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  * Wireshark - Network traffic analyzer
   6  * By Gerald Combs <gerald@wireshark.org>
   7  * Copyright 1998 Gerald Combs
   8  *
   9  * SPDX-License-Identifier: GPL-2.0-or-later
  10  */
  11
  12 #include "config.h"
  13
  14 #include <epan/packet.h>
  15 #include <epan/etypes.h>
  16 #include <epan/prefs.h>
  17
  18 /* Bitmasks for the flags in the fourth byte of the packet */
  19 #define TDMOE_YELLOW_ALARM_BITMASK 0x01
  20 #define TDMOE_SIGBITS_BITMASK      0x02
  21
  22 void proto_reg_handoff_tdmoe(void);
  23 void proto_register_tdmoe(void);
  24
  25 static dissector_handle_t tdmoe_handle;
  26
  27 /* protocols and header fields */
  28 static int proto_tdmoe;
  29
  30 static int hf_tdmoe_subaddress;
  31 static int hf_tdmoe_samples;
  32 static int hf_tdmoe_flags;
  33 static int hf_tdmoe_yellow_alarm;
  34 static int hf_tdmoe_sig_bits_present;
  35 static int hf_tdmoe_packet_counter;
  36 static int hf_tdmoe_channels;
  37 static int hf_tdmoe_sig_bits;
  38
  39 static int ett_tdmoe;
  40 static int ett_tdmoe_flags;
  41
  42 static dissector_handle_t lapd_handle;
  43
  44 static int pref_tdmoe_d_channel = 24;
  45
  46 static int
  47 dissect_tdmoe(tvbuff_t *tvb, packet_info *pinfo, proto_tree *tree, void *data _U_)
  48 {
  49         proto_item *ti;
  50         proto_tree *tdmoe_tree;
  51         tvbuff_t   *next_client;
  52         uint16_t    channels;
  53         uint16_t    subaddress;
  54         int32_t offset = 0;
  55         static int * const flags[] = { &hf_tdmoe_yellow_alarm, &hf_tdmoe_sig_bits_present, NULL };
  56         int         chan;
  57
  58         /* Check that there's enough data */
  59         if (tvb_captured_length(tvb) < 8)
  60                 return 0;
  61
  62         subaddress = tvb_get_ntohs(tvb, 0);
  63         channels   = tvb_get_ntohs(tvb, 6);
  64
  65         col_set_str(pinfo->cinfo, COL_PROTOCOL, "TDMoE");
  66         col_add_fstr(pinfo->cinfo, COL_INFO, "Subaddress: %d Channels: %d %s",
  67                 subaddress,
  68                 channels,
  69                 (tvb_get_uint8(tvb, 3) & TDMOE_YELLOW_ALARM_BITMASK ? "[YELLOW ALARM]" : "")
  70         );
  71
  72
  73         /* create display subtree for the protocol */
  74         ti = proto_tree_add_item(tree, proto_tdmoe, tvb, 0, -1, ENC_NA);
  75         tdmoe_tree = proto_item_add_subtree(ti, ett_tdmoe);
  76
  77         /* Subaddress */
  78         proto_tree_add_item(tdmoe_tree, hf_tdmoe_subaddress, tvb, offset, 2, ENC_BIG_ENDIAN);
  79         offset+=2;
  80
  81         /* Samples (1 byte) */
  82         proto_tree_add_item(tdmoe_tree, hf_tdmoe_samples, tvb, offset, 1, ENC_BIG_ENDIAN);
  83         offset++;
  84
  85         /* Yellow alarm & "Sig bits present" bits (1 byte) */
  86         proto_tree_add_bitmask(tdmoe_tree, tvb, offset, hf_tdmoe_flags, ett_tdmoe_flags, flags, ENC_BIG_ENDIAN);
  87         offset++;
  88
  89         /* Packet counter (2 bytes) */
  90         proto_tree_add_item(tdmoe_tree, hf_tdmoe_packet_counter, tvb, offset, 2, ENC_BIG_ENDIAN);
  91         offset+=2;
  92
  93         /* Number of channels in packet (2 bytes) */
  94         proto_tree_add_item(tdmoe_tree, hf_tdmoe_channels, tvb, offset, 2, ENC_BIG_ENDIAN);
  95         offset+=2;
  96
  97         if (tvb_get_uint8(tvb, 3) & TDMOE_SIGBITS_BITMASK) {
  98                 /* 4 sigbits per channel. Might be different on other sub-protocols? */
  99                 uint16_t length = (channels >> 1) + ((channels & 0x01) ? 1 : 0);
 100
 101                 proto_tree_add_item(tdmoe_tree, hf_tdmoe_sig_bits, tvb, offset, length, ENC_NA);
 102                 offset += length;
 103         }
 104
 105         /* The rest is SAMPLES * CHANNELS bytes of channel data */
 106         for (chan = 1; chan <= channels; chan++) {
 107                 next_client = tvb_new_subset_length(tvb, offset + ((chan - 1) * 8), 8);
 108                 if (chan == pref_tdmoe_d_channel) {
 109                         call_dissector(lapd_handle, next_client, pinfo, tree);
 110                 } else {
 111                         call_data_dissector(next_client, pinfo, tree);
 112                 }
 113         }
 114         return 1;
 115 }
 116
 117 void
 118 proto_register_tdmoe(void)
 119 {
 120         static hf_register_info hf[] = {
 121
 122                 { &hf_tdmoe_subaddress,
 123                   { "Subaddress",       "tdmoe.subaddress", FT_UINT16, BASE_DEC, NULL, 0x0,
 124                     NULL, HFILL }},
 125                 { &hf_tdmoe_samples,
 126                   { "Samples",  "tdmoe.samples", FT_UINT8, BASE_DEC, NULL, 0x0,
 127                     "Samples per channel", HFILL }},
 128                 { &hf_tdmoe_flags,
 129                   { "Flags",    "tdmoe.flags", FT_UINT8, BASE_HEX, NULL, 0x0,
 130                     NULL, HFILL }},
 131                 { &hf_tdmoe_yellow_alarm,
 132                   { "Yellow Alarm", "tdmoe.yellowalarm", FT_BOOLEAN, 8, NULL, TDMOE_YELLOW_ALARM_BITMASK,
 133                     NULL, HFILL }},
 134                 { &hf_tdmoe_sig_bits_present,
 135                   { "Sig bits present", "tdmoe.sig_bits_present", FT_BOOLEAN, 8, NULL, TDMOE_SIGBITS_BITMASK,
 136                     NULL, HFILL }},
 137                 { &hf_tdmoe_packet_counter,
 138                   { "Counter", "tdmoe.counter", FT_UINT16, BASE_DEC, NULL, 0x0,
 139                     "Packet number", HFILL }},
 140                 { &hf_tdmoe_channels,
 141                   { "Channels", "tdmoe.channels", FT_UINT16, BASE_DEC, NULL, 0x0,
 142                     NULL, HFILL }},
 143                 { &hf_tdmoe_sig_bits,
 144                   { "Sig bits", "tdmoe.sig_bits", FT_BYTES, BASE_NONE, NULL, 0x0,
 145                     NULL, HFILL }},
 146         };
 147         static int *ett[] = {
 148                 &ett_tdmoe,
 149                 &ett_tdmoe_flags
 150         };
 151         module_t *tdmoe_module;
 152
 153         proto_tdmoe = proto_register_protocol("Digium TDMoE Protocol", "TDMoE", "tdmoe");
 154         proto_register_field_array(proto_tdmoe, hf, array_length(hf));
 155         proto_register_subtree_array(ett, array_length(ett));
 156         tdmoe_handle = register_dissector("tdmoe", dissect_tdmoe, proto_tdmoe);
 157         tdmoe_module = prefs_register_protocol(proto_tdmoe, NULL);
 158         prefs_register_uint_preference(tdmoe_module, "d_channel",
 159                                        "TDMoE D-Channel",
 160                                        "The TDMoE channel that contains the D-Channel.",
 161                                        10, &pref_tdmoe_d_channel);
 162 }
 163
 164 void
 165 proto_reg_handoff_tdmoe(void)
 166 {
 167         dissector_add_uint("ethertype", ETHERTYPE_TDMOE, tdmoe_handle);
 168
 169         lapd_handle = find_dissector_add_dependency("lapd-bitstream", proto_tdmoe);
 170 }
 171
 172 /*
 173  * Editor modelines  -  https://www.wireshark.org/tools/modelines.html
 174  *
 175  * Local variables:
 176  * c-basic-offset: 8
 177  * tab-width: 8
 178  * indent-tabs-mode: t
 179  * End:
 180  *
 181  * vi: set shiftwidth=8 tabstop=8 noexpandtab:
 182  * :indentSize=8:tabSize=8:noTabs=false:
 183  */