Harald Welte | 96c0b08 | 2009-11-29 22:56:14 +0100 | [diff] [blame] | 1 | /* Handover Logic for Inter-BTS (Intra-BSC) Handover. This does not |
| 2 | * actually implement the handover algorithm/decision, but executes a |
| 3 | * handover decision */ |
| 4 | |
| 5 | /* (C) 2009 by Harald Welte <laforge@gnumonks.org> |
| 6 | * |
| 7 | * All Rights Reserved |
| 8 | * |
| 9 | * This program is free software; you can redistribute it and/or modify |
| 10 | * it under the terms of the GNU General Public License as published by |
| 11 | * the Free Software Foundation; either version 2 of the License, or |
| 12 | * (at your option) any later version. |
| 13 | * |
| 14 | * This program is distributed in the hope that it will be useful, |
| 15 | * but WITHOUT ANY WARRANTY; without even the implied warranty of |
| 16 | * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the |
| 17 | * GNU General Public License for more details. |
| 18 | * |
| 19 | * You should have received a copy of the GNU General Public License along |
| 20 | * with this program; if not, write to the Free Software Foundation, Inc., |
| 21 | * 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA. |
| 22 | * |
| 23 | */ |
| 24 | |
| 25 | #include <stdio.h> |
| 26 | #include <stdlib.h> |
| 27 | #include <string.h> |
| 28 | #include <errno.h> |
| 29 | #include <time.h> |
| 30 | #include <netinet/in.h> |
| 31 | |
| 32 | #include <openbsc/msgb.h> |
| 33 | #include <openbsc/debug.h> |
| 34 | #include <openbsc/gsm_data.h> |
| 35 | #include <openbsc/gsm_utils.h> |
| 36 | #include <openbsc/gsm_subscriber.h> |
| 37 | #include <openbsc/gsm_04_08.h> |
| 38 | #include <openbsc/abis_rsl.h> |
| 39 | #include <openbsc/chan_alloc.h> |
| 40 | #include <openbsc/signal.h> |
| 41 | #include <openbsc/talloc.h> |
| 42 | #include <openbsc/transaction.h> |
| 43 | |
| 44 | struct bsc_handover { |
| 45 | struct llist_head list; |
| 46 | |
| 47 | struct gsm_lchan *old_lchan; |
| 48 | struct gsm_lchan *new_lchan; |
| 49 | |
| 50 | struct timer_list T3103; |
| 51 | |
| 52 | u_int8_t ho_ref; |
| 53 | }; |
| 54 | |
| 55 | static LLIST_HEAD(bsc_handovers); |
| 56 | |
| 57 | static struct bsc_handover *bsc_ho_by_new_lchan(struct gsm_lchan *new_lchan) |
| 58 | { |
| 59 | struct bsc_handover *ho; |
| 60 | |
| 61 | llist_for_each_entry(ho, &bsc_handovers, list) { |
| 62 | if (ho->new_lchan == new_lchan) |
| 63 | return ho; |
| 64 | } |
| 65 | |
| 66 | return NULL; |
| 67 | } |
| 68 | |
| 69 | static struct bsc_handover *bsc_ho_by_old_lchan(struct gsm_lchan *old_lchan) |
| 70 | { |
| 71 | struct bsc_handover *ho; |
| 72 | |
| 73 | llist_for_each_entry(ho, &bsc_handovers, list) { |
| 74 | if (ho->old_lchan == old_lchan) |
| 75 | return ho; |
| 76 | } |
| 77 | |
| 78 | return NULL; |
| 79 | } |
| 80 | |
| 81 | /* Hand over the specified logical channel to the specified new BTS. |
| 82 | * This is the main entry point for the actual handover algorithm, |
| 83 | * after it has decided it wants to initiate HO to a specific BTS */ |
| 84 | int bsc_handover_start(struct gsm_lchan *old_lchan, struct gsm_bts *bts) |
| 85 | { |
| 86 | struct gsm_lchan *new_lchan; |
| 87 | struct bsc_handover *ho; |
| 88 | int rc; |
| 89 | |
| 90 | new_lchan = lchan_alloc(bts, old_lchan->type); |
| 91 | if (!new_lchan) |
| 92 | return -ENOSPC; |
| 93 | |
| 94 | ho = talloc_zero(NULL, struct bsc_handover); |
| 95 | if (!ho) { |
| 96 | lchan_free(new_lchan); |
| 97 | return -ENOMEM; |
| 98 | } |
| 99 | ho->old_lchan = old_lchan; |
| 100 | ho->new_lchan = new_lchan; |
| 101 | |
| 102 | /* FIXME: do we have a better idea of the timing advance? */ |
| 103 | rc = rsl_chan_activate_lchan(new_lchan, RSL_ACT_INTER_ASYNC, 0); |
| 104 | if (rc < 0) { |
| 105 | talloc_free(ho); |
| 106 | lchan_free(new_lchan); |
| 107 | return rc; |
| 108 | } |
| 109 | |
| 110 | llist_add(&ho->list, &bsc_handovers); |
| 111 | /* we continue in the SS_LCHAN handler / ho_chan_activ_ack */ |
| 112 | |
| 113 | return 0; |
| 114 | } |
| 115 | |
| 116 | /* T3103 expired: Handover has failed without HO COMPLETE or HO FAIL */ |
| 117 | static void ho_T3103_cb(void *_ho) |
| 118 | { |
| 119 | struct bsc_handover *ho = _ho; |
| 120 | |
| 121 | lchan_free(ho->new_lchan); |
| 122 | llist_del(&ho->list); |
| 123 | talloc_free(ho); |
| 124 | } |
| 125 | |
| 126 | /* RSL has acknowledged activation of the new lchan */ |
| 127 | static int ho_chan_activ_ack(struct gsm_lchan *new_lchan) |
| 128 | { |
| 129 | struct bsc_handover *ho; |
| 130 | int rc; |
| 131 | |
| 132 | ho = bsc_ho_by_new_lchan(new_lchan); |
| 133 | if (!ho) |
| 134 | return -ENODEV; |
| 135 | |
| 136 | /* we can now send the 04.08 HANDOVER COMMAND to the MS |
| 137 | * using the old lchan */ |
| 138 | |
| 139 | rc = gsm48_send_ho_cmd(ho->old_lchan, new_lchan, 0); |
| 140 | |
| 141 | /* start T3103. We can continue either with T3103 expiration, |
| 142 | * 04.08 HANDOVER COMPLETE or 04.08 HANDOVER FAIL */ |
| 143 | ho->T3103.cb = ho_T3103_cb; |
| 144 | bsc_schedule_timer(&ho->T3103, 10, 0); |
| 145 | |
| 146 | return 0; |
| 147 | } |
| 148 | |
| 149 | /* RSL has not acknowledged activation of the new lchan */ |
| 150 | static int ho_chan_activ_nack(struct gsm_lchan *new_lchan) |
| 151 | { |
| 152 | struct bsc_handover *ho; |
| 153 | |
| 154 | ho = bsc_ho_by_new_lchan(new_lchan); |
| 155 | if (!ho) |
| 156 | return -ENODEV; |
| 157 | |
| 158 | llist_del(&ho->list); |
| 159 | talloc_free(ho); |
| 160 | |
| 161 | /* FIXME: maybe we should try to allocate a new LCHAN here? */ |
| 162 | |
| 163 | return 0; |
| 164 | } |
| 165 | |
| 166 | /* GSM 04.08 HANDOVER COMPLETE has been received on new channel */ |
| 167 | static int ho_gsm48_ho_compl(struct gsm_lchan *new_lchan) |
| 168 | { |
| 169 | struct bsc_handover *ho; |
| 170 | |
| 171 | ho = bsc_ho_by_new_lchan(new_lchan); |
| 172 | if (!ho) |
| 173 | return -ENODEV; |
| 174 | |
| 175 | bsc_del_timer(&ho->T3103); |
| 176 | llist_del(&ho->list); |
| 177 | |
| 178 | /* do something to re-route the actual speech frames ! */ |
| 179 | //tch_remap(ho->old_lchan, ho->new_lchan); |
| 180 | |
| 181 | /* release old lchan */ |
| 182 | put_lchan(ho->old_lchan); |
| 183 | |
| 184 | talloc_free(ho); |
| 185 | |
| 186 | return 0; |
| 187 | } |
| 188 | |
| 189 | /* GSM 04.08 HANDOVER FAIL has been received */ |
| 190 | static int ho_gsm48_ho_fail(struct gsm_lchan *old_lchan) |
| 191 | { |
| 192 | struct bsc_handover *ho; |
| 193 | |
| 194 | ho = bsc_ho_by_old_lchan(old_lchan); |
| 195 | if (!ho) |
| 196 | return -ENODEV; |
| 197 | |
| 198 | bsc_del_timer(&ho->T3103); |
| 199 | llist_del(&ho->list); |
| 200 | put_lchan(ho->new_lchan); |
| 201 | talloc_free(ho); |
| 202 | |
| 203 | return 0; |
| 204 | } |
| 205 | |
| 206 | /* GSM 08.58 HANDOVER DETECT has been received */ |
| 207 | static int ho_rsl_detect(struct gsm_lchan *new_lchan) |
| 208 | { |
| 209 | struct bsc_handover *ho; |
| 210 | |
| 211 | ho = bsc_ho_by_old_lchan(new_lchan); |
| 212 | if (!ho) |
| 213 | return -ENODEV; |
| 214 | |
| 215 | /* FIXME: do we actually want to do something here ? */ |
| 216 | |
| 217 | return 0; |
| 218 | } |
| 219 | |
| 220 | static int ho_logic_sig_cb(unsigned int subsys, unsigned int signal, |
| 221 | void *handler_data, void *signal_data) |
| 222 | { |
| 223 | struct gsm_lchan *lchan; |
| 224 | |
| 225 | switch (subsys) { |
| 226 | case SS_LCHAN: |
| 227 | lchan = signal_data; |
| 228 | switch (signal) { |
| 229 | case S_LCHAN_ACTIVATE_ACK: |
| 230 | return ho_chan_activ_ack(lchan); |
| 231 | case S_LCHAN_ACTIVATE_NACK: |
| 232 | return ho_chan_activ_nack(lchan); |
| 233 | case S_LCHAN_HANDOVER_DETECT: |
| 234 | return ho_rsl_detect(lchan); |
| 235 | case S_LCHAN_HANDOVER_COMPL: |
| 236 | return ho_gsm48_ho_compl(lchan); |
| 237 | case S_LCHAN_HANDOVER_FAIL: |
| 238 | return ho_gsm48_ho_fail(lchan); |
| 239 | } |
| 240 | break; |
| 241 | default: |
| 242 | break; |
| 243 | } |
| 244 | |
| 245 | return 0; |
| 246 | } |
| 247 | |
| 248 | static __attribute__((constructor)) void on_dso_load_ho_logic(void) |
| 249 | { |
| 250 | register_signal_handler(SS_LCHAN, ho_logic_sig_cb, NULL); |
| 251 | } |