Fix Unix remote watchdog socket leak

src/fenrirscreenreader/remoteDriver/unixDriver.py

@@ -329,48 +329,54 @@ class driver(remoteDriver):
     def watch_dog(self, active, event_queue):
         # echo "command say this is a test" | socat -
         # UNIX-CLIENT:/tmp/fenrirscreenreader-daemon.sock
-        for socket_file, optional in self._get_socket_candidates():
-            fenrir_sock = self._bind_socket(socket_file, optional)
-            if fenrir_sock is None:
-                continue
-            self.fenrirSocks.append(fenrir_sock)
-            self.bound_sockets.append((fenrir_sock, socket_file))
+        try:
+            for socket_file, optional in self._get_socket_candidates():
+                fenrir_sock = self._bind_socket(socket_file, optional)
+                if fenrir_sock is None:
+                    continue
+                self.fenrirSocks.append(fenrir_sock)
+                self.bound_sockets.append((fenrir_sock, socket_file))
 
-        if not self.fenrirSocks:
-            return
+            if not self.fenrirSocks:
+                return
 
-        self._try_register_instance()
-        last_register = time.time()
-        while active.value:
-            if time.time() - last_register > 10.0:
-                self._try_register_instance()
-                last_register = time.time()
+            self._try_register_instance()
+            last_register = time.time()
+            while active.value:
+                if time.time() - last_register > 10.0:
+                    self._try_register_instance()
+                    last_register = time.time()
 
-            # Check if the client is still connected and if data is available:
-            try:
-                r, _, _ = select.select(self.fenrirSocks, [], [], 0.8)
-            except select.error:
-                break
-            if r == []:
-                continue
-            for fenrir_sock in r:
-                client_sock, client_addr = fenrir_sock.accept()
-                socket_file = self._socket_file_for_socket(fenrir_sock)
-                # Ensure client socket is always closed to prevent resource
-                # leaks
+                # Check if the client is still connected and data is available.
                 try:
-                    self._handle_client(client_sock, event_queue, socket_file)
-                finally:
-                    # Always close client socket, even if data processing fails
+                    r, _, _ = select.select(self.fenrirSocks, [], [], 0.8)
+                except select.error:
+                    break
+                if r == []:
+                    continue
+                for fenrir_sock in r:
+                    client_sock, _client_addr = fenrir_sock.accept()
+                    socket_file = self._socket_file_for_socket(fenrir_sock)
                     try:
-                        client_sock.close()
-                    except Exception as e:
-                        self.env["runtime"]["DebugManager"].write_debug_out(
-                            "unixDriver watch_dog: Error closing client socket: "
-                            + str(e),
-                            debug.DebugLevel.ERROR,
+                        self._handle_client(
+                            client_sock, event_queue, socket_file
                         )
-        self._cleanup()
+                    finally:
+                        try:
+                            client_sock.close()
+                        except Exception as e:
+                            self.env["runtime"][
+                                "DebugManager"
+                            ].write_debug_out(
+                                "unixDriver watch_dog: Error closing client "
+                                "socket: "
+                                + str(e),
+                                debug.DebugLevel.ERROR,
+                            )
+        finally:
+            # ProcessManager restarts a failed watchdog. Always release the
+            # old listeners first so each restart cannot leak another socket.
+            self._cleanup()
 
     def shutdown(self):
         self._cleanup()

tests/unit/test_unix_remote_driver.py

@@ -1,5 +1,7 @@
 from unittest.mock import Mock, mock_open, patch
 
+import pytest
+
 from fenrirscreenreader.remoteDriver import unixDriver
 
 
@@ -27,6 +29,40 @@ def test_watchdog_keeps_serving_when_instance_registration_fails(
     select_call.assert_called_once()
 
 
+def test_watchdog_closes_listeners_when_unexpected_error_escapes(
+    mock_environment,
+):
+    driver = unixDriver.driver()
+    driver.env = mock_environment
+    listener = Mock()
+    active = Mock(value=True)
+
+    with patch.object(
+        driver,
+        "_get_socket_candidates",
+        return_value=[("/tmp/fenrir-test.sock", False)],
+    ), patch.object(
+        driver, "_bind_socket", return_value=listener
+    ), patch.object(
+        driver, "_try_register_instance"
+    ), patch(
+        "fenrirscreenreader.remoteDriver.unixDriver.select.select",
+        side_effect=RuntimeError("unexpected failure"),
+    ), patch(
+        "fenrirscreenreader.remoteDriver.unixDriver.os.path.exists",
+        return_value=False,
+    ), patch(
+        "fenrirscreenreader.remoteDriver.unixDriver.remoteInstanceRegistry.remove_instance"
+    ) as remove_instance:
+        with pytest.raises(RuntimeError, match="unexpected failure"):
+            driver.watch_dog(active, Mock())
+
+    listener.close.assert_called_once_with()
+    assert driver.fenrirSocks == []
+    assert driver.bound_sockets == []
+    remove_instance.assert_called_once_with()
+
+
 class FakeClientSocket:
     def __init__(self, data):
         self.data = data