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b1585064f

Adam Tkac

2009-11-22

FAILED Duration: 36s

Subject

ntpd: new applet by Adam Tkac. +5k.

Binary

No binary (build failed)

Architecture & Compiler Flags

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

—

Build Log

(log yok)

Commit Diff GitHub →

include/applets.h +1 -0 include/usage.h +11 -0 networking/Config.in +14 -0 networking/Kbuild +1 -0 networking/ntpd.c +999 -0

include/applets.h+1 -0

@@ -285,6 +285,7 @@ IF_NICE(APPLET(nice, _BB_DIR_BIN, _BB_SUID_DROP))
	IF_NMETER(APPLET(nmeter, _BB_DIR_USR_BIN, _BB_SUID_DROP))
	IF_NOHUP(APPLET(nohup, _BB_DIR_USR_BIN, _BB_SUID_DROP))
	IF_NSLOOKUP(APPLET(nslookup, _BB_DIR_USR_BIN, _BB_SUID_DROP))
+	IF_NTPD(APPLET(ntpd, _BB_DIR_USR_SBIN, _BB_SUID_DROP))
	IF_OD(APPLET(od, _BB_DIR_USR_BIN, _BB_SUID_DROP))
	IF_OPENVT(APPLET(openvt, _BB_DIR_USR_BIN, _BB_SUID_DROP))
	//IF_PARSE(APPLET(parse, _BB_DIR_USR_BIN, _BB_SUID_DROP))

include/usage.h+11 -0

@@ -3210,6 +3210,17 @@
	"Name: debian\n" \
	"Address: 127.0.0.1\n"

+	#define ntpd_trivial_usage \
+	"[-dngl] [-p PEER]..."
+	#define ntpd_full_usage "\n\n" \
+	"NTP client/server\n" \
+	"\nOptions:" \
+	"\n -d Verbose" \
+	"\n -n Do not daemonize" \
+	"\n -g Set system time even if offset is > 1000 sec" \
+	"\n -l Run as server on port 123" \
+	"\n -p PEER Obtain time from PEER (may be repeated)" \
+
	#define od_trivial_usage \
	"[-aBbcDdeFfHhIiLlOovXx] " IF_DESKTOP("[-t TYPE] ") "[FILE]"
	#define od_full_usage "\n\n" \

networking/Config.in+14 -0

@@ -661,6 +661,20 @@ config NSLOOKUP
	help
	nslookup is a tool to query Internet name servers.

+	config NTPD
+	bool "ntpd"
+	default n
+	help
+	The NTP client/server daemon.
+
+	config FEATURE_NTPD_SERVER
+	bool "Make ntpd usable as a NTP server"
+	default y
+	depends on NTPD
+	help
+	Make ntpd usable as a NTP server. If you disable this option
+	ntpd will be usable only as a NTP client.
+
	config PING
	bool "ping"
	default n

networking/Kbuild+1 -0

@@ -27,6 +27,7 @@ lib-$(CONFIG_NAMEIF) += nameif.o
	lib-$(CONFIG_NC) += nc.o
	lib-$(CONFIG_NETSTAT) += netstat.o
	lib-$(CONFIG_NSLOOKUP) += nslookup.o
+	lib-$(CONFIG_NTPD) += ntpd.o
	lib-$(CONFIG_PING) += ping.o
	lib-$(CONFIG_PING6) += ping.o
	lib-$(CONFIG_PSCAN) += pscan.o

networking/ntpd.c+999 -0

@@ -0,0 +1,999 @@
+	/*
+	* NTP client/server, based on OpenNTPD 3.9p1
+	*
+	* Author: Adam Tkac <[email protected]>
+	*
+	* Licensed under GPLv2, see file LICENSE in this tarball for details.
+	*/
+
+	#include "libbb.h"
+	#include <netinet/ip.h> /* For IPTOS_LOWDELAY definition */
+
+	#ifndef IP_PKTINFO
+	# error "Sorry, your kernel has to support IP_PKTINFO"
+	#endif
+
+	#define INTERVAL_QUERY_NORMAL 30 /* sync to peers every n secs */
+	#define INTERVAL_QUERY_PATHETIC 60
+	#define INTERVAL_QUERY_AGRESSIVE 5
+
+	#define TRUSTLEVEL_BADPEER 6
+	#define TRUSTLEVEL_PATHETIC 2
+	#define TRUSTLEVEL_AGRESSIVE 8
+	#define TRUSTLEVEL_MAX 10
+
+	#define QSCALE_OFF_MIN 0.05
+	#define QSCALE_OFF_MAX 0.50
+
+	#define QUERYTIME_MAX 15 /* single query might take n secs max */
+	#define OFFSET_ARRAY_SIZE 8
+	#define SETTIME_MIN_OFFSET 180 /* min offset for settime at start */
+	#define SETTIME_TIMEOUT 15 /* max seconds to wait with -s */
+
+	/* Style borrowed from NTP ref/tcpdump and updated for SNTPv4 (RFC2030). */
+
+	/*
+	* RFC Section 3
+	*
+	* 0 1 2 3
+	* 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+	* +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
+	* \| Integer Part \|
+	* +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
+	* \| Fraction Part \|
+	* +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
+	*
+	* 0 1 2 3
+	* 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+	* +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
+	* \| Integer Part \| Fraction Part \|
+	* +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
+	*/
+	typedef struct {
+	uint32_t int_partl;
+	uint32_t fractionl;
+	} l_fixedpt_t;
+
+	typedef struct {
+	uint16_t int_parts;
+	uint16_t fractions;
+	} s_fixedpt_t;
+
+	#define NTP_DIGESTSIZE 16
+	#define NTP_MSGSIZE_NOAUTH 48
+	#define NTP_MSGSIZE (NTP_MSGSIZE_NOAUTH + 4 + NTP_DIGESTSIZE)
+
+	typedef struct {
+	uint8_t status; /* status of local clock and leap info */
+	uint8_t stratum; /* Stratum level */
+	uint8_t ppoll; /* poll value */
+	int8_t precision;
+	s_fixedpt_t rootdelay;
+	s_fixedpt_t dispersion;
+	uint32_t refid;
+	l_fixedpt_t reftime;
+	l_fixedpt_t orgtime;
+	l_fixedpt_t rectime;
+	l_fixedpt_t xmttime;
+	uint32_t keyid;
+	uint8_t digest[NTP_DIGESTSIZE];
+	} ntp_msg_t;
+
+	typedef struct {
+	int fd;
+	ntp_msg_t msg;
+	double xmttime;
+	} ntp_query_t;
+
+	enum {
+	NTP_VERSION = 4,
+	NTP_MAXSTRATUM = 15,
+	/* Leap Second Codes (high order two bits) */
+	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 */
+
+	/* Status Masks */
+	MODE_MASK = (7 << 0),
+	VERSION_MASK = (7 << 3),
+	LI_MASK = (3 << 6),
+
+	/* 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 */
+	};
+
+	#define JAN_1970 2208988800UL /* 1970 - 1900 in seconds */
+
+	enum client_state {
+	STATE_NONE,
+	STATE_QUERY_SENT,
+	STATE_REPLY_RECEIVED
+	};
+
+	typedef struct {
+	double rootdelay;
+	double rootdispersion;
+	double reftime;
+	uint32_t refid;
+	uint32_t refid4;
+	uint8_t synced;
+	uint8_t leap;
+	int8_t precision;
+	uint8_t poll;
+	uint8_t stratum;
+	} ntp_status_t;
+
+	typedef struct {
+	ntp_status_t status;
+	double offset;
+	double delay;
+	double error;
+	time_t rcvd;
+	uint8_t good;
+	} ntp_offset_t;
+
+	typedef struct {
+	len_and_sockaddr *lsa;
+	ntp_query_t query;
+	ntp_offset_t reply[OFFSET_ARRAY_SIZE];
+	ntp_offset_t update;
+	enum client_state state;
+	time_t next;
+	time_t deadline;
+	uint8_t shift;
+	uint8_t trustlevel;
+	} ntp_peer_t;
+
+
+	struct globals {
+	unsigned verbose;
+	#if ENABLE_FEATURE_NTPD_SERVER
+	int listen_fd;
+	#endif
+	llist_t *ntp_peers;
+	ntp_status_t status;
+	uint32_t scale;
+	uint8_t settime;
+	uint8_t firstadj;
+	smallint peer_cnt;
+
+	};
+	#define G (*ptr_to_globals)
+
+
+	static const int const_IPTOS_LOWDELAY = IPTOS_LOWDELAY;
+
+
+	static void
+	set_next(ntp_peer_t *p, time_t t)
+	{
+	p->next = time(NULL) + t;
+	p->deadline = 0;
+	}
+
+	static void
+	add_peers(const char *s)
+	{
+	ntp_peer_t *p;
+
+	p = xzalloc(sizeof(*p));
+	//TODO: big ntpd uses all IPs, not just 1st, do we need to mimic that?
+	p->lsa = xhost2sockaddr(s, 123);
+	p->query.fd = -1;
+	p->query.msg.status = MODE_CLIENT \| (NTP_VERSION << 3);
+	if (STATE_NONE != 0)
+	p->state = STATE_NONE;
+	p->trustlevel = TRUSTLEVEL_PATHETIC;
+	p->query.fd = -1;
+	set_next(p, 0);
+
+	llist_add_to(&G.ntp_peers, p);
+	G.peer_cnt++;
+	}
+
+	static double
+	gettime(void)
+	{
+	struct timeval tv;
+
+	gettimeofday(&tv, NULL); /* never fails */
+	return (tv.tv_sec + JAN_1970 + 1.0e-6 * tv.tv_usec);
+	}
+
+
+	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;
+	}
+
+	#if ENABLE_FEATURE_NTPD_SERVER
+	static l_fixedpt_t
+	d_to_lfp(double d)
+	{
+	l_fixedpt_t lfp;
+
+	lfp.int_partl = htonl((uint32_t)d);
+	lfp.fractionl = htonl((uint32_t)((d - (u_int32_t)d) * UINT_MAX));
+	return lfp;
+	}
+	#endif
+
+	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 s_fixedpt_t
+	d_to_sfp(double d)
+	{
+	s_fixedpt_t sfp;
+
+	sfp.int_parts = htons((uint16_t)d);
+	sfp.fractions = htons((uint16_t)((d - (u_int16_t)d) * USHRT_MAX));
+	return sfp;
+	}
+	#endif
+
+	static void
+	set_deadline(ntp_peer_t *p, time_t t)
+	{
+	p->deadline = time(NULL) + t;
+	p->next = 0;
+	}
+
+	static time_t
+	error_interval(void)
+	{
+	time_t interval, r;
+
+	interval = INTERVAL_QUERY_PATHETIC * QSCALE_OFF_MAX / QSCALE_OFF_MIN;
+	r = random() % (interval / 10);
+	return (interval + r);
+	}
+
+	static int
+	sendmsg_wrap(int fd,
+	const struct sockaddr from, const struct sockaddr to, socklen_t addrlen,
+	ntp_msg_t *msg, ssize_t len)
+	{
+	ssize_t ret;
+
+	errno = 0;
+	if (!from) {
+	ret = sendto(fd, msg, len, 0, to, addrlen);
+	} else {
+	ret = send_to_from(fd, msg, len, 0, to, from, addrlen);
+	}
+	if (ret != len) {
+	bb_perror_msg("send failed");
+	return -1;
+	}
+	return 0;
+	}
+
+	static int
+	client_query(ntp_peer_t *p)
+	{
+	if (p->query.fd == -1) {
+	p->query.fd = xsocket(p->lsa->u.sa.sa_family, SOCK_DGRAM, 0);
+	#if ENABLE_FEATURE_IPV6
+	if (p->lsa->u.sa.sa_family == AF_INET)
+	#endif
+	setsockopt(p->query.fd, IPPROTO_IP, IP_TOS, &const_IPTOS_LOWDELAY, sizeof(const_IPTOS_LOWDELAY));
+	}
+
+	/*
+	* 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->query.msg.xmttime.int_partl = random();
+	p->query.msg.xmttime.fractionl = random();
+	p->query.xmttime = gettime();
+
+	if (sendmsg_wrap(p->query.fd, /from:/ NULL, /to:/ &p->lsa->u.sa, /addrlen:/ p->lsa->len,
+	&p->query.msg, NTP_MSGSIZE_NOAUTH) == -1) {
+	set_next(p, INTERVAL_QUERY_PATHETIC);
+	return -1;
+	}
+
+	p->state = STATE_QUERY_SENT;
+	set_deadline(p, QUERYTIME_MAX);
+
+	return 0;
+	}
+
+	static int
+	offset_compare(const void aa, const void bb)
+	{
+	const ntp_peer_t * const *a;
+	const ntp_peer_t * const *b;
+
+	a = aa;
+	b = bb;
+
+	if ((a)->update.offset < (b)->update.offset)
+	return -1;
+	return ((a)->update.offset > (b)->update.offset);
+	}
+
+	static uint32_t
+	updated_scale(double offset)
+	{
+	if (offset < 0)
+	offset = -offset;
+
+	if (offset > QSCALE_OFF_MAX)
+	return 1;
+	if (offset < QSCALE_OFF_MIN)
+	return QSCALE_OFF_MAX / QSCALE_OFF_MIN;
+	return QSCALE_OFF_MAX / offset;
+	}
+
+	static void
+	adjtime_wrap(void)
+	{
+	ntp_peer_t *p;
+	unsigned offset_cnt;
+	int i = 0;
+	ntp_peer_t **peers;
+	double offset_median;
+	llist_t *item;
+	len_and_sockaddr *lsa;
+	struct timeval tv, olddelta;
+
+	offset_cnt = 0;
+	for (item = G.ntp_peers; item != NULL; item = item->link) {
+	p = (ntp_peer_t *) item->data;
+	if (p->trustlevel < TRUSTLEVEL_BADPEER)
+	continue;
+	if (!p->update.good)
+	return;
+	offset_cnt++;
+	}
+
+	peers = xzalloc(sizeof(ntp_peer_t ) offset_cnt);
+	for (item = G.ntp_peers; item != NULL; item = item->link) {
+	p = (ntp_peer_t *) item->data;
+	if (p->trustlevel < TRUSTLEVEL_BADPEER)
+	continue;
+	peers[i++] = p;
+	}
+
+	qsort(peers, offset_cnt, sizeof(ntp_peer_t *), offset_compare);
+
+	if (offset_cnt != 0) {
+	if ((offset_cnt & 1) == 0) {
+	//TODO: try offset_cnt /= 2...
+	offset_median =
+	(peers[offset_cnt / 2 - 1]->update.offset +
+	peers[offset_cnt / 2]->update.offset) / 2;
+	G.status.rootdelay =
+	(peers[offset_cnt / 2 - 1]->update.delay +
+	peers[offset_cnt / 2]->update.delay) / 2;
+	G.status.stratum = MAX(
+	peers[offset_cnt / 2 - 1]->update.status.stratum,
+	peers[offset_cnt / 2]->update.status.stratum);
+	} else {
+	offset_median = peers[offset_cnt / 2]->update.offset;
+	G.status.rootdelay = peers[offset_cnt / 2]->update.delay;
+	G.status.stratum = peers[offset_cnt / 2]->update.status.stratum;
+	}
+	G.status.leap = peers[offset_cnt / 2]->update.status.leap;
+
+	bb_info_msg("adjusting local clock by %fs", offset_median);
+
+	d_to_tv(offset_median, &tv);
+	if (adjtime(&tv, &olddelta) == -1)
+	bb_error_msg("adjtime failed");
+	else if (!G.firstadj
+	&& olddelta.tv_sec == 0
+	&& olddelta.tv_usec == 0
+	&& !G.status.synced
+	) {
+	bb_info_msg("clock synced");
+	G.status.synced = 1;
+	} else if (G.status.synced) {
+	bb_info_msg("clock unsynced");
+	G.status.synced = 0;
+	}
+
+	G.firstadj = 0;
+	G.status.reftime = gettime();
+	G.status.stratum++; /* one more than selected peer */
+	G.scale = updated_scale(offset_median);
+
+	G.status.refid4 = peers[offset_cnt / 2]->update.status.refid4;
+
+	lsa = peers[offset_cnt / 2]->lsa;
+	G.status.refid =
+	#if ENABLE_FEATURE_IPV6
+	lsa->u.sa.sa_family != AF_INET ?
+	G.status.refid4 :
+	#endif
+	lsa->u.sin.sin_addr.s_addr;
+	}
+
+	free(peers);
+
+	for (item = G.ntp_peers; item != NULL; item = item->link) {
+	p = (ntp_peer_t *) item->data;
+	p->update.good = 0;
+	}
+	}
+
+	static void
+	settime(double offset)
+	{
+	ntp_peer_t *p;
+	llist_t *item;
+	struct timeval tv, curtime;
+	char buf[80];
+	time_t tval;
+
+	#if 0
+	if (!G.settime)
+	return;
+	#endif
+
+	/* if the offset is small, don't call settimeofday */
+	if (offset < SETTIME_MIN_OFFSET && offset > -SETTIME_MIN_OFFSET)
+	return;
+
+	gettimeofday(&curtime, NULL); /* never fails */
+
+	d_to_tv(offset, &tv);
+	curtime.tv_usec += tv.tv_usec + 1000000;
+	curtime.tv_sec += tv.tv_sec - 1 + (curtime.tv_usec / 1000000);
+	curtime.tv_usec %= 1000000;
+
+	if (settimeofday(&curtime, NULL) == -1) {
+	bb_error_msg("settimeofday");
+	return;
+	}
+
+	G.settime = 0;
+
+	tval = curtime.tv_sec;
+	strftime(buf, sizeof(buf), "%a %b %e %H:%M:%S %Z %Y", localtime(&tval));
+
+	/* Do we want to print message below to system log when daemonized? */
+	bb_info_msg("set local clock to %s (offset %fs)", buf, offset);
+
+	for (item = G.ntp_peers; item != NULL; item = item->link) {
+	p = (ntp_peer_t *) item->data;
+	if (p->next)
+	p->next -= offset;
+	if (p->deadline)
+	p->deadline -= offset;
+	}
+	}
+
+	static void
+	client_update(ntp_peer_t *p)
+	{
+	int i, best = 0, good = 0;
+
+	/*
+	* clock filter
+	* find the offset which arrived with the lowest delay
+	* use that as the peer update
+	* invalidate it and all older ones
+	*/
+
+	for (i = 0; good == 0 && i < OFFSET_ARRAY_SIZE; i++) {
+	if (p->reply[i].good) {
+	good++;
+	best = i;
+	}
+	}
+
+	for (; i < OFFSET_ARRAY_SIZE; i++) {
+	if (p->reply[i].good) {
+	good++;
+	if (p->reply[i].delay < p->reply[best].delay)
+	best = i;
+	}
+	}
+
+	if (good < 8)
+	return;
+
+	memcpy(&p->update, &p->reply[best], sizeof(p->update));
+	adjtime_wrap();
+
+	for (i = 0; i < OFFSET_ARRAY_SIZE; i++)
+	if (p->reply[i].rcvd <= p->reply[best].rcvd)
+	p->reply[i].good = 0;
+	}
+
+	static time_t
+	scale_interval(time_t requested)
+	{
+	time_t interval, r;
+
+	interval = requested * G.scale;
+	r = random() % MAX(5, interval / 10);
+	return (interval + r);
+	}
+
+	static void
+	client_dispatch(ntp_peer_t *p)
+	{
+	char *addr;
+	ssize_t size;
+	ntp_msg_t msg;
+	double T1, T2, T3, T4;
+	time_t interval;
+	ntp_offset_t *offset;
+
+	addr = xmalloc_sockaddr2dotted_noport(&p->lsa->u.sa);
+
+	size = recvfrom(p->query.fd, &msg, sizeof(msg), 0, NULL, NULL);
+	if (size == -1) {
+	bb_perror_msg("recvfrom(%s) error", addr);
+	if (errno == EHOSTUNREACH \|\| errno == EHOSTDOWN
+	\|\| errno == ENETUNREACH \|\| errno == ENETDOWN
+	\|\| errno == ECONNREFUSED \|\| errno == EADDRNOTAVAIL
+	) {
+	//TODO: always do this?
+	set_next(p, error_interval());
+	goto bail;
+	}
+	xfunc_die();
+	}
+
+	T4 = gettime();
+
+	if (size != NTP_MSGSIZE_NOAUTH && size != NTP_MSGSIZE) {
+	bb_error_msg("malformed packet received from %s", addr);
+	goto bail;
+	}
+
+	if (msg.orgtime.int_partl != p->query.msg.xmttime.int_partl
+	\|\| msg.orgtime.fractionl != p->query.msg.xmttime.fractionl
+	) {
+	goto bail;
+	}
+
+	if ((msg.status & LI_ALARM) == LI_ALARM
+	\|\| msg.stratum == 0
+	\|\| msg.stratum > NTP_MAXSTRATUM
+	) {
+	interval = error_interval();
+	bb_info_msg("reply from %s: not synced, next query %ds", addr, (int) interval);
+	goto bail;
+	}
+
+	/*
+	* 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 d and local clock offset t are defined as
+	*
+	* d = (T4 - T1) - (T3 - T2) t = ((T2 - T1) + (T3 - T4)) / 2.
+	*/
+
+	T1 = p->query.xmttime;
+	T2 = lfp_to_d(msg.rectime);
+	T3 = lfp_to_d(msg.xmttime);
+
+	offset = &p->reply[p->shift];
+
+	offset->offset = ((T2 - T1) + (T3 - T4)) / 2;
+	offset->delay = (T4 - T1) - (T3 - T2);
+	if (offset->delay < 0) {
+	interval = error_interval();
+	set_next(p, interval);
+	bb_info_msg("reply from %s: negative delay %f", addr, p->reply[p->shift].delay);
+	goto bail;
+	}
+	offset->error = (T2 - T1) - (T3 - T4);
+	offset->rcvd = time(NULL);
+	offset->good = 1;
+
+	offset->status.leap = (msg.status & LI_MASK);
+	offset->status.precision = msg.precision;
+	offset->status.rootdelay = sfp_to_d(msg.rootdelay);
+	offset->status.rootdispersion = sfp_to_d(msg.dispersion);
+	offset->status.refid = ntohl(msg.refid);
+	offset->status.refid4 = msg.xmttime.fractionl;
+	offset->status.reftime = lfp_to_d(msg.reftime);
+	offset->status.poll = msg.ppoll;
+	offset->status.stratum = msg.stratum;
+
+	if (p->trustlevel < TRUSTLEVEL_PATHETIC)
+	interval = scale_interval(INTERVAL_QUERY_PATHETIC);
+	else if (p->trustlevel < TRUSTLEVEL_AGRESSIVE)
+	interval = scale_interval(INTERVAL_QUERY_AGRESSIVE);
+	else
+	interval = scale_interval(INTERVAL_QUERY_NORMAL);
+
+	set_next(p, interval);
+	p->state = STATE_REPLY_RECEIVED;
+
+	/* every received reply which we do not discard increases trust */
+	if (p->trustlevel < TRUSTLEVEL_MAX) {
+	if (p->trustlevel < TRUSTLEVEL_BADPEER
+	&& p->trustlevel + 1 >= TRUSTLEVEL_BADPEER
+	) {
+	bb_info_msg("peer %s now valid", addr);
+	}
+	p->trustlevel++;
+	}
+
+	bb_info_msg("reply from %s: offset %f delay %f, next query %ds", addr,
+	offset->offset, offset->delay, (int) interval);
+
+	client_update(p);
+	if (!G.settime)
+	settime(offset->offset);
+
+	if (++p->shift >= OFFSET_ARRAY_SIZE)
+	p->shift = 0;
+
+	bail:
+	free(addr);
+	}
+
+	#if ENABLE_FEATURE_NTPD_SERVER
+	static void
+	server_dispatch(int fd)
+	{
+	ssize_t size;
+	uint8_t version;
+	double rectime;
+	len_and_sockaddr *to;
+	struct sockaddr *from;
+	ntp_msg_t query, reply;
+
+	to = get_sock_lsa(G.listen_fd);
+	from = xzalloc(to->len);
+
+	size = recv_from_to(fd, &query, sizeof(query), 0, from, &to->u.sa, to->len);
+	if (size == -1)
+	bb_error_msg_and_die("recv_from_to");
+	if (size != NTP_MSGSIZE_NOAUTH && size != NTP_MSGSIZE) {
+	char *addr = xmalloc_sockaddr2dotted_noport(from);
+	bb_error_msg("malformed packet received from %s", addr);
+	free(addr);
+	goto bail;
+	}
+
+	rectime = gettime();
+	version = (query.status & VERSION_MASK) >> 3;
+
+	memset(&reply, 0, sizeof(reply));
+	reply.status = G.status.synced ? G.status.leap : LI_ALARM;
+	reply.status \|= (query.status & VERSION_MASK);
+	reply.status \|= ((query.status & MODE_MASK) == MODE_CLIENT) ?
+	MODE_SERVER : MODE_SYM_PAS;
+	reply.stratum = G.status.stratum;
+	reply.ppoll = query.ppoll;
+	reply.precision = G.status.precision;
+	reply.rectime = d_to_lfp(rectime);
+	reply.reftime = d_to_lfp(G.status.reftime);
+	reply.xmttime = d_to_lfp(gettime());
+	reply.orgtime = query.xmttime;
+	reply.rootdelay = d_to_sfp(G.status.rootdelay);
+	reply.refid = (version > 3) ? G.status.refid4 : G.status.refid;
+
+	/* We reply from the address packet was sent to,
+	* this makes to/from look swapped here: */
+	sendmsg_wrap(fd, /from:/ &to->u.sa, /to:/ from, /addrlen:/ to->len,
+	&reply, 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.
+	*/
+
+	enum {
+	OPT_n = (1 << 0),
+	OPT_g = (1 << 1),
+	OPT_p = (1 << 2),
+	OPT_l = (1 << 3),
+	};
+
+	/* 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;
+
+	tzset();
+
+	if (getuid())
+	bb_error_msg_and_die("need root privileges");
+
+	peers = NULL;
+	opt_complementary = "dd:p::"; /* d: counter, p: list */
+	opts = getopt32(argv,
+	"ng" /* compat */
+	"p:"IF_FEATURE_NTPD_SERVER("l") /* NOT compat */
+	"d" /* compat */
+	"46aAbLNx", /* compat, ignored */
+	&peers, &G.verbose);
+	#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
+	if (opts & OPT_g)
+	G.settime = 1;
+	while (peers)
+	add_peers(llist_pop(&peers));
+	if (!(opts & OPT_n)) {
+	logmode = LOGMODE_NONE;
+	bb_daemonize(DAEMON_DEVNULL_STDIO);
+	}
+
+	/* Set some globals */
+	{
+	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.status.precision = prec;
+	}
+	G.scale = 1;
+	G.firstadj = 1;
+
+	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;
+	unsigned new_cnt;
+	struct pollfd *pfd;
+	ntp_peer_t **idx2peer;
+
+	memset(&g, 0, sizeof(g));
+	SET_PTR_TO_GLOBALS(&g);
+
+	ntp_init(argv);
+
+	new_cnt = g.peer_cnt;
+	idx2peer = xzalloc(sizeof(void ) new_cnt);
+	#if ENABLE_FEATURE_NTPD_SERVER
+	if (g.listen_fd != -1)
+	new_cnt++;
+	#endif
+	pfd = xzalloc(sizeof(pfd[0]) * new_cnt);
+
+	while (!bb_got_signal) {
+	llist_t *item;
+	unsigned i, j, idx_peers;
+	unsigned sent_cnt, trial_cnt;
+	int nfds, timeout;
+	time_t nextaction;
+
+	nextaction = time(NULL) + 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
+	idx_peers = i;
+	sent_cnt = trial_cnt = 0;
+	for (item = g.ntp_peers; item != NULL; item = item->link) {
+	ntp_peer_t p = (ntp_peer_t ) item->data;
+
+	if (p->next > 0 && p->next <= time(NULL)) {
+	trial_cnt++;
+	if (client_query(p) == 0)
+	sent_cnt++;
+	}
+	if (p->next > 0 && p->next < nextaction)
+	nextaction = p->next;
+	if (p->deadline > 0 && p->deadline < nextaction)
+	nextaction = p->deadline;
+
+	if (p->deadline > 0 && p->deadline <= time(NULL)) {
+	char *addr = xmalloc_sockaddr2dotted_noport(&p->lsa->u.sa);
+
+	timeout = error_interval();
+	bb_info_msg("no reply from %s received in time, "
+	"next query %ds", addr, timeout);
+	if (p->trustlevel >= TRUSTLEVEL_BADPEER) {
+	p->trustlevel /= 2;
+	if (p->trustlevel < TRUSTLEVEL_BADPEER)
+	bb_info_msg("peer %s now invalid", addr);
+	}
+	free(addr);
+
+	set_next(p, timeout);
+	}
+
+	if (p->state == STATE_QUERY_SENT) {
+	pfd[i].fd = p->query.fd;
+	pfd[i].events = POLLIN;
+	idx2peer[i - idx_peers] = p;
+	i++;
+	}
+	}
+
+	if (g.settime
+	&& ((trial_cnt > 0 && sent_cnt == 0) \|\| g.peer_cnt == 0)
+	) {
+	settime(0); /* no good peers, don't wait */
+	}
+
+	timeout = nextaction - time(NULL);
+	if (timeout < 0)
+	timeout = 0;
+
+	if (g.verbose)
+	bb_error_msg("entering poll %u secs", timeout);
+	nfds = poll(pfd, i, timeout * 1000);
+
+	j = 0;
+	#if ENABLE_FEATURE_NTPD_SERVER
+	for (; nfds > 0 && j < idx_peers; j++) {
+	if (pfd[j].revents & (POLLIN\|POLLERR)) {
+	nfds--;
+	server_dispatch(pfd[j].fd);
+	}
+	}
+	#endif
+	for (; nfds > 0 && j < i; j++) {
+	if (pfd[j].revents & (POLLIN\|POLLERR)) {
+	nfds--;
+	client_dispatch(idx2peer[j - idx_peers]);
+	}
+	}
+	} /* while (!bb_got_signal) */
+
+	kill_myself_with_sig(bb_got_signal);
+	}