Note that iptables can do it as well
-rw-r--r-- 17976 COPYING
-rw-r--r-- 101 Makefile
-rw-r--r-- 2971 README.md
-rw-r--r-- 10875 main.c
-rw-r--r-- 1049 ppp-if.up-local
-rw-r--r-- 1104 udp-broadcast-relay.8