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 * $Id: uucplock.c,v 1.7 1997/08/05 12:58:02 ache Exp $ 34 * 35 */ 36 37 #ifndef lint 38 static const char sccsid[] = "@(#)uucplock.c 8.1 (Berkeley) 6/6/93"; 39 #endif /* not lint */ 40 41 #include <sys/types.h> 42 #include <sys/file.h> 43 #include <dirent.h> 44 #include <errno.h> 45 #include <unistd.h> 46 #include <signal.h> 47 #include <stdio.h> 48 #include <stdlib.h> 49 #include <paths.h> 50 #include <string.h> 51 #include "libutil.h" 52 53 #define MAXTRIES 5 54 55 #define LOCKTMP "LCKTMP..%d" 56 #define LOCKFMT "LCK..%s" 57 58 #define GORET(level, val) { err = errno; uuerr = (val); \ 59 goto __CONCAT(ret, level); } 60 61 /* Forward declarations */ 62 static int put_pid (int fd, pid_t pid); 63 static pid_t get_pid (int fd,int *err); 64 65 /* 66 * uucp style locking routines 67 */ 68 69 int uu_lock (const char *ttyname) 70 { 71 int fd, tmpfd, i; 72 pid_t pid; 73 char lckname[sizeof(_PATH_UUCPLOCK) + MAXNAMLEN], 74 lcktmpname[sizeof(_PATH_UUCPLOCK) + MAXNAMLEN]; 75 int err, uuerr; 76 77 pid = getpid(); 78 (void)snprintf(lcktmpname, sizeof(lcktmpname), _PATH_UUCPLOCK LOCKTMP, 79 pid); 80 (void)snprintf(lckname, sizeof(lckname), _PATH_UUCPLOCK LOCKFMT, 81 ttyname); 82 if ((tmpfd = creat(lcktmpname, 0664)) < 0) 83 GORET(0, UU_LOCK_CREAT_ERR); 84 85 for (i = 0; i < MAXTRIES; i++) { 86 if (link (lcktmpname, lckname) < 0) { 87 if (errno != EEXIST) 88 GORET(1, UU_LOCK_LINK_ERR); 89 /* 90 * file is already locked 91 * check to see if the process holding the lock 92 * still exists 93 */ 94 if ((fd = open(lckname, O_RDONLY)) < 0) 95 GORET(1, UU_LOCK_OPEN_ERR); 96 97 if ((pid = get_pid (fd, &err)) == -1) 98 GORET(2, UU_LOCK_READ_ERR); 99 100 close(fd); 101 102 if (kill(pid, 0) == 0 || errno != ESRCH) 103 GORET(1, UU_LOCK_INUSE); 104 /* 105 * The process that locked the file isn't running, so 106 * we'll lock it ourselves 107 */ 108 (void)unlink(lckname); 109 } else { 110 if (!put_pid (tmpfd, pid)) 111 GORET(3, UU_LOCK_WRITE_ERR); 112 break; 113 } 114 } 115 GORET(1, (i >= MAXTRIES) ? UU_LOCK_TRY_ERR : UU_LOCK_OK); 116 117 ret3: 118 (void)unlink(lckname); 119 goto ret1; 120 ret2: 121 (void)close(fd); 122 ret1: 123 (void)close(tmpfd); 124 (void)unlink(lcktmpname); 125 ret0: 126 errno = err; 127 return uuerr; 128 } 129 130 int uu_unlock (const char *ttyname) 131 { 132 char tbuf[sizeof(_PATH_UUCPLOCK) + MAXNAMLEN]; 133 134 (void)snprintf(tbuf, sizeof(tbuf), _PATH_UUCPLOCK LOCKFMT, ttyname); 135 return unlink(tbuf); 136 } 137 138 const char *uu_lockerr (int uu_lockresult) 139 { 140 static char errbuf[128]; 141 char *fmt; 142 143 switch (uu_lockresult) { 144 case UU_LOCK_INUSE: 145 return "device in use"; 146 case UU_LOCK_OK: 147 return ""; 148 case UU_LOCK_OPEN_ERR: 149 fmt = "open error: %s"; 150 break; 151 case UU_LOCK_READ_ERR: 152 fmt = "read error: %s"; 153 break; 154 case UU_LOCK_CREAT_ERR: 155 fmt = "creat error: %s"; 156 break; 157 case UU_LOCK_WRITE_ERR: 158 fmt = "write error: %s"; 159 break; 160 case UU_LOCK_LINK_ERR: 161 fmt = "link error: %s"; 162 break; 163 case UU_LOCK_TRY_ERR: 164 fmt = "too many tries: %s"; 165 break; 166 default: 167 fmt = "undefined error: %s"; 168 break; 169 } 170 171 (void)snprintf(errbuf, sizeof(errbuf), fmt, strerror(errno)); 172 return errbuf; 173 } 174 175 static int put_pid (int fd, pid_t pid) 176 { 177 char buf[32]; 178 int len; 179 180 len = sprintf (buf, "%10d\n", pid); 181 return write (fd, buf, len) == len; 182 } 183 184 static pid_t get_pid (int fd, int *err) 185 { 186 int bytes_read; 187 char buf[32]; 188 pid_t pid; 189 190 bytes_read = read (fd, buf, sizeof (buf) - 1); 191 if (bytes_read > 0) { 192 buf[bytes_read] = '\0'; 193 pid = strtol (buf, (char **) NULL, 10); 194 } else { 195 pid = -1; 196 *err = bytes_read ? errno : EINVAL; 197 } 198 return pid; 199 } 200 201 /* end of uucplock.c */ 202