Correct buffer_overrun test.

Author: janiversen

pymodbus/transport/transport.py

@@ -308,6 +308,7 @@ def datagram_received(self, data: bytes, addr: tuple | None) -> None:
         self.recv_buffer += data
         if len(self.recv_buffer) > 1024:
             self.recv_buffer = b""
+            return
         cut = self.callback_data(self.recv_buffer, addr=addr)
         self.recv_buffer = self.recv_buffer[cut:]
         if self.recv_buffer:

test/transport/test_protocol.py

@@ -142,7 +142,7 @@ async def test_datagram_buffer_overrun(self, client):
         client.callback_data = mock.MagicMock(return_value=0)
         client.recv_buffer = bytearray([0x01] * 2000)
         client.datagram_received(b"abc", "127.0.0.1")
-        assert client.recv_buffer == b"abc"
+        assert client.recv_buffer == b""
 
     async def test_callback_connected(self, use_clc, dummy_protocol):
         """Test callbacks."""