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
|
/* packet-nb_rtpmux.c
* Routines for 3GPP RTP Multiplex dissection, 3GPP TS 29.414
* Copyright 2009, ip.access ltd <amp@ipaccess.com>
*
* Wireshark - Network traffic analyzer
* By Gerald Combs <gerald@wireshark.org>
* Copyright 1998 Gerald Combs
*
* SPDX-License-Identifier: GPL-2.0-or-later
*/
#include "config.h"
#include <epan/packet.h>
void proto_register_nb_rtpmux(void);
void proto_reg_handoff_nb_rtpmux(void);
/* Initialize the protocol and registered fields */
static int proto_nb_rtpmux = -1;
static int hf_nb_rtpmux_compressed = -1;
static int hf_nb_rtpmux_dstport = -1;
static int hf_nb_rtpmux_length = -1;
static int hf_nb_r_bit = -1;
static int hf_nb_rtpmux_srcport = -1;
static int hf_nb_rtpmux_data = -1;
static int hf_nb_rtpmux_cmp_rtp_sequence_no = -1;
static int hf_nb_rtpmux_cmp_rtp_timestamp = -1;
static int hf_nb_rtpmux_cmp_rtp_data = -1;
/* Initialize the subtree pointers */
static gint ett_nb_rtpmux = -1;
static gint ett_nb_rtpmux_cmp_rtp_hdr = -1;
static dissector_handle_t nb_rtpmux_handle;
static dissector_handle_t rtpdissector;
static int
dissect_nb_rtpmux(tvbuff_t *tvb, packet_info *pinfo, proto_tree *tree, void *data _U_)
{
/* Set up structures needed to add the protocol subtree and manage it */
proto_item *ti;
proto_tree *nb_rtpmux_tree, *nb_rtpmux_cmp_rtp_tree;
unsigned int offset = 0;
gboolean first_rtp_payload_seen = FALSE;
/* First, if at all possible, do some heuristics to check if the packet cannot
* possibly belong to your protocol. This is especially important for
* protocols directly on top of TCP or UDP where port collisions are
* common place (e.g., even though your protocol uses a well known port,
* someone else may set up, for example, a web server on that port which,
* if someone analyzed that web server's traffic in Wireshark, would result
* in Wireshark handing an HTTP packet to your dissector). For example:
*/
/*
* XXX - this is *FAR* too weak a heuristic; it could cause all sorts
* of stuff to be incorrectly identified as Nb_RTPmux. Either this
* needs a stronger heuristic, or it needs to have a preference to
* set the port on which to dissect it, or it needs to be a non-heuristic
* dissector and *require* that a user use "Decode As..." to decode
* traffic as Nb_RTPmux.
*
* Look for a payload that looks like an RTP packet, using the
* same (weakish) heuristics as RTP uses?
*/
/* Check that there's enough data */
if (tvb_captured_length(tvb) < 6)
return 0;
/* Make entries in Protocol column and Info column on summary display */
col_set_str(pinfo->cinfo, COL_PROTOCOL, "NB_RTPMUX");
/* NOTE: The offset and length values in the call to
"proto_tree_add_item()" define what data bytes to highlight in the hex
display window when the line in the protocol tree display
corresponding to that item is selected.
Supplying a length of -1 is the way to highlight all data from the
offset to the end of the packet. */
/* create display subtree for the protocol */
while (offset < tvb_reported_length(tvb)-5)
{
guint16 dstport, srcport;
unsigned int length;
gint captured_length;
tvbuff_t *next_tvb;
gboolean tbit;
length = tvb_get_guint8(tvb, offset+2);
ti = proto_tree_add_item(tree, proto_nb_rtpmux, tvb, offset, length+5, ENC_NA);
nb_rtpmux_tree = proto_item_add_subtree(ti, ett_nb_rtpmux);
/* T bit */
proto_tree_add_item(nb_rtpmux_tree, hf_nb_rtpmux_compressed, tvb, offset, 2, ENC_BIG_ENDIAN);
tbit = tvb_get_guint8(tvb,offset)>>7;
if(tbit == 1){
/* 6.4.2.4 Transport Format for multiplexing with RTP header compression */
dstport = (tvb_get_ntohs(tvb, offset) & 0x7fff) << 1;
proto_tree_add_uint(nb_rtpmux_tree, hf_nb_rtpmux_dstport, tvb, offset, 2, dstport );
proto_tree_add_item(nb_rtpmux_tree, hf_nb_rtpmux_length, tvb, offset+2, 1, ENC_BIG_ENDIAN);
proto_tree_add_item(nb_rtpmux_tree, hf_nb_r_bit, tvb, offset+3, 2, ENC_BIG_ENDIAN);
srcport = (tvb_get_ntohs(tvb, offset+3) & 0x7fff) << 1;
proto_tree_add_uint(nb_rtpmux_tree, hf_nb_rtpmux_srcport, tvb, offset+3, 2, srcport );
nb_rtpmux_cmp_rtp_tree = proto_tree_add_subtree( nb_rtpmux_tree, tvb, offset+5, 3, ett_nb_rtpmux_cmp_rtp_hdr, NULL, "Compressed RTP header" );
/* Sequence Number (SN) */
proto_tree_add_item(nb_rtpmux_cmp_rtp_tree, hf_nb_rtpmux_cmp_rtp_sequence_no, tvb, offset+5, 1, ENC_BIG_ENDIAN);
/* Timestamp (TS) */
proto_tree_add_item(nb_rtpmux_cmp_rtp_tree, hf_nb_rtpmux_cmp_rtp_timestamp, tvb, offset+6, 2, ENC_BIG_ENDIAN);
if (length != 0)
proto_tree_add_item(nb_rtpmux_cmp_rtp_tree, hf_nb_rtpmux_cmp_rtp_data,tvb, offset+8, length-3, ENC_NA);
/* Not trying to decompress... */
/* Add summary to protocol root */
proto_item_append_text(ti, ", Src Port: %u, Dst Port: %u Length: %u", srcport, dstport, length);
}else{
/* 6.4.2.3 Transport Format for multiplexing without RTP Header Compression */
dstport = (tvb_get_ntohs(tvb, offset) & 0x7fff) << 1;
proto_tree_add_uint(nb_rtpmux_tree, hf_nb_rtpmux_dstport, tvb, offset, 2, dstport );
proto_tree_add_item(nb_rtpmux_tree,
hf_nb_rtpmux_length, tvb, offset+2, 1, ENC_BIG_ENDIAN);
proto_tree_add_item(nb_rtpmux_tree, hf_nb_r_bit, tvb, offset+3, 1, ENC_BIG_ENDIAN);
srcport = (tvb_get_ntohs(tvb, offset+3) & 0x7fff) << 1;
proto_tree_add_uint(nb_rtpmux_tree, hf_nb_rtpmux_srcport, tvb, offset+3, 2, srcport );
/* Add summary to protocol root */
proto_item_append_text(ti, ", Src Port: %u, Dst Port: %u Length: %u", srcport, dstport, length);
if (length != 0)
{
/* We have an RTP payload. */
if (rtpdissector)
{
captured_length = tvb_reported_length_remaining(tvb, offset + 5);
if (captured_length > (gint)length)
captured_length = length;
next_tvb = tvb_new_subset_length_caplen(tvb, offset+5, captured_length,
length);
if (first_rtp_payload_seen)
{
/* Don't want to clear the column, instead show where multiple
RTP frames are being carried */
col_append_str(pinfo->cinfo, COL_INFO, " | ");
col_set_fence(pinfo->cinfo, COL_INFO);
}
call_dissector(rtpdissector, next_tvb, pinfo, nb_rtpmux_tree);
first_rtp_payload_seen = TRUE;
}
else
{
proto_tree_add_item(nb_rtpmux_tree,
hf_nb_rtpmux_data, tvb, offset+5, length, ENC_NA);
}
}
} /* if tbit */
offset += 5+length;
}
/* Return the amount of data this dissector was able to dissect */
return tvb_reported_length(tvb);
}
/* Register the protocol with Wireshark */
void
proto_register_nb_rtpmux(void)
{
static hf_register_info hf[] = {
{ &hf_nb_rtpmux_compressed,
{ "Compressed headers(T bit)", "nb_rtpmux.compressed",
FT_BOOLEAN, 16, NULL, 0x8000,
NULL, HFILL }
},
{ &hf_nb_rtpmux_dstport,
{ "Dst port", "nb_rtpmux.dstport",
FT_UINT16, BASE_DEC, NULL, 0x0,
NULL, HFILL }
},
{ &hf_nb_rtpmux_length,
{ "Length", "nb_rtpmux.length",
FT_UINT8, BASE_DEC, NULL, 0x00,
NULL, HFILL }
},
{ &hf_nb_r_bit,
{ "R bit", "nb_rtpmux.r_bit",
FT_BOOLEAN, 16, NULL, 0x8000,
NULL, HFILL }
},
{ &hf_nb_rtpmux_srcport,
{ "Src port", "nb_rtpmux.srcport",
FT_UINT16, BASE_DEC, NULL, 0x0,
NULL, HFILL }
},
{ &hf_nb_rtpmux_data,
{ "RTP Packet", "nb_rtpmux.data",
FT_BYTES, BASE_NONE, NULL, 0x00,
NULL, HFILL }
},
{ &hf_nb_rtpmux_cmp_rtp_sequence_no,
{ "Sequence Number", "nb_rtpmux.cmp_rtp.sequence_no",
FT_UINT16, BASE_DEC, NULL, 0x00,
NULL, HFILL }
},
{ &hf_nb_rtpmux_cmp_rtp_timestamp,
{ "Timestamp", "nb_rtpmux.cmp_rtp.timestamp",
FT_UINT16, BASE_DEC, NULL, 0x00,
NULL, HFILL }
},
{ &hf_nb_rtpmux_cmp_rtp_data,
{ "RTP Data", "nb_rtpmux.cmp_rtp.data",
FT_BYTES, BASE_NONE, NULL, 0x00,
NULL,HFILL }
}
};
/* Setup protocol subtree array */
static gint *ett[] = {
&ett_nb_rtpmux,
&ett_nb_rtpmux_cmp_rtp_hdr
};
/* Register the protocol name and description */
proto_nb_rtpmux = proto_register_protocol("3GPP Nb Interface RTP Multiplex", "NB_RTPMUX", "nb_rtpmux");
nb_rtpmux_handle = register_dissector("nb_rtpmux", dissect_nb_rtpmux, proto_nb_rtpmux);
/* Required function calls to register the header fields and subtrees used */
proto_register_field_array(proto_nb_rtpmux, hf, array_length(hf));
proto_register_subtree_array(ett, array_length(ett));
}
void
proto_reg_handoff_nb_rtpmux(void)
{
dissector_add_uint_range_with_preference("udp.port", "", nb_rtpmux_handle);
rtpdissector = find_dissector_add_dependency("rtp", proto_nb_rtpmux);
}
/*
* 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:
*/
|
