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bsnmpd: Return the correct uptime.

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Do not assume that the kernel boot time is invariant. It is not. FreeBSD
uses the formula:
	wall_time = boot_time + uptime
where uptime is monotinically increasing and boot_time is adjusted to
get the proper time of day.  FreeBSD offers a way to retrieve the uptime
directly, so use that instead of trying to compute it by subtracting
boot_time from wall_time.

Sponsored by:		Netflix
Reviewed by:		cy@
Differential Revision:	https://reviews.freebsd.org/D30114
This commit is contained in:
Warner Losh 2021-05-05 15:11:56 -06:00
parent 6c34dde83e
commit f009aedae4
1 changed files with 7 additions and 30 deletions
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37
usr.sbin/bsnmpd/modules/snmp_hostres/hostres_scalars.c
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@ -47,9 +47,6 @@
#include "hostres_oid.h"
#include "hostres_tree.h"
/* boot timestamp in centi-seconds */
static uint64_t kernel_boot;
/* physical memory size in Kb */
static uint64_t phys_mem_size;
@ -76,39 +73,19 @@ fini_scalars(void)
static int
OS_getSystemUptime(uint32_t *ut)
{
struct timeval right_now;
uint64_t now;
uint64_t uptime;
struct timespec ts;
if (kernel_boot == 0) {
/* first time, do the sysctl */
struct timeval kernel_boot_timestamp;
int mib[2] = { CTL_KERN, KERN_BOOTTIME };
size_t len = sizeof(kernel_boot_timestamp);
if (sysctl(mib, nitems(mib), &kernel_boot_timestamp,
&len, NULL, 0) == -1) {
syslog(LOG_ERR, "sysctl KERN_BOOTTIME failed: %m");
return (SNMP_ERR_GENERR);
}
HRDBG("boot timestamp from kernel: {%lld, %ld}",
(long long)kernel_boot_timestamp.tv_sec,
(long)kernel_boot_timestamp.tv_usec);
kernel_boot = ((uint64_t)kernel_boot_timestamp.tv_sec * 100) +
(kernel_boot_timestamp.tv_usec / 10000);
}
if (gettimeofday(&right_now, NULL) < 0) {
syslog(LOG_ERR, "gettimeofday failed: %m");
if (clock_gettime(CLOCK_UPTIME, &ts)) {
syslog(LOG_ERR, "clock_gettime failed: %m");
return (SNMP_ERR_GENERR);
}
now = ((uint64_t)right_now.tv_sec * 100) + (right_now.tv_usec / 10000);
if (now - kernel_boot > UINT32_MAX)
uptime = ts.tv_sec * 100 + ts.tv_nsec / 1000000;
if (uptime > UINT32_MAX)
*ut = UINT32_MAX;
else
*ut = now - kernel_boot;
*ut = (uint32_t)uptime;
return (SNMP_ERR_NOERROR);
}