uucplock.c revision 1.4 
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 * 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 * $Id: uucplock.c,v 1.4 1998/06/10 00:16:19 brian Exp $
34 *
35 */
36
37#ifndef lint
38static const char sccsid[] = "@(#)uucplock.c	8.1 (Berkeley) 6/6/93";
39#endif /* not lint */
40
41#include <sys/types.h>
42#include <sys/file.h>
43#include <dirent.h>
44#include <errno.h>
45#include <unistd.h>
46#include <signal.h>
47#include <stdio.h>
48#include <stdlib.h>
49#include <paths.h>
50#include <string.h>
51#include "util.h"
52
53#define MAXTRIES 5
54
55#define LOCKTMP "LCKTMP..%d"
56#define LOCKFMT "LCK..%s"
57
58#define GORET(level, val) { err = errno; uuerr = (val); \
59			    goto __CONCAT(ret, level); }
60
61/* Forward declarations */
62static int put_pid __P((int fd, pid_t pid));
63static pid_t get_pid __P((int fd,int *err));
64
65/*
66 * uucp style locking routines
67 */
68
69int
70uu_lock(ttyname)
71	const char *ttyname;
72{
73	int fd, tmpfd, i;
74	pid_t pid;
75	char lckname[sizeof(_PATH_UUCPLOCK) + MAXNAMLEN],
76	     lcktmpname[sizeof(_PATH_UUCPLOCK) + MAXNAMLEN];
77	int err, uuerr;
78
79	pid = getpid();
80	(void)snprintf(lcktmpname, sizeof(lcktmpname), _PATH_UUCPLOCK LOCKTMP,
81			pid);
82	(void)snprintf(lckname, sizeof(lckname), _PATH_UUCPLOCK LOCKFMT,
83			ttyname);
84	if ((tmpfd = creat(lcktmpname, 0664)) < 0)
85		GORET(0, UU_LOCK_CREAT_ERR);
86
87	for (i = 0; i < MAXTRIES; i++) {
88		if (link (lcktmpname, lckname) < 0) {
89			if (errno != EEXIST)
90				GORET(1, UU_LOCK_LINK_ERR);
91			/*
92			 * file is already locked
93			 * check to see if the process holding the lock
94			 * still exists
95			 */
96			if ((fd = open(lckname, O_RDONLY)) < 0)
97				GORET(1, UU_LOCK_OPEN_ERR);
98
99			if ((pid = get_pid (fd, &err)) == -1)
100				GORET(2, UU_LOCK_READ_ERR);
101
102			close(fd);
103
104			if (kill(pid, 0) == 0 || errno != ESRCH)
105				GORET(1, UU_LOCK_INUSE);
106			/*
107			 * The process that locked the file isn't running, so
108			 * we'll lock it ourselves
109			 */
110			(void)unlink(lckname);
111		} else {
112			if (!put_pid (tmpfd, pid))
113				GORET(3, UU_LOCK_WRITE_ERR);
114			break;
115		}
116	}
117	GORET(1, (i >= MAXTRIES) ? UU_LOCK_TRY_ERR : UU_LOCK_OK);
118
119ret3:
120	(void)unlink(lckname);
121	goto ret1;
122ret2:
123	(void)close(fd);
124ret1:
125	(void)close(tmpfd);
126	(void)unlink(lcktmpname);
127ret0:
128	errno = err;
129	return uuerr;
130}
131
132int
133uu_lock_txfr(ttyname, pid)
134	const char *ttyname;
135	pid_t pid;
136{
137	int fd, err;
138	char lckname[sizeof(_PATH_UUCPLOCK) + MAXNAMLEN];
139
140	snprintf(lckname, sizeof(lckname), _PATH_UUCPLOCK LOCKFMT, ttyname);
141
142	if ((fd = open(lckname, O_RDWR)) < 0)
143		return UU_LOCK_OWNER_ERR;
144	if (get_pid(fd, &err) != getpid())
145		return UU_LOCK_OWNER_ERR;
146        lseek(fd, 0, SEEK_SET);
147	if (put_pid(fd, pid))
148		return UU_LOCK_WRITE_ERR;
149	close(fd);
150
151	return UU_LOCK_OK;
152}
153
154int
155uu_unlock(ttyname)
156	const char *ttyname;
157{
158	char tbuf[sizeof(_PATH_UUCPLOCK) + MAXNAMLEN];
159
160	(void)snprintf(tbuf, sizeof(tbuf), _PATH_UUCPLOCK LOCKFMT, ttyname);
161	return unlink(tbuf);
162}
163
164const char *
165uu_lockerr(uu_lockresult)
166	int uu_lockresult;
167{
168	static char errbuf[128];
169	char *fmt;
170
171	switch (uu_lockresult) {
172	case UU_LOCK_INUSE:
173		return "device in use";
174	case UU_LOCK_OK:
175		return "";
176	case UU_LOCK_OPEN_ERR:
177		fmt = "open error: %s";
178		break;
179	case UU_LOCK_READ_ERR:
180		fmt = "read error: %s";
181		break;
182	case UU_LOCK_CREAT_ERR:
183		fmt = "creat error: %s";
184		break;
185	case UU_LOCK_WRITE_ERR:
186		fmt = "write error: %s";
187		break;
188	case UU_LOCK_LINK_ERR:
189		fmt = "link error: %s";
190		break;
191	case UU_LOCK_TRY_ERR:
192		fmt = "too many tries: %s";
193		break;
194	case UU_LOCK_OWNER_ERR:
195		fmt = "not locking process: %s";
196		break;
197	default:
198		fmt = "undefined error: %s";
199		break;
200	}
201
202	(void)snprintf(errbuf, sizeof(errbuf), fmt, strerror(errno));
203	return errbuf;
204}
205
206static int
207put_pid(fd, pid)
208	int fd;
209	pid_t pid;
210{
211	char buf[32];
212	int len;
213
214	len = sprintf (buf, "%10d\n", (int)pid);
215
216	if (write (fd, buf, len) == len) {
217		/* We don't mind too much if ftruncate() fails - see get_pid */
218		ftruncate(fd, len);
219		return 1;
220	}
221	return 0;
222}
223
224static pid_t
225get_pid(fd, err)
226	int fd;
227	int *err;
228{
229	int bytes_read;
230	char buf[32];
231	pid_t pid;
232
233	bytes_read = read (fd, buf, sizeof (buf) - 1);
234	if (bytes_read > 0) {
235		buf[bytes_read] = '\0';
236		pid = strtoul (buf, (char **) NULL, 10);
237	} else {
238		pid = -1;
239		*err = bytes_read ? errno : EINVAL;
240	}
241	return pid;
242}
243