broadcast-relay

This utility will relay limited broadcasts (255.255.255.255) from an interface to another interface (or on the same interface). You can use this utility for VPN servers to forward limited broadcast.

Using on Debain Jessie

Install dependencies

apt install libnl-3-200 libnl-genl-3-200 dbus

Setup

Download the utility and install the systemd service.

URI=$(curl -s https://api.github.com/repos/Golit/broadcast-relay/releases | grep browser_download_url | head -n 1 | cut -d '"' -f 4)
curl -L -o /usr/local/bin/broadcast-relay $URI
chmod +x /usr/local/bin/broadcast-relay
cat > /etc/systemd/system/broadcast-relay@.service <<EOF
[Unit]
Description=Relay For Limited Broadcasts On Interface %I
After=openvpn@server.service

[Service]
Type=simple
ExecStart=/usr/local/bin/broadcast-relay --interface-in %i --interface-out %i

[Install]
WantedBy=multi-user.target
EOF
systemctl enable broadcast-relay@tap0
systemctl start broadcast-relay@tap0

Usage

broadcast-relay [-i <interface with broadcasts>] [-o <interface where to relay broadcasts>] [-h] [-l <loglevel>]
broadcast-relay --interface-in tap0 --interface-out tap0

Compile on Alpine Linux

apk add gcc git make libpcap-dev libc-dev libnl3-dev dbus-dev linux-headers
make
cp broadcast-relay /usr/local/bin/

Contribution

Contributions are welcome.

References for developer

libpcap

http://www.tcpdump.org/pcap.html

http://eecs.wsu.edu/~sshaikot/docs/lbpcap/libpcap-tutorial.pdf

getopt

https://linux.die.net/man/3/getopt_long

raw sockets

http://opensourceforu.com/2015/03/a-guide-to-using-raw-sockets/

http://www.pdbuchan.com/rawsock/rawsock.html