/* packet-bt-utp.c
 * Routines for BT-UTP dissection
 * Copyright 2011, Xiao Xiangquan <xiaoxiangquan@gmail.com>
 *
 * $Id$
 *
 * Wireshark - Network traffic analyzer
 * By Gerald Combs <gerald@wireshark.org>
 * Copyright 1999 Gerald Combs
 *
 * 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 2
 * 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, write to the Free Software
 * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA.
 */

#include "config.h"

#include <epan/packet.h>
#include <epan/conversation.h>
#include <epan/prefs.h>

enum {
  ST_DATA  = 0,
  ST_FIN   = 1,
  ST_STATE = 2,
  ST_RESET = 3,
  ST_SYN   = 4,
  ST_NUM_STATES
};

/* V0 hdr: "flags"; V1 hdr: "type" */
static const value_string bt_utp_type_vals[] = {
  { ST_DATA,  "Data"  },
  { ST_FIN,   "Fin"   },
  { ST_STATE, "State" },
  { ST_RESET, "Reset" },
  { ST_SYN,   "Syn"   },
  { 0, NULL }
};

enum {
  EXT_NO_EXTENSION    = 0,
  EXT_SELECTION_ACKS  = 1,
  EXT_EXTENSION_BITS  = 2,
  EXT_NUM_EXT
};

static const value_string bt_utp_extension_type_vals[] = {
  { EXT_NO_EXTENSION,   "No Extension" },
  { EXT_SELECTION_ACKS, "Selective ACKs" },
  { EXT_EXTENSION_BITS, "Extension bits" },
  { 0, NULL }
};

static int proto_bt_utp = -1;

static gboolean bt_utp_enable_heuristic_dissection = FALSE; /* disabled by default since heuristic is weak */

/* ---  "Original" uTP Header ("version 0" ?) --------------

See utp.cpp source code @ https://github.com/bittorrent/libutp

-- Fixed Header --
0       4       8               16              24              32
+-------+-------+---------------+---------------+---------------+
| connection_id                                                 |
+-------+-------+---------------+---------------+---------------+
| timestamp_seconds                                             |
+---------------+---------------+---------------+---------------+
| timestamp_microseconds                                        |
+---------------+---------------+---------------+---------------+
| timestamp_difference_microseconds                             |
+---------------+---------------+---------------+---------------+
| wnd_size      | ext           | flags         | seq_nr [ho]   |
+---------------+---------------+---------------+---------------+
| seq_nr [lo]   | ack_nr                        |
+---------------+---------------+---------------+

-- Extension Field(s) --
0               8               16
+---------------+---------------+---------------+---------------+
| extension     | len           | bitmask
+---------------+---------------+---------------+---------------+
                                |
+---------------+---------------+....

*/

/* --- Version 1 Header ----------------

Specifications: BEP-0029
http://www.bittorrent.org/beps/bep_0029.html

-- Fixed Header --
Fields Types
0       4       8               16              24              32
+-------+-------+---------------+---------------+---------------+
| type  | ver   | extension     | connection_id                 |
+-------+-------+---------------+---------------+---------------+
| timestamp_microseconds                                        |
+---------------+---------------+---------------+---------------+
| timestamp_difference_microseconds                             |
+---------------+---------------+---------------+---------------+
| wnd_size                                                      |
+---------------+---------------+---------------+---------------+
| seq_nr                        | ack_nr                        |
+---------------+---------------+---------------+---------------+

-- Extension Field(s) --
0               8               16
+---------------+---------------+---------------+---------------+
| extension     | len           | bitmask
+---------------+---------------+---------------+---------------+
                                |
+---------------+---------------+....
*/

#define V0_FIXED_HDR_SIZE 23
#define V1_FIXED_HDR_SIZE 20

static dissector_handle_t bt_utp_handle;

static int hf_bt_utp_ver = -1;
static int hf_bt_utp_type = -1;
static int hf_bt_utp_flags = -1;
static int hf_bt_utp_extension = -1;
static int hf_bt_utp_next_extension_type = -1;
static int hf_bt_utp_extension_len = -1;
static int hf_bt_utp_extension_bitmask = -1;
static int hf_bt_utp_extension_unknown = -1;
static int hf_bt_utp_connection_id_v0 = -1;
static int hf_bt_utp_connection_id_v1 = -1;
static int hf_bt_utp_timestamp_sec = -1;
static int hf_bt_utp_timestamp_us = -1;
static int hf_bt_utp_timestamp_diff_us = -1;
static int hf_bt_utp_wnd_size_v0 = -1;
static int hf_bt_utp_wnd_size_v1 = -1;
static int hf_bt_utp_seq_nr = -1;
static int hf_bt_utp_ack_nr = -1;
static int hf_bt_utp_data = -1;

static gint ett_bt_utp = -1;
static gint ett_bt_utp_extension = -1;

void proto_reg_handoff_bt_utp(void);

static gint
get_utp_version(tvbuff_t *tvb) {
  guint8 v0_flags, v0_ext;
  guint8 v1_ver_type, v1_ext;
  guint  len;

  /* Simple heuristics inspired by code from utp.cpp */

  len = tvb_length(tvb);

  /* Version 1? */
  if (len < V1_FIXED_HDR_SIZE) {
    return -1;
  }

  v1_ver_type = tvb_get_guint8(tvb, 0);
  v1_ext = tvb_get_guint8(tvb, 1);
  if (((v1_ver_type & 0x0f) == 1) && ((v1_ver_type>>4) < ST_NUM_STATES) &&
      (v1_ext < EXT_NUM_EXT)) {
    return 1;
  }

  /* Version 0? */
  if (len < V0_FIXED_HDR_SIZE) {
    return -1;
  }

  v0_flags = tvb_get_guint8(tvb, 18);
  v0_ext = tvb_get_guint8(tvb, 17);
  if ((v0_flags < ST_NUM_STATES) || (v0_ext < EXT_NUM_EXT)) {
    return 0;
  }

  return -1;
}

static int
dissect_utp_header_v0(tvbuff_t *tvb, packet_info *pinfo, proto_tree *tree, int offset, guint8 *extension_type)
{
    /* "Original" (V0) */
  proto_tree_add_item(tree, hf_bt_utp_connection_id_v0, tvb, offset, 4, ENC_BIG_ENDIAN);
  offset += 4;
  proto_tree_add_item(tree, hf_bt_utp_timestamp_sec, tvb, offset, 4, ENC_BIG_ENDIAN);
  offset += 4;
  proto_tree_add_item(tree, hf_bt_utp_timestamp_us, tvb, offset, 4, ENC_BIG_ENDIAN);
  offset += 4;
  proto_tree_add_item(tree, hf_bt_utp_timestamp_diff_us, tvb, offset, 4, ENC_BIG_ENDIAN);
  offset += 4;
  proto_tree_add_item(tree, hf_bt_utp_wnd_size_v0, tvb, offset, 1, ENC_BIG_ENDIAN);
  offset += 1;
  proto_tree_add_item(tree, hf_bt_utp_next_extension_type, tvb, offset, 1, ENC_BIG_ENDIAN);

  *extension_type = tvb_get_guint8(tvb, offset);
  offset += 1;
  proto_tree_add_item(tree, hf_bt_utp_flags, tvb, offset, 1, ENC_BIG_ENDIAN);
  col_append_fstr(pinfo->cinfo, COL_INFO, " Type: %s", val_to_str(tvb_get_guint8(tvb, offset), bt_utp_type_vals, "Unknown %d"));
  offset += 1;
  proto_tree_add_item(tree, hf_bt_utp_seq_nr, tvb, offset, 2, ENC_BIG_ENDIAN);
  offset += 2;
  proto_tree_add_item(tree, hf_bt_utp_ack_nr, tvb, offset, 2, ENC_BIG_ENDIAN);
  offset += 2;

  return offset;
}

static int
dissect_utp_header_v1(tvbuff_t *tvb, packet_info *pinfo, proto_tree *tree, int offset, guint8 *extension_type)
{
  /* V1 */
  proto_tree_add_item(tree, hf_bt_utp_ver, tvb, offset, 1, ENC_BIG_ENDIAN);
  proto_tree_add_item(tree, hf_bt_utp_type, tvb, offset, 1, ENC_BIG_ENDIAN);
  col_append_fstr(pinfo->cinfo, COL_INFO, " Type: %s", val_to_str((tvb_get_guint8(tvb, offset) >> 4), bt_utp_type_vals, "Unknown %d"));
  offset += 1;
  proto_tree_add_item(tree, hf_bt_utp_next_extension_type, tvb, offset, 1, ENC_BIG_ENDIAN);
  *extension_type = tvb_get_guint8(tvb, offset);
  offset += 1;
  proto_tree_add_item(tree, hf_bt_utp_connection_id_v1, tvb, offset, 2, ENC_BIG_ENDIAN);
  offset += 2;
  proto_tree_add_item(tree, hf_bt_utp_timestamp_us, tvb, offset, 4, ENC_BIG_ENDIAN);
  offset += 4;
  proto_tree_add_item(tree, hf_bt_utp_timestamp_diff_us, tvb, offset, 4, ENC_BIG_ENDIAN);
  offset += 4;
  proto_tree_add_item(tree, hf_bt_utp_wnd_size_v1, tvb, offset, 4, ENC_BIG_ENDIAN);
  offset += 4;
  proto_tree_add_item(tree, hf_bt_utp_seq_nr, tvb, offset, 2, ENC_BIG_ENDIAN);
  offset += 2;
  proto_tree_add_item(tree, hf_bt_utp_ack_nr, tvb, offset, 2, ENC_BIG_ENDIAN);
  offset += 2;

  return offset;
}

static int
dissect_utp_extension(tvbuff_t *tvb, packet_info _U_*pinfo, proto_tree *tree, int offset, guint8 *extension_type)
{
  proto_item *ti;
  proto_tree *ext_tree;
  guint8 extension_length;
  /* display the extension tree */

  while(*extension_type != EXT_NO_EXTENSION && offset < (int)tvb_reported_length(tvb))
  {
    switch(*extension_type){
      case EXT_SELECTION_ACKS: /* 1 */
      {
        ti = proto_tree_add_item(tree, hf_bt_utp_extension, tvb, offset, -1, ENC_NA);
        ext_tree = proto_item_add_subtree(ti, ett_bt_utp_extension);

        proto_tree_add_item(ext_tree, hf_bt_utp_next_extension_type, tvb, offset, 1, ENC_BIG_ENDIAN);
        *extension_type = tvb_get_guint8(tvb, offset);
        offset += 1;

        proto_tree_add_item(ext_tree, hf_bt_utp_extension_len, tvb, offset, 1, ENC_BIG_ENDIAN);
        extension_length = tvb_get_guint8(tvb, offset);
        proto_item_append_text(ti, " Selection ACKs, Len=%d", extension_length);
        offset += 1;

        proto_tree_add_item(ext_tree, hf_bt_utp_extension_bitmask, tvb, offset, extension_length, ENC_NA);
        offset += extension_length;
        proto_item_set_len(ti, 1 + 1 + extension_length);
        break;
      }
      case EXT_EXTENSION_BITS: /* 2 */
      {
        ti = proto_tree_add_item(tree, hf_bt_utp_extension, tvb, offset, -1, ENC_NA);
        ext_tree = proto_item_add_subtree(ti, ett_bt_utp_extension);

        proto_tree_add_item(ext_tree, hf_bt_utp_next_extension_type, tvb, offset, 1, ENC_BIG_ENDIAN);
        *extension_type = tvb_get_guint8(tvb, offset);
        offset += 1;

        proto_tree_add_item(ext_tree, hf_bt_utp_extension_len, tvb, offset, 1, ENC_BIG_ENDIAN);
        extension_length = tvb_get_guint8(tvb, offset);
        proto_item_append_text(ti, " Extension Bits, Len=%d", extension_length);
        offset += 1;

        proto_tree_add_item(ext_tree, hf_bt_utp_extension_bitmask, tvb, offset, extension_length, ENC_NA);
        offset += extension_length;
        proto_item_set_len(ti, 1 + 1 + extension_length);
        break;
      }
      default:
        ti = proto_tree_add_item(tree, hf_bt_utp_extension, tvb, offset, -1, ENC_NA);
        ext_tree = proto_item_add_subtree(ti, ett_bt_utp_extension);

        proto_tree_add_item(ext_tree, hf_bt_utp_next_extension_type, tvb, offset, 1, ENC_BIG_ENDIAN);
        *extension_type = tvb_get_guint8(tvb, offset);
        offset += 1;

        proto_tree_add_item(ext_tree, hf_bt_utp_extension_len, tvb, offset, 1, ENC_BIG_ENDIAN);
        extension_length = tvb_get_guint8(tvb, offset);
        proto_item_append_text(ti, " Unknown, Len=%d", extension_length);
        offset += 1;

        proto_tree_add_item(ext_tree, hf_bt_utp_extension_unknown, tvb, offset, extension_length, ENC_NA);
        offset += extension_length;
        proto_item_set_len(ti, 1 + 1 + extension_length);
      break;
    }
  }

  return offset;
}

static int
dissect_bt_utp(tvbuff_t *tvb, packet_info *pinfo, proto_tree *tree, void *data _U_)
{
  gint version;
  version = get_utp_version(tvb);

  /* try dissecting */
  if (version >= 0)
  {
    conversation_t *conversation;
    guint len_tvb;
    proto_tree *sub_tree = NULL;
    proto_item *ti;
    gint offset = 0;
    guint8 extension_type;

    conversation = find_or_create_conversation(pinfo);
    conversation_set_dissector(conversation, bt_utp_handle);

    /* set the protocol column */
    col_set_str(pinfo->cinfo, COL_PROTOCOL, "BT-uTP");
    /* set the info column */
    col_set_str( pinfo->cinfo, COL_INFO, "uTorrent Transport Protocol" );

    len_tvb = tvb_reported_length(tvb);
    ti = proto_tree_add_protocol_format(tree, proto_bt_utp, tvb, 0, -1,
                                        "uTorrent Transport Protocol V%d (%d bytes)",
                                        version, len_tvb);
    sub_tree = proto_item_add_subtree(ti, ett_bt_utp);

    /* Determine header version */

    if (version == 0) {
      offset = dissect_utp_header_v0(tvb, pinfo, sub_tree, offset, &extension_type);
    } else {
      offset = dissect_utp_header_v1(tvb, pinfo, sub_tree, offset, &extension_type);
    }

    offset = dissect_utp_extension(tvb, pinfo, sub_tree, offset, &extension_type);

    len_tvb = tvb_length_remaining(tvb, offset);
    if(len_tvb > 0)
      proto_tree_add_item(sub_tree, hf_bt_utp_data, tvb, offset, len_tvb, ENC_NA);

    return offset+len_tvb;
  }
  return 0;
}

void
proto_register_bt_utp(void)
{
  static hf_register_info hf[] = {
    { &hf_bt_utp_ver,
      { "Version", "bt-utp.ver",
      FT_UINT8, BASE_DEC, NULL, 0x0F,
      NULL, HFILL }
    },
    { &hf_bt_utp_flags,
      { "Flags", "bt-utp.flags",
      FT_UINT8, BASE_DEC,  VALS(bt_utp_type_vals), 0x0,
      NULL, HFILL }
    },
    { &hf_bt_utp_type,
      { "Type", "bt-utp.type",
      FT_UINT8, BASE_DEC,  VALS(bt_utp_type_vals), 0xF0,
      NULL, HFILL }
    },
    { &hf_bt_utp_extension,
      { "Extension", "bt-utp.extension",
      FT_NONE, BASE_NONE, NULL, 0x0,
      NULL, HFILL }
    },
    { &hf_bt_utp_next_extension_type,
      { "Next Extension Type", "bt-utp.next_extension_type",
      FT_UINT8, BASE_DEC, VALS(bt_utp_extension_type_vals), 0x0,
      NULL, HFILL }
    },
    { &hf_bt_utp_extension_len,
      { "Extension Length", "bt-utp.extension_len",
      FT_UINT8, BASE_DEC, NULL, 0x0,
      NULL, HFILL }
    },
    { &hf_bt_utp_extension_bitmask,
      { "Extension Bitmask", "bt-utp.extension_bitmask",
      FT_BYTES, BASE_NONE, NULL, 0x0,
      NULL, HFILL }
    },
    { &hf_bt_utp_extension_unknown,
      { "Extension Unknown", "bt-utp.extension_unknown",
      FT_BYTES, BASE_NONE, NULL, 0x0,
      NULL, HFILL }
    },
    { &hf_bt_utp_connection_id_v0,
      { "Connection ID", "bt-utp.connection_id",
      FT_UINT32, BASE_DEC, NULL, 0x0,
      NULL, HFILL }
    },
    { &hf_bt_utp_connection_id_v1,
      { "Connection ID", "bt-utp.connection_id",
      FT_UINT16, BASE_DEC, NULL, 0x0,
      NULL, HFILL }
    },
    { &hf_bt_utp_timestamp_sec,
      { "Timestamp seconds", "bt-utp.timestamp_sec",
      FT_UINT32, BASE_DEC, NULL, 0x0,
      NULL, HFILL }
    },
    { &hf_bt_utp_timestamp_us,
      { "Timestamp Microseconds", "bt-utp.timestamp_us",
      FT_UINT32, BASE_DEC, NULL, 0x0,
      NULL, HFILL }
    },
    { &hf_bt_utp_timestamp_diff_us,
      { "Timestamp Difference Microseconds", "bt-utp.timestamp_diff_us",
      FT_UINT32, BASE_DEC, NULL, 0x0,
      NULL, HFILL }
    },
    { &hf_bt_utp_wnd_size_v0,
      { "Windows Size", "bt-utp.wnd_size",
      FT_UINT8, BASE_DEC, NULL, 0x0,
      NULL, HFILL }
    },
    { &hf_bt_utp_wnd_size_v1,
      { "Windows Size", "bt-utp.wnd_size",
      FT_UINT32, BASE_DEC, NULL, 0x0,
      NULL, HFILL }
    },
    { &hf_bt_utp_seq_nr,
      { "Sequence number", "bt-utp.seq_nr",
      FT_UINT16, BASE_DEC, NULL, 0x0,
      NULL, HFILL }
    },
    { &hf_bt_utp_ack_nr,
      { "ACK number", "bt-utp.ack_nr",
      FT_UINT16, BASE_DEC, NULL, 0x0,
      NULL, HFILL }
    },
    { &hf_bt_utp_data,
      { "Data", "bt-utp.data",
      FT_BYTES, BASE_NONE, NULL, 0x0,
      NULL, HFILL }
    },
  };

  /* Setup protocol subtree array */
  static gint *ett[] = { &ett_bt_utp, &ett_bt_utp_extension };

  module_t *bt_utp_module;

  /* Register protocol */
  proto_bt_utp = proto_register_protocol (
                        "uTorrent Transport Protocol",  /* name */
                        "BT-uTP",               /* short name */
                        "bt-utp"                /* abbrev */
                        );

  bt_utp_module = prefs_register_protocol(proto_bt_utp, proto_reg_handoff_bt_utp);
  prefs_register_bool_preference(bt_utp_module, "enable", "Enable BT-uTP heuristic dissection",
                                 "Enable BT-uTP heuristic dissection (default is disabled)",
                                 &bt_utp_enable_heuristic_dissection);

  proto_register_field_array(proto_bt_utp, hf, array_length(hf));
  proto_register_subtree_array(ett, array_length(ett));
}

void
proto_reg_handoff_bt_utp(void)
{
  static gboolean prefs_initialized = FALSE;

  if (!prefs_initialized) {
    heur_dissector_add("udp", dissect_bt_utp, proto_bt_utp);

    bt_utp_handle = new_create_dissector_handle(dissect_bt_utp, proto_bt_utp);
    dissector_add_handle("udp.port", bt_utp_handle);

    prefs_initialized = TRUE;
  }

  heur_dissector_set_enabled("udp", dissect_bt_utp, proto_bt_utp, bt_utp_enable_heuristic_dissection);
}

/*
 * Editor modelines
 *
 * Local Variables:
 * c-basic-offset: 2
 * tab-width: 8
 * indent-tabs-mode: nil
 * End:
 *
 * ex: set shiftwidth=2 tabstop=8 expandtab:
 * :indentSize=2:tabSize=8:noTabs=true:
 */

