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. 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 * $FreeBSD: head/lib/libutil/uucplock.c 255007 2013-08-28 21:10:37Z jilles $
30 *
31 * @(#)uucplock.c 8.1 (Berkeley) 6/6/93
32 */
33
34 #include <sys/types.h>
35 #include <dirent.h>
36 #include <limits.h>
37 #include <errno.h>
38 #include <fcntl.h>
39 #include <paths.h>
40 #include <signal.h>
41 #include <stdio.h>
42 #include <stdlib.h>
43 #include <string.h>
44 #include <unistd.h>
45 #include <libutil.h>
46
47 #define MAXTRIES 5
48
49 #define LOCKTMP "LCKTMP..%d"
50 #define LOCKFMT "LCK..%s"
51
52 #define GORET(level, val) { err = errno; uuerr = (val); \
53 goto __CONCAT(ret, level); }
54
55 /* Forward declarations */
56 static int put_pid (int fd, pid_t pid);
57 static pid_t get_pid (int fd,int *err);
58
59 /*
60 * uucp style locking routines
61 */
62
63 int
uu_lock(const char * tty_name)64 uu_lock(const char *tty_name)
65 {
66 int fd, tmpfd, i;
67 pid_t pid, pid_old;
68 char lckname[sizeof(_PATH_UUCPLOCK) + NAME_MAX],
69 lcktmpname[sizeof(_PATH_UUCPLOCK) + NAME_MAX];
70 int err, uuerr;
71
72 pid = getpid();
73 (void)snprintf(lcktmpname, sizeof(lcktmpname), _PATH_UUCPLOCK LOCKTMP,
74 pid);
75 (void)snprintf(lckname, sizeof(lckname), _PATH_UUCPLOCK LOCKFMT,
76 tty_name);
77 if ((tmpfd = open(lcktmpname, O_CREAT | O_TRUNC | O_WRONLY | O_CLOEXEC,
78 0664)) < 0)
79 GORET(0, UU_LOCK_CREAT_ERR);
80
81 for (i = 0; i < MAXTRIES; i++) {
82 if (link (lcktmpname, lckname) < 0) {
83 if (errno != EEXIST)
84 GORET(1, UU_LOCK_LINK_ERR);
85 /*
86 * file is already locked
87 * check to see if the process holding the lock
88 * still exists
89 */
90 if ((fd = open(lckname, O_RDONLY | O_CLOEXEC)) < 0)
91 GORET(1, UU_LOCK_OPEN_ERR);
92
93 if ((pid_old = get_pid (fd, &err)) == -1)
94 GORET(2, UU_LOCK_READ_ERR);
95
96 close(fd);
97
98 if (kill(pid_old, 0) == 0 || errno != ESRCH)
99 GORET(1, UU_LOCK_INUSE);
100 /*
101 * The process that locked the file isn't running, so
102 * we'll lock it ourselves
103 */
104 (void)unlink(lckname);
105 } else {
106 if (!put_pid (tmpfd, pid))
107 GORET(3, UU_LOCK_WRITE_ERR);
108 break;
109 }
110 }
111 GORET(1, (i >= MAXTRIES) ? UU_LOCK_TRY_ERR : UU_LOCK_OK);
112
113 ret3:
114 (void)unlink(lckname);
115 goto ret1;
116 ret2:
117 (void)close(fd);
118 ret1:
119 (void)close(tmpfd);
120 (void)unlink(lcktmpname);
121 ret0:
122 errno = err;
123 return uuerr;
124 }
125
126 int
uu_lock_txfr(const char * tty_name,pid_t pid)127 uu_lock_txfr(const char *tty_name, pid_t pid)
128 {
129 int fd, err;
130 char lckname[sizeof(_PATH_UUCPLOCK) + NAME_MAX];
131
132 snprintf(lckname, sizeof(lckname), _PATH_UUCPLOCK LOCKFMT, tty_name);
133
134 if ((fd = open(lckname, O_RDWR | O_CLOEXEC)) < 0)
135 return UU_LOCK_OWNER_ERR;
136 if (get_pid(fd, &err) != getpid())
137 err = UU_LOCK_OWNER_ERR;
138 else {
139 lseek(fd, (off_t)0, SEEK_SET);
140 err = put_pid(fd, pid) ? 0 : UU_LOCK_WRITE_ERR;
141 }
142 close(fd);
143
144 return err;
145 }
146
147 int
uu_unlock(const char * tty_name)148 uu_unlock(const char *tty_name)
149 {
150 char tbuf[sizeof(_PATH_UUCPLOCK) + NAME_MAX];
151
152 (void)snprintf(tbuf, sizeof(tbuf), _PATH_UUCPLOCK LOCKFMT, tty_name);
153 return unlink(tbuf);
154 }
155
156 const char *
uu_lockerr(int uu_lockresult)157 uu_lockerr(int uu_lockresult)
158 {
159 static char errbuf[128];
160 const char *fmt;
161
162 switch (uu_lockresult) {
163 case UU_LOCK_INUSE:
164 return "device in use";
165 case UU_LOCK_OK:
166 return "";
167 case UU_LOCK_OPEN_ERR:
168 fmt = "open error: %s";
169 break;
170 case UU_LOCK_READ_ERR:
171 fmt = "read error: %s";
172 break;
173 case UU_LOCK_CREAT_ERR:
174 fmt = "creat error: %s";
175 break;
176 case UU_LOCK_WRITE_ERR:
177 fmt = "write error: %s";
178 break;
179 case UU_LOCK_LINK_ERR:
180 fmt = "link error: %s";
181 break;
182 case UU_LOCK_TRY_ERR:
183 fmt = "too many tries: %s";
184 break;
185 case UU_LOCK_OWNER_ERR:
186 fmt = "not locking process: %s";
187 break;
188 default:
189 fmt = "undefined error: %s";
190 break;
191 }
192
193 (void)snprintf(errbuf, sizeof(errbuf), fmt, strerror(errno));
194 return errbuf;
195 }
196
197 static int
put_pid(int fd,pid_t pid)198 put_pid(int fd, pid_t pid)
199 {
200 char buf[32];
201 int len;
202
203 len = sprintf (buf, "%10d\n", (int)pid);
204 return write (fd, buf, (size_t)len) == len;
205 }
206
207 static pid_t
get_pid(int fd,int * err)208 get_pid(int fd, int *err)
209 {
210 int bytes_read;
211 char buf[32];
212 pid_t pid;
213
214 bytes_read = read (fd, buf, sizeof (buf) - 1);
215 if (bytes_read > 0) {
216 buf[bytes_read] = '\0';
217 pid = (pid_t)strtol (buf, NULL, 10);
218 } else {
219 pid = -1;
220 *err = bytes_read ? errno : EINVAL;
221 }
222 return pid;
223 }
224
225 /* end of uucplock.c */
226