Having stuck my head into the kernel routing code for a few weeks now I thought I would take a look at this problem since it partially affects what I'm trying to do.
I don't think it's good idea to delete the downed routes. You'll need something to add the statics back when the interface comes back up including the default route. What I see going on is rn_match finds the most specific route whether the route is up or down. In your case it's finding the arp entry which is an exact match. Once the arp entry expires then the next specific route will be the directly connected interface route which is also down. Thus it's broke. I would probably add a flag argument to tell rn_match and rn_lookup to skip entries that aren't RTF_UP. rn_match is indeed very "hairy" and I'm not sure where even to check for RTF_UP. I haven't gained enough experience points to wield the right tools to combat that beast. I'll leave it to a much higher leveled kernel sorcerer to craft the proper enchantment. dmo
