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| Current File : //usr/src/contrib/ntp/ntpd/ntp_loopfilter.c |
/*
* ntp_loopfilter.c - implements the NTP loop filter algorithm
*
* ATTENTION: Get approval from Dave Mills on all changes to this file!
*
*/
#ifdef HAVE_CONFIG_H
# include <config.h>
#endif
#include "ntpd.h"
#include "ntp_io.h"
#include "ntp_unixtime.h"
#include "ntp_stdlib.h"
#include <stdio.h>
#include <ctype.h>
#include <signal.h>
#include <setjmp.h>
#if defined(VMS) && defined(VMS_LOCALUNIT) /*wjm*/
#include "ntp_refclock.h"
#endif /* VMS */
#ifdef KERNEL_PLL
#include "ntp_syscall.h"
#endif /* KERNEL_PLL */
/*
* This is an implementation of the clock discipline algorithm described
* in UDel TR 97-4-3, as amended. It operates as an adaptive parameter,
* hybrid phase/frequency-lock loop. A number of sanity checks are
* included to protect against timewarps, timespikes and general mayhem.
* All units are in s and s/s, unless noted otherwise.
*/
#define CLOCK_MAX .128 /* default step threshold (s) */
#define CLOCK_MINSTEP 900. /* default stepout threshold (s) */
#define CLOCK_PANIC 1000. /* default panic threshold (s) */
#define CLOCK_PHI 15e-6 /* max frequency error (s/s) */
#define CLOCK_PLL 16. /* PLL loop gain (log2) */
#define CLOCK_AVG 8. /* parameter averaging constant */
#define CLOCK_FLL (NTP_MAXPOLL + CLOCK_AVG) /* FLL loop gain */
#define CLOCK_ALLAN 1500. /* compromise Allan intercept (s) */
#define CLOCK_DAY 86400. /* one day in seconds (s) */
#define CLOCK_JUNE (CLOCK_DAY * 30) /* June in seconds (s) */
#define CLOCK_LIMIT 30 /* poll-adjust threshold */
#define CLOCK_PGATE 4. /* poll-adjust gate */
#define PPS_MAXAGE 120 /* kernel pps signal timeout (s) */
/*
* Clock discipline state machine. This is used to control the
* synchronization behavior during initialization and following a
* timewarp.
*
* State < step > step Comments
* ====================================================
* NSET FREQ step, FREQ no ntp.drift
*
* FSET SYNC step, SYNC ntp.drift
*
* FREQ if (mu < 900) if (mu < 900) set freq
* ignore ignore
* else else
* freq, SYNC freq, step, SYNC
*
* SYNC SYNC if (mu < 900) adjust phase/freq
* ignore
* else
* SPIK
*
* SPIK SYNC step, SYNC set phase
*/
#define S_NSET 0 /* clock never set */
#define S_FSET 1 /* frequency set from the drift file */
#define S_SPIK 2 /* spike detected */
#define S_FREQ 3 /* frequency mode */
#define S_SYNC 4 /* clock synchronized */
/*
* Kernel PLL/PPS state machine. This is used with the kernel PLL
* modifications described in the README.kernel file.
*
* If kernel support for the ntp_adjtime() system call is available, the
* ntp_control flag is set. The ntp_enable and kern_enable flags can be
* set at configuration time or run time using ntpdc. If ntp_enable is
* false, the discipline loop is unlocked and no corrections of any kind
* are made. If both ntp_control and kern_enable are set, the kernel
* support is used as described above; if false, the kernel is bypassed
* entirely and the daemon discipline used instead.
*
* There have been three versions of the kernel discipline code. The
* first (microkernel) now in Solaris discipilnes the microseconds. The
* second and third (nanokernel) disciplines the clock in nanoseconds.
* These versions are identifed if the symbol STA_PLL is present in the
* header file /usr/include/sys/timex.h. The third and current version
* includes TAI offset and is identified by the symbol NTP_API with
* value 4.
*
* Each update to a prefer peer sets pps_stratum if it survives the
* intersection algorithm and its time is within range. The PPS time
* discipline is enabled (STA_PPSTIME bit set in the status word) when
* pps_stratum is true and the PPS frequency discipline is enabled. If
* the PPS time discipline is enabled and the kernel reports a PPS
* signal is present, the pps_control variable is set to the current
* time. If the current time is later than pps_control by PPS_MAXAGE
* (120 s), this variable is set to zero.
*
* If an external clock is present, the clock driver sets STA_CLK in the
* status word. When the local clock driver sees this bit, it updates
* via this routine, which then calls ntp_adjtime() with the STA_PLL bit
* set to zero, in which case the system clock is not adjusted. This is
* also a signal for the external clock driver to discipline the system
* clock.
*/
/*
* Program variables that can be tinkered.
*/
double clock_max = CLOCK_MAX; /* step threshold (s) */
double clock_minstep = CLOCK_MINSTEP; /* stepout threshold (s) */
double clock_panic = CLOCK_PANIC; /* panic threshold (s) */
double clock_phi = CLOCK_PHI; /* dispersion rate (s/s) */
double allan_xpt = CLOCK_ALLAN; /* Allan intercept (s) */
/*
* Program variables
*/
static double clock_offset; /* offset (s) */
double clock_jitter; /* offset jitter (s) */
double drift_comp; /* frequency (s/s) */
double clock_stability; /* frequency stability (wander) (s/s) */
u_long sys_clocktime; /* last system clock update */
u_long pps_control; /* last pps update */
u_long sys_tai; /* UTC offset from TAI (s) */
static void rstclock P((int, u_long, double)); /* transition function */
#ifdef KERNEL_PLL
struct timex ntv; /* kernel API parameters */
int pll_status; /* status bits for kernel pll */
#endif /* KERNEL_PLL */
/*
* Clock state machine control flags
*/
int ntp_enable; /* clock discipline enabled */
int pll_control; /* kernel support available */
int kern_enable; /* kernel support enabled */
int pps_enable; /* kernel PPS discipline enabled */
int ext_enable; /* external clock enabled */
int pps_stratum; /* pps stratum */
int allow_panic = FALSE; /* allow panic correction */
int mode_ntpdate = FALSE; /* exit on first clock set */
/*
* Clock state machine variables
*/
int state; /* clock discipline state */
u_char sys_poll = NTP_MINDPOLL; /* time constant/poll (log2 s) */
int tc_counter; /* jiggle counter */
double last_offset; /* last offset (s) */
/*
* Huff-n'-puff filter variables
*/
static double *sys_huffpuff; /* huff-n'-puff filter */
static int sys_hufflen; /* huff-n'-puff filter stages */
static int sys_huffptr; /* huff-n'-puff filter pointer */
static double sys_mindly; /* huff-n'-puff filter min delay */
#if defined(KERNEL_PLL)
/* Emacs cc-mode goes nuts if we split the next line... */
#define MOD_BITS (MOD_OFFSET | MOD_MAXERROR | MOD_ESTERROR | \
MOD_STATUS | MOD_TIMECONST)
#ifdef SIGSYS
static void pll_trap P((int)); /* configuration trap */
static struct sigaction sigsys; /* current sigaction status */
static struct sigaction newsigsys; /* new sigaction status */
static sigjmp_buf env; /* environment var. for pll_trap() */
#endif /* SIGSYS */
#endif /* KERNEL_PLL */
/*
* init_loopfilter - initialize loop filter data
*/
void
init_loopfilter(void)
{
/*
* Initialize state variables. Initially, we expect no drift
* file, so set the state to S_NSET. If a drift file is present,
* it will be detected later and the state set to S_FSET.
*/
rstclock(S_NSET, 0, 0);
clock_jitter = LOGTOD(sys_precision);
}
/*
* local_clock - the NTP logical clock loop filter.
*
* Return codes:
* -1 update ignored: exceeds panic threshold
* 0 update ignored: popcorn or exceeds step threshold
* 1 clock was slewed
* 2 clock was stepped
*
* LOCKCLOCK: The only thing this routine does is set the
* sys_rootdispersion variable equal to the peer dispersion.
*/
int
local_clock(
struct peer *peer, /* synch source peer structure */
double fp_offset /* clock offset (s) */
)
{
int rval; /* return code */
u_long mu; /* interval since last update (s) */
double flladj; /* FLL frequency adjustment (ppm) */
double plladj; /* PLL frequency adjustment (ppm) */
double clock_frequency; /* clock frequency adjustment (ppm) */
double dtemp, etemp; /* double temps */
#ifdef OPENSSL
u_int32 *tpt;
int i;
u_int len;
long togo;
#endif /* OPENSSL */
/*
* If the loop is opened or the NIST LOCKCLOCK is in use,
* monitor and record the offsets anyway in order to determine
* the open-loop response and then go home.
*/
#ifdef DEBUG
if (debug)
printf(
"local_clock: assocID %d offset %.9f freq %.3f state %d\n",
peer->associd, fp_offset, drift_comp * 1e6, state);
#endif
#ifdef LOCKCLOCK
return (0);
#else /* LOCKCLOCK */
if (!ntp_enable) {
record_loop_stats(fp_offset, drift_comp, clock_jitter,
clock_stability, sys_poll);
return (0);
}
/*
* If the clock is way off, panic is declared. The clock_panic
* defaults to 1000 s; if set to zero, the panic will never
* occur. The allow_panic defaults to FALSE, so the first panic
* will exit. It can be set TRUE by a command line option, in
* which case the clock will be set anyway and time marches on.
* But, allow_panic will be set FALSE when the update is less
* than the step threshold; so, subsequent panics will exit.
*/
if (fabs(fp_offset) > clock_panic && clock_panic > 0 &&
!allow_panic) {
msyslog(LOG_ERR,
"time correction of %.0f seconds exceeds sanity limit (%.0f); set clock manually to the correct UTC time.",
fp_offset, clock_panic);
return (-1);
}
/*
* If simulating ntpdate, set the clock directly, rather than
* using the discipline. The clock_max defines the step
* threshold, above which the clock will be stepped instead of
* slewed. The value defaults to 128 ms, but can be set to even
* unreasonable values. If set to zero, the clock will never be
* stepped. Note that a slew will persist beyond the life of
* this program.
*
* Note that if ntpdate is active, the terminal does not detach,
* so the termination comments print directly to the console.
*/
if (mode_ntpdate) {
if (fabs(fp_offset) > clock_max && clock_max > 0) {
step_systime(fp_offset);
msyslog(LOG_NOTICE, "time reset %+.6f s",
fp_offset);
printf("ntpd: time set %+.6fs\n", fp_offset);
} else {
adj_systime(fp_offset);
msyslog(LOG_NOTICE, "time slew %+.6f s",
fp_offset);
printf("ntpd: time slew %+.6fs\n", fp_offset);
}
record_loop_stats(fp_offset, drift_comp, clock_jitter,
clock_stability, sys_poll);
exit (0);
}
/*
* The huff-n'-puff filter finds the lowest delay in the recent
* interval. This is used to correct the offset by one-half the
* difference between the sample delay and minimum delay. This
* is most effective if the delays are highly assymetric and
* clockhopping is avoided and the clock frequency wander is
* relatively small.
*
* Note either there is no prefer peer or this update is from
* the prefer peer.
*/
if (sys_huffpuff != NULL && (sys_prefer == NULL || sys_prefer ==
peer)) {
if (peer->delay < sys_huffpuff[sys_huffptr])
sys_huffpuff[sys_huffptr] = peer->delay;
if (peer->delay < sys_mindly)
sys_mindly = peer->delay;
if (fp_offset > 0)
dtemp = -(peer->delay - sys_mindly) / 2;
else
dtemp = (peer->delay - sys_mindly) / 2;
fp_offset += dtemp;
#ifdef DEBUG
if (debug)
printf(
"local_clock: size %d mindly %.6f huffpuff %.6f\n",
sys_hufflen, sys_mindly, dtemp);
#endif
}
/*
* Clock state machine transition function. This is where the
* action is and defines how the system reacts to large phase
* and frequency errors. There are two main regimes: when the
* offset exceeds the step threshold and when it does not.
* However, if the step threshold is set to zero, a step will
* never occur. See the instruction manual for the details how
* these actions interact with the command line options.
*
* Note the system poll is set to minpoll only if the clock is
* stepped. Note also the kernel is disabled if step is
* disabled or greater than 0.5 s.
*/
clock_frequency = flladj = plladj = 0;
mu = peer->epoch - sys_clocktime;
if (clock_max == 0 || clock_max > 0.5)
kern_enable = 0;
rval = 1;
if (fabs(fp_offset) > clock_max && clock_max > 0) {
switch (state) {
/*
* In S_SYNC state we ignore the first outlyer amd
* switch to S_SPIK state.
*/
case S_SYNC:
state = S_SPIK;
return (0);
/*
* In S_FREQ state we ignore outlyers and inlyers. At
* the first outlyer after the stepout threshold,
* compute the apparent frequency correction and step
* the phase.
*/
case S_FREQ:
if (mu < clock_minstep)
return (0);
clock_frequency = (fp_offset - clock_offset) /
mu;
/* fall through to S_SPIK */
/*
* In S_SPIK state we ignore succeeding outlyers until
* either an inlyer is found or the stepout threshold is
* exceeded.
*/
case S_SPIK:
if (mu < clock_minstep)
return (0);
/* fall through to default */
/*
* We get here by default in S_NSET and S_FSET states
* and from above in S_FREQ or S_SPIK states.
*
* In S_NSET state an initial frequency correction is
* not available, usually because the frequency file has
* not yet been written. Since the time is outside the
* step threshold, the clock is stepped. The frequency
* will be set directly following the stepout interval.
*
* In S_FSET state the initial frequency has been set
* from the frequency file. Since the time is outside
* the step threshold, the clock is stepped immediately,
* rather than after the stepout interval. Guys get
* nervous if it takes 17 minutes to set the clock for
* the first time.
*
* In S_FREQ and S_SPIK states the stepout threshold has
* expired and the phase is still above the step
* threshold. Note that a single spike greater than the
* step threshold is always suppressed, even at the
* longer poll intervals.
*/
default:
step_systime(fp_offset);
msyslog(LOG_NOTICE, "time reset %+.6f s",
fp_offset);
reinit_timer();
tc_counter = 0;
sys_poll = NTP_MINPOLL;
sys_tai = 0;
clock_jitter = LOGTOD(sys_precision);
rval = 2;
if (state == S_NSET) {
rstclock(S_FREQ, peer->epoch, 0);
return (rval);
}
break;
}
rstclock(S_SYNC, peer->epoch, 0);
} else {
/*
* The offset is less than the step threshold. Calculate
* the jitter as the exponentially weighted offset
* differences.
*/
etemp = SQUARE(clock_jitter);
dtemp = SQUARE(max(fabs(fp_offset - last_offset),
LOGTOD(sys_precision)));
clock_jitter = SQRT(etemp + (dtemp - etemp) /
CLOCK_AVG);
switch (state) {
/*
* In S_NSET state this is the first update received and
* the frequency has not been initialized. Adjust the
* phase, but do not adjust the frequency until after
* the stepout threshold.
*/
case S_NSET:
rstclock(S_FREQ, peer->epoch, fp_offset);
break;
/*
* In S_FSET state this is the first update received and
* the frequency has been initialized. Adjust the phase,
* but do not adjust the frequency until the next
* update.
*/
case S_FSET:
rstclock(S_SYNC, peer->epoch, fp_offset);
break;
/*
* In S_FREQ state ignore updates until the stepout
* threshold. After that, correct the phase and
* frequency and switch to S_SYNC state.
*/
case S_FREQ:
if (mu < clock_minstep)
return (0);
clock_frequency = (fp_offset - clock_offset) /
mu;
rstclock(S_SYNC, peer->epoch, fp_offset);
break;
/*
* We get here by default in S_SYNC and S_SPIK states.
* Here we compute the frequency update due to PLL and
* FLL contributions.
*/
default:
allow_panic = FALSE;
/*
* The FLL and PLL frequency gain constants
* depend on the poll interval and Allan
* intercept. The PLL is always used, but
* becomes ineffective above the Allan
* intercept. The FLL is not used below one-half
* the Allan intercept. Above that the loop gain
* increases in steps to 1 / CLOCK_AVG.
*/
if (ULOGTOD(sys_poll) > allan_xpt / 2) {
dtemp = CLOCK_FLL - sys_poll;
flladj = (fp_offset - clock_offset) /
(max(mu, allan_xpt) * dtemp);
}
/*
* For the PLL the integration interval
* (numerator) is the minimum of the update
* interval and poll interval. This allows
* oversampling, but not undersampling.
*/
etemp = min(mu, (u_long)ULOGTOD(sys_poll));
dtemp = 4 * CLOCK_PLL * ULOGTOD(sys_poll);
plladj = fp_offset * etemp / (dtemp * dtemp);
rstclock(S_SYNC, peer->epoch, fp_offset);
break;
}
}
#ifdef OPENSSL
/*
* Scan the loopsecond table to determine the TAI offset. If
* there is a scheduled leap in future, set the leap warning,
* but only if less than 30 days before the leap.
*/
tpt = (u_int32 *)tai_leap.ptr;
len = ntohl(tai_leap.vallen) / sizeof(u_int32);
if (tpt != NULL) {
for (i = 0; i < len; i++) {
togo = (long)ntohl(tpt[i]) -
(long)peer->rec.l_ui;
if (togo > 0) {
if (togo < CLOCK_JUNE)
leap_next |= LEAP_ADDSECOND;
break;
}
}
#if defined(STA_NANO) && NTP_API == 4
if (pll_control && kern_enable && sys_tai == 0) {
memset(&ntv, 0, sizeof(ntv));
ntv.modes = MOD_TAI;
ntv.constant = i + TAI_1972 - 1;
ntp_adjtime(&ntv);
}
#endif /* STA_NANO */
sys_tai = i + TAI_1972 - 1;
}
#endif /* OPENSSL */
#ifdef KERNEL_PLL
/*
* This code segment works when clock adjustments are made using
* precision time kernel support and the ntp_adjtime() system
* call. This support is available in Solaris 2.6 and later,
* Digital Unix 4.0 and later, FreeBSD, Linux and specially
* modified kernels for HP-UX 9 and Ultrix 4. In the case of the
* DECstation 5000/240 and Alpha AXP, additional kernel
* modifications provide a true microsecond clock and nanosecond
* clock, respectively.
*
* Important note: The kernel discipline is used only if the
* step threshold is less than 0.5 s, as anything higher can
* lead to overflow problems. This might occur if some misguided
* lad set the step threshold to something ridiculous.
*/
if (pll_control && kern_enable) {
/*
* We initialize the structure for the ntp_adjtime()
* system call. We have to convert everything to
* microseconds or nanoseconds first. Do not update the
* system variables if the ext_enable flag is set. In
* this case, the external clock driver will update the
* variables, which will be read later by the local
* clock driver. Afterwards, remember the time and
* frequency offsets for jitter and stability values and
* to update the frequency file.
*/
memset(&ntv, 0, sizeof(ntv));
if (ext_enable) {
ntv.modes = MOD_STATUS;
} else {
struct tm *tm = NULL;
time_t tstamp;
#ifdef STA_NANO
ntv.modes = MOD_BITS | MOD_NANO;
#else /* STA_NANO */
ntv.modes = MOD_BITS;
#endif /* STA_NANO */
if (clock_offset < 0)
dtemp = -.5;
else
dtemp = .5;
#ifdef STA_NANO
ntv.offset = (int32)(clock_offset * 1e9 +
dtemp);
ntv.constant = sys_poll;
#else /* STA_NANO */
ntv.offset = (int32)(clock_offset * 1e6 +
dtemp);
ntv.constant = sys_poll - 4;
#endif /* STA_NANO */
/*
* The frequency is set directly only if
* clock_frequency is nonzero coming out of FREQ
* state.
*/
if (clock_frequency != 0) {
ntv.modes |= MOD_FREQUENCY;
ntv.freq = (int32)((clock_frequency +
drift_comp) * 65536e6);
}
ntv.esterror = (u_int32)(clock_jitter * 1e6);
ntv.maxerror = (u_int32)((sys_rootdelay / 2 +
sys_rootdispersion) * 1e6);
ntv.status = STA_PLL;
/*
* Set the leap bits in the status word, but
* only on the last day of June or December.
*/
tstamp = peer->rec.l_ui - JAN_1970;
tm = gmtime(&tstamp);
if (tm != NULL) {
if ((tm->tm_mon + 1 == 6 &&
tm->tm_mday == 30) || (tm->tm_mon +
1 == 12 && tm->tm_mday == 31)) {
if (leap_next & LEAP_ADDSECOND)
ntv.status |= STA_INS;
else if (leap_next &
LEAP_DELSECOND)
ntv.status |= STA_DEL;
}
}
/*
* If the PPS signal is up and enabled, light
* the frequency bit. If the PPS driver is
* working, light the phase bit as well. If not,
* douse the lights, since somebody else may
* have left the switch on.
*/
if (pps_enable && pll_status & STA_PPSSIGNAL) {
ntv.status |= STA_PPSFREQ;
if (pps_stratum < STRATUM_UNSPEC)
ntv.status |= STA_PPSTIME;
} else {
ntv.status &= ~(STA_PPSFREQ |
STA_PPSTIME);
}
}
/*
* Pass the stuff to the kernel. If it squeals, turn off
* the pig. In any case, fetch the kernel offset and
* frequency and pretend we did it here.
*/
if (ntp_adjtime(&ntv) == TIME_ERROR) {
NLOG(NLOG_SYNCEVENT | NLOG_SYSEVENT)
msyslog(LOG_NOTICE,
"kernel time sync error %04x", ntv.status);
ntv.status &= ~(STA_PPSFREQ | STA_PPSTIME);
}
pll_status = ntv.status;
#ifdef STA_NANO
clock_offset = ntv.offset / 1e9;
#else /* STA_NANO */
clock_offset = ntv.offset / 1e6;
#endif /* STA_NANO */
clock_frequency = ntv.freq / 65536e6;
flladj = plladj = 0;
/*
* If the kernel PPS is lit, monitor its performance.
*/
if (ntv.status & STA_PPSTIME) {
pps_control = current_time;
#ifdef STA_NANO
clock_jitter = ntv.jitter / 1e9;
#else /* STA_NANO */
clock_jitter = ntv.jitter / 1e6;
#endif /* STA_NANO */
}
} else {
#endif /* KERNEL_PLL */
/*
* We get here if the kernel discipline is not enabled.
* Adjust the clock frequency as the sum of the directly
* computed frequency (if measured) and the PLL and FLL
* increments.
*/
clock_frequency = drift_comp + clock_frequency +
flladj + plladj;
#ifdef KERNEL_PLL
}
#endif /* KERNEL_PLL */
/*
* Clamp the frequency within the tolerance range and calculate
* the frequency change since the last update.
*/
if (fabs(clock_frequency) > NTP_MAXFREQ)
NLOG(NLOG_SYNCEVENT | NLOG_SYSEVENT)
msyslog(LOG_NOTICE,
"frequency error %.0f PPM exceeds tolerance %.0f PPM",
clock_frequency * 1e6, NTP_MAXFREQ * 1e6);
dtemp = SQUARE(clock_frequency - drift_comp);
if (clock_frequency > NTP_MAXFREQ)
drift_comp = NTP_MAXFREQ;
else if (clock_frequency < -NTP_MAXFREQ)
drift_comp = -NTP_MAXFREQ;
else
drift_comp = clock_frequency;
/*
* Calculate the wander as the exponentially weighted frequency
* differences.
*/
etemp = SQUARE(clock_stability);
clock_stability = SQRT(etemp + (dtemp - etemp) / CLOCK_AVG);
/*
* Here we adjust the poll interval by comparing the current
* offset with the clock jitter. If the offset is less than the
* clock jitter times a constant, then the averaging interval is
* increased, otherwise it is decreased. A bit of hysteresis
* helps calm the dance. Works best using burst mode.
*/
if (fabs(clock_offset) < CLOCK_PGATE * clock_jitter) {
tc_counter += sys_poll;
if (tc_counter > CLOCK_LIMIT) {
tc_counter = CLOCK_LIMIT;
if (sys_poll < peer->maxpoll) {
tc_counter = 0;
sys_poll++;
}
}
} else {
tc_counter -= sys_poll << 1;
if (tc_counter < -CLOCK_LIMIT) {
tc_counter = -CLOCK_LIMIT;
if (sys_poll > peer->minpoll) {
tc_counter = 0;
sys_poll--;
}
}
}
/*
* Yibbidy, yibbbidy, yibbidy; that'h all folks.
*/
record_loop_stats(clock_offset, drift_comp, clock_jitter,
clock_stability, sys_poll);
#ifdef DEBUG
if (debug)
printf(
"local_clock: mu %lu jitr %.6f freq %.3f stab %.6f poll %d count %d\n",
mu, clock_jitter, drift_comp * 1e6,
clock_stability * 1e6, sys_poll, tc_counter);
#endif /* DEBUG */
return (rval);
#endif /* LOCKCLOCK */
}
/*
* adj_host_clock - Called once every second to update the local clock.
*
* LOCKCLOCK: The only thing this routine does is increment the
* sys_rootdispersion variable.
*/
void
adj_host_clock(
void
)
{
double adjustment;
/*
* Update the dispersion since the last update. In contrast to
* NTPv3, NTPv4 does not declare unsynchronized after one day,
* since the dispersion check serves this function. Also,
* since the poll interval can exceed one day, the old test
* would be counterproductive. Note we do this even with
* external clocks, since the clock driver will recompute the
* maximum error and the local clock driver will pick it up and
* pass to the common refclock routines. Very elegant.
*/
sys_rootdispersion += clock_phi;
#ifndef LOCKCLOCK
/*
* If clock discipline is disabled or if the kernel is enabled,
* get out of Dodge quick.
*/
if (!ntp_enable || mode_ntpdate || (pll_control &&
kern_enable))
return;
/*
* Declare PPS kernel unsync if the pps signal has not been
* heard for a few minutes.
*/
if (pps_control && current_time - pps_control > PPS_MAXAGE) {
if (pps_control)
NLOG(NLOG_SYNCEVENT | NLOG_SYSEVENT)
msyslog(LOG_NOTICE, "pps sync disabled");
pps_control = 0;
}
/*
* Implement the phase and frequency adjustments. The gain
* factor (denominator) is not allowed to increase beyond the
* Allan intercept. It doesn't make sense to average phase noise
* beyond this point and it helps to damp residual offset at the
* longer poll intervals.
*/
adjustment = clock_offset / (CLOCK_PLL * min(ULOGTOD(sys_poll),
allan_xpt));
clock_offset -= adjustment;
adj_systime(adjustment + drift_comp);
#endif /* LOCKCLOCK */
}
/*
* Clock state machine. Enter new state and set state variables. Note we
* use the time of the last clock filter sample, which may be earlier
* than the current time.
*/
static void
rstclock(
int trans, /* new state */
u_long update, /* new update time */
double offset /* new offset */
)
{
#ifdef DEBUG
if (debug)
printf("local_clock: time %lu offset %.6f freq %.3f state %d\n",
update, offset, drift_comp * 1e6, trans);
#endif
state = trans;
sys_clocktime = update;
last_offset = clock_offset = offset;
}
/*
* huff-n'-puff filter
*/
void
huffpuff()
{
int i;
if (sys_huffpuff == NULL)
return;
sys_huffptr = (sys_huffptr + 1) % sys_hufflen;
sys_huffpuff[sys_huffptr] = 1e9;
sys_mindly = 1e9;
for (i = 0; i < sys_hufflen; i++) {
if (sys_huffpuff[i] < sys_mindly)
sys_mindly = sys_huffpuff[i];
}
}
/*
* loop_config - configure the loop filter
*
* LOCKCLOCK: The LOOP_DRIFTINIT and LOOP_DRIFTCOMP cases are no-ops.
*/
void
loop_config(
int item,
double freq
)
{
int i;
switch (item) {
case LOOP_DRIFTINIT:
#ifndef LOCKCLOCK
#ifdef KERNEL_PLL
/*
* Assume the kernel supports the ntp_adjtime() syscall.
* If that syscall works, initialize the kernel time
* variables. Otherwise, continue leaving no harm
* behind. While at it, ask to set nanosecond mode. If
* the kernel agrees, rejoice; othewise, it does only
* microseconds.
*/
if (mode_ntpdate)
break;
pll_control = 1;
memset(&ntv, 0, sizeof(ntv));
#ifdef STA_NANO
ntv.modes = MOD_BITS | MOD_NANO;
#else /* STA_NANO */
ntv.modes = MOD_BITS;
#endif /* STA_NANO */
ntv.maxerror = MAXDISPERSE;
ntv.esterror = MAXDISPERSE;
ntv.status = STA_UNSYNC;
#ifdef SIGSYS
/*
* Use sigsetjmp() to save state and then call
* ntp_adjtime(); if it fails, then siglongjmp() is used
* to return control
*/
newsigsys.sa_handler = pll_trap;
newsigsys.sa_flags = 0;
if (sigaction(SIGSYS, &newsigsys, &sigsys)) {
msyslog(LOG_ERR,
"sigaction() fails to save SIGSYS trap: %m");
pll_control = 0;
}
if (sigsetjmp(env, 1) == 0)
ntp_adjtime(&ntv);
if ((sigaction(SIGSYS, &sigsys,
(struct sigaction *)NULL))) {
msyslog(LOG_ERR,
"sigaction() fails to restore SIGSYS trap: %m");
pll_control = 0;
}
#else /* SIGSYS */
ntp_adjtime(&ntv);
#endif /* SIGSYS */
/*
* Save the result status and light up an external clock
* if available.
*/
pll_status = ntv.status;
if (pll_control) {
#ifdef STA_NANO
if (pll_status & STA_CLK)
ext_enable = 1;
#endif /* STA_NANO */
NLOG(NLOG_SYNCEVENT | NLOG_SYSEVENT)
msyslog(LOG_INFO,
"kernel time sync status %04x",
pll_status);
}
#endif /* KERNEL_PLL */
#endif /* LOCKCLOCK */
break;
case LOOP_DRIFTCOMP:
#ifndef LOCKCLOCK
/*
* If the frequency value is reasonable, set the initial
* frequency to the given value and the state to S_FSET.
* Otherwise, the drift file may be missing or broken,
* so set the frequency to zero. This erases past
* history should somebody break something.
*/
if (freq <= NTP_MAXFREQ && freq >= -NTP_MAXFREQ) {
drift_comp = freq;
rstclock(S_FSET, 0, 0);
} else {
drift_comp = 0;
}
#ifdef KERNEL_PLL
/*
* Sanity check. If the kernel is available, load the
* frequency and light up the loop. Make sure the offset
* is zero to cancel any previous nonsense. If you don't
* want this initialization, remove the ntp.drift file.
*/
if (pll_control && kern_enable) {
memset((char *)&ntv, 0, sizeof(ntv));
ntv.modes = MOD_OFFSET | MOD_FREQUENCY;
ntv.freq = (int32)(drift_comp * 65536e6);
ntp_adjtime(&ntv);
}
#endif /* KERNEL_PLL */
#endif /* LOCKCLOCK */
break;
case LOOP_KERN_CLEAR:
#ifndef LOCKCLOCK
#ifdef KERNEL_PLL
/* Completely turn off the kernel time adjustments. */
if (pll_control) {
memset((char *)&ntv, 0, sizeof(ntv));
ntv.modes = MOD_BITS | MOD_OFFSET | MOD_FREQUENCY;
ntv.status = STA_UNSYNC;
ntp_adjtime(&ntv);
NLOG(NLOG_SYNCEVENT | NLOG_SYSEVENT)
msyslog(LOG_INFO,
"kernel time sync disabled %04x",
ntv.status);
}
#endif /* KERNEL_PLL */
#endif /* LOCKCLOCK */
break;
/*
* Special tinker variables for Ulrich Windl. Very dangerous.
*/
case LOOP_MAX: /* step threshold */
clock_max = freq;
break;
case LOOP_PANIC: /* panic threshold */
clock_panic = freq;
break;
case LOOP_PHI: /* dispersion rate */
clock_phi = freq;
break;
case LOOP_MINSTEP: /* watchdog bark */
clock_minstep = freq;
break;
case LOOP_ALLAN: /* Allan intercept */
allan_xpt = freq;
break;
case LOOP_HUFFPUFF: /* huff-n'-puff filter length */
if (freq < HUFFPUFF)
freq = HUFFPUFF;
sys_hufflen = (int)(freq / HUFFPUFF);
sys_huffpuff = (double *)emalloc(sizeof(double) *
sys_hufflen);
for (i = 0; i < sys_hufflen; i++)
sys_huffpuff[i] = 1e9;
sys_mindly = 1e9;
break;
case LOOP_FREQ: /* initial frequency */
drift_comp = freq / 1e6;
rstclock(S_FSET, 0, 0);
break;
}
}
#if defined(KERNEL_PLL) && defined(SIGSYS)
/*
* _trap - trap processor for undefined syscalls
*
* This nugget is called by the kernel when the SYS_ntp_adjtime()
* syscall bombs because the silly thing has not been implemented in
* the kernel. In this case the phase-lock loop is emulated by
* the stock adjtime() syscall and a lot of indelicate abuse.
*/
static RETSIGTYPE
pll_trap(
int arg
)
{
pll_control = 0;
siglongjmp(env, 1);
}
#endif /* KERNEL_PLL && SIGSYS */