/openvpn/otime.c
index 640168a9..d27d1f9d 100644
--- a/src/openvpn/otime.c
+++ b/src/openvpn/otime.c
@@ -73,7 +73,7 @@ update_now_usec(struct timeval *tv)
{
const time_t last = now;
update_now(tv->tv_sec);
- if (now > last || (now == last && tv->tv_usec > now_usec))
+ if (now >= last)
{
now_usec = tv->tv_usec;
}
--
2.17.1
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