150 lines
3.6 KiB
C
150 lines
3.6 KiB
C
/*
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* (C) 2017-2018 by sysmocom - s.f.m.c. GmbH, Author: Max <msuraev@sysmocom.de>
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* (C) 2018 by Vadim Yanitskiy <axilirator@gmail.com>
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* (C) 2011-2012 by Luca Melette <luca@srlabs.de>
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*
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* All Rights Reserved
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*
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* SPDX-License-Identifier: GPL-2.0+
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*
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* This program is free software; you can redistribute it and/or modify
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* it under the terms of the GNU General Public License as published by
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* the Free Software Foundation; either version 2 of the License, or
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* (at your option) any later version.
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*
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* This program is distributed in the hope that it will be useful,
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* but WITHOUT ANY WARRANTY; without even the implied warranty of
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* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
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* GNU General Public License for more details.
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*
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*/
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#include <stdio.h>
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#include <errno.h>
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#include <stdlib.h>
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#include <string.h>
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#include <stdbool.h>
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#include <arpa/inet.h>
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#include <osmocom/core/bits.h>
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#include <osmocom/core/gsmtap.h>
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#include <osmocom/coding/gsm0503_coding.h>
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#include "l1ctl_proto.h"
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#include "rlcmac.h"
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#include "gprs.h"
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/**
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* We store both DL and UL burst buffers
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* for all possible timeslots...
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*/
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static struct burst_buf burst_buf_dl[8] = { 0 };
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static struct burst_buf burst_buf_ul[8] = { 0 };
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int process_pdch(struct l1ctl_burst_ind *bi, bool verbose)
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{
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int n_errors, n_bits_total, rc, len, i;
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ubit_t buf[GSM_BURST_PL_LEN];
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struct gprs_message *gm;
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struct burst_buf *bb;
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uint8_t l2[200];
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uint16_t arfcn;
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uint32_t fn;
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uint8_t tn;
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bool ul;
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/* Get burst parameters */
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fn = ntohl(bi->frame_nr);
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arfcn = ntohs(bi->band_arfcn);
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ul = !!(arfcn & GSMTAP_ARFCN_F_UPLINK);
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tn = bi->chan_nr & 7;
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/* Select a proper DL / UL buffer */
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bb = ul ? &burst_buf_ul[tn] : &burst_buf_dl[tn];
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/* Align to first frame */
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if ((bb->count == 0) && (((fn % 13) % 4) != 0))
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return 0;
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/* Debug print */
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if (verbose)
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printf("Processing %s burst fn=%u, tn=%u\n",
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ul ? "UL" : "DL", fn, tn);
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/* Unpack hard-bits (1 or 0) */
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osmo_pbit2ubit_ext(buf, 0, bi->bits, 0, 57, 0);
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osmo_pbit2ubit_ext(buf, 59, bi->bits, 57, 57, 0);
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/* Set the stealing flags */
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buf[57] = bi->bits[14] & 0x10;
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buf[58] = bi->bits[14] & 0x20;
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/* Convert hard-bits (1 or 0) to soft-bits (-127..127) */
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for (i = 0; i < GSM_BURST_PL_LEN; i++)
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bb->bursts[GSM_BURST_PL_LEN * bb->count + i] = buf[i] ?
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-(bi->snr >> 1) : (bi->snr >> 1);
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/* Store the first frame number */
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if (bb->count == 0)
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bb->fn_first = fn;
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/* Collect the measurements */
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bb->rxl[bb->count] = bi->rx_level;
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bb->snr[bb->count] = bi->snr;
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/* Wait until complete set of bursts (4/4) */
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if (++bb->count < 4)
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return 0;
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/* Debug print */
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if (verbose)
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printf("Collected 4/4 bursts on tn=%u\n", tn);
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/* Flush the burst counter */
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bb->count = 0;
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/* Attempt to decode */
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len = gsm0503_pdtch_decode(l2, bb->bursts, NULL,
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&n_errors, &n_bits_total);
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/* Debug print */
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if (verbose)
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printf("GSM 05.03 decoding %s (%s=%d)\n",
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len <= 0 ? "failed" : "success",
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len <= 0 ? "rc" : "len", len);
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/* Skip bad blocks... */
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if (len <= 0)
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return -EIO;
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/**
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* HACK: for some reason, the handler expects
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* 53-byte messages, while libosmocoding
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* generates 54 bytes ?? O_o ??
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*/
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len--;
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/* Handle decoded message */
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gm = (struct gprs_message *) malloc(sizeof(struct gprs_message) + len);
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if (!gm)
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return -ENOMEM;
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gm->fn = bb->fn_first;
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gm->arfcn = arfcn;
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gm->len = len;
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gm->tn = tn;
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/* Average the measurements */
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gm->rxl = MEAS_AVG(bb->rxl);
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gm->snr = MEAS_AVG(bb->snr);
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/* Copy the message payload */
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memcpy(gm->msg, l2, len);
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/* Handle the message */
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rc = rlc_type_handler(gm);
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free(gm);
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return rc;
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}
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