fix: ble: bluez: force manual MTU negotiation

Author: pkoscik

catprinter/ble.py

@@ -6,6 +6,7 @@
 from bleak import BleakClient, BleakScanner
 from bleak.backends.scanner import AdvertisementData
 from bleak.backends.device import BLEDevice
+from bleak.backends.bluezdbus.client import BleakClientBlueZDBus
 from catprinter import logger
 
 # For some reason, bleak reports the 0xaf30 service on my macOS, while it reports
@@ -96,6 +97,11 @@ async def run_ble(data, device: Optional[str]):
         return
     logger.info(f"⏳ Connecting to {address}...")
     async with BleakClient(address) as client:
+        # XXX: BlueZ incorrectly reports a fixed MTU of 23; force MTU negotiation manually.
+        # https://bleak.readthedocs.io/en/latest/api/client.html#bleak.BleakClient.mtu_size
+        if isinstance(client, BleakClientBlueZDBus):
+            await client._acquire_mtu()
+
         logger.info(f"✅ Connected: {client.is_connected}; MTU: {client.mtu_size}")
         chunk_size = client.mtu_size - 3
         event = asyncio.Event()