Multiple SITL instances on one host connecting to multiple MicroXRCEAgent on different IPs

[JacopoPan]

Describe problem solved by the proposed feature

I have a setup here where I run:

• Gazebo and N PX4 SITL instances in one Docker container
• and I want to connect them to N MicroXRCEAgents (each one in its own separate Docker container)

Each container has its own IP (using docker network) and ROS_DOMAIN_ID

The main motivation is isolating the multi-drone "simulation" (Gazebo + NxSITL) from the "deployable" edge compute autonomy using separate containers

Describe your preferred solution

Right now, I achieve this with

PX4_SYS_AUTOSTART=<%= autostart %> ROS_DOMAIN_ID=<%= drone_id %> 
PX4_UXRCE_DDS_NS="Drone<%= drone_id %>" PX4_UXRCE_DDS_AG_IP=<%= "#{sim_subnet}.90.#{drone_id}" %> PX4_UXRCE_DDS_PORT=8888
/PX4-Autopilot/build/px4_sitl_default/bin/px4 -i <%= sitl_instance %>

and adding a new env variable PX4_UXRCE_DDS_AG_IP here

PX4-Autopilot/ROMFS/px4fmu_common/init.d-posix/rcS

Line 324 in 24833f4

uxrce_dds_client start -t udp -p $uxrce_dds_port $uxrce_dds_ns

like this

uxrce_dds_client start -t udp -h "${PX4_UXRCE_DDS_AG_IP:-127.0.0.1}" -p $uxrce_dds_port $uxrce_dds_ns

Describe possible alternatives

I'm not sure if this could be done natively/differently and/or more concisely modifying

PX4-Autopilot/ROMFS/px4fmu_common/init.d-posix/rcS

Lines 183 to 184 in 24833f4

	# set default IP to localhost
	param set-default UXRCE_DDS_AG_IP 2130706433 # 127.0.0.1

Additional context

No response