/* packet-bittorrent.c

 * Routines for bittorrent packet dissection

 * Copyright (C) 2004 Jelmer Vernooij <jelmer@samba.org>

 *

 * Wireshark - Network traffic analyzer

 * By Gerald Combs <gerald@wireshark.org>

 * Copyright 1998 Gerald Combs

 *

 * Copied from packet-pop.c

 *

 * SPDX-License-Identifier: GPL-2.0-or-later

 */

#include "config.h"

#include <epan/packet.h>

#include <epan/prefs.h>

#include <epan/strutil.h>

#include "packet-tcp.h"

#include "packet-bt-utp.h"

void proto_register_bittorrent(void);

void proto_reg_handoff_bittorrent(void);

/*

 * See

 *

 * http://bittorrent.com/protocol.html

 * http://wiki.theory.org/BitTorrentSpecification

 * http://bitconjurer.org/BitTorrent/protocol.html

 */

#define DEFAULT_TCP_PORT_RANGE  "6881-6889" /* Not IANA registered */

#define BITTORRENT_MESSAGE_CHOKE            0

#define BITTORRENT_MESSAGE_UNCHOKE          1

#define BITTORRENT_MESSAGE_INTERESTED       2

#define BITTORRENT_MESSAGE_NOT_INTERESTED   3

#define BITTORRENT_MESSAGE_HAVE             4

#define BITTORRENT_MESSAGE_BITFIELD         5

#define BITTORRENT_MESSAGE_REQUEST          6

#define BITTORRENT_MESSAGE_PIECE            7

#define BITTORRENT_MESSAGE_CANCEL           8

#define BITTORRENT_MESSAGE_PORT             9

/*

 * BitTorrent BEP 06

 * Fast Extension message type

 *

 */

#define BITT_FAST_EX_SUGGEST_PIECE         13

#define BITT_FAST_EX_HAVE_ALL              14

#define BITT_FAST_EX_HAVE_NONE             15

#define BITT_FAST_EX_REJECT_REQUEST        16

#define BITT_FAST_EX_ALLOWED_FAST          17

#define BITTORRENT_MESSAGE_EXTENDED        20

#define BITTORRENT_HEADER_LENGTH            4

/*

 * Azureus messages are specified by name so these are made up numbers

 * for internal identification only.

 *

 * Standard BT message types are a single byte, so these won't clash

 */

#define AZUREUS_MESSAGE_HANDSHAKE         256

#define AZUREUS_MESSAGE_KEEP_ALIVE        257

#define AZUREUS_MESSAGE_BT_HANDSHAKE      258

#define AZUREUS_MESSAGE_PEER_EXCHANGE     259

#define AZUREUS_MESSAGE_JPC_HELLO         260

#define AZUREUS_MESSAGE_JPC_REPLY         261

static const value_string bittorrent_messages[] = {

   { BITTORRENT_MESSAGE_CHOKE,          "Choke" },

   { BITTORRENT_MESSAGE_UNCHOKE,        "Unchoke" },

   { BITTORRENT_MESSAGE_INTERESTED,     "Interested" },

   { BITTORRENT_MESSAGE_NOT_INTERESTED, "Not Interested" },

   { BITTORRENT_MESSAGE_HAVE,           "Have" },

   { BITTORRENT_MESSAGE_BITFIELD,       "Bitfield" },

   { BITTORRENT_MESSAGE_REQUEST,        "Request" },

   { BITTORRENT_MESSAGE_PIECE,          "Piece" },

   { BITTORRENT_MESSAGE_CANCEL,         "Cancel" },

   { BITTORRENT_MESSAGE_PORT,           "Port" },

   { BITT_FAST_EX_SUGGEST_PIECE,        "Suggest Piece" },

   { BITT_FAST_EX_HAVE_ALL,             "Have All" },

   { BITT_FAST_EX_HAVE_NONE,            "Have None" },

   { BITT_FAST_EX_REJECT_REQUEST,       "Reject Request" },

   { BITT_FAST_EX_ALLOWED_FAST,         "Allowed Fast" },

   { BITTORRENT_MESSAGE_EXTENDED,       "Extended" },

   { AZUREUS_MESSAGE_HANDSHAKE,         "Azureus Handshake" },

   { AZUREUS_MESSAGE_KEEP_ALIVE,        "Keepalive" },

   { AZUREUS_MESSAGE_BT_HANDSHAKE,      "Azureus BitTorrent Handshake" },

   { AZUREUS_MESSAGE_PEER_EXCHANGE,     "Azureus Peer Exchange" },

   { AZUREUS_MESSAGE_JPC_HELLO,         "Azureus PeerCache Hello" },

   { AZUREUS_MESSAGE_JPC_REPLY,         "Azureus PeerCache Reply" },

   { 0, NULL }

};

static const value_string azureus_priorities[] = {

   { 0, "Low" },

   { 1, "Normal" },

   { 2, "High" },

   { 0, NULL }

};

struct amp_message {

   const char *name;

   uint32_t    value;

};

static const struct amp_message amp_messages[] = {

   { "BT_KEEP_ALIVE",    AZUREUS_MESSAGE_KEEP_ALIVE },

   { "BT_CHOKE",         BITTORRENT_MESSAGE_CHOKE },

   { "BT_UNCHOKE",       BITTORRENT_MESSAGE_UNCHOKE },

   { "BT_INTERESTED",    BITTORRENT_MESSAGE_INTERESTED },

   { "BT_UNINTERESTED",  BITTORRENT_MESSAGE_NOT_INTERESTED },

   { "BT_HAVE",          BITTORRENT_MESSAGE_HAVE },

   { "BT_BITFIELD",      BITTORRENT_MESSAGE_BITFIELD },

   { "BT_REQUEST",       BITTORRENT_MESSAGE_REQUEST },

   { "BT_PIECE",         BITTORRENT_MESSAGE_PIECE },

   { "BT_CANCEL",        BITTORRENT_MESSAGE_CANCEL },

   { "BT_PORT",          BITTORRENT_MESSAGE_PORT },

   { "BT_SUGGEST",       BITT_FAST_EX_SUGGEST_PIECE },

   { "BT_HAVE_ALL",      BITT_FAST_EX_HAVE_ALL },

   { "BT_HAVE_NONE",     BITT_FAST_EX_HAVE_NONE },

   { "BT_REJECT_REQUEST",BITT_FAST_EX_REJECT_REQUEST },

   { "BT_ALLOWED_FAST",  BITT_FAST_EX_ALLOWED_FAST },

   { "BT_EXTENDED",      BITTORRENT_MESSAGE_EXTENDED },

   { "AZ_HANDSHAKE",     AZUREUS_MESSAGE_HANDSHAKE },

   { "BT_HANDSHAKE",     AZUREUS_MESSAGE_BT_HANDSHAKE },

   { "AZ_PEER_EXCHANGE", AZUREUS_MESSAGE_PEER_EXCHANGE },

   { "JPC_HELLO",        AZUREUS_MESSAGE_JPC_HELLO },

   { "JPC_REPLY",        AZUREUS_MESSAGE_JPC_REPLY },

   { NULL, 0 }

};

static dissector_handle_t dissector_handle;

static dissector_handle_t bencode_handle;

static int proto_bittorrent;

/* static int hf_bittorrent_field_length; */

static int hf_bittorrent_prot_name_len;

static int hf_bittorrent_prot_name;

static int hf_bittorrent_reserved;

static int hf_bittorrent_sha1_hash;

static int hf_bittorrent_peer_id;

static int hf_bittorrent_msg;

static int hf_bittorrent_msg_len;

static int hf_bittorrent_msg_type;

static int hf_azureus_msg;

static int hf_azureus_msg_type_len;

static int hf_azureus_msg_type;

static int hf_azureus_msg_prio;

static int hf_bittorrent_bitfield_data;

static int hf_bittorrent_piece_index;

static int hf_bittorrent_piece_begin;

static int hf_bittorrent_piece_length;

static int hf_bittorrent_piece_data;

static int hf_azureus_jpc_addrlen;

static int hf_azureus_jpc_addr;

static int hf_azureus_jpc_port;

static int hf_azureus_jpc_session;

static int hf_bittorrent_port;

static int hf_bittorrent_extended_id;

static int hf_bittorrent_extended;

static int hf_bittorrent_continuous_data;

static int hf_bittorrent_version;

static int ett_bittorrent;

static int ett_bittorrent_msg;

static int ett_peer_id;

static bool bittorrent_desegment      = true;

static bool decode_client_information;

struct client_information {

   char        id[5];     /* string length must be <= 4 to allow space for NUL termination byte */

   char        ver_len;

   const char *name;      /* NULL means array entry terminates the array */

};

static const struct client_information peer_id[] = {

   {"-AG",  4, "Ares"},

   {"-A~",  4, "Ares"},

   {"-AR",  4, "Arctic"},

   {"-AT",  4, "Artemis"},

   {"-AV",  4, "Avicora"},

   {"-AX",  4, "BitPump"},

   {"-AZ",  4, "Azureus"},

   {"-BB",  4, "BitBuddy"},

   {"-BC",  4, "BitComet"},

   {"-BF",  4, "Bitflu"},

   {"-BG",  4, "BTG (uses Rasterbar libtorrent)"},

   {"-BOW", 3, "Bits on Wheels"},

   {"-BP",  4, "BitTorrent Pro (Azereus + spyware)"},

   {"-BR",  4, "BitRocket"},

   {"-BS",  4, "BTSlave"},

   {"-BW",  4, "BitWombat"},

   {"-BX",  4, "Bittorrent X"},

   {"-CD",  4, "Enhanced CTorrent"},

   {"-CT",  4, "CTorrent"},

   {"-DE",  4, "DelugeTorrent"},

   {"-DP",  4, "Propagate Data Client"},

   {"-EB",  4, "EBit"},

   {"-ES",  4, "electric sheep"},

   {"-FC",  4, "FileCroc"},

   {"-FG",  4, "FlashGet"},

   {"-FT",  4, "FoxTorrent"},

   {"-GS",  4, "GSTorrent"},

   {"-HK",  4, "Hekate"},

   {"-HL",  4, "Halite"},

   {"-HN",  4, "Hydranode"},

   {"-KG",  4, "KGet"},

   {"-KT",  4, "KTorrent"},

   {"-LC",  4, "LeechCraft"},

   {"-LH",  4, "LH-ABC"},

   {"-LP",  4, "Lphant"},

   {"-LT",  4, "libtorrent"},

   {"-lt",  4, "libTorrent"},

   {"-LW",  4, "LimeWire"},

   {"-MO",  4, "MonoTorrent"},

   {"-MP",  4, "MooPolice"},

   {"-MR",  4, "Miro"},

   {"-MT",  4, "MoonlightTorrent"},

   {"-NE",  4, "BT Next Evolution"},

   {"-NX",  4, "Net Transport"},

   {"-OS",  4, "OneSwarm"},

   {"-OT",  4, "OmegaTorrent"},

   {"-PD",  4, "Pando"},

   {"-qB",  4, "qBittorrent"},

   {"-QD",  4, "QQDownload"},

   {"-QT",  4, "Qt 4 Torrent example"},

   {"-RT",  4, "Retriever"},

   {"-S~",  4, "Shareaza alpha/beta"},

   {"-SB",  4, "Swiftbit"},

   {"-SD",  4, "Thunder (aka XunLei)"},

   {"-SS",  4, "SwarmScope"},

   {"-ST",  4, "SymTorrent"},

   {"-st",  4, "sharktorrent"},

   {"-SZ",  4, "Shareaza"},

   {"-TN",  4, "TorrentDotNET"},

   {"-TR",  4, "Transmission"},

   {"-TS",  4, "Torrentstorm"},

   {"-TT",  4, "TuoTu"},

   {"-UL",  4, "uLeecher!"},

   {"-UM",  4, "(my)Torrent for Mac"},

   {"-UT",  4, "(my)Torrent"},

   {"-VG",  4, "Vagaa"},

   {"-WT",  4, "BitLet"},

   {"-WY",  4, "FireTorrent"},

   {"-XL",  4, "Xunlei"},

   {"-XT",  4, "XanTorrent"},

   {"-XX",  4, "Xtorrent"},

   {"-ZT",  4, "ZipTorrent"},

   {"exbc", 2, "BitComet"},

   {"OP",   4, "Opera"},

   {"QVOD", 4, "Qvod"},

   {"XBT",  3, "XBT Client"},

   {"A",    3, "ABC"},

   {"O",    3, "Osprey Permaseed"},

   {"Q",    3, "BTQueue"},

   {"R",    3, "Tribler"},

   {"S",    3, "Shadow's client"},

   {"T",    3, "BitTornado"},

   {"U",    3, "UPnP NAT Bit Torrent"},

   {"",     0, NULL}

};

/* Tests a given length for a message type to see if it looks valid.

 * The exact length is known for many message types, which prevents us

 * from returning a false positive match based on a single byte when

 * we're in the middle of Continuation Data or an encrypted transfer.

 */

static bool

test_type_length(uint16_t type, uint32_t length)

{

   switch (type) {

   case BITTORRENT_MESSAGE_UNCHOKE:

   case BITTORRENT_MESSAGE_INTERESTED:

   case BITTORRENT_MESSAGE_NOT_INTERESTED:

   case BITT_FAST_EX_HAVE_ALL:

   case BITT_FAST_EX_HAVE_NONE:

      /* No payload */

      if (length != 1) {

         return false;

      }

      return true;

   case BITTORRENT_MESSAGE_PORT:

      if (length != 3) {

         return false;

      }

      return true;

   case BITTORRENT_MESSAGE_HAVE:

   case BITT_FAST_EX_SUGGEST_PIECE:

   case BITT_FAST_EX_ALLOWED_FAST:

      if (length != 5) {

         return false;

      }

      return true;

   case BITTORRENT_MESSAGE_REQUEST:

   case BITTORRENT_MESSAGE_CANCEL:

   case BITT_FAST_EX_REJECT_REQUEST:

      if (length != 13) {

         return false;

      }

      return true;

   /* Now to the messages that can have variable and longer lengths. */

   case BITTORRENT_MESSAGE_EXTENDED:

   case BITTORRENT_MESSAGE_PIECE:

      /* All known implementations use 0x4000 for the piece length by default

       * (only smaller for the last piece at EOF), and disconnect from clients

       * that use a larger value, which is mentioned in BEP-3. Including the

       * other parts of the message, that yields a length of 0x4009. There

       * might exist some non-standard traffic somewhere, I suppose.

       *

       * This is excessively long for any extension message.

       */

      if (length > 0x4009) {

         return false;

      }

      return true;

   case BITTORRENT_MESSAGE_CHOKE:

      /* Choke could be an Azureus message instead, which could be any

       * of the other messages, so it has to be as long as our longest

       * message. XXX: To reduce false positives (since 0 is a common

       * byte to see), a pref to disable Azureus support could be useful.

       * Alternatively, if we tracked conversations, we could disable

       * support for AMP if the extension bits in the handshake (if seen)

       * indicated that it's not supported.

       */

   case AZUREUS_MESSAGE_HANDSHAKE:

   case AZUREUS_MESSAGE_KEEP_ALIVE:

   case AZUREUS_MESSAGE_BT_HANDSHAKE:

   case AZUREUS_MESSAGE_PEER_EXCHANGE:

   case AZUREUS_MESSAGE_JPC_HELLO:

   case AZUREUS_MESSAGE_JPC_REPLY:

   case BITTORRENT_MESSAGE_BITFIELD:

      /* A bitfield length is N bits, where N is the number of pieces

       * in the torrent. The absolute boundary is 2^32 pieces (because

       * it has to fit in the piece message). In practice the piece

       * length varies to balance a number of factors. (Some clients

       * don't work with too many pieces; at one point 2^16 was a common

       * maximum.) The minimum common piece length is 2^18 bytes, and higher

       * powers of two are also frequently used.

       *

       * 0x20000 allows 0x100000 pieces, or over a million. That's more

       * than most clients support, and cuts down on false positives.

       */

      if (length > 0x20000) {

         return false;

      }

      return true;

   default:

      if (!try_val_to_str(type, bittorrent_messages)) {

         return false;

      }

   }

   return true;

}

static unsigned

get_bittorrent_pdu_length(packet_info *pinfo _U_, tvbuff_t *tvb,

                          int offset, void *data _U_)

{

   uint8_t type;

   uint32_t length;

   if (tvb_get_uint8(tvb, offset) == 19 &&

       tvb_memeql(tvb, offset + 1, (const uint8_t*)"BitTorrent protocol", 19) == 0) {

      /* Return the length of a Handshake message */

      return  1 + /* pstrlen */

             19 + /* pstr */

              8 + /* reserved */

             20 + /* SHA1 hash of the info key */

             20;  /* peer id */

   } else {

      /* Try to validate the length of the message indicated by the header. */

      length = tvb_get_ntohl(tvb, offset);

      if(length == 0) {

        /* keep-alive - no message ID */

        return BITTORRENT_HEADER_LENGTH;

      }

      /* Do some sanity checking of the message, if we have the ID byte */

      if(tvb_offset_exists(tvb, offset + BITTORRENT_HEADER_LENGTH)) {

         type = tvb_get_uint8(tvb, offset + BITTORRENT_HEADER_LENGTH);

         if (test_type_length(type, length)) {

            /* This seems to be a valid BitTorrent header with a known

               type identifier and valid length */

            return BITTORRENT_HEADER_LENGTH + length;

         } else {

            /* The type is not known, so this message cannot be decoded

               properly by this dissector.  We assume it's continuation

               data from the middle of a message, and just return the

               remaining length in the tvbuff so the rest of the tvbuff

               is displayed as continuation data. */

            return tvb_reported_length_remaining(tvb, offset);

         }

      } else {

         /* We don't have the type field, so we can't determine

            whether this is a valid message.  Return 0, which

            tcp_dissect_pdus (and utp_dissect_pdus) treats as

            "variable length, needs one more segment". */

         return 0;

      }

   }

}

static void

dissect_bittorrent_message(tvbuff_t *tvb, packet_info *pinfo, proto_tree *tree)

{

   int         offset  = 0;

   int         i;

   int         isamp   = 0;

   proto_tree *mtree;

   uint16_t    type    = 0;

   uint32_t    typelen = 0;

   uint8_t     prio    = 0;

   uint32_t    ext_id  = 0;

   uint32_t    length;

   const char *msgtype = NULL;

   proto_item *ti;

   uint32_t    piece_index, piece_begin, piece_length;

   uint32_t    stringlen;

   tvbuff_t   *subtvb;

   /* Guaranteed BITTORRENT_HEADER_LENGTH by tcp_dissect_pdus */

   length = tvb_get_ntohl(tvb, offset);

   /* Keepalive message */

   if (length == 0) {

      ti = proto_tree_add_item(tree, hf_bittorrent_msg, tvb, offset, length + BITTORRENT_HEADER_LENGTH, ENC_NA);

      mtree = proto_item_add_subtree(ti, ett_bittorrent_msg);

      proto_tree_add_item(mtree, hf_bittorrent_msg_len, tvb, offset, BITTORRENT_HEADER_LENGTH, ENC_BIG_ENDIAN);

      col_set_str(pinfo->cinfo, COL_INFO, "KeepAlive");

      return;

   }

   if (tvb_bytes_exist(tvb, offset + BITTORRENT_HEADER_LENGTH, 1)) {

      /* Check for data from the middle of a message. */

      type = tvb_get_uint8(tvb, offset + BITTORRENT_HEADER_LENGTH);

      if (type==BITTORRENT_MESSAGE_CHOKE && length>4) {

         /*

          * Choke messages have no payload, so this is likely an Azureus

          * Messaging Protocol packet

          */

         if (!tvb_bytes_exist(tvb, offset + BITTORRENT_HEADER_LENGTH, 4))

            return;

         typelen = tvb_get_ntohl(tvb, offset + BITTORRENT_HEADER_LENGTH);

         if (4+typelen+1<=length) {

            if (!tvb_bytes_exist(tvb, offset + BITTORRENT_HEADER_LENGTH + 4, typelen+1))

               return;

            for ( i=0 ; amp_messages[i].name ; i++ ) {

               if (strlen(amp_messages[i].name)==typelen &&

                   tvb_strneql(tvb, offset + BITTORRENT_HEADER_LENGTH + 4,

                              amp_messages[i].name, (int)strlen(amp_messages[i].name))==0) {

                  prio = tvb_get_uint8(tvb, offset + BITTORRENT_HEADER_LENGTH + 4 + typelen);

                  if (prio==0 || prio==1 || prio==2) {

                     type = amp_messages[i].value;

                     isamp = 1;

                  }

                  break;

               }

            }

         }

      }

      msgtype = try_val_to_str(type, bittorrent_messages);

#if 0

      if (msgtype == NULL && isamp) {

         msgtype = try_val_to_str(type, azureus_messages);

      }

#endif

      if (msgtype == NULL || !(test_type_length(type, length))) {

         /* In modern captures, this is likely Protocol Encryption/

          * Message Stream Encryption, particularly if we're actually

          * desegmenting and have the whole connection starting from

          * the SYN. We don't try to do that yet.

          */

         proto_tree_add_item(tree, hf_bittorrent_continuous_data, tvb, offset, -1, ENC_NA);

         col_set_str(pinfo->cinfo, COL_INFO, "Continuation data");

         return;

      }

   } else {

      /* not enough bytes of the header, stop here */

      return;

   }

   if (isamp) {

      ti = proto_tree_add_item(tree, hf_azureus_msg, tvb, offset, length + BITTORRENT_HEADER_LENGTH, ENC_NA);

   } else {

      ti = proto_tree_add_item(tree, hf_bittorrent_msg, tvb, offset, length + BITTORRENT_HEADER_LENGTH, ENC_NA);

   }

   mtree = proto_item_add_subtree(ti, ett_bittorrent_msg);

   proto_tree_add_item(mtree, hf_bittorrent_msg_len, tvb, offset, BITTORRENT_HEADER_LENGTH, ENC_BIG_ENDIAN);

   offset += BITTORRENT_HEADER_LENGTH;

   /* If the tvb_bytes_exist() call above returned false, this will

      throw an exception, so we won't use msgtype or type. */

   if (isamp) {

      proto_tree_add_item(mtree, hf_azureus_msg_type_len, tvb, offset, 4, ENC_BIG_ENDIAN);

      proto_tree_add_item(mtree, hf_azureus_msg_type, tvb, offset+4, typelen, ENC_ASCII);

      proto_item_append_text(ti, ": Len %u, %s", length, msgtype);

      proto_tree_add_item(mtree, hf_azureus_msg_prio, tvb, offset+4+typelen, 1, ENC_BIG_ENDIAN);

      offset += 4+typelen+1;

      length -= 4+typelen+1;

   } else {

      proto_tree_add_item(mtree, hf_bittorrent_msg_type, tvb, offset, 1, ENC_BIG_ENDIAN);

      proto_item_append_text(ti, ": Len:%u, %s", length, msgtype);

      offset += 1;

      length -= 1;

   }

   col_set_str(pinfo->cinfo, COL_INFO, msgtype);

   switch (type) {

   case BITTORRENT_MESSAGE_CHOKE:

   case BITTORRENT_MESSAGE_UNCHOKE:

   case BITTORRENT_MESSAGE_INTERESTED:

   case BITTORRENT_MESSAGE_NOT_INTERESTED:

   case BITT_FAST_EX_HAVE_ALL:

   case BITT_FAST_EX_HAVE_NONE:

      /* No payload */

      break;

   case BITTORRENT_MESSAGE_REQUEST:

   case BITTORRENT_MESSAGE_CANCEL:

   case BITT_FAST_EX_REJECT_REQUEST:

      proto_tree_add_item_ret_uint(mtree, hf_bittorrent_piece_index, tvb, offset, 4, ENC_BIG_ENDIAN, &piece_index); offset += 4;

      proto_tree_add_item_ret_uint(mtree, hf_bittorrent_piece_begin, tvb, offset, 4, ENC_BIG_ENDIAN, &piece_begin); offset += 4;

      proto_tree_add_item_ret_uint(mtree, hf_bittorrent_piece_length, tvb, offset, 4, ENC_BIG_ENDIAN, &piece_length);

      proto_item_append_text(ti, ", Piece (Idx:0x%x,Begin:0x%x,Len:0x%x)", piece_index, piece_begin, piece_length);

      col_append_fstr(pinfo->cinfo, COL_INFO, ", Piece (Idx:0x%x,Begin:0x%x,Len:0x%x)", piece_index, piece_begin, piece_length);

      break;

   case BITTORRENT_MESSAGE_PORT:

      /* port as payload */

      proto_tree_add_item(mtree, hf_bittorrent_port, tvb, offset, 2, ENC_BIG_ENDIAN);

      break;

   case BITTORRENT_MESSAGE_EXTENDED:

      /* extended message content */

      proto_tree_add_item_ret_uint(mtree, hf_bittorrent_extended_id, tvb, offset, 1, ENC_NA, &ext_id);

      offset += 1;

      length -= 1;

      if (ext_id == 0) {

         call_dissector(bencode_handle, tvb_new_subset_length(tvb, offset, length), pinfo, mtree);

      } else {

         proto_tree_add_item(mtree, hf_bittorrent_extended, tvb, offset, length, ENC_NA);

      }

      break;

   case BITTORRENT_MESSAGE_HAVE:

   case BITT_FAST_EX_SUGGEST_PIECE:

   case BITT_FAST_EX_ALLOWED_FAST:

      proto_tree_add_item_ret_uint(mtree, hf_bittorrent_piece_index, tvb, offset, 4, ENC_BIG_ENDIAN, &piece_index);

      proto_item_append_text(ti, ", Piece (Idx:0x%x)", piece_index);

      col_append_fstr(pinfo->cinfo, COL_INFO, ", Piece (Idx:0x%x)", piece_index);

      break;

   case BITTORRENT_MESSAGE_BITFIELD:

      proto_tree_add_item(mtree, hf_bittorrent_bitfield_data, tvb, offset, length, ENC_NA);

      proto_item_append_text(ti, ", Len:0x%x", length);

      col_append_fstr(pinfo->cinfo, COL_INFO, ", Len:0x%x", length);

      break;

   case BITTORRENT_MESSAGE_PIECE:

      piece_index = tvb_get_ntohl(tvb, offset);

      proto_tree_add_uint(mtree, hf_bittorrent_piece_index, tvb, offset, 4, piece_index);

      offset += 4;

      length -= 4;

      piece_begin = tvb_get_ntohl(tvb, offset);

      proto_tree_add_uint(mtree, hf_bittorrent_piece_begin, tvb, offset, 4, piece_begin);

      offset += 4;

      length -= 4;

      proto_tree_add_item(mtree, hf_bittorrent_piece_data, tvb, offset, length, ENC_NA);

      proto_item_append_text(ti, ", Idx:0x%x,Begin:0x%x,Len:0x%x", piece_index, piece_begin, length);

      col_append_fstr(pinfo->cinfo, COL_INFO, ", Idx:0x%x,Begin:0x%x,Len:0x%x", piece_index, piece_begin, length);

      break;

   case AZUREUS_MESSAGE_HANDSHAKE:

   case AZUREUS_MESSAGE_PEER_EXCHANGE:

      subtvb = tvb_new_subset_length(tvb, offset, length);

      call_dissector(bencode_handle, subtvb, pinfo, mtree);

      break;

   case AZUREUS_MESSAGE_JPC_HELLO:

      stringlen = tvb_get_ntohl(tvb, offset);

      proto_tree_add_item(mtree, hf_azureus_jpc_addrlen, tvb, offset, 4, ENC_BIG_ENDIAN);

      proto_tree_add_item(mtree, hf_azureus_jpc_addr, tvb, offset+4, stringlen, ENC_ASCII);

      proto_tree_add_item(mtree, hf_azureus_jpc_port, tvb, offset+4+stringlen, 4, ENC_BIG_ENDIAN);

      proto_tree_add_item(mtree, hf_azureus_jpc_session, tvb, offset+4+stringlen+4, 4, ENC_BIG_ENDIAN);

      break;

   case AZUREUS_MESSAGE_JPC_REPLY:

      proto_tree_add_item(mtree, hf_azureus_jpc_session, tvb, offset, 4, ENC_BIG_ENDIAN);

      break;

   default:

      break;

   }

}

static int

dissect_bittorrent_welcome (tvbuff_t *tvb, packet_info *pinfo, proto_tree *tree)

{

   int   offset = 0;

   int   i;

   char *version;

   col_set_str(pinfo->cinfo, COL_INFO, "Handshake");

   proto_tree_add_item(tree, hf_bittorrent_prot_name_len, tvb, offset, 1, ENC_BIG_ENDIAN); offset+=1;

   proto_tree_add_item(tree, hf_bittorrent_prot_name, tvb, offset, 19, ENC_ASCII); offset += 19;

   proto_tree_add_item(tree, hf_bittorrent_reserved, tvb, offset, 8, ENC_NA); offset += 8;

   proto_tree_add_item(tree, hf_bittorrent_sha1_hash, tvb, offset, 20, ENC_NA);

   offset += 20;

   proto_tree_add_item(tree, hf_bittorrent_peer_id, tvb, offset, 20, ENC_NA);

   if(decode_client_information) {

      for(i = 0; peer_id[i].name != NULL; ++i)

      {

         if(tvb_memeql(tvb, offset, (const uint8_t*)peer_id[i].id, (int)strlen(peer_id[i].id)) == 0) {

            version = (char*)tvb_get_string_enc(pinfo->pool, tvb, offset + (int)strlen(peer_id[i].id),

                                     peer_id[i].ver_len, ENC_ASCII);

            proto_tree_add_string_format(tree, hf_bittorrent_version, tvb, offset, 20, version, "Client is %s v%s",

                                peer_id[i].name, format_text(pinfo->pool, version, peer_id[i].ver_len));

            break;

         }

      }

   }

   offset += 20;

   return offset;

}

static

int dissect_bittorrent_tcp_pdu (tvbuff_t *tvb, packet_info *pinfo, proto_tree *tree, void* data _U_)

{

   proto_item *ti;

   col_set_str(pinfo->cinfo, COL_PROTOCOL, "BitTorrent");

   col_set_str(pinfo->cinfo, COL_INFO, "BitTorrent ");

   ti = proto_tree_add_item (tree, proto_bittorrent, tvb, 0, -1, ENC_NA);

   tree = proto_item_add_subtree(ti, ett_bittorrent);

   if (tvb_get_uint8(tvb, 0) == 19 &&

       tvb_memeql(tvb, 1, (const uint8_t*)"BitTorrent protocol", 19) == 0) {

      dissect_bittorrent_welcome(tvb, pinfo, tree);

   } else {

      dissect_bittorrent_message(tvb, pinfo, tree);

   }

    col_append_str(pinfo->cinfo, COL_INFO, "  ");

    col_set_fence(pinfo->cinfo, COL_INFO);

    return tvb_reported_length(tvb);

}

static

int dissect_bittorrent (tvbuff_t *tvb, packet_info *pinfo, proto_tree *tree, void* data)

{

   tcp_dissect_pdus(tvb, pinfo, tree, bittorrent_desegment, BITTORRENT_HEADER_LENGTH,

                    get_bittorrent_pdu_length, dissect_bittorrent_tcp_pdu, data);

   return tvb_reported_length(tvb);

}

static

int dissect_bittorrent_utp(tvbuff_t *tvb, packet_info *pinfo, proto_tree *tree, void* data)

{

   utp_dissect_pdus(tvb, pinfo, tree, bittorrent_desegment, BITTORRENT_HEADER_LENGTH,

                    get_bittorrent_pdu_length, dissect_bittorrent_tcp_pdu, data);

   return tvb_reported_length(tvb);

}

static

bool test_bittorrent_packet (tvbuff_t *tvb, packet_info *pinfo,

                                 proto_tree *tree, void *data)

{

   conversation_t *conversation;

   if (tvb_captured_length(tvb) >= 20 &&

       tvb_get_uint8(tvb, 0) == 19 &&

       tvb_memeql(tvb, 1, (const uint8_t*)"BitTorrent protocol", 19) == 0) {

      conversation = find_or_create_conversation(pinfo);

      conversation_set_dissector(conversation, dissector_handle);

      dissect_bittorrent(tvb, pinfo, tree, data);

      return true;

   }

   return false;

}

void

proto_register_bittorrent(void)

{

   static hf_register_info hf[] = {

#if 0

      { &hf_bittorrent_field_length,

        { "Field Length", "bittorrent.length", FT_UINT32, BASE_DEC, NULL, 0x0, NULL, HFILL }

      },

#endif

      { &hf_bittorrent_prot_name_len,

        { "Protocol Name Length", "bittorrent.protocol.name.length", FT_UINT8, BASE_DEC, NULL, 0x0, NULL, HFILL }

      },

      { &hf_bittorrent_prot_name,

        { "Protocol Name", "bittorrent.protocol.name", FT_STRING, BASE_NONE, NULL, 0x0, NULL, HFILL }

      },

      { &hf_bittorrent_reserved,

        { "Reserved Extension Bytes", "bittorrent.reserved", FT_BYTES, BASE_NONE, NULL, 0x0, NULL, HFILL }

      },

      { &hf_bittorrent_sha1_hash,

        { "SHA1 Hash of info dictionary", "bittorrent.info_hash", FT_BYTES, BASE_NONE, NULL, 0x0, NULL, HFILL }

      },

      { &hf_bittorrent_peer_id,

        { "Peer ID", "bittorrent.peer_id", FT_BYTES, BASE_NONE, NULL, 0x0, NULL, HFILL }

      },

      { &hf_bittorrent_msg,

        { "Message", "bittorrent.msg", FT_NONE, BASE_NONE, NULL, 0x0, NULL, HFILL }

      },

      { &hf_bittorrent_msg_len,

        { "Message Length", "bittorrent.msg.length", FT_UINT32, BASE_DEC, NULL, 0x0, NULL, HFILL }

      },

      { &hf_bittorrent_msg_type,

        { "Message Type", "bittorrent.msg.type", FT_UINT16, BASE_DEC, VALS(bittorrent_messages), 0x0, NULL, HFILL }

      },

      { &hf_azureus_msg,

        { "Azureus Message", "bittorrent.azureus_msg", FT_NONE, BASE_NONE, NULL, 0x0, NULL, HFILL }

      },

      { &hf_azureus_msg_type_len,

        { "Message Type Length", "bittorrent.msg.typelen", FT_UINT32, BASE_DEC, NULL, 0x0, NULL, HFILL }

      },

      { &hf_azureus_msg_type,

        { "Message Type", "bittorrent.msg.aztype", FT_STRING, BASE_NONE, NULL, 0x0, NULL, HFILL }

      },

      { &hf_azureus_msg_prio,

        { "Message Priority", "bittorrent.msg.prio", FT_UINT8, BASE_DEC, VALS(azureus_priorities), 0x0, NULL, HFILL }

      },

      { &hf_bittorrent_bitfield_data,

        { "Bitfield data", "bittorrent.msg.bitfield", FT_BYTES, BASE_NONE, NULL, 0x0, NULL, HFILL }

      },

      { &hf_bittorrent_piece_index,

        { "Piece index", "bittorrent.piece.index", FT_UINT32, BASE_HEX, NULL, 0x0, NULL, HFILL }

      },

      { &hf_bittorrent_piece_begin,

        { "Begin offset of piece", "bittorrent.piece.begin", FT_UINT32, BASE_HEX, NULL, 0x0, NULL, HFILL }

      },

      { &hf_bittorrent_piece_data,

        { "Data in a piece", "bittorrent.piece.data", FT_BYTES, BASE_NONE, NULL, 0x0, NULL, HFILL }

      },

      { &hf_bittorrent_piece_length,

        { "Piece Length", "bittorrent.piece.length", FT_UINT32, BASE_HEX, NULL, 0x0, NULL, HFILL }

      },

      { &hf_azureus_jpc_addrlen,

        { "Cache Address Length", "bittorrent.jpc.addr.length", FT_UINT32, BASE_DEC, NULL, 0x0, NULL, HFILL }

      },

      { &hf_azureus_jpc_addr,

        { "Cache Address", "bittorrent.jpc.addr", FT_STRING, BASE_NONE, NULL, 0x0, NULL, HFILL }

      },

      { &hf_azureus_jpc_port,

        { "Port", "bittorrent.jpc.port", FT_UINT32, BASE_DEC, NULL, 0x0, NULL, HFILL }

      },

      { &hf_azureus_jpc_session,

        { "Session ID", "bittorrent.jpc.session", FT_UINT32, BASE_HEX, NULL, 0x0, NULL, HFILL }

      },

      { &hf_bittorrent_port,

        { "Port", "bittorrent.port", FT_UINT16, BASE_DEC, NULL, 0x0, NULL, HFILL }

      },

      { &hf_bittorrent_extended_id,

        { "Extended Message ID", "bittorrent.extended.id", FT_UINT8, BASE_DEC, NULL, 0x0, NULL, HFILL }

      },

      { &hf_bittorrent_extended,

        { "Extended Message", "bittorrent.extended", FT_BYTES, BASE_NONE, NULL, 0x0, NULL, HFILL }

      },

      { &hf_bittorrent_continuous_data,

        { "Extended Message", "bittorrent.continuous_data", FT_BYTES, BASE_NONE, NULL, 0x0, NULL, HFILL }

      },

      { &hf_bittorrent_version,

        { "Client version", "bittorrent.version", FT_STRING, BASE_NONE, NULL, 0x0, NULL, HFILL }

      },

   };

   static int *ett[] = {

      &ett_bittorrent,

      &ett_bittorrent_msg,

      &ett_peer_id,

   };

   module_t *bittorrent_module;

   proto_bittorrent = proto_register_protocol("BitTorrent", "BitTorrent", "bittorrent");

   proto_register_field_array(proto_bittorrent, hf, array_length(hf));

   proto_register_subtree_array(ett, array_length(ett));

   dissector_handle = register_dissector("bittorrent.tcp", dissect_bittorrent, proto_bittorrent);

   register_dissector("bittorrent.utp", dissect_bittorrent_utp, proto_bittorrent);

   bittorrent_module = prefs_register_protocol(proto_bittorrent, NULL);

   prefs_register_bool_preference(bittorrent_module, "desegment",

                                  "Reassemble BitTorrent messages spanning multiple TCP segments",

                                  "Whether the BitTorrent dissector should reassemble messages spanning multiple TCP segments."

                                  " To use this option, you must also enable \"Allow subdissectors to reassemble TCP streams\" in the TCP protocol settings.",

                                  &bittorrent_desegment);

   prefs_register_bool_preference(bittorrent_module, "decode_client",

                                  "Decode the peer_id of the handshake messages",

                                  "Enabling this will tell which BitTorrent client that produced the handshake message",

                                  &decode_client_information);

}

void

proto_reg_handoff_bittorrent(void)

{

   bencode_handle = find_dissector_add_dependency("bencode", proto_bittorrent);

   dissector_add_uint_range_with_preference("tcp.port", DEFAULT_TCP_PORT_RANGE, dissector_handle);

   heur_dissector_add("tcp", test_bittorrent_packet, "BitTorrent over TCP", "bittorrent_tcp", proto_bittorrent, HEURISTIC_ENABLE);

}

/*

 * Editor modelines

 *

 * Local Variables:

 * c-basic-offset: 3

 * tab-width: 8

 * indent-tabs-mode: nil

 * End:

 *

 * ex: set shiftwidth=3 tabstop=8 expandtab:

 * :indentSize=3:tabSize=8:noTabs=true:

 */