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., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA.
  24  */
  25
  26
  27 #include "config.h"
  28
  29 #include <glib.h>
  30 #include <epan/packet.h>
  31 #include <epan/prefs.h>
  32 #include <epan/circuit.h>
  33
  34 static int proto_gsm_um = -1;
  35 static int hf_gsm_um_direction = -1;
  36 static int hf_gsm_um_channel = -1;
  37 static int hf_gsm_um_bsic = -1;
  38 static int hf_gsm_um_arfcn = -1;
  39 static int hf_gsm_um_frame = -1;
  40 static int hf_gsm_um_error = -1;
  41 static int hf_gsm_um_timeshift = -1;
  42 static int hf_gsm_um_l2_pseudo_len = -1;
  43
  44 static gint ett_gsm_um = -1;
  45
  46 static dissector_handle_t lapdm_handle;
  47 static dissector_handle_t dtap_handle;
  48 static dissector_handle_t data_handle;
  49
  50 static gboolean dcs1800_gsm = TRUE;
  51
  52 #define GSM_UM_L2_PSEUDO_LEN            0xfc
  53
  54
  55 static void
  56 decode_arfcn(guint16 arfcn, const char **band, guint *uplink, guint *downlink)
  57 {
  58         /* Decode ARFCN to frequency using GSM 05.05 */
  59         if( arfcn >= 1 && arfcn <= 124 ) {
  60                 *band = "P-GSM 900";
  61                 *uplink = 890000 + 200 * arfcn;
  62                 *downlink = *uplink + 45000;
  63         }
  64         else if( arfcn == 0 ) {
  65                 *band = "E-GSM 900";
  66                 *uplink = 890000 + 200 * arfcn;
  67                 *downlink = *uplink + 45000;
  68         }
  69         else if( arfcn >= 975 && arfcn <= 1023 ) {
  70                 *band = "E-GSM 900";
  71                 *uplink = 890000 + 200 * (arfcn - 1024);
  72                 *downlink = *uplink + 45000;
  73         }
  74         else if( arfcn >= 955 && arfcn <= 1023 ) {
  75                 *band = "R-GSM 900";
  76                 *uplink = 890000 + 200 * (arfcn - 1024);
  77                 *downlink = *uplink + 45000;
  78         }
  79         else if( arfcn >= 512 && arfcn <= 885 && dcs1800_gsm) {
  80                 *band = "DCS 1800";
  81                 *uplink = 1710200 + 200 * (arfcn - 512);
  82                 *downlink = *uplink + 95000;
  83         }
  84         else if( arfcn >= 512 && arfcn <= 810 && !dcs1800_gsm) {
  85                 *band = "PCS 1900";
  86                 *uplink = 1850200 + 200 * (arfcn - 512);
  87                 *downlink = *uplink + 80000;
  88         }
  89         else if( arfcn >= 259 && arfcn <= 293 ) {
  90                 *band = "GSM 450";
  91                 *uplink = 450600 + 200 * (arfcn - 259);
  92                 *downlink = *uplink + 10000;
  93         }
  94         else if( arfcn >= 306 && arfcn <= 340 ) {
  95                 *band = "GSM 480";
  96                 *uplink = 479000 + 200 * (arfcn - 306);
  97                 *downlink = *uplink + 10000;
  98         }
  99         else if( arfcn >= 128 && arfcn <= 251 ) {
 100                 *band = "GSM 850";
 101                 *uplink = 824200 + 200 * (arfcn - 128);
 102                 *downlink = *uplink + 45000;
 103         }
 104         else {
 105                 *band = "Unknown";
 106                 *uplink = *downlink = 0;
 107         }
 108 }
 109
 110
 111 static void
 112 dissect_gsm_um(tvbuff_t *tvb, packet_info *pinfo, proto_tree *tree)
 113 {
 114         proto_tree *gsm_um_tree = NULL;
 115         proto_item *ti;
 116
 117         col_set_str(pinfo->cinfo, COL_PROTOCOL, "GSM Um");
 118
 119         if (pinfo->pseudo_header->gsm_um.uplink) {
 120                 col_set_str(pinfo->cinfo, COL_RES_DL_DST, "BTS");
 121                 col_set_str(pinfo->cinfo, COL_RES_DL_SRC, "MS");
 122         }
 123         else {
 124                 switch (pinfo->pseudo_header->gsm_um.channel) {
 125                         case GSM_UM_CHANNEL_BCCH:
 126                         case GSM_UM_CHANNEL_CCCH:
 127                         case GSM_UM_CHANNEL_PCH:
 128                         case GSM_UM_CHANNEL_AGCH:
 129                                 col_set_str(pinfo->cinfo, COL_RES_DL_DST, "Broadcast");
 130                                 break;
 131                         default:
 132                                 col_set_str(pinfo->cinfo, COL_RES_DL_DST, "MS");
 133                                 break;
 134                 }
 135                 col_set_str(pinfo->cinfo, COL_RES_DL_SRC, "BTS");
 136         }
 137
 138         if (tree) {
 139                 const char *channel;
 140
 141                 ti = proto_tree_add_item(tree, proto_gsm_um, tvb, 0, 0, ENC_NA);
 142                 gsm_um_tree = proto_item_add_subtree(ti, ett_gsm_um);
 143
 144                 switch( pinfo->pseudo_header->gsm_um.channel ) {
 145                         case GSM_UM_CHANNEL_BCCH: channel = "BCCH"; break;
 146                         case GSM_UM_CHANNEL_CCCH: channel = "CCCH"; break;
 147                         case GSM_UM_CHANNEL_PCH: channel = "PCH"; break;
 148                         case GSM_UM_CHANNEL_AGCH: channel = "AGCH"; break;
 149                         case GSM_UM_CHANNEL_SACCH: channel = "SACCH"; break;
 150                         case GSM_UM_CHANNEL_FACCH: channel = "FACCH"; break;
 151                         case GSM_UM_CHANNEL_SDCCH: channel = "SDCCH"; break;
 152                         default: channel = "Unknown"; break;
 153                 }
 154
 155                 if( pinfo->pseudo_header->gsm_um.uplink ) {
 156                         proto_tree_add_string(gsm_um_tree, hf_gsm_um_direction, tvb, 0, 0, "Uplink");
 157                 }
 158                 else {
 159                         proto_tree_add_string(gsm_um_tree, hf_gsm_um_direction, tvb, 0, 0, "Downlink");
 160                 }
 161
 162                 proto_tree_add_string(gsm_um_tree, hf_gsm_um_channel, tvb, 0, 0, channel);
 163
 164                 /* Show the other fields, if we have them (ie. downlink, BTS->MS) */
 165                 if( !pinfo->pseudo_header->gsm_um.uplink ) {
 166                         const char *band;
 167                         guint downlink, uplink;
 168
 169                         decode_arfcn(pinfo->pseudo_header->gsm_um.arfcn, &band, &uplink, &downlink);
 170
 171                         proto_tree_add_uint(gsm_um_tree, hf_gsm_um_arfcn, tvb, 0, 0,
 172                                 pinfo->pseudo_header->gsm_um.arfcn);
 173                         proto_tree_add_text(gsm_um_tree, tvb, 0, 0,
 174                                 "Band: %s, Frequency: %u.%03uMHz", band,
 175                                 downlink / 1000, downlink % 1000);
 176                         proto_tree_add_uint(gsm_um_tree, hf_gsm_um_bsic, tvb, 0, 0,
 177                                 pinfo->pseudo_header->gsm_um.bsic);
 178                         proto_tree_add_uint(gsm_um_tree, hf_gsm_um_frame, tvb, 0, 0,
 179                                 pinfo->pseudo_header->gsm_um.tdma_frame);
 180                         proto_tree_add_uint(gsm_um_tree, hf_gsm_um_error, tvb, 0, 0,
 181                                 pinfo->pseudo_header->gsm_um.error);
 182                         proto_tree_add_uint(gsm_um_tree, hf_gsm_um_timeshift, tvb, 0, 0,
 183                                 pinfo->pseudo_header->gsm_um.timeshift);
 184                 }
 185         }
 186
 187         /* TODO: If CCCH downlink could work out of PCH or AGCH by peeking at next bytes, uplink is RACH */
 188
 189         switch( pinfo->pseudo_header->gsm_um.channel ) {
 190                 case GSM_UM_CHANNEL_BCCH:
 191                 case GSM_UM_CHANNEL_CCCH:
 192                 case GSM_UM_CHANNEL_PCH:
 193                 case GSM_UM_CHANNEL_AGCH:
 194                         if( !pinfo->pseudo_header->gsm_um.uplink ) {
 195                                 tvbuff_t *next_tvb;
 196                                 guint8 pseudo_len, len_left, len_byte;
 197
 198                                 len_left = tvb_length(tvb);
 199                                 len_byte = tvb_get_guint8(tvb, 0);
 200                                 pseudo_len = len_byte >> 2;
 201                                 next_tvb = tvb_new_subset(tvb, 1, MIN(len_left, pseudo_len), -1);
 202
 203                                 if (tree) {
 204                                         proto_tree_add_uint(gsm_um_tree, hf_gsm_um_l2_pseudo_len, tvb, 0, 1,
 205                                                 len_byte);
 206                                 }
 207
 208                                 /* Only dissect non-empty frames */
 209                                 if( tvb_length(next_tvb) ) {
 210                                         call_dissector(dtap_handle, next_tvb, pinfo, tree);
 211                                 }
 212                         }
 213                         else {
 214                                 /* Either RACH, or something invalid */
 215                                 call_dissector(data_handle, tvb, pinfo, tree);
 216                         }
 217                         break;
 218                 case GSM_UM_CHANNEL_SACCH:
 219                 case GSM_UM_CHANNEL_FACCH:
 220                 case GSM_UM_CHANNEL_SDCCH:
 221                         call_dissector(lapdm_handle, tvb, pinfo, tree);
 222                         break;
 223                 default:
 224                         call_dissector(data_handle, tvb, pinfo, tree);
 225                         break;
 226         }
 227 }
 228
 229 void
 230 proto_register_gsm_um(void)
 231 {
 232         static hf_register_info hf[] = {
 233                 { &hf_gsm_um_direction,
 234                 { "Direction",  "gsm_um.direction", FT_STRINGZ, BASE_NONE,
 235                   NULL, 0x0, NULL, HFILL }},
 236
 237                 { &hf_gsm_um_channel,
 238                 { "Channel",    "gsm_um.channel", FT_STRINGZ, BASE_NONE,
 239                   NULL, 0x0, NULL, HFILL }},
 240
 241                 { &hf_gsm_um_bsic,
 242                 { "BSIC",       "gsm_um.bsic", FT_UINT8, BASE_DEC,
 243                   NULL, 0x0, "Base station identity code", HFILL }},
 244
 245                 { &hf_gsm_um_arfcn,
 246                 { "ARFCN",      "gsm_um.arfcn", FT_UINT16, BASE_DEC,
 247                   NULL, 0x0, "Absolute radio frequency channel number", HFILL }},
 248
 249                 { &hf_gsm_um_frame,
 250                 { "TDMA Frame", "gsm_um.frame", FT_UINT32, BASE_DEC,
 251                   NULL, 0x0, NULL, HFILL }},
 252
 253                 { &hf_gsm_um_error,
 254                 { "Error",      "gsm_um.error", FT_UINT8, BASE_DEC,
 255                   NULL, 0x0, NULL, HFILL }},
 256
 257                 { &hf_gsm_um_timeshift,
 258                 { "Timeshift",  "gsm_um.timeshift", FT_UINT16, BASE_DEC,
 259                   NULL, 0x0, NULL, HFILL }},
 260
 261                 { &hf_gsm_um_l2_pseudo_len,
 262                 { "L2 Pseudo Length",   "gsm_um.l2_pseudo_len", FT_UINT8, BASE_DEC,
 263                   NULL, GSM_UM_L2_PSEUDO_LEN, NULL, HFILL }}
 264
 265         };
 266         static gint *ett[] = {
 267                 &ett_gsm_um
 268         };
 269         module_t *gsm_um_module;
 270
 271         proto_gsm_um = proto_register_protocol("GSM Um Interface", "GSM Um", "gsm_um");
 272         proto_register_field_array(proto_gsm_um, hf, array_length(hf));
 273         proto_register_subtree_array(ett, array_length(ett));
 274
 275         gsm_um_module = prefs_register_protocol(proto_gsm_um, NULL);
 276         prefs_register_bool_preference(gsm_um_module, "dcs1800",
 277                                    "Treat ARFCN 512-810 as DCS 1800 rather than PCS 1900",
 278                                    "Treat ARFCN 512-810 as DCS 1800 rather than PCS 1900",
 279                                    &dcs1800_gsm);
 280
 281 }
 282
 283 void
 284 proto_reg_handoff_gsm_um(void)
 285 {
 286         dissector_handle_t gsm_um_handle;
 287
 288         lapdm_handle = find_dissector("lapdm");
 289         dtap_handle = find_dissector("gsm_a_dtap");
 290         data_handle = find_dissector("data");
 291
 292         gsm_um_handle = create_dissector_handle(dissect_gsm_um, proto_gsm_um);
 293
 294         dissector_add_uint("wtap_encap", WTAP_ENCAP_GSM_UM, gsm_um_handle);
 295 }
 296