120 lines
3.0 KiB
C
120 lines
3.0 KiB
C
/*
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* OsmocomBB <-> SDR connection bridge
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* TDMA scheduler: handlers for DL / UL bursts on logical channels
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*
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* (C) 2017-2022 by Vadim Yanitskiy <axilirator@gmail.com>
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* Contributions by sysmocom - s.f.m.c. GmbH
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*
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* All Rights Reserved
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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 <errno.h>
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#include <string.h>
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#include <talloc.h>
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#include <stdint.h>
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#include <arpa/inet.h>
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#include <osmocom/core/logging.h>
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#include <osmocom/core/bits.h>
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#include <osmocom/gsm/gsm_utils.h>
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#include <osmocom/coding/gsm0503_coding.h>
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#include <osmocom/bb/l1sched/l1sched.h>
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#include <osmocom/bb/l1sched/logging.h>
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static void decode_sb(struct gsm_time *time, uint8_t *bsic, uint8_t *sb_info)
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{
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uint8_t t3p;
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uint32_t sb;
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sb = ((uint32_t)sb_info[3] << 24)
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| (sb_info[2] << 16)
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| (sb_info[1] << 8)
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| sb_info[0];
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*bsic = (sb >> 2) & 0x3f;
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/* TS 05.02 Chapter 3.3.2.2.1 SCH Frame Numbers */
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time->t1 = ((sb >> 23) & 0x01)
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| ((sb >> 7) & 0x1fe)
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| ((sb << 9) & 0x600);
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time->t2 = (sb >> 18) & 0x1f;
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t3p = ((sb >> 24) & 0x01) | ((sb >> 15) & 0x06);
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time->t3 = t3p * 10 + 1;
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/* TS 05.02 Chapter 4.3.3 TDMA frame number */
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time->fn = gsm_gsmtime2fn(time);
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}
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static int handle_sch_ind(struct l1sched_state *sched, uint32_t fn, uint8_t bsic)
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{
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struct l1sched_prim *prim;
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struct msgb *msg;
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msg = l1sched_prim_alloc(L1SCHED_PRIM_T_SCH, PRIM_OP_INDICATION);
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OSMO_ASSERT(msg != NULL);
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prim = l1sched_prim_from_msgb(msg);
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prim->sch_ind.frame_nr = fn;
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prim->sch_ind.bsic = bsic;
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return l1sched_prim_to_user(sched, msg);
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}
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int rx_sch_fn(struct l1sched_lchan_state *lchan,
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const struct l1sched_burst_ind *bi)
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{
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sbit_t payload[2 * 39];
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struct gsm_time time;
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uint8_t sb_info[4];
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uint8_t bsic;
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int rc;
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/* Obtain payload from burst */
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memcpy(payload, bi->burst + 3, 39);
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memcpy(payload + 39, bi->burst + 3 + 39 + 64, 39);
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/* Attempt to decode */
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rc = gsm0503_sch_decode(sb_info, payload);
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if (rc) {
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LOGP_LCHAND(lchan, LOGL_ERROR,
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"Received bad SCH burst at fn=%u\n", bi->fn);
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return rc;
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}
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/* Decode BSIC and TDMA frame number */
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decode_sb(&time, &bsic, sb_info);
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LOGP_LCHAND(lchan, LOGL_DEBUG,
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"Received SCH: bsic=%u, fn=%u, sched_fn=%u\n",
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bsic, time.fn, bi->fn);
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/* Check if decoded frame number matches */
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if (time.fn != bi->fn) {
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LOGP_LCHAND(lchan, LOGL_ERROR,
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"Decoded fn=%u does not match sched_fn=%u\n",
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time.fn, bi->fn);
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return -EINVAL;
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}
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/* Update BSIC value in the scheduler state */
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lchan->ts->sched->bsic = bsic;
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return handle_sch_ind(lchan->ts->sched, time.fn, bsic);
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}
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