pci_to_mac.rb

class SysInventory
  def self.getInventory
    unless @inventory
      lshw = Facter::Util::Resolution.exec('lshw -json -quiet')

      require 'json'
      @inventory = JSON.parse lshw
    end
    @inventory
  end
end

if SysInventory.getInventory

# I am so very very sorry for this
  SysInventory.getInventory['children'].each do |c|
    if c['id'] == 'core'
      c['children'].each do |cc|
        if cc['id'] == 'pci'
          cc['children'].each do |ccc|
            if ccc['class'] == 'bridge' and ccc['children']
              ccc['children'].each do |dev|
                if dev['class'] == 'network'
                  Facter.add("pci_eth_mac_#{dev['businfo']}") do
                    setcode do
                      dev['serial']
                    end
                  end
                end
              end
            end
          end
        end
      end
    end
  end
end