epan/dissectors/packet-tdmoe.c

   1 /* packet-tdmoe.c
   2  * Routines for TDM over Ethernet packet disassembly
   3  * Copyright 2010, Haakon Nessjoen <haakon.nessjoen@gmail.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 #include "config.h"
  27
  28 #include <glib.h>
  29
  30 #include <epan/packet.h>
  31 #include <epan/etypes.h>
  32 #include <epan/prefs.h>
  33
  34 /* Bitmasks for the flags in the fourth byte of the packet */
  35 #define TDMOE_YELLOW_ALARM_BITMASK 0x01
  36 #define TDMOE_SIGBITS_BITMASK      0x02
  37
  38 /* protocols and header fields */
  39 static int proto_tdmoe = -1;
  40
  41 static int hf_tdmoe_subaddress = -1;
  42 static int hf_tdmoe_samples = -1;
  43 static int hf_tdmoe_flags = -1;
  44 static int hf_tdmoe_yellow_alarm = -1;
  45 static int hf_tdmoe_sig_bits_present = -1;
  46 static int hf_tdmoe_packet_counter = -1;
  47 static int hf_tdmoe_channels = -1;
  48 static int hf_tdmoe_sig_bits = -1;
  49
  50 static gint ett_tdmoe = -1;
  51 static gint ett_tdmoe_flags = -1;
  52
  53 static dissector_handle_t lapd_handle;
  54 static dissector_handle_t data_handle;
  55
  56 static gint pref_tdmoe_d_channel = 24;
  57
  58 void proto_reg_handoff_tdmoe(void);
  59
  60 static int
  61 dissect_tdmoe(tvbuff_t *tvb, packet_info *pinfo, proto_tree *tree, void *data _U_)
  62 {
  63         proto_item *ti;
  64         proto_tree *tdmoe_tree;
  65         tvbuff_t   *next_client;
  66         guint16     channels;
  67         guint16     subaddress;
  68         gint32 offset = 0;
  69         static const gint *flags[] = { &hf_tdmoe_yellow_alarm, &hf_tdmoe_sig_bits_present, NULL };
  70         int         chan;
  71
  72         /* Check that there's enough data */
  73         if (tvb_length(tvb) < 8)
  74                 return 0;
  75
  76         subaddress = tvb_get_ntohs(tvb, 0);
  77         channels   = tvb_get_ntohs(tvb, 6);
  78
  79         col_set_str(pinfo->cinfo, COL_PROTOCOL, "TDMoE");
  80         col_add_fstr(pinfo->cinfo, COL_INFO, "Subaddress: %d Channels: %d %s",
  81                 subaddress,
  82                 channels,
  83                 (tvb_get_guint8(tvb, 3) & TDMOE_YELLOW_ALARM_BITMASK ? "[YELLOW ALARM]" : "")
  84         );
  85
  86
  87         /* create display subtree for the protocol */
  88         ti = proto_tree_add_item(tree, proto_tdmoe, tvb, 0, -1, ENC_NA);
  89         tdmoe_tree = proto_item_add_subtree(ti, ett_tdmoe);
  90
  91         /* Subaddress */
  92         proto_tree_add_item(tdmoe_tree, hf_tdmoe_subaddress, tvb, offset, 2, ENC_BIG_ENDIAN);
  93         offset+=2;
  94
  95         /* Samples (1 byte) */
  96         proto_tree_add_item(tdmoe_tree, hf_tdmoe_samples, tvb, offset, 1, ENC_NA);
  97         offset++;
  98
  99         /* Yellow alarm & "Sig bits present" bits (1 byte) */
 100         proto_tree_add_bitmask(tdmoe_tree, tvb, offset, hf_tdmoe_flags, ett_tdmoe_flags, flags, ENC_BIG_ENDIAN);
 101         offset++;
 102
 103         /* Packet counter (2 bytes) */
 104         proto_tree_add_item(tdmoe_tree, hf_tdmoe_packet_counter, tvb, offset, 2, ENC_BIG_ENDIAN);
 105         offset+=2;
 106
 107         /* Number of channels in packet (2 bytes) */
 108         proto_tree_add_item(tdmoe_tree, hf_tdmoe_channels, tvb, offset, 2, ENC_BIG_ENDIAN);
 109         offset+=2;
 110
 111         if (tvb_get_guint8(tvb, 3) & TDMOE_SIGBITS_BITMASK) {
 112                 /* 4 sigbits per channel. Might be different on other sub-protocols? */
 113                 guint16 length = (channels >> 1) + ((channels & 0x01) ? 1 : 0);
 114
 115                 proto_tree_add_item(tdmoe_tree, hf_tdmoe_sig_bits, tvb, offset, length, ENC_NA);
 116                 offset += length;
 117         }
 118
 119         /* The rest is SAMPLES * CHANNELS bytes of channel data */
 120         for (chan = 1; chan <= channels; chan++) {
 121                 next_client = tvb_new_subset_length(tvb, offset + ((chan - 1) * 8), 8);
 122                 if (chan == pref_tdmoe_d_channel) {
 123                         call_dissector(lapd_handle, next_client, pinfo, tree);
 124                 } else {
 125                         call_dissector(data_handle, next_client, pinfo, tree);
 126                 }
 127         }
 128         return 1;
 129 }
 130
 131 void
 132 proto_register_tdmoe(void)
 133 {
 134         static hf_register_info hf[] = {
 135
 136                 { &hf_tdmoe_subaddress,
 137                 { "Subaddress", "tdmoe.subaddress", FT_UINT8, BASE_DEC, NULL, 0x0,
 138                         NULL, HFILL }},
 139                 { &hf_tdmoe_samples,
 140                 { "Samples",    "tdmoe.samples", FT_UINT8, BASE_DEC, NULL, 0x0,
 141                         "Samples per channel", HFILL }},
 142                 { &hf_tdmoe_flags,
 143                 { "Flags",      "tdmoe.flags", FT_UINT8, BASE_HEX, NULL, 0x0,
 144                         NULL, HFILL }},
 145                 { &hf_tdmoe_yellow_alarm,
 146                 { "Yellow Alarm", "tdmoe.yellowalarm", FT_BOOLEAN, 8, NULL, TDMOE_YELLOW_ALARM_BITMASK,
 147                         NULL, HFILL }},
 148                 { &hf_tdmoe_sig_bits_present,
 149                 { "Sig bits present", "tdmoe.sig_bits_present", FT_BOOLEAN, 8, NULL, TDMOE_SIGBITS_BITMASK,
 150                         NULL, HFILL }},
 151                 { &hf_tdmoe_packet_counter,
 152                 { "Counter", "tdmoe.counter", FT_UINT16, BASE_DEC, NULL, 0x0,
 153                         "Packet number", HFILL }},
 154                 { &hf_tdmoe_channels,
 155                 { "Channels", "tdmoe.channels", FT_UINT16, BASE_DEC, NULL, 0x0,
 156                         NULL, HFILL }},
 157                 { &hf_tdmoe_sig_bits,
 158                 { "Sig bits", "tdmoe.sig_bits", FT_BYTES, BASE_NONE, NULL, 0x0,
 159                         NULL, HFILL }},
 160         };
 161         static gint *ett[] = {
 162                 &ett_tdmoe,
 163                 &ett_tdmoe_flags
 164         };
 165         module_t *tdmoe_module;
 166
 167         proto_tdmoe = proto_register_protocol("Digium TDMoE Protocol", "TDMoE", "tdmoe");
 168         proto_register_field_array(proto_tdmoe, hf, array_length(hf));
 169         proto_register_subtree_array(ett, array_length(ett));
 170         tdmoe_module = prefs_register_protocol(proto_tdmoe, proto_reg_handoff_tdmoe);
 171         prefs_register_uint_preference(tdmoe_module, "d_channel",
 172                 "TDMoE D-Channel",
 173                 "The TDMoE channel that contains the D-Channel.",
 174                 10, &pref_tdmoe_d_channel);
 175 }
 176
 177 void
 178 proto_reg_handoff_tdmoe(void)
 179 {
 180         dissector_handle_t tdmoe_handle;
 181
 182         tdmoe_handle = new_create_dissector_handle(dissect_tdmoe, proto_tdmoe);
 183         dissector_add_uint("ethertype", ETHERTYPE_TDMOE, tdmoe_handle);
 184
 185         lapd_handle = find_dissector("lapd-bitstream");
 186         data_handle = find_dissector("data");
 187 }