Net2/usr/src/usr.sbin/timed/timed/measure.c
/*
* Copyright (c) 1983 Regents of the University of California.
* All rights reserved.
*
* Redistribution and use in source and binary forms, with or without
* modification, are permitted provided that the following conditions
* are met:
* 1. Redistributions of source code must retain the above copyright
* notice, this list of conditions and the following disclaimer.
* 2. Redistributions in binary form must reproduce the above copyright
* notice, this list of conditions and the following disclaimer in the
* documentation and/or other materials provided with the distribution.
* 3. All advertising materials mentioning features or use of this software
* must display the following acknowledgement:
* This product includes software developed by the University of
* California, Berkeley and its contributors.
* 4. Neither the name of the University nor the names of its contributors
* may be used to endorse or promote products derived from this software
* without specific prior written permission.
*
* THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
* ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
* IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
* ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
* FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
* DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
* OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
* HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
* LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
* OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
* SUCH DAMAGE.
*/
#ifndef lint
static char sccsid[] = "@(#)measure.c 2.8 (Berkeley) 3/2/91";
#endif /* not lint */
#include "globals.h"
#include <protocols/timed.h>
#include <netinet/in_systm.h>
#include <netinet/ip.h>
#include <netinet/ip_icmp.h>
#define BIASP 43199999
#define BIASN -43200000
#define MODULO 86400000
#define PROCESSING_TIME 5 /* ms. to reduce error in measurement */
#define PACKET_IN 1024
extern int id;
int measure_delta;
extern int sock_raw;
static n_short seqno = 0;
/*
* Measures the differences between machines' clocks using
* ICMP timestamp messages.
*/
measure(wait, addr)
struct timeval *wait;
struct sockaddr_in *addr;
{
int length;
int status;
int msgcount, trials;
int cc, count;
fd_set ready;
long sendtime, recvtime, histime;
long min1, min2, diff;
register long delta1, delta2;
struct timeval tv1, tout;
u_char packet[PACKET_IN], opacket[64];
register struct icmp *icp = (struct icmp *) packet;
register struct icmp *oicp = (struct icmp *) opacket;
struct ip *ip = (struct ip *) packet;
min1 = min2 = 0x7fffffff;
status = HOSTDOWN;
measure_delta = HOSTDOWN;
/* empties the icmp input queue */
FD_ZERO(&ready);
empty:
tout.tv_sec = tout.tv_usec = 0;
FD_SET(sock_raw, &ready);
if (select(FD_SETSIZE, &ready, (fd_set *)0, (fd_set *)0, &tout)) {
length = sizeof(struct sockaddr_in);
cc = recvfrom(sock_raw, (char *)packet, PACKET_IN, 0,
(struct sockaddr *)NULL, &length);
if (cc < 0)
return(-1);
goto empty;
}
/*
* To measure the difference, select MSGS messages whose round-trip
* time is smaller than RANGE if ckrange is 1, otherwise simply
* select MSGS messages regardless of round-trip transmission time.
* Choose the smallest transmission time in each of the two directions.
* Use these two latter quantities to compute the delta between
* the two clocks.
*/
length = sizeof(struct sockaddr_in);
oicp->icmp_type = ICMP_TSTAMP;
oicp->icmp_code = 0;
oicp->icmp_cksum = 0;
oicp->icmp_id = id;
oicp->icmp_rtime = 0;
oicp->icmp_ttime = 0;
FD_ZERO(&ready);
msgcount = 0;
for (trials = 0; msgcount < MSGS && trials < TRIALS; ++trials) {
oicp->icmp_seq = ++seqno;
oicp->icmp_cksum = 0;
tout.tv_sec = wait->tv_sec;
tout.tv_usec = wait->tv_usec;
(void)gettimeofday (&tv1, (struct timezone *)0);
sendtime = oicp->icmp_otime = (tv1.tv_sec % (24*60*60)) * 1000
+ tv1.tv_usec / 1000;
oicp->icmp_cksum = in_cksum((u_short *)oicp, sizeof(*oicp));
count = sendto(sock_raw, (char *)opacket, sizeof(*oicp), 0,
(struct sockaddr *)addr, sizeof(struct sockaddr_in));
if (count < 0) {
status = UNREACHABLE;
return(-1);
}
for (;;) {
FD_SET(sock_raw, &ready);
if ((count = select(FD_SETSIZE, &ready, (fd_set *)0,
(fd_set *)0, &tout)) <= 0)
break;
cc = recvfrom(sock_raw, (char *)packet, PACKET_IN, 0,
(struct sockaddr *)NULL, &length);
(void)gettimeofday(&tv1, (struct timezone *)0);
if (cc < 0)
return(-1);
icp = (struct icmp *)(packet + (ip->ip_hl << 2));
if((icp->icmp_type == ICMP_TSTAMPREPLY) &&
icp->icmp_id == id && icp->icmp_seq == seqno)
break;
}
if (count <= 0)
continue; /* resend */
recvtime = (tv1.tv_sec % (24*60*60)) * 1000 +
tv1.tv_usec / 1000;
diff = recvtime - sendtime;
/*
* diff can be less than 0 aroud midnight
*/
if (diff < 0)
continue;
msgcount++;
histime = ntohl((u_long)icp->icmp_rtime);
/*
* a hosts using a time format different from
* ms. since midnight UT (as per RFC792) should
* set the high order bit of the 32-bit time
* value it transmits.
*/
if ((histime & 0x80000000) != 0) {
status = NONSTDTIME;
break;
}
status = GOOD;
delta1 = histime - sendtime;
/*
* Handles wrap-around to avoid that around
* midnight small time differences appear
* enormous. However, the two machine's clocks
* must be within 12 hours from each other.
*/
if (delta1 < BIASN)
delta1 += MODULO;
else if (delta1 > BIASP)
delta1 -= MODULO;
delta2 = recvtime - histime;
if (delta2 < BIASN)
delta2 += MODULO;
else if (delta2 > BIASP)
delta2 -= MODULO;
if (delta1 < min1)
min1 = delta1;
if (delta2 < min2)
min2 = delta2;
if (diff < RANGE) {
min1 = delta1;
min2 = delta2;
break;
}
}
/*
* If no answer is received for TRIALS consecutive times,
* the machine is assumed to be down
*/
if (status == GOOD) {
measure_delta = (min1 - min2)/2 + PROCESSING_TIME;
}
return(status);
}