Connecting to the host network¶

Renode allows you to connect a host network interface to a simulated wired network.

To do that you need to create a Tap interface or VMNET interface based on vmnet-helper (the latter is supported only on macOS).

Regarding time flow¶

All devices simulated in Renode operate in virtual time, which is typically slower than the real time flow. Moreover, network packets are delivered in periodical synchronisation points, delaying the communication even further.

This means that time constraints (e.g. timeouts) placed by applications trying to connect to the simulated network from the host may need to be altered to take these delays into account.

Opening a TAP interface¶

To create and open a TAP interface which will be listed on your host system as tap0 and inside Renode as host.tap, run:

(monitor) emulation CreateTap "tap0" "tap"

If you want the interface to be retained after Renode closes, add a true parameter:

(monitor) emulation CreateTap "tap0" "tap" true

Depending on your system configuration, you may be asked for a password to open the interface.

Using TAP interface on Windows¶

In order to create a TAP device on Windows, you need to install a third-party driver that is a part of the OpenVPN project. If OpenVPN is installed on your computer, Renode should detect it when trying to create a TAP interface. The feature has been specifically tested with OpenVPN 2.5.6.

To create a TAP interface on your Windows PC, first, you need to create a new TAP interface in Renode using the usual command:

(monitor) emulation CreateTap "tap0" "tap"

Then you need to assign an IP address to your TAP using the command prompt:

netsh interface ipv4 set address name=tap0 static X.X.X.X

tapctl.exe create --name tap0

netsh interface ipv4 set address name=tap0 static X.X.X.X

(monitor) emulation CreateTap "tap0" "tap"

Connecting TAP interface to a switch¶

Assuming you have already configured the simulated network, you can connect a TAP interface to a switch device by running:

(monitor) emulation CreateSwitch "switch"
(monitor) connector Connect host.tap switch

Using VMNET interface on macOS¶

Preparing vmnet-helper¶

Before setting up the interface in Renode, install the vmnet-helper program by running the following command:

brew install nirs/vmnet-helper/vmnet-helper

or, if you’re on a macOS version earlier than 26, run:

curl -fsSL https://github.com/nirs/vmnet-helper/releases/latest/download/install.sh | bash

Starting vmnet-helper¶

VMNET configuration consists of three steps:

1. Spawning a background vmnet-helper process:

   vmnet_helper \
          --socket=${SOCKET_PATH:-vmnet_helper.sock} \
          --operation-mode=${mode:-shared} \
          --start-address=${start_ipv4:-172.16.0.0} \
          --end-address=${end_ipv4:-172.16.0.10} \
          --subnet-mask=${mask:-255.240.0.0}
   

   where:

   • start-address: the IP address assigned to the host-side interface. This address also acts as the default gateway for the guests.

   • end-address: the last IP address in the DHCP pool available for the guests.

   • subnet-mask: the subnet mask defining the network size in dotted decimal notation (e.g. 255.255.255.0). The subnet mask enables vmnet to communicate with other vmnet interfaces on the same subnet that are in shared mode.

   • operation-mode:

     • host creates an isolated network where the guest (the VM inside the Renode simulation) can communicate with the host (your computer) but with no access to the Internet. You can use this mode to increase security and privacy.

     Note

     The --start-address, --end-address, and --subnet-mask options are ignored in host operation mode in each version of vmnet-helper prior to v0.12.0.

     • shared where the VM reaches the Internet through a network address translator (NAT) and the host’s IP address.

   • For full instructions on using the vmnet-helper process, refer to its README.

2. Connecting Renode to the vmnet-helper process via a Monitor command:

   emulation CreateVmnetHelper "${SOCKET_PATH}" "vmnet"
   

3. Connecting the machine interface and host.vmnet to the same switch to allow packet transmission between them:

   emulation CreateSwitch "switch"
   connector Connect host.vmnet switch
   connector Connect gem0 switch # use your platform's interface name instead of `gem0`
   

If the guest runs Linux, you can test Internet connectivity in the following way:

ifconfig eth0 up $(($start_ip+1)) # assign any address available in the pool (e.g. the first available address)
ping -c 5 ${start_ip} # any address accessible via the vmnet_helper interface (i.e. your local computer)

Connecting VMNET interface to a switch¶

Assuming you have already configured the simulated network, you can connect the VMNET interface vmnet1 to the switch device by running:

(monitor) emulation CreateSwitch "switch"
(monitor) connector Connect host.vmnet1 switch

Starting the interface¶

The TAP and VMNET interfaces are created as “paused”. To enable communication with the host system you must start it manually, either by running:

(monitor) start

or, if your emulation is already started, with:

(monitor) host.tap Start

(monitor) host.vmnet Start

Transferring files from host¶

If you successfully created a TAP interface, files can be transferred from the host computer to emulation using wget. To do it you will need to use an IP address associated with the TAP interface on the host machine, for example:

wget http://192.168.100.1/home/user/file.txt