code: func (h *Handle) neighAdd(neigh *Neigh, mode int) error {
  	req := h.newNetlinkRequest(unix.RTM_NEWNEIGH, mode|unix.NLM_F_ACK)
  	return neighHandle(neigh, req)
  }
docs: // NeighAppend will append an entry to FDB
  // Equivalent to: `bridge fdb append...`