iptables-lite

A lightweight firewall for nuttx

Prerequisites

The first step to get started with NuttX is to install a series of required tools. They can be found here.

Initialize Configuration

The first step is to initialize NuttX configuration for a given board, based from a pre-existing configuration.

$ cd nuttx
$ ./tools/configure.sh -l sim:nsh

The -l tells use that we’re on Linux (macOS and Windows builds are possible). Use the -h argument to see all available options.

Build NuttX

We can now build NuttX. To do so, you can simply run:

$ cd nuttx
$ make

Run the Simulator

$ ./nuttx
login: admin
password: Administrator

Run the Network Simulator

make distclean
./tools/configure.sh -l sim:tcpblaster
make

On recent Linux distributions, you need to give the nuttx program the capabilities (similar to permissions) to access the network:

sudo setcap cap_net_admin+ep ./nuttx

Bring Up the Network Interfaces On Apache NuttX:

nsh> ifup eth0

Then, on Linux do this to set up the tap network interface and route that will let the Apache NuttX simulator access the network:

sudo ./tools/simhostroute.sh enp0s3 on

If you use ifconfig, you'll se that enp0se is the wireless interface. Note that it has an IP address on the local net. There may be other interfaces listed, you’ll need to pick the one that’s right for your system.

Run the Netcat

netcat -l -p 31337

Debugging with GDB

Initiate a nuttx process:

./nuttx

Collect the process PID:

ps aux | grep nuttx

Start GDB with this process id:

sudo gdb -p {pid}

Set breakpoints and continue to debugging:

(gdb) break file:lineno
(gdb) continue

Up interface eth0:

nsh > ifup eth0

Ping to linux:

nsh > ping -c 1 {ip_linux}

Got any trouble? Check the official NuttX quickstart guide: http://nuttx.incubator.apache.org/docs/latest/quickstart/index.html

NuttX Tips

This section is a bonus in order to summarize the main commands that are most used and show some simple and typical problems that can happen in your journey and how to work around them.

make distclean

It removes the configuration of the previous board and makes it available for the user to select another board or another configuration of the same board.

./tools/configure.sh boardname:configname

It selects the board (in this example it was esp32-devkitc) and the configuration to be used (in this example it was nsh config, which includes only the nuttx shell). There are other configurations that include support for certain peripherals and examples.

make menuconfig

It opens the configuration screen for the user to customize what he/she wants to add or to remove on the board. For example, it allows you to add drivers for a specific device, add debug messages, examples, etc.

make clean

It removes binary files generated from the previous built.

make apps_distclean

It cleans only application binaries. Kernel and driver binaries are kept.

make

It only builds your application.