candidate.c revision 8857 
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
35static char sccsid[] = "@(#)candidate.c	8.1 (Berkeley) 6/6/93";
36#endif /* not lint */
37
38#ifdef sgi
39#ident "$Revision: 1.1.1.1 $"
40#endif
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48 * candidate sends an election request, the candidature is withdrawn.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)strcpy(msg.tsp_name, hostname);
84	bytenetorder(&msg);
85	if (sendto(sock, (char *)&msg, sizeof(struct tsp), 0,
86		   (struct sockaddr*)&net->dest_addr,
87		   sizeof(struct sockaddr)) < 0) {
88		trace_sendto_err(net->dest_addr.sin_addr);
89		return(SLAVE);
90	}
91
92	(void)gettimeofday(&then, 0);
93	then.tv_sec += 3;
94	for (;;) {
95		(void)gettimeofday(&wait, 0);
96		timevalsub(&wait,&then,&wait);
97		resp = readmsg(TSP_ANY, ANYADDR, &wait, net);
98		if (!resp)
99			return(MASTER);
100
101		switch (resp->tsp_type) {
102
103		case TSP_ACCEPT:
104			(void)addmach(resp->tsp_name, &from,fromnet);
105			break;
106
107		case TSP_MASTERUP:
108		case TSP_MASTERREQ:
109			/*
110			 * If another timedaemon is coming up at the same
111			 * time, give up, and let it be the master.
112			 */
113			if (++loop_lim < 5
114			    && !good_host_name(resp->tsp_name)) {
115				(void)addmach(resp->tsp_name, &from,fromnet);
116				suppress(&from, resp->tsp_name, net);
117				goto again;
118			}
119			rmnetmachs(net);
120			return(SLAVE);
121
122		case TSP_QUIT:
123		case TSP_REFUSE:
124			/*
125			 * Collision: change value of election timer
126			 * using exponential backoff.
127			 *
128			 *  Fooey.
129			 * An exponential backoff on a delay starting at
130			 * 6 to 15 minutes for a process that takes
131			 * milliseconds is silly.  It is particularly
132			 * strange that the original code would increase
133			 * the backoff without bound.
134			 */
135			rmnetmachs(net);
136			return(SLAVE);
137
138		case TSP_ELECTION:
139			/* no master for another round */
140			htp = addmach(resp->tsp_name,&from,fromnet);
141			msg.tsp_type = TSP_REFUSE;
142			(void)strcpy(msg.tsp_name, hostname);
143			answer = acksend(&msg, &htp->addr, htp->name,
144					 TSP_ACK, 0, htp->noanswer);
145			if (!answer) {
146				syslog(LOG_ERR, "error in election from %s",
147				       htp->name);
148			}
149			break;
150
151		case TSP_SLAVEUP:
152			(void)addmach(resp->tsp_name, &from,fromnet);
153			break;
154
155		case TSP_SETDATE:
156		case TSP_SETDATEREQ:
157			break;
158
159		default:
160			if (trace) {
161				fprintf(fd, "candidate: ");
162				print(resp, &from);
163			}
164			break;
165		}
166	}
167}
168