/*
     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-helper.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_configuration_lib.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"
#include "gnunet-vpn-checksum.h"
#include "gnunet-helper-vpn-api.h"

struct GNUNET_VPN_HELPER_Handle *helper_handle;

/**
 * Start the helper-process
 *
 * If cls != NULL it is assumed that this function is called as a result of a dying
 * helper. cls is then taken as handle to the old helper and is cleaned up.
 * {{{
 */
void
start_helper_and_schedule(void *cls,
			  const struct GNUNET_SCHEDULER_TaskContext *tc) {
    if (0 != (tc->reason & GNUNET_SCHEDULER_REASON_SHUTDOWN))
      return;

    if (cls != NULL)
      cleanup_helper(cls);
    cls = NULL;

    char* ifname;
    char* ipv6addr;
    char* ipv6prefix;
    char* ipv4addr;
    char* ipv4mask;

    if (GNUNET_SYSERR == GNUNET_CONFIGURATION_get_value_string(cfg, "vpn", "IFNAME", &ifname))
      {
	GNUNET_log(GNUNET_ERROR_TYPE_ERROR, "No entry 'IFNAME' in configuration!\n");
	exit(1);
      }

    if (GNUNET_SYSERR == GNUNET_CONFIGURATION_get_value_string(cfg, "vpn", "IPV6ADDR", &ipv6addr))
      {
	GNUNET_log(GNUNET_ERROR_TYPE_ERROR, "No entry 'IPV6ADDR' in configuration!\n");
	exit(1);
      }

    if (GNUNET_SYSERR == GNUNET_CONFIGURATION_get_value_string(cfg, "vpn", "IPV6PREFIX", &ipv6prefix))
      {
	GNUNET_log(GNUNET_ERROR_TYPE_ERROR, "No entry 'IPV6PREFIX' in configuration!\n");
	exit(1);
      }

    if (GNUNET_SYSERR == GNUNET_CONFIGURATION_get_value_string(cfg, "vpn", "IPV4ADDR", &ipv4addr))
      {
	GNUNET_log(GNUNET_ERROR_TYPE_ERROR, "No entry 'IPV4ADDR' in configuration!\n");
	exit(1);
      }

    if (GNUNET_SYSERR == GNUNET_CONFIGURATION_get_value_string(cfg, "vpn", "IPV4MASK", &ipv4mask))
      {
	GNUNET_log(GNUNET_ERROR_TYPE_ERROR, "No entry 'IPV4MASK' in configuration!\n");
	exit(1);
      }

    /* Start the helper
     * Messages get passed to the function message_token
     * When the helper dies, this function will be called again with the
     * helper_handle as cls.
     */
    helper_handle = start_helper(ifname,
				 ipv6addr,
				 ipv6prefix,
				 ipv4addr,
				 ipv4mask,
				 "vpn-gnunet",
				 start_helper_and_schedule,
				 message_token,
				 NULL,
				 NULL);

    GNUNET_free(ipv6addr);
    GNUNET_free(ipv6prefix);
    GNUNET_free(ipv4addr);
    GNUNET_free(ipv4mask);
    GNUNET_free(ifname);

    /* Tell the dns-service to rehijack the dns-port
     * The routing-table gets flushed if an interface disappears.
     */
    restart_hijack = 1;
    if (NULL != dns_connection)
      GNUNET_CLIENT_notify_transmit_ready(dns_connection, sizeof(struct GNUNET_MessageHeader), GNUNET_TIME_UNIT_FOREVER_REL, GNUNET_YES, &send_query, NULL);
}
/*}}}*/

/**
 * Send an dns-answer-packet to the helper
 */
void
helper_write(void* cls, const struct GNUNET_SCHEDULER_TaskContext* tsdkctx) {
    if (tsdkctx->reason & GNUNET_SCHEDULER_REASON_SHUTDOWN)
      return;

    struct answer_packet_list* ans = answer_proc_head;
    size_t len = ntohs(ans->pkt.hdr.size);

    GNUNET_assert(ans->pkt.subtype == GNUNET_DNS_ANSWER_TYPE_IP);

    GNUNET_assert (20 == sizeof (struct ip_hdr));
    GNUNET_assert (8 == sizeof (struct udp_pkt));
    size_t data_len = len - sizeof(struct answer_packet) + 1;
    size_t net_len = sizeof(struct ip_hdr) + sizeof(struct udp_dns) + data_len;
    size_t pkt_len = sizeof(struct GNUNET_MessageHeader) + sizeof(struct pkt_tun) + net_len;

    struct ip_udp_dns* pkt = alloca(pkt_len);
    GNUNET_assert(pkt != NULL);
    memset(pkt, 0, pkt_len);

    /* set the gnunet-header */
    pkt->shdr.size = htons(pkt_len);
    pkt->shdr.type = htons(GNUNET_MESSAGE_TYPE_VPN_HELPER);

    /* set the tun-header (no flags and ethertype of IPv4) */
    pkt->tun.flags = 0;
    pkt->tun.type = htons(0x0800);

    /* set the ip-header */
    pkt->ip_hdr.version = 4;
    pkt->ip_hdr.hdr_lngth = 5;
    pkt->ip_hdr.diff_serv = 0;
    pkt->ip_hdr.tot_lngth = htons(net_len);
    pkt->ip_hdr.ident = 0;
    pkt->ip_hdr.flags = 0;
    pkt->ip_hdr.frag_off = 0;
    pkt->ip_hdr.ttl = 255;
    pkt->ip_hdr.proto = 0x11; /* UDP */
    pkt->ip_hdr.chks = 0; /* Will be calculated later*/
    pkt->ip_hdr.sadr = ans->pkt.from;
    pkt->ip_hdr.dadr = ans->pkt.to;

    pkt->ip_hdr.chks = calculate_ip_checksum((uint16_t*)&pkt->ip_hdr, 5*4);

    /* set the udp-header */
    pkt->udp_dns.udp_hdr.spt = htons(53);
    pkt->udp_dns.udp_hdr.dpt = ans->pkt.dst_port;
    pkt->udp_dns.udp_hdr.len = htons(net_len - sizeof(struct ip_hdr));
    pkt->udp_dns.udp_hdr.crc = 0; /* Optional for IPv4 */

    memcpy(&pkt->udp_dns.data, ans->pkt.data, data_len);

    GNUNET_CONTAINER_DLL_remove (answer_proc_head, answer_proc_tail, ans);
    GNUNET_free(ans);

    if (GNUNET_DISK_file_write(helper_handle->fh_to_helper, pkt, pkt_len) < 0)
      {
        cleanup_helper(helper_handle);
        GNUNET_SCHEDULER_add_now(start_helper_and_schedule, NULL);
        return;
      }

    /* if more packets are available, reschedule */
    if (answer_proc_head != NULL)
      GNUNET_SCHEDULER_add_write_file (GNUNET_TIME_UNIT_FOREVER_REL,
				       helper_handle->fh_to_helper,
				       &helper_write,
				       NULL);
}

/**
 * Receive packets from the helper-process
 */
void
message_token (void *cls,
               void *client, const struct GNUNET_MessageHeader *message)
{
  GNUNET_assert (ntohs (message->type) == GNUNET_MESSAGE_TYPE_VPN_HELPER);

  struct tun_pkt *pkt_tun = (struct tun_pkt *) message;

  /* ethertype is ipv6 */
  if (ntohs (pkt_tun->tun.type) == 0x86dd)
    {
      struct ip6_pkt *pkt6 = (struct ip6_pkt *) message;
      GNUNET_assert (pkt6->ip6_hdr.version == 6);
      struct ip6_tcp *pkt6_tcp;
      struct ip6_udp *pkt6_udp;
      struct ip6_icmp *pkt6_icmp;
      GNUNET_HashCode *key;

      switch (pkt6->ip6_hdr.nxthdr)
        {
        case 0x06:             /* TCP */
        case 0x11:             /* UDP */
          pkt6_tcp = (struct ip6_tcp *) pkt6;
          pkt6_udp = (struct ip6_udp *) pkt6;

          if ((key = address_mapping_exists (pkt6->ip6_hdr.dadr)) != NULL)
            {
              struct map_entry *me =
                GNUNET_CONTAINER_multihashmap_get (hashmap, key);
              GNUNET_assert (me != NULL);
              GNUNET_free (key);

              size_t size =
                sizeof (struct GNUNET_MESH_Tunnel *) +
                sizeof (struct GNUNET_MessageHeader) +
                sizeof (GNUNET_HashCode) + ntohs (pkt6->ip6_hdr.paylgth);

              struct GNUNET_MESH_Tunnel **cls = GNUNET_malloc (size);
              struct GNUNET_MessageHeader *hdr =
                (struct GNUNET_MessageHeader *) (cls + 1);
              GNUNET_HashCode *hc = (GNUNET_HashCode *) (hdr + 1);

              hdr->size = htons (sizeof (struct GNUNET_MessageHeader) +
                                 sizeof (GNUNET_HashCode) +
                                 ntohs (pkt6->ip6_hdr.paylgth));

              memcpy (hc, &me->desc.service_descriptor,
                      sizeof (GNUNET_HashCode));

              if (0x11 == pkt6->ip6_hdr.nxthdr
                  && (me->desc.
                      service_type & htonl (GNUNET_DNS_SERVICE_TYPE_UDP))
                  && (port_in_ports (me->desc.ports, pkt6_udp->udp_hdr.dpt)
                      || testBit (me->additional_ports,
                                  ntohs (pkt6_udp->udp_hdr.dpt))))
                {
                  hdr->type = ntohs (GNUNET_MESSAGE_TYPE_SERVICE_UDP);

                  memcpy (hc + 1, &pkt6_udp->udp_hdr,
                          ntohs (pkt6_udp->udp_hdr.len));

                }
              else if (0x06 == pkt6->ip6_hdr.nxthdr
                       && (me->desc.
                           service_type & htonl (GNUNET_DNS_SERVICE_TYPE_TCP))
                       &&
                       (port_in_ports (me->desc.ports, pkt6_tcp->tcp_hdr.dpt)))
                {
                  hdr->type = ntohs (GNUNET_MESSAGE_TYPE_SERVICE_TCP);

                  memcpy (hc + 1, &pkt6_tcp->tcp_hdr,
                          ntohs (pkt6->ip6_hdr.paylgth));

                }
              else
                {
                  GNUNET_log(GNUNET_ERROR_TYPE_DEBUG, "Dropping packet. nxthdr=%d, type=%d, dpt=%x, flg=%d, ports=%x\n",
                             pkt6->ip6_hdr.nxthdr, ntohl(me->desc.service_type),
                             ntohs(pkt6_tcp->tcp_hdr.dpt), pkt6_tcp->tcp_hdr.flg, me->desc.ports);
                  GNUNET_free (cls);
                  cls = NULL;
                }
              if (me->tunnel == NULL && NULL != cls)
                {
                  *cls =
                    GNUNET_MESH_peer_request_connect_all (mesh_handle,
                                                          GNUNET_TIME_UNIT_FOREVER_REL,
                                                          1,
                                                          (struct
                                                           GNUNET_PeerIdentity
                                                           *) &me->desc.peer,
                                                          send_pkt_to_peer,
                                                          NULL, cls);
                  me->tunnel = *cls;
                }
              else if (NULL != cls)
                {
                  *cls = me->tunnel;
                  send_pkt_to_peer (cls, (struct GNUNET_PeerIdentity *) 1,
                                    NULL);
                  GNUNET_log (GNUNET_ERROR_TYPE_DEBUG,
                              "Queued to send to peer %x, type %d\n",
                              *((unsigned int *) &me->desc.peer), ntohs(hdr->type));
                }
            }
          break;
        case 0x3a:
          /* ICMPv6 */
          pkt6_icmp = (struct ip6_icmp *) pkt6;
          /* If this packet is an icmp-echo-request and a mapping exists, answer */
          if (pkt6_icmp->icmp_hdr.type == 0x80
              && (key = address_mapping_exists (pkt6->ip6_hdr.dadr)) != NULL)
            {
              GNUNET_free (key);
              pkt6_icmp = GNUNET_malloc (ntohs (pkt6->shdr.size));
              memcpy (pkt6_icmp, pkt6, ntohs (pkt6->shdr.size));
              GNUNET_SCHEDULER_add_now (&send_icmp_response, pkt6_icmp);
            }
          break;
        }
    }
  /* ethertype is ipv4 */
  else if (ntohs (pkt_tun->tun.type) == 0x0800)
    {
      struct ip_pkt *pkt = (struct ip_pkt *) message;
      struct ip_udp *udp = (struct ip_udp *) message;
      GNUNET_assert (pkt->ip_hdr.version == 4);

      /* Send dns-packets to the service-dns */
      if (pkt->ip_hdr.proto == 0x11 && ntohs (udp->udp_hdr.dpt) == 53)
        {
          /* 9 = 8 for the udp-header + 1 for the unsigned char data[1]; */
          size_t len =
            sizeof (struct query_packet) + ntohs (udp->udp_hdr.len) - 9;

          struct query_packet_list *query =
            GNUNET_malloc (len + 2 * sizeof (struct query_packet_list *));
          query->pkt.hdr.type = htons (GNUNET_MESSAGE_TYPE_LOCAL_QUERY_DNS);
          query->pkt.hdr.size = htons (len);
          query->pkt.orig_to = pkt->ip_hdr.dadr;
          query->pkt.orig_from = pkt->ip_hdr.sadr;
          query->pkt.src_port = udp->udp_hdr.spt;
          memcpy (query->pkt.data, udp->data, ntohs (udp->udp_hdr.len) - 8);

          GNUNET_CONTAINER_DLL_insert_after (head, tail, tail, query);

          GNUNET_assert (head != NULL);

          if (dns_connection != NULL)
            GNUNET_CLIENT_notify_transmit_ready (dns_connection,
                                                 len,
                                                 GNUNET_TIME_UNIT_FOREVER_REL,
                                                 GNUNET_YES,
                                                 &send_query, NULL);
        }
    }
}

void write_to_helper(void* buf, size_t len)
{
  (void)GNUNET_DISK_file_write(helper_handle->fh_to_helper, buf, len);
}

void schedule_helper_write(struct GNUNET_TIME_Relative time, void* cls)
{
  GNUNET_SCHEDULER_add_write_file (time, helper_handle->fh_to_helper, &helper_write, cls);
}