From Patrik Lundquist Updated V1 header description to reflect corrected specification (BEP 0029). Removed if(tree) in dissect. New style dissector, right? Added heuristics for V0 header. Removed length checking in heuristics since uTP packets can have any lenght, even odd ones, and they do. Fixed Extensions looping over whole packets and added a Data field for the trailing payload. https://bugs.wireshark.org/bugzilla/show_bug.cgi?id=8048

svn path=/trunk/; revision=46373

1 files changed, 72 insertions, 64 deletions

diff --git a/epan/dissectors/packet-bt-utp.c b/epan/dissectors/packet-bt-utp.c
index cc985d27ce..fe2c29dc38 100644
--- a/epan/dissectors/packet-bt-utp.c
+++ b/epan/dissectors/packet-bt-utp.c
@@ -56,19 +56,19 @@ enum {
 
 static const value_string bt_utp_extension_type_vals[] = {
   { EXT_NO_EXTENSION,   "No Extension" },
-  { EXT_SELECTION_ACKS, "Selective acks" },
+  { EXT_SELECTION_ACKS, "Selective ACKs" },
   { EXT_EXTENSION_BITS, "Extension bits" },
   { 0, NULL }
 };
 
 static int proto_bt_utp = -1;
 
-/* ---  "Original" utp Header ("version 0" ?) --------------
+/* ---  "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                                                 |
 +-------+-------+---------------+---------------+---------------+
@@ -84,7 +84,6 @@ See utp.cpp source code @ https://github.com/bittorrent/libutp
 +---------------+---------------+---------------+
 
 -- Extension Field(s) --
-
 0               8               16
 +---------------+---------------+---------------+---------------+
 | extension     | len           | bitmask
@@ -103,7 +102,7 @@ http://www.bittorrent.org/beps/bep_0029.html
 Fields Types
 0       4       8               16              24              32
 +-------+-------+---------------+---------------+---------------+
-| ver   | type  | extension     | connection_id                 |
+| type  | ver   | extension     | connection_id                 |
 +-------+-------+---------------+---------------+---------------+
 | timestamp_microseconds                                        |
 +---------------+---------------+---------------+---------------+
@@ -114,10 +113,6 @@ Fields Types
 | seq_nr                        | ack_nr                        |
 +---------------+---------------+---------------+---------------+
 
-XXX: It appears that the above is to be interpreted as indicating
-     that 'ver' is in the low-order 4 bits of byte 0 (mask: 0x0f).
-     (See utp.cpp @ https://github.com/bittorrent/libutp)
-
 -- Extension Field(s) --
 0               8               16
 +---------------+---------------+---------------+---------------+
@@ -127,6 +122,7 @@ XXX: It appears that the above is to be interpreted as indicating
 +---------------+---------------+....
 */
 
+#define V0_FIXED_HDR_SIZE 23
 #define V1_FIXED_HDR_SIZE 20
 
 static dissector_handle_t bt_utp_handle;
@@ -148,50 +144,58 @@ static int hf_bt_utp_wnd_size_v0 = -1;
 static int hf_bt_utp_wnd_size_v1 = -1;
 static int hf_bt_utp_seq_nr = -1;
 static int hf_bt_utp_ack_nr = -1;
+static int hf_bt_utp_data = -1;
 
 static gint ett_bt_utp = -1;
 static gint ett_bt_utp_extension = -1;
 
 void proto_reg_handoff_bt_utp(void);
 
-static gboolean
-utp_is_v1(tvbuff_t *tvb) {
-  guint8 v1_ver_type;
-  guint8 v1_ext;
+static gint
+get_utp_version(tvbuff_t *tvb) {
+  guint8 v0_flags, v0_ext;
+  guint8 v1_ver_type, v1_ext;
+  gint   version;
   guint  len;
 
+  /* Simple heuristics inspired by code from utp.cpp */
+
   v1_ver_type = tvb_get_guint8(tvb, 0);
   v1_ext      = tvb_get_guint8(tvb, 1);
 
-  if (((v1_ver_type & 0x0f) != 1)             ||
-      ((v1_ver_type>>4)     >= ST_NUM_STATES) ||
-      (v1_ext               >= EXT_NUM_EXT)) {
-    return FALSE;  /* Not V1 (or corrupt) */
+  v0_flags    = tvb_get_guint8(tvb, 18);
+  v0_ext      = tvb_get_guint8(tvb, 17);
+
+  if (!(((v1_ver_type & 0x0f) != 1)             ||
+        ((v1_ver_type>>4)     >= ST_NUM_STATES) ||
+        (v1_ext               >= EXT_NUM_EXT))) {
+    version = 1;  /* V1 */
+  }
+  else if (!((v0_flags >= ST_NUM_STATES) ||
+             (v0_ext   >= EXT_NUM_EXT))) {
+    version = 0;  /* V0 */
   }
+  else
+    return -1;
 
-  /* The simple heuristic above (based upon code from utp.cpp) suggests the header is "V1";
-   *  However, based upon a capture seen, the simple heuristic does not appear to be sufficient.
-   *  So: Also do some length checking:
-   *   The length of "V1" frames should be 20, 26, 30, 34, 36, 38, ...
-   *   fixed hdr len:    20
-   *   extension(s) len:  6, 10, 14, 16, 18, 20, ...
-   *   XXX: this is a hack and should be replaced !!
-   *        In fact this heuristic probably fails for some SF_DATA packets since they
-   *        presumably can contain a variable number of data bytes after the header.
-   */
   len = tvb_reported_length(tvb);
-  if (len < V1_FIXED_HDR_SIZE) {
-    return TRUE;  /* Invalid ?: pretend V1 anyways */
-  }
-  len -= V1_FIXED_HDR_SIZE;
-  if ((len ==  0) ||
-      (len ==  6) ||
-      (len == 10) ||
-      (len == 14) ||
-      ((len > 14) && (len%2 == 0))) {
-    return TRUE; /* looks like V1 */
+
+  switch(version) {
+  case 0:
+    if (len < V0_FIXED_HDR_SIZE)
+      return -1;
+    break;
+
+  case 1:
+    if (len < V1_FIXED_HDR_SIZE)
+      return -1;
+    break;
+
+  default:
+    return -1;
   }
-  return FALSE;   /* Not V1 (or corrupt) */
+
+  return version;
 }
 
 static int
@@ -227,10 +231,6 @@ static int
 dissect_utp_header_v1(tvbuff_t *tvb, packet_info *pinfo, proto_tree *tree, int offset, guint8 *extension_type)
 {
   /* V1 */
-  /* Strange: Contrary to BEP-29, in LibuTP (utp.cpp) the first byte has the following definition:
-     packet_type (4 high bits)
-     protocol version (4 low bits)
-  */
   proto_tree_add_item(tree, hf_bt_utp_ver, tvb, offset, 1, ENC_BIG_ENDIAN);
   proto_tree_add_item(tree, hf_bt_utp_type, tvb, offset, 1, ENC_BIG_ENDIAN);
   col_append_fstr(pinfo->cinfo, COL_INFO, " Type: %s", val_to_str((tvb_get_guint8(tvb, offset) >> 4), bt_utp_type_vals, "Unknown %d"));
@@ -262,11 +262,7 @@ dissect_utp_extension(tvbuff_t *tvb, packet_info _U_*pinfo, proto_tree *tree, in
   guint8 extension_length;
   /* display the extension tree */
 
-  /* XXX: This code loops thru the packet bytes until reaching the end of the PDU
-   *      ignoring the "end-of-list" [EXT_NO_EXTENSION] extension type.
-   *      Should we just quit when EXT_NO_EXTENSION is encountered ?
-   */
-  while(offset < (int)tvb_reported_length(tvb))
+  while(*extension_type != EXT_NO_EXTENSION && offset < (int)tvb_reported_length(tvb))
   {
     switch(*extension_type){
       case EXT_SELECTION_ACKS: /* 1 */
@@ -280,7 +276,7 @@ dissect_utp_extension(tvbuff_t *tvb, packet_info _U_*pinfo, proto_tree *tree, in
 
         proto_tree_add_item(ext_tree, hf_bt_utp_extension_len, tvb, offset, 1, ENC_BIG_ENDIAN);
         extension_length = tvb_get_guint8(tvb, offset);
-        proto_item_append_text(ti, " Selection Acks, Len=%d", extension_length);
+        proto_item_append_text(ti, " Selection ACKs, Len=%d", extension_length);
         offset += 1;
 
         proto_tree_add_item(ext_tree, hf_bt_utp_extension_bitmask, tvb, offset, extension_length, ENC_NA);
@@ -333,13 +329,17 @@ dissect_utp_extension(tvbuff_t *tvb, packet_info _U_*pinfo, proto_tree *tree, in
 static int
 dissect_bt_utp(tvbuff_t *tvb, packet_info *pinfo, proto_tree *tree, void *data _U_)
 {
-  conversation_t *conversation;
+  gint version;
+  version = get_utp_version(tvb);
 
   /* try dissecting */
-  if( tvb_get_guint8(tvb,0)=='d' )
+  if(version >= 0)
   {
+    conversation_t *conversation;
+    guint tvb_length;
     proto_tree *sub_tree = NULL;
-    int decoded_length = 0;
+    proto_item *ti;
+    gint offset = 0;
     guint8 extension_type;
 
     conversation = find_or_create_conversation(pinfo);
@@ -350,24 +350,27 @@ dissect_bt_utp(tvbuff_t *tvb, packet_info *pinfo, proto_tree *tree, void *data _
     /* set the info column */
     col_set_str( pinfo->cinfo, COL_INFO, "uTorrent Transport Protocol" );
 
-    if(tree)
-    {
-      proto_item *ti;
-      ti = proto_tree_add_item(tree, proto_bt_utp, tvb, 0, -1, ENC_NA);
-      sub_tree = proto_item_add_subtree(ti, ett_bt_utp);
-    }
+    tvb_length = tvb_reported_length(tvb);
+    ti = proto_tree_add_protocol_format(tree, proto_bt_utp, tvb, 0, -1,
+                                        "uTorrent Transport Protocol V%d (%d bytes)",
+                                        version, tvb_length);
+    sub_tree = proto_item_add_subtree(ti, ett_bt_utp);
 
     /* Determine header version */
 
-    if (!utp_is_v1(tvb)) {
-      decoded_length = dissect_utp_header_v0(tvb, pinfo, sub_tree, decoded_length, &extension_type);
+    if (version == 0) {
+      offset = dissect_utp_header_v0(tvb, pinfo, sub_tree, offset, &extension_type);
     } else {
-      decoded_length = dissect_utp_header_v1(tvb, pinfo, sub_tree,  decoded_length, &extension_type);
+      offset = dissect_utp_header_v1(tvb, pinfo, sub_tree, offset, &extension_type);
     }
 
-    decoded_length = dissect_utp_extension(tvb, pinfo, sub_tree, decoded_length, &extension_type);
+    offset = dissect_utp_extension(tvb, pinfo, sub_tree, offset, &extension_type);
 
-    return decoded_length;
+    tvb_length = tvb_length_remaining(tvb, offset);
+    if(tvb_length > 0)
+      proto_tree_add_item(sub_tree, hf_bt_utp_data, tvb, offset, tvb_length, ENC_NA);
+
+    return offset+tvb_length;
   }
   return 0;
 }
@@ -452,15 +455,20 @@ proto_register_bt_utp(void)
       NULL, HFILL }
     },
     { &hf_bt_utp_seq_nr,
-      { "Sequence NR", "bt-utp.seq_nr",
+      { "Sequence number", "bt-utp.seq_nr",
       FT_UINT16, BASE_DEC, NULL, 0x0,
       NULL, HFILL }
     },
     { &hf_bt_utp_ack_nr,
-      { "ACK NR", "bt-utp.ack_nr",
+      { "ACK number", "bt-utp.ack_nr",
       FT_UINT16, BASE_DEC, NULL, 0x0,
       NULL, HFILL }
     },
+    { &hf_bt_utp_data,
+      { "Data", "bt-utp.data",
+      FT_BYTES, BASE_NONE, NULL, 0x0,
+      NULL, HFILL }
+    },
   };
 
   /* Setup protocol subtree array */