lib/libutil/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  * $FreeBSD: head/lib/libutil/pidfile.c 255007 2013-08-28 21:10:37Z jilles $
  27  */
  28
  29 #include <sys/param.h>
  30 #include <sys/stat.h>
  31
  32 #include <stdio.h>
  33 #include <stdlib.h>
  34 #include <unistd.h>
  35 #include <fcntl.h>
  36 #include <string.h>
  37 #include <time.h>
  38 #include <err.h>
  39 #include <errno.h>
  40 #include <libutil.h>
  41
  42 struct pidfh {
  43         int     pf_fd;
  44         char    pf_path[MAXPATHLEN + 1];
  45         dev_t   pf_dev;
  46         ino_t   pf_ino;
  47 };
  48
  49 static int _pidfile_remove(struct pidfh *pfh, int freeit);
  50
  51 static int
  52 pidfile_verify(const struct pidfh *pfh)
  53 {
  54         struct stat sb;
  55
  56         if (pfh == NULL || pfh->pf_fd == -1)
  57                 return (EDOOFUS);
  58         /*
  59          * Check remembered descriptor.
  60          */
  61         if (fstat(pfh->pf_fd, &sb) == -1)
  62                 return (errno);
  63         if (sb.st_dev != pfh->pf_dev || sb.st_ino != pfh->pf_ino)
  64                 return (EDOOFUS);
  65         return (0);
  66 }
  67
  68 static int
  69 pidfile_read(const char *path, pid_t *pidptr)
  70 {
  71         char buf[16], *endptr;
  72         int error, fd, i;
  73
  74         fd = open(path, O_RDONLY | O_CLOEXEC);
  75         if (fd == -1)
  76                 return (errno);
  77
  78         i = read(fd, buf, sizeof(buf) - 1);
  79         error = errno;  /* Remember errno in case close() wants to change it. */
  80         close(fd);
  81         if (i == -1)
  82                 return (error);
  83         else if (i == 0)
  84                 return (EAGAIN);
  85         buf[i] = '\0';
  86
  87         *pidptr = strtol(buf, &endptr, 10);
  88         if (endptr != &buf[i])
  89                 return (EINVAL);
  90
  91         return (0);
  92 }
  93
  94 struct pidfh *
  95 pidfile_open(const char *path, mode_t mode, pid_t *pidptr)
  96 {
  97         struct pidfh *pfh;
  98         struct stat sb;
  99         int error, fd, len, count;
 100         struct timespec rqtp;
 101
 102         pfh = malloc(sizeof(*pfh));
 103         if (pfh == NULL)
 104                 return (NULL);
 105
 106         if (path == NULL)
 107                 len = snprintf(pfh->pf_path, sizeof(pfh->pf_path),
 108                     "/var/run/%s.pid", getprogname());
 109         else
 110                 len = snprintf(pfh->pf_path, sizeof(pfh->pf_path),
 111                     "%s", path);
 112         if (len >= (int)sizeof(pfh->pf_path)) {
 113                 free(pfh);
 114                 errno = ENAMETOOLONG;
 115                 return (NULL);
 116         }
 117
 118         /*
 119          * Open the PID file and obtain exclusive lock.
 120          * We truncate PID file here only to remove old PID immediatelly,
 121          * PID file will be truncated again in pidfile_write(), so
 122          * pidfile_write() can be called multiple times.
 123          */
 124         fd = flopen(pfh->pf_path,
 125             O_WRONLY | O_CREAT | O_TRUNC | O_CLOEXEC | O_NONBLOCK, mode);
 126         if (fd == -1) {
 127                 if (errno == EWOULDBLOCK) {
 128                         if (pidptr == NULL) {
 129                                 errno = EEXIST;
 130                         } else {
 131                                 count = 20;
 132                                 rqtp.tv_sec = 0;
 133                                 rqtp.tv_nsec = 5000000;
 134                                 for (;;) {
 135                                         errno = pidfile_read(pfh->pf_path,
 136                                             pidptr);
 137                                         if (errno != EAGAIN || --count == 0)
 138                                                 break;
 139                                         nanosleep(&rqtp, 0);
 140                                 }
 141                                 if (errno == EAGAIN)
 142                                         *pidptr = -1;
 143                                 if (errno == 0 || errno == EAGAIN)
 144                                         errno = EEXIST;
 145                         }
 146                 }
 147                 free(pfh);
 148                 return (NULL);
 149         }
 150
 151         /*
 152          * Remember file information, so in pidfile_write() we are sure we write
 153          * to the proper descriptor.
 154          */
 155         if (fstat(fd, &sb) == -1) {
 156                 error = errno;
 157                 unlink(pfh->pf_path);
 158                 close(fd);
 159                 free(pfh);
 160                 errno = error;
 161                 return (NULL);
 162         }
 163
 164         pfh->pf_fd = fd;
 165         pfh->pf_dev = sb.st_dev;
 166         pfh->pf_ino = sb.st_ino;
 167
 168         return (pfh);
 169 }
 170
 171 int
 172 pidfile_write(struct pidfh *pfh)
 173 {
 174         char pidstr[16];
 175         int error, fd;
 176
 177         /*
 178          * Check remembered descriptor, so we don't overwrite some other
 179          * file if pidfile was closed and descriptor reused.
 180          */
 181         errno = pidfile_verify(pfh);
 182         if (errno != 0) {
 183                 /*
 184                  * Don't close descriptor, because we are not sure if it's ours.
 185                  */
 186                 return (-1);
 187         }
 188         fd = pfh->pf_fd;
 189
 190         /*
 191          * Truncate PID file, so multiple calls of pidfile_write() are allowed.
 192          */
 193         if (ftruncate(fd, 0) == -1) {
 194                 error = errno;
 195                 _pidfile_remove(pfh, 0);
 196                 errno = error;
 197                 return (-1);
 198         }
 199
 200         snprintf(pidstr, sizeof(pidstr), "%u", getpid());
 201         if (pwrite(fd, pidstr, strlen(pidstr), 0) != (ssize_t)strlen(pidstr)) {
 202                 error = errno;
 203                 _pidfile_remove(pfh, 0);
 204                 errno = error;
 205                 return (-1);
 206         }
 207
 208         return (0);
 209 }
 210
 211 int
 212 pidfile_close(struct pidfh *pfh)
 213 {
 214         int error;
 215
 216         error = pidfile_verify(pfh);
 217         if (error != 0) {
 218                 errno = error;
 219                 return (-1);
 220         }
 221
 222         if (close(pfh->pf_fd) == -1)
 223                 error = errno;
 224         free(pfh);
 225         if (error != 0) {
 226                 errno = error;
 227                 return (-1);
 228         }
 229         return (0);
 230 }
 231
 232 static int
 233 _pidfile_remove(struct pidfh *pfh, int freeit)
 234 {
 235         int error;
 236
 237         error = pidfile_verify(pfh);
 238         if (error != 0) {
 239                 errno = error;
 240                 return (-1);
 241         }
 242
 243         if (unlink(pfh->pf_path) == -1)
 244                 error = errno;
 245         if (close(pfh->pf_fd) == -1) {
 246                 if (error == 0)
 247                         error = errno;
 248         }
 249         if (freeit)
 250                 free(pfh);
 251         else
 252                 pfh->pf_fd = -1;
 253         if (error != 0) {
 254                 errno = error;
 255                 return (-1);
 256         }
 257         return (0);
 258 }
 259
 260 int
 261 pidfile_remove(struct pidfh *pfh)
 262 {
 263
 264         return (_pidfile_remove(pfh, 1));
 265 }
 266
 267 int
 268 pidfile_fileno(const struct pidfh *pfh)
 269 {
 270
 271         if (pfh == NULL || pfh->pf_fd == -1) {
 272                 errno = EDOOFUS;
 273                 return (-1);
 274         }
 275         return (pfh->pf_fd);
 276 }