From: Neil Horman <nhorman@tuxdriver.com>
Date: Wed, 28 Dec 2011 14:21:50 -0500

Clearly I misread the RFC the first time through and the test as it existed is
incorrect.  I'm wondering though if what we need is a way to lookup if we've
received a RA on the interface, and check to see if it has a source link layer
option attached to it.

Yes, we could implement this with a new neigh lookup routine, that allows
keying on device pointer and flags.

So in this case we'd pass the device and NTF_ROUTER.  If the lookup returns
non-NULL then we've seen an RA with SLLAO specified.