.. include:: /substitutions.rst .. _simulator:
========= Simulator
Apache NuttX has a simulator that can run as a regular program on Linux, Mac, and Windows computers. It's useful for debugging operating system features that aren't associated with particular device drivers— for instance the TCP/IP stack itself, a web interface or API for your application, or other communication protocols. It's also handy for trying out Apache NuttX without having a piece of embedded hardware.
This guide assumes you're on Linux. It works on Windows and Mac too— if you know how, submit a PR to improve this guide!
.. todo:: Windows instructions
Prerequisites For macOS
We need genromfs to build simulators(NON GUI).
.. code-block:: console
$ git clone https://github.com/chexum/genromfs.git
$ cd genromfs
$ make
$ make install
Now Copy the built genromfs exec to /opt/local/bin.
For GUI Applications we need X11 Libraries, libx11 can also be built using Homebrew or by Installing XQuartz.
.. code-block:: console
$ sudo port install xorg-libX11
$ sudo port install xorg-server
Compiling
#. Configure the Simulator
There are a lot of simulator configurations available that set you up to test various operating system features.
Here we'll use the sim:nsh basic NuttX Shell configuration.
.. code-block:: console
$ cd nuttx
$ ./tools/configure.sh sim:nsh
#. Compile
.. code-block:: console
$ make
#. Run the simulator:
.. code-block:: console
$ ./nuttx
login: admin
password: Administrator
User Logged-in!
NuttShell (NSH) NuttX-9.1.0
MOTD: username=admin password=Administrator
nsh> help
help usage: help [-v] [<cmd>]
[ cp exit losetup mv rmdir true
? cmp false ls mw set uname
basename dirname free mb poweroff sh unset
break dd help mkdir ps sleep usleep
cat echo hexdump mkfatfs pwd test xd
cd exec kill mh rm time
Builtin Apps:
hello nsh
nsh>
#. Stop the simulator:
.. code-block:: console
nsh> poweroff
$
$ # we're back at the Linux prompt.
.. _simulator_accessing_the_network:
Accessing the Network
#. Here we'll use the sim:tcpblaster configuration because it comes with networking
that is ready to use.
.. code-block:: console
$ make distclean
$ ./tools/configure.sh sim:tcpblaster
$ make
#. Give the Simulator Privileges
On recent Linux distributions, you need to give the nuttx program the capabilities
(similar to permissions) to access the network:
.. code-block:: console
$ sudo setcap cap_net_admin+ep ./nuttx
#. Run the simulator:
.. code-block:: console
$ ./nuttx
#. Bring Up the Network Interfaces
On Apache NuttX:
.. code-block:: console
nsh> ifup eth0
On Linux, first you need to find your main network interface— this will usually either be an ethernet or wireless network adapter. Do this:
.. code-block:: console
$ ifconfig
lo: flags=73<UP,LOOPBACK,RUNNING> mtu 65536
inet 127.0.0.1 netmask 255.0.0.0
inet6 ::1 prefixlen 128 scopeid 0x10<host>
loop txqueuelen 1000 (Local Loopback)
RX packets 5846 bytes 614351 (614.3 KB)
RX errors 0 dropped 0 overruns 0 frame 0
TX packets 5846 bytes 614351 (614.3 KB)
TX errors 0 dropped 0 overruns 0 carrier 0 collisions 0
wlp0s20f3: flags=4163<UP,BROADCAST,RUNNING,MULTICAST> mtu 1500
inet 192.168.1.209 netmask 255.255.255.0 broadcast 192.168.1.255
inet6 fe80::1161:c26b:af05:d784 prefixlen 64 scopeid 0x20<link>
ether 24:41:8c:a8:30:d1 txqueuelen 1000 (Ethernet)
RX packets 219369 bytes 176416490 (176.4 MB)
RX errors 0 dropped 0 overruns 0 frame 0
TX packets 108399 bytes 27213617 (27.2 MB)
TX errors 0 dropped 0 overruns 0 carrier 0 collisions 0
lo0 is the Loopback Interface, so wlp0s20f3 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.
Then, on Linux do this to set up the tap network interface and route that will let the Apache NuttX simulator access the network:
.. code-block:: console
$ sudo ./tools/simhostroute.sh wlp0s20f3 on
$ ping -c 1 10.0.1.2 # nuttx system
PING 10.0.1.2 (10.0.1.2) 56(84) bytes of data.
64 bytes from 10.0.1.2: icmp_seq=1 ttl=64 time=7.52 ms
--- 10.0.1.2 ping statistics ---
1 packets transmitted, 1 received, 0% packet loss, time 0ms
rtt min/avg/max/mdev = 7.529/7.529/7.529/0.000 m
#. Test that Apache NuttX can access the Internet
First let's ping the network interface of our Linux host to prove we can see the gateway to the Internet:
.. code-block:: console
nsh> ping -c 1 10.0.1.1
nsh> ping -c 1 10.0.1.1
PING 10.0.1.1 56 bytes of data
56 bytes from 10.0.1.1: icmp_seq=0 time=0 ms
1 packets transmitted, 1 received, 0% packet loss, time 1010 ms
Now let's ping one of Google's DNS servers to prove we can access the rest of the
Internet:
.. code-block:: console
nsh> ping -c 1 8.8.8.8
PING 8.8.8.8 56 bytes of data
56 bytes from 8.8.8.8: icmp_seq=0 time=10 ms
1 packets transmitted, 1 received, 0% packet loss, time 1010 ms
If it doesn't work, then you need to enable the IP forward on your computer:
.. code-block:: console
sudo sysctl -w net.ipv4.ip_forward=1
Success!
Testing / capturing TCP network traffic
#. Start Wireshark (or tcpdump) on Linux and capture the appeared tap0 interface.
#. Optionally activate emulating packet loss on Linux:
.. code-block:: console
$ sudo iptables -A INPUT -p tcp --dport 31337 -m statistic --mode random --probability 0.01 -j DROP
#. Run netcat server on Linux:
.. code-block:: console
$ netcat -l -p 31337
#. Run netcat client on Apache NuttX:
.. code-block:: console
nsh> dd if=/dev/zero of=/tmp/test.bin count=1000
nsh> netcat LINUX_HOST_IP_ADDRESS 31337 /tmp/test.bin
#. Observe TCP network traffic in Wireshark / tcpdump on Linux.
Stopping
#. The normal way to stop:
.. code-block:: console
nsh> poweroff
$
$ # we're back at the Linux prompt.
If you don't have an nsh prompt, the only effective way to stop the simulator is kill it from another terminal:
.. code-block:: console
$ pkill nuttx
#. Optionally deactivate emulating packet loss on Linux:
.. code-block:: console
$ sudo iptables -D INPUT -p tcp --dport 31337 -m statistic --mode random --probability 0.01 -j DROP
#. If you do not need tap0 interface anymore, it can be disabled on Linux as follows:
.. code-block:: console
$ sudo ./tools/simhostroute.sh wlan0 off
Debugging
You can debug the simulator like any regular Linux program.