uucplock.c revision 1.12 
1/*	$OpenBSD: uucplock.c,v 1.12 2004/05/28 07:03:48 deraadt Exp $	*/
2/*
3 * Copyright (c) 1988, 1993
4 *	The Regents of the University of California.  All rights reserved.
5 *
6 * Redistribution and use in source and binary forms, with or without
7 * modification, are permitted provided that the following conditions
8 * are met:
9 * 1. Redistributions of source code must retain the above copyright
10 *    notice, this list of conditions and the following disclaimer.
11 * 2. Redistributions in binary form must reproduce the above copyright
12 *    notice, this list of conditions and the following disclaimer in the
13 *    documentation and/or other materials provided with the distribution.
14 * 3. Neither the name of the University nor the names of its contributors
15 *    may be used to endorse or promote products derived from this software
16 *    without specific prior written permission.
17 *
18 * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
19 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
20 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
21 * ARE DISCLAIMED.  IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
22 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
23 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
24 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
25 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
26 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
27 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
28 * SUCH DAMAGE.
29 *
30 *
31 */
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 <dirent.h>
39#include <errno.h>
40#include <fcntl.h>
41#include <unistd.h>
42#include <signal.h>
43#include <stdio.h>
44#include <stdlib.h>
45#include <paths.h>
46#include <string.h>
47#include "util.h"
48
49#define MAXTRIES 5
50
51#define LOCKTMP "LCKTMP..%ld"
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 */
64int
65uu_lock(const char *ttyname)
66{
67	char lckname[sizeof(_PATH_UUCPLOCK) + MAXNAMLEN],
68	     lcktmpname[sizeof(_PATH_UUCPLOCK) + MAXNAMLEN];
69	int fd, tmpfd, i, err, uuerr;
70	pid_t pid, pid_old;
71
72	pid = getpid();
73	(void)snprintf(lcktmpname, sizeof(lcktmpname), _PATH_UUCPLOCK LOCKTMP,
74	    (long)pid);
75	(void)snprintf(lckname, sizeof(lckname), _PATH_UUCPLOCK LOCKFMT,
76	    ttyname);
77	if ((tmpfd = creat(lcktmpname, 0664)) < 0)
78		GORET(0, UU_LOCK_CREAT_ERR);
79
80	for (i = 0; i < MAXTRIES; i++) {
81		if (link (lcktmpname, lckname) < 0) {
82			if (errno != EEXIST)
83				GORET(1, UU_LOCK_LINK_ERR);
84			/*
85			 * file is already locked
86			 * check to see if the process holding the lock
87			 * still exists
88			 */
89			if ((fd = open(lckname, O_RDONLY)) < 0)
90				GORET(1, UU_LOCK_OPEN_ERR);
91
92			if ((pid_old = get_pid (fd, &err)) == -1)
93				GORET(2, UU_LOCK_READ_ERR);
94
95			close(fd);
96
97			if (kill(pid_old, 0) == 0 || errno != ESRCH)
98				GORET(1, UU_LOCK_INUSE);
99			/*
100			 * The process that locked the file isn't running, so
101			 * we'll lock it ourselves
102			 */
103			(void)unlink(lckname);
104		} else {
105			if (!put_pid (tmpfd, pid))
106				GORET(3, UU_LOCK_WRITE_ERR);
107			break;
108		}
109	}
110	GORET(1, (i >= MAXTRIES) ? UU_LOCK_TRY_ERR : UU_LOCK_OK);
111
112ret3:
113	(void)unlink(lckname);
114	goto ret1;
115ret2:
116	(void)close(fd);
117ret1:
118	(void)close(tmpfd);
119	(void)unlink(lcktmpname);
120ret0:
121	errno = err;
122	return uuerr;
123}
124
125int
126uu_lock_txfr(const char *ttyname, pid_t pid)
127{
128	char lckname[sizeof(_PATH_UUCPLOCK) + MAXNAMLEN];
129	int fd, err;
130
131	snprintf(lckname, sizeof(lckname), _PATH_UUCPLOCK LOCKFMT, ttyname);
132
133	if ((fd = open(lckname, O_RDWR)) < 0)
134		return UU_LOCK_OWNER_ERR;
135	if (get_pid(fd, &err) != getpid())
136		return UU_LOCK_OWNER_ERR;
137        lseek(fd, 0, SEEK_SET);
138	if (put_pid(fd, pid))
139		return UU_LOCK_WRITE_ERR;
140	close(fd);
141
142	return UU_LOCK_OK;
143}
144
145int
146uu_unlock(const char *ttyname)
147{
148	char tbuf[sizeof(_PATH_UUCPLOCK) + MAXNAMLEN];
149
150	(void)snprintf(tbuf, sizeof(tbuf), _PATH_UUCPLOCK LOCKFMT, ttyname);
151	return unlink(tbuf);
152}
153
154const char *
155uu_lockerr(int uu_lockresult)
156{
157	static char errbuf[128];
158	char *fmt;
159
160	switch (uu_lockresult) {
161	case UU_LOCK_INUSE:
162		return "device in use";
163	case UU_LOCK_OK:
164		return "";
165	case UU_LOCK_OPEN_ERR:
166		fmt = "open error: %s";
167		break;
168	case UU_LOCK_READ_ERR:
169		fmt = "read error: %s";
170		break;
171	case UU_LOCK_CREAT_ERR:
172		fmt = "creat error: %s";
173		break;
174	case UU_LOCK_WRITE_ERR:
175		fmt = "write error: %s";
176		break;
177	case UU_LOCK_LINK_ERR:
178		fmt = "link error: %s";
179		break;
180	case UU_LOCK_TRY_ERR:
181		fmt = "too many tries: %s";
182		break;
183	case UU_LOCK_OWNER_ERR:
184		fmt = "not locking process: %s";
185		break;
186	default:
187		fmt = "undefined error: %s";
188		break;
189	}
190
191	(void)snprintf(errbuf, sizeof(errbuf), fmt, strerror(errno));
192	return errbuf;
193}
194
195static int
196put_pid(int fd, pid_t pid)
197{
198	char buf[32];
199	int len;
200
201	len = snprintf(buf, sizeof buf, "%10ld\n", (long)pid);
202
203	if (write (fd, buf, len) == len) {
204		/* We don't mind too much if ftruncate() fails - see get_pid */
205		ftruncate(fd, len);
206		return 1;
207	}
208	return 0;
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 = strtoul (buf, (char **) NULL, 10);
222	} else {
223		pid = -1;
224		*err = bytes_read ? errno : EINVAL;
225	}
226	return pid;
227}
228