ipfw2 interface / examples

[Dirk-Willem van Gulik]

I am recoding some firewall management code which acts on data on the
application layer (to open ports etc) from ipfw to the new ipfw2. And am
struggling a bit understanding what exactly to pass.

-	Needless to say - a bug in your rule gives one
	a 'Adding rule: Invalid argument' errno; is there
	any way/tool to decode how the IP_FW_ADD struct is
	passed and get some more insight ?

-	Is there a simpler example than ipfw2.c, or an raw docs
	for the getsockopt() api which helps me understand this better.
	In particular the from/to 'O_IN/(!O_IN)' versus the ability
	of ipfw.c to set both IP_FW_F_IN and IP_FW_F_OUT to make
	the rule symetrical around from/to.

Thanks.

Dw