/* packet-lapd.c

 * Routines for LAPD frame disassembly

 * Gilbert Ramirez <gram@alumni.rice.edu>

 *

 * Wireshark - Network traffic analyzer

 * By Gerald Combs <gerald@wireshark.org>

 * Copyright 1998

 *

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

 */

/*

 * LAPD bitstream over RTP handling

 * Copyright 2008, Ericsson AB

 * Written by Balint Reczey <balint.reczey@ericsson.com>

 *

 * ISDN/LAPD references:

 *

 * http://www.cisco.com/univercd/cc/td/doc/cisintwk/ito_doc/isdn.htm

 * http://www.ece.wpi.edu/courses/ee535/hwk11cd95/agrebe/agrebe.html

 * http://www.acacia-net.com/Clarinet/Protocol/q9213o84.htm

 * http://www.itu.int/rec/T-REC-Q.921/en

 * Base Station Controller - Base Transceiver Station (BSC - BTS) interface; Layer 2 specification

 * http://www.3gpp.org/ftp/Specs/html-info/48056.htm

 */

#include "config.h"

#include <epan/packet.h>

#include <epan/conversation.h>

#include <epan/crc16-tvb.h>

#include <epan/prefs.h>

#include <wiretap/wtap.h>

#include <epan/expert.h>

#include <epan/proto_data.h>

#include <epan/tfs.h>

#include <wsutil/array.h>

#include "packet-lapd.h"

#include "packet-xdlc.h"

void proto_register_lapd(void);

void proto_reg_handoff_lapd(void);

static int proto_lapd;

static int hf_lapd_direction;

static int hf_lapd_address;

static int hf_lapd_sapi;

static int hf_lapd_gsm_sapi;

static int hf_lapd_cr;

static int hf_lapd_ea1;

static int hf_lapd_tei;

static int hf_lapd_ea2;

static int hf_lapd_control;

static int hf_lapd_n_r;

static int hf_lapd_n_s;

static int hf_lapd_p;

static int hf_lapd_p_ext;

static int hf_lapd_f;

static int hf_lapd_f_ext;

static int hf_lapd_s_ftype;

static int hf_lapd_u_modifier_cmd;

static int hf_lapd_u_modifier_resp;

static int hf_lapd_ftype_i;

static int hf_lapd_ftype_s_u;

static int hf_lapd_ftype_s_u_ext;

static int hf_lapd_checksum;

static int hf_lapd_checksum_status;

static int ett_lapd;

static int ett_lapd_address;

static int ett_lapd_control;

static int ett_lapd_checksum;

static expert_field ei_lapd_abort;

static expert_field ei_lapd_checksum_bad;

static dissector_handle_t lapd_handle;

static dissector_handle_t lapd_phdr_handle;

static dissector_handle_t linux_lapd_handle;

static dissector_handle_t lapd_bitstream_handle;

static dissector_table_t lapd_sapi_dissector_table;

static dissector_table_t lapd_gsm_sapi_dissector_table;

/* Whether to use GSM SAPI vals or not */

static bool global_lapd_gsm_sapis;

/*

 * Bits in the address field.

 */

#define LAPD_SAPI   0xfc00  /* Service Access Point Identifier */

#define LAPD_SAPI_SHIFT   10

#define LAPD_CR     0x0200  /* Command/Response bit */

#define LAPD_EA1    0x0100  /* First Address Extension bit */

#define LAPD_TEI    0x00fe  /* Terminal Endpoint Identifier */

#define LAPD_TEI_SHIFT    1

#define LAPD_EA2    0x0001  /* Second Address Extension bit */

#define LAPD_DIR_USER_TO_NETWORK  0

#define LAPD_DIR_NETWORK_TO_USER  1

static const value_string lapd_direction_vals[] = {

  { LAPD_DIR_USER_TO_NETWORK,   "User->Network"},

  { LAPD_DIR_NETWORK_TO_USER,   "Network->User"},

  { 0,          NULL }

};

static const value_string lapd_sapi_vals[] = {

  { LAPD_SAPI_Q931, "Q.931 Call control procedure" },

  { LAPD_SAPI_PM_Q931,  "Packet mode Q.931 Call control procedure" },

  { LAPD_SAPI_X25,  "X.25 Level 3 procedures" },

  { LAPD_SAPI_L2,   "Layer 2 management procedures" },

  { 0,      NULL }

};

static const value_string lapd_gsm_sapi_vals[] = {

  { LAPD_GSM_SAPI_RA_SIG_PROC,  "Radio signalling procedures" },

  { LAPD_GSM_SAPI_NOT_USED_1, "(Not used in GSM PLMN)" },

  { LAPD_GSM_SAPI_NOT_USED_16,  "(Not used in GSM PLMN)" },

  { LAPD_GSM_SAPI_OM_PROC,  "Operation and maintenance procedure" },

  { LAPD_SAPI_L2,     "Layer 2 management procedures" },

  { 0,        NULL }

};

/* Used only for U frames */

static const xdlc_cf_items lapd_cf_items = {

  NULL,

  NULL,

  &hf_lapd_p,

  &hf_lapd_f,

  NULL,

  &hf_lapd_u_modifier_cmd,

  &hf_lapd_u_modifier_resp,

  NULL,

  &hf_lapd_ftype_s_u

};

/* Used only for I and S frames */

static const xdlc_cf_items lapd_cf_items_ext = {

  &hf_lapd_n_r,

  &hf_lapd_n_s,

  &hf_lapd_p_ext,

  &hf_lapd_f_ext,

  &hf_lapd_s_ftype,

  NULL,

  NULL,

  &hf_lapd_ftype_i,

  &hf_lapd_ftype_s_u_ext

};

#define MAX_LAPD_PACKET_LEN 1024

/* LAPD frame detection state */

enum lapd_bitstream_states {OUT_OF_SYNC, FLAGS, DATA};

typedef struct lapd_byte_state {

  enum lapd_bitstream_states state; /* frame detection state */

  char    full_byte;    /* part of a full byte */

  char    bit_offset;   /* number of bits already got in the full byte */

  int   ones;     /* number of consecutive ones since the last zero */

  uint8_t         data[MAX_LAPD_PACKET_LEN];

  int             data_len;

} lapd_byte_state_t;

typedef struct lapd_ppi {

  bool    has_crc;    /* CRC is captured with LAPD the frames */

  lapd_byte_state_t start_byte_state;   /* LAPD bitstream byte state at the beginning of processing the packet */

} lapd_ppi_t;

/* Fill values in lapd_byte_state struct */

static void

fill_lapd_byte_state(lapd_byte_state_t *ptr, enum lapd_bitstream_states state, char full_byte, char bit_offset, int ones, const uint8_t *data, int data_len)

{

  ptr->state = state;

  ptr->full_byte = full_byte;

  ptr->bit_offset = bit_offset;

  ptr->ones = ones;

  ptr->data_len = MIN((int)sizeof(ptr->data), data_len);

  memcpy(ptr->data, data, ptr->data_len);

}

typedef struct lapd_convo_data {

  address   addr_a;

  address   addr_b;

  uint32_t    port_a;

  uint32_t    port_b;

  lapd_byte_state_t *byte_state_a;

  lapd_byte_state_t *byte_state_b;

} lapd_convo_data_t;

static void

dissect_lapd_full(tvbuff_t*, packet_info*, proto_tree*, uint32_t);

/* got new LAPD frame byte */

static void new_byte(char full_byte, uint8_t data[], int *data_len) {

  if (*data_len < MAX_LAPD_PACKET_LEN) {

    data[*data_len] = full_byte;

    (*data_len)++;

  } else {

    /* XXX : we are not prepared for that big messages, drop the last byte */

  }

}

static void

lapd_log_abort(tvbuff_t *tvb, packet_info *pinfo, proto_tree *tree, unsigned offset, const char *msg)

{

  proto_item *ti;

  ti = proto_tree_add_item(tree, proto_lapd, tvb, offset, 1, ENC_NA);

  expert_add_info_format(pinfo, ti, &ei_lapd_abort, "%s", msg);

}

/*

 * Flags to pass to dissect_lapd_full.

 */

#define LAPD_HAS_CRC      0x00000001

#define LAPD_HAS_DIRECTION    0x00000002

#define LAPD_HAS_LINUX_SLL    0x00000004

#define LAPD_USER_TO_NETWORK    0x00000008

#define LAPD_NETWORK_IS_REMOTE    0x00000010

#define LAPD_USER_IS_REMOTE   0x00000020

static int

dissect_lapd_bitstream(tvbuff_t *tvb, packet_info *pinfo, proto_tree *tree, void* dissector_data _U_)

{

  uint8_t   byte, full_byte = 0x00, bit_offset = 0;

  bool  bit;

  uint8_t   i, ones = 0, data[MAX_LAPD_PACKET_LEN];

  int   data_len = 0;

  int   offset = 0, available;

  uint8_t   *buff;

  tvbuff_t  *new_tvb;

  enum lapd_bitstream_states state = OUT_OF_SYNC;

  lapd_ppi_t    *lapd_ppi;

  conversation_t    *conversation = NULL;

  lapd_convo_data_t *convo_data = NULL;

  lapd_byte_state_t *lapd_byte_state, *prev_byte_state = NULL;

  bool    forward_stream = true;

  /* get remaining data from previous packets */

  conversation = find_or_create_conversation(pinfo);

  lapd_ppi = (lapd_ppi_t*)p_get_proto_data(wmem_file_scope(), pinfo, proto_lapd, 0);

  if (lapd_ppi) {

    prev_byte_state = &lapd_ppi->start_byte_state;

    if (prev_byte_state) {

      state = prev_byte_state->state;

      full_byte = prev_byte_state->full_byte;

      bit_offset = prev_byte_state->bit_offset;

      ones = prev_byte_state->ones;

      memcpy(data, prev_byte_state->data, prev_byte_state->data_len);

      data_len = prev_byte_state->data_len;

    }

  } else if (conversation) {

    convo_data = (lapd_convo_data_t*)conversation_get_proto_data(conversation, proto_lapd);

    if (NULL != convo_data) {

      if (addresses_equal(&convo_data->addr_a, &pinfo->src)

          && addresses_equal(&convo_data->addr_b, &pinfo->dst)

          && convo_data-> port_a == pinfo->srcport

          && convo_data-> port_b == pinfo->destport) {

        /* "forward" direction */

        forward_stream = true;

        prev_byte_state = convo_data->byte_state_a;

      } else if (addresses_equal(&convo_data-> addr_b, &pinfo->src)

          && addresses_equal(&convo_data->addr_a, &pinfo->dst)

          && convo_data-> port_b == pinfo->srcport

          && convo_data-> port_a == pinfo->destport) {

        /* "backward" direction */

        forward_stream = false;

        prev_byte_state = convo_data->byte_state_b;

      }

    }

    if (prev_byte_state) {

      state = prev_byte_state->state;

      full_byte = prev_byte_state->full_byte;

      bit_offset = prev_byte_state->bit_offset;

      ones = prev_byte_state->ones;

      memcpy(data, prev_byte_state->data, prev_byte_state->data_len);

      data_len = prev_byte_state->data_len;

    }

  }

  /* Consume tvb bytes */

  available = tvb_reported_length_remaining(tvb, offset);

  while (offset < available) {

    byte = tvb_get_uint8(tvb,offset);

    offset++;

    for (i=0; i < 8; i++) { /* cycle through bits */

      bit = byte & (0x80 >> i) ? true : false;

      /* consume a bit */

      if (bit) {

        ones++;

        full_byte |= (1 << bit_offset++);

      } else {

        if (ones == 5 && state == DATA) {

          /* we don't increase bit_offset, it is an inserted zero */

        } else if (ones == 6 && state == DATA) { /* probably starting flag sequence */

          buff = (uint8_t *)wmem_memdup(pinfo->pool, data, data_len);

          /* Allocate new tvb for the LAPD frame */

          new_tvb = tvb_new_child_real_data(tvb, buff, data_len, data_len);

          add_new_data_source(pinfo, new_tvb, "Decoded LAPD bitstream");

          data_len = 0;

          state = FLAGS;

          bit_offset++;

          if (full_byte != 0x7E) {

            data_len = 0;

            state = OUT_OF_SYNC;

            lapd_log_abort(tvb, pinfo, tree, offset, "Abort! 6 ones that don't match 0x7e!");

          }

          dissect_lapd_full(new_tvb, pinfo, tree, LAPD_HAS_CRC);

        } else if (ones >= 7) { /* frame reset or 11111111 flag byte */

          data_len = 0;

          state = OUT_OF_SYNC;

          bit_offset++;

          lapd_log_abort(tvb, pinfo, tree, offset, "Abort! 7 ones!");

        } else {

          bit_offset++;

        }

        ones = 0;

      }

      if (bit_offset == 8) { /* we have a new complete byte */

        switch (state) {

          case OUT_OF_SYNC:

            if (full_byte == 0x7E) { /* we have a flag byte */

              state = FLAGS;

              full_byte = 0x00;

              bit_offset = 0;

            } else { /* no sync yet, wait for a new byte */

              full_byte = (full_byte >> 1) & 0x7F;

              bit_offset--;

            }

            break;

          case FLAGS:

            if (full_byte == 0x7E) { /* we have a flag byte */

              full_byte = 0x00;

              bit_offset = 0;

            } else { /* we got the first data byte */

              state = DATA;

              new_byte(full_byte, data, &data_len);

              full_byte = 0x00;

              bit_offset = 0;

            }

            break;

          case DATA:

            /* we got a new data byte */

            new_byte(full_byte, data, &data_len);

            full_byte = 0x00;

            bit_offset = 0;

            break;

        }

      }

    }

  }

  {

    if (NULL == p_get_proto_data(wmem_file_scope(), pinfo, proto_lapd, 0)) {

      /* Per packet information */

      lapd_ppi = wmem_new(wmem_file_scope(), lapd_ppi_t);

      lapd_ppi->has_crc = true;

      if (prev_byte_state)

        fill_lapd_byte_state(&lapd_ppi->start_byte_state, prev_byte_state->state,

            prev_byte_state->full_byte, prev_byte_state->bit_offset,

            prev_byte_state->ones, prev_byte_state->data, prev_byte_state->data_len);

      else

        fill_lapd_byte_state(&lapd_ppi->start_byte_state, OUT_OF_SYNC, 0x00, 0, 0, data, 0);

      p_add_proto_data(wmem_file_scope(), pinfo, proto_lapd, 0, lapd_ppi);

      /* Conversation info*/

      if (conversation) {

        if (convo_data) { /* already have lapd convo data */

          if (forward_stream) {

            if (!convo_data->byte_state_a)

              convo_data->byte_state_a = wmem_new(wmem_file_scope(), lapd_byte_state_t);

            fill_lapd_byte_state(convo_data->byte_state_a, state, full_byte, bit_offset, ones, data, data_len);

          } else {

            if (!convo_data->byte_state_b)

              convo_data->byte_state_b = wmem_new(wmem_file_scope(), lapd_byte_state_t);

            fill_lapd_byte_state(convo_data->byte_state_b, state, full_byte, bit_offset, ones, data, data_len);

          }

        } else { /* lapd convo data has to be created */

          lapd_byte_state = wmem_new(wmem_file_scope(), lapd_byte_state_t);

          fill_lapd_byte_state(lapd_byte_state, state, full_byte, bit_offset, ones, data, data_len);

          convo_data = wmem_new(wmem_file_scope(), lapd_convo_data_t);

          copy_address_wmem(wmem_file_scope(), &convo_data->addr_a, &pinfo->src);

          copy_address_wmem(wmem_file_scope(), &convo_data->addr_b, &pinfo->dst);

          convo_data->port_a = pinfo->srcport;

          convo_data->port_b = pinfo->destport;

          convo_data->byte_state_a = lapd_byte_state;

          convo_data->byte_state_b = NULL;

          conversation_add_proto_data(conversation, proto_lapd, convo_data);

        }

      }

    }

  }

  return tvb_captured_length(tvb);

}

static int

dissect_linux_lapd(tvbuff_t *tvb, packet_info *pinfo, proto_tree *tree, void* data _U_)

{

  uint32_t flags = LAPD_HAS_LINUX_SLL | LAPD_HAS_DIRECTION;

  /* frame is captured via libpcap */

  if (pinfo->pseudo_header->lapd.pkttype == 4 /*PACKET_OUTGOING*/) {

    if (pinfo->pseudo_header->lapd.we_network) {

      /*

       * We're the network side, so the user is remote,

       * and we're sending it, so this is Network->User.

       */

      flags |= LAPD_USER_IS_REMOTE;

    } else {

      /*

       * We're the user side, so the network is remote,

       * and we're sending it, so this is User->Network.

       */

      flags |= LAPD_NETWORK_IS_REMOTE | LAPD_USER_TO_NETWORK;

    }

  }

  else if (pinfo->pseudo_header->lapd.pkttype == 3 /*PACKET_OTHERHOST*/) {

    /*

     * We must be a TE, sniffing what other TE transmit, so

     * both sides are remote.

     *

     * XXX - do we know whether it's User->Network or

     * Network->User?

     */

    flags |= LAPD_USER_IS_REMOTE | LAPD_NETWORK_IS_REMOTE | LAPD_USER_TO_NETWORK;

  }

  else {

    /* The frame is incoming */

    if (pinfo->pseudo_header->lapd.we_network) {

      /*

       * We're the network side, so the user is remote,

       * and we received it, so this is User->Network.

       */

      flags |= LAPD_USER_IS_REMOTE | LAPD_USER_TO_NETWORK;

    } else {

      /*

       * We're the user side, so the network is remote,

       * and we received it, so this is Network->User.

       */

      flags |= LAPD_NETWORK_IS_REMOTE;

    }

  }

  dissect_lapd_full(tvb, pinfo, tree, flags);

  return tvb_captured_length(tvb);

}

/*

 * Called from dissectors, such as the ISDN dissector, that supply a

 * struct isdn_pndr giving the packet direction.

 */

static int

dissect_lapd_phdr(tvbuff_t *tvb, packet_info *pinfo, proto_tree *tree, void *data)

{

  struct isdn_phdr *isdn = (struct isdn_phdr *)data;

  uint32_t flags = LAPD_HAS_DIRECTION;

  if (isdn->uton)

    flags |= LAPD_USER_TO_NETWORK;

  dissect_lapd_full(tvb, pinfo, tree, flags);

  return tvb_captured_length(tvb);

}

/*

 * Called for link-layer encapsulation.

 */

static int

dissect_lapd_frame(tvbuff_t *tvb, packet_info *pinfo, proto_tree *tree, void *data _U_)

{

  uint32_t flags;

  uint32_t lapd_flags = 0;

  /*

   * If we have direction flags, we have a direction;

   * "outbound" packets are presumed to be User->Network and

   * "inbound" packets are presumed to be Network->User.

   * Other packets, we have no idea.

   */

  if (WTAP_OPTTYPE_SUCCESS == wtap_block_get_uint32_option_value(pinfo->rec->block, OPT_PKT_FLAGS, &flags)) {

    switch (PACK_FLAGS_DIRECTION(flags)) {

    case PACK_FLAGS_DIRECTION_OUTBOUND:

      lapd_flags |= LAPD_HAS_DIRECTION | LAPD_USER_TO_NETWORK;

      break;

    case PACK_FLAGS_DIRECTION_INBOUND:

      lapd_flags |= LAPD_HAS_DIRECTION;

      break;

    default:

      break;

    }

  }

  dissect_lapd_full(tvb, pinfo, tree, lapd_flags);

  return tvb_captured_length(tvb);

}

static int

dissect_lapd(tvbuff_t *tvb, packet_info *pinfo, proto_tree *tree, void *data _U_)

{

  /* XXX - direction is unknown */

  dissect_lapd_full(tvb, pinfo, tree, 0);

  return tvb_captured_length(tvb);

}

static void

dissect_lapd_full(tvbuff_t *tvb, packet_info *pinfo, proto_tree *tree, uint32_t flags)

{

  proto_tree  *lapd_tree, *addr_tree;

  proto_item  *lapd_ti, *addr_ti;

  uint16_t    control;

  int   lapd_header_len, checksum_offset;

  uint16_t    addr, cr, sapi, tei;

  bool  is_response = 0;

  tvbuff_t  *next_tvb;

  const char  *srcname = "?";

  const char  *dstname = "?";

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

  col_clear(pinfo->cinfo, COL_INFO);

  addr = tvb_get_ntohs(tvb, 0);

  cr = addr & LAPD_CR;

  tei = (addr & LAPD_TEI) >> LAPD_TEI_SHIFT;

  sapi = (addr & LAPD_SAPI) >> LAPD_SAPI_SHIFT;

  lapd_header_len = 2;  /* addr */

  /* Append TEI to info field */

  col_append_fstr(pinfo->cinfo, COL_INFO, "TEI:%02u ", tei);

  col_set_fence(pinfo->cinfo, COL_INFO);

  if (flags & LAPD_HAS_DIRECTION) {

    if (flags & LAPD_USER_TO_NETWORK) {

      is_response = cr ? true : false;

      if (flags & LAPD_HAS_LINUX_SLL) {

        srcname = (flags & LAPD_USER_IS_REMOTE) ?

            "Remote User" : "Local User";

        dstname = (flags & LAPD_NETWORK_IS_REMOTE) ?

            "Remote Network" : "Local Network";

      } else {

        srcname = "User";

        dstname = "Network";

      }

    } else {

      is_response = cr ? false : true;

      if (flags & LAPD_HAS_LINUX_SLL) {

        srcname = (flags & LAPD_NETWORK_IS_REMOTE) ?

            "Remote Network" : "Local Network";

        dstname = (flags & LAPD_USER_IS_REMOTE) ?

            "Remote User" : "Local User";

      } else {

        srcname = "Network";

        dstname = "User";

      }

    }

  }

  set_address(&pinfo->dl_dst, AT_STRINGZ, (int)strlen(dstname) + 1, dstname);

  set_address(&pinfo->dl_src, AT_STRINGZ, (int)strlen(srcname) + 1, srcname);

  copy_address_shallow(&pinfo->dst, &pinfo->dl_dst);

  copy_address_shallow(&pinfo->src, &pinfo->dl_src);

  if (tree) {

    proto_item *direction_ti;

    lapd_ti = proto_tree_add_item(tree, proto_lapd, tvb, 0, -1,

        ENC_NA);

    lapd_tree = proto_item_add_subtree(lapd_ti, ett_lapd);

    /*

     * Don't show the direction if we don't know it.

     */

    if (flags & LAPD_HAS_DIRECTION) {

      direction_ti = proto_tree_add_uint(lapd_tree, hf_lapd_direction,

                                         tvb, 0, 0,

                                         (flags & LAPD_USER_TO_NETWORK) ? LAPD_DIR_USER_TO_NETWORK : LAPD_DIR_NETWORK_TO_USER);

      proto_item_set_generated(direction_ti);

    }

    addr_ti = proto_tree_add_uint(lapd_tree, hf_lapd_address, tvb,

        0, 2, addr);

    addr_tree = proto_item_add_subtree(addr_ti, ett_lapd_address);

    if(global_lapd_gsm_sapis){

      proto_tree_add_uint(addr_tree, hf_lapd_gsm_sapi,tvb, 0, 1, addr);

    }else{

      proto_tree_add_uint(addr_tree, hf_lapd_sapi,tvb, 0, 1, addr);

    }

    proto_tree_add_uint(addr_tree, hf_lapd_cr,  tvb, 0, 1, addr);

    proto_tree_add_uint(addr_tree, hf_lapd_ea1, tvb, 0, 1, addr);

    proto_tree_add_uint(addr_tree, hf_lapd_tei, tvb, 1, 1, addr);

    proto_tree_add_uint(addr_tree, hf_lapd_ea2, tvb, 1, 1, addr);

  }

  else {

    lapd_ti = NULL;

    lapd_tree = NULL;

  }

  control = dissect_xdlc_control(tvb, 2, pinfo, lapd_tree, hf_lapd_control,

      ett_lapd_control, &lapd_cf_items, &lapd_cf_items_ext, NULL, NULL,

      is_response, true, false);

  lapd_header_len += XDLC_CONTROL_LEN(control, true);

  if (tree)

    proto_item_set_len(lapd_ti, lapd_header_len);

  if (flags & LAPD_HAS_CRC) {

    /* check checksum */

    checksum_offset = tvb_reported_length(tvb) - 2;

    proto_tree_add_checksum(lapd_tree, tvb, checksum_offset, hf_lapd_checksum, hf_lapd_checksum_status, &ei_lapd_checksum_bad, pinfo,

                crc16_ccitt_tvb(tvb, tvb_reported_length(tvb) - 2), ENC_BIG_ENDIAN, PROTO_CHECKSUM_VERIFY);

    next_tvb = tvb_new_subset_length(tvb, lapd_header_len, tvb_reported_length_remaining(tvb,lapd_header_len) - 2);

  } else

    next_tvb = tvb_new_subset_remaining(tvb, lapd_header_len);

  /* Dissection done, append " | " to COL_INFO */

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

  col_set_fence(pinfo->cinfo, COL_INFO);

  if (XDLC_IS_INFORMATION(control)) {

    /* call next protocol */

    if(global_lapd_gsm_sapis){

      if (!dissector_try_uint(lapd_gsm_sapi_dissector_table, sapi,

        next_tvb, pinfo, tree))

        call_data_dissector(next_tvb, pinfo, tree);

    }else{

      if (!dissector_try_uint(lapd_sapi_dissector_table, sapi,

        next_tvb, pinfo, tree))

        call_data_dissector(next_tvb, pinfo, tree);

    }

  } else

    call_data_dissector(next_tvb, pinfo, tree);

}

void

proto_register_lapd(void)

{

  static hf_register_info hf[] = {

    { &hf_lapd_direction,

      { "Direction", "lapd.direction", FT_UINT32, BASE_DEC, VALS(lapd_direction_vals), 0x0,

        NULL, HFILL }},

    { &hf_lapd_address,

      { "Address Field", "lapd.address", FT_UINT16, BASE_HEX, NULL, 0x0,

        NULL, HFILL }},

    { &hf_lapd_sapi,

      { "SAPI", "lapd.sapi", FT_UINT16, BASE_DEC, VALS(lapd_sapi_vals), LAPD_SAPI,

        "Service Access Point Identifier", HFILL }},

    { &hf_lapd_gsm_sapi,

      { "SAPI", "lapd.sapi", FT_UINT16, BASE_DEC, VALS(lapd_gsm_sapi_vals), LAPD_SAPI,

        "Service Access Point Identifier", HFILL }},

    { &hf_lapd_cr,

      { "C/R", "lapd.cr", FT_UINT16, BASE_DEC, NULL, LAPD_CR,

        "Command/Response bit", HFILL }},

    { &hf_lapd_ea1,

      { "EA1", "lapd.ea1", FT_UINT16, BASE_DEC, NULL, LAPD_EA1,

        "First Address Extension bit", HFILL }},

    { &hf_lapd_tei,

      { "TEI", "lapd.tei", FT_UINT16, BASE_DEC, NULL, LAPD_TEI,

        "Terminal Endpoint Identifier", HFILL }},

    { &hf_lapd_ea2,

      { "EA2", "lapd.ea2", FT_UINT16, BASE_DEC, NULL, LAPD_EA2,

        "Second Address Extension bit", HFILL }},

    { &hf_lapd_control,

      { "Control Field", "lapd.control", FT_UINT16, BASE_HEX, NULL, 0x0,

        NULL, HFILL }},

    { &hf_lapd_n_r,

      { "N(R)", "lapd.control.n_r", FT_UINT16, BASE_DEC,

        NULL, XDLC_N_R_EXT_MASK, NULL, HFILL }},

    { &hf_lapd_n_s,

      { "N(S)", "lapd.control.n_s", FT_UINT16, BASE_DEC,

        NULL, XDLC_N_S_EXT_MASK, NULL, HFILL }},

    { &hf_lapd_p,

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

        TFS(&tfs_set_notset), XDLC_P_F, NULL, HFILL }},

    { &hf_lapd_p_ext,

      { "Poll", "lapd.control.p", FT_BOOLEAN, 16,

        TFS(&tfs_set_notset), XDLC_P_F_EXT, NULL, HFILL }},

    { &hf_lapd_f,

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

        TFS(&tfs_set_notset), XDLC_P_F, NULL, HFILL }},

    { &hf_lapd_f_ext,

      { "Final", "lapd.control.f", FT_BOOLEAN, 16,

        TFS(&tfs_set_notset), XDLC_P_F_EXT, NULL, HFILL }},

    { &hf_lapd_s_ftype,

      { "Supervisory frame type", "lapd.control.s_ftype", FT_UINT16, BASE_HEX,

        VALS(stype_vals), XDLC_S_FTYPE_MASK, NULL, HFILL }},

    { &hf_lapd_u_modifier_cmd,

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

        VALS(modifier_vals_cmd), XDLC_U_MODIFIER_MASK, NULL, HFILL }},

    { &hf_lapd_u_modifier_resp,

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

        VALS(modifier_vals_resp), XDLC_U_MODIFIER_MASK, NULL, HFILL }},

    { &hf_lapd_ftype_i,

      { "Frame type", "lapd.control.ftype", FT_UINT16, BASE_HEX,

        VALS(ftype_vals), XDLC_I_MASK, NULL, HFILL }},

    { &hf_lapd_ftype_s_u,

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

        VALS(ftype_vals), XDLC_S_U_MASK, NULL, HFILL }},

    { &hf_lapd_ftype_s_u_ext,

      { "Frame type", "lapd.control.ftype", FT_UINT16, BASE_HEX,

        VALS(ftype_vals), XDLC_S_U_MASK, NULL, HFILL }},

    { &hf_lapd_checksum,

      { "Checksum", "lapd.checksum", FT_UINT16, BASE_HEX,

        NULL, 0x0, "Details at: https://www.wireshark.org/docs/wsug_html_chunked/ChAdvChecksums.html", HFILL }},

    { &hf_lapd_checksum_status,

      { "Checksum Status", "lapd.checksum.status", FT_UINT8, BASE_NONE,

        VALS(proto_checksum_vals), 0x0, NULL, HFILL }},

  };

  static int *ett[] = {

    &ett_lapd,

    &ett_lapd_address,

    &ett_lapd_control,

    &ett_lapd_checksum

  };

  static ei_register_info ei[] = {

    { &ei_lapd_abort, { "lapd.abort.expert", PI_PROTOCOL, PI_ERROR, "Formatted message", EXPFILL }},

    { &ei_lapd_checksum_bad, { "lapd.checksum_bad.expert", PI_CHECKSUM, PI_WARN, "Bad FCS", EXPFILL }},

  };

  module_t *lapd_module;

  expert_module_t* expert_lapd;

  proto_lapd = proto_register_protocol("Link Access Procedure, Channel D (LAPD)",

               "LAPD", "lapd");

  proto_register_field_array (proto_lapd, hf, array_length(hf));

  proto_register_subtree_array(ett, array_length(ett));

  expert_lapd = expert_register_protocol(proto_lapd);

  expert_register_field_array(expert_lapd, ei, array_length(ei));

  lapd_handle = register_dissector("lapd", dissect_lapd, proto_lapd);

  lapd_phdr_handle = register_dissector("lapd-phdr", dissect_lapd_phdr, proto_lapd);

  linux_lapd_handle = register_dissector("linux-lapd", dissect_linux_lapd, proto_lapd);

  lapd_bitstream_handle = register_dissector("lapd-bitstream", dissect_lapd_bitstream, proto_lapd);

  lapd_sapi_dissector_table = register_dissector_table("lapd.sapi",

                   "LAPD SAPI", proto_lapd, FT_UINT16, BASE_DEC);

  lapd_gsm_sapi_dissector_table = register_dissector_table("lapd.gsm.sapi",

                 "LAPD GSM SAPI", proto_lapd, FT_UINT16, BASE_DEC);

  lapd_module = prefs_register_protocol(proto_lapd, NULL);

  prefs_register_bool_preference(lapd_module, "use_gsm_sapi_values",

               "Use GSM SAPI values",

               "Use SAPI values as specified in TS 48 056",

               &global_lapd_gsm_sapis);

  prefs_register_obsolete_preference(lapd_module, "rtp_payload_type");

}

void

proto_reg_handoff_lapd(void)

{

  dissector_handle_t lapd_frame_handle;

  dissector_add_uint("wtap_encap", WTAP_ENCAP_LINUX_LAPD, linux_lapd_handle);

  lapd_frame_handle = create_dissector_handle(dissect_lapd_frame, proto_lapd);

  dissector_add_uint("wtap_encap", WTAP_ENCAP_LAPD, lapd_frame_handle);

  dissector_add_for_decode_as("l2tp.pw_type", lapd_handle);

  dissector_add_for_decode_as_with_preference("sctp.ppi", lapd_handle);

  dissector_add_for_decode_as("sctp.port", lapd_handle);

  dissector_add_uint_range_with_preference("udp.port", "", lapd_handle);

  dissector_add_uint_range_with_preference("rtp.pt", "", lapd_bitstream_handle);

}

/*

 * Editor modelines  -  https://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:

 */