ipfw(8) on FreeBSD
The text 188172e25eff, as FreeBSD 8.1-RELEASE shipped it.
User interface for firewall, traffic shaper, packet scheduler, in-kernel NAT.
Flags it lists
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-N -
-S -
-T -
-a -
-b -
-c -
-d -
-e -
-f -
-i -
-n -
-q -
-s -
-t