aboutsummaryrefslogtreecommitdiffstats
path: root/src/gsm/lapdm.c
blob: 1c08113ebd5d244abf62c1c9413ada27d67a439e (plain)
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
208
209
210
211
212
213
214
215
216
217
218
219
220
221
222
223
224
225
226
227
228
229
230
231
232
233
234
235
236
237
238
239
240
241
242
243
244
245
246
247
248
249
250
251
252
253
254
255
256
257
258
259
260
261
262
263
264
265
266
267
268
269
270
271
272
273
274
275
276
277
278
279
280
281
282
283
284
285
286
287
288
289
290
291
292
293
294
295
296
297
298
299
300
301
302
303
304
305
306
307
308
309
310
311
312
313
314
315
316
317
318
319
320
321
322
323
324
325
326
327
328
329
330
331
332
333
334
335
336
337
338
339
340
341
342
343
344
345
346
347
348
349
350
351
352
353
354
355
356
357
358
359
360
361
362
363
364
365
366
367
368
369
370
371
372
373
374
375
376
377
378
379
380
381
382
383
384
385
386
387
388
389
390
391
392
393
394
395
396
397
398
399
400
401
402
403
404
405
406
407
408
409
410
411
412
413
414
415
416
417
418
419
420
421
422
423
424
425
426
427
428
429
430
431
432
433
434
435
436
437
438
439
440
441
442
443
444
445
446
447
448
449
450
451
452
453
454
455
456
457
458
459
460
461
462
463
464
465
466
467
468
469
470
471
472
473
474
475
476
477
478
479
480
481
482
483
484
485
486
487
488
489
490
491
492
493
494
495
496
497
498
499
500
501
502
503
504
505
506
507
508
509
510
511
512
513
514
515
516
517
518
519
520
521
522
523
524
525
526
527
528
529
530
531
532
533
534
535
536
537
538
539
540
541
542
543
544
545
546
547
548
549
550
551
552
553
554
555
556
557
558
559
560
561
562
563
564
565
566
567
568
569
570
571
572
573
574
575
576
577
578
579
580
581
582
583
584
585
586
587
588
589
590
591
592
593
594
595
596
597
598
599
600
601
602
603
604
605
606
607
608
609
610
611
612
613
614
615
616
617
618
619
620
621
622
623
624
625
626
627
628
629
630
631
632
633
634
635
636
637
638
639
640
641
642
643
644
645
646
647
648
649
650
651
652
653
654
655
656
657
658
659
660
661
662
663
664
665
666
667
668
669
670
671
672
673
674
675
676
677
678
679
680
681
682
683
684
685
686
687
688
689
690
691
692
693
694
695
696
697
698
699
700
701
702
703
704
705
706
707
708
709
710
711
712
713
714
715
716
717
718
719
720
721
722
723
724
725
726
727
728
729
730
731
732
733
734
735
736
737
738
739
740
741
742
743
744
745
746
747
748
749
750
751
752
753
754
755
756
757
758
759
760
761
762
763
764
765
766
767
768
769
770
771
772
773
774
775
776
777
778
779
780
781
782
783
784
785
786
787
788
789
790
791
792
793
794
795
796
797
798
799
800
801
802
803
804
805
806
807
808
809
810
811
812
813
814
815
816
817
818
819
820
821
822
823
824
825
826
827
828
829
830
831
832
833
834
835
836
837
838
839
840
841
842
843
844
845
846
847
848
849
850
851
852
853
854
855
856
857
858
859
860
861
862
863
864
865
866
867
868
869
870
871
872
873
874
875
876
877
878
879
880
881
882
883
884
885
886
887
888
889
890
891
892
893
894
895
896
897
898
899
900
901
902
903
904
905
906
907
908
909
910
911
912
913
914
915
916
917
918
919
920
921
922
923
924
925
926
927
928
929
930
931
932
933
934
935
936
937
938
939
940
941
942
943
944
945
946
947
948
949
950
951
952
953
954
955
956
957
958
959
960
961
962
963
964
965
966
967
968
969
970
971
972
973
974
975
976
977
978
979
980
981
982
983
984
985
986
987
988
989
990
991
992
993
994
995
996
997
998
999
1000
1001
1002
1003
1004
1005
1006
1007
1008
1009
1010
1011
1012
1013
1014
1015
1016
1017
1018
1019
1020
1021
1022
1023
1024
1025
1026
1027
1028
1029
1030
1031
1032
1033
1034
1035
1036
1037
1038
1039
1040
1041
1042
1043
1044
1045
1046
1047
1048
1049
1050
1051
1052
1053
1054
1055
1056
1057
1058
1059
1060
1061
1062
1063
1064
1065
1066
1067
1068
1069
1070
1071
1072
1073
1074
1075
1076
1077
1078
1079
1080
1081
1082
1083
1084
1085
1086
1087
1088
1089
1090
1091
1092
1093
1094
1095
1096
1097
1098
1099
1100
1101
1102
1103
1104
1105
1106
1107
1108
1109
1110
1111
1112
1113
1114
1115
1116
1117
1118
1119
1120
1121
1122
1123
1124
1125
1126
1127
1128
1129
1130
1131
1132
1133
1134
1135
1136
1137
1138
1139
1140
1141
1142
1143
1144
1145
1146
1147
1148
1149
1150
1151
1152
1153
1154
1155
1156
1157
1158
1159
1160
1161
1162
1163
1164
1165
1166
1167
1168
1169
1170
1171
1172
1173
1174
1175
1176
1177
1178
1179
1180
1181
1182
1183
1184
1185
1186
1187
1188
1189
1190
1191
1192
1193
1194
1195
1196
1197
1198
1199
1200
1201
1202
1203
1204
1205
1206
1207
1208
1209
1210
1211
1212
1213
1214
1215
1216
1217
1218
1219
1220
1221
1222
1223
1224
1225
1226
1227
1228
1229
1230
1231
1232
1233
1234
1235
1236
1237
1238
1239
1240
1241
1242
1243
1244
1245
1246
1247
1248
1249
/* GSM LAPDm (TS 04.06) implementation */

/* (C) 2010-2011 by Harald Welte <laforge@gnumonks.org>
 * (C) 2010-2011 by Andreas Eversberg <jolly@eversberg.eu>
 *
 * All Rights Reserved
 *
 * This program is free software; you can redistribute it and/or modify
 * it under the terms of the GNU General Public License as published by
 * the Free Software Foundation; either version 2 of the License, or
 * (at your option) any later version.
 *
 * This program is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 * GNU General Public License for more details.
 *
 * You should have received a copy of the GNU General Public License along
 * with this program; if not, write to the Free Software Foundation, Inc.,
 * 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA.
 *
 */

/*! \addtogroup lapdm
 *  @{
 */

/*! \file lapdm.c */

#include <stdio.h>
#include <stdint.h>
#include <string.h>
#include <errno.h>
#include <arpa/inet.h>

#include <osmocom/core/logging.h>
#include <osmocom/core/timer.h>
#include <osmocom/core/msgb.h>
#include <osmocom/core/utils.h>

#include <osmocom/gsm/tlv.h>
#include <osmocom/gsm/rsl.h>
#include <osmocom/gsm/prim.h>
#include <osmocom/gsm/gsm_utils.h>
#include <osmocom/gsm/lapdm.h>

#include <osmocom/gsm/protocol/gsm_04_08.h>
#include <osmocom/gsm/protocol/gsm_08_58.h>

/* TS 04.06 Figure 4 / Section 3.2 */
#define LAPDm_LPD_NORMAL  0
#define LAPDm_LPD_SMSCB	  1
#define LAPDm_SAPI_NORMAL 0
#define LAPDm_SAPI_SMS	  3
#define LAPDm_ADDR(lpd, sapi, cr) ((((lpd) & 0x3) << 5) | (((sapi) & 0x7) << 2) | (((cr) & 0x1) << 1) | 0x1)

#define LAPDm_ADDR_LPD(addr) (((addr) >> 5) & 0x3)
#define LAPDm_ADDR_SAPI(addr) (((addr) >> 2) & 0x7)
#define LAPDm_ADDR_CR(addr) (((addr) >> 1) & 0x1)
#define LAPDm_ADDR_EA(addr) ((addr) & 0x1)

/* TS 04.06 Table 3 / Section 3.4.3 */
#define LAPDm_CTRL_I(nr, ns, p)	((((nr) & 0x7) << 5) | (((p) & 0x1) << 4) | (((ns) & 0x7) << 1))
#define LAPDm_CTRL_S(nr, s, p)	((((nr) & 0x7) << 5) | (((p) & 0x1) << 4) | (((s) & 0x3) << 2) | 0x1)
#define LAPDm_CTRL_U(u, p)	((((u) & 0x1c) << (5-2)) | (((p) & 0x1) << 4) | (((u) & 0x3) << 2) | 0x3)

#define LAPDm_CTRL_is_I(ctrl)	(((ctrl) & 0x1) == 0)
#define LAPDm_CTRL_is_S(ctrl)	(((ctrl) & 0x3) == 1)
#define LAPDm_CTRL_is_U(ctrl)	(((ctrl) & 0x3) == 3)

#define LAPDm_CTRL_U_BITS(ctrl)	((((ctrl) & 0xC) >> 2) | ((ctrl) & 0xE0) >> 3)
#define LAPDm_CTRL_PF_BIT(ctrl)	(((ctrl) >> 4) & 0x1)

#define LAPDm_CTRL_S_BITS(ctrl)	(((ctrl) & 0xC) >> 2)

#define LAPDm_CTRL_I_Ns(ctrl)	(((ctrl) & 0xE) >> 1)
#define LAPDm_CTRL_Nr(ctrl)	(((ctrl) & 0xE0) >> 5)

#define LAPDm_LEN(len)	((len << 2) | 0x1)
#define LAPDm_MORE	0x2
#define LAPDm_EL	0x1

#define LAPDm_U_UI	0x0

/* TS 04.06 Section 5.8.3 */
#define N201_AB_SACCH		18
#define N201_AB_SDCCH		20
#define N201_AB_FACCH		20
#define N201_Bbis		23
#define N201_Bter_SACCH		21
#define N201_Bter_SDCCH		23
#define N201_Bter_FACCH		23
#define N201_B4			19

/* 5.8.2.1 N200 during establish and release */
#define N200_EST_REL		5
/* 5.8.2.1 N200 during timer recovery state */
#define N200_TR_SACCH		5
#define N200_TR_SDCCH		23
#define N200_TR_FACCH_FR	34
#define N200_TR_EFACCH_FR	48
#define N200_TR_FACCH_HR	29
/* FIXME: set N200 depending on chan_nr */
#define N200 N200_TR_SDCCH

enum lapdm_format {
	LAPDm_FMT_A,
	LAPDm_FMT_B,
	LAPDm_FMT_Bbis,
	LAPDm_FMT_Bter,
	LAPDm_FMT_B4,
};

static int lapdm_send_ph_data_req(struct lapd_msg_ctx *lctx, struct msgb *msg);
static int send_rslms_dlsap(struct osmo_dlsap_prim *dp,
	struct lapd_msg_ctx *lctx);

static void lapdm_dl_init(struct lapdm_datalink *dl,
			  struct lapdm_entity *entity, int t200)
{
	memset(dl, 0, sizeof(*dl));
	dl->entity = entity;
	lapd_dl_init(&dl->dl, 1, 8, 200);
	dl->dl.reestablish = 0; /* GSM uses no reestablish */
	dl->dl.send_ph_data_req = lapdm_send_ph_data_req;
	dl->dl.send_dlsap = send_rslms_dlsap;
	dl->dl.n200_est_rel = N200_EST_REL;
	dl->dl.n200 = N200;
	dl->dl.t203_sec = 0; dl->dl.t203_usec = 0;
	dl->dl.t200_sec = t200; dl->dl.t200_usec = 0;
}

/*! \brief initialize a LAPDm entity and all datalinks inside
 *  \param[in] le LAPDm entity
 *  \param[in] mode \ref lapdm_mode (BTS/MS)
 */
void lapdm_entity_init(struct lapdm_entity *le, enum lapdm_mode mode, int t200)
{
	unsigned int i;

	for (i = 0; i < ARRAY_SIZE(le->datalink); i++)
		lapdm_dl_init(&le->datalink[i], le, t200);

	lapdm_entity_set_mode(le, mode);
}

/*! \brief initialize a LAPDm channel and all its channels
 *  \param[in] lc \ref lapdm_channel to be initialized
 *  \param[in] mode \ref lapdm_mode (BTS/MS)
 *
 * This really is a convenience wrapper around calling \ref
 * lapdm_entity_init twice.
 */
void lapdm_channel_init(struct lapdm_channel *lc, enum lapdm_mode mode)
{
	lapdm_entity_init(&lc->lapdm_acch, mode, 2);
	/* FIXME: this depends on chan type */
	lapdm_entity_init(&lc->lapdm_dcch, mode, 1);
}

/*! \brief flush and release all resoures in LAPDm entity */
void lapdm_entity_exit(struct lapdm_entity *le)
{
	unsigned int i;
	struct lapdm_datalink *dl;

	for (i = 0; i < ARRAY_SIZE(le->datalink); i++) {
		dl = &le->datalink[i];
		lapd_dl_exit(&dl->dl);
	}
}

/* \brief lfush and release all resources in LAPDm channel
 *
 * A convenience wrapper calling \ref lapdm_entity_exit on both
 * entities inside the \ref lapdm_channel
 */
void lapdm_channel_exit(struct lapdm_channel *lc)
{
	lapdm_entity_exit(&lc->lapdm_acch);
	lapdm_entity_exit(&lc->lapdm_dcch);
}

static struct lapdm_datalink *datalink_for_sapi(struct lapdm_entity *le, uint8_t sapi)
{
	switch (sapi) {
	case LAPDm_SAPI_NORMAL:
		return &le->datalink[0];
	case LAPDm_SAPI_SMS:
		return &le->datalink[1];
	default:
		return NULL;
	}
}

/* remove the L2 header from a MSGB */
static inline unsigned char *msgb_pull_l2h(struct msgb *msg)
{
	unsigned char *ret = msgb_pull(msg, msg->l3h - msg->l2h);
	msg->l2h = NULL;
	return ret;
}

/* Append padding (if required) */
static void lapdm_pad_msgb(struct msgb *msg, uint8_t n201)
{
	int pad_len = n201 - msgb_l2len(msg);
	uint8_t *data;

	if (pad_len < 0) {
		LOGP(DLLAPD, LOGL_ERROR,
		     "cannot pad message that is already too big!\n");
		return;
	}

	data = msgb_put(msg, pad_len);
	memset(data, 0x2B, pad_len);
}

/* input function that L2 calls when sending messages up to L3 */
static int rslms_sendmsg(struct msgb *msg, struct lapdm_entity *le)
{
	if (!le->l3_cb) {
		msgb_free(msg);
		return -EIO;
	}

	/* call the layer2 message handler that is registered */
	return le->l3_cb(msg, le, le->l3_ctx);
}

/* write a frame into the tx queue */
static int tx_ph_data_enqueue(struct lapdm_datalink *dl, struct msgb *msg,
				uint8_t chan_nr, uint8_t link_id, uint8_t pad)
{
	struct lapdm_entity *le = dl->entity;
	struct osmo_phsap_prim pp;

	/* if there is a pending message, queue it */
	if (le->tx_pending || le->flags & LAPDM_ENT_F_POLLING_ONLY) {
		*msgb_push(msg, 1) = pad;
		*msgb_push(msg, 1) = link_id;
		*msgb_push(msg, 1) = chan_nr;
		msgb_enqueue(&dl->dl.tx_queue, msg);
		return -EBUSY;
	}

	osmo_prim_init(&pp.oph, SAP_GSM_PH, PRIM_PH_DATA,
			PRIM_OP_REQUEST, msg);
	pp.u.data.chan_nr = chan_nr;
	pp.u.data.link_id = link_id;

	/* send the frame now */
	le->tx_pending = 0; /* disabled flow control */
	lapdm_pad_msgb(msg, pad);

	return le->l1_prim_cb(&pp.oph, le->l1_ctx);
}

static struct msgb *tx_dequeue_msgb(struct lapdm_entity *le)
{
	struct lapdm_datalink *dl;
	int last = le->last_tx_dequeue;
	int i = last, n = ARRAY_SIZE(le->datalink);
	struct msgb *msg = NULL;

	/* round-robin dequeue */
	do {
		/* next */
		i = (i + 1) % n;
		dl = &le->datalink[i];
		if ((msg = msgb_dequeue(&dl->dl.tx_queue)))
			break;
	} while (i != last);

	if (msg) {
		/* Set last dequeue position */
		le->last_tx_dequeue = i;
	}

	return msg;
}

/*! \brief dequeue a msg that's pending transmission via L1 and wrap it into
 * a osmo_phsap_prim */
int lapdm_phsap_dequeue_prim(struct lapdm_entity *le, struct osmo_phsap_prim *pp)
{
	struct msgb *msg;
	uint8_t pad;

	msg = tx_dequeue_msgb(le);
	if (!msg)
		return -ENODEV;

	/* if we have a message, send PH-DATA.req */
	osmo_prim_init(&pp->oph, SAP_GSM_PH, PRIM_PH_DATA,
			PRIM_OP_REQUEST, msg);

	/* Pull chan_nr and link_id */
	pp->u.data.chan_nr = *msg->data;
	msgb_pull(msg, 1);
	pp->u.data.link_id = *msg->data;
	msgb_pull(msg, 1);
	pad = *msg->data;
	msgb_pull(msg, 1);

	/* Pad the frame, we can transmit now */
	lapdm_pad_msgb(msg, pad);

	return 0;
}

/* get next frame from the tx queue. because the ms has multiple datalinks,
 * each datalink's queue is read round-robin.
 */
static int l2_ph_data_conf(struct msgb *msg, struct lapdm_entity *le)
{
	struct osmo_phsap_prim pp;

	/* we may send again */
	le->tx_pending = 0;

	/* free confirm message */
	if (msg)
		msgb_free(msg);

	if (lapdm_phsap_dequeue_prim(le, &pp) < 0) {
		/* no message in all queues */

		/* If user didn't request PH-EMPTY_FRAME.req, abort */
		if (!(le->flags & LAPDM_ENT_F_EMPTY_FRAME))
			return 0;

		/* otherwise, send PH-EMPTY_FRAME.req */
		osmo_prim_init(&pp.oph, SAP_GSM_PH,
				PRIM_PH_EMPTY_FRAME,
				PRIM_OP_REQUEST, NULL);
	} else {
		le->tx_pending = 1;
	}

	return le->l1_prim_cb(&pp.oph, le->l1_ctx);
}

/* Create RSLms various RSLms messages */
static int send_rslms_rll_l3(uint8_t msg_type, struct lapdm_msg_ctx *mctx,
			     struct msgb *msg)
{
	/* Add the RSL + RLL header */
	rsl_rll_push_l3(msg, msg_type, mctx->chan_nr, mctx->link_id, 1);

	/* send off the RSLms message to L3 */
	return rslms_sendmsg(msg, mctx->dl->entity);
}

/* Take a B4 format message from L1 and create RSLms UNIT DATA IND */
static int send_rslms_rll_l3_ui(struct lapdm_msg_ctx *mctx, struct msgb *msg)
{
	uint8_t l3_len = msg->tail - (uint8_t *)msgb_l3(msg);
	struct abis_rsl_rll_hdr *rllh;

	/* Add the RSL + RLL header */
	msgb_tv16_push(msg, RSL_IE_L3_INFO, l3_len);
	msgb_push(msg, 2 + 2);
	rsl_rll_push_hdr(msg, RSL_MT_UNIT_DATA_IND, mctx->chan_nr,
		mctx->link_id, 1);
	rllh = (struct abis_rsl_rll_hdr *)msgb_l2(msg);

	rllh->data[0] = RSL_IE_TIMING_ADVANCE;
	rllh->data[1] = mctx->ta_ind;

	rllh->data[2] = RSL_IE_MS_POWER;
	rllh->data[3] = mctx->tx_power_ind;
	
	return rslms_sendmsg(msg, mctx->dl->entity);
}

static int send_rll_simple(uint8_t msg_type, struct lapdm_msg_ctx *mctx)
{
	struct msgb *msg;

	msg = rsl_rll_simple(msg_type, mctx->chan_nr, mctx->link_id, 1);

	/* send off the RSLms message to L3 */
	return rslms_sendmsg(msg, mctx->dl->entity);
}

static int rsl_rll_error(uint8_t cause, struct lapdm_msg_ctx *mctx)
{
	struct msgb *msg;

	LOGP(DLLAPD, LOGL_NOTICE, "sending MDL-ERROR-IND %d\n", cause);
	msg = rsl_rll_simple(RSL_MT_ERROR_IND, mctx->chan_nr, mctx->link_id, 1);
	msgb_tlv_put(msg, RSL_IE_RLM_CAUSE, 1, &cause);
	return rslms_sendmsg(msg, mctx->dl->entity);
}

/* DLSAP L2 -> L3 (RSLms) */
static int send_rslms_dlsap(struct osmo_dlsap_prim *dp,
	struct lapd_msg_ctx *lctx)
{
	struct lapd_datalink *dl = lctx->dl;
	struct lapdm_datalink *mdl =
		container_of(dl, struct lapdm_datalink, dl);
	struct lapdm_msg_ctx *mctx = &mdl->mctx;
	uint8_t rll_msg = 0;

	switch (OSMO_PRIM_HDR(&dp->oph)) {
	case OSMO_PRIM(PRIM_DL_EST, PRIM_OP_INDICATION):
		rll_msg = RSL_MT_EST_IND;
		break;
	case OSMO_PRIM(PRIM_DL_EST, PRIM_OP_CONFIRM):
		rll_msg = RSL_MT_EST_CONF;
		break;
	case OSMO_PRIM(PRIM_DL_DATA, PRIM_OP_INDICATION):
		rll_msg = RSL_MT_DATA_IND;
		break;
	case OSMO_PRIM(PRIM_DL_UNIT_DATA, PRIM_OP_INDICATION):
		return send_rslms_rll_l3_ui(mctx, dp->oph.msg);
	case OSMO_PRIM(PRIM_DL_REL, PRIM_OP_INDICATION):
		rll_msg = RSL_MT_REL_IND;
		break;
	case OSMO_PRIM(PRIM_DL_REL, PRIM_OP_CONFIRM):
		rll_msg = RSL_MT_REL_CONF;
		break;
	case OSMO_PRIM(PRIM_DL_SUSP, PRIM_OP_CONFIRM):
		rll_msg = RSL_MT_SUSP_CONF;
		break;
	case OSMO_PRIM(PRIM_MDL_ERROR, PRIM_OP_INDICATION):
		rsl_rll_error(dp->u.error_ind.cause, mctx);
		if (dp->oph.msg)
			msgb_free(dp->oph.msg);
		return 0;
	}

	if (!rll_msg) {
		LOGP(DLLAPD, LOGL_ERROR, "Unsupported op %d, prim %d. Please "
			"fix!\n", dp->oph.primitive, dp->oph.operation);
		return -EINVAL;
	}

	if (!dp->oph.msg)
		return send_rll_simple(rll_msg, mctx);

	return send_rslms_rll_l3(rll_msg, mctx, dp->oph.msg);
}

/* send a data frame to layer 1 */
static int lapdm_send_ph_data_req(struct lapd_msg_ctx *lctx, struct msgb *msg)
{
	uint8_t l3_len = msg->tail - msg->data;
	struct lapd_datalink *dl = lctx->dl;
	struct lapdm_datalink *mdl =
		container_of(dl, struct lapdm_datalink, dl);
	struct lapdm_msg_ctx *mctx = &mdl->mctx;
	int format = lctx->format;

	/* prepend l2 header */
	msg->l2h = msgb_push(msg, 3);
	msg->l2h[0] = LAPDm_ADDR(lctx->lpd, lctx->sapi, lctx->cr);
					/* EA is set here too */
	switch (format) {
	case LAPD_FORM_I:
		msg->l2h[1] = LAPDm_CTRL_I(lctx->n_recv, lctx->n_send,
						lctx->p_f);
		break;
	case LAPD_FORM_S:
		msg->l2h[1] = LAPDm_CTRL_S(lctx->n_recv, lctx->s_u, lctx->p_f);
		break;
	case LAPD_FORM_U:
		msg->l2h[1] = LAPDm_CTRL_U(lctx->s_u, lctx->p_f);
		break;
	default:
		msgb_free(msg);
		return -EINVAL;
	}
	msg->l2h[2] = LAPDm_LEN(l3_len); /* EL is set here too */
	if (lctx->more)
		msg->l2h[2] |= LAPDm_MORE;

	/* add ACCH header with last indicated tx-power and TA */
	if ((mctx->link_id & 0x40)) {
		struct lapdm_entity *le = mdl->entity;

		msg->l2h = msgb_push(msg, 2);
		msg->l2h[0] = le->tx_power;
		msg->l2h[1] = le->ta;
	}

	return tx_ph_data_enqueue(mctx->dl, msg, mctx->chan_nr, mctx->link_id,
			23);
}

/* input into layer2 (from layer 1) */
static int l2_ph_data_ind(struct msgb *msg, struct lapdm_entity *le,
	uint8_t chan_nr, uint8_t link_id)
{
	uint8_t cbits = chan_nr >> 3;
	uint8_t sapi; /* we cannot take SAPI from link_id, as L1 has no clue */
	struct lapdm_msg_ctx mctx;
	struct lapd_msg_ctx lctx;
	int rc = 0;
	int n201;

	/* when we reach here, we have a msgb with l2h pointing to the raw
	 * 23byte mac block. The l1h has already been purged. */

	memset(&mctx, 0, sizeof(mctx));
	mctx.chan_nr = chan_nr;
	mctx.link_id = link_id;

	/* check for L1 chan_nr/link_id and determine LAPDm hdr format */
	if (cbits == 0x10 || cbits == 0x12) {
		/* Format Bbis is used on BCCH and CCCH(PCH, NCH and AGCH) */
		mctx.lapdm_fmt = LAPDm_FMT_Bbis;
		n201 = N201_Bbis;
		sapi = 0;
	} else {
		if (mctx.link_id & 0x40) {
			/* It was received from network on SACCH */

			/* If UI on SACCH sent by BTS, lapdm_fmt must be B4 */
			if (le->mode == LAPDM_MODE_MS
			 && LAPDm_CTRL_is_U(msg->l2h[3])
			 && LAPDm_CTRL_U_BITS(msg->l2h[3]) == 0) {
				mctx.lapdm_fmt = LAPDm_FMT_B4;
				n201 = N201_B4;
				LOGP(DLLAPD, LOGL_INFO, "fmt=B4\n");
			} else {
				mctx.lapdm_fmt = LAPDm_FMT_B;
				n201 = N201_AB_SACCH;
				LOGP(DLLAPD, LOGL_INFO, "fmt=B\n");
			}
			/* SACCH frames have a two-byte L1 header that
			 * OsmocomBB L1 doesn't strip */
			mctx.tx_power_ind = msg->l2h[0] & 0x1f;
			mctx.ta_ind = msg->l2h[1];
			msgb_pull(msg, 2);
			msg->l2h += 2;
			sapi = (msg->l2h[0] >> 2) & 7;
		} else {
			mctx.lapdm_fmt = LAPDm_FMT_B;
			LOGP(DLLAPD, LOGL_INFO, "fmt=B\n");
			n201 = N201_AB_SDCCH;
			sapi = (msg->l2h[0] >> 2) & 7;
		}
	}

	mctx.dl = datalink_for_sapi(le, sapi);
	/* G.2.1 No action on frames containing an unallocated SAPI. */
	if (!mctx.dl) {
		LOGP(DLLAPD, LOGL_NOTICE, "Received frame for unsupported "
			"SAPI %d!\n", sapi);
		msgb_free(msg);
		return -EIO;
	}

	switch (mctx.lapdm_fmt) {
	case LAPDm_FMT_A:
	case LAPDm_FMT_B:
	case LAPDm_FMT_B4:
		lctx.dl = &mctx.dl->dl;
		/* obtain SAPI from address field */
		mctx.link_id |= LAPDm_ADDR_SAPI(msg->l2h[0]);
		/* G.2.3 EA bit set to "0" is not allowed in GSM */
		if (!LAPDm_ADDR_EA(msg->l2h[0])) {
			LOGP(DLLAPD, LOGL_NOTICE, "EA bit 0 is not allowed in "
				"GSM\n");
			msgb_free(msg);
			rsl_rll_error(RLL_CAUSE_FRM_UNIMPL, &mctx);
			return -EINVAL;
		}
		/* adress field */
		lctx.lpd = LAPDm_ADDR_LPD(msg->l2h[0]);
		lctx.sapi = LAPDm_ADDR_SAPI(msg->l2h[0]);
		lctx.cr = LAPDm_ADDR_CR(msg->l2h[0]);
		/* command field */
		if (LAPDm_CTRL_is_I(msg->l2h[1])) {
			lctx.format = LAPD_FORM_I;
			lctx.n_send = LAPDm_CTRL_I_Ns(msg->l2h[1]);
			lctx.n_recv = LAPDm_CTRL_Nr(msg->l2h[1]);
		} else if (LAPDm_CTRL_is_S(msg->l2h[1])) {
			lctx.format = LAPD_FORM_S;
			lctx.n_recv = LAPDm_CTRL_Nr(msg->l2h[1]);
			lctx.s_u = LAPDm_CTRL_S_BITS(msg->l2h[1]);
		} else if (LAPDm_CTRL_is_U(msg->l2h[1])) {
			lctx.format = LAPD_FORM_U;
			lctx.s_u = LAPDm_CTRL_U_BITS(msg->l2h[1]);
		} else
			lctx.format = LAPD_FORM_UKN;
		lctx.p_f = LAPDm_CTRL_PF_BIT(msg->l2h[1]);
		if (lctx.sapi != LAPDm_SAPI_NORMAL
		 && lctx.sapi != LAPDm_SAPI_SMS
		 && lctx.format == LAPD_FORM_U
		 && lctx.s_u == LAPDm_U_UI) {
			/* 5.3.3 UI frames with invalid SAPI values shall be
			 * discarded
			 */
			LOGP(DLLAPD, LOGL_INFO, "sapi=%u (discarding)\n",
				lctx.sapi);
			msgb_free(msg);
			return 0;
		}
		if (mctx.lapdm_fmt == LAPDm_FMT_B4) {
			lctx.n201 = n201;
			lctx.length = n201;
			lctx.more = 0;
			msg->l3h = msg->l2h + 2;
			msgb_pull_l2h(msg);
		} else {
			/* length field */
			if (!(msg->l2h[2] & LAPDm_EL)) {
				/* G.4.1 If the EL bit is set to "0", an
				 * MDL-ERROR-INDICATION primitive with cause
				 * "frame not implemented" is sent to the
				 * mobile management entity. */
				LOGP(DLLAPD, LOGL_NOTICE, "we don't support "
					"multi-octet length\n");
				msgb_free(msg);
				rsl_rll_error(RLL_CAUSE_FRM_UNIMPL, &mctx);
				return -EINVAL;
			}
			lctx.n201 = n201;
			lctx.length = msg->l2h[2] >> 2;
			lctx.more = !!(msg->l2h[2] & LAPDm_MORE);
			msg->l3h = msg->l2h + 3;
			msgb_pull_l2h(msg);
		}
		/* store context for messages from lapd */
		memcpy(&mctx.dl->mctx, &mctx, sizeof(mctx.dl->mctx));
		/* send to LAPD */
		rc = lapd_ph_data_ind(msg, &lctx);
		break;
	case LAPDm_FMT_Bter:
		/* FIXME */
		msgb_free(msg);
		break;
	case LAPDm_FMT_Bbis:
		/* directly pass up to layer3 */
		LOGP(DLLAPD, LOGL_INFO, "fmt=Bbis UI\n");
		msg->l3h = msg->l2h;
		msgb_pull_l2h(msg);
		rc = send_rslms_rll_l3(RSL_MT_UNIT_DATA_IND, &mctx, msg);
		break;
	default:
		msgb_free(msg);
	}

	return rc;
}

/* input into layer2 (from layer 1) */
static int l2_ph_rach_ind(struct lapdm_entity *le, uint8_t ra, uint32_t fn, uint8_t acc_delay)
{
	struct abis_rsl_cchan_hdr *ch;
	struct gsm48_req_ref req_ref;
	struct gsm_time gt;
	struct msgb *msg = msgb_alloc_headroom(512, 64, "RSL CHAN RQD");

	msg->l2h = msgb_push(msg, sizeof(*ch));
	ch = (struct abis_rsl_cchan_hdr *)msg->l2h;
	rsl_init_cchan_hdr(ch, RSL_MT_CHAN_RQD);
	ch->chan_nr = RSL_CHAN_RACH;

	/* generate a RSL CHANNEL REQUIRED message */
	gsm_fn2gsmtime(&gt, fn);
	req_ref.ra = ra;
	req_ref.t1 = gt.t1; /* FIXME: modulo? */
	req_ref.t2 = gt.t2;
	req_ref.t3_low = gt.t3 & 7;
	req_ref.t3_high = gt.t3 >> 3;

	msgb_tv_fixed_put(msg, RSL_IE_REQ_REFERENCE, 3, (uint8_t *) &req_ref);
	msgb_tv_put(msg, RSL_IE_ACCESS_DELAY, acc_delay);

	return rslms_sendmsg(msg, le);
}

static int l2_ph_chan_conf(struct msgb *msg, struct lapdm_entity *le, uint32_t frame_nr);

/*! \brief Receive a PH-SAP primitive from L1 */
int lapdm_phsap_up(struct osmo_prim_hdr *oph, struct lapdm_entity *le)
{
	struct osmo_phsap_prim *pp = (struct osmo_phsap_prim *) oph;
	int rc = 0;

	if (oph->sap != SAP_GSM_PH) {
		LOGP(DLLAPD, LOGL_ERROR, "primitive for unknown SAP %u\n",
			oph->sap);
		return -ENODEV;
	}

	switch (oph->primitive) {
	case PRIM_PH_DATA:
		if (oph->operation != PRIM_OP_INDICATION) {
			LOGP(DLLAPD, LOGL_ERROR, "PH_DATA is not INDICATION %u\n",
				oph->operation);
			return -ENODEV;
		}
		rc = l2_ph_data_ind(oph->msg, le, pp->u.data.chan_nr,
				    pp->u.data.link_id);
		break;
	case PRIM_PH_RTS:
		if (oph->operation != PRIM_OP_INDICATION) {
			LOGP(DLLAPD, LOGL_ERROR, "PH_RTS is not INDICATION %u\n",
				oph->operation);
			return -ENODEV;
		}
		rc = l2_ph_data_conf(oph->msg, le);
		break;
	case PRIM_PH_RACH:
		switch (oph->operation) {
		case PRIM_OP_INDICATION:
			rc = l2_ph_rach_ind(le, pp->u.rach_ind.ra, pp->u.rach_ind.fn,
					    pp->u.rach_ind.acc_delay);
			break;
		case PRIM_OP_CONFIRM:
			rc = l2_ph_chan_conf(oph->msg, le, pp->u.rach_ind.fn);
			break;
		default:
			return -EIO;
		}
		break;
	}

	return rc;
}


/* L3 -> L2 / RSLMS -> LAPDm */

/* Set LAPDm context for established connection */
static int set_lapdm_context(struct lapdm_datalink *dl, uint8_t chan_nr,
	uint8_t link_id, int n201, uint8_t sapi)
{
	memset(&dl->mctx, 0, sizeof(dl->mctx));
	dl->mctx.dl = dl;
	dl->mctx.chan_nr = chan_nr;
	dl->mctx.link_id = link_id;
	dl->dl.lctx.dl = &dl->dl;
	dl->dl.lctx.n201 = n201;
	dl->dl.lctx.sapi = sapi;

	return 0;
}

/* L3 requests establishment of data link */
static int rslms_rx_rll_est_req(struct msgb *msg, struct lapdm_datalink *dl)
{
	struct abis_rsl_rll_hdr *rllh = msgb_l2(msg);
	uint8_t chan_nr = rllh->chan_nr;
	uint8_t link_id = rllh->link_id;
	uint8_t sapi = rllh->link_id & 7;
	struct tlv_parsed tv;
	uint8_t length;
	uint8_t n201 = (rllh->link_id & 0x40) ? N201_AB_SACCH : N201_AB_SDCCH;
	struct osmo_dlsap_prim dp;

	/* Set LAPDm context for established connection */
	set_lapdm_context(dl, chan_nr, link_id, n201, sapi);

	rsl_tlv_parse(&tv, rllh->data, msgb_l2len(msg) - sizeof(*rllh));
	if (TLVP_PRESENT(&tv, RSL_IE_L3_INFO)) {
		msg->l3h = (uint8_t *) TLVP_VAL(&tv, RSL_IE_L3_INFO);
		/* contention resolution establishment procedure */
		if (sapi != 0) {
			/* According to clause 6, the contention resolution
			 * procedure is only permitted with SAPI value 0 */
			LOGP(DLLAPD, LOGL_ERROR, "SAPI != 0 but contention"
				"resolution (discarding)\n");
			msgb_free(msg);
			return send_rll_simple(RSL_MT_REL_IND, &dl->mctx);
		}
		/* transmit a SABM command with the P bit set to "1". The SABM
		 * command shall contain the layer 3 message unit */
		length = TLVP_LEN(&tv, RSL_IE_L3_INFO);
	} else {
		/* normal establishment procedure */
		msg->l3h = msg->l2h + sizeof(*rllh);
		length = 0;
	}

	/* check if the layer3 message length exceeds N201 */
	if (length > n201) {
		LOGP(DLLAPD, LOGL_ERROR, "frame too large: %d > N201(%d) "
			"(discarding)\n", length, n201);
		msgb_free(msg);
		return send_rll_simple(RSL_MT_REL_IND, &dl->mctx);
	}

	/* Remove RLL header from msgb and set length to L3-info */
	msgb_pull_l2h(msg);
	msg->len = length;
	msg->tail = msg->l3h + length;

	/* prepare prim */
	osmo_prim_init(&dp.oph, 0, PRIM_DL_EST, PRIM_OP_REQUEST, msg);

	/* send to L2 */
	return lapd_recv_dlsap(&dp, &dl->dl.lctx);
}

/* L3 requests transfer of unnumbered information */
static int rslms_rx_rll_udata_req(struct msgb *msg, struct lapdm_datalink *dl)
{
	struct lapdm_entity *le = dl->entity;
	int ui_bts = (le->mode == LAPDM_MODE_BTS);
	struct abis_rsl_rll_hdr *rllh = msgb_l2(msg);
	uint8_t chan_nr = rllh->chan_nr;
	uint8_t link_id = rllh->link_id;
	uint8_t sapi = link_id & 7;
	struct tlv_parsed tv;
	int length;

	/* check if the layer3 message length exceeds N201 */

	rsl_tlv_parse(&tv, rllh->data, msgb_l2len(msg)-sizeof(*rllh));

	if (TLVP_PRESENT(&tv, RSL_IE_TIMING_ADVANCE)) {
		le->ta = *TLVP_VAL(&tv, RSL_IE_TIMING_ADVANCE);
	}
	if (TLVP_PRESENT(&tv, RSL_IE_MS_POWER)) {
		le->tx_power = *TLVP_VAL(&tv, RSL_IE_MS_POWER);
	}
	if (!TLVP_PRESENT(&tv, RSL_IE_L3_INFO)) {
		LOGP(DLLAPD, LOGL_ERROR, "unit data request without message "
			"error\n");
		msgb_free(msg);
		return -EINVAL;
	}
	msg->l3h = (uint8_t *) TLVP_VAL(&tv, RSL_IE_L3_INFO);
	length = TLVP_LEN(&tv, RSL_IE_L3_INFO);
	/* check if the layer3 message length exceeds N201 */
	if (length + 4 + !ui_bts > 23) {
		LOGP(DLLAPD, LOGL_ERROR, "frame too large: %d > N201(%d) "
			"(discarding)\n", length, 18 + ui_bts);
		msgb_free(msg);
		return -EIO;
	}

	LOGP(DLLAPD, LOGL_INFO, "sending unit data (tx_power=%d, ta=%d)\n",
		le->tx_power, le->ta);

	/* Remove RLL header from msgb and set length to L3-info */
	msgb_pull_l2h(msg);
	msg->len = length;
	msg->tail = msg->l3h + length;

	/* Push L1 + LAPDm header on msgb */
	msg->l2h = msgb_push(msg, 4 + !ui_bts);
	msg->l2h[0] = le->tx_power;
	msg->l2h[1] = le->ta;
	msg->l2h[2] = LAPDm_ADDR(LAPDm_LPD_NORMAL, sapi, dl->dl.cr.loc2rem.cmd);
	msg->l2h[3] = LAPDm_CTRL_U(LAPDm_U_UI, 0);
	if (!ui_bts)
		msg->l2h[4] = LAPDm_LEN(length);

	/* Tramsmit */
	return tx_ph_data_enqueue(dl, msg, chan_nr, link_id, 23);
}

/* L3 requests transfer of acknowledged information */
static int rslms_rx_rll_data_req(struct msgb *msg, struct lapdm_datalink *dl)
{
	struct abis_rsl_rll_hdr *rllh = msgb_l2(msg);
	struct tlv_parsed tv;
	int length;
	struct osmo_dlsap_prim dp;

	rsl_tlv_parse(&tv, rllh->data, msgb_l2len(msg)-sizeof(*rllh));
	if (!TLVP_PRESENT(&tv, RSL_IE_L3_INFO)) {
		LOGP(DLLAPD, LOGL_ERROR, "data request without message "
			"error\n");
		msgb_free(msg);
		return -EINVAL;
	}
	msg->l3h = (uint8_t *) TLVP_VAL(&tv, RSL_IE_L3_INFO);
	length = TLVP_LEN(&tv, RSL_IE_L3_INFO);

	/* Remove RLL header from msgb and set length to L3-info */
	msgb_pull_l2h(msg);
	msg->len = length;
	msg->tail = msg->l3h + length;

	/* prepare prim */
	osmo_prim_init(&dp.oph, 0, PRIM_DL_DATA, PRIM_OP_REQUEST, msg);

	/* send to L2 */
	return lapd_recv_dlsap(&dp, &dl->dl.lctx);
}

/* L3 requests suspension of data link */
static int rslms_rx_rll_susp_req(struct msgb *msg, struct lapdm_datalink *dl)
{
	struct abis_rsl_rll_hdr *rllh = msgb_l2(msg);
	uint8_t sapi = rllh->link_id & 7;
	struct osmo_dlsap_prim dp;

	if (sapi != 0) {
		LOGP(DLLAPD, LOGL_ERROR, "SAPI != 0 while suspending\n");
		msgb_free(msg);
		return -EINVAL;
	}

	/* prepare prim */
	osmo_prim_init(&dp.oph, 0, PRIM_DL_SUSP, PRIM_OP_REQUEST, msg);

	/* send to L2 */
	return lapd_recv_dlsap(&dp, &dl->dl.lctx);
}

/* L3 requests resume of data link */
static int rslms_rx_rll_res_req(struct msgb *msg, struct lapdm_datalink *dl)
{
	struct abis_rsl_rll_hdr *rllh = msgb_l2(msg);
	int msg_type = rllh->c.msg_type;
	uint8_t chan_nr = rllh->chan_nr;
	uint8_t link_id = rllh->link_id;
	uint8_t sapi = rllh->link_id & 7;
	struct tlv_parsed tv;
	uint8_t length;
	uint8_t n201 = (rllh->link_id & 0x40) ? N201_AB_SACCH : N201_AB_SDCCH;
	struct osmo_dlsap_prim dp;

	/* Set LAPDm context for established connection */
	set_lapdm_context(dl, chan_nr, link_id, n201, sapi);

	rsl_tlv_parse(&tv, rllh->data, msgb_l2len(msg)-sizeof(*rllh));
	if (!TLVP_PRESENT(&tv, RSL_IE_L3_INFO)) {
		LOGP(DLLAPD, LOGL_ERROR, "resume without message error\n");
		msgb_free(msg);
		return send_rll_simple(RSL_MT_REL_IND, &dl->mctx);
	}
	msg->l3h = (uint8_t *) TLVP_VAL(&tv, RSL_IE_L3_INFO);
	length = TLVP_LEN(&tv, RSL_IE_L3_INFO);

	/* Remove RLL header from msgb and set length to L3-info */
	msgb_pull_l2h(msg);
	msg->len = length;
	msg->tail = msg->l3h + length;

	/* prepare prim */
	osmo_prim_init(&dp.oph, 0, (msg_type == RSL_MT_RES_REQ) ? PRIM_DL_RES
		: PRIM_DL_RECON, PRIM_OP_REQUEST, msg);

	/* send to L2 */
	return lapd_recv_dlsap(&dp, &dl->dl.lctx);
}

/* L3 requests release of data link */
static int rslms_rx_rll_rel_req(struct msgb *msg, struct lapdm_datalink *dl)
{
	struct abis_rsl_rll_hdr *rllh = msgb_l2(msg);
	uint8_t mode = 0;
	struct osmo_dlsap_prim dp;

	/* get release mode */
	if (rllh->data[0] == RSL_IE_RELEASE_MODE)
		mode = rllh->data[1] & 1;

	/* Pull rllh */
	msgb_pull_l2h(msg);

	/* 04.06 3.8.3: No information field is permitted with the DISC
	 * command. */
	msg->len = 0;
	msg->tail = msg->l3h = msg->data;

	/* prepare prim */
	osmo_prim_init(&dp.oph, 0, PRIM_DL_REL, PRIM_OP_REQUEST, msg);
	dp.u.rel_req.mode = mode;

	/* send to L2 */
	return lapd_recv_dlsap(&dp, &dl->dl.lctx);
}

/* L3 requests channel in idle state */
static int rslms_rx_chan_rqd(struct lapdm_channel *lc, struct msgb *msg)
{
	struct abis_rsl_cchan_hdr *cch = msgb_l2(msg);
	void *l1ctx = lc->lapdm_dcch.l1_ctx;
	struct osmo_phsap_prim pp;

	osmo_prim_init(&pp.oph, SAP_GSM_PH, PRIM_PH_RACH,
			PRIM_OP_REQUEST, NULL);

	if (msgb_l2len(msg) < sizeof(*cch) + 4 + 2 + 2) {
		LOGP(DLLAPD, LOGL_ERROR, "Message too short for CHAN RQD!\n");
		return -EINVAL;
	}
	if (cch->data[0] != RSL_IE_REQ_REFERENCE) {
		LOGP(DLLAPD, LOGL_ERROR, "Missing REQ REFERENCE IE\n");
		return -EINVAL;
	}
	pp.u.rach_req.ra = cch->data[1];
	pp.u.rach_req.offset = ((cch->data[2] & 0x7f) << 8) | cch->data[3];
	pp.u.rach_req.is_combined_ccch = cch->data[2] >> 7;

	if (cch->data[4] != RSL_IE_ACCESS_DELAY) {
		LOGP(DLLAPD, LOGL_ERROR, "Missing ACCESS_DELAY IE\n");
		return -EINVAL;
	}
	/* TA = 0 - delay */
	pp.u.rach_req.ta = 0 - cch->data[5];

	if (cch->data[6] != RSL_IE_MS_POWER) {
		LOGP(DLLAPD, LOGL_ERROR, "Missing MS POWER IE\n");
		return -EINVAL;
	}
	pp.u.rach_req.tx_power = cch->data[7];

	msgb_free(msg);

	return lc->lapdm_dcch.l1_prim_cb(&pp.oph, l1ctx);
}

/* L1 confirms channel request */
static int l2_ph_chan_conf(struct msgb *msg, struct lapdm_entity *le, uint32_t frame_nr)
{
	struct abis_rsl_cchan_hdr *ch;
	struct gsm_time tm;
	struct gsm48_req_ref *ref;

	gsm_fn2gsmtime(&tm, frame_nr);

	msgb_pull_l2h(msg);
	msg->l2h = msgb_push(msg, sizeof(*ch) + sizeof(*ref));
	ch = (struct abis_rsl_cchan_hdr *)msg->l2h;
	rsl_init_cchan_hdr(ch, RSL_MT_CHAN_CONF);
	ch->chan_nr = RSL_CHAN_RACH;
	ch->data[0] = RSL_IE_REQ_REFERENCE;
	ref = (struct gsm48_req_ref *) (ch->data + 1);
	ref->t1 = tm.t1;
	ref->t2 = tm.t2;
	ref->t3_low = tm.t3 & 0x7;
	ref->t3_high = tm.t3 >> 3;
	
	return rslms_sendmsg(msg, le);
}

/* incoming RSLms RLL message from L3 */
static int rslms_rx_rll(struct msgb *msg, struct lapdm_channel *lc)
{
	struct abis_rsl_rll_hdr *rllh = msgb_l2(msg);
	int msg_type = rllh->c.msg_type;
	uint8_t sapi = rllh->link_id & 7;
	struct lapdm_entity *le;
	struct lapdm_datalink *dl;
	int rc = 0;

	if (msgb_l2len(msg) < sizeof(*rllh)) {
		LOGP(DLLAPD, LOGL_ERROR, "Message too short for RLL hdr!\n");
		msgb_free(msg);
		return -EINVAL;
	}

	if (rllh->link_id & 0x40)
		le = &lc->lapdm_acch;
	else
		le = &lc->lapdm_dcch;

	/* G.2.1 No action schall be taken on frames containing an unallocated
	 * SAPI.
	 */
	dl = datalink_for_sapi(le, sapi);
	if (!dl) {
		LOGP(DLLAPD, LOGL_ERROR, "No instance for SAPI %d!\n", sapi);
		msgb_free(msg);
		return -EINVAL;
	}

	LOGP(DLLAPD, LOGL_INFO, "(%p) RLL Message '%s' received. (sapi %d)\n",
		lc->name, rsl_msg_name(msg_type), sapi);

	switch (msg_type) {
	case RSL_MT_UNIT_DATA_REQ:
		rc = rslms_rx_rll_udata_req(msg, dl);
		break;
	case RSL_MT_EST_REQ:
		rc = rslms_rx_rll_est_req(msg, dl);
		break;
	case RSL_MT_DATA_REQ:
		rc = rslms_rx_rll_data_req(msg, dl);
		break;
	case RSL_MT_SUSP_REQ:
		rc = rslms_rx_rll_susp_req(msg, dl);
		break;
	case RSL_MT_RES_REQ:
		rc = rslms_rx_rll_res_req(msg, dl);
		break;
	case RSL_MT_RECON_REQ:
		rc = rslms_rx_rll_res_req(msg, dl);
		break;
	case RSL_MT_REL_REQ:
		rc = rslms_rx_rll_rel_req(msg, dl);
		break;
	default:
		LOGP(DLLAPD, LOGL_NOTICE, "Message unsupported.\n");
		msgb_free(msg);
		rc = -EINVAL;
	}

	return rc;
}

/* incoming RSLms COMMON CHANNEL message from L3 */
static int rslms_rx_com_chan(struct msgb *msg, struct lapdm_channel *lc)
{
	struct abis_rsl_cchan_hdr *cch = msgb_l2(msg);
	int msg_type = cch->c.msg_type;
	int rc = 0;

	if (msgb_l2len(msg) < sizeof(*cch)) {
		LOGP(DLLAPD, LOGL_ERROR, "Message too short for COM CHAN hdr!\n");
		return -EINVAL;
	}

	switch (msg_type) {
	case RSL_MT_CHAN_RQD:
		/* create and send RACH request */
		rc = rslms_rx_chan_rqd(lc, msg);
		break;
	default:
		LOGP(DLLAPD, LOGL_NOTICE, "Unknown COMMON CHANNEL msg %d!\n",
			msg_type);
		msgb_free(msg);
		return 0;
	}

	return rc;
}

/*! \brief Receive a RSLms \ref msgb from Layer 3 */
int lapdm_rslms_recvmsg(struct msgb *msg, struct lapdm_channel *lc)
{
	struct abis_rsl_common_hdr *rslh = msgb_l2(msg);
	int rc = 0;

	if (msgb_l2len(msg) < sizeof(*rslh)) {
		LOGP(DLLAPD, LOGL_ERROR, "Message too short RSL hdr!\n");
		return -EINVAL;
	}

	switch (rslh->msg_discr & 0xfe) {
	case ABIS_RSL_MDISC_RLL:
		rc = rslms_rx_rll(msg, lc);
		break;
	case ABIS_RSL_MDISC_COM_CHAN:
		rc = rslms_rx_com_chan(msg, lc);
		break;
	default:
		LOGP(DLLAPD, LOGL_ERROR, "unknown RSLms message "
			"discriminator 0x%02x", rslh->msg_discr);
		msgb_free(msg);
		return -EINVAL;
	}

	return rc;
}

/*! \brief Set the \ref lapdm_mode of a LAPDm entity */
int lapdm_entity_set_mode(struct lapdm_entity *le, enum lapdm_mode mode)
{
	int i;
	enum lapd_mode lm;

	switch (mode) {
	case LAPDM_MODE_MS:
		lm = LAPD_MODE_USER;
		break;
	case LAPDM_MODE_BTS:
		lm = LAPD_MODE_NETWORK;
		break;
	default:
		return -EINVAL;
	}

	for (i = 0; i < ARRAY_SIZE(le->datalink); i++) {
		lapd_set_mode(&le->datalink[i].dl, lm);
	}

	le->mode = mode;

	return 0;
}

/*! \brief Set the \ref lapdm_mode of a LAPDm channel*/
int lapdm_channel_set_mode(struct lapdm_channel *lc, enum lapdm_mode mode)
{
	int rc;

	rc = lapdm_entity_set_mode(&lc->lapdm_dcch, mode);
	if (rc < 0)
		return rc;

	return lapdm_entity_set_mode(&lc->lapdm_acch, mode);
}

/*! \brief Set the L1 callback and context of a LAPDm channel */
void lapdm_channel_set_l1(struct lapdm_channel *lc, osmo_prim_cb cb, void *ctx)
{
	lc->lapdm_dcch.l1_prim_cb = cb;
	lc->lapdm_acch.l1_prim_cb = cb;
	lc->lapdm_dcch.l1_ctx = ctx;
	lc->lapdm_acch.l1_ctx = ctx;
}

/*! \brief Set the L3 callback and context of a LAPDm channel */
void lapdm_channel_set_l3(struct lapdm_channel *lc, lapdm_cb_t cb, void *ctx)
{
	lc->lapdm_dcch.l3_cb = cb;
	lc->lapdm_acch.l3_cb = cb;
	lc->lapdm_dcch.l3_ctx = ctx;
	lc->lapdm_acch.l3_ctx = ctx;
}

/*! \brief Reset an entire LAPDm entity and all its datalinks */
void lapdm_entity_reset(struct lapdm_entity *le)
{
	struct lapdm_datalink *dl;
	int i;

	for (i = 0; i < ARRAY_SIZE(le->datalink); i++) {
		dl = &le->datalink[i];
		lapd_dl_reset(&dl->dl);
	}
}

/*! \brief Reset a LAPDm channel with all its entities */
void lapdm_channel_reset(struct lapdm_channel *lc)
{
	lapdm_entity_reset(&lc->lapdm_dcch);
	lapdm_entity_reset(&lc->lapdm_acch);
}

/*! \brief Set the flags of a LAPDm entity */
void lapdm_entity_set_flags(struct lapdm_entity *le, unsigned int flags)
{
	le->flags = flags;
}

/*! \brief Set the flags of all LAPDm entities in a LAPDm channel */
void lapdm_channel_set_flags(struct lapdm_channel *lc, unsigned int flags)
{
	lapdm_entity_set_flags(&lc->lapdm_dcch, flags);
	lapdm_entity_set_flags(&lc->lapdm_acch, flags);
}

/*! @} */