2 * NTP client/server, based on OpenNTPD 3.9p1
4 * Author: Adam Tkac <vonsch@gmail.com>
6 * Licensed under GPLv2, see file LICENSE in this source tree.
8 * Parts of OpenNTPD clock syncronization code is replaced by
9 * code which is based on ntp-4.2.6, whuch carries the following
12 ***********************************************************************
14 * Copyright (c) University of Delaware 1992-2009 *
16 * Permission to use, copy, modify, and distribute this software and *
17 * its documentation for any purpose with or without fee is hereby *
18 * granted, provided that the above copyright notice appears in all *
19 * copies and that both the copyright notice and this permission *
20 * notice appear in supporting documentation, and that the name *
21 * University of Delaware not be used in advertising or publicity *
22 * pertaining to distribution of the software without specific, *
23 * written prior permission. The University of Delaware makes no *
24 * representations about the suitability this software for any *
25 * purpose. It is provided "as is" without express or implied *
28 ***********************************************************************
31 //usage:#define ntpd_trivial_usage
32 //usage: "[-dnqNw"IF_FEATURE_NTPD_SERVER("l")"] [-S PROG] [-p PEER]..."
33 //usage:#define ntpd_full_usage "\n\n"
34 //usage: "NTP client/server\n"
35 //usage: "\n -d Verbose"
36 //usage: "\n -n Do not daemonize"
37 //usage: "\n -q Quit after clock is set"
38 //usage: "\n -N Run at high priority"
39 //usage: "\n -w Do not set time (only query peers), implies -n"
40 //usage: IF_FEATURE_NTPD_SERVER(
41 //usage: "\n -l Run as server on port 123"
43 //usage: "\n -S PROG Run PROG after stepping time, stratum change, and every 11 mins"
44 //usage: "\n -p PEER Obtain time from PEER (may be repeated)"
48 #include <netinet/ip.h> /* For IPTOS_LOWDELAY definition */
49 #include <sys/resource.h> /* setpriority */
50 #include <sys/timex.h>
51 #ifndef IPTOS_LOWDELAY
52 # define IPTOS_LOWDELAY 0x10
56 /* Verbosity control (max level of -dddd options accepted).
57 * max 6 is very talkative (and bloated). 3 is non-bloated,
58 * production level setting.
63 /* High-level description of the algorithm:
65 * We start running with very small poll_exp, BURSTPOLL,
66 * in order to quickly accumulate INITIAL_SAMPLES datapoints
67 * for each peer. Then, time is stepped if the offset is larger
68 * than STEP_THRESHOLD, otherwise it isn't; anyway, we enlarge
69 * poll_exp to MINPOLL and enter frequency measurement step:
70 * we collect new datapoints but ignore them for WATCH_THRESHOLD
71 * seconds. After WATCH_THRESHOLD seconds we look at accumulated
72 * offset and estimate frequency drift.
74 * (frequency measurement step seems to not be strictly needed,
75 * it is conditionally disabled with USING_INITIAL_FREQ_ESTIMATION
78 * After this, we enter "steady state": we collect a datapoint,
79 * we select the best peer, if this datapoint is not a new one
80 * (IOW: if this datapoint isn't for selected peer), sleep
81 * and collect another one; otherwise, use its offset to update
82 * frequency drift, if offset is somewhat large, reduce poll_exp,
83 * otherwise increase poll_exp.
85 * If offset is larger than STEP_THRESHOLD, which shouldn't normally
86 * happen, we assume that something "bad" happened (computer
87 * was hibernated, someone set totally wrong date, etc),
88 * then the time is stepped, all datapoints are discarded,
89 * and we go back to steady state.
91 * Made some changes to speed up re-syncing after our clock goes bad
92 * (tested with suspending my laptop):
93 * - if largish offset (>= STEP_THRESHOLD * 8 == 1 sec) is seen
94 * from a peer, schedule next query for this peer soon
95 * without drastically lowering poll interval for everybody.
96 * This makes us collect enough data for step much faster:
97 * e.g. at poll = 10 (1024 secs), step was done within 5 minutes
98 * after first reply which indicated that our clock is 14 seconds off.
99 * - on step, do not discard d_dispersion data of the existing datapoints,
100 * do not clear reachable_bits. This prevents discarding first ~8
101 * datapoints after the step.
104 #define RETRY_INTERVAL 5 /* on error, retry in N secs */
105 #define RESPONSE_INTERVAL 15 /* wait for reply up to N secs */
106 #define INITIAL_SAMPLES 4 /* how many samples do we want for init */
107 #define BAD_DELAY_GROWTH 4 /* drop packet if its delay grew by more than this */
109 /* Clock discipline parameters and constants */
111 /* Step threshold (sec). std ntpd uses 0.128.
112 * Using exact power of 2 (1/8) results in smaller code */
113 #define STEP_THRESHOLD 0.125
114 #define WATCH_THRESHOLD 128 /* stepout threshold (sec). std ntpd uses 900 (11 mins (!)) */
115 /* NB: set WATCH_THRESHOLD to ~60 when debugging to save time) */
116 //UNUSED: #define PANIC_THRESHOLD 1000 /* panic threshold (sec) */
118 #define FREQ_TOLERANCE 0.000015 /* frequency tolerance (15 PPM) */
119 #define BURSTPOLL 0 /* initial poll */
120 #define MINPOLL 5 /* minimum poll interval. std ntpd uses 6 (6: 64 sec) */
121 /* If we got largish offset from a peer, cap next query interval
122 * for this peer by this many seconds:
124 #define BIGOFF_INTERVAL (1 << 6)
125 /* If offset > discipline_jitter * POLLADJ_GATE, and poll interval is >= 2^BIGPOLL,
126 * then it is decreased _at once_. (If < 2^BIGPOLL, it will be decreased _eventually_).
128 #define BIGPOLL 10 /* 2^10 sec ~= 17 min */
129 #define MAXPOLL 12 /* maximum poll interval (12: 1.1h, 17: 36.4h). std ntpd uses 17 */
130 /* Actively lower poll when we see such big offsets.
131 * With STEP_THRESHOLD = 0.125, it means we try to sync more aggressively
132 * if offset increases over ~0.04 sec */
133 #define POLLDOWN_OFFSET (STEP_THRESHOLD / 3)
134 #define MINDISP 0.01 /* minimum dispersion (sec) */
135 #define MAXDISP 16 /* maximum dispersion (sec) */
136 #define MAXSTRAT 16 /* maximum stratum (infinity metric) */
137 #define MAXDIST 1 /* distance threshold (sec) */
138 #define MIN_SELECTED 1 /* minimum intersection survivors */
139 #define MIN_CLUSTERED 3 /* minimum cluster survivors */
141 #define MAXDRIFT 0.000500 /* frequency drift we can correct (500 PPM) */
143 /* Poll-adjust threshold.
144 * When we see that offset is small enough compared to discipline jitter,
145 * we grow a counter: += MINPOLL. When counter goes over POLLADJ_LIMIT,
146 * we poll_exp++. If offset isn't small, counter -= poll_exp*2,
147 * and when it goes below -POLLADJ_LIMIT, we poll_exp--.
148 * (Bumped from 30 to 40 since otherwise I often see poll_exp going *2* steps down)
150 #define POLLADJ_LIMIT 40
151 /* If offset < discipline_jitter * POLLADJ_GATE, then we decide to increase
152 * poll interval (we think we can't improve timekeeping
153 * by staying at smaller poll).
155 #define POLLADJ_GATE 4
156 #define TIMECONST_HACK_GATE 2
157 /* Compromise Allan intercept (sec). doc uses 1500, std ntpd uses 512 */
161 /* FLL loop gain [why it depends on MAXPOLL??] */
162 #define FLL (MAXPOLL + 1)
163 /* Parameter averaging constant */
172 NTP_MSGSIZE_NOAUTH = 48,
173 NTP_MSGSIZE = (NTP_MSGSIZE_NOAUTH + 4 + NTP_DIGESTSIZE),
176 MODE_MASK = (7 << 0),
177 VERSION_MASK = (7 << 3),
181 /* Leap Second Codes (high order two bits of m_status) */
182 LI_NOWARNING = (0 << 6), /* no warning */
183 LI_PLUSSEC = (1 << 6), /* add a second (61 seconds) */
184 LI_MINUSSEC = (2 << 6), /* minus a second (59 seconds) */
185 LI_ALARM = (3 << 6), /* alarm condition */
188 MODE_RES0 = 0, /* reserved */
189 MODE_SYM_ACT = 1, /* symmetric active */
190 MODE_SYM_PAS = 2, /* symmetric passive */
191 MODE_CLIENT = 3, /* client */
192 MODE_SERVER = 4, /* server */
193 MODE_BROADCAST = 5, /* broadcast */
194 MODE_RES1 = 6, /* reserved for NTP control message */
195 MODE_RES2 = 7, /* reserved for private use */
198 //TODO: better base selection
199 #define OFFSET_1900_1970 2208988800UL /* 1970 - 1900 in seconds */
201 #define NUM_DATAPOINTS 8
214 uint8_t m_status; /* status of local clock and leap info */
216 uint8_t m_ppoll; /* poll value */
217 int8_t m_precision_exp;
218 s_fixedpt_t m_rootdelay;
219 s_fixedpt_t m_rootdisp;
221 l_fixedpt_t m_reftime;
222 l_fixedpt_t m_orgtime;
223 l_fixedpt_t m_rectime;
224 l_fixedpt_t m_xmttime;
226 uint8_t m_digest[NTP_DIGESTSIZE];
236 len_and_sockaddr *p_lsa;
240 uint32_t lastpkt_refid;
241 uint8_t lastpkt_status;
242 uint8_t lastpkt_stratum;
243 uint8_t reachable_bits;
244 /* when to send new query (if p_fd == -1)
245 * or when receive times out (if p_fd >= 0): */
246 double next_action_time;
248 double lastpkt_recv_time;
249 double lastpkt_delay;
250 double lastpkt_rootdelay;
251 double lastpkt_rootdisp;
252 /* produced by filter algorithm: */
253 double filter_offset;
254 double filter_dispersion;
255 double filter_jitter;
256 datapoint_t filter_datapoint[NUM_DATAPOINTS];
257 /* last sent packet: */
262 #define USING_KERNEL_PLL_LOOP 1
263 #define USING_INITIAL_FREQ_ESTIMATION 0
270 /* Insert new options above this line. */
271 /* Non-compat options: */
275 OPT_l = (1 << 7) * ENABLE_FEATURE_NTPD_SERVER,
276 /* We hijack some bits for other purposes */
282 /* total round trip delay to currently selected reference clock */
284 /* reference timestamp: time when the system clock was last set or corrected */
286 /* total dispersion to currently selected reference clock */
289 double last_script_run;
292 #if ENABLE_FEATURE_NTPD_SERVER
294 # define G_listen_fd (G.listen_fd)
296 # define G_listen_fd (-1)
300 /* refid: 32-bit code identifying the particular server or reference clock
301 * in stratum 0 packets this is a four-character ASCII string,
302 * called the kiss code, used for debugging and monitoring
303 * in stratum 1 packets this is a four-character ASCII string
304 * assigned to the reference clock by IANA. Example: "GPS "
305 * in stratum 2+ packets, it's IPv4 address or 4 first bytes
306 * of MD5 hash of IPv6
310 /* precision is defined as the larger of the resolution and time to
311 * read the clock, in log2 units. For instance, the precision of a
312 * mains-frequency clock incrementing at 60 Hz is 16 ms, even when the
313 * system clock hardware representation is to the nanosecond.
315 * Delays, jitters of various kinds are clamped down to precision.
317 * If precision_sec is too large, discipline_jitter gets clamped to it
318 * and if offset is smaller than discipline_jitter * POLLADJ_GATE, poll
319 * interval grows even though we really can benefit from staying at
320 * smaller one, collecting non-lagged datapoits and correcting offset.
321 * (Lagged datapoits exist when poll_exp is large but we still have
322 * systematic offset error - the time distance between datapoints
323 * is significant and older datapoints have smaller offsets.
324 * This makes our offset estimation a bit smaller than reality)
325 * Due to this effect, setting G_precision_sec close to
326 * STEP_THRESHOLD isn't such a good idea - offsets may grow
327 * too big and we will step. I observed it with -6.
329 * OTOH, setting precision_sec far too small would result in futile
330 * attempts to syncronize to an unachievable precision.
332 * -6 is 1/64 sec, -7 is 1/128 sec and so on.
333 * -8 is 1/256 ~= 0.003906 (worked well for me --vda)
334 * -9 is 1/512 ~= 0.001953 (let's try this for some time)
336 #define G_precision_exp -9
338 * G_precision_exp is used only for construction outgoing packets.
339 * It's ok to set G_precision_sec to a slightly different value
340 * (One which is "nicer looking" in logs).
341 * Exact value would be (1.0 / (1 << (- G_precision_exp))):
343 #define G_precision_sec 0.002
345 /* Bool. After set to 1, never goes back to 0: */
346 smallint initial_poll_complete;
348 #define STATE_NSET 0 /* initial state, "nothing is set" */
349 //#define STATE_FSET 1 /* frequency set from file */
350 //#define STATE_SPIK 2 /* spike detected */
351 //#define STATE_FREQ 3 /* initial frequency */
352 #define STATE_SYNC 4 /* clock synchronized (normal operation) */
353 uint8_t discipline_state; // doc calls it c.state
354 uint8_t poll_exp; // s.poll
355 int polladj_count; // c.count
356 long kernel_freq_drift;
357 peer_t *last_update_peer;
358 double last_update_offset; // c.last
359 double last_update_recv_time; // s.t
360 double discipline_jitter; // c.jitter
361 /* Since we only compare it with ints, can simplify code
362 * by not making this variable floating point:
364 unsigned offset_to_jitter_ratio;
365 //double cluster_offset; // s.offset
366 //double cluster_jitter; // s.jitter
367 #if !USING_KERNEL_PLL_LOOP
368 double discipline_freq_drift; // c.freq
369 /* Maybe conditionally calculate wander? it's used only for logging */
370 double discipline_wander; // c.wander
373 #define G (*ptr_to_globals)
375 static const int const_IPTOS_LOWDELAY = IPTOS_LOWDELAY;
378 #define VERB1 if (MAX_VERBOSE && G.verbose)
379 #define VERB2 if (MAX_VERBOSE >= 2 && G.verbose >= 2)
380 #define VERB3 if (MAX_VERBOSE >= 3 && G.verbose >= 3)
381 #define VERB4 if (MAX_VERBOSE >= 4 && G.verbose >= 4)
382 #define VERB5 if (MAX_VERBOSE >= 5 && G.verbose >= 5)
383 #define VERB6 if (MAX_VERBOSE >= 6 && G.verbose >= 6)
386 static double LOG2D(int a)
389 return 1.0 / (1UL << -a);
392 static ALWAYS_INLINE double SQUARE(double x)
396 static ALWAYS_INLINE double MAXD(double a, double b)
402 static ALWAYS_INLINE double MIND(double a, double b)
408 static NOINLINE double my_SQRT(double X)
415 double Xhalf = X * 0.5;
417 /* Fast and good approximation to 1/sqrt(X), black magic */
419 /*v.i = 0x5f3759df - (v.i >> 1);*/
420 v.i = 0x5f375a86 - (v.i >> 1); /* - this constant is slightly better */
421 invsqrt = v.f; /* better than 0.2% accuracy */
423 /* Refining it using Newton's method: x1 = x0 - f(x0)/f'(x0)
424 * f(x) = 1/(x*x) - X (f==0 when x = 1/sqrt(X))
426 * f(x)/f'(x) = (X - 1/(x*x)) / (2/(x*x*x)) = X*x*x*x/2 - x/2
427 * x1 = x0 - (X*x0*x0*x0/2 - x0/2) = 1.5*x0 - X*x0*x0*x0/2 = x0*(1.5 - (X/2)*x0*x0)
429 invsqrt = invsqrt * (1.5 - Xhalf * invsqrt * invsqrt); /* ~0.05% accuracy */
430 /* invsqrt = invsqrt * (1.5 - Xhalf * invsqrt * invsqrt); 2nd iter: ~0.0001% accuracy */
431 /* With 4 iterations, more than half results will be exact,
432 * at 6th iterations result stabilizes with about 72% results exact.
433 * We are well satisfied with 0.05% accuracy.
436 return X * invsqrt; /* X * 1/sqrt(X) ~= sqrt(X) */
438 static ALWAYS_INLINE double SQRT(double X)
440 /* If this arch doesn't use IEEE 754 floats, fall back to using libm */
441 if (sizeof(float) != 4)
444 /* This avoids needing libm, saves about 0.5k on x86-32 */
452 gettimeofday(&tv, NULL); /* never fails */
453 G.cur_time = tv.tv_sec + (1.0e-6 * tv.tv_usec) + OFFSET_1900_1970;
458 d_to_tv(double d, struct timeval *tv)
460 tv->tv_sec = (long)d;
461 tv->tv_usec = (d - tv->tv_sec) * 1000000;
465 lfp_to_d(l_fixedpt_t lfp)
468 lfp.int_partl = ntohl(lfp.int_partl);
469 lfp.fractionl = ntohl(lfp.fractionl);
470 ret = (double)lfp.int_partl + ((double)lfp.fractionl / UINT_MAX);
474 sfp_to_d(s_fixedpt_t sfp)
477 sfp.int_parts = ntohs(sfp.int_parts);
478 sfp.fractions = ntohs(sfp.fractions);
479 ret = (double)sfp.int_parts + ((double)sfp.fractions / USHRT_MAX);
482 #if ENABLE_FEATURE_NTPD_SERVER
487 lfp.int_partl = (uint32_t)d;
488 lfp.fractionl = (uint32_t)((d - lfp.int_partl) * UINT_MAX);
489 lfp.int_partl = htonl(lfp.int_partl);
490 lfp.fractionl = htonl(lfp.fractionl);
497 sfp.int_parts = (uint16_t)d;
498 sfp.fractions = (uint16_t)((d - sfp.int_parts) * USHRT_MAX);
499 sfp.int_parts = htons(sfp.int_parts);
500 sfp.fractions = htons(sfp.fractions);
506 dispersion(const datapoint_t *dp)
508 return dp->d_dispersion + FREQ_TOLERANCE * (G.cur_time - dp->d_recv_time);
512 root_distance(peer_t *p)
514 /* The root synchronization distance is the maximum error due to
515 * all causes of the local clock relative to the primary server.
516 * It is defined as half the total delay plus total dispersion
519 return MAXD(MINDISP, p->lastpkt_rootdelay + p->lastpkt_delay) / 2
520 + p->lastpkt_rootdisp
521 + p->filter_dispersion
522 + FREQ_TOLERANCE * (G.cur_time - p->lastpkt_recv_time)
527 set_next(peer_t *p, unsigned t)
529 p->next_action_time = G.cur_time + t;
533 * Peer clock filter and its helpers
536 filter_datapoints(peer_t *p)
543 /* Simulations have shown that use of *averaged* offset for p->filter_offset
544 * is in fact worse than simply using last received one: with large poll intervals
545 * (>= 2048) averaging code uses offset values which are outdated by hours,
546 * and time/frequency correction goes totally wrong when fed essentially bogus offsets.
549 double minoff, maxoff, w;
550 double x = x; /* for compiler */
551 double oldest_off = oldest_off;
552 double oldest_age = oldest_age;
553 double newest_off = newest_off;
554 double newest_age = newest_age;
556 fdp = p->filter_datapoint;
558 minoff = maxoff = fdp[0].d_offset;
559 for (i = 1; i < NUM_DATAPOINTS; i++) {
560 if (minoff > fdp[i].d_offset)
561 minoff = fdp[i].d_offset;
562 if (maxoff < fdp[i].d_offset)
563 maxoff = fdp[i].d_offset;
566 idx = p->datapoint_idx; /* most recent datapoint's index */
568 * Drop two outliers and take weighted average of the rest:
569 * most_recent/2 + older1/4 + older2/8 ... + older5/32 + older6/32
570 * we use older6/32, not older6/64 since sum of weights should be 1:
571 * 1/2 + 1/4 + 1/8 + 1/16 + 1/32 + 1/32 = 1
577 * filter_dispersion = \ -------------
584 for (i = 0; i < NUM_DATAPOINTS; i++) {
586 bb_error_msg("datapoint[%d]: off:%f disp:%f(%f) age:%f%s",
589 fdp[idx].d_dispersion, dispersion(&fdp[idx]),
590 G.cur_time - fdp[idx].d_recv_time,
591 (minoff == fdp[idx].d_offset || maxoff == fdp[idx].d_offset)
592 ? " (outlier by offset)" : ""
596 sum += dispersion(&fdp[idx]) / (2 << i);
598 if (minoff == fdp[idx].d_offset) {
599 minoff -= 1; /* so that we don't match it ever again */
601 if (maxoff == fdp[idx].d_offset) {
604 oldest_off = fdp[idx].d_offset;
605 oldest_age = G.cur_time - fdp[idx].d_recv_time;
608 newest_off = oldest_off;
609 newest_age = oldest_age;
616 idx = (idx - 1) & (NUM_DATAPOINTS - 1);
618 p->filter_dispersion = sum;
619 wavg += x; /* add another older6/64 to form older6/32 */
620 /* Fix systematic underestimation with large poll intervals.
621 * Imagine that we still have a bit of uncorrected drift,
622 * and poll interval is big (say, 100 sec). Offsets form a progression:
623 * 0.0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 - 0.7 is most recent.
624 * The algorithm above drops 0.0 and 0.7 as outliers,
625 * and then we have this estimation, ~25% off from 0.7:
626 * 0.1/32 + 0.2/32 + 0.3/16 + 0.4/8 + 0.5/4 + 0.6/2 = 0.503125
628 x = oldest_age - newest_age;
630 x = newest_age / x; /* in above example, 100 / (600 - 100) */
631 if (x < 1) { /* paranoia check */
632 x = (newest_off - oldest_off) * x; /* 0.5 * 100/500 = 0.1 */
636 p->filter_offset = wavg;
640 fdp = p->filter_datapoint;
641 idx = p->datapoint_idx; /* most recent datapoint's index */
643 /* filter_offset: simply use the most recent value */
644 p->filter_offset = fdp[idx].d_offset;
648 * filter_dispersion = \ -------------
655 for (i = 0; i < NUM_DATAPOINTS; i++) {
656 sum += dispersion(&fdp[idx]) / (2 << i);
657 wavg += fdp[idx].d_offset;
658 idx = (idx - 1) & (NUM_DATAPOINTS - 1);
660 wavg /= NUM_DATAPOINTS;
661 p->filter_dispersion = sum;
664 /* +----- -----+ ^ 1/2
668 * filter_jitter = | --- * / (avg-offset_j) |
672 * where n is the number of valid datapoints in the filter (n > 1);
673 * if filter_jitter < precision then filter_jitter = precision
676 for (i = 0; i < NUM_DATAPOINTS; i++) {
677 sum += SQUARE(wavg - fdp[i].d_offset);
679 sum = SQRT(sum / NUM_DATAPOINTS);
680 p->filter_jitter = sum > G_precision_sec ? sum : G_precision_sec;
682 VERB4 bb_error_msg("filter offset:%+f disp:%f jitter:%f",
684 p->filter_dispersion,
689 reset_peer_stats(peer_t *p, double offset)
692 bool small_ofs = fabs(offset) < 16 * STEP_THRESHOLD;
694 /* Used to set p->filter_datapoint[i].d_dispersion = MAXDISP
695 * and clear reachable bits, but this proved to be too agressive:
696 * after step (tested with suspinding laptop for ~30 secs),
697 * this caused all previous data to be considered invalid,
698 * making us needing to collect full ~8 datapoins per peer
699 * after step in order to start trusting them.
700 * In turn, this was making poll interval decrease even after
701 * step was done. (Poll interval decreases already before step
702 * in this scenario, because we see large offsets and end up with
703 * no good peer to select).
706 for (i = 0; i < NUM_DATAPOINTS; i++) {
708 p->filter_datapoint[i].d_recv_time += offset;
709 if (p->filter_datapoint[i].d_offset != 0) {
710 p->filter_datapoint[i].d_offset -= offset;
711 //bb_error_msg("p->filter_datapoint[%d].d_offset %f -> %f",
713 // p->filter_datapoint[i].d_offset + offset,
714 // p->filter_datapoint[i].d_offset);
717 p->filter_datapoint[i].d_recv_time = G.cur_time;
718 p->filter_datapoint[i].d_offset = 0;
719 /*p->filter_datapoint[i].d_dispersion = MAXDISP;*/
723 p->lastpkt_recv_time += offset;
725 /*p->reachable_bits = 0;*/
726 p->lastpkt_recv_time = G.cur_time;
728 filter_datapoints(p); /* recalc p->filter_xxx */
729 VERB6 bb_error_msg("%s->lastpkt_recv_time=%f", p->p_dotted, p->lastpkt_recv_time);
737 p = xzalloc(sizeof(*p));
738 p->p_lsa = xhost2sockaddr(s, 123);
739 p->p_dotted = xmalloc_sockaddr2dotted_noport(&p->p_lsa->u.sa);
741 p->p_xmt_msg.m_status = MODE_CLIENT | (NTP_VERSION << 3);
742 p->next_action_time = G.cur_time; /* = set_next(p, 0); */
743 reset_peer_stats(p, 16 * STEP_THRESHOLD);
745 llist_add_to(&G.ntp_peers, p);
751 const struct sockaddr *from, const struct sockaddr *to, socklen_t addrlen,
752 msg_t *msg, ssize_t len)
758 ret = sendto(fd, msg, len, MSG_DONTWAIT, to, addrlen);
760 ret = send_to_from(fd, msg, len, MSG_DONTWAIT, to, from, addrlen);
763 bb_perror_msg("send failed");
770 send_query_to_peer(peer_t *p)
772 /* Why do we need to bind()?
773 * See what happens when we don't bind:
775 * socket(PF_INET, SOCK_DGRAM, IPPROTO_IP) = 3
776 * setsockopt(3, SOL_IP, IP_TOS, [16], 4) = 0
777 * gettimeofday({1259071266, 327885}, NULL) = 0
778 * sendto(3, "xxx", 48, MSG_DONTWAIT, {sa_family=AF_INET, sin_port=htons(123), sin_addr=inet_addr("10.34.32.125")}, 16) = 48
779 * ^^^ we sent it from some source port picked by kernel.
780 * time(NULL) = 1259071266
781 * write(2, "ntpd: entering poll 15 secs\n", 28) = 28
782 * poll([{fd=3, events=POLLIN}], 1, 15000) = 1 ([{fd=3, revents=POLLIN}])
783 * recv(3, "yyy", 68, MSG_DONTWAIT) = 48
784 * ^^^ this recv will receive packets to any local port!
786 * Uncomment this and use strace to see it in action:
788 #define PROBE_LOCAL_ADDR /* { len_and_sockaddr lsa; lsa.len = LSA_SIZEOF_SA; getsockname(p->query.fd, &lsa.u.sa, &lsa.len); } */
792 len_and_sockaddr *local_lsa;
794 family = p->p_lsa->u.sa.sa_family;
795 p->p_fd = fd = xsocket_type(&local_lsa, family, SOCK_DGRAM);
796 /* local_lsa has "null" address and port 0 now.
797 * bind() ensures we have a *particular port* selected by kernel
798 * and remembered in p->p_fd, thus later recv(p->p_fd)
799 * receives only packets sent to this port.
802 xbind(fd, &local_lsa->u.sa, local_lsa->len);
804 #if ENABLE_FEATURE_IPV6
805 if (family == AF_INET)
807 setsockopt(fd, IPPROTO_IP, IP_TOS, &const_IPTOS_LOWDELAY, sizeof(const_IPTOS_LOWDELAY));
811 /* Emit message _before_ attempted send. Think of a very short
812 * roundtrip networks: we need to go back to recv loop ASAP,
813 * to reduce delay. Printing messages after send works against that.
815 VERB1 bb_error_msg("sending query to %s", p->p_dotted);
818 * Send out a random 64-bit number as our transmit time. The NTP
819 * server will copy said number into the originate field on the
820 * response that it sends us. This is totally legal per the SNTP spec.
822 * The impact of this is two fold: we no longer send out the current
823 * system time for the world to see (which may aid an attacker), and
824 * it gives us a (not very secure) way of knowing that we're not
825 * getting spoofed by an attacker that can't capture our traffic
826 * but can spoof packets from the NTP server we're communicating with.
828 * Save the real transmit timestamp locally.
830 p->p_xmt_msg.m_xmttime.int_partl = random();
831 p->p_xmt_msg.m_xmttime.fractionl = random();
832 p->p_xmttime = gettime1900d();
834 /* Were doing it only if sendto worked, but
835 * loss of sync detection needs reachable_bits updated
836 * even if sending fails *locally*:
837 * "network is unreachable" because cable was pulled?
838 * We still need to declare "unsync" if this condition persists.
840 p->reachable_bits <<= 1;
842 if (do_sendto(p->p_fd, /*from:*/ NULL, /*to:*/ &p->p_lsa->u.sa, /*addrlen:*/ p->p_lsa->len,
843 &p->p_xmt_msg, NTP_MSGSIZE_NOAUTH) == -1
848 * We know that we sent nothing.
849 * We can retry *soon* without fearing
850 * that we are flooding the peer.
852 set_next(p, RETRY_INTERVAL);
856 set_next(p, RESPONSE_INTERVAL);
860 /* Note that there is no provision to prevent several run_scripts
861 * to be started in quick succession. In fact, it happens rather often
862 * if initial syncronization results in a step.
863 * You will see "step" and then "stratum" script runs, sometimes
864 * as close as only 0.002 seconds apart.
865 * Script should be ready to deal with this.
867 static void run_script(const char *action, double offset)
870 char *env1, *env2, *env3, *env4;
872 G.last_script_run = G.cur_time;
877 argv[0] = (char*) G.script_name;
878 argv[1] = (char*) action;
881 VERB1 bb_error_msg("executing '%s %s'", G.script_name, action);
883 env1 = xasprintf("%s=%u", "stratum", G.stratum);
885 env2 = xasprintf("%s=%ld", "freq_drift_ppm", G.kernel_freq_drift);
887 env3 = xasprintf("%s=%u", "poll_interval", 1 << G.poll_exp);
889 env4 = xasprintf("%s=%f", "offset", offset);
891 /* Other items of potential interest: selected peer,
892 * rootdelay, reftime, rootdisp, refid, ntp_status,
893 * last_update_offset, last_update_recv_time, discipline_jitter,
894 * how many peers have reachable_bits = 0?
897 /* Don't want to wait: it may run hwclock --systohc, and that
898 * may take some time (seconds): */
899 /*spawn_and_wait(argv);*/
903 unsetenv("freq_drift_ppm");
904 unsetenv("poll_interval");
913 step_time(double offset)
917 struct timeval tvc, tvn;
918 char buf[sizeof("yyyy-mm-dd hh:mm:ss") + /*paranoia:*/ 4];
921 gettimeofday(&tvc, NULL); /* never fails */
922 dtime = tvc.tv_sec + (1.0e-6 * tvc.tv_usec) + offset;
923 d_to_tv(dtime, &tvn);
924 if (settimeofday(&tvn, NULL) == -1)
925 bb_perror_msg_and_die("settimeofday");
929 strftime_YYYYMMDDHHMMSS(buf, sizeof(buf), &tval);
930 bb_error_msg("current time is %s.%06u", buf, (unsigned)tvc.tv_usec);
933 strftime_YYYYMMDDHHMMSS(buf, sizeof(buf), &tval);
934 bb_error_msg("setting time to %s.%06u (offset %+fs)", buf, (unsigned)tvn.tv_usec, offset);
936 /* Correct various fields which contain time-relative values: */
939 G.cur_time += offset;
940 G.last_update_recv_time += offset;
941 G.last_script_run += offset;
943 /* p->lastpkt_recv_time, p->next_action_time and such: */
944 for (item = G.ntp_peers; item != NULL; item = item->link) {
945 peer_t *pp = (peer_t *) item->data;
946 reset_peer_stats(pp, offset);
947 //bb_error_msg("offset:%+f pp->next_action_time:%f -> %f",
948 // offset, pp->next_action_time, pp->next_action_time + offset);
949 pp->next_action_time += offset;
951 /* We wait for reply from this peer too.
952 * But due to step we are doing, reply's data is no longer
953 * useful (in fact, it'll be bogus). Stop waiting for it.
957 set_next(pp, RETRY_INTERVAL);
964 * Selection and clustering, and their helpers
970 double opt_rd; /* optimization */
973 compare_point_edge(const void *aa, const void *bb)
975 const point_t *a = aa;
976 const point_t *b = bb;
977 if (a->edge < b->edge) {
980 return (a->edge > b->edge);
987 compare_survivor_metric(const void *aa, const void *bb)
989 const survivor_t *a = aa;
990 const survivor_t *b = bb;
991 if (a->metric < b->metric) {
994 return (a->metric > b->metric);
997 fit(peer_t *p, double rd)
999 if ((p->reachable_bits & (p->reachable_bits-1)) == 0) {
1000 /* One or zero bits in reachable_bits */
1001 VERB4 bb_error_msg("peer %s unfit for selection: unreachable", p->p_dotted);
1004 #if 0 /* we filter out such packets earlier */
1005 if ((p->lastpkt_status & LI_ALARM) == LI_ALARM
1006 || p->lastpkt_stratum >= MAXSTRAT
1008 VERB4 bb_error_msg("peer %s unfit for selection: bad status/stratum", p->p_dotted);
1012 /* rd is root_distance(p) */
1013 if (rd > MAXDIST + FREQ_TOLERANCE * (1 << G.poll_exp)) {
1014 VERB4 bb_error_msg("peer %s unfit for selection: root distance too high", p->p_dotted);
1018 // /* Do we have a loop? */
1019 // if (p->refid == p->dstaddr || p->refid == s.refid)
1024 select_and_cluster(void)
1029 int size = 3 * G.peer_cnt;
1030 /* for selection algorithm */
1031 point_t point[size];
1032 unsigned num_points, num_candidates;
1034 unsigned num_falsetickers;
1035 /* for cluster algorithm */
1036 survivor_t survivor[size];
1037 unsigned num_survivors;
1043 if (G.initial_poll_complete) while (item != NULL) {
1046 p = (peer_t *) item->data;
1047 rd = root_distance(p);
1048 offset = p->filter_offset;
1054 VERB5 bb_error_msg("interval: [%f %f %f] %s",
1060 point[num_points].p = p;
1061 point[num_points].type = -1;
1062 point[num_points].edge = offset - rd;
1063 point[num_points].opt_rd = rd;
1065 point[num_points].p = p;
1066 point[num_points].type = 0;
1067 point[num_points].edge = offset;
1068 point[num_points].opt_rd = rd;
1070 point[num_points].p = p;
1071 point[num_points].type = 1;
1072 point[num_points].edge = offset + rd;
1073 point[num_points].opt_rd = rd;
1077 num_candidates = num_points / 3;
1078 if (num_candidates == 0) {
1079 VERB3 bb_error_msg("no valid datapoints%s", ", no peer selected");
1082 //TODO: sorting does not seem to be done in reference code
1083 qsort(point, num_points, sizeof(point[0]), compare_point_edge);
1085 /* Start with the assumption that there are no falsetickers.
1086 * Attempt to find a nonempty intersection interval containing
1087 * the midpoints of all truechimers.
1088 * If a nonempty interval cannot be found, increase the number
1089 * of assumed falsetickers by one and try again.
1090 * If a nonempty interval is found and the number of falsetickers
1091 * is less than the number of truechimers, a majority has been found
1092 * and the midpoint of each truechimer represents
1093 * the candidates available to the cluster algorithm.
1095 num_falsetickers = 0;
1098 unsigned num_midpoints = 0;
1103 for (i = 0; i < num_points; i++) {
1105 * if (point[i].type == -1) c++;
1106 * if (point[i].type == 1) c--;
1107 * and it's simpler to do it this way:
1110 if (c >= num_candidates - num_falsetickers) {
1111 /* If it was c++ and it got big enough... */
1112 low = point[i].edge;
1115 if (point[i].type == 0)
1119 for (i = num_points-1; i >= 0; i--) {
1121 if (c >= num_candidates - num_falsetickers) {
1122 high = point[i].edge;
1125 if (point[i].type == 0)
1128 /* If the number of midpoints is greater than the number
1129 * of allowed falsetickers, the intersection contains at
1130 * least one truechimer with no midpoint - bad.
1131 * Also, interval should be nonempty.
1133 if (num_midpoints <= num_falsetickers && low < high)
1136 if (num_falsetickers * 2 >= num_candidates) {
1137 VERB3 bb_error_msg("falsetickers:%d, candidates:%d%s",
1138 num_falsetickers, num_candidates,
1139 ", no peer selected");
1143 VERB4 bb_error_msg("selected interval: [%f, %f]; candidates:%d falsetickers:%d",
1144 low, high, num_candidates, num_falsetickers);
1148 /* Construct a list of survivors (p, metric)
1149 * from the chime list, where metric is dominated
1150 * first by stratum and then by root distance.
1151 * All other things being equal, this is the order of preference.
1154 for (i = 0; i < num_points; i++) {
1155 if (point[i].edge < low || point[i].edge > high)
1158 survivor[num_survivors].p = p;
1159 /* x.opt_rd == root_distance(p); */
1160 survivor[num_survivors].metric = MAXDIST * p->lastpkt_stratum + point[i].opt_rd;
1161 VERB5 bb_error_msg("survivor[%d] metric:%f peer:%s",
1162 num_survivors, survivor[num_survivors].metric, p->p_dotted);
1165 /* There must be at least MIN_SELECTED survivors to satisfy the
1166 * correctness assertions. Ordinarily, the Byzantine criteria
1167 * require four survivors, but for the demonstration here, one
1170 if (num_survivors < MIN_SELECTED) {
1171 VERB3 bb_error_msg("survivors:%d%s",
1173 ", no peer selected");
1177 //looks like this is ONLY used by the fact that later we pick survivor[0].
1178 //we can avoid sorting then, just find the minimum once!
1179 qsort(survivor, num_survivors, sizeof(survivor[0]), compare_survivor_metric);
1181 /* For each association p in turn, calculate the selection
1182 * jitter p->sjitter as the square root of the sum of squares
1183 * (p->offset - q->offset) over all q associations. The idea is
1184 * to repeatedly discard the survivor with maximum selection
1185 * jitter until a termination condition is met.
1188 unsigned max_idx = max_idx;
1189 double max_selection_jitter = max_selection_jitter;
1190 double min_jitter = min_jitter;
1192 if (num_survivors <= MIN_CLUSTERED) {
1193 VERB4 bb_error_msg("num_survivors %d <= %d, not discarding more",
1194 num_survivors, MIN_CLUSTERED);
1198 /* To make sure a few survivors are left
1199 * for the clustering algorithm to chew on,
1200 * we stop if the number of survivors
1201 * is less than or equal to MIN_CLUSTERED (3).
1203 for (i = 0; i < num_survivors; i++) {
1204 double selection_jitter_sq;
1207 if (i == 0 || p->filter_jitter < min_jitter)
1208 min_jitter = p->filter_jitter;
1210 selection_jitter_sq = 0;
1211 for (j = 0; j < num_survivors; j++) {
1212 peer_t *q = survivor[j].p;
1213 selection_jitter_sq += SQUARE(p->filter_offset - q->filter_offset);
1215 if (i == 0 || selection_jitter_sq > max_selection_jitter) {
1216 max_selection_jitter = selection_jitter_sq;
1219 VERB6 bb_error_msg("survivor %d selection_jitter^2:%f",
1220 i, selection_jitter_sq);
1222 max_selection_jitter = SQRT(max_selection_jitter / num_survivors);
1223 VERB5 bb_error_msg("max_selection_jitter (at %d):%f min_jitter:%f",
1224 max_idx, max_selection_jitter, min_jitter);
1226 /* If the maximum selection jitter is less than the
1227 * minimum peer jitter, then tossing out more survivors
1228 * will not lower the minimum peer jitter, so we might
1231 if (max_selection_jitter < min_jitter) {
1232 VERB4 bb_error_msg("max_selection_jitter:%f < min_jitter:%f, num_survivors:%d, not discarding more",
1233 max_selection_jitter, min_jitter, num_survivors);
1237 /* Delete survivor[max_idx] from the list
1238 * and go around again.
1240 VERB6 bb_error_msg("dropping survivor %d", max_idx);
1242 while (max_idx < num_survivors) {
1243 survivor[max_idx] = survivor[max_idx + 1];
1249 /* Combine the offsets of the clustering algorithm survivors
1250 * using a weighted average with weight determined by the root
1251 * distance. Compute the selection jitter as the weighted RMS
1252 * difference between the first survivor and the remaining
1253 * survivors. In some cases the inherent clock jitter can be
1254 * reduced by not using this algorithm, especially when frequent
1255 * clockhopping is involved. bbox: thus we don't do it.
1259 for (i = 0; i < num_survivors; i++) {
1261 x = root_distance(p);
1263 z += p->filter_offset / x;
1264 w += SQUARE(p->filter_offset - survivor[0].p->filter_offset) / x;
1266 //G.cluster_offset = z / y;
1267 //G.cluster_jitter = SQRT(w / y);
1270 /* Pick the best clock. If the old system peer is on the list
1271 * and at the same stratum as the first survivor on the list,
1272 * then don't do a clock hop. Otherwise, select the first
1273 * survivor on the list as the new system peer.
1276 if (G.last_update_peer
1277 && G.last_update_peer->lastpkt_stratum <= p->lastpkt_stratum
1279 /* Starting from 1 is ok here */
1280 for (i = 1; i < num_survivors; i++) {
1281 if (G.last_update_peer == survivor[i].p) {
1282 VERB5 bb_error_msg("keeping old synced peer");
1283 p = G.last_update_peer;
1288 G.last_update_peer = p;
1290 VERB4 bb_error_msg("selected peer %s filter_offset:%+f age:%f",
1293 G.cur_time - p->lastpkt_recv_time
1300 * Local clock discipline and its helpers
1303 set_new_values(int disc_state, double offset, double recv_time)
1305 /* Enter new state and set state variables. Note we use the time
1306 * of the last clock filter sample, which must be earlier than
1309 VERB4 bb_error_msg("disc_state=%d last update offset=%f recv_time=%f",
1310 disc_state, offset, recv_time);
1311 G.discipline_state = disc_state;
1312 G.last_update_offset = offset;
1313 G.last_update_recv_time = recv_time;
1315 /* Return: -1: decrease poll interval, 0: leave as is, 1: increase */
1317 update_local_clock(peer_t *p)
1321 /* Note: can use G.cluster_offset instead: */
1322 double offset = p->filter_offset;
1323 double recv_time = p->lastpkt_recv_time;
1325 #if !USING_KERNEL_PLL_LOOP
1328 #if !USING_KERNEL_PLL_LOOP || USING_INITIAL_FREQ_ESTIMATION
1329 double since_last_update;
1331 double etemp, dtemp;
1333 abs_offset = fabs(offset);
1336 /* If needed, -S script can do it by looking at $offset
1337 * env var and killing parent */
1338 /* If the offset is too large, give up and go home */
1339 if (abs_offset > PANIC_THRESHOLD) {
1340 bb_error_msg_and_die("offset %f far too big, exiting", offset);
1344 /* If this is an old update, for instance as the result
1345 * of a system peer change, avoid it. We never use
1346 * an old sample or the same sample twice.
1348 if (recv_time <= G.last_update_recv_time) {
1349 VERB3 bb_error_msg("update from %s: same or older datapoint, not using it",
1351 return 0; /* "leave poll interval as is" */
1354 /* Clock state machine transition function. This is where the
1355 * action is and defines how the system reacts to large time
1356 * and frequency errors.
1358 #if !USING_KERNEL_PLL_LOOP || USING_INITIAL_FREQ_ESTIMATION
1359 since_last_update = recv_time - G.reftime;
1361 #if !USING_KERNEL_PLL_LOOP
1364 #if USING_INITIAL_FREQ_ESTIMATION
1365 if (G.discipline_state == STATE_FREQ) {
1366 /* Ignore updates until the stepout threshold */
1367 if (since_last_update < WATCH_THRESHOLD) {
1368 VERB4 bb_error_msg("measuring drift, datapoint ignored, %f sec remains",
1369 WATCH_THRESHOLD - since_last_update);
1370 return 0; /* "leave poll interval as is" */
1372 # if !USING_KERNEL_PLL_LOOP
1373 freq_drift = (offset - G.last_update_offset) / since_last_update;
1378 /* There are two main regimes: when the
1379 * offset exceeds the step threshold and when it does not.
1381 if (abs_offset > STEP_THRESHOLD) {
1385 // This "spike state" seems to be useless, peer selection already drops
1386 // occassional "bad" datapoints. If we are here, there were _many_
1387 // large offsets. When a few first large offsets are seen,
1388 // we end up in "no valid datapoints, no peer selected" state.
1389 // Only when enough of them are seen (which means it's not a fluke),
1390 // we end up here. Looks like _our_ clock is off.
1391 switch (G.discipline_state) {
1393 /* The first outlyer: ignore it, switch to SPIK state */
1394 VERB3 bb_error_msg("update from %s: offset:%+f, spike%s",
1395 p->p_dotted, offset,
1397 G.discipline_state = STATE_SPIK;
1398 return -1; /* "decrease poll interval" */
1401 /* Ignore succeeding outlyers until either an inlyer
1402 * is found or the stepout threshold is exceeded.
1404 remains = WATCH_THRESHOLD - since_last_update;
1406 VERB3 bb_error_msg("update from %s: offset:%+f, spike%s",
1407 p->p_dotted, offset,
1408 ", datapoint ignored");
1409 return -1; /* "decrease poll interval" */
1411 /* fall through: we need to step */
1415 /* Step the time and clamp down the poll interval.
1417 * In NSET state an initial frequency correction is
1418 * not available, usually because the frequency file has
1419 * not yet been written. Since the time is outside the
1420 * capture range, the clock is stepped. The frequency
1421 * will be set directly following the stepout interval.
1423 * In FSET state the initial frequency has been set
1424 * from the frequency file. Since the time is outside
1425 * the capture range, the clock is stepped immediately,
1426 * rather than after the stepout interval. Guys get
1427 * nervous if it takes 17 minutes to set the clock for
1430 * In SPIK state the stepout threshold has expired and
1431 * the phase is still above the step threshold. Note
1432 * that a single spike greater than the step threshold
1433 * is always suppressed, even at the longer poll
1436 VERB4 bb_error_msg("stepping time by %+f; poll_exp=MINPOLL", offset);
1438 if (option_mask32 & OPT_q) {
1439 /* We were only asked to set time once. Done. */
1443 G.polladj_count = 0;
1444 G.poll_exp = MINPOLL;
1445 G.stratum = MAXSTRAT;
1447 run_script("step", offset);
1449 recv_time += offset;
1451 #if USING_INITIAL_FREQ_ESTIMATION
1452 if (G.discipline_state == STATE_NSET) {
1453 set_new_values(STATE_FREQ, /*offset:*/ 0, recv_time);
1454 return 1; /* "ok to increase poll interval" */
1457 abs_offset = offset = 0;
1458 set_new_values(STATE_SYNC, offset, recv_time);
1460 } else { /* abs_offset <= STEP_THRESHOLD */
1462 if (G.poll_exp < MINPOLL && G.initial_poll_complete) {
1463 VERB4 bb_error_msg("small offset:%+f, disabling burst mode", offset);
1464 G.polladj_count = 0;
1465 G.poll_exp = MINPOLL;
1468 /* Compute the clock jitter as the RMS of exponentially
1469 * weighted offset differences. Used by the poll adjust code.
1471 etemp = SQUARE(G.discipline_jitter);
1472 dtemp = SQUARE(offset - G.last_update_offset);
1473 G.discipline_jitter = SQRT(etemp + (dtemp - etemp) / AVG);
1475 switch (G.discipline_state) {
1477 if (option_mask32 & OPT_q) {
1478 /* We were only asked to set time once.
1479 * The clock is precise enough, no need to step.
1483 #if USING_INITIAL_FREQ_ESTIMATION
1484 /* This is the first update received and the frequency
1485 * has not been initialized. The first thing to do
1486 * is directly measure the oscillator frequency.
1488 set_new_values(STATE_FREQ, offset, recv_time);
1490 set_new_values(STATE_SYNC, offset, recv_time);
1492 VERB4 bb_error_msg("transitioning to FREQ, datapoint ignored");
1493 return 0; /* "leave poll interval as is" */
1495 #if 0 /* this is dead code for now */
1497 /* This is the first update and the frequency
1498 * has been initialized. Adjust the phase, but
1499 * don't adjust the frequency until the next update.
1501 set_new_values(STATE_SYNC, offset, recv_time);
1502 /* freq_drift remains 0 */
1506 #if USING_INITIAL_FREQ_ESTIMATION
1508 /* since_last_update >= WATCH_THRESHOLD, we waited enough.
1509 * Correct the phase and frequency and switch to SYNC state.
1510 * freq_drift was already estimated (see code above)
1512 set_new_values(STATE_SYNC, offset, recv_time);
1517 #if !USING_KERNEL_PLL_LOOP
1518 /* Compute freq_drift due to PLL and FLL contributions.
1520 * The FLL and PLL frequency gain constants
1521 * depend on the poll interval and Allan
1522 * intercept. The FLL is not used below one-half
1523 * the Allan intercept. Above that the loop gain
1524 * increases in steps to 1 / AVG.
1526 if ((1 << G.poll_exp) > ALLAN / 2) {
1527 etemp = FLL - G.poll_exp;
1530 freq_drift += (offset - G.last_update_offset) / (MAXD(since_last_update, ALLAN) * etemp);
1532 /* For the PLL the integration interval
1533 * (numerator) is the minimum of the update
1534 * interval and poll interval. This allows
1535 * oversampling, but not undersampling.
1537 etemp = MIND(since_last_update, (1 << G.poll_exp));
1538 dtemp = (4 * PLL) << G.poll_exp;
1539 freq_drift += offset * etemp / SQUARE(dtemp);
1541 set_new_values(STATE_SYNC, offset, recv_time);
1544 if (G.stratum != p->lastpkt_stratum + 1) {
1545 G.stratum = p->lastpkt_stratum + 1;
1546 run_script("stratum", offset);
1550 if (G.discipline_jitter < G_precision_sec)
1551 G.discipline_jitter = G_precision_sec;
1552 G.offset_to_jitter_ratio = abs_offset / G.discipline_jitter;
1554 G.reftime = G.cur_time;
1555 G.ntp_status = p->lastpkt_status;
1556 G.refid = p->lastpkt_refid;
1557 G.rootdelay = p->lastpkt_rootdelay + p->lastpkt_delay;
1558 dtemp = p->filter_jitter; // SQRT(SQUARE(p->filter_jitter) + SQUARE(G.cluster_jitter));
1559 dtemp += MAXD(p->filter_dispersion + FREQ_TOLERANCE * (G.cur_time - p->lastpkt_recv_time) + abs_offset, MINDISP);
1560 G.rootdisp = p->lastpkt_rootdisp + dtemp;
1561 VERB4 bb_error_msg("updating leap/refid/reftime/rootdisp from peer %s", p->p_dotted);
1563 /* We are in STATE_SYNC now, but did not do adjtimex yet.
1564 * (Any other state does not reach this, they all return earlier)
1565 * By this time, freq_drift and offset are set
1566 * to values suitable for adjtimex.
1568 #if !USING_KERNEL_PLL_LOOP
1569 /* Calculate the new frequency drift and frequency stability (wander).
1570 * Compute the clock wander as the RMS of exponentially weighted
1571 * frequency differences. This is not used directly, but can,
1572 * along with the jitter, be a highly useful monitoring and
1575 dtemp = G.discipline_freq_drift + freq_drift;
1576 G.discipline_freq_drift = MAXD(MIND(MAXDRIFT, dtemp), -MAXDRIFT);
1577 etemp = SQUARE(G.discipline_wander);
1578 dtemp = SQUARE(dtemp);
1579 G.discipline_wander = SQRT(etemp + (dtemp - etemp) / AVG);
1581 VERB4 bb_error_msg("discipline freq_drift=%.9f(int:%ld corr:%e) wander=%f",
1582 G.discipline_freq_drift,
1583 (long)(G.discipline_freq_drift * 65536e6),
1585 G.discipline_wander);
1588 memset(&tmx, 0, sizeof(tmx));
1589 if (adjtimex(&tmx) < 0)
1590 bb_perror_msg_and_die("adjtimex");
1591 bb_error_msg("p adjtimex freq:%ld offset:%+ld status:0x%x tc:%ld",
1592 tmx.freq, tmx.offset, tmx.status, tmx.constant);
1595 memset(&tmx, 0, sizeof(tmx));
1597 //doesn't work, offset remains 0 (!) in kernel:
1598 //ntpd: set adjtimex freq:1786097 tmx.offset:77487
1599 //ntpd: prev adjtimex freq:1786097 tmx.offset:0
1600 //ntpd: cur adjtimex freq:1786097 tmx.offset:0
1601 tmx.modes = ADJ_FREQUENCY | ADJ_OFFSET;
1602 /* 65536 is one ppm */
1603 tmx.freq = G.discipline_freq_drift * 65536e6;
1605 tmx.modes = ADJ_OFFSET | ADJ_STATUS | ADJ_TIMECONST;// | ADJ_MAXERROR | ADJ_ESTERROR;
1606 tmx.offset = (offset * 1000000); /* usec */
1607 tmx.status = STA_PLL;
1608 if (G.ntp_status & LI_PLUSSEC)
1609 tmx.status |= STA_INS;
1610 if (G.ntp_status & LI_MINUSSEC)
1611 tmx.status |= STA_DEL;
1613 tmx.constant = G.poll_exp - 4;
1615 * The below if statement should be unnecessary, but...
1616 * It looks like Linux kernel's PLL is far too gentle in changing
1617 * tmx.freq in response to clock offset. Offset keeps growing
1618 * and eventually we fall back to smaller poll intervals.
1619 * We can make correction more agressive (about x2) by supplying
1620 * PLL time constant which is one less than the real one.
1621 * To be on a safe side, let's do it only if offset is significantly
1622 * larger than jitter.
1624 if (tmx.constant > 0 && G.offset_to_jitter_ratio >= TIMECONST_HACK_GATE)
1627 //tmx.esterror = (uint32_t)(clock_jitter * 1e6);
1628 //tmx.maxerror = (uint32_t)((sys_rootdelay / 2 + sys_rootdisp) * 1e6);
1629 rc = adjtimex(&tmx);
1631 bb_perror_msg_and_die("adjtimex");
1632 /* NB: here kernel returns constant == G.poll_exp, not == G.poll_exp - 4.
1633 * Not sure why. Perhaps it is normal.
1635 VERB4 bb_error_msg("adjtimex:%d freq:%ld offset:%+ld status:0x%x",
1636 rc, tmx.freq, tmx.offset, tmx.status);
1637 G.kernel_freq_drift = tmx.freq / 65536;
1638 VERB2 bb_error_msg("update from:%s offset:%+f jitter:%f clock drift:%+.3fppm tc:%d",
1639 p->p_dotted, offset, G.discipline_jitter, (double)tmx.freq / 65536, (int)tmx.constant);
1641 return 1; /* "ok to increase poll interval" */
1646 * We've got a new reply packet from a peer, process it
1650 retry_interval(void)
1652 /* Local problem, want to retry soon */
1653 unsigned interval, r;
1654 interval = RETRY_INTERVAL;
1656 interval += r % (unsigned)(RETRY_INTERVAL / 4);
1657 VERB4 bb_error_msg("chose retry interval:%u", interval);
1661 poll_interval(int exponent)
1663 unsigned interval, r, mask;
1664 exponent = G.poll_exp + exponent;
1667 interval = 1 << exponent;
1668 mask = ((interval-1) >> 4) | 1;
1670 interval += r & mask; /* ~ random(0..1) * interval/16 */
1671 VERB4 bb_error_msg("chose poll interval:%u (poll_exp:%d exp:%d)", interval, G.poll_exp, exponent);
1674 static NOINLINE void
1675 recv_and_process_peer_pkt(peer_t *p)
1680 double T1, T2, T3, T4;
1683 datapoint_t *datapoint;
1688 /* We can recvfrom here and check from.IP, but some multihomed
1689 * ntp servers reply from their *other IP*.
1690 * TODO: maybe we should check at least what we can: from.port == 123?
1692 size = recv(p->p_fd, &msg, sizeof(msg), MSG_DONTWAIT);
1694 bb_perror_msg("recv(%s) error", p->p_dotted);
1695 if (errno == EHOSTUNREACH || errno == EHOSTDOWN
1696 || errno == ENETUNREACH || errno == ENETDOWN
1697 || errno == ECONNREFUSED || errno == EADDRNOTAVAIL
1700 //TODO: always do this?
1701 interval = retry_interval();
1702 goto set_next_and_ret;
1707 if (size != NTP_MSGSIZE_NOAUTH && size != NTP_MSGSIZE) {
1708 bb_error_msg("malformed packet received from %s", p->p_dotted);
1712 if (msg.m_orgtime.int_partl != p->p_xmt_msg.m_xmttime.int_partl
1713 || msg.m_orgtime.fractionl != p->p_xmt_msg.m_xmttime.fractionl
1715 /* Somebody else's packet */
1719 /* We do not expect any more packets from this peer for now.
1720 * Closing the socket informs kernel about it.
1721 * We open a new socket when we send a new query.
1726 if ((msg.m_status & LI_ALARM) == LI_ALARM
1727 || msg.m_stratum == 0
1728 || msg.m_stratum > NTP_MAXSTRATUM
1730 // TODO: stratum 0 responses may have commands in 32-bit m_refid field:
1731 // "DENY", "RSTR" - peer does not like us at all
1732 // "RATE" - peer is overloaded, reduce polling freq
1733 bb_error_msg("reply from %s: peer is unsynced", p->p_dotted);
1734 goto pick_normal_interval;
1737 // /* Verify valid root distance */
1738 // if (msg.m_rootdelay / 2 + msg.m_rootdisp >= MAXDISP || p->lastpkt_reftime > msg.m_xmt)
1739 // return; /* invalid header values */
1741 p->lastpkt_status = msg.m_status;
1742 p->lastpkt_stratum = msg.m_stratum;
1743 p->lastpkt_rootdelay = sfp_to_d(msg.m_rootdelay);
1744 p->lastpkt_rootdisp = sfp_to_d(msg.m_rootdisp);
1745 p->lastpkt_refid = msg.m_refid;
1748 * From RFC 2030 (with a correction to the delay math):
1750 * Timestamp Name ID When Generated
1751 * ------------------------------------------------------------
1752 * Originate Timestamp T1 time request sent by client
1753 * Receive Timestamp T2 time request received by server
1754 * Transmit Timestamp T3 time reply sent by server
1755 * Destination Timestamp T4 time reply received by client
1757 * The roundtrip delay and local clock offset are defined as
1759 * delay = (T4 - T1) - (T3 - T2); offset = ((T2 - T1) + (T3 - T4)) / 2
1762 T2 = lfp_to_d(msg.m_rectime);
1763 T3 = lfp_to_d(msg.m_xmttime);
1766 p->lastpkt_recv_time = T4;
1767 VERB6 bb_error_msg("%s->lastpkt_recv_time=%f", p->p_dotted, p->lastpkt_recv_time);
1769 /* The delay calculation is a special case. In cases where the
1770 * server and client clocks are running at different rates and
1771 * with very fast networks, the delay can appear negative. In
1772 * order to avoid violating the Principle of Least Astonishment,
1773 * the delay is clamped not less than the system precision.
1775 dv = p->lastpkt_delay;
1776 p->lastpkt_delay = (T4 - T1) - (T3 - T2);
1777 if (p->lastpkt_delay < G_precision_sec)
1778 p->lastpkt_delay = G_precision_sec;
1780 * If this packet's delay is much bigger than the last one,
1781 * it's better to just ignore it than use its much less precise value.
1783 if (p->reachable_bits && p->lastpkt_delay > dv * BAD_DELAY_GROWTH) {
1784 bb_error_msg("reply from %s: delay %f is too high, ignoring", p->p_dotted, p->lastpkt_delay);
1785 goto pick_normal_interval;
1788 p->datapoint_idx = p->reachable_bits ? (p->datapoint_idx + 1) % NUM_DATAPOINTS : 0;
1789 datapoint = &p->filter_datapoint[p->datapoint_idx];
1790 datapoint->d_recv_time = T4;
1791 datapoint->d_offset = offset = ((T2 - T1) + (T3 - T4)) / 2;
1792 datapoint->d_dispersion = LOG2D(msg.m_precision_exp) + G_precision_sec;
1793 if (!p->reachable_bits) {
1794 /* 1st datapoint ever - replicate offset in every element */
1796 for (i = 0; i < NUM_DATAPOINTS; i++) {
1797 p->filter_datapoint[i].d_offset = offset;
1801 p->reachable_bits |= 1;
1802 if ((MAX_VERBOSE && G.verbose) || (option_mask32 & OPT_w)) {
1803 bb_error_msg("reply from %s: offset:%+f delay:%f status:0x%02x strat:%d refid:0x%08x rootdelay:%f reach:0x%02x",
1810 p->lastpkt_rootdelay,
1812 /* not shown: m_ppoll, m_precision_exp, m_rootdisp,
1813 * m_reftime, m_orgtime, m_rectime, m_xmttime
1818 /* Muck with statictics and update the clock */
1819 filter_datapoints(p);
1820 q = select_and_cluster();
1824 if (!(option_mask32 & OPT_w)) {
1825 rc = update_local_clock(q);
1826 /* If drift is dangerously large, immediately
1827 * drop poll interval one step down.
1829 if (fabs(q->filter_offset) >= POLLDOWN_OFFSET) {
1830 VERB4 bb_error_msg("offset:%+f > POLLDOWN_OFFSET", q->filter_offset);
1835 /* else: no peer selected, rc = -1: we want to poll more often */
1838 /* Adjust the poll interval by comparing the current offset
1839 * with the clock jitter. If the offset is less than
1840 * the clock jitter times a constant, then the averaging interval
1841 * is increased, otherwise it is decreased. A bit of hysteresis
1842 * helps calm the dance. Works best using burst mode.
1844 if (rc > 0 && G.offset_to_jitter_ratio <= POLLADJ_GATE) {
1845 /* was += G.poll_exp but it is a bit
1846 * too optimistic for my taste at high poll_exp's */
1847 G.polladj_count += MINPOLL;
1848 if (G.polladj_count > POLLADJ_LIMIT) {
1849 G.polladj_count = 0;
1850 if (G.poll_exp < MAXPOLL) {
1852 VERB4 bb_error_msg("polladj: discipline_jitter:%f ++poll_exp=%d",
1853 G.discipline_jitter, G.poll_exp);
1856 VERB4 bb_error_msg("polladj: incr:%d", G.polladj_count);
1859 G.polladj_count -= G.poll_exp * 2;
1860 if (G.polladj_count < -POLLADJ_LIMIT || G.poll_exp >= BIGPOLL) {
1862 G.polladj_count = 0;
1863 if (G.poll_exp > MINPOLL) {
1867 /* Correct p->next_action_time in each peer
1868 * which waits for sending, so that they send earlier.
1869 * Old pp->next_action_time are on the order
1870 * of t + (1 << old_poll_exp) + small_random,
1871 * we simply need to subtract ~half of that.
1873 for (item = G.ntp_peers; item != NULL; item = item->link) {
1874 peer_t *pp = (peer_t *) item->data;
1876 pp->next_action_time -= (1 << G.poll_exp);
1878 VERB4 bb_error_msg("polladj: discipline_jitter:%f --poll_exp=%d",
1879 G.discipline_jitter, G.poll_exp);
1882 VERB4 bb_error_msg("polladj: decr:%d", G.polladj_count);
1887 /* Decide when to send new query for this peer */
1888 pick_normal_interval:
1889 interval = poll_interval(0);
1890 if (fabs(offset) >= STEP_THRESHOLD * 8 && interval > BIGOFF_INTERVAL) {
1891 /* If we are synced, offsets are less than STEP_THRESHOLD,
1892 * or at the very least not much larger than it.
1893 * Now we see a largish one.
1894 * Either this peer is feeling bad, or packet got corrupted,
1895 * or _our_ clock is wrong now and _all_ peers will show similar
1896 * largish offsets too.
1897 * I observed this with laptop suspend stopping clock.
1898 * In any case, it makes sense to make next request soonish:
1899 * cases 1 and 2: get a better datapoint,
1900 * case 3: allows to resync faster.
1902 interval = BIGOFF_INTERVAL;
1906 set_next(p, interval);
1909 #if ENABLE_FEATURE_NTPD_SERVER
1910 static NOINLINE void
1911 recv_and_process_client_pkt(void /*int fd*/)
1915 len_and_sockaddr *to;
1916 struct sockaddr *from;
1918 uint8_t query_status;
1919 l_fixedpt_t query_xmttime;
1921 to = get_sock_lsa(G_listen_fd);
1922 from = xzalloc(to->len);
1924 size = recv_from_to(G_listen_fd, &msg, sizeof(msg), MSG_DONTWAIT, from, &to->u.sa, to->len);
1925 if (size != NTP_MSGSIZE_NOAUTH && size != NTP_MSGSIZE) {
1928 if (errno == EAGAIN)
1930 bb_perror_msg_and_die("recv");
1932 addr = xmalloc_sockaddr2dotted_noport(from);
1933 bb_error_msg("malformed packet received from %s: size %u", addr, (int)size);
1938 query_status = msg.m_status;
1939 query_xmttime = msg.m_xmttime;
1941 /* Build a reply packet */
1942 memset(&msg, 0, sizeof(msg));
1943 msg.m_status = G.stratum < MAXSTRAT ? (G.ntp_status & LI_MASK) : LI_ALARM;
1944 msg.m_status |= (query_status & VERSION_MASK);
1945 msg.m_status |= ((query_status & MODE_MASK) == MODE_CLIENT) ?
1946 MODE_SERVER : MODE_SYM_PAS;
1947 msg.m_stratum = G.stratum;
1948 msg.m_ppoll = G.poll_exp;
1949 msg.m_precision_exp = G_precision_exp;
1950 /* this time was obtained between poll() and recv() */
1951 msg.m_rectime = d_to_lfp(G.cur_time);
1952 msg.m_xmttime = d_to_lfp(gettime1900d()); /* this instant */
1953 if (G.peer_cnt == 0) {
1954 /* we have no peers: "stratum 1 server" mode. reftime = our own time */
1955 G.reftime = G.cur_time;
1957 msg.m_reftime = d_to_lfp(G.reftime);
1958 msg.m_orgtime = query_xmttime;
1959 msg.m_rootdelay = d_to_sfp(G.rootdelay);
1960 //simple code does not do this, fix simple code!
1961 msg.m_rootdisp = d_to_sfp(G.rootdisp);
1962 //version = (query_status & VERSION_MASK); /* ... >> VERSION_SHIFT - done below instead */
1963 msg.m_refid = G.refid; // (version > (3 << VERSION_SHIFT)) ? G.refid : G.refid3;
1965 /* We reply from the local address packet was sent to,
1966 * this makes to/from look swapped here: */
1967 do_sendto(G_listen_fd,
1968 /*from:*/ &to->u.sa, /*to:*/ from, /*addrlen:*/ to->len,
1977 /* Upstream ntpd's options:
1979 * -4 Force DNS resolution of host names to the IPv4 namespace.
1980 * -6 Force DNS resolution of host names to the IPv6 namespace.
1981 * -a Require cryptographic authentication for broadcast client,
1982 * multicast client and symmetric passive associations.
1983 * This is the default.
1984 * -A Do not require cryptographic authentication for broadcast client,
1985 * multicast client and symmetric passive associations.
1986 * This is almost never a good idea.
1987 * -b Enable the client to synchronize to broadcast servers.
1989 * Specify the name and path of the configuration file,
1990 * default /etc/ntp.conf
1991 * -d Specify debugging mode. This option may occur more than once,
1992 * with each occurrence indicating greater detail of display.
1994 * Specify debugging level directly.
1996 * Specify the name and path of the frequency file.
1997 * This is the same operation as the "driftfile FILE"
1998 * configuration command.
1999 * -g Normally, ntpd exits with a message to the system log
2000 * if the offset exceeds the panic threshold, which is 1000 s
2001 * by default. This option allows the time to be set to any value
2002 * without restriction; however, this can happen only once.
2003 * If the threshold is exceeded after that, ntpd will exit
2004 * with a message to the system log. This option can be used
2005 * with the -q and -x options. See the tinker command for other options.
2007 * Chroot the server to the directory jaildir. This option also implies
2008 * that the server attempts to drop root privileges at startup
2009 * (otherwise, chroot gives very little additional security).
2010 * You may need to also specify a -u option.
2012 * Specify the name and path of the symmetric key file,
2013 * default /etc/ntp/keys. This is the same operation
2014 * as the "keys FILE" configuration command.
2016 * Specify the name and path of the log file. The default
2017 * is the system log file. This is the same operation as
2018 * the "logfile FILE" configuration command.
2019 * -L Do not listen to virtual IPs. The default is to listen.
2021 * -N To the extent permitted by the operating system,
2022 * run the ntpd at the highest priority.
2024 * Specify the name and path of the file used to record the ntpd
2025 * process ID. This is the same operation as the "pidfile FILE"
2026 * configuration command.
2028 * To the extent permitted by the operating system,
2029 * run the ntpd at the specified priority.
2030 * -q Exit the ntpd just after the first time the clock is set.
2031 * This behavior mimics that of the ntpdate program, which is
2032 * to be retired. The -g and -x options can be used with this option.
2033 * Note: The kernel time discipline is disabled with this option.
2035 * Specify the default propagation delay from the broadcast/multicast
2036 * server to this client. This is necessary only if the delay
2037 * cannot be computed automatically by the protocol.
2039 * Specify the directory path for files created by the statistics
2040 * facility. This is the same operation as the "statsdir DIR"
2041 * configuration command.
2043 * Add a key number to the trusted key list. This option can occur
2046 * Specify a user, and optionally a group, to switch to.
2049 * Add a system variable listed by default.
2050 * -x Normally, the time is slewed if the offset is less than the step
2051 * threshold, which is 128 ms by default, and stepped if above
2052 * the threshold. This option sets the threshold to 600 s, which is
2053 * well within the accuracy window to set the clock manually.
2054 * Note: since the slew rate of typical Unix kernels is limited
2055 * to 0.5 ms/s, each second of adjustment requires an amortization
2056 * interval of 2000 s. Thus, an adjustment as much as 600 s
2057 * will take almost 14 days to complete. This option can be used
2058 * with the -g and -q options. See the tinker command for other options.
2059 * Note: The kernel time discipline is disabled with this option.
2062 /* By doing init in a separate function we decrease stack usage
2065 static NOINLINE void ntp_init(char **argv)
2073 bb_error_msg_and_die(bb_msg_you_must_be_root);
2075 /* Set some globals */
2076 G.stratum = MAXSTRAT;
2078 G.poll_exp = BURSTPOLL; /* speeds up initial sync */
2079 G.last_script_run = G.reftime = G.last_update_recv_time = gettime1900d(); /* sets G.cur_time too */
2083 opt_complementary = "dd:p::wn"; /* d: counter; p: list; -w implies -n */
2084 opts = getopt32(argv,
2086 "wp:S:"IF_FEATURE_NTPD_SERVER("l") /* NOT compat */
2088 "46aAbgL", /* compat, ignored */
2089 &peers, &G.script_name, &G.verbose);
2090 if (!(opts & (OPT_p|OPT_l)))
2092 // if (opts & OPT_x) /* disable stepping, only slew is allowed */
2093 // G.time_was_stepped = 1;
2096 add_peers(llist_pop(&peers));
2098 /* -l but no peers: "stratum 1 server" mode */
2101 if (!(opts & OPT_n)) {
2102 bb_daemonize_or_rexec(DAEMON_DEVNULL_STDIO, argv);
2103 logmode = LOGMODE_NONE;
2105 #if ENABLE_FEATURE_NTPD_SERVER
2108 G_listen_fd = create_and_bind_dgram_or_die(NULL, 123);
2109 socket_want_pktinfo(G_listen_fd);
2110 setsockopt(G_listen_fd, IPPROTO_IP, IP_TOS, &const_IPTOS_LOWDELAY, sizeof(const_IPTOS_LOWDELAY));
2113 /* I hesitate to set -20 prio. -15 should be high enough for timekeeping */
2115 setpriority(PRIO_PROCESS, 0, -15);
2117 /* If network is up, syncronization occurs in ~10 seconds.
2118 * We give "ntpd -q" 10 seconds to get first reply,
2119 * then another 50 seconds to finish syncing.
2121 * I tested ntpd 4.2.6p1 and apparently it never exits
2122 * (will try forever), but it does not feel right.
2123 * The goal of -q is to act like ntpdate: set time
2124 * after a reasonably small period of polling, or fail.
2127 option_mask32 |= OPT_qq;
2144 int ntpd_main(int argc UNUSED_PARAM, char **argv) MAIN_EXTERNALLY_VISIBLE;
2145 int ntpd_main(int argc UNUSED_PARAM, char **argv)
2153 memset(&G, 0, sizeof(G));
2154 SET_PTR_TO_GLOBALS(&G);
2158 /* If ENABLE_FEATURE_NTPD_SERVER, + 1 for listen_fd: */
2159 cnt = G.peer_cnt + ENABLE_FEATURE_NTPD_SERVER;
2160 idx2peer = xzalloc(sizeof(idx2peer[0]) * cnt);
2161 pfd = xzalloc(sizeof(pfd[0]) * cnt);
2163 /* Countdown: we never sync before we sent INITIAL_SAMPLES+1
2164 * packets to each peer.
2165 * NB: if some peer is not responding, we may end up sending
2166 * fewer packets to it and more to other peers.
2167 * NB2: sync usually happens using INITIAL_SAMPLES packets,
2168 * since last reply does not come back instantaneously.
2170 cnt = G.peer_cnt * (INITIAL_SAMPLES + 1);
2172 write_pidfile(CONFIG_PID_FILE_PATH "/ntpd.pid");
2174 while (!bb_got_signal) {
2180 /* Nothing between here and poll() blocks for any significant time */
2182 nextaction = G.cur_time + 3600;
2185 #if ENABLE_FEATURE_NTPD_SERVER
2186 if (G_listen_fd != -1) {
2187 pfd[0].fd = G_listen_fd;
2188 pfd[0].events = POLLIN;
2192 /* Pass over peer list, send requests, time out on receives */
2193 for (item = G.ntp_peers; item != NULL; item = item->link) {
2194 peer_t *p = (peer_t *) item->data;
2196 if (p->next_action_time <= G.cur_time) {
2197 if (p->p_fd == -1) {
2198 /* Time to send new req */
2200 G.initial_poll_complete = 1;
2202 send_query_to_peer(p);
2204 /* Timed out waiting for reply */
2207 timeout = poll_interval(-2); /* -2: try a bit sooner */
2208 bb_error_msg("timed out waiting for %s, reach 0x%02x, next query in %us",
2209 p->p_dotted, p->reachable_bits, timeout);
2210 set_next(p, timeout);
2214 if (p->next_action_time < nextaction)
2215 nextaction = p->next_action_time;
2218 /* Wait for reply from this peer */
2219 pfd[i].fd = p->p_fd;
2220 pfd[i].events = POLLIN;
2226 timeout = nextaction - G.cur_time;
2229 timeout++; /* (nextaction - G.cur_time) rounds down, compensating */
2231 /* Here we may block */
2233 if (i > (ENABLE_FEATURE_NTPD_SERVER && G_listen_fd != -1)) {
2234 /* We wait for at least one reply.
2235 * Poll for it, without wasting time for message.
2236 * Since replies often come under 1 second, this also
2237 * reduces clutter in logs.
2239 nfds = poll(pfd, i, 1000);
2245 bb_error_msg("poll:%us sockets:%u interval:%us", timeout, i, 1 << G.poll_exp);
2247 nfds = poll(pfd, i, timeout * 1000);
2249 gettime1900d(); /* sets G.cur_time */
2251 if (!bb_got_signal /* poll wasn't interrupted by a signal */
2252 && G.cur_time - G.last_script_run > 11*60
2254 /* Useful for updating battery-backed RTC and such */
2255 run_script("periodic", G.last_update_offset);
2256 gettime1900d(); /* sets G.cur_time */
2261 /* Process any received packets */
2263 #if ENABLE_FEATURE_NTPD_SERVER
2264 if (G.listen_fd != -1) {
2265 if (pfd[0].revents /* & (POLLIN|POLLERR)*/) {
2267 recv_and_process_client_pkt(/*G.listen_fd*/);
2268 gettime1900d(); /* sets G.cur_time */
2273 for (; nfds != 0 && j < i; j++) {
2274 if (pfd[j].revents /* & (POLLIN|POLLERR)*/) {
2276 * At init, alarm was set to 10 sec.
2277 * Now we did get a reply.
2278 * Increase timeout to 50 seconds to finish syncing.
2280 if (option_mask32 & OPT_qq) {
2281 option_mask32 &= ~OPT_qq;
2285 recv_and_process_peer_pkt(idx2peer[j]);
2286 gettime1900d(); /* sets G.cur_time */
2291 if (G.ntp_peers && G.stratum != MAXSTRAT) {
2292 for (item = G.ntp_peers; item != NULL; item = item->link) {
2293 peer_t *p = (peer_t *) item->data;
2294 if (p->reachable_bits)
2295 goto have_reachable_peer;
2297 /* No peer responded for last 8 packets, panic */
2298 G.polladj_count = 0;
2299 G.poll_exp = MINPOLL;
2300 G.stratum = MAXSTRAT;
2301 run_script("unsync", 0.0);
2302 have_reachable_peer: ;
2304 } /* while (!bb_got_signal) */
2306 remove_pidfile(CONFIG_PID_FILE_PATH "/ntpd.pid");
2307 kill_myself_with_sig(bb_got_signal);
2315 /*** openntpd-4.6 uses only adjtime, not adjtimex ***/
2317 /*** ntp-4.2.6/ntpd/ntp_loopfilter.c - adjtimex usage ***/
2321 direct_freq(double fp_offset)
2325 * If the kernel is enabled, we need the residual offset to
2326 * calculate the frequency correction.
2328 if (pll_control && kern_enable) {
2329 memset(&ntv, 0, sizeof(ntv));
2332 clock_offset = ntv.offset / 1e9;
2333 #else /* STA_NANO */
2334 clock_offset = ntv.offset / 1e6;
2335 #endif /* STA_NANO */
2336 drift_comp = FREQTOD(ntv.freq);
2338 #endif /* KERNEL_PLL */
2339 set_freq((fp_offset - clock_offset) / (current_time - clock_epoch) + drift_comp);
2345 set_freq(double freq) /* frequency update */
2353 * If the kernel is enabled, update the kernel frequency.
2355 if (pll_control && kern_enable) {
2356 memset(&ntv, 0, sizeof(ntv));
2357 ntv.modes = MOD_FREQUENCY;
2358 ntv.freq = DTOFREQ(drift_comp);
2360 snprintf(tbuf, sizeof(tbuf), "kernel %.3f PPM", drift_comp * 1e6);
2361 report_event(EVNT_FSET, NULL, tbuf);
2363 snprintf(tbuf, sizeof(tbuf), "ntpd %.3f PPM", drift_comp * 1e6);
2364 report_event(EVNT_FSET, NULL, tbuf);
2366 #else /* KERNEL_PLL */
2367 snprintf(tbuf, sizeof(tbuf), "ntpd %.3f PPM", drift_comp * 1e6);
2368 report_event(EVNT_FSET, NULL, tbuf);
2369 #endif /* KERNEL_PLL */
2378 * This code segment works when clock adjustments are made using
2379 * precision time kernel support and the ntp_adjtime() system
2380 * call. This support is available in Solaris 2.6 and later,
2381 * Digital Unix 4.0 and later, FreeBSD, Linux and specially
2382 * modified kernels for HP-UX 9 and Ultrix 4. In the case of the
2383 * DECstation 5000/240 and Alpha AXP, additional kernel
2384 * modifications provide a true microsecond clock and nanosecond
2385 * clock, respectively.
2387 * Important note: The kernel discipline is used only if the
2388 * step threshold is less than 0.5 s, as anything higher can
2389 * lead to overflow problems. This might occur if some misguided
2390 * lad set the step threshold to something ridiculous.
2392 if (pll_control && kern_enable) {
2394 #define MOD_BITS (MOD_OFFSET | MOD_MAXERROR | MOD_ESTERROR | MOD_STATUS | MOD_TIMECONST)
2397 * We initialize the structure for the ntp_adjtime()
2398 * system call. We have to convert everything to
2399 * microseconds or nanoseconds first. Do not update the
2400 * system variables if the ext_enable flag is set. In
2401 * this case, the external clock driver will update the
2402 * variables, which will be read later by the local
2403 * clock driver. Afterwards, remember the time and
2404 * frequency offsets for jitter and stability values and
2405 * to update the frequency file.
2407 memset(&ntv, 0, sizeof(ntv));
2409 ntv.modes = MOD_STATUS;
2412 ntv.modes = MOD_BITS | MOD_NANO;
2413 #else /* STA_NANO */
2414 ntv.modes = MOD_BITS;
2415 #endif /* STA_NANO */
2416 if (clock_offset < 0)
2421 ntv.offset = (int32)(clock_offset * 1e9 + dtemp);
2422 ntv.constant = sys_poll;
2423 #else /* STA_NANO */
2424 ntv.offset = (int32)(clock_offset * 1e6 + dtemp);
2425 ntv.constant = sys_poll - 4;
2426 #endif /* STA_NANO */
2427 ntv.esterror = (u_int32)(clock_jitter * 1e6);
2428 ntv.maxerror = (u_int32)((sys_rootdelay / 2 + sys_rootdisp) * 1e6);
2429 ntv.status = STA_PLL;
2432 * Enable/disable the PPS if requested.
2435 if (!(pll_status & STA_PPSTIME))
2436 report_event(EVNT_KERN,
2437 NULL, "PPS enabled");
2438 ntv.status |= STA_PPSTIME | STA_PPSFREQ;
2440 if (pll_status & STA_PPSTIME)
2441 report_event(EVNT_KERN,
2442 NULL, "PPS disabled");
2443 ntv.status &= ~(STA_PPSTIME | STA_PPSFREQ);
2445 if (sys_leap == LEAP_ADDSECOND)
2446 ntv.status |= STA_INS;
2447 else if (sys_leap == LEAP_DELSECOND)
2448 ntv.status |= STA_DEL;
2452 * Pass the stuff to the kernel. If it squeals, turn off
2453 * the pps. In any case, fetch the kernel offset,
2454 * frequency and jitter.
2456 if (ntp_adjtime(&ntv) == TIME_ERROR) {
2457 if (!(ntv.status & STA_PPSSIGNAL))
2458 report_event(EVNT_KERN, NULL,
2461 pll_status = ntv.status;
2463 clock_offset = ntv.offset / 1e9;
2464 #else /* STA_NANO */
2465 clock_offset = ntv.offset / 1e6;
2466 #endif /* STA_NANO */
2467 clock_frequency = FREQTOD(ntv.freq);
2470 * If the kernel PPS is lit, monitor its performance.
2472 if (ntv.status & STA_PPSTIME) {
2474 clock_jitter = ntv.jitter / 1e9;
2475 #else /* STA_NANO */
2476 clock_jitter = ntv.jitter / 1e6;
2477 #endif /* STA_NANO */
2480 #if defined(STA_NANO) && NTP_API == 4
2482 * If the TAI changes, update the kernel TAI.
2484 if (loop_tai != sys_tai) {
2486 ntv.modes = MOD_TAI;
2487 ntv.constant = sys_tai;
2490 #endif /* STA_NANO */
2492 #endif /* KERNEL_PLL */