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