source is found at ftp://ftp.fml.org/pub/libtransparent/
Brief description is within my home page.
struct sockaddr_in *dstp;
ipfilter_modify_dst() overwrite *dstp to the real destination.
You can use this function to make application level gateway with ipfilter.
For example, consider ssh proxy (ssh-gw).
Firstly run proxy which listens 10022/tcp.
Secondly redirect ssh connection from 22/tcp to localhost 10022/tcp at
the internal interface by ipfilter (ipnat).
You can get ssh-gw.
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