Processes started by ros2 launch inherit its DDS sockets

[erfanMhi]

Operating System:

Ubuntu 22.04.5 (arm64) and macOS 26.5.2 (arm64)

ROS version or commit hash:

Humble from apt (launch 1.0.15, osrf_pycommon 2.1.6) and Jazzy from RoboStack (launch 3.4.11, osrf_pycommon 2.1.7). Rolling has the same code.

RMW implementation (if applicable):

rmw_fastrtps_cpp

RMW Configuration (if applicable):

Defaults on Ubuntu, FASTDDS_BUILTIN_TRANSPORTS=UDPv4 on macOS

Client library (if applicable):

rclcpp, rclpy

'ros2 doctor --report' output

n/a

Steps to reproduce issue

Loading a component makes launch create its own node, even before the container process starts. Save this as leak.launch.py:

from launch import LaunchDescription
from launch.actions import TimerAction
from launch_ros.actions import ComposableNodeContainer, Node
from launch_ros.descriptions import ComposableNode


def generate_launch_description():
    container = ComposableNodeContainer(
        name='container', namespace='', package='rclcpp_components',
        executable='component_container',
        composable_node_descriptions=[ComposableNode(
            package='tf2_ros', plugin='tf2_ros::StaticTransformBroadcasterNode',
            name='stf_component',
            parameters=[{'frame_id': 'a', 'child_frame_id': 'b'}])])
    late = TimerAction(period=4.0, actions=[Node(
        package='tf2_ros', executable='static_transform_publisher',
        arguments=['--frame-id', 'a', '--child-frame-id', 'c'])])
    return LaunchDescription([container, late])

1. ros2 launch leak.launch.py

2. After 5 s, in a second terminal:

   L=$(pgrep -f 'ros2 launch leak.launch.py'); s() { ls -l /proc/$1/fd | grep -o 'socket:\[[0-9]*\]' | sort; }; for c in $(pgrep -P $L); do echo "$(cat /proc/$c/comm) holds $(comm -12 <(s $L) <(s $c) | wc -l) of launch's $(s $L | wc -l) sockets"; done

   On macOS, compare the DEVICE column of lsof -a -p <pid> -i UDP instead.

Expected behavior

Each child holds only its own sockets, so step 2 prints holds 0 for both.

Actual behavior

On Ubuntu, step 2 prints:

component_conta holds 8 of launch's 12 sockets
static_transfor holds 8 of launch's 12 sockets

All 5 of launch's UDP sockets are among them. On macOS, both children hold all 8 of launch's UDP sockets.

Additional information

ExecuteLocal starts processes with osrf_pycommon's async_execute_process, which passes close_fds=False (impl.py#L40-L47). Fast DDS opens its sockets without close-on-exec, so once launch creates its own node, every process it starts inherits that node's sockets. On macOS, when the kernel shuts down a child's sockets after a network-buffer shortage, launch's DDS goes down too, because the sockets are shared.

I'll open an osrf_pycommon PR that adds a close_fds option, so ExecuteLocal could pass close_fds=True.

Assisted-by: Claude Opus 5.5