RFCOMM: Avoid receive packets before DLC sink set

bumble/rfcomm.py

@@ -470,6 +470,7 @@ def __init__(
         self.connection_result = None
         self.drained = asyncio.Event()
         self.drained.set()
+        self.opened = asyncio.Event()
 
         # Compute the MTU
         max_overhead = 4 + 1  # header with 2-byte length + fcs
@@ -505,6 +506,8 @@ def on_sabm_frame(self, _frame: RFCOMM_Frame) -> None:
 
         self.change_state(DLC.State.CONNECTED)
         self.emit('open')
+        # Opened as responder
+        self.opened.set()
 
     def on_ua_frame(self, _frame: RFCOMM_Frame) -> None:
         if self.state != DLC.State.CONNECTING:
@@ -521,6 +524,8 @@ def on_ua_frame(self, _frame: RFCOMM_Frame) -> None:
 
         self.change_state(DLC.State.CONNECTED)
         self.multiplexer.on_dlc_open_complete(self)
+        # Opened as initiator
+        self.opened.set()
 
     def on_dm_frame(self, frame: RFCOMM_Frame) -> None:
         # TODO: handle all states
@@ -549,8 +554,7 @@ def on_uih_frame(self, frame: RFCOMM_Frame) -> None:
             f'rx_credits={self.rx_credits}: {data.hex()}'
         )
         if data:
-            if self.sink:
-                self.sink(data)  # pylint: disable=not-callable
+            asyncio.create_task(self._dispatch_data(data))
 
             # Update the credits
             if self.rx_credits > 0:
@@ -664,6 +668,14 @@ def write(self, data: Union[bytes, str]) -> None:
     async def drain(self) -> None:
         await self.drained.wait()
 
+    async def _dispatch_data(self, data: bytes) -> None:
+        # Make sure the DLC has been opened, otherwise the sink may not be set when the
+        # PDU is dispatched.
+        await self.opened.wait()
+
+        if self.sink:
+            self.sink(data)  # pylint: disable=not-callable
+
     def __str__(self) -> str:
         return f'DLC(dlci={self.dlci},state={self.state.name})'
 

tests/rfcomm_test.py

@@ -32,6 +32,8 @@
     RFCOMM_PSM,
 )
 
+_TIMEOUT = 0.1
+
 
 # -----------------------------------------------------------------------------
 def basic_frame_check(x):
@@ -82,6 +84,29 @@ async def test_basic_connection() -> None:
     assert await queues[0].get() == b'Lorem ipsum dolor sit amet'
 
 
+# -----------------------------------------------------------------------------
+@pytest.mark.asyncio
+async def test_receive_pdu_before_open_dlc_returns() -> None:
+    devices = await test_utils.TwoDevices.create_with_connection()
+    DATA = b'123'
+
+    accept_future: asyncio.Future[DLC] = asyncio.get_running_loop().create_future()
+    channel = Server(devices[0]).listen(acceptor=accept_future.set_result)
+
+    assert devices.connections[1]
+    multiplexer = await Client(devices.connections[1]).start()
+    open_dlc_task = asyncio.create_task(multiplexer.open_dlc(channel))
+
+    dlc_responder = await accept_future
+    dlc_responder.write(DATA)
+
+    dlc_initiator = await open_dlc_task
+    dlc_initiator_queue = asyncio.Queue()  # type: ignore[var-annotated]
+    dlc_initiator.sink = dlc_initiator_queue.put_nowait
+
+    assert await asyncio.wait_for(dlc_initiator_queue.get(), timeout=_TIMEOUT) == DATA
+
+
 # -----------------------------------------------------------------------------
 @pytest.mark.asyncio
 async def test_service_record():

tests/test_utils.py

@@ -16,7 +16,8 @@
 # Imports
 # -----------------------------------------------------------------------------
 import asyncio
-from typing import List, Optional
+from typing import List, Optional, Type
+from typing_extensions import Self
 
 from bumble.controller import Controller
 from bumble.link import LocalLink
@@ -81,6 +82,12 @@ async def setup_connection(self) -> None:
     def __getitem__(self, index: int) -> Device:
         return self.devices[index]
 
+    @classmethod
+    async def create_with_connection(cls: Type[Self]) -> Self:
+        devices = cls()
+        await devices.setup_connection()
+        return devices
+
 
 # -----------------------------------------------------------------------------
 async def async_barrier():