/* tbf_dl_fsm.c * * Copyright (C) 2021-2022 by sysmocom - s.f.m.c. GmbH * Author: Pau Espin Pedrol * * 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 #define X(s) (1 << (s)) static const struct osmo_tdef_state_timeout tbf_dl_fsm_timeouts[32] = { [TBF_ST_NEW] = {}, [TBF_ST_ASSIGN] = {}, [TBF_ST_FLOW] = {}, [TBF_ST_FINISHED] = {}, [TBF_ST_WAIT_RELEASE] = { .T = 3192 }, [TBF_ST_WAIT_REUSE_TFI] = { /* .T = 3193 set manually onenter subtracting T3192 */ }, [TBF_ST_RELEASING] = { .T = 3195 }, }; /* Transition to a state, using the T timer defined in tbf_dl_fsm_timeouts. * The actual timeout value is in turn obtained from T_defs_bts. */ #define tbf_dl_fsm_state_chg(fi, NEXT_STATE) \ osmo_tdef_fsm_inst_state_chg(fi, NEXT_STATE, \ tbf_dl_fsm_timeouts, \ tbf_ms(((struct tbf_dl_fsm_ctx *)(fi->priv))->tbf)->bts->T_defs_bts, \ -1) static void mod_ass_type(struct tbf_dl_fsm_ctx *ctx, uint8_t t, bool set) { const char *ch = "UNKNOWN"; bool prev_set = ctx->state_flags & (1 << t); switch (t) { case GPRS_RLCMAC_FLAG_CCCH: ch = "CCCH"; break; case GPRS_RLCMAC_FLAG_PACCH: ch = "PACCH"; break; default: OSMO_ASSERT(0); } LOGPTBFDL(ctx->dl_tbf, LOGL_INFO, "%sset ass. type %s [prev CCCH:%u, PACCH:%u]\n", set ? "" : "un", ch, !!(ctx->state_flags & (1 << GPRS_RLCMAC_FLAG_CCCH)), !!(ctx->state_flags & (1 << GPRS_RLCMAC_FLAG_PACCH))); if (set && prev_set) { LOGPTBFDL(ctx->dl_tbf, LOGL_ERROR, "Attempted to set ass. type %s which is already set\n", ch); return; } if (!set && !prev_set) return; if (set) ctx->state_flags |= (1 << t); else ctx->state_flags &= ~(1 << t); } static void st_new(struct osmo_fsm_inst *fi, uint32_t event, void *data) { struct tbf_dl_fsm_ctx *ctx = (struct tbf_dl_fsm_ctx *)fi->priv; switch (event) { case TBF_EV_ASSIGN_ADD_CCCH: mod_ass_type(ctx, GPRS_RLCMAC_FLAG_CCCH, true); tbf_dl_fsm_state_chg(fi, TBF_ST_ASSIGN); break; case TBF_EV_ASSIGN_ADD_PACCH: mod_ass_type(ctx, GPRS_RLCMAC_FLAG_PACCH, true); tbf_dl_fsm_state_chg(fi, TBF_ST_ASSIGN); break; default: OSMO_ASSERT(0); } } static void st_assign_on_enter(struct osmo_fsm_inst *fi, uint32_t prev_state) { struct tbf_dl_fsm_ctx *ctx = (struct tbf_dl_fsm_ctx *)fi->priv; struct GprsMs *ms = tbf_ms(ctx->tbf); unsigned long val; unsigned int sec, micro; /* If assignment for this TBF is happening on PACCH, that means the * actual Assignment procedure (tx/rx) is happening on another TBF (eg * Ul TBF vs DL TBF). Hence we add a security timer here to free it in * case the other TBF doesn't succeed in informing (assigning) the MS * about this TBF, or simply because the scheduler takes too long to * schedule it. This timer can probably be dropped once we make the * other TBF always signal us assignment failure (we already get * assignment success through TBF_EV_ASSIGN_ACK_PACCH) */ if (ctx->state_flags & (1 << GPRS_RLCMAC_FLAG_PACCH)) { fi->T = -2001; val = osmo_tdef_get(the_pcu->T_defs, fi->T, OSMO_TDEF_MS, -1); sec = val / 1000; micro = (val % 1000) * 1000; LOGPTBFDL(ctx->dl_tbf, LOGL_DEBUG, "Starting timer X2001 [assignment (PACCH)] with %u sec. %u microsec\n", sec, micro); osmo_timer_schedule(&fi->timer, sec, micro); } else { /* GPRS_RLCMAC_FLAG_CCCH is set, so here we submit a DL Ass * through PCUIF on CCCH */ OSMO_ASSERT(ctx->state_flags & (1 << GPRS_RLCMAC_FLAG_CCCH)); /* Send CCCH (PCH) Immediate Assignment over PCUIF: */ bts_snd_dl_ass(ms->bts, ctx->dl_tbf); } } static void st_assign(struct osmo_fsm_inst *fi, uint32_t event, void *data) { struct tbf_dl_fsm_ctx *ctx = (struct tbf_dl_fsm_ctx *)fi->priv; struct GprsMs *ms; unsigned long val; unsigned int sec, micro; switch (event) { case TBF_EV_ASSIGN_ADD_CCCH: /* Note: This code path is not really used nowadays, since ADD_CCCH is * only dispatched during dl_tbf allocation (st=NEW) */ ms = tbf_ms(ctx->tbf); mod_ass_type(ctx, GPRS_RLCMAC_FLAG_CCCH, true); /* Re-send CCCH (PCH) Immediate Assignment over PCUIF: */ bts_snd_dl_ass(ms->bts, ctx->dl_tbf); break; case TBF_EV_ASSIGN_ADD_PACCH: mod_ass_type(ctx, GPRS_RLCMAC_FLAG_PACCH, true); break; case TBF_EV_ASSIGN_ACK_PACCH: tbf_assign_control_ts(ctx->tbf); if (ctx->state_flags & (1 << GPRS_RLCMAC_FLAG_CCCH)) { /* We now know that the PACCH really existed */ LOGPTBFDL(ctx->dl_tbf, LOGL_INFO, "The TBF has been confirmed on the PACCH, " "changed type from CCCH to PACCH\n"); mod_ass_type(ctx, GPRS_RLCMAC_FLAG_CCCH, false); mod_ass_type(ctx, GPRS_RLCMAC_FLAG_PACCH, true); } tbf_dl_fsm_state_chg(fi, TBF_ST_FLOW); break; case TBF_EV_ASSIGN_PCUIF_CNF: /* BTS informs us it sent Imm Ass for DL TBF over CCCH. We now * have to wait for X2002 to trigger (meaning MS is already * listening on PDCH) in order to move to FLOW state and start * transmitting data to it. When X2002 triggers (see cb timer * end of the file) it will send TBF_EV_ASSIGN_READY_CCCH back * to us here. */ if (!(ctx->state_flags & (1 << GPRS_RLCMAC_FLAG_CCCH))) { /* This can happen if we initiated a CCCH DlAss from an * older TBF object (same TLLI) towards BTS, and the DL-TBF * was recreated and is now trying to be assigned through * PACCH. */ LOGPTBFDL(ctx->dl_tbf, LOGL_INFO, "Ignoring event ASSIGN_PCUIF_CNF from BTS " "(CCCH was not requested on current assignment)\n"); break; } fi->T = -2002; val = osmo_tdef_get(the_pcu->T_defs, fi->T, OSMO_TDEF_MS, -1); sec = val / 1000; micro = (val % 1000) * 1000; LOGPTBFDL(ctx->dl_tbf, LOGL_DEBUG, "Starting timer X2002 [assignment (PCH)] with %u sec. %u microsec\n", sec, micro); osmo_timer_schedule(&fi->timer, sec, micro); break; case TBF_EV_ASSIGN_READY_CCCH: /* change state to FLOW, so scheduler will start transmission */ tbf_dl_fsm_state_chg(fi, TBF_ST_FLOW); break; case TBF_EV_MAX_N3105: /* We are going to release, so abort any Pkt Ul Ass pending to be scheduled: */ osmo_fsm_inst_dispatch(tbf_ul_ass_fi(ctx->tbf), TBF_UL_ASS_EV_ABORT, NULL); tbf_dl_fsm_state_chg(fi, TBF_ST_RELEASING); break; default: OSMO_ASSERT(0); } } static void st_flow(struct osmo_fsm_inst *fi, uint32_t event, void *data) { struct tbf_dl_fsm_ctx *ctx = (struct tbf_dl_fsm_ctx *)fi->priv; switch (event) { case TBF_EV_ASSIGN_PCUIF_CNF: if (!(ctx->state_flags & (1 << GPRS_RLCMAC_FLAG_CCCH))) { /* This can happen if we initiated a CCCH DlAss from an * older TBF object (same TLLI) towards BTS, and the DL-TBF * was recreated (this one) and was successfully assigned over PACCH. * This is usually the case if MS requests 2phase access * to get an UL TBF while we were waiting for a DL TBF * assignment for that same MS over PCH. */ LOGPTBFDL(ctx->dl_tbf, LOGL_INFO, "Ignoring event ASSIGN_PCUIF_CNF from BTS " "(CCCH was not requested on current assignment)\n"); } break; case TBF_EV_DL_ACKNACK_MISS: /* DL TBF: we missed a DL ACK/NACK. If we started assignment * over CCCH and never received any DL ACK/NACK yet, it means we * don't even know if the MS successfully received the Imm Ass on * CCCH and hence is listening on PDCH. Let's better refrain * from continuing and start assignment on CCCH again */ if ((ctx->state_flags & (1 << GPRS_RLCMAC_FLAG_CCCH)) && !dl_tbf_first_dl_ack_rcvd(ctx->dl_tbf)) { LOGPTBFDL(ctx->dl_tbf, LOGL_DEBUG, "Retransmit ImmAss[PktDlAss] on PCH\n"); tbf_dl_fsm_state_chg(fi, TBF_ST_ASSIGN); } break; case TBF_EV_LAST_DL_DATA_SENT: /* All data has been sent or received, change state to FINISHED */ tbf_dl_fsm_state_chg(fi, TBF_ST_FINISHED); break; case TBF_EV_MAX_N3105: tbf_dl_fsm_state_chg(fi, TBF_ST_RELEASING); break; default: OSMO_ASSERT(0); } } static void st_finished(struct osmo_fsm_inst *fi, uint32_t event, void *data) { switch (event) { case TBF_EV_DL_ACKNACK_MISS: break; case TBF_EV_FINAL_ACK_RECVD: /* We received Final Ack (DL ACK/NACK) from MS. move to * WAIT_RELEASE, where MS stays monitoring PDCH over T3192 span, * where we can use this DL TBF to assign a new one in case we * receive more DL data to Tx */ tbf_dl_fsm_state_chg(fi, TBF_ST_WAIT_RELEASE); break; case TBF_EV_MAX_N3105: tbf_dl_fsm_state_chg(fi, TBF_ST_RELEASING); break; default: OSMO_ASSERT(0); } } static void st_wait_release_on_enter(struct osmo_fsm_inst *fi, uint32_t prev_state) { struct tbf_dl_fsm_ctx *ctx = (struct tbf_dl_fsm_ctx *)fi->priv; struct GprsMs *ms = tbf_ms(ctx->tbf); /* This state was entered because FinalACK was received; now T3192 is * running on the MS and has also been armed by this FSM. * During that time, it is possible to reach the MS over PACCH to assign * new DL TBF. * Upon T3192 expiration, FSM will transition to TBF_ST_WAIT_REUSE_TFI * for some more time (T3193 - T3192) until internally freeing the TBF * object, at which time the resources can be reused. */ mod_ass_type(ctx, GPRS_RLCMAC_FLAG_CCCH, false); /* check for LLC PDU in the LLC Queue */ if (llc_queue_size(ms_llc_queue(ms)) > 0) { /* we have more data so we will re-use this tbf */ ms_new_dl_tbf_assigned_on_pacch(ms, ctx->tbf); } } static void st_wait_release(struct osmo_fsm_inst *fi, uint32_t event, void *data) { switch (event) { case TBF_EV_FINAL_ACK_RECVD: /* ignore, duplicate ACK, we already know about since we left ST_FINISHED */ break; case TBF_EV_DL_ACKNACK_MISS: /* ignore, miss for retransmitted ACK, but a previous one was * already ACKED since we left ST_FINISHED. This happens due to * fn-advance scheduling several DL blocks in advance. */ break; case TBF_EV_MAX_N3105: /* Triggered potentially by a poll timeout of PKT UL/DL TBF ASS. * Reached N3105, the MS is not responding, so stop attempting * using the TBF for DL assignment and change to ST_RELEASING in * order to simply wait until resources can be reused (see * st_releasing_on_enter()). */ tbf_dl_fsm_state_chg(fi, TBF_ST_RELEASING); break; default: OSMO_ASSERT(0); } } static void st_wait_reuse_tfi_on_enter(struct osmo_fsm_inst *fi, uint32_t prev_state) { struct tbf_dl_fsm_ctx *ctx = (struct tbf_dl_fsm_ctx *)fi->priv; struct GprsMs *ms = tbf_ms(ctx->tbf); unsigned long t3192, t3193, res; /* T3192 has expired, so the MS is not listening on that PACCH anymore. * Still, wait until remaining of T3193 expiration (>T3192) to internally * free the TBF, at which point the TFI and other allocated resources * will be freed and can then be reused. */ t3192 = osmo_tdef_get(ms->bts->T_defs_bts, 3192, OSMO_TDEF_MS, -1); t3193 = osmo_tdef_get(ms->bts->T_defs_bts, 3193, OSMO_TDEF_MS, -1); /* As per spec T3193 shall be greater than T3192, but let's be safe against wrong configs: */ res = (t3193 >= t3192) ? (t3193 - t3192) : 0; fi->T = 3193; LOGPTBF(ctx->tbf, LOGL_DEBUG, "Waiting %lu sec. %lu microsec (T3193 - T3192) [REUSE TFI]\n", res / 1000, (res % 1000) * 1000); osmo_timer_schedule(&fi->timer, res / 1000, (res % 1000) * 1000); } static void st_wait_reuse_tfi(struct osmo_fsm_inst *fi, uint32_t event, void *data) { /* Simply wait for T3193 timeout, it will tbf_free() */ switch (event) { case TBF_EV_FINAL_ACK_RECVD: /* ignore, duplicate ACK, we already know about since we left ST_FINISHED */ break; case TBF_EV_DL_ACKNACK_MISS: /* ignore, miss for retransmitted ACK, but a previous one was * already ACKED since we left ST_FINISHED. This happens due to * fn-advance scheduling several DL blocks in advance. */ break; default: OSMO_ASSERT(0); } } static void st_releasing_on_enter(struct osmo_fsm_inst *fi, uint32_t prev_state) { /* T3195 has been set entering this state: Wait for reuse of TFI(s) when * there is no response from the MS (radio failure or cell change) for this * TBF/MBMS radio bearer. Upon timeout, the timer_cb does tbf_free(). */ } static void st_releasing(struct osmo_fsm_inst *fi, uint32_t event, void *data) { switch (event) { case TBF_EV_DL_ACKNACK_MISS: /* Ignore, we don't care about missed DL ACK/NACK poll timeouts * anymore, we are already releasing the TBF */ break; default: OSMO_ASSERT(0); } } static void handle_timeout_X2002(struct osmo_fsm_inst *fi) { struct tbf_dl_fsm_ctx *ctx = (struct tbf_dl_fsm_ctx *)fi->priv; int rc; if (fi->state != TBF_ST_ASSIGN) { LOGPTBFDL(ctx->dl_tbf, LOGL_NOTICE, "Continue flow after IMM.ASS confirm\n"); return; } /* state TBF_ST_ASSIGN: */ tbf_assign_control_ts(ctx->tbf); if (!tbf_can_upgrade_to_multislot(ctx->tbf)) { /* change state to FLOW, so scheduler will start transmission */ osmo_fsm_inst_dispatch(fi, TBF_EV_ASSIGN_READY_CCCH, NULL); return; } /* This tbf can be upgraded to use multiple DL timeslots and now that there is already * one slot assigned send another DL assignment via PDCH. */ /* Reset state flags */ ctx->state_flags = 0x00; rc = dl_tbf_upgrade_to_multislot(ctx->dl_tbf); if (rc < 0) tbf_free(ctx->tbf); } static int tbf_dl_fsm_timer_cb(struct osmo_fsm_inst *fi) { struct tbf_dl_fsm_ctx *ctx = (struct tbf_dl_fsm_ctx *)fi->priv; switch (fi->T) { case -2002: handle_timeout_X2002(fi); break; case 3192: tbf_dl_fsm_state_chg(fi, TBF_ST_WAIT_REUSE_TFI); break; case -2001: LOGPTBFDL(ctx->dl_tbf, LOGL_NOTICE, "releasing due to PACCH assignment timeout.\n"); /* fall-through */ case 3193: case 3195: tbf_free(ctx->tbf); break; default: OSMO_ASSERT(0); } return 0; } static struct osmo_fsm_state tbf_dl_fsm_states[] = { [TBF_ST_NEW] = { .in_event_mask = X(TBF_EV_ASSIGN_ADD_CCCH) | X(TBF_EV_ASSIGN_ADD_PACCH), .out_state_mask = X(TBF_ST_ASSIGN), .name = "NEW", .action = st_new, }, [TBF_ST_ASSIGN] = { .in_event_mask = X(TBF_EV_ASSIGN_ADD_CCCH) | X(TBF_EV_ASSIGN_ADD_PACCH) | X(TBF_EV_ASSIGN_ACK_PACCH) | X(TBF_EV_ASSIGN_PCUIF_CNF) | X(TBF_EV_ASSIGN_READY_CCCH) | X(TBF_EV_MAX_N3105), .out_state_mask = X(TBF_ST_FLOW) | X(TBF_ST_FINISHED) | X(TBF_ST_RELEASING), .name = "ASSIGN", .action = st_assign, .onenter = st_assign_on_enter, }, [TBF_ST_FLOW] = { .in_event_mask = X(TBF_EV_ASSIGN_PCUIF_CNF) | X(TBF_EV_DL_ACKNACK_MISS) | X(TBF_EV_LAST_DL_DATA_SENT) | X(TBF_EV_MAX_N3105), .out_state_mask = X(TBF_ST_ASSIGN) | X(TBF_ST_FINISHED) | X(TBF_ST_RELEASING), .name = "FLOW", .action = st_flow, }, [TBF_ST_FINISHED] = { .in_event_mask = X(TBF_EV_DL_ACKNACK_MISS) | X(TBF_EV_FINAL_ACK_RECVD) | X(TBF_EV_MAX_N3105), .out_state_mask = X(TBF_ST_WAIT_RELEASE) | X(TBF_ST_RELEASING), .name = "FINISHED", .action = st_finished, }, [TBF_ST_WAIT_RELEASE] = { .in_event_mask = X(TBF_EV_DL_ACKNACK_MISS) | X(TBF_EV_FINAL_ACK_RECVD) | X(TBF_EV_MAX_N3105), .out_state_mask = X(TBF_ST_WAIT_REUSE_TFI) | X(TBF_ST_RELEASING), .name = "WAIT_RELEASE", .action = st_wait_release, .onenter = st_wait_release_on_enter, }, [TBF_ST_WAIT_REUSE_TFI] = { .in_event_mask = X(TBF_EV_DL_ACKNACK_MISS) | X(TBF_EV_FINAL_ACK_RECVD), .out_state_mask = X(TBF_ST_RELEASING), .name = "WAIT_REUSE_TFI", .action = st_wait_reuse_tfi, .onenter = st_wait_reuse_tfi_on_enter, }, [TBF_ST_RELEASING] = { .in_event_mask = X(TBF_EV_DL_ACKNACK_MISS), .out_state_mask = 0, .name = "RELEASING", .action = st_releasing, .onenter = st_releasing_on_enter, }, }; struct osmo_fsm tbf_dl_fsm = { .name = "DL_TBF", .states = tbf_dl_fsm_states, .num_states = ARRAY_SIZE(tbf_dl_fsm_states), .timer_cb = tbf_dl_fsm_timer_cb, .log_subsys = DTBFDL, .event_names = tbf_fsm_event_names, }; static __attribute__((constructor)) void tbf_dl_fsm_init(void) { OSMO_ASSERT(osmo_fsm_register(&tbf_dl_fsm) == 0); }