lib/libutil/uucplock.c

   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 15:00:12 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 */