macaddress.rb

Facter.add(:macaddress) do
  confine :kernel => 'Linux'
  has_weight  10                # about an order of magnitude faster
  setcode do
    begin
      result = nil 
      Dir.glob('/sys/class/net/*').each do |path|
        mac = File.read(path + "/address").chomp
        unless /^(?:00:)+00$|^\s*/.match(mac)
            result = mac 
        end 
        break unless result == nil 
      end 
      result
    rescue Exception
      nil 
    end 
  end 
end

macaddress_spec.rb

  describe "when run on Linux" do
    before :each do
      Facter.fact(:kernel).stubs(:value).returns("Linux")
      Facter.fact(:operatingsystem).stubs(:value).returns("Linux")
      Facter::Util::IP.stubs(:get_ifconfig).returns("/sbin/ifconfig")
    end 

    describe "with /sys available" do
      before :each do
        Dir.stubs(:glob).with('/sys/class/net/*').returns( [
          '/sys/class/net/lo',
          '/sys/class/net/eth0',
          '/sys/class/net/eth1',
          '/sys/class/net/sit0',
          '/sys/class/net/ip6tnl0',
          '/sys/class/net/tunvpn0',
          '/sys/class/net/tunvpn1',
        ])  
        File.stubs(:read).with('/sys/class/net/lo/address').returns("00:00:00:00:00:00\n")
        File.stubs(:read).with('/sys/class/net/eth0/address').returns("00:12:3f:be:22:01\n")
        File.stubs(:read).with('/sys/class/net/eth1/address').returns("00:12:3f:be:22:02\n")
        File.stubs(:read).with('/sys/class/net/sit0/address').returns("00:00:00:00")
        File.stubs(:read).with('/sys/class/net/ip6tnl0/address').returns("00:00:00:00:00:00:00:00:00:00:00:00")
        File.stubs(:read).with('/sys/class/net/tunvpn0/address').returns("")
        File.stubs(:read).with('/sys/class/net/tunvpn1/address').returns(" \n")
      end 

      it "should glob /sys/class/net" do
        Dir.expects(:glob).with('/sys/class/net/*').returns([ '/sys/class/net/lo', '/sys/class/ne/eth0' ])

        Facter.value(:macaddress)
      end 

      it "should open the address file of the first interface" do
        File.expects(:read).with('/sys/class/net/lo/address').returns( "00:00:00:00:00:00\n" )

        Facter.value(:macaddress)
      end 


      it "should open the address file of the second interface" do
        File.expects(:read).with('/sys/class/net/eth0/address').returns( "00:12:3f:be:22:01\n" )

        Facter.value(:macaddress)
      end 

      it "should not open the address file of the third interface" do
        File.expects(:read).with('/sys/class/net/eth1/address').returns( "00:12:3f:be:22:02\n" ).never

        Facter.value(:macaddress)
      end 

      it "should not return an empty address" do
        File.expects(:read).with('/sys/class/net/tunvpn0/address').returns( "" )

        Facter.value(:macaddress).should == nil 
      end 

      it "should not return a whitespace-only address" do
        File.expects(:read).with('/sys/class/net/tunvpn1/address').returns( " \n")

        Facter.value(:macaddress).should == nil 
      end 

      it "should not return a shortened zero-only address" do
        File.expects(:read).with('/sys/class/net/sit0/address').returns( "00:00:00:00\n")

        Facter.value(:macaddress).should == nil 
      end 

      it "should not return a double-length zero-only address" do
        File.expects(:read).with('/sys/class/net/ip6tnl0/address').returns( "00:00:00:00:00:00:00:00:00:00:00:00\n" )

        Facter.value(:macaddress).should == nil 
      end

      it "should return the macaddress of the first interface with a proper macaddress" do
        Facter.value(:macaddress).should == "00:12:3f:be:22:01"
      end

      # the local loopback interface (lo) doesn't have a macaddress/has its macaddress zero-filled
      it "should return nil for zero-only macaddresses" do
          Dir.stubs(:glob).returns( [ '/sys/class/net/lo' ])
          File.stubs(:read).returns( "00:00:00:00:00:00\n" )

          Facter.value(:macaddress).should == nil
      end
    end