tcp-md5 check for incomming connection

[Ingo Flaschberger]

Hi Bjoern,

> both of this (incoming validation + SPD integ) is on my TODO list on
> position 10 (I am currently working on item 3) and there is more ipsec
> work in the middle.
>
> I also have tcp-md5 for IPv6 implementation on the same card.
>
> I am willing to help or review patches in case someone wants to do it
> now.

Yes, I want todo it now. So rules how it should implemented would be 
great. (I can do it, but just to be shure that I have to to write the 
patch twice.)

netbsd hint is also a good idea.

Kind regards,
 	Ingo Flaschberger