From: Ben Hutchings <redacted>
Date: Tue, 14 Aug 2012 23:33:44 +0100

I think we will also need to limit the depth of the device stack so we
don't run out of stack space here.  __netif_receive() implements a kind
of tail recursion whenever a packet is passed up, but
__netdev_has_upper_dev() can't avoid doing real recursion (without the
addition of a flag to net_device so it can mark its progress).

Agreed, we need some kind of limit here.