Fix and rework some code a bit:

-No prefs so prefs calback not req'd;
-Remove (seemingly) not needed dissector registration on UDP port 0;
-Rework dissect_applemidi_heur() and related so that once dissect_applemidi_heur()
  determines that a pair of UDP addr/ports are being used for the AppleMIDI protocol,
  dissect_apple_midi() will always be called directly for UDP packets with that pair 
  (rather than dissect_applemidi_heur() always be called for every packet).

svn path=/trunk/; revision=31824

1 files changed, 62 insertions, 77 deletions

diff --git a/epan/dissectors/packet-applemidi.c b/epan/dissectors/packet-applemidi.c
index 5d158e933f..20e25cba04 100644
--- a/epan/dissectors/packet-applemidi.c
+++ b/epan/dissectors/packet-applemidi.c
@@ -44,7 +44,6 @@
 
 #include <glib.h>
 #include <epan/packet.h>
-#include <epan/prefs.h>
 #include <epan/conversation.h>
 
 /* Definitions for protocol name during dissector-register */
@@ -94,29 +93,22 @@ static const value_string applemidi_commands[] = {
 };
 
 
-void   proto_reg_handoff_applemidi( void );
-
-static guint			udp_port			= 0;
-
 static int			proto_applemidi			= -1;
-static dissector_handle_t	applemidi_handle		= NULL;
-static dissector_handle_t	rtp_handle			= NULL;
-
-
 
+static dissector_handle_t	applemidi_handle;
+static dissector_handle_t	rtp_handle;
 
 
 
 static void
-dissect_applemidi( tvbuff_t *tvb, packet_info *pinfo _U_ , proto_tree *tree ) {
+dissect_applemidi_common( tvbuff_t *tvb, packet_info *pinfo, proto_tree *tree, guint16 command ) {
 
-	guint16		 command;
 	guint16		 seq_num;
 	guint8		 count;
 	guint8		*name;
 	unsigned int	 offset			= 0;
-	proto_tree	*applemidi_tree		= NULL;
-	proto_tree	*applemidi_tree_seq_num = NULL;
+	proto_tree	*applemidi_tree;
+	proto_tree	*applemidi_tree_seq_num;
 
 
 	col_set_str( pinfo->cinfo, COL_PROTOCOL, APPLEMIDI_DISSECTOR_SHORTNAME );
@@ -124,12 +116,10 @@ dissect_applemidi( tvbuff_t *tvb, packet_info *pinfo _U_ , proto_tree *tree ) {
 	/* Clear out stuff in the info column */
 	col_clear( pinfo->cinfo, COL_INFO );
 
-	command   = tvb_get_ntohs( tvb, offset + 2 );
-
 	col_add_fstr( pinfo->cinfo, COL_INFO, "%s", val_to_str( command, applemidi_commands, "Unknown Command: 0x%04x" ) );
 
 	if ( tree ) {
-		proto_item *ti = NULL;
+		proto_item *ti;
 		ti = proto_tree_add_item( tree, proto_applemidi, tvb, 0, -1, FALSE );
 		applemidi_tree = proto_item_add_subtree( ti, ett_applemidi );
 
@@ -140,7 +130,7 @@ dissect_applemidi( tvbuff_t *tvb, packet_info *pinfo _U_ , proto_tree *tree ) {
 		offset += 2;
 
 		/* the format of packets for "IN", "NO", "OK" and "BY" is identical and contains
-		 * the protocol version, a random number generated by the initiator of the session
+		 * the protocol version, a random number generated by the initiator of the session,
 		 * the SSRC that is used by the respective sides RTP-entity and optionally the
 		 * name of the participant */
 		if ( ( APPLEMIDI_COMMAND_INVITATION == command ) || ( APPLEMIDI_COMMAND_INVITATION_REJECTED == command ) || ( APLLEMIDI_COMMAND_INVITATION_ACCEPTED == command ) || ( APPLEMIDI_COMMAND_ENDSESSION == command ) ) {
@@ -155,7 +145,7 @@ dissect_applemidi( tvbuff_t *tvb, packet_info *pinfo _U_ , proto_tree *tree ) {
 			proto_tree_add_item( applemidi_tree, hf_applemidi_ssrc, tvb, offset, 4, FALSE );
 			offset += 4;
 
-			len = tvb->length - offset;
+			len = tvb_reported_length(tvb) - offset;
 
 			/* Name is optional */
 			if ( len > 0 ) {
@@ -187,14 +177,14 @@ dissect_applemidi( tvbuff_t *tvb, packet_info *pinfo _U_ , proto_tree *tree ) {
 			proto_tree_add_item( applemidi_tree, hf_applemidi_timestamp3, tvb, offset, 8, FALSE );
 			offset += 8;
 		/* With the receiver feedback packet, the recipient can tell the sender up to what sequence
-		 * number in the RTP-stream the packets have been received, this can be used to shorten the
+		 * number in the RTP-stream the packets have been received; this can be used to shorten the
 		 * recovery-journal-section in the RTP-session */
 		} else if ( APPLEMIDI_COMMAND_RECEIVER_FEEDBACK == command ) {
 			proto_tree_add_item( applemidi_tree, hf_applemidi_ssrc, tvb, offset, 4, FALSE );
 			offset += 4;
 
 			ti = proto_tree_add_item( applemidi_tree, hf_applemidi_sequence_num, tvb, offset, 4, FALSE );
-			/* Apple includes a 32bit sequence-number, but the RTP-packet only specifies 16bit
+			/* Apple includes a 32bit sequence-number, but the RTP-packet only specifies 16bit.
 			 * this subtree and subitem are added to be able to associate the sequence-number
 			 * here easier with the one specified in the corresponding RTP-packet */
 			applemidi_tree_seq_num = proto_item_add_subtree( ti, ett_applemidi_seq_num );
@@ -207,73 +197,74 @@ dissect_applemidi( tvbuff_t *tvb, packet_info *pinfo _U_ , proto_tree *tree ) {
 	}
 }
 
-
 static gboolean
-dissect_applemidi_heur( tvbuff_t *tvb, packet_info *pinfo, proto_tree *tree ) {
+test_applemidi(tvbuff_t *tvb, guint16 *command_p) {
 
-	unsigned int	 offset	= 0;
-	guint16			 signature;
-	guint16			 command;
-	conversation_t	*p_conv;
-	gboolean		 result	= FALSE;
+	*command_p = 0xffff;
 
+	/* An applemidi session protocol UDP-packet must start with the "magic value" of 0xffff ... */
+	if ( APPLEMIDI_PROTOCOL_SIGNATURE != tvb_get_ntohs( tvb, 0 ) )
+		return FALSE;
 
+	*command_p = tvb_get_ntohs( tvb, 2 );
 
-	/* Get the two octets making up the magic value */
-	signature = tvb_get_ntohs( tvb, offset );
+	/* ... followed by packet-command: "IN", "NO", "OK", "BY", "CK" and "RS" */
+	if ( ( APPLEMIDI_COMMAND_INVITATION          == *command_p ) ||
+	     ( APPLEMIDI_COMMAND_INVITATION_REJECTED == *command_p ) ||
+	     ( APLLEMIDI_COMMAND_INVITATION_ACCEPTED == *command_p ) ||
+	     ( APPLEMIDI_COMMAND_ENDSESSION          == *command_p ) ||
+	     ( APPLEMIDI_COMMAND_SYNCHRONIZATION     == *command_p ) ||
+	     ( APPLEMIDI_COMMAND_RECEIVER_FEEDBACK   == *command_p ) )
+		return TRUE;
 
+	return FALSE;
+}
 
-	/* An applemidi session protocol UDP-packet must start with the "magic value" of 0xffff ... */
-	if ( APPLEMIDI_PROTOCOL_SIGNATURE == signature ) {
-
-		command = tvb_get_ntohs( tvb, offset + 2 );
-
-		/* ... followed by packet-command: "IN", "NO", "OK", "BY", "CK" and "RS" */
-		if( APPLEMIDI_COMMAND_INVITATION == command )
-		  result = TRUE;
-		else if( APPLEMIDI_COMMAND_INVITATION_REJECTED == command )
-		  result = TRUE;
-		else if( APLLEMIDI_COMMAND_INVITATION_ACCEPTED == command )
-		  result = TRUE;
-		else if( APPLEMIDI_COMMAND_ENDSESSION == command )
-		  result = TRUE;
-		else if( APPLEMIDI_COMMAND_SYNCHRONIZATION == command )
-		  result = TRUE;
-		else if( APPLEMIDI_COMMAND_RECEIVER_FEEDBACK == command )
-		  result = TRUE;
 
-	}
+/* dissect_applemidi() is called when a packet is seen from a previously identified applemidi conversation */
+/*  If the packet isn't a valid applemidi packet, assume it's an RTP-MIDI packet.                          */
 
-	p_conv=find_conversation( pinfo->fd->num, &pinfo->src, &pinfo->dst, pinfo->ptype, pinfo->srcport, pinfo->destport, 0 );
+static void
+dissect_applemidi( tvbuff_t *tvb, packet_info *pinfo, proto_tree *tree ) {
+	guint16		command;
 
-	if( result ) {
-		if( !p_conv ) {
-			p_conv = conversation_new( 0, &pinfo->src, &pinfo->dst, pinfo->ptype, pinfo->srcport, pinfo->destport, 0 );
-		}
-		if( p_conv ) {
-			conversation_set_dissector( p_conv, applemidi_handle );
-		}
+	if ( test_applemidi( tvb, &command ) )
+		dissect_applemidi_common( tvb, pinfo, tree, command );
+	else
+		call_dissector( rtp_handle, tvb, pinfo, tree );
+}
 
-		dissect_applemidi( tvb, pinfo, tree );
-	} else {
-		if( p_conv )  {
-			if( p_conv->dissector_handle == applemidi_handle ) {
-				result = TRUE;
-				/* punt packets not containing valid AppleMIDI-commands to RTP (or in
-				 * case it exists, the more specialized RTP-MIDI-dissector */
-				call_dissector( rtp_handle, tvb, pinfo, tree );
-			}
-		}
+static gboolean
+dissect_applemidi_heur( tvbuff_t *tvb, packet_info *pinfo, proto_tree *tree ) {
+
+	guint16		 command;
+	conversation_t	*p_conv;
+
+	if ( tvb_length( tvb ) < 4)
+		return FALSE;  /* not enough bytes to check */
+
+	if ( !test_applemidi( tvb, &command ) ) {
+		return FALSE;
+	}
+
+	/* call dissect_applemidi() from now on for UDP packets on this "connection" */
+	p_conv=find_conversation( pinfo->fd->num, &pinfo->src, &pinfo->dst, pinfo->ptype,
+				  pinfo->srcport, pinfo->destport, 0 );
+	if( !p_conv ) {
+		p_conv = conversation_new( pinfo->fd->num, &pinfo->src, &pinfo->dst, pinfo->ptype,
+					   pinfo->srcport, pinfo->destport, 0 );
 	}
-	return result;
+	conversation_set_dissector( p_conv, applemidi_handle );
+
+	dissect_applemidi_common( tvb, pinfo, tree, command );
+	return TRUE;
+
 }
 
 
 void
 proto_register_applemidi( void )
 {
-	module_t *applemidi_module;
-
 	static hf_register_info hf[] =	{
 		{
 			&hf_applemidi_signature,
@@ -439,21 +430,17 @@ proto_register_applemidi( void )
 		&ett_applemidi_seq_num
 	};
 
-    proto_applemidi = proto_register_protocol( APPLEMIDI_DISSECTOR_NAME, APPLEMIDI_DISSECTOR_SHORTNAME, APPLEMIDI_DISSECTOR_ABBREVIATION );
+	proto_applemidi = proto_register_protocol( APPLEMIDI_DISSECTOR_NAME, APPLEMIDI_DISSECTOR_SHORTNAME, APPLEMIDI_DISSECTOR_ABBREVIATION );
 	proto_register_field_array( proto_applemidi, hf, array_length( hf ) );
 	proto_register_subtree_array( ett, array_length( ett ) );
 
-	applemidi_module = prefs_register_protocol( proto_applemidi, proto_reg_handoff_applemidi );
-
 }
 
 void
 proto_reg_handoff_applemidi( void ) {
 
 
-	if ( !applemidi_handle ) {
-		applemidi_handle = create_dissector_handle( dissect_applemidi, proto_applemidi );
-	}
+	applemidi_handle = create_dissector_handle( dissect_applemidi, proto_applemidi );
 
 	/* If we cannot decode the data it will be RTP-MIDI since the Apple session protocol uses
 	 * two ports: the control-port and the MIDI-port.  On both ports an invitation is being sent.
@@ -461,8 +448,6 @@ proto_reg_handoff_applemidi( void ) {
 	 * packets, it will be most likely RTP-MIDI...
 	 */
 	rtp_handle = find_dissector( "rtp" );
-	dissector_add( "udp.port" , udp_port, applemidi_handle );
 	heur_dissector_add( "udp", dissect_applemidi_heur, proto_applemidi );
-	applemidi_handle = find_dissector( "applemidi" );
 
 }