/*
 * Copyright (C) 1997-2009 Andre Noll <maan@systemlinux.org>
 *
 * Licensed under the GPL v2. For licencing details see COPYING.
 */

/** \file server.c Paraslash's main server. */


/**
 * \mainpage Paraslash API Reference
 *
 * Starting points for getting an overview:
 *
 *
 * 	- The main programs: \ref server.c, \ref audiod.c, \ref client.c,
 *	  \ref audioc.c, \ref fsck.c, \ref afh.c
 *	- Server: \ref server_command, \ref sender,
 *	- Audio file selector: \ref audio_format_handler, \ref mood, \ref afs_table,
 *	- Client: \ref receiver, \ref receiver_node, \ref filter, \ref filter_node.
 *
 *
 * The gory details, listed by topic:
 *
 * 	- Audio format handlers: \ref send_common.c \ref mp3_afh.c, \ref ogg_afh.c, \ref aac_afh.c,
 * 	- Decoders: \ref mp3dec_filter.c, \ref oggdec_filter.c, \ref aacdec_filter.c,
 *	- Volume normalizer: \ref compress_filter.c,
 *	- Output: \ref alsa_write.c, \ref osx_write.c,
 * 	- http: \ref http_recv.c, \ref http_send.c,
 *	- udp: \ref udp_recv.c, \ref udp_send.c,
 *	- dccp: \ref dccp_recv.c, \ref dccp_send.c,
 *	- Audio file selector: \ref afs.c, \ref aft.c, \ref mood.c,
 *	- Afs structures: \ref afs_table, \ref audio_file_data,
 *	  \ref afs_info \ref afh_info,
 *	- Afs tables: \ref aft.c, \ref mood.c, \ref playlist.c,
 *	  \ref attribute.c, \ref score.c,
 *	- The virtual streaming system: \ref vss.c, \ref chunk_queue.c.
 *
 * Lower levels:
 *
 *	- Scheduling: \ref sched.c, \ref sched.h,
 * 	- Networking: \ref net.c,
 *	- File descriptors: \ref fd.c,
 *	- Signals: \ref signal.c,
 *	- Daemons: \ref daemon.c,
 *	- Strings: \ref string.c, \ref string.h,
 *	- Time: \ref time.c,
 *	- Spawning processes: \ref exec.c,
 *	- Inter process communication: \ref ipc.c,
 *	- The object storage layer: \ref osl.c,
 *	- Blob tables: \ref blob.c,
 *	- The error subssystem: \ref error.h.
 *	- Access control for paraslash senders: \ref acl.c, \ref acl.h.
 *
 * Low-level data structures:
 *
 *	- Doubly linked lists: \ref list.h,
 *	- Red-black trees: \ref rbtree.h, \ref rbtree.c,
 *	- Ring buffer: \ref ringbuffer.c, \ref ringbuffer.h,
 *	- Hashing: \ref hash.h, \ref sha1.h, \ref sha1.c,
 *	- Crypto: \ref crypt.c.
 *	- Forward error correction: \ref fec.c
 */

#include <signal.h>
#include <dirent.h>
#include <sys/time.h>

#include "para.h"
#include "error.h"
#include "server.cmdline.h"
#include "afh.h"
#include "string.h"
#include "afs.h"
#include "server.h"
#include "vss.h"
#include "config.h"
#include "close_on_fork.h"
#include "list.h"
#include "send.h"
#include "net.h"
#include "daemon.h"
#include "ipc.h"
#include "fd.h"
#include "sched.h"
#include "signal.h"
#include "user_list.h"
#include "color.h"

/** Define the array of error lists needed by para_server. */
INIT_SERVER_ERRLISTS;

/** Shut down non-authorized connections after that many seconds. */
#define ALARM_TIMEOUT 10

/**
 * Pointer to shared memory area for communication between para_server
 * and its children. Exported to vss.c. command.c and to afs.
 */
struct misc_meta_data *mmd;

/**
 * The configuration of para_server
 *
 * It also contains the options for the audio file selector, audio format
 * handler and all supported senders.
 */
struct server_args_info conf;

/** A random value used in child context for authentication. */
uint32_t afs_socket_cookie;

/** The mutex protecting the shared memory area containing the mmd struct. */
int mmd_mutex;

/** The file containing user information (public key, permissions). */
static char *user_list_file = NULL;


/** The task responsible for server command handling. */
struct server_command_task {
	/** TCP port on which para_server listens for connections. */
	int listen_fd;
	/** Copied from para_server's main function. */
	int argc;
	/** Argument vector passed to para_server's main function. */
	char **argv;
	/** The command task structure for scheduling. */
	struct task task;
};

static int want_colors(void)
{
	if (conf.color_arg == color_arg_no)
		return 0;
	if (conf.color_arg == color_arg_yes)
		return 1;
	if (conf.logfile_given)
		return 0;
	return isatty(STDERR_FILENO);
}

static void init_colors_or_die(void)
{
	int ret, i;

	if (!want_colors())
		return;
	daemon_set_flag(DF_COLOR_LOG);
	daemon_set_default_log_colors();
	for (i = 0; i < conf.log_color_given; i++) {
		ret = daemon_set_log_color(conf.log_color_arg[i]);
		if (ret < 0)
			exit(EXIT_FAILURE);
	}
}

/*
 * setup shared memory area and get mutex for locking
 */
static void init_ipc_or_die(void)
{
	void *shm;
	int shmid, ret = shm_new(sizeof(struct misc_meta_data));

	if (ret < 0)
		goto err_out;
	shmid = ret;
	ret = shm_attach(shmid, ATTACH_RW, &shm);
	shm_destroy(shmid);
	if (ret < 0)
		goto err_out;
	mmd = shm;

	ret = mutex_new();
	if (ret < 0)
		goto err_out;
	mmd_mutex = ret;

	mmd->num_played = 0;
	mmd->num_commands = 0;
	mmd->events = 0;
	mmd->num_connects = 0;
	mmd->active_connections = 0;
	mmd->vss_status_flags = VSS_NEXT;
	mmd->new_vss_status_flags = VSS_NEXT;
	return;
err_out:
	PARA_EMERG_LOG("%s\n", para_strerror(-ret));
	exit(EXIT_FAILURE);
}

/**
 * (Re-)read the server configuration files.
 *
 * \param override Passed to gengetopt to activate the override feature.
 *
 * This function also re-opens the logfile and sets the global \a
 * user_list_file variable.
 */
void parse_config_or_die(int override)
{
	char *home = para_homedir();
	int ret;
	char *cf;

	daemon_close_log();
	if (conf.config_file_given)
		cf = para_strdup(conf.config_file_arg);
	else
		cf = make_message("%s/.paraslash/server.conf", home);
	free(user_list_file);
	if (!conf.user_list_given)
		user_list_file = make_message("%s/.paraslash/server.users", home);
	else
		user_list_file = para_strdup(conf.user_list_arg);
	ret = file_exists(cf);
	if (conf.config_file_given && !ret)  {
		ret = -1;
		PARA_EMERG_LOG("can not read config file %s\n", cf);
		goto out;
	}
	if (ret) {
		int tmp = conf.daemon_given;
		struct server_cmdline_parser_params params = {
			.override = override,
			.initialize = 0,
			.check_required = 1,
			.check_ambiguity = 0,
			.print_errors = !conf.daemon_given
		};
		server_cmdline_parser_config_file(cf, &conf, &params);
		conf.daemon_given = tmp;
	}
	if (conf.logfile_given) {
		daemon_set_logfile(conf.logfile_arg);
		daemon_open_log_or_die();
	}
	daemon_set_loglevel(conf.loglevel_arg);
	init_colors_or_die();
	daemon_set_flag(DF_LOG_PID);
	daemon_set_flag(DF_LOG_LL);
	daemon_set_flag(DF_LOG_TIME);
	ret = 1;
out:
	free(cf);
	free(home);
	if (ret > 0)
		return;
	free(user_list_file);
	user_list_file = NULL;
	exit(EXIT_FAILURE);
}

static void signal_pre_select(struct sched *s, struct task *t)
{
	struct signal_task *st = container_of(t, struct signal_task, task);
	para_fd_set(st->fd, &s->rfds, &s->max_fileno);
}

/*
 * called when server gets SIGHUP or when client invokes hup command.
 */
static void handle_sighup(void)
{
	PARA_NOTICE_LOG("SIGHUP\n");
	parse_config_or_die(1); /* reopens log */
	init_user_list(user_list_file); /* reload user list */
	if (mmd->afs_pid)
		kill(mmd->afs_pid, SIGHUP);
}

static void signal_post_select(struct sched *s, struct task *t)
{
	struct signal_task *st = container_of(t, struct signal_task, task);

	if (!FD_ISSET(st->fd, &s->rfds))
		return;

	st->signum = para_next_signal();
	switch (st->signum) {
	case SIGHUP:
		handle_sighup();
		break;
	case SIGCHLD:
		for (;;) {
			pid_t pid;
			int ret = para_reap_child(&pid);
			if (ret <= 0)
				break;
			if (pid != mmd->afs_pid)
				continue;
			PARA_EMERG_LOG("fatal: afs died\n");
			kill(0, SIGTERM);
			goto cleanup;
		}
		break;
	/* die on sigint/sigterm. Kill all children too. */
	case SIGINT:
	case SIGTERM:
		PARA_EMERG_LOG("terminating on signal %d\n", st->signum);
		kill(0, SIGTERM);
		/*
		 * We must wait for afs because afs catches SIGINT/SIGTERM.
		 * Before reacting to the signal, afs might want to use the
		 * shared memory area and the mmd mutex.  If we destroy this
		 * mutex too early and afs tries to lock the shared memory
		 * area, the call to mutex_lock() will fail and terminate the
		 * afs process. This leads to dirty osl tables.
		 *
		 * There's no such problem with the other children of the
		 * server process (the command handlers) as these reset their
		 * SIGINT/SIGTERM handlers to the default action, i.e.  these
		 * processes get killed immediately by the above kill().
		 */
		PARA_INFO_LOG("waiting for afs (pid %d) to die\n",
			(int)mmd->afs_pid);
		waitpid(mmd->afs_pid, NULL, 0);
cleanup:
		free(mmd->afd.afhi.chunk_table);
		free(mmd->afd.afhi.info_string);
		close_listed_fds();
		mutex_destroy(mmd_mutex);
		shm_detach(mmd);
		exit(EXIT_FAILURE);
	}
}

static void init_signal_task(void)
{
	static struct signal_task signal_task_struct,
		*st = &signal_task_struct;

	st->task.pre_select = signal_pre_select;
	st->task.post_select = signal_post_select;
	sprintf(st->task.status, "signal task");

	PARA_NOTICE_LOG("setting up signal handling\n");
	st->fd = para_signal_init(); /* always successful */
	para_install_sighandler(SIGINT);
	para_install_sighandler(SIGTERM);
	para_install_sighandler(SIGHUP);
	para_install_sighandler(SIGCHLD);
	para_sigaction(SIGPIPE, SIG_IGN);
	add_close_on_fork_list(st->fd);
	register_task(&st->task);
}

static void command_pre_select(struct sched *s, struct task *t)
{
	struct server_command_task *sct = container_of(t, struct server_command_task, task);
	para_fd_set(sct->listen_fd, &s->rfds, &s->max_fileno);
}

static void command_post_select(struct sched *s, struct task *t)
{
	struct server_command_task *sct = container_of(t, struct server_command_task, task);

	int new_fd, ret, i;
	char *peer_name;
	pid_t child_pid;
	uint32_t *chunk_table;
	char *info_string;

	if (!FD_ISSET(sct->listen_fd, &s->rfds))
		return;
	ret = para_accept(sct->listen_fd, NULL, 0);
	if (ret < 0)
		goto out;
	new_fd = ret;
	peer_name = remote_name(new_fd);
	PARA_INFO_LOG("got connection from %s, forking\n", peer_name);
	mmd->num_connects++;
	mmd->active_connections++;
	random();
	/* The chunk table and the info_string are pointers located in the
	 * mmd struct that point to dynamically allocated memory that must be
	 * freed by the parent and the child. However, as the mmd struct is in
	 * a shared memory area, there's no guarantee that after the fork these
	 * pointers are still valid in child context. As these two pointers are
	 * not used in the child anyway, we save them to local variables and
	 * free the memory via that copy in the child.
	 */
	info_string = mmd->afd.afhi.info_string;
	chunk_table = mmd->afd.afhi.chunk_table;
	child_pid = fork();
	if (child_pid < 0) {
		ret = -ERRNO_TO_PARA_ERROR(errno);
		goto out;
	}
	if (child_pid) {
		close(new_fd);
		/* parent keeps accepting connections */
		return;
	}
	/* mmd might already have changed at this point */
	free(info_string);
	free(chunk_table);
	alarm(ALARM_TIMEOUT);
	close_listed_fds();
	para_signal_shutdown();
	/*
	 * put info on who we are serving into argv[0] to make
	 * client ip visible in top/ps
	 */
	for (i = sct->argc - 1; i >= 0; i--)
		memset(sct->argv[i], 0, strlen(sct->argv[i]));
	sprintf(sct->argv[0], "para_server (serving %s)", peer_name);
	return handle_connect(new_fd, peer_name);
out:
	if (ret < 0)
		PARA_CRIT_LOG("%s\n", para_strerror(-ret));
}

static void init_server_command_task(int argc, char **argv)
{
	int ret;
	static struct server_command_task server_command_task_struct,
		*sct = &server_command_task_struct;

	PARA_NOTICE_LOG("initializing tcp command socket\n");
	sct->task.pre_select = command_pre_select;
	sct->task.post_select = command_post_select;
	sct->argc = argc;
	sct->argv = argv;
	ret = para_listen(AF_UNSPEC, IPPROTO_TCP, conf.port_arg);
	if (ret < 0)
		goto err;
	sct->listen_fd = ret;
	ret = mark_fd_nonblocking(sct->listen_fd);
	if (ret < 0)
		goto err;
	add_close_on_fork_list(sct->listen_fd); /* child doesn't need the listener */
	register_task(&sct->task);
	return;
err:
	PARA_EMERG_LOG("%s\n", para_strerror(-ret));
	exit(EXIT_FAILURE);
}

static void init_random_seed(void)
{
	unsigned int seed;
	int fd, ret = para_open("/dev/urandom", O_RDONLY, 0);

	if (ret < 0)
		goto err;
	fd = ret;
	ret = read(fd, &seed, sizeof(seed));
	if (ret < 0) {
		ret = -ERRNO_TO_PARA_ERROR(errno);
		goto out;
	}
	if (ret != sizeof(seed)) {
		ret = -ERRNO_TO_PARA_ERROR(EIO);
		goto out;
	}
	srandom(seed);
	ret = 1;
out:
	close(fd);
	if (ret >= 0)
		return;
err:
	PARA_EMERG_LOG("can not seed pseudo random number generator: %s\n",
		para_strerror(-ret));
	exit(EXIT_FAILURE);
}

static int init_afs(void)
{
	int ret, afs_server_socket[2];
	pid_t afs_pid;

	ret = socketpair(PF_UNIX, SOCK_DGRAM, 0, afs_server_socket);
	if (ret < 0)
		exit(EXIT_FAILURE);
	afs_socket_cookie = para_random((uint32_t)-1);
	afs_pid = fork();
	if (afs_pid < 0)
		exit(EXIT_FAILURE);
	if (afs_pid == 0) { /* child (afs) */
		close(afs_server_socket[0]);
		afs_init(afs_socket_cookie, afs_server_socket[1]);
	}
	mmd->afs_pid = afs_pid;
	close(afs_server_socket[1]);
	ret = mark_fd_nonblocking(afs_server_socket[0]);
	if (ret < 0)
		exit(EXIT_FAILURE);
	add_close_on_fork_list(afs_server_socket[0]);
	PARA_INFO_LOG("afs_socket: %d, afs_socket_cookie: %u\n",
		afs_server_socket[0], (unsigned) afs_socket_cookie);
	return afs_server_socket[0];
}

__noreturn static void tmp_sigchld_handler(__a_unused int s)
{
	PARA_EMERG_LOG("caught early SIGCHLD\n");
	exit(EXIT_FAILURE);
}

static void server_init(int argc, char **argv)
{
	struct server_cmdline_parser_params params = {
		.override = 0,
		.initialize = 1,
		.check_required = 0,
		.check_ambiguity = 0,
		.print_errors = 1
	};
	int afs_socket;

	valid_fd_012();
	init_random_seed();
	/* parse command line options */
	server_cmdline_parser_ext(argc, argv, &conf, &params);
	HANDLE_VERSION_FLAG("server", conf);
	drop_privileges_or_die(conf.user_arg, conf.group_arg);
	/* parse config file, open log and set defaults */
	parse_config_or_die(0);
	log_welcome("para_server");
	init_ipc_or_die(); /* init mmd struct and mmd->lock */
	/* make sure, the global now pointer is uptodate */
	gettimeofday(now, NULL);
	server_uptime(UPTIME_SET); /* reset server uptime */
	init_user_list(user_list_file);
	/* become daemon */
	if (conf.daemon_given)
		daemonize();
	PARA_NOTICE_LOG("initializing audio format handlers\n");
	afh_init();

	/*
	 * Although afs uses its own signal handling we must ignore SIGUSR1
	 * _before_ the afs child process gets born by init_afs() below.  It's
	 * racy to do this in the child because the parent might send SIGUSR1
	 * before the child gets a chance to ignore this signal -- only the
	 * good die young.
	 */
	para_sigaction(SIGUSR1, SIG_IGN);
	/*
	 * We have to install a SIGCHLD handler before the afs process is being
	 * forked off. Otherwise, para_server does not notice if afs dies before
	 * the SIGCHLD handler has been installed by init_signal_task() below.
	 */
	para_sigaction(SIGCHLD, tmp_sigchld_handler);
	PARA_NOTICE_LOG("initializing the audio file selector\n");
	afs_socket = init_afs();
	init_signal_task();
	PARA_NOTICE_LOG("initializing virtual streaming system\n");
	init_vss_task(afs_socket);
	init_server_command_task(argc, argv);
	PARA_NOTICE_LOG("server init complete\n");
}

static void status_refresh(void)
{
	static int prev_uptime = -1, prev_events = -1;
	int uptime = server_uptime(UPTIME_GET), ret = 1;

	if (prev_events != mmd->events)
		goto out;
	if (mmd->new_vss_status_flags != mmd->vss_status_flags)
		goto out_inc_events;
	if (uptime / 60 != prev_uptime / 60)
		goto out_inc_events;
	return;
out_inc_events:
	mmd->events++;
out:
	prev_uptime = uptime;
	prev_events = mmd->events;
	mmd->vss_status_flags = mmd->new_vss_status_flags;
	if (ret) {
		PARA_DEBUG_LOG("%d events, forcing status update\n",
			mmd->events);
		killpg(0, SIGUSR1);
	}
}

static int server_select(int max_fileno, fd_set *readfds, fd_set *writefds,
		struct timeval *timeout_tv)
{
	int ret;

	status_refresh();
	mutex_unlock(mmd_mutex);
	ret = para_select(max_fileno + 1, readfds, writefds, timeout_tv);
	mutex_lock(mmd_mutex);
	return ret;
}

/**
 * The main function of para_server.
 *
 * \param argc Usual argument count.
 * \param argv Usual argument vector.
 *
 * \return EXIT_SUCCESS or EXIT_FAILURE.
 */
int main(int argc, char *argv[])
{
	int ret;
	static struct sched s = {
		.default_timeout = {
			.tv_sec = 1,
			.tv_usec = 0
		},
		.select_function = server_select
	};
	server_init(argc, argv);
	mutex_lock(mmd_mutex);
	ret = schedule(&s);
	if (ret < 0) {
		PARA_EMERG_LOG("%s\n", para_strerror(-ret));
		exit(EXIT_FAILURE);
	}
	exit(EXIT_SUCCESS);
}