epan/dissectors/asn1/atn-cm/packet-atn-cm-template.c

   1 /* packet-atn-cm.c
   2  * By Mathias Guettler <guettler@web.de>
   3  * Copyright 2013
   4  *
   5  * Routines for ATN context management protocol packet disassembly.
   6  * ATN context management allows an aircraft
   7  * to log on to a ground facility.
   8  *
   9  * details see:
  10  * https://en.wikipedia.org/wiki/CPDLC
  11  * https://members.optusnet.com.au/~cjr/introduction.htm
  12  *
  13  * standards:
  14  * We are dealing with ATN/CPDLC aka ICAO Doc 9705 Second Edition here
  15  * (CPDLC may also be transmitted via ACARS/AOA aka "FANS-1/A ").
  16  * https://www.icao.int/safety/acp/repository/_%20Doc9705_ed2_1999.pdf
  17  *
  18  * Wireshark - Network traffic analyzer
  19  * By Gerald Combs <gerald@wireshark.org>
  20  * Copyright 1998 Gerald Combs
  21  *
  22  * SPDX-License-Identifier: GPL-2.0-or-later
  23  */
  24
  25 #include "config.h"
  26
  27 #include <epan/packet.h>
  28 #include <epan/exceptions.h>
  29 #include <epan/conversation.h>
  30 #include <wsutil/array.h>
  31 #include "packet-ber.h"
  32 #include "packet-per.h"
  33 #include "packet-atn-ulcs.h"
  34
  35 #define ATN_CM_PROTO "ICAO Doc9705 CM"
  36
  37 void proto_register_atn_cm(void);
  38 void proto_reg_handoff_atn_cm(void);
  39
  40 #include "packet-atn-cm-hf.c"
  41
  42 #include "packet-atn-cm-ett.c"
  43 static int ett_atn_cm;
  44
  45 #include "packet-atn-cm-fn.c"
  46 static int proto_atn_cm;
  47
  48 static int
  49 dissect_atn_cm(
  50     tvbuff_t *tvb,
  51     packet_info *pinfo,
  52     proto_tree *tree,
  53     void *data _U_)
  54 {
  55     int   type;
  56     proto_tree *sub_tree;
  57
  58     sub_tree = proto_tree_add_subtree(
  59       tree, tvb, 0, -1, ett_atn_cm, NULL, ATN_CM_PROTO);
  60
  61     /* ti = proto_tree_add_item(tree, proto_atn_cm, tvb, 0, 0 , ENC_NA); */
  62     /* sub_tree = proto_item_add_subtree(ti, ett_atn_cm_pdu); */
  63
  64     /* determine whether it is uplink or downlink */
  65     type = check_heur_msg_type(pinfo);
  66
  67     switch(type){
  68         case um:
  69             dissect_CMGroundMessage_PDU(
  70               tvb,
  71               pinfo,
  72               sub_tree, NULL);
  73             break;
  74         case dm:
  75             dissect_CMAircraftMessage_PDU(
  76               tvb,
  77               pinfo,
  78               sub_tree, NULL);
  79             break;
  80         default:
  81             break;
  82     }
  83     return tvb_reported_length_remaining(tvb, 0);
  84 }
  85
  86 static bool
  87 dissect_atn_cm_heur(
  88     tvbuff_t *tvb,
  89     packet_info *pinfo,
  90     proto_tree *tree,
  91     void *data _U_)
  92 {
  93     atn_conversation_t *volatile atn_cv = NULL;
  94     volatile bool is_atn_cm = false;
  95     int type;
  96
  97     /* determine whether it is uplink or downlink */
  98     type = check_heur_msg_type(pinfo);
  99
 100     /* heuristically decode message */
 101     switch(type){
 102         case um:
 103             TRY {
 104                 dissect_CMGroundMessage_PDU(
 105                   tvb,
 106                   pinfo,
 107                   NULL, NULL);
 108                 /* no exception thrown: looks like it is a CM PDU */
 109                 is_atn_cm = true; }
 110             CATCH_ALL {
 111                 is_atn_cm = false; }
 112             ENDTRY;
 113             break;
 114         case dm:
 115             TRY {
 116                 dissect_CMAircraftMessage_PDU(
 117                     tvb,
 118                     pinfo,
 119                     NULL, NULL);
 120                 /* no exception thrown: looks like it is a CM PDU */
 121                 is_atn_cm = true;}
 122             CATCH_ALL {
 123                 is_atn_cm = false; }
 124             ENDTRY;
 125             break;
 126         default:
 127             break;
 128     }
 129
 130     if (is_atn_cm  == true) {
 131         /* note: */
 132         /* all subsequent PDU's belonging to this conversation are considered CM */
 133         /* if the first CM PDU has been decoded successfully */
 134         /* (This is done in "atn-ulcs" by using "call_dissector_with_data()") */
 135
 136         /* DT: dstref present, srcref is always zero */
 137         if((pinfo->clnp_dstref) &&
 138             (!pinfo->clnp_srcref)){
 139
 140           atn_cv = find_atn_conversation(
 141                 &pinfo->dst,
 142                 pinfo->clnp_dstref,
 143                 &pinfo->src );
 144         }
 145         /* CR: srcref present, dstref is always zero */
 146         if((!pinfo->clnp_dstref) &&
 147             (pinfo->clnp_srcref)){
 148
 149           atn_cv = find_atn_conversation(
 150                 &pinfo->src,
 151                 pinfo->clnp_srcref,
 152                 &pinfo->dst );
 153
 154         }
 155         /* CC: srcref and dstref present  */
 156         if((pinfo->clnp_dstref) &&
 157             (pinfo->clnp_srcref)){
 158             atn_cv = find_atn_conversation(
 159                 &pinfo->src,
 160                 pinfo->clnp_srcref,
 161                 &pinfo->dst );
 162         }
 163         if(atn_cv){
 164             atn_cv->ae_qualifier = cma;
 165         }
 166         dissect_atn_cm(
 167             tvb,
 168             pinfo,
 169             tree,
 170             NULL);
 171     }
 172
 173     return is_atn_cm;
 174 }
 175
 176
 177 void proto_register_atn_cm (void)
 178 {
 179     static hf_register_info hf_atn_cm[] = {
 180           #include "packet-atn-cm-hfarr.c"
 181     };
 182     static int *ett[] = {
 183       #include "packet-atn-cm-ettarr.c"
 184       &ett_atn_cm
 185     };
 186
 187     /* register CM application */
 188     proto_atn_cm = proto_register_protocol(ATN_CM_PROTO, "ATN-CM", "atn-cm");
 189
 190     proto_register_field_array(
 191         proto_atn_cm,
 192         hf_atn_cm,
 193         array_length(hf_atn_cm));
 194
 195     proto_register_subtree_array(
 196         ett,
 197         array_length(ett));
 198
 199     register_dissector(
 200         "atn-cm",
 201         dissect_atn_cm,
 202         proto_atn_cm);
 203 }
 204
 205 void proto_reg_handoff_atn_cm(void)
 206 {
 207     /* add session dissector to subdissector list*/
 208     heur_dissector_add(
 209         "atn-ulcs",
 210         dissect_atn_cm_heur,
 211         "ATN-CM over ATN-ULCS",
 212         "atn-cm-ulcs",
 213         proto_atn_cm, HEURISTIC_ENABLE);
 214 }
 215
 216 /*
 217  * Editor modelines  -  https://www.wireshark.org/tools/modelines.html
 218  *
 219  * Local variables:
 220  * c-basic-offset: 4
 221  * tab-width: 8
 222  * indent-tabs-mode: nil
 223  * End:
 224  *
 225  * vi: set shiftwidth=4 tabstop=8 expandtab:
 226  * :indentSize=4:tabSize=8:noTabs=true:
 227  */