/* packet-lapdm.c
 * Routines for LAPDm frame disassembly
 * Duncan Salerno <duncan.salerno@googlemail.com>
 *
 * $Id: packet-lapdm.c 35705 2011-01-30 21:01:07Z stig $
 *
 * Wireshark - Network traffic analyzer
 * By Gerald Combs <gerald@wireshark.org>
 * 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.
 */

/* LAPDm references:
 *
 * Mobile Station - Base Stations System (MS - BSS) Interface Data Link (DL) Layer Specification
 * Base Station Controller - Base Transceiver Station (BSC - BTS) interface; Layer 2 specification
 * http://www.3gpp.org/ftp/Specs/html-info/44006.htm
 *
 * From 3GPP TS 44.006:
 *
 * LAPDm is used for information sent on the control channels BCCH, AGCH, NCH,
 * PCH, FACCH, SACCH and SDCCH as defined in 3GPP TS 44.003.
 *
 * AGCH, NCH and PCH are sometimes referred to by the collective name CCCH.
 * FACCH, SACCH and SDCCH are, similarly, referred to by the collective name DCCH.
 *
 * Format A is used on DCCHs for frames where there is no information field.
 * Formats B, Bter and B4 are used on DCCHs for frames containing an information field:
 * Format Bter is used on request of higher layers if and only if short L2 header type 1 is
 * supported and a UI command is to be transmitted on SAPI 0;
 * Format B4 is used for UI frames transmitted by the network on SACCH;
 * Format B is applied in all other cases.
 * Format Bbis is used only on BCCH, PCH, NCH, and AGCH.
 * In addition there is a Format C for transmission of random access signals.
 *
 * This module currently supports A, B, B4
 * In the future will support Bter
 * Bbis and C should be supported elsewhere
 */

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

#include <glib.h>
#include <epan/packet.h>
#include <epan/prefs.h>
#include <epan/xdlc.h>
#include <epan/reassemble.h>

static int proto_lapdm = -1;
static int hf_lapdm_address = -1;
static int hf_lapdm_ea = -1;
static int hf_lapdm_cr = -1;
static int hf_lapdm_sapi = -1;
static int hf_lapdm_lpd = -1;

static int hf_lapdm_control = -1;
static int hf_lapdm_n_r = -1;
static int hf_lapdm_n_s = -1;
static int hf_lapdm_p = -1;
static int hf_lapdm_f = -1;
static int hf_lapdm_s_ftype = -1;
static int hf_lapdm_u_modifier_cmd = -1;
static int hf_lapdm_u_modifier_resp = -1;
static int hf_lapdm_ftype_i = -1;
static int hf_lapdm_ftype_s_u = -1;

static int hf_lapdm_length = -1;
static int hf_lapdm_el = -1;
static int hf_lapdm_m = -1;
static int hf_lapdm_len = -1;

/*
 * LAPDm fragment handling
 */
static int hf_lapdm_fragments = -1;
static int hf_lapdm_fragment = -1;
static int hf_lapdm_fragment_overlap = -1;
static int hf_lapdm_fragment_overlap_conflicts = -1;
static int hf_lapdm_fragment_multiple_tails = -1;
static int hf_lapdm_fragment_too_long_fragment = -1;
static int hf_lapdm_fragment_error = -1;
static int hf_lapdm_fragment_count = -1;
static int hf_lapdm_reassembled_in = -1;
static int hf_lapdm_reassembled_length = -1;

static gint ett_lapdm = -1;
static gint ett_lapdm_address = -1;
static gint ett_lapdm_control = -1;
static gint ett_lapdm_length = -1;
static gint ett_lapdm_fragment = -1;
static gint ett_lapdm_fragments = -1;

static GHashTable *lapdm_fragment_table = NULL;
static GHashTable *lapdm_reassembled_table = NULL;

static dissector_table_t lapdm_sapi_dissector_table;

static dissector_handle_t data_handle;

static gboolean reassemble_lapdm = TRUE;

/*
 * Bits in the address field.
 */
#define	LAPDM_SAPI		0x1c	/* Service Access Point Identifier */
#define	LAPDM_SAPI_SHIFT	2
#define	LAPDM_CR		0x02	/* Command/Response bit */
#define	LAPDM_EA		0x01	/* First Address Extension bit */
#define	LAPDM_LPD		0x60	/* Link Protocol Discriminator */

/*
 * Bits in the length field.
 */
#define	LAPDM_EL		0x01	/* Extended Length = 1 */
#define	LAPDM_M			0x02	/* More fragments */
#define	LAPDM_M_SHIFT		1
#define	LAPDM_LEN		0xfc	/* Length */
#define	LAPDM_LEN_SHIFT		2

#define LAPDM_HEADER_LEN 3

#define LAPDM_SAPI_RR_CC_MM	0
#define LAPDM_SAPI_SMS		3

/* Used only for U frames */
static const xdlc_cf_items lapdm_cf_items = {
    &hf_lapdm_n_r,
    &hf_lapdm_n_s,
    &hf_lapdm_p,
    &hf_lapdm_f,
    &hf_lapdm_s_ftype,
    &hf_lapdm_u_modifier_cmd,
    &hf_lapdm_u_modifier_resp,
    &hf_lapdm_ftype_i,
    &hf_lapdm_ftype_s_u
};

static const value_string lapdm_ea_vals[] = {
    { 0,		"More octets" },
    { 1,		"Final octet" },
    { 0,		NULL }
};

static const value_string lapdm_sapi_vals[] = {
    { LAPDM_SAPI_RR_CC_MM,	"RR/MM/CC" },
    { LAPDM_SAPI_SMS,		"SMS/SS" },
    { 0,			NULL }
};

static const value_string lapdm_lpd_vals[] = {
    { 0,		"Normal GSM" },
    { 1,		"Cell broadcast service" },
    { 0,		NULL }
};

static const value_string lapdm_m_vals[] = {
    { 0,		"Last segment" },
    { 1,		"More segments" },
    { 0,		NULL }
};

static const value_string lapdm_el_vals[] = {
    { 0,		"More octets" },
    { 1,		"Final octet" },
    { 0,		NULL }
};


static const fragment_items lapdm_frag_items = {
    /* Fragment subtrees */
    &ett_lapdm_fragment,
    &ett_lapdm_fragments,
    /* Fragment fields */
    &hf_lapdm_fragments,
    &hf_lapdm_fragment,
    &hf_lapdm_fragment_overlap,
    &hf_lapdm_fragment_overlap_conflicts,
    &hf_lapdm_fragment_multiple_tails,
    &hf_lapdm_fragment_too_long_fragment,
    &hf_lapdm_fragment_error,
    &hf_lapdm_fragment_count,
    /* Reassembled in field */
    &hf_lapdm_reassembled_in,
    /* Reassembled length field */
    &hf_lapdm_reassembled_length,
    /* Tag */
    "fragments"
};

static void
lapdm_defragment_init (void)
{
    fragment_table_init (&lapdm_fragment_table);
    reassembled_table_init(&lapdm_reassembled_table);
}


static void
dissect_lapdm(tvbuff_t *tvb, packet_info *pinfo, proto_tree *tree)
{
    proto_tree *lapdm_tree, *addr_tree, *length_tree;
    proto_item *lapdm_ti, *addr_ti, *length_ti;
    guint8 addr, length, cr, sapi, len, n_s;
    int control;
    gboolean m;
    tvbuff_t *payload;
    int available_length;
    gboolean is_response = FALSE;

    /* Check that there's enough data */
    if (tvb_length(tvb) < LAPDM_HEADER_LEN)
        return;

    col_set_str(pinfo->cinfo, COL_PROTOCOL, "LAPDm");

    addr = tvb_get_guint8(tvb, 0);
    length = tvb_get_guint8(tvb, 2);

    cr = addr & LAPDM_CR;
    if (pinfo->p2p_dir == P2P_DIR_RECV) {
        is_response = cr ? FALSE : TRUE;
    }
    else if (pinfo->p2p_dir == P2P_DIR_SENT) {
        is_response = cr ? TRUE : FALSE;
    }

    if (tree) {
        lapdm_ti = proto_tree_add_item(tree, proto_lapdm, tvb, 0, LAPDM_HEADER_LEN, FALSE);
        lapdm_tree = proto_item_add_subtree(lapdm_ti, ett_lapdm);

        addr_ti = proto_tree_add_uint(lapdm_tree, hf_lapdm_address, tvb, 0, 1, addr);
        addr_tree = proto_item_add_subtree(addr_ti, ett_lapdm_address);

        proto_tree_add_uint(addr_tree, hf_lapdm_lpd, tvb, 0, 1, addr);
        proto_tree_add_uint(addr_tree, hf_lapdm_sapi, tvb, 0, 1, addr);
        proto_tree_add_uint(addr_tree, hf_lapdm_cr, tvb, 0, 1, addr);
        proto_tree_add_uint(addr_tree, hf_lapdm_ea, tvb, 0, 1, addr);
    }
    else {
        lapdm_ti = NULL;
        lapdm_tree = NULL;
    }

    control = dissect_xdlc_control(tvb, 1, pinfo, lapdm_tree, hf_lapdm_control,
              ett_lapdm_control, &lapdm_cf_items, NULL /* LAPDm doesnt support extended */, NULL, NULL,
              is_response, FALSE, FALSE);

    if (tree) {
        length_ti = proto_tree_add_uint(lapdm_tree, hf_lapdm_length, tvb,
                    2, 1, length);
        length_tree = proto_item_add_subtree(length_ti, ett_lapdm_length);

        proto_tree_add_uint(length_tree, hf_lapdm_len, tvb, 2, 1, length);
        proto_tree_add_uint(length_tree, hf_lapdm_m, tvb, 2, 1, length);
        proto_tree_add_uint(length_tree, hf_lapdm_el, tvb, 2, 1, length);
    }

    sapi = (addr & LAPDM_SAPI) >> LAPDM_SAPI_SHIFT;
    len = (length & LAPDM_LEN) >> LAPDM_LEN_SHIFT;
    n_s = (control & XDLC_N_S_MASK) >> XDLC_N_S_SHIFT;
    m = (length & LAPDM_M) >> LAPDM_M_SHIFT;
    available_length = tvb_length(tvb) - LAPDM_HEADER_LEN;

    /* No point in doing anything if no payload
     */
    if( !MIN(len, available_length) )
        return;

    payload = tvb_new_subset(tvb, LAPDM_HEADER_LEN, MIN(len,available_length), -1);

    /* Potentially segmented I frame
     */
    if( (control & XDLC_I_MASK) == XDLC_I && reassemble_lapdm )
    {
            fragment_data *fd_m = NULL;
            tvbuff_t *reassembled = NULL;
            gboolean save_fragmented = pinfo->fragmented;

            pinfo->fragmented = m;
            /* This doesn't seem the best way of doing it as doesn't
               take N(S) into account, but N(S) isn't always 0 for
               the first fragment!
             */
            fd_m = fragment_add_seq_next (payload, 0, pinfo,
                                0, /* guint32 ID for fragments belonging together */
                                lapdm_fragment_table, /* list of message fragments */
                                lapdm_reassembled_table, /* list of reassembled messages */
                                /*n_s guint32 fragment sequence number */
                                len, /* guint32 fragment length */
                                m); /* More fragments? */

            reassembled = process_reassembled_data(payload, 0, pinfo,
                    "Reassembled LAPDm", fd_m, &lapdm_frag_items,
                    NULL, lapdm_tree);

            /* Reassembled into this packet
             */
            if (fd_m && pinfo->fd->num == fd_m->reassembled_in) {
                    if (!dissector_try_uint(lapdm_sapi_dissector_table, sapi,
                                reassembled, pinfo, tree))
                        call_dissector(data_handle, reassembled, pinfo, tree);
            }
            else {
                col_append_str(pinfo->cinfo, COL_INFO, " (Fragment)");
                if (tree) {
                    proto_tree_add_text(lapdm_tree, payload, 0, -1, "Fragment Data");
                }
            }

            /* Now reset fragmentation information in pinfo
             */
            pinfo->fragmented = save_fragmented;
    }
    else
    {
        /* Whole packet
           If we have some data, try and dissect it (only happens for UI, SABM, UA or I frames)
         */
        if (!dissector_try_uint(lapdm_sapi_dissector_table, sapi,
                payload, pinfo, tree))
            call_dissector(data_handle,payload, pinfo, tree);
    }
}

void
proto_register_lapdm(void)
{
    static hf_register_info hf[] = {

        { &hf_lapdm_address,
        { "Address Field", "lapdm.address_field", FT_UINT8, BASE_HEX, NULL, 0x0,
        "Address", HFILL }},

        { &hf_lapdm_ea,
        { "EA", "lapdm.ea", FT_UINT8, BASE_DEC, VALS(lapdm_ea_vals), LAPDM_EA,
        "Address field extension bit", HFILL }},

        { &hf_lapdm_cr,
        { "C/R", "lapdm.cr", FT_UINT8, BASE_DEC, NULL, LAPDM_CR,
        "Command/response field bit", HFILL }},

        { &hf_lapdm_lpd,
        { "LPD", "lapdm.lpd", FT_UINT8, BASE_DEC, VALS(lapdm_lpd_vals), LAPDM_LPD,
        "Link Protocol Discriminator", HFILL }},

        { &hf_lapdm_sapi,
        { "SAPI", "lapdm.sapi", FT_UINT8, BASE_DEC, VALS(lapdm_sapi_vals), LAPDM_SAPI,
        "Service access point identifier", HFILL }},

        { &hf_lapdm_control,
        { "Control Field", "lapdm.control_field", FT_UINT8, BASE_HEX, NULL, 0x0,
        NULL, HFILL }},

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

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

        { &hf_lapdm_p,
        { "Poll", "lapdm.control.p", FT_BOOLEAN, 8,
        TFS(&tfs_true_false), XDLC_P_F, NULL, HFILL }},

        { &hf_lapdm_f,
        { "Final", "lapdm.control.f", FT_BOOLEAN, 8,
        TFS(&tfs_true_false), XDLC_P_F, NULL, HFILL }},

        { &hf_lapdm_s_ftype,
        { "Supervisory frame type", "lapdm.control.s_ftype", FT_UINT8, BASE_HEX,
        VALS(stype_vals), XDLC_S_FTYPE_MASK, NULL, HFILL }},

        { &hf_lapdm_u_modifier_cmd,
        { "Command", "lapdm.control.u_modifier_cmd", FT_UINT8, BASE_HEX,
        VALS(modifier_vals_cmd), XDLC_U_MODIFIER_MASK, NULL, HFILL }},

        { &hf_lapdm_u_modifier_resp,
        { "Response", "lapdm.control.u_modifier_resp", FT_UINT8, BASE_HEX,
        VALS(modifier_vals_resp), XDLC_U_MODIFIER_MASK, NULL, HFILL }},

        { &hf_lapdm_ftype_i,
        { "Frame type", "lapdm.control.ftype", FT_UINT8, BASE_HEX,
        VALS(ftype_vals), XDLC_I_MASK, NULL, HFILL }},

        { &hf_lapdm_ftype_s_u,
        { "Frame type", "lapdm.control.ftype", FT_UINT8, BASE_HEX,
        VALS(ftype_vals), XDLC_S_U_MASK, NULL, HFILL }},

        { &hf_lapdm_length,
        { "Length Field", "lapdm.length_field", FT_UINT8, BASE_HEX,
        NULL, 0x0, NULL, HFILL }},

        { &hf_lapdm_el,
        { "EL", "lapdm.el", FT_UINT8, BASE_DEC,
        VALS(lapdm_el_vals), LAPDM_EL, "Length indicator field extension bit", HFILL }},

        { &hf_lapdm_m,
        { "M", "lapdm.m", FT_UINT8, BASE_DEC,
        VALS(lapdm_m_vals), LAPDM_M, "More data bit", HFILL }},

        { &hf_lapdm_len,
        { "Length", "lapdm.length", FT_UINT8, BASE_DEC,
        NULL, LAPDM_LEN, "Length indicator", HFILL }},

	/* Fragment reassembly
	 */
        { &hf_lapdm_fragments,
        { "Message fragments", "lapdm.fragments", FT_NONE, BASE_NONE,
        NULL, 0x00, "LAPDm Message fragments", HFILL }},

        { &hf_lapdm_fragment,
        { "Message fragment", "lapdm.fragment", FT_FRAMENUM, BASE_NONE,
        NULL, 0x00, "LAPDm Message fragment", HFILL }},

        { &hf_lapdm_fragment_overlap,
        { "Message fragment overlap", "lapdm.fragment.overlap", FT_BOOLEAN, BASE_NONE,
        NULL, 0x0, "LAPDm Message fragment overlaps with other fragment(s)", HFILL }},

        { &hf_lapdm_fragment_overlap_conflicts,
        { "Message fragment overlapping with conflicting data", "lapdm.fragment.overlap.conflicts", FT_BOOLEAN, BASE_NONE,
        NULL, 0x0, "LAPDm Message fragment overlaps with conflicting data", HFILL }},

        { &hf_lapdm_fragment_multiple_tails,
        { "Message has multiple tail fragments", "lapdm.fragment.multiple_tails", FT_BOOLEAN, BASE_NONE,
        NULL, 0x0, "LAPDm Message fragment has multiple tail fragments", HFILL }},

        { &hf_lapdm_fragment_too_long_fragment,
        { "Message fragment too long", "lapdm.fragment.too_long_fragment", FT_BOOLEAN, BASE_NONE,
        NULL, 0x0, "LAPDm Message fragment data goes beyond the packet end", HFILL }},

        { &hf_lapdm_fragment_error,
        { "Message defragmentation error", "lapdm.fragment.error", FT_FRAMENUM, BASE_NONE,
        NULL, 0x00, "LAPDm Message defragmentation error due to illegal fragments", HFILL }},

        { &hf_lapdm_fragment_count,
        { "Message fragment count", "lapdm.fragment.count", FT_UINT32, BASE_DEC,
        NULL, 0x00, NULL, HFILL }},

        { &hf_lapdm_reassembled_in,
        { "Reassembled in", "lapdm.reassembled.in", FT_FRAMENUM, BASE_NONE,
	NULL, 0x00, "LAPDm Message has been reassembled in this packet.", HFILL }},

        { &hf_lapdm_reassembled_length,
        { "Reassembled LAPDm length", "lapdm.reassembled.length", FT_UINT32, BASE_DEC,
        NULL, 0x00, "The total length of the reassembled payload", HFILL }}

    };
    static gint *ett[] = {
        &ett_lapdm,
        &ett_lapdm_address,
        &ett_lapdm_control,
        &ett_lapdm_length,
        &ett_lapdm_fragment,
        &ett_lapdm_fragments
    };

    module_t *lapdm_module;

    proto_lapdm = proto_register_protocol("Link Access Procedure, Channel Dm (LAPDm)", "LAPDm", "lapdm");
    proto_register_field_array (proto_lapdm, hf, array_length(hf));
    proto_register_subtree_array(ett, array_length(ett));

    register_dissector("lapdm", dissect_lapdm, proto_lapdm);

    lapdm_sapi_dissector_table = register_dissector_table("lapdm.sapi", "LAPDm SAPI", FT_UINT8, BASE_DEC);

    lapdm_module = prefs_register_protocol(proto_lapdm, NULL);
    prefs_register_bool_preference(lapdm_module, "reassemble",
        "Reassemble fragmented LAPDm packets",
        "Whether the dissector should defragment LAPDm messages spanning multiple packets.",
        &reassemble_lapdm);
    register_init_routine (lapdm_defragment_init);
}

void
proto_reg_handoff_lapdm(void)
{
    data_handle = find_dissector("data");
}

