[PATCH BlueZ] shared/bap: wait for GATT client ready before ASCS/PACS discovery

BAP client fails to find endpoints if GATT services are not resolved
when the GATT client is attached to the session.  This condition
almost always occurs on the first BAP connection to a device between
bluetoothd restarts, and may occur also otherwise.

The BAP client code discovers ASCS/PACS services and characteristics at
client attach time.

Fix the connection issue by postponing PAC/ASE discovery until the
GATT client is ready, if it was not ready at attach time.
---

Notes:
    Typical bluetoothctl output in the failing case, without this patch:
    
    $ sudo systemctl restart bluetooth
    $ bluetoothctl
    ...
    [bluetooth]# connect XX:XX:XX:XX:XX:XX
    Attempting to connect to XX:XX:XX:XX:XX:XX
    [CHG] Device XX:XX:XX:XX:XX:XX Connected: yes
    [CHG] Device XX:XX:XX:XX:XX:XX UUIDs: 0000184e-0000-1000-8000-00805f9b34fb
    [CHG] Device XX:XX:XX:XX:XX:XX UUIDs: 00001850-0000-1000-8000-00805f9b34fb
    [CHG] Device XX:XX:XX:XX:XX:XX UUIDs: 03b80e5a-ede8-4b33-a751-6ce34ec4c700
    Connection successful
    [NEW] Primary Service (Handle 0x0000)
            /org/bluez/hci0/dev_XX_XX_XX_XX_XX_XX/service0008
            00001801-0000-1000-8000-00805f9b34fb
            Generic Attribute Profile
    ...
    [NEW] Descriptor (Handle 0x0000)
            /org/bluez/hci0/dev_XX_XX_XX_XX_XX_XX/service0065/char0066/desc0069
            00002901-0000-1000-8000-00805f9b34fb
            Characteristic User Description
    [CHG] Device XX:XX:XX:XX:XX:XX UUIDs: 00001800-0000-1000-8000-00805f9b34fb
    [CHG] Device XX:XX:XX:XX:XX:XX UUIDs: 00001801-0000-1000-8000-00805f9b34fb
    [CHG] Device XX:XX:XX:XX:XX:XX UUIDs: 0000180a-0000-1000-8000-00805f9b34fb
    [CHG] Device XX:XX:XX:XX:XX:XX UUIDs: 00001844-0000-1000-8000-00805f9b34fb
    [CHG] Device XX:XX:XX:XX:XX:XX UUIDs: 0000184e-0000-1000-8000-00805f9b34fb
    [CHG] Device XX:XX:XX:XX:XX:XX UUIDs: 00001850-0000-1000-8000-00805f9b34fb
    [CHG] Device XX:XX:XX:XX:XX:XX UUIDs: 03b80e5a-ede8-4b33-a751-6ce34ec4c700
    [CHG] Device XX:XX:XX:XX:XX:XX ServicesResolved: yes
    [CHG] Device XX:XX:XX:XX:XX:XX Paired: yes
    [xxx]# endpoint.list
    [xxx]# disconnect
    Attempting to disconnect from XX:XX:XX:XX:XX:XX
    [CHG] Device XX:XX:XX:XX:XX:XX ServicesResolved: no
    Successful disconnected
    [CHG] Device XX:XX:XX:XX:XX:XX Connected: no
    [bluetooth]# connect XX:XX:XX:XX:XX:XX
    Attempting to connect to XX:XX:XX:XX:XX:XX
    [CHG] Device XX:XX:XX:XX:XX:XX Connected: yes
    Connection successful
    [NEW] Endpoint /org/bluez/hci0/dev_XX_XX_XX_XX_XX_XX/pac_source0
    [NEW] Endpoint /org/bluez/hci0/dev_XX_XX_XX_XX_XX_XX/pac_sink0
    [NEW] Transport /org/bluez/hci0/dev_XX_XX_XX_XX_XX_XX/pac_source0/fd0
    [NEW] Transport /org/bluez/hci0/dev_XX_XX_XX_XX_XX_XX/pac_sink0/fd1
    [CHG] Transport /org/bluez/hci0/dev_XX_XX_XX_XX_XX_XX/pac_source0/fd0 Links: /org/bluez/hci0/dev_XX_XX_XX_XX_XX_XX/pac_sink0/fd1
    [CHG] Transport /org/bluez/hci0/dev_XX_XX_XX_XX_XX_XX/pac_sink0/fd1 Links: /org/bluez/hci0/dev_XX_XX_XX_XX_XX_XX/pac_source0/fd0
    [CHG] Device XX:XX:XX:XX:XX:XX ServicesResolved: yes
    [xxx]# endpoint.list
    Endpoint /org/bluez/hci0/dev_XX_XX_XX_XX_XX_XX/pac_source0
    Endpoint /org/bluez/hci0/dev_XX_XX_XX_XX_XX_XX/pac_sink0
    [xxx]#
    
    Endpoints and transports failed to appear on the first connect to the
    BAP server, since GATT discovery was not yet completed when the BAP code
    tried to discover the endpoints. Second connection succeeded.
    Occasionally, it also happens that endpoints appear but transports do
    not, but this is hard to reproduce.
    
    With this patch:
    
    $ sudo systemctl restart bluetooth
    $ bluetoothctl
    ...
    [bluetooth]# connect XX:XX:XX:XX:XX:XX
    Attempting to connect to XX:XX:XX:XX:XX:XX
    [CHG] Device XX:XX:XX:XX:XX:XX Connected: yes
    [CHG] Device XX:XX:XX:XX:XX:XX UUIDs: 0000184e-0000-1000-8000-00805f9b34fb
    [CHG] Device XX:XX:XX:XX:XX:XX UUIDs: 00001850-0000-1000-8000-00805f9b34fb
    [CHG] Device XX:XX:XX:XX:XX:XX UUIDs: 03b80e5a-ede8-4b33-a751-6ce34ec4c700
    Connection successful
    [NEW] Primary Service (Handle 0x0000)
            /org/bluez/hci0/dev_XX_XX_XX_XX_XX_XX/service0008
            00001801-0000-1000-8000-00805f9b34fb
            Generic Attribute Profile
    ...
    [NEW] Descriptor (Handle 0x0000)
            /org/bluez/hci0/dev_XX_XX_XX_XX_XX_XX/service0065/char0066/desc0069
            00002901-0000-1000-8000-00805f9b34fb
            Characteristic User Description
    [CHG] Device XX:XX:XX:XX:XX:XX ServicesResolved: yes
    [CHG] Device XX:XX:XX:XX:XX:XX Paired: yes
    [NEW] Endpoint /org/bluez/hci0/dev_XX_XX_XX_XX_XX_XX/pac_source0
    [NEW] Endpoint /org/bluez/hci0/dev_XX_XX_XX_XX_XX_XX/pac_sink0
    [NEW] Transport /org/bluez/hci0/dev_XX_XX_XX_XX_XX_XX/pac_source0/fd0
    [NEW] Transport /org/bluez/hci0/dev_XX_XX_XX_XX_XX_XX/pac_sink0/fd1
    [CHG] Transport /org/bluez/hci0/dev_XX_XX_XX_XX_XX_XX/pac_source0/fd0 Links: /org/bluez/hci0/dev_XX_XX_XX_XX_XX_XX/pac_sink0/fd1
    [CHG] Transport /org/bluez/hci0/dev_XX_XX_XX_XX_XX_XX/pac_sink0/fd1 Links: /org/bluez/hci0/dev_XX_XX_XX_XX_XX_XX/pac_source0/fd0
    [xxx]#
    
    Now the first connection works properly.
    
    On first reading, the spec does not seem to clearly comment if ASEs and
    PACs could be removed/added by the server while client is connected. If
    that's allowed, then we'd need some bigger changes here. Regardless,
    waiting for GATT client ready before first scan seems good also in this
    case.

 src/shared/bap.c | 93 +++++++++++++++++++++++++++++++-----------------
 1 file changed, 60 insertions(+), 33 deletions(-)

diff --git a/src/shared/bap.c b/src/shared/bap.c
index 22f2e6714..2d676d96f 100644
--- a/src/shared/bap.c
+++ b/src/shared/bap.c

@@ -158,6 +158,7 @@ struct bt_bap {
 	struct bt_att *att;
 	struct bt_bap_req *req;
 	unsigned int cp_id;
+	unsigned int client_ready_id;
 
 	unsigned int process_id;
 	unsigned int disconn_id;

@@ -3733,41 +3734,10 @@ static void bap_attach_att(struct bt_bap *bap, struct bt_att *att)
 							bap, NULL);
 }
 
-bool bt_bap_attach(struct bt_bap *bap, struct bt_gatt_client *client)
+static void bap_attach_finish(struct bt_bap *bap)
 {
 	bt_uuid_t uuid;
 
-	if (queue_find(sessions, NULL, bap)) {
-		/* If instance already been set but there is no client proceed
-		 * to clone it otherwise considered it already attached.
-		 */
-		if (client && !bap->client)
-			goto clone;
-		return true;
-	}
-
-	if (!sessions)
-		sessions = queue_new();
-
-	queue_push_tail(sessions, bap);
-
-	queue_foreach(bap_cbs, bap_attached, bap);
-
-	if (!client) {
-		bap_attach_att(bap, bap->att);
-		return true;
-	}
-
-	if (bap->client)
-		return false;
-
-clone:
-	bap->client = bt_gatt_client_clone(client);
-	if (!bap->client)
-		return false;
-
-	bap_attach_att(bap, bt_gatt_client_get_att(client));
-
 	if (bap->rdb->pacs) {
 		uint16_t value_handle;
 		struct bt_pacs *pacs = bap->rdb->pacs;

@@ -3798,7 +3768,7 @@ clone:
 
 		bap_notify_ready(bap);
 
-		return true;
+		return;
 	}
 
 	bt_uuid16_create(&uuid, PACS_UUID);

@@ -3806,6 +3776,57 @@ clone:
 
 	bt_uuid16_create(&uuid, ASCS_UUID);
 	gatt_db_foreach_service(bap->rdb->db, &uuid, foreach_ascs_service, bap);
+}
+
+static void bap_attach_ready_cb(bool success, uint8_t att_ecode,
+								void *user_data)
+{
+	struct bt_bap *bap = user_data;
+
+	bap->client_ready_id = 0;
+
+	bap_attach_finish(bap);
+}
+
+bool bt_bap_attach(struct bt_bap *bap, struct bt_gatt_client *client)
+{
+	if (queue_find(sessions, NULL, bap)) {
+		/* If instance already been set but there is no client proceed
+		 * to clone it otherwise considered it already attached.
+		 */
+		if (client && !bap->client)
+			goto clone;
+		return true;
+	}
+
+	if (!sessions)
+		sessions = queue_new();
+
+	queue_push_tail(sessions, bap);
+
+	queue_foreach(bap_cbs, bap_attached, bap);
+
+	if (!client) {
+		bap_attach_att(bap, bap->att);
+		return true;
+	}
+
+	if (bap->client)
+		return false;
+
+clone:
+	bap->client = bt_gatt_client_clone(client);
+	if (!bap->client)
+		return false;
+
+	bap_attach_att(bap, bt_gatt_client_get_att(bap->client));
+
+	if (bt_gatt_client_is_ready(bap->client)) {
+		bap_attach_finish(bap);
+	} else {
+		bap->client_ready_id = bt_gatt_client_ready_register(
+				bap->client, bap_attach_ready_cb, bap, NULL);
+	}
 
 	return true;
 }

@@ -3824,6 +3845,12 @@ void bt_bap_detach(struct bt_bap *bap)
 	if (!queue_remove(sessions, bap))
 		return;
 
+	if (bap->client_ready_id) {
+		bt_gatt_client_ready_unregister(bap->client,
+						bap->client_ready_id);
+		bap->client_ready_id = 0;
+	}
+
 	bt_gatt_client_unref(bap->client);
 	bap->client = NULL;
 

-- 
2.39.1