/* packet-dect-dlc.c

 *

 * Dissector for the DECT (Digital Enhanced Cordless Telecommunications)

 * DLC protocol layer as described in ETSI EN 300 175-4 V2.7.1 (2017-11)

 *

 * DLC is sometimes also called LAPC, which is a derivative of LAPDm (GSM),

 * which is a derivative of LAPD (ISDN).

 *

 * Copyright 2018 by Harald Welte <laforge@gnumonks.org>

 *

 * Wireshark - Network traffic analyzer

 * By Gerald Combs <gerald@wireshark.org>

 * Copyright 1998 Gerald Combs

 *

 * SPDX-License-Identifier: GPL-2.0-or-later

 */

#include "config.h"

#include <epan/conversation.h>

#include <epan/packet.h>

#include <epan/prefs.h>

#include <epan/reassemble.h>

#include <epan/xdlc.h>

void proto_register_dect_dlc(void);

static int proto_dect_dlc;

static int hf_dect_dlc_address;

static int hf_dect_dlc_nlf;

static int hf_dect_dlc_lln;

static int hf_dect_dlc_sapi;

static int hf_dect_dlc_cr;

static int hf_dect_dlc_control;

static int hf_dect_dlc_n_r;

static int hf_dect_dlc_n_s;

static int hf_dect_dlc_p;

static int hf_dect_dlc_f;

static int hf_dect_dlc_s_ftype;

static int hf_dect_dlc_u_modifier_cmd;

static int hf_dect_dlc_u_modifier_resp;

static int hf_dect_dlc_ftype_i;

static int hf_dect_dlc_ftype_s_u;

static int hf_dect_dlc_length;

static int hf_dect_dlc_el;

static int hf_dect_dlc_m;

static int hf_dect_dlc_len;

static int ett_dect_dlc;

static int ett_dect_dlc_address;

static int ett_dect_dlc_control;

static int ett_dect_dlc_length;

static dissector_handle_t data_handle;

static dissector_table_t dlc_sapi_dissector_table;

static reassembly_table dect_dlc_reassembly_table;

static int hf_dect_dlc_fragment_data;

static int hf_dect_dlc_fragment;

static int hf_dect_dlc_fragments;

static int hf_dect_dlc_fragment_overlap;

static int hf_dect_dlc_fragment_overlap_conflicts;

static int hf_dect_dlc_fragment_multiple_tails;

static int hf_dect_dlc_fragment_too_long_fragment;

static int hf_dect_dlc_fragment_error;

static int hf_dect_dlc_fragment_count;

static int hf_dect_dlc_reassembled_in;

static int hf_dect_dlc_reassembled_length;

static int ett_dect_dlc_fragment;

static int ett_dect_dlc_fragments;

static const fragment_items dect_dlc_frag_items = {

    /* Fragment subtrees */

    &ett_dect_dlc_fragment,

    &ett_dect_dlc_fragments,

    /* Fragment fields */

    &hf_dect_dlc_fragments,

    &hf_dect_dlc_fragment,

    &hf_dect_dlc_fragment_overlap,

    &hf_dect_dlc_fragment_overlap_conflicts,

    &hf_dect_dlc_fragment_multiple_tails,

    &hf_dect_dlc_fragment_too_long_fragment,

    &hf_dect_dlc_fragment_error,

    &hf_dect_dlc_fragment_count,

    /* Reassembled in field */

    &hf_dect_dlc_reassembled_in,

    /* Reassembled length field */

    &hf_dect_dlc_reassembled_length,

    /* Reassembled data field */

    NULL,

    /* Tag */

    "fragments"

};

static wmem_map_t *dect_dlc_last_n_s_map;

#define DECT_DLC_M          0x02

#define DECT_DLC_M_SHIFT    1

static bool reassemble_dect_dlc = true;

static const xdlc_cf_items dect_dlc_cf_items = {

  &hf_dect_dlc_n_r,

  &hf_dect_dlc_n_s,

  &hf_dect_dlc_p,

  &hf_dect_dlc_f,

  &hf_dect_dlc_s_ftype,

  &hf_dect_dlc_u_modifier_cmd,

  &hf_dect_dlc_u_modifier_resp,

  &hf_dect_dlc_ftype_i,

  &hf_dect_dlc_ftype_s_u

};

static const value_string dect_dlc_sapi_vals[] = {

  { 0, "Connection oriented signalling" },

  { 3, "Connectionless signalling" },

  { 0, NULL }

};

static const value_string dect_dlc_lln_vals[] = {

  { 0, "U0" },

  { 1, "A1" },

  { 2, "B2" },

  { 3, "B3" },

  { 4, "B4" },

  { 5, "B5" },

  { 6, "B6" },

  { 7, "unassigned" },

  { 0, NULL }

};

static const value_string dect_dlc_m_vals[] = {

  { 0, "Last segment" },

  { 1, "More segments" },

  { 0, NULL }

};

static const value_string dect_dlc_el_vals[] = {

  { 0, "More octets" },

  { 1, "Final octet" },

  { 0, NULL }

};

static int dissect_dect_dlc(tvbuff_t *tvb, packet_info *pinfo, proto_tree *tree, void _U_ *data)

{

  proto_tree *dlc_tree, *addr_tree, *length_tree;

  proto_item *dlc_ti, *addr_ti, *length_ti;

  bool is_response = false;

  bool m;

  int available_length;

  int control;

  tvbuff_t *payload;

  uint8_t cr, sapi, length, len, n_s;

  col_set_str(pinfo->cinfo, COL_PROTOCOL, "DECT-DLC");

  cr = tvb_get_uint8(tvb, 0) & 0x02;

  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;

  dlc_ti = proto_tree_add_item(tree, proto_dect_dlc, tvb, 0, 3, ENC_NA);

  dlc_tree = proto_item_add_subtree(dlc_ti, ett_dect_dlc);

  addr_ti = proto_tree_add_item(dlc_tree, hf_dect_dlc_address, tvb, 0, 1, ENC_NA);

  addr_tree = proto_item_add_subtree(addr_ti, ett_dect_dlc_address);

  sapi = (tvb_get_uint8(tvb, 0) & 0x0C) >> 2;

  proto_tree_add_item(addr_tree, hf_dect_dlc_nlf, tvb, 0, 1, ENC_NA);

  proto_tree_add_item(addr_tree, hf_dect_dlc_lln, tvb, 0, 1, ENC_NA);

  proto_tree_add_item(addr_tree, hf_dect_dlc_sapi, tvb, 0, 1, ENC_NA);

  proto_tree_add_item(addr_tree, hf_dect_dlc_cr, tvb, 0, 1, ENC_NA);

  control = dissect_xdlc_control(tvb, 1, pinfo, dlc_tree, hf_dect_dlc_control,

        ett_dect_dlc_control, &dect_dlc_cf_items, NULL, NULL, NULL,

        is_response, false, false);

  n_s = (control & XDLC_N_S_MASK) >> XDLC_N_S_SHIFT;

  length_ti = proto_tree_add_item(dlc_tree, hf_dect_dlc_length, tvb, 2, 1, ENC_NA);

  length_tree = proto_item_add_subtree(length_ti, ett_dect_dlc_length);

  length = tvb_get_uint8(tvb, 2);

  proto_tree_add_uint(length_tree, hf_dect_dlc_len, tvb, 2, 1, length);

  proto_tree_add_uint(length_tree, hf_dect_dlc_m, tvb, 2, 1, length);

  proto_tree_add_uint(length_tree, hf_dect_dlc_el, tvb, 2, 1, length);

  len = length >> 2;

  available_length = tvb_captured_length(tvb) - 3;

  if (available_length > 0) {

    payload = tvb_new_subset_length_caplen(tvb, 3, MIN(len, available_length), len);

    /* Potentially segmented I frame */

    if( (control & XDLC_I_MASK) == XDLC_I && reassemble_dect_dlc && !pinfo->flags.in_error_pkt )

    {

      fragment_head *fd_m = NULL;

      tvbuff_t *reassembled = NULL;

      uint32_t fragment_id;

      bool save_fragmented = pinfo->fragmented, add_frag;

      m = (length & DECT_DLC_M) >> DECT_DLC_M_SHIFT;

      pinfo->fragmented = m;

      fragment_id = (conversation_get_id_from_elements(pinfo, CONVERSATION_NONE, USE_LAST_ENDPOINT) << 3) | ( sapi << 1) | pinfo->p2p_dir;

      if (!PINFO_FD_VISITED(pinfo)) {

        /* Check if new N(S) is equal to previous N(S) (to avoid adding retransmissions in reassembly table)

        As GUINT_TO_POINTER macro does not allow to differentiate NULL from 0, use 1-8 range instead of 0-7 */

        unsigned *p_last_n_s = (unsigned*)wmem_map_lookup(dect_dlc_last_n_s_map, GUINT_TO_POINTER(fragment_id));

        if (GPOINTER_TO_UINT(p_last_n_s) == (unsigned)(n_s+1)) {

          add_frag = false;

        } else {

          add_frag = true;

          wmem_map_insert(dect_dlc_last_n_s_map, GUINT_TO_POINTER(fragment_id), GUINT_TO_POINTER(n_s+1));

        }

      } else {

        add_frag = true;

      }

      if (add_frag) {

        /* 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 (&dect_dlc_reassembly_table, payload, 0,

                      pinfo,

                      fragment_id, /* uint32_t ID for fragments belonging together */

                      NULL,

                      /*n_s uint32_t fragment sequence number */

                      len, /* uint32_t fragment length */

                      m); /* More fragments? */

        reassembled = process_reassembled_data(payload, 0, pinfo,

                          "Reassembled DLC", fd_m, &dect_dlc_frag_items,

                          NULL, dlc_tree);

        /* Reassembled into this packet */

        if (fd_m && pinfo->num == fd_m->reassembled_in) {

          if (!dissector_try_uint(dlc_sapi_dissector_table, sapi,

                      reassembled, pinfo, tree))

            call_data_dissector(reassembled, pinfo, tree);

        }

        else {

          col_append_str(pinfo->cinfo, COL_INFO, " (Fragment)");

          proto_tree_add_item(dlc_tree, hf_dect_dlc_fragment_data, payload, 0, -1, ENC_NA);

        }

      }

      /* Now reset fragmentation information in pinfo */

      pinfo->fragmented = save_fragmented;

    }

    else

    {

      if (!PINFO_FD_VISITED(pinfo) && ((control & XDLC_S_U_MASK) == XDLC_U) && ((control & XDLC_U_MODIFIER_MASK) == XDLC_SABM)) {

        /* SABM frame; reset the last N(S) to an invalid value */

        uint32_t fragment_id = (conversation_get_id_from_elements(pinfo, CONVERSATION_GSMTAP, USE_LAST_ENDPOINT) << 3) | (sapi << 1) | pinfo->p2p_dir;

        wmem_map_insert(dect_dlc_last_n_s_map, GUINT_TO_POINTER(fragment_id), GUINT_TO_POINTER(0));

      }

      if (!dissector_try_uint(dlc_sapi_dissector_table, sapi, payload, pinfo, tree))

        call_data_dissector(payload, pinfo, tree);

    }

  }

  return tvb_captured_length(tvb);

}

void proto_register_dect_dlc(void)

{

  static hf_register_info hf[] =

  {

    { &hf_dect_dlc_address,

      { "Address Field", "dect_dlc.address_field", FT_UINT8, BASE_HEX,

         NULL, 0x0, NULL, HFILL

      }

    },

    { &hf_dect_dlc_nlf,

      { "NLF", "dect_dlc.nlf", FT_UINT8, BASE_DEC,

        NULL, 0x80, "New Link Flag", HFILL

      }

    },

    { &hf_dect_dlc_lln,

      { "LLN", "dect_dlc.lln", FT_UINT8, BASE_DEC,

        VALS(dect_dlc_lln_vals), 0x70, "Logical Link Number", HFILL

      }

    },

    { &hf_dect_dlc_sapi,

      { "SAPI", "dect_dlc.sapi", FT_UINT8, BASE_DEC,

        VALS(dect_dlc_sapi_vals), 0x0C, "Service Access Point Identifier", HFILL

      }

    },

    { &hf_dect_dlc_cr,

      { "C/R", "dect_dlc.cr", FT_UINT8, BASE_DEC,

        NULL, 0x02, "Command/Response field bit", HFILL

      }

    },

    { &hf_dect_dlc_control,

      { "Control Field", "dect_dlc.control_field", FT_UINT8, BASE_HEX,

        NULL, 0x0, NULL, HFILL

      }

    },

    { &hf_dect_dlc_n_r,

      { "N(R)", "dect_dlc.control.n_r", FT_UINT8, BASE_DEC,

        NULL, 0xE0, NULL, HFILL

      }

    },

    { &hf_dect_dlc_n_s,

      { "N(S)", "dect_dlc.control.n_s", FT_UINT8, BASE_DEC,

        NULL, 0x0E, NULL, HFILL

      }

    },

    { &hf_dect_dlc_p,

      { "Poll", "dect_dlc.control.p", FT_BOOLEAN, 8,

        NULL, 0x10, NULL, HFILL

      }

    },

    { &hf_dect_dlc_f,

      { "Final", "dect_dlc.control.f", FT_BOOLEAN, 8,

        NULL, 0x10, NULL, HFILL

      }

    },

    { &hf_dect_dlc_s_ftype,

      { "Supervisory frame type", "dect_dlc.control.s_ftype", FT_UINT8, BASE_HEX,

        VALS(stype_vals), XDLC_S_FTYPE_MASK, NULL, HFILL

      }

    },

    { &hf_dect_dlc_u_modifier_cmd,

      { "Command", "dect_dlc.control.u_modifier_cmd", FT_UINT8, BASE_HEX,

        VALS(modifier_vals_cmd), XDLC_U_MODIFIER_MASK, NULL, HFILL

      }

    },

    { &hf_dect_dlc_u_modifier_resp,

      { "Response", "dect_dlc.control.u_modifier_resp", FT_UINT8, BASE_HEX,

        VALS(modifier_vals_resp), XDLC_U_MODIFIER_MASK, NULL, HFILL

      }

    },

    { &hf_dect_dlc_ftype_i,

      { "Frame type", "dect_dlc.control.ftype", FT_UINT8, BASE_HEX,

        VALS(ftype_vals), XDLC_I_MASK, NULL, HFILL

      }

    },

    { &hf_dect_dlc_ftype_s_u,

      { "Frame type", "dect_dlc.control.ftype", FT_UINT8, BASE_HEX,

        VALS(ftype_vals), XDLC_S_U_MASK, NULL, HFILL

      }

    },

    { &hf_dect_dlc_length,

      { "Length Field", "dect_dlc.length_field", FT_UINT8, BASE_HEX,

        NULL, 0x0, NULL, HFILL

      }

    },

    { &hf_dect_dlc_el,

      { "EL", "dect_dlc.el", FT_UINT8, BASE_DEC,

        VALS(dect_dlc_el_vals), 0x01, "Length indicator field extension bit", HFILL

      }

    },

    { &hf_dect_dlc_m,

      { "M", "dect_dlc.m", FT_UINT8, BASE_DEC,

        VALS(dect_dlc_m_vals), 0x02, "More data bit", HFILL

      }

    },

    { &hf_dect_dlc_len,

      { "Length", "dect_dlc.length", FT_UINT8, BASE_DEC,

        NULL, 0xFC, "Length indicator", HFILL

      }

    },

    /* Fragment reassembly */

    { &hf_dect_dlc_fragment_data,

      { "Fragment Data", "dect_dlc.fragment_data", FT_NONE, BASE_NONE,

        NULL, 0x00, NULL, HFILL

      }

    },

    { &hf_dect_dlc_fragments,

      { "Message fragments", "dect_dlc.fragments",

        FT_NONE, BASE_NONE, NULL, 0x00, NULL, HFILL

      }

    },

    { &hf_dect_dlc_fragment,

      { "Message fragment", "dect_dlc.fragment",

        FT_FRAMENUM, BASE_NONE, NULL, 0x00, NULL, HFILL

      }

    },

    { &hf_dect_dlc_fragment_overlap,

      { "Message fragment overlap", "dect_dlc.fragment.overlap",

        FT_BOOLEAN, BASE_NONE, NULL, 0x00, NULL, HFILL

      }

    },

    { &hf_dect_dlc_fragment_overlap_conflicts,

      { "Message fragment overlapping with conflicting data",

        "dect_dlc.fragment.overlap.conflicts",

        FT_BOOLEAN, BASE_NONE, NULL, 0x00, NULL, HFILL

      }

    },

    { &hf_dect_dlc_fragment_multiple_tails,

      { "Message has multiple tail fragments",

        "dect_dlc.fragment.multiple_tails",

        FT_BOOLEAN, BASE_NONE, NULL, 0x00, NULL, HFILL

      }

    },

    { &hf_dect_dlc_fragment_too_long_fragment,

      { "Message fragment too long", "dect_dlc.fragment.too_long_fragment",

        FT_BOOLEAN, BASE_NONE, NULL, 0x00, NULL, HFILL

      }

    },

    { &hf_dect_dlc_fragment_error,

      { "Message defragmentation error", "dect_dlc.fragment.error",

        FT_FRAMENUM, BASE_NONE, NULL, 0x00, NULL, HFILL

      }

    },

    { &hf_dect_dlc_fragment_count,

      { "Message fragment count", "dect_dlc.fragment.count",

        FT_UINT32, BASE_DEC, NULL, 0x00, NULL, HFILL

      }

    },

    { &hf_dect_dlc_reassembled_in,

      { "Reassembled in", "dect_dlc.reassembled.in",

        FT_FRAMENUM, BASE_NONE, NULL, 0x00, NULL, HFILL

      }

    },

    { &hf_dect_dlc_reassembled_length,

      { "Reassembled length", "dect_dlc.reassembled.length",

        FT_UINT32, BASE_DEC, NULL, 0x00, NULL, HFILL

      }

    },

  };

  static int *ett[] = {

    &ett_dect_dlc,

    &ett_dect_dlc_address,

    &ett_dect_dlc_control,

    &ett_dect_dlc_length,

    &ett_dect_dlc_fragment,

    &ett_dect_dlc_fragments,

  };

  /* Register protocol */

  proto_dect_dlc = proto_register_protocol("DECT DLC (LAPC)", "DECT-DLC", "dect_dlc");

  proto_register_subtree_array(ett, array_length(ett));

  proto_register_field_array(proto_dect_dlc, hf, array_length(hf));

  register_dissector("dect_dlc", dissect_dect_dlc, proto_dect_dlc);

  dlc_sapi_dissector_table = register_dissector_table("dect_dlc.sapi", "DECT DLC SAPI", proto_dect_dlc, FT_UINT8, BASE_DEC);

  data_handle = find_dissector("data");

  reassembly_table_register(&dect_dlc_reassembly_table,

                           &addresses_reassembly_table_functions);

  dect_dlc_last_n_s_map = wmem_map_new_autoreset(wmem_epan_scope(), wmem_file_scope(), g_direct_hash, g_direct_equal);

}

/*

 * Editor modelines  -  http://www.wireshark.org/tools/modelines.html

 *

 * Local variables:

 * c-basic-offset: 8

 * tab-width: 8

 * indent-tabs-mode: t

 * End:

 *

 * vi: set shiftwidth=8 tabstop=8 noexpandtab:

 * :indentSize=8:tabSize=8:noTabs=false:

 */