Use libwireshark's xDLC handling functions and macros to process the

control field.  This means processing the AX.25 header data in one pass.

The field after the control field is the "protocol identifier" field,
not the "packet identifier" field.

svn path=/trunk/; revision=44772

1 files changed, 44 insertions, 62 deletions

diff --git a/epan/dissectors/packet-ax25.c b/epan/dissectors/packet-ax25.c
index 678c9d5f88..9124e13201 100644
--- a/epan/dissectors/packet-ax25.c
+++ b/epan/dissectors/packet-ax25.c
@@ -1,6 +1,7 @@
 /* packet-ax25.c
  *
  * Routines for Amateur Packet Radio protocol dissection
+ * AX.25 frames
  * Copyright 2005,2006,2007,2008,2009,2010,2012 R.W. Stearn <richard@rns-stearn.demon.co.uk>
  *
  * $Id$
@@ -70,9 +71,6 @@
 #define AX25_HEADER_SIZE	15 /* length of src_addr + dst_addr + cntl */
 #define AX25_MAX_DIGIS		8
 
-#define I_FRAME( control )  ( ( control & 0x01) == 0 )
-#define UI_FRAME( control ) ( ( ( control & 0x03) == 3 ) && ( ( ( ( ( control >> 5 ) & 0x07) << 2) | ( ( control >> 2 ) & 0x03) ) == 0 ) )
-
 /* Forward declaration we need below */
 void proto_reg_handoff_ax25(void);
 
@@ -145,8 +143,6 @@ dissect_ax25( tvbuff_t *tvb, packet_info *pinfo, proto_tree *parent_tree )
 	proto_item *ti;
 	proto_tree *ax25_tree;
 	int offset;
-	int control_offset;
-	int hdr_len;
 	int via_index;
 	char *info_buffer;
 	/* char v2cmdresp; */
@@ -170,25 +166,35 @@ dissect_ax25( tvbuff_t *tvb, packet_info *pinfo, proto_tree *parent_tree )
 
 	col_clear( pinfo->cinfo, COL_INFO );
 
-	/* protocol offset for an AX.25 packet */
 	/* start at the dst addr */
 	offset = 0;
+	/* create display subtree for the protocol */
+	ti = proto_tree_add_protocol_format( parent_tree, proto_ax25, tvb, offset, -1, "AX.25");
+	ax25_tree = proto_item_add_subtree( ti, ett_ax25 );
 
 	dst_addr = tvb_get_ptr( tvb,  offset, AX25_ADDR_LEN );
+	proto_tree_add_ax25( ax25_tree, hf_ax25_dst, tvb, offset, AX25_ADDR_LEN, dst_addr );
 	SET_ADDRESS( &pinfo->dl_dst,	AT_AX25, AX25_ADDR_LEN, dst_addr );
 	SET_ADDRESS( &pinfo->dst,	AT_AX25, AX25_ADDR_LEN, dst_addr );
 	dst_ssid = *(dst_addr + 6);
-	offset += AX25_ADDR_LEN; /* step over dst addr point at src addr */
+
+	/* step over dst addr point at src addr */
+	offset += AX25_ADDR_LEN;
 
 	src_addr = tvb_get_ptr( tvb,  offset, AX25_ADDR_LEN );
+	proto_tree_add_ax25( ax25_tree, hf_ax25_src, tvb, offset, AX25_ADDR_LEN, src_addr );
 	SET_ADDRESS( &pinfo->dl_src,	AT_AX25, AX25_ADDR_LEN, src_addr );
 	SET_ADDRESS( &pinfo->src,	AT_AX25, AX25_ADDR_LEN, src_addr );
 	src_ssid = *(src_addr + 6);
-	offset += AX25_ADDR_LEN; /* step over src addr point at either 1st via addr or control byte */
 
-	/* step over any vias */
-	while ( ( tvb_get_guint8( tvb, offset - 1 ) & 0x01 ) == 0 )
-		offset += AX25_ADDR_LEN; /* step over a via addr */
+	/* step over src addr point at either 1st via addr or control byte */
+	offset += AX25_ADDR_LEN;
+
+	proto_item_append_text( ti, ", Src: %s (%s), Dst: %s (%s)",
+		get_ax25_name( src_addr ),
+		ax25_to_str( src_addr ),
+		get_ax25_name( dst_addr ),
+		ax25_to_str( dst_addr ) );
 
 	/* decode the cmd/resp field */
 	/* v2cmdresp = '.'; */
@@ -210,37 +216,7 @@ dissect_ax25( tvbuff_t *tvb, packet_info *pinfo, proto_tree *parent_tree )
 			is_response = FALSE;
 			break;
 		}
-
-	/* decode the control field */
-	control_offset = offset;
-	control  = tvb_get_guint8( tvb, control_offset );
-
-	/* start at the dst addr */
-	offset = 0;
-	/* create display subtree for the protocol */
-	hdr_len = AX25_HEADER_SIZE;
-	if ( I_FRAME( control ) || UI_FRAME( control ) )
-		hdr_len += 1;
-
-	ti = proto_tree_add_protocol_format( parent_tree, proto_ax25, tvb, offset, hdr_len,
-		"AX.25, Src: %s (%s), Dst: %s (%s), Ver: %s",
-		get_ax25_name( src_addr ),
-		ax25_to_str( src_addr ),
-		get_ax25_name( dst_addr ),
-		ax25_to_str( dst_addr ),
-		ax25_version
-		);
-
-	ax25_tree = proto_item_add_subtree( ti, ett_ax25 );
-
-	proto_tree_add_ax25( ax25_tree, hf_ax25_dst, tvb, offset, AX25_ADDR_LEN, dst_addr );
-
-	/* step over dst addr point at src addr */
-	offset += AX25_ADDR_LEN;
-	proto_tree_add_ax25( ax25_tree, hf_ax25_src, tvb, offset, AX25_ADDR_LEN, src_addr );
-
-	/* step over src addr point at either 1st via addr or control byte */
-	offset += AX25_ADDR_LEN;
+	proto_item_append_text( ti, ", Ver: %s", ax25_version );
 
 	/* handle the vias, if any */
 	via_index = 0;
@@ -256,23 +232,25 @@ dissect_ax25( tvbuff_t *tvb, packet_info *pinfo, proto_tree *parent_tree )
 		offset += AX25_ADDR_LEN;
 		}
 
-	dissect_xdlc_control(	tvb,
-				control_offset,
-				pinfo,
-				ax25_tree,
-				hf_ax25_ctl,
-				ett_ax25_ctl,
-				&ax25_cf_items,
-				NULL,
-				NULL,
-				NULL,
-				is_response,
-				FALSE,
-				FALSE );
-
-	if ( I_FRAME( control ) || UI_FRAME( control ) )
+	/* XXX - next-to-last argument should be TRUE if modulo 128 operation */
+	control = dissect_xdlc_control(	tvb,
+					offset,
+					pinfo,
+					ax25_tree,
+					hf_ax25_ctl,
+					ett_ax25_ctl,
+					&ax25_cf_items,
+					NULL,
+					NULL,
+					NULL,
+					is_response,
+					FALSE,
+					FALSE );
+	/* XXX - second argument should be TRUE if modulo 128 operation */
+	offset += XDLC_CONTROL_LEN(control, FALSE); /* step over control field */
+
+	if ( XDLC_IS_INFORMATION( control ) )
 		{
-		offset += 1; /* step over control byte point at pid */
 
 		pid      = tvb_get_guint8( tvb, offset );
 		col_append_fstr( pinfo->cinfo, COL_INFO, ", %s", val_to_str(pid, pid_vals, "Unknown (0x%02x)") );
@@ -282,9 +260,11 @@ dissect_ax25( tvbuff_t *tvb, packet_info *pinfo, proto_tree *parent_tree )
 
 		offset += 1; /* step over pid to the 1st byte of the payload */
 
+		proto_item_set_end(ti, tvb, offset);
+
 		saved_private_data = pinfo->private_data;
 
-		next_tvb = tvb_new_subset(tvb, offset, -1, -1);
+		next_tvb = tvb_new_subset_remaining(tvb, offset);
 
 		if (!dissector_try_uint(ax25_dissector_table, pid, next_tvb, pinfo, parent_tree))
 			{
@@ -293,6 +273,8 @@ dissect_ax25( tvbuff_t *tvb, packet_info *pinfo, proto_tree *parent_tree )
 
 		pinfo->private_data = saved_private_data;
 		}
+	else
+		proto_item_set_end(ti, tvb, offset);
 }
 
 void
@@ -408,9 +390,9 @@ proto_register_ax25(void)
 			"", HFILL }
 		},
 		{ &hf_ax25_pid,
-			{ "Packet ID",			"ax25.pid",
+			{ "Protocol ID",		"ax25.pid",
 			FT_UINT8, BASE_HEX, VALS(pid_vals), 0x0,
-			"Packet identifier", HFILL }
+			"Protocol identifier", HFILL }
 		},
 	};
 
@@ -475,7 +457,7 @@ capture_ax25( const guchar *pd, int offset, int len, packet_counts *ld)
 	control = pd[ l_offset ];
 
 	/* decode the pid field (if appropriate) */
-	if ( I_FRAME( control ) || UI_FRAME( control ) )
+	if ( XDLC_IS_INFORMATION( control ) )
 		{
 		l_offset += 1; /* step over control byte point at pid */
 		pid = pd[ l_offset ];