ntpdate.c

网络时间协议NTP 源码 版本v4.2.0b 该源码用于linux平台下

#ifdef SYS_WINNT
	process_handle = GetCurrentProcess();
	if (!SetPriorityClass(process_handle, (DWORD) REALTIME_PRIORITY_CLASS)) {
		msyslog(LOG_ERR, "SetPriorityClass failed: %m");
	}
#endif /* SYS_WINNT */



	initializing = 0;
	was_alarmed = 0;
	rbuflist = (struct recvbuf *)0;

	while (complete_servers < sys_numservers) {
#ifdef HAVE_POLL_H
		struct pollfd* rdfdes;
		rdfdes = fdmask;
#else
		fd_set rdfdes;
		rdfdes = fdmask;
#endif

		if (alarm_flag) {		/* alarmed? */
			was_alarmed = 1;
			alarm_flag = 0;
		}
		rbuflist = getrecvbufs();	/* get received buffers */

		if (!was_alarmed && rbuflist == (struct recvbuf *)0) {
			/*
			 * Nothing to do.	 Wait for something.
			 */
#ifdef HAVE_POLL_H
			nfound = poll(rdfdes, (unsigned int)nbsock, timeout.tv_sec * 1000);

#else
			nfound = select(maxfd, &rdfdes, (fd_set *)0,
					(fd_set *)0, &timeout);
#endif
			if (nfound > 0)
				input_handler();
			else if (nfound == SOCKET_ERROR)
			{
#ifndef SYS_WINNT
				if (errno != EINTR)
#else
				if (WSAGetLastError() != WSAEINTR)
#endif
					netsyslog(LOG_ERR,
#ifdef HAVE_POLL_H
						"poll() error: %m"
#else
						"select() error: %m"
#endif
						);
			} else if (errno != 0) {
#ifndef SYS_VXWORKS
				netsyslog(LOG_DEBUG,
#ifdef HAVE_POLL_H
					"poll(): nfound = %d, error: %m",
#else
					"select(): nfound = %d, error: %m",
#endif
					nfound);
#endif
			}
			if (alarm_flag) {		/* alarmed? */
				was_alarmed = 1;
				alarm_flag = 0;
			}
			rbuflist = getrecvbufs();	/* get received buffers */
		}

		/*
		 * Out here, signals are unblocked.  Call receive
		 * procedure for each incoming packet.
		 */
		while (rbuflist != (struct recvbuf *)0) {
			rbuf = rbuflist;
			rbuflist = rbuf->next;
			receive(rbuf);
			freerecvbuf(rbuf);
		}

		/*
		 * Call timer to process any timeouts
		 */
		if (was_alarmed) {
			timer();
			was_alarmed = 0;
		}

		/*
		 * Go around again
		 */
	}

	/*
	 * When we get here we've completed the polling of all servers.
	 * Adjust the clock, then exit.
	 */
#ifdef SYS_WINNT
	WSACleanup();
#endif
#ifdef SYS_VXWORKS
	close (fd);
	timer_delete(ntpdate_timerid);
#endif

	return clock_adjust();
}


/*
 * transmit - transmit a packet to the given server, or mark it completed.
 *		This is called by the timeout routine and by the receive
 *		procedure.
 */
static void
transmit(
	register struct server *server
	)
{
	struct pkt xpkt;

	if (debug)
		printf("transmit(%s)\n", stoa(&(server->srcadr)));

	if (server->filter_nextpt < server->xmtcnt) {
		l_fp ts;
		/*
		 * Last message to this server timed out.  Shift
		 * zeros into the filter.
		 */
		L_CLR(&ts);
		server_data(server, 0, &ts, 0);
	}

	if ((int)server->filter_nextpt >= sys_samples) {
		/*
		 * Got all the data we need.  Mark this guy
		 * completed and return.
		 */
		server->event_time = 0;
		complete_servers++;
		return;
	}

	/*
	 * If we're here, send another message to the server.  Fill in
	 * the packet and let 'er rip.
	 */
	xpkt.li_vn_mode = PKT_LI_VN_MODE(LEAP_NOTINSYNC,
					 sys_version, MODE_CLIENT);
	xpkt.stratum = STRATUM_TO_PKT(STRATUM_UNSPEC);
	xpkt.ppoll = NTP_MINPOLL;
	xpkt.precision = NTPDATE_PRECISION;
	xpkt.rootdelay = htonl(NTPDATE_DISTANCE);
	xpkt.rootdispersion = htonl(NTPDATE_DISP);
	xpkt.refid = htonl(NTPDATE_REFID);
	L_CLR(&xpkt.reftime);
	L_CLR(&xpkt.org);
	L_CLR(&xpkt.rec);

	/*
	 * Determine whether to authenticate or not.	If so,
	 * fill in the extended part of the packet and do it.
	 * If not, just timestamp it and send it away.
	 */
	if (sys_authenticate) {
		int len;

		xpkt.exten[0] = htonl(sys_authkey);
		get_systime(&server->xmt);
		L_ADDUF(&server->xmt, sys_authdelay);
		HTONL_FP(&server->xmt, &xpkt.xmt);
		len = authencrypt(sys_authkey, (u_int32 *)&xpkt, LEN_PKT_NOMAC);
		sendpkt(&(server->srcadr), &xpkt, (int)(LEN_PKT_NOMAC + len));

		if (debug > 1)
			printf("transmit auth to %s\n",
			   stoa(&(server->srcadr)));
	} else {
		get_systime(&(server->xmt));
		HTONL_FP(&server->xmt, &xpkt.xmt);
		sendpkt(&(server->srcadr), &xpkt, LEN_PKT_NOMAC);

		if (debug > 1)
			printf("transmit to %s\n", stoa(&(server->srcadr)));
	}

	/*
	 * Update the server timeout and transmit count
	 */
	server->event_time = current_time + sys_timeout;
	server->xmtcnt++;
}


/*
 * receive - receive and process an incoming frame
 */
static void
receive(
	struct recvbuf *rbufp
	)
{
	register struct pkt *rpkt;
	register struct server *server;
	register s_fp di;
	l_fp t10, t23, tmp;
	l_fp org;
	l_fp rec;
	l_fp ci;
	int has_mac;
	int is_authentic;

	if (debug)
		printf("receive(%s)\n", stoa(&rbufp->recv_srcadr));
	/*
	 * Check to see if the packet basically looks like something
	 * intended for us.
	 */
	if (rbufp->recv_length == LEN_PKT_NOMAC)
		has_mac = 0;
	else if (rbufp->recv_length >= LEN_PKT_NOMAC)
		has_mac = 1;
	else {
		if (debug)
			printf("receive: packet length %d\n",
			   rbufp->recv_length);
		return; 		/* funny length packet */
	}

	rpkt = &(rbufp->recv_pkt);
	if (PKT_VERSION(rpkt->li_vn_mode) < NTP_OLDVERSION ||
		PKT_VERSION(rpkt->li_vn_mode) > NTP_VERSION) {
		return;
	}

	if ((PKT_MODE(rpkt->li_vn_mode) != MODE_SERVER
		 && PKT_MODE(rpkt->li_vn_mode) != MODE_PASSIVE)
		|| rpkt->stratum >= STRATUM_UNSPEC) {
		if (debug)
			printf("receive: mode %d stratum %d\n",
			   PKT_MODE(rpkt->li_vn_mode), rpkt->stratum);
		return;
	}

	/*
	 * So far, so good.  See if this is from a server we know.
	 */
	server = findserver(&(rbufp->recv_srcadr));
	if (server == NULL) {
		if (debug)
			printf("receive: server not found\n");
		return;
	}

	/*
	 * Decode the org timestamp and make sure we're getting a response
	 * to our last request.
	 */
	NTOHL_FP(&rpkt->org, &org);
	if (!L_ISEQU(&org, &server->xmt)) {
		if (debug)
			printf("receive: pkt.org and peer.xmt differ\n");
		return;
	}

	/*
	 * Check out the authenticity if we're doing that.
	 */
	if (!sys_authenticate)
		is_authentic = 1;
	else {
		is_authentic = 0;

		if (debug > 3)
			printf("receive: rpkt keyid=%ld sys_authkey=%ld decrypt=%ld\n",
			   (long int)ntohl(rpkt->exten[0]), (long int)sys_authkey,
			   (long int)authdecrypt(sys_authkey, (u_int32 *)rpkt,
				LEN_PKT_NOMAC, (int)(rbufp->recv_length - LEN_PKT_NOMAC)));

		if (has_mac && ntohl(rpkt->exten[0]) == sys_authkey &&
			authdecrypt(sys_authkey, (u_int32 *)rpkt, LEN_PKT_NOMAC,
			(int)(rbufp->recv_length - LEN_PKT_NOMAC)))
			is_authentic = 1;
		if (debug)
			printf("receive: authentication %s\n",
			   is_authentic ? "passed" : "failed");
	}
	server->trust <<= 1;
	if (!is_authentic)
		server->trust |= 1;

	/*
	 * Looks good.	Record info from the packet.
	 */
	server->leap = PKT_LEAP(rpkt->li_vn_mode);
	server->stratum = PKT_TO_STRATUM(rpkt->stratum);
	server->precision = rpkt->precision;
	server->rootdelay = ntohl(rpkt->rootdelay);
	server->rootdispersion = ntohl(rpkt->rootdispersion);
	server->refid = rpkt->refid;
	NTOHL_FP(&rpkt->reftime, &server->reftime);
	NTOHL_FP(&rpkt->rec, &rec);
	NTOHL_FP(&rpkt->xmt, &server->org);

	/*
	 * Make sure the server is at least somewhat sane.	If not, try
	 * again.
	 */
	if (L_ISZERO(&rec) || !L_ISHIS(&server->org, &rec)) {
		transmit(server);
		return;
	}

	/*
	 * Calculate the round trip delay (di) and the clock offset (ci).
	 * We use the equations (reordered from those in the spec):
	 *
	 * d = (t2 - t3) - (t1 - t0)
	 * c = ((t2 - t3) + (t1 - t0)) / 2
	 */
	t10 = server->org;		/* pkt.xmt == t1 */
	L_SUB(&t10, &rbufp->recv_time); /* recv_time == t0*/

	t23 = rec;			/* pkt.rec == t2 */
	L_SUB(&t23, &org);		/* pkt->org == t3 */

	/* now have (t2 - t3) and (t0 - t1).	Calculate (ci) and (di) */
	/*
	 * Calculate (ci) = ((t1 - t0) / 2) + ((t2 - t3) / 2)
	 * For large offsets this may prevent an overflow on '+'
	 */
	ci = t10;
	L_RSHIFT(&ci);
	tmp = t23;
	L_RSHIFT(&tmp);
	L_ADD(&ci, &tmp);

	/*
	 * Calculate di in t23 in full precision, then truncate
	 * to an s_fp.
	 */
	L_SUB(&t23, &t10);
	di = LFPTOFP(&t23);

	if (debug > 3)
		printf("offset: %s, delay %s\n", lfptoa(&ci, 6), fptoa(di, 5));

	di += (FP_SECOND >> (-(int)NTPDATE_PRECISION))
		+ (FP_SECOND >> (-(int)server->precision)) + NTP_MAXSKW;

	if (di <= 0) {		/* value still too raunchy to use? */
		L_CLR(&ci);
		di = 0;
	} else {
		di = max(di, NTP_MINDIST);
	}

	/*
	 * Shift this data in, then transmit again.
	 */
	server_data(server, (s_fp) di, &ci, 0);
	transmit(server);
}


/*
 * server_data - add a sample to the server's filter registers
 */
static void
server_data(
	register struct server *server,
	s_fp d,
	l_fp *c,
	u_fp e
	)
{
	u_short i;

	i = server->filter_nextpt;
	if (i < NTP_SHIFT) {
		server->filter_delay[i] = d;
		server->filter_offset[i] = *c;
		server->filter_soffset[i] = LFPTOFP(c);
		server->filter_error[i] = e;
		server->filter_nextpt = (u_short)(i + 1);
	}
}


/*
 * clock_filter - determine a server's delay, dispersion and offset
 */
static void
clock_filter(
	register struct server *server
	)
{
	register int i, j;
	int ord[NTP_SHIFT];

	/*
	 * Sort indices into increasing delay order
	 */
	for (i = 0; i < sys_samples; i++)
		ord[i] = i;

	for (i = 0; i < (sys_samples-1); i++) {
		for (j = i+1; j < sys_samples; j++) {
			if (server->filter_delay[ord[j]] == 0)
				continue;
			if (server->filter_delay[ord[i]] == 0
				|| (server->filter_delay[ord[i]]
				> server->filter_delay[ord[j]])) {
				register int tmp;

				tmp = ord[i];
				ord[i] = ord[j];
				ord[j] = tmp;
			}
		}
	}

	/*
	 * Now compute the dispersion, and assign values to delay and
	 * offset.	If there are no samples in the register, delay and
	 * offset go to zero and dispersion is set to the maximum.
	 */
	if (server->filter_delay[ord[0]] == 0) {
		server->delay = 0;
		L_CLR(&server->offset);
		server->soffset = 0;
		server->dispersion = PEER_MAXDISP;
	} else {
		register s_fp d;

		server->delay = server->filter_delay[ord[0]];
		server->offset = server->filter_offset[ord[0]];
		server->soffset = LFPTOFP(&server->offset);
		server->dispersion = 0;
		for (i = 1; i < sys_samples; i++) {
			if (server->filter_delay[ord[i]] == 0)
				d = PEER_MAXDISP;
			else {
				d = server->filter_soffset[ord[i]]
					- server->filter_soffset[ord[0]];
				if (d < 0)
					d = -d;
				if (d > PEER_MAXDISP)
					d = PEER_MAXDISP;
			}
			/*
			 * XXX This *knows* PEER_FILTER is 1/2
			 */
			server->dispersion += (u_fp)(d) >> i;
		}
	}
	/*
	 * We're done
	 */
}


/*
 * clock_select - select the pick-of-the-litter clock from the samples
 *		  we've got.
 */
static struct server *
clock_select(void)
{
	register struct server *server;
	register int i;
	register int nlist;
	register s_fp d;
	register int j;
	register int n;
	s_fp local_threshold;
	struct server *server_list[NTP_MAXCLOCK];
	u_fp server_badness[NTP_MAXCLOCK];
	struct server *sys_server;

	/*
	 * This first chunk of code is supposed to go through all
	 * servers we know about to find the NTP_MAXLIST servers which
	 * are most likely to succeed.	We run through the list
	 * doing the sanity checks and trying to insert anyone who
	 * looks okay.	We are at all times aware that we should
	 * only keep samples from the top two strata and we only need
	 * NTP_MAXLIST of them.
	 */
	nlist = 0;	/* none yet */
	for (server = sys_servers; server != NULL; server = server->next_server) {
		if (server->delay == 0) {
			if (debug)
				printf("%s: Server dropped: no data\n", ntoa(&server->srcadr));
			continue;	/* no data */
		}
		if (server->stratum > NTP_INFIN) {
			if (debug)
				printf("%s: Server dropped: strata too high\n", ntoa(&server->srcadr));
			continue;	/* stratum no good */
		}
		if (server->delay > NTP_MAXWGT) {
			if (debug)
				printf("%s: Server dropped: server too far away\n", 
					ntoa(&server->srcadr));
			continue;	/* too far away */
		}
		if (server->leap == LEAP_NOTINSYNC) {
			if (debug)
				printf("%s: Server dropped: Leap not in sync\n", ntoa(&server->srcadr));
			continue;	/* he's in trouble */
		}
		if (!L_ISHIS(&server->org, &server->reftime)) {
			if (debug)
				printf("%s: Server dropped: server is very broken\n", 
				       ntoa(&server->srcadr));
			continue;	/* very broken host */
		}
		if ((server->org.l_ui - server->reftime.l_ui)
		    >= NTP_MAXAGE) {
			if (debug)
				printf("%s: Server dropped: Server has gone too long without sync\n", 
				       ntoa(&server->srcadr));
			continue;	/* too long without sync */
		}
		if (server->trust != 0) {
			if (debug)
				printf("%s: Server dropped: Server is untrusted\n",
				       ntoa(&server->srcadr));
			continue;
		}

		/*
		 * This one seems sane.  Find where he belongs
		 * on the list.
		 */
		d = server->dispersion + server->dispersion;
		for (i = 0; i < nlist; i++)
			if (server->stratum <= server_list[i]->stratum)
			break;
		for ( ; i < nlist; i++) {
			if (server->stratum < server_list[i]->stratum)
				break;
			if (d < (s_fp) server_badness[i])
				break;
		}

		/*
		 * If i points past the end of the list, this
		 * guy is a loser, else stick him in.
		 */
		if (i >= NTP_MAXLIST)
			continue;
		for (j = nlist; j > i; j--)
			if (j < NTP_MAXLIST) {
				server_list[j] = server_list[j-1];
				server_badness[j]
					= server_badness[j-1];
			}

		server_list[i] = server;
		server_badness[i] = d;
		if (nlist < NTP_MAXLIST)
			nlist++;
	}

	/*
	 * Got the five-or-less best.	 Cut the list where the number of
	 * strata exceeds two.
	 */
	j = 0;
	for (i = 1; i < nlist; i++)
		if (server_list[i]->stratum > server_list[i-1]->stratum)
		if (++j == 2) {
			nlist = i;
			break;
		}