Bluetooth: Add support for L2CAP SREJ exception

When L2CAP loses an I-frame we send a SREJ frame to the transmitter side
requesting the lost packet. This patch implement all Recv I-frame events
on SREJ_SENT state table except the ones that deal with SendRej (the REJ
exception at receiver side is yet not implemented).

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

1 files changed, 196 insertions, 24 deletions

diff --git a/net/bluetooth/l2cap.c b/net/bluetooth/l2cap.c
index 4c319003c290..70aff921db8c 100644
--- a/net/bluetooth/l2cap.c
+++ b/net/bluetooth/l2cap.c
@@ -1292,6 +1292,50 @@ static int l2cap_streaming_send(struct sock *sk)
         return 0;
 }
 
+static int l2cap_retransmit_frame(struct sock *sk, u8 tx_seq)
+{
+        struct l2cap_pinfo *pi = l2cap_pi(sk);
+        struct sk_buff *skb, *tx_skb;
+        u16 control, fcs;
+        int err;
+
+        skb = skb_peek(TX_QUEUE(sk));
+        do {
+                if (bt_cb(skb)->tx_seq != tx_seq) {
+                        if (skb_queue_is_last(TX_QUEUE(sk), skb))
+                                break;
+                        skb = skb_queue_next(TX_QUEUE(sk), skb);
+                        continue;
+                }
+
+                if (pi->remote_max_tx &&
+                                bt_cb(skb)->retries == pi->remote_max_tx) {
+                        l2cap_send_disconn_req(pi->conn, sk);
+                        break;
+                }
+
+                tx_skb = skb_clone(skb, GFP_ATOMIC);
+                bt_cb(skb)->retries++;
+                control = get_unaligned_le16(tx_skb->data + L2CAP_HDR_SIZE);
+                control |= (pi->req_seq << L2CAP_CTRL_REQSEQ_SHIFT)
+                                | (tx_seq << L2CAP_CTRL_TXSEQ_SHIFT);
+                put_unaligned_le16(control, tx_skb->data + L2CAP_HDR_SIZE);
+
+                if (l2cap_pi(sk)->fcs == L2CAP_FCS_CRC16) {
+                        fcs = crc16(0, (u8 *)tx_skb->data, tx_skb->len - 2);
+                        put_unaligned_le16(fcs, tx_skb->data + tx_skb->len - 2);
+                }
+
+                err = l2cap_do_send(sk, tx_skb);
+                if (err < 0) {
+                        l2cap_send_disconn_req(pi->conn, sk);
+                        return err;
+                }
+                break;
+        } while(1);
+        return 0;
+}
+
 static int l2cap_ertm_send(struct sock *sk)
 {
         struct sk_buff *skb, *tx_skb;
@@ -2705,6 +2749,7 @@ static inline int l2cap_config_req(struct l2cap_conn *conn, struct l2cap_cmd_hdr
                                 l2cap_monitor_timeout, (unsigned long) sk);
 
                 __skb_queue_head_init(TX_QUEUE(sk));
+                __skb_queue_head_init(SREJ_QUEUE(sk));
                 l2cap_chan_ready(sk);
                 goto unlock;
         }
@@ -2784,8 +2829,10 @@ static inline int l2cap_config_rsp(struct l2cap_conn *conn, struct l2cap_cmd_hdr
 
                 sk->sk_state = BT_CONNECTED;
                 l2cap_pi(sk)->expected_tx_seq = 0;
+                l2cap_pi(sk)->buffer_seq = 0;
                 l2cap_pi(sk)->num_to_ack = 0;
                 __skb_queue_head_init(TX_QUEUE(sk));
+                __skb_queue_head_init(SREJ_QUEUE(sk));
                 l2cap_chan_ready(sk);
         }
 
@@ -2817,6 +2864,7 @@ static inline int l2cap_disconnect_req(struct l2cap_conn *conn, struct l2cap_cmd
         sk->sk_shutdown = SHUTDOWN_MASK;
 
         skb_queue_purge(TX_QUEUE(sk));
+        skb_queue_purge(SREJ_QUEUE(sk));
         del_timer(&l2cap_pi(sk)->retrans_timer);
         del_timer(&l2cap_pi(sk)->monitor_timer);
 
@@ -2843,6 +2891,7 @@ static inline int l2cap_disconnect_rsp(struct l2cap_conn *conn, struct l2cap_cmd
                 return 0;
 
         skb_queue_purge(TX_QUEUE(sk));
+        skb_queue_purge(SREJ_QUEUE(sk));
         del_timer(&l2cap_pi(sk)->retrans_timer);
         del_timer(&l2cap_pi(sk)->monitor_timer);
 
@@ -3038,6 +3087,33 @@ static int l2cap_check_fcs(struct l2cap_pinfo *pi,  struct sk_buff *skb)
         return 0;
 }
 
+static void l2cap_add_to_srej_queue(struct sock *sk, struct sk_buff *skb, u8 tx_seq, u8 sar)
+{
+        struct sk_buff *next_skb;
+
+        bt_cb(skb)->tx_seq = tx_seq;
+        bt_cb(skb)->sar = sar;
+
+        next_skb = skb_peek(SREJ_QUEUE(sk));
+        if (!next_skb) {
+                __skb_queue_tail(SREJ_QUEUE(sk), skb);
+                return;
+        }
+
+        do {
+                if (bt_cb(next_skb)->tx_seq > tx_seq) {
+                        __skb_queue_before(SREJ_QUEUE(sk), next_skb, skb);
+                        return;
+                }
+
+                if (skb_queue_is_last(SREJ_QUEUE(sk), next_skb))
+                        break;
+
+        } while((next_skb = skb_queue_next(SREJ_QUEUE(sk), next_skb)));
+
+        __skb_queue_tail(SREJ_QUEUE(sk), skb);
+}
+
 static int l2cap_sar_reassembly_sdu(struct sock *sk, struct sk_buff *skb, u16 control)
 {
         struct l2cap_pinfo *pi = l2cap_pi(sk);
@@ -3118,50 +3194,143 @@ static int l2cap_sar_reassembly_sdu(struct sock *sk, struct sk_buff *skb, u16 co
         return err;
 }
 
+static void l2cap_check_srej_gap(struct sock *sk, u8 tx_seq)
+{
+        struct sk_buff *skb;
+        u16 control = 0;
+
+        while((skb = skb_peek(SREJ_QUEUE(sk)))) {
+                if (bt_cb(skb)->tx_seq != tx_seq)
+                        break;
+
+                skb = skb_dequeue(SREJ_QUEUE(sk));
+                control |= bt_cb(skb)->sar << L2CAP_CTRL_SAR_SHIFT;
+                l2cap_sar_reassembly_sdu(sk, skb, control);
+                l2cap_pi(sk)->buffer_seq_srej =
+                        (l2cap_pi(sk)->buffer_seq_srej + 1) % 64;
+                tx_seq++;
+        }
+}
+
+static void l2cap_resend_srejframe(struct sock *sk, u8 tx_seq)
+{
+        struct l2cap_pinfo *pi = l2cap_pi(sk);
+        struct srej_list *l, *tmp;
+        u16 control;
+
+        list_for_each_entry_safe(l,tmp, SREJ_LIST(sk), list) {
+                if (l->tx_seq == tx_seq) {
+                        list_del(&l->list);
+                        kfree(l);
+                        return;
+                }
+                control = L2CAP_SUPER_SELECT_REJECT;
+                control |= l->tx_seq << L2CAP_CTRL_REQSEQ_SHIFT;
+                l2cap_send_sframe(pi, control);
+                list_del(&l->list);
+                list_add_tail(&l->list, SREJ_LIST(sk));
+        }
+}
+
+static void l2cap_send_srejframe(struct sock *sk, u8 tx_seq)
+{
+        struct l2cap_pinfo *pi = l2cap_pi(sk);
+        struct srej_list *new;
+        u16 control;
+
+        while (tx_seq != pi->expected_tx_seq) {
+                control = L2CAP_SUPER_SELECT_REJECT;
+                control |= pi->expected_tx_seq << L2CAP_CTRL_REQSEQ_SHIFT;
+                l2cap_send_sframe(pi, control);
+
+                new = kzalloc(sizeof(struct srej_list), GFP_ATOMIC);
+                new->tx_seq = pi->expected_tx_seq++;
+                list_add_tail(&new->list, SREJ_LIST(sk));
+        }
+        pi->expected_tx_seq++;
+}
+
 static inline int l2cap_data_channel_iframe(struct sock *sk, u16 rx_control, struct sk_buff *skb)
 {
         struct l2cap_pinfo *pi = l2cap_pi(sk);
         u8 tx_seq = __get_txseq(rx_control);
         u16 tx_control = 0;
+        u8 sar = rx_control >> L2CAP_CTRL_SAR_SHIFT;
         int err = 0;
 
         BT_DBG("sk %p rx_control 0x%4.4x len %d", sk, rx_control, skb->len);
 
-        if (tx_seq == pi->expected_tx_seq) {
-                if (pi->conn_state & L2CAP_CONN_UNDER_REJ)
-                        pi->conn_state &= ~L2CAP_CONN_UNDER_REJ;
+        if (tx_seq == pi->expected_tx_seq)
+                goto expected;
 
-                err = l2cap_sar_reassembly_sdu(sk, skb, rx_control);
-                if (err < 0)
-                        return err;
+        if (pi->conn_state & L2CAP_CONN_SREJ_SENT) {
+                struct srej_list *first;
 
-                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;
+                first = list_first_entry(SREJ_LIST(sk),
+                                struct srej_list, list);
+                if (tx_seq == first->tx_seq) {
+                        l2cap_add_to_srej_queue(sk, skb, tx_seq, sar);
+                        l2cap_check_srej_gap(sk, tx_seq);
+
+                        list_del(&first->list);
+                        kfree(first);
+
+                        if (list_empty(SREJ_LIST(sk))) {
+                                pi->buffer_seq = pi->buffer_seq_srej;
+                                pi->conn_state &= ~L2CAP_CONN_SREJ_SENT;
+                        }
+                } else {
+                        struct srej_list *l;
+                        l2cap_add_to_srej_queue(sk, skb, tx_seq, sar);
+
+                        list_for_each_entry(l, SREJ_LIST(sk), list) {
+                                if (l->tx_seq == tx_seq) {
+                                        l2cap_resend_srejframe(sk, tx_seq);
+                                        return 0;
+                                }
+                        }
+                        l2cap_send_srejframe(sk, tx_seq);
                 }
         } 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->conn_state |= L2CAP_CONN_SREJ_SENT;
 
-                        goto send;
-                }
+                INIT_LIST_HEAD(SREJ_LIST(sk));
+                pi->buffer_seq_srej = pi->buffer_seq;
+
+                __skb_queue_head_init(SREJ_QUEUE(sk));
+                l2cap_add_to_srej_queue(sk, skb, tx_seq, sar);
+
+                l2cap_send_srejframe(sk, tx_seq);
         }
         return 0;
 
-send:
-        return l2cap_send_sframe(pi, tx_control);
+expected:
+        pi->expected_tx_seq = (pi->expected_tx_seq + 1) % 64;
+
+        if (pi->conn_state & L2CAP_CONN_SREJ_SENT) {
+                l2cap_add_to_srej_queue(sk, skb, tx_seq, sar);
+                return 0;
+        }
+
+        pi->buffer_seq = (pi->buffer_seq + 1) % 64;
+
+        err = l2cap_sar_reassembly_sdu(sk, skb, rx_control);
+        if (err < 0)
+                return err;
+
+        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->buffer_seq << L2CAP_CTRL_REQSEQ_SHIFT;
+                l2cap_send_sframe(pi, tx_control);
+        }
+        return 0;
 }
 
 static inline int l2cap_data_channel_sframe(struct sock *sk, u16 rx_control, struct sk_buff *skb)
 {
         struct l2cap_pinfo *pi = l2cap_pi(sk);
+        u8 tx_seq = __get_reqseq(rx_control);
 
         BT_DBG("sk %p rx_control 0x%4.4x len %d", sk, rx_control, skb->len);
 
@@ -3181,7 +3350,7 @@ static inline int l2cap_data_channel_sframe(struct sock *sk, u16 rx_control, str
                         if (pi->unacked_frames > 0)
                                 __mod_retrans_timer();
                 } else {
-                        pi->expected_ack_seq = __get_reqseq(rx_control);
+                        pi->expected_ack_seq = tx_seq;
                         l2cap_drop_acked_frames(sk);
                         if (pi->unacked_frames > 0)
                                 __mod_retrans_timer();
@@ -3200,8 +3369,11 @@ static inline int l2cap_data_channel_sframe(struct sock *sk, u16 rx_control, str
 
                 break;
 
-        case L2CAP_SUPER_RCV_NOT_READY:
         case L2CAP_SUPER_SELECT_REJECT:
+                l2cap_retransmit_frame(sk, tx_seq);
+                break;
+
+        case L2CAP_SUPER_RCV_NOT_READY:
                 break;
         }