Make is possible to access the microRTPS bridge inside the px4-sitl c…

…ontainer from the host by mapping shared memory (see discussion here: eProsima/Fast-DDS#1698). This is needed e.g. if you want to run GISNav on host while using the containerized SITL environment. Also make ROS_DOMAIN_ID a build argument for the px4-sitl container image and add a short related note to the README.md troubleshooting section.

README.md

@@ -63,6 +63,14 @@ docker run -it --env="DISPLAY" --volume="/tmp/.X11-unix:/tmp/.X11-unix:rw" --gpu
   --entrypoint="/bin/bash" gisnav-docker_px4-sitl
 ```
 
+If you are trying to connect to the PX4-ROS 2 bridge inside the container from the host but it seems like the messages 
+are not coming through, ensure your `ROS_DOMAIN_ID` environment variable on your host matches what is used inside the 
+container (0 by default):
+
+```bash
+export ROS_DOMAIN_ID=0
+```
+
 ## Repository Structure
 
 This repository is structured as follows:

docker-compose.yaml

@@ -19,6 +19,7 @@ services:
       - DISPLAY=${DISPLAY}
     volumes:
       - /tmp/.X11-unix:/tmp/.X11-unix:ro
+      - /dev/shm:/dev/shm
     network_mode: host
     stdin_open: true
     tty: true

docker/px4-sitl/Dockerfile

@@ -83,6 +83,7 @@ COPY Makefile /
 RUN sudo mv Makefile $HOME/
 
 # See https://docs.ros.org/en/dashing/Concepts/About-Domain-ID.html
-ENV ROS_DOMAIN_ID=0
+ARG ROS_DOMAIN_ID=0
+ENV ROS_DOMAIN_ID=${ROS_DOMAIN_ID}
 
 CMD cd $HOME && make HOME=$HOME gazebo