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 5 is very talkative (and bloated). 2 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)
372 static double LOG2D(int a)
375 return 1.0 / (1UL << -a);
378 static ALWAYS_INLINE double SQUARE(double x)
382 static ALWAYS_INLINE double MAXD(double a, double b)
388 static ALWAYS_INLINE double MIND(double a, double b)
394 static NOINLINE double my_SQRT(double X)
401 double Xhalf = X * 0.5;
403 /* Fast and good approximation to 1/sqrt(X), black magic */
405 /*v.i = 0x5f3759df - (v.i >> 1);*/
406 v.i = 0x5f375a86 - (v.i >> 1); /* - this constant is slightly better */
407 invsqrt = v.f; /* better than 0.2% accuracy */
409 /* Refining it using Newton's method: x1 = x0 - f(x0)/f'(x0)
410 * f(x) = 1/(x*x) - X (f==0 when x = 1/sqrt(X))
412 * f(x)/f'(x) = (X - 1/(x*x)) / (2/(x*x*x)) = X*x*x*x/2 - x/2
413 * x1 = x0 - (X*x0*x0*x0/2 - x0/2) = 1.5*x0 - X*x0*x0*x0/2 = x0*(1.5 - (X/2)*x0*x0)
415 invsqrt = invsqrt * (1.5 - Xhalf * invsqrt * invsqrt); /* ~0.05% accuracy */
416 /* invsqrt = invsqrt * (1.5 - Xhalf * invsqrt * invsqrt); 2nd iter: ~0.0001% accuracy */
417 /* With 4 iterations, more than half results will be exact,
418 * at 6th iterations result stabilizes with about 72% results exact.
419 * We are well satisfied with 0.05% accuracy.
422 return X * invsqrt; /* X * 1/sqrt(X) ~= sqrt(X) */
424 static ALWAYS_INLINE double SQRT(double X)
426 /* If this arch doesn't use IEEE 754 floats, fall back to using libm */
427 if (sizeof(float) != 4)
430 /* This avoids needing libm, saves about 0.5k on x86-32 */
438 gettimeofday(&tv, NULL); /* never fails */
439 G.cur_time = tv.tv_sec + (1.0e-6 * tv.tv_usec) + OFFSET_1900_1970;
444 d_to_tv(double d, struct timeval *tv)
446 tv->tv_sec = (long)d;
447 tv->tv_usec = (d - tv->tv_sec) * 1000000;
451 lfp_to_d(l_fixedpt_t lfp)
454 lfp.int_partl = ntohl(lfp.int_partl);
455 lfp.fractionl = ntohl(lfp.fractionl);
456 ret = (double)lfp.int_partl + ((double)lfp.fractionl / UINT_MAX);
460 sfp_to_d(s_fixedpt_t sfp)
463 sfp.int_parts = ntohs(sfp.int_parts);
464 sfp.fractions = ntohs(sfp.fractions);
465 ret = (double)sfp.int_parts + ((double)sfp.fractions / USHRT_MAX);
468 #if ENABLE_FEATURE_NTPD_SERVER
473 lfp.int_partl = (uint32_t)d;
474 lfp.fractionl = (uint32_t)((d - lfp.int_partl) * UINT_MAX);
475 lfp.int_partl = htonl(lfp.int_partl);
476 lfp.fractionl = htonl(lfp.fractionl);
483 sfp.int_parts = (uint16_t)d;
484 sfp.fractions = (uint16_t)((d - sfp.int_parts) * USHRT_MAX);
485 sfp.int_parts = htons(sfp.int_parts);
486 sfp.fractions = htons(sfp.fractions);
492 dispersion(const datapoint_t *dp)
494 return dp->d_dispersion + FREQ_TOLERANCE * (G.cur_time - dp->d_recv_time);
498 root_distance(peer_t *p)
500 /* The root synchronization distance is the maximum error due to
501 * all causes of the local clock relative to the primary server.
502 * It is defined as half the total delay plus total dispersion
505 return MAXD(MINDISP, p->lastpkt_rootdelay + p->lastpkt_delay) / 2
506 + p->lastpkt_rootdisp
507 + p->filter_dispersion
508 + FREQ_TOLERANCE * (G.cur_time - p->lastpkt_recv_time)
513 set_next(peer_t *p, unsigned t)
515 p->next_action_time = G.cur_time + t;
519 * Peer clock filter and its helpers
522 filter_datapoints(peer_t *p)
529 /* Simulations have shown that use of *averaged* offset for p->filter_offset
530 * is in fact worse than simply using last received one: with large poll intervals
531 * (>= 2048) averaging code uses offset values which are outdated by hours,
532 * and time/frequency correction goes totally wrong when fed essentially bogus offsets.
535 double minoff, maxoff, w;
536 double x = x; /* for compiler */
537 double oldest_off = oldest_off;
538 double oldest_age = oldest_age;
539 double newest_off = newest_off;
540 double newest_age = newest_age;
542 fdp = p->filter_datapoint;
544 minoff = maxoff = fdp[0].d_offset;
545 for (i = 1; i < NUM_DATAPOINTS; i++) {
546 if (minoff > fdp[i].d_offset)
547 minoff = fdp[i].d_offset;
548 if (maxoff < fdp[i].d_offset)
549 maxoff = fdp[i].d_offset;
552 idx = p->datapoint_idx; /* most recent datapoint's index */
554 * Drop two outliers and take weighted average of the rest:
555 * most_recent/2 + older1/4 + older2/8 ... + older5/32 + older6/32
556 * we use older6/32, not older6/64 since sum of weights should be 1:
557 * 1/2 + 1/4 + 1/8 + 1/16 + 1/32 + 1/32 = 1
563 * filter_dispersion = \ -------------
570 for (i = 0; i < NUM_DATAPOINTS; i++) {
572 bb_error_msg("datapoint[%d]: off:%f disp:%f(%f) age:%f%s",
575 fdp[idx].d_dispersion, dispersion(&fdp[idx]),
576 G.cur_time - fdp[idx].d_recv_time,
577 (minoff == fdp[idx].d_offset || maxoff == fdp[idx].d_offset)
578 ? " (outlier by offset)" : ""
582 sum += dispersion(&fdp[idx]) / (2 << i);
584 if (minoff == fdp[idx].d_offset) {
585 minoff -= 1; /* so that we don't match it ever again */
587 if (maxoff == fdp[idx].d_offset) {
590 oldest_off = fdp[idx].d_offset;
591 oldest_age = G.cur_time - fdp[idx].d_recv_time;
594 newest_off = oldest_off;
595 newest_age = oldest_age;
602 idx = (idx - 1) & (NUM_DATAPOINTS - 1);
604 p->filter_dispersion = sum;
605 wavg += x; /* add another older6/64 to form older6/32 */
606 /* Fix systematic underestimation with large poll intervals.
607 * Imagine that we still have a bit of uncorrected drift,
608 * and poll interval is big (say, 100 sec). Offsets form a progression:
609 * 0.0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 - 0.7 is most recent.
610 * The algorithm above drops 0.0 and 0.7 as outliers,
611 * and then we have this estimation, ~25% off from 0.7:
612 * 0.1/32 + 0.2/32 + 0.3/16 + 0.4/8 + 0.5/4 + 0.6/2 = 0.503125
614 x = oldest_age - newest_age;
616 x = newest_age / x; /* in above example, 100 / (600 - 100) */
617 if (x < 1) { /* paranoia check */
618 x = (newest_off - oldest_off) * x; /* 0.5 * 100/500 = 0.1 */
622 p->filter_offset = wavg;
626 fdp = p->filter_datapoint;
627 idx = p->datapoint_idx; /* most recent datapoint's index */
629 /* filter_offset: simply use the most recent value */
630 p->filter_offset = fdp[idx].d_offset;
634 * filter_dispersion = \ -------------
641 for (i = 0; i < NUM_DATAPOINTS; i++) {
642 sum += dispersion(&fdp[idx]) / (2 << i);
643 wavg += fdp[idx].d_offset;
644 idx = (idx - 1) & (NUM_DATAPOINTS - 1);
646 wavg /= NUM_DATAPOINTS;
647 p->filter_dispersion = sum;
650 /* +----- -----+ ^ 1/2
654 * filter_jitter = | --- * / (avg-offset_j) |
658 * where n is the number of valid datapoints in the filter (n > 1);
659 * if filter_jitter < precision then filter_jitter = precision
662 for (i = 0; i < NUM_DATAPOINTS; i++) {
663 sum += SQUARE(wavg - fdp[i].d_offset);
665 sum = SQRT(sum / NUM_DATAPOINTS);
666 p->filter_jitter = sum > G_precision_sec ? sum : G_precision_sec;
668 VERB3 bb_error_msg("filter offset:%+f disp:%f jitter:%f",
670 p->filter_dispersion,
675 reset_peer_stats(peer_t *p, double offset)
678 bool small_ofs = fabs(offset) < 16 * STEP_THRESHOLD;
680 for (i = 0; i < NUM_DATAPOINTS; i++) {
682 p->filter_datapoint[i].d_recv_time += offset;
683 if (p->filter_datapoint[i].d_offset != 0) {
684 p->filter_datapoint[i].d_offset -= offset;
685 //bb_error_msg("p->filter_datapoint[%d].d_offset %f -> %f",
687 // p->filter_datapoint[i].d_offset + offset,
688 // p->filter_datapoint[i].d_offset);
691 p->filter_datapoint[i].d_recv_time = G.cur_time;
692 p->filter_datapoint[i].d_offset = 0;
693 p->filter_datapoint[i].d_dispersion = MAXDISP;
697 p->lastpkt_recv_time += offset;
699 p->reachable_bits = 0;
700 p->lastpkt_recv_time = G.cur_time;
702 filter_datapoints(p); /* recalc p->filter_xxx */
703 VERB5 bb_error_msg("%s->lastpkt_recv_time=%f", p->p_dotted, p->lastpkt_recv_time);
711 p = xzalloc(sizeof(*p));
712 p->p_lsa = xhost2sockaddr(s, 123);
713 p->p_dotted = xmalloc_sockaddr2dotted_noport(&p->p_lsa->u.sa);
715 p->p_xmt_msg.m_status = MODE_CLIENT | (NTP_VERSION << 3);
716 p->next_action_time = G.cur_time; /* = set_next(p, 0); */
717 reset_peer_stats(p, 16 * STEP_THRESHOLD);
719 llist_add_to(&G.ntp_peers, p);
725 const struct sockaddr *from, const struct sockaddr *to, socklen_t addrlen,
726 msg_t *msg, ssize_t len)
732 ret = sendto(fd, msg, len, MSG_DONTWAIT, to, addrlen);
734 ret = send_to_from(fd, msg, len, MSG_DONTWAIT, to, from, addrlen);
737 bb_perror_msg("send failed");
744 send_query_to_peer(peer_t *p)
746 /* Why do we need to bind()?
747 * See what happens when we don't bind:
749 * socket(PF_INET, SOCK_DGRAM, IPPROTO_IP) = 3
750 * setsockopt(3, SOL_IP, IP_TOS, [16], 4) = 0
751 * gettimeofday({1259071266, 327885}, NULL) = 0
752 * sendto(3, "xxx", 48, MSG_DONTWAIT, {sa_family=AF_INET, sin_port=htons(123), sin_addr=inet_addr("10.34.32.125")}, 16) = 48
753 * ^^^ we sent it from some source port picked by kernel.
754 * time(NULL) = 1259071266
755 * write(2, "ntpd: entering poll 15 secs\n", 28) = 28
756 * poll([{fd=3, events=POLLIN}], 1, 15000) = 1 ([{fd=3, revents=POLLIN}])
757 * recv(3, "yyy", 68, MSG_DONTWAIT) = 48
758 * ^^^ this recv will receive packets to any local port!
760 * Uncomment this and use strace to see it in action:
762 #define PROBE_LOCAL_ADDR /* { len_and_sockaddr lsa; lsa.len = LSA_SIZEOF_SA; getsockname(p->query.fd, &lsa.u.sa, &lsa.len); } */
766 len_and_sockaddr *local_lsa;
768 family = p->p_lsa->u.sa.sa_family;
769 p->p_fd = fd = xsocket_type(&local_lsa, family, SOCK_DGRAM);
770 /* local_lsa has "null" address and port 0 now.
771 * bind() ensures we have a *particular port* selected by kernel
772 * and remembered in p->p_fd, thus later recv(p->p_fd)
773 * receives only packets sent to this port.
776 xbind(fd, &local_lsa->u.sa, local_lsa->len);
778 #if ENABLE_FEATURE_IPV6
779 if (family == AF_INET)
781 setsockopt(fd, IPPROTO_IP, IP_TOS, &const_IPTOS_LOWDELAY, sizeof(const_IPTOS_LOWDELAY));
785 /* Emit message _before_ attempted send. Think of a very short
786 * roundtrip networks: we need to go back to recv loop ASAP,
787 * to reduce delay. Printing messages after send works against that.
789 VERB1 bb_error_msg("sending query to %s", p->p_dotted);
792 * Send out a random 64-bit number as our transmit time. The NTP
793 * server will copy said number into the originate field on the
794 * response that it sends us. This is totally legal per the SNTP spec.
796 * The impact of this is two fold: we no longer send out the current
797 * system time for the world to see (which may aid an attacker), and
798 * it gives us a (not very secure) way of knowing that we're not
799 * getting spoofed by an attacker that can't capture our traffic
800 * but can spoof packets from the NTP server we're communicating with.
802 * Save the real transmit timestamp locally.
804 p->p_xmt_msg.m_xmttime.int_partl = random();
805 p->p_xmt_msg.m_xmttime.fractionl = random();
806 p->p_xmttime = gettime1900d();
808 /* Were doing it only if sendto worked, but
809 * loss of sync detection needs reachable_bits updated
810 * even if sending fails *locally*:
811 * "network is unreachable" because cable was pulled?
812 * We still need to declare "unsync" if this condition persists.
814 p->reachable_bits <<= 1;
816 if (do_sendto(p->p_fd, /*from:*/ NULL, /*to:*/ &p->p_lsa->u.sa, /*addrlen:*/ p->p_lsa->len,
817 &p->p_xmt_msg, NTP_MSGSIZE_NOAUTH) == -1
822 * We know that we sent nothing.
823 * We can retry *soon* without fearing
824 * that we are flooding the peer.
826 set_next(p, RETRY_INTERVAL);
830 set_next(p, RESPONSE_INTERVAL);
834 /* Note that there is no provision to prevent several run_scripts
835 * to be started in quick succession. In fact, it happens rather often
836 * if initial syncronization results in a step.
837 * You will see "step" and then "stratum" script runs, sometimes
838 * as close as only 0.002 seconds apart.
839 * Script should be ready to deal with this.
841 static void run_script(const char *action, double offset)
844 char *env1, *env2, *env3, *env4;
846 G.last_script_run = G.cur_time;
851 argv[0] = (char*) G.script_name;
852 argv[1] = (char*) action;
855 VERB1 bb_error_msg("executing '%s %s'", G.script_name, action);
857 env1 = xasprintf("%s=%u", "stratum", G.stratum);
859 env2 = xasprintf("%s=%ld", "freq_drift_ppm", G.kernel_freq_drift);
861 env3 = xasprintf("%s=%u", "poll_interval", 1 << G.poll_exp);
863 env4 = xasprintf("%s=%f", "offset", offset);
865 /* Other items of potential interest: selected peer,
866 * rootdelay, reftime, rootdisp, refid, ntp_status,
867 * last_update_offset, last_update_recv_time, discipline_jitter,
868 * how many peers have reachable_bits = 0?
871 /* Don't want to wait: it may run hwclock --systohc, and that
872 * may take some time (seconds): */
873 /*spawn_and_wait(argv);*/
877 unsetenv("freq_drift_ppm");
878 unsetenv("poll_interval");
887 step_time(double offset)
891 struct timeval tvc, tvn;
892 char buf[sizeof("yyyy-mm-dd hh:mm:ss") + /*paranoia:*/ 4];
895 gettimeofday(&tvc, NULL); /* never fails */
896 dtime = tvc.tv_sec + (1.0e-6 * tvc.tv_usec) + offset;
897 d_to_tv(dtime, &tvn);
898 if (settimeofday(&tvn, NULL) == -1)
899 bb_perror_msg_and_die("settimeofday");
903 strftime_YYYYMMDDHHMMSS(buf, sizeof(buf), &tval);
904 bb_error_msg("current time is %s.%06u", buf, (unsigned)tvc.tv_usec);
907 strftime_YYYYMMDDHHMMSS(buf, sizeof(buf), &tval);
908 bb_error_msg("setting time to %s.%06u (offset %+fs)", buf, (unsigned)tvn.tv_usec, offset);
910 /* Correct various fields which contain time-relative values: */
913 G.cur_time += offset;
914 G.last_update_recv_time += offset;
915 G.last_script_run += offset;
917 /* p->lastpkt_recv_time, p->next_action_time and such: */
918 for (item = G.ntp_peers; item != NULL; item = item->link) {
919 peer_t *pp = (peer_t *) item->data;
920 reset_peer_stats(pp, offset);
921 //bb_error_msg("offset:%+f pp->next_action_time:%f -> %f",
922 // offset, pp->next_action_time, pp->next_action_time + offset);
923 pp->next_action_time += offset;
925 /* We wait for reply from this peer too.
926 * But due to step we are doing, reply's data is no longer
927 * useful (in fact, it'll be bogus). Stop waiting for it.
931 set_next(pp, RETRY_INTERVAL);
938 * Selection and clustering, and their helpers
944 double opt_rd; /* optimization */
947 compare_point_edge(const void *aa, const void *bb)
949 const point_t *a = aa;
950 const point_t *b = bb;
951 if (a->edge < b->edge) {
954 return (a->edge > b->edge);
961 compare_survivor_metric(const void *aa, const void *bb)
963 const survivor_t *a = aa;
964 const survivor_t *b = bb;
965 if (a->metric < b->metric) {
968 return (a->metric > b->metric);
971 fit(peer_t *p, double rd)
973 if ((p->reachable_bits & (p->reachable_bits-1)) == 0) {
974 /* One or zero bits in reachable_bits */
975 VERB3 bb_error_msg("peer %s unfit for selection: unreachable", p->p_dotted);
978 #if 0 /* we filter out such packets earlier */
979 if ((p->lastpkt_status & LI_ALARM) == LI_ALARM
980 || p->lastpkt_stratum >= MAXSTRAT
982 VERB3 bb_error_msg("peer %s unfit for selection: bad status/stratum", p->p_dotted);
986 /* rd is root_distance(p) */
987 if (rd > MAXDIST + FREQ_TOLERANCE * (1 << G.poll_exp)) {
988 VERB3 bb_error_msg("peer %s unfit for selection: root distance too high", p->p_dotted);
992 // /* Do we have a loop? */
993 // if (p->refid == p->dstaddr || p->refid == s.refid)
998 select_and_cluster(void)
1003 int size = 3 * G.peer_cnt;
1004 /* for selection algorithm */
1005 point_t point[size];
1006 unsigned num_points, num_candidates;
1008 unsigned num_falsetickers;
1009 /* for cluster algorithm */
1010 survivor_t survivor[size];
1011 unsigned num_survivors;
1017 if (G.initial_poll_complete) while (item != NULL) {
1020 p = (peer_t *) item->data;
1021 rd = root_distance(p);
1022 offset = p->filter_offset;
1028 VERB4 bb_error_msg("interval: [%f %f %f] %s",
1034 point[num_points].p = p;
1035 point[num_points].type = -1;
1036 point[num_points].edge = offset - rd;
1037 point[num_points].opt_rd = rd;
1039 point[num_points].p = p;
1040 point[num_points].type = 0;
1041 point[num_points].edge = offset;
1042 point[num_points].opt_rd = rd;
1044 point[num_points].p = p;
1045 point[num_points].type = 1;
1046 point[num_points].edge = offset + rd;
1047 point[num_points].opt_rd = rd;
1051 num_candidates = num_points / 3;
1052 if (num_candidates == 0) {
1053 VERB3 bb_error_msg("no valid datapoints, no peer selected");
1056 //TODO: sorting does not seem to be done in reference code
1057 qsort(point, num_points, sizeof(point[0]), compare_point_edge);
1059 /* Start with the assumption that there are no falsetickers.
1060 * Attempt to find a nonempty intersection interval containing
1061 * the midpoints of all truechimers.
1062 * If a nonempty interval cannot be found, increase the number
1063 * of assumed falsetickers by one and try again.
1064 * If a nonempty interval is found and the number of falsetickers
1065 * is less than the number of truechimers, a majority has been found
1066 * and the midpoint of each truechimer represents
1067 * the candidates available to the cluster algorithm.
1069 num_falsetickers = 0;
1072 unsigned num_midpoints = 0;
1077 for (i = 0; i < num_points; i++) {
1079 * if (point[i].type == -1) c++;
1080 * if (point[i].type == 1) c--;
1081 * and it's simpler to do it this way:
1084 if (c >= num_candidates - num_falsetickers) {
1085 /* If it was c++ and it got big enough... */
1086 low = point[i].edge;
1089 if (point[i].type == 0)
1093 for (i = num_points-1; i >= 0; i--) {
1095 if (c >= num_candidates - num_falsetickers) {
1096 high = point[i].edge;
1099 if (point[i].type == 0)
1102 /* If the number of midpoints is greater than the number
1103 * of allowed falsetickers, the intersection contains at
1104 * least one truechimer with no midpoint - bad.
1105 * Also, interval should be nonempty.
1107 if (num_midpoints <= num_falsetickers && low < high)
1110 if (num_falsetickers * 2 >= num_candidates) {
1111 VERB3 bb_error_msg("too many falsetickers:%d (candidates:%d), no peer selected",
1112 num_falsetickers, num_candidates);
1116 VERB3 bb_error_msg("selected interval: [%f, %f]; candidates:%d falsetickers:%d",
1117 low, high, num_candidates, num_falsetickers);
1121 /* Construct a list of survivors (p, metric)
1122 * from the chime list, where metric is dominated
1123 * first by stratum and then by root distance.
1124 * All other things being equal, this is the order of preference.
1127 for (i = 0; i < num_points; i++) {
1128 if (point[i].edge < low || point[i].edge > high)
1131 survivor[num_survivors].p = p;
1132 /* x.opt_rd == root_distance(p); */
1133 survivor[num_survivors].metric = MAXDIST * p->lastpkt_stratum + point[i].opt_rd;
1134 VERB4 bb_error_msg("survivor[%d] metric:%f peer:%s",
1135 num_survivors, survivor[num_survivors].metric, p->p_dotted);
1138 /* There must be at least MIN_SELECTED survivors to satisfy the
1139 * correctness assertions. Ordinarily, the Byzantine criteria
1140 * require four survivors, but for the demonstration here, one
1143 if (num_survivors < MIN_SELECTED) {
1144 VERB3 bb_error_msg("num_survivors %d < %d, no peer selected",
1145 num_survivors, MIN_SELECTED);
1149 //looks like this is ONLY used by the fact that later we pick survivor[0].
1150 //we can avoid sorting then, just find the minimum once!
1151 qsort(survivor, num_survivors, sizeof(survivor[0]), compare_survivor_metric);
1153 /* For each association p in turn, calculate the selection
1154 * jitter p->sjitter as the square root of the sum of squares
1155 * (p->offset - q->offset) over all q associations. The idea is
1156 * to repeatedly discard the survivor with maximum selection
1157 * jitter until a termination condition is met.
1160 unsigned max_idx = max_idx;
1161 double max_selection_jitter = max_selection_jitter;
1162 double min_jitter = min_jitter;
1164 if (num_survivors <= MIN_CLUSTERED) {
1165 VERB3 bb_error_msg("num_survivors %d <= %d, not discarding more",
1166 num_survivors, MIN_CLUSTERED);
1170 /* To make sure a few survivors are left
1171 * for the clustering algorithm to chew on,
1172 * we stop if the number of survivors
1173 * is less than or equal to MIN_CLUSTERED (3).
1175 for (i = 0; i < num_survivors; i++) {
1176 double selection_jitter_sq;
1179 if (i == 0 || p->filter_jitter < min_jitter)
1180 min_jitter = p->filter_jitter;
1182 selection_jitter_sq = 0;
1183 for (j = 0; j < num_survivors; j++) {
1184 peer_t *q = survivor[j].p;
1185 selection_jitter_sq += SQUARE(p->filter_offset - q->filter_offset);
1187 if (i == 0 || selection_jitter_sq > max_selection_jitter) {
1188 max_selection_jitter = selection_jitter_sq;
1191 VERB5 bb_error_msg("survivor %d selection_jitter^2:%f",
1192 i, selection_jitter_sq);
1194 max_selection_jitter = SQRT(max_selection_jitter / num_survivors);
1195 VERB4 bb_error_msg("max_selection_jitter (at %d):%f min_jitter:%f",
1196 max_idx, max_selection_jitter, min_jitter);
1198 /* If the maximum selection jitter is less than the
1199 * minimum peer jitter, then tossing out more survivors
1200 * will not lower the minimum peer jitter, so we might
1203 if (max_selection_jitter < min_jitter) {
1204 VERB3 bb_error_msg("max_selection_jitter:%f < min_jitter:%f, num_survivors:%d, not discarding more",
1205 max_selection_jitter, min_jitter, num_survivors);
1209 /* Delete survivor[max_idx] from the list
1210 * and go around again.
1212 VERB5 bb_error_msg("dropping survivor %d", max_idx);
1214 while (max_idx < num_survivors) {
1215 survivor[max_idx] = survivor[max_idx + 1];
1221 /* Combine the offsets of the clustering algorithm survivors
1222 * using a weighted average with weight determined by the root
1223 * distance. Compute the selection jitter as the weighted RMS
1224 * difference between the first survivor and the remaining
1225 * survivors. In some cases the inherent clock jitter can be
1226 * reduced by not using this algorithm, especially when frequent
1227 * clockhopping is involved. bbox: thus we don't do it.
1231 for (i = 0; i < num_survivors; i++) {
1233 x = root_distance(p);
1235 z += p->filter_offset / x;
1236 w += SQUARE(p->filter_offset - survivor[0].p->filter_offset) / x;
1238 //G.cluster_offset = z / y;
1239 //G.cluster_jitter = SQRT(w / y);
1242 /* Pick the best clock. If the old system peer is on the list
1243 * and at the same stratum as the first survivor on the list,
1244 * then don't do a clock hop. Otherwise, select the first
1245 * survivor on the list as the new system peer.
1248 if (G.last_update_peer
1249 && G.last_update_peer->lastpkt_stratum <= p->lastpkt_stratum
1251 /* Starting from 1 is ok here */
1252 for (i = 1; i < num_survivors; i++) {
1253 if (G.last_update_peer == survivor[i].p) {
1254 VERB4 bb_error_msg("keeping old synced peer");
1255 p = G.last_update_peer;
1260 G.last_update_peer = p;
1262 VERB3 bb_error_msg("selected peer %s filter_offset:%+f age:%f",
1265 G.cur_time - p->lastpkt_recv_time
1272 * Local clock discipline and its helpers
1275 set_new_values(int disc_state, double offset, double recv_time)
1277 /* Enter new state and set state variables. Note we use the time
1278 * of the last clock filter sample, which must be earlier than
1281 VERB3 bb_error_msg("disc_state=%d last update offset=%f recv_time=%f",
1282 disc_state, offset, recv_time);
1283 G.discipline_state = disc_state;
1284 G.last_update_offset = offset;
1285 G.last_update_recv_time = recv_time;
1287 /* Return: -1: decrease poll interval, 0: leave as is, 1: increase */
1289 update_local_clock(peer_t *p)
1293 /* Note: can use G.cluster_offset instead: */
1294 double offset = p->filter_offset;
1295 double recv_time = p->lastpkt_recv_time;
1297 #if !USING_KERNEL_PLL_LOOP
1300 double since_last_update;
1301 double etemp, dtemp;
1303 abs_offset = fabs(offset);
1306 /* If needed, -S script can do it by looking at $offset
1307 * env var and killing parent */
1308 /* If the offset is too large, give up and go home */
1309 if (abs_offset > PANIC_THRESHOLD) {
1310 bb_error_msg_and_die("offset %f far too big, exiting", offset);
1314 /* If this is an old update, for instance as the result
1315 * of a system peer change, avoid it. We never use
1316 * an old sample or the same sample twice.
1318 if (recv_time <= G.last_update_recv_time) {
1319 VERB3 bb_error_msg("same or older datapoint: %f >= %f, not using it",
1320 G.last_update_recv_time, recv_time);
1321 return 0; /* "leave poll interval as is" */
1324 /* Clock state machine transition function. This is where the
1325 * action is and defines how the system reacts to large time
1326 * and frequency errors.
1328 since_last_update = recv_time - G.reftime;
1329 #if !USING_KERNEL_PLL_LOOP
1332 #if USING_INITIAL_FREQ_ESTIMATION
1333 if (G.discipline_state == STATE_FREQ) {
1334 /* Ignore updates until the stepout threshold */
1335 if (since_last_update < WATCH_THRESHOLD) {
1336 VERB3 bb_error_msg("measuring drift, datapoint ignored, %f sec remains",
1337 WATCH_THRESHOLD - since_last_update);
1338 return 0; /* "leave poll interval as is" */
1340 # if !USING_KERNEL_PLL_LOOP
1341 freq_drift = (offset - G.last_update_offset) / since_last_update;
1346 /* There are two main regimes: when the
1347 * offset exceeds the step threshold and when it does not.
1349 if (abs_offset > STEP_THRESHOLD) {
1352 switch (G.discipline_state) {
1354 /* The first outlyer: ignore it, switch to SPIK state */
1355 VERB2 bb_error_msg("offset:%+f - spike", offset);
1356 G.discipline_state = STATE_SPIK;
1357 return -1; /* "decrease poll interval" */
1360 /* Ignore succeeding outlyers until either an inlyer
1361 * is found or the stepout threshold is exceeded.
1363 remains = WATCH_THRESHOLD - since_last_update;
1365 VERB2 bb_error_msg("spike, datapoint ignored, %f sec remains",
1367 return -1; /* "decrease poll interval" */
1369 /* fall through: we need to step */
1372 /* Step the time and clamp down the poll interval.
1374 * In NSET state an initial frequency correction is
1375 * not available, usually because the frequency file has
1376 * not yet been written. Since the time is outside the
1377 * capture range, the clock is stepped. The frequency
1378 * will be set directly following the stepout interval.
1380 * In FSET state the initial frequency has been set
1381 * from the frequency file. Since the time is outside
1382 * the capture range, the clock is stepped immediately,
1383 * rather than after the stepout interval. Guys get
1384 * nervous if it takes 17 minutes to set the clock for
1387 * In SPIK state the stepout threshold has expired and
1388 * the phase is still above the step threshold. Note
1389 * that a single spike greater than the step threshold
1390 * is always suppressed, even at the longer poll
1393 VERB3 bb_error_msg("stepping time by %+f; poll_exp=MINPOLL", offset);
1395 if (option_mask32 & OPT_q) {
1396 /* We were only asked to set time once. Done. */
1400 G.polladj_count = 0;
1401 G.poll_exp = MINPOLL;
1402 G.stratum = MAXSTRAT;
1404 run_script("step", offset);
1406 #if USING_INITIAL_FREQ_ESTIMATION
1407 if (G.discipline_state == STATE_NSET) {
1408 set_new_values(STATE_FREQ, /*offset:*/ 0, recv_time);
1409 return 1; /* "ok to increase poll interval" */
1412 abs_offset = offset = 0;
1413 set_new_values(STATE_SYNC, offset, recv_time);
1415 } else { /* abs_offset <= STEP_THRESHOLD */
1417 if (G.poll_exp < MINPOLL && G.initial_poll_complete) {
1418 VERB3 bb_error_msg("small offset:%+f, disabling burst mode", offset);
1419 G.polladj_count = 0;
1420 G.poll_exp = MINPOLL;
1423 /* Compute the clock jitter as the RMS of exponentially
1424 * weighted offset differences. Used by the poll adjust code.
1426 etemp = SQUARE(G.discipline_jitter);
1427 dtemp = SQUARE(offset - G.last_update_offset);
1428 G.discipline_jitter = SQRT(etemp + (dtemp - etemp) / AVG);
1430 switch (G.discipline_state) {
1432 if (option_mask32 & OPT_q) {
1433 /* We were only asked to set time once.
1434 * The clock is precise enough, no need to step.
1438 #if USING_INITIAL_FREQ_ESTIMATION
1439 /* This is the first update received and the frequency
1440 * has not been initialized. The first thing to do
1441 * is directly measure the oscillator frequency.
1443 set_new_values(STATE_FREQ, offset, recv_time);
1445 set_new_values(STATE_SYNC, offset, recv_time);
1447 VERB3 bb_error_msg("transitioning to FREQ, datapoint ignored");
1448 return 0; /* "leave poll interval as is" */
1450 #if 0 /* this is dead code for now */
1452 /* This is the first update and the frequency
1453 * has been initialized. Adjust the phase, but
1454 * don't adjust the frequency until the next update.
1456 set_new_values(STATE_SYNC, offset, recv_time);
1457 /* freq_drift remains 0 */
1461 #if USING_INITIAL_FREQ_ESTIMATION
1463 /* since_last_update >= WATCH_THRESHOLD, we waited enough.
1464 * Correct the phase and frequency and switch to SYNC state.
1465 * freq_drift was already estimated (see code above)
1467 set_new_values(STATE_SYNC, offset, recv_time);
1472 #if !USING_KERNEL_PLL_LOOP
1473 /* Compute freq_drift due to PLL and FLL contributions.
1475 * The FLL and PLL frequency gain constants
1476 * depend on the poll interval and Allan
1477 * intercept. The FLL is not used below one-half
1478 * the Allan intercept. Above that the loop gain
1479 * increases in steps to 1 / AVG.
1481 if ((1 << G.poll_exp) > ALLAN / 2) {
1482 etemp = FLL - G.poll_exp;
1485 freq_drift += (offset - G.last_update_offset) / (MAXD(since_last_update, ALLAN) * etemp);
1487 /* For the PLL the integration interval
1488 * (numerator) is the minimum of the update
1489 * interval and poll interval. This allows
1490 * oversampling, but not undersampling.
1492 etemp = MIND(since_last_update, (1 << G.poll_exp));
1493 dtemp = (4 * PLL) << G.poll_exp;
1494 freq_drift += offset * etemp / SQUARE(dtemp);
1496 set_new_values(STATE_SYNC, offset, recv_time);
1499 if (G.stratum != p->lastpkt_stratum + 1) {
1500 G.stratum = p->lastpkt_stratum + 1;
1501 run_script("stratum", offset);
1505 if (G.discipline_jitter < G_precision_sec)
1506 G.discipline_jitter = G_precision_sec;
1507 G.offset_to_jitter_ratio = abs_offset / G.discipline_jitter;
1509 G.reftime = G.cur_time;
1510 G.ntp_status = p->lastpkt_status;
1511 G.refid = p->lastpkt_refid;
1512 G.rootdelay = p->lastpkt_rootdelay + p->lastpkt_delay;
1513 dtemp = p->filter_jitter; // SQRT(SQUARE(p->filter_jitter) + SQUARE(G.cluster_jitter));
1514 dtemp += MAXD(p->filter_dispersion + FREQ_TOLERANCE * (G.cur_time - p->lastpkt_recv_time) + abs_offset, MINDISP);
1515 G.rootdisp = p->lastpkt_rootdisp + dtemp;
1516 VERB3 bb_error_msg("updating leap/refid/reftime/rootdisp from peer %s", p->p_dotted);
1518 /* We are in STATE_SYNC now, but did not do adjtimex yet.
1519 * (Any other state does not reach this, they all return earlier)
1520 * By this time, freq_drift and offset are set
1521 * to values suitable for adjtimex.
1523 #if !USING_KERNEL_PLL_LOOP
1524 /* Calculate the new frequency drift and frequency stability (wander).
1525 * Compute the clock wander as the RMS of exponentially weighted
1526 * frequency differences. This is not used directly, but can,
1527 * along with the jitter, be a highly useful monitoring and
1530 dtemp = G.discipline_freq_drift + freq_drift;
1531 G.discipline_freq_drift = MAXD(MIND(MAXDRIFT, dtemp), -MAXDRIFT);
1532 etemp = SQUARE(G.discipline_wander);
1533 dtemp = SQUARE(dtemp);
1534 G.discipline_wander = SQRT(etemp + (dtemp - etemp) / AVG);
1536 VERB3 bb_error_msg("discipline freq_drift=%.9f(int:%ld corr:%e) wander=%f",
1537 G.discipline_freq_drift,
1538 (long)(G.discipline_freq_drift * 65536e6),
1540 G.discipline_wander);
1543 memset(&tmx, 0, sizeof(tmx));
1544 if (adjtimex(&tmx) < 0)
1545 bb_perror_msg_and_die("adjtimex");
1546 bb_error_msg("p adjtimex freq:%ld offset:%+ld status:0x%x tc:%ld",
1547 tmx.freq, tmx.offset, tmx.status, tmx.constant);
1550 memset(&tmx, 0, sizeof(tmx));
1552 //doesn't work, offset remains 0 (!) in kernel:
1553 //ntpd: set adjtimex freq:1786097 tmx.offset:77487
1554 //ntpd: prev adjtimex freq:1786097 tmx.offset:0
1555 //ntpd: cur adjtimex freq:1786097 tmx.offset:0
1556 tmx.modes = ADJ_FREQUENCY | ADJ_OFFSET;
1557 /* 65536 is one ppm */
1558 tmx.freq = G.discipline_freq_drift * 65536e6;
1560 tmx.modes = ADJ_OFFSET | ADJ_STATUS | ADJ_TIMECONST;// | ADJ_MAXERROR | ADJ_ESTERROR;
1561 tmx.offset = (offset * 1000000); /* usec */
1562 tmx.status = STA_PLL;
1563 if (G.ntp_status & LI_PLUSSEC)
1564 tmx.status |= STA_INS;
1565 if (G.ntp_status & LI_MINUSSEC)
1566 tmx.status |= STA_DEL;
1568 tmx.constant = G.poll_exp - 4;
1570 * The below if statement should be unnecessary, but...
1571 * It looks like Linux kernel's PLL is far too gentle in changing
1572 * tmx.freq in response to clock offset. Offset keeps growing
1573 * and eventually we fall back to smaller poll intervals.
1574 * We can make correction more agressive (about x2) by supplying
1575 * PLL time constant which is one less than the real one.
1576 * To be on a safe side, let's do it only if offset is significantly
1577 * larger than jitter.
1579 if (tmx.constant > 0 && G.offset_to_jitter_ratio >= TIMECONST_HACK_GATE)
1582 //tmx.esterror = (uint32_t)(clock_jitter * 1e6);
1583 //tmx.maxerror = (uint32_t)((sys_rootdelay / 2 + sys_rootdisp) * 1e6);
1584 rc = adjtimex(&tmx);
1586 bb_perror_msg_and_die("adjtimex");
1587 /* NB: here kernel returns constant == G.poll_exp, not == G.poll_exp - 4.
1588 * Not sure why. Perhaps it is normal.
1590 VERB3 bb_error_msg("adjtimex:%d freq:%ld offset:%+ld status:0x%x",
1591 rc, tmx.freq, tmx.offset, tmx.status);
1592 G.kernel_freq_drift = tmx.freq / 65536;
1593 VERB2 bb_error_msg("update from:%s offset:%+f jitter:%f clock drift:%+.3fppm tc:%d",
1594 p->p_dotted, offset, G.discipline_jitter, (double)tmx.freq / 65536, (int)tmx.constant);
1596 return 1; /* "ok to increase poll interval" */
1601 * We've got a new reply packet from a peer, process it
1605 retry_interval(void)
1607 /* Local problem, want to retry soon */
1608 unsigned interval, r;
1609 interval = RETRY_INTERVAL;
1611 interval += r % (unsigned)(RETRY_INTERVAL / 4);
1612 VERB3 bb_error_msg("chose retry interval:%u", interval);
1616 poll_interval(int exponent)
1618 unsigned interval, r;
1619 exponent = G.poll_exp + exponent;
1622 interval = 1 << exponent;
1624 interval += ((r & (interval-1)) >> 4) + ((r >> 8) & 1); /* + 1/16 of interval, max */
1625 VERB3 bb_error_msg("chose poll interval:%u (poll_exp:%d exp:%d)", interval, G.poll_exp, exponent);
1628 static NOINLINE void
1629 recv_and_process_peer_pkt(peer_t *p)
1634 double T1, T2, T3, T4;
1637 datapoint_t *datapoint;
1640 /* We can recvfrom here and check from.IP, but some multihomed
1641 * ntp servers reply from their *other IP*.
1642 * TODO: maybe we should check at least what we can: from.port == 123?
1644 size = recv(p->p_fd, &msg, sizeof(msg), MSG_DONTWAIT);
1646 bb_perror_msg("recv(%s) error", p->p_dotted);
1647 if (errno == EHOSTUNREACH || errno == EHOSTDOWN
1648 || errno == ENETUNREACH || errno == ENETDOWN
1649 || errno == ECONNREFUSED || errno == EADDRNOTAVAIL
1652 //TODO: always do this?
1653 interval = retry_interval();
1654 goto set_next_and_ret;
1659 if (size != NTP_MSGSIZE_NOAUTH && size != NTP_MSGSIZE) {
1660 bb_error_msg("malformed packet received from %s", p->p_dotted);
1664 if (msg.m_orgtime.int_partl != p->p_xmt_msg.m_xmttime.int_partl
1665 || msg.m_orgtime.fractionl != p->p_xmt_msg.m_xmttime.fractionl
1667 /* Somebody else's packet */
1671 /* We do not expect any more packets from this peer for now.
1672 * Closing the socket informs kernel about it.
1673 * We open a new socket when we send a new query.
1678 if ((msg.m_status & LI_ALARM) == LI_ALARM
1679 || msg.m_stratum == 0
1680 || msg.m_stratum > NTP_MAXSTRATUM
1682 // TODO: stratum 0 responses may have commands in 32-bit m_refid field:
1683 // "DENY", "RSTR" - peer does not like us at all
1684 // "RATE" - peer is overloaded, reduce polling freq
1685 bb_error_msg("reply from %s: peer is unsynced", p->p_dotted);
1686 goto pick_normal_interval;
1689 // /* Verify valid root distance */
1690 // if (msg.m_rootdelay / 2 + msg.m_rootdisp >= MAXDISP || p->lastpkt_reftime > msg.m_xmt)
1691 // return; /* invalid header values */
1693 p->lastpkt_status = msg.m_status;
1694 p->lastpkt_stratum = msg.m_stratum;
1695 p->lastpkt_rootdelay = sfp_to_d(msg.m_rootdelay);
1696 p->lastpkt_rootdisp = sfp_to_d(msg.m_rootdisp);
1697 p->lastpkt_refid = msg.m_refid;
1700 * From RFC 2030 (with a correction to the delay math):
1702 * Timestamp Name ID When Generated
1703 * ------------------------------------------------------------
1704 * Originate Timestamp T1 time request sent by client
1705 * Receive Timestamp T2 time request received by server
1706 * Transmit Timestamp T3 time reply sent by server
1707 * Destination Timestamp T4 time reply received by client
1709 * The roundtrip delay and local clock offset are defined as
1711 * delay = (T4 - T1) - (T3 - T2); offset = ((T2 - T1) + (T3 - T4)) / 2
1714 T2 = lfp_to_d(msg.m_rectime);
1715 T3 = lfp_to_d(msg.m_xmttime);
1718 p->lastpkt_recv_time = T4;
1719 VERB5 bb_error_msg("%s->lastpkt_recv_time=%f", p->p_dotted, p->lastpkt_recv_time);
1721 /* The delay calculation is a special case. In cases where the
1722 * server and client clocks are running at different rates and
1723 * with very fast networks, the delay can appear negative. In
1724 * order to avoid violating the Principle of Least Astonishment,
1725 * the delay is clamped not less than the system precision.
1727 dv = p->lastpkt_delay;
1728 p->lastpkt_delay = (T4 - T1) - (T3 - T2);
1729 if (p->lastpkt_delay < G_precision_sec)
1730 p->lastpkt_delay = G_precision_sec;
1732 * If this packet's delay is much bigger than the last one,
1733 * it's better to just ignore it than use its much less precise value.
1735 if (p->reachable_bits && p->lastpkt_delay > dv * BAD_DELAY_GROWTH) {
1736 bb_error_msg("reply from %s: delay %f is too high, ignoring", p->p_dotted, p->lastpkt_delay);
1737 goto pick_normal_interval;
1740 p->datapoint_idx = p->reachable_bits ? (p->datapoint_idx + 1) % NUM_DATAPOINTS : 0;
1741 datapoint = &p->filter_datapoint[p->datapoint_idx];
1742 datapoint->d_recv_time = T4;
1743 datapoint->d_offset = ((T2 - T1) + (T3 - T4)) / 2;
1744 datapoint->d_dispersion = LOG2D(msg.m_precision_exp) + G_precision_sec;
1745 if (!p->reachable_bits) {
1746 /* 1st datapoint ever - replicate offset in every element */
1748 for (i = 0; i < NUM_DATAPOINTS; i++) {
1749 p->filter_datapoint[i].d_offset = datapoint->d_offset;
1753 p->reachable_bits |= 1;
1754 if ((MAX_VERBOSE && G.verbose) || (option_mask32 & OPT_w)) {
1755 bb_error_msg("reply from %s: offset:%+f delay:%f status:0x%02x strat:%d refid:0x%08x rootdelay:%f reach:0x%02x",
1757 datapoint->d_offset,
1762 p->lastpkt_rootdelay,
1764 /* not shown: m_ppoll, m_precision_exp, m_rootdisp,
1765 * m_reftime, m_orgtime, m_rectime, m_xmttime
1770 /* Muck with statictics and update the clock */
1771 filter_datapoints(p);
1772 q = select_and_cluster();
1776 if (!(option_mask32 & OPT_w)) {
1777 rc = update_local_clock(q);
1778 /* If drift is dangerously large, immediately
1779 * drop poll interval one step down.
1781 if (fabs(q->filter_offset) >= POLLDOWN_OFFSET) {
1782 VERB3 bb_error_msg("offset:%+f > POLLDOWN_OFFSET", q->filter_offset);
1787 /* else: no peer selected, rc = -1: we want to poll more often */
1790 /* Adjust the poll interval by comparing the current offset
1791 * with the clock jitter. If the offset is less than
1792 * the clock jitter times a constant, then the averaging interval
1793 * is increased, otherwise it is decreased. A bit of hysteresis
1794 * helps calm the dance. Works best using burst mode.
1796 if (rc > 0 && G.offset_to_jitter_ratio <= POLLADJ_GATE) {
1797 /* was += G.poll_exp but it is a bit
1798 * too optimistic for my taste at high poll_exp's */
1799 G.polladj_count += MINPOLL;
1800 if (G.polladj_count > POLLADJ_LIMIT) {
1801 G.polladj_count = 0;
1802 if (G.poll_exp < MAXPOLL) {
1804 VERB3 bb_error_msg("polladj: discipline_jitter:%f ++poll_exp=%d",
1805 G.discipline_jitter, G.poll_exp);
1808 VERB3 bb_error_msg("polladj: incr:%d", G.polladj_count);
1811 G.polladj_count -= G.poll_exp * 2;
1812 if (G.polladj_count < -POLLADJ_LIMIT || G.poll_exp >= BIGPOLL) {
1814 G.polladj_count = 0;
1815 if (G.poll_exp > MINPOLL) {
1819 /* Correct p->next_action_time in each peer
1820 * which waits for sending, so that they send earlier.
1821 * Old pp->next_action_time are on the order
1822 * of t + (1 << old_poll_exp) + small_random,
1823 * we simply need to subtract ~half of that.
1825 for (item = G.ntp_peers; item != NULL; item = item->link) {
1826 peer_t *pp = (peer_t *) item->data;
1828 pp->next_action_time -= (1 << G.poll_exp);
1830 VERB3 bb_error_msg("polladj: discipline_jitter:%f --poll_exp=%d",
1831 G.discipline_jitter, G.poll_exp);
1834 VERB3 bb_error_msg("polladj: decr:%d", G.polladj_count);
1839 /* Decide when to send new query for this peer */
1840 pick_normal_interval:
1841 interval = poll_interval(0);
1844 set_next(p, interval);
1847 #if ENABLE_FEATURE_NTPD_SERVER
1848 static NOINLINE void
1849 recv_and_process_client_pkt(void /*int fd*/)
1853 len_and_sockaddr *to;
1854 struct sockaddr *from;
1856 uint8_t query_status;
1857 l_fixedpt_t query_xmttime;
1859 to = get_sock_lsa(G_listen_fd);
1860 from = xzalloc(to->len);
1862 size = recv_from_to(G_listen_fd, &msg, sizeof(msg), MSG_DONTWAIT, from, &to->u.sa, to->len);
1863 if (size != NTP_MSGSIZE_NOAUTH && size != NTP_MSGSIZE) {
1866 if (errno == EAGAIN)
1868 bb_perror_msg_and_die("recv");
1870 addr = xmalloc_sockaddr2dotted_noport(from);
1871 bb_error_msg("malformed packet received from %s: size %u", addr, (int)size);
1876 query_status = msg.m_status;
1877 query_xmttime = msg.m_xmttime;
1879 /* Build a reply packet */
1880 memset(&msg, 0, sizeof(msg));
1881 msg.m_status = G.stratum < MAXSTRAT ? (G.ntp_status & LI_MASK) : LI_ALARM;
1882 msg.m_status |= (query_status & VERSION_MASK);
1883 msg.m_status |= ((query_status & MODE_MASK) == MODE_CLIENT) ?
1884 MODE_SERVER : MODE_SYM_PAS;
1885 msg.m_stratum = G.stratum;
1886 msg.m_ppoll = G.poll_exp;
1887 msg.m_precision_exp = G_precision_exp;
1888 /* this time was obtained between poll() and recv() */
1889 msg.m_rectime = d_to_lfp(G.cur_time);
1890 msg.m_xmttime = d_to_lfp(gettime1900d()); /* this instant */
1891 if (G.peer_cnt == 0) {
1892 /* we have no peers: "stratum 1 server" mode. reftime = our own time */
1893 G.reftime = G.cur_time;
1895 msg.m_reftime = d_to_lfp(G.reftime);
1896 msg.m_orgtime = query_xmttime;
1897 msg.m_rootdelay = d_to_sfp(G.rootdelay);
1898 //simple code does not do this, fix simple code!
1899 msg.m_rootdisp = d_to_sfp(G.rootdisp);
1900 //version = (query_status & VERSION_MASK); /* ... >> VERSION_SHIFT - done below instead */
1901 msg.m_refid = G.refid; // (version > (3 << VERSION_SHIFT)) ? G.refid : G.refid3;
1903 /* We reply from the local address packet was sent to,
1904 * this makes to/from look swapped here: */
1905 do_sendto(G_listen_fd,
1906 /*from:*/ &to->u.sa, /*to:*/ from, /*addrlen:*/ to->len,
1915 /* Upstream ntpd's options:
1917 * -4 Force DNS resolution of host names to the IPv4 namespace.
1918 * -6 Force DNS resolution of host names to the IPv6 namespace.
1919 * -a Require cryptographic authentication for broadcast client,
1920 * multicast client and symmetric passive associations.
1921 * This is the default.
1922 * -A Do not require cryptographic authentication for broadcast client,
1923 * multicast client and symmetric passive associations.
1924 * This is almost never a good idea.
1925 * -b Enable the client to synchronize to broadcast servers.
1927 * Specify the name and path of the configuration file,
1928 * default /etc/ntp.conf
1929 * -d Specify debugging mode. This option may occur more than once,
1930 * with each occurrence indicating greater detail of display.
1932 * Specify debugging level directly.
1934 * Specify the name and path of the frequency file.
1935 * This is the same operation as the "driftfile FILE"
1936 * configuration command.
1937 * -g Normally, ntpd exits with a message to the system log
1938 * if the offset exceeds the panic threshold, which is 1000 s
1939 * by default. This option allows the time to be set to any value
1940 * without restriction; however, this can happen only once.
1941 * If the threshold is exceeded after that, ntpd will exit
1942 * with a message to the system log. This option can be used
1943 * with the -q and -x options. See the tinker command for other options.
1945 * Chroot the server to the directory jaildir. This option also implies
1946 * that the server attempts to drop root privileges at startup
1947 * (otherwise, chroot gives very little additional security).
1948 * You may need to also specify a -u option.
1950 * Specify the name and path of the symmetric key file,
1951 * default /etc/ntp/keys. This is the same operation
1952 * as the "keys FILE" configuration command.
1954 * Specify the name and path of the log file. The default
1955 * is the system log file. This is the same operation as
1956 * the "logfile FILE" configuration command.
1957 * -L Do not listen to virtual IPs. The default is to listen.
1959 * -N To the extent permitted by the operating system,
1960 * run the ntpd at the highest priority.
1962 * Specify the name and path of the file used to record the ntpd
1963 * process ID. This is the same operation as the "pidfile FILE"
1964 * configuration command.
1966 * To the extent permitted by the operating system,
1967 * run the ntpd at the specified priority.
1968 * -q Exit the ntpd just after the first time the clock is set.
1969 * This behavior mimics that of the ntpdate program, which is
1970 * to be retired. The -g and -x options can be used with this option.
1971 * Note: The kernel time discipline is disabled with this option.
1973 * Specify the default propagation delay from the broadcast/multicast
1974 * server to this client. This is necessary only if the delay
1975 * cannot be computed automatically by the protocol.
1977 * Specify the directory path for files created by the statistics
1978 * facility. This is the same operation as the "statsdir DIR"
1979 * configuration command.
1981 * Add a key number to the trusted key list. This option can occur
1984 * Specify a user, and optionally a group, to switch to.
1987 * Add a system variable listed by default.
1988 * -x Normally, the time is slewed if the offset is less than the step
1989 * threshold, which is 128 ms by default, and stepped if above
1990 * the threshold. This option sets the threshold to 600 s, which is
1991 * well within the accuracy window to set the clock manually.
1992 * Note: since the slew rate of typical Unix kernels is limited
1993 * to 0.5 ms/s, each second of adjustment requires an amortization
1994 * interval of 2000 s. Thus, an adjustment as much as 600 s
1995 * will take almost 14 days to complete. This option can be used
1996 * with the -g and -q options. See the tinker command for other options.
1997 * Note: The kernel time discipline is disabled with this option.
2000 /* By doing init in a separate function we decrease stack usage
2003 static NOINLINE void ntp_init(char **argv)
2011 bb_error_msg_and_die(bb_msg_you_must_be_root);
2013 /* Set some globals */
2014 G.stratum = MAXSTRAT;
2016 G.poll_exp = BURSTPOLL; /* speeds up initial sync */
2017 G.last_script_run = G.reftime = G.last_update_recv_time = gettime1900d(); /* sets G.cur_time too */
2021 opt_complementary = "dd:p::wn"; /* d: counter; p: list; -w implies -n */
2022 opts = getopt32(argv,
2024 "wp:S:"IF_FEATURE_NTPD_SERVER("l") /* NOT compat */
2026 "46aAbgL", /* compat, ignored */
2027 &peers, &G.script_name, &G.verbose);
2028 if (!(opts & (OPT_p|OPT_l)))
2030 // if (opts & OPT_x) /* disable stepping, only slew is allowed */
2031 // G.time_was_stepped = 1;
2034 add_peers(llist_pop(&peers));
2036 /* -l but no peers: "stratum 1 server" mode */
2039 if (!(opts & OPT_n)) {
2040 bb_daemonize_or_rexec(DAEMON_DEVNULL_STDIO, argv);
2041 logmode = LOGMODE_NONE;
2043 #if ENABLE_FEATURE_NTPD_SERVER
2046 G_listen_fd = create_and_bind_dgram_or_die(NULL, 123);
2047 socket_want_pktinfo(G_listen_fd);
2048 setsockopt(G_listen_fd, IPPROTO_IP, IP_TOS, &const_IPTOS_LOWDELAY, sizeof(const_IPTOS_LOWDELAY));
2051 /* I hesitate to set -20 prio. -15 should be high enough for timekeeping */
2053 setpriority(PRIO_PROCESS, 0, -15);
2055 /* If network is up, syncronization occurs in ~10 seconds.
2056 * We give "ntpd -q" 10 seconds to get first reply,
2057 * then another 50 seconds to finish syncing.
2059 * I tested ntpd 4.2.6p1 and apparently it never exits
2060 * (will try forever), but it does not feel right.
2061 * The goal of -q is to act like ntpdate: set time
2062 * after a reasonably small period of polling, or fail.
2065 option_mask32 |= OPT_qq;
2082 int ntpd_main(int argc UNUSED_PARAM, char **argv) MAIN_EXTERNALLY_VISIBLE;
2083 int ntpd_main(int argc UNUSED_PARAM, char **argv)
2091 memset(&G, 0, sizeof(G));
2092 SET_PTR_TO_GLOBALS(&G);
2096 /* If ENABLE_FEATURE_NTPD_SERVER, + 1 for listen_fd: */
2097 cnt = G.peer_cnt + ENABLE_FEATURE_NTPD_SERVER;
2098 idx2peer = xzalloc(sizeof(idx2peer[0]) * cnt);
2099 pfd = xzalloc(sizeof(pfd[0]) * cnt);
2101 /* Countdown: we never sync before we sent INITIAL_SAMPLES+1
2102 * packets to each peer.
2103 * NB: if some peer is not responding, we may end up sending
2104 * fewer packets to it and more to other peers.
2105 * NB2: sync usually happens using INITIAL_SAMPLES packets,
2106 * since last reply does not come back instantaneously.
2108 cnt = G.peer_cnt * (INITIAL_SAMPLES + 1);
2110 write_pidfile(CONFIG_PID_FILE_PATH "/ntpd.pid");
2112 while (!bb_got_signal) {
2118 /* Nothing between here and poll() blocks for any significant time */
2120 nextaction = G.cur_time + 3600;
2123 #if ENABLE_FEATURE_NTPD_SERVER
2124 if (G_listen_fd != -1) {
2125 pfd[0].fd = G_listen_fd;
2126 pfd[0].events = POLLIN;
2130 /* Pass over peer list, send requests, time out on receives */
2131 for (item = G.ntp_peers; item != NULL; item = item->link) {
2132 peer_t *p = (peer_t *) item->data;
2134 if (p->next_action_time <= G.cur_time) {
2135 if (p->p_fd == -1) {
2136 /* Time to send new req */
2138 G.initial_poll_complete = 1;
2140 send_query_to_peer(p);
2142 /* Timed out waiting for reply */
2145 timeout = poll_interval(-2); /* -2: try a bit sooner */
2146 bb_error_msg("timed out waiting for %s, reach 0x%02x, next query in %us",
2147 p->p_dotted, p->reachable_bits, timeout);
2148 set_next(p, timeout);
2152 if (p->next_action_time < nextaction)
2153 nextaction = p->next_action_time;
2156 /* Wait for reply from this peer */
2157 pfd[i].fd = p->p_fd;
2158 pfd[i].events = POLLIN;
2164 timeout = nextaction - G.cur_time;
2167 timeout++; /* (nextaction - G.cur_time) rounds down, compensating */
2169 /* Here we may block */
2171 if (i > (ENABLE_FEATURE_NTPD_SERVER && G_listen_fd != -1)) {
2172 /* We wait for at least one reply.
2173 * Poll for it, without wasting time for message.
2174 * Since replies often come under 1 second, this also
2175 * reduces clutter in logs.
2177 nfds = poll(pfd, i, 1000);
2183 bb_error_msg("poll:%us sockets:%u interval:%us", timeout, i, 1 << G.poll_exp);
2185 nfds = poll(pfd, i, timeout * 1000);
2187 gettime1900d(); /* sets G.cur_time */
2189 if (!bb_got_signal /* poll wasn't interrupted by a signal */
2190 && G.cur_time - G.last_script_run > 11*60
2192 /* Useful for updating battery-backed RTC and such */
2193 run_script("periodic", G.last_update_offset);
2194 gettime1900d(); /* sets G.cur_time */
2199 /* Process any received packets */
2201 #if ENABLE_FEATURE_NTPD_SERVER
2202 if (G.listen_fd != -1) {
2203 if (pfd[0].revents /* & (POLLIN|POLLERR)*/) {
2205 recv_and_process_client_pkt(/*G.listen_fd*/);
2206 gettime1900d(); /* sets G.cur_time */
2211 for (; nfds != 0 && j < i; j++) {
2212 if (pfd[j].revents /* & (POLLIN|POLLERR)*/) {
2214 * At init, alarm was set to 10 sec.
2215 * Now we did get a reply.
2216 * Increase timeout to 50 seconds to finish syncing.
2218 if (option_mask32 & OPT_qq) {
2219 option_mask32 &= ~OPT_qq;
2223 recv_and_process_peer_pkt(idx2peer[j]);
2224 gettime1900d(); /* sets G.cur_time */
2229 if (G.ntp_peers && G.stratum != MAXSTRAT) {
2230 for (item = G.ntp_peers; item != NULL; item = item->link) {
2231 peer_t *p = (peer_t *) item->data;
2232 if (p->reachable_bits)
2233 goto have_reachable_peer;
2235 /* No peer responded for last 8 packets, panic */
2236 G.polladj_count = 0;
2237 G.poll_exp = MINPOLL;
2238 G.stratum = MAXSTRAT;
2239 run_script("unsync", 0.0);
2240 have_reachable_peer: ;
2242 } /* while (!bb_got_signal) */
2244 remove_pidfile(CONFIG_PID_FILE_PATH "/ntpd.pid");
2245 kill_myself_with_sig(bb_got_signal);
2253 /*** openntpd-4.6 uses only adjtime, not adjtimex ***/
2255 /*** ntp-4.2.6/ntpd/ntp_loopfilter.c - adjtimex usage ***/
2259 direct_freq(double fp_offset)
2263 * If the kernel is enabled, we need the residual offset to
2264 * calculate the frequency correction.
2266 if (pll_control && kern_enable) {
2267 memset(&ntv, 0, sizeof(ntv));
2270 clock_offset = ntv.offset / 1e9;
2271 #else /* STA_NANO */
2272 clock_offset = ntv.offset / 1e6;
2273 #endif /* STA_NANO */
2274 drift_comp = FREQTOD(ntv.freq);
2276 #endif /* KERNEL_PLL */
2277 set_freq((fp_offset - clock_offset) / (current_time - clock_epoch) + drift_comp);
2283 set_freq(double freq) /* frequency update */
2291 * If the kernel is enabled, update the kernel frequency.
2293 if (pll_control && kern_enable) {
2294 memset(&ntv, 0, sizeof(ntv));
2295 ntv.modes = MOD_FREQUENCY;
2296 ntv.freq = DTOFREQ(drift_comp);
2298 snprintf(tbuf, sizeof(tbuf), "kernel %.3f PPM", drift_comp * 1e6);
2299 report_event(EVNT_FSET, NULL, tbuf);
2301 snprintf(tbuf, sizeof(tbuf), "ntpd %.3f PPM", drift_comp * 1e6);
2302 report_event(EVNT_FSET, NULL, tbuf);
2304 #else /* KERNEL_PLL */
2305 snprintf(tbuf, sizeof(tbuf), "ntpd %.3f PPM", drift_comp * 1e6);
2306 report_event(EVNT_FSET, NULL, tbuf);
2307 #endif /* KERNEL_PLL */
2316 * This code segment works when clock adjustments are made using
2317 * precision time kernel support and the ntp_adjtime() system
2318 * call. This support is available in Solaris 2.6 and later,
2319 * Digital Unix 4.0 and later, FreeBSD, Linux and specially
2320 * modified kernels for HP-UX 9 and Ultrix 4. In the case of the
2321 * DECstation 5000/240 and Alpha AXP, additional kernel
2322 * modifications provide a true microsecond clock and nanosecond
2323 * clock, respectively.
2325 * Important note: The kernel discipline is used only if the
2326 * step threshold is less than 0.5 s, as anything higher can
2327 * lead to overflow problems. This might occur if some misguided
2328 * lad set the step threshold to something ridiculous.
2330 if (pll_control && kern_enable) {
2332 #define MOD_BITS (MOD_OFFSET | MOD_MAXERROR | MOD_ESTERROR | MOD_STATUS | MOD_TIMECONST)
2335 * We initialize the structure for the ntp_adjtime()
2336 * system call. We have to convert everything to
2337 * microseconds or nanoseconds first. Do not update the
2338 * system variables if the ext_enable flag is set. In
2339 * this case, the external clock driver will update the
2340 * variables, which will be read later by the local
2341 * clock driver. Afterwards, remember the time and
2342 * frequency offsets for jitter and stability values and
2343 * to update the frequency file.
2345 memset(&ntv, 0, sizeof(ntv));
2347 ntv.modes = MOD_STATUS;
2350 ntv.modes = MOD_BITS | MOD_NANO;
2351 #else /* STA_NANO */
2352 ntv.modes = MOD_BITS;
2353 #endif /* STA_NANO */
2354 if (clock_offset < 0)
2359 ntv.offset = (int32)(clock_offset * 1e9 + dtemp);
2360 ntv.constant = sys_poll;
2361 #else /* STA_NANO */
2362 ntv.offset = (int32)(clock_offset * 1e6 + dtemp);
2363 ntv.constant = sys_poll - 4;
2364 #endif /* STA_NANO */
2365 ntv.esterror = (u_int32)(clock_jitter * 1e6);
2366 ntv.maxerror = (u_int32)((sys_rootdelay / 2 + sys_rootdisp) * 1e6);
2367 ntv.status = STA_PLL;
2370 * Enable/disable the PPS if requested.
2373 if (!(pll_status & STA_PPSTIME))
2374 report_event(EVNT_KERN,
2375 NULL, "PPS enabled");
2376 ntv.status |= STA_PPSTIME | STA_PPSFREQ;
2378 if (pll_status & STA_PPSTIME)
2379 report_event(EVNT_KERN,
2380 NULL, "PPS disabled");
2381 ntv.status &= ~(STA_PPSTIME | STA_PPSFREQ);
2383 if (sys_leap == LEAP_ADDSECOND)
2384 ntv.status |= STA_INS;
2385 else if (sys_leap == LEAP_DELSECOND)
2386 ntv.status |= STA_DEL;
2390 * Pass the stuff to the kernel. If it squeals, turn off
2391 * the pps. In any case, fetch the kernel offset,
2392 * frequency and jitter.
2394 if (ntp_adjtime(&ntv) == TIME_ERROR) {
2395 if (!(ntv.status & STA_PPSSIGNAL))
2396 report_event(EVNT_KERN, NULL,
2399 pll_status = ntv.status;
2401 clock_offset = ntv.offset / 1e9;
2402 #else /* STA_NANO */
2403 clock_offset = ntv.offset / 1e6;
2404 #endif /* STA_NANO */
2405 clock_frequency = FREQTOD(ntv.freq);
2408 * If the kernel PPS is lit, monitor its performance.
2410 if (ntv.status & STA_PPSTIME) {
2412 clock_jitter = ntv.jitter / 1e9;
2413 #else /* STA_NANO */
2414 clock_jitter = ntv.jitter / 1e6;
2415 #endif /* STA_NANO */
2418 #if defined(STA_NANO) && NTP_API == 4
2420 * If the TAI changes, update the kernel TAI.
2422 if (loop_tai != sys_tai) {
2424 ntv.modes = MOD_TAI;
2425 ntv.constant = sys_tai;
2428 #endif /* STA_NANO */
2430 #endif /* KERNEL_PLL */