epan/dissectors/packet-isdn.c

   1 /* packet-isdn.c
   2  * Routines for ISDN packet disassembly
   3  *
   4  * Wireshark - Network traffic analyzer
   5  * By Gerald Combs <gerald@wireshark.org>
   6  * Copyright 1998 Gerald Combs
   7  *
   8  * SPDX-License-Identifier: GPL-2.0-or-later
   9  */
  10
  11 #include "config.h"
  12
  13 #include <epan/packet.h>
  14 #include <epan/prefs.h>
  15 #include <epan/tfs.h>
  16 #include <wsutil/array.h>
  17 #include <wiretap/wtap.h>
  18 #include <epan/conversation.h>
  19
  20 void proto_register_isdn(void);
  21 void proto_reg_handoff_isdn(void);
  22
  23 static int proto_isdn;
  24 static int hf_isdn_direction;
  25 static int hf_isdn_channel;
  26
  27 static int ett_isdn;
  28
  29 static dissector_handle_t isdn_handle;
  30
  31 /*
  32  * Protocol used on the D channel.
  33  */
  34 #define DCHANNEL_LAPD   0       /* LAPD */
  35 #define DCHANNEL_DPNSS  1       /* DPNSS link layer */
  36
  37 static const enum_val_t dchannel_protocol_options[] = {
  38         { "lapd",  "LAPD",  DCHANNEL_LAPD },
  39         { "DPNSS", "DPNSS", DCHANNEL_DPNSS },
  40         { NULL, NULL, 0 }
  41 };
  42
  43 static int dchannel_protocol = DCHANNEL_LAPD;
  44
  45 static dissector_handle_t lapd_phdr_handle;
  46 static dissector_handle_t dpnss_link_handle;
  47 static dissector_handle_t ppp_hdlc_handle;
  48 static dissector_handle_t v120_handle;
  49
  50 static const true_false_string isdn_direction_tfs = {
  51         "User->Network",
  52         "Network->User"
  53 };
  54
  55 static const value_string channel_vals[] = {
  56         {  0,   "D" },
  57         {  1,   "B1" },
  58         {  2,   "B2" },
  59         {  3,   "B3" },
  60         {  4,   "B4" },
  61         {  5,   "B5" },
  62         {  6,   "B6" },
  63         {  7,   "B7" },
  64         {  8,   "B8" },
  65         {  9,   "B9" },
  66         { 10,   "B10" },
  67         { 11,   "B11" },
  68         { 12,   "B12" },
  69         { 13,   "B13" },
  70         { 14,   "B14" },
  71         { 15,   "B15" },
  72         { 16,   "B16" },
  73         { 17,   "B17" },
  74         { 18,   "B18" },
  75         { 19,   "B19" },
  76         { 20,   "B20" },
  77         { 21,   "B21" },
  78         { 22,   "B22" },
  79         { 23,   "B23" },
  80         { 24,   "B24" },
  81         { 25,   "B25" },
  82         { 26,   "B26" },
  83         { 27,   "B27" },
  84         { 28,   "B28" },
  85         { 29,   "B29" },
  86         { 30,   "B30" },
  87         { 0,    NULL }
  88 };
  89
  90 static int
  91 dissect_isdn(tvbuff_t *tvb, packet_info *pinfo, proto_tree *tree, void *data)
  92 {
  93         struct isdn_phdr *isdn = (struct isdn_phdr *)data;
  94         proto_tree *isdn_tree;
  95         proto_item *ti;
  96         static const uint8_t v120_sabme[3] = { 0x08, 0x01, 0x7F };
  97         static const uint8_t ppp[2] = { 0xFF, 0x03 };
  98         conversation_t *conv;
  99
 100         col_set_str(pinfo->cinfo, COL_PROTOCOL, "ISDN");
 101
 102         if (isdn->uton) {
 103                 col_set_str(pinfo->cinfo, COL_RES_DL_DST, "Network");
 104                 col_set_str(pinfo->cinfo, COL_RES_DL_SRC, "User");
 105                 pinfo->p2p_dir = P2P_DIR_SENT;
 106         } else {
 107                 col_set_str(pinfo->cinfo, COL_RES_DL_DST, "User");
 108                 col_set_str(pinfo->cinfo, COL_RES_DL_SRC, "Network");
 109                 pinfo->p2p_dir = P2P_DIR_RECV;
 110         }
 111
 112         if (tree) {
 113                 ti = proto_tree_add_item(tree, proto_isdn, tvb, 0, 0, ENC_NA);
 114                 isdn_tree = proto_item_add_subtree(ti, ett_isdn);
 115
 116                 proto_tree_add_boolean(isdn_tree, hf_isdn_direction, tvb, 0, 0,
 117                      isdn->uton);
 118
 119                 proto_tree_add_uint(isdn_tree, hf_isdn_channel, tvb, 0, 0,
 120                     isdn->channel);
 121         }
 122
 123         /*
 124          * Set up a circuit for this channel, and assign it a dissector.
 125          */
 126         conv = find_or_create_conversation_by_id(pinfo, CONVERSATION_ISDN,
 127             isdn->channel);
 128
 129         if (conversation_get_dissector(conv, 0) == NULL) {
 130                 /*
 131                  * We don't yet know the type of traffic on the circuit.
 132                  */
 133                 switch (isdn->channel) {
 134
 135                 case 0:
 136                         /*
 137                          * D-channel.  Dissect it with whatever protocol
 138                          * the user specified, or the default of LAPD if
 139                          * they didn't specify one.
 140                          */
 141                         switch (dchannel_protocol) {
 142
 143                         case DCHANNEL_LAPD:
 144                                 conversation_set_dissector(conv, lapd_phdr_handle);
 145                                 break;
 146
 147                         case DCHANNEL_DPNSS:
 148                                 conversation_set_dissector(conv,
 149                                     dpnss_link_handle);
 150                                 break;
 151                         }
 152                         break;
 153
 154                 default:
 155                         /*
 156                          * B-channel.
 157                          *
 158                          * We don't know yet whether the datastream is
 159                          * V.120 or not; this heuristic tries to figure
 160                          * that out.
 161                          *
 162                          * We cannot glean this from the Q.931 SETUP message,
 163                          * because no commercial V.120 implementation I've
 164                          * seen actually sets the V.120 protocol discriminator
 165                          * (that, or I'm misreading the spec badly).
 166                          *
 167                          * TODO: close the circuit after a close on the B
 168                          * channel is detected.
 169                          *
 170                          *      -Bert Driehuis (from the i4btrace reader;
 171                          *       this heuristic was moved from there to
 172                          *       here)
 173                          *
 174                          * XXX - I don't know that one can guarantee that
 175                          * the SABME will appear in the first frame on
 176                          * the channels, so we probably can't just say
 177                          * "it must be PPP" if we don't immediately see
 178                          * the V.120 SABME frame, so we do so only if
 179                          * we see the 0xFF 0x03.  Unfortunately, that
 180                          * won't do the right thing if the PPP-over-HDLC
 181                          * headers aren't being used....
 182                          */
 183                         if (tvb_memeql(tvb, 0, v120_sabme, 3) == 0) {
 184                                 /*
 185                                  * We assume this is V.120.
 186                                  */
 187                                 conversation_set_dissector(conv, v120_handle);
 188                         } else if (tvb_memeql(tvb, 0, ppp, 2) == 0) {
 189                                 /*
 190                                  * We assume this is PPP.
 191                                  */
 192                                 conversation_set_dissector(conv, ppp_hdlc_handle);
 193                         }
 194                         break;
 195                 }
 196         }
 197
 198         if (!try_conversation_dissector_by_id(CONVERSATION_ISDN, isdn->channel,
 199                 tvb, pinfo, tree, data))
 200                 call_data_dissector(tvb, pinfo, tree);
 201
 202         return tvb_captured_length(tvb);
 203 }
 204
 205 void
 206 proto_register_isdn(void)
 207 {
 208         static hf_register_info hf[] = {
 209                 { &hf_isdn_direction,
 210                 { "Direction", "isdn.direction", FT_BOOLEAN, BASE_NONE,
 211                   TFS(&isdn_direction_tfs), 0x0, NULL, HFILL }},
 212
 213                 { &hf_isdn_channel,
 214                 { "Channel",    "isdn.channel", FT_UINT8, BASE_DEC,
 215                   VALS(channel_vals), 0x0, NULL, HFILL }},
 216         };
 217         static int *ett[] = {
 218                 &ett_isdn,
 219         };
 220         module_t *isdn_module;
 221
 222         proto_isdn = proto_register_protocol("ISDN", "ISDN", "isdn");
 223         proto_register_field_array(proto_isdn, hf, array_length(hf));
 224         proto_register_subtree_array(ett, array_length(ett));
 225
 226         isdn_module = prefs_register_protocol(proto_isdn, NULL);
 227
 228         prefs_register_enum_preference(isdn_module, "dchannel_protocol",
 229             "D-channel protocol",
 230             "The protocol running on the D channel",
 231             &dchannel_protocol, dchannel_protocol_options, false);
 232
 233         isdn_handle = register_dissector("isdn", dissect_isdn, proto_isdn);
 234 }
 235
 236 void
 237 proto_reg_handoff_isdn(void)
 238 {
 239         /*
 240          * Get handles for the LAPD-with-pseudoheader, DPNSS link-layer,
 241          * PPP, and V.120 dissectors.
 242          */
 243         lapd_phdr_handle = find_dissector("lapd-phdr");
 244         dpnss_link_handle = find_dissector("dpnss_link");
 245         ppp_hdlc_handle = find_dissector("ppp_hdlc");
 246         v120_handle = find_dissector("v120");
 247
 248         dissector_add_uint("wtap_encap", WTAP_ENCAP_ISDN, isdn_handle);
 249 }
 250
 251 /*
 252  * Editor modelines  -  https://www.wireshark.org/tools/modelines.html
 253  *
 254  * Local variables:
 255  * c-basic-offset: 8
 256  * tab-width: 8
 257  * indent-tabs-mode: t
 258  * End:
 259  *
 260  * vi: set shiftwidth=8 tabstop=8 noexpandtab:
 261  * :indentSize=8:tabSize=8:noTabs=false:
 262  */