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

[Luiz Augusto von Dentz <luiz.dentz@gmail.com>]

Hi Marcel,

On Fri, Nov 19, 2021 at 2:02 AM Marcel Holtmann <marcel@holtmann.org> wrote:
>
> 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.

> Regards
>
> Marcel
>


-- 
Luiz Augusto von Dentz