udp-bridge

UDP-Bridge - Tunnel UDP traffic over TCP with fixed endpoints on both sites

This repo contains the code for a program that allows to tunnel UDP traffic over TCP between two applications on different hosts that a) listen on fixed port numbers b) expect the remote applications to listen on fixed port numbers

Our current use-case is to create a tunnel between two external Border Router interfaces in SCION, in case some firewall is only allowing TCP traffic. However, it can be used for other use-cases, too.

The name of this tool is intended to be different from the existing udptunnel which provides similar functionalities, but did not fulfill our use-case.

Idea

Configuration for this example

We now build the setup depicted in the figure above with udp-bridge. Assuming Application1 listens on 10.0.0.1:30001 and Application2 on 10.0.0.2:40001, and there is a firewall in between filtering UDP traffic. We now configure udp-bridge1 to listen on 10.0.1.1:30000 on UDP and send incoming traffic (from the TCP connection) to 10.0.1.1:30001 over UDP. Udp-bridge2 will listen on 10.0.0.2:40000 on UDP and send incoming traffic (from the TCP connection) to 10.0.0.2:40001 over UDP. Udp-bridge1 will now connect to udp-bridge2 via TCP to 10.0.0.2:40000 and both brdges are ready to tunnel traffic bidirectionally.

The commandlines for both sites look like the following:

• Host1: udp-bridge -c 10.0.0.2:40000 -d 10.0.0.1:30001 -u 10.0.0.1:30000 (Listen on UDP 10.0.0.1:30000, send UDP to 10.0.0.1:30001, connect to TCP 10.0.0.2:40000)
• Host2: udp-bridge -s 10.0.0.2:40000 -d 10.0.0.2:40001 -u 10.0.0.2:40000 (Listen on UDP 10.0.0.2:40000, send UDP to 10.0.0.2:40001, listen on TCP 10.0.0.2:40000)

Application1 now only needs to send UDP traffic to 10.0.0.1:30000 to reach Application2 and Application2 needs to send UDP traffic to 10.0.0.2:40000 to reach Application1.

Usage

Build it locally and then run it go build && ./udp-bridge [OPTIONS] or run it via go run github.com/netsys-lab/udp-bridge [OPTIONS]

Usage:
  udp-bridge [OPTIONS]

Application Options:
  -s, --server=  Configure the TCP Addr IP:Port to listen in Server Mode
  -c, --client=  Configure the TCP Addr IP:Port to connect to in Client Mode
  -u, --udp=     Configure the UDP Addr IP:Port to listen for incoming packets
  -d, --dest=    Configure the UDP Addr IP:Port to sent incoming packets to
  -v, --verbose  Show verbose debug information

Help Options:
  -h, --help     Show this help message