+static int l2cap_ertm_data_rcv(struct sock *sk, struct sk_buff *skb)
+{
+ struct l2cap_pinfo *pi = l2cap_pi(sk);
+ u16 control;
+ u8 req_seq;
+ int len, next_tx_seq_offset, req_seq_offset;
+
+ control = get_unaligned_le16(skb->data);
+ skb_pull(skb, 2);
+ len = skb->len;
+
+ /*
+ * We can just drop the corrupted I-frame here.
+ * Receiver will miss it and start proper recovery
+ * procedures and ask retransmission.
+ */
+ if (l2cap_check_fcs(pi, skb))
+ goto drop;
+
+ if (__is_sar_start(control) && __is_iframe(control))
+ len -= 2;
+
+ if (pi->fcs == L2CAP_FCS_CRC16)
+ len -= 2;
+
+ if (len > pi->mps) {
+ l2cap_send_disconn_req(pi->conn, sk, ECONNRESET);
+ goto drop;
+ }
+
+ req_seq = __get_reqseq(control);
+ req_seq_offset = (req_seq - pi->expected_ack_seq) % 64;
+ if (req_seq_offset < 0)
+ req_seq_offset += 64;
+
+ next_tx_seq_offset =
+ (pi->next_tx_seq - pi->expected_ack_seq) % 64;
+ if (next_tx_seq_offset < 0)
+ next_tx_seq_offset += 64;
+
+ /* check for invalid req-seq */
+ if (req_seq_offset > next_tx_seq_offset) {
+ l2cap_send_disconn_req(pi->conn, sk, ECONNRESET);
+ goto drop;
+ }
+
+ if (__is_iframe(control)) {
+ if (len < 0) {
+ l2cap_send_disconn_req(pi->conn, sk, ECONNRESET);
+ goto drop;
+ }
+
+ l2cap_data_channel_iframe(sk, control, skb);
+ } else {
+ if (len != 0) {
+ BT_ERR("%d", len);
+ l2cap_send_disconn_req(pi->conn, sk, ECONNRESET);
+ goto drop;
+ }
+
+ l2cap_data_channel_sframe(sk, control, skb);
+ }
+
+ return 0;
+
+drop:
+ kfree_skb(skb);
+ return 0;
+}
+