uucplock.c revision 36451 
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 1.8 1997/08/10 18:42:39 ache 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 "libutil.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 (int fd, pid_t pid);
63static pid_t get_pid (int fd,int *err);
64
65/*
66 * uucp style locking routines
67 */
68
69int
70uu_lock(const char *ttyname)
71{
72	int fd, tmpfd, i;
73	pid_t pid;
74	char lckname[sizeof(_PATH_UUCPLOCK) + MAXNAMLEN],
75	     lcktmpname[sizeof(_PATH_UUCPLOCK) + MAXNAMLEN];
76	int err, uuerr;
77
78	pid = getpid();
79	(void)snprintf(lcktmpname, sizeof(lcktmpname), _PATH_UUCPLOCK LOCKTMP,
80			pid);
81	(void)snprintf(lckname, sizeof(lckname), _PATH_UUCPLOCK LOCKFMT,
82			ttyname);
83	if ((tmpfd = creat(lcktmpname, 0664)) < 0)
84		GORET(0, UU_LOCK_CREAT_ERR);
85
86	for (i = 0; i < MAXTRIES; i++) {
87		if (link (lcktmpname, lckname) < 0) {
88			if (errno != EEXIST)
89				GORET(1, UU_LOCK_LINK_ERR);
90			/*
91			 * file is already locked
92			 * check to see if the process holding the lock
93			 * still exists
94			 */
95			if ((fd = open(lckname, O_RDONLY)) < 0)
96				GORET(1, UU_LOCK_OPEN_ERR);
97
98			if ((pid = get_pid (fd, &err)) == -1)
99				GORET(2, UU_LOCK_READ_ERR);
100
101			close(fd);
102
103			if (kill(pid, 0) == 0 || errno != ESRCH)
104				GORET(1, UU_LOCK_INUSE);
105			/*
106			 * The process that locked the file isn't running, so
107			 * we'll lock it ourselves
108			 */
109			(void)unlink(lckname);
110		} else {
111			if (!put_pid (tmpfd, pid))
112				GORET(3, UU_LOCK_WRITE_ERR);
113			break;
114		}
115	}
116	GORET(1, (i >= MAXTRIES) ? UU_LOCK_TRY_ERR : UU_LOCK_OK);
117
118ret3:
119	(void)unlink(lckname);
120	goto ret1;
121ret2:
122	(void)close(fd);
123ret1:
124	(void)close(tmpfd);
125	(void)unlink(lcktmpname);
126ret0:
127	errno = err;
128	return uuerr;
129}
130
131int
132uu_lock_txfr(const char *ttyname, pid_t pid)
133{
134	int fd, err;
135	char lckname[sizeof(_PATH_UUCPLOCK) + MAXNAMLEN];
136
137	snprintf(lckname, sizeof(lckname), _PATH_UUCPLOCK LOCKFMT, ttyname);
138
139	if ((fd = open(lckname, O_RDWR)) < 0)
140		return UU_LOCK_OWNER_ERR;
141	if (get_pid(fd, &err) != getpid())
142		return UU_LOCK_OWNER_ERR;
143        lseek(fd, 0, SEEK_SET);
144	if (put_pid(fd, pid))
145		return UU_LOCK_WRITE_ERR;
146	close(fd);
147
148	return UU_LOCK_OK;
149}
150
151int
152uu_unlock(const char *ttyname)
153{
154	char tbuf[sizeof(_PATH_UUCPLOCK) + MAXNAMLEN];
155
156	(void)snprintf(tbuf, sizeof(tbuf), _PATH_UUCPLOCK LOCKFMT, ttyname);
157	return unlink(tbuf);
158}
159
160const char *
161uu_lockerr(int uu_lockresult)
162{
163	static char errbuf[128];
164	char *fmt;
165
166	switch (uu_lockresult) {
167		case UU_LOCK_INUSE:
168			return "device in use";
169		case UU_LOCK_OK:
170			return "";
171		case UU_LOCK_OPEN_ERR:
172			fmt = "open error: %s";
173			break;
174		case UU_LOCK_READ_ERR:
175			fmt = "read error: %s";
176			break;
177		case UU_LOCK_CREAT_ERR:
178			fmt = "creat error: %s";
179			break;
180		case UU_LOCK_WRITE_ERR:
181			fmt = "write error: %s";
182			break;
183		case UU_LOCK_LINK_ERR:
184			fmt = "link error: %s";
185			break;
186		case UU_LOCK_TRY_ERR:
187			fmt = "too many tries: %s";
188			break;
189		case UU_LOCK_OWNER_ERR:
190			fmt = "not locking process: %s";
191			break;
192		default:
193			fmt = "undefined error: %s";
194			break;
195	}
196
197	(void)snprintf(errbuf, sizeof(errbuf), fmt, strerror(errno));
198	return errbuf;
199}
200
201static int
202put_pid(int fd, pid_t pid)
203{
204	char buf[32];
205	int len;
206
207	len = sprintf (buf, "%10d\n", pid);
208	return write (fd, buf, len) == len;
209}
210
211static pid_t
212get_pid(int fd, int *err)
213{
214	int bytes_read;
215	char buf[32];
216	pid_t pid;
217
218	bytes_read = read (fd, buf, sizeof (buf) - 1);
219	if (bytes_read > 0) {
220		buf[bytes_read] = '\0';
221		pid = strtol (buf, (char **) NULL, 10);
222	} else {
223		pid = -1;
224		*err = bytes_read ? errno : EINVAL;
225	}
226	return pid;
227}
228
229/* end of uucplock.c */
230