pidfile.c

   1 /*-
   2  * Copyright (c) 2005 Pawel Jakub Dawidek <pjd@FreeBSD.org>
   3  * 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  *
  14  * THIS SOFTWARE IS PROVIDED BY THE AUTHORS AND CONTRIBUTORS ``AS IS'' AND
  15  * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
  16  * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
  17  * ARE DISCLAIMED.  IN NO EVENT SHALL THE AUTHORS OR CONTRIBUTORS BE LIABLE
  18  * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
  19  * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
  20  * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
  21  * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
  22  * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
  23  * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
  24  * SUCH DAMAGE.
  25  */
  26
  27 #include <sys/cdefs.h>
  28
  29 #include <sys/param.h>
  30 #include <sys/file.h>
  31 #include <sys/stat.h>
  32
  33 #include <stdio.h>
  34 #include <stdlib.h>
  35 #include <unistd.h>
  36 #include <fcntl.h>
  37 #include <string.h>
  38 #include <err.h>
  39 #include <errno.h>
  40 #include <libutil.h>
  41
  42 static int _pidfile_remove(struct pidfh *pfh, int freeit);
  43
  44 static int
  45 pidfile_verify(struct pidfh *pfh)
  46 {
  47         struct stat sb;
  48
  49         if (pfh == NULL || pfh->pf_fd == -1)
  50           return EINVAL;
  51         /*
  52          * Check remembered descriptor.
  53          */
  54         if (fstat(pfh->pf_fd, &sb) == -1)
  55                 return (errno);
  56         if (sb.st_dev != pfh->pf_dev || sb.st_ino != pfh->pf_ino)
  57           return EINVAL;
  58         return (0);
  59 }
  60
  61 static int
  62 pidfile_read(const char *path, pid_t *pidptr)
  63 {
  64         char buf[16], *endptr;
  65         int error, fd, i;
  66
  67         fd = open(path, O_RDONLY);
  68         if (fd == -1)
  69                 return (errno);
  70
  71         i = read(fd, buf, sizeof(buf) - 1);
  72         error = errno;  /* Remember errno in case close() wants to change it. */
  73         close(fd);
  74         if (i == -1)
  75                 return (error);
  76         buf[i] = '\0';
  77
  78         *pidptr = strtol(buf, &endptr, 10);
  79         if (endptr != &buf[i])
  80                 return (EINVAL);
  81
  82         return (0);
  83 }
  84
  85 struct pidfh *
  86 pidfile_open(const char *path, mode_t mode, pid_t *pidptr)
  87 {
  88         struct pidfh *pfh;
  89         struct stat sb;
  90         int error, fd;
  91
  92         pfh = malloc(sizeof(*pfh));
  93         if (pfh == NULL)
  94                 return (NULL);
  95
  96         if (path == NULL) {
  97                 snprintf(pfh->pf_path, sizeof(pfh->pf_path), "/var/run/%s.pid",
  98                     getprogname());
  99         } else {
 100                 strlcpy(pfh->pf_path, path, sizeof(pfh->pf_path));
 101         }
 102         if (strlen(pfh->pf_path) == sizeof(pfh->pf_path) - 1) {
 103                 free(pfh);
 104                 errno = ENAMETOOLONG;
 105                 return (NULL);
 106         }
 107
 108         /*
 109          * Open the PID file and obtain exclusive lock.
 110          * We truncate PID file here only to remove old PID immediatelly,
 111          * PID file will be truncated again in pidfile_write(), so
 112          * pidfile_write() can be called multiple times.
 113          */
 114         fd = open(pfh->pf_path,
 115             O_WRONLY | O_CREAT | O_EXLOCK | O_TRUNC | O_NONBLOCK, mode);
 116         if (fd == -1) {
 117                 if (errno == EWOULDBLOCK && pidptr != NULL) {
 118                         errno = pidfile_read(pfh->pf_path, pidptr);
 119                         if (errno == 0)
 120                                 errno = EEXIST;
 121                 }
 122                 free(pfh);
 123                 return (NULL);
 124         }
 125         /*
 126          * Remember file information, so in pidfile_write() we are sure we write
 127          * to the proper descriptor.
 128          */
 129         if (fstat(fd, &sb) == -1) {
 130                 error = errno;
 131                 unlink(pfh->pf_path);
 132                 close(fd);
 133                 free(pfh);
 134                 errno = error;
 135                 return (NULL);
 136         }
 137
 138         pfh->pf_fd = fd;
 139         pfh->pf_dev = sb.st_dev;
 140         pfh->pf_ino = sb.st_ino;
 141
 142         return (pfh);
 143 }
 144
 145 int
 146 pidfile_write(struct pidfh *pfh)
 147 {
 148         char pidstr[16];
 149         int error, fd;
 150
 151         /*
 152          * Check remembered descriptor, so we don't overwrite some other
 153          * file if pidfile was closed and descriptor reused.
 154          */
 155         errno = pidfile_verify(pfh);
 156         if (errno != 0) {
 157                 /*
 158                  * Don't close descriptor, because we are not sure if it's ours.
 159                  */
 160                 return (-1);
 161         }
 162         fd = pfh->pf_fd;
 163
 164         /*
 165          * Truncate PID file, so multiple calls of pidfile_write() are allowed.
 166          */
 167         if (ftruncate(fd, 0) == -1) {
 168                 error = errno;
 169                 _pidfile_remove(pfh, 0);
 170                 errno = error;
 171                 return (-1);
 172         }
 173
 174         snprintf(pidstr, sizeof(pidstr), "%u", getpid());
 175         if (pwrite(fd, pidstr, strlen(pidstr), 0) != (ssize_t)strlen(pidstr)) {
 176                 error = errno;
 177                 _pidfile_remove(pfh, 0);
 178                 errno = error;
 179                 return (-1);
 180         }
 181
 182         return (0);
 183 }
 184
 185 int
 186 pidfile_close(struct pidfh *pfh)
 187 {
 188         int error;
 189
 190         error = pidfile_verify(pfh);
 191         if (error != 0) {
 192                 errno = error;
 193                 return (-1);
 194         }
 195
 196         if (close(pfh->pf_fd) == -1)
 197                 error = errno;
 198         free(pfh);
 199         if (error != 0) {
 200                 errno = error;
 201                 return (-1);
 202         }
 203         return (0);
 204 }
 205
 206 static int
 207 _pidfile_remove(struct pidfh *pfh, int freeit)
 208 {
 209         int error;
 210
 211         error = pidfile_verify(pfh);
 212         if (error != 0) {
 213                 errno = error;
 214                 return (-1);
 215         }
 216
 217         if (unlink(pfh->pf_path) == -1)
 218                 error = errno;
 219         if (flock(pfh->pf_fd, LOCK_UN) == -1) {
 220                 if (error == 0)
 221                         error = errno;
 222         }
 223         if (close(pfh->pf_fd) == -1) {
 224                 if (error == 0)
 225                         error = errno;
 226         }
 227         if (freeit)
 228                 free(pfh);
 229         else
 230                 pfh->pf_fd = -1;
 231         if (error != 0) {
 232                 errno = error;
 233                 return (-1);
 234         }
 235         return (0);
 236 }
 237
 238 int
 239 pidfile_remove(struct pidfh *pfh)
 240 {
 241
 242         return (_pidfile_remove(pfh, 1));
 243 }