2 * NTP client/server, based on OpenNTPD 3.9p1
4 * Busybox port author: Adam Tkac (C) 2009 <vonsch@gmail.com>
6 * OpenNTPd 3.9p1 copyright holders:
7 * Copyright (c) 2003, 2004 Henning Brauer <henning@openbsd.org>
8 * Copyright (c) 2004 Alexander Guy <alexander.guy@andern.org>
10 * OpenNTPd code is licensed under ISC-style licence:
12 * Permission to use, copy, modify, and distribute this software for any
13 * purpose with or without fee is hereby granted, provided that the above
14 * copyright notice and this permission notice appear in all copies.
16 * THE SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL WARRANTIES
17 * WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF
18 * MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR
19 * ANY SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES
20 * WHATSOEVER RESULTING FROM LOSS OF MIND, USE, DATA OR PROFITS, WHETHER
21 * IN AN ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING
22 * OUT OF OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE.
23 ***********************************************************************
25 * Parts of OpenNTPD clock syncronization code is replaced by
26 * code which is based on ntp-4.2.6, which carries the following
29 * Copyright (c) University of Delaware 1992-2009
31 * Permission to use, copy, modify, and distribute this software and
32 * its documentation for any purpose with or without fee is hereby
33 * granted, provided that the above copyright notice appears in all
34 * copies and that both the copyright notice and this permission
35 * notice appear in supporting documentation, and that the name
36 * University of Delaware not be used in advertising or publicity
37 * pertaining to distribution of the software without specific,
38 * written prior permission. The University of Delaware makes no
39 * representations about the suitability this software for any
40 * purpose. It is provided "as is" without express or implied warranty.
41 ***********************************************************************
44 //config: bool "ntpd (22 kb)"
46 //config: select PLATFORM_LINUX
48 //config: The NTP client/server daemon.
50 //config:config FEATURE_NTPD_SERVER
51 //config: bool "Make ntpd usable as a NTP server"
53 //config: depends on NTPD
55 //config: Make ntpd usable as a NTP server. If you disable this option
56 //config: ntpd will be usable only as a NTP client.
58 //config:config FEATURE_NTPD_CONF
59 //config: bool "Make ntpd understand /etc/ntp.conf"
61 //config: depends on NTPD
63 //config: Make ntpd look in /etc/ntp.conf for peers. Only "server address"
64 //config: is supported.
66 //config:config FEATURE_NTP_AUTH
67 //config: bool "Support md5/sha1 message authentication codes"
69 //config: depends on NTPD
71 //applet:IF_NTPD(APPLET(ntpd, BB_DIR_USR_SBIN, BB_SUID_DROP))
73 //kbuild:lib-$(CONFIG_NTPD) += ntpd.o
75 //usage:#define ntpd_trivial_usage
76 //usage: "[-dnqNw"IF_FEATURE_NTPD_SERVER("l] [-I IFACE")"] [-S PROG]"
77 //usage: IF_NOT_FEATURE_NTP_AUTH(" [-p PEER]...")
78 //usage: IF_FEATURE_NTP_AUTH(" [-k KEYFILE] [-p [keyno:N:]PEER]...")
79 //usage:#define ntpd_full_usage "\n\n"
80 //usage: "NTP client/server\n"
81 //usage: "\n -d Verbose (may be repeated)"
82 //usage: "\n -n Do not daemonize"
83 //usage: "\n -q Quit after clock is set"
84 //usage: "\n -N Run at high priority"
85 //usage: "\n -w Do not set time (only query peers), implies -n"
86 //usage: "\n -S PROG Run PROG after stepping time, stratum change, and every 11 min"
87 //usage: IF_NOT_FEATURE_NTP_AUTH(
88 //usage: "\n -p PEER Obtain time from PEER (may be repeated)"
90 //usage: IF_FEATURE_NTP_AUTH(
91 //usage: "\n -k FILE Key file (ntp.keys compatible)"
92 //usage: "\n -p [keyno:NUM:]PEER"
93 //usage: "\n Obtain time from PEER (may be repeated)"
94 //usage: "\n Use key NUM for authentication"
96 //usage: IF_FEATURE_NTPD_CONF(
97 //usage: "\n If -p is not given, 'server HOST' lines"
98 //usage: "\n from /etc/ntp.conf are used"
100 //usage: IF_FEATURE_NTPD_SERVER(
101 //usage: "\n -l Also run as server on port 123"
102 //usage: "\n -I IFACE Bind server to IFACE, implies -l"
105 // -l and -p options are not compatible with "standard" ntpd:
106 // it has them as "-l logfile" and "-p pidfile".
107 // -S and -w are not compat either, "standard" ntpd has no such opts.
111 #include <netinet/ip.h> /* For IPTOS_DSCP_AF21 definition */
112 #include <sys/timex.h>
113 #ifndef IPTOS_DSCP_AF21
114 # define IPTOS_DSCP_AF21 0x48
118 /* Verbosity control (max level of -dddd options accepted).
119 * max 6 is very talkative (and bloated). 3 is non-bloated,
120 * production level setting.
122 #define MAX_VERBOSE 3
125 /* High-level description of the algorithm:
127 * We start running with very small poll_exp, BURSTPOLL,
128 * in order to quickly accumulate INITIAL_SAMPLES datapoints
129 * for each peer. Then, time is stepped if the offset is larger
130 * than STEP_THRESHOLD, otherwise it isn't; anyway, we enlarge
131 * poll_exp to MINPOLL and enter frequency measurement step:
132 * we collect new datapoints but ignore them for WATCH_THRESHOLD
133 * seconds. After WATCH_THRESHOLD seconds we look at accumulated
134 * offset and estimate frequency drift.
136 * (frequency measurement step seems to not be strictly needed,
137 * it is conditionally disabled with USING_INITIAL_FREQ_ESTIMATION
140 * After this, we enter "steady state": we collect a datapoint,
141 * we select the best peer, if this datapoint is not a new one
142 * (IOW: if this datapoint isn't for selected peer), sleep
143 * and collect another one; otherwise, use its offset to update
144 * frequency drift, if offset is somewhat large, reduce poll_exp,
145 * otherwise increase poll_exp.
147 * If offset is larger than STEP_THRESHOLD, which shouldn't normally
148 * happen, we assume that something "bad" happened (computer
149 * was hibernated, someone set totally wrong date, etc),
150 * then the time is stepped, all datapoints are discarded,
151 * and we go back to steady state.
153 * Made some changes to speed up re-syncing after our clock goes bad
154 * (tested with suspending my laptop):
155 * - if largish offset (>= STEP_THRESHOLD == 1 sec) is seen
156 * from a peer, schedule next query for this peer soon
157 * without drastically lowering poll interval for everybody.
158 * This makes us collect enough data for step much faster:
159 * e.g. at poll = 10 (1024 secs), step was done within 5 minutes
160 * after first reply which indicated that our clock is 14 seconds off.
161 * - on step, do not discard d_dispersion data of the existing datapoints,
162 * do not clear reachable_bits. This prevents discarding first ~8
163 * datapoints after the step.
166 #define INITIAL_SAMPLES 4 /* how many samples do we want for init */
167 #define MIN_FREQHOLD 12 /* adjust offset, but not freq in this many first adjustments */
168 #define BAD_DELAY_GROWTH 4 /* drop packet if its delay grew by more than this factor */
170 #define RETRY_INTERVAL 32 /* on send/recv error, retry in N secs (need to be power of 2) */
171 #define NOREPLY_INTERVAL 512 /* sent, but got no reply: cap next query by this many seconds */
172 #define RESPONSE_INTERVAL 16 /* wait for reply up to N secs */
173 #define HOSTNAME_INTERVAL 4 /* hostname lookup failed. Wait N * peer->dns_errors secs for next try */
174 #define DNS_ERRORS_CAP 0x3f /* peer->dns_errors is in [0..63] */
176 /* Step threshold (sec). std ntpd uses 0.128.
178 #define STEP_THRESHOLD 1
179 /* Slew threshold (sec): adjtimex() won't accept offsets larger than this.
180 * Using exact power of 2 (1/8, 1/2 etc) results in smaller code
182 #define SLEW_THRESHOLD 0.5
183 // ^^^^ used to be 0.125.
184 // Since Linux 2.6.26 (circa 2006), kernel accepts (-0.5s, +0.5s) range
186 /* Stepout threshold (sec). std ntpd uses 900 (11 mins (!)) */
187 //UNUSED: #define WATCH_THRESHOLD 128
188 /* NB: set WATCH_THRESHOLD to ~60 when debugging to save time) */
189 //UNUSED: #define PANIC_THRESHOLD 1000 /* panic threshold (sec) */
192 * If we got |offset| > BIGOFF from a peer, cap next query interval
193 * for this peer by this many seconds:
195 #define BIGOFF STEP_THRESHOLD
196 #define BIGOFF_INTERVAL (1 << 7) /* 128 s */
198 #define FREQ_TOLERANCE 0.000015 /* frequency tolerance (15 PPM) */
199 #define BURSTPOLL 0 /* initial poll */
200 #define MINPOLL 5 /* minimum poll interval. std ntpd uses 6 (6: 64 sec) */
202 * If offset > discipline_jitter * POLLADJ_GATE, and poll interval is > 2^BIGPOLL,
203 * then it is decreased _at once_. (If <= 2^BIGPOLL, it will be decreased _eventually_).
205 #define BIGPOLL 9 /* 2^9 sec ~= 8.5 min */
206 #define MAXPOLL 12 /* maximum poll interval (12: 1.1h, 17: 36.4h). std ntpd uses 17 */
208 * Actively lower poll when we see such big offsets.
209 * With SLEW_THRESHOLD = 0.125, it means we try to sync more aggressively
210 * if offset increases over ~0.04 sec
212 //#define POLLDOWN_OFFSET (SLEW_THRESHOLD / 3)
213 #define MINDISP 0.01 /* minimum dispersion (sec) */
214 #define MAXDISP 16 /* maximum dispersion (sec) */
215 #define MAXSTRAT 16 /* maximum stratum (infinity metric) */
216 #define MAXDIST 1 /* distance threshold (sec) */
217 #define MIN_SELECTED 1 /* minimum intersection survivors */
218 #define MIN_CLUSTERED 3 /* minimum cluster survivors */
220 #define MAXDRIFT 0.000500 /* frequency drift we can correct (500 PPM) */
222 /* Poll-adjust threshold.
223 * When we see that offset is small enough compared to discipline jitter,
224 * we grow a counter: += MINPOLL. When counter goes over POLLADJ_LIMIT,
225 * we poll_exp++. If offset isn't small, counter -= poll_exp*2,
226 * and when it goes below -POLLADJ_LIMIT, we poll_exp--.
227 * (Bumped from 30 to 40 since otherwise I often see poll_exp going *2* steps down)
229 #define POLLADJ_LIMIT 40
230 /* If offset < discipline_jitter * POLLADJ_GATE, then we decide to increase
231 * poll interval (we think we can't improve timekeeping
232 * by staying at smaller poll).
234 #define POLLADJ_GATE 4
235 #define TIMECONST_HACK_GATE 2
236 /* Compromise Allan intercept (sec). doc uses 1500, std ntpd uses 512 */
240 /* FLL loop gain [why it depends on MAXPOLL??] */
241 #define FLL (MAXPOLL + 1)
242 /* Parameter averaging constant */
245 #define MAX_KEY_NUMBER 65535
246 #define KEYID_SIZE sizeof(uint32_t)
252 NTP_MD5_DIGESTSIZE = 16,
253 NTP_MSGSIZE_NOAUTH = 48,
254 NTP_MSGSIZE_MD5_AUTH = NTP_MSGSIZE_NOAUTH + KEYID_SIZE + NTP_MD5_DIGESTSIZE,
255 NTP_SHA1_DIGESTSIZE = 20,
256 NTP_MSGSIZE_SHA1_AUTH = NTP_MSGSIZE_NOAUTH + KEYID_SIZE + NTP_SHA1_DIGESTSIZE,
259 MODE_MASK = (7 << 0),
260 VERSION_MASK = (7 << 3),
264 /* Leap Second Codes (high order two bits of m_status) */
265 LI_NOWARNING = (0 << 6), /* no warning */
266 LI_PLUSSEC = (1 << 6), /* add a second (61 seconds) */
267 LI_MINUSSEC = (2 << 6), /* minus a second (59 seconds) */
268 LI_ALARM = (3 << 6), /* alarm condition */
271 MODE_RES0 = 0, /* reserved */
272 MODE_SYM_ACT = 1, /* symmetric active */
273 MODE_SYM_PAS = 2, /* symmetric passive */
274 MODE_CLIENT = 3, /* client */
275 MODE_SERVER = 4, /* server */
276 MODE_BROADCAST = 5, /* broadcast */
277 MODE_RES1 = 6, /* reserved for NTP control message */
278 MODE_RES2 = 7, /* reserved for private use */
281 //TODO: better base selection
282 #define OFFSET_1900_1970 2208988800UL /* 1970 - 1900 in seconds */
284 #define NUM_DATAPOINTS 8
297 uint8_t m_status; /* status of local clock and leap info */
299 uint8_t m_ppoll; /* poll value */
300 int8_t m_precision_exp;
301 s_fixedpt_t m_rootdelay;
302 s_fixedpt_t m_rootdisp;
304 l_fixedpt_t m_reftime;
305 l_fixedpt_t m_orgtime;
306 l_fixedpt_t m_rectime;
307 l_fixedpt_t m_xmttime;
309 uint8_t m_digest[ENABLE_FEATURE_NTP_AUTH ? NTP_SHA1_DIGESTSIZE : NTP_MD5_DIGESTSIZE];
318 #if ENABLE_FEATURE_NTP_AUTH
324 unsigned id; //try uint16_t?
327 smalluint key_length;
333 len_and_sockaddr *p_lsa;
335 #if ENABLE_FEATURE_NTP_AUTH
336 key_entry_t *key_entry;
340 uint32_t lastpkt_refid;
341 uint8_t lastpkt_status;
342 uint8_t lastpkt_stratum;
343 uint8_t reachable_bits;
345 /* when to send new query (if p_fd == -1)
346 * or when receive times out (if p_fd >= 0): */
347 double next_action_time;
350 /* p_raw_delay is set even by "high delay" packets */
351 /* lastpkt_delay isn't */
352 double lastpkt_recv_time;
353 double lastpkt_delay;
354 double lastpkt_rootdelay;
355 double lastpkt_rootdisp;
356 /* produced by filter algorithm: */
357 double filter_offset;
358 double filter_dispersion;
359 double filter_jitter;
360 datapoint_t filter_datapoint[NUM_DATAPOINTS];
361 /* last sent packet: */
367 #define USING_KERNEL_PLL_LOOP 1
368 #define USING_INITIAL_FREQ_ESTIMATION 0
375 OPT_k = (1 << 4) * ENABLE_FEATURE_NTP_AUTH,
376 /* Insert new options above this line. */
377 /* Non-compat options: */
378 OPT_w = (1 << (4+ENABLE_FEATURE_NTP_AUTH)),
379 OPT_p = (1 << (5+ENABLE_FEATURE_NTP_AUTH)),
380 OPT_S = (1 << (6+ENABLE_FEATURE_NTP_AUTH)),
381 OPT_l = (1 << (7+ENABLE_FEATURE_NTP_AUTH)) * ENABLE_FEATURE_NTPD_SERVER,
382 OPT_I = (1 << (8+ENABLE_FEATURE_NTP_AUTH)) * ENABLE_FEATURE_NTPD_SERVER,
383 /* We hijack some bits for other purposes */
389 /* total round trip delay to currently selected reference clock */
391 /* reference timestamp: time when the system clock was last set or corrected */
393 /* total dispersion to currently selected reference clock */
396 double last_script_run;
399 #if ENABLE_FEATURE_NTPD_SERVER
402 # define G_listen_fd (G.listen_fd)
404 # define G_listen_fd (-1)
408 /* refid: 32-bit code identifying the particular server or reference clock
409 * in stratum 0 packets this is a four-character ASCII string,
410 * called the kiss code, used for debugging and monitoring
411 * in stratum 1 packets this is a four-character ASCII string
412 * assigned to the reference clock by IANA. Example: "GPS "
413 * in stratum 2+ packets, it's IPv4 address or 4 first bytes
414 * of MD5 hash of IPv6
418 /* precision is defined as the larger of the resolution and time to
419 * read the clock, in log2 units. For instance, the precision of a
420 * mains-frequency clock incrementing at 60 Hz is 16 ms, even when the
421 * system clock hardware representation is to the nanosecond.
423 * Delays, jitters of various kinds are clamped down to precision.
425 * If precision_sec is too large, discipline_jitter gets clamped to it
426 * and if offset is smaller than discipline_jitter * POLLADJ_GATE, poll
427 * interval grows even though we really can benefit from staying at
428 * smaller one, collecting non-lagged datapoits and correcting offset.
429 * (Lagged datapoits exist when poll_exp is large but we still have
430 * systematic offset error - the time distance between datapoints
431 * is significant and older datapoints have smaller offsets.
432 * This makes our offset estimation a bit smaller than reality)
433 * Due to this effect, setting G_precision_sec close to
434 * STEP_THRESHOLD isn't such a good idea - offsets may grow
435 * too big and we will step. I observed it with -6.
437 * OTOH, setting precision_sec far too small would result in futile
438 * attempts to synchronize to an unachievable precision.
440 * -6 is 1/64 sec, -7 is 1/128 sec and so on.
441 * -8 is 1/256 ~= 0.003906 (worked well for me --vda)
442 * -9 is 1/512 ~= 0.001953 (let's try this for some time)
444 #define G_precision_exp -9
446 * G_precision_exp is used only for construction outgoing packets.
447 * It's ok to set G_precision_sec to a slightly different value
448 * (One which is "nicer looking" in logs).
449 * Exact value would be (1.0 / (1 << (- G_precision_exp))):
451 #define G_precision_sec 0.002
454 #define STATE_NSET 0 /* initial state, "nothing is set" */
455 //#define STATE_FSET 1 /* frequency set from file */
456 //#define STATE_SPIK 2 /* spike detected */
457 //#define STATE_FREQ 3 /* initial frequency */
458 #define STATE_SYNC 4 /* clock synchronized (normal operation) */
459 uint8_t discipline_state; // doc calls it c.state
460 uint8_t poll_exp; // s.poll
461 int polladj_count; // c.count
463 long kernel_freq_drift;
464 peer_t *last_update_peer;
465 double last_update_offset; // c.last
466 double last_update_recv_time; // s.t
467 double discipline_jitter; // c.jitter
468 /* Since we only compare it with ints, can simplify code
469 * by not making this variable floating point:
471 unsigned offset_to_jitter_ratio;
472 //double cluster_offset; // s.offset
473 //double cluster_jitter; // s.jitter
474 #if !USING_KERNEL_PLL_LOOP
475 double discipline_freq_drift; // c.freq
476 /* Maybe conditionally calculate wander? it's used only for logging */
477 double discipline_wander; // c.wander
480 #define G (*ptr_to_globals)
483 #define VERB1 if (MAX_VERBOSE && G.verbose)
484 #define VERB2 if (MAX_VERBOSE >= 2 && G.verbose >= 2)
485 #define VERB3 if (MAX_VERBOSE >= 3 && G.verbose >= 3)
486 #define VERB4 if (MAX_VERBOSE >= 4 && G.verbose >= 4)
487 #define VERB5 if (MAX_VERBOSE >= 5 && G.verbose >= 5)
488 #define VERB6 if (MAX_VERBOSE >= 6 && G.verbose >= 6)
491 static double LOG2D(int a)
494 return 1.0 / (1UL << -a);
497 static ALWAYS_INLINE double SQUARE(double x)
501 static ALWAYS_INLINE double MAXD(double a, double b)
507 static ALWAYS_INLINE double MIND(double a, double b)
513 static NOINLINE double my_SQRT(double X)
520 double Xhalf = X * 0.5;
522 /* Fast and good approximation to 1/sqrt(X), black magic */
524 /*v.i = 0x5f3759df - (v.i >> 1);*/
525 v.i = 0x5f375a86 - (v.i >> 1); /* - this constant is slightly better */
526 invsqrt = v.f; /* better than 0.2% accuracy */
528 /* Refining it using Newton's method: x1 = x0 - f(x0)/f'(x0)
529 * f(x) = 1/(x*x) - X (f==0 when x = 1/sqrt(X))
531 * f(x)/f'(x) = (X - 1/(x*x)) / (2/(x*x*x)) = X*x*x*x/2 - x/2
532 * x1 = x0 - (X*x0*x0*x0/2 - x0/2) = 1.5*x0 - X*x0*x0*x0/2 = x0*(1.5 - (X/2)*x0*x0)
534 invsqrt = invsqrt * (1.5 - Xhalf * invsqrt * invsqrt); /* ~0.05% accuracy */
535 /* invsqrt = invsqrt * (1.5 - Xhalf * invsqrt * invsqrt); 2nd iter: ~0.0001% accuracy */
536 /* With 4 iterations, more than half results will be exact,
537 * at 6th iterations result stabilizes with about 72% results exact.
538 * We are well satisfied with 0.05% accuracy.
541 return X * invsqrt; /* X * 1/sqrt(X) ~= sqrt(X) */
543 static ALWAYS_INLINE double SQRT(double X)
545 /* If this arch doesn't use IEEE 754 floats, fall back to using libm */
546 if (sizeof(float) != 4)
549 /* This avoids needing libm, saves about 0.5k on x86-32 */
557 gettimeofday(&tv, NULL); /* never fails */
558 G.cur_time = tv.tv_sec + (1.0e-6 * tv.tv_usec) + OFFSET_1900_1970;
563 d_to_tv(double d, struct timeval *tv)
565 tv->tv_sec = (long)d;
566 tv->tv_usec = (d - tv->tv_sec) * 1000000;
570 lfp_to_d(l_fixedpt_t lfp)
573 lfp.int_partl = ntohl(lfp.int_partl);
574 lfp.fractionl = ntohl(lfp.fractionl);
575 ret = (double)lfp.int_partl + ((double)lfp.fractionl / UINT_MAX);
579 sfp_to_d(s_fixedpt_t sfp)
582 sfp.int_parts = ntohs(sfp.int_parts);
583 sfp.fractions = ntohs(sfp.fractions);
584 ret = (double)sfp.int_parts + ((double)sfp.fractions / USHRT_MAX);
587 #if ENABLE_FEATURE_NTPD_SERVER
592 lfp.int_partl = (uint32_t)d;
593 lfp.fractionl = (uint32_t)((d - lfp.int_partl) * UINT_MAX);
594 lfp.int_partl = htonl(lfp.int_partl);
595 lfp.fractionl = htonl(lfp.fractionl);
602 sfp.int_parts = (uint16_t)d;
603 sfp.fractions = (uint16_t)((d - sfp.int_parts) * USHRT_MAX);
604 sfp.int_parts = htons(sfp.int_parts);
605 sfp.fractions = htons(sfp.fractions);
611 dispersion(const datapoint_t *dp)
613 return dp->d_dispersion + FREQ_TOLERANCE * (G.cur_time - dp->d_recv_time);
617 root_distance(peer_t *p)
619 /* The root synchronization distance is the maximum error due to
620 * all causes of the local clock relative to the primary server.
621 * It is defined as half the total delay plus total dispersion
624 return MAXD(MINDISP, p->lastpkt_rootdelay + p->lastpkt_delay) / 2
625 + p->lastpkt_rootdisp
626 + p->filter_dispersion
627 + FREQ_TOLERANCE * (G.cur_time - p->lastpkt_recv_time)
632 set_next(peer_t *p, unsigned t)
634 p->next_action_time = G.cur_time + t;
638 * Peer clock filter and its helpers
641 filter_datapoints(peer_t *p)
648 /* Simulations have shown that use of *averaged* offset for p->filter_offset
649 * is in fact worse than simply using last received one: with large poll intervals
650 * (>= 2048) averaging code uses offset values which are outdated by hours,
651 * and time/frequency correction goes totally wrong when fed essentially bogus offsets.
654 double minoff, maxoff, w;
655 double x = x; /* for compiler */
656 double oldest_off = oldest_off;
657 double oldest_age = oldest_age;
658 double newest_off = newest_off;
659 double newest_age = newest_age;
661 fdp = p->filter_datapoint;
663 minoff = maxoff = fdp[0].d_offset;
664 for (i = 1; i < NUM_DATAPOINTS; i++) {
665 if (minoff > fdp[i].d_offset)
666 minoff = fdp[i].d_offset;
667 if (maxoff < fdp[i].d_offset)
668 maxoff = fdp[i].d_offset;
671 idx = p->datapoint_idx; /* most recent datapoint's index */
673 * Drop two outliers and take weighted average of the rest:
674 * most_recent/2 + older1/4 + older2/8 ... + older5/32 + older6/32
675 * we use older6/32, not older6/64 since sum of weights should be 1:
676 * 1/2 + 1/4 + 1/8 + 1/16 + 1/32 + 1/32 = 1
682 * filter_dispersion = \ -------------
689 for (i = 0; i < NUM_DATAPOINTS; i++) {
691 bb_error_msg("datapoint[%d]: off:%f disp:%f(%f) age:%f%s",
694 fdp[idx].d_dispersion, dispersion(&fdp[idx]),
695 G.cur_time - fdp[idx].d_recv_time,
696 (minoff == fdp[idx].d_offset || maxoff == fdp[idx].d_offset)
697 ? " (outlier by offset)" : ""
701 sum += dispersion(&fdp[idx]) / (2 << i);
703 if (minoff == fdp[idx].d_offset) {
704 minoff -= 1; /* so that we don't match it ever again */
706 if (maxoff == fdp[idx].d_offset) {
709 oldest_off = fdp[idx].d_offset;
710 oldest_age = G.cur_time - fdp[idx].d_recv_time;
713 newest_off = oldest_off;
714 newest_age = oldest_age;
721 idx = (idx - 1) & (NUM_DATAPOINTS - 1);
723 p->filter_dispersion = sum;
724 wavg += x; /* add another older6/64 to form older6/32 */
725 /* Fix systematic underestimation with large poll intervals.
726 * Imagine that we still have a bit of uncorrected drift,
727 * and poll interval is big (say, 100 sec). Offsets form a progression:
728 * 0.0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 - 0.7 is most recent.
729 * The algorithm above drops 0.0 and 0.7 as outliers,
730 * and then we have this estimation, ~25% off from 0.7:
731 * 0.1/32 + 0.2/32 + 0.3/16 + 0.4/8 + 0.5/4 + 0.6/2 = 0.503125
733 x = oldest_age - newest_age;
735 x = newest_age / x; /* in above example, 100 / (600 - 100) */
736 if (x < 1) { /* paranoia check */
737 x = (newest_off - oldest_off) * x; /* 0.5 * 100/500 = 0.1 */
741 p->filter_offset = wavg;
745 fdp = p->filter_datapoint;
746 idx = p->datapoint_idx; /* most recent datapoint's index */
748 /* filter_offset: simply use the most recent value */
749 p->filter_offset = fdp[idx].d_offset;
753 * filter_dispersion = \ -------------
760 for (i = 0; i < NUM_DATAPOINTS; i++) {
761 sum += dispersion(&fdp[idx]) / (2 << i);
762 wavg += fdp[idx].d_offset;
763 idx = (idx - 1) & (NUM_DATAPOINTS - 1);
765 wavg /= NUM_DATAPOINTS;
766 p->filter_dispersion = sum;
769 /* +----- -----+ ^ 1/2
773 * filter_jitter = | --- * / (avg-offset_j) |
777 * where n is the number of valid datapoints in the filter (n > 1);
778 * if filter_jitter < precision then filter_jitter = precision
781 for (i = 0; i < NUM_DATAPOINTS; i++) {
782 sum += SQUARE(wavg - fdp[i].d_offset);
784 sum = SQRT(sum / NUM_DATAPOINTS);
785 p->filter_jitter = sum > G_precision_sec ? sum : G_precision_sec;
787 VERB4 bb_error_msg("filter offset:%+f disp:%f jitter:%f",
789 p->filter_dispersion,
794 reset_peer_stats(peer_t *p, double offset)
797 bool small_ofs = fabs(offset) < STEP_THRESHOLD;
799 /* Used to set p->filter_datapoint[i].d_dispersion = MAXDISP
800 * and clear reachable bits, but this proved to be too aggressive:
801 * after step (tested with suspending laptop for ~30 secs),
802 * this caused all previous data to be considered invalid,
803 * making us needing to collect full ~8 datapoints per peer
804 * after step in order to start trusting them.
805 * In turn, this was making poll interval decrease even after
806 * step was done. (Poll interval decreases already before step
807 * in this scenario, because we see large offsets and end up with
808 * no good peer to select).
811 for (i = 0; i < NUM_DATAPOINTS; i++) {
813 p->filter_datapoint[i].d_recv_time += offset;
814 if (p->filter_datapoint[i].d_offset != 0) {
815 p->filter_datapoint[i].d_offset -= offset;
816 //bb_error_msg("p->filter_datapoint[%d].d_offset %f -> %f",
818 // p->filter_datapoint[i].d_offset + offset,
819 // p->filter_datapoint[i].d_offset);
822 p->filter_datapoint[i].d_recv_time = G.cur_time;
823 p->filter_datapoint[i].d_offset = 0;
824 /*p->filter_datapoint[i].d_dispersion = MAXDISP;*/
828 p->lastpkt_recv_time += offset;
830 /*p->reachable_bits = 0;*/
831 p->lastpkt_recv_time = G.cur_time;
833 filter_datapoints(p); /* recalc p->filter_xxx */
834 VERB6 bb_error_msg("%s->lastpkt_recv_time=%f", p->p_dotted, p->lastpkt_recv_time);
837 static len_and_sockaddr*
838 resolve_peer_hostname(peer_t *p)
840 len_and_sockaddr *lsa = host2sockaddr(p->p_hostname, 123);
845 p->p_dotted = xmalloc_sockaddr2dotted_noport(&lsa->u.sa);
846 VERB1 if (strcmp(p->p_hostname, p->p_dotted) != 0)
847 bb_error_msg("'%s' is %s", p->p_hostname, p->p_dotted);
851 p->dns_errors = ((p->dns_errors << 1) | 1) & DNS_ERRORS_CAP;
855 #if !ENABLE_FEATURE_NTP_AUTH
856 #define add_peers(s, key_entry) \
860 add_peers(const char *s, key_entry_t *key_entry)
865 p = xzalloc(sizeof(*p) + strlen(s));
866 strcpy(p->p_hostname, s);
868 p->p_xmt_msg.m_status = MODE_CLIENT | (NTP_VERSION << 3);
869 p->next_action_time = G.cur_time; /* = set_next(p, 0); */
870 reset_peer_stats(p, STEP_THRESHOLD);
872 /* Names like N.<country2chars>.pool.ntp.org are randomly resolved
873 * to a pool of machines. Sometimes different N's resolve to the same IP.
874 * It is not useful to have two peers with same IP. We skip duplicates.
876 if (resolve_peer_hostname(p)) {
877 for (item = G.ntp_peers; item != NULL; item = item->link) {
878 peer_t *pp = (peer_t *) item->data;
879 if (pp->p_dotted && strcmp(p->p_dotted, pp->p_dotted) == 0) {
880 bb_error_msg("duplicate peer %s (%s)", s, p->p_dotted);
889 IF_FEATURE_NTP_AUTH(p->key_entry = key_entry;)
890 llist_add_to(&G.ntp_peers, p);
896 const struct sockaddr *from, const struct sockaddr *to, socklen_t addrlen,
897 msg_t *msg, ssize_t len)
903 ret = sendto(fd, msg, len, MSG_DONTWAIT, to, addrlen);
905 ret = send_to_from(fd, msg, len, MSG_DONTWAIT, to, from, addrlen);
908 bb_perror_msg("send failed");
914 #if ENABLE_FEATURE_NTP_AUTH
916 hash(key_entry_t *key_entry, const msg_t *msg, uint8_t *output)
922 unsigned hash_size = sizeof(*msg) - sizeof(msg->m_keyid) - sizeof(msg->m_digest);
924 switch (key_entry->type) {
927 md5_hash(&ctx.m, key_entry->key, key_entry->key_length);
928 md5_hash(&ctx.m, msg, hash_size);
929 md5_end(&ctx.m, output);
931 default: /* it's HASH_SHA1 */
933 sha1_hash(&ctx.s, key_entry->key, key_entry->key_length);
934 sha1_hash(&ctx.s, msg, hash_size);
935 sha1_end(&ctx.s, output);
943 p->p_xmt_msg.m_keyid = htonl(p->key_entry->id);
944 hash(p->key_entry, &p->p_xmt_msg, p->p_xmt_msg.m_digest);
948 hashes_differ(peer_t *p, const msg_t *msg)
950 uint8_t digest[NTP_SHA1_DIGESTSIZE];
951 hash(p->key_entry, msg, digest);
952 return memcmp(digest, msg->m_digest, p->key_entry->msg_size - NTP_MSGSIZE_NOAUTH - KEYID_SIZE);
957 send_query_to_peer(peer_t *p)
962 /* Why do we need to bind()?
963 * See what happens when we don't bind:
965 * socket(PF_INET, SOCK_DGRAM, IPPROTO_IP) = 3
966 * setsockopt(3, SOL_IP, IP_TOS, [16], 4) = 0
967 * gettimeofday({1259071266, 327885}, NULL) = 0
968 * sendto(3, "xxx", 48, MSG_DONTWAIT, {sa_family=AF_INET, sin_port=htons(123), sin_addr=inet_addr("10.34.32.125")}, 16) = 48
969 * ^^^ we sent it from some source port picked by kernel.
970 * time(NULL) = 1259071266
971 * write(2, "ntpd: entering poll 15 secs\n", 28) = 28
972 * poll([{fd=3, events=POLLIN}], 1, 15000) = 1 ([{fd=3, revents=POLLIN}])
973 * recv(3, "yyy", 68, MSG_DONTWAIT) = 48
974 * ^^^ this recv will receive packets to any local port!
976 * Uncomment this and use strace to see it in action:
978 #define PROBE_LOCAL_ADDR /* { len_and_sockaddr lsa; lsa.len = LSA_SIZEOF_SA; getsockname(p->query.fd, &lsa.u.sa, &lsa.len); } */
982 len_and_sockaddr *local_lsa;
984 family = p->p_lsa->u.sa.sa_family;
985 p->p_fd = fd = xsocket_type(&local_lsa, family, SOCK_DGRAM);
986 /* local_lsa has "null" address and port 0 now.
987 * bind() ensures we have a *particular port* selected by kernel
988 * and remembered in p->p_fd, thus later recv(p->p_fd)
989 * receives only packets sent to this port.
992 xbind(fd, &local_lsa->u.sa, local_lsa->len);
994 #if ENABLE_FEATURE_IPV6
995 if (family == AF_INET)
997 setsockopt_int(fd, IPPROTO_IP, IP_TOS, IPTOS_DSCP_AF21);
1001 /* Emit message _before_ attempted send. Think of a very short
1002 * roundtrip networks: we need to go back to recv loop ASAP,
1003 * to reduce delay. Printing messages after send works against that.
1005 VERB1 bb_error_msg("sending query to %s", p->p_dotted);
1008 * Send out a random 64-bit number as our transmit time. The NTP
1009 * server will copy said number into the originate field on the
1010 * response that it sends us. This is totally legal per the SNTP spec.
1012 * The impact of this is two fold: we no longer send out the current
1013 * system time for the world to see (which may aid an attacker), and
1014 * it gives us a (not very secure) way of knowing that we're not
1015 * getting spoofed by an attacker that can't capture our traffic
1016 * but can spoof packets from the NTP server we're communicating with.
1018 * Save the real transmit timestamp locally.
1020 p->p_xmt_msg.m_xmttime.int_partl = rand();
1021 p->p_xmt_msg.m_xmttime.fractionl = rand();
1022 p->p_xmttime = gettime1900d();
1024 /* Were doing it only if sendto worked, but
1025 * loss of sync detection needs reachable_bits updated
1026 * even if sending fails *locally*:
1027 * "network is unreachable" because cable was pulled?
1028 * We still need to declare "unsync" if this condition persists.
1030 p->reachable_bits <<= 1;
1032 #if ENABLE_FEATURE_NTP_AUTH
1035 if (do_sendto(p->p_fd, /*from:*/ NULL, /*to:*/ &p->p_lsa->u.sa, /*addrlen:*/ p->p_lsa->len,
1036 &p->p_xmt_msg, !p->key_entry ? NTP_MSGSIZE_NOAUTH : p->key_entry->msg_size) == -1
1039 if (do_sendto(p->p_fd, /*from:*/ NULL, /*to:*/ &p->p_lsa->u.sa, /*addrlen:*/ p->p_lsa->len,
1040 &p->p_xmt_msg, NTP_MSGSIZE_NOAUTH) == -1
1047 * We know that we sent nothing.
1048 * We can retry *soon* without fearing
1049 * that we are flooding the peer.
1051 set_next(p, RETRY_INTERVAL);
1055 set_next(p, RESPONSE_INTERVAL);
1059 /* Note that there is no provision to prevent several run_scripts
1060 * to be started in quick succession. In fact, it happens rather often
1061 * if initial syncronization results in a step.
1062 * You will see "step" and then "stratum" script runs, sometimes
1063 * as close as only 0.002 seconds apart.
1064 * Script should be ready to deal with this.
1066 static void run_script(const char *action, double offset)
1069 char *env1, *env2, *env3, *env4;
1071 G.last_script_run = G.cur_time;
1076 argv[0] = (char*) G.script_name;
1077 argv[1] = (char*) action;
1080 VERB1 bb_error_msg("executing '%s %s'", G.script_name, action);
1082 env1 = xasprintf("%s=%u", "stratum", G.stratum);
1084 env2 = xasprintf("%s=%ld", "freq_drift_ppm", G.kernel_freq_drift);
1086 env3 = xasprintf("%s=%u", "poll_interval", 1 << G.poll_exp);
1088 env4 = xasprintf("%s=%f", "offset", offset);
1090 /* Other items of potential interest: selected peer,
1091 * rootdelay, reftime, rootdisp, refid, ntp_status,
1092 * last_update_offset, last_update_recv_time, discipline_jitter,
1093 * how many peers have reachable_bits = 0?
1096 /* Don't want to wait: it may run hwclock --systohc, and that
1097 * may take some time (seconds): */
1098 /*spawn_and_wait(argv);*/
1101 unsetenv("stratum");
1102 unsetenv("freq_drift_ppm");
1103 unsetenv("poll_interval");
1111 static NOINLINE void
1112 step_time(double offset)
1116 struct timeval tvc, tvn;
1117 char buf[sizeof("yyyy-mm-dd hh:mm:ss") + /*paranoia:*/ 4];
1120 gettimeofday(&tvc, NULL); /* never fails */
1121 dtime = tvc.tv_sec + (1.0e-6 * tvc.tv_usec) + offset;
1122 d_to_tv(dtime, &tvn);
1123 if (settimeofday(&tvn, NULL) == -1)
1124 bb_perror_msg_and_die("settimeofday");
1128 strftime_YYYYMMDDHHMMSS(buf, sizeof(buf), &tval);
1129 bb_error_msg("current time is %s.%06u", buf, (unsigned)tvc.tv_usec);
1132 strftime_YYYYMMDDHHMMSS(buf, sizeof(buf), &tval);
1133 bb_info_msg("setting time to %s.%06u (offset %+fs)", buf, (unsigned)tvn.tv_usec, offset);
1134 //maybe? G.FREQHOLD_cnt = 0;
1136 /* Correct various fields which contain time-relative values: */
1139 G.cur_time += offset;
1140 G.last_update_recv_time += offset;
1141 G.last_script_run += offset;
1143 /* p->lastpkt_recv_time, p->next_action_time and such: */
1144 for (item = G.ntp_peers; item != NULL; item = item->link) {
1145 peer_t *pp = (peer_t *) item->data;
1146 reset_peer_stats(pp, offset);
1147 //bb_error_msg("offset:%+f pp->next_action_time:%f -> %f",
1148 // offset, pp->next_action_time, pp->next_action_time + offset);
1149 pp->next_action_time += offset;
1150 if (pp->p_fd >= 0) {
1151 /* We wait for reply from this peer too.
1152 * But due to step we are doing, reply's data is no longer
1153 * useful (in fact, it'll be bogus). Stop waiting for it.
1157 set_next(pp, RETRY_INTERVAL);
1162 static void clamp_pollexp_and_set_MAXSTRAT(void)
1164 if (G.poll_exp < MINPOLL)
1165 G.poll_exp = MINPOLL;
1166 if (G.poll_exp > BIGPOLL)
1167 G.poll_exp = BIGPOLL;
1168 G.polladj_count = 0;
1169 G.stratum = MAXSTRAT;
1174 * Selection and clustering, and their helpers
1180 double opt_rd; /* optimization */
1183 compare_point_edge(const void *aa, const void *bb)
1185 const point_t *a = aa;
1186 const point_t *b = bb;
1187 if (a->edge < b->edge) {
1190 return (a->edge > b->edge);
1197 compare_survivor_metric(const void *aa, const void *bb)
1199 const survivor_t *a = aa;
1200 const survivor_t *b = bb;
1201 if (a->metric < b->metric) {
1204 return (a->metric > b->metric);
1207 fit(peer_t *p, double rd)
1209 if ((p->reachable_bits & (p->reachable_bits-1)) == 0) {
1210 /* One or zero bits in reachable_bits */
1211 VERB4 bb_error_msg("peer %s unfit for selection: "
1212 "unreachable", p->p_dotted);
1215 #if 0 /* we filter out such packets earlier */
1216 if ((p->lastpkt_status & LI_ALARM) == LI_ALARM
1217 || p->lastpkt_stratum >= MAXSTRAT
1219 VERB4 bb_error_msg("peer %s unfit for selection: "
1220 "bad status/stratum", p->p_dotted);
1224 /* rd is root_distance(p) */
1225 if (rd > MAXDIST + FREQ_TOLERANCE * (1 << G.poll_exp)) {
1226 VERB3 bb_error_msg("peer %s unfit for selection: "
1227 "root distance %f too high, jitter:%f",
1228 p->p_dotted, rd, p->filter_jitter
1233 // /* Do we have a loop? */
1234 // if (p->refid == p->dstaddr || p->refid == s.refid)
1239 select_and_cluster(void)
1244 int size = 3 * G.peer_cnt;
1245 /* for selection algorithm */
1246 point_t point[size];
1247 unsigned num_points, num_candidates;
1249 unsigned num_falsetickers;
1250 /* for cluster algorithm */
1251 survivor_t survivor[size];
1252 unsigned num_survivors;
1258 while (item != NULL) {
1261 p = (peer_t *) item->data;
1262 rd = root_distance(p);
1263 offset = p->filter_offset;
1269 VERB5 bb_error_msg("interval: [%f %f %f] %s",
1275 point[num_points].p = p;
1276 point[num_points].type = -1;
1277 point[num_points].edge = offset - rd;
1278 point[num_points].opt_rd = rd;
1280 point[num_points].p = p;
1281 point[num_points].type = 0;
1282 point[num_points].edge = offset;
1283 point[num_points].opt_rd = rd;
1285 point[num_points].p = p;
1286 point[num_points].type = 1;
1287 point[num_points].edge = offset + rd;
1288 point[num_points].opt_rd = rd;
1292 num_candidates = num_points / 3;
1293 if (num_candidates == 0) {
1294 VERB3 bb_error_msg("no valid datapoints%s", ", no peer selected");
1297 //TODO: sorting does not seem to be done in reference code
1298 qsort(point, num_points, sizeof(point[0]), compare_point_edge);
1300 /* Start with the assumption that there are no falsetickers.
1301 * Attempt to find a nonempty intersection interval containing
1302 * the midpoints of all truechimers.
1303 * If a nonempty interval cannot be found, increase the number
1304 * of assumed falsetickers by one and try again.
1305 * If a nonempty interval is found and the number of falsetickers
1306 * is less than the number of truechimers, a majority has been found
1307 * and the midpoint of each truechimer represents
1308 * the candidates available to the cluster algorithm.
1310 num_falsetickers = 0;
1313 unsigned num_midpoints = 0;
1318 for (i = 0; i < num_points; i++) {
1320 * if (point[i].type == -1) c++;
1321 * if (point[i].type == 1) c--;
1322 * and it's simpler to do it this way:
1325 if (c >= num_candidates - num_falsetickers) {
1326 /* If it was c++ and it got big enough... */
1327 low = point[i].edge;
1330 if (point[i].type == 0)
1334 for (i = num_points-1; i >= 0; i--) {
1336 if (c >= num_candidates - num_falsetickers) {
1337 high = point[i].edge;
1340 if (point[i].type == 0)
1343 /* If the number of midpoints is greater than the number
1344 * of allowed falsetickers, the intersection contains at
1345 * least one truechimer with no midpoint - bad.
1346 * Also, interval should be nonempty.
1348 if (num_midpoints <= num_falsetickers && low < high)
1351 if (num_falsetickers * 2 >= num_candidates) {
1352 VERB3 bb_error_msg("falsetickers:%d, candidates:%d%s",
1353 num_falsetickers, num_candidates,
1354 ", no peer selected");
1358 VERB4 bb_error_msg("selected interval: [%f, %f]; candidates:%d falsetickers:%d",
1359 low, high, num_candidates, num_falsetickers);
1363 /* Construct a list of survivors (p, metric)
1364 * from the chime list, where metric is dominated
1365 * first by stratum and then by root distance.
1366 * All other things being equal, this is the order of preference.
1369 for (i = 0; i < num_points; i++) {
1370 if (point[i].edge < low || point[i].edge > high)
1373 survivor[num_survivors].p = p;
1374 /* x.opt_rd == root_distance(p); */
1375 survivor[num_survivors].metric = MAXDIST * p->lastpkt_stratum + point[i].opt_rd;
1376 VERB5 bb_error_msg("survivor[%d] metric:%f peer:%s",
1377 num_survivors, survivor[num_survivors].metric, p->p_dotted);
1380 /* There must be at least MIN_SELECTED survivors to satisfy the
1381 * correctness assertions. Ordinarily, the Byzantine criteria
1382 * require four survivors, but for the demonstration here, one
1385 if (num_survivors < MIN_SELECTED) {
1386 VERB3 bb_error_msg("survivors:%d%s",
1388 ", no peer selected");
1392 //looks like this is ONLY used by the fact that later we pick survivor[0].
1393 //we can avoid sorting then, just find the minimum once!
1394 qsort(survivor, num_survivors, sizeof(survivor[0]), compare_survivor_metric);
1396 /* For each association p in turn, calculate the selection
1397 * jitter p->sjitter as the square root of the sum of squares
1398 * (p->offset - q->offset) over all q associations. The idea is
1399 * to repeatedly discard the survivor with maximum selection
1400 * jitter until a termination condition is met.
1403 unsigned max_idx = max_idx;
1404 double max_selection_jitter = max_selection_jitter;
1405 double min_jitter = min_jitter;
1407 if (num_survivors <= MIN_CLUSTERED) {
1408 VERB4 bb_error_msg("num_survivors %d <= %d, not discarding more",
1409 num_survivors, MIN_CLUSTERED);
1413 /* To make sure a few survivors are left
1414 * for the clustering algorithm to chew on,
1415 * we stop if the number of survivors
1416 * is less than or equal to MIN_CLUSTERED (3).
1418 for (i = 0; i < num_survivors; i++) {
1419 double selection_jitter_sq;
1422 if (i == 0 || p->filter_jitter < min_jitter)
1423 min_jitter = p->filter_jitter;
1425 selection_jitter_sq = 0;
1426 for (j = 0; j < num_survivors; j++) {
1427 peer_t *q = survivor[j].p;
1428 selection_jitter_sq += SQUARE(p->filter_offset - q->filter_offset);
1430 if (i == 0 || selection_jitter_sq > max_selection_jitter) {
1431 max_selection_jitter = selection_jitter_sq;
1434 VERB6 bb_error_msg("survivor %d selection_jitter^2:%f",
1435 i, selection_jitter_sq);
1437 max_selection_jitter = SQRT(max_selection_jitter / num_survivors);
1438 VERB5 bb_error_msg("max_selection_jitter (at %d):%f min_jitter:%f",
1439 max_idx, max_selection_jitter, min_jitter);
1441 /* If the maximum selection jitter is less than the
1442 * minimum peer jitter, then tossing out more survivors
1443 * will not lower the minimum peer jitter, so we might
1446 if (max_selection_jitter < min_jitter) {
1447 VERB4 bb_error_msg("max_selection_jitter:%f < min_jitter:%f, num_survivors:%d, not discarding more",
1448 max_selection_jitter, min_jitter, num_survivors);
1452 /* Delete survivor[max_idx] from the list
1453 * and go around again.
1455 VERB6 bb_error_msg("dropping survivor %d", max_idx);
1457 while (max_idx < num_survivors) {
1458 survivor[max_idx] = survivor[max_idx + 1];
1464 /* Combine the offsets of the clustering algorithm survivors
1465 * using a weighted average with weight determined by the root
1466 * distance. Compute the selection jitter as the weighted RMS
1467 * difference between the first survivor and the remaining
1468 * survivors. In some cases the inherent clock jitter can be
1469 * reduced by not using this algorithm, especially when frequent
1470 * clockhopping is involved. bbox: thus we don't do it.
1474 for (i = 0; i < num_survivors; i++) {
1476 x = root_distance(p);
1478 z += p->filter_offset / x;
1479 w += SQUARE(p->filter_offset - survivor[0].p->filter_offset) / x;
1481 //G.cluster_offset = z / y;
1482 //G.cluster_jitter = SQRT(w / y);
1485 /* Pick the best clock. If the old system peer is on the list
1486 * and at the same stratum as the first survivor on the list,
1487 * then don't do a clock hop. Otherwise, select the first
1488 * survivor on the list as the new system peer.
1491 if (G.last_update_peer
1492 && G.last_update_peer->lastpkt_stratum <= p->lastpkt_stratum
1494 /* Starting from 1 is ok here */
1495 for (i = 1; i < num_survivors; i++) {
1496 if (G.last_update_peer == survivor[i].p) {
1497 VERB5 bb_error_msg("keeping old synced peer");
1498 p = G.last_update_peer;
1503 G.last_update_peer = p;
1505 VERB4 bb_error_msg("selected peer %s filter_offset:%+f age:%f",
1508 G.cur_time - p->lastpkt_recv_time
1515 * Local clock discipline and its helpers
1518 set_new_values(int disc_state, double offset, double recv_time)
1520 /* Enter new state and set state variables. Note we use the time
1521 * of the last clock filter sample, which must be earlier than
1524 VERB4 bb_error_msg("disc_state=%d last update offset=%f recv_time=%f",
1525 disc_state, offset, recv_time);
1526 G.discipline_state = disc_state;
1527 G.last_update_offset = offset;
1528 G.last_update_recv_time = recv_time;
1530 /* Return: -1: decrease poll interval, 0: leave as is, 1: increase */
1532 update_local_clock(peer_t *p)
1536 /* Note: can use G.cluster_offset instead: */
1537 double offset = p->filter_offset;
1538 double recv_time = p->lastpkt_recv_time;
1540 #if !USING_KERNEL_PLL_LOOP
1543 #if !USING_KERNEL_PLL_LOOP || USING_INITIAL_FREQ_ESTIMATION
1544 double since_last_update;
1546 double etemp, dtemp;
1548 abs_offset = fabs(offset);
1551 /* If needed, -S script can do it by looking at $offset
1552 * env var and killing parent */
1553 /* If the offset is too large, give up and go home */
1554 if (abs_offset > PANIC_THRESHOLD) {
1555 bb_error_msg_and_die("offset %f far too big, exiting", offset);
1559 /* If this is an old update, for instance as the result
1560 * of a system peer change, avoid it. We never use
1561 * an old sample or the same sample twice.
1563 if (recv_time <= G.last_update_recv_time) {
1564 VERB3 bb_error_msg("update from %s: same or older datapoint, not using it",
1566 return 0; /* "leave poll interval as is" */
1569 /* Clock state machine transition function. This is where the
1570 * action is and defines how the system reacts to large time
1571 * and frequency errors.
1573 #if !USING_KERNEL_PLL_LOOP || USING_INITIAL_FREQ_ESTIMATION
1574 since_last_update = recv_time - G.reftime;
1576 #if !USING_KERNEL_PLL_LOOP
1579 #if USING_INITIAL_FREQ_ESTIMATION
1580 if (G.discipline_state == STATE_FREQ) {
1581 /* Ignore updates until the stepout threshold */
1582 if (since_last_update < WATCH_THRESHOLD) {
1583 VERB4 bb_error_msg("measuring drift, datapoint ignored, %f sec remains",
1584 WATCH_THRESHOLD - since_last_update);
1585 return 0; /* "leave poll interval as is" */
1587 # if !USING_KERNEL_PLL_LOOP
1588 freq_drift = (offset - G.last_update_offset) / since_last_update;
1593 /* There are two main regimes: when the
1594 * offset exceeds the step threshold and when it does not.
1596 if (abs_offset > STEP_THRESHOLD) {
1600 // This "spike state" seems to be useless, peer selection already drops
1601 // occassional "bad" datapoints. If we are here, there were _many_
1602 // large offsets. When a few first large offsets are seen,
1603 // we end up in "no valid datapoints, no peer selected" state.
1604 // Only when enough of them are seen (which means it's not a fluke),
1605 // we end up here. Looks like _our_ clock is off.
1606 switch (G.discipline_state) {
1608 /* The first outlyer: ignore it, switch to SPIK state */
1609 VERB3 bb_error_msg("update from %s: offset:%+f, spike%s",
1610 p->p_dotted, offset,
1612 G.discipline_state = STATE_SPIK;
1613 return -1; /* "decrease poll interval" */
1616 /* Ignore succeeding outlyers until either an inlyer
1617 * is found or the stepout threshold is exceeded.
1619 remains = WATCH_THRESHOLD - since_last_update;
1621 VERB3 bb_error_msg("update from %s: offset:%+f, spike%s",
1622 p->p_dotted, offset,
1623 ", datapoint ignored");
1624 return -1; /* "decrease poll interval" */
1626 /* fall through: we need to step */
1630 /* Step the time and clamp down the poll interval.
1632 * In NSET state an initial frequency correction is
1633 * not available, usually because the frequency file has
1634 * not yet been written. Since the time is outside the
1635 * capture range, the clock is stepped. The frequency
1636 * will be set directly following the stepout interval.
1638 * In FSET state the initial frequency has been set
1639 * from the frequency file. Since the time is outside
1640 * the capture range, the clock is stepped immediately,
1641 * rather than after the stepout interval. Guys get
1642 * nervous if it takes 17 minutes to set the clock for
1645 * In SPIK state the stepout threshold has expired and
1646 * the phase is still above the step threshold. Note
1647 * that a single spike greater than the step threshold
1648 * is always suppressed, even at the longer poll
1651 VERB4 bb_error_msg("stepping time by %+f; poll_exp=MINPOLL", offset);
1653 if (option_mask32 & OPT_q) {
1654 /* We were only asked to set time once. Done. */
1658 clamp_pollexp_and_set_MAXSTRAT();
1660 run_script("step", offset);
1662 recv_time += offset;
1664 #if USING_INITIAL_FREQ_ESTIMATION
1665 if (G.discipline_state == STATE_NSET) {
1666 set_new_values(STATE_FREQ, /*offset:*/ 0, recv_time);
1667 return 1; /* "ok to increase poll interval" */
1670 abs_offset = offset = 0;
1671 set_new_values(STATE_SYNC, offset, recv_time);
1672 } else { /* abs_offset <= STEP_THRESHOLD */
1674 /* The ratio is calculated before jitter is updated to make
1675 * poll adjust code more sensitive to large offsets.
1677 G.offset_to_jitter_ratio = abs_offset / G.discipline_jitter;
1679 /* Compute the clock jitter as the RMS of exponentially
1680 * weighted offset differences. Used by the poll adjust code.
1682 etemp = SQUARE(G.discipline_jitter);
1683 dtemp = SQUARE(offset - G.last_update_offset);
1684 G.discipline_jitter = SQRT(etemp + (dtemp - etemp) / AVG);
1685 if (G.discipline_jitter < G_precision_sec)
1686 G.discipline_jitter = G_precision_sec;
1688 switch (G.discipline_state) {
1690 if (option_mask32 & OPT_q) {
1691 /* We were only asked to set time once.
1692 * The clock is precise enough, no need to step.
1696 #if USING_INITIAL_FREQ_ESTIMATION
1697 /* This is the first update received and the frequency
1698 * has not been initialized. The first thing to do
1699 * is directly measure the oscillator frequency.
1701 set_new_values(STATE_FREQ, offset, recv_time);
1703 set_new_values(STATE_SYNC, offset, recv_time);
1705 VERB4 bb_error_msg("transitioning to FREQ, datapoint ignored");
1706 return 0; /* "leave poll interval as is" */
1708 #if 0 /* this is dead code for now */
1710 /* This is the first update and the frequency
1711 * has been initialized. Adjust the phase, but
1712 * don't adjust the frequency until the next update.
1714 set_new_values(STATE_SYNC, offset, recv_time);
1715 /* freq_drift remains 0 */
1719 #if USING_INITIAL_FREQ_ESTIMATION
1721 /* since_last_update >= WATCH_THRESHOLD, we waited enough.
1722 * Correct the phase and frequency and switch to SYNC state.
1723 * freq_drift was already estimated (see code above)
1725 set_new_values(STATE_SYNC, offset, recv_time);
1730 #if !USING_KERNEL_PLL_LOOP
1731 /* Compute freq_drift due to PLL and FLL contributions.
1733 * The FLL and PLL frequency gain constants
1734 * depend on the poll interval and Allan
1735 * intercept. The FLL is not used below one-half
1736 * the Allan intercept. Above that the loop gain
1737 * increases in steps to 1 / AVG.
1739 if ((1 << G.poll_exp) > ALLAN / 2) {
1740 etemp = FLL - G.poll_exp;
1743 freq_drift += (offset - G.last_update_offset) / (MAXD(since_last_update, ALLAN) * etemp);
1745 /* For the PLL the integration interval
1746 * (numerator) is the minimum of the update
1747 * interval and poll interval. This allows
1748 * oversampling, but not undersampling.
1750 etemp = MIND(since_last_update, (1 << G.poll_exp));
1751 dtemp = (4 * PLL) << G.poll_exp;
1752 freq_drift += offset * etemp / SQUARE(dtemp);
1754 set_new_values(STATE_SYNC, offset, recv_time);
1757 if (G.stratum != p->lastpkt_stratum + 1) {
1758 G.stratum = p->lastpkt_stratum + 1;
1759 run_script("stratum", offset);
1763 G.reftime = G.cur_time;
1764 G.ntp_status = p->lastpkt_status;
1765 G.refid = p->lastpkt_refid;
1766 G.rootdelay = p->lastpkt_rootdelay + p->lastpkt_delay;
1767 dtemp = p->filter_jitter; // SQRT(SQUARE(p->filter_jitter) + SQUARE(G.cluster_jitter));
1768 dtemp += MAXD(p->filter_dispersion + FREQ_TOLERANCE * (G.cur_time - p->lastpkt_recv_time) + abs_offset, MINDISP);
1769 G.rootdisp = p->lastpkt_rootdisp + dtemp;
1770 VERB4 bb_error_msg("updating leap/refid/reftime/rootdisp from peer %s", p->p_dotted);
1772 /* We are in STATE_SYNC now, but did not do adjtimex yet.
1773 * (Any other state does not reach this, they all return earlier)
1774 * By this time, freq_drift and offset are set
1775 * to values suitable for adjtimex.
1777 #if !USING_KERNEL_PLL_LOOP
1778 /* Calculate the new frequency drift and frequency stability (wander).
1779 * Compute the clock wander as the RMS of exponentially weighted
1780 * frequency differences. This is not used directly, but can,
1781 * along with the jitter, be a highly useful monitoring and
1784 dtemp = G.discipline_freq_drift + freq_drift;
1785 G.discipline_freq_drift = MAXD(MIND(MAXDRIFT, dtemp), -MAXDRIFT);
1786 etemp = SQUARE(G.discipline_wander);
1787 dtemp = SQUARE(dtemp);
1788 G.discipline_wander = SQRT(etemp + (dtemp - etemp) / AVG);
1790 VERB4 bb_error_msg("discipline freq_drift=%.9f(int:%ld corr:%e) wander=%f",
1791 G.discipline_freq_drift,
1792 (long)(G.discipline_freq_drift * 65536e6),
1794 G.discipline_wander);
1797 memset(&tmx, 0, sizeof(tmx));
1798 if (adjtimex(&tmx) < 0)
1799 bb_perror_msg_and_die("adjtimex");
1800 bb_error_msg("p adjtimex freq:%ld offset:%+ld status:0x%x tc:%ld",
1801 tmx.freq, tmx.offset, tmx.status, tmx.constant);
1804 memset(&tmx, 0, sizeof(tmx));
1806 //doesn't work, offset remains 0 (!) in kernel:
1807 //ntpd: set adjtimex freq:1786097 tmx.offset:77487
1808 //ntpd: prev adjtimex freq:1786097 tmx.offset:0
1809 //ntpd: cur adjtimex freq:1786097 tmx.offset:0
1810 tmx.modes = ADJ_FREQUENCY | ADJ_OFFSET;
1811 /* 65536 is one ppm */
1812 tmx.freq = G.discipline_freq_drift * 65536e6;
1814 tmx.modes = ADJ_OFFSET | ADJ_STATUS | ADJ_TIMECONST;// | ADJ_MAXERROR | ADJ_ESTERROR;
1816 tmx.offset = (long)(offset * 1000000); /* usec */
1817 if (SLEW_THRESHOLD < STEP_THRESHOLD) {
1818 if (tmx.offset > (long)(SLEW_THRESHOLD * 1000000)) {
1819 tmx.offset = (long)(SLEW_THRESHOLD * 1000000);
1821 if (tmx.offset < -(long)(SLEW_THRESHOLD * 1000000)) {
1822 tmx.offset = -(long)(SLEW_THRESHOLD * 1000000);
1826 tmx.status = STA_PLL;
1827 if (G.FREQHOLD_cnt != 0) {
1828 /* man adjtimex on STA_FREQHOLD:
1829 * "Normally adjustments made via ADJ_OFFSET result in dampened
1830 * frequency adjustments also being made.
1831 * This flag prevents the small frequency adjustment from being
1832 * made when correcting for an ADJ_OFFSET value."
1834 * Use this flag for a few first adjustments at the beginning
1835 * of ntpd execution, otherwise even relatively small initial
1836 * offset tend to cause largish changes to in-kernel tmx.freq.
1837 * If ntpd was restarted due to e.g. switch to another network,
1838 * this destroys already well-established tmx.freq value.
1840 if (G.FREQHOLD_cnt < 0) {
1842 // Example: a laptop whose clock runs slower when hibernated,
1843 // after wake up it still has good tmx.freq, but accumulated ~0.5 sec offset:
1844 // Run with code where initial G.FREQHOLD_cnt was always 8:
1845 //15:17:52.947 no valid datapoints, no peer selected
1846 //15:17:56.515 update from:<IP> offset:+0.485133 delay:0.157762 jitter:0.209310 clock drift:-1.393ppm tc:4
1847 //15:17:57.719 update from:<IP> offset:+0.483825 delay:0.158070 jitter:0.181159 clock drift:-1.393ppm tc:4
1848 //15:17:59.925 update from:<IP> offset:+0.479504 delay:0.158147 jitter:0.156657 clock drift:-1.393ppm tc:4
1849 //15:18:33.322 update from:<IP> offset:+0.428119 delay:0.158317 jitter:0.138071 clock drift:-1.393ppm tc:4
1850 //15:19:06.718 update from:<IP> offset:+0.376932 delay:0.158276 jitter:0.122075 clock drift:-1.393ppm tc:4
1851 //15:19:39.114 update from:<IP> offset:+0.327022 delay:0.158384 jitter:0.108538 clock drift:-1.393ppm tc:4
1852 //15:20:12.715 update from:<IP> offset:+0.275596 delay:0.158297 jitter:0.097292 clock drift:-1.393ppm tc:4
1853 //15:20:45.111 update from:<IP> offset:+0.225715 delay:0.158271 jitter:0.087841 clock drift:-1.393ppm tc:4
1854 // If allowed to continue, it would start increasing tmx.freq now.
1855 // Instead, it was ^Ced, and started anew:
1856 //15:21:15.043 no valid datapoints, no peer selected
1857 //15:21:17.408 update from:<IP> offset:+0.175910 delay:0.158314 jitter:0.076683 clock drift:-1.393ppm tc:4
1858 //15:21:19.774 update from:<IP> offset:+0.171784 delay:0.158401 jitter:0.066436 clock drift:-1.393ppm tc:4
1859 //15:21:22.140 update from:<IP> offset:+0.171660 delay:0.158592 jitter:0.057536 clock drift:-1.393ppm tc:4
1860 //15:21:22.140 update from:<IP> offset:+0.167126 delay:0.158507 jitter:0.049792 clock drift:-1.393ppm tc:4
1861 //15:21:55.696 update from:<IP> offset:+0.115223 delay:0.158277 jitter:0.050240 clock drift:-1.393ppm tc:4
1862 //15:22:29.093 update from:<IP> offset:+0.068051 delay:0.158243 jitter:0.049405 clock drift:-1.393ppm tc:5
1863 //15:23:02.490 update from:<IP> offset:+0.051632 delay:0.158215 jitter:0.043545 clock drift:-1.393ppm tc:5
1864 //15:23:34.726 update from:<IP> offset:+0.039984 delay:0.158157 jitter:0.038106 clock drift:-1.393ppm tc:5
1865 // STA_FREQHOLD no longer set, started increasing tmx.freq now:
1866 //15:24:06.961 update from:<IP> offset:+0.030968 delay:0.158190 jitter:0.033306 clock drift:+2.387ppm tc:5
1867 //15:24:40.357 update from:<IP> offset:+0.023648 delay:0.158211 jitter:0.029072 clock drift:+5.454ppm tc:5
1868 //15:25:13.774 update from:<IP> offset:+0.018068 delay:0.157660 jitter:0.025288 clock drift:+7.728ppm tc:5
1869 //15:26:19.173 update from:<IP> offset:+0.010057 delay:0.157969 jitter:0.022255 clock drift:+8.361ppm tc:6
1870 //15:27:26.602 update from:<IP> offset:+0.006737 delay:0.158103 jitter:0.019316 clock drift:+8.792ppm tc:6
1871 //15:28:33.030 update from:<IP> offset:+0.004513 delay:0.158294 jitter:0.016765 clock drift:+9.080ppm tc:6
1872 //15:29:40.617 update from:<IP> offset:+0.002787 delay:0.157745 jitter:0.014543 clock drift:+9.258ppm tc:6
1873 //15:30:47.045 update from:<IP> offset:+0.001324 delay:0.157709 jitter:0.012594 clock drift:+9.342ppm tc:6
1874 //15:31:53.473 update from:<IP> offset:+0.000007 delay:0.158142 jitter:0.010922 clock drift:+9.343ppm tc:6
1875 //15:32:58.902 update from:<IP> offset:-0.000728 delay:0.158222 jitter:0.009454 clock drift:+9.298ppm tc:6
1877 * This expression would choose MIN_FREQHOLD + 8 in the above example.
1879 G.FREQHOLD_cnt = 1 + MIN_FREQHOLD + ((unsigned)(abs(tmx.offset)) >> 16);
1882 tmx.status |= STA_FREQHOLD;
1884 if (G.ntp_status & LI_PLUSSEC)
1885 tmx.status |= STA_INS;
1886 if (G.ntp_status & LI_MINUSSEC)
1887 tmx.status |= STA_DEL;
1889 tmx.constant = (int)G.poll_exp - 4;
1891 * The below if statement should be unnecessary, but...
1892 * It looks like Linux kernel's PLL is far too gentle in changing
1893 * tmx.freq in response to clock offset. Offset keeps growing
1894 * and eventually we fall back to smaller poll intervals.
1895 * We can make correction more aggressive (about x2) by supplying
1896 * PLL time constant which is one less than the real one.
1897 * To be on a safe side, let's do it only if offset is significantly
1898 * larger than jitter.
1900 if (G.offset_to_jitter_ratio >= TIMECONST_HACK_GATE)
1902 if (tmx.constant < 0)
1905 //tmx.esterror = (uint32_t)(clock_jitter * 1e6);
1906 //tmx.maxerror = (uint32_t)((sys_rootdelay / 2 + sys_rootdisp) * 1e6);
1907 rc = adjtimex(&tmx);
1909 bb_perror_msg_and_die("adjtimex");
1910 /* NB: here kernel returns constant == G.poll_exp, not == G.poll_exp - 4.
1911 * Not sure why. Perhaps it is normal.
1913 VERB4 bb_error_msg("adjtimex:%d freq:%ld offset:%+ld status:0x%x",
1914 rc, tmx.freq, tmx.offset, tmx.status);
1915 G.kernel_freq_drift = tmx.freq / 65536;
1916 VERB2 bb_error_msg("update from:%s offset:%+f delay:%f jitter:%f clock drift:%+.3fppm tc:%d",
1920 G.discipline_jitter,
1921 (double)tmx.freq / 65536,
1925 return 1; /* "ok to increase poll interval" */
1930 * We've got a new reply packet from a peer, process it
1934 poll_interval(int upper_bound)
1936 unsigned interval, r, mask;
1937 interval = 1 << G.poll_exp;
1938 if (interval > upper_bound)
1939 interval = upper_bound;
1940 mask = ((interval-1) >> 4) | 1;
1942 interval += r & mask; /* ~ random(0..1) * interval/16 */
1943 VERB4 bb_error_msg("chose poll interval:%u (poll_exp:%d)", interval, G.poll_exp);
1947 adjust_poll(int count)
1949 G.polladj_count += count;
1950 if (G.polladj_count > POLLADJ_LIMIT) {
1951 G.polladj_count = 0;
1952 if (G.poll_exp < MAXPOLL) {
1954 VERB4 bb_error_msg("polladj: discipline_jitter:%f ++poll_exp=%d",
1955 G.discipline_jitter, G.poll_exp);
1957 } else if (G.polladj_count < -POLLADJ_LIMIT || (count < 0 && G.poll_exp > BIGPOLL)) {
1958 G.polladj_count = 0;
1959 if (G.poll_exp > MINPOLL) {
1963 /* Correct p->next_action_time in each peer
1964 * which waits for sending, so that they send earlier.
1965 * Old pp->next_action_time are on the order
1966 * of t + (1 << old_poll_exp) + small_random,
1967 * we simply need to subtract ~half of that.
1969 for (item = G.ntp_peers; item != NULL; item = item->link) {
1970 peer_t *pp = (peer_t *) item->data;
1972 pp->next_action_time -= (1 << G.poll_exp);
1974 VERB4 bb_error_msg("polladj: discipline_jitter:%f --poll_exp=%d",
1975 G.discipline_jitter, G.poll_exp);
1978 VERB4 bb_error_msg("polladj: count:%d", G.polladj_count);
1981 static NOINLINE void
1982 recv_and_process_peer_pkt(peer_t *p)
1987 double T1, T2, T3, T4;
1989 double prev_delay, delay;
1991 datapoint_t *datapoint;
1996 /* We can recvfrom here and check from.IP, but some multihomed
1997 * ntp servers reply from their *other IP*.
1998 * TODO: maybe we should check at least what we can: from.port == 123?
2001 size = recv(p->p_fd, &msg, sizeof(msg), MSG_DONTWAIT);
2006 if (errno == EAGAIN)
2007 /* There was no packet after all
2008 * (poll() returning POLLIN for a fd
2009 * is not a ironclad guarantee that data is there)
2013 * If you need a different handling for a specific
2014 * errno, always explain it in comment.
2016 bb_perror_msg_and_die("recv(%s) error", p->p_dotted);
2019 #if ENABLE_FEATURE_NTP_AUTH
2020 if (size != NTP_MSGSIZE_NOAUTH && size != NTP_MSGSIZE_MD5_AUTH && size != NTP_MSGSIZE_SHA1_AUTH) {
2021 bb_error_msg("malformed packet received from %s", p->p_dotted);
2024 if (p->key_entry && hashes_differ(p, &msg)) {
2025 bb_error_msg("invalid cryptographic hash received from %s", p->p_dotted);
2029 if (size != NTP_MSGSIZE_NOAUTH && size != NTP_MSGSIZE_MD5_AUTH) {
2030 bb_error_msg("malformed packet received from %s", p->p_dotted);
2035 if (msg.m_orgtime.int_partl != p->p_xmt_msg.m_xmttime.int_partl
2036 || msg.m_orgtime.fractionl != p->p_xmt_msg.m_xmttime.fractionl
2038 /* Somebody else's packet */
2042 /* We do not expect any more packets from this peer for now.
2043 * Closing the socket informs kernel about it.
2044 * We open a new socket when we send a new query.
2049 if ((msg.m_status & LI_ALARM) == LI_ALARM
2050 || msg.m_stratum == 0
2051 || msg.m_stratum > NTP_MAXSTRATUM
2053 bb_error_msg("reply from %s: peer is unsynced", p->p_dotted);
2055 * Stratum 0 responses may have commands in 32-bit m_refid field:
2056 * "DENY", "RSTR" - peer does not like us at all,
2057 * "RATE" - peer is overloaded, reduce polling freq.
2058 * If poll interval is small, increase it.
2060 if (G.poll_exp < BIGPOLL)
2061 goto increase_interval;
2062 goto pick_normal_interval;
2065 // /* Verify valid root distance */
2066 // if (msg.m_rootdelay / 2 + msg.m_rootdisp >= MAXDISP || p->lastpkt_reftime > msg.m_xmt)
2067 // return; /* invalid header values */
2070 * From RFC 2030 (with a correction to the delay math):
2072 * Timestamp Name ID When Generated
2073 * ------------------------------------------------------------
2074 * Originate Timestamp T1 time request sent by client
2075 * Receive Timestamp T2 time request received by server
2076 * Transmit Timestamp T3 time reply sent by server
2077 * Destination Timestamp T4 time reply received by client
2079 * The roundtrip delay and local clock offset are defined as
2081 * delay = (T4 - T1) - (T3 - T2); offset = ((T2 - T1) + (T3 - T4)) / 2
2084 T2 = lfp_to_d(msg.m_rectime);
2085 T3 = lfp_to_d(msg.m_xmttime);
2087 delay = (T4 - T1) - (T3 - T2);
2090 * If this packet's delay is much bigger than the last one,
2091 * it's better to just ignore it than use its much less precise value.
2093 prev_delay = p->p_raw_delay;
2094 p->p_raw_delay = (delay < 0 ? 0.0 : delay);
2095 if (p->reachable_bits
2096 && delay > prev_delay * BAD_DELAY_GROWTH
2097 && delay > 1.0 / (8 * 1024) /* larger than ~0.000122 */
2099 bb_error_msg("reply from %s: delay %f is too high, ignoring", p->p_dotted, delay);
2100 goto pick_normal_interval;
2103 /* The delay calculation is a special case. In cases where the
2104 * server and client clocks are running at different rates and
2105 * with very fast networks, the delay can appear negative. In
2106 * order to avoid violating the Principle of Least Astonishment,
2107 * the delay is clamped not less than the system precision.
2109 if (delay < G_precision_sec)
2110 delay = G_precision_sec;
2111 p->lastpkt_delay = delay;
2112 p->lastpkt_recv_time = T4;
2113 VERB6 bb_error_msg("%s->lastpkt_recv_time=%f", p->p_dotted, p->lastpkt_recv_time);
2114 p->lastpkt_status = msg.m_status;
2115 p->lastpkt_stratum = msg.m_stratum;
2116 p->lastpkt_rootdelay = sfp_to_d(msg.m_rootdelay);
2117 p->lastpkt_rootdisp = sfp_to_d(msg.m_rootdisp);
2118 p->lastpkt_refid = msg.m_refid;
2120 p->datapoint_idx = p->reachable_bits ? (p->datapoint_idx + 1) % NUM_DATAPOINTS : 0;
2121 datapoint = &p->filter_datapoint[p->datapoint_idx];
2122 datapoint->d_recv_time = T4;
2123 datapoint->d_offset = offset = ((T2 - T1) + (T3 - T4)) / 2;
2124 datapoint->d_dispersion = LOG2D(msg.m_precision_exp) + G_precision_sec;
2125 if (!p->reachable_bits) {
2126 /* 1st datapoint ever - replicate offset in every element */
2128 for (i = 0; i < NUM_DATAPOINTS; i++) {
2129 p->filter_datapoint[i].d_offset = offset;
2133 p->reachable_bits |= 1;
2134 if ((MAX_VERBOSE && G.verbose) || (option_mask32 & OPT_w)) {
2135 bb_info_msg("reply from %s: offset:%+f delay:%f status:0x%02x strat:%d refid:0x%08x rootdelay:%f reach:0x%02x",
2142 p->lastpkt_rootdelay,
2144 /* not shown: m_ppoll, m_precision_exp, m_rootdisp,
2145 * m_reftime, m_orgtime, m_rectime, m_xmttime
2150 /* Muck with statictics and update the clock */
2151 filter_datapoints(p);
2152 q = select_and_cluster();
2155 if (!(option_mask32 & OPT_w)) {
2156 rc = update_local_clock(q);
2158 //Disabled this because there is a case where largish offsets
2159 //are unavoidable: if network round-trip delay is, say, ~0.6s,
2160 //error in offset estimation would be ~delay/2 ~= 0.3s.
2161 //Thus, offsets will be usually in -0.3...0.3s range.
2162 //In this case, this code would keep poll interval small,
2163 //but it won't be helping.
2164 //BIGOFF check below deals with a case of seeing multi-second offsets.
2166 /* If drift is dangerously large, immediately
2167 * drop poll interval one step down.
2169 if (fabs(q->filter_offset) >= POLLDOWN_OFFSET) {
2170 VERB4 bb_error_msg("offset:%+f > POLLDOWN_OFFSET", q->filter_offset);
2171 adjust_poll(-POLLADJ_LIMIT * 3);
2177 /* No peer selected.
2178 * If poll interval is small, increase it.
2180 if (G.poll_exp < BIGPOLL)
2181 goto increase_interval;
2185 /* Adjust the poll interval by comparing the current offset
2186 * with the clock jitter. If the offset is less than
2187 * the clock jitter times a constant, then the averaging interval
2188 * is increased, otherwise it is decreased. A bit of hysteresis
2189 * helps calm the dance. Works best using burst mode.
2191 if (rc > 0 && G.offset_to_jitter_ratio <= POLLADJ_GATE) {
2192 /* was += G.poll_exp but it is a bit
2193 * too optimistic for my taste at high poll_exp's */
2195 adjust_poll(MINPOLL);
2198 bb_error_msg("want smaller interval: offset/jitter = %u",
2199 G.offset_to_jitter_ratio);
2200 adjust_poll(-G.poll_exp * 2);
2204 /* Decide when to send new query for this peer */
2205 pick_normal_interval:
2206 interval = poll_interval(INT_MAX);
2207 if (fabs(offset) >= BIGOFF && interval > BIGOFF_INTERVAL) {
2208 /* If we are synced, offsets are less than SLEW_THRESHOLD,
2209 * or at the very least not much larger than it.
2210 * Now we see a largish one.
2211 * Either this peer is feeling bad, or packet got corrupted,
2212 * or _our_ clock is wrong now and _all_ peers will show similar
2213 * largish offsets too.
2214 * I observed this with laptop suspend stopping clock.
2215 * In any case, it makes sense to make next request soonish:
2216 * cases 1 and 2: get a better datapoint,
2217 * case 3: allows to resync faster.
2219 interval = BIGOFF_INTERVAL;
2222 set_next(p, interval);
2225 #if ENABLE_FEATURE_NTPD_SERVER
2226 static NOINLINE void
2227 recv_and_process_client_pkt(void /*int fd*/)
2231 len_and_sockaddr *to;
2232 struct sockaddr *from;
2234 uint8_t query_status;
2235 l_fixedpt_t query_xmttime;
2237 to = get_sock_lsa(G_listen_fd);
2238 from = xzalloc(to->len);
2240 size = recv_from_to(G_listen_fd, &msg, sizeof(msg), MSG_DONTWAIT, from, &to->u.sa, to->len);
2241 #if ENABLE_FEATURE_NTP_AUTH
2242 if (size != NTP_MSGSIZE_NOAUTH && size != NTP_MSGSIZE_MD5_AUTH && size != NTP_MSGSIZE_SHA1_AUTH)
2244 if (size != NTP_MSGSIZE_NOAUTH && size != NTP_MSGSIZE_MD5_AUTH)
2249 if (errno == EAGAIN)
2251 bb_perror_msg_and_die("recv");
2253 addr = xmalloc_sockaddr2dotted_noport(from);
2254 bb_error_msg("malformed packet received from %s: size %u", addr, (int)size);
2259 /* Respond only to client and symmetric active packets */
2260 if ((msg.m_status & MODE_MASK) != MODE_CLIENT
2261 && (msg.m_status & MODE_MASK) != MODE_SYM_ACT
2266 query_status = msg.m_status;
2267 query_xmttime = msg.m_xmttime;
2269 /* Build a reply packet */
2270 memset(&msg, 0, sizeof(msg));
2271 msg.m_status = G.stratum < MAXSTRAT ? (G.ntp_status & LI_MASK) : LI_ALARM;
2272 msg.m_status |= (query_status & VERSION_MASK);
2273 msg.m_status |= ((query_status & MODE_MASK) == MODE_CLIENT) ?
2274 MODE_SERVER : MODE_SYM_PAS;
2275 msg.m_stratum = G.stratum;
2276 msg.m_ppoll = G.poll_exp;
2277 msg.m_precision_exp = G_precision_exp;
2278 /* this time was obtained between poll() and recv() */
2279 msg.m_rectime = d_to_lfp(G.cur_time);
2280 msg.m_xmttime = d_to_lfp(gettime1900d()); /* this instant */
2281 if (G.peer_cnt == 0) {
2282 /* we have no peers: "stratum 1 server" mode. reftime = our own time */
2283 G.reftime = G.cur_time;
2285 msg.m_reftime = d_to_lfp(G.reftime);
2286 msg.m_orgtime = query_xmttime;
2287 msg.m_rootdelay = d_to_sfp(G.rootdelay);
2288 //simple code does not do this, fix simple code!
2289 msg.m_rootdisp = d_to_sfp(G.rootdisp);
2290 //version = (query_status & VERSION_MASK); /* ... >> VERSION_SHIFT - done below instead */
2291 msg.m_refid = G.refid; // (version > (3 << VERSION_SHIFT)) ? G.refid : G.refid3;
2293 /* We reply from the local address packet was sent to,
2294 * this makes to/from look swapped here: */
2295 do_sendto(G_listen_fd,
2296 /*from:*/ &to->u.sa, /*to:*/ from, /*addrlen:*/ to->len,
2305 /* Upstream ntpd's options:
2307 * -4 Force DNS resolution of host names to the IPv4 namespace.
2308 * -6 Force DNS resolution of host names to the IPv6 namespace.
2309 * -a Require cryptographic authentication for broadcast client,
2310 * multicast client and symmetric passive associations.
2311 * This is the default.
2312 * -A Do not require cryptographic authentication for broadcast client,
2313 * multicast client and symmetric passive associations.
2314 * This is almost never a good idea.
2315 * -b Enable the client to synchronize to broadcast servers.
2317 * Specify the name and path of the configuration file,
2318 * default /etc/ntp.conf
2319 * -d Specify debugging mode. This option may occur more than once,
2320 * with each occurrence indicating greater detail of display.
2322 * Specify debugging level directly.
2324 * Specify the name and path of the frequency file.
2325 * This is the same operation as the "driftfile FILE"
2326 * configuration command.
2327 * -g Normally, ntpd exits with a message to the system log
2328 * if the offset exceeds the panic threshold, which is 1000 s
2329 * by default. This option allows the time to be set to any value
2330 * without restriction; however, this can happen only once.
2331 * If the threshold is exceeded after that, ntpd will exit
2332 * with a message to the system log. This option can be used
2333 * with the -q and -x options. See the tinker command for other options.
2335 * Chroot the server to the directory jaildir. This option also implies
2336 * that the server attempts to drop root privileges at startup
2337 * (otherwise, chroot gives very little additional security).
2338 * You may need to also specify a -u option.
2340 * Specify the name and path of the symmetric key file,
2341 * default /etc/ntp/keys. This is the same operation
2342 * as the "keys FILE" configuration command.
2344 * Specify the name and path of the log file. The default
2345 * is the system log file. This is the same operation as
2346 * the "logfile FILE" configuration command.
2347 * -L Do not listen to virtual IPs. The default is to listen.
2349 * -N To the extent permitted by the operating system,
2350 * run the ntpd at the highest priority.
2352 * Specify the name and path of the file used to record the ntpd
2353 * process ID. This is the same operation as the "pidfile FILE"
2354 * configuration command.
2356 * To the extent permitted by the operating system,
2357 * run the ntpd at the specified priority.
2358 * -q Exit the ntpd just after the first time the clock is set.
2359 * This behavior mimics that of the ntpdate program, which is
2360 * to be retired. The -g and -x options can be used with this option.
2361 * Note: The kernel time discipline is disabled with this option.
2363 * Specify the default propagation delay from the broadcast/multicast
2364 * server to this client. This is necessary only if the delay
2365 * cannot be computed automatically by the protocol.
2367 * Specify the directory path for files created by the statistics
2368 * facility. This is the same operation as the "statsdir DIR"
2369 * configuration command.
2371 * Add a key number to the trusted key list. This option can occur
2374 * Specify a user, and optionally a group, to switch to.
2377 * Add a system variable listed by default.
2378 * -x Normally, the time is slewed if the offset is less than the step
2379 * threshold, which is 128 ms by default, and stepped if above
2380 * the threshold. This option sets the threshold to 600 s, which is
2381 * well within the accuracy window to set the clock manually.
2382 * Note: since the slew rate of typical Unix kernels is limited
2383 * to 0.5 ms/s, each second of adjustment requires an amortization
2384 * interval of 2000 s. Thus, an adjustment as much as 600 s
2385 * will take almost 14 days to complete. This option can be used
2386 * with the -g and -q options. See the tinker command for other options.
2387 * Note: The kernel time discipline is disabled with this option.
2389 #if ENABLE_FEATURE_NTP_AUTH
2390 static key_entry_t *
2391 find_key_entry(llist_t *key_entries, unsigned id)
2393 while (key_entries) {
2394 key_entry_t *cur = (key_entry_t*) key_entries->data;
2397 key_entries = key_entries->link;
2399 bb_error_msg_and_die("key %u is not defined", id);
2403 /* By doing init in a separate function we decrease stack usage
2406 static NOINLINE void ntp_init(char **argv)
2410 #if ENABLE_FEATURE_NTP_AUTH
2411 llist_t *key_entries;
2412 char *key_file_path;
2418 bb_error_msg_and_die(bb_msg_you_must_be_root);
2420 /* Set some globals */
2421 G.discipline_jitter = G_precision_sec;
2422 G.stratum = MAXSTRAT;
2424 G.poll_exp = BURSTPOLL; /* speeds up initial sync */
2425 G.last_script_run = G.reftime = G.last_update_recv_time = gettime1900d(); /* sets G.cur_time too */
2426 G.FREQHOLD_cnt = -1;
2430 IF_FEATURE_NTP_AUTH(key_entries = NULL;)
2431 opts = getopt32(argv, "^"
2433 IF_FEATURE_NTP_AUTH("k:") /* compat */
2434 "wp:*S:"IF_FEATURE_NTPD_SERVER("l") /* NOT compat */
2435 IF_FEATURE_NTPD_SERVER("I:") /* compat */
2437 "46aAbgL" /* compat, ignored */
2439 "dd:wn" /* -d: counter; -p: list; -w implies -n */
2440 IF_FEATURE_NTPD_SERVER(":Il") /* -I implies -l */
2441 IF_FEATURE_NTP_AUTH(, &key_file_path)
2442 , &peers, &G.script_name
2443 IF_FEATURE_NTPD_SERVER(, &G.if_name)
2447 // if (opts & OPT_x) /* disable stepping, only slew is allowed */
2448 // G.time_was_stepped = 1;
2450 #if ENABLE_FEATURE_NTPD_SERVER
2453 G_listen_fd = create_and_bind_dgram_or_die(NULL, 123);
2455 if (setsockopt_bindtodevice(G_listen_fd, G.if_name))
2458 socket_want_pktinfo(G_listen_fd);
2459 setsockopt_int(G_listen_fd, IPPROTO_IP, IP_TOS, IPTOS_DSCP_AF21);
2462 /* I hesitate to set -20 prio. -15 should be high enough for timekeeping */
2464 setpriority(PRIO_PROCESS, 0, -15);
2466 if (!(opts & OPT_n)) {
2467 bb_daemonize_or_rexec(DAEMON_DEVNULL_STDIO, argv);
2468 logmode = LOGMODE_NONE;
2471 #if ENABLE_FEATURE_NTP_AUTH
2476 parser = config_open(key_file_path);
2477 while (config_read(parser, tokens, 4, 3, "# \t", PARSE_NORMAL | PARSE_MIN_DIE) == 3) {
2478 key_entry_t *key_entry;
2480 smalluint hash_type;
2482 smalluint key_length;
2485 if ((tokens[1][0] | 0x20) == 'm')
2486 /* supports 'M' and 'md5' formats */
2487 hash_type = HASH_MD5;
2489 if (strncasecmp(tokens[1], "sha", 3) == 0)
2490 /* supports 'sha' and 'sha1' formats */
2491 hash_type = HASH_SHA1;
2493 bb_error_msg_and_die("only MD5 and SHA1 keys supported");
2495 * MD5 The key is 1 to 16 printable characters terminated by an EOL,
2496 * whitespace, or a # (which is the "start of comment" character).
2499 * RMD160 The key is a hex-encoded ASCII string of 40 characters, which
2500 * is truncated as necessary.
2502 key_length = strnlen(tokens[2], sizeof(buffer)+1);
2503 if (key_length >= sizeof(buffer)+1) {
2505 bb_error_msg_and_die("malformed key at line %u", parser->lineno);
2507 if (hash_type == HASH_MD5) {
2509 msg_size = NTP_MSGSIZE_MD5_AUTH;
2510 } else /* it's hash_type == HASH_SHA1 */
2511 if (!(key_length & 1)) {
2513 if (!hex2bin(buffer, tokens[2], key_length))
2516 msg_size = NTP_MSGSIZE_SHA1_AUTH;
2520 key_entry = xzalloc(sizeof(*key_entry) + key_length);
2521 key_entry->type = hash_type;
2522 key_entry->msg_size = msg_size;
2523 key_entry->key_length = key_length;
2524 memcpy(key_entry->key, key, key_length);
2525 key_entry->id = xatou_range(tokens[0], 1, MAX_KEY_NUMBER);
2526 llist_add_to(&key_entries, key_entry);
2528 config_close(parser);
2532 #if ENABLE_FEATURE_NTP_AUTH
2534 char *peer = llist_pop(&peers);
2535 key_entry_t *key_entry = NULL;
2536 if (strncmp(peer, "keyno:", 6) == 0) {
2540 end = strchr(peer, ':');
2541 if (!end) bb_show_usage();
2543 key_id = xatou_range(peer, 1, MAX_KEY_NUMBER);
2545 key_entry = find_key_entry(key_entries, key_id);
2548 add_peers(peer, key_entry);
2552 add_peers(llist_pop(&peers), NULL);
2555 #if ENABLE_FEATURE_NTPD_CONF
2558 char *token[3 + 2*ENABLE_FEATURE_NTP_AUTH];
2560 parser = config_open("/etc/ntp.conf");
2561 while (config_read(parser, token, 3 + 2*ENABLE_FEATURE_NTP_AUTH, 1, "# \t", PARSE_NORMAL)) {
2562 if (strcmp(token[0], "server") == 0 && token[1]) {
2563 # if ENABLE_FEATURE_NTP_AUTH
2564 key_entry_t *key_entry = NULL;
2565 if (token[2] && token[3] && strcmp(token[2], "key") == 0) {
2566 unsigned key_id = xatou_range(token[3], 1, MAX_KEY_NUMBER);
2567 key_entry = find_key_entry(key_entries, key_id);
2569 add_peers(token[1], key_entry);
2571 add_peers(token[1], NULL);
2575 bb_error_msg("skipping %s:%u: unimplemented command '%s'",
2576 "/etc/ntp.conf", parser->lineno, token[0]
2579 config_close(parser);
2582 if (G.peer_cnt == 0) {
2583 if (!(opts & OPT_l))
2585 /* -l but no peers: "stratum 1 server" mode */
2589 if (!(opts & OPT_n)) /* only if backgrounded: */
2590 write_pidfile_std_path_and_ext("ntpd");
2592 /* If network is up, syncronization occurs in ~10 seconds.
2593 * We give "ntpd -q" 10 seconds to get first reply,
2594 * then another 50 seconds to finish syncing.
2596 * I tested ntpd 4.2.6p1 and apparently it never exits
2597 * (will try forever), but it does not feel right.
2598 * The goal of -q is to act like ntpdate: set time
2599 * after a reasonably small period of polling, or fail.
2602 option_mask32 |= OPT_qq;
2617 //TODO: free unused elements of key_entries?
2620 int ntpd_main(int argc UNUSED_PARAM, char **argv) MAIN_EXTERNALLY_VISIBLE;
2621 int ntpd_main(int argc UNUSED_PARAM, char **argv)
2629 memset(&G, 0, sizeof(G));
2630 SET_PTR_TO_GLOBALS(&G);
2634 /* If ENABLE_FEATURE_NTPD_SERVER, + 1 for listen_fd: */
2635 cnt = G.peer_cnt + ENABLE_FEATURE_NTPD_SERVER;
2636 idx2peer = xzalloc(sizeof(idx2peer[0]) * cnt);
2637 pfd = xzalloc(sizeof(pfd[0]) * cnt);
2639 /* Countdown: we never sync before we sent INITIAL_SAMPLES+1
2640 * packets to each peer.
2641 * NB: if some peer is not responding, we may end up sending
2642 * fewer packets to it and more to other peers.
2643 * NB2: sync usually happens using INITIAL_SAMPLES packets,
2644 * since last reply does not come back instantaneously.
2646 cnt = G.peer_cnt * (INITIAL_SAMPLES + 1);
2648 while (!bb_got_signal) {
2654 /* Nothing between here and poll() blocks for any significant time */
2656 nextaction = G.last_script_run + (11*60);
2657 if (nextaction < G.cur_time + 1)
2658 nextaction = G.cur_time + 1;
2661 #if ENABLE_FEATURE_NTPD_SERVER
2662 if (G_listen_fd != -1) {
2663 pfd[0].fd = G_listen_fd;
2664 pfd[0].events = POLLIN;
2668 /* Pass over peer list, send requests, time out on receives */
2669 for (item = G.ntp_peers; item != NULL; item = item->link) {
2670 peer_t *p = (peer_t *) item->data;
2672 if (p->next_action_time <= G.cur_time) {
2673 if (p->p_fd == -1) {
2674 /* Time to send new req */
2676 VERB4 bb_error_msg("disabling burst mode");
2677 G.polladj_count = 0;
2678 G.poll_exp = MINPOLL;
2680 send_query_to_peer(p);
2682 /* Timed out waiting for reply */
2685 /* If poll interval is small, increase it */
2686 if (G.poll_exp < BIGPOLL)
2687 adjust_poll(MINPOLL);
2688 timeout = poll_interval(NOREPLY_INTERVAL);
2689 bb_error_msg("timed out waiting for %s, reach 0x%02x, next query in %us",
2690 p->p_dotted, p->reachable_bits, timeout);
2692 /* What if don't see it because it changed its IP? */
2693 if (p->reachable_bits == 0)
2694 resolve_peer_hostname(p);
2696 set_next(p, timeout);
2700 if (p->next_action_time < nextaction)
2701 nextaction = p->next_action_time;
2704 /* Wait for reply from this peer */
2705 pfd[i].fd = p->p_fd;
2706 pfd[i].events = POLLIN;
2712 timeout = nextaction - G.cur_time;
2715 timeout++; /* (nextaction - G.cur_time) rounds down, compensating */
2717 /* Here we may block */
2719 if (i > (ENABLE_FEATURE_NTPD_SERVER && G_listen_fd != -1)) {
2720 /* We wait for at least one reply.
2721 * Poll for it, without wasting time for message.
2722 * Since replies often come under 1 second, this also
2723 * reduces clutter in logs.
2725 nfds = poll(pfd, i, 1000);
2731 bb_error_msg("poll:%us sockets:%u interval:%us", timeout, i, 1 << G.poll_exp);
2733 nfds = poll(pfd, i, timeout * 1000);
2735 gettime1900d(); /* sets G.cur_time */
2741 break; /* poll was interrupted by a signal */
2743 if (G.cur_time - G.last_script_run > 11*60) {
2744 /* Useful for updating battery-backed RTC and such */
2745 run_script("periodic", G.last_update_offset);
2746 gettime1900d(); /* sets G.cur_time */
2749 /* Resolve peer names to IPs, if not resolved yet.
2750 * We do it only when poll timed out:
2751 * this way, we almost never overlap DNS resolution with
2752 * "request-reply" packet round trip.
2756 for (item = G.ntp_peers; item != NULL; item = item->link) {
2757 peer_t *p = (peer_t *) item->data;
2758 if (p->next_action_time <= ct && !p->p_lsa) {
2759 /* This can take up to ~10 sec per each DNS query */
2760 dns_error |= (!resolve_peer_hostname(p));
2765 /* Set next time for those which are still not resolved */
2766 gettime1900d(); /* sets G.cur_time (needed for set_next()) */
2767 for (item = G.ntp_peers; item != NULL; item = item->link) {
2768 peer_t *p = (peer_t *) item->data;
2769 if (p->next_action_time <= ct && !p->p_lsa) {
2770 set_next(p, HOSTNAME_INTERVAL * p->dns_errors);
2776 /* Process any received packets */
2778 #if ENABLE_FEATURE_NTPD_SERVER
2779 if (G.listen_fd != -1) {
2780 if (pfd[0].revents /* & (POLLIN|POLLERR)*/) {
2782 recv_and_process_client_pkt(/*G.listen_fd*/);
2783 gettime1900d(); /* sets G.cur_time */
2788 for (; nfds != 0 && j < i; j++) {
2789 if (pfd[j].revents /* & (POLLIN|POLLERR)*/) {
2791 * At init, alarm was set to 10 sec.
2792 * Now we did get a reply.
2793 * Increase timeout to 50 seconds to finish syncing.
2795 if (option_mask32 & OPT_qq) {
2796 option_mask32 &= ~OPT_qq;
2800 recv_and_process_peer_pkt(idx2peer[j]);
2801 gettime1900d(); /* sets G.cur_time */
2806 if (G.ntp_peers && G.stratum != MAXSTRAT) {
2807 for (item = G.ntp_peers; item != NULL; item = item->link) {
2808 peer_t *p = (peer_t *) item->data;
2809 if (p->reachable_bits)
2810 goto have_reachable_peer;
2812 /* No peer responded for last 8 packets, panic */
2813 clamp_pollexp_and_set_MAXSTRAT();
2814 run_script("unsync", 0.0);
2815 have_reachable_peer: ;
2817 } /* while (!bb_got_signal) */
2819 remove_pidfile_std_path_and_ext("ntpd");
2820 kill_myself_with_sig(bb_got_signal);
2828 /*** openntpd-4.6 uses only adjtime, not adjtimex ***/
2830 /*** ntp-4.2.6/ntpd/ntp_loopfilter.c - adjtimex usage ***/
2834 direct_freq(double fp_offset)
2838 * If the kernel is enabled, we need the residual offset to
2839 * calculate the frequency correction.
2841 if (pll_control && kern_enable) {
2842 memset(&ntv, 0, sizeof(ntv));
2845 clock_offset = ntv.offset / 1e9;
2846 #else /* STA_NANO */
2847 clock_offset = ntv.offset / 1e6;
2848 #endif /* STA_NANO */
2849 drift_comp = FREQTOD(ntv.freq);
2851 #endif /* KERNEL_PLL */
2852 set_freq((fp_offset - clock_offset) / (current_time - clock_epoch) + drift_comp);
2858 set_freq(double freq) /* frequency update */
2866 * If the kernel is enabled, update the kernel frequency.
2868 if (pll_control && kern_enable) {
2869 memset(&ntv, 0, sizeof(ntv));
2870 ntv.modes = MOD_FREQUENCY;
2871 ntv.freq = DTOFREQ(drift_comp);
2873 snprintf(tbuf, sizeof(tbuf), "kernel %.3f PPM", drift_comp * 1e6);
2874 report_event(EVNT_FSET, NULL, tbuf);
2876 snprintf(tbuf, sizeof(tbuf), "ntpd %.3f PPM", drift_comp * 1e6);
2877 report_event(EVNT_FSET, NULL, tbuf);
2879 #else /* KERNEL_PLL */
2880 snprintf(tbuf, sizeof(tbuf), "ntpd %.3f PPM", drift_comp * 1e6);
2881 report_event(EVNT_FSET, NULL, tbuf);
2882 #endif /* KERNEL_PLL */
2891 * This code segment works when clock adjustments are made using
2892 * precision time kernel support and the ntp_adjtime() system
2893 * call. This support is available in Solaris 2.6 and later,
2894 * Digital Unix 4.0 and later, FreeBSD, Linux and specially
2895 * modified kernels for HP-UX 9 and Ultrix 4. In the case of the
2896 * DECstation 5000/240 and Alpha AXP, additional kernel
2897 * modifications provide a true microsecond clock and nanosecond
2898 * clock, respectively.
2900 * Important note: The kernel discipline is used only if the
2901 * step threshold is less than 0.5 s, as anything higher can
2902 * lead to overflow problems. This might occur if some misguided
2903 * lad set the step threshold to something ridiculous.
2905 if (pll_control && kern_enable) {
2907 #define MOD_BITS (MOD_OFFSET | MOD_MAXERROR | MOD_ESTERROR | MOD_STATUS | MOD_TIMECONST)
2910 * We initialize the structure for the ntp_adjtime()
2911 * system call. We have to convert everything to
2912 * microseconds or nanoseconds first. Do not update the
2913 * system variables if the ext_enable flag is set. In
2914 * this case, the external clock driver will update the
2915 * variables, which will be read later by the local
2916 * clock driver. Afterwards, remember the time and
2917 * frequency offsets for jitter and stability values and
2918 * to update the frequency file.
2920 memset(&ntv, 0, sizeof(ntv));
2922 ntv.modes = MOD_STATUS;
2925 ntv.modes = MOD_BITS | MOD_NANO;
2926 #else /* STA_NANO */
2927 ntv.modes = MOD_BITS;
2928 #endif /* STA_NANO */
2929 if (clock_offset < 0)
2934 ntv.offset = (int32)(clock_offset * 1e9 + dtemp);
2935 ntv.constant = sys_poll;
2936 #else /* STA_NANO */
2937 ntv.offset = (int32)(clock_offset * 1e6 + dtemp);
2938 ntv.constant = sys_poll - 4;
2939 #endif /* STA_NANO */
2940 ntv.esterror = (u_int32)(clock_jitter * 1e6);
2941 ntv.maxerror = (u_int32)((sys_rootdelay / 2 + sys_rootdisp) * 1e6);
2942 ntv.status = STA_PLL;
2945 * Enable/disable the PPS if requested.
2948 if (!(pll_status & STA_PPSTIME))
2949 report_event(EVNT_KERN,
2950 NULL, "PPS enabled");
2951 ntv.status |= STA_PPSTIME | STA_PPSFREQ;
2953 if (pll_status & STA_PPSTIME)
2954 report_event(EVNT_KERN,
2955 NULL, "PPS disabled");
2956 ntv.status &= ~(STA_PPSTIME | STA_PPSFREQ);
2958 if (sys_leap == LEAP_ADDSECOND)
2959 ntv.status |= STA_INS;
2960 else if (sys_leap == LEAP_DELSECOND)
2961 ntv.status |= STA_DEL;
2965 * Pass the stuff to the kernel. If it squeals, turn off
2966 * the pps. In any case, fetch the kernel offset,
2967 * frequency and jitter.
2969 if (ntp_adjtime(&ntv) == TIME_ERROR) {
2970 if (!(ntv.status & STA_PPSSIGNAL))
2971 report_event(EVNT_KERN, NULL,
2974 pll_status = ntv.status;
2976 clock_offset = ntv.offset / 1e9;
2977 #else /* STA_NANO */
2978 clock_offset = ntv.offset / 1e6;
2979 #endif /* STA_NANO */
2980 clock_frequency = FREQTOD(ntv.freq);
2983 * If the kernel PPS is lit, monitor its performance.
2985 if (ntv.status & STA_PPSTIME) {
2987 clock_jitter = ntv.jitter / 1e9;
2988 #else /* STA_NANO */
2989 clock_jitter = ntv.jitter / 1e6;
2990 #endif /* STA_NANO */
2993 #if defined(STA_NANO) && NTP_API == 4
2995 * If the TAI changes, update the kernel TAI.
2997 if (loop_tai != sys_tai) {
2999 ntv.modes = MOD_TAI;
3000 ntv.constant = sys_tai;
3003 #endif /* STA_NANO */
3005 #endif /* KERNEL_PLL */