epan/dissectors/packet-lapd.c

   1 /* packet-lapd.c
   2  * Routines for LAPD frame disassembly
   3  * Gilbert Ramirez <gram@alumni.rice.edu>
   4  *
   5  * $Id$
   6  *
   7  * Wireshark - Network traffic analyzer
   8  * By Gerald Combs <gerald@wireshark.org>
   9  * Copyright 1998
  10  *
  11  * This program is free software; you can redistribute it and/or
  12  * modify it under the terms of the GNU General Public License
  13  * as published by the Free Software Foundation; either version 2
  14  * of the License, or (at your option) any later version.
  15  *
  16  * This program is distributed in the hope that it will be useful,
  17  * but WITHOUT ANY WARRANTY; without even the implied warranty of
  18  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  19  * GNU General Public License for more details.
  20  *
  21  * You should have received a copy of the GNU General Public License
  22  * along with this program; if not, write to the Free Software
  23  * Foundation, Inc., 59 Temple Place - Suite 330, Boston, MA  02111-1307, USA.
  24  */
  25 /*
  26  * LAPD bitstream over RTP handling
  27  * Copyright 2008, Ericsson AB
  28  * Written by Balint Reczey <balint.reczey@ericsson.com>
  29  *
  30  * ISDN/LAPD references:
  31  *
  32  * http://www.cisco.com/univercd/cc/td/doc/cisintwk/ito_doc/isdn.htm
  33  * http://www.ece.wpi.edu/courses/ee535/hwk11cd95/agrebe/agrebe.html
  34  * http://www.acacia-net.com/Clarinet/Protocol/q9213o84.htm
  35  * http://www.itu.int/rec/T-REC-Q.921/en
  36  * Base Station Controller - Base Transceiver Station (BSC - BTS) interface; Layer 2 specification
  37  * http://www.3gpp.org/ftp/Specs/html-info/48056.htm
  38  */
  39
  40 #ifdef HAVE_CONFIG_H
  41 # include "config.h"
  42 #endif
  43
  44 #include <glib.h>
  45 #include <string.h>
  46 #include <epan/packet.h>
  47 #include <epan/conversation.h>
  48 #include <epan/xdlc.h>
  49 #include <epan/crc16-tvb.h>
  50 #include <epan/prefs.h>
  51 #include <epan/lapd_sapi.h>
  52
  53 static int proto_lapd = -1;
  54 static int hf_lapd_direction = -1;
  55 static int hf_lapd_address = -1;
  56 static int hf_lapd_sapi = -1;
  57 static int hf_lapd_gsm_sapi = -1;
  58 static int hf_lapd_cr = -1;
  59 static int hf_lapd_ea1 = -1;
  60 static int hf_lapd_tei = -1;
  61 static int hf_lapd_ea2 = -1;
  62 static int hf_lapd_control = -1;
  63 static int hf_lapd_n_r = -1;
  64 static int hf_lapd_n_s = -1;
  65 static int hf_lapd_p = -1;
  66 static int hf_lapd_p_ext = -1;
  67 static int hf_lapd_f = -1;
  68 static int hf_lapd_f_ext = -1;
  69 static int hf_lapd_s_ftype = -1;
  70 static int hf_lapd_u_modifier_cmd = -1;
  71 static int hf_lapd_u_modifier_resp = -1;
  72 static int hf_lapd_ftype_i = -1;
  73 static int hf_lapd_ftype_s_u = -1;
  74 static int hf_lapd_ftype_s_u_ext = -1;
  75 static int hf_lapd_checksum = -1;
  76 static int hf_lapd_checksum_good = -1;
  77 static int hf_lapd_checksum_bad = -1;
  78
  79 static gint ett_lapd = -1;
  80 static gint ett_lapd_address = -1;
  81 static gint ett_lapd_control = -1;
  82 static gint ett_lapd_checksum = -1;
  83 static gint pref_lapd_rtp_payload_type = 0;
  84
  85 static dissector_table_t lapd_sapi_dissector_table;
  86 static dissector_table_t lapd_gsm_sapi_dissector_table;
  87
  88 /* Whether to use GSM SAPI vals or not */
  89 static gboolean global_lapd_gsm_sapis = FALSE;
  90
  91 static dissector_handle_t data_handle;
  92
  93 /*
  94  * Bits in the address field.
  95  */
  96 #define LAPD_SAPI               0xfc00  /* Service Access Point Identifier */
  97 #define LAPD_SAPI_SHIFT         10
  98 #define LAPD_CR                 0x0200  /* Command/Response bit */
  99 #define LAPD_EA1                0x0100  /* First Address Extension bit */
 100 #define LAPD_TEI                0x00fe  /* Terminal Endpoint Identifier */
 101 #define LAPD_TEI_SHIFT          1
 102 #define LAPD_EA2                0x0001  /* Second Address Extension bit */
 103
 104 static const value_string lapd_direction_vals[] = {
 105         { P2P_DIR_RECV,         "Network->User"},
 106         { P2P_DIR_SENT,         "User->Network"},
 107         { 0,                    NULL }
 108 };
 109
 110 static const value_string lapd_sapi_vals[] = {
 111         { LAPD_SAPI_Q931,       "Q.931 Call control procedure" },
 112         { LAPD_SAPI_PM_Q931,    "Packet mode Q.931 Call control procedure" },
 113         { LAPD_SAPI_X25,        "X.25 Level 3 procedures" },
 114         { LAPD_SAPI_L2,         "Layer 2 management procedures" },
 115         { 0,                    NULL }
 116 };
 117
 118 static const value_string lapd_gsm_sapi_vals[] = {
 119         { LAPD_GSM_SAPI_RA_SIG_PROC,    "Radio signalling procedures" },
 120         { LAPD_GSM_SAPI_NOT_USED_1,     "(Not used in GSM PLMN)" },
 121         { LAPD_GSM_SAPI_NOT_USED_16,    "(Not used in GSM PLMN)" },
 122         { LAPD_GSM_SAPI_OM_PROC,        "Operation and maintenance procedure" },
 123         { LAPD_SAPI_L2,                 "Layer 2 management procedures" },
 124         { 0,                            NULL }
 125 };
 126
 127 /* Used only for U frames */
 128 static const xdlc_cf_items lapd_cf_items = {
 129         NULL,
 130         NULL,
 131         &hf_lapd_p,
 132         &hf_lapd_f,
 133         NULL,
 134         &hf_lapd_u_modifier_cmd,
 135         &hf_lapd_u_modifier_resp,
 136         NULL,
 137         &hf_lapd_ftype_s_u
 138 };
 139
 140 /* Used only for I and S frames */
 141 static const xdlc_cf_items lapd_cf_items_ext = {
 142         &hf_lapd_n_r,
 143         &hf_lapd_n_s,
 144         &hf_lapd_p_ext,
 145         &hf_lapd_f_ext,
 146         &hf_lapd_s_ftype,
 147         NULL,
 148         NULL,
 149         &hf_lapd_ftype_i,
 150         &hf_lapd_ftype_s_u_ext
 151 };
 152
 153
 154 /* LAPD frame detection state */
 155 enum lapd_bitstream_states {OUT_OF_SYNC, FLAGS, DATA};
 156
 157 typedef struct lapd_byte_state {
 158         enum lapd_bitstream_states state;       /* frame detection state */
 159         char            full_byte;              /* part of a full byte */
 160         char            bit_offset;             /* number of bits already got in the full byte */
 161         int             ones;                   /* number of consecutive ones since the last zero */
 162 } lapd_byte_state_t;
 163
 164 typedef struct lapd_ppi {
 165         gboolean                has_crc;                /* CRC is captured with LAPD the frames */
 166         lapd_byte_state_t       start_byte_state;       /* LAPD bitstream byte state at the beginnigng of processing the packet */
 167 } lapd_ppi_t;
 168
 169 /* Fill values in lapd_byte_state struct */
 170 static void
 171 fill_lapd_byte_state(lapd_byte_state_t *ptr, enum lapd_bitstream_states state, char full_byte, char bit_offset, int ones)
 172 {
 173         ptr->state = state;
 174         ptr->full_byte = full_byte;
 175         ptr->bit_offset = bit_offset;
 176         ptr->ones = ones;
 177 }
 178
 179 typedef struct lapd_convo_data {
 180         address         addr_a;
 181         address         addr_b;
 182         guint32         port_a;
 183         guint32         port_b;
 184         lapd_byte_state_t       *byte_state_a;
 185         lapd_byte_state_t       *byte_state_b;
 186 } lapd_convo_data_t;
 187
 188 #define MAX_LAPD_PACKET_LEN 1024
 189
 190 static void
 191 dissect_lapd(tvbuff_t*, packet_info*, proto_tree*);
 192
 193 /* got new LAPD frame byte */
 194 static void new_byte(char full_byte, char data[], int *data_len) {
 195         if (*data_len < MAX_LAPD_PACKET_LEN) {
 196                 data[*data_len] = full_byte;
 197                 (*data_len)++;
 198         } else {
 199                 /* XXX : we are not prepared for that big messages, drop the last byte */
 200         }
 201 }
 202
 203 static void
 204 dissect_lapd_bitstream(tvbuff_t *tvb, packet_info *pinfo, proto_tree *tree)
 205 {
 206         guint8          byte, full_byte = 0x00, bit_offset = 0;
 207         gboolean        bit;
 208         guint8          i, ones = 0, data[MAX_LAPD_PACKET_LEN];
 209         int             data_len = 0;
 210         guint           offset = 0, available;
 211         guint8          *buff;
 212         tvbuff_t        *new_tvb;
 213
 214         enum lapd_bitstream_states state = OUT_OF_SYNC;
 215         lapd_ppi_t              *lapd_ppi;
 216         conversation_t          *conversation = NULL;
 217         lapd_convo_data_t       *convo_data = NULL;
 218         lapd_byte_state_t       *lapd_byte_state, *prev_byte_state = NULL;
 219         gboolean                forward_stream = TRUE;
 220
 221         /* get remaining data from previous packets */
 222         conversation = find_conversation(pinfo->fd->num, &pinfo->src, &pinfo->dst,
 223                 pinfo->ptype, pinfo->srcport, pinfo->destport, 0);
 224         lapd_ppi = (lapd_ppi_t*)p_get_proto_data(pinfo->fd, proto_lapd);
 225         if (lapd_ppi) {
 226                 prev_byte_state = &lapd_ppi->start_byte_state;
 227                 if (prev_byte_state) {
 228                         state = prev_byte_state->state;
 229                         full_byte = prev_byte_state->full_byte;
 230                         bit_offset = prev_byte_state->bit_offset;
 231                         ones = prev_byte_state->ones;
 232                 }
 233
 234         } else if (conversation) {
 235                 convo_data = (lapd_convo_data_t*)conversation_get_proto_data(conversation, proto_lapd);
 236                 if (NULL != convo_data) {
 237                         if (ADDRESSES_EQUAL(&convo_data->addr_a, &pinfo->src)
 238                                         && ADDRESSES_EQUAL(&convo_data->addr_b, &pinfo->dst)
 239                                         && convo_data-> port_a == pinfo->srcport
 240                                         && convo_data-> port_b == pinfo->destport) {
 241                                 /* "forward" direction */
 242                                 forward_stream = TRUE;
 243                                 prev_byte_state = convo_data->byte_state_a;
 244                         } else if (ADDRESSES_EQUAL(&convo_data-> addr_b, &pinfo->src)
 245                                         && ADDRESSES_EQUAL(&convo_data->addr_a, &pinfo->dst)
 246                                         && convo_data-> port_b == pinfo->srcport
 247                                         && convo_data-> port_a == pinfo->destport) {
 248                                 /* "backward" direction */
 249                                 forward_stream = FALSE;
 250                                 prev_byte_state = convo_data->byte_state_b;
 251                         }
 252                 }
 253                 if (prev_byte_state) {
 254                         state = prev_byte_state->state;
 255                         full_byte = prev_byte_state->full_byte;
 256                         bit_offset = prev_byte_state->bit_offset;
 257                         ones = prev_byte_state->ones;
 258                 }
 259         }
 260
 261         /* Consume tvb bytes */
 262         available = tvb_length_remaining(tvb, offset);
 263         while (offset < available) {
 264                 byte = tvb_get_guint8(tvb,offset);
 265                 offset++;
 266                 for (i=0; i < 8; i++) { /* cycle through bits */
 267                         bit = byte & (0x80 >> i) ? TRUE : FALSE;
 268
 269                         /* consume a bit */
 270                         if (bit) {
 271                                 ones++;
 272                                 full_byte |= (1 << bit_offset++);
 273                         } else {
 274                                 if (ones == 5 && state == DATA) {
 275                                         /* we don't increase bit_offset, it is an inserted zero */
 276                                 } else if (ones == 6 && state == DATA) { /* probably starting flag sequence */
 277                                         buff = g_memdup(data, data_len);
 278                                         /* Allocate new tvb for the LAPD frame */
 279                                         new_tvb = tvb_new_child_real_data(tvb, buff, data_len, data_len);
 280                                         tvb_set_free_cb(new_tvb, g_free);
 281                                         add_new_data_source(pinfo, new_tvb, "Decoded LAPD bitstream");
 282                                         dissect_lapd(new_tvb, pinfo, tree);
 283                                         data_len = 0;
 284                                         state = FLAGS;
 285                                         bit_offset++;
 286                                 } else if (ones >= 7) { /* frame reset or 11111111 flag byte */
 287                                         data_len = 0;
 288                                         state = OUT_OF_SYNC;
 289                                         bit_offset++;
 290                                 } else {
 291                                         bit_offset++;
 292                                 }
 293                                 ones = 0;
 294                         }
 295
 296                         if (bit_offset == 8) { /* we have a new complete byte */
 297                                 switch (state) {
 298                                         case OUT_OF_SYNC:
 299                                                 if (full_byte == 0x7E) { /* we have a flag byte */
 300                                                         state = FLAGS;
 301                                                         full_byte = 0x00;
 302                                                         bit_offset = 0;
 303                                                 } else { /* no sync yet, wait for a new byte */
 304                                                         full_byte = (full_byte >> 1) & 0x7F;
 305                                                         bit_offset--;
 306                                                 }
 307                                                 break;
 308
 309                                         case FLAGS:
 310                                                 if (full_byte == 0x7E) { /* we have a flag byte */
 311                                                         full_byte = 0x00;
 312                                                         bit_offset = 0;
 313                                                 } else { /* we got the first data byte */
 314                                                         state = DATA;
 315                                                         new_byte(full_byte, data, &data_len);
 316                                                         full_byte = 0x00;
 317                                                         bit_offset = 0;
 318                                                 }
 319                                                 break;
 320
 321                                         case DATA:
 322                                                 /* we got a new data byte */
 323                                                 new_byte(full_byte, data, &data_len);
 324                                                 full_byte = 0x00;
 325                                                 bit_offset = 0;
 326                                                 break;
 327                                 }
 328                         }
 329                 }
 330         }
 331
 332         if (state == DATA) { /* we are in the middle of an LAPD frame, we need more bytes */
 333                 pinfo->desegment_offset = 0;
 334                 pinfo->desegment_len = DESEGMENT_ONE_MORE_SEGMENT;
 335                 return;
 336         } else { /* finished processing LAPD frame(s) */
 337                 if (NULL == p_get_proto_data(pinfo->fd, proto_lapd)) {
 338                         /* Per packet information */
 339                         lapd_ppi = g_malloc(sizeof(lapd_ppi_t));
 340                         lapd_ppi->has_crc = TRUE;
 341                         if (prev_byte_state)
 342                                 fill_lapd_byte_state(&lapd_ppi->start_byte_state, prev_byte_state->state,
 343                                                 prev_byte_state->full_byte, prev_byte_state->bit_offset,
 344                                                 prev_byte_state->ones);
 345                         else
 346                                 fill_lapd_byte_state(&lapd_ppi->start_byte_state, OUT_OF_SYNC, 0x00, 0, 0);
 347
 348                         p_add_proto_data(pinfo->fd, proto_lapd, lapd_ppi);
 349
 350
 351                         /* Conversation info*/
 352
 353                         if (conversation) {
 354                                 if (convo_data) { /* already have lapd convo data */
 355                                         if (forward_stream)
 356                                                 fill_lapd_byte_state(convo_data->byte_state_a, state, full_byte, bit_offset, ones);
 357                                         else {
 358                                                 if (!convo_data->byte_state_b)
 359                                                         convo_data->byte_state_b = g_malloc(sizeof(lapd_byte_state_t));
 360                                                 fill_lapd_byte_state(convo_data->byte_state_b, state, full_byte, bit_offset, ones);
 361                                         }
 362                                 } else { /* lapd convo data has to be created */
 363                                         lapd_byte_state = g_malloc(sizeof(lapd_byte_state_t));
 364                                         fill_lapd_byte_state(lapd_byte_state, state, full_byte, bit_offset, ones);
 365                                         convo_data = g_malloc(sizeof(lapd_convo_data_t));
 366                                         COPY_ADDRESS(&convo_data->addr_a, &pinfo->src);
 367                                         COPY_ADDRESS(&convo_data->addr_b, &pinfo->dst);
 368                                         convo_data->port_a = pinfo->srcport;
 369                                         convo_data->port_b = pinfo->destport;
 370                                         convo_data->byte_state_a = lapd_byte_state;
 371                                         convo_data->byte_state_b = NULL;
 372                                         conversation_add_proto_data(conversation, proto_lapd, convo_data);
 373                                 }
 374                         }
 375                 }
 376         }
 377 }
 378
 379
 380 static void
 381 dissect_lapd(tvbuff_t *tvb, packet_info *pinfo, proto_tree *tree)
 382 {
 383         proto_tree      *lapd_tree, *addr_tree, *checksum_tree;
 384         proto_item      *lapd_ti, *addr_ti, *checksum_ti;
 385         int             direction;
 386         guint16         control, checksum, checksum_calculated;
 387         int             lapd_header_len, checksum_offset;
 388         guint16         addr, cr, sapi, tei;
 389         gboolean        is_response = 0;
 390         tvbuff_t        *next_tvb;
 391         const char      *srcname = "?";
 392         const char      *dstname = "?";
 393
 394         col_set_str(pinfo->cinfo, COL_PROTOCOL, "LAPD");
 395         col_clear(pinfo->cinfo, COL_INFO);
 396
 397         addr = tvb_get_ntohs(tvb, 0);
 398         cr = addr & LAPD_CR;
 399         tei = (addr & LAPD_TEI) >> LAPD_TEI_SHIFT;
 400         sapi = (addr & LAPD_SAPI) >> LAPD_SAPI_SHIFT;
 401         lapd_header_len = 2;    /* addr */
 402
 403         if (check_col(pinfo->cinfo, COL_TEI))
 404                 col_add_fstr(pinfo->cinfo, COL_TEI, "%u", tei);
 405
 406         if (pinfo->fd->lnk_t == WTAP_ENCAP_LINUX_LAPD) {
 407                 /* frame is captured via libpcap */
 408                 if (pinfo->pseudo_header->lapd.pkttype == 4 /*PACKET_OUTGOING*/) {
 409                         if (pinfo->pseudo_header->lapd.we_network) {
 410                                 is_response = cr ? FALSE : TRUE;
 411                                 srcname = "Local Network";
 412                                 dstname = "Remote User";
 413                                 direction = P2P_DIR_RECV;       /* Network->User */
 414                         } else {
 415                                 srcname = "Local User";
 416                                 dstname = "Remote Network";
 417                                 direction = P2P_DIR_SENT;       /* User->Network */
 418                         }
 419                 }
 420                 else if (pinfo->pseudo_header->lapd.pkttype == 3 /*PACKET_OTHERHOST*/) {
 421                         /* We must be a TE, sniffing what other TE transmit */
 422
 423                         is_response = cr ? TRUE : FALSE;
 424                         srcname = "Remote User";
 425                         dstname = "Remote Network";
 426                         direction = P2P_DIR_SENT;       /* User->Network */
 427                 }
 428                 else {
 429                         /* The frame is incoming */
 430                         if (pinfo->pseudo_header->lapd.we_network) {
 431                                 is_response = cr ? TRUE : FALSE;
 432                                 srcname = "Remote User";
 433                                 dstname = "Local Network";
 434                                 direction = P2P_DIR_SENT;       /* User->Network */
 435                         } else {
 436                                 is_response = cr ? FALSE : TRUE;
 437                                 srcname = "Remote Network";
 438                                 dstname = "Local User";
 439                                 direction = P2P_DIR_RECV;       /* Network->User */
 440                         }
 441                 }
 442         } else {
 443                 direction = pinfo->p2p_dir;
 444                 if (pinfo->p2p_dir == P2P_DIR_RECV) {
 445                         is_response = cr ? FALSE : TRUE;
 446                         srcname = "Network";
 447                         dstname = "User";
 448                 }
 449                 else if (pinfo->p2p_dir == P2P_DIR_SENT) {
 450                         is_response = cr ? TRUE : FALSE;
 451                         srcname = "User";
 452                         dstname = "Network";
 453                 }
 454         }
 455
 456         col_set_str(pinfo->cinfo, COL_RES_DL_SRC, srcname);
 457         col_set_str(pinfo->cinfo, COL_RES_DL_DST, dstname);
 458
 459         if (tree) {
 460                 proto_item *direction_ti;
 461
 462                 lapd_ti = proto_tree_add_item(tree, proto_lapd, tvb, 0, -1,
 463                     ENC_NA);
 464                 lapd_tree = proto_item_add_subtree(lapd_ti, ett_lapd);
 465
 466                 /*
 467                  * Don't show the direction if we don't know it.
 468                  */
 469                 if (direction != P2P_DIR_UNKNOWN) {
 470                         direction_ti = proto_tree_add_uint(lapd_tree, hf_lapd_direction,
 471                                                            tvb, 0, 0, pinfo->p2p_dir);
 472                         PROTO_ITEM_SET_GENERATED(direction_ti);
 473                 }
 474
 475                 addr_ti = proto_tree_add_uint(lapd_tree, hf_lapd_address, tvb,
 476                     0, 2, addr);
 477                 addr_tree = proto_item_add_subtree(addr_ti, ett_lapd_address);
 478
 479                 if(global_lapd_gsm_sapis){
 480                         proto_tree_add_uint(addr_tree, hf_lapd_gsm_sapi,tvb, 0, 1, addr);
 481                 }else{
 482                         proto_tree_add_uint(addr_tree, hf_lapd_sapi,tvb, 0, 1, addr);
 483                 }
 484                 proto_tree_add_uint(addr_tree, hf_lapd_cr,  tvb, 0, 1, addr);
 485                 proto_tree_add_uint(addr_tree, hf_lapd_ea1, tvb, 0, 1, addr);
 486                 proto_tree_add_uint(addr_tree, hf_lapd_tei, tvb, 1, 1, addr);
 487                 proto_tree_add_uint(addr_tree, hf_lapd_ea2, tvb, 1, 1, addr);
 488         }
 489         else {
 490                 lapd_ti = NULL;
 491                 lapd_tree = NULL;
 492         }
 493
 494         control = dissect_xdlc_control(tvb, 2, pinfo, lapd_tree, hf_lapd_control,
 495             ett_lapd_control, &lapd_cf_items, &lapd_cf_items_ext, NULL, NULL,
 496             is_response, TRUE, FALSE);
 497         lapd_header_len += XDLC_CONTROL_LEN(control, TRUE);
 498
 499         if (tree)
 500                 proto_item_set_len(lapd_ti, lapd_header_len);
 501
 502         if (NULL != p_get_proto_data(pinfo->fd, proto_lapd)
 503                         && ((lapd_ppi_t*)p_get_proto_data(pinfo->fd, proto_lapd))->has_crc) {
 504
 505                 /* check checksum */
 506                 checksum_offset = tvb_length(tvb) - 2;
 507                 checksum = tvb_get_guint8(tvb, checksum_offset); /* high byte */
 508                 checksum <<= 8;
 509                 checksum |= tvb_get_guint8(tvb, checksum_offset+1) & 0x00FF; /* low byte */
 510                 checksum_calculated = g_htons(crc16_ccitt_tvb(tvb, tvb_length(tvb) - 2));
 511
 512                 if (checksum == checksum_calculated) {
 513                         checksum_ti = proto_tree_add_uint_format(lapd_tree, hf_lapd_checksum, tvb, checksum_offset, 2, 0,"Checksum: 0x%04x [correct]", checksum);
 514                         checksum_tree = proto_item_add_subtree(checksum_ti, ett_lapd_checksum);
 515                         proto_tree_add_boolean(checksum_tree, hf_lapd_checksum_good, tvb, checksum_offset, 2, TRUE);
 516                         proto_tree_add_boolean(checksum_tree, hf_lapd_checksum_bad, tvb, checksum_offset, 2, FALSE);
 517                 } else {
 518                         checksum_ti = proto_tree_add_uint_format(lapd_tree, hf_lapd_checksum, tvb, checksum_offset, 2, 0,"Checksum: 0x%04x [incorrect, should be 0x%04x]", checksum, checksum_calculated);
 519                         checksum_tree = proto_item_add_subtree(checksum_ti, ett_lapd_checksum);
 520                         proto_tree_add_boolean(checksum_tree, hf_lapd_checksum_good, tvb, checksum_offset, 2, FALSE);
 521                         proto_tree_add_boolean(checksum_tree, hf_lapd_checksum_bad, tvb, checksum_offset, 2, TRUE);
 522                 }
 523
 524                 next_tvb = tvb_new_subset(tvb, lapd_header_len, tvb_length_remaining(tvb,lapd_header_len) - 2, -1);
 525
 526         } else
 527                 next_tvb = tvb_new_subset_remaining(tvb, lapd_header_len);
 528
 529         if (XDLC_IS_INFORMATION(control)) {
 530                 /* call next protocol */
 531                 if(global_lapd_gsm_sapis){
 532                         if (!dissector_try_uint(lapd_gsm_sapi_dissector_table, sapi,
 533                                 next_tvb, pinfo, tree))
 534                                 call_dissector(data_handle,next_tvb, pinfo, tree);
 535                 }else{
 536                         if (!dissector_try_uint(lapd_sapi_dissector_table, sapi,
 537                                 next_tvb, pinfo, tree))
 538                                 call_dissector(data_handle,next_tvb, pinfo, tree);
 539                 }
 540         } else
 541                 call_dissector(data_handle,next_tvb, pinfo, tree);
 542 }
 543
 544 void
 545 proto_reg_handoff_lapd(void);
 546
 547 void
 548 proto_register_lapd(void)
 549 {
 550     static hf_register_info hf[] = {
 551
 552         { &hf_lapd_direction,
 553           { "Direction", "lapd.direction", FT_UINT8, BASE_DEC, VALS(lapd_direction_vals), 0x0,
 554                 NULL, HFILL }},
 555
 556         { &hf_lapd_address,
 557           { "Address Field", "lapd.address", FT_UINT16, BASE_HEX, NULL, 0x0,
 558                 "Address", HFILL }},
 559
 560         { &hf_lapd_sapi,
 561           { "SAPI", "lapd.sapi", FT_UINT16, BASE_DEC, VALS(lapd_sapi_vals), LAPD_SAPI,
 562                 "Service Access Point Identifier", HFILL }},
 563
 564         { &hf_lapd_gsm_sapi,
 565           { "SAPI", "lapd.sapi", FT_UINT16, BASE_DEC, VALS(lapd_gsm_sapi_vals), LAPD_SAPI,
 566                 "Service Access Point Identifier", HFILL }},
 567
 568         { &hf_lapd_cr,
 569           { "C/R", "lapd.cr", FT_UINT16, BASE_DEC, NULL, LAPD_CR,
 570                 "Command/Response bit", HFILL }},
 571
 572         { &hf_lapd_ea1,
 573           { "EA1", "lapd.ea1", FT_UINT16, BASE_DEC, NULL, LAPD_EA1,
 574                 "First Address Extension bit", HFILL }},
 575
 576         { &hf_lapd_tei,
 577           { "TEI", "lapd.tei", FT_UINT16, BASE_DEC, NULL, LAPD_TEI,
 578                 "Terminal Endpoint Identifier", HFILL }},
 579
 580         { &hf_lapd_ea2,
 581           { "EA2", "lapd.ea2", FT_UINT16, BASE_DEC, NULL, LAPD_EA2,
 582                 "Second Address Extension bit", HFILL }},
 583
 584         { &hf_lapd_control,
 585           { "Control Field", "lapd.control", FT_UINT16, BASE_HEX, NULL, 0x0,
 586                 NULL, HFILL }},
 587
 588         { &hf_lapd_n_r,
 589             { "N(R)", "lapd.control.n_r", FT_UINT16, BASE_DEC,
 590                 NULL, XDLC_N_R_EXT_MASK, NULL, HFILL }},
 591
 592         { &hf_lapd_n_s,
 593             { "N(S)", "lapd.control.n_s", FT_UINT16, BASE_DEC,
 594                 NULL, XDLC_N_S_EXT_MASK, NULL, HFILL }},
 595
 596         { &hf_lapd_p,
 597             { "Poll", "lapd.control.p", FT_BOOLEAN, 8,
 598                 TFS(&tfs_set_notset), XDLC_P_F, NULL, HFILL }},
 599
 600         { &hf_lapd_p_ext,
 601             { "Poll", "lapd.control.p", FT_BOOLEAN, 16,
 602                 TFS(&tfs_set_notset), XDLC_P_F_EXT, NULL, HFILL }},
 603
 604         { &hf_lapd_f,
 605             { "Final", "lapd.control.f", FT_BOOLEAN, 8,
 606                 TFS(&tfs_set_notset), XDLC_P_F, NULL, HFILL }},
 607
 608         { &hf_lapd_f_ext,
 609             { "Final", "lapd.control.f", FT_BOOLEAN, 16,
 610                 TFS(&tfs_set_notset), XDLC_P_F_EXT, NULL, HFILL }},
 611
 612         { &hf_lapd_s_ftype,
 613             { "Supervisory frame type", "lapd.control.s_ftype", FT_UINT16, BASE_HEX,
 614                 VALS(stype_vals), XDLC_S_FTYPE_MASK, NULL, HFILL }},
 615
 616         { &hf_lapd_u_modifier_cmd,
 617             { "Command", "lapd.control.u_modifier_cmd", FT_UINT8, BASE_HEX,
 618                 VALS(modifier_vals_cmd), XDLC_U_MODIFIER_MASK, NULL, HFILL }},
 619
 620         { &hf_lapd_u_modifier_resp,
 621             { "Response", "lapd.control.u_modifier_resp", FT_UINT8, BASE_HEX,
 622                 VALS(modifier_vals_resp), XDLC_U_MODIFIER_MASK, NULL, HFILL }},
 623
 624         { &hf_lapd_ftype_i,
 625             { "Frame type", "lapd.control.ftype", FT_UINT16, BASE_HEX,
 626                 VALS(ftype_vals), XDLC_I_MASK, NULL, HFILL }},
 627
 628         { &hf_lapd_ftype_s_u,
 629             { "Frame type", "lapd.control.ftype", FT_UINT8, BASE_HEX,
 630                 VALS(ftype_vals), XDLC_S_U_MASK, NULL, HFILL }},
 631
 632         { &hf_lapd_ftype_s_u_ext,
 633             { "Frame type", "lapd.control.ftype", FT_UINT16, BASE_HEX,
 634                 VALS(ftype_vals), XDLC_S_U_MASK, NULL, HFILL }},
 635
 636         { &hf_lapd_checksum,
 637             { "Checksum", "lapd.checksum", FT_UINT16, BASE_HEX,
 638                 NULL, 0x0, "Details at: http://www.wireshark.org/docs/wsug_html_chunked/ChAdvChecksums.html", HFILL }},
 639
 640         { &hf_lapd_checksum_good,
 641             { "Good Checksum", "lapd.checksum_good", FT_BOOLEAN, BASE_NONE,
 642                 NULL, 0x0, "True: checksum matches packet content; False: doesn't match content or not checked", HFILL }},
 643
 644         { &hf_lapd_checksum_bad,
 645             { "Bad Checksum", "lapd.checksum_bad", FT_BOOLEAN, BASE_NONE,
 646                 NULL, 0x0, "True: checksum doesn't match packet content; False: matches content or not checked", HFILL }}
 647     };
 648
 649     static gint *ett[] = {
 650         &ett_lapd,
 651         &ett_lapd_address,
 652         &ett_lapd_control,
 653         &ett_lapd_checksum
 654     };
 655
 656         module_t *lapd_module;
 657
 658         proto_lapd = proto_register_protocol("Link Access Procedure, Channel D (LAPD)",
 659                                          "LAPD", "lapd");
 660         proto_register_field_array (proto_lapd, hf, array_length(hf));
 661         proto_register_subtree_array(ett, array_length(ett));
 662
 663         register_dissector("lapd", dissect_lapd, proto_lapd);
 664
 665         lapd_sapi_dissector_table = register_dissector_table("lapd.sapi",
 666                                                              "LAPD SAPI", FT_UINT16, BASE_DEC);
 667
 668         lapd_gsm_sapi_dissector_table = register_dissector_table("lapd.gsm.sapi",
 669                                                                  "LAPD GSM SAPI", FT_UINT16, BASE_DEC);
 670
 671         lapd_module = prefs_register_protocol(proto_lapd, proto_reg_handoff_lapd);
 672
 673         prefs_register_bool_preference(lapd_module, "use_gsm_sapi_values",
 674                 "Use GSM SAPI values",
 675                 "Use SAPI values as specified in TS 48 056",
 676                 &global_lapd_gsm_sapis);
 677         prefs_register_uint_preference(lapd_module, "rtp_payload_type",
 678                 "RTP payload type for embedded LAPD",
 679                 "RTP payload type for embedded LAPD. It must be one of the dynamic types "
 680                 "from 96 to 127. Set it to 0 to disable.",
 681                  10, &pref_lapd_rtp_payload_type);
 682
 683 }
 684
 685 void
 686 proto_reg_handoff_lapd(void)
 687 {
 688         static gboolean init = FALSE;
 689         static dissector_handle_t lapd_bitstream_handle;
 690         static gint lapd_rtp_payload_type;
 691
 692         if (!init) {
 693                 dissector_handle_t lapd_handle;
 694
 695                 lapd_handle = find_dissector("lapd");
 696                 dissector_add_uint("wtap_encap", WTAP_ENCAP_LINUX_LAPD, lapd_handle);
 697                 dissector_add_uint("wtap_encap", WTAP_ENCAP_LAPD, lapd_handle);
 698
 699                 lapd_bitstream_handle = create_dissector_handle(dissect_lapd_bitstream, proto_lapd);
 700                 data_handle = find_dissector("data");
 701
 702                 init = TRUE;
 703         } else {
 704                 if ((lapd_rtp_payload_type > 95) && (lapd_rtp_payload_type < 128))
 705                         dissector_delete_uint("rtp.pt", lapd_rtp_payload_type, lapd_bitstream_handle);
 706         }
 707
 708         lapd_rtp_payload_type = pref_lapd_rtp_payload_type;
 709         if ((lapd_rtp_payload_type > 95) && (lapd_rtp_payload_type < 128))
 710                 dissector_add_uint("rtp.pt", lapd_rtp_payload_type, lapd_bitstream_handle);
 711 }