src/daemon.c

   1 /*
   2  * Copyright (C) 2003-2009 The Music Player Daemon Project
   3  * http://www.musicpd.org
   4  *
   5  * This program is free software; you can redistribute it and/or modify
   6  * it under the terms of the GNU General Public License as published by
   7  * the Free Software Foundation; either version 2 of the License, or
   8  * (at your option) any later version.
   9  *
  10  * This program is distributed in the hope that it will be useful,
  11  * but WITHOUT ANY WARRANTY; without even the implied warranty of
  12  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  13  * GNU General Public License for more details.
  14  *
  15  * You should have received a copy of the GNU General Public License along
  16  * with this program; if not, write to the Free Software Foundation, Inc.,
  17  * 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA.
  18  */
  19
  20 #include "config.h"
  21 #include "daemon.h"
  22
  23 #include <glib.h>
  24
  25 #include <stdio.h>
  26 #include <stdlib.h>
  27 #include <unistd.h>
  28 #include <errno.h>
  29 #include <string.h>
  30 #include <sys/types.h>
  31 #include <sys/stat.h>
  32 #include <fcntl.h>
  33
  34 #ifndef WIN32
  35 #include <signal.h>
  36 #include <pwd.h>
  37 #include <grp.h>
  38 #endif
  39
  40 #undef G_LOG_DOMAIN
  41 #define G_LOG_DOMAIN "daemon"
  42
  43 #ifndef WIN32
  44
  45 /** the Unix user name which MPD runs as */
  46 static char *user_name;
  47
  48 /** the Unix user id which MPD runs as */
  49 static uid_t user_uid = (uid_t)-1;
  50
  51 /** the Unix group id which MPD runs as */
  52 static gid_t user_gid = (pid_t)-1;
  53
  54 /** the absolute path of the pidfile */
  55 static char *pidfile;
  56
  57 /* whether "group" conf. option was given */
  58 static bool had_group = false;
  59
  60
  61 void
  62 daemonize_kill(void)
  63 {
  64         FILE *fp;
  65         int pid, ret;
  66
  67         if (pidfile == NULL)
  68                 g_error("no pid_file specified in the config file");
  69
  70         fp = fopen(pidfile, "r");
  71         if (fp == NULL)
  72                 g_error("unable to open pid file \"%s\": %s",
  73                         pidfile, g_strerror(errno));
  74
  75         if (fscanf(fp, "%i", &pid) != 1) {
  76                 g_error("unable to read the pid from file \"%s\"",
  77                         pidfile);
  78         }
  79         fclose(fp);
  80
  81         ret = kill(pid, SIGTERM);
  82         if (ret < 0)
  83                 g_error("unable to kill proccess %i: %s",
  84                         pid, g_strerror(errno));
  85
  86         exit(EXIT_SUCCESS);
  87 }
  88
  89 void
  90 daemonize_close_stdin(void)
  91 {
  92         close(STDIN_FILENO);
  93         open("/dev/null", O_RDONLY);
  94 }
  95
  96 void
  97 daemonize_set_user(void)
  98 {
  99         if (user_name == NULL)
 100                 return;
 101
 102         /* set gid */
 103         if (user_gid != (gid_t)-1 && user_gid != getgid()) {
 104                 if (setgid(user_gid) == -1) {
 105                         g_error("cannot setgid to %d: %s",
 106                                 (int)user_gid, g_strerror(errno));
 107                 }
 108         }
 109
 110 #ifdef _BSD_SOURCE
 111         /* init suplementary groups
 112          * (must be done before we change our uid)
 113          */
 114         if (!had_group && initgroups(user_name, user_gid) == -1) {
 115                 g_warning("cannot init supplementary groups "
 116                           "of user \"%s\": %s",
 117                           user_name, g_strerror(errno));
 118         }
 119 #endif
 120
 121         /* set uid */
 122         if (user_uid != (uid_t)-1 && user_uid != getuid() &&
 123             setuid(user_uid) == -1) {
 124                 g_error("cannot change to uid of user \"%s\": %s",
 125                         user_name, g_strerror(errno));
 126         }
 127 }
 128
 129 static void
 130 daemonize_detach(void)
 131 {
 132         /* flush all file handles before duplicating the buffers */
 133
 134         fflush(NULL);
 135
 136 #ifdef HAVE_DAEMON
 137
 138         if (daemon(0, 1))
 139                 g_error("daemon() failed: %s", g_strerror(errno));
 140
 141 #elif defined(HAVE_FORK)
 142
 143         /* detach from parent process */
 144
 145         switch (fork()) {
 146         case -1:
 147                 g_error("fork() failed: %s", g_strerror(errno));
 148         case 0:
 149                 break;
 150         default:
 151                 /* exit the parent process */
 152                 _exit(EXIT_SUCCESS);
 153         }
 154
 155         /* release the current working directory */
 156
 157         if (chdir("/") < 0)
 158                 g_error("problems changing to root directory");
 159
 160         /* detach from the current session */
 161
 162         setsid();
 163
 164 #else
 165         g_error("no support for daemonizing");
 166 #endif
 167
 168         g_debug("daemonized!");
 169 }
 170
 171 void
 172 daemonize(bool detach)
 173 {
 174         FILE *fp = NULL;
 175
 176         if (pidfile != NULL) {
 177                 /* do this before daemon'izing so we can fail gracefully if we can't
 178                  * write to the pid file */
 179                 g_debug("opening pid file");
 180                 fp = fopen(pidfile, "w+");
 181                 if (!fp) {
 182                         g_error("could not create pid file \"%s\": %s",
 183                                 pidfile, g_strerror(errno));
 184                 }
 185         }
 186
 187         if (detach)
 188                 daemonize_detach();
 189
 190         if (pidfile != NULL) {
 191                 g_debug("writing pid file");
 192                 fprintf(fp, "%lu\n", (unsigned long)getpid());
 193                 fclose(fp);
 194         }
 195 }
 196
 197 void
 198 daemonize_init(const char *user, const char *group, const char *_pidfile)
 199 {
 200         if (user) {
 201                 struct passwd *pwd = getpwnam(user);
 202                 if (!pwd)
 203                         g_error("no such user \"%s\"", user);
 204
 205                 user_uid = pwd->pw_uid;
 206                 user_gid = pwd->pw_gid;
 207
 208                 user_name = g_strdup(user);
 209
 210                 /* this is needed by libs such as arts */
 211                 g_setenv("HOME", pwd->pw_dir, true);
 212         }
 213
 214         if (group) {
 215                 struct group *grp = grp = getgrnam(group);
 216                 if (!grp)
 217                         g_error("no such group \"%s\"", group);
 218                 user_gid = grp->gr_gid;
 219                 had_group = true;
 220         }
 221
 222
 223         pidfile = g_strdup(_pidfile);
 224 }
 225
 226 void
 227 daemonize_finish(void)
 228 {
 229         if (pidfile != NULL)
 230                 unlink(pidfile);
 231
 232         g_free(user_name);
 233         g_free(pidfile);
 234 }
 235
 236 #endif