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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 scaling 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 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, 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@FreeBSD.org〉.