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Bluetooth: Fix sending incorrect MTU in the Exchange MTU response

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According to the Core Spec 4.2 Vol 3 Part G
The server shall respond with the Server Rx MTU parameter set to the
maximum MTU that this server can receive.
Once the messages have been exchanged, the ATT_MTU shall be set
to the minimum of the Client Rx MTU and Server Rx MTU values.

bt: att_mtu_req (0x0010fd04): Client MTU 672
bt: att_mtu_req (0x0010fd04): Server MTU 65
bt: att_mtu_req (0x0010fd04): Negotiated MTU 65

bt: att_mtu_req (0x0010fd04): Client MTU 42
bt: att_mtu_req (0x0010fd04): Server MTU 65
bt: att_mtu_req (0x0010fd04): Negotiated MTU 42

Change-Id: I13f2f0fc99e99d8188ed15bf7972a9b892612e11
Signed-off-by: Mariusz Skamra <mariusz.skamra@tieto.com>
This commit is contained in:
Mariusz Skamra 2015-10-14 16:41:02 +02:00 • committed by Anas Nashif
commit 2ba3c9aa1d
1 changed files with 10 additions and 9 deletions
Download patch file Download diff file Expand all files Collapse all files

19
net/bluetooth/att.c
View file

@ -134,16 +134,16 @@ static uint8_t att_mtu_req(struct bt_conn *conn, struct bt_buf *buf)
struct bt_att_exchange_mtu_req *req;
struct bt_att_exchange_mtu_rsp *rsp;
struct bt_buf *pdu;
uint16_t mtu;
uint16_t mtu_client, mtu_server;
req = (void *)buf->data;
mtu = sys_le16_to_cpu(req->mtu);
mtu_client = sys_le16_to_cpu(req->mtu);
BT_DBG("Client MTU %u\n", mtu);
BT_DBG("Client MTU %u\n", mtu_client);
/* Check if MTU is valid */
if (mtu < BT_ATT_DEFAULT_LE_MTU) {
if (mtu_client < BT_ATT_DEFAULT_LE_MTU) {
return BT_ATT_ERR_INVALID_PDU;
}
@ -155,17 +155,18 @@ static uint8_t att_mtu_req(struct bt_conn *conn, struct bt_buf *buf)
/* Select MTU based on the amount of room we have in bt_buf including
* one extra byte for ATT header.
*/
mtu = min(mtu, bt_buf_tailroom(pdu) + 1);
mtu_server = bt_buf_tailroom(pdu) + 1;
BT_DBG("Server MTU %u\n", mtu);
att->mtu = mtu;
BT_DBG("Server MTU %u\n", mtu_server);
rsp = bt_buf_add(pdu, sizeof(*rsp));
rsp->mtu = sys_cpu_to_le16(mtu);
rsp->mtu = sys_cpu_to_le16(mtu_server);
bt_l2cap_send(conn, BT_L2CAP_CID_ATT, pdu);
att->mtu = min(mtu_client, mtu_server);
BT_DBG("Negotiated MTU %u\n", att->mtu);
return 0;
}