/*
    ether_emu.C -- ethernet "emulator" library
    Copyright (C) 2003-2008 Marc Lehmann <gvpe@schmorp.de>
 
    This file is part of GVPE.

    GVPE 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/>.
   
    Additional permission under GNU GPL version 3 section 7
   
    If you modify this Program, or any covered work, by linking or
    combining it with the OpenSSL project's OpenSSL library (or a modified
    version of that library), containing parts covered by the terms of the
    OpenSSL or SSLeay licenses, the licensors of this Program grant you
    additional permission to convey the resulting work.  Corresponding
    Source for a non-source form of such a combination shall include the
    source code for the parts of OpenSSL used as well as that of the
    covered work.
*/

#include "config.h"

#include <map>

#include "vpn.h"

extern struct vpn network;

struct ether_emu : map<u32, int>
{
  typedef map<u32, int> ipv4map;
  ipv4map ipv4;

  bool tun_to_tap (tap_packet *pkt);
  bool tap_to_tun (tap_packet *pkt);

  void set_ipv4 (u32 ip, int dst)
    {
      (ipv4.insert (pair<u32, int>(ip, dst)).first)->second = dst;
    }
};

static struct ether_emu ether_emu;

bool
ether_emu::tun_to_tap (tap_packet *pkt)
{
  int dst;

  if (pkt->is_ipv4 ())
    {
      // update arp cache for _local_ hosts
      set_ipv4 (pkt->ipv4_src (), THISNODE->id);

      ipv4map::iterator i = ipv4.find (pkt->ipv4_dst ());

      if (i == ipv4.end ())
        {
          u32 ip_src = pkt->ipv4_src ();
          u32 ip_dst = pkt->ipv4_dst ();

          // throw away current packet and make it an arp request
          (*pkt)[12] = 0x08; (*pkt)[13] = 0x06;
          (*pkt)[14] = 0x00; (*pkt)[15] = 0x01; // hw
          (*pkt)[16] = 0x08; (*pkt)[17] = 0x00; // prot
          (*pkt)[18] = 0x06; // hw_len
          (*pkt)[19] = 0x04; // prot_len
          (*pkt)[20] = 0x00; (*pkt)[21] = 0x01; // op

          id2mac (THISNODE->id, &(*pkt)[22]);
          *(u32 *)&(*pkt)[28] = ip_src;
          id2mac (0, &(*pkt)[32]);
          *(u32 *)&(*pkt)[38] = ip_dst;

          pkt->len = 42;

          dst = 0;
        }
      else
        dst = i->second;
    }
  else
    dst = 0; // broadcast non-ip

  id2mac (THISNODE->id, pkt->src);
  id2mac (dst, pkt->dst);

  return true;
}

bool
ether_emu::tap_to_tun (tap_packet *pkt)
{
  if (pkt->is_arp ())
    {
      u32 ip_src = *(u32 *)&(*pkt)[28];

      // always update with all info we can get. in this case, the arp sender.
      set_ipv4 (ip_src, mac2id (&(*pkt)[22]));

      //TODO: remove cache dumper
      //for (ipv4map::iterator i = ipv4.begin (); i != ipv4.end (); ++i) printf ("%08lx => %d\n", i->first, i->second);

      if ((*pkt)[20] == 0x00 && (*pkt)[21] == 0x01) // arp request
        {
          // send a reply, if applicable
          u32 ip_dst = *(u32 *)&(*pkt)[38];
          ipv4map::iterator i = ipv4.find (ip_dst);
          
          // TODO: look up list of local networks and answer for them
          if (i != ipv4.end () && i->second == THISNODE->id)
            {
              // create an arp reply
              tap_packet *rep = new tap_packet;

              id2mac (THISNODE->id, rep->src);
              memcpy (rep->dst, pkt->src, sizeof (mac));

              (*rep)[12] = 0x08; (*rep)[13] = 0x06;
              (*rep)[14] = 0x00; (*rep)[15] = 0x01; // hw
              (*rep)[16] = 0x08; (*rep)[17] = 0x00; // prot
              (*rep)[18] = 0x06; // hw_len
              (*rep)[19] = 0x04; // prot_len
              (*rep)[20] = 0x00; (*rep)[21] = 0x02; // op

              id2mac (THISNODE->id, &(*rep)[22]);
              *(u32 *)&(*rep)[28] = ip_dst;
              memcpy (&(*rep)[32], &(*pkt)[22], sizeof (mac));
              *(u32 *)&(*rep)[38] = ip_src;

              rep->len = 42;

              network.inject_data_packet (rep, mac2id (rep->dst));

              delete rep;
            }
        }
      else if ((*pkt)[20] == 0x00 && (*pkt)[21] == 0x02) // arp reply
        set_ipv4 (*(u32 *)&(*pkt)[28], mac2id (&(*pkt)[22]));

      return false;
    }
  else if (pkt->is_ipv4 ())
    {
      // update arp cache
      set_ipv4 (pkt->ipv4_src (), mac2id (pkt->src));
      set_ipv4 (pkt->ipv4_dst (), mac2id (pkt->dst));
    }

  return true;
}