pmtud + ipnat RELENG_6_2 appears to be broken

[Pete French]

> Great, thanks for testing.

Intyeresting side effect of the patch appears to be that I am getting 25%
*lower* throughput on my ether connections between two machines plugged into
the same switch. Not what I expected! I assume this is something to do with
the behaviour of the switches as the BSD side change was simply copying an
address, but it's interesting none-the-less.

I will give your new patch a try today as well,

thanks,

-pete.