Hi Marcel,
On Wed, Feb 26, 2014 at 3:31 AM, Marcel Holtmann <marcel@xxxxxxxxxxxx> wrote:
> Hi Andre,
>
>> This patch introduces the LE auto connection infrastructure which
>> will be used to implement the LE auto connection options.
>>
>> In summary, the auto connection mechanism works as follows: Once the
>> first pending LE connection is created, the background scanning is
>> started. When the target device is found in range, the kernel
>> autonomously starts the connection attempt. If connection is
>> established successfully, that pending LE connection is deleted and
>> the background is stopped.
>>
>> To achieve that, this patch introduces the hci_update_background_scan()
>> which controls the background scanning state. This function starts or
>> stops the background scanning based on the hdev->pend_le_conns list. If
>> there is no pending LE connection, the background scanning is stopped.
>> Otherwise, we start the background scanning.
>>
>> Then, every time a pending LE connection is added we call hci_update_
>> background_scan() so the background scanning is started (in case it is
>> not already running). Likewise, every time a pending LE connection is
>> deleted we call hci_update_background_scan() so the background scanning
>> is stopped (in case this was the last pending LE connection) or it is
>> started again (in case we have more pending LE connections). Finally,
>> we also call hci_update_background_scan() in hci_le_conn_failed() so
>> the background scan is restarted in case the connection establishment
>> fails. This way the background scanning keeps running until all pending
>> LE connection are established.
>>
>> At this point, resolvable addresses are not support by this
>> infrastructure. The proper support is added in upcoming patches.
>>
>> Signed-off-by: Andre Guedes <andre.guedes@xxxxxxxxxxxxx>
>> ---
>> include/net/bluetooth/hci_core.h | 2 +
>> net/bluetooth/hci_conn.c | 5 +++
>> net/bluetooth/hci_core.c | 93 +++++++++++++++++++++++++++++++++++++++-
>> net/bluetooth/hci_event.c | 38 ++++++++++++++++
>> 4 files changed, 136 insertions(+), 2 deletions(-)
>>
>> diff --git a/include/net/bluetooth/hci_core.h b/include/net/bluetooth/hci_core.h
>> index e08405d..617cf49 100644
>> --- a/include/net/bluetooth/hci_core.h
>> +++ b/include/net/bluetooth/hci_core.h
>> @@ -806,6 +806,8 @@ void hci_pend_le_conn_add(struct hci_dev *hdev, bdaddr_t *addr, u8 addr_type);
>> void hci_pend_le_conn_del(struct hci_dev *hdev, bdaddr_t *addr, u8 addr_type);
>> void hci_pend_le_conns_clear(struct hci_dev *hdev);
>>
>> +void hci_update_background_scan(struct hci_dev *hdev);
>> +
>> void hci_uuids_clear(struct hci_dev *hdev);
>>
>> void hci_link_keys_clear(struct hci_dev *hdev);
>> diff --git a/net/bluetooth/hci_conn.c b/net/bluetooth/hci_conn.c
>> index ccf4a4f..e79351c 100644
>> --- a/net/bluetooth/hci_conn.c
>> +++ b/net/bluetooth/hci_conn.c
>> @@ -527,6 +527,11 @@ void hci_le_conn_failed(struct hci_conn *conn, u8 status)
>> hci_proto_connect_cfm(conn, status);
>>
>> hci_conn_del(conn);
>> +
>> + /* Since we may have temporarily stopped the background scanning in
>> + * favor of connection establishment, we should restart it.
>> + */
>> + hci_update_background_scan(hdev);
>> }
>>
>> static void create_le_conn_complete(struct hci_dev *hdev, u8 status)
>> diff --git a/net/bluetooth/hci_core.c b/net/bluetooth/hci_core.c
>> index 142ecd8..d242217 100644
>> --- a/net/bluetooth/hci_core.c
>> +++ b/net/bluetooth/hci_core.c
>> @@ -3281,7 +3281,7 @@ void hci_pend_le_conn_add(struct hci_dev *hdev, bdaddr_t *addr, u8 addr_type)
>>
>> entry = hci_pend_le_conn_lookup(hdev, addr, addr_type);
>> if (entry)
>> - return;
>> + goto done;
>>
>> entry = kzalloc(sizeof(*entry), GFP_KERNEL);
>> if (!entry) {
>> @@ -3295,6 +3295,9 @@ void hci_pend_le_conn_add(struct hci_dev *hdev, bdaddr_t *addr, u8 addr_type)
>> list_add(&entry->list, &hdev->pend_le_conns);
>>
>> BT_DBG("addr %pMR (type %u)", addr, addr_type);
>> +
>> +done:
>> + hci_update_background_scan(hdev);
>> }
>>
>> /* This function requires the caller holds hdev->lock */
>> @@ -3304,12 +3307,15 @@ void hci_pend_le_conn_del(struct hci_dev *hdev, bdaddr_t *addr, u8 addr_type)
>>
>> entry = hci_pend_le_conn_lookup(hdev, addr, addr_type);
>> if (!entry)
>> - return;
>> + goto done;
>>
>> list_del(&entry->list);
>> kfree(entry);
>>
>> BT_DBG("addr %pMR (type %u)", addr, addr_type);
>> +
>> +done:
>> + hci_update_background_scan(hdev);
>> }
>>
>> /* This function requires the caller holds hdev->lock */
>> @@ -4946,3 +4952,86 @@ void hci_req_add_le_scan_disable(struct hci_request *req)
>> cp.enable = LE_SCAN_DISABLE;
>> hci_req_add(req, HCI_OP_LE_SET_SCAN_ENABLE, sizeof(cp), &cp);
>> }
>> +
>> +static void update_background_scan_complete(struct hci_dev *hdev, u8 status)
>> +{
>> + if (status)
>> + BT_DBG("HCI request failed to update background scanning: "
>> + "status 0x%2.2x", status);
>> +}
>> +
>> +/* This function controls the background scanning based on hdev->pend_le_conns
>> + * list. If there are pending LE connection we start the background scanning,
>> + * otherwise we stop it.
>> + *
>> + * This function requires the caller holds hdev->lock.
>> + */
>> +void hci_update_background_scan(struct hci_dev *hdev)
>> +{
>> + struct hci_cp_le_set_scan_param param_cp;
>> + struct hci_cp_le_set_scan_enable enable_cp;
>> + struct hci_request req;
>> + struct hci_conn *conn;
>> + int err;
>> +
>> + hci_req_init(&req, hdev);
>> +
>> + if (list_empty(&hdev->pend_le_conns)) {
>> + /* If there is no pending LE connections, we should stop
>> + * the background scanning.
>> + */
>> +
>> + /* If controller is not scanning we are done. */
>> + if (!test_bit(HCI_LE_SCAN, &hdev->dev_flags))
>> + return;
>> +
>> + hci_req_add_le_scan_disable(&req);
>> +
>> + BT_DBG("%s stopping background scanning", hdev->name);
>> + } else {
>> + u8 own_addr_type;
>> +
>> + /* If there is at least one pending LE connection, we should
>> + * keep the background scan running.
>> + */
>> +
>> + /* If controller is already scanning we are done. */
>> + if (test_bit(HCI_LE_SCAN, &hdev->dev_flags))
>> + return;
>> +
>> + /* If controller is connecting, we should not start scanning
>> + * since some controllers are not able to scan and connect at
>> + * the same time.
>> + */
>> + conn = hci_conn_hash_lookup_state(hdev, LE_LINK, BT_CONNECT);
>> + if (conn)
>> + return;
>> +
>> + /* Use private address since remote doesn't need to identify us.
>> + * Strictly speaking, this is not required since no SCAN_REQ is
>> + * sent in passive scanning.
>> + */
>> + if (hci_update_random_address(&req, true, &own_addr_type))
>> + return;
>
> the comment above is confusing. Reason is simple. We might use a RPA if LE Privacy has been enabled. The require_privacy == true will fallback to URPA in case privacy is not enabled. If privacy is enabled, then no matter what require_privacy is set to, we will use a random address.
>
> It should say something along the lines of this:
>
> /* Set require_privacy to true to avoid identification from
> * unknown peer devices. Since this is passive scanning, no
> * SCAN_REQ using the local identity should be sent. Mandating
> * privacy is just an extra precaution.
> */
Ok, I'll fix this comment.
BR,
Andre
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