User-space TCP/UDP port forwarding services

Summary

This project contains two applications: tcpfwd, udpfwd, which are for TCP and UDP port forwarding literally. Written in pure C, with libevent2 library.

Usage

tcpfwd|udpfwd <local_addr:local_port> <dest_addr:dest_port> [-d] [-o]
 
Options:
  -d              run in background
  -o              accept IPv6 connections only for IPv6 listener
  -p <pidfile>    write PID to file

Examples

Map local TCP port 1022 to 192.168.1.77:22

tcpfwd 0.0.0.0:1022 192.168.1.77:22     # allow access from all hosts
tcpfwd 127.0.0.1:1022 192.168.1.77:22   # only allow localhost
tcpfwd [::]:1022 192.168.1.77:22        # allow access to port 1022 via both IPv4 and IPv6

Map local UDP port 53 to 8.8.8.8:53

udpfwd 0.0.0.0:53 8.8.8.8:53
udpfwd [::]:53 8.8.8.8:53

IPv4-IPv6 transforming

udpfwd [::]:1701 localhost:1701         # add IPv6 support for a local L2TP service
tcpfwd 0.0.0.0:80 [2001:db8:3::2]:80    # enable IPv4 access for an IPv6-only web service