ng_sbinat – (Symmetric | Simple) Bidirectional NAT

Requirements

• FreeBSD >= 7.0 (tested on 7.2, should work on all 7.x, and, maybe, on 6.x too)
• NetGraph
• kernel sources (for building)

Memory usage & speed

Lightning fast! B/c there’s no any heavy data processing and no packet checksums recalculation.
And negligible memory usage b/c there’s no remembering of ip<—>ip translation pairs.

Limitations

• only symmetrinc mapping of one /16 subnet to another /16 subnet is possible now (f.ex. 192.168.×.y <—> 10.22.×.y)
• passive FTP will not work

Installation

  git clone git://github.com/zed-0xff/ng_sbinat.git
  cd ng_sbinat
  make
  make install

Configuration

  kldload ng_sbinat
  kldload ng_ether
  ngctl mkpeer em0: sbinat upper in
  ngctl name em0:upper sbinat
  ngctl conn sbinat: em0: out lower
  ngctl msg sbinat: setinaddr 192.168.0.0
  ngctl msg sbinat: setoutaddr 10.22.0.0

Credits

• thanks to Gleb Smirnoff (glebius@FreeBSD.org) for ng_nat & ng_netflow
• thanks to Alexey Popov (lollypop@flexuser.ru) for ng_tcpmss’s TCPMSS_ADJUST_CHECKSUM()