/* Osmocom Software Defined E1 * Implements ITU-T Rec. G.704 Section 2.3 * * (C) 2018 by Harald Welte * All Rights Reserved * * SPDX-License-Identifier: GPL-2.0-or-later * * 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 #include #include #include #include #include #include #include #include #include "crc4itu.h" #include "osmo_e1f.h" #define S(x) (1 << (x)) /* Frame Alignment Signal (BIT1 may be overwritten with CRC-4) */ #define G704_E1_FAS 0x1B static inline bool is_correct_fas(uint8_t bt) { if ((bt & 0x7F) == G704_E1_FAS) return true; else return false; } /* are we in SMF II (true) or I (false) */ static inline bool is_smf_II(const struct osmo_e1f_tx_state *tx) { if (tx->frame_nr >= 8) return true; return false; } static struct osmo_fsm e1_align_fsm; static void align_fsm_reset(struct osmo_e1f_instance *e1i); static void notify_user(struct osmo_e1f_instance *e1i, enum osmo_e1f_notify_event evt, bool present, void *priv) { if (!e1i->notify_cb) return; e1i->notify_cb(e1i, evt, present, priv); } /*! Initialize a (caller-allocated) Osmocom E1 Instance * \param[inout] e1i E1 Instance to be initialized * \returns 0 on success, negative on error */ int osmo_e1f_instance_init(struct osmo_e1f_instance *e1i, const char *name, e1_notify_cb cb, bool crc4_enabled, void *priv) { int i; e1i->crc4_enabled = crc4_enabled; e1i->notify_cb = cb; e1i->tx.sa4_sa8 = 0x00; e1i->priv = priv; for (i = 1; i < ARRAY_SIZE(e1i->ts); i++) { struct osmo_e1f_instance_ts *e1t = &e1i->ts[i]; e1t->ts_nr = i; e1t->inst = e1i; INIT_LLIST_HEAD(&e1t->tx.queue); e1t->rx.granularity = 256; } e1i->rx.fi = osmo_fsm_inst_alloc(&e1_align_fsm, NULL, e1i, LOGL_DEBUG, name); if (!e1i->rx.fi) return -1; osmo_e1f_instance_reset(e1i); return 0; } /*! stop E1 timeslot; release any pending rx/tx buffers * \param[in] e1t Timeslot which we are to stop, disable and release buffers */ void osmo_e1f_ts_reset(struct osmo_e1f_instance_ts *e1t) { e1t->tx.underruns = 0; msgb_queue_free(&e1t->tx.queue); e1t->rx.enabled = false; msgb_free(e1t->rx.msg); e1t->rx.msg = NULL; osmo_isdnhdlc_rcv_init(&e1t->rx.hdlc, OSMO_HDLC_F_BITREVERSE); //osmo_isdnhdlc_rcv_init(&e1t->rx.hdlc, 0); osmo_isdnhdlc_out_init(&e1t->tx.hdlc, 0); } /*! stop E1 instance; stops all timeslots and releases any pending rx/tx buffers * \param[in] e1t E1 instance which we are to stop */ void osmo_e1f_instance_reset(struct osmo_e1f_instance *e1i) { int i; align_fsm_reset(e1i); e1i->tx.remote_alarm = false; e1i->tx.crc4_error = false; e1i->tx.frame_nr = 0; e1i->tx.crc4_last_smf = 0; e1i->tx.crc4 = crc4itu_init(); e1i->rx.frame_nr = 0; memset(&e1i->rx.ts0_history, 0, sizeof(e1i->rx.ts0_history)); e1i->rx.ts0_hist_len = 0; e1i->rx.remote_alarm = false; e1i->rx.remote_crc4_error = false; e1i->rx.num_ts0_in_mframe_search = 0; for (i = 1; i < ARRAY_SIZE(e1i->ts); i++) { struct osmo_e1f_instance_ts *e1t = &e1i->ts[i]; osmo_e1f_ts_reset(e1t); } } /*! obtain pointer to TS given by instance + timeslot number * \param[in] e1i E1 intance on which we work * \param[in] ts_nr E1 timeslot number (1..31) * \returns pointer to timeslot; NULL on error */ struct osmo_e1f_instance_ts *osmo_e1f_instance_ts(struct osmo_e1f_instance *e1i, uint8_t ts_nr) { if (ts_nr == 0 || ts_nr >= ARRAY_SIZE(e1i->ts)) return NULL; return &e1i->ts[ts_nr]; } /*! configure an E1 timeslot * \param[in] e1t Timeslot which we are to configure * \param[in] granularity granularity (buffer size) to use on Rx * \param[in] enable enable (true) or disalble (false) receiving on this TS * \param[in] mode the mode for this timeslot (raw or hdlc) * \return 0 on success; negative on error */ int osmo_e1f_ts_config(struct osmo_e1f_instance_ts *e1t, e1_data_cb cb, unsigned int granularity, bool enable, enum osmo_e1f_ts_mode mode) { e1t->rx.data_cb = cb; e1t->rx.enabled = enable; e1t->rx.granularity = granularity; e1t->mode = mode; return 0; } const struct value_string osmo_e1f_notifv_evt_names[] = { { E1_NTFY_EVT_ALIGN_FRAME, "Aligned to Frame" }, { E1_NTFY_EVT_ALIGN_CRC_MFRAME, "Aligned to CRC4-Multiframe" }, { E1_NTFY_EVT_CRC_ERROR, "CRC Error detected (local)" }, { E1_NTFY_EVT_REMOTE_CRC_ERROR, "CRC Error reported (remote)" }, { E1_NTFY_EVT_REMOTE_ALARM, "Remote Alarm condition repoorted" }, { 0, NULL } }; /*********************************************************************** * Transmit Side ***********************************************************************/ /*! Enqueue a message buffer of to-be-transmitted data for a timeslot * \param[in] e1i E1 instance for which to enqueue * \param[in] ts_nr Timeslot number on which data is to be transmitted * \param[in] msg Message buffer storing the to-be-transmitted data * \returns 0 on success; negative in case of error. * * Ownership of \a msg is transferred from caller into this function, but only * in case of successful execution (return 0)! */ void osmo_e1f_ts_enqueue(struct osmo_e1f_instance_ts *e1t, struct msgb *msg) { msgb_enqueue(&e1t->tx.queue, msg); } /* obtain a CRC4 bit for the current frame number */ static uint8_t e1_pull_crc4_bit(struct osmo_e1f_instance *e1i) { /* If CRC-4 is disabled, all CRC bits shall be '1' */ if (e1i->crc4_enabled == 0) return 0x01; /* CRC is transmitted MSB first */ switch (e1i->tx.frame_nr % 8) { case 0: return (e1i->tx.crc4_last_smf >> 3) & 1; case 2: return (e1i->tx.crc4_last_smf >> 2) & 1; case 4: return (e1i->tx.crc4_last_smf >> 1) & 1; case 6: return (e1i->tx.crc4_last_smf >> 0) & 1; default: OSMO_ASSERT(0); } } /* pull a single to-be-transmitted byte for TS0 */ static uint8_t e1_pull_ts0(struct osmo_e1f_instance *e1i) { uint8_t ret; /* according to Table 5B/G.704 - CRC-4 multiframe structure */ if ((e1i->tx.frame_nr % 2) == 0) { /* FAS */ ret = G704_E1_FAS | (e1_pull_crc4_bit(e1i) << 7); } else { switch (e1i->tx.frame_nr) { case 1: case 3: case 7: ret = 0x40; break; case 5: case 9: case 11: ret = 0xC0; break; case 13: case 15: ret = 0x40; if (e1i->tx.crc4_error) ret |= 0x80; break; } ret |= e1i->tx.sa4_sa8; if (e1i->tx.remote_alarm) ret |= 0x20; } /* re-set CRC4 at start of sub-multiframe */ if (e1i->tx.frame_nr == 0 || e1i->tx.frame_nr == 8) { e1i->tx.crc4_last_smf = e1i->tx.crc4; e1i->tx.crc4 = 0; } /* increment frame number modulo 16 */ e1i->tx.frame_nr = (e1i->tx.frame_nr + 1) % 16; return ret; } /* pull a single to-be-transmitted byte for TS1..31 */ static uint8_t e1_pull_tsN(struct osmo_e1f_instance_ts *e1t) { struct msgb *msg = llist_first_entry_or_null(&e1t->tx.queue, struct msgb, list); uint8_t *cur; retry: /* if there's no message to transmit */ if (!msg) { e1t->tx.underruns++; return 0xFF; } if (msgb_length(msg) <= 0) { llist_del(&msg->list); msgb_free(msg); msg = llist_first_entry_or_null(&e1t->tx.queue, struct msgb, list); goto retry; } cur = msgb_pull(msg, 1); return *cur; } /* update the current in-progress CRC4 value with data from \a out_frame */ static void e1_tx_update_crc4(struct osmo_e1f_instance *e1i, const uint8_t *out_frame) { uint8_t ts0; ts0 = out_frame[0]; /* mask off the C bits */ if (is_correct_fas(ts0)) ts0 &= 0x7F; e1i->tx.crc4 = crc4itu_update(e1i->tx.crc4, &ts0, 1); /* add the remaining bytes/bits */ e1i->tx.crc4 = crc4itu_update(e1i->tx.crc4, out_frame+1, ARRAY_SIZE(e1i->ts)-1); } /*! Pull one to-be-transmitted E1 frame (256bits) from the E1 instance * \param e1i E1 instance for which the frame shall be generated * \param[out] out_frame callee-allocated buffer to which function stores 32 bytes * \returns 0 on success, negative on error */ int osmo_e1f_pull_tx_frame(struct osmo_e1f_instance *e1i, uint8_t *out_frame) { int i; /* generate TS0 */ out_frame[0] = e1_pull_ts0(e1i); /* generate TS1..31 */ for (i = 1; i < ARRAY_SIZE(e1i->ts); i++) { struct osmo_e1f_instance_ts *e1t = &e1i->ts[i]; /* get next to-be-transmitted byte from the TS */ out_frame[i] = e1_pull_tsN(e1t); } /* update our CRC4 computation */ e1_tx_update_crc4(e1i, out_frame); return 0; } /*********************************************************************** * Receiver Side ***********************************************************************/ /* According to Figure 2 / ITU-T G.706 */ enum e1_align_state { /* Frame Alignment Search */ E1_AS_SEARCH_FRAME, /* CRC multiframe alignment search */ E1_AS_SEARCH_CRC_MFRAME, /* monitoring for incorrect frame alignment and error performance using CRC */ E1_AS_ALIGNED_CRC_MFRAME, /* no CRC: just frame alignment loss check */ E1_AS_ALIGNED_BASIC, }; enum e1_align_event { /* received a TS0 octet */ E1_AE_RX_TS0, E1_AE_RESET }; static const struct value_string e1_align_evt_names[] = { { E1_AE_RX_TS0, "E1_AE_RX_TS0" }, { E1_AE_RESET, "E1_AE_RESET" }, { 0, NULL } }; /* get a TS0 byte from the history. delta 0 == current, delte 1 == previous, ... */ static uint8_t get_ts0_hist(struct osmo_e1f_instance *e1i, uint8_t delta) { return e1i->rx.ts0_history[((e1i->rx.frame_nr + 16)-delta) % 16]; } /* ITU-T G.706 Section 4.1.1 */ static bool frame_alignment_lost(struct osmo_e1f_instance *e1i) { if (e1i->rx.frame_nr % 2) return false; /* Frame alignment will be assumed to have been lost when three consecutive incorrect * frame alignment signals have been received. */ if (!is_correct_fas(get_ts0_hist(e1i, 0)) && !is_correct_fas(get_ts0_hist(e1i, 2)) && !is_correct_fas(get_ts0_hist(e1i, 4))) return true; else return false; } /* ITU-T G.706 Section 4.1.2 */ static bool frame_alignment_recovered(struct osmo_e1f_instance *e1i) { /* two consecutive FAS with one non-FAS interspersed */ if (is_correct_fas(get_ts0_hist(e1i, 0)) && !is_correct_fas(get_ts0_hist(e1i, 1)) && is_correct_fas(get_ts0_hist(e1i, 2))) return true; else return false; } /* ITU-T G.706 Section 4.2 */ static bool crc_mframe_alignment_achieved(struct osmo_e1f_instance *e1i) { /* if current TS0 byte is FAS, we cannot detect alignment */ if (is_correct_fas(get_ts0_hist(e1i, 0))) return false; if ((get_ts0_hist(e1i, 0) >> 7) == 1 && (get_ts0_hist(e1i, 2) >> 7) == 1 && (get_ts0_hist(e1i, 4) >> 7) == 0 && (get_ts0_hist(e1i, 6) >> 7) == 1 && (get_ts0_hist(e1i, 8) >> 7) == 0 && (get_ts0_hist(e1i, 10) >> 7) == 0) return true; else return false; } /* Get the CRC4 that was received from our Rx TS0 history */ static uint8_t crc4_from_ts0_hist(struct osmo_e1f_instance *e1i, bool smf2) { uint8_t crc = 0; uint8_t offset = 0; if (smf2) offset = 8; crc |= (e1i->rx.ts0_history[0+offset] >> 7) << 3; crc |= (e1i->rx.ts0_history[2+offset] >> 7) << 2; crc |= (e1i->rx.ts0_history[4+offset] >> 7) << 1; crc |= (e1i->rx.ts0_history[6+offset] >> 7) << 0; return crc; } /* update the current in-progress CRC4 value with data from \a rx_frame */ static void e1_rx_update_crc4(struct osmo_e1f_instance *e1i, const uint8_t *rx_frame) { uint8_t ts0; ts0 = rx_frame[0]; /* mask off the C bits */ if (is_correct_fas(ts0)) ts0 &= 0x7F; e1i->rx.crc4 = crc4itu_update(e1i->rx.crc4, &ts0, 1); /* add the remaining bytes/bits */ e1i->rx.crc4 = crc4itu_update(e1i->rx.crc4, rx_frame+1, ARRAY_SIZE(e1i->ts)-1); } /* FSM State handler */ static void e1_align_search_frame(struct osmo_fsm_inst *fi, uint32_t event, void *data) { struct osmo_e1f_instance *e1i = (struct osmo_e1f_instance *) fi->priv; if (frame_alignment_recovered(e1i)) { /* if we detected the 2nd FAS, we must be in FN 2 (or at least FN%2=0 */ e1i->rx.frame_nr = 2; notify_user(e1i, E1_NTFY_EVT_ALIGN_FRAME, true, NULL); osmo_fsm_inst_state_chg(fi, E1_AS_SEARCH_CRC_MFRAME, 0, 0); } } /* FSM State handler */ static void e1_align_search_crc_mframe(struct osmo_fsm_inst *fi, uint32_t event, void *data) { struct osmo_e1f_instance *e1i = (struct osmo_e1f_instance *) fi->priv; if (crc_mframe_alignment_achieved(e1i)) { /* if we detected the 6-bit CRC multiframe signal, we must be in FN 11 */ e1i->rx.frame_nr = 11; /* FIXME: "at least two valid CRC multiframe alignment signals can be located within * 8 ms, the time separating two CRC multiframe alignment signals being 2 ms or a * multiple of 2 ms" */ notify_user(e1i, E1_NTFY_EVT_ALIGN_CRC_MFRAME, true, NULL); osmo_fsm_inst_state_chg(fi, E1_AS_ALIGNED_CRC_MFRAME, 0, 0); } else { /* if no mframe alignment is established within 8ms (64 frames), fall back */ if (e1i->rx.num_ts0_in_mframe_search >= 64) { e1i->rx.num_ts0_in_mframe_search = 0; osmo_fsm_inst_state_chg(fi, E1_AS_SEARCH_FRAME, 0, 0); } e1i->rx.num_ts0_in_mframe_search++; } } static void e1_aligned_common(struct osmo_e1f_instance *e1i) { uint8_t inb = get_ts0_hist(e1i, 0); /* All non-FAS frames contain "A" bit in TS0 */ if (!is_correct_fas(inb & 0x7F)) { bool old_alarm = e1i->rx.remote_alarm; /* frame not containing the frame alignment signal */ if (inb & 0x20) e1i->rx.remote_alarm = true; else e1i->rx.remote_alarm = false; if (old_alarm != e1i->rx.remote_alarm) notify_user(e1i, E1_NTFY_EVT_REMOTE_ALARM, e1i->rx.remote_alarm, NULL); } } /* FSM State handler */ static void e1_aligned_crc_mframe(struct osmo_fsm_inst *fi, uint32_t event, void *data) { struct osmo_e1f_instance *e1i = (struct osmo_e1f_instance *) fi->priv; if (frame_alignment_lost(e1i)) { osmo_fsm_inst_state_chg(fi, E1_AS_SEARCH_FRAME, 0, 0); return; } if (e1i->crc4_enabled) { uint8_t crc_rx; bool crc4_error; /* check if we just received a complete CRC4 */ switch (e1i->rx.frame_nr) { case 7: case 15: crc_rx = crc4_from_ts0_hist(e1i, e1i->rx.frame_nr == 15 ? true : false); if (crc_rx != e1i->rx.crc4_last_smf) crc4_error = true; else crc4_error = false; if (crc4_error != e1i->tx.crc4_error) { notify_user(e1i, E1_NTFY_EVT_CRC_ERROR, crc4_error, NULL); e1i->tx.crc4_error = crc4_error; } /* rotate computed CRC4 one further */ e1i->rx.crc4_last_smf = e1i->rx.crc4; e1i->rx.crc4 = crc4itu_init(); break; default: break; } /* check if the remote side reports any CRC errors */ switch (e1i->rx.frame_nr) { case 13: case 15: crc4_error = false; if ((get_ts0_hist(e1i, 0) >> 7) == 0) crc4_error = true; if (crc4_error != e1i->rx.remote_crc4_error) { notify_user(e1i, E1_NTFY_EVT_REMOTE_CRC_ERROR, crc4_error, NULL); e1i->rx.remote_crc4_error = crc4_error; } break; } } e1_aligned_common(e1i); } /* FSM State handler */ static void e1_aligned_basic(struct osmo_fsm_inst *fi, uint32_t event, void *data) { struct osmo_e1f_instance *e1i = (struct osmo_e1f_instance *) fi->priv; if (frame_alignment_lost(e1i)) { osmo_fsm_inst_state_chg(fi, E1_AS_SEARCH_FRAME, 0, 0); return; } e1_aligned_common(e1i); } static const struct osmo_fsm_state e1_align_states[] = { [E1_AS_SEARCH_FRAME] = { .name = "SEARCH_FRAME", .in_event_mask = S(E1_AE_RX_TS0), .out_state_mask = S(E1_AS_SEARCH_FRAME) | S(E1_AS_SEARCH_CRC_MFRAME) | S(E1_AS_ALIGNED_BASIC), .action = e1_align_search_frame, }, [E1_AS_SEARCH_CRC_MFRAME] = { .name = "SEARCH_CRC_MFRAME", .in_event_mask = S(E1_AE_RX_TS0), .out_state_mask = S(E1_AS_SEARCH_FRAME) | S(E1_AS_SEARCH_CRC_MFRAME) | S(E1_AS_ALIGNED_CRC_MFRAME), .action = e1_align_search_crc_mframe, }, [E1_AS_ALIGNED_CRC_MFRAME] = { .name = "ALIGNED_CRC_MFRAME", .in_event_mask = S(E1_AE_RX_TS0), .out_state_mask = S(E1_AS_SEARCH_FRAME) | S(E1_AS_SEARCH_CRC_MFRAME) | S(E1_AS_ALIGNED_CRC_MFRAME), .action = e1_aligned_crc_mframe, }, [E1_AS_ALIGNED_BASIC] = { .name = "ALIGNED_BASIC", .in_event_mask = S(E1_AE_RX_TS0), .out_state_mask = S(E1_AS_SEARCH_FRAME), .action = e1_aligned_basic, }, }; static void e1_allstate(struct osmo_fsm_inst *fi, uint32_t event, void *data) { struct osmo_e1f_instance *e1i = (struct osmo_e1f_instance *) fi->priv; switch (event) { case E1_AE_RESET: e1i->rx.num_ts0_in_mframe_search = 0; osmo_fsm_inst_state_chg(fi, E1_AS_SEARCH_FRAME, 0, 0); break; } } static struct osmo_fsm e1_align_fsm = { .name = "e1-align", .states = e1_align_states, .num_states = ARRAY_SIZE(e1_align_states), .allstate_event_mask = S(E1_AE_RESET), .allstate_action = e1_allstate, .log_subsys = DLGLOBAL, .event_names = e1_align_evt_names, }; static void align_fsm_reset(struct osmo_e1f_instance *e1i) { osmo_fsm_inst_dispatch(e1i->rx.fi, E1_AE_RESET, NULL); } static void e1_rx_hist_add(struct osmo_e1f_instance *e1i, uint8_t inb) { e1i->rx.ts0_history[e1i->rx.frame_nr] = inb; if (e1i->rx.ts0_hist_len < 16) e1i->rx.ts0_hist_len++; } static void e1_rx_ts0(struct osmo_e1f_instance *e1i, uint8_t inb) { /* append just-received byte to the TS0 receive history buffer */ e1_rx_hist_add(e1i, inb); /* notify the FSM that a new TS0 byte was received */ osmo_fsm_inst_dispatch(e1i->rx.fi, E1_AE_RX_TS0, NULL); e1i->rx.frame_nr = (e1i->rx.frame_nr + 1) % 16; } static void e1_rx_tsN(struct osmo_e1f_instance_ts *e1t, uint8_t inb) { struct msgb *msg; int count, rc; if (!e1t->rx.enabled) return; if (!e1t->rx.msg) e1t->rx.msg = msgb_alloc(e1t->rx.granularity, "E1 Rx"); msg = e1t->rx.msg; OSMO_ASSERT(msg); switch (e1t->mode) { case OSMO_E1F_TS_RAW: /* append byte at end of msgb */ msgb_put_u8(msg, inb); /* flush msgb, if full */ if (msgb_tailroom(msg) <= 0) { goto flush; } break; case OSMO_E1F_TS_HDLC_CRC: rc = osmo_isdnhdlc_decode(&e1t->rx.hdlc, &inb, 1, &count, msgb_data(msg), msgb_tailroom(msg)); switch (rc) { case -OSMO_HDLC_FRAMING_ERROR: fprintf(stdout, "Framing Error\n"); break; case -OSMO_HDLC_CRC_ERROR: fprintf(stdout, "CRC Error\n"); break; case -OSMO_HDLC_LENGTH_ERROR: fprintf(stdout, "Length Error\n"); break; case 0: /* no output yet */ break; default: msgb_put(msg, rc); goto flush; } break; } return; flush: if (!e1t->rx.data_cb) msgb_free(msg); else e1t->rx.data_cb(e1t, msg); e1t->rx.msg = NULL; } /*! Receive a single E1 frame of 32x8 (=256) bits * \param e1i E1 instance for which the frame was received * \param[in] in_frame caller-provided buffer of 32 octets * * The idea is that whoever calls us will already have done the bit-alignment, * i.e. the first bit of TS0 of the frame will be octet-aligned and hence the * entire 256bit buffer is provided as octet-aligned 32bytes in \a in_frame. */ int osmo_e1f_rx_frame(struct osmo_e1f_instance *e1i, const uint8_t *in_frame) { int i; e1_rx_update_crc4(e1i, in_frame); e1_rx_ts0(e1i, in_frame[0]); for (i = 1; i < ARRAY_SIZE(e1i->ts); i++) { struct osmo_e1f_instance_ts *e1t = &e1i->ts[i]; e1_rx_tsN(e1t, in_frame[i]); } return 0; } int osmo_e1f_init(void) { return osmo_fsm_register(&e1_align_fsm); }