Hi Gustavo,
> When receiving an I-frame with unexpected txSeq, receiver side start the
> recovery procedure by send 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 to packet retransmission.
>
> Signed-off-by: Gustavo F. Padovan <gustavo@xxxxxxxxxxxxxxxxx>
> ---
> include/net/bluetooth/l2cap.h | 1 +
> net/bluetooth/l2cap.c | 57 ++++++++++++++++++++++++++++++-----------
> 2 files changed, 43 insertions(+), 15 deletions(-)
>
> diff --git a/include/net/bluetooth/l2cap.h b/include/net/bluetooth/l2cap.h
> index 233a2fa..653c313 100644
> --- a/include/net/bluetooth/l2cap.h
> +++ b/include/net/bluetooth/l2cap.h
> @@ -354,6 +354,7 @@ 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 dcde60b..938d6db 100644
> --- a/net/bluetooth/l2cap.c
> +++ b/net/bluetooth/l2cap.c
> @@ -2903,25 +2903,37 @@ 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;
This is &= ~ again.
>
> - err = l2cap_sar_reassembly_sdu(sk, skb, rx_control, tx_seq);
> - if (unlikely(err < 0))
> - return err;
> + err = l2cap_sar_reassembly_sdu(sk, skb, rx_control, tx_seq);
> + if (unlikely(err < 0))
> + return err;
No unlikely please.
>
> - L2CAP_SEQ_NUM_INC(pi->expected_tx_seq);
> - L2CAP_NUM_TO_ACK_INC(pi->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;
> + L2CAP_SEQ_NUM_INC(pi->expected_tx_seq);
> + L2CAP_NUM_TO_ACK_INC(pi->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;
>
> - err = l2cap_send_sframe(pi, tx_control);
> - if (unlikely(err))
> - return err;
> + goto send;
> + }
> }
> 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)
> @@ -2937,8 +2949,18 @@ 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;
> }
> @@ -2985,6 +3007,11 @@ static inline int l2cap_data_channel(struct l2cap_conn *conn, u16 cid, struct sk
> if (__is_sar_sdu_start(control))
> len -= 2;
>
> + /*
> + * We can just drop the corrupted I-frames here.
> + * Receiver will miss it and start proper recovery
> + * procedures and ask retransmission.
> + */
> if (L2CAP_DEFAULT_MAX_PDU_SIZE < len)
> goto drop;
>
Regards
Marcel
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