/* 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/tfs.h>

#include <wsutil/array.h>

#include "packet-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:

 */