2 * NTP client/server, based on OpenNTPD 3.9p1
4 * Author: Adam Tkac <vonsch@gmail.com>
6 * Licensed under GPLv2, see file LICENSE in this tarball for details.
9 #include <netinet/ip.h> /* For IPTOS_LOWDELAY definition */
10 #ifndef IPTOS_LOWDELAY
11 # define IPTOS_LOWDELAY 0x10
14 # error "Sorry, your kernel has to support IP_PKTINFO"
18 /* Sync to peers every N secs */
19 #define INTERVAL_QUERY_NORMAL 30
20 #define INTERVAL_QUERY_PATHETIC 60
21 #define INTERVAL_QUERY_AGRESSIVE 5
23 /* Bad if *less than* TRUSTLEVEL_BADPEER */
24 #define TRUSTLEVEL_BADPEER 6
25 #define TRUSTLEVEL_PATHETIC 2
26 #define TRUSTLEVEL_AGRESSIVE 8
27 #define TRUSTLEVEL_MAX 10
29 #define QSCALE_OFF_MIN 0.05
30 #define QSCALE_OFF_MAX 0.50
32 /* Single query might take n secs max */
33 #define QUERYTIME_MAX 15
34 /* Min offset for settime at start. "man ntpd" says it's 128 ms */
35 #define STEPTIME_MIN_OFFSET 0.128
49 NTP_MSGSIZE_NOAUTH = 48,
50 NTP_MSGSIZE = (NTP_MSGSIZE_NOAUTH + 4 + NTP_DIGESTSIZE),
54 uint8_t m_status; /* status of local clock and leap info */
55 uint8_t m_stratum; /* stratum level */
56 uint8_t m_ppoll; /* poll value */
58 s_fixedpt_t m_rootdelay;
59 s_fixedpt_t m_dispersion;
61 l_fixedpt_t m_reftime;
62 l_fixedpt_t m_orgtime;
63 l_fixedpt_t m_rectime;
64 l_fixedpt_t m_xmttime;
66 uint8_t m_digest[NTP_DIGESTSIZE];
72 /* Leap Second Codes (high order two bits of m_status) */
73 LI_NOWARNING = (0 << 6), /* no warning */
74 LI_PLUSSEC = (1 << 6), /* add a second (61 seconds) */
75 LI_MINUSSEC = (2 << 6), /* minus a second (59 seconds) */
76 LI_ALARM = (3 << 6), /* alarm condition */
80 VERSION_MASK = (7 << 3),
85 MODE_RES0 = 0, /* reserved */
86 MODE_SYM_ACT = 1, /* symmetric active */
87 MODE_SYM_PAS = 2, /* symmetric passive */
88 MODE_CLIENT = 3, /* client */
89 MODE_SERVER = 4, /* server */
90 MODE_BROADCAST = 5, /* broadcast */
91 MODE_RES1 = 6, /* reserved for NTP control message */
92 MODE_RES2 = 7, /* reserved for private use */
95 #define OFFSET_1900_1970 2208988800UL /* 1970 - 1900 in seconds */
100 //UNUSED: double d_error;
108 #define NUM_DATAPOINTS 8
110 len_and_sockaddr *p_lsa;
112 /* When to send new query (if p_fd == -1)
113 * or when receive times out (if p_fd >= 0): */
114 time_t next_action_time;
116 uint8_t p_datapoint_idx;
120 ntp_datapoint_t update;
121 ntp_datapoint_t p_datapoint[NUM_DATAPOINTS];
129 /* Insert new options above this line. */
130 /* Non-compat options: */
132 OPT_l = (1 << 5) * ENABLE_FEATURE_NTPD_SERVER,
140 #if ENABLE_FEATURE_NTPD_SERVER
150 #define G_precision -6
153 uint8_t time_was_stepped;
154 uint8_t first_adj_done;
156 #define G (*ptr_to_globals)
159 static const int const_IPTOS_LOWDELAY = IPTOS_LOWDELAY;
163 set_next(ntp_peer_t *p, unsigned t)
165 p->next_action_time = time(NULL) + t;
173 p = xzalloc(sizeof(*p));
174 p->p_lsa = xhost2sockaddr(s, 123);
175 p->p_dotted = xmalloc_sockaddr2dotted_noport(&p->p_lsa->u.sa);
177 p->msg.m_status = MODE_CLIENT | (NTP_VERSION << 3);
178 p->trustlevel = TRUSTLEVEL_PATHETIC;
179 p->next_action_time = time(NULL); /* = set_next(p, 0); */
181 llist_add_to(&G.ntp_peers, p);
189 gettimeofday(&tv, NULL); /* never fails */
190 return (tv.tv_sec + 1.0e-6 * tv.tv_usec + OFFSET_1900_1970);
194 d_to_tv(double d, struct timeval *tv)
196 tv->tv_sec = (long)d;
197 tv->tv_usec = (d - tv->tv_sec) * 1000000;
201 lfp_to_d(l_fixedpt_t lfp)
204 lfp.int_partl = ntohl(lfp.int_partl);
205 lfp.fractionl = ntohl(lfp.fractionl);
206 ret = (double)lfp.int_partl + ((double)lfp.fractionl / UINT_MAX);
212 sfp_to_d(s_fixedpt_t sfp)
215 sfp.int_parts = ntohs(sfp.int_parts);
216 sfp.fractions = ntohs(sfp.fractions);
217 ret = (double)sfp.int_parts + ((double)sfp.fractions / USHRT_MAX);
222 #if ENABLE_FEATURE_NTPD_SERVER
227 lfp.int_partl = (uint32_t)d;
228 lfp.fractionl = (uint32_t)((d - lfp.int_partl) * UINT_MAX);
229 lfp.int_partl = htonl(lfp.int_partl);
230 lfp.fractionl = htonl(lfp.fractionl);
238 sfp.int_parts = (uint16_t)d;
239 sfp.fractions = (uint16_t)((d - sfp.int_parts) * USHRT_MAX);
240 sfp.int_parts = htons(sfp.int_parts);
241 sfp.fractions = htons(sfp.fractions);
249 unsigned interval, r;
250 interval = INTERVAL_QUERY_PATHETIC * QSCALE_OFF_MAX / QSCALE_OFF_MIN;
251 r = (unsigned)random() % (unsigned)(interval / 10);
252 return (interval + r);
257 const struct sockaddr *from, const struct sockaddr *to, socklen_t addrlen,
258 ntp_msg_t *msg, ssize_t len)
264 ret = sendto(fd, msg, len, MSG_DONTWAIT, to, addrlen);
266 ret = send_to_from(fd, msg, len, MSG_DONTWAIT, to, from, addrlen);
269 bb_perror_msg("send failed");
276 send_query_to_peer(ntp_peer_t *p)
278 // Why do we need to bind()?
279 // See what happens when we don't bind:
281 // socket(PF_INET, SOCK_DGRAM, IPPROTO_IP) = 3
282 // setsockopt(3, SOL_IP, IP_TOS, [16], 4) = 0
283 // gettimeofday({1259071266, 327885}, NULL) = 0
284 // sendto(3, "xxx", 48, MSG_DONTWAIT, {sa_family=AF_INET, sin_port=htons(123), sin_addr=inet_addr("10.34.32.125")}, 16) = 48
285 // ^^^ we sent it from some source port picked by kernel.
286 // time(NULL) = 1259071266
287 // write(2, "ntpd: entering poll 15 secs\n", 28) = 28
288 // poll([{fd=3, events=POLLIN}], 1, 15000) = 1 ([{fd=3, revents=POLLIN}])
289 // recv(3, "yyy", 68, MSG_DONTWAIT) = 48
290 // ^^^ this recv will receive packets to any local port!
292 // Uncomment this and use strace to see it in action:
293 #define PROBE_LOCAL_ADDR // { len_and_sockaddr lsa; lsa.len = LSA_SIZEOF_SA; getsockname(p->query.fd, &lsa.u.sa, &lsa.len); }
297 len_and_sockaddr *local_lsa;
299 family = p->p_lsa->u.sa.sa_family;
300 p->p_fd = fd = xsocket_type(&local_lsa, family, SOCK_DGRAM);
301 /* local_lsa has "null" address and port 0 now.
302 * bind() ensures we have a *particular port* selected by kernel
303 * and remembered in p->p_fd, thus later recv(p->p_fd)
304 * receives only packets sent to this port.
307 xbind(fd, &local_lsa->u.sa, local_lsa->len);
309 #if ENABLE_FEATURE_IPV6
310 if (family == AF_INET)
312 setsockopt(fd, IPPROTO_IP, IP_TOS, &const_IPTOS_LOWDELAY, sizeof(const_IPTOS_LOWDELAY));
317 * Send out a random 64-bit number as our transmit time. The NTP
318 * server will copy said number into the originate field on the
319 * response that it sends us. This is totally legal per the SNTP spec.
321 * The impact of this is two fold: we no longer send out the current
322 * system time for the world to see (which may aid an attacker), and
323 * it gives us a (not very secure) way of knowing that we're not
324 * getting spoofed by an attacker that can't capture our traffic
325 * but can spoof packets from the NTP server we're communicating with.
327 * Save the real transmit timestamp locally.
329 p->msg.m_xmttime.int_partl = random();
330 p->msg.m_xmttime.fractionl = random();
331 p->p_xmttime = gettime1900d();
333 if (do_sendto(p->p_fd, /*from:*/ NULL, /*to:*/ &p->p_lsa->u.sa, /*addrlen:*/ p->p_lsa->len,
334 &p->msg, NTP_MSGSIZE_NOAUTH) == -1
338 set_next(p, INTERVAL_QUERY_PATHETIC);
343 bb_error_msg("sent query to %s", p->p_dotted);
344 set_next(p, QUERYTIME_MAX);
350 /* Time is stepped only once, when the first packet from a peer is received.
353 step_time_once(double offset)
360 if (G.time_was_stepped)
362 G.time_was_stepped = 1;
364 /* if the offset is small, don't step, slew (later) */
365 if (offset < STEPTIME_MIN_OFFSET && offset > -STEPTIME_MIN_OFFSET)
368 gettimeofday(&tv, NULL); /* never fails */
370 offset += 1.0e-6 * tv.tv_usec;
371 d_to_tv(offset, &tv);
373 if (settimeofday(&tv, NULL) == -1)
374 bb_perror_msg_and_die("settimeofday");
377 strftime(buf, sizeof(buf), "%a %b %e %H:%M:%S %Z %Y", localtime(&tval));
379 bb_error_msg("setting clock to %s (offset %fs)", buf, offset);
381 for (item = G.ntp_peers; item != NULL; item = item->link) {
382 ntp_peer_t *p = (ntp_peer_t *) item->data;
383 p->next_action_time -= offset;
387 if (option_mask32 & OPT_q)
392 /* Time is periodically slewed when we collect enough
396 compare_offsets(const void *aa, const void *bb)
398 const ntp_peer_t *const *a = aa;
399 const ntp_peer_t *const *b = bb;
400 if ((*a)->update.d_offset < (*b)->update.d_offset)
402 return ((*a)->update.d_offset > (*b)->update.d_offset);
405 updated_scale(double offset)
409 if (offset > QSCALE_OFF_MAX)
411 if (offset < QSCALE_OFF_MIN)
412 return QSCALE_OFF_MAX / QSCALE_OFF_MIN;
413 return QSCALE_OFF_MAX / offset;
419 double offset_median;
423 ntp_peer_t **peers = xzalloc(sizeof(peers[0]) * G.peer_cnt);
424 unsigned goodpeer_cnt = 0;
427 for (item = G.ntp_peers; item != NULL; item = item->link) {
428 ntp_peer_t *p = (ntp_peer_t *) item->data;
429 if (p->trustlevel < TRUSTLEVEL_BADPEER)
431 if (!p->update.d_good) {
435 peers[goodpeer_cnt++] = p;
438 if (goodpeer_cnt == 0) {
443 qsort(peers, goodpeer_cnt, sizeof(peers[0]), compare_offsets);
445 middle = goodpeer_cnt / 2;
446 if (middle != 0 && (goodpeer_cnt & 1) == 0) {
447 offset_median = (peers[middle-1]->update.d_offset + peers[middle]->update.d_offset) / 2;
448 G.rootdelay = (peers[middle-1]->update.d_delay + peers[middle]->update.d_delay) / 2;
449 G.stratum = 1 + MAX(peers[middle-1]->update.d_stratum, peers[middle]->update.d_stratum);
451 offset_median = peers[middle]->update.d_offset;
452 G.rootdelay = peers[middle]->update.d_delay;
453 G.stratum = 1 + peers[middle]->update.d_stratum;
455 G.leap = peers[middle]->update.d_leap;
456 G.refid4 = peers[middle]->update.d_refid4;
458 #if ENABLE_FEATURE_IPV6
459 peers[middle]->p_lsa->u.sa.sa_family != AF_INET ?
462 peers[middle]->p_lsa->u.sin.sin_addr.s_addr;
465 //TODO: if (offset_median > BIG) step_time(offset_median)?
467 G.scale = updated_scale(offset_median);
469 bb_error_msg("adjusting clock by %fs, our stratum is %u, time scale %u",
470 offset_median, G.stratum, G.scale);
473 d_to_tv(offset_median, &tv);
474 if (adjtime(&tv, &tv) == -1)
475 bb_perror_msg_and_die("adjtime failed");
477 bb_error_msg("old adjust: %d.%06u", (int)tv.tv_sec, (unsigned)tv.tv_usec);
479 if (G.first_adj_done) {
480 uint8_t synced = (tv.tv_sec == 0 && tv.tv_usec == 0);
481 if (synced != G.synced) {
483 bb_error_msg("clock is %ssynced", synced ? "" : "un");
486 G.first_adj_done = 1;
488 G.reftime = gettime1900d();
491 for (item = G.ntp_peers; item != NULL; item = item->link) {
492 ntp_peer_t *p = (ntp_peer_t *) item->data;
493 p->update.d_good = 0;
498 update_peer_data(ntp_peer_t *p)
501 * Find the datapoint with the lowest delay.
502 * Use that as the peer update.
503 * Invalidate it and all older ones.
509 for (i = 0; i < NUM_DATAPOINTS; i++) {
510 if (p->p_datapoint[i].d_good) {
512 if (best < 0 || p->p_datapoint[i].d_delay < p->p_datapoint[best].d_delay)
517 if (good < 8) //FIXME: was it meant to be NUM_DATAPOINTS, not 8?
520 memcpy(&p->update, &p->p_datapoint[best], sizeof(p->update));
523 for (i = 0; i < NUM_DATAPOINTS; i++)
524 if (p->p_datapoint[i].d_rcvd <= p->p_datapoint[best].d_rcvd)
525 p->p_datapoint[i].d_good = 0;
529 scale_interval(unsigned requested)
531 unsigned interval, r;
532 interval = requested * G.scale;
533 r = (unsigned)random() % (unsigned)(MAX(5, interval / 10));
534 return (interval + r);
537 recv_and_process_peer_pkt(ntp_peer_t *p)
541 double T1, T2, T3, T4;
543 ntp_datapoint_t *datapoint;
545 /* We can recvfrom here and check from.IP, but some multihomed
546 * ntp servers reply from their *other IP*.
547 * TODO: maybe we should check at least what we can: from.port == 123?
549 size = recv(p->p_fd, &msg, sizeof(msg), MSG_DONTWAIT);
551 bb_perror_msg("recv(%s) error", p->p_dotted);
552 if (errno == EHOSTUNREACH || errno == EHOSTDOWN
553 || errno == ENETUNREACH || errno == ENETDOWN
554 || errno == ECONNREFUSED || errno == EADDRNOTAVAIL
557 //TODO: always do this?
558 set_next(p, error_interval());
564 if (size != NTP_MSGSIZE_NOAUTH && size != NTP_MSGSIZE) {
565 bb_error_msg("malformed packet received from %s", p->p_dotted);
569 if (msg.m_orgtime.int_partl != p->msg.m_xmttime.int_partl
570 || msg.m_orgtime.fractionl != p->msg.m_xmttime.fractionl
575 if ((msg.m_status & LI_ALARM) == LI_ALARM
576 || msg.m_stratum == 0
577 || msg.m_stratum > NTP_MAXSTRATUM
579 // TODO: stratum 0 responses may have commands in 32-bit m_refid field:
580 // "DENY", "RSTR" - peer does not like us at all
581 // "RATE" - peer is overloaded, reduce polling freq
582 interval = error_interval();
583 bb_error_msg("reply from %s: not synced, next query in %us", p->p_dotted, interval);
588 * From RFC 2030 (with a correction to the delay math):
590 * Timestamp Name ID When Generated
591 * ------------------------------------------------------------
592 * Originate Timestamp T1 time request sent by client
593 * Receive Timestamp T2 time request received by server
594 * Transmit Timestamp T3 time reply sent by server
595 * Destination Timestamp T4 time reply received by client
597 * The roundtrip delay and local clock offset are defined as
599 * delay = (T4 - T1) - (T3 - T2); offset = ((T2 - T1) + (T3 - T4)) / 2
603 T2 = lfp_to_d(msg.m_rectime);
604 T3 = lfp_to_d(msg.m_xmttime);
606 datapoint = &p->p_datapoint[p->p_datapoint_idx];
608 datapoint->d_offset = ((T2 - T1) + (T3 - T4)) / 2;
609 datapoint->d_delay = (T4 - T1) - (T3 - T2);
610 if (datapoint->d_delay < 0) {
611 bb_error_msg("reply from %s: negative delay %f", p->p_dotted, datapoint->d_delay);
612 interval = error_interval();
613 set_next(p, interval);
616 //UNUSED: datapoint->d_error = (T2 - T1) - (T3 - T4);
617 datapoint->d_rcvd = (time_t)(T4 - OFFSET_1900_1970); /* = time(NULL); */
618 datapoint->d_good = 1;
620 datapoint->d_leap = (msg.m_status & LI_MASK);
621 //UNUSED: datapoint->o_precision = msg.m_precision;
622 //UNUSED: datapoint->o_rootdelay = sfp_to_d(msg.m_rootdelay);
623 //UNUSED: datapoint->o_rootdispersion = sfp_to_d(msg.m_dispersion);
624 //UNUSED: datapoint->d_refid = ntohl(msg.m_refid);
625 datapoint->d_refid4 = msg.m_xmttime.fractionl;
626 //UNUSED: datapoint->o_reftime = lfp_to_d(msg.m_reftime);
627 //UNUSED: datapoint->o_poll = msg.m_ppoll;
628 datapoint->d_stratum = msg.m_stratum;
630 if (p->trustlevel < TRUSTLEVEL_PATHETIC)
631 interval = scale_interval(INTERVAL_QUERY_PATHETIC);
632 else if (p->trustlevel < TRUSTLEVEL_AGRESSIVE)
633 interval = scale_interval(INTERVAL_QUERY_AGRESSIVE);
635 interval = scale_interval(INTERVAL_QUERY_NORMAL);
637 set_next(p, interval);
639 /* every received reply which we do not discard increases trust */
640 if (p->trustlevel < TRUSTLEVEL_MAX) {
642 if (p->trustlevel == TRUSTLEVEL_BADPEER)
643 bb_error_msg("peer %s now valid", p->p_dotted);
647 bb_error_msg("reply from %s: offset %f delay %f, next query in %us", p->p_dotted,
648 datapoint->d_offset, datapoint->d_delay, interval);
651 //TODO: do it after all peers had a chance to return at least one reply?
652 step_time_once(datapoint->d_offset);
654 p->p_datapoint_idx++;
655 if (p->p_datapoint_idx >= NUM_DATAPOINTS)
656 p->p_datapoint_idx = 0;
659 /* We do not expect any more packets from this peer for now.
660 * Closing the socket informs kernel about it.
661 * We open a new socket when we send a new query.
669 #if ENABLE_FEATURE_NTPD_SERVER
671 recv_and_process_client_pkt(void /*int fd*/)
676 len_and_sockaddr *to;
677 struct sockaddr *from;
679 uint8_t query_status;
681 l_fixedpt_t query_xmttime;
683 to = get_sock_lsa(G.listen_fd);
684 from = xzalloc(to->len);
686 size = recv_from_to(G.listen_fd, &msg, sizeof(msg), MSG_DONTWAIT, from, &to->u.sa, to->len);
687 if (size != NTP_MSGSIZE_NOAUTH && size != NTP_MSGSIZE) {
692 bb_perror_msg_and_die("recv");
694 addr = xmalloc_sockaddr2dotted_noport(from);
695 bb_error_msg("malformed packet received from %s: size %u", addr, (int)size);
700 query_status = msg.m_status;
701 query_ppoll = msg.m_ppoll;
702 query_xmttime = msg.m_xmttime;
704 /* Build a reply packet */
705 memset(&msg, 0, sizeof(msg));
706 msg.m_status = G.synced ? G.leap : LI_ALARM;
707 msg.m_status |= (query_status & VERSION_MASK);
708 msg.m_status |= ((query_status & MODE_MASK) == MODE_CLIENT) ?
709 MODE_SERVER : MODE_SYM_PAS;
710 msg.m_stratum = G.stratum;
711 msg.m_ppoll = query_ppoll;
712 msg.m_precision = G_precision;
713 rectime = gettime1900d();
714 msg.m_xmttime = msg.m_rectime = d_to_lfp(rectime);
715 msg.m_reftime = d_to_lfp(G.reftime);
716 //msg.m_xmttime = d_to_lfp(gettime1900d()); // = msg.m_rectime
717 msg.m_orgtime = query_xmttime;
718 msg.m_rootdelay = d_to_sfp(G.rootdelay);
719 version = (query_status & VERSION_MASK); /* ... >> VERSION_SHIFT - done below instead */
720 msg.m_refid = (version > (3 << VERSION_SHIFT)) ? G.refid4 : G.refid;
722 /* We reply from the local address packet was sent to,
723 * this makes to/from look swapped here: */
724 do_sendto(G.listen_fd,
725 /*from:*/ &to->u.sa, /*to:*/ from, /*addrlen:*/ to->len,
734 /* Upstream ntpd's options:
736 * -4 Force DNS resolution of host names to the IPv4 namespace.
737 * -6 Force DNS resolution of host names to the IPv6 namespace.
738 * -a Require cryptographic authentication for broadcast client,
739 * multicast client and symmetric passive associations.
740 * This is the default.
741 * -A Do not require cryptographic authentication for broadcast client,
742 * multicast client and symmetric passive associations.
743 * This is almost never a good idea.
744 * -b Enable the client to synchronize to broadcast servers.
746 * Specify the name and path of the configuration file,
747 * default /etc/ntp.conf
748 * -d Specify debugging mode. This option may occur more than once,
749 * with each occurrence indicating greater detail of display.
751 * Specify debugging level directly.
753 * Specify the name and path of the frequency file.
754 * This is the same operation as the "driftfile FILE"
755 * configuration command.
756 * -g Normally, ntpd exits with a message to the system log
757 * if the offset exceeds the panic threshold, which is 1000 s
758 * by default. This option allows the time to be set to any value
759 * without restriction; however, this can happen only once.
760 * If the threshold is exceeded after that, ntpd will exit
761 * with a message to the system log. This option can be used
762 * with the -q and -x options. See the tinker command for other options.
764 * Chroot the server to the directory jaildir. This option also implies
765 * that the server attempts to drop root privileges at startup
766 * (otherwise, chroot gives very little additional security).
767 * You may need to also specify a -u option.
769 * Specify the name and path of the symmetric key file,
770 * default /etc/ntp/keys. This is the same operation
771 * as the "keys FILE" configuration command.
773 * Specify the name and path of the log file. The default
774 * is the system log file. This is the same operation as
775 * the "logfile FILE" configuration command.
776 * -L Do not listen to virtual IPs. The default is to listen.
778 * -N To the extent permitted by the operating system,
779 * run the ntpd at the highest priority.
781 * Specify the name and path of the file used to record the ntpd
782 * process ID. This is the same operation as the "pidfile FILE"
783 * configuration command.
785 * To the extent permitted by the operating system,
786 * run the ntpd at the specified priority.
787 * -q Exit the ntpd just after the first time the clock is set.
788 * This behavior mimics that of the ntpdate program, which is
789 * to be retired. The -g and -x options can be used with this option.
790 * Note: The kernel time discipline is disabled with this option.
792 * Specify the default propagation delay from the broadcast/multicast
793 * server to this client. This is necessary only if the delay
794 * cannot be computed automatically by the protocol.
796 * Specify the directory path for files created by the statistics
797 * facility. This is the same operation as the "statsdir DIR"
798 * configuration command.
800 * Add a key number to the trusted key list. This option can occur
803 * Specify a user, and optionally a group, to switch to.
806 * Add a system variable listed by default.
807 * -x Normally, the time is slewed if the offset is less than the step
808 * threshold, which is 128 ms by default, and stepped if above
809 * the threshold. This option sets the threshold to 600 s, which is
810 * well within the accuracy window to set the clock manually.
811 * Note: since the slew rate of typical Unix kernels is limited
812 * to 0.5 ms/s, each second of adjustment requires an amortization
813 * interval of 2000 s. Thus, an adjustment as much as 600 s
814 * will take almost 14 days to complete. This option can be used
815 * with the -g and -q options. See the tinker command for other options.
816 * Note: The kernel time discipline is disabled with this option.
819 /* By doing init in a separate function we decrease stack usage
822 static NOINLINE void ntp_init(char **argv)
830 bb_error_msg_and_die(bb_msg_you_must_be_root);
833 opt_complementary = "dd:p::"; /* d: counter, p: list */
834 opts = getopt32(argv,
836 "p:"IF_FEATURE_NTPD_SERVER("l") /* NOT compat */
838 "46aAbgL", /* compat, ignored */
840 if (!(opts & (OPT_p|OPT_l)))
842 if (opts & OPT_x) /* disable stepping, only slew is allowed */
843 G.time_was_stepped = 1;
845 add_peers(llist_pop(&peers));
846 if (!(opts & OPT_n)) {
847 bb_daemonize_or_rexec(DAEMON_DEVNULL_STDIO, argv);
848 logmode = LOGMODE_NONE;
850 #if ENABLE_FEATURE_NTPD_SERVER
853 G.listen_fd = create_and_bind_dgram_or_die(NULL, 123);
854 socket_want_pktinfo(G.listen_fd);
855 setsockopt(G.listen_fd, IPPROTO_IP, IP_TOS, &const_IPTOS_LOWDELAY, sizeof(const_IPTOS_LOWDELAY));
858 /* I hesitate to set -20 prio. -15 should be high enough for timekeeping */
860 setpriority(PRIO_PROCESS, 0, -15);
862 /* Set some globals */
864 /* With constant b = 100, G.precision is also constant -6.
865 * Uncomment this and you'll see */
871 /* We can use sys_clock_getres but assuming 10ms tick should be fine */
872 clock_getres(CLOCK_REALTIME, &tp);
874 tp.tv_nsec = 10000000;
875 b = 1000000000 / tp.tv_nsec; /* convert to Hz */
877 b = 100; /* b = 1000000000/10000000 = 100 */
881 //G.precision = prec;
882 bb_error_msg("G.precision:%d", prec); /* -6 */
887 bb_signals((1 << SIGTERM) | (1 << SIGINT), record_signo);
888 bb_signals((1 << SIGPIPE) | (1 << SIGHUP), SIG_IGN);
891 int ntpd_main(int argc UNUSED_PARAM, char **argv) MAIN_EXTERNALLY_VISIBLE;
892 int ntpd_main(int argc UNUSED_PARAM, char **argv)
896 ntp_peer_t **idx2peer;
898 memset(&g, 0, sizeof(g));
899 SET_PTR_TO_GLOBALS(&g);
904 unsigned cnt = g.peer_cnt;
905 /* if ENABLE_FEATURE_NTPD_SERVER, + 1 for listen_fd: */
906 idx2peer = xzalloc(sizeof(void *) * (cnt + ENABLE_FEATURE_NTPD_SERVER));
907 pfd = xzalloc(sizeof(pfd[0]) * (cnt + ENABLE_FEATURE_NTPD_SERVER));
910 while (!bb_got_signal) {
913 unsigned sent_cnt, trial_cnt;
915 time_t cur_time, nextaction;
917 /* Nothing between here and poll() blocks for any significant time */
919 cur_time = time(NULL);
920 nextaction = cur_time + 3600;
923 #if ENABLE_FEATURE_NTPD_SERVER
924 if (g.listen_fd != -1) {
925 pfd[0].fd = g.listen_fd;
926 pfd[0].events = POLLIN;
930 /* Pass over peer list, send requests, time out on receives */
931 sent_cnt = trial_cnt = 0;
932 for (item = g.ntp_peers; item != NULL; item = item->link) {
933 ntp_peer_t *p = (ntp_peer_t *) item->data;
935 /* Overflow-safe "if (p->next_action_time <= cur_time) ..." */
936 if ((int)(cur_time - p->next_action_time) >= 0) {
938 /* Time to send new req */
940 if (send_query_to_peer(p) == 0)
943 /* Timed out waiting for reply */
946 timeout = error_interval();
947 bb_error_msg("timed out waiting for %s, "
948 "next query in %us", p->p_dotted, timeout);
949 if (p->trustlevel >= TRUSTLEVEL_BADPEER) {
951 if (p->trustlevel < TRUSTLEVEL_BADPEER)
952 bb_error_msg("peer %s now invalid", p->p_dotted);
954 set_next(p, timeout);
958 if (p->next_action_time < nextaction)
959 nextaction = p->next_action_time;
962 /* Wait for reply from this peer */
964 pfd[i].events = POLLIN;
970 if ((trial_cnt > 0 && sent_cnt == 0) || g.peer_cnt == 0)
971 step_time_once(0); /* no good peers, don't wait */
973 timeout = nextaction - cur_time;
977 /* Here we may block */
979 bb_error_msg("poll %us, sockets:%u", timeout, i);
980 nfds = poll(pfd, i, timeout * 1000);
984 /* Process any received packets */
986 #if ENABLE_FEATURE_NTPD_SERVER
987 if (g.listen_fd != -1) {
988 if (pfd[0].revents /* & (POLLIN|POLLERR)*/) {
990 recv_and_process_client_pkt(/*g.listen_fd*/);
995 for (; nfds != 0 && j < i; j++) {
996 if (pfd[j].revents /* & (POLLIN|POLLERR)*/) {
998 recv_and_process_peer_pkt(idx2peer[j]);
1001 } /* while (!bb_got_signal) */
1003 kill_myself_with_sig(bb_got_signal);