/* 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 * * 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 #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include 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)\n", old_lchan->ts->trx->bts->nr, bts->nr); new_lchan = lchan_alloc(bts, old_lchan->type); if (!new_lchan) { LOGP(DHO, LOGL_NOTICE, "No free channel\n"); return -ENOSPC; } ho = talloc_zero(NULL, 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++; /* 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; new_lchan->subscr = subscr_get(old_lchan->subscr); /* 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) { LOGP(DHO, LOGL_ERROR, "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; /* 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; DEBUGP(DHO, "handover activate ack, send HO Command\n"); /* 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; ho->T3103.data = ho; 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) { LOGP(DHO, LOGL_ERROR, "unable to find HO record\n"); 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) { LOGP(DHO, LOGL_ERROR, "unable to find HO record\n"); 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); 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) { LOGP(DHO, LOGL_ERROR, "unable to find HO record\n"); 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_new_lchan(new_lchan); if (!ho) { LOGP(DHO, LOGL_ERROR, "unable to find HO record\n"); 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); }