candidate.c revision 216372 
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 * 4. Neither the name of the University nor the names of its contributors
14 *    may be used to endorse or promote products derived from this software
15 *    without specific prior written permission.
16 *
17 * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
18 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
19 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
20 * ARE DISCLAIMED.  IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
21 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
22 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
23 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
24 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
25 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
26 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
27 * SUCH DAMAGE.
28 */
29
30#ifndef lint
31#if 0
32static char sccsid[] = "@(#)candidate.c	8.1 (Berkeley) 6/6/93";
33#endif
34static const char rcsid[] =
35  "$FreeBSD: head/usr.sbin/timed/timed/candidate.c 216372 2010-12-11 09:38:12Z joel $";
36#endif /* not lint */
37
38#include "globals.h"
39
40/*
41 * `election' candidates a host as master: it is called by a slave
42 * which runs with the -M option set when its election timeout expires.
43 * Note the conservative approach: if a new timed comes up, or another
44 * candidate sends an election request, the candidature is withdrawn.
45 */
46int
47election(net)
48	struct netinfo *net;
49{
50	struct tsp *resp, msg;
51	struct timeval then, wait;
52	struct tsp *answer;
53	struct hosttbl *htp;
54	char loop_lim = 0;
55
56/* This code can get totally confused if it gets slightly behind.  For
57 *	example, if readmsg() has some QUIT messages waiting from the last
58 *	round, we would send an ELECTION message, get the stale QUIT,
59 *	and give up.  This results in network storms when several machines
60 *	do it at once.
61 */
62	wait.tv_sec = 0;
63	wait.tv_usec = 0;
64	while (0 != readmsg(TSP_REFUSE, ANYADDR, &wait, net)) {
65		if (trace)
66			fprintf(fd, "election: discarded stale REFUSE\n");
67	}
68	while (0 != readmsg(TSP_QUIT, ANYADDR, &wait, net)) {
69		if (trace)
70			fprintf(fd, "election: discarded stale QUIT\n");
71	}
72
73again:
74	syslog(LOG_INFO, "This machine is a candidate time master");
75	if (trace)
76		fprintf(fd, "This machine is a candidate time master\n");
77	msg.tsp_type = TSP_ELECTION;
78	msg.tsp_vers = TSPVERSION;
79	(void)strcpy(msg.tsp_name, hostname);
80	bytenetorder(&msg);
81	if (sendto(sock, (char *)&msg, sizeof(struct tsp), 0,
82		   (struct sockaddr*)&net->dest_addr,
83		   sizeof(struct sockaddr)) < 0) {
84		trace_sendto_err(net->dest_addr.sin_addr);
85		return(SLAVE);
86	}
87
88	(void)gettimeofday(&then, 0);
89	then.tv_sec += 3;
90	for (;;) {
91		(void)gettimeofday(&wait, 0);
92		timevalsub(&wait,&then,&wait);
93		resp = readmsg(TSP_ANY, ANYADDR, &wait, net);
94		if (!resp)
95			return(MASTER);
96
97		switch (resp->tsp_type) {
98
99		case TSP_ACCEPT:
100			(void)addmach(resp->tsp_name, &from,fromnet);
101			break;
102
103		case TSP_MASTERUP:
104		case TSP_MASTERREQ:
105			/*
106			 * If another timedaemon is coming up at the same
107			 * time, give up, and let it be the master.
108			 */
109			if (++loop_lim < 5
110			    && !good_host_name(resp->tsp_name)) {
111				(void)addmach(resp->tsp_name, &from,fromnet);
112				suppress(&from, resp->tsp_name, net);
113				goto again;
114			}
115			rmnetmachs(net);
116			return(SLAVE);
117
118		case TSP_QUIT:
119		case TSP_REFUSE:
120			/*
121			 * Collision: change value of election timer
122			 * using exponential backoff.
123			 *
124			 *  Fooey.
125			 * An exponential backoff on a delay starting at
126			 * 6 to 15 minutes for a process that takes
127			 * milliseconds is silly.  It is particularly
128			 * strange that the original code would increase
129			 * the backoff without bound.
130			 */
131			rmnetmachs(net);
132			return(SLAVE);
133
134		case TSP_ELECTION:
135			/* no master for another round */
136			htp = addmach(resp->tsp_name,&from,fromnet);
137			msg.tsp_type = TSP_REFUSE;
138			(void)strcpy(msg.tsp_name, hostname);
139			answer = acksend(&msg, &htp->addr, htp->name,
140					 TSP_ACK, 0, htp->noanswer);
141			if (!answer) {
142				syslog(LOG_ERR, "error in election from %s",
143				       htp->name);
144			}
145			break;
146
147		case TSP_SLAVEUP:
148			(void)addmach(resp->tsp_name, &from,fromnet);
149			break;
150
151		case TSP_SETDATE:
152		case TSP_SETDATEREQ:
153			break;
154
155		default:
156			if (trace) {
157				fprintf(fd, "candidate: ");
158				print(resp, &from);
159			}
160			break;
161		}
162	}
163}
164