UDP Broadcast Packet Relay

This program listens for packets on a specified UDP broadcast port. When a packet is received, it sends that packet to all specified interfaces but the one it came from as though it originated from the original sender.

The primary purpose of this is to allow games on machines on separated local networks (Ethernet, WLAN) that use udp broadcasts to find each other to do so.

It also works on ppp links, so you can log in from windows boxes (e.g. using pptp) and play LAN-based games together. Currently, you have to care about upcoming or downgoing interfaces yourself.

Note that it is possible to achieve this using iptables as well.

INSTALL

make 
cp udp-broadcast-relay /some/where

USAGE

/some/where/udp-broadcast-relay id udp-port eth0 eth1...

udp-broadcast-relay must be run as root to be able to create a raw socket (necessary) to send packets as though they originated from the original sender.

COMPATIBILITY

• I run debian woody with Linux 2.4.20, and here it works.

EXAMPLE

/some/where/udp-broadcast-relay -f 1 6112 eth0 eth1  # forward Warcraft 3 broadcast packets

CONTRIBUTORS

Over the last years, various people submitted code to the project. Note that I do not use udp-broadcast-relay any more myself, so these changes were not tested by me.

• Patrick Huesmann submitted a patch to make udp-broadcast-relay send the packes to those NICs it did not recieve it from, based on the actual socket, not the broadcast IP. This is useful if more than one physical networks share the same broadcast range.
• Савченко В. М. submitted an ip-up.local an ip-down.local file to automatically restart udp-broadcast-relay when new ppp-interfaces come up, see ppp-if.up-local for details.
• Roman Hoog Antink contributed the option -s to spoof the source IP of forwarded packages.

Thanks to all contributors!

BUGS/CRITICISM/PATCHES/ETC

• Web: http://www.joachim-breitner.de/udp-broadcast-relay/
• e-mail: Joachim Breitner <[email protected]>
• Github: https://github.com/nomeata/udp-broadcast-relay/

HISTORY

• 0.3 2003-09-28

  Sending packets also to ppp addresses

• 0.2 2003-09-18

  Flags for debugging and forking, Compilefixes, Makefile-Target "clean"

• 0.1 2003-09-15

  Initial rewrite of udp_broadcast_fw

CREDITS

This is based upon udp_broadcast_fw by Nathan O'Sullivan.

HISTORY of udp_broadcast_fw

• 0.1.1 - 19 Feb 02

  Moved fork() code to just before main loop so that errors would appear

• 0.1 - 18 Feb 02

  Initial release

LICENSE

This code is made available under the GPL. Read the COPYING file inside the archive for more info.