xref: /freebsd/contrib/ntp/libntp/systime.c (revision e9ac41698b2f322d55ccf9da50a3596edb2c1800)
1 /*
2  * systime -- routines to fiddle a UNIX clock.
3  *
4  * ATTENTION: Get approval from Dave Mills on all changes to this file!
5  *
6  */
7 #include <config.h>
8 #include <math.h>
9 
10 #include "ntp.h"
11 #include "ntpd.h"
12 #include "ntp_syslog.h"
13 #include "ntp_stdlib.h"
14 #include "ntp_random.h"
15 #include "iosignal.h"
16 #include "timevalops.h"
17 #include "timespecops.h"
18 #include "ntp_calendar.h"
19 
20 #ifdef HAVE_SYS_PARAM_H
21 # include <sys/param.h>
22 #endif
23 #ifdef HAVE_UTMP_H
24 # include <utmp.h>
25 #endif /* HAVE_UTMP_H */
26 #ifdef HAVE_UTMPX_H
27 # include <utmpx.h>
28 #endif /* HAVE_UTMPX_H */
29 
30 int	allow_panic = FALSE;		/* allow panic correction (-g) */
31 int	enable_panic_check = TRUE;	/* Can we check allow_panic's state? */
32 
33 u_long	sys_lamport;			/* Lamport violation */
34 u_long	sys_tsrounding;			/* timestamp rounding errors */
35 
36 #ifndef USE_COMPILETIME_PIVOT
37 # define USE_COMPILETIME_PIVOT 1
38 #endif
39 
40 /*
41  * These routines (get_systime, step_systime, adj_systime) implement an
42  * interface between the system independent NTP clock and the Unix
43  * system clock in various architectures and operating systems. Time is
44  * a precious quantity in these routines and every effort is made to
45  * minimize errors by unbiased rounding and amortizing adjustment
46  * residues.
47  *
48  * In order to improve the apparent resolution, provide unbiased
49  * rounding and most importantly ensure that the readings cannot be
50  * predicted, the low-order unused portion of the time below the minimum
51  * time to read the clock is filled with an unbiased random fuzz.
52  *
53  * The sys_tick variable specifies the system clock tick interval in
54  * seconds, for stepping clocks, defined as those which return times
55  * less than MINSTEP greater than the previous reading. For systems that
56  * use a high-resolution counter such that each clock reading is always
57  * at least MINSTEP greater than the prior, sys_tick is the time to read
58  * the system clock.
59  *
60  * The sys_fuzz variable measures the minimum time to read the system
61  * clock, regardless of its precision.  When reading the system clock
62  * using get_systime() after sys_tick and sys_fuzz have been determined,
63  * ntpd ensures each unprocessed clock reading is no less than sys_fuzz
64  * later than the prior unprocessed reading, and then fuzzes the bits
65  * below sys_fuzz in the timestamp returned, ensuring each of its
66  * resulting readings is strictly later than the previous.
67  *
68  * When slewing the system clock using adj_systime() (with the kernel
69  * loop discipline unavailable or disabled), adjtime() offsets are
70  * quantized to sys_tick, if sys_tick is greater than sys_fuzz, which
71  * is to say if the OS presents a stepping clock.  Otherwise, offsets
72  * are quantized to the microsecond resolution of adjtime()'s timeval
73  * input.  The remaining correction sys_residual is carried into the
74  * next adjtime() and meanwhile is also factored into get_systime()
75  * readings.
76  */
77 double	sys_tick = 0;		/* tick size or time to read (s) */
78 double	sys_fuzz = 0;		/* min. time to read the clock (s) */
79 long	sys_fuzz_nsec = 0;	/* min. time to read the clock (ns) */
80 double	measured_tick;		/* non-overridable sys_tick (s) */
81 double	sys_residual = 0;	/* adjustment residue (s) */
82 int	trunc_os_clock;		/* sys_tick > measured_tick */
83 time_stepped_callback	step_callback;
84 
85 #ifndef SIM
86 /* perlinger@ntp.org: As 'get_sysime()' does it's own check for clock
87  * backstepping, this could probably become a local variable in
88  * 'get_systime()' and the cruft associated with communicating via a
89  * static value could be removed after the v4.2.8 release.
90  */
91 static int lamport_violated;	/* clock was stepped back */
92 #endif	/* !SIM */
93 
94 #ifdef DEBUG
95 static int systime_init_done;
96 # define DONE_SYSTIME_INIT()	systime_init_done = TRUE
97 #else
98 # define DONE_SYSTIME_INIT()	do {} while (FALSE)
99 #endif
100 
101 #ifdef HAVE_SIGNALED_IO
102 int using_sigio;
103 #endif
104 
105 #ifdef SYS_WINNT
106 CRITICAL_SECTION get_systime_cs;
107 #endif
108 
109 
110 void
111 set_sys_fuzz(
112 	double	fuzz_val
113 	)
114 {
115 	sys_fuzz = fuzz_val;
116 	INSIST(sys_fuzz >= 0);
117 	INSIST(sys_fuzz <= 1.0);
118 	/* [Bug 3450] ensure nsec fuzz >= sys_fuzz to reduce chance of
119 	 * short-falling fuzz advance
120 	 */
121 	sys_fuzz_nsec = (long)ceil(sys_fuzz * 1e9);
122 }
123 
124 
125 void
126 init_systime(void)
127 {
128 	INIT_GET_SYSTIME_CRITSEC();
129 	INIT_WIN_PRECISE_TIME();
130 	DONE_SYSTIME_INIT();
131 }
132 
133 
134 #ifndef SIM	/* ntpsim.c has get_systime() and friends for sim */
135 
136 static inline void
137 get_ostime(
138 	struct timespec *	tsp
139 	)
140 {
141 	int	rc;
142 	long	ticks;
143 
144 #if defined(HAVE_CLOCK_GETTIME)
145 	rc = clock_gettime(CLOCK_REALTIME, tsp);
146 #elif defined(HAVE_GETCLOCK)
147 	rc = getclock(TIMEOFDAY, tsp);
148 #else
149 	struct timeval		tv;
150 
151 	rc = GETTIMEOFDAY(&tv, NULL);
152 	tsp->tv_sec = tv.tv_sec;
153 	tsp->tv_nsec = tv.tv_usec * 1000;
154 #endif
155 	if (rc < 0) {
156 		msyslog(LOG_ERR, "read system clock failed: %m (%d)",
157 			errno);
158 		exit(1);
159 	}
160 
161 	if (trunc_os_clock) {
162 		ticks = (long)((tsp->tv_nsec * 1e-9) / sys_tick);
163 		tsp->tv_nsec = (long)(ticks * 1e9 * sys_tick);
164 	}
165 }
166 
167 
168 /*
169  * get_systime - return system time in NTP timestamp format.
170  */
171 void
172 get_systime(
173 	l_fp *now		/* system time */
174 	)
175 {
176         static struct timespec  ts_last;        /* last sampled os time */
177 	static struct timespec	ts_prev;	/* prior os time */
178 	static l_fp		lfp_prev;	/* prior result */
179 	struct timespec ts;	/* seconds and nanoseconds */
180 	struct timespec ts_min;	/* earliest permissible */
181 	struct timespec ts_lam;	/* lamport fictional increment */
182 	double	dfuzz;
183 	l_fp	result;
184 	l_fp	lfpfuzz;
185 	l_fp	lfpdelta;
186 
187 	get_ostime(&ts);
188 	DEBUG_REQUIRE(systime_init_done);
189 	ENTER_GET_SYSTIME_CRITSEC();
190 
191         /* First check if here was a Lamport violation, that is, two
192          * successive calls to 'get_ostime()' resulted in negative
193          * time difference. Use a few milliseconds of permissible
194          * tolerance -- being too sharp can hurt here. (This is intented
195          * for the Win32 target, where the HPC interpolation might
196          * introduce small steps backward. It should not be an issue on
197          * systems where get_ostime() results in a true syscall.)
198          */
199         if (cmp_tspec(add_tspec_ns(ts, 50000000), ts_last) < 0) {
200                 lamport_violated = 1;
201                 sys_lamport++;
202 	}
203         ts_last = ts;
204 
205 	/*
206 	 * After default_get_precision() has set a nonzero sys_fuzz,
207 	 * ensure every reading of the OS clock advances by at least
208 	 * sys_fuzz over the prior reading, thereby assuring each
209 	 * fuzzed result is strictly later than the prior.  Limit the
210 	 * necessary fiction to 1 second.
211 	 */
212 	if (!USING_SIGIO()) {
213 		ts_min = add_tspec_ns(ts_prev, sys_fuzz_nsec);
214 		if (cmp_tspec(ts, ts_min) < 0) {
215 			ts_lam = sub_tspec(ts_min, ts);
216 			if (ts_lam.tv_sec > 0 && !lamport_violated) {
217 				msyslog(LOG_ERR,
218 					"get_systime Lamport advance exceeds one second (%.9f)",
219 					ts_lam.tv_sec +
220 					    1e-9 * ts_lam.tv_nsec);
221 				exit(1);
222 			}
223 			if (!lamport_violated)
224 				ts = ts_min;
225 		}
226 		ts_prev = ts;
227 	}
228 
229 	/* convert from timespec to l_fp fixed-point */
230 	result = tspec_stamp_to_lfp(ts);
231 
232 	/*
233 	 * Add in the fuzz. 'ntp_random()' returns [0..2**31-1] so we
234 	 * must scale up the result by 2.0 to cover the full fractional
235 	 * range.
236 	 */
237 	dfuzz = ntp_uurandom() * sys_fuzz;
238 	DTOLFP(dfuzz, &lfpfuzz);
239 	L_ADD(&result, &lfpfuzz);
240 
241 	/*
242 	 * Ensure result is strictly greater than prior result (ignoring
243 	 * sys_residual's effect for now) once sys_fuzz has been
244 	 * determined.
245 	 *
246 	 * [Bug 3450] Rounding errors and time slew can lead to a
247 	 * violation of the expected postcondition. This is bound to
248 	 * happen from time to time (depending on state of the random
249 	 * generator, the current slew and the closeness of system time
250 	 * stamps drawn) and does not warrant a syslog entry. Instead it
251 	 * makes much more sense to ensure the postcondition and hop
252 	 * along silently.
253 	 */
254 	if (!USING_SIGIO()) {
255 		if (   !L_ISZERO(&lfp_prev)
256 		    && !lamport_violated
257 		    && (sys_fuzz > 0.0)
258 		   ) {
259 			lfpdelta = result;
260 			L_SUB(&lfpdelta, &lfp_prev);
261 			L_SUBUF(&lfpdelta, 1);
262 			if (lfpdelta.l_i < 0)
263 			{
264 				L_NEG(&lfpdelta);
265 				DPRINTF(1, ("get_systime: postcond failed by %s secs, fixed\n",
266 					    lfptoa(&lfpdelta, 9)));
267 				result = lfp_prev;
268 				L_ADDUF(&result, 1);
269 				sys_tsrounding++;
270 			}
271 		}
272 		lfp_prev = result;
273 		if (lamport_violated)
274 			lamport_violated = FALSE;
275 	}
276 	LEAVE_GET_SYSTIME_CRITSEC();
277 	*now = result;
278 }
279 
280 
281 /*
282  * adj_systime - adjust system time by the argument.
283  */
284 #if !defined SYS_WINNT
285 int				/* 0 okay, 1 error */
286 adj_systime(
287 	double now		/* adjustment (s) */
288 	)
289 {
290 	struct timeval adjtv;	/* new adjustment */
291 	struct timeval oadjtv;	/* residual adjustment */
292 	double	quant;		/* quantize to multiples of */
293 	double	dtemp;
294 	long	ticks;
295 	int	isneg = 0;
296 
297 	/*
298 	 * The Windows port adj_systime() depends on being called each
299 	 * second even when there's no additional correction, to allow
300 	 * emulation of adjtime() behavior on top of an API that simply
301 	 * sets the current rate.  This POSIX implementation needs to
302 	 * ignore invocations with zero correction, otherwise ongoing
303 	 * EVNT_NSET adjtime() can be aborted by a tiny adjtime()
304 	 * triggered by sys_residual.
305 	 */
306 	if (0. == now) {
307 		if (enable_panic_check && allow_panic) {
308 			msyslog(LOG_ERR, "adj_systime: allow_panic is TRUE!");
309 			INSIST(!allow_panic);
310 		}
311 		return TRUE;
312 	}
313 
314 	/*
315 	 * Most Unix adjtime() implementations adjust the system clock
316 	 * in microsecond quanta, but some adjust in 10-ms quanta. We
317 	 * carefully round the adjustment to the nearest quantum, then
318 	 * adjust in quanta and keep the residue for later.
319 	 */
320 	dtemp = now + sys_residual;
321 	if (dtemp < 0) {
322 		isneg = 1;
323 		dtemp = -dtemp;
324 	}
325 	adjtv.tv_sec = (long)dtemp;
326 	dtemp -= adjtv.tv_sec;
327 	if (sys_tick > sys_fuzz)
328 		quant = sys_tick;
329 	else
330 		quant = 1e-6;
331 	ticks = (long)(dtemp / quant + .5);
332 	adjtv.tv_usec = (long)(ticks * quant * 1.e6 + .5);
333 	/* The rounding in the conversions could us push over the
334 	 * limits: make sure the result is properly normalised!
335 	 * note: sign comes later, all numbers non-negative here.
336 	 */
337 	if (adjtv.tv_usec >= 1000000) {
338 		adjtv.tv_sec  += 1;
339 		adjtv.tv_usec -= 1000000;
340 		dtemp         -= 1.;
341 	}
342 	/* set the new residual with leftover from correction */
343 	sys_residual = dtemp - adjtv.tv_usec * 1.e-6;
344 
345 	/*
346 	 * Convert to signed seconds and microseconds for the Unix
347 	 * adjtime() system call. Note we purposely lose the adjtime()
348 	 * leftover.
349 	 */
350 	if (isneg) {
351 		adjtv.tv_sec = -adjtv.tv_sec;
352 		adjtv.tv_usec = -adjtv.tv_usec;
353 		sys_residual = -sys_residual;
354 	}
355 	if (adjtv.tv_sec != 0 || adjtv.tv_usec != 0) {
356 		if (adjtime(&adjtv, &oadjtv) < 0) {
357 			msyslog(LOG_ERR, "adj_systime: %m");
358 			if (enable_panic_check && allow_panic) {
359 				msyslog(LOG_ERR, "adj_systime: allow_panic is TRUE!");
360 			}
361 			return FALSE;
362 		}
363 	}
364 	if (enable_panic_check && allow_panic) {
365 		msyslog(LOG_ERR, "adj_systime: allow_panic is TRUE!");
366 	}
367 	return TRUE;
368 }
369 #endif
370 
371 /*
372  * helper to keep utmp/wtmp up to date
373  */
374 static void
375 update_uwtmp(
376 	struct timeval timetv,
377 	struct timeval tvlast
378 	)
379 {
380 	struct timeval tvdiff;
381 	/*
382 	 * FreeBSD, for example, has:
383 	 * struct utmp {
384 	 *	   char    ut_line[UT_LINESIZE];
385 	 *	   char    ut_name[UT_NAMESIZE];
386 	 *	   char    ut_host[UT_HOSTSIZE];
387 	 *	   long    ut_time;
388 	 * };
389 	 * and appends line="|", name="date", host="", time for the OLD
390 	 * and appends line="{", name="date", host="", time for the NEW // }
391 	 * to _PATH_WTMP .
392 	 *
393 	 * Some OSes have utmp, some have utmpx.
394 	 */
395 
396 	/*
397 	 * Write old and new time entries in utmp and wtmp if step
398 	 * adjustment is greater than one second.
399 	 *
400 	 * This might become even Uglier...
401 	 */
402 	tvdiff = abs_tval(sub_tval(timetv, tvlast));
403 	if (tvdiff.tv_sec > 0) {
404 #ifdef HAVE_UTMP_H
405 		struct utmp ut;
406 #endif
407 #ifdef HAVE_UTMPX_H
408 		struct utmpx utx;
409 #endif
410 
411 #ifdef HAVE_UTMP_H
412 		ZERO(ut);
413 #endif
414 #ifdef HAVE_UTMPX_H
415 		ZERO(utx);
416 #endif
417 
418 		/* UTMP */
419 
420 #ifdef UPDATE_UTMP
421 # ifdef HAVE_PUTUTLINE
422 #  ifndef _PATH_UTMP
423 #   define _PATH_UTMP UTMP_FILE
424 #  endif
425 		utmpname(_PATH_UTMP);
426 		ut.ut_type = OLD_TIME;
427 		strlcpy(ut.ut_line, OTIME_MSG, sizeof(ut.ut_line));
428 		ut.ut_time = tvlast.tv_sec;
429 		setutent();
430 		pututline(&ut);
431 		ut.ut_type = NEW_TIME;
432 		strlcpy(ut.ut_line, NTIME_MSG, sizeof(ut.ut_line));
433 		ut.ut_time = timetv.tv_sec;
434 		setutent();
435 		pututline(&ut);
436 		endutent();
437 # else /* not HAVE_PUTUTLINE */
438 # endif /* not HAVE_PUTUTLINE */
439 #endif /* UPDATE_UTMP */
440 
441 		/* UTMPX */
442 
443 #ifdef UPDATE_UTMPX
444 # ifdef HAVE_PUTUTXLINE
445 		utx.ut_type = OLD_TIME;
446 		strlcpy(utx.ut_line, OTIME_MSG, sizeof(utx.ut_line));
447 		utx.ut_tv = tvlast;
448 		setutxent();
449 		pututxline(&utx);
450 		utx.ut_type = NEW_TIME;
451 		strlcpy(utx.ut_line, NTIME_MSG, sizeof(utx.ut_line));
452 		utx.ut_tv = timetv;
453 		setutxent();
454 		pututxline(&utx);
455 		endutxent();
456 # else /* not HAVE_PUTUTXLINE */
457 # endif /* not HAVE_PUTUTXLINE */
458 #endif /* UPDATE_UTMPX */
459 
460 		/* WTMP */
461 
462 #ifdef UPDATE_WTMP
463 # ifdef HAVE_PUTUTLINE
464 #  ifndef _PATH_WTMP
465 #   define _PATH_WTMP WTMP_FILE
466 #  endif
467 		utmpname(_PATH_WTMP);
468 		ut.ut_type = OLD_TIME;
469 		strlcpy(ut.ut_line, OTIME_MSG, sizeof(ut.ut_line));
470 		ut.ut_time = tvlast.tv_sec;
471 		setutent();
472 		pututline(&ut);
473 		ut.ut_type = NEW_TIME;
474 		strlcpy(ut.ut_line, NTIME_MSG, sizeof(ut.ut_line));
475 		ut.ut_time = timetv.tv_sec;
476 		setutent();
477 		pututline(&ut);
478 		endutent();
479 # else /* not HAVE_PUTUTLINE */
480 # endif /* not HAVE_PUTUTLINE */
481 #endif /* UPDATE_WTMP */
482 
483 		/* WTMPX */
484 
485 #ifdef UPDATE_WTMPX
486 # ifdef HAVE_PUTUTXLINE
487 		utx.ut_type = OLD_TIME;
488 		utx.ut_tv = tvlast;
489 		strlcpy(utx.ut_line, OTIME_MSG, sizeof(utx.ut_line));
490 #  ifdef HAVE_UPDWTMPX
491 		updwtmpx(WTMPX_FILE, &utx);
492 #  else /* not HAVE_UPDWTMPX */
493 #  endif /* not HAVE_UPDWTMPX */
494 # else /* not HAVE_PUTUTXLINE */
495 # endif /* not HAVE_PUTUTXLINE */
496 # ifdef HAVE_PUTUTXLINE
497 		utx.ut_type = NEW_TIME;
498 		utx.ut_tv = timetv;
499 		strlcpy(utx.ut_line, NTIME_MSG, sizeof(utx.ut_line));
500 #  ifdef HAVE_UPDWTMPX
501 		updwtmpx(WTMPX_FILE, &utx);
502 #  else /* not HAVE_UPDWTMPX */
503 #  endif /* not HAVE_UPDWTMPX */
504 # else /* not HAVE_PUTUTXLINE */
505 # endif /* not HAVE_PUTUTXLINE */
506 #endif /* UPDATE_WTMPX */
507 
508 	}
509 }
510 
511 /*
512  * step_systime - step the system clock.
513  */
514 
515 int
516 step_systime(
517 	double step
518 	)
519 {
520 	time_t pivot; /* for ntp era unfolding */
521 	struct timeval timetv, tvlast;
522 	struct timespec timets;
523 	l_fp fp_ofs, fp_sys; /* offset and target system time in FP */
524 
525 	/*
526 	 * Get pivot time for NTP era unfolding. Since we don't step
527 	 * very often, we can afford to do the whole calculation from
528 	 * scratch. And we're not in the time-critical path yet.
529 	 */
530 #if SIZEOF_TIME_T > 4
531 	pivot = basedate_get_eracenter();
532 #else
533 	/* This makes sure the resulting time stamp is on or after
534 	 * 1969-12-31/23:59:59 UTC and gives us additional two years,
535 	 * from the change of NTP era in 2036 to the UNIX rollover in
536 	 * 2038. (Minus one second, but that won't hurt.) We *really*
537 	 * need a longer 'time_t' after that!  Or a different baseline,
538 	 * but that would cause other serious trouble, too.
539 	 */
540 	pivot = 0x7FFFFFFF;
541 #endif
542 
543 	/* get the complete jump distance as l_fp */
544 	DTOLFP(sys_residual, &fp_sys);
545 	DTOLFP(step,         &fp_ofs);
546 	L_ADD(&fp_ofs, &fp_sys);
547 
548 	/* ---> time-critical path starts ---> */
549 
550 	/* get the current time as l_fp (without fuzz) and as struct timeval */
551 	get_ostime(&timets);
552 	fp_sys = tspec_stamp_to_lfp(timets);
553 	tvlast.tv_sec = timets.tv_sec;
554 	tvlast.tv_usec = (timets.tv_nsec + 500) / 1000;
555 
556 	/* get the target time as l_fp */
557 	L_ADD(&fp_sys, &fp_ofs);
558 
559 	/* unfold the new system time */
560 	timetv = lfp_stamp_to_tval(fp_sys, &pivot);
561 
562 	/* now set new system time */
563 	if (ntp_set_tod(&timetv, NULL) != 0) {
564 		msyslog(LOG_ERR, "step-systime: %m");
565 		if (enable_panic_check && allow_panic) {
566 			msyslog(LOG_ERR, "step_systime: allow_panic is TRUE!");
567 		}
568 		return FALSE;
569 	}
570 
571 	/* <--- time-critical path ended with 'ntp_set_tod()' <--- */
572 
573 	sys_residual = 0;
574 	lamport_violated = (step < 0);
575 	if (step_callback)
576 		(*step_callback)();
577 
578 #ifdef NEED_HPUX_ADJTIME
579 	/*
580 	 * CHECKME: is this correct when called by ntpdate?????
581 	 */
582 	_clear_adjtime();
583 #endif
584 
585 	update_uwtmp(timetv, tvlast);
586 	if (enable_panic_check && allow_panic) {
587 		msyslog(LOG_ERR, "step_systime: allow_panic is TRUE!");
588 		INSIST(!allow_panic);
589 	}
590 	return TRUE;
591 }
592 
593 
594 #if SIZEOF_TIME_T > 4
595 static const char *
596 tv_fmt_libbuf(
597 	const struct timeval * ptv
598 	)
599 {
600 	char *		retv;
601 	vint64		secs;
602 	ntpcal_split	dds;
603 	struct calendar	jd;
604 
605 	secs = time_to_vint64(&ptv->tv_sec);
606 	dds  = ntpcal_daysplit(&secs);
607 	ntpcal_daysplit_to_date(&jd, &dds, DAY_UNIX_STARTS);
608 	LIB_GETBUF(retv);
609 	snprintf(retv, LIB_BUFLENGTH,
610 		 "%04hu-%02hu-%02hu/%02hu:%02hu:%02hu.%06u",
611 		 jd.year, (u_short)jd.month, (u_short)jd.monthday,
612 		 (u_short)jd.hour, (u_short)jd.minute, (u_short)jd.second,
613 		 (u_int)ptv->tv_usec);
614 	return retv;
615 }
616 #endif	/* SIZEOF_TIME_T > 4 */
617 
618 
619 int /*BOOL*/
620 clamp_systime(void)
621 {
622 #if SIZEOF_TIME_T > 4
623 
624 	struct timeval  tvbase, tvlast;
625 	struct timespec timets;
626 
627 	tvbase.tv_sec  = basedate_get_erabase();
628 	tvbase.tv_usec = 0;
629 
630 	/* ---> time-critical path starts ---> */
631 
632 	/* get the current time as l_fp (without fuzz) and as struct timeval */
633 	get_ostime(&timets);
634 	tvlast.tv_sec = timets.tv_sec;
635 	tvlast.tv_usec = (timets.tv_nsec + 500) / 1000;
636 	if (tvlast.tv_usec >= 1000000) {
637 		tvlast.tv_usec -= 1000000;
638 		tvlast.tv_sec  += 1;
639 	}
640 
641 	if (tvbase.tv_sec > tvlast.tv_sec) {
642 		/* now set new system time */
643 		if (ntp_set_tod(&tvbase, NULL) != 0) {
644 			msyslog(LOG_ERR, "clamp-systime: %m");
645 			return FALSE;
646 		}
647 	} else {
648 		msyslog(LOG_INFO,
649 			"clamp-systime: clock (%s) in allowed range",
650 			tv_fmt_libbuf(&tvlast));
651 		return FALSE;
652 	}
653 
654 	/* <--- time-critical path ended with 'ntp_set_tod()' <--- */
655 
656 	sys_residual = 0;
657 	lamport_violated = (tvbase.tv_sec < tvlast.tv_sec);
658 	if (step_callback)
659 		(*step_callback)();
660 
661 #   ifdef NEED_HPUX_ADJTIME
662 	/*
663 	 * CHECKME: is this correct when called by ntpdate?????
664 	 */
665 	_clear_adjtime();
666 #   endif
667 
668 	update_uwtmp(tvbase, tvlast);
669 	msyslog(LOG_WARNING,
670 		"clamp-systime: clock stepped from %s to %s!",
671 		tv_fmt_libbuf(&tvlast), tv_fmt_libbuf(&tvbase));
672 	return TRUE;
673 
674 #else
675 
676 	return FALSE;
677 
678 #endif
679 }
680 
681 #endif	/* !SIM */
682