2 * Routines for lapb frame disassembly
3 * Olivier Abad <oabad@noos.fr>
5 * $Id: packet-lapb.c,v 1.40 2003/09/26 08:19:55 guy 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;
44 static dissector_handle_t x25_handle;
47 dissect_lapb(tvbuff_t *tvb, packet_info *pinfo, proto_tree *tree)
49 proto_tree *lapb_tree, *ti;
54 if (check_col(pinfo->cinfo, COL_PROTOCOL))
55 col_set_str(pinfo->cinfo, COL_PROTOCOL, "LAPB");
56 if (check_col(pinfo->cinfo, COL_INFO))
57 col_clear(pinfo->cinfo, COL_INFO);
59 switch (pinfo->p2p_dir) {
62 if(check_col(pinfo->cinfo, COL_RES_DL_SRC))
63 col_set_str(pinfo->cinfo, COL_RES_DL_SRC, "DTE");
64 if(check_col(pinfo->cinfo, COL_RES_DL_DST))
65 col_set_str(pinfo->cinfo, COL_RES_DL_DST, "DCE");
69 if(check_col(pinfo->cinfo, COL_RES_DL_SRC))
70 col_set_str(pinfo->cinfo, COL_RES_DL_SRC, "DCE");
71 if(check_col(pinfo->cinfo, COL_RES_DL_DST))
72 col_set_str(pinfo->cinfo, COL_RES_DL_DST, "DTE");
76 if(check_col(pinfo->cinfo, COL_RES_DL_SRC))
77 col_set_str(pinfo->cinfo, COL_RES_DL_SRC, "N/A");
78 if(check_col(pinfo->cinfo, COL_RES_DL_DST))
79 col_set_str(pinfo->cinfo, COL_RES_DL_DST, "N/A");
83 byte0 = tvb_get_guint8(tvb, 0);
85 if (byte0 != 0x01 && byte0 != 0x03) /* invalid LAPB frame */
87 if (check_col(pinfo->cinfo, COL_INFO))
88 col_set_str(pinfo->cinfo, COL_INFO, "Invalid LAPB frame");
90 ti = proto_tree_add_protocol_format(tree, proto_lapb, tvb, 0, -1,
91 "Invalid LAPB frame");
95 switch (pinfo->p2p_dir) {
113 * XXX - should we base this on the source and destination
114 * addresses? The problem is that we can tell one direction
115 * from another with that, but we can't say which is DTE->DCE
116 * and which is DCE->DTE.
123 ti = proto_tree_add_protocol_format(tree, proto_lapb, tvb, 0, 2,
125 lapb_tree = proto_item_add_subtree(ti, ett_lapb);
126 proto_tree_add_uint_format(lapb_tree, hf_lapb_address, tvb, 0, 1, byte0,
127 "Address: 0x%02X", byte0);
132 dissect_xdlc_control(tvb, 1, pinfo, lapb_tree, hf_lapb_control,
133 ett_lapb_control, is_response, FALSE, FALSE);
135 /* not end of frame ==> X.25 */
136 if (tvb_reported_length(tvb) > 2) {
137 next_tvb = tvb_new_subset(tvb, 2, -1, -1);
138 switch (pinfo->p2p_dir) {
142 call_dissector(x25_dir_handle, next_tvb, pinfo, tree);
146 call_dissector(x25_handle, next_tvb, pinfo, tree);
153 proto_register_lapb(void)
155 static hf_register_info hf[] = {
157 { "Address Field", "lapb.address", FT_UINT8, BASE_HEX, NULL, 0x0,
161 { "Control Field", "lapb.control", FT_UINT8, BASE_HEX, NULL, 0x0,
162 "Control field", HFILL }},
164 static gint *ett[] = {
169 proto_lapb = proto_register_protocol("Link Access Procedure Balanced (LAPB)",
171 proto_register_field_array (proto_lapb, hf, array_length(hf));
172 proto_register_subtree_array(ett, array_length(ett));
174 register_dissector("lapb", dissect_lapb, proto_lapb);
178 proto_reg_handoff_lapb(void)
180 dissector_handle_t lapb_handle;
183 * Get handles for the X.25 dissectors; we don't get an X.25
184 * pseudo-header for LAPB-over-Ethernet, but we do get it
187 x25_dir_handle = find_dissector("x.25_dir");
188 x25_handle = find_dissector("x.25");
190 lapb_handle = find_dissector("lapb");
191 dissector_add("wtap_encap", WTAP_ENCAP_LAPB, lapb_handle);