MIP6: Proxy forwarding

• Required by HA with physical home link support:

  • Respond to unicast ND for proxy entry
  • Do not learn neighbors in our own Proxy ND list
    • Either its link-layer address is own or such address is off-link.
  • Provide an interface to specify router/host flag to announce NA for each proxy entry respectively.
    • Proxied node may NOT be a router but a host.