1/*
2 * Copyright (c) 1988, 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#include <sys/cdefs.h>
31__FBSDID("$FreeBSD$");
32
33#ifndef lint
34static const char sccsid[] = "@(#)uucplock.c	8.1 (Berkeley) 6/6/93";
35#endif /* not lint */
36
37#include <sys/types.h>
38#include <sys/file.h>
39#include <dirent.h>
40#include <errno.h>
41#include <paths.h>
42#include <signal.h>
43#include <stdio.h>
44#include <stdlib.h>
45#include <string.h>
46#include <unistd.h>
47#include "libutil.h"
48
49#define MAXTRIES 5
50
51#define LOCKTMP "LCKTMP..%d"
52#define LOCKFMT "LCK..%s"
53
54#define GORET(level, val) { err = errno; uuerr = (val); \
55			    goto __CONCAT(ret, level); }
56
57/* Forward declarations */
58static int put_pid (int fd, pid_t pid);
59static pid_t get_pid (int fd,int *err);
60
61/*
62 * uucp style locking routines
63 */
64
65int
66uu_lock(const char *tty_name)
67{
68	int fd, tmpfd, i;
69	pid_t pid, pid_old;
70	char lckname[sizeof(_PATH_UUCPLOCK) + MAXNAMLEN],
71	     lcktmpname[sizeof(_PATH_UUCPLOCK) + MAXNAMLEN];
72	int err, uuerr;
73
74	pid = getpid();
75	(void)snprintf(lcktmpname, sizeof(lcktmpname), _PATH_UUCPLOCK LOCKTMP,
76			pid);
77	(void)snprintf(lckname, sizeof(lckname), _PATH_UUCPLOCK LOCKFMT,
78			tty_name);
79	if ((tmpfd = open(lcktmpname, O_CREAT | O_TRUNC | O_WRONLY | O_CLOEXEC,
80	    0664)) < 0)
81		GORET(0, UU_LOCK_CREAT_ERR);
82
83	for (i = 0; i < MAXTRIES; i++) {
84		if (link (lcktmpname, lckname) < 0) {
85			if (errno != EEXIST)
86				GORET(1, UU_LOCK_LINK_ERR);
87			/*
88			 * file is already locked
89			 * check to see if the process holding the lock
90			 * still exists
91			 */
92			if ((fd = open(lckname, O_RDONLY | O_CLOEXEC)) < 0)
93				GORET(1, UU_LOCK_OPEN_ERR);
94
95			if ((pid_old = get_pid (fd, &err)) == -1)
96				GORET(2, UU_LOCK_READ_ERR);
97
98			close(fd);
99
100			if (kill(pid_old, 0) == 0 || errno != ESRCH)
101				GORET(1, UU_LOCK_INUSE);
102			/*
103			 * The process that locked the file isn't running, so
104			 * we'll lock it ourselves
105			 */
106			(void)unlink(lckname);
107		} else {
108			if (!put_pid (tmpfd, pid))
109				GORET(3, UU_LOCK_WRITE_ERR);
110			break;
111		}
112	}
113	GORET(1, (i >= MAXTRIES) ? UU_LOCK_TRY_ERR : UU_LOCK_OK);
114
115ret3:
116	(void)unlink(lckname);
117	goto ret1;
118ret2:
119	(void)close(fd);
120ret1:
121	(void)close(tmpfd);
122	(void)unlink(lcktmpname);
123ret0:
124	errno = err;
125	return uuerr;
126}
127
128int
129uu_lock_txfr(const char *tty_name, pid_t pid)
130{
131	int fd, err;
132	char lckname[sizeof(_PATH_UUCPLOCK) + MAXNAMLEN];
133
134	snprintf(lckname, sizeof(lckname), _PATH_UUCPLOCK LOCKFMT, tty_name);
135
136	if ((fd = open(lckname, O_RDWR | O_CLOEXEC)) < 0)
137		return UU_LOCK_OWNER_ERR;
138	if (get_pid(fd, &err) != getpid())
139		err = UU_LOCK_OWNER_ERR;
140	else {
141        	lseek(fd, (off_t)0, SEEK_SET);
142		err = put_pid(fd, pid) ? 0 : UU_LOCK_WRITE_ERR;
143	}
144	close(fd);
145
146	return err;
147}
148
149int
150uu_unlock(const char *tty_name)
151{
152	char tbuf[sizeof(_PATH_UUCPLOCK) + MAXNAMLEN];
153
154	(void)snprintf(tbuf, sizeof(tbuf), _PATH_UUCPLOCK LOCKFMT, tty_name);
155	return unlink(tbuf);
156}
157
158const char *
159uu_lockerr(int uu_lockresult)
160{
161	static char errbuf[128];
162	const char *fmt;
163
164	switch (uu_lockresult) {
165		case UU_LOCK_INUSE:
166			return "device in use";
167		case UU_LOCK_OK:
168			return "";
169		case UU_LOCK_OPEN_ERR:
170			fmt = "open error: %s";
171			break;
172		case UU_LOCK_READ_ERR:
173			fmt = "read error: %s";
174			break;
175		case UU_LOCK_CREAT_ERR:
176			fmt = "creat error: %s";
177			break;
178		case UU_LOCK_WRITE_ERR:
179			fmt = "write error: %s";
180			break;
181		case UU_LOCK_LINK_ERR:
182			fmt = "link error: %s";
183			break;
184		case UU_LOCK_TRY_ERR:
185			fmt = "too many tries: %s";
186			break;
187		case UU_LOCK_OWNER_ERR:
188			fmt = "not locking process: %s";
189			break;
190		default:
191			fmt = "undefined error: %s";
192			break;
193	}
194
195	(void)snprintf(errbuf, sizeof(errbuf), fmt, strerror(errno));
196	return errbuf;
197}
198
199static int
200put_pid(int fd, pid_t pid)
201{
202	char buf[32];
203	int len;
204
205	len = sprintf (buf, "%10d\n", (int)pid);
206	return write (fd, buf, (size_t)len) == len;
207}
208
209static pid_t
210get_pid(int fd, int *err)
211{
212	int bytes_read;
213	char buf[32];
214	pid_t pid;
215
216	bytes_read = read (fd, buf, sizeof (buf) - 1);
217	if (bytes_read > 0) {
218		buf[bytes_read] = '\0';
219		pid = (pid_t)strtol (buf, (char **) NULL, 10);
220	} else {
221		pid = -1;
222		*err = bytes_read ? errno : EINVAL;
223	}
224	return pid;
225}
226
227/* end of uucplock.c */
228