Split of LAPDm into a core part and a GSM specific part

Instead of mixing together the GSM layer 1 interface and RSL interface
with the implementation of LAPD, the core function of LAPD is now
extracted from LAPDm. The core implementation is now in lapd_core.c
and lapd_core.h respectively.

The lapd_core.c implements exactly one datalink instance for one SAP.
The surrounding implementation "lapdm.c" codes/decodes the layer 2
headers and handles multiplexing and datalink instances, as well as
translates primitives from/to RSL layer.

lapd_core.c can now be used for other LAPD implementations. (ISDN/ABIS)

1 files changed, 327 insertions, 1620 deletions

diff --git a/src/gsm/lapdm.c b/src/gsm/lapdm.c
index a2212785..9e7172d6 100644
--- a/src/gsm/lapdm.c
+++ b/src/gsm/lapdm.c
@@ -1,7 +1,7 @@
 /* GSM LAPDm (TS 04.06) implementation */
 
 /* (C) 2010-2011 by Harald Welte <laforge@gnumonks.org>
- * (C) 2010 by Andreas Eversberg <jolly@eversberg.eu>
+ * (C) 2010-2011 by Andreas Eversberg <jolly@eversberg.eu>
  *
  * All Rights Reserved
  *
@@ -27,36 +27,6 @@
 
 /*! \file lapdm.c */
 
-/*!
- * Notes on Buffering: rcv_buffer, tx_queue, tx_hist, send_buffer, send_queue
- *
- * RX data is stored in the rcv_buffer (pointer). If the message is complete, it
- * is removed from rcv_buffer pointer and forwarded to L3. If the RX data is
- * received while there is an incomplete rcv_buffer, it is appended to it.
- *
- * TX data is stored in the send_queue first. When transmitting a frame,
- * the first message in the send_queue is moved to the send_buffer. There it
- * resides until all fragments are acknowledged. Fragments to be sent by I
- * frames are stored in the tx_hist buffer for resend, if required. Also the
- * current fragment is copied into the tx_queue. There it resides until it is
- * forwarded to layer 1.
- *
- * In case we have SAPI 0, we only have a window size of 1, so the unack-
- * nowledged message resides always in the send_buffer. In case of a suspend,
- * it can be written back to the first position of the send_queue.
- *
- * The layer 1 normally sends a PH-READY-TO-SEND. But because we use
- * asynchronous transfer between layer 1 and layer 2 (serial link), we must
- * send a frame before layer 1 reaches the right timeslot to send it. So we
- * move the tx_queue to layer 1 when there is not already a pending frame, and
- * wait until acknowledge after the frame has been sent. If we receive an
- * acknowledge, we can send the next frame from the buffer, if any.
- *
- * The moving of tx_queue to layer 1 may also trigger T200, if desired. Also it
- * will trigger next I frame, if possible.
- *
- */
-
 #include <stdio.h>
 #include <stdint.h>
 #include <string.h>
@@ -84,6 +54,7 @@
 #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)
@@ -105,19 +76,11 @@
 #define LAPDm_CTRL_I_Ns(ctrl)	(((ctrl) & 0xE) >> 1)
 #define LAPDm_CTRL_Nr(ctrl)	(((ctrl) & 0xE0) >> 5)
 
-/* TS 04.06 Table 4 / Section 3.8.1 */
-#define LAPDm_U_SABM	0x7
-#define LAPDm_U_DM	0x3
-#define LAPDm_U_UI	0x0
-#define LAPDm_U_DISC	0x8
-#define LAPDm_U_UA	0xC
-
-#define LAPDm_S_RR	0x0
-#define LAPDm_S_RNR	0x1
-#define LAPDm_S_REJ	0x2
-
 #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
@@ -137,19 +100,8 @@
 #define N200_TR_FACCH_FR	34
 #define N200_TR_EFACCH_FR	48
 #define N200_TR_FACCH_HR	29
-/* FIXME: this depends on chan type */
-#define N200	N200_TR_SACCH
-
-#define CR_MS2BS_CMD	0
-#define CR_MS2BS_RESP	1
-#define CR_BS2MS_CMD	1
-#define CR_BS2MS_RESP	0
-
-/* Set T200 to 1 Second (OpenBTS uses 900ms) */
-#define T200	1, 0
-
-/* k value for each SAPI */
-static uint8_t k_sapi[] = {1, 1, 1, 1, 1, 1, 1, 1};
+/* FIXME: set N200 depending on chan_nr */
+#define N200 N200_TR_SDCCH
 
 enum lapdm_format {
 	LAPDm_FMT_A,
@@ -159,36 +111,22 @@ enum lapdm_format {
 	LAPDm_FMT_B4,
 };
 
-static void lapdm_t200_cb(void *data);
-static int rslms_send_i(struct lapdm_msg_ctx *mctx, int line);
-
-/* UTILITY FUNCTIONS */
-
-static inline uint8_t inc_mod8(uint8_t x)
-{
-	return (x + 1) & 7;
-}
-
-static inline uint8_t add_mod8(uint8_t x, uint8_t y)
-{
-	return (x + y) & 7;
-}
-
-static inline uint8_t sub_mod8(uint8_t x, uint8_t y)
-{
-	return (x - y) & 7; /* handle negative results correctly */
-}
+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)
 {
 	memset(dl, 0, sizeof(*dl));
-	INIT_LLIST_HEAD(&dl->send_queue);
-	INIT_LLIST_HEAD(&dl->tx_queue);
-	dl->state = LAPDm_STATE_IDLE;
-	dl->t200.data = dl;
-	dl->t200.cb = &lapdm_t200_cb;
 	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;
 }
 
 /*! \brief initialize a LAPDm entity and all datalinks inside
@@ -215,35 +153,10 @@ void lapdm_entity_init(struct lapdm_entity *le, enum lapdm_mode mode)
 void lapdm_channel_init(struct lapdm_channel *lc, enum lapdm_mode mode)
 {
 	lapdm_entity_init(&lc->lapdm_acch, mode);
+	/* FIXME: this depends on chan type */
 	lapdm_entity_init(&lc->lapdm_dcch, mode);
 }
 
-static void lapdm_dl_flush_send(struct lapdm_datalink *dl)
-{
-	struct msgb *msg;
-
-	/* Flush send-queue */
-	while ((msg = msgb_dequeue(&dl->send_queue)))
-		msgb_free(msg);
-
-	/* Clear send-buffer */
-	if (dl->send_buffer) {
-		msgb_free(dl->send_buffer);
-		dl->send_buffer = NULL;
-	}
-}
-
-static void lapdm_dl_flush_tx(struct lapdm_datalink *dl)
-{
-	struct msgb *msg;
-	unsigned int i;
-
-	while ((msg = msgb_dequeue(&dl->tx_queue)))
-		msgb_free(msg);
-	for (i = 0; i < 8; i++)
-		dl->tx_length[i] = 0;
-}
-
 /*! \brief flush and release all resoures in LAPDm entity */
 void lapdm_entity_exit(struct lapdm_entity *le)
 {
@@ -252,10 +165,7 @@ void lapdm_entity_exit(struct lapdm_entity *le)
 
 	for (i = 0; i < ARRAY_SIZE(le->datalink); i++) {
 		dl = &le->datalink[i];
-		lapdm_dl_flush_tx(dl);
-		lapdm_dl_flush_send(dl);
-		if (dl->rcv_buffer)
-			msgb_free(dl->rcv_buffer);
+		lapd_dl_exit(&dl->dl);
 	}
 }
 
@@ -270,14 +180,6 @@ void lapdm_channel_exit(struct lapdm_channel *lc)
 	lapdm_entity_exit(&lc->lapdm_dcch);
 }
 
-static void lapdm_dl_newstate(struct lapdm_datalink *dl, uint32_t state)
-{
-	LOGP(DLLAPDM, LOGL_INFO, "new state %s -> %s\n",
-		lapdm_state_names[dl->state], lapdm_state_names[state]);
-	
-	dl->state = state;
-}
-
 static struct lapdm_datalink *datalink_for_sapi(struct lapdm_entity *le, uint8_t sapi)
 {
 	switch (sapi) {
@@ -305,7 +207,7 @@ static void lapdm_pad_msgb(struct msgb *msg, uint8_t n201)
 	uint8_t *data;
 
 	if (pad_len < 0) {
-		LOGP(DLLAPDM, LOGL_ERROR,
+		LOGP(DLLAPD, LOGL_ERROR,
 		     "cannot pad message that is already too big!\n");
 		return;
 	}
@@ -328,17 +230,17 @@ static int rslms_sendmsg(struct msgb *msg, struct lapdm_entity *le)
 
 /* 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 n201)
+				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) = n201;
+		*msgb_push(msg, 1) = pad;
 		*msgb_push(msg, 1) = link_id;
 		*msgb_push(msg, 1) = chan_nr;
-		msgb_enqueue(&dl->tx_queue, msg);
+		msgb_enqueue(&dl->dl.tx_queue, msg);
 		return -EBUSY;
 	}
 
@@ -349,7 +251,7 @@ static int tx_ph_data_enqueue(struct lapdm_datalink *dl, struct msgb *msg,
 
 	/* send the frame now */
 	le->tx_pending = 0; /* disabled flow control */
-	lapdm_pad_msgb(msg, n201);
+	lapdm_pad_msgb(msg, pad);
 
 	return le->l1_prim_cb(&pp.oph, le->l1_ctx);
 }
@@ -366,7 +268,7 @@ static struct msgb *tx_dequeue_msgb(struct lapdm_entity *le)
 		/* next */
 		i = (i + 1) % n;
 		dl = &le->datalink[i];
-		if ((msg = msgb_dequeue(&dl->tx_queue)))
+		if ((msg = msgb_dequeue(&dl->dl.tx_queue)))
 			break;
 	} while (i != last);
 
@@ -383,7 +285,7 @@ static struct msgb *tx_dequeue_msgb(struct lapdm_entity *le)
 int lapdm_phsap_dequeue_prim(struct lapdm_entity *le, struct osmo_phsap_prim *pp)
 {
 	struct msgb *msg;
-	uint8_t n201;
+	uint8_t pad;
 
 	msg = tx_dequeue_msgb(le);
 	if (!msg)
@@ -398,11 +300,11 @@ int lapdm_phsap_dequeue_prim(struct lapdm_entity *le, struct osmo_phsap_prim *pp
 	msgb_pull(msg, 1);
 	pp->u.data.link_id = *msg->data;
 	msgb_pull(msg, 1);
-	n201 = *msg->data;
+	pad = *msg->data;
 	msgb_pull(msg, 1);
 
 	/* Pad the frame, we can transmit now */
-	lapdm_pad_msgb(msg, n201);
+	lapdm_pad_msgb(msg, pad);
 
 	return 0;
 }
@@ -486,1142 +388,161 @@ static int rsl_rll_error(uint8_t cause, struct lapdm_msg_ctx *mctx)
 {
 	struct msgb *msg;
 
-	LOGP(DLLAPDM, LOGL_NOTICE, "sending MDL-ERROR-IND %d\n", cause);
+	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);
+	msg->l2h = msgb_put(msg, sizeof(struct abis_rsl_rll_hdr));
 	msgb_tlv_put(msg, RSL_IE_RLM_CAUSE, 1, &cause);
 	return rslms_sendmsg(msg, mctx->dl->entity);
 }
 
-static int check_length_ind(struct lapdm_msg_ctx *mctx, uint8_t length_ind)
-{
-	if (!(length_ind & 0x01)) {
-		/* 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(DLLAPDM, LOGL_NOTICE,
-			"we don't support multi-octet length\n");
-		rsl_rll_error(RLL_CAUSE_FRM_UNIMPL, mctx);
-		return -EINVAL;
-	}
-	return 0;
-}
-
-static int lapdm_send_resend(struct lapdm_datalink *dl)
-{
-	struct msgb *msg = msgb_alloc_headroom(23+10, 10, "LAPDm resend");
-	int length;
-
-	/* Resend SABM/DISC from tx_hist */
-	length = dl->tx_length[0];
-	msg->l2h = msgb_put(msg, length);
-	memcpy(msg->l2h, dl->tx_hist[dl->V_send], length);
-
-	return tx_ph_data_enqueue(dl, msg, dl->mctx.chan_nr, dl->mctx.link_id,
-			dl->mctx.n201);
-}
-
-static int lapdm_send_ua(struct lapdm_msg_ctx *mctx, uint8_t len, uint8_t *data)
+/* DLSAP L2 -> L3 (RSLms) */
+static int send_rslms_dlsap(struct osmo_dlsap_prim *dp,
+	struct lapd_msg_ctx *lctx)
 {
-	uint8_t sapi = mctx->link_id & 7;
-	uint8_t f_bit = LAPDm_CTRL_PF_BIT(mctx->ctrl);
-	struct msgb *msg = msgb_alloc_headroom(23+10, 10, "LAPDm UA");
-	struct lapdm_entity *le = mctx->dl->entity;
-
-	msg->l2h = msgb_put(msg, 3 + len);
-	msg->l2h[0] = LAPDm_ADDR(LAPDm_LPD_NORMAL, sapi, le->cr.loc2rem.resp);
-	msg->l2h[1] = LAPDm_CTRL_U(LAPDm_U_UA, f_bit);
-	msg->l2h[2] = LAPDm_LEN(len);
-	if (len)
-		memcpy(msg->l2h + 3, data, len);
-
-	return tx_ph_data_enqueue(mctx->dl, msg, mctx->chan_nr, mctx->link_id,
-			mctx->n201);
-}
-
-static int lapdm_send_dm(struct lapdm_msg_ctx *mctx)
-{
-	uint8_t sapi = mctx->link_id & 7;
-	uint8_t f_bit = LAPDm_CTRL_PF_BIT(mctx->ctrl);
-	struct msgb *msg = msgb_alloc_headroom(23+10, 10, "LAPDm DM");
-	struct lapdm_entity *le = mctx->dl->entity;
-
-	msg->l2h = msgb_put(msg, 3);
-	msg->l2h[0] = LAPDm_ADDR(LAPDm_LPD_NORMAL, sapi, le->cr.loc2rem.resp);
-	msg->l2h[1] = LAPDm_CTRL_U(LAPDm_U_DM, f_bit);
-	msg->l2h[2] = 0;
-
-	return tx_ph_data_enqueue(mctx->dl, msg, mctx->chan_nr, mctx->link_id,
-			mctx->n201);
-}
-
-static int lapdm_send_rr(struct lapdm_msg_ctx *mctx, uint8_t f_bit)
-{
-	uint8_t sapi = mctx->link_id & 7;
-	struct msgb *msg = msgb_alloc_headroom(23+10, 10, "LAPDm RR");
-	struct lapdm_entity *le = mctx->dl->entity;
-
-	msg->l2h = msgb_put(msg, 3);
-	msg->l2h[0] = LAPDm_ADDR(LAPDm_LPD_NORMAL, sapi, le->cr.loc2rem.resp);
-	msg->l2h[1] = LAPDm_CTRL_S(mctx->dl->V_recv, LAPDm_S_RR, f_bit);
-	msg->l2h[2] = LAPDm_LEN(0);
-
-	return tx_ph_data_enqueue(mctx->dl, msg, mctx->chan_nr, mctx->link_id,
-			mctx->n201);
-}
-
-static int lapdm_send_rnr(struct lapdm_msg_ctx *mctx, uint8_t f_bit)
-{
-	uint8_t sapi = mctx->link_id & 7;
-	struct msgb *msg = msgb_alloc_headroom(23+10, 10, "LAPDm RNR");
-	struct lapdm_entity *le = mctx->dl->entity;
-
-	msg->l2h = msgb_put(msg, 3);
-	msg->l2h[0] = LAPDm_ADDR(LAPDm_LPD_NORMAL, sapi, le->cr.loc2rem.resp);
-	msg->l2h[1] = LAPDm_CTRL_S(mctx->dl->V_recv, LAPDm_S_RNR, f_bit);
-	msg->l2h[2] = LAPDm_LEN(0);
-
-	return tx_ph_data_enqueue(mctx->dl, msg, mctx->chan_nr, mctx->link_id,
-			mctx->n201);
-}
-
-static int lapdm_send_rej(struct lapdm_msg_ctx *mctx, uint8_t f_bit)
-{
-	uint8_t sapi = mctx->link_id & 7;
-	struct msgb *msg = msgb_alloc_headroom(23+10, 10, "LAPDm REJ");
-	struct lapdm_entity *le = mctx->dl->entity;
-
-	msg->l2h = msgb_put(msg, 3);
-	msg->l2h[0] = LAPDm_ADDR(LAPDm_LPD_NORMAL, sapi, le->cr.loc2rem.resp);
-	msg->l2h[1] = LAPDm_CTRL_S(mctx->dl->V_recv, LAPDm_S_REJ, f_bit);
-	msg->l2h[2] = LAPDm_LEN(0);
-
-	return tx_ph_data_enqueue(mctx->dl, msg, mctx->chan_nr, mctx->link_id,
-			mctx->n201);
-}
-
-/* Timer callback on T200 expiry */
-static void lapdm_t200_cb(void *data)
-{
-	struct lapdm_datalink *dl = data;
-
-	LOGP(DLLAPDM, LOGL_INFO, "lapdm_t200_cb(%p) state=%u\n", dl, dl->state);
-
-	switch (dl->state) {
-	case LAPDm_STATE_SABM_SENT:
-		/* 5.4.1.3 */
-		if (dl->retrans_ctr + 1 >= N200_EST_REL + 1) {
-			/* send RELEASE INDICATION to L3 */
-			send_rll_simple(RSL_MT_REL_IND, &dl->mctx);
-			/* send MDL ERROR INIDCATION to L3 */
-			rsl_rll_error(RLL_CAUSE_T200_EXPIRED, &dl->mctx);
-			/* flush tx buffers */
-			lapdm_dl_flush_tx(dl);
-			lapdm_dl_flush_send(dl);
-			/* go back to idle state */
-			lapdm_dl_newstate(dl, LAPDm_STATE_IDLE);
-			/* NOTE: we must not change any other states or buffers
-			 * and queues, since we may reconnect after handover
-			 * failure. the buffered messages is replaced there */
+	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 (dp->oph.primitive) {
+	case PRIM_DL_EST:
+		switch (dp->oph.operation) {
+		case PRIM_OP_INDICATION:
+			rll_msg = RSL_MT_EST_IND;
 			break;
-		}
-		/* retransmit SABM command */
-		lapdm_send_resend(dl);
-		/* increment re-transmission counter */
-		dl->retrans_ctr++;
-		/* restart T200 (PH-READY-TO-SEND) */
-		osmo_timer_schedule(&dl->t200, T200);
-		break;
-	case LAPDm_STATE_DISC_SENT:
-		/* 5.4.4.3 */
-		if (dl->retrans_ctr + 1 >= N200_EST_REL + 1) {
-			/* send RELEASE INDICATION to L3 */
-			send_rll_simple(RSL_MT_REL_CONF, &dl->mctx);
-			/* send MDL ERROR INIDCATION to L3 */
-			rsl_rll_error(RLL_CAUSE_T200_EXPIRED, &dl->mctx);
-			/* flush buffers */
-			lapdm_dl_flush_tx(dl);
-			lapdm_dl_flush_send(dl);
-			/* go back to idle state */
-			lapdm_dl_newstate(dl, LAPDm_STATE_IDLE);
-			/* NOTE: we must not change any other states or buffers
-			 * and queues, since we may reconnect after handover
-			 * failure. the buffered messages is replaced there */
+		case PRIM_OP_CONFIRM:
+			rll_msg = RSL_MT_EST_CONF;
 			break;
-		}
-		/* retransmit DISC command */
-		lapdm_send_resend(dl);
-		/* increment re-transmission counter */
-		dl->retrans_ctr++;
-		/* restart T200 (PH-READY-TO-SEND) */
-		osmo_timer_schedule(&dl->t200, T200);
-		break;
-	case LAPDm_STATE_MF_EST:
-		/* 5.5.7 */
-		dl->retrans_ctr = 0;
-		lapdm_dl_newstate(dl, LAPDm_STATE_TIMER_RECOV);
-		/* fall through */
-	case LAPDm_STATE_TIMER_RECOV:
-		dl->retrans_ctr++;
-		if (dl->retrans_ctr < N200) {
-			/* retransmit I frame (V_s-1) with P=1, if any */
-			if (dl->tx_length[sub_mod8(dl->V_send, 1)]) {
-				struct msgb *msg;
-				int length;
-
-				LOGP(DLLAPDM, LOGL_INFO, "retransmit last frame "
-					"V(S)=%d\n", sub_mod8(dl->V_send, 1));
-				/* Create I frame (segment) from tx_hist */
-				length = dl->tx_length[sub_mod8(dl->V_send, 1)];
-				msg = msgb_alloc_headroom(23+10, 10, "LAPDm I");
-				msg->l2h = msgb_put(msg, length);
-				memcpy(msg->l2h,
-					dl->tx_hist[sub_mod8(dl->V_send, 1)],
-					length);
-				msg->l2h[1] = LAPDm_CTRL_I(dl->V_recv,
-					sub_mod8(dl->V_send, 1), 1); /* P=1 */
-				tx_ph_data_enqueue(dl, msg, dl->mctx.chan_nr,
-					dl->mctx.link_id, dl->mctx.n201);
-			} else {
-			/* OR send appropriate supervision frame with P=1 */
-				if (!dl->own_busy && !dl->seq_err_cond) {
-					lapdm_send_rr(&dl->mctx, 1);
-					/* NOTE: In case of sequence error
-					 * condition, the REJ frame has been
-					 * transmitted when entering the
-					 * condition, so it has not be done
-					 * here
-				 	 */
-				} else if (dl->own_busy) {
-					lapdm_send_rnr(&dl->mctx, 1);
-				} else {
-					LOGP(DLLAPDM, LOGL_INFO, "unhandled, "
-						"pls. fix\n");
-				}
-			}
-			/* restart T200 (PH-READY-TO-SEND) */
-			osmo_timer_schedule(&dl->t200, T200);
-		} else {
-			/* send MDL ERROR INIDCATION to L3 */
-			rsl_rll_error(RLL_CAUSE_T200_EXPIRED, &dl->mctx);
+		default:
+			;
 		}
 		break;
-	default:
-		LOGP(DLLAPDM, LOGL_INFO, "T200 expired in unexpected "
-			"dl->state %u\n", dl->state);
-	}
-}
-
-/* 5.5.3.1: Common function to acknowlege frames up to the given N(R) value */
-static void lapdm_acknowledge(struct lapdm_msg_ctx *mctx)
-{
-	struct lapdm_datalink *dl = mctx->dl;
-	uint8_t nr = LAPDm_CTRL_Nr(mctx->ctrl);
-	int s = 0, rej = 0, t200_reset = 0;
-	int i;
-
-	/* supervisory frame ? */
-	if (LAPDm_CTRL_is_S(mctx->ctrl))
-		s = 1;
-	/* REJ frame ? */
-	if (s && LAPDm_CTRL_S_BITS(mctx->ctrl) == LAPDm_S_REJ)
-	 	rej = 1;
-
-	/* Flush all transmit buffers of acknowledged frames */
-	for (i = dl->V_ack; i != nr; i = inc_mod8(i)) {
-		if (dl->tx_length[i]) {
-			dl->tx_length[i] = 0;
-			LOGP(DLLAPDM, LOGL_INFO, "ack frame %d\n", i);
-		}
-	}
-
-	if (dl->state != LAPDm_STATE_TIMER_RECOV) {
-		/* When not in the timer recovery condition, the data
-		 * link layer entity shall reset the timer T200 on
-		 * receipt of a valid I frame with N(R) higher than V(A),
-		 * or an REJ with an N(R) equal to V(A). */
-		if ((!rej && nr != dl->V_ack)
-		 || (rej && nr == dl->V_ack)) {
-			LOGP(DLLAPDM, LOGL_INFO, "reset t200\n");
-		 	t200_reset = 1;
-			osmo_timer_del(&dl->t200);
-			/* 5.5.3.1 Note 1 + 2 imply timer recovery cond. */
-		}
-		/* 5.7.4: N(R) sequence error
-		 * N(R) is called valid, if and only if
-		 * (N(R)-V(A)) mod 8 <= (V(S)-V(A)) mod 8.
-		 */
-		if (sub_mod8(nr, dl->V_ack) > sub_mod8(dl->V_send, dl->V_ack)) {
-			LOGP(DLLAPDM, LOGL_NOTICE, "N(R) sequence error\n");
-			rsl_rll_error(RLL_CAUSE_SEQ_ERR, mctx);
-		}
-	}
-
-	/* V(A) shall be set to the value of N(R) */
-	dl->V_ack = nr;
-
-	/* If T200 has been reset by the receipt of an I, RR or RNR frame,
-	 * and if there are outstanding I frames, restart T200 */
-	if (t200_reset && !rej) {
-		if (dl->tx_length[dl->V_send - 1]) {
-			LOGP(DLLAPDM, LOGL_INFO, "start T200, due to unacked I "
-				"frame(s)\n");
-			osmo_timer_schedule(&dl->t200, T200);
-		}
-	}
-}
-
-/* L1 -> L2 */
-
-/* Receive a LAPDm U (Unnumbered) message from L1 */
-static int lapdm_rx_u(struct msgb *msg, struct lapdm_msg_ctx *mctx)
-{
-	struct lapdm_datalink *dl = mctx->dl;
-	struct lapdm_entity *le = dl->entity;
-	uint8_t length;
-	int rc;
-	int rsl_msg;
-
-	switch (LAPDm_CTRL_U_BITS(mctx->ctrl)) {
-	case LAPDm_U_SABM:
-		rsl_msg = RSL_MT_EST_IND;
-
-		LOGP(DLLAPDM, LOGL_INFO, "SABM received\n");
-		/* 5.7.1 */
-		dl->seq_err_cond = 0;
-		/* G.2.2 Wrong value of the C/R bit */
-		if (LAPDm_ADDR_CR(mctx->addr) == le->cr.rem2loc.resp) {
-			LOGP(DLLAPDM, LOGL_NOTICE, "SABM response error\n");
-			msgb_free(msg);
-			rsl_rll_error(RLL_CAUSE_FRM_UNIMPL, mctx);
-			return -EINVAL;
-		}
-
-		length = msg->l2h[2] >> 2;
-		/* G.4.5 If SABM is received with L>N201 or with M bit
-		 * set, AN MDL-ERROR-INDICATION is sent to MM.
-		 */
-		if ((msg->l2h[2] & LAPDm_MORE) || length + 3 > mctx->n201) {
-			LOGP(DLLAPDM, LOGL_NOTICE, "SABM too large error\n");
-			msgb_free(msg);
-			rsl_rll_error(RLL_CAUSE_UFRM_INC_PARAM, mctx);
-			return -EIO;
-		}
-
-		/* Must be Format B */
-		rc = check_length_ind(mctx, msg->l2h[2]);
-		if (rc < 0) {
-			msgb_free(msg);
-			return rc;
-		}
-		switch (dl->state) {
-		case LAPDm_STATE_IDLE:
-			/* Set chan_nr and link_id for established connection */
-			memset(&dl->mctx, 0, sizeof(dl->mctx));
-			dl->mctx.dl = dl;
-			dl->mctx.chan_nr = mctx->chan_nr;
-			dl->mctx.link_id = mctx->link_id;
-			dl->mctx.n201 = mctx->n201;
+	case PRIM_DL_DATA:
+		switch (dp->oph.operation) {
+		case PRIM_OP_INDICATION:
+			rll_msg = RSL_MT_DATA_IND;
 			break;
-		case LAPDm_STATE_MF_EST:
-			if (length == 0) {
-				rsl_msg = RSL_MT_EST_CONF;
-				break;
-			}
-			LOGP(DLLAPDM, LOGL_INFO, "SABM command, multiple "
-				"frame established state\n");
-			/* check for contention resoultion */
-			if (dl->tx_hist[0][2] >> 2) {
-				LOGP(DLLAPDM, LOGL_NOTICE, "SABM not allowed "
-					"during contention resolution\n");
-				rsl_rll_error(RLL_CAUSE_SABM_INFO_NOTALL, mctx);
-			}
-			msgb_free(msg);
-			return 0;
-		case LAPDm_STATE_DISC_SENT:
-			/* 5.4.6.2 send DM with F=P */
-			lapdm_send_dm(mctx);
-			/* reset Timer T200 */
-			osmo_timer_del(&dl->t200);
-			msgb_free(msg);
-			return send_rll_simple(RSL_MT_REL_CONF, mctx);
 		default:
-			lapdm_send_ua(mctx, length, msg->l2h + 3);
-			msgb_free(msg);
-			return 0;
-		}
-		/* send UA response */
-		lapdm_send_ua(mctx, length, msg->l2h + 3);
-		/* set Vs, Vr and Va to 0 */
-		dl->V_send = dl->V_recv = dl->V_ack = 0;
-		/* clear tx_hist */
-		dl->tx_length[0] = 0;
-		/* enter multiple-frame-established state */
-		lapdm_dl_newstate(dl, LAPDm_STATE_MF_EST);
-		/* send notification to L3 */
-		if (length == 0) {
-			/* 5.4.1.2 Normal establishment procedures */
-			rc = send_rll_simple(rsl_msg, mctx);
-			msgb_free(msg);
-		} else {
-			/* 5.4.1.4 Contention resolution establishment */
-			msg->l3h = msg->l2h + 3;
-			msgb_pull_l2h(msg);
-			rc = send_rslms_rll_l3(rsl_msg, mctx, msg);
+			;
 		}
 		break;
-	case LAPDm_U_DM:
-		LOGP(DLLAPDM, LOGL_INFO, "DM received\n");
-		/* G.2.2 Wrong value of the C/R bit */
-		if (LAPDm_ADDR_CR(mctx->addr) == le->cr.rem2loc.cmd) {
-			LOGP(DLLAPDM, LOGL_NOTICE, "DM command error\n");
-			msgb_free(msg);
-			rsl_rll_error(RLL_CAUSE_FRM_UNIMPL, mctx);
-			return -EINVAL;
-		}
-		if (!LAPDm_CTRL_PF_BIT(mctx->ctrl)) {
-			/* 5.4.1.2 DM responses with the F bit set to "0"
-			 * shall be ignored.
-			 */
-			msgb_free(msg);
-			return 0;
-		}
-		switch (dl->state) {
-		case LAPDm_STATE_SABM_SENT:
-			break;
-		case LAPDm_STATE_MF_EST:
-			if (LAPDm_CTRL_PF_BIT(mctx->ctrl) == 1) {
-				LOGP(DLLAPDM, LOGL_INFO, "unsolicited DM "
-					"response\n");
-				rsl_rll_error(RLL_CAUSE_UNSOL_DM_RESP, mctx);
-			} else {
-				LOGP(DLLAPDM, LOGL_INFO, "unsolicited DM "
-					"response, multiple frame established "
-					"state\n");
-				rsl_rll_error(RLL_CAUSE_UNSOL_DM_RESP_MF, mctx);
-			}
-			msgb_free(msg);
-			return 0;
-		case LAPDm_STATE_TIMER_RECOV:
-			/* DM is normal in case PF = 1 */
-			if (LAPDm_CTRL_PF_BIT(mctx->ctrl) == 0) {
-				LOGP(DLLAPDM, LOGL_INFO, "unsolicited DM "
-					"response, multiple frame established "
-					"state\n");
-				rsl_rll_error(RLL_CAUSE_UNSOL_DM_RESP_MF, mctx);
-				msgb_free(msg);
-				return 0;
-			}
-			break;
-		case LAPDm_STATE_DISC_SENT:
-			/* reset Timer T200 */
-			osmo_timer_del(&dl->t200);
-			/* go to idle state */
-			lapdm_dl_flush_tx(dl);
-			lapdm_dl_flush_send(dl);
-			lapdm_dl_newstate(dl, LAPDm_STATE_IDLE);
-			rc = send_rll_simple(RSL_MT_REL_CONF, mctx);
-			msgb_free(msg);
-			return 0;
-		case LAPDm_STATE_IDLE:
-			/* 5.4.5 all other frame types shall be discarded */
+	case PRIM_DL_UNIT_DATA:
+		switch (dp->oph.operation) {
+		case PRIM_OP_INDICATION:
+			return send_rslms_rll_l3_ui(mctx, dp->oph.msg);
 		default:
-			LOGP(DLLAPDM, LOGL_INFO, "unsolicited DM response! "
-				"(discarding)\n");
-			msgb_free(msg);
-			return 0;
+			;
 		}
-		/* reset T200 */
-		osmo_timer_del(&dl->t200);
-		rc = send_rll_simple(RSL_MT_REL_IND, mctx);
-		msgb_free(msg);
 		break;
-	case LAPDm_U_UI:
-		LOGP(DLLAPDM, LOGL_INFO, "UI received\n");
-		/* G.2.2 Wrong value of the C/R bit */
-		if (LAPDm_ADDR_CR(mctx->addr) == le->cr.rem2loc.resp) {
-			LOGP(DLLAPDM, LOGL_NOTICE, "UI indicates response "
-				"error\n");
-			msgb_free(msg);
-			rsl_rll_error(RLL_CAUSE_FRM_UNIMPL, mctx);
-			return -EINVAL;
-		}
-
-		length = msg->l2h[2] >> 2;
-		/* FIXME: G.4.5 If UI is received with L>N201 or with M bit
-		 * set, AN MDL-ERROR-INDICATION is sent to MM.
-		 */
-
-		if (mctx->lapdm_fmt == LAPDm_FMT_B4) {
-			length = N201_B4;
-			msg->l3h = msg->l2h + 2;
-		} else {
-			rc = check_length_ind(mctx, msg->l2h[2]);
-			if (rc < 0) {
-				msgb_free(msg);
-				return rc;
-			}
-			length = msg->l2h[2] >> 2;
-			msg->l3h = msg->l2h + 3;
-		}
-		/* do some length checks */
-		if (length == 0) {
-			/* 5.3.3 UI frames received with the length indicator
-			 * set to "0" shall be ignored
-			 */
-			LOGP(DLLAPDM, LOGL_INFO, "length=0 (discarding)\n");
-			msgb_free(msg);
-			return 0;
-		}
-		switch (LAPDm_ADDR_SAPI(mctx->addr)) {
-		case LAPDm_SAPI_NORMAL:
-		case LAPDm_SAPI_SMS:
+	case PRIM_DL_REL:
+		switch (dp->oph.operation) {
+		case PRIM_OP_INDICATION:
+			rll_msg = RSL_MT_REL_IND;
+			break;
+		case PRIM_OP_CONFIRM:
+			rll_msg = RSL_MT_REL_CONF;
 			break;
 		default:
-			/* 5.3.3 UI frames with invalid SAPI values shall be
-			 * discarded
-			 */
-			LOGP(DLLAPDM, LOGL_INFO, "sapi=%u (discarding)\n",
-				LAPDm_ADDR_SAPI(mctx->addr));
-			msgb_free(msg);
-			return 0;
+			;
 		}
-		msgb_pull_l2h(msg);
-		rc = send_rslms_rll_l3_ui(mctx, msg);
 		break;
-	case LAPDm_U_DISC:
-		rsl_msg = RSL_MT_REL_IND;
-
-		LOGP(DLLAPDM, LOGL_INFO, "DISC received\n");
-		/* flush buffers */
-		lapdm_dl_flush_tx(dl);
-		lapdm_dl_flush_send(dl);
-		/* 5.7.1 */
-		dl->seq_err_cond = 0;
-		/* G.2.2 Wrong value of the C/R bit */
-		if (LAPDm_ADDR_CR(mctx->addr) == le->cr.rem2loc.resp) {
-			LOGP(DLLAPDM, LOGL_NOTICE, "DISC response error\n");
-			msgb_free(msg);
-			rsl_rll_error(RLL_CAUSE_FRM_UNIMPL, mctx);
-			return -EINVAL;
-		}
-		length = msg->l2h[2] >> 2;
-		if (length > 0 || msg->l2h[2] & 0x02) {
-			/* G.4.4 If a DISC or DM frame is received with L>0 or
-			 * with the M bit set to "1", an MDL-ERROR-INDICATION
-			 * primitive with cause "U frame with incorrect
-			 * parameters" is sent to the mobile management entity.
-			 */
-			LOGP(DLLAPDM, LOGL_NOTICE,
-				"U frame iwth incorrect parameters ");
-			msgb_free(msg);
-			rsl_rll_error(RLL_CAUSE_UFRM_INC_PARAM, mctx);
-			return -EIO;
-		}
-		switch (dl->state) {
-		case LAPDm_STATE_IDLE:
-			LOGP(DLLAPDM, LOGL_INFO, "DISC in idle state\n");
-			/* send DM with F=P */
-			msgb_free(msg);
-			return lapdm_send_dm(mctx);
-		case LAPDm_STATE_SABM_SENT:
-			LOGP(DLLAPDM, LOGL_INFO, "DISC in SABM state\n");
-			/* 5.4.6.2 send DM with F=P */
-			lapdm_send_dm(mctx);
-			/* reset Timer T200 */
-			osmo_timer_del(&dl->t200);
-			msgb_free(msg);
-			return send_rll_simple(RSL_MT_REL_IND, mctx);
-		case LAPDm_STATE_MF_EST:
-		case LAPDm_STATE_TIMER_RECOV:
-			LOGP(DLLAPDM, LOGL_INFO, "DISC in est state\n");
-			break;
-		case LAPDm_STATE_DISC_SENT:
-			LOGP(DLLAPDM, LOGL_INFO, "DISC in disc state\n");
-			rsl_msg = RSL_MT_REL_CONF;
+	case PRIM_DL_SUSP:
+		switch (dp->oph.operation) {
+		case PRIM_OP_CONFIRM:
+			rll_msg = RSL_MT_SUSP_CONF;
 			break;
 		default:
-			lapdm_send_ua(mctx, length, msg->l2h + 3);
-			msgb_free(msg);
-			return 0;
+			;
 		}
-		/* send UA response */
-		lapdm_send_ua(mctx, length, msg->l2h + 3);
-		/* reset Timer T200 */
-		osmo_timer_del(&dl->t200);
-		/* enter idle state */
-		lapdm_dl_flush_tx(dl);
-		lapdm_dl_flush_send(dl);
-		lapdm_dl_newstate(dl, LAPDm_STATE_IDLE);
-		/* send notification to L3 */
-		rc = send_rll_simple(rsl_msg, mctx);
-		msgb_free(msg);
 		break;
-	case LAPDm_U_UA:
-		LOGP(DLLAPDM, LOGL_INFO, "UA received\n");
-		/* G.2.2 Wrong value of the C/R bit */
-		if (LAPDm_ADDR_CR(mctx->addr) == le->cr.rem2loc.cmd) {
-			LOGP(DLLAPDM, LOGL_NOTICE, "UA indicates command "
-				"error\n");
-			msgb_free(msg);
-			rsl_rll_error(RLL_CAUSE_FRM_UNIMPL, mctx);
-			return -EINVAL;
-		}
-
-		length = msg->l2h[2] >> 2;
-		/* G.4.5 If UA is received with L>N201 or with M bit
-		 * set, AN MDL-ERROR-INDICATION is sent to MM.
-		 */
-		if ((msg->l2h[2] & LAPDm_MORE) || length + 3 > mctx->n201) {
-			LOGP(DLLAPDM, LOGL_NOTICE, "UA too large error\n");
-			msgb_free(msg);
-			rsl_rll_error(RLL_CAUSE_UFRM_INC_PARAM, mctx);
-			return -EIO;
-		}
-
-		if (!LAPDm_CTRL_PF_BIT(mctx->ctrl)) {
-			/* 5.4.1.2 A UA response with the F bit set to "0"
-			 * shall be ignored.
-			 */
-			LOGP(DLLAPDM, LOGL_INFO, "F=0 (discarding)\n");
-			msgb_free(msg);
-			return 0;
-		}
-		switch (dl->state) {
-		case LAPDm_STATE_SABM_SENT:
-			break;
-		case LAPDm_STATE_MF_EST:
-		case LAPDm_STATE_TIMER_RECOV:
-			LOGP(DLLAPDM, LOGL_INFO, "unsolicited UA response! "
-				"(discarding)\n");
-			rsl_rll_error(RLL_CAUSE_UNSOL_UA_RESP, mctx);
-			msgb_free(msg);
-			return 0;
-		case LAPDm_STATE_DISC_SENT:
-			LOGP(DLLAPDM, LOGL_INFO, "UA in disconnect state\n");
-			/* reset Timer T200 */
-			osmo_timer_del(&dl->t200);
-			/* go to idle state */
-			lapdm_dl_flush_tx(dl);
-			lapdm_dl_flush_send(dl);
-			lapdm_dl_newstate(dl, LAPDm_STATE_IDLE);
-			rc = send_rll_simple(RSL_MT_REL_CONF, mctx);
-			msgb_free(msg);
+	case PRIM_MDL_ERROR:
+		switch (dp->oph.operation) {
+		case PRIM_OP_INDICATION:
+			rsl_rll_error(dp->u.error_ind.cause, mctx);
+			if (dp->oph.msg)
+				msgb_free(dp->oph.msg);
 			return 0;
-		case LAPDm_STATE_IDLE:
-			/* 5.4.5 all other frame types shall be discarded */
 		default:
-			LOGP(DLLAPDM, LOGL_INFO, "unsolicited UA response! "
-				"(discarding)\n");
-			msgb_free(msg);
-			return 0;
-		}
-		LOGP(DLLAPDM, LOGL_INFO, "UA in SABM state\n");
-		/* reset Timer T200 */
-		osmo_timer_del(&dl->t200);
-		/* compare UA with SABME if contention resolution is applied */
-		if (dl->tx_hist[0][2] >> 2) {
-			rc = check_length_ind(mctx, msg->l2h[2]);
-			if (rc < 0) {
-				rc = send_rll_simple(RSL_MT_REL_IND, mctx);
-				msgb_free(msg);
-				/* go to idle state */
-				lapdm_dl_flush_tx(dl);
-				lapdm_dl_flush_send(dl);
-				lapdm_dl_newstate(dl, LAPDm_STATE_IDLE);
-				return 0;
-			}
-			length = msg->l2h[2] >> 2;
-			if (length != (dl->tx_hist[0][2] >> 2)
-			 || !!memcmp(dl->tx_hist[0] + 3, msg->l2h + 3,
-			 		length)) {
-				LOGP(DLLAPDM, LOGL_INFO, "**** UA response "
-					"mismatches ****\n");
-				rc = send_rll_simple(RSL_MT_REL_IND, mctx);
-				msgb_free(msg);
-				/* go to idle state */
-				lapdm_dl_flush_tx(dl);
-				lapdm_dl_flush_send(dl);
-				lapdm_dl_newstate(dl, LAPDm_STATE_IDLE);
-				return 0;
-			}
+			;
 		}
-		/* set Vs, Vr and Va to 0 */
-		dl->V_send = dl->V_recv = dl->V_ack = 0;
-		/* clear tx_hist */
-		dl->tx_length[0] = 0;
-		/* enter multiple-frame-established state */
-		lapdm_dl_newstate(dl, LAPDm_STATE_MF_EST);
-		/* send outstanding frames, if any (resume / reconnect) */
-		rslms_send_i(mctx, __LINE__);
-		/* send notification to L3 */
-		rc = send_rll_simple(RSL_MT_EST_CONF, mctx);
-		msgb_free(msg);
 		break;
 	default:
-		/* G.3.1 */
-		LOGP(DLLAPDM, LOGL_NOTICE, "Unnumbered frame not allowed.\n");
-		msgb_free(msg);
-		rsl_rll_error(RLL_CAUSE_FRM_UNIMPL, mctx);
-		return -EINVAL;
+		;
 	}
-	return rc;
-}
 
-/* Receive a LAPDm S (Supervisory) message from L1 */
-static int lapdm_rx_s(struct msgb *msg, struct lapdm_msg_ctx *mctx)
-{
-	struct lapdm_datalink *dl = mctx->dl;
-	struct lapdm_entity *le = dl->entity;
-	uint8_t length;
-
-	length = msg->l2h[2] >> 2;
-	if (length > 0 || msg->l2h[2] & 0x02) {
-		/* G.4.3 If a supervisory frame is received with L>0 or
-		 * with the M bit set to "1", an MDL-ERROR-INDICATION
-		 * primitive with cause "S frame with incorrect
-		 * parameters" is sent to the mobile management entity. */
-		LOGP(DLLAPDM, LOGL_NOTICE,
-				"S frame with incorrect parameters\n");
-		msgb_free(msg);
-		rsl_rll_error(RLL_CAUSE_SFRM_INC_PARAM, mctx);
-		return -EIO;
+	if (!rll_msg) {
+		LOGP(DLLAPD, LOGL_ERROR, "Unsupported op %d, prim %d. Please "
+			"fix!\n", dp->oph.primitive, dp->oph.operation);
+		return -EINVAL;
 	}
 
-	if (LAPDm_ADDR_CR(mctx->addr) == le->cr.rem2loc.resp
-	 && LAPDm_CTRL_PF_BIT(mctx->ctrl)
-	 && dl->state != LAPDm_STATE_TIMER_RECOV) {
-		/* 5.4.2.2: Inidcate error on supervisory reponse F=1 */
-		LOGP(DLLAPDM, LOGL_NOTICE, "S frame response with F=1 error\n");
-		rsl_rll_error(RLL_CAUSE_UNSOL_SPRV_RESP, mctx);
-	}
+	if (!dp->oph.msg)
+		return send_rll_simple(rll_msg, mctx);
 
-	switch (dl->state) {
-	case LAPDm_STATE_IDLE:
-		/* if P=1, respond DM with F=1 (5.2.2) */
-		/* 5.4.5 all other frame types shall be discarded */
-		if (LAPDm_CTRL_PF_BIT(mctx->ctrl))
-			lapdm_send_dm(mctx); /* F=P */
-		/* fall though */
-	case LAPDm_STATE_SABM_SENT:
-	case LAPDm_STATE_DISC_SENT:
-		LOGP(DLLAPDM, LOGL_NOTICE, "S frame ignored in this state\n");
-		msgb_free(msg);
-		return 0;
-	}
-	switch (LAPDm_CTRL_S_BITS(mctx->ctrl)) {
-	case LAPDm_S_RR:
-		LOGP(DLLAPDM, LOGL_INFO, "RR received\n");
-		/* 5.5.3.1: Acknowlege all tx frames up the the N(R)-1 */
-		lapdm_acknowledge(mctx);
-
-		/* 5.5.3.2 */
-		if (LAPDm_ADDR_CR(mctx->addr) == le->cr.rem2loc.cmd
-		 && LAPDm_CTRL_PF_BIT(mctx->ctrl)) {
-		 	if (!dl->own_busy && !dl->seq_err_cond) {
-				LOGP(DLLAPDM, LOGL_NOTICE, "RR frame command "
-					"with polling bit set and we are not "
-					"busy, so we reply with RR frame\n");
-				lapdm_send_rr(mctx, 1);
-				/* NOTE: In case of sequence error condition,
-				 * the REJ frame has been transmitted when
-				 * entering the condition, so it has not be
-				 * done here
-				 */
-			} else if (dl->own_busy) {
-				LOGP(DLLAPDM, LOGL_NOTICE, "RR frame command "
-					"with polling bit set and we are busy, "
-					"so we reply with RR frame\n");
-				lapdm_send_rnr(mctx, 1);
-			}
-		} else if (LAPDm_ADDR_CR(mctx->addr) == le->cr.rem2loc.resp
-			&& LAPDm_CTRL_PF_BIT(mctx->ctrl)
-			&& dl->state == LAPDm_STATE_TIMER_RECOV) {
-			LOGP(DLLAPDM, LOGL_INFO, "RR response with F==1, "
-				"and we are in timer recovery state, so "
-				"we leave that state\n");
-			/* V(S) to the N(R) in the RR frame */
-			dl->V_send = LAPDm_CTRL_Nr(mctx->ctrl);
-			/* reset Timer T200 */
-			osmo_timer_del(&dl->t200);
-			/* 5.5.7 Clear timer recovery condition */
-			lapdm_dl_newstate(dl, LAPDm_STATE_MF_EST);
-		}
-		/* Send message, if possible due to acknowledged data */
-		rslms_send_i(mctx, __LINE__);
+	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 LAPDm_S_RNR:
-		LOGP(DLLAPDM, LOGL_INFO, "RNR received\n");
-		/* 5.5.3.1: Acknowlege all tx frames up the the N(R)-1 */
-		lapdm_acknowledge(mctx);
-
-		/* 5.5.5 */
-		/* Set peer receiver busy condition */
-		dl->peer_busy = 1;
-
-		if (LAPDm_CTRL_PF_BIT(mctx->ctrl)) {
-			if (LAPDm_ADDR_CR(mctx->addr) == le->cr.rem2loc.cmd) {
-				if (!dl->own_busy) {
-					LOGP(DLLAPDM, LOGL_INFO, "RNR poll "
-						"command and we are not busy, "
-						"so we reply with RR final "
-						"response\n");
-					/* Send RR with F=1 */
-					lapdm_send_rr(mctx, 1);
-				} else {
-					LOGP(DLLAPDM, LOGL_INFO, "RNR poll "
-						"command and we are busy, so "
-						"we reply with RNR final "
-						"response\n");
-					/* Send RNR with F=1 */
-					lapdm_send_rnr(mctx, 1);
-				}
-			} else if (dl->state == LAPDm_STATE_TIMER_RECOV) {
-				LOGP(DLLAPDM, LOGL_INFO, "RNR poll response "
-					"and we in timer recovery state, so "
-					"we leave that state\n");
-				/* 5.5.7 Clear timer recovery condition */
-				lapdm_dl_newstate(dl, LAPDm_STATE_MF_EST);
-				/* V(S) to the N(R) in the RNR frame */
-				dl->V_send = LAPDm_CTRL_Nr(mctx->ctrl);
-			}
-		} else
-			LOGP(DLLAPDM, LOGL_INFO, "RNR not polling/final state "
-				"received\n");
-
-		/* Send message, if possible due to acknowledged data */
-		rslms_send_i(mctx, __LINE__);
-
+	case LAPD_FORM_S:
+		msg->l2h[1] = LAPDm_CTRL_S(lctx->n_recv, lctx->s_u, lctx->p_f);
 		break;
-	case LAPDm_S_REJ:
-		LOGP(DLLAPDM, LOGL_INFO, "REJ received\n");
-		/* 5.5.3.1: Acknowlege all tx frames up the the N(R)-1 */
-		lapdm_acknowledge(mctx);
-
-		/* 5.5.4.1 */
-		if (dl->state != LAPDm_STATE_TIMER_RECOV) {
-			/* Clear an existing peer receiver busy condition */
-			dl->peer_busy = 0;
-			/* V(S) and V(A) to the N(R) in the REJ frame */
-			dl->V_send = dl->V_ack = LAPDm_CTRL_Nr(mctx->ctrl);
-			/* reset Timer T200 */
-			osmo_timer_del(&dl->t200);
-			/* 5.5.3.2 */
-			if (LAPDm_ADDR_CR(mctx->addr) == le->cr.rem2loc.cmd
-			 && LAPDm_CTRL_PF_BIT(mctx->ctrl)) {
-				if (!dl->own_busy && !dl->seq_err_cond) {
-					LOGP(DLLAPDM, LOGL_INFO, "REJ poll "
-						"command not in timer recovery "
-						"state and not in own busy "
-						"condition received, so we "
-						"respond with RR final "
-						"response\n");
-					lapdm_send_rr(mctx, 1);
-					/* NOTE: In case of sequence error
-					 * condition, the REJ frame has been
-					 * transmitted when entering the
-					 * condition, so it has not be done
-					 * here
-				 	 */
-				} else if (dl->own_busy) {
-					LOGP(DLLAPDM, LOGL_INFO, "REJ poll "
-						"command not in timer recovery "
-						"state and in own busy "
-						"condition received, so we "
-						"respond with RNR final "
-						"response\n");
-					lapdm_send_rnr(mctx, 1);
-				}
-			} else
-				LOGP(DLLAPDM, LOGL_INFO, "REJ response or not "
-					"polling command not in timer recovery "
-					"state received\n");
-			/* send MDL ERROR INIDCATION to L3 */
-			if (LAPDm_ADDR_CR(mctx->addr) == le->cr.rem2loc.resp
-			 && LAPDm_CTRL_PF_BIT(mctx->ctrl)) {
-				rsl_rll_error(RLL_CAUSE_UNSOL_SPRV_RESP, mctx);
-			}
-
-		} else if (LAPDm_ADDR_CR(mctx->addr) == le->cr.rem2loc.resp
-			&& LAPDm_CTRL_PF_BIT(mctx->ctrl)) {
-			LOGP(DLLAPDM, LOGL_INFO, "REJ poll response in timer "
-				"recovery state received\n");
-			/* Clear an existing peer receiver busy condition */
-			dl->peer_busy = 0;
-			/* 5.5.7 Clear timer recovery condition */
-			lapdm_dl_newstate(dl, LAPDm_STATE_MF_EST);
-			/* V(S) and V(A) to the N(R) in the REJ frame */
-			dl->V_send = dl->V_ack = LAPDm_CTRL_Nr(mctx->ctrl);
-			/* reset Timer T200 */
-			osmo_timer_del(&dl->t200);
-		} else {
-			/* Clear an existing peer receiver busy condition */
-			dl->peer_busy = 0;
-			/* V(S) and V(A) to the N(R) in the REJ frame */
-			dl->V_send = dl->V_ack = LAPDm_CTRL_Nr(mctx->ctrl);
-			/* 5.5.3.2 */
-			if (LAPDm_ADDR_CR(mctx->addr) == le->cr.rem2loc.cmd
-			 && LAPDm_CTRL_PF_BIT(mctx->ctrl)) {
-				if (!dl->own_busy && !dl->seq_err_cond) {
-					LOGP(DLLAPDM, LOGL_INFO, "REJ poll "
-						"command in timer recovery "
-						"state and not in own busy "
-						"condition received, so we "
-						"respond with RR final "
-						"response\n");
-					lapdm_send_rr(mctx, 1);
-					/* NOTE: In case of sequence error
-					 * condition, the REJ frame has been
-					 * transmitted when entering the
-					 * condition, so it has not be done
-					 * here
-				 	 */
-				} else if (dl->own_busy) {
-					LOGP(DLLAPDM, LOGL_INFO, "REJ poll "
-						"command in timer recovery "
-						"state and in own busy "
-						"condition received, so we "
-						"respond with RNR final "
-						"response\n");
-					lapdm_send_rnr(mctx, 1);
-				}
-			} else
-				LOGP(DLLAPDM, LOGL_INFO, "REJ response or not "
-					"polling command in timer recovery "
-					"state received\n");
-		}
-
-		/* FIXME: 5.5.4.2 2) */
-
-		/* Send message, if possible due to acknowledged data */
-		rslms_send_i(mctx, __LINE__);
-
+	case LAPD_FORM_U:
+		msg->l2h[1] = LAPDm_CTRL_U(lctx->s_u, lctx->p_f);
 		break;
 	default:
-		/* G.3.1 */
-		LOGP(DLLAPDM, LOGL_NOTICE, "Supervisory frame not allowed.\n");
-		msgb_free(msg);
-		rsl_rll_error(RLL_CAUSE_FRM_UNIMPL, mctx);
-		return -EINVAL;
-	}
-	msgb_free(msg);
-	return 0;
-}
-
-/* Receive a LAPDm I (Information) message from L1 */
-static int lapdm_rx_i(struct msgb *msg, struct lapdm_msg_ctx *mctx)
-{
-	struct lapdm_datalink *dl = mctx->dl;
-	struct lapdm_entity *le = dl->entity;
-	//uint8_t nr = LAPDm_CTRL_Nr(mctx->ctrl);
-	uint8_t ns = LAPDm_CTRL_I_Ns(mctx->ctrl);
-	uint8_t length;
-	int rc;
-
-	LOGP(DLLAPDM, LOGL_NOTICE, "I received\n");
-		
-	/* G.2.2 Wrong value of the C/R bit */
-	if (LAPDm_ADDR_CR(mctx->addr) == le->cr.rem2loc.resp) {
-		LOGP(DLLAPDM, LOGL_NOTICE, "I frame response not allowed\n");
 		msgb_free(msg);
-		rsl_rll_error(RLL_CAUSE_FRM_UNIMPL, mctx);
 		return -EINVAL;
 	}
+	msg->l2h[2] = LAPDm_LEN(l3_len); /* EL is set here too */
+	if (lctx->more)
+		msg->l2h[2] |= LAPDm_MORE;
 
-	length = msg->l2h[2] >> 2;
-	if (length == 0 || length + 3 > mctx->n201) {
-		/* G.4.2 If the length indicator of an I frame is set
-		 * to a numerical value L>N201 or L=0, an MDL-ERROR-INDICATION
-		 * primitive with cause "I frame with incorrect length"
-		 * is sent to the mobile management entity. */
-		LOGP(DLLAPDM, LOGL_NOTICE, "I frame length not allowed\n");
-		msgb_free(msg);
-		rsl_rll_error(RLL_CAUSE_IFRM_INC_LEN, mctx);
-		return -EIO;
-	}
-
-	/* G.4.2 If the numerical value of L is L<N201 and the M
-	 * bit is set to "1", then an MDL-ERROR-INDICATION primitive with
-	 * cause "I frame with incorrect use of M bit" is sent to the
-	 * mobile management entity. */
-	if ((msg->l2h[2] & LAPDm_MORE) && length + 3 < mctx->n201) {
-		LOGP(DLLAPDM, LOGL_NOTICE, "I frame with M bit too short\n");
-		msgb_free(msg);
-		rsl_rll_error(RLL_CAUSE_IFRM_INC_MBITS, mctx);
-		return -EIO;
-	}
-
-	switch (dl->state) {
-	case LAPDm_STATE_IDLE:
-		/* if P=1, respond DM with F=1 (5.2.2) */
-		/* 5.4.5 all other frame types shall be discarded */
-		if (LAPDm_CTRL_PF_BIT(mctx->ctrl))
-			lapdm_send_dm(mctx); /* F=P */
-		/* fall though */
-	case LAPDm_STATE_SABM_SENT:
-	case LAPDm_STATE_DISC_SENT:
-		LOGP(DLLAPDM, LOGL_NOTICE, "I frame ignored in this state\n");
-		msgb_free(msg);
-		return 0;
-	}
-
-	/* 5.7.1: N(s) sequence error */
-	if (ns != dl->V_recv) {
-		LOGP(DLLAPDM, LOGL_NOTICE, "N(S) sequence error: N(S)=%u, "
-		     "V(R)=%u\n", ns, dl->V_recv);
-		/* discard data */
-		msgb_free(msg);
-		if (!dl->seq_err_cond) {
-			/* FIXME: help me understand what exactly todo here
-			dl->seq_err_cond = 1;
-			*/
-			lapdm_send_rej(mctx, LAPDm_CTRL_PF_BIT(mctx->ctrl));
-		} else {
-		}
-		return -EIO;
-	}
-	dl->seq_err_cond = 0;
-
-	/* Increment receiver state */
-	dl->V_recv = inc_mod8(dl->V_recv);
-	LOGP(DLLAPDM, LOGL_NOTICE, "incrementing V(R) to %u\n", dl->V_recv);
-
-	/* 5.5.3.1: Acknowlege all transmitted frames up the the N(R)-1 */
-	lapdm_acknowledge(mctx); /* V(A) is also set here */
-
-	/* Only if we are not in own receiver busy condition */
-	if (!dl->own_busy) {
-		/* if the frame carries a complete segment */
-		if (!(msg->l2h[2] & LAPDm_MORE)
-		 && !dl->rcv_buffer) {
-			LOGP(DLLAPDM, LOGL_INFO, "message in single I frame\n");
-			/* send a DATA INDICATION to L3 */
-			msg->l3h = msg->l2h + 3;
-			msgb_pull_l2h(msg);
-			msg->len = length;
-			msg->tail = msg->data + length;
-			rc = send_rslms_rll_l3(RSL_MT_DATA_IND, mctx, msg);
-		} else {
-			/* create rcv_buffer */
-			if (!dl->rcv_buffer) {
-				LOGP(DLLAPDM, LOGL_INFO, "message in multiple I "
-					"frames (first message)\n");
-				dl->rcv_buffer = msgb_alloc_headroom(200+56, 56,
-								"LAPDm RX");
-				dl->rcv_buffer->l3h = dl->rcv_buffer->data;
-			}
-			/* concat. rcv_buffer */
-			if (msgb_l3len(dl->rcv_buffer) + length > 200) {
-				LOGP(DLLAPDM, LOGL_NOTICE, "Received frame "
-					"overflow!\n");
-			} else {
-				memcpy(msgb_put(dl->rcv_buffer, length),
-					msg->l2h + 3, length);
-			}
-			/* if the last segment was received */
-			if (!(msg->l2h[2] & LAPDm_MORE)) {
-				LOGP(DLLAPDM, LOGL_INFO, "message in multiple I "
-					"frames (last message)\n");
-				rc = send_rslms_rll_l3(RSL_MT_DATA_IND, mctx,
-					dl->rcv_buffer);
-				dl->rcv_buffer = NULL;
-			} else
-				LOGP(DLLAPDM, LOGL_INFO, "message in multiple I "
-					"frames (next message)\n");
-			msgb_free(msg);
-
-		}
-	} else
-		LOGP(DLLAPDM, LOGL_INFO, "I frame ignored during own receiver "
-			"busy condition\n");
-
-	/* Check for P bit */
-	if (LAPDm_CTRL_PF_BIT(mctx->ctrl)) {
-		/* 5.5.2.1 */
-		/* check if we are not in own receiver busy */
-		if (!dl->own_busy) {
-			LOGP(DLLAPDM, LOGL_INFO, "we are not busy, send RR\n");
-			/* Send RR with F=1 */
-			rc = lapdm_send_rr(mctx, 1);
-		} else {
-			LOGP(DLLAPDM, LOGL_INFO, "we are busy, send RNR\n");
-			/* Send RNR with F=1 */
-			rc = lapdm_send_rnr(mctx, 1);
-		}
-	} else {
-		/* 5.5.2.2 */
-		/* check if we are not in own receiver busy */
-		if (!dl->own_busy) {
-			/* NOTE: V(R) is already set above */
-			rc = rslms_send_i(mctx, __LINE__);
-			if (rc) {
-				LOGP(DLLAPDM, LOGL_INFO, "we are not busy and "
-					"have no pending data, send RR\n");
-				/* Send RR with F=0 */
-				return lapdm_send_rr(mctx, 0);
-			}
-			/* all I or one RR is sent, we are done */
-			return 0;
-		} else {
-			LOGP(DLLAPDM, LOGL_INFO, "we are busy, send RNR\n");
-			/* Send RNR with F=0 */
-			rc = lapdm_send_rnr(mctx, 0);
-		}
-	}
-
-	/* Send message, if possible due to acknowledged data */
-	rslms_send_i(mctx, __LINE__);
-
-	return rc;
-}
-
-/* Receive a LAPDm message from L1 */
-static int lapdm_ph_data_ind(struct msgb *msg, struct lapdm_msg_ctx *mctx)
-{
-	int rc;
-
-	/* G.2.3 EA bit set to "0" is not allowed in GSM */
-	if (!LAPDm_ADDR_EA(mctx->addr)) {
-		LOGP(DLLAPDM, LOGL_NOTICE, "EA bit 0 is not allowed in GSM\n");
-		msgb_free(msg);
-		rsl_rll_error(RLL_CAUSE_FRM_UNIMPL, mctx);
-		return -EINVAL;
-	}
-
-	if (LAPDm_CTRL_is_U(mctx->ctrl))
-		rc = lapdm_rx_u(msg, mctx);
-	else if (LAPDm_CTRL_is_S(mctx->ctrl))
-		rc = lapdm_rx_s(msg, mctx);
-	else if (LAPDm_CTRL_is_I(mctx->ctrl))
-		rc = lapdm_rx_i(msg, mctx);
-	else {
-		LOGP(DLLAPDM, LOGL_NOTICE, "unknown LAPDm format\n");
-		msgb_free(msg);
-		rc = -EINVAL;
-	}
-	return rc;
+	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)
+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;
-	mctx.addr = mctx.ctrl = 0;
 
 	/* 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;
-		mctx.n201 = N201_Bbis;
+		n201 = N201_Bbis;
 		sapi = 0;
 	} else {
 		if (mctx.link_id & 0x40) {
@@ -1630,12 +551,12 @@ static int l2_ph_data_ind(struct msgb *msg, struct lapdm_entity *le, uint8_t cha
 			/* If sent by BTS, lapdm_fmt must be B4 */
 			if (le->mode == LAPDM_MODE_MS) {
 				mctx.lapdm_fmt = LAPDm_FMT_B4;
-				mctx.n201 = N201_B4;
-				LOGP(DLLAPDM, LOGL_INFO, "fmt=B4\n");
+				n201 = N201_B4;
+				LOGP(DLLAPD, LOGL_INFO, "fmt=B4\n");
 			} else {
 				mctx.lapdm_fmt = LAPDm_FMT_B;
-				mctx.n201 = N201_AB_SACCH;
-				LOGP(DLLAPDM, LOGL_INFO, "fmt=B\n");
+				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 */
@@ -1646,8 +567,8 @@ static int l2_ph_data_ind(struct msgb *msg, struct lapdm_entity *le, uint8_t cha
 			sapi = (msg->l2h[0] >> 2) & 7;
 		} else {
 			mctx.lapdm_fmt = LAPDm_FMT_B;
-			LOGP(DLLAPDM, LOGL_INFO, "fmt=B\n");
-			mctx.n201 = 23; // FIXME: select correct size by chan.
+			LOGP(DLLAPD, LOGL_INFO, "fmt=B\n");
+			n201 = 20; // FIXME: select correct size by chan.
 			sapi = (msg->l2h[0] >> 2) & 7;
 		}
 	}
@@ -1655,7 +576,7 @@ static int l2_ph_data_ind(struct msgb *msg, struct lapdm_entity *le, uint8_t cha
 	mctx.dl = datalink_for_sapi(le, sapi);
 	/* G.2.1 No action on frames containing an unallocated SAPI. */
 	if (!mctx.dl) {
-		LOGP(DLLAPDM, LOGL_NOTICE, "Received frame for unsupported "
+		LOGP(DLLAPD, LOGL_NOTICE, "Received frame for unsupported "
 			"SAPI %d!\n", sapi);
 		msgb_free(msg);
 		return -EIO;
@@ -1665,17 +586,77 @@ static int l2_ph_data_ind(struct msgb *msg, struct lapdm_entity *le, uint8_t cha
 	case LAPDm_FMT_A:
 	case LAPDm_FMT_B:
 	case LAPDm_FMT_B4:
-		mctx.addr = msg->l2h[0];
-		if (!(mctx.addr & 0x01)) {
-			LOGP(DLLAPDM, LOGL_ERROR, "we don't support "
-				"multibyte addresses (discarding)\n");
+		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;
 		}
-		mctx.ctrl = msg->l2h[1];
-		/* obtain SAPI from address field */
-		mctx.link_id |= LAPDm_ADDR_SAPI(mctx.addr);
-		rc = lapdm_ph_data_ind(msg, &mctx);
+		/* 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 */
@@ -1683,7 +664,7 @@ static int l2_ph_data_ind(struct msgb *msg, struct lapdm_entity *le, uint8_t cha
 		break;
 	case LAPDm_FMT_Bbis:
 		/* directly pass up to layer3 */
-		LOGP(DLLAPDM, LOGL_INFO, "fmt=Bbis UI\n");
+		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);
@@ -1731,7 +712,7 @@ int lapdm_phsap_up(struct osmo_prim_hdr *oph, struct lapdm_entity *le)
 	int rc = 0;
 
 	if (oph->sap != SAP_GSM_PH) {
-		LOGP(DLLAPDM, LOGL_ERROR, "primitive for unknown SAP %u\n",
+		LOGP(DLLAPD, LOGL_ERROR, "primitive for unknown SAP %u\n",
 			oph->sap);
 		return -ENODEV;
 	}
@@ -1739,7 +720,7 @@ int lapdm_phsap_up(struct osmo_prim_hdr *oph, struct lapdm_entity *le)
 	switch (oph->primitive) {
 	case PRIM_PH_DATA:
 		if (oph->operation != PRIM_OP_INDICATION) {
-			LOGP(DLLAPDM, LOGL_ERROR, "PH_DATA is not INDICATION %u\n",
+			LOGP(DLLAPD, LOGL_ERROR, "PH_DATA is not INDICATION %u\n",
 				oph->operation);
 			return -ENODEV;
 		}
@@ -1748,7 +729,7 @@ int lapdm_phsap_up(struct osmo_prim_hdr *oph, struct lapdm_entity *le)
 		break;
 	case PRIM_PH_RTS:
 		if (oph->operation != PRIM_OP_INDICATION) {
-			LOGP(DLLAPDM, LOGL_ERROR, "PH_RTS is not INDICATION %u\n",
+			LOGP(DLLAPD, LOGL_ERROR, "PH_RTS is not INDICATION %u\n",
 				oph->operation);
 			return -ENODEV;
 		}
@@ -1775,33 +756,44 @@ int lapdm_phsap_up(struct osmo_prim_hdr *oph, struct lapdm_entity *le)
 
 /* 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 lapdm_entity *le = dl->entity;
 	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 = 23; //FIXME
+	int n201 = 20; //FIXME
+	struct osmo_dlsap_prim dp;
 
-	/* Set chan_nr and link_id for established connection */
-	memset(&dl->mctx, 0, sizeof(dl->mctx));
-	dl->mctx.dl = dl;
-	dl->mctx.n201 = n201;
-	dl->mctx.chan_nr = chan_nr;
-	dl->mctx.link_id = link_id;
+	/* 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));
+	rsl_tlv_parse(&tv, rllh->data, msgb_l2len(msg) - sizeof(*rllh));
 	if (TLVP_PRESENT(&tv, RSL_IE_L3_INFO)) {
-		msg->l3h = TLVP_VAL(&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(DLLAPDM, LOGL_ERROR, "SAPI != 0 but contention"
+			LOGP(DLLAPD, LOGL_ERROR, "SAPI != 0 but contention"
 				"resolution (discarding)\n");
 			msgb_free(msg);
 			return send_rll_simple(RSL_MT_REL_IND, &dl->mctx);
@@ -1809,67 +801,41 @@ static int rslms_rx_rll_est_req(struct msgb *msg, struct lapdm_datalink *dl)
 		/* 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);
-		LOGP(DLLAPDM, LOGL_INFO, "perform establishment with content "
-			"(SABM)\n");
 	} else {
 		/* normal establishment procedure */
+		msg->l3h = msg->l2h + sizeof(*rllh);
 		length = 0;
-		LOGP(DLLAPDM, LOGL_INFO, "perform normal establishm. (SABM)\n");
 	}
 
 	/* check if the layer3 message length exceeds N201 */
 	if (length + 3 > 21) { /* FIXME: do we know the channel N201? */
-		LOGP(DLLAPDM, LOGL_ERROR, "frame too large: %d > N201(%d) "
+		LOGP(DLLAPD, LOGL_ERROR, "frame too large: %d > N201(%d) "
 			"(discarding)\n", length + 3, 21);
 		msgb_free(msg);
 		return send_rll_simple(RSL_MT_REL_IND, &dl->mctx);
 	}
 
-	/* Flush send-queue */
-	/* Clear send-buffer */
-	lapdm_dl_flush_send(dl);
-
-	/* Discard partly received L3 message */
-	if (dl->rcv_buffer) {
-		msgb_free(dl->rcv_buffer);
-		dl->rcv_buffer = NULL;
-	}
-
-	/* Remove RLL header from msgb */
+	/* Remove RLL header from msgb and set length to L3-info */
 	msgb_pull_l2h(msg);
+	msg->len = length;
+	msg->tail = msg->data + length;
 
-	/* Push LAPDm header on msgb */
-	msg->l2h = msgb_push(msg, 3);
-	msg->l2h[0] = LAPDm_ADDR(LAPDm_LPD_NORMAL, sapi, le->cr.loc2rem.cmd);
-	msg->l2h[1] = LAPDm_CTRL_U(LAPDm_U_SABM, 1);
-	msg->l2h[2] = LAPDm_LEN(length);
-	/* Transmit-buffer carries exactly one segment */
-	memcpy(dl->tx_hist[0], msg->l2h, 3 + length);
-	dl->tx_length[0] = 3 + length;
-	/* set Vs to 0, because it is used as index when resending SABM */
-	dl->V_send = 0;
-	
-	/* Set states */
-	dl->own_busy = dl->peer_busy = 0;
-	dl->retrans_ctr = 0;
-	lapdm_dl_newstate(dl, LAPDm_STATE_SABM_SENT);
-
-	/* Tramsmit and start T200 */
-	osmo_timer_schedule(&dl->t200, T200);
-	return tx_ph_data_enqueue(dl, msg, chan_nr, link_id, n201);
+	/* 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;
 	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;
-	uint8_t n201 = 23; //FIXME
 	uint8_t ta = 0, tx_power = 0;
 
 	/* check if the layer3 message length exceeds N201 */
@@ -1883,38 +849,40 @@ static int rslms_rx_rll_udata_req(struct msgb *msg, struct lapdm_datalink *dl)
 		tx_power = *TLVP_VAL(&tv, RSL_IE_MS_POWER);
 	}
 	if (!TLVP_PRESENT(&tv, RSL_IE_L3_INFO)) {
-		LOGP(DLLAPDM, LOGL_ERROR, "unit data request without message "
+		LOGP(DLLAPD, LOGL_ERROR, "unit data request without message "
 			"error\n");
 		msgb_free(msg);
 		return -EINVAL;
 	}
-	msg->l3h = TLVP_VAL(&tv, RSL_IE_L3_INFO);
+	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 + 5 > 23) { /* FIXME: do we know the channel N201? */
-		LOGP(DLLAPDM, LOGL_ERROR, "frame too large: %d > N201(%d) "
+		LOGP(DLLAPD, LOGL_ERROR, "frame too large: %d > N201(%d) "
 			"(discarding)\n", length + 5, 23);
 		msgb_free(msg);
 		return -EIO;
 	}
 
-	LOGP(DLLAPDM, LOGL_INFO, "sending unit data (tx_power=%d, ta=%d)\n",
+	LOGP(DLLAPD, LOGL_INFO, "sending unit data (tx_power=%d, ta=%d)\n",
 		tx_power, ta);
 
-	/* Remove RLL header from msgb */
+	/* Remove RLL header from msgb and set length to L3-info */
 	msgb_pull_l2h(msg);
+	msg->len = length;
+	msg->tail = msg->data + length;
 
 	/* Push L1 + LAPDm header on msgb */
 	msg->l2h = msgb_push(msg, 2 + 3);
 	msg->l2h[0] = tx_power;
 	msg->l2h[1] = ta;
-	msg->l2h[2] = LAPDm_ADDR(LAPDm_LPD_NORMAL, sapi, le->cr.loc2rem.cmd);
+	msg->l2h[2] = LAPDm_ADDR(LAPDm_LPD_NORMAL, sapi, dl->dl.cr.loc2rem.cmd);
 	msg->l2h[3] = LAPDm_CTRL_U(LAPDm_U_UI, 0);
 	msg->l2h[4] = LAPDm_LEN(length);
 	// FIXME: short L2 header support
 
 	/* Tramsmit */
-	return tx_ph_data_enqueue(dl, msg, chan_nr, link_id, n201);
+	return tx_ph_data_enqueue(dl, msg, chan_nr, link_id, 23);
 }
 
 /* L3 requests transfer of acknowledged information */
@@ -1922,143 +890,29 @@ 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(DLLAPDM, LOGL_ERROR, "data request without message "
+		LOGP(DLLAPD, LOGL_ERROR, "data request without message "
 			"error\n");
 		msgb_free(msg);
 		return -EINVAL;
 	}
-	msg->l3h = TLVP_VAL(&tv, RSL_IE_L3_INFO);
-
-	LOGP(DLLAPDM, LOGL_INFO, "writing message to send-queue\n");
+	msg->l3h = (uint8_t *) TLVP_VAL(&tv, RSL_IE_L3_INFO);
+	length = TLVP_LEN(&tv, RSL_IE_L3_INFO);
 
-	/* Remove the RSL/RLL header */
+	/* Remove RLL header from msgb and set length to L3-info */
 	msgb_pull_l2h(msg);
+	msg->len = length;
+	msg->tail = msg->data + length;
 
-	/* Write data into the send queue */
-	msgb_enqueue(&dl->send_queue, msg);
-
-	/* Send message, if possible */
-	rslms_send_i(&dl->mctx, __LINE__);
-	return 0;
-}
-
-/* Send next I frame from queued/buffered data */
-static int rslms_send_i(struct lapdm_msg_ctx *mctx, int line)
-{
-	struct lapdm_datalink *dl = mctx->dl;
-	struct lapdm_entity *le = dl->entity;
-	uint8_t chan_nr = mctx->chan_nr;
-	uint8_t link_id = mctx->link_id;
-	uint8_t sapi = link_id & 7;
-	int k = k_sapi[sapi];
-	struct msgb *msg;
-	int length, left;
-	int rc = - 1; /* we sent nothing */
-
-	LOGP(DLLAPDM, LOGL_INFO, "%s() called from line %d\n", __func__, line);
-
-	next_frame:
-
-	if (dl->peer_busy) {
-		LOGP(DLLAPDM, LOGL_INFO, "peer busy, not sending\n");
-		return rc;
-	}
-
-	if (dl->state == LAPDm_STATE_TIMER_RECOV) {
-		LOGP(DLLAPDM, LOGL_INFO, "timer recovery, not sending\n");
-		return rc;
-	}
-
-	/* If the send state variable V(S) is equal to V(A) plus k
-	 * (where k is the maximum number of outstanding I frames - see
-	 * subclause 5.8.4), the data link layer entity shall not transmit any
-	 * new I frames, but shall retransmit an I frame as a result
-	 * of the error recovery procedures as described in subclauses 5.5.4 and
-	 * 5.5.7. */
-	if (dl->V_send == add_mod8(dl->V_ack, k)) {
-		LOGP(DLLAPDM, LOGL_INFO, "k frames outstanding, not sending "
-			"more (k=%u V(S)=%u V(A)=%u)\n", k, dl->V_send,
-			dl->V_ack);
-		return rc;
-	}
-
-	/* if we have no tx_hist yet, we create it */
-	if (!dl->tx_length[dl->V_send]) {
-		/* Get next message into send-buffer, if any */
-		if (!dl->send_buffer) {
-			next_message:
-			dl->send_out = 0;
-			dl->send_buffer = msgb_dequeue(&dl->send_queue);
-			/* No more data to be sent */
-			if (!dl->send_buffer)
-				return rc;
-			LOGP(DLLAPDM, LOGL_INFO, "get message from "
-				"send-queue\n");
-		}
-
-		/* How much is left in the send-buffer? */
-		left = msgb_l3len(dl->send_buffer) - dl->send_out;
-		/* Segment, if data exceeds N201 */
-		length = left;
-		if (length > mctx->n201 - 3)
-			length = mctx->n201 - 3;
-		LOGP(DLLAPDM, LOGL_INFO, "msg-len %d sent %d left %d N201 %d "
-			"length %d first byte %02x\n",
-			msgb_l3len(dl->send_buffer), dl->send_out, left,
-			mctx->n201, length, dl->send_buffer->l3h[0]);
-		/* If message in send-buffer is completely sent */
-		if (left == 0) {
-			msgb_free(dl->send_buffer);
-			dl->send_buffer = NULL;
-			goto next_message;
-		}
-
-		LOGP(DLLAPDM, LOGL_INFO, "send I frame %sV(S)=%d\n",
-			(left > length) ? "segment " : "", dl->V_send);
-
-		/* Create I frame (segment) and transmit-buffer content */
-		msg = msgb_alloc_headroom(23+10, 10, "LAPDm I");
-		msg->l2h = msgb_put(msg, 3 + length);
-		msg->l2h[0] = LAPDm_ADDR(LAPDm_LPD_NORMAL, sapi, le->cr.loc2rem.cmd);
-		msg->l2h[1] = LAPDm_CTRL_I(dl->V_recv, dl->V_send, 0);
-		msg->l2h[2] = LAPDm_LEN(length);
-		if (left > length)
-			msg->l2h[2] |= LAPDm_MORE;
-		memcpy(msg->l2h + 3, dl->send_buffer->l3h + dl->send_out,
-			length);
-		memcpy(dl->tx_hist[dl->V_send], msg->l2h, 3 + length);
-		dl->tx_length[dl->V_send] = 3 + length;
-		/* Add length to track how much is already in the tx buffer */
-		dl->send_out += length;
-	} else {
-		LOGP(DLLAPDM, LOGL_INFO, "resend I frame from tx buffer "
-			"V(S)=%d\n", dl->V_send);
-
-		/* Create I frame (segment) from tx_hist */
-		length = dl->tx_length[dl->V_send];
-		msg = msgb_alloc_headroom(23+10, 10, "LAPDm I");
-		msg->l2h = msgb_put(msg, length);
-		memcpy(msg->l2h, dl->tx_hist[dl->V_send], length);
-		msg->l2h[1] = LAPDm_CTRL_I(dl->V_recv, dl->V_send, 0);
-	}
-
-	/* The value of the send state variable V(S) shall be incremented by 1
-	 * at the end of the transmission of the I frame */
-	dl->V_send = inc_mod8(dl->V_send);
-
-	/* If timer T200 is not running at the time right before transmitting a
-	 * frame, when the PH-READY-TO-SEND primitive is received from the
-	 * physical layer., it shall be set. */
-	if (!osmo_timer_pending(&dl->t200))
-		osmo_timer_schedule(&dl->t200, T200);
+	/* prepare prim */
+	osmo_prim_init(&dp.oph, 0, PRIM_DL_DATA, PRIM_OP_REQUEST, msg);
 
-	tx_ph_data_enqueue(dl, msg, chan_nr, link_id, mctx->n201);
-
-	rc = 0; /* we sent something */
-	goto next_frame;
+	/* send to L2 */
+	return lapd_recv_dlsap(&dp, &dl->dl.lctx);
 }
 
 /* L3 requests suspension of data link */
@@ -2066,165 +920,79 @@ 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(DLLAPDM, LOGL_ERROR, "SAPI != 0 while suspending\n");
+		LOGP(DLLAPD, LOGL_ERROR, "SAPI != 0 while suspending\n");
 		msgb_free(msg);
 		return -EINVAL;
 	}
 
-	LOGP(DLLAPDM, LOGL_INFO, "perform suspension\n");
-
-	/* put back the send-buffer to the send-queue (first position) */
-	if (dl->send_buffer) {
-		LOGP(DLLAPDM, LOGL_INFO, "put frame in sendbuffer back to "
-			"queue\n");
-		llist_add(&dl->send_buffer->list, &dl->send_queue);
-		dl->send_buffer = NULL;
-	} else
-		LOGP(DLLAPDM, LOGL_INFO, "no frame in sendbuffer\n");
-
-	/* Clear transmit buffer, but keep send buffer */
-	lapdm_dl_flush_tx(dl);
+	/* prepare prim */
+	osmo_prim_init(&dp.oph, 0, PRIM_DL_SUSP, PRIM_OP_REQUEST, msg);
 
-	msgb_free(msg);
-
-	return send_rll_simple(RSL_MT_SUSP_CONF, &dl->mctx);
+	/* 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 lapdm_entity *le = dl->entity;
 	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 = 23; //FIXME
+	uint8_t n201 = 20; //FIXME
+	struct osmo_dlsap_prim dp;
 
-	/* Set chan_nr and link_id for established connection */
-	memset(&dl->mctx, 0, sizeof(dl->mctx));
-	dl->mctx.dl = dl;
-	dl->mctx.n201 = n201;
-	dl->mctx.chan_nr = chan_nr;
-	dl->mctx.link_id = link_id;
+	/* 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(DLLAPDM, LOGL_ERROR, "resume without message error\n");
+		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);
 
-	LOGP(DLLAPDM, LOGL_INFO, "perform re-establishment (SABM) length=%d\n",
-		length);
-	
-	/* Replace message in the send-buffer (reconnect) */
-	if (dl->send_buffer)
-		msgb_free(dl->send_buffer);
-	dl->send_out = 0;
-	if (length) {
-		/* Remove the RSL/RLL header */
-		msgb_pull_l2h(msg);
-		/* Write data into the send buffer, to be sent first */
-		dl->send_buffer = msg;
-	}
+	/* Remove RLL header from msgb and set length to L3-info */
+	msgb_pull_l2h(msg);
+	msg->len = length;
+	msg->tail = msg->data + length;
 
-	/* Discard partly received L3 message */
-	if (dl->rcv_buffer) {
-		msgb_free(dl->rcv_buffer);
-		dl->rcv_buffer = NULL;
-	}
+	/* prepare prim */
+	osmo_prim_init(&dp.oph, 0, (msg_type == RSL_MT_RES_REQ) ? PRIM_DL_RES
+		: PRIM_DL_RECON, PRIM_OP_REQUEST, msg);
 
-	/* Create new msgb (old one is now free) */
-	msg = msgb_alloc_headroom(23+10, 10, "LAPDm SABM");
-	msg->l2h = msgb_put(msg, 3);
-	msg->l2h[0] = LAPDm_ADDR(LAPDm_LPD_NORMAL, sapi, le->cr.loc2rem.cmd);
-	msg->l2h[1] = LAPDm_CTRL_U(LAPDm_U_SABM, 1);
-	msg->l2h[2] = LAPDm_LEN(0);
-	/* Transmit-buffer carries exactly one segment */
-	memcpy(dl->tx_hist[0], msg->l2h, 3);
-	dl->tx_length[0] = 3;
-	/* set Vs to 0, because it is used as index when resending SABM */
-	dl->V_send = 0;
-
-	/* Set states */
-	dl->own_busy = dl->peer_busy = 0;
-	dl->retrans_ctr = 0;
-	lapdm_dl_newstate(dl, LAPDm_STATE_SABM_SENT);
-
-	/* Tramsmit and start T200 */
-	osmo_timer_schedule(&dl->t200, T200);
-	return tx_ph_data_enqueue(dl, msg, chan_nr, link_id, n201);
+	/* 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 lapdm_entity *le = dl->entity;
 	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;
 	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;
 
-	/* local release */
-	if (mode) {
-		LOGP(DLLAPDM, LOGL_INFO, "perform local release\n");
-		msgb_free(msg);
-		/* reset Timer T200 */
-		osmo_timer_del(&dl->t200);
-		/* enter idle state */
-		lapdm_dl_newstate(dl, LAPDm_STATE_IDLE);
-		/* flush buffers */
-		lapdm_dl_flush_tx(dl);
-		lapdm_dl_flush_send(dl);
-		/* send notification to L3 */
-		return send_rll_simple(RSL_MT_REL_CONF, &dl->mctx);
-	}
-
-	/* in case we are already disconnecting */
-	if (dl->state == LAPDm_STATE_DISC_SENT)
-		return -EBUSY;
-
-	LOGP(DLLAPDM, LOGL_INFO, "perform normal release (DISC)\n");
-
 	/* Pull rllh */
 	msgb_pull(msg, msg->tail - msg->l2h);
 
-	/* Push LAPDm header on msgb */
-	msg->l2h = msgb_push(msg, 3);
-	msg->l2h[0] = LAPDm_ADDR(LAPDm_LPD_NORMAL, sapi, le->cr.loc2rem.cmd);
-	msg->l2h[1] = LAPDm_CTRL_U(LAPDm_U_DISC, 1);
-	msg->l2h[2] = LAPDm_LEN(0);
-	/* Transmit-buffer carries exactly one segment */
-	memcpy(dl->tx_hist[0], msg->l2h, 3);
-	dl->tx_length[0] = 3;
-	
-	/* Set states */
-	dl->own_busy = dl->peer_busy = 0;
-	dl->retrans_ctr = 0;
-	lapdm_dl_newstate(dl, LAPDm_STATE_DISC_SENT);
-
-	/* Tramsmit and start T200 */
-	osmo_timer_schedule(&dl->t200, T200);
-	return tx_ph_data_enqueue(dl, msg, chan_nr, link_id, dl->mctx.n201);
-}
-
-/* L3 requests release in idle state */
-static int rslms_rx_rll_rel_req_idle(struct msgb *msg, struct lapdm_datalink *dl)
-{
-	msgb_free(msg);
+	/* prepare prim */
+	osmo_prim_init(&dp.oph, 0, PRIM_DL_REL, PRIM_OP_REQUEST, msg);
+	dp.u.rel_req.mode = mode;
 
-	/* send notification to L3 */
-	return send_rll_simple(RSL_MT_REL_CONF, &dl->mctx);
+	/* send to L2 */
+	return lapd_recv_dlsap(&dp, &dl->dl.lctx);
 }
 
 /* L3 requests channel in idle state */
@@ -2238,11 +1006,11 @@ static int rslms_rx_chan_rqd(struct lapdm_channel *lc, struct msgb *msg)
 			PRIM_OP_REQUEST, NULL);
 
 	if (msgb_l2len(msg) < sizeof(*cch) + 4 + 2 + 2) {
-		LOGP(DLLAPDM, LOGL_ERROR, "Message too short for CHAN RQD!\n");
+		LOGP(DLLAPD, LOGL_ERROR, "Message too short for CHAN RQD!\n");
 		return -EINVAL;
 	}
 	if (cch->data[0] != RSL_IE_REQ_REFERENCE) {
-		LOGP(DLLAPDM, LOGL_ERROR, "Missing REQ REFERENCE IE\n");
+		LOGP(DLLAPD, LOGL_ERROR, "Missing REQ REFERENCE IE\n");
 		return -EINVAL;
 	}
 	pp.u.rach_req.ra = cch->data[1];
@@ -2250,14 +1018,14 @@ static int rslms_rx_chan_rqd(struct lapdm_channel *lc, struct msgb *msg)
 	pp.u.rach_req.is_combined_ccch = cch->data[2] >> 7;
 
 	if (cch->data[4] != RSL_IE_ACCESS_DELAY) {
-		LOGP(DLLAPDM, LOGL_ERROR, "Missing ACCESS_DELAY IE\n");
+		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(DLLAPDM, LOGL_ERROR, "Missing MS POWER IE\n");
+		LOGP(DLLAPD, LOGL_ERROR, "Missing MS POWER IE\n");
 		return -EINVAL;
 	}
 	pp.u.rach_req.tx_power = cch->data[7];
@@ -2291,65 +1059,6 @@ static int l2_ph_chan_conf(struct msgb *msg, struct lapdm_entity *le, uint32_t f
 	return rslms_sendmsg(msg, le);
 }
 
-const char *lapdm_state_names[] = {
-	"LAPDm_STATE_NULL",
-	"LAPDm_STATE_IDLE",
-	"LAPDm_STATE_SABM_SENT",
-	"LAPDm_STATE_MF_EST",
-	"LAPDm_STATE_TIMER_RECOV",
-	"LAPDm_STATE_DISC_SENT",
-};
-
-/* statefull handling for RSLms RLL messages from L3 */
-static struct l2downstate {
-	uint32_t	states;
-	int		type;
-	int		(*rout) (struct msgb *msg, struct lapdm_datalink *dl);
-} l2downstatelist[] = {
-	/* create and send UI command */
-	{ALL_STATES,
-	 RSL_MT_UNIT_DATA_REQ, rslms_rx_rll_udata_req},
-
-	/* create and send SABM command */
-	{SBIT(LAPDm_STATE_IDLE),
-	 RSL_MT_EST_REQ, rslms_rx_rll_est_req},
-
-	/* create and send I command */
-	{SBIT(LAPDm_STATE_MF_EST) |
-	 SBIT(LAPDm_STATE_TIMER_RECOV),
-	 RSL_MT_DATA_REQ, rslms_rx_rll_data_req},
-
-	/* suspend datalink */
-	{SBIT(LAPDm_STATE_MF_EST) |
-	 SBIT(LAPDm_STATE_TIMER_RECOV),
-	 RSL_MT_SUSP_REQ, rslms_rx_rll_susp_req},
-
-	/* create and send SABM command (resume) */
-	{SBIT(LAPDm_STATE_MF_EST) |
-	 SBIT(LAPDm_STATE_TIMER_RECOV),
-	 RSL_MT_RES_REQ, rslms_rx_rll_res_req},
-
-	/* create and send SABM command (reconnect) */
-	{SBIT(LAPDm_STATE_IDLE) |
-	 SBIT(LAPDm_STATE_MF_EST) |
-	 SBIT(LAPDm_STATE_TIMER_RECOV),
-	 RSL_MT_RECON_REQ, rslms_rx_rll_res_req},
-
-	/* create and send DISC command */
-	{SBIT(LAPDm_STATE_SABM_SENT) |
-	 SBIT(LAPDm_STATE_MF_EST) |
-	 SBIT(LAPDm_STATE_TIMER_RECOV) |
-	 SBIT(LAPDm_STATE_DISC_SENT),
-	 RSL_MT_REL_REQ, rslms_rx_rll_rel_req},
-
-	/* release in idle state */
-	{SBIT(LAPDm_STATE_IDLE),
-	 RSL_MT_REL_REQ, rslms_rx_rll_rel_req_idle},
-};
-
-#define L2DOWNSLLEN \
-	(sizeof(l2downstatelist) / sizeof(struct l2downstate))
-
 /* incoming RSLms RLL message from L3 */
 static int rslms_rx_rll(struct msgb *msg, struct lapdm_channel *lc)
 {
@@ -2358,11 +1067,10 @@ static int rslms_rx_rll(struct msgb *msg, struct lapdm_channel *lc)
 	uint8_t sapi = rllh->link_id & 7;
 	struct lapdm_entity *le;
 	struct lapdm_datalink *dl;
-	int i, supported = 0;
 	int rc = 0;
 
 	if (msgb_l2len(msg) < sizeof(*rllh)) {
-		LOGP(DLLAPDM, LOGL_ERROR, "Message too short for RLL hdr!\n");
+		LOGP(DLLAPD, LOGL_ERROR, "Message too short for RLL hdr!\n");
 		return -EINVAL;
 	}
 
@@ -2376,34 +1084,41 @@ static int rslms_rx_rll(struct msgb *msg, struct lapdm_channel *lc)
 	 */
 	dl = datalink_for_sapi(le, sapi);
 	if (!dl) {
-		LOGP(DLLAPDM, LOGL_ERROR, "No instance for SAPI %d!\n", sapi);
+		LOGP(DLLAPD, LOGL_ERROR, "No instance for SAPI %d!\n", sapi);
 		return -EINVAL;
 	}
 
-	LOGP(DLLAPDM, LOGL_INFO, "(%p) RLL Message '%s' received in state %s\n",
-		lc->name, rsl_msg_name(msg_type), lapdm_state_names[dl->state]);
+	LOGP(DLLAPD, LOGL_INFO, "(%p) RLL Message '%s' received.\n",
+		lc->name, rsl_msg_name(msg_type));
 
-	/* find function for current state and message */
-	for (i = 0; i < L2DOWNSLLEN; i++) {
-		if (msg_type == l2downstatelist[i].type)
-			supported = 1;
-		if ((msg_type == l2downstatelist[i].type)
-		 && ((1 << dl->state) & l2downstatelist[i].states))
-			break;
-	}
-	if (!supported) {
-		LOGP(DLLAPDM, LOGL_NOTICE, "Message unsupported.\n");
-		msgb_free(msg);
-		return 0;
-	}
-	if (i == L2DOWNSLLEN) {
-		LOGP(DLLAPDM, LOGL_NOTICE, "Message unhandled at this state.\n");
+	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);
-		return 0;
+		rc = -EINVAL;
 	}
 
-	rc = l2downstatelist[i].rout(msg, dl);
-
 	return rc;
 }
 
@@ -2415,7 +1130,7 @@ static int rslms_rx_com_chan(struct msgb *msg, struct lapdm_channel *lc)
 	int rc = 0;
 
 	if (msgb_l2len(msg) < sizeof(*cch)) {
-		LOGP(DLLAPDM, LOGL_ERROR, "Message too short for COM CHAN hdr!\n");
+		LOGP(DLLAPD, LOGL_ERROR, "Message too short for COM CHAN hdr!\n");
 		return -EINVAL;
 	}
 
@@ -2425,7 +1140,7 @@ static int rslms_rx_com_chan(struct msgb *msg, struct lapdm_channel *lc)
 		rc = rslms_rx_chan_rqd(lc, msg);
 		break;
 	default:
-		LOGP(DLLAPDM, LOGL_NOTICE, "Unknown COMMON CHANNEL msg %d!\n",
+		LOGP(DLLAPD, LOGL_NOTICE, "Unknown COMMON CHANNEL msg %d!\n",
 			msg_type);
 		msgb_free(msg);
 		return 0;
@@ -2441,7 +1156,7 @@ int lapdm_rslms_recvmsg(struct msgb *msg, struct lapdm_channel *lc)
 	int rc = 0;
 
 	if (msgb_l2len(msg) < sizeof(*rslh)) {
-		LOGP(DLLAPDM, LOGL_ERROR, "Message too short RSL hdr!\n");
+		LOGP(DLLAPD, LOGL_ERROR, "Message too short RSL hdr!\n");
 		return -EINVAL;
 	}
 
@@ -2453,7 +1168,7 @@ int lapdm_rslms_recvmsg(struct msgb *msg, struct lapdm_channel *lc)
 		rc = rslms_rx_com_chan(msg, lc);
 		break;
 	default:
-		LOGP(DLLAPDM, LOGL_ERROR, "unknown RSLms message "
+		LOGP(DLLAPD, LOGL_ERROR, "unknown RSLms message "
 			"discriminator 0x%02x", rslh->msg_discr);
 		msgb_free(msg);
 		return -EINVAL;
@@ -2465,23 +1180,24 @@ int lapdm_rslms_recvmsg(struct msgb *msg, struct lapdm_channel *lc)
 /*! \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:
-		le->cr.loc2rem.cmd = CR_MS2BS_CMD;
-		le->cr.loc2rem.resp = CR_MS2BS_RESP;
-		le->cr.rem2loc.cmd = CR_BS2MS_CMD;
-		le->cr.rem2loc.resp = CR_BS2MS_RESP;
+		lm = LAPD_MODE_USER;
 		break;
 	case LAPDM_MODE_BTS:
-		le->cr.loc2rem.cmd = CR_BS2MS_CMD;
-		le->cr.loc2rem.resp = CR_BS2MS_RESP;
-		le->cr.rem2loc.cmd = CR_MS2BS_CMD;
-		le->cr.rem2loc.resp = CR_MS2BS_RESP;
+		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;
@@ -2525,16 +1241,7 @@ void lapdm_entity_reset(struct lapdm_entity *le)
 
 	for (i = 0; i < ARRAY_SIZE(le->datalink); i++) {
 		dl = &le->datalink[i];
-		if (dl->state == LAPDm_STATE_IDLE)
-			continue;
-		LOGP(DLLAPDM, LOGL_INFO, "Resetting LAPDm instance\n");
-		/* reset Timer T200 */
-		osmo_timer_del(&dl->t200);
-		/* enter idle state */
-		dl->state = LAPDm_STATE_IDLE;
-		/* flush buffer */
-		lapdm_dl_flush_tx(dl);
-		lapdm_dl_flush_send(dl);
+		lapd_dl_reset(&dl->dl);
 	}
 }