diff options
Diffstat (limited to 'src/libbsc/handover_logic.c')
-rw-r--r-- | src/libbsc/handover_logic.c | 378 |
1 files changed, 378 insertions, 0 deletions
diff --git a/src/libbsc/handover_logic.c b/src/libbsc/handover_logic.c new file mode 100644 index 000000000..4dd913b15 --- /dev/null +++ b/src/libbsc/handover_logic.c @@ -0,0 +1,378 @@ +/* Handover Logic for Inter-BTS (Intra-BSC) Handover. This does not + * actually implement the handover algorithm/decision, but executes a + * handover decision */ + +/* (C) 2009 by Harald Welte <laforge@gnumonks.org> + * + * All Rights Reserved + * + * This program is free software; you can redistribute it and/or modify + * it under the terms of the GNU Affero General Public License as published by + * the Free Software Foundation; either version 3 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 Affero General Public License for more details. + * + * You should have received a copy of the GNU Affero General Public License + * along with this program. If not, see <http://www.gnu.org/licenses/>. + * + */ + +#include <stdio.h> +#include <stdlib.h> +#include <string.h> +#include <errno.h> +#include <time.h> +#include <netinet/in.h> + +#include <osmocom/core/msgb.h> +#include <openbsc/debug.h> +#include <openbsc/gsm_data.h> +#include <osmocom/gsm/gsm_utils.h> +#include <openbsc/gsm_subscriber.h> +#include <openbsc/gsm_04_08.h> +#include <openbsc/abis_rsl.h> +#include <openbsc/chan_alloc.h> +#include <openbsc/signal.h> +#include <osmocom/core/talloc.h> +#include <openbsc/transaction.h> +#include <openbsc/trau_mux.h> + +struct bsc_handover { + struct llist_head list; + + struct gsm_lchan *old_lchan; + struct gsm_lchan *new_lchan; + + struct osmo_timer_list T3103; + + uint8_t ho_ref; +}; + +static LLIST_HEAD(bsc_handovers); + +static void handover_free(struct bsc_handover *ho) +{ + osmo_timer_del(&ho->T3103); + llist_del(&ho->list); + talloc_free(ho); +} + +static struct bsc_handover *bsc_ho_by_new_lchan(struct gsm_lchan *new_lchan) +{ + struct bsc_handover *ho; + + llist_for_each_entry(ho, &bsc_handovers, list) { + if (ho->new_lchan == new_lchan) + return ho; + } + + return NULL; +} + +static struct bsc_handover *bsc_ho_by_old_lchan(struct gsm_lchan *old_lchan) +{ + struct bsc_handover *ho; + + llist_for_each_entry(ho, &bsc_handovers, list) { + if (ho->old_lchan == old_lchan) + return ho; + } + + return NULL; +} + +/*! \brief Hand over the specified logical channel to the specified new BTS. + * This is the main entry point for the actual handover algorithm, after the + * decision whether to initiate HO to a specific BTS. */ +int bsc_handover_start(struct gsm_lchan *old_lchan, struct gsm_bts *bts) +{ + struct gsm_lchan *new_lchan; + struct bsc_handover *ho; + static uint8_t ho_ref; + int rc; + + /* don't attempt multiple handovers for the same lchan at + * the same time */ + if (bsc_ho_by_old_lchan(old_lchan)) + return -EBUSY; + + DEBUGP(DHO, "(old_lchan on BTS %u, new BTS %u)\n", + old_lchan->ts->trx->bts->nr, bts->nr); + + rate_ctr_inc(&bts->network->bsc_ctrs->ctr[BSC_CTR_HANDOVER_ATTEMPTED]); + + if (!old_lchan->conn) { + LOGP(DHO, LOGL_ERROR, "Old lchan lacks connection data.\n"); + return -ENOSPC; + } + + new_lchan = lchan_alloc(bts, old_lchan->type, 0); + if (!new_lchan) { + LOGP(DHO, LOGL_NOTICE, "No free channel\n"); + rate_ctr_inc(&bts->network->bsc_ctrs->ctr[BSC_CTR_HANDOVER_NO_CHANNEL]); + return -ENOSPC; + } + + ho = talloc_zero(tall_bsc_ctx, struct bsc_handover); + if (!ho) { + LOGP(DHO, LOGL_FATAL, "Out of Memory\n"); + lchan_free(new_lchan); + return -ENOMEM; + } + ho->old_lchan = old_lchan; + ho->new_lchan = new_lchan; + ho->ho_ref = ho_ref++; + + /* copy some parameters from old lchan */ + memcpy(&new_lchan->encr, &old_lchan->encr, sizeof(new_lchan->encr)); + new_lchan->ms_power = old_lchan->ms_power; + new_lchan->bs_power = old_lchan->bs_power; + new_lchan->rsl_cmode = old_lchan->rsl_cmode; + new_lchan->tch_mode = old_lchan->tch_mode; + memcpy(&new_lchan->mr_ms_lv, &old_lchan->mr_ms_lv, ARRAY_SIZE(new_lchan->mr_ms_lv)); + memcpy(&new_lchan->mr_bts_lv, &old_lchan->mr_bts_lv, ARRAY_SIZE(new_lchan->mr_bts_lv)); + + new_lchan->conn = old_lchan->conn; + new_lchan->conn->ho_lchan = new_lchan; + + /* FIXME: do we have a better idea of the timing advance? */ + rc = rsl_chan_activate_lchan(new_lchan, RSL_ACT_INTER_ASYNC, ho->ho_ref); + if (rc < 0) { + LOGP(DHO, LOGL_ERROR, "could not activate channel\n"); + new_lchan->conn->ho_lchan = NULL; + new_lchan->conn = NULL; + talloc_free(ho); + lchan_free(new_lchan); + return rc; + } + + rsl_lchan_set_state(new_lchan, LCHAN_S_ACT_REQ); + llist_add(&ho->list, &bsc_handovers); + /* we continue in the SS_LCHAN handler / ho_chan_activ_ack */ + + return 0; +} + +void bsc_clear_handover(struct gsm_subscriber_connection *conn, int free_lchan) +{ + struct bsc_handover *ho; + + ho = bsc_ho_by_new_lchan(conn->ho_lchan); + + + if (!ho && conn->ho_lchan) + LOGP(DHO, LOGL_ERROR, "BUG: We lost some state.\n"); + + if (!ho) { + LOGP(DHO, LOGL_ERROR, "unable to find HO record\n"); + return; + } + + conn->ho_lchan->conn = NULL; + conn->ho_lchan = NULL; + + if (free_lchan) + lchan_release(ho->new_lchan, 0, RSL_REL_LOCAL_END); + + handover_free(ho); +} + +/* T3103 expired: Handover has failed without HO COMPLETE or HO FAIL */ +static void ho_T3103_cb(void *_ho) +{ + struct bsc_handover *ho = _ho; + struct gsm_network *net = ho->new_lchan->ts->trx->bts->network; + + DEBUGP(DHO, "HO T3103 expired\n"); + rate_ctr_inc(&net->bsc_ctrs->ctr[BSC_CTR_HANDOVER_TIMEOUT]); + + ho->new_lchan->conn->ho_lchan = NULL; + ho->new_lchan->conn = NULL; + lchan_release(ho->new_lchan, 0, RSL_REL_LOCAL_END); + handover_free(ho); +} + +/* RSL has acknowledged activation of the new lchan */ +static int ho_chan_activ_ack(struct gsm_lchan *new_lchan) +{ + struct bsc_handover *ho; + + /* we need to check if this channel activation is related to + * a handover at all (and if, which particular handover) */ + ho = bsc_ho_by_new_lchan(new_lchan); + if (!ho) + return -ENODEV; + + DEBUGP(DHO, "handover activate ack, send HO Command\n"); + + /* we can now send the 04.08 HANDOVER COMMAND to the MS + * using the old lchan */ + + gsm48_send_ho_cmd(ho->old_lchan, new_lchan, 0, ho->ho_ref); + + /* start T3103. We can continue either with T3103 expiration, + * 04.08 HANDOVER COMPLETE or 04.08 HANDOVER FAIL */ + osmo_timer_setup(&ho->T3103, ho_T3103_cb, ho); + osmo_timer_schedule(&ho->T3103, 10, 0); + + /* create a RTP connection */ + if (is_ipaccess_bts(new_lchan->ts->trx->bts)) + rsl_ipacc_crcx(new_lchan); + + return 0; +} + +/* RSL has not acknowledged activation of the new lchan */ +static int ho_chan_activ_nack(struct gsm_lchan *new_lchan) +{ + struct bsc_handover *ho; + + ho = bsc_ho_by_new_lchan(new_lchan); + if (!ho) { + LOGP(DHO, LOGL_INFO, "ACT NACK: unable to find HO record\n"); + return -ENODEV; + } + + new_lchan->conn->ho_lchan = NULL; + new_lchan->conn = NULL; + handover_free(ho); + + /* FIXME: maybe we should try to allocate a new LCHAN here? */ + + return 0; +} + +/* GSM 04.08 HANDOVER COMPLETE has been received on new channel */ +static int ho_gsm48_ho_compl(struct gsm_lchan *new_lchan) +{ + struct gsm_network *net; + struct bsc_handover *ho; + + ho = bsc_ho_by_new_lchan(new_lchan); + if (!ho) { + LOGP(DHO, LOGL_ERROR, "unable to find HO record\n"); + return -ENODEV; + } + + net = new_lchan->ts->trx->bts->network; + LOGP(DHO, LOGL_INFO, "Subscriber %s HO from BTS %u->%u on ARFCN " + "%u->%u\n", subscr_name(ho->old_lchan->conn->subscr), + ho->old_lchan->ts->trx->bts->nr, new_lchan->ts->trx->bts->nr, + ho->old_lchan->ts->trx->arfcn, new_lchan->ts->trx->arfcn); + + rate_ctr_inc(&net->bsc_ctrs->ctr[BSC_CTR_HANDOVER_COMPLETED]); + + osmo_timer_del(&ho->T3103); + + /* switch TRAU muxer for E1 based BTS from one channel to another */ + if (is_e1_bts(new_lchan->conn->bts)) + switch_trau_mux(ho->old_lchan, new_lchan); + + /* Replace the ho lchan with the primary one */ + if (ho->old_lchan != new_lchan->conn->lchan) + LOGP(DHO, LOGL_ERROR, "Primary lchan changed during handover.\n"); + + if (new_lchan != new_lchan->conn->ho_lchan) + LOGP(DHO, LOGL_ERROR, "Handover channel changed during this handover.\n"); + + new_lchan->conn->ho_lchan = NULL; + new_lchan->conn->lchan = new_lchan; + ho->old_lchan->conn = NULL; + + lchan_release(ho->old_lchan, 0, RSL_REL_LOCAL_END); + + handover_free(ho); + return 0; +} + +/* GSM 04.08 HANDOVER FAIL has been received */ +static int ho_gsm48_ho_fail(struct gsm_lchan *old_lchan) +{ + struct gsm_network *net = old_lchan->ts->trx->bts->network; + struct bsc_handover *ho; + struct gsm_lchan *new_lchan; + + ho = bsc_ho_by_old_lchan(old_lchan); + if (!ho) { + LOGP(DHO, LOGL_ERROR, "unable to find HO record\n"); + return -ENODEV; + } + + rate_ctr_inc(&net->bsc_ctrs->ctr[BSC_CTR_HANDOVER_FAILED]); + + new_lchan = ho->new_lchan; + + /* release the channel and forget about it */ + ho->new_lchan->conn->ho_lchan = NULL; + ho->new_lchan->conn = NULL; + handover_free(ho); + + lchan_release(new_lchan, 0, RSL_REL_LOCAL_END); + + + return 0; +} + +/* GSM 08.58 HANDOVER DETECT has been received */ +static int ho_rsl_detect(struct gsm_lchan *new_lchan) +{ + struct bsc_handover *ho; + + ho = bsc_ho_by_new_lchan(new_lchan); + if (!ho) { + LOGP(DHO, LOGL_ERROR, "unable to find HO record\n"); + return -ENODEV; + } + + /* FIXME: do we actually want to do something here ? */ + + return 0; +} + +static int ho_logic_sig_cb(unsigned int subsys, unsigned int signal, + void *handler_data, void *signal_data) +{ + struct lchan_signal_data *lchan_data; + struct gsm_lchan *lchan; + + lchan_data = signal_data; + switch (subsys) { + case SS_LCHAN: + lchan = lchan_data->lchan; + switch (signal) { + case S_LCHAN_ACTIVATE_ACK: + return ho_chan_activ_ack(lchan); + case S_LCHAN_ACTIVATE_NACK: + return ho_chan_activ_nack(lchan); + case S_LCHAN_HANDOVER_DETECT: + return ho_rsl_detect(lchan); + case S_LCHAN_HANDOVER_COMPL: + return ho_gsm48_ho_compl(lchan); + case S_LCHAN_HANDOVER_FAIL: + return ho_gsm48_ho_fail(lchan); + } + break; + default: + break; + } + + return 0; +} + +struct gsm_lchan *bsc_handover_pending(struct gsm_lchan *new_lchan) +{ + struct bsc_handover *ho; + ho = bsc_ho_by_new_lchan(new_lchan); + if (!ho) + return NULL; + return ho->old_lchan; +} + +static __attribute__((constructor)) void on_dso_load_ho_logic(void) +{ + osmo_signal_register_handler(SS_LCHAN, ho_logic_sig_cb, NULL); +} |