2 * Copyright (c) 1985, 1993
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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.
59 * maxmsec wait this many msec at most
60 * wmsec msec to wait for an answer
61 * print print complaints on stderr
63 int /* status val defined in globals.h */
64 measure(u_long maxmsec, u_long wmsec, char *hname, struct sockaddr_in *addr, int print)
71 long sendtime, recvtime, histime1, histime2;
72 long idelta, odelta, total;
73 long min_idelta, min_odelta;
74 struct timeval tdone, tcur, ttrans, twait, tout;
75 u_char packet[PACKET_IN], opacket[64];
76 register struct icmp *icp = (struct icmp *) packet;
77 register struct icmp *oicp = (struct icmp *) opacket;
78 struct ip *ip = (struct ip *) packet;
80 min_idelta = min_odelta = 0x7fffffff;
81 measure_status = HOSTDOWN;
82 measure_delta = HOSTDOWN;
86 /* open raw socket used to measure time differences */
88 sock_raw = socket(AF_INET, SOCK_RAW, IPPROTO_ICMP);
90 syslog(LOG_ERR, "opening raw socket: %m");
97 * empty the icmp input queue
101 tout.tv_sec = tout.tv_usec = 0;
102 FD_SET(sock_raw, &ready);
103 if (select(sock_raw+1, &ready, 0,0, &tout)) {
104 length = sizeof(struct sockaddr_in);
105 cc = recvfrom(sock_raw, (char *)packet, PACKET_IN, 0,
115 * Choose the smallest transmission time in each of the two
116 * directions. Use these two latter quantities to compute the delta
117 * between the two clocks.
120 oicp->icmp_type = ICMP_TSTAMP;
122 oicp->icmp_id = getpid();
123 oicp->icmp_rtime = 0;
124 oicp->icmp_ttime = 0;
125 oicp->icmp_seq = seqno;
129 (void)gettimeofday(&tdone, NULL);
130 mstotvround(&tout, maxmsec);
131 timevaladd(&tdone, &tout); /* when we give up */
133 mstotvround(&twait, wmsec);
136 while (rcvcount < MSGS) {
137 (void)gettimeofday(&tcur, NULL);
140 * keep sending until we have sent the max
142 if (trials < TRIALS) {
144 oicp->icmp_otime = htonl((tcur.tv_sec % SECDAY) * 1000
145 + tcur.tv_usec / 1000);
146 oicp->icmp_cksum = 0;
147 oicp->icmp_cksum = in_cksum((u_short*)oicp,
150 count = sendto(sock_raw, opacket, sizeof(*oicp), 0,
151 (struct sockaddr*)addr,
152 sizeof(struct sockaddr));
154 if (measure_status == HOSTDOWN)
155 measure_status = UNREACHABLE;
161 timevaladd(&ttrans, &twait);
166 while (rcvcount < trials) {
167 timevalsub(&tout, &ttrans, &tcur);
171 FD_SET(sock_raw, &ready);
172 count = select(sock_raw+1, &ready, (fd_set *)0,
174 (void)gettimeofday(&tcur, NULL);
178 length = sizeof(struct sockaddr_in);
179 cc = recvfrom(sock_raw, (char *)packet, PACKET_IN, 0,
185 * got something. See if it is ours
187 icp = (struct icmp *)(packet + (ip->ip_hl << 2));
189 || icp->icmp_type != ICMP_TSTAMPREPLY
190 || icp->icmp_id != oicp->icmp_id
191 || icp->icmp_seq < seqno
192 || icp->icmp_seq >= oicp->icmp_seq)
196 sendtime = ntohl(icp->icmp_otime);
197 recvtime = ((tcur.tv_sec % SECDAY) * 1000 +
198 tcur.tv_usec / 1000);
200 total = recvtime-sendtime;
201 if (total < 0) /* do not hassle midnight */
205 histime1 = ntohl(icp->icmp_rtime);
206 histime2 = ntohl(icp->icmp_ttime);
208 * a host using a time format different from
209 * msec. since midnight UT (as per RFC792) should
210 * set the high order bit of the 32-bit time
211 * value it transmits.
213 if ((histime1 & 0x80000000) != 0) {
214 measure_status = NONSTDTIME;
217 measure_status = GOOD;
219 idelta = recvtime-histime2;
220 odelta = histime1-sendtime;
222 /* do not be confused by midnight */
223 if (idelta < -MSEC_DAY/2) idelta += MSEC_DAY;
224 else if (idelta > MSEC_DAY/2) idelta -= MSEC_DAY;
226 if (odelta < -MSEC_DAY/2) odelta += MSEC_DAY;
227 else if (odelta > MSEC_DAY/2) odelta -= MSEC_DAY;
229 /* save the quantization error so that we can get a
230 * measurement finer than our system clock.
232 if (total < MIN_ROUND) {
233 measure_delta = (odelta - idelta)/2;
237 if (idelta < min_idelta)
239 if (odelta < min_odelta)
242 measure_delta = (min_odelta - min_idelta)/2;
245 if (tcur.tv_sec > tdone.tv_sec
246 || (tcur.tv_sec == tdone.tv_sec
247 && tcur.tv_usec >= tdone.tv_usec))
252 seqno += TRIALS; /* allocate our sequence numbers */
255 * If no answer is received for TRIALS consecutive times,
256 * the machine is assumed to be down
258 if (measure_status == GOOD) {
261 "measured delta %4d, %d trials to %-15s %s\n",
262 measure_delta, trials,
263 inet_ntoa(addr->sin_addr), hname);
267 warn("measure %s", hname);
270 syslog(LOG_ERR, "measure %s: %m", hname);
272 syslog(LOG_ERR, "measure: %s did not respond", hname);
276 "measure: %s failed after %d trials\n",
282 return(measure_status);
290 * round a number of milliseconds into a struct timeval
293 mstotvround(struct timeval *res, long x)
300 res->tv_sec = x/1000;
301 res->tv_usec = (x-res->tv_sec*1000)*1000;
302 if (res->tv_usec < 0) {
303 res->tv_usec += 1000000;
309 timevaladd(struct timeval *tv1, struct timeval *tv2)
311 tv1->tv_sec += tv2->tv_sec;
312 tv1->tv_usec += tv2->tv_usec;
313 if (tv1->tv_usec >= 1000000) {
315 tv1->tv_usec -= 1000000;
317 if (tv1->tv_usec < 0) {
319 tv1->tv_usec += 1000000;
324 timevalsub(struct timeval *res, struct timeval *tv1, struct timeval *tv2)
326 res->tv_sec = tv1->tv_sec - tv2->tv_sec;
327 res->tv_usec = tv1->tv_usec - tv2->tv_usec;
328 if (res->tv_usec >= 1000000) {
330 res->tv_usec -= 1000000;
332 if (res->tv_usec < 0) {
334 res->tv_usec += 1000000;