1 /* $OpenBSD: uucplock.c,v 1.13 2005/03/03 00:14:17 cloder 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
34 static 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 */
58 static int put_pid(int fd, pid_t pid);
59 static pid_t get_pid(int fd,int *err);
60
61 /*
62 * uucp style locking routines
63 */
64 int
uu_lock(const char * ttyname)65 uu_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
112 ret3:
113 (void)unlink(lckname);
114 goto ret1;
115 ret2:
116 (void)close(fd);
117 ret1:
118 (void)close(tmpfd);
119 (void)unlink(lcktmpname);
120 ret0:
121 errno = err;
122 return uuerr;
123 }
124
125 int
uu_lock_txfr(const char * ttyname,pid_t pid)126 uu_lock_txfr(const char *ttyname, pid_t pid)
127 {
128 char lckname[sizeof(_PATH_UUCPLOCK) + MAXNAMLEN];
129 int fd, err, ret;
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 ret = UU_LOCK_OWNER_ERR;
137 else {
138 lseek(fd, 0, SEEK_SET);
139 ret = put_pid(fd, pid) ? UU_LOCK_OK : UU_LOCK_WRITE_ERR;
140 }
141
142 close(fd);
143 return ret;
144 }
145
146 int
uu_unlock(const char * ttyname)147 uu_unlock(const char *ttyname)
148 {
149 char tbuf[sizeof(_PATH_UUCPLOCK) + MAXNAMLEN];
150
151 (void)snprintf(tbuf, sizeof(tbuf), _PATH_UUCPLOCK LOCKFMT, ttyname);
152 return unlink(tbuf);
153 }
154
155 const char *
uu_lockerr(int uu_lockresult)156 uu_lockerr(int uu_lockresult)
157 {
158 static char errbuf[128];
159 char *fmt;
160
161 switch (uu_lockresult) {
162 case UU_LOCK_INUSE:
163 return "device in use";
164 case UU_LOCK_OK:
165 return "";
166 case UU_LOCK_OPEN_ERR:
167 fmt = "open error: %s";
168 break;
169 case UU_LOCK_READ_ERR:
170 fmt = "read error: %s";
171 break;
172 case UU_LOCK_CREAT_ERR:
173 fmt = "creat error: %s";
174 break;
175 case UU_LOCK_WRITE_ERR:
176 fmt = "write error: %s";
177 break;
178 case UU_LOCK_LINK_ERR:
179 fmt = "link error: %s";
180 break;
181 case UU_LOCK_TRY_ERR:
182 fmt = "too many tries: %s";
183 break;
184 case UU_LOCK_OWNER_ERR:
185 fmt = "not locking process: %s";
186 break;
187 default:
188 fmt = "undefined error: %s";
189 break;
190 }
191
192 (void)snprintf(errbuf, sizeof(errbuf), fmt, strerror(errno));
193 return errbuf;
194 }
195
196 static int
put_pid(int fd,pid_t pid)197 put_pid(int fd, pid_t pid)
198 {
199 char buf[32];
200 int len;
201
202 len = snprintf(buf, sizeof buf, "%10ld\n", (long)pid);
203
204 if (len < sizeof buf && len != -1 && write (fd, buf, len) == len) {
205 /* We don't mind too much if ftruncate() fails - see get_pid */
206 ftruncate(fd, len);
207 return 1;
208 }
209 return 0;
210 }
211
212 static pid_t
get_pid(int fd,int * err)213 get_pid(int fd, int *err)
214 {
215 int bytes_read;
216 char buf[32];
217 pid_t pid;
218
219 bytes_read = read (fd, buf, sizeof (buf) - 1);
220 if (bytes_read > 0) {
221 buf[bytes_read] = '\0';
222 pid = strtoul (buf, (char **) NULL, 10);
223 } else {
224 pid = -1;
225 *err = bytes_read ? errno : EINVAL;
226 }
227 return pid;
228 }
229