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Bluetooth: Add support for L2CAP SREJ exception
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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>
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Gustavo F. Padovan authored and Marcel Holtmann committed Aug 22, 2009
1 parent fcc203c commit 8f17154
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Showing 3 changed files with 210 additions and 25 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 @@ -140,6 +140,7 @@ struct bt_skb_cb {
__u8 incoming;
__u8 tx_seq;
__u8 retries;
__u8 sar;
};
#define bt_cb(skb) ((struct bt_skb_cb *)((skb)->cb))

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14 changes: 13 additions & 1 deletion include/net/bluetooth/l2cap.h
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Original file line number Diff line number Diff line change
Expand Up @@ -108,6 +108,7 @@ struct l2cap_conninfo {

#define L2CAP_CTRL_TXSEQ_SHIFT 1
#define L2CAP_CTRL_REQSEQ_SHIFT 8
#define L2CAP_CTRL_SAR_SHIFT 14

/* L2CAP Supervisory Function */
#define L2CAP_SUPER_RCV_READY 0x0000
Expand Down Expand Up @@ -290,6 +291,13 @@ struct l2cap_conn {
/* ----- L2CAP channel and socket info ----- */
#define l2cap_pi(sk) ((struct l2cap_pinfo *) sk)
#define TX_QUEUE(sk) (&l2cap_pi(sk)->tx_queue)
#define SREJ_QUEUE(sk) (&l2cap_pi(sk)->srej_queue)
#define SREJ_LIST(sk) (&l2cap_pi(sk)->srej_l.list)

struct srej_list {
__u8 tx_seq;
struct list_head list;
};

struct l2cap_pinfo {
struct bt_sock bt;
Expand Down Expand Up @@ -318,6 +326,8 @@ struct l2cap_pinfo {
__u8 expected_ack_seq;
__u8 req_seq;
__u8 expected_tx_seq;
__u8 buffer_seq;
__u8 buffer_seq_srej;
__u8 unacked_frames;
__u8 retry_count;
__u8 num_to_ack;
Expand All @@ -338,6 +348,8 @@ struct l2cap_pinfo {
struct timer_list retrans_timer;
struct timer_list monitor_timer;
struct sk_buff_head tx_queue;
struct sk_buff_head srej_queue;
struct srej_list srej_l;
struct l2cap_conn *conn;
struct sock *next_c;
struct sock *prev_c;
Expand All @@ -356,7 +368,7 @@ struct l2cap_pinfo {
#define L2CAP_CONF_MAX_CONF_RSP 2

#define L2CAP_CONN_SAR_SDU 0x01
#define L2CAP_CONN_UNDER_REJ 0x02
#define L2CAP_CONN_SREJ_SENT 0x02
#define L2CAP_CONN_WAIT_F 0x04

#define __mod_retrans_timer() mod_timer(&l2cap_pi(sk)->retrans_timer, \
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220 changes: 196 additions & 24 deletions net/bluetooth/l2cap.c
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Original file line number Diff line number Diff line change
Expand Up @@ -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;
Expand Down Expand Up @@ -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;
}
Expand Down Expand Up @@ -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);
}

Expand Down Expand Up @@ -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);

Expand All @@ -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);

Expand Down Expand Up @@ -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);
Expand Down Expand Up @@ -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);

Expand All @@ -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();
Expand All @@ -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;
}

Expand Down

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