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/*
* 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"
#include "out_pcap.h"
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("tvoid.pcap");
if (ctx->pcap_fd < 0)
fprintf(stderr, "cannot open PCAP file: %s\n", strerror(errno));
ctx->burst_pcap_fd = open_pcap_file("tvoid-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 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++;
}
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);
}
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