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 <sys/file.h> 36 #include <dirent.h> 37 #include <limits.h> 38 #include <errno.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 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 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 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 * 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 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 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