/*
     This file is part of GNUnet.
     (C) 2010 Christian Grothoff

     GNUnet 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, or (at your
     option) any later version.

     GNUnet 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 GNUnet; see the file COPYING.  If not, write to the
     Free Software Foundation, Inc., 59 Temple Place - Suite 330,
     Boston, MA 02111-1307, USA.
*/

/**
 * @file vpn/gnunet-daemon-vpn-dns.c
 * @brief
 * @author Philipp Toelke
 */
#include <platform.h>
#include <gnunet_common.h>
#include <gnunet_client_lib.h>
#include <gnunet_os_lib.h>
#include <gnunet_mesh_service.h>
#include <gnunet_protocols.h>
#include <gnunet_server_lib.h>
#include <gnunet_container_lib.h>
#include <block_dns.h>

#include "gnunet-daemon-vpn-dns.h"
#include "gnunet-daemon-vpn.h"
#include "gnunet-daemon-vpn-helper.h"
#include "gnunet-service-dns-p.h"
#include "gnunet-vpn-packet.h"

/**
 * Callback called by notify_transmit_ready; sends dns-queries or rehijack-messages
 * to the service-dns
 * {{{
 */
size_t
send_query(void* cls, size_t size, void* buf) {
    size_t len;
    /*
     * Send the rehijack-message
     */
    if (restart_hijack == 1)
      {
	restart_hijack = 0;
	/*
	 * The message is just a header
	 */
	GNUNET_assert(sizeof(struct GNUNET_MessageHeader) <= size);
	struct GNUNET_MessageHeader* hdr = buf;
	len = sizeof(struct GNUNET_MessageHeader);
	hdr->size = htons(len);
	hdr->type = htons(GNUNET_MESSAGE_TYPE_REHIJACK);
      }
    else if (head != NULL)
      {
	struct query_packet_list* query = head;
	len = ntohs(query->pkt.hdr.size);

	GNUNET_assert(len <= size);

	memcpy(buf, &query->pkt.hdr, len);

	GNUNET_CONTAINER_DLL_remove (head, tail, query);

	GNUNET_free(query);
      }
    else
      {
	GNUNET_break(0);
	len = 0;
      }

    /*
     * Check whether more data is to be sent
     */
    if (head != NULL)
      {
	GNUNET_CLIENT_notify_transmit_ready(dns_connection, ntohs(head->pkt.hdr.size), GNUNET_TIME_UNIT_FOREVER_REL, GNUNET_YES, &send_query, NULL);
      }
    else if (restart_hijack == 1)
      {
	GNUNET_CLIENT_notify_transmit_ready(dns_connection, sizeof(struct GNUNET_MessageHeader), GNUNET_TIME_UNIT_FOREVER_REL, GNUNET_YES, &send_query, NULL);
      }

    return len;
}
/* }}} */


/**
 * Connect to the service-dns
 */
void
connect_to_service_dns (void *cls,
			const struct GNUNET_SCHEDULER_TaskContext *tc) {
    if (0 != (tc->reason & GNUNET_SCHEDULER_REASON_SHUTDOWN))
      return;
    GNUNET_log(GNUNET_ERROR_TYPE_DEBUG, "Connecting to service-dns\n");
    GNUNET_assert (dns_connection == NULL);
    dns_connection = GNUNET_CLIENT_connect ("dns", cfg);
    /* This would most likely be a misconfiguration */
    GNUNET_assert(dns_connection != NULL);
    GNUNET_CLIENT_receive(dns_connection, &dns_answer_handler, NULL, GNUNET_TIME_UNIT_FOREVER_REL);

    /* If a packet is already in the list, schedule to send it */
    if (head != NULL)
      GNUNET_CLIENT_notify_transmit_ready(dns_connection,
					  ntohs(head->pkt.hdr.size),
					  GNUNET_TIME_UNIT_FOREVER_REL,
					  GNUNET_YES,
					  &send_query,
					  NULL);
    else if (restart_hijack == 1)
      {
	GNUNET_CLIENT_notify_transmit_ready(dns_connection, sizeof(struct GNUNET_MessageHeader), GNUNET_TIME_UNIT_FOREVER_REL, GNUNET_YES, &send_query, NULL);
      }
}

/**
 * This receives packets from the service-dns and schedules process_answer to
 * handle it
 */
void
dns_answer_handler(void* cls, const struct GNUNET_MessageHeader *msg) {
    /* the service disconnected, reconnect after short wait */
    if (msg == NULL)
      {
	GNUNET_CLIENT_disconnect(dns_connection, GNUNET_NO);
	dns_connection = NULL;
	GNUNET_SCHEDULER_add_delayed (GNUNET_TIME_UNIT_SECONDS,
				      &connect_to_service_dns,
				      NULL);
	return;
      }

    /* the service did something strange, reconnect immediately */
    if (msg->type != htons(GNUNET_MESSAGE_TYPE_LOCAL_RESPONSE_DNS))
      {
	GNUNET_break (0);
	GNUNET_CLIENT_disconnect(dns_connection, GNUNET_NO);
	dns_connection = NULL;
	GNUNET_SCHEDULER_add_now (&connect_to_service_dns,
				  NULL);
	return;
      }
    void *pkt = GNUNET_malloc(ntohs(msg->size));

    memcpy(pkt, msg, ntohs(msg->size));

    GNUNET_SCHEDULER_add_now(process_answer, pkt);
    GNUNET_CLIENT_receive(dns_connection, &dns_answer_handler, NULL, GNUNET_TIME_UNIT_FOREVER_REL);
}