| /* 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 <osmocom/bsc/debug.h> |
| #include <osmocom/bsc/gsm_data.h> |
| #include <osmocom/gsm/gsm_utils.h> |
| #include <osmocom/bsc/abis_rsl.h> |
| #include <osmocom/bsc/chan_alloc.h> |
| #include <osmocom/bsc/signal.h> |
| #include <osmocom/core/talloc.h> |
| #include <osmocom/bsc/bsc_subscriber.h> |
| #include <osmocom/bsc/gsm_04_08_utils.h> |
| #include <osmocom/bsc/handover.h> |
| |
| #define LOGPHOLCHANTOLCHAN(lchan, new_lchan, level, fmt, args...) \ |
| LOGP(DHODEC, level, "(BTS %u trx %u arfcn %u ts %u lchan %u %s)->(BTS %u trx %u arfcn %u ts %u lchan %u %s) (subscr %s) " fmt, \ |
| lchan->ts->trx->bts->nr, \ |
| lchan->ts->trx->nr, \ |
| lchan->ts->trx->arfcn, \ |
| lchan->ts->nr, \ |
| lchan->nr, \ |
| gsm_pchan_name(lchan->ts->pchan), \ |
| new_lchan->ts->trx->bts->nr, \ |
| new_lchan->ts->trx->nr, \ |
| new_lchan->ts->trx->arfcn, \ |
| new_lchan->ts->nr, \ |
| new_lchan->nr, \ |
| gsm_pchan_name(new_lchan->ts->pchan), \ |
| bsc_subscr_name(lchan->conn->bsub), \ |
| ## args) |
| |
| #define LOGPHO(struct_bsc_handover, level, fmt, args ...) \ |
| LOGPHOLCHANTOLCHAN(struct_bsc_handover->old_lchan, struct_bsc_handover->new_lchan, level, fmt, ## args) |
| |
| 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; |
| |
| bool inter_cell; |
| bool async; |
| }; |
| |
| 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; |
| } |
| |
| /*! Hand over the specified logical channel to the specified new BTS and possibly change the lchan type. |
| * This is the main entry point for the actual handover algorithm, after the decision whether to initiate |
| * HO to a specific BTS. To not change the lchan type, pass old_lchan->type. */ |
| int bsc_handover_start(struct gsm_lchan *old_lchan, struct gsm_bts *new_bts, |
| enum gsm_chan_t new_lchan_type) |
| { |
| struct gsm_network *network; |
| struct gsm_lchan *new_lchan; |
| struct bsc_handover *ho; |
| static uint8_t ho_ref = 0; |
| int rc; |
| bool do_assignment = false; |
| |
| /* don't attempt multiple handovers for the same lchan at |
| * the same time */ |
| if (bsc_ho_by_old_lchan(old_lchan)) |
| return -EBUSY; |
| |
| if (!new_bts) |
| new_bts = old_lchan->ts->trx->bts; |
| do_assignment = (new_bts == old_lchan->ts->trx->bts); |
| |
| network = new_bts->network; |
| |
| rate_ctr_inc(&network->bsc_ctrs->ctr[BSC_CTR_HANDOVER_ATTEMPTED]); |
| |
| if (!old_lchan->conn) { |
| LOGP(DHO, LOGL_ERROR, "Old lchan lacks connection data.\n"); |
| return -ENOSPC; |
| } |
| |
| DEBUGP(DHO, "(BTS %u trx %u ts %u lchan %u %s)->(BTS %u lchan %s) Beginning with handover operation...\n", |
| old_lchan->ts->trx->bts->nr, |
| old_lchan->ts->trx->nr, |
| old_lchan->ts->nr, |
| old_lchan->nr, |
| gsm_pchan_name(old_lchan->ts->pchan), |
| new_bts->nr, |
| gsm_lchant_name(new_lchan_type)); |
| |
| new_lchan = lchan_alloc(new_bts, new_lchan_type, 0); |
| if (!new_lchan) { |
| LOGP(DHO, LOGL_NOTICE, "No free channel for %s\n", gsm_lchant_name(new_lchan_type)); |
| rate_ctr_inc(&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++; |
| ho->inter_cell = !do_assignment; |
| ho->async = true; |
| |
| LOGPHO(ho, LOGL_INFO, "Triggering %s\n", do_assignment? "Assignment" : "Handover"); |
| |
| /* copy some parameters from old lchan */ |
| memcpy(&new_lchan->encr, &old_lchan->encr, sizeof(new_lchan->encr)); |
| if (do_assignment) { |
| new_lchan->ms_power = old_lchan->ms_power; |
| new_lchan->rqd_ta = old_lchan->rqd_ta; |
| } else { |
| new_lchan->ms_power = |
| ms_pwr_ctl_lvl(new_bts->band, new_bts->ms_max_power); |
| /* FIXME: do we have a better idea of the timing advance? */ |
| //new_lchan->rqd_ta = old_lchan->rqd_ta; |
| } |
| 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, sizeof(new_lchan->mr_ms_lv)); |
| memcpy(&new_lchan->mr_bts_lv, &old_lchan->mr_bts_lv, sizeof(new_lchan->mr_bts_lv)); |
| |
| new_lchan->conn = old_lchan->conn; |
| new_lchan->conn->ho_lchan = new_lchan; |
| |
| rc = rsl_chan_activate_lchan(new_lchan, |
| ho->async ? RSL_ACT_INTER_ASYNC : RSL_ACT_INTER_SYNC, |
| ho->ho_ref); |
| if (rc < 0) { |
| LOGPHO(ho, LOGL_INFO, "%s Failure: activate lchan rc = %d\n", |
| do_assignment? "Assignment" : "Handover", rc); |
| 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; |
| } |
| |
| /* clear any operation for this connection */ |
| 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; |
| |
| LOGPHO(ho, LOGL_INFO, "Channel Activate Ack, send %s COMMAND\n", ho->inter_cell? "HANDOVER" : "ASSIGNMENT"); |
| |
| /* 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, new_lchan->ms_power, 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; |
| |
| LOGPHO(ho, LOGL_INFO, "%s Complete\n", ho->inter_cell ? "Handover" : "Assignment"); |
| |
| rate_ctr_inc(&net->bsc_ctrs->ctr[BSC_CTR_HANDOVER_COMPLETED]); |
| |
| osmo_timer_del(&ho->T3103); |
| |
| /* Replace the ho lchan with the primary one */ |
| if (ho->old_lchan != new_lchan->conn->lchan) |
| LOGPHO(ho, LOGL_ERROR, "Primary lchan changed during handover.\n"); |
| |
| if (new_lchan != new_lchan->conn->ho_lchan) |
| LOGPHO(ho, 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; |
| } |
| |
| LOGPHO(ho, LOGL_DEBUG, "Handover RACH detected\n"); |
| |
| /* This is just for logging on the DHO category. The actual MGCP switchover happens in |
| * osmo_bsc_mgcp.c by receiving the same S_LCHAN_HANDOVER_DETECT signal. |
| * (Calling mgcp_handover() directly currently breaks linking in utils/...) */ |
| |
| 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; |
| } |
| |
| /* Return the old lchan or NULL. This is meant for audio handling */ |
| 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); |
| } |
| |
| /* Count number of currently ongoing handovers |
| * inter_cell: if true, count only handovers between two cells. If false, count only handovers within one |
| * cell. */ |
| int bsc_ho_count(struct gsm_bts *bts, bool inter_cell) |
| { |
| struct bsc_handover *ho; |
| int count = 0; |
| |
| llist_for_each_entry(ho, &bsc_handovers, list) { |
| if (ho->inter_cell != inter_cell) |
| continue; |
| if (ho->new_lchan->ts->trx->bts == bts) |
| count++; |
| } |
| |
| return count; |
| } |