Friendly Neighbor is a network server that responds to ARP and NDP requests on behalf of other LAN devices. Think of it as applying a set of static IP-to-MAC address mappings for all devices on your LAN.

Its main use-case is enabling network packets to be sent to sleeping machines so that they can be woken up on demand using wake-on-unicast. This blog post explains the technique in detail.

• Super lightweight and performant, built with Zig
• Built with libpcap for efficient, low-overhead packet filtering
• Supports different CPU architectures, including x86_64 and Raspberry Pi (ARM64)
• Distributed as a universal Snap package for easy installation on many Linux distros
• Can respond on behalf of multiple machines at once
• IPv4 and IPv6 support

• Linux (any distro supporting Snap packages, kernel version 2.6.27+)
• Wired Ethernet network interface

sudo snap install friendly-neighbor
sudo snap connect friendly-neighbor:hardware-observe
sudo snap connect friendly-neighbor:network-control
# Replace the values for "mac-ip-mappings" and "interface-name" below with your real ones:
sudo snap set friendly-neighbor mac-ip-mappings=AA:BB:CC:DD:EE:FF,10.0.8.3 interface-name=eth0
sudo snap restart friendly-neighbor

The Snap package is configured to run automatically Friendly Neighbor as a network service (daemon). After performing the steps above, the service should be running and should automatically start on subsequent system startups.

The following usage details are only relevant when running the service directly. If using the Snap package, service parameters are set using snap set friendly-neighbor ...

USAGE
    friendly_neighbor [-hv] [-i <IFACE>] [-m <MAPPING>...] [--mappings <MAPPINGS>]

OPTIONS
    -i, --interface <IFACE>
            Name of network interface on which to listen and send packets

    -m, --mapping <MAPPING>...
            One or more MAC to IP (v4 or v6) address mappings, each in the
            format <MAC address>,<IP address>

        --mappings <MAPPINGS>
            A single string containing one or more mappings in the format <MAC
            address>,<IP address> with mappings separated by a space

    -h, --help
            Display this help and exit

    -v, --version
            Print program version and exit

EXAMPLES
    friendly_neighbor -i eth0 \
        -m 11:22:33:44:55:66,192.168.1.2 \
        -m 11:22:33:44:55:66,fd12:3456:789a:1::1

    friendly_neighbor -i eno1 --mappings \
        "AA:BB:CC:DD:EE:FF,10.0.8.3 AA:BB:CC:DD:EE:FF,fd9a:bc83:57e4:2::1"

Contributions are welcome, pull requests and issues can be created at https://github.com/danielpgross/friendly_neighbor

MIT

Happy networking, and remember to be a friendly neighbor! 🌐💻