1/*	$OpenBSD: uucplock.c,v 1.11 2006/03/16 19:32:46 deraadt Exp $	*/
2/*	$NetBSD: uucplock.c,v 1.7 1997/02/11 09:24:08 mrg Exp $	*/
3
4/*
5 * Copyright (c) 1988, 1993
6 *	The Regents of the University of California.  All rights reserved.
7 *
8 * Redistribution and use in source and binary forms, with or without
9 * modification, are permitted provided that the following conditions
10 * are met:
11 * 1. Redistributions of source code must retain the above copyright
12 *    notice, this list of conditions and the following disclaimer.
13 * 2. Redistributions in binary form must reproduce the above copyright
14 *    notice, this list of conditions and the following disclaimer in the
15 *    documentation and/or other materials provided with the distribution.
16 * 3. Neither the name of the University nor the names of its contributors
17 *    may be used to endorse or promote products derived from this software
18 *    without specific prior written permission.
19 *
20 * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
21 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
22 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
23 * ARE DISCLAIMED.  IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
24 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
25 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
26 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
27 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
28 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
29 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
30 * SUCH DAMAGE.
31 */
32
33#include <sys/cdefs.h>
34__FBSDID("$FreeBSD$");
35
36#ifndef lint
37#if 0
38static char sccsid[] = "@(#)uucplock.c	8.1 (Berkeley) 6/6/93";
39static const char rcsid[] = "$OpenBSD: uucplock.c,v 1.11 2006/03/16 19:32:46 deraadt Exp $";
40#endif
41#endif /* not lint */
42
43#include <sys/types.h>
44#include <sys/file.h>
45#include <sys/dirent.h>
46#include <stdio.h>
47#include <string.h>
48#include <signal.h>
49#include <unistd.h>
50#include <stdlib.h>
51#include <errno.h>
52#include "tip.h"
53#include "pathnames.h"
54
55/*
56 * uucp style locking routines
57 * return: 0 - success
58 *	  -1 - failure
59 */
60
61int
62uu_lock(char *ttyname)
63{
64	int fd, len;
65	char tbuf[sizeof(_PATH_LOCKDIRNAME) + MAXNAMLEN];
66	char text_pid[81];
67	pid_t pid;
68
69	(void)snprintf(tbuf, sizeof tbuf, _PATH_LOCKDIRNAME, ttyname);
70	fd = open(tbuf, O_RDWR|O_CREAT|O_EXCL, 0660);
71	if (fd < 0) {
72		/*
73		 * file is already locked
74		 * check to see if the process holding the lock still exists
75		 */
76		fd = open(tbuf, O_RDWR, 0);
77		if (fd < 0) {
78			perror(tbuf);
79			fprintf(stderr, "Can't open lock file.\n");
80			return(-1);
81		}
82		len = read(fd, text_pid, sizeof(text_pid)-1);
83		if (len<=0) {
84			perror(tbuf);
85			(void)close(fd);
86			fprintf(stderr, "Can't read lock file.\n");
87			return(-1);
88		}
89		text_pid[len] = 0;
90		pid = atol(text_pid);
91
92		if (kill(pid, 0) == 0 || errno != ESRCH) {
93			(void)close(fd);	/* process is still running */
94			return(-1);
95		}
96		/*
97		 * The process that locked the file isn't running, so
98		 * we'll lock it ourselves
99		 */
100		fprintf(stderr, "Stale lock on %s PID=%ld... overriding.\n",
101			ttyname, (long)pid);
102		if (lseek(fd, (off_t)0, SEEK_SET) < 0) {
103			perror(tbuf);
104			(void)close(fd);
105			fprintf(stderr, "Can't seek lock file.\n");
106			return(-1);
107		}
108		/* fall out and finish the locking process */
109	}
110	pid = getpid();
111	(void)snprintf(text_pid, sizeof text_pid, "%10ld\n", (long)pid);
112	len = strlen(text_pid);
113	if (write(fd, text_pid, len) != len) {
114		(void)close(fd);
115		(void)unlink(tbuf);
116		perror("lock write");
117		return(-1);
118	}
119	(void)close(fd);
120	return(0);
121}
122
123int
124uu_unlock(char *ttyname)
125{
126	char tbuf[sizeof(_PATH_LOCKDIRNAME) + MAXNAMLEN];
127
128	(void)snprintf(tbuf, sizeof tbuf, _PATH_LOCKDIRNAME, ttyname);
129	unexcl();
130	return(unlink(tbuf));
131}
132