lib/util/pidfile.c

   1 /*
   2    Unix SMB/CIFS implementation.
   3    pidfile handling
   4    Copyright (C) Andrew Tridgell 1998
   5    Copyright (C) Amitay Isaccs  2016
   6
   7    This program is free software; you can redistribute it and/or modify
   8    it under the terms of the GNU General Public License as published by
   9    the Free Software Foundation; either version 3 of the License, or
  10    (at your option) any later version.
  11
  12    This program is distributed in the hope that it will be useful,
  13    but WITHOUT ANY WARRANTY; without even the implied warranty of
  14    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  15    GNU General Public License for more details.
  16
  17    You should have received a copy of the GNU General Public License
  18    along with this program.  If not, see <http://www.gnu.org/licenses/>.
  19 */
  20
  21 #include "replace.h"
  22 #include "system/filesys.h"
  23
  24 #include "lib/util/blocking.h"
  25 #include "lib/util/debug.h"
  26 #include "lib/util/samba_util.h"  /* For process_exists_by_pid() */
  27
  28 #include "lib/util/pidfile.h"
  29
  30 int pidfile_path_create(const char *path, int *pfd, pid_t *existing_pid)
  31 {
  32         struct flock lck;
  33         char tmp[64] = { 0 };
  34         int fd, ret = 0;
  35         int len;
  36         ssize_t nwritten;
  37         bool retried = false;
  38
  39         fd = open(path, O_CREAT|O_WRONLY|O_NONBLOCK, 0644);
  40         if (fd == -1) {
  41                 return errno;
  42         }
  43
  44         if (! set_close_on_exec(fd)) {
  45                 ret = errno;
  46                 goto fail;
  47         }
  48
  49 retry:
  50         lck = (struct flock) {
  51                 .l_type = F_WRLCK,
  52                 .l_whence = SEEK_SET,
  53         };
  54
  55         do {
  56                 ret = fcntl(fd, F_SETLK, &lck);
  57         } while ((ret == -1) && (errno == EINTR));
  58
  59         if (ret != 0) {
  60                 ret = errno;
  61
  62                 if ((ret == EACCES) || (ret == EAGAIN)) {
  63                         do {
  64                                 ret = fcntl(fd, F_GETLK, &lck);
  65                         } while ((ret == -1) && (errno == EINTR));
  66
  67                         if (ret == -1) {
  68                                 ret = errno;
  69                                 goto fail;
  70                         }
  71
  72                         if (lck.l_type == F_UNLCK) {
  73                                 if (!retried) {
  74                                         /* Lock holder died, retry once */
  75                                         retried = true;
  76                                         goto retry;
  77                                 }
  78                                 /* Something badly wrong */
  79                                 ret = EIO;
  80                                 goto fail;
  81                         }
  82
  83                         if (existing_pid != NULL) {
  84                                 *existing_pid = lck.l_pid;
  85                         }
  86                         return EAGAIN;
  87                 }
  88                 goto fail;
  89         }
  90
  91         /*
  92          * PID file is locked by us so from here on we should unlink
  93          * on failure
  94          */
  95         len = snprintf(tmp, sizeof(tmp), "%u\n", getpid());
  96         if (len < 0) {
  97                 ret = errno;
  98                 goto fail_unlink;
  99         }
 100         if ((size_t)len >= sizeof(tmp)) {
 101                 ret = ENOSPC;
 102                 goto fail_unlink;
 103         }
 104
 105         do {
 106                 nwritten = write(fd, tmp, len);
 107         } while ((nwritten == -1) && (errno == EINTR));
 108
 109         if ((nwritten == -1) || (nwritten != len)) {
 110                 ret = errno;
 111                 goto fail_unlink;
 112         }
 113
 114         do {
 115                 ret = ftruncate(fd, len);
 116         } while ((ret == -1) && (errno == EINTR));
 117
 118         if (ret == -1) {
 119                 ret = errno;
 120                 goto fail_unlink;
 121         }
 122
 123         *pfd = fd;
 124         return 0;
 125
 126 fail_unlink:
 127         unlink(path);
 128 fail:
 129         close(fd);
 130         return ret;
 131 }
 132
 133 void pidfile_fd_close(int fd)
 134 {
 135         struct flock lck = {
 136                 .l_type = F_UNLCK,
 137                 .l_whence = SEEK_SET,
 138         };
 139         int ret;
 140
 141         do {
 142                 ret = fcntl(fd, F_SETLK, &lck);
 143         } while ((ret == -1) && (errno == EINTR));
 144
 145         do {
 146                 ret = close(fd);
 147         } while ((ret == -1) && (errno == EINTR));
 148 }
 149
 150
 151 /**
 152  * return the pid in a pidfile. return 0 if the process (or pidfile)
 153  * does not exist
 154  */
 155 pid_t pidfile_pid(const char *piddir, const char *name)
 156 {
 157         size_t len = strlen(piddir) + strlen(name) + 6;
 158         char pidFile[len];
 159         int fd;
 160         char pidstr[20] = { 0, };
 161         pid_t ret = -1;
 162
 163         snprintf(pidFile, sizeof(pidFile), "%s/%s.pid", piddir, name);
 164
 165         fd = open(pidFile, O_NONBLOCK | O_RDONLY, 0644);
 166
 167         if (fd == -1) {
 168                 return 0;
 169         }
 170
 171         if (read(fd, pidstr, sizeof(pidstr)-1) <= 0) {
 172                 goto noproc;
 173         }
 174
 175         ret = (pid_t)atoi(pidstr);
 176         if (ret <= 0) {
 177                 DEBUG(1, ("Could not parse contents of pidfile %s\n",
 178                         pidFile));
 179                 goto noproc;
 180         }
 181
 182         if (!process_exists_by_pid(ret)) {
 183                 DEBUG(10, ("Process with PID=%d does not exist.\n", (int)ret));
 184                 goto noproc;
 185         }
 186
 187         if (fcntl_lock(fd,F_SETLK,0,1,F_RDLCK)) {
 188                 /* we could get the lock - it can't be a Samba process */
 189                 DEBUG(10, ("Process with PID=%d is not a Samba process.\n",
 190                         (int)ret));
 191                 goto noproc;
 192         }
 193
 194         close(fd);
 195         DEBUG(10, ("Process with PID=%d is running.\n", (int)ret));
 196         return ret;
 197
 198  noproc:
 199         close(fd);
 200         return 0;
 201 }
 202
 203 /**
 204  * create a pid file in the pid directory. open it and leave it locked
 205  */
 206 void pidfile_create(const char *piddir, const char *name)
 207 {
 208         size_t len = strlen(piddir) + strlen(name) + 6;
 209         char pidFile[len];
 210         pid_t pid = (pid_t)-1;
 211         int ret, fd;
 212
 213         snprintf(pidFile, sizeof(pidFile), "%s/%s.pid", piddir, name);
 214
 215         ret = pidfile_path_create(pidFile, &fd, &pid);
 216         if (ret == EAGAIN) {
 217                 DEBUG(0,("ERROR: %s is already running. File %s exists and process id %d is running.\n",
 218                          name, pidFile, (int)pid));
 219                 exit(1);
 220         }
 221
 222         /* Leave pid file open & locked for the duration... */
 223 }
 224
 225 void pidfile_unlink(const char *piddir, const char *name)
 226 {
 227         size_t len = strlen(piddir) + strlen(name) + 6;
 228         char pidFile[len];
 229         int ret;
 230
 231         snprintf(pidFile, sizeof(pidFile), "%s/%s.pid", piddir, name);
 232
 233         ret = unlink(pidFile);
 234         if (ret == -1) {
 235                 DEBUG(0,("Failed to delete pidfile %s. Error was %s\n",
 236                         pidFile, strerror(errno)));
 237         }
 238 }