epan/dissectors/packet-egnos-ems.c

   1 /* packet-ems.c
   2  * EGNOS Message Server file format dissection.
   3  *
   4  * By Timo Warns <timo.warns@gmail.com>
   5  * Copyright 2023 Timo Warns
   6  *
   7  * Wireshark - Network traffic analyzer
   8  * By Gerald Combs <gerald@unicom.net>
   9  * Copyright 1998 Gerald Combs
  10  *
  11  * SPDX-License-Identifier: GPL-2.0-or-later
  12  */
  13
  14 #include "config.h"
  15 #include <epan/packet.h>
  16 #include <wiretap/wtap.h>
  17
  18 /*
  19  * Dissects PCAPs mapped from the EMS file format as defined by the "EGNOS
  20  * Messager Server User Interface Document" (E-RD-SYS-E31-011-ESA, Issue 2)
  21  */
  22
  23 /* Initialize the protocol and registered fields */
  24 static int proto_ems;
  25
  26 static int hf_ems_prn;
  27 static int hf_ems_year;
  28 static int hf_ems_month;
  29 static int hf_ems_day;
  30 static int hf_ems_hour;
  31 static int hf_ems_minute;
  32 static int hf_ems_second;
  33 static int hf_ems_mt;
  34
  35 static int ett_ems;
  36
  37 static dissector_handle_t  ems_handle;
  38
  39 /* Dissect EMS data record */
  40 static int dissect_ems(tvbuff_t *tvb, packet_info *pinfo, proto_tree *tree, void *data _U_) {
  41     tvbuff_t *next_tvb;
  42
  43     col_set_str(pinfo->cinfo, COL_PROTOCOL, "EMS");
  44     col_clear(pinfo->cinfo, COL_INFO);
  45
  46     uint8_t prn, year, month, day, hour, minute, second, mt;
  47     prn    = tvb_get_uint8(tvb, 0);
  48     year   = tvb_get_uint8(tvb, 1);
  49     month  = tvb_get_uint8(tvb, 2);
  50     day    = tvb_get_uint8(tvb, 3);
  51     hour   = tvb_get_uint8(tvb, 4);
  52     minute = tvb_get_uint8(tvb, 5);
  53     second = tvb_get_uint8(tvb, 6);
  54     mt     = tvb_get_uint8(tvb, 7);
  55
  56     proto_tree *ems_tree = proto_tree_add_subtree_format(tree, tvb, 0, 40,
  57             ett_ems, NULL, "EMS (%04d-%02d-%02d %02d:%02d:%02d PRN%d MT%d)",
  58             2000 + year, month, day, hour, minute, second, prn, mt);
  59
  60     proto_tree_add_item(ems_tree, hf_ems_prn,    tvb, 0, 1, ENC_BIG_ENDIAN);
  61     proto_tree_add_item(ems_tree, hf_ems_year,   tvb, 1, 1, ENC_BIG_ENDIAN);
  62     proto_tree_add_item(ems_tree, hf_ems_month,  tvb, 2, 1, ENC_BIG_ENDIAN);
  63     proto_tree_add_item(ems_tree, hf_ems_day,    tvb, 3, 1, ENC_BIG_ENDIAN);
  64     proto_tree_add_item(ems_tree, hf_ems_hour,   tvb, 4, 1, ENC_BIG_ENDIAN);
  65     proto_tree_add_item(ems_tree, hf_ems_minute, tvb, 5, 1, ENC_BIG_ENDIAN);
  66     proto_tree_add_item(ems_tree, hf_ems_second, tvb, 6, 1, ENC_BIG_ENDIAN);
  67     proto_tree_add_item(ems_tree, hf_ems_mt,     tvb, 7, 1, ENC_BIG_ENDIAN);
  68
  69     next_tvb = tvb_new_subset_remaining(tvb, 8);
  70
  71     dissector_handle_t sbas_l1_dissector_handle = find_dissector("sbas_l1");
  72     if (sbas_l1_dissector_handle) {
  73         call_dissector(sbas_l1_dissector_handle, next_tvb, pinfo, tree);
  74     }
  75     else {
  76         call_data_dissector(next_tvb, pinfo, tree);
  77     }
  78
  79     return tvb_captured_length(tvb);
  80 }
  81
  82 void proto_register_ems(void) {
  83
  84     static hf_register_info hf[] = {
  85         {&hf_ems_prn,    {"PRN",          "ems.prn",    FT_UINT8, BASE_DEC, NULL, 0x0, NULL, HFILL }},
  86         {&hf_ems_year,   {"Year",         "ems.year",   FT_UINT8, BASE_DEC, NULL, 0x0, NULL, HFILL }},
  87         {&hf_ems_month,  {"Month",        "ems.month",  FT_UINT8, BASE_DEC, NULL, 0x0, NULL, HFILL }},
  88         {&hf_ems_day,    {"Day",          "ems.day",    FT_UINT8, BASE_DEC, NULL, 0x0, NULL, HFILL }},
  89         {&hf_ems_hour,   {"Hour",         "ems.hour",   FT_UINT8, BASE_DEC, NULL, 0x0, NULL, HFILL }},
  90         {&hf_ems_minute, {"Minute",       "ems.minute", FT_UINT8, BASE_DEC, NULL, 0x0, NULL, HFILL }},
  91         {&hf_ems_second, {"Second",       "ems.second", FT_UINT8, BASE_DEC, NULL, 0x0, NULL, HFILL }},
  92         {&hf_ems_mt,     {"Message Type", "ems.mt",     FT_UINT8, BASE_DEC, NULL, 0x0, NULL, HFILL }},
  93     };
  94
  95     static int *ett[] = {
  96         &ett_ems,
  97     };
  98
  99     proto_ems = proto_register_protocol("EGNOS Message Server file", "EMS", "ems");
 100     ems_handle = register_dissector("ems", dissect_ems, proto_ems);
 101
 102     proto_register_field_array(proto_ems, hf, array_length(hf));
 103     proto_register_subtree_array(ett, array_length(ett));
 104 }
 105
 106 void proto_reg_handoff_ems(void) {
 107     static bool initialized = false;
 108
 109     if (!initialized) {
 110         dissector_add_uint("wtap_encap", WTAP_ENCAP_EMS, ems_handle);
 111     }
 112 }