/*
    process.c -- process management functions
    Copyright (C) 1999-2005 Ivo Timmermans,
                  2000-2015 Guus Sliepen <guus@tinc-vpn.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 "system.h"

#include "conf.h"
#include "connection.h"
#include "device.h"
#include "edge.h"
#include "logger.h"
#include "net.h"
#include "node.h"
#include "pidfile.h"
#include "process.h"
#include "subnet.h"
#include "utils.h"
#include "xalloc.h"

/* If zero, don't detach from the terminal. */
bool do_detach = true;
bool sighup = false;
bool sigalrm = false;

extern char *identname;
extern char *pidfilename;
extern char **g_argv;
extern bool use_logfile;

#ifndef HAVE_MINGW
static sigset_t emptysigset;
#endif

/* Some functions the less gifted operating systems might lack... */

#ifdef HAVE_MINGW
extern char *identname;
extern char *program_name;
extern char **g_argv;

static SC_HANDLE manager = NULL;
static SC_HANDLE service = NULL;
static SERVICE_STATUS status = {0};
static SERVICE_STATUS_HANDLE statushandle = 0;

bool install_service(void) {
	char command[4096] = "\"";
	char **argp;
	bool space;
	SERVICE_DESCRIPTION description = {"Virtual Private Network daemon"};

	manager = OpenSCManager(NULL, NULL, SC_MANAGER_ALL_ACCESS);

	if(!manager) {
		logger(LOG_ERR, "Could not open service manager: %s", winerror(GetLastError()));
		return false;
	}

	if(!strchr(program_name, '\\')) {
		GetCurrentDirectory(sizeof(command) - 1, command + 1);
		strncat(command, "\\", sizeof(command) - strlen(command));
	}

	strncat(command, program_name, sizeof(command) - strlen(command));

	strncat(command, "\"", sizeof(command) - strlen(command));

	for(argp = g_argv + 1; *argp; argp++) {
		space = strchr(*argp, ' ');
		strncat(command, " ", sizeof(command) - strlen(command));

		if(space) {
			strncat(command, "\"", sizeof(command) - strlen(command));
		}

		strncat(command, *argp, sizeof(command) - strlen(command));

		if(space) {
			strncat(command, "\"", sizeof(command) - strlen(command));
		}
	}

	service = CreateService(manager, identname, identname,
	                        SERVICE_ALL_ACCESS, SERVICE_WIN32_OWN_PROCESS, SERVICE_AUTO_START, SERVICE_ERROR_NORMAL,
	                        command, NULL, NULL, NULL, NULL, NULL);

	if(!service) {
		DWORD lasterror = GetLastError();
		logger(LOG_ERR, "Could not create %s service: %s", identname, winerror(lasterror));

		if(lasterror != ERROR_SERVICE_EXISTS) {
			return false;
		}
	}

	if(service) {
		ChangeServiceConfig2(service, SERVICE_CONFIG_DESCRIPTION, &description);
		logger(LOG_INFO, "%s service installed", identname);
	} else {
		service = OpenService(manager, identname, SERVICE_ALL_ACCESS);
	}

	if(!StartService(service, 0, NULL)) {
		logger(LOG_WARNING, "Could not start %s service: %s", identname, winerror(GetLastError()));
	} else {
		logger(LOG_INFO, "%s service started", identname);
	}

	return true;
}

bool remove_service(void) {
	manager = OpenSCManager(NULL, NULL, SC_MANAGER_ALL_ACCESS);

	if(!manager) {
		logger(LOG_ERR, "Could not open service manager: %s", winerror(GetLastError()));
		return false;
	}

	service = OpenService(manager, identname, SERVICE_ALL_ACCESS);

	if(!service) {
		logger(LOG_ERR, "Could not open %s service: %s", identname, winerror(GetLastError()));
		return false;
	}

	if(!ControlService(service, SERVICE_CONTROL_STOP, &status)) {
		logger(LOG_ERR, "Could not stop %s service: %s", identname, winerror(GetLastError()));
	} else {
		logger(LOG_INFO, "%s service stopped", identname);
	}

	if(!DeleteService(service)) {
		logger(LOG_ERR, "Could not remove %s service: %s", identname, winerror(GetLastError()));
		return false;
	}

	logger(LOG_INFO, "%s service removed", identname);

	return true;
}

DWORD WINAPI controlhandler(DWORD request, DWORD type, LPVOID boe, LPVOID bah) {
	switch(request) {
	case SERVICE_CONTROL_INTERROGATE:
		SetServiceStatus(statushandle, &status);
		return NO_ERROR;

	case SERVICE_CONTROL_STOP:
		logger(LOG_NOTICE, "Got %s request", "SERVICE_CONTROL_STOP");
		break;

	case SERVICE_CONTROL_SHUTDOWN:
		logger(LOG_NOTICE, "Got %s request", "SERVICE_CONTROL_SHUTDOWN");
		break;

	default:
		logger(LOG_WARNING, "Got unexpected request %d", (int)request);
		return ERROR_CALL_NOT_IMPLEMENTED;
	}

	if(running) {
		running = false;
		status.dwWaitHint = 30000;
		status.dwCurrentState = SERVICE_STOP_PENDING;
		SetServiceStatus(statushandle, &status);
		return NO_ERROR;
	} else {
		status.dwWaitHint = 0;
		status.dwCurrentState = SERVICE_STOPPED;
		SetServiceStatus(statushandle, &status);
		exit(1);
	}

}

VOID WINAPI run_service(DWORD argc, LPTSTR *argv) {
	extern int main2(int argc, char **argv);

	status.dwServiceType = SERVICE_WIN32;
	status.dwControlsAccepted = SERVICE_ACCEPT_STOP | SERVICE_ACCEPT_SHUTDOWN;
	status.dwWin32ExitCode = 0;
	status.dwServiceSpecificExitCode = 0;
	status.dwCheckPoint = 0;

	statushandle = RegisterServiceCtrlHandlerEx(identname, controlhandler, NULL);

	if(!statushandle) {
		logger(LOG_ERR, "System call `%s' failed: %s", "RegisterServiceCtrlHandlerEx", winerror(GetLastError()));
	} else {
		status.dwWaitHint = 30000;
		status.dwCurrentState = SERVICE_START_PENDING;
		SetServiceStatus(statushandle, &status);

		status.dwWaitHint = 0;
		status.dwCurrentState = SERVICE_RUNNING;
		SetServiceStatus(statushandle, &status);

		main2(argc, argv);

		status.dwWaitHint = 0;
		status.dwCurrentState = SERVICE_STOPPED;
		SetServiceStatus(statushandle, &status);
	}

	return;
}

bool init_service(void) {
	SERVICE_TABLE_ENTRY services[] = {
		{identname, run_service},
		{NULL, NULL}
	};

	if(!StartServiceCtrlDispatcher(services)) {
		if(GetLastError() == ERROR_FAILED_SERVICE_CONTROLLER_CONNECT) {
			return false;
		} else {
			logger(LOG_ERR, "System call `%s' failed: %s", "StartServiceCtrlDispatcher", winerror(GetLastError()));
		}
	}

	return true;
}
#endif

#ifndef HAVE_MINGW
/*
  check for an existing tinc for this net, and write pid to pidfile
*/
static bool write_pidfile(void) {
	pid_t pid;

	pid = check_pid(pidfilename);

	if(pid) {
		if(netname)
			fprintf(stderr, "A tincd is already running for net `%s' with pid %ld.\n",
			        netname, (long)pid);
		else {
			fprintf(stderr, "A tincd is already running with pid %ld.\n", (long)pid);
		}

		return false;
	}

	/* if it's locked, write-protected, or whatever */
	if(!write_pid(pidfilename)) {
		fprintf(stderr, "Couldn't write pid file %s: %s\n", pidfilename, strerror(errno));
		return false;
	}

	return true;
}
#endif

/*
  kill older tincd for this net
*/
bool kill_other(int signal) {
#ifndef HAVE_MINGW
	pid_t pid;

	pid = read_pid(pidfilename);

	if(!pid) {
		if(netname)
			fprintf(stderr, "No other tincd is running for net `%s'.\n",
			        netname);
		else {
			fprintf(stderr, "No other tincd is running.\n");
		}

		return false;
	}

	errno = 0;                                      /* No error, sometimes errno is only changed on error */

	/* ESRCH is returned when no process with that pid is found */
	if(kill(pid, signal) && errno == ESRCH) {
		if(netname)
			fprintf(stderr, "The tincd for net `%s' is no longer running. ",
			        netname);
		else {
			fprintf(stderr, "The tincd is no longer running. ");
		}

		fprintf(stderr, "Removing stale lock file.\n");
		remove_pid(pidfilename);
	}

	return true;
#else
	return remove_service();
#endif
}

/*
  Detach from current terminal, write pidfile, kill parent
*/
bool detach(void) {
	setup_signals();

	/* First check if we can open a fresh new pidfile */

#ifndef HAVE_MINGW

	if(!write_pidfile()) {
		return false;
	}

	/* If we succeeded in doing that, detach */

	closelogger();
#endif

	if(do_detach) {
#ifndef HAVE_MINGW

		if(daemon(0, 0)) {
			fprintf(stderr, "Couldn't detach from terminal: %s",
			        strerror(errno));
			return false;
		}

		/* Now UPDATE the pid in the pidfile, because we changed it... */

		if(!write_pid(pidfilename)) {
			fprintf(stderr, "Could not write pid file %s: %s\n", pidfilename, strerror(errno));
			return false;
		}

#else

		if(!statushandle) {
			exit(install_service());
		}

#endif
	}

	openlogger(identname, use_logfile ? LOGMODE_FILE : (do_detach ? LOGMODE_SYSLOG : LOGMODE_STDERR));

	logger(LOG_NOTICE, "tincd %s starting, debug level %d",
	       VERSION, debug_level);

	return true;
}

#ifdef HAVE_PUTENV
void unputenv(char *p) {
	char *e = strchr(p, '=');

	if(!e) {
		return;
	}

	int len = e - p;
#ifndef HAVE_UNSETENV
#ifdef HAVE_MINGW
	// Windows requires putenv("FOO=") to unset %FOO%
	len++;
#endif
#endif
	char var[len + 1];
	memcpy(var, p, len);
	var[len] = 0;
#ifdef HAVE_UNSETENV
	unsetenv(var);
#else
	// We must keep what we putenv() around in memory.
	// To do this without memory leaks, keep things in a list and reuse if possible.
	static list_t list = {};

	for(list_node_t *node = list.head; node; node = node->next) {
		char *data = node->data;

		if(!strcmp(data, var)) {
			putenv(data);
			return;
		}
	}

	char *data = xstrdup(var);
	list_insert_tail(&list, data);
	putenv(data);
#endif
}
#else
void putenv(const char *p) {}
void unputenv(const char *p) {}
#endif

bool execute_script(const char *name, char **envp) {
#ifdef HAVE_SYSTEM
	char *scriptname;
	char *interpreter = NULL;
	config_t *cfg_interpreter;
	int status, len, i;

	cfg_interpreter = lookup_config(config_tree, "ScriptsInterpreter");
#ifndef HAVE_MINGW
	len = xasprintf(&scriptname, "\"%s/%s\"", confbase, name);
#else

	if(cfg_interpreter) {
		len = xasprintf(&scriptname, "\"%s/%s\"", confbase, name);
	} else {
		len = xasprintf(&scriptname, "\"%s/%s.bat\"", confbase, name);
	}

#endif

	if(len < 0) {
		return false;
	}

	scriptname[len - 1] = '\0';

	/* First check if there is a script */
	if(access(scriptname + 1, F_OK)) {
		free(scriptname);
		return true;
	}

	// Custom scripts interpreter
	if(get_config_string(cfg_interpreter, &interpreter)) {
		// Force custom scripts interpreter allowing execution of scripts on android without execution flag (such as on /sdcard)
		free(scriptname);
		len = xasprintf(&scriptname, "%s \"%s/%s\"", interpreter, confbase, name);
		free(interpreter);

		if(len < 0) {
			return false;
		}
	}

	ifdebug(STATUS) logger(LOG_INFO, "Executing script %s", name);

	/* Set environment */

	for(i = 0; envp[i]; i++) {
		putenv(envp[i]);
	}

	scriptname[len - 1] = '\"';
	status = system(scriptname);

	free(scriptname);

	/* Unset environment */

	for(i = 0; envp[i]; i++) {
		unputenv(envp[i]);
	}

	if(status != -1) {
#ifdef WEXITSTATUS

		if(WIFEXITED(status)) { /* Child exited by itself */
			if(WEXITSTATUS(status)) {
				logger(LOG_ERR, "Script %s exited with non-zero status %d",
				       name, WEXITSTATUS(status));
				return false;
			}
		} else if(WIFSIGNALED(status)) {        /* Child was killed by a signal */
			logger(LOG_ERR, "Script %s was killed by signal %d (%s)",
			       name, WTERMSIG(status), strsignal(WTERMSIG(status)));
			return false;
		} else {                        /* Something strange happened */
			logger(LOG_ERR, "Script %s terminated abnormally", name);
			return false;
		}

#endif
	} else {
		logger(LOG_ERR, "System call `%s' failed: %s", "system", strerror(errno));
		return false;
	}

#endif
	return true;
}


/*
  Signal handlers.
*/

#ifndef HAVE_MINGW
static RETSIGTYPE sigterm_handler(int a) {
	(void)a;
	logger(LOG_NOTICE, "Got %s signal", "TERM");

	if(running) {
		running = false;
	} else {
		exit(1);
	}
}

static RETSIGTYPE sigquit_handler(int a) {
	(void)a;
	logger(LOG_NOTICE, "Got %s signal", "QUIT");

	if(running) {
		running = false;
	} else {
		exit(1);
	}
}

static RETSIGTYPE fatal_signal_square(int a) {
	logger(LOG_ERR, "Got another fatal signal %d (%s): not restarting.", a,
	       strsignal(a));
	exit(1);
}

static RETSIGTYPE fatal_signal_handler(int a) {
	struct sigaction act;
	logger(LOG_ERR, "Got fatal signal %d (%s)", a, strsignal(a));

	if(do_detach) {
		logger(LOG_NOTICE, "Trying to re-execute in 5 seconds...");

		act.sa_handler = fatal_signal_square;
		act.sa_mask = emptysigset;
		act.sa_flags = 0;
		sigaction(SIGSEGV, &act, NULL);

		close_network_connections();
		sleep(5);
		remove_pid(pidfilename);
		execvp(g_argv[0], g_argv);
	} else {
		logger(LOG_NOTICE, "Not restarting.");
		exit(1);
	}
}

static RETSIGTYPE sighup_handler(int a) {
	(void)a;
	logger(LOG_NOTICE, "Got %s signal", "HUP");
	sighup = true;
}

static RETSIGTYPE sigint_handler(int a) {
	(void)a;
	static int saved_debug_level = -1;

	logger(LOG_NOTICE, "Got %s signal", "INT");

	if(saved_debug_level != -1) {
		logger(LOG_NOTICE, "Reverting to old debug level (%d)",
		       saved_debug_level);
		debug_level = saved_debug_level;
		saved_debug_level = -1;
	} else {
		logger(LOG_NOTICE,
		       "Temporarily setting debug level to 5.  Kill me with SIGINT again to go back to level %d.",
		       debug_level);
		saved_debug_level = debug_level;
		debug_level = 5;
	}
}

static RETSIGTYPE sigalrm_handler(int a) {
	(void)a;
	logger(LOG_NOTICE, "Got %s signal", "ALRM");
	sigalrm = true;
}

static RETSIGTYPE sigusr1_handler(int a) {
	(void)a;
	dump_connections();
}

static RETSIGTYPE sigusr2_handler(int a) {
	(void)a;
	devops.dump_stats();
	dump_nodes();
	dump_edges();
	dump_subnets();
}

static RETSIGTYPE sigwinch_handler(int a) {
	(void)a;
	do_purge = true;
}

static RETSIGTYPE unexpected_signal_handler(int a) {
	(void)a;
	logger(LOG_WARNING, "Got unexpected signal %d (%s)", a, strsignal(a));
}

static RETSIGTYPE ignore_signal_handler(int a) {
	(void)a;
	ifdebug(SCARY_THINGS) logger(LOG_DEBUG, "Ignored signal %d (%s)", a, strsignal(a));
}

static struct {
	int signal;
	void (*handler)(int);
} sighandlers[] = {
	{SIGHUP, sighup_handler},
	{SIGTERM, sigterm_handler},
	{SIGQUIT, sigquit_handler},
	{SIGSEGV, fatal_signal_handler},
	{SIGBUS, fatal_signal_handler},
	{SIGILL, fatal_signal_handler},
	{SIGPIPE, ignore_signal_handler},
	{SIGINT, sigint_handler},
	{SIGUSR1, sigusr1_handler},
	{SIGUSR2, sigusr2_handler},
	{SIGCHLD, ignore_signal_handler},
	{SIGALRM, sigalrm_handler},
	{SIGWINCH, sigwinch_handler},
	{SIGABRT, SIG_DFL},
	{0, NULL}
};
#endif

void setup_signals(void) {
#ifndef HAVE_MINGW
	int i;
	struct sigaction act;

	sigemptyset(&emptysigset);
	act.sa_handler = NULL;
	act.sa_mask = emptysigset;
	act.sa_flags = 0;

	/* Set a default signal handler for every signal, errors will be
	   ignored. */
	for(i = 1; i < NSIG; i++) {
		if(!do_detach) {
			act.sa_handler = SIG_DFL;
		} else {
			act.sa_handler = unexpected_signal_handler;
		}

		sigaction(i, &act, NULL);
	}

	/* If we didn't detach, allow coredumps */
	if(!do_detach) {
		sighandlers[3].handler = SIG_DFL;
	}

	/* Then, for each known signal that we want to catch, assign a
	   handler to the signal, with error checking this time. */
	for(i = 0; sighandlers[i].signal; i++) {
		act.sa_handler = sighandlers[i].handler;

		if(sigaction(sighandlers[i].signal, &act, NULL) < 0)
			fprintf(stderr, "Installing signal handler for signal %d (%s) failed: %s\n",
			        sighandlers[i].signal, strsignal(sighandlers[i].signal),
			        strerror(errno));
	}

#endif
}