path: root/src/mds-registry/mds-registry.c

/**
 * mds — A micro-display server
 * Copyright © 2014, 2015, 2016, 2017  Mattias Andrée (maandree@kth.se)
 * 
 * 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 3 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, see <http://www.gnu.org/licenses/>.
 */
#include "mds-registry.h"

#include "util.h"
#include "globals.h"
#include "registry.h"

#include <libmdsserver/util.h>
#include <libmdsserver/macros.h>
#include <libmdsserver/hash-help.h>
#include <libmdsserver/linked-list.h>

#include <errno.h>
#include <stdio.h>
#define reconnect_to_display() -1



/**
 * This variable should declared by the actual server implementation.
 * It must be configured before `main` is invoked.
 * 
 * This tells the server-base how to behave
 */
server_characteristics_t server_characteristics = {
	.require_privileges = 0,
	.require_display = 1,
	.require_respawn_info = 0,
	.sanity_check_argc = 1,
	.fork_for_safety = 0,
	.danger_is_deadly = 0
};



/**
 * Send a full message even if interrupted
 * 
 * @param   message:const char*  The message to send
 * @param   length:size_t        The length of the message
 * @return  :int                 Zero on success, -1 on error
 */
#define full_send(message, length)\
	((full_send)(socket_fd, message, length))


/**
 * This function will be invoked before `initialise_server` (if not re-exec:ing)
 * or before `unmarshal_server` (if re-exec:ing)
 * 
 * @return  Non-zero on error
 */
int preinitialise_server(void)
{
	int stage = 0;

	fail_if ((errno = pthread_mutex_init(&slave_mutex, NULL))); stage++;
	fail_if ((errno = pthread_cond_init(&slave_cond, NULL))); stage++;

	linked_list_create(&slave_list, 2);

	return 0;

fail:
	xperror(*argv);
	if (stage >= 1) pthread_mutex_destroy(&slave_mutex);
	if (stage >= 2) pthread_cond_destroy(&slave_cond);
	return 1;
}


/**
 * This function should initialise the server,
 * and it not invoked after a re-exec.
 * 
 * @return  Non-zero on error
 */
int
initialise_server(void)
{
	int stage = 0;
	const char *const message =
		"Command: intercept\n"
		"Message ID: 0\n"
		"Length: 32\n"
		"\n"
		"Command: register\n"
		"Client closed\n"
		/* -- NEXT MESSAGE -- */
		"Command: reregister\n"
		"Message ID: 1\n"
		"\n";

	/* We are asking all servers to reregister their
	   protocols for two reasons:

	   1) The server would otherwise not get registrations
	      from servers started before this server.
	   2) If this server crashes we may miss registrations
	      that happen between the crash and the recovery.
	*/

	fail_if (full_send(message, strlen(message)));  stage++;
	fail_if (hash_table_create_tuned(&reg_table, 32));
	reg_table.key_comparator = (compare_func*)string_comparator;
	reg_table.hasher = (hash_func*)string_hash;
	fail_if (server_initialised() < 0);  stage++;
	fail_if (mds_message_initialise(&received));

	return 0;  
fail:
	xperror(*argv);
	if (stage >= 1) hash_table_destroy(&reg_table, NULL, NULL);
	if (stage >= 2) mds_message_destroy(&received);
	return 1;
}


/**
 * This function will be invoked after `initialise_server` (if not re-exec:ing)
 * or after `unmarshal_server` (if re-exec:ing)
 * 
 * @return  Non-zero on error
 */
int
postinitialise_server(void)
{
	if (connected)
		return 0;

	fail_if (reconnect_to_display());
	connected = 1;
	return 0;
fail:
	mds_message_destroy(&received);
	return 1;
}


/**
 * Perform the server's mission
 * 
 * @return  Non-zero on error
 */
int
master_loop(void)
{
	int rc = 1, r;

	while (!reexecing && !terminating) {
		if (danger) {
			danger = 0;
			free(send_buffer);
			send_buffer = NULL;
			send_buffer_size = 0;
			with_mutex (slave_mutex, linked_list_pack(&slave_list););
		}

		if (!(r = mds_message_read(&received, socket_fd)))
			if (!(r = handle_message()))
				continue;

		if (r == -2) {
			eprint("corrupt message received, aborting.");
			goto done;
		} else if (errno == EINTR) {
			continue;
		} else {
			fail_if (errno != ECONNRESET);
		}

		eprint("lost connection to server.");
		mds_message_destroy(&received);
		mds_message_initialise(&received);
		connected = 0;
		fail_if (reconnect_to_display());
		connected = 1;
	}

	rc = 0;
	goto done;
fail:
	xperror(*argv);
 done:
	/* Join with all slaves threads. */
	with_mutex (slave_mutex,
	            while (running_slaves > 0)
	                    pthread_cond_wait(&slave_cond, &slave_mutex););

	if (rc || !reexecing) {
		hash_table_destroy(&reg_table, (free_func*)reg_table_free_key, (free_func*)reg_table_free_value);
		mds_message_destroy(&received);
	}
	pthread_mutex_destroy(&slave_mutex);
	pthread_cond_destroy(&slave_cond);
	free(send_buffer);
	return rc;
}