usr.sbin/nscd/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: src/lib/libutil/pidfile.c,v 1.9 2008/10/20 17:41:08 des Exp $
  27  */
  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 <time.h>
  39 #include <err.h>
  40 #include <errno.h>
  41 #include <libutil.h>
  42
  43 #include "pidfile.h"
  44
  45 static int _pidfile_remove(struct pidfh *pfh, int freeit);
  46
  47 static int
  48 pidfile_verify(struct pidfh *pfh)
  49 {
  50         struct stat sb;
  51
  52         if (pfh == NULL || pfh->pf_fd == -1)
  53                 return (EDOOFUS);
  54         /*
  55          * Check remembered descriptor.
  56          */
  57         if (fstat(pfh->pf_fd, &sb) == -1)
  58                 return (errno);
  59         if (sb.st_dev != pfh->pf_dev || sb.st_ino != pfh->pf_ino)
  60                 return (EDOOFUS);
  61         return (0);
  62 }
  63
  64 static int
  65 pidfile_read(const char *path, pid_t *pidptr)
  66 {
  67         char buf[16], *endptr;
  68         int error, fd, i;
  69
  70         fd = open(path, O_RDONLY);
  71         if (fd == -1)
  72                 return (errno);
  73
  74         i = read(fd, buf, sizeof(buf) - 1);
  75         error = errno;  /* Remember errno in case close() wants to change it. */
  76         close(fd);
  77         if (i == -1)
  78                 return (error);
  79         else if (i == 0)
  80                 return (EAGAIN);
  81         buf[i] = '\0';
  82
  83         *pidptr = strtol(buf, &endptr, 10);
  84         if (endptr != &buf[i])
  85                 return (EINVAL);
  86
  87         return (0);
  88 }
  89
  90 struct pidfh *
  91 pidfile_open(const char *path, mode_t mode, pid_t *pidptr)
  92 {
  93         struct pidfh *pfh;
  94         struct stat sb;
  95         int error, fd, len, count;
  96         struct timespec rqtp;
  97
  98         pfh = malloc(sizeof(*pfh));
  99         if (pfh == NULL)
 100                 return (NULL);
 101
 102         if (path == NULL)
 103                 len = snprintf(pfh->pf_path, sizeof(pfh->pf_path),
 104                     "/var/run/%s.pid", getprogname());
 105         else
 106                 len = snprintf(pfh->pf_path, sizeof(pfh->pf_path),
 107                     "%s", path);
 108         if (len >= (int)sizeof(pfh->pf_path)) {
 109                 free(pfh);
 110                 errno = ENAMETOOLONG;
 111                 return (NULL);
 112         }
 113
 114         /*
 115          * Open the PID file and obtain exclusive lock.
 116          * We truncate PID file here only to remove old PID immediatelly,
 117          * PID file will be truncated again in pidfile_write(), so
 118          * pidfile_write() can be called multiple times.
 119          */
 120         fd = flopen(pfh->pf_path,
 121             O_WRONLY | O_CREAT | O_TRUNC | O_NONBLOCK, mode);
 122         if (fd == -1) {
 123                 count = 0;
 124                 rqtp.tv_sec = 0;
 125                 rqtp.tv_nsec = 5000000;
 126                 if (errno == EWOULDBLOCK && pidptr != NULL) {
 127                 again:
 128                         errno = pidfile_read(pfh->pf_path, pidptr);
 129                         if (errno == 0)
 130                                 errno = EEXIST;
 131                         else if (errno == EAGAIN) {
 132                                 if (++count <= 3) {
 133                                         nanosleep(&rqtp, 0);
 134                                         goto again;
 135                                 }
 136                         }
 137                 }
 138                 free(pfh);
 139                 return (NULL);
 140         }
 141         /*
 142          * Remember file information, so in pidfile_write() we are sure we write
 143          * to the proper descriptor.
 144          */
 145         if (fstat(fd, &sb) == -1) {
 146                 error = errno;
 147                 unlink(pfh->pf_path);
 148                 close(fd);
 149                 free(pfh);
 150                 errno = error;
 151                 return (NULL);
 152         }
 153
 154         pfh->pf_fd = fd;
 155         pfh->pf_dev = sb.st_dev;
 156         pfh->pf_ino = sb.st_ino;
 157
 158         return (pfh);
 159 }
 160
 161 int
 162 pidfile_write(struct pidfh *pfh)
 163 {
 164         char pidstr[16];
 165         int error, fd;
 166
 167         /*
 168          * Check remembered descriptor, so we don't overwrite some other
 169          * file if pidfile was closed and descriptor reused.
 170          */
 171         errno = pidfile_verify(pfh);
 172         if (errno != 0) {
 173                 /*
 174                  * Don't close descriptor, because we are not sure if it's ours.
 175                  */
 176                 return (-1);
 177         }
 178         fd = pfh->pf_fd;
 179
 180         /*
 181          * Truncate PID file, so multiple calls of pidfile_write() are allowed.
 182          */
 183         if (ftruncate(fd, 0) == -1) {
 184                 error = errno;
 185                 _pidfile_remove(pfh, 0);
 186                 errno = error;
 187                 return (-1);
 188         }
 189
 190         snprintf(pidstr, sizeof(pidstr), "%u", getpid());
 191         if (pwrite(fd, pidstr, strlen(pidstr), 0) != (ssize_t)strlen(pidstr)) {
 192                 error = errno;
 193                 _pidfile_remove(pfh, 0);
 194                 errno = error;
 195                 return (-1);
 196         }
 197
 198         return (0);
 199 }
 200
 201 int
 202 pidfile_close(struct pidfh *pfh)
 203 {
 204         int error;
 205
 206         error = pidfile_verify(pfh);
 207         if (error != 0) {
 208                 errno = error;
 209                 return (-1);
 210         }
 211
 212         if (close(pfh->pf_fd) == -1)
 213                 error = errno;
 214         free(pfh);
 215         if (error != 0) {
 216                 errno = error;
 217                 return (-1);
 218         }
 219         return (0);
 220 }
 221
 222 static int
 223 _pidfile_remove(struct pidfh *pfh, int freeit)
 224 {
 225         int error;
 226
 227         error = pidfile_verify(pfh);
 228         if (error != 0) {
 229                 errno = error;
 230                 return (-1);
 231         }
 232
 233         if (unlink(pfh->pf_path) == -1)
 234                 error = errno;
 235         if (close(pfh->pf_fd) == -1) {
 236                 if (error == 0)
 237                         error = errno;
 238         }
 239         if (freeit)
 240                 free(pfh);
 241         else
 242                 pfh->pf_fd = -1;
 243         if (error != 0) {
 244                 errno = error;
 245                 return (-1);
 246         }
 247         return (0);
 248 }
 249
 250 int
 251 pidfile_remove(struct pidfh *pfh)
 252 {
 253
 254         return (_pidfile_remove(pfh, 1));
 255 }