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
55 # error "Sorry, your kernel has to support IP_PKTINFO"
59 /* Verbosity control (max level of -dddd options accepted).
60 * max 6 is very talkative (and bloated). 3 is non-bloated,
61 * production level setting.
66 /* High-level description of the algorithm:
68 * We start running with very small poll_exp, BURSTPOLL,
69 * in order to quickly accumulate INITIAL_SAMPLES datapoints
70 * for each peer. Then, time is stepped if the offset is larger
71 * than STEP_THRESHOLD, otherwise it isn't; anyway, we enlarge
72 * poll_exp to MINPOLL and enter frequency measurement step:
73 * we collect new datapoints but ignore them for WATCH_THRESHOLD
74 * seconds. After WATCH_THRESHOLD seconds we look at accumulated
75 * offset and estimate frequency drift.
77 * (frequency measurement step seems to not be strictly needed,
78 * it is conditionally disabled with USING_INITIAL_FREQ_ESTIMATION
81 * After this, we enter "steady state": we collect a datapoint,
82 * we select the best peer, if this datapoint is not a new one
83 * (IOW: if this datapoint isn't for selected peer), sleep
84 * and collect another one; otherwise, use its offset to update
85 * frequency drift, if offset is somewhat large, reduce poll_exp,
86 * otherwise increase poll_exp.
88 * If offset is larger than STEP_THRESHOLD, which shouldn't normally
89 * happen, we assume that something "bad" happened (computer
90 * was hibernated, someone set totally wrong date, etc),
91 * then the time is stepped, all datapoints are discarded,
92 * and we go back to steady state.
95 #define RETRY_INTERVAL 5 /* on error, retry in N secs */
96 #define RESPONSE_INTERVAL 15 /* wait for reply up to N secs */
97 #define INITIAL_SAMPLES 4 /* how many samples do we want for init */
98 #define BAD_DELAY_GROWTH 4 /* drop packet if its delay grew by more than this */
100 /* Clock discipline parameters and constants */
102 /* Step threshold (sec). std ntpd uses 0.128.
103 * Using exact power of 2 (1/8) results in smaller code */
104 #define STEP_THRESHOLD 0.125
105 #define WATCH_THRESHOLD 128 /* stepout threshold (sec). std ntpd uses 900 (11 mins (!)) */
106 /* NB: set WATCH_THRESHOLD to ~60 when debugging to save time) */
107 //UNUSED: #define PANIC_THRESHOLD 1000 /* panic threshold (sec) */
109 #define FREQ_TOLERANCE 0.000015 /* frequency tolerance (15 PPM) */
110 #define BURSTPOLL 0 /* initial poll */
111 #define MINPOLL 5 /* minimum poll interval. std ntpd uses 6 (6: 64 sec) */
112 /* If offset > discipline_jitter * POLLADJ_GATE, and poll interval is >= 2^BIGPOLL,
113 * then it is decreased _at once_. (If < 2^BIGPOLL, it will be decreased _eventually_).
115 #define BIGPOLL 10 /* 2^10 sec ~= 17 min */
116 #define MAXPOLL 12 /* maximum poll interval (12: 1.1h, 17: 36.4h). std ntpd uses 17 */
117 /* Actively lower poll when we see such big offsets.
118 * With STEP_THRESHOLD = 0.125, it means we try to sync more aggressively
119 * if offset increases over ~0.04 sec */
120 #define POLLDOWN_OFFSET (STEP_THRESHOLD / 3)
121 #define MINDISP 0.01 /* minimum dispersion (sec) */
122 #define MAXDISP 16 /* maximum dispersion (sec) */
123 #define MAXSTRAT 16 /* maximum stratum (infinity metric) */
124 #define MAXDIST 1 /* distance threshold (sec) */
125 #define MIN_SELECTED 1 /* minimum intersection survivors */
126 #define MIN_CLUSTERED 3 /* minimum cluster survivors */
128 #define MAXDRIFT 0.000500 /* frequency drift we can correct (500 PPM) */
130 /* Poll-adjust threshold.
131 * When we see that offset is small enough compared to discipline jitter,
132 * we grow a counter: += MINPOLL. When counter goes over POLLADJ_LIMIT,
133 * we poll_exp++. If offset isn't small, counter -= poll_exp*2,
134 * and when it goes below -POLLADJ_LIMIT, we poll_exp--.
135 * (Bumped from 30 to 40 since otherwise I often see poll_exp going *2* steps down)
137 #define POLLADJ_LIMIT 40
138 /* If offset < discipline_jitter * POLLADJ_GATE, then we decide to increase
139 * poll interval (we think we can't improve timekeeping
140 * by staying at smaller poll).
142 #define POLLADJ_GATE 4
143 #define TIMECONST_HACK_GATE 2
144 /* Compromise Allan intercept (sec). doc uses 1500, std ntpd uses 512 */
148 /* FLL loop gain [why it depends on MAXPOLL??] */
149 #define FLL (MAXPOLL + 1)
150 /* Parameter averaging constant */
159 NTP_MSGSIZE_NOAUTH = 48,
160 NTP_MSGSIZE = (NTP_MSGSIZE_NOAUTH + 4 + NTP_DIGESTSIZE),
163 MODE_MASK = (7 << 0),
164 VERSION_MASK = (7 << 3),
168 /* Leap Second Codes (high order two bits of m_status) */
169 LI_NOWARNING = (0 << 6), /* no warning */
170 LI_PLUSSEC = (1 << 6), /* add a second (61 seconds) */
171 LI_MINUSSEC = (2 << 6), /* minus a second (59 seconds) */
172 LI_ALARM = (3 << 6), /* alarm condition */
175 MODE_RES0 = 0, /* reserved */
176 MODE_SYM_ACT = 1, /* symmetric active */
177 MODE_SYM_PAS = 2, /* symmetric passive */
178 MODE_CLIENT = 3, /* client */
179 MODE_SERVER = 4, /* server */
180 MODE_BROADCAST = 5, /* broadcast */
181 MODE_RES1 = 6, /* reserved for NTP control message */
182 MODE_RES2 = 7, /* reserved for private use */
185 //TODO: better base selection
186 #define OFFSET_1900_1970 2208988800UL /* 1970 - 1900 in seconds */
188 #define NUM_DATAPOINTS 8
201 uint8_t m_status; /* status of local clock and leap info */
203 uint8_t m_ppoll; /* poll value */
204 int8_t m_precision_exp;
205 s_fixedpt_t m_rootdelay;
206 s_fixedpt_t m_rootdisp;
208 l_fixedpt_t m_reftime;
209 l_fixedpt_t m_orgtime;
210 l_fixedpt_t m_rectime;
211 l_fixedpt_t m_xmttime;
213 uint8_t m_digest[NTP_DIGESTSIZE];
223 len_and_sockaddr *p_lsa;
227 uint32_t lastpkt_refid;
228 uint8_t lastpkt_status;
229 uint8_t lastpkt_stratum;
230 uint8_t reachable_bits;
231 /* when to send new query (if p_fd == -1)
232 * or when receive times out (if p_fd >= 0): */
233 double next_action_time;
235 double lastpkt_recv_time;
236 double lastpkt_delay;
237 double lastpkt_rootdelay;
238 double lastpkt_rootdisp;
239 /* produced by filter algorithm: */
240 double filter_offset;
241 double filter_dispersion;
242 double filter_jitter;
243 datapoint_t filter_datapoint[NUM_DATAPOINTS];
244 /* last sent packet: */
249 #define USING_KERNEL_PLL_LOOP 1
250 #define USING_INITIAL_FREQ_ESTIMATION 0
257 /* Insert new options above this line. */
258 /* Non-compat options: */
262 OPT_l = (1 << 7) * ENABLE_FEATURE_NTPD_SERVER,
263 /* We hijack some bits for other purposes */
269 /* total round trip delay to currently selected reference clock */
271 /* reference timestamp: time when the system clock was last set or corrected */
273 /* total dispersion to currently selected reference clock */
276 double last_script_run;
279 #if ENABLE_FEATURE_NTPD_SERVER
281 # define G_listen_fd (G.listen_fd)
283 # define G_listen_fd (-1)
287 /* refid: 32-bit code identifying the particular server or reference clock
288 * in stratum 0 packets this is a four-character ASCII string,
289 * called the kiss code, used for debugging and monitoring
290 * in stratum 1 packets this is a four-character ASCII string
291 * assigned to the reference clock by IANA. Example: "GPS "
292 * in stratum 2+ packets, it's IPv4 address or 4 first bytes
293 * of MD5 hash of IPv6
297 /* precision is defined as the larger of the resolution and time to
298 * read the clock, in log2 units. For instance, the precision of a
299 * mains-frequency clock incrementing at 60 Hz is 16 ms, even when the
300 * system clock hardware representation is to the nanosecond.
302 * Delays, jitters of various kinds are clamped down to precision.
304 * If precision_sec is too large, discipline_jitter gets clamped to it
305 * and if offset is smaller than discipline_jitter * POLLADJ_GATE, poll
306 * interval grows even though we really can benefit from staying at
307 * smaller one, collecting non-lagged datapoits and correcting offset.
308 * (Lagged datapoits exist when poll_exp is large but we still have
309 * systematic offset error - the time distance between datapoints
310 * is significant and older datapoints have smaller offsets.
311 * This makes our offset estimation a bit smaller than reality)
312 * Due to this effect, setting G_precision_sec close to
313 * STEP_THRESHOLD isn't such a good idea - offsets may grow
314 * too big and we will step. I observed it with -6.
316 * OTOH, setting precision_sec far too small would result in futile
317 * attempts to syncronize to an unachievable precision.
319 * -6 is 1/64 sec, -7 is 1/128 sec and so on.
320 * -8 is 1/256 ~= 0.003906 (worked well for me --vda)
321 * -9 is 1/512 ~= 0.001953 (let's try this for some time)
323 #define G_precision_exp -9
325 * G_precision_exp is used only for construction outgoing packets.
326 * It's ok to set G_precision_sec to a slightly different value
327 * (One which is "nicer looking" in logs).
328 * Exact value would be (1.0 / (1 << (- G_precision_exp))):
330 #define G_precision_sec 0.002
332 /* Bool. After set to 1, never goes back to 0: */
333 smallint initial_poll_complete;
335 #define STATE_NSET 0 /* initial state, "nothing is set" */
336 //#define STATE_FSET 1 /* frequency set from file */
337 #define STATE_SPIK 2 /* spike detected */
338 //#define STATE_FREQ 3 /* initial frequency */
339 #define STATE_SYNC 4 /* clock synchronized (normal operation) */
340 uint8_t discipline_state; // doc calls it c.state
341 uint8_t poll_exp; // s.poll
342 int polladj_count; // c.count
343 long kernel_freq_drift;
344 peer_t *last_update_peer;
345 double last_update_offset; // c.last
346 double last_update_recv_time; // s.t
347 double discipline_jitter; // c.jitter
348 /* Since we only compare it with ints, can simplify code
349 * by not making this variable floating point:
351 unsigned offset_to_jitter_ratio;
352 //double cluster_offset; // s.offset
353 //double cluster_jitter; // s.jitter
354 #if !USING_KERNEL_PLL_LOOP
355 double discipline_freq_drift; // c.freq
356 /* Maybe conditionally calculate wander? it's used only for logging */
357 double discipline_wander; // c.wander
360 #define G (*ptr_to_globals)
362 static const int const_IPTOS_LOWDELAY = IPTOS_LOWDELAY;
365 #define VERB1 if (MAX_VERBOSE && G.verbose)
366 #define VERB2 if (MAX_VERBOSE >= 2 && G.verbose >= 2)
367 #define VERB3 if (MAX_VERBOSE >= 3 && G.verbose >= 3)
368 #define VERB4 if (MAX_VERBOSE >= 4 && G.verbose >= 4)
369 #define VERB5 if (MAX_VERBOSE >= 5 && G.verbose >= 5)
370 #define VERB6 if (MAX_VERBOSE >= 6 && G.verbose >= 6)
373 static double LOG2D(int a)
376 return 1.0 / (1UL << -a);
379 static ALWAYS_INLINE double SQUARE(double x)
383 static ALWAYS_INLINE double MAXD(double a, double b)
389 static ALWAYS_INLINE double MIND(double a, double b)
395 static NOINLINE double my_SQRT(double X)
402 double Xhalf = X * 0.5;
404 /* Fast and good approximation to 1/sqrt(X), black magic */
406 /*v.i = 0x5f3759df - (v.i >> 1);*/
407 v.i = 0x5f375a86 - (v.i >> 1); /* - this constant is slightly better */
408 invsqrt = v.f; /* better than 0.2% accuracy */
410 /* Refining it using Newton's method: x1 = x0 - f(x0)/f'(x0)
411 * f(x) = 1/(x*x) - X (f==0 when x = 1/sqrt(X))
413 * f(x)/f'(x) = (X - 1/(x*x)) / (2/(x*x*x)) = X*x*x*x/2 - x/2
414 * x1 = x0 - (X*x0*x0*x0/2 - x0/2) = 1.5*x0 - X*x0*x0*x0/2 = x0*(1.5 - (X/2)*x0*x0)
416 invsqrt = invsqrt * (1.5 - Xhalf * invsqrt * invsqrt); /* ~0.05% accuracy */
417 /* invsqrt = invsqrt * (1.5 - Xhalf * invsqrt * invsqrt); 2nd iter: ~0.0001% accuracy */
418 /* With 4 iterations, more than half results will be exact,
419 * at 6th iterations result stabilizes with about 72% results exact.
420 * We are well satisfied with 0.05% accuracy.
423 return X * invsqrt; /* X * 1/sqrt(X) ~= sqrt(X) */
425 static ALWAYS_INLINE double SQRT(double X)
427 /* If this arch doesn't use IEEE 754 floats, fall back to using libm */
428 if (sizeof(float) != 4)
431 /* This avoids needing libm, saves about 0.5k on x86-32 */
439 gettimeofday(&tv, NULL); /* never fails */
440 G.cur_time = tv.tv_sec + (1.0e-6 * tv.tv_usec) + OFFSET_1900_1970;
445 d_to_tv(double d, struct timeval *tv)
447 tv->tv_sec = (long)d;
448 tv->tv_usec = (d - tv->tv_sec) * 1000000;
452 lfp_to_d(l_fixedpt_t lfp)
455 lfp.int_partl = ntohl(lfp.int_partl);
456 lfp.fractionl = ntohl(lfp.fractionl);
457 ret = (double)lfp.int_partl + ((double)lfp.fractionl / UINT_MAX);
461 sfp_to_d(s_fixedpt_t sfp)
464 sfp.int_parts = ntohs(sfp.int_parts);
465 sfp.fractions = ntohs(sfp.fractions);
466 ret = (double)sfp.int_parts + ((double)sfp.fractions / USHRT_MAX);
469 #if ENABLE_FEATURE_NTPD_SERVER
474 lfp.int_partl = (uint32_t)d;
475 lfp.fractionl = (uint32_t)((d - lfp.int_partl) * UINT_MAX);
476 lfp.int_partl = htonl(lfp.int_partl);
477 lfp.fractionl = htonl(lfp.fractionl);
484 sfp.int_parts = (uint16_t)d;
485 sfp.fractions = (uint16_t)((d - sfp.int_parts) * USHRT_MAX);
486 sfp.int_parts = htons(sfp.int_parts);
487 sfp.fractions = htons(sfp.fractions);
493 dispersion(const datapoint_t *dp)
495 return dp->d_dispersion + FREQ_TOLERANCE * (G.cur_time - dp->d_recv_time);
499 root_distance(peer_t *p)
501 /* The root synchronization distance is the maximum error due to
502 * all causes of the local clock relative to the primary server.
503 * It is defined as half the total delay plus total dispersion
506 return MAXD(MINDISP, p->lastpkt_rootdelay + p->lastpkt_delay) / 2
507 + p->lastpkt_rootdisp
508 + p->filter_dispersion
509 + FREQ_TOLERANCE * (G.cur_time - p->lastpkt_recv_time)
514 set_next(peer_t *p, unsigned t)
516 p->next_action_time = G.cur_time + t;
520 * Peer clock filter and its helpers
523 filter_datapoints(peer_t *p)
530 /* Simulations have shown that use of *averaged* offset for p->filter_offset
531 * is in fact worse than simply using last received one: with large poll intervals
532 * (>= 2048) averaging code uses offset values which are outdated by hours,
533 * and time/frequency correction goes totally wrong when fed essentially bogus offsets.
536 double minoff, maxoff, w;
537 double x = x; /* for compiler */
538 double oldest_off = oldest_off;
539 double oldest_age = oldest_age;
540 double newest_off = newest_off;
541 double newest_age = newest_age;
543 fdp = p->filter_datapoint;
545 minoff = maxoff = fdp[0].d_offset;
546 for (i = 1; i < NUM_DATAPOINTS; i++) {
547 if (minoff > fdp[i].d_offset)
548 minoff = fdp[i].d_offset;
549 if (maxoff < fdp[i].d_offset)
550 maxoff = fdp[i].d_offset;
553 idx = p->datapoint_idx; /* most recent datapoint's index */
555 * Drop two outliers and take weighted average of the rest:
556 * most_recent/2 + older1/4 + older2/8 ... + older5/32 + older6/32
557 * we use older6/32, not older6/64 since sum of weights should be 1:
558 * 1/2 + 1/4 + 1/8 + 1/16 + 1/32 + 1/32 = 1
564 * filter_dispersion = \ -------------
571 for (i = 0; i < NUM_DATAPOINTS; i++) {
573 bb_error_msg("datapoint[%d]: off:%f disp:%f(%f) age:%f%s",
576 fdp[idx].d_dispersion, dispersion(&fdp[idx]),
577 G.cur_time - fdp[idx].d_recv_time,
578 (minoff == fdp[idx].d_offset || maxoff == fdp[idx].d_offset)
579 ? " (outlier by offset)" : ""
583 sum += dispersion(&fdp[idx]) / (2 << i);
585 if (minoff == fdp[idx].d_offset) {
586 minoff -= 1; /* so that we don't match it ever again */
588 if (maxoff == fdp[idx].d_offset) {
591 oldest_off = fdp[idx].d_offset;
592 oldest_age = G.cur_time - fdp[idx].d_recv_time;
595 newest_off = oldest_off;
596 newest_age = oldest_age;
603 idx = (idx - 1) & (NUM_DATAPOINTS - 1);
605 p->filter_dispersion = sum;
606 wavg += x; /* add another older6/64 to form older6/32 */
607 /* Fix systematic underestimation with large poll intervals.
608 * Imagine that we still have a bit of uncorrected drift,
609 * and poll interval is big (say, 100 sec). Offsets form a progression:
610 * 0.0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 - 0.7 is most recent.
611 * The algorithm above drops 0.0 and 0.7 as outliers,
612 * and then we have this estimation, ~25% off from 0.7:
613 * 0.1/32 + 0.2/32 + 0.3/16 + 0.4/8 + 0.5/4 + 0.6/2 = 0.503125
615 x = oldest_age - newest_age;
617 x = newest_age / x; /* in above example, 100 / (600 - 100) */
618 if (x < 1) { /* paranoia check */
619 x = (newest_off - oldest_off) * x; /* 0.5 * 100/500 = 0.1 */
623 p->filter_offset = wavg;
627 fdp = p->filter_datapoint;
628 idx = p->datapoint_idx; /* most recent datapoint's index */
630 /* filter_offset: simply use the most recent value */
631 p->filter_offset = fdp[idx].d_offset;
635 * filter_dispersion = \ -------------
642 for (i = 0; i < NUM_DATAPOINTS; i++) {
643 sum += dispersion(&fdp[idx]) / (2 << i);
644 wavg += fdp[idx].d_offset;
645 idx = (idx - 1) & (NUM_DATAPOINTS - 1);
647 wavg /= NUM_DATAPOINTS;
648 p->filter_dispersion = sum;
651 /* +----- -----+ ^ 1/2
655 * filter_jitter = | --- * / (avg-offset_j) |
659 * where n is the number of valid datapoints in the filter (n > 1);
660 * if filter_jitter < precision then filter_jitter = precision
663 for (i = 0; i < NUM_DATAPOINTS; i++) {
664 sum += SQUARE(wavg - fdp[i].d_offset);
666 sum = SQRT(sum / NUM_DATAPOINTS);
667 p->filter_jitter = sum > G_precision_sec ? sum : G_precision_sec;
669 VERB4 bb_error_msg("filter offset:%+f disp:%f jitter:%f",
671 p->filter_dispersion,
676 reset_peer_stats(peer_t *p, double offset)
679 bool small_ofs = fabs(offset) < 16 * STEP_THRESHOLD;
681 for (i = 0; i < NUM_DATAPOINTS; i++) {
683 p->filter_datapoint[i].d_recv_time += offset;
684 if (p->filter_datapoint[i].d_offset != 0) {
685 p->filter_datapoint[i].d_offset -= offset;
686 //bb_error_msg("p->filter_datapoint[%d].d_offset %f -> %f",
688 // p->filter_datapoint[i].d_offset + offset,
689 // p->filter_datapoint[i].d_offset);
692 p->filter_datapoint[i].d_recv_time = G.cur_time;
693 p->filter_datapoint[i].d_offset = 0;
694 p->filter_datapoint[i].d_dispersion = MAXDISP;
698 p->lastpkt_recv_time += offset;
700 p->reachable_bits = 0;
701 p->lastpkt_recv_time = G.cur_time;
703 filter_datapoints(p); /* recalc p->filter_xxx */
704 VERB6 bb_error_msg("%s->lastpkt_recv_time=%f", p->p_dotted, p->lastpkt_recv_time);
712 p = xzalloc(sizeof(*p));
713 p->p_lsa = xhost2sockaddr(s, 123);
714 p->p_dotted = xmalloc_sockaddr2dotted_noport(&p->p_lsa->u.sa);
716 p->p_xmt_msg.m_status = MODE_CLIENT | (NTP_VERSION << 3);
717 p->next_action_time = G.cur_time; /* = set_next(p, 0); */
718 reset_peer_stats(p, 16 * STEP_THRESHOLD);
720 llist_add_to(&G.ntp_peers, p);
726 const struct sockaddr *from, const struct sockaddr *to, socklen_t addrlen,
727 msg_t *msg, ssize_t len)
733 ret = sendto(fd, msg, len, MSG_DONTWAIT, to, addrlen);
735 ret = send_to_from(fd, msg, len, MSG_DONTWAIT, to, from, addrlen);
738 bb_perror_msg("send failed");
745 send_query_to_peer(peer_t *p)
747 /* Why do we need to bind()?
748 * See what happens when we don't bind:
750 * socket(PF_INET, SOCK_DGRAM, IPPROTO_IP) = 3
751 * setsockopt(3, SOL_IP, IP_TOS, [16], 4) = 0
752 * gettimeofday({1259071266, 327885}, NULL) = 0
753 * sendto(3, "xxx", 48, MSG_DONTWAIT, {sa_family=AF_INET, sin_port=htons(123), sin_addr=inet_addr("10.34.32.125")}, 16) = 48
754 * ^^^ we sent it from some source port picked by kernel.
755 * time(NULL) = 1259071266
756 * write(2, "ntpd: entering poll 15 secs\n", 28) = 28
757 * poll([{fd=3, events=POLLIN}], 1, 15000) = 1 ([{fd=3, revents=POLLIN}])
758 * recv(3, "yyy", 68, MSG_DONTWAIT) = 48
759 * ^^^ this recv will receive packets to any local port!
761 * Uncomment this and use strace to see it in action:
763 #define PROBE_LOCAL_ADDR /* { len_and_sockaddr lsa; lsa.len = LSA_SIZEOF_SA; getsockname(p->query.fd, &lsa.u.sa, &lsa.len); } */
767 len_and_sockaddr *local_lsa;
769 family = p->p_lsa->u.sa.sa_family;
770 p->p_fd = fd = xsocket_type(&local_lsa, family, SOCK_DGRAM);
771 /* local_lsa has "null" address and port 0 now.
772 * bind() ensures we have a *particular port* selected by kernel
773 * and remembered in p->p_fd, thus later recv(p->p_fd)
774 * receives only packets sent to this port.
777 xbind(fd, &local_lsa->u.sa, local_lsa->len);
779 #if ENABLE_FEATURE_IPV6
780 if (family == AF_INET)
782 setsockopt(fd, IPPROTO_IP, IP_TOS, &const_IPTOS_LOWDELAY, sizeof(const_IPTOS_LOWDELAY));
786 /* Emit message _before_ attempted send. Think of a very short
787 * roundtrip networks: we need to go back to recv loop ASAP,
788 * to reduce delay. Printing messages after send works against that.
790 VERB1 bb_error_msg("sending query to %s", p->p_dotted);
793 * Send out a random 64-bit number as our transmit time. The NTP
794 * server will copy said number into the originate field on the
795 * response that it sends us. This is totally legal per the SNTP spec.
797 * The impact of this is two fold: we no longer send out the current
798 * system time for the world to see (which may aid an attacker), and
799 * it gives us a (not very secure) way of knowing that we're not
800 * getting spoofed by an attacker that can't capture our traffic
801 * but can spoof packets from the NTP server we're communicating with.
803 * Save the real transmit timestamp locally.
805 p->p_xmt_msg.m_xmttime.int_partl = random();
806 p->p_xmt_msg.m_xmttime.fractionl = random();
807 p->p_xmttime = gettime1900d();
809 /* Were doing it only if sendto worked, but
810 * loss of sync detection needs reachable_bits updated
811 * even if sending fails *locally*:
812 * "network is unreachable" because cable was pulled?
813 * We still need to declare "unsync" if this condition persists.
815 p->reachable_bits <<= 1;
817 if (do_sendto(p->p_fd, /*from:*/ NULL, /*to:*/ &p->p_lsa->u.sa, /*addrlen:*/ p->p_lsa->len,
818 &p->p_xmt_msg, NTP_MSGSIZE_NOAUTH) == -1
823 * We know that we sent nothing.
824 * We can retry *soon* without fearing
825 * that we are flooding the peer.
827 set_next(p, RETRY_INTERVAL);
831 set_next(p, RESPONSE_INTERVAL);
835 /* Note that there is no provision to prevent several run_scripts
836 * to be started in quick succession. In fact, it happens rather often
837 * if initial syncronization results in a step.
838 * You will see "step" and then "stratum" script runs, sometimes
839 * as close as only 0.002 seconds apart.
840 * Script should be ready to deal with this.
842 static void run_script(const char *action, double offset)
845 char *env1, *env2, *env3, *env4;
847 G.last_script_run = G.cur_time;
852 argv[0] = (char*) G.script_name;
853 argv[1] = (char*) action;
856 VERB1 bb_error_msg("executing '%s %s'", G.script_name, action);
858 env1 = xasprintf("%s=%u", "stratum", G.stratum);
860 env2 = xasprintf("%s=%ld", "freq_drift_ppm", G.kernel_freq_drift);
862 env3 = xasprintf("%s=%u", "poll_interval", 1 << G.poll_exp);
864 env4 = xasprintf("%s=%f", "offset", offset);
866 /* Other items of potential interest: selected peer,
867 * rootdelay, reftime, rootdisp, refid, ntp_status,
868 * last_update_offset, last_update_recv_time, discipline_jitter,
869 * how many peers have reachable_bits = 0?
872 /* Don't want to wait: it may run hwclock --systohc, and that
873 * may take some time (seconds): */
874 /*spawn_and_wait(argv);*/
878 unsetenv("freq_drift_ppm");
879 unsetenv("poll_interval");
888 step_time(double offset)
892 struct timeval tvc, tvn;
893 char buf[sizeof("yyyy-mm-dd hh:mm:ss") + /*paranoia:*/ 4];
896 gettimeofday(&tvc, NULL); /* never fails */
897 dtime = tvc.tv_sec + (1.0e-6 * tvc.tv_usec) + offset;
898 d_to_tv(dtime, &tvn);
899 if (settimeofday(&tvn, NULL) == -1)
900 bb_perror_msg_and_die("settimeofday");
904 strftime_YYYYMMDDHHMMSS(buf, sizeof(buf), &tval);
905 bb_error_msg("current time is %s.%06u", buf, (unsigned)tvc.tv_usec);
908 strftime_YYYYMMDDHHMMSS(buf, sizeof(buf), &tval);
909 bb_error_msg("setting time to %s.%06u (offset %+fs)", buf, (unsigned)tvn.tv_usec, offset);
911 /* Correct various fields which contain time-relative values: */
914 G.cur_time += offset;
915 G.last_update_recv_time += offset;
916 G.last_script_run += offset;
918 /* p->lastpkt_recv_time, p->next_action_time and such: */
919 for (item = G.ntp_peers; item != NULL; item = item->link) {
920 peer_t *pp = (peer_t *) item->data;
921 reset_peer_stats(pp, offset);
922 //bb_error_msg("offset:%+f pp->next_action_time:%f -> %f",
923 // offset, pp->next_action_time, pp->next_action_time + offset);
924 pp->next_action_time += offset;
926 /* We wait for reply from this peer too.
927 * But due to step we are doing, reply's data is no longer
928 * useful (in fact, it'll be bogus). Stop waiting for it.
932 set_next(pp, RETRY_INTERVAL);
939 * Selection and clustering, and their helpers
945 double opt_rd; /* optimization */
948 compare_point_edge(const void *aa, const void *bb)
950 const point_t *a = aa;
951 const point_t *b = bb;
952 if (a->edge < b->edge) {
955 return (a->edge > b->edge);
962 compare_survivor_metric(const void *aa, const void *bb)
964 const survivor_t *a = aa;
965 const survivor_t *b = bb;
966 if (a->metric < b->metric) {
969 return (a->metric > b->metric);
972 fit(peer_t *p, double rd)
974 if ((p->reachable_bits & (p->reachable_bits-1)) == 0) {
975 /* One or zero bits in reachable_bits */
976 VERB4 bb_error_msg("peer %s unfit for selection: unreachable", p->p_dotted);
979 #if 0 /* we filter out such packets earlier */
980 if ((p->lastpkt_status & LI_ALARM) == LI_ALARM
981 || p->lastpkt_stratum >= MAXSTRAT
983 VERB4 bb_error_msg("peer %s unfit for selection: bad status/stratum", p->p_dotted);
987 /* rd is root_distance(p) */
988 if (rd > MAXDIST + FREQ_TOLERANCE * (1 << G.poll_exp)) {
989 VERB4 bb_error_msg("peer %s unfit for selection: root distance too high", p->p_dotted);
993 // /* Do we have a loop? */
994 // if (p->refid == p->dstaddr || p->refid == s.refid)
999 select_and_cluster(void)
1004 int size = 3 * G.peer_cnt;
1005 /* for selection algorithm */
1006 point_t point[size];
1007 unsigned num_points, num_candidates;
1009 unsigned num_falsetickers;
1010 /* for cluster algorithm */
1011 survivor_t survivor[size];
1012 unsigned num_survivors;
1018 if (G.initial_poll_complete) while (item != NULL) {
1021 p = (peer_t *) item->data;
1022 rd = root_distance(p);
1023 offset = p->filter_offset;
1029 VERB5 bb_error_msg("interval: [%f %f %f] %s",
1035 point[num_points].p = p;
1036 point[num_points].type = -1;
1037 point[num_points].edge = offset - rd;
1038 point[num_points].opt_rd = rd;
1040 point[num_points].p = p;
1041 point[num_points].type = 0;
1042 point[num_points].edge = offset;
1043 point[num_points].opt_rd = rd;
1045 point[num_points].p = p;
1046 point[num_points].type = 1;
1047 point[num_points].edge = offset + rd;
1048 point[num_points].opt_rd = rd;
1052 num_candidates = num_points / 3;
1053 if (num_candidates == 0) {
1054 VERB3 bb_error_msg("no valid datapoints%s", ", no peer selected");
1057 //TODO: sorting does not seem to be done in reference code
1058 qsort(point, num_points, sizeof(point[0]), compare_point_edge);
1060 /* Start with the assumption that there are no falsetickers.
1061 * Attempt to find a nonempty intersection interval containing
1062 * the midpoints of all truechimers.
1063 * If a nonempty interval cannot be found, increase the number
1064 * of assumed falsetickers by one and try again.
1065 * If a nonempty interval is found and the number of falsetickers
1066 * is less than the number of truechimers, a majority has been found
1067 * and the midpoint of each truechimer represents
1068 * the candidates available to the cluster algorithm.
1070 num_falsetickers = 0;
1073 unsigned num_midpoints = 0;
1078 for (i = 0; i < num_points; i++) {
1080 * if (point[i].type == -1) c++;
1081 * if (point[i].type == 1) c--;
1082 * and it's simpler to do it this way:
1085 if (c >= num_candidates - num_falsetickers) {
1086 /* If it was c++ and it got big enough... */
1087 low = point[i].edge;
1090 if (point[i].type == 0)
1094 for (i = num_points-1; i >= 0; i--) {
1096 if (c >= num_candidates - num_falsetickers) {
1097 high = point[i].edge;
1100 if (point[i].type == 0)
1103 /* If the number of midpoints is greater than the number
1104 * of allowed falsetickers, the intersection contains at
1105 * least one truechimer with no midpoint - bad.
1106 * Also, interval should be nonempty.
1108 if (num_midpoints <= num_falsetickers && low < high)
1111 if (num_falsetickers * 2 >= num_candidates) {
1112 VERB3 bb_error_msg("falsetickers:%d, candidates:%d%s",
1113 num_falsetickers, num_candidates,
1114 ", no peer selected");
1118 VERB4 bb_error_msg("selected interval: [%f, %f]; candidates:%d falsetickers:%d",
1119 low, high, num_candidates, num_falsetickers);
1123 /* Construct a list of survivors (p, metric)
1124 * from the chime list, where metric is dominated
1125 * first by stratum and then by root distance.
1126 * All other things being equal, this is the order of preference.
1129 for (i = 0; i < num_points; i++) {
1130 if (point[i].edge < low || point[i].edge > high)
1133 survivor[num_survivors].p = p;
1134 /* x.opt_rd == root_distance(p); */
1135 survivor[num_survivors].metric = MAXDIST * p->lastpkt_stratum + point[i].opt_rd;
1136 VERB5 bb_error_msg("survivor[%d] metric:%f peer:%s",
1137 num_survivors, survivor[num_survivors].metric, p->p_dotted);
1140 /* There must be at least MIN_SELECTED survivors to satisfy the
1141 * correctness assertions. Ordinarily, the Byzantine criteria
1142 * require four survivors, but for the demonstration here, one
1145 if (num_survivors < MIN_SELECTED) {
1146 VERB3 bb_error_msg("survivors:%d%s",
1148 ", no peer selected");
1152 //looks like this is ONLY used by the fact that later we pick survivor[0].
1153 //we can avoid sorting then, just find the minimum once!
1154 qsort(survivor, num_survivors, sizeof(survivor[0]), compare_survivor_metric);
1156 /* For each association p in turn, calculate the selection
1157 * jitter p->sjitter as the square root of the sum of squares
1158 * (p->offset - q->offset) over all q associations. The idea is
1159 * to repeatedly discard the survivor with maximum selection
1160 * jitter until a termination condition is met.
1163 unsigned max_idx = max_idx;
1164 double max_selection_jitter = max_selection_jitter;
1165 double min_jitter = min_jitter;
1167 if (num_survivors <= MIN_CLUSTERED) {
1168 VERB4 bb_error_msg("num_survivors %d <= %d, not discarding more",
1169 num_survivors, MIN_CLUSTERED);
1173 /* To make sure a few survivors are left
1174 * for the clustering algorithm to chew on,
1175 * we stop if the number of survivors
1176 * is less than or equal to MIN_CLUSTERED (3).
1178 for (i = 0; i < num_survivors; i++) {
1179 double selection_jitter_sq;
1182 if (i == 0 || p->filter_jitter < min_jitter)
1183 min_jitter = p->filter_jitter;
1185 selection_jitter_sq = 0;
1186 for (j = 0; j < num_survivors; j++) {
1187 peer_t *q = survivor[j].p;
1188 selection_jitter_sq += SQUARE(p->filter_offset - q->filter_offset);
1190 if (i == 0 || selection_jitter_sq > max_selection_jitter) {
1191 max_selection_jitter = selection_jitter_sq;
1194 VERB6 bb_error_msg("survivor %d selection_jitter^2:%f",
1195 i, selection_jitter_sq);
1197 max_selection_jitter = SQRT(max_selection_jitter / num_survivors);
1198 VERB5 bb_error_msg("max_selection_jitter (at %d):%f min_jitter:%f",
1199 max_idx, max_selection_jitter, min_jitter);
1201 /* If the maximum selection jitter is less than the
1202 * minimum peer jitter, then tossing out more survivors
1203 * will not lower the minimum peer jitter, so we might
1206 if (max_selection_jitter < min_jitter) {
1207 VERB4 bb_error_msg("max_selection_jitter:%f < min_jitter:%f, num_survivors:%d, not discarding more",
1208 max_selection_jitter, min_jitter, num_survivors);
1212 /* Delete survivor[max_idx] from the list
1213 * and go around again.
1215 VERB6 bb_error_msg("dropping survivor %d", max_idx);
1217 while (max_idx < num_survivors) {
1218 survivor[max_idx] = survivor[max_idx + 1];
1224 /* Combine the offsets of the clustering algorithm survivors
1225 * using a weighted average with weight determined by the root
1226 * distance. Compute the selection jitter as the weighted RMS
1227 * difference between the first survivor and the remaining
1228 * survivors. In some cases the inherent clock jitter can be
1229 * reduced by not using this algorithm, especially when frequent
1230 * clockhopping is involved. bbox: thus we don't do it.
1234 for (i = 0; i < num_survivors; i++) {
1236 x = root_distance(p);
1238 z += p->filter_offset / x;
1239 w += SQUARE(p->filter_offset - survivor[0].p->filter_offset) / x;
1241 //G.cluster_offset = z / y;
1242 //G.cluster_jitter = SQRT(w / y);
1245 /* Pick the best clock. If the old system peer is on the list
1246 * and at the same stratum as the first survivor on the list,
1247 * then don't do a clock hop. Otherwise, select the first
1248 * survivor on the list as the new system peer.
1251 if (G.last_update_peer
1252 && G.last_update_peer->lastpkt_stratum <= p->lastpkt_stratum
1254 /* Starting from 1 is ok here */
1255 for (i = 1; i < num_survivors; i++) {
1256 if (G.last_update_peer == survivor[i].p) {
1257 VERB5 bb_error_msg("keeping old synced peer");
1258 p = G.last_update_peer;
1263 G.last_update_peer = p;
1265 VERB4 bb_error_msg("selected peer %s filter_offset:%+f age:%f",
1268 G.cur_time - p->lastpkt_recv_time
1275 * Local clock discipline and its helpers
1278 set_new_values(int disc_state, double offset, double recv_time)
1280 /* Enter new state and set state variables. Note we use the time
1281 * of the last clock filter sample, which must be earlier than
1284 VERB4 bb_error_msg("disc_state=%d last update offset=%f recv_time=%f",
1285 disc_state, offset, recv_time);
1286 G.discipline_state = disc_state;
1287 G.last_update_offset = offset;
1288 G.last_update_recv_time = recv_time;
1290 /* Return: -1: decrease poll interval, 0: leave as is, 1: increase */
1292 update_local_clock(peer_t *p)
1296 /* Note: can use G.cluster_offset instead: */
1297 double offset = p->filter_offset;
1298 double recv_time = p->lastpkt_recv_time;
1300 #if !USING_KERNEL_PLL_LOOP
1303 double since_last_update;
1304 double etemp, dtemp;
1306 abs_offset = fabs(offset);
1309 /* If needed, -S script can do it by looking at $offset
1310 * env var and killing parent */
1311 /* If the offset is too large, give up and go home */
1312 if (abs_offset > PANIC_THRESHOLD) {
1313 bb_error_msg_and_die("offset %f far too big, exiting", offset);
1317 /* If this is an old update, for instance as the result
1318 * of a system peer change, avoid it. We never use
1319 * an old sample or the same sample twice.
1321 if (recv_time <= G.last_update_recv_time) {
1322 VERB3 bb_error_msg("update from %s: same or older datapoint, not using it",
1324 return 0; /* "leave poll interval as is" */
1327 /* Clock state machine transition function. This is where the
1328 * action is and defines how the system reacts to large time
1329 * and frequency errors.
1331 since_last_update = recv_time - G.reftime;
1332 #if !USING_KERNEL_PLL_LOOP
1335 #if USING_INITIAL_FREQ_ESTIMATION
1336 if (G.discipline_state == STATE_FREQ) {
1337 /* Ignore updates until the stepout threshold */
1338 if (since_last_update < WATCH_THRESHOLD) {
1339 VERB4 bb_error_msg("measuring drift, datapoint ignored, %f sec remains",
1340 WATCH_THRESHOLD - since_last_update);
1341 return 0; /* "leave poll interval as is" */
1343 # if !USING_KERNEL_PLL_LOOP
1344 freq_drift = (offset - G.last_update_offset) / since_last_update;
1349 /* There are two main regimes: when the
1350 * offset exceeds the step threshold and when it does not.
1352 if (abs_offset > STEP_THRESHOLD) {
1355 // TODO: this "spike state" seems to be useless, peer selection already drops
1356 // occassional "bad" datapoints. If we are here, there were _many_ large offsets -
1357 // looks like _our_ clock is off.
1358 switch (G.discipline_state) {
1360 /* The first outlyer: ignore it, switch to SPIK state */
1361 VERB3 bb_error_msg("update from %s: offset:%+f, spike%s",
1362 p->p_dotted, offset,
1364 G.discipline_state = STATE_SPIK;
1365 return -1; /* "decrease poll interval" */
1368 /* Ignore succeeding outlyers until either an inlyer
1369 * is found or the stepout threshold is exceeded.
1371 remains = WATCH_THRESHOLD - since_last_update;
1373 VERB3 bb_error_msg("update from %s: offset:%+f, spike%s",
1374 p->p_dotted, offset,
1375 ", datapoint ignored");
1376 return -1; /* "decrease poll interval" */
1378 /* fall through: we need to step */
1381 /* Step the time and clamp down the poll interval.
1383 * In NSET state an initial frequency correction is
1384 * not available, usually because the frequency file has
1385 * not yet been written. Since the time is outside the
1386 * capture range, the clock is stepped. The frequency
1387 * will be set directly following the stepout interval.
1389 * In FSET state the initial frequency has been set
1390 * from the frequency file. Since the time is outside
1391 * the capture range, the clock is stepped immediately,
1392 * rather than after the stepout interval. Guys get
1393 * nervous if it takes 17 minutes to set the clock for
1396 * In SPIK state the stepout threshold has expired and
1397 * the phase is still above the step threshold. Note
1398 * that a single spike greater than the step threshold
1399 * is always suppressed, even at the longer poll
1402 VERB4 bb_error_msg("stepping time by %+f; poll_exp=MINPOLL", offset);
1404 if (option_mask32 & OPT_q) {
1405 /* We were only asked to set time once. Done. */
1409 G.polladj_count = 0;
1410 G.poll_exp = MINPOLL;
1411 G.stratum = MAXSTRAT;
1413 run_script("step", offset);
1415 #if USING_INITIAL_FREQ_ESTIMATION
1416 if (G.discipline_state == STATE_NSET) {
1417 set_new_values(STATE_FREQ, /*offset:*/ 0, recv_time);
1418 return 1; /* "ok to increase poll interval" */
1421 abs_offset = offset = 0;
1422 set_new_values(STATE_SYNC, offset, recv_time);
1424 } else { /* abs_offset <= STEP_THRESHOLD */
1426 if (G.poll_exp < MINPOLL && G.initial_poll_complete) {
1427 VERB4 bb_error_msg("small offset:%+f, disabling burst mode", offset);
1428 G.polladj_count = 0;
1429 G.poll_exp = MINPOLL;
1432 /* Compute the clock jitter as the RMS of exponentially
1433 * weighted offset differences. Used by the poll adjust code.
1435 etemp = SQUARE(G.discipline_jitter);
1436 dtemp = SQUARE(offset - G.last_update_offset);
1437 G.discipline_jitter = SQRT(etemp + (dtemp - etemp) / AVG);
1439 switch (G.discipline_state) {
1441 if (option_mask32 & OPT_q) {
1442 /* We were only asked to set time once.
1443 * The clock is precise enough, no need to step.
1447 #if USING_INITIAL_FREQ_ESTIMATION
1448 /* This is the first update received and the frequency
1449 * has not been initialized. The first thing to do
1450 * is directly measure the oscillator frequency.
1452 set_new_values(STATE_FREQ, offset, recv_time);
1454 set_new_values(STATE_SYNC, offset, recv_time);
1456 VERB4 bb_error_msg("transitioning to FREQ, datapoint ignored");
1457 return 0; /* "leave poll interval as is" */
1459 #if 0 /* this is dead code for now */
1461 /* This is the first update and the frequency
1462 * has been initialized. Adjust the phase, but
1463 * don't adjust the frequency until the next update.
1465 set_new_values(STATE_SYNC, offset, recv_time);
1466 /* freq_drift remains 0 */
1470 #if USING_INITIAL_FREQ_ESTIMATION
1472 /* since_last_update >= WATCH_THRESHOLD, we waited enough.
1473 * Correct the phase and frequency and switch to SYNC state.
1474 * freq_drift was already estimated (see code above)
1476 set_new_values(STATE_SYNC, offset, recv_time);
1481 #if !USING_KERNEL_PLL_LOOP
1482 /* Compute freq_drift due to PLL and FLL contributions.
1484 * The FLL and PLL frequency gain constants
1485 * depend on the poll interval and Allan
1486 * intercept. The FLL is not used below one-half
1487 * the Allan intercept. Above that the loop gain
1488 * increases in steps to 1 / AVG.
1490 if ((1 << G.poll_exp) > ALLAN / 2) {
1491 etemp = FLL - G.poll_exp;
1494 freq_drift += (offset - G.last_update_offset) / (MAXD(since_last_update, ALLAN) * etemp);
1496 /* For the PLL the integration interval
1497 * (numerator) is the minimum of the update
1498 * interval and poll interval. This allows
1499 * oversampling, but not undersampling.
1501 etemp = MIND(since_last_update, (1 << G.poll_exp));
1502 dtemp = (4 * PLL) << G.poll_exp;
1503 freq_drift += offset * etemp / SQUARE(dtemp);
1505 set_new_values(STATE_SYNC, offset, recv_time);
1508 if (G.stratum != p->lastpkt_stratum + 1) {
1509 G.stratum = p->lastpkt_stratum + 1;
1510 run_script("stratum", offset);
1514 if (G.discipline_jitter < G_precision_sec)
1515 G.discipline_jitter = G_precision_sec;
1516 G.offset_to_jitter_ratio = abs_offset / G.discipline_jitter;
1518 G.reftime = G.cur_time;
1519 G.ntp_status = p->lastpkt_status;
1520 G.refid = p->lastpkt_refid;
1521 G.rootdelay = p->lastpkt_rootdelay + p->lastpkt_delay;
1522 dtemp = p->filter_jitter; // SQRT(SQUARE(p->filter_jitter) + SQUARE(G.cluster_jitter));
1523 dtemp += MAXD(p->filter_dispersion + FREQ_TOLERANCE * (G.cur_time - p->lastpkt_recv_time) + abs_offset, MINDISP);
1524 G.rootdisp = p->lastpkt_rootdisp + dtemp;
1525 VERB4 bb_error_msg("updating leap/refid/reftime/rootdisp from peer %s", p->p_dotted);
1527 /* We are in STATE_SYNC now, but did not do adjtimex yet.
1528 * (Any other state does not reach this, they all return earlier)
1529 * By this time, freq_drift and offset are set
1530 * to values suitable for adjtimex.
1532 #if !USING_KERNEL_PLL_LOOP
1533 /* Calculate the new frequency drift and frequency stability (wander).
1534 * Compute the clock wander as the RMS of exponentially weighted
1535 * frequency differences. This is not used directly, but can,
1536 * along with the jitter, be a highly useful monitoring and
1539 dtemp = G.discipline_freq_drift + freq_drift;
1540 G.discipline_freq_drift = MAXD(MIND(MAXDRIFT, dtemp), -MAXDRIFT);
1541 etemp = SQUARE(G.discipline_wander);
1542 dtemp = SQUARE(dtemp);
1543 G.discipline_wander = SQRT(etemp + (dtemp - etemp) / AVG);
1545 VERB4 bb_error_msg("discipline freq_drift=%.9f(int:%ld corr:%e) wander=%f",
1546 G.discipline_freq_drift,
1547 (long)(G.discipline_freq_drift * 65536e6),
1549 G.discipline_wander);
1552 memset(&tmx, 0, sizeof(tmx));
1553 if (adjtimex(&tmx) < 0)
1554 bb_perror_msg_and_die("adjtimex");
1555 bb_error_msg("p adjtimex freq:%ld offset:%+ld status:0x%x tc:%ld",
1556 tmx.freq, tmx.offset, tmx.status, tmx.constant);
1559 memset(&tmx, 0, sizeof(tmx));
1561 //doesn't work, offset remains 0 (!) in kernel:
1562 //ntpd: set adjtimex freq:1786097 tmx.offset:77487
1563 //ntpd: prev adjtimex freq:1786097 tmx.offset:0
1564 //ntpd: cur adjtimex freq:1786097 tmx.offset:0
1565 tmx.modes = ADJ_FREQUENCY | ADJ_OFFSET;
1566 /* 65536 is one ppm */
1567 tmx.freq = G.discipline_freq_drift * 65536e6;
1569 tmx.modes = ADJ_OFFSET | ADJ_STATUS | ADJ_TIMECONST;// | ADJ_MAXERROR | ADJ_ESTERROR;
1570 tmx.offset = (offset * 1000000); /* usec */
1571 tmx.status = STA_PLL;
1572 if (G.ntp_status & LI_PLUSSEC)
1573 tmx.status |= STA_INS;
1574 if (G.ntp_status & LI_MINUSSEC)
1575 tmx.status |= STA_DEL;
1577 tmx.constant = G.poll_exp - 4;
1579 * The below if statement should be unnecessary, but...
1580 * It looks like Linux kernel's PLL is far too gentle in changing
1581 * tmx.freq in response to clock offset. Offset keeps growing
1582 * and eventually we fall back to smaller poll intervals.
1583 * We can make correction more agressive (about x2) by supplying
1584 * PLL time constant which is one less than the real one.
1585 * To be on a safe side, let's do it only if offset is significantly
1586 * larger than jitter.
1588 if (tmx.constant > 0 && G.offset_to_jitter_ratio >= TIMECONST_HACK_GATE)
1591 //tmx.esterror = (uint32_t)(clock_jitter * 1e6);
1592 //tmx.maxerror = (uint32_t)((sys_rootdelay / 2 + sys_rootdisp) * 1e6);
1593 rc = adjtimex(&tmx);
1595 bb_perror_msg_and_die("adjtimex");
1596 /* NB: here kernel returns constant == G.poll_exp, not == G.poll_exp - 4.
1597 * Not sure why. Perhaps it is normal.
1599 VERB4 bb_error_msg("adjtimex:%d freq:%ld offset:%+ld status:0x%x",
1600 rc, tmx.freq, tmx.offset, tmx.status);
1601 G.kernel_freq_drift = tmx.freq / 65536;
1602 VERB2 bb_error_msg("update from:%s offset:%+f jitter:%f clock drift:%+.3fppm tc:%d",
1603 p->p_dotted, offset, G.discipline_jitter, (double)tmx.freq / 65536, (int)tmx.constant);
1605 return 1; /* "ok to increase poll interval" */
1610 * We've got a new reply packet from a peer, process it
1614 retry_interval(void)
1616 /* Local problem, want to retry soon */
1617 unsigned interval, r;
1618 interval = RETRY_INTERVAL;
1620 interval += r % (unsigned)(RETRY_INTERVAL / 4);
1621 VERB4 bb_error_msg("chose retry interval:%u", interval);
1625 poll_interval(int exponent)
1627 unsigned interval, r;
1628 exponent = G.poll_exp + exponent;
1631 interval = 1 << exponent;
1633 interval += ((r & (interval-1)) >> 4) + ((r >> 8) & 1); /* + 1/16 of interval, max */
1634 VERB4 bb_error_msg("chose poll interval:%u (poll_exp:%d exp:%d)", interval, G.poll_exp, exponent);
1637 static NOINLINE void
1638 recv_and_process_peer_pkt(peer_t *p)
1643 double T1, T2, T3, T4;
1646 datapoint_t *datapoint;
1649 /* We can recvfrom here and check from.IP, but some multihomed
1650 * ntp servers reply from their *other IP*.
1651 * TODO: maybe we should check at least what we can: from.port == 123?
1653 size = recv(p->p_fd, &msg, sizeof(msg), MSG_DONTWAIT);
1655 bb_perror_msg("recv(%s) error", p->p_dotted);
1656 if (errno == EHOSTUNREACH || errno == EHOSTDOWN
1657 || errno == ENETUNREACH || errno == ENETDOWN
1658 || errno == ECONNREFUSED || errno == EADDRNOTAVAIL
1661 //TODO: always do this?
1662 interval = retry_interval();
1663 goto set_next_and_ret;
1668 if (size != NTP_MSGSIZE_NOAUTH && size != NTP_MSGSIZE) {
1669 bb_error_msg("malformed packet received from %s", p->p_dotted);
1673 if (msg.m_orgtime.int_partl != p->p_xmt_msg.m_xmttime.int_partl
1674 || msg.m_orgtime.fractionl != p->p_xmt_msg.m_xmttime.fractionl
1676 /* Somebody else's packet */
1680 /* We do not expect any more packets from this peer for now.
1681 * Closing the socket informs kernel about it.
1682 * We open a new socket when we send a new query.
1687 if ((msg.m_status & LI_ALARM) == LI_ALARM
1688 || msg.m_stratum == 0
1689 || msg.m_stratum > NTP_MAXSTRATUM
1691 // TODO: stratum 0 responses may have commands in 32-bit m_refid field:
1692 // "DENY", "RSTR" - peer does not like us at all
1693 // "RATE" - peer is overloaded, reduce polling freq
1694 bb_error_msg("reply from %s: peer is unsynced", p->p_dotted);
1695 goto pick_normal_interval;
1698 // /* Verify valid root distance */
1699 // if (msg.m_rootdelay / 2 + msg.m_rootdisp >= MAXDISP || p->lastpkt_reftime > msg.m_xmt)
1700 // return; /* invalid header values */
1702 p->lastpkt_status = msg.m_status;
1703 p->lastpkt_stratum = msg.m_stratum;
1704 p->lastpkt_rootdelay = sfp_to_d(msg.m_rootdelay);
1705 p->lastpkt_rootdisp = sfp_to_d(msg.m_rootdisp);
1706 p->lastpkt_refid = msg.m_refid;
1709 * From RFC 2030 (with a correction to the delay math):
1711 * Timestamp Name ID When Generated
1712 * ------------------------------------------------------------
1713 * Originate Timestamp T1 time request sent by client
1714 * Receive Timestamp T2 time request received by server
1715 * Transmit Timestamp T3 time reply sent by server
1716 * Destination Timestamp T4 time reply received by client
1718 * The roundtrip delay and local clock offset are defined as
1720 * delay = (T4 - T1) - (T3 - T2); offset = ((T2 - T1) + (T3 - T4)) / 2
1723 T2 = lfp_to_d(msg.m_rectime);
1724 T3 = lfp_to_d(msg.m_xmttime);
1727 p->lastpkt_recv_time = T4;
1728 VERB6 bb_error_msg("%s->lastpkt_recv_time=%f", p->p_dotted, p->lastpkt_recv_time);
1730 /* The delay calculation is a special case. In cases where the
1731 * server and client clocks are running at different rates and
1732 * with very fast networks, the delay can appear negative. In
1733 * order to avoid violating the Principle of Least Astonishment,
1734 * the delay is clamped not less than the system precision.
1736 dv = p->lastpkt_delay;
1737 p->lastpkt_delay = (T4 - T1) - (T3 - T2);
1738 if (p->lastpkt_delay < G_precision_sec)
1739 p->lastpkt_delay = G_precision_sec;
1741 * If this packet's delay is much bigger than the last one,
1742 * it's better to just ignore it than use its much less precise value.
1744 if (p->reachable_bits && p->lastpkt_delay > dv * BAD_DELAY_GROWTH) {
1745 bb_error_msg("reply from %s: delay %f is too high, ignoring", p->p_dotted, p->lastpkt_delay);
1746 goto pick_normal_interval;
1749 p->datapoint_idx = p->reachable_bits ? (p->datapoint_idx + 1) % NUM_DATAPOINTS : 0;
1750 datapoint = &p->filter_datapoint[p->datapoint_idx];
1751 datapoint->d_recv_time = T4;
1752 datapoint->d_offset = ((T2 - T1) + (T3 - T4)) / 2;
1753 datapoint->d_dispersion = LOG2D(msg.m_precision_exp) + G_precision_sec;
1754 if (!p->reachable_bits) {
1755 /* 1st datapoint ever - replicate offset in every element */
1757 for (i = 0; i < NUM_DATAPOINTS; i++) {
1758 p->filter_datapoint[i].d_offset = datapoint->d_offset;
1762 p->reachable_bits |= 1;
1763 if ((MAX_VERBOSE && G.verbose) || (option_mask32 & OPT_w)) {
1764 bb_error_msg("reply from %s: offset:%+f delay:%f status:0x%02x strat:%d refid:0x%08x rootdelay:%f reach:0x%02x",
1766 datapoint->d_offset,
1771 p->lastpkt_rootdelay,
1773 /* not shown: m_ppoll, m_precision_exp, m_rootdisp,
1774 * m_reftime, m_orgtime, m_rectime, m_xmttime
1779 /* Muck with statictics and update the clock */
1780 filter_datapoints(p);
1781 q = select_and_cluster();
1785 if (!(option_mask32 & OPT_w)) {
1786 rc = update_local_clock(q);
1787 /* If drift is dangerously large, immediately
1788 * drop poll interval one step down.
1790 if (fabs(q->filter_offset) >= POLLDOWN_OFFSET) {
1791 VERB4 bb_error_msg("offset:%+f > POLLDOWN_OFFSET", q->filter_offset);
1796 /* else: no peer selected, rc = -1: we want to poll more often */
1799 /* Adjust the poll interval by comparing the current offset
1800 * with the clock jitter. If the offset is less than
1801 * the clock jitter times a constant, then the averaging interval
1802 * is increased, otherwise it is decreased. A bit of hysteresis
1803 * helps calm the dance. Works best using burst mode.
1805 if (rc > 0 && G.offset_to_jitter_ratio <= POLLADJ_GATE) {
1806 /* was += G.poll_exp but it is a bit
1807 * too optimistic for my taste at high poll_exp's */
1808 G.polladj_count += MINPOLL;
1809 if (G.polladj_count > POLLADJ_LIMIT) {
1810 G.polladj_count = 0;
1811 if (G.poll_exp < MAXPOLL) {
1813 VERB4 bb_error_msg("polladj: discipline_jitter:%f ++poll_exp=%d",
1814 G.discipline_jitter, G.poll_exp);
1817 VERB4 bb_error_msg("polladj: incr:%d", G.polladj_count);
1820 G.polladj_count -= G.poll_exp * 2;
1821 if (G.polladj_count < -POLLADJ_LIMIT || G.poll_exp >= BIGPOLL) {
1823 G.polladj_count = 0;
1824 if (G.poll_exp > MINPOLL) {
1828 /* Correct p->next_action_time in each peer
1829 * which waits for sending, so that they send earlier.
1830 * Old pp->next_action_time are on the order
1831 * of t + (1 << old_poll_exp) + small_random,
1832 * we simply need to subtract ~half of that.
1834 for (item = G.ntp_peers; item != NULL; item = item->link) {
1835 peer_t *pp = (peer_t *) item->data;
1837 pp->next_action_time -= (1 << G.poll_exp);
1839 VERB4 bb_error_msg("polladj: discipline_jitter:%f --poll_exp=%d",
1840 G.discipline_jitter, G.poll_exp);
1843 VERB4 bb_error_msg("polladj: decr:%d", G.polladj_count);
1848 /* Decide when to send new query for this peer */
1849 pick_normal_interval:
1850 interval = poll_interval(0);
1853 set_next(p, interval);
1856 #if ENABLE_FEATURE_NTPD_SERVER
1857 static NOINLINE void
1858 recv_and_process_client_pkt(void /*int fd*/)
1862 len_and_sockaddr *to;
1863 struct sockaddr *from;
1865 uint8_t query_status;
1866 l_fixedpt_t query_xmttime;
1868 to = get_sock_lsa(G_listen_fd);
1869 from = xzalloc(to->len);
1871 size = recv_from_to(G_listen_fd, &msg, sizeof(msg), MSG_DONTWAIT, from, &to->u.sa, to->len);
1872 if (size != NTP_MSGSIZE_NOAUTH && size != NTP_MSGSIZE) {
1875 if (errno == EAGAIN)
1877 bb_perror_msg_and_die("recv");
1879 addr = xmalloc_sockaddr2dotted_noport(from);
1880 bb_error_msg("malformed packet received from %s: size %u", addr, (int)size);
1885 query_status = msg.m_status;
1886 query_xmttime = msg.m_xmttime;
1888 /* Build a reply packet */
1889 memset(&msg, 0, sizeof(msg));
1890 msg.m_status = G.stratum < MAXSTRAT ? (G.ntp_status & LI_MASK) : LI_ALARM;
1891 msg.m_status |= (query_status & VERSION_MASK);
1892 msg.m_status |= ((query_status & MODE_MASK) == MODE_CLIENT) ?
1893 MODE_SERVER : MODE_SYM_PAS;
1894 msg.m_stratum = G.stratum;
1895 msg.m_ppoll = G.poll_exp;
1896 msg.m_precision_exp = G_precision_exp;
1897 /* this time was obtained between poll() and recv() */
1898 msg.m_rectime = d_to_lfp(G.cur_time);
1899 msg.m_xmttime = d_to_lfp(gettime1900d()); /* this instant */
1900 if (G.peer_cnt == 0) {
1901 /* we have no peers: "stratum 1 server" mode. reftime = our own time */
1902 G.reftime = G.cur_time;
1904 msg.m_reftime = d_to_lfp(G.reftime);
1905 msg.m_orgtime = query_xmttime;
1906 msg.m_rootdelay = d_to_sfp(G.rootdelay);
1907 //simple code does not do this, fix simple code!
1908 msg.m_rootdisp = d_to_sfp(G.rootdisp);
1909 //version = (query_status & VERSION_MASK); /* ... >> VERSION_SHIFT - done below instead */
1910 msg.m_refid = G.refid; // (version > (3 << VERSION_SHIFT)) ? G.refid : G.refid3;
1912 /* We reply from the local address packet was sent to,
1913 * this makes to/from look swapped here: */
1914 do_sendto(G_listen_fd,
1915 /*from:*/ &to->u.sa, /*to:*/ from, /*addrlen:*/ to->len,
1924 /* Upstream ntpd's options:
1926 * -4 Force DNS resolution of host names to the IPv4 namespace.
1927 * -6 Force DNS resolution of host names to the IPv6 namespace.
1928 * -a Require cryptographic authentication for broadcast client,
1929 * multicast client and symmetric passive associations.
1930 * This is the default.
1931 * -A Do not require cryptographic authentication for broadcast client,
1932 * multicast client and symmetric passive associations.
1933 * This is almost never a good idea.
1934 * -b Enable the client to synchronize to broadcast servers.
1936 * Specify the name and path of the configuration file,
1937 * default /etc/ntp.conf
1938 * -d Specify debugging mode. This option may occur more than once,
1939 * with each occurrence indicating greater detail of display.
1941 * Specify debugging level directly.
1943 * Specify the name and path of the frequency file.
1944 * This is the same operation as the "driftfile FILE"
1945 * configuration command.
1946 * -g Normally, ntpd exits with a message to the system log
1947 * if the offset exceeds the panic threshold, which is 1000 s
1948 * by default. This option allows the time to be set to any value
1949 * without restriction; however, this can happen only once.
1950 * If the threshold is exceeded after that, ntpd will exit
1951 * with a message to the system log. This option can be used
1952 * with the -q and -x options. See the tinker command for other options.
1954 * Chroot the server to the directory jaildir. This option also implies
1955 * that the server attempts to drop root privileges at startup
1956 * (otherwise, chroot gives very little additional security).
1957 * You may need to also specify a -u option.
1959 * Specify the name and path of the symmetric key file,
1960 * default /etc/ntp/keys. This is the same operation
1961 * as the "keys FILE" configuration command.
1963 * Specify the name and path of the log file. The default
1964 * is the system log file. This is the same operation as
1965 * the "logfile FILE" configuration command.
1966 * -L Do not listen to virtual IPs. The default is to listen.
1968 * -N To the extent permitted by the operating system,
1969 * run the ntpd at the highest priority.
1971 * Specify the name and path of the file used to record the ntpd
1972 * process ID. This is the same operation as the "pidfile FILE"
1973 * configuration command.
1975 * To the extent permitted by the operating system,
1976 * run the ntpd at the specified priority.
1977 * -q Exit the ntpd just after the first time the clock is set.
1978 * This behavior mimics that of the ntpdate program, which is
1979 * to be retired. The -g and -x options can be used with this option.
1980 * Note: The kernel time discipline is disabled with this option.
1982 * Specify the default propagation delay from the broadcast/multicast
1983 * server to this client. This is necessary only if the delay
1984 * cannot be computed automatically by the protocol.
1986 * Specify the directory path for files created by the statistics
1987 * facility. This is the same operation as the "statsdir DIR"
1988 * configuration command.
1990 * Add a key number to the trusted key list. This option can occur
1993 * Specify a user, and optionally a group, to switch to.
1996 * Add a system variable listed by default.
1997 * -x Normally, the time is slewed if the offset is less than the step
1998 * threshold, which is 128 ms by default, and stepped if above
1999 * the threshold. This option sets the threshold to 600 s, which is
2000 * well within the accuracy window to set the clock manually.
2001 * Note: since the slew rate of typical Unix kernels is limited
2002 * to 0.5 ms/s, each second of adjustment requires an amortization
2003 * interval of 2000 s. Thus, an adjustment as much as 600 s
2004 * will take almost 14 days to complete. This option can be used
2005 * with the -g and -q options. See the tinker command for other options.
2006 * Note: The kernel time discipline is disabled with this option.
2009 /* By doing init in a separate function we decrease stack usage
2012 static NOINLINE void ntp_init(char **argv)
2020 bb_error_msg_and_die(bb_msg_you_must_be_root);
2022 /* Set some globals */
2023 G.stratum = MAXSTRAT;
2025 G.poll_exp = BURSTPOLL; /* speeds up initial sync */
2026 G.last_script_run = G.reftime = G.last_update_recv_time = gettime1900d(); /* sets G.cur_time too */
2030 opt_complementary = "dd:p::wn"; /* d: counter; p: list; -w implies -n */
2031 opts = getopt32(argv,
2033 "wp:S:"IF_FEATURE_NTPD_SERVER("l") /* NOT compat */
2035 "46aAbgL", /* compat, ignored */
2036 &peers, &G.script_name, &G.verbose);
2037 if (!(opts & (OPT_p|OPT_l)))
2039 // if (opts & OPT_x) /* disable stepping, only slew is allowed */
2040 // G.time_was_stepped = 1;
2043 add_peers(llist_pop(&peers));
2045 /* -l but no peers: "stratum 1 server" mode */
2048 if (!(opts & OPT_n)) {
2049 bb_daemonize_or_rexec(DAEMON_DEVNULL_STDIO, argv);
2050 logmode = LOGMODE_NONE;
2052 #if ENABLE_FEATURE_NTPD_SERVER
2055 G_listen_fd = create_and_bind_dgram_or_die(NULL, 123);
2056 socket_want_pktinfo(G_listen_fd);
2057 setsockopt(G_listen_fd, IPPROTO_IP, IP_TOS, &const_IPTOS_LOWDELAY, sizeof(const_IPTOS_LOWDELAY));
2060 /* I hesitate to set -20 prio. -15 should be high enough for timekeeping */
2062 setpriority(PRIO_PROCESS, 0, -15);
2064 /* If network is up, syncronization occurs in ~10 seconds.
2065 * We give "ntpd -q" 10 seconds to get first reply,
2066 * then another 50 seconds to finish syncing.
2068 * I tested ntpd 4.2.6p1 and apparently it never exits
2069 * (will try forever), but it does not feel right.
2070 * The goal of -q is to act like ntpdate: set time
2071 * after a reasonably small period of polling, or fail.
2074 option_mask32 |= OPT_qq;
2091 int ntpd_main(int argc UNUSED_PARAM, char **argv) MAIN_EXTERNALLY_VISIBLE;
2092 int ntpd_main(int argc UNUSED_PARAM, char **argv)
2100 memset(&G, 0, sizeof(G));
2101 SET_PTR_TO_GLOBALS(&G);
2105 /* If ENABLE_FEATURE_NTPD_SERVER, + 1 for listen_fd: */
2106 cnt = G.peer_cnt + ENABLE_FEATURE_NTPD_SERVER;
2107 idx2peer = xzalloc(sizeof(idx2peer[0]) * cnt);
2108 pfd = xzalloc(sizeof(pfd[0]) * cnt);
2110 /* Countdown: we never sync before we sent INITIAL_SAMPLES+1
2111 * packets to each peer.
2112 * NB: if some peer is not responding, we may end up sending
2113 * fewer packets to it and more to other peers.
2114 * NB2: sync usually happens using INITIAL_SAMPLES packets,
2115 * since last reply does not come back instantaneously.
2117 cnt = G.peer_cnt * (INITIAL_SAMPLES + 1);
2119 write_pidfile(CONFIG_PID_FILE_PATH "/ntpd.pid");
2121 while (!bb_got_signal) {
2127 /* Nothing between here and poll() blocks for any significant time */
2129 nextaction = G.cur_time + 3600;
2132 #if ENABLE_FEATURE_NTPD_SERVER
2133 if (G_listen_fd != -1) {
2134 pfd[0].fd = G_listen_fd;
2135 pfd[0].events = POLLIN;
2139 /* Pass over peer list, send requests, time out on receives */
2140 for (item = G.ntp_peers; item != NULL; item = item->link) {
2141 peer_t *p = (peer_t *) item->data;
2143 if (p->next_action_time <= G.cur_time) {
2144 if (p->p_fd == -1) {
2145 /* Time to send new req */
2147 G.initial_poll_complete = 1;
2149 send_query_to_peer(p);
2151 /* Timed out waiting for reply */
2154 timeout = poll_interval(-2); /* -2: try a bit sooner */
2155 bb_error_msg("timed out waiting for %s, reach 0x%02x, next query in %us",
2156 p->p_dotted, p->reachable_bits, timeout);
2157 set_next(p, timeout);
2161 if (p->next_action_time < nextaction)
2162 nextaction = p->next_action_time;
2165 /* Wait for reply from this peer */
2166 pfd[i].fd = p->p_fd;
2167 pfd[i].events = POLLIN;
2173 timeout = nextaction - G.cur_time;
2176 timeout++; /* (nextaction - G.cur_time) rounds down, compensating */
2178 /* Here we may block */
2180 if (i > (ENABLE_FEATURE_NTPD_SERVER && G_listen_fd != -1)) {
2181 /* We wait for at least one reply.
2182 * Poll for it, without wasting time for message.
2183 * Since replies often come under 1 second, this also
2184 * reduces clutter in logs.
2186 nfds = poll(pfd, i, 1000);
2192 bb_error_msg("poll:%us sockets:%u interval:%us", timeout, i, 1 << G.poll_exp);
2194 nfds = poll(pfd, i, timeout * 1000);
2196 gettime1900d(); /* sets G.cur_time */
2198 if (!bb_got_signal /* poll wasn't interrupted by a signal */
2199 && G.cur_time - G.last_script_run > 11*60
2201 /* Useful for updating battery-backed RTC and such */
2202 run_script("periodic", G.last_update_offset);
2203 gettime1900d(); /* sets G.cur_time */
2208 /* Process any received packets */
2210 #if ENABLE_FEATURE_NTPD_SERVER
2211 if (G.listen_fd != -1) {
2212 if (pfd[0].revents /* & (POLLIN|POLLERR)*/) {
2214 recv_and_process_client_pkt(/*G.listen_fd*/);
2215 gettime1900d(); /* sets G.cur_time */
2220 for (; nfds != 0 && j < i; j++) {
2221 if (pfd[j].revents /* & (POLLIN|POLLERR)*/) {
2223 * At init, alarm was set to 10 sec.
2224 * Now we did get a reply.
2225 * Increase timeout to 50 seconds to finish syncing.
2227 if (option_mask32 & OPT_qq) {
2228 option_mask32 &= ~OPT_qq;
2232 recv_and_process_peer_pkt(idx2peer[j]);
2233 gettime1900d(); /* sets G.cur_time */
2238 if (G.ntp_peers && G.stratum != MAXSTRAT) {
2239 for (item = G.ntp_peers; item != NULL; item = item->link) {
2240 peer_t *p = (peer_t *) item->data;
2241 if (p->reachable_bits)
2242 goto have_reachable_peer;
2244 /* No peer responded for last 8 packets, panic */
2245 G.polladj_count = 0;
2246 G.poll_exp = MINPOLL;
2247 G.stratum = MAXSTRAT;
2248 run_script("unsync", 0.0);
2249 have_reachable_peer: ;
2251 } /* while (!bb_got_signal) */
2253 remove_pidfile(CONFIG_PID_FILE_PATH "/ntpd.pid");
2254 kill_myself_with_sig(bb_got_signal);
2262 /*** openntpd-4.6 uses only adjtime, not adjtimex ***/
2264 /*** ntp-4.2.6/ntpd/ntp_loopfilter.c - adjtimex usage ***/
2268 direct_freq(double fp_offset)
2272 * If the kernel is enabled, we need the residual offset to
2273 * calculate the frequency correction.
2275 if (pll_control && kern_enable) {
2276 memset(&ntv, 0, sizeof(ntv));
2279 clock_offset = ntv.offset / 1e9;
2280 #else /* STA_NANO */
2281 clock_offset = ntv.offset / 1e6;
2282 #endif /* STA_NANO */
2283 drift_comp = FREQTOD(ntv.freq);
2285 #endif /* KERNEL_PLL */
2286 set_freq((fp_offset - clock_offset) / (current_time - clock_epoch) + drift_comp);
2292 set_freq(double freq) /* frequency update */
2300 * If the kernel is enabled, update the kernel frequency.
2302 if (pll_control && kern_enable) {
2303 memset(&ntv, 0, sizeof(ntv));
2304 ntv.modes = MOD_FREQUENCY;
2305 ntv.freq = DTOFREQ(drift_comp);
2307 snprintf(tbuf, sizeof(tbuf), "kernel %.3f PPM", drift_comp * 1e6);
2308 report_event(EVNT_FSET, NULL, tbuf);
2310 snprintf(tbuf, sizeof(tbuf), "ntpd %.3f PPM", drift_comp * 1e6);
2311 report_event(EVNT_FSET, NULL, tbuf);
2313 #else /* KERNEL_PLL */
2314 snprintf(tbuf, sizeof(tbuf), "ntpd %.3f PPM", drift_comp * 1e6);
2315 report_event(EVNT_FSET, NULL, tbuf);
2316 #endif /* KERNEL_PLL */
2325 * This code segment works when clock adjustments are made using
2326 * precision time kernel support and the ntp_adjtime() system
2327 * call. This support is available in Solaris 2.6 and later,
2328 * Digital Unix 4.0 and later, FreeBSD, Linux and specially
2329 * modified kernels for HP-UX 9 and Ultrix 4. In the case of the
2330 * DECstation 5000/240 and Alpha AXP, additional kernel
2331 * modifications provide a true microsecond clock and nanosecond
2332 * clock, respectively.
2334 * Important note: The kernel discipline is used only if the
2335 * step threshold is less than 0.5 s, as anything higher can
2336 * lead to overflow problems. This might occur if some misguided
2337 * lad set the step threshold to something ridiculous.
2339 if (pll_control && kern_enable) {
2341 #define MOD_BITS (MOD_OFFSET | MOD_MAXERROR | MOD_ESTERROR | MOD_STATUS | MOD_TIMECONST)
2344 * We initialize the structure for the ntp_adjtime()
2345 * system call. We have to convert everything to
2346 * microseconds or nanoseconds first. Do not update the
2347 * system variables if the ext_enable flag is set. In
2348 * this case, the external clock driver will update the
2349 * variables, which will be read later by the local
2350 * clock driver. Afterwards, remember the time and
2351 * frequency offsets for jitter and stability values and
2352 * to update the frequency file.
2354 memset(&ntv, 0, sizeof(ntv));
2356 ntv.modes = MOD_STATUS;
2359 ntv.modes = MOD_BITS | MOD_NANO;
2360 #else /* STA_NANO */
2361 ntv.modes = MOD_BITS;
2362 #endif /* STA_NANO */
2363 if (clock_offset < 0)
2368 ntv.offset = (int32)(clock_offset * 1e9 + dtemp);
2369 ntv.constant = sys_poll;
2370 #else /* STA_NANO */
2371 ntv.offset = (int32)(clock_offset * 1e6 + dtemp);
2372 ntv.constant = sys_poll - 4;
2373 #endif /* STA_NANO */
2374 ntv.esterror = (u_int32)(clock_jitter * 1e6);
2375 ntv.maxerror = (u_int32)((sys_rootdelay / 2 + sys_rootdisp) * 1e6);
2376 ntv.status = STA_PLL;
2379 * Enable/disable the PPS if requested.
2382 if (!(pll_status & STA_PPSTIME))
2383 report_event(EVNT_KERN,
2384 NULL, "PPS enabled");
2385 ntv.status |= STA_PPSTIME | STA_PPSFREQ;
2387 if (pll_status & STA_PPSTIME)
2388 report_event(EVNT_KERN,
2389 NULL, "PPS disabled");
2390 ntv.status &= ~(STA_PPSTIME | STA_PPSFREQ);
2392 if (sys_leap == LEAP_ADDSECOND)
2393 ntv.status |= STA_INS;
2394 else if (sys_leap == LEAP_DELSECOND)
2395 ntv.status |= STA_DEL;
2399 * Pass the stuff to the kernel. If it squeals, turn off
2400 * the pps. In any case, fetch the kernel offset,
2401 * frequency and jitter.
2403 if (ntp_adjtime(&ntv) == TIME_ERROR) {
2404 if (!(ntv.status & STA_PPSSIGNAL))
2405 report_event(EVNT_KERN, NULL,
2408 pll_status = ntv.status;
2410 clock_offset = ntv.offset / 1e9;
2411 #else /* STA_NANO */
2412 clock_offset = ntv.offset / 1e6;
2413 #endif /* STA_NANO */
2414 clock_frequency = FREQTOD(ntv.freq);
2417 * If the kernel PPS is lit, monitor its performance.
2419 if (ntv.status & STA_PPSTIME) {
2421 clock_jitter = ntv.jitter / 1e9;
2422 #else /* STA_NANO */
2423 clock_jitter = ntv.jitter / 1e6;
2424 #endif /* STA_NANO */
2427 #if defined(STA_NANO) && NTP_API == 4
2429 * If the TAI changes, update the kernel TAI.
2431 if (loop_tai != sys_tai) {
2433 ntv.modes = MOD_TAI;
2434 ntv.constant = sys_tai;
2437 #endif /* STA_NANO */
2439 #endif /* KERNEL_PLL */