'Mask off any flags except for L{TunnelType.IFF_TUN} and
L{TunnelType.IFF_TAP}.
@param flags: Flags from L{TunnelType} to mask.
@type flags: L{FlagConstant}
@return: The flags given by C{flags} except the two type flags.
@rtype: L{FlagConstant}'

def _tunnelTypeOnly(self, flags):

    return (flags & (TunnelFlags.IFF_TUN | TunnelFlags.IFF_TAP))
