ntpclient.c

A NTP client is a program which user can synchronize the time with time server assigned. This prog

	prec    = Data(0)       & 0xff;
	if (prec & 0x80) prec|=0xffffff00;
	delay   = Data(1);
	disp    = Data(2);
	refid   = Data(3);
	reftime.coarse = Data(4);
	reftime.fine   = Data(5);
	orgtime.coarse = Data(6);
	orgtime.fine   = Data(7);
	rectime.coarse = Data(8);
	rectime.fine   = Data(9);
	xmttime.coarse = Data(10);
	xmttime.fine   = Data(11);
#undef Data

	if (set_clock) {   /* you'd better be root, or ntpclient will crash! */
		struct timeval tv_set;
		/* it would be even better to subtract half the slop */
		tv_set.tv_sec  = xmttime.coarse - JAN_1970 + SyncTimeZone(); 
		/* divide xmttime.fine by 4294.967296 */
		tv_set.tv_usec = USEC(xmttime.fine);
		if (settimeofday(&tv_set,NULL)<0) {
			perror("settimeofday");
			exit(1);
		}
		if (debug) {
			printf("set time to %lu.%.6lu\n", tv_set.tv_sec, tv_set.tv_usec);
		}
	}

	if (debug) {
	printf("LI=%d  VN=%d  Mode=%d  Stratum=%d  Poll=%d  Precision=%d\n",
		li, vn, mode, stratum, poll, prec);
	printf("Delay=%.1f  Dispersion=%.1f  Refid=%u.%u.%u.%u\n",
		sec2u(delay),sec2u(disp),
		refid>>24&0xff, refid>>16&0xff, refid>>8&0xff, refid&0xff);
	printf("Reference %u.%.10u\n", reftime.coarse, reftime.fine);
	printf("Originate %u.%.10u\n", orgtime.coarse, orgtime.fine);
	printf("Receive   %u.%.10u\n", rectime.coarse, rectime.fine);
	printf("Transmit  %u.%.10u\n", xmttime.coarse, xmttime.fine);
	printf("Our recv  %u.%.10u\n", arrival->coarse, arrival->fine);
	}
	el_time=ntpdiff(&orgtime,arrival);   /* elapsed */
	st_time=ntpdiff(&rectime,&xmttime);  /* stall */
	skew1=ntpdiff(&orgtime,&rectime);
	skew2=ntpdiff(&xmttime,arrival);
	freq=get_current_freq();
	if (debug) {
	printf("Total elapsed: %9.2f\n"
	       "Server stall:  %9.2f\n"
	       "Slop:          %9.2f\n",
		el_time, st_time, el_time-st_time);
	printf("Skew:          %9.2f\n"
	       "Frequency:     %9d\n"
	       " day   second     elapsed    stall     skew  dispersion  freq\n",
		(skew1-skew2)/2, freq);
	}
	/* Not the ideal order for printing, but we want to be sure
	 * to do all the time-sensitive thinking (and time setting)
	 * before we start the output, especially fflush() (which
	 * could be slow).  Of course, if debug is turned on, speed
	 * has gone down the drain anyway. */
	if (live) {
		int new_freq;
		new_freq = contemplate_data(arrival->coarse, (skew1-skew2)/2,
			el_time+sec2u(disp), freq);
		if (!debug && new_freq != freq) set_freq(new_freq);
	}
	printf("%d %.5d.%.3d  %8.1f %8.1f  %8.1f %8.1f %9d\n",
		arrival->coarse/86400, arrival->coarse%86400,
		arrival->fine/4294967, el_time, st_time,
		(skew1-skew2)/2, sec2u(disp), freq);
	fflush(stdout);
	return(el_time-st_time);
}

void stuff_net_addr(struct in_addr *p, char *hostname)
{
	struct hostent *ntpserver;
	ntpserver=gethostbyname(hostname);
	if (ntpserver == NULL) {
		herror(hostname);
		exit(1);
	}
	if (ntpserver->h_length != 4) {
		fprintf(stderr,"oops %d\n",ntpserver->h_length);
		exit(1);
	}
	memcpy(&(p->s_addr),ntpserver->h_addr_list[0],4);
}

void setup_receive(int usd, unsigned int interface, short port)
{
	struct sockaddr_in sa_rcvr;
	bzero((char *) &sa_rcvr, sizeof(sa_rcvr));
	sa_rcvr.sin_family=AF_INET;
	sa_rcvr.sin_addr.s_addr=htonl(interface);
	sa_rcvr.sin_port=htons(port);
	if(bind(usd,(struct sockaddr *) &sa_rcvr,sizeof(sa_rcvr)) == -1) {
		fprintf(stderr,"could not bind to udp port %d\n",port);
		perror("bind");
		exit(1);
	}
	listen(usd,3);
}

void setup_transmit(int usd, char *host, short port)
{
	struct sockaddr_in sa_dest;
	bzero((char *) &sa_dest, sizeof(sa_dest));
	sa_dest.sin_family=AF_INET;
	stuff_net_addr(&(sa_dest.sin_addr),host);
	sa_dest.sin_port=htons(port);
	if (connect(usd,(struct sockaddr *)&sa_dest,sizeof(sa_dest))==-1)
		{perror("connect");exit(1);}
}

void primary_loop(int usd, int num_probes, int interval, int goodness)
{
	fd_set fds;
	struct sockaddr sa_xmit;
	int i, pack_len, sa_xmit_len, probes_sent, error;
	struct timeval to;
	struct ntptime udp_arrival_ntp;

	if (debug) printf("Listening...\n");
		
	if (debug && getenv("TZ")) printf("TZ is %s\n",getenv("TZ"));

	probes_sent=0;
	sa_xmit_len=sizeof(sa_xmit);
	to.tv_sec=0;
	to.tv_usec=0;
	for (;;) {
		FD_ZERO(&fds);
		FD_SET(usd,&fds);
		i=select(usd+1,&fds,NULL,NULL,&to);  /* Wait on read or error */
		if (debug) printf("select:%d\n",i);
		if ((i!=1)||(!FD_ISSET(usd,&fds))) {
			if (debug) printf("complex 1\n");
			if (i==EINTR) continue;
			if (debug) printf("complex 2\n");
			if (i<0) perror("select");
			if (debug) printf("complex 3,to.tv_sec : %x\n",to.tv_sec);
			if (to.tv_sec == 0) {
				if (probes_sent >= num_probes &&
					num_probes != 0) break;
				send_packet(usd);
				++probes_sent;
				to.tv_sec=interval;
				to.tv_usec=0;
			}	
			continue;
		}
		pack_len=recvfrom(usd,incoming,sizeof_incoming,0,
		                  &sa_xmit,&sa_xmit_len);
		if (debug) printf("rece pack_len:%d\n",pack_len);
		error = goodness+1;
		if (pack_len<0) {
			perror("recvfrom");
		} else if (pack_len>0 && (unsigned)pack_len<sizeof_incoming){
			get_packet_timestamp(usd, &udp_arrival_ntp);
			check_source(pack_len, &sa_xmit, sa_xmit_len);
			error = rfc1305print(incoming_word, &udp_arrival_ntp);
			/* udp_handle(usd,incoming,pack_len,&sa_xmit,sa_xmit_len); */
			if (debug) printf("Setup time successfully\n");
			break;
		} else {
			printf("Ooops.  pack_len=%d\n",pack_len);
			fflush(stdout);
		}
		if (debug) printf("check  error < goodness && goodness != 0\n");
		if ( error < goodness && goodness != 0) break;
		if (debug) printf("check  probes_sent >= num_probes && num_probes != 0\n");
		if (probes_sent >= num_probes && num_probes != 0) break;
	}
	
	if (debug) printf("exist primary_loop\n");
}

void do_replay(void)
{
	char line[100];
	int n, day, freq, absolute;
	float sec, el_time, st_time, disp;
	double skew, errorbar;
	int simulated_freq = 0;
	unsigned int last_fake_time = 0;
	double fake_delta_time = 0.0;

	while (fgets(line,sizeof(line),stdin)) {
		n=sscanf(line,"%d %f %f %f %lf %f %d",
			&day, &sec, &el_time, &st_time, &skew, &disp, &freq);
		if (n==7) {
			fputs(line,stdout);
			absolute=day*86400+(int)sec;
			errorbar=el_time+disp;
			if (debug) printf("contemplate %u %.1f %.1f %d\n",
				absolute,skew,errorbar,freq);
			if (last_fake_time==0) simulated_freq=freq;
			fake_delta_time += (absolute-last_fake_time)*((double)(freq-simulated_freq))/65536;
			if (debug) printf("fake %f %d \n", fake_delta_time, simulated_freq);
			skew += fake_delta_time;
			freq = simulated_freq;
			last_fake_time=absolute;
			simulated_freq = contemplate_data(absolute, skew, errorbar, freq);
		} else {
			fprintf(stderr,"Replay input error\n");
			exit(2);
		}
	}
}

void usage(char *argv0)
{
	fprintf(stderr,
	"Usage: %s [-c count] [-d] [-g goodness] -h hostname [-i interval]\n"
	"\t[-l] [-p port] [-r] [-s] \n",
	argv0);
}

int main(int argc, char *argv[]) {
	int usd;  /* socket */
	int c;
	/* These parameters are settable from the command line
	   the initializations here provide default behavior */
	short int udp_local_port=0;   /* default of 0 means kernel chooses */
	int cycle_time=600;           /* seconds */
	int probe_count=0;            /* default of 0 means loop forever */
	/* int debug=0; is a global above */
	int goodness=0;
	char *hostname=NULL;          /* must be set */
	int replay=0;                 /* replay mode overrides everything */

	for (;;) {
		c = getopt( argc, argv, "c:" DEBUG_OPTION "g:h:i:lp:rs");
		if (c == EOF) break;
		switch (c) {
			case 'c':
				probe_count = atoi(optarg);
				break;
#ifdef ENABLE_DEBUG
			case 'd':
				++debug;
				break;
#endif
			case 'g':
				goodness = atoi(optarg);
				break;
			case 'h':
				hostname = optarg;
				break;
			case 'i':
				cycle_time = atoi(optarg);
				break;
			case 'l':
				live++;
				break;
			case 'p':
				udp_local_port = atoi(optarg);
				break;
			case 'r':
				replay++;
				break;
			case 's':
				set_clock++;				
				break;
			default:
				usage(argv[0]);
				exit(1);
		}
	}
	if (replay) {
		do_replay();
		exit(0);
	}
	if (hostname == NULL) {
		usage(argv[0]);
		exit(1);
	}
	if (debug) {
		printf("Configuration:\n"
		"  -c probe_count %d\n"
		"  -d (debug)     %d\n"
		"  -g goodness    %d\n"
		"  -h hostname    %s\n"
		"  -i interval    %d\n"
		"  -l live        %d\n"
		"  -p local_port  %d\n"
		"  -s set_clock   %d\n",
		probe_count, debug, goodness, hostname, cycle_time,
		live, udp_local_port, set_clock );
	}

	/* Startup sequence */
	if ((usd=socket(AF_INET,SOCK_DGRAM,IPPROTO_UDP))==-1)
		{perror ("socket");exit(1);}

	setup_receive(usd, INADDR_ANY, udp_local_port);

	setup_transmit(usd, hostname, NTP_PORT);

	primary_loop(usd, probe_count, cycle_time, goodness);

	close(usd);
	return 0;
}