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
|
/*
* Invoke gsmstack() with any kind of burst. Automaticly decode and retrieve
* information.
*/
#include "system.h"
#include <stdlib.h>
#include <stdio.h>
#include <errno.h>
#include <string.h>
#include "gsmstack.h"
//#include "gsm_constants.h"
#include "interleave.h"
//#include "sch.h"
#include "cch.h"
static const int USEFUL_BITS = 142;
//#include "out_pcap.h"
enum BURST_TYPE {
UNKNOWN,
FCCH,
PARTIAL_SCH, //successful correlation, but missing data ^
SCH,
CTS_SCH,
COMPACT_SCH,
NORMAL,
DUMMY,
ACCESS
};
static void out_gsmdecode(char type, int arfcn, int ts, int fn, char *data, int len);
/* encode a decoded burst (1 bit per byte) into 8-bit-per-byte */
static void burst_octify(unsigned char *dest,
const unsigned char *data, int length)
{
int bitpos = 0;
while (bitpos < USEFUL_BITS) {
unsigned char tbyte;
int i;
tbyte = 0;
for (i = 0; (i < 8) && (bitpos < length); i++) {
tbyte <<= 1;
tbyte |= data[bitpos++];
}
if (i < 8)
tbyte <<= 8 - i;
*dest++ = tbyte;
}
}
#if 0
static void
diff_decode(char *dst, char *src, int len)
{
const char *end = src + len;
unsigned char last;
src += 3;
last = 0;
memset(dst, 0, 3);
dst += 3;
while (src < end)
{
*dst = !*src ^ last;
last = *dst;
src++;
dst++;
}
}
#endif
/*
* Initialize a new GSMSTACK context.
*/
int
GS_new(GS_CTX *ctx)
{
memset(ctx, 0, sizeof *ctx);
interleave_init(&ctx->interleave_ctx, 456, 114);
ctx->fn = -1;
ctx->bsic = -1;
ctx->tun_fd = mktun("gsm", ctx->ether_addr);
if (ctx->tun_fd < 0)
fprintf(stderr, "cannot open 'gsm' tun device, did you create it?\n");
ctx->pcap_fd = open_pcap_file("gsm-receiver.pcap");
if (ctx->pcap_fd < 0)
fprintf(stderr, "cannot open PCAP file: %s\n", strerror(errno));
ctx->burst_pcap_fd = open_pcap_file("gsm-receiver-burst.pcap");
if (ctx->burst_pcap_fd < 0)
fprintf(stderr, "cannot open burst PCAP file: %s\n", strerror(errno));
return 0;
}
#define BURST_BYTES ((USEFUL_BITS/8)+1)
/*
* 142 bit
*/
int
GS_process(GS_CTX *ctx, int ts, int type, const unsigned char *src, int fn)
{
// int fn;
int bsic;
int ret;
unsigned char *data;
int len;
struct gs_ts_ctx *ts_ctx = &ctx->ts_ctx[ts];
unsigned char octified[BURST_BYTES];
memset(ctx->msg, 0, sizeof(ctx->msg));
/* write burst to burst PCAP file */
burst_octify(octified, src, USEFUL_BITS);
write_pcap_packet(ctx->burst_pcap_fd, 0 /* arfcn */, ts, ctx->fn,
1, type, octified, BURST_BYTES);
#if 0
if (ts != 0) {
/* non-0 timeslots should end up in PCAP */
data = decode_cch(ctx, ctx->burst, &len);
if (data == NULL)
return -1;
// write_pcap_packet(ctx->pcap_fd, 0 /* arfcn */, ts, ctx->fn, data, len);
return;
}
#endif
/* if (ts == 0) {
if (type == SCH) {
// ret = decode_sch(src, &fn, &bsic);
if (ret != 0)
return 0;
if ((ctx->bsic > 0) && (bsic != ctx->bsic))
fprintf(stderr, "WARN: BSIC changed.\n");
//DEBUGF("FN %d, BSIC %d\n", fn, bsic);
ctx->fn = fn;
ctx->bsic = bsic;
/* Reset message concatenator */
// ts_ctx->burst_count = 0;
// return 0;
// }
/* If we did not get Frame Number yet then return */
// if (ctx->fn < 0)
// return 0;
// ctx->fn++;
// }
ctx->fn = fn;
if (type == NORMAL) {
/* Interested in these frame numbers (cch)
* 2-5, 12-15, 22-25, 23-35, 42-45
* 6-9, 16-19, 26-29, 36-39, 46-49
*/
/* Copy content data into new array */
//DEBUGF("burst count %d\n", ctx->burst_count);
memcpy(ts_ctx->burst + (116 * ts_ctx->burst_count), src, 58);
memcpy(ts_ctx->burst + (116 * ts_ctx->burst_count) + 58, src + 58 + 26, 58);
ts_ctx->burst_count++;
/* Return if not enough bursts for a full gsm message */
if (ts_ctx->burst_count < 4)
return 0;
ts_ctx->burst_count = 0;
data = decode_cch(ctx, ts_ctx->burst, &len);
if (data == NULL) {
DEBUGF("cannot decode fnr=0x%08x ts=%d\n", ctx->fn, ts);
return -1;
}
//DEBUGF("OK TS %d, len %d\n", ts, len);
out_gsmdecode(0, 0, ts, ctx->fn - 4, data, len);
write_interface(ctx->tun_fd, data+1, len-1, ctx->ether_addr);
write_pcap_packet(ctx->pcap_fd, 0 /* arfcn */, ts, ctx->fn,
0, NORMAL, data, len);
#if 0
if (ctx->fn % 51 != 0) && ( (((ctx->fn % 51 + 5) % 10 == 0) || (((ctx->fn % 51) + 1) % 10 ==0) ) )
ready = 1;
#endif
return 0;
}
}
/*
* Output data so that it can be parsed from gsmdeocde.
*/
static void
out_gsmdecode(char type, int arfcn, int ts, int fn, char *data, int len)
{
char *end = data + len;
/* FIXME: speed this up by first printing into an array */
while (data < end)
printf(" %02.2x", (unsigned char)*data++);
printf("\n");
fflush(stdout);
}
|
