Hi Luiz,
On Wed, Mar 21, 2018 at 7:31 PM, Luiz Augusto von Dentz
<luiz.dentz@xxxxxxxxx> wrote:
> Hi Andrzej
>
> On Wed, Mar 21, 2018 at 7:47 PM, Andrzej Kaczmarek
> <andrzej.kaczmarek@xxxxxxxxxxx> wrote:
>> If local cache of peer's database has gaps where new services appear
>> after reconnection, GATT client will attempt to discover all included
>> services and characteristics definitions between starting handle of
>> first service and end handle of last service. This means the result
>> will contain also attributes which are already present in active
>> services in local database and thus attempting to add them again will
>> fail.
>
> This is actually by design since that means we can discover
> characteristics of more than one service at once, otherwise we cannot
> take advantage of setting a big MTU since we end up with multiple
> round trips which are normally a lot slower than having the same
> attribute rediscovered. The insert logic should probably be updated to
> ignore if an attribute already exists.
I know it's by design but there are many factors that can actually
make it slower instead of faster and in this particular case it breaks
discovery. In most common scenario (i.e. discovery of contiguous
database) both versions will perform exactly the same since my fix
also merges adjacent services ranges to discover them at once if
possible. One more optimization I can see here is to also merge free
space between consecutive services - this will also save me some time
fixing GATT unit tests ;-)
>> To fix this, instead of discovering whole range we'll only discover
>> ranges for missing services - starting with included services then
>> characteristics. To optimize this process we'll merge ranges of
>> adjacent services.
>>
>> This issue can sometimes be observed with iOS devices as ANCS and CTS
>> services may not be available all the time.
>> ---
>> src/shared/gatt-client.c | 75 +++++++++++++++++++++++++++++++++++++++---------
>> 1 file changed, 61 insertions(+), 14 deletions(-)
>>
>> diff --git a/src/shared/gatt-client.c b/src/shared/gatt-client.c
>> index f0850e0fe..96b4ee034 100644
>> --- a/src/shared/gatt-client.c
>> +++ b/src/shared/gatt-client.c
>> @@ -320,6 +320,7 @@ typedef void (*discovery_op_fail_func_t)(struct discovery_op *op);
>>
>> struct discovery_op {
>> struct bt_gatt_client *client;
>> + struct queue *discov_ranges;
>> struct queue *pending_svcs;
>> struct queue *pending_chrcs;
>> struct queue *ext_prop_desc;
>> @@ -328,8 +329,6 @@ struct discovery_op {
>> uint16_t start;
>> uint16_t end;
>> uint16_t last;
>> - uint16_t svc_first;
>> - uint16_t svc_last;
>> unsigned int db_id;
>> int ref_count;
>> discovery_op_complete_func_t complete_func;
>> @@ -341,6 +340,7 @@ static void discovery_op_free(struct discovery_op *op)
>> if (op->db_id > 0)
>> gatt_db_unregister(op->client->db, op->db_id);
>>
>> + queue_destroy(op->discov_ranges, free);
>> queue_destroy(op->pending_svcs, NULL);
>> queue_destroy(op->pending_chrcs, free);
>> queue_destroy(op->ext_prop_desc, NULL);
>> @@ -406,6 +406,7 @@ static struct discovery_op *discovery_op_create(struct bt_gatt_client *client,
>> struct discovery_op *op;
>>
>> op = new0(struct discovery_op, 1);
>> + op->discov_ranges = queue_new();
>> op->pending_svcs = queue_new();
>> op->pending_chrcs = queue_new();
>> op->ext_prop_desc = queue_new();
>> @@ -477,6 +478,7 @@ static void discover_incl_cb(bool success, uint8_t att_ecode,
>> bt_uuid_t uuid;
>> char uuid_str[MAX_LEN_UUID_STR];
>> unsigned int includes_count, i;
>> + struct handle_range *range;
>>
>> discovery_req_clear(client);
>>
>> @@ -530,12 +532,17 @@ static void discover_incl_cb(bool success, uint8_t att_ecode,
>> }
>>
>> next:
>> + range = queue_pop_head(op->discov_ranges);
>> + if (!range)
>> + goto failed;
>> +
>> client->discovery_req = bt_gatt_discover_characteristics(client->att,
>> - op->svc_first,
>> - op->svc_last,
>> + range->start,
>> + range->end,
>> discover_chrcs_cb,
>> discovery_op_ref(op),
>> discovery_op_unref);
>> + free(range);
>> if (client->discovery_req)
>> return;
>>
>> @@ -871,6 +878,36 @@ static void discover_chrcs_cb(bool success, uint8_t att_ecode,
>> queue_push_tail(op->pending_chrcs, chrc_data);
>> }
>>
>> +next:
>> + /*
>> + * Before attempting to process discovered characteristics make sure we
>> + * discovered all missing ranges.
>> + */
>> + if (queue_length(op->discov_ranges)) {
>> + struct handle_range *range;
>> +
>> + range = queue_peek_head(op->discov_ranges);
>> + if (!range)
>> + goto failed;
>> +
>> + client->discovery_req =
>> + bt_gatt_discover_included_services(client->att,
>> + range->start,
>> + range->end,
>> + discover_incl_cb,
>> + discovery_op_ref(op),
>> + discovery_op_unref);
>> + if (client->discovery_req)
>> + return;
>> +
>> + util_debug(client->debug_callback, client->debug_data,
>> + "Failed to start included services discovery");
>> +
>> + discovery_op_unref(op);
>> +
>> + goto failed;
>> + }
>> +
>> /*
>> * Sequentially discover descriptors for each characteristic and insert
>> * the characteristics into the database as we proceed.
>> @@ -881,7 +918,6 @@ static void discover_chrcs_cb(bool success, uint8_t att_ecode,
>> if (discovering)
>> return;
>>
>> -next:
>> /* Done with the current service */
>> gatt_db_service_set_active(op->cur_svc, true);
>>
>> @@ -900,17 +936,25 @@ static void discovery_found_service(struct discovery_op *op,
>> {
>> /* Skip if service already active */
>> if (!gatt_db_service_get_active(attr)) {
>> + struct handle_range *range;
>> +
>> /* Skip if there are no attributes */
>> if (end == start)
>> gatt_db_service_set_active(attr, true);
>> - else
>> + else {
>> queue_push_tail(op->pending_svcs, attr);
>>
>> - /* Update discovery range */
>> - if (!op->svc_first || op->svc_first > start)
>> - op->svc_first = start;
>> - if (op->svc_last < end)
>> - op->svc_last = end;
>> + /* Update discovery range */
>> + range = queue_peek_tail(op->discov_ranges);
>> + if (!range || (range->end + 1 != start)) {
>> + range = new0(struct handle_range, 1);
>> + range->start = start;
>> + range->end = end;
>> + queue_push_tail(op->discov_ranges, range);
>> + } else {
>> + range->end = end;
>> + }
>> + }
>> } else
>> /* Remove from pending if active */
>> queue_remove(op->pending_svcs, attr);
>> @@ -932,6 +976,7 @@ static void discover_secondary_cb(bool success, uint8_t att_ecode,
>> uint128_t u128;
>> bt_uuid_t uuid;
>> char uuid_str[MAX_LEN_UUID_STR];
>> + struct handle_range *range;
>>
>> discovery_req_clear(client);
>>
>> @@ -991,12 +1036,14 @@ static void discover_secondary_cb(bool success, uint8_t att_ecode,
>> }
>>
>> next:
>> - if (queue_isempty(op->pending_svcs) || !op->svc_first)
>> + if (queue_isempty(op->pending_svcs) || queue_isempty(op->discov_ranges))
>> goto done;
>>
>> + range = queue_peek_head(op->discov_ranges);
>> +
>> client->discovery_req = bt_gatt_discover_included_services(client->att,
>> - op->svc_first,
>> - op->svc_last,
>> + range->start,
>> + range->end,
>> discover_incl_cb,
>> discovery_op_ref(op),
>> discovery_op_unref);
>> --
>> 2.16.2
>>
>> --
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>
>
>
> --
> Luiz Augusto von Dentz
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