text: /*  Bluetooth Mesh */
  
  /*
   * Copyright (c) 2017 Intel Corporation
   *
   * SPDX-License-Identifier: Apache-2.0
   */
  
  #include "syscfg/syscfg.h"
  #define MESH_LOG_MODULE BLE_MESH_TRANS_LOG
  
  #include <errno.h>
  #include <string.h>
  
  #include "mesh/mesh.h"
  #include "mesh/glue.h"
  #include "mesh_priv.h"
  
  #include "crypto.h"
  #include "adv.h"
  #include "net.h"
  #include "app_keys.h"
  #include "rpl.h"
  #include "lpn.h"
  #include "friend.h"
  #include "access.h"
  #include "foundation.h"
  #include "settings.h"
  #include "heartbeat.h"
  #include "transport.h"
  #include "testing.h"
  
  #define AID_MASK                    ((uint8_t)(BIT_MASK(6)))
  
  #define SEG(data)                   ((data)[0] >> 7)
  #define AKF(data)                   (((data)[0] >> 6) & 0x01)
  #define AID(data)                   ((data)[0] & AID_MASK)
  #define ASZMIC(data)                (((data)[1] >> 7) & 1)
  
  #define APP_MIC_LEN(aszmic) ((aszmic) ? BT_MESH_MIC_LONG : BT_MESH_MIC_SHORT)
  
  #define UNSEG_HDR(akf, aid)         ((akf << 6) | (aid & AID_MASK))
  #define SEG_HDR(akf, aid)           (UNSEG_HDR(akf, aid) | 0x80)
  
  #define BLOCK_COMPLETE(seg_n)       (uint32_t)(((uint64_t)1 << (seg_n + 1)) - 1)
  
  #define SEQ_AUTH(iv_index, seq)     (((uint64_t)iv_index) << 24 | (uint64_t)seq)
  
  /* Number of retransmit attempts (after the initial transmit) per segment */
  #define SEG_RETRANSMIT_ATTEMPTS     (MYNEWT_VAL(BLE_MESH_SEG_RETRANSMIT_ATTEMPTS))
  
  /* "This timer shall be set to a minimum of 200 + 50 * TTL milliseconds.".
   * We use 400 since 300 is a common send duration for standard HCI, and we
   * need to have a timeout that's bigger than that.
   */
  #define SEG_RETRANSMIT_TIMEOUT_UNICAST(tx) \
  	(MYNEWT_VAL(BLE_MESH_TX_SEG_RETRANS_TIMEOUT_UNICAST) + 50 * (tx)->ttl)
  /* When sending to a group, the messages are not acknowledged, and there's no
   * reason to delay the repetitions significantly. Delaying by more than 0 ms
   * to avoid flooding the network.
   */
  #define SEG_RETRANSMIT_TIMEOUT_GROUP \
  	MYNEWT_VAL(BLE_MESH_TX_SEG_RETRANS_TIMEOUT_GROUP)
  
  #define SEG_RETRANSMIT_TIMEOUT(tx)                                             \
  	(BT_MESH_ADDR_IS_UNICAST(tx->dst) ?                                    \
  		 SEG_RETRANSMIT_TIMEOUT_UNICAST(tx) :                          \
  		 SEG_RETRANSMIT_TIMEOUT_GROUP)
  /* How long to wait for available buffers before giving up */
  #define BUF_TIMEOUT                 K_NO_WAIT
  
  static struct seg_tx {
  	struct bt_mesh_subnet *sub;
  	void                  *seg[CONFIG_BT_MESH_TX_SEG_MAX];
  	uint64_t              seq_auth;
  	uint16_t              src;
  	uint16_t              dst;
  	uint16_t              len;
  	uint8_t               hdr;
  	uint8_t               xmit;
  	uint8_t               seg_n;         /* Last segment index */
  	uint8_t               seg_o;         /* Segment being sent */
  	uint8_t               nack_count;    /* Number of unacked segs */
  	uint8_t               attempts;      /* Remaining tx attempts */
  	uint8_t               ttl;           /* Transmitted TTL value */
  	uint8_t               seg_pending;   /* Number of segments pending */
  	uint8_t               blocked:1,     /* Blocked by ongoing tx */
  					      ctl:1,         /* Control packet */
  			      		  aszmic:1,      /* MIC size */
  			      		  started:1,     /* Start cb called */
  			      		  sending:1,     /* Sending is in progress */
  			      		  friend_cred:1; /* Using Friend credentials */
  	const struct bt_mesh_send_cb *cb;
  	void                  *cb_data;
  	struct k_delayed_work retransmit; /* Retransmit timer */
  } seg_tx[MYNEWT_VAL(BLE_MESH_TX_SEG_MSG_COUNT)];
  
  static struct seg_rx {
  	struct bt_mesh_subnet   *sub;
  	void                    *seg[CONFIG_BT_MESH_RX_SEG_MAX];
  	uint64_t                    seq_auth;
  	uint16_t                    src;
  	uint16_t                    dst;
  	uint16_t                    len;
  	uint8_t                     hdr;
  	uint8_t                     seg_n:5,
  							 ctl:1,
  							 in_use:1,
  							 obo:1;
  	uint8_t                     ttl;
  	uint32_t                    block;
  	uint32_t                    last;
  	struct k_delayed_work    ack;
  } seg_rx[CONFIG_BT_MESH_RX_SEG_MSG_COUNT];
  
  
  char _k_mem_slab_buffer_[OS_ALIGN((BT_MESH_APP_SEG_SDU_MAX)*(CONFIG_BT_MESH_SEG_BUFS), OS_ALIGNMENT)];
  
  struct k_mem_slab segs = {
  	.num_blocks = CONFIG_BT_MESH_SEG_BUFS,
  	.block_size = OS_ALIGN(BT_MESH_APP_SEG_SDU_MAX, OS_ALIGNMENT),
  	.buffer = _k_mem_slab_buffer_,
  	.free_list = NULL,
  	.num_used = 0
  };
  
  static struct bt_mesh_va virtual_addrs[CONFIG_BT_MESH_LABEL_COUNT];
  
  static int send_unseg(struct bt_mesh_net_tx *tx, struct os_mbuf *sdu,
  		      const struct bt_mesh_send_cb *cb, void *cb_data,
  		      const uint8_t *ctl_op)
  {
  	struct os_mbuf *buf;
  
  	buf = bt_mesh_adv_create(BT_MESH_ADV_DATA, tx->xmit, BUF_TIMEOUT);
  	if (!buf) {
  		BT_ERR("Out of network buffers");
  		return -ENOBUFS;
  	}
  
  	net_buf_reserve(buf, BT_MESH_NET_HDR_LEN);
  
  	if (ctl_op) {
  		net_buf_add_u8(buf, TRANS_CTL_HDR(*ctl_op, 0));
  	} else if (BT_MESH_IS_DEV_KEY(tx->ctx->app_idx)) {
  		net_buf_add_u8(buf, UNSEG_HDR(0, 0));
  	} else {
  		net_buf_add_u8(buf, UNSEG_HDR(1, tx->aid));
  	}
  
  	net_buf_add_mem(buf, sdu->om_data, sdu->om_len);
  
  	if (IS_ENABLED(CONFIG_BT_MESH_FRIEND)) {
  		if (!bt_mesh_friend_queue_has_space(tx->sub->net_idx,
  						    tx->src, tx->ctx->addr,
  						    NULL, 1)) {
  			if (BT_MESH_ADDR_IS_UNICAST(tx->ctx->addr)) {
  				BT_ERR("Not enough space in Friend Queue");
  				net_buf_unref(buf);
  				return -ENOBUFS;
  			} else {
  				BT_WARN("No space in Friend Queue");
  				goto send;
  			}
  		}
  
  		if (bt_mesh_friend_enqueue_tx(tx, BT_MESH_FRIEND_PDU_SINGLE,
  					      NULL, 1, buf) &&
  		    BT_MESH_ADDR_IS_UNICAST(tx->ctx->addr)) {
  			/* PDUs for a specific Friend should only go
  			 * out through the Friend Queue.
  			 */
  			net_buf_unref(buf);
  			send_cb_finalize(cb, cb_data);
  			return 0;
  		}
  	}
  
  send:
  	return bt_mesh_net_send(tx, buf, cb, cb_data);
  }
  
  static inline uint8_t seg_len(bool ctl)
  {
  	if (ctl) {
  		return BT_MESH_CTL_SEG_SDU_MAX;
  	} else {
  		return BT_MESH_APP_SEG_SDU_MAX;
  	}
  }
  
  bool bt_mesh_tx_in_progress(void)
  {
  	int i;
  
  	for (i = 0; i < ARRAY_SIZE(seg_tx); i++) {
  		if (seg_tx[i].nack_count) {
  			return true;
  		}
  	}
  
  	return false;
  }
  
  static void seg_tx_done(struct seg_tx *tx, uint8_t seg_idx)
  {
  	k_mem_slab_free(&segs, (void **)&tx->seg[seg_idx]);
  	tx->seg[seg_idx] = NULL;
  	tx->nack_count--;
  }
  
  static bool seg_tx_blocks(struct seg_tx *tx, uint16_t src, uint16_t dst)
  {
  	return (tx->src == src) && (tx->dst == dst);
  }
  
  static void seg_tx_unblock_check(struct seg_tx *tx)
  {
  	struct seg_tx *blocked = NULL;
  	int i;
  
  	/* Unblock the first blocked tx with the same params. */
  	for (i = 0; i < ARRAY_SIZE(seg_tx); ++i) {
  		if (&seg_tx[i] != tx &&
  		    seg_tx[i].blocked &&
  		    seg_tx_blocks(tx, seg_tx[i].src, seg_tx[i].dst) &&
  		    (!blocked || seg_tx[i].seq_auth < blocked->seq_auth)) {
  			blocked = &seg_tx[i];
  		}
  	}
  
  	if (blocked) {
  		BT_DBG("Unblocked 0x%04x",
  		       (uint16_t)(blocked->seq_auth & TRANS_SEQ_ZERO_MASK));
  		blocked->blocked = false;
  		k_delayed_work_submit(&blocked->retransmit, 0);
  	}
  }
  
  static void seg_tx_reset(struct seg_tx *tx)
  {
  	int i;
  
  	k_delayed_work_cancel(&tx->retransmit);
  
  	tx->cb = NULL;
  	tx->cb_data = NULL;
  	tx->seq_auth = 0;
  	tx->sub = NULL;
  	tx->src = BT_MESH_ADDR_UNASSIGNED;
  	tx->dst = BT_MESH_ADDR_UNASSIGNED;
  	tx->blocked = false;
  
  	for (i = 0; i <= tx->seg_n && tx->nack_count; i++) {
  		if (!tx->seg[i]) {
  			continue;
  		}
  
  		seg_tx_done(tx, i);
  	}
  
  	tx->nack_count = 0;
  
  	if (atomic_test_and_clear_bit(bt_mesh.flags, BT_MESH_IVU_PENDING)) {
  		BT_DBG("Proceding with pending IV Update");
  
  		/* bt_mesh_net_iv_update() will re-enable the flag if this
  		 * wasn't the only transfer.
  		 */
  		bt_mesh_net_iv_update(bt_mesh.iv_index, false);
  	}
  }
  
  static inline void seg_tx_complete(struct seg_tx *tx, int err)
  {
  	const struct bt_mesh_send_cb *cb = tx->cb;
  	void *cb_data = tx->cb_data;
  
  	seg_tx_unblock_check(tx);
  
  	seg_tx_reset(tx);
  
  	if (cb && cb->end) {
  		cb->end(err, cb_data);
  	}
  }
  
  static void schedule_retransmit(struct seg_tx *tx)
  {
  	if (!tx->nack_count) {
  		return;
  	}
  
  	if (--tx->seg_pending || tx->sending) {
  		return;
  	}
  
  	BT_DBG("");
  
  	/* If we haven't gone through all the segments for this attempt yet,
  	 * (likely because of a buffer allocation failure or because we
  	 * called this from inside bt_mesh_net_send), we should continue the
  	 * retransmit immediately, as we just freed up a tx buffer.
  	 */
  	k_delayed_work_submit(&tx->retransmit,
  			      tx->seg_o ? 0 : K_MSEC(SEG_RETRANSMIT_TIMEOUT(tx)));
  }
  
  static void seg_send_start(uint16_t duration, int err, void *user_data)
  {
  	struct seg_tx *tx = user_data;
  
  	if (!tx->started && tx->cb && tx->cb->start) {
  		tx->cb->start(duration, err, tx->cb_data);
  		tx->started = 1U;
  	}
  
  	/* If there's an error in transmitting the 'sent' callback will never
  	 * be called. Make sure that we kick the retransmit timer also in this
  	 * case since otherwise we risk the transmission of becoming stale.
  	 */
  	if (err) {
  		schedule_retransmit(tx);
  	}
  }
  
  static void seg_sent(int err, void *user_data)
  {
  	struct seg_tx *tx = user_data;
  
  	schedule_retransmit(tx);
  }
  
  static const struct bt_mesh_send_cb seg_sent_cb = {
  	.start = seg_send_start,
  	.end = seg_sent,
  };
  
  static void seg_tx_buf_build(struct seg_tx *tx, uint8_t seg_o,
  			     struct os_mbuf *buf)
  {
  	uint16_t seq_zero = tx->seq_auth & TRANS_SEQ_ZERO_MASK;
  	uint8_t len = MIN(seg_len(tx->ctl), tx->len - (seg_len(tx->ctl) * seg_o));
  
  	net_buf_simple_add_u8(buf, tx->hdr);
  	net_buf_simple_add_u8(buf, (tx->aszmic << 7) | seq_zero >> 6);
  	net_buf_simple_add_u8(buf, (((seq_zero & 0x3f) << 2) | (seg_o >> 3)));
  	net_buf_simple_add_u8(buf, ((seg_o & 0x07) << 5) | tx->seg_n);
  	net_buf_simple_add_mem(buf, tx->seg[seg_o], len);
  }
  
  static void seg_tx_send_unacked(struct seg_tx *tx)
  {
  	if (!tx->nack_count) {
  		return;
  	}
  
  	struct bt_mesh_msg_ctx ctx = {
  		.net_idx = tx->sub->net_idx,
  		/* App idx only used by network to detect control messages: */
  		.app_idx = (tx->ctl ? BT_MESH_KEY_UNUSED : 0),
  		.addr = tx->dst,
  		.send_rel = true,
  		.send_ttl = tx->ttl,
  	};
  	struct bt_mesh_net_tx net_tx = {
  		.sub = tx->sub,
  		.ctx = &ctx,
  		.src = tx->src,
  		.xmit = tx->xmit,
  		.friend_cred = tx->friend_cred,
  		.aid = tx->hdr & AID_MASK,
  	};
  
  	if (!tx->attempts) {
  		if (BT_MESH_ADDR_IS_UNICAST(tx->dst)) {
  			BT_ERR("Ran out of retransmit attempts");
  			seg_tx_complete(tx, -ETIMEDOUT);
  		} else {
  			/* Segmented sending to groups doesn't have acks, so
  			 * running out of attempts is the expected behavior.
  			 */
  			seg_tx_complete(tx, 0);
  		}
  
  		return;
  	}
  
  	BT_DBG("SeqZero: 0x%04x Attempts: %u",
  	       (uint16_t)(tx->seq_auth & TRANS_SEQ_ZERO_MASK), tx->attempts);
  
  	tx->sending = 1U;
  
  	for (; tx->seg_o <= tx->seg_n; tx->seg_o++) {
  		struct os_mbuf *seg;
  		int err;
  
  		if (!tx->seg[tx->seg_o]) {
  			continue;
  		}
  
  		seg = bt_mesh_adv_create(BT_MESH_ADV_DATA, tx->xmit,
  					 BUF_TIMEOUT);
  		if (!seg) {
  			BT_DBG("Allocating segment failed");
  			goto end;
  		}
  
  		net_buf_reserve(seg, BT_MESH_NET_HDR_LEN);
  		seg_tx_buf_build(tx, tx->seg_o, seg);
  
  		tx->seg_pending++;
  
  		BT_DBG("Sending %u/%u", tx->seg_o, tx->seg_n);
  
  		err = bt_mesh_net_send(&net_tx, seg, &seg_sent_cb, tx);
  		if (err) {
  			BT_DBG("Sending segment failed");
  			tx->seg_pending--;
  			goto end;
  		}
  	}
  	tx->seg_o = 0U;
  	tx->attempts--;
  end:
  	if (!tx->seg_pending) {
  		k_delayed_work_submit(&tx->retransmit,
  					  SEG_RETRANSMIT_TIMEOUT(tx));
  	}
  
  	tx->sending = 0U;
  }
  
  static void seg_retransmit(struct ble_npl_event *work)
  {
  	struct seg_tx *tx = ble_npl_event_get_arg(work);
  	seg_tx_send_unacked(tx);
  }
  
  static int send_seg(struct bt_mesh_net_tx *net_tx, struct os_mbuf *sdu,
  		    const struct bt_mesh_send_cb *cb, void *cb_data,
  		    uint8_t *ctl_op)
  {
  	bool blocked = false;
  	struct seg_tx *tx;
  	uint8_t seg_o;
  	int i;
  
  	BT_DBG("src 0x%04x dst 0x%04x app_idx 0x%04x aszmic %u sdu_len %u",
  	       net_tx->src, net_tx->ctx->addr, net_tx->ctx->app_idx,
  	       net_tx->aszmic, sdu->om_len);
  
  	for (tx = NULL, i = 0; i < ARRAY_SIZE(seg_tx); i++) {
  		if (seg_tx[i].nack_count) {
  			blocked |= seg_tx_blocks(&seg_tx[i], net_tx->src,
  						 net_tx->ctx->addr);
  		} else if (!tx) {
  			tx = &seg_tx[i];
  		}
  	}
  
  	if (!tx) {
  		BT_ERR("No multi-segment message contexts available");
  		return -EBUSY;
  	}
  
  	if (ctl_op) {
  		tx->hdr = TRANS_CTL_HDR(*ctl_op, 1);
  	} else if (BT_MESH_IS_DEV_KEY(net_tx->ctx->app_idx)) {
  		tx->hdr = SEG_HDR(0, 0);
  	} else {
  		tx->hdr = SEG_HDR(1, net_tx->aid);
  	}
  
  	tx->src = net_tx->src;
  	tx->dst = net_tx->ctx->addr;
  	tx->seg_n = (sdu->om_len - 1) / seg_len(!!ctl_op);
  	tx->seg_o = 0;
  	tx->len = sdu->om_len;
  	tx->nack_count = tx->seg_n + 1;
  	tx->seq_auth = SEQ_AUTH(BT_MESH_NET_IVI_TX, bt_mesh.seq);
  	tx->sub = net_tx->sub;
  	tx->cb = cb;
  	tx->cb_data = cb_data;
  	tx->attempts = SEG_RETRANSMIT_ATTEMPTS;
  	tx->seg_pending = 0;
  	tx->xmit = net_tx->xmit;
  	tx->aszmic = net_tx->aszmic;
  	tx->friend_cred = net_tx->friend_cred;
  	tx->blocked = blocked;
  	tx->started = 0;
  	tx->ctl = !!ctl_op;
  
  	tx->ttl = net_tx->ctx->send_ttl;
  
  	BT_DBG("SeqZero 0x%04x (segs: %u)",
  	       (uint16_t)(tx->seq_auth & TRANS_SEQ_ZERO_MASK), tx->nack_count);
  
  	if (IS_ENABLED(CONFIG_BT_MESH_FRIEND) &&
  	    !bt_mesh_friend_queue_has_space(tx->sub->net_idx, net_tx->src,
  					    tx->dst, &tx->seq_auth,
  					    tx->seg_n + 1) &&
  	    BT_MESH_ADDR_IS_UNICAST(tx->dst)) {
  		BT_ERR("Not enough space in Friend Queue for %u segments",
  		       tx->seg_n + 1);
  		seg_tx_reset(tx);
  		return -ENOBUFS;
  	}
  
  	for (seg_o = 0; sdu->om_len; seg_o++) {
  		void *buf;
  		uint16_t len;
  		int err;
  
  		err = k_mem_slab_alloc(&segs, &buf);
  		if (err) {
  			BT_ERR("Out of segment buffers");
  			seg_tx_reset(tx);
  			return -ENOBUFS;
  		}
  
  		len = MIN(sdu->om_len, seg_len(!!ctl_op));
  		memcpy(buf, net_buf_simple_pull_mem(sdu, len), len);
  		BT_DBG("seg %u: %s", seg_o, bt_hex(buf, len));
  
  		tx->seg[seg_o] = buf;
  
  		if (IS_ENABLED(CONFIG_BT_MESH_FRIEND)) {
  			enum bt_mesh_friend_pdu_type type;
  
  			struct os_mbuf *seg = NET_BUF_SIMPLE(16);
  			seg_tx_buf_build(tx, seg_o, seg);
  
  			if (seg_o == tx->seg_n) {
  				type = BT_MESH_FRIEND_PDU_COMPLETE;
  			} else {
  				type = BT_MESH_FRIEND_PDU_PARTIAL;
  			}
  
  			if (bt_mesh_friend_enqueue_tx(
  				    net_tx, type, ctl_op ? NULL : &tx->seq_auth,
  				    tx->seg_n + 1, seg) &&
  			    BT_MESH_ADDR_IS_UNICAST(net_tx->ctx->addr)) {
  				/* PDUs for a specific Friend should only go
  				 * out through the Friend Queue.
  				 */
  				k_mem_slab_free(&segs, &buf);
  				tx->seg[seg_o] = NULL;
  			}
  			os_mbuf_free_chain(seg);
  		}
  
  	}
  
  	/* This can happen if segments only went into the Friend Queue */
  	if (IS_ENABLED(CONFIG_BT_MESH_FRIEND) && !tx->seg[0]) {
  		seg_tx_reset(tx);
  
  		/* If there was a callback notify sending immediately since
  		 * there's no other way to track this (at least currently)
  		 * with the Friend Queue.
  		 */
  		send_cb_finalize(cb, cb_data);
  		return 0;
  	}
  
  	if (blocked) {
  		/* Move the sequence number, so we don't end up creating
  		 * another segmented transmission with the same SeqZero while
  		 * this one is blocked.
  		 */
  		bt_mesh_next_seq();
  		BT_DBG("Blocked.");
  		return 0;
  	}
  
  	seg_tx_send_unacked(tx);
  
  	if (IS_ENABLED(CONFIG_BT_MESH_LOW_POWER) &&
  	    bt_mesh_lpn_established()) {
  		bt_mesh_lpn_poll();
  	}
  
  	return 0;
  }
  
  static int trans_encrypt(const struct bt_mesh_net_tx *tx, const uint8_t *key,
  			 struct os_mbuf *msg)
  {
  	struct bt_mesh_app_crypto_ctx crypto = {
  		.dev_key = BT_MESH_IS_DEV_KEY(tx->ctx->app_idx),
  		.aszmic = tx->aszmic,
  		.src = tx->src,
  		.dst = tx->ctx->addr,
  		.seq_num = bt_mesh.seq,
  		.iv_index = BT_MESH_NET_IVI_TX,
  	};
  
  	if (BT_MESH_ADDR_IS_VIRTUAL(tx->ctx->addr)) {
  		crypto.ad = bt_mesh_va_label_get(tx->ctx->addr);
  	}
  
  	return bt_mesh_app_encrypt(key, &crypto, msg);
  }
  
  int bt_mesh_trans_send(struct bt_mesh_net_tx *tx, struct os_mbuf *msg,
  		       const struct bt_mesh_send_cb *cb, void *cb_data)
  {
  	const uint8_t *key;
  	uint8_t aid;
  	int err;
  
  	if (msg->om_len < 1) {
  		BT_ERR("Zero-length SDU not allowed");
  		return -EINVAL;
  	}
  
  	if (msg->om_len > BT_MESH_TX_SDU_MAX) {
  		BT_ERR("Not enough segment buffers for length %u", msg->om_len);
  		return -EMSGSIZE;
  	}
  
  	if (net_buf_simple_tailroom(msg) < 4) {
  		BT_ERR("Insufficient tailroom for Transport MIC");
  		return -EINVAL;
  	}
  
  	if (tx->ctx->send_ttl == BT_MESH_TTL_DEFAULT) {
  		tx->ctx->send_ttl = bt_mesh_default_ttl_get();
  	} else if (tx->ctx->send_ttl > BT_MESH_TTL_MAX) {
  		BT_ERR("TTL too large (max 127)");
  		return -EINVAL;
  	}
  
  	if (msg->om_len > BT_MESH_SDU_UNSEG_MAX) {
  		tx->ctx->send_rel = true;
  	}
  
  	if (tx->ctx->addr == BT_MESH_ADDR_UNASSIGNED ||
  	    (!BT_MESH_ADDR_IS_UNICAST(tx->ctx->addr) &&
  	     BT_MESH_IS_DEV_KEY(tx->ctx->app_idx))) {
  		BT_ERR("Invalid destination address");
  		return -EINVAL;
  	}
  
  	err = bt_mesh_keys_resolve(tx->ctx, &tx->sub, &key, &aid);
  	if (err) {
  		return err;
  	}
  
  	BT_DBG("net_idx 0x%04x app_idx 0x%04x dst 0x%04x", tx->sub->net_idx,
  	       tx->ctx->app_idx, tx->ctx->addr);
  	BT_DBG("len %u: %s", msg->om_len, bt_hex(msg->om_data, msg->om_len));
  
  	tx->xmit = bt_mesh_net_transmit_get();
  	tx->aid = aid;
  
  	if (!tx->ctx->send_rel || net_buf_simple_tailroom(msg) < 8) {
  		tx->aszmic = 0;
  	} else {
  		tx->aszmic = 1;
  	}
  
  	err = trans_encrypt(tx, key, msg);
  	if (err) {
  		return err;
  	}
  
  	if (tx->ctx->send_rel) {
  		err = send_seg(tx, msg, cb, cb_data, NULL);
  	} else {
  		err = send_unseg(tx, msg, cb, cb_data, NULL);
  	}
  
  	return err;
  }
  
  static void seg_rx_assemble(struct seg_rx *rx, struct os_mbuf *buf,
  			    uint8_t aszmic)
  {
  	int i;
  
  	net_buf_simple_reset(buf);
  
  	for (i = 0; i <= rx->seg_n; i++) {
  		net_buf_simple_add_mem(buf, rx->seg[i],
  				       MIN(seg_len(rx->ctl),
  					   rx->len - (i * seg_len(rx->ctl))));
  	}
  
  	/* Adjust the length to not contain the MIC at the end */
  	if (!rx->ctl) {
  		buf->om_len -= APP_MIC_LEN(aszmic);
  	}
  }
  
  struct decrypt_ctx {
  	struct bt_mesh_app_crypto_ctx crypto;
  	struct os_mbuf *buf;
  	struct os_mbuf *sdu;
  	struct seg_rx *seg;
  };
  
  static int sdu_try_decrypt(struct bt_mesh_net_rx *rx, const uint8_t key[16],
  			   void *cb_data)
  {
  	const struct decrypt_ctx *ctx = cb_data;
  
  	if (ctx->seg) {
  		seg_rx_assemble(ctx->seg, ctx->buf, ctx->crypto.aszmic);
  	}
  
  	net_buf_simple_reset(ctx->sdu);
  
  	return bt_mesh_app_decrypt(key, &ctx->crypto, ctx->buf, ctx->sdu);
  }
  
  static int sdu_recv(struct bt_mesh_net_rx *rx, uint8_t hdr, uint8_t aszmic,
  		    struct os_mbuf *buf, struct os_mbuf *sdu,
  		    struct seg_rx *seg)
  {
  	struct decrypt_ctx ctx = {
  		.crypto = {
  			.dev_key = !AKF(&hdr),
  			.aszmic = aszmic,
  			.src = rx->ctx.addr,
  			.dst = rx->ctx.recv_dst,
  			.seq_num = seg ? (seg->seq_auth & 0xffffff) : rx->seq,
  			.iv_index = BT_MESH_NET_IVI_RX(rx),
  		},
  		.buf = buf,
  		.sdu = sdu,
  		.seg = seg,
  	};
  
  	BT_DBG("AKF %u AID 0x%02x", !ctx.crypto.dev_key, AID(&hdr));
  
  	if (IS_ENABLED(CONFIG_BT_MESH_FRIEND) && !rx->local_match) {
  		BT_DBG("Ignoring PDU for LPN 0x%04x of this Friend",
  		       rx->ctx.recv_dst);
  		goto done;
  	}
  
  	if (BT_MESH_ADDR_IS_VIRTUAL(rx->ctx.recv_dst)) {
  		ctx.crypto.ad = bt_mesh_va_label_get(rx->ctx.recv_dst);
  	}
  
  	rx->ctx.app_idx = bt_mesh_app_key_find(ctx.crypto.dev_key, AID(&hdr),
  					       rx, sdu_try_decrypt, &ctx);
  	if (rx->ctx.app_idx == BT_MESH_KEY_UNUSED) {
  		BT_DBG("No matching AppKey");
  		goto done;
  	}
  
  	BT_DBG("Decrypted (AppIdx: 0x%03x)", rx->ctx.app_idx);
  
  	bt_mesh_model_recv(rx, sdu);
  
  done:
      os_mbuf_free_chain(sdu);
      return 0;
  }
  
  static struct seg_tx *seg_tx_lookup(uint16_t seq_zero, uint8_t obo, uint16_t addr)
  {
  	struct seg_tx *tx;
  	int i;
  
  	for (i = 0; i < ARRAY_SIZE(seg_tx); i++) {
  		tx = &seg_tx[i];
  
  		if ((tx->seq_auth & TRANS_SEQ_ZERO_MASK) != seq_zero) {
  			continue;
  		}
  
  		if (tx->dst == addr) {
  			return tx;
  		}
  
  		/* If the expected remote address doesn't match,
  		 * but the OBO flag is set and this is the first
  		 * acknowledgement, assume it's a Friend that's
  		 * responding and therefore accept the message.
  		 */
  		if (obo && tx->nack_count == tx->seg_n + 1) {
  			tx->dst = addr;
  			return tx;
  		}
  	}
  
  	return NULL;
  }
  
  static int trans_ack(struct bt_mesh_net_rx *rx, uint8_t hdr,
  		     struct os_mbuf *buf, uint64_t *seq_auth)
  {
  	struct seg_tx *tx;
  	unsigned int bit;
  	uint32_t ack;
  	uint16_t seq_zero;
  	uint8_t obo;
  
  	if (buf->om_len < 6) {
  		BT_ERR("Too short ack message");
  		return -EINVAL;
  	}
  
  	seq_zero = net_buf_simple_pull_be16(buf);
  	obo = seq_zero >> 15;
  	seq_zero = (seq_zero >> 2) & TRANS_SEQ_ZERO_MASK;
  
  	if (IS_ENABLED(CONFIG_BT_MESH_FRIEND) && rx->friend_match) {
  		BT_DBG("Ack for LPN 0x%04x of this Friend", rx->ctx.recv_dst);
  		/* Best effort - we don't have enough info for true SeqAuth */
  		*seq_auth = SEQ_AUTH(BT_MESH_NET_IVI_RX(rx), seq_zero);
  		return 0;
  	}
  
  	ack = net_buf_simple_pull_be32(buf);
  
  	BT_DBG("OBO %u seq_zero 0x%04x ack 0x%08x", obo, seq_zero,
  	       (unsigned) ack);
  
  	tx = seg_tx_lookup(seq_zero, obo, rx->ctx.addr);
  	if (!tx) {
  		BT_WARN("No matching TX context for ack");
  		return -EINVAL;
  	}
  
  	if (!BT_MESH_ADDR_IS_UNICAST(tx->dst)) {
  		BT_ERR("Received ack for group seg");
  		return -EINVAL;
  	}
  
  	*seq_auth = tx->seq_auth;
  
  	if (!ack) {
  		BT_WARN("SDU canceled");
  		seg_tx_complete(tx, -ECANCELED);
  		return 0;
  	}
  
  	if (find_msb_set(ack) - 1 > tx->seg_n) {
  		BT_ERR("Too large segment number in ack");
  		return -EINVAL;
  	}
  
  	k_delayed_work_cancel(&tx->retransmit);
  
  	while ((bit = find_lsb_set(ack))) {
  		if (tx->seg[bit - 1]) {
  			BT_DBG("seg %u/%u acked", bit - 1, tx->seg_n);
  			seg_tx_done(tx, bit - 1);
  		}
  
  		ack &= ~BIT(bit - 1);
  	}
  
  	if (tx->nack_count) {
  		seg_tx_send_unacked(tx);
  	} else {
  		BT_DBG("SDU TX complete");
  		seg_tx_complete(tx, 0);
  	}
  
  	return 0;
  }
  
  static int ctl_recv(struct bt_mesh_net_rx *rx, uint8_t hdr,
  		    struct os_mbuf *buf, uint64_t *seq_auth)
  {
  	uint8_t ctl_op = TRANS_CTL_OP(&hdr);
  
  	BT_DBG("OpCode 0x%02x len %u", ctl_op, buf->om_len);
  
  	switch (ctl_op) {
  	case TRANS_CTL_OP_ACK:
  		return trans_ack(rx, hdr, buf, seq_auth);
  	case TRANS_CTL_OP_HEARTBEAT:
  		return bt_mesh_hb_recv(rx, buf);
  	}
  
  	/* Only acks and heartbeats may need processing without local_match */
  	if (!rx->local_match) {
  		return 0;
  	}
  
  	if (IS_ENABLED(CONFIG_BT_MESH_FRIEND) && !bt_mesh_lpn_established()) {
  		switch (ctl_op) {
  		case TRANS_CTL_OP_FRIEND_POLL:
  			return bt_mesh_friend_poll(rx, buf);
  		case TRANS_CTL_OP_FRIEND_REQ:
  			return bt_mesh_friend_req(rx, buf);
  		case TRANS_CTL_OP_FRIEND_CLEAR:
  			return bt_mesh_friend_clear(rx, buf);
  		case TRANS_CTL_OP_FRIEND_CLEAR_CFM:
  			return bt_mesh_friend_clear_cfm(rx, buf);
  		case TRANS_CTL_OP_FRIEND_SUB_ADD:
  			return bt_mesh_friend_sub_add(rx, buf);
  		case TRANS_CTL_OP_FRIEND_SUB_REM:
  			return bt_mesh_friend_sub_rem(rx, buf);
  		}
  	}
  
  #if (MYNEWT_VAL(BLE_MESH_LOW_POWER))
  	if (ctl_op == TRANS_CTL_OP_FRIEND_OFFER) {
  		return bt_mesh_lpn_friend_offer(rx, buf);
  	}
  
  	if (rx->ctx.addr == bt_mesh.lpn.frnd) {
  		if (ctl_op == TRANS_CTL_OP_FRIEND_CLEAR_CFM) {
  			return bt_mesh_lpn_friend_clear_cfm(rx, buf);
  		}
  
  		if (!rx->friend_cred) {
  			BT_WARN("Message from friend with wrong credentials");
  			return -EINVAL;
  		}
  
  		switch (ctl_op) {
  		case TRANS_CTL_OP_FRIEND_UPDATE:
  			return bt_mesh_lpn_friend_update(rx, buf);
  		case TRANS_CTL_OP_FRIEND_SUB_CFM:
  			return bt_mesh_lpn_friend_sub_cfm(rx, buf);
  		}
  	}
  #endif /* MYNEWT_VAL(BLE_MESH_LOW_POWER) */
  
  	BT_WARN("Unhandled TransOpCode 0x%02x", ctl_op);
  
  	return -ENOENT;
  }
  
  static int trans_unseg(struct os_mbuf *buf, struct bt_mesh_net_rx *rx,
  		       uint64_t *seq_auth)
  {
  	struct os_mbuf *sdu = NET_BUF_SIMPLE(BT_MESH_SDU_UNSEG_MAX);
  	uint8_t hdr;
  
  	BT_DBG("AFK %u AID 0x%02x", AKF(buf->om_data), AID(buf->om_data));
  
  	if (buf->om_len < 1) {
  		BT_ERR("Too small unsegmented PDU");
  		return -EINVAL;
  	}
  
  	if (bt_mesh_rpl_check(rx, NULL)) {
  		BT_WARN("Replay: src 0x%04x dst 0x%04x seq 0x%06x",
  			rx->ctx.addr, rx->ctx.recv_dst, (unsigned) rx->seq);
  		return -EINVAL;
  	}
  
  	hdr = net_buf_simple_pull_u8(buf);
  
  	if (rx->ctl) {
  		return ctl_recv(rx, hdr, buf, seq_auth);
  	}
  
  	if (buf->om_len < 1 + APP_MIC_LEN(0)) {
  		BT_ERR("Too short SDU + MIC");
  		return -EINVAL;
  	}
  
  	/* Adjust the length to not contain the MIC at the end */
  	buf->om_len -= APP_MIC_LEN(0);
  
  	return sdu_recv(rx, hdr, 0, buf, sdu, NULL);
  }
  
  static inline int32_t ack_timeout(struct seg_rx *rx)
  {
  	int32_t to;
  	uint8_t ttl;
  
  	if (rx->ttl == BT_MESH_TTL_DEFAULT) {
  		ttl = bt_mesh_default_ttl_get();
  	} else {
  		ttl = rx->ttl;
  	}
  
  	/* The acknowledgment timer shall be set to a minimum of
  	 * 150 + 50 * TTL milliseconds.
  	 */
  	to = K_MSEC(150 + (50 * ttl));
  
  	/* 100 ms for every not yet received segment */
  	to += K_MSEC(((rx->seg_n + 1) - popcount(rx->block)) * 100);
  
  	/* Make sure we don't send more frequently than the duration for
  	 * each packet (default is 300ms).
  	 */
  	return max(to, K_MSEC(400));
  }
  
  int bt_mesh_ctl_send(struct bt_mesh_net_tx *tx, uint8_t ctl_op, void *data,
  		     size_t data_len, const struct bt_mesh_send_cb *cb, void *cb_data)
  {
  	int err;
  	struct os_mbuf *buf = NET_BUF_SIMPLE(data_len);
  
  	net_buf_simple_init_with_data(buf, data, data_len);
  
  	if (tx->ctx->send_ttl == BT_MESH_TTL_DEFAULT) {
  		tx->ctx->send_ttl = bt_mesh_default_ttl_get();
  	} else if (tx->ctx->send_ttl > BT_MESH_TTL_MAX) {
  		BT_ERR("TTL too large (max 127)");
  		return -EINVAL;
  	}
  
  	if (data_len > BT_MESH_SDU_UNSEG_MAX) {
  		tx->ctx->send_rel = true;
  	}
  
  	tx->ctx->app_idx = BT_MESH_KEY_UNUSED;
  
  	if (tx->ctx->addr == BT_MESH_ADDR_UNASSIGNED ||
  	    BT_MESH_ADDR_IS_VIRTUAL(tx->ctx->addr)) {
  		BT_ERR("Invalid destination address");
  		return -EINVAL;
  	}
  
  	BT_DBG("src 0x%04x dst 0x%04x ttl 0x%02x ctl 0x%02x", tx->src,
  	       tx->ctx->addr, tx->ctx->send_ttl, ctl_op);
  	BT_DBG("len %zu: %s", data_len, bt_hex(data, data_len));
  
  	if (tx->ctx->send_rel) {
  		err = send_seg(tx, buf, cb, cb_data, &ctl_op);
  	} else {
  		err = send_unseg(tx, buf, cb, cb_data, &ctl_op);
  	}
  	os_mbuf_free_chain(buf);
  	return err;
  }
  
  static int send_ack(struct bt_mesh_subnet *sub, uint16_t src, uint16_t dst,
  		    uint8_t ttl, uint64_t *seq_auth, uint32_t block, uint8_t obo)
  {
  	struct bt_mesh_msg_ctx ctx = {
  		.net_idx = sub->net_idx,
  		.app_idx = BT_MESH_KEY_UNUSED,
  		.addr = dst,
  		.send_ttl = ttl,
  	};
  	struct bt_mesh_net_tx tx = {
  		.sub = sub,
  		.ctx = &ctx,
  		.src = obo ? bt_mesh_primary_addr() : src,
  		.xmit = bt_mesh_net_transmit_get(),
  	};
  	uint16_t seq_zero = *seq_auth & TRANS_SEQ_ZERO_MASK;
  	uint8_t buf[6];
  
  	BT_DBG("SeqZero 0x%04x Block 0x%08x OBO %u", seq_zero,
  	       (unsigned) block, obo);
  
  	if (bt_mesh_lpn_established()) {
  		BT_WARN("Not sending ack when LPN is enabled");
  		return 0;
  	}
  
  	/* This can happen if the segmented message was destined for a group
  	 * or virtual address.
  	 */
  	if (!BT_MESH_ADDR_IS_UNICAST(src)) {
  		BT_DBG("Not sending ack for non-unicast address");
  		return 0;
  	}
  
  	sys_put_be16(((seq_zero << 2) & 0x7ffc) | (obo << 15), buf);
  	sys_put_be32(block, &buf[2]);
  
  	return bt_mesh_ctl_send(&tx, TRANS_CTL_OP_ACK, buf, sizeof(buf),
  				NULL, NULL);
  }
  
  static void seg_rx_reset(struct seg_rx *rx, bool full_reset)
  {
  	int i;
  
  	BT_DBG("rx %p", rx);
  
  	k_delayed_work_cancel(&rx->ack);
  
  	if (IS_ENABLED(CONFIG_BT_MESH_FRIEND) && rx->obo &&
  	    rx->block != BLOCK_COMPLETE(rx->seg_n)) {
  		BT_WARN("Clearing incomplete buffers from Friend queue");
  		bt_mesh_friend_clear_incomplete(rx->sub, rx->src, rx->dst,
  						&rx->seq_auth);
  	}
  
  	for (i = 0; i <= rx->seg_n; i++) {
  		if (!rx->seg[i]) {
  			continue;
  		}
  
  		k_mem_slab_free(&segs, &rx->seg[i]);
  		rx->seg[i] = NULL;
  	}
  
  	rx->in_use = 0;
  
  	/* We don't always reset these values since we need to be able to
  	 * send an ack if we receive a segment after we've already received
  	 * the full SDU.
  	 */
  	if (full_reset) {
  		rx->seq_auth = 0;
  		rx->sub = NULL;
  		rx->src = BT_MESH_ADDR_UNASSIGNED;
  		rx->dst = BT_MESH_ADDR_UNASSIGNED;
  	}
  }
  
  static void seg_ack(struct ble_npl_event *work)
  {
  	struct seg_rx *rx = ble_npl_event_get_arg(work);
  	int32_t timeout;
  
  	BT_DBG("rx %p", rx);
  
  	if (k_uptime_get_32() - rx->last > K_SECONDS(60)) {
  		BT_WARN("Incomplete timer expired");
  		seg_rx_reset(rx, false);
  
  		if (IS_ENABLED(CONFIG_BT_TESTING)) {
  			bt_test_mesh_trans_incomp_timer_exp();
  		}
  
  		return;
  	}
  
  	send_ack(rx->sub, rx->dst, rx->src, rx->ttl, &rx->seq_auth,
  		 rx->block, rx->obo);
  
  	timeout = ack_timeout(rx);
  	k_delayed_work_submit(&rx->ack, K_MSEC(timeout));
  }
  
  static inline bool sdu_len_is_ok(bool ctl, uint8_t seg_n)
  {
  	return (seg_n < CONFIG_BT_MESH_RX_SEG_MAX);
  }
  
  static struct seg_rx *seg_rx_find(struct bt_mesh_net_rx *net_rx,
  				  const uint64_t *seq_auth)
  {
  	int i;
  
  	for (i = 0; i < ARRAY_SIZE(seg_rx); i++) {
  		struct seg_rx *rx = &seg_rx[i];
  
  		if (rx->src != net_rx->ctx.addr ||
  		    rx->dst != net_rx->ctx.recv_dst) {
  			continue;
  		}
  
  		/* Return newer RX context in addition to an exact match, so
  		 * the calling function can properly discard an old SeqAuth.
  		 */
  		if (rx->seq_auth >= *seq_auth) {
  			return rx;
  		}
  
  		if (rx->in_use) {
  			BT_WARN("Duplicate SDU from src 0x%04x",
  				net_rx->ctx.addr);
  
  			/* Clear out the old context since the sender
  			 * has apparently started sending a new SDU.
  			 */
  			seg_rx_reset(rx, true);
  
  			/* Return non-match so caller can re-allocate */
  			return NULL;
  		}
  	}
  
  	return NULL;
  }
  
  static bool seg_rx_is_valid(struct seg_rx *rx, struct bt_mesh_net_rx *net_rx,
  			    const uint8_t *hdr, uint8_t seg_n)
  {
  	if (rx->hdr != *hdr || rx->seg_n != seg_n) {
  		BT_ERR("Invalid segment for ongoing session");
  		return false;
  	}
  
  	if (rx->src != net_rx->ctx.addr || rx->dst != net_rx->ctx.recv_dst) {
  		BT_ERR("Invalid source or destination for segment");
  		return false;
  	}
  
  	if (rx->ctl != net_rx->ctl) {
  		BT_ERR("Inconsistent CTL in segment");
  		return false;
  	}
  
  	return true;
  }
  
  static struct seg_rx *seg_rx_alloc(struct bt_mesh_net_rx *net_rx,
  				   const uint8_t *hdr, const uint64_t *seq_auth,
  				   uint8_t seg_n)
  {
  	int i;
  
  	/* No race condition on this check, as this function only executes in
  	 * the collaborative Bluetooth rx thread:
  	 */
  	if (k_mem_slab_num_free_get(&segs) < 1) {
  		BT_WARN("Not enough segments for incoming message");
  		return NULL;
  	}
  
  	for (i = 0; i < ARRAY_SIZE(seg_rx); i++) {
  		struct seg_rx *rx = &seg_rx[i];
  
  		if (rx->in_use) {
  			continue;
  		}
  
  		rx->in_use = 1;
  		rx->sub = net_rx->sub;
  		rx->ctl = net_rx->ctl;
  		rx->seq_auth = *seq_auth;
  		rx->seg_n = seg_n;
  		rx->hdr = *hdr;
  		rx->ttl = net_rx->ctx.send_ttl;
  		rx->src = net_rx->ctx.addr;
  		rx->dst = net_rx->ctx.recv_dst;
  		rx->block = 0;
  
  		BT_DBG("New RX context. Block Complete 0x%08x",
  		       (unsigned) BLOCK_COMPLETE(seg_n));
  
  		return rx;
  	}
  
  	return NULL;
  }
  
  static int trans_seg(struct os_mbuf *buf, struct bt_mesh_net_rx *net_rx,
  		     enum bt_mesh_friend_pdu_type *pdu_type, uint64_t *seq_auth,
  		     uint8_t *seg_count)
  {
  	struct bt_mesh_rpl *rpl = NULL;
  	struct seg_rx *rx;
  	uint8_t *hdr = buf->om_data;
  	uint16_t seq_zero;
  	uint8_t seg_n;
  	uint8_t seg_o;
  	int err;
  
  	if (buf->om_len < 5) {
  		BT_ERR("Too short segmented message (len %u)", buf->om_len);
  		return -EINVAL;
  	}
  
  	if (bt_mesh_rpl_check(net_rx, &rpl)) {
  		BT_WARN("Replay: src 0x%04x dst 0x%04x seq 0x%06x",
  			net_rx->ctx.addr, net_rx->ctx.recv_dst, net_rx->seq);
  		return -EINVAL;
  	}
  
  	BT_DBG("ASZMIC %u AKF %u AID 0x%02x", ASZMIC(hdr), AKF(hdr), AID(hdr));
  
  	net_buf_simple_pull(buf, 1);
  
  	seq_zero = net_buf_simple_pull_be16(buf);
  	seg_o = (seq_zero & 0x03) << 3;
  	seq_zero = (seq_zero >> 2) & TRANS_SEQ_ZERO_MASK;
  	seg_n = net_buf_simple_pull_u8(buf);
  	seg_o |= seg_n >> 5;
  	seg_n &= 0x1f;
  
  	BT_DBG("SeqZero 0x%04x SegO %u SegN %u", seq_zero, seg_o, seg_n);
  
  	if (seg_o > seg_n) {
  		BT_ERR("SegO greater than SegN (%u > %u)", seg_o, seg_n);
  		return -EINVAL;
  	}
  
  	/* According to Mesh 1.0 specification:
  	 * "The SeqAuth is composed of the IV Index and the sequence number
  	 *  (SEQ) of the first segment"
  	 *
  	 * Therefore we need to calculate very first SEQ in order to find
  	 * seqAuth. We can calculate as below:
  	 *
  	 * SEQ(0) = SEQ(n) - (delta between seqZero and SEQ(n) by looking into
  	 * 14 least significant bits of SEQ(n))
  	 *
  	 * Mentioned delta shall be >= 0, if it is not then seq_auth will
  	 * be broken and it will be verified by the code below.
  	 */
  	*seq_auth = SEQ_AUTH(BT_MESH_NET_IVI_RX(net_rx),
  			     (net_rx->seq -
  			      ((((net_rx->seq & BIT_MASK(14)) - seq_zero)) &
  			       BIT_MASK(13))));
  
  	*seg_count = seg_n + 1;
  
  	/* Look for old RX sessions */
  	rx = seg_rx_find(net_rx, seq_auth);
  	if (rx) {
  		/* Discard old SeqAuth packet */
  		if (rx->seq_auth > *seq_auth) {
  			BT_WARN("Ignoring old SeqAuth");
  			return -EINVAL;
  		}
  
  		if (!seg_rx_is_valid(rx, net_rx, hdr, seg_n)) {
  			return -EINVAL;
  		}
  
  		if (rx->in_use) {
  			BT_DBG("Existing RX context. Block 0x%08x",
  			       (unsigned) rx->block);
  			goto found_rx;
  		}
  
  		if (rx->block == BLOCK_COMPLETE(rx->seg_n)) {
  			BT_DBG("Got segment for already complete SDU");
  
  			send_ack(net_rx->sub, net_rx->ctx.recv_dst,
  				 net_rx->ctx.addr, net_rx->ctx.send_ttl,
  				 seq_auth, rx->block, rx->obo);
  
  			if (rpl) {
  				bt_mesh_rpl_update(rpl, net_rx);
  			}
  
  			return -EALREADY;
  		}
  
  		/* We ignore instead of sending block ack 0 since the
  		 * ack timer is always smaller than the incomplete
  		 * timer, i.e. the sender is misbehaving.
  		 */
  		BT_WARN("Got segment for canceled SDU");
  		return -EINVAL;
  	}
  
  	/* Bail out early if we're not ready to receive such a large SDU */
  	if (!sdu_len_is_ok(net_rx->ctl, seg_n)) {
  		BT_ERR("Too big incoming SDU length");
  		send_ack(net_rx->sub, net_rx->ctx.recv_dst, net_rx->ctx.addr,
  			 net_rx->ctx.send_ttl, seq_auth, 0,
  			 net_rx->friend_match);
  		return -EMSGSIZE;
  	}
  
  	/* Verify early that there will be space in the Friend Queue(s) in
  	 * case this message is destined to an LPN of ours.
  	 */
  	if (IS_ENABLED(CONFIG_BT_MESH_FRIEND) &&
  	    net_rx->friend_match && !net_rx->local_match &&
  	    !bt_mesh_friend_queue_has_space(net_rx->sub->net_idx,
  					    net_rx->ctx.addr,
  					    net_rx->ctx.recv_dst, seq_auth,
  					    *seg_count)) {
  		BT_ERR("No space in Friend Queue for %u segments", *seg_count);
  		send_ack(net_rx->sub, net_rx->ctx.recv_dst, net_rx->ctx.addr,
  			 net_rx->ctx.send_ttl, seq_auth, 0,
  			 net_rx->friend_match);
  		return -ENOBUFS;
  	}
  
  	/* Look for free slot for a new RX session */
  	rx = seg_rx_alloc(net_rx, hdr, seq_auth, seg_n);
  	if (!rx) {
  		/* Warn but don't cancel since the existing slots willl
  		 * eventually be freed up and we'll be able to process
  		 * this one.
  		 */
  		BT_WARN("No free slots for new incoming segmented messages");
  		return -ENOMEM;
  	}
  
  	rx->obo = net_rx->friend_match;
  
  found_rx:
  	if (BIT(seg_o) & rx->block) {
  		BT_DBG("Received already received fragment");
  		return -EALREADY;
  	}
  
  	/* All segments, except the last one, must either have 8 bytes of
  	 * payload (for 64bit Net MIC) or 12 bytes of payload (for 32bit
  	 * Net MIC).
  	 */
  	if (seg_o == seg_n) {
  		/* Set the expected final buffer length */
  		rx->len = seg_n * seg_len(rx->ctl) + buf->om_len;
  		BT_DBG("Target len %u * %u + %u = %u", seg_n, seg_len(rx->ctl),
  		       buf->om_len, rx->len);
  
  		if (rx->len > BT_MESH_RX_SDU_MAX) {
  			BT_ERR("Too large SDU len");
  			send_ack(net_rx->sub, net_rx->ctx.recv_dst,
  				 net_rx->ctx.addr, net_rx->ctx.send_ttl,
  				 seq_auth, 0, rx->obo);
  			seg_rx_reset(rx, true);
  			return -EMSGSIZE;
  		}
  	} else {
  		if (buf->om_len != seg_len(rx->ctl)) {
  			BT_ERR("Incorrect segment size for message type");
  			return -EINVAL;
  		}
  	}
  
  	/* Reset the Incomplete Timer */
  	rx->last = k_uptime_get_32();
  
  	if (!k_delayed_work_remaining_get(&rx->ack) &&
  	    !bt_mesh_lpn_established()) {
  		int32_t timeout = ack_timeout(rx);
  
  		k_delayed_work_submit(&rx->ack, K_MSEC(timeout));
  	}
  
  	/* Allocated segment here */
  	err = k_mem_slab_alloc(&segs, &rx->seg[seg_o]);
  	if (err) {
  		BT_WARN("Unable allocate buffer for Seg %u", seg_o);
  		return -ENOBUFS;
  	}
  
  	os_mbuf_copydata(buf, 0, buf->om_len, rx->seg[seg_o]);
  	BT_DBG("copied %s", bt_hex(rx->seg[seg_o], rx->len));
  
  	BT_DBG("Received %u/%u", seg_o, seg_n);
  
  	/* Mark segment as received */
  	rx->block |= BIT(seg_o);
  
  	if (rx->block != BLOCK_COMPLETE(seg_n)) {
  		*pdu_type = BT_MESH_FRIEND_PDU_PARTIAL;
  		return 0;
  	}
  
  	BT_DBG("Complete SDU");
  
  	if (rpl) {
  		bt_mesh_rpl_update(rpl, net_rx);
  	}
  
  	*pdu_type = BT_MESH_FRIEND_PDU_COMPLETE;
  
  	k_delayed_work_cancel(&rx->ack);
  	send_ack(net_rx->sub, net_rx->ctx.recv_dst, net_rx->ctx.addr,
  		 net_rx->ctx.send_ttl, seq_auth, rx->block, rx->obo);
  
  	if (net_rx->ctl) {
  		struct os_mbuf *sdu = NET_BUF_SIMPLE(BT_MESH_RX_CTL_MAX);
  		seg_rx_assemble(rx, sdu, 0U);
  		err = ctl_recv(net_rx, *hdr, sdu, seq_auth);
  	} else if (rx->len < 1 + APP_MIC_LEN(ASZMIC(hdr))) {
  		BT_ERR("Too short SDU + MIC");
  		err = -EINVAL;
  	} else {
  		struct os_mbuf *seg_buf = NET_BUF_SIMPLE(BT_MESH_RX_SDU_MAX);
  		struct os_mbuf *sdu;
  
  		/* Decrypting in place to avoid creating two assembly buffers.
  		 * We'll reassemble the buffer from the segments before each
  		 * decryption attempt.
  		 */
  		net_buf_simple_init(seg_buf, 0);
  
  	    sdu = NET_BUF_SIMPLE(rx->len - APP_MIC_LEN(ASZMIC(hdr)));
  		net_buf_simple_init_with_data(
  			sdu, seg_buf->om_data, rx->len - APP_MIC_LEN(ASZMIC(hdr)));
  
  		err = sdu_recv(net_rx, *hdr, ASZMIC(hdr), seg_buf, sdu, rx);
  		os_mbuf_free_chain(seg_buf);
  	}
  
  	seg_rx_reset(rx, false);
  	return err;
  }
  
  int bt_mesh_trans_recv(struct os_mbuf *buf, struct bt_mesh_net_rx *rx)
  {
  	uint64_t seq_auth = TRANS_SEQ_AUTH_NVAL;
  	enum bt_mesh_friend_pdu_type pdu_type = BT_MESH_FRIEND_PDU_SINGLE;
  	struct net_buf_simple_state state;
  	uint8_t seg_count = 0;
  	int err;
  
  	if (IS_ENABLED(CONFIG_BT_MESH_FRIEND)) {
  		rx->friend_match = bt_mesh_friend_match(rx->sub->net_idx,
  							rx->ctx.recv_dst);
  	} else {
  		rx->friend_match = false;
  	}
  
  	BT_DBG("src 0x%04x dst 0x%04x seq 0x%08x friend_match %u",
  	       rx->ctx.addr, rx->ctx.recv_dst, (unsigned) rx->seq,
  	       rx->friend_match);
  
  	/* Remove network headers */
  	net_buf_simple_pull(buf, BT_MESH_NET_HDR_LEN);
  
  	BT_DBG("Payload %s", bt_hex(buf->om_data, buf->om_len));
  
  	if (IS_ENABLED(CONFIG_BT_TESTING)) {
  		bt_test_mesh_net_recv(rx->ctx.recv_ttl, rx->ctl, rx->ctx.addr,
  				      rx->ctx.recv_dst, buf->om_data, buf->om_len);
  	}
  
  	/* If LPN mode is enabled messages are only accepted when we've
  	 * requested the Friend to send them. The messages must also
  	 * be encrypted using the Friend Credentials.
  	 */
  	if ((MYNEWT_VAL(BLE_MESH_LOW_POWER)) &&
  	    bt_mesh_lpn_established() && rx->net_if == BT_MESH_NET_IF_ADV &&
  	    (!bt_mesh_lpn_waiting_update() || !rx->friend_cred)) {
  		BT_WARN("Ignoring unexpected message in Low Power mode");
  		return -EAGAIN;
  	}
  
  	/* Save the app-level state so the buffer can later be placed in
  	 * the Friend Queue.
  	 */
  	net_buf_simple_save(buf, &state);
  
  	if (SEG(buf->om_data)) {
  		/* Segmented messages must match a local element or an
  		 * LPN of this Friend.
  		 */
  		if (!rx->local_match && !rx->friend_match) {
  			return 0;
  		}
  
  		err = trans_seg(buf, rx, &pdu_type, &seq_auth, &seg_count);
  	} else {
  		seg_count = 1;
  		err = trans_unseg(buf, rx, &seq_auth);
  	}
  
  	/* Notify LPN state machine so a Friend Poll will be sent. If the
  	 * message was a Friend Update it's possible that a Poll was already
  	 * queued for sending, however that's fine since then the
  	 * bt_mesh_lpn_waiting_update() function will return false:
  	 * we still need to go through the actual sending to the bearer and
  	 * wait for ReceiveDelay before transitioning to WAIT_UPDATE state.
  	 * Another situation where we want to notify the LPN state machine
  	 * is if it's configured to use an automatic Friendship establishment
  	 * timer, in which case we want to reset the timer at this point.
  	 *
  	 */
  	if (IS_ENABLED(CONFIG_BT_MESH_LOW_POWER) &&
  	    (bt_mesh_lpn_timer() ||
  	     (bt_mesh_lpn_established() && bt_mesh_lpn_waiting_update()))) {
  		bt_mesh_lpn_msg_received(rx);
  	}
  
  	net_buf_simple_restore(buf, &state);
  
  	if (IS_ENABLED(CONFIG_BT_MESH_FRIEND) && rx->friend_match && !err) {
  		if (seq_auth == TRANS_SEQ_AUTH_NVAL) {
  			bt_mesh_friend_enqueue_rx(rx, pdu_type, NULL,
  						  seg_count, buf);
  		} else {
  			bt_mesh_friend_enqueue_rx(rx, pdu_type, &seq_auth,
  						  seg_count, buf);
  		}
  	}
  
  	return err;
  }
  
  void bt_mesh_rx_reset(void)
  {
  	int i;
  
  	BT_DBG("");
  
  	for (i = 0; i < ARRAY_SIZE(seg_rx); i++) {
  		seg_rx_reset(&seg_rx[i], true);
  	}
  }
  
  void bt_mesh_trans_reset(void)
  {
  	int i;
  
  	bt_mesh_rx_reset();
  
  	BT_DBG("");
  
  	for (i = 0; i < ARRAY_SIZE(seg_tx); i++) {
  		seg_tx_reset(&seg_tx[i]);
  	}
  
  	for (i = 0; i < ARRAY_SIZE(virtual_addrs); i++) {
  		if (virtual_addrs[i].ref) {
  			virtual_addrs[i].ref = 0U;
  			virtual_addrs[i].changed = 1U;
  		}
  	}
  
  	bt_mesh_rpl_clear();
  
  	if (IS_ENABLED(CONFIG_BT_SETTINGS)) {
  		bt_mesh_store_label();
  	}
  }
  
  void bt_mesh_trans_init(void)
  {
  	int i, rc;
  
  	/* We need to initialize memslab free list here */
  	rc = create_free_list(&segs);
  	if (rc) {
  		BT_ERR("Failed to create free memslab list (error: %d)", rc);
  	}
  
  	for (i = 0; i < ARRAY_SIZE(seg_tx); i++) {
  		k_delayed_work_init(&seg_tx[i].retransmit, seg_retransmit);
  		k_delayed_work_add_arg(&seg_tx[i].retransmit, &seg_tx[i]);
  	}
  
  	/* XXX Probably we need mempool for that.
  	 *  For now we increase MSYS_1_BLOCK_COUNT
  	 */
  	for (i = 0; i < ARRAY_SIZE(seg_rx); i++) {
  		k_delayed_work_init(&seg_rx[i].ack, seg_ack);
  		k_delayed_work_add_arg(&seg_rx[i].ack, &seg_rx[i]);
  	}
  }
  
  struct bt_mesh_va *bt_mesh_va_get(uint16_t index)
  {
  	if (index >= ARRAY_SIZE(virtual_addrs)) {
  		return NULL;
  	}
  
  	return &virtual_addrs[index];
  }
  
  static inline void va_store(struct bt_mesh_va *store)
  {
  	store->changed = 1U;
  	if (IS_ENABLED(CONFIG_BT_SETTINGS)) {
  		bt_mesh_store_label();
  	}
  }
  
  uint8_t bt_mesh_va_add(const uint8_t uuid[16], uint16_t *addr)
  {
  	struct bt_mesh_va *va = NULL;
  	int err;
  
  	for (int i = 0; i < ARRAY_SIZE(virtual_addrs); i++) {
  		if (!virtual_addrs[i].ref) {
  			if (!va) {
  				va = &virtual_addrs[i];
  			}
  
  			continue;
  		}
  
  		if (!memcmp(uuid, virtual_addrs[i].uuid,
  			    ARRAY_SIZE(virtual_addrs[i].uuid))) {
  			*addr = virtual_addrs[i].addr;
  			virtual_addrs[i].ref++;
  			va_store(&virtual_addrs[i]);
  			return STATUS_SUCCESS;
  		}
  	}
  
  	if (!va) {
  		return STATUS_INSUFF_RESOURCES;
  	}
  
  	memcpy(va->uuid, uuid, ARRAY_SIZE(va->uuid));
  	err = bt_mesh_virtual_addr(uuid, &va->addr);
  	if (err) {
  		va->addr = BT_MESH_ADDR_UNASSIGNED;
  		return STATUS_UNSPECIFIED;
  	}
  
  	va->ref = 1;
  	va_store(va);
  
  	*addr = va->addr;
  
  	return STATUS_SUCCESS;
  }
  
  uint8_t bt_mesh_va_del(const uint8_t uuid[16], uint16_t *addr)
  {
  	struct bt_mesh_va *va = NULL;
  
  	for (int i = 0; i < ARRAY_SIZE(virtual_addrs); i++) {
  		if (virtual_addrs[i].ref &&
  		    !memcmp(uuid, virtual_addrs[i].uuid,
  			    ARRAY_SIZE(virtual_addrs[i].uuid))) {
  			va = &virtual_addrs[i];
  			break;
  		}
  	}
  
  	if (!va) {
  		return STATUS_CANNOT_REMOVE;
  	}
  
  	va->ref--;
  	if (addr) {
  		*addr = va->addr;
  	}
  
  	va_store(va);
  	return STATUS_SUCCESS;
  }
  
  struct bt_mesh_va *bt_mesh_va_find(uint8_t uuid[16])
  {
  	for (int i = 0; i < ARRAY_SIZE(virtual_addrs); i++) {
  		if (virtual_addrs[i].ref &&
  		    !memcmp(uuid, virtual_addrs[i].uuid,
  			    ARRAY_SIZE(virtual_addrs[i].uuid))) {
  			return &virtual_addrs[i];
  		}
  	}
  
  	return NULL;
  }
  
  uint8_t *bt_mesh_va_label_get(uint16_t addr)
  {
  	int i;
  
  	BT_DBG("addr 0x%04x", addr);
  
  	for (i = 0; i < ARRAY_SIZE(virtual_addrs); i++) {
  		if (virtual_addrs[i].ref && virtual_addrs[i].addr == addr) {
  			BT_DBG("Found Label UUID for 0x%04x: %s", addr,
  			       bt_hex(virtual_addrs[i].uuid, 16));
  			return virtual_addrs[i].uuid;
  		}
  	}
  
  	BT_WARN("No matching Label UUID for 0x%04x", addr);
  
  	return NULL;
  }
  