ipnat(4) on FreeBSD
The text ce0083f28247, as FreeBSD 3.5.1-RELEASE, FreeBSD 3.5-RELEASE, FreeBSD 3.4-RELEASE, FreeBSD 3.3-RELEASE, FreeBSD 3.2-RELEASE, FreeBSD 3.1-RELEASE, FreeBSD 3.0-RELEASE shipped it.
Network Address Translation kernel interface