candidate.c revision 30642 
1/*-
2 * Copyright (c) 1985, 1993
3 *	The Regents of the University of California.  All rights reserved.
4 *
5 * Redistribution and use in source and binary forms, with or without
6 * modification, are permitted provided that the following conditions
7 * are met:
8 * 1. Redistributions of source code must retain the above copyright
9 *    notice, this list of conditions and the following disclaimer.
10 * 2. Redistributions in binary form must reproduce the above copyright
11 *    notice, this list of conditions and the following disclaimer in the
12 *    documentation and/or other materials provided with the distribution.
13 * 3. All advertising materials mentioning features or use of this software
14 *    must display the following acknowledgement:
15 *	This product includes software developed by the University of
16 *	California, Berkeley and its contributors.
17 * 4. Neither the name of the University nor the names of its contributors
18 *    may be used to endorse or promote products derived from this software
19 *    without specific prior written permission.
20 *
21 * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
22 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
23 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
24 * ARE DISCLAIMED.  IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
25 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
26 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
27 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
28 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
29 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
30 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
31 * SUCH DAMAGE.
32 */
33
34#ifndef lint
35#if 0
36static char sccsid[] = "@(#)candidate.c	8.1 (Berkeley) 6/6/93";
37#endif
38static const char rcsid[] =
39	"$Id$";
40#endif /* not lint */
41
42#include "globals.h"
43
44/*
45 * `election' candidates a host as master: it is called by a slave
46 * which runs with the -M option set when its election timeout expires.
47 * Note the conservative approach: if a new timed comes up, or another
48 * candidate sends an election request, the candidature is withdrawn.
49 */
50int
51election(net)
52	struct netinfo *net;
53{
54	struct tsp *resp, msg;
55	struct timeval then, wait;
56	struct tsp *answer;
57	struct hosttbl *htp;
58	char loop_lim = 0;
59
60/* This code can get totally confused if it gets slightly behind.  For
61 *	example, if readmsg() has some QUIT messages waiting from the last
62 *	round, we would send an ELECTION message, get the stale QUIT,
63 *	and give up.  This results in network storms when several machines
64 *	do it at once.
65 */
66	wait.tv_sec = 0;
67	wait.tv_usec = 0;
68	while (0 != readmsg(TSP_REFUSE, ANYADDR, &wait, net)) {
69		if (trace)
70			fprintf(fd, "election: discarded stale REFUSE\n");
71	}
72	while (0 != readmsg(TSP_QUIT, ANYADDR, &wait, net)) {
73		if (trace)
74			fprintf(fd, "election: discarded stale QUIT\n");
75	}
76
77again:
78	syslog(LOG_INFO, "This machine is a candidate time master");
79	if (trace)
80		fprintf(fd, "This machine is a candidate time master\n");
81	msg.tsp_type = TSP_ELECTION;
82	msg.tsp_vers = TSPVERSION;
83	(void)strncpy(msg.tsp_name, hostname, sizeof msg.tsp_name-1);
84	msg.tsp_name[sizeof msg.tsp_name-1] = '\0';
85	bytenetorder(&msg);
86	if (sendto(sock, (char *)&msg, sizeof(struct tsp), 0,
87		   (struct sockaddr*)&net->dest_addr,
88		   sizeof(struct sockaddr)) < 0) {
89		trace_sendto_err(net->dest_addr.sin_addr);
90		return(SLAVE);
91	}
92
93	(void)gettimeofday(&then, 0);
94	then.tv_sec += 3;
95	for (;;) {
96		(void)gettimeofday(&wait, 0);
97		timevalsub(&wait,&then,&wait);
98		resp = readmsg(TSP_ANY, ANYADDR, &wait, net);
99		if (!resp)
100			return(MASTER);
101
102		switch (resp->tsp_type) {
103
104		case TSP_ACCEPT:
105			(void)addmach(resp->tsp_name, &from,fromnet);
106			break;
107
108		case TSP_MASTERUP:
109		case TSP_MASTERREQ:
110			/*
111			 * If another timedaemon is coming up at the same
112			 * time, give up, and let it be the master.
113			 */
114			if (++loop_lim < 5
115			    && !good_host_name(resp->tsp_name)) {
116				(void)addmach(resp->tsp_name, &from,fromnet);
117				suppress(&from, resp->tsp_name, net);
118				goto again;
119			}
120			rmnetmachs(net);
121			return(SLAVE);
122
123		case TSP_QUIT:
124		case TSP_REFUSE:
125			/*
126			 * Collision: change value of election timer
127			 * using exponential backoff.
128			 *
129			 *  Fooey.
130			 * An exponential backoff on a delay starting at
131			 * 6 to 15 minutes for a process that takes
132			 * milliseconds is silly.  It is particularly
133			 * strange that the original code would increase
134			 * the backoff without bound.
135			 */
136			rmnetmachs(net);
137			return(SLAVE);
138
139		case TSP_ELECTION:
140			/* no master for another round */
141			htp = addmach(resp->tsp_name,&from,fromnet);
142			msg.tsp_type = TSP_REFUSE;
143			(void)strncpy(msg.tsp_name, hostname,
144					sizeof msg.tsp_name-1);
145			msg.tsp_name[sizeof msg.tsp_name-1] = '\0';
146			answer = acksend(&msg, &htp->addr, htp->name,
147					 TSP_ACK, 0, htp->noanswer);
148			if (!answer) {
149				syslog(LOG_ERR, "error in election from %s",
150				       htp->name);
151			}
152			break;
153
154		case TSP_SLAVEUP:
155			(void)addmach(resp->tsp_name, &from,fromnet);
156			break;
157
158		case TSP_SETDATE:
159		case TSP_SETDATEREQ:
160			break;
161
162		default:
163			if (trace) {
164				fprintf(fd, "candidate: ");
165				print(resp, &from);
166			}
167			break;
168		}
169	}
170}
171