377 lines
9.3 KiB
C
377 lines
9.3 KiB
C
/* 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 <osmocore/msgb.h>
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#include <openbsc/debug.h>
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#include <openbsc/gsm_data.h>
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#include <osmocore/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 <osmocore/talloc.h>
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#include <openbsc/transaction.h>
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#include <openbsc/rtp_proxy.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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static u_int8_t ho_ref;
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int rc;
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/* don't attempt multiple handovers for the same lchan at
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* the same time */
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if (bsc_ho_by_old_lchan(old_lchan))
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return -EBUSY;
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DEBUGP(DHO, "(old_lchan on BTS %u, new BTS %u)\n",
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old_lchan->ts->trx->bts->nr, bts->nr);
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counter_inc(bts->network->stats.handover.attempted);
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new_lchan = lchan_alloc(bts, old_lchan->type);
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if (!new_lchan) {
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LOGP(DHO, LOGL_NOTICE, "No free channel\n");
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counter_inc(bts->network->stats.handover.no_channel);
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return -ENOSPC;
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}
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ho = talloc_zero(NULL, struct bsc_handover);
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if (!ho) {
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LOGP(DHO, LOGL_FATAL, "Out of Memory\n");
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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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ho->ho_ref = ho_ref++;
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/* copy some parameters from old lchan */
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memcpy(&new_lchan->encr, &old_lchan->encr, sizeof(new_lchan->encr));
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new_lchan->ms_power = old_lchan->ms_power;
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new_lchan->bs_power = old_lchan->bs_power;
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new_lchan->rsl_cmode = old_lchan->rsl_cmode;
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new_lchan->tch_mode = old_lchan->tch_mode;
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new_lchan->subscr = subscr_get(old_lchan->subscr);
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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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ho->ho_ref);
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if (rc < 0) {
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LOGP(DHO, LOGL_ERROR, "could not activate channel\n");
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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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struct gsm_network *net = ho->new_lchan->ts->trx->bts->network;
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DEBUGP(DHO, "HO T3103 expired\n");
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counter_inc(net->stats.handover.timeout);
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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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/* we need to check if this channel activation is related to
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* a handover at all (and if, which particular handover) */
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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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DEBUGP(DHO, "handover activate ack, send HO Command\n");
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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, ho->ho_ref);
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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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ho->T3103.data = ho;
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bsc_schedule_timer(&ho->T3103, 10, 0);
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/* create a RTP connection */
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if (is_ipaccess_bts(new_lchan->ts->trx->bts))
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rsl_ipacc_crcx(new_lchan);
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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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LOGP(DHO, LOGL_ERROR, "unable to find HO record\n");
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return -ENODEV;
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}
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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 gsm_network *net = new_lchan->ts->trx->bts->network;
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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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LOGP(DHO, LOGL_ERROR, "unable to find HO record\n");
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return -ENODEV;
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}
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LOGP(DHO, LOGL_INFO, "Subscriber %s HO from BTS %u->%u on ARFCN "
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"%u->%u\n", subscr_name(ho->old_lchan->subscr),
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ho->old_lchan->ts->trx->bts->nr, new_lchan->ts->trx->bts->nr,
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ho->old_lchan->ts->trx->arfcn, new_lchan->ts->trx->arfcn);
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counter_inc(net->stats.handover.completed);
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bsc_del_timer(&ho->T3103);
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/* update lchan pointer of transaction */
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trans_lchan_change(ho->old_lchan, new_lchan);
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ho->old_lchan->state = LCHAN_S_INACTIVE;
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lchan_auto_release(ho->old_lchan);
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/* do something to re-route the actual speech frames ! */
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llist_del(&ho->list);
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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 gsm_network *net = old_lchan->ts->trx->bts->network;
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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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LOGP(DHO, LOGL_ERROR, "unable to find HO record\n");
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return -ENODEV;
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}
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counter_inc(net->stats.handover.failed);
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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_new_lchan(new_lchan);
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if (!ho) {
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LOGP(DHO, LOGL_ERROR, "unable to find HO record\n");
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return -ENODEV;
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}
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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_ipac_crcx_ack(struct gsm_lchan *new_lchan)
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{
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struct bsc_handover *ho;
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struct rtp_socket *old_rs, *new_rs, *other_rs;
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ho = bsc_ho_by_new_lchan(new_lchan);
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if (!ho) {
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/* it is perfectly normal, we have CRCX even in non-HO cases */
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return 0;
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}
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if (ipacc_rtp_direct) {
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LOGP(DHO, LOGL_ERROR, "unable to handover in direct RTP mode\n");
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return 0;
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}
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/* RTP Proxy mode */
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new_rs = new_lchan->abis_ip.rtp_socket;
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old_rs = ho->old_lchan->abis_ip.rtp_socket;
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if (!new_rs) {
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LOGP(DHO, LOGL_ERROR, "no RTP socket for new_lchan\n");
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return -EIO;
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}
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rsl_ipacc_mdcx_to_rtpsock(new_lchan);
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if (!old_rs) {
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LOGP(DHO, LOGL_ERROR, "no RTP socekt for old_lchan\n");
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return -EIO;
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}
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/* copy rx_action and reference to other sock */
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new_rs->rx_action = old_rs->rx_action;
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new_rs->tx_action = old_rs->tx_action;
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new_rs->transmit = old_rs->transmit;
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switch (ho->old_lchan->abis_ip.rtp_socket->rx_action) {
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case RTP_PROXY:
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other_rs = old_rs->proxy.other_sock;
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rtp_socket_proxy(new_rs, other_rs);
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/* delete reference to other end socket to prevent
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* rtp_socket_free() from removing the inverse reference */
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old_rs->proxy.other_sock = NULL;
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break;
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case RTP_RECV_UPSTREAM:
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new_rs->receive = old_rs->receive;
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break;
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case RTP_NONE:
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break;
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}
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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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case SS_ABISIP:
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lchan = signal_data;
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switch (signal) {
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case S_ABISIP_CRCX_ACK:
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return ho_ipac_crcx_ack(lchan);
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break;
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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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register_signal_handler(SS_ABISIP, ho_logic_sig_cb, NULL);
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}
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