2 * Routines for lapb frame disassembly
3 * Olivier Abad <oabad@cybercable.fr>
5 * $Id: packet-lapb.c,v 1.36 2002/08/02 23:35:53 jmayer Exp $
7 * Ethereal - Network traffic analyzer
8 * By Gerald Combs <gerald@ethereal.com>
11 * This program is free software; you can redistribute it and/or
12 * modify it under the terms of the GNU General Public License
13 * as published by the Free Software Foundation; either version 2
14 * of the License, or (at your option) any later version.
16 * This program is distributed in the hope that it will be useful,
17 * but WITHOUT ANY WARRANTY; without even the implied warranty of
18 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
19 * GNU General Public License for more details.
21 * You should have received a copy of the GNU General Public License
22 * along with this program; if not, write to the Free Software
23 * Foundation, Inc., 59 Temple Place - Suite 330, Boston, MA 02111-1307, USA.
33 #include <epan/packet.h>
36 static int proto_lapb = -1;
37 static int hf_lapb_address = -1;
38 static int hf_lapb_control = -1;
40 static gint ett_lapb = -1;
41 static gint ett_lapb_control = -1;
43 static dissector_handle_t x25_dir_handle;
46 dissect_lapb(tvbuff_t *tvb, packet_info *pinfo, proto_tree *tree)
48 proto_tree *lapb_tree, *ti;
53 if (check_col(pinfo->cinfo, COL_PROTOCOL))
54 col_set_str(pinfo->cinfo, COL_PROTOCOL, "LAPB");
55 if (check_col(pinfo->cinfo, COL_INFO))
56 col_clear(pinfo->cinfo, COL_INFO);
58 if (pinfo->pseudo_header->x25.flags & FROM_DCE) {
59 if(check_col(pinfo->cinfo, COL_RES_DL_DST))
60 col_set_str(pinfo->cinfo, COL_RES_DL_DST, "DTE");
61 if(check_col(pinfo->cinfo, COL_RES_DL_SRC))
62 col_set_str(pinfo->cinfo, COL_RES_DL_SRC, "DCE");
65 if(check_col(pinfo->cinfo, COL_RES_DL_DST))
66 col_set_str(pinfo->cinfo, COL_RES_DL_DST, "DCE");
67 if(check_col(pinfo->cinfo, COL_RES_DL_SRC))
68 col_set_str(pinfo->cinfo, COL_RES_DL_SRC, "DTE");
71 byte0 = tvb_get_guint8(tvb, 0);
73 if (byte0 != 0x01 && byte0 != 0x03) /* invalid LAPB frame */
75 if (check_col(pinfo->cinfo, COL_INFO))
76 col_set_str(pinfo->cinfo, COL_INFO, "Invalid LAPB frame");
78 ti = proto_tree_add_protocol_format(tree, proto_lapb, tvb, 0, -1,
79 "Invalid LAPB frame");
83 if (((pinfo->pseudo_header->x25.flags & FROM_DCE) && byte0 == 0x01) ||
84 (!(pinfo->pseudo_header->x25.flags & FROM_DCE) && byte0 == 0x03))
90 ti = proto_tree_add_protocol_format(tree, proto_lapb, tvb, 0, 2,
92 lapb_tree = proto_item_add_subtree(ti, ett_lapb);
93 proto_tree_add_uint_format(lapb_tree, hf_lapb_address, tvb, 0, 1, byte0,
94 "Address: 0x%02X", byte0);
99 dissect_xdlc_control(tvb, 1, pinfo, lapb_tree, hf_lapb_control,
100 ett_lapb_control, is_response, FALSE);
102 /* not end of frame ==> X.25 */
103 if (tvb_reported_length(tvb) > 2) {
104 next_tvb = tvb_new_subset(tvb, 2, -1, -1);
105 call_dissector(x25_dir_handle, next_tvb, pinfo, tree);
110 proto_register_lapb(void)
112 static hf_register_info hf[] = {
114 { "Address Field", "lapb.address", FT_UINT8, BASE_HEX, NULL, 0x0,
118 { "Control Field", "lapb.control", FT_UINT8, BASE_HEX, NULL, 0x0,
119 "Control field", HFILL }},
121 static gint *ett[] = {
126 proto_lapb = proto_register_protocol("Link Access Procedure Balanced (LAPB)",
128 proto_register_field_array (proto_lapb, hf, array_length(hf));
129 proto_register_subtree_array(ett, array_length(ett));
131 register_dissector("lapb", dissect_lapb, proto_lapb);
135 proto_reg_handoff_lapb(void)
137 dissector_handle_t lapb_handle;
140 * Get a handle for the X.25 dissector; we will be getting an
141 * X.25 pseudo-header, so call the dissector that can handle it.
143 x25_dir_handle = find_dissector("x.25_dir");
145 lapb_handle = find_dissector("lapb");
146 dissector_add("wtap_encap", WTAP_ENCAP_LAPB, lapb_handle);