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. 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: head/lib/libutil/uucplock.c 255007 2013-08-28 21:10:37Z jilles $
  30  *
  31  * @(#)uucplock.c       8.1 (Berkeley) 6/6/93
  32  */
  33
  34 #include <sys/types.h>
  35 #include <sys/file.h>
  36 #include <dirent.h>
  37 #include <limits.h>
  38 #include <errno.h>
  39 #include <paths.h>
  40 #include <signal.h>
  41 #include <stdio.h>
  42 #include <stdlib.h>
  43 #include <string.h>
  44 #include <unistd.h>
  45 #include <libutil.h>
  46
  47 #define MAXTRIES 5
  48
  49 #define LOCKTMP "LCKTMP..%d"
  50 #define LOCKFMT "LCK..%s"
  51
  52 #define GORET(level, val) { err = errno; uuerr = (val); \
  53                             goto __CONCAT(ret, level); }
  54
  55 /* Forward declarations */
  56 static int put_pid (int fd, pid_t pid);
  57 static pid_t get_pid (int fd,int *err);
  58
  59 /*
  60  * uucp style locking routines
  61  */
  62
  63 int
  64 uu_lock(const char *tty_name)
  65 {
  66         int fd, tmpfd, i;
  67         pid_t pid, pid_old;
  68         char lckname[sizeof(_PATH_UUCPLOCK) + NAME_MAX],
  69              lcktmpname[sizeof(_PATH_UUCPLOCK) + NAME_MAX];
  70         int err, uuerr;
  71
  72         pid = getpid();
  73         (void)snprintf(lcktmpname, sizeof(lcktmpname), _PATH_UUCPLOCK LOCKTMP,
  74                         pid);
  75         (void)snprintf(lckname, sizeof(lckname), _PATH_UUCPLOCK LOCKFMT,
  76                         tty_name);
  77         if ((tmpfd = open(lcktmpname, O_CREAT | O_TRUNC | O_WRONLY | O_CLOEXEC,
  78             0664)) < 0)
  79                 GORET(0, UU_LOCK_CREAT_ERR);
  80
  81         for (i = 0; i < MAXTRIES; i++) {
  82                 if (link (lcktmpname, lckname) < 0) {
  83                         if (errno != EEXIST)
  84                                 GORET(1, UU_LOCK_LINK_ERR);
  85                         /*
  86                          * file is already locked
  87                          * check to see if the process holding the lock
  88                          * still exists
  89                          */
  90                         if ((fd = open(lckname, O_RDONLY | O_CLOEXEC)) < 0)
  91                                 GORET(1, UU_LOCK_OPEN_ERR);
  92
  93                         if ((pid_old = get_pid (fd, &err)) == -1)
  94                                 GORET(2, UU_LOCK_READ_ERR);
  95
  96                         close(fd);
  97
  98                         if (kill(pid_old, 0) == 0 || errno != ESRCH)
  99                                 GORET(1, UU_LOCK_INUSE);
 100                         /*
 101                          * The process that locked the file isn't running, so
 102                          * we'll lock it ourselves
 103                          */
 104                         (void)unlink(lckname);
 105                 } else {
 106                         if (!put_pid (tmpfd, pid))
 107                                 GORET(3, UU_LOCK_WRITE_ERR);
 108                         break;
 109                 }
 110         }
 111         GORET(1, (i >= MAXTRIES) ? UU_LOCK_TRY_ERR : UU_LOCK_OK);
 112
 113 ret3:
 114         (void)unlink(lckname);
 115         goto ret1;
 116 ret2:
 117         (void)close(fd);
 118 ret1:
 119         (void)close(tmpfd);
 120         (void)unlink(lcktmpname);
 121 ret0:
 122         errno = err;
 123         return uuerr;
 124 }
 125
 126 int
 127 uu_lock_txfr(const char *tty_name, pid_t pid)
 128 {
 129         int fd, err;
 130         char lckname[sizeof(_PATH_UUCPLOCK) + NAME_MAX];
 131
 132         snprintf(lckname, sizeof(lckname), _PATH_UUCPLOCK LOCKFMT, tty_name);
 133
 134         if ((fd = open(lckname, O_RDWR | O_CLOEXEC)) < 0)
 135                 return UU_LOCK_OWNER_ERR;
 136         if (get_pid(fd, &err) != getpid())
 137                 err = UU_LOCK_OWNER_ERR;
 138         else {
 139                 lseek(fd, (off_t)0, SEEK_SET);
 140                 err = put_pid(fd, pid) ? 0 : UU_LOCK_WRITE_ERR;
 141         }
 142         close(fd);
 143
 144         return err;
 145 }
 146
 147 int
 148 uu_unlock(const char *tty_name)
 149 {
 150         char tbuf[sizeof(_PATH_UUCPLOCK) + NAME_MAX];
 151
 152         (void)snprintf(tbuf, sizeof(tbuf), _PATH_UUCPLOCK LOCKFMT, tty_name);
 153         return unlink(tbuf);
 154 }
 155
 156 const char *
 157 uu_lockerr(int uu_lockresult)
 158 {
 159         static char errbuf[128];
 160         const char *fmt;
 161
 162         switch (uu_lockresult) {
 163                 case UU_LOCK_INUSE:
 164                         return "device in use";
 165                 case UU_LOCK_OK:
 166                         return "";
 167                 case UU_LOCK_OPEN_ERR:
 168                         fmt = "open error: %s";
 169                         break;
 170                 case UU_LOCK_READ_ERR:
 171                         fmt = "read error: %s";
 172                         break;
 173                 case UU_LOCK_CREAT_ERR:
 174                         fmt = "creat error: %s";
 175                         break;
 176                 case UU_LOCK_WRITE_ERR:
 177                         fmt = "write error: %s";
 178                         break;
 179                 case UU_LOCK_LINK_ERR:
 180                         fmt = "link error: %s";
 181                         break;
 182                 case UU_LOCK_TRY_ERR:
 183                         fmt = "too many tries: %s";
 184                         break;
 185                 case UU_LOCK_OWNER_ERR:
 186                         fmt = "not locking process: %s";
 187                         break;
 188                 default:
 189                         fmt = "undefined error: %s";
 190                         break;
 191         }
 192
 193         (void)snprintf(errbuf, sizeof(errbuf), fmt, strerror(errno));
 194         return errbuf;
 195 }
 196
 197 static int
 198 put_pid(int fd, pid_t pid)
 199 {
 200         char buf[32];
 201         int len;
 202
 203         len = sprintf (buf, "%10d\n", (int)pid);
 204         return write (fd, buf, (size_t)len) == len;
 205 }
 206
 207 static pid_t
 208 get_pid(int fd, int *err)
 209 {
 210         int bytes_read;
 211         char buf[32];
 212         pid_t pid;
 213
 214         bytes_read = read (fd, buf, sizeof (buf) - 1);
 215         if (bytes_read > 0) {
 216                 buf[bytes_read] = '\0';
 217                 pid = (pid_t)strtol (buf, NULL, 10);
 218         } else {
 219                 pid = -1;
 220                 *err = bytes_read ? errno : EINVAL;
 221         }
 222         return pid;
 223 }
 224
 225 /* end of uucplock.c */