From 299ff2b23ffbd3c4511768f7bfbf427315b0650d Mon Sep 17 00:00:00 2001
From: Max Kellermann <max@duempel.org>
Date: Fri, 24 Jan 2014 16:12:10 +0100
Subject: move daemonization code to unix/
---
src/unix/Daemon.cxx | 268 ++++++++++++++++++++++++++++++++++++++++++++++++++++
1 file changed, 268 insertions(+)
create mode 100644 src/unix/Daemon.cxx
(limited to 'src/unix/Daemon.cxx')
diff --git a/src/unix/Daemon.cxx b/src/unix/Daemon.cxx
new file mode 100644
index 000000000..490b2def5
--- /dev/null
+++ b/src/unix/Daemon.cxx
@@ -0,0 +1,268 @@
+/*
+ * Copyright (C) 2003-2014 The Music Player Daemon Project
+ * http://www.musicpd.org
+ *
+ * This program is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License as published by
+ * the Free Software Foundation; either version 2 of the License, or
+ * (at your option) any later version.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
+ * GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License along
+ * with this program; if not, write to the Free Software Foundation, Inc.,
+ * 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA.
+ */
+
+#include "config.h"
+#include "Daemon.hxx"
+#include "system/FatalError.hxx"
+#include "fs/AllocatedPath.hxx"
+#include "fs/FileSystem.hxx"
+#include "util/Domain.hxx"
+#include "PidFile.hxx"
+#include "Log.hxx"
+
+#include <stdlib.h>
+#include <unistd.h>
+#include <fcntl.h>
+
+#ifndef WIN32
+#include <sys/wait.h>
+#include <signal.h>
+#include <pwd.h>
+#include <grp.h>
+#endif
+
+static constexpr Domain daemon_domain("daemon");
+
+#ifndef WIN32
+
+/** the Unix user name which MPD runs as */
+static char *user_name;
+
+/** the Unix user id which MPD runs as */
+static uid_t user_uid = (uid_t)-1;
+
+/** the Unix group id which MPD runs as */
+static gid_t user_gid = (gid_t)-1;
+
+/** the absolute path of the pidfile */
+static AllocatedPath pidfile = AllocatedPath::Null();
+
+/* whether "group" conf. option was given */
+static bool had_group = false;
+
+/**
+ * The write end of a pipe that is used to notify the parent process
+ * that initialization has finished and that it should detach.
+ */
+static int detach_fd = -1;
+
+void
+daemonize_kill(void)
+{
+ FILE *fp;
+ int pid, ret;
+
+ if (pidfile.IsNull())
+ FatalError("no pid_file specified in the config file");
+
+ fp = FOpen(pidfile, "r");
+ if (fp == nullptr) {
+ const std::string utf8 = pidfile.ToUTF8();
+ FormatFatalSystemError("Unable to open pid file \"%s\"",
+ utf8.c_str());
+ }
+
+ if (fscanf(fp, "%i", &pid) != 1) {
+ const std::string utf8 = pidfile.ToUTF8();
+ FormatFatalError("unable to read the pid from file \"%s\"",
+ utf8.c_str());
+ }
+ fclose(fp);
+
+ ret = kill(pid, SIGTERM);
+ if (ret < 0)
+ FormatFatalSystemError("unable to kill process %i",
+ int(pid));
+
+ exit(EXIT_SUCCESS);
+}
+
+void
+daemonize_close_stdin(void)
+{
+ close(STDIN_FILENO);
+ open("/dev/null", O_RDONLY);
+}
+
+void
+daemonize_set_user(void)
+{
+ if (user_name == nullptr)
+ return;
+
+ /* set gid */
+ if (user_gid != (gid_t)-1 && user_gid != getgid() &&
+ setgid(user_gid) == -1) {
+ FormatFatalSystemError("Failed to set group %d",
+ (int)user_gid);
+ }
+
+#ifdef _BSD_SOURCE
+ /* init supplementary groups
+ * (must be done before we change our uid)
+ */
+ if (!had_group &&
+ /* no need to set the new user's supplementary groups if
+ we are already this user */
+ user_uid != getuid() &&
+ initgroups(user_name, user_gid) == -1) {
+ FormatFatalSystemError("Failed to set supplementary groups "
+ "of user \"%s\"",
+ user_name);
+ }
+#endif
+
+ /* set uid */
+ if (user_uid != (uid_t)-1 && user_uid != getuid() &&
+ setuid(user_uid) == -1) {
+ FormatFatalSystemError("Failed to set user \"%s\"",
+ user_name);
+ }
+}
+
+void
+daemonize_begin(bool detach)
+{
+ /* release the current working directory */
+ if (chdir("/") < 0)
+ FatalError("problems changing to root directory");
+
+ if (!detach)
+ /* the rest of this function deals with detaching the
+ process */
+ return;
+
+ /* do this before daemonizing so we can fail gracefully if we
+ can't write to the pid file */
+ PidFile pidfile2(pidfile);
+
+ /* flush all file handles before duplicating the buffers */
+
+ fflush(nullptr);
+
+ /* create a pipe to synchronize the parent and the child */
+
+ int fds[2];
+ if (pipe(fds) < 0)
+ FatalSystemError("pipe() failed");
+
+ /* move to a child process */
+
+ pid_t pid = fork();
+ if (pid < 0)
+ FatalSystemError("fork() failed");
+
+ if (pid == 0) {
+ /* in the child process */
+
+ pidfile2.Close();
+ close(fds[0]);
+ detach_fd = fds[1];
+
+ /* detach from the current session */
+ setsid();
+
+ /* continue starting MPD */
+ return;
+ }
+
+ /* in the parent process */
+
+ close(fds[1]);
+
+ int result;
+ ssize_t nbytes = read(fds[0], &result, sizeof(result));
+ if (nbytes == (ssize_t)sizeof(result)) {
+ /* the child process was successful */
+ pidfile2.Write(pid);
+ exit(EXIT_SUCCESS);
+ }
+
+ /* something bad happened in the child process */
+
+ pidfile2.Delete(pidfile);
+
+ int status;
+ pid_t pid2 = waitpid(pid, &status, 0);
+ if (pid2 < 0)
+ FatalSystemError("waitpid() failed");
+
+ if (WIFSIGNALED(status))
+ FormatFatalError("MPD died from signal %d%s", WTERMSIG(status),
+ WCOREDUMP(status) ? " (core dumped)" : "");
+
+ exit(WEXITSTATUS(status));
+}
+
+void
+daemonize_commit()
+{
+ if (detach_fd >= 0) {
+ /* tell the parent process to let go of us and exit
+ indicating success */
+ int result = 0;
+ write(detach_fd, &result, sizeof(result));
+ close(detach_fd);
+ } else
+ /* the pidfile was not written by the parent because
+ there is no parent - do it now */
+ PidFile(pidfile).Write();
+}
+
+void
+daemonize_init(const char *user, const char *group, AllocatedPath &&_pidfile)
+{
+ if (user) {
+ struct passwd *pwd = getpwnam(user);
+ if (pwd == nullptr)
+ FormatFatalError("no such user \"%s\"", user);
+
+ user_uid = pwd->pw_uid;
+ user_gid = pwd->pw_gid;
+
+ user_name = strdup(user);
+
+ /* this is needed by libs such as arts */
+ setenv("HOME", pwd->pw_dir, true);
+ }
+
+ if (group) {
+ struct group *grp = getgrnam(group);
+ if (grp == nullptr)
+ FormatFatalError("no such group \"%s\"", group);
+ user_gid = grp->gr_gid;
+ had_group = true;
+ }
+
+
+ pidfile = std::move(_pidfile);
+}
+
+void
+daemonize_finish(void)
+{
+ if (!pidfile.IsNull()) {
+ RemoveFile(pidfile);
+ pidfile = AllocatedPath::Null();
+ }
+
+ free(user_name);
+}
+
+#endif
--
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