Merge pull request #2669 from arl1984/fix/telnet-proxy-reader-cleanup-2344

Fix telnet console silent-proxy hang on non-ConnectionError exit (#2344)

gns3server/utils/asyncio/telnet_server.py

@@ -215,18 +215,32 @@ class AsyncioTelnetServer:
             await self._write_intro(network_writer, echo=self._echo, binary=self._binary, naws=self._naws)
             await connection.connected()
             await self._process(network_reader, network_writer, connection)
-        except (ConnectionError, OSError):
+        except (ConnectionError, OSError, asyncio.CancelledError):
+            pass
+        except Exception:
+            # Catch any unexpected exception so the cleanup below still runs.
+            # Without the try/finally, an uncaught exception here would leave
+            # _reader_process pinned to a dead reader, and subsequent client
+            # connections would see _get_reader() return None and never
+            # receive node output -- the "silent proxy" hang (issue #2344).
+            log.exception("Unexpected error in telnet proxy; cleaning up client connection...")
+        finally:
             async with self._lock:
+                try:
                     network_writer.close()
-                # await network_writer.wait_closed()  # this doesn't work in Python 3.6
+                finally:
                     if self._reader_process == network_reader:
                         self._reader_process = None
                         # Cancel current read from this reader
                         if self._current_read is not None:
                             self._current_read.cancel()
-
+                            self._current_read = None
+            try:
                 await connection.disconnected()
-            del self._connections[network_writer]
+            finally:
+                # Use pop() to avoid KeyError if connection was already removed
+                # elsewhere (e.g. by the broadcast loop's timeout handler)
+                self._connections.pop(network_writer, None)
 
     async def close(self):
         for writer, connection in self._connections.items():
@@ -318,7 +332,7 @@ class AsyncioTelnetServer:
                         except (OSError, ConnectionError, asyncio.TimeoutError) as e:
                             log.debug(f"Error sending data to client {client_info}: {e}, closing and removing from connection table.")
                             connection.close()
-                            del self._connections[connection_key]
+                            self._connections.pop(connection_key, None)
 
     async def _read(self, cmd, buffer, location, reader):
         """ Reads next op from the buffer or reader"""