BT-DHT, BT-uTP: Use conversation_set_dissector_from_frame_number

Since the UDP connection switches back and forth between DHT and uTP,
use conversation_set_dissector_from_frame_number so that the dissector
called by try_conversation_dissector in packet-udp.c doesn't change for
a given frame based on the last packet clicked in the GUI.

Split out a heuristic dissector from uTP so that conversation_set_dissector
is only called from the heuristic dissector.

This doesn't make a difference when the heuristics are accurate but
might in some edge cases.

2 files changed, 22 insertions, 6 deletions

diff --git a/epan/dissectors/packet-bt-dht.c b/epan/dissectors/packet-bt-dht.c
index b53f89f67a..b5d059a455 100644
--- a/epan/dissectors/packet-bt-dht.c
+++ b/epan/dissectors/packet-bt-dht.c
@@ -608,7 +608,7 @@ gboolean dissect_bt_dht_heur (tvbuff_t *tvb, packet_info *pinfo,
   }
 
   conversation = find_or_create_conversation(pinfo);
-  conversation_set_dissector(conversation, bt_dht_handle);
+  conversation_set_dissector_from_frame_number(conversation, pinfo->num, bt_dht_handle);
 
   dissect_bt_dht(tvb, pinfo, tree, NULL);
   return TRUE;
diff --git a/epan/dissectors/packet-bt-utp.c b/epan/dissectors/packet-bt-utp.c
index 79477bfb95..b231c7087c 100644
--- a/epan/dissectors/packet-bt-utp.c
+++ b/epan/dissectors/packet-bt-utp.c
@@ -354,16 +354,12 @@ dissect_bt_utp(tvbuff_t *tvb, packet_info *pinfo, proto_tree *tree, void *data _
   /* try dissecting */
   if (version >= 0)
   {
-    conversation_t *conversation;
     guint len_tvb;
     proto_tree *sub_tree = NULL;
     proto_item *ti;
     gint offset = 0;
     guint8 extension_type;
 
-    conversation = find_or_create_conversation(pinfo);
-    conversation_set_dissector(conversation, bt_utp_handle);
-
     /* set the protocol column */
     col_set_str(pinfo->cinfo, COL_PROTOCOL, "BT-uTP");
     /* set the info column */
@@ -395,6 +391,26 @@ dissect_bt_utp(tvbuff_t *tvb, packet_info *pinfo, proto_tree *tree, void *data _
   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;
+}
+
 void
 proto_register_bt_utp(void)
 {
@@ -529,7 +545,7 @@ proto_reg_handoff_bt_utp(void)
    * on packets with lots of zero bytes. Needs more testing before enabling
    * by default.
    */
-  heur_dissector_add("udp", dissect_bt_utp, "BitTorrent UTP over UDP", "bt_utp_udp", proto_bt_utp, HEURISTIC_DISABLE);
+  heur_dissector_add("udp", dissect_bt_utp_heur, "BitTorrent UTP over UDP", "bt_utp_udp", proto_bt_utp, HEURISTIC_DISABLE);
 
   bt_utp_handle = create_dissector_handle(dissect_bt_utp, proto_bt_utp);
   dissector_add_for_decode_as_with_preference("udp.port", bt_utp_handle);