Post

Raspberry Pi - Wifi to Ethernet Bridge (Through Wireguard VPN)

Posted Updated
By JAlcocerT 10 min read

Raspberry Pi: Wifi Bridge

I was inspired by the awsome work of William Halley in his blog, where I was able to follow succesfully the option 2 that it is proposed: to share Wifi through Ethernet on a separated subnet.

  • What do we need? 🎯
    • A Raspberry Pi (Im using a Pi4 2gb, ARM32) with Raspberry Pi OS installed
    • A custom script to route our RPi Wifi connectivity to Ethernet and pass its VPN connectivity
    • (Optional) Change the Rpi DNS to a custom ones
    • A Wireguard Server: You can use any provider like Mullvad VPN, Proton VPN, NordVPN
or create your own VPN Server
    • An Ethernet Cable - Most likely you Router brought some
    • (Optional) USB-C to Ethernet or some HUB with multiple ports if your device does not have Ethernet

Initial Setup: Option 2 - Separate Subnet

This original approach does not require any VPN, as we are just providing the same internet connection that our RPi receives via Wifi, to our laptop/any other device, via ethernet.

The Raspberry and your device will have the same connection details ☝

The script that is provided is this one (again, credits to William):

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#!/usr/bin/env bash

set -e

[ $EUID -ne 0 ] && echo "run as root" >&2 && exit 1

apt update && \
  DEBIAN_FRONTEND=noninteractive apt install -y \
    dnsmasq netfilter-persistent iptables-persistent

# Create and persist iptables rule.
iptables -t nat -A POSTROUTING -o wlan0 -j MASQUERADE
netfilter-persistent save

# Enable ipv4 forwarding.
sed -i'' s/#net.ipv4.ip_forward=1/net.ipv4.ip_forward=1/ /etc/sysctl.conf

# The Ethernet adapter will use a static IP of 10.1.1.1 on this new subnet.
cat <<'EOF' >/etc/network/interfaces.d/eth0
auto eth0
allow-hotplug eth0
iface eth0 inet static
  address 10.1.1.1
  netmask 255.255.255.0
  gateway 10.1.1.1
EOF

# Create a dnsmasq DHCP config at /etc/dnsmasq.d/bridge.conf. The Raspberry Pi
# will act as a DHCP server to the client connected over ethernet.
cat <<'EOF' >/etc/dnsmasq.d/bridge.conf
interface=eth0
bind-interfaces
server=8.8.8.8
domain-needed
bogus-priv
dhcp-range=10.1.1.2,10.1.1.254,12h
EOF

systemctl mask networking.service
  • If like me you are new to networking, I think going line by line and taking time to understand what we are doing is important:
    • #!/usr/bin/env bash: This is the shebang line that determines the script’s interpreter. In this case, the script will be run using bash shell.
    • set -e: This command causes the shell to exit if any invoked command fails.
    • [ $EUID -ne 0 ] && echo “run as root” >&2 && exit 1: This line checks if the script is run as root. If not, it prints an error message and exits. Root privileges are required to modify system configurations.
    • apt update && : This command updates the list of available packages from the repositories.
    • DEBIAN_FRONTEND=noninteractive apt install -y : This installs the necessary packages non-interactively, meaning it won’t prompt for user input during installation.
    • dnsmasq netfilter-persistent iptables-persistent: These are the packages being installed. Dnsmasq is a lightweight DHCP and caching DNS server. Netfilter-persistent and iptables-persistent are used for managing and saving iptables rules.
    • iptables -t nat -A POSTROUTING -o wlan0 -j MASQUERADE: This line adds a rule to iptables that will masquerade all outgoing traffic from the Raspberry Pi as coming from itself, essentially making the Pi act as a gateway for the connected device.
      • We are using wlan0 as is it the default for the Raspberry Pi
    • netfilter-persistent save: This saves the iptables rules so they persist across reboots.
    • sed -i’’ s/#net.ipv4.ip_forward=1/net.ipv4.ip_forward=1/ /etc/sysctl.conf: This line enables IP forwarding, which is necessary for routing traffic.
    • The cat «‘EOF’ >/etc/network/interfaces.d/eth0 block: This block creates a network configuration file for the eth0 interface. It sets the interface to use a static IP address (10.1.1.1) and acts as a gateway on the 10.1.1.0/24 subnet.
    • The cat «‘EOF’ >/etc/dnsmasq.d/bridge.conf block: This block creates a dnsmasq configuration file that sets the Raspberry Pi to act as a DHCP server on the eth0 interface. This will assign IP addresses to devices connected to the Pi over Ethernet.
    • systemctl mask networking.service: This command prevents the networking service from being started on boot. This is necessary because the script manually configures the network interfaces, and the networking service could interfere with this.
  • Remember, the names of wlan0 and eth0 used, can be different in other devices, check it with:
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ifconfig

The end result is that the Raspberry Pi will act as a bridge between the WiFi connection and the Ethernet connection, providing Internet access to devices connected via Ethernet- to the RPi.

RPi Bridge: Wifi to Eth (With VPN)

That was really great and I was really impressed and happy that it worked perfectly the first time I tried.

Then, I wondered
if the Raspberry Pi would be having a VPN connection, could we provide to the ethernet connected device that same connection?

Before we start, I would recommend you to change the RPi DNS Settings (Optional):

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#echo "nameserver 9.9.9.9" | sudo tee /etc/resolv.conf > /dev/null
echo -e "\nnameserver 9.9.9.9\nnameserver 149.112.112.112" | sudo tee -a /etc/resolv.conf > /dev/null

cat /etc/resolv.conf  #https://www.quad9.net/

I decided to try with Wireguard (you will need a working VPN server that generates Wireguard config) and surprisingly it worked with some modification:

1) First, we need to have wireguard installed:

  • This approach will work for any Wireguard protocol compatible VPNs like Mullvad or ProtonVPN
    • Mullvad ->
    • ProtonVPN -> I got proton same as the conf used
    • YOur own Wireguard VPN Server somwhere in the world
  • If you are using NordVPN, which just allow OpenVPN protocol, you can use NordVPN propietary VPN App in the RPi (and you can skip installing the Wireguard Client below - All steps are valid, just use whatever VPN Internet configuration name you are getting with ifconfig)
    • I got nordlynx
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sudo apt install wireguard #The wireguard client
sudo apt install resolvconf #required

cp /home/Downloads/your_vpn_wireguard_configuration.conf /etc/wireguard #download the wireguard config: account-wireguard configuration
sudo wg-quick your_vpn_wireguard_configuration #the name of the .conf file that you have downloaded
#sudo wg-quick up proton #the file name would be proton.conf

This made your wireguard client (RPi) to be connected to the VPN server.

Do you want to check your RPi public IP? Just do:

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sudo wg #ensure the wireguard interface is running
curl -sS https://ipinfo.io/json #the command to use to check the IP of your RPi

And if you need, to disconnect from Wireguard, just:

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wg-quick down <name>
sudo wg-quick down your_vpn_wireguard_configuration

#sudo nano /etc/resolv.conf #to check/adapt DNS name (optional)
#sudo reboot (optional)

2) Use this command to check which network interface your Wireguard VPN has:

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ifconfig
#ip a

Remember to be connected to either Wireguard or any other VPN Client in the RPi before using this command, as before that the network interface

And if you want that the RPi connects automatically to this Wireguard Server, just do:

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sudo systemctl status wg-quick@your_vpn_wireguard_configuration
#sudo systemctl status wg-quick@proton

sudo systemctl enable wg-quick@your_vpn_wireguard_configuration
#sudo systemctl enable wg-quick@proton

3) This will be our new bridge_wireguard.sh script to route the WIFI to ethernet and provide VPN connection at the same time:

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sudo nano bridge_wireguard.sh

Just adapt the value of your_vpn_wireguard_netw_interface and save the script:

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#!/usr/bin/env bash

set -e

[ $EUID -ne 0 ] && echo "run as root" >&2 && exit 1

apt update && \
  DEBIAN_FRONTEND=noninteractive apt install -y \
    dnsmasq netfilter-persistent iptables-persistent

# Create and persist iptables rule.
# The change: we're using the WireGuard interface (your_vpn_wireguard_netw_interface) instead of the WiFi interface (wlan0).
iptables -t nat -A POSTROUTING -o proton -j MASQUERADE
netfilter-persistent save

# Enable ipv4 forwarding.
sed -i'' s/#net.ipv4.ip_forward=1/net.ipv4.ip_forward=1/ /etc/sysctl.conf

# The Ethernet adapter will use a static IP of 10.1.1.1 on this new subnet.
cat <<'EOF' >/etc/network/interfaces.d/eth0
auto eth0
allow-hotplug eth0
iface eth0 inet static
  address 10.1.1.1
  netmask 255.255.255.0
  gateway 10.1.1.1
EOF

# Create a dnsmasq DHCP config at /etc/dnsmasq.d/bridge.conf. The Raspberry Pi
# will act as a DHCP server to the client connected over ethernet.
cat <<'EOF' >/etc/dnsmasq.d/bridge.conf
interface=eth0
bind-interfaces
server=8.8.8.8
domain-needed
bogus-priv
dhcp-range=10.1.1.2,10.1.1.254,12h
EOF

systemctl mask networking.service

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sudo bash bridge_wireguard.sh
sudo reboot

Now, when connecting your device via Ethernet to the RPI, you should see that now the Eth connectivity is VPN routed:

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curl -sS https://ipinfo.io/json #the command to use
#wget -qO- https://ipinfo.io/json

#for windows you would use
#powershell -Command "(Invoke-WebRequest -Uri https://ipinfo.io/json).Content"

You can have a quick look to the quality of your internet when routing the traffic with the VPN with:

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#sudo apt update
sudo apt install speedtest-cli
speedtest-cli

You can try similar project with a RPi and RaspAP

FAQ

Aknowledgments

Original idea from William Halley in his blog

VPN Providers

These VPN Providers can also be used with Docker

  • https://mullvad.net/en/account

  • ProtonVPN https://account.protonvpn.com

    • Downloads → WireGuard configuration - https://account.protonvpn.com/downloads#wireguard-configuration

The (Wireguard) Configuration looks like:

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[Interface]
# Bouncing = 3
# NAT-PMP (Port Forwarding) = off
# VPN Accelerator = on
PrivateKey = some_private_key
Address = 10.2.0.2/32
DNS = 10.2.0.1

[Peer]
# NL-FREE#208056
PublicKey = some_public_key
AllowedIPs = 0.0.0.0/0
Endpoint = cool_ip:51820
  • NordVPN - https://my.nordaccount.com/dashboard/
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sh <(curl -sSf https://downloads.nordcdn.com/apps/linux/install.sh)
# wget "https://repo.nordvpn.com/deb/nordvpn/debian/pool/main/nordvpn-release_1.0.0_all.deb?nv_tri=TC_7139823260542166_1715430552755&nv_trs=1715430552756_1715430943116_1_25" -O nordvpn-release_1.0.0_all.deb
# sudo dpkg -i nordvpn-release_1.0.0_all.deb

nordvpn --version

#sudo usermod -aG nordvpn $USER #to get access to: /run/nordvpn/nordvpnd.sock.
#sudo reboot

You can see other NordVPN commands here

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nordvpn login
#nordvpn set dns 9.9.9.9 149.112.112.112 #https://www.quad9.net/service/service-addresses-and-features

#nordvpn countries — see the country list.
#nordvpn cities switzerland

#DONT FORGET THIS ONE OR YOU WILL LOOSE SSH CONNECTIVITY
nordvpn set lan-discovery enable #— enable/disable LAN discovery.

nordvpn connect #https://nordvpn.com/servers/tools/
nordvpn connect switzerland
#nordvpn status 

curl -sS https://ipinfo.io/json #the command to use

#nordvpn disconnect

How to Run your Wireguard VPN Server

  • PiVPN is a set of shell scripts developed to easily turn your Raspberry Piℱ into a VPN server using two free, open-source protocols: Wireguard & OpenVPN https://github.com/pivpn/pivpn

How to revert the Wifi2Ethernet Bridge

Create a revert_bridge.sh file - remember to adapt the your_vpn_wireguard_netw_interface according to ifconfig:

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#!/usr/bin/env bash

set -e

[ $EUID -ne 0 ] && echo "run as root" >&2 && exit 1

# Remove the iptables rule.
iptables -t nat -D POSTROUTING -o nordlynx -j MASQUERADE
netfilter-persistent save

# Disable ipv4 forwarding.
sed -i'' s/net.ipv4.ip_forward=1/#net.ipv4.ip_forward=1/ /etc/sysctl.conf

# Restore original eth0 configuration or remove custom settings.
# Here you might need to replace this with the original configuration of eth0.
rm /etc/network/interfaces.d/eth0

# Remove the dnsmasq configuration file.
rm /etc/dnsmasq.d/bridge.conf

# Unmask networking.service if it was previously unmasked.
systemctl unmask networking.service

# Optional: Remove packages if they were not installed before.
# apt-get remove --purge -y dnsmasq netfilter-persistent iptables-persistent

echo "Revert completed."

Once saved, execute:

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sudo bash revert_bridge.sh

sudo iptables -F
sudo iptables -t nat -F

sudo reboot

How to Monitor Internet Quality

  • https://jalcocert.github.io/RPi/posts/self-internet-monit/
  • https://jalcocert.github.io/RPi/posts/selfh-grafana-monit/
Make your Raspberry Useful, Networking
Networking
This post is licensed under CC BY 4.0 by the author.