ntp_adjtime(2)

NAME

ntp_adjtime - NTP daemon application interface

SYNOPSIS

#include <sys/types.h>
#include <sys/timex.h>
int
ntp_adjtime(struct timex *tp);

DESCRIPTION

The ntp_adjtime() system call is used as a kernel interface

for the Network Time Protocol daemon, ntpd(8). Certain fields of the

timex structure are interpreted in either microseconds or nanoseconds,

according to
the state of the STA_NANO bit in the status word.

In the FreeBSD kernel, the ntp_adjtime() and ntp_gettime(2)

system calls
can be used to determine which resolution is in use, and to

select either
one at any time. The resolution selected affects the scal

ing of certain
fields in the ntp_gettime() and ntp_adjtime() system calls.

Take note that this API is extremely complex and stateful.

Users should
not attempt modification without first reviewing the ntpd(8)

sources in
depth.

/*

* NTP daemon interface (ntp_adjtime()) - used to discipline

CPU clock
* oscillator and determine status.
*
* Note: The offset, precision and jitter members are in mi

croseconds if
* STA_NANO is zero and nanoseconds if not.
*/

struct timex {

unsigned int modes; /* clock mode bits (wo) */
long offset; /* time offset (ns/us) (rw)

*/
long freq; /* frequency offset (scaled

PPM) (rw) */
long maxerror; /* maximum error (us) (rw)

*/
long esterror; /* estimated error (us) (rw)

*/
int status; /* clock status bits (rw) */
long constant; /* poll interval (log2 s)

(rw) */
long precision; /* clock precision (ns/us)

(ro) */
long tolerance; /* clock frequency tolerance

(scaled

* PPM) (ro) */

/*

* The following read-only structure members are im

plemented
* only if the PPS signal discipline is configured

in the
* kernel. They are included in all configurations

to insure
* portability.
*/

long ppsfreq; /* PPS frequency (scaled

PPM) (ro) */
long jitter; /* PPS jitter (ns/us) (ro)

*/
int shift; /* interval duration (s)

(shift) (ro) */
long stabil; /* PPS stability (scaled

PPM) (ro) */
long jitcnt; /* jitter limit exceeded

(ro) */
long calcnt; /* calibration intervals

(ro) */
long errcnt; /* calibration errors (ro)

*/
long stbcnt; /* stability limit exceeded

(ro) */

};

Upon successful completion, ntp_adjtime() will fill the tp

argument with
the current clock state.

RETURN VALUES

Upon successful completion the clock state is returned.

Otherwise a -1
is returned and the global variable errno is set to indicate

the error.

Possible states of the clock are:

TIME_OK Everything okay, no leap second warning.
TIME_INS insert leap second warning.
TIME_DEL delete leap second warning.
TIME_OOP Leap second in progress.
TIME_WAIT Leap second has occurred.
TIME_ERROR Clock not synchronized.

ERRORS

The ntp_gettime() system call may return EPERM if the caller

does not
have sufficient permissions.

SEE ALSO

ntp_gettime(2), ntpd(8)

AUTHORS

This manual page was written by Tom Rhodes <trhodes@FreeB

SD.org>.

BSD April 1, 2003

BSD