From: Nicolas Cavallari <redacted>
Date: Fri, 12 Sep 2014 16:14:20 +0200

If we cache them, the kernel will reuse them, independently of
whether forwarding is enabled or not.  Which means that if forwarding is
disabled on the input interface where the first routing request comes
from, then that unreachable result will be cached and reused for
other interfaces, even if forwarding is enabled on them.

This can be verified with two interfaces A and B and an output interface
C, where B has forwarding enabled, but not A and trying
ip route get $dst iif A from $src && ip route get $dst iif B from $src

Signed-off-by: Nicolas Cavallari <redacted>
---
based on net-next, but not really tested on top of it.

Sorry Nicolas, this seems to have fallen on the floor.  Could you please
resubmit your most uptodate version of this patch so I can apply it?

Thanks.