Bluetooth: Add support for Retransmission and Monitor Timers

L2CAP uses retransmission and monitor timers to inquiry the other side
about unacked I-frames. After sending each I-frame we (re)start the
retransmission timer. If it expires, we start a monitor timer that send a
S-frame with P bit set and wait for S-frame with F bit set. If monitor
timer expires, try again, at a maximum of L2CAP_DEFAULT_MAX_TX.

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

1 files changed, 82 insertions, 4 deletions

diff --git a/net/bluetooth/l2cap.c b/net/bluetooth/l2cap.c
index 35e9f5b80545..97172f7c0a6a 100644
--- a/net/bluetooth/l2cap.c
+++ b/net/bluetooth/l2cap.c
@@ -1178,6 +1178,39 @@ static int l2cap_sock_getname(struct socket *sock, struct sockaddr *addr, int *l
         return 0;
 }
 
+static void l2cap_monitor_timeout(unsigned long arg)
+{
+        struct sock *sk = (void *) arg;
+        u16 control;
+
+        if (l2cap_pi(sk)->retry_count >= l2cap_pi(sk)->remote_max_tx) {
+                l2cap_send_disconn_req(l2cap_pi(sk)->conn, sk);
+                return;
+        }
+
+        l2cap_pi(sk)->retry_count++;
+        __mod_monitor_timer();
+
+        control = L2CAP_CTRL_POLL;
+        control |= L2CAP_SUPER_RCV_READY;
+        l2cap_send_sframe(l2cap_pi(sk), control);
+}
+
+static void l2cap_retrans_timeout(unsigned long arg)
+{
+        struct sock *sk = (void *) arg;
+        u16 control;
+
+        l2cap_pi(sk)->retry_count = 1;
+        __mod_monitor_timer();
+
+        l2cap_pi(sk)->conn_state |= L2CAP_CONN_WAIT_F;
+
+        control = L2CAP_CTRL_POLL;
+        control |= L2CAP_SUPER_RCV_READY;
+        l2cap_send_sframe(l2cap_pi(sk), control);
+}
+
 static void l2cap_drop_acked_frames(struct sock *sk)
 {
         struct sk_buff *skb;
@@ -1192,6 +1225,9 @@ static void l2cap_drop_acked_frames(struct sock *sk)
                 l2cap_pi(sk)->unacked_frames--;
         }
 
+        if (!l2cap_pi(sk)->unacked_frames)
+                del_timer(&l2cap_pi(sk)->retrans_timer);
+
         return;
 }
 
@@ -1216,19 +1252,32 @@ static int l2cap_ertm_send(struct sock *sk)
         u16 control;
         int err;
 
+        if (pi->conn_state & L2CAP_CONN_WAIT_F)
+                return 0;
+
         while ((skb = sk->sk_send_head) && (!l2cap_tx_window_full(sk))) {
                 tx_skb = skb_clone(skb, GFP_ATOMIC);
 
+                if (pi->remote_max_tx &&
+                                bt_cb(skb)->retries == pi->remote_max_tx) {
+                        l2cap_send_disconn_req(pi->conn, sk);
+                        break;
+                }
+
+                bt_cb(skb)->retries++;
+
                 control = get_unaligned_le16(tx_skb->data + L2CAP_HDR_SIZE);
                 control |= (pi->req_seq << L2CAP_CTRL_REQSEQ_SHIFT)
                                 | (pi->next_tx_seq << L2CAP_CTRL_TXSEQ_SHIFT);
                 put_unaligned_le16(control, tx_skb->data + L2CAP_HDR_SIZE);
 
+
                 err = l2cap_do_send(sk, tx_skb);
                 if (err < 0) {
                         l2cap_send_disconn_req(pi->conn, sk);
                         return err;
                 }
+                __mod_retrans_timer();
 
                 bt_cb(skb)->tx_seq = pi->next_tx_seq;
                 pi->next_tx_seq = (pi->next_tx_seq + 1) % 64;
@@ -1365,6 +1414,8 @@ static struct sk_buff *l2cap_create_ertm_pdu(struct sock *sk, struct msghdr *msg
                 kfree_skb(skb);
                 return ERR_PTR(err);
         }
+
+        bt_cb(skb)->retries = 0;
         return skb;
 }
 
@@ -2058,7 +2109,7 @@ done:
         case L2CAP_MODE_ERTM:
                 rfc.mode            = L2CAP_MODE_ERTM;
                 rfc.txwin_size      = L2CAP_DEFAULT_TX_WINDOW;
-                rfc.max_transmit    = L2CAP_DEFAULT_MAX_RECEIVE;
+                rfc.max_transmit    = L2CAP_DEFAULT_MAX_TX;
                 rfc.retrans_timeout = 0;
                 rfc.monitor_timeout = 0;
                 rfc.max_pdu_size    = cpu_to_le16(L2CAP_DEFAULT_MAX_PDU_SIZE);
@@ -2553,6 +2604,12 @@ static inline int l2cap_config_req(struct l2cap_conn *conn, struct l2cap_cmd_hdr
                 l2cap_pi(sk)->next_tx_seq = 0;
                 l2cap_pi(sk)->expected_ack_seq = 0;
                 l2cap_pi(sk)->unacked_frames = 0;
+
+                setup_timer(&l2cap_pi(sk)->retrans_timer,
+                                l2cap_retrans_timeout, (unsigned long) sk);
+                setup_timer(&l2cap_pi(sk)->monitor_timer,
+                                l2cap_monitor_timeout, (unsigned long) sk);
+
                 __skb_queue_head_init(TX_QUEUE(sk));
                 l2cap_chan_ready(sk);
                 goto unlock;
@@ -2662,6 +2719,8 @@ static inline int l2cap_disconnect_req(struct l2cap_conn *conn, struct l2cap_cmd
         sk->sk_shutdown = SHUTDOWN_MASK;
 
         skb_queue_purge(TX_QUEUE(sk));
+        del_timer(&l2cap_pi(sk)->retrans_timer);
+        del_timer(&l2cap_pi(sk)->monitor_timer);
 
         l2cap_chan_del(sk, ECONNRESET);
         bh_unlock_sock(sk);
@@ -2686,6 +2745,8 @@ static inline int l2cap_disconnect_rsp(struct l2cap_conn *conn, struct l2cap_cmd
                 return 0;
 
         skb_queue_purge(TX_QUEUE(sk));
+        del_timer(&l2cap_pi(sk)->retrans_timer);
+        del_timer(&l2cap_pi(sk)->monitor_timer);
 
         l2cap_chan_del(sk, 0);
         bh_unlock_sock(sk);
@@ -2991,9 +3052,26 @@ static inline int l2cap_data_channel_sframe(struct sock *sk, u16 rx_control, str
 
         switch (rx_control & L2CAP_CTRL_SUPERVISE) {
         case L2CAP_SUPER_RCV_READY:
-                pi->expected_ack_seq = __get_reqseq(rx_control);
-                l2cap_drop_acked_frames(sk);
-                l2cap_ertm_send(sk);
+                if (rx_control & L2CAP_CTRL_POLL) {
+                        u16 control = L2CAP_CTRL_FINAL;
+                        control |= L2CAP_SUPER_RCV_READY;
+                        l2cap_send_sframe(l2cap_pi(sk), control);
+                } else if (rx_control & L2CAP_CTRL_FINAL) {
+                        if (!(pi->conn_state & L2CAP_CONN_WAIT_F))
+                                break;
+
+                        pi->conn_state &= ~L2CAP_CONN_WAIT_F;
+                        del_timer(&pi->monitor_timer);
+
+                        if (pi->unacked_frames > 0)
+                                __mod_retrans_timer();
+                } else {
+                        pi->expected_ack_seq = __get_reqseq(rx_control);
+                        l2cap_drop_acked_frames(sk);
+                        if (pi->unacked_frames > 0)
+                                __mod_retrans_timer();
+                        l2cap_ertm_send(sk);
+                }
                 break;
 
         case L2CAP_SUPER_REJECT: