The dnsmasq_time() function, in the case of HAVE_BROKEN_RTC, was calling
times() to read the number of ticks "elapsed since an arbitrary point in
the past" and then dividing that by sysconf(_SC_CLK_TCK) to compute the
number of seconds elapsed since that arbitrary instant. This works fine
until the number of ticks exceeds 2^31, beyond which time the function
would begin erroneously returning negative times. On my system this
happens after approximately 248 days of uptime. A symptom is that
dnsmasq no longer populates the resolver cache with DHCP-derived names
at startup, as the inserted cache entries immediately expire due to
having negative expiration times that cause is_expired() to return true
when called with now==0.
This commit replaces the archaic implementation of dnsmasq_time() with a
call to the POSIX-standardized clock_gettime(CLOCK_MONOTONIC), thereby
eliminating the need to convert manually from ticks to seconds. The new
implementation will yield correct results until the system uptime
exceeds approximately 68 years.
Signed-off-by: Matt Whitlock <dnsm...@mattwhitlock.name>
---
src/util.c | 9 ++++-----
1 file changed, 4 insertions(+), 5 deletions(-)
diff --git a/src/util.c b/src/util.c
index 1425764..b2179d0 100644
--- a/src/util.c
+++ b/src/util.c
@@ -408,13 +408,12 @@ int hostname_issubdomain(char *a, char *b)
time_t dnsmasq_time(void)
{
#ifdef HAVE_BROKEN_RTC
- struct tms dummy;
- static long tps = 0;
+ struct timespec ts;
- if (tps == 0)
- tps = sysconf(_SC_CLK_TCK);
+ if (clock_gettime(CLOCK_MONOTONIC, &ts) < 0)
+ die(_("cannot read monotonic clock: %s"), NULL, EC_MISC);
- return (time_t)(times(&dummy)/tps);
+ return ts.tv_sec;
#else
return time(NULL);
#endif
--
2.33.0
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