summaryrefslogtreecommitdiffstats
path: root/epan/dissectors/packet-gsm_rlp.c
blob: c13cde9856762ba13e9594e72688c24e560f1312 (plain)
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
208
209
210
211
212
213
214
215
216
217
218
219
220
221
222
223
224
225
226
227
228
229
230
231
232
233
234
235
236
237
238
239
240
241
242
243
244
245
246
247
248
249
250
251
252
253
254
255
256
257
258
259
260
261
262
263
264
265
266
267
268
269
270
271
272
273
274
275
276
277
278
279
280
281
282
283
284
285
286
287
288
289
290
291
292
293
294
295
296
297
298
299
300
301
302
303
304
305
306
307
308
309
310
311
312
313
314
315
316
317
318
319
320
321
322
323
324
325
326
327
328
329
330
331
332
333
334
335
336
337
338
339
340
341
342
343
344
345
346
347
348
349
/* packet-gsm_rlp.c
 * Routines for GSM RLP (3GPP TS 24.022) frame dissection
 * (C) 2023 Harald Welte <laforge@osmocom.org>
 *
 * Wireshark - Network traffic analyzer
 * By Gerald Combs <gerald@wireshark.org>
 * Copyright 1998
 *
 * SPDX-License-Identifier: GPL-2.0-or-later
 */

#include "config.h"

#include <epan/packet.h>
#include <epan/prefs.h>
#include <epan/expert.h>
#include <epan/reassemble.h>
#include <epan/conversation.h>

void proto_register_gsmrlp(void);

static int proto_gsmrlp = -1;

static int hf_gsmrlp_cr = -1;
static int hf_gsmrlp_pf = -1;
static int hf_gsmrlp_n_r = -1;
static int hf_gsmrlp_n_s = -1;
static int hf_gsmrlp_ftype = -1;
static int hf_gsmrlp_s_ftype = -1;
static int hf_gsmrlp_u_ftype = -1;
static int hf_gsmrlp_fcs = -1;
static int hf_gsmrlp_fcs_status = -1;

static int hf_gsmrlp_xid_p_type = -1;
static int hf_gsmrlp_xid_p_len = -1;
static int hf_gsmrlp_xid_p_val = -1;

static int ett_gsmrlp = -1;
static int ett_gsmrlp_xid = -1;

static expert_field ei_gsmrlp_fcs_bad = EI_INIT;

static dissector_handle_t l2rcop_handle;
static gboolean decode_as_l2rcop = true;

/* 3GPP TS 24.002 Section 5.2.1 */
enum rlp_ftype {
	RLP_FT_U,
	RLP_FT_S,
	RLP_FT_IS,
};

static const value_string rlp_ftype_vals[] = {
	{ RLP_FT_U,	"U" },
	{ RLP_FT_S,	"S" },
	{ RLP_FT_IS,	"IS" },
	{ 0, NULL }
};

/* 3GPP TS 24.002 Section 5.2.1 */
enum rlp_u_ftype {
	RLP_U_FT_SABM	= 0x07,
	RLP_U_FT_UA	= 0x0c,
	RLP_U_FT_DISC	= 0x08,
	RLP_U_FT_DM	= 0x03,
	RLP_U_FT_NULL	= 0x0f,
	RLP_U_FT_UI	= 0x00,
	RLP_U_FT_XID	= 0x17,
	RLP_U_FT_TEST	= 0x1c,
	RLP_U_FT_REMAP	= 0x11,
};
static const value_string rlp_ftype_u_vals[] = {
	{ RLP_U_FT_SABM,	"SABM" },
	{ RLP_U_FT_UA,		"UA" },
	{ RLP_U_FT_DISC,	"DISC" },
	{ RLP_U_FT_DM,		"DM" },
	{ RLP_U_FT_NULL,	"NULL" },
	{ RLP_U_FT_UI,		"UI" },
	{ RLP_U_FT_XID,		"XID" },
	{ RLP_U_FT_TEST,	"TEST" },
	{ RLP_U_FT_REMAP,	"REMAP" },
	{ 0, NULL }
};

/* 3GPP TS 24.002 Section 5.2.1 */
enum rlp_s_ftype {
	RLP_S_FT_RR	= 0,
	RLP_S_FT_REJ	= 2,
	RLP_S_FT_RNR	= 1,
	RLP_S_FT_SREJ	= 3,
};
static const value_string rlp_ftype_s_vals[] = {
	{ RLP_S_FT_RR,		"RR" },
	{ RLP_S_FT_REJ,		"REJ" },
	{ RLP_S_FT_RNR,		"RNR" },
	{ RLP_S_FT_SREJ,	"SREJ" },
	{ 0, NULL }
};

/* 3GPP TS 24.002 Section 5.2.2.6 */
enum rlp_xid_param_type {
	XID_P_DELIMITER			= 0,
	XID_P_RLP_VERSION		= 1,
	XID_P_IWF_TO_UE_WIN_SIZE	= 2,
	XID_P_UE_TO_IWF_WIN_SIZE	= 3,
	XID_P_ACK_TIMER_T1		= 4,
	XID_P_RETRANS_ATTEMPTS_N2	= 5,
	XID_P_REPLY_DELAY_T2		= 6,
	XID_P_COMPRESSION_PT		= 7,
	XID_P_RESEQUENCING_T4		= 8,
	XID_P_OPTIONAL_FEATURES		= 9,
};

static const value_string rlp_xid_param_vals[] = {
	{ XID_P_DELIMITER,		"Delimiter (end of parameters)" },
	{ XID_P_RLP_VERSION, 		"RLP version number" },
	{ XID_P_IWF_TO_UE_WIN_SIZE,	"IWF to UE window size" },
	{ XID_P_UE_TO_IWF_WIN_SIZE,	"UE to IWF window size" },
	{ XID_P_ACK_TIMER_T1,		"Acknowledgement Timer (T1)" },
	{ XID_P_RETRANS_ATTEMPTS_N2,	"Retransmission attempts (N2)" },
	{ XID_P_REPLY_DELAY_T2,		"Reply delay (T2)" },
	{ XID_P_COMPRESSION_PT,		"Compression PT" },
	{ XID_P_RESEQUENCING_T4,	"Re-sequencing timer (T4)" },
	{ XID_P_OPTIONAL_FEATURES,	"Optional Features" },
	{ 0, NULL }
};

static const guint32 rlp_fcs_table[256] = {
	0x00B29D2D, 0x00643A5B, 0x0044D87A, 0x00927F0C, 0x00051C38, 0x00D3BB4E, 0x00F3596F, 0x0025FE19,
	0x008694BC, 0x005033CA, 0x0070D1EB, 0x00A6769D, 0x003115A9, 0x00E7B2DF, 0x00C750FE, 0x0011F788,
	0x00DA8E0F, 0x000C2979, 0x002CCB58, 0x00FA6C2E, 0x006D0F1A, 0x00BBA86C, 0x009B4A4D, 0x004DED3B,
	0x00EE879E, 0x003820E8, 0x0018C2C9, 0x00CE65BF, 0x0059068B, 0x008FA1FD, 0x00AF43DC, 0x0079E4AA,
	0x0062BB69, 0x00B41C1F, 0x0094FE3E, 0x00425948, 0x00D53A7C, 0x00039D0A, 0x00237F2B, 0x00F5D85D,
	0x0056B2F8, 0x0080158E, 0x00A0F7AF, 0x007650D9, 0x00E133ED, 0x0037949B, 0x001776BA, 0x00C1D1CC,
	0x000AA84B, 0x00DC0F3D, 0x00FCED1C, 0x002A4A6A, 0x00BD295E, 0x006B8E28, 0x004B6C09, 0x009DCB7F,
	0x003EA1DA, 0x00E806AC, 0x00C8E48D, 0x001E43FB, 0x008920CF, 0x005F87B9, 0x007F6598, 0x00A9C2EE,
	0x0049DA1E, 0x009F7D68, 0x00BF9F49, 0x0069383F, 0x00FE5B0B, 0x0028FC7D, 0x00081E5C, 0x00DEB92A,
	0x007DD38F, 0x00AB74F9, 0x008B96D8, 0x005D31AE, 0x00CA529A, 0x001CF5EC, 0x003C17CD, 0x00EAB0BB,
	0x0021C93C, 0x00F76E4A, 0x00D78C6B, 0x00012B1D, 0x00964829, 0x0040EF5F, 0x00600D7E, 0x00B6AA08,
	0x0015C0AD, 0x00C367DB, 0x00E385FA, 0x0035228C, 0x00A241B8, 0x0074E6CE, 0x005404EF, 0x0082A399,
	0x0099FC5A, 0x004F5B2C, 0x006FB90D, 0x00B91E7B, 0x002E7D4F, 0x00F8DA39, 0x00D83818, 0x000E9F6E,
	0x00ADF5CB, 0x007B52BD, 0x005BB09C, 0x008D17EA, 0x001A74DE, 0x00CCD3A8, 0x00EC3189, 0x003A96FF,
	0x00F1EF78, 0x0027480E, 0x0007AA2F, 0x00D10D59, 0x00466E6D, 0x0090C91B, 0x00B02B3A, 0x00668C4C,
	0x00C5E6E9, 0x0013419F, 0x0033A3BE, 0x00E504C8, 0x007267FC, 0x00A4C08A, 0x008422AB, 0x005285DD,
	0x001F18F0, 0x00C9BF86, 0x00E95DA7, 0x003FFAD1, 0x00A899E5, 0x007E3E93, 0x005EDCB2, 0x00887BC4,
	0x002B1161, 0x00FDB617, 0x00DD5436, 0x000BF340, 0x009C9074, 0x004A3702, 0x006AD523, 0x00BC7255,
	0x00770BD2, 0x00A1ACA4, 0x00814E85, 0x0057E9F3, 0x00C08AC7, 0x00162DB1, 0x0036CF90, 0x00E068E6,
	0x00430243, 0x0095A535, 0x00B54714, 0x0063E062, 0x00F48356, 0x00222420, 0x0002C601, 0x00D46177,
	0x00CF3EB4, 0x001999C2, 0x00397BE3, 0x00EFDC95, 0x0078BFA1, 0x00AE18D7, 0x008EFAF6, 0x00585D80,
	0x00FB3725, 0x002D9053, 0x000D7272, 0x00DBD504, 0x004CB630, 0x009A1146, 0x00BAF367, 0x006C5411,
	0x00A72D96, 0x00718AE0, 0x005168C1, 0x0087CFB7, 0x0010AC83, 0x00C60BF5, 0x00E6E9D4, 0x00304EA2,
	0x00932407, 0x00458371, 0x00656150, 0x00B3C626, 0x0024A512, 0x00F20264, 0x00D2E045, 0x00044733,
	0x00E45FC3, 0x0032F8B5, 0x00121A94, 0x00C4BDE2, 0x0053DED6, 0x008579A0, 0x00A59B81, 0x00733CF7,
	0x00D05652, 0x0006F124, 0x00261305, 0x00F0B473, 0x0067D747, 0x00B17031, 0x00919210, 0x00473566,
	0x008C4CE1, 0x005AEB97, 0x007A09B6, 0x00ACAEC0, 0x003BCDF4, 0x00ED6A82, 0x00CD88A3, 0x001B2FD5,
	0x00B84570, 0x006EE206, 0x004E0027, 0x0098A751, 0x000FC465, 0x00D96313, 0x00F98132, 0x002F2644,
	0x00347987, 0x00E2DEF1, 0x00C23CD0, 0x00149BA6, 0x0083F892, 0x00555FE4, 0x0075BDC5, 0x00A31AB3,
	0x00007016, 0x00D6D760, 0x00F63541, 0x00209237, 0x00B7F103, 0x00615675, 0x0041B454, 0x00971322,
	0x005C6AA5, 0x008ACDD3, 0x00AA2FF2, 0x007C8884, 0x00EBEBB0, 0x003D4CC6, 0x001DAEE7, 0x00CB0991,
	0x00686334, 0x00BEC442, 0x009E2663, 0x00488115, 0x00DFE221, 0x00094557, 0x0029A776, 0x00FF0000
};

/*! compute RLP FCS according to 3GPP TS 24.022 Section 4.4 */
static guint32 rlp_fcs_compute(const guchar *in, size_t in_len)
{
	guint32 divider = 0;
	size_t i;

	for (i = 0; i < in_len; i++) {
		guchar input = in[i] ^ (divider & 0xff);
		divider = (divider >> 8) ^ rlp_fcs_table[input];
	}

	return ((divider & 0xff) << 16) | (divider & 0xff00) | ((divider & 0xff0000) >> 16);
}

static int
dissect_gsmrlp_xid(tvbuff_t *tvb, gint offset, packet_info *pinfo _U_, proto_tree *tree)
{
	gint cur;

	for (cur = offset; cur < (gint) tvb_reported_length(tvb);) {
		guint8 len = tvb_get_guint8(tvb, cur) & 0x0f;
		guint8 type = tvb_get_guint8(tvb, cur) >> 4;
		proto_tree *xid_tree;

		proto_tree_add_subtree_format(tree, tvb, cur, 1 + len, ett_gsmrlp_xid, &xid_tree, "XID Parameter: %s",
		                        val_to_str_const(type, rlp_xid_param_vals, "Unknown"));
		proto_tree_add_item(xid_tree, hf_gsmrlp_xid_p_type, tvb, cur, 1, ENC_BIG_ENDIAN);
		proto_tree_add_item(xid_tree, hf_gsmrlp_xid_p_len, tvb, cur, 1, ENC_BIG_ENDIAN);
		if (len)
			proto_tree_add_item(xid_tree, hf_gsmrlp_xid_p_val, tvb, cur + 1, len, ENC_BIG_ENDIAN);
		cur += 1 + len;
		if (type == XID_P_DELIMITER)
			break;
	}

	return cur - offset;
}


/* Dissect a RLP v0/v1 message as described in TS 24.022 section 5.2 */
static int
dissect_gsmrlp(tvbuff_t *tvb, packet_info *pinfo, proto_tree *tree, void* data _U_)
{
	int reported_len = tvb_reported_length(tvb);
	proto_tree *rlp_tree;
	proto_item *ti;
	guint8 n_s, n_r;

	/* we currently support the 16bit header of RLP v0 + v1 */

	col_set_str(pinfo->cinfo, COL_PROTOCOL, "GSM-RLP");

	n_s = (tvb_get_guint8(tvb, 0)) >> 3 | ((tvb_get_guint8(tvb, 1) & 1) << 5);
	n_r = (tvb_get_guint8(tvb, 1) >> 2);

	ti = proto_tree_add_protocol_format(tree, proto_gsmrlp, tvb, 0, reported_len,
					    "GSM RLP");
	rlp_tree = proto_item_add_subtree(ti, ett_gsmrlp);

	proto_tree_add_item(rlp_tree, hf_gsmrlp_cr, tvb, 0, 1, ENC_BIG_ENDIAN);
	proto_tree_add_item(rlp_tree, hf_gsmrlp_pf, tvb, 1, 1, ENC_BIG_ENDIAN);
	if (n_s == 0x3f) { /* U frame */
		guint u_ftype;
		proto_tree_add_uint(rlp_tree, hf_gsmrlp_ftype, tvb, 0, 1, RLP_FT_U);
		proto_tree_add_item_ret_uint(rlp_tree, hf_gsmrlp_u_ftype, tvb, 1, 1, ENC_BIG_ENDIAN, &u_ftype);
		if ((n_r & 0x1f) == RLP_U_FT_XID)
			dissect_gsmrlp_xid(tvb, 2, pinfo, rlp_tree);
		proto_item_append_text(ti, " U-Frame: %s", val_to_str(u_ftype, rlp_ftype_u_vals, "Unknown 0x%02x"));
	} else if (n_s == 0x3e) { /* S Frame */
		guint s_ftype;
		proto_tree_add_uint(rlp_tree, hf_gsmrlp_ftype, tvb, 0, 1, RLP_FT_S);
		proto_tree_add_item_ret_uint(rlp_tree, hf_gsmrlp_s_ftype, tvb, 0, 1, ENC_BIG_ENDIAN, &s_ftype);
		proto_tree_add_uint(rlp_tree, hf_gsmrlp_n_r, tvb, 1, 1, n_r);
		proto_item_append_text(ti, " S-Frame: %s, N(S): %u, N(R): %u",
				       val_to_str(s_ftype, rlp_ftype_s_vals, "Unknown 0x%02x"), n_s, n_r);
	} else { /* IS Frame */
		tvbuff_t *next_tvb;
		guint s_ftype;
		int data_len;

		proto_tree_add_uint(rlp_tree, hf_gsmrlp_ftype, tvb, 0, 1, RLP_FT_IS);
		proto_tree_add_item_ret_uint(rlp_tree, hf_gsmrlp_s_ftype, tvb, 0, 1, ENC_BIG_ENDIAN, &s_ftype);
		proto_tree_add_uint(rlp_tree, hf_gsmrlp_n_s, tvb, 0, 2, n_s);
		proto_tree_add_uint(rlp_tree, hf_gsmrlp_n_r, tvb, 1, 1, n_r);
		proto_item_append_text(ti, " IS-Frame: %s, N(S): %u, N(R): %u",
				       val_to_str(s_ftype, rlp_ftype_s_vals, "Unknown 0x%02x"), n_s, n_r);

		/* dispatch user data */
		data_len = reported_len - 2 /* header */ - 3 /* FCS */;
		next_tvb = tvb_new_subset_length(tvb, 2, data_len);
		if (decode_as_l2rcop && l2rcop_handle)
			call_dissector(l2rcop_handle, next_tvb, pinfo, rlp_tree);
		else
			call_data_dissector(next_tvb, pinfo, rlp_tree);
	}

	/* FCS is always the last 3 bytes of the message */
	tvb_ensure_bytes_exist(tvb, 0, reported_len - 3);
	guint32 fcs_computed = rlp_fcs_compute(tvb_get_ptr(tvb, 0, reported_len - 3), reported_len - 3);
	proto_tree_add_checksum(rlp_tree, tvb, reported_len - 3, hf_gsmrlp_fcs, hf_gsmrlp_fcs_status,
				&ei_gsmrlp_fcs_bad, pinfo, fcs_computed, ENC_BIG_ENDIAN, PROTO_CHECKSUM_VERIFY);

	return tvb_reported_length(tvb);
}

void
proto_register_gsmrlp(void)
{
	static hf_register_info hf[] = {
	    { &hf_gsmrlp_cr,
	      { "C/R", "gsm_rlp.cr", FT_UINT8, BASE_DEC, NULL, 0x01,
		"Command/Response bit", HFILL }},
	    { &hf_gsmrlp_pf,
	      { "P/F", "gsm_rlp.pf", FT_UINT8, BASE_DEC, NULL, 0x02,
		"Poll/Final bit", HFILL }},
	    { &hf_gsmrlp_n_r,
	      { "N(R)", "gsm_rlp.n_r", FT_UINT8, BASE_DEC, NULL, 0,
		"Receive Sequence Number", HFILL }},
	    { &hf_gsmrlp_n_s,
	      { "N(S)", "gsm_rlp.n_s", FT_UINT8, BASE_DEC, NULL, 0,
		"Send Sequence Number", HFILL }},
	    { &hf_gsmrlp_ftype,
	      { "Frame type", "gsm_rlp.ftype", FT_UINT8, BASE_HEX,
		VALS(rlp_ftype_vals), 0, NULL, HFILL }},
	    { &hf_gsmrlp_u_ftype,
	      { "U Frame type", "gsm_rlp.u_ftype", FT_UINT8, BASE_HEX,
		VALS(rlp_ftype_u_vals), 0x7c, NULL, HFILL }},
	    { &hf_gsmrlp_s_ftype,
	      { "S frame type", "gsm_rlp.s_ftype", FT_UINT8, BASE_HEX,
		VALS(rlp_ftype_s_vals), 0x06, NULL, HFILL }},
	    { &hf_gsmrlp_fcs,
	      { "Frame Check Sequence", "gsm_rlp.fcs", FT_UINT24, BASE_HEX,
		NULL, 0, NULL, HFILL }},
	    { &hf_gsmrlp_fcs_status,
	      { "FCS Status", "gsm_rlp.fcs.status", FT_UINT8, BASE_NONE,
		VALS(proto_checksum_vals), 0, NULL, HFILL }},

	    { &hf_gsmrlp_xid_p_type,
	      { "XID Parameter Type", "gsm_rlp.xid.param_type", FT_UINT8, BASE_HEX,
		VALS(rlp_xid_param_vals), 0xf0, NULL, HFILL }},
	    { &hf_gsmrlp_xid_p_len,
	      { "XID Parameter Length", "gsm_rlp.xid.param_len", FT_UINT8, BASE_DEC,
		NULL, 0x0f, NULL, HFILL }},
	    { &hf_gsmrlp_xid_p_val,
	      { "XID Parameter Value", "gsm_rlp.xid.param_value", FT_UINT8, BASE_DEC,
		NULL, 0, NULL, HFILL }},
	};
	static gint *ett[] = {
		&ett_gsmrlp,
		&ett_gsmrlp_xid,
	};
	static ei_register_info ei[] = {
		{ &ei_gsmrlp_fcs_bad, { "gsm_rlp.fcs_bad", PI_CHECKSUM, PI_ERROR, "Bad checksum" , EXPFILL }},
	};
	module_t *rlp_module;
	expert_module_t *expert_gsmrlp;

	proto_gsmrlp = proto_register_protocol("GSM Radio Link Protocol (RLP)", "GSM-RLP", "gsm_rlp");
	proto_register_field_array(proto_gsmrlp, hf, array_length(hf));
	proto_register_subtree_array(ett, array_length(ett));
	expert_gsmrlp = expert_register_protocol(proto_gsmrlp);
	expert_register_field_array(expert_gsmrlp, ei, array_length(ei));

	register_dissector("gsm_rlp", dissect_gsmrlp, proto_gsmrlp);

	rlp_module = prefs_register_protocol(proto_gsmrlp, NULL);
	prefs_register_bool_preference(rlp_module, "decode_as_l2rcop", "Decode payload as L2RCOP",
				       NULL, &decode_as_l2rcop);
}
void
proto_reg_handoff_gsmrlp(void)
{
	l2rcop_handle = find_dissector_add_dependency("gsm_l2rcop", proto_gsmrlp);
}

/*
 * Editor modelines  -  https://www.wireshark.org/tools/modelines.html
 *
 * Local variables:
 * c-basic-offset: 4
 * tab-width: 8
 * indent-tabs-mode: nil
 * End:
 *
 * vi: set shiftwidth=4 tabstop=8 expandtab:
 * :indentSize=4:tabSize=8:noTabs=true:
 */