Bluetooth: Implement RejActioned flag

RejActioned is used to prevent retransmission when a entity is on the
WAIT_F state, i.e., waiting for a frame with F-bit set due local busy
condition or a expired retransmission timer. (When these two events raise
they send a frame with the Poll bit set and enters in the WAIT_F state to
wait for a frame with the Final bit set.)
The local entity doesn't send I-frames(the data frames) until the receipt
of a frame with F-bit set. When that happens it also set RejActioned to false.
RejActioned is a mandatory feature of ERTM spec.

Signed-off-by: Gustavo F. Padovan <gustavo@las.ic.unicamp.br>
Signed-off-by: Marcel Holtmann <marcel@holtmann.org>

include/net/bluetooth/l2cap.h

@@ -374,6 +374,7 @@ struct l2cap_pinfo {
 #define L2CAP_CONN_SEND_PBIT       0x10
 #define L2CAP_CONN_REMOTE_BUSY     0x20
 #define L2CAP_CONN_LOCAL_BUSY      0x40
+#define L2CAP_CONN_REJ_ACT         0x80
 
 #define __mod_retrans_timer() mod_timer(&l2cap_pi(sk)->retrans_timer, \
 		jiffies +  msecs_to_jiffies(L2CAP_DEFAULT_RETRANS_TO));

net/bluetooth/l2cap.c

@@ -3362,6 +3362,16 @@ static inline int l2cap_data_channel_iframe(struct sock *sk, u16 rx_control, str
 		return 0;
 	}
 
+	if (rx_control & L2CAP_CTRL_FINAL) {
+		if (pi->conn_state & L2CAP_CONN_REJ_ACT)
+			pi->conn_state &= ~L2CAP_CONN_REJ_ACT;
+		else {
+			sk->sk_send_head = TX_QUEUE(sk)->next;
+			pi->next_tx_seq = pi->expected_ack_seq;
+			l2cap_ertm_send(sk);
+		}
+	}
+
 	pi->buffer_seq = (pi->buffer_seq + 1) % 64;
 
 	err = l2cap_sar_reassembly_sdu(sk, skb, rx_control);
@@ -3398,6 +3408,14 @@ static inline int l2cap_data_channel_sframe(struct sock *sk, u16 rx_control, str
 			pi->expected_ack_seq = tx_seq;
 			l2cap_drop_acked_frames(sk);
 
+			if (pi->conn_state & L2CAP_CONN_REJ_ACT)
+				pi->conn_state &= ~L2CAP_CONN_REJ_ACT;
+			else {
+				sk->sk_send_head = TX_QUEUE(sk)->next;
+				pi->next_tx_seq = pi->expected_ack_seq;
+				l2cap_ertm_send(sk);
+			}
+
 			if (!(pi->conn_state & L2CAP_CONN_WAIT_F))
 				break;
 
@@ -3425,10 +3443,24 @@ static inline int l2cap_data_channel_sframe(struct sock *sk, u16 rx_control, str
 		pi->expected_ack_seq = __get_reqseq(rx_control);
 		l2cap_drop_acked_frames(sk);
 
-		sk->sk_send_head = TX_QUEUE(sk)->next;
-		pi->next_tx_seq = pi->expected_ack_seq;
+		if (rx_control & L2CAP_CTRL_FINAL) {
+			if (pi->conn_state & L2CAP_CONN_REJ_ACT)
+				pi->conn_state &= ~L2CAP_CONN_REJ_ACT;
+			else {
+				sk->sk_send_head = TX_QUEUE(sk)->next;
+				pi->next_tx_seq = pi->expected_ack_seq;
+				l2cap_ertm_send(sk);
+			}
+		} else {
+			sk->sk_send_head = TX_QUEUE(sk)->next;
+			pi->next_tx_seq = pi->expected_ack_seq;
+			l2cap_ertm_send(sk);
 
-		l2cap_ertm_send(sk);
+			if (pi->conn_state & L2CAP_CONN_WAIT_F) {
+				pi->srej_save_reqseq = tx_seq;
+				pi->conn_state |= L2CAP_CONN_REJ_ACT;
+			}
+		}
 
 		break;