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  * 4. 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 */