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 */
99 /* Clock discipline parameters and constants */
101 /* Step threshold (sec). std ntpd uses 0.128.
102 * Using exact power of 2 (1/8) results in smaller code */
103 #define STEP_THRESHOLD 0.125
104 #define WATCH_THRESHOLD 128 /* stepout threshold (sec). std ntpd uses 900 (11 mins (!)) */
105 /* NB: set WATCH_THRESHOLD to ~60 when debugging to save time) */
106 //UNUSED: #define PANIC_THRESHOLD 1000 /* panic threshold (sec) */
108 #define FREQ_TOLERANCE 0.000015 /* frequency tolerance (15 PPM) */
109 #define BURSTPOLL 0 /* initial poll */
110 #define MINPOLL 5 /* minimum poll interval. std ntpd uses 6 (6: 64 sec) */
111 /* If offset > discipline_jitter * POLLADJ_GATE, and poll interval is >= 2^BIGPOLL,
112 * then it is decreased _at once_. (If < 2^BIGPOLL, it will be decreased _eventually_).
114 #define BIGPOLL 10 /* 2^10 sec ~= 17 min */
115 #define MAXPOLL 12 /* maximum poll interval (12: 1.1h, 17: 36.4h). std ntpd uses 17 */
116 /* Actively lower poll when we see such big offsets.
117 * With STEP_THRESHOLD = 0.125, it means we try to sync more aggressively
118 * if offset increases over ~0.04 sec */
119 #define POLLDOWN_OFFSET (STEP_THRESHOLD / 3)
120 #define MINDISP 0.01 /* minimum dispersion (sec) */
121 #define MAXDISP 16 /* maximum dispersion (sec) */
122 #define MAXSTRAT 16 /* maximum stratum (infinity metric) */
123 #define MAXDIST 1 /* distance threshold (sec) */
124 #define MIN_SELECTED 1 /* minimum intersection survivors */
125 #define MIN_CLUSTERED 3 /* minimum cluster survivors */
127 #define MAXDRIFT 0.000500 /* frequency drift we can correct (500 PPM) */
129 /* Poll-adjust threshold.
130 * When we see that offset is small enough compared to discipline jitter,
131 * we grow a counter: += MINPOLL. When counter goes over POLLADJ_LIMIT,
132 * we poll_exp++. If offset isn't small, counter -= poll_exp*2,
133 * and when it goes below -POLLADJ_LIMIT, we poll_exp--.
134 * (Bumped from 30 to 40 since otherwise I often see poll_exp going *2* steps down)
136 #define POLLADJ_LIMIT 40
137 /* If offset < discipline_jitter * POLLADJ_GATE, then we decide to increase
138 * poll interval (we think we can't improve timekeeping
139 * by staying at smaller poll).
141 #define POLLADJ_GATE 4
142 #define TIMECONST_HACK_GATE 2
143 /* Compromise Allan intercept (sec). doc uses 1500, std ntpd uses 512 */
147 /* FLL loop gain [why it depends on MAXPOLL??] */
148 #define FLL (MAXPOLL + 1)
149 /* Parameter averaging constant */
158 NTP_MSGSIZE_NOAUTH = 48,
159 NTP_MSGSIZE = (NTP_MSGSIZE_NOAUTH + 4 + NTP_DIGESTSIZE),
162 MODE_MASK = (7 << 0),
163 VERSION_MASK = (7 << 3),
167 /* Leap Second Codes (high order two bits of m_status) */
168 LI_NOWARNING = (0 << 6), /* no warning */
169 LI_PLUSSEC = (1 << 6), /* add a second (61 seconds) */
170 LI_MINUSSEC = (2 << 6), /* minus a second (59 seconds) */
171 LI_ALARM = (3 << 6), /* alarm condition */
174 MODE_RES0 = 0, /* reserved */
175 MODE_SYM_ACT = 1, /* symmetric active */
176 MODE_SYM_PAS = 2, /* symmetric passive */
177 MODE_CLIENT = 3, /* client */
178 MODE_SERVER = 4, /* server */
179 MODE_BROADCAST = 5, /* broadcast */
180 MODE_RES1 = 6, /* reserved for NTP control message */
181 MODE_RES2 = 7, /* reserved for private use */
184 //TODO: better base selection
185 #define OFFSET_1900_1970 2208988800UL /* 1970 - 1900 in seconds */
187 #define NUM_DATAPOINTS 8
200 uint8_t m_status; /* status of local clock and leap info */
202 uint8_t m_ppoll; /* poll value */
203 int8_t m_precision_exp;
204 s_fixedpt_t m_rootdelay;
205 s_fixedpt_t m_rootdisp;
207 l_fixedpt_t m_reftime;
208 l_fixedpt_t m_orgtime;
209 l_fixedpt_t m_rectime;
210 l_fixedpt_t m_xmttime;
212 uint8_t m_digest[NTP_DIGESTSIZE];
222 len_and_sockaddr *p_lsa;
226 uint32_t lastpkt_refid;
227 uint8_t lastpkt_status;
228 uint8_t lastpkt_stratum;
229 uint8_t reachable_bits;
230 /* when to send new query (if p_fd == -1)
231 * or when receive times out (if p_fd >= 0): */
232 double next_action_time;
234 double lastpkt_recv_time;
235 double lastpkt_delay;
236 double lastpkt_rootdelay;
237 double lastpkt_rootdisp;
238 /* produced by filter algorithm: */
239 double filter_offset;
240 double filter_dispersion;
241 double filter_jitter;
242 datapoint_t filter_datapoint[NUM_DATAPOINTS];
243 /* last sent packet: */
248 #define USING_KERNEL_PLL_LOOP 1
249 #define USING_INITIAL_FREQ_ESTIMATION 0
256 /* Insert new options above this line. */
257 /* Non-compat options: */
261 OPT_l = (1 << 7) * ENABLE_FEATURE_NTPD_SERVER,
262 /* We hijack some bits for other purposes */
268 /* total round trip delay to currently selected reference clock */
270 /* reference timestamp: time when the system clock was last set or corrected */
272 /* total dispersion to currently selected reference clock */
275 double last_script_run;
278 #if ENABLE_FEATURE_NTPD_SERVER
280 # define G_listen_fd (G.listen_fd)
282 # define G_listen_fd (-1)
286 /* refid: 32-bit code identifying the particular server or reference clock
287 * in stratum 0 packets this is a four-character ASCII string,
288 * called the kiss code, used for debugging and monitoring
289 * in stratum 1 packets this is a four-character ASCII string
290 * assigned to the reference clock by IANA. Example: "GPS "
291 * in stratum 2+ packets, it's IPv4 address or 4 first bytes
292 * of MD5 hash of IPv6
296 /* precision is defined as the larger of the resolution and time to
297 * read the clock, in log2 units. For instance, the precision of a
298 * mains-frequency clock incrementing at 60 Hz is 16 ms, even when the
299 * system clock hardware representation is to the nanosecond.
301 * Delays, jitters of various kinds are clamped down to precision.
303 * If precision_sec is too large, discipline_jitter gets clamped to it
304 * and if offset is smaller than discipline_jitter * POLLADJ_GATE, poll
305 * interval grows even though we really can benefit from staying at
306 * smaller one, collecting non-lagged datapoits and correcting offset.
307 * (Lagged datapoits exist when poll_exp is large but we still have
308 * systematic offset error - the time distance between datapoints
309 * is significant and older datapoints have smaller offsets.
310 * This makes our offset estimation a bit smaller than reality)
311 * Due to this effect, setting G_precision_sec close to
312 * STEP_THRESHOLD isn't such a good idea - offsets may grow
313 * too big and we will step. I observed it with -6.
315 * OTOH, setting precision_sec far too small would result in futile
316 * attempts to syncronize to an unachievable precision.
318 * -6 is 1/64 sec, -7 is 1/128 sec and so on.
319 * -8 is 1/256 ~= 0.003906 (worked well for me --vda)
320 * -9 is 1/512 ~= 0.001953 (let's try this for some time)
322 #define G_precision_exp -9
324 * G_precision_exp is used only for construction outgoing packets.
325 * It's ok to set G_precision_sec to a slightly different value
326 * (One which is "nicer looking" in logs).
327 * Exact value would be (1.0 / (1 << (- G_precision_exp))):
329 #define G_precision_sec 0.002
331 /* Bool. After set to 1, never goes back to 0: */
332 smallint initial_poll_complete;
334 #define STATE_NSET 0 /* initial state, "nothing is set" */
335 //#define STATE_FSET 1 /* frequency set from file */
336 #define STATE_SPIK 2 /* spike detected */
337 //#define STATE_FREQ 3 /* initial frequency */
338 #define STATE_SYNC 4 /* clock synchronized (normal operation) */
339 uint8_t discipline_state; // doc calls it c.state
340 uint8_t poll_exp; // s.poll
341 int polladj_count; // c.count
342 long kernel_freq_drift;
343 peer_t *last_update_peer;
344 double last_update_offset; // c.last
345 double last_update_recv_time; // s.t
346 double discipline_jitter; // c.jitter
347 /* Since we only compare it with ints, can simplify code
348 * by not making this variable floating point:
350 unsigned offset_to_jitter_ratio;
351 //double cluster_offset; // s.offset
352 //double cluster_jitter; // s.jitter
353 #if !USING_KERNEL_PLL_LOOP
354 double discipline_freq_drift; // c.freq
355 /* Maybe conditionally calculate wander? it's used only for logging */
356 double discipline_wander; // c.wander
359 #define G (*ptr_to_globals)
361 static const int const_IPTOS_LOWDELAY = IPTOS_LOWDELAY;
364 #define VERB1 if (MAX_VERBOSE && G.verbose)
365 #define VERB2 if (MAX_VERBOSE >= 2 && G.verbose >= 2)
366 #define VERB3 if (MAX_VERBOSE >= 3 && G.verbose >= 3)
367 #define VERB4 if (MAX_VERBOSE >= 4 && G.verbose >= 4)
368 #define VERB5 if (MAX_VERBOSE >= 5 && G.verbose >= 5)
371 static double LOG2D(int a)
374 return 1.0 / (1UL << -a);
377 static ALWAYS_INLINE double SQUARE(double x)
381 static ALWAYS_INLINE double MAXD(double a, double b)
387 static ALWAYS_INLINE double MIND(double a, double b)
393 static NOINLINE double my_SQRT(double X)
400 double Xhalf = X * 0.5;
402 /* Fast and good approximation to 1/sqrt(X), black magic */
404 /*v.i = 0x5f3759df - (v.i >> 1);*/
405 v.i = 0x5f375a86 - (v.i >> 1); /* - this constant is slightly better */
406 invsqrt = v.f; /* better than 0.2% accuracy */
408 /* Refining it using Newton's method: x1 = x0 - f(x0)/f'(x0)
409 * f(x) = 1/(x*x) - X (f==0 when x = 1/sqrt(X))
411 * f(x)/f'(x) = (X - 1/(x*x)) / (2/(x*x*x)) = X*x*x*x/2 - x/2
412 * x1 = x0 - (X*x0*x0*x0/2 - x0/2) = 1.5*x0 - X*x0*x0*x0/2 = x0*(1.5 - (X/2)*x0*x0)
414 invsqrt = invsqrt * (1.5 - Xhalf * invsqrt * invsqrt); /* ~0.05% accuracy */
415 /* invsqrt = invsqrt * (1.5 - Xhalf * invsqrt * invsqrt); 2nd iter: ~0.0001% accuracy */
416 /* With 4 iterations, more than half results will be exact,
417 * at 6th iterations result stabilizes with about 72% results exact.
418 * We are well satisfied with 0.05% accuracy.
421 return X * invsqrt; /* X * 1/sqrt(X) ~= sqrt(X) */
423 static ALWAYS_INLINE double SQRT(double X)
425 /* If this arch doesn't use IEEE 754 floats, fall back to using libm */
426 if (sizeof(float) != 4)
429 /* This avoids needing libm, saves about 0.5k on x86-32 */
437 gettimeofday(&tv, NULL); /* never fails */
438 G.cur_time = tv.tv_sec + (1.0e-6 * tv.tv_usec) + OFFSET_1900_1970;
443 d_to_tv(double d, struct timeval *tv)
445 tv->tv_sec = (long)d;
446 tv->tv_usec = (d - tv->tv_sec) * 1000000;
450 lfp_to_d(l_fixedpt_t lfp)
453 lfp.int_partl = ntohl(lfp.int_partl);
454 lfp.fractionl = ntohl(lfp.fractionl);
455 ret = (double)lfp.int_partl + ((double)lfp.fractionl / UINT_MAX);
459 sfp_to_d(s_fixedpt_t sfp)
462 sfp.int_parts = ntohs(sfp.int_parts);
463 sfp.fractions = ntohs(sfp.fractions);
464 ret = (double)sfp.int_parts + ((double)sfp.fractions / USHRT_MAX);
467 #if ENABLE_FEATURE_NTPD_SERVER
472 lfp.int_partl = (uint32_t)d;
473 lfp.fractionl = (uint32_t)((d - lfp.int_partl) * UINT_MAX);
474 lfp.int_partl = htonl(lfp.int_partl);
475 lfp.fractionl = htonl(lfp.fractionl);
482 sfp.int_parts = (uint16_t)d;
483 sfp.fractions = (uint16_t)((d - sfp.int_parts) * USHRT_MAX);
484 sfp.int_parts = htons(sfp.int_parts);
485 sfp.fractions = htons(sfp.fractions);
491 dispersion(const datapoint_t *dp)
493 return dp->d_dispersion + FREQ_TOLERANCE * (G.cur_time - dp->d_recv_time);
497 root_distance(peer_t *p)
499 /* The root synchronization distance is the maximum error due to
500 * all causes of the local clock relative to the primary server.
501 * It is defined as half the total delay plus total dispersion
504 return MAXD(MINDISP, p->lastpkt_rootdelay + p->lastpkt_delay) / 2
505 + p->lastpkt_rootdisp
506 + p->filter_dispersion
507 + FREQ_TOLERANCE * (G.cur_time - p->lastpkt_recv_time)
512 set_next(peer_t *p, unsigned t)
514 p->next_action_time = G.cur_time + t;
518 * Peer clock filter and its helpers
521 filter_datapoints(peer_t *p)
528 /* Simulations have shown that use of *averaged* offset for p->filter_offset
529 * is in fact worse than simply using last received one: with large poll intervals
530 * (>= 2048) averaging code uses offset values which are outdated by hours,
531 * and time/frequency correction goes totally wrong when fed essentially bogus offsets.
534 double minoff, maxoff, w;
535 double x = x; /* for compiler */
536 double oldest_off = oldest_off;
537 double oldest_age = oldest_age;
538 double newest_off = newest_off;
539 double newest_age = newest_age;
541 fdp = p->filter_datapoint;
543 minoff = maxoff = fdp[0].d_offset;
544 for (i = 1; i < NUM_DATAPOINTS; i++) {
545 if (minoff > fdp[i].d_offset)
546 minoff = fdp[i].d_offset;
547 if (maxoff < fdp[i].d_offset)
548 maxoff = fdp[i].d_offset;
551 idx = p->datapoint_idx; /* most recent datapoint's index */
553 * Drop two outliers and take weighted average of the rest:
554 * most_recent/2 + older1/4 + older2/8 ... + older5/32 + older6/32
555 * we use older6/32, not older6/64 since sum of weights should be 1:
556 * 1/2 + 1/4 + 1/8 + 1/16 + 1/32 + 1/32 = 1
562 * filter_dispersion = \ -------------
569 for (i = 0; i < NUM_DATAPOINTS; i++) {
571 bb_error_msg("datapoint[%d]: off:%f disp:%f(%f) age:%f%s",
574 fdp[idx].d_dispersion, dispersion(&fdp[idx]),
575 G.cur_time - fdp[idx].d_recv_time,
576 (minoff == fdp[idx].d_offset || maxoff == fdp[idx].d_offset)
577 ? " (outlier by offset)" : ""
581 sum += dispersion(&fdp[idx]) / (2 << i);
583 if (minoff == fdp[idx].d_offset) {
584 minoff -= 1; /* so that we don't match it ever again */
586 if (maxoff == fdp[idx].d_offset) {
589 oldest_off = fdp[idx].d_offset;
590 oldest_age = G.cur_time - fdp[idx].d_recv_time;
593 newest_off = oldest_off;
594 newest_age = oldest_age;
601 idx = (idx - 1) & (NUM_DATAPOINTS - 1);
603 p->filter_dispersion = sum;
604 wavg += x; /* add another older6/64 to form older6/32 */
605 /* Fix systematic underestimation with large poll intervals.
606 * Imagine that we still have a bit of uncorrected drift,
607 * and poll interval is big (say, 100 sec). Offsets form a progression:
608 * 0.0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 - 0.7 is most recent.
609 * The algorithm above drops 0.0 and 0.7 as outliers,
610 * and then we have this estimation, ~25% off from 0.7:
611 * 0.1/32 + 0.2/32 + 0.3/16 + 0.4/8 + 0.5/4 + 0.6/2 = 0.503125
613 x = oldest_age - newest_age;
615 x = newest_age / x; /* in above example, 100 / (600 - 100) */
616 if (x < 1) { /* paranoia check */
617 x = (newest_off - oldest_off) * x; /* 0.5 * 100/500 = 0.1 */
621 p->filter_offset = wavg;
625 fdp = p->filter_datapoint;
626 idx = p->datapoint_idx; /* most recent datapoint's index */
628 /* filter_offset: simply use the most recent value */
629 p->filter_offset = fdp[idx].d_offset;
633 * filter_dispersion = \ -------------
640 for (i = 0; i < NUM_DATAPOINTS; i++) {
641 sum += dispersion(&fdp[idx]) / (2 << i);
642 wavg += fdp[idx].d_offset;
643 idx = (idx - 1) & (NUM_DATAPOINTS - 1);
645 wavg /= NUM_DATAPOINTS;
646 p->filter_dispersion = sum;
649 /* +----- -----+ ^ 1/2
653 * filter_jitter = | --- * / (avg-offset_j) |
657 * where n is the number of valid datapoints in the filter (n > 1);
658 * if filter_jitter < precision then filter_jitter = precision
661 for (i = 0; i < NUM_DATAPOINTS; i++) {
662 sum += SQUARE(wavg - fdp[i].d_offset);
664 sum = SQRT(sum / NUM_DATAPOINTS);
665 p->filter_jitter = sum > G_precision_sec ? sum : G_precision_sec;
667 VERB3 bb_error_msg("filter offset:%+f disp:%f jitter:%f",
669 p->filter_dispersion,
674 reset_peer_stats(peer_t *p, double offset)
677 bool small_ofs = fabs(offset) < 16 * STEP_THRESHOLD;
679 for (i = 0; i < NUM_DATAPOINTS; i++) {
681 p->filter_datapoint[i].d_recv_time += offset;
682 if (p->filter_datapoint[i].d_offset != 0) {
683 p->filter_datapoint[i].d_offset -= offset;
684 //bb_error_msg("p->filter_datapoint[%d].d_offset %f -> %f",
686 // p->filter_datapoint[i].d_offset + offset,
687 // p->filter_datapoint[i].d_offset);
690 p->filter_datapoint[i].d_recv_time = G.cur_time;
691 p->filter_datapoint[i].d_offset = 0;
692 p->filter_datapoint[i].d_dispersion = MAXDISP;
696 p->lastpkt_recv_time += offset;
698 p->reachable_bits = 0;
699 p->lastpkt_recv_time = G.cur_time;
701 filter_datapoints(p); /* recalc p->filter_xxx */
702 VERB5 bb_error_msg("%s->lastpkt_recv_time=%f", p->p_dotted, p->lastpkt_recv_time);
710 p = xzalloc(sizeof(*p));
711 p->p_lsa = xhost2sockaddr(s, 123);
712 p->p_dotted = xmalloc_sockaddr2dotted_noport(&p->p_lsa->u.sa);
714 p->p_xmt_msg.m_status = MODE_CLIENT | (NTP_VERSION << 3);
715 p->next_action_time = G.cur_time; /* = set_next(p, 0); */
716 reset_peer_stats(p, 16 * STEP_THRESHOLD);
718 llist_add_to(&G.ntp_peers, p);
724 const struct sockaddr *from, const struct sockaddr *to, socklen_t addrlen,
725 msg_t *msg, ssize_t len)
731 ret = sendto(fd, msg, len, MSG_DONTWAIT, to, addrlen);
733 ret = send_to_from(fd, msg, len, MSG_DONTWAIT, to, from, addrlen);
736 bb_perror_msg("send failed");
743 send_query_to_peer(peer_t *p)
745 /* Why do we need to bind()?
746 * See what happens when we don't bind:
748 * socket(PF_INET, SOCK_DGRAM, IPPROTO_IP) = 3
749 * setsockopt(3, SOL_IP, IP_TOS, [16], 4) = 0
750 * gettimeofday({1259071266, 327885}, NULL) = 0
751 * sendto(3, "xxx", 48, MSG_DONTWAIT, {sa_family=AF_INET, sin_port=htons(123), sin_addr=inet_addr("10.34.32.125")}, 16) = 48
752 * ^^^ we sent it from some source port picked by kernel.
753 * time(NULL) = 1259071266
754 * write(2, "ntpd: entering poll 15 secs\n", 28) = 28
755 * poll([{fd=3, events=POLLIN}], 1, 15000) = 1 ([{fd=3, revents=POLLIN}])
756 * recv(3, "yyy", 68, MSG_DONTWAIT) = 48
757 * ^^^ this recv will receive packets to any local port!
759 * Uncomment this and use strace to see it in action:
761 #define PROBE_LOCAL_ADDR /* { len_and_sockaddr lsa; lsa.len = LSA_SIZEOF_SA; getsockname(p->query.fd, &lsa.u.sa, &lsa.len); } */
765 len_and_sockaddr *local_lsa;
767 family = p->p_lsa->u.sa.sa_family;
768 p->p_fd = fd = xsocket_type(&local_lsa, family, SOCK_DGRAM);
769 /* local_lsa has "null" address and port 0 now.
770 * bind() ensures we have a *particular port* selected by kernel
771 * and remembered in p->p_fd, thus later recv(p->p_fd)
772 * receives only packets sent to this port.
775 xbind(fd, &local_lsa->u.sa, local_lsa->len);
777 #if ENABLE_FEATURE_IPV6
778 if (family == AF_INET)
780 setsockopt(fd, IPPROTO_IP, IP_TOS, &const_IPTOS_LOWDELAY, sizeof(const_IPTOS_LOWDELAY));
784 /* Emit message _before_ attempted send. Think of a very short
785 * roundtrip networks: we need to go back to recv loop ASAP,
786 * to reduce delay. Printing messages after send works against that.
788 VERB1 bb_error_msg("sending query to %s", p->p_dotted);
791 * Send out a random 64-bit number as our transmit time. The NTP
792 * server will copy said number into the originate field on the
793 * response that it sends us. This is totally legal per the SNTP spec.
795 * The impact of this is two fold: we no longer send out the current
796 * system time for the world to see (which may aid an attacker), and
797 * it gives us a (not very secure) way of knowing that we're not
798 * getting spoofed by an attacker that can't capture our traffic
799 * but can spoof packets from the NTP server we're communicating with.
801 * Save the real transmit timestamp locally.
803 p->p_xmt_msg.m_xmttime.int_partl = random();
804 p->p_xmt_msg.m_xmttime.fractionl = random();
805 p->p_xmttime = gettime1900d();
807 if (do_sendto(p->p_fd, /*from:*/ NULL, /*to:*/ &p->p_lsa->u.sa, /*addrlen:*/ p->p_lsa->len,
808 &p->p_xmt_msg, NTP_MSGSIZE_NOAUTH) == -1
812 set_next(p, RETRY_INTERVAL);
816 p->reachable_bits <<= 1;
817 set_next(p, RESPONSE_INTERVAL);
821 /* Note that there is no provision to prevent several run_scripts
822 * to be done in quick succession. In fact, it happens rather often
823 * if initial syncronization results in a step.
824 * You will see "step" and then "stratum" script runs, sometimes
825 * as close as only 0.002 seconds apart.
826 * Script should be ready to deal with this.
828 static void run_script(const char *action, double offset)
831 char *env1, *env2, *env3, *env4;
836 argv[0] = (char*) G.script_name;
837 argv[1] = (char*) action;
840 VERB1 bb_error_msg("executing '%s %s'", G.script_name, action);
842 env1 = xasprintf("%s=%u", "stratum", G.stratum);
844 env2 = xasprintf("%s=%ld", "freq_drift_ppm", G.kernel_freq_drift);
846 env3 = xasprintf("%s=%u", "poll_interval", 1 << G.poll_exp);
848 env4 = xasprintf("%s=%f", "offset", offset);
850 /* Other items of potential interest: selected peer,
851 * rootdelay, reftime, rootdisp, refid, ntp_status,
852 * last_update_offset, last_update_recv_time, discipline_jitter,
853 * how many peers have reachable_bits = 0?
856 /* Don't want to wait: it may run hwclock --systohc, and that
857 * may take some time (seconds): */
858 /*spawn_and_wait(argv);*/
862 unsetenv("freq_drift_ppm");
863 unsetenv("poll_interval");
870 G.last_script_run = G.cur_time;
874 step_time(double offset)
878 struct timeval tvc, tvn;
879 char buf[sizeof("yyyy-mm-dd hh:mm:ss") + /*paranoia:*/ 4];
882 gettimeofday(&tvc, NULL); /* never fails */
883 dtime = tvc.tv_sec + (1.0e-6 * tvc.tv_usec) + offset;
884 d_to_tv(dtime, &tvn);
885 if (settimeofday(&tvn, NULL) == -1)
886 bb_perror_msg_and_die("settimeofday");
890 strftime(buf, sizeof(buf), "%Y-%m-%d %H:%M:%S", localtime(&tval));
891 bb_error_msg("current time is %s.%06u", buf, (unsigned)tvc.tv_usec);
894 strftime(buf, sizeof(buf), "%Y-%m-%d %H:%M:%S", localtime(&tval));
895 bb_error_msg("setting time to %s.%06u (offset %+fs)", buf, (unsigned)tvn.tv_usec, offset);
897 /* Correct various fields which contain time-relative values: */
900 G.cur_time += offset;
901 G.last_update_recv_time += offset;
902 G.last_script_run += offset;
904 /* p->lastpkt_recv_time, p->next_action_time and such: */
905 for (item = G.ntp_peers; item != NULL; item = item->link) {
906 peer_t *pp = (peer_t *) item->data;
907 reset_peer_stats(pp, offset);
908 //bb_error_msg("offset:%+f pp->next_action_time:%f -> %f",
909 // offset, pp->next_action_time, pp->next_action_time + offset);
910 pp->next_action_time += offset;
912 /* We wait for reply from this peer too.
913 * But due to step we are doing, reply's data is no longer
914 * useful (in fact, it'll be bogus). Stop waiting for it.
918 set_next(pp, RETRY_INTERVAL);
925 * Selection and clustering, and their helpers
931 double opt_rd; /* optimization */
934 compare_point_edge(const void *aa, const void *bb)
936 const point_t *a = aa;
937 const point_t *b = bb;
938 if (a->edge < b->edge) {
941 return (a->edge > b->edge);
948 compare_survivor_metric(const void *aa, const void *bb)
950 const survivor_t *a = aa;
951 const survivor_t *b = bb;
952 if (a->metric < b->metric) {
955 return (a->metric > b->metric);
958 fit(peer_t *p, double rd)
960 if ((p->reachable_bits & (p->reachable_bits-1)) == 0) {
961 /* One or zero bits in reachable_bits */
962 VERB3 bb_error_msg("peer %s unfit for selection: unreachable", p->p_dotted);
965 #if 0 /* we filter out such packets earlier */
966 if ((p->lastpkt_status & LI_ALARM) == LI_ALARM
967 || p->lastpkt_stratum >= MAXSTRAT
969 VERB3 bb_error_msg("peer %s unfit for selection: bad status/stratum", p->p_dotted);
973 /* rd is root_distance(p) */
974 if (rd > MAXDIST + FREQ_TOLERANCE * (1 << G.poll_exp)) {
975 VERB3 bb_error_msg("peer %s unfit for selection: root distance too high", p->p_dotted);
979 // /* Do we have a loop? */
980 // if (p->refid == p->dstaddr || p->refid == s.refid)
985 select_and_cluster(void)
990 int size = 3 * G.peer_cnt;
991 /* for selection algorithm */
993 unsigned num_points, num_candidates;
995 unsigned num_falsetickers;
996 /* for cluster algorithm */
997 survivor_t survivor[size];
998 unsigned num_survivors;
1004 if (G.initial_poll_complete) while (item != NULL) {
1007 p = (peer_t *) item->data;
1008 rd = root_distance(p);
1009 offset = p->filter_offset;
1015 VERB4 bb_error_msg("interval: [%f %f %f] %s",
1021 point[num_points].p = p;
1022 point[num_points].type = -1;
1023 point[num_points].edge = offset - rd;
1024 point[num_points].opt_rd = rd;
1026 point[num_points].p = p;
1027 point[num_points].type = 0;
1028 point[num_points].edge = offset;
1029 point[num_points].opt_rd = rd;
1031 point[num_points].p = p;
1032 point[num_points].type = 1;
1033 point[num_points].edge = offset + rd;
1034 point[num_points].opt_rd = rd;
1038 num_candidates = num_points / 3;
1039 if (num_candidates == 0) {
1040 VERB3 bb_error_msg("no valid datapoints, no peer selected");
1043 //TODO: sorting does not seem to be done in reference code
1044 qsort(point, num_points, sizeof(point[0]), compare_point_edge);
1046 /* Start with the assumption that there are no falsetickers.
1047 * Attempt to find a nonempty intersection interval containing
1048 * the midpoints of all truechimers.
1049 * If a nonempty interval cannot be found, increase the number
1050 * of assumed falsetickers by one and try again.
1051 * If a nonempty interval is found and the number of falsetickers
1052 * is less than the number of truechimers, a majority has been found
1053 * and the midpoint of each truechimer represents
1054 * the candidates available to the cluster algorithm.
1056 num_falsetickers = 0;
1059 unsigned num_midpoints = 0;
1064 for (i = 0; i < num_points; i++) {
1066 * if (point[i].type == -1) c++;
1067 * if (point[i].type == 1) c--;
1068 * and it's simpler to do it this way:
1071 if (c >= num_candidates - num_falsetickers) {
1072 /* If it was c++ and it got big enough... */
1073 low = point[i].edge;
1076 if (point[i].type == 0)
1080 for (i = num_points-1; i >= 0; i--) {
1082 if (c >= num_candidates - num_falsetickers) {
1083 high = point[i].edge;
1086 if (point[i].type == 0)
1089 /* If the number of midpoints is greater than the number
1090 * of allowed falsetickers, the intersection contains at
1091 * least one truechimer with no midpoint - bad.
1092 * Also, interval should be nonempty.
1094 if (num_midpoints <= num_falsetickers && low < high)
1097 if (num_falsetickers * 2 >= num_candidates) {
1098 VERB3 bb_error_msg("too many falsetickers:%d (candidates:%d), no peer selected",
1099 num_falsetickers, num_candidates);
1103 VERB3 bb_error_msg("selected interval: [%f, %f]; candidates:%d falsetickers:%d",
1104 low, high, num_candidates, num_falsetickers);
1108 /* Construct a list of survivors (p, metric)
1109 * from the chime list, where metric is dominated
1110 * first by stratum and then by root distance.
1111 * All other things being equal, this is the order of preference.
1114 for (i = 0; i < num_points; i++) {
1115 if (point[i].edge < low || point[i].edge > high)
1118 survivor[num_survivors].p = p;
1119 /* x.opt_rd == root_distance(p); */
1120 survivor[num_survivors].metric = MAXDIST * p->lastpkt_stratum + point[i].opt_rd;
1121 VERB4 bb_error_msg("survivor[%d] metric:%f peer:%s",
1122 num_survivors, survivor[num_survivors].metric, p->p_dotted);
1125 /* There must be at least MIN_SELECTED survivors to satisfy the
1126 * correctness assertions. Ordinarily, the Byzantine criteria
1127 * require four survivors, but for the demonstration here, one
1130 if (num_survivors < MIN_SELECTED) {
1131 VERB3 bb_error_msg("num_survivors %d < %d, no peer selected",
1132 num_survivors, MIN_SELECTED);
1136 //looks like this is ONLY used by the fact that later we pick survivor[0].
1137 //we can avoid sorting then, just find the minimum once!
1138 qsort(survivor, num_survivors, sizeof(survivor[0]), compare_survivor_metric);
1140 /* For each association p in turn, calculate the selection
1141 * jitter p->sjitter as the square root of the sum of squares
1142 * (p->offset - q->offset) over all q associations. The idea is
1143 * to repeatedly discard the survivor with maximum selection
1144 * jitter until a termination condition is met.
1147 unsigned max_idx = max_idx;
1148 double max_selection_jitter = max_selection_jitter;
1149 double min_jitter = min_jitter;
1151 if (num_survivors <= MIN_CLUSTERED) {
1152 VERB3 bb_error_msg("num_survivors %d <= %d, not discarding more",
1153 num_survivors, MIN_CLUSTERED);
1157 /* To make sure a few survivors are left
1158 * for the clustering algorithm to chew on,
1159 * we stop if the number of survivors
1160 * is less than or equal to MIN_CLUSTERED (3).
1162 for (i = 0; i < num_survivors; i++) {
1163 double selection_jitter_sq;
1166 if (i == 0 || p->filter_jitter < min_jitter)
1167 min_jitter = p->filter_jitter;
1169 selection_jitter_sq = 0;
1170 for (j = 0; j < num_survivors; j++) {
1171 peer_t *q = survivor[j].p;
1172 selection_jitter_sq += SQUARE(p->filter_offset - q->filter_offset);
1174 if (i == 0 || selection_jitter_sq > max_selection_jitter) {
1175 max_selection_jitter = selection_jitter_sq;
1178 VERB5 bb_error_msg("survivor %d selection_jitter^2:%f",
1179 i, selection_jitter_sq);
1181 max_selection_jitter = SQRT(max_selection_jitter / num_survivors);
1182 VERB4 bb_error_msg("max_selection_jitter (at %d):%f min_jitter:%f",
1183 max_idx, max_selection_jitter, min_jitter);
1185 /* If the maximum selection jitter is less than the
1186 * minimum peer jitter, then tossing out more survivors
1187 * will not lower the minimum peer jitter, so we might
1190 if (max_selection_jitter < min_jitter) {
1191 VERB3 bb_error_msg("max_selection_jitter:%f < min_jitter:%f, num_survivors:%d, not discarding more",
1192 max_selection_jitter, min_jitter, num_survivors);
1196 /* Delete survivor[max_idx] from the list
1197 * and go around again.
1199 VERB5 bb_error_msg("dropping survivor %d", max_idx);
1201 while (max_idx < num_survivors) {
1202 survivor[max_idx] = survivor[max_idx + 1];
1208 /* Combine the offsets of the clustering algorithm survivors
1209 * using a weighted average with weight determined by the root
1210 * distance. Compute the selection jitter as the weighted RMS
1211 * difference between the first survivor and the remaining
1212 * survivors. In some cases the inherent clock jitter can be
1213 * reduced by not using this algorithm, especially when frequent
1214 * clockhopping is involved. bbox: thus we don't do it.
1218 for (i = 0; i < num_survivors; i++) {
1220 x = root_distance(p);
1222 z += p->filter_offset / x;
1223 w += SQUARE(p->filter_offset - survivor[0].p->filter_offset) / x;
1225 //G.cluster_offset = z / y;
1226 //G.cluster_jitter = SQRT(w / y);
1229 /* Pick the best clock. If the old system peer is on the list
1230 * and at the same stratum as the first survivor on the list,
1231 * then don't do a clock hop. Otherwise, select the first
1232 * survivor on the list as the new system peer.
1235 if (G.last_update_peer
1236 && G.last_update_peer->lastpkt_stratum <= p->lastpkt_stratum
1238 /* Starting from 1 is ok here */
1239 for (i = 1; i < num_survivors; i++) {
1240 if (G.last_update_peer == survivor[i].p) {
1241 VERB4 bb_error_msg("keeping old synced peer");
1242 p = G.last_update_peer;
1247 G.last_update_peer = p;
1249 VERB3 bb_error_msg("selected peer %s filter_offset:%+f age:%f",
1252 G.cur_time - p->lastpkt_recv_time
1259 * Local clock discipline and its helpers
1262 set_new_values(int disc_state, double offset, double recv_time)
1264 /* Enter new state and set state variables. Note we use the time
1265 * of the last clock filter sample, which must be earlier than
1268 VERB3 bb_error_msg("disc_state=%d last update offset=%f recv_time=%f",
1269 disc_state, offset, recv_time);
1270 G.discipline_state = disc_state;
1271 G.last_update_offset = offset;
1272 G.last_update_recv_time = recv_time;
1274 /* Return: -1: decrease poll interval, 0: leave as is, 1: increase */
1276 update_local_clock(peer_t *p)
1280 /* Note: can use G.cluster_offset instead: */
1281 double offset = p->filter_offset;
1282 double recv_time = p->lastpkt_recv_time;
1284 #if !USING_KERNEL_PLL_LOOP
1287 double since_last_update;
1288 double etemp, dtemp;
1290 abs_offset = fabs(offset);
1293 /* If needed, -S script can do it by looking at $offset
1294 * env var and killing parent */
1295 /* If the offset is too large, give up and go home */
1296 if (abs_offset > PANIC_THRESHOLD) {
1297 bb_error_msg_and_die("offset %f far too big, exiting", offset);
1301 /* If this is an old update, for instance as the result
1302 * of a system peer change, avoid it. We never use
1303 * an old sample or the same sample twice.
1305 if (recv_time <= G.last_update_recv_time) {
1306 VERB3 bb_error_msg("same or older datapoint: %f >= %f, not using it",
1307 G.last_update_recv_time, recv_time);
1308 return 0; /* "leave poll interval as is" */
1311 /* Clock state machine transition function. This is where the
1312 * action is and defines how the system reacts to large time
1313 * and frequency errors.
1315 since_last_update = recv_time - G.reftime;
1316 #if !USING_KERNEL_PLL_LOOP
1319 #if USING_INITIAL_FREQ_ESTIMATION
1320 if (G.discipline_state == STATE_FREQ) {
1321 /* Ignore updates until the stepout threshold */
1322 if (since_last_update < WATCH_THRESHOLD) {
1323 VERB3 bb_error_msg("measuring drift, datapoint ignored, %f sec remains",
1324 WATCH_THRESHOLD - since_last_update);
1325 return 0; /* "leave poll interval as is" */
1327 # if !USING_KERNEL_PLL_LOOP
1328 freq_drift = (offset - G.last_update_offset) / since_last_update;
1333 /* There are two main regimes: when the
1334 * offset exceeds the step threshold and when it does not.
1336 if (abs_offset > STEP_THRESHOLD) {
1337 switch (G.discipline_state) {
1339 /* The first outlyer: ignore it, switch to SPIK state */
1340 VERB3 bb_error_msg("offset:%+f - spike detected", offset);
1341 G.discipline_state = STATE_SPIK;
1342 return -1; /* "decrease poll interval" */
1345 /* Ignore succeeding outlyers until either an inlyer
1346 * is found or the stepout threshold is exceeded.
1348 if (since_last_update < WATCH_THRESHOLD) {
1349 VERB3 bb_error_msg("spike detected, datapoint ignored, %f sec remains",
1350 WATCH_THRESHOLD - since_last_update);
1351 return -1; /* "decrease poll interval" */
1353 /* fall through: we need to step */
1356 /* Step the time and clamp down the poll interval.
1358 * In NSET state an initial frequency correction is
1359 * not available, usually because the frequency file has
1360 * not yet been written. Since the time is outside the
1361 * capture range, the clock is stepped. The frequency
1362 * will be set directly following the stepout interval.
1364 * In FSET state the initial frequency has been set
1365 * from the frequency file. Since the time is outside
1366 * the capture range, the clock is stepped immediately,
1367 * rather than after the stepout interval. Guys get
1368 * nervous if it takes 17 minutes to set the clock for
1371 * In SPIK state the stepout threshold has expired and
1372 * the phase is still above the step threshold. Note
1373 * that a single spike greater than the step threshold
1374 * is always suppressed, even at the longer poll
1377 VERB3 bb_error_msg("stepping time by %+f; poll_exp=MINPOLL", offset);
1379 if (option_mask32 & OPT_q) {
1380 /* We were only asked to set time once. Done. */
1384 G.polladj_count = 0;
1385 G.poll_exp = MINPOLL;
1386 G.stratum = MAXSTRAT;
1388 run_script("step", offset);
1390 #if USING_INITIAL_FREQ_ESTIMATION
1391 if (G.discipline_state == STATE_NSET) {
1392 set_new_values(STATE_FREQ, /*offset:*/ 0, recv_time);
1393 return 1; /* "ok to increase poll interval" */
1396 abs_offset = offset = 0;
1397 set_new_values(STATE_SYNC, offset, recv_time);
1399 } else { /* abs_offset <= STEP_THRESHOLD */
1401 if (G.poll_exp < MINPOLL && G.initial_poll_complete) {
1402 VERB3 bb_error_msg("small offset:%+f, disabling burst mode", offset);
1403 G.polladj_count = 0;
1404 G.poll_exp = MINPOLL;
1407 /* Compute the clock jitter as the RMS of exponentially
1408 * weighted offset differences. Used by the poll adjust code.
1410 etemp = SQUARE(G.discipline_jitter);
1411 dtemp = SQUARE(offset - G.last_update_offset);
1412 G.discipline_jitter = SQRT(etemp + (dtemp - etemp) / AVG);
1414 switch (G.discipline_state) {
1416 if (option_mask32 & OPT_q) {
1417 /* We were only asked to set time once.
1418 * The clock is precise enough, no need to step.
1422 #if USING_INITIAL_FREQ_ESTIMATION
1423 /* This is the first update received and the frequency
1424 * has not been initialized. The first thing to do
1425 * is directly measure the oscillator frequency.
1427 set_new_values(STATE_FREQ, offset, recv_time);
1429 set_new_values(STATE_SYNC, offset, recv_time);
1431 VERB3 bb_error_msg("transitioning to FREQ, datapoint ignored");
1432 return 0; /* "leave poll interval as is" */
1434 #if 0 /* this is dead code for now */
1436 /* This is the first update and the frequency
1437 * has been initialized. Adjust the phase, but
1438 * don't adjust the frequency until the next update.
1440 set_new_values(STATE_SYNC, offset, recv_time);
1441 /* freq_drift remains 0 */
1445 #if USING_INITIAL_FREQ_ESTIMATION
1447 /* since_last_update >= WATCH_THRESHOLD, we waited enough.
1448 * Correct the phase and frequency and switch to SYNC state.
1449 * freq_drift was already estimated (see code above)
1451 set_new_values(STATE_SYNC, offset, recv_time);
1456 #if !USING_KERNEL_PLL_LOOP
1457 /* Compute freq_drift due to PLL and FLL contributions.
1459 * The FLL and PLL frequency gain constants
1460 * depend on the poll interval and Allan
1461 * intercept. The FLL is not used below one-half
1462 * the Allan intercept. Above that the loop gain
1463 * increases in steps to 1 / AVG.
1465 if ((1 << G.poll_exp) > ALLAN / 2) {
1466 etemp = FLL - G.poll_exp;
1469 freq_drift += (offset - G.last_update_offset) / (MAXD(since_last_update, ALLAN) * etemp);
1471 /* For the PLL the integration interval
1472 * (numerator) is the minimum of the update
1473 * interval and poll interval. This allows
1474 * oversampling, but not undersampling.
1476 etemp = MIND(since_last_update, (1 << G.poll_exp));
1477 dtemp = (4 * PLL) << G.poll_exp;
1478 freq_drift += offset * etemp / SQUARE(dtemp);
1480 set_new_values(STATE_SYNC, offset, recv_time);
1483 if (G.stratum != p->lastpkt_stratum + 1) {
1484 G.stratum = p->lastpkt_stratum + 1;
1485 run_script("stratum", offset);
1489 if (G.discipline_jitter < G_precision_sec)
1490 G.discipline_jitter = G_precision_sec;
1491 G.offset_to_jitter_ratio = abs_offset / G.discipline_jitter;
1493 G.reftime = G.cur_time;
1494 G.ntp_status = p->lastpkt_status;
1495 G.refid = p->lastpkt_refid;
1496 G.rootdelay = p->lastpkt_rootdelay + p->lastpkt_delay;
1497 dtemp = p->filter_jitter; // SQRT(SQUARE(p->filter_jitter) + SQUARE(G.cluster_jitter));
1498 dtemp += MAXD(p->filter_dispersion + FREQ_TOLERANCE * (G.cur_time - p->lastpkt_recv_time) + abs_offset, MINDISP);
1499 G.rootdisp = p->lastpkt_rootdisp + dtemp;
1500 VERB3 bb_error_msg("updating leap/refid/reftime/rootdisp from peer %s", p->p_dotted);
1502 /* We are in STATE_SYNC now, but did not do adjtimex yet.
1503 * (Any other state does not reach this, they all return earlier)
1504 * By this time, freq_drift and offset are set
1505 * to values suitable for adjtimex.
1507 #if !USING_KERNEL_PLL_LOOP
1508 /* Calculate the new frequency drift and frequency stability (wander).
1509 * Compute the clock wander as the RMS of exponentially weighted
1510 * frequency differences. This is not used directly, but can,
1511 * along with the jitter, be a highly useful monitoring and
1514 dtemp = G.discipline_freq_drift + freq_drift;
1515 G.discipline_freq_drift = MAXD(MIND(MAXDRIFT, dtemp), -MAXDRIFT);
1516 etemp = SQUARE(G.discipline_wander);
1517 dtemp = SQUARE(dtemp);
1518 G.discipline_wander = SQRT(etemp + (dtemp - etemp) / AVG);
1520 VERB3 bb_error_msg("discipline freq_drift=%.9f(int:%ld corr:%e) wander=%f",
1521 G.discipline_freq_drift,
1522 (long)(G.discipline_freq_drift * 65536e6),
1524 G.discipline_wander);
1527 memset(&tmx, 0, sizeof(tmx));
1528 if (adjtimex(&tmx) < 0)
1529 bb_perror_msg_and_die("adjtimex");
1530 bb_error_msg("p adjtimex freq:%ld offset:%+ld status:0x%x tc:%ld",
1531 tmx.freq, tmx.offset, tmx.status, tmx.constant);
1534 memset(&tmx, 0, sizeof(tmx));
1536 //doesn't work, offset remains 0 (!) in kernel:
1537 //ntpd: set adjtimex freq:1786097 tmx.offset:77487
1538 //ntpd: prev adjtimex freq:1786097 tmx.offset:0
1539 //ntpd: cur adjtimex freq:1786097 tmx.offset:0
1540 tmx.modes = ADJ_FREQUENCY | ADJ_OFFSET;
1541 /* 65536 is one ppm */
1542 tmx.freq = G.discipline_freq_drift * 65536e6;
1544 tmx.modes = ADJ_OFFSET | ADJ_STATUS | ADJ_TIMECONST;// | ADJ_MAXERROR | ADJ_ESTERROR;
1545 tmx.offset = (offset * 1000000); /* usec */
1546 tmx.status = STA_PLL;
1547 if (G.ntp_status & LI_PLUSSEC)
1548 tmx.status |= STA_INS;
1549 if (G.ntp_status & LI_MINUSSEC)
1550 tmx.status |= STA_DEL;
1552 tmx.constant = G.poll_exp - 4;
1554 * The below if statement should be unnecessary, but...
1555 * It looks like Linux kernel's PLL is far too gentle in changing
1556 * tmx.freq in response to clock offset. Offset keeps growing
1557 * and eventually we fall back to smaller poll intervals.
1558 * We can make correction more agressive (about x2) by supplying
1559 * PLL time constant which is one less than the real one.
1560 * To be on a safe side, let's do it only if offset is significantly
1561 * larger than jitter.
1563 if (tmx.constant > 0 && G.offset_to_jitter_ratio >= TIMECONST_HACK_GATE)
1566 //tmx.esterror = (uint32_t)(clock_jitter * 1e6);
1567 //tmx.maxerror = (uint32_t)((sys_rootdelay / 2 + sys_rootdisp) * 1e6);
1568 rc = adjtimex(&tmx);
1570 bb_perror_msg_and_die("adjtimex");
1571 /* NB: here kernel returns constant == G.poll_exp, not == G.poll_exp - 4.
1572 * Not sure why. Perhaps it is normal.
1574 VERB3 bb_error_msg("adjtimex:%d freq:%ld offset:%+ld status:0x%x",
1575 rc, tmx.freq, tmx.offset, tmx.status);
1576 G.kernel_freq_drift = tmx.freq / 65536;
1577 VERB2 bb_error_msg("update from:%s offset:%+f jitter:%f clock drift:%+.3fppm tc:%d",
1578 p->p_dotted, offset, G.discipline_jitter, (double)tmx.freq / 65536, (int)tmx.constant);
1580 return 1; /* "ok to increase poll interval" */
1585 * We've got a new reply packet from a peer, process it
1589 retry_interval(void)
1591 /* Local problem, want to retry soon */
1592 unsigned interval, r;
1593 interval = RETRY_INTERVAL;
1595 interval += r % (unsigned)(RETRY_INTERVAL / 4);
1596 VERB3 bb_error_msg("chose retry interval:%u", interval);
1600 poll_interval(int exponent)
1602 unsigned interval, r;
1603 exponent = G.poll_exp + exponent;
1606 interval = 1 << exponent;
1608 interval += ((r & (interval-1)) >> 4) + ((r >> 8) & 1); /* + 1/16 of interval, max */
1609 VERB3 bb_error_msg("chose poll interval:%u (poll_exp:%d exp:%d)", interval, G.poll_exp, exponent);
1612 static NOINLINE void
1613 recv_and_process_peer_pkt(peer_t *p)
1618 double T1, T2, T3, T4;
1620 datapoint_t *datapoint;
1623 /* We can recvfrom here and check from.IP, but some multihomed
1624 * ntp servers reply from their *other IP*.
1625 * TODO: maybe we should check at least what we can: from.port == 123?
1627 size = recv(p->p_fd, &msg, sizeof(msg), MSG_DONTWAIT);
1629 bb_perror_msg("recv(%s) error", p->p_dotted);
1630 if (errno == EHOSTUNREACH || errno == EHOSTDOWN
1631 || errno == ENETUNREACH || errno == ENETDOWN
1632 || errno == ECONNREFUSED || errno == EADDRNOTAVAIL
1635 //TODO: always do this?
1636 interval = retry_interval();
1637 goto set_next_and_ret;
1642 if (size != NTP_MSGSIZE_NOAUTH && size != NTP_MSGSIZE) {
1643 bb_error_msg("malformed packet received from %s", p->p_dotted);
1647 if (msg.m_orgtime.int_partl != p->p_xmt_msg.m_xmttime.int_partl
1648 || msg.m_orgtime.fractionl != p->p_xmt_msg.m_xmttime.fractionl
1650 /* Somebody else's packet */
1654 /* We do not expect any more packets from this peer for now.
1655 * Closing the socket informs kernel about it.
1656 * We open a new socket when we send a new query.
1661 if ((msg.m_status & LI_ALARM) == LI_ALARM
1662 || msg.m_stratum == 0
1663 || msg.m_stratum > NTP_MAXSTRATUM
1665 // TODO: stratum 0 responses may have commands in 32-bit m_refid field:
1666 // "DENY", "RSTR" - peer does not like us at all
1667 // "RATE" - peer is overloaded, reduce polling freq
1668 interval = poll_interval(0);
1669 bb_error_msg("reply from %s: peer is unsynced, next query in %us", p->p_dotted, interval);
1670 goto set_next_and_ret;
1673 // /* Verify valid root distance */
1674 // if (msg.m_rootdelay / 2 + msg.m_rootdisp >= MAXDISP || p->lastpkt_reftime > msg.m_xmt)
1675 // return; /* invalid header values */
1677 p->lastpkt_status = msg.m_status;
1678 p->lastpkt_stratum = msg.m_stratum;
1679 p->lastpkt_rootdelay = sfp_to_d(msg.m_rootdelay);
1680 p->lastpkt_rootdisp = sfp_to_d(msg.m_rootdisp);
1681 p->lastpkt_refid = msg.m_refid;
1684 * From RFC 2030 (with a correction to the delay math):
1686 * Timestamp Name ID When Generated
1687 * ------------------------------------------------------------
1688 * Originate Timestamp T1 time request sent by client
1689 * Receive Timestamp T2 time request received by server
1690 * Transmit Timestamp T3 time reply sent by server
1691 * Destination Timestamp T4 time reply received by client
1693 * The roundtrip delay and local clock offset are defined as
1695 * delay = (T4 - T1) - (T3 - T2); offset = ((T2 - T1) + (T3 - T4)) / 2
1698 T2 = lfp_to_d(msg.m_rectime);
1699 T3 = lfp_to_d(msg.m_xmttime);
1702 p->lastpkt_recv_time = T4;
1704 VERB5 bb_error_msg("%s->lastpkt_recv_time=%f", p->p_dotted, p->lastpkt_recv_time);
1705 p->datapoint_idx = p->reachable_bits ? (p->datapoint_idx + 1) % NUM_DATAPOINTS : 0;
1706 datapoint = &p->filter_datapoint[p->datapoint_idx];
1707 datapoint->d_recv_time = T4;
1708 datapoint->d_offset = ((T2 - T1) + (T3 - T4)) / 2;
1709 /* The delay calculation is a special case. In cases where the
1710 * server and client clocks are running at different rates and
1711 * with very fast networks, the delay can appear negative. In
1712 * order to avoid violating the Principle of Least Astonishment,
1713 * the delay is clamped not less than the system precision.
1715 p->lastpkt_delay = (T4 - T1) - (T3 - T2);
1716 if (p->lastpkt_delay < G_precision_sec)
1717 p->lastpkt_delay = G_precision_sec;
1718 datapoint->d_dispersion = LOG2D(msg.m_precision_exp) + G_precision_sec;
1719 if (!p->reachable_bits) {
1720 /* 1st datapoint ever - replicate offset in every element */
1722 for (i = 0; i < NUM_DATAPOINTS; i++) {
1723 p->filter_datapoint[i].d_offset = datapoint->d_offset;
1727 p->reachable_bits |= 1;
1728 if ((MAX_VERBOSE && G.verbose) || (option_mask32 & OPT_w)) {
1729 bb_error_msg("reply from %s: offset:%+f delay:%f status:0x%02x strat:%d refid:0x%08x rootdelay:%f reach:0x%02x",
1731 datapoint->d_offset,
1736 p->lastpkt_rootdelay,
1738 /* not shown: m_ppoll, m_precision_exp, m_rootdisp,
1739 * m_reftime, m_orgtime, m_rectime, m_xmttime
1744 /* Muck with statictics and update the clock */
1745 filter_datapoints(p);
1746 q = select_and_cluster();
1750 if (!(option_mask32 & OPT_w)) {
1751 rc = update_local_clock(q);
1752 /* If drift is dangerously large, immediately
1753 * drop poll interval one step down.
1755 if (fabs(q->filter_offset) >= POLLDOWN_OFFSET) {
1756 VERB3 bb_error_msg("offset:%+f > POLLDOWN_OFFSET", q->filter_offset);
1761 /* else: no peer selected, rc = -1: we want to poll more often */
1764 /* Adjust the poll interval by comparing the current offset
1765 * with the clock jitter. If the offset is less than
1766 * the clock jitter times a constant, then the averaging interval
1767 * is increased, otherwise it is decreased. A bit of hysteresis
1768 * helps calm the dance. Works best using burst mode.
1770 if (rc > 0 && G.offset_to_jitter_ratio <= POLLADJ_GATE) {
1771 /* was += G.poll_exp but it is a bit
1772 * too optimistic for my taste at high poll_exp's */
1773 G.polladj_count += MINPOLL;
1774 if (G.polladj_count > POLLADJ_LIMIT) {
1775 G.polladj_count = 0;
1776 if (G.poll_exp < MAXPOLL) {
1778 VERB3 bb_error_msg("polladj: discipline_jitter:%f ++poll_exp=%d",
1779 G.discipline_jitter, G.poll_exp);
1782 VERB3 bb_error_msg("polladj: incr:%d", G.polladj_count);
1785 G.polladj_count -= G.poll_exp * 2;
1786 if (G.polladj_count < -POLLADJ_LIMIT || G.poll_exp >= BIGPOLL) {
1788 G.polladj_count = 0;
1789 if (G.poll_exp > MINPOLL) {
1793 /* Correct p->next_action_time in each peer
1794 * which waits for sending, so that they send earlier.
1795 * Old pp->next_action_time are on the order
1796 * of t + (1 << old_poll_exp) + small_random,
1797 * we simply need to subtract ~half of that.
1799 for (item = G.ntp_peers; item != NULL; item = item->link) {
1800 peer_t *pp = (peer_t *) item->data;
1802 pp->next_action_time -= (1 << G.poll_exp);
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: decr:%d", G.polladj_count);
1813 /* Decide when to send new query for this peer */
1814 interval = poll_interval(0);
1817 set_next(p, interval);
1820 #if ENABLE_FEATURE_NTPD_SERVER
1821 static NOINLINE void
1822 recv_and_process_client_pkt(void /*int fd*/)
1826 len_and_sockaddr *to;
1827 struct sockaddr *from;
1829 uint8_t query_status;
1830 l_fixedpt_t query_xmttime;
1832 to = get_sock_lsa(G_listen_fd);
1833 from = xzalloc(to->len);
1835 size = recv_from_to(G_listen_fd, &msg, sizeof(msg), MSG_DONTWAIT, from, &to->u.sa, to->len);
1836 if (size != NTP_MSGSIZE_NOAUTH && size != NTP_MSGSIZE) {
1839 if (errno == EAGAIN)
1841 bb_perror_msg_and_die("recv");
1843 addr = xmalloc_sockaddr2dotted_noport(from);
1844 bb_error_msg("malformed packet received from %s: size %u", addr, (int)size);
1849 query_status = msg.m_status;
1850 query_xmttime = msg.m_xmttime;
1852 /* Build a reply packet */
1853 memset(&msg, 0, sizeof(msg));
1854 msg.m_status = G.stratum < MAXSTRAT ? (G.ntp_status & LI_MASK) : LI_ALARM;
1855 msg.m_status |= (query_status & VERSION_MASK);
1856 msg.m_status |= ((query_status & MODE_MASK) == MODE_CLIENT) ?
1857 MODE_SERVER : MODE_SYM_PAS;
1858 msg.m_stratum = G.stratum;
1859 msg.m_ppoll = G.poll_exp;
1860 msg.m_precision_exp = G_precision_exp;
1861 /* this time was obtained between poll() and recv() */
1862 msg.m_rectime = d_to_lfp(G.cur_time);
1863 msg.m_xmttime = d_to_lfp(gettime1900d()); /* this instant */
1864 if (G.peer_cnt == 0) {
1865 /* we have no peers: "stratum 1 server" mode. reftime = our own time */
1866 G.reftime = G.cur_time;
1868 msg.m_reftime = d_to_lfp(G.reftime);
1869 msg.m_orgtime = query_xmttime;
1870 msg.m_rootdelay = d_to_sfp(G.rootdelay);
1871 //simple code does not do this, fix simple code!
1872 msg.m_rootdisp = d_to_sfp(G.rootdisp);
1873 //version = (query_status & VERSION_MASK); /* ... >> VERSION_SHIFT - done below instead */
1874 msg.m_refid = G.refid; // (version > (3 << VERSION_SHIFT)) ? G.refid : G.refid3;
1876 /* We reply from the local address packet was sent to,
1877 * this makes to/from look swapped here: */
1878 do_sendto(G_listen_fd,
1879 /*from:*/ &to->u.sa, /*to:*/ from, /*addrlen:*/ to->len,
1888 /* Upstream ntpd's options:
1890 * -4 Force DNS resolution of host names to the IPv4 namespace.
1891 * -6 Force DNS resolution of host names to the IPv6 namespace.
1892 * -a Require cryptographic authentication for broadcast client,
1893 * multicast client and symmetric passive associations.
1894 * This is the default.
1895 * -A Do not require cryptographic authentication for broadcast client,
1896 * multicast client and symmetric passive associations.
1897 * This is almost never a good idea.
1898 * -b Enable the client to synchronize to broadcast servers.
1900 * Specify the name and path of the configuration file,
1901 * default /etc/ntp.conf
1902 * -d Specify debugging mode. This option may occur more than once,
1903 * with each occurrence indicating greater detail of display.
1905 * Specify debugging level directly.
1907 * Specify the name and path of the frequency file.
1908 * This is the same operation as the "driftfile FILE"
1909 * configuration command.
1910 * -g Normally, ntpd exits with a message to the system log
1911 * if the offset exceeds the panic threshold, which is 1000 s
1912 * by default. This option allows the time to be set to any value
1913 * without restriction; however, this can happen only once.
1914 * If the threshold is exceeded after that, ntpd will exit
1915 * with a message to the system log. This option can be used
1916 * with the -q and -x options. See the tinker command for other options.
1918 * Chroot the server to the directory jaildir. This option also implies
1919 * that the server attempts to drop root privileges at startup
1920 * (otherwise, chroot gives very little additional security).
1921 * You may need to also specify a -u option.
1923 * Specify the name and path of the symmetric key file,
1924 * default /etc/ntp/keys. This is the same operation
1925 * as the "keys FILE" configuration command.
1927 * Specify the name and path of the log file. The default
1928 * is the system log file. This is the same operation as
1929 * the "logfile FILE" configuration command.
1930 * -L Do not listen to virtual IPs. The default is to listen.
1932 * -N To the extent permitted by the operating system,
1933 * run the ntpd at the highest priority.
1935 * Specify the name and path of the file used to record the ntpd
1936 * process ID. This is the same operation as the "pidfile FILE"
1937 * configuration command.
1939 * To the extent permitted by the operating system,
1940 * run the ntpd at the specified priority.
1941 * -q Exit the ntpd just after the first time the clock is set.
1942 * This behavior mimics that of the ntpdate program, which is
1943 * to be retired. The -g and -x options can be used with this option.
1944 * Note: The kernel time discipline is disabled with this option.
1946 * Specify the default propagation delay from the broadcast/multicast
1947 * server to this client. This is necessary only if the delay
1948 * cannot be computed automatically by the protocol.
1950 * Specify the directory path for files created by the statistics
1951 * facility. This is the same operation as the "statsdir DIR"
1952 * configuration command.
1954 * Add a key number to the trusted key list. This option can occur
1957 * Specify a user, and optionally a group, to switch to.
1960 * Add a system variable listed by default.
1961 * -x Normally, the time is slewed if the offset is less than the step
1962 * threshold, which is 128 ms by default, and stepped if above
1963 * the threshold. This option sets the threshold to 600 s, which is
1964 * well within the accuracy window to set the clock manually.
1965 * Note: since the slew rate of typical Unix kernels is limited
1966 * to 0.5 ms/s, each second of adjustment requires an amortization
1967 * interval of 2000 s. Thus, an adjustment as much as 600 s
1968 * will take almost 14 days to complete. This option can be used
1969 * with the -g and -q options. See the tinker command for other options.
1970 * Note: The kernel time discipline is disabled with this option.
1973 /* By doing init in a separate function we decrease stack usage
1976 static NOINLINE void ntp_init(char **argv)
1984 bb_error_msg_and_die(bb_msg_you_must_be_root);
1986 /* Set some globals */
1987 G.stratum = MAXSTRAT;
1989 G.poll_exp = BURSTPOLL; /* speeds up initial sync */
1990 G.last_script_run = G.reftime = G.last_update_recv_time = gettime1900d(); /* sets G.cur_time too */
1994 opt_complementary = "dd:p::wn"; /* d: counter; p: list; -w implies -n */
1995 opts = getopt32(argv,
1997 "wp:S:"IF_FEATURE_NTPD_SERVER("l") /* NOT compat */
1999 "46aAbgL", /* compat, ignored */
2000 &peers, &G.script_name, &G.verbose);
2001 if (!(opts & (OPT_p|OPT_l)))
2003 // if (opts & OPT_x) /* disable stepping, only slew is allowed */
2004 // G.time_was_stepped = 1;
2007 add_peers(llist_pop(&peers));
2009 /* -l but no peers: "stratum 1 server" mode */
2012 if (!(opts & OPT_n)) {
2013 bb_daemonize_or_rexec(DAEMON_DEVNULL_STDIO, argv);
2014 logmode = LOGMODE_NONE;
2016 #if ENABLE_FEATURE_NTPD_SERVER
2019 G_listen_fd = create_and_bind_dgram_or_die(NULL, 123);
2020 socket_want_pktinfo(G_listen_fd);
2021 setsockopt(G_listen_fd, IPPROTO_IP, IP_TOS, &const_IPTOS_LOWDELAY, sizeof(const_IPTOS_LOWDELAY));
2024 /* I hesitate to set -20 prio. -15 should be high enough for timekeeping */
2026 setpriority(PRIO_PROCESS, 0, -15);
2028 /* If network is up, syncronization occurs in ~10 seconds.
2029 * We give "ntpd -q" 10 seconds to get first reply,
2030 * then another 50 seconds to finish syncing.
2032 * I tested ntpd 4.2.6p1 and apparently it never exits
2033 * (will try forever), but it does not feel right.
2034 * The goal of -q is to act like ntpdate: set time
2035 * after a reasonably small period of polling, or fail.
2038 option_mask32 |= OPT_qq;
2055 int ntpd_main(int argc UNUSED_PARAM, char **argv) MAIN_EXTERNALLY_VISIBLE;
2056 int ntpd_main(int argc UNUSED_PARAM, char **argv)
2064 memset(&G, 0, sizeof(G));
2065 SET_PTR_TO_GLOBALS(&G);
2069 /* If ENABLE_FEATURE_NTPD_SERVER, + 1 for listen_fd: */
2070 cnt = G.peer_cnt + ENABLE_FEATURE_NTPD_SERVER;
2071 idx2peer = xzalloc(sizeof(idx2peer[0]) * cnt);
2072 pfd = xzalloc(sizeof(pfd[0]) * cnt);
2074 /* Countdown: we never sync before we sent INITIAL_SAMPLES+1
2075 * packets to each peer.
2076 * NB: if some peer is not responding, we may end up sending
2077 * fewer packets to it and more to other peers.
2078 * NB2: sync usually happens using INITIAL_SAMPLES packets,
2079 * since last reply does not come back instantaneously.
2081 cnt = G.peer_cnt * (INITIAL_SAMPLES + 1);
2083 write_pidfile(CONFIG_PID_FILE_PATH "/ntpd.pid");
2085 while (!bb_got_signal) {
2091 /* Nothing between here and poll() blocks for any significant time */
2093 nextaction = G.cur_time + 3600;
2096 #if ENABLE_FEATURE_NTPD_SERVER
2097 if (G_listen_fd != -1) {
2098 pfd[0].fd = G_listen_fd;
2099 pfd[0].events = POLLIN;
2103 /* Pass over peer list, send requests, time out on receives */
2104 for (item = G.ntp_peers; item != NULL; item = item->link) {
2105 peer_t *p = (peer_t *) item->data;
2107 if (p->next_action_time <= G.cur_time) {
2108 if (p->p_fd == -1) {
2109 /* Time to send new req */
2111 G.initial_poll_complete = 1;
2113 send_query_to_peer(p);
2115 /* Timed out waiting for reply */
2118 timeout = poll_interval(-2); /* -2: try a bit sooner */
2119 bb_error_msg("timed out waiting for %s, reach 0x%02x, next query in %us",
2120 p->p_dotted, p->reachable_bits, timeout);
2121 set_next(p, timeout);
2125 if (p->next_action_time < nextaction)
2126 nextaction = p->next_action_time;
2129 /* Wait for reply from this peer */
2130 pfd[i].fd = p->p_fd;
2131 pfd[i].events = POLLIN;
2137 timeout = nextaction - G.cur_time;
2140 timeout++; /* (nextaction - G.cur_time) rounds down, compensating */
2142 /* Here we may block */
2144 if (i > (ENABLE_FEATURE_NTPD_SERVER && G_listen_fd != -1)) {
2145 /* We wait for at least one reply.
2146 * Poll for it, without wasting time for message.
2147 * Since replies often come under 1 second, this also
2148 * reduces clutter in logs.
2150 nfds = poll(pfd, i, 1000);
2156 bb_error_msg("poll:%us sockets:%u interval:%us", timeout, i, 1 << G.poll_exp);
2158 nfds = poll(pfd, i, timeout * 1000);
2160 gettime1900d(); /* sets G.cur_time */
2162 if (G.script_name && G.cur_time - G.last_script_run > 11*60) {
2163 /* Useful for updating battery-backed RTC and such */
2164 run_script("periodic", G.last_update_offset);
2165 gettime1900d(); /* sets G.cur_time */
2170 /* Process any received packets */
2172 #if ENABLE_FEATURE_NTPD_SERVER
2173 if (G.listen_fd != -1) {
2174 if (pfd[0].revents /* & (POLLIN|POLLERR)*/) {
2176 recv_and_process_client_pkt(/*G.listen_fd*/);
2177 gettime1900d(); /* sets G.cur_time */
2182 for (; nfds != 0 && j < i; j++) {
2183 if (pfd[j].revents /* & (POLLIN|POLLERR)*/) {
2185 * At init, alarm was set to 10 sec.
2186 * Now we did get a reply.
2187 * Increase timeout to 50 seconds to finish syncing.
2189 if (option_mask32 & OPT_qq) {
2190 option_mask32 &= ~OPT_qq;
2194 recv_and_process_peer_pkt(idx2peer[j]);
2195 gettime1900d(); /* sets G.cur_time */
2198 } /* while (!bb_got_signal) */
2200 remove_pidfile(CONFIG_PID_FILE_PATH "/ntpd.pid");
2201 kill_myself_with_sig(bb_got_signal);
2209 /*** openntpd-4.6 uses only adjtime, not adjtimex ***/
2211 /*** ntp-4.2.6/ntpd/ntp_loopfilter.c - adjtimex usage ***/
2215 direct_freq(double fp_offset)
2219 * If the kernel is enabled, we need the residual offset to
2220 * calculate the frequency correction.
2222 if (pll_control && kern_enable) {
2223 memset(&ntv, 0, sizeof(ntv));
2226 clock_offset = ntv.offset / 1e9;
2227 #else /* STA_NANO */
2228 clock_offset = ntv.offset / 1e6;
2229 #endif /* STA_NANO */
2230 drift_comp = FREQTOD(ntv.freq);
2232 #endif /* KERNEL_PLL */
2233 set_freq((fp_offset - clock_offset) / (current_time - clock_epoch) + drift_comp);
2239 set_freq(double freq) /* frequency update */
2247 * If the kernel is enabled, update the kernel frequency.
2249 if (pll_control && kern_enable) {
2250 memset(&ntv, 0, sizeof(ntv));
2251 ntv.modes = MOD_FREQUENCY;
2252 ntv.freq = DTOFREQ(drift_comp);
2254 snprintf(tbuf, sizeof(tbuf), "kernel %.3f PPM", drift_comp * 1e6);
2255 report_event(EVNT_FSET, NULL, tbuf);
2257 snprintf(tbuf, sizeof(tbuf), "ntpd %.3f PPM", drift_comp * 1e6);
2258 report_event(EVNT_FSET, NULL, tbuf);
2260 #else /* KERNEL_PLL */
2261 snprintf(tbuf, sizeof(tbuf), "ntpd %.3f PPM", drift_comp * 1e6);
2262 report_event(EVNT_FSET, NULL, tbuf);
2263 #endif /* KERNEL_PLL */
2272 * This code segment works when clock adjustments are made using
2273 * precision time kernel support and the ntp_adjtime() system
2274 * call. This support is available in Solaris 2.6 and later,
2275 * Digital Unix 4.0 and later, FreeBSD, Linux and specially
2276 * modified kernels for HP-UX 9 and Ultrix 4. In the case of the
2277 * DECstation 5000/240 and Alpha AXP, additional kernel
2278 * modifications provide a true microsecond clock and nanosecond
2279 * clock, respectively.
2281 * Important note: The kernel discipline is used only if the
2282 * step threshold is less than 0.5 s, as anything higher can
2283 * lead to overflow problems. This might occur if some misguided
2284 * lad set the step threshold to something ridiculous.
2286 if (pll_control && kern_enable) {
2288 #define MOD_BITS (MOD_OFFSET | MOD_MAXERROR | MOD_ESTERROR | MOD_STATUS | MOD_TIMECONST)
2291 * We initialize the structure for the ntp_adjtime()
2292 * system call. We have to convert everything to
2293 * microseconds or nanoseconds first. Do not update the
2294 * system variables if the ext_enable flag is set. In
2295 * this case, the external clock driver will update the
2296 * variables, which will be read later by the local
2297 * clock driver. Afterwards, remember the time and
2298 * frequency offsets for jitter and stability values and
2299 * to update the frequency file.
2301 memset(&ntv, 0, sizeof(ntv));
2303 ntv.modes = MOD_STATUS;
2306 ntv.modes = MOD_BITS | MOD_NANO;
2307 #else /* STA_NANO */
2308 ntv.modes = MOD_BITS;
2309 #endif /* STA_NANO */
2310 if (clock_offset < 0)
2315 ntv.offset = (int32)(clock_offset * 1e9 + dtemp);
2316 ntv.constant = sys_poll;
2317 #else /* STA_NANO */
2318 ntv.offset = (int32)(clock_offset * 1e6 + dtemp);
2319 ntv.constant = sys_poll - 4;
2320 #endif /* STA_NANO */
2321 ntv.esterror = (u_int32)(clock_jitter * 1e6);
2322 ntv.maxerror = (u_int32)((sys_rootdelay / 2 + sys_rootdisp) * 1e6);
2323 ntv.status = STA_PLL;
2326 * Enable/disable the PPS if requested.
2329 if (!(pll_status & STA_PPSTIME))
2330 report_event(EVNT_KERN,
2331 NULL, "PPS enabled");
2332 ntv.status |= STA_PPSTIME | STA_PPSFREQ;
2334 if (pll_status & STA_PPSTIME)
2335 report_event(EVNT_KERN,
2336 NULL, "PPS disabled");
2337 ntv.status &= ~(STA_PPSTIME | STA_PPSFREQ);
2339 if (sys_leap == LEAP_ADDSECOND)
2340 ntv.status |= STA_INS;
2341 else if (sys_leap == LEAP_DELSECOND)
2342 ntv.status |= STA_DEL;
2346 * Pass the stuff to the kernel. If it squeals, turn off
2347 * the pps. In any case, fetch the kernel offset,
2348 * frequency and jitter.
2350 if (ntp_adjtime(&ntv) == TIME_ERROR) {
2351 if (!(ntv.status & STA_PPSSIGNAL))
2352 report_event(EVNT_KERN, NULL,
2355 pll_status = ntv.status;
2357 clock_offset = ntv.offset / 1e9;
2358 #else /* STA_NANO */
2359 clock_offset = ntv.offset / 1e6;
2360 #endif /* STA_NANO */
2361 clock_frequency = FREQTOD(ntv.freq);
2364 * If the kernel PPS is lit, monitor its performance.
2366 if (ntv.status & STA_PPSTIME) {
2368 clock_jitter = ntv.jitter / 1e9;
2369 #else /* STA_NANO */
2370 clock_jitter = ntv.jitter / 1e6;
2371 #endif /* STA_NANO */
2374 #if defined(STA_NANO) && NTP_API == 4
2376 * If the TAI changes, update the kernel TAI.
2378 if (loop_tai != sys_tai) {
2380 ntv.modes = MOD_TAI;
2381 ntv.constant = sys_tai;
2384 #endif /* STA_NANO */
2386 #endif /* KERNEL_PLL */