Bluetooth: Initial support for retransmission of packets with REJ frames

When receiving an I-frame with unexpected txSeq, receiver side start the
recovery procedure by sending a REJ S-frame to the transmitter side. So
the transmitter can re-send the lost I-frame.

This patch just adds a basic support for retransmission, it doesn't
mean that ERTM now has full support for packet retransmission.

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

diff --git a/include/net/bluetooth/l2cap.h b/include/net/bluetooth/l2cap.h
index 0afde8d..a1d8ec4 100644 (file)
--- a/include/net/bluetooth/l2cap.h
+++ b/include/net/bluetooth/l2cap.h
@@ -351,6 +351,7 @@ struct l2cap_pinfo {
 #define L2CAP_CONF_MAX_CONF_RSP 2
 
 #define L2CAP_CONN_SAR_SDU         0x01
+#define L2CAP_CONN_UNDER_REJ       0x02
 
 static inline int l2cap_tx_window_full(struct sock *sk)
 {

diff --git a/net/bluetooth/l2cap.c b/net/bluetooth/l2cap.c
index 167e025..35e9f5b 100644 (file)
--- a/net/bluetooth/l2cap.c
+++ b/net/bluetooth/l2cap.c
@@ -2951,22 +2951,36 @@ static inline int l2cap_data_channel_iframe(struct sock *sk, u16 rx_control, str
 
        BT_DBG("sk %p rx_control 0x%4.4x len %d", sk, rx_control, skb->len);
 
-       if (tx_seq != pi->expected_tx_seq)
-               return -EINVAL;
+       if (tx_seq == pi->expected_tx_seq) {
+               if (pi->conn_state & L2CAP_CONN_UNDER_REJ)
+                       pi->conn_state &= ~L2CAP_CONN_UNDER_REJ;
 
-       err = l2cap_sar_reassembly_sdu(sk, skb, rx_control);
-       if (err < 0)
-               return err;
+               err = l2cap_sar_reassembly_sdu(sk, skb, rx_control);
+               if (err < 0)
+                       return err;
+
+               pi->expected_tx_seq = (pi->expected_tx_seq + 1) % 64;
+               pi->num_to_ack = (pi->num_to_ack + 1) % L2CAP_DEFAULT_NUM_TO_ACK;
+               if (pi->num_to_ack == L2CAP_DEFAULT_NUM_TO_ACK - 1) {
+                       tx_control |= L2CAP_SUPER_RCV_READY;
+                       tx_control |= pi->expected_tx_seq << L2CAP_CTRL_REQSEQ_SHIFT;
+                       goto send;
+               }
+       } else {
+               /* Unexpected txSeq. Send a REJ S-frame */
+               kfree_skb(skb);
+               if (!(pi->conn_state & L2CAP_CONN_UNDER_REJ)) {
+                       tx_control |= L2CAP_SUPER_REJECT;
+                       tx_control |= pi->expected_tx_seq << L2CAP_CTRL_REQSEQ_SHIFT;
+                       pi->conn_state |= L2CAP_CONN_UNDER_REJ;
 
-       pi->expected_tx_seq = (pi->expected_tx_seq + 1) % 64;
-       pi->num_to_ack = (pi->num_to_ack + 1) % L2CAP_DEFAULT_NUM_TO_ACK;
-       if (pi->num_to_ack == L2CAP_DEFAULT_NUM_TO_ACK - 1) {
-               tx_control |= L2CAP_CTRL_FRAME_TYPE;
-               tx_control |= L2CAP_SUPER_RCV_READY;
-               tx_control |= pi->expected_tx_seq << L2CAP_CTRL_REQSEQ_SHIFT;
-               err = l2cap_send_sframe(pi, tx_control);
+                       goto send;
+               }
        }
-       return err;
+       return 0;
+
+send:
+       return l2cap_send_sframe(pi, tx_control);
 }
 
 static inline int l2cap_data_channel_sframe(struct sock *sk, u16 rx_control, struct sk_buff *skb)
@@ -2982,8 +2996,18 @@ static inline int l2cap_data_channel_sframe(struct sock *sk, u16 rx_control, str
                l2cap_ertm_send(sk);
                break;
 
-       case L2CAP_SUPER_RCV_NOT_READY:
        case L2CAP_SUPER_REJECT:
+               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;
+
+               l2cap_ertm_send(sk);
+
+               break;
+
+       case L2CAP_SUPER_RCV_NOT_READY:
        case L2CAP_SUPER_SELECT_REJECT:
                break;
        }
@@ -3030,6 +3054,11 @@ static inline int l2cap_data_channel(struct l2cap_conn *conn, u16 cid, struct sk
                if (__is_sar_start(control))
                        len -= 2;
 
+               /*
+                * We can just drop the corrupted I-frame here.
+                * Receiver will miss it and start proper recovery
+                * procedures and ask retransmission.
+                */
                if (len > L2CAP_DEFAULT_MAX_PDU_SIZE)
                        goto drop;