/*
  Copyright (c) 2012-2014, Matthias Schiffer <mschiffer@universe-factory.net>
  All rights reserved.

  Redistribution and use in source and binary forms, with or without
  modification, are permitted provided that the following conditions are met:

    1. Redistributions of source code must retain the above copyright notice,
       this list of conditions and the following disclaimer.
    2. Redistributions in binary form must reproduce the above copyright notice,
       this list of conditions and the following disclaimer in the documentation
       and/or other materials provided with the distribution.

  THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS"
  AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
  IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE
  DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT HOLDER OR CONTRIBUTORS BE LIABLE
  FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
  DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR
  SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER
  CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY,
  OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
  OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
*/


#include "fastd.h"
#include "async.h"
#include "config.h"
#include "crypto.h"
#include "handshake.h"
#include "peer.h"
#include "peer_hashtable.h"
#include "poll.h"
#include <fastd_version.h>

#include <fcntl.h>
#include <grp.h>
#include <pthread.h>
#include <signal.h>
#include <string.h>
#include <syslog.h>
#include <sys/resource.h>
#include <sys/wait.h>

#ifdef HAVE_LIBSODIUM
#include <sodium/core.h>
#endif

#ifdef ENABLE_OPENSSL
#include <openssl/conf.h>
#include <openssl/evp.h>
#include <openssl/err.h>
#endif

#ifdef USE_SYSTEMD
#include <sys/un.h>
#endif


fastd_context_t ctx;


static volatile bool sighup = false;
static volatile bool terminate = false;
static volatile bool dump = false;


static void on_sighup(int signo UNUSED) {
	sighup = true;
}

static void on_terminate(int signo UNUSED) {
	terminate = true;
}

static void on_sigusr1(int signo UNUSED) {
	dump = true;
}

static void on_sigchld(int signo UNUSED) {
	while (waitpid(-1, NULL, WNOHANG) > 0) {}
}

static void init_signals(void) {
	struct sigaction action;

	action.sa_flags = 0;
	sigemptyset(&action.sa_mask);

	/* unblock all signals */
	sigprocmask(SIG_SETMASK, &action.sa_mask, NULL);

	action.sa_handler = on_sighup;
	if (sigaction(SIGHUP, &action, NULL))
		exit_errno("sigaction");

	action.sa_handler = on_terminate;
	if (sigaction(SIGTERM, &action, NULL))
		exit_errno("sigaction");
	if (sigaction(SIGQUIT, &action, NULL))
		exit_errno("sigaction");
	if (sigaction(SIGINT, &action, NULL))
		exit_errno("sigaction");

	action.sa_handler = on_sigusr1;
	if (sigaction(SIGUSR1, &action, NULL))
		exit_errno("sigaction");

	action.sa_handler = on_sigchld;
	if (sigaction(SIGCHLD, &action, NULL))
		exit_errno("sigaction");

	action.sa_handler = SIG_IGN;
	if (sigaction(SIGPIPE, &action, NULL))
		exit_errno("sigaction");
	if (sigaction(SIGTTIN, &action, NULL))
		exit_errno("sigaction");
	if (sigaction(SIGTTOU, &action, NULL))
		exit_errno("sigaction");

}

void fastd_open_pipe(int *readfd, int *writefd) {
	int pipefd[2];

	/* use socketpair with SOCK_DGRAM instead of pipe2 with O_DIRECT to keep this portable */
	if (socketpair(AF_UNIX, SOCK_DGRAM, 0, pipefd))
		exit_errno("socketpair");

	fastd_setfd(pipefd[0], FD_CLOEXEC, 0);
	fastd_setfd(pipefd[1], FD_CLOEXEC, 0);

	*readfd = pipefd[0];
	*writefd = pipefd[1];
}

static void init_log(void) {
	uid_t uid = geteuid();
	gid_t gid = getegid();

	if (conf.user || conf.group) {
		if (setegid(conf.gid) < 0)
			pr_debug_errno("setegid");
		if (seteuid(conf.uid) < 0)
			pr_debug_errno("seteuid");
	}

	if (conf.log_syslog_level > LL_UNSPEC)
		openlog(conf.log_syslog_ident, LOG_PID, LOG_DAEMON);

	fastd_log_file_t *config;
	for (config = conf.log_files; config; config = config->next) {
		fastd_log_fd_t *file = malloc(sizeof(fastd_log_fd_t));

		file->config = config;
		file->fd = open(config->filename, O_WRONLY|O_APPEND|O_CREAT, 0600);

		file->next = ctx.log_files;
		ctx.log_files = file;
	}

	ctx.log_initialized = true;

	if (seteuid(uid) < 0)
		pr_debug_errno("seteuid");
	if (setegid(gid) < 0)
		pr_debug_errno("setegid");
}

static void close_log(void) {
	while (ctx.log_files) {
		fastd_log_fd_t *next = ctx.log_files->next;

		close(ctx.log_files->fd);
		free(ctx.log_files);

		ctx.log_files = next;
	}

	closelog();
}


static void init_sockets(void) {
	ctx.socks = malloc(conf.n_bind_addrs * sizeof(fastd_socket_t));

	size_t i;
	fastd_bind_address_t *addr = conf.bind_addrs;
	for (i = 0; i < conf.n_bind_addrs; i++) {
		ctx.socks[i] = (fastd_socket_t){ .fd = -2, .addr = addr };

		if (addr == conf.bind_addr_default_v4)
			ctx.sock_default_v4 = &ctx.socks[i];

		if (addr == conf.bind_addr_default_v6)
			ctx.sock_default_v6 = &ctx.socks[i];

		addr = addr->next;
	}

	ctx.n_socks = conf.n_bind_addrs;
}


void fastd_setfd(const int fd, int set, int unset) {
	int flags = fcntl(fd, F_GETFD);
	if (flags < 0)
		exit_errno("Getting file descriptor flags failed: fcntl");

	if (fcntl(fd, F_SETFD, (flags|set) & (~unset)) < 0)
		exit_errno("Setting file descriptor flags failed: fcntl");
}

void fastd_setfl(const int fd, int set, int unset) {
	int flags = fcntl(fd, F_GETFL);
	if (flags < 0)
		exit_errno("Getting file status flags failed: fcntl");

	if (fcntl(fd, F_SETFL, (flags|set) & (~unset)) < 0)
		exit_errno("Setting file status flags failed: fcntl");
}

static void close_sockets(void) {
	size_t i;
	for (i = 0; i < ctx.n_socks; i++)
		fastd_socket_close(&ctx.socks[i]);

	free(ctx.socks);
}

static inline void handle_forward(fastd_peer_t *source_peer, fastd_buffer_t buffer) {
	fastd_eth_addr_t dest_addr = fastd_get_dest_address(buffer);

	if (fastd_eth_addr_is_unicast(dest_addr)) {
		fastd_peer_t *dest_peer = fastd_peer_find_by_eth_addr(dest_addr);

		if (dest_peer) {
			if (dest_peer != source_peer)
				conf.protocol->send(dest_peer, buffer);
			else
				fastd_buffer_free(buffer);

			return;
		}
	}

	fastd_send_all(source_peer, buffer);
}

void fastd_handle_receive(fastd_peer_t *peer, fastd_buffer_t buffer) {
	if (conf.mode == MODE_TAP) {
		if (buffer.len < ETH_HLEN) {
			pr_debug("received truncated packet");
			fastd_buffer_free(buffer);
			return;
		}

		fastd_eth_addr_t src_addr = fastd_get_source_address(buffer);

		if (fastd_eth_addr_is_unicast(src_addr))
			fastd_peer_eth_addr_add(peer, src_addr);
	}

	ctx.rx.packets++;
	ctx.rx.bytes += buffer.len;

	fastd_tuntap_write(buffer);

	if (conf.mode == MODE_TAP && conf.forward) {
		handle_forward(peer, buffer);
		return;
	}

	fastd_buffer_free(buffer);
}

static inline void on_pre_up(void) {
	fastd_shell_command_exec(&conf.on_pre_up, NULL);
}

static inline void on_up(void) {
	fastd_shell_command_exec(&conf.on_up, NULL);
}

static inline void on_down(void) {
	fastd_shell_command_exec(&conf.on_down, NULL);
}

static inline void on_post_down(void) {
	fastd_shell_command_exec(&conf.on_post_down, NULL);
}

static fastd_peer_group_t* init_peer_group(const fastd_peer_group_config_t *config, fastd_peer_group_t *parent) {
	fastd_peer_group_t *ret = calloc(1, sizeof(fastd_peer_group_t));

	ret->conf = config;
	ret->parent = parent;

	fastd_peer_group_t **children = &ret->children;
	fastd_peer_group_config_t *child_config;

	for (child_config = config->children; child_config; child_config = child_config->next) {
		*children = init_peer_group(child_config, ret);
		children = &(*children)->next;
	}

	return ret;
}

static void init_peer_groups(void) {
	ctx.peer_group = init_peer_group(conf.peer_group, NULL);
}

static void free_peer_group(fastd_peer_group_t *group) {
	while (group->children) {
		fastd_peer_group_t *child = group->children;
		group->children = group->children->next;

		free_peer_group(child);
	}

	free(group);
}

static void delete_peer_groups(void) {
	free_peer_group(ctx.peer_group);
}

static void init_peers(void) {
	fastd_peer_config_t *peer_conf;
	for (peer_conf = conf.peers; peer_conf; peer_conf = peer_conf->next)
		conf.protocol->peer_configure(peer_conf);

	for (peer_conf = conf.peers; peer_conf; peer_conf = peer_conf->next) {
		bool enable = conf.protocol->peer_check(peer_conf);

		if (enable && !peer_conf->enabled)
			fastd_peer_add(peer_conf);

		peer_conf->enabled = enable;
	}

	size_t i;
	for (i = 0; i < VECTOR_LEN(ctx.peers);) {
		fastd_peer_t *peer = VECTOR_INDEX(ctx.peers, i);

		if (peer->config) {
			if (!peer->config->enabled) {
				pr_info("previously enabled peer %P disabled, deleting.", peer);
				fastd_peer_delete(peer);
				continue;
			}
		}
		else {
			if (!conf.protocol->peer_check_temporary(peer)) {
				fastd_peer_delete(peer);
				continue;
			}
		}

		i++;
	}
}

static void delete_peers(void) {
	while (VECTOR_LEN(ctx.peers))
		fastd_peer_delete(VECTOR_INDEX(ctx.peers, VECTOR_LEN(ctx.peers)-1));
}

static void dump_state(void) {
	pr_info("TX stats: %U packet(s), %U byte(s); dropped: %U packet(s), %U byte(s); error: %U packet(s), %U byte(s)",
		ctx.tx.packets, ctx.tx.bytes, ctx.tx_dropped.packets, ctx.tx_dropped.bytes, ctx.tx_error.packets, ctx.tx_error.bytes);
	pr_info("RX stats: %U packet(s), %U byte(s)", ctx.rx.packets, ctx.rx.bytes);

	pr_info("dumping peers:");

	size_t i;
	for (i = 0; i < VECTOR_LEN(ctx.peers);) {
		fastd_peer_t *peer = VECTOR_INDEX(ctx.peers, i);

		if (!fastd_peer_is_established(peer)) {
			pr_info("peer %P not connected, address: %I", peer, &peer->address);
			continue;
		}

		if (conf.mode == MODE_TAP) {
			size_t i, eth_addresses = 0;
			for (i = 0; i < VECTOR_LEN(ctx.eth_addrs); i++) {
				if (VECTOR_INDEX(ctx.eth_addrs, i).peer == peer)
					eth_addresses++;
			}

			pr_info("peer %P connected, address: %I, associated MAC addresses: %u", peer, &peer->address, eth_addresses);
		}
		else {
			pr_info("peer %P connected, address: %I", peer, &peer->address);
		}
	}

	pr_info("dump finished.");
}

static inline void maintenance(void) {
	if (!fastd_timed_out(&ctx.next_maintenance))
		return;

	fastd_socket_handle_binds();
	fastd_peer_maintenance();

	ctx.next_maintenance.tv_sec += conf.maintenance_interval;
}


static void close_fds(void) {
	struct rlimit rl;
	int fd, maxfd;

	if (getrlimit(RLIMIT_NOFILE, &rl) > 0)
		maxfd = (int)rl.rlim_max;
	else
		maxfd = sysconf(_SC_OPEN_MAX);

	for (fd = 3; fd < maxfd; fd++) {
		if (close(fd) < 0) {
			if (errno == EINTR) {
				fd--;
				continue;
			}

			if (errno != EBADF)
				pr_error_errno("close");
		}
	}
}

static void write_pid(pid_t pid) {
	if (!conf.pid_file)
		return;

	uid_t uid = geteuid();
	gid_t gid = getegid();

	if (conf.user || conf.group) {
		if (setegid(conf.gid) < 0)
			pr_debug_errno("setegid");
		if (seteuid(conf.uid) < 0)
			pr_debug_errno("seteuid");
	}

	int fd = open(conf.pid_file, O_WRONLY|O_CREAT|O_TRUNC, 0666);
	if (fd < 0) {
		pr_error_errno("can't write PID file: open");
		goto end;
	}

	if (dprintf(fd, "%i", pid) < 0)
		pr_error_errno("can't write PID file: dprintf");

	if (close(fd) < 0)
		pr_warn_errno("close");

 end:
	if (seteuid(uid) < 0)
		pr_debug_errno("seteuid");
	if (setegid(gid) < 0)
		pr_debug_errno("setegid");
}

static void set_user(void) {
	if (conf.user || conf.group) {
		if (setgid(conf.gid) < 0)
			exit_errno("setgid");

		if (setuid(conf.uid) < 0)
			exit_errno("setuid");

		pr_info("Changed to UID %i, GID %i.", conf.uid, conf.gid);
	}
}

static void set_groups(void) {
	if (conf.groups) {
		if (setgroups(conf.n_groups, conf.groups) < 0) {
			if (errno != EPERM)
				pr_debug_errno("setgroups");
		}
	}
	else if (conf.user || conf.group) {
		if (setgroups(1, &conf.gid) < 0) {
			if (errno != EPERM)
				pr_debug_errno("setgroups");
		}
	}
}

static void drop_caps(void) {
	set_user();
	fastd_cap_drop();
}

/* will double fork and forward potential exit codes from the child to the parent */
static int daemonize(void) {
	uint8_t status = 1;
	int pipefd[2];

	if (pipe(pipefd))
		exit_errno("pipe");

	pid_t fork1 = fork();

	if (fork1 < 0) {
		exit_errno("fork");
	}
	else if (fork1 > 0) {
		/* parent */
		if (close(pipefd[1]) < 0)
			exit_errno("close");

		if (waitpid(fork1, NULL, 0) < 0)
			exit_errno("waitpid");

		if (read(pipefd[0], &status, 1) < 0)
			exit_errno("read");

		exit(status);
	}
	else {
		/* child 1 */
		if (close(pipefd[0]) < 0)
			pr_error_errno("close");

		if (setsid() < 0)
			pr_error_errno("setsid");

		pid_t fork2 = fork();

		if (fork2 < 0) {
			exit_errno("fork");
		}
		else if (fork2 > 0) {
			/* still child 1 */
			_exit(0);
		}
		else {
			/* child 2 */
			fastd_setfd(pipefd[1], FD_CLOEXEC, 0);
			return pipefd[1];
		}
	}
}

#ifdef USE_SYSTEMD
static void notify_systemd(const char *notify_socket) {
	int fd;
	struct sockaddr_un sa = {};

	if ((notify_socket[0] != '@' && notify_socket[0] != '/') || notify_socket[1] == 0)
		return;

	fd = socket(AF_UNIX, SOCK_DGRAM|SOCK_CLOEXEC, 0);
	if (fd < 0)
		return;

	sa.sun_family = AF_UNIX;

	strncpy(sa.sun_path, notify_socket, sizeof(sa.sun_path));
	if (sa.sun_path[0] == '@')
		sa.sun_path[0] = 0;

	if (connect(fd, (struct sockaddr*)&sa, offsetof(struct sockaddr_un, sun_path) + strnlen(notify_socket, sizeof(sa.sun_path))) < 0) {
		pr_debug_errno("unable to connect to notify socket: connect");
		close(fd);
		return;
	}

	dprintf(fd, "READY=1\nMAINPID=%lu", (unsigned long) getpid());
	pr_debug("sent startup notification to systemd");

	close(fd);
}
#endif

int main(int argc, char *argv[]) {
	memset(&ctx, 0, sizeof(ctx));
	int status_fd = -1;

#ifdef USE_SYSTEMD
	char *notify_socket = getenv("NOTIFY_SOCKET");

	if (notify_socket) {
		notify_socket = strdup(notify_socket);

		/* unset the socket to allow calling on_pre_up safely */
		unsetenv("NOTIFY_SOCKET");
	}
#endif

	close_fds();

	fastd_random_bytes(&ctx.randseed, sizeof(ctx.randseed), false);

	fastd_configure(argc, argv);

	if (conf.verify_config) {
		fastd_config_verify();
		exit(0);
	}

	if (conf.generate_key) {
		conf.protocol->generate_key();
		exit(0);
	}

	conf.protocol_config = conf.protocol->init();

	if (conf.show_key) {
		conf.protocol->show_key();
		exit(0);
	}

	init_signals();

	if (conf.daemon)
		status_fd = daemonize();

	if (chdir("/"))
		pr_error("can't chdir to `/': %s", strerror(errno));

	init_log();

#ifdef HAVE_LIBSODIUM
	sodium_init();
#endif

#ifdef ENABLE_OPENSSL
	ERR_load_crypto_strings();
	OpenSSL_add_all_algorithms();
	OPENSSL_config(NULL);
#endif

	fastd_config_check();

	fastd_update_time();

	ctx.next_maintenance = fastd_in_seconds(conf.maintenance_interval);

	ctx.unknown_handshakes[0].timeout = ctx.now;

	pr_info("fastd " FASTD_VERSION " starting");

	fastd_cap_init();

	/* change groups early as the can be relevant for file access (for PID file & log files) */
	set_groups();

	init_sockets();
	fastd_async_init();
	fastd_poll_init();

	if (!fastd_socket_handle_binds())
		exit_error("unable to bind default socket");

	on_pre_up();

	fastd_tuntap_open();

	init_peer_groups();

	write_pid(getpid());

#ifdef USE_SYSTEMD
	if (notify_socket) {
		notify_systemd(notify_socket);
		free(notify_socket);
	}
#endif

	if (status_fd >= 0) {
		static const uint8_t STATUS = 0;
		if (write(status_fd, &STATUS, 1) < 0)
			exit_errno("status: write");
		if (close(status_fd))
			exit_errno("status: close");
	}

	if (conf.drop_caps == DROP_CAPS_EARLY)
		drop_caps();

	on_up();

	if (conf.drop_caps == DROP_CAPS_ON)
		drop_caps();
	else if (conf.drop_caps == DROP_CAPS_OFF)
		set_user();

	fastd_config_load_peer_dirs();

	VECTOR_ALLOC(ctx.eth_addrs, 0);
	VECTOR_ALLOC(ctx.peers, 0);

	fastd_peer_hashtable_init();

	init_peers();

	while (!terminate) {
		fastd_peer_handle_handshake_queue();

		fastd_poll_handle();

		maintenance();

		sigset_t set, oldset;
		sigemptyset(&set);
		pthread_sigmask(SIG_SETMASK, &set, &oldset);

		if (sighup) {
			sighup = false;

			pr_info("reconfigure triggered");

			close_log();
			init_log();

			fastd_config_load_peer_dirs();
			init_peers();
		}

		if (dump) {
			dump = false;
			dump_state();
		}

		pthread_sigmask(SIG_SETMASK, &oldset, NULL);
	}

	on_down();

	delete_peers();
	delete_peer_groups();

	fastd_tuntap_close();
	close_sockets();
	fastd_poll_free();

	on_post_down();

	fastd_peer_hashtable_free();

	VECTOR_FREE(ctx.peers);
	VECTOR_FREE(ctx.eth_addrs);

	free(ctx.protocol_state);
	free(ctx.ifname);

#ifdef ENABLE_OPENSSL
	CONF_modules_free();
	EVP_cleanup();
	ERR_free_strings();
#endif

	close_log();
	fastd_config_release();

	return 0;
}