anchor.diff:  let pkgs = import nixpkgs { config = {}; inherit system; }; in
   
   with pkgs;
  +with import ../lib/qemu-flags.nix;
   
   rec {
   
  
positive.code:                          "${config.networking.hostName}\n"));
                    
                    virtualisation.qemu.options =
                      lib.flip lib.concatMapStrings interfacesNumbered ({ first, second }:
                        "-net nic,vlan=${toString second},model=virtio " +
                        # Use 232.0.1.<vlan> as the multicast address to
                        # connect VMs on the same vlan, but allow it to
                        # be overriden using the $QEMU_MCAST_ADDR_<vlan>
                        # environment variable.  The test driver sets
                        # this variable to prevent collisions between
                        # parallel builds.
                        "-net socket,vlan=${toString second},mcast=" +
                        "\${QEMU_MCAST_ADDR_${toString first}:-232.0.1.${toString first}:1234} "
                      );
  
                  };
              }
            )
  
negative.code: 
      in lib.listToAttrs nodes_;
  
  
    # Zip two lists together.  Should be moved to pkgs.lib.
    zip = xs: ys:
      if xs != [] && ys != [] then
  