src/gsm/lapdm.c

   1 /* GSM LAPDm (TS 04.06) implementation */
   2
   3 /* (C) 2010-2011 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 <osmocom/core/logging.h>
  60 #include <osmocom/core/timer.h>
  61 #include <osmocom/core/msgb.h>
  62 #include <osmocom/core/utils.h>
  63
  64 #include <osmocom/gsm/tlv.h>
  65 #include <osmocom/gsm/rsl.h>
  66 #include <osmocom/gsm/prim.h>
  67 #include <osmocom/gsm/gsm_utils.h>
  68 #include <osmocom/gsm/lapdm.h>
  69
  70 #include <osmocom/gsm/protocol/gsm_04_08.h>
  71 #include <osmocom/gsm/protocol/gsm_08_58.h>
  72
  73 /* TS 04.06 Figure 4 / Section 3.2 */
  74 #define LAPDm_LPD_NORMAL  0
  75 #define LAPDm_LPD_SMSCB   1
  76 #define LAPDm_SAPI_NORMAL 0
  77 #define LAPDm_SAPI_SMS    3
  78 #define LAPDm_ADDR(lpd, sapi, cr) ((((lpd) & 0x3) << 5) | (((sapi) & 0x7) << 2) | (((cr) & 0x1) << 1) | 0x1)
  79
  80 #define LAPDm_ADDR_SAPI(addr) (((addr) >> 2) & 0x7)
  81 #define LAPDm_ADDR_CR(addr) (((addr) >> 1) & 0x1)
  82 #define LAPDm_ADDR_EA(addr) ((addr) & 0x1)
  83
  84 /* TS 04.06 Table 3 / Section 3.4.3 */
  85 #define LAPDm_CTRL_I(nr, ns, p) ((((nr) & 0x7) << 5) | (((p) & 0x1) << 4) | (((ns) & 0x7) << 1))
  86 #define LAPDm_CTRL_S(nr, s, p)  ((((nr) & 0x7) << 5) | (((p) & 0x1) << 4) | (((s) & 0x3) << 2) | 0x1)
  87 #define LAPDm_CTRL_U(u, p)      ((((u) & 0x1c) << (5-2)) | (((p) & 0x1) << 4) | (((u) & 0x3) << 2) | 0x3)
  88
  89 #define LAPDm_CTRL_is_I(ctrl)   (((ctrl) & 0x1) == 0)
  90 #define LAPDm_CTRL_is_S(ctrl)   (((ctrl) & 0x3) == 1)
  91 #define LAPDm_CTRL_is_U(ctrl)   (((ctrl) & 0x3) == 3)
  92
  93 #define LAPDm_CTRL_U_BITS(ctrl) ((((ctrl) & 0xC) >> 2) | ((ctrl) & 0xE0) >> 3)
  94 #define LAPDm_CTRL_PF_BIT(ctrl) (((ctrl) >> 4) & 0x1)
  95
  96 #define LAPDm_CTRL_S_BITS(ctrl) (((ctrl) & 0xC) >> 2)
  97
  98 #define LAPDm_CTRL_I_Ns(ctrl)   (((ctrl) & 0xE) >> 1)
  99 #define LAPDm_CTRL_Nr(ctrl)     (((ctrl) & 0xE0) >> 5)
 100
 101 /* TS 04.06 Table 4 / Section 3.8.1 */
 102 #define LAPDm_U_SABM    0x7
 103 #define LAPDm_U_DM      0x3
 104 #define LAPDm_U_UI      0x0
 105 #define LAPDm_U_DISC    0x8
 106 #define LAPDm_U_UA      0xC
 107
 108 #define LAPDm_S_RR      0x0
 109 #define LAPDm_S_RNR     0x1
 110 #define LAPDm_S_REJ     0x2
 111
 112 #define LAPDm_LEN(len)  ((len << 2) | 0x1)
 113 #define LAPDm_MORE      0x2
 114
 115 /* TS 04.06 Section 5.8.3 */
 116 #define N201_AB_SACCH           18
 117 #define N201_AB_SDCCH           20
 118 #define N201_AB_FACCH           20
 119 #define N201_Bbis               23
 120 #define N201_Bter_SACCH         21
 121 #define N201_Bter_SDCCH         23
 122 #define N201_Bter_FACCH         23
 123 #define N201_B4                 19
 124
 125 /* 5.8.2.1 N200 during establish and release */
 126 #define N200_EST_REL            5
 127 /* 5.8.2.1 N200 during timer recovery state */
 128 #define N200_TR_SACCH           5
 129 #define N200_TR_SDCCH           23
 130 #define N200_TR_FACCH_FR        34
 131 #define N200_TR_EFACCH_FR       48
 132 #define N200_TR_FACCH_HR        29
 133 /* FIXME: this depends on chan type */
 134 #define N200    N200_TR_SACCH
 135
 136 #define CR_MS2BS_CMD    0
 137 #define CR_MS2BS_RESP   1
 138 #define CR_BS2MS_CMD    1
 139 #define CR_BS2MS_RESP   0
 140
 141 /* Set T200 to 1 Second (OpenBTS uses 900ms) */
 142 #define T200    1, 0
 143
 144 /* k value for each SAPI */
 145 static uint8_t k_sapi[] = {1, 1, 1, 1, 1, 1, 1, 1};
 146
 147 enum lapdm_format {
 148         LAPDm_FMT_A,
 149         LAPDm_FMT_B,
 150         LAPDm_FMT_Bbis,
 151         LAPDm_FMT_Bter,
 152         LAPDm_FMT_B4,
 153 };
 154
 155 static void lapdm_t200_cb(void *data);
 156 static int rslms_send_i(struct lapdm_msg_ctx *mctx, int line);
 157
 158 /* UTILITY FUNCTIONS */
 159
 160 static inline uint8_t inc_mod8(uint8_t x)
 161 {
 162         return (x + 1) & 7;
 163 }
 164
 165 static inline uint8_t add_mod8(uint8_t x, uint8_t y)
 166 {
 167         return (x + y) & 7;
 168 }
 169
 170 static inline uint8_t sub_mod8(uint8_t x, uint8_t y)
 171 {
 172         return (x - y) & 7; /* handle negative results correctly */
 173 }
 174
 175 static void lapdm_dl_init(struct lapdm_datalink *dl,
 176                           struct lapdm_entity *entity)
 177 {
 178         memset(dl, 0, sizeof(*dl));
 179         INIT_LLIST_HEAD(&dl->send_queue);
 180         INIT_LLIST_HEAD(&dl->tx_queue);
 181         dl->state = LAPDm_STATE_IDLE;
 182         dl->t200.data = dl;
 183         dl->t200.cb = &lapdm_t200_cb;
 184         dl->entity = entity;
 185 }
 186
 187 void lapdm_entity_init(struct lapdm_entity *le, enum lapdm_mode mode)
 188 {
 189         unsigned int i;
 190
 191         for (i = 0; i < ARRAY_SIZE(le->datalink); i++)
 192                 lapdm_dl_init(&le->datalink[i], le);
 193
 194         lapdm_entity_set_mode(le, mode);
 195 }
 196
 197 void lapdm_channel_init(struct lapdm_channel *lc, enum lapdm_mode mode)
 198 {
 199         lapdm_entity_init(&lc->lapdm_acch, mode);
 200         lapdm_entity_init(&lc->lapdm_dcch, mode);
 201 }
 202
 203
 204 static void lapdm_dl_flush_send(struct lapdm_datalink *dl)
 205 {
 206         struct msgb *msg;
 207
 208         /* Flush send-queue */
 209         while ((msg = msgb_dequeue(&dl->send_queue)))
 210                 msgb_free(msg);
 211
 212         /* Clear send-buffer */
 213         if (dl->send_buffer) {
 214                 msgb_free(dl->send_buffer);
 215                 dl->send_buffer = NULL;
 216         }
 217 }
 218
 219 static void lapdm_dl_flush_tx(struct lapdm_datalink *dl)
 220 {
 221         struct msgb *msg;
 222         unsigned int i;
 223
 224         while ((msg = msgb_dequeue(&dl->tx_queue)))
 225                 msgb_free(msg);
 226         for (i = 0; i < 8; i++)
 227                 dl->tx_length[i] = 0;
 228 }
 229
 230 void lapdm_entity_exit(struct lapdm_entity *le)
 231 {
 232         unsigned int i;
 233         struct lapdm_datalink *dl;
 234
 235         for (i = 0; i < ARRAY_SIZE(le->datalink); i++) {
 236                 dl = &le->datalink[i];
 237                 lapdm_dl_flush_tx(dl);
 238                 lapdm_dl_flush_send(dl);
 239                 if (dl->rcv_buffer)
 240                         msgb_free(dl->rcv_buffer);
 241         }
 242 }
 243
 244 void lapdm_channel_exit(struct lapdm_channel *lc)
 245 {
 246         lapdm_entity_exit(&lc->lapdm_acch);
 247         lapdm_entity_exit(&lc->lapdm_dcch);
 248 }
 249
 250 static void lapdm_dl_newstate(struct lapdm_datalink *dl, uint32_t state)
 251 {
 252         LOGP(DLLAPDM, LOGL_INFO, "new state %s -> %s\n",
 253                 lapdm_state_names[dl->state], lapdm_state_names[state]);
 254
 255         dl->state = state;
 256 }
 257
 258 static struct lapdm_datalink *datalink_for_sapi(struct lapdm_entity *le, uint8_t sapi)
 259 {
 260         switch (sapi) {
 261         case LAPDm_SAPI_NORMAL:
 262                 return &le->datalink[0];
 263         case LAPDm_SAPI_SMS:
 264                 return &le->datalink[1];
 265         default:
 266                 return NULL;
 267         }
 268 }
 269
 270 /* remove the L2 header from a MSGB */
 271 static inline unsigned char *msgb_pull_l2h(struct msgb *msg)
 272 {
 273         unsigned char *ret = msgb_pull(msg, msg->l3h - msg->l2h);
 274         msg->l2h = NULL;
 275         return ret;
 276 }
 277
 278 /* Append padding (if required) */
 279 static void lapdm_pad_msgb(struct msgb *msg, uint8_t n201)
 280 {
 281         int pad_len = n201 - msgb_l2len(msg);
 282         uint8_t *data;
 283
 284         if (pad_len < 0) {
 285                 LOGP(DLLAPDM, LOGL_ERROR,
 286                      "cannot pad message that is already too big!\n");
 287                 return;
 288         }
 289
 290         data = msgb_put(msg, pad_len);
 291         memset(data, 0x2B, pad_len);
 292 }
 293
 294 /* input function that L2 calls when sending messages up to L3 */
 295 static int rslms_sendmsg(struct msgb *msg, struct lapdm_entity *le)
 296 {
 297         if (!le->l3_cb) {
 298                 msgb_free(msg);
 299                 return -EIO;
 300         }
 301
 302         /* call the layer2 message handler that is registered */
 303         return le->l3_cb(msg, le, le->l3_ctx);
 304 }
 305
 306 /* write a frame into the tx queue */
 307 static int tx_ph_data_enqueue(struct lapdm_datalink *dl, struct msgb *msg,
 308                                 uint8_t chan_nr, uint8_t link_id, uint8_t n201)
 309 {
 310         struct lapdm_entity *le = dl->entity;
 311         struct osmo_phsap_prim pp;
 312
 313         /* if there is a pending message, queue it */
 314         if (le->tx_pending || le->flags & LAPDM_ENT_F_POLLING_ONLY) {
 315                 *msgb_push(msg, 1) = n201;
 316                 *msgb_push(msg, 1) = link_id;
 317                 *msgb_push(msg, 1) = chan_nr;
 318                 msgb_enqueue(&dl->tx_queue, msg);
 319                 return -EBUSY;
 320         }
 321
 322         osmo_prim_init(&pp.oph, SAP_GSM_PH, PRIM_PH_DATA,
 323                         PRIM_OP_REQUEST, msg);
 324         pp.u.data.chan_nr = chan_nr;
 325         pp.u.data.link_id = link_id;
 326
 327         /* send the frame now */
 328         le->tx_pending = 0; /* disabled flow control */
 329         lapdm_pad_msgb(msg, n201);
 330
 331         return le->l1_prim_cb(&pp.oph, le->l1_ctx);
 332 }
 333
 334 static struct msgb *tx_dequeue_msgb(struct lapdm_entity *le)
 335 {
 336         struct lapdm_datalink *dl;
 337         int last = le->last_tx_dequeue;
 338         int i = last, n = ARRAY_SIZE(le->datalink);
 339         struct msgb *msg = NULL;
 340
 341         /* round-robin dequeue */
 342         do {
 343                 /* next */
 344                 i = (i + 1) % n;
 345                 dl = &le->datalink[i];
 346                 if ((msg = msgb_dequeue(&dl->tx_queue)))
 347                         break;
 348         } while (i != last);
 349
 350         if (msg) {
 351                 /* Set last dequeue position */
 352                 le->last_tx_dequeue = i;
 353         }
 354
 355         return msg;
 356 }
 357
 358 /* dequeue a msg that's pending transmission via L1 and wrap it into
 359  * a osmo_phsap_prim */
 360 int lapdm_phsap_dequeue_prim(struct lapdm_entity *le, struct osmo_phsap_prim *pp)
 361 {
 362         struct msgb *msg;
 363         uint8_t n201;
 364
 365         msg = tx_dequeue_msgb(le);
 366         if (!msg)
 367                 return -ENODEV;
 368
 369         /* if we have a message, send PH-DATA.req */
 370         osmo_prim_init(&pp->oph, SAP_GSM_PH, PRIM_PH_DATA,
 371                         PRIM_OP_REQUEST, msg);
 372
 373         /* Pull chan_nr and link_id */
 374         pp->u.data.chan_nr = *msg->data;
 375         msgb_pull(msg, 1);
 376         pp->u.data.link_id = *msg->data;
 377         msgb_pull(msg, 1);
 378         n201 = *msg->data;
 379         msgb_pull(msg, 1);
 380
 381         /* Pad the frame, we can transmit now */
 382         lapdm_pad_msgb(msg, n201);
 383
 384         return 0;
 385 }
 386
 387 /* get next frame from the tx queue. because the ms has multiple datalinks,
 388  * each datalink's queue is read round-robin.
 389  */
 390 static int l2_ph_data_conf(struct msgb *msg, struct lapdm_entity *le)
 391 {
 392         struct osmo_phsap_prim pp;
 393
 394         /* we may send again */
 395         le->tx_pending = 0;
 396
 397         /* free confirm message */
 398         if (msg)
 399                 msgb_free(msg);
 400
 401         if (lapdm_phsap_dequeue_prim(le, &pp) < 0) {
 402                 /* no message in all queues */
 403
 404                 /* If user didn't request PH-EMPTY_FRAME.req, abort */
 405                 if (!(le->flags & LAPDM_ENT_F_EMPTY_FRAME))
 406                         return 0;
 407
 408                 /* otherwise, send PH-EMPTY_FRAME.req */
 409                 osmo_prim_init(&pp.oph, SAP_GSM_PH,
 410                                 PRIM_PH_EMPTY_FRAME,
 411                                 PRIM_OP_REQUEST, NULL);
 412         } else {
 413                 le->tx_pending = 1;
 414         }
 415
 416         return le->l1_prim_cb(&pp.oph, le->l1_ctx);
 417 }
 418
 419 /* Create RSLms various RSLms messages */
 420 static int send_rslms_rll_l3(uint8_t msg_type, struct lapdm_msg_ctx *mctx,
 421                              struct msgb *msg)
 422 {
 423         /* Add the RSL + RLL header */
 424         rsl_rll_push_l3(msg, msg_type, mctx->chan_nr, mctx->link_id, 1);
 425
 426         /* send off the RSLms message to L3 */
 427         return rslms_sendmsg(msg, mctx->dl->entity);
 428 }
 429
 430 /* Take a B4 format message from L1 and create RSLms UNIT DATA IND */
 431 static int send_rslms_rll_l3_ui(struct lapdm_msg_ctx *mctx, struct msgb *msg)
 432 {
 433         uint8_t l3_len = msg->tail - (uint8_t *)msgb_l3(msg);
 434         struct abis_rsl_rll_hdr *rllh;
 435
 436         /* Add the RSL + RLL header */
 437         msgb_tv16_push(msg, RSL_IE_L3_INFO, l3_len);
 438         msgb_push(msg, 2 + 2);
 439         rsl_rll_push_hdr(msg, RSL_MT_UNIT_DATA_IND, mctx->chan_nr,
 440                 mctx->link_id, 1);
 441         rllh = (struct abis_rsl_rll_hdr *)msgb_l2(msg);
 442
 443         rllh->data[0] = RSL_IE_TIMING_ADVANCE;
 444         rllh->data[1] = mctx->ta_ind;
 445
 446         rllh->data[2] = RSL_IE_MS_POWER;
 447         rllh->data[3] = mctx->tx_power_ind;
 448
 449         return rslms_sendmsg(msg, mctx->dl->entity);
 450 }
 451
 452 static int send_rll_simple(uint8_t msg_type, struct lapdm_msg_ctx *mctx)
 453 {
 454         struct msgb *msg;
 455
 456         msg = rsl_rll_simple(msg_type, mctx->chan_nr, mctx->link_id, 1);
 457
 458         /* send off the RSLms message to L3 */
 459         return rslms_sendmsg(msg, mctx->dl->entity);
 460 }
 461
 462 static int rsl_rll_error(uint8_t cause, struct lapdm_msg_ctx *mctx)
 463 {
 464         struct msgb *msg;
 465
 466         LOGP(DLLAPDM, LOGL_NOTICE, "sending MDL-ERROR-IND %d\n", cause);
 467         msg = rsl_rll_simple(RSL_MT_ERROR_IND, mctx->chan_nr, mctx->link_id, 1);
 468         msg->l2h = msgb_put(msg, sizeof(struct abis_rsl_rll_hdr));
 469         msgb_tlv_put(msg, RSL_IE_RLM_CAUSE, 1, &cause);
 470         return rslms_sendmsg(msg, mctx->dl->entity);
 471 }
 472
 473 static int check_length_ind(struct lapdm_msg_ctx *mctx, uint8_t length_ind)
 474 {
 475         if (!(length_ind & 0x01)) {
 476                 /* G.4.1 If the EL bit is set to "0", an MDL-ERROR-INDICATION
 477                  * primitive with cause "frame not implemented" is sent to the
 478                  * mobile management entity. */
 479                 LOGP(DLLAPDM, LOGL_NOTICE,
 480                         "we don't support multi-octet length\n");
 481                 rsl_rll_error(RLL_CAUSE_FRM_UNIMPL, mctx);
 482                 return -EINVAL;
 483         }
 484         return 0;
 485 }
 486
 487 static int lapdm_send_resend(struct lapdm_datalink *dl)
 488 {
 489         struct msgb *msg = msgb_alloc_headroom(23+10, 10, "LAPDm resend");
 490         int length;
 491
 492         /* Resend SABM/DISC from tx_hist */
 493         length = dl->tx_length[0];
 494         msg->l2h = msgb_put(msg, length);
 495         memcpy(msg->l2h, dl->tx_hist[dl->V_send], length);
 496
 497         return tx_ph_data_enqueue(dl, msg, dl->mctx.chan_nr, dl->mctx.link_id,
 498                         dl->mctx.n201);
 499 }
 500
 501 static int lapdm_send_ua(struct lapdm_msg_ctx *mctx, uint8_t len, uint8_t *data)
 502 {
 503         uint8_t sapi = mctx->link_id & 7;
 504         uint8_t f_bit = LAPDm_CTRL_PF_BIT(mctx->ctrl);
 505         struct msgb *msg = msgb_alloc_headroom(23+10, 10, "LAPDm UA");
 506         struct lapdm_entity *le = mctx->dl->entity;
 507
 508         msg->l2h = msgb_put(msg, 3 + len);
 509         msg->l2h[0] = LAPDm_ADDR(LAPDm_LPD_NORMAL, sapi, le->cr.loc2rem.resp);
 510         msg->l2h[1] = LAPDm_CTRL_U(LAPDm_U_UA, f_bit);
 511         msg->l2h[2] = LAPDm_LEN(len);
 512         if (len)
 513                 memcpy(msg->l2h + 3, data, len);
 514
 515         return tx_ph_data_enqueue(mctx->dl, msg, mctx->chan_nr, mctx->link_id,
 516                         mctx->n201);
 517 }
 518
 519 static int lapdm_send_dm(struct lapdm_msg_ctx *mctx)
 520 {
 521         uint8_t sapi = mctx->link_id & 7;
 522         uint8_t f_bit = LAPDm_CTRL_PF_BIT(mctx->ctrl);
 523         struct msgb *msg = msgb_alloc_headroom(23+10, 10, "LAPDm DM");
 524         struct lapdm_entity *le = mctx->dl->entity;
 525
 526         msg->l2h = msgb_put(msg, 3);
 527         msg->l2h[0] = LAPDm_ADDR(LAPDm_LPD_NORMAL, sapi, le->cr.loc2rem.resp);
 528         msg->l2h[1] = LAPDm_CTRL_U(LAPDm_U_DM, f_bit);
 529         msg->l2h[2] = 0;
 530
 531         return tx_ph_data_enqueue(mctx->dl, msg, mctx->chan_nr, mctx->link_id,
 532                         mctx->n201);
 533 }
 534
 535 static int lapdm_send_rr(struct lapdm_msg_ctx *mctx, uint8_t f_bit)
 536 {
 537         uint8_t sapi = mctx->link_id & 7;
 538         struct msgb *msg = msgb_alloc_headroom(23+10, 10, "LAPDm RR");
 539         struct lapdm_entity *le = mctx->dl->entity;
 540
 541         msg->l2h = msgb_put(msg, 3);
 542         msg->l2h[0] = LAPDm_ADDR(LAPDm_LPD_NORMAL, sapi, le->cr.loc2rem.resp);
 543         msg->l2h[1] = LAPDm_CTRL_S(mctx->dl->V_recv, LAPDm_S_RR, f_bit);
 544         msg->l2h[2] = LAPDm_LEN(0);
 545
 546         return tx_ph_data_enqueue(mctx->dl, msg, mctx->chan_nr, mctx->link_id,
 547                         mctx->n201);
 548 }
 549
 550 static int lapdm_send_rnr(struct lapdm_msg_ctx *mctx, uint8_t f_bit)
 551 {
 552         uint8_t sapi = mctx->link_id & 7;
 553         struct msgb *msg = msgb_alloc_headroom(23+10, 10, "LAPDm RNR");
 554         struct lapdm_entity *le = mctx->dl->entity;
 555
 556         msg->l2h = msgb_put(msg, 3);
 557         msg->l2h[0] = LAPDm_ADDR(LAPDm_LPD_NORMAL, sapi, le->cr.loc2rem.resp);
 558         msg->l2h[1] = LAPDm_CTRL_S(mctx->dl->V_recv, LAPDm_S_RNR, f_bit);
 559         msg->l2h[2] = LAPDm_LEN(0);
 560
 561         return tx_ph_data_enqueue(mctx->dl, msg, mctx->chan_nr, mctx->link_id,
 562                         mctx->n201);
 563 }
 564
 565 static int lapdm_send_rej(struct lapdm_msg_ctx *mctx, uint8_t f_bit)
 566 {
 567         uint8_t sapi = mctx->link_id & 7;
 568         struct msgb *msg = msgb_alloc_headroom(23+10, 10, "LAPDm REJ");
 569         struct lapdm_entity *le = mctx->dl->entity;
 570
 571         msg->l2h = msgb_put(msg, 3);
 572         msg->l2h[0] = LAPDm_ADDR(LAPDm_LPD_NORMAL, sapi, le->cr.loc2rem.resp);
 573         msg->l2h[1] = LAPDm_CTRL_S(mctx->dl->V_recv, LAPDm_S_REJ, f_bit);
 574         msg->l2h[2] = LAPDm_LEN(0);
 575
 576         return tx_ph_data_enqueue(mctx->dl, msg, mctx->chan_nr, mctx->link_id,
 577                         mctx->n201);
 578 }
 579
 580 /* Timer callback on T200 expiry */
 581 static void lapdm_t200_cb(void *data)
 582 {
 583         struct lapdm_datalink *dl = data;
 584
 585         LOGP(DLLAPDM, LOGL_INFO, "lapdm_t200_cb(%p) state=%u\n", dl, dl->state);
 586
 587         switch (dl->state) {
 588         case LAPDm_STATE_SABM_SENT:
 589                 /* 5.4.1.3 */
 590                 if (dl->retrans_ctr + 1 >= N200_EST_REL + 1) {
 591                         /* send RELEASE INDICATION to L3 */
 592                         send_rll_simple(RSL_MT_REL_IND, &dl->mctx);
 593                         /* send MDL ERROR INIDCATION to L3 */
 594                         rsl_rll_error(RLL_CAUSE_T200_EXPIRED, &dl->mctx);
 595                         /* flush tx buffers */
 596                         lapdm_dl_flush_tx(dl);
 597                         lapdm_dl_flush_send(dl);
 598                         /* go back to idle state */
 599                         lapdm_dl_newstate(dl, LAPDm_STATE_IDLE);
 600                         /* NOTE: we must not change any other states or buffers
 601                          * and queues, since we may reconnect after handover
 602                          * failure. the buffered messages is replaced there */
 603                         break;
 604                 }
 605                 /* retransmit SABM command */
 606                 lapdm_send_resend(dl);
 607                 /* increment re-transmission counter */
 608                 dl->retrans_ctr++;
 609                 /* restart T200 (PH-READY-TO-SEND) */
 610                 osmo_timer_schedule(&dl->t200, T200);
 611                 break;
 612         case LAPDm_STATE_DISC_SENT:
 613                 /* 5.4.4.3 */
 614                 if (dl->retrans_ctr + 1 >= N200_EST_REL + 1) {
 615                         /* send RELEASE INDICATION to L3 */
 616                         send_rll_simple(RSL_MT_REL_CONF, &dl->mctx);
 617                         /* send MDL ERROR INIDCATION to L3 */
 618                         rsl_rll_error(RLL_CAUSE_T200_EXPIRED, &dl->mctx);
 619                         /* flush buffers */
 620                         lapdm_dl_flush_tx(dl);
 621                         lapdm_dl_flush_send(dl);
 622                         /* go back to idle state */
 623                         lapdm_dl_newstate(dl, LAPDm_STATE_IDLE);
 624                         /* NOTE: we must not change any other states or buffers
 625                          * and queues, since we may reconnect after handover
 626                          * failure. the buffered messages is replaced there */
 627                         break;
 628                 }
 629                 /* retransmit DISC command */
 630                 lapdm_send_resend(dl);
 631                 /* increment re-transmission counter */
 632                 dl->retrans_ctr++;
 633                 /* restart T200 (PH-READY-TO-SEND) */
 634                 osmo_timer_schedule(&dl->t200, T200);
 635                 break;
 636         case LAPDm_STATE_MF_EST:
 637                 /* 5.5.7 */
 638                 dl->retrans_ctr = 0;
 639                 lapdm_dl_newstate(dl, LAPDm_STATE_TIMER_RECOV);
 640                 /* fall through */
 641         case LAPDm_STATE_TIMER_RECOV:
 642                 dl->retrans_ctr++;
 643                 if (dl->retrans_ctr < N200) {
 644                         /* retransmit I frame (V_s-1) with P=1, if any */
 645                         if (dl->tx_length[sub_mod8(dl->V_send, 1)]) {
 646                                 struct msgb *msg;
 647                                 int length;
 648
 649                                 LOGP(DLLAPDM, LOGL_INFO, "retransmit last frame "
 650                                         "V(S)=%d\n", sub_mod8(dl->V_send, 1));
 651                                 /* Create I frame (segment) from tx_hist */
 652                                 length = dl->tx_length[sub_mod8(dl->V_send, 1)];
 653                                 msg = msgb_alloc_headroom(23+10, 10, "LAPDm I");
 654                                 msg->l2h = msgb_put(msg, length);
 655                                 memcpy(msg->l2h,
 656                                         dl->tx_hist[sub_mod8(dl->V_send, 1)],
 657                                         length);
 658                                 msg->l2h[1] = LAPDm_CTRL_I(dl->V_recv,
 659                                         sub_mod8(dl->V_send, 1), 1); /* P=1 */
 660                                 tx_ph_data_enqueue(dl, msg, dl->mctx.chan_nr,
 661                                         dl->mctx.link_id, dl->mctx.n201);
 662                         } else {
 663                         /* OR send appropriate supervision frame with P=1 */
 664                                 if (!dl->own_busy && !dl->seq_err_cond) {
 665                                         lapdm_send_rr(&dl->mctx, 1);
 666                                         /* NOTE: In case of sequence error
 667                                          * condition, the REJ frame has been
 668                                          * transmitted when entering the
 669                                          * condition, so it has not be done
 670                                          * here
 671                                          */
 672                                 } else if (dl->own_busy) {
 673                                         lapdm_send_rnr(&dl->mctx, 1);
 674                                 } else {
 675                                         LOGP(DLLAPDM, LOGL_INFO, "unhandled, "
 676                                                 "pls. fix\n");
 677                                 }
 678                         }
 679                         /* restart T200 (PH-READY-TO-SEND) */
 680                         osmo_timer_schedule(&dl->t200, T200);
 681                 } else {
 682                         /* send MDL ERROR INIDCATION to L3 */
 683                         rsl_rll_error(RLL_CAUSE_T200_EXPIRED, &dl->mctx);
 684                 }
 685                 break;
 686         default:
 687                 LOGP(DLLAPDM, LOGL_INFO, "T200 expired in unexpected "
 688                         "dl->state %u\n", dl->state);
 689         }
 690 }
 691
 692 /* 5.5.3.1: Common function to acknowlege frames up to the given N(R) value */
 693 static void lapdm_acknowledge(struct lapdm_msg_ctx *mctx)
 694 {
 695         struct lapdm_datalink *dl = mctx->dl;
 696         uint8_t nr = LAPDm_CTRL_Nr(mctx->ctrl);
 697         int s = 0, rej = 0, t200_reset = 0;
 698         int i;
 699
 700         /* supervisory frame ? */
 701         if (LAPDm_CTRL_is_S(mctx->ctrl))
 702                 s = 1;
 703         /* REJ frame ? */
 704         if (s && LAPDm_CTRL_S_BITS(mctx->ctrl) == LAPDm_S_REJ)
 705                 rej = 1;
 706
 707         /* Flush all transmit buffers of acknowledged frames */
 708         for (i = dl->V_ack; i != nr; i = inc_mod8(i)) {
 709                 if (dl->tx_length[i]) {
 710                         dl->tx_length[i] = 0;
 711                         LOGP(DLLAPDM, LOGL_INFO, "ack frame %d\n", i);
 712                 }
 713         }
 714
 715         if (dl->state != LAPDm_STATE_TIMER_RECOV) {
 716                 /* When not in the timer recovery condition, the data
 717                  * link layer entity shall reset the timer T200 on
 718                  * receipt of a valid I frame with N(R) higher than V(A),
 719                  * or an REJ with an N(R) equal to V(A). */
 720                 if ((!rej && nr != dl->V_ack)
 721                  || (rej && nr == dl->V_ack)) {
 722                         LOGP(DLLAPDM, LOGL_INFO, "reset t200\n");
 723                         t200_reset = 1;
 724                         osmo_timer_del(&dl->t200);
 725                         /* 5.5.3.1 Note 1 + 2 imply timer recovery cond. */
 726                 }
 727                 /* 5.7.4: N(R) sequence error
 728                  * N(R) is called valid, if and only if
 729                  * (N(R)-V(A)) mod 8 <= (V(S)-V(A)) mod 8.
 730                  */
 731                 if (sub_mod8(nr, dl->V_ack) > sub_mod8(dl->V_send, dl->V_ack)) {
 732                         LOGP(DLLAPDM, LOGL_NOTICE, "N(R) sequence error\n");
 733                         rsl_rll_error(RLL_CAUSE_SEQ_ERR, mctx);
 734                 }
 735         }
 736
 737         /* V(A) shall be set to the value of N(R) */
 738         dl->V_ack = nr;
 739
 740         /* If T200 has been reset by the receipt of an I, RR or RNR frame,
 741          * and if there are outstanding I frames, restart T200 */
 742         if (t200_reset && !rej) {
 743                 if (dl->tx_length[dl->V_send - 1]) {
 744                         LOGP(DLLAPDM, LOGL_INFO, "start T200, due to unacked I "
 745                                 "frame(s)\n");
 746                         osmo_timer_schedule(&dl->t200, T200);
 747                 }
 748         }
 749 }
 750
 751 /* L1 -> L2 */
 752
 753 /* Receive a LAPDm U (Unnumbered) message from L1 */
 754 static int lapdm_rx_u(struct msgb *msg, struct lapdm_msg_ctx *mctx)
 755 {
 756         struct lapdm_datalink *dl = mctx->dl;
 757         struct lapdm_entity *le = dl->entity;
 758         uint8_t length;
 759         int rc;
 760         int rsl_msg;
 761
 762         switch (LAPDm_CTRL_U_BITS(mctx->ctrl)) {
 763         case LAPDm_U_SABM:
 764                 rsl_msg = RSL_MT_EST_IND;
 765
 766                 LOGP(DLLAPDM, LOGL_INFO, "SABM received\n");
 767                 /* 5.7.1 */
 768                 dl->seq_err_cond = 0;
 769                 /* G.2.2 Wrong value of the C/R bit */
 770                 if (LAPDm_ADDR_CR(mctx->addr) == le->cr.rem2loc.resp) {
 771                         LOGP(DLLAPDM, LOGL_NOTICE, "SABM response error\n");
 772                         msgb_free(msg);
 773                         rsl_rll_error(RLL_CAUSE_FRM_UNIMPL, mctx);
 774                         return -EINVAL;
 775                 }
 776
 777                 length = msg->l2h[2] >> 2;
 778                 /* G.4.5 If SABM is received with L>N201 or with M bit
 779                  * set, AN MDL-ERROR-INDICATION is sent to MM.
 780                  */
 781                 if ((msg->l2h[2] & LAPDm_MORE) || length + 3 > mctx->n201) {
 782                         LOGP(DLLAPDM, LOGL_NOTICE, "SABM too large error\n");
 783                         msgb_free(msg);
 784                         rsl_rll_error(RLL_CAUSE_UFRM_INC_PARAM, mctx);
 785                         return -EIO;
 786                 }
 787
 788                 /* Must be Format B */
 789                 rc = check_length_ind(mctx, msg->l2h[2]);
 790                 if (rc < 0) {
 791                         msgb_free(msg);
 792                         return rc;
 793                 }
 794                 switch (dl->state) {
 795                 case LAPDm_STATE_IDLE:
 796                         /* Set chan_nr and link_id for established connection */
 797                         memset(&dl->mctx, 0, sizeof(dl->mctx));
 798                         dl->mctx.dl = dl;
 799                         dl->mctx.chan_nr = mctx->chan_nr;
 800                         dl->mctx.link_id = mctx->link_id;
 801                         dl->mctx.n201 = mctx->n201;
 802                         break;
 803                 case LAPDm_STATE_MF_EST:
 804                         if (length == 0) {
 805                                 rsl_msg = RSL_MT_EST_CONF;
 806                                 break;
 807                         }
 808                         LOGP(DLLAPDM, LOGL_INFO, "SABM command, multiple "
 809                                 "frame established state\n");
 810                         /* check for contention resoultion */
 811                         if (dl->tx_hist[0][2] >> 2) {
 812                                 LOGP(DLLAPDM, LOGL_NOTICE, "SABM not allowed "
 813                                         "during contention resolution\n");
 814                                 rsl_rll_error(RLL_CAUSE_SABM_INFO_NOTALL, mctx);
 815                         }
 816                         msgb_free(msg);
 817                         return 0;
 818                 case LAPDm_STATE_DISC_SENT:
 819                         /* 5.4.6.2 send DM with F=P */
 820                         lapdm_send_dm(mctx);
 821                         /* reset Timer T200 */
 822                         osmo_timer_del(&dl->t200);
 823                         msgb_free(msg);
 824                         return send_rll_simple(RSL_MT_REL_CONF, mctx);
 825                 default:
 826                         lapdm_send_ua(mctx, length, msg->l2h + 3);
 827                         msgb_free(msg);
 828                         return 0;
 829                 }
 830                 /* send UA response */
 831                 lapdm_send_ua(mctx, length, msg->l2h + 3);
 832                 /* set Vs, Vr and Va to 0 */
 833                 dl->V_send = dl->V_recv = dl->V_ack = 0;
 834                 /* clear tx_hist */
 835                 dl->tx_length[0] = 0;
 836                 /* enter multiple-frame-established state */
 837                 lapdm_dl_newstate(dl, LAPDm_STATE_MF_EST);
 838                 /* send notification to L3 */
 839                 if (length == 0) {
 840                         /* 5.4.1.2 Normal establishment procedures */
 841                         rc = send_rll_simple(rsl_msg, mctx);
 842                         msgb_free(msg);
 843                 } else {
 844                         /* 5.4.1.4 Contention resolution establishment */
 845                         msg->l3h = msg->l2h + 3;
 846                         msgb_pull_l2h(msg);
 847                         rc = send_rslms_rll_l3(rsl_msg, mctx, msg);
 848                 }
 849                 break;
 850         case LAPDm_U_DM:
 851                 LOGP(DLLAPDM, LOGL_INFO, "DM received\n");
 852                 /* G.2.2 Wrong value of the C/R bit */
 853                 if (LAPDm_ADDR_CR(mctx->addr) == le->cr.rem2loc.cmd) {
 854                         LOGP(DLLAPDM, LOGL_NOTICE, "DM command error\n");
 855                         msgb_free(msg);
 856                         rsl_rll_error(RLL_CAUSE_FRM_UNIMPL, mctx);
 857                         return -EINVAL;
 858                 }
 859                 if (!LAPDm_CTRL_PF_BIT(mctx->ctrl)) {
 860                         /* 5.4.1.2 DM responses with the F bit set to "0"
 861                          * shall be ignored.
 862                          */
 863                         msgb_free(msg);
 864                         return 0;
 865                 }
 866                 switch (dl->state) {
 867                 case LAPDm_STATE_SABM_SENT:
 868                         break;
 869                 case LAPDm_STATE_MF_EST:
 870                         if (LAPDm_CTRL_PF_BIT(mctx->ctrl) == 1) {
 871                                 LOGP(DLLAPDM, LOGL_INFO, "unsolicited DM "
 872                                         "response\n");
 873                                 rsl_rll_error(RLL_CAUSE_UNSOL_DM_RESP, mctx);
 874                         } else {
 875                                 LOGP(DLLAPDM, LOGL_INFO, "unsolicited DM "
 876                                         "response, multiple frame established "
 877                                         "state\n");
 878                                 rsl_rll_error(RLL_CAUSE_UNSOL_DM_RESP_MF, mctx);
 879                         }
 880                         msgb_free(msg);
 881                         return 0;
 882                 case LAPDm_STATE_TIMER_RECOV:
 883                         /* DM is normal in case PF = 1 */
 884                         if (LAPDm_CTRL_PF_BIT(mctx->ctrl) == 0) {
 885                                 LOGP(DLLAPDM, LOGL_INFO, "unsolicited DM "
 886                                         "response, multiple frame established "
 887                                         "state\n");
 888                                 rsl_rll_error(RLL_CAUSE_UNSOL_DM_RESP_MF, mctx);
 889                                 msgb_free(msg);
 890                                 return 0;
 891                         }
 892                         break;
 893                 case LAPDm_STATE_DISC_SENT:
 894                         /* reset Timer T200 */
 895                         osmo_timer_del(&dl->t200);
 896                         /* go to idle state */
 897                         lapdm_dl_flush_tx(dl);
 898                         lapdm_dl_flush_send(dl);
 899                         lapdm_dl_newstate(dl, LAPDm_STATE_IDLE);
 900                         rc = send_rll_simple(RSL_MT_REL_CONF, mctx);
 901                         msgb_free(msg);
 902                         return 0;
 903                 case LAPDm_STATE_IDLE:
 904                         /* 5.4.5 all other frame types shall be discarded */
 905                 default:
 906                         LOGP(DLLAPDM, LOGL_INFO, "unsolicited DM response! "
 907                                 "(discarding)\n");
 908                         msgb_free(msg);
 909                         return 0;
 910                 }
 911                 /* reset T200 */
 912                 osmo_timer_del(&dl->t200);
 913                 rc = send_rll_simple(RSL_MT_REL_IND, mctx);
 914                 msgb_free(msg);
 915                 break;
 916         case LAPDm_U_UI:
 917                 LOGP(DLLAPDM, LOGL_INFO, "UI received\n");
 918                 /* G.2.2 Wrong value of the C/R bit */
 919                 if (LAPDm_ADDR_CR(mctx->addr) == le->cr.rem2loc.resp) {
 920                         LOGP(DLLAPDM, LOGL_NOTICE, "UI indicates response "
 921                                 "error\n");
 922                         msgb_free(msg);
 923                         rsl_rll_error(RLL_CAUSE_FRM_UNIMPL, mctx);
 924                         return -EINVAL;
 925                 }
 926
 927                 length = msg->l2h[2] >> 2;
 928                 /* FIXME: G.4.5 If UI is received with L>N201 or with M bit
 929                  * set, AN MDL-ERROR-INDICATION is sent to MM.
 930                  */
 931
 932                 if (mctx->lapdm_fmt == LAPDm_FMT_B4) {
 933                         length = N201_B4;
 934                         msg->l3h = msg->l2h + 2;
 935                 } else {
 936                         rc = check_length_ind(mctx, msg->l2h[2]);
 937                         if (rc < 0) {
 938                                 msgb_free(msg);
 939                                 return rc;
 940                         }
 941                         length = msg->l2h[2] >> 2;
 942                         msg->l3h = msg->l2h + 3;
 943                 }
 944                 /* do some length checks */
 945                 if (length == 0) {
 946                         /* 5.3.3 UI frames received with the length indicator
 947                          * set to "0" shall be ignored
 948                          */
 949                         LOGP(DLLAPDM, LOGL_INFO, "length=0 (discarding)\n");
 950                         msgb_free(msg);
 951                         return 0;
 952                 }
 953                 switch (LAPDm_ADDR_SAPI(mctx->addr)) {
 954                 case LAPDm_SAPI_NORMAL:
 955                 case LAPDm_SAPI_SMS:
 956                         break;
 957                 default:
 958                         /* 5.3.3 UI frames with invalid SAPI values shall be
 959                          * discarded
 960                          */
 961                         LOGP(DLLAPDM, LOGL_INFO, "sapi=%u (discarding)\n",
 962                                 LAPDm_ADDR_SAPI(mctx->addr));
 963                         msgb_free(msg);
 964                         return 0;
 965                 }
 966                 msgb_pull_l2h(msg);
 967                 rc = send_rslms_rll_l3_ui(mctx, msg);
 968                 break;
 969         case LAPDm_U_DISC:
 970                 rsl_msg = RSL_MT_REL_IND;
 971
 972                 LOGP(DLLAPDM, LOGL_INFO, "DISC received\n");
 973                 /* flush buffers */
 974                 lapdm_dl_flush_tx(dl);
 975                 lapdm_dl_flush_send(dl);
 976                 /* 5.7.1 */
 977                 dl->seq_err_cond = 0;
 978                 /* G.2.2 Wrong value of the C/R bit */
 979                 if (LAPDm_ADDR_CR(mctx->addr) == le->cr.rem2loc.resp) {
 980                         LOGP(DLLAPDM, LOGL_NOTICE, "DISC response error\n");
 981                         msgb_free(msg);
 982                         rsl_rll_error(RLL_CAUSE_FRM_UNIMPL, mctx);
 983                         return -EINVAL;
 984                 }
 985                 length = msg->l2h[2] >> 2;
 986                 if (length > 0 || msg->l2h[2] & 0x02) {
 987                         /* G.4.4 If a DISC or DM frame is received with L>0 or
 988                          * with the M bit set to "1", an MDL-ERROR-INDICATION
 989                          * primitive with cause "U frame with incorrect
 990                          * parameters" is sent to the mobile management entity.
 991                          */
 992                         LOGP(DLLAPDM, LOGL_NOTICE,
 993                                 "U frame iwth incorrect parameters ");
 994                         msgb_free(msg);
 995                         rsl_rll_error(RLL_CAUSE_UFRM_INC_PARAM, mctx);
 996                         return -EIO;
 997                 }
 998                 switch (dl->state) {
 999                 case LAPDm_STATE_IDLE:
1000                         LOGP(DLLAPDM, LOGL_INFO, "DISC in idle state\n");
1001                         /* send DM with F=P */
1002                         msgb_free(msg);
1003                         return lapdm_send_dm(mctx);
1004                 case LAPDm_STATE_SABM_SENT:
1005                         LOGP(DLLAPDM, LOGL_INFO, "DISC in SABM state\n");
1006                         /* 5.4.6.2 send DM with F=P */
1007                         lapdm_send_dm(mctx);
1008                         /* reset Timer T200 */
1009                         osmo_timer_del(&dl->t200);
1010                         msgb_free(msg);
1011                         return send_rll_simple(RSL_MT_REL_IND, mctx);
1012                 case LAPDm_STATE_MF_EST:
1013                 case LAPDm_STATE_TIMER_RECOV:
1014                         LOGP(DLLAPDM, LOGL_INFO, "DISC in est state\n");
1015                         break;
1016                 case LAPDm_STATE_DISC_SENT:
1017                         LOGP(DLLAPDM, LOGL_INFO, "DISC in disc state\n");
1018                         rsl_msg = RSL_MT_REL_CONF;
1019                         break;
1020                 default:
1021                         lapdm_send_ua(mctx, length, msg->l2h + 3);
1022                         msgb_free(msg);
1023                         return 0;
1024                 }
1025                 /* send UA response */
1026                 lapdm_send_ua(mctx, length, msg->l2h + 3);
1027                 /* reset Timer T200 */
1028                 osmo_timer_del(&dl->t200);
1029                 /* enter idle state */
1030                 lapdm_dl_flush_tx(dl);
1031                 lapdm_dl_flush_send(dl);
1032                 lapdm_dl_newstate(dl, LAPDm_STATE_IDLE);
1033                 /* send notification to L3 */
1034                 rc = send_rll_simple(rsl_msg, mctx);
1035                 msgb_free(msg);
1036                 break;
1037         case LAPDm_U_UA:
1038                 LOGP(DLLAPDM, LOGL_INFO, "UA received\n");
1039                 /* G.2.2 Wrong value of the C/R bit */
1040                 if (LAPDm_ADDR_CR(mctx->addr) == le->cr.rem2loc.cmd) {
1041                         LOGP(DLLAPDM, LOGL_NOTICE, "UA indicates command "
1042                                 "error\n");
1043                         msgb_free(msg);
1044                         rsl_rll_error(RLL_CAUSE_FRM_UNIMPL, mctx);
1045                         return -EINVAL;
1046                 }
1047
1048                 length = msg->l2h[2] >> 2;
1049                 /* G.4.5 If UA is received with L>N201 or with M bit
1050                  * set, AN MDL-ERROR-INDICATION is sent to MM.
1051                  */
1052                 if ((msg->l2h[2] & LAPDm_MORE) || length + 3 > mctx->n201) {
1053                         LOGP(DLLAPDM, LOGL_NOTICE, "UA too large error\n");
1054                         msgb_free(msg);
1055                         rsl_rll_error(RLL_CAUSE_UFRM_INC_PARAM, mctx);
1056                         return -EIO;
1057                 }
1058
1059                 if (!LAPDm_CTRL_PF_BIT(mctx->ctrl)) {
1060                         /* 5.4.1.2 A UA response with the F bit set to "0"
1061                          * shall be ignored.
1062                          */
1063                         LOGP(DLLAPDM, LOGL_INFO, "F=0 (discarding)\n");
1064                         msgb_free(msg);
1065                         return 0;
1066                 }
1067                 switch (dl->state) {
1068                 case LAPDm_STATE_SABM_SENT:
1069                         break;
1070                 case LAPDm_STATE_MF_EST:
1071                 case LAPDm_STATE_TIMER_RECOV:
1072                         LOGP(DLLAPDM, LOGL_INFO, "unsolicited UA response! "
1073                                 "(discarding)\n");
1074                         rsl_rll_error(RLL_CAUSE_UNSOL_UA_RESP, mctx);
1075                         msgb_free(msg);
1076                         return 0;
1077                 case LAPDm_STATE_DISC_SENT:
1078                         LOGP(DLLAPDM, LOGL_INFO, "UA in disconnect state\n");
1079                         /* reset Timer T200 */
1080                         osmo_timer_del(&dl->t200);
1081                         /* go to idle state */
1082                         lapdm_dl_flush_tx(dl);
1083                         lapdm_dl_flush_send(dl);
1084                         lapdm_dl_newstate(dl, LAPDm_STATE_IDLE);
1085                         rc = send_rll_simple(RSL_MT_REL_CONF, mctx);
1086                         msgb_free(msg);
1087                         return 0;
1088                 case LAPDm_STATE_IDLE:
1089                         /* 5.4.5 all other frame types shall be discarded */
1090                 default:
1091                         LOGP(DLLAPDM, LOGL_INFO, "unsolicited UA response! "
1092                                 "(discarding)\n");
1093                         msgb_free(msg);
1094                         return 0;
1095                 }
1096                 LOGP(DLLAPDM, LOGL_INFO, "UA in SABM state\n");
1097                 /* reset Timer T200 */
1098                 osmo_timer_del(&dl->t200);
1099                 /* compare UA with SABME if contention resolution is applied */
1100                 if (dl->tx_hist[0][2] >> 2) {
1101                         rc = check_length_ind(mctx, msg->l2h[2]);
1102                         if (rc < 0) {
1103                                 rc = send_rll_simple(RSL_MT_REL_IND, mctx);
1104                                 msgb_free(msg);
1105                                 /* go to idle state */
1106                                 lapdm_dl_flush_tx(dl);
1107                                 lapdm_dl_flush_send(dl);
1108                                 lapdm_dl_newstate(dl, LAPDm_STATE_IDLE);
1109                                 return 0;
1110                         }
1111                         length = msg->l2h[2] >> 2;
1112                         if (length != (dl->tx_hist[0][2] >> 2)
1113                          || !!memcmp(dl->tx_hist[0] + 3, msg->l2h + 3,
1114                                         length)) {
1115                                 LOGP(DLLAPDM, LOGL_INFO, "**** UA response "
1116                                         "mismatches ****\n");
1117                                 rc = send_rll_simple(RSL_MT_REL_IND, mctx);
1118                                 msgb_free(msg);
1119                                 /* go to idle state */
1120                                 lapdm_dl_flush_tx(dl);
1121                                 lapdm_dl_flush_send(dl);
1122                                 lapdm_dl_newstate(dl, LAPDm_STATE_IDLE);
1123                                 return 0;
1124                         }
1125                 }
1126                 /* set Vs, Vr and Va to 0 */
1127                 dl->V_send = dl->V_recv = dl->V_ack = 0;
1128                 /* clear tx_hist */
1129                 dl->tx_length[0] = 0;
1130                 /* enter multiple-frame-established state */
1131                 lapdm_dl_newstate(dl, LAPDm_STATE_MF_EST);
1132                 /* send outstanding frames, if any (resume / reconnect) */
1133                 rslms_send_i(mctx, __LINE__);
1134                 /* send notification to L3 */
1135                 rc = send_rll_simple(RSL_MT_EST_CONF, mctx);
1136                 msgb_free(msg);
1137                 break;
1138         default:
1139                 /* G.3.1 */
1140                 LOGP(DLLAPDM, LOGL_NOTICE, "Unnumbered frame not allowed.\n");
1141                 msgb_free(msg);
1142                 rsl_rll_error(RLL_CAUSE_FRM_UNIMPL, mctx);
1143                 return -EINVAL;
1144         }
1145         return rc;
1146 }
1147
1148 /* Receive a LAPDm S (Supervisory) message from L1 */
1149 static int lapdm_rx_s(struct msgb *msg, struct lapdm_msg_ctx *mctx)
1150 {
1151         struct lapdm_datalink *dl = mctx->dl;
1152         struct lapdm_entity *le = dl->entity;
1153         uint8_t length;
1154
1155         length = msg->l2h[2] >> 2;
1156         if (length > 0 || msg->l2h[2] & 0x02) {
1157                 /* G.4.3 If a supervisory frame is received with L>0 or
1158                  * with the M bit set to "1", an MDL-ERROR-INDICATION
1159                  * primitive with cause "S frame with incorrect
1160                  * parameters" is sent to the mobile management entity. */
1161                 LOGP(DLLAPDM, LOGL_NOTICE,
1162                                 "S frame with incorrect parameters\n");
1163                 msgb_free(msg);
1164                 rsl_rll_error(RLL_CAUSE_SFRM_INC_PARAM, mctx);
1165                 return -EIO;
1166         }
1167
1168         if (LAPDm_ADDR_CR(mctx->addr) == le->cr.rem2loc.resp
1169          && LAPDm_CTRL_PF_BIT(mctx->ctrl)
1170          && dl->state != LAPDm_STATE_TIMER_RECOV) {
1171                 /* 5.4.2.2: Inidcate error on supervisory reponse F=1 */
1172                 LOGP(DLLAPDM, LOGL_NOTICE, "S frame response with F=1 error\n");
1173                 rsl_rll_error(RLL_CAUSE_UNSOL_SPRV_RESP, mctx);
1174         }
1175
1176         switch (dl->state) {
1177         case LAPDm_STATE_IDLE:
1178                 /* if P=1, respond DM with F=1 (5.2.2) */
1179                 /* 5.4.5 all other frame types shall be discarded */
1180                 if (LAPDm_CTRL_PF_BIT(mctx->ctrl))
1181                         lapdm_send_dm(mctx); /* F=P */
1182                 /* fall though */
1183         case LAPDm_STATE_SABM_SENT:
1184         case LAPDm_STATE_DISC_SENT:
1185                 LOGP(DLLAPDM, LOGL_NOTICE, "S frame ignored in this state\n");
1186                 msgb_free(msg);
1187                 return 0;
1188         }
1189         switch (LAPDm_CTRL_S_BITS(mctx->ctrl)) {
1190         case LAPDm_S_RR:
1191                 LOGP(DLLAPDM, LOGL_INFO, "RR received\n");
1192                 /* 5.5.3.1: Acknowlege all tx frames up the the N(R)-1 */
1193                 lapdm_acknowledge(mctx);
1194
1195                 /* 5.5.3.2 */
1196                 if (LAPDm_ADDR_CR(mctx->addr) == le->cr.rem2loc.cmd
1197                  && LAPDm_CTRL_PF_BIT(mctx->ctrl)) {
1198                         if (!dl->own_busy && !dl->seq_err_cond) {
1199                                 LOGP(DLLAPDM, LOGL_NOTICE, "RR frame command "
1200                                         "with polling bit set and we are not "
1201                                         "busy, so we reply with RR frame\n");
1202                                 lapdm_send_rr(mctx, 1);
1203                                 /* NOTE: In case of sequence error condition,
1204                                  * the REJ frame has been transmitted when
1205                                  * entering the condition, so it has not be
1206                                  * done here
1207                                  */
1208                         } else if (dl->own_busy) {
1209                                 LOGP(DLLAPDM, LOGL_NOTICE, "RR frame command "
1210                                         "with polling bit set and we are busy, "
1211                                         "so we reply with RR frame\n");
1212                                 lapdm_send_rnr(mctx, 1);
1213                         }
1214                 } else if (LAPDm_ADDR_CR(mctx->addr) == le->cr.rem2loc.resp
1215                         && LAPDm_CTRL_PF_BIT(mctx->ctrl)
1216                         && dl->state == LAPDm_STATE_TIMER_RECOV) {
1217                         LOGP(DLLAPDM, LOGL_INFO, "RR response with F==1, "
1218                                 "and we are in timer recovery state, so "
1219                                 "we leave that state\n");
1220                         /* V(S) to the N(R) in the RR frame */
1221                         dl->V_send = LAPDm_CTRL_Nr(mctx->ctrl);
1222                         /* reset Timer T200 */
1223                         osmo_timer_del(&dl->t200);
1224                         /* 5.5.7 Clear timer recovery condition */
1225                         lapdm_dl_newstate(dl, LAPDm_STATE_MF_EST);
1226                 }
1227                 /* Send message, if possible due to acknowledged data */
1228                 rslms_send_i(mctx, __LINE__);
1229
1230                 break;
1231         case LAPDm_S_RNR:
1232                 LOGP(DLLAPDM, LOGL_INFO, "RNR received\n");
1233                 /* 5.5.3.1: Acknowlege all tx frames up the the N(R)-1 */
1234                 lapdm_acknowledge(mctx);
1235
1236                 /* 5.5.5 */
1237                 /* Set peer receiver busy condition */
1238                 dl->peer_busy = 1;
1239
1240                 if (LAPDm_CTRL_PF_BIT(mctx->ctrl)) {
1241                         if (LAPDm_ADDR_CR(mctx->addr) == le->cr.rem2loc.cmd) {
1242                                 if (!dl->own_busy) {
1243                                         LOGP(DLLAPDM, LOGL_INFO, "RNR poll "
1244                                                 "command and we are not busy, "
1245                                                 "so we reply with RR final "
1246                                                 "response\n");
1247                                         /* Send RR with F=1 */
1248                                         lapdm_send_rr(mctx, 1);
1249                                 } else {
1250                                         LOGP(DLLAPDM, LOGL_INFO, "RNR poll "
1251                                                 "command and we are busy, so "
1252                                                 "we reply with RNR final "
1253                                                 "response\n");
1254                                         /* Send RNR with F=1 */
1255                                         lapdm_send_rnr(mctx, 1);
1256                                 }
1257                         } else if (dl->state == LAPDm_STATE_TIMER_RECOV) {
1258                                 LOGP(DLLAPDM, LOGL_INFO, "RNR poll response "
1259                                         "and we in timer recovery state, so "
1260                                         "we leave that state\n");
1261                                 /* 5.5.7 Clear timer recovery condition */
1262                                 lapdm_dl_newstate(dl, LAPDm_STATE_MF_EST);
1263                                 /* V(S) to the N(R) in the RNR frame */
1264                                 dl->V_send = LAPDm_CTRL_Nr(mctx->ctrl);
1265                         }
1266                 } else
1267                         LOGP(DLLAPDM, LOGL_INFO, "RNR not polling/final state "
1268                                 "received\n");
1269
1270                 /* Send message, if possible due to acknowledged data */
1271                 rslms_send_i(mctx, __LINE__);
1272
1273                 break;
1274         case LAPDm_S_REJ:
1275                 LOGP(DLLAPDM, LOGL_INFO, "REJ received\n");
1276                 /* 5.5.3.1: Acknowlege all tx frames up the the N(R)-1 */
1277                 lapdm_acknowledge(mctx);
1278
1279                 /* 5.5.4.1 */
1280                 if (dl->state != LAPDm_STATE_TIMER_RECOV) {
1281                         /* Clear an existing peer receiver busy condition */
1282                         dl->peer_busy = 0;
1283                         /* V(S) and V(A) to the N(R) in the REJ frame */
1284                         dl->V_send = dl->V_ack = LAPDm_CTRL_Nr(mctx->ctrl);
1285                         /* reset Timer T200 */
1286                         osmo_timer_del(&dl->t200);
1287                         /* 5.5.3.2 */
1288                         if (LAPDm_ADDR_CR(mctx->addr) == le->cr.rem2loc.cmd
1289                          && LAPDm_CTRL_PF_BIT(mctx->ctrl)) {
1290                                 if (!dl->own_busy && !dl->seq_err_cond) {
1291                                         LOGP(DLLAPDM, LOGL_INFO, "REJ poll "
1292                                                 "command not in timer recovery "
1293                                                 "state and not in own busy "
1294                                                 "condition received, so we "
1295                                                 "respond with RR final "
1296                                                 "response\n");
1297                                         lapdm_send_rr(mctx, 1);
1298                                         /* NOTE: In case of sequence error
1299                                          * condition, the REJ frame has been
1300                                          * transmitted when entering the
1301                                          * condition, so it has not be done
1302                                          * here
1303                                          */
1304                                 } else if (dl->own_busy) {
1305                                         LOGP(DLLAPDM, LOGL_INFO, "REJ poll "
1306                                                 "command not in timer recovery "
1307                                                 "state and in own busy "
1308                                                 "condition received, so we "
1309                                                 "respond with RNR final "
1310                                                 "response\n");
1311                                         lapdm_send_rnr(mctx, 1);
1312                                 }
1313                         } else
1314                                 LOGP(DLLAPDM, LOGL_INFO, "REJ response or not "
1315                                         "polling command not in timer recovery "
1316                                         "state received\n");
1317                         /* send MDL ERROR INIDCATION to L3 */
1318                         if (LAPDm_ADDR_CR(mctx->addr) == le->cr.rem2loc.resp
1319                          && LAPDm_CTRL_PF_BIT(mctx->ctrl)) {
1320                                 rsl_rll_error(RLL_CAUSE_UNSOL_SPRV_RESP, mctx);
1321                         }
1322
1323                 } else if (LAPDm_ADDR_CR(mctx->addr) == le->cr.rem2loc.resp
1324                         && LAPDm_CTRL_PF_BIT(mctx->ctrl)) {
1325                         LOGP(DLLAPDM, LOGL_INFO, "REJ poll response in timer "
1326                                 "recovery state received\n");
1327                         /* Clear an existing peer receiver busy condition */
1328                         dl->peer_busy = 0;
1329                         /* 5.5.7 Clear timer recovery condition */
1330                         lapdm_dl_newstate(dl, LAPDm_STATE_MF_EST);
1331                         /* V(S) and V(A) to the N(R) in the REJ frame */
1332                         dl->V_send = dl->V_ack = LAPDm_CTRL_Nr(mctx->ctrl);
1333                         /* reset Timer T200 */
1334                         osmo_timer_del(&dl->t200);
1335                 } else {
1336                         /* Clear an existing peer receiver busy condition */
1337                         dl->peer_busy = 0;
1338                         /* V(S) and V(A) to the N(R) in the REJ frame */
1339                         dl->V_send = dl->V_ack = LAPDm_CTRL_Nr(mctx->ctrl);
1340                         /* 5.5.3.2 */
1341                         if (LAPDm_ADDR_CR(mctx->addr) == le->cr.rem2loc.cmd
1342                          && LAPDm_CTRL_PF_BIT(mctx->ctrl)) {
1343                                 if (!dl->own_busy && !dl->seq_err_cond) {
1344                                         LOGP(DLLAPDM, LOGL_INFO, "REJ poll "
1345                                                 "command in timer recovery "
1346                                                 "state and not in own busy "
1347                                                 "condition received, so we "
1348                                                 "respond with RR final "
1349                                                 "response\n");
1350                                         lapdm_send_rr(mctx, 1);
1351                                         /* NOTE: In case of sequence error
1352                                          * condition, the REJ frame has been
1353                                          * transmitted when entering the
1354                                          * condition, so it has not be done
1355                                          * here
1356                                          */
1357                                 } else if (dl->own_busy) {
1358                                         LOGP(DLLAPDM, LOGL_INFO, "REJ poll "
1359                                                 "command in timer recovery "
1360                                                 "state and in own busy "
1361                                                 "condition received, so we "
1362                                                 "respond with RNR final "
1363                                                 "response\n");
1364                                         lapdm_send_rnr(mctx, 1);
1365                                 }
1366                         } else
1367                                 LOGP(DLLAPDM, LOGL_INFO, "REJ response or not "
1368                                         "polling command in timer recovery "
1369                                         "state received\n");
1370                 }
1371
1372                 /* FIXME: 5.5.4.2 2) */
1373
1374                 /* Send message, if possible due to acknowledged data */
1375                 rslms_send_i(mctx, __LINE__);
1376
1377                 break;
1378         default:
1379                 /* G.3.1 */
1380                 LOGP(DLLAPDM, LOGL_NOTICE, "Supervisory frame not allowed.\n");
1381                 msgb_free(msg);
1382                 rsl_rll_error(RLL_CAUSE_FRM_UNIMPL, mctx);
1383                 return -EINVAL;
1384         }
1385         msgb_free(msg);
1386         return 0;
1387 }
1388
1389 /* Receive a LAPDm I (Information) message from L1 */
1390 static int lapdm_rx_i(struct msgb *msg, struct lapdm_msg_ctx *mctx)
1391 {
1392         struct lapdm_datalink *dl = mctx->dl;
1393         struct lapdm_entity *le = dl->entity;
1394         //uint8_t nr = LAPDm_CTRL_Nr(mctx->ctrl);
1395         uint8_t ns = LAPDm_CTRL_I_Ns(mctx->ctrl);
1396         uint8_t length;
1397         int rc;
1398
1399         LOGP(DLLAPDM, LOGL_NOTICE, "I received\n");
1400
1401         /* G.2.2 Wrong value of the C/R bit */
1402         if (LAPDm_ADDR_CR(mctx->addr) == le->cr.rem2loc.resp) {
1403                 LOGP(DLLAPDM, LOGL_NOTICE, "I frame response not allowed\n");
1404                 msgb_free(msg);
1405                 rsl_rll_error(RLL_CAUSE_FRM_UNIMPL, mctx);
1406                 return -EINVAL;
1407         }
1408
1409         length = msg->l2h[2] >> 2;
1410         if (length == 0 || length + 3 > mctx->n201) {
1411                 /* G.4.2 If the length indicator of an I frame is set
1412                  * to a numerical value L>N201 or L=0, an MDL-ERROR-INDICATION
1413                  * primitive with cause "I frame with incorrect length"
1414                  * is sent to the mobile management entity. */
1415                 LOGP(DLLAPDM, LOGL_NOTICE, "I frame length not allowed\n");
1416                 msgb_free(msg);
1417                 rsl_rll_error(RLL_CAUSE_IFRM_INC_LEN, mctx);
1418                 return -EIO;
1419         }
1420
1421         /* G.4.2 If the numerical value of L is L<N201 and the M
1422          * bit is set to "1", then an MDL-ERROR-INDICATION primitive with
1423          * cause "I frame with incorrect use of M bit" is sent to the
1424          * mobile management entity. */
1425         if ((msg->l2h[2] & LAPDm_MORE) && length + 3 < mctx->n201) {
1426                 LOGP(DLLAPDM, LOGL_NOTICE, "I frame with M bit too short\n");
1427                 msgb_free(msg);
1428                 rsl_rll_error(RLL_CAUSE_IFRM_INC_MBITS, mctx);
1429                 return -EIO;
1430         }
1431
1432         switch (dl->state) {
1433         case LAPDm_STATE_IDLE:
1434                 /* if P=1, respond DM with F=1 (5.2.2) */
1435                 /* 5.4.5 all other frame types shall be discarded */
1436                 if (LAPDm_CTRL_PF_BIT(mctx->ctrl))
1437                         lapdm_send_dm(mctx); /* F=P */
1438                 /* fall though */
1439         case LAPDm_STATE_SABM_SENT:
1440         case LAPDm_STATE_DISC_SENT:
1441                 LOGP(DLLAPDM, LOGL_NOTICE, "I frame ignored in this state\n");
1442                 msgb_free(msg);
1443                 return 0;
1444         }
1445
1446         /* 5.7.1: N(s) sequence error */
1447         if (ns != dl->V_recv) {
1448                 LOGP(DLLAPDM, LOGL_NOTICE, "N(S) sequence error: N(S)=%u, "
1449                      "V(R)=%u\n", ns, dl->V_recv);
1450                 /* discard data */
1451                 msgb_free(msg);
1452                 if (!dl->seq_err_cond) {
1453                         /* FIXME: help me understand what exactly todo here
1454                         dl->seq_err_cond = 1;
1455                         */
1456                         lapdm_send_rej(mctx, LAPDm_CTRL_PF_BIT(mctx->ctrl));
1457                 } else {
1458                 }
1459                 return -EIO;
1460         }
1461         dl->seq_err_cond = 0;
1462
1463         /* Increment receiver state */
1464         dl->V_recv = inc_mod8(dl->V_recv);
1465         LOGP(DLLAPDM, LOGL_NOTICE, "incrementing V(R) to %u\n", dl->V_recv);
1466
1467         /* 5.5.3.1: Acknowlege all transmitted frames up the the N(R)-1 */
1468         lapdm_acknowledge(mctx); /* V(A) is also set here */
1469
1470         /* Only if we are not in own receiver busy condition */
1471         if (!dl->own_busy) {
1472                 /* if the frame carries a complete segment */
1473                 if (!(msg->l2h[2] & LAPDm_MORE)
1474                  && !dl->rcv_buffer) {
1475                         LOGP(DLLAPDM, LOGL_INFO, "message in single I frame\n");
1476                         /* send a DATA INDICATION to L3 */
1477                         msg->l3h = msg->l2h + 3;
1478                         msgb_pull_l2h(msg);
1479                         msg->len = length;
1480                         msg->tail = msg->data + length;
1481                         rc = send_rslms_rll_l3(RSL_MT_DATA_IND, mctx, msg);
1482                 } else {
1483                         /* create rcv_buffer */
1484                         if (!dl->rcv_buffer) {
1485                                 LOGP(DLLAPDM, LOGL_INFO, "message in multiple I "
1486                                         "frames (first message)\n");
1487                                 dl->rcv_buffer = msgb_alloc_headroom(200+56, 56,
1488                                                                 "LAPDm RX");
1489                                 dl->rcv_buffer->l3h = dl->rcv_buffer->data;
1490                         }
1491                         /* concat. rcv_buffer */
1492                         if (msgb_l3len(dl->rcv_buffer) + length > 200) {
1493                                 LOGP(DLLAPDM, LOGL_NOTICE, "Received frame "
1494                                         "overflow!\n");
1495                         } else {
1496                                 memcpy(msgb_put(dl->rcv_buffer, length),
1497                                         msg->l2h + 3, length);
1498                         }
1499                         /* if the last segment was received */
1500                         if (!(msg->l2h[2] & LAPDm_MORE)) {
1501                                 LOGP(DLLAPDM, LOGL_INFO, "message in multiple I "
1502                                         "frames (last message)\n");
1503                                 rc = send_rslms_rll_l3(RSL_MT_DATA_IND, mctx,
1504                                         dl->rcv_buffer);
1505                                 dl->rcv_buffer = NULL;
1506                         } else
1507                                 LOGP(DLLAPDM, LOGL_INFO, "message in multiple I "
1508                                         "frames (next message)\n");
1509                         msgb_free(msg);
1510
1511                 }
1512         } else
1513                 LOGP(DLLAPDM, LOGL_INFO, "I frame ignored during own receiver "
1514                         "busy condition\n");
1515
1516         /* Check for P bit */
1517         if (LAPDm_CTRL_PF_BIT(mctx->ctrl)) {
1518                 /* 5.5.2.1 */
1519                 /* check if we are not in own receiver busy */
1520                 if (!dl->own_busy) {
1521                         LOGP(DLLAPDM, LOGL_INFO, "we are not busy, send RR\n");
1522                         /* Send RR with F=1 */
1523                         rc = lapdm_send_rr(mctx, 1);
1524                 } else {
1525                         LOGP(DLLAPDM, LOGL_INFO, "we are busy, send RNR\n");
1526                         /* Send RNR with F=1 */
1527                         rc = lapdm_send_rnr(mctx, 1);
1528                 }
1529         } else {
1530                 /* 5.5.2.2 */
1531                 /* check if we are not in own receiver busy */
1532                 if (!dl->own_busy) {
1533                         /* NOTE: V(R) is already set above */
1534                         rc = rslms_send_i(mctx, __LINE__);
1535                         if (rc) {
1536                                 LOGP(DLLAPDM, LOGL_INFO, "we are not busy and "
1537                                         "have no pending data, send RR\n");
1538                                 /* Send RR with F=0 */
1539                                 return lapdm_send_rr(mctx, 0);
1540                         }
1541                         /* all I or one RR is sent, we are done */
1542                         return 0;
1543                 } else {
1544                         LOGP(DLLAPDM, LOGL_INFO, "we are busy, send RNR\n");
1545                         /* Send RNR with F=0 */
1546                         rc = lapdm_send_rnr(mctx, 0);
1547                 }
1548         }
1549
1550         /* Send message, if possible due to acknowledged data */
1551         rslms_send_i(mctx, __LINE__);
1552
1553         return rc;
1554 }
1555
1556 /* Receive a LAPDm message from L1 */
1557 static int lapdm_ph_data_ind(struct msgb *msg, struct lapdm_msg_ctx *mctx)
1558 {
1559         int rc;
1560
1561         /* G.2.3 EA bit set to "0" is not allowed in GSM */
1562         if (!LAPDm_ADDR_EA(mctx->addr)) {
1563                 LOGP(DLLAPDM, LOGL_NOTICE, "EA bit 0 is not allowed in GSM\n");
1564                 msgb_free(msg);
1565                 rsl_rll_error(RLL_CAUSE_FRM_UNIMPL, mctx);
1566                 return -EINVAL;
1567         }
1568
1569         if (LAPDm_CTRL_is_U(mctx->ctrl))
1570                 rc = lapdm_rx_u(msg, mctx);
1571         else if (LAPDm_CTRL_is_S(mctx->ctrl))
1572                 rc = lapdm_rx_s(msg, mctx);
1573         else if (LAPDm_CTRL_is_I(mctx->ctrl))
1574                 rc = lapdm_rx_i(msg, mctx);
1575         else {
1576                 LOGP(DLLAPDM, LOGL_NOTICE, "unknown LAPDm format\n");
1577                 msgb_free(msg);
1578                 rc = -EINVAL;
1579         }
1580         return rc;
1581 }
1582
1583 /* input into layer2 (from layer 1) */
1584 static int l2_ph_data_ind(struct msgb *msg, struct lapdm_entity *le, uint8_t chan_nr, uint8_t link_id)
1585 {
1586         uint8_t cbits = chan_nr >> 3;
1587         uint8_t sapi; /* we cannot take SAPI from link_id, as L1 has no clue */
1588         struct lapdm_msg_ctx mctx;
1589         int rc = 0;
1590
1591         /* when we reach here, we have a msgb with l2h pointing to the raw
1592          * 23byte mac block. The l1h has already been purged. */
1593
1594         mctx.chan_nr = chan_nr;
1595         mctx.link_id = link_id;
1596         mctx.addr = mctx.ctrl = 0;
1597
1598         /* check for L1 chan_nr/link_id and determine LAPDm hdr format */
1599         if (cbits == 0x10 || cbits == 0x12) {
1600                 /* Format Bbis is used on BCCH and CCCH(PCH, NCH and AGCH) */
1601                 mctx.lapdm_fmt = LAPDm_FMT_Bbis;
1602                 mctx.n201 = N201_Bbis;
1603                 sapi = 0;
1604         } else {
1605                 if (mctx.link_id & 0x40) {
1606                         /* It was received from network on SACCH */
1607
1608                         /* If sent by BTS, lapdm_fmt must be B4 */
1609                         if (le->mode == LAPDM_MODE_MS) {
1610                                 mctx.lapdm_fmt = LAPDm_FMT_B4;
1611                                 mctx.n201 = N201_B4;
1612                                 LOGP(DLLAPDM, LOGL_INFO, "fmt=B4\n");
1613                         } else {
1614                                 mctx.lapdm_fmt = LAPDm_FMT_B;
1615                                 mctx.n201 = N201_AB_SACCH;
1616                                 LOGP(DLLAPDM, LOGL_INFO, "fmt=B\n");
1617                         }
1618                         /* SACCH frames have a two-byte L1 header that
1619                          * OsmocomBB L1 doesn't strip */
1620                         mctx.tx_power_ind = msg->l2h[0] & 0x1f;
1621                         mctx.ta_ind = msg->l2h[1];
1622                         msgb_pull(msg, 2);
1623                         msg->l2h += 2;
1624                         sapi = (msg->l2h[0] >> 2) & 7;
1625                 } else {
1626                         mctx.lapdm_fmt = LAPDm_FMT_B;
1627                         LOGP(DLLAPDM, LOGL_INFO, "fmt=B\n");
1628                         mctx.n201 = 23; // FIXME: select correct size by chan.
1629                         sapi = (msg->l2h[0] >> 2) & 7;
1630                 }
1631         }
1632
1633         mctx.dl = datalink_for_sapi(le, sapi);
1634         /* G.2.1 No action on frames containing an unallocated SAPI. */
1635         if (!mctx.dl) {
1636                 LOGP(DLLAPDM, LOGL_NOTICE, "Received frame for unsupported "
1637                         "SAPI %d!\n", sapi);
1638                 msgb_free(msg);
1639                 return -EIO;
1640         }
1641
1642         switch (mctx.lapdm_fmt) {
1643         case LAPDm_FMT_A:
1644         case LAPDm_FMT_B:
1645         case LAPDm_FMT_B4:
1646                 mctx.addr = msg->l2h[0];
1647                 if (!(mctx.addr & 0x01)) {
1648                         LOGP(DLLAPDM, LOGL_ERROR, "we don't support "
1649                                 "multibyte addresses (discarding)\n");
1650                         msgb_free(msg);
1651                         return -EINVAL;
1652                 }
1653                 mctx.ctrl = msg->l2h[1];
1654                 /* obtain SAPI from address field */
1655                 mctx.link_id |= LAPDm_ADDR_SAPI(mctx.addr);
1656                 rc = lapdm_ph_data_ind(msg, &mctx);
1657                 break;
1658         case LAPDm_FMT_Bter:
1659                 /* FIXME */
1660                 msgb_free(msg);
1661                 break;
1662         case LAPDm_FMT_Bbis:
1663                 /* directly pass up to layer3 */
1664                 LOGP(DLLAPDM, LOGL_INFO, "fmt=Bbis UI\n");
1665                 msg->l3h = msg->l2h;
1666                 msgb_pull_l2h(msg);
1667                 rc = send_rslms_rll_l3(RSL_MT_UNIT_DATA_IND, &mctx, msg);
1668                 break;
1669         default:
1670                 msgb_free(msg);
1671         }
1672
1673         return rc;
1674 }
1675
1676 /* input into layer2 (from layer 1) */
1677 static int l2_ph_rach_ind(struct lapdm_entity *le, uint8_t ra, uint32_t fn, uint8_t acc_delay)
1678 {
1679         struct abis_rsl_cchan_hdr *ch;
1680         struct gsm48_req_ref req_ref;
1681         struct gsm_time gt;
1682         struct msgb *msg = msgb_alloc_headroom(512, 64, "RSL CHAN RQD");
1683
1684         msg->l2h = msgb_push(msg, sizeof(*ch));
1685         ch = (struct abis_rsl_cchan_hdr *)msg->l2h;
1686         rsl_init_cchan_hdr(ch, RSL_MT_CHAN_RQD);
1687         ch->chan_nr = RSL_CHAN_RACH;
1688
1689         /* generate a RSL CHANNEL REQUIRED message */
1690         gsm_fn2gsmtime(&gt, fn);
1691         req_ref.ra = ra;
1692         req_ref.t1 = gt.t1; /* FIXME: modulo? */
1693         req_ref.t2 = gt.t2;
1694         req_ref.t3_low = gt.t3 & 7;
1695         req_ref.t3_high = gt.t3 >> 3;
1696
1697         msgb_tv_fixed_put(msg, RSL_IE_REQ_REFERENCE, 3, (uint8_t *) &req_ref);
1698         msgb_tv_put(msg, RSL_IE_ACCESS_DELAY, acc_delay);
1699
1700         return rslms_sendmsg(msg, le);
1701 }
1702
1703 static int l2_ph_chan_conf(struct msgb *msg, struct lapdm_entity *le, uint32_t frame_nr);
1704
1705 int lapdm_phsap_up(struct osmo_prim_hdr *oph, struct lapdm_entity *le)
1706 {
1707         struct osmo_phsap_prim *pp = (struct osmo_phsap_prim *) oph;
1708         int rc = 0;
1709
1710         if (oph->sap != SAP_GSM_PH) {
1711                 LOGP(DLLAPDM, LOGL_ERROR, "primitive for unknown SAP %u\n",
1712                         oph->sap);
1713                 return -ENODEV;
1714         }
1715
1716         switch (oph->primitive) {
1717         case PRIM_PH_DATA:
1718                 if (oph->operation != PRIM_OP_INDICATION) {
1719                         LOGP(DLLAPDM, LOGL_ERROR, "PH_DATA is not INDICATION %u\n",
1720                                 oph->operation);
1721                         return -ENODEV;
1722                 }
1723                 rc = l2_ph_data_ind(oph->msg, le, pp->u.data.chan_nr,
1724                                     pp->u.data.link_id);
1725                 break;
1726         case PRIM_PH_RTS:
1727                 if (oph->operation != PRIM_OP_INDICATION) {
1728                         LOGP(DLLAPDM, LOGL_ERROR, "PH_RTS is not INDICATION %u\n",
1729                                 oph->operation);
1730                         return -ENODEV;
1731                 }
1732                 rc = l2_ph_data_conf(oph->msg, le);
1733                 break;
1734         case PRIM_PH_RACH:
1735                 switch (oph->operation) {
1736                 case PRIM_OP_INDICATION:
1737                         rc = l2_ph_rach_ind(le, pp->u.rach_ind.ra, pp->u.rach_ind.fn,
1738                                             pp->u.rach_ind.acc_delay);
1739                         break;
1740                 case PRIM_OP_CONFIRM:
1741                         rc = l2_ph_chan_conf(oph->msg, le, pp->u.rach_ind.fn);
1742                         break;
1743                 default:
1744                         return -EIO;
1745                 }
1746                 break;
1747         }
1748
1749         return rc;
1750 }
1751
1752
1753 /* L3 -> L2 / RSLMS -> LAPDm */
1754
1755 /* L3 requests establishment of data link */
1756 static int rslms_rx_rll_est_req(struct msgb *msg, struct lapdm_datalink *dl)
1757 {
1758         struct lapdm_entity *le = dl->entity;
1759         struct abis_rsl_rll_hdr *rllh = msgb_l2(msg);
1760         uint8_t chan_nr = rllh->chan_nr;
1761         uint8_t link_id = rllh->link_id;
1762         uint8_t sapi = rllh->link_id & 7;
1763         struct tlv_parsed tv;
1764         uint8_t length;
1765         uint8_t n201 = 23; //FIXME
1766
1767         /* Set chan_nr and link_id for established connection */
1768         memset(&dl->mctx, 0, sizeof(dl->mctx));
1769         dl->mctx.dl = dl;
1770         dl->mctx.n201 = n201;
1771         dl->mctx.chan_nr = chan_nr;
1772         dl->mctx.link_id = link_id;
1773
1774         rsl_tlv_parse(&tv, rllh->data, msgb_l2len(msg)-sizeof(*rllh));
1775         if (TLVP_PRESENT(&tv, RSL_IE_L3_INFO)) {
1776                 msg->l3h = TLVP_VAL(&tv, RSL_IE_L3_INFO);
1777                 /* contention resolution establishment procedure */
1778                 if (sapi != 0) {
1779                         /* According to clause 6, the contention resolution
1780                          * procedure is only permitted with SAPI value 0 */
1781                         LOGP(DLLAPDM, LOGL_ERROR, "SAPI != 0 but contention"
1782                                 "resolution (discarding)\n");
1783                         msgb_free(msg);
1784                         return send_rll_simple(RSL_MT_REL_IND, &dl->mctx);
1785                 }
1786                 /* transmit a SABM command with the P bit set to "1". The SABM
1787                  * command shall contain the layer 3 message unit */
1788                 length = TLVP_LEN(&tv, RSL_IE_L3_INFO);
1789                 LOGP(DLLAPDM, LOGL_INFO, "perform establishment with content "
1790                         "(SABM)\n");
1791         } else {
1792                 /* normal establishment procedure */
1793                 length = 0;
1794                 LOGP(DLLAPDM, LOGL_INFO, "perform normal establishm. (SABM)\n");
1795         }
1796
1797         /* check if the layer3 message length exceeds N201 */
1798         if (length + 3 > 21) { /* FIXME: do we know the channel N201? */
1799                 LOGP(DLLAPDM, LOGL_ERROR, "frame too large: %d > N201(%d) "
1800                         "(discarding)\n", length + 3, 21);
1801                 msgb_free(msg);
1802                 return send_rll_simple(RSL_MT_REL_IND, &dl->mctx);
1803         }
1804
1805         /* Flush send-queue */
1806         /* Clear send-buffer */
1807         lapdm_dl_flush_send(dl);
1808
1809         /* Discard partly received L3 message */
1810         if (dl->rcv_buffer) {
1811                 msgb_free(dl->rcv_buffer);
1812                 dl->rcv_buffer = NULL;
1813         }
1814
1815         /* Remove RLL header from msgb */
1816         msgb_pull_l2h(msg);
1817
1818         /* Push LAPDm header on msgb */
1819         msg->l2h = msgb_push(msg, 3);
1820         msg->l2h[0] = LAPDm_ADDR(LAPDm_LPD_NORMAL, sapi, le->cr.loc2rem.cmd);
1821         msg->l2h[1] = LAPDm_CTRL_U(LAPDm_U_SABM, 1);
1822         msg->l2h[2] = LAPDm_LEN(length);
1823         /* Transmit-buffer carries exactly one segment */
1824         memcpy(dl->tx_hist[0], msg->l2h, 3 + length);
1825         dl->tx_length[0] = 3 + length;
1826         /* set Vs to 0, because it is used as index when resending SABM */
1827         dl->V_send = 0;
1828
1829         /* Set states */
1830         dl->own_busy = dl->peer_busy = 0;
1831         dl->retrans_ctr = 0;
1832         lapdm_dl_newstate(dl, LAPDm_STATE_SABM_SENT);
1833
1834         /* Tramsmit and start T200 */
1835         osmo_timer_schedule(&dl->t200, T200);
1836         return tx_ph_data_enqueue(dl, msg, chan_nr, link_id, n201);
1837 }
1838
1839 /* L3 requests transfer of unnumbered information */
1840 static int rslms_rx_rll_udata_req(struct msgb *msg, struct lapdm_datalink *dl)
1841 {
1842         struct lapdm_entity *le = dl->entity;
1843         struct abis_rsl_rll_hdr *rllh = msgb_l2(msg);
1844         uint8_t chan_nr = rllh->chan_nr;
1845         uint8_t link_id = rllh->link_id;
1846         uint8_t sapi = link_id & 7;
1847         struct tlv_parsed tv;
1848         int length;
1849         uint8_t n201 = 23; //FIXME
1850         uint8_t ta = 0, tx_power = 0;
1851
1852         /* check if the layer3 message length exceeds N201 */
1853
1854         rsl_tlv_parse(&tv, rllh->data, msgb_l2len(msg)-sizeof(*rllh));
1855
1856         if (TLVP_PRESENT(&tv, RSL_IE_TIMING_ADVANCE)) {
1857                 ta = *TLVP_VAL(&tv, RSL_IE_TIMING_ADVANCE);
1858         }
1859         if (TLVP_PRESENT(&tv, RSL_IE_MS_POWER)) {
1860                 tx_power = *TLVP_VAL(&tv, RSL_IE_MS_POWER);
1861         }
1862         if (!TLVP_PRESENT(&tv, RSL_IE_L3_INFO)) {
1863                 LOGP(DLLAPDM, LOGL_ERROR, "unit data request without message "
1864                         "error\n");
1865                 msgb_free(msg);
1866                 return -EINVAL;
1867         }
1868         msg->l3h = TLVP_VAL(&tv, RSL_IE_L3_INFO);
1869         length = TLVP_LEN(&tv, RSL_IE_L3_INFO);
1870         /* check if the layer3 message length exceeds N201 */
1871         if (length + 5 > 23) { /* FIXME: do we know the channel N201? */
1872                 LOGP(DLLAPDM, LOGL_ERROR, "frame too large: %d > N201(%d) "
1873                         "(discarding)\n", length + 5, 23);
1874                 msgb_free(msg);
1875                 return -EIO;
1876         }
1877
1878         LOGP(DLLAPDM, LOGL_INFO, "sending unit data (tx_power=%d, ta=%d)\n",
1879                 tx_power, ta);
1880
1881         /* Remove RLL header from msgb */
1882         msgb_pull_l2h(msg);
1883
1884         /* Push L1 + LAPDm header on msgb */
1885         msg->l2h = msgb_push(msg, 2 + 3);
1886         msg->l2h[0] = tx_power;
1887         msg->l2h[1] = ta;
1888         msg->l2h[2] = LAPDm_ADDR(LAPDm_LPD_NORMAL, sapi, le->cr.loc2rem.cmd);
1889         msg->l2h[3] = LAPDm_CTRL_U(LAPDm_U_UI, 0);
1890         msg->l2h[4] = LAPDm_LEN(length);
1891         // FIXME: short L2 header support
1892
1893         /* Tramsmit */
1894         return tx_ph_data_enqueue(dl, msg, chan_nr, link_id, n201);
1895 }
1896
1897 /* L3 requests transfer of acknowledged information */
1898 static int rslms_rx_rll_data_req(struct msgb *msg, struct lapdm_datalink *dl)
1899 {
1900         struct abis_rsl_rll_hdr *rllh = msgb_l2(msg);
1901         struct tlv_parsed tv;
1902
1903         rsl_tlv_parse(&tv, rllh->data, msgb_l2len(msg)-sizeof(*rllh));
1904         if (!TLVP_PRESENT(&tv, RSL_IE_L3_INFO)) {
1905                 LOGP(DLLAPDM, LOGL_ERROR, "data request without message "
1906                         "error\n");
1907                 msgb_free(msg);
1908                 return -EINVAL;
1909         }
1910         msg->l3h = TLVP_VAL(&tv, RSL_IE_L3_INFO);
1911
1912         LOGP(DLLAPDM, LOGL_INFO, "writing message to send-queue\n");
1913
1914         /* Remove the RSL/RLL header */
1915         msgb_pull_l2h(msg);
1916
1917         /* Write data into the send queue */
1918         msgb_enqueue(&dl->send_queue, msg);
1919
1920         /* Send message, if possible */
1921         rslms_send_i(&dl->mctx, __LINE__);
1922         return 0;
1923 }
1924
1925 /* Send next I frame from queued/buffered data */
1926 static int rslms_send_i(struct lapdm_msg_ctx *mctx, int line)
1927 {
1928         struct lapdm_datalink *dl = mctx->dl;
1929         struct lapdm_entity *le = dl->entity;
1930         uint8_t chan_nr = mctx->chan_nr;
1931         uint8_t link_id = mctx->link_id;
1932         uint8_t sapi = link_id & 7;
1933         int k = k_sapi[sapi];
1934         struct msgb *msg;
1935         int length, left;
1936         int rc = - 1; /* we sent nothing */
1937
1938         LOGP(DLLAPDM, LOGL_INFO, "%s() called from line %d\n", __func__, line);
1939
1940         next_frame:
1941
1942         if (dl->peer_busy) {
1943                 LOGP(DLLAPDM, LOGL_INFO, "peer busy, not sending\n");
1944                 return rc;
1945         }
1946
1947         if (dl->state == LAPDm_STATE_TIMER_RECOV) {
1948                 LOGP(DLLAPDM, LOGL_INFO, "timer recovery, not sending\n");
1949                 return rc;
1950         }
1951
1952         /* If the send state variable V(S) is equal to V(A) plus k
1953          * (where k is the maximum number of outstanding I frames - see
1954          * subclause 5.8.4), the data link layer entity shall not transmit any
1955          * new I frames, but shall retransmit an I frame as a result
1956          * of the error recovery procedures as described in subclauses 5.5.4 and
1957          * 5.5.7. */
1958         if (dl->V_send == add_mod8(dl->V_ack, k)) {
1959                 LOGP(DLLAPDM, LOGL_INFO, "k frames outstanding, not sending "
1960                         "more (k=%u V(S)=%u V(A)=%u)\n", k, dl->V_send,
1961                         dl->V_ack);
1962                 return rc;
1963         }
1964
1965         /* if we have no tx_hist yet, we create it */
1966         if (!dl->tx_length[dl->V_send]) {
1967                 /* Get next message into send-buffer, if any */
1968                 if (!dl->send_buffer) {
1969                         next_message:
1970                         dl->send_out = 0;
1971                         dl->send_buffer = msgb_dequeue(&dl->send_queue);
1972                         /* No more data to be sent */
1973                         if (!dl->send_buffer)
1974                                 return rc;
1975                         LOGP(DLLAPDM, LOGL_INFO, "get message from "
1976                                 "send-queue\n");
1977                 }
1978
1979                 /* How much is left in the send-buffer? */
1980                 left = msgb_l3len(dl->send_buffer) - dl->send_out;
1981                 /* Segment, if data exceeds N201 */
1982                 length = left;
1983                 if (length > mctx->n201 - 3)
1984                         length = mctx->n201 - 3;
1985                 LOGP(DLLAPDM, LOGL_INFO, "msg-len %d sent %d left %d N201 %d "
1986                         "length %d first byte %02x\n",
1987                         msgb_l3len(dl->send_buffer), dl->send_out, left,
1988                         mctx->n201, length, dl->send_buffer->l3h[0]);
1989                 /* If message in send-buffer is completely sent */
1990                 if (left == 0) {
1991                         msgb_free(dl->send_buffer);
1992                         dl->send_buffer = NULL;
1993                         goto next_message;
1994                 }
1995
1996                 LOGP(DLLAPDM, LOGL_INFO, "send I frame %sV(S)=%d\n",
1997                         (left > length) ? "segment " : "", dl->V_send);
1998
1999                 /* Create I frame (segment) and transmit-buffer content */
2000                 msg = msgb_alloc_headroom(23+10, 10, "LAPDm I");
2001                 msg->l2h = msgb_put(msg, 3 + length);
2002                 msg->l2h[0] = LAPDm_ADDR(LAPDm_LPD_NORMAL, sapi, le->cr.loc2rem.cmd);
2003                 msg->l2h[1] = LAPDm_CTRL_I(dl->V_recv, dl->V_send, 0);
2004                 msg->l2h[2] = LAPDm_LEN(length);
2005                 if (left > length)
2006                         msg->l2h[2] |= LAPDm_MORE;
2007                 memcpy(msg->l2h + 3, dl->send_buffer->l3h + dl->send_out,
2008                         length);
2009                 memcpy(dl->tx_hist[dl->V_send], msg->l2h, 3 + length);
2010                 dl->tx_length[dl->V_send] = 3 + length;
2011                 /* Add length to track how much is already in the tx buffer */
2012                 dl->send_out += length;
2013         } else {
2014                 LOGP(DLLAPDM, LOGL_INFO, "resend I frame from tx buffer "
2015                         "V(S)=%d\n", dl->V_send);
2016
2017                 /* Create I frame (segment) from tx_hist */
2018                 length = dl->tx_length[dl->V_send];
2019                 msg = msgb_alloc_headroom(23+10, 10, "LAPDm I");
2020                 msg->l2h = msgb_put(msg, length);
2021                 memcpy(msg->l2h, dl->tx_hist[dl->V_send], length);
2022                 msg->l2h[1] = LAPDm_CTRL_I(dl->V_recv, dl->V_send, 0);
2023         }
2024
2025         /* The value of the send state variable V(S) shall be incremented by 1
2026          * at the end of the transmission of the I frame */
2027         dl->V_send = inc_mod8(dl->V_send);
2028
2029         /* If timer T200 is not running at the time right before transmitting a
2030          * frame, when the PH-READY-TO-SEND primitive is received from the
2031          * physical layer., it shall be set. */
2032         if (!osmo_timer_pending(&dl->t200))
2033                 osmo_timer_schedule(&dl->t200, T200);
2034
2035         tx_ph_data_enqueue(dl, msg, chan_nr, link_id, mctx->n201);
2036
2037         rc = 0; /* we sent something */
2038         goto next_frame;
2039 }
2040
2041 /* L3 requests suspension of data link */
2042 static int rslms_rx_rll_susp_req(struct msgb *msg, struct lapdm_datalink *dl)
2043 {
2044         struct abis_rsl_rll_hdr *rllh = msgb_l2(msg);
2045         uint8_t sapi = rllh->link_id & 7;
2046
2047         if (sapi != 0) {
2048                 LOGP(DLLAPDM, LOGL_ERROR, "SAPI != 0 while suspending\n");
2049                 msgb_free(msg);
2050                 return -EINVAL;
2051         }
2052
2053         LOGP(DLLAPDM, LOGL_INFO, "perform suspension\n");
2054
2055         /* put back the send-buffer to the send-queue (first position) */
2056         if (dl->send_buffer) {
2057                 LOGP(DLLAPDM, LOGL_INFO, "put frame in sendbuffer back to "
2058                         "queue\n");
2059                 llist_add(&dl->send_buffer->list, &dl->send_queue);
2060                 dl->send_buffer = NULL;
2061         } else
2062                 LOGP(DLLAPDM, LOGL_INFO, "no frame in sendbuffer\n");
2063
2064         /* Clear transmit buffer, but keep send buffer */
2065         lapdm_dl_flush_tx(dl);
2066
2067         msgb_free(msg);
2068
2069         return send_rll_simple(RSL_MT_SUSP_CONF, &dl->mctx);
2070 }
2071
2072 /* L3 requests resume of data link */
2073 static int rslms_rx_rll_res_req(struct msgb *msg, struct lapdm_datalink *dl)
2074 {
2075         struct lapdm_entity *le = dl->entity;
2076         struct abis_rsl_rll_hdr *rllh = msgb_l2(msg);
2077         uint8_t chan_nr = rllh->chan_nr;
2078         uint8_t link_id = rllh->link_id;
2079         uint8_t sapi = rllh->link_id & 7;
2080         struct tlv_parsed tv;
2081         uint8_t length;
2082         uint8_t n201 = 23; //FIXME
2083
2084         /* Set chan_nr and link_id for established connection */
2085         memset(&dl->mctx, 0, sizeof(dl->mctx));
2086         dl->mctx.dl = dl;
2087         dl->mctx.n201 = n201;
2088         dl->mctx.chan_nr = chan_nr;
2089         dl->mctx.link_id = link_id;
2090
2091         rsl_tlv_parse(&tv, rllh->data, msgb_l2len(msg)-sizeof(*rllh));
2092         if (!TLVP_PRESENT(&tv, RSL_IE_L3_INFO)) {
2093                 LOGP(DLLAPDM, LOGL_ERROR, "resume without message error\n");
2094                 msgb_free(msg);
2095                 return send_rll_simple(RSL_MT_REL_IND, &dl->mctx);
2096         }
2097         length = TLVP_LEN(&tv, RSL_IE_L3_INFO);
2098
2099         LOGP(DLLAPDM, LOGL_INFO, "perform re-establishment (SABM) length=%d\n",
2100                 length);
2101
2102         /* Replace message in the send-buffer (reconnect) */
2103         if (dl->send_buffer)
2104                 msgb_free(dl->send_buffer);
2105         dl->send_out = 0;
2106         if (length) {
2107                 /* Remove the RSL/RLL header */
2108                 msgb_pull_l2h(msg);
2109                 /* Write data into the send buffer, to be sent first */
2110                 dl->send_buffer = msg;
2111         }
2112
2113         /* Discard partly received L3 message */
2114         if (dl->rcv_buffer) {
2115                 msgb_free(dl->rcv_buffer);
2116                 dl->rcv_buffer = NULL;
2117         }
2118
2119         /* Create new msgb (old one is now free) */
2120         msg = msgb_alloc_headroom(23+10, 10, "LAPDm SABM");
2121         msg->l2h = msgb_put(msg, 3);
2122         msg->l2h[0] = LAPDm_ADDR(LAPDm_LPD_NORMAL, sapi, le->cr.loc2rem.cmd);
2123         msg->l2h[1] = LAPDm_CTRL_U(LAPDm_U_SABM, 1);
2124         msg->l2h[2] = LAPDm_LEN(0);
2125         /* Transmit-buffer carries exactly one segment */
2126         memcpy(dl->tx_hist[0], msg->l2h, 3);
2127         dl->tx_length[0] = 3;
2128         /* set Vs to 0, because it is used as index when resending SABM */
2129         dl->V_send = 0;
2130
2131         /* Set states */
2132         dl->own_busy = dl->peer_busy = 0;
2133         dl->retrans_ctr = 0;
2134         lapdm_dl_newstate(dl, LAPDm_STATE_SABM_SENT);
2135
2136         /* Tramsmit and start T200 */
2137         osmo_timer_schedule(&dl->t200, T200);
2138         return tx_ph_data_enqueue(dl, msg, chan_nr, link_id, n201);
2139 }
2140
2141 /* L3 requests release of data link */
2142 static int rslms_rx_rll_rel_req(struct msgb *msg, struct lapdm_datalink *dl)
2143 {
2144         struct lapdm_entity *le = dl->entity;
2145         struct abis_rsl_rll_hdr *rllh = msgb_l2(msg);
2146         uint8_t chan_nr = rllh->chan_nr;
2147         uint8_t link_id = rllh->link_id;
2148         uint8_t sapi = rllh->link_id & 7;
2149         uint8_t mode = 0;
2150
2151         /* get release mode */
2152         if (rllh->data[0] == RSL_IE_RELEASE_MODE)
2153                 mode = rllh->data[1] & 1;
2154
2155         /* local release */
2156         if (mode) {
2157                 LOGP(DLLAPDM, LOGL_INFO, "perform local release\n");
2158                 msgb_free(msg);
2159                 /* reset Timer T200 */
2160                 osmo_timer_del(&dl->t200);
2161                 /* enter idle state */
2162                 lapdm_dl_newstate(dl, LAPDm_STATE_IDLE);
2163                 /* flush buffers */
2164                 lapdm_dl_flush_tx(dl);
2165                 lapdm_dl_flush_send(dl);
2166                 /* send notification to L3 */
2167                 return send_rll_simple(RSL_MT_REL_CONF, &dl->mctx);
2168         }
2169
2170         /* in case we are already disconnecting */
2171         if (dl->state == LAPDm_STATE_DISC_SENT)
2172                 return -EBUSY;
2173
2174         LOGP(DLLAPDM, LOGL_INFO, "perform normal release (DISC)\n");
2175
2176         /* Pull rllh */
2177         msgb_pull(msg, msg->tail - msg->l2h);
2178
2179         /* Push LAPDm header on msgb */
2180         msg->l2h = msgb_push(msg, 3);
2181         msg->l2h[0] = LAPDm_ADDR(LAPDm_LPD_NORMAL, sapi, le->cr.loc2rem.cmd);
2182         msg->l2h[1] = LAPDm_CTRL_U(LAPDm_U_DISC, 1);
2183         msg->l2h[2] = LAPDm_LEN(0);
2184         /* Transmit-buffer carries exactly one segment */
2185         memcpy(dl->tx_hist[0], msg->l2h, 3);
2186         dl->tx_length[0] = 3;
2187
2188         /* Set states */
2189         dl->own_busy = dl->peer_busy = 0;
2190         dl->retrans_ctr = 0;
2191         lapdm_dl_newstate(dl, LAPDm_STATE_DISC_SENT);
2192
2193         /* Tramsmit and start T200 */
2194         osmo_timer_schedule(&dl->t200, T200);
2195         return tx_ph_data_enqueue(dl, msg, chan_nr, link_id, dl->mctx.n201);
2196 }
2197
2198 /* L3 requests release in idle state */
2199 static int rslms_rx_rll_rel_req_idle(struct msgb *msg, struct lapdm_datalink *dl)
2200 {
2201         msgb_free(msg);
2202
2203         /* send notification to L3 */
2204         return send_rll_simple(RSL_MT_REL_CONF, &dl->mctx);
2205 }
2206
2207 /* L3 requests channel in idle state */
2208 static int rslms_rx_chan_rqd(struct lapdm_channel *lc, struct msgb *msg)
2209 {
2210         struct abis_rsl_cchan_hdr *cch = msgb_l2(msg);
2211         void *l1ctx = lc->lapdm_dcch.l1_ctx;
2212         struct osmo_phsap_prim pp;
2213
2214         osmo_prim_init(&pp.oph, SAP_GSM_PH, PRIM_PH_RACH,
2215                         PRIM_OP_REQUEST, NULL);
2216
2217         if (msgb_l2len(msg) < sizeof(*cch) + 4 + 2 + 2) {
2218                 LOGP(DLLAPDM, LOGL_ERROR, "Message too short for CHAN RQD!\n");
2219                 return -EINVAL;
2220         }
2221         if (cch->data[0] != RSL_IE_REQ_REFERENCE) {
2222                 LOGP(DLLAPDM, LOGL_ERROR, "Missing REQ REFERENCE IE\n");
2223                 return -EINVAL;
2224         }
2225         pp.u.rach_req.ra = cch->data[1];
2226         pp.u.rach_req.offset = ((cch->data[2] & 0x7f) << 8) | cch->data[3];
2227         pp.u.rach_req.is_combined_ccch = cch->data[2] >> 7;
2228
2229         if (cch->data[4] != RSL_IE_ACCESS_DELAY) {
2230                 LOGP(DLLAPDM, LOGL_ERROR, "Missing ACCESS_DELAY IE\n");
2231                 return -EINVAL;
2232         }
2233         /* TA = 0 - delay */
2234         pp.u.rach_req.ta = 0 - cch->data[5];
2235
2236         if (cch->data[6] != RSL_IE_MS_POWER) {
2237                 LOGP(DLLAPDM, LOGL_ERROR, "Missing MS POWER IE\n");
2238                 return -EINVAL;
2239         }
2240         pp.u.rach_req.tx_power = cch->data[7];
2241
2242         msgb_free(msg);
2243
2244         return lc->lapdm_dcch.l1_prim_cb(&pp.oph, l1ctx);
2245 }
2246
2247 /* L1 confirms channel request */
2248 static int l2_ph_chan_conf(struct msgb *msg, struct lapdm_entity *le, uint32_t frame_nr)
2249 {
2250         struct abis_rsl_cchan_hdr *ch;
2251         struct gsm_time tm;
2252         struct gsm48_req_ref *ref;
2253
2254         gsm_fn2gsmtime(&tm, frame_nr);
2255
2256         msgb_pull_l2h(msg);
2257         msg->l2h = msgb_push(msg, sizeof(*ch) + sizeof(*ref));
2258         ch = (struct abis_rsl_cchan_hdr *)msg->l2h;
2259         rsl_init_cchan_hdr(ch, RSL_MT_CHAN_CONF);
2260         ch->chan_nr = RSL_CHAN_RACH;
2261         ch->data[0] = RSL_IE_REQ_REFERENCE;
2262         ref = (struct gsm48_req_ref *) (ch->data + 1);
2263         ref->t1 = tm.t1;
2264         ref->t2 = tm.t2;
2265         ref->t3_low = tm.t3 & 0x7;
2266         ref->t3_high = tm.t3 >> 3;
2267
2268         return rslms_sendmsg(msg, le);
2269 }
2270
2271 const char *lapdm_state_names[] = {
2272         "LAPDm_STATE_NULL",
2273         "LAPDm_STATE_IDLE",
2274         "LAPDm_STATE_SABM_SENT",
2275         "LAPDm_STATE_MF_EST",
2276         "LAPDm_STATE_TIMER_RECOV",
2277         "LAPDm_STATE_DISC_SENT",
2278 };
2279
2280 /* statefull handling for RSLms RLL messages from L3 */
2281 static struct l2downstate {
2282         uint32_t        states;
2283         int             type;
2284         int             (*rout) (struct msgb *msg, struct lapdm_datalink *dl);
2285 } l2downstatelist[] = {
2286         /* create and send UI command */
2287         {ALL_STATES,
2288          RSL_MT_UNIT_DATA_REQ, rslms_rx_rll_udata_req},
2289
2290         /* create and send SABM command */
2291         {SBIT(LAPDm_STATE_IDLE),
2292          RSL_MT_EST_REQ, rslms_rx_rll_est_req},
2293
2294         /* create and send I command */
2295         {SBIT(LAPDm_STATE_MF_EST) |
2296          SBIT(LAPDm_STATE_TIMER_RECOV),
2297          RSL_MT_DATA_REQ, rslms_rx_rll_data_req},
2298
2299         /* suspend datalink */
2300         {SBIT(LAPDm_STATE_MF_EST) |
2301          SBIT(LAPDm_STATE_TIMER_RECOV),
2302          RSL_MT_SUSP_REQ, rslms_rx_rll_susp_req},
2303
2304         /* create and send SABM command (resume) */
2305         {SBIT(LAPDm_STATE_MF_EST) |
2306          SBIT(LAPDm_STATE_TIMER_RECOV),
2307          RSL_MT_RES_REQ, rslms_rx_rll_res_req},
2308
2309         /* create and send SABM command (reconnect) */
2310         {SBIT(LAPDm_STATE_IDLE) |
2311          SBIT(LAPDm_STATE_MF_EST) |
2312          SBIT(LAPDm_STATE_TIMER_RECOV),
2313          RSL_MT_RECON_REQ, rslms_rx_rll_res_req},
2314
2315         /* create and send DISC command */
2316         {SBIT(LAPDm_STATE_SABM_SENT) |
2317          SBIT(LAPDm_STATE_MF_EST) |
2318          SBIT(LAPDm_STATE_TIMER_RECOV) |
2319          SBIT(LAPDm_STATE_DISC_SENT),
2320          RSL_MT_REL_REQ, rslms_rx_rll_rel_req},
2321
2322         /* release in idle state */
2323         {SBIT(LAPDm_STATE_IDLE),
2324          RSL_MT_REL_REQ, rslms_rx_rll_rel_req_idle},
2325 };
2326
2327 #define L2DOWNSLLEN \
2328         (sizeof(l2downstatelist) / sizeof(struct l2downstate))
2329
2330 /* incoming RSLms RLL message from L3 */
2331 static int rslms_rx_rll(struct msgb *msg, struct lapdm_channel *lc)
2332 {
2333         struct abis_rsl_rll_hdr *rllh = msgb_l2(msg);
2334         int msg_type = rllh->c.msg_type;
2335         uint8_t sapi = rllh->link_id & 7;
2336         struct lapdm_entity *le;
2337         struct lapdm_datalink *dl;
2338         int i, supported = 0;
2339         int rc = 0;
2340
2341         if (msgb_l2len(msg) < sizeof(*rllh)) {
2342                 LOGP(DLLAPDM, LOGL_ERROR, "Message too short for RLL hdr!\n");
2343                 return -EINVAL;
2344         }
2345
2346         if (rllh->link_id & 0x40)
2347                 le = &lc->lapdm_acch;
2348         else
2349                 le = &lc->lapdm_dcch;
2350
2351         /* G.2.1 No action schall be taken on frames containing an unallocated
2352          * SAPI.
2353          */
2354         dl = datalink_for_sapi(le, sapi);
2355         if (!dl) {
2356                 LOGP(DLLAPDM, LOGL_ERROR, "No instance for SAPI %d!\n", sapi);
2357                 return -EINVAL;
2358         }
2359
2360         LOGP(DLLAPDM, LOGL_INFO, "(%p) RLL Message '%s' received in state %s\n",
2361                 lc->name, rsl_msg_name(msg_type), lapdm_state_names[dl->state]);
2362
2363         /* find function for current state and message */
2364         for (i = 0; i < L2DOWNSLLEN; i++) {
2365                 if (msg_type == l2downstatelist[i].type)
2366                         supported = 1;
2367                 if ((msg_type == l2downstatelist[i].type)
2368                  && ((1 << dl->state) & l2downstatelist[i].states))
2369                         break;
2370         }
2371         if (!supported) {
2372                 LOGP(DLLAPDM, LOGL_NOTICE, "Message unsupported.\n");
2373                 msgb_free(msg);
2374                 return 0;
2375         }
2376         if (i == L2DOWNSLLEN) {
2377                 LOGP(DLLAPDM, LOGL_NOTICE, "Message unhandled at this state.\n");
2378                 msgb_free(msg);
2379                 return 0;
2380         }
2381
2382         rc = l2downstatelist[i].rout(msg, dl);
2383
2384         return rc;
2385 }
2386
2387 /* incoming RSLms COMMON CHANNEL message from L3 */
2388 static int rslms_rx_com_chan(struct msgb *msg, struct lapdm_channel *lc)
2389 {
2390         struct abis_rsl_cchan_hdr *cch = msgb_l2(msg);
2391         int msg_type = cch->c.msg_type;
2392         int rc = 0;
2393
2394         if (msgb_l2len(msg) < sizeof(*cch)) {
2395                 LOGP(DLLAPDM, LOGL_ERROR, "Message too short for COM CHAN hdr!\n");
2396                 return -EINVAL;
2397         }
2398
2399         switch (msg_type) {
2400         case RSL_MT_CHAN_RQD:
2401                 /* create and send RACH request */
2402                 rc = rslms_rx_chan_rqd(lc, msg);
2403                 break;
2404         default:
2405                 LOGP(DLLAPDM, LOGL_NOTICE, "Unknown COMMON CHANNEL msg %d!\n",
2406                         msg_type);
2407                 msgb_free(msg);
2408                 return 0;
2409         }
2410
2411         return rc;
2412 }
2413
2414 /* input into layer2 (from layer 3) */
2415 int lapdm_rslms_recvmsg(struct msgb *msg, struct lapdm_channel *lc)
2416 {
2417         struct abis_rsl_common_hdr *rslh = msgb_l2(msg);
2418         int rc = 0;
2419
2420         if (msgb_l2len(msg) < sizeof(*rslh)) {
2421                 LOGP(DLLAPDM, LOGL_ERROR, "Message too short RSL hdr!\n");
2422                 return -EINVAL;
2423         }
2424
2425         switch (rslh->msg_discr & 0xfe) {
2426         case ABIS_RSL_MDISC_RLL:
2427                 rc = rslms_rx_rll(msg, lc);
2428                 break;
2429         case ABIS_RSL_MDISC_COM_CHAN:
2430                 rc = rslms_rx_com_chan(msg, lc);
2431                 break;
2432         default:
2433                 LOGP(DLLAPDM, LOGL_ERROR, "unknown RSLms message "
2434                         "discriminator 0x%02x", rslh->msg_discr);
2435                 msgb_free(msg);
2436                 return -EINVAL;
2437         }
2438
2439         return rc;
2440 }
2441
2442 int lapdm_entity_set_mode(struct lapdm_entity *le, enum lapdm_mode mode)
2443 {
2444         switch (mode) {
2445         case LAPDM_MODE_MS:
2446                 le->cr.loc2rem.cmd = CR_MS2BS_CMD;
2447                 le->cr.loc2rem.resp = CR_MS2BS_RESP;
2448                 le->cr.rem2loc.cmd = CR_BS2MS_CMD;
2449                 le->cr.rem2loc.resp = CR_BS2MS_RESP;
2450                 break;
2451         case LAPDM_MODE_BTS:
2452                 le->cr.loc2rem.cmd = CR_BS2MS_CMD;
2453                 le->cr.loc2rem.resp = CR_BS2MS_RESP;
2454                 le->cr.rem2loc.cmd = CR_MS2BS_CMD;
2455                 le->cr.rem2loc.resp = CR_MS2BS_RESP;
2456                 break;
2457         default:
2458                 return -EINVAL;
2459         }
2460
2461         le->mode = mode;
2462
2463         return 0;
2464 }
2465
2466 int lapdm_channel_set_mode(struct lapdm_channel *lc, enum lapdm_mode mode)
2467 {
2468         int rc;
2469
2470         rc = lapdm_entity_set_mode(&lc->lapdm_dcch, mode);
2471         if (rc < 0)
2472                 return rc;
2473
2474         return lapdm_entity_set_mode(&lc->lapdm_acch, mode);
2475 }
2476
2477 void lapdm_channel_set_l1(struct lapdm_channel *lc, osmo_prim_cb cb, void *ctx)
2478 {
2479         lc->lapdm_dcch.l1_prim_cb = cb;
2480         lc->lapdm_acch.l1_prim_cb = cb;
2481         lc->lapdm_dcch.l1_ctx = ctx;
2482         lc->lapdm_acch.l1_ctx = ctx;
2483 }
2484
2485 void lapdm_channel_set_l3(struct lapdm_channel *lc, lapdm_cb_t cb, void *ctx)
2486 {
2487         lc->lapdm_dcch.l3_cb = cb;
2488         lc->lapdm_acch.l3_cb = cb;
2489         lc->lapdm_dcch.l3_ctx = ctx;
2490         lc->lapdm_acch.l3_ctx = ctx;
2491 }
2492
2493 void lapdm_entity_reset(struct lapdm_entity *le)
2494 {
2495         struct lapdm_datalink *dl;
2496         int i;
2497
2498         for (i = 0; i < ARRAY_SIZE(le->datalink); i++) {
2499                 dl = &le->datalink[i];
2500                 if (dl->state == LAPDm_STATE_IDLE)
2501                         continue;
2502                 LOGP(DLLAPDM, LOGL_INFO, "Resetting LAPDm instance\n");
2503                 /* reset Timer T200 */
2504                 osmo_timer_del(&dl->t200);
2505                 /* enter idle state */
2506                 dl->state = LAPDm_STATE_IDLE;
2507                 /* flush buffer */
2508                 lapdm_dl_flush_tx(dl);
2509                 lapdm_dl_flush_send(dl);
2510         }
2511 }
2512
2513 void lapdm_channel_reset(struct lapdm_channel *lc)
2514 {
2515         lapdm_entity_reset(&lc->lapdm_dcch);
2516         lapdm_entity_reset(&lc->lapdm_acch);
2517 }
2518
2519 void lapdm_entity_set_flags(struct lapdm_entity *le, unsigned int flags)
2520 {
2521         le->flags = flags;
2522 }
2523
2524 void lapdm_channel_set_flags(struct lapdm_channel *lc, unsigned int flags)
2525 {
2526         lapdm_entity_set_flags(&lc->lapdm_dcch, flags);
2527         lapdm_entity_set_flags(&lc->lapdm_acch, flags);
2528 }