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packet-bittorrent.c

/* packet-bittorrent.c
 * Routines for bittorrent packet dissection
 * Copyright (C) 2004 Jelmer Vernooij <jelmer@samba.org>
 *
 * $Id: packet-bittorrent.c 18196 2006-05-21 04:49:01Z sahlberg $
 *
 * Wireshark - Network traffic analyzer
 * By Gerald Combs <gerald@wireshark.org>
 * Copyright 1998 Gerald Combs
 *
 * Copied from packet-pop.c
 *
 * 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., 59 Temple Place - Suite 330, Boston, MA  02111-1307, USA.
 */

#ifdef HAVE_CONFIG_H
# include "config.h"
#endif

#include <stdio.h>

#include <string.h>
#include <glib.h>
#include <epan/prefs.h>
#include <epan/conversation.h>
#include <epan/packet.h>
#include <epan/strutil.h>
#include <epan/emem.h>

#include "packet-tcp.h"

/*
 * See
 *
 * http://bittorrent.com/protocol.html
 * http://wiki.theory.org/BitTorrentSpecification
 * http://bitconjurer.org/BitTorrent/protocol.html
 */

#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_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" },
   { AZUREUS_MESSAGE_KEEP_ALIVE, "Keepalive" },
   { AZUREUS_MESSAGE_HANDSHAKE, "Azureus Handshake" },
   { 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 {
  char *name;
  guint32 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 },
  { "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 int proto_bittorrent = -1;

static gint hf_bittorrent_field_length  = -1;
static gint hf_bittorrent_prot_name_len = -1;
static gint hf_bittorrent_prot_name     = -1;
static gint hf_bittorrent_reserved      = -1;
static gint hf_bittorrent_sha1_hash     = -1;
static gint hf_bittorrent_peer_id       = -1;
static gint hf_bittorrent_msg           = -1;
static gint hf_bittorrent_msg_len       = -1;
static gint hf_bittorrent_msg_type      = -1;
static gint hf_azureus_msg              = -1;
static gint hf_azureus_msg_type_len     = -1;
static gint hf_azureus_msg_type         = -1;
static gint hf_azureus_msg_prio         = -1;
static gint hf_bittorrent_bitfield_data = -1;
static gint hf_bittorrent_piece_index   = -1;
static gint hf_bittorrent_piece_begin   = -1;
static gint hf_bittorrent_piece_length  = -1;
static gint hf_bittorrent_piece_data    = -1;
static gint hf_bittorrent_bstr_length   = -1;
static gint hf_bittorrent_bstr          = -1;
static gint hf_bittorrent_bint          = -1;
static gint hf_bittorrent_bdict         = -1;
static gint hf_bittorrent_bdict_entry   = -1;
static gint hf_bittorrent_blist         = -1;
static gint hf_azureus_jpc_addrlen      = -1;
static gint hf_azureus_jpc_addr         = -1;
static gint hf_azureus_jpc_port         = -1;
static gint hf_azureus_jpc_session      = -1;

static gint ett_bittorrent = -1;
static gint ett_bittorrent_msg = -1;
static gint ett_peer_id = -1;
static gint ett_bittorrent_bdict = -1;
static gint ett_bittorrent_bdict_entry = -1;
static gint ett_bittorrent_blist = -1;

static gboolean bittorrent_desegment = TRUE;
static gboolean decode_client_information = FALSE;

struct client_information {
   char id[4];
   char *name;
};

static struct client_information peer_id[] = {
   {"-AZ", "Azureus"},
   {"-BB", "BitBuddy"},
   {"-CT", "CTorrent"},
   {"-MT", "MoonlightTorrent"},
   {"-LT", "libtorrent"},
   {"-BX", "Bittorrent X"},
   {"-TS", "Torrentstorm"},
   {"-TN", "TorrnetDotNET"},
   {"-SS", "SwarmScope"},
   {"-XT", "XanTorrent"},
   {"-BS", "BTSlave"},
   {"-ZT", "ZipTorrent"},
   {"S",   "Shadow's client"},
   {"U",   "UPnP NAT Bit Torrent"},
   {"T",   "BitTornado"},
   {"A",   "ABC"},
   {"",    NULL}
};

static guint get_bittorrent_pdu_length(tvbuff_t *tvb, int offset)
{
   guint8 type;
   guint32 length;

   if (tvb_get_guint8(tvb, offset) == 19 &&
      tvb_memeql(tvb, offset + 1, "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_guint8(tvb, offset + BITTORRENT_HEADER_LENGTH);
         if(type <= BITTORRENT_MESSAGE_CANCEL && length<0x1000000) {
            /* This seems to be a valid BitTorrent header with a known
               type identifier */
            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_length_remaining(tvb, offset);
         }
      } else {
         /* We don't have the type field, so we can't determine
            whether this is a valid message.  For now, 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_length_remaining(tvb, offset);
      }
   }
}

static int dissect_bencoding_str(tvbuff_t *tvb, packet_info *pinfo _U_,
                         int offset, int length, proto_tree *tree, proto_item *ti, int treeadd)
{
  guint8 ch;
  int stringlen = 0, nextstringlen;
  int used;
  int izero = 0;

  if (length<2) {
    if (tree) {
      proto_tree_add_text(tree, tvb, offset, length, "Decode Aborted: Invalid String");
    }
    return -1;
  }

  used = 0;

  while (length>=1) {
    ch = tvb_get_guint8(tvb, offset+used);
    length--;
    used++;

    if (ch==':' && used>1) {
      if (stringlen>length || stringlen<0) {
      if (tree) {
        proto_tree_add_text(tree, tvb, offset, length, "Decode Aborted: Invalid String Length");
      }
      return -1;
      }
      if (tree) {
      proto_tree_add_uint(tree, hf_bittorrent_bstr_length, tvb, offset, used, stringlen);
      proto_tree_add_item(tree, hf_bittorrent_bstr, tvb, offset+used, stringlen, FALSE);

      if (treeadd==1) {
        proto_item_append_text(ti, " Key: %s", format_text(ep_tvb_memdup(tvb, offset+used, stringlen), stringlen));
      }
      if (treeadd==2) {
        proto_item_append_text(ti, "  Value: %s", format_text(ep_tvb_memdup(tvb, offset+used, stringlen), stringlen));
      }       
      }
      return used+stringlen;
    }

    if (!izero && ch>='0' && ch<='9') {
      if (ch=='0' && used==1) {
      izero = 1;
      }

      nextstringlen = (stringlen * 10) + (ch - '0');
      if (nextstringlen>=stringlen) {
      stringlen = nextstringlen;
      continue;
      }
    }

    if (tree) {
      proto_tree_add_text(tree, tvb, offset, length, "Decode Aborted: Invalid String");
    }
    return -1;
  }

  if (tree) {
    proto_tree_add_text(tree, tvb, offset, length, "Truncated Data");
  }
  return -1;
}

static int dissect_bencoding_int(tvbuff_t *tvb, packet_info *pinfo _U_,
                         int offset, int length, proto_tree *tree, proto_item *ti, int treeadd)
{
  gint32 ival=0;
  int neg = 0;
  int izero = 0;
  int used;
  guint8 ch;

  if (length<3) {
    if (tree) {
      proto_tree_add_text(tree, tvb, offset, length, "Decode Aborted: Invalid Integer");
    }
    return -1;
  }

  length--;
  used = 1;

  while (length>=1) {
    ch = tvb_get_guint8(tvb, offset+used);
    length--;
    used++;

    switch (ch) {
    case 'e':
      if (tree) {
      if (neg) ival = -ival;
      proto_tree_add_int(tree, hf_bittorrent_bint, tvb, offset, used, ival);
      if (treeadd==2) {
        proto_item_append_text(ti, "  Value: %d", ival);
      }       
      }
      return used;

    case '-':
      if (used==2) {
      neg = 1;
      break;
      }
      /* Fall through */

    default:
      if (!(ch=='0' && used==3 && neg)) { /* -0 is invalid */
      if (ch=='0' && used==2) { /* as is 0[0-9]+ */
        izero = 1;
        break;
      }
      if (!izero && ch>='0' && ch<='9') {
        ival = (ival * 10) + (ch - '0');
        break;
      }
      }

      if (tree) {
      proto_tree_add_text(tree, tvb, offset, length, "Decode Aborted: Invalid Integer");
      }
      return -1;
    }
  }

  if (tree) {
    proto_tree_add_text(tree, tvb, offset, length, "Truncated Data");
  }
  return -1;
}

static int dissect_bencoding_rec(tvbuff_t *tvb, packet_info *pinfo _U_,
                         int offset, int length, proto_tree *tree, int level, proto_item *treei, int treeadd)
{
  guint8 op;
  int oplen = 0, op1len, op2len;
  int used;

  proto_item *ti = NULL, *td = NULL;
  proto_tree *itree = NULL, *dtree = NULL;

  if (level>10) {
    proto_tree_add_text(tree, tvb, offset, -1, "Decode Aborted: Nested Too Deep");
    return -1;
  }
  if (length<1) {
    proto_tree_add_text(tree, tvb, offset, -1, "Truncated Data");
    return length;
  }

  op = tvb_get_guint8(tvb, offset);
  if (tree) {
    oplen = dissect_bencoding_rec(tvb, pinfo, offset, length, NULL, level, NULL, 0);
    if (oplen<0) oplen = length;
  }

  switch (op) {
  case 'd':
    if (tree) {
      td = proto_tree_add_item(tree, hf_bittorrent_bdict, tvb, offset, oplen, FALSE);
      dtree = proto_item_add_subtree(td, ett_bittorrent_bdict);
    }

    used = 1;
    length--;

    while (length>=1) {
      op = tvb_get_guint8(tvb, offset+used);

      if (op=='e') {
      return used+1;
      }

      op1len = dissect_bencoding_str(tvb, pinfo, offset+used, length, NULL, NULL, 0);
      if (op1len<0) {
      if (dtree) {
        proto_tree_add_text(dtree, tvb, offset+used, -1, "Decode Aborted: Invalid Dictionary Key");
      }
      return op1len;
      }

      op2len = -1;
      if (length-op1len>2)
      op2len = dissect_bencoding_rec(tvb, pinfo, offset+used+op1len, length-op1len, NULL, level+1, NULL, 0);
      if (op2len<0) {
      if (dtree) {
        proto_tree_add_text(dtree, tvb, offset+used+op1len, -1, "Decode Aborted: Invalid Dictionary Value");
      }
      return op2len;
      }
      
      if (dtree) {
      ti = proto_tree_add_item(dtree, hf_bittorrent_bdict_entry, tvb, offset+used, op1len+op2len, FALSE);
      itree = proto_item_add_subtree(ti, ett_bittorrent_bdict_entry);

      dissect_bencoding_str(tvb, pinfo, offset+used, length, itree, ti, 1);
      dissect_bencoding_rec(tvb, pinfo, offset+used+op1len, length-op1len, itree, level+1, ti, 2);
      }
      
      used += op1len+op2len;
      length -= op1len+op2len;
    }
    if (dtree) {
      proto_tree_add_text(dtree, tvb, offset+used, -1, "Truncated Data");
    }
    return -1;

  case 'l':
    if (tree) {
      ti = proto_tree_add_item(tree, hf_bittorrent_blist, tvb, offset, oplen, FALSE);
      itree = proto_item_add_subtree(ti, ett_bittorrent_blist);
    }

    used = 1;
    length--;

    while (length>=1) {
      op = tvb_get_guint8(tvb, offset+used);

      if (op=='e') {
      return used+1;
      }
     
      oplen = dissect_bencoding_rec(tvb, pinfo, offset+used, length, itree, level+1, ti, 0);
      if (oplen<1) return oplen;

      used += oplen;
      length -= oplen;
    }
    if (itree) {
      proto_tree_add_text(itree, tvb, offset+used, -1, "Truncated Data");
    }
    return -1;

  case 'i':
    return dissect_bencoding_int(tvb, pinfo, offset, length, tree, treei, treeadd);

  default:
    if (op>='1' && op<='9') {
      return dissect_bencoding_str(tvb, pinfo, offset, length, tree, treei, treeadd);
    }

    if (tree) {
      proto_tree_add_text(tree, tvb, offset, -1, "Decode Aborted: Invalid Bencoding");
    }
    return -1;
  }

  if (tree) {
    proto_tree_add_text(tree, tvb, offset, -1, "Decode Aborted: Internal Error");
  }
  return -1;
}

static void dissect_bencoding(tvbuff_t *tvb, packet_info *pinfo _U_,
                       int offset, int length, proto_tree *tree)
{
  dissect_bencoding_rec(tvb, pinfo, offset, length, tree, 0, NULL, 0);
}
    
static void dissect_bittorrent_message (tvbuff_t *tvb, packet_info *pinfo, proto_tree *tree)
{
   int offset = 0;
   int i;
   int doffset = BITTORRENT_HEADER_LENGTH;
   int isamp = 0;
   proto_tree *mtree;
   guint16 type = 0;
   guint32 typelen = 0;
   guint8 prio = 0;
   guint32 length;
   const char *msgtype = NULL;
   proto_item *ti;
   guint32 piece_index, piece_begin, piece_length;
   guint32 stringlen;

   if (tvb_bytes_exist(tvb, offset + BITTORRENT_HEADER_LENGTH, 1)) {
      /* Check for data from the middle of a message. */
      length = tvb_get_ntohl(tvb, offset);
      type = tvb_get_guint8(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_memeql(tvb, offset + BITTORRENT_HEADER_LENGTH + 4,
                     amp_messages[i].name, strlen(amp_messages[i].name))==0) {

            prio = tvb_get_guint8(tvb, offset + BITTORRENT_HEADER_LENGTH + 4 + typelen);
            if (prio==0 || prio==1 || prio==2) {
            type = amp_messages[i].value;
            doffset = BITTORRENT_HEADER_LENGTH + 4 + typelen + 1;
            isamp = 1;
            }
            break;
          }
        }
      }
      }

      msgtype = match_strval(type, bittorrent_messages);
      /*      if (msgtype == NULL && isamp) {
      msgtype = match_strval(type, azureus_messages);
      } */
      if (msgtype == NULL) {
         proto_tree_add_text(tree, tvb, offset, -1, "Continuation data"); 
         if (check_col(pinfo->cinfo, COL_INFO)) {
            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, FALSE);
   } else {
     ti = proto_tree_add_item(tree, hf_bittorrent_msg, tvb, offset, length + BITTORRENT_HEADER_LENGTH, FALSE);
   }
   mtree = proto_item_add_subtree(ti, ett_bittorrent_msg);

   /* Keepalive message */
   if (length == 0) {
      proto_tree_add_item(mtree, hf_bittorrent_msg_len, tvb, offset, BITTORRENT_HEADER_LENGTH, FALSE);
      if (check_col(pinfo->cinfo, COL_INFO)) {
         col_set_str(pinfo->cinfo, COL_INFO, "KeepAlive");
      }
      return;
   }

   proto_tree_add_item(mtree, hf_bittorrent_msg_len, tvb, offset, BITTORRENT_HEADER_LENGTH, FALSE);
   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, FALSE);
     proto_tree_add_item(mtree, hf_azureus_msg_type, tvb, offset+4, typelen, FALSE);
     proto_item_append_text(ti, ": Len %u, %s", length, msgtype);
     proto_tree_add_item(mtree, hf_azureus_msg_prio, tvb, offset+4+typelen, 1, FALSE);
     offset += 4+typelen+1;
     length -= 4+typelen+1;
   } else {
     proto_tree_add_item(mtree, hf_bittorrent_msg_type, tvb, offset, 1, FALSE);
     proto_item_append_text(ti, ": Len:%u, %s", length, msgtype);
     offset += 1;
     length -= 1;
   }
   if (check_col(pinfo->cinfo, COL_INFO)) {
      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:
      /* No payload */
      break;

   case BITTORRENT_MESSAGE_REQUEST:
   case BITTORRENT_MESSAGE_CANCEL:
        piece_index = tvb_get_ntohl(tvb, offset);
      proto_tree_add_uint(mtree, hf_bittorrent_piece_index, tvb, offset, 4, piece_index); offset += 4;
        piece_begin = tvb_get_ntohl(tvb, offset);
      proto_tree_add_uint(mtree, hf_bittorrent_piece_begin, tvb, offset, 4, piece_begin); offset += 4;
        piece_length = tvb_get_ntohl(tvb, offset);
      proto_tree_add_uint(mtree, hf_bittorrent_piece_length, tvb, offset, 4, piece_length);
      proto_item_append_text(ti, ", Piece (Idx:0x%x,Begin:0x%x,Len:0x%x)", piece_index, piece_begin, piece_length);
      if (check_col(pinfo->cinfo, COL_INFO)) {
         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_HAVE:
        piece_index = tvb_get_ntohl(tvb, offset);
      proto_tree_add_item(mtree, hf_bittorrent_piece_index, tvb, offset, 4, FALSE);
      proto_item_append_text(ti, ", Piece (Idx:0x%x)", piece_index);
      if (check_col(pinfo->cinfo, COL_INFO)) {
         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, FALSE); 
      proto_item_append_text(ti, ", Len:0x%x", length);
      if (check_col(pinfo->cinfo, COL_INFO)) {
         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_item(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, FALSE);
      proto_item_append_text(ti, ", Idx:0x%x,Begin:0x%x,Len:0x%x", piece_index, piece_begin, length);
      if (check_col(pinfo->cinfo, COL_INFO)) {
         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:
     dissect_bencoding(tvb, pinfo, offset, length, 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, FALSE);
     proto_tree_add_item(mtree, hf_azureus_jpc_addr, tvb, offset+4, stringlen, FALSE);
     proto_tree_add_item(mtree, hf_azureus_jpc_port, tvb, offset+4+stringlen, 4, FALSE);
     proto_tree_add_item(mtree, hf_azureus_jpc_session, tvb, offset+4+stringlen+4, 4, FALSE);
     break;

   case AZUREUS_MESSAGE_JPC_REPLY:
     proto_tree_add_item(mtree, hf_azureus_jpc_session, tvb, offset, 4, FALSE);
     break;

   default:
      break;
   }
}

static void dissect_bittorrent_welcome (tvbuff_t *tvb, packet_info *pinfo _U_, proto_tree *tree)
{
   int offset = 0;
   int i;
   char *version;
   
   if (check_col(pinfo->cinfo, COL_INFO)) {
      col_set_str(pinfo->cinfo, COL_INFO, "Handshake");
   }
   
   proto_tree_add_item(tree, hf_bittorrent_prot_name_len, tvb, offset, 1, FALSE); offset+=1;
   proto_tree_add_item(tree, hf_bittorrent_prot_name, tvb, offset, 19, FALSE); offset += 19;
   proto_tree_add_item(tree, hf_bittorrent_reserved, tvb, offset, 8, FALSE); offset += 8;
   
   proto_tree_add_item(tree, hf_bittorrent_sha1_hash, tvb, offset, 20, FALSE);
   offset += 20;

   proto_tree_add_item(tree, hf_bittorrent_peer_id, tvb, offset, 20, FALSE);
   if(decode_client_information) {
      for(i = 0; peer_id[i].id[0] != '\0'; ++i)
      {
         if(tvb_memeql(tvb, offset, peer_id[i].id, strlen(peer_id[i].id)) == 0) {
            /* The version number is 4 numeric characters for the
               client ids beginning with '-' and 3 characters for the
               rest. */
            version = tvb_get_string(tvb, offset + strlen(peer_id[i].id),
               (peer_id[i].id[0] == '-') ? 4 : 3);
            proto_tree_add_text(tree, tvb, offset, 20, "Client is %s v%s",
               peer_id[i].name,
               format_text(version, (peer_id[i].id[0] == '-') ? 4 : 3));
            g_free(version);
            break;
         }
      }
   }
   offset += 20;
}

static void dissect_bittorrent_tcp_pdu (tvbuff_t *tvb, packet_info *pinfo, proto_tree *tree)
{
   proto_item *ti;
   
   if (check_col(pinfo->cinfo, COL_PROTOCOL)) {
      col_set_str(pinfo->cinfo, COL_PROTOCOL, "BitTorrent");
   }
   
   if (check_col(pinfo->cinfo, COL_INFO)) {
      col_set_str(pinfo->cinfo, COL_INFO, "BitTorrent ");
   }
   
   ti = proto_tree_add_item (tree, proto_bittorrent, tvb, 0, -1, FALSE);   
   tree = proto_item_add_subtree(ti, ett_bittorrent);
   
   if (tvb_get_guint8(tvb, 0) == 19 &&
      tvb_memeql(tvb, 1, "BitTorrent protocol", 19) == 0) {
      dissect_bittorrent_welcome(tvb, pinfo, tree);
   } else {
      dissect_bittorrent_message(tvb, pinfo, tree);
   }

   if (check_col(pinfo->cinfo, COL_INFO)) {
      col_append_str(pinfo->cinfo, COL_INFO, "  ");
      col_set_fence(pinfo->cinfo, COL_INFO);
   }
}

static void dissect_bittorrent (tvbuff_t *tvb, packet_info *pinfo, proto_tree *tree)
{
   tcp_dissect_pdus(tvb, pinfo, tree, bittorrent_desegment, BITTORRENT_HEADER_LENGTH,
                    get_bittorrent_pdu_length, dissect_bittorrent_tcp_pdu);
}

static gboolean test_bittorrent_packet (tvbuff_t *tvb, packet_info *pinfo,
                                        proto_tree *tree)
{
   conversation_t *conversation;

   if (tvb_bytes_exist(tvb, 0, 20) &&
       tvb_get_guint8(tvb, 0) == 19 &&
       tvb_memeql(tvb, 1, "BitTorrent protocol", 19) == 0) {
      conversation = conversation_new (pinfo->fd->num, &pinfo->src, &pinfo->dst, pinfo->ptype, pinfo->srcport, pinfo->destport, 0);

      conversation_set_dissector(conversation, dissector_handle);

      dissect_bittorrent(tvb, pinfo, tree);

      return TRUE;
   }

   return FALSE;
}

void
proto_register_bittorrent(void)
{
   static hf_register_info hf[] = {
      { &hf_bittorrent_field_length, 
      { "Field Length", "bittorrent.length", FT_UINT32, BASE_DEC, NULL, 0x0, "", HFILL }
      },
      { &hf_bittorrent_prot_name_len,
      { "Protocol Name Length", "bittorrent.protocol.name.length", FT_UINT8, BASE_DEC, NULL, 0x0, "", HFILL }
      },
      { &hf_bittorrent_prot_name,
      { "Protocol Name", "bittorrent.protocol.name", FT_STRING, BASE_DEC, NULL, 0x0, "", HFILL }
      },
      { &hf_bittorrent_reserved,
      { "Reserved Extension Bytes", "bittorrent.reserved", FT_BYTES, BASE_DEC, NULL, 0x0, "", HFILL }
      },
      { &hf_bittorrent_sha1_hash,
      { "SHA1 Hash of info dictionary", "bittorrent.info_hash", FT_BYTES, BASE_DEC, NULL, 0x0, "", HFILL }
      },
      { &hf_bittorrent_peer_id,
      { "Peer ID", "bittorrent.peer_id", FT_BYTES, BASE_DEC, NULL, 0x0, "", HFILL }
      },
      { &hf_bittorrent_msg, 
      { "Message", "bittorrent.msg", FT_NONE, BASE_NONE, NULL, 0x0, "", HFILL }
      },
      { &hf_bittorrent_msg_len,
      { "Message Length", "bittorrent.msg.length", FT_UINT32, BASE_DEC, NULL, 0x0, "", HFILL }
      }, 
      { &hf_bittorrent_msg_type,
      { "Message Type", "bittorrent.msg.type", FT_UINT8, BASE_DEC, VALS(bittorrent_messages), 0x0, "", HFILL }
      },
      { &hf_azureus_msg,
      { "Azureus Message", "bittorrent.azureus_msg", FT_NONE, BASE_NONE, NULL, 0x0, "", HFILL }
      },
      { &hf_azureus_msg_type_len,
      { "Message Type Length", "bittorrent.msg.typelen", FT_UINT32, BASE_DEC, NULL, 0x0, "", HFILL }
      },
      { &hf_azureus_msg_type,
      { "Message Type", "bittorrent.msg.aztype", FT_STRING, BASE_DEC, NULL, 0x0, "", HFILL }
      },
      { &hf_azureus_msg_prio,
      { "Message Priority", "bittorrent.msg.prio", FT_UINT8, BASE_DEC, VALS(azureus_priorities), 0x0, "", HFILL }
      },
      { &hf_bittorrent_bitfield_data,
     { "Bitfield data", "bittorrent.msg.bitfield", FT_BYTES, BASE_HEX, NULL, 0x0, "", HFILL }
      },
      { &hf_bittorrent_piece_index,
      { "Piece index", "bittorrent.piece.index", FT_UINT32, BASE_HEX, NULL, 0x0, "", HFILL }
      },
      { &hf_bittorrent_piece_begin,
      { "Begin offset of piece", "bittorrent.piece.begin", FT_UINT32, BASE_HEX, NULL, 0x0, "", HFILL }
      },
      { &hf_bittorrent_piece_data, 
      { "Data in a piece", "bittorrent.piece.data", FT_BYTES, BASE_HEX, NULL, 0x0, "", HFILL }
      },
      { &hf_bittorrent_piece_length,
         { "Piece Length", "bittorrent.piece.length", FT_UINT32, BASE_HEX, NULL, 0x0, "", HFILL }
      },
      { &hf_bittorrent_bstr_length,
      { "String Length", "bittorrent.bstr.length", FT_UINT32, BASE_DEC, NULL, 0x0, "", HFILL }
      },
      { &hf_bittorrent_bstr,
      { "String", "bittorrent.bstr", FT_STRING, BASE_DEC, NULL, 0x0, "", HFILL }
      },
      { &hf_bittorrent_bint,
      { "Integer", "bittorrent.bint", FT_INT32, BASE_DEC, NULL, 0x0, "", HFILL }
      },
      { &hf_bittorrent_bdict,
      { "Dictionary", "bittorrent.bdict", FT_NONE, BASE_NONE, NULL, 0x0, "", HFILL }
      },
      { &hf_bittorrent_bdict_entry,
      { "Entry", "bittorrent.bdict.entry", FT_NONE, BASE_NONE, NULL, 0x0, "", HFILL }
      },
      { &hf_bittorrent_blist,
      { "List", "bittorrent.blist", FT_NONE, BASE_NONE, NULL, 0x0, "", HFILL }
      },
      { &hf_azureus_jpc_addrlen,
      { "Cache Address Length", "bittorrent.jpc.addr.length", FT_UINT32, BASE_DEC, NULL, 0x0, "", HFILL }
      },
      { &hf_azureus_jpc_addr,
      { "Cache Address", "bittorrent.jpc.addr", FT_STRING, BASE_DEC, NULL, 0x0, "", HFILL }
      },
      { &hf_azureus_jpc_port,
      { "Port", "bittorrent.jpc.port", FT_UINT32, BASE_DEC, NULL, 0x0, "", HFILL }
      },
      { &hf_azureus_jpc_session,
      { "Session ID", "bittorrent.jpc.session", FT_UINT32, BASE_HEX, NULL, 0x0, "", HFILL }
      }
  };

  static gint *ett[] = {
    &ett_bittorrent,
    &ett_bittorrent_msg,
    &ett_peer_id,
    &ett_bittorrent_bdict,
    &ett_bittorrent_bdict_entry,
    &ett_bittorrent_blist
  };

  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));

  register_dissector("bittorrent.tcp", dissect_bittorrent, 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)
{
/*   dissector_handle = create_dissector_handle(dissect_bittorrent, proto_bittorrent); */
   dissector_handle = find_dissector("bittorrent.tcp");
#if 0
   dissector_add("tcp.port", 6881, dissector_handle);
   dissector_add("tcp.port", 6882, dissector_handle);
   dissector_add("tcp.port", 6883, dissector_handle);
   dissector_add("tcp.port", 6884, dissector_handle);
   dissector_add("tcp.port", 6885, dissector_handle);
   dissector_add("tcp.port", 6886, dissector_handle);
   dissector_add("tcp.port", 6887, dissector_handle);
   dissector_add("tcp.port", 6888, dissector_handle);
   dissector_add("tcp.port", 6889, dissector_handle);
#endif
   heur_dissector_add("tcp", test_bittorrent_packet, proto_bittorrent);
}

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