This patch adds an lle_event handler to make an incoming ARP reply send an RTM_ADD/DELETE message to the routing socket. ARP on FreeBSD did not report changes to the ARP table to the routing socket while IPv6 NDP does. It is reasonable to send out an RTM_ADD/DELETE message when an L2-L3 address mapping is resolved even for IPv4 because userland programs can receive it.
This patch also includes a minor change to nd6_lle_event() to make it report the L2 address on expiration of the entry. This additional information is sometimes useful, and reporting it is harmless even if it is not used on the receiver side.