epan/dissectors/packet-gsm_um.c

   1 /* packet-gsm_um.c
   2  * Routines for GSM Um packet 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 Gerald Combs
  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
  27 #ifdef HAVE_CONFIG_H
  28 # include "config.h"
  29 #endif
  30
  31 #include <stdio.h>
  32 #include <glib.h>
  33 #include <epan/packet.h>
  34 #include <epan/prefs.h>
  35 #include <epan/circuit.h>
  36
  37 static int proto_gsm_um = -1;
  38 static int hf_gsm_um_direction = -1;
  39 static int hf_gsm_um_channel = -1;
  40 static int hf_gsm_um_bsic = -1;
  41 static int hf_gsm_um_arfcn = -1;
  42 static int hf_gsm_um_frame = -1;
  43 static int hf_gsm_um_error = -1;
  44 static int hf_gsm_um_timeshift = -1;
  45 static int hf_gsm_um_l2_pseudo_len = -1;
  46
  47 static gint ett_gsm_um = -1;
  48
  49 static dissector_handle_t lapdm_handle;
  50 static dissector_handle_t dtap_handle;
  51 static dissector_handle_t data_handle;
  52
  53 static gboolean dcs1800_gsm = TRUE;
  54
  55 #define GSM_UM_L2_PSEUDO_LEN            0xfc
  56
  57
  58 static void
  59 decode_arfcn(guint16 arfcn, const char **band, guint *uplink, guint *downlink)
  60 {
  61         /* Decode ARFCN to frequency using GSM 05.05 */
  62         if( arfcn >= 1 && arfcn <= 124 ) {
  63                 *band = "P-GSM 900";
  64                 *uplink = 890000 + 200 * arfcn;
  65                 *downlink = *uplink + 45000;
  66         }
  67         else if( arfcn == 0 ) {
  68                 *band = "E-GSM 900";
  69                 *uplink = 890000 + 200 * arfcn;
  70                 *downlink = *uplink + 45000;
  71         }
  72         else if( arfcn >= 975 && arfcn <= 1023 ) {
  73                 *band = "E-GSM 900";
  74                 *uplink = 890000 + 200 * (arfcn - 1024);
  75                 *downlink = *uplink + 45000;
  76         }
  77         else if( arfcn >= 955 && arfcn <= 1023 ) {
  78                 *band = "R-GSM 900";
  79                 *uplink = 890000 + 200 * (arfcn - 1024);
  80                 *downlink = *uplink + 45000;
  81         }
  82         else if( arfcn >= 512 && arfcn <= 885 && dcs1800_gsm) {
  83                 *band = "DCS 1800";
  84                 *uplink = 1710200 + 200 * (arfcn - 512);
  85                 *downlink = *uplink + 95000;
  86         }
  87         else if( arfcn >= 512 && arfcn <= 810 && !dcs1800_gsm) {
  88                 *band = "PCS 1900";
  89                 *uplink = 1850200 + 200 * (arfcn - 512);
  90                 *downlink = *uplink + 80000;
  91         }
  92         else if( arfcn >= 259 && arfcn <= 293 ) {
  93                 *band = "GSM 450";
  94                 *uplink = 450600 + 200 * (arfcn - 259);
  95                 *downlink = *uplink + 10000;
  96         }
  97         else if( arfcn >= 306 && arfcn <= 340 ) {
  98                 *band = "GSM 480";
  99                 *uplink = 479000 + 200 * (arfcn - 306);
 100                 *downlink = *uplink + 10000;
 101         }
 102         else if( arfcn >= 128 && arfcn <= 251 ) {
 103                 *band = "GSM 850";
 104                 *uplink = 824200 + 200 * (arfcn - 128);
 105                 *downlink = *uplink + 45000;
 106         }
 107         else {
 108                 *band = "Unknown";
 109                 *uplink = *downlink = 0;
 110         }
 111 }
 112
 113
 114 static void
 115 dissect_gsm_um(tvbuff_t *tvb, packet_info *pinfo, proto_tree *tree)
 116 {
 117         proto_tree *gsm_um_tree = NULL;
 118         proto_item *ti;
 119
 120         if (check_col(pinfo->cinfo, COL_PROTOCOL))
 121                 col_set_str(pinfo->cinfo, COL_PROTOCOL, "GSM Um");
 122
 123         if (pinfo->pseudo_header->gsm_um.uplink) {
 124                 if (check_col(pinfo->cinfo, COL_RES_DL_DST))
 125                         col_set_str(pinfo->cinfo, COL_RES_DL_DST, "BTS");
 126                 if (check_col(pinfo->cinfo, COL_RES_DL_SRC))
 127                         col_set_str(pinfo->cinfo, COL_RES_DL_SRC, "MS");
 128         }
 129         else {
 130                 switch (pinfo->pseudo_header->gsm_um.channel) {
 131                         case GSM_UM_CHANNEL_BCCH:
 132                         case GSM_UM_CHANNEL_CCCH:
 133                         case GSM_UM_CHANNEL_PCH:
 134                         case GSM_UM_CHANNEL_AGCH:
 135                                 if (check_col(pinfo->cinfo, COL_RES_DL_DST))
 136                                     col_set_str(pinfo->cinfo, COL_RES_DL_DST, "Broadcast");
 137                                 break;
 138                         default:
 139                                 if (check_col(pinfo->cinfo, COL_RES_DL_DST))
 140                                     col_set_str(pinfo->cinfo, COL_RES_DL_DST, "MS");
 141                                 break;
 142                 }
 143                 if (check_col(pinfo->cinfo, COL_RES_DL_SRC))
 144                     col_set_str(pinfo->cinfo, COL_RES_DL_SRC, "BTS");
 145         }
 146
 147         if (tree) {
 148                 const char *channel;
 149
 150                 ti = proto_tree_add_item(tree, proto_gsm_um, tvb, 0, 0, FALSE);
 151                 gsm_um_tree = proto_item_add_subtree(ti, ett_gsm_um);
 152
 153                 switch( pinfo->pseudo_header->gsm_um.channel ) {
 154                         case GSM_UM_CHANNEL_BCCH: channel = "BCCH"; break;
 155                         case GSM_UM_CHANNEL_CCCH: channel = "CCCH"; break;
 156                         case GSM_UM_CHANNEL_PCH: channel = "PCH"; break;
 157                         case GSM_UM_CHANNEL_AGCH: channel = "AGCH"; break;
 158                         case GSM_UM_CHANNEL_SACCH: channel = "SACCH"; break;
 159                         case GSM_UM_CHANNEL_FACCH: channel = "FACCH"; break;
 160                         case GSM_UM_CHANNEL_SDCCH: channel = "SDCCH"; break;
 161                         default: channel = "Unknown"; break;
 162                 }
 163
 164                 if( pinfo->pseudo_header->gsm_um.uplink ) {
 165                         proto_tree_add_string(gsm_um_tree, hf_gsm_um_direction, tvb, 0, 0, "Uplink");
 166                 }
 167                 else {
 168                         proto_tree_add_string(gsm_um_tree, hf_gsm_um_direction, tvb, 0, 0, "Downlink");
 169                 }
 170
 171                 proto_tree_add_string(gsm_um_tree, hf_gsm_um_channel, tvb, 0, 0, channel);
 172
 173                 /* Show the other fields, if we have them (ie. downlink, BTS->MS) */
 174                 if( !pinfo->pseudo_header->gsm_um.uplink ) {
 175                         const char *band;
 176                         guint downlink, uplink;
 177
 178                         decode_arfcn(pinfo->pseudo_header->gsm_um.arfcn, &band, &uplink, &downlink);
 179
 180                         proto_tree_add_uint(gsm_um_tree, hf_gsm_um_arfcn, tvb, 0, 0,
 181                                 pinfo->pseudo_header->gsm_um.arfcn);
 182                         proto_tree_add_text(gsm_um_tree, tvb, 0, 0,
 183                                 "Band: %s, Frequency: %u.%03uMHz", band,
 184                                 downlink / 1000, downlink % 1000);
 185                         proto_tree_add_uint(gsm_um_tree, hf_gsm_um_bsic, tvb, 0, 0,
 186                                 pinfo->pseudo_header->gsm_um.bsic);
 187                         proto_tree_add_uint(gsm_um_tree, hf_gsm_um_frame, tvb, 0, 0,
 188                                 pinfo->pseudo_header->gsm_um.tdma_frame);
 189                         proto_tree_add_uint(gsm_um_tree, hf_gsm_um_error, tvb, 0, 0,
 190                                 pinfo->pseudo_header->gsm_um.error);
 191                         proto_tree_add_uint(gsm_um_tree, hf_gsm_um_timeshift, tvb, 0, 0,
 192                                 pinfo->pseudo_header->gsm_um.timeshift);
 193                 }
 194         }
 195
 196         /* TODO: If CCCH downlink could work out of PCH or AGCH by peeking at next bytes, uplink is RACH */
 197
 198         switch( pinfo->pseudo_header->gsm_um.channel ) {
 199                 case GSM_UM_CHANNEL_BCCH:
 200                 case GSM_UM_CHANNEL_CCCH:
 201                 case GSM_UM_CHANNEL_PCH:
 202                 case GSM_UM_CHANNEL_AGCH:
 203                         if( !pinfo->pseudo_header->gsm_um.uplink ) {
 204                                 tvbuff_t *next_tvb;
 205                                 guint8 pseudo_len, len_left, len_byte;
 206
 207                                 len_left = tvb_length(tvb);
 208                                 len_byte = tvb_get_guint8(tvb, 0);
 209                                 pseudo_len = len_byte >> 2;
 210                                 next_tvb = tvb_new_subset(tvb, 1, MIN(len_left, pseudo_len), -1);
 211
 212                                 if (tree) {
 213                                         proto_tree_add_uint(gsm_um_tree, hf_gsm_um_l2_pseudo_len, tvb, 0, 1,
 214                                                 len_byte);
 215                                 }
 216
 217                                 /* Only dissect non-empty frames */
 218                                 if( tvb_length(next_tvb) ) {
 219                                         call_dissector(dtap_handle, next_tvb, pinfo, tree);
 220                                 }
 221                         }
 222                         else {
 223                                 /* Either RACH, or something invalid */
 224                                 call_dissector(data_handle, tvb, pinfo, tree);
 225                         }
 226                         break;
 227                 case GSM_UM_CHANNEL_SACCH:
 228                 case GSM_UM_CHANNEL_FACCH:
 229                 case GSM_UM_CHANNEL_SDCCH:
 230                         call_dissector(lapdm_handle, tvb, pinfo, tree);
 231                         break;
 232                 default:
 233                         call_dissector(data_handle, tvb, pinfo, tree);
 234                         break;
 235         }
 236 }
 237
 238 void
 239 proto_register_gsm_um(void)
 240 {
 241         static hf_register_info hf[] = {
 242                 { &hf_gsm_um_direction,
 243                 { "Direction",  "gsm_um.direction", FT_STRINGZ, BASE_NONE,
 244                   NULL, 0x0, NULL, HFILL }},
 245
 246                 { &hf_gsm_um_channel,
 247                 { "Channel",    "gsm_um.channel", FT_STRINGZ, BASE_NONE,
 248                   NULL, 0x0, NULL, HFILL }},
 249
 250                 { &hf_gsm_um_bsic,
 251                 { "BSIC",       "gsm_um.bsic", FT_UINT8, BASE_DEC,
 252                   NULL, 0x0, "Base station identity code", HFILL }},
 253
 254                 { &hf_gsm_um_arfcn,
 255                 { "ARFCN",      "gsm_um.arfcn", FT_UINT16, BASE_DEC,
 256                   NULL, 0x0, "Absolute radio frequency channel number", HFILL }},
 257
 258                 { &hf_gsm_um_frame,
 259                 { "TDMA Frame", "gsm_um.frame", FT_UINT32, BASE_DEC,
 260                   NULL, 0x0, NULL, HFILL }},
 261
 262                 { &hf_gsm_um_error,
 263                 { "Error",      "gsm_um.error", FT_UINT8, BASE_DEC,
 264                   NULL, 0x0, NULL, HFILL }},
 265
 266                 { &hf_gsm_um_timeshift,
 267                 { "Timeshift",  "gsm_um.timeshift", FT_UINT16, BASE_DEC,
 268                   NULL, 0x0, NULL, HFILL }},
 269
 270                 { &hf_gsm_um_l2_pseudo_len,
 271                 { "L2 Pseudo Length",   "gsm_um.l2_pseudo_len", FT_UINT8, BASE_DEC,
 272                   NULL, GSM_UM_L2_PSEUDO_LEN, NULL, HFILL }}
 273
 274         };
 275         static gint *ett[] = {
 276                 &ett_gsm_um
 277         };
 278         module_t *gsm_um_module;
 279
 280         proto_gsm_um = proto_register_protocol("GSM Um Interface", "GSM Um", "gsm_um");
 281         proto_register_field_array(proto_gsm_um, hf, array_length(hf));
 282         proto_register_subtree_array(ett, array_length(ett));
 283
 284         gsm_um_module = prefs_register_protocol(proto_gsm_um, NULL);
 285         prefs_register_bool_preference(gsm_um_module, "dcs1800",
 286                                    "Treat ARFCN 512-810 as DCS 1800 rather than PCS 1900",
 287                                    "Treat ARFCN 512-810 as DCS 1800 rather than PCS 1900",
 288                                    &dcs1800_gsm);
 289
 290 }
 291
 292 void
 293 proto_reg_handoff_gsm_um(void)
 294 {
 295         dissector_handle_t gsm_um_handle;
 296
 297         lapdm_handle = find_dissector("lapdm");
 298         dtap_handle = find_dissector("gsm_a_dtap");
 299         data_handle = find_dissector("data");
 300
 301         gsm_um_handle = create_dissector_handle(dissect_gsm_um, proto_gsm_um);
 302
 303         dissector_add("wtap_encap", WTAP_ENCAP_GSM_UM, gsm_um_handle);
 304 }
 305