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Bluetooth: Perform L2CAP SDU reassembly without copying data
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Use sk_buff fragment capabilities to link together incoming skbs
instead of allocating a new skb for reassembly and copying.

The new reassembly code works equally well for ERTM and streaming
mode, so there is now one reassembly function instead of two.

Signed-off-by: Mat Martineau <mathewm@codeaurora.org>
Signed-off-by: Gustavo F. Padovan <padovan@profusion.mobi>
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Mat Martineau authored and Gustavo F. Padovan committed Sep 27, 2011
1 parent 5b668eb commit 84084a3
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Showing 2 changed files with 81 additions and 165 deletions.
3 changes: 1 addition & 2 deletions include/net/bluetooth/l2cap.h
View file
Original file line number Diff line number Diff line change
Expand Up @@ -354,8 +354,8 @@ struct l2cap_chan {
__u8 retry_count;
__u8 num_acked;
__u16 sdu_len;
__u16 partial_sdu_len;
struct sk_buff *sdu;
struct sk_buff *sdu_last_frag;

__u8 remote_tx_win;
__u8 remote_max_tx;
Expand Down Expand Up @@ -448,7 +448,6 @@ enum {
#define L2CAP_CONF_MAX_CONF_RSP 2

enum {
CONN_SAR_SDU,
CONN_SREJ_SENT,
CONN_WAIT_F,
CONN_SREJ_ACT,
Expand Down
243 changes: 80 additions & 163 deletions net/bluetooth/l2cap_core.c
View file
Original file line number Diff line number Diff line change
Expand Up @@ -3128,102 +3128,104 @@ static int l2cap_add_to_srej_queue(struct l2cap_chan *chan, struct sk_buff *skb,
return 0;
}

static int l2cap_ertm_reassembly_sdu(struct l2cap_chan *chan, struct sk_buff *skb, u16 control)
static void append_skb_frag(struct sk_buff *skb,
struct sk_buff *new_frag, struct sk_buff **last_frag)
{
struct sk_buff *_skb;
int err;
/* skb->len reflects data in skb as well as all fragments
* skb->data_len reflects only data in fragments
*/
if (!skb_has_frag_list(skb))
skb_shinfo(skb)->frag_list = new_frag;

new_frag->next = NULL;

(*last_frag)->next = new_frag;
*last_frag = new_frag;

skb->len += new_frag->len;
skb->data_len += new_frag->len;
skb->truesize += new_frag->truesize;
}

static int l2cap_reassemble_sdu(struct l2cap_chan *chan, struct sk_buff *skb, u16 control)
{
int err = -EINVAL;

switch (control & L2CAP_CTRL_SAR) {
case L2CAP_SDU_UNSEGMENTED:
if (test_bit(CONN_SAR_SDU, &chan->conn_state))
goto drop;
if (chan->sdu)
break;

return chan->ops->recv(chan->data, skb);
err = chan->ops->recv(chan->data, skb);
break;

case L2CAP_SDU_START:
if (test_bit(CONN_SAR_SDU, &chan->conn_state))
goto drop;
if (chan->sdu)
break;

chan->sdu_len = get_unaligned_le16(skb->data);
skb_pull(skb, 2);

if (chan->sdu_len > chan->imtu)
goto disconnect;

chan->sdu = bt_skb_alloc(chan->sdu_len, GFP_ATOMIC);
if (!chan->sdu)
return -ENOMEM;
if (chan->sdu_len > chan->imtu) {
err = -EMSGSIZE;
break;
}

/* pull sdu_len bytes only after alloc, because of Local Busy
* condition we have to be sure that this will be executed
* only once, i.e., when alloc does not fail */
skb_pull(skb, 2);
if (skb->len >= chan->sdu_len)
break;

memcpy(skb_put(chan->sdu, skb->len), skb->data, skb->len);
chan->sdu = skb;
chan->sdu_last_frag = skb;

set_bit(CONN_SAR_SDU, &chan->conn_state);
chan->partial_sdu_len = skb->len;
skb = NULL;
err = 0;
break;

case L2CAP_SDU_CONTINUE:
if (!test_bit(CONN_SAR_SDU, &chan->conn_state))
goto disconnect;

if (!chan->sdu)
goto disconnect;
break;

chan->partial_sdu_len += skb->len;
if (chan->partial_sdu_len > chan->sdu_len)
goto drop;
append_skb_frag(chan->sdu, skb,
&chan->sdu_last_frag);
skb = NULL;

memcpy(skb_put(chan->sdu, skb->len), skb->data, skb->len);
if (chan->sdu->len >= chan->sdu_len)
break;

err = 0;
break;

case L2CAP_SDU_END:
if (!test_bit(CONN_SAR_SDU, &chan->conn_state))
goto disconnect;

if (!chan->sdu)
goto disconnect;

chan->partial_sdu_len += skb->len;

if (chan->partial_sdu_len > chan->imtu)
goto drop;
break;

if (chan->partial_sdu_len != chan->sdu_len)
goto drop;
append_skb_frag(chan->sdu, skb,
&chan->sdu_last_frag);
skb = NULL;

memcpy(skb_put(chan->sdu, skb->len), skb->data, skb->len);
if (chan->sdu->len != chan->sdu_len)
break;

_skb = skb_clone(chan->sdu, GFP_ATOMIC);
if (!_skb) {
return -ENOMEM;
}
err = chan->ops->recv(chan->data, chan->sdu);

err = chan->ops->recv(chan->data, _skb);
if (err < 0) {
kfree_skb(_skb);
return err;
if (!err) {
/* Reassembly complete */
chan->sdu = NULL;
chan->sdu_last_frag = NULL;
chan->sdu_len = 0;
}

clear_bit(CONN_SAR_SDU, &chan->conn_state);

kfree_skb(chan->sdu);
break;
}

kfree_skb(skb);
return 0;

drop:
kfree_skb(chan->sdu);
chan->sdu = NULL;
if (err) {
kfree_skb(skb);
kfree_skb(chan->sdu);
chan->sdu = NULL;
chan->sdu_last_frag = NULL;
chan->sdu_len = 0;
}

disconnect:
l2cap_send_disconn_req(chan->conn, chan, ECONNRESET);
kfree_skb(skb);
return 0;
return err;
}

static void l2cap_ertm_enter_local_busy(struct l2cap_chan *chan)
Expand Down Expand Up @@ -3277,99 +3279,6 @@ void l2cap_chan_busy(struct l2cap_chan *chan, int busy)
}
}

static int l2cap_streaming_reassembly_sdu(struct l2cap_chan *chan, struct sk_buff *skb, u16 control)
{
struct sk_buff *_skb;
int err = -EINVAL;

/*
* TODO: We have to notify the userland if some data is lost with the
* Streaming Mode.
*/

switch (control & L2CAP_CTRL_SAR) {
case L2CAP_SDU_UNSEGMENTED:
if (test_bit(CONN_SAR_SDU, &chan->conn_state)) {
kfree_skb(chan->sdu);
break;
}

err = chan->ops->recv(chan->data, skb);
if (!err)
return 0;

break;

case L2CAP_SDU_START:
if (test_bit(CONN_SAR_SDU, &chan->conn_state)) {
kfree_skb(chan->sdu);
break;
}

chan->sdu_len = get_unaligned_le16(skb->data);
skb_pull(skb, 2);

if (chan->sdu_len > chan->imtu) {
err = -EMSGSIZE;
break;
}

chan->sdu = bt_skb_alloc(chan->sdu_len, GFP_ATOMIC);
if (!chan->sdu) {
err = -ENOMEM;
break;
}

memcpy(skb_put(chan->sdu, skb->len), skb->data, skb->len);

set_bit(CONN_SAR_SDU, &chan->conn_state);
chan->partial_sdu_len = skb->len;
err = 0;
break;

case L2CAP_SDU_CONTINUE:
if (!test_bit(CONN_SAR_SDU, &chan->conn_state))
break;

memcpy(skb_put(chan->sdu, skb->len), skb->data, skb->len);

chan->partial_sdu_len += skb->len;
if (chan->partial_sdu_len > chan->sdu_len)
kfree_skb(chan->sdu);
else
err = 0;

break;

case L2CAP_SDU_END:
if (!test_bit(CONN_SAR_SDU, &chan->conn_state))
break;

memcpy(skb_put(chan->sdu, skb->len), skb->data, skb->len);

clear_bit(CONN_SAR_SDU, &chan->conn_state);
chan->partial_sdu_len += skb->len;

if (chan->partial_sdu_len > chan->imtu)
goto drop;

if (chan->partial_sdu_len == chan->sdu_len) {
_skb = skb_clone(chan->sdu, GFP_ATOMIC);
err = chan->ops->recv(chan->data, _skb);
if (err < 0)
kfree_skb(_skb);
}
err = 0;

drop:
kfree_skb(chan->sdu);
break;
}

kfree_skb(skb);
return err;
}

static void l2cap_check_srej_gap(struct l2cap_chan *chan, u8 tx_seq)
{
struct sk_buff *skb;
Expand All @@ -3384,7 +3293,7 @@ static void l2cap_check_srej_gap(struct l2cap_chan *chan, u8 tx_seq)

skb = skb_dequeue(&chan->srej_q);
control = bt_cb(skb)->sar << L2CAP_CTRL_SAR_SHIFT;
err = l2cap_ertm_reassembly_sdu(chan, skb, control);
err = l2cap_reassemble_sdu(chan, skb, control);

if (err < 0) {
l2cap_send_disconn_req(chan->conn, chan, ECONNRESET);
Expand Down Expand Up @@ -3544,7 +3453,7 @@ static inline int l2cap_data_channel_iframe(struct l2cap_chan *chan, u16 rx_cont
return 0;
}

err = l2cap_ertm_reassembly_sdu(chan, skb, rx_control);
err = l2cap_reassemble_sdu(chan, skb, rx_control);
chan->buffer_seq = (chan->buffer_seq + 1) % 64;
if (err < 0) {
l2cap_send_disconn_req(chan->conn, chan, ECONNRESET);
Expand Down Expand Up @@ -3860,12 +3769,20 @@ static inline int l2cap_data_channel(struct l2cap_conn *conn, u16 cid, struct sk

tx_seq = __get_txseq(control);

if (chan->expected_tx_seq == tx_seq)
chan->expected_tx_seq = (chan->expected_tx_seq + 1) % 64;
else
chan->expected_tx_seq = (tx_seq + 1) % 64;
if (chan->expected_tx_seq != tx_seq) {
/* Frame(s) missing - must discard partial SDU */
kfree_skb(chan->sdu);
chan->sdu = NULL;
chan->sdu_last_frag = NULL;
chan->sdu_len = 0;

l2cap_streaming_reassembly_sdu(chan, skb, control);
/* TODO: Notify userland of missing data */
}

chan->expected_tx_seq = (tx_seq + 1) % 64;

if (l2cap_reassemble_sdu(chan, skb, control) == -EMSGSIZE)
l2cap_send_disconn_req(chan->conn, chan, ECONNRESET);

goto done;

Expand Down

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