| /* 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 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, write to the Free Software Foundation, Inc., |
| * 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA. |
| * |
| */ |
| |
| #include <stdio.h> |
| #include <stdlib.h> |
| #include <string.h> |
| #include <errno.h> |
| #include <time.h> |
| #include <netinet/in.h> |
| |
| #include <openbsc/msgb.h> |
| #include <openbsc/debug.h> |
| #include <openbsc/gsm_data.h> |
| #include <openbsc/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 <openbsc/talloc.h> |
| #include <openbsc/transaction.h> |
| |
| struct bsc_handover { |
| struct llist_head list; |
| |
| struct gsm_lchan *old_lchan; |
| struct gsm_lchan *new_lchan; |
| |
| struct timer_list T3103; |
| |
| u_int8_t ho_ref; |
| }; |
| |
| static LLIST_HEAD(bsc_handovers); |
| |
| 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. |
| * This is the main entry point for the actual handover algorithm, |
| * after it has decided it wants 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; |
| int rc; |
| |
| new_lchan = lchan_alloc(bts, old_lchan->type); |
| if (!new_lchan) |
| return -ENOSPC; |
| |
| ho = talloc_zero(NULL, struct bsc_handover); |
| if (!ho) { |
| lchan_free(new_lchan); |
| return -ENOMEM; |
| } |
| ho->old_lchan = old_lchan; |
| ho->new_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, 0); |
| if (rc < 0) { |
| talloc_free(ho); |
| lchan_free(new_lchan); |
| return rc; |
| } |
| |
| llist_add(&ho->list, &bsc_handovers); |
| /* we continue in the SS_LCHAN handler / ho_chan_activ_ack */ |
| |
| return 0; |
| } |
| |
| /* T3103 expired: Handover has failed without HO COMPLETE or HO FAIL */ |
| static void ho_T3103_cb(void *_ho) |
| { |
| struct bsc_handover *ho = _ho; |
| |
| lchan_free(ho->new_lchan); |
| llist_del(&ho->list); |
| talloc_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; |
| int rc; |
| |
| ho = bsc_ho_by_new_lchan(new_lchan); |
| if (!ho) |
| return -ENODEV; |
| |
| /* we can now send the 04.08 HANDOVER COMMAND to the MS |
| * using the old lchan */ |
| |
| rc = gsm48_send_ho_cmd(ho->old_lchan, new_lchan, 0); |
| |
| /* start T3103. We can continue either with T3103 expiration, |
| * 04.08 HANDOVER COMPLETE or 04.08 HANDOVER FAIL */ |
| ho->T3103.cb = ho_T3103_cb; |
| bsc_schedule_timer(&ho->T3103, 10, 0); |
| |
| 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) |
| return -ENODEV; |
| |
| llist_del(&ho->list); |
| talloc_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 bsc_handover *ho; |
| |
| ho = bsc_ho_by_new_lchan(new_lchan); |
| if (!ho) |
| return -ENODEV; |
| |
| bsc_del_timer(&ho->T3103); |
| llist_del(&ho->list); |
| |
| /* do something to re-route the actual speech frames ! */ |
| //tch_remap(ho->old_lchan, ho->new_lchan); |
| |
| /* release old lchan */ |
| put_lchan(ho->old_lchan); |
| |
| talloc_free(ho); |
| |
| return 0; |
| } |
| |
| /* GSM 04.08 HANDOVER FAIL has been received */ |
| static int ho_gsm48_ho_fail(struct gsm_lchan *old_lchan) |
| { |
| struct bsc_handover *ho; |
| |
| ho = bsc_ho_by_old_lchan(old_lchan); |
| if (!ho) |
| return -ENODEV; |
| |
| bsc_del_timer(&ho->T3103); |
| llist_del(&ho->list); |
| put_lchan(ho->new_lchan); |
| talloc_free(ho); |
| |
| 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_old_lchan(new_lchan); |
| if (!ho) |
| 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 gsm_lchan *lchan; |
| |
| switch (subsys) { |
| case SS_LCHAN: |
| lchan = signal_data; |
| 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; |
| } |
| |
| static __attribute__((constructor)) void on_dso_load_ho_logic(void) |
| { |
| register_signal_handler(SS_LCHAN, ho_logic_sig_cb, NULL); |
| } |