1 /* $OpenBSD: uucplock.c,v 1.11 2003/06/02 20:18:42 millert Exp $ */ 2 /* 3 * Copyright (c) 1988, 1993 4 * The Regents of the University of California. All rights reserved. 5 * 6 * Redistribution and use in source and binary forms, with or without 7 * modification, are permitted provided that the following conditions 8 * are met: 9 * 1. Redistributions of source code must retain the above copyright 10 * notice, this list of conditions and the following disclaimer. 11 * 2. Redistributions in binary form must reproduce the above copyright 12 * notice, this list of conditions and the following disclaimer in the 13 * documentation and/or other materials provided with the distribution. 14 * 3. Neither the name of the University nor the names of its contributors 15 * may be used to endorse or promote products derived from this software 16 * without specific prior written permission. 17 * 18 * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND 19 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE 20 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE 21 * ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE 22 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL 23 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS 24 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) 25 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT 26 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY 27 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF 28 * SUCH DAMAGE. 29 * 30 * 31 */ 32 33 #ifndef lint 34 static const char sccsid[] = "@(#)uucplock.c 8.1 (Berkeley) 6/6/93"; 35 #endif /* not lint */ 36 37 #include <sys/types.h> 38 #include <dirent.h> 39 #include <errno.h> 40 #include <fcntl.h> 41 #include <unistd.h> 42 #include <signal.h> 43 #include <stdio.h> 44 #include <stdlib.h> 45 #include <paths.h> 46 #include <string.h> 47 #include "util.h" 48 49 #define MAXTRIES 5 50 51 #define LOCKTMP "LCKTMP..%ld" 52 #define LOCKFMT "LCK..%s" 53 54 #define GORET(level, val) { err = errno; uuerr = (val); \ 55 goto __CONCAT(ret, level); } 56 57 /* Forward declarations */ 58 static int put_pid(int fd, pid_t pid); 59 static pid_t get_pid(int fd,int *err); 60 61 /* 62 * uucp style locking routines 63 */ 64 65 int 66 uu_lock(ttyname) 67 const char *ttyname; 68 { 69 int fd, tmpfd, i; 70 pid_t pid, pid_old; 71 char lckname[sizeof(_PATH_UUCPLOCK) + MAXNAMLEN], 72 lcktmpname[sizeof(_PATH_UUCPLOCK) + MAXNAMLEN]; 73 int err, uuerr; 74 75 pid = getpid(); 76 (void)snprintf(lcktmpname, sizeof(lcktmpname), _PATH_UUCPLOCK LOCKTMP, 77 (long)pid); 78 (void)snprintf(lckname, sizeof(lckname), _PATH_UUCPLOCK LOCKFMT, 79 ttyname); 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(ttyname, pid) 130 const char *ttyname; 131 pid_t pid; 132 { 133 int fd, err; 134 char lckname[sizeof(_PATH_UUCPLOCK) + MAXNAMLEN]; 135 136 snprintf(lckname, sizeof(lckname), _PATH_UUCPLOCK LOCKFMT, ttyname); 137 138 if ((fd = open(lckname, O_RDWR)) < 0) 139 return UU_LOCK_OWNER_ERR; 140 if (get_pid(fd, &err) != getpid()) 141 return UU_LOCK_OWNER_ERR; 142 lseek(fd, 0, SEEK_SET); 143 if (put_pid(fd, pid)) 144 return UU_LOCK_WRITE_ERR; 145 close(fd); 146 147 return UU_LOCK_OK; 148 } 149 150 int 151 uu_unlock(ttyname) 152 const char *ttyname; 153 { 154 char tbuf[sizeof(_PATH_UUCPLOCK) + MAXNAMLEN]; 155 156 (void)snprintf(tbuf, sizeof(tbuf), _PATH_UUCPLOCK LOCKFMT, ttyname); 157 return unlink(tbuf); 158 } 159 160 const char * 161 uu_lockerr(uu_lockresult) 162 int uu_lockresult; 163 { 164 static char errbuf[128]; 165 char *fmt; 166 167 switch (uu_lockresult) { 168 case UU_LOCK_INUSE: 169 return "device in use"; 170 case UU_LOCK_OK: 171 return ""; 172 case UU_LOCK_OPEN_ERR: 173 fmt = "open error: %s"; 174 break; 175 case UU_LOCK_READ_ERR: 176 fmt = "read error: %s"; 177 break; 178 case UU_LOCK_CREAT_ERR: 179 fmt = "creat error: %s"; 180 break; 181 case UU_LOCK_WRITE_ERR: 182 fmt = "write error: %s"; 183 break; 184 case UU_LOCK_LINK_ERR: 185 fmt = "link error: %s"; 186 break; 187 case UU_LOCK_TRY_ERR: 188 fmt = "too many tries: %s"; 189 break; 190 case UU_LOCK_OWNER_ERR: 191 fmt = "not locking process: %s"; 192 break; 193 default: 194 fmt = "undefined error: %s"; 195 break; 196 } 197 198 (void)snprintf(errbuf, sizeof(errbuf), fmt, strerror(errno)); 199 return errbuf; 200 } 201 202 static int 203 put_pid(fd, pid) 204 int fd; 205 pid_t pid; 206 { 207 char buf[32]; 208 int len; 209 210 len = snprintf(buf, sizeof buf, "%10ld\n", (long)pid); 211 212 if (write (fd, buf, len) == len) { 213 /* We don't mind too much if ftruncate() fails - see get_pid */ 214 ftruncate(fd, len); 215 return 1; 216 } 217 return 0; 218 } 219 220 static pid_t 221 get_pid(fd, err) 222 int fd; 223 int *err; 224 { 225 int bytes_read; 226 char buf[32]; 227 pid_t pid; 228 229 bytes_read = read (fd, buf, sizeof (buf) - 1); 230 if (bytes_read > 0) { 231 buf[bytes_read] = '\0'; 232 pid = strtoul (buf, (char **) NULL, 10); 233 } else { 234 pid = -1; 235 *err = bytes_read ? errno : EINVAL; 236 } 237 return pid; 238 } 239