> Why is this (having a route pointing to a gateway that's not on net
> for any interface) not supported, even if there is a route for this
> gateway pointing at another gateway which is on-net?

My guess is, because it does not match IP's routing model, so whoever
did the code either didn't consider it at all or didn't think it worth
supporting.  However, I didn't write the code in question, so I don't
really _know_.

> I. e. could the routing table be searched recursively, until a
> directly-reachable gateway is found?

It could.  But quite aside from what it does to the assumptions
underlying IP, how would you cut off infinite loops?

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