Adding upstream version 4.2.2.upstream/4.2.2

Signed-off-by: Daniel Baumann <daniel.baumann@progress-linux.org>

1 files changed, 1326 insertions, 0 deletions

diff --git a/epan/dissectors/packet-bt-utp.c b/epan/dissectors/packet-bt-utp.c
new file mode 100644
index 00000000..af05ca44
--- /dev/null
+++ b/epan/dissectors/packet-bt-utp.c
@@ -0,0 +1,1326 @@
+/* packet-bt-utp.c
+ * Routines for BT-UTP dissection
+ * Copyright 2011, Xiao Xiangquan <xiaoxiangquan@gmail.com>
+ * Copyright 2021, John Thacker <johnthacker@gmail.com>
+ *
+ * Wireshark - Network traffic analyzer
+ * By Gerald Combs <gerald@wireshark.org>
+ * Copyright 1999 Gerald Combs
+ *
+ * SPDX-License-Identifier: GPL-2.0-or-later
+ */
+
+#include "config.h"
+
+#include <epan/packet.h>
+#include <epan/conversation.h>
+#include <epan/exceptions.h>
+#include <epan/show_exception.h>
+#include <epan/expert.h>
+#include <epan/prefs.h>
+#include <epan/proto_data.h>
+#include <epan/reassemble.h>
+
+#include "packet-udp.h"
+#include "packet-bt-utp.h"
+
+void proto_register_bt_utp(void);
+void proto_reg_handoff_bt_utp(void);
+
+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_SELECTIVE_ACKS  = 1,
+  EXT_EXTENSION_BITS  = 2,
+  EXT_CLOSE_REASON    = 3,
+  EXT_NUM_EXT
+};
+
+static const value_string bt_utp_extension_type_vals[] = {
+  { EXT_NO_EXTENSION,   "No Extension" },
+  { EXT_SELECTIVE_ACKS, "Selective ACKs" },
+  { EXT_EXTENSION_BITS, "Extension bits" },
+  { EXT_CLOSE_REASON,   "Close reason" },
+  { 0, NULL }
+};
+
+/* https://github.com/arvidn/libtorrent/blob/master/include/libtorrent/close_reason.hpp */
+static const value_string bt_utp_close_reason_vals[] = {
+  {  0, "None" },
+  {  1, "Duplicate peer ID" },
+  {  2, "Torrent removed" },
+  {  3, "Memory allocation failed" },
+  {  4, "Port blocked" },
+  {  5, "Address blocked" },
+  {  6, "Upload to upload" },
+  {  7, "Not interested upload only" },
+  {  8, "Timeout" },
+  {  9, "Timeout: interest" },
+  { 10, "Timeout: activity" },
+  { 11, "Timeout: handshake" },
+  { 12, "Timeout: request" },
+  { 13, "Protocol blocked" },
+  { 14, "Peer churn" },
+  { 15, "Too many connections" },
+  { 16, "Too many files" },
+  /* Reasons caused by the peer sending unexpected data are 256 and up */
+  {256, "Encryption error" },
+  {257, "Invalid info hash" },
+  {258, "Self connection" },
+  {259, "Invalid metadata" },
+  {260, "Metadata too big" },
+  {261, "Message too big" },
+  {262, "Invalid message id" },
+  {263, "Invalid message" },
+  {264, "Invalid piece message" },
+  {265, "Invalid have message" },
+  {266, "Invalid bitfield message" },
+  {267, "Invalid choke message" },
+  {268, "Invalid unchoke message" },
+  {269, "Invalid interested message" },
+  {270, "Invalid not interested message" },
+  {271, "Invalid request message" },
+  {272, "Invalid reject message" },
+  {273, "Invalid allow fast message" },
+  {274, "Invalid extended message" },
+  {275, "Invalid cancel message" },
+  {276, "Invalid DHT port message" },
+  {277, "Invalid suggest message" },
+  {278, "Invalid have all message" },
+  {279, "Invalid don't have message" },
+  {280, "Invalid PEX message" },
+  {281, "Invalid metadata request message" },
+  {282, "Invalid metadata message" },
+  {283, "Invalid metadata offset" },
+  {284, "Request when choked" },
+  {285, "Corrupt pieces" },
+  {286, "PEX message too big" },
+  {287, "PEX too frequent" },
+  {  0, NULL }
+};
+
+static int proto_bt_utp = -1;
+
+/* ---  "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
+
+/* Very early versions of libutp (still used by Transmission) set the max
+ * recv window size to 0x00380000, versions from 2013 and later set it to
+ * 0x00100000, and some other clients use 0x00040000. This is one of the
+ * few possible sources of heuristics.
+ */
+
+#define V1_MAX_WINDOW_SIZE 0x380000U
+
+static dissector_handle_t bt_utp_handle;
+static dissector_handle_t bittorrent_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_close_reason = -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_stream = -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_len = -1;
+static int hf_bt_utp_data = -1;
+static int hf_bt_utp_pdu_size = -1;
+static int hf_bt_utp_continuation_to = -1;
+
+static expert_field ei_extension_len_invalid = EI_INIT;
+
+static gint ett_bt_utp = -1;
+static gint ett_bt_utp_extension = -1;
+
+static gboolean enable_version0 = FALSE;
+static guint max_window_size = V1_MAX_WINDOW_SIZE;
+/* XXX: Desegementation and OOO-reassembly are not supported yet */
+static gboolean utp_desegment = FALSE;
+/*static gboolean utp_reassemble_out_of_order = FALSE;*/
+static gboolean utp_analyze_seq = TRUE;
+
+static guint32 bt_utp_stream_count = 0;
+
+typedef struct _utp_multisegment_pdu {
+
+  guint16 first_seq;
+  guint16 last_seq;
+  guint first_seq_start_offset;
+  guint last_seq_end_offset;
+  /*gint length;
+  guint32 reassembly_id;*/
+  guint32 first_frame;
+
+} utp_multisegment_pdu;
+
+typedef struct _utp_flow_t {
+#if 0
+  /* XXX: Some other things to add in later. */
+  gboolean base_seq_set;
+  guint16 base_seq;
+  guint32 fin;
+  guint32 window;
+  guint32 maxnextseq;
+#endif
+
+  wmem_tree_t *multisegment_pdus;
+} utp_flow_t;
+
+typedef struct {
+  guint32 stream;
+
+  utp_flow_t flow[2];
+  utp_flow_t *fwd;
+  utp_flow_t *rev;
+#if 0
+  /* XXX: Some other things to add in later. */
+  nstime_t ts_first;
+  nstime_t ts_prev;
+  guint8 conversation_completeness;
+#endif
+} utp_stream_info_t;
+
+/* Per-packet header information. */
+typedef struct {
+  guint8  type;
+  gboolean v0;
+  guint32 connection; /* The prelease "V0" version is 32 bit */
+  guint32 stream;
+  guint16 seq;
+  guint16 ack;
+  guint32 seglen; /* reported length remaining */
+  gboolean have_seglen;
+
+  proto_tree *tree; /* For the bittorrent subdissector to access */
+} utp_info_t;
+
+static utp_stream_info_t*
+get_utp_stream_info(packet_info *pinfo, utp_info_t *utp_info)
+{
+  conversation_t* conv;
+  utp_stream_info_t *stream_info;
+  guint32 id_up, id_down;
+  int direction;
+
+  /* Handle connection ID wrapping correctly. (Mainline libutp source
+   * does not appear to do this, probably fails to connect if the random
+   * connection ID is GMAX_UINT16 and tries again.)
+   */
+  if (utp_info->v0) {
+    id_up = utp_info->connection+1;
+    id_down = utp_info->connection-1;
+  } else {
+    id_up = (guint16)(utp_info->connection+1);
+    id_down = (guint16)(utp_info->connection-1);
+  }
+
+  if (utp_info->type == ST_SYN) {
+    /* SYN packets are special, they have the connection ID for the other
+     * side, and allow us to know both.
+     */
+    conv = find_conversation(pinfo->num, &pinfo->src, &pinfo->dst, CONVERSATION_BT_UTP,
+ id_up, utp_info->connection, 0);
+    if (!conv) {
+      /* XXX: A SYN for between the same pair of hosts with a duplicate
+       * connection ID in the same direction is almost surely a retransmission
+       * (unless there's a client that doesn't actually generate random IDs.)
+       * We could check to see if we've gotten a FIN or RST on that same
+       * connection, and also could do like TCP and see if the initial sequence
+       * number matches. (The latter still doesn't help if the client also
+       * doesn't start with random sequence numbers.)
+       */
+      conv = conversation_new(pinfo->num, &pinfo->src, &pinfo->dst, CONVERSATION_BT_UTP, id_up, utp_info->connection, 0);
+    }
+  } else {
+    /* For non-SYN packets, we know our connection ID, but we don't know if
+     * the other side has our ID+1 (src initiated the connection) or our ID-1
+     * (dst initiated). We also don't want find_conversation() to accidentally
+     * call conversation_set_port2() with the wrong ID. So first we see if
+     * we have a wildcarded conversation around (if we've seen previous
+     * non-SYN packets from our current direction but none in the other.)
+     */
+    conv = find_conversation(pinfo->num, &pinfo->src, &pinfo->dst, CONVERSATION_BT_UTP, utp_info->connection, 0, NO_PORT_B);
+    if (!conv) {
+      /* Do we have a complete conversation originated by our src, or
+       * possibly a wildcarded conversation originated in this direction
+       * (but we saw a non-SYN for the non-initiating side first)? */
+      conv = find_conversation(pinfo->num, &pinfo->src, &pinfo->dst, CONVERSATION_BT_UTP, utp_info->connection, id_up, 0);
+      if (!conv) {
+        /* As above, but dst initiated? */
+        conv = find_conversation(pinfo->num, &pinfo->src, &pinfo->dst, CONVERSATION_BT_UTP, utp_info->connection, id_down, 0);
+        if (!conv) {
+          /* Didn't find it, so create a new wildcarded conversation. When we
+           * get a packet for the other direction, find_conversation() above
+           * will set port2 with the other connection ID.
+           */
+          conv = conversation_new(pinfo->num, &pinfo->src, &pinfo->dst, CONVERSATION_BT_UTP, utp_info->connection, 0, NO_PORT2);
+        }
+      }
+    }
+  }
+
+  stream_info = (utp_stream_info_t *)conversation_get_proto_data(conv, proto_bt_utp);
+  if (!stream_info) {
+    stream_info = wmem_new0(wmem_file_scope(), utp_stream_info_t);
+    stream_info->stream = bt_utp_stream_count++;
+    stream_info->flow[0].multisegment_pdus=wmem_tree_new(wmem_file_scope());
+    stream_info->flow[1].multisegment_pdus=wmem_tree_new(wmem_file_scope());
+    conversation_add_proto_data(conv, proto_bt_utp, stream_info);
+  }
+
+  /* check direction */
+  direction=cmp_address(&pinfo->src, &pinfo->dst);
+  /* if the addresses are equal, match the ports instead. Use
+   * the UDP ports instead of the uTP connection IDs because
+   * we don't know which ID is smaller if we don't have both. */
+  if(direction==0) {
+      direction= (pinfo->srcport > pinfo->destport) ? 1 : -1;
+  }
+  if(direction>=0) {
+      stream_info->fwd=&(stream_info->flow[0]);
+      stream_info->rev=&(stream_info->flow[1]);
+  } else {
+      stream_info->fwd=&(stream_info->flow[1]);
+      stream_info->rev=&(stream_info->flow[0]);
+  }
+
+  return stream_info;
+}
+
+static void
+print_pdu_tracking_data(packet_info *pinfo, tvbuff_t *tvb, proto_tree *utp_tree, utp_multisegment_pdu *msp)
+{
+    proto_item *item;
+
+    col_prepend_fence_fstr(pinfo->cinfo, COL_INFO, "[Continuation to #%u] ", msp->first_frame);
+    item=proto_tree_add_uint(utp_tree, hf_bt_utp_continuation_to,
+        tvb, 0, 0, msp->first_frame);
+    proto_item_set_generated(item);
+}
+
+static int
+scan_for_next_pdu(tvbuff_t *tvb, proto_tree *utp_tree, packet_info *pinfo, wmem_tree_t *multisegment_pdus)
+{
+  utp_multisegment_pdu *msp;
+  utp_info_t *p_utp_info;
+  guint16 seq, prev_seq;
+
+  p_utp_info = (utp_info_t *)p_get_proto_data(pinfo->pool, pinfo, proto_bt_utp, pinfo->curr_layer_num);
+
+  /* XXX: Wraparound is possible, as is cycling through all 16 bit
+   * sequence numbers in a connection. We only do this path if
+   * "seq analysis" is on; that ought to do something (relative
+   * sequence numbers definitely, maybe extend the width?) to help,
+   * but doesn't yet.
+   */
+  seq = p_utp_info->seq;
+  prev_seq = seq - 1;
+  msp = (utp_multisegment_pdu *)wmem_tree_lookup32_le(multisegment_pdus, prev_seq);
+  if (msp) {
+
+    if(seq>msp->first_seq && seq<=msp->last_seq) {
+      print_pdu_tracking_data(pinfo, tvb, utp_tree, msp);
+    }
+
+    /* If this segment is completely within a previous PDU
+     * then we just skip this packet
+     */
+    if(seq>msp->first_seq && seq<msp->last_seq) {
+      return -1;
+    }
+
+    if(seq>msp->first_seq && seq==msp->last_seq) {
+      if (!PINFO_FD_VISITED(pinfo) && p_utp_info->have_seglen) {
+        /* Unlike TCP, the sequence numbers don't measure bytes, so
+         * we can only really update the end of the MSP when the packets
+         * are in order, and if we have the real segment length (so not
+         * an unreassembled IP fragment).
+         */
+        if (p_utp_info->seglen >= msp->last_seq_end_offset) {
+          return msp->last_seq_end_offset;
+        } else {
+          msp->last_seq++;
+          msp->last_seq_end_offset -= p_utp_info->seglen;
+          return -1;
+        }
+      } else {
+        /* We can still provide a hint to the offset start in some
+         * cases even when we can't update the MSP.
+         */
+        if (msp->last_seq_end_offset < tvb_reported_length(tvb)) {
+          return msp->last_seq_end_offset;
+        } else {
+          return -1;
+        }
+      }
+    }
+  }
+
+  return 0;
+}
+
+static utp_multisegment_pdu *
+pdu_store_sequencenumber_of_next_pdu(packet_info *pinfo, guint16 seq, int offset, guint32 bytes_until_next_pdu, wmem_tree_t *multisegment_pdus)
+{
+  utp_multisegment_pdu *msp;
+
+  msp = wmem_new(wmem_file_scope(), utp_multisegment_pdu);
+  msp->first_seq = seq;
+  msp->first_seq_start_offset = offset;
+  msp->last_seq = seq+1;
+  msp->last_seq_end_offset = bytes_until_next_pdu;
+  msp->first_frame = pinfo->num;
+  wmem_tree_insert32(multisegment_pdus, seq, (void *)msp);
+
+  return msp;
+}
+
+#if 0
+static void
+desegment_utp(tvbuff_t *tvb, packet_info *pinfo, int offset,
+              guint32 seq, guint32 nxtseq,
+              proto_tree *tree, proto_tree *utp_tree,
+              utp_stream_info_t *stream_info)
+{
+
+}
+#endif
+
+void
+utp_dissect_pdus(tvbuff_t *tvb, packet_info *pinfo, proto_tree *tree,
+                 gboolean proto_desegment, guint fixed_len,
+                 guint (*get_pdu_len)(packet_info *, tvbuff_t *, int, void*),
+                 dissector_t dissect_pdu, void* dissector_data)
+{
+  volatile int offset = 0;
+  int offset_before;
+  guint captured_length_remaining;
+  volatile guint plen;
+  guint length;
+  tvbuff_t *next_tvb;
+  proto_item *item=NULL;
+  const char *saved_proto;
+  guint8 curr_layer_num;
+  wmem_list_frame_t *frame;
+
+  while (tvb_reported_length_remaining(tvb, offset) > 0) {
+    /*
+     * We use "tvb_ensure_captured_length_remaining()" to make
+     * sure there actually *is* data remaining.  The protocol
+     * we're handling could conceivably consists of a sequence of
+     * fixed-length PDUs, and therefore the "get_pdu_len" routine
+     * might not actually fetch anything from the tvbuff, and thus
+     * might not cause an exception to be thrown if we've run past
+     * the end of the tvbuff.
+     *
+     * This means we're guaranteed that "captured_length_remaining" is positive.
+     */
+    captured_length_remaining = tvb_ensure_captured_length_remaining(tvb, offset);
+
+    /*
+     * Can we do reassembly?
+     */
+    if (proto_desegment && pinfo->can_desegment) {
+      /*
+       * Yes - is the fixed-length part of the PDU split across segment
+       * boundaries?
+       */
+      if (captured_length_remaining < fixed_len) {
+        /*
+         * Yes.  Tell the uTP dissector where the data for this message
+         * starts in the data it handed us and that we need "some more
+         * data."  Don't tell it exactly how many bytes we need because
+         * if/when we ask for even more (after the header) that will
+         * break reassembly.
+         */
+        pinfo->desegment_offset = offset;
+        pinfo->desegment_len = DESEGMENT_ONE_MORE_SEGMENT;
+        return;
+      }
+    }
+
+    /*
+     * Get the length of the PDU.
+     */
+    plen = (*get_pdu_len)(pinfo, tvb, offset, dissector_data);
+    if (plen == 0) {
+      /*
+       * Support protocols which have a variable length which cannot
+       * always be determined within the given fixed_len.
+       */
+      DISSECTOR_ASSERT(proto_desegment && pinfo->can_desegment);
+      pinfo->desegment_offset = offset;
+      pinfo->desegment_len = DESEGMENT_ONE_MORE_SEGMENT;
+      return;
+    }
+    if (plen < fixed_len) {
+      /*
+       * Either:
+       *
+       *  1) the length value extracted from the fixed-length portion
+       *     doesn't include the fixed-length portion's length, and
+       *     was so large that, when the fixed-length portion's
+       *     length was added to it, the total length overflowed;
+       *
+       *  2) the length value extracted from the fixed-length portion
+       *     includes the fixed-length portion's length, and the value
+       *     was less than the fixed-length portion's length, i.e. it
+       *     was bogus.
+       *
+       * Report this as a bounds error.
+       */
+      show_reported_bounds_error(tvb, pinfo, tree);
+      return;
+    }
+
+    /* give a hint to uTP where the next PDU starts
+     * so that it can attempt to find it in case it starts
+     * somewhere in the middle of a segment.
+     */
+    if(!pinfo->fd->visited && utp_analyze_seq) {
+      guint remaining_bytes;
+      remaining_bytes = tvb_reported_length_remaining(tvb, offset);
+      if(plen>remaining_bytes) {
+        pinfo->want_pdu_tracking=2;
+        pinfo->bytes_until_next_pdu=plen-remaining_bytes;
+      }
+    }
+
+    /*
+     * Can we do reassembly?
+     */
+    if (proto_desegment && pinfo->can_desegment) {
+      /*
+       * Yes - is the PDU split across segment boundaries?
+       */
+      if (captured_length_remaining < plen) {
+        /*
+         * Yes.  Tell the TCP dissector where the data for this message
+         * starts in the data it handed us, and how many more bytes we
+         * need, and return.
+         */
+        pinfo->desegment_offset = offset;
+        pinfo->desegment_len = plen - captured_length_remaining;
+        return;
+      }
+    }
+
+    curr_layer_num = pinfo->curr_layer_num-1;
+    frame = wmem_list_frame_prev(wmem_list_tail(pinfo->layers));
+    while (frame && (proto_bt_utp != (gint) GPOINTER_TO_UINT(wmem_list_frame_data(frame)))) {
+      frame = wmem_list_frame_prev(frame);
+      curr_layer_num--;
+    }
+#if 0
+    if (captured_length_remaining >= plen || there are more packets)
+    {
+#endif
+          /*
+           * Display the PDU length as a field
+           */
+          item=proto_tree_add_uint(((utp_info_t *)p_get_proto_data(pinfo->pool, pinfo, proto_bt_utp, curr_layer_num))->tree,
+                                   hf_bt_utp_pdu_size,
+                                   tvb, offset, plen, plen);
+          proto_item_set_generated(item);
+#if 0
+    } else {
+          item = proto_tree_add_expert_format((proto_tree *)p_get_proto_data(pinfo->pool, pinfo, proto_bt_utp, curr_layer_num),
+                                  tvb, offset, -1,
+              "PDU Size: %u cut short at %u",plen,captured_length_remaining);
+          proto_item_set_generated(item);
+    }
+#endif
+
+    /*
+     * Construct a tvbuff containing the amount of the payload we have
+     * available.  Make its reported length the amount of data in the PDU.
+     */
+    length = captured_length_remaining;
+    if (length > plen) {
+      length = plen;
+    }
+    next_tvb = tvb_new_subset_length_caplen(tvb, offset, length, plen);
+    if (!(proto_desegment && pinfo->can_desegment)) {
+      /* If we can't do reassembly, give a hint that bounds errors
+       * are probably fragment errors. */
+      tvb_set_fragment(next_tvb);
+    }
+
+    /*
+     * Dissect the PDU.
+     *
+     * If it gets an error that means there's no point in
+     * dissecting any more PDUs, rethrow the exception in
+     * question.
+     *
+     * If it gets any other error, report it and continue, as that
+     * means that PDU got an error, but that doesn't mean we should
+     * stop dissecting PDUs within this frame or chunk of reassembled
+     * data.
+     */
+    saved_proto = pinfo->current_proto;
+    TRY {
+      (*dissect_pdu)(next_tvb, pinfo, tree, dissector_data);
+    }
+    CATCH_NONFATAL_ERRORS {
+      show_exception(tvb, pinfo, tree, EXCEPT_CODE, GET_MESSAGE);
+      /*
+       * Restore the saved protocol as well; we do this after
+       * show_exception(), so that the "Malformed packet" indication
+       * shows the protocol for which dissection failed.
+       */
+      pinfo->current_proto = saved_proto;
+    }
+    ENDTRY;
+
+    /*
+     * Step to the next PDU.
+     * Make sure we don't overflow.
+     */
+    offset_before = offset;
+    offset += plen;
+    if (offset <= offset_before)
+        break;
+  }
+}
+
+static gint
+get_utp_version(tvbuff_t *tvb) {
+  guint8  v0_flags;
+  guint8  v1_ver_type, ext, ext_len;
+  guint32 window;
+  guint   len, offset = 0;
+  gint    ver = -1;
+
+  /* Simple heuristics inspired by code from utp.cpp */
+
+  len = tvb_captured_length(tvb);
+
+  /* Version 1? */
+  if (len < V1_FIXED_HDR_SIZE) {
+    return -1;
+  }
+
+  v1_ver_type = tvb_get_guint8(tvb, 0);
+  ext = tvb_get_guint8(tvb, 1);
+  if (((v1_ver_type & 0x0f) == 1) && ((v1_ver_type>>4) < ST_NUM_STATES) &&
+      (ext < EXT_NUM_EXT)) {
+    window = tvb_get_guint32(tvb, 12, ENC_BIG_ENDIAN);
+    if (window > max_window_size) {
+      return -1;
+    }
+    ver = 1;
+    offset = V1_FIXED_HDR_SIZE;
+  } else if (enable_version0) {
+    /* Version 0? */
+    if (len < V0_FIXED_HDR_SIZE) {
+      return -1;
+    }
+    v0_flags = tvb_get_guint8(tvb, 18);
+    ext = tvb_get_guint8(tvb, 17);
+    if ((v0_flags < ST_NUM_STATES) && (ext < EXT_NUM_EXT)) {
+      ver = 0;
+      offset = V0_FIXED_HDR_SIZE;
+    }
+  }
+
+  if (ver < 0) {
+    return ver;
+  }
+
+  /* In V0 we could use the microseconds value as a heuristic, because
+   * it was tv_usec, but in the modern V1 we cannot, because it is
+   * computed by converting a time_t into a 64 bit quantity of microseconds
+   * and then taking the lower 32 bits, so all possible values are likely.
+   */
+  /* If we have an extension, then check the next two bytes,
+   * the first of which is another extension type (likely NO_EXTENSION)
+   * and the second of which is a length, which must be at least 4.
+   */
+  if (ext != EXT_NO_EXTENSION) {
+    if (len < offset + 2) {
+      return -1;
+    }
+    ext = tvb_get_guint8(tvb, offset);
+    ext_len = tvb_get_guint8(tvb, offset+1);
+    if (ext >= EXT_NUM_EXT || ext_len < 4) {
+      return -1;
+    }
+  }
+
+  return ver;
+}
+
+static int
+dissect_utp_header_v0(tvbuff_t *tvb, packet_info *pinfo, proto_tree *tree, int offset, guint8 *extension_type)
+{
+  /* "Original" (V0) */
+  utp_info_t        *p_utp_info = NULL;
+  utp_stream_info_t *stream_info = NULL;
+
+  proto_item     *ti;
+  guint32 type, connection, win, seq, ack;
+
+  p_utp_info = wmem_new(pinfo->pool, utp_info_t);
+  p_utp_info->v0 = TRUE;
+  p_add_proto_data(pinfo->pool, pinfo, proto_bt_utp, pinfo->curr_layer_num, p_utp_info);
+
+  proto_tree_add_item_ret_uint(tree, hf_bt_utp_connection_id_v0, tvb, offset, 4, ENC_BIG_ENDIAN, &connection);
+  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_ret_uint(tree, hf_bt_utp_wnd_size_v0, tvb, offset, 1, ENC_BIG_ENDIAN, &win);
+  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_ret_uint(tree, hf_bt_utp_flags, tvb, offset, 1, ENC_BIG_ENDIAN, &type);
+  offset += 1;
+
+  col_append_fstr(pinfo->cinfo, COL_INFO, "Connection ID:%d [%s]", connection, val_to_str(type, bt_utp_type_vals, "Unknown %d"));
+  p_utp_info->type = type;
+  p_utp_info->connection = connection;
+
+  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;
+
+  proto_tree_add_item_ret_uint(tree, hf_bt_utp_seq_nr, tvb, offset, 2, ENC_BIG_ENDIAN, &seq);
+  col_append_str_uint(pinfo->cinfo, COL_INFO, "Seq", seq, " ");
+  p_utp_info->seq = seq;
+  offset += 2;
+  proto_tree_add_item_ret_uint(tree, hf_bt_utp_ack_nr, tvb, offset, 2, ENC_BIG_ENDIAN, &ack);
+  col_append_str_uint(pinfo->cinfo, COL_INFO, "Ack", ack, " ");
+  p_utp_info->ack = ack;
+  offset += 2;
+  col_append_str_uint(pinfo->cinfo, COL_INFO, "Win", win, " ");
+
+  stream_info = get_utp_stream_info(pinfo, p_utp_info);
+  ti = proto_tree_add_uint(tree, hf_bt_utp_stream, tvb, offset, 0, stream_info->stream);
+  p_utp_info->stream = stream_info->stream;
+  proto_item_set_generated(ti);
+
+  return offset;
+}
+
+static int
+dissect_utp_header_v1(tvbuff_t *tvb, packet_info *pinfo, proto_tree *tree, int offset, guint8 *extension_type)
+{
+  /* V1 */
+  utp_info_t        *p_utp_info = NULL;
+  utp_stream_info_t *stream_info = NULL;
+
+  proto_item     *ti;
+
+  guint32 type, connection, win, seq, ack;
+
+  p_utp_info = wmem_new(pinfo->pool, utp_info_t);
+  p_utp_info->v0 = FALSE;
+  p_add_proto_data(pinfo->pool, pinfo, proto_bt_utp, pinfo->curr_layer_num, p_utp_info);
+
+  proto_tree_add_item(tree, hf_bt_utp_ver, tvb, offset, 1, ENC_BIG_ENDIAN);
+  proto_tree_add_item_ret_uint(tree, hf_bt_utp_type, tvb, offset, 1, ENC_BIG_ENDIAN, &type);
+  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_ret_uint(tree, hf_bt_utp_connection_id_v1, tvb, offset, 2, ENC_BIG_ENDIAN, &connection);
+  offset += 2;
+
+  col_append_fstr(pinfo->cinfo, COL_INFO, "Connection ID:%d [%s]", connection, val_to_str(type, bt_utp_type_vals, "Unknown %d"));
+  p_utp_info->type = type;
+  p_utp_info->connection = connection;
+
+  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_ret_uint(tree, hf_bt_utp_wnd_size_v1, tvb, offset, 4, ENC_BIG_ENDIAN, &win);
+  offset += 4;
+  proto_tree_add_item_ret_uint(tree, hf_bt_utp_seq_nr, tvb, offset, 2, ENC_BIG_ENDIAN, &seq);
+  col_append_str_uint(pinfo->cinfo, COL_INFO, "Seq", seq, " ");
+  p_utp_info->seq = seq;
+  offset += 2;
+  proto_tree_add_item_ret_uint(tree, hf_bt_utp_ack_nr, tvb, offset, 2, ENC_BIG_ENDIAN, &ack);
+  col_append_str_uint(pinfo->cinfo, COL_INFO, "Ack", ack, " ");
+  p_utp_info->ack = ack;
+  offset += 2;
+  col_append_str_uint(pinfo->cinfo, COL_INFO, "Win", win, " ");
+
+  stream_info = get_utp_stream_info(pinfo, p_utp_info);
+  ti = proto_tree_add_uint(tree, hf_bt_utp_stream, tvb, offset, 0, stream_info->stream);
+  p_utp_info->stream = stream_info->stream;
+  proto_item_set_generated(ti);
+
+  /* XXX: Multisegment PDUs are the top priority to add, but a number of
+   * other features in the TCP dissector would be useful- relative sequence
+   * numbers, conversation completeness, maybe even tracking SACKs.
+   */
+  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;
+  guint32 next_extension, extension_length;
+  /* display the extension tree */
+
+  while(*extension_type != EXT_NO_EXTENSION && offset < (int)tvb_reported_length(tvb))
+  {
+    ti = proto_tree_add_none_format(tree, hf_bt_utp_extension, tvb, offset, -1, "Extension: %s", val_to_str_const(*extension_type, bt_utp_extension_type_vals, "Unknown"));
+    ext_tree = proto_item_add_subtree(ti, ett_bt_utp_extension);
+
+    proto_tree_add_item_ret_uint(ext_tree, hf_bt_utp_next_extension_type, tvb, offset, 1, ENC_BIG_ENDIAN, &next_extension);
+    offset += 1;
+
+    proto_tree_add_item_ret_uint(ext_tree, hf_bt_utp_extension_len, tvb, offset, 1, ENC_BIG_ENDIAN, &extension_length);
+    proto_item_append_text(ti, ", Len=%d", extension_length);
+    offset += 1;
+
+    switch(*extension_type){
+      case EXT_SELECTIVE_ACKS: /* 1 */
+      {
+        proto_tree_add_item(ext_tree, hf_bt_utp_extension_bitmask, tvb, offset, extension_length, ENC_NA);
+        break;
+      }
+      case EXT_EXTENSION_BITS: /* 2 */
+      {
+        proto_tree_add_item(ext_tree, hf_bt_utp_extension_bitmask, tvb, offset, extension_length, ENC_NA);
+        break;
+      }
+      case EXT_CLOSE_REASON: /* 3 */
+      {
+        if (extension_length != 4) {
+          expert_add_info(pinfo, ti, &ei_extension_len_invalid);
+        }
+        proto_tree_add_item(ext_tree, hf_bt_utp_extension_close_reason, tvb, offset, 4, ENC_NA);
+        break;
+      }
+      default:
+        proto_tree_add_item(ext_tree, hf_bt_utp_extension_unknown, tvb, offset, extension_length, ENC_NA);
+      break;
+    }
+    offset += extension_length;
+    proto_item_set_len(ti, 1 + 1 + extension_length);
+    *extension_type = next_extension;
+  }
+
+  return offset;
+}
+
+static gboolean
+decode_utp(tvbuff_t *tvb, int offset, packet_info *pinfo,
+    proto_tree *tree)
+{
+  proto_tree *parent_tree;
+  tvbuff_t *next_tvb;
+  int save_desegment_offset;
+  guint32 save_desegment_len;
+
+  /* XXX: Check for retransmission? */
+
+  next_tvb = tvb_new_subset_remaining(tvb, offset);
+
+  save_desegment_offset = pinfo->desegment_offset;
+  save_desegment_len = pinfo->desegment_len;
+
+  /* The only possible payload is bittorrent */
+
+  parent_tree = proto_tree_get_parent_tree(tree);
+  if (call_dissector_with_data(bittorrent_handle, next_tvb, pinfo, parent_tree, NULL)) {
+    pinfo->want_pdu_tracking -= !!(pinfo->want_pdu_tracking);
+    return TRUE;
+  }
+
+  DISSECTOR_ASSERT(save_desegment_offset == pinfo->desegment_offset &&
+                   save_desegment_len == pinfo->desegment_len);
+
+  call_data_dissector(tvb, pinfo, parent_tree);
+  pinfo->want_pdu_tracking -= !!(pinfo->want_pdu_tracking);
+
+  return FALSE;
+}
+
+static void
+process_utp_payload(tvbuff_t *tvb, packet_info *pinfo,
+    proto_tree *tree, guint16 seq, gboolean is_utp_segment,
+    utp_stream_info_t *stream_info)
+{
+  volatile int offset = 0;
+  pinfo->want_pdu_tracking = 0;
+
+  TRY {
+    if (is_utp_segment) {
+      /* See if an unaligned PDU */
+      if (stream_info && utp_analyze_seq && (!utp_desegment)) {
+        offset = scan_for_next_pdu(tvb, tree, pinfo,
+                stream_info->fwd->multisegment_pdus);
+      }
+    }
+
+    if ((offset != -1) && decode_utp(tvb, offset, pinfo, tree)) {
+      /*
+       * We succeeded in handing off to bittorent.
+       *
+       * Is this a segment (so we're not desegmenting for whatever
+       * reason)? Then at least do rudimentary PDU tracking.
+       */
+      if(is_utp_segment) {
+        /* if !visited, check want_pdu_tracking and
+           store it in table */
+        if(stream_info && (!pinfo->fd->visited) &&
+            utp_analyze_seq && pinfo->want_pdu_tracking) {
+              pdu_store_sequencenumber_of_next_pdu(
+                  pinfo,
+                  seq,
+                  offset,
+                  pinfo->bytes_until_next_pdu,
+                  stream_info->fwd->multisegment_pdus);
+        }
+      }
+    }
+  }
+  CATCH_ALL {
+    /* We got an exception. Before dissection is aborted and execution
+     * is transferred back to (probably) the frame dissector, do PDU
+     * tracking if we need to because this is a segment.
+     */
+    if (is_utp_segment) {
+        if(stream_info && (!pinfo->fd->visited) &&
+            utp_analyze_seq && pinfo->want_pdu_tracking) {
+              pdu_store_sequencenumber_of_next_pdu(
+                  pinfo,
+                  seq,
+                  offset,
+                  pinfo->bytes_until_next_pdu,
+                  stream_info->fwd->multisegment_pdus);
+        }
+    }
+    RETHROW;
+  }
+  ENDTRY;
+}
+
+static guint
+dissect_utp_payload(tvbuff_t *tvb, packet_info *pinfo, proto_tree *tree)
+{
+  proto_item *ti;
+
+  utp_info_t *p_utp_info;
+  guint len_tvb;
+  gboolean save_fragmented;
+
+  p_utp_info = (utp_info_t *)p_get_proto_data(pinfo->pool, pinfo, proto_bt_utp, pinfo->curr_layer_num);
+
+  p_utp_info->tree = tree;
+
+  utp_stream_info_t *stream_info;
+  stream_info = get_utp_stream_info(pinfo, p_utp_info);
+
+  len_tvb = tvb_reported_length(tvb);
+
+  /* As with TCP, if we've been handed an IP fragment, we don't really
+   * know how big the segment is, and we don't really want to do anything
+   * if this is an error packet from ICMP or similar.
+   *
+   * XXX: We don't want to desegment if the UDP checksum is bad either.
+   * Need to add that to the per-packet info that UDP stores and access
+   * it.
+   */
+  pinfo->can_desegment = 0;
+  if (!pinfo->fragmented && !pinfo->flags.in_error_pkt) {
+    p_utp_info->seglen = len_tvb;
+    p_utp_info->have_seglen = TRUE;
+
+    ti = proto_tree_add_uint(tree, hf_bt_utp_len, tvb, 0, 0, len_tvb);
+    proto_item_set_generated(ti);
+    col_append_str_uint(pinfo->cinfo, COL_INFO, "Len", len_tvb, " ");
+
+    if (utp_desegment && tvb_bytes_exist(tvb, 0, len_tvb)) {
+      /* If we actually have the bytes too then we can desegment. */
+      pinfo->can_desegment = 2;
+    }
+  } else {
+    p_utp_info->have_seglen = FALSE;
+  }
+
+  if(tvb_captured_length(tvb)) {
+    proto_tree_add_item(tree, hf_bt_utp_data, tvb, 0, len_tvb, ENC_NA);
+    if (pinfo->can_desegment) {
+      /* XXX: desegment_utp() is not implemented, but we can't get
+       * into this code path yet because utp_desegment is FALSE. */
+    } else {
+      save_fragmented = pinfo->fragmented;
+      pinfo->fragmented = TRUE;
+      process_utp_payload(tvb, pinfo, tree, p_utp_info->seq, TRUE, stream_info);
+      pinfo->fragmented = save_fragmented;
+    }
+  }
+
+  return len_tvb;
+}
+
+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)
+  {
+    proto_tree *sub_tree = NULL;
+    proto_item *ti;
+    gint offset = 0;
+    guint8 extension_type;
+
+    /* set the protocol column */
+    col_set_str(pinfo->cinfo, COL_PROTOCOL, "BT-uTP");
+    col_clear(pinfo->cinfo, COL_INFO);
+
+    /* Determine header version */
+
+    if (version == 0) {
+      ti = proto_tree_add_protocol_format(tree, proto_bt_utp, tvb, 0, -1,
+                                          "uTorrent Transport Protocol V0");
+      sub_tree = proto_item_add_subtree(ti, ett_bt_utp);
+      offset = dissect_utp_header_v0(tvb, pinfo, sub_tree, offset, &extension_type);
+    } else {
+      ti = proto_tree_add_item(tree, proto_bt_utp, tvb, 0, -1, ENC_NA);
+      sub_tree = proto_item_add_subtree(ti, ett_bt_utp);
+      offset = dissect_utp_header_v1(tvb, pinfo, sub_tree, offset, &extension_type);
+    }
+
+    offset = dissect_utp_extension(tvb, pinfo, sub_tree, offset, &extension_type);
+
+    offset += dissect_utp_payload(tvb_new_subset_remaining(tvb, offset), pinfo, sub_tree);
+
+    return offset;
+  }
+  return 0;
+}
+
+static gboolean
+dissect_bt_utp_heur(tvbuff_t *tvb, packet_info *pinfo, proto_tree *tree, void *data _U_)
+{
+  gint version;
+  version = get_utp_version(tvb);
+
+  if (version >= 0)
+  {
+    conversation_t *conversation;
+
+    conversation = find_or_create_conversation(pinfo);
+    conversation_set_dissector_from_frame_number(conversation, pinfo->num, bt_utp_handle);
+
+    dissect_bt_utp(tvb, pinfo, tree, data);
+    return TRUE;
+  }
+
+  return FALSE;
+}
+
+static void
+utp_init(void)
+{
+  bt_utp_stream_count = 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|BASE_UNIT_STRING, &units_byte_bytes, 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_close_reason,
+      { "Close Reason", "bt-utp.extension_close_reason",
+      FT_UINT32, BASE_DEC, VALS(bt_utp_close_reason_vals), 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_stream,
+      { "Stream index", "bt-utp.stream",
+      FT_UINT32, 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,
+      { "Window Size", "bt-utp.wnd_size",
+      FT_UINT8, BASE_DEC, NULL, 0x0,
+      "V0 receive window size, in multiples of 350 bytes", HFILL }
+    },
+    { &hf_bt_utp_wnd_size_v1,
+      { "Window Size", "bt-utp.wnd_size",
+      FT_UINT32, BASE_DEC|BASE_UNIT_STRING, &units_byte_bytes, 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_len,
+      { "uTP Segment Len", "bt-utp.len",
+      FT_UINT32, BASE_DEC, NULL, 0x0,
+      NULL, HFILL }
+    },
+    { &hf_bt_utp_data,
+      { "Data", "bt-utp.data",
+      FT_BYTES, BASE_NONE, NULL, 0x0,
+      NULL, HFILL }
+    },
+    { &hf_bt_utp_pdu_size,
+      { "PDU Size", "bt-utp.pdu.size",
+      FT_UINT32, BASE_DEC, NULL, 0x0,
+      "The size of this PDU", HFILL }
+    },
+    { &hf_bt_utp_continuation_to,
+      { "This is a continuation to the PDU in frame",
+      "bt-utp.continuation_to", FT_FRAMENUM, BASE_NONE,
+      NULL, 0x0, "This is a continuation to the PDU in frame #", HFILL }
+    },
+  };
+
+  static ei_register_info ei[] = {
+    { &ei_extension_len_invalid,
+      { "bt-utp.extension_len.invalid", PI_PROTOCOL, PI_WARN,
+        "The extension is an unexpected length", EXPFILL }
+    },
+  };
+
+  /* Setup protocol subtree array */
+  static gint *ett[] = { &ett_bt_utp, &ett_bt_utp_extension };
+
+  module_t *bt_utp_module;
+  expert_module_t *expert_bt_utp;
+
+  /* Register protocol */
+  proto_bt_utp = proto_register_protocol ("uTorrent Transport Protocol", "BT-uTP", "bt-utp");
+
+  bt_utp_module = prefs_register_protocol(proto_bt_utp, NULL);
+  prefs_register_obsolete_preference(bt_utp_module, "enable");
+  prefs_register_bool_preference(bt_utp_module,
+      "analyze_sequence_numbers",
+      "Analyze uTP sequence numbers",
+      "Make the uTP dissector analyze uTP sequence numbers. Currently this "
+      "just means that it tries to find the correct start offset of a PDU "
+      "if it detected that previous in-order packets spanned multiple "
+      "frames.",
+      &utp_analyze_seq);
+  prefs_register_bool_preference(bt_utp_module,
+      "enable_version0",
+      "Dissect prerelease (version 0) packets",
+      "Whether the dissector should attempt to dissect packets with the "
+      "obsolete format (version 0) that predates BEP 29 (22-Jun-2009)",
+      &enable_version0);
+  prefs_register_uint_preference(bt_utp_module,
+      "max_window_size",
+      "Maximum window size (in hex)",
+      "Maximum receive window size allowed by the dissector. Early clients "
+      "(and a few modern ones) set this value to 0x380000 (the default), "
+      "later ones use smaller values like 0x100000 and 0x40000. A higher "
+      "value can detect nonstandard packets, but at the cost of false "
+      "positives.",
+      16, &max_window_size);
+
+  proto_register_field_array(proto_bt_utp, hf, array_length(hf));
+  proto_register_subtree_array(ett, array_length(ett));
+
+  expert_bt_utp = expert_register_protocol(proto_bt_utp);
+  expert_register_field_array(expert_bt_utp, ei, array_length(ei));
+
+  register_init_routine(utp_init);
+
+  bt_utp_handle = register_dissector("bt-utp", dissect_bt_utp, proto_bt_utp);
+}
+
+void
+proto_reg_handoff_bt_utp(void)
+{
+  /* disabled by default since heuristic is weak */
+  /* XXX: The heuristic is stronger now, but might still get false positives
+   * on packets with lots of zero bytes. Needs more testing before enabling
+   * by default.
+   */
+  heur_dissector_add("udp", dissect_bt_utp_heur, "BitTorrent UTP over UDP", "bt_utp_udp", proto_bt_utp, HEURISTIC_DISABLE);
+
+  dissector_add_for_decode_as_with_preference("udp.port", bt_utp_handle);
+
+  bittorrent_handle = find_dissector_add_dependency("bittorrent.utp", proto_bt_utp);
+}
+
+/*
+ * 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:
+ */
+