/contrib/ntp/ntpd/refclock_local.c
https://bitbucket.org/freebsd/freebsd-head/ · C · 258 lines · 110 code · 25 blank · 123 comment · 6 complexity · 2765899891e6b683c73f1940f25d2fa0 MD5 · raw file
- /*
- * refclock_local - local pseudo-clock driver
- *
- * wjm 17-aug-1995: add a hook for special treatment of VMS_LOCALUNIT
- */
- #ifdef HAVE_CONFIG_H
- #include <config.h>
- #endif
- #ifdef REFCLOCK
- #include "ntpd.h"
- #include "ntp_refclock.h"
- #include "ntp_stdlib.h"
- #include <stdio.h>
- #include <ctype.h>
- #ifdef KERNEL_PLL
- #include "ntp_syscall.h"
- #endif
- /*
- * 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 5) 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.
- *
- * THis driver includes provisions to telegraph synchronization state
- * and related variables by means of kernel variables with specially
- * modified kernels. This is done using the ntp_adjtime() syscall.
- * In the cases where another protocol or device synchronizes the local
- * host, the data given to the kernel can be slurped up by this driver
- * and distributed to clients by ordinary NTP messaging.
- *
- * 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 set at 5 by default, but it can be
- * changed by the fudge command and/or the ntpdc utility. The reference
- * ID is 127.0.0.1 by default, but can be changed using the same mechanism.
- * *NEVER* configure this driver to operate at a stratum which might
- * possibly disrupt a client with access to a bona fide primary server,
- * unless the 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. Always remember that
- * an improperly configured local clock driver let loose in the Internet
- * can cause very serious disruption. This is why most of us who care
- * about good time use cryptographic authentication.
- *
- * 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. The fudge time1
- * parameter is additive; that is, it adds an increment to the current
- * time. The fudge time2 parameter directly sets the frequency.
- */
- /*
- * Local interface definitions
- */
- #define PRECISION (-7) /* about 10 ms precision */
- #define DESCRIPTION "Undisciplined local clock" /* WRU */
- #define STRATUM 5 /* default stratum */
- #define DISPERSION .01 /* default dispersion (10 ms) */
- /*
- * Imported from the timer module
- */
- extern u_long current_time;
- /*
- * Imported from ntp_proto
- */
- extern s_char sys_precision;
- #ifdef KERNEL_PLL
- /*
- * Imported from ntp_loopfilter
- */
- extern int pll_control; /* kernel pll control */
- extern int kern_enable; /* kernel pll enabled */
- extern int ext_enable; /* external clock enable */
- #endif /* KERNEL_PLL */
- /*
- * Function prototypes
- */
- static int local_start P((int, struct peer *));
- static void local_poll P((int, struct peer *));
- /*
- * Local variables
- */
- static u_long poll_time; /* last time polled */
-
- /*
- * 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
- local_start(
- int unit,
- struct peer *peer
- )
- {
- struct refclockproc *pp;
- pp = peer->procptr;
- /*
- * Initialize miscellaneous variables
- */
- peer->precision = sys_precision;
- pp->leap = LEAP_NOTINSYNC;
- peer->stratum = STRATUM;
- pp->stratum = STRATUM;
- pp->clockdesc = DESCRIPTION;
- memcpy(&pp->refid, "LOCL", 4);
- poll_time = current_time;
- return (1);
- }
- /*
- * local_poll - called by the transmit procedure
- *
- * LOCKCLOCK: If the kernel supports the nanokernel or microkernel
- * system calls, the leap bits are extracted from the kernel. If there
- * is a kernel error or the kernel leap bits are set to 11, the NTP leap
- * bits are set to 11 and the stratum is set to infinity. Otherwise, the
- * NTP leap bits are set to the kernel leap bits and the stratum is set
- * as fudged. This behavior does not faithfully follow the
- * specification, but is probably more appropriate in a multiple-server
- * national laboratory network.
- */
- static void
- local_poll(
- int unit,
- struct peer *peer
- )
- {
- #if defined(KERNEL_PLL) && defined(LOCKCLOCK)
- struct timex ntv;
- #endif /* KERNEL_PLL LOCKCLOCK */
- struct refclockproc *pp;
- #if defined(VMS) && defined(VMS_LOCALUNIT)
- if (unit == VMS_LOCALUNIT) {
- extern void vms_local_poll(struct peer *);
- vms_local_poll(peer);
- return;
- }
- #endif /* VMS && VMS_LOCALUNIT */
- pp = peer->procptr;
- pp->polls++;
- /*
- * Ramble through the usual filtering and grooming code, which
- * is essentially a no-op and included mostly for pretty
- * billboards. We allow a one-time time adjustment using fudge
- * time1 (s) and a continuous frequency adjustment using fudge
- * time 2 (ppm).
- */
- get_systime(&pp->lastrec);
- pp->fudgetime1 += pp->fudgetime2 * 1e-6 * (current_time -
- poll_time);
- poll_time = current_time;
- refclock_process_offset(pp, pp->lastrec, pp->lastrec,
- pp->fudgetime1);
- /*
- * If another process is disciplining the system clock, we set
- * the leap bits and quality indicators from the kernel.
- */
- #if defined(KERNEL_PLL) && defined(LOCKCLOCK)
- memset(&ntv, 0, sizeof ntv);
- switch (ntp_adjtime(&ntv)) {
- case TIME_OK:
- pp->leap = LEAP_NOWARNING;
- peer->stratum = pp->stratum;
- break;
- case TIME_INS:
- pp->leap = LEAP_ADDSECOND;
- peer->stratum = pp->stratum;
- break;
- case TIME_DEL:
- pp->leap = LEAP_DELSECOND;
- peer->stratum = pp->stratum;
- break;
- default:
- pp->leap = LEAP_NOTINSYNC;
- peer->stratum = STRATUM_UNSPEC;
- }
- pp->disp = 0;
- pp->jitter = 0;
- #else /* KERNEL_PLL LOCKCLOCK */
- pp->leap = LEAP_NOWARNING;
- pp->disp = DISPERSION;
- pp->jitter = 0;
- #endif /* KERNEL_PLL LOCKCLOCK */
- pp->lastref = pp->lastrec;
- refclock_receive(peer);
- pp->fudgetime1 = 0;
- }
- #else
- int refclock_local_bs;
- #endif /* REFCLOCK */