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

/**
 * mds — A micro-display server
 * Copyright © 2014, 2015, 2016  Mattias Andrée (maandree@member.fsf.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 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 "reexec.h"

#include "util.h"
#include "globals.h"
#include "slave.h"

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

#include <stddef.h>
#include <stdlib.h>
#include <string.h>
#include <errno.h>



/**
 * Calculate the number of bytes that will be stored by `marshal_server`
 * 
 * On failure the program should `abort()` or exit by other means.
 * However it should not be possible for this function to fail.
 * 
 * @return  The number of bytes that will be stored by `marshal_server`
 */
size_t
marshal_server_size(void)
{
	size_t i, rc = 2 * sizeof(int) + sizeof(uint32_t) + 4 * sizeof(size_t);
	hash_entry_t *entry;
	ssize_t node;
	char *command;
	size_t len;
	client_list_t *list;
	slave_t *slave;

	rc += mds_message_marshal_size(&received);
	rc += linked_list_marshal_size(&slave_list);

	foreach_hash_table_entry (reg_table, i, entry) {
		command = (void *)entry->key;
		len = strlen(command) + 1;
		list = (void *)entry->value;

		rc += len + sizeof(size_t) + client_list_marshal_size(list);
	}

	foreach_linked_list_node (slave_list, node) {
		slave = (void *)slave_list.values[node];
		rc += slave_marshal_size(slave);
	}

	return rc;
}


/**
 * Marshal server implementation specific data into a buffer
 * 
 * @param   state_buf  The buffer for the marshalled data
 * @return             Non-zero on error
 */
int
marshal_server(char *state_buf)
{
	size_t i, n = mds_message_marshal_size(&received);
	hash_entry_t *entry;
	ssize_t node;
	char *command;
	size_t len;
	client_list_t *list;
	slave_t *slave;

	buf_set_next(state_buf, int, MDS_REGISTRY_VARS_VERSION);
	buf_set_next(state_buf, int, connected);
	buf_set_next(state_buf, uint32_t, message_id);
	buf_set_next(state_buf, size_t, n);
	mds_message_marshal(&received, state_buf);
	state_buf += n / sizeof(char);

	buf_set_next(state_buf, size_t, reg_table.capacity);
	buf_set_next(state_buf, size_t, reg_table.size);
	foreach_hash_table_entry (reg_table, i, entry) {
		command = (void *)(entry->key);
		len = strlen(command) + 1;
		list = (void *)(entry->value);

		memcpy(state_buf, command, len * sizeof(char));
		state_buf += len;

		n = client_list_marshal_size(list);
		buf_set_next(state_buf, size_t, n);
		client_list_marshal(list, state_buf);
		state_buf += n / sizeof(char);
	}

	n = linked_list_marshal_size(&slave_list);
	buf_set_next(state_buf, size_t, n);
	linked_list_marshal(&slave_list, state_buf);
	state_buf += n / sizeof(char);

	foreach_linked_list_node (slave_list, node) {
		slave = (void *)(slave_list.values[node]);
		state_buf += slave_marshal(slave, state_buf) / sizeof(char);
		slave_destroy(slave);
	}

	hash_table_destroy(&reg_table, (free_func *)reg_table_free_key, (free_func *)reg_table_free_value);
	mds_message_destroy(&received);
	linked_list_destroy(&slave_list);
	return 0;
}


/**
 * Unmarshal server implementation specific data and update the servers state accordingly
 * 
 * On critical failure the program should `abort()` or exit by other means.
 * That is, do not let `reexec_failure_recover` run successfully, if it unrecoverable
 * error has occurred or one severe enough that it is better to simply respawn.
 * 
 * @param   state_buf  The marshalled data that as not been read already
 * @return             Non-zero on error
 */
int
unmarshal_server(char *state_buf)
{
	char *command;
	client_list_t *list;
	slave_t *slave;
	size_t i, n, m;
	ssize_t node;
	int stage = 0;

	/* buf_get_next(state_buf, int, MDS_REGISTRY_VARS_VERSION); */
	buf_next(state_buf, int, 1);
	buf_get_next(state_buf, int, connected);
	buf_get_next(state_buf, uint32_t, message_id);
	buf_get_next(state_buf, size_t, n);
	fail_if (mds_message_unmarshal(&received, state_buf));
	state_buf += n / sizeof(char);
	stage = 1;

	buf_get_next(state_buf, size_t, n);
	fail_if (hash_table_create_tuned(&reg_table, n));
	buf_get_next(state_buf, size_t, n);
	for (i = 0; i < n; i++) {
		stage = 1;
		fail_if (xstrdup(command, state_buf));
		state_buf += strlen(command) + 1;

		stage = 2;
		fail_if (xmalloc(list, 1, client_list_t));
		buf_get_next(state_buf, size_t, m);
		stage = 3;
		fail_if (client_list_unmarshal(list, state_buf));
		state_buf += m / sizeof(char);

		hash_table_put(&reg_table, (size_t)(void *)command, (size_t)(void *)list);
		fail_if (errno);
	}
	command = NULL;
	stage = 4;

	reg_table.key_comparator = (compare_func*)string_comparator;
	reg_table.hasher = (hash_func*)string_hash;

	buf_get_next(state_buf, size_t, n);
	fail_if (linked_list_unmarshal(&slave_list, state_buf));
	state_buf += n / sizeof(char);

	foreach_linked_list_node (slave_list, node) {
		stage = 5;
		fail_if (xmalloc(slave, 1, slave_t));
		stage = 6;
		fail_if ((n = slave_unmarshal(slave, state_buf)) == 0);
		state_buf += n / sizeof(char);
		slave_list.values[node] = (size_t)(void *)slave;
	}

	foreach_linked_list_node (slave_list, node) {
		slave = (slave_t *)(void *)(slave_list.values[node]);
		fail_if (start_created_slave(slave));
	}

	return 0;
fail:
	xperror(*argv);
	mds_message_destroy(&received);
	if (stage >= 1)
		hash_table_destroy(&reg_table, (free_func *)reg_table_free_key, (free_func *)reg_table_free_value);
	if (stage >= 2) free(command);
	if (stage >= 3) client_list_destroy(list), free(list);
	if (stage >= 5) linked_list_destroy(&slave_list);
	if (stage >= 6) slave_destroy(slave), free(slave);
	abort();
	return -1;
}


/**
 * Attempt to recover from a re-exec failure that has been
 * detected after the server successfully updated it execution image
 * 
 * @return  Non-zero on error
 */
int __attribute__((const))
reexec_failure_recover(void)
{
	return -1;
}