refclock_local.c revision 7c478bd95313f5f23a4c958a745db2134aa03244
/*
* Copyright (c) 1996 by Sun Microsystems, Inc.
* All Rights Reserved.
*/
#pragma ident "%Z%%M% %I% %E% SMI"
/* wjm 17-aug-1995: add a hook for special treatment of VMS_LOCALUNIT */
/*
* refclock_local - local pseudo-clock driver
*/
#ifdef HAVE_CONFIG_H
#include <config.h>
#endif
#if defined(REFCLOCK) && defined(LOCAL_CLOCK)
#include <stdio.h>
#include <ctype.h>
#include "ntpd.h"
#include "ntp_refclock.h"
#include "ntp_stdlib.h"
/*
* This is a hack to allow a machine to use its own system clock as a
* reference clock, i.e., to free-run using no outside clock discipline
* source. This is useful if you want to use NTP in an isolated
* environment with no radio clock or NIST modem available. Pick a
* machine that you figure has a good clock oscillator and configure it
* with this driver. Set the clock using the best means available, like
* eyeball-and-wristwatch. Then, point all the other machines at this
* one or use broadcast (not multicast) mode to distribute time.
*
* Another application for this driver is if you want to use a
* particular server's clock as the clock of last resort when all other
* normal synchronization sources have gone away. This is especially
* useful if that server has an ovenized oscillator. For this you would
* configure this driver at a higher stratum (say 3 or 4) to prevent the
* server's stratum from falling below that.
*
* A third application for this driver is when an external discipline
* source is available, such as the NIST "lockclock" program, which
* synchronizes the local clock via a telephone modem and the NIST
* Automated Computer Time Service (ACTS), or the Digital Time
* Synchronization Service (DTSS), which runs on DCE machines. In this
* case the stratum should be set at zero, indicating a bona fide
* stratum-1 source. Exercise some caution with this, since there is no
* easy way to telegraph via NTP that something might be wrong in the
* discipline source itself. In the case of DTSS, the local clock can
* have a rather large jitter, depending on the interval between
* corrections and the intrinsic frequency error of the clock
* oscillator. In extreme cases, this can cause clients to exceed the
* 128-ms slew window and drop off the NTP subnet.
*
* In the default mode the behavior of the clock selection algorithm is
* modified when this driver is in use. The algorithm is designed so
* that this driver will never be selected unless no other discipline
* source is available. This can be overriden with the prefer keyword of
* the server configuration command, in which case only this driver will
* be selected for synchronization and all other discipline sources will
* be ignored. This behavior is intended for use when an external
* discipline source controls the system clock.
*
* Fudge Factors
*
* The stratum for this driver LCLSTRATUM is set at 3 by default, but
* reference ID is "LCL" by default, but can be changed using the same
* mechanisms. *NEVER* configure this driver to operate at a stratum
* which might possibly disrupt a client with access to a bona fide
* primary server, unless athe local clock oscillator is reliably
* disciplined by another source. *NEVER NEVER* configure a server which
* might devolve to an undisciplined local clock to use multicast mode.
*
* This driver provides a mechanism to trim the local clock in both time
* and frequency, as well as a way to manipulate the leap bits. The
* fudge time1 parameter adjusts the time, in seconds, and the fudge
* time2 parameter adjusts the frequency, in ppm. Both parameters are
* additive; that is, they add increments in time or frequency to the
* present values. The fudge flag1 and fudge flag2 bits set the
* corresponding leap bits; for example, setting flag1 causes a leap
* second to be added at the end of the UTC day. These bits are not
* reset automatically when the leap takes place; they must be turned
* off manually after the leap event.
*/
/*
* Local interface definitions
*/
/*
* Imported from the timer module
*/
extern u_long current_time;
/*
* Imported from ntp_proto
*/
extern s_char sys_precision;
/*
* Function prototypes
*/
static int local_start P((int, struct peer *));
static void local_poll P((int, struct peer *));
/*
* Transfer vector
*/
struct refclock refclock_local = {
local_start, /* start up driver */
noentry, /* shut down driver (not used) */
local_poll, /* transmit poll message */
noentry, /* not used (old lcl_control) */
noentry, /* initialize driver (not used) */
noentry, /* not used (old lcl_buginfo) */
NOFLAGS /* not used */
};
/*
* local_start - start up the clock
*/
static int
int unit;
{
register struct refclockproc *pp;
/*
* Initialize miscellaneous variables
*/
#if defined(VMS) && defined(VMS_LOCALUNIT)
/* provide a non-standard REFID */
#endif /* VMS && VMS_LOCALUNIT */
return (1);
}
/*
* local_poll - called by the transmit procedure
*/
static void
int unit;
{
struct refclockproc *pp;
#if defined(VMS) && defined(VMS_LOCALUNIT)
if(unit == VMS_LOCALUNIT) {
extern void vms_local_poll(struct peer *);
return;
}
#endif /* VMS && VMS_LOCALUNIT */
/*
* Ramble through the usual filtering and grooming code, which
* is essentially a no-op and included mostly for pretty
* billboards. We fudge flags as the leap indicators and allow a
* one-time adjustment in time using fudge time1 (s) and
* frequency using fudge time 2 (ppm).
*/
}
#else /* not (REFCLOCK && LOCAL_CLOCK) */
int refclock_local_bs;
#endif /* not (REFCLOCK && LOCAL_CLOCK) */