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    SubjectRe: Bluetooth: Add framework for device found filtering based on UUID
    From
    On Thu, Dec 11, 2014 at 11:48 PM, Linux Kernel Mailing List
    <linux-kernel@vger.kernel.org> wrote:
    > Gitweb: http://git.kernel.org/linus/;a=commit;h=b487b9ce9340a6e98d7f8277399304b23b7be456
    > Commit: b487b9ce9340a6e98d7f8277399304b23b7be456
    > Parent: bda157a40077447b25a1172a17b8ef81a2905cb7
    > Refname: refs/heads/master
    > Author: Marcel Holtmann <marcel@holtmann.org>
    > AuthorDate: Fri Dec 5 10:55:57 2014 +0100
    > Committer: Johan Hedberg <johan.hedberg@intel.com>
    > CommitDate: Fri Dec 5 12:37:35 2014 +0200
    >
    > Bluetooth: Add framework for device found filtering based on UUID
    >
    > Using Start Service Discovery provides the option to specifiy a list
    > of UUID that are used to filter out device found events. This patch
    > provides the framework for hooking up the UUID filter.
    >
    > Signed-off-by: Marcel Holtmann <marcel@holtmann.org>
    > Signed-off-by: Johan Hedberg <johan.hedberg@intel.com>
    > ---
    > net/bluetooth/mgmt.c | 54 ++++++++++++++++++++++++++++++++++++++++++++++++++--
    > 1 file changed, 52 insertions(+), 2 deletions(-)
    >
    > diff --git a/net/bluetooth/mgmt.c b/net/bluetooth/mgmt.c
    > index 1715c91..e39190a 100644
    > --- a/net/bluetooth/mgmt.c
    > +++ b/net/bluetooth/mgmt.c
    > @@ -6802,6 +6802,11 @@ void mgmt_read_local_oob_data_complete(struct hci_dev *hdev, u8 *hash192,
    > mgmt_pending_remove(cmd);
    > }
    >
    > +static bool eir_has_uuids(u8 *eir, u16 eir_len, u16 uuid_count, u8 (*uuids)[16])
    > +{
    > + return false;
    > +}
    > +
    > void mgmt_device_found(struct hci_dev *hdev, bdaddr_t *bdaddr, u8 link_type,
    > u8 addr_type, u8 *dev_class, s8 rssi, u32 flags,
    > u8 *eir, u16 eir_len, u8 *scan_rsp, u8 scan_rsp_len)
    > @@ -6809,6 +6814,7 @@ void mgmt_device_found(struct hci_dev *hdev, bdaddr_t *bdaddr, u8 link_type,
    > char buf[512];
    > struct mgmt_ev_device_found *ev = (void *) buf;
    > size_t ev_size;
    > + bool match;

    net/bluetooth/mgmt.c: In function ‘mgmt_device_found’:
    net/bluetooth/mgmt.c:6993: warning: ‘match’ may be used uninitialized
    in this function

    All tests for "match" are protected by "if (hdev->discovery.uuid_count > 0)",
    so we only have to care about that case.

    > /* Don't send events for a non-kernel initiated discovery. With
    > * LE one exception is if we have pend_le_reports > 0 in which
    > @@ -6843,15 +6849,59 @@ void mgmt_device_found(struct hci_dev *hdev, bdaddr_t *bdaddr, u8 link_type,
    > ev->rssi = rssi;
    > ev->flags = cpu_to_le32(flags);
    >
    > - if (eir_len > 0)
    > + if (eir_len > 0) {
    > + /* When using service discovery and a list of UUID is
    > + * provided, results with no matching UUID should be
    > + * dropped. In case there is a match the result is
    > + * kept and checking possible scan response data
    > + * will be skipped.
    > + */
    > + if (hdev->discovery.uuid_count > 0) {
    > + match = eir_has_uuids(eir, eir_len,
    > + hdev->discovery.uuid_count,
    > + hdev->discovery.uuids);
    > + if (!match)
    > + return;
    > + }

    If we get here and if (hdev->discovery.uuid_count > 0), "match" must be true.

    > +
    > + /* Copy EIR or advertising data into event */
    > memcpy(ev->eir, eir, eir_len);
    > + } else {
    > + /* When using service discovery and a list of UUID is
    > + * provided, results with empty EIR or advertising data
    > + * should be dropped since they do not match any UUID.
    > + */
    > + if (hdev->discovery.uuid_count > 0)
    > + return;

    We will never get here if (hdev->discovery.uuid_count > 0).

    > + }

    Hence if we get here and if (hdev->discovery.uuid_count > 0),
    "match" is always true.

    > if (dev_class && !eir_has_data_type(ev->eir, eir_len, EIR_CLASS_OF_DEV))
    > eir_len = eir_append_data(ev->eir, eir_len, EIR_CLASS_OF_DEV,
    > dev_class, 3);
    >
    > - if (scan_rsp_len > 0)
    > + if (scan_rsp_len > 0) {
    > + /* When using service discovery and a list of UUID is
    > + * provided, results with no matching UUID should be
    > + * dropped if there is no previous match from the
    > + * advertising data.
    > + */
    > + if (hdev->discovery.uuid_count > 0) {
    > + if (!match && !eir_has_uuids(scan_rsp, scan_rsp_len,

    "match" is true, so this whole block is useless.

    > + hdev->discovery.uuid_count,
    > + hdev->discovery.uuids))
    > + return;
    > + }
    > +
    > + /* Append scan response data to event */
    > memcpy(ev->eir + eir_len, scan_rsp, scan_rsp_len);
    > + } else {
    > + /* When using service discovery and a list of UUID is
    > + * provided, results with empty scan response and no
    > + * previous matched advertising data should be dropped.
    > + */
    > + if (hdev->discovery.uuid_count > 0 && !match)

    "match" is true, so this whole block is useless.

    > + return;
    > + }
    >
    > ev->eir_len = cpu_to_le16(eir_len + scan_rsp_len);
    > ev_size = sizeof(*ev) + eir_len + scan_rsp_len;

    Is my analysis correct?
    Am I missing something?

    Gr{oetje,eeting}s,

    Geert

    --
    Geert Uytterhoeven -- There's lots of Linux beyond ia32 -- geert@linux-m68k.org
    In personal conversations with technical people, I call myself a hacker. But
    when I'm talking to journalists I just say "programmer" or something like that.
    -- Linus Torvalds


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