2 * Copyright (c) 1985, 1993
3 * The Regents of the University of California. All rights reserved.
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32 static char sccsid[] = "@(#)measure.c 8.1 (Berkeley) 6/6/93";
34 static const char rcsid[] =
39 #include <netinet/in_systm.h>
40 #include <netinet/ip.h>
41 #include <netinet/ip_icmp.h>
43 #define MSEC_DAY (SECDAY*1000)
45 #define PACKET_IN 1024
47 #define MSGS 5 /* timestamps to average */
48 #define TRIALS 10 /* max # of timestamps sent */
54 static n_short seqno = 0;
57 * Measures the differences between machines' clocks using
58 * ICMP timestamp messages.
60 int /* status val defined in globals.h */
61 measure(maxmsec, wmsec, hname, addr, print)
62 u_long maxmsec; /* wait this many msec at most */
63 u_long wmsec; /* msec to wait for an answer */
65 struct sockaddr_in *addr;
66 int print; /* print complaints on stderr */
73 long sendtime, recvtime, histime1, histime2;
74 long idelta, odelta, total;
75 long min_idelta, min_odelta;
76 struct timeval tdone, tcur, ttrans, twait, tout;
77 u_char packet[PACKET_IN], opacket[64];
78 register struct icmp *icp = (struct icmp *) packet;
79 register struct icmp *oicp = (struct icmp *) opacket;
80 struct ip *ip = (struct ip *) packet;
82 min_idelta = min_odelta = 0x7fffffff;
83 measure_status = HOSTDOWN;
84 measure_delta = HOSTDOWN;
88 /* open raw socket used to measure time differences */
90 sock_raw = socket(AF_INET, SOCK_RAW, IPPROTO_ICMP);
92 syslog(LOG_ERR, "opening raw socket: %m");
99 * empty the icmp input queue
103 tout.tv_sec = tout.tv_usec = 0;
104 FD_SET(sock_raw, &ready);
105 if (select(sock_raw+1, &ready, 0,0, &tout)) {
106 length = sizeof(struct sockaddr_in);
107 cc = recvfrom(sock_raw, (char *)packet, PACKET_IN, 0,
117 * Choose the smallest transmission time in each of the two
118 * directions. Use these two latter quantities to compute the delta
119 * between the two clocks.
122 oicp->icmp_type = ICMP_TSTAMP;
124 oicp->icmp_id = getpid();
125 oicp->icmp_rtime = 0;
126 oicp->icmp_ttime = 0;
127 oicp->icmp_seq = seqno;
131 (void)gettimeofday(&tdone, 0);
132 mstotvround(&tout, maxmsec);
133 timevaladd(&tdone, &tout); /* when we give up */
135 mstotvround(&twait, wmsec);
138 while (rcvcount < MSGS) {
139 (void)gettimeofday(&tcur, 0);
142 * keep sending until we have sent the max
144 if (trials < TRIALS) {
146 oicp->icmp_otime = htonl((tcur.tv_sec % SECDAY) * 1000
147 + tcur.tv_usec / 1000);
148 oicp->icmp_cksum = 0;
149 oicp->icmp_cksum = in_cksum((u_short*)oicp,
152 count = sendto(sock_raw, opacket, sizeof(*oicp), 0,
153 (struct sockaddr*)addr,
154 sizeof(struct sockaddr));
156 if (measure_status == HOSTDOWN)
157 measure_status = UNREACHABLE;
163 timevaladd(&ttrans, &twait);
168 while (rcvcount < trials) {
169 timevalsub(&tout, &ttrans, &tcur);
173 FD_SET(sock_raw, &ready);
174 count = select(sock_raw+1, &ready, (fd_set *)0,
176 (void)gettimeofday(&tcur, (struct timezone *)0);
180 length = sizeof(struct sockaddr_in);
181 cc = recvfrom(sock_raw, (char *)packet, PACKET_IN, 0,
187 * got something. See if it is ours
189 icp = (struct icmp *)(packet + (ip->ip_hl << 2));
191 || icp->icmp_type != ICMP_TSTAMPREPLY
192 || icp->icmp_id != oicp->icmp_id
193 || icp->icmp_seq < seqno
194 || icp->icmp_seq >= oicp->icmp_seq)
198 sendtime = ntohl(icp->icmp_otime);
199 recvtime = ((tcur.tv_sec % SECDAY) * 1000 +
200 tcur.tv_usec / 1000);
202 total = recvtime-sendtime;
203 if (total < 0) /* do not hassle midnight */
207 histime1 = ntohl(icp->icmp_rtime);
208 histime2 = ntohl(icp->icmp_ttime);
210 * a host using a time format different from
211 * msec. since midnight UT (as per RFC792) should
212 * set the high order bit of the 32-bit time
213 * value it transmits.
215 if ((histime1 & 0x80000000) != 0) {
216 measure_status = NONSTDTIME;
219 measure_status = GOOD;
221 idelta = recvtime-histime2;
222 odelta = histime1-sendtime;
224 /* do not be confused by midnight */
225 if (idelta < -MSEC_DAY/2) idelta += MSEC_DAY;
226 else if (idelta > MSEC_DAY/2) idelta -= MSEC_DAY;
228 if (odelta < -MSEC_DAY/2) odelta += MSEC_DAY;
229 else if (odelta > MSEC_DAY/2) odelta -= MSEC_DAY;
231 /* save the quantization error so that we can get a
232 * measurement finer than our system clock.
234 if (total < MIN_ROUND) {
235 measure_delta = (odelta - idelta)/2;
239 if (idelta < min_idelta)
241 if (odelta < min_odelta)
244 measure_delta = (min_odelta - min_idelta)/2;
247 if (tcur.tv_sec > tdone.tv_sec
248 || (tcur.tv_sec == tdone.tv_sec
249 && tcur.tv_usec >= tdone.tv_usec))
254 seqno += TRIALS; /* allocate our sequence numbers */
257 * If no answer is received for TRIALS consecutive times,
258 * the machine is assumed to be down
260 if (measure_status == GOOD) {
263 "measured delta %4d, %d trials to %-15s %s\n",
264 measure_delta, trials,
265 inet_ntoa(addr->sin_addr), hname);
269 warn("measure %s", hname);
272 syslog(LOG_ERR, "measure %s: %m", hname);
274 syslog(LOG_ERR, "measure: %s did not respond", hname);
278 "measure: %s failed after %d trials\n",
284 return(measure_status);
292 * round a number of milliseconds into a struct timeval
304 res->tv_sec = x/1000;
305 res->tv_usec = (x-res->tv_sec*1000)*1000;
306 if (res->tv_usec < 0) {
307 res->tv_usec += 1000000;
314 struct timeval *tv1, *tv2;
316 tv1->tv_sec += tv2->tv_sec;
317 tv1->tv_usec += tv2->tv_usec;
318 if (tv1->tv_usec >= 1000000) {
320 tv1->tv_usec -= 1000000;
322 if (tv1->tv_usec < 0) {
324 tv1->tv_usec += 1000000;
329 timevalsub(res, tv1, tv2)
330 struct timeval *res, *tv1, *tv2;
332 res->tv_sec = tv1->tv_sec - tv2->tv_sec;
333 res->tv_usec = tv1->tv_usec - tv2->tv_usec;
334 if (res->tv_usec >= 1000000) {
336 res->tv_usec -= 1000000;
338 if (res->tv_usec < 0) {
340 res->tv_usec += 1000000;