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: src/lib/libutil/uucplock.c,v 1.12.2.1 2000/10/09 20:20:52 brian Exp $ 30 * $DragonFly: src/lib/libutil/uucplock.c,v 1.6 2007/12/30 13:44:33 matthias Exp $ 31 * 32 * @(#)uucplock.c 8.1 (Berkeley) 6/6/93 33 */ 34 35 #include <sys/types.h> 36 #include <sys/file.h> 37 38 #include <dirent.h> 39 #include <errno.h> 40 #include <limits.h> 41 #include <paths.h> 42 #include <signal.h> 43 #include <stdio.h> 44 #include <stdlib.h> 45 #include <string.h> 46 #include <unistd.h> 47 48 #include "libutil.h" 49 50 #define MAXTRIES 5 51 52 #define LOCKTMP "LCKTMP..%d" 53 #define LOCKFMT "LCK..%s" 54 55 #define GORET(level, val) { err = errno; uuerr = (val); \ 56 goto __CONCAT(ret, level); } 57 58 /* Forward declarations */ 59 static int put_pid (int fd, pid_t pid); 60 static pid_t get_pid (int fd,int *err); 61 62 /* 63 * uucp style locking routines 64 */ 65 66 int 67 uu_lock(const char *tty_name) 68 { 69 int fd, tmpfd, i; 70 pid_t pid, pid_old; 71 char lckname[PATH_MAX], 72 lcktmpname[PATH_MAX]; 73 int err, uuerr; 74 75 pid = getpid(); 76 (void)snprintf(lcktmpname, sizeof(lcktmpname), _PATH_UUCPLOCK LOCKTMP, 77 pid); 78 (void)snprintf(lckname, sizeof(lckname), _PATH_UUCPLOCK LOCKFMT, 79 tty_name); 80 if ((tmpfd = creat(lcktmpname, 0664)) < 0) 81 GORET(0, UU_LOCK_CREAT_ERR); 82 83 for (i = 0; i < MAXTRIES; i++) { 84 if (link (lcktmpname, lckname) < 0) { 85 if (errno != EEXIST) 86 GORET(1, UU_LOCK_LINK_ERR); 87 /* 88 * file is already locked 89 * check to see if the process holding the lock 90 * still exists 91 */ 92 if ((fd = open(lckname, O_RDONLY)) < 0) 93 GORET(1, UU_LOCK_OPEN_ERR); 94 95 if ((pid_old = get_pid (fd, &err)) == -1) 96 GORET(2, UU_LOCK_READ_ERR); 97 98 close(fd); 99 100 if (kill(pid_old, 0) == 0 || errno != ESRCH) 101 GORET(1, UU_LOCK_INUSE); 102 /* 103 * The process that locked the file isn't running, so 104 * we'll lock it ourselves 105 */ 106 (void)unlink(lckname); 107 } else { 108 if (!put_pid (tmpfd, pid)) 109 GORET(3, UU_LOCK_WRITE_ERR); 110 break; 111 } 112 } 113 GORET(1, (i >= MAXTRIES) ? UU_LOCK_TRY_ERR : UU_LOCK_OK); 114 115 ret3: 116 (void)unlink(lckname); 117 goto ret1; 118 ret2: 119 (void)close(fd); 120 ret1: 121 (void)close(tmpfd); 122 (void)unlink(lcktmpname); 123 ret0: 124 errno = err; 125 return uuerr; 126 } 127 128 int 129 uu_lock_txfr(const char *tty_name, pid_t pid) 130 { 131 int fd, err; 132 char lckname[PATH_MAX]; 133 134 snprintf(lckname, sizeof(lckname), _PATH_UUCPLOCK LOCKFMT, tty_name); 135 136 if ((fd = open(lckname, O_RDWR)) < 0) 137 return UU_LOCK_OWNER_ERR; 138 if (get_pid(fd, &err) != getpid()) 139 err = UU_LOCK_OWNER_ERR; 140 else { 141 lseek(fd, 0, SEEK_SET); 142 err = put_pid(fd, pid) ? 0 : UU_LOCK_WRITE_ERR; 143 } 144 close(fd); 145 146 return err; 147 } 148 149 int 150 uu_unlock(const char *tty_name) 151 { 152 char tbuf[PATH_MAX]; 153 154 (void)snprintf(tbuf, sizeof(tbuf), _PATH_UUCPLOCK LOCKFMT, tty_name); 155 return unlink(tbuf); 156 } 157 158 const char * 159 uu_lockerr(int uu_lockresult) 160 { 161 static char errbuf[128]; 162 const char *fmt; 163 164 switch (uu_lockresult) { 165 case UU_LOCK_INUSE: 166 return "device in use"; 167 case UU_LOCK_OK: 168 return ""; 169 case UU_LOCK_OPEN_ERR: 170 fmt = "open error: %s"; 171 break; 172 case UU_LOCK_READ_ERR: 173 fmt = "read error: %s"; 174 break; 175 case UU_LOCK_CREAT_ERR: 176 fmt = "creat error: %s"; 177 break; 178 case UU_LOCK_WRITE_ERR: 179 fmt = "write error: %s"; 180 break; 181 case UU_LOCK_LINK_ERR: 182 fmt = "link error: %s"; 183 break; 184 case UU_LOCK_TRY_ERR: 185 fmt = "too many tries: %s"; 186 break; 187 case UU_LOCK_OWNER_ERR: 188 fmt = "not locking process: %s"; 189 break; 190 default: 191 fmt = "undefined error: %s"; 192 break; 193 } 194 195 (void)snprintf(errbuf, sizeof(errbuf), fmt, strerror(errno)); 196 return errbuf; 197 } 198 199 static int 200 put_pid(int fd, pid_t pid) 201 { 202 char buf[32]; 203 int len; 204 205 len = sprintf (buf, "%10d\n", (int)pid); 206 return write (fd, buf, len) == len; 207 } 208 209 static pid_t 210 get_pid(int fd, int *err) 211 { 212 int bytes_read; 213 char buf[32]; 214 pid_t pid; 215 216 bytes_read = read (fd, buf, sizeof (buf) - 1); 217 if (bytes_read > 0) { 218 buf[bytes_read] = '\0'; 219 pid = strtol (buf, NULL, 10); 220 } else { 221 pid = -1; 222 *err = bytes_read ? errno : EINVAL; 223 } 224 return pid; 225 } 226 227 /* end of uucplock.c */ 228