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Date:   Tue, 22 Sep 2020 14:52:04 -0700
From:   Luiz Augusto von Dentz <luiz.dentz@...il.com>
To:     Howard Chung <howardchung@...gle.com>
Cc:     "linux-bluetooth@...r.kernel.org" <linux-bluetooth@...r.kernel.org>,
        Marcel Holtmann <marcel@...tmann.org>,
        Alain Michaud <alainm@...omium.org>,
        Miao-chen Chou <mcchou@...omium.org>, mmandlik@...omium.orgi,
        Manish Mandlik <mmandlik@...omium.org>,
        "David S. Miller" <davem@...emloft.net>,
        Jakub Kicinski <kuba@...nel.org>,
        Johan Hedberg <johan.hedberg@...il.com>,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
        "open list:NETWORKING [GENERAL]" <netdev@...r.kernel.org>
Subject: Re: [PATCH v4 1/4] Bluetooth: Interleave with allowlist scan

Hi Howard,

On Sun, Sep 20, 2020 at 9:23 PM Howard Chung <howardchung@...gle.com> wrote:
>
> This patch implements the interleaving between allowlist scan and
> no-filter scan. It'll be used to save power when at least one monitor is
> registered and at least one pending connection or one device to be
> scanned for.
>
> The durations of the allowlist scan and the no-filter scan are
> controlled by MGMT command: Set Default System Configuration. The
> default values are set randomly for now.
>
> Signed-off-by: Howard Chung <howardchung@...gle.com>
> Reviewed-by: Alain Michaud <alainm@...omium.org>
> Reviewed-by: Manish Mandlik <mmandlik@...omium.org>
> ---
>
> Changes in v4:
> - Rebase to bluetooth-next/master (previous 2 patches are applied)
> - Fix over 80 chars limit in mgmt_config.c
> - Set EnableAdvMonInterleaveScan default to Disable
>
> Changes in v3:
> - Remove 'Bluez' prefix
>
> Changes in v2:
> - remove 'case 0x001c' in mgmt_config.c
>
>  include/net/bluetooth/hci_core.h |  10 +++
>  net/bluetooth/hci_core.c         |   4 +
>  net/bluetooth/hci_request.c      | 137 +++++++++++++++++++++++++++++--
>  net/bluetooth/mgmt_config.c      |  10 +++
>  4 files changed, 153 insertions(+), 8 deletions(-)
>
> diff --git a/include/net/bluetooth/hci_core.h b/include/net/bluetooth/hci_core.h
> index 9873e1c8cd163..179350f869fdb 100644
> --- a/include/net/bluetooth/hci_core.h
> +++ b/include/net/bluetooth/hci_core.h
> @@ -361,6 +361,8 @@ struct hci_dev {
>         __u8            ssp_debug_mode;
>         __u8            hw_error_code;
>         __u32           clock;
> +       __u16           advmon_allowlist_duration;
> +       __u16           advmon_no_filter_duration;
>
>         __u16           devid_source;
>         __u16           devid_vendor;
> @@ -542,6 +544,14 @@ struct hci_dev {
>         struct delayed_work     rpa_expired;
>         bdaddr_t                rpa;
>
> +       enum {
> +               ADV_MONITOR_SCAN_NONE,
> +               ADV_MONITOR_SCAN_NO_FILTER,
> +               ADV_MONITOR_SCAN_ALLOWLIST
> +       } adv_monitor_scan_state;
> +
> +       struct delayed_work     interleave_adv_monitor_scan;
> +
>  #if IS_ENABLED(CONFIG_BT_LEDS)
>         struct led_trigger      *power_led;
>  #endif
> diff --git a/net/bluetooth/hci_core.c b/net/bluetooth/hci_core.c
> index f30a1f5950e15..6c8850149265a 100644
> --- a/net/bluetooth/hci_core.c
> +++ b/net/bluetooth/hci_core.c
> @@ -3592,6 +3592,10 @@ struct hci_dev *hci_alloc_dev(void)
>         hdev->cur_adv_instance = 0x00;
>         hdev->adv_instance_timeout = 0;
>
> +       /* The default values will be chosen in the future */
> +       hdev->advmon_allowlist_duration = 300;
> +       hdev->advmon_no_filter_duration = 500;
> +
>         hdev->sniff_max_interval = 800;
>         hdev->sniff_min_interval = 80;
>
> diff --git a/net/bluetooth/hci_request.c b/net/bluetooth/hci_request.c
> index d2b06f5c93804..89443b48d90ce 100644
> --- a/net/bluetooth/hci_request.c
> +++ b/net/bluetooth/hci_request.c
> @@ -378,6 +378,57 @@ void __hci_req_write_fast_connectable(struct hci_request *req, bool enable)
>                 hci_req_add(req, HCI_OP_WRITE_PAGE_SCAN_TYPE, 1, &type);
>  }
>
> +static void start_interleave_scan(struct hci_dev *hdev)
> +{
> +       hdev->adv_monitor_scan_state = ADV_MONITOR_SCAN_NO_FILTER;
> +       queue_delayed_work(hdev->req_workqueue,
> +                          &hdev->interleave_adv_monitor_scan, 0);
> +}
> +
> +static bool is_interleave_scanning(struct hci_dev *hdev)
> +{
> +       return hdev->adv_monitor_scan_state != ADV_MONITOR_SCAN_NONE;
> +}
> +
> +static void cancel_interleave_scan(struct hci_dev *hdev)
> +{
> +       bt_dev_dbg(hdev, "%s cancelling interleave scan", hdev->name);
> +
> +       cancel_delayed_work_sync(&hdev->interleave_adv_monitor_scan);
> +
> +       hdev->adv_monitor_scan_state = ADV_MONITOR_SCAN_NONE;
> +}
> +
> +/* Return true if interleave_scan is running after exiting this function,
> + * otherwise, return false
> + */
> +static bool update_adv_monitor_scan_state(struct hci_dev *hdev)
> +{
> +       if (!hci_is_adv_monitoring(hdev) ||
> +           (list_empty(&hdev->pend_le_conns) &&
> +            list_empty(&hdev->pend_le_reports))) {
> +               if (is_interleave_scanning(hdev)) {
> +                       /* If the interleave condition no longer holds, cancel
> +                        * the existed interleave scan.
> +                        */
> +                       cancel_interleave_scan(hdev);
> +               }
> +               return false;
> +       }
> +
> +       if (!is_interleave_scanning(hdev)) {
> +               /* If there is at least one ADV monitors and one pending LE
> +                * connection or one device to be scanned for, we should
> +                * alternate between allowlist scan and one without any filters
> +                * to save power.
> +                */
> +               start_interleave_scan(hdev);
> +               bt_dev_dbg(hdev, "%s starting interleave scan", hdev->name);
> +       }
> +
> +       return true;
> +}
> +
>  /* 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.
> @@ -449,9 +500,11 @@ static void __hci_update_background_scan(struct hci_request *req)
>                 if (hci_dev_test_flag(hdev, HCI_LE_SCAN))
>                         hci_req_add_le_scan_disable(req, false);
>
> -               hci_req_add_le_passive_scan(req);
> -
> -               BT_DBG("%s starting background scanning", hdev->name);
> +               if (!update_adv_monitor_scan_state(hdev)) {
> +                       hci_req_add_le_passive_scan(req);
> +                       bt_dev_dbg(hdev, "%s starting background scanning",
> +                                  hdev->name);
> +               }

We should probably try to follow the same names as used for
background_scan here, e.g. name it __hci_update_interleaved_scan, also
perhaps that should fallback to hci_req_add_le_passive_scan on its
own.

>         }
>  }
>
> @@ -844,12 +897,17 @@ static u8 update_white_list(struct hci_request *req)
>                         return 0x00;
>         }
>
> -       /* Once the controller offloading of advertisement monitor is in place,
> -        * the if condition should include the support of MSFT extension
> -        * support. If suspend is ongoing, whitelist should be the default to
> -        * prevent waking by random advertisements.
> +       /* Use the allowlist unless the following conditions are all true:
> +        * - We are not currently suspending
> +        * - There are 1 or more ADV monitors registered
> +        * - Interleaved scanning is not currently using the allowlist
> +        *
> +        * Once the controller offloading of advertisement monitor is in place,
> +        * the above condition should include the support of MSFT extension
> +        * support.
>          */
> -       if (!idr_is_empty(&hdev->adv_monitors_idr) && !hdev->suspended)
> +       if (!idr_is_empty(&hdev->adv_monitors_idr) && !hdev->suspended &&
> +           hdev->adv_monitor_scan_state != ADV_MONITOR_SCAN_ALLOWLIST)
>                 return 0x00;
>
>         /* Select filter policy to use white list */
> @@ -1002,6 +1060,7 @@ void hci_req_add_le_passive_scan(struct hci_request *req)
>                                       &own_addr_type))
>                 return;
>
> +       bt_dev_dbg(hdev, "interleave state %d", hdev->adv_monitor_scan_state);

Is this really needed here, I though hci_req_add_le_passive_scan would
only be used if interleaved scanning was not used.

>         /* Adding or removing entries from the white list must
>          * happen before enabling scanning. The controller does
>          * not allow white list modification while scanning.
> @@ -1871,6 +1930,64 @@ static void adv_timeout_expire(struct work_struct *work)
>         hci_dev_unlock(hdev);
>  }
>
> +static int add_le_interleave_adv_monitor_scan(struct hci_request *req,
> +                                             unsigned long opt)

Rename to hci_req_add_le_interleaved_scan

> +{
> +       struct hci_dev *hdev = req->hdev;
> +       int ret = 0;
> +
> +       hci_dev_lock(hdev);
> +
> +       if (hci_dev_test_flag(hdev, HCI_LE_SCAN))
> +               hci_req_add_le_scan_disable(req, false);
> +       hci_req_add_le_passive_scan(req);
> +
> +       switch (hdev->adv_monitor_scan_state) {
> +       case ADV_MONITOR_SCAN_ALLOWLIST:
> +               bt_dev_dbg(hdev, "next state: allowlist");
> +               hdev->adv_monitor_scan_state = ADV_MONITOR_SCAN_NO_FILTER;
> +               break;
> +       case ADV_MONITOR_SCAN_NO_FILTER:
> +               bt_dev_dbg(hdev, "next state: no filter");
> +               hdev->adv_monitor_scan_state = ADV_MONITOR_SCAN_ALLOWLIST;
> +               break;
> +       case ADV_MONITOR_SCAN_NONE:
> +       default:
> +               BT_ERR("unexpected error");
> +               ret = -1;
> +       }
> +
> +       hci_dev_unlock(hdev);
> +
> +       return ret;
> +}
> +
> +static void interleave_adv_monitor_scan_work(struct work_struct *work)

Rename to interleave_scan_work

> +{
> +       struct hci_dev *hdev = container_of(work, struct hci_dev,
> +                                           interleave_adv_monitor_scan.work);
> +       u8 status;
> +       unsigned long timeout;
> +
> +       if (hdev->adv_monitor_scan_state == ADV_MONITOR_SCAN_ALLOWLIST) {
> +               timeout = msecs_to_jiffies(hdev->advmon_allowlist_duration);
> +       } else if (hdev->adv_monitor_scan_state == ADV_MONITOR_SCAN_NO_FILTER) {
> +               timeout = msecs_to_jiffies(hdev->advmon_no_filter_duration);
> +       } else {
> +               bt_dev_err(hdev, "unexpected error");
> +               return;
> +       }
> +
> +       hci_req_sync(hdev, add_le_interleave_adv_monitor_scan, 0,
> +                    HCI_CMD_TIMEOUT, &status);
> +
> +       /* Don't continue interleaving if it was canceled */
> +       if (is_interleave_scanning(hdev)) {
> +               queue_delayed_work(hdev->req_workqueue,
> +                                  &hdev->interleave_adv_monitor_scan, timeout);
> +       }
> +}
> +
>  int hci_get_random_address(struct hci_dev *hdev, bool require_privacy,
>                            bool use_rpa, struct adv_info *adv_instance,
>                            u8 *own_addr_type, bdaddr_t *rand_addr)
> @@ -3292,6 +3409,8 @@ void hci_request_setup(struct hci_dev *hdev)
>         INIT_DELAYED_WORK(&hdev->le_scan_disable, le_scan_disable_work);
>         INIT_DELAYED_WORK(&hdev->le_scan_restart, le_scan_restart_work);
>         INIT_DELAYED_WORK(&hdev->adv_instance_expire, adv_timeout_expire);
> +       INIT_DELAYED_WORK(&hdev->interleave_adv_monitor_scan,
> +                         interleave_adv_monitor_scan_work);

We can probably remove adv_monitor term on functions/variables and
just use interleave_scan.

>  }
>
>  void hci_request_cancel_all(struct hci_dev *hdev)
> @@ -3311,4 +3430,6 @@ void hci_request_cancel_all(struct hci_dev *hdev)
>                 cancel_delayed_work_sync(&hdev->adv_instance_expire);
>                 hdev->adv_instance_timeout = 0;
>         }
> +
> +       cancel_interleave_scan(hdev);
>  }
> diff --git a/net/bluetooth/mgmt_config.c b/net/bluetooth/mgmt_config.c
> index b30b571f8caf8..2d3ad288c78ac 100644
> --- a/net/bluetooth/mgmt_config.c
> +++ b/net/bluetooth/mgmt_config.c
> @@ -67,6 +67,8 @@ int read_def_system_config(struct sock *sk, struct hci_dev *hdev, void *data,
>                 HDEV_PARAM_U16(0x001a, le_supv_timeout),
>                 HDEV_PARAM_U16_JIFFIES_TO_MSECS(0x001b,
>                                                 def_le_autoconnect_timeout),
> +               HDEV_PARAM_U16(0x001d, advmon_allowlist_duration),
> +               HDEV_PARAM_U16(0x001e, advmon_no_filter_duration),
>         };
>         struct mgmt_rp_read_def_system_config *rp = (void *)params;
>
> @@ -138,6 +140,8 @@ int set_def_system_config(struct sock *sk, struct hci_dev *hdev, void *data,
>                 case 0x0019:
>                 case 0x001a:
>                 case 0x001b:
> +               case 0x001d:
> +               case 0x001e:
>                         if (len != sizeof(u16)) {
>                                 bt_dev_warn(hdev, "invalid length %d, exp %zu for type %d",
>                                             len, sizeof(u16), type);
> @@ -251,6 +255,12 @@ int set_def_system_config(struct sock *sk, struct hci_dev *hdev, void *data,
>                         hdev->def_le_autoconnect_timeout =
>                                         msecs_to_jiffies(TLV_GET_LE16(buffer));
>                         break;
> +               case 0x0001d:
> +                       hdev->advmon_allowlist_duration = TLV_GET_LE16(buffer);
> +                       break;
> +               case 0x0001e:
> +                       hdev->advmon_no_filter_duration = TLV_GET_LE16(buffer);
> +                       break;
>                 default:
>                         bt_dev_warn(hdev, "unsupported parameter %u", type);
>                         break;
> --
> 2.28.0.681.g6f77f65b4e-goog
>


-- 
Luiz Augusto von Dentz

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