# Extension
[Following the documentation here](https://github.com/rshu-bd/spot_ros2/tree/rshu-bd/spot_core_extension/spot_coreio_extension)
## [Build The Extension](https://github.com/rshu-bd/spot_ros2/tree/rshu-bd/spot_core_extension/spot_coreio_extension#build-the-extension)
This directory contains a script create\_extension.sh that can be used to create an l4t-based Spot Extension for this example. This will create a file spot\_detect\_and\_follow.spx, which can be uploaded to the CORE I/O. The extension requires that the payload be authorized on the robot admin console to run.
If building on a host system architecture that is not `ARM64` based run the following before continuing.
```bash
sudo apt-get install qemu binfmt-support qemu-user-static
```
Installing and running qemu will allow us to build ARM binaries on an x86 machine without needing a cross compiler, see [Build Docker Images Documentation](https://dev.bostondynamics.com/docs/payload/docker_containers#build-docker-images) for more details.
This directory contains a script `create_extension.sh` that can be used to build a `ARM64` docker image and package all the files into an Extension. From the `ros2_driver` directory run the script
```bash
./create_extension.sh
```
This will create the `spot_ros2_driver.spx` extension file that you can upload to the CORE I/O or Scout platform. The script was tested on Ubuntu 22.04 with x86 architecture.
---
Before you install and run the `spot_ros2_driver.spx` you need to configure the port range used by a connection in the CORE I/O to be within the allowable port range.
### [Limit the ports used by a connection in the CORE I/O](https://github.com/rshu-bd/spot_ros2/tree/rshu-bd/spot_core_extension/spot_coreio_extension#limit-the-ports-used-by-a-connection-in-the-core-io)
SSH into the CORE I/O from the robot’s WiFi
```bash
ssh -p 20022 spot@192.168.80.3
```
Make a copy of the default port range (not currently working with our CORE io)
```bash
cat /proc/sys/net/ipv4/ip_local_port_range > /proc/sys/net/ipv4/ip_local_port_range.bak
```
The default configuration of the ip\_local\_port\_range
```bash
32768 60999
```
Limit the ports a networking connection can use to those reachable through the CORE I/O's firewall
```bash
echo "21000 22000" | sudo tee /proc/sys/net/ipv4/ip_local_port_range
```
This will force all connections from the CORE I/O to be on the port range 21000 - 22000.