masterserver.c

/* masterserver.c: A generic masterserver for various games. */
/* Copyright (C) 2003  Andre' Schulz
 * This file is part of masterserver.
 *
 * masterserver 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.
 *
 * masterserver 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 masterserver; if not, write to the Free Software
 * Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA  02111-1307  USA
 *
 * The author can be contacted at andre@malchen.de
 */
/*
 * vim:sw=4:ts=4
 */

#include <pthread.h>
#include <stdio.h>
#include <stdarg.h>
#include <stdlib.h>
#include <string.h>
#include <unistd.h>
#include <signal.h>
#include <errno.h>
#include <dirent.h> 	// opendir()
#include <dlfcn.h> 		// for dlopen() etc.
#include <fcntl.h>
#include <grp.h> 		// for changing user
#include <pwd.h> 		// for changing user

#if defined(SOLARIS)
#include <sys/time.h>
#include <syslimits.h>		// PATH_MAX
#elif defined(__FreeBSD__)
#include <limits.h>
#endif

#include <sys/stat.h>
#include <sys/types.h>
#include <sys/select.h> // for select()
#include <sys/socket.h> // for socket() etc.
#include <netinet/in.h>
#include <arpa/inet.h>
#include <net/if.h> 	// IFNAMSIZ

#include "masterserver.h" // masterserver stuff

#define MAX_PKT_LEN	1024 // max packet length

#undef LOG_SUBNAME
#define LOG_SUBNAME "main" // logging subcategory description

// linked list for keeping track of plugins
// beware! it's a pointer array! :)
struct masterserver_plugin *plugins = NULL;


// function prototypes
void change_user_and_group_to(char *, char *); // self explanatory
extern void delete_server(struct masterserver_plugin *, int); // generic function for removing servers from server list
void exit_printhelp(void); // print help and exit
void exit_printversion(void); // print version and exit
int load_plugins(char *, void ***); // load plugins from the given directory
void plugin_thread(void *); // main thread calling plugin routines
void plugin_heartbeat_thread(void *); // remove dead servers from server list
extern void register_plugin(struct masterserver_plugin *); // plugins call this functions to register themselves
void sigint_handler(int); // SIGINT handler

void
exit_printhelp(void)
{
	fprintf(stdout,
"Usage: masterserver [options]\n"
"Options:\n"
"  -D\t\tgo into daemon mode\n"
"  -d\t\tdebug mode\n"
"  -g groupname\tgroup under which masterserver shall run\n"
"    \t\t(only together with -u)\n"
"  -h\t\toutput this help text\n"
"  -i interface\tbind the masterserver to specific interfaces\n"
"    \t\t(use more than once for multiple interfaces)\n"
"  -l filename\tlog stdout to a file\n"
/*"  -L\tset log level\n"
"    \t0 = INFO\n"
"    \t1 = WARNING\n"
"    \t2 = ERROR\n"*/
"  -p path\tset location of plugins\n"
"  -u username\tusername under which masterserver shall run\n"
"  -V\t\tdisplay version information and exit\n"
"Report bugs to <chickenman@exhale.de>.\n");
}

void
exit_printversion(void)
{
	fprintf(stdout,
"Copyright (C) 2003,2004,2005 André Schulz and Ingo Rohlfs\n"
"masterserver comes with NO WARRANTY,\n"
"to the extent permitted by law.\n"
"You may redistribute copies of masterserver\n"
"under the terms of the GNU General Public License.\n"
"For more information about these matters,\n"
"see the files named COPYING.\n\n");

	exit(EXIT_SUCCESS);
}

void
change_user_and_group_to(char *user, char *group)
{
	int retval = 0;
	struct passwd *passwd_temp;
	struct group *group_temp;

	DEBUG("getting uid of user \"%s\"\n", user);
	// check if user exists and get user infos
	passwd_temp = getpwnam(user);
	if (passwd_temp == NULL) {
		ERRORV("getpwnam() (errno: %d - %s)\n", errno, strerror(errno));
		exit(EXIT_FAILURE);
	}

	if (group == NULL)
		group_temp = getgrgid(passwd_temp->pw_gid);
	else
		group_temp = getgrnam(group);
	if (group_temp == NULL) {
		ERRORV("getgrgid() (errno: %d - %s)\n", errno, strerror(errno));
		exit(EXIT_FAILURE);
	}
	DEBUG("setting gid to %d (\"%s\")\n",
		group_temp->gr_gid, group_temp->gr_name);
	// change uid/gid to drop privileges
	retval = setgid(group_temp->gr_gid);
	if (retval == -1) {
		ERRORV("setgid() (errno: %d - %s)\n", errno, strerror(errno));
		exit(EXIT_FAILURE);
	}

	DEBUG("setting uid to %d (\"%s\")\n",
		passwd_temp->pw_uid, passwd_temp->pw_name);
	retval = setuid(passwd_temp->pw_uid);
	if (retval == -1) {
		ERRORV("setuid() (errno: %d - %s)\n", errno, strerror(errno));
		exit(EXIT_FAILURE);
	}
	INFO("uid/gid change successful\n");
}

int
load_plugins(char *masterserver_plugin_dir, void ***handle)
{
	int retval = 0;
	int num_plugins = 0;
	DIR *plugin_dir; // for opening the plugin dir
	struct dirent *plugin_dir_entry; 
	char path[PATH_MAX]; // path to plugin dir

	// open plugin directory
	DEBUG("opening %s\n", masterserver_plugin_dir);
	plugin_dir = opendir(masterserver_plugin_dir);
	if (plugin_dir == NULL) {
		ERRORV("opendir(%s) (errno: %d - %s)\n", masterserver_plugin_dir, errno, strerror(errno));
		return -1;
	}

	// load all plugins in masterserver_plugin_dir
	while ((plugin_dir_entry = readdir(plugin_dir))) {
		// omit ., .. and files non-.so suffix
		if ((strcmp(plugin_dir_entry->d_name, ".") == 0)
				|| (strcmp(plugin_dir_entry->d_name, "..") == 0)
				|| (strcmp(plugin_dir_entry->d_name+strlen(plugin_dir_entry->d_name)-3, ".so") != 0))
			continue;

		snprintf(path,
			strlen(masterserver_plugin_dir)+plugin_dir_entry->d_reclen+2,
			"%s/%s", masterserver_plugin_dir, plugin_dir_entry->d_name);
		DEBUG("path: \"%s\"\n", path);

		// allocate memory for the new handle
		*handle = realloc(*handle, (num_plugins+1)*sizeof(void*));
		if (*handle == NULL) {
			ERRORV("realloc() failed trying to get %d bytes!\n",
					(num_plugins+1)*sizeof(void *));
			return -1;
		}
		(*handle)[num_plugins] = dlopen(path, RTLD_NOW);
		if ((*handle)[num_plugins] == NULL)
		{
			ERRORV("dlopen (%s)\n", dlerror());
			return -1;
		}
		DEBUG("dlopen() successful (0x%x)\n", (*handle)[num_plugins]);
		INFO("%s loaded\n", plugin_dir_entry->d_name);
		num_plugins++;
	}

	retval = closedir(plugin_dir);
	if (retval == -1)
	{
		ERRORV("closedir(%s) (errno: %d - %s)\n", plugin_dir, errno, strerror(errno));
		return -1;
	}
	DEBUG("closedir succeeded\n");

	return num_plugins;
}

extern void
register_plugin(struct masterserver_plugin *me)
{
	struct masterserver_plugin **i;

	if (strcmp(me->cversion, masterserver_version) != 0) {
		WARNING("plugin %s was compiled for masterserver version %s (this is %s)\n", me->name, me->cversion, masterserver_version);
		WARNING("plugin %s disabled\n", me->name);
		me->enabled = 0;
	} else {
		me->enabled = 1; // plugin is enabled
	}

	// append to linked list
	for (i = &plugins; *i; i = &(*i)->next);
	me->next = NULL;
	*i = me;

	// initialize plugin structure
	// me->mutex = PTHREAD_MUTEX_INITIALIZER;
	pthread_mutex_init(&me->mutex, NULL);
	me->num_servers = 0;
	me->list = calloc(1, sizeof(serverlist_t)); // initialize server list
	if (me->list == NULL) {
		ERRORV("calloc() failed to get %d bytes!\n", sizeof(serverlist_t));
		exit(EXIT_FAILURE);
	}
	me->num_sockets = 0;
	me->socket_d = NULL;
	me->server = calloc(me->num_ports, sizeof(struct sockaddr_in));
	if (me->server == NULL) {
		ERRORV("calloc() failed trying to get %d bytes!\n", me->num_ports*sizeof(struct sockaddr_in));
		exit(EXIT_FAILURE);
	}
	me->msg_out = NULL;
	me->msg_out_length = NULL;
	me->info(); // display plugin info
}

int
main(int argc, char *argv[])
{
	// cmdline options
	int option_logfile = 0;
	int option_bind_to_interface = 0;
	int option_daemon = 0;
	int option_plugin_dir = 0;
	int option_change_user_and_group = 0;
	char *user = NULL;
	char *group = NULL;
	int i, k, l, num_plugins;

	void **handle = NULL; // for dlopen() calls
	int retval;	// return value of syscalls
	unsigned int num_plugins_enabled, num_listen_interfaces = 0;
	char *logfile; // pointer to argv argument
	char *masterserver_plugin_dir; // pointer to argv argument
	char **listen_interface = NULL; // ptr array for storing interface/device names
	struct masterserver_plugin **j; // temporary variable

	// temporary variables
	int setsockopt_temp = 1;
	pid_t temp_pid;

	// seed the rng; needed for challenge creation in q3 plugin
	srand(time(NULL));

	log_init(NULL, "masterserver");
	INFO("masterserver v%s\n", masterserver_version);

	// TODO: read config

	// cmdline parser
	while (1) {
		//retval = getopt(argc, argv, "?dDhi:l:L:p:V");
		retval = getopt(argc, argv, "?dDg:hi:l:p:u:V");
		if (retval == -1) break;

		switch (retval) {
			// debug
			case 'd':
				debug = 1;
				break;
			// daemon mode
			case 'D':
				option_daemon = 1;
				break;
			// run masterserver under a certain group
			case 'g':
				group = argv[optind-1];
				break;
			// bind to interface
			case 'i':
				if (getuid() != 0) {
					ERRORV("you have to be root to bind to specific interfaces\n");
					exit(EXIT_FAILURE);
				}
				if (strlen(argv[optind-1]) > IFNAMSIZ) {
					ERRORV("interface/device name is longer than IFNAMSIZ = %d"
							" chars\n", IFNAMSIZ);
					exit(EXIT_FAILURE);
				}

				num_listen_interfaces++;
				listen_interface = realloc(listen_interface, num_listen_interfaces*sizeof(char *));
				listen_interface[num_listen_interfaces-1] = argv[optind-1];
				option_bind_to_interface = 1;
				break;
			// log messages to a file
			case 'l':
				option_logfile = 1;
				logfile = argv[optind-1];
				break;
			/*case 'L':
				_log_level = atoi(argv[optind-1]);
				if ((_log_level < 0) || (_log_level > 2)) {
					ERROR("log level must be 0 <= x <= 2\n");
					return -1;
				}
				break;*/
			// plugin path
			case 'p':
				masterserver_plugin_dir = argv[optind-1];
				option_plugin_dir = 1;
				break;
			// run masterserver as a certain user
			case 'u':
				if (getuid() != 0) {
					ERRORV("you have to be root to change user/group\n");
					exit(EXIT_FAILURE);
				}
				user = argv[optind-1];
				option_change_user_and_group = 1;
				break;
			// version information
			case 'V':
				exit_printversion();
			// help
			case 'h':
			case '?':
			default:
				exit_printhelp();
				return EXIT_FAILURE;
		} // switch(retval)
	} // while(1)

	if ((group != NULL) && !option_change_user_and_group) {
		ERROR("-g can only be used together with -u\n");
		return EXIT_FAILURE;
	}
	// XXX: this is a hack to get multi port working
	if ((num_listen_interfaces == 0) && !option_bind_to_interface) num_listen_interfaces = 1;

	// check -l cmdline argument
	if (option_logfile) {
		INFO("masterserver: logging stdout to %s\n", logfile);

		// initialize log file
		retval = log_init(logfile, "masterserver");
		if (retval == -1) {
			ERROR("log_init()\n");
			return EXIT_FAILURE;
		}

		// log stdout to log file
		/*if (freopen(logfile, "a", stdout) != stdout) {
			ERRORV("freopen() (errno: %d - %s)\n", errno, strerror(errno));
			return -1;
		}*/

		// change buffering to per line so we actually see something in the logfile
		setvbuf(stdout, NULL, _IOLBF, BUFSIZ);
	}

	// check -D cmdline argument
	if (option_daemon) {
		INFO("masterserver: becoming a daemon ... bye, bye\n");
		if ( (temp_pid = fork()) < 0) {
			ERRORV("fork() (errno: %d - %s)\n", errno, strerror(errno));
			return -1;
		} else if (temp_pid != 0) {
			exit(EXIT_SUCCESS);
		}

		retval = setsid();
		if (retval == -1) {
			ERRORV("setsid() (errno: %d - %s)\n", errno, strerror(errno));
			exit(EXIT_FAILURE);
		}

		retval = chdir("/");
		if (retval == -1) {
			ERRORV("chdir() (errno: %d - %s)\n", errno, strerror(errno));
			exit(EXIT_FAILURE);
		}

		umask(0);

		if (option_logfile == 0) {
			if (freopen("/dev/null", "a", stdout) != stdout) {
				ERRORV("freopen() (errno: %d - %s)\n", errno, strerror(errno));
				return EXIT_FAILURE;
			}
		}
	}

	// check if user specified an alternative plugin dir
	// if he did well we already set it above
	// else we set the default here
	if (!option_plugin_dir)
		masterserver_plugin_dir = MASTERSERVER_LIB_DIR;

	// register signal handler
	signal(SIGINT, &sigint_handler);

	// load all libs in plugin_dir
	num_plugins = load_plugins(masterserver_plugin_dir, &handle);
	if (num_plugins <= 0) {
		ERRORV("no plugins found in \"%s\"\n", masterserver_plugin_dir);
		return EXIT_FAILURE;
	}

	// print out a summary
	INFO("%d plugins loaded\n", num_plugins);

	// create sockets and bind them
	// had to be done because threads inherit the original user
	// and we don't want the threads to be root
	// TODO: sanity checks (e.g. duplicate ports)
	// TODO: check for plugin protocol
	j = &plugins;
	DEBUG("going to listen on %d interfaces ...\n", num_listen_interfaces);
	for (i = 0; i < num_plugins; i++) {
		if (*j == NULL) break;
		if ((*j)->enabled == 0) {
			WARNING("plugin nr %d %s disabled\n", i, (*j)->name);
			continue;
		}
	
		// create socket(s) for plugin
		for (k = 0; k < (*j)->num_ports; k++) {
			// fill sockaddr_in structure
			(*j)->server[k].sin_family = AF_INET;
			(*j)->server[k].sin_port = htons((*j)->port[k].num); // port number from plugin
			(*j)->server[k].sin_addr.s_addr = htonl(INADDR_ANY);

			for (l = 0; l < num_listen_interfaces; l++, (*j)->num_sockets++) {
				(*j)->socket_d = realloc((*j)->socket_d, ((*j)->num_sockets+1)*sizeof(int));
				if ((*j)->socket_d == NULL) {
					ERRORV("realloc() failed trying to get %d bytes\n",
							(*j)->num_sockets+1*sizeof(int));
					return EXIT_FAILURE;
				}

				(*j)->socket_d[(*j)->num_sockets] = socket(PF_INET, SOCK_DGRAM, IPPROTO_UDP);
				DEBUG("plugin #%d %s | socket_d[%d] is %d\n", i, (*j)->name,
						(*j)->num_sockets, (*j)->socket_d[(*j)->num_sockets]);

				// receive broadcast packets
				retval = setsockopt((*j)->socket_d[(*j)->num_sockets], SOL_SOCKET,
						SO_BROADCAST, &setsockopt_temp, sizeof(setsockopt_temp));
				if (retval == -1) {
					ERRORV("setsockopt() (errno: %d - %s)\n", errno,
							strerror(errno));
					return EXIT_FAILURE;
				}

				// bind socket to the interfaces specified in -i
				if (option_bind_to_interface) {
#ifdef __linux__
					DEBUG("setsockopt(..., \"%s\", %d+1);\n",
							listen_interface[l], strlen(listen_interface[l]));
					retval = setsockopt((*j)->socket_d[(*j)->num_sockets],
							SOL_SOCKET, SO_BINDTODEVICE, listen_interface[l],
							strlen(listen_interface[l])+1);
					if (retval == -1) {
						ERRORV("setsockopt() (errno: %d - %s)\n", errno,
								strerror(errno));
						return EXIT_FAILURE;
					}
					DEBUG("%s socket #%d successfully bound to %s\n",
							(*j)->name, (*j)->num_sockets, listen_interface[l]);
					INFO("listening on %s UDP port %d\n", listen_interface[l],
							(*j)->port[k].num);
#endif					
				} else INFO("listening on UDP port %d\n", (*j)->port[k].num);

				// bind socket to structure
				retval = bind((*j)->socket_d[(*j)->num_sockets],
						(struct sockaddr *) &(*j)->server[k],
						sizeof(struct sockaddr_in));
				if (retval == -1) {
					ERRORV("bind() (errno: %d - %s)\n", errno, strerror(errno));
					return EXIT_FAILURE;
				}
			}
		}
		j = &(*j)->next;
	}
	DEBUG("sockets successfully created and bound\n");

	if (option_bind_to_interface
		|| option_change_user_and_group)
	{
		change_user_and_group_to(user, group);
	}

	// main part
	DEBUG("creating plugin threads...\n");
	j = &plugins;
	for (i = 0; i < num_plugins; i++) {
		if (*j == NULL) break;
		if ((*j)->enabled == 0) continue;

		// create plugin thread
		retval = pthread_create(&(*j)->thread_nr, NULL, (void *) plugin_thread, (void *) *j);
		if (retval != 0) {
			switch(retval) {
				case EAGAIN:
					ERROR("pthread_create returned an error; not enough system"
						" resources to create a process for the new thread\n");
					return EXIT_FAILURE;
			}
		}
		INFO("created %s plugin thread\n", (*j)->name);
		j = &(*j)->next; // point j to next plugin in linked list
	}

	// create heartbeat threads
	DEBUG("creating heartbeat threads...\n");
	j = &plugins;
	for (i = 0; i < num_plugins; i++) {
		if (*j == NULL) break;
		if ((*j)->enabled == 0) continue;

		retval = pthread_create(&(*j)->heartbeat_thread_nr, NULL,
				(void *) plugin_heartbeat_thread, (void *) *j);
		if (retval != 0) {
			switch(retval) {
				case EAGAIN:
					ERROR("pthread_create returned an error; not enough system"
						" resources to create a process for the new thread\n");
	                return EXIT_FAILURE;
			}
		}
		INFO("created heartbeat thread for %s\n", (*j)->name);
		j = &(*j)->next;
	}

	// admin interface
	// TODO

	// cleanup and exit
	// (not really; this is just to stop the parent from eating cpu time)
	// XXX: paranoid cleanup ?
	//		check if pointers are != NULL
	//		destroy mutexes
	//		free private data
	INFO("joining plugin threads for graceful cleanup/shutdown... \n");
	for (j = &plugins; *j; j = &(*j)->next) {
		DEBUG("joining %s thread (#%ld)\n", (*j)->name, (*j)->thread_nr);
		retval = pthread_join((*j)->thread_nr, NULL);
		if (retval != 0) {
			ERROR("pthread_join()\n");
			return EXIT_FAILURE;
		}

		DEBUG("joining %s heartbeat thread (#%ld)\n", (*j)->name, (*j)->heartbeat_thread_nr);
		retval = pthread_join((*j)->heartbeat_thread_nr, NULL);
		if (retval != 0) {
			ERROR("pthread_join()\n");
			return EXIT_FAILURE;
		}
		DEBUG("thread #%ld exited; calling plugin cleanup() function\n", (*j)->heartbeat_thread_nr);

		// free private data
		// to really free all private data we have to call a cleanup function
		// of the plugin
		if ((*j)->cleanup != NULL) (*j)->cleanup();

		// free server list
		free((*j)->list);
		for (i = 0; i < (*j)->num_sockets; i++) close((*j)->socket_d[i]);
		for (i = 0; i < (*j)->num_msgs; i++) free((*j)->msg_out[i]);
		free((*j)->msg_out);
		free((*j)->msg_out_length);
		DEBUG("%s clean up successful\n", (*j)->name);
	}

	DEBUG("closing dynamic libs ...\n");
	INFO("unload plugins\n");
	while (num_plugins-- > 0) {
		DEBUG("closing dynamic lib %d (0x%x)\n", num_plugins, handle[num_plugins]);
		dlclose(handle[num_plugins]);
	}
	DEBUG("dynamic libs successfully closed\n");

	log_close();
	return EXIT_SUCCESS;
}

void
plugin_thread(void *arg)
{
	int retval; // temp var for return values
	int i, j, packetlen;
	char msg_in[MAX_PKT_LEN]; // buffer for incoming packet
	struct masterserver_plugin *me = (struct masterserver_plugin *) arg;
	unsigned int client_len = sizeof(me->client);
	int n = 0; // for select()
	fd_set rfds;

	DEBUG("%s_thread: hello world\n", me->name);

	// initialize msg_in buffer
	memset(msg_in, 0, MAX_PKT_LEN);

	// main loop
	while (!master_shutdown) {
		FD_ZERO(&rfds);
		for (i = 0; i < me->num_sockets; i++) {
			if (me->socket_d[i] > n) n = me->socket_d[i];
			FD_SET(me->socket_d[i], &rfds);
		}
		retval = select(n+1, &rfds, NULL, NULL, NULL);
		if (retval == -1) {
			if (errno == EINTR) continue;
			ERRORV("%s_thread: select() (errno: %d - %s)\n", me->name, errno,
					strerror(errno));
			pthread_exit((void *) -1);
		}
		for (i = 0; i < me->num_sockets; i++) {
			if (FD_ISSET(me->socket_d[i], &rfds)) {
				packetlen = recvfrom(me->socket_d[i], &msg_in, MAX_PKT_LEN-1, 0,
						(struct sockaddr *) &me->client, &client_len);
				if (packetlen == -1) {
					ERRORV("%s_thread: recvfrom() (errno: %d - %s)\n", me->name,
							errno, strerror(errno));
					ERRORV("%s_thread: socket_d is %d\n", me->name,
							me->socket_d[i]);
					ERRORV("%s_thread: MAX_PKT_LEN is %d\n",
						me->name, MAX_PKT_LEN);
					pthread_exit((void *) -1);
				}
				DEBUG("%d bytes received\n", packetlen);

				DEBUG("locking mutex\n");
				retval = pthread_mutex_lock(&me->mutex);
				if (retval != 0) {
					ERRORV("%s_thread: pthread_mutex_lock() (retval: %d)\n",
							me->name, retval);
					pthread_exit((void *) -1);
				}
				DEBUG("mutex succesfully locked\n");

				retval = me->process(msg_in, packetlen);
				if (retval == -2) {
					ERRORV("%s_thread: plugin reported: out of memory\n", me->name);
					// TODO: cleanup?
					pthread_exit((void *) -1);
				} else if (retval == -1) {
					//WARNING("%s_thread: plugin reported: invalid packet received\n", me->name);
				} else if (retval == 0) {
					//INFO("%s_thread: plugin reported: server successfully added\n", me->name);
				} else if (retval == 1) {
					DEBUG("sending %d packets to %s:%u\n",
							me->num_msgs, inet_ntoa(me->client.sin_addr),
							ntohs(me->client.sin_port));

					for (j = 0; j < me->num_msgs; j++) {
						retval = sendto(me->socket_d[i], me->msg_out[j],
								me->msg_out_length[j], 0,
								(struct sockaddr *) &me->client, client_len);
						if (retval == -1) {
							ERRORV("sendto() (errno: %d - %s)\n",
									errno, strerror(errno));
						} else DEBUG("%d bytes sent\n", retval);
					}
				} else if (retval == 2) {
					// INFO("%s_thread: plugin reported: server deleted\n", me->name);
				}

				// clean up
				memset(msg_in, 0, MAX_PKT_LEN);
				if (me->num_msgs > 0) {
					DEBUG("freeing outgoing packets\n");
					for (j = 0; j < me->num_msgs; j++)
						free(me->msg_out[j]);
					me->num_msgs = 0;
					free(me->msg_out);
					free(me->msg_out_length);
					me->msg_out = NULL;
					me->msg_out_length = NULL;
				}

				DEBUG("unlocking mutex\n");
				retval = pthread_mutex_unlock(&me->mutex);
				if (retval != 0) {
					ERROR("pthread_mutex_unlock()\n");
					pthread_exit((void *) -1);
				}
			} // if(FD_ISSET())
		} // for(i)
	} // while()
}

void
plugin_heartbeat_thread(void *arg)
{
	struct masterserver_plugin *me = (struct masterserver_plugin *) arg;
	int i = 0;
	int heartbeat_diff = 0;
	int retval; // temp var for return values

	DEBUG("%s_heartbeat_thread: hello world\n", me->name);

	// main loop
	while (!master_shutdown) {
		DEBUG("sleeping %d seconds ...\n", me->heartbeat_timeout);
		sleep(me->heartbeat_timeout);
		DEBUG("waking up\n");

		DEBUG("locking plugin mutex\n");
		retval = pthread_mutex_lock(&me->mutex);
		if (retval != 0) {
			ERROR("pthread_mutex_lock()\n");
			pthread_exit((void *) -1);
		}

		for (i = 0; i < me->num_servers; i++) {
			heartbeat_diff = time(NULL) - me->list[i].lastheartbeat;
			if (heartbeat_diff > 300) {
				INFO("%s_heartbeat_thread: server %s:%d died (heartbeat_diff %d)\n",
					me->name, inet_ntoa(me->list[i].ip), ntohs(me->list[i].port), heartbeat_diff);
				delete_server(me, i);
				i--;
			} else {
				DEBUG("server %s:%d is alive (heartbeat_diff %d)\n",
						inet_ntoa(me->list[i].ip), ntohs(me->list[i].port),
						heartbeat_diff);
			}
		}

		DEBUG("unlocking mutex\n");
		retval = pthread_mutex_unlock(&me->mutex);
		if (retval != 0) {
			ERROR("pthread_mutex_unlock\n");
			pthread_exit((void *) -1);
		}
	} // while()
}

extern void
delete_server(struct masterserver_plugin *me, int server_num)
{
	if (me->free_privdata != NULL) me->free_privdata(me->list[server_num].private_data);
	me->num_servers--;
	me->list[server_num] = me->list[me->num_servers];

	DEBUG("reallocating server list (old size: %d -> new size: %d)\n",
			(me->num_servers+2)*sizeof(serverlist_t),
			(me->num_servers+1)*sizeof(serverlist_t));
	me->list = (serverlist_t *) realloc(me->list, (me->num_servers+1)*sizeof(serverlist_t));
	if (me->list == NULL) {
		ERROR("(__)\n");
		ERROR(" °°\\\\\\~\n");
		ERROR("  !!!!\n");
		pthread_exit((void *) -1);
	}
	DEBUG("reallocation successful\n");
}

void
sigint_handler(int signum)
{
	DEBUG("caught SIGINT!\n");
	master_shutdown = 1;
}