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

   1 /* GSM LAPDm (TS 04.06) implementation */
   2
   3 /* (C) 2010 by Harald Welte <laforge@gnumonks.org>
   4  * (C) 2010 by Andreas Eversberg <jolly@eversberg.eu>
   5  *
   6  * All Rights Reserved
   7  *
   8  * This program is free software; you can redistribute it and/or modify
   9  * it under the terms of the GNU General Public License as published by
  10  * the Free Software Foundation; either version 2 of the License, or
  11  * (at your option) any later version.
  12  *
  13  * This program is distributed in the hope that it will be useful,
  14  * but WITHOUT ANY WARRANTY; without even the implied warranty of
  15  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  16  * GNU General Public License for more details.
  17  *
  18  * You should have received a copy of the GNU General Public License along
  19  * with this program; if not, write to the Free Software Foundation, Inc.,
  20  * 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA.
  21  *
  22  */
  23
  24 /* Notes on Buffering: rcv_buffer, tx_queue, tx_hist, send_buffer, send_queue
  25  *
  26  * RX data is stored in the rcv_buffer (pointer). If the message is complete, it
  27  * is removed from rcv_buffer pointer and forwarded to L3. If the RX data is
  28  * received while there is an incomplete rcv_buffer, it is appended to it.
  29  *
  30  * TX data is stored in the send_queue first. When transmitting a frame,
  31  * the first message in the send_queue is moved to the send_buffer. There it
  32  * resides until all fragments are acknowledged. Fragments to be sent by I
  33  * frames are stored in the tx_hist buffer for resend, if required. Also the
  34  * current fragment is copied into the tx_queue. There it resides until it is
  35  * forwarded to layer 1.
  36  *
  37  * In case we have SAPI 0, we only have a window size of 1, so the unack-
  38  * nowledged message resides always in the send_buffer. In case of a suspend,
  39  * it can be written back to the first position of the send_queue.
  40  *
  41  * The layer 1 normally sends a PH-READY-TO-SEND. But because we use
  42  * asynchronous transfer between layer 1 and layer 2 (serial link), we must
  43  * send a frame before layer 1 reaches the right timeslot to send it. So we
  44  * move the tx_queue to layer 1 when there is not already a pending frame, and
  45  * wait until acknowledge after the frame has been sent. If we receive an
  46  * acknowledge, we can send the next frame from the buffer, if any.
  47  *
  48  * The moving of tx_queue to layer 1 may also trigger T200, if desired. Also it
  49  * will trigger next I frame, if possible.
  50  *
  51  */
  52
  53 #include <stdio.h>
  54 #include <stdint.h>
  55 #include <string.h>
  56 #include <errno.h>
  57 #include <arpa/inet.h>
  58
  59 #include <osmocom/core/logging.h>
  60 #include <osmocom/core/timer.h>
  61 #include <osmocom/core/msgb.h>
  62 #include <osmocom/gsm/tlv.h>
  63 #include <osmocom/core/utils.h>
  64 #include <osmocom/gsm/rsl.h>
  65 #include <osmocom/gsm/protocol/gsm_04_08.h>
  66 #include <osmocom/gsm/protocol/gsm_08_58.h>
  67
  68 #include <osmocom/bb/common/osmocom_data.h>
  69 #include <osmocom/bb/common/l1ctl.h>
  70 #include <osmocom/bb/common/lapdm.h>
  71 #include <osmocom/bb/common/logging.h>
  72
  73 #include <l1ctl_proto.h>
  74
  75 /* TS 04.06 Figure 4 / Section 3.2 */
  76 #define LAPDm_LPD_NORMAL  0
  77 #define LAPDm_LPD_SMSCB   1
  78 #define LAPDm_SAPI_NORMAL 0
  79 #define LAPDm_SAPI_SMS    3
  80 #define LAPDm_ADDR(lpd, sapi, cr) ((((lpd) & 0x3) << 5) | (((sapi) & 0x7) << 2) | (((cr) & 0x1) << 1) | 0x1)
  81
  82 #define LAPDm_ADDR_SAPI(addr) (((addr) >> 2) & 0x7)
  83 #define LAPDm_ADDR_CR(addr) (((addr) >> 1) & 0x1)
  84 #define LAPDm_ADDR_EA(addr) ((addr) & 0x1)
  85
  86 /* TS 04.06 Table 3 / Section 3.4.3 */
  87 #define LAPDm_CTRL_I(nr, ns, p) ((((nr) & 0x7) << 5) | (((p) & 0x1) << 4) | (((ns) & 0x7) << 1))
  88 #define LAPDm_CTRL_S(nr, s, p)  ((((nr) & 0x7) << 5) | (((p) & 0x1) << 4) | (((s) & 0x3) << 2) | 0x1)
  89 #define LAPDm_CTRL_U(u, p)      ((((u) & 0x1c) << (5-2)) | (((p) & 0x1) << 4) | (((u) & 0x3) << 2) | 0x3)
  90
  91 #define LAPDm_CTRL_is_I(ctrl)   (((ctrl) & 0x1) == 0)
  92 #define LAPDm_CTRL_is_S(ctrl)   (((ctrl) & 0x3) == 1)
  93 #define LAPDm_CTRL_is_U(ctrl)   (((ctrl) & 0x3) == 3)
  94
  95 #define LAPDm_CTRL_U_BITS(ctrl) ((((ctrl) & 0xC) >> 2) | ((ctrl) & 0xE0) >> 3)
  96 #define LAPDm_CTRL_PF_BIT(ctrl) (((ctrl) >> 4) & 0x1)
  97
  98 #define LAPDm_CTRL_S_BITS(ctrl) (((ctrl) & 0xC) >> 2)
  99
 100 #define LAPDm_CTRL_I_Ns(ctrl)   (((ctrl) & 0xE) >> 1)
 101 #define LAPDm_CTRL_Nr(ctrl)     (((ctrl) & 0xE0) >> 5)
 102
 103 /* TS 04.06 Table 4 / Section 3.8.1 */
 104 #define LAPDm_U_SABM    0x7
 105 #define LAPDm_U_DM      0x3
 106 #define LAPDm_U_UI      0x0
 107 #define LAPDm_U_DISC    0x8
 108 #define LAPDm_U_UA      0xC
 109
 110 #define LAPDm_S_RR      0x0
 111 #define LAPDm_S_RNR     0x1
 112 #define LAPDm_S_REJ     0x2
 113
 114 #define LAPDm_LEN(len)  ((len << 2) | 0x1)
 115 #define LAPDm_MORE      0x2
 116
 117 /* TS 04.06 Section 5.8.3 */
 118 #define N201_AB_SACCH           18
 119 #define N201_AB_SDCCH           20
 120 #define N201_AB_FACCH           20
 121 #define N201_Bbis               23
 122 #define N201_Bter_SACCH         21
 123 #define N201_Bter_SDCCH         23
 124 #define N201_Bter_FACCH         23
 125 #define N201_B4                 19
 126
 127 /* 5.8.2.1 N200 during establish and release */
 128 #define N200_EST_REL            5
 129 /* 5.8.2.1 N200 during timer recovery state */
 130 #define N200_TR_SACCH           5
 131 #define N200_TR_SDCCH           23
 132 #define N200_TR_FACCH_FR        34
 133 #define N200_TR_EFACCH_FR       48
 134 #define N200_TR_FACCH_HR        29
 135 /* FIXME: this depends on chan type */
 136 #define N200    N200_TR_SACCH
 137
 138 #define CR_MS2BS_CMD    0
 139 #define CR_MS2BS_RESP   1
 140 #define CR_BS2MS_CMD    1
 141 #define CR_BS2MS_RESP   0
 142
 143 /* Set T200 to 1 Second (OpenBTS uses 900ms) */
 144 #define T200    1, 0
 145
 146 /* k value for each SAPI */
 147 static uint8_t k_sapi[] = {1, 1, 1, 1, 1, 1, 1, 1};
 148
 149 enum lapdm_format {
 150         LAPDm_FMT_A,
 151         LAPDm_FMT_B,
 152         LAPDm_FMT_Bbis,
 153         LAPDm_FMT_Bter,
 154         LAPDm_FMT_B4,
 155 };
 156
 157 static void lapdm_t200_cb(void *data);
 158 static int rslms_send_i(struct lapdm_msg_ctx *mctx, int line);
 159
 160 /* UTILITY FUNCTIONS */
 161
 162 static inline uint8_t inc_mod8(uint8_t x)
 163 {
 164         return (x + 1) & 7;
 165 }
 166
 167 static inline uint8_t add_mod8(uint8_t x, uint8_t y)
 168 {
 169         return (x + y) & 7;
 170 }
 171
 172 static inline uint8_t sub_mod8(uint8_t x, uint8_t y)
 173 {
 174         return (x - y) & 7; /* handle negative results correctly */
 175 }
 176
 177 static void lapdm_dl_init(struct lapdm_datalink *dl,
 178                           struct lapdm_entity *entity)
 179 {
 180         memset(dl, 0, sizeof(*dl));
 181         INIT_LLIST_HEAD(&dl->send_queue);
 182         INIT_LLIST_HEAD(&dl->tx_queue);
 183         dl->state = LAPDm_STATE_IDLE;
 184         dl->t200.data = dl;
 185         dl->t200.cb = &lapdm_t200_cb;
 186         dl->entity = entity;
 187 }
 188
 189 void lapdm_init(struct lapdm_entity *le, struct osmocom_ms *ms)
 190 {
 191         unsigned int i;
 192
 193         for (i = 0; i < ARRAY_SIZE(le->datalink); i++)
 194                 lapdm_dl_init(&le->datalink[i], le);
 195
 196         le->ms = ms;
 197 }
 198
 199 static void lapdm_dl_flush_send(struct lapdm_datalink *dl)
 200 {
 201         struct msgb *msg;
 202
 203         /* Flush send-queue */
 204         while ((msg = msgb_dequeue(&dl->send_queue)))
 205                 msgb_free(msg);
 206
 207         /* Clear send-buffer */
 208         if (dl->send_buffer) {
 209                 msgb_free(dl->send_buffer);
 210                 dl->send_buffer = NULL;
 211         }
 212 }
 213
 214 static void lapdm_dl_flush_tx(struct lapdm_datalink *dl)
 215 {
 216         struct msgb *msg;
 217         unsigned int i;
 218
 219         while ((msg = msgb_dequeue(&dl->tx_queue)))
 220                 msgb_free(msg);
 221         for (i = 0; i < 8; i++)
 222                 dl->tx_length[i] = 0;
 223 }
 224
 225 void lapdm_exit(struct lapdm_entity *le)
 226 {
 227         unsigned int i;
 228         struct lapdm_datalink *dl;
 229
 230         for (i = 0; i < ARRAY_SIZE(le->datalink); i++) {
 231                 dl = &le->datalink[i];
 232                 lapdm_dl_flush_tx(dl);
 233                 lapdm_dl_flush_send(dl);
 234                 if (dl->rcv_buffer)
 235                         msgb_free(dl->rcv_buffer);
 236         }
 237 }
 238
 239 static void lapdm_dl_newstate(struct lapdm_datalink *dl, uint32_t state)
 240 {
 241         LOGP(DLAPDM, LOGL_INFO, "new state %s -> %s\n",
 242                 lapdm_state_names[dl->state], lapdm_state_names[state]);
 243
 244         dl->state = state;
 245 }
 246
 247 static struct lapdm_datalink *datalink_for_sapi(struct lapdm_entity *le, uint8_t sapi)
 248 {
 249         switch (sapi) {
 250         case LAPDm_SAPI_NORMAL:
 251                 return &le->datalink[0];
 252         case LAPDm_SAPI_SMS:
 253                 return &le->datalink[1];
 254         default:
 255                 return NULL;
 256         }
 257 }
 258
 259 /* remove the L2 header from a MSGB */
 260 static inline unsigned char *msgb_pull_l2h(struct msgb *msg)
 261 {
 262         unsigned char *ret = msgb_pull(msg, msg->l3h - msg->l2h);
 263         msg->l2h = NULL;
 264         return ret;
 265 }
 266
 267 /* Append padding (if required) */
 268 static void lapdm_pad_msgb(struct msgb *msg, uint8_t n201)
 269 {
 270         int pad_len = n201 - msgb_l2len(msg);
 271         uint8_t *data;
 272
 273         if (pad_len < 0) {
 274                 LOGP(DLAPDM, LOGL_ERROR,
 275                      "cannot pad message that is already too big!\n");
 276                 return;
 277         }
 278
 279         data = msgb_put(msg, pad_len);
 280         memset(data, 0x2B, pad_len);
 281 }
 282
 283 /* write a frame into the tx queue */
 284 static int tx_ph_data_enqueue(struct lapdm_datalink *dl, struct msgb *msg,
 285                                 uint8_t chan_nr, uint8_t link_id, uint8_t n201)
 286 {
 287         struct lapdm_entity *le = dl->entity;
 288         struct osmocom_ms *ms = le->ms;
 289
 290         /* if there is a pending message, queue it */
 291         if (le->tx_pending) {
 292                 *msgb_push(msg, 1) = n201;
 293                 *msgb_push(msg, 1) = link_id;
 294                 *msgb_push(msg, 1) = chan_nr;
 295                 msgb_enqueue(&dl->tx_queue, msg);
 296                 return -EBUSY;
 297         }
 298
 299         /* send the frame now */
 300         le->tx_pending = 0; /* disabled flow control */
 301         lapdm_pad_msgb(msg, n201);
 302         return l1ctl_tx_data_req(ms, msg, chan_nr, link_id);
 303 }
 304
 305 /* get next frame from the tx queue. because the ms has multiple datalinks,
 306  * each datalink's queue is read round-robin.
 307  */
 308 int l2_ph_data_conf(struct msgb *msg, struct lapdm_entity *le)
 309 {
 310         struct osmocom_ms *ms = le->ms;
 311         struct lapdm_datalink *dl;
 312         int last = le->last_tx_dequeue;
 313         int i = last, n = ARRAY_SIZE(le->datalink);
 314         uint8_t chan_nr, link_id, n201;
 315
 316         /* we may send again */
 317         le->tx_pending = 0;
 318
 319         /* free confirm message */
 320         msgb_free(msg);
 321
 322         /* round-robin dequeue */
 323         do {
 324                 /* next */
 325                 i = (i + 1) % n;
 326                 dl = &le->datalink[i];
 327                 if ((msg = msgb_dequeue(&dl->tx_queue)))
 328                         break;
 329         } while (i != last);
 330
 331         /* no message in all queues */
 332         if (!msg)
 333                 return 0;
 334
 335         /* Pull chan_nr and link_id */
 336         chan_nr = *msg->data;
 337         msgb_pull(msg, 1);
 338         link_id = *msg->data;
 339         msgb_pull(msg, 1);
 340         n201 = *msg->data;
 341         msgb_pull(msg, 1);
 342
 343         /* Set last dequeue position */
 344         le->last_tx_dequeue = i;
 345
 346         /* Pad the frame, we can transmit now */
 347         le->tx_pending = 1;
 348         lapdm_pad_msgb(msg, n201);
 349         return l1ctl_tx_data_req(ms, msg, chan_nr, link_id);
 350 }
 351
 352 /* Create RSLms various RSLms messages */
 353 static int send_rslms_rll_l3(uint8_t msg_type, struct lapdm_msg_ctx *mctx,
 354                              struct msgb *msg)
 355 {
 356         /* Add the RSL + RLL header */
 357         rsl_rll_push_l3(msg, msg_type, mctx->chan_nr, mctx->link_id, 1);
 358
 359         /* send off the RSLms message to L3 */
 360         return rslms_sendmsg(msg, mctx->dl->entity->ms);
 361 }
 362
 363 /* Take a B4 format message from L1 and create RSLms UNIT DATA IND */
 364 static int send_rslms_rll_l3_ui(struct lapdm_msg_ctx *mctx, struct msgb *msg)
 365 {
 366         uint8_t l3_len = msg->tail - (uint8_t *)msgb_l3(msg);
 367         struct abis_rsl_rll_hdr *rllh;
 368
 369         /* Add the RSL + RLL header */
 370         msgb_tv16_push(msg, RSL_IE_L3_INFO, l3_len);
 371         msgb_push(msg, 2 + 2);
 372         rsl_rll_push_hdr(msg, RSL_MT_UNIT_DATA_IND, mctx->chan_nr,
 373                 mctx->link_id, 1);
 374         rllh = (struct abis_rsl_rll_hdr *)msgb_l2(msg);
 375
 376         rllh->data[0] = RSL_IE_TIMING_ADVANCE;
 377         rllh->data[1] = mctx->ta_ind;
 378
 379         rllh->data[2] = RSL_IE_MS_POWER;
 380         rllh->data[3] = mctx->tx_power_ind;
 381
 382         return rslms_sendmsg(msg, mctx->dl->entity->ms);
 383 }
 384
 385 static int send_rll_simple(uint8_t msg_type, struct lapdm_msg_ctx *mctx)
 386 {
 387         struct msgb *msg;
 388
 389         msg = rsl_rll_simple(msg_type, mctx->chan_nr, mctx->link_id, 1);
 390
 391         /* send off the RSLms message to L3 */
 392         return rslms_sendmsg(msg, mctx->dl->entity->ms);
 393 }
 394
 395 static int rsl_rll_error(uint8_t cause, struct lapdm_msg_ctx *mctx)
 396 {
 397         struct msgb *msg;
 398         uint8_t *tlv;
 399
 400         LOGP(DLAPDM, LOGL_NOTICE, "sending MDL-ERROR-IND %d\n", cause);
 401         msg = rsl_rll_simple(RSL_MT_ERROR_IND, mctx->chan_nr, mctx->link_id, 1);
 402         msg->l2h = msgb_put(msg, sizeof(struct abis_rsl_rll_hdr) + 3);
 403         tlv = msg->l2h + sizeof(struct abis_rsl_rll_hdr);
 404         tlv[0] = RSL_IE_RLM_CAUSE;
 405         tlv[1] = 1;
 406         tlv[2] = cause;
 407         return rslms_sendmsg(msg, mctx->dl->entity->ms);
 408 }
 409
 410 static int check_length_ind(struct lapdm_msg_ctx *mctx, uint8_t length_ind)
 411 {
 412         if (!(length_ind & 0x01)) {
 413                 /* G.4.1 If the EL bit is set to "0", an MDL-ERROR-INDICATION
 414                  * primitive with cause "frame not implemented" is sent to the
 415                  * mobile management entity. */
 416                 LOGP(DLAPDM, LOGL_NOTICE,
 417                         "we don't support multi-octet length\n");
 418                 rsl_rll_error(RLL_CAUSE_FRM_UNIMPL, mctx);
 419                 return -EINVAL;
 420         }
 421         return 0;
 422 }
 423
 424 static int lapdm_send_resend(struct lapdm_datalink *dl)
 425 {
 426         struct msgb *msg = msgb_alloc_headroom(23+10, 10, "LAPDm resend");
 427         int length;
 428
 429         /* Resend SABM/DISC from tx_hist */
 430         length = dl->tx_length[0];
 431         msg->l2h = msgb_put(msg, length);
 432         memcpy(msg->l2h, dl->tx_hist[dl->V_send], length);
 433
 434         return tx_ph_data_enqueue(dl, msg, dl->mctx.chan_nr, dl->mctx.link_id,
 435                         dl->mctx.n201);
 436 }
 437
 438 static int lapdm_send_ua(struct lapdm_msg_ctx *mctx, uint8_t len, uint8_t *data)
 439 {
 440         uint8_t sapi = mctx->link_id & 7;
 441         uint8_t f_bit = LAPDm_CTRL_PF_BIT(mctx->ctrl);
 442         struct msgb *msg = msgb_alloc_headroom(23+10, 10, "LAPDm UA");
 443         msg->l2h = msgb_put(msg, 3 + len);
 444
 445         msg->l2h[0] = LAPDm_ADDR(LAPDm_LPD_NORMAL, sapi, CR_MS2BS_RESP);
 446         msg->l2h[1] = LAPDm_CTRL_U(LAPDm_U_UA, f_bit);
 447         msg->l2h[2] = LAPDm_LEN(len);
 448         if (len)
 449                 memcpy(msg->l2h + 3, data, len);
 450
 451         return tx_ph_data_enqueue(mctx->dl, msg, mctx->chan_nr, mctx->link_id,
 452                         mctx->n201);
 453 }
 454
 455 static int lapdm_send_dm(struct lapdm_msg_ctx *mctx)
 456 {
 457         uint8_t sapi = mctx->link_id & 7;
 458         uint8_t f_bit = LAPDm_CTRL_PF_BIT(mctx->ctrl);
 459         struct msgb *msg = msgb_alloc_headroom(23+10, 10, "LAPDm DM");
 460         msg->l2h = msgb_put(msg, 3);
 461
 462         msg->l2h[0] = LAPDm_ADDR(LAPDm_LPD_NORMAL, sapi, CR_MS2BS_RESP);
 463         msg->l2h[1] = LAPDm_CTRL_U(LAPDm_U_DM, f_bit);
 464         msg->l2h[2] = 0;
 465
 466         return tx_ph_data_enqueue(mctx->dl, msg, mctx->chan_nr, mctx->link_id,
 467                         mctx->n201);
 468 }
 469
 470 static int lapdm_send_rr(struct lapdm_msg_ctx *mctx, uint8_t f_bit)
 471 {
 472         uint8_t sapi = mctx->link_id & 7;
 473         struct msgb *msg = msgb_alloc_headroom(23+10, 10, "LAPDm RR");
 474         msg->l2h = msgb_put(msg, 3);
 475
 476         msg->l2h[0] = LAPDm_ADDR(LAPDm_LPD_NORMAL, sapi, CR_MS2BS_RESP);
 477         msg->l2h[1] = LAPDm_CTRL_S(mctx->dl->V_recv, LAPDm_S_RR, f_bit);
 478         msg->l2h[2] = LAPDm_LEN(0);
 479
 480         return tx_ph_data_enqueue(mctx->dl, msg, mctx->chan_nr, mctx->link_id,
 481                         mctx->n201);
 482 }
 483
 484 static int lapdm_send_rnr(struct lapdm_msg_ctx *mctx, uint8_t f_bit)
 485 {
 486         uint8_t sapi = mctx->link_id & 7;
 487         struct msgb *msg = msgb_alloc_headroom(23+10, 10, "LAPDm RNR");
 488         msg->l2h = msgb_put(msg, 3);
 489
 490         msg->l2h[0] = LAPDm_ADDR(LAPDm_LPD_NORMAL, sapi, CR_MS2BS_RESP);
 491         msg->l2h[1] = LAPDm_CTRL_S(mctx->dl->V_recv, LAPDm_S_RNR, f_bit);
 492         msg->l2h[2] = LAPDm_LEN(0);
 493
 494         return tx_ph_data_enqueue(mctx->dl, msg, mctx->chan_nr, mctx->link_id,
 495                         mctx->n201);
 496 }
 497
 498 static int lapdm_send_rej(struct lapdm_msg_ctx *mctx, uint8_t f_bit)
 499 {
 500         uint8_t sapi = mctx->link_id & 7;
 501         struct msgb *msg = msgb_alloc_headroom(23+10, 10, "LAPDm REJ");
 502         msg->l2h = msgb_put(msg, 3);
 503
 504         msg->l2h[0] = LAPDm_ADDR(LAPDm_LPD_NORMAL, sapi, CR_MS2BS_RESP);
 505         msg->l2h[1] = LAPDm_CTRL_S(mctx->dl->V_recv, LAPDm_S_REJ, f_bit);
 506         msg->l2h[2] = LAPDm_LEN(0);
 507
 508         return tx_ph_data_enqueue(mctx->dl, msg, mctx->chan_nr, mctx->link_id,
 509                         mctx->n201);
 510 }
 511
 512 /* Timer callback on T200 expiry */
 513 static void lapdm_t200_cb(void *data)
 514 {
 515         struct lapdm_datalink *dl = data;
 516
 517         LOGP(DLAPDM, LOGL_INFO, "lapdm_t200_cb(%p) state=%u\n", dl, dl->state);
 518
 519         switch (dl->state) {
 520         case LAPDm_STATE_SABM_SENT:
 521                 /* 5.4.1.3 */
 522                 if (dl->retrans_ctr + 1 >= N200_EST_REL + 1) {
 523                         /* send RELEASE INDICATION to L3 */
 524                         send_rll_simple(RSL_MT_REL_IND, &dl->mctx);
 525                         /* send MDL ERROR INIDCATION to L3 */
 526                         rsl_rll_error(RLL_CAUSE_T200_EXPIRED, &dl->mctx);
 527                         /* flush tx buffers */
 528                         lapdm_dl_flush_tx(dl);
 529                         /* go back to idle state */
 530                         lapdm_dl_newstate(dl, LAPDm_STATE_IDLE);
 531                         /* NOTE: we must not change any other states or buffers
 532                          * and queues, since we may reconnect after handover
 533                          * failure. the buffered messages is replaced there */
 534                         break;
 535                 }
 536                 /* retransmit SABM command */
 537                 lapdm_send_resend(dl);
 538                 /* increment re-transmission counter */
 539                 dl->retrans_ctr++;
 540                 /* restart T200 (PH-READY-TO-SEND) */
 541                 osmo_timer_schedule(&dl->t200, T200);
 542                 break;
 543         case LAPDm_STATE_DISC_SENT:
 544                 /* 5.4.4.3 */
 545                 if (dl->retrans_ctr + 1 >= N200_EST_REL + 1) {
 546                         /* send RELEASE INDICATION to L3 */
 547                         send_rll_simple(RSL_MT_REL_CONF, &dl->mctx);
 548                         /* send MDL ERROR INIDCATION to L3 */
 549                         rsl_rll_error(RLL_CAUSE_T200_EXPIRED, &dl->mctx);
 550                         /* flush buffers */
 551                         lapdm_dl_flush_tx(dl);
 552                         lapdm_dl_flush_send(dl);
 553                         /* go back to idle state */
 554                         lapdm_dl_newstate(dl, LAPDm_STATE_IDLE);
 555                         /* NOTE: we must not change any other states or buffers
 556                          * and queues, since we may reconnect after handover
 557                          * failure. the buffered messages is replaced there */
 558                         break;
 559                 }
 560                 /* retransmit DISC command */
 561                 lapdm_send_resend(dl);
 562                 /* increment re-transmission counter */
 563                 dl->retrans_ctr++;
 564                 /* restart T200 (PH-READY-TO-SEND) */
 565                 osmo_timer_schedule(&dl->t200, T200);
 566                 break;
 567         case LAPDm_STATE_MF_EST:
 568                 /* 5.5.7 */
 569                 dl->retrans_ctr = 0;
 570                 lapdm_dl_newstate(dl, LAPDm_STATE_TIMER_RECOV);
 571                 /* fall through */
 572         case LAPDm_STATE_TIMER_RECOV:
 573                 dl->retrans_ctr++;
 574                 if (dl->retrans_ctr < N200) {
 575                         /* retransmit I frame (V_s-1) with P=1, if any */
 576                         if (dl->tx_length[sub_mod8(dl->V_send, 1)]) {
 577                                 struct msgb *msg;
 578                                 int length;
 579
 580                                 LOGP(DLAPDM, LOGL_INFO, "retransmit last frame "
 581                                         "V(S)=%d\n", sub_mod8(dl->V_send, 1));
 582                                 /* Create I frame (segment) from tx_hist */
 583                                 length = dl->tx_length[sub_mod8(dl->V_send, 1)];
 584                                 msg = msgb_alloc_headroom(23+10, 10, "LAPDm I");
 585                                 msg->l2h = msgb_put(msg, length);
 586                                 memcpy(msg->l2h,
 587                                         dl->tx_hist[sub_mod8(dl->V_send, 1)],
 588                                         length);
 589                                 msg->l2h[1] = LAPDm_CTRL_I(dl->V_recv,
 590                                         sub_mod8(dl->V_send, 1), 1); /* P=1 */
 591                                 tx_ph_data_enqueue(dl, msg, dl->mctx.chan_nr,
 592                                         dl->mctx.link_id, dl->mctx.n201);
 593                         } else {
 594                         /* OR send appropriate supervision frame with P=1 */
 595                                 if (!dl->own_busy && !dl->seq_err_cond) {
 596                                         lapdm_send_rr(&dl->mctx, 1);
 597                                         /* NOTE: In case of sequence error
 598                                          * condition, the REJ frame has been
 599                                          * transmitted when entering the
 600                                          * condition, so it has not be done
 601                                          * here
 602                                          */
 603                                 } else if (dl->own_busy) {
 604                                         lapdm_send_rnr(&dl->mctx, 1);
 605                                 } else {
 606                                         LOGP(DLAPDM, LOGL_INFO, "unhandled, "
 607                                                 "pls. fix\n");
 608                                 }
 609                         }
 610                         /* restart T200 (PH-READY-TO-SEND) */
 611                         osmo_timer_schedule(&dl->t200, T200);
 612                 } else {
 613                         /* send MDL ERROR INIDCATION to L3 */
 614                         rsl_rll_error(RLL_CAUSE_T200_EXPIRED, &dl->mctx);
 615                 }
 616                 break;
 617         default:
 618                 LOGP(DLAPDM, LOGL_INFO, "T200 expired in unexpected "
 619                         "dl->state %u\n", dl->state);
 620         }
 621 }
 622
 623 /* 5.5.3.1: Common function to acknowlege frames up to the given N(R) value */
 624 static void lapdm_acknowledge(struct lapdm_msg_ctx *mctx)
 625 {
 626         struct lapdm_datalink *dl = mctx->dl;
 627         uint8_t nr = LAPDm_CTRL_Nr(mctx->ctrl);
 628         int s = 0, rej = 0, t200_reset = 0;
 629         int i;
 630
 631         /* supervisory frame ? */
 632         if (LAPDm_CTRL_is_S(mctx->ctrl))
 633                 s = 1;
 634         /* REJ frame ? */
 635         if (s && LAPDm_CTRL_S_BITS(mctx->ctrl) == LAPDm_S_REJ)
 636                 rej = 1;
 637
 638         /* Flush all transmit buffers of acknowledged frames */
 639         for (i = dl->V_ack; i != nr; i = inc_mod8(i)) {
 640                 if (dl->tx_length[i]) {
 641                         dl->tx_length[i] = 0;
 642                         LOGP(DLAPDM, LOGL_INFO, "ack frame %d\n", i);
 643                 }
 644         }
 645
 646         if (dl->state != LAPDm_STATE_TIMER_RECOV) {
 647                 /* When not in the timer recovery condition, the data
 648                  * link layer entity shall reset the timer T200 on
 649                  * receipt of a valid I frame with N(R) higher than V(A),
 650                  * or an REJ with an N(R) equal to V(A). */
 651                 if ((!rej && nr != dl->V_ack)
 652                  || (rej && nr == dl->V_ack)) {
 653                         LOGP(DLAPDM, LOGL_INFO, "reset t200\n");
 654                         t200_reset = 1;
 655                         osmo_timer_del(&dl->t200);
 656                         /* 5.5.3.1 Note 1 + 2 imply timer recovery cond. */
 657                 }
 658                 /* 5.7.4: N(R) sequence error
 659                  * N(R) is called valid, if and only if
 660                  * (N(R)-V(A)) mod 8 <= (V(S)-V(A)) mod 8.
 661                  */
 662                 if (sub_mod8(nr, dl->V_ack) > sub_mod8(dl->V_send, dl->V_ack)) {
 663                         LOGP(DLAPDM, LOGL_NOTICE, "N(R) sequence error\n");
 664                         rsl_rll_error(RLL_CAUSE_SEQ_ERR, mctx);
 665                 }
 666         }
 667
 668         /* V(A) shall be set to the value of N(R) */
 669         dl->V_ack = nr;
 670
 671         /* If T200 has been reset by the receipt of an I, RR or RNR frame,
 672          * and if there are outstanding I frames, restart T200 */
 673         if (t200_reset && !rej) {
 674                 if (dl->tx_length[dl->V_send - 1]) {
 675                         LOGP(DLAPDM, LOGL_INFO, "start T200, due to unacked I "
 676                                 "frame(s)\n");
 677                         osmo_timer_schedule(&dl->t200, T200);
 678                 }
 679         }
 680 }
 681
 682 /* L1 -> L2 */
 683
 684 /* Receive a LAPDm U (Unnumbered) message from L1 */
 685 static int lapdm_rx_u(struct msgb *msg, struct lapdm_msg_ctx *mctx)
 686 {
 687         struct lapdm_datalink *dl = mctx->dl;
 688         uint8_t length;
 689         int rc;
 690         int rsl_msg;
 691
 692         switch (LAPDm_CTRL_U_BITS(mctx->ctrl)) {
 693         case LAPDm_U_SABM:
 694                 rsl_msg = RSL_MT_EST_IND;
 695
 696                 LOGP(DLAPDM, LOGL_INFO, "SABM received\n");
 697                 /* 5.7.1 */
 698                 dl->seq_err_cond = 0;
 699                 /* G.2.2 Wrong value of the C/R bit */
 700                 if (LAPDm_ADDR_CR(mctx->addr) == CR_BS2MS_RESP) {
 701                         LOGP(DLAPDM, LOGL_NOTICE, "SABM response error\n");
 702                         msgb_free(msg);
 703                         rsl_rll_error(RLL_CAUSE_FRM_UNIMPL, mctx);
 704                         return -EINVAL;
 705                 }
 706
 707                 length = msg->l2h[2] >> 2;
 708                 /* G.4.5 If SABM is received with L>N201 or with M bit
 709                  * set, AN MDL-ERROR-INDICATION is sent to MM.
 710                  */
 711                 if ((msg->l2h[2] & LAPDm_MORE) || length + 3 > mctx->n201) {
 712                         LOGP(DLAPDM, LOGL_NOTICE, "SABM too large error\n");
 713                         msgb_free(msg);
 714                         rsl_rll_error(RLL_CAUSE_UFRM_INC_PARAM, mctx);
 715                         return -EIO;
 716                 }
 717
 718                 /* Must be Format B */
 719                 rc = check_length_ind(mctx, msg->l2h[2]);
 720                 if (rc < 0) {
 721                         msgb_free(msg);
 722                         return rc;
 723                 }
 724                 switch (dl->state) {
 725                 case LAPDm_STATE_IDLE:
 726                         /* Set chan_nr and link_id for established connection */
 727                         memset(&dl->mctx, 0, sizeof(dl->mctx));
 728                         dl->mctx.dl = dl;
 729                         dl->mctx.chan_nr = mctx->chan_nr;
 730                         dl->mctx.link_id = mctx->link_id;
 731                         break;
 732                 case LAPDm_STATE_MF_EST:
 733                         if (length == 0) {
 734                                 rsl_msg = RSL_MT_EST_CONF;
 735                                 break;
 736                         }
 737                         LOGP(DLAPDM, LOGL_INFO, "SABM command, multiple "
 738                                 "frame established state\n");
 739                         /* check for contention resoultion */
 740                         if (dl->tx_hist[0][2] >> 2) {
 741                                 LOGP(DLAPDM, LOGL_NOTICE, "SABM not allowed "
 742                                         "during contention resolution\n");
 743                                 rsl_rll_error(RLL_CAUSE_SABM_INFO_NOTALL, mctx);
 744                         }
 745                         msgb_free(msg);
 746                         return 0;
 747                 case LAPDm_STATE_DISC_SENT:
 748                         /* 5.4.6.2 send DM with F=P */
 749                         lapdm_send_dm(mctx);
 750                         /* reset Timer T200 */
 751                         osmo_timer_del(&dl->t200);
 752                         msgb_free(msg);
 753                         return send_rll_simple(RSL_MT_REL_CONF, mctx);
 754                 default:
 755                         lapdm_send_ua(mctx, length, msg->l2h + 3);
 756                         msgb_free(msg);
 757                         return 0;
 758                 }
 759                 /* send UA response */
 760                 lapdm_send_ua(mctx, length, msg->l2h + 3);
 761                 /* set Vs, Vr and Va to 0 */
 762                 dl->V_send = dl->V_recv = dl->V_ack = 0;
 763                 /* clear tx_hist */
 764                 dl->tx_length[0] = 0;
 765                 /* enter multiple-frame-established state */
 766                 lapdm_dl_newstate(dl, LAPDm_STATE_MF_EST);
 767                 /* send notification to L3 */
 768                 if (length == 0) {
 769                         /* 5.4.1.2 Normal establishment procedures */
 770                         rc = send_rll_simple(rsl_msg, mctx);
 771                         msgb_free(msg);
 772                 } else {
 773                         /* 5.4.1.4 Contention resolution establishment */
 774                         msg->l3h = msg->l2h + 3;
 775                         msgb_pull_l2h(msg);
 776                         rc = send_rslms_rll_l3(rsl_msg, mctx, msg);
 777                 }
 778                 break;
 779         case LAPDm_U_DM:
 780                 LOGP(DLAPDM, LOGL_INFO, "DM received\n");
 781                 /* G.2.2 Wrong value of the C/R bit */
 782                 if (LAPDm_ADDR_CR(mctx->addr) == CR_BS2MS_CMD) {
 783                         LOGP(DLAPDM, LOGL_NOTICE, "DM command error\n");
 784                         msgb_free(msg);
 785                         rsl_rll_error(RLL_CAUSE_FRM_UNIMPL, mctx);
 786                         return -EINVAL;
 787                 }
 788                 if (!LAPDm_CTRL_PF_BIT(mctx->ctrl)) {
 789                         /* 5.4.1.2 DM responses with the F bit set to "0"
 790                          * shall be ignored.
 791                          */
 792                         msgb_free(msg);
 793                         return 0;
 794                 }
 795                 switch (dl->state) {
 796                 case LAPDm_STATE_SABM_SENT:
 797                         break;
 798                 case LAPDm_STATE_MF_EST:
 799                         if (LAPDm_CTRL_PF_BIT(mctx->ctrl) == 1) {
 800                                 LOGP(DLAPDM, LOGL_INFO, "unsolicited DM "
 801                                         "response\n");
 802                                 rsl_rll_error(RLL_CAUSE_UNSOL_DM_RESP, mctx);
 803                         } else {
 804                                 LOGP(DLAPDM, LOGL_INFO, "unsolicited DM "
 805                                         "response, multiple frame established "
 806                                         "state\n");
 807                                 rsl_rll_error(RLL_CAUSE_UNSOL_DM_RESP_MF, mctx);
 808                         }
 809                         msgb_free(msg);
 810                         return 0;
 811                 case LAPDm_STATE_TIMER_RECOV:
 812                         /* DM is normal in case PF = 1 */
 813                         if (LAPDm_CTRL_PF_BIT(mctx->ctrl) == 0) {
 814                                 LOGP(DLAPDM, LOGL_INFO, "unsolicited DM "
 815                                         "response, multiple frame established "
 816                                         "state\n");
 817                                 rsl_rll_error(RLL_CAUSE_UNSOL_DM_RESP_MF, mctx);
 818                                 msgb_free(msg);
 819                                 return 0;
 820                         }
 821                         break;
 822                 case LAPDm_STATE_DISC_SENT:
 823                         /* reset Timer T200 */
 824                         osmo_timer_del(&dl->t200);
 825                         /* go to idle state */
 826                         lapdm_dl_newstate(dl, LAPDm_STATE_IDLE);
 827                         rc = send_rll_simple(RSL_MT_REL_CONF, mctx);
 828                         msgb_free(msg);
 829                         return 0;
 830                 case LAPDm_STATE_IDLE:
 831                         /* 5.4.5 all other frame types shall be discarded */
 832                 default:
 833                         LOGP(DLAPDM, LOGL_INFO, "unsolicited DM response! "
 834                                 "(discarding)\n");
 835                         msgb_free(msg);
 836                         return 0;
 837                 }
 838                 /* reset T200 */
 839                 osmo_timer_del(&dl->t200);
 840                 rc = send_rll_simple(RSL_MT_REL_IND, mctx);
 841                 msgb_free(msg);
 842                 break;
 843         case LAPDm_U_UI:
 844                 LOGP(DLAPDM, LOGL_INFO, "UI received\n");
 845                 /* G.2.2 Wrong value of the C/R bit */
 846                 if (LAPDm_ADDR_CR(mctx->addr) == CR_BS2MS_RESP) {
 847                         LOGP(DLAPDM, LOGL_NOTICE, "UI indicates response "
 848                                 "error\n");
 849                         msgb_free(msg);
 850                         rsl_rll_error(RLL_CAUSE_FRM_UNIMPL, mctx);
 851                         return -EINVAL;
 852                 }
 853
 854                 length = msg->l2h[2] >> 2;
 855                 /* FIXME: G.4.5 If UI is received with L>N201 or with M bit
 856                  * set, AN MDL-ERROR-INDICATION is sent to MM.
 857                  */
 858
 859                 if (mctx->lapdm_fmt == LAPDm_FMT_B4) {
 860                         length = N201_B4;
 861                         msg->l3h = msg->l2h + 2;
 862                 } else {
 863                         rc = check_length_ind(mctx, msg->l2h[2]);
 864                         if (rc < 0) {
 865                                 msgb_free(msg);
 866                                 return rc;
 867                         }
 868                         length = msg->l2h[2] >> 2;
 869                         msg->l3h = msg->l2h + 3;
 870                 }
 871                 /* do some length checks */
 872                 if (length == 0) {
 873                         /* 5.3.3 UI frames received with the length indicator
 874                          * set to "0" shall be ignored
 875                          */
 876                         LOGP(DLAPDM, LOGL_INFO, "length=0 (discarding)\n");
 877                         msgb_free(msg);
 878                         return 0;
 879                 }
 880                 switch (LAPDm_ADDR_SAPI(mctx->addr)) {
 881                 case LAPDm_SAPI_NORMAL:
 882                 case LAPDm_SAPI_SMS:
 883                         break;
 884                 default:
 885                         /* 5.3.3 UI frames with invalid SAPI values shall be
 886                          * discarded
 887                          */
 888                         LOGP(DLAPDM, LOGL_INFO, "sapi=%u (discarding)\n",
 889                                 LAPDm_ADDR_SAPI(mctx->addr));
 890                         msgb_free(msg);
 891                         return 0;
 892                 }
 893                 msgb_pull_l2h(msg);
 894                 rc = send_rslms_rll_l3_ui(mctx, msg);
 895                 break;
 896         case LAPDm_U_DISC:
 897                 rsl_msg = RSL_MT_REL_IND;
 898
 899                 LOGP(DLAPDM, LOGL_INFO, "DISC received\n");
 900                 /* flush buffers */
 901                 lapdm_dl_flush_tx(dl);
 902                 lapdm_dl_flush_send(dl);
 903                 /* 5.7.1 */
 904                 dl->seq_err_cond = 0;
 905                 /* G.2.2 Wrong value of the C/R bit */
 906                 if (LAPDm_ADDR_CR(mctx->addr) == CR_BS2MS_RESP) {
 907                         LOGP(DLAPDM, LOGL_NOTICE, "DISC response error\n");
 908                         msgb_free(msg);
 909                         rsl_rll_error(RLL_CAUSE_FRM_UNIMPL, mctx);
 910                         return -EINVAL;
 911                 }
 912                 length = msg->l2h[2] >> 2;
 913                 if (length > 0 || msg->l2h[2] & 0x02) {
 914                         /* G.4.4 If a DISC or DM frame is received with L>0 or
 915                          * with the M bit set to "1", an MDL-ERROR-INDICATION
 916                          * primitive with cause "U frame with incorrect
 917                          * parameters" is sent to the mobile management entity.
 918                          */
 919                         LOGP(DLAPDM, LOGL_NOTICE,
 920                                 "U frame iwth incorrect parameters ");
 921                         msgb_free(msg);
 922                         rsl_rll_error(RLL_CAUSE_UFRM_INC_PARAM, mctx);
 923                         return -EIO;
 924                 }
 925                 msgb_free(msg);
 926                 switch (dl->state) {
 927                 case LAPDm_STATE_IDLE:
 928                         LOGP(DLAPDM, LOGL_INFO, "DISC in idle state\n");
 929                         /* send DM with F=P */
 930                         return lapdm_send_dm(mctx);
 931                 case LAPDm_STATE_SABM_SENT:
 932                         LOGP(DLAPDM, LOGL_INFO, "DISC in SABM state\n");
 933                         /* 5.4.6.2 send DM with F=P */
 934                         lapdm_send_dm(mctx);
 935                         /* reset Timer T200 */
 936                         osmo_timer_del(&dl->t200);
 937                         return send_rll_simple(RSL_MT_REL_IND, mctx);
 938                 case LAPDm_STATE_MF_EST:
 939                 case LAPDm_STATE_TIMER_RECOV:
 940                         LOGP(DLAPDM, LOGL_INFO, "DISC in est state\n");
 941                         break;
 942                 case LAPDm_STATE_DISC_SENT:
 943                         LOGP(DLAPDM, LOGL_INFO, "DISC in disc state\n");
 944                         rsl_msg = RSL_MT_REL_CONF;
 945                         break;
 946                 default:
 947                         lapdm_send_ua(mctx, length, msg->l2h + 3);
 948                         return 0;
 949                 }
 950                 /* send UA response */
 951                 lapdm_send_ua(mctx, length, msg->l2h + 3);
 952                 /* reset Timer T200 */
 953                 osmo_timer_del(&dl->t200);
 954                 /* enter idle state */
 955                 lapdm_dl_newstate(dl, LAPDm_STATE_IDLE);
 956                 /* send notification to L3 */
 957                 rc = send_rll_simple(rsl_msg, mctx);
 958                 break;
 959         case LAPDm_U_UA:
 960                 LOGP(DLAPDM, LOGL_INFO, "UA received\n");
 961                 /* G.2.2 Wrong value of the C/R bit */
 962                 if (LAPDm_ADDR_CR(mctx->addr) == CR_BS2MS_CMD) {
 963                         LOGP(DLAPDM, LOGL_NOTICE, "UA indicates command "
 964                                 "error\n");
 965                         msgb_free(msg);
 966                         rsl_rll_error(RLL_CAUSE_FRM_UNIMPL, mctx);
 967                         return -EINVAL;
 968                 }
 969
 970                 length = msg->l2h[2] >> 2;
 971                 /* G.4.5 If UA is received with L>N201 or with M bit
 972                  * set, AN MDL-ERROR-INDICATION is sent to MM.
 973                  */
 974                 if ((msg->l2h[2] & LAPDm_MORE) || length + 3 > mctx->n201) {
 975                         LOGP(DLAPDM, LOGL_NOTICE, "UA too large error\n");
 976                         msgb_free(msg);
 977                         rsl_rll_error(RLL_CAUSE_UFRM_INC_PARAM, mctx);
 978                         return -EIO;
 979                 }
 980
 981                 if (!LAPDm_CTRL_PF_BIT(mctx->ctrl)) {
 982                         /* 5.4.1.2 A UA response with the F bit set to "0"
 983                          * shall be ignored.
 984                          */
 985                         LOGP(DLAPDM, LOGL_INFO, "F=0 (discarding)\n");
 986                         msgb_free(msg);
 987                         return 0;
 988                 }
 989                 switch (dl->state) {
 990                 case LAPDm_STATE_SABM_SENT:
 991                         break;
 992                 case LAPDm_STATE_MF_EST:
 993                 case LAPDm_STATE_TIMER_RECOV:
 994                         LOGP(DLAPDM, LOGL_INFO, "unsolicited UA response! "
 995                                 "(discarding)\n");
 996                         rsl_rll_error(RLL_CAUSE_UNSOL_UA_RESP, mctx);
 997                         msgb_free(msg);
 998                         return 0;
 999                 case LAPDm_STATE_DISC_SENT:
1000                         LOGP(DLAPDM, LOGL_INFO, "UA in disconnect state\n");
1001                         /* reset Timer T200 */
1002                         osmo_timer_del(&dl->t200);
1003                         /* go to idle state */
1004                         lapdm_dl_newstate(dl, LAPDm_STATE_IDLE);
1005                         rc = send_rll_simple(RSL_MT_REL_CONF, mctx);
1006                         msgb_free(msg);
1007                         return 0;
1008                 case LAPDm_STATE_IDLE:
1009                         /* 5.4.5 all other frame types shall be discarded */
1010                 default:
1011                         LOGP(DLAPDM, LOGL_INFO, "unsolicited UA response! "
1012                                 "(discarding)\n");
1013                         msgb_free(msg);
1014                         return 0;
1015                 }
1016                 LOGP(DLAPDM, LOGL_INFO, "UA in SABM state\n");
1017                 /* reset Timer T200 */
1018                 osmo_timer_del(&dl->t200);
1019                 /* compare UA with SABME if contention resolution is applied */
1020                 if (dl->tx_hist[0][2] >> 2) {
1021                         rc = check_length_ind(mctx, msg->l2h[2]);
1022                         if (rc < 0) {
1023                                 rc = send_rll_simple(RSL_MT_REL_IND, mctx);
1024                                 msgb_free(msg);
1025                                 /* go to idle state */
1026                                 lapdm_dl_newstate(dl, LAPDm_STATE_IDLE);
1027                                 return 0;
1028                         }
1029                         length = msg->l2h[2] >> 2;
1030                         if (length != (dl->tx_hist[0][2] >> 2)
1031                          || !!memcmp(dl->tx_hist[0] + 3, msg->l2h + 3,
1032                                         length)) {
1033                                 LOGP(DLAPDM, LOGL_INFO, "**** UA response "
1034                                         "mismatches ****\n");
1035                                 rc = send_rll_simple(RSL_MT_REL_IND, mctx);
1036                                 msgb_free(msg);
1037                                 /* go to idle state */
1038                                 lapdm_dl_newstate(dl, LAPDm_STATE_IDLE);
1039                                 return 0;
1040                         }
1041                 }
1042                 /* set Vs, Vr and Va to 0 */
1043                 dl->V_send = dl->V_recv = dl->V_ack = 0;
1044                 /* clear tx_hist */
1045                 dl->tx_length[0] = 0;
1046                 /* enter multiple-frame-established state */
1047                 lapdm_dl_newstate(dl, LAPDm_STATE_MF_EST);
1048                 /* send outstanding frames, if any (resume / reconnect) */
1049                 rslms_send_i(mctx, __LINE__);
1050                 /* send notification to L3 */
1051                 rc = send_rll_simple(RSL_MT_EST_CONF, mctx);
1052                 msgb_free(msg);
1053                 break;
1054         default:
1055                 /* G.3.1 */
1056                 LOGP(DLAPDM, LOGL_NOTICE, "Unnumbered frame not allowed.\n");
1057                 msgb_free(msg);
1058                 rsl_rll_error(RLL_CAUSE_FRM_UNIMPL, mctx);
1059                 return -EINVAL;
1060         }
1061         return rc;
1062 }
1063
1064 /* Receive a LAPDm S (Supervisory) message from L1 */
1065 static int lapdm_rx_s(struct msgb *msg, struct lapdm_msg_ctx *mctx)
1066 {
1067         struct lapdm_datalink *dl = mctx->dl;
1068         uint8_t length;
1069
1070         length = msg->l2h[2] >> 2;
1071         if (length > 0 || msg->l2h[2] & 0x02) {
1072                 /* G.4.3 If a supervisory frame is received with L>0 or
1073                  * with the M bit set to "1", an MDL-ERROR-INDICATION
1074                  * primitive with cause "S frame with incorrect
1075                  * parameters" is sent to the mobile management entity. */
1076                 LOGP(DLAPDM, LOGL_NOTICE,
1077                                 "S frame with incorrect parameters\n");
1078                 msgb_free(msg);
1079                 rsl_rll_error(RLL_CAUSE_SFRM_INC_PARAM, mctx);
1080                 return -EIO;
1081         }
1082
1083         if (LAPDm_ADDR_CR(mctx->addr) == CR_BS2MS_RESP
1084          && LAPDm_CTRL_PF_BIT(mctx->ctrl)
1085          && dl->state != LAPDm_STATE_TIMER_RECOV) {
1086                 /* 5.4.2.2: Inidcate error on supervisory reponse F=1 */
1087                 LOGP(DLAPDM, LOGL_NOTICE, "S frame response with F=1 error\n");
1088                 rsl_rll_error(RLL_CAUSE_UNSOL_SPRV_RESP, mctx);
1089         }
1090
1091         switch (dl->state) {
1092         case LAPDm_STATE_IDLE:
1093                 /* if P=1, respond DM with F=1 (5.2.2) */
1094                 /* 5.4.5 all other frame types shall be discarded */
1095                 if (LAPDm_CTRL_PF_BIT(mctx->ctrl))
1096                         lapdm_send_dm(mctx); /* F=P */
1097                 /* fall though */
1098         case LAPDm_STATE_SABM_SENT:
1099         case LAPDm_STATE_DISC_SENT:
1100                 LOGP(DLAPDM, LOGL_NOTICE, "S frame ignored in this state\n");
1101                 msgb_free(msg);
1102                 return 0;
1103         }
1104         switch (LAPDm_CTRL_S_BITS(mctx->ctrl)) {
1105         case LAPDm_S_RR:
1106                 LOGP(DLAPDM, LOGL_INFO, "RR received\n");
1107                 /* 5.5.3.1: Acknowlege all tx frames up the the N(R)-1 */
1108                 lapdm_acknowledge(mctx);
1109
1110                 /* 5.5.3.2 */
1111                 if (LAPDm_ADDR_CR(mctx->addr) == CR_BS2MS_CMD
1112                  && LAPDm_CTRL_PF_BIT(mctx->ctrl)) {
1113                         if (!dl->own_busy && !dl->seq_err_cond) {
1114                                 LOGP(DLAPDM, LOGL_NOTICE, "RR frame command "
1115                                         "with polling bit set and we are not "
1116                                         "busy, so we reply with RR frame\n");
1117                                 lapdm_send_rr(mctx, 1);
1118                                 /* NOTE: In case of sequence error condition,
1119                                  * the REJ frame has been transmitted when
1120                                  * entering the condition, so it has not be
1121                                  * done here
1122                                  */
1123                         } else if (dl->own_busy) {
1124                                 LOGP(DLAPDM, LOGL_NOTICE, "RR frame command "
1125                                         "with polling bit set and we are busy, "
1126                                         "so we reply with RR frame\n");
1127                                 lapdm_send_rnr(mctx, 1);
1128                         }
1129                 } else if (LAPDm_ADDR_CR(mctx->addr) == CR_BS2MS_RESP
1130                         && LAPDm_CTRL_PF_BIT(mctx->ctrl)
1131                         && dl->state == LAPDm_STATE_TIMER_RECOV) {
1132                         LOGP(DLAPDM, LOGL_INFO, "RR response with F==1, "
1133                                 "and we are in timer recovery state, so "
1134                                 "we leave that state\n");
1135                         /* V(S) to the N(R) in the RR frame */
1136                         dl->V_send = LAPDm_CTRL_Nr(mctx->ctrl);
1137                         /* reset Timer T200 */
1138                         osmo_timer_del(&dl->t200);
1139                         /* 5.5.7 Clear timer recovery condition */
1140                         lapdm_dl_newstate(dl, LAPDm_STATE_MF_EST);
1141                 }
1142                 /* Send message, if possible due to acknowledged data */
1143                 rslms_send_i(mctx, __LINE__);
1144
1145                 break;
1146         case LAPDm_S_RNR:
1147                 LOGP(DLAPDM, LOGL_INFO, "RNR received\n");
1148                 /* 5.5.3.1: Acknowlege all tx frames up the the N(R)-1 */
1149                 lapdm_acknowledge(mctx);
1150
1151                 /* 5.5.5 */
1152                 /* Set peer receiver busy condition */
1153                 dl->peer_busy = 1;
1154
1155                 if (LAPDm_CTRL_PF_BIT(mctx->ctrl)) {
1156                         if (LAPDm_ADDR_CR(mctx->addr) == CR_BS2MS_CMD) {
1157                                 if (!dl->own_busy) {
1158                                         LOGP(DLAPDM, LOGL_INFO, "RNR poll "
1159                                                 "command and we are not busy, "
1160                                                 "so we reply with RR final "
1161                                                 "response\n");
1162                                         /* Send RR with F=1 */
1163                                         lapdm_send_rr(mctx, 1);
1164                                 } else {
1165                                         LOGP(DLAPDM, LOGL_INFO, "RNR poll "
1166                                                 "command and we are busy, so "
1167                                                 "we reply with RNR final "
1168                                                 "response\n");
1169                                         /* Send RNR with F=1 */
1170                                         lapdm_send_rnr(mctx, 1);
1171                                 }
1172                         } else if (dl->state == LAPDm_STATE_TIMER_RECOV) {
1173                                 LOGP(DLAPDM, LOGL_INFO, "RNR poll response "
1174                                         "and we in timer recovery state, so "
1175                                         "we leave that state\n");
1176                                 /* 5.5.7 Clear timer recovery condition */
1177                                 lapdm_dl_newstate(dl, LAPDm_STATE_MF_EST);
1178                                 /* V(S) to the N(R) in the RNR frame */
1179                                 dl->V_send = LAPDm_CTRL_Nr(mctx->ctrl);
1180                         }
1181                 } else
1182                         LOGP(DLAPDM, LOGL_INFO, "RNR not polling/final state "
1183                                 "received\n");
1184
1185                 /* Send message, if possible due to acknowledged data */
1186                 rslms_send_i(mctx, __LINE__);
1187
1188                 break;
1189         case LAPDm_S_REJ:
1190                 LOGP(DLAPDM, LOGL_INFO, "REJ received\n");
1191                 /* 5.5.3.1: Acknowlege all tx frames up the the N(R)-1 */
1192                 lapdm_acknowledge(mctx);
1193
1194                 /* 5.5.4.1 */
1195                 if (dl->state != LAPDm_STATE_TIMER_RECOV) {
1196                         /* Clear an existing peer receiver busy condition */
1197                         dl->peer_busy = 0;
1198                         /* V(S) and V(A) to the N(R) in the REJ frame */
1199                         dl->V_send = dl->V_ack = LAPDm_CTRL_Nr(mctx->ctrl);
1200                         /* reset Timer T200 */
1201                         osmo_timer_del(&dl->t200);
1202                         /* 5.5.3.2 */
1203                         if (LAPDm_ADDR_CR(mctx->addr) == CR_BS2MS_CMD
1204                          && LAPDm_CTRL_PF_BIT(mctx->ctrl)) {
1205                                 if (!dl->own_busy && !dl->seq_err_cond) {
1206                                         LOGP(DLAPDM, LOGL_INFO, "REJ poll "
1207                                                 "command not in timer recovery "
1208                                                 "state and not in own busy "
1209                                                 "condition received, so we "
1210                                                 "respond with RR final "
1211                                                 "response\n");
1212                                         lapdm_send_rr(mctx, 1);
1213                                         /* NOTE: In case of sequence error
1214                                          * condition, the REJ frame has been
1215                                          * transmitted when entering the
1216                                          * condition, so it has not be done
1217                                          * here
1218                                          */
1219                                 } else if (dl->own_busy) {
1220                                         LOGP(DLAPDM, LOGL_INFO, "REJ poll "
1221                                                 "command not in timer recovery "
1222                                                 "state and in own busy "
1223                                                 "condition received, so we "
1224                                                 "respond with RNR final "
1225                                                 "response\n");
1226                                         lapdm_send_rnr(mctx, 1);
1227                                 }
1228                         } else
1229                                 LOGP(DLAPDM, LOGL_INFO, "REJ response or not "
1230                                         "polling command not in timer recovery "
1231                                         "state received\n");
1232                         /* send MDL ERROR INIDCATION to L3 */
1233                         if (LAPDm_ADDR_CR(mctx->addr) == CR_BS2MS_RESP
1234                          && LAPDm_CTRL_PF_BIT(mctx->ctrl)) {
1235                                 rsl_rll_error(RLL_CAUSE_UNSOL_SPRV_RESP, mctx);
1236                         }
1237
1238                 } else if (LAPDm_ADDR_CR(mctx->addr) == CR_BS2MS_RESP
1239                         && LAPDm_CTRL_PF_BIT(mctx->ctrl)) {
1240                         LOGP(DLAPDM, LOGL_INFO, "REJ poll response in timer "
1241                                 "recovery state received\n");
1242                         /* Clear an existing peer receiver busy condition */
1243                         dl->peer_busy = 0;
1244                         /* 5.5.7 Clear timer recovery condition */
1245                         lapdm_dl_newstate(dl, LAPDm_STATE_MF_EST);
1246                         /* V(S) and V(A) to the N(R) in the REJ frame */
1247                         dl->V_send = dl->V_ack = LAPDm_CTRL_Nr(mctx->ctrl);
1248                         /* reset Timer T200 */
1249                         osmo_timer_del(&dl->t200);
1250                 } else {
1251                         /* Clear an existing peer receiver busy condition */
1252                         dl->peer_busy = 0;
1253                         /* V(S) and V(A) to the N(R) in the REJ frame */
1254                         dl->V_send = dl->V_ack = LAPDm_CTRL_Nr(mctx->ctrl);
1255                         /* 5.5.3.2 */
1256                         if (LAPDm_ADDR_CR(mctx->addr) == CR_BS2MS_CMD
1257                          && LAPDm_CTRL_PF_BIT(mctx->ctrl)) {
1258                                 if (!dl->own_busy && !dl->seq_err_cond) {
1259                                         LOGP(DLAPDM, LOGL_INFO, "REJ poll "
1260                                                 "command in timer recovery "
1261                                                 "state and not in own busy "
1262                                                 "condition received, so we "
1263                                                 "respond with RR final "
1264                                                 "response\n");
1265                                         lapdm_send_rr(mctx, 1);
1266                                         /* NOTE: In case of sequence error
1267                                          * condition, the REJ frame has been
1268                                          * transmitted when entering the
1269                                          * condition, so it has not be done
1270                                          * here
1271                                          */
1272                                 } else if (dl->own_busy) {
1273                                         LOGP(DLAPDM, LOGL_INFO, "REJ poll "
1274                                                 "command in timer recovery "
1275                                                 "state and in own busy "
1276                                                 "condition received, so we "
1277                                                 "respond with RNR final "
1278                                                 "response\n");
1279                                         lapdm_send_rnr(mctx, 1);
1280                                 }
1281                         } else
1282                                 LOGP(DLAPDM, LOGL_INFO, "REJ response or not "
1283                                         "polling command in timer recovery "
1284                                         "state received\n");
1285                 }
1286
1287                 /* FIXME: 5.5.4.2 2) */
1288
1289                 /* Send message, if possible due to acknowledged data */
1290                 rslms_send_i(mctx, __LINE__);
1291
1292                 break;
1293         default:
1294                 /* G.3.1 */
1295                 LOGP(DLAPDM, LOGL_NOTICE, "Supervisory frame not allowed.\n");
1296                 msgb_free(msg);
1297                 rsl_rll_error(RLL_CAUSE_FRM_UNIMPL, mctx);
1298                 return -EINVAL;
1299         }
1300         msgb_free(msg);
1301         return 0;
1302 }
1303
1304 /* Receive a LAPDm I (Information) message from L1 */
1305 static int lapdm_rx_i(struct msgb *msg, struct lapdm_msg_ctx *mctx)
1306 {
1307         struct lapdm_datalink *dl = mctx->dl;
1308         //uint8_t nr = LAPDm_CTRL_Nr(mctx->ctrl);
1309         uint8_t ns = LAPDm_CTRL_I_Ns(mctx->ctrl);
1310         uint8_t length;
1311         int rc;
1312
1313         LOGP(DLAPDM, LOGL_NOTICE, "I received\n");
1314
1315         /* G.2.2 Wrong value of the C/R bit */
1316         if (LAPDm_ADDR_CR(mctx->addr) == CR_BS2MS_RESP) {
1317                 LOGP(DLAPDM, LOGL_NOTICE, "I frame response not allowed\n");
1318                 msgb_free(msg);
1319                 rsl_rll_error(RLL_CAUSE_FRM_UNIMPL, mctx);
1320                 return -EINVAL;
1321         }
1322
1323         length = msg->l2h[2] >> 2;
1324         if (length == 0 || length + 3 > mctx->n201) {
1325                 /* G.4.2 If the length indicator of an I frame is set
1326                  * to a numerical value L>N201 or L=0, an MDL-ERROR-INDICATION
1327                  * primitive with cause "I frame with incorrect length"
1328                  * is sent to the mobile management entity. */
1329                 LOGP(DLAPDM, LOGL_NOTICE, "I frame length not allowed\n");
1330                 msgb_free(msg);
1331                 rsl_rll_error(RLL_CAUSE_IFRM_INC_LEN, mctx);
1332                 return -EIO;
1333         }
1334
1335         /* G.4.2 If the numerical value of L is L<N201 and the M
1336          * bit is set to "1", then an MDL-ERROR-INDICATION primitive with
1337          * cause "I frame with incorrect use of M bit" is sent to the
1338          * mobile management entity. */
1339         if ((msg->l2h[2] & LAPDm_MORE) && length + 3 < mctx->n201) {
1340                 LOGP(DLAPDM, LOGL_NOTICE, "I frame with M bit too short\n");
1341                 msgb_free(msg);
1342                 rsl_rll_error(RLL_CAUSE_IFRM_INC_MBITS, mctx);
1343                 return -EIO;
1344         }
1345
1346         switch (dl->state) {
1347         case LAPDm_STATE_IDLE:
1348                 /* if P=1, respond DM with F=1 (5.2.2) */
1349                 /* 5.4.5 all other frame types shall be discarded */
1350                 if (LAPDm_CTRL_PF_BIT(mctx->ctrl))
1351                         lapdm_send_dm(mctx); /* F=P */
1352                 /* fall though */
1353         case LAPDm_STATE_SABM_SENT:
1354         case LAPDm_STATE_DISC_SENT:
1355                 LOGP(DLAPDM, LOGL_NOTICE, "I frame ignored in this state\n");
1356                 msgb_free(msg);
1357                 return 0;
1358         }
1359
1360         /* 5.7.1: N(s) sequence error */
1361         if (ns != dl->V_recv) {
1362                 LOGP(DLAPDM, LOGL_NOTICE, "N(S) sequence error: N(S)=%u, "
1363                      "V(R)=%u\n", ns, dl->V_recv);
1364                 /* discard data */
1365                 msgb_free(msg);
1366                 if (!dl->seq_err_cond) {
1367                         /* FIXME: help me understand what exactly todo here
1368                         dl->seq_err_cond = 1;
1369                         */
1370                         lapdm_send_rej(mctx, LAPDm_CTRL_PF_BIT(mctx->ctrl));
1371                 } else {
1372                 }
1373                 return -EIO;
1374         }
1375         dl->seq_err_cond = 0;
1376
1377         /* Increment receiver state */
1378         dl->V_recv = inc_mod8(dl->V_recv);
1379         LOGP(DLAPDM, LOGL_NOTICE, "incrementing V(R) to %u\n", dl->V_recv);
1380
1381         /* 5.5.3.1: Acknowlege all transmitted frames up the the N(R)-1 */
1382         lapdm_acknowledge(mctx); /* V(A) is also set here */
1383
1384         /* Only if we are not in own receiver busy condition */
1385         if (!dl->own_busy) {
1386                 /* if the frame carries a complete segment */
1387                 if (!(msg->l2h[2] & LAPDm_MORE)
1388                  && !dl->rcv_buffer) {
1389                         LOGP(DLAPDM, LOGL_INFO, "message in single I frame\n");
1390                         /* send a DATA INDICATION to L3 */
1391                         msg->l3h = msg->l2h + 3;
1392                         msgb_pull_l2h(msg);
1393                         msg->len = length;
1394                         msg->tail = msg->data + length;
1395                         rc = send_rslms_rll_l3(RSL_MT_DATA_IND, mctx, msg);
1396                 } else {
1397                         /* create rcv_buffer */
1398                         if (!dl->rcv_buffer) {
1399                                 LOGP(DLAPDM, LOGL_INFO, "message in multiple I "
1400                                         "frames (first message)\n");
1401                                 dl->rcv_buffer = msgb_alloc_headroom(200+56, 56,
1402                                                                 "LAPDm RX");
1403                                 dl->rcv_buffer->l3h = dl->rcv_buffer->data;
1404                         }
1405                         /* concat. rcv_buffer */
1406                         if (msgb_l3len(dl->rcv_buffer) + length > 200) {
1407                                 LOGP(DLAPDM, LOGL_NOTICE, "Received frame "
1408                                         "overflow!\n");
1409                         } else {
1410                                 memcpy(msgb_put(dl->rcv_buffer, length),
1411                                         msg->l2h + 3, length);
1412                         }
1413                         /* if the last segment was received */
1414                         if (!(msg->l2h[2] & LAPDm_MORE)) {
1415                                 LOGP(DLAPDM, LOGL_INFO, "message in multiple I "
1416                                         "frames (last message)\n");
1417                                 rc = send_rslms_rll_l3(RSL_MT_DATA_IND, mctx,
1418                                         dl->rcv_buffer);
1419                                 dl->rcv_buffer = NULL;
1420                         } else
1421                                 LOGP(DLAPDM, LOGL_INFO, "message in multiple I "
1422                                         "frames (next message)\n");
1423                         msgb_free(msg);
1424
1425                 }
1426         } else
1427                 LOGP(DLAPDM, LOGL_INFO, "I frame ignored during own receiver "
1428                         "busy condition\n");
1429
1430         /* Check for P bit */
1431         if (LAPDm_CTRL_PF_BIT(mctx->ctrl)) {
1432                 /* 5.5.2.1 */
1433                 /* check if we are not in own receiver busy */
1434                 if (!dl->own_busy) {
1435                         LOGP(DLAPDM, LOGL_INFO, "we are not busy, send RR\n");
1436                         /* Send RR with F=1 */
1437                         rc = lapdm_send_rr(mctx, 1);
1438                 } else {
1439                         LOGP(DLAPDM, LOGL_INFO, "we are busy, send RNR\n");
1440                         /* Send RNR with F=1 */
1441                         rc = lapdm_send_rnr(mctx, 1);
1442                 }
1443         } else {
1444                 /* 5.5.2.2 */
1445                 /* check if we are not in own receiver busy */
1446                 if (!dl->own_busy) {
1447                         /* NOTE: V(R) is already set above */
1448                         rc = rslms_send_i(mctx, __LINE__);
1449                         if (rc) {
1450                                 LOGP(DLAPDM, LOGL_INFO, "we are not busy and "
1451                                         "have no pending data, send RR\n");
1452                                 /* Send RR with F=0 */
1453                                 return lapdm_send_rr(mctx, 0);
1454                         }
1455                         /* all I or one RR is sent, we are done */
1456                         return 0;
1457                 } else {
1458                         LOGP(DLAPDM, LOGL_INFO, "we are busy, send RNR\n");
1459                         /* Send RNR with F=0 */
1460                         rc = lapdm_send_rnr(mctx, 0);
1461                 }
1462         }
1463
1464         /* Send message, if possible due to acknowledged data */
1465         rslms_send_i(mctx, __LINE__);
1466
1467         return rc;
1468 }
1469
1470 /* Receive a LAPDm message from L1 */
1471 static int lapdm_ph_data_ind(struct msgb *msg, struct lapdm_msg_ctx *mctx)
1472 {
1473         int rc;
1474
1475         /* G.2.3 EA bit set to "0" is not allowed in GSM */
1476         if (!LAPDm_ADDR_EA(mctx->addr)) {
1477                 LOGP(DLAPDM, LOGL_NOTICE, "EA bit 0 is not allowed in GSM\n");
1478                 msgb_free(msg);
1479                 rsl_rll_error(RLL_CAUSE_FRM_UNIMPL, mctx);
1480                 return -EINVAL;
1481         }
1482
1483         if (LAPDm_CTRL_is_U(mctx->ctrl))
1484                 rc = lapdm_rx_u(msg, mctx);
1485         else if (LAPDm_CTRL_is_S(mctx->ctrl))
1486                 rc = lapdm_rx_s(msg, mctx);
1487         else if (LAPDm_CTRL_is_I(mctx->ctrl))
1488                 rc = lapdm_rx_i(msg, mctx);
1489         else {
1490                 LOGP(DLAPDM, LOGL_NOTICE, "unknown LAPDm format\n");
1491                 msgb_free(msg);
1492                 rc = -EINVAL;
1493         }
1494         return rc;
1495 }
1496
1497 /* input into layer2 (from layer 1) */
1498 int l2_ph_data_ind(struct msgb *msg, struct lapdm_entity *le, struct l1ctl_info_dl *l1i)
1499 {
1500         uint8_t cbits = l1i->chan_nr >> 3;
1501         uint8_t sapi = l1i->link_id & 7;
1502         struct lapdm_msg_ctx mctx;
1503         int rc = 0;
1504
1505         /* when we reach here, we have a msgb with l2h pointing to the raw
1506          * 23byte mac block. The l1h has already been purged. */
1507
1508         mctx.dl = datalink_for_sapi(le, sapi);
1509         mctx.chan_nr = l1i->chan_nr;
1510         mctx.link_id = l1i->link_id;
1511         mctx.addr = mctx.ctrl = 0;
1512
1513         /* G.2.1 No action schall be taken on frames containing an unallocated
1514          * SAPI.
1515          */
1516         if (!mctx.dl) {
1517                 LOGP(DLAPDM, LOGL_NOTICE, "Received frame for unsupported "
1518                         "SAPI %d!\n", sapi);
1519                 return -EINVAL;
1520                 msgb_free(msg);
1521                 return -EIO;
1522         }
1523
1524         /* check for L1 chan_nr/link_id and determine LAPDm hdr format */
1525         if (cbits == 0x10 || cbits == 0x12) {
1526                 /* Format Bbis is used on BCCH and CCCH(PCH, NCH and AGCH) */
1527                 mctx.lapdm_fmt = LAPDm_FMT_Bbis;
1528                 mctx.n201 = N201_Bbis;
1529         } else {
1530                 if (mctx.link_id & 0x40) {
1531                         /* It was received from network on SACCH, thus
1532                          * lapdm_fmt must be B4 */
1533                         mctx.lapdm_fmt = LAPDm_FMT_B4;
1534                         mctx.n201 = N201_B4;
1535                         LOGP(DLAPDM, LOGL_INFO, "fmt=B4\n");
1536                         /* SACCH frames have a two-byte L1 header that
1537                          * OsmocomBB L1 doesn't strip */
1538                         mctx.tx_power_ind = msg->l2h[0] & 0x1f;
1539                         mctx.ta_ind = msg->l2h[1];
1540                         msgb_pull(msg, 2);
1541                         msg->l2h += 2;
1542                 } else {
1543                         mctx.lapdm_fmt = LAPDm_FMT_B;
1544                         LOGP(DLAPDM, LOGL_INFO, "fmt=B\n");
1545                         mctx.n201 = 23; // FIXME: select correct size by chan.
1546                 }
1547         }
1548
1549         switch (mctx.lapdm_fmt) {
1550         case LAPDm_FMT_A:
1551         case LAPDm_FMT_B:
1552         case LAPDm_FMT_B4:
1553                 mctx.addr = msg->l2h[0];
1554                 if (!(mctx.addr & 0x01)) {
1555                         LOGP(DLAPDM, LOGL_ERROR, "we don't support "
1556                                 "multibyte addresses (discarding)\n");
1557                         msgb_free(msg);
1558                         return -EINVAL;
1559                 }
1560                 mctx.ctrl = msg->l2h[1];
1561                 /* obtain SAPI from address field */
1562                 mctx.link_id |= LAPDm_ADDR_SAPI(mctx.addr);
1563                 rc = lapdm_ph_data_ind(msg, &mctx);
1564                 break;
1565         case LAPDm_FMT_Bter:
1566                 /* FIXME */
1567                 msgb_free(msg);
1568                 break;
1569         case LAPDm_FMT_Bbis:
1570                 /* directly pass up to layer3 */
1571                 LOGP(DLAPDM, LOGL_INFO, "fmt=Bbis UI\n");
1572                 msg->l3h = msg->l2h;
1573                 msgb_pull_l2h(msg);
1574                 rc = send_rslms_rll_l3(RSL_MT_UNIT_DATA_IND, &mctx, msg);
1575                 break;
1576         default:
1577                 msgb_free(msg);
1578         }
1579
1580         return rc;
1581 }
1582
1583 /* L3 -> L2 / RSLMS -> LAPDm */
1584
1585 /* L3 requests establishment of data link */
1586 static int rslms_rx_rll_est_req(struct msgb *msg, struct lapdm_datalink *dl)
1587 {
1588         struct abis_rsl_rll_hdr *rllh = msgb_l2(msg);
1589         uint8_t chan_nr = rllh->chan_nr;
1590         uint8_t link_id = rllh->link_id;
1591         uint8_t sapi = rllh->link_id & 7;
1592         struct tlv_parsed tv;
1593         uint8_t length;
1594         uint8_t n201 = 23; //FIXME
1595
1596         /* Set chan_nr and link_id for established connection */
1597         memset(&dl->mctx, 0, sizeof(dl->mctx));
1598         dl->mctx.dl = dl;
1599         dl->mctx.n201 = n201;
1600         dl->mctx.chan_nr = chan_nr;
1601         dl->mctx.link_id = link_id;
1602
1603         rsl_tlv_parse(&tv, rllh->data, msgb_l2len(msg)-sizeof(*rllh));
1604         if (TLVP_PRESENT(&tv, RSL_IE_L3_INFO)) {
1605                 /* contention resolution establishment procedure */
1606                 if (sapi != 0) {
1607                         /* According to clause 6, the contention resolution
1608                          * procedure is only permitted with SAPI value 0 */
1609                         LOGP(DLAPDM, LOGL_ERROR, "SAPI != 0 but contention"
1610                                 "resolution (discarding)\n");
1611                         msgb_free(msg);
1612                         return send_rll_simple(RSL_MT_REL_IND, &dl->mctx);
1613                 }
1614                 /* transmit a SABM command with the P bit set to "1". The SABM
1615                  * command shall contain the layer 3 message unit */
1616                 length = TLVP_LEN(&tv, RSL_IE_L3_INFO);
1617                 LOGP(DLAPDM, LOGL_INFO, "perform establishment with content "
1618                         "(SABM)\n");
1619         } else {
1620                 /* normal establishment procedure */
1621                 length = 0;
1622                 LOGP(DLAPDM, LOGL_INFO, "perform normal establishm. (SABM)\n");
1623         }
1624
1625         /* check if the layer3 message length exceeds N201 */
1626         if (length + 3 > 21) { /* FIXME: do we know the channel N201? */
1627                 LOGP(DLAPDM, LOGL_ERROR, "frame too large: %d > N201(%d) "
1628                         "(discarding)\n", length + 3, 21);
1629                 msgb_free(msg);
1630                 return send_rll_simple(RSL_MT_REL_IND, &dl->mctx);
1631         }
1632
1633         /* Flush send-queue */
1634         /* Clear send-buffer */
1635         lapdm_dl_flush_send(dl);
1636
1637         /* Discard partly received L3 message */
1638         if (dl->rcv_buffer) {
1639                 msgb_free(dl->rcv_buffer);
1640                 dl->rcv_buffer = NULL;
1641         }
1642
1643         /* Remove RLL header from msgb */
1644         msgb_pull_l2h(msg);
1645
1646         /* Push LAPDm header on msgb */
1647         msg->l2h = msgb_push(msg, 3);
1648         msg->l2h[0] = LAPDm_ADDR(LAPDm_LPD_NORMAL, sapi, CR_MS2BS_CMD);
1649         msg->l2h[1] = LAPDm_CTRL_U(LAPDm_U_SABM, 1);
1650         msg->l2h[2] = LAPDm_LEN(length);
1651         /* Transmit-buffer carries exactly one segment */
1652         memcpy(dl->tx_hist[0], msg->l2h, 3 + length);
1653         dl->tx_length[0] = 3 + length;
1654         /* set Vs to 0, because it is used as index when resending SABM */
1655         dl->V_send = 0;
1656
1657         /* Set states */
1658         dl->own_busy = dl->peer_busy = 0;
1659         dl->retrans_ctr = 0;
1660         lapdm_dl_newstate(dl, LAPDm_STATE_SABM_SENT);
1661
1662         /* Tramsmit and start T200 */
1663         osmo_timer_schedule(&dl->t200, T200);
1664         return tx_ph_data_enqueue(dl, msg, chan_nr, link_id, n201);
1665 }
1666
1667 /* L3 requests transfer of unnumbered information */
1668 static int rslms_rx_rll_udata_req(struct msgb *msg, struct lapdm_datalink *dl)
1669 {
1670         struct abis_rsl_rll_hdr *rllh = msgb_l2(msg);
1671         uint8_t chan_nr = rllh->chan_nr;
1672         uint8_t link_id = rllh->link_id;
1673         uint8_t sapi = link_id & 7;
1674         struct tlv_parsed tv;
1675         int length;
1676         uint8_t n201 = 23; //FIXME
1677         uint8_t ta = 0, tx_power = 0;
1678
1679         /* check if the layer3 message length exceeds N201 */
1680
1681         rsl_tlv_parse(&tv, rllh->data, msgb_l2len(msg)-sizeof(*rllh));
1682
1683         if (TLVP_PRESENT(&tv, RSL_IE_TIMING_ADVANCE)) {
1684                 ta = *TLVP_VAL(&tv, RSL_IE_TIMING_ADVANCE);
1685         }
1686         if (TLVP_PRESENT(&tv, RSL_IE_MS_POWER)) {
1687                 tx_power = *TLVP_VAL(&tv, RSL_IE_MS_POWER);
1688         }
1689         if (!TLVP_PRESENT(&tv, RSL_IE_L3_INFO)) {
1690                 LOGP(DLAPDM, LOGL_ERROR, "unit data request without message "
1691                         "error\n");
1692                 msgb_free(msg);
1693                 return -EINVAL;
1694         }
1695         length = TLVP_LEN(&tv, RSL_IE_L3_INFO);
1696         /* check if the layer3 message length exceeds N201 */
1697         if (length + 5 > 23) { /* FIXME: do we know the channel N201? */
1698                 LOGP(DLAPDM, LOGL_ERROR, "frame too large: %d > N201(%d) "
1699                         "(discarding)\n", length + 5, 23);
1700                 msgb_free(msg);
1701                 return -EIO;
1702         }
1703
1704         LOGP(DLAPDM, LOGL_INFO, "sending unit data (tx_power=%d, ta=%d)\n",
1705                 tx_power, ta);
1706
1707         /* Remove RLL header from msgb */
1708         msgb_pull_l2h(msg);
1709
1710         /* Push L1 + LAPDm header on msgb */
1711         msg->l2h = msgb_push(msg, 2 + 3);
1712         msg->l2h[0] = tx_power;
1713         msg->l2h[1] = ta;
1714         msg->l2h[2] = LAPDm_ADDR(LAPDm_LPD_NORMAL, sapi, CR_MS2BS_CMD);
1715         msg->l2h[3] = LAPDm_CTRL_U(LAPDm_U_UI, 0);
1716         msg->l2h[4] = LAPDm_LEN(length);
1717         // FIXME: short L2 header support
1718
1719         /* Tramsmit */
1720         return tx_ph_data_enqueue(dl, msg, chan_nr, link_id, n201);
1721 }
1722
1723 /* L3 requests transfer of acknowledged information */
1724 static int rslms_rx_rll_data_req(struct msgb *msg, struct lapdm_datalink *dl)
1725 {
1726         struct abis_rsl_rll_hdr *rllh = msgb_l2(msg);
1727         struct tlv_parsed tv;
1728
1729         rsl_tlv_parse(&tv, rllh->data, msgb_l2len(msg)-sizeof(*rllh));
1730         if (!TLVP_PRESENT(&tv, RSL_IE_L3_INFO)) {
1731                 LOGP(DLAPDM, LOGL_ERROR, "data request without message "
1732                         "error\n");
1733                 msgb_free(msg);
1734                 return -EINVAL;
1735         }
1736
1737         LOGP(DLAPDM, LOGL_INFO, "writing message to send-queue\n");
1738
1739         /* Remove the RSL/RLL header */
1740         msgb_pull_l2h(msg);
1741
1742         /* Write data into the send queue */
1743         msgb_enqueue(&dl->send_queue, msg);
1744
1745         /* Send message, if possible */
1746         rslms_send_i(&dl->mctx, __LINE__);
1747         return 0;
1748 }
1749
1750 /* Send next I frame from queued/buffered data */
1751 static int rslms_send_i(struct lapdm_msg_ctx *mctx, int line)
1752 {
1753         struct lapdm_datalink *dl = mctx->dl;
1754         uint8_t chan_nr = mctx->chan_nr;
1755         uint8_t link_id = mctx->link_id;
1756         uint8_t sapi = link_id & 7;
1757         int k = k_sapi[sapi];
1758         struct msgb *msg;
1759         int length, left;
1760         int rc = - 1; /* we sent nothing */
1761
1762         LOGP(DLAPDM, LOGL_INFO, "%s() called from line %d\n", __func__, line);
1763
1764         next_frame:
1765
1766         if (dl->peer_busy) {
1767                 LOGP(DLAPDM, LOGL_INFO, "peer busy, not sending\n");
1768                 return rc;
1769         }
1770
1771         if (dl->state == LAPDm_STATE_TIMER_RECOV) {
1772                 LOGP(DLAPDM, LOGL_INFO, "timer recovery, not sending\n");
1773                 return rc;
1774         }
1775
1776         /* If the send state variable V(S) is equal to V(A) plus k
1777          * (where k is the maximum number of outstanding I frames - see
1778          * subclause 5.8.4), the data link layer entity shall not transmit any
1779          * new I frames, but shall retransmit an I frame as a result
1780          * of the error recovery procedures as described in subclauses 5.5.4 and
1781          * 5.5.7. */
1782         if (dl->V_send == add_mod8(dl->V_ack, k)) {
1783                 LOGP(DLAPDM, LOGL_INFO, "k frames outstanding, not sending "
1784                         "more (k=%u V(S)=%u V(A)=%u)\n", k, dl->V_send,
1785                         dl->V_ack);
1786                 return rc;
1787         }
1788
1789         /* if we have no tx_hist yet, we create it */
1790         if (!dl->tx_length[dl->V_send]) {
1791                 /* Get next message into send-buffer, if any */
1792                 if (!dl->send_buffer) {
1793                         next_message:
1794                         dl->send_out = 0;
1795                         dl->send_buffer = msgb_dequeue(&dl->send_queue);
1796                         /* No more data to be sent */
1797                         if (!dl->send_buffer)
1798                                 return rc;
1799                         LOGP(DLAPDM, LOGL_INFO, "get message from "
1800                                 "send-queue\n");
1801                 }
1802
1803                 /* How much is left in the send-buffer? */
1804                 left = msgb_l3len(dl->send_buffer) - dl->send_out;
1805                 /* Segment, if data exceeds N201 */
1806                 length = left;
1807                 if (length > mctx->n201 - 3)
1808                         length = mctx->n201 - 3;
1809                 LOGP(DLAPDM, LOGL_INFO, "msg-len %d sent %d left %d N201 %d "
1810                         "length %d first byte %02x\n",
1811                         msgb_l3len(dl->send_buffer), dl->send_out, left,
1812                         mctx->n201, length, dl->send_buffer->l3h[0]);
1813                 /* If message in send-buffer is completely sent */
1814                 if (left == 0) {
1815                         msgb_free(dl->send_buffer);
1816                         dl->send_buffer = NULL;
1817                         goto next_message;
1818                 }
1819
1820                 LOGP(DLAPDM, LOGL_INFO, "send I frame %sV(S)=%d\n",
1821                         (left > length) ? "segment " : "", dl->V_send);
1822
1823                 /* Create I frame (segment) and transmit-buffer content */
1824                 msg = msgb_alloc_headroom(23+10, 10, "LAPDm I");
1825                 msg->l2h = msgb_put(msg, 3 + length);
1826                 msg->l2h[0] = LAPDm_ADDR(LAPDm_LPD_NORMAL, sapi, CR_MS2BS_CMD);
1827                 msg->l2h[1] = LAPDm_CTRL_I(dl->V_recv, dl->V_send, 0);
1828                 msg->l2h[2] = LAPDm_LEN(length);
1829                 if (left > length)
1830                         msg->l2h[2] |= LAPDm_MORE;
1831                 memcpy(msg->l2h + 3, dl->send_buffer->l3h + dl->send_out,
1832                         length);
1833                 memcpy(dl->tx_hist[dl->V_send], msg->l2h, 3 + length);
1834                 dl->tx_length[dl->V_send] = 3 + length;
1835                 /* Add length to track how much is already in the tx buffer */
1836                 dl->send_out += length;
1837         } else {
1838                 LOGP(DLAPDM, LOGL_INFO, "resend I frame from tx buffer "
1839                         "V(S)=%d\n", dl->V_send);
1840
1841                 /* Create I frame (segment) from tx_hist */
1842                 length = dl->tx_length[dl->V_send];
1843                 msg = msgb_alloc_headroom(23+10, 10, "LAPDm I");
1844                 msg->l2h = msgb_put(msg, length);
1845                 memcpy(msg->l2h, dl->tx_hist[dl->V_send], length);
1846                 msg->l2h[1] = LAPDm_CTRL_I(dl->V_recv, dl->V_send, 0);
1847         }
1848
1849         /* The value of the send state variable V(S) shall be incremented by 1
1850          * at the end of the transmission of the I frame */
1851         dl->V_send = inc_mod8(dl->V_send);
1852
1853         /* If timer T200 is not running at the time right before transmitting a
1854          * frame, when the PH-READY-TO-SEND primitive is received from the
1855          * physical layer., it shall be set. */
1856         if (!osmo_timer_pending(&dl->t200))
1857                 osmo_timer_schedule(&dl->t200, T200);
1858
1859         tx_ph_data_enqueue(dl, msg, chan_nr, link_id, mctx->n201);
1860
1861         rc = 0; /* we sent something */
1862         goto next_frame;
1863 }
1864
1865 /* L3 requests suspension of data link */
1866 static int rslms_rx_rll_susp_req(struct msgb *msg, struct lapdm_datalink *dl)
1867 {
1868         struct abis_rsl_rll_hdr *rllh = msgb_l2(msg);
1869         uint8_t sapi = rllh->link_id & 7;
1870
1871         if (sapi != 0) {
1872                 LOGP(DLAPDM, LOGL_ERROR, "SAPI != 0 while suspending\n");
1873                 msgb_free(msg);
1874                 return -EINVAL;
1875         }
1876
1877         LOGP(DLAPDM, LOGL_INFO, "perform suspension\n");
1878
1879         /* put back the send-buffer to the send-queue (first position) */
1880         if (dl->send_buffer) {
1881                 LOGP(DLAPDM, LOGL_INFO, "put frame in sendbuffer back to "
1882                         "queue\n");
1883                 llist_add(&dl->send_buffer->list, &dl->send_queue);
1884                 dl->send_buffer = NULL;
1885         } else
1886                 LOGP(DLAPDM, LOGL_INFO, "no frame in sendbuffer\n");
1887
1888         /* Clear transmit buffer, but keep send buffer */
1889         lapdm_dl_flush_tx(dl);
1890
1891         msgb_free(msg);
1892
1893         return send_rll_simple(RSL_MT_SUSP_CONF, &dl->mctx);
1894 }
1895
1896 /* L3 requests resume of data link */
1897 static int rslms_rx_rll_res_req(struct msgb *msg, struct lapdm_datalink *dl)
1898 {
1899         struct abis_rsl_rll_hdr *rllh = msgb_l2(msg);
1900         uint8_t chan_nr = rllh->chan_nr;
1901         uint8_t link_id = rllh->link_id;
1902         uint8_t sapi = rllh->link_id & 7;
1903         struct tlv_parsed tv;
1904         uint8_t length;
1905         uint8_t n201 = 23; //FIXME
1906
1907         /* Set chan_nr and link_id for established connection */
1908         memset(&dl->mctx, 0, sizeof(dl->mctx));
1909         dl->mctx.dl = dl;
1910         dl->mctx.n201 = n201;
1911         dl->mctx.chan_nr = chan_nr;
1912         dl->mctx.link_id = link_id;
1913
1914         rsl_tlv_parse(&tv, rllh->data, msgb_l2len(msg)-sizeof(*rllh));
1915         if (!TLVP_PRESENT(&tv, RSL_IE_L3_INFO)) {
1916                 LOGP(DLAPDM, LOGL_ERROR, "resume without message error\n");
1917                 msgb_free(msg);
1918                 return send_rll_simple(RSL_MT_REL_IND, &dl->mctx);
1919         }
1920         length = TLVP_LEN(&tv, RSL_IE_L3_INFO);
1921
1922         LOGP(DLAPDM, LOGL_INFO, "perform re-establishment (SABM) length=%d\n",
1923                 length);
1924
1925         /* Replace message in the send-buffer (reconnect) */
1926         if (dl->send_buffer)
1927                 msgb_free(dl->send_buffer);
1928         dl->send_out = 0;
1929         if (length) {
1930                 /* Remove the RSL/RLL header */
1931                 msgb_pull_l2h(msg);
1932                 /* Write data into the send buffer, to be sent first */
1933                 dl->send_buffer = msg;
1934         }
1935
1936         /* Discard partly received L3 message */
1937         if (dl->rcv_buffer) {
1938                 msgb_free(dl->rcv_buffer);
1939                 dl->rcv_buffer = NULL;
1940         }
1941
1942         /* Create new msgb (old one is now free) */
1943         msg = msgb_alloc_headroom(23+10, 10, "LAPDm SABM");
1944         msg->l2h = msgb_put(msg, 3);
1945         msg->l2h[0] = LAPDm_ADDR(LAPDm_LPD_NORMAL, sapi, CR_MS2BS_CMD);
1946         msg->l2h[1] = LAPDm_CTRL_U(LAPDm_U_SABM, 1);
1947         msg->l2h[2] = LAPDm_LEN(0);
1948         /* Transmit-buffer carries exactly one segment */
1949         memcpy(dl->tx_hist[0], msg->l2h, 3);
1950         dl->tx_length[0] = 3;
1951         /* set Vs to 0, because it is used as index when resending SABM */
1952         dl->V_send = 0;
1953
1954         /* Set states */
1955         dl->own_busy = dl->peer_busy = 0;
1956         dl->retrans_ctr = 0;
1957         lapdm_dl_newstate(dl, LAPDm_STATE_SABM_SENT);
1958
1959         /* Tramsmit and start T200 */
1960         osmo_timer_schedule(&dl->t200, T200);
1961         return tx_ph_data_enqueue(dl, msg, chan_nr, link_id, n201);
1962 }
1963
1964 /* L3 requests release of data link */
1965 static int rslms_rx_rll_rel_req(struct msgb *msg, struct lapdm_datalink *dl)
1966 {
1967         struct abis_rsl_rll_hdr *rllh = msgb_l2(msg);
1968         uint8_t chan_nr = rllh->chan_nr;
1969         uint8_t link_id = rllh->link_id;
1970         uint8_t sapi = rllh->link_id & 7;
1971         uint8_t mode = 0;
1972
1973         /* get release mode */
1974         if (rllh->data[0] == RSL_IE_RELEASE_MODE)
1975                 mode = rllh->data[1] & 1;
1976
1977         /* local release */
1978         if (mode) {
1979                 LOGP(DLAPDM, LOGL_INFO, "perform local release\n");
1980                 msgb_free(msg);
1981                 /* reset Timer T200 */
1982                 osmo_timer_del(&dl->t200);
1983                 /* enter idle state */
1984                 lapdm_dl_newstate(dl, LAPDm_STATE_IDLE);
1985                 /* flush buffers */
1986                 lapdm_dl_flush_tx(dl);
1987                 lapdm_dl_flush_send(dl);
1988                 /* send notification to L3 */
1989                 return send_rll_simple(RSL_MT_REL_CONF, &dl->mctx);
1990         }
1991
1992         /* in case we are already disconnecting */
1993         if (dl->state == LAPDm_STATE_DISC_SENT)
1994                 return -EBUSY;
1995
1996         LOGP(DLAPDM, LOGL_INFO, "perform normal release (DISC)\n");
1997
1998         /* Pull rllh */
1999         msgb_pull(msg, msg->tail - msg->l2h);
2000
2001         /* Push LAPDm header on msgb */
2002         msg->l2h = msgb_push(msg, 3);
2003         msg->l2h[0] = LAPDm_ADDR(LAPDm_LPD_NORMAL, sapi, CR_MS2BS_CMD);
2004         msg->l2h[1] = LAPDm_CTRL_U(LAPDm_U_DISC, 1);
2005         msg->l2h[2] = LAPDm_LEN(0);
2006         /* Transmit-buffer carries exactly one segment */
2007         memcpy(dl->tx_hist[0], msg->l2h, 3);
2008         dl->tx_length[0] = 3;
2009
2010         /* Set states */
2011         dl->own_busy = dl->peer_busy = 0;
2012         dl->retrans_ctr = 0;
2013         lapdm_dl_newstate(dl, LAPDm_STATE_DISC_SENT);
2014
2015         /* Tramsmit and start T200 */
2016         osmo_timer_schedule(&dl->t200, T200);
2017         return tx_ph_data_enqueue(dl, msg, chan_nr, link_id, dl->mctx.n201);
2018 }
2019
2020 /* L3 requests release in idle state */
2021 static int rslms_rx_rll_rel_req_idle(struct msgb *msg, struct lapdm_datalink *dl)
2022 {
2023         msgb_free(msg);
2024
2025         /* send notification to L3 */
2026         return send_rll_simple(RSL_MT_REL_CONF, &dl->mctx);
2027 }
2028
2029 /* L3 requests channel in idle state */
2030 static int rslms_rx_chan_rqd(struct osmocom_ms *ms, struct msgb *msg)
2031 {
2032         struct abis_rsl_cchan_hdr *cch = msgb_l2(msg);
2033         int rc;
2034
2035         if (msgb_l2len(msg) < sizeof(*cch) + 4 + 2 + 2) {
2036                 LOGP(DRSL, LOGL_ERROR, "Message too short for CHAN RQD!\n");
2037                 return -EINVAL;
2038         }
2039         if (cch->data[0] != RSL_IE_REQ_REFERENCE) {
2040                 LOGP(DRSL, LOGL_ERROR, "Missing REQ REFERENCE IE\n");
2041                 return -EINVAL;
2042         }
2043         if (cch->data[4] != RSL_IE_ACCESS_DELAY) {
2044                 LOGP(DRSL, LOGL_ERROR, "Missing ACCESS_DELAY IE\n");
2045                 return -EINVAL;
2046         }
2047         if (cch->data[6] != RSL_IE_MS_POWER) {
2048                 LOGP(DRSL, LOGL_ERROR, "Missing MS POWER IE\n");
2049                 return -EINVAL;
2050         }
2051
2052         /* TA = 0 - delay */
2053         rc = l1ctl_tx_param_req(ms, 0 - cch->data[5], cch->data[7]);
2054
2055         rc = l1ctl_tx_rach_req(ms, cch->data[1],
2056                 ((cch->data[2] & 0x7f) << 8) | cch->data[3], cch->data[2] >> 7);
2057
2058         msgb_free(msg);
2059
2060         return rc;
2061 }
2062
2063 /* L1 confirms channel request */
2064 int l2_ph_chan_conf(struct msgb *msg, struct osmocom_ms *ms,
2065                         struct l1ctl_info_dl *dl)
2066 {
2067         struct abis_rsl_cchan_hdr *ch;
2068         struct gsm_time tm;
2069         struct gsm48_req_ref *ref;
2070
2071         gsm_fn2gsmtime(&tm, htonl(dl->frame_nr));
2072
2073         msgb_pull_l2h(msg);
2074         msg->l2h = msgb_push(msg, sizeof(*ch) + sizeof(*ref));
2075         ch = (struct abis_rsl_cchan_hdr *)msg->l2h;
2076         rsl_init_cchan_hdr(ch, RSL_MT_CHAN_CONF);
2077         ch->chan_nr = RSL_CHAN_RACH;
2078         ch->data[0] = RSL_IE_REQ_REFERENCE;
2079         ref = (struct gsm48_req_ref *) (ch->data + 1);
2080         ref->t1 = tm.t1;
2081         ref->t2 = tm.t2;
2082         ref->t3_low = tm.t3 & 0x7;
2083         ref->t3_high = tm.t3 >> 3;
2084
2085         return rslms_sendmsg(msg, ms);
2086 }
2087
2088 /* Names for Radio Link Layer Management */
2089 static const struct value_string rsl_msg_names[] = {
2090         { RSL_MT_DATA_REQ,              "RSL_MT_DATA_REQ" },
2091         { RSL_MT_DATA_IND,              "RSL_MT_DATA_IND" },
2092         { RSL_MT_ERROR_IND,             "RSL_MT_ERROR_IND" },
2093         { RSL_MT_EST_REQ,               "RSL_MT_EST_REQ" },
2094         { RSL_MT_EST_CONF,              "RSL_MT_EST_CONF" },
2095         { RSL_MT_EST_IND,               "RSL_MT_EST_IND" },
2096         { RSL_MT_EST_IND,               "RSL_MT_REL_REQ" },
2097         { RSL_MT_REL_REQ,               "RSL_MT_REL_REQ" },
2098         { RSL_MT_REL_CONF,              "RSL_MT_REL_CONF" },
2099         { RSL_MT_REL_IND,               "RSL_MT_REL_IND" },
2100         { RSL_MT_UNIT_DATA_REQ,         "RSL_MT_UNIT_DATA_REQ" },
2101         { RSL_MT_UNIT_DATA_IND,         "RSL_MT_UNIT_DATA_IND" },
2102         { RSL_MT_SUSP_REQ,              "RSL_MT_SUSP_REQ" },
2103         { RSL_MT_SUSP_CONF,             "RSL_MT_SUSP_CONF" },
2104         { RSL_MT_RES_REQ,               "RSL_MT_RES_REQ" },
2105         { RSL_MT_RECON_REQ,             "RSL_MT_RECON_REQ" },
2106         { RSL_MT_CHAN_RQD,              "RSL_MT_CHAN_RQD" },
2107         { RSL_MT_CHAN_CONF,             "RSL_MT_CHAN_CONF" },
2108         { 0,                            NULL }
2109 };
2110
2111 const char *get_rsl_name(int value)
2112 {
2113         return get_value_string(rsl_msg_names, value);
2114 }
2115
2116 const char *lapdm_state_names[] = {
2117         "LAPDm_STATE_NULL",
2118         "LAPDm_STATE_IDLE",
2119         "LAPDm_STATE_SABM_SENT",
2120         "LAPDm_STATE_MF_EST",
2121         "LAPDm_STATE_TIMER_RECOV",
2122         "LAPDm_STATE_DISC_SENT",
2123 };
2124
2125 /* statefull handling for RSLms RLL messages from L3 */
2126 static struct l2downstate {
2127         uint32_t        states;
2128         int             type;
2129         int             (*rout) (struct msgb *msg, struct lapdm_datalink *dl);
2130 } l2downstatelist[] = {
2131         /* create and send UI command */
2132         {ALL_STATES,
2133          RSL_MT_UNIT_DATA_REQ, rslms_rx_rll_udata_req},
2134
2135         /* create and send SABM command */
2136         {SBIT(LAPDm_STATE_IDLE),
2137          RSL_MT_EST_REQ, rslms_rx_rll_est_req},
2138
2139         /* create and send I command */
2140         {SBIT(LAPDm_STATE_MF_EST) |
2141          SBIT(LAPDm_STATE_TIMER_RECOV),
2142          RSL_MT_DATA_REQ, rslms_rx_rll_data_req},
2143
2144         /* suspend datalink */
2145         {SBIT(LAPDm_STATE_MF_EST) |
2146          SBIT(LAPDm_STATE_TIMER_RECOV),
2147          RSL_MT_SUSP_REQ, rslms_rx_rll_susp_req},
2148
2149         /* create and send SABM command (resume) */
2150         {SBIT(LAPDm_STATE_MF_EST) |
2151          SBIT(LAPDm_STATE_TIMER_RECOV),
2152          RSL_MT_RES_REQ, rslms_rx_rll_res_req},
2153
2154         /* create and send SABM command (reconnect) */
2155         {SBIT(LAPDm_STATE_IDLE) |
2156          SBIT(LAPDm_STATE_MF_EST) |
2157          SBIT(LAPDm_STATE_TIMER_RECOV),
2158          RSL_MT_RECON_REQ, rslms_rx_rll_res_req},
2159
2160         /* create and send DISC command */
2161         {SBIT(LAPDm_STATE_SABM_SENT) |
2162          SBIT(LAPDm_STATE_MF_EST) |
2163          SBIT(LAPDm_STATE_TIMER_RECOV) |
2164          SBIT(LAPDm_STATE_DISC_SENT),
2165          RSL_MT_REL_REQ, rslms_rx_rll_rel_req},
2166
2167         /* release in idle state */
2168         {SBIT(LAPDm_STATE_IDLE),
2169          RSL_MT_REL_REQ, rslms_rx_rll_rel_req_idle},
2170 };
2171
2172 #define L2DOWNSLLEN \
2173         (sizeof(l2downstatelist) / sizeof(struct l2downstate))
2174
2175 /* incoming RSLms RLL message from L3 */
2176 static int rslms_rx_rll(struct msgb *msg, struct osmocom_ms *ms)
2177 {
2178         struct abis_rsl_rll_hdr *rllh = msgb_l2(msg);
2179         int msg_type = rllh->c.msg_type;
2180         uint8_t sapi = rllh->link_id & 7;
2181         struct lapdm_entity *le;
2182         struct lapdm_datalink *dl;
2183         int i, supported = 0;
2184         int rc = 0;
2185
2186         if (msgb_l2len(msg) < sizeof(*rllh)) {
2187                 LOGP(DRSL, LOGL_ERROR, "Message too short for RLL hdr!\n");
2188                 return -EINVAL;
2189         }
2190
2191         if (rllh->link_id & 0x40)
2192                 le = &ms->l2_entity.lapdm_acch;
2193         else
2194                 le = &ms->l2_entity.lapdm_dcch;
2195
2196         /* G.2.1 No action schall be taken on frames containing an unallocated
2197          * SAPI.
2198          */
2199         dl = datalink_for_sapi(le, sapi);
2200         if (!dl) {
2201                 LOGP(DRSL, LOGL_ERROR, "No instance for SAPI %d!\n", sapi);
2202                 return -EINVAL;
2203         }
2204
2205         LOGP(DRSL, LOGL_INFO, "(ms %s) RLL Message '%s' received in state %s\n",
2206                 ms->name, get_rsl_name(msg_type), lapdm_state_names[dl->state]);
2207
2208         /* find function for current state and message */
2209         for (i = 0; i < L2DOWNSLLEN; i++) {
2210                 if (msg_type == l2downstatelist[i].type)
2211                         supported = 1;
2212                 if ((msg_type == l2downstatelist[i].type)
2213                  && ((1 << dl->state) & l2downstatelist[i].states))
2214                         break;
2215         }
2216         if (!supported) {
2217                 LOGP(DRSL, LOGL_NOTICE, "Message unsupported.\n");
2218                 msgb_free(msg);
2219                 return 0;
2220         }
2221         if (i == L2DOWNSLLEN) {
2222                 LOGP(DRSL, LOGL_NOTICE, "Message unhandled at this state.\n");
2223                 msgb_free(msg);
2224                 return 0;
2225         }
2226
2227         rc = l2downstatelist[i].rout(msg, dl);
2228
2229         return rc;
2230 }
2231
2232 /* incoming RSLms COMMON CHANNEL message from L3 */
2233 static int rslms_rx_com_chan(struct msgb *msg, struct osmocom_ms *ms)
2234 {
2235         struct abis_rsl_cchan_hdr *cch = msgb_l2(msg);
2236         int msg_type = cch->c.msg_type;
2237         int rc = 0;
2238
2239         if (msgb_l2len(msg) < sizeof(*cch)) {
2240                 LOGP(DRSL, LOGL_ERROR, "Message too short for COM CHAN hdr!\n");
2241                 return -EINVAL;
2242         }
2243
2244         switch (msg_type) {
2245         case RSL_MT_CHAN_RQD:
2246                 /* create and send RACH request */
2247                 rc = rslms_rx_chan_rqd(ms, msg);
2248                 break;
2249         default:
2250                 LOGP(DRSL, LOGL_NOTICE, "Unknown COMMON CHANNEL msg %d!\n",
2251                         msg_type);
2252                 msgb_free(msg);
2253                 return 0;
2254         }
2255
2256         return rc;
2257 }
2258
2259 /* input into layer2 (from layer 3) */
2260 int rslms_recvmsg(struct msgb *msg, struct osmocom_ms *ms)
2261 {
2262         struct abis_rsl_common_hdr *rslh = msgb_l2(msg);
2263         int rc = 0;
2264
2265         if (msgb_l2len(msg) < sizeof(*rslh)) {
2266                 LOGP(DRSL, LOGL_ERROR, "Message too short RSL hdr!\n");
2267                 return -EINVAL;
2268         }
2269
2270         switch (rslh->msg_discr & 0xfe) {
2271         case ABIS_RSL_MDISC_RLL:
2272                 rc = rslms_rx_rll(msg, ms);
2273                 break;
2274         case ABIS_RSL_MDISC_COM_CHAN:
2275                 rc = rslms_rx_com_chan(msg, ms);
2276                 break;
2277         default:
2278                 LOGP(DRSL, LOGL_ERROR, "unknown RSLms message "
2279                         "discriminator 0x%02x", rslh->msg_discr);
2280                 msgb_free(msg);
2281                 return -EINVAL;
2282         }
2283
2284         return rc;
2285 }
2286
2287 /* input function that L2 calls when sending messages up to L3 */
2288 int rslms_sendmsg(struct msgb *msg, struct osmocom_ms *ms)
2289 {
2290         if (!ms->l2_entity.msg_handler) {
2291                 msgb_free(msg);
2292                 return -EIO;
2293         }
2294
2295         /* call the layer2 message handler that is registered */
2296         return ms->l2_entity.msg_handler(msg, ms);
2297 }
2298
2299 /* register message handler for messages that are sent from L2->L3 */
2300 int osmol2_register_handler(struct osmocom_ms *ms, osmol2_cb_t cb)
2301 {
2302         ms->l2_entity.msg_handler = cb;
2303
2304         return 0;
2305 }