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Bluetooth: Add support for Retransmission and Monitor Timers
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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>
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Gustavo F. Padovan authored and Marcel Holtmann committed Aug 22, 2009
1 parent 30afb5b commit e90bac0
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Showing 3 changed files with 95 additions and 7 deletions.
1 change: 1 addition & 0 deletions include/net/bluetooth/bluetooth.h
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Original file line number Diff line number Diff line change
Expand Up @@ -139,6 +139,7 @@ struct bt_skb_cb {
__u8 pkt_type;
__u8 incoming;
__u8 tx_seq;
__u8 retries;
};
#define bt_cb(skb) ((struct bt_skb_cb *)((skb)->cb))

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15 changes: 12 additions & 3 deletions include/net/bluetooth/l2cap.h
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Original file line number Diff line number Diff line change
Expand Up @@ -31,9 +31,9 @@
#define L2CAP_DEFAULT_FLUSH_TO 0xffff
#define L2CAP_DEFAULT_TX_WINDOW 63
#define L2CAP_DEFAULT_NUM_TO_ACK (L2CAP_DEFAULT_TX_WINDOW/5)
#define L2CAP_DEFAULT_MAX_RECEIVE 1
#define L2CAP_DEFAULT_RETRANS_TO 300 /* 300 milliseconds */
#define L2CAP_DEFAULT_MONITOR_TO 1000 /* 1 second */
#define L2CAP_DEFAULT_MAX_TX 3
#define L2CAP_DEFAULT_RETRANS_TO 1000 /* 1 second */
#define L2CAP_DEFAULT_MONITOR_TO 12000 /* 12 seconds */
#define L2CAP_DEFAULT_MAX_PDU_SIZE 672

#define L2CAP_CONN_TIMEOUT (40000) /* 40 seconds */
Expand Down Expand Up @@ -318,6 +318,7 @@ struct l2cap_pinfo {
__u8 req_seq;
__u8 expected_tx_seq;
__u8 unacked_frames;
__u8 retry_count;
__u8 num_to_ack;
__u16 sdu_len;
__u16 partial_sdu_len;
Expand All @@ -333,6 +334,8 @@ struct l2cap_pinfo {

__le16 sport;

struct timer_list retrans_timer;
struct timer_list monitor_timer;
struct sk_buff_head tx_queue;
struct l2cap_conn *conn;
struct sock *next_c;
Expand All @@ -352,6 +355,12 @@ struct l2cap_pinfo {

#define L2CAP_CONN_SAR_SDU 0x01
#define L2CAP_CONN_UNDER_REJ 0x02
#define L2CAP_CONN_WAIT_F 0x04

#define __mod_retrans_timer() mod_timer(&l2cap_pi(sk)->retrans_timer, \
jiffies + msecs_to_jiffies(L2CAP_DEFAULT_RETRANS_TO));
#define __mod_monitor_timer() mod_timer(&l2cap_pi(sk)->monitor_timer, \
jiffies + msecs_to_jiffies(L2CAP_DEFAULT_MONITOR_TO));

static inline int l2cap_tx_window_full(struct sock *sk)
{
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86 changes: 82 additions & 4 deletions net/bluetooth/l2cap.c
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Original file line number Diff line number Diff line change
Expand Up @@ -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;
Expand All @@ -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;
}

Expand All @@ -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;
Expand Down Expand Up @@ -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;
}

Expand Down Expand Up @@ -2058,7 +2109,7 @@ static int l2cap_build_conf_req(struct sock *sk, void *data)
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);
Expand Down Expand Up @@ -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;
Expand Down Expand Up @@ -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);
Expand All @@ -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);
Expand Down Expand Up @@ -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:
Expand Down

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