move daemonization code to unix/

1 files changed, 268 insertions, 0 deletions

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