[PATCH 3/6] Bluetooth: Fix configuration of the MPS value

Gustavo F. Padovan
2010-03-26T19:19:16Z

We were accepting values bigger than we can accept. This was leading
ERTM to drop packets because of wrong FCS checks.

Signed-off-by: Gustavo F. Padovan <padovan@profusion.mobi>
---
include/net/bluetooth/l2cap.h | 3 ++-
net/bluetooth/l2cap.c | 36 ++++++++++++++++++++----------------
2 files changed, 22 insertions(+), 17 deletions(-)

diff --git a/include/net/bluetooth/l2cap.h b/include/net/bluetooth/l2cap.h
index 48f10f4..0f4e423 100644
--- a/include/net/bluetooth/l2cap.h
+++ b/include/net/bluetooth/l2cap.h
@@ -343,7 +343,8 @@ struct l2cap_pinfo {
__u8 remote_max_tx;
__u16 retrans_timeout;
__u16 monitor_timeout;
- __u16 max_pdu_size;
+ __u16 remote_mps;
+ __u16 mps;

__le16 sport;

diff --git a/net/bluetooth/l2cap.c b/net/bluetooth/l2cap.c
index 40aff8d..4c98e3c 100644
--- a/net/bluetooth/l2cap.c
+++ b/net/bluetooth/l2cap.c
@@ -1605,21 +1605,21 @@ static inline int l2cap_sar_segment_sdu(struct sock *sk, struct msghdr *msg, siz

__skb_queue_head_init(&sar_queue);
control = L2CAP_SDU_START;
- skb = l2cap_create_iframe_pdu(sk, msg, pi->max_pdu_size, control, len);
+ skb = l2cap_create_iframe_pdu(sk, msg, pi->remote_mps, 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;
+ len -= pi->remote_mps;
+ size +=pi->remote_mps;
control = 0;

while (len > 0) {
size_t buflen;

- if (len > pi->max_pdu_size) {
+ if (len > pi->remote_mps) {
control |= L2CAP_SDU_CONTINUE;
- buflen = pi->max_pdu_size;
+ buflen = pi->remote_mps;
} else {
control |= L2CAP_SDU_END;
buflen = len;
@@ -1697,7 +1697,7 @@ static int l2cap_sock_sendmsg(struct kiocb *iocb, struct socket *sock, struct ms
case L2CAP_MODE_ERTM:
case L2CAP_MODE_STREAMING:
/* Entire SDU fits into one PDU */
- if (len <= pi->max_pdu_size) {
+ if (len <= pi->remote_mps) {
control = L2CAP_SDU_UNSEGMENTED;
skb = l2cap_create_iframe_pdu(sk, msg, len, control, 0);
if (IS_ERR(skb)) {
@@ -2326,7 +2326,7 @@ done:
rfc.monitor_timeout = 0;
rfc.max_pdu_size = cpu_to_le16(L2CAP_DEFAULT_MAX_PDU_SIZE);
if (L2CAP_DEFAULT_MAX_PDU_SIZE > pi->conn->mtu - 10)
- rfc.max_pdu_size = pi->conn->mtu - 10;
+ rfc.max_pdu_size = cpu_to_le16(pi->conn->mtu - 10);

l2cap_add_conf_opt(&ptr, L2CAP_CONF_RFC,
sizeof(rfc), (unsigned long) &rfc);
@@ -2349,7 +2349,7 @@ done:
rfc.monitor_timeout = 0;
rfc.max_pdu_size = cpu_to_le16(L2CAP_DEFAULT_MAX_PDU_SIZE);
if (L2CAP_DEFAULT_MAX_PDU_SIZE > pi->conn->mtu - 10)
- rfc.max_pdu_size = pi->conn->mtu - 10;
+ rfc.max_pdu_size = cpu_to_le16(pi->conn->mtu - 10);

l2cap_add_conf_opt(&ptr, L2CAP_CONF_RFC,
sizeof(rfc), (unsigned long) &rfc);
@@ -2478,7 +2478,10 @@ done:
case L2CAP_MODE_ERTM:
pi->remote_tx_win = rfc.txwin_size;
pi->remote_max_tx = rfc.max_transmit;
- pi->max_pdu_size = rfc.max_pdu_size;
+ if (rfc.max_pdu_size > pi->conn->mtu - 10)
+ rfc.max_pdu_size = le16_to_cpu(pi->conn->mtu - 10);
+
+ pi->remote_mps = le16_to_cpu(rfc.max_pdu_size);

rfc.retrans_timeout = L2CAP_DEFAULT_RETRANS_TO;
rfc.monitor_timeout = L2CAP_DEFAULT_MONITOR_TO;
@@ -2491,7 +2494,10 @@ done:
break;

case L2CAP_MODE_STREAMING:
- pi->max_pdu_size = rfc.max_pdu_size;
+ if (rfc.max_pdu_size > pi->conn->mtu - 10)
+ rfc.max_pdu_size = le16_to_cpu(pi->conn->mtu - 10);
+
+ pi->remote_mps = le16_to_cpu(rfc.max_pdu_size);

pi->conf_state |= L2CAP_CONF_MODE_DONE;

@@ -2570,11 +2576,10 @@ static int l2cap_parse_conf_rsp(struct sock *sk, void *rsp, int len, void *data,
pi->remote_tx_win = rfc.txwin_size;
pi->retrans_timeout = rfc.retrans_timeout;
pi->monitor_timeout = rfc.monitor_timeout;
- pi->max_pdu_size = le16_to_cpu(rfc.max_pdu_size);
+ pi->mps = le16_to_cpu(rfc.max_pdu_size);
break;
case L2CAP_MODE_STREAMING:
- pi->max_pdu_size = le16_to_cpu(rfc.max_pdu_size);
- break;
+ pi->mps = le16_to_cpu(rfc.max_pdu_size);
}
}

@@ -3758,7 +3763,7 @@ static inline int l2cap_data_channel(struct l2cap_conn *conn, u16 cid, struct sk
* Receiver will miss it and start proper recovery
* procedures and ask retransmission.
*/
- if (len > L2CAP_DEFAULT_MAX_PDU_SIZE)
+ if (len > pi->mps)
goto drop;

if (l2cap_check_fcs(pi, skb))
@@ -3789,8 +3794,7 @@ static inline int l2cap_data_channel(struct l2cap_conn *conn, u16 cid, struct sk
if (pi->fcs == L2CAP_FCS_CRC16)
len -= 2;

- if (len > L2CAP_DEFAULT_MAX_PDU_SIZE || len < 4
- || __is_sframe(control))
+ if (len > pi->mps || len < 4 || __is_sframe(control))
goto drop;

if (l2cap_check_fcs(pi, skb))
--
1.6.4.4