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 * $FreeBSD: src/lib/libutil/uucplock.c,v 1.12.2.1 2000/10/09 20:20:52 brian Exp $ 34 * $DragonFly: src/lib/libutil/uucplock.c,v 1.5 2005/08/08 13:00:12 joerg Exp $ 35 * 36 * @(#)uucplock.c 8.1 (Berkeley) 6/6/93 37 */ 38 39 #include <sys/types.h> 40 #include <sys/file.h> 41 42 #include <dirent.h> 43 #include <errno.h> 44 #include <limits.h> 45 #include <paths.h> 46 #include <signal.h> 47 #include <stdio.h> 48 #include <stdlib.h> 49 #include <string.h> 50 #include <unistd.h> 51 52 #include "libutil.h" 53 54 #define MAXTRIES 5 55 56 #define LOCKTMP "LCKTMP..%d" 57 #define LOCKFMT "LCK..%s" 58 59 #define GORET(level, val) { err = errno; uuerr = (val); \ 60 goto __CONCAT(ret, level); } 61 62 /* Forward declarations */ 63 static int put_pid (int fd, pid_t pid); 64 static pid_t get_pid (int fd,int *err); 65 66 /* 67 * uucp style locking routines 68 */ 69 70 int 71 uu_lock(const char *tty_name) 72 { 73 int fd, tmpfd, i; 74 pid_t pid, pid_old; 75 char lckname[PATH_MAX], 76 lcktmpname[PATH_MAX]; 77 int err, uuerr; 78 79 pid = getpid(); 80 (void)snprintf(lcktmpname, sizeof(lcktmpname), _PATH_UUCPLOCK LOCKTMP, 81 pid); 82 (void)snprintf(lckname, sizeof(lckname), _PATH_UUCPLOCK LOCKFMT, 83 tty_name); 84 if ((tmpfd = creat(lcktmpname, 0664)) < 0) 85 GORET(0, UU_LOCK_CREAT_ERR); 86 87 for (i = 0; i < MAXTRIES; i++) { 88 if (link (lcktmpname, lckname) < 0) { 89 if (errno != EEXIST) 90 GORET(1, UU_LOCK_LINK_ERR); 91 /* 92 * file is already locked 93 * check to see if the process holding the lock 94 * still exists 95 */ 96 if ((fd = open(lckname, O_RDONLY)) < 0) 97 GORET(1, UU_LOCK_OPEN_ERR); 98 99 if ((pid_old = get_pid (fd, &err)) == -1) 100 GORET(2, UU_LOCK_READ_ERR); 101 102 close(fd); 103 104 if (kill(pid_old, 0) == 0 || errno != ESRCH) 105 GORET(1, UU_LOCK_INUSE); 106 /* 107 * The process that locked the file isn't running, so 108 * we'll lock it ourselves 109 */ 110 (void)unlink(lckname); 111 } else { 112 if (!put_pid (tmpfd, pid)) 113 GORET(3, UU_LOCK_WRITE_ERR); 114 break; 115 } 116 } 117 GORET(1, (i >= MAXTRIES) ? UU_LOCK_TRY_ERR : UU_LOCK_OK); 118 119 ret3: 120 (void)unlink(lckname); 121 goto ret1; 122 ret2: 123 (void)close(fd); 124 ret1: 125 (void)close(tmpfd); 126 (void)unlink(lcktmpname); 127 ret0: 128 errno = err; 129 return uuerr; 130 } 131 132 int 133 uu_lock_txfr(const char *tty_name, pid_t pid) 134 { 135 int fd, err; 136 char lckname[PATH_MAX]; 137 138 snprintf(lckname, sizeof(lckname), _PATH_UUCPLOCK LOCKFMT, tty_name); 139 140 if ((fd = open(lckname, O_RDWR)) < 0) 141 return UU_LOCK_OWNER_ERR; 142 if (get_pid(fd, &err) != getpid()) 143 err = UU_LOCK_OWNER_ERR; 144 else { 145 lseek(fd, 0, SEEK_SET); 146 err = put_pid(fd, pid) ? 0 : UU_LOCK_WRITE_ERR; 147 } 148 close(fd); 149 150 return err; 151 } 152 153 int 154 uu_unlock(const char *tty_name) 155 { 156 char tbuf[PATH_MAX]; 157 158 (void)snprintf(tbuf, sizeof(tbuf), _PATH_UUCPLOCK LOCKFMT, tty_name); 159 return unlink(tbuf); 160 } 161 162 const char * 163 uu_lockerr(int uu_lockresult) 164 { 165 static char errbuf[128]; 166 const char *fmt; 167 168 switch (uu_lockresult) { 169 case UU_LOCK_INUSE: 170 return "device in use"; 171 case UU_LOCK_OK: 172 return ""; 173 case UU_LOCK_OPEN_ERR: 174 fmt = "open error: %s"; 175 break; 176 case UU_LOCK_READ_ERR: 177 fmt = "read error: %s"; 178 break; 179 case UU_LOCK_CREAT_ERR: 180 fmt = "creat error: %s"; 181 break; 182 case UU_LOCK_WRITE_ERR: 183 fmt = "write error: %s"; 184 break; 185 case UU_LOCK_LINK_ERR: 186 fmt = "link error: %s"; 187 break; 188 case UU_LOCK_TRY_ERR: 189 fmt = "too many tries: %s"; 190 break; 191 case UU_LOCK_OWNER_ERR: 192 fmt = "not locking process: %s"; 193 break; 194 default: 195 fmt = "undefined error: %s"; 196 break; 197 } 198 199 (void)snprintf(errbuf, sizeof(errbuf), fmt, strerror(errno)); 200 return errbuf; 201 } 202 203 static int 204 put_pid(int fd, pid_t pid) 205 { 206 char buf[32]; 207 int len; 208 209 len = sprintf (buf, "%10d\n", (int)pid); 210 return write (fd, buf, len) == len; 211 } 212 213 static pid_t 214 get_pid(int fd, int *err) 215 { 216 int bytes_read; 217 char buf[32]; 218 pid_t pid; 219 220 bytes_read = read (fd, buf, sizeof (buf) - 1); 221 if (bytes_read > 0) { 222 buf[bytes_read] = '\0'; 223 pid = strtol (buf, (char **) NULL, 10); 224 } else { 225 pid = -1; 226 *err = bytes_read ? errno : EINVAL; 227 } 228 return pid; 229 } 230 231 /* end of uucplock.c */ 232