/* * NTP client/server, based on OpenNTPD 3.9p1 * * Author: Adam Tkac * * Licensed under GPLv2, see file LICENSE in this tarball for details. */ #include "libbb.h" #include /* For IPTOS_LOWDELAY definition */ #ifndef IPTOS_LOWDELAY # define IPTOS_LOWDELAY 0x10 #endif #ifndef IP_PKTINFO # error "Sorry, your kernel has to support IP_PKTINFO" #endif /* Sync to peers every N secs */ #define INTERVAL_QUERY_NORMAL 30 #define INTERVAL_QUERY_PATHETIC 60 #define INTERVAL_QUERY_AGRESSIVE 5 /* Bad if *less than* TRUSTLEVEL_BADPEER */ #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 /* Single query might take N secs max */ #define QUERYTIME_MAX 15 /* Min offset for settime at start. "man ntpd" says it's 128 ms */ #define STEPTIME_MIN_OFFSET 0.128 typedef struct { uint32_t int_partl; uint32_t fractionl; } l_fixedpt_t; typedef struct { uint16_t int_parts; uint16_t fractions; } s_fixedpt_t; enum { NTP_DIGESTSIZE = 16, NTP_MSGSIZE_NOAUTH = 48, NTP_MSGSIZE = (NTP_MSGSIZE_NOAUTH + 4 + NTP_DIGESTSIZE), }; typedef struct { uint8_t m_status; /* status of local clock and leap info */ uint8_t m_stratum; /* stratum level */ uint8_t m_ppoll; /* poll value */ int8_t m_precision_exp; s_fixedpt_t m_rootdelay; s_fixedpt_t m_dispersion; 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; enum { NTP_VERSION = 4, NTP_MAXSTRATUM = 15, /* 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 */ }; #define OFFSET_1900_1970 2208988800UL /* 1970 - 1900 in seconds */ typedef struct { double d_offset; double d_delay; //UNUSED: double d_error; time_t d_rcv_time; uint32_t d_refid4; uint8_t d_leap; uint8_t d_stratum; uint8_t d_good; } datapoint_t; #define NUM_DATAPOINTS 8 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; uint8_t p_datapoint_idx; uint8_t p_trustlevel; double p_xmttime; datapoint_t update; datapoint_t p_datapoint[NUM_DATAPOINTS]; 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; llist_t *ntp_peers; #if ENABLE_FEATURE_NTPD_SERVER int listen_fd; #endif unsigned verbose; unsigned peer_cnt; unsigned scale; uint32_t refid; uint32_t refid4; uint8_t synced; uint8_t leap; #define G_precision_exp -6 // int8_t precision_exp; uint8_t stratum; uint8_t time_was_stepped; uint8_t first_adj_done; }; #define G (*ptr_to_globals) static const int const_IPTOS_LOWDELAY = IPTOS_LOWDELAY; static void set_next(peer_t *p, unsigned t) { p->next_action_time = time(NULL) + t; } 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->p_trustlevel = TRUSTLEVEL_PATHETIC; p->next_action_time = time(NULL); /* = set_next(p, 0); */ llist_add_to(&G.ntp_peers, p); G.peer_cnt++; } 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; } #if 0 //UNUSED 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; } #endif #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 unsigned error_interval(void) { unsigned interval, r; interval = INTERVAL_QUERY_PATHETIC * QSCALE_OFF_MAX / QSCALE_OFF_MIN; r = (unsigned)random() % (unsigned)(interval / 10); return (interval + r); } 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, INTERVAL_QUERY_PATHETIC); return -1; } if (G.verbose) bb_error_msg("sent query to %s", p->p_dotted); set_next(p, QUERYTIME_MAX); return 0; } /* Time is stepped only once, when the first packet from a peer is received. */ static void step_time_once(double offset) { double dtime; llist_t *item; struct timeval tv; char buf[80]; time_t tval; if (G.time_was_stepped) goto bail; G.time_was_stepped = 1; /* if the offset is small, don't step, slew (later) */ if (offset < STEPTIME_MIN_OFFSET && offset > -STEPTIME_MIN_OFFSET) goto bail; 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); for (item = G.ntp_peers; item != NULL; item = item->link) { peer_t *p = (peer_t *) item->data; p->next_action_time -= (time_t)offset; } bail: if (option_mask32 & OPT_q) exit(0); } /* Time is periodically slewed when we collect enough * good data points. */ static int compare_offsets(const void *aa, const void *bb) { const peer_t *const *a = aa; const peer_t *const *b = bb; if ((*a)->update.d_offset < (*b)->update.d_offset) return -1; return ((*a)->update.d_offset > (*b)->update.d_offset); } static unsigned 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 slew_time(void) { llist_t *item; double offset_median; struct timeval tv; { peer_t **peers = xzalloc(sizeof(peers[0]) * G.peer_cnt); unsigned goodpeer_cnt = 0; unsigned middle; for (item = G.ntp_peers; item != NULL; item = item->link) { peer_t *p = (peer_t *) item->data; if (p->p_trustlevel < TRUSTLEVEL_BADPEER) continue; if (!p->update.d_good) { free(peers); return; } peers[goodpeer_cnt++] = p; } if (goodpeer_cnt == 0) { free(peers); goto clear_good; } qsort(peers, goodpeer_cnt, sizeof(peers[0]), compare_offsets); middle = goodpeer_cnt / 2; if (middle != 0 && (goodpeer_cnt & 1) == 0) { offset_median = (peers[middle-1]->update.d_offset + peers[middle]->update.d_offset) / 2; G.rootdelay = (peers[middle-1]->update.d_delay + peers[middle]->update.d_delay) / 2; G.stratum = 1 + MAX(peers[middle-1]->update.d_stratum, peers[middle]->update.d_stratum); } else { offset_median = peers[middle]->update.d_offset; G.rootdelay = peers[middle]->update.d_delay; G.stratum = 1 + peers[middle]->update.d_stratum; } G.leap = peers[middle]->update.d_leap; G.refid4 = peers[middle]->update.d_refid4; G.refid = #if ENABLE_FEATURE_IPV6 peers[middle]->p_lsa->u.sa.sa_family != AF_INET ? G.refid4 : #endif peers[middle]->p_lsa->u.sin.sin_addr.s_addr; free(peers); } //TODO: if (offset_median > BIG) step_time(offset_median)? G.scale = updated_scale(offset_median); bb_error_msg("adjusting clock by %fs, our stratum is %u, time scale %u", offset_median, G.stratum, G.scale); errno = 0; d_to_tv(offset_median, &tv); if (adjtime(&tv, &tv) == -1) bb_perror_msg_and_die("adjtime failed"); if (G.verbose >= 2) bb_error_msg("old adjust: %d.%06u", (int)tv.tv_sec, (unsigned)tv.tv_usec); if (G.first_adj_done) { uint8_t synced = (tv.tv_sec == 0 && tv.tv_usec == 0); if (synced != G.synced) { G.synced = synced; bb_error_msg("clock is %ssynced", synced ? "" : "un"); } } G.first_adj_done = 1; G.reftime = gettime1900d(); clear_good: for (item = G.ntp_peers; item != NULL; item = item->link) { peer_t *p = (peer_t *) item->data; p->update.d_good = 0; } } static void update_peer_data(peer_t *p) { /* Clock filter. * Find the datapoint with the lowest delay. * Use that as the peer update. * Invalidate it and all older ones. */ int i; int best = -1; int good = 0; for (i = 0; i < NUM_DATAPOINTS; i++) { if (p->p_datapoint[i].d_good) { good++; if (best < 0 || p->p_datapoint[i].d_delay < p->p_datapoint[best].d_delay) best = i; } } if (good < 8) //FIXME: was it meant to be NUM_DATAPOINTS, not 8? return; p->update = p->p_datapoint[best]; /* struct copy */ slew_time(); for (i = 0; i < NUM_DATAPOINTS; i++) if (p->p_datapoint[i].d_rcv_time <= p->p_datapoint[best].d_rcv_time) p->p_datapoint[i].d_good = 0; } static unsigned scale_interval(unsigned requested) { unsigned interval, r; interval = requested * G.scale; r = (unsigned)random() % (unsigned)(MAX(5, interval / 10)); return (interval + r); } static void recv_and_process_peer_pkt(peer_t *p) { ssize_t size; msg_t msg; double T1, T2, T3, T4; unsigned interval; datapoint_t *datapoint; /* 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, error_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 = error_interval(); bb_error_msg("reply from %s: not synced, next query in %us", p->p_dotted, interval); goto close_sock; } /* * 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(); datapoint = &p->p_datapoint[p->p_datapoint_idx]; datapoint->d_offset = ((T2 - T1) + (T3 - T4)) / 2; datapoint->d_delay = (T4 - T1) - (T3 - T2); if (datapoint->d_delay < 0) { bb_error_msg("reply from %s: negative delay %f", p->p_dotted, datapoint->d_delay); interval = error_interval(); set_next(p, interval); goto close_sock; } //UNUSED: datapoint->d_error = (T2 - T1) - (T3 - T4); datapoint->d_rcv_time = (time_t)(T4 - OFFSET_1900_1970); /* = time(NULL); */ datapoint->d_good = 1; datapoint->d_leap = (msg.m_status & LI_MASK); //UNUSED: datapoint->o_precision = msg.m_precision_exp; //UNUSED: datapoint->o_rootdelay = sfp_to_d(msg.m_rootdelay); //UNUSED: datapoint->o_rootdispersion = sfp_to_d(msg.m_dispersion); //UNUSED: datapoint->d_refid = ntohl(msg.m_refid); datapoint->d_refid4 = msg.m_xmttime.fractionl; //UNUSED: datapoint->o_reftime = lfp_to_d(msg.m_reftime); //UNUSED: datapoint->o_poll = msg.m_ppoll; datapoint->d_stratum = msg.m_stratum; if (p->p_trustlevel < TRUSTLEVEL_PATHETIC) interval = scale_interval(INTERVAL_QUERY_PATHETIC); else if (p->p_trustlevel < TRUSTLEVEL_AGRESSIVE) interval = scale_interval(INTERVAL_QUERY_AGRESSIVE); else interval = scale_interval(INTERVAL_QUERY_NORMAL); set_next(p, interval); /* Every received reply which we do not discard increases trust */ if (p->p_trustlevel < TRUSTLEVEL_MAX) { p->p_trustlevel++; if (p->p_trustlevel == TRUSTLEVEL_BADPEER) bb_error_msg("peer %s now valid", p->p_dotted); } if (G.verbose) bb_error_msg("reply from %s: offset %f delay %f, next query in %us", p->p_dotted, datapoint->d_offset, datapoint->d_delay, interval); update_peer_data(p); //TODO: do it after all peers had a chance to return at least one reply? step_time_once(datapoint->d_offset); p->p_datapoint_idx++; if (p->p_datapoint_idx >= NUM_DATAPOINTS) p->p_datapoint_idx = 0; 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; uint8_t query_ppoll; 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_ppoll = msg.m_ppoll; query_xmttime = msg.m_xmttime; /* Build a reply packet */ memset(&msg, 0, sizeof(msg)); msg.m_status = G.synced ? 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 = query_ppoll; 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_xmttime = d_to_lfp(gettime1900d()); // = msg.m_rectime msg.m_orgtime = query_xmttime; msg.m_rootdelay = d_to_sfp(G.rootdelay); version = (query_status & VERSION_MASK); /* ... >> VERSION_SHIFT - done below instead */ msg.m_refid = (version > (3 << VERSION_SHIFT)) ? G.refid4 : G.refid; /* 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); 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); /* Set some globals */ #if 0 /* With constant b = 100, G.precision_exp is also constant -6. * Uncomment this and you'll see */ { 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; bb_error_msg("G.precision_exp:%d", prec); /* -6 */ } #endif G.scale = 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; 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 = error_interval(); bb_error_msg("timed out waiting for %s, " "next query in %us", p->p_dotted, timeout); if (p->p_trustlevel >= TRUSTLEVEL_BADPEER) { p->p_trustlevel /= 2; if (p->p_trustlevel < TRUSTLEVEL_BADPEER) bb_error_msg("peer %s now invalid", p->p_dotted); } 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) step_time_once(0); /* no good peers, don't wait */ timeout = nextaction - cur_time; if (timeout < 1) timeout = 1; /* Here we may block */ if (g.verbose >= 2) 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); }