diff options
Diffstat (limited to 'gsm-receiver/src/lib/decoder/gsmstack.c')
| -rw-r--r-- | gsm-receiver/src/lib/decoder/gsmstack.c | 206 |
1 files changed, 206 insertions, 0 deletions
diff --git a/gsm-receiver/src/lib/decoder/gsmstack.c b/gsm-receiver/src/lib/decoder/gsmstack.c new file mode 100644 index 0000000..c3f1921 --- /dev/null +++ b/gsm-receiver/src/lib/decoder/gsmstack.c @@ -0,0 +1,206 @@ +/* + * 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); +} |