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ntp_adjtime

BSD mandoc

NAME

ntp_adjtime - NTP daemon application interface

SYNOPSIS

In sys/types.h In sys/timex.h Ft int Fn ntp_adjtime struct timex *tp

DESCRIPTION

The Fn ntp_adjtime system call is used as a kernel interface for the Network Time Protocol daemon, ntpd(8). Certain fields of the Vt timex structure are interpreted in either microseconds or nanoseconds, according to the state of the STA_NANO bit in the status word.

In the Fx kernel, the Fn ntp_adjtime and ntp_gettime2 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.

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 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) */
 };
 

Upon successful completion, Fn ntp_adjtime will fill the Fa 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 Fn ntp_gettime system call may return Er EPERM if the caller does not have sufficient permissions.

SEE ALSO

ntp_gettime2, ntpd(8)

AUTHORS

This manual page was written by An Tom Rhodes Aq trhodes@FreeBSD.org .