path: root/networking/ntpd.c (plain)
blob: 1c1c38f536dc35591008931e6d664bf3e4615ca3

1	/*
2	* NTP client/server, based on OpenNTPD 3.9p1
3	*
4	* Author: Adam Tkac <vonsch@gmail.com>
5	*
6	* Licensed under GPLv2, see file LICENSE in this source tree.
7	*
8	* Parts of OpenNTPD clock syncronization code is replaced by
9	* code which is based on ntp-4.2.6, whuch carries the following
10	* copyright notice:
11	*
12	***********************************************************************
13	* *
14	* Copyright (c) University of Delaware 1992-2009 *
15	* *
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 *
26	* warranty. *
27	* *
28	***********************************************************************
29	*/
30
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"
42	//usage: )
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)"
45
46	#include "libbb.h"
47	#include <math.h>
48	#include <netinet/ip.h> /* For IPTOS_LOWDELAY definition */
49	#include <sys/resource.h> /* setpriority */
50
51	#ifdef __BIONIC__
52	#include <linux/timex.h>
53	extern int adjtimex (struct timex *);
54	#else
55	#include <sys/timex.h>
56	#endif
57	#ifndef IPTOS_LOWDELAY
58	# define IPTOS_LOWDELAY 0x10
59	#endif
60	#ifndef IP_PKTINFO
61	# error "Sorry, your kernel has to support IP_PKTINFO"
62	#endif
63
64
65	/* Verbosity control (max level of -dddd options accepted).
66	* max 6 is very talkative (and bloated). 3 is non-bloated,
67	* production level setting.
68	*/
69	#define MAX_VERBOSE 3
70
71
72	/* High-level description of the algorithm:
73	*
74	* We start running with very small poll_exp, BURSTPOLL,
75	* in order to quickly accumulate INITIAL_SAMPLES datapoints
76	* for each peer. Then, time is stepped if the offset is larger
77	* than STEP_THRESHOLD, otherwise it isn't; anyway, we enlarge
78	* poll_exp to MINPOLL and enter frequency measurement step:
79	* we collect new datapoints but ignore them for WATCH_THRESHOLD
80	* seconds. After WATCH_THRESHOLD seconds we look at accumulated
81	* offset and estimate frequency drift.
82	*
83	* (frequency measurement step seems to not be strictly needed,
84	* it is conditionally disabled with USING_INITIAL_FREQ_ESTIMATION
85	* define set to 0)
86	*
87	* After this, we enter "steady state": we collect a datapoint,
88	* we select the best peer, if this datapoint is not a new one
89	* (IOW: if this datapoint isn't for selected peer), sleep
90	* and collect another one; otherwise, use its offset to update
91	* frequency drift, if offset is somewhat large, reduce poll_exp,
92	* otherwise increase poll_exp.
93	*
94	* If offset is larger than STEP_THRESHOLD, which shouldn't normally
95	* happen, we assume that something "bad" happened (computer
96	* was hibernated, someone set totally wrong date, etc),
97	* then the time is stepped, all datapoints are discarded,
98	* and we go back to steady state.
99	*
100	* Made some changes to speed up re-syncing after our clock goes bad
101	* (tested with suspending my laptop):
102	* - if largish offset (>= STEP_THRESHOLD * 8 == 1 sec) is seen
103	* from a peer, schedule next query for this peer soon
104	* without drastically lowering poll interval for everybody.
105	* This makes us collect enough data for step much faster:
106	* e.g. at poll = 10 (1024 secs), step was done within 5 minutes
107	* after first reply which indicated that our clock is 14 seconds off.
108	* - on step, do not discard d_dispersion data of the existing datapoints,
109	* do not clear reachable_bits. This prevents discarding first ~8
110	* datapoints after the step.
111	*/
112
113	#define RETRY_INTERVAL 5 /* on error, retry in N secs */
114	#define RESPONSE_INTERVAL 15 /* wait for reply up to N secs */
115	#define INITIAL_SAMPLES 4 /* how many samples do we want for init */
116	#define BAD_DELAY_GROWTH 4 /* drop packet if its delay grew by more than this */
117
118	/* Clock discipline parameters and constants */
119
120	/* Step threshold (sec). std ntpd uses 0.128.
121	* Using exact power of 2 (1/8) results in smaller code */
122	#define STEP_THRESHOLD 0.125
123	#define WATCH_THRESHOLD 128 /* stepout threshold (sec). std ntpd uses 900 (11 mins (!)) */
124	/* NB: set WATCH_THRESHOLD to ~60 when debugging to save time) */
125	//UNUSED: #define PANIC_THRESHOLD 1000 /* panic threshold (sec) */
126
127	#define FREQ_TOLERANCE 0.000015 /* frequency tolerance (15 PPM) */
128	#define BURSTPOLL 0 /* initial poll */
129	#define MINPOLL 5 /* minimum poll interval. std ntpd uses 6 (6: 64 sec) */
130	/* If we got largish offset from a peer, cap next query interval
131	* for this peer by this many seconds:
132	*/
133	#define BIGOFF_INTERVAL (1 << 6)
134	/* If offset > discipline_jitter * POLLADJ_GATE, and poll interval is >= 2^BIGPOLL,
135	* then it is decreased _at once_. (If < 2^BIGPOLL, it will be decreased _eventually_).
136	*/
137	#define BIGPOLL 10 /* 2^10 sec ~= 17 min */
138	#define MAXPOLL 12 /* maximum poll interval (12: 1.1h, 17: 36.4h). std ntpd uses 17 */
139	/* Actively lower poll when we see such big offsets.
140	* With STEP_THRESHOLD = 0.125, it means we try to sync more aggressively
141	* if offset increases over ~0.04 sec */
142	#define POLLDOWN_OFFSET (STEP_THRESHOLD / 3)
143	#define MINDISP 0.01 /* minimum dispersion (sec) */
144	#define MAXDISP 16 /* maximum dispersion (sec) */
145	#define MAXSTRAT 16 /* maximum stratum (infinity metric) */
146	#define MAXDIST 1 /* distance threshold (sec) */
147	#define MIN_SELECTED 1 /* minimum intersection survivors */
148	#define MIN_CLUSTERED 3 /* minimum cluster survivors */
149
150	#define MAXDRIFT 0.000500 /* frequency drift we can correct (500 PPM) */
151
152	/* Poll-adjust threshold.
153	* When we see that offset is small enough compared to discipline jitter,
154	* we grow a counter: += MINPOLL. When counter goes over POLLADJ_LIMIT,
155	* we poll_exp++. If offset isn't small, counter -= poll_exp*2,
156	* and when it goes below -POLLADJ_LIMIT, we poll_exp--.
157	* (Bumped from 30 to 40 since otherwise I often see poll_exp going *2* steps down)
158	*/
159	#define POLLADJ_LIMIT 40
160	/* If offset < discipline_jitter * POLLADJ_GATE, then we decide to increase
161	* poll interval (we think we can't improve timekeeping
162	* by staying at smaller poll).
163	*/
164	#define POLLADJ_GATE 4
165	#define TIMECONST_HACK_GATE 2
166	/* Compromise Allan intercept (sec). doc uses 1500, std ntpd uses 512 */
167	#define ALLAN 512
168	/* PLL loop gain */
169	#define PLL 65536
170	/* FLL loop gain [why it depends on MAXPOLL??] */
171	#define FLL (MAXPOLL + 1)
172	/* Parameter averaging constant */
173	#define AVG 4
174
175
176	enum {
177	NTP_VERSION = 4,
178	NTP_MAXSTRATUM = 15,
179
180	NTP_DIGESTSIZE = 16,
181	NTP_MSGSIZE_NOAUTH = 48,
182	NTP_MSGSIZE = (NTP_MSGSIZE_NOAUTH + 4 + NTP_DIGESTSIZE),
183
184	/* Status Masks */
185	MODE_MASK = (7 << 0),
186	VERSION_MASK = (7 << 3),
187	VERSION_SHIFT = 3,
188	LI_MASK = (3 << 6),
189
190	/* Leap Second Codes (high order two bits of m_status) */
191	LI_NOWARNING = (0 << 6), /* no warning */
192	LI_PLUSSEC = (1 << 6), /* add a second (61 seconds) */
193	LI_MINUSSEC = (2 << 6), /* minus a second (59 seconds) */
194	LI_ALARM = (3 << 6), /* alarm condition */
195
196	/* Mode values */
197	MODE_RES0 = 0, /* reserved */
198	MODE_SYM_ACT = 1, /* symmetric active */
199	MODE_SYM_PAS = 2, /* symmetric passive */
200	MODE_CLIENT = 3, /* client */
201	MODE_SERVER = 4, /* server */
202	MODE_BROADCAST = 5, /* broadcast */
203	MODE_RES1 = 6, /* reserved for NTP control message */
204	MODE_RES2 = 7, /* reserved for private use */
205	};
206
207	//TODO: better base selection
208	#define OFFSET_1900_1970 2208988800UL /* 1970 - 1900 in seconds */
209
210	#define NUM_DATAPOINTS 8
211
212	typedef struct {
213	uint32_t int_partl;
214	uint32_t fractionl;
215	} l_fixedpt_t;
216
217	typedef struct {
218	uint16_t int_parts;
219	uint16_t fractions;
220	} s_fixedpt_t;
221
222	typedef struct {
223	uint8_t m_status; /* status of local clock and leap info */
224	uint8_t m_stratum;
225	uint8_t m_ppoll; /* poll value */
226	int8_t m_precision_exp;
227	s_fixedpt_t m_rootdelay;
228	s_fixedpt_t m_rootdisp;
229	uint32_t m_refid;
230	l_fixedpt_t m_reftime;
231	l_fixedpt_t m_orgtime;
232	l_fixedpt_t m_rectime;
233	l_fixedpt_t m_xmttime;
234	uint32_t m_keyid;
235	uint8_t m_digest[NTP_DIGESTSIZE];
236	} msg_t;
237
238	typedef struct {
239	double d_offset;
240	double d_recv_time;
241	double d_dispersion;
242	} datapoint_t;
243
244	typedef struct {
245	len_and_sockaddr *p_lsa;
246	char *p_dotted;
247	int p_fd;
248	int datapoint_idx;
249	uint32_t lastpkt_refid;
250	uint8_t lastpkt_status;
251	uint8_t lastpkt_stratum;
252	uint8_t reachable_bits;
253	/* when to send new query (if p_fd == -1)
254	* or when receive times out (if p_fd >= 0): */
255	double next_action_time;
256	double p_xmttime;
257	double lastpkt_recv_time;
258	double lastpkt_delay;
259	double lastpkt_rootdelay;
260	double lastpkt_rootdisp;
261	/* produced by filter algorithm: */
262	double filter_offset;
263	double filter_dispersion;
264	double filter_jitter;
265	datapoint_t filter_datapoint[NUM_DATAPOINTS];
266	/* last sent packet: */
267	msg_t p_xmt_msg;
268	} peer_t;
269
270
271	#define USING_KERNEL_PLL_LOOP 1
272	#define USING_INITIAL_FREQ_ESTIMATION 0
273
274	enum {
275	OPT_n = (1 << 0),
276	OPT_q = (1 << 1),
277	OPT_N = (1 << 2),
278	OPT_x = (1 << 3),
279	/* Insert new options above this line. */
280	/* Non-compat options: */
281	OPT_w = (1 << 4),
282	OPT_p = (1 << 5),
283	OPT_S = (1 << 6),
284	OPT_l = (1 << 7) * ENABLE_FEATURE_NTPD_SERVER,
285	/* We hijack some bits for other purposes */
286	OPT_qq = (1 << 31),
287	};
288
289	struct globals {
290	double cur_time;
291	/* total round trip delay to currently selected reference clock */
292	double rootdelay;
293	/* reference timestamp: time when the system clock was last set or corrected */
294	double reftime;
295	/* total dispersion to currently selected reference clock */
296	double rootdisp;
297
298	double last_script_run;
299	char *script_name;
300	llist_t *ntp_peers;
301	#if ENABLE_FEATURE_NTPD_SERVER
302	int listen_fd;
303	# define G_listen_fd (G.listen_fd)
304	#else
305	# define G_listen_fd (-1)
306	#endif
307	unsigned verbose;
308	unsigned peer_cnt;
309	/* refid: 32-bit code identifying the particular server or reference clock
310	* in stratum 0 packets this is a four-character ASCII string,
311	* called the kiss code, used for debugging and monitoring
312	* in stratum 1 packets this is a four-character ASCII string
313	* assigned to the reference clock by IANA. Example: "GPS "
314	* in stratum 2+ packets, it's IPv4 address or 4 first bytes
315	* of MD5 hash of IPv6
316	*/
317	uint32_t refid;
318	uint8_t ntp_status;
319	/* precision is defined as the larger of the resolution and time to
320	* read the clock, in log2 units. For instance, the precision of a
321	* mains-frequency clock incrementing at 60 Hz is 16 ms, even when the
322	* system clock hardware representation is to the nanosecond.
323	*
324	* Delays, jitters of various kinds are clamped down to precision.
325	*
326	* If precision_sec is too large, discipline_jitter gets clamped to it
327	* and if offset is smaller than discipline_jitter * POLLADJ_GATE, poll
328	* interval grows even though we really can benefit from staying at
329	* smaller one, collecting non-lagged datapoits and correcting offset.
330	* (Lagged datapoits exist when poll_exp is large but we still have
331	* systematic offset error - the time distance between datapoints
332	* is significant and older datapoints have smaller offsets.
333	* This makes our offset estimation a bit smaller than reality)
334	* Due to this effect, setting G_precision_sec close to
335	* STEP_THRESHOLD isn't such a good idea - offsets may grow
336	* too big and we will step. I observed it with -6.
337	*
338	* OTOH, setting precision_sec far too small would result in futile
339	* attempts to syncronize to an unachievable precision.
340	*
341	* -6 is 1/64 sec, -7 is 1/128 sec and so on.
342	* -8 is 1/256 ~= 0.003906 (worked well for me --vda)
343	* -9 is 1/512 ~= 0.001953 (let's try this for some time)
344	*/
345	#define G_precision_exp -9
346	/*
347	* G_precision_exp is used only for construction outgoing packets.
348	* It's ok to set G_precision_sec to a slightly different value
349	* (One which is "nicer looking" in logs).
350	* Exact value would be (1.0 / (1 << (- G_precision_exp))):
351	*/
352	#define G_precision_sec 0.002
353	uint8_t stratum;
354	/* Bool. After set to 1, never goes back to 0: */
355	smallint initial_poll_complete;
356
357	#define STATE_NSET 0 /* initial state, "nothing is set" */
358	//#define STATE_FSET 1 /* frequency set from file */
359	//#define STATE_SPIK 2 /* spike detected */
360	//#define STATE_FREQ 3 /* initial frequency */
361	#define STATE_SYNC 4 /* clock synchronized (normal operation) */
362	uint8_t discipline_state; // doc calls it c.state
363	uint8_t poll_exp; // s.poll
364	int polladj_count; // c.count
365	long kernel_freq_drift;
366	peer_t *last_update_peer;
367	double last_update_offset; // c.last
368	double last_update_recv_time; // s.t
369	double discipline_jitter; // c.jitter
370	/* Since we only compare it with ints, can simplify code
371	* by not making this variable floating point:
372	*/
373	unsigned offset_to_jitter_ratio;
374	//double cluster_offset; // s.offset
375	//double cluster_jitter; // s.jitter
376	#if !USING_KERNEL_PLL_LOOP
377	double discipline_freq_drift; // c.freq
378	/* Maybe conditionally calculate wander? it's used only for logging */
379	double discipline_wander; // c.wander
380	#endif
381	};
382	#define G (*ptr_to_globals)
383
384	static const int const_IPTOS_LOWDELAY = IPTOS_LOWDELAY;
385
386
387	#define VERB1 if (MAX_VERBOSE && G.verbose)
388	#define VERB2 if (MAX_VERBOSE >= 2 && G.verbose >= 2)
389	#define VERB3 if (MAX_VERBOSE >= 3 && G.verbose >= 3)
390	#define VERB4 if (MAX_VERBOSE >= 4 && G.verbose >= 4)
391	#define VERB5 if (MAX_VERBOSE >= 5 && G.verbose >= 5)
392	#define VERB6 if (MAX_VERBOSE >= 6 && G.verbose >= 6)
393
394
395	static double LOG2D(int a)
396	{
397	if (a < 0)
398	return 1.0 / (1UL << -a);
399	return 1UL << a;
400	}
401	static ALWAYS_INLINE double SQUARE(double x)
402	{
403	return x * x;
404	}
405	static ALWAYS_INLINE double MAXD(double a, double b)
406	{
407	if (a > b)
408	return a;
409	return b;
410	}
411	static ALWAYS_INLINE double MIND(double a, double b)
412	{
413	if (a < b)
414	return a;
415	return b;
416	}
417	static NOINLINE double my_SQRT(double X)
418	{
419	union {
420	float f;
421	int32_t i;
422	} v;
423	double invsqrt;
424	double Xhalf = X * 0.5;
425
426	/* Fast and good approximation to 1/sqrt(X), black magic */
427	v.f = X;
428	/*v.i = 0x5f3759df - (v.i >> 1);*/
429	v.i = 0x5f375a86 - (v.i >> 1); /* - this constant is slightly better */
430	invsqrt = v.f; /* better than 0.2% accuracy */
431
432	/* Refining it using Newton's method: x1 = x0 - f(x0)/f'(x0)
433	* f(x) = 1/(x*x) - X (f==0 when x = 1/sqrt(X))
434	* f'(x) = -2/(x*x*x)
435	* f(x)/f'(x) = (X - 1/(x*x)) / (2/(x*x*x)) = X*x*x*x/2 - x/2
436	* x1 = x0 - (X*x0*x0*x0/2 - x0/2) = 1.5*x0 - X*x0*x0*x0/2 = x0*(1.5 - (X/2)*x0*x0)
437	*/
438	invsqrt = invsqrt * (1.5 - Xhalf * invsqrt * invsqrt); /* ~0.05% accuracy */
439	/* invsqrt = invsqrt * (1.5 - Xhalf * invsqrt * invsqrt); 2nd iter: ~0.0001% accuracy */
440	/* With 4 iterations, more than half results will be exact,
441	* at 6th iterations result stabilizes with about 72% results exact.
442	* We are well satisfied with 0.05% accuracy.
443	*/
444
445	return X * invsqrt; /* X * 1/sqrt(X) ~= sqrt(X) */
446	}
447	static ALWAYS_INLINE double SQRT(double X)
448	{
449	/* If this arch doesn't use IEEE 754 floats, fall back to using libm */
450	if (sizeof(float) != 4)
451	return sqrt(X);
452
453	/* This avoids needing libm, saves about 0.5k on x86-32 */
454	return my_SQRT(X);
455	}
456
457	static double
458	gettime1900d(void)
459	{
460	struct timeval tv;
461	gettimeofday(&tv, NULL); /* never fails */
462	G.cur_time = tv.tv_sec + (1.0e-6 * tv.tv_usec) + OFFSET_1900_1970;
463	return G.cur_time;
464	}
465
466	static void
467	d_to_tv(double d, struct timeval *tv)
468	{
469	tv->tv_sec = (long)d;
470	tv->tv_usec = (d - tv->tv_sec) * 1000000;
471	}
472
473	static double
474	lfp_to_d(l_fixedpt_t lfp)
475	{
476	double ret;
477	lfp.int_partl = ntohl(lfp.int_partl);
478	lfp.fractionl = ntohl(lfp.fractionl);
479	ret = (double)lfp.int_partl + ((double)lfp.fractionl / UINT_MAX);
480	return ret;
481	}
482	static double
483	sfp_to_d(s_fixedpt_t sfp)
484	{
485	double ret;
486	sfp.int_parts = ntohs(sfp.int_parts);
487	sfp.fractions = ntohs(sfp.fractions);
488	ret = (double)sfp.int_parts + ((double)sfp.fractions / USHRT_MAX);
489	return ret;
490	}
491	#if ENABLE_FEATURE_NTPD_SERVER
492	static l_fixedpt_t
493	d_to_lfp(double d)
494	{
495	l_fixedpt_t lfp;
496	lfp.int_partl = (uint32_t)d;
497	lfp.fractionl = (uint32_t)((d - lfp.int_partl) * UINT_MAX);
498	lfp.int_partl = htonl(lfp.int_partl);
499	lfp.fractionl = htonl(lfp.fractionl);
500	return lfp;
501	}
502	static s_fixedpt_t
503	d_to_sfp(double d)
504	{
505	s_fixedpt_t sfp;
506	sfp.int_parts = (uint16_t)d;
507	sfp.fractions = (uint16_t)((d - sfp.int_parts) * USHRT_MAX);
508	sfp.int_parts = htons(sfp.int_parts);
509	sfp.fractions = htons(sfp.fractions);
510	return sfp;
511	}
512	#endif
513
514	static double
515	dispersion(const datapoint_t *dp)
516	{
517	return dp->d_dispersion + FREQ_TOLERANCE * (G.cur_time - dp->d_recv_time);
518	}
519
520	static double
521	root_distance(peer_t *p)
522	{
523	/* The root synchronization distance is the maximum error due to
524	* all causes of the local clock relative to the primary server.
525	* It is defined as half the total delay plus total dispersion
526	* plus peer jitter.
527	*/
528	return MAXD(MINDISP, p->lastpkt_rootdelay + p->lastpkt_delay) / 2
529	+ p->lastpkt_rootdisp
530	+ p->filter_dispersion
531	+ FREQ_TOLERANCE * (G.cur_time - p->lastpkt_recv_time)
532	+ p->filter_jitter;
533	}
534
535	static void
536	set_next(peer_t *p, unsigned t)
537	{
538	p->next_action_time = G.cur_time + t;
539	}
540
541	/*
542	* Peer clock filter and its helpers
543	*/
544	static void
545	filter_datapoints(peer_t *p)
546	{
547	int i, idx;
548	double sum, wavg;
549	datapoint_t *fdp;
550
551	#if 0
552	/* Simulations have shown that use of *averaged* offset for p->filter_offset
553	* is in fact worse than simply using last received one: with large poll intervals
554	* (>= 2048) averaging code uses offset values which are outdated by hours,
555	* and time/frequency correction goes totally wrong when fed essentially bogus offsets.
556	*/
557	int got_newest;
558	double minoff, maxoff, w;
559	double x = x; /* for compiler */
560	double oldest_off = oldest_off;
561	double oldest_age = oldest_age;
562	double newest_off = newest_off;
563	double newest_age = newest_age;
564
565	fdp = p->filter_datapoint;
566
567	minoff = maxoff = fdp[0].d_offset;
568	for (i = 1; i < NUM_DATAPOINTS; i++) {
569	if (minoff > fdp[i].d_offset)
570	minoff = fdp[i].d_offset;
571	if (maxoff < fdp[i].d_offset)
572	maxoff = fdp[i].d_offset;
573	}
574
575	idx = p->datapoint_idx; /* most recent datapoint's index */
576	/* Average offset:
577	* Drop two outliers and take weighted average of the rest:
578	* most_recent/2 + older1/4 + older2/8 ... + older5/32 + older6/32
579	* we use older6/32, not older6/64 since sum of weights should be 1:
580	* 1/2 + 1/4 + 1/8 + 1/16 + 1/32 + 1/32 = 1
581	*/
582	wavg = 0;
583	w = 0.5;
584	/* n-1
585	* --- dispersion(i)
586	* filter_dispersion = \ -------------
587	* / (i+1)
588	* --- 2
589	* i=0
590	*/
591	got_newest = 0;
592	sum = 0;
593	for (i = 0; i < NUM_DATAPOINTS; i++) {
594	VERB5 {
595	bb_error_msg("datapoint[%d]: off:%f disp:%f(%f) age:%f%s",
596	i,
597	fdp[idx].d_offset,
598	fdp[idx].d_dispersion, dispersion(&fdp[idx]),
599	G.cur_time - fdp[idx].d_recv_time,
600	(minoff == fdp[idx].d_offset || maxoff == fdp[idx].d_offset)
601	? " (outlier by offset)" : ""
602	);
603	}
604
605	sum += dispersion(&fdp[idx]) / (2 << i);
606
607	if (minoff == fdp[idx].d_offset) {
608	minoff -= 1; /* so that we don't match it ever again */
609	} else
610	if (maxoff == fdp[idx].d_offset) {
611	maxoff += 1;
612	} else {
613	oldest_off = fdp[idx].d_offset;
614	oldest_age = G.cur_time - fdp[idx].d_recv_time;
615	if (!got_newest) {
616	got_newest = 1;
617	newest_off = oldest_off;
618	newest_age = oldest_age;
619	}
620	x = oldest_off * w;
621	wavg += x;
622	w /= 2;
623	}
624
625	idx = (idx - 1) & (NUM_DATAPOINTS - 1);
626	}
627	p->filter_dispersion = sum;
628	wavg += x; /* add another older6/64 to form older6/32 */
629	/* Fix systematic underestimation with large poll intervals.
630	* Imagine that we still have a bit of uncorrected drift,
631	* and poll interval is big (say, 100 sec). Offsets form a progression:
632	* 0.0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 - 0.7 is most recent.
633	* The algorithm above drops 0.0 and 0.7 as outliers,
634	* and then we have this estimation, ~25% off from 0.7:
635	* 0.1/32 + 0.2/32 + 0.3/16 + 0.4/8 + 0.5/4 + 0.6/2 = 0.503125
636	*/
637	x = oldest_age - newest_age;
638	if (x != 0) {
639	x = newest_age / x; /* in above example, 100 / (600 - 100) */
640	if (x < 1) { /* paranoia check */
641	x = (newest_off - oldest_off) * x; /* 0.5 * 100/500 = 0.1 */
642	wavg += x;
643	}
644	}
645	p->filter_offset = wavg;
646
647	#else
648
649	fdp = p->filter_datapoint;
650	idx = p->datapoint_idx; /* most recent datapoint's index */
651
652	/* filter_offset: simply use the most recent value */
653	p->filter_offset = fdp[idx].d_offset;
654
655	/* n-1
656	* --- dispersion(i)
657	* filter_dispersion = \ -------------
658	* / (i+1)
659	* --- 2
660	* i=0
661	*/
662	wavg = 0;
663	sum = 0;
664	for (i = 0; i < NUM_DATAPOINTS; i++) {
665	sum += dispersion(&fdp[idx]) / (2 << i);
666	wavg += fdp[idx].d_offset;
667	idx = (idx - 1) & (NUM_DATAPOINTS - 1);
668	}
669	wavg /= NUM_DATAPOINTS;
670	p->filter_dispersion = sum;
671	#endif
672
673	/* +----- -----+ ^ 1/2
674	* | n-1 |
675	* | --- |
676	* | 1 \ 2 |
677	* filter_jitter = | --- * / (avg-offset_j) |
678	* | n --- |
679	* | j=0 |
680	* +----- -----+
681	* where n is the number of valid datapoints in the filter (n > 1);
682	* if filter_jitter < precision then filter_jitter = precision
683	*/
684	sum = 0;
685	for (i = 0; i < NUM_DATAPOINTS; i++) {
686	sum += SQUARE(wavg - fdp[i].d_offset);
687	}
688	sum = SQRT(sum / NUM_DATAPOINTS);
689	p->filter_jitter = sum > G_precision_sec ? sum : G_precision_sec;
690
691	VERB4 bb_error_msg("filter offset:%+f disp:%f jitter:%f",
692	p->filter_offset,
693	p->filter_dispersion,
694	p->filter_jitter);
695	}
696
697	static void
698	reset_peer_stats(peer_t *p, double offset)
699	{
700	int i;
701	bool small_ofs = fabs(offset) < 16 * STEP_THRESHOLD;
702
703	/* Used to set p->filter_datapoint[i].d_dispersion = MAXDISP
704	* and clear reachable bits, but this proved to be too agressive:
705	* after step (tested with suspinding laptop for ~30 secs),
706	* this caused all previous data to be considered invalid,
707	* making us needing to collect full ~8 datapoins per peer
708	* after step in order to start trusting them.
709	* In turn, this was making poll interval decrease even after
710	* step was done. (Poll interval decreases already before step
711	* in this scenario, because we see large offsets and end up with
712	* no good peer to select).
713	*/
714
715	for (i = 0; i < NUM_DATAPOINTS; i++) {
716	if (small_ofs) {
717	p->filter_datapoint[i].d_recv_time += offset;
718	if (p->filter_datapoint[i].d_offset != 0) {
719	p->filter_datapoint[i].d_offset -= offset;
720	//bb_error_msg("p->filter_datapoint[%d].d_offset %f -> %f",
721	// i,
722	// p->filter_datapoint[i].d_offset + offset,
723	// p->filter_datapoint[i].d_offset);
724	}
725	} else {
726	p->filter_datapoint[i].d_recv_time = G.cur_time;
727	p->filter_datapoint[i].d_offset = 0;
728	/*p->filter_datapoint[i].d_dispersion = MAXDISP;*/
729	}
730	}
731	if (small_ofs) {
732	p->lastpkt_recv_time += offset;
733	} else {
734	/*p->reachable_bits = 0;*/
735	p->lastpkt_recv_time = G.cur_time;
736	}
737	filter_datapoints(p); /* recalc p->filter_xxx */
738	VERB6 bb_error_msg("%s->lastpkt_recv_time=%f", p->p_dotted, p->lastpkt_recv_time);
739	}
740
741	static void
742	add_peers(char *s)
743	{
744	peer_t *p;
745
746	p = xzalloc(sizeof(*p));
747	p->p_lsa = xhost2sockaddr(s, 123);
748	p->p_dotted = xmalloc_sockaddr2dotted_noport(&p->p_lsa->u.sa);
749	p->p_fd = -1;
750	p->p_xmt_msg.m_status = MODE_CLIENT | (NTP_VERSION << 3);
751	p->next_action_time = G.cur_time; /* = set_next(p, 0); */
752	reset_peer_stats(p, 16 * STEP_THRESHOLD);
753
754	llist_add_to(&G.ntp_peers, p);
755	G.peer_cnt++;
756	}
757
758	static int
759	do_sendto(int fd,
760	const struct sockaddr *from, const struct sockaddr *to, socklen_t addrlen,
761	msg_t *msg, ssize_t len)
762	{
763	ssize_t ret;
764
765	errno = 0;
766	if (!from) {
767	ret = sendto(fd, msg, len, MSG_DONTWAIT, to, addrlen);
768	} else {
769	ret = send_to_from(fd, msg, len, MSG_DONTWAIT, to, from, addrlen);
770	}
771	if (ret != len) {
772	bb_perror_msg("send failed");
773	return -1;
774	}
775	return 0;
776	}
777
778	static void
779	send_query_to_peer(peer_t *p)
780	{
781	/* Why do we need to bind()?
782	* See what happens when we don't bind:
783	*
784	* socket(PF_INET, SOCK_DGRAM, IPPROTO_IP) = 3
785	* setsockopt(3, SOL_IP, IP_TOS, [16], 4) = 0
786	* gettimeofday({1259071266, 327885}, NULL) = 0
787	* sendto(3, "xxx", 48, MSG_DONTWAIT, {sa_family=AF_INET, sin_port=htons(123), sin_addr=inet_addr("10.34.32.125")}, 16) = 48
788	* ^^^ we sent it from some source port picked by kernel.
789	* time(NULL) = 1259071266
790	* write(2, "ntpd: entering poll 15 secs\n", 28) = 28
791	* poll([{fd=3, events=POLLIN}], 1, 15000) = 1 ([{fd=3, revents=POLLIN}])
792	* recv(3, "yyy", 68, MSG_DONTWAIT) = 48
793	* ^^^ this recv will receive packets to any local port!
794	*
795	* Uncomment this and use strace to see it in action:
796	*/
797	#define PROBE_LOCAL_ADDR /* { len_and_sockaddr lsa; lsa.len = LSA_SIZEOF_SA; getsockname(p->query.fd, &lsa.u.sa, &lsa.len); } */
798
799	if (p->p_fd == -1) {
800	int fd, family;
801	len_and_sockaddr *local_lsa;
802
803	family = p->p_lsa->u.sa.sa_family;
804	p->p_fd = fd = xsocket_type(&local_lsa, family, SOCK_DGRAM);
805	/* local_lsa has "null" address and port 0 now.
806	* bind() ensures we have a *particular port* selected by kernel
807	* and remembered in p->p_fd, thus later recv(p->p_fd)
808	* receives only packets sent to this port.
809	*/
810	PROBE_LOCAL_ADDR
811	xbind(fd, &local_lsa->u.sa, local_lsa->len);
812	PROBE_LOCAL_ADDR
813	#if ENABLE_FEATURE_IPV6
814	if (family == AF_INET)
815	#endif
816	setsockopt(fd, IPPROTO_IP, IP_TOS, &const_IPTOS_LOWDELAY, sizeof(const_IPTOS_LOWDELAY));
817	free(local_lsa);
818	}
819
820	/* Emit message _before_ attempted send. Think of a very short
821	* roundtrip networks: we need to go back to recv loop ASAP,
822	* to reduce delay. Printing messages after send works against that.
823	*/
824	VERB1 bb_error_msg("sending query to %s", p->p_dotted);
825
826	/*
827	* Send out a random 64-bit number as our transmit time. The NTP
828	* server will copy said number into the originate field on the
829	* response that it sends us. This is totally legal per the SNTP spec.
830	*
831	* The impact of this is two fold: we no longer send out the current
832	* system time for the world to see (which may aid an attacker), and
833	* it gives us a (not very secure) way of knowing that we're not
834	* getting spoofed by an attacker that can't capture our traffic
835	* but can spoof packets from the NTP server we're communicating with.
836	*
837	* Save the real transmit timestamp locally.
838	*/
839	p->p_xmt_msg.m_xmttime.int_partl = random();
840	p->p_xmt_msg.m_xmttime.fractionl = random();
841	p->p_xmttime = gettime1900d();
842
843	/* Were doing it only if sendto worked, but
844	* loss of sync detection needs reachable_bits updated
845	* even if sending fails *locally*:
846	* "network is unreachable" because cable was pulled?
847	* We still need to declare "unsync" if this condition persists.
848	*/
849	p->reachable_bits <<= 1;
850
851	if (do_sendto(p->p_fd, /*from:*/ NULL, /*to:*/ &p->p_lsa->u.sa, /*addrlen:*/ p->p_lsa->len,
852	&p->p_xmt_msg, NTP_MSGSIZE_NOAUTH) == -1
853	) {
854	close(p->p_fd);
855	p->p_fd = -1;
856	/*
857	* We know that we sent nothing.
858	* We can retry *soon* without fearing
859	* that we are flooding the peer.
860	*/
861	set_next(p, RETRY_INTERVAL);
862	return;
863	}
864
865	set_next(p, RESPONSE_INTERVAL);
866	}
867
868
869	/* Note that there is no provision to prevent several run_scripts
870	* to be started in quick succession. In fact, it happens rather often
871	* if initial syncronization results in a step.
872	* You will see "step" and then "stratum" script runs, sometimes
873	* as close as only 0.002 seconds apart.
874	* Script should be ready to deal with this.
875	*/
876	static void run_script(const char *action, double offset)
877	{
878	char *argv[3];
879	char *env1, *env2, *env3, *env4;
880
881	G.last_script_run = G.cur_time;
882
883	if (!G.script_name)
884	return;
885
886	argv[0] = (char*) G.script_name;
887	argv[1] = (char*) action;
888	argv[2] = NULL;
889
890	VERB1 bb_error_msg("executing '%s %s'", G.script_name, action);
891
892	env1 = xasprintf("%s=%u", "stratum", G.stratum);
893	putenv(env1);
894	env2 = xasprintf("%s=%ld", "freq_drift_ppm", G.kernel_freq_drift);
895	putenv(env2);
896	env3 = xasprintf("%s=%u", "poll_interval", 1 << G.poll_exp);
897	putenv(env3);
898	env4 = xasprintf("%s=%f", "offset", offset);
899	putenv(env4);
900	/* Other items of potential interest: selected peer,
901	* rootdelay, reftime, rootdisp, refid, ntp_status,
902	* last_update_offset, last_update_recv_time, discipline_jitter,
903	* how many peers have reachable_bits = 0?
904	*/
905
906	/* Don't want to wait: it may run hwclock --systohc, and that
907	* may take some time (seconds): */
908	/*spawn_and_wait(argv);*/
909	spawn(argv);
910
911	unsetenv("stratum");
912	unsetenv("freq_drift_ppm");
913	unsetenv("poll_interval");
914	unsetenv("offset");
915	free(env1);
916	free(env2);
917	free(env3);
918	free(env4);
919	}
920
921	static NOINLINE void
922	step_time(double offset)
923	{
924	llist_t *item;
925	double dtime;
926	struct timeval tvc, tvn;
927	char buf[sizeof("yyyy-mm-dd hh:mm:ss") + /*paranoia:*/ 4];
928	time_t tval;
929
930	gettimeofday(&tvc, NULL); /* never fails */
931	dtime = tvc.tv_sec + (1.0e-6 * tvc.tv_usec) + offset;
932	d_to_tv(dtime, &tvn);
933	if (settimeofday(&tvn, NULL) == -1)
934	bb_perror_msg_and_die("settimeofday");
935
936	VERB2 {
937	tval = tvc.tv_sec;
938	strftime_YYYYMMDDHHMMSS(buf, sizeof(buf), &tval);
939	bb_error_msg("current time is %s.%06u", buf, (unsigned)tvc.tv_usec);
940	}
941	tval = tvn.tv_sec;
942	strftime_YYYYMMDDHHMMSS(buf, sizeof(buf), &tval);
943	bb_error_msg("setting time to %s.%06u (offset %+fs)", buf, (unsigned)tvn.tv_usec, offset);
944
945	/* Correct various fields which contain time-relative values: */
946
947	/* Globals: */
948	G.cur_time += offset;
949	G.last_update_recv_time += offset;
950	G.last_script_run += offset;
951
952	/* p->lastpkt_recv_time, p->next_action_time and such: */
953	for (item = G.ntp_peers; item != NULL; item = item->link) {
954	peer_t *pp = (peer_t *) item->data;
955	reset_peer_stats(pp, offset);
956	//bb_error_msg("offset:%+f pp->next_action_time:%f -> %f",
957	// offset, pp->next_action_time, pp->next_action_time + offset);
958	pp->next_action_time += offset;
959	if (pp->p_fd >= 0) {
960	/* We wait for reply from this peer too.
961	* But due to step we are doing, reply's data is no longer
962	* useful (in fact, it'll be bogus). Stop waiting for it.
963	*/
964	close(pp->p_fd);
965	pp->p_fd = -1;
966	set_next(pp, RETRY_INTERVAL);
967	}
968	}
969	}
970
971
972	/*
973	* Selection and clustering, and their helpers
974	*/
975	typedef struct {
976	peer_t *p;
977	int type;
978	double edge;
979	double opt_rd; /* optimization */
980	} point_t;
981	static int
982	compare_point_edge(const void *aa, const void *bb)
983	{
984	const point_t *a = aa;
985	const point_t *b = bb;
986	if (a->edge < b->edge) {
987	return -1;
988	}
989	return (a->edge > b->edge);
990	}
991	typedef struct {
992	peer_t *p;
993	double metric;
994	} survivor_t;
995	static int
996	compare_survivor_metric(const void *aa, const void *bb)
997	{
998	const survivor_t *a = aa;
999	const survivor_t *b = bb;
1000	if (a->metric < b->metric) {
1001	return -1;
1002	}
1003	return (a->metric > b->metric);
1004	}
1005	static int
1006	fit(peer_t *p, double rd)
1007	{
1008	if ((p->reachable_bits & (p->reachable_bits-1)) == 0) {
1009	/* One or zero bits in reachable_bits */
1010	VERB4 bb_error_msg("peer %s unfit for selection: unreachable", p->p_dotted);
1011	return 0;
1012	}
1013	#if 0 /* we filter out such packets earlier */
1014	if ((p->lastpkt_status & LI_ALARM) == LI_ALARM
1015	|| p->lastpkt_stratum >= MAXSTRAT
1016	) {
1017	VERB4 bb_error_msg("peer %s unfit for selection: bad status/stratum", p->p_dotted);
1018	return 0;
1019	}
1020	#endif
1021	/* rd is root_distance(p) */
1022	if (rd > MAXDIST + FREQ_TOLERANCE * (1 << G.poll_exp)) {
1023	VERB4 bb_error_msg("peer %s unfit for selection: root distance too high", p->p_dotted);
1024	return 0;
1025	}
1026	//TODO
1027	// /* Do we have a loop? */
1028	// if (p->refid == p->dstaddr || p->refid == s.refid)
1029	// return 0;
1030	return 1;
1031	}
1032	static peer_t*
1033	select_and_cluster(void)
1034	{
1035	peer_t *p;
1036	llist_t *item;
1037	int i, j;
1038	int size = 3 * G.peer_cnt;
1039	/* for selection algorithm */
1040	point_t point[size];
1041	int num_points, num_candidates;
1042	double low, high;
1043	int num_falsetickers;
1044	/* for cluster algorithm */
1045	survivor_t survivor[size];
1046	int num_survivors;
1047
1048	/* Selection */
1049
1050	num_points = 0;
1051	item = G.ntp_peers;
1052	if (G.initial_poll_complete) while (item != NULL) {
1053	double rd, offset;
1054
1055	p = (peer_t *) item->data;
1056	rd = root_distance(p);
1057	offset = p->filter_offset;
1058	if (!fit(p, rd)) {
1059	item = item->link;
1060	continue;
1061	}
1062
1063	VERB5 bb_error_msg("interval: [%f %f %f] %s",
1064	offset - rd,
1065	offset,
1066	offset + rd,
1067	p->p_dotted
1068	);
1069	point[num_points].p = p;
1070	point[num_points].type = -1;
1071	point[num_points].edge = offset - rd;
1072	point[num_points].opt_rd = rd;
1073	num_points++;
1074	point[num_points].p = p;
1075	point[num_points].type = 0;
1076	point[num_points].edge = offset;
1077	point[num_points].opt_rd = rd;
1078	num_points++;
1079	point[num_points].p = p;
1080	point[num_points].type = 1;
1081	point[num_points].edge = offset + rd;
1082	point[num_points].opt_rd = rd;
1083	num_points++;
1084	item = item->link;
1085	}
1086	num_candidates = num_points / 3;
1087	if (num_candidates == 0) {
1088	VERB3 bb_error_msg("no valid datapoints%s", ", no peer selected");
1089	return NULL;
1090	}
1091	//TODO: sorting does not seem to be done in reference code
1092	qsort(point, num_points, sizeof(point[0]), compare_point_edge);
1093
1094	/* Start with the assumption that there are no falsetickers.
1095	* Attempt to find a nonempty intersection interval containing
1096	* the midpoints of all truechimers.
1097	* If a nonempty interval cannot be found, increase the number
1098	* of assumed falsetickers by one and try again.
1099	* If a nonempty interval is found and the number of falsetickers
1100	* is less than the number of truechimers, a majority has been found
1101	* and the midpoint of each truechimer represents
1102	* the candidates available to the cluster algorithm.
1103	*/
1104	num_falsetickers = 0;
1105	while (1) {
1106	int c;
1107	int num_midpoints = 0;
1108
1109	low = 1 << 9;
1110	high = - (1 << 9);
1111	c = 0;
1112	for (i = 0; i < (int) num_points; i++) {
1113	/* We want to do:
1114	* if (point[i].type == -1) c++;
1115	* if (point[i].type == 1) c--;
1116	* and it's simpler to do it this way:
1117	*/
1118	c -= point[i].type;
1119	if (c >= num_candidates - num_falsetickers) {
1120	/* If it was c++ and it got big enough... */
1121	low = point[i].edge;
1122	break;
1123	}
1124	if (point[i].type == 0)
1125	num_midpoints++;
1126	}
1127	c = 0;
1128	for (i = num_points-1; i >= 0; i--) {
1129	c += point[i].type;
1130	if (c >= num_candidates - num_falsetickers) {
1131	high = point[i].edge;
1132	break;
1133	}
1134	if (point[i].type == 0)
1135	num_midpoints++;
1136	}
1137	/* If the number of midpoints is greater than the number
1138	* of allowed falsetickers, the intersection contains at
1139	* least one truechimer with no midpoint - bad.
1140	* Also, interval should be nonempty.
1141	*/
1142	if (num_midpoints <= num_falsetickers && low < high)
1143	break;
1144	num_falsetickers++;
1145	if (num_falsetickers * 2 >= num_candidates) {
1146	VERB3 bb_error_msg("falsetickers:%d, candidates:%d%s",
1147	num_falsetickers, num_candidates,
1148	", no peer selected");
1149	return NULL;
1150	}
1151	}
1152	VERB4 bb_error_msg("selected interval: [%f, %f]; candidates:%d falsetickers:%d",
1153	low, high, num_candidates, num_falsetickers);
1154
1155	/* Clustering */
1156
1157	/* Construct a list of survivors (p, metric)
1158	* from the chime list, where metric is dominated
1159	* first by stratum and then by root distance.
1160	* All other things being equal, this is the order of preference.
1161	*/
1162	num_survivors = 0;
1163	for (i = 0; i < num_points; i++) {
1164	if (point[i].edge < low || point[i].edge > high)
1165	continue;
1166	p = point[i].p;
1167	survivor[num_survivors].p = p;
1168	/* x.opt_rd == root_distance(p); */
1169	survivor[num_survivors].metric = MAXDIST * p->lastpkt_stratum + point[i].opt_rd;
1170	VERB5 bb_error_msg("survivor[%d] metric:%f peer:%s",
1171	num_survivors, survivor[num_survivors].metric, p->p_dotted);
1172	num_survivors++;
1173	}
1174	/* There must be at least MIN_SELECTED survivors to satisfy the
1175	* correctness assertions. Ordinarily, the Byzantine criteria
1176	* require four survivors, but for the demonstration here, one
1177	* is acceptable.
1178	*/
1179	if (num_survivors < MIN_SELECTED) {
1180	VERB3 bb_error_msg("survivors:%d%s",
1181	num_survivors,
1182	", no peer selected");
1183	return NULL;
1184	}
1185
1186	//looks like this is ONLY used by the fact that later we pick survivor[0].
1187	//we can avoid sorting then, just find the minimum once!
1188	qsort(survivor, num_survivors, sizeof(survivor[0]), compare_survivor_metric);
1189
1190	/* For each association p in turn, calculate the selection
1191	* jitter p->sjitter as the square root of the sum of squares
1192	* (p->offset - q->offset) over all q associations. The idea is
1193	* to repeatedly discard the survivor with maximum selection
1194	* jitter until a termination condition is met.
1195	*/
1196	while (1) {
1197	static int max_idx;
1198	double max_selection_jitter = max_selection_jitter;
1199	double min_jitter = min_jitter;
1200
1201	if (num_survivors <= MIN_CLUSTERED) {
1202	VERB4 bb_error_msg("num_survivors %d <= %d, not discarding more",
1203	num_survivors, MIN_CLUSTERED);
1204	break;
1205	}
1206
1207	/* To make sure a few survivors are left
1208	* for the clustering algorithm to chew on,
1209	* we stop if the number of survivors
1210	* is less than or equal to MIN_CLUSTERED (3).
1211	*/
1212	for (i = 0; i < num_survivors; i++) {
1213	double selection_jitter_sq;
1214
1215	p = survivor[i].p;
1216	if (i == 0 || p->filter_jitter < min_jitter)
1217	min_jitter = p->filter_jitter;
1218
1219	selection_jitter_sq = 0;
1220	for (j = 0; j < num_survivors; j++) {
1221	peer_t *q = survivor[j].p;
1222	selection_jitter_sq += SQUARE(p->filter_offset - q->filter_offset);
1223	}
1224	if (i == 0 || selection_jitter_sq > max_selection_jitter) {
1225	max_selection_jitter = selection_jitter_sq;
1226	max_idx = i;
1227	}
1228	VERB6 bb_error_msg("survivor %d selection_jitter^2:%f",
1229	i, selection_jitter_sq);
1230	}
1231	max_selection_jitter = SQRT(max_selection_jitter / num_survivors);
1232	VERB5 bb_error_msg("max_selection_jitter (at %d):%f min_jitter:%f",
1233	max_idx, max_selection_jitter, min_jitter);
1234
1235	/* If the maximum selection jitter is less than the
1236	* minimum peer jitter, then tossing out more survivors
1237	* will not lower the minimum peer jitter, so we might
1238	* as well stop.
1239	*/
1240	if (max_selection_jitter < min_jitter) {
1241	VERB4 bb_error_msg("max_selection_jitter:%f < min_jitter:%f, num_survivors:%d, not discarding more",
1242	max_selection_jitter, min_jitter, num_survivors);
1243	break;
1244	}
1245
1246	/* Delete survivor[max_idx] from the list
1247	* and go around again.
1248	*/
1249	VERB6 bb_error_msg("dropping survivor %d", max_idx);
1250	num_survivors--;
1251	while (max_idx < num_survivors) {
1252	survivor[max_idx] = survivor[max_idx + 1];
1253	max_idx++;
1254	}
1255	}
1256
1257	if (0) {
1258	/* Combine the offsets of the clustering algorithm survivors
1259	* using a weighted average with weight determined by the root
1260	* distance. Compute the selection jitter as the weighted RMS
1261	* difference between the first survivor and the remaining
1262	* survivors. In some cases the inherent clock jitter can be
1263	* reduced by not using this algorithm, especially when frequent
1264	* clockhopping is involved. bbox: thus we don't do it.
1265	*/
1266	double x, y, z, w;
1267	y = z = w = 0;
1268	for (i = 0; i < num_survivors; i++) {
1269	p = survivor[i].p;
1270	x = root_distance(p);
1271	y += 1 / x;
1272	z += p->filter_offset / x;
1273	w += SQUARE(p->filter_offset - survivor[0].p->filter_offset) / x;
1274	}
1275	//G.cluster_offset = z / y;
1276	//G.cluster_jitter = SQRT(w / y);
1277	}
1278
1279	/* Pick the best clock. If the old system peer is on the list
1280	* and at the same stratum as the first survivor on the list,
1281	* then don't do a clock hop. Otherwise, select the first
1282	* survivor on the list as the new system peer.
1283	*/
1284	p = survivor[0].p;
1285	if (G.last_update_peer
1286	&& G.last_update_peer->lastpkt_stratum <= p->lastpkt_stratum
1287	) {
1288	/* Starting from 1 is ok here */
1289	for (i = 1; i < num_survivors; i++) {
1290	if (G.last_update_peer == survivor[i].p) {
1291	VERB5 bb_error_msg("keeping old synced peer");
1292	p = G.last_update_peer;
1293	goto keep_old;
1294	}
1295	}
1296	}
1297	G.last_update_peer = p;
1298	keep_old:
1299	VERB4 bb_error_msg("selected peer %s filter_offset:%+f age:%f",
1300	p->p_dotted,
1301	p->filter_offset,
1302	G.cur_time - p->lastpkt_recv_time
1303	);
1304	return p;
1305	}
1306
1307
1308	/*
1309	* Local clock discipline and its helpers
1310	*/
1311	static void
1312	set_new_values(int disc_state, double offset, double recv_time)
1313	{
1314	/* Enter new state and set state variables. Note we use the time
1315	* of the last clock filter sample, which must be earlier than
1316	* the current time.
1317	*/
1318	VERB4 bb_error_msg("disc_state=%d last update offset=%f recv_time=%f",
1319	disc_state, offset, recv_time);
1320	G.discipline_state = disc_state;
1321	G.last_update_offset = offset;
1322	G.last_update_recv_time = recv_time;
1323	}
1324	/* Return: -1: decrease poll interval, 0: leave as is, 1: increase */
1325	static NOINLINE int
1326	update_local_clock(peer_t *p)
1327	{
1328	int rc;
1329	struct timex tmx;
1330	/* Note: can use G.cluster_offset instead: */
1331	double offset = p->filter_offset;
1332	double recv_time = p->lastpkt_recv_time;
1333	double abs_offset;
1334	#if !USING_KERNEL_PLL_LOOP
1335	double freq_drift;
1336	#endif
1337	double since_last_update;
1338	double etemp, dtemp;
1339
1340	abs_offset = fabs(offset);
1341
1342	#if 0
1343	/* If needed, -S script can do it by looking at $offset
1344	* env var and killing parent */
1345	/* If the offset is too large, give up and go home */
1346	if (abs_offset > PANIC_THRESHOLD) {
1347	bb_error_msg_and_die("offset %f far too big, exiting", offset);
1348	}
1349	#endif
1350
1351	/* If this is an old update, for instance as the result
1352	* of a system peer change, avoid it. We never use
1353	* an old sample or the same sample twice.
1354	*/
1355	if (recv_time <= G.last_update_recv_time) {
1356	VERB3 bb_error_msg("update from %s: same or older datapoint, not using it",
1357	p->p_dotted);
1358	return 0; /* "leave poll interval as is" */
1359	}
1360
1361	/* Clock state machine transition function. This is where the
1362	* action is and defines how the system reacts to large time
1363	* and frequency errors.
1364	*/
1365	since_last_update = recv_time - G.reftime;
1366	#if !USING_KERNEL_PLL_LOOP
1367	freq_drift = 0;
1368	#endif
1369	#if USING_INITIAL_FREQ_ESTIMATION
1370	if (G.discipline_state == STATE_FREQ) {
1371	/* Ignore updates until the stepout threshold */
1372	if (since_last_update < WATCH_THRESHOLD) {
1373	VERB4 bb_error_msg("measuring drift, datapoint ignored, %f sec remains",
1374	WATCH_THRESHOLD - since_last_update);
1375	return 0; /* "leave poll interval as is" */
1376	}
1377	# if !USING_KERNEL_PLL_LOOP
1378	freq_drift = (offset - G.last_update_offset) / since_last_update;
1379	# endif
1380	}
1381	#endif
1382
1383	/* There are two main regimes: when the
1384	* offset exceeds the step threshold and when it does not.
1385	*/
1386	if (abs_offset > STEP_THRESHOLD) {
1387	#if 0
1388	double remains;
1389
1390	// This "spike state" seems to be useless, peer selection already drops
1391	// occassional "bad" datapoints. If we are here, there were _many_
1392	// large offsets. When a few first large offsets are seen,
1393	// we end up in "no valid datapoints, no peer selected" state.
1394	// Only when enough of them are seen (which means it's not a fluke),
1395	// we end up here. Looks like _our_ clock is off.
1396	switch (G.discipline_state) {
1397	case STATE_SYNC:
1398	/* The first outlyer: ignore it, switch to SPIK state */
1399	VERB3 bb_error_msg("update from %s: offset:%+f, spike%s",
1400	p->p_dotted, offset,
1401	"");
1402	G.discipline_state = STATE_SPIK;
1403	return -1; /* "decrease poll interval" */
1404
1405	case STATE_SPIK:
1406	/* Ignore succeeding outlyers until either an inlyer
1407	* is found or the stepout threshold is exceeded.
1408	*/
1409	remains = WATCH_THRESHOLD - since_last_update;
1410	if (remains > 0) {
1411	VERB3 bb_error_msg("update from %s: offset:%+f, spike%s",
1412	p->p_dotted, offset,
1413	", datapoint ignored");
1414	return -1; /* "decrease poll interval" */
1415	}
1416	/* fall through: we need to step */
1417	} /* switch */
1418	#endif
1419
1420	/* Step the time and clamp down the poll interval.
1421	*
1422	* In NSET state an initial frequency correction is
1423	* not available, usually because the frequency file has
1424	* not yet been written. Since the time is outside the
1425	* capture range, the clock is stepped. The frequency
1426	* will be set directly following the stepout interval.
1427	*
1428	* In FSET state the initial frequency has been set
1429	* from the frequency file. Since the time is outside
1430	* the capture range, the clock is stepped immediately,
1431	* rather than after the stepout interval. Guys get
1432	* nervous if it takes 17 minutes to set the clock for
1433	* the first time.
1434	*
1435	* In SPIK state the stepout threshold has expired and
1436	* the phase is still above the step threshold. Note
1437	* that a single spike greater than the step threshold
1438	* is always suppressed, even at the longer poll
1439	* intervals.
1440	*/
1441	VERB4 bb_error_msg("stepping time by %+f; poll_exp=MINPOLL", offset);
1442	step_time(offset);
1443	if (option_mask32 & OPT_q) {
1444	/* We were only asked to set time once. Done. */
1445	exit(0);
1446	}
1447
1448	G.polladj_count = 0;
1449	G.poll_exp = MINPOLL;
1450	G.stratum = MAXSTRAT;
1451
1452	run_script("step", offset);
1453
1454	recv_time += offset;
1455
1456	#if USING_INITIAL_FREQ_ESTIMATION
1457	if (G.discipline_state == STATE_NSET) {
1458	set_new_values(STATE_FREQ, /*offset:*/ 0, recv_time);
1459	return 1; /* "ok to increase poll interval" */
1460	}
1461	#endif
1462	abs_offset = offset = 0;
1463	set_new_values(STATE_SYNC, offset, recv_time);
1464
1465	} else { /* abs_offset <= STEP_THRESHOLD */
1466
1467	if (G.poll_exp < MINPOLL && G.initial_poll_complete) {
1468	VERB4 bb_error_msg("small offset:%+f, disabling burst mode", offset);
1469	G.polladj_count = 0;
1470	G.poll_exp = MINPOLL;
1471	}
1472
1473	/* Compute the clock jitter as the RMS of exponentially
1474	* weighted offset differences. Used by the poll adjust code.
1475	*/
1476	etemp = SQUARE(G.discipline_jitter);
1477	dtemp = SQUARE(offset - G.last_update_offset);
1478	G.discipline_jitter = SQRT(etemp + (dtemp - etemp) / AVG);
1479
1480	switch (G.discipline_state) {
1481	case STATE_NSET:
1482	if (option_mask32 & OPT_q) {
1483	/* We were only asked to set time once.
1484	* The clock is precise enough, no need to step.
1485	*/
1486	exit(0);
1487	}
1488	#if USING_INITIAL_FREQ_ESTIMATION
1489	/* This is the first update received and the frequency
1490	* has not been initialized. The first thing to do
1491	* is directly measure the oscillator frequency.
1492	*/
1493	set_new_values(STATE_FREQ, offset, recv_time);
1494	#else
1495	set_new_values(STATE_SYNC, offset, recv_time);
1496	#endif
1497	VERB4 bb_error_msg("transitioning to FREQ, datapoint ignored");
1498	return 0; /* "leave poll interval as is" */
1499
1500	#if 0 /* this is dead code for now */
1501	case STATE_FSET:
1502	/* This is the first update and the frequency
1503	* has been initialized. Adjust the phase, but
1504	* don't adjust the frequency until the next update.
1505	*/
1506	set_new_values(STATE_SYNC, offset, recv_time);
1507	/* freq_drift remains 0 */
1508	break;
1509	#endif
1510
1511	#if USING_INITIAL_FREQ_ESTIMATION
1512	case STATE_FREQ:
1513	/* since_last_update >= WATCH_THRESHOLD, we waited enough.
1514	* Correct the phase and frequency and switch to SYNC state.
1515	* freq_drift was already estimated (see code above)
1516	*/
1517	set_new_values(STATE_SYNC, offset, recv_time);
1518	break;
1519	#endif
1520
1521	default:
1522	#if !USING_KERNEL_PLL_LOOP
1523	/* Compute freq_drift due to PLL and FLL contributions.
1524	*
1525	* The FLL and PLL frequency gain constants
1526	* depend on the poll interval and Allan
1527	* intercept. The FLL is not used below one-half
1528	* the Allan intercept. Above that the loop gain
1529	* increases in steps to 1 / AVG.
1530	*/
1531	if ((1 << G.poll_exp) > ALLAN / 2) {
1532	etemp = FLL - G.poll_exp;
1533	if (etemp < AVG)
1534	etemp = AVG;
1535	freq_drift += (offset - G.last_update_offset) / (MAXD(since_last_update, ALLAN) * etemp);
1536	}
1537	/* For the PLL the integration interval
1538	* (numerator) is the minimum of the update
1539	* interval and poll interval. This allows
1540	* oversampling, but not undersampling.
1541	*/
1542	etemp = MIND(since_last_update, (1 << G.poll_exp));
1543	dtemp = (4 * PLL) << G.poll_exp;
1544	freq_drift += offset * etemp / SQUARE(dtemp);
1545	#endif
1546	set_new_values(STATE_SYNC, offset, recv_time);
1547	break;
1548	}
1549	if (G.stratum != p->lastpkt_stratum + 1) {
1550	G.stratum = p->lastpkt_stratum + 1;
1551	run_script("stratum", offset);
1552	}
1553	}
1554
1555	if (G.discipline_jitter < G_precision_sec)
1556	G.discipline_jitter = G_precision_sec;
1557	G.offset_to_jitter_ratio = abs_offset / G.discipline_jitter;
1558
1559	G.reftime = G.cur_time;
1560	G.ntp_status = p->lastpkt_status;
1561	G.refid = p->lastpkt_refid;
1562	G.rootdelay = p->lastpkt_rootdelay + p->lastpkt_delay;
1563	dtemp = p->filter_jitter; // SQRT(SQUARE(p->filter_jitter) + SQUARE(G.cluster_jitter));
1564	dtemp += MAXD(p->filter_dispersion + FREQ_TOLERANCE * (G.cur_time - p->lastpkt_recv_time) + abs_offset, MINDISP);
1565	G.rootdisp = p->lastpkt_rootdisp + dtemp;
1566	VERB4 bb_error_msg("updating leap/refid/reftime/rootdisp from peer %s", p->p_dotted);
1567
1568	/* We are in STATE_SYNC now, but did not do adjtimex yet.
1569	* (Any other state does not reach this, they all return earlier)
1570	* By this time, freq_drift and offset are set
1571	* to values suitable for adjtimex.
1572	*/
1573	#if !USING_KERNEL_PLL_LOOP
1574	/* Calculate the new frequency drift and frequency stability (wander).
1575	* Compute the clock wander as the RMS of exponentially weighted
1576	* frequency differences. This is not used directly, but can,
1577	* along with the jitter, be a highly useful monitoring and
1578	* debugging tool.
1579	*/
1580	dtemp = G.discipline_freq_drift + freq_drift;
1581	G.discipline_freq_drift = MAXD(MIND(MAXDRIFT, dtemp), -MAXDRIFT);
1582	etemp = SQUARE(G.discipline_wander);
1583	dtemp = SQUARE(dtemp);
1584	G.discipline_wander = SQRT(etemp + (dtemp - etemp) / AVG);
1585
1586	VERB4 bb_error_msg("discipline freq_drift=%.9f(int:%ld corr:%e) wander=%f",
1587	G.discipline_freq_drift,
1588	(long)(G.discipline_freq_drift * 65536e6),
1589	freq_drift,
1590	G.discipline_wander);
1591	#endif
1592	VERB4 {
1593	memset(&tmx, 0, sizeof(tmx));
1594	if (adjtimex(&tmx) < 0)
1595	bb_perror_msg_and_die("adjtimex");
1596	bb_error_msg("p adjtimex freq:%ld offset:%+ld status:0x%x tc:%ld",
1597	tmx.freq, tmx.offset, tmx.status, tmx.constant);
1598	}
1599
1600	memset(&tmx, 0, sizeof(tmx));
1601	#if 0
1602	//doesn't work, offset remains 0 (!) in kernel:
1603	//ntpd: set adjtimex freq:1786097 tmx.offset:77487
1604	//ntpd: prev adjtimex freq:1786097 tmx.offset:0
1605	//ntpd: cur adjtimex freq:1786097 tmx.offset:0
1606	tmx.modes = ADJ_FREQUENCY | ADJ_OFFSET;
1607	/* 65536 is one ppm */
1608	tmx.freq = G.discipline_freq_drift * 65536e6;
1609	#endif
1610	tmx.modes = ADJ_OFFSET | ADJ_STATUS | ADJ_TIMECONST;// | ADJ_MAXERROR | ADJ_ESTERROR;
1611	tmx.offset = (offset * 1000000); /* usec */
1612	tmx.status = STA_PLL;
1613	if (G.ntp_status & LI_PLUSSEC)
1614	tmx.status |= STA_INS;
1615	if (G.ntp_status & LI_MINUSSEC)
1616	tmx.status |= STA_DEL;
1617
1618	tmx.constant = G.poll_exp - 4;
1619	/* EXPERIMENTAL.
1620	* The below if statement should be unnecessary, but...
1621	* It looks like Linux kernel's PLL is far too gentle in changing
1622	* tmx.freq in response to clock offset. Offset keeps growing
1623	* and eventually we fall back to smaller poll intervals.
1624	* We can make correction more agressive (about x2) by supplying
1625	* PLL time constant which is one less than the real one.
1626	* To be on a safe side, let's do it only if offset is significantly
1627	* larger than jitter.
1628	*/
1629	if (tmx.constant > 0 && G.offset_to_jitter_ratio >= TIMECONST_HACK_GATE)
1630	tmx.constant--;
1631
1632	//tmx.esterror = (uint32_t)(clock_jitter * 1e6);
1633	//tmx.maxerror = (uint32_t)((sys_rootdelay / 2 + sys_rootdisp) * 1e6);
1634	rc = adjtimex(&tmx);
1635	if (rc < 0)
1636	bb_perror_msg_and_die("adjtimex");
1637	/* NB: here kernel returns constant == G.poll_exp, not == G.poll_exp - 4.
1638	* Not sure why. Perhaps it is normal.
1639	*/
1640	VERB4 bb_error_msg("adjtimex:%d freq:%ld offset:%+ld status:0x%x",
1641	rc, tmx.freq, tmx.offset, tmx.status);
1642	G.kernel_freq_drift = tmx.freq / 65536;
1643	VERB2 bb_error_msg("update from:%s offset:%+f jitter:%f clock drift:%+.3fppm tc:%d",
1644	p->p_dotted, offset, G.discipline_jitter, (double)tmx.freq / 65536, (int)tmx.constant);
1645
1646	return 1; /* "ok to increase poll interval" */
1647	}
1648
1649
1650	/*
1651	* We've got a new reply packet from a peer, process it
1652	* (helpers first)
1653	*/
1654	static unsigned
1655	retry_interval(void)
1656	{
1657	/* Local problem, want to retry soon */
1658	unsigned interval, r;
1659	interval = RETRY_INTERVAL;
1660	r = random();
1661	interval += r % (unsigned)(RETRY_INTERVAL / 4);
1662	VERB4 bb_error_msg("chose retry interval:%u", interval);
1663	return interval;
1664	}
1665	static unsigned
1666	poll_interval(int exponent)
1667	{
1668	unsigned interval, r;
1669	exponent = G.poll_exp + exponent;
1670	if (exponent < 0)
1671	exponent = 0;
1672	interval = 1 << exponent;
1673	r = random();
1674	interval += ((r & (interval-1)) >> 4) + ((r >> 8) & 1); /* + 1/16 of interval, max */
1675	VERB4 bb_error_msg("chose poll interval:%u (poll_exp:%d exp:%d)", interval, G.poll_exp, exponent);
1676	return interval;
1677	}
1678	static NOINLINE void
1679	recv_and_process_peer_pkt(peer_t *p)
1680	{
1681	int rc;
1682	ssize_t size;
1683	msg_t msg;
1684	double T1, T2, T3, T4;
1685	double dv, offset;
1686	unsigned interval;
1687	datapoint_t *datapoint;
1688	peer_t *q;
1689
1690	offset = 0;
1691
1692	/* We can recvfrom here and check from.IP, but some multihomed
1693	* ntp servers reply from their *other IP*.
1694	* TODO: maybe we should check at least what we can: from.port == 123?
1695	*/
1696	size = recv(p->p_fd, &msg, sizeof(msg), MSG_DONTWAIT);
1697	if (size == -1) {
1698	bb_perror_msg("recv(%s) error", p->p_dotted);
1699	if (errno == EHOSTUNREACH || errno == EHOSTDOWN
1700	|| errno == ENETUNREACH || errno == ENETDOWN
1701	|| errno == ECONNREFUSED || errno == EADDRNOTAVAIL
1702	|| errno == EAGAIN
1703	) {
1704	//TODO: always do this?
1705	interval = retry_interval();
1706	goto set_next_and_ret;
1707	}
1708	xfunc_die();
1709	}
1710
1711	if (size != NTP_MSGSIZE_NOAUTH && size != NTP_MSGSIZE) {
1712	bb_error_msg("malformed packet received from %s", p->p_dotted);
1713	return;
1714	}
1715
1716	if (msg.m_orgtime.int_partl != p->p_xmt_msg.m_xmttime.int_partl
1717	|| msg.m_orgtime.fractionl != p->p_xmt_msg.m_xmttime.fractionl
1718	) {
1719	/* Somebody else's packet */
1720	return;
1721	}
1722
1723	/* We do not expect any more packets from this peer for now.
1724	* Closing the socket informs kernel about it.
1725	* We open a new socket when we send a new query.
1726	*/
1727	close(p->p_fd);
1728	p->p_fd = -1;
1729
1730	if ((msg.m_status & LI_ALARM) == LI_ALARM
1731	|| msg.m_stratum == 0
1732	|| msg.m_stratum > NTP_MAXSTRATUM
1733	) {
1734	// TODO: stratum 0 responses may have commands in 32-bit m_refid field:
1735	// "DENY", "RSTR" - peer does not like us at all
1736	// "RATE" - peer is overloaded, reduce polling freq
1737	bb_error_msg("reply from %s: peer is unsynced", p->p_dotted);
1738	goto pick_normal_interval;
1739	}
1740
1741	// /* Verify valid root distance */
1742	// if (msg.m_rootdelay / 2 + msg.m_rootdisp >= MAXDISP || p->lastpkt_reftime > msg.m_xmt)
1743	// return; /* invalid header values */
1744
1745	p->lastpkt_status = msg.m_status;
1746	p->lastpkt_stratum = msg.m_stratum;
1747	p->lastpkt_rootdelay = sfp_to_d(msg.m_rootdelay);
1748	p->lastpkt_rootdisp = sfp_to_d(msg.m_rootdisp);
1749	p->lastpkt_refid = msg.m_refid;
1750
1751	/*
1752	* From RFC 2030 (with a correction to the delay math):
1753	*
1754	* Timestamp Name ID When Generated
1755	* ------------------------------------------------------------
1756	* Originate Timestamp T1 time request sent by client
1757	* Receive Timestamp T2 time request received by server
1758	* Transmit Timestamp T3 time reply sent by server
1759	* Destination Timestamp T4 time reply received by client
1760	*
1761	* The roundtrip delay and local clock offset are defined as
1762	*
1763	* delay = (T4 - T1) - (T3 - T2); offset = ((T2 - T1) + (T3 - T4)) / 2
1764	*/
1765	T1 = p->p_xmttime;
1766	T2 = lfp_to_d(msg.m_rectime);
1767	T3 = lfp_to_d(msg.m_xmttime);
1768	T4 = G.cur_time;
1769
1770	p->lastpkt_recv_time = T4;
1771	VERB6 bb_error_msg("%s->lastpkt_recv_time=%f", p->p_dotted, p->lastpkt_recv_time);
1772
1773	/* The delay calculation is a special case. In cases where the
1774	* server and client clocks are running at different rates and
1775	* with very fast networks, the delay can appear negative. In
1776	* order to avoid violating the Principle of Least Astonishment,
1777	* the delay is clamped not less than the system precision.
1778	*/
1779	dv = p->lastpkt_delay;
1780	p->lastpkt_delay = (T4 - T1) - (T3 - T2);
1781	if (p->lastpkt_delay < G_precision_sec)
1782	p->lastpkt_delay = G_precision_sec;
1783	/*
1784	* If this packet's delay is much bigger than the last one,
1785	* it's better to just ignore it than use its much less precise value.
1786	*/
1787	if (p->reachable_bits && p->lastpkt_delay > dv * BAD_DELAY_GROWTH) {
1788	bb_error_msg("reply from %s: delay %f is too high, ignoring", p->p_dotted, p->lastpkt_delay);
1789	goto pick_normal_interval;
1790	}
1791
1792	p->datapoint_idx = p->reachable_bits ? (p->datapoint_idx + 1) % NUM_DATAPOINTS : 0;
1793	datapoint = &p->filter_datapoint[p->datapoint_idx];
1794	datapoint->d_recv_time = T4;
1795	datapoint->d_offset = offset = ((T2 - T1) + (T3 - T4)) / 2;
1796	datapoint->d_dispersion = LOG2D(msg.m_precision_exp) + G_precision_sec;
1797	if (!p->reachable_bits) {
1798	/* 1st datapoint ever - replicate offset in every element */
1799	int i;
1800	for (i = 0; i < NUM_DATAPOINTS; i++) {
1801	p->filter_datapoint[i].d_offset = offset;
1802	}
1803	}
1804
1805	p->reachable_bits |= 1;
1806	if ((MAX_VERBOSE && G.verbose) || (option_mask32 & OPT_w)) {
1807	bb_error_msg("reply from %s: offset:%+f delay:%f status:0x%02x strat:%d refid:0x%08x rootdelay:%f reach:0x%02x",
1808	p->p_dotted,
1809	offset,
1810	p->lastpkt_delay,
1811	p->lastpkt_status,
1812	p->lastpkt_stratum,
1813	p->lastpkt_refid,
1814	p->lastpkt_rootdelay,
1815	p->reachable_bits
1816	/* not shown: m_ppoll, m_precision_exp, m_rootdisp,
1817	* m_reftime, m_orgtime, m_rectime, m_xmttime
1818	*/
1819	);
1820	}
1821
1822	/* Muck with statictics and update the clock */
1823	filter_datapoints(p);
1824	q = select_and_cluster();
1825	rc = -1;
1826	if (q) {
1827	rc = 0;
1828	if (!(option_mask32 & OPT_w)) {
1829	rc = update_local_clock(q);
1830	/* If drift is dangerously large, immediately
1831	* drop poll interval one step down.
1832	*/
1833	if (fabs(q->filter_offset) >= POLLDOWN_OFFSET) {
1834	VERB4 bb_error_msg("offset:%+f > POLLDOWN_OFFSET", q->filter_offset);
1835	goto poll_down;
1836	}
1837	}
1838	}
1839	/* else: no peer selected, rc = -1: we want to poll more often */
1840
1841	if (rc != 0) {
1842	/* Adjust the poll interval by comparing the current offset
1843	* with the clock jitter. If the offset is less than
1844	* the clock jitter times a constant, then the averaging interval
1845	* is increased, otherwise it is decreased. A bit of hysteresis
1846	* helps calm the dance. Works best using burst mode.
1847	*/
1848	if (rc > 0 && G.offset_to_jitter_ratio <= POLLADJ_GATE) {
1849	/* was += G.poll_exp but it is a bit
1850	* too optimistic for my taste at high poll_exp's */
1851	G.polladj_count += MINPOLL;
1852	if (G.polladj_count > POLLADJ_LIMIT) {
1853	G.polladj_count = 0;
1854	if (G.poll_exp < MAXPOLL) {
1855	G.poll_exp++;
1856	VERB4 bb_error_msg("polladj: discipline_jitter:%f ++poll_exp=%d",
1857	G.discipline_jitter, G.poll_exp);
1858	}
1859	} else {
1860	VERB4 bb_error_msg("polladj: incr:%d", G.polladj_count);
1861	}
1862	} else {
1863	G.polladj_count -= G.poll_exp * 2;
1864	if (G.polladj_count < -POLLADJ_LIMIT || G.poll_exp >= BIGPOLL) {
1865	poll_down:
1866	G.polladj_count = 0;
1867	if (G.poll_exp > MINPOLL) {
1868	llist_t *item;
1869
1870	G.poll_exp--;
1871	/* Correct p->next_action_time in each peer
1872	* which waits for sending, so that they send earlier.
1873	* Old pp->next_action_time are on the order
1874	* of t + (1 << old_poll_exp) + small_random,
1875	* we simply need to subtract ~half of that.
1876	*/
1877	for (item = G.ntp_peers; item != NULL; item = item->link) {
1878	peer_t *pp = (peer_t *) item->data;
1879	if (pp->p_fd < 0)
1880	pp->next_action_time -= (1 << G.poll_exp);
1881	}
1882	VERB4 bb_error_msg("polladj: discipline_jitter:%f --poll_exp=%d",
1883	G.discipline_jitter, G.poll_exp);
1884	}
1885	} else {
1886	VERB4 bb_error_msg("polladj: decr:%d", G.polladj_count);
1887	}
1888	}
1889	}
1890
1891	/* Decide when to send new query for this peer */
1892	pick_normal_interval:
1893	interval = poll_interval(0);
1894	if (fabs(offset) >= STEP_THRESHOLD * 8 && interval > BIGOFF_INTERVAL) {
1895	/* If we are synced, offsets are less than STEP_THRESHOLD,
1896	* or at the very least not much larger than it.
1897	* Now we see a largish one.
1898	* Either this peer is feeling bad, or packet got corrupted,
1899	* or _our_ clock is wrong now and _all_ peers will show similar
1900	* largish offsets too.
1901	* I observed this with laptop suspend stopping clock.
1902	* In any case, it makes sense to make next request soonish:
1903	* cases 1 and 2: get a better datapoint,
1904	* case 3: allows to resync faster.
1905	*/
1906	interval = BIGOFF_INTERVAL;
1907	}
1908
1909	set_next_and_ret:
1910	set_next(p, interval);
1911	}
1912
1913	#if ENABLE_FEATURE_NTPD_SERVER
1914	static NOINLINE void
1915	recv_and_process_client_pkt(void /*int fd*/)
1916	{
1917	ssize_t size;
1918	//uint8_t version;
1919	len_and_sockaddr *to;
1920	struct sockaddr *from;
1921	msg_t msg;
1922	uint8_t query_status;
1923	l_fixedpt_t query_xmttime;
1924
1925	to = get_sock_lsa(G_listen_fd);
1926	from = xzalloc(to->len);
1927
1928	size = recv_from_to(G_listen_fd, &msg, sizeof(msg), MSG_DONTWAIT, from, &to->u.sa, to->len);
1929	if (size != NTP_MSGSIZE_NOAUTH && size != NTP_MSGSIZE) {
1930	char *addr;
1931	if (size < 0) {
1932	if (errno == EAGAIN)
1933	goto bail;
1934	bb_perror_msg_and_die("recv");
1935	}
1936	addr = xmalloc_sockaddr2dotted_noport(from);
1937	bb_error_msg("malformed packet received from %s: size %u", addr, (int)size);
1938	free(addr);
1939	goto bail;
1940	}
1941
1942	query_status = msg.m_status;
1943	query_xmttime = msg.m_xmttime;
1944
1945	/* Build a reply packet */
1946	memset(&msg, 0, sizeof(msg));
1947	msg.m_status = G.stratum < MAXSTRAT ? (G.ntp_status & LI_MASK) : LI_ALARM;
1948	msg.m_status |= (query_status & VERSION_MASK);
1949	msg.m_status |= ((query_status & MODE_MASK) == MODE_CLIENT) ?
1950	MODE_SERVER : MODE_SYM_PAS;
1951	msg.m_stratum = G.stratum;
1952	msg.m_ppoll = G.poll_exp;
1953	msg.m_precision_exp = G_precision_exp;
1954	/* this time was obtained between poll() and recv() */
1955	msg.m_rectime = d_to_lfp(G.cur_time);
1956	msg.m_xmttime = d_to_lfp(gettime1900d()); /* this instant */
1957	if (G.peer_cnt == 0) {
1958	/* we have no peers: "stratum 1 server" mode. reftime = our own time */
1959	G.reftime = G.cur_time;
1960	}
1961	msg.m_reftime = d_to_lfp(G.reftime);
1962	msg.m_orgtime = query_xmttime;
1963	msg.m_rootdelay = d_to_sfp(G.rootdelay);
1964	//simple code does not do this, fix simple code!
1965	msg.m_rootdisp = d_to_sfp(G.rootdisp);
1966	//version = (query_status & VERSION_MASK); /* ... >> VERSION_SHIFT - done below instead */
1967	msg.m_refid = G.refid; // (version > (3 << VERSION_SHIFT)) ? G.refid : G.refid3;
1968
1969	/* We reply from the local address packet was sent to,
1970	* this makes to/from look swapped here: */
1971	do_sendto(G_listen_fd,
1972	/*from:*/ &to->u.sa, /*to:*/ from, /*addrlen:*/ to->len,
1973	&msg, size);
1974
1975	bail:
1976	free(to);
1977	free(from);
1978	}
1979	#endif
1980
1981	/* Upstream ntpd's options:
1982	*
1983	* -4 Force DNS resolution of host names to the IPv4 namespace.
1984	* -6 Force DNS resolution of host names to the IPv6 namespace.
1985	* -a Require cryptographic authentication for broadcast client,
1986	* multicast client and symmetric passive associations.
1987	* This is the default.
1988	* -A Do not require cryptographic authentication for broadcast client,
1989	* multicast client and symmetric passive associations.
1990	* This is almost never a good idea.
1991	* -b Enable the client to synchronize to broadcast servers.
1992	* -c conffile
1993	* Specify the name and path of the configuration file,
1994	* default /etc/ntp.conf
1995	* -d Specify debugging mode. This option may occur more than once,
1996	* with each occurrence indicating greater detail of display.
1997	* -D level
1998	* Specify debugging level directly.
1999	* -f driftfile
2000	* Specify the name and path of the frequency file.
2001	* This is the same operation as the "driftfile FILE"
2002	* configuration command.
2003	* -g Normally, ntpd exits with a message to the system log
2004	* if the offset exceeds the panic threshold, which is 1000 s
2005	* by default. This option allows the time to be set to any value
2006	* without restriction; however, this can happen only once.
2007	* If the threshold is exceeded after that, ntpd will exit
2008	* with a message to the system log. This option can be used
2009	* with the -q and -x options. See the tinker command for other options.
2010	* -i jaildir
2011	* Chroot the server to the directory jaildir. This option also implies
2012	* that the server attempts to drop root privileges at startup
2013	* (otherwise, chroot gives very little additional security).
2014	* You may need to also specify a -u option.
2015	* -k keyfile
2016	* Specify the name and path of the symmetric key file,
2017	* default /etc/ntp/keys. This is the same operation
2018	* as the "keys FILE" configuration command.
2019	* -l logfile
2020	* Specify the name and path of the log file. The default
2021	* is the system log file. This is the same operation as
2022	* the "logfile FILE" configuration command.
2023	* -L Do not listen to virtual IPs. The default is to listen.
2024	* -n Don't fork.
2025	* -N To the extent permitted by the operating system,
2026	* run the ntpd at the highest priority.
2027	* -p pidfile
2028	* Specify the name and path of the file used to record the ntpd
2029	* process ID. This is the same operation as the "pidfile FILE"
2030	* configuration command.
2031	* -P priority
2032	* To the extent permitted by the operating system,
2033	* run the ntpd at the specified priority.
2034	* -q Exit the ntpd just after the first time the clock is set.
2035	* This behavior mimics that of the ntpdate program, which is
2036	* to be retired. The -g and -x options can be used with this option.
2037	* Note: The kernel time discipline is disabled with this option.
2038	* -r broadcastdelay
2039	* Specify the default propagation delay from the broadcast/multicast
2040	* server to this client. This is necessary only if the delay
2041	* cannot be computed automatically by the protocol.
2042	* -s statsdir
2043	* Specify the directory path for files created by the statistics
2044	* facility. This is the same operation as the "statsdir DIR"
2045	* configuration command.
2046	* -t key
2047	* Add a key number to the trusted key list. This option can occur
2048	* more than once.
2049	* -u user[:group]
2050	* Specify a user, and optionally a group, to switch to.
2051	* -v variable
2052	* -V variable
2053	* Add a system variable listed by default.
2054	* -x Normally, the time is slewed if the offset is less than the step
2055	* threshold, which is 128 ms by default, and stepped if above
2056	* the threshold. This option sets the threshold to 600 s, which is
2057	* well within the accuracy window to set the clock manually.
2058	* Note: since the slew rate of typical Unix kernels is limited
2059	* to 0.5 ms/s, each second of adjustment requires an amortization
2060	* interval of 2000 s. Thus, an adjustment as much as 600 s
2061	* will take almost 14 days to complete. This option can be used
2062	* with the -g and -q options. See the tinker command for other options.
2063	* Note: The kernel time discipline is disabled with this option.
2064	*/
2065
2066	/* By doing init in a separate function we decrease stack usage
2067	* in main loop.
2068	*/
2069	static NOINLINE void ntp_init(char **argv)
2070	{
2071	unsigned opts;
2072	llist_t *peers;
2073
2074	srandom(getpid());
2075
2076	if (getuid())
2077	bb_error_msg_and_die("%s", bb_msg_you_must_be_root);
2078
2079	/* Set some globals */
2080	G.stratum = MAXSTRAT;
2081	if (BURSTPOLL != 0)
2082	G.poll_exp = BURSTPOLL; /* speeds up initial sync */
2083	G.last_script_run = G.reftime = G.last_update_recv_time = gettime1900d(); /* sets G.cur_time too */
2084
2085	/* Parse options */
2086	peers = NULL;
2087	opt_complementary = "dd:p::wn"; /* d: counter; p: list; -w implies -n */
2088	opts = getopt32(argv,
2089	"nqNx" /* compat */
2090	"wp:S:"IF_FEATURE_NTPD_SERVER("l") /* NOT compat */
2091	"d" /* compat */
2092	"46aAbgL", /* compat, ignored */
2093	&peers, &G.script_name, &G.verbose);
2094	if (!(opts & (OPT_p|OPT_l)))
2095	bb_show_usage();
2096	// if (opts & OPT_x) /* disable stepping, only slew is allowed */
2097	// G.time_was_stepped = 1;
2098	if (peers) {
2099	while (peers)
2100	add_peers(llist_pop(&peers));
2101	} else {
2102	/* -l but no peers: "stratum 1 server" mode */
2103	G.stratum = 1;
2104	}
2105	if (!(opts & OPT_n)) {
2106	bb_daemonize_or_rexec(DAEMON_DEVNULL_STDIO, argv);
2107	logmode = LOGMODE_NONE;
2108	}
2109	#if ENABLE_FEATURE_NTPD_SERVER
2110	G_listen_fd = -1;
2111	if (opts & OPT_l) {
2112	G_listen_fd = create_and_bind_dgram_or_die(NULL, 123);
2113	socket_want_pktinfo(G_listen_fd);
2114	setsockopt(G_listen_fd, IPPROTO_IP, IP_TOS, &const_IPTOS_LOWDELAY, sizeof(const_IPTOS_LOWDELAY));
2115	}
2116	#endif
2117	/* I hesitate to set -20 prio. -15 should be high enough for timekeeping */
2118	if (opts & OPT_N)
2119	setpriority(PRIO_PROCESS, 0, -15);
2120
2121	/* If network is up, syncronization occurs in ~10 seconds.
2122	* We give "ntpd -q" 10 seconds to get first reply,
2123	* then another 50 seconds to finish syncing.
2124	*
2125	* I tested ntpd 4.2.6p1 and apparently it never exits
2126	* (will try forever), but it does not feel right.
2127	* The goal of -q is to act like ntpdate: set time
2128	* after a reasonably small period of polling, or fail.
2129	*/
2130	if (opts & OPT_q) {
2131	option_mask32 |= OPT_qq;
2132	alarm(10);
2133	}
2134
2135	bb_signals(0
2136	| (1 << SIGTERM)
2137	| (1 << SIGINT)
2138	| (1 << SIGALRM)
2139	, record_signo
2140	);
2141	bb_signals(0
2142	| (1 << SIGPIPE)
2143	| (1 << SIGCHLD)
2144	, SIG_IGN
2145	);
2146	}
2147
2148	int ntpd_main(int argc UNUSED_PARAM, char **argv) MAIN_EXTERNALLY_VISIBLE;
2149	int ntpd_main(int argc UNUSED_PARAM, char **argv)
2150	{
2151	#undef G
2152	struct globals G;
2153	struct pollfd *pfd;
2154	peer_t **idx2peer;
2155	unsigned cnt;
2156
2157	memset(&G, 0, sizeof(G));
2158	SET_PTR_TO_GLOBALS(&G);
2159
2160	ntp_init(argv);
2161
2162	/* If ENABLE_FEATURE_NTPD_SERVER, + 1 for listen_fd: */
2163	cnt = G.peer_cnt + ENABLE_FEATURE_NTPD_SERVER;
2164	idx2peer = xzalloc(sizeof(idx2peer[0]) * cnt);
2165	pfd = xzalloc(sizeof(pfd[0]) * cnt);
2166
2167	/* Countdown: we never sync before we sent INITIAL_SAMPLES+1
2168	* packets to each peer.
2169	* NB: if some peer is not responding, we may end up sending
2170	* fewer packets to it and more to other peers.
2171	* NB2: sync usually happens using INITIAL_SAMPLES packets,
2172	* since last reply does not come back instantaneously.
2173	*/
2174	cnt = G.peer_cnt * (INITIAL_SAMPLES + 1);
2175
2176	write_pidfile(CONFIG_PID_FILE_PATH "/ntpd.pid");
2177
2178	while (!bb_got_signal) {
2179	llist_t *item;
2180	unsigned i, j;
2181	int nfds, timeout;
2182	double nextaction;
2183
2184	/* Nothing between here and poll() blocks for any significant time */
2185
2186	nextaction = G.cur_time + 3600;
2187
2188	i = 0;
2189	#if ENABLE_FEATURE_NTPD_SERVER
2190	if (G_listen_fd != -1) {
2191	pfd[0].fd = G_listen_fd;
2192	pfd[0].events = POLLIN;
2193	i++;
2194	}
2195	#endif
2196	/* Pass over peer list, send requests, time out on receives */
2197	for (item = G.ntp_peers; item != NULL; item = item->link) {
2198	peer_t *p = (peer_t *) item->data;
2199
2200	if (p->next_action_time <= G.cur_time) {
2201	if (p->p_fd == -1) {
2202	/* Time to send new req */
2203	if (--cnt == 0) {
2204	G.initial_poll_complete = 1;
2205	}
2206	send_query_to_peer(p);
2207	} else {
2208	/* Timed out waiting for reply */
2209	close(p->p_fd);
2210	p->p_fd = -1;
2211	timeout = poll_interval(-2); /* -2: try a bit sooner */
2212	bb_error_msg("timed out waiting for %s, reach 0x%02x, next query in %us",
2213	p->p_dotted, p->reachable_bits, timeout);
2214	set_next(p, timeout);
2215	}
2216	}
2217
2218	if (p->next_action_time < nextaction)
2219	nextaction = p->next_action_time;
2220
2221	if (p->p_fd >= 0) {
2222	/* Wait for reply from this peer */
2223	pfd[i].fd = p->p_fd;
2224	pfd[i].events = POLLIN;
2225	idx2peer[i] = p;
2226	i++;
2227	}
2228	}
2229
2230	timeout = nextaction - G.cur_time;
2231	if (timeout < 0)
2232	timeout = 0;
2233	timeout++; /* (nextaction - G.cur_time) rounds down, compensating */
2234
2235	/* Here we may block */
2236	VERB2 {
2237	if (i > (ENABLE_FEATURE_NTPD_SERVER && G_listen_fd != -1)) {
2238	/* We wait for at least one reply.
2239	* Poll for it, without wasting time for message.
2240	* Since replies often come under 1 second, this also
2241	* reduces clutter in logs.
2242	*/
2243	nfds = poll(pfd, i, 1000);
2244	if (nfds != 0)
2245	goto did_poll;
2246	if (--timeout <= 0)
2247	goto did_poll;
2248	}
2249	bb_error_msg("poll:%us sockets:%u interval:%us", timeout, i, 1 << G.poll_exp);
2250	}
2251	nfds = poll(pfd, i, timeout * 1000);
2252	did_poll:
2253	gettime1900d(); /* sets G.cur_time */
2254	if (nfds <= 0) {
2255	if (!bb_got_signal /* poll wasn't interrupted by a signal */
2256	&& G.cur_time - G.last_script_run > 11*60
2257	) {
2258	/* Useful for updating battery-backed RTC and such */
2259	run_script("periodic", G.last_update_offset);
2260	gettime1900d(); /* sets G.cur_time */
2261	}
2262	goto check_unsync;
2263	}
2264
2265	/* Process any received packets */
2266	j = 0;
2267	#if ENABLE_FEATURE_NTPD_SERVER
2268	if (G.listen_fd != -1) {
2269	if (pfd[0].revents /* & (POLLIN|POLLERR)*/) {
2270	nfds--;
2271	recv_and_process_client_pkt(/*G.listen_fd*/);
2272	gettime1900d(); /* sets G.cur_time */
2273	}
2274	j = 1;
2275	}
2276	#endif
2277	for (; nfds != 0 && j < i; j++) {
2278	if (pfd[j].revents /* & (POLLIN|POLLERR)*/) {
2279	/*
2280	* At init, alarm was set to 10 sec.
2281	* Now we did get a reply.
2282	* Increase timeout to 50 seconds to finish syncing.
2283	*/
2284	if (option_mask32 & OPT_qq) {
2285	option_mask32 &= ~OPT_qq;
2286	alarm(50);
2287	}
2288	nfds--;
2289	recv_and_process_peer_pkt(idx2peer[j]);
2290	gettime1900d(); /* sets G.cur_time */
2291	}
2292	}
2293
2294	check_unsync:
2295	if (G.ntp_peers && G.stratum != MAXSTRAT) {
2296	for (item = G.ntp_peers; item != NULL; item = item->link) {
2297	peer_t *p = (peer_t *) item->data;
2298	if (p->reachable_bits)
2299	goto have_reachable_peer;
2300	}
2301	/* No peer responded for last 8 packets, panic */
2302	G.polladj_count = 0;
2303	G.poll_exp = MINPOLL;
2304	G.stratum = MAXSTRAT;
2305	run_script("unsync", 0.0);
2306	have_reachable_peer: ;
2307	}
2308	} /* while (!bb_got_signal) */
2309
2310	remove_pidfile(CONFIG_PID_FILE_PATH "/ntpd.pid");
2311	kill_myself_with_sig(bb_got_signal);
2312	}
2313
2314
2315
2316
2317
2318
2319	/*** openntpd-4.6 uses only adjtime, not adjtimex ***/
2320
2321	/*** ntp-4.2.6/ntpd/ntp_loopfilter.c - adjtimex usage ***/
2322
2323	#if 0
2324	static double
2325	direct_freq(double fp_offset)
2326	{
2327	#ifdef KERNEL_PLL
2328	/*
2329	* If the kernel is enabled, we need the residual offset to
2330	* calculate the frequency correction.
2331	*/
2332	if (pll_control && kern_enable) {
2333	memset(&ntv, 0, sizeof(ntv));
2334	ntp_adjtime(&ntv);
2335	#ifdef STA_NANO
2336	clock_offset = ntv.offset / 1e9;
2337	#else /* STA_NANO */
2338	clock_offset = ntv.offset / 1e6;
2339	#endif /* STA_NANO */
2340	drift_comp = FREQTOD(ntv.freq);
2341	}
2342	#endif /* KERNEL_PLL */
2343	set_freq((fp_offset - clock_offset) / (current_time - clock_epoch) + drift_comp);
2344	wander_resid = 0;
2345	return drift_comp;
2346	}
2347
2348	static void
2349	set_freq(double freq) /* frequency update */
2350	{
2351	char tbuf[80];
2352
2353	drift_comp = freq;
2354
2355	#ifdef KERNEL_PLL
2356	/*
2357	* If the kernel is enabled, update the kernel frequency.
2358	*/
2359	if (pll_control && kern_enable) {
2360	memset(&ntv, 0, sizeof(ntv));
2361	ntv.modes = MOD_FREQUENCY;
2362	ntv.freq = DTOFREQ(drift_comp);
2363	ntp_adjtime(&ntv);
2364	snprintf(tbuf, sizeof(tbuf), "kernel %.3f PPM", drift_comp * 1e6);
2365	report_event(EVNT_FSET, NULL, tbuf);
2366	} else {
2367	snprintf(tbuf, sizeof(tbuf), "ntpd %.3f PPM", drift_comp * 1e6);
2368	report_event(EVNT_FSET, NULL, tbuf);
2369	}
2370	#else /* KERNEL_PLL */
2371	snprintf(tbuf, sizeof(tbuf), "ntpd %.3f PPM", drift_comp * 1e6);
2372	report_event(EVNT_FSET, NULL, tbuf);
2373	#endif /* KERNEL_PLL */
2374	}
2375
2376	...
2377	...
2378	...
2379
2380	#ifdef KERNEL_PLL
2381	/*
2382	* This code segment works when clock adjustments are made using
2383	* precision time kernel support and the ntp_adjtime() system
2384	* call. This support is available in Solaris 2.6 and later,
2385	* Digital Unix 4.0 and later, FreeBSD, Linux and specially
2386	* modified kernels for HP-UX 9 and Ultrix 4. In the case of the
2387	* DECstation 5000/240 and Alpha AXP, additional kernel
2388	* modifications provide a true microsecond clock and nanosecond
2389	* clock, respectively.
2390	*
2391	* Important note: The kernel discipline is used only if the
2392	* step threshold is less than 0.5 s, as anything higher can
2393	* lead to overflow problems. This might occur if some misguided
2394	* lad set the step threshold to something ridiculous.
2395	*/
2396	if (pll_control && kern_enable) {
2397
2398	#define MOD_BITS (MOD_OFFSET | MOD_MAXERROR | MOD_ESTERROR | MOD_STATUS | MOD_TIMECONST)
2399
2400	/*
2401	* We initialize the structure for the ntp_adjtime()
2402	* system call. We have to convert everything to
2403	* microseconds or nanoseconds first. Do not update the
2404	* system variables if the ext_enable flag is set. In
2405	* this case, the external clock driver will update the
2406	* variables, which will be read later by the local
2407	* clock driver. Afterwards, remember the time and
2408	* frequency offsets for jitter and stability values and
2409	* to update the frequency file.
2410	*/
2411	memset(&ntv, 0, sizeof(ntv));
2412	if (ext_enable) {
2413	ntv.modes = MOD_STATUS;
2414	} else {
2415	#ifdef STA_NANO
2416	ntv.modes = MOD_BITS | MOD_NANO;
2417	#else /* STA_NANO */
2418	ntv.modes = MOD_BITS;
2419	#endif /* STA_NANO */
2420	if (clock_offset < 0)
2421	dtemp = -.5;
2422	else
2423	dtemp = .5;
2424	#ifdef STA_NANO
2425	ntv.offset = (int32)(clock_offset * 1e9 + dtemp);
2426	ntv.constant = sys_poll;
2427	#else /* STA_NANO */
2428	ntv.offset = (int32)(clock_offset * 1e6 + dtemp);
2429	ntv.constant = sys_poll - 4;
2430	#endif /* STA_NANO */
2431	ntv.esterror = (u_int32)(clock_jitter * 1e6);
2432	ntv.maxerror = (u_int32)((sys_rootdelay / 2 + sys_rootdisp) * 1e6);
2433	ntv.status = STA_PLL;
2434
2435	/*
2436	* Enable/disable the PPS if requested.
2437	*/
2438	if (pps_enable) {
2439	if (!(pll_status & STA_PPSTIME))
2440	report_event(EVNT_KERN,
2441	NULL, "PPS enabled");
2442	ntv.status |= STA_PPSTIME | STA_PPSFREQ;
2443	} else {
2444	if (pll_status & STA_PPSTIME)
2445	report_event(EVNT_KERN,
2446	NULL, "PPS disabled");
2447	ntv.status &= ~(STA_PPSTIME | STA_PPSFREQ);
2448	}
2449	if (sys_leap == LEAP_ADDSECOND)
2450	ntv.status |= STA_INS;
2451	else if (sys_leap == LEAP_DELSECOND)
2452	ntv.status |= STA_DEL;
2453	}
2454
2455	/*
2456	* Pass the stuff to the kernel. If it squeals, turn off
2457	* the pps. In any case, fetch the kernel offset,
2458	* frequency and jitter.
2459	*/
2460	if (ntp_adjtime(&ntv) == TIME_ERROR) {
2461	if (!(ntv.status & STA_PPSSIGNAL))
2462	report_event(EVNT_KERN, NULL,
2463	"PPS no signal");
2464	}
2465	pll_status = ntv.status;
2466	#ifdef STA_NANO
2467	clock_offset = ntv.offset / 1e9;
2468	#else /* STA_NANO */
2469	clock_offset = ntv.offset / 1e6;
2470	#endif /* STA_NANO */
2471	clock_frequency = FREQTOD(ntv.freq);
2472
2473	/*
2474	* If the kernel PPS is lit, monitor its performance.
2475	*/
2476	if (ntv.status & STA_PPSTIME) {
2477	#ifdef STA_NANO
2478	clock_jitter = ntv.jitter / 1e9;
2479	#else /* STA_NANO */
2480	clock_jitter = ntv.jitter / 1e6;
2481	#endif /* STA_NANO */
2482	}
2483
2484	#if defined(STA_NANO) && NTP_API == 4
2485	/*
2486	* If the TAI changes, update the kernel TAI.
2487	*/
2488	if (loop_tai != sys_tai) {
2489	loop_tai = sys_tai;
2490	ntv.modes = MOD_TAI;
2491	ntv.constant = sys_tai;
2492	ntp_adjtime(&ntv);
2493	}
2494	#endif /* STA_NANO */
2495	}
2496	#endif /* KERNEL_PLL */
2497	#endif
2498