/*
* refclock_sample - process a pile of samples from the clock
*
* This routine implements a recursive median filter to suppress spikes
* in the data, as well as determine a performance statistic. It
* calculates the mean offset and RMS jitter. A time adjustment
* fudgetime1 can be added to the final offset to compensate for various
* systematic errors. The routine returns the number of samples
* processed, which could be zero.
*/
static int
refclock_sample(
struct refclockproc *pp /* refclock structure pointer */
)
{
size_t i, j, k, m, n;
double off[MAXSTAGE];
double offset;
/*
* Copy the raw offsets and sort into ascending order. Don't do
* anything if the buffer is empty.
*/
n = 0;
while (pp->codeproc != pp->coderecv) {
pp->codeproc = (pp->codeproc + 1) % MAXSTAGE;
off[n] = pp->filter[pp->codeproc];
n++;
}
if (n == 0)
return (0);
if (n > 1)
qsort((void *)off, n, sizeof(off[0]), refclock_cmpl_fp);
/*
* Reject the furthest from the median of the samples until
* approximately 60 percent of the samples remain.
*/
i = 0; j = n;
m = n - (n * 4) / 10;
while ((j - i) > m) {
offset = off[(j + i) / 2];
if (off[j - 1] - offset < offset - off[i])
i++; /* reject low end */
else
j--; /* reject high end */
}
/*
* Determine the offset and jitter.
*/
pp->offset = 0;
pp->jitter = 0;
for (k = i; k < j; k++) {
pp->offset += off[k];
if (k > i)
pp->jitter += SQUARE(off[k] - off[k - 1]);
}
pp->offset /= m;
pp->jitter = max(SQRT(pp->jitter / m), LOGTOD(sys_precision));
#ifdef DEBUG
if (debug)
printf(
"refclock_sample: n %d offset %.6f disp %.6f jitter %.6f\n",
n, pp->offset, pp->disp, pp->jitter);
#endif
return (int)n;
}
/*
* init_loopfilter - initialize loop filter data
*/
void
init_loopfilter(void)
{
/*
* Initialize state variables.
*/
sys_poll = ntp_minpoll;
clock_jitter = LOGTOD(sys_precision);
}
/*
* 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);
}
static void decode_msg(struct ntp_data *nd, void *base, size_t len,
struct timeval *tv, struct timespec *mrx_time)
{
struct ntp_msg *msg = base;
double m_delta, org, rec, xmt, dst;
double delay, offset;
static guint transmit_delay;
struct timex tmx = {};
if (len < sizeof(*msg)) {
connman_error("Invalid response from time server");
return;
}
if (!tv) {
connman_error("Invalid packet timestamp from time server");
return;
}
DBG("flags : 0x%02x", msg->flags);
DBG("stratum : %u", msg->stratum);
DBG("poll : %f seconds (%d)",
LOGTOD(msg->poll), msg->poll);
DBG("precision : %f seconds (%d)",
LOGTOD(msg->precision), msg->precision);
DBG("root delay : %u seconds (fraction %u)",
msg->rootdelay.seconds, msg->rootdelay.fraction);
DBG("root disp. : %u seconds (fraction %u)",
msg->rootdisp.seconds, msg->rootdisp.fraction);
DBG("reference : 0x%04x", msg->refid);
if (!msg->stratum) {
/* RFC 4330 ch 8 Kiss-of-Death packet */
uint32_t code = ntohl(msg->refid);
connman_info("Skipping server %s KoD code %c%c%c%c",
nd->timeserver, code >> 24, code >> 16 & 0xff,
code >> 8 & 0xff, code & 0xff);
nd->cb(false, nd->user_data);
return;
}
void
offset_calculation (
struct pkt *rpkt,
int rpktl,
struct timeval *tv_dst,
double *offset,
double *precision,
double *root_dispersion
)
{
l_fp p_rec, p_xmt, p_ref, p_org, tmp, dst;
u_fp p_rdly, p_rdsp;
double t21, t34, delta;
/* Convert timestamps from network to host byte order */
p_rdly = NTOHS_FP(rpkt->rootdelay);
p_rdsp = NTOHS_FP(rpkt->rootdisp);
NTOHL_FP(&rpkt->reftime, &p_ref);
NTOHL_FP(&rpkt->org, &p_org);
NTOHL_FP(&rpkt->rec, &p_rec);
NTOHL_FP(&rpkt->xmt, &p_xmt);
*precision = LOGTOD(rpkt->precision);
#ifdef DEBUG
printf("sntp precision: %f\n", *precision);
#endif /* DEBUG */
*root_dispersion = FPTOD(p_rdsp);
#ifdef DEBUG
printf("sntp rootdelay: %f\n", FPTOD(p_rdly));
printf("sntp rootdisp: %f\n", *root_dispersion);
pkt_output(rpkt, rpktl, stdout);
printf("sntp offset_calculation: rpkt->reftime:\n");
l_fp_output(&(rpkt->reftime), stdout);
printf("sntp offset_calculation: rpkt->org:\n");
l_fp_output(&(rpkt->org), stdout);
printf("sntp offset_calculation: rpkt->rec:\n");
l_fp_output(&(rpkt->rec), stdout);
printf("sntp offset_calculation: rpkt->rec:\n");
l_fp_output_bin(&(rpkt->rec), stdout);
printf("sntp offset_calculation: rpkt->rec:\n");
l_fp_output_dec(&(rpkt->rec), stdout);
printf("sntp offset_calculation: rpkt->xmt:\n");
l_fp_output(&(rpkt->xmt), stdout);
#endif
/* Compute offset etc. */
tmp = p_rec;
L_SUB(&tmp, &p_org);
LFPTOD(&tmp, t21);
TVTOTS(tv_dst, &dst);
dst.l_ui += JAN_1970;
tmp = p_xmt;
L_SUB(&tmp, &dst);
LFPTOD(&tmp, t34);
*offset = (t21 + t34) / 2.;
delta = t21 - t34;
if (ENABLED_OPT(NORMALVERBOSE))
printf("sntp offset_calculation:\tt21: %.6f\t\t t34: %.6f\n\t\tdelta: %.6f\t offset: %.6f\n",
t21, t34, delta, *offset);
}
/*
* 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_rootdisp 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 */
int osys_poll; /* old system poll */
int ntp_adj_ret; /* returned by ntp_adjtime */
double mu; /* interval since last update */
double clock_frequency; /* clock frequency */
double dtemp, etemp; /* double temps */
char tbuf[80]; /* report buffer */
/*
* 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 LOCKCLOCK
{
#else
if (!ntp_enable) {
#endif /* LOCKCLOCK */
record_loop_stats(fp_offset, drift_comp, clock_jitter,
clock_stability, sys_poll);
return (0);
}
#ifndef LOCKCLOCK
/*
* 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) {
snprintf(tbuf, sizeof(tbuf),
"%+.0f s; set clock manually within %.0f s.",
fp_offset, clock_panic);
report_event(EVNT_SYSFAULT, NULL, tbuf);
return (-1);
}
/*
* This section simulates ntpdate. If the offset exceeds the
* step threshold (128 ms), step the clock to that time and
* exit. Otherwise, slew the clock to that time and exit. Note
* that the slew will persist and eventually complete beyond the
* life of this program. Note that while ntpdate is active, the
* terminal does not detach, so the termination message prints
* directly to the terminal.
*/
if (mode_ntpdate) {
if ( ( fp_offset > clock_max_fwd && clock_max_fwd > 0)
|| (-fp_offset > clock_max_back && clock_max_back > 0)) {
step_systime(fp_offset);
msyslog(LOG_NOTICE, "ntpd: time set %+.6f s",
fp_offset);
printf("ntpd: time set %+.6fs\n", fp_offset);
} else {
adj_systime(fp_offset);
msyslog(LOG_NOTICE, "ntpd: 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.
*/
if (sys_huffpuff != NULL) {
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 which defines how the
* system reacts to large phase and frequency excursion. There
* are two main regimes: when the offset exceeds the step
* threshold (128 ms) and when it does not. Under certain
* conditions updates are suspended until the stepout theshold
* (900 s) is exceeded. See the documentation on how these
* thresholds interact with commands and command line options.
*
* Note the kernel is disabled if step is disabled or greater
* than 0.5 s or in ntpdate mode.
*/
osys_poll = sys_poll;
if (sys_poll < peer->minpoll)
sys_poll = peer->minpoll;
if (sys_poll > peer->maxpoll)
sys_poll = peer->maxpoll;
mu = current_time - clock_epoch;
clock_frequency = drift_comp;
rval = 1;
if ( ( fp_offset > clock_max_fwd && clock_max_fwd > 0)
|| (-fp_offset > clock_max_back && clock_max_back > 0)
|| force_step_once ) {
if (force_step_once) {
force_step_once = FALSE; /* we want this only once after startup */
msyslog(LOG_NOTICE, "Doing intital time step" );
}
switch (state) {
/*
* In SYNC state we ignore the first outlyer and switch
* to SPIK state.
*/
case EVNT_SYNC:
snprintf(tbuf, sizeof(tbuf), "%+.6f s",
fp_offset);
report_event(EVNT_SPIK, NULL, tbuf);
state = EVNT_SPIK;
return (0);
/*
* In 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 EVNT_FREQ:
if (mu < clock_minstep)
return (0);
clock_frequency = direct_freq(fp_offset);
/* fall through to EVNT_SPIK */
/*
* In SPIK state we ignore succeeding outlyers until
* either an inlyer is found or the stepout threshold is
* exceeded.
*/
case EVNT_SPIK:
if (mu < clock_minstep)
return (0);
/* fall through to default */
/*
* We get here by default in NSET and FSET states and
* from above in FREQ or SPIK states.
*
* In 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 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 15 minutes to set the clock for
* the first time.
*
* In FREQ and 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 with a
* long time constant.
*/
default:
snprintf(tbuf, sizeof(tbuf), "%+.6f s",
fp_offset);
report_event(EVNT_CLOCKRESET, NULL, tbuf);
step_systime(fp_offset);
reinit_timer();
tc_counter = 0;
clock_jitter = LOGTOD(sys_precision);
rval = 2;
if (state == EVNT_NSET) {
rstclock(EVNT_FREQ, 0);
return (rval);
}
break;
}
rstclock(EVNT_SYNC, 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 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 EVNT_NSET:
adj_systime(fp_offset);
rstclock(EVNT_FREQ, fp_offset);
break;
/*
* In FREQ state ignore updates until the stepout
* threshold. After that, compute the new frequency, but
* do not adjust the frequency until the holdoff counter
* decrements to zero.
*/
case EVNT_FREQ:
if (mu < clock_minstep)
return (0);
clock_frequency = direct_freq(fp_offset);
/* fall through */
/*
* We get here by default in FSET, SPIK and SYNC states.
* Here compute the frequency update due to PLL and FLL
* contributions. Note, we avoid frequency discipline at
* startup until the initial transient has subsided.
*/
default:
allow_panic = FALSE;
if (freq_cnt == 0) {
/*
* The FLL and PLL frequency gain constants
* depend on the time constant and Allan
* intercept. The PLL is always used, but
* becomes ineffective above the Allan intercept
* where the FLL becomes effective.
*/
if (sys_poll >= allan_xpt)
clock_frequency += (fp_offset -
clock_offset) / max(ULOGTOD(sys_poll),
mu) * CLOCK_FLL;
/*
* The PLL frequency gain (numerator) depends on
* the minimum of the update interval and Allan
* intercept. This reduces the PLL gain when the
* FLL becomes effective.
*/
etemp = min(ULOGTOD(allan_xpt), mu);
dtemp = 4 * CLOCK_PLL * ULOGTOD(sys_poll);
clock_frequency += fp_offset * etemp / (dtemp *
dtemp);
}
rstclock(EVNT_SYNC, fp_offset);
if (fabs(fp_offset) < CLOCK_FLOOR)
freq_cnt = 0;
break;
}
}
#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 && freq_cnt == 0) {
/*
* 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.
*/
ZERO(ntv);
if (ext_enable) {
ntv.modes = MOD_STATUS;
} else {
#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 */
if (ntv.constant < 0)
ntv.constant = 0;
ntv.esterror = (u_int32)(clock_jitter * 1e6);
ntv.maxerror = (u_int32)((sys_rootdelay / 2 +
sys_rootdisp) * 1e6);
ntv.status = STA_PLL;
/*
* Enable/disable the PPS if requested.
*/
if (hardpps_enable) {
ntv.status |= (STA_PPSTIME | STA_PPSFREQ);
if (!(pll_status & STA_PPSTIME))
sync_status("PPS enabled",
pll_status,
ntv.status);
} else {
ntv.status &= ~(STA_PPSTIME | STA_PPSFREQ);
if (pll_status & STA_PPSTIME)
sync_status("PPS disabled",
pll_status,
ntv.status);
}
if (sys_leap == LEAP_ADDSECOND)
ntv.status |= STA_INS;
else if (sys_leap == LEAP_DELSECOND)
ntv.status |= STA_DEL;
}
/*
* Pass the stuff to the kernel. If it squeals, turn off
* the pps. In any case, fetch the kernel offset,
* frequency and jitter.
*/
ntp_adj_ret = ntp_adjtime(&ntv);
/*
* A squeal is a return status < 0, or a state change.
*/
if ((0 > ntp_adj_ret) || (ntp_adj_ret != kernel_status)) {
kernel_status = ntp_adj_ret;
ntp_adjtime_error_handler(__func__, &ntv, ntp_adj_ret, errno, hardpps_enable, 0, __LINE__ - 1);
}
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 = FREQTOD(ntv.freq);
/*
* If the kernel PPS is lit, monitor its performance.
*/
if (ntv.status & STA_PPSTIME) {
#ifdef STA_NANO
clock_jitter = ntv.jitter / 1e9;
#else /* STA_NANO */
clock_jitter = ntv.jitter / 1e6;
#endif /* STA_NANO */
}
#if defined(STA_NANO) && NTP_API == 4
/*
* If the TAI changes, update the kernel TAI.
*/
if (loop_tai != sys_tai) {
loop_tai = sys_tai;
ntv.modes = MOD_TAI;
ntv.constant = sys_tai;
if ((ntp_adj_ret = ntp_adjtime(&ntv)) != 0) {
ntp_adjtime_error_handler(__func__, &ntv, ntp_adj_ret, errno, 0, 1, __LINE__ - 1);
}
}
#endif /* STA_NANO */
}
#endif /* KERNEL_PLL */
/*
* Clamp the frequency within the tolerance range and calculate
* the frequency difference since the last update.
*/
if (fabs(clock_frequency) > NTP_MAXFREQ)
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 RMS
* frequency differences. Record the change for the frequency
* file update.
*/
etemp = SQUARE(clock_stability);
clock_stability = SQRT(etemp + (dtemp - etemp) / CLOCK_AVG);
/*
* Here we adjust the time constant 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. Don't
* fiddle with the poll during the startup clamp period.
*/
if (freq_cnt > 0) {
tc_counter = 0;
} else 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--;
}
}
}
/*
* If the time constant has changed, update the poll variables.
*/
if (osys_poll != sys_poll)
poll_update(peer, 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: offset %.9f jit %.9f freq %.3f stab %.3f poll %d\n",
clock_offset, clock_jitter, drift_comp * 1e6,
clock_stability * 1e6, sys_poll);
#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_rootdisp variable.
*/
void
adj_host_clock(
void
)
{
double offset_adj;
double freq_adj;
/*
* 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. During the startup clamp period, the
* time constant is clamped at 2.
*/
sys_rootdisp += clock_phi;
#ifndef LOCKCLOCK
if (!ntp_enable || mode_ntpdate)
return;
/*
* Determine the phase adjustment. The gain factor (denominator)
* increases with poll interval, so is dominated by the FLL
* above the Allan intercept. Note the reduced time constant at
* startup.
*/
if (state != EVNT_SYNC) {
offset_adj = 0.;
} else if (freq_cnt > 0) {
offset_adj = clock_offset / (CLOCK_PLL * ULOGTOD(1));
freq_cnt--;
#ifdef KERNEL_PLL
} else if (pll_control && kern_enable) {
offset_adj = 0.;
#endif /* KERNEL_PLL */
} else {
offset_adj = clock_offset / (CLOCK_PLL * ULOGTOD(sys_poll));
}
/*
* If the kernel discipline is enabled the frequency correction
* drift_comp has already been engaged via ntp_adjtime() in
* set_freq(). Otherwise it is a component of the adj_systime()
* offset.
*/
#ifdef KERNEL_PLL
if (pll_control && kern_enable)
freq_adj = 0.;
else
#endif /* KERNEL_PLL */
freq_adj = drift_comp;
/* Bound absolute value of total adjustment to NTP_MAXFREQ. */
if (offset_adj + freq_adj > NTP_MAXFREQ)
offset_adj = NTP_MAXFREQ - freq_adj;
else if (offset_adj + freq_adj < -NTP_MAXFREQ)
offset_adj = -NTP_MAXFREQ - freq_adj;
clock_offset -= offset_adj;
/*
* Windows port adj_systime() must be called each second,
* even if the argument is zero, to ease emulation of
* adjtime() using Windows' slew API which controls the rate
* but does not automatically stop slewing when an offset
* has decayed to zero.
*/
adj_systime(offset_adj + freq_adj);
#endif /* LOCKCLOCK */
}
void
offset_calculation(
struct pkt *rpkt,
int rpktl,
struct timeval *tv_dst,
double *offset,
double *precision,
double *synch_distance
)
{
l_fp p_rec, p_xmt, p_ref, p_org, tmp, dst;
u_fp p_rdly, p_rdsp;
double t21, t34, delta;
/* Convert timestamps from network to host byte order */
p_rdly = NTOHS_FP(rpkt->rootdelay);
p_rdsp = NTOHS_FP(rpkt->rootdisp);
NTOHL_FP(&rpkt->reftime, &p_ref);
NTOHL_FP(&rpkt->org, &p_org);
NTOHL_FP(&rpkt->rec, &p_rec);
NTOHL_FP(&rpkt->xmt, &p_xmt);
*precision = LOGTOD(rpkt->precision);
TRACE(3, ("offset_calculation: LOGTOD(rpkt->precision): %f\n", *precision));
/* Compute offset etc. */
tmp = p_rec;
L_SUB(&tmp, &p_org);
LFPTOD(&tmp, t21);
TVTOTS(tv_dst, &dst);
dst.l_ui += JAN_1970;
tmp = p_xmt;
L_SUB(&tmp, &dst);
LFPTOD(&tmp, t34);
*offset = (t21 + t34) / 2.;
delta = t21 - t34;
// synch_distance is:
// (peer->delay + peer->rootdelay) / 2 + peer->disp
// + peer->rootdisp + clock_phi * (current_time - peer->update)
// + peer->jitter;
//
// and peer->delay = fabs(peer->offset - p_offset) * 2;
// and peer->offset needs history, so we're left with
// p_offset = (t21 + t34) / 2.;
// peer->disp = 0; (we have no history to augment this)
// clock_phi = 15e-6;
// peer->jitter = LOGTOD(sys_precision); (we have no history to augment this)
// and ntp_proto.c:set_sys_tick_precision() should get us sys_precision.
//
// so our answer seems to be:
//
// (fabs(t21 + t34) + peer->rootdelay) / 3.
// + 0 (peer->disp)
// + peer->rootdisp
// + 15e-6 (clock_phi)
// + LOGTOD(sys_precision)
INSIST( FPTOD(p_rdly) >= 0. );
#if 1
*synch_distance = (fabs(t21 + t34) + FPTOD(p_rdly)) / 3.
+ 0.
+ FPTOD(p_rdsp)
+ 15e-6
+ 0. /* LOGTOD(sys_precision) when we can get it */
;
INSIST( *synch_distance >= 0. );
#else
*synch_distance = (FPTOD(p_rdly) + FPTOD(p_rdsp))/2.0;
#endif
#ifdef DEBUG
if (debug > 3) {
printf("sntp rootdelay: %f\n", FPTOD(p_rdly));
printf("sntp rootdisp: %f\n", FPTOD(p_rdsp));
printf("sntp syncdist: %f\n", *synch_distance);
pkt_output(rpkt, rpktl, stdout);
printf("sntp offset_calculation: rpkt->reftime:\n");
l_fp_output(&p_ref, stdout);
printf("sntp offset_calculation: rpkt->org:\n");
l_fp_output(&p_org, stdout);
printf("sntp offset_calculation: rpkt->rec:\n");
l_fp_output(&p_rec, stdout);
printf("sntp offset_calculation: rpkt->xmt:\n");
l_fp_output(&p_xmt, stdout);
}
#endif
TRACE(3, ("sntp offset_calculation:\trec - org t21: %.6f\n"
"\txmt - dst t34: %.6f\tdelta: %.6f\toffset: %.6f\n",
t21, t34, delta, *offset));
return;
}
static void decode_msg(void *base, size_t len, struct timeval *tv,
struct timespec *mrx_time)
{
struct ntp_msg *msg = base;
double m_delta, org, rec, xmt, dst;
double delay, offset;
static guint transmit_delay;
if (len < sizeof(*msg)) {
connman_error("Invalid response from time server");
return;
}
if (!tv) {
connman_error("Invalid packet timestamp from time server");
return;
}
DBG("flags : 0x%02x", msg->flags);
DBG("stratum : %u", msg->stratum);
DBG("poll : %f seconds (%d)",
LOGTOD(msg->poll), msg->poll);
DBG("precision : %f seconds (%d)",
LOGTOD(msg->precision), msg->precision);
DBG("root delay : %u seconds (fraction %u)",
msg->rootdelay.seconds, msg->rootdelay.fraction);
DBG("root disp. : %u seconds (fraction %u)",
msg->rootdisp.seconds, msg->rootdisp.fraction);
DBG("reference : 0x%04x", msg->refid);
transmit_delay = LOGTOD(msg->poll);
if (NTP_FLAGS_LI_DECODE(msg->flags) == NTP_FLAG_LI_NOTINSYNC) {
DBG("ignoring unsynchronized peer");
return;
}
if (NTP_FLAGS_VN_DECODE(msg->flags) != NTP_FLAG_VN_VER4) {
if (NTP_FLAGS_VN_DECODE(msg->flags) == NTP_FLAG_VN_VER3) {
DBG("requested version %d, accepting version %d",
NTP_FLAG_VN_VER4, NTP_FLAGS_VN_DECODE(msg->flags));
} else {
DBG("unsupported version %d", NTP_FLAGS_VN_DECODE(msg->flags));
return;
}
}
if (NTP_FLAGS_MD_DECODE(msg->flags) != NTP_FLAG_MD_SERVER) {
DBG("unsupported mode %d", NTP_FLAGS_MD_DECODE(msg->flags));
return;
}
m_delta = mrx_time->tv_sec - mtx_time.tv_sec +
1.0e-9 * (mrx_time->tv_nsec - mtx_time.tv_nsec);
org = tv->tv_sec + (1.0e-6 * tv->tv_usec) - m_delta + OFFSET_1900_1970;
rec = ntohl(msg->rectime.seconds) +
((double) ntohl(msg->rectime.fraction) / UINT_MAX);
xmt = ntohl(msg->xmttime.seconds) +
((double) ntohl(msg->xmttime.fraction) / UINT_MAX);
dst = tv->tv_sec + (1.0e-6 * tv->tv_usec) + OFFSET_1900_1970;
DBG("org=%f rec=%f xmt=%f dst=%f", org, rec, xmt, dst);
offset = ((rec - org) + (xmt - dst)) / 2;
delay = (dst - org) - (xmt - rec);
DBG("offset=%f delay=%f", offset, delay);
/* Remove the timeout, as timeserver has responded */
reset_timeout();
/*
* Now poll the server every transmit_delay seconds
* for time correction.
*/
if (poll_id > 0)
g_source_remove(poll_id);
DBG("Timeserver %s, next sync in %d seconds", timeserver, transmit_delay);
poll_id = g_timeout_add_seconds(transmit_delay, next_poll, NULL);
connman_info("ntp: time slew %+.6f s", offset);
if (offset < STEPTIME_MIN_OFFSET && offset > -STEPTIME_MIN_OFFSET) {
struct timeval adj;
adj.tv_sec = (long) offset;
adj.tv_usec = (offset - adj.tv_sec) * 1000000;
DBG("adjusting time");
if (adjtime(&adj, &adj) < 0) {
connman_error("Failed to adjust time");
return;
}
DBG("%lu seconds, %lu msecs", adj.tv_sec, adj.tv_usec);
} else {
struct timeval cur;
double dtime;
gettimeofday(&cur, NULL);
dtime = offset + cur.tv_sec + 1.0e-6 * cur.tv_usec;
cur.tv_sec = (long) dtime;
cur.tv_usec = (dtime - cur.tv_sec) * 1000000;
DBG("setting time");
if (settimeofday(&cur, NULL) < 0) {
connman_error("Failed to set time");
return;
}
DBG("%lu seconds, %lu msecs", cur.tv_sec, cur.tv_usec);
}
}
DBG("root disp. : %u seconds (fraction %u)",
msg->rootdisp.seconds, msg->rootdisp.fraction);
DBG("reference : 0x%04x", msg->refid);
if (!msg->stratum) {
/* RFC 4330 ch 8 Kiss-of-Death packet */
uint32_t code = ntohl(msg->refid);
connman_info("Skipping server %s KoD code %c%c%c%c",
nd->timeserver, code >> 24, code >> 16 & 0xff,
code >> 8 & 0xff, code & 0xff);
nd->cb(false, nd->user_data);
return;
}
transmit_delay = LOGTOD(msg->poll);
if (NTP_FLAGS_LI_DECODE(msg->flags) == NTP_FLAG_LI_NOTINSYNC) {
DBG("ignoring unsynchronized peer");
nd->cb(false, nd->user_data);
return;
}
if (NTP_FLAGS_VN_DECODE(msg->flags) != NTP_FLAG_VN_VER4) {
if (NTP_FLAGS_VN_DECODE(msg->flags) == NTP_FLAG_VN_VER3) {
DBG("requested version %d, accepting version %d",
NTP_FLAG_VN_VER4, NTP_FLAGS_VN_DECODE(msg->flags));
} else {
DBG("unsupported version %d", NTP_FLAGS_VN_DECODE(msg->flags));
nd->cb(false, nd->user_data);
/*
* 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 */
}