Re: [PATCH v2 2/2] Bluetooth: hci_sync: Set Privacy Mode when updating the resolving list

[Marcel Holtmann <marcel@holtmann.org>]

Hi Luiz,

>>> This adds support for Set Privacy Mode when updating the resolving list
>>> when HCI_CONN_FLAG_DEVICE_PRIVACY so the controller shall use Device
>>> Mode for devices programmed in the resolving list, Device Mode is
>>> actually required when the remote device are not able to use RPA as
>>> otherwise the default mode is Network Privacy Mode in which only
>>> allows RPAs thus the controller would filter out advertisement using
>>> identity addresses for which there is an IRK.
>>> 
>>> Signed-off-by: Luiz Augusto von Dentz <luiz.von.dentz@intel.com>
>>> ---
>>> include/net/bluetooth/hci.h      | 10 ++++++
>>> include/net/bluetooth/hci_core.h |  1 +
>>> net/bluetooth/hci_event.c        | 29 +++++++++++++++++
>>> net/bluetooth/hci_sync.c         | 53 ++++++++++++++++++++++++++++----
>>> 4 files changed, 87 insertions(+), 6 deletions(-)
>>> 
>>> diff --git a/include/net/bluetooth/hci.h b/include/net/bluetooth/hci.h
>>> index 84db6b275231..7444d286e6be 100644
>>> --- a/include/net/bluetooth/hci.h
>>> +++ b/include/net/bluetooth/hci.h
>>> @@ -1931,6 +1931,16 @@ struct hci_rp_le_read_transmit_power {
>>>      __s8  max_le_tx_power;
>>> } __packed;
>>> 
>>> +#define HCI_NETWORK_PRIVACY          0x00
>>> +#define HCI_DEVICE_PRIVACY           0x01
>>> +
>>> +#define HCI_OP_LE_SET_PRIVACY_MODE   0x204e
>>> +struct hci_cp_le_set_privacy_mode {
>>> +     __u8  bdaddr_type;
>>> +     bdaddr_t  bdaddr;
>>> +     __u8  mode;
>>> +} __packed;
>>> +
>>> #define HCI_OP_LE_READ_BUFFER_SIZE_V2 0x2060
>>> struct hci_rp_le_read_buffer_size_v2 {
>>>      __u8    status;
>>> diff --git a/include/net/bluetooth/hci_core.h b/include/net/bluetooth/hci_core.h
>>> index 42ba40df6e20..0b3de5411948 100644
>>> --- a/include/net/bluetooth/hci_core.h
>>> +++ b/include/net/bluetooth/hci_core.h
>>> @@ -755,6 +755,7 @@ struct hci_conn_params {
>>> 
>>>      struct hci_conn *conn;
>>>      bool explicit_connect;
>>> +     u8  privacy_mode;
>>>      u32 current_flags;
>>> };
>>> 
>>> diff --git a/net/bluetooth/hci_event.c b/net/bluetooth/hci_event.c
>>> index efc5458b1345..51c88f4f1274 100644
>>> --- a/net/bluetooth/hci_event.c
>>> +++ b/net/bluetooth/hci_event.c
>>> @@ -1300,6 +1300,31 @@ static void hci_cc_le_read_transmit_power(struct hci_dev *hdev,
>>>      hdev->max_le_tx_power = rp->max_le_tx_power;
>>> }
>>> 
>>> +static void hci_cc_le_set_privacy_mode(struct hci_dev *hdev,
>>> +                                    struct sk_buff *skb)
>>> +{
>>> +     __u8 status = *((__u8 *)skb->data);
>>> +     struct hci_cp_le_set_privacy_mode *cp;
>>> +     struct hci_conn_params *params;
>>> +
>>> +     bt_dev_dbg(hdev, "status 0x%2.2x", status);
>>> +
>>> +     if (status)
>>> +             return;
>>> +
>>> +     cp = hci_sent_cmd_data(hdev, HCI_OP_LE_SET_PRIVACY_MODE);
>>> +     if (!cp)
>>> +             return;
>>> +
>>> +     hci_dev_lock(hdev);
>>> +
>>> +     params = hci_conn_params_lookup(hdev, &cp->bdaddr, cp->bdaddr_type);
>>> +     if (params)
>>> +             params->privacy_mode = cp->mode;
>>> +
>>> +     hci_dev_unlock(hdev);
>>> +}
>>> +
>>> static void hci_cc_le_set_adv_enable(struct hci_dev *hdev, struct sk_buff *skb)
>>> {
>>>      __u8 *sent, status = *((__u8 *) skb->data);
>>> @@ -3812,6 +3837,10 @@ static void hci_cmd_complete_evt(struct hci_dev *hdev, struct sk_buff *skb,
>>>              hci_cc_le_read_transmit_power(hdev, skb);
>>>              break;
>>> 
>>> +     case HCI_OP_LE_SET_PRIVACY_MODE:
>>> +             hci_cc_le_set_privacy_mode(hdev, skb);
>>> +             break;
>>> +
>>>      default:
>>>              BT_DBG("%s opcode 0x%4.4x", hdev->name, *opcode);
>>>              break;
>>> diff --git a/net/bluetooth/hci_sync.c b/net/bluetooth/hci_sync.c
>>> index ad86caf41f91..08acd664590b 100644
>>> --- a/net/bluetooth/hci_sync.c
>>> +++ b/net/bluetooth/hci_sync.c
>>> @@ -1580,8 +1580,42 @@ static int hci_le_add_resolve_list_sync(struct hci_dev *hdev,
>>>                                   sizeof(cp), &cp, HCI_CMD_TIMEOUT);
>>> }
>>> 
>>> +/* Set Device Privacy Mode. */
>>> +static int hci_le_set_privacy_mode_sync(struct hci_dev *hdev,
>>> +                                     struct hci_conn_params *params)
>>> +{
>>> +     struct hci_cp_le_set_privacy_mode cp;
>>> +     struct smp_irk *irk;
>>> +
>>> +     /* If device privacy mode has already been set there is nothing to do */
>>> +     if (params->privacy_mode == HCI_DEVICE_PRIVACY)
>>> +             return 0;
>>> +
>>> +     /* Set Privacy Mode requires the use of resolving list (aka. LL Privacy)
>>> +      * by default Network Mode is used so only really send the command if
>>> +      * Device Mode is required (HCI_CONN_FLAG_DEVICE_PRIVACY).
>>> +      */
>>> +     if (!privacy_mode_capable(hdev) ||
>>> +         !hci_conn_test_flag(HCI_CONN_FLAG_DEVICE_PRIVACY,
>>> +                             params->current_flags))
>>> +             return 0;
>> 
>> does this also account for the fact that LL Privacy is behind an experimental option. I think in the previous patch it is more important to check if LL Privacy is actually enabled via experimental setting.
> 
> Yep, it does check it:
> 
> #define privacy_mode_capable(dev) (use_ll_privacy(dev) && \
>   (hdev->commands[39] & 0x04))
> 
> That said, maybe we should check it again since one wouldn't be able
> to set HCI_CONN_FLAG_DEVICE_PRIVACY as it wouldn't be supported.

I think we should just store the supported device flags in hdev determined during power on. And then just allow setting or unsetting of it based on the fact that it is supported.

On a different note, while checking above, I found this:

	changed = !hci_dev_test_flag(hdev, HCI_ENABLE_LL_PRIVACY);
	hci_dev_set_flag(hdev, HCI_ENABLE_LL_PRIVACY);

This is not ok. It is fully racy. We need to have hci_dev_test_and_set_flag() and hci_dev_test_and_clear_flag() helpers.

Regards

Marcel