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/*
* OsmocomBB <-> SDR connection bridge
* TDMA scheduler: handlers for DL / UL bursts on logical channels
*
* (C) 2017-2022 by Vadim Yanitskiy <axilirator@gmail.com>
* Contributions by sysmocom - s.f.m.c. GmbH
*
* All Rights Reserved
*
* This program is free software; you can redistribute it and/or modify
* it under the terms of the GNU General Public License as published by
* the Free Software Foundation; either version 2 of the License, or
* (at your option) any later version.
*
* This program is distributed in the hope that it will be useful,
* but WITHOUT ANY WARRANTY; without even the implied warranty of
* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
* GNU General Public License for more details.
*
*/
#include <errno.h>
#include <string.h>
#include <stdint.h>
#include <osmocom/core/logging.h>
#include <osmocom/core/bits.h>
#include <osmocom/gsm/gsm_utils.h>
#include <osmocom/gsm/protocol/gsm_04_08.h>
#include <osmocom/coding/gsm0503_coding.h>
#include <osmocom/bb/l1sched/l1sched.h>
#include <osmocom/bb/l1sched/logging.h>
int rx_data_fn(struct l1sched_lchan_state *lchan,
const struct l1sched_burst_ind *bi)
{
uint8_t l2[GSM_MACBLOCK_LEN], *mask;
int n_errors, n_bits_total, rc;
sbit_t *bursts_p, *burst;
/* Set up pointers */
mask = &lchan->rx_burst_mask;
bursts_p = lchan->rx_bursts;
LOGP_LCHAND(lchan, LOGL_DEBUG,
"Data received: fn=%u bid=%u\n", bi->fn, bi->bid);
/* Align to the first burst of a block */
if (*mask == 0x00 && bi->bid != 0)
return 0;
/* Update mask */
*mask |= (1 << bi->bid);
/* Store the measurements */
l1sched_lchan_meas_push(lchan, bi);
/* Copy burst to buffer of 4 bursts */
burst = bursts_p + bi->bid * 116;
memcpy(burst, bi->burst + 3, 58);
memcpy(burst + 58, bi->burst + 87, 58);
/* Wait until complete set of bursts */
if (bi->bid != 3)
return 0;
/* Calculate AVG of the measurements */
l1sched_lchan_meas_avg(lchan, 4);
/* Check for complete set of bursts */
if ((*mask & 0xf) != 0xf) {
LOGP_LCHAND(lchan, LOGL_ERROR,
"Received incomplete (%s) data frame at fn=%u (%u/%u)\n",
l1sched_burst_mask2str(mask, 4), lchan->meas_avg.fn,
lchan->meas_avg.fn % lchan->ts->mf_layout->period,
lchan->ts->mf_layout->period);
/* NOTE: xCCH has an insane amount of redundancy for error
* correction, so even just 2 valid bursts might be enough
* to reconstruct some L2 frames. This is why we do not
* abort here. */
}
/* Keep the mask updated */
*mask = *mask << 4;
/* Attempt to decode */
rc = gsm0503_xcch_decode(l2, bursts_p, &n_errors, &n_bits_total);
if (rc) {
LOGP_LCHAND(lchan, LOGL_ERROR,
"Received bad frame (rc=%d, ber=%d/%d) at fn=%u\n",
rc, n_errors, n_bits_total, lchan->meas_avg.fn);
}
/* Send a L2 frame to the higher layers */
return l1sched_lchan_emit_data_ind(lchan, l2, rc ? 0 : GSM_MACBLOCK_LEN,
n_errors, n_bits_total, false);
}
static struct msgb *prim_dequeue_xcch(struct l1sched_lchan_state *lchan)
{
struct msgb *msg;
if (L1SCHED_CHAN_IS_SACCH(lchan->type))
return l1sched_lchan_prim_dequeue_sacch(lchan);
if ((msg = msgb_dequeue(&lchan->tx_prims)) == NULL)
return NULL;
/* Check the prim payload length */
if (msgb_l2len(msg) != GSM_MACBLOCK_LEN) {
LOGP_LCHAND(lchan, LOGL_ERROR,
"Primitive has odd length %u (expected %u), so dropping...\n",
msgb_l2len(msg), GSM_MACBLOCK_LEN);
msgb_free(msg);
return NULL;
}
return msg;
}
int tx_data_fn(struct l1sched_lchan_state *lchan,
struct l1sched_burst_req *br)
{
ubit_t *bursts_p, *burst;
const uint8_t *tsc;
uint8_t *mask;
int rc;
/* Set up pointers */
mask = &lchan->tx_burst_mask;
bursts_p = lchan->tx_bursts;
if (br->bid > 0) {
if ((*mask & 0x01) != 0x01)
return -ENOENT;
goto send_burst;
}
*mask = *mask << 4;
struct msgb *msg = prim_dequeue_xcch(lchan);
if (msg == NULL)
msg = l1sched_lchan_prim_dummy_lapdm(lchan);
OSMO_ASSERT(msg != NULL);
/* Encode payload */
rc = gsm0503_xcch_encode(bursts_p, msgb_l2(msg));
if (rc) {
LOGP_LCHAND(lchan, LOGL_ERROR, "Failed to encode L2 payload (len=%u): %s\n",
msgb_l2len(msg), msgb_hexdump_l2(msg));
msgb_free(msg);
return -EINVAL;
}
/* Confirm data sending (pass ownership of the msgb/prim) */
l1sched_lchan_emit_data_cnf(lchan, msg, br->fn);
send_burst:
/* Determine which burst should be sent */
burst = bursts_p + br->bid * 116;
/* Update mask */
*mask |= (1 << br->bid);
/* Choose proper TSC */
tsc = l1sched_nb_training_bits[lchan->tsc];
/* Compose a new burst */
memset(br->burst, 0, 3); /* TB */
memcpy(br->burst + 3, burst, 58); /* Payload 1/2 */
memcpy(br->burst + 61, tsc, 26); /* TSC */
memcpy(br->burst + 87, burst + 58, 58); /* Payload 2/2 */
memset(br->burst + 145, 0, 3); /* TB */
br->burst_len = GSM_NBITS_NB_GMSK_BURST;
LOGP_LCHAND(lchan, LOGL_DEBUG, "Scheduled fn=%u burst=%u\n", br->fn, br->bid);
return 0;
}
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