Fix dissection of MEGACO over TCP, there will be a TPKT header included.

svn path=/trunk/; revision=12043

1 files changed, 49 insertions, 14 deletions

diff --git a/plugins/megaco/packet-megaco.c b/plugins/megaco/packet-megaco.c
index 9dd33514e9..a8ab911bd8 100644
--- a/plugins/megaco/packet-megaco.c
+++ b/plugins/megaco/packet-megaco.c
@@ -11,6 +11,10 @@
 * Christoph Wiest,		2003/06/28
 * Modified 2003 by		Christoph Wiest
 *						<ch.wiest@tesionmail.de>
+* Modifyed 2004 by		Anders Broman
+*						<anders.broman@ericsson.com>
+* To handle TPKT headers if over TCP
+*
 * Ethereal - Network traffic analyzer
 * By Gerald Combs <gerald@ethereal.com>
 * Copyright 1999 Gerald Combs
@@ -49,6 +53,7 @@
 #include "prefs.h"
 #include <epan/strutil.h>
 #include "sctpppids.h"
+#include <epan/dissectors/packet-tpkt.h>
 
 #include "plugins/plugin_api_defs.h"
 
@@ -125,6 +130,8 @@ static int ett_megaco_signalsdescriptor			= -1;
 static int ett_megaco_requestedsignal			= -1;
 static int ett_megaco_h245 						= -1;
 
+static dissector_handle_t megaco_text_handle;
+
 
 /*
 * Here are the global variables associated with
@@ -206,16 +213,42 @@ static void
 dissect_megaco_Packagesdescriptor(tvbuff_t *tvb, proto_tree *tree, gint tvb_next_offset, gint tvb_current_offset);
 static void 
 tvb_raw_text_add(tvbuff_t *tvb, proto_tree *tree);
+static void
+dissect_megaco_text(tvbuff_t *tvb, packet_info *pinfo, proto_tree *tree);
 
 static dissector_handle_t sdp_handle;
 static dissector_handle_t h245_handle;
 static proto_tree *top_tree;
-
 /*
-* dissect_megaco_text - The dissector for the MEGACO Protocol, using
-* text encoding.
-*/
-
+ * dissect_megaco_text over TCP, there will be a TPKT header there 
+ * 
+ */
+static void dissect_megaco_text_tcp(tvbuff_t *tvb, packet_info *pinfo, proto_tree *tree)
+{
+	int lv_tpkt_len;
+
+	/* This code is copied from the Q.931 dissector, some parts skipped.
+	 * Check whether this looks like a TPKT-encapsulated
+	 * MEGACO packet.
+	 *
+	 * The minimum length of a MEGACO message is 6?:
+	 * Re-assembly ?
+	 */
+	lv_tpkt_len = is_tpkt(tvb, 6);
+	if (lv_tpkt_len == -1) {
+		/*
+		 * It's not a TPKT packet;
+		 * Is in MEGACO ?
+		 */
+		dissect_megaco_text(tvb, pinfo, tree);
+	}
+	dissect_tpkt_encap(tvb, pinfo, tree, TRUE,
+	    megaco_text_handle);
+}
+/*
+ * dissect_megaco_text - The dissector for the MEGACO Protocol, using
+ * text encoding.
+ */
 static void
 dissect_megaco_text(tvbuff_t *tvb, packet_info *pinfo, proto_tree *tree)
 {
@@ -255,12 +288,11 @@ dissect_megaco_text(tvbuff_t *tvb, packet_info *pinfo, proto_tree *tree)
 	 * binary encodings. Bugfix add skipping of leading spaces.
 	 */
 	tvb_offset = tvb_skip_wsp(tvb, tvb_offset);
-	/* Quick fix for MEGACO not following the RFC, hopfully not breaking any thing 
-	 * If any of the first 5 chars is junk, skip them.Only works for M(EGACO) with capital m ( Hmm)
+	/* Quick fix for MEGACO not following the RFC, hopfully not breaking any thing
+	 * Turned out to be TPKT in case of TCP, added some code to handle that.
+	 * 
+	 * tvb_offset = tvb_find_guint8(tvb, tvb_offset, 5, 'M');
 	 */
-	tvb_next_offset = tvb_find_guint8(tvb, tvb_offset, 5, 'M');
-	if  ( tvb_next_offset != -1 )
-		tvb_offset = tvb_next_offset;
 	if(!tvb_get_nstringz0(tvb,tvb_offset,sizeof(word),word)) return;
 	if (strncasecmp(word, "MEGACO", 6) != 0 && tvb_get_guint8(tvb, tvb_offset ) != '!'){
 			return;
@@ -2619,7 +2651,7 @@ void
 proto_reg_handoff_megaco(void)
 {
 	static int megaco_prefs_initialized = FALSE;
-	static dissector_handle_t megaco_text_handle;
+	static dissector_handle_t megaco_text_tcp_handle;
 	
 	sdp_handle = find_dissector("sdp");
 	h245_handle = find_dissector("h245dg");
@@ -2627,13 +2659,16 @@ proto_reg_handoff_megaco(void)
 	if (!megaco_prefs_initialized) {
 		megaco_text_handle = create_dissector_handle(dissect_megaco_text,
 			proto_megaco);
+		megaco_text_tcp_handle = create_dissector_handle(dissect_megaco_text_tcp,
+			proto_megaco);
+
 		megaco_prefs_initialized = TRUE;
 	}
 	else {
-		dissector_delete("tcp.port", txt_tcp_port, megaco_text_handle);
+		dissector_delete("tcp.port", txt_tcp_port, megaco_text_tcp_handle);
 		dissector_delete("udp.port", txt_udp_port, megaco_text_handle);
 #if 0
-		dissector_delete("tcp.port", bin_tcp_port, megaco_bin_handle);
+		dissector_delete("tcp.port", bin_tcp_port, megaco_text_tcp_handle);
 		dissector_delete("udp.port", bin_udp_port, megaco_bin_handle);
 #endif
 	}
@@ -2648,7 +2683,7 @@ proto_reg_handoff_megaco(void)
 	bin_udp_port = global_megaco_bin_udp_port;
 #endif
 	
-	dissector_add("tcp.port", global_megaco_txt_tcp_port, megaco_text_handle);
+	dissector_add("tcp.port", global_megaco_txt_tcp_port, megaco_text_tcp_handle);
 	dissector_add("udp.port", global_megaco_txt_udp_port, megaco_text_handle);
 #if 0
 	dissector_add("tcp.port", global_megaco_bin_tcp_port, megaco_bin_handle);