Multiple IPv6 addresses of the same prefix can be installed on the same interface. The first address will install the prefix route into the kernel routing table and that prefix will be marked as on-link. Without RADIX_MPATH enabled, the other address aliases of the same prefix will update the prefix reference count but no other routes will be installed. Consequently the prefixes associated with these addresses would not be marked as on-link. As such, incoming packets destined to these address aliases will fail the ND6 on-link check on input. This patch fixes the above problem by searching the kernel routing table and try to find an on-link prefix on the given interface.
Multiple IPv6 addresses of the same prefix can be installed on the
same interface. The first address will install the prefix route into
the kernel routing table and that prefix will be marked as on-link.
Without RADIX_MPATH enabled, the other address aliases of the same
prefix will update the prefix reference count but no other routes
will be installed. Consequently the prefixes associated with these
addresses would not be marked as on-link. As such, incoming packets
destined to these address aliases will fail the ND6 on-link check
on input. This patch fixes the above problem by searching the kernel
routing table and try to find an on-link prefix on the given interface.

MFC after:	5 days

jrobhoward/SCADAbase,jrobhoward/SCADAbase,jrobhoward/SCADAbase,jrobhoward/SCADAbase,jrobhoward/SCADAbase,jrobhoward/SCADAbase,jrobhoward/SCADAbase,jrobhoward/SCADAbase,jrobhoward/SCADAbase,jrobhoward/SCADAbase,jrobhoward/SCADAbase