ARP:  Add support for the case where there are multiple networks:  One being Etherenet and the other not (say slip or perhaps someday PPP).  In that case, we need to suppress ARP-related operations on the SLIP/PPP interface only

I don't think that the net_route function has ever worked correctly.  The source ip was updated in the match struct instead of the route ip.  From Brennan Ashton.