Add call-through function for notifying about network interfaces

jakymiws commented 1 year ago

clalancette commented 1 year ago

@jakymiws Can you please give us an overview of what you are attempting to accomplish with this series of PRs?

jakymiws commented 1 year ago

@jakymiws Can you please give us an overview of what you are attempting to accomplish with this series of PRs?

The goal is to be able to call into fast-dds to get it to re-scan network interfaces. The specific feature in question is enabled by calling the set_qos function as documented here: https://fast-dds.docs.eprosima.com/en/latest/fastdds/use_cases/dynamic_network_interfaces/dynamic_network_interfaces.html#dynamic-network-interfaces

alsora commented 1 year ago

@fujitatomoya sure, we can definitely have a discussion during the next middleware WG.

The use-case is the following: all the existing DDS implementations currently scan for available network interfaces only once, i.e. when a DDS participant is created. This usually happens when you call rclcpp::init(). If a network interface is not available at that time it will be ignored. For example: you start a ROS application, then you bring up WiFi -> the ROS application will not use WiFi.

We had a discussion in the past about how to get around this and it is ultimately problematic for the middlewares to know whether they have to wait for interfaces, keep scanning for them, republish messages on new interfaces etc. This API is a trigger to tell the middleware to scan for existing interfaces.

The current default RMW implementation (Fast-DDS) supports this feature: https://fast-dds.docs.eprosima.com/en/latest/fastdds/use_cases/dynamic_network_interfaces/dynamic_network_interfaces.html#dynamic-network-interfaces

fujitatomoya commented 1 year ago

@alsora appreciate the information, thanks for sharing. apparently we almost have the same use cases 😄

I have considered this kind of feature before, so posting my note here. hopefully this could bring more discussion.

Network Detection / Awareness

Overview

I just want to come up with questions and possible requirements in robots, robotics and edge devices. As described below, nodes could be connected, disconnected or transited the network status based on dynamic physical environment.

Possible Situations

Participation (OFF -> ON): right after boot the system, there would be no network connection at all. but as robots move around, it eventually find the network interface.
Transition (ON -> ON): as robots are moving in long distance, network interface could be changed. (Internally, ON -> OFF -> OF)
Leave (ON -> OFF): as robots are moving, they eventually leave from the network range.

Requirements / Capabilities

Application should be able to know the network connectivity status and configuration? (set and get network configuration.)
Application should be notified with network status or configuration change event? so that it can issue the API to reconfigure the network once it is back online? (event notification)

Consideration / Note

AFAIK, ROS 2 / DDS is NOT aware of network. it just relies on network but cannot detect those status or events to restart the application.
most devices currently we have in home, we by here end users can physically help to fix the network problems, such as smartphone, tablets and so on to access the system. but this is not likely robots use cases, so that it should be able to self-healing?
specific use cases like factory and logistics, we probably want to use specific network interfaces only nothing else. this means that user can configure possible network interfaces as we like.
network infrastructure in edge IoT devices could be not stable enough, sometimes network connection is gone.

Currently i was thinking that this is doable with following and restarting ROS 2 node (DDS participants), but happy to discuss.

use linux interfaces. (man 7 netlink NETLINK_ROUTE) create/delete/up/down events https://man7.org/linux/man-pages/man7/netlink.7.html
NetworkManager DBus event. e.g) nmcli
systemd device units via DBus, https://unix.stackexchange.com/questions/159641/systemd-restart-service-when-ip-address-changed

ros-discourse commented 1 year ago

This pull request has been mentioned on ROS Discourse. There might be relevant details there:

https://discourse.ros.org/t/network-issues-ros-topic-visibility-dependency-to-network-interfaces/29385/2

fujitatomoya commented 1 year ago

@alsora quick question, i think that @wjwwood mentioned in MW WG today. How we(application or DDS) can get the event that network configuration changed? is there already some APIs or interfaces provided by Fast-DDS?

mauropasse commented 1 year ago

@fujitatomoya there are currently no APIs on Fast-DDS to be notified about a change on the network interfaces. They did a quick investigation about it, but would only apply for Linux and wouldn't work in an platform agnostic way.

ros-discourse commented 1 year ago

This pull request has been mentioned on ROS Discourse. There might be relevant details there:

https://discourse.ros.org/t/ros-2-tsc-meeting-minutes-2023-02-16/29927/1

ros2 / rmw