/* packet-lapb.c
 * Routines for lapb frame disassembly
 * Olivier Abad <oabad@noos.fr>
 *
 * $Id: packet-lapb.c 12127 2004-09-28 23:48:02Z guy $
 *
 * Ethereal - Network traffic analyzer
 * By Gerald Combs <gerald@ethereal.com>
 * Copyright 1998
 *
 * This program is free software; you can redistribute it and/or
 * modify it under the terms of the GNU General Public License
 * as published by the Free Software Foundation; either version 2
 * of the License, or (at your option) any later version.
 *
 * This program is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 * GNU General Public License for more details.
 *
 * You should have received a copy of the GNU General Public License
 * along with this program; if not, write to the Free Software
 * Foundation, Inc., 59 Temple Place - Suite 330, Boston, MA  02111-1307, USA.
 */

#ifdef HAVE_CONFIG_H
# include "config.h"
#endif

#include <stdio.h>
#include <glib.h>
#include <string.h>
#include <epan/packet.h>
#include <epan/xdlc.h>

static int proto_lapb = -1;
static int hf_lapb_address = -1;
static int hf_lapb_control = -1;
static int hf_lapb_n_r = -1;
static int hf_lapb_n_s = -1;
static int hf_lapb_p = -1;
static int hf_lapb_f = -1;
static int hf_lapb_s_ftype = -1;
static int hf_lapb_u_modifier_cmd = -1;
static int hf_lapb_u_modifier_resp = -1;
static int hf_lapb_ftype_i = -1;
static int hf_lapb_ftype_s_u = -1;

static gint ett_lapb = -1;
static gint ett_lapb_control = -1;

static dissector_handle_t x25_dir_handle;
static dissector_handle_t x25_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 void
dissect_lapb(tvbuff_t *tvb, packet_info *pinfo, proto_tree *tree)
{
    proto_tree		*lapb_tree, *ti;
    int			is_response;
    guint8		byte0;
    tvbuff_t		*next_tvb;

    if (check_col(pinfo->cinfo, COL_PROTOCOL))
	col_set_str(pinfo->cinfo, COL_PROTOCOL, "LAPB");
    if (check_col(pinfo->cinfo, COL_INFO))
	col_clear(pinfo->cinfo, COL_INFO);

    switch (pinfo->p2p_dir) {

    case P2P_DIR_SENT:
	if(check_col(pinfo->cinfo, COL_RES_DL_SRC))
	    col_set_str(pinfo->cinfo, COL_RES_DL_SRC, "DTE");
	if(check_col(pinfo->cinfo, COL_RES_DL_DST))
	    col_set_str(pinfo->cinfo, COL_RES_DL_DST, "DCE");
	break;

    case P2P_DIR_RECV:
	if(check_col(pinfo->cinfo, COL_RES_DL_SRC))
	    col_set_str(pinfo->cinfo, COL_RES_DL_SRC, "DCE");
	if(check_col(pinfo->cinfo, COL_RES_DL_DST))
	    col_set_str(pinfo->cinfo, COL_RES_DL_DST, "DTE");
	break;

    default:
	if(check_col(pinfo->cinfo, COL_RES_DL_SRC))
	    col_set_str(pinfo->cinfo, COL_RES_DL_SRC, "N/A");
	if(check_col(pinfo->cinfo, COL_RES_DL_DST))
	    col_set_str(pinfo->cinfo, COL_RES_DL_DST, "N/A");
	break;
    }

    byte0 = tvb_get_guint8(tvb, 0);

    if (byte0 != 0x01 && byte0 != 0x03) /* invalid LAPB frame */
    {
	if (check_col(pinfo->cinfo, COL_INFO))
	    col_set_str(pinfo->cinfo, COL_INFO, "Invalid LAPB frame");
	if (tree)
	    ti = proto_tree_add_protocol_format(tree, proto_lapb, tvb, 0, -1,
			    "Invalid LAPB frame");
	return;
    }

    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;
    }

    if (tree) {
	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_format(lapb_tree, hf_lapb_address, tvb, 0, 1, byte0,
				       "Address: 0x%02X", byte0);
    }
    else
        lapb_tree = NULL;

    dissect_xdlc_control(tvb, 1, pinfo, lapb_tree, hf_lapb_control,
	    ett_lapb_control, &lapb_cf_items, NULL, NULL, NULL,
	    is_response, FALSE, FALSE);

    /* not end of frame ==> X.25 */
    if (tvb_reported_length(tvb) > 2) {
	next_tvb = tvb_new_subset(tvb, 2, -1, -1);
	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;
	}
    }
}

void
proto_register_lapb(void)
{
    static hf_register_info hf[] = {
	{ &hf_lapb_address,
	  { "Address Field", "lapb.address", FT_UINT8, BASE_HEX, NULL, 0x0,
	  	"Address", HFILL }},

	{ &hf_lapb_control,
	  { "Control Field", "lapb.control", FT_UINT8, BASE_HEX, NULL, 0x0,
	  	"Control field", HFILL }},

	{ &hf_lapb_n_r,
	    { "N(R)", "lapb.control.n_r", FT_UINT8, BASE_DEC,
	      NULL, XDLC_N_R_MASK, "", HFILL }},

	{ &hf_lapb_n_s,
	    { "N(S)", "lapb.control.n_s", FT_UINT8, BASE_DEC,
	      NULL, XDLC_N_S_MASK, "", HFILL }},

	{ &hf_lapb_p,
	    { "Poll", "lapb.control.p", FT_BOOLEAN, 8,
	      TFS(&flags_set_truth), XDLC_P_F, "", HFILL }},

	{ &hf_lapb_f,
	    { "Final", "lapb.control.f", FT_BOOLEAN, 8,
	      TFS(&flags_set_truth), XDLC_P_F, "", HFILL }},

	{ &hf_lapb_s_ftype,
	    { "Supervisory frame type", "lapb.control.s_ftype", FT_UINT8, BASE_HEX,
	      VALS(stype_vals), XDLC_S_FTYPE_MASK, "", HFILL }},

	{ &hf_lapb_u_modifier_cmd,
	    { "Command", "lapb.control.u_modifier_cmd", FT_UINT8, BASE_HEX,
	      VALS(modifier_vals_cmd), XDLC_U_MODIFIER_MASK, "", HFILL }},

	{ &hf_lapb_u_modifier_resp,
	    { "Response", "lapb.control.u_modifier_resp", FT_UINT8, BASE_HEX,
	      VALS(modifier_vals_resp), XDLC_U_MODIFIER_MASK, "", HFILL }},

	{ &hf_lapb_ftype_i,
	    { "Frame type", "lapb.control.ftype", FT_UINT8, BASE_HEX,
	      VALS(ftype_vals), XDLC_I_MASK, "", HFILL }},

	{ &hf_lapb_ftype_s_u,
	    { "Frame type", "lapb.control.ftype", FT_UINT8, BASE_HEX,
	      VALS(ftype_vals), XDLC_S_U_MASK, "", HFILL }},
    };
    static gint *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));

    register_dissector("lapb", dissect_lapb, proto_lapb);
}

void
proto_reg_handoff_lapb(void)
{
    dissector_handle_t lapb_handle;

    /*
     * 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("x.25_dir");
    x25_handle = find_dissector("x.25");

    lapb_handle = find_dissector("lapb");
    dissector_add("wtap_encap", WTAP_ENCAP_LAPB, lapb_handle);
}
