| /* GSM A-bis TRAU frame synchronization as per TS 48.060 / 48.061 */ |
| |
| /* (C) 2020 by Harald Welte <laforge@gnumonks.org> |
| * All Rights Reserved |
| * |
| * SPDX-License-Identifier: GPL-2.0+ |
| * |
| * 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. |
| * |
| * You should have received a copy of the GNU General Public License |
| * along with this program. If not, see <http://www.gnu.org/licenses/>. |
| * |
| */ |
| |
| #include <stdint.h> |
| |
| #include <osmocom/core/msgb.h> |
| #include <osmocom/core/bits.h> |
| #include <osmocom/core/fsm.h> |
| |
| #include "ubit_buf.h" |
| #include <osmocom/trau/trau_sync.h> |
| |
| #define S(x) (1 << (x)) |
| |
| #define MAX_TRAU_BYTES 40 |
| |
| #define T_SYNC 1 |
| |
| struct sync_pattern { |
| /* provided by user */ |
| const char *name; /*!< human-readable name */ |
| const uint8_t byte_pattern[MAX_TRAU_BYTES]; /*!< bytes to match against */ |
| const uint8_t byte_mask[MAX_TRAU_BYTES]; /*!< mask applied before matching */ |
| uint8_t byte_len; /*!< length of mask in bytes */ |
| |
| /* generated by code */ |
| ubit_t ubit_pattern[MAX_TRAU_BYTES*8]; /*!< bits to match against */ |
| ubit_t ubit_mask[MAX_TRAU_BYTES*8]; /*!< mask applied before matching */ |
| uint8_t bitcount; /*!< number of high bits in mask */ |
| }; |
| |
| static struct sync_pattern sync_patterns[] = { |
| [OSMO_TRAU_SYNCP_16_FR_EFR] = { |
| /* TS 08.60 Section 4.8.1 */ |
| .name = "FR/EFR", |
| .byte_pattern = { |
| 0x00, 0x00, 0x80, 0x00, 0x80, 0x00, 0x80, 0x00, |
| 0x80, 0x00, 0x80, 0x00, 0x80, 0x00, 0x80, 0x00, |
| 0x80, 0x00, 0x80, 0x00, 0x80, 0x00, 0x80, 0x00, |
| 0x80, 0x00, 0x80, 0x00, 0x80, 0x00, 0x80, 0x00, |
| 0x80, 0x00, 0x80, 0x00, 0x80, 0x00, 0x80, 0x00, |
| }, |
| .byte_mask = { |
| 0xff, 0xff, 0x80, 0x00, 0x80, 0x00, 0x80, 0x00, |
| 0x80, 0x00, 0x80, 0x00, 0x80, 0x00, 0x80, 0x00, |
| 0x80, 0x00, 0x80, 0x00, 0x80, 0x00, 0x80, 0x00, |
| 0x80, 0x00, 0x80, 0x00, 0x80, 0x00, 0x80, 0x00, |
| 0x80, 0x00, 0x80, 0x00, 0x80, 0x00, 0x80, 0x00, |
| }, |
| .byte_len = 40, |
| }, |
| [OSMO_TRAU_SYNCP_8_HR] = { |
| /* TS 08.61 Section 6.8.2.1.1 */ |
| .name = "HR8", |
| .byte_pattern = { |
| 0x00, 0x80, 0x40, 0x80, |
| 0x80, 0x80, 0x80, 0x80, |
| 0x80, 0x80, 0x80, 0x80, |
| 0x80, 0x80, 0x80, 0x80, |
| 0x80, 0x80, 0x80, 0x80, |
| }, |
| .byte_mask = { |
| 0xff, 0x80, 0xC0, 0x80, |
| 0x80, 0x80, 0x80, 0x80, |
| 0x80, 0x80, 0x80, 0x80, |
| 0x80, 0x80, 0x80, 0x80, |
| 0x80, 0x80, 0x80, 0x80, |
| }, |
| .byte_len = 20, |
| }, |
| [OSMO_TRAU_SYNCP_8_AMR_LOW] = { |
| /* TS 08.61 Section 6.8.2.1.2 */ |
| /* The frame synchronisation for No_Speech frames and the speech frames of the three lower codec modes */ |
| .name = "AMR8_LOW", |
| .byte_pattern = { |
| 0x00, 0x80, 0x80, 0x40, |
| 0x80, 0x80, 0x80, 0x80, |
| 0x80, 0x80, 0x80, 0x80, |
| 0x80, 0x80, 0x80, 0x80, |
| 0x80, 0x80, 0x80, 0x80, |
| }, |
| .byte_mask = { |
| 0xff, 0x80, 0x80, 0xC0, |
| 0x80, 0x80, 0x80, 0x80, |
| 0x80, 0x80, 0x80, 0x80, |
| 0x80, 0x80, 0x80, 0x80, |
| 0x80, 0x80, 0x80, 0x80, |
| }, |
| .byte_len = 20, |
| }, |
| [OSMO_TRAU_SYNCP_8_AMR_6K7] = { |
| /* The frame synchronisation for the speech frames for codec mode 6,70 kBit/s */ |
| .name = "AMR8_67", |
| .byte_pattern = { |
| 0x00, 0x80, 0x80, 0x80, |
| 0x80, 0x00, 0x80, 0x00, |
| 0x80, 0x00, 0x80, 0x00, |
| 0x80, 0x00, 0x80, 0x00, |
| 0x80, 0x00, 0x80, 0x00, |
| }, |
| .byte_mask = { |
| 0xff, 0x80, 0x80, 0x80, |
| 0x80, 0x80, 0x80, 0x00, |
| 0x80, 0x00, 0x80, 0x00, |
| 0x80, 0x00, 0x80, 0x00, |
| 0x80, 0x00, 0x80, 0x00, |
| }, |
| .byte_len = 20 |
| }, |
| [OSMO_TRAU_SYNCP_8_AMR_7K4] = { |
| /* The frame synchronisation for the speech frames for codec mode 7,40 kBit/s */ |
| .name = "AMR8_74", |
| .byte_pattern = { |
| 0x20, 0x00, 0x80, 0x00, |
| 0x00, 0x00, 0x00, 0x00, |
| 0x00, 0x00, 0x00, 0x00, |
| 0x00, 0x00, 0x00, 0x00, |
| 0x00, 0x00, 0x00, 0x00, |
| }, |
| .byte_mask = { |
| 0xe0, 0x80, 0x80, 0x80, |
| 0x00, 0x00, 0x00, 0x00, |
| 0x00, 0x00, 0x00, 0x00, |
| 0x00, 0x00, 0x00, 0x00, |
| 0x00, 0x00, 0x00, 0x00, |
| }, |
| .byte_len = 20, |
| }, |
| }; |
| |
| #if 0 |
| static struct sync_pattern rbs_ccu_sync_ind_16_pattern = { |
| .name ="RBS_CCU_SYNC_IND_16", |
| .byte_pattern = { |
| 0x00, 0x00, 0x01, 0x00, |
| 0x00, 0x00, 0x01, 0x00, |
| 0x01, 0x00, 0x01, 0x00, |
| }, |
| .byte_mask = { |
| 0xff, 0xff, 0x01, 0x00, |
| 0x01, 0x00, 0x01, 0x00, |
| 0x01, 0x00, 0x01, 0x00, |
| }, |
| }; |
| |
| static struct sync_pattern rbs_ccu_data_ind_16_pattern = { |
| .name ="RBS_CCU_DATA_IND_16", |
| .byte_pattern = { |
| 0x00, 0x00, 0x01, 0x00, |
| }, |
| .byte_mask = { |
| 0xff, 0xff, 0x01, 0x00, |
| }, |
| }; |
| #endif |
| |
| |
| static void expand_sync_pattern(struct sync_pattern *pat) |
| { |
| osmo_pbit2ubit(pat->ubit_pattern, pat->byte_pattern, pat->byte_len*8); |
| osmo_pbit2ubit(pat->ubit_mask, pat->byte_mask, pat->byte_len*8); |
| } |
| |
| static unsigned int count_one_bits(const ubit_t *in, unsigned int in_bits) |
| { |
| unsigned int i, count = 0; |
| |
| for (i = 0; i < in_bits; i++) { |
| if (in[i]) |
| count++; |
| } |
| return count; |
| } |
| |
| static void sync_pattern_register(struct sync_pattern *p) |
| { |
| expand_sync_pattern(p); |
| p->bitcount = count_one_bits(p->ubit_mask, p->byte_len*8); |
| } |
| |
| #if 0 |
| /*! correlate pattern with unpacked bits from buffer. |
| * \param[in] pattern sync_pattern against which we shall compare |
| * \param[in] bits unpacked bits to compare against pattern |
| * \param[in] num_bits number of unpacked bits |
| * \returns number of bits not matching pattern; -1 if insufficient bits available. */ |
| static int correlate_pattern_ubits(const struct sync_pattern *pattern, |
| const ubit_t *bits, size_t num_bits) |
| { |
| int i, num_wrong = 0; |
| |
| if (num_bits < pattern->byte_len*8) |
| return -1; /* insufficient data */ |
| |
| for (i = 0; i < pattern->byte_len *8; i++) { |
| /* if mask doesn't contain '1', we can skip this octet */ |
| if (!pattern->ubit_mask) |
| continue; |
| if (bits[i] != pattern->ubit_pattern[i]) |
| num_wrong++; |
| } |
| |
| return num_wrong; |
| } |
| #endif |
| |
| struct trau_rx_sync_state { |
| /*! call-back to be called for every TRAU frame (called with |
| * bits=NULL in case of frame sync loss */ |
| frame_out_cb_t out_cb; |
| /*! opaque user data; passed to out_cb */ |
| void *user_data; |
| |
| /*! history of received bits */ |
| ubit_t history[MAX_TRAU_BYTES*8+1]; /* +1 not required, but helps to expose bugs */ |
| /*! index of next-to-be-written ubit in history */ |
| unsigned int history_idx; |
| /*! the pattern we are trying to sync to */ |
| const struct sync_pattern *pattern; |
| /*! number of consecutive frames without sync */ |
| unsigned int num_consecutive_errors; |
| }; |
| |
| /* correlate the history (up to the last received bit) against the pattern */ |
| static int correlate_history_against_pattern(struct trau_rx_sync_state *tss) |
| { |
| const struct sync_pattern *pattern = tss->pattern; |
| int i, start, num_wrong = 0; |
| |
| /* compute index of first bit in history array */ |
| start = (ARRAY_SIZE(tss->history) + tss->history_idx - pattern->byte_len*8) |
| % ARRAY_SIZE(tss->history); |
| |
| OSMO_ASSERT(ARRAY_SIZE(tss->history) >= pattern->byte_len*8); |
| |
| for (i = 0; i < pattern->byte_len*8; i++) { |
| unsigned int pos = (start + i) % ARRAY_SIZE(tss->history); |
| |
| /* if mask doesn't contain '1', we can skip this octet */ |
| if (!pattern->ubit_mask[i]) |
| continue; |
| if (tss->history[pos] != pattern->ubit_pattern[i]) |
| num_wrong++; |
| } |
| |
| return num_wrong; |
| } |
| |
| /* add (append) one ubit to the history; wrap as needed */ |
| static void rx_history_add_bit(struct trau_rx_sync_state *tss, ubit_t bit) |
| { |
| tss->history[tss->history_idx] = bit; |
| /* simply wrap around at the end */ |
| tss->history_idx = (tss->history_idx + 1) % ARRAY_SIZE(tss->history); |
| } |
| |
| /* append bits to history. We assume that this does NOT wrap */ |
| static void rx_history_add_bits(struct trau_rx_sync_state *tss, const ubit_t *bits, size_t n_bits) |
| { |
| unsigned int frame_bits_remaining = tss->pattern->byte_len*8 - tss->history_idx; |
| OSMO_ASSERT(frame_bits_remaining >= n_bits); |
| memcpy(&tss->history[tss->history_idx], bits, n_bits); |
| tss->history_idx = tss->history_idx + n_bits; |
| } |
| |
| /* align the history, i.e. next received bit is start of frame */ |
| static void rx_history_align(struct trau_rx_sync_state *tss) |
| { |
| ubit_t tmp[sizeof(tss->history)]; |
| size_t history_size = sizeof(tss->history); |
| size_t pattern_bits = tss->pattern->byte_len*8; |
| size_t first_bit = (history_size + tss->history_idx - pattern_bits) % history_size; |
| int i; |
| |
| /* we need to shift the last received frame to the start of the history buffer; |
| * do this in two steps: First copy to a local buffer on the stack, using modulo-arithmetic |
| * as index into the history. Second, copy it back to history */ |
| |
| for (i = 0; i < pattern_bits; i++) |
| tmp[i] = tss->history[(first_bit + i) % history_size]; |
| |
| memcpy(tss->history, tmp, history_size); |
| tss->history_idx = 0; |
| } |
| |
| enum trau_sync_state { |
| WAIT_FRAME_ALIGN, |
| FRAME_ALIGNED, |
| /* if at least 3 consecutive frames with each at least one framing error have been received */ |
| FRAME_ALIGNMENT_LOST, |
| }; |
| |
| enum trau_sync_event { |
| TRAUSYNC_E_RESET, |
| /*! a buffer of bits was received (msgb with ubits) */ |
| TRAUSYNC_E_RX_BITS, |
| }; |
| |
| static const struct value_string trau_sync_event_names[] = { |
| { TRAUSYNC_E_RESET, "RESET" }, |
| { TRAUSYNC_E_RX_BITS, "RX_BITS" }, |
| { 0, NULL } |
| }; |
| |
| |
| static void trau_sync_wait_align(struct osmo_fsm_inst *fi, uint32_t event, void *data) |
| { |
| struct trau_rx_sync_state *tss = (struct trau_rx_sync_state *) fi->priv; |
| struct ubit_buf *ubb; |
| |
| switch (event) { |
| case TRAUSYNC_E_RX_BITS: |
| ubb = data; |
| /* append every bit individually + check if we have sync */ |
| while (ubb_length(ubb) > 0) { |
| ubit_t bit = ubb_pull_ubit(ubb); |
| int rc; |
| |
| rx_history_add_bit(tss, bit); |
| rc = correlate_history_against_pattern(tss); |
| if (!rc) { |
| osmo_fsm_inst_state_chg(fi, FRAME_ALIGNED, 0, 0); |
| /* treat remainder of input bits in correct state */ |
| osmo_fsm_inst_dispatch(fi, TRAUSYNC_E_RX_BITS, ubb); |
| return; |
| } |
| } |
| break; |
| default: |
| OSMO_ASSERT(0); |
| } |
| } |
| |
| static void trau_sync_aligned_onenter(struct osmo_fsm_inst *fi, uint32_t prev_state) |
| { |
| struct trau_rx_sync_state *tss = (struct trau_rx_sync_state *) fi->priv; |
| /* dispatch aligned frame to user */ |
| rx_history_align(tss); |
| tss->out_cb(tss->user_data, tss->history, tss->pattern->byte_len*8); |
| } |
| |
| static void trau_sync_aligned(struct osmo_fsm_inst *fi, uint32_t event, void *data) |
| { |
| struct trau_rx_sync_state *tss = (struct trau_rx_sync_state *) fi->priv; |
| struct ubit_buf *ubb; |
| int rc; |
| |
| switch (event) { |
| case TRAUSYNC_E_RX_BITS: |
| ubb = data; |
| while (ubb_length(ubb)) { |
| unsigned int frame_bits_remaining = tss->pattern->byte_len*8 - tss->history_idx; |
| if (ubb_length(ubb) < frame_bits_remaining) { |
| /* frame not filled by this message; just add data */ |
| rx_history_add_bits(tss, ubb_data(ubb), ubb_length(ubb)); |
| ubb_pull(ubb, ubb_length(ubb)); |
| } else { |
| /* append as many bits as are missing in the current frame */ |
| rx_history_add_bits(tss, ubb_data(ubb), frame_bits_remaining); |
| ubb_pull(ubb, frame_bits_remaining); |
| |
| /* check if we still have frame sync */ |
| rc = correlate_history_against_pattern(tss); |
| if (rc > 0) { |
| tss->num_consecutive_errors++; |
| if (tss->num_consecutive_errors >= 3) { |
| tss->history_idx = 0; |
| /* send NULL frame to user */ |
| tss->out_cb(tss->user_data, NULL, 0); |
| osmo_fsm_inst_state_chg(fi, FRAME_ALIGNMENT_LOST, 1, T_SYNC); |
| osmo_fsm_inst_dispatch(fi, TRAUSYNC_E_RX_BITS, ubb); |
| return; |
| } |
| } else |
| tss->num_consecutive_errors = 0; |
| |
| /* dispatch aligned frame to user */ |
| tss->out_cb(tss->user_data, tss->history, tss->history_idx); |
| tss->history_idx = 0; |
| } |
| } |
| break; |
| default: |
| OSMO_ASSERT(0); |
| } |
| } |
| |
| static void trau_sync_alignment_lost(struct osmo_fsm_inst *fi, uint32_t event, void *data) |
| { |
| /* we try to restore sync for some amount of time before generating an error */ |
| |
| switch (event) { |
| case TRAUSYNC_E_RX_BITS: |
| trau_sync_wait_align(fi, event, data); |
| break; |
| default: |
| OSMO_ASSERT(0); |
| } |
| } |
| |
| static void trau_sync_allstate(struct osmo_fsm_inst *fi, uint32_t event, void *data) |
| { |
| switch (event) { |
| case TRAUSYNC_E_RESET: |
| osmo_fsm_inst_state_chg(fi, WAIT_FRAME_ALIGN, 0, 0); |
| break; |
| default: |
| OSMO_ASSERT(0); |
| } |
| } |
| |
| static int trau_sync_timeout(struct osmo_fsm_inst *fi) |
| { |
| switch (fi->T) { |
| case T_SYNC: |
| /* if Tsync expires before frame synchronization is |
| * again obtained the TRAU initiates sending of the |
| * urgent alarm pattern described in clause 4.10.2. */ |
| osmo_fsm_inst_state_chg(fi, WAIT_FRAME_ALIGN, 0, 0); |
| break; |
| default: |
| OSMO_ASSERT(0); |
| } |
| return 0; |
| } |
| |
| static const struct osmo_fsm_state trau_sync_states[] = { |
| [WAIT_FRAME_ALIGN] = { |
| .name = "WAIT_FRAME_ALIGN", |
| .in_event_mask = S(TRAUSYNC_E_RX_BITS), |
| .out_state_mask = S(FRAME_ALIGNED), |
| .action = trau_sync_wait_align, |
| }, |
| [FRAME_ALIGNED] = { |
| .name = "FRAME_ALIGNED", |
| .in_event_mask = S(TRAUSYNC_E_RX_BITS), |
| .out_state_mask = S(FRAME_ALIGNMENT_LOST) | S(WAIT_FRAME_ALIGN), |
| .action = trau_sync_aligned, |
| .onenter = trau_sync_aligned_onenter, |
| }, |
| [FRAME_ALIGNMENT_LOST] = { |
| .name = "FRAME_ALIGNMENT_LOST", |
| .in_event_mask = S(TRAUSYNC_E_RX_BITS), |
| .out_state_mask = S(WAIT_FRAME_ALIGN) | S(FRAME_ALIGNED), |
| .action = trau_sync_alignment_lost, |
| }, |
| }; |
| |
| static struct osmo_fsm trau_sync_fsm = { |
| .name = "trau_sync", |
| .states = trau_sync_states, |
| .num_states = ARRAY_SIZE(trau_sync_states), |
| .allstate_event_mask = S(TRAUSYNC_E_RESET), |
| .allstate_action = trau_sync_allstate, |
| .timer_cb = trau_sync_timeout, |
| .log_subsys = DLGLOBAL, |
| .event_names = trau_sync_event_names, |
| }; |
| |
| |
| struct osmo_fsm_inst * |
| osmo_trau_sync_alloc(void *ctx, const char *name, frame_out_cb_t frame_out_cb, |
| enum osmo_tray_sync_pat_id pat_id, void *user_data) |
| { |
| struct trau_rx_sync_state *tss; |
| struct osmo_fsm_inst *fi; |
| |
| if (pat_id >= ARRAY_SIZE(sync_patterns)) |
| return NULL; |
| |
| fi = osmo_fsm_inst_alloc(&trau_sync_fsm, ctx, NULL, LOGL_NOTICE, name); |
| if (!fi) |
| return NULL; |
| tss = talloc_zero(fi, struct trau_rx_sync_state); |
| if (!tss) { |
| osmo_fsm_inst_term(fi, OSMO_FSM_TERM_ERROR, NULL); |
| return NULL; |
| } |
| fi->priv = tss; |
| |
| tss->out_cb = frame_out_cb; |
| tss->user_data = user_data; |
| /* FIXME: this must be configurable */ |
| tss->pattern = &sync_patterns[pat_id]; |
| |
| /* An unusued E1 timeslot normally would send an idle signal that |
| * has all bits set to one. In order to prevent false-positive |
| * synchronization on startup we set all history bits to 1, to make |
| * it look like a signal from an unused timeslot. */ |
| memset(tss->history, 1, sizeof(tss->history)); |
| |
| return fi; |
| } |
| |
| void osmo_trau_sync_rx_ubits(struct osmo_fsm_inst *fi, const ubit_t *bits, size_t n_bits) |
| { |
| struct ubit_buf ubb; |
| ubb_init(&ubb, bits, n_bits); |
| osmo_fsm_inst_dispatch(fi, TRAUSYNC_E_RX_BITS, &ubb); |
| } |
| |
| static void __attribute__((constructor)) on_dso_load_sync(void) |
| { |
| int i; |
| |
| for (i = 0; i < ARRAY_SIZE(sync_patterns); i++) |
| sync_pattern_register(&sync_patterns[i]); |
| OSMO_ASSERT(osmo_fsm_register(&trau_sync_fsm) == 0); |
| } |