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dd6673bac

Denys Vlasenko

2010-01-01

FAILED Duration: 33s

Subject

ntpd: replace openntp's clock discipline with ntpd's

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Architecture: x86_64-linux-gnu Compiler: gcc (Ubuntu 11.4.0-1ubuntu1~22.04.3) 11.4.0

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Commit Diff GitHub →

networking/ntpd.c +1985 -0

networking/ntpd.c+1985 -0

@@ -0,0 +1,1985 @@
+	/*
+	* NTP client/server, based on OpenNTPD 3.9p1
+	*
+	* Author: Adam Tkac <[email protected]>
+	*
+	* Licensed under GPLv2, see file LICENSE in this tarball for details.
+	*
+	* Parts of OpenNTPD clock syncronization code is replaced by
+	* code which is based on ntp-4.2.6. It carries the following
+	* copyright notice:
+	*
+	***********************************************************************
+	* *
+	* Copyright (c) University of Delaware 1992-2009 *
+	* *
+	* Permission to use, copy, modify, and distribute this software and *
+	* its documentation for any purpose with or without fee is hereby *
+	* granted, provided that the above copyright notice appears in all *
+	* copies and that both the copyright notice and this permission *
+	* notice appear in supporting documentation, and that the name *
+	* University of Delaware not be used in advertising or publicity *
+	* pertaining to distribution of the software without specific, *
+	* written prior permission. The University of Delaware makes no *
+	* representations about the suitability this software for any *
+	* purpose. It is provided "as is" without express or implied *
+	* warranty. *
+	* *
+	***********************************************************************
+	*/
+	#include "libbb.h"
+	#include <math.h>
+	#include <netinet/ip.h> /* For IPTOS_LOWDELAY definition */
+	#include <sys/timex.h>
+	#ifndef IPTOS_LOWDELAY
+	# define IPTOS_LOWDELAY 0x10
+	#endif
+	#ifndef IP_PKTINFO
+	# error "Sorry, your kernel has to support IP_PKTINFO"
+	#endif
+
+
+	#define RETRY_INTERVAL 5 /* on error, retry in N secs */
+	#define QUERYTIME_MAX 15 /* wait for reply up to N secs */
+
+	#define FREQ_TOLERANCE 15e-6 /* % frequency tolerance (15 PPM) */
+	#define MINPOLL 4 /* % minimum poll interval (6: 64 s) */
+	#define MAXPOLL 12 /* % maximum poll interval (12: 1.1h, 17: 36.4h) (was 17) */
+	#define MINDISP 0.01 /* % minimum dispersion (s) */
+	#define MAXDISP 16 /* maximum dispersion (s) */
+	#define MAXSTRAT 16 /* maximum stratum (infinity metric) */
+	#define MAXDIST 1 /* % distance threshold (s) */
+	#define MIN_SELECTED 1 /* % minimum intersection survivors */
+	#define MIN_CLUSTERED 3 /* % minimum cluster survivors */
+
+	#define MAXFREQ 0.000500 /* frequency tolerance (500 PPM) */
+
+	/* Clock discipline parameters and constants */
+	#define STEP_THRESHOLD 0.128 /* step threshold (s) */
+	#define WATCH_THRESHOLD 150 /* stepout threshold (s). std ntpd uses 900 (11 mins (!)) */
+	/* NB: set WATCH_THRESHOLD to ~60 when debugging to save time) */
+	#define PANIC_THRESHOLD 1000 /* panic threshold (s) */
+
+	/* Poll-adjust threshold.
+	* When we see that offset is small enough compared to discipline jitter,
+	* we grow a counter: += poll_ext. When it goes over POLLADJ_LIMIT,
+	* we poll_ext++. If offset isn't small, counter -= poll_ext*2,
+	* and when it goes below -POLLADJ_LIMIT, we poll_ext--
+	*/
+	#define POLLADJ_LIMIT 30
+	/* If offset < POLLADJ_GATE * discipline_jitter, then we can increase
+	* poll interval (we think we can't improve timekeeping
+	* by staying at smaller poll).
+	*/
+	#define POLLADJ_GATE 4
+	/* Compromise Allan intercept (s). doc uses 1500, std ntpd uses 512 */
+	#define ALLAN 512
+	/* PLL loop gain */
+	#define PLL 65536
+	/* FLL loop gain [why it depends on MAXPOLL??] */
+	#define FLL (MAXPOLL + 1)
+	/* Parameter averaging constant */
+	#define AVG 4
+
+	/* Verbosity control (max level of -dddd options accepted).
+	* max 5 is very talkative (and bloated). 2 is non-bloated,
+	* production level setting.
+	*/
+	#define MAX_VERBOSE 2
+
+	#define VERB1 if (MAX_VERBOSE && G.verbose)
+	#define VERB2 if (MAX_VERBOSE >= 2 && G.verbose >= 2)
+	#define VERB3 if (MAX_VERBOSE >= 3 && G.verbose >= 3)
+	#define VERB4 if (MAX_VERBOSE >= 4 && G.verbose >= 4)
+	#define VERB5 if (MAX_VERBOSE >= 5 && G.verbose >= 5)
+
+
+	enum {
+	NTP_VERSION = 4,
+	NTP_MAXSTRATUM = 15,
+
+	NTP_DIGESTSIZE = 16,
+	NTP_MSGSIZE_NOAUTH = 48,
+	NTP_MSGSIZE = (NTP_MSGSIZE_NOAUTH + 4 + NTP_DIGESTSIZE),
+
+	/* Status Masks */
+	MODE_MASK = (7 << 0),
+	VERSION_MASK = (7 << 3),
+	VERSION_SHIFT = 3,
+	LI_MASK = (3 << 6),
+
+	/* Leap Second Codes (high order two bits of m_status) */
+	LI_NOWARNING = (0 << 6), /* no warning */
+	LI_PLUSSEC = (1 << 6), /* add a second (61 seconds) */
+	LI_MINUSSEC = (2 << 6), /* minus a second (59 seconds) */
+	LI_ALARM = (3 << 6), /* alarm condition */
+
+	/* Mode values */
+	MODE_RES0 = 0, /* reserved */
+	MODE_SYM_ACT = 1, /* symmetric active */
+	MODE_SYM_PAS = 2, /* symmetric passive */
+	MODE_CLIENT = 3, /* client */
+	MODE_SERVER = 4, /* server */
+	MODE_BROADCAST = 5, /* broadcast */
+	MODE_RES1 = 6, /* reserved for NTP control message */
+	MODE_RES2 = 7, /* reserved for private use */
+	};
+
+	//TODO: better base selection
+	#define OFFSET_1900_1970 2208988800UL /* 1970 - 1900 in seconds */
+
+	#define NUM_DATAPOINTS 8
+
+	typedef struct {
+	uint32_t int_partl;
+	uint32_t fractionl;
+	} l_fixedpt_t;
+
+	typedef struct {
+	uint16_t int_parts;
+	uint16_t fractions;
+	} s_fixedpt_t;
+
+	typedef struct {
+	uint8_t m_status; /* status of local clock and leap info */
+	uint8_t m_stratum;
+	uint8_t m_ppoll; /* poll value */
+	int8_t m_precision_exp;
+	s_fixedpt_t m_rootdelay;
+	s_fixedpt_t m_rootdisp;
+	uint32_t m_refid;
+	l_fixedpt_t m_reftime;
+	l_fixedpt_t m_orgtime;
+	l_fixedpt_t m_rectime;
+	l_fixedpt_t m_xmttime;
+	uint32_t m_keyid;
+	uint8_t m_digest[NTP_DIGESTSIZE];
+	} msg_t;
+
+	typedef struct {
+	double d_recv_time;
+	double d_offset;
+	double d_dispersion;
+	} datapoint_t;
+
+	typedef struct {
+	len_and_sockaddr *p_lsa;
+	char *p_dotted;
+	/* when to send new query (if p_fd == -1)
+	* or when receive times out (if p_fd >= 0): */
+	time_t next_action_time;
+	int p_fd;
+	int datapoint_idx;
+	uint32_t lastpkt_refid;
+	uint8_t lastpkt_leap;
+	uint8_t lastpkt_stratum;
+	uint8_t p_reachable_bits;
+	double p_xmttime;
+	double lastpkt_recv_time;
+	double lastpkt_delay;
+	double lastpkt_rootdelay;
+	double lastpkt_rootdisp;
+	/* produced by filter algorithm: */
+	double filter_offset;
+	double filter_dispersion;
+	double filter_jitter;
+	datapoint_t filter_datapoint[NUM_DATAPOINTS];
+	/* last sent packet: */
+	msg_t p_xmt_msg;
+	} peer_t;
+
+
+	enum {
+	OPT_n = (1 << 0),
+	OPT_q = (1 << 1),
+	OPT_N = (1 << 2),
+	OPT_x = (1 << 3),
+	/* Insert new options above this line. */
+	/* Non-compat options: */
+	OPT_p = (1 << 4),
+	OPT_l = (1 << 5) * ENABLE_FEATURE_NTPD_SERVER,
+	};
+
+	struct globals {
+	/* total round trip delay to currently selected reference clock */
+	double rootdelay;
+	/* reference timestamp: time when the system clock was last set or corrected */
+	double reftime;
+	/* total dispersion to currently selected reference clock */
+	double rootdisp;
+	llist_t *ntp_peers;
+	#if ENABLE_FEATURE_NTPD_SERVER
+	int listen_fd;
+	#endif
+	unsigned verbose;
+	unsigned peer_cnt;
+	/* refid: 32-bit code identifying the particular server or reference clock
+	* in stratum 0 packets this is a four-character ASCII string,
+	* called the kiss code, used for debugging and monitoring
+	* in stratum 1 packets this is a four-character ASCII string
+	* assigned to the reference clock by IANA. Example: "GPS "
+	* in stratum 2+ packets, it's IPv4 address or 4 first bytes of MD5 hash of IPv6
+	*/
+	uint32_t refid;
+	uint8_t leap;
+	/* precision is defined as the larger of the resolution and time to
+	* read the clock, in log2 units. For instance, the precision of a
+	* mains-frequency clock incrementing at 60 Hz is 16 ms, even when the
+	* system clock hardware representation is to the nanosecond.
+	*
+	* Delays, jitters of various kinds are clamper down to precision.
+	*
+	* If precision_sec is too large, discipline_jitter gets clamped to it
+	* and if offset is much smaller than discipline_jitter, poll interval
+	* grows even though we really can benefit from staying at smaller one,
+	* collecting non-lagged datapoits and correcting the offset.
+	* (Lagged datapoits exist when poll_exp is large but we still have
+	* systematic offset error - the time distance between datapoints
+	* is significat and older datapoints have smaller offsets.
+	* This makes our offset estimation a bit smaller than reality)
+	* Due to this effect, setting G_precision_sec close to
+	* STEP_THRESHOLD isn't such a good idea - offsets may grow
+	* too big and we will step. I observed it with -6.
+	*
+	* OTOH, setting precision too small would result in futile attempts
+	* to syncronize to the unachievable precision.
+	*
+	* -6 is 1/64 sec, -7 is 1/128 sec and so on.
+	*/
+	#define G_precision_exp -8
+	#define G_precision_sec (1.0 / (1 << (- G_precision_exp)))
+	uint8_t stratum;
+	/* Bool. After set to 1, never goes back to 0: */
+	//TODO: fix logic:
+	// uint8_t time_was_stepped;
+	uint8_t adjtimex_was_done;
+
+	uint8_t discipline_state; // doc calls it c.state
+	uint8_t poll_exp; // s.poll
+	int polladj_count; // c.count
+	double discipline_jitter; // c.jitter
+	double last_update_offset; // c.last
+	double discipline_freq_drift; // c.freq
+	//TODO: conditionally calculate wander? it's used only for logging
+	double discipline_wander; // c.wander
+	double last_update_recv_time; // s.t
+	//TODO: add s.jitter - grep for it here and see clock_combine() in doc
+	};
+	#define G (*ptr_to_globals)
+
+	static const int const_IPTOS_LOWDELAY = IPTOS_LOWDELAY;
+
+
+	static double LOG2D(int a)
+	{
+	if (a < 0)
+	return 1.0 / (1UL << -a);
+	return 1UL << a;
+	}
+	static ALWAYS_INLINE double SQUARE(double x)
+	{
+	return x * x;
+	}
+	static ALWAYS_INLINE double MAXD(double a, double b)
+	{
+	if (a > b)
+	return a;
+	return b;
+	}
+	static ALWAYS_INLINE double MIND(double a, double b)
+	{
+	if (a < b)
+	return a;
+	return b;
+	}
+	#define SQRT(x) (sqrt(x))
+
+	static double
+	gettime1900d(void)
+	{
+	struct timeval tv;
+	gettimeofday(&tv, NULL); /* never fails */
+	return (tv.tv_sec + 1.0e-6 * tv.tv_usec + OFFSET_1900_1970);
+	}
+
+	static void
+	d_to_tv(double d, struct timeval *tv)
+	{
+	tv->tv_sec = (long)d;
+	tv->tv_usec = (d - tv->tv_sec) * 1000000;
+	}
+
+	static double
+	lfp_to_d(l_fixedpt_t lfp)
+	{
+	double ret;
+	lfp.int_partl = ntohl(lfp.int_partl);
+	lfp.fractionl = ntohl(lfp.fractionl);
+	ret = (double)lfp.int_partl + ((double)lfp.fractionl / UINT_MAX);
+	return ret;
+	}
+	static double
+	sfp_to_d(s_fixedpt_t sfp)
+	{
+	double ret;
+	sfp.int_parts = ntohs(sfp.int_parts);
+	sfp.fractions = ntohs(sfp.fractions);
+	ret = (double)sfp.int_parts + ((double)sfp.fractions / USHRT_MAX);
+	return ret;
+	}
+	#if ENABLE_FEATURE_NTPD_SERVER
+	static l_fixedpt_t
+	d_to_lfp(double d)
+	{
+	l_fixedpt_t lfp;
+	lfp.int_partl = (uint32_t)d;
+	lfp.fractionl = (uint32_t)((d - lfp.int_partl) * UINT_MAX);
+	lfp.int_partl = htonl(lfp.int_partl);
+	lfp.fractionl = htonl(lfp.fractionl);
+	return lfp;
+	}
+	static s_fixedpt_t
+	d_to_sfp(double d)
+	{
+	s_fixedpt_t sfp;
+	sfp.int_parts = (uint16_t)d;
+	sfp.fractions = (uint16_t)((d - sfp.int_parts) * USHRT_MAX);
+	sfp.int_parts = htons(sfp.int_parts);
+	sfp.fractions = htons(sfp.fractions);
+	return sfp;
+	}
+	#endif
+
+	static double
+	dispersion(const datapoint_t *dp, double t)
+	{
+	return dp->d_dispersion + FREQ_TOLERANCE * (t - dp->d_recv_time);
+	}
+
+	static double
+	root_distance(peer_t *p, double t)
+	{
+	/* The root synchronization distance is the maximum error due to
+	* all causes of the local clock relative to the primary server.
+	* It is defined as half the total delay plus total dispersion
+	* plus peer jitter.
+	*/
+	return MAXD(MINDISP, p->lastpkt_rootdelay + p->lastpkt_delay) / 2
+	+ p->lastpkt_rootdisp
+	+ p->filter_dispersion
+	+ FREQ_TOLERANCE * (t - p->lastpkt_recv_time)
+	+ p->filter_jitter;
+	}
+
+	static void
+	set_next(peer_t *p, unsigned t)
+	{
+	p->next_action_time = time(NULL) + t;
+	}
+
+	/*
+	* Peer clock filter and its helpers
+	*/
+	static void
+	filter_datapoints(peer_t *p, double t)
+	{
+	int i, idx;
+	double minoff, maxoff, wavg, sum, w;
+	double x = x;
+
+	minoff = maxoff = p->filter_datapoint[0].d_offset;
+	for (i = 1; i < NUM_DATAPOINTS; i++) {
+	if (minoff > p->filter_datapoint[i].d_offset)
+	minoff = p->filter_datapoint[i].d_offset;
+	if (maxoff < p->filter_datapoint[i].d_offset)
+	maxoff = p->filter_datapoint[i].d_offset;
+	}
+
+	idx = p->datapoint_idx; /* most recent datapoint */
+	/* Average offset:
+	* Drop two outliers and take weighted average of the rest:
+	* most_recent/2 + older1/4 + older2/8 ... + older5/32 + older6/32
+	* we use older6/32, not older6/64 since sum of weights should be 1:
+	* 1/2 + 1/4 + 1/8 + 1/16 + 1/32 + 1/32 = 1
+	*/
+	wavg = 0;
+	w = 0.5;
+	// n-1
+	// --- dispersion(i)
+	// filter_dispersion = \ -------------
+	// / (i+1)
+	// --- 2
+	// i=0
+	sum = 0;
+	for (i = 0; i < NUM_DATAPOINTS; i++) {
+	VERB4 {
+	bb_error_msg("datapoint[%d]: off:%f disp:%f(%f) age:%f%s",
+	i,
+	p->filter_datapoint[idx].d_offset,
+	p->filter_datapoint[idx].d_dispersion, dispersion(&p->filter_datapoint[idx], t),
+	t - p->filter_datapoint[idx].d_recv_time,
+	(minoff == p->filter_datapoint[idx].d_offset \|\| maxoff == p->filter_datapoint[idx].d_offset)
+	? " (outlier by offset)" : ""
+	);
+	}
+
+	sum += dispersion(&p->filter_datapoint[idx], t) / (2 << i);
+
+	if (minoff == p->filter_datapoint[idx].d_offset) {
+	minoff -= 1;
+	} else
+	if (maxoff == p->filter_datapoint[idx].d_offset) {
+	maxoff += 1;
+	} else {
+	x = p->filter_datapoint[idx].d_offset * w;
+	wavg += x;
+	w /= 2;
+	}
+
+	idx = (idx - 1) & (NUM_DATAPOINTS - 1);
+	}
+	wavg += x; /* add another older6/64 to form older6/32 */
+	p->filter_offset = wavg;
+	p->filter_dispersion = sum;
+
+	// +----- -----+ ^ 1/2
+	// \| n-1 \|
+	// \| --- \|
+	// 1 \| \ 2 \|
+	// filter_jitter = --- * \| / (avg-offset_j) \|
+	// n \| --- \|
+	// \| j=0 \|
+	// +----- -----+
+	// where n is the number of valid datapoints in the filter (n > 1);
+	// if filter_jitter < precision then filter_jitter = precision
+	sum = 0;
+	for (i = 0; i < NUM_DATAPOINTS; i++) {
+	sum += SQUARE(wavg - p->filter_datapoint[i].d_offset);
+	}
+	sum = SQRT(sum) / NUM_DATAPOINTS;
+	p->filter_jitter = sum > G_precision_sec ? sum : G_precision_sec;
+
+	VERB3 bb_error_msg("filter offset:%f disp:%f jitter:%f",
+	p->filter_offset, p->filter_dispersion, p->filter_jitter);
+
+	}
+
+	static void
+	reset_peer_stats(peer_t *p, double t, double offset)
+	{
+	int i;
+	for (i = 0; i < NUM_DATAPOINTS; i++) {
+	if (offset < 16 * STEP_THRESHOLD) {
+	p->filter_datapoint[i].d_recv_time -= offset;
+	if (p->filter_datapoint[i].d_offset != 0) {
+	p->filter_datapoint[i].d_offset -= offset;
+	}
+	} else {
+	p->filter_datapoint[i].d_recv_time = t;
+	p->filter_datapoint[i].d_offset = 0;
+	p->filter_datapoint[i].d_dispersion = MAXDISP;
+	}
+	}
+	if (offset < 16 * STEP_THRESHOLD) {
+	p->lastpkt_recv_time -= offset;
+	} else {
+	p->p_reachable_bits = 0;
+	p->lastpkt_recv_time = t;
+	}
+	filter_datapoints(p, t); /* recalc p->filter_xxx */
+	p->next_action_time -= (time_t)offset;
+	VERB5 bb_error_msg("%s->lastpkt_recv_time=%f", p->p_dotted, p->lastpkt_recv_time);
+	}
+
+	static void
+	add_peers(char *s)
+	{
+	peer_t *p;
+
+	p = xzalloc(sizeof(*p));
+	p->p_lsa = xhost2sockaddr(s, 123);
+	p->p_dotted = xmalloc_sockaddr2dotted_noport(&p->p_lsa->u.sa);
+	p->p_fd = -1;
+	p->p_xmt_msg.m_status = MODE_CLIENT \| (NTP_VERSION << 3);
+	p->next_action_time = time(NULL); /* = set_next(p, 0); */
+	reset_peer_stats(p, gettime1900d(), 16 * STEP_THRESHOLD);
+	/* Speed up initial sync: with small offsets from peers,
+	* 3 samples will sync
+	*/
+	p->filter_datapoint[6].d_dispersion = 0;
+	p->filter_datapoint[7].d_dispersion = 0;
+
+	llist_add_to(&G.ntp_peers, p);
+	G.peer_cnt++;
+	}
+
+	static int
+	do_sendto(int fd,
+	const struct sockaddr from, const struct sockaddr to, socklen_t addrlen,
+	msg_t *msg, ssize_t len)
+	{
+	ssize_t ret;
+
+	errno = 0;
+	if (!from) {
+	ret = sendto(fd, msg, len, MSG_DONTWAIT, to, addrlen);
+	} else {
+	ret = send_to_from(fd, msg, len, MSG_DONTWAIT, to, from, addrlen);
+	}
+	if (ret != len) {
+	bb_perror_msg("send failed");
+	return -1;
+	}
+	return 0;
+	}
+
+	static int
+	send_query_to_peer(peer_t *p)
+	{
+	// Why do we need to bind()?
+	// See what happens when we don't bind:
+	//
+	// socket(PF_INET, SOCK_DGRAM, IPPROTO_IP) = 3
+	// setsockopt(3, SOL_IP, IP_TOS, [16], 4) = 0
+	// gettimeofday({1259071266, 327885}, NULL) = 0
+	// sendto(3, "xxx", 48, MSG_DONTWAIT, {sa_family=AF_INET, sin_port=htons(123), sin_addr=inet_addr("10.34.32.125")}, 16) = 48
+	// ^^^ we sent it from some source port picked by kernel.
+	// time(NULL) = 1259071266
+	// write(2, "ntpd: entering poll 15 secs\n", 28) = 28
+	// poll([{fd=3, events=POLLIN}], 1, 15000) = 1 ([{fd=3, revents=POLLIN}])
+	// recv(3, "yyy", 68, MSG_DONTWAIT) = 48
+	// ^^^ this recv will receive packets to any local port!
+	//
+	// Uncomment this and use strace to see it in action:
+	#define PROBE_LOCAL_ADDR // { len_and_sockaddr lsa; lsa.len = LSA_SIZEOF_SA; getsockname(p->query.fd, &lsa.u.sa, &lsa.len); }
+
+	if (p->p_fd == -1) {
+	int fd, family;
+	len_and_sockaddr *local_lsa;
+
+	family = p->p_lsa->u.sa.sa_family;
+	p->p_fd = fd = xsocket_type(&local_lsa, family, SOCK_DGRAM);
+	/* local_lsa has "null" address and port 0 now.
+	* bind() ensures we have a particular port selected by kernel
+	* and remembered in p->p_fd, thus later recv(p->p_fd)
+	* receives only packets sent to this port.
+	*/
+	PROBE_LOCAL_ADDR
+	xbind(fd, &local_lsa->u.sa, local_lsa->len);
+	PROBE_LOCAL_ADDR
+	#if ENABLE_FEATURE_IPV6
+	if (family == AF_INET)
+	#endif
+	setsockopt(fd, IPPROTO_IP, IP_TOS, &const_IPTOS_LOWDELAY, sizeof(const_IPTOS_LOWDELAY));
+	free(local_lsa);
+	}
+
+	/*
+	* Send out a random 64-bit number as our transmit time. The NTP
+	* server will copy said number into the originate field on the
+	* response that it sends us. This is totally legal per the SNTP spec.
+	*
+	* The impact of this is two fold: we no longer send out the current
+	* system time for the world to see (which may aid an attacker), and
+	* it gives us a (not very secure) way of knowing that we're not
+	* getting spoofed by an attacker that can't capture our traffic
+	* but can spoof packets from the NTP server we're communicating with.
+	*
+	* Save the real transmit timestamp locally.
+	*/
+	p->p_xmt_msg.m_xmttime.int_partl = random();
+	p->p_xmt_msg.m_xmttime.fractionl = random();
+	p->p_xmttime = gettime1900d();
+
+	if (do_sendto(p->p_fd, /from:/ NULL, /to:/ &p->p_lsa->u.sa, /addrlen:/ p->p_lsa->len,
+	&p->p_xmt_msg, NTP_MSGSIZE_NOAUTH) == -1
+	) {
+	close(p->p_fd);
+	p->p_fd = -1;
+	set_next(p, RETRY_INTERVAL);
+	return -1;
+	}
+
+	p->p_reachable_bits <<= 1;
+	VERB1 bb_error_msg("sent query to %s", p->p_dotted);
+	set_next(p, QUERYTIME_MAX);
+
+	return 0;
+	}
+
+
+	static void
+	step_time(double offset)
+	{
+	double dtime;
+	struct timeval tv;
+	char buf[80];
+	time_t tval;
+
+	gettimeofday(&tv, NULL); /* never fails */
+	dtime = offset + tv.tv_sec;
+	dtime += 1.0e-6 * tv.tv_usec;
+	d_to_tv(dtime, &tv);
+
+	if (settimeofday(&tv, NULL) == -1)
+	bb_perror_msg_and_die("settimeofday");
+
+	tval = tv.tv_sec;
+	strftime(buf, sizeof(buf), "%a %b %e %H:%M:%S %Z %Y", localtime(&tval));
+
+	bb_error_msg("setting clock to %s (offset %fs)", buf, offset);
+
+	// G.time_was_stepped = 1;
+	}
+
+
+	/*
+	* Selection and clustering, and their helpers
+	*/
+	typedef struct {
+	peer_t *p;
+	int type;
+	double edge;
+	} point_t;
+	static int
+	compare_point_edge(const void aa, const void bb)
+	{
+	const point_t *a = aa;
+	const point_t *b = bb;
+	if (a->edge < b->edge) {
+	return -1;
+	}
+	return (a->edge > b->edge);
+	}
+	typedef struct {
+	peer_t *p;
+	double metric;
+	} survivor_t;
+	static int
+	compare_survivor_metric(const void aa, const void bb)
+	{
+	const survivor_t *a = aa;
+	const survivor_t *b = bb;
+	if (a->metric < b->metric)
+	return -1;
+	return (a->metric > b->metric);
+	}
+	static int
+	fit(peer_t *p, double rd)
+	{
+	if (p->p_reachable_bits == 0) {
+	VERB3 bb_error_msg("peer %s unfit for selection: unreachable", p->p_dotted);
+	return 0;
+	}
+	//TODO: we never accept such packets anyway, right?
+	if ((p->lastpkt_leap & LI_ALARM) == LI_ALARM
+	\|\| p->lastpkt_stratum >= MAXSTRAT
+	) {
+	VERB3 bb_error_msg("peer %s unfit for selection: bad status/stratum", p->p_dotted);
+	return 0;
+	}
+	/* rd is root_distance(p, t) */
+	if (rd > MAXDIST + FREQ_TOLERANCE * (1 << G.poll_exp)) {
+	VERB3 bb_error_msg("peer %s unfit for selection: root distance too high", p->p_dotted);
+	return 0;
+	}
+	//TODO
+	// /* Do we have a loop? */
+	// if (p->refid == p->dstaddr \|\| p->refid == s.refid)
+	// return 0;
+	return 1;
+	}
+	static peer_t*
+	select_and_cluster(double t)
+	{
+	llist_t *item;
+	int i, j;
+	int size = 3 * G.peer_cnt;
+	/* for selection algorithm */
+	point_t point[size];
+	unsigned num_points, num_candidates;
+	double low, high;
+	unsigned num_falsetickers;
+	/* for cluster algorithm */
+	survivor_t survivor[size];
+	unsigned num_survivors;
+
+	/* Selection */
+
+	num_points = 0;
+	item = G.ntp_peers;
+	while (item != NULL) {
+	peer_t p = (peer_t ) item->data;
+	double rd = root_distance(p, t);
+	double offset = p->filter_offset;
+
+	if (!fit(p, rd)) {
+	item = item->link;
+	continue;
+	}
+
+	VERB4 bb_error_msg("interval: [%f %f %f] %s",
+	offset - rd,
+	offset,
+	offset + rd,
+	p->p_dotted
+	);
+	point[num_points].p = p;
+	point[num_points].type = -1;
+	point[num_points].edge = offset - rd;
+	num_points++;
+	point[num_points].p = p;
+	point[num_points].type = 0;
+	point[num_points].edge = offset;
+	num_points++;
+	point[num_points].p = p;
+	point[num_points].type = 1;
+	point[num_points].edge = offset + rd;
+	num_points++;
+	item = item->link;
+	}
+	num_candidates = num_points / 3;
+	if (num_candidates == 0) {
+	VERB3 bb_error_msg("no valid datapoints, no peer selected");
+	return NULL; /* never happers? */
+	}
+	//TODO: sorting does not seem to be done in reference code
+	qsort(point, num_points, sizeof(point[0]), compare_point_edge);
+
+	/* Start with the assumption that there are no falsetickers.
+	* Attempt to find a nonempty intersection interval containing
+	* the midpoints of all truechimers.
+	* If a nonempty interval cannot be found, increase the number
+	* of assumed falsetickers by one and try again.
+	* If a nonempty interval is found and the number of falsetickers
+	* is less than the number of truechimers, a majority has been found
+	* and the midpoint of each truechimer represents
+	* the candidates available to the cluster algorithm.
+	*/
+	num_falsetickers = 0;
+	while (1) {
+	int c;
+	unsigned num_midpoints = 0;
+
+	low = 1 << 9;
+	high = - (1 << 9);
+	c = 0;
+	for (i = 0; i < num_points; i++) {
+	/* We want to do:
+	* if (point[i].type == -1) c++;
+	* if (point[i].type == 1) c--;
+	* and it's simpler to do it this way:
+	*/
+	c -= point[i].type;
+	if (c >= num_candidates - num_falsetickers) {
+	/* If it was c++ and it got big enough... */
+	low = point[i].edge;
+	break;
+	}
+	if (point[i].type == 0)
+	num_midpoints++;
+	}
+	c = 0;
+	for (i = num_points-1; i >= 0; i--) {
+	c += point[i].type;
+	if (c >= num_candidates - num_falsetickers) {
+	high = point[i].edge;
+	break;
+	}
+	if (point[i].type == 0)
+	num_midpoints++;
+	}
+	/* If the number of midpoints is greater than the number
+	* of allowed falsetickers, the intersection contains at
+	* least one truechimer with no midpoint - bad.
+	* Also, interval should be nonempty.
+	*/
+	if (num_midpoints <= num_falsetickers && low < high)
+	break;
+	num_falsetickers++;
+	if (num_falsetickers * 2 >= num_candidates) {
+	VERB3 bb_error_msg("too many falsetickers:%d (candidates:%d), no peer selected",
+	num_falsetickers, num_candidates);
+	return NULL;
+	}
+	}
+	VERB3 bb_error_msg("selected interval: [%f, %f]; candidates:%d falsetickers:%d",
+	low, high, num_candidates, num_falsetickers);
+
+	/* Clustering */
+
+	/* Construct a list of survivors (p, metric)
+	* from the chime list, where metric is dominated
+	* first by stratum and then by root distance.
+	* All other things being equal, this is the order of preference.
+	*/
+	num_survivors = 0;
+	for (i = 0; i < num_points; i++) {
+	peer_t *p;
+
+	if (point[i].edge < low \|\| point[i].edge > high)
+	continue;
+	p = point[i].p;
+	survivor[num_survivors].p = p;
+	//TODO: save root_distance in point_t and reuse here?
+	survivor[num_survivors].metric = MAXDIST * p->lastpkt_stratum + root_distance(p, t);
+	VERB4 bb_error_msg("survivor[%d] metric:%f peer:%s",
+	num_survivors, survivor[num_survivors].metric, p->p_dotted);
+	num_survivors++;
+	}
+	/* There must be at least MIN_SELECTED survivors to satisfy the
+	* correctness assertions. Ordinarily, the Byzantine criteria
+	* require four survivors, but for the demonstration here, one
+	* is acceptable.
+	*/
+	if (num_survivors < MIN_SELECTED) {
+	VERB3 bb_error_msg("num_survivors %d < %d, no peer selected",
+	num_survivors, MIN_SELECTED);
+	return NULL;
+	}
+
+	//looks like this is ONLY used by the fact that later we pick survivor[0].
+	//we can avoid sorting then, just find the minimum once!
+	qsort(survivor, num_survivors, sizeof(survivor[0]), compare_survivor_metric);
+
+	/* For each association p in turn, calculate the selection
+	* jitter p->sjitter as the square root of the sum of squares
+	* (p->offset - q->offset) over all q associations. The idea is
+	* to repeatedly discard the survivor with maximum selection
+	* jitter until a termination condition is met.
+	*/
+	while (1) {
+	unsigned max_idx = max_idx;
+	double max_selection_jitter = max_selection_jitter;
+	double min_jitter = min_jitter;
+
+	if (num_survivors <= MIN_CLUSTERED) {
+	bb_error_msg("num_survivors %d <= %d, not discarding more",
+	num_survivors, MIN_CLUSTERED);
+	break;
+	}
+
+	/* To make sure a few survivors are left
+	* for the clustering algorithm to chew on,
+	* we stop if the number of survivors
+	* is less than or equal to MIN_CLUSTERED (3).
+	*/
+	for (i = 0; i < num_survivors; i++) {
+	double selection_jitter_sq;
+	peer_t *p = survivor[i].p;
+
+	if (i == 0 \|\| p->filter_jitter < min_jitter)
+	min_jitter = p->filter_jitter;
+
+	selection_jitter_sq = 0;
+	for (j = 0; j < num_survivors; j++) {
+	peer_t *q = survivor[j].p;
+	//TODO: where is 1/(n-1) * ... multiplier?
+	selection_jitter_sq += SQUARE(p->filter_offset - q->filter_offset);
+	}
+	if (i == 0 \|\| selection_jitter_sq > max_selection_jitter) {
+	max_selection_jitter = selection_jitter_sq;
+	max_idx = i;
+	}
+	VERB5 bb_error_msg("survivor %d selection_jitter^2:%f",
+	i, selection_jitter_sq);
+	}
+	max_selection_jitter = SQRT(max_selection_jitter);
+	VERB4 bb_error_msg("max_selection_jitter (at %d):%f min_jitter:%f",
+	max_idx, max_selection_jitter, min_jitter);
+
+	/* If the maximum selection jitter is less than the
+	* minimum peer jitter, then tossing out more survivors
+	* will not lower the minimum peer jitter, so we might
+	* as well stop.
+	*/
+	if (max_selection_jitter < min_jitter) {
+	VERB3 bb_error_msg("max_selection_jitter:%f < min_jitter:%f, num_survivors:%d, not discarding more",
+	max_selection_jitter, min_jitter, num_survivors);
+	break;
+	}
+
+	/* Delete survivor[max_idx] from the list
+	* and go around again.
+	*/
+	VERB5 bb_error_msg("dropping survivor %d", max_idx);
+	num_survivors--;
+	while (max_idx < num_survivors) {
+	survivor[max_idx] = survivor[max_idx + 1];
+	max_idx++;
+	}
+	}
+
+	/* Pick the best clock. If the old system peer is on the list
+	* and at the same stratum as the first survivor on the list,
+	* then don't do a clock hop. Otherwise, select the first
+	* survivor on the list as the new system peer.
+	*/
+	//TODO - see clock_combine()
+	VERB3 bb_error_msg("selected peer %s filter_offset:%f age:%f",
+	survivor[0].p->p_dotted,
+	survivor[0].p->filter_offset,
+	t - survivor[0].p->lastpkt_recv_time
+	);
+	return survivor[0].p;
+	}
+
+
+	/*
+	* Local clock discipline and its helpers
+	*/
+	static void
+	set_new_values(int disc_state, double offset, double recv_time)
+	{
+	/* Enter new state and set state variables. Note we use the time
+	* of the last clock filter sample, which must be earlier than
+	* the current time.
+	*/
+	VERB3 bb_error_msg("disc_state=%d last_update_offset=%f last_update_recv_time=%f",
+	disc_state, offset, recv_time);
+	G.discipline_state = disc_state;
+	G.last_update_offset = offset;
+	G.last_update_recv_time = recv_time;
+	}
+	/* Clock state definitions */
+	#define STATE_NSET 0 /* initial state, "nothing is set" */
+	#define STATE_FSET 1 /* frequency set from file */
+	#define STATE_SPIK 2 /* spike detected */
+	#define STATE_FREQ 3 /* initial frequency */
+	#define STATE_SYNC 4 /* clock synchronized (normal operation) */
+	/* Return: -1: decrease poll interval, 0: leave as is, 1: increase */
+	static int
+	update_local_clock(peer_t *p, double t)
+	{
+	int rc;
+	long old_tmx_offset;
+	struct timex tmx;
+	double offset = p->filter_offset;
+	double recv_time = p->lastpkt_recv_time;
+	double abs_offset;
+	double freq_drift;
+	double since_last_update;
+	double etemp, dtemp;
+
+	abs_offset = fabs(offset);
+
+	/* If the offset is too large, give up and go home */
+	if (abs_offset > PANIC_THRESHOLD) {
+	bb_error_msg_and_die("offset %f far too big, exiting", offset);
+	}
+
+	/* If this is an old update, for instance as the result
+	* of a system peer change, avoid it. We never use
+	* an old sample or the same sample twice.
+	*/
+	if (recv_time <= G.last_update_recv_time) {
+	VERB3 bb_error_msg("same or older datapoint: %f >= %f, not using it",
+	G.last_update_recv_time, recv_time);
+	return 0; /* "leave poll interval as is" */
+	}
+
+	/* Clock state machine transition function. This is where the
+	* action is and defines how the system reacts to large time
+	* and frequency errors.
+	*/
+	since_last_update = recv_time - G.reftime;
+	freq_drift = 0;
+	if (G.discipline_state == STATE_FREQ) {
+	/* Ignore updates until the stepout threshold */
+	if (since_last_update < WATCH_THRESHOLD) {
+	VERB3 bb_error_msg("measuring drift, datapoint ignored, %f sec remains",
+	WATCH_THRESHOLD - since_last_update);
+	return 0; /* "leave poll interval as is" */
+	}
+	freq_drift = (offset - G.last_update_offset) / since_last_update;
+	}
+
+	/* There are two main regimes: when the
+	* offset exceeds the step threshold and when it does not.
+	*/
+	if (abs_offset > STEP_THRESHOLD) {
+	llist_t *item;
+
+	switch (G.discipline_state) {
+	case STATE_SYNC:
+	/* The first outlyer: ignore it, switch to SPIK state */
+	VERB3 bb_error_msg("offset:%f - spike detected", offset);
+	G.discipline_state = STATE_SPIK;
+	return -1; /* "decrease poll interval" */
+
+	case STATE_SPIK:
+	/* Ignore succeeding outlyers until either an inlyer
+	* is found or the stepout threshold is exceeded.
+	*/
+	if (since_last_update < WATCH_THRESHOLD) {
+	VERB3 bb_error_msg("spike detected, datapoint ignored, %f sec remains",
+	WATCH_THRESHOLD - since_last_update);
+	return -1; /* "decrease poll interval" */
+	}
+	/* fall through: we need to step */
+	} /* switch */
+
+	/* Step the time and clamp down the poll interval.
+	*
+	* In NSET state an initial frequency correction is
+	* not available, usually because the frequency file has
+	* not yet been written. Since the time is outside the
+	* capture range, the clock is stepped. The frequency
+	* will be set directly following the stepout interval.
+	*
+	* In FSET state the initial frequency has been set
+	* from the frequency file. Since the time is outside
+	* the capture range, the clock is stepped immediately,
+	* rather than after the stepout interval. Guys get
+	* nervous if it takes 17 minutes to set the clock for
+	* the first time.
+	*
+	* In SPIK state the stepout threshold has expired and
+	* the phase is still above the step threshold. Note
+	* that a single spike greater than the step threshold
+	* is always suppressed, even at the longer poll
+	* intervals.
+	*/
+	VERB3 bb_error_msg("stepping time by %f; poll_exp=MINPOLL", offset);
+	step_time(offset);
+	if (option_mask32 & OPT_q) {
+	/* We were only asked to set time once. Done. */
+	exit(0);
+	}
+
+	G.polladj_count = 0;
+	G.poll_exp = MINPOLL;
+	G.stratum = MAXSTRAT;
+	for (item = G.ntp_peers; item != NULL; item = item->link) {
+	peer_t pp = (peer_t ) item->data;
+	reset_peer_stats(pp, t, offset);
+	}
+	if (G.discipline_state == STATE_NSET) {
+	set_new_values(STATE_FREQ, /offset:/ 0, recv_time);
+	return 1; /* "ok to increase poll interval" */
+	}
+	set_new_values(STATE_SYNC, /offset:/ 0, recv_time);
+
+	} else { /* abs_offset <= STEP_THRESHOLD */
+
+	if (G.poll_exp < MINPOLL) {
+	VERB3 bb_error_msg("saw small offset %f, disabling burst mode", offset);
+	G.poll_exp = MINPOLL;
+	}
+
+	/* Compute the clock jitter as the RMS of exponentially
+	* weighted offset differences. Used by the poll adjust code.
+	*/
+	etemp = SQUARE(G.discipline_jitter);
+	dtemp = SQUARE(MAXD(fabs(offset - G.last_update_offset), G_precision_sec));
+	G.discipline_jitter = SQRT(etemp + (dtemp - etemp) / AVG);
+	VERB3 bb_error_msg("discipline jitter=%f", G.discipline_jitter);
+
+	switch (G.discipline_state) {
+	case STATE_NSET:
+	if (option_mask32 & OPT_q) {
+	/* We were only asked to set time once.
+	* The clock is precise enough, no need to step.
+	*/
+	exit(0);
+	}
+	/* This is the first update received and the frequency
+	* has not been initialized. The first thing to do
+	* is directly measure the oscillator frequency.
+	*/
+	set_new_values(STATE_FREQ, offset, recv_time);
+	VERB3 bb_error_msg("transitioning to FREQ, datapoint ignored");
+	return -1; /* "decrease poll interval" */
+
+	#if 0 /* this is dead code for now */
+	case STATE_FSET:
+	/* This is the first update and the frequency
+	* has been initialized. Adjust the phase, but
+	* don't adjust the frequency until the next update.
+	*/
+	set_new_values(STATE_SYNC, offset, recv_time);
+	/* freq_drift remains 0 */
+	break;
+	#endif
+
+	case STATE_FREQ:
+	/* since_last_update >= WATCH_THRESHOLD, we waited enough.
+	* Correct the phase and frequency and switch to SYNC state.
+	* freq_drift was already estimated (see code above)
+	*/
+	set_new_values(STATE_SYNC, offset, recv_time);
+	break;
+
+	default:
+	/* Compute freq_drift due to PLL and FLL contributions.
+	*
+	* The FLL and PLL frequency gain constants
+	* depend on the poll interval and Allan
+	* intercept. The FLL is not used below one-half
+	* the Allan intercept. Above that the loop gain
+	* increases in steps to 1 / AVG.
+	*/
+	if ((1 << G.poll_exp) > ALLAN / 2) {
+	etemp = FLL - G.poll_exp;
+	if (etemp < AVG)
+	etemp = AVG;
+	freq_drift += (offset - G.last_update_offset) / (MAXD(since_last_update, ALLAN) * etemp);
+	}
+	/* For the PLL the integration interval
+	* (numerator) is the minimum of the update
+	* interval and poll interval. This allows
+	* oversampling, but not undersampling.
+	*/
+	etemp = MIND(since_last_update, (1 << G.poll_exp));
+	dtemp = (4 * PLL) << G.poll_exp;
+	freq_drift += offset * etemp / SQUARE(dtemp);
+	set_new_values(STATE_SYNC, offset, recv_time);
+	break;
+	}
+	G.stratum = p->lastpkt_stratum + 1;
+	}
+
+	G.reftime = t;
+	G.leap = p->lastpkt_leap;
+	G.refid = p->lastpkt_refid;
+	G.rootdelay = p->lastpkt_rootdelay + p->lastpkt_delay;
+	dtemp = p->filter_jitter; // SQRT(SQUARE(p->filter_jitter) + SQUARE(s.jitter));
+	dtemp += MAXD(p->filter_dispersion + FREQ_TOLERANCE * (t - p->lastpkt_recv_time) + abs_offset, MINDISP);
+	G.rootdisp = p->lastpkt_rootdisp + dtemp;
+	VERB3 bb_error_msg("updating leap/refid/reftime/rootdisp from peer %s", p->p_dotted);
+
+	/* We are in STATE_SYNC now, but did not do adjtimex yet.
+	* (Any other state does not reach this, they all return earlier)
+	* By this time, freq_drift and G.last_update_offset are set
+	* to values suitable for adjtimex.
+	*
+	* Calculate the new frequency drift and frequency stability (wander).
+	* Compute the clock wander as the RMS of exponentially weighted
+	* frequency differences. This is not used directly, but can,
+	* along with the jitter, be a highly useful monitoring and
+	* debugging tool.
+	*/
+	dtemp = G.discipline_freq_drift + freq_drift;
+	G.discipline_freq_drift = MAXD(MIND(MAXFREQ, dtemp), -MAXFREQ);
+	etemp = SQUARE(G.discipline_wander);
+	dtemp = SQUARE(dtemp);
+	G.discipline_wander = SQRT(etemp + (dtemp - etemp) / AVG);
+
+	VERB3 {
+	bb_error_msg("discipline freq_drift=%.9f(int:%ld corr:%e) wander=%f",
+	G.discipline_freq_drift,
+	(long)(G.discipline_freq_drift * 65536e6),
+	freq_drift,
+	G.discipline_wander);
+	memset(&tmx, 0, sizeof(tmx));
+	if (adjtimex(&tmx) < 0)
+	bb_perror_msg_and_die("adjtimex");
+	VERB3 bb_error_msg("p adjtimex freq:%ld offset:%ld constant:%ld status:0x%x",
+	tmx.freq, tmx.offset, tmx.constant, tmx.status);
+	}
+
+	old_tmx_offset = 0;
+	if (!G.adjtimex_was_done) {
+	G.adjtimex_was_done = 1;
+	/* When we use adjtimex for the very first time,
+	* we need to ADD to pre-existing tmx.offset - it may be !0
+	*/
+	memset(&tmx, 0, sizeof(tmx));
+	if (adjtimex(&tmx) < 0)
+	bb_perror_msg_and_die("adjtimex");
+	old_tmx_offset = tmx.offset;
+	}
+	memset(&tmx, 0, sizeof(tmx));
+	#if 0
+	//doesn't work, offset remains 0 (!):
+	//ntpd: set adjtimex freq:1786097 tmx.offset:77487
+	//ntpd: prev adjtimex freq:1786097 tmx.offset:0
+	//ntpd: cur adjtimex freq:1786097 tmx.offset:0
+	tmx.modes = ADJ_FREQUENCY \| ADJ_OFFSET;
+	/* 65536 is one ppm */
+	tmx.freq = G.discipline_freq_drift * 65536e6;
+	tmx.offset = G.last_update_offset * 1000000; /* usec */
+	#endif
+	tmx.modes = ADJ_OFFSET \| ADJ_STATUS \| ADJ_TIMECONST;// \| ADJ_MAXERROR \| ADJ_ESTERROR;
+	tmx.offset = (G.last_update_offset * 1000000) /* usec */
+	/* + (G.last_update_offset < 0 ? -0.5 : 0.5) - too small to bother */
+	+ old_tmx_offset; /* almost always 0 */
+	tmx.status = STA_PLL;
+	//if (sys_leap == LEAP_ADDSECOND)
+	// tmx.status \|= STA_INS;
+	//else if (sys_leap == LEAP_DELSECOND)
+	// tmx.status \|= STA_DEL;
+	tmx.constant = G.poll_exp - 4;
+	//tmx.esterror = (u_int32)(clock_jitter * 1e6);
+	//tmx.maxerror = (u_int32)((sys_rootdelay / 2 + sys_rootdisp) * 1e6);
+	VERB3 bb_error_msg("b adjtimex freq:%ld offset:%ld constant:%ld status:0x%x",
+	tmx.freq, tmx.offset, tmx.constant, tmx.status);
+	rc = adjtimex(&tmx);
+	if (rc < 0)
+	bb_perror_msg_and_die("adjtimex");
+	VERB3 {
+	bb_error_msg("adjtimex:%d freq:%ld offset:%ld constant:%ld status:0x%x",
+	rc, tmx.freq, tmx.offset, tmx.constant, tmx.status);
+	memset(&tmx, 0, sizeof(tmx));
+	if (adjtimex(&tmx) < 0)
+	bb_perror_msg_and_die("adjtimex");
+	VERB3 bb_error_msg("c adjtimex freq:%ld offset:%ld constant:%ld status:0x%x",
+	tmx.freq, tmx.offset, tmx.constant, tmx.status);
+	}
+	// #define STA_MODE 0x4000 /* mode (0 = PLL, 1 = FLL) (ro) */ - ?
+	// it appeared after a while:
+	//ntpd: p adjtimex freq:-14545653 offset:-5396 constant:10 status:0x41
+	//ntpd: c adjtimex freq:-14547835 offset:-8307 constant:10 status:0x1
+	//ntpd: p adjtimex freq:-14547835 offset:-6398 constant:10 status:0x41
+	//ntpd: c adjtimex freq:-14550486 offset:-10158 constant:10 status:0x1
+	//ntpd: p adjtimex freq:-14550486 offset:-6132 constant:10 status:0x41
+	//ntpd: c adjtimex freq:-14636129 offset:-10158 constant:10 status:0x4001
+	//ntpd: p adjtimex freq:-14636129 offset:-10002 constant:10 status:0x4041
+	//ntpd: c adjtimex freq:-14636245 offset:-7497 constant:10 status:0x1
+	//ntpd: p adjtimex freq:-14636245 offset:-4573 constant:10 status:0x41
+	//ntpd: c adjtimex freq:-14642034 offset:-11715 constant:10 status:0x1
+	//ntpd: p adjtimex freq:-14642034 offset:-4098 constant:10 status:0x41
+	//ntpd: c adjtimex freq:-14699112 offset:-11746 constant:10 status:0x4001
+	//ntpd: p adjtimex freq:-14699112 offset:-4239 constant:10 status:0x4041
+	//ntpd: c adjtimex freq:-14762330 offset:-12786 constant:10 status:0x4001
+	//ntpd: p adjtimex freq:-14762330 offset:-4434 constant:10 status:0x4041
+	//ntpd: b adjtimex freq:0 offset:-9669 constant:8 status:0x1
+	//ntpd: adjtimex:0 freq:-14809095 offset:-9669 constant:10 status:0x4001
+	//ntpd: c adjtimex freq:-14809095 offset:-9669 constant:10 status:0x4001
+
+	return 1; /* "ok to increase poll interval" */
+	}
+
+
+	/*
+	* We've got a new reply packet from a peer, process it
+	* (helpers first)
+	*/
+	static unsigned
+	retry_interval(void)
+	{
+	/* Local problem, want to retry soon */
+	unsigned interval, r;
+	interval = RETRY_INTERVAL;
+	r = random();
+	interval += r % (unsigned)(RETRY_INTERVAL / 4);
+	VERB3 bb_error_msg("chose retry interval:%u", interval);
+	return interval;
+	}
+	static unsigned
+	poll_interval(int exponent) /* exp is always -1 or 0 */
+	{
+	/* Want to send next packet at (1 << G.poll_exp) + small random value */
+	unsigned interval, r;
+	exponent += G.poll_exp; /* G.poll_exp is always > 0 */
+	/* never true: if (exp < 0) exp = 0; */
+	interval = 1 << exponent;
+	r = random();
+	interval += ((r & (interval-1)) >> 4) + ((r >> 8) & 1); /* + 1/16 of interval, max */
+	VERB3 bb_error_msg("chose poll interval:%u (poll_exp:%d exp:%d)", interval, G.poll_exp, exponent);
+	return interval;
+	}
+	static void
+	recv_and_process_peer_pkt(peer_t *p)
+	{
+	int rc;
+	ssize_t size;
+	msg_t msg;
+	double T1, T2, T3, T4;
+	unsigned interval;
+	datapoint_t *datapoint;
+	peer_t *q;
+
+	/* We can recvfrom here and check from.IP, but some multihomed
+	* ntp servers reply from their other IP.
+	* TODO: maybe we should check at least what we can: from.port == 123?
+	*/
+	size = recv(p->p_fd, &msg, sizeof(msg), MSG_DONTWAIT);
+	if (size == -1) {
+	bb_perror_msg("recv(%s) error", p->p_dotted);
+	if (errno == EHOSTUNREACH \|\| errno == EHOSTDOWN
+	\|\| errno == ENETUNREACH \|\| errno == ENETDOWN
+	\|\| errno == ECONNREFUSED \|\| errno == EADDRNOTAVAIL
+	\|\| errno == EAGAIN
+	) {
+	//TODO: always do this?
+	set_next(p, retry_interval());
+	goto close_sock;
+	}
+	xfunc_die();
+	}
+
+	if (size != NTP_MSGSIZE_NOAUTH && size != NTP_MSGSIZE) {
+	bb_error_msg("malformed packet received from %s", p->p_dotted);
+	goto bail;
+	}
+
+	if (msg.m_orgtime.int_partl != p->p_xmt_msg.m_xmttime.int_partl
+	\|\| msg.m_orgtime.fractionl != p->p_xmt_msg.m_xmttime.fractionl
+	) {
+	goto bail;
+	}
+
+	if ((msg.m_status & LI_ALARM) == LI_ALARM
+	\|\| msg.m_stratum == 0
+	\|\| msg.m_stratum > NTP_MAXSTRATUM
+	) {
+	// TODO: stratum 0 responses may have commands in 32-bit m_refid field:
+	// "DENY", "RSTR" - peer does not like us at all
+	// "RATE" - peer is overloaded, reduce polling freq
+	interval = poll_interval(0);
+	bb_error_msg("reply from %s: not synced, next query in %us", p->p_dotted, interval);
+	goto close_sock;
+	}
+
+	// /*
+	// * Verify the server is synchronized with valid stratum and
+	// * reference time not later than the transmit time.
+	// */
+	// if (p->lastpkt_leap == NOSYNC \|\| p->lastpkt_stratum >= MAXSTRAT)
+	// return; /* unsynchronized */
+	//
+	// /* Verify valid root distance */
+	// if (msg.m_rootdelay / 2 + msg.m_rootdisp >= MAXDISP \|\| p->lastpkt_reftime > msg.m_xmt)
+	// return; /* invalid header values */
+
+	p->lastpkt_leap = msg.m_status;
+	p->lastpkt_rootdelay = sfp_to_d(msg.m_rootdelay);
+	p->lastpkt_rootdisp = sfp_to_d(msg.m_rootdisp);
+	p->lastpkt_refid = msg.m_refid;
+
+	/*
+	* From RFC 2030 (with a correction to the delay math):
+	*
+	* Timestamp Name ID When Generated
+	* ------------------------------------------------------------
+	* Originate Timestamp T1 time request sent by client
+	* Receive Timestamp T2 time request received by server
+	* Transmit Timestamp T3 time reply sent by server
+	* Destination Timestamp T4 time reply received by client
+	*
+	* The roundtrip delay and local clock offset are defined as
+	*
+	* delay = (T4 - T1) - (T3 - T2); offset = ((T2 - T1) + (T3 - T4)) / 2
+	*/
+	T1 = p->p_xmttime;
+	T2 = lfp_to_d(msg.m_rectime);
+	T3 = lfp_to_d(msg.m_xmttime);
+	T4 = gettime1900d();
+
+	p->lastpkt_recv_time = T4;
+
+	VERB5 bb_error_msg("%s->lastpkt_recv_time=%f", p->p_dotted, p->lastpkt_recv_time);
+	p->datapoint_idx = p->p_reachable_bits ? (p->datapoint_idx + 1) % NUM_DATAPOINTS : 0;
+	datapoint = &p->filter_datapoint[p->datapoint_idx];
+	datapoint->d_recv_time = T4;
+	datapoint->d_offset = ((T2 - T1) + (T3 - T4)) / 2;
+	/* The delay calculation is a special case. In cases where the
+	* server and client clocks are running at different rates and
+	* with very fast networks, the delay can appear negative. In
+	* order to avoid violating the Principle of Least Astonishment,
+	* the delay is clamped not less than the system precision.
+	*/
+	p->lastpkt_delay = (T4 - T1) - (T3 - T2);
+	datapoint->d_dispersion = LOG2D(msg.m_precision_exp) + G_precision_sec;
+	if (!p->p_reachable_bits) {
+	/* 1st datapoint ever - replicate offset in every element */
+	int i;
+	for (i = 1; i < NUM_DATAPOINTS; i++) {
+	p->filter_datapoint[i].d_offset = datapoint->d_offset;
+	}
+	}
+
+	p->p_reachable_bits \|= 1;
+	VERB1 {
+	bb_error_msg("reply from %s: reach 0x%02x offset %f delay %f",
+	p->p_dotted,
+	p->p_reachable_bits,
+	datapoint->d_offset, p->lastpkt_delay);
+	}
+
+	/* Muck with statictics and update the clock */
+	filter_datapoints(p, T4);
+	q = select_and_cluster(T4);
+	rc = -1;
+	if (q)
+	rc = update_local_clock(q, T4);
+
+	if (rc != 0) {
+	/* Adjust the poll interval by comparing the current offset
+	* with the clock jitter. If the offset is less than
+	* the clock jitter times a constant, then the averaging interval
+	* is increased, otherwise it is decreased. A bit of hysteresis
+	* helps calm the dance. Works best using burst mode.
+	*/
+	VERB4 if (rc > 0) {
+	bb_error_msg("offset:%f POLLADJ_GATE*discipline_jitter:%f poll:%s",
+	q->filter_offset, POLLADJ_GATE * G.discipline_jitter,
+	fabs(q->filter_offset) < POLLADJ_GATE * G.discipline_jitter
+	? "grows" : "falls"
+	);
+	}
+	if (rc > 0 && fabs(q->filter_offset) < POLLADJ_GATE * G.discipline_jitter) {
+	G.polladj_count += G.poll_exp;
+	if (G.polladj_count > POLLADJ_LIMIT) {
+	G.polladj_count = 0;
+	if (G.poll_exp < MAXPOLL) {
+	G.poll_exp++;
+	VERB3 bb_error_msg("polladj: discipline_jitter:%f ++poll_exp=%d",
+	G.discipline_jitter, G.poll_exp);
+	}
+	} else {
+	VERB3 bb_error_msg("polladj: incr:%d", G.polladj_count);
+	}
+	} else {
+	G.polladj_count -= G.poll_exp * 2;
+	if (G.polladj_count < -POLLADJ_LIMIT) {
+	G.polladj_count = 0;
+	if (G.poll_exp > MINPOLL) {
+	G.poll_exp--;
+	VERB3 bb_error_msg("polladj: discipline_jitter:%f --poll_exp=%d",
+	G.discipline_jitter, G.poll_exp);
+	}
+	} else {
+	VERB3 bb_error_msg("polladj: decr:%d", G.polladj_count);
+	}
+	}
+	}
+
+	/* Decide when to send new query for this peer */
+	interval = poll_interval(0);
+	set_next(p, interval);
+
+	close_sock:
+	/* We do not expect any more packets from this peer for now.
+	* Closing the socket informs kernel about it.
+	* We open a new socket when we send a new query.
+	*/
+	close(p->p_fd);
+	p->p_fd = -1;
+	bail:
+	return;
+	}
+
+	#if ENABLE_FEATURE_NTPD_SERVER
+	static void
+	recv_and_process_client_pkt(void /int fd/)
+	{
+	ssize_t size;
+	uint8_t version;
+	double rectime;
+	len_and_sockaddr *to;
+	struct sockaddr *from;
+	msg_t msg;
+	uint8_t query_status;
+	l_fixedpt_t query_xmttime;
+
+	to = get_sock_lsa(G.listen_fd);
+	from = xzalloc(to->len);
+
+	size = recv_from_to(G.listen_fd, &msg, sizeof(msg), MSG_DONTWAIT, from, &to->u.sa, to->len);
+	if (size != NTP_MSGSIZE_NOAUTH && size != NTP_MSGSIZE) {
+	char *addr;
+	if (size < 0) {
+	if (errno == EAGAIN)
+	goto bail;
+	bb_perror_msg_and_die("recv");
+	}
+	addr = xmalloc_sockaddr2dotted_noport(from);
+	bb_error_msg("malformed packet received from %s: size %u", addr, (int)size);
+	free(addr);
+	goto bail;
+	}
+
+	query_status = msg.m_status;
+	query_xmttime = msg.m_xmttime;
+
+	/* Build a reply packet */
+	memset(&msg, 0, sizeof(msg));
+	msg.m_status = G.stratum < MAXSTRAT ? G.leap : LI_ALARM;
+	msg.m_status \|= (query_status & VERSION_MASK);
+	msg.m_status \|= ((query_status & MODE_MASK) == MODE_CLIENT) ?
+	MODE_SERVER : MODE_SYM_PAS;
+	msg.m_stratum = G.stratum;
+	msg.m_ppoll = G.poll_exp;
+	msg.m_precision_exp = G_precision_exp;
+	rectime = gettime1900d();
+	msg.m_xmttime = msg.m_rectime = d_to_lfp(rectime);
+	msg.m_reftime = d_to_lfp(G.reftime);
+	msg.m_orgtime = query_xmttime;
+	msg.m_rootdelay = d_to_sfp(G.rootdelay);
+	//simple code does not do this, fix simple code!
+	msg.m_rootdisp = d_to_sfp(G.rootdisp);
+	version = (query_status & VERSION_MASK); /* ... >> VERSION_SHIFT - done below instead */
+	msg.m_refid = G.refid; // (version > (3 << VERSION_SHIFT)) ? G.refid : G.refid3;
+
+	/* We reply from the local address packet was sent to,
+	* this makes to/from look swapped here: */
+	do_sendto(G.listen_fd,
+	/from:/ &to->u.sa, /to:/ from, /addrlen:/ to->len,
+	&msg, size);
+
+	bail:
+	free(to);
+	free(from);
+	}
+	#endif
+
+	/* Upstream ntpd's options:
+	*
+	* -4 Force DNS resolution of host names to the IPv4 namespace.
+	* -6 Force DNS resolution of host names to the IPv6 namespace.
+	* -a Require cryptographic authentication for broadcast client,
+	* multicast client and symmetric passive associations.
+	* This is the default.
+	* -A Do not require cryptographic authentication for broadcast client,
+	* multicast client and symmetric passive associations.
+	* This is almost never a good idea.
+	* -b Enable the client to synchronize to broadcast servers.
+	* -c conffile
+	* Specify the name and path of the configuration file,
+	* default /etc/ntp.conf
+	* -d Specify debugging mode. This option may occur more than once,
+	* with each occurrence indicating greater detail of display.
+	* -D level
+	* Specify debugging level directly.
+	* -f driftfile
+	* Specify the name and path of the frequency file.
+	* This is the same operation as the "driftfile FILE"
+	* configuration command.
+	* -g Normally, ntpd exits with a message to the system log
+	* if the offset exceeds the panic threshold, which is 1000 s
+	* by default. This option allows the time to be set to any value
+	* without restriction; however, this can happen only once.
+	* If the threshold is exceeded after that, ntpd will exit
+	* with a message to the system log. This option can be used
+	* with the -q and -x options. See the tinker command for other options.
+	* -i jaildir
+	* Chroot the server to the directory jaildir. This option also implies
+	* that the server attempts to drop root privileges at startup
+	* (otherwise, chroot gives very little additional security).
+	* You may need to also specify a -u option.
+	* -k keyfile
+	* Specify the name and path of the symmetric key file,
+	* default /etc/ntp/keys. This is the same operation
+	* as the "keys FILE" configuration command.
+	* -l logfile
+	* Specify the name and path of the log file. The default
+	* is the system log file. This is the same operation as
+	* the "logfile FILE" configuration command.
+	* -L Do not listen to virtual IPs. The default is to listen.
+	* -n Don't fork.
+	* -N To the extent permitted by the operating system,
+	* run the ntpd at the highest priority.
+	* -p pidfile
+	* Specify the name and path of the file used to record the ntpd
+	* process ID. This is the same operation as the "pidfile FILE"
+	* configuration command.
+	* -P priority
+	* To the extent permitted by the operating system,
+	* run the ntpd at the specified priority.
+	* -q Exit the ntpd just after the first time the clock is set.
+	* This behavior mimics that of the ntpdate program, which is
+	* to be retired. The -g and -x options can be used with this option.
+	* Note: The kernel time discipline is disabled with this option.
+	* -r broadcastdelay
+	* Specify the default propagation delay from the broadcast/multicast
+	* server to this client. This is necessary only if the delay
+	* cannot be computed automatically by the protocol.
+	* -s statsdir
+	* Specify the directory path for files created by the statistics
+	* facility. This is the same operation as the "statsdir DIR"
+	* configuration command.
+	* -t key
+	* Add a key number to the trusted key list. This option can occur
+	* more than once.
+	* -u user[:group]
+	* Specify a user, and optionally a group, to switch to.
+	* -v variable
+	* -V variable
+	* Add a system variable listed by default.
+	* -x Normally, the time is slewed if the offset is less than the step
+	* threshold, which is 128 ms by default, and stepped if above
+	* the threshold. This option sets the threshold to 600 s, which is
+	* well within the accuracy window to set the clock manually.
+	* Note: since the slew rate of typical Unix kernels is limited
+	* to 0.5 ms/s, each second of adjustment requires an amortization
+	* interval of 2000 s. Thus, an adjustment as much as 600 s
+	* will take almost 14 days to complete. This option can be used
+	* with the -g and -q options. See the tinker command for other options.
+	* Note: The kernel time discipline is disabled with this option.
+	*/
+
+	/* By doing init in a separate function we decrease stack usage
+	* in main loop.
+	*/
+	static NOINLINE void ntp_init(char **argv)
+	{
+	unsigned opts;
+	llist_t *peers;
+
+	srandom(getpid());
+
+	if (getuid())
+	bb_error_msg_and_die(bb_msg_you_must_be_root);
+
+	/* Set some globals */
+	#if 0
+	/* With constant b = 100, G.precision_exp is also constant -6.
+	* Uncomment this to verify.
+	*/
+	{
+	int prec = 0;
+	int b;
+	# if 0
+	struct timespec tp;
+	/* We can use sys_clock_getres but assuming 10ms tick should be fine */
+	clock_getres(CLOCK_REALTIME, &tp);
+	tp.tv_sec = 0;
+	tp.tv_nsec = 10000000;
+	b = 1000000000 / tp.tv_nsec; /* convert to Hz */
+	# else
+	b = 100; /* b = 1000000000/10000000 = 100 */
+	# endif
+	while (b > 1)
+	prec--, b >>= 1;
+	/G.precision_exp = prec;/
+	/G.precision_sec = (1.0 / (1 << (- prec)));/
+	bb_error_msg("G.precision_exp:%d sec:%f", prec, G_precision_sec); /* -6 */
+	}
+	#endif
+	G.stratum = MAXSTRAT;
+	G.poll_exp = 1; /* should use MINPOLL, but 1 speeds up initial sync */
+	G.reftime = G.last_update_recv_time = gettime1900d();
+
+	/* Parse options */
+	peers = NULL;
+	opt_complementary = "dd:p::"; /* d: counter, p: list */
+	opts = getopt32(argv,
+	"nqNx" /* compat */
+	"p:"IF_FEATURE_NTPD_SERVER("l") /* NOT compat */
+	"d" /* compat */
+	"46aAbgL", /* compat, ignored */
+	&peers, &G.verbose);
+	if (!(opts & (OPT_p\|OPT_l)))
+	bb_show_usage();
+	// if (opts & OPT_x) /* disable stepping, only slew is allowed */
+	// G.time_was_stepped = 1;
+	while (peers)
+	add_peers(llist_pop(&peers));
+	if (!(opts & OPT_n)) {
+	bb_daemonize_or_rexec(DAEMON_DEVNULL_STDIO, argv);
+	logmode = LOGMODE_NONE;
+	}
+	#if ENABLE_FEATURE_NTPD_SERVER
+	G.listen_fd = -1;
+	if (opts & OPT_l) {
+	G.listen_fd = create_and_bind_dgram_or_die(NULL, 123);
+	socket_want_pktinfo(G.listen_fd);
+	setsockopt(G.listen_fd, IPPROTO_IP, IP_TOS, &const_IPTOS_LOWDELAY, sizeof(const_IPTOS_LOWDELAY));
+	}
+	#endif
+	/* I hesitate to set -20 prio. -15 should be high enough for timekeeping */
+	if (opts & OPT_N)
+	setpriority(PRIO_PROCESS, 0, -15);
+
+	bb_signals((1 << SIGTERM) \| (1 << SIGINT), record_signo);
+	bb_signals((1 << SIGPIPE) \| (1 << SIGHUP), SIG_IGN);
+	}
+
+	int ntpd_main(int argc UNUSED_PARAM, char **argv) MAIN_EXTERNALLY_VISIBLE;
+	int ntpd_main(int argc UNUSED_PARAM, char **argv)
+	{
+	struct globals g;
+	struct pollfd *pfd;
+	peer_t **idx2peer;
+
+	memset(&g, 0, sizeof(g));
+	SET_PTR_TO_GLOBALS(&g);
+
+	ntp_init(argv);
+
+	{
+	/* if ENABLE_FEATURE_NTPD_SERVER, + 1 for listen_fd: */
+	unsigned cnt = g.peer_cnt + ENABLE_FEATURE_NTPD_SERVER;
+	idx2peer = xzalloc(sizeof(idx2peer[0]) * cnt);
+	pfd = xzalloc(sizeof(pfd[0]) * cnt);
+	}
+
+	while (!bb_got_signal) {
+	llist_t *item;
+	unsigned i, j;
+	unsigned sent_cnt, trial_cnt;
+	int nfds, timeout;
+	time_t cur_time, nextaction;
+
+	/* Nothing between here and poll() blocks for any significant time */
+
+	cur_time = time(NULL);
+	nextaction = cur_time + 3600;
+
+	i = 0;
+	#if ENABLE_FEATURE_NTPD_SERVER
+	if (g.listen_fd != -1) {
+	pfd[0].fd = g.listen_fd;
+	pfd[0].events = POLLIN;
+	i++;
+	}
+	#endif
+	/* Pass over peer list, send requests, time out on receives */
+	sent_cnt = trial_cnt = 0;
+	for (item = g.ntp_peers; item != NULL; item = item->link) {
+	peer_t p = (peer_t ) item->data;
+
+	/* Overflow-safe "if (p->next_action_time <= cur_time) ..." */
+	if ((int)(cur_time - p->next_action_time) >= 0) {
+	if (p->p_fd == -1) {
+	/* Time to send new req */
+	trial_cnt++;
+	if (send_query_to_peer(p) == 0)
+	sent_cnt++;
+	} else {
+	/* Timed out waiting for reply */
+	close(p->p_fd);
+	p->p_fd = -1;
+	timeout = poll_interval(-1); /* try a bit faster */
+	bb_error_msg("timed out waiting for %s, reach 0x%02x, next query in %us",
+	p->p_dotted, p->p_reachable_bits, timeout);
+	set_next(p, timeout);
+	}
+	}
+
+	if (p->next_action_time < nextaction)
+	nextaction = p->next_action_time;
+
+	if (p->p_fd >= 0) {
+	/* Wait for reply from this peer */
+	pfd[i].fd = p->p_fd;
+	pfd[i].events = POLLIN;
+	idx2peer[i] = p;
+	i++;
+	}
+	}
+
+	// if ((trial_cnt > 0 && sent_cnt == 0) \|\| g.peer_cnt == 0) {
+	// G.time_was_stepped = 1;
+	// }
+
+	timeout = nextaction - cur_time;
+	if (timeout < 1)
+	timeout = 1;
+
+	/* Here we may block */
+	VERB2 bb_error_msg("poll %us, sockets:%u", timeout, i);
+	nfds = poll(pfd, i, timeout * 1000);
+	if (nfds <= 0)
+	continue;
+
+	/* Process any received packets */
+	j = 0;
+	#if ENABLE_FEATURE_NTPD_SERVER
+	if (g.listen_fd != -1) {
+	if (pfd[0].revents /* & (POLLIN\|POLLERR)*/) {
+	nfds--;
+	recv_and_process_client_pkt(/g.listen_fd/);
+	}
+	j = 1;
+	}
+	#endif
+	for (; nfds != 0 && j < i; j++) {
+	if (pfd[j].revents /* & (POLLIN\|POLLERR)*/) {
+	nfds--;
+	recv_and_process_peer_pkt(idx2peer[j]);
+	}
+	}
+	} /* while (!bb_got_signal) */
+
+	kill_myself_with_sig(bb_got_signal);
+	}
+
+
+
+
+
+
+	/* openntpd-4.6 uses only adjtime, not adjtimex */
+
+	/* ntp-4.2.6/ntpd/ntp_loopfilter.c - adjtimex usage */
+
+	#if 0
+	static double
+	direct_freq(double fp_offset)
+	{
+
+	#ifdef KERNEL_PLL
+	/*
+	* If the kernel is enabled, we need the residual offset to
+	* calculate the frequency correction.
+	*/
+	if (pll_control && kern_enable) {
+	memset(&ntv, 0, sizeof(ntv));
+	ntp_adjtime(&ntv);
+	#ifdef STA_NANO
+	clock_offset = ntv.offset / 1e9;
+	#else /* STA_NANO */
+	clock_offset = ntv.offset / 1e6;
+	#endif /* STA_NANO */
+	drift_comp = FREQTOD(ntv.freq);
+	}
+	#endif /* KERNEL_PLL */
+	set_freq((fp_offset - clock_offset) / (current_time - clock_epoch) + drift_comp);
+	wander_resid = 0;
+	return drift_comp;
+	}
+
+	static void
+	set_freq(double freq) /* frequency update */
+	{
+	char tbuf[80];
+
+	drift_comp = freq;
+
+	#ifdef KERNEL_PLL
+	/*
+	* If the kernel is enabled, update the kernel frequency.
+	*/
+	if (pll_control && kern_enable) {
+	memset(&ntv, 0, sizeof(ntv));
+	ntv.modes = MOD_FREQUENCY;
+	ntv.freq = DTOFREQ(drift_comp);
+	ntp_adjtime(&ntv);
+	snprintf(tbuf, sizeof(tbuf), "kernel %.3f PPM", drift_comp * 1e6);
+	report_event(EVNT_FSET, NULL, tbuf);
+	} else {
+	snprintf(tbuf, sizeof(tbuf), "ntpd %.3f PPM", drift_comp * 1e6);
+	report_event(EVNT_FSET, NULL, tbuf);
+	}
+	#else /* KERNEL_PLL */
+	snprintf(tbuf, sizeof(tbuf), "ntpd %.3f PPM", drift_comp * 1e6);
+	report_event(EVNT_FSET, NULL, tbuf);
+	#endif /* KERNEL_PLL */
+	}
+
+	...
+	...
+	...
+
+	#ifdef KERNEL_PLL
+	/*
+	* This code segment works when clock adjustments are made using
+	* precision time kernel support and the ntp_adjtime() system
+	* call. This support is available in Solaris 2.6 and later,
+	* Digital Unix 4.0 and later, FreeBSD, Linux and specially
+	* modified kernels for HP-UX 9 and Ultrix 4. In the case of the
+	* DECstation 5000/240 and Alpha AXP, additional kernel
+	* modifications provide a true microsecond clock and nanosecond
+	* clock, respectively.
+	*
+	* Important note: The kernel discipline is used only if the
+	* step threshold is less than 0.5 s, as anything higher can
+	* lead to overflow problems. This might occur if some misguided
+	* lad set the step threshold to something ridiculous.
+	*/
+	if (pll_control && kern_enable) {
+
+	#define MOD_BITS (MOD_OFFSET \| MOD_MAXERROR \| MOD_ESTERROR \| MOD_STATUS \| MOD_TIMECONST)
+
+	/*
+	* We initialize the structure for the ntp_adjtime()
+	* system call. We have to convert everything to
+	* microseconds or nanoseconds first. Do not update the
+	* system variables if the ext_enable flag is set. In
+	* this case, the external clock driver will update the
+	* variables, which will be read later by the local
+	* clock driver. Afterwards, remember the time and
+	* frequency offsets for jitter and stability values and
+	* to update the frequency file.
+	*/
+	memset(&ntv, 0, sizeof(ntv));
+	if (ext_enable) {
+	ntv.modes = MOD_STATUS;
+	} else {
+	#ifdef STA_NANO
+	ntv.modes = MOD_BITS \| MOD_NANO;
+	#else /* STA_NANO */
+	ntv.modes = MOD_BITS;
+	#endif /* STA_NANO */
+	if (clock_offset < 0)
+	dtemp = -.5;
+	else
+	dtemp = .5;
+	#ifdef STA_NANO
+	ntv.offset = (int32)(clock_offset * 1e9 + dtemp);
+	ntv.constant = sys_poll;
+	#else /* STA_NANO */
+	ntv.offset = (int32)(clock_offset * 1e6 + dtemp);
+	ntv.constant = sys_poll - 4;
+	#endif /* STA_NANO */
+	ntv.esterror = (u_int32)(clock_jitter * 1e6);
+	ntv.maxerror = (u_int32)((sys_rootdelay / 2 + sys_rootdisp) * 1e6);
+	ntv.status = STA_PLL;
+
+	/*
+	* Enable/disable the PPS if requested.
+	*/
+	if (pps_enable) {
+	if (!(pll_status & STA_PPSTIME))
+	report_event(EVNT_KERN,
+	NULL, "PPS enabled");
+	ntv.status \|= STA_PPSTIME \| STA_PPSFREQ;
+	} else {
+	if (pll_status & STA_PPSTIME)
+	report_event(EVNT_KERN,
+	NULL, "PPS disabled");
+	ntv.status &= ~(STA_PPSTIME \|
+	STA_PPSFREQ);
+	}
+	if (sys_leap == LEAP_ADDSECOND)
+	ntv.status \|= STA_INS;
+	else if (sys_leap == LEAP_DELSECOND)
+	ntv.status \|= STA_DEL;
+	}
+
+	/*
+	* Pass the stuff to the kernel. If it squeals, turn off
+	* the pps. In any case, fetch the kernel offset,
+	* frequency and jitter.
+	*/
+	if (ntp_adjtime(&ntv) == TIME_ERROR) {
+	if (!(ntv.status & STA_PPSSIGNAL))
+	report_event(EVNT_KERN, NULL,
+	"PPS no signal");
+	}
+	pll_status = ntv.status;
+	#ifdef STA_NANO
+	clock_offset = ntv.offset / 1e9;
+	#else /* STA_NANO */
+	clock_offset = ntv.offset / 1e6;
+	#endif /* STA_NANO */
+	clock_frequency = FREQTOD(ntv.freq);
+
+	/*
+	* If the kernel PPS is lit, monitor its performance.
+	*/
+	if (ntv.status & STA_PPSTIME) {
+	#ifdef STA_NANO
+	clock_jitter = ntv.jitter / 1e9;
+	#else /* STA_NANO */
+	clock_jitter = ntv.jitter / 1e6;
+	#endif /* STA_NANO */
+	}
+
+	#if defined(STA_NANO) && NTP_API == 4
+	/*
+	* If the TAI changes, update the kernel TAI.
+	*/
+	if (loop_tai != sys_tai) {
+	loop_tai = sys_tai;
+	ntv.modes = MOD_TAI;
+	ntv.constant = sys_tai;
+	ntp_adjtime(&ntv);
+	}
+	#endif /* STA_NANO */
+	}
+	#endif /* KERNEL_PLL */
+	#endif