freebsd-dev/lib/libc/sys/ntp_adjtime.2

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.\"
.\" Copyright (c) 2003 Tom Rhodes
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.\" $FreeBSD$
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.Dd April 1, 2003
.Dt NTP_ADJTIME 2
.Os
.Sh NAME
.Nm ntp_adjtime
.Nd NTP daemon application interface
.Sh SYNOPSIS
.In sys/types.h
.In sys/timex.h
.Ft int
.Fn ntp_adjtime "struct timex *tp"
.Sh DESCRIPTION
The
.Fn ntp_adjtime
system call is used as a kernel interface
for the Network Time Protocol daemon,
.Xr ntpd 8 .
Certain fields of the
.Vt timex
structure are interpreted in either
microseconds or nanoseconds, according to the state of the
.Dv STA_NANO
bit in the
.Va status
word.
.Pp
In the
.Fx
kernel, the
.Fn ntp_adjtime
and
.Xr 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 scaling of certain fields in the
.Fn ntp_gettime
and
.Fn ntp_adjtime
system calls.
.Pp
Take note that this
.Tn API
is extremely complex and stateful.
Users should not attempt modification without first
reviewing the
.Xr ntpd 8
sources in depth.
.Bd -literal
/*
* NTP daemon interface (ntp_adjtime()) - used to discipline CPU clock
* oscillator and determine status.
*
* Note: The offset, precision and jitter members are in microseconds 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 implemented
* 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) */
};
.Ed
.Pp
Upon successful completion,
.Fn ntp_adjtime
will fill the
.Fa tp
argument with the current clock state.
.Sh RETURN VALUES
Upon successful completion the clock state is returned.
Otherwise a -1 is returned and the global variable
.Va errno
is set to indicate the error.
.Pp
Possible states of the clock are:
.Pp
.Bl -tag -compact -width ".Dv TIME_ERROR"
.It Dv TIME_OK
Everything okay, no leap second warning.
.It Dv TIME_INS
insert leap second warning.
.It Dv TIME_DEL
delete leap second warning.
.It Dv TIME_OOP
Leap second in progress.
.It Dv TIME_WAIT
Leap second has occurred.
.It Dv TIME_ERROR
Clock not synchronized.
.El
.Sh ERRORS
The
.Fn ntp_gettime
system call may return
.Er EPERM
if the caller
does not have sufficient permissions.
.Sh SEE ALSO
.Xr ntp_gettime 2 ,
.Xr ntpd 8
.Sh AUTHORS
This manual page was written by
.An Tom Rhodes Aq trhodes@FreeBSD.org .