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/* 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;
static u_int8_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): ",
old_lchan->ts->trx->bts->nr, bts->nr);
new_lchan = lchan_alloc(bts, old_lchan->type);
if (!new_lchan) {
DEBUGPC(DHO, "No free channel\n");
return -ENOSPC;
}
ho = talloc_zero(NULL, struct bsc_handover);
if (!ho) {
DEBUGPC(DHO, "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;
/* FIXME: do we have a better idea of the timing advance? */
rc = rsl_chan_activate_lchan(new_lchan, RSL_ACT_INTER_ASYNC, 0,
ho->ho_ref);
if (rc < 0) {
DEBUGPC(DHO, "could not activate channel\n");
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;
DEBUGP(DHO, "HO T3103 expired\n");
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;
DEBUGP(DHO, "handover activate ack, send HO Command\n");
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, ho->ho_ref);
/* 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);
/* update lchan pointer of transaction */
trans_lchan_change(ho->old_lchan, new_lchan);
/* 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);
}
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