Hi,
On Thu, May 25, 2017 at 3:10 AM, <mcchou@xxxxxxxxxxxx> wrote:
> From: Miao-chen Chou <mcchou@xxxxxxxxxxxx>
>
> This patch adds gatt_db_cleanup() function to clear client-role GATT DB for the
> unpaired device. According to Core Specification v4.2 [1] and v5.0 [2], the
> attributes should be cleared between unbonded devices after disconnection, since
> the attributes are no long valid.
>
> [1] Page 525, Section 2.5.2 Attribute Caching, Part G, Volume 3: "For clients
> that do not have a trusted relationship with the server, the attribute cache is
> valid only during the connection."
> [2] Page 2227, Section 2.5.2 Attribute Caching, Part G, Volume 3: "For clients
> that do not have a trusted relationship with the server, the attribute cache is
> valid only during the connection."
This ignores the fact that devices which don't implement service
changed characteristic shall not change its database so the discovery
may be skipped:
BLUETOOTH SPECIFICATION Version 5.0 | Vol 3, Part C
page 2079
"If the client had previously determined that the server did not have
the «Service Changed» characteristic then service discovery may be
skipped."
Also note that we do persist the cache to be able to persist
configuration such as notifications and indications, perhaps in chrome
you don't really have a use for it but in systems where reconnection
is supported, afaik chrome OS doesn't, it is a must have since
notifications and indications would not work during the discovery if
we remove the cache. And please remember that discovery is a very slow
procedure, in most cases it takes a good 3-5 seconds to rediscover,
depending on db size it may take over 10 seconds and until it is
completed no attribute can be accessed.
We could, however, have a config option to select the behavior of the
cache or have an option for auto-connect so disabling it also disable
caching.
> ---
> src/device.c | 13 +++++++++++++
> 1 file changed, 13 insertions(+)
>
> diff --git a/src/device.c b/src/device.c
> index 1b05561e4..f8cde0b43 100644
> --- a/src/device.c
> +++ b/src/device.c
> @@ -267,6 +267,7 @@ struct pending_sdp_query {
>
> static int device_browse_gatt(struct btd_device *device, DBusMessage *msg);
> static int device_browse_sdp(struct btd_device *device, DBusMessage *msg);
> +static void store_gatt_db(struct btd_device *device);
>
> static struct pending_sdp_query *pending_sdp_query_new(DBusConnection *conn,
> DBusMessage *msg, const struct btd_device *dev)
> @@ -546,6 +547,15 @@ static void browse_request_free(struct browse_req *req)
> g_free(req);
> }
>
> +static void gatt_db_cleanup(struct btd_device* device)
> +{
> + if (!device->db)
> + return;
> +
> + gatt_db_clear(device->db);
> + store_gatt_db(device);
> +}
> +
> static void gatt_client_cleanup(struct btd_device *device)
> {
> if (!device->client)
> @@ -578,6 +588,9 @@ static void attio_cleanup(struct btd_device *device)
> device->att_io = NULL;
> }
>
> + if (!device->bredr_state.bonded && !device->le_state.bonded)
> + gatt_db_cleanup(device);
> +
> gatt_client_cleanup(device);
> gatt_server_cleanup(device);
>
> --
> 2.13.0.219.gdb65acc882-goog
>
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