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/* packet-lapb.c
* Routines for lapb frame disassembly
* Olivier Abad <oabad@noos.fr>
*
* Wireshark - Network traffic analyzer
* By Gerald Combs <gerald@wireshark.org>
* Copyright 1998
*
* SPDX-License-Identifier: GPL-2.0-or-later
*/
#include "config.h"
#include <epan/packet.h>
#include <wiretap/wtap.h>
#include <epan/xdlc.h>
void proto_register_lapb(void);
void proto_reg_handoff_lapb(void);
static int proto_lapb;
static int hf_lapb_address;
static int hf_lapb_control;
static int hf_lapb_n_r;
static int hf_lapb_n_s;
static int hf_lapb_p;
static int hf_lapb_f;
static int hf_lapb_s_ftype;
static int hf_lapb_u_modifier_cmd;
static int hf_lapb_u_modifier_resp;
static int hf_lapb_ftype_i;
static int hf_lapb_ftype_s_u;
static int ett_lapb;
static int ett_lapb_control;
static dissector_handle_t x25_dir_handle;
static dissector_handle_t x25_handle;
static dissector_handle_t lapb_handle;
static const xdlc_cf_items lapb_cf_items = {
&hf_lapb_n_r,
&hf_lapb_n_s,
&hf_lapb_p,
&hf_lapb_f,
&hf_lapb_s_ftype,
&hf_lapb_u_modifier_cmd,
&hf_lapb_u_modifier_resp,
&hf_lapb_ftype_i,
&hf_lapb_ftype_s_u
};
static int
dissect_lapb(tvbuff_t *tvb, packet_info *pinfo, proto_tree *tree, void* data _U_)
{
proto_tree *lapb_tree, *ti;
uint16_t control;
int is_response;
uint8_t byte0;
tvbuff_t *next_tvb;
col_set_str(pinfo->cinfo, COL_PROTOCOL, "LAPB");
col_clear(pinfo->cinfo, COL_INFO);
switch (pinfo->p2p_dir) {
case P2P_DIR_SENT:
col_set_str(pinfo->cinfo, COL_RES_DL_SRC, "DTE");
col_set_str(pinfo->cinfo, COL_RES_DL_DST, "DCE");
break;
case P2P_DIR_RECV:
col_set_str(pinfo->cinfo, COL_RES_DL_SRC, "DCE");
col_set_str(pinfo->cinfo, COL_RES_DL_DST, "DTE");
break;
default:
col_set_str(pinfo->cinfo, COL_RES_DL_SRC, "N/A");
col_set_str(pinfo->cinfo, COL_RES_DL_DST, "N/A");
break;
}
byte0 = tvb_get_uint8(tvb, 0);
if (byte0 != 0x01 && byte0 != 0x03 && byte0 != 0x07 && byte0 != 0x0f) /* invalid LAPB frame */
{
col_set_str(pinfo->cinfo, COL_INFO, "Invalid LAPB frame");
if (tree)
proto_tree_add_protocol_format(tree, proto_lapb, tvb, 0, -1,
"Invalid LAPB frame");
return 1;
}
switch (pinfo->p2p_dir) {
case P2P_DIR_SENT:
if (byte0 == 0x03)
is_response = true;
else
is_response = false;
break;
case P2P_DIR_RECV:
if (byte0 == 0x01)
is_response = true;
else
is_response = false;
break;
default:
/*
* XXX - should we base this on the source and destination
* addresses? The problem is that we can tell one direction
* from another with that, but we can't say which is DTE->DCE
* and which is DCE->DTE.
*/
is_response = false;
break;
}
ti = proto_tree_add_protocol_format(tree, proto_lapb, tvb, 0, 2,
"LAPB");
lapb_tree = proto_item_add_subtree(ti, ett_lapb);
proto_tree_add_uint(lapb_tree, hf_lapb_address, tvb, 0, 1, byte0);
control = dissect_xdlc_control(tvb, 1, pinfo, lapb_tree, hf_lapb_control,
ett_lapb_control, &lapb_cf_items, NULL, NULL, NULL,
is_response, false, false);
/* information frame ==> X.25 */
if (XDLC_IS_INFORMATION(control)) {
next_tvb = tvb_new_subset_remaining(tvb, 2);
switch (pinfo->p2p_dir) {
case P2P_DIR_SENT:
case P2P_DIR_RECV:
call_dissector(x25_dir_handle, next_tvb, pinfo, tree);
break;
default:
call_dissector(x25_handle, next_tvb, pinfo, tree);
break;
}
}
return tvb_captured_length(tvb);
}
void
proto_register_lapb(void)
{
static hf_register_info hf[] = {
{ &hf_lapb_address,
{ "Address", "lapb.address", FT_UINT8, BASE_HEX, NULL, 0x0,
NULL, HFILL }},
{ &hf_lapb_control,
{ "Control Field", "lapb.control", FT_UINT8, BASE_HEX, NULL, 0x0,
NULL, HFILL }},
{ &hf_lapb_n_r,
{ "N(R)", "lapb.control.n_r", FT_UINT8, BASE_DEC,
NULL, XDLC_N_R_MASK, NULL, HFILL }},
{ &hf_lapb_n_s,
{ "N(S)", "lapb.control.n_s", FT_UINT8, BASE_DEC,
NULL, XDLC_N_S_MASK, NULL, HFILL }},
{ &hf_lapb_p,
{ "Poll", "lapb.control.p", FT_BOOLEAN, 8,
TFS(&tfs_set_notset), XDLC_P_F, NULL, HFILL }},
{ &hf_lapb_f,
{ "Final", "lapb.control.f", FT_BOOLEAN, 8,
TFS(&tfs_set_notset), XDLC_P_F, NULL, HFILL }},
{ &hf_lapb_s_ftype,
{ "Supervisory frame type", "lapb.control.s_ftype", FT_UINT8, BASE_HEX,
VALS(stype_vals), XDLC_S_FTYPE_MASK, NULL, HFILL }},
{ &hf_lapb_u_modifier_cmd,
{ "Command", "lapb.control.u_modifier_cmd", FT_UINT8, BASE_HEX,
VALS(modifier_vals_cmd), XDLC_U_MODIFIER_MASK, NULL, HFILL }},
{ &hf_lapb_u_modifier_resp,
{ "Response", "lapb.control.u_modifier_resp", FT_UINT8, BASE_HEX,
VALS(modifier_vals_resp), XDLC_U_MODIFIER_MASK, NULL, HFILL }},
{ &hf_lapb_ftype_i,
{ "Frame type", "lapb.control.ftype", FT_UINT8, BASE_HEX,
VALS(ftype_vals), XDLC_I_MASK, NULL, HFILL }},
{ &hf_lapb_ftype_s_u,
{ "Frame type", "lapb.control.ftype", FT_UINT8, BASE_HEX,
VALS(ftype_vals), XDLC_S_U_MASK, NULL, HFILL }},
};
static int *ett[] = {
&ett_lapb,
&ett_lapb_control,
};
proto_lapb = proto_register_protocol("Link Access Procedure Balanced (LAPB)",
"LAPB", "lapb");
proto_register_field_array (proto_lapb, hf, array_length(hf));
proto_register_subtree_array(ett, array_length(ett));
lapb_handle = register_dissector("lapb", dissect_lapb, proto_lapb);
}
void
proto_reg_handoff_lapb(void)
{
/*
* Get handles for the X.25 dissectors; we don't get an X.25
* pseudo-header for LAPB-over-Ethernet, but we do get it
* for raw LAPB.
*/
x25_dir_handle = find_dissector_add_dependency("x.25_dir", proto_lapb);
x25_handle = find_dissector_add_dependency("x.25", proto_lapb);
dissector_add_uint("wtap_encap", WTAP_ENCAP_LAPB, lapb_handle);
}
/*
* Editor modelines - https://www.wireshark.org/tools/modelines.html
*
* Local variables:
* c-basic-offset: 4
* tab-width: 8
* indent-tabs-mode: nil
* End:
*
* vi: set shiftwidth=4 tabstop=8 expandtab:
* :indentSize=4:tabSize=8:noTabs=true:
*/
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