Embedded Files
Since the Raspberry Pi has 2 built in network devices we can custumise the Pi to act as a Bridge. A network bridge's basic purpose is to connect two disparate LANs . In this case using the Pi as a wireless adapter for a non wireless PC or other non wireless device.
Thanks to the work of Will Haley at WillHaley.com This script seems to work fine.
Works without issue on the Pi 4 with bookworm running GUI or light version with CLI.
Select and copy the text on the right
nano bridge.sh
Paste (ctrl+shift+v) and save (ctrl+x then y)
Run the script file,
sudo bash bridge.sh
Reboot and connect the PC to the Pi with an ethernet cable
Subsequent changes I have made have been installing Raspberry PI Connect to remotely access the PI. and reverting the PI to CLI
#!/usr/bin/env bash
set -e
[ $EUID -ne 0 ] && echo "run as root" >&2 && exit 1
##########################################################
# You should not need to update anything below this line #
##########################################################
# parprouted - Proxy ARP IP bridging daemon
# dhcp-helper - DHCP/BOOTP relay agent
# dhcpcd - Roy Marples' DHCP client daemon
# systemd-resolved - systemd network name resolution
apt update && apt install -y parprouted dhcp-helper dhcpcd systemd-resolved
systemctl stop dhcpcd dhcp-helper systemd-resolved
systemctl enable dhcpcd dhcp-helper systemd-resolved
# Enable the wpa_supplicant hook for dhcpcd.
ln -s /usr/share/dhcpcd/hooks/10-wpa_supplicant /usr/lib/dhcpcd/dhcpcd-hooks/
# Enable ipv4 forwarding.
sed -i'' s/#net.ipv4.ip_forward=1/net.ipv4.ip_forward=1/ /etc/sysctl.conf
# Disable dhcpcd control of eth0.
grep '^denyinterfaces eth0$' /etc/dhcpcd.conf || printf "denyinterfaces eth0\n" >> /etc/dhcpcd.conf
# Configure dhcp-helper.
cat > /etc/default/dhcp-helper <<EOF
DHCPHELPER_OPTS="-b wlan0"
EOF
# Import the NetworkManager wifi connection profile.
ssid="$(grep -r '^ssid=' /etc/NetworkManager/system-connections/preconfigured.nmconnection | awk '{print $2}' FS='[=]')"
psk="$(grep -r '^psk=' /etc/NetworkManager/system-connections/preconfigured.nmconnection | awk '{print $2}' FS='[=]')"
cat << EOF > "/etc/wpa_supplicant/wpa_supplicant.conf"
ctrl_interface=DIR=/var/run/wpa_supplicant GROUP=netdev
update_config=1
country=US
network={
ssid="${ssid}"
psk=${psk}
key_mgmt=WPA-PSK
}
EOF
# Enable avahi reflector if it's not already enabled.
sed -i'' 's/#enable-reflector=no/enable-reflector=yes/' /etc/avahi/avahi-daemon.conf
grep '^enable-reflector=yes$' /etc/avahi/avahi-daemon.conf || {
printf "something went wrong...\n\n"
printf "Manually set 'enable-reflector=yes in /etc/avahi/avahi-daemon.conf'\n"
}
# I have to admit, I do not understand ARP and IP forwarding enough to explain
# exactly what is happening here. I am building off the work of others. In short
# this is a service to forward traffic from WiFi to Ethernet.
cat <<'EOF' >/usr/lib/systemd/system/parprouted.service
[Unit]
Description=proxy arp routing service
Documentation=https://raspberrypi.stackexchange.com/q/88954/79866
Requires=sys-subsystem-net-devices-wlan0.device dhcpcd.service
After=sys-subsystem-net-devices-wlan0.device dhcpcd.service
[Service]
Type=forking
# Restart until wlan0 gained carrier
Restart=on-failure
RestartSec=5
TimeoutStartSec=30
# clone the dhcp-allocated IP to eth0 so dhcp-helper will relay for the correct subnet
ExecStartPre=/bin/bash -c '/sbin/ip addr add $(/sbin/ip -4 -br addr show wlan0 | /bin/grep -Po "\\d+\\.\\d+\\.\\d+\\.\\d+")/32 dev eth0'
ExecStartPre=/sbin/ip link set dev eth0 up
ExecStartPre=/sbin/ip link set wlan0 promisc on
ExecStart=-/usr/sbin/parprouted eth0 wlan0
ExecStopPost=/sbin/ip link set wlan0 promisc off
ExecStopPost=/sbin/ip link set dev eth0 down
ExecStopPost=/bin/bash -c '/sbin/ip addr del $(/sbin/ip -4 -br addr show wlan0 | /bin/grep -Po "\\d+\\.\\d+\\.\\d+\\.\\d+")/32 dev eth0'
[Install]
WantedBy=wpa_supplicant.service
EOF
systemctl disable NetworkManager
systemctl daemon-reload
systemctl enable parprouted
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