cdns_rs/

cfg_resolv_parser.rs

/*-
 * cdns-rs - a simple sync/async DNS query library
 * 
 * Copyright (C) 2020  Aleksandr Morozov
 * 
 * Copyright (C) 2025 Aleksandr Morozov
 * 
 * The syslog-rs crate can be redistributed and/or modified
 * under the terms of either of the following licenses:
 *
 *   1. the Mozilla Public License Version 2.0 (the “MPL”) OR
 *                     
 *   2. EUROPEAN UNION PUBLIC LICENCE v. 1.2 EUPL © the European Union 2007, 2016
 */

use std::fmt;
/// This file contains the config file parsers.


use std::hash::Hash;
use std::net::{IpAddr, SocketAddr};
use std::str::FromStr;
use std::sync::atomic::{AtomicUsize, Ordering};
use std::sync::Arc;

use bitflags::bitflags;

use crate::common::{bind_all, DEF_HTTPS_PORT, DEF_TLS_PORT};
use crate::{error::*, internal_error, internal_error_map, write_error};
use crate::portable::*;
use crate::tokenizer::*;

/// A rounrobin counter. It was intentionally designed to count forward as
/// it is not expected that the counter will ever be overflowed.
static ROUND_ROBIN_CNT: AtomicUsize = AtomicUsize::new(0);



/// An implementaion of RoundRobin iterator. This iterator is sharing a single
/// source of counting to implement roundrobin functionality.
pub struct RoundRobinIterator<'iterator, I>
{
    end_index: usize,
    current_index: usize,
    slice: &'iterator [I]
}

impl<'iterator, I> RoundRobinIterator<'iterator, I>
{
    pub 
    fn new(start_index: usize, slice: &'iterator [I]) -> RoundRobinIterator<'iterator, I>
    {        
        return 
            RoundRobinIterator
            {
                end_index: start_index + slice.len(),
                current_index: start_index,
                slice: slice
            };
    }

    pub 
    fn len(&self) -> usize
    {
        return self.slice.len();
    }
} 

impl<'iterator, I> Iterator for RoundRobinIterator<'iterator, I>
{
    type Item = &'iterator I;

    fn next(&mut self) -> Option<Self::Item> 
    {
        let temp_index = self.current_index;
        
        self.current_index += 1;

        if temp_index == self.end_index
        {
            return None;
        }

        // compute real index
        let real_index = temp_index % self.slice.len();

        return self.slice.get(real_index);
    }
}

#[derive(Clone, Copy, Debug, PartialEq, Eq)]
pub enum ConfigEntryTls
{
    None, Tls, Https
}

impl fmt::Display for ConfigEntryTls
{
    fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result 
    {
        match self
        {
            Self::None => write!(f, "unencrypted"),
            Self::Tls => write!(f, "TLS"),
            Self::Https => write!(f, "HTTPS"),
        }
    }
}

/// A resolve.conf parser
#[derive(Clone, Debug, PartialEq, Eq)]
pub struct ResolveConfEntry 
{
    ip: SocketAddr,
    tls_domain: Option<String>,
    https_req_path: Option<String>,
    adapter_ip: SocketAddr,
    tls_type: ConfigEntryTls,
}

impl ResolveConfEntry
{
    pub 
    fn new(ip: SocketAddr, tls_url: Option<String>, adapter_ip: SocketAddr) -> CDnsResult<Self>
    {
        let (tls_type, https_domain, https_req_path) = 
            if let Some(tlsd) = tls_url.as_ref()
            {
                if let Some(domain_path_https) = tlsd.strip_prefix("https://")
                {
                    let Some ((domain, path)) = domain_path_https.split_once("/")
                        else 
                        {
                            internal_error!(CDnsErrorType::ConfigError, 
                                "in /etc/resolv.conf - invalid TLS/HTTPS URL '{}'", 
                                domain_path_https
                            )
                        };

                    (ConfigEntryTls::Https, Some(domain.to_string()), Some(path.to_string()))
                }
                else
                {
                    // TLS
                    let domain = 
                        tlsd
                            .split_once("://")
                            .map_or(tlsd.as_str(), |(_, d)| d);


                    let domain = 
                        domain
                            .split_once("/")
                            .map_or(domain, |(d, _)| d);

                    
                    (ConfigEntryTls::Tls, Some(domain.to_string()), None)
                }
            }
            else
            {
                if ip.port() == DEF_HTTPS_PORT 
                {
                    (ConfigEntryTls::Https, None, None)
                }
                else if ip.port() == DEF_TLS_PORT
                {
                    (ConfigEntryTls::Tls, None, None)
                }
                else
                {
                    (ConfigEntryTls::None, None, None)
                }
            };

        return Ok(Self {ip, tls_domain: https_domain, https_req_path: https_req_path, adapter_ip, tls_type});
    }

    pub 
    fn get_resolver_ip(&self) -> IpAddr
    {
        return self.ip.ip();
    }

    pub 
    fn get_resolver_sa(&self) -> &SocketAddr
    {
        return &self.ip;
    }

    pub 
    fn get_tls_domain(&self) -> Option<&String>
    {
        return self.tls_domain.as_ref();
    }

    pub 
    fn get_adapter_ip(&self) -> &SocketAddr
    {
        return &self.adapter_ip;
    }

    pub 
    fn get_tls_type(&self) -> ConfigEntryTls
    {
        return self.tls_type;
    }

    pub 
    fn get_tls_path(&self) -> Option<&String>
    {
        return self.https_req_path.as_ref();
    }
}

/*
#[derive(Clone, Debug, PartialEq, Eq)]
pub enum ResolveConfigLookup
{
    File, Bind
}*/

bitflags! {
    /// An 'option' flags which can be set in /etc/resolv.conf
    #[derive(Clone, Debug, PartialEq, Eq, Copy)]
    pub struct ResolveConfigLookup: u32 
    {
        /// Sets the bit order flag that first is FILE
        const FILE_BIND  = 0x10;
        /// Sets the bit order flag that first is BIND
        const BIND_FILE  = 0x20;
        /// FILE is enabled
        const FILE       = 0x01;
        /// BIND is enabled
        const BIND       = 0x02;
    }
}


impl ResolveConfigLookup
{
    pub 
    fn is_file(&self) -> bool
    {
        return self.contains(Self::FILE);
    }

    pub 
    fn is_bind(&self) -> bool
    {
        return self.contains(Self::BIND);
    }

    pub 
    fn is_file_first(&self) -> bool
    {
        return self.contains(Self::FILE_BIND);
    }
}

impl Default for ResolveConfigLookup
{
    fn default() -> Self 
    {
        return Self::FILE_BIND | Self::FILE | Self::BIND;
    }
}

const LOOKUP_FILE: &'static str = "file";
const LOOKUP_BIND: &'static str = "bind";

impl TryFrom<&[String]> for ResolveConfigLookup
{
    type Error = CDnsError;

    fn try_from(value: &[String]) -> Result<Self, Self::Error> 
    {
        if value.is_empty() == true
        {
            internal_error!(CDnsErrorType::ConfigError, "'lookup' is empty");
        }
        else if value.len() > 2
        {
            internal_error!(CDnsErrorType::ConfigError, "'lookup' is set with too many paramenters: '{:?}'", value);
        }

        //let lookup_flags: Self = Self::empty();

        let first = 
            if value[0] == LOOKUP_FILE
            {
                Self::FILE
            }
            else if value[0] == LOOKUP_BIND
            {
                Self::BIND
            }
            else
            {
                internal_error!(CDnsErrorType::ConfigError, "'lookup' is set with unknown parameter: '{}'", value[0]);
            };

        let second: Self = 
            if value.len() == 2
            {
                if value[1] == LOOKUP_FILE
                {
                    if first.contains(Self::FILE) == true
                    {
                        internal_error!(CDnsErrorType::ConfigError, "'lookup' is set with duplicate parameter: '{}'", value[1]);
                    }
                    
                    Self::BIND_FILE | Self::FILE
                }
                else if value[1] == LOOKUP_BIND
                {
                    if first.contains(Self::BIND) == true
                    {
                        internal_error!(CDnsErrorType::ConfigError, "'lookup' is set with duplicate parameter: '{}'", value[1]);
                    }
                    
                    Self::FILE_BIND | Self::BIND
                }
                else
                {
                    internal_error!(CDnsErrorType::ConfigError, "'lookup' is set with unknown parameter: '{}'", value[0]);
                }
            }
            else
            {
                Self::empty()
            };

        return Ok(Self::from(first | second));
        
    }
}

bitflags! {
    /// An 'option' flags which can be set in /etc/resolv.conf
    #[derive(Copy, Clone, Debug, PartialEq, Eq)]
    pub struct ResolveConfigFamily: u32 
    {
        /// Sets the bit order flag that first is INET4
        const INET4_INET6 = 0x10;
        /// Sets the bit order flag that first is INET6
        const INET6_INET4 = 0x20;
        /// INET 4 is enabled
        const INET4       = 0x01;
        /// INET 6 is enabled
        const INET6       = 0x02;
    }
}

impl ResolveConfigFamily
{
    pub 
    fn is_inet4(&self) -> bool
    {
        return self.contains(Self::INET4);
    }

    pub 
    fn is_inet6(&self) -> bool
    {
        return self.contains(Self::INET6);
    }

    pub 
    fn is_inet4_first(&self) -> bool
    {
        return self.contains(Self::INET4_INET6);
    }

    fn inverted_default() -> Self
    {
        return Self::INET6_INET4 | Self::INET4 | Self::INET6;
    }
}

impl Default for ResolveConfigFamily
{
    fn default() -> Self 
    {
        return Self::INET4_INET6 | Self::INET4 | Self::INET6;
    }
}

const FAMILY_INET4: &'static str = "inet4";
const FAMILY_INET6: &'static str = "inet6";

impl TryFrom<&[String]> for ResolveConfigFamily
{
    type Error = CDnsError;

    fn try_from(value: &[String]) -> Result<Self, Self::Error> 
    {
        if value.is_empty() == true
        {
            internal_error!(CDnsErrorType::ConfigError, "'family' is empty");
        }
        else if value.len() > 2
        {
            internal_error!(CDnsErrorType::ConfigError, "'family' is set with too many paramenters: '{:?}'", value);
        }

        let mut family = 
            if value[0] == FAMILY_INET4
            {
                // setting order 4 -> 6, enable 4
                Self::INET4_INET6 | Self::INET4
            }
            else if value[0] == FAMILY_INET6
            {
                // setting order 6 -> 4, enable 6
                Self::INET6_INET4 | Self::INET6
            }
            else
            {
                internal_error!(CDnsErrorType::ConfigError, "'family' is set with unknown parameter: '{}'", value[0]);
            };

        if value.len() == 2
        {
            if value[1] == FAMILY_INET4
            {
                if family.contains(Self::INET4) == true
                {
                    internal_error!(CDnsErrorType::ConfigError, "'family' is set with duplicate parameter: '{}'", value[1]);
                }
                
                // enable INET4
                family |= Self::INET4
            }
            else if value[1] == FAMILY_INET6
            {
                if family.contains(Self::INET6) == true
                {
                    internal_error!(CDnsErrorType::ConfigError, "'family' is set with duplicate parameter: '{}'", value[1]);
                }
                
                // enable INET6
                family |= Self::INET6
            }
            else
            {
                internal_error!(CDnsErrorType::ConfigError, "'family' is set with unknown parameter: '{}'", value[0]);
            }
        }

        return Ok(family);
    }
}


bitflags! {
    /// An 'option' flags which can be set in /etc/resolv.conf
    #[derive(Debug, Copy, Clone, PartialEq, Eq)]
    pub struct OptionFlags: u16 
    {
        /// Effective only if cdns-rs was built with debug support
        const OPT_DEBUG                    = 0x0001;

        /// Causes round-robin selection of name servers from among those listed (i)
        const OPT_ROTATE                   = 0x0002;
        
        /// Disables the modern BIND checking of incoming hostnames and mail names 
        /// for invalid characters such as underscore (_), non-ASCII, or control
        /// characters
        const OPT_NO_CHECK_NAMES           = 0x0004;

        /// Trying an AAAA query before an A query
        const OPT_INET6                    = 0x0008;

        /// This option disables the parallel IPv4 and IPv6 lookups and
        /// requests sequentially.
        const OPT_SINGLE_REQUEST           = 0x0010;

        /// Changes this behavior so that it will close the socket and open a new 
        /// one before sending the second request
        const OPT_SINGLE_REQUEST_REOPEN    = 0x0020;

        ///This option disables automatic reloading of a changed configuration file. (i)
        const OPT_NO_RELOAD                = 0x0040;

        /// Controls the AD bit behavior of the stub resolver
        const OPT_TRUST_AD                 = 0x0080;

        /// This option forces the use of TCP for DNS resolutions.
        const OPT_USE_VC                   = 0x0100;
    }
}

impl Default for OptionFlags
{
    fn default() -> Self 
    {
        return Self::empty();
    }
}

impl OptionFlags
{
    pub 
    fn is_debug(&self) -> bool
    {
        return self.contains(Self::OPT_DEBUG);
    }

    pub 
    fn is_rotate(&self) -> bool
    {
        return self.contains(Self::OPT_ROTATE);
    }

    pub 
    fn is_no_check_names(&self) -> bool
    {
        return self.contains(Self::OPT_NO_CHECK_NAMES);
    }

    pub 
    fn is_no_parallel(&self) -> bool
    {
        return self.contains(Self::OPT_SINGLE_REQUEST);
    }

    pub 
    fn is_reopen_socket(&self) -> bool
    {
        return self.contains(Self::OPT_SINGLE_REQUEST_REOPEN);
    }

    pub 
    fn is_force_tcp(&self) -> bool
    {
        return self.contains(Self::OPT_USE_VC);
    }
}


#[derive(Clone, Debug, PartialEq, Eq)]
pub struct ResolveConfig
{
    pub nameservers: Vec<Arc<ResolveConfEntry>>,
    pub lookup: ResolveConfigLookup,
    pub family: ResolveConfigFamily,
    pub search_list: Vec<String>,
    pub domain: Option<String>,
    pub option_flags: OptionFlags,
    pub ndots: usize,
    pub timeout: u16,
    pub attempts: usize,
}

impl Default for ResolveConfig
{
    fn default() -> Self 
    {
        return
            ResolveConfig 
            {
                nameservers: vec![],
                lookup: ResolveConfigLookup::default(),
                family: ResolveConfigFamily::default(),
                search_list: vec![],
                domain: None,
                option_flags: OptionFlags::default(),
                ndots: 1,
                timeout: 5,
                attempts: 2,
            };
    }
}

impl ResolveConfig
{
    /// This function will either return the [RoundRobinIterator] which always 
    /// starts from zero offset OR it will return the same instace but the initial
    /// offset will be ROUND_ROBIN_CNT shared atomic counter. The ROUND_ROBIN_CNT
    /// counts always forward. It is not expected that it will ever be overflowed.
    /// 
    /// # Returns
    /// 
    /// * [RoundRobinIterator] instance
    pub 
    fn get_resolvers_iter(&self) -> RoundRobinIterator<Arc<ResolveConfEntry>> 
    {
        if self.option_flags.is_rotate() == true
        {
            let start_index = ROUND_ROBIN_CNT.fetch_add(1, Ordering::SeqCst);

            return RoundRobinIterator::new(start_index, self.nameservers.as_slice());
        }
        else
        {
            return RoundRobinIterator::new(0, self.nameservers.as_slice());
        };
    }

    /// Splits the extension i.e nameserver 1.1.1.1%lo#@853#domainname where extension
    /// starts right after the first # which is not separated by the space.
    fn split_ext(field_data: &str) -> CDnsResult<(&str, u16, Option<String>)>
    {
        let splited = field_data.split("#").collect::<Vec<&str>>();
        let mut port: u16 = 53;
        let mut domain: Option<String> = None;
        
        if splited.is_empty() == true
        {
            return Ok((field_data, port, domain));
        }

        let mut splt_iter = splited.into_iter();
        let without_ext = splt_iter.nth(0).unwrap();
        

        for ext in splt_iter
        {
            if ext.starts_with("@") == true
            {
                // port number
                port = 
                    u16::from_str_radix(&ext[1..], 10).map_err(|e|
                        internal_error_map!(CDnsErrorType::InternalError, "can not parse port number, {}", e)
                    )?;
            }
            else
            {
                // domain
                domain = Some(ext.to_string());
            }
        }
        
        return Ok((without_ext, port, domain));
    }

    fn split_dns_ifr(field_data: &str, ifr: &IfInfo) -> CDnsResult<(IpAddr, SocketAddr)>
    {
        if let Some((ip, intf)) = field_data.split_once("%")
        {   
            let ip_addr: IpAddr = 
                ip.parse().map_err(|e| 
                    internal_error_map!(CDnsErrorType::InternalError, "parse IP: '{}' failed: '{}'", ip, e)
                )?;


            match unsafe { ifr.get_ifr_ip(intf, &ip_addr)? }
            {
                Some(ip_ifr) => 
                    return Ok( (ip_addr, SocketAddr::from((ip_ifr, 0))) ),
                None => 
                    internal_error!(CDnsErrorType::InternalError, "interface: '{}' does not exist", intf),
            }
        }
        else
        {
            let ip_addr: IpAddr = 
                field_data.parse().map_err(|e|
                    internal_error_map!(CDnsErrorType::InternalError, "parse IP: '{}' failed: '{}'", field_data, e)
                )?;

            let ip_ifr = bind_all(ip_addr);
               /* match ip_addr
                {
                    IpAddr::V4(_) => 
                        SocketAddr::from((IPV4_BIND_ALL, 0)),
                    IpAddr::V6(_) => 
                        SocketAddr::from((IPV6_BIND_ALL, 0)),
                };*/

            return Ok((ip_addr, ip_ifr))
        }
    }

    #[inline]
    fn set_option(
        optname: &'static str, 
        right: Option<&str>, 
        option_flags: &mut OptionFlags, 
        opt_flag: OptionFlags
    ) -> CDnsResult<()>
    {
        if right.is_some() == true
        {
            internal_error!(CDnsErrorType::ConfigError, 
                "in /etc/resolv.conf - 'option' '{}' is defined \
                with parameter: '{}', but it does not have parameters", optname, right.unwrap());
        }

        option_flags.set(opt_flag, true);

        return Ok(());
    }

    #[inline]
    fn read_parameter<P: FromStr>(optname: &'static str, right: Option<&str>) -> CDnsResult<P>
    {
        if right.is_none() == true
        {
            internal_error!(CDnsErrorType::ConfigError, 
                "in /etc/resolv.conf - 'option' '{}' is defined without parameter", optname);
        }
        else
        {
            return 
                right.unwrap()
                    .parse::<P>()
                    .map_err(|_| 
                        internal_error_map!(
                            CDnsErrorType::ConfigError,
                            "in /etc/resolv.conf - 'option' '{}' is defined with invalid \
                            parameter: '{}'", optname, right.unwrap()
                        )
                    );
        }
    }

    /// Parses the /etc/resolv.conf
    /// Different OSes like GNU/Linux, FreeBSD and OpenBSD uses different 
    /// configuration options. As this lib is licensed as EUPL, it is not really
    /// the BSD way. The main implementation is like it is described in 
    /// resolv.conf(5) of Linux man.
    pub(crate)
    fn parser_resolv_internal(file_content: &str) -> CDnsResult<Self>
    {
        let mut tk = ConfTokenizer::from_str(&file_content)?;

        let mut dns_list: Vec<Arc<ResolveConfEntry>> = Vec::new();
        let mut lookup_list: ResolveConfigLookup = ResolveConfigLookup::default();
        let mut family_list: ResolveConfigFamily = ResolveConfigFamily::default();
        
        //Since glibc 2.26, the search list is unlimited.
        let mut search_list: Vec<String> = Vec::new();

        let mut domain: Option<String> = None;
        let mut option_flags: OptionFlags = OptionFlags::empty();
        let mut ndots: usize = 1;
        let mut timeout: u16 = 5;
        let mut attempts: usize = 2;

        let if_info: IfInfo = unsafe { IfInfo::get_interfaces_info()? };

        loop
        {
            let field_name = tk.read_next()?;

            if field_name.is_none() == true
            {
                // reached EOF
                break;
            }

            let field_name = field_name.unwrap();

            if field_name == "nameserver"
            {
                // read second component
                let Some(field_data) = tk.read_next()?
                    else
                    {
                        // reached unexpected EOF
                        internal_error!(CDnsErrorType::ConfigError, "unexpected EOF near nameserver");
                    };

                // parse IP and convert Interface to its IP i.e nameserver 127.0.0.1%lo#<Extension>
                let ext_split_res = Self::split_ext(field_data);

                let Ok((without_ext, port, domain)) = ext_split_res
                    else
                    {
                        internal_error!(CDnsErrorType::ConfigError, "{}", ext_split_res.err().unwrap());
                    };

                let split = Self::split_dns_ifr(without_ext, &if_info);
                
                let Ok((dns_ip, ifr_ip)) = split
                    else
                    {
                        internal_error!(CDnsErrorType::ConfigError, "{}", split.err().unwrap());
                    };
                    

                dns_list.push(
                    Arc::new(ResolveConfEntry::new(SocketAddr::new(dns_ip, port), domain, ifr_ip)?)
                );
                
                
            }
            else if field_name == "lookup" // this is OpenBSD specific
            {
                // lookup file bind
                let lookups = tk.read_upto_eol()?;

                if lookups.len() == 0
                {
                    write_error!(internal_error_map!(CDnsErrorType::ConfigError, "in /etc/resolv.conf - 'lookup' is set but no args provided, setting defaults file, bind"));

                    continue;
                }

                lookup_list = 
                    match ResolveConfigLookup::try_from(lookups.as_slice())
                    {
                        Ok(r) => r,
                        Err(e) => 
                        {
                            write_error!(internal_error_map!(CDnsErrorType::ConfigError, "in /etc/resolv.conf - {}", e));

                            continue;
                        }
                    };
            }
            else if field_name == "family" // this is OpenBSD specific
            {
                // parse option
                let families = tk.read_upto_eol()?;

                if families.len() == 0
                {
                    write_error!(internal_error_map!(CDnsErrorType::ConfigError, "in /etc/resolv.conf - 'family' is set but no args provided, setting defaults inet4, inet6"));

                    continue;
                }

                family_list = 
                    match ResolveConfigFamily::try_from(families.as_slice())
                    {
                        Ok(r) => r,
                        Err(e) =>
                        {
                            write_error!(internal_error_map!(CDnsErrorType::ConfigError, "in /etc/resolv.conf - {}", e));
                            continue;
                        }
                    };
            }
            else if field_name == "search"
            {
                // parse search
                let searches = tk.read_upto_eol()?;

                if searches.len() == 0
                {
                    write_error!(internal_error_map!(CDnsErrorType::ConfigError, "in /etc/resolv.conf - 'search' is defined but empty"));
                }
                else
                {
                    search_list.extend(searches);
                }
            }
            else if field_name == "domain"
            {
                let mut domains = tk.read_upto_eol()?;

                if domain.is_some() == true
                {
                    write_error!(internal_error_map!(CDnsErrorType::ConfigError, "in /etc/resolv.conf - 'domain' is defined more than once: {:?} {:?}", domain, domains));
                }

                if domains.len() > 1
                {
                    write_error!(internal_error_map!(CDnsErrorType::ConfigError, "in /etc/resolv.conf - 'domain' is defined with more than 1 address: {:?}", domains));
                }
                else if domains.len() == 0
                {
                    write_error!(internal_error_map!(CDnsErrorType::ConfigError, "in /etc/resolv.conf - 'domain' is defined but empty"));
                }
                else
                {
                    domain = Some(domains.pop().unwrap());
                }
            }
            else if field_name == "options"
            {
                
                let options_vec = tk.read_upto_eol()?;

                if options_vec.is_empty() == true
                {
                    write_error!(internal_error_map!(CDnsErrorType::ConfigError, "in /etc/resolv.conf - 'option' is empty!"));

                    // reached EOL
                    continue;
                }

                for option in options_vec
                {
                    let (left, right) = 
                        match option.split_once(":")
                        {
                            Some((l, r)) => (l, Some(r)),
                            None => (option.as_str(), None),
                        };

                    match left
                    {
                        // This option forces the use of TCP for DNS resolutions.
                        "use-vc" | "usevc" | "tcp" => // linux | freebsd | openbsd
                        {
                            match Self::set_option("usevc", right, &mut option_flags, OptionFlags::OPT_USE_VC)
                            {
                                Err(e) => 
                                    write_error!(e),
                                Ok(_) => {}
                            }
                        },
                        "debug" => 
                        {
                            match Self::set_option("debug", right, &mut option_flags, OptionFlags::OPT_DEBUG)
                            {
                                Err(e) => 
                                    write_error!(e),
                                Ok(_) => {}
                            }
                        },
                        "ndots" => 
                        {
                            match Self::read_parameter("ndots", right)
                            {
                                Ok(val) => 
                                {
                                    ndots = if val > 15 { 15 } else { val };
                                },
                                Err(e) => 
                                {
                                    write_error!(e);
                                }
                            }
                        },
                        "timeout" => 
                        {
                            match Self::read_parameter::<u16>("timeout", right)
                            {
                                Ok(val) => 
                                {
                                    timeout = if val > 30 { 30 } else { val };
                                },
                                Err(e) => 
                                {
                                    write_error!(e);
                                }
                            }
                        },
                        "attempts" => 
                        {
                            match Self::read_parameter("attempts", right)
                            {
                                Ok(val) => 
                                {
                                    attempts = if val > 5 { 5 } else { val };
                                },
                                Err(e) => 
                                {
                                    write_error!(e);
                                }
                            }
                        },
                        "rotate" => 
                        {
                            match Self::set_option("rotate", right, &mut option_flags, OptionFlags::OPT_ROTATE)
                            {
                                Err(e) => 
                                    write_error!(e),
                                Ok(_) => {}
                            }
                        },
                        "no-check-names" => 
                        {
                            match Self::set_option("no-check-names", right, &mut option_flags, OptionFlags::OPT_NO_CHECK_NAMES)
                            {
                                Err(e) => 
                                    write_error!(e),
                                Ok(_) => {}
                            }
                        },
                        "no-reload" =>
                        {
                            match Self::set_option("no-reload", right, &mut option_flags, OptionFlags::OPT_NO_RELOAD)
                            {
                                Err(e) => 
                                    write_error!(e),
                                Ok(_) => {}
                            }
                        },
                        "inet6" => 
                        {
                            // see 'family'
                            match Self::set_option("inet6", right, &mut option_flags, OptionFlags::OPT_INET6)
                            {
                                Err(e) => 
                                    write_error!(e),
                                Ok(_) => {}
                            }
                        },
                        "edns0" =>
                        {
                            // RFC 2671 not implemented! skip
                        },
                        "single-request" =>
                        {
                            match Self::set_option("single-request", right, &mut option_flags, OptionFlags::OPT_SINGLE_REQUEST)
                            {
                                Err(e) => 
                                    write_error!(e),
                                Ok(_) => {}
                            }
                        },
                        "single-request-reopen" => 
                        {
                            match Self::set_option("single-request-reopen", right, &mut option_flags, OptionFlags::OPT_SINGLE_REQUEST_REOPEN)
                            {
                                Err(e) => 
                                    write_error!(e),
                                Ok(_) => {}
                            }
                        },
                        "trust-ad" => 
                        {
                            match Self::set_option("trust-ad", right, &mut option_flags, OptionFlags::OPT_TRUST_AD)
                            {
                                Err(e) => 
                                    write_error!(e),
                                Ok(_) => {}
                            }
                        },
                        _ => 
                        {
                            write_error!(internal_error_map!(CDnsErrorType::ConfigError, "in /etc/resolv.conf - 'option' '{}' is unknown \
                                    with parameter: '{:?}'", left, right));
                        },
                    }

                    
                }
            }
            else
            {
                // skip until end of line or EOF
                tk.skip_upto_eol();
            }
        }        

        if option_flags.contains(OptionFlags::OPT_INET6) == true
        {
            family_list = ResolveConfigFamily::inverted_default();
        }
    

        return Ok(
            Self
            {
                nameservers: dns_list,
                lookup: lookup_list,
                family: family_list,
                search_list: search_list,
                domain: domain,
                option_flags: option_flags,
                ndots: ndots,
                timeout: timeout,
                attempts: attempts,
            }
        );
    }
}

#[cfg(feature = "use_sync")]
#[cfg(test)]
mod tests
{
    use std::{net::{IpAddr, Ipv4Addr, Ipv6Addr, SocketAddr}, str::FromStr};

    use crate::{cfg_resolv_parser::{OptionFlags, ResolveConfigFamily, ResolveConfigLookup}, sync::ResolveConfig};

    #[test]
    fn test_parser_resolv_tls_0() 
    {
        let ip1 = SocketAddr::new("1.1.1.1".parse::<IpAddr>().unwrap(), 853);
        let tls_domain1 = Some(String::from("cloudflare-dns.com"));
        let ip2 = SocketAddr::new("2606:4700:4700::1001".parse::<IpAddr>().unwrap(), 853);
        let tls_domain2 = Some(String::from("cloudflare-dns.com"));
        let ip3 = SocketAddr::new("127.0.0.1".parse().unwrap(), 853);
        let tls_domain3 = Some(String::from("localdomain"));
        let ip3_if: SocketAddr = SocketAddr::from((Ipv4Addr::from_str("127.0.0.1").unwrap(), 0));
        let ip4 = SocketAddr::new("8.8.8.8".parse().unwrap(), 55);
        let ip5 = SocketAddr::new("1.0.0.2".parse().unwrap(), 53);
        let ip6 = SocketAddr::new("1.1.1.1".parse::<IpAddr>().unwrap(), 443);

        let test = 
        "nameserver 1.1.1.1#@853#cloudflare-dns.com\n\
        nameserver 2606:4700:4700::1001#@853#cloudflare-dns.com\n\
        nameserver 127.0.0.1%lo#@853#localdomain\n\
        nameserver 8.8.8.8#@55\n\
        nameserver 1.0.0.2 #@853\n\
        nameserver 1.1.1.1#@443#https://cloudflare-dns.com/dns-query\n";

        let res = ResolveConfig::parser_resolv_internal(test);

        assert_eq!(res.is_ok(), true, "{}", res.err().unwrap());
        let res = res.unwrap();

        assert_eq!(res.family, ResolveConfigFamily::INET4_INET6 | ResolveConfigFamily::INET6 | ResolveConfigFamily::INET4);

        assert_eq!(res.nameservers[0].ip, ip1);
        assert_eq!(res.nameservers[0].tls_domain.as_ref(), tls_domain1.as_ref());
        assert_eq!(res.nameservers[0].https_req_path, None);
        assert_eq!(res.nameservers[1].ip, ip2);
        assert_eq!(res.nameservers[1].tls_domain.as_ref(), tls_domain2.as_ref());
        assert_eq!(res.nameservers[2].ip, ip3);
        assert_eq!(res.nameservers[2].tls_domain.as_ref(), tls_domain3.as_ref());
        assert_eq!(res.nameservers[2].adapter_ip, ip3_if);
        assert_eq!(res.nameservers[3].ip, ip4);
        assert_eq!(res.nameservers[4].ip, ip5);
        assert_eq!(res.nameservers[5].ip, ip6);
        assert_eq!(res.nameservers[5].tls_domain, Some("cloudflare-dns.com".to_string()));
        assert_eq!(res.nameservers[5].https_req_path, Some("dns-query".to_string()));
    }

    #[test]
    fn test_parser_resolv_internal_0() 
    {
        let ip1 = SocketAddr::new("192.168.2.1".parse().unwrap(), 53);
        let ip2 = SocketAddr::new("127.0.0.1".parse().unwrap(), 53);
        let ip3 = SocketAddr::new("8.8.8.8".parse().unwrap(), 53);
        let ip4 = SocketAddr::new("127.0.0.1".parse().unwrap(), 53);
        let ip4_if: SocketAddr = SocketAddr::from((Ipv4Addr::from_str("127.0.0.1").unwrap(), 0));
        let ip5 = SocketAddr::new("fe80::1".parse().unwrap(), 53);
        let ip5_if: SocketAddr = SocketAddr::from((Ipv6Addr::from_str("::1").unwrap(), 0));

        let test = 
        "nameserver 192.168.2.1\n\
        nameserver  127.0.0.1\n\
        lookup bind\n\
        nameserver  8.8.8.8\n
        nameserver 127.0.0.1%lo\n
        nameserver fe80::1%lo\n";


        let res = ResolveConfig::parser_resolv_internal(test);
    
        assert_eq!(res.is_ok(), true, "{}", res.err().unwrap());
        let res = res.unwrap();

        assert_eq!(res.lookup, ResolveConfigLookup::BIND);

        assert_eq!(res.family, ResolveConfigFamily::INET4_INET6 | ResolveConfigFamily::INET6 | ResolveConfigFamily::INET4);

        assert_eq!(res.nameservers[0].ip, ip1);
        assert_eq!(res.nameservers[1].ip, ip2);
        assert_eq!(res.nameservers[2].ip, ip3);
        assert_eq!(res.nameservers[3].ip, ip4);
        assert_eq!(res.nameservers[3].adapter_ip, ip4_if);
        assert_eq!(res.nameservers[4].ip, ip5);
        assert_eq!(res.nameservers[4].adapter_ip, ip5_if);
    }

    #[test]
    fn test_parser_resolv_internal() 
    {
        let ip1 = SocketAddr::new("192.168.2.1".parse().unwrap(), 53);
        let ip2 = SocketAddr::new("127.0.0.1".parse().unwrap(), 53);
        let ip3 = SocketAddr::new("8.8.8.8".parse().unwrap(), 53);

        let test = 
        "nameserver 192.168.2.1\n\
        nameserver  127.0.0.1\n\
        lookup bind file\n\
        nameserver  8.8.8.8";

        let res = ResolveConfig::parser_resolv_internal(test);
        assert_eq!(res.is_ok(), true, "{}", res.err().unwrap());
        let res = res.unwrap();

        assert_eq!(res.lookup, ResolveConfigLookup::BIND | ResolveConfigLookup::FILE | ResolveConfigLookup::BIND_FILE);

        assert_eq!(res.family, ResolveConfigFamily::INET4_INET6 | ResolveConfigFamily::INET6 | ResolveConfigFamily::INET4);

        assert_eq!(res.nameservers[0].ip, ip1);
        assert_eq!(res.nameservers[1].ip, ip2);
        assert_eq!(res.nameservers[2].ip, ip3);
    }

    #[test]
    fn test_parser_resolv_internal2() 
    {
        let ip1 = SocketAddr::new("192.168.2.1".parse().unwrap(), 53);
        let ip2 = SocketAddr::new("127.0.0.1".parse().unwrap(), 53);
        let ip3 = SocketAddr::new("8.8.8.8".parse().unwrap(), 53);

        let test = 
        "# test 12345\n\
        # nameserver 192.168.3.1
        nameserver 192.168.2.1  \n\
        nameserver  127.0.0.1   \n\
        lookup file\n\
        family inet4\n\
        nameserver  8.8.8.8\n";

        let res = ResolveConfig::parser_resolv_internal(test);
        assert_eq!(res.is_ok(), true, "{}", res.err().unwrap());
        let res = res.unwrap();

        assert_eq!(res.lookup, ResolveConfigLookup::FILE);

        assert_eq!(res.family, ResolveConfigFamily::INET4 | ResolveConfigFamily::INET4_INET6);

        assert_eq!(res.nameservers.len(), 3);
        assert_eq!(res.nameservers[0].ip, ip1);
        assert_eq!(res.nameservers[1].ip, ip2);
        assert_eq!(res.nameservers[2].ip, ip3);
    }

    #[test]
    fn test_parser_resolv_internal3() 
    {
        let ip1 = SocketAddr::new("192.168.2.1".parse().unwrap(), 53);
        let ip2 = SocketAddr::new("127.0.0.1".parse().unwrap(), 53);
        let ip3 = SocketAddr::new("8.8.8.8".parse().unwrap(), 53);

        let test = 
        "# test 12345\n\
        # nameserver 192.168.3.1
        nameserver 192.168.2.1  \n\
        nameserver  127.0.0.1   \n\
        lookup file\n\
        family inet4\n\
        nameserver  8.8.8.8\n
        options attempts:1 timeout:3 debug use-vc single-request-reopen\n
        search localdomain";

        let res = ResolveConfig::parser_resolv_internal(test);
        assert_eq!(res.is_ok(), true, "{}", res.err().unwrap());
        let res = res.unwrap();

        assert_eq!(res.lookup, ResolveConfigLookup::FILE);

        assert_eq!(res.family, ResolveConfigFamily::INET4_INET6 | ResolveConfigFamily::INET4);

        assert_eq!(res.nameservers.len(), 3);
        assert_eq!(res.nameservers[0].ip, ip1);
        assert_eq!(res.nameservers[1].ip, ip2);
        assert_eq!(res.nameservers[2].ip, ip3);

        assert_eq!(res.search_list[0], "localdomain");

        assert_eq!(res.timeout, 3);
        assert_eq!(res.attempts, 1);

        assert_eq!(res.option_flags.contains(OptionFlags::OPT_DEBUG), true);
        assert_eq!(res.option_flags.contains(OptionFlags::OPT_USE_VC), true);
        assert_eq!(res.option_flags.contains(OptionFlags::OPT_SINGLE_REQUEST_REOPEN), true);
    }

    #[test]
    fn test_parser_resolv_internal4() 
    {
        let ip1 = SocketAddr::new("192.168.2.1".parse().unwrap(), 53);
        let ip2 = SocketAddr::new("127.0.0.1".parse().unwrap(), 53);
        let ip3 = SocketAddr::new("8.8.8.8".parse().unwrap(), 53);

        let test = 
    "\
    # test 12345\n\
    # nameserver    192.168.3.1\n\
    nameserver  192.168.2.1  \n\
    nameserver       127.0.0.1   \n\
    lookup file\n\
    family inet4       \n\
    nameserver  8.8.8.8\n\
    options    attempts:1    timeout:3 debug use-vc     single-request-reopen\n\
    search   localdomain\n\
    ";


        let res = ResolveConfig::parser_resolv_internal(test);
        assert_eq!(res.is_ok(), true, "{}", res.err().unwrap());
        let res = res.unwrap();

        assert_eq!(res.lookup, ResolveConfigLookup::FILE);

        assert_eq!(res.family, ResolveConfigFamily::INET4_INET6 | ResolveConfigFamily::INET4);

        assert_eq!(res.nameservers.len(), 3);
        assert_eq!(res.nameservers[0].ip, ip1);
        assert_eq!(res.nameservers[1].ip, ip2);
        assert_eq!(res.nameservers[2].ip, ip3);

        assert_eq!(res.search_list[0], "localdomain");

        assert_eq!(res.timeout, 3);
        assert_eq!(res.attempts, 1);

        assert_eq!(res.option_flags.contains(OptionFlags::OPT_DEBUG), true);
        assert_eq!(res.option_flags.contains(OptionFlags::OPT_USE_VC), true);
        assert_eq!(res.option_flags.contains(OptionFlags::OPT_SINGLE_REQUEST_REOPEN), true);
    }

    #[test]
    fn test_roundrobin_iter_1() 
    {
        use std::time::Instant;

        fn check_order(res: &ResolveConfig, ipl: &[SocketAddr], indx: usize)
        {
            let mut i = indx;
            let assert_i = (indx + ipl.len()) % ipl.len();
            let now = Instant::now();

            let itr = res.get_resolvers_iter();

            assert_eq!(itr.len(), ipl.len());

            for n in itr
            {
                //println!("cmp: {} {}", n.ip, ipl[i]);
                assert_eq!(n.ip, ipl[i]);

                i += 1;

                i %= ipl.len();

            }

            assert_eq!(i, assert_i);

            let elapsed = now.elapsed();
            println!("Iter Elapsed: {:.2?}", elapsed);
        }

        let ip1 = SocketAddr::new("192.168.2.1".parse().unwrap(),  53);

        let ip_list: Vec<SocketAddr> = vec![ip1];

        let test = 
    "\
    # test 12345\n\
    # nameserver    192.168.3.1\n\
    nameserver  192.168.2.1  \n\
    #nameserver       127.0.0.1   \n\
    lookup file\n\
    family inet4       \n\
    #nameserver  8.8.8.8\n\
    options    attempts:1  rotate   timeout:3 debug use-vc     single-request-reopen\n\
    search   localdomain\n\
    ";
    
    let now = Instant::now();


        let res = ResolveConfig::parser_resolv_internal(test);

    let elapsed = now.elapsed();
    println!("parser_resolv_internal elapsed: {:.2?}", elapsed);

        assert_eq!(res.is_ok(), true, "{}", res.err().unwrap());
        let res = res.unwrap();

        check_order(&res, &ip_list, 0);
        check_order(&res, &ip_list, 0);
        check_order(&res, &ip_list, 0);
        check_order(&res, &ip_list, 0);
        check_order(&res, &ip_list, 0);
        check_order(&res, &ip_list, 0);
        check_order(&res, &ip_list, 0);
        check_order(&res, &ip_list, 0);
        check_order(&res, &ip_list, 0);
    }

    #[test]
    fn test_roundrobin_iter() 
    {
        use std::time::Instant;

        fn check_order(res: &ResolveConfig, ipl: &[SocketAddr], indx: usize)
        {
            let mut i = indx;
            let assert_i = (indx + ipl.len()) % ipl.len();
            let now = Instant::now();

            let itr = res.get_resolvers_iter();

            assert_eq!(itr.len(), ipl.len());

            for n in itr
            {
                //println!("cmp: {} {}", n.ip, ipl[i]);
                assert_eq!(n.ip, ipl[i]);

                i += 1;

                i %= ipl.len();

            }

            assert_eq!(i, assert_i);

            let elapsed = now.elapsed();
            println!("Iter Elapsed: {:.2?}", elapsed);
        }

        let ip1 = SocketAddr::new("192.168.2.1".parse().unwrap(), 53);
        let ip2 = SocketAddr::new("127.0.0.1".parse().unwrap(), 53);
        let ip3 = SocketAddr::new("8.8.8.8".parse().unwrap(), 53);

        let ip_list: Vec<SocketAddr> = vec![ip1, ip2, ip3];

        let test = 
    "\
    # test 12345\n\
    # nameserver    192.168.3.1\n\
    nameserver  192.168.2.1  \n\
    nameserver       127.0.0.1   \n\
    lookup file\n\
    family inet4       \n\
    nameserver  8.8.8.8\n\
    options    attempts:1  rotate   timeout:3 debug use-vc     single-request-reopen\n\
    search   localdomain\n\
    ";
    
    let now = Instant::now();

        let res = ResolveConfig::parser_resolv_internal(test);

    let elapsed = now.elapsed();
    println!("parser_resolv_internal elapsed: {:.2?}", elapsed);

        assert_eq!(res.is_ok(), true, "{}", res.err().unwrap());
        let res = res.unwrap();

        check_order(&res, &ip_list, 0);
        check_order(&res, &ip_list, 1);
        check_order(&res, &ip_list, 2);
        check_order(&res, &ip_list, 0);
        check_order(&res, &ip_list, 1);
        check_order(&res, &ip_list, 2);
        check_order(&res, &ip_list, 0);
        check_order(&res, &ip_list, 1);
        check_order(&res, &ip_list, 2);
    }

    #[test]
    fn test_direct_iter() 
    {
        use std::time::Instant;

        let ip1 = SocketAddr::new("192.168.2.1".parse().unwrap(), 53);
        let ip2 = SocketAddr::new("192.168.2.2".parse().unwrap(), 53);

        let test = 
    "\
    # test 12345\n\
    # nameserver    192.168.3.1\n\
    nameserver  192.168.2.1  \n\
    nameserver  192.168.2.2  \n\
    lookup file\n\
    family inet4       \n\
    options    attempts:1  timeout:3 debug use-vc     single-request-reopen\n\
    search   localdomain\n\
    ";
    
    let now = Instant::now();


        let res = ResolveConfig::parser_resolv_internal(test);

    let elapsed = now.elapsed();
    println!("Elapsed: {:.2?}", elapsed);

        assert_eq!(res.is_ok(), true, "{}", res.err().unwrap());
        let res = res.unwrap();

        let mut i: usize = 0;
        
        let now = Instant::now();

        for n in res.get_resolvers_iter()
        {
            match i
            {
                0 => { assert_eq!(n.ip, ip1); i += 1; },
                1 => { assert_eq!(n.ip, ip2); i += 1; },
                _ => panic!("!")
            }
        }

        let elapsed = now.elapsed();
        println!("Iter Elapsed: {:.2?}", elapsed);

        assert_eq!(i, 2);

        i = 0;
        for n in res.get_resolvers_iter()
        {
            match i
            {
                0 => { assert_eq!(n.ip, ip1); i += 1; },
                1 => { assert_eq!(n.ip, ip2); i += 1; },
                _ => panic!("!")
            }
        }

        assert_eq!(i, 2);
    }

}