From ebf2d7935690c00c7fd12768177e2023fc63c9fe Mon Sep 17 00:00:00 2001 From: Javier de San Pedro Date: Sat, 27 Nov 2021 23:21:36 +0100 Subject: gatt-client: Fix disconnecting due to GattCharacteristic1.MTU After the MTU dbus property patches in 5.62 we are seeing bluetoothd terminate frequently with "Disconnected from D-Bus. Exiting." msgs. Apparently this is because bluetoothd sent an invalid reply to a D-Bus Property Get (for GattCharacteristic1's MTU). Multiple issues in bluez Github.com project reported similar behavior; at least #235 (see Fixes:), #219, and likely #238. When the Characteristic1 object is still cached/alive, but the underlying att connection is not (e.g. someone just called Disconnect), the property getter (characteristic_get_mtu) right now returns false. However, gdbus seems to ignore the return value and sends the empty reply message anyway (rather than a dbus error?), and this seems to cause the dbus connection to be terminated (due to the ill-formed reply?). bluetoothd then aborts. This patch makes the property value BT_ATT_DEFAULT_LE_MTU if the underlying att object does not exist, rather than returning an invalid message. This is consistent with the existing PropertyChanged signal behavior (we will emit a PropertyChange only if a larger MTU is exchanged), and fixes the issue on my machines. An alternative could be to change gdbus behavior, but I'm not sure if we are allowed to return an error here anyway without causing problems in other dbus libraries/wrappers. Fixes: aaa0c4996ae9 ("gatt: Add implementation of GattCharacteristic1.MTU") Fixes: https://github.com/bluez/bluez/issues/235 --- src/gatt-client.c | 5 +---- 1 file changed, 1 insertion(+), 4 deletions(-) diff --git a/src/gatt-client.c b/src/gatt-client.c index de18bea97..6ee984db9 100644 --- a/src/gatt-client.c +++ b/src/gatt-client.c @@ -883,10 +883,7 @@ static gboolean characteristic_get_mtu(const GDBusPropertyTable *property, uint16_t mtu; att = bt_gatt_client_get_att(gatt); - if (!att) - return FALSE; - - mtu = bt_att_get_mtu(att); + mtu = att ? bt_att_get_mtu(att) : BT_ATT_DEFAULT_LE_MTU; dbus_message_iter_append_basic(iter, DBUS_TYPE_UINT16, &mtu); -- cgit 1.2.3-1.el7