1 /* packet-v5dl.c
2 * Routines for V5 data link frame disassembly
3 * Rolf Fiedler <rolf.fiedler@innoventif.de> using the LAPD code of
4 * Gilbert Ramirez <gram@alumni.rice.edu>
5 *
6 * Wireshark - Network traffic analyzer
7 * By Gerald Combs <gerald@wireshark.org>
8 * Copyright 1998
9 *
10 * SPDX-License-Identifier: GPL-2.0-or-later
11 */
12 /*
13 * V5 Data Link Layer
14 *
15 * V5 references:
16 * ETS 300 324-1
17 * ETS 300 347-1
18 *
19 */
20
21 #include "config.h"
22
23 #include <epan/packet.h>
24 #include <epan/expert.h>
25 #include <epan/xdlc.h>
26
27 void proto_register_v5dl(void);
28
29 static int proto_v5dl = -1;
30 static int hf_v5dl_direction = -1;
31 /* static int hf_v5dl_address = -1; */
32 static int hf_v5dl_ef = -1;
33 static int hf_v5dl_eah = -1;
34 static int hf_v5dl_cr = -1;
35 static int hf_v5dl_ea1 = -1;
36 static int hf_v5dl_eal = -1;
37 static int hf_v5dl_ea2 = -1;
38 static int hf_v5dl_control = -1;
39 static int hf_v5dl_n_r = -1;
40 static int hf_v5dl_n_s = -1;
41 static int hf_v5dl_p = -1;
42 static int hf_v5dl_p_ext = -1;
43 static int hf_v5dl_f = -1;
44 static int hf_v5dl_f_ext = -1;
45 static int hf_v5dl_s_ftype = -1;
46 static int hf_v5dl_u_modifier_cmd = -1;
47 static int hf_v5dl_u_modifier_resp = -1;
48 static int hf_v5dl_ftype_i = -1;
49 static int hf_v5dl_ftype_s_u = -1;
50 static int hf_v5dl_ftype_s_u_ext = -1;
51 #if 0
52 static int hf_v5dl_checksum = -1;
53 static int hf_v5dl_checksum_status = -1;
54 #endif
55 static gint ett_v5dl = -1;
56 static gint ett_v5dl_address = -1;
57 static gint ett_v5dl_control = -1;
58 /* static gint ett_v5dl_checksum = -1; */
59
60 static expert_field ei_v5dl_checksum = EI_INIT;
61
62 static dissector_handle_t v52_handle;
63
64 /*
65 * Bits in the address field.
66 */
67 #define V5DL_EAH 0xfc00 /* Service Access Point Identifier */
68 #define V5DL_EAH_SHIFT 10
69 #define V5DL_CR 0x0200 /* Command/Response bit */
70 #define V5DL_EA1 0x0100 /* First Address Extension bit */
71 #define V5DL_EAL 0x00fe /* Terminal Endpoint Identifier */
72 #define V5DL_EAL_SHIFT 1
73 #define V5DL_EA2 0x0001 /* Second Address Extension bit */
74
75 static const value_string v5dl_direction_vals[] = {
76 { P2P_DIR_RECV, "Network->User"},
77 { P2P_DIR_SENT, "User->Network"},
78 { 0, NULL }
79 };
80
81 static const value_string v5dl_addr_vals[] = {
82 { 8175, "ISDN Protocol" },
83 { 8176, "PSTN Protocol" },
84 { 8177, "CONTROL Protocol" },
85 { 8178, "BCC Protocol" },
86 { 8179, "PROT Protocol" },
87 { 8180, "Link Control Protocol" },
88 { 8191, "VALUE RESERVED" },
89 { 0, NULL } };
90
91 /* Used only for U frames */
92 static const xdlc_cf_items v5dl_cf_items = {
93 NULL,
94 NULL,
95 &hf_v5dl_p,
96 &hf_v5dl_f,
97 NULL,
98 &hf_v5dl_u_modifier_cmd,
99 &hf_v5dl_u_modifier_resp,
100 NULL,
101 &hf_v5dl_ftype_s_u
102 };
103
104 /* Used only for I and S frames */
105 static const xdlc_cf_items v5dl_cf_items_ext = {
106 &hf_v5dl_n_r,
107 &hf_v5dl_n_s,
108 &hf_v5dl_p_ext,
109 &hf_v5dl_f_ext,
110 &hf_v5dl_s_ftype,
111 NULL,
112 NULL,
113 &hf_v5dl_ftype_i,
114 &hf_v5dl_ftype_s_u_ext
115 };
116
117
118 #define MAX_V5DL_PACKET_LEN 1024
119
120 static int
dissect_v5dl(tvbuff_t * tvb,packet_info * pinfo,proto_tree * tree,void * data _U_)121 dissect_v5dl(tvbuff_t *tvb, packet_info *pinfo, proto_tree *tree, void* data _U_)
122 {
123 proto_tree *v5dl_tree, *addr_tree;
124 proto_item *v5dl_ti, *addr_ti;
125 int direction;
126 guint v5dl_header_len;
127 guint16 control;
128 #if 0
129 proto_tree *checksum_tree;
130 proto_item *checksum_ti;
131 guint16 checksum, checksum_calculated;
132 guint checksum_offset;
133 #endif
134 guint16 addr, cr, eah, eal, v5addr;
135 gboolean is_response = 0;
136 #if 0
137 guint length, reported_length;
138 #endif
139 tvbuff_t *next_tvb;
140 const char *srcname = "?";
141 const char *dstname = "?";
142
143 col_set_str(pinfo->cinfo, COL_PROTOCOL, "V5DL");
144 col_clear(pinfo->cinfo, COL_INFO);
145
146 addr = tvb_get_ntohs(tvb, 0);
147 cr = addr & V5DL_CR;
148 eal = (addr & V5DL_EAL) >> V5DL_EAL_SHIFT;
149 eah = (addr & V5DL_EAH) >> V5DL_EAH_SHIFT;
150 v5addr = (eah << 7) + eal;
151 v5dl_header_len = 2; /* addr */
152
153 direction = pinfo->p2p_dir;
154 if (pinfo->p2p_dir == P2P_DIR_RECV) {
155 is_response = cr ? FALSE : TRUE;
156 srcname = "Network";
157 dstname = "User";
158 }
159 else if (pinfo->p2p_dir == P2P_DIR_SENT) {
160 is_response = cr ? TRUE : FALSE;
161 srcname = "User";
162 dstname = "Network";
163 }
164
165 col_set_str(pinfo->cinfo, COL_RES_DL_SRC, srcname);
166 col_set_str(pinfo->cinfo, COL_RES_DL_DST, dstname);
167
168 if (tree) {
169 proto_item *direction_ti;
170
171 v5dl_ti = proto_tree_add_item(tree, proto_v5dl, tvb, 0, -1,
172 ENC_NA);
173 v5dl_tree = proto_item_add_subtree(v5dl_ti, ett_v5dl);
174
175 /*
176 * Don't show the direction if we don't know it.
177 */
178 if (direction != P2P_DIR_UNKNOWN) {
179 direction_ti = proto_tree_add_uint(v5dl_tree, hf_v5dl_direction,
180 tvb, 0, 0, pinfo->p2p_dir);
181 proto_item_set_generated(direction_ti);
182 }
183
184 addr_ti = proto_tree_add_uint(v5dl_tree, hf_v5dl_ef, tvb,
185 0, 2, v5addr);
186 addr_tree = proto_item_add_subtree(addr_ti, ett_v5dl_address);
187 proto_tree_add_uint(addr_tree, hf_v5dl_eah, tvb, 0, 1, addr);
188 proto_tree_add_uint(addr_tree, hf_v5dl_cr, tvb, 0, 1, addr);
189 proto_tree_add_uint(addr_tree, hf_v5dl_ea1, tvb, 0, 1, addr);
190 proto_tree_add_uint(addr_tree, hf_v5dl_eal, tvb, 1, 1, addr);
191 proto_tree_add_uint(addr_tree, hf_v5dl_ea2, tvb, 1, 1, addr);
192 }
193 else {
194 v5dl_ti = NULL;
195 v5dl_tree = NULL;
196 }
197
198 control = dissect_xdlc_control(tvb, 2, pinfo, v5dl_tree, hf_v5dl_control,
199 ett_v5dl_control, &v5dl_cf_items, &v5dl_cf_items_ext, NULL, NULL,
200 is_response, TRUE, FALSE);
201 v5dl_header_len += XDLC_CONTROL_LEN(control, TRUE);
202
203 if (tree)
204 proto_item_set_len(v5dl_ti, v5dl_header_len);
205
206 /*
207 * XXX - the sample capture supplied with bug 7027 does not
208 * appear to include checksums in the packets.
209 */
210 #if 0
211 /*
212 * Check the checksum, if available.
213 * The checksum is a CCITT CRC-16 at the end of the packet, so
214 * if we don't have the entire packet in the capture - i.e., if
215 * tvb_captured_length(tvb) != tvb_reported_length(tvb) we can't check it.
216 */
217 length = tvb_captured_length(tvb);
218 reported_length = tvb_reported_length(tvb);
219
220 /*
221 * If the reported length isn't big enough for the V5DL header
222 * and 2 bytes of checksum, the packet is malformed, as the
223 * checksum overlaps the header.
224 */
225 if (reported_length < v5dl_header_len + 2)
226 return;
227
228 if (length == reported_length) {
229 /*
230 * There's no snapshot length cutting off any of the
231 * packet.
232 */
233 checksum_offset = reported_length - 2;
234 checksum_calculated = crc16_ccitt_tvb(tvb, checksum_offset);
235 checksum_calculated = g_htons(checksum_calculated); /* Note: g_htons() macro may eval arg multiple times */
236
237 proto_tree_add_checksum(v5dl_tree, tvb, checksum_offset, hf_v5dl_checksum, hf_v5dl_checksum_status, &ei_v5dl_checksum,
238 pinfo, checksum_calculated, ENC_BIG_ENDIAN, PROTO_CHECKSUM_VERIFY);
239 /*
240 * Remove the V5DL header *and* the checksum.
241 */
242 next_tvb = tvb_new_subset_length_caplen(tvb, v5dl_header_len,
243 tvb_captured_length_remaining(tvb, v5dl_header_len) - 2,
244 tvb_reported_length_remaining(tvb, v5dl_header_len) - 2);
245 } else {
246 /*
247 * Some or all of the packet is cut off by a snapshot
248 * length.
249 */
250 if (length == reported_length - 1) {
251 /*
252 * One byte is cut off, so there's only one
253 * byte of checksum in the captured data.
254 * Remove that byte from the captured length
255 * and both bytes from the reported length.
256 */
257 next_tvb = tvb_new_subset_length_caplen(tvb, v5dl_header_len,
258 tvb_captured_length_remaining(tvb, v5dl_header_len) - 1,
259 tvb_reported_length_remaining(tvb, v5dl_header_len) - 2);
260 } else {
261 /*
262 * Two or more bytes are cut off, so there are
263 * no bytes of checksum in the captured data.
264 * Just remove the checksum from the reported
265 * length.
266 */
267 next_tvb = tvb_new_subset_length_caplen(tvb, v5dl_header_len,
268 tvb_captured_length_remaining(tvb, v5dl_header_len),
269 tvb_reported_length_remaining(tvb, v5dl_header_len) - 2);
270 }
271 }
272 #else
273 next_tvb = tvb_new_subset_remaining(tvb, v5dl_header_len);
274 #endif
275
276 if (XDLC_IS_INFORMATION(control)) {
277 /* call V5.2 dissector */
278 call_dissector(v52_handle, next_tvb, pinfo, tree);
279 }
280 return tvb_captured_length(tvb);
281 }
282
283 void
284 proto_reg_handoff_v5dl(void);
285
286 void
proto_register_v5dl(void)287 proto_register_v5dl(void)
288 {
289 static hf_register_info hf[] = {
290
291 { &hf_v5dl_direction,
292 { "Direction", "v5dl.direction", FT_UINT8, BASE_DEC, VALS(v5dl_direction_vals), 0x0,
293 NULL, HFILL }},
294
295 #if 0
296 { &hf_v5dl_address,
297 { "Address Field", "v5dl.address", FT_UINT16, BASE_HEX, NULL, 0x0,
298 "Address", HFILL }},
299 #endif
300
301 { &hf_v5dl_ef,
302 { "EF", "v5dl.ef", FT_UINT16, BASE_DEC, VALS(v5dl_addr_vals), 0x0,
303 "Envelope Function Address", HFILL }},
304
305 { &hf_v5dl_eah,
306 { "EAH", "v5dl.eah", FT_UINT16, BASE_DEC, NULL, V5DL_EAH,
307 "Envelope Address High", HFILL }},
308
309 { &hf_v5dl_cr,
310 { "C/R", "v5dl.cr", FT_UINT16, BASE_DEC, NULL, V5DL_CR,
311 "Command/Response bit", HFILL }},
312
313 { &hf_v5dl_ea1,
314 { "EA1", "v5dl.ea1", FT_UINT16, BASE_DEC, NULL, V5DL_EA1,
315 "First Address Extension bit", HFILL }},
316
317 { &hf_v5dl_eal,
318 { "EAL", "v5dl.eal", FT_UINT16, BASE_DEC, NULL, V5DL_EAL,
319 "Envelope Address Low", HFILL }},
320
321 { &hf_v5dl_ea2,
322 { "EA2", "v5dl.ea2", FT_UINT16, BASE_DEC, NULL, V5DL_EA2,
323 "Second Address Extension bit", HFILL }},
324
325 { &hf_v5dl_control,
326 { "Control Field", "v5dl.control", FT_UINT16, BASE_HEX, NULL, 0x0,
327 NULL, HFILL }},
328
329 { &hf_v5dl_n_r,
330 { "N(R)", "v5dl.control.n_r", FT_UINT16, BASE_DEC,
331 NULL, XDLC_N_R_EXT_MASK, NULL, HFILL }},
332
333 { &hf_v5dl_n_s,
334 { "N(S)", "v5dl.control.n_s", FT_UINT16, BASE_DEC,
335 NULL, XDLC_N_S_EXT_MASK, NULL, HFILL }},
336
337 { &hf_v5dl_p,
338 { "Poll", "v5dl.control.p", FT_BOOLEAN, 8,
339 TFS(&tfs_set_notset), XDLC_P_F, NULL, HFILL }},
340
341 { &hf_v5dl_p_ext,
342 { "Poll", "v5dl.control.p", FT_BOOLEAN, 16,
343 TFS(&tfs_set_notset), XDLC_P_F_EXT, NULL, HFILL }},
344
345 { &hf_v5dl_f,
346 { "Final", "v5dl.control.f", FT_BOOLEAN, 8,
347 TFS(&tfs_set_notset), XDLC_P_F, NULL, HFILL }},
348
349 { &hf_v5dl_f_ext,
350 { "Final", "v5dl.control.f", FT_BOOLEAN, 16,
351 TFS(&tfs_set_notset), XDLC_P_F_EXT, NULL, HFILL }},
352
353 { &hf_v5dl_s_ftype,
354 { "Supervisory frame type", "v5dl.control.s_ftype", FT_UINT16, BASE_HEX,
355 VALS(stype_vals), XDLC_S_FTYPE_MASK, NULL, HFILL }},
356
357 { &hf_v5dl_u_modifier_cmd,
358 { "Command", "v5dl.control.u_modifier_cmd", FT_UINT8, BASE_HEX,
359 VALS(modifier_vals_cmd), XDLC_U_MODIFIER_MASK, NULL, HFILL }},
360
361 { &hf_v5dl_u_modifier_resp,
362 { "Response", "v5dl.control.u_modifier_resp", FT_UINT8, BASE_HEX,
363 VALS(modifier_vals_resp), XDLC_U_MODIFIER_MASK, NULL, HFILL }},
364
365 { &hf_v5dl_ftype_i,
366 { "Frame type", "v5dl.control.ftype", FT_UINT16, BASE_HEX,
367 VALS(ftype_vals), XDLC_I_MASK, NULL, HFILL }},
368
369 { &hf_v5dl_ftype_s_u,
370 { "Frame type", "v5dl.control.ftype", FT_UINT8, BASE_HEX,
371 VALS(ftype_vals), XDLC_S_U_MASK, NULL, HFILL }},
372
373 { &hf_v5dl_ftype_s_u_ext,
374 { "Frame type", "v5dl.control.ftype", FT_UINT16, BASE_HEX,
375 VALS(ftype_vals), XDLC_S_U_MASK, NULL, HFILL }},
376
377 #if 0
378 { &hf_v5dl_checksum,
379 { "Checksum", "v5dl.checksum", FT_UINT16, BASE_HEX,
380 NULL, 0x0, "Details at: https://www.wireshark.org/docs/wsug_html_chunked/ChAdvChecksums.html", HFILL }},
381
382 { &hf_v5dl_checksum_status,
383 { "Checksum Status", "v5dl.checksum.status", FT_UINT8, BASE_NONE,
384 VALS(proto_checksum_vals), 0x0, NULL, HFILL }},
385 #endif
386 };
387
388 static gint *ett[] = {
389 &ett_v5dl,
390 &ett_v5dl_address,
391 &ett_v5dl_control,
392 /* &ett_v5dl_checksum */
393 };
394
395 static ei_register_info ei[] = {
396 { &ei_v5dl_checksum, { "v5dl.bad_checksum", PI_CHECKSUM, PI_ERROR, "Bad checksum", EXPFILL }},
397 };
398
399 expert_module_t* expert_v5dl;
400
401 proto_v5dl = proto_register_protocol("V5 Data Link Layer", "V5DL", "v5dl");
402 proto_register_field_array (proto_v5dl, hf, array_length(hf));
403 proto_register_subtree_array(ett, array_length(ett));
404 expert_v5dl = expert_register_protocol(proto_v5dl);
405 expert_register_field_array(expert_v5dl, ei, array_length(ei));
406
407 register_dissector("v5dl", dissect_v5dl, proto_v5dl);
408 }
409
410 void
proto_reg_handoff_v5dl(void)411 proto_reg_handoff_v5dl(void)
412 {
413 v52_handle = find_dissector_add_dependency("v52", proto_v5dl);
414 }
415
416 /*
417 * Editor modelines - https://www.wireshark.org/tools/modelines.html
418 *
419 * Local variables:
420 * c-basic-offset: 8
421 * tab-width: 8
422 * indent-tabs-mode: t
423 * End:
424 *
425 * vi: set shiftwidth=8 tabstop=8 noexpandtab:
426 * :indentSize=8:tabSize=8:noTabs=false:
427 */
428