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Bluetooth: Add support for Segmentation and Reassembly of SDUs
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ERTM should use Segmentation and Reassembly to break down a SDU in many
PDUs on sending data to the other side.

On sending packets we queue all 'segments' until end of segmentation and
just the add them to the queue for sending. On receiving we create a new
SKB with the SDU reassembled.

Initially based on a patch from Nathan Holstein <nathan@lampreynetworks.com>

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 1c2acff commit c74e560
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Showing 2 changed files with 162 additions and 17 deletions.
9 changes: 8 additions & 1 deletion include/net/bluetooth/l2cap.h
View file
Original file line number Diff line number Diff line change
Expand Up @@ -34,7 +34,7 @@
#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_RX_APDU 0xfff7
#define L2CAP_DEFAULT_MAX_PDU_SIZE 672

#define L2CAP_CONN_TIMEOUT (40000) /* 40 seconds */
#define L2CAP_INFO_TIMEOUT (4000) /* 4 seconds */
Expand Down Expand Up @@ -311,13 +311,17 @@ struct l2cap_pinfo {
__u8 conf_req[64];
__u8 conf_len;
__u8 conf_state;
__u8 conn_state;

__u8 next_tx_seq;
__u8 expected_ack_seq;
__u8 req_seq;
__u8 expected_tx_seq;
__u8 unacked_frames;
__u8 num_to_ack;
__u16 sdu_len;
__u16 partial_sdu_len;
struct sk_buff *sdu;

__u8 ident;

Expand Down Expand Up @@ -346,6 +350,8 @@ struct l2cap_pinfo {
#define L2CAP_CONF_MAX_CONF_REQ 2
#define L2CAP_CONF_MAX_CONF_RSP 2

#define L2CAP_CONN_SAR_SDU 0x01

static inline int l2cap_tx_window_full(struct sock *sk)
{
struct l2cap_pinfo *pi = l2cap_pi(sk);
Expand All @@ -363,6 +369,7 @@ static inline int l2cap_tx_window_full(struct sock *sk)
#define __get_reqseq(ctrl) ((ctrl) & L2CAP_CTRL_REQSEQ) >> 8
#define __is_iframe(ctrl) !((ctrl) & L2CAP_CTRL_FRAME_TYPE)
#define __is_sframe(ctrl) (ctrl) & L2CAP_CTRL_FRAME_TYPE
#define __is_sar_start(ctrl) ((ctrl) & L2CAP_CTRL_SAR) == L2CAP_SDU_START

void l2cap_load(void);

Expand Down
170 changes: 154 additions & 16 deletions net/bluetooth/l2cap.c
View file
Original file line number Diff line number Diff line change
Expand Up @@ -1334,7 +1334,7 @@ static struct sk_buff *l2cap_create_basic_pdu(struct sock *sk, struct msghdr *ms
return skb;
}

static struct sk_buff *l2cap_create_ertm_pdu(struct sock *sk, struct msghdr *msg, size_t len, u16 control)
static struct sk_buff *l2cap_create_ertm_pdu(struct sock *sk, struct msghdr *msg, size_t len, u16 control, u16 sdulen)
{
struct l2cap_conn *conn = l2cap_pi(sk)->conn;
struct sk_buff *skb;
Expand All @@ -1343,6 +1343,9 @@ static struct sk_buff *l2cap_create_ertm_pdu(struct sock *sk, struct msghdr *msg

BT_DBG("sk %p len %d", sk, (int)len);

if (sdulen)
hlen += 2;

count = min_t(unsigned int, (conn->mtu - hlen), len);
skb = bt_skb_send_alloc(sk, count + hlen,
msg->msg_flags & MSG_DONTWAIT, &err);
Expand All @@ -1354,6 +1357,8 @@ static struct sk_buff *l2cap_create_ertm_pdu(struct sock *sk, struct msghdr *msg
lh->cid = cpu_to_le16(l2cap_pi(sk)->dcid);
lh->len = cpu_to_le16(len + (hlen - L2CAP_HDR_SIZE));
put_unaligned_le16(control, skb_put(skb, 2));
if (sdulen)
put_unaligned_le16(sdulen, skb_put(skb, 2));

err = l2cap_skbuff_fromiovec(sk, msg, len, count, skb);
if (unlikely(err < 0)) {
Expand All @@ -1363,6 +1368,54 @@ static struct sk_buff *l2cap_create_ertm_pdu(struct sock *sk, struct msghdr *msg
return skb;
}

static inline int l2cap_sar_segment_sdu(struct sock *sk, struct msghdr *msg, size_t len)
{
struct l2cap_pinfo *pi = l2cap_pi(sk);
struct sk_buff *skb;
struct sk_buff_head sar_queue;
u16 control;
size_t size = 0;

__skb_queue_head_init(&sar_queue);
control = L2CAP_SDU_START;
skb = l2cap_create_ertm_pdu(sk, msg, pi->max_pdu_size, control, len);
if (IS_ERR(skb))
return PTR_ERR(skb);

__skb_queue_tail(&sar_queue, skb);
len -= pi->max_pdu_size;
size +=pi->max_pdu_size;
control = 0;

while (len > 0) {
size_t buflen;

if (len > pi->max_pdu_size) {
control |= L2CAP_SDU_CONTINUE;
buflen = pi->max_pdu_size;
} else {
control |= L2CAP_SDU_END;
buflen = len;
}

skb = l2cap_create_ertm_pdu(sk, msg, buflen, control, 0);
if (IS_ERR(skb)) {
skb_queue_purge(&sar_queue);
return PTR_ERR(skb);
}

__skb_queue_tail(&sar_queue, skb);
len -= buflen;
size += buflen;
control = 0;
}
skb_queue_splice_tail(&sar_queue, TX_QUEUE(sk));
if (sk->sk_send_head == NULL)
sk->sk_send_head = sar_queue.next;

return size;
}

static int l2cap_sock_sendmsg(struct kiocb *iocb, struct socket *sock, struct msghdr *msg, size_t len)
{
struct sock *sk = sock->sk;
Expand Down Expand Up @@ -1415,21 +1468,22 @@ static int l2cap_sock_sendmsg(struct kiocb *iocb, struct socket *sock, struct ms

case L2CAP_MODE_ERTM:
/* Entire SDU fits into one PDU */
if (len <= pi->omtu) {
if (len <= pi->max_pdu_size) {
control = L2CAP_SDU_UNSEGMENTED;
skb = l2cap_create_ertm_pdu(sk, msg, len, control);
skb = l2cap_create_ertm_pdu(sk, msg, len, control, 0);
if (IS_ERR(skb)) {
err = PTR_ERR(skb);
goto done;
}
__skb_queue_tail(TX_QUEUE(sk), skb);
if (sk->sk_send_head == NULL)
sk->sk_send_head = skb;
} else {
/* FIXME: Segmentation will be added later */
err = -EINVAL;
goto done;
/* Segment SDU into multiples PDUs */
err = l2cap_sar_segment_sdu(sk, msg, len);
if (err < 0)
goto done;
}
__skb_queue_tail(TX_QUEUE(sk), skb);
if (sk->sk_send_head == NULL)
sk->sk_send_head = skb;

err = l2cap_ertm_send(sk);
if (!err)
Expand Down Expand Up @@ -2007,7 +2061,7 @@ static int l2cap_build_conf_req(struct sock *sk, void *data)
rfc.max_transmit = L2CAP_DEFAULT_MAX_RECEIVE;
rfc.retrans_timeout = 0;
rfc.monitor_timeout = 0;
rfc.max_pdu_size = cpu_to_le16(L2CAP_DEFAULT_MAX_RX_APDU);
rfc.max_pdu_size = cpu_to_le16(L2CAP_DEFAULT_MAX_PDU_SIZE);

l2cap_add_conf_opt(&ptr, L2CAP_CONF_RFC,
sizeof(rfc), (unsigned long) &rfc);
Expand All @@ -2019,7 +2073,7 @@ static int l2cap_build_conf_req(struct sock *sk, void *data)
rfc.max_transmit = 0;
rfc.retrans_timeout = 0;
rfc.monitor_timeout = 0;
rfc.max_pdu_size = cpu_to_le16(L2CAP_DEFAULT_MAX_RX_APDU);
rfc.max_pdu_size = cpu_to_le16(L2CAP_DEFAULT_MAX_PDU_SIZE);

l2cap_add_conf_opt(&ptr, L2CAP_CONF_RFC,
sizeof(rfc), (unsigned long) &rfc);
Expand Down Expand Up @@ -2808,6 +2862,86 @@ static inline void l2cap_sig_channel(struct l2cap_conn *conn, struct sk_buff *sk
kfree_skb(skb);
}

static int l2cap_sar_reassembly_sdu(struct sock *sk, struct sk_buff *skb, u16 control)
{
struct l2cap_pinfo *pi = l2cap_pi(sk);
struct sk_buff *_skb;
int err = -EINVAL;

switch (control & L2CAP_CTRL_SAR) {
case L2CAP_SDU_UNSEGMENTED:
if (pi->conn_state & L2CAP_CONN_SAR_SDU) {
kfree_skb(pi->sdu);
break;
}

err = sock_queue_rcv_skb(sk, skb);
if (!err)
return 0;

break;

case L2CAP_SDU_START:
if (pi->conn_state & L2CAP_CONN_SAR_SDU) {
kfree_skb(pi->sdu);
break;
}

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

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

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

pi->conn_state |= L2CAP_CONN_SAR_SDU;
pi->partial_sdu_len = skb->len;
err = 0;
break;

case L2CAP_SDU_CONTINUE:
if (!(pi->conn_state & L2CAP_CONN_SAR_SDU))
break;

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

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

break;

case L2CAP_SDU_END:
if (!(pi->conn_state & L2CAP_CONN_SAR_SDU))
break;

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

pi->conn_state &= ~L2CAP_CONN_SAR_SDU;
pi->partial_sdu_len += skb->len;

if (pi->partial_sdu_len == pi->sdu_len) {
_skb = skb_clone(pi->sdu, GFP_ATOMIC);
err = sock_queue_rcv_skb(sk, _skb);
if (err < 0)
kfree_skb(_skb);
}
kfree_skb(pi->sdu);
err = 0;

break;
}

kfree_skb(skb);
return err;
}

static inline int l2cap_data_channel_iframe(struct sock *sk, u16 rx_control, struct sk_buff *skb)
{
struct l2cap_pinfo *pi = l2cap_pi(sk);
Expand All @@ -2820,11 +2954,11 @@ static inline int l2cap_data_channel_iframe(struct sock *sk, u16 rx_control, str
if (tx_seq != pi->expected_tx_seq)
return -EINVAL;

pi->expected_tx_seq = (pi->expected_tx_seq + 1) % 64;
err = sock_queue_rcv_skb(sk, skb);
if (err)
err = l2cap_sar_reassembly_sdu(sk, skb, rx_control);
if (err < 0)
return err;

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_CTRL_FRAME_TYPE;
Expand Down Expand Up @@ -2860,7 +2994,7 @@ static inline int l2cap_data_channel_sframe(struct sock *sk, u16 rx_control, str
static inline int l2cap_data_channel(struct l2cap_conn *conn, u16 cid, struct sk_buff *skb)
{
struct sock *sk;
u16 control;
u16 control, len;
int err;

sk = l2cap_get_chan_by_scid(&conn->chan_list, cid);
Expand Down Expand Up @@ -2891,8 +3025,12 @@ static inline int l2cap_data_channel(struct l2cap_conn *conn, u16 cid, struct sk
case L2CAP_MODE_ERTM:
control = get_unaligned_le16(skb->data);
skb_pull(skb, 2);
len = skb->len;

if (l2cap_pi(sk)->imtu < skb->len)
if (__is_sar_start(control))
len -= 2;

if (len > L2CAP_DEFAULT_MAX_PDU_SIZE)
goto drop;

if (__is_iframe(control))
Expand Down

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