src/host/layer23/src/common/lapdm.c

   1 /* GSM LAPDm (TS 04.06) implementation */
   2
   3 /* (C) 2010 by Harald Welte <laforge@gnumonks.org>
   4  * (C) 2010 by Andreas Eversberg <jolly@eversberg.eu>
   5  *
   6  * All Rights Reserved
   7  *
   8  * This program is free software; you can redistribute it and/or modify
   9  * it under the terms of the GNU General Public License as published by
  10  * the Free Software Foundation; either version 2 of the License, or
  11  * (at your option) any later version.
  12  *
  13  * This program is distributed in the hope that it will be useful,
  14  * but WITHOUT ANY WARRANTY; without even the implied warranty of
  15  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  16  * GNU General Public License for more details.
  17  *
  18  * You should have received a copy of the GNU General Public License along
  19  * with this program; if not, write to the Free Software Foundation, Inc.,
  20  * 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA.
  21  *
  22  */
  23
  24 /* Notes on Buffering: rcv_buffer, tx_queue, tx_hist, send_buffer, send_queue
  25  *
  26  * RX data is stored in the rcv_buffer (pointer). If the message is complete, it
  27  * is removed from rcv_buffer pointer and forwarded to L3. If the RX data is
  28  * received while there is an incomplete rcv_buffer, it is appended to it.
  29  *
  30  * TX data is stored in the send_queue first. When transmitting a frame,
  31  * the first message in the send_queue is moved to the send_buffer. There it
  32  * resides until all fragments are acknowledged. Fragments to be sent by I
  33  * frames are stored in the tx_hist buffer for resend, if required. Also the
  34  * current fragment is copied into the tx_queue. There it resides until it is
  35  * forwarded to layer 1.
  36  *
  37  * In case we have SAPI 0, we only have a window size of 1, so the unack-
  38  * nowledged message resides always in the send_buffer. In case of a suspend,
  39  * it can be written back to the first position of the send_queue.
  40  *
  41  * The layer 1 normally sends a PH-READY-TO-SEND. But because we use
  42  * asynchronous transfer between layer 1 and layer 2 (serial link), we must
  43  * send a frame before layer 1 reaches the right timeslot to send it. So we
  44  * move the tx_queue to layer 1 when there is not already a pending frame, and
  45  * wait until acknowledge after the frame has been sent. If we receive an
  46  * acknowledge, we can send the next frame from the buffer, if any.
  47  *
  48  * The moving of tx_queue to layer 1 may also trigger T200, if desired. Also it
  49  * will trigger next I frame, if possible.
  50  *
  51  */
  52
  53 #include <stdio.h>
  54 #include <stdint.h>
  55 #include <string.h>
  56 #include <errno.h>
  57 #include <arpa/inet.h>
  58
  59 #include <osmocore/logging.h>
  60 #include <osmocore/timer.h>
  61 #include <osmocore/msgb.h>
  62 #include <osmocore/tlv.h>
  63 #include <osmocore/utils.h>
  64 #include <osmocore/rsl.h>
  65 #include <osmocore/protocol/gsm_04_08.h>
  66 #include <osmocore/protocol/gsm_08_58.h>
  67
  68 #include <osmocom/bb/common/osmocom_data.h>
  69 #include <osmocom/bb/common/l1ctl.h>
  70 #include <osmocom/bb/common/lapdm.h>
  71 #include <osmocom/bb/common/logging.h>
  72
  73 #include <l1ctl_proto.h>
  74
  75 /* TS 04.06 Figure 4 / Section 3.2 */
  76 #define LAPDm_LPD_NORMAL  0
  77 #define LAPDm_LPD_SMSCB   1
  78 #define LAPDm_SAPI_NORMAL 0
  79 #define LAPDm_SAPI_SMS    3
  80 #define LAPDm_ADDR(lpd, sapi, cr) ((((lpd) & 0x3) << 5) | (((sapi) & 0x7) << 2) | (((cr) & 0x1) << 1) | 0x1)
  81
  82 #define LAPDm_ADDR_SAPI(addr) (((addr) >> 2) & 0x7)
  83 #define LAPDm_ADDR_CR(addr) (((addr) >> 1) & 0x1)
  84 #define LAPDm_ADDR_EA(addr) ((addr) & 0x1)
  85
  86 /* TS 04.06 Table 3 / Section 3.4.3 */
  87 #define LAPDm_CTRL_I(nr, ns, p) ((((nr) & 0x7) << 5) | (((p) & 0x1) << 4) | (((ns) & 0x7) << 1))
  88 #define LAPDm_CTRL_S(nr, s, p)  ((((nr) & 0x7) << 5) | (((p) & 0x1) << 4) | (((s) & 0x3) << 2) | 0x1)
  89 #define LAPDm_CTRL_U(u, p)      ((((u) & 0x1c) << (5-2)) | (((p) & 0x1) << 4) | (((u) & 0x3) << 2) | 0x3)
  90
  91 #define LAPDm_CTRL_is_I(ctrl)   (((ctrl) & 0x1) == 0)
  92 #define LAPDm_CTRL_is_S(ctrl)   (((ctrl) & 0x3) == 1)
  93 #define LAPDm_CTRL_is_U(ctrl)   (((ctrl) & 0x3) == 3)
  94
  95 #define LAPDm_CTRL_U_BITS(ctrl) ((((ctrl) & 0xC) >> 2) | ((ctrl) & 0xE0) >> 3)
  96 #define LAPDm_CTRL_PF_BIT(ctrl) (((ctrl) >> 4) & 0x1)
  97
  98 #define LAPDm_CTRL_S_BITS(ctrl) (((ctrl) & 0xC) >> 2)
  99
 100 #define LAPDm_CTRL_I_Ns(ctrl)   (((ctrl) & 0xE) >> 1)
 101 #define LAPDm_CTRL_Nr(ctrl)     (((ctrl) & 0xE0) >> 5)
 102
 103 /* TS 04.06 Table 4 / Section 3.8.1 */
 104 #define LAPDm_U_SABM    0x7
 105 #define LAPDm_U_DM      0x3
 106 #define LAPDm_U_UI      0x0
 107 #define LAPDm_U_DISC    0x8
 108 #define LAPDm_U_UA      0xC
 109
 110 #define LAPDm_S_RR      0x0
 111 #define LAPDm_S_RNR     0x1
 112 #define LAPDm_S_REJ     0x2
 113
 114 #define LAPDm_LEN(len)  ((len << 2) | 0x1)
 115 #define LAPDm_MORE      0x2
 116
 117 /* TS 04.06 Section 5.8.3 */
 118 #define N201_AB_SACCH           18
 119 #define N201_AB_SDCCH           20
 120 #define N201_AB_FACCH           20
 121 #define N201_Bbis               23
 122 #define N201_Bter_SACCH         21
 123 #define N201_Bter_SDCCH         23
 124 #define N201_Bter_FACCH         23
 125 #define N201_B4                 19
 126
 127 /* 5.8.2.1 N200 during establish and release */
 128 #define N200_EST_REL            5
 129 /* 5.8.2.1 N200 during timer recovery state */
 130 #define N200_TR_SACCH           5
 131 #define N200_TR_SDCCH           23
 132 #define N200_TR_FACCH_FR        34
 133 #define N200_TR_EFACCH_FR       48
 134 #define N200_TR_FACCH_HR        29
 135 /* FIXME: this depends on chan type */
 136 #define N200    N200_TR_SACCH
 137
 138 #define CR_MS2BS_CMD    0
 139 #define CR_MS2BS_RESP   1
 140 #define CR_BS2MS_CMD    1
 141 #define CR_BS2MS_RESP   0
 142
 143 /* Set T200 to 1 Second (OpenBTS uses 900ms) */
 144 #define T200    1, 0
 145
 146 /* k value for each SAPI */
 147 static uint8_t k_sapi[] = {1, 1, 1, 1, 1, 1, 1, 1};
 148
 149 enum lapdm_format {
 150         LAPDm_FMT_A,
 151         LAPDm_FMT_B,
 152         LAPDm_FMT_Bbis,
 153         LAPDm_FMT_Bter,
 154         LAPDm_FMT_B4,
 155 };
 156
 157 static void lapdm_t200_cb(void *data);
 158 static int rslms_send_i(struct lapdm_msg_ctx *mctx);
 159
 160 /* UTILITY FUNCTIONS */
 161
 162 static inline uint8_t inc_mod8(uint8_t x)
 163 {
 164         return (x + 1) & 7;
 165 }
 166
 167 static inline uint8_t add_mod8(uint8_t x, uint8_t y)
 168 {
 169         return (x + y) & 7;
 170 }
 171
 172 static inline uint8_t sub_mod8(uint8_t x, uint8_t y)
 173 {
 174         return (x - y) & 7; /* handle negative results correctly */
 175 }
 176
 177 static void lapdm_dl_init(struct lapdm_datalink *dl,
 178                           struct lapdm_entity *entity)
 179 {
 180         memset(dl, 0, sizeof(*dl));
 181         INIT_LLIST_HEAD(&dl->send_queue);
 182         INIT_LLIST_HEAD(&dl->tx_queue);
 183         dl->state = LAPDm_STATE_IDLE;
 184         dl->t200.data = dl;
 185         dl->t200.cb = &lapdm_t200_cb;
 186         dl->entity = entity;
 187 }
 188
 189 void lapdm_init(struct lapdm_entity *le, struct osmocom_ms *ms)
 190 {
 191         unsigned int i;
 192
 193         for (i = 0; i < ARRAY_SIZE(le->datalink); i++)
 194                 lapdm_dl_init(&le->datalink[i], le);
 195
 196         le->ms = ms;
 197 }
 198
 199 static void lapdm_dl_flush_send(struct lapdm_datalink *dl)
 200 {
 201         struct msgb *msg;
 202
 203         /* Flush send-queue */
 204         while ((msg = msgb_dequeue(&dl->send_queue)))
 205                 msgb_free(msg);
 206
 207         /* Clear send-buffer */
 208         if (dl->send_buffer) {
 209                 msgb_free(dl->send_buffer);
 210                 dl->send_buffer = NULL;
 211         }
 212 }
 213
 214 static void lapdm_dl_flush_tx(struct lapdm_datalink *dl)
 215 {
 216         struct msgb *msg;
 217         unsigned int i;
 218
 219         while ((msg = msgb_dequeue(&dl->tx_queue)))
 220                 msgb_free(msg);
 221         for (i = 0; i < 8; i++)
 222                 dl->tx_length[i] = 0;
 223 }
 224
 225 void lapdm_exit(struct lapdm_entity *le)
 226 {
 227         unsigned int i;
 228         struct lapdm_datalink *dl;
 229
 230         for (i = 0; i < ARRAY_SIZE(le->datalink); i++) {
 231                 dl = &le->datalink[i];
 232                 lapdm_dl_flush_tx(dl);
 233                 lapdm_dl_flush_send(dl);
 234                 if (dl->rcv_buffer)
 235                         msgb_free(dl->rcv_buffer);
 236         }
 237 }
 238
 239 static void lapdm_dl_newstate(struct lapdm_datalink *dl, uint32_t state)
 240 {
 241         LOGP(DLAPDM, LOGL_INFO, "new state %s -> %s\n",
 242                 lapdm_state_names[dl->state], lapdm_state_names[state]);
 243
 244         dl->state = state;
 245 }
 246
 247 static struct lapdm_datalink *datalink_for_sapi(struct lapdm_entity *le, uint8_t sapi)
 248 {
 249         switch (sapi) {
 250         case LAPDm_SAPI_NORMAL:
 251                 return &le->datalink[0];
 252         case LAPDm_SAPI_SMS:
 253                 return &le->datalink[1];
 254         default:
 255                 return NULL;
 256         }
 257 }
 258
 259 /* remove the L2 header from a MSGB */
 260 static inline unsigned char *msgb_pull_l2h(struct msgb *msg)
 261 {
 262         unsigned char *ret = msgb_pull(msg, msg->l3h - msg->l2h);
 263         msg->l2h = NULL;
 264         return ret;
 265 }
 266
 267 /* Append padding (if required) */
 268 static void lapdm_pad_msgb(struct msgb *msg, uint8_t n201)
 269 {
 270         int pad_len = n201 - msgb_l2len(msg);
 271         uint8_t *data;
 272
 273         if (pad_len < 0) {
 274                 LOGP(DLAPDM, LOGL_ERROR,
 275                      "cannot pad message that is already too big!\n");
 276                 return;
 277         }
 278
 279         data = msgb_put(msg, pad_len);
 280         memset(data, 0x2B, pad_len);
 281 }
 282
 283 /* write a frame into the tx queue */
 284 static int tx_ph_data_enqueue(struct lapdm_datalink *dl, struct msgb *msg,
 285                                 uint8_t chan_nr, uint8_t link_id, uint8_t n201)
 286 {
 287         struct lapdm_entity *le = dl->entity;
 288         struct osmocom_ms *ms = le->ms;
 289
 290         /* if there is a pending message, queue it */
 291         if (le->tx_pending) {
 292                 *msgb_push(msg, 1) = n201;
 293                 *msgb_push(msg, 1) = link_id;
 294                 *msgb_push(msg, 1) = chan_nr;
 295                 msgb_enqueue(&dl->tx_queue, msg);
 296                 return -EBUSY;
 297         }
 298
 299         /* send the frame now */
 300         le->tx_pending = 0; /* disabled flow control */
 301         lapdm_pad_msgb(msg, n201);
 302         return l1ctl_tx_data_req(ms, msg, chan_nr, link_id);
 303 }
 304
 305 /* get next frame from the tx queue. because the ms has multiple datalinks,
 306  * each datalink's queue is read round-robin.
 307  */
 308 int l2_ph_data_conf(struct msgb *msg, struct lapdm_entity *le)
 309 {
 310         struct osmocom_ms *ms = le->ms;
 311         struct lapdm_datalink *dl;
 312         int last = le->last_tx_dequeue;
 313         int i = last, n = ARRAY_SIZE(le->datalink);
 314         uint8_t chan_nr, link_id, n201;
 315
 316         /* we may send again */
 317         le->tx_pending = 0;
 318
 319         /* free confirm message */
 320         msgb_free(msg);
 321
 322         /* round-robin dequeue */
 323         do {
 324                 /* next */
 325                 i = (i + 1) % n;
 326                 dl = &le->datalink[i];
 327                 if ((msg = msgb_dequeue(&dl->tx_queue)))
 328                         break;
 329         } while (i != last);
 330
 331         /* no message in all queues */
 332         if (!msg)
 333                 return 0;
 334
 335         /* Pull chan_nr and link_id */
 336         chan_nr = *msg->data;
 337         msgb_pull(msg, 1);
 338         link_id = *msg->data;
 339         msgb_pull(msg, 1);
 340         n201 = *msg->data;
 341         msgb_pull(msg, 1);
 342
 343         /* Set last dequeue position */
 344         le->last_tx_dequeue = i;
 345
 346         /* Pad the frame, we can transmit now */
 347         le->tx_pending = 1;
 348         lapdm_pad_msgb(msg, n201);
 349         return l1ctl_tx_data_req(ms, msg, chan_nr, link_id);
 350 }
 351
 352 /* Create RSLms various RSLms messages */
 353 static int send_rslms_rll_l3(uint8_t msg_type, struct lapdm_msg_ctx *mctx,
 354                              struct msgb *msg)
 355 {
 356         /* Add the RSL + RLL header */
 357         rsl_rll_push_l3(msg, msg_type, mctx->chan_nr, mctx->link_id, 1);
 358
 359         /* send off the RSLms message to L3 */
 360         return rslms_sendmsg(msg, mctx->dl->entity->ms);
 361 }
 362
 363 /* Take a B4 format message from L1 and create RSLms UNIT DATA IND */
 364 static int send_rslms_rll_l3_ui(struct lapdm_msg_ctx *mctx, struct msgb *msg)
 365 {
 366         uint8_t l3_len = msg->tail - (uint8_t *)msgb_l3(msg);
 367         struct abis_rsl_rll_hdr *rllh;
 368
 369         /* Add the RSL + RLL header */
 370         msgb_tv16_push(msg, RSL_IE_L3_INFO, l3_len);
 371         msgb_push(msg, 2 + 2);
 372         rsl_rll_push_hdr(msg, RSL_MT_UNIT_DATA_IND, mctx->chan_nr,
 373                 mctx->link_id, 1);
 374         rllh = (struct abis_rsl_rll_hdr *)msgb_l2(msg);
 375
 376         rllh->data[0] = RSL_IE_ACCESS_DELAY;
 377         rllh->data[1] = mctx->ta_ind;
 378
 379         rllh->data[2] = RSL_IE_MS_POWER;
 380         rllh->data[3] = mctx->tx_power_ind;
 381
 382         return rslms_sendmsg(msg, mctx->dl->entity->ms);
 383 }
 384
 385 static int send_rll_simple(uint8_t msg_type, struct lapdm_msg_ctx *mctx)
 386 {
 387         struct msgb *msg;
 388
 389         msg = rsl_rll_simple(msg_type, mctx->chan_nr, mctx->link_id, 1);
 390
 391         /* send off the RSLms message to L3 */
 392         return rslms_sendmsg(msg, mctx->dl->entity->ms);
 393 }
 394
 395 static int rsl_rll_error(uint8_t cause, struct lapdm_msg_ctx *mctx)
 396 {
 397         struct msgb *msg;
 398         uint8_t *tlv;
 399
 400         LOGP(DLAPDM, LOGL_NOTICE, "sending MDL-ERROR-IND %d\n", cause);
 401         msg = rsl_rll_simple(RSL_MT_ERROR_IND, mctx->chan_nr, mctx->link_id, 1);
 402         msg->l2h = msgb_put(msg, sizeof(struct abis_rsl_rll_hdr) + 3);
 403         tlv = msg->l2h + sizeof(struct abis_rsl_rll_hdr);
 404         tlv[0] = RSL_IE_RLM_CAUSE;
 405         tlv[1] = 1;
 406         tlv[2] = cause;
 407         return rslms_sendmsg(msg, mctx->dl->entity->ms);
 408 }
 409
 410 static int check_length_ind(struct lapdm_msg_ctx *mctx, uint8_t length_ind)
 411 {
 412         if (!(length_ind & 0x01)) {
 413                 /* G.4.1 If the EL bit is set to "0", an MDL-ERROR-INDICATION
 414                  * primitive with cause "frame not implemented" is sent to the
 415                  * mobile management entity. */
 416                 LOGP(DLAPDM, LOGL_NOTICE,
 417                         "we don't support multi-octet length\n");
 418                 rsl_rll_error(RLL_CAUSE_FRM_UNIMPL, mctx);
 419                 return -EINVAL;
 420         }
 421         return 0;
 422 }
 423
 424 static int lapdm_send_resend(struct lapdm_datalink *dl)
 425 {
 426         struct msgb *msg = msgb_alloc_headroom(23+10, 10, "LAPDm resend");
 427         int length;
 428
 429         /* Resend SABM/DISC from tx_hist */
 430         length = dl->tx_length[0];
 431         msg->l2h = msgb_put(msg, length);
 432         memcpy(msg->l2h, dl->tx_hist[dl->V_send], length);
 433
 434         return tx_ph_data_enqueue(dl, msg, dl->mctx.chan_nr, dl->mctx.link_id,
 435                         dl->mctx.n201);
 436 }
 437
 438 static int lapdm_send_ua(struct lapdm_msg_ctx *mctx, uint8_t len, uint8_t *data)
 439 {
 440         uint8_t sapi = mctx->link_id & 7;
 441         uint8_t f_bit = LAPDm_CTRL_PF_BIT(mctx->ctrl);
 442         struct msgb *msg = msgb_alloc_headroom(23+10, 10, "LAPDm UA");
 443         msg->l2h = msgb_put(msg, 3 + len);
 444
 445         msg->l2h[0] = LAPDm_ADDR(LAPDm_LPD_NORMAL, sapi, CR_MS2BS_RESP);
 446         msg->l2h[1] = LAPDm_CTRL_U(LAPDm_U_UA, f_bit);
 447         msg->l2h[2] = LAPDm_LEN(len);
 448         if (len)
 449                 memcpy(msg->l2h + 3, data, len);
 450
 451         return tx_ph_data_enqueue(mctx->dl, msg, mctx->chan_nr, mctx->link_id,
 452                         mctx->n201);
 453 }
 454
 455 static int lapdm_send_dm(struct lapdm_msg_ctx *mctx)
 456 {
 457         uint8_t sapi = mctx->link_id & 7;
 458         uint8_t f_bit = LAPDm_CTRL_PF_BIT(mctx->ctrl);
 459         struct msgb *msg = msgb_alloc_headroom(23+10, 10, "LAPDm DM");
 460         msg->l2h = msgb_put(msg, 3);
 461
 462         msg->l2h[0] = LAPDm_ADDR(LAPDm_LPD_NORMAL, sapi, CR_MS2BS_RESP);
 463         msg->l2h[1] = LAPDm_CTRL_U(LAPDm_U_DM, f_bit);
 464         msg->l2h[2] = 0;
 465
 466         return tx_ph_data_enqueue(mctx->dl, msg, mctx->chan_nr, mctx->link_id,
 467                         mctx->n201);
 468 }
 469
 470 static int lapdm_send_rr(struct lapdm_msg_ctx *mctx, uint8_t f_bit)
 471 {
 472         uint8_t sapi = mctx->link_id & 7;
 473         struct msgb *msg = msgb_alloc_headroom(23+10, 10, "LAPDm RR");
 474         msg->l2h = msgb_put(msg, 3);
 475
 476         msg->l2h[0] = LAPDm_ADDR(LAPDm_LPD_NORMAL, sapi, CR_MS2BS_RESP);
 477         msg->l2h[1] = LAPDm_CTRL_S(mctx->dl->V_recv, LAPDm_S_RR, f_bit);
 478         msg->l2h[2] = LAPDm_LEN(0);
 479
 480         return tx_ph_data_enqueue(mctx->dl, msg, mctx->chan_nr, mctx->link_id,
 481                         mctx->n201);
 482 }
 483
 484 static int lapdm_send_rnr(struct lapdm_msg_ctx *mctx, uint8_t f_bit)
 485 {
 486         uint8_t sapi = mctx->link_id & 7;
 487         struct msgb *msg = msgb_alloc_headroom(23+10, 10, "LAPDm RNR");
 488         msg->l2h = msgb_put(msg, 3);
 489
 490         msg->l2h[0] = LAPDm_ADDR(LAPDm_LPD_NORMAL, sapi, CR_MS2BS_RESP);
 491         msg->l2h[1] = LAPDm_CTRL_S(mctx->dl->V_recv, LAPDm_S_RNR, f_bit);
 492         msg->l2h[2] = LAPDm_LEN(0);
 493
 494         return tx_ph_data_enqueue(mctx->dl, msg, mctx->chan_nr, mctx->link_id,
 495                         mctx->n201);
 496 }
 497
 498 static int lapdm_send_rej(struct lapdm_msg_ctx *mctx, uint8_t f_bit)
 499 {
 500         uint8_t sapi = mctx->link_id & 7;
 501         struct msgb *msg = msgb_alloc_headroom(23+10, 10, "LAPDm REJ");
 502         msg->l2h = msgb_put(msg, 3);
 503
 504         msg->l2h[0] = LAPDm_ADDR(LAPDm_LPD_NORMAL, sapi, CR_MS2BS_RESP);
 505         msg->l2h[1] = LAPDm_CTRL_S(mctx->dl->V_recv, LAPDm_S_REJ, f_bit);
 506         msg->l2h[2] = LAPDm_LEN(0);
 507
 508         return tx_ph_data_enqueue(mctx->dl, msg, mctx->chan_nr, mctx->link_id,
 509                         mctx->n201);
 510 }
 511
 512 /* Timer callback on T200 expiry */
 513 static void lapdm_t200_cb(void *data)
 514 {
 515         struct lapdm_datalink *dl = data;
 516
 517         LOGP(DLAPDM, LOGL_INFO, "lapdm_t200_cb(%p) state=%u\n", dl, dl->state);
 518
 519         switch (dl->state) {
 520         case LAPDm_STATE_SABM_SENT:
 521                 /* 5.4.1.3 */
 522                 if (dl->retrans_ctr + 1 >= N200_EST_REL + 1) {
 523                         /* send RELEASE INDICATION to L3 */
 524                         send_rll_simple(RSL_MT_REL_IND, &dl->mctx);
 525                         /* send MDL ERROR INIDCATION to L3 */
 526                         rsl_rll_error(RLL_CAUSE_T200_EXPIRED, &dl->mctx);
 527                         /* flush buffers */
 528                         lapdm_dl_flush_tx(dl);
 529                         lapdm_dl_flush_send(dl);
 530                         /* go back to idle state */
 531                         lapdm_dl_newstate(dl, LAPDm_STATE_IDLE);
 532                         /* NOTE: we must not change any other states or buffers
 533                          * and queues, since we may reconnect after handover
 534                          * failure. the buffered messages is replaced there */
 535                         break;
 536                 }
 537                 /* retransmit SABM command */
 538                 lapdm_send_resend(dl);
 539                 /* increment re-transmission counter */
 540                 dl->retrans_ctr++;
 541                 /* restart T200 (PH-READY-TO-SEND) */
 542                 bsc_schedule_timer(&dl->t200, T200);
 543                 break;
 544         case LAPDm_STATE_DISC_SENT:
 545                 /* 5.4.4.3 */
 546                 if (dl->retrans_ctr + 1 >= N200_EST_REL + 1) {
 547                         /* send RELEASE INDICATION to L3 */
 548                         send_rll_simple(RSL_MT_REL_CONF, &dl->mctx);
 549                         /* send MDL ERROR INIDCATION to L3 */
 550                         rsl_rll_error(RLL_CAUSE_T200_EXPIRED, &dl->mctx);
 551                         /* flush buffers */
 552                         lapdm_dl_flush_tx(dl);
 553                         lapdm_dl_flush_send(dl);
 554                         /* go back to idle state */
 555                         lapdm_dl_newstate(dl, LAPDm_STATE_IDLE);
 556                         /* NOTE: we must not change any other states or buffers
 557                          * and queues, since we may reconnect after handover
 558                          * failure. the buffered messages is replaced there */
 559                         break;
 560                 }
 561                 /* retransmit DISC command */
 562                 lapdm_send_resend(dl);
 563                 /* increment re-transmission counter */
 564                 dl->retrans_ctr++;
 565                 /* restart T200 (PH-READY-TO-SEND) */
 566                 bsc_schedule_timer(&dl->t200, T200);
 567                 break;
 568         case LAPDm_STATE_MF_EST:
 569                 /* 5.5.7 */
 570                 dl->retrans_ctr = 0;
 571                 lapdm_dl_newstate(dl, LAPDm_STATE_TIMER_RECOV);
 572                 /* fall through */
 573         case LAPDm_STATE_TIMER_RECOV:
 574                 dl->retrans_ctr++;
 575                 if (dl->retrans_ctr < N200) {
 576                         /* retransmit I frame (V_s-1) with P=1, if any */
 577                         if (dl->tx_length[dl->V_send - 1]) {
 578                                 struct msgb *msg;
 579                                 int length;
 580
 581                                 LOGP(DLAPDM, LOGL_INFO, "retransmit last frame "
 582                                         "V(S)=%d\n", dl->V_send - 1);
 583                                 /* Create I frame (segment) from tx_hist */
 584                                 length = dl->tx_length[dl->V_send - 1];
 585                                 msg = msgb_alloc_headroom(23+10, 10, "LAPDm I");
 586                                 msg->l2h = msgb_put(msg, length);
 587                                 memcpy(msg->l2h, dl->tx_hist[dl->V_send - 1],
 588                                         length);
 589                                 msg->l2h[1] = LAPDm_CTRL_I(dl->V_recv,
 590                                                 dl->V_send - 1, 1); /* P=1 */
 591                                 tx_ph_data_enqueue(dl, msg, dl->mctx.chan_nr,
 592                                         dl->mctx.link_id, dl->mctx.n201);
 593                         } else {
 594                         /* OR send appropriate supervision frame with P=1 */
 595                                 if (!dl->own_busy && !dl->seq_err_cond) {
 596                                         lapdm_send_rr(&dl->mctx, 1);
 597                                         /* NOTE: In case of sequence error
 598                                          * condition, the REJ frame has been
 599                                          * transmitted when entering the
 600                                          * condition, so it has not be done
 601                                          * here
 602                                          */
 603                                 } else if (dl->own_busy) {
 604                                         lapdm_send_rnr(&dl->mctx, 1);
 605                                 } else {
 606                                         LOGP(DLAPDM, LOGL_INFO, "unhandled, "
 607                                                 "pls. fix\n");
 608                                 }
 609                         }
 610                         /* restart T200 (PH-READY-TO-SEND) */
 611                         bsc_schedule_timer(&dl->t200, T200);
 612                 } else {
 613                         /* send MDL ERROR INIDCATION to L3 */
 614                         rsl_rll_error(RLL_CAUSE_T200_EXPIRED, &dl->mctx);
 615                 }
 616                 break;
 617         default:
 618                 LOGP(DLAPDM, LOGL_INFO, "T200 expired in unexpected "
 619                         "dl->state %u\n", dl->state);
 620         }
 621 }
 622
 623 /* 5.5.3.1: Common function to acknowlege frames up to the given N(R) value */
 624 static void lapdm_acknowledge(struct lapdm_msg_ctx *mctx)
 625 {
 626         struct lapdm_datalink *dl = mctx->dl;
 627         uint8_t nr = LAPDm_CTRL_Nr(mctx->ctrl);
 628         int s = 0, rej = 0, t200_reset = 0;
 629         int i;
 630
 631         /* supervisory frame ? */
 632         if (LAPDm_CTRL_is_S(mctx->ctrl))
 633                 s = 1;
 634         /* REJ frame ? */
 635         if (s && LAPDm_CTRL_S_BITS(mctx->ctrl) == LAPDm_S_REJ)
 636                 rej = 1;
 637
 638         /* Flush all transmit buffers of acknowledged frames */
 639         for (i = dl->V_ack; i != nr; i = inc_mod8(i)) {
 640                 if (dl->tx_length[i]) {
 641                         dl->tx_length[i] = 0;
 642                         LOGP(DLAPDM, LOGL_INFO, "ack frame %d\n", i);
 643                 }
 644         }
 645
 646         if (dl->state != LAPDm_STATE_TIMER_RECOV) {
 647                 /* When not in the timer recovery condition, the data
 648                  * link layer entity shall reset the timer T200 on
 649                  * receipt of a valid I frame with N(R) higher than V(A),
 650                  * or an REJ with an N(R) equal to V(A). */
 651                 if ((!rej && nr != dl->V_ack)
 652                  || (rej && nr == dl->V_ack)) {
 653                         LOGP(DLAPDM, LOGL_INFO, "reset t200\n");
 654                         t200_reset = 1;
 655                         bsc_del_timer(&dl->t200);
 656                         /* 5.5.3.1 Note 1 + 2 imply timer recovery cond. */
 657                 }
 658                 /* 5.7.4: N(R) sequence error
 659                  * N(R) is called valid, if and only if
 660                  * (N(R)-V(A)) mod 8 <= (V(S)-V(A)) mod 8.
 661                  */
 662                 if (sub_mod8(nr, dl->V_ack) > sub_mod8(dl->V_send, dl->V_ack)) {
 663                         LOGP(DLAPDM, LOGL_NOTICE, "N(R) sequence error\n");
 664                         rsl_rll_error(RLL_CAUSE_SEQ_ERR, mctx);
 665                 }
 666         }
 667
 668         /* V(A) shall be set to the value of N(R) */
 669         dl->V_ack = nr;
 670
 671         /* If T200 has been reset by the receipt of an I, RR or RNR frame,
 672          * and if there are outstanding I frames, restart T200 */
 673         if (t200_reset && !rej) {
 674                 if (dl->tx_length[dl->V_send - 1]) {
 675                         LOGP(DLAPDM, LOGL_INFO, "start T200, due to unacked I "
 676                                 "frame(s)\n");
 677                         bsc_schedule_timer(&dl->t200, T200);
 678                 }
 679         }
 680 }
 681
 682 /* L1 -> L2 */
 683
 684 /* Receive a LAPDm U (Unnumbered) message from L1 */
 685 static int lapdm_rx_u(struct msgb *msg, struct lapdm_msg_ctx *mctx)
 686 {
 687         struct lapdm_datalink *dl = mctx->dl;
 688         uint8_t length;
 689         int rc;
 690         int rsl_msg;
 691
 692         switch (LAPDm_CTRL_U_BITS(mctx->ctrl)) {
 693         case LAPDm_U_SABM:
 694                 rsl_msg = RSL_MT_EST_IND;
 695
 696                 LOGP(DLAPDM, LOGL_INFO, "SABM received\n");
 697                 /* 5.7.1 */
 698                 dl->seq_err_cond = 0;
 699                 /* G.2.2 Wrong value of the C/R bit */
 700                 if (LAPDm_ADDR_CR(mctx->addr) == CR_BS2MS_RESP) {
 701                         LOGP(DLAPDM, LOGL_NOTICE, "SABM response error\n");
 702                         msgb_free(msg);
 703                         rsl_rll_error(RLL_CAUSE_FRM_UNIMPL, mctx);
 704                         return -EINVAL;
 705                 }
 706
 707                 length = msg->l2h[2] >> 2;
 708                 /* G.4.5 If SABM is received with L>N201 or with M bit
 709                  * set, AN MDL-ERROR-INDICATION is sent to MM.
 710                  */
 711                 if ((msg->l2h[2] & LAPDm_MORE) || length + 3 > mctx->n201) {
 712                         LOGP(DLAPDM, LOGL_NOTICE, "SABM too large error\n");
 713                         msgb_free(msg);
 714                         rsl_rll_error(RLL_CAUSE_UFRM_INC_PARAM, mctx);
 715                         return -EIO;
 716                 }
 717
 718                 /* Must be Format B */
 719                 rc = check_length_ind(mctx, msg->l2h[2]);
 720                 if (rc < 0) {
 721                         msgb_free(msg);
 722                         return rc;
 723                 }
 724                 switch (dl->state) {
 725                 case LAPDm_STATE_IDLE:
 726                         /* Set chan_nr and link_id for established connection */
 727                         memset(&dl->mctx, 0, sizeof(dl->mctx));
 728                         dl->mctx.dl = dl;
 729                         dl->mctx.chan_nr = mctx->chan_nr;
 730                         dl->mctx.link_id = mctx->link_id;
 731                         break;
 732                 case LAPDm_STATE_MF_EST:
 733                         if (length == 0) {
 734                                 rsl_msg = RSL_MT_EST_CONF;
 735                                 break;
 736                         }
 737                         LOGP(DLAPDM, LOGL_INFO, "SABM command, multiple "
 738                                 "frame established state\n");
 739                         /* check for contention resoultion */
 740                         if (dl->tx_hist[0][2] >> 2) {
 741                                 LOGP(DLAPDM, LOGL_NOTICE, "SABM not allowed "
 742                                         "during contention resolution\n");
 743                                 rsl_rll_error(RLL_CAUSE_SABM_INFO_NOTALL, mctx);
 744                         }
 745                         msgb_free(msg);
 746                         return 0;
 747                 case LAPDm_STATE_DISC_SENT:
 748                         /* 5.4.6.2 send DM with F=P */
 749                         lapdm_send_dm(mctx);
 750                         /* reset Timer T200 */
 751                         bsc_del_timer(&dl->t200);
 752                         msgb_free(msg);
 753                         return send_rll_simple(RSL_MT_REL_CONF, mctx);
 754                 default:
 755                         lapdm_send_ua(mctx, length, msg->l2h + 3);
 756                         msgb_free(msg);
 757                         return 0;
 758                 }
 759                 /* send UA response */
 760                 lapdm_send_ua(mctx, length, msg->l2h + 3);
 761                 /* set Vs, Vr and Va to 0 */
 762                 dl->V_send = dl->V_recv = dl->V_ack = 0;
 763                 /* clear tx_hist */
 764                 dl->tx_length[0] = 0;
 765                 /* enter multiple-frame-established state */
 766                 lapdm_dl_newstate(dl, LAPDm_STATE_MF_EST);
 767                 /* send notification to L3 */
 768                 if (length == 0) {
 769                         /* 5.4.1.2 Normal establishment procedures */
 770                         rc = send_rll_simple(rsl_msg, mctx);
 771                         msgb_free(msg);
 772                 } else {
 773                         /* 5.4.1.4 Contention resolution establishment */
 774                         msg->l3h = msg->l2h + 3;
 775                         msgb_pull_l2h(msg);
 776                         rc = send_rslms_rll_l3(rsl_msg, mctx, msg);
 777                 }
 778                 break;
 779         case LAPDm_U_DM:
 780                 LOGP(DLAPDM, LOGL_INFO, "DM received\n");
 781                 /* G.2.2 Wrong value of the C/R bit */
 782                 if (LAPDm_ADDR_CR(mctx->addr) == CR_BS2MS_CMD) {
 783                         LOGP(DLAPDM, LOGL_NOTICE, "DM command error\n");
 784                         msgb_free(msg);
 785                         rsl_rll_error(RLL_CAUSE_FRM_UNIMPL, mctx);
 786                         return -EINVAL;
 787                 }
 788                 if (!LAPDm_CTRL_PF_BIT(mctx->ctrl)) {
 789                         /* 5.4.1.2 DM responses with the F bit set to "0"
 790                          * shall be ignored.
 791                          */
 792                         msgb_free(msg);
 793                         return 0;
 794                 }
 795                 switch (dl->state) {
 796                 case LAPDm_STATE_SABM_SENT:
 797                         break;
 798                 case LAPDm_STATE_MF_EST:
 799                         if (LAPDm_CTRL_PF_BIT(mctx->ctrl) == 1) {
 800                                 LOGP(DLAPDM, LOGL_INFO, "unsolicited DM "
 801                                         "response\n");
 802                                 rsl_rll_error(RLL_CAUSE_UNSOL_DM_RESP, mctx);
 803                         } else {
 804                                 LOGP(DLAPDM, LOGL_INFO, "unsolicited DM "
 805                                         "response, multiple frame established "
 806                                         "state\n");
 807                                 rsl_rll_error(RLL_CAUSE_UNSOL_DM_RESP_MF, mctx);
 808                         }
 809                         msgb_free(msg);
 810                         return 0;
 811                 case LAPDm_STATE_TIMER_RECOV:
 812                         /* DM is normal in case PF = 1 */
 813                         if (LAPDm_CTRL_PF_BIT(mctx->ctrl) == 0) {
 814                                 LOGP(DLAPDM, LOGL_INFO, "unsolicited DM "
 815                                         "response, multiple frame established "
 816                                         "state\n");
 817                                 rsl_rll_error(RLL_CAUSE_UNSOL_DM_RESP_MF, mctx);
 818                                 msgb_free(msg);
 819                                 return 0;
 820                         }
 821                         break;
 822                 case LAPDm_STATE_DISC_SENT:
 823                         /* reset Timer T200 */
 824                         bsc_del_timer(&dl->t200);
 825                         /* go to idle state */
 826                         lapdm_dl_newstate(dl, LAPDm_STATE_IDLE);
 827                         rc = send_rll_simple(RSL_MT_REL_CONF, mctx);
 828                         msgb_free(msg);
 829                         return 0;
 830                 case LAPDm_STATE_IDLE:
 831                         /* 5.4.5 all other frame types shall be discarded */
 832                 default:
 833                         LOGP(DLAPDM, LOGL_INFO, "unsolicited DM response! "
 834                                 "(discarding)\n");
 835                         msgb_free(msg);
 836                         return 0;
 837                 }
 838                 /* reset T200 */
 839                 bsc_del_timer(&dl->t200);
 840                 rc = send_rll_simple(RSL_MT_REL_IND, mctx);
 841                 msgb_free(msg);
 842                 break;
 843         case LAPDm_U_UI:
 844                 LOGP(DLAPDM, LOGL_INFO, "UI received\n");
 845                 /* G.2.2 Wrong value of the C/R bit */
 846                 if (LAPDm_ADDR_CR(mctx->addr) == CR_BS2MS_RESP) {
 847                         LOGP(DLAPDM, LOGL_NOTICE, "UI indicates response "
 848                                 "error\n");
 849                         msgb_free(msg);
 850                         rsl_rll_error(RLL_CAUSE_FRM_UNIMPL, mctx);
 851                         return -EINVAL;
 852                 }
 853
 854                 length = msg->l2h[2] >> 2;
 855                 /* FIXME: G.4.5 If UI is received with L>N201 or with M bit
 856                  * set, AN MDL-ERROR-INDICATION is sent to MM.
 857                  */
 858
 859                 if (mctx->lapdm_fmt == LAPDm_FMT_B4) {
 860                         length = N201_B4;
 861                         msg->l3h = msg->l2h + 2;
 862                 } else {
 863                         rc = check_length_ind(mctx, msg->l2h[2]);
 864                         if (rc < 0) {
 865                                 msgb_free(msg);
 866                                 return rc;
 867                         }
 868                         length = msg->l2h[2] >> 2;
 869                         msg->l3h = msg->l2h + 3;
 870                 }
 871                 /* do some length checks */
 872                 if (length == 0) {
 873                         /* 5.3.3 UI frames received with the length indicator
 874                          * set to "0" shall be ignored
 875                          */
 876                         LOGP(DLAPDM, LOGL_INFO, "length=0 (discarding)\n");
 877                         msgb_free(msg);
 878                         return 0;
 879                 }
 880                 switch (LAPDm_ADDR_SAPI(mctx->addr)) {
 881                 case LAPDm_SAPI_NORMAL:
 882                 case LAPDm_SAPI_SMS:
 883                         break;
 884                 default:
 885                         /* 5.3.3 UI frames with invalid SAPI values shall be
 886                          * discarded
 887                          */
 888                         LOGP(DLAPDM, LOGL_INFO, "sapi=%u (discarding)\n",
 889                                 LAPDm_ADDR_SAPI(mctx->addr));
 890                         msgb_free(msg);
 891                         return 0;
 892                 }
 893                 msgb_pull_l2h(msg);
 894                 rc = send_rslms_rll_l3_ui(mctx, msg);
 895                 break;
 896         case LAPDm_U_DISC:
 897                 rsl_msg = RSL_MT_REL_IND;
 898
 899                 LOGP(DLAPDM, LOGL_INFO, "DISC received\n");
 900                 /* flush buffers */
 901                 lapdm_dl_flush_tx(dl);
 902                 lapdm_dl_flush_send(dl);
 903                 /* 5.7.1 */
 904                 dl->seq_err_cond = 0;
 905                 /* G.2.2 Wrong value of the C/R bit */
 906                 if (LAPDm_ADDR_CR(mctx->addr) == CR_BS2MS_RESP) {
 907                         LOGP(DLAPDM, LOGL_NOTICE, "DISC response error\n");
 908                         msgb_free(msg);
 909                         rsl_rll_error(RLL_CAUSE_FRM_UNIMPL, mctx);
 910                         return -EINVAL;
 911                 }
 912                 length = msg->l2h[2] >> 2;
 913                 if (length > 0 || msg->l2h[2] & 0x02) {
 914                         /* G.4.4 If a DISC or DM frame is received with L>0 or
 915                          * with the M bit set to "1", an MDL-ERROR-INDICATION
 916                          * primitive with cause "U frame with incorrect
 917                          * parameters" is sent to the mobile management entity.
 918                          */
 919                         LOGP(DLAPDM, LOGL_NOTICE,
 920                                 "U frame iwth incorrect parameters ");
 921                         msgb_free(msg);
 922                         rsl_rll_error(RLL_CAUSE_UFRM_INC_PARAM, mctx);
 923                         return -EIO;
 924                 }
 925                 msgb_free(msg);
 926                 switch (dl->state) {
 927                 case LAPDm_STATE_IDLE:
 928                         LOGP(DLAPDM, LOGL_INFO, "DISC in idle state\n");
 929                         /* send DM with F=P */
 930                         return lapdm_send_dm(mctx);
 931                 case LAPDm_STATE_SABM_SENT:
 932                         LOGP(DLAPDM, LOGL_INFO, "DISC in SABM state\n");
 933                         /* 5.4.6.2 send DM with F=P */
 934                         lapdm_send_dm(mctx);
 935                         /* reset Timer T200 */
 936                         bsc_del_timer(&dl->t200);
 937                         return send_rll_simple(RSL_MT_REL_IND, mctx);
 938                 case LAPDm_STATE_MF_EST:
 939                 case LAPDm_STATE_TIMER_RECOV:
 940                         LOGP(DLAPDM, LOGL_INFO, "DISC in est state\n");
 941                         break;
 942                 case LAPDm_STATE_DISC_SENT:
 943                         LOGP(DLAPDM, LOGL_INFO, "DISC in disc state\n");
 944                         rsl_msg = RSL_MT_REL_CONF;
 945                         break;
 946                 default:
 947                         lapdm_send_ua(mctx, length, msg->l2h + 3);
 948                         return 0;
 949                 }
 950                 /* send UA response */
 951                 lapdm_send_ua(mctx, length, msg->l2h + 3);
 952                 /* reset Timer T200 */
 953                 bsc_del_timer(&dl->t200);
 954                 /* enter idle state */
 955                 lapdm_dl_newstate(dl, LAPDm_STATE_IDLE);
 956                 /* send notification to L3 */
 957                 rc = send_rll_simple(rsl_msg, mctx);
 958                 break;
 959         case LAPDm_U_UA:
 960                 LOGP(DLAPDM, LOGL_INFO, "UA received\n");
 961                 /* G.2.2 Wrong value of the C/R bit */
 962                 if (LAPDm_ADDR_CR(mctx->addr) == CR_BS2MS_CMD) {
 963                         LOGP(DLAPDM, LOGL_NOTICE, "UA indicates command "
 964                                 "error\n");
 965                         msgb_free(msg);
 966                         rsl_rll_error(RLL_CAUSE_FRM_UNIMPL, mctx);
 967                         return -EINVAL;
 968                 }
 969
 970                 length = msg->l2h[2] >> 2;
 971                 /* G.4.5 If UA is received with L>N201 or with M bit
 972                  * set, AN MDL-ERROR-INDICATION is sent to MM.
 973                  */
 974                 if ((msg->l2h[2] & LAPDm_MORE) || length + 3 > mctx->n201) {
 975                         LOGP(DLAPDM, LOGL_NOTICE, "UA too large error\n");
 976                         msgb_free(msg);
 977                         rsl_rll_error(RLL_CAUSE_UFRM_INC_PARAM, mctx);
 978                         return -EIO;
 979                 }
 980
 981                 if (!LAPDm_CTRL_PF_BIT(mctx->ctrl)) {
 982                         /* 5.4.1.2 A UA response with the F bit set to "0"
 983                          * shall be ignored.
 984                          */
 985                         LOGP(DLAPDM, LOGL_INFO, "F=0 (discarding)\n");
 986                         msgb_free(msg);
 987                         return 0;
 988                 }
 989                 switch (dl->state) {
 990                 case LAPDm_STATE_SABM_SENT:
 991                         break;
 992                 case LAPDm_STATE_MF_EST:
 993                 case LAPDm_STATE_TIMER_RECOV:
 994                         LOGP(DLAPDM, LOGL_INFO, "unsolicited UA response! "
 995                                 "(discarding)\n");
 996                         rsl_rll_error(RLL_CAUSE_UNSOL_UA_RESP, mctx);
 997                         msgb_free(msg);
 998                         return 0;
 999                 case LAPDm_STATE_DISC_SENT:
1000                         LOGP(DLAPDM, LOGL_INFO, "UA in disconnect state\n");
1001                         /* reset Timer T200 */
1002                         bsc_del_timer(&dl->t200);
1003                         /* go to idle state */
1004                         lapdm_dl_newstate(dl, LAPDm_STATE_IDLE);
1005                         rc = send_rll_simple(RSL_MT_REL_CONF, mctx);
1006                         msgb_free(msg);
1007                         return 0;
1008                 case LAPDm_STATE_IDLE:
1009                         /* 5.4.5 all other frame types shall be discarded */
1010                 default:
1011                         LOGP(DLAPDM, LOGL_INFO, "unsolicited UA response! "
1012                                 "(discarding)\n");
1013                         msgb_free(msg);
1014                         return 0;
1015                 }
1016                 LOGP(DLAPDM, LOGL_INFO, "UA in SABM state\n");
1017                 /* reset Timer T200 */
1018                 bsc_del_timer(&dl->t200);
1019                 /* compare UA with SABME if contention resolution is applied */
1020                 if (dl->tx_hist[0][2] >> 2) {
1021                         rc = check_length_ind(mctx, msg->l2h[2]);
1022                         if (rc < 0) {
1023                                 rc = send_rll_simple(RSL_MT_REL_IND, mctx);
1024                                 msgb_free(msg);
1025                                 /* go to idle state */
1026                                 lapdm_dl_newstate(dl, LAPDm_STATE_IDLE);
1027                                 return 0;
1028                         }
1029                         length = msg->l2h[2] >> 2;
1030                         if (length != (dl->tx_hist[0][2] >> 2)
1031                          || !!memcmp(dl->tx_hist[0] + 3, msg->l2h + 3,
1032                                         length)) {
1033                                 LOGP(DLAPDM, LOGL_INFO, "**** UA response "
1034                                         "mismatches ****\n");
1035                                 rc = send_rll_simple(RSL_MT_REL_IND, mctx);
1036                                 msgb_free(msg);
1037                                 /* go to idle state */
1038                                 lapdm_dl_newstate(dl, LAPDm_STATE_IDLE);
1039                                 return 0;
1040                         }
1041                 }
1042                 /* set Vs, Vr and Va to 0 */
1043                 dl->V_send = dl->V_recv = dl->V_ack = 0;
1044                 /* clear tx_hist */
1045                 dl->tx_length[0] = 0;
1046                 /* enter multiple-frame-established state */
1047                 lapdm_dl_newstate(dl, LAPDm_STATE_MF_EST);
1048                 /* send outstanding frames, if any (resume / reconnect) */
1049                 rslms_send_i(mctx);
1050                 /* send notification to L3 */
1051                 rc = send_rll_simple(RSL_MT_EST_CONF, mctx);
1052                 msgb_free(msg);
1053                 break;
1054         default:
1055                 /* G.3.1 */
1056                 LOGP(DLAPDM, LOGL_NOTICE, "Unnumbered frame not allowed.\n");
1057                 msgb_free(msg);
1058                 rsl_rll_error(RLL_CAUSE_FRM_UNIMPL, mctx);
1059                 return -EINVAL;
1060         }
1061         return rc;
1062 }
1063
1064 /* Receive a LAPDm S (Supervisory) message from L1 */
1065 static int lapdm_rx_s(struct msgb *msg, struct lapdm_msg_ctx *mctx)
1066 {
1067         struct lapdm_datalink *dl = mctx->dl;
1068         uint8_t length;
1069
1070         length = msg->l2h[2] >> 2;
1071         if (length > 0 || msg->l2h[2] & 0x02) {
1072                 /* G.4.3 If a supervisory frame is received with L>0 or
1073                  * with the M bit set to "1", an MDL-ERROR-INDICATION
1074                  * primitive with cause "S frame with incorrect
1075                  * parameters" is sent to the mobile management entity. */
1076                 LOGP(DLAPDM, LOGL_NOTICE,
1077                                 "S frame with incorrect parameters\n");
1078                 msgb_free(msg);
1079                 rsl_rll_error(RLL_CAUSE_SFRM_INC_PARAM, mctx);
1080                 return -EIO;
1081         }
1082         /* 5.4.2.2: Inidcate error on supervisory reponse F=1 */
1083         if (LAPDm_ADDR_CR(mctx->addr) == CR_BS2MS_RESP
1084          && LAPDm_CTRL_PF_BIT(mctx->ctrl)) {
1085                 LOGP(DLAPDM, LOGL_NOTICE, "S frame response with F=1 error\n");
1086                 rsl_rll_error(RLL_CAUSE_UNSOL_SPRV_RESP, mctx);
1087         }
1088
1089         switch (dl->state) {
1090         case LAPDm_STATE_IDLE:
1091                 /* if P=1, respond DM with F=1 (5.2.2) */
1092                 /* 5.4.5 all other frame types shall be discarded */
1093                 if (LAPDm_CTRL_PF_BIT(mctx->ctrl))
1094                         lapdm_send_dm(mctx); /* F=P */
1095                 /* fall though */
1096         case LAPDm_STATE_SABM_SENT:
1097         case LAPDm_STATE_DISC_SENT:
1098                 LOGP(DLAPDM, LOGL_NOTICE, "S frame ignored in this state\n");
1099                 msgb_free(msg);
1100                 return 0;
1101         }
1102         switch (LAPDm_CTRL_S_BITS(mctx->ctrl)) {
1103         case LAPDm_S_RR:
1104                 LOGP(DLAPDM, LOGL_INFO, "RR received\n");
1105                 /* 5.5.3.1: Acknowlege all tx frames up the the N(R)-1 */
1106                 lapdm_acknowledge(mctx);
1107
1108                 /* 5.5.3.2 */
1109                 if (LAPDm_ADDR_CR(mctx->addr) == CR_BS2MS_CMD
1110                  && LAPDm_CTRL_PF_BIT(mctx->ctrl)) {
1111                         if (!dl->own_busy && !dl->seq_err_cond) {
1112                                 LOGP(DLAPDM, LOGL_NOTICE, "RR frame command "
1113                                         "with polling bit set and we are not "
1114                                         "busy, so we reply with RR frame\n");
1115                                 lapdm_send_rr(mctx, 1);
1116                                 /* NOTE: In case of sequence error condition,
1117                                  * the REJ frame has been transmitted when
1118                                  * entering the condition, so it has not be
1119                                  * done here
1120                                  */
1121                         } else if (dl->own_busy) {
1122                                 LOGP(DLAPDM, LOGL_NOTICE, "RR frame command "
1123                                         "with polling bit set and we are busy, "
1124                                         "so we reply with RR frame\n");
1125                                 lapdm_send_rnr(mctx, 1);
1126                         }
1127                 }
1128                 /* Send message, if possible due to acknowledged data */
1129                 rslms_send_i(mctx);
1130
1131                 break;
1132         case LAPDm_S_RNR:
1133                 LOGP(DLAPDM, LOGL_INFO, "RNR received\n");
1134                 /* 5.5.3.1: Acknowlege all tx frames up the the N(R)-1 */
1135                 lapdm_acknowledge(mctx);
1136
1137                 /* 5.5.5 */
1138                 /* Set peer receiver busy condition */
1139                 dl->peer_busy = 1;
1140
1141                 if (LAPDm_CTRL_PF_BIT(mctx->ctrl)) {
1142                         if (LAPDm_ADDR_CR(mctx->addr) == CR_BS2MS_CMD) {
1143                                 if (!dl->own_busy) {
1144                                         LOGP(DLAPDM, LOGL_INFO, "RNR poll "
1145                                                 "command and we are not busy, "
1146                                                 "so we reply with RR final "
1147                                                 "response\n");
1148                                         /* Send RR with F=1 */
1149                                         lapdm_send_rr(mctx, 1);
1150                                 } else {
1151                                         LOGP(DLAPDM, LOGL_INFO, "RNR poll "
1152                                                 "command and we are busy, so "
1153                                                 "we reply with RNR final "
1154                                                 "response\n");
1155                                         /* Send RNR with F=1 */
1156                                         lapdm_send_rnr(mctx, 1);
1157                                 }
1158                         } else if (dl->state == LAPDm_STATE_TIMER_RECOV) {
1159                                 LOGP(DLAPDM, LOGL_INFO, "RNR poll response "
1160                                         "and we in timer recovery state, so "
1161                                         "we leave that state\n");
1162                                 /* Clear timer recovery condition */
1163                                 lapdm_dl_newstate(dl, LAPDm_STATE_MF_EST);
1164                                 /* V(S) to the N(R) in the RNR frame */
1165                                 dl->V_send = LAPDm_CTRL_Nr(mctx->ctrl);
1166                         }
1167                 } else
1168                         LOGP(DLAPDM, LOGL_INFO, "RNR not polling/final state "
1169                                 "received\n");
1170
1171                 /* Send message, if possible due to acknowledged data */
1172                 rslms_send_i(mctx);
1173
1174                 break;
1175         case LAPDm_S_REJ:
1176                 LOGP(DLAPDM, LOGL_INFO, "REJ received\n");
1177                 /* 5.5.3.1: Acknowlege all tx frames up the the N(R)-1 */
1178                 lapdm_acknowledge(mctx);
1179
1180                 /* 5.5.4.1 */
1181                 if (dl->state != LAPDm_STATE_TIMER_RECOV) {
1182                         /* Clear an existing peer receiver busy condition */
1183                         dl->peer_busy = 0;
1184                         /* V(S) and V(A) to the N(R) in the REJ frame */
1185                         dl->V_send = dl->V_ack = LAPDm_CTRL_Nr(mctx->ctrl);
1186                         /* reset Timer T200 */
1187                         bsc_del_timer(&dl->t200);
1188                         /* 5.5.3.2 */
1189                         if (LAPDm_ADDR_CR(mctx->addr) == CR_BS2MS_CMD
1190                          && LAPDm_CTRL_PF_BIT(mctx->ctrl)) {
1191                                 if (!dl->own_busy && !dl->seq_err_cond) {
1192                                         LOGP(DLAPDM, LOGL_INFO, "REJ poll "
1193                                                 "command not in timer recovery "
1194                                                 "state and not in own busy "
1195                                                 "condition received, so we "
1196                                                 "respond with RR final "
1197                                                 "response\n");
1198                                         lapdm_send_rr(mctx, 1);
1199                                         /* NOTE: In case of sequence error
1200                                          * condition, the REJ frame has been
1201                                          * transmitted when entering the
1202                                          * condition, so it has not be done
1203                                          * here
1204                                          */
1205                                 } else if (dl->own_busy) {
1206                                         LOGP(DLAPDM, LOGL_INFO, "REJ poll "
1207                                                 "command not in timer recovery "
1208                                                 "state and in own busy "
1209                                                 "condition received, so we "
1210                                                 "respond with RNR final "
1211                                                 "response\n");
1212                                         lapdm_send_rnr(mctx, 1);
1213                                 }
1214                         } else
1215                                 LOGP(DLAPDM, LOGL_INFO, "REJ response or not "
1216                                         "polling command not in timer recovery "
1217                                         "state received\n");
1218                         /* send MDL ERROR INIDCATION to L3 */
1219                         if (LAPDm_ADDR_CR(mctx->addr) == CR_BS2MS_RESP
1220                          && LAPDm_CTRL_PF_BIT(mctx->ctrl)) {
1221                                 rsl_rll_error(RLL_CAUSE_UNSOL_SPRV_RESP, mctx);
1222                         }
1223
1224                 } else if (LAPDm_ADDR_CR(mctx->addr) == CR_BS2MS_RESP
1225                         && LAPDm_CTRL_PF_BIT(mctx->ctrl)) {
1226                         LOGP(DLAPDM, LOGL_INFO, "REJ poll response in timer "
1227                                 "recovery state received\n");
1228                         /* Clear an existing peer receiver busy condition */
1229                         dl->peer_busy = 0;
1230                         /* Clear timer recovery condition */
1231                         lapdm_dl_newstate(dl, LAPDm_STATE_MF_EST);
1232                         /* V(S) and V(A) to the N(R) in the REJ frame */
1233                         dl->V_send = dl->V_ack = LAPDm_CTRL_Nr(mctx->ctrl);
1234                         /* reset Timer T200 */
1235                         bsc_del_timer(&dl->t200);
1236                 } else {
1237                         /* Clear an existing peer receiver busy condition */
1238                         dl->peer_busy = 0;
1239                         /* V(S) and V(A) to the N(R) in the REJ frame */
1240                         dl->V_send = dl->V_ack = LAPDm_CTRL_Nr(mctx->ctrl);
1241                         /* 5.5.3.2 */
1242                         if (LAPDm_ADDR_CR(mctx->addr) == CR_BS2MS_CMD
1243                          && LAPDm_CTRL_PF_BIT(mctx->ctrl)) {
1244                                 if (!dl->own_busy && !dl->seq_err_cond) {
1245                                         LOGP(DLAPDM, LOGL_INFO, "REJ poll "
1246                                                 "command in timer recovery "
1247                                                 "state and not in own busy "
1248                                                 "condition received, so we "
1249                                                 "respond with RR final "
1250                                                 "response\n");
1251                                         lapdm_send_rr(mctx, 1);
1252                                         /* NOTE: In case of sequence error
1253                                          * condition, the REJ frame has been
1254                                          * transmitted when entering the
1255                                          * condition, so it has not be done
1256                                          * here
1257                                          */
1258                                 } else if (dl->own_busy) {
1259                                         LOGP(DLAPDM, LOGL_INFO, "REJ poll "
1260                                                 "command in timer recovery "
1261                                                 "state and in own busy "
1262                                                 "condition received, so we "
1263                                                 "respond with RNR final "
1264                                                 "response\n");
1265                                         lapdm_send_rnr(mctx, 1);
1266                                 }
1267                         } else
1268                                 LOGP(DLAPDM, LOGL_INFO, "REJ response or not "
1269                                         "polling command in timer recovery "
1270                                         "state received\n");
1271                 }
1272
1273                 /* FIXME: 5.5.4.2 2) */
1274
1275                 /* Send message, if possible due to acknowledged data */
1276                 rslms_send_i(mctx);
1277
1278                 break;
1279         default:
1280                 /* G.3.1 */
1281                 LOGP(DLAPDM, LOGL_NOTICE, "Supervisory frame not allowed.\n");
1282                 msgb_free(msg);
1283                 rsl_rll_error(RLL_CAUSE_FRM_UNIMPL, mctx);
1284                 return -EINVAL;
1285         }
1286         msgb_free(msg);
1287         return 0;
1288 }
1289
1290 /* Receive a LAPDm I (Information) message from L1 */
1291 static int lapdm_rx_i(struct msgb *msg, struct lapdm_msg_ctx *mctx)
1292 {
1293         struct lapdm_datalink *dl = mctx->dl;
1294         //uint8_t nr = LAPDm_CTRL_Nr(mctx->ctrl);
1295         uint8_t ns = LAPDm_CTRL_I_Ns(mctx->ctrl);
1296         uint8_t length;
1297         int rc;
1298
1299         LOGP(DLAPDM, LOGL_NOTICE, "I received\n");
1300
1301         /* G.2.2 Wrong value of the C/R bit */
1302         if (LAPDm_ADDR_CR(mctx->addr) == CR_BS2MS_RESP) {
1303                 LOGP(DLAPDM, LOGL_NOTICE, "I frame response not allowed\n");
1304                 msgb_free(msg);
1305                 rsl_rll_error(RLL_CAUSE_FRM_UNIMPL, mctx);
1306                 return -EINVAL;
1307         }
1308
1309         length = msg->l2h[2] >> 2;
1310         if (length == 0 || length + 3 > mctx->n201) {
1311                 /* G.4.2 If the length indicator of an I frame is set
1312                  * to a numerical value L>N201 or L=0, an MDL-ERROR-INDICATION
1313                  * primitive with cause "I frame with incorrect length"
1314                  * is sent to the mobile management entity. */
1315                 LOGP(DLAPDM, LOGL_NOTICE, "I frame length not allowed\n");
1316                 msgb_free(msg);
1317                 rsl_rll_error(RLL_CAUSE_IFRM_INC_LEN, mctx);
1318                 return -EIO;
1319         }
1320
1321         /* G.4.2 If the numerical value of L is L<N201 and the M
1322          * bit is set to "1", then an MDL-ERROR-INDICATION primitive with
1323          * cause "I frame with incorrect use of M bit" is sent to the
1324          * mobile management entity. */
1325         if ((msg->l2h[2] & LAPDm_MORE) && length + 3 < mctx->n201) {
1326                 LOGP(DLAPDM, LOGL_NOTICE, "I frame with M bit too short\n");
1327                 msgb_free(msg);
1328                 rsl_rll_error(RLL_CAUSE_IFRM_INC_MBITS, mctx);
1329                 return -EIO;
1330         }
1331
1332         switch (dl->state) {
1333         case LAPDm_STATE_IDLE:
1334                 /* if P=1, respond DM with F=1 (5.2.2) */
1335                 /* 5.4.5 all other frame types shall be discarded */
1336                 if (LAPDm_CTRL_PF_BIT(mctx->ctrl))
1337                         lapdm_send_dm(mctx); /* F=P */
1338                 /* fall though */
1339         case LAPDm_STATE_SABM_SENT:
1340         case LAPDm_STATE_DISC_SENT:
1341                 LOGP(DLAPDM, LOGL_NOTICE, "I frame ignored in this state\n");
1342                 msgb_free(msg);
1343                 return 0;
1344         }
1345
1346         /* 5.7.1: N(s) sequence error */
1347         if (ns != dl->V_recv) {
1348                 LOGP(DLAPDM, LOGL_NOTICE, "N(S) sequence error: N(S)=%u, "
1349                      "V(R)=%u\n", ns, dl->V_recv);
1350                 /* discard data */
1351                 msgb_free(msg);
1352                 if (!dl->seq_err_cond) {
1353                         /* FIXME: help me understand what exactly todo here
1354                         dl->seq_err_cond = 1;
1355                         */
1356                         lapdm_send_rej(mctx, LAPDm_CTRL_PF_BIT(mctx->ctrl));
1357                 } else {
1358                 }
1359                 return -EIO;
1360         }
1361         dl->seq_err_cond = 0;
1362
1363         /* Increment receiver state */
1364         dl->V_recv = inc_mod8(dl->V_recv);
1365         LOGP(DLAPDM, LOGL_NOTICE, "incrementing V(R) to %u\n", dl->V_recv);
1366
1367         /* 5.5.3.1: Acknowlege all transmitted frames up the the N(R)-1 */
1368         lapdm_acknowledge(mctx); /* V(A) is also set here */
1369
1370         /* Only if we are not in own receiver busy condition */
1371         if (!dl->own_busy) {
1372                 /* if the frame carries a complete segment */
1373                 if (!(msg->l2h[2] & LAPDm_MORE)
1374                  && !dl->rcv_buffer) {
1375                         LOGP(DLAPDM, LOGL_INFO, "message in single I frame\n");
1376                         /* send a DATA INDICATION to L3 */
1377                         msg->l3h = msg->l2h + 3;
1378                         msgb_pull_l2h(msg);
1379                         rc = send_rslms_rll_l3(RSL_MT_DATA_IND, mctx, msg);
1380                 } else {
1381                         /* create rcv_buffer */
1382                         if (!dl->rcv_buffer) {
1383                                 LOGP(DLAPDM, LOGL_INFO, "message in multiple I "
1384                                         "frames (first message)\n");
1385                                 dl->rcv_buffer = msgb_alloc_headroom(200+56, 56,
1386                                                                 "LAPDm RX");
1387                                 dl->rcv_buffer->l3h = dl->rcv_buffer->data;
1388                         }
1389                         /* concat. rcv_buffer */
1390                         if (msgb_l3len(dl->rcv_buffer) + length > 200) {
1391                                 LOGP(DLAPDM, LOGL_NOTICE, "Received frame "
1392                                         "overflow!\n");
1393                         } else {
1394                                 memcpy(msgb_put(dl->rcv_buffer, length),
1395                                         msg->l2h + 3, length);
1396                         }
1397                         /* if the last segment was received */
1398                         if (!(msg->l2h[2] & LAPDm_MORE)) {
1399                                 LOGP(DLAPDM, LOGL_INFO, "message in multiple I "
1400                                         "frames (next message)\n");
1401                                 rc = send_rslms_rll_l3(RSL_MT_DATA_IND, mctx,
1402                                         dl->rcv_buffer);
1403                                 dl->rcv_buffer = NULL;
1404                         } else
1405                                 LOGP(DLAPDM, LOGL_INFO, "message in multiple I "
1406                                         "frames (last message)\n");
1407                         msgb_free(msg);
1408
1409                 }
1410         } else
1411                 LOGP(DLAPDM, LOGL_INFO, "I frame ignored during own receiver "
1412                         "busy condition\n");
1413
1414         /* Check for P bit */
1415         if (LAPDm_CTRL_PF_BIT(mctx->ctrl)) {
1416                 /* 5.5.2.1 */
1417                 /* check if we are not in own receiver busy */
1418                 if (!dl->own_busy) {
1419                         LOGP(DLAPDM, LOGL_INFO, "we are not busy, send RR\n");
1420                         /* Send RR with F=1 */
1421                         rc = lapdm_send_rr(mctx, 1);
1422                 } else {
1423                         LOGP(DLAPDM, LOGL_INFO, "we are busy, send RNR\n");
1424                         /* Send RNR with F=1 */
1425                         rc = lapdm_send_rnr(mctx, 1);
1426                 }
1427         } else {
1428                 /* 5.5.2.2 */
1429                 /* check if we are not in own receiver busy */
1430                 if (!dl->own_busy) {
1431                         /* NOTE: V(R) is already set above */
1432                         rc = rslms_send_i(mctx);
1433                         if (rc) {
1434                                 LOGP(DLAPDM, LOGL_INFO, "we are not busy and "
1435                                         "have no pending data, send RR\n");
1436                                 /* Send RR with F=0 */
1437                                 return lapdm_send_rr(mctx, 0);
1438                         }
1439                 } else {
1440                         LOGP(DLAPDM, LOGL_INFO, "we are busy, send RNR\n");
1441                         /* Send RNR with F=0 */
1442                         rc = lapdm_send_rnr(mctx, 0);
1443                 }
1444         }
1445
1446         /* Send message, if possible due to acknowledged data */
1447         rslms_send_i(mctx);
1448
1449         return rc;
1450 }
1451
1452 /* Receive a LAPDm message from L1 */
1453 static int lapdm_ph_data_ind(struct msgb *msg, struct lapdm_msg_ctx *mctx)
1454 {
1455         int rc;
1456
1457         /* G.2.3 EA bit set to "0" is not allowed in GSM */
1458         if (!LAPDm_ADDR_EA(mctx->addr)) {
1459                 LOGP(DLAPDM, LOGL_NOTICE, "EA bit 0 is not allowed in GSM\n");
1460                 msgb_free(msg);
1461                 rsl_rll_error(RLL_CAUSE_FRM_UNIMPL, mctx);
1462                 return -EINVAL;
1463         }
1464
1465         if (LAPDm_CTRL_is_U(mctx->ctrl))
1466                 rc = lapdm_rx_u(msg, mctx);
1467         else if (LAPDm_CTRL_is_S(mctx->ctrl))
1468                 rc = lapdm_rx_s(msg, mctx);
1469         else if (LAPDm_CTRL_is_I(mctx->ctrl))
1470                 rc = lapdm_rx_i(msg, mctx);
1471         else {
1472                 LOGP(DLAPDM, LOGL_NOTICE, "unknown LAPDm format\n");
1473                 msgb_free(msg);
1474                 rc = -EINVAL;
1475         }
1476         return rc;
1477 }
1478
1479 /* input into layer2 (from layer 1) */
1480 int l2_ph_data_ind(struct msgb *msg, struct lapdm_entity *le, struct l1ctl_info_dl *l1i)
1481 {
1482         uint8_t cbits = l1i->chan_nr >> 3;
1483         uint8_t sapi = l1i->link_id & 7;
1484         struct lapdm_msg_ctx mctx;
1485         int rc = 0;
1486
1487         /* when we reach here, we have a msgb with l2h pointing to the raw
1488          * 23byte mac block. The l1h has already been purged. */
1489
1490         mctx.dl = datalink_for_sapi(le, sapi);
1491         mctx.chan_nr = l1i->chan_nr;
1492         mctx.link_id = l1i->link_id;
1493         mctx.addr = mctx.ctrl = 0;
1494
1495         /* G.2.1 No action schall be taken on frames containing an unallocated
1496          * SAPI.
1497          */
1498         if (!mctx.dl) {
1499                 LOGP(DLAPDM, LOGL_NOTICE, "Received frame for unsupported "
1500                         "SAPI %d!\n", sapi);
1501                 return -EINVAL;
1502                 msgb_free(msg);
1503                 return -EIO;
1504         }
1505
1506         /* check for L1 chan_nr/link_id and determine LAPDm hdr format */
1507         if (cbits == 0x10 || cbits == 0x12) {
1508                 /* Format Bbis is used on BCCH and CCCH(PCH, NCH and AGCH) */
1509                 mctx.lapdm_fmt = LAPDm_FMT_Bbis;
1510                 mctx.n201 = N201_Bbis;
1511         } else {
1512                 if (mctx.link_id & 0x40) {
1513                         /* It was received from network on SACCH, thus
1514                          * lapdm_fmt must be B4 */
1515                         mctx.lapdm_fmt = LAPDm_FMT_B4;
1516                         mctx.n201 = N201_B4;
1517                         LOGP(DLAPDM, LOGL_INFO, "fmt=B4\n");
1518                         /* SACCH frames have a two-byte L1 header that
1519                          * OsmocomBB L1 doesn't strip */
1520                         mctx.tx_power_ind = msg->l2h[0] & 0x1f;
1521                         mctx.ta_ind = msg->l2h[1];
1522                         msgb_pull(msg, 2);
1523                         msg->l2h += 2;
1524                 } else {
1525                         mctx.lapdm_fmt = LAPDm_FMT_B;
1526                         LOGP(DLAPDM, LOGL_INFO, "fmt=B\n");
1527                         mctx.n201 = 23; // FIXME: select correct size by chan.
1528                 }
1529         }
1530
1531         switch (mctx.lapdm_fmt) {
1532         case LAPDm_FMT_A:
1533         case LAPDm_FMT_B:
1534         case LAPDm_FMT_B4:
1535                 mctx.addr = msg->l2h[0];
1536                 if (!(mctx.addr & 0x01)) {
1537                         LOGP(DLAPDM, LOGL_ERROR, "we don't support "
1538                                 "multibyte addresses (discarding)\n");
1539                         msgb_free(msg);
1540                         return -EINVAL;
1541                 }
1542                 mctx.ctrl = msg->l2h[1];
1543                 /* obtain SAPI from address field */
1544                 mctx.link_id |= LAPDm_ADDR_SAPI(mctx.addr);
1545                 rc = lapdm_ph_data_ind(msg, &mctx);
1546                 break;
1547         case LAPDm_FMT_Bter:
1548                 /* FIXME */
1549                 msgb_free(msg);
1550                 break;
1551         case LAPDm_FMT_Bbis:
1552                 /* directly pass up to layer3 */
1553                 LOGP(DLAPDM, LOGL_INFO, "fmt=Bbis UI\n");
1554                 msg->l3h = msg->l2h;
1555                 msgb_pull_l2h(msg);
1556                 rc = send_rslms_rll_l3(RSL_MT_UNIT_DATA_IND, &mctx, msg);
1557                 break;
1558         default:
1559                 msgb_free(msg);
1560         }
1561
1562         return rc;
1563 }
1564
1565 /* L3 -> L2 / RSLMS -> LAPDm */
1566
1567 /* L3 requests establishment of data link */
1568 static int rslms_rx_rll_est_req(struct msgb *msg, struct lapdm_datalink *dl)
1569 {
1570         struct abis_rsl_rll_hdr *rllh = msgb_l2(msg);
1571         uint8_t chan_nr = rllh->chan_nr;
1572         uint8_t link_id = rllh->link_id;
1573         uint8_t sapi = rllh->link_id & 7;
1574         struct tlv_parsed tv;
1575         uint8_t length;
1576         uint8_t n201 = 23; //FIXME
1577
1578         /* Set chan_nr and link_id for established connection */
1579         memset(&dl->mctx, 0, sizeof(dl->mctx));
1580         dl->mctx.dl = dl;
1581         dl->mctx.n201 = n201;
1582         dl->mctx.chan_nr = chan_nr;
1583         dl->mctx.link_id = link_id;
1584
1585         rsl_tlv_parse(&tv, rllh->data, msgb_l2len(msg)-sizeof(*rllh));
1586         if (TLVP_PRESENT(&tv, RSL_IE_L3_INFO)) {
1587                 /* contention resolution establishment procedure */
1588                 if (sapi != 0) {
1589                         /* According to clause 6, the contention resolution
1590                          * procedure is only permitted with SAPI value 0 */
1591                         LOGP(DLAPDM, LOGL_ERROR, "SAPI != 0 but contention"
1592                                 "resolution (discarding)\n");
1593                         msgb_free(msg);
1594                         return send_rll_simple(RSL_MT_REL_IND, &dl->mctx);
1595                 }
1596                 /* transmit a SABM command with the P bit set to "1". The SABM
1597                  * command shall contain the layer 3 message unit */
1598                 length = TLVP_LEN(&tv, RSL_IE_L3_INFO);
1599                 LOGP(DLAPDM, LOGL_INFO, "perform establishment with content "
1600                         "(SAMB)\n");
1601         } else {
1602                 /* normal establishment procedure */
1603                 length = 0;
1604                 LOGP(DLAPDM, LOGL_INFO, "perform normal establishm. (SAMB)\n");
1605         }
1606
1607         /* check if the layer3 message length exceeds N201 */
1608         if (length + 3 > 21) { /* FIXME: do we know the channel N201? */
1609                 LOGP(DLAPDM, LOGL_ERROR, "frame too large: %d > N201(%d) "
1610                         "(discarding)\n", length + 3, 21);
1611                 msgb_free(msg);
1612                 return send_rll_simple(RSL_MT_REL_IND, &dl->mctx);
1613         }
1614
1615         /* Flush send-queue */
1616         /* Clear send-buffer */
1617         lapdm_dl_flush_send(dl);
1618
1619         /* Discard partly received L3 message */
1620         if (dl->rcv_buffer) {
1621                 msgb_free(dl->rcv_buffer);
1622                 dl->rcv_buffer = NULL;
1623         }
1624
1625         /* Remove RLL header from msgb */
1626         msgb_pull_l2h(msg);
1627
1628         /* Push LAPDm header on msgb */
1629         msg->l2h = msgb_push(msg, 3);
1630         msg->l2h[0] = LAPDm_ADDR(LAPDm_LPD_NORMAL, sapi, CR_MS2BS_CMD);
1631         msg->l2h[1] = LAPDm_CTRL_U(LAPDm_U_SABM, 1);
1632         msg->l2h[2] = LAPDm_LEN(length);
1633         /* Transmit-buffer carries exactly one segment */
1634         memcpy(dl->tx_hist[0], msg->l2h, 3 + length);
1635         dl->tx_length[0] = 3 + length;
1636         /* set Vs to 0, because it is used as index when resending SAMB */
1637         dl->V_send = 0;
1638
1639         /* Set states */
1640         dl->own_busy = dl->peer_busy = 0;
1641         dl->retrans_ctr = 0;
1642         lapdm_dl_newstate(dl, LAPDm_STATE_SABM_SENT);
1643
1644         /* Tramsmit and start T200 */
1645         bsc_schedule_timer(&dl->t200, T200);
1646         return tx_ph_data_enqueue(dl, msg, chan_nr, link_id, n201);
1647 }
1648
1649 /* L3 requests transfer of unnumbered information */
1650 static int rslms_rx_rll_udata_req(struct msgb *msg, struct lapdm_datalink *dl)
1651 {
1652         struct abis_rsl_rll_hdr *rllh = msgb_l2(msg);
1653         uint8_t chan_nr = rllh->chan_nr;
1654         uint8_t link_id = rllh->link_id;
1655         uint8_t sapi = link_id & 7;
1656         struct tlv_parsed tv;
1657         int length;
1658         uint8_t n201 = 23; //FIXME
1659         uint8_t ta = 0, tx_power = 0;
1660
1661         /* check if the layer3 message length exceeds N201 */
1662
1663         rsl_tlv_parse(&tv, rllh->data, msgb_l2len(msg)-sizeof(*rllh));
1664
1665         if (TLVP_PRESENT(&tv, RSL_IE_ACCESS_DELAY)) {
1666                 ta = *TLVP_VAL(&tv, RSL_IE_ACCESS_DELAY);
1667         }
1668         if (TLVP_PRESENT(&tv, RSL_IE_MS_POWER)) {
1669                 tx_power = *TLVP_VAL(&tv, RSL_IE_MS_POWER);
1670         }
1671         if (!TLVP_PRESENT(&tv, RSL_IE_L3_INFO)) {
1672                 LOGP(DLAPDM, LOGL_ERROR, "unit data request without message "
1673                         "error\n");
1674                 msgb_free(msg);
1675                 return -EINVAL;
1676         }
1677         length = TLVP_LEN(&tv, RSL_IE_L3_INFO);
1678         /* check if the layer3 message length exceeds N201 */
1679         if (length + 5 > 23) { /* FIXME: do we know the channel N201? */
1680                 LOGP(DLAPDM, LOGL_ERROR, "frame too large: %d > N201(%d) "
1681                         "(discarding)\n", length + 5, 23);
1682                 msgb_free(msg);
1683                 return -EIO;
1684         }
1685
1686         LOGP(DLAPDM, LOGL_INFO, "sending unit data (tx_power=%d, ta=%d)\n",
1687                 tx_power, ta);
1688
1689         /* Remove RLL header from msgb */
1690         msgb_pull_l2h(msg);
1691
1692         /* Push L1 + LAPDm header on msgb */
1693         msg->l2h = msgb_push(msg, 2 + 3);
1694         msg->l2h[0] = tx_power;
1695         msg->l2h[1] = ta;
1696         msg->l2h[2] = LAPDm_ADDR(LAPDm_LPD_NORMAL, sapi, CR_MS2BS_CMD);
1697         msg->l2h[3] = LAPDm_CTRL_U(LAPDm_U_UI, 0);
1698         msg->l2h[4] = LAPDm_LEN(length);
1699         // FIXME: short L2 header support
1700
1701         /* Tramsmit */
1702         return tx_ph_data_enqueue(dl, msg, chan_nr, link_id, n201);
1703 }
1704
1705 /* L3 requests transfer of acknowledged information */
1706 static int rslms_rx_rll_data_req(struct msgb *msg, struct lapdm_datalink *dl)
1707 {
1708         struct abis_rsl_rll_hdr *rllh = msgb_l2(msg);
1709         struct tlv_parsed tv;
1710
1711         rsl_tlv_parse(&tv, rllh->data, msgb_l2len(msg)-sizeof(*rllh));
1712         if (!TLVP_PRESENT(&tv, RSL_IE_L3_INFO)) {
1713                 LOGP(DLAPDM, LOGL_ERROR, "data request without message "
1714                         "error\n");
1715                 msgb_free(msg);
1716                 return -EINVAL;
1717         }
1718
1719         LOGP(DLAPDM, LOGL_INFO, "writing message to send-queue\n");
1720
1721         /* Remove the RSL/RLL header */
1722         msgb_pull_l2h(msg);
1723
1724         /* Write data into the send queue */
1725         msgb_enqueue(&dl->send_queue, msg);
1726
1727         /* Send message, if possible */
1728         rslms_send_i(&dl->mctx);
1729         return 0;
1730 }
1731
1732 /* Send next I frame from queued/buffered data */
1733 static int rslms_send_i(struct lapdm_msg_ctx *mctx)
1734 {
1735         struct lapdm_datalink *dl = mctx->dl;
1736         uint8_t chan_nr = mctx->chan_nr;
1737         uint8_t link_id = mctx->link_id;
1738         uint8_t sapi = link_id & 7;
1739         int k = k_sapi[sapi];
1740         struct msgb *msg;
1741         int length, left;
1742         int rc = -1; /* we sent nothing */
1743
1744         next_frame:
1745
1746         if (dl->peer_busy) {
1747                 LOGP(DLAPDM, LOGL_INFO, "peer busy, not sending\n");
1748                 return rc;
1749         }
1750
1751         if (dl->state == LAPDm_STATE_TIMER_RECOV) {
1752                 LOGP(DLAPDM, LOGL_INFO, "timer recovery, not sending\n");
1753                 return rc;
1754         }
1755
1756         /* If the send state variable V(S) is equal to V(A) plus k
1757          * (where k is the maximum number of outstanding I frames - see
1758          * subclause 5.8.4), the data link layer entity shall not transmit any
1759          * new I frames, but shall retransmit an I frame as a result
1760          * of the error recovery procedures as described in subclauses 5.5.4 and
1761          * 5.5.7. */
1762         if (dl->V_send == add_mod8(dl->V_ack, k)) {
1763                 LOGP(DLAPDM, LOGL_INFO, "k frames outstanding, not sending "
1764                         "more (k=%u V(S)=%u V(A)=%u)\n", k, dl->V_send,
1765                         dl->V_ack);
1766                 return rc;
1767         }
1768
1769         /* if we have no tx_hist yet, we create it */
1770         if (!dl->tx_length[dl->V_send]) {
1771                 /* Get next message into send-buffer, if any */
1772                 if (!dl->send_buffer) {
1773                         next_message:
1774                         dl->send_out = 0;
1775                         dl->send_buffer = msgb_dequeue(&dl->send_queue);
1776                         /* No more data to be sent */
1777                         if (!dl->send_buffer)
1778                                 return rc;
1779                         LOGP(DLAPDM, LOGL_INFO, "get message from "
1780                                 "send-queue\n");
1781                 }
1782
1783                 /* How much is left in the send-buffer? */
1784                 left = msgb_l3len(dl->send_buffer) - dl->send_out;
1785                 /* Segment, if data exceeds N201 */
1786                 length = left;
1787                 if (length > mctx->n201 - 3)
1788                         length = mctx->n201 - 3;
1789 printf("msg-len %d sent %d left %d N201 %d length %d first byte %02x\n", msgb_l3len(dl->send_buffer), dl->send_out, left, mctx->n201, length, dl->send_buffer->l3h[0]);
1790                 /* If message in send-buffer is completely sent */
1791                 if (left == 0) {
1792                         msgb_free(dl->send_buffer);
1793                         dl->send_buffer = NULL;
1794                         goto next_message;
1795                 }
1796
1797                 LOGP(DLAPDM, LOGL_INFO, "send I frame %sV(S)=%d\n",
1798                         (left > length) ? "segment " : "", dl->V_send);
1799
1800                 /* Create I frame (segment) and transmit-buffer content */
1801                 msg = msgb_alloc_headroom(23+10, 10, "LAPDm I");
1802                 msg->l2h = msgb_put(msg, 3 + length);
1803                 msg->l2h[0] = LAPDm_ADDR(LAPDm_LPD_NORMAL, sapi, CR_MS2BS_CMD);
1804                 msg->l2h[1] = LAPDm_CTRL_I(dl->V_recv, dl->V_send, 0);
1805                 msg->l2h[2] = LAPDm_LEN(length);
1806                 if (left > length)
1807                         msg->l2h[2] |= LAPDm_MORE;
1808                 memcpy(msg->l2h + 3, dl->send_buffer->l3h + dl->send_out,
1809                         length);
1810                 memcpy(dl->tx_hist[dl->V_send], msg->l2h, 3 + length);
1811                 dl->tx_length[dl->V_send] = 3 + length;
1812                 /* Add length to track how much is already in the tx buffer */
1813                 dl->send_out += length;
1814         } else {
1815                 LOGP(DLAPDM, LOGL_INFO, "resend I frame from tx buffer "
1816                         "V(S)=%d\n", dl->V_send);
1817
1818                 /* Create I frame (segment) from tx_hist */
1819                 length = dl->tx_length[dl->V_send];
1820                 msg = msgb_alloc_headroom(23+10, 10, "LAPDm I");
1821                 msg->l2h = msgb_put(msg, length);
1822                 memcpy(msg->l2h, dl->tx_hist[dl->V_send], length);
1823                 msg->l2h[1] = LAPDm_CTRL_I(dl->V_recv, dl->V_send, 0);
1824         }
1825
1826         /* The value of the send state variable V(S) shall be incremented by 1
1827          * at the end of the transmission of the I frame */
1828         dl->V_send = inc_mod8(dl->V_send);
1829
1830         /* If timer T200 is not running at the time right before transmitting a
1831          * frame, when the PH-READY-TO-SEND primitive is received from the
1832          * physical layer., it shall be set. */
1833         if (!bsc_timer_pending(&dl->t200))
1834                 bsc_schedule_timer(&dl->t200, T200);
1835
1836         tx_ph_data_enqueue(dl, msg, chan_nr, link_id, mctx->n201);
1837
1838         rc = 0; /* we sent something */
1839         goto next_frame;
1840 }
1841
1842 /* L3 requests suspension of data link */
1843 static int rslms_rx_rll_susp_req(struct msgb *msg, struct lapdm_datalink *dl)
1844 {
1845         struct abis_rsl_rll_hdr *rllh = msgb_l2(msg);
1846         uint8_t sapi = rllh->link_id & 7;
1847
1848         if (sapi != 0) {
1849                 LOGP(DLAPDM, LOGL_ERROR, "SAPI != 0 while suspending\n");
1850                 msgb_free(msg);
1851                 return -EINVAL;
1852         }
1853
1854         LOGP(DLAPDM, LOGL_INFO, "perform suspension\n");
1855
1856         /* put back the send-buffer to the send-queue (first position) */
1857         if (dl->send_buffer) {
1858                 llist_add(&dl->send_buffer->list, &dl->send_queue);
1859                 dl->send_buffer = NULL;
1860         }
1861
1862         /* Clear transmit and send buffer, if any */
1863         lapdm_dl_flush_tx(dl);
1864         lapdm_dl_flush_send(dl);
1865
1866         msgb_free(msg);
1867
1868         return send_rll_simple(RSL_MT_SUSP_CONF, &dl->mctx);
1869 }
1870
1871 /* L3 requests resume of data link */
1872 static int rslms_rx_rll_res_req(struct msgb *msg, struct lapdm_datalink *dl)
1873 {
1874         struct abis_rsl_rll_hdr *rllh = msgb_l2(msg);
1875         uint8_t chan_nr = rllh->chan_nr;
1876         uint8_t link_id = rllh->link_id;
1877         uint8_t sapi = rllh->link_id & 7;
1878         struct tlv_parsed tv;
1879         uint8_t length;
1880         uint8_t n201 = 23; //FIXME
1881
1882         /* Set chan_nr and link_id for established connection */
1883         memset(&dl->mctx, 0, sizeof(dl->mctx));
1884         dl->mctx.dl = dl;
1885         dl->mctx.n201 = n201;
1886         dl->mctx.chan_nr = chan_nr;
1887         dl->mctx.link_id = link_id;
1888
1889         rsl_tlv_parse(&tv, rllh->data, msgb_l2len(msg)-sizeof(*rllh));
1890         if (!TLVP_PRESENT(&tv, RSL_IE_L3_INFO)) {
1891                 LOGP(DLAPDM, LOGL_ERROR, "resume without message error\n");
1892                 msgb_free(msg);
1893                 return send_rll_simple(RSL_MT_REL_IND, &dl->mctx);
1894         }
1895         length = TLVP_LEN(&tv, RSL_IE_L3_INFO);
1896
1897         LOGP(DLAPDM, LOGL_INFO, "perform re-establishment (SAMB)\n");
1898
1899         /* Replace message in the send-buffer (reconnect) */
1900         if (dl->send_buffer)
1901                 msgb_free(dl->send_buffer);
1902         dl->send_out = 0;
1903         dl->send_buffer = msg;
1904
1905         /* Discard partly received L3 message */
1906         if (dl->rcv_buffer) {
1907                 msgb_free(dl->rcv_buffer);
1908                 dl->rcv_buffer = NULL;
1909         }
1910
1911         /* Create new msgb (old one is now free) */
1912         msg = msgb_alloc_headroom(23+10, 10, "LAPDm SABM");
1913         msg->l2h = msgb_put(msg, 3);
1914         msg->l2h[0] = LAPDm_ADDR(LAPDm_LPD_NORMAL, sapi, CR_MS2BS_CMD);
1915         msg->l2h[1] = LAPDm_CTRL_U(LAPDm_U_SABM, 1);
1916         msg->l2h[2] = LAPDm_LEN(0);
1917         /* Transmit-buffer carries exactly one segment */
1918         memcpy(dl->tx_hist[0], msg->l2h, 3);
1919         dl->tx_length[0] = 3;
1920         /* set Vs to 0, because it is used as index when resending SAMB */
1921         dl->V_send = 0;
1922
1923         /* Set states */
1924         dl->own_busy = dl->peer_busy = 0;
1925         dl->retrans_ctr = 0;
1926         lapdm_dl_newstate(dl, LAPDm_STATE_SABM_SENT);
1927
1928         /* Tramsmit and start T200 */
1929         bsc_schedule_timer(&dl->t200, T200);
1930         return tx_ph_data_enqueue(dl, msg, chan_nr, link_id, n201);
1931 }
1932
1933 /* L3 requests release of data link */
1934 static int rslms_rx_rll_rel_req(struct msgb *msg, struct lapdm_datalink *dl)
1935 {
1936         struct abis_rsl_rll_hdr *rllh = msgb_l2(msg);
1937         uint8_t chan_nr = rllh->chan_nr;
1938         uint8_t link_id = rllh->link_id;
1939         uint8_t sapi = rllh->link_id & 7;
1940         uint8_t mode = 0;
1941
1942         /* get release mode */
1943         if (rllh->data[0] == RSL_IE_RELEASE_MODE)
1944                 mode = rllh->data[1] & 1;
1945
1946         /* local release */
1947         if (mode) {
1948                 LOGP(DLAPDM, LOGL_INFO, "perform local release\n");
1949                 msgb_free(msg);
1950                 /* reset Timer T200 */
1951                 bsc_del_timer(&dl->t200);
1952                 /* enter idle state */
1953                 lapdm_dl_newstate(dl, LAPDm_STATE_IDLE);
1954                 /* flush buffers */
1955                 lapdm_dl_flush_tx(dl);
1956                 lapdm_dl_flush_send(dl);
1957                 /* send notification to L3 */
1958                 return send_rll_simple(RSL_MT_REL_CONF, &dl->mctx);
1959         }
1960
1961         /* in case we are already disconnecting */
1962         if (dl->state == LAPDm_STATE_DISC_SENT)
1963                 return -EBUSY;
1964
1965         LOGP(DLAPDM, LOGL_INFO, "perform normal release (DISC)\n");
1966
1967         /* Pull rllh */
1968         msgb_pull(msg, msg->tail - msg->l2h);
1969
1970         /* Push LAPDm header on msgb */
1971         msg->l2h = msgb_push(msg, 3);
1972         msg->l2h[0] = LAPDm_ADDR(LAPDm_LPD_NORMAL, sapi, CR_MS2BS_CMD);
1973         msg->l2h[1] = LAPDm_CTRL_U(LAPDm_U_DISC, 1);
1974         msg->l2h[2] = LAPDm_LEN(0);
1975         /* Transmit-buffer carries exactly one segment */
1976         memcpy(dl->tx_hist[0], msg->l2h, 3);
1977         dl->tx_length[0] = 3;
1978
1979         /* Set states */
1980         dl->own_busy = dl->peer_busy = 0;
1981         dl->retrans_ctr = 0;
1982         lapdm_dl_newstate(dl, LAPDm_STATE_DISC_SENT);
1983
1984         /* Tramsmit and start T200 */
1985         bsc_schedule_timer(&dl->t200, T200);
1986         return tx_ph_data_enqueue(dl, msg, chan_nr, link_id, dl->mctx.n201);
1987 }
1988
1989 /* L3 requests release in idle state */
1990 static int rslms_rx_rll_rel_req_idle(struct msgb *msg, struct lapdm_datalink *dl)
1991 {
1992         msgb_free(msg);
1993
1994         /* send notification to L3 */
1995         return send_rll_simple(RSL_MT_REL_CONF, &dl->mctx);
1996 }
1997
1998 /* L3 requests channel in idle state */
1999 static int rslms_rx_chan_rqd(struct osmocom_ms *ms, struct msgb *msg)
2000 {
2001         struct abis_rsl_cchan_hdr *cch = msgb_l2(msg);
2002         int rc;
2003
2004         if (msgb_l2len(msg) < sizeof(*cch) + 4 + 2 + 2) {
2005                 LOGP(DRSL, LOGL_ERROR, "Message too short for CHAN RQD!\n");
2006                 return -EINVAL;
2007         }
2008         if (cch->data[0] != RSL_IE_REQ_REFERENCE) {
2009                 LOGP(DRSL, LOGL_ERROR, "Missing REQ REFERENCE IE\n");
2010                 return -EINVAL;
2011         }
2012         if (cch->data[4] != RSL_IE_ACCESS_DELAY) {
2013                 LOGP(DRSL, LOGL_ERROR, "Missing ACCESS_DELAY IE\n");
2014                 return -EINVAL;
2015         }
2016         if (cch->data[6] != RSL_IE_MS_POWER) {
2017                 LOGP(DRSL, LOGL_ERROR, "Missing MS POWER IE\n");
2018                 return -EINVAL;
2019         }
2020
2021         /* TA = 0 - delay */
2022         rc = l1ctl_tx_param_req(ms, 0 - cch->data[5], cch->data[7]);
2023
2024         rc = l1ctl_tx_rach_req(ms, cch->data[1], cch->data[2], cch->data[3]);
2025
2026         msgb_free(msg);
2027
2028         return rc;
2029 }
2030
2031 /* L1 confirms channel request */
2032 int l2_ph_chan_conf(struct msgb *msg, struct osmocom_ms *ms,
2033                         struct l1ctl_info_dl *dl)
2034 {
2035         struct abis_rsl_cchan_hdr *ch;
2036         struct gsm_time tm;
2037         struct gsm48_req_ref *ref;
2038
2039         gsm_fn2gsmtime(&tm, htonl(dl->frame_nr));
2040
2041         msgb_pull_l2h(msg);
2042         msg->l2h = msgb_push(msg, sizeof(*ch) + sizeof(*ref));
2043         ch = (struct abis_rsl_cchan_hdr *)msg->l2h;
2044         rsl_init_cchan_hdr(ch, RSL_MT_CHAN_CONF);
2045         ch->chan_nr = RSL_CHAN_RACH;
2046         ch->data[0] = RSL_IE_REQ_REFERENCE;
2047         ref = (struct gsm48_req_ref *) (ch->data + 1);
2048         ref->t1 = tm.t1;
2049         ref->t2 = tm.t2;
2050         ref->t3_low = tm.t3 & 0x3;
2051         ref->t3_high = tm.t3 >> 3;
2052
2053         return rslms_sendmsg(msg, ms);
2054 }
2055
2056 /* Names for Radio Link Layer Management */
2057 static const struct value_string rsl_msg_names[] = {
2058         { RSL_MT_DATA_REQ,              "RSL_MT_DATA_REQ" },
2059         { RSL_MT_DATA_IND,              "RSL_MT_DATA_IND" },
2060         { RSL_MT_ERROR_IND,             "RSL_MT_ERROR_IND" },
2061         { RSL_MT_EST_REQ,               "RSL_MT_EST_REQ" },
2062         { RSL_MT_EST_CONF,              "RSL_MT_EST_CONF" },
2063         { RSL_MT_EST_IND,               "RSL_MT_EST_IND" },
2064         { RSL_MT_EST_IND,               "RSL_MT_REL_REQ" },
2065         { RSL_MT_REL_REQ,               "RSL_MT_REL_REQ" },
2066         { RSL_MT_REL_CONF,              "RSL_MT_REL_CONF" },
2067         { RSL_MT_REL_IND,               "RSL_MT_REL_IND" },
2068         { RSL_MT_UNIT_DATA_REQ,         "RSL_MT_UNIT_DATA_REQ" },
2069         { RSL_MT_UNIT_DATA_IND,         "RSL_MT_UNIT_DATA_IND" },
2070         { RSL_MT_SUSP_REQ,              "RSL_MT_SUSP_REQ" },
2071         { RSL_MT_SUSP_CONF,             "RSL_MT_SUSP_CONF" },
2072         { RSL_MT_RES_REQ,               "RSL_MT_RES_REQ" },
2073         { RSL_MT_RECON_REQ,             "RSL_MT_RECON_REQ" },
2074         { RSL_MT_CHAN_RQD,              "RSL_MT_CHAN_RQD" },
2075         { RSL_MT_CHAN_CONF,             "RSL_MT_CHAN_CONF" },
2076         { 0,                            NULL }
2077 };
2078
2079 const char *get_rsl_name(int value)
2080 {
2081         return get_value_string(rsl_msg_names, value);
2082 }
2083
2084 const char *lapdm_state_names[] = {
2085         "LAPDm_STATE_NULL",
2086         "LAPDm_STATE_IDLE",
2087         "LAPDm_STATE_SABM_SENT",
2088         "LAPDm_STATE_MF_EST",
2089         "LAPDm_STATE_TIMER_RECOV",
2090         "LAPDm_STATE_DISC_SENT",
2091 };
2092
2093 /* statefull handling for RSLms RLL messages from L3 */
2094 static struct l2downstate {
2095         uint32_t        states;
2096         int             type;
2097         int             (*rout) (struct msgb *msg, struct lapdm_datalink *dl);
2098 } l2downstatelist[] = {
2099         /* create and send UI command */
2100         {ALL_STATES,
2101          RSL_MT_UNIT_DATA_REQ, rslms_rx_rll_udata_req},
2102
2103         /* create and send SABM command */
2104         {SBIT(LAPDm_STATE_IDLE),
2105          RSL_MT_EST_REQ, rslms_rx_rll_est_req},
2106
2107         /* create and send I command */
2108         {SBIT(LAPDm_STATE_MF_EST) |
2109          SBIT(LAPDm_STATE_TIMER_RECOV),
2110          RSL_MT_DATA_REQ, rslms_rx_rll_data_req},
2111
2112         /* suspend datalink */
2113         {SBIT(LAPDm_STATE_MF_EST) |
2114          SBIT(LAPDm_STATE_TIMER_RECOV),
2115          RSL_MT_SUSP_REQ, rslms_rx_rll_susp_req},
2116
2117         /* create and send SABM command (resume) */
2118         {SBIT(LAPDm_STATE_MF_EST) |
2119          SBIT(LAPDm_STATE_TIMER_RECOV),
2120          RSL_MT_RES_REQ, rslms_rx_rll_res_req},
2121
2122         /* create and send SABM command (reconnect) */
2123         {SBIT(LAPDm_STATE_MF_EST) |
2124          SBIT(LAPDm_STATE_TIMER_RECOV),
2125          RSL_MT_RECON_REQ, rslms_rx_rll_res_req},
2126
2127         /* create and send DISC command */
2128         {SBIT(LAPDm_STATE_SABM_SENT) |
2129          SBIT(LAPDm_STATE_MF_EST) |
2130          SBIT(LAPDm_STATE_TIMER_RECOV) |
2131          SBIT(LAPDm_STATE_DISC_SENT),
2132          RSL_MT_REL_REQ, rslms_rx_rll_rel_req},
2133
2134         /* release in idle state */
2135         {SBIT(LAPDm_STATE_IDLE),
2136          RSL_MT_REL_REQ, rslms_rx_rll_rel_req_idle},
2137 };
2138
2139 #define L2DOWNSLLEN \
2140         (sizeof(l2downstatelist) / sizeof(struct l2downstate))
2141
2142 /* incoming RSLms RLL message from L3 */
2143 static int rslms_rx_rll(struct msgb *msg, struct osmocom_ms *ms)
2144 {
2145         struct abis_rsl_rll_hdr *rllh = msgb_l2(msg);
2146         int msg_type = rllh->c.msg_type;
2147         uint8_t sapi = rllh->link_id & 7;
2148         struct lapdm_entity *le;
2149         struct lapdm_datalink *dl;
2150         int i, supported = 0;
2151         int rc = 0;
2152
2153         if (msgb_l2len(msg) < sizeof(*rllh)) {
2154                 LOGP(DRSL, LOGL_ERROR, "Message too short for RLL hdr!\n");
2155                 return -EINVAL;
2156         }
2157
2158         if (rllh->link_id & 0x40)
2159                 le = &ms->l2_entity.lapdm_acch;
2160         else
2161                 le = &ms->l2_entity.lapdm_dcch;
2162
2163         /* G.2.1 No action schall be taken on frames containing an unallocated
2164          * SAPI.
2165          */
2166         dl = datalink_for_sapi(le, sapi);
2167         if (!dl) {
2168                 LOGP(DRSL, LOGL_ERROR, "No instance for SAPI %d!\n", sapi);
2169                 return -EINVAL;
2170         }
2171
2172         LOGP(DRSL, LOGL_INFO, "(ms %s) RLL Message '%s' received in state %s\n",
2173                 ms->name, get_rsl_name(msg_type), lapdm_state_names[dl->state]);
2174
2175         /* find function for current state and message */
2176         for (i = 0; i < L2DOWNSLLEN; i++) {
2177                 if (msg_type == l2downstatelist[i].type)
2178                         supported = 1;
2179                 if ((msg_type == l2downstatelist[i].type)
2180                  && ((1 << dl->state) & l2downstatelist[i].states))
2181                         break;
2182         }
2183         if (!supported) {
2184                 LOGP(DRSL, LOGL_NOTICE, "Message unsupported.\n");
2185                 msgb_free(msg);
2186                 return 0;
2187         }
2188         if (i == L2DOWNSLLEN) {
2189                 LOGP(DRSL, LOGL_NOTICE, "Message unhandled at this state.\n");
2190                 msgb_free(msg);
2191                 return 0;
2192         }
2193
2194         rc = l2downstatelist[i].rout(msg, dl);
2195
2196         return rc;
2197 }
2198
2199 /* incoming RSLms COMMON CHANNEL message from L3 */
2200 static int rslms_rx_com_chan(struct msgb *msg, struct osmocom_ms *ms)
2201 {
2202         struct abis_rsl_cchan_hdr *cch = msgb_l2(msg);
2203         int msg_type = cch->c.msg_type;
2204         int rc = 0;
2205
2206         if (msgb_l2len(msg) < sizeof(*cch)) {
2207                 LOGP(DRSL, LOGL_ERROR, "Message too short for COM CHAN hdr!\n");
2208                 return -EINVAL;
2209         }
2210
2211         switch (msg_type) {
2212         case RSL_MT_CHAN_RQD:
2213                 /* create and send RACH request */
2214                 rc = rslms_rx_chan_rqd(ms, msg);
2215                 break;
2216         default:
2217                 LOGP(DRSL, LOGL_NOTICE, "Unknown COMMON CHANNEL msg %d!\n",
2218                         msg_type);
2219                 msgb_free(msg);
2220                 return 0;
2221         }
2222
2223         return rc;
2224 }
2225
2226 /* input into layer2 (from layer 3) */
2227 int rslms_recvmsg(struct msgb *msg, struct osmocom_ms *ms)
2228 {
2229         struct abis_rsl_common_hdr *rslh = msgb_l2(msg);
2230         int rc = 0;
2231
2232         if (msgb_l2len(msg) < sizeof(*rslh)) {
2233                 LOGP(DRSL, LOGL_ERROR, "Message too short RSL hdr!\n");
2234                 return -EINVAL;
2235         }
2236
2237         switch (rslh->msg_discr & 0xfe) {
2238         case ABIS_RSL_MDISC_RLL:
2239                 rc = rslms_rx_rll(msg, ms);
2240                 break;
2241         case ABIS_RSL_MDISC_COM_CHAN:
2242                 rc = rslms_rx_com_chan(msg, ms);
2243                 break;
2244         default:
2245                 LOGP(DRSL, LOGL_ERROR, "unknown RSLms message "
2246                         "discriminator 0x%02x", rslh->msg_discr);
2247                 msgb_free(msg);
2248                 return -EINVAL;
2249         }
2250
2251         return rc;
2252 }
2253
2254 /* input function that L2 calls when sending messages up to L3 */
2255 int rslms_sendmsg(struct msgb *msg, struct osmocom_ms *ms)
2256 {
2257         if (!ms->l2_entity.msg_handler) {
2258                 msgb_free(msg);
2259                 return -EIO;
2260         }
2261
2262         /* call the layer2 message handler that is registered */
2263         return ms->l2_entity.msg_handler(msg, ms);
2264 }
2265
2266 /* register message handler for messages that are sent from L2->L3 */
2267 int osmol2_register_handler(struct osmocom_ms *ms, osmol2_cb_t cb)
2268 {
2269         ms->l2_entity.msg_handler = cb;
2270
2271         return 0;
2272 }