epan/dissectors/packet-lapdm.c

   1 /* packet-lapdm.c
   2  * Routines for LAPDm frame disassembly
   3  * Duncan Salerno <duncan.salerno@googlemail.com>
   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., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA.
  24  */
  25
  26 /* LAPDm references:
  27  *
  28  * Mobile Station - Base Stations System (MS - BSS) Interface Data Link (DL) Layer Specification
  29  * Base Station Controller - Base Transceiver Station (BSC - BTS) interface; Layer 2 specification
  30  * http://www.3gpp.org/ftp/Specs/html-info/44006.htm
  31  *
  32  * From 3GPP TS 44.006:
  33  *
  34  * LAPDm is used for information sent on the control channels BCCH, AGCH, NCH,
  35  * PCH, FACCH, SACCH and SDCCH as defined in 3GPP TS 44.003.
  36  *
  37  * AGCH, NCH and PCH are sometimes referred to by the collective name CCCH.
  38  * FACCH, SACCH and SDCCH are, similarly, referred to by the collective name DCCH.
  39  *
  40  * Format A is used on DCCHs for frames where there is no information field.
  41  * Formats B, Bter and B4 are used on DCCHs for frames containing an information field:
  42  * Format Bter is used on request of higher layers if and only if short L2 header type 1 is
  43  * supported and a UI command is to be transmitted on SAPI 0;
  44  * Format B4 is used for UI frames transmitted by the network on SACCH;
  45  * Format B is applied in all other cases.
  46  * Format Bbis is used only on BCCH, PCH, NCH, and AGCH.
  47  * In addition there is a Format C for transmission of random access signals.
  48  *
  49  * This module currently supports A, B, B4
  50  * In the future will support Bter
  51  * Bbis and C should be supported elsewhere
  52  */
  53
  54 #include "config.h"
  55
  56 #include <glib.h>
  57 #include <epan/packet.h>
  58 #include <epan/prefs.h>
  59 #include <epan/xdlc.h>
  60 #include <epan/reassemble.h>
  61
  62 static int proto_lapdm = -1;
  63 static int hf_lapdm_address = -1;
  64 static int hf_lapdm_ea = -1;
  65 static int hf_lapdm_cr = -1;
  66 static int hf_lapdm_sapi = -1;
  67 static int hf_lapdm_lpd = -1;
  68
  69 static int hf_lapdm_control = -1;
  70 static int hf_lapdm_n_r = -1;
  71 static int hf_lapdm_n_s = -1;
  72 static int hf_lapdm_p = -1;
  73 static int hf_lapdm_f = -1;
  74 static int hf_lapdm_s_ftype = -1;
  75 static int hf_lapdm_u_modifier_cmd = -1;
  76 static int hf_lapdm_u_modifier_resp = -1;
  77 static int hf_lapdm_ftype_i = -1;
  78 static int hf_lapdm_ftype_s_u = -1;
  79
  80 static int hf_lapdm_length = -1;
  81 static int hf_lapdm_el = -1;
  82 static int hf_lapdm_m = -1;
  83 static int hf_lapdm_len = -1;
  84
  85 /*
  86  * LAPDm fragment handling
  87  */
  88 static int hf_lapdm_fragments = -1;
  89 static int hf_lapdm_fragment = -1;
  90 static int hf_lapdm_fragment_overlap = -1;
  91 static int hf_lapdm_fragment_overlap_conflicts = -1;
  92 static int hf_lapdm_fragment_multiple_tails = -1;
  93 static int hf_lapdm_fragment_too_long_fragment = -1;
  94 static int hf_lapdm_fragment_error = -1;
  95 static int hf_lapdm_fragment_count = -1;
  96 static int hf_lapdm_reassembled_in = -1;
  97 static int hf_lapdm_reassembled_length = -1;
  98
  99 static gint ett_lapdm = -1;
 100 static gint ett_lapdm_address = -1;
 101 static gint ett_lapdm_control = -1;
 102 static gint ett_lapdm_length = -1;
 103 static gint ett_lapdm_fragment = -1;
 104 static gint ett_lapdm_fragments = -1;
 105
 106 static reassembly_table lapdm_reassembly_table;
 107
 108 static dissector_table_t lapdm_sapi_dissector_table;
 109
 110 static dissector_handle_t data_handle;
 111
 112 static gboolean reassemble_lapdm = TRUE;
 113
 114 /*
 115  * Bits in the address field.
 116  */
 117 #define LAPDM_SAPI              0x1c    /* Service Access Point Identifier */
 118 #define LAPDM_SAPI_SHIFT        2
 119 #define LAPDM_CR                0x02    /* Command/Response bit */
 120 #define LAPDM_EA                0x01    /* First Address Extension bit */
 121 #define LAPDM_LPD               0x60    /* Link Protocol Discriminator */
 122
 123 /*
 124  * Bits in the length field.
 125  */
 126 #define LAPDM_EL                0x01    /* Extended Length = 1 */
 127 #define LAPDM_M                 0x02    /* More fragments */
 128 #define LAPDM_M_SHIFT           1
 129 #define LAPDM_LEN               0xfc    /* Length */
 130 #define LAPDM_LEN_SHIFT         2
 131
 132 #define LAPDM_HEADER_LEN 3
 133
 134 #define LAPDM_SAPI_RR_CC_MM     0
 135 #define LAPDM_SAPI_SMS          3
 136
 137 /* Used only for U frames */
 138 static const xdlc_cf_items lapdm_cf_items = {
 139     &hf_lapdm_n_r,
 140     &hf_lapdm_n_s,
 141     &hf_lapdm_p,
 142     &hf_lapdm_f,
 143     &hf_lapdm_s_ftype,
 144     &hf_lapdm_u_modifier_cmd,
 145     &hf_lapdm_u_modifier_resp,
 146     &hf_lapdm_ftype_i,
 147     &hf_lapdm_ftype_s_u
 148 };
 149
 150 static const value_string lapdm_ea_vals[] = {
 151     { 0,                "More octets" },
 152     { 1,                "Final octet" },
 153     { 0,                NULL }
 154 };
 155
 156 static const value_string lapdm_sapi_vals[] = {
 157     { LAPDM_SAPI_RR_CC_MM,      "RR/MM/CC" },
 158     { LAPDM_SAPI_SMS,           "SMS/SS" },
 159     { 0,                        NULL }
 160 };
 161
 162 static const value_string lapdm_lpd_vals[] = {
 163     { 0,                "Normal GSM" },
 164     { 1,                "Cell broadcast service" },
 165     { 0,                NULL }
 166 };
 167
 168 static const value_string lapdm_m_vals[] = {
 169     { 0,                "Last segment" },
 170     { 1,                "More segments" },
 171     { 0,                NULL }
 172 };
 173
 174 static const value_string lapdm_el_vals[] = {
 175     { 0,                "More octets" },
 176     { 1,                "Final octet" },
 177     { 0,                NULL }
 178 };
 179
 180
 181 static const fragment_items lapdm_frag_items = {
 182     /* Fragment subtrees */
 183     &ett_lapdm_fragment,
 184     &ett_lapdm_fragments,
 185     /* Fragment fields */
 186     &hf_lapdm_fragments,
 187     &hf_lapdm_fragment,
 188     &hf_lapdm_fragment_overlap,
 189     &hf_lapdm_fragment_overlap_conflicts,
 190     &hf_lapdm_fragment_multiple_tails,
 191     &hf_lapdm_fragment_too_long_fragment,
 192     &hf_lapdm_fragment_error,
 193     &hf_lapdm_fragment_count,
 194     /* Reassembled in field */
 195     &hf_lapdm_reassembled_in,
 196     /* Reassembled length field */
 197     &hf_lapdm_reassembled_length,
 198     /* Reassembled data field */
 199     NULL,
 200     /* Tag */
 201     "fragments"
 202 };
 203
 204 static void
 205 lapdm_defragment_init (void)
 206 {
 207     reassembly_table_init (&lapdm_reassembly_table,
 208                            &addresses_reassembly_table_functions);
 209 }
 210
 211
 212 static void
 213 dissect_lapdm(tvbuff_t *tvb, packet_info *pinfo, proto_tree *tree)
 214 {
 215     proto_tree *lapdm_tree, *addr_tree, *length_tree;
 216     proto_item *lapdm_ti, *addr_ti, *length_ti;
 217     guint8 addr, length, cr, sapi, len/*, n_s*/;
 218     int control;
 219     gboolean m;
 220     tvbuff_t *payload;
 221     int available_length;
 222     gboolean is_response = FALSE;
 223
 224     /* Check that there's enough data */
 225     if (tvb_length(tvb) < LAPDM_HEADER_LEN)
 226         return;
 227
 228     col_set_str(pinfo->cinfo, COL_PROTOCOL, "LAPDm");
 229
 230     addr = tvb_get_guint8(tvb, 0);
 231     length = tvb_get_guint8(tvb, 2);
 232
 233     cr = addr & LAPDM_CR;
 234     if (pinfo->p2p_dir == P2P_DIR_RECV) {
 235         is_response = cr ? FALSE : TRUE;
 236     }
 237     else if (pinfo->p2p_dir == P2P_DIR_SENT) {
 238         is_response = cr ? TRUE : FALSE;
 239     }
 240
 241     if (tree) {
 242         lapdm_ti = proto_tree_add_item(tree, proto_lapdm, tvb, 0, LAPDM_HEADER_LEN, ENC_NA);
 243         lapdm_tree = proto_item_add_subtree(lapdm_ti, ett_lapdm);
 244
 245         addr_ti = proto_tree_add_uint(lapdm_tree, hf_lapdm_address, tvb, 0, 1, addr);
 246         addr_tree = proto_item_add_subtree(addr_ti, ett_lapdm_address);
 247
 248         proto_tree_add_uint(addr_tree, hf_lapdm_lpd, tvb, 0, 1, addr);
 249         proto_tree_add_uint(addr_tree, hf_lapdm_sapi, tvb, 0, 1, addr);
 250         proto_tree_add_uint(addr_tree, hf_lapdm_cr, tvb, 0, 1, addr);
 251         proto_tree_add_uint(addr_tree, hf_lapdm_ea, tvb, 0, 1, addr);
 252     }
 253     else {
 254         lapdm_ti = NULL;
 255         lapdm_tree = NULL;
 256     }
 257
 258     control = dissect_xdlc_control(tvb, 1, pinfo, lapdm_tree, hf_lapdm_control,
 259               ett_lapdm_control, &lapdm_cf_items, NULL /* LAPDm doesnt support extended */, NULL, NULL,
 260               is_response, FALSE, FALSE);
 261
 262     if (tree) {
 263         length_ti = proto_tree_add_uint(lapdm_tree, hf_lapdm_length, tvb,
 264                     2, 1, length);
 265         length_tree = proto_item_add_subtree(length_ti, ett_lapdm_length);
 266
 267         proto_tree_add_uint(length_tree, hf_lapdm_len, tvb, 2, 1, length);
 268         proto_tree_add_uint(length_tree, hf_lapdm_m, tvb, 2, 1, length);
 269         proto_tree_add_uint(length_tree, hf_lapdm_el, tvb, 2, 1, length);
 270     }
 271
 272     sapi = (addr & LAPDM_SAPI) >> LAPDM_SAPI_SHIFT;
 273     len = (length & LAPDM_LEN) >> LAPDM_LEN_SHIFT;
 274     /*n_s = (control & XDLC_N_S_MASK) >> XDLC_N_S_SHIFT;*/
 275     m = (length & LAPDM_M) >> LAPDM_M_SHIFT;
 276     available_length = tvb_length(tvb) - LAPDM_HEADER_LEN;
 277
 278     /* No point in doing anything if no payload
 279      */
 280     if( !MIN(len, available_length) )
 281         return;
 282
 283     payload = tvb_new_subset(tvb, LAPDM_HEADER_LEN, MIN(len,available_length), -1);
 284
 285     /* Potentially segmented I frame
 286      */
 287     if( (control & XDLC_I_MASK) == XDLC_I && reassemble_lapdm )
 288     {
 289             fragment_head *fd_m = NULL;
 290             tvbuff_t *reassembled = NULL;
 291             guint32 fragment_id;
 292             gboolean save_fragmented = pinfo->fragmented;
 293
 294             pinfo->fragmented = m;
 295
 296             /* Rely on caller to provide a way to group fragments */
 297             fragment_id = (pinfo->circuit_id << 4) | (sapi << 1) | pinfo->p2p_dir;
 298
 299             /* This doesn't seem the best way of doing it as doesn't
 300                take N(S) into account, but N(S) isn't always 0 for
 301                the first fragment!
 302              */
 303             fd_m = fragment_add_seq_next (&lapdm_reassembly_table, payload, 0,
 304                                 pinfo,
 305                                 fragment_id, /* guint32 ID for fragments belonging together */
 306                                 NULL,
 307                                 /*n_s guint32 fragment sequence number */
 308                                 len, /* guint32 fragment length */
 309                                 m); /* More fragments? */
 310
 311             reassembled = process_reassembled_data(payload, 0, pinfo,
 312                     "Reassembled LAPDm", fd_m, &lapdm_frag_items,
 313                     NULL, lapdm_tree);
 314
 315             /* Reassembled into this packet
 316              */
 317             if (fd_m && pinfo->fd->num == fd_m->reassembled_in) {
 318                     if (!dissector_try_uint(lapdm_sapi_dissector_table, sapi,
 319                                 reassembled, pinfo, tree))
 320                         call_dissector(data_handle, reassembled, pinfo, tree);
 321             }
 322             else {
 323                 col_append_str(pinfo->cinfo, COL_INFO, " (Fragment)");
 324                 if (tree) {
 325                     proto_tree_add_text(lapdm_tree, payload, 0, -1, "Fragment Data");
 326                 }
 327             }
 328
 329             /* Now reset fragmentation information in pinfo
 330              */
 331             pinfo->fragmented = save_fragmented;
 332     }
 333     else
 334     {
 335         /* Whole packet
 336            If we have some data, try and dissect it (only happens for UI, SABM, UA or I frames)
 337          */
 338         if (!dissector_try_uint(lapdm_sapi_dissector_table, sapi,
 339                 payload, pinfo, tree))
 340             call_dissector(data_handle,payload, pinfo, tree);
 341     }
 342 }
 343
 344 void
 345 proto_register_lapdm(void)
 346 {
 347     static hf_register_info hf[] = {
 348
 349         { &hf_lapdm_address,
 350         { "Address Field", "lapdm.address_field", FT_UINT8, BASE_HEX, NULL, 0x0,
 351         "Address", HFILL }},
 352
 353         { &hf_lapdm_ea,
 354         { "EA", "lapdm.ea", FT_UINT8, BASE_DEC, VALS(lapdm_ea_vals), LAPDM_EA,
 355         "Address field extension bit", HFILL }},
 356
 357         { &hf_lapdm_cr,
 358         { "C/R", "lapdm.cr", FT_UINT8, BASE_DEC, NULL, LAPDM_CR,
 359         "Command/response field bit", HFILL }},
 360
 361         { &hf_lapdm_lpd,
 362         { "LPD", "lapdm.lpd", FT_UINT8, BASE_DEC, VALS(lapdm_lpd_vals), LAPDM_LPD,
 363         "Link Protocol Discriminator", HFILL }},
 364
 365         { &hf_lapdm_sapi,
 366         { "SAPI", "lapdm.sapi", FT_UINT8, BASE_DEC, VALS(lapdm_sapi_vals), LAPDM_SAPI,
 367         "Service access point identifier", HFILL }},
 368
 369         { &hf_lapdm_control,
 370         { "Control Field", "lapdm.control_field", FT_UINT8, BASE_HEX, NULL, 0x0,
 371         NULL, HFILL }},
 372
 373         { &hf_lapdm_n_r,
 374         { "N(R)", "lapdm.control.n_r", FT_UINT8, BASE_DEC,
 375         NULL, XDLC_N_R_MASK, NULL, HFILL }},
 376
 377         { &hf_lapdm_n_s,
 378         { "N(S)", "lapdm.control.n_s", FT_UINT8, BASE_DEC,
 379         NULL, XDLC_N_S_MASK, NULL, HFILL }},
 380
 381         { &hf_lapdm_p,
 382         { "Poll", "lapdm.control.p", FT_BOOLEAN, 8,
 383         TFS(&tfs_true_false), XDLC_P_F, NULL, HFILL }},
 384
 385         { &hf_lapdm_f,
 386         { "Final", "lapdm.control.f", FT_BOOLEAN, 8,
 387         TFS(&tfs_true_false), XDLC_P_F, NULL, HFILL }},
 388
 389         { &hf_lapdm_s_ftype,
 390         { "Supervisory frame type", "lapdm.control.s_ftype", FT_UINT8, BASE_HEX,
 391         VALS(stype_vals), XDLC_S_FTYPE_MASK, NULL, HFILL }},
 392
 393         { &hf_lapdm_u_modifier_cmd,
 394         { "Command", "lapdm.control.u_modifier_cmd", FT_UINT8, BASE_HEX,
 395         VALS(modifier_vals_cmd), XDLC_U_MODIFIER_MASK, NULL, HFILL }},
 396
 397         { &hf_lapdm_u_modifier_resp,
 398         { "Response", "lapdm.control.u_modifier_resp", FT_UINT8, BASE_HEX,
 399         VALS(modifier_vals_resp), XDLC_U_MODIFIER_MASK, NULL, HFILL }},
 400
 401         { &hf_lapdm_ftype_i,
 402         { "Frame type", "lapdm.control.ftype", FT_UINT8, BASE_HEX,
 403         VALS(ftype_vals), XDLC_I_MASK, NULL, HFILL }},
 404
 405         { &hf_lapdm_ftype_s_u,
 406         { "Frame type", "lapdm.control.ftype", FT_UINT8, BASE_HEX,
 407         VALS(ftype_vals), XDLC_S_U_MASK, NULL, HFILL }},
 408
 409         { &hf_lapdm_length,
 410         { "Length Field", "lapdm.length_field", FT_UINT8, BASE_HEX,
 411         NULL, 0x0, NULL, HFILL }},
 412
 413         { &hf_lapdm_el,
 414         { "EL", "lapdm.el", FT_UINT8, BASE_DEC,
 415         VALS(lapdm_el_vals), LAPDM_EL, "Length indicator field extension bit", HFILL }},
 416
 417         { &hf_lapdm_m,
 418         { "M", "lapdm.m", FT_UINT8, BASE_DEC,
 419         VALS(lapdm_m_vals), LAPDM_M, "More data bit", HFILL }},
 420
 421         { &hf_lapdm_len,
 422         { "Length", "lapdm.length", FT_UINT8, BASE_DEC,
 423         NULL, LAPDM_LEN, "Length indicator", HFILL }},
 424
 425         /* Fragment reassembly
 426          */
 427         { &hf_lapdm_fragments,
 428         { "Message fragments", "lapdm.fragments", FT_NONE, BASE_NONE,
 429         NULL, 0x00, "LAPDm Message fragments", HFILL }},
 430
 431         { &hf_lapdm_fragment,
 432         { "Message fragment", "lapdm.fragment", FT_FRAMENUM, BASE_NONE,
 433         NULL, 0x00, "LAPDm Message fragment", HFILL }},
 434
 435         { &hf_lapdm_fragment_overlap,
 436         { "Message fragment overlap", "lapdm.fragment.overlap", FT_BOOLEAN, BASE_NONE,
 437         NULL, 0x0, "LAPDm Message fragment overlaps with other fragment(s)", HFILL }},
 438
 439         { &hf_lapdm_fragment_overlap_conflicts,
 440         { "Message fragment overlapping with conflicting data", "lapdm.fragment.overlap.conflicts", FT_BOOLEAN, BASE_NONE,
 441         NULL, 0x0, "LAPDm Message fragment overlaps with conflicting data", HFILL }},
 442
 443         { &hf_lapdm_fragment_multiple_tails,
 444         { "Message has multiple tail fragments", "lapdm.fragment.multiple_tails", FT_BOOLEAN, BASE_NONE,
 445         NULL, 0x0, "LAPDm Message fragment has multiple tail fragments", HFILL }},
 446
 447         { &hf_lapdm_fragment_too_long_fragment,
 448         { "Message fragment too long", "lapdm.fragment.too_long_fragment", FT_BOOLEAN, BASE_NONE,
 449         NULL, 0x0, "LAPDm Message fragment data goes beyond the packet end", HFILL }},
 450
 451         { &hf_lapdm_fragment_error,
 452         { "Message defragmentation error", "lapdm.fragment.error", FT_FRAMENUM, BASE_NONE,
 453         NULL, 0x00, "LAPDm Message defragmentation error due to illegal fragments", HFILL }},
 454
 455         { &hf_lapdm_fragment_count,
 456         { "Message fragment count", "lapdm.fragment.count", FT_UINT32, BASE_DEC,
 457         NULL, 0x00, NULL, HFILL }},
 458
 459         { &hf_lapdm_reassembled_in,
 460         { "Reassembled in", "lapdm.reassembled.in", FT_FRAMENUM, BASE_NONE,
 461         NULL, 0x00, "LAPDm Message has been reassembled in this packet.", HFILL }},
 462
 463         { &hf_lapdm_reassembled_length,
 464         { "Reassembled LAPDm length", "lapdm.reassembled.length", FT_UINT32, BASE_DEC,
 465         NULL, 0x00, "The total length of the reassembled payload", HFILL }}
 466
 467     };
 468     static gint *ett[] = {
 469         &ett_lapdm,
 470         &ett_lapdm_address,
 471         &ett_lapdm_control,
 472         &ett_lapdm_length,
 473         &ett_lapdm_fragment,
 474         &ett_lapdm_fragments
 475     };
 476
 477     module_t *lapdm_module;
 478
 479     proto_lapdm = proto_register_protocol("Link Access Procedure, Channel Dm (LAPDm)", "LAPDm", "lapdm");
 480     proto_register_field_array (proto_lapdm, hf, array_length(hf));
 481     proto_register_subtree_array(ett, array_length(ett));
 482
 483     register_dissector("lapdm", dissect_lapdm, proto_lapdm);
 484
 485     lapdm_sapi_dissector_table = register_dissector_table("lapdm.sapi", "LAPDm SAPI", FT_UINT8, BASE_DEC);
 486
 487     lapdm_module = prefs_register_protocol(proto_lapdm, NULL);
 488     prefs_register_bool_preference(lapdm_module, "reassemble",
 489         "Reassemble fragmented LAPDm packets",
 490         "Whether the dissector should defragment LAPDm messages spanning multiple packets.",
 491         &reassemble_lapdm);
 492     register_init_routine (lapdm_defragment_init);
 493 }
 494
 495 void
 496 proto_reg_handoff_lapdm(void)
 497 {
 498     data_handle = find_dissector("data");
 499 }
 500