[handover] Implement handover control logic
Code to implement handover control logic. A yet-to-be-implemented handover algorithm will call bsc_handover_start(old_lchan, new_bts) to start the handover process.
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@ -757,6 +757,8 @@ int gsm48_send_rr_ciph_mode(struct gsm_lchan *lchan, int want_imeisv);
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int gsm48_send_rr_app_info(struct gsm_lchan *lchan, u_int8_t apdu_id,
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u_int8_t apdu_len, const u_int8_t *apdu);
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int gsm48_send_rr_ass_cmd(struct gsm_lchan *lchan, u_int8_t power_class);
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int gsm48_send_ho_cmd(struct gsm_lchan *old_lchan,
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struct gsm_lchan *new_lchan, u_int8_t power_command);
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int bsc_upqueue(struct gsm_network *net);
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@ -7,7 +7,7 @@ noinst_LIBRARIES = libbsc.a libmsc.a libvty.a libsccp.a
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noinst_HEADERS = vty/cardshell.h
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libbsc_a_SOURCES = abis_rsl.c abis_nm.c gsm_data.c gsm_04_08_utils.c \
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msgb.c select.c chan_alloc.c timer.c debug.c \
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msgb.c select.c chan_alloc.c timer.c debug.c handover_logic.c \
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gsm_subscriber_base.c subchan_demux.c bsc_rll.c transaction.c \
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trau_frame.c trau_mux.c paging.c e1_config.c e1_input.c tlv_parser.c \
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input/misdn.c input/ipaccess.c signal.c gsm_utils.c talloc.c \
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@ -0,0 +1,251 @@
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/* Handover Logic for Inter-BTS (Intra-BSC) Handover. This does not
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* actually implement the handover algorithm/decision, but executes a
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* handover decision */
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/* (C) 2009 by Harald Welte <laforge@gnumonks.org>
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*
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* All Rights Reserved
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*
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* This program is free software; you can redistribute it and/or modify
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* it under the terms of the GNU General Public License as published by
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* the Free Software Foundation; either version 2 of the License, or
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* (at your option) any later version.
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*
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* This program is distributed in the hope that it will be useful,
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* but WITHOUT ANY WARRANTY; without even the implied warranty of
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* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
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* GNU General Public License for more details.
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*
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* You should have received a copy of the GNU General Public License along
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* with this program; if not, write to the Free Software Foundation, Inc.,
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* 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA.
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*
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*/
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#include <stdio.h>
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#include <stdlib.h>
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#include <string.h>
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#include <errno.h>
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#include <time.h>
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#include <netinet/in.h>
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#include <openbsc/msgb.h>
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#include <openbsc/debug.h>
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#include <openbsc/gsm_data.h>
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#include <openbsc/gsm_utils.h>
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#include <openbsc/gsm_subscriber.h>
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#include <openbsc/gsm_04_08.h>
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#include <openbsc/abis_rsl.h>
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#include <openbsc/chan_alloc.h>
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#include <openbsc/signal.h>
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#include <openbsc/talloc.h>
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#include <openbsc/transaction.h>
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struct bsc_handover {
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struct llist_head list;
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struct gsm_lchan *old_lchan;
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struct gsm_lchan *new_lchan;
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struct timer_list T3103;
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u_int8_t ho_ref;
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};
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static LLIST_HEAD(bsc_handovers);
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static struct bsc_handover *bsc_ho_by_new_lchan(struct gsm_lchan *new_lchan)
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{
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struct bsc_handover *ho;
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llist_for_each_entry(ho, &bsc_handovers, list) {
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if (ho->new_lchan == new_lchan)
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return ho;
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}
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return NULL;
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}
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static struct bsc_handover *bsc_ho_by_old_lchan(struct gsm_lchan *old_lchan)
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{
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struct bsc_handover *ho;
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llist_for_each_entry(ho, &bsc_handovers, list) {
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if (ho->old_lchan == old_lchan)
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return ho;
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}
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return NULL;
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}
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/* Hand over the specified logical channel to the specified new BTS.
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* This is the main entry point for the actual handover algorithm,
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* after it has decided it wants to initiate HO to a specific BTS */
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int bsc_handover_start(struct gsm_lchan *old_lchan, struct gsm_bts *bts)
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{
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struct gsm_lchan *new_lchan;
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struct bsc_handover *ho;
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int rc;
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new_lchan = lchan_alloc(bts, old_lchan->type);
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if (!new_lchan)
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return -ENOSPC;
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ho = talloc_zero(NULL, struct bsc_handover);
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if (!ho) {
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lchan_free(new_lchan);
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return -ENOMEM;
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}
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ho->old_lchan = old_lchan;
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ho->new_lchan = new_lchan;
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/* FIXME: do we have a better idea of the timing advance? */
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rc = rsl_chan_activate_lchan(new_lchan, RSL_ACT_INTER_ASYNC, 0);
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if (rc < 0) {
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talloc_free(ho);
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lchan_free(new_lchan);
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return rc;
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}
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llist_add(&ho->list, &bsc_handovers);
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/* we continue in the SS_LCHAN handler / ho_chan_activ_ack */
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return 0;
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}
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/* T3103 expired: Handover has failed without HO COMPLETE or HO FAIL */
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static void ho_T3103_cb(void *_ho)
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{
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struct bsc_handover *ho = _ho;
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lchan_free(ho->new_lchan);
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llist_del(&ho->list);
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talloc_free(ho);
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}
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/* RSL has acknowledged activation of the new lchan */
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static int ho_chan_activ_ack(struct gsm_lchan *new_lchan)
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{
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struct bsc_handover *ho;
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int rc;
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ho = bsc_ho_by_new_lchan(new_lchan);
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if (!ho)
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return -ENODEV;
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/* we can now send the 04.08 HANDOVER COMMAND to the MS
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* using the old lchan */
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rc = gsm48_send_ho_cmd(ho->old_lchan, new_lchan, 0);
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/* start T3103. We can continue either with T3103 expiration,
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* 04.08 HANDOVER COMPLETE or 04.08 HANDOVER FAIL */
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ho->T3103.cb = ho_T3103_cb;
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bsc_schedule_timer(&ho->T3103, 10, 0);
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return 0;
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}
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/* RSL has not acknowledged activation of the new lchan */
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static int ho_chan_activ_nack(struct gsm_lchan *new_lchan)
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{
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struct bsc_handover *ho;
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ho = bsc_ho_by_new_lchan(new_lchan);
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if (!ho)
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return -ENODEV;
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llist_del(&ho->list);
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talloc_free(ho);
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/* FIXME: maybe we should try to allocate a new LCHAN here? */
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return 0;
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}
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/* GSM 04.08 HANDOVER COMPLETE has been received on new channel */
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static int ho_gsm48_ho_compl(struct gsm_lchan *new_lchan)
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{
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struct bsc_handover *ho;
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ho = bsc_ho_by_new_lchan(new_lchan);
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if (!ho)
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return -ENODEV;
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bsc_del_timer(&ho->T3103);
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llist_del(&ho->list);
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/* do something to re-route the actual speech frames ! */
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//tch_remap(ho->old_lchan, ho->new_lchan);
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/* release old lchan */
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put_lchan(ho->old_lchan);
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talloc_free(ho);
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return 0;
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}
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/* GSM 04.08 HANDOVER FAIL has been received */
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static int ho_gsm48_ho_fail(struct gsm_lchan *old_lchan)
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{
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struct bsc_handover *ho;
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ho = bsc_ho_by_old_lchan(old_lchan);
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if (!ho)
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return -ENODEV;
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bsc_del_timer(&ho->T3103);
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llist_del(&ho->list);
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put_lchan(ho->new_lchan);
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talloc_free(ho);
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return 0;
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}
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/* GSM 08.58 HANDOVER DETECT has been received */
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static int ho_rsl_detect(struct gsm_lchan *new_lchan)
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{
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struct bsc_handover *ho;
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ho = bsc_ho_by_old_lchan(new_lchan);
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if (!ho)
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return -ENODEV;
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/* FIXME: do we actually want to do something here ? */
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return 0;
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}
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static int ho_logic_sig_cb(unsigned int subsys, unsigned int signal,
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void *handler_data, void *signal_data)
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{
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struct gsm_lchan *lchan;
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switch (subsys) {
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case SS_LCHAN:
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lchan = signal_data;
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switch (signal) {
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case S_LCHAN_ACTIVATE_ACK:
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return ho_chan_activ_ack(lchan);
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case S_LCHAN_ACTIVATE_NACK:
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return ho_chan_activ_nack(lchan);
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case S_LCHAN_HANDOVER_DETECT:
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return ho_rsl_detect(lchan);
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case S_LCHAN_HANDOVER_COMPL:
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return ho_gsm48_ho_compl(lchan);
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case S_LCHAN_HANDOVER_FAIL:
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return ho_gsm48_ho_fail(lchan);
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}
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break;
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default:
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break;
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}
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return 0;
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}
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static __attribute__((constructor)) void on_dso_load_ho_logic(void)
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{
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register_signal_handler(SS_LCHAN, ho_logic_sig_cb, NULL);
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}
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