[feature] Support DNS Decode

2 files changed, 3884 insertions, 1 deletions

diff --git a/src/protocol/dns.rs b/src/protocol/dns.rs
new file mode 100644
index 0000000..27dde8a
--- /dev/null
+++ b/src/protocol/dns.rs
@@ -0,0 +1,3882 @@
+use nom::bits;
+use nom::character;
+use nom::combinator;
+use nom::error::Error;
+use nom::error::ErrorKind;
+use nom::multi;
+use nom::number;
+use nom::sequence;
+use nom::Err;
+use nom::IResult;
+use nom::Needed;
+use std::fmt;
+use std::fmt::Display;
+use std::str;
+
+/******************************************************************************
+ * DNS Header Definitions
+ ******************************************************************************/
+
+/*
+ * DNS Header Definitions
+ *                                 1  1  1  1  1  1
+ *   0  1  2  3  4  5  6  7  8  9  0  1  2  3  4  5
+ *  +--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+
+ *  |                      ID                       |
+ *  +--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+
+ *  |QR|   Opcode  |AA|TC|RD|RA|   Z    |   RCODE   |
+ *  +--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+
+ *  |                    QDCOUNT                    |
+ *  +--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+
+ *  |                    ANCOUNT                    |
+ *  +--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+
+ *  |                    NSCOUNT                    |
+ *  +--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+
+ *  |                    ARCOUNT                    |
+ *  +--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+
+ */
+
+/****************************** DNS_HDR_QR ******************************/
+
+#[allow(non_camel_case_types)]
+#[derive(Clone, Copy, Debug, PartialEq, Eq)]
+pub enum DNS_HDR_QR {
+    Query = 0,
+    Response = 1,
+    Other = 2,
+}
+
+impl DNS_HDR_QR {
+    fn from_u8(n: u8) -> DNS_HDR_QR {
+        match n {
+            0 => DNS_HDR_QR::Query,
+            1 => DNS_HDR_QR::Response,
+            _ => DNS_HDR_QR::Other,
+        }
+    }
+}
+
+impl Display for DNS_HDR_QR {
+    fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
+        match self {
+            DNS_HDR_QR::Query => write!(f, "QUERY"),
+            DNS_HDR_QR::Response => write!(f, "RESPONSE"),
+            DNS_HDR_QR::Other => write!(f, "OTHER"),
+        }
+    }
+}
+
+/****************************** DNS_HDR_OPCODE ******************************/
+
+// https://www.iana.org/assignments/dns-parameters/dns-parameters.xhtml#dns-parameters-5
+#[allow(non_camel_case_types)]
+#[derive(Clone, Copy, Debug, PartialEq, Eq)]
+pub enum DNS_HDR_OPCODE {
+    Query,
+    IQuery,
+    Status,
+    Notify,
+    Update,
+    DSO, // DNS Stateful Operations
+    Other(u8),
+}
+
+impl DNS_HDR_OPCODE {
+    fn from_u8(n: u8) -> DNS_HDR_OPCODE {
+        match n {
+            0 => DNS_HDR_OPCODE::Query,
+            1 => DNS_HDR_OPCODE::IQuery,
+            2 => DNS_HDR_OPCODE::Status,
+            // 3 => Unassigned
+            4 => DNS_HDR_OPCODE::Notify,
+            5 => DNS_HDR_OPCODE::Update,
+            6 => DNS_HDR_OPCODE::DSO,
+            n => DNS_HDR_OPCODE::Other(n),
+        }
+    }
+}
+
+impl Display for DNS_HDR_OPCODE {
+    fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
+        match self {
+            DNS_HDR_OPCODE::Query => write!(f, "QUERY"),
+            DNS_HDR_OPCODE::IQuery => write!(f, "IQUERY"),
+            DNS_HDR_OPCODE::Status => write!(f, "STATUS"),
+            DNS_HDR_OPCODE::Notify => write!(f, "NOTIFY"),
+            DNS_HDR_OPCODE::Update => write!(f, "UPDATE"),
+            DNS_HDR_OPCODE::DSO => write!(f, "DSO"),
+            DNS_HDR_OPCODE::Other(n) => write!(f, "OTHER {}", n),
+        }
+    }
+}
+
+/****************************** DNS_HDR_RCODE ******************************/
+
+// https://www.iana.org/assignments/dns-parameters/dns-parameters.xhtml#dns-parameters-6
+#[allow(non_camel_case_types)]
+#[derive(Clone, Copy, Debug, PartialEq, Eq)]
+pub enum DNS_HDR_RCODE {
+    NoError,   // No Error
+    FormErr,   // Format Error
+    ServFail,  // Server Failure
+    NXDomain,  // Non-Existent Domain
+    NotImp,    // Not Implemented
+    Refused,   // Query Refused
+    YXDomain,  // Name Exists when it should not
+    YXRRSet,   // RR Set Exists when it should not
+    NXRRSet,   // RR Set that should exist does not
+    NotAuth,   // Server Not Authoritative for zone / Not Authorized
+    NotZone,   // Name not contained in zone
+    DSOTYPENI, // DSO-TYPE Not Implemented
+    BADSIG,    // TSIG Signature Failure
+    BADKEY,    // Key not recognized
+    BADTIME,   // Signature out of time window
+    BADMODE,   // Bad TKEY Mode
+    BADNAME,   // Duplicate key name
+    BADALG,    // Algorithm not supported
+    BADTRUNC,  // Bad Truncation
+    BADCOOKIE, // Bad/missing Server Cookie
+    Other(u8),
+}
+
+impl DNS_HDR_RCODE {
+    fn from_u8(n: u8) -> DNS_HDR_RCODE {
+        match n {
+            0 => DNS_HDR_RCODE::NoError,
+            1 => DNS_HDR_RCODE::FormErr,
+            2 => DNS_HDR_RCODE::ServFail,
+            3 => DNS_HDR_RCODE::NXDomain,
+            4 => DNS_HDR_RCODE::NotImp,
+            5 => DNS_HDR_RCODE::Refused,
+            6 => DNS_HDR_RCODE::YXDomain,
+            7 => DNS_HDR_RCODE::YXRRSet,
+            8 => DNS_HDR_RCODE::NXRRSet,
+            9 => DNS_HDR_RCODE::NotAuth,
+            10 => DNS_HDR_RCODE::NotZone,
+            11 => DNS_HDR_RCODE::DSOTYPENI,
+            // hole
+            16 => DNS_HDR_RCODE::BADSIG,
+            17 => DNS_HDR_RCODE::BADKEY,
+            18 => DNS_HDR_RCODE::BADTIME,
+            19 => DNS_HDR_RCODE::BADMODE,
+            20 => DNS_HDR_RCODE::BADNAME,
+            21 => DNS_HDR_RCODE::BADALG,
+            22 => DNS_HDR_RCODE::BADTRUNC,
+            23 => DNS_HDR_RCODE::BADCOOKIE,
+            n => DNS_HDR_RCODE::Other(n),
+        }
+    }
+}
+
+impl Display for DNS_HDR_RCODE {
+    fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
+        match self {
+            DNS_HDR_RCODE::NoError => write!(f, "NOERROR"),
+            DNS_HDR_RCODE::FormErr => write!(f, "FORMERR"),
+            DNS_HDR_RCODE::ServFail => write!(f, "SERVFAIL"),
+            DNS_HDR_RCODE::NXDomain => write!(f, "NXDOMAIN"),
+            DNS_HDR_RCODE::NotImp => write!(f, "NOTIMP"),
+            DNS_HDR_RCODE::Refused => write!(f, "REFUSED"),
+            DNS_HDR_RCODE::YXDomain => write!(f, "YXDOMAIN"),
+            DNS_HDR_RCODE::YXRRSet => write!(f, "YXRRSET"),
+            DNS_HDR_RCODE::NXRRSet => write!(f, "NXRRSET"),
+            DNS_HDR_RCODE::NotAuth => write!(f, "NOTAUTH"),
+            DNS_HDR_RCODE::NotZone => write!(f, "NOTZONE"),
+            DNS_HDR_RCODE::DSOTYPENI => write!(f, "DSOTYPENI"),
+            DNS_HDR_RCODE::BADSIG => write!(f, "BADSIG"),
+            DNS_HDR_RCODE::BADKEY => write!(f, "BADKEY"),
+            DNS_HDR_RCODE::BADTIME => write!(f, "BADTIME"),
+            DNS_HDR_RCODE::BADMODE => write!(f, "BADMODE"),
+            DNS_HDR_RCODE::BADNAME => write!(f, "BADNAME"),
+            DNS_HDR_RCODE::BADALG => write!(f, "BADALG"),
+            DNS_HDR_RCODE::BADTRUNC => write!(f, "BADTRUNC"),
+            DNS_HDR_RCODE::BADCOOKIE => write!(f, "BADCOOKIE"),
+            DNS_HDR_RCODE::Other(n) => write!(f, "OTHER {}", n),
+        }
+    }
+}
+
+/****************************** DNS_HEADER ******************************/
+
+#[allow(non_camel_case_types)]
+#[derive(Clone, Copy, Debug, PartialEq, Eq)]
+pub struct DNS_HEADER {
+    pub id: u16,
+    pub qr: DNS_HDR_QR,
+    pub op_code: DNS_HDR_OPCODE,
+    pub aa: bool,              // Authoritative Answer
+    pub tc: bool,              // TrunCation
+    pub rd: bool,              // Recursion Desired
+    pub ra: bool,              // Recursion Available
+    pub ad: bool,              // TODO ???
+    pub cd: bool,              // TODO ???
+    pub r_code: DNS_HDR_RCODE, // Response Code
+    pub qd_count: u16,
+    pub an_count: u16,
+    pub ns_count: u16,
+    pub ar_count: u16,
+}
+
+fn hdr_bits_decode(
+    input: &[u8],
+) -> IResult<
+    &[u8],
+    (
+        DNS_HDR_QR,
+        DNS_HDR_OPCODE,
+        bool,
+        bool,
+        bool,
+        bool,
+        bool,
+        bool,
+        DNS_HDR_RCODE,
+    ),
+> {
+    bits::<_, _, Error<(&[u8], usize)>, _, _>(sequence::tuple((
+        bits::streaming::take(1usize),
+        bits::streaming::take(4usize),
+        bits::streaming::take(1usize),
+        bits::streaming::take(1usize),
+        bits::streaming::take(1usize),
+        bits::streaming::take(1usize),
+        combinator::verify(bits::streaming::take(1usize), |res: &u8| *res == 0), // Reserved 1 bit
+        bits::streaming::take(1usize),
+        bits::streaming::take(1usize),
+        bits::streaming::take(4usize),
+    )))(input)
+    .map(
+        |(rest, res): (&[u8], (u8, u8, u8, u8, u8, u8, u8, u8, u8, u8))| {
+            (
+                rest,
+                (
+                    DNS_HDR_QR::from_u8(res.0),
+                    DNS_HDR_OPCODE::from_u8(res.1),
+                    res.2 == 1,
+                    res.3 == 1,
+                    res.4 == 1,
+                    res.5 == 1,
+                    res.7 == 1,
+                    res.8 == 1,
+                    DNS_HDR_RCODE::from_u8(res.9),
+                ),
+            )
+        },
+    )
+}
+
+impl DNS_HEADER {
+    fn decode(input: &[u8]) -> IResult<&[u8], DNS_HEADER> {
+        sequence::tuple((
+            number::streaming::be_u16,
+            hdr_bits_decode,
+            number::streaming::be_u16,
+            number::streaming::be_u16,
+            number::streaming::be_u16,
+            number::streaming::be_u16,
+        ))(input)
+        .map(|(rest, res)| {
+            (
+                rest,
+                DNS_HEADER {
+                    id: res.0,
+                    qr: res.1 .0,
+                    op_code: res.1 .1,
+                    aa: res.1 .2,
+                    tc: res.1 .3,
+                    rd: res.1 .4,
+                    ra: res.1 .5,
+                    ad: res.1 .6,
+                    cd: res.1 .7,
+                    r_code: res.1 .8,
+                    qd_count: res.2,
+                    an_count: res.3,
+                    ns_count: res.4,
+                    ar_count: res.5,
+                },
+            )
+        })
+    }
+}
+
+impl Display for DNS_HEADER {
+    fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
+        write!(
+            f,
+            ";; ->>HEADER<<- opcode: {}, status: {}, id: {}\n;; flags:",
+            self.op_code, self.r_code, self.id,
+        )?;
+        if self.qr == DNS_HDR_QR::Response {
+            write!(f, " qr")?;
+        }
+        if self.aa {
+            write!(f, " aa")?;
+        }
+        if self.tc {
+            write!(f, " tc")?;
+        }
+        if self.rd {
+            write!(f, " rd")?;
+        }
+        if self.ra {
+            write!(f, " ra")?;
+        }
+        if self.ad {
+            write!(f, " ad")?;
+        }
+        if self.cd {
+            write!(f, " cd")?;
+        }
+        write!(
+            f,
+            "; QUERY: {}, ANSWER: {}, AUTHORITY: {}, ADDITIONAL: {}\n",
+            self.qd_count, self.an_count, self.ns_count, self.ar_count
+        )
+    }
+}
+
+/******************************************************************************
+ * DNS Question Section Definitions
+ ******************************************************************************/
+
+/*
+ * DNS Question Section Definitions
+ *                                  1  1  1  1  1  1
+ *    0  1  2  3  4  5  6  7  8  9  0  1  2  3  4  5
+ *  +--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+
+ *  |                                               |
+ *  /                     QNAME                     /
+ *  /                                               /
+ *  +--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+
+ *  |                     QTYPE                     |
+ *  +--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+
+ *  |                     QCLASS                    |
+ *  +--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+
+ */
+
+/****************************** DNS_QTYPE ******************************/
+
+// https://www.iana.org/assignments/dns-parameters/dns-parameters.xhtml#dns-parameters-4
+#[allow(non_camel_case_types)]
+#[derive(Clone, Copy, Debug, PartialEq, Eq)]
+pub enum DNS_QTYPE {
+    A,          // a host address
+    NS,         // an authoritative name server
+    MD,         // a mail destination (OBSOLETE - use MX)
+    MF,         // a mail forwarder (OBSOLETE - use MX)
+    CNAME,      // the canonical name for an alias
+    SOA,        // marks the start of a zone of authority
+    MB,         // a mailbox domain name (EXPERIMENTAL)
+    MG,         // a mail group member (EXPERIMENTAL)
+    MR,         // a mail rename domain name (EXPERIMENTAL)
+    NULL,       // a null RR (EXPERIMENTAL)
+    WKS,        // a well known service description
+    PTR,        // a domain name pointer
+    HINFO,      // host information
+    MINFO,      // mailbox or mail list information
+    MX,         // mail exchange
+    TXT,        // text strings
+    RP,         // for Responsible Person
+    AFSDB,      // for AFS Data Base location
+    X25,        // for X.25 PSDN address
+    ISDN,       // for ISDN address
+    RT,         // for Route Through
+    NSAP,       // for NSAP address, NSAP style A record
+    NSAPPTR,    // for domain name pointer, NSAP style
+    SIG,        // for security signature
+    KEY,        // for security signature
+    PX,         // X.400 mail mapping information
+    GPOS,       // Geographical Position
+    AAAA,       // IP6 Address
+    LOC,        // Location Information
+    NXT,        // Next Domain (OBSOLETE)
+    EID,        // Endpoint Identifier
+    NIMLOC,     // Nimrod Locator
+    SRV,        // Server Selection
+    ATMA,       // ATM Address
+    NAPTR,      // Naming Authority Pointer
+    KX,         // Key Exchanger
+    CERT,       // CERT
+    A6,         // A6 (OBSOLETE - use AAAA)
+    DNAME,      // DNAME
+    SINK,       // SINK
+    OPT,        // OPT
+    APL,        // APL
+    DS,         // Delegation Signer
+    SSHFP,      // SSH Key Fingerprint
+    IPSECKEY,   // IPSECKEY
+    RRSIG,      // RRSIG
+    NSEC,       // NSEC
+    DNSKEY,     // DNSKEY
+    DHCID,      // DHCID
+    NSEC3,      // NSEC3
+    NSEC3PARAM, // NSEC3PARAM
+    TLSA,       // TLSA
+    SMIMEA,     // S/MIME cert association
+    HIP,        // Host Identity Protocol
+    NINFO,      // NINFO
+    RKEY,       // RKEY
+    TALINK,     // Trust Anchor LINK
+    CDS,        // Child DS
+    CDNSKEY,    // DNSKEY(s) the Child wants reflected in DS
+    OPENPGPKEY, // OpenPGP Key
+    CSYNC,      // Child-To-Parent Synchronization
+    ZONEMD,     // Message Digest Over Zone Data
+    SVCB,       // General Purpose Service Binding
+    HTTPS,      // Service Binding type for use with HTTP
+    SPF,
+    UINFO,
+    UID,
+    GID,
+    UNSPEC,
+    NID,
+    L32,
+    L64,
+    LP,
+    EUI48,    // an EUI-48 address
+    EUI64,    // an EUI-64 address
+    TKEY,     // Transaction Key
+    TSIG,     // Transaction Signature
+    IXFR,     // incremental transfer
+    AXFR,     // transfer of an entire zone
+    MAILB,    // mailbox-related RRs (MB, MG or MR)
+    MAILA,    // mail agent RRs (OBSOLETE - see MX)
+    ANY,      // A request for some or all records the server has available
+    URI,      // URI
+    CAA,      // Certification Authority Restriction
+    AVC,      // Application Visibility and Control
+    DOA,      // Digital Object Architecture
+    AMTRELAY, // Automatic Multicast Tunneling Relay
+    TA,       // DNSSEC Trust Authorities
+    DLV,      // DNSSEC Lookaside Validation (OBSOLETE)
+    Other(u16),
+}
+
+impl DNS_QTYPE {
+    fn from_u16(n: u16) -> DNS_QTYPE {
+        match n {
+            1 => DNS_QTYPE::A,
+            2 => DNS_QTYPE::NS,
+            3 => DNS_QTYPE::MD,
+            4 => DNS_QTYPE::MF,
+            5 => DNS_QTYPE::CNAME,
+            6 => DNS_QTYPE::SOA,
+            7 => DNS_QTYPE::MB,
+            8 => DNS_QTYPE::MG,
+            9 => DNS_QTYPE::MR,
+            10 => DNS_QTYPE::NULL,
+            11 => DNS_QTYPE::WKS,
+            12 => DNS_QTYPE::PTR,
+            13 => DNS_QTYPE::HINFO,
+            14 => DNS_QTYPE::MINFO,
+            15 => DNS_QTYPE::MX,
+            16 => DNS_QTYPE::TXT,
+            17 => DNS_QTYPE::RP,
+            18 => DNS_QTYPE::AFSDB,
+            19 => DNS_QTYPE::X25,
+            20 => DNS_QTYPE::ISDN,
+            21 => DNS_QTYPE::RT,
+            22 => DNS_QTYPE::NSAP,
+            23 => DNS_QTYPE::NSAPPTR,
+            24 => DNS_QTYPE::SIG,
+            25 => DNS_QTYPE::KEY,
+            26 => DNS_QTYPE::PX,
+            27 => DNS_QTYPE::GPOS,
+            28 => DNS_QTYPE::AAAA,
+            29 => DNS_QTYPE::LOC,
+            30 => DNS_QTYPE::NXT,
+            31 => DNS_QTYPE::EID,
+            32 => DNS_QTYPE::NIMLOC,
+            33 => DNS_QTYPE::SRV,
+            34 => DNS_QTYPE::ATMA,
+            35 => DNS_QTYPE::NAPTR,
+            36 => DNS_QTYPE::KX,
+            37 => DNS_QTYPE::CERT,
+            38 => DNS_QTYPE::A6,
+            39 => DNS_QTYPE::DNAME,
+            40 => DNS_QTYPE::SINK,
+            41 => DNS_QTYPE::OPT,
+            42 => DNS_QTYPE::APL,
+            43 => DNS_QTYPE::DS,
+            44 => DNS_QTYPE::SSHFP,
+            45 => DNS_QTYPE::IPSECKEY,
+            46 => DNS_QTYPE::RRSIG,
+            47 => DNS_QTYPE::NSEC,
+            48 => DNS_QTYPE::DNSKEY,
+            49 => DNS_QTYPE::DHCID,
+            50 => DNS_QTYPE::NSEC3,
+            51 => DNS_QTYPE::NSEC3PARAM,
+            52 => DNS_QTYPE::TLSA,
+            53 => DNS_QTYPE::SMIMEA,
+            // hole
+            55 => DNS_QTYPE::HIP,
+            56 => DNS_QTYPE::NINFO,
+            57 => DNS_QTYPE::RKEY,
+            58 => DNS_QTYPE::TALINK,
+            59 => DNS_QTYPE::CDS,
+            60 => DNS_QTYPE::CDNSKEY,
+            61 => DNS_QTYPE::OPENPGPKEY,
+            62 => DNS_QTYPE::CSYNC,
+            63 => DNS_QTYPE::ZONEMD,
+            64 => DNS_QTYPE::SVCB,
+            65 => DNS_QTYPE::HTTPS,
+            // hole
+            99 => DNS_QTYPE::SPF,
+            100 => DNS_QTYPE::UINFO,
+            101 => DNS_QTYPE::UID,
+            102 => DNS_QTYPE::GID,
+            103 => DNS_QTYPE::UNSPEC,
+            104 => DNS_QTYPE::NID,
+            105 => DNS_QTYPE::L32,
+            106 => DNS_QTYPE::L64,
+            107 => DNS_QTYPE::LP,
+            108 => DNS_QTYPE::EUI48,
+            109 => DNS_QTYPE::EUI64,
+            // hole
+            249 => DNS_QTYPE::TKEY,
+            250 => DNS_QTYPE::TSIG,
+            251 => DNS_QTYPE::IXFR,
+            252 => DNS_QTYPE::AXFR,
+            253 => DNS_QTYPE::MAILB,
+            254 => DNS_QTYPE::MAILA,
+            255 => DNS_QTYPE::ANY,
+            256 => DNS_QTYPE::URI,
+            257 => DNS_QTYPE::CAA,
+            258 => DNS_QTYPE::AVC,
+            259 => DNS_QTYPE::DOA,
+            260 => DNS_QTYPE::AMTRELAY,
+            // hole
+            32768 => DNS_QTYPE::TA,
+            32769 => DNS_QTYPE::DLV,
+            n => DNS_QTYPE::Other(n),
+        }
+    }
+}
+
+impl Display for DNS_QTYPE {
+    fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
+        match self {
+            DNS_QTYPE::A => write!(f, "A"),
+            DNS_QTYPE::NS => write!(f, "NS"),
+            DNS_QTYPE::MD => write!(f, "MD"),
+            DNS_QTYPE::MF => write!(f, "MF"),
+            DNS_QTYPE::CNAME => write!(f, "CNAME"),
+            DNS_QTYPE::SOA => write!(f, "SOA"),
+            DNS_QTYPE::MB => write!(f, "MB"),
+            DNS_QTYPE::MG => write!(f, "MG"),
+            DNS_QTYPE::MR => write!(f, "MR"),
+            DNS_QTYPE::NULL => write!(f, "NULL"),
+            DNS_QTYPE::WKS => write!(f, "WKS"),
+            DNS_QTYPE::PTR => write!(f, "PTR"),
+            DNS_QTYPE::HINFO => write!(f, "HINFO"),
+            DNS_QTYPE::MINFO => write!(f, "MINFO"),
+            DNS_QTYPE::MX => write!(f, "MX"),
+            DNS_QTYPE::TXT => write!(f, "TXT"),
+            DNS_QTYPE::RP => write!(f, "RP"),
+            DNS_QTYPE::AFSDB => write!(f, "AFSDB"),
+            DNS_QTYPE::X25 => write!(f, "X25"),
+            DNS_QTYPE::ISDN => write!(f, "ISDN"),
+            DNS_QTYPE::RT => write!(f, "RT"),
+            DNS_QTYPE::NSAP => write!(f, "NSAP"),
+            DNS_QTYPE::NSAPPTR => write!(f, "NSAPPTR"),
+            DNS_QTYPE::SIG => write!(f, "SIG"),
+            DNS_QTYPE::KEY => write!(f, "KEY"),
+            DNS_QTYPE::PX => write!(f, "PX"),
+            DNS_QTYPE::GPOS => write!(f, "GPOS"),
+            DNS_QTYPE::AAAA => write!(f, "AAAA"),
+            DNS_QTYPE::LOC => write!(f, "LOC"),
+            DNS_QTYPE::NXT => write!(f, "NXT"),
+            DNS_QTYPE::EID => write!(f, "EID"),
+            DNS_QTYPE::NIMLOC => write!(f, "NIMLOC"),
+            DNS_QTYPE::SRV => write!(f, "SRV"),
+            DNS_QTYPE::ATMA => write!(f, "ATMA"),
+            DNS_QTYPE::NAPTR => write!(f, "NAPTR"),
+            DNS_QTYPE::KX => write!(f, "KX"),
+            DNS_QTYPE::CERT => write!(f, "CERT"),
+            DNS_QTYPE::A6 => write!(f, "A6"),
+            DNS_QTYPE::DNAME => write!(f, "DNAME"),
+            DNS_QTYPE::SINK => write!(f, "SINK"),
+            DNS_QTYPE::OPT => write!(f, "OPT"),
+            DNS_QTYPE::APL => write!(f, "APL"),
+            DNS_QTYPE::DS => write!(f, "DS"),
+            DNS_QTYPE::SSHFP => write!(f, "SSHFP"),
+            DNS_QTYPE::IPSECKEY => write!(f, "IPSECKEY"),
+            DNS_QTYPE::RRSIG => write!(f, "RRSIG"),
+            DNS_QTYPE::NSEC => write!(f, "NSEC"),
+            DNS_QTYPE::DNSKEY => write!(f, "DNSKEY"),
+            DNS_QTYPE::DHCID => write!(f, "DHCID"),
+            DNS_QTYPE::NSEC3 => write!(f, "NSEC3"),
+            DNS_QTYPE::NSEC3PARAM => write!(f, "NSEC3PARAM"),
+            DNS_QTYPE::TLSA => write!(f, "TLSA"),
+            DNS_QTYPE::SMIMEA => write!(f, "SMIMEA"),
+            DNS_QTYPE::HIP => write!(f, "HIP"),
+            DNS_QTYPE::NINFO => write!(f, "NINFO"),
+            DNS_QTYPE::RKEY => write!(f, "RKEY"),
+            DNS_QTYPE::TALINK => write!(f, "TALINK"),
+            DNS_QTYPE::CDS => write!(f, "CDS"),
+            DNS_QTYPE::CDNSKEY => write!(f, "CDNSKEY"),
+            DNS_QTYPE::OPENPGPKEY => write!(f, "OPENPGPKEY"),
+            DNS_QTYPE::CSYNC => write!(f, "CSYNC"),
+            DNS_QTYPE::ZONEMD => write!(f, "ZONEMD"),
+            DNS_QTYPE::SVCB => write!(f, "SVCB"),
+            DNS_QTYPE::HTTPS => write!(f, "HTTPS"),
+            DNS_QTYPE::SPF => write!(f, "SPF"),
+            DNS_QTYPE::UINFO => write!(f, "UINFO"),
+            DNS_QTYPE::UID => write!(f, "UID"),
+            DNS_QTYPE::GID => write!(f, "GID"),
+            DNS_QTYPE::UNSPEC => write!(f, "UNSPEC"),
+            DNS_QTYPE::NID => write!(f, "NID"),
+            DNS_QTYPE::L32 => write!(f, "L32"),
+            DNS_QTYPE::L64 => write!(f, "L64"),
+            DNS_QTYPE::LP => write!(f, "LP"),
+            DNS_QTYPE::EUI48 => write!(f, "EUI48"),
+            DNS_QTYPE::EUI64 => write!(f, "EUI64"),
+            DNS_QTYPE::TKEY => write!(f, "TKEY"),
+            DNS_QTYPE::TSIG => write!(f, "TSIG"),
+            DNS_QTYPE::IXFR => write!(f, "IXFR"),
+            DNS_QTYPE::AXFR => write!(f, "AXFR"),
+            DNS_QTYPE::MAILB => write!(f, "MAILB"),
+            DNS_QTYPE::MAILA => write!(f, "MAILA"),
+            DNS_QTYPE::ANY => write!(f, "ANY"),
+            DNS_QTYPE::URI => write!(f, "URI"),
+            DNS_QTYPE::CAA => write!(f, "CAA"),
+            DNS_QTYPE::AVC => write!(f, "AVC"),
+            DNS_QTYPE::DOA => write!(f, "DOA"),
+            DNS_QTYPE::AMTRELAY => write!(f, "AMTRELAY"),
+            DNS_QTYPE::TA => write!(f, "TA"),
+            DNS_QTYPE::DLV => write!(f, "DLV"),
+            DNS_QTYPE::Other(n) => write!(f, "TYPE{}", n),
+        }
+    }
+}
+
+/****************************** DNS_QCLASS ******************************/
+
+// https://www.iana.org/assignments/dns-parameters/dns-parameters.xhtml#dns-parameters-2
+#[allow(non_camel_case_types)]
+#[derive(Clone, Copy, Debug, PartialEq, Eq)]
+pub enum DNS_QCLASS {
+    Internet,
+    Unassigned,
+    Chaos,
+    Hesiod,
+    QCLASS_NONE,
+    QCLASS_ANY,
+    Other(u16),
+}
+
+impl DNS_QCLASS {
+    fn from_u16(n: u16) -> DNS_QCLASS {
+        match n {
+            1 => DNS_QCLASS::Internet,
+            2 => DNS_QCLASS::Unassigned,
+            3 => DNS_QCLASS::Chaos,
+            4 => DNS_QCLASS::Hesiod,
+            254 => DNS_QCLASS::QCLASS_NONE,
+            255 => DNS_QCLASS::QCLASS_ANY,
+            n => DNS_QCLASS::Other(n),
+        }
+    }
+}
+
+impl Display for DNS_QCLASS {
+    fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
+        match self {
+            DNS_QCLASS::Internet => write!(f, "Internet"),
+            DNS_QCLASS::Unassigned => write!(f, "Unassigned"),
+            DNS_QCLASS::Chaos => write!(f, "Chaos"),
+            DNS_QCLASS::Hesiod => write!(f, "Hesiod"),
+            DNS_QCLASS::QCLASS_NONE => write!(f, "QCLASS_NONE"),
+            DNS_QCLASS::QCLASS_ANY => write!(f, "QCLASS_ANY"),
+            DNS_QCLASS::Other(n) => write!(f, "CLASS{}", n),
+        }
+    }
+}
+
+/****************************** DNS_QUESTION_SECTION ******************************/
+
+#[allow(non_camel_case_types)]
+#[derive(Clone, Debug, PartialEq, Eq)]
+pub struct DNS_QUESTION_SECTION {
+    pub qname: String,
+    pub qtype: DNS_QTYPE,
+    pub qclass: DNS_QCLASS,
+    size: usize, // DNS 原始数据中 DNS_QUESTION_SECTION 占多少字节
+}
+
+impl DNS_QUESTION_SECTION {
+    fn decode<'a, 'b>(
+        input: &'a [u8],
+        labels: &'b mut DNS_LABEL_TABLE,
+        position: usize,
+    ) -> IResult<&'a [u8], DNS_QUESTION_SECTION> {
+        let (input, (name, size)) = dname_decode(input, labels, position)?;
+        let (input, qtype) = number::streaming::be_u16(input)?;
+        let (input, qclass) = number::streaming::be_u16(input)?;
+
+        Ok((
+            input,
+            DNS_QUESTION_SECTION {
+                qname: name.to_string(),
+                qtype: DNS_QTYPE::from_u16(qtype),
+                qclass: DNS_QCLASS::from_u16(qclass),
+                size: 4 + size,
+            },
+        ))
+    }
+}
+
+impl Display for DNS_QUESTION_SECTION {
+    fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
+        write!(f, ";{}\t{}\t{}\n", self.qname, self.qclass, self.qtype)
+    }
+}
+
+/******************************************************************************
+ * DNS Resource Record Definitions
+ ******************************************************************************/
+
+/*
+ * DNS Resource Record Definitions
+ *                                  1  1  1  1  1  1
+ *    0  1  2  3  4  5  6  7  8  9  0  1  2  3  4  5
+ *  +--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+
+ *  |                                               |
+ *  /                                               /
+ *  /                      NAME                     /
+ *  |                                               |
+ *  +--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+
+ *  |                      TYPE                     |
+ *  +--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+
+ *  |                     CLASS                     |
+ *  +--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+
+ *  |                      TTL                      |
+ *  |                                               |
+ *  +--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+
+ *  |                   RDLENGTH                    |
+ *  +--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--|
+ *  /                     RDATA                     /
+ *  /                                               /
+ *  +--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+
+ */
+
+#[allow(non_camel_case_types)]
+#[derive(Clone, Debug, PartialEq, Eq)]
+pub struct DNS_RR_HDR {
+    pub qname: String,
+    pub rr_type: DNS_QTYPE,
+    pub rr_class: DNS_QCLASS,
+    pub ttl: i32,
+    pub rd_length: u16,
+    size: usize, // DNS 原始数据中 DNS_RR_HDR 占多少字节
+}
+
+impl DNS_RR_HDR {
+    fn decode<'a>(
+        input: &'a [u8],
+        labels: &mut DNS_LABEL_TABLE,
+        position: usize,
+    ) -> IResult<&'a [u8], DNS_RR_HDR> {
+        let (input, (name, size)) = dname_decode(input, labels, position)?;
+        let (input, rr_type) = number::streaming::be_u16(input)?;
+        let (input, rr_class) = number::streaming::be_u16(input)?;
+        let (input, rr_ttl) = number::streaming::be_i32(input)?;
+        let (input, rr_rdlength) = number::streaming::be_u16(input)?;
+
+        Ok((
+            input,
+            DNS_RR_HDR {
+                qname: name.to_string(),
+                rr_type: DNS_QTYPE::from_u16(rr_type),
+                rr_class: DNS_QCLASS::from_u16(rr_class),
+                ttl: rr_ttl,
+                rd_length: rr_rdlength,
+                size: 10 + size,
+            },
+        ))
+    }
+}
+
+/*
+ * A RDATA format
+ *                                  1  1  1  1  1  1
+ *    0  1  2  3  4  5  6  7  8  9  0  1  2  3  4  5
+ *  +--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+
+ *  |                    ADDRESS                    |
+ *  +--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+
+ *
+ *  ADDRESS : A 32 bit Internet address
+ */
+
+/*
+ * AAAA RDATA format
+ *                                  1  1  1  1  1  1
+ *    0  1  2  3  4  5  6  7  8  9  0  1  2  3  4  5
+ *  +--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+
+ *  |                    ADDRESS                    |
+ *  |                                               |
+ *  |                                               |
+ *  |                                               |
+ *  |                                               |
+ *  |                                               |
+ *  |                                               |
+ *  |                                               |
+ *  +--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+
+ *
+ *  ADDRESS : A 128 bit IPv6 address is encoded in the data portion of an AAAA
+ *            resource record in network byte order (high-order byte first).
+ */
+
+/*
+ * CNAME RDATA format
+ *                                  1  1  1  1  1  1
+ *    0  1  2  3  4  5  6  7  8  9  0  1  2  3  4  5
+ *  +--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+
+ *  /                     CNAME                     /
+ *  /                                               /
+ *  +--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+
+ *
+ *  CNAME : A <domain-name> which specifies the canonical or primary
+ *          name for the owner.  The owner name is an alias.
+ */
+
+/*
+ * HINFO RDATA format
+ *                                  1  1  1  1  1  1
+ *    0  1  2  3  4  5  6  7  8  9  0  1  2  3  4  5
+ *  +--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+
+ *  /                      CPU                      /
+ *  +--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+
+ *  /                       OS                      /
+ *  +--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+
+ *
+ *  CPU : A <character-string> which specifies the CPU type.
+ *  OS  : A <character-string> which specifies the operating system type.
+ */
+
+/*
+ * MX RDATA format
+ *                                  1  1  1  1  1  1
+ *    0  1  2  3  4  5  6  7  8  9  0  1  2  3  4  5
+ *  +--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+
+ *  |                  PREFERENCE                   |
+ *  +--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+
+ *  /                   EXCHANGE                    /
+ *  /                                               /
+ *  +--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+
+ *
+ *  PREFERENCE : A 16 bit integer which specifies the preference given to
+ *               this RR among others at the same owner. Lower values are preferred.
+ *  EXCHANGE   : A <domain-name> which specifies a host willing to act as a mail exchange for the owner name.
+ */
+
+/*
+ * NS RDATA format
+ *                                  1  1  1  1  1  1
+ *    0  1  2  3  4  5  6  7  8  9  0  1  2  3  4  5
+ *  +--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+
+ *  /                   NSDNAME                     /
+ *  /                                               /
+ *  +--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+
+ *
+ *  NSDNAME : A <domain-name> which specifies a host which should be
+ *            authoritative for the specified class and domain.
+ */
+
+/*
+ * PTR RDATA format
+ *                                  1  1  1  1  1  1
+ *    0  1  2  3  4  5  6  7  8  9  0  1  2  3  4  5
+ *  +--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+
+ *  /                   PTRDNAME                    /
+ *  +--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+
+ *
+ *  PTRDNAME : A <domain-name> which points to some location in the domain name space.
+ */
+
+/*
+ * SOA RDATA format
+ *                                  1  1  1  1  1  1
+ *    0  1  2  3  4  5  6  7  8  9  0  1  2  3  4  5
+ *  +--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+
+ *  /                     MNAME                     /
+ *  /                                               /
+ *  +--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+
+ *  /                     RNAME                     /
+ *  +--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+
+ *  |                    SERIAL                     |
+ *  |                                               |
+ *  +--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+
+ *  |                    REFRESH                    |
+ *  |                                               |
+ *  +--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+
+ *  |                     RETRY                     |
+ *  |                                               |
+ *  +--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+
+ *  |                    EXPIRE                     |
+ *  |                                               |
+ *  +--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+
+ *  |                    MINIMUM                    |
+ *  |                                               |
+ *  +--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+
+ *
+ *  MNAME   : The <domain-name> of the name server that was the original or primary source of data for this zone.
+ *  RNAME   : A <domain-name> which specifies the mailbox of the person responsible for this zone.
+ *  SERIAL  : The unsigned 32 bit version number of the original copy of the zone.
+ *            Zone transfers preserve this value. This value wraps and should be
+ *            compared using sequence space arithmetic.
+ *  REFRESH : A 32 bit time interval before the zone should be refreshed.
+ *  RETRY   : A 32 bit time interval that should elapse before a failed refresh should be retried.
+ *  EXPIRE  : A 32 bit time value that specifies the upper limit on
+ *            the time interval that can elapse before the zone is no longer authoritative.
+ *  MINIMUM : The unsigned 32 bit minimum TTL field that should beexported with any RR from this zone.
+ */
+
+/*
+ * TXT RDATA format
+ *                                  1  1  1  1  1  1
+ *    0  1  2  3  4  5  6  7  8  9  0  1  2  3  4  5
+ *  +--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+
+ *  /                   TXT-DATA                    /
+ *  +--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+
+ *
+ *  TXT-DATA : One or more <character-string>s.
+ */
+
+#[allow(non_camel_case_types)]
+#[derive(Clone, Debug, PartialEq, Eq)]
+pub enum DNS_RR_DATA {
+    A {
+        address: String,
+    },
+    AAAA {
+        address: String,
+    },
+    CNAME {
+        cname: String,
+    },
+    HINFO {
+        cpu: Vec<u8>,
+        os: Vec<u8>,
+    },
+    MX {
+        preference: u16,
+        exchange: String,
+    },
+    NS {
+        nsdname: String,
+    },
+    PTR {
+        ptrdnmae: String,
+    },
+    SOA {
+        mname: String,
+        rname: String,
+        serial: u32,
+        refresh: i32,
+        retry: i32,
+        expire: i32,
+        minimum: i32,
+    },
+    TXT {
+        txtdata: Vec<String>,
+    },
+    Other {
+        qtype: DNS_QTYPE,
+        data: Vec<u8>,
+    },
+}
+
+impl DNS_RR_DATA {
+    fn decode<'a>(
+        input: &'a [u8],
+        labels: &mut DNS_LABEL_TABLE,
+        position: usize,
+        rr_hdr: &DNS_RR_HDR,
+    ) -> IResult<&'a [u8], DNS_RR_DATA> {
+        match (rr_hdr.rr_class, rr_hdr.rr_type) {
+            (DNS_QCLASS::Internet, DNS_QTYPE::A) => {
+                let (input, num) = number::streaming::be_u32(input)?;
+                Ok((
+                    input,
+                    DNS_RR_DATA::A {
+                        address: address_v4_decode(num),
+                    },
+                ))
+            }
+            (DNS_QCLASS::Internet, DNS_QTYPE::AAAA) => {
+                let (input, num) = number::streaming::be_u128(input)?;
+                Ok((
+                    input,
+                    DNS_RR_DATA::AAAA {
+                        address: address_v6_decode(num),
+                    },
+                ))
+            }
+            (_, DNS_QTYPE::CNAME) => {
+                let (input, (name, _size)) = dname_decode(input, labels, position)?;
+                Ok((
+                    input,
+                    DNS_RR_DATA::CNAME {
+                        cname: name.to_string(),
+                    },
+                ))
+            }
+            (_, DNS_QTYPE::HINFO) => {
+                let (input, _cpu) = multi::length_data(number::streaming::be_u8)(input)?;
+                let (input, _os) = multi::length_data(number::streaming::be_u8)(input)?;
+                Ok((
+                    input,
+                    DNS_RR_DATA::HINFO {
+                        cpu: _cpu.to_vec(),
+                        os: _os.to_vec(),
+                    },
+                ))
+            }
+            (_, DNS_QTYPE::MX) => {
+                let (input, _preference) = number::streaming::be_u16(input)?;
+                let (input, (name, _size)) = dname_decode(input, labels, position + 2)?;
+                Ok((
+                    input,
+                    DNS_RR_DATA::MX {
+                        preference: _preference,
+                        exchange: name.to_string(),
+                    },
+                ))
+            }
+            (_, DNS_QTYPE::NS) => {
+                let (input, (name, _size)) = dname_decode(input, labels, position)?;
+                Ok((
+                    input,
+                    DNS_RR_DATA::NS {
+                        nsdname: name.to_string(),
+                    },
+                ))
+            }
+            (_, DNS_QTYPE::PTR) => {
+                let (input, (name, _size)) = dname_decode(input, labels, position)?;
+                Ok((
+                    input,
+                    DNS_RR_DATA::PTR {
+                        ptrdnmae: name.to_string(),
+                    },
+                ))
+            }
+            (_, DNS_QTYPE::SOA) => {
+                let (input, (_mname, mname_size)) = dname_decode(input, labels, position)?;
+                let mname_string = _mname.to_string();
+                let (input, (_rname, _rname_size)) =
+                    dname_decode(input, labels, position + mname_size)?;
+                let (input, _serial) = number::streaming::be_u32(input)?;
+                let (input, _refresh) = number::streaming::be_i32(input)?;
+                let (input, _retry) = number::streaming::be_i32(input)?;
+                let (input, _expire) = number::streaming::be_i32(input)?;
+                let (input, _minimum) = number::streaming::be_i32(input)?;
+                Ok((
+                    input,
+                    DNS_RR_DATA::SOA {
+                        mname: mname_string,
+                        rname: _rname.to_string(),
+                        serial: _serial,
+                        refresh: _refresh,
+                        retry: _retry,
+                        expire: _expire,
+                        minimum: _minimum,
+                    },
+                ))
+            }
+            (_, DNS_QTYPE::TXT) => {
+                let mut input = input;
+                let mut nleft = rr_hdr.rd_length;
+                let mut ret = Vec::new();
+                loop {
+                    let (__input, data) = character_string_decode(input)?;
+                    ret.push(str::from_utf8(data).unwrap().to_string());
+
+                    input = __input;
+                    nleft = nleft - 1 - (data.len() as u16);
+
+                    if nleft < 2 {
+                        break;
+                    }
+                }
+                Ok((input, DNS_RR_DATA::TXT { txtdata: ret }))
+            }
+            (_, _) => {
+                let slen: usize = rr_hdr.rd_length.into();
+                let rdata = &input[0..slen];
+                Ok((
+                    &input[slen..],
+                    DNS_RR_DATA::Other {
+                        qtype: rr_hdr.rr_type,
+                        data: rdata.to_vec(),
+                    },
+                ))
+            }
+        }
+    }
+}
+
+/****************************** DNS_RR_SECTION ******************************/
+
+#[allow(non_camel_case_types)]
+#[derive(Clone, Debug, PartialEq, Eq)]
+pub struct DNS_RR_SECTION {
+    pub hdr: DNS_RR_HDR,
+    pub data: DNS_RR_DATA,
+}
+
+impl DNS_RR_SECTION {
+    fn decode<'a, 'b>(
+        input: &'a [u8],
+        labels: &'b mut DNS_LABEL_TABLE,
+        position: usize,
+    ) -> IResult<&'a [u8], DNS_RR_SECTION> {
+        let (left, rr_hdr) = DNS_RR_HDR::decode(input, labels, position)?;
+        let (left, rr_data) = DNS_RR_DATA::decode(left, labels, position + rr_hdr.size, &rr_hdr)?;
+
+        Ok((
+            left,
+            DNS_RR_SECTION {
+                hdr: rr_hdr,
+                data: rr_data,
+            },
+        ))
+    }
+}
+
+impl Display for DNS_RR_SECTION {
+    fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
+        write!(
+            f,
+            "{}\t\t{}\t{}\t{}\t",
+            self.hdr.qname, self.hdr.ttl, self.hdr.rr_class, self.hdr.rr_type
+        )?;
+        match &self.data {
+            DNS_RR_DATA::A { address: _address } => {
+                write!(f, "{}\n", _address)
+            }
+            DNS_RR_DATA::AAAA { address: _address } => {
+                write!(f, "{}\n", _address)
+            }
+            DNS_RR_DATA::CNAME { cname: _cname } => {
+                write!(f, "{}\n", _cname)
+            }
+            DNS_RR_DATA::HINFO { cpu: _cpu, os: _os } => {
+                write!(f, "\\# ")?;
+                for i in &*_cpu {
+                    write!(f, "{:02X}", i)?;
+                }
+                write!(f, "\n\\# ")?;
+                for i in &*_os {
+                    write!(f, "{:02X}", i)?;
+                }
+                write!(f, "\n")
+            }
+            DNS_RR_DATA::MX {
+                preference: _preference,
+                exchange: _exchange,
+            } => {
+                write!(f, "{} {}\n", _preference, _exchange)
+            }
+            DNS_RR_DATA::NS { nsdname: _nsdname } => {
+                write!(f, "{}\n", _nsdname)
+            }
+            DNS_RR_DATA::PTR {
+                ptrdnmae: _ptrdnmae,
+            } => {
+                write!(f, "{}\n", _ptrdnmae)
+            }
+            DNS_RR_DATA::SOA {
+                mname: _mname,
+                rname: _rname,
+                serial: _serial,
+                refresh: _refresh,
+                retry: _retry,
+                expire: _expire,
+                minimum: _minimum,
+            } => {
+                write!(
+                    f,
+                    "{} {} {} {} {} {} {}\n",
+                    _mname, _rname, _serial, _refresh, _retry, _expire, _minimum,
+                )
+            }
+            DNS_RR_DATA::TXT { txtdata: _txtdata } => {
+                for i in _txtdata {
+                    write!(f, "{}", i)?;
+                }
+                Ok(())
+            }
+            DNS_RR_DATA::Other {
+                qtype: _qtype,
+                data: _data,
+            } => {
+                write!(f, "\\# ")?;
+                for i in &*_data {
+                    write!(f, "{:02X}", i)?;
+                }
+                write!(f, "\n")
+            }
+        }
+    }
+}
+
+/******************************************************************************
+ * DNS Message
+ ******************************************************************************/
+
+/****************************** DNS_LABEL_TYPE ******************************/
+
+// https://www.iana.org/assignments/dns-parameters/dns-parameters.xhtml#dns-parameters-10
+#[allow(non_camel_case_types)]
+#[derive(Clone, Copy, Debug, PartialEq, Eq)]
+enum DNS_LABEL_TYPE {
+    Normal(usize),  // Normal label lower 6 bits is the length of the label
+    Pointer(usize), // Compressed label the lower 6 bits and the 8 bits from next octet form a pointer to the compression target
+    End,
+    Other,
+}
+
+impl DNS_LABEL_TYPE {
+    fn peek(input: &[u8]) -> IResult<&[u8], (u8, u8)> {
+        combinator::peek(bits::<_, _, Error<(&[u8], usize)>, _, _>(sequence::tuple(
+            (bits::streaming::take(1usize), bits::streaming::take(1usize)),
+        )))(input)
+    }
+
+    fn decode(input: &[u8]) -> IResult<&[u8], DNS_LABEL_TYPE> {
+        match Self::peek(input) {
+            // 域名压缩
+            Ok((_, (1u8, 1u8))) => bits::<_, _, Error<(&[u8], usize)>, _, _>(sequence::tuple((
+                bits::streaming::take(1usize),
+                bits::streaming::take(1usize),
+                bits::streaming::take(6usize),
+                bits::streaming::take(8usize),
+            )))(input)
+            .map(|(input, (_, _, left, right)): (&[u8], (u8, u8, u8, u8))| {
+                (
+                    input,
+                    DNS_LABEL_TYPE::Pointer((((left as u16) << 8) | right as u16) as usize),
+                )
+            }),
+            // 域名未压缩
+            Ok((_, (0u8, 0u8))) => bits::<_, _, Error<(&[u8], usize)>, _, _>(sequence::tuple((
+                bits::streaming::take(1usize),
+                bits::streaming::take(1usize),
+                bits::streaming::take(6usize),
+            )))(input)
+            .map(|(input, (_, _, size)): (&[u8], (u8, u8, u8))| {
+                if size == 0 {
+                    // 域名未压缩时，需要在域名最后加 0x00 表示名域名结束
+                    // 域名压缩时，就不用在最后加 0x00 了
+                    return (input, DNS_LABEL_TYPE::End);
+                } else {
+                    return (input, DNS_LABEL_TYPE::Normal(size as usize));
+                }
+            }),
+            _ => Ok((input, DNS_LABEL_TYPE::Other)),
+        }
+    }
+}
+
+/****************************** DNS_LABEL_TABLE ******************************/
+
+#[allow(non_camel_case_types)]
+#[derive(Clone, Debug, PartialEq, Eq)]
+pub struct DNS_LABEL_TABLE {
+    pub labels: Vec<((usize, usize), String)>,
+}
+
+impl DNS_LABEL_TABLE {
+    fn new() -> DNS_LABEL_TABLE {
+        DNS_LABEL_TABLE { labels: vec![] }
+    }
+
+    /*
+     * position : byte position in message
+     * size     : byte size in message (can be smaller than domain's size)
+     * domain   : the full domain
+     */
+    fn set(&mut self, position: usize, size: usize, domain: &str) -> &str {
+        self.labels.push(((position, size), domain.to_string()));
+        &self.labels.last().unwrap().1
+    }
+
+    fn get(&self, position: usize) -> Option<&str> {
+        // labels 为空
+        if self.labels.len() == 0 {
+            return None;
+        }
+
+        // position 太小
+        let mut cursor = self.labels.first().unwrap();
+        if position < cursor.0 .0 {
+            return None;
+        }
+
+        let mut index: usize = 0;
+        while position >= (cursor.0 .0 + cursor.0 .1) {
+            cursor = match self.labels.get(index + 1) {
+                Some(c) => c,
+                _ => {
+                    return None;
+                }
+            };
+            index += 1;
+        }
+
+        if position < cursor.0 .0 {
+            // hole
+            return None;
+        }
+
+        if position == cursor.0 .0 {
+            return Some(&cursor.1);
+        }
+
+        if cursor.1.as_bytes()[position - cursor.0 .0 - 1] == b'.' {
+            return Some(cursor.1.split_at(position - cursor.0 .0).1);
+        }
+        None
+    }
+}
+
+/****************************** DNS_MESSAGE ******************************/
+
+#[allow(non_camel_case_types)]
+#[derive(Clone, Debug, PartialEq, Eq)]
+pub struct DNS_MESSAGE {
+    pub header: DNS_HEADER,
+    labels: DNS_LABEL_TABLE,
+    pub qd: Vec<DNS_QUESTION_SECTION>,
+    pub an: Vec<DNS_RR_SECTION>,
+    pub ns: Vec<DNS_RR_SECTION>,
+    pub ar: Vec<DNS_RR_SECTION>,
+}
+
+impl DNS_MESSAGE {
+    fn new(header: DNS_HEADER) -> DNS_MESSAGE {
+        DNS_MESSAGE {
+            header: header,
+            labels: DNS_LABEL_TABLE::new(),
+            qd: vec![],
+            an: vec![],
+            ns: vec![],
+            ar: vec![],
+        }
+    }
+
+    pub fn decode(input: &[u8]) -> IResult<&[u8], DNS_MESSAGE> {
+        let (mut input, header) = DNS_HEADER::decode(input)?;
+        let mut message = DNS_MESSAGE::new(header);
+        let mut position = 12;
+
+        // QDCOUNT
+        for _ in 0..header.qd_count {
+            let (left, qd) = DNS_QUESTION_SECTION::decode(input, &mut message.labels, position)?;
+            input = left;
+            position += qd.size;
+            message.qd.push(qd);
+        }
+
+        // ANCOUNT
+        for _ in 0..header.an_count {
+            let (left, rr) = DNS_RR_SECTION::decode(input, &mut message.labels, position)?;
+            position += rr.hdr.size + rr.hdr.rd_length as usize;
+
+            message.an.push(rr);
+            input = left;
+        }
+
+        // NSCOUNT
+        for _ in 0..header.ns_count {
+            let (left, rr) = DNS_RR_SECTION::decode(input, &mut message.labels, position)?;
+            position += rr.hdr.size + rr.hdr.rd_length as usize;
+
+            message.ns.push(rr);
+            input = left;
+        }
+
+        // ARCOUNT
+        for _ in 0..header.ar_count {
+            let (left, rr) = DNS_RR_SECTION::decode(input, &mut message.labels, position)?;
+            position += rr.hdr.size + rr.hdr.rd_length as usize;
+
+            message.ar.push(rr);
+            input = left;
+        }
+
+        Ok((input, message))
+    }
+}
+
+impl Display for DNS_MESSAGE {
+    fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
+        write!(f, "{}\n", self.header)?;
+        if self.qd.len() > 0 {
+            write!(f, ";; QUESTION SECTION:\n")?;
+            for qde in &self.qd {
+                write!(f, "{}\n", qde)?;
+            }
+        }
+        if self.an.len() > 0 {
+            write!(f, ";; ANSWER SECTION:\n")?;
+            for ane in &self.an {
+                ane.fmt(f)?;
+            }
+        }
+        if self.ns.len() > 0 {
+            write!(f, ";; AUTHORITY SECTION:\n")?;
+            for nse in &self.ns {
+                nse.fmt(f)?;
+            }
+        }
+        if self.ar.len() > 0 {
+            write!(f, ";; ADDITIONAL SECTION:\n")?;
+            for are in &self.ar {
+                are.fmt(f)?;
+            }
+        }
+        Ok(())
+    }
+}
+
+/******************************************************************************
+ * Utils
+ ******************************************************************************/
+
+fn address_v4_decode(n: u32) -> String {
+    let ipb = n.to_be_bytes();
+    format!("{}.{}.{}.{}", ipb[0], ipb[1], ipb[2], ipb[3])
+}
+
+fn address_v6_decode(n: u128) -> String {
+    let ipb = n.to_be_bytes();
+    format!("{:02X}{:02X}:{:02X}{:02X}:{:02X}{:02X}:{:02X}{:02X}:{:02X}{:02X}:{:02X}{:02X}:{:02X}{:02X}:{:02X}{:02X}", ipb[0], ipb[1], ipb[2], ipb[3], ipb[4], ipb[5], ipb[6], ipb[7], ipb[8], ipb[9], ipb[10], ipb[11], ipb[12], ipb[13], ipb[14], ipb[15])
+}
+
+/* https://www.ietf.org/rfc/rfc1035.txt
+ *
+ * 3.3. Standard RRs
+ *
+ * <character-string> is a single length octet followed by that number of characters.
+ * <character-string> is treated as binary information, and can be up to 256 characters in length (including the length octet).
+ */
+fn character_string_decode(input: &[u8]) -> IResult<&[u8], &[u8]> {
+    multi::length_data(number::streaming::be_u8)(input)
+}
+
+/*
+ * https://www.ietf.org/rfc/rfc1035.txt
+ *
+ * 2.3.1. Preferred name syntax
+ *
+ * The labels must follow the rules for ARPANET host names. They must
+ * start with a letter, end with a letter or digit, and have as interior
+ * characters only letters, digits, and hyphen. There are also some
+ * restrictions on the length. Labels must be 63 characters or less.
+ */
+// 为了解析出更多的域名，此处未严格遵守 RFC 中规定的 “字母” “数字” 和 “-” 的顺序，并增加了 ‘_’ 字符
+fn label_character_verify(c: u8) -> bool {
+    character::is_alphabetic(c) || character::is_digit(c) || (c == b'-') || (c == b'_')
+}
+
+fn label_decode<'a>(
+    input: &'a [u8],
+    size: usize,
+    name: &mut String,
+) -> IResult<&'a [u8], &'static str> {
+    if input.len() < size {
+        return Err(Err::Incomplete(Needed::new(size - input.len())));
+    }
+
+    for i in 0..size {
+        if !label_character_verify(input[i]) {
+            return Err(Err::Failure(Error::new(input, ErrorKind::Fail)));
+        }
+    }
+
+    name.push_str(str::from_utf8(&input[0..size]).unwrap());
+    return Ok((input.get(size..).unwrap(), "OK"));
+}
+
+/*
+ * https://www.ietf.org/rfc/rfc1035.txt
+ *
+ * 4.1.4. Message compression
+ *
+ * The compression scheme allows a domain name in a message to be represented as either:
+ *
+ * - a sequence of labels ending in a zero octet
+ * - a pointer
+ * - a sequence of labels ending with a pointer
+ */
+fn dname_decode<'a, 'b>(
+    data: &'a [u8],
+    labels: &'b mut DNS_LABEL_TABLE,
+    position: usize,
+) -> IResult<&'a [u8], (&'b str, usize)> {
+    let mut input = data;
+    let mut total_size = 0usize;
+    let mut name = String::new();
+    loop {
+        match DNS_LABEL_TYPE::decode(input) {
+            Ok((inner_input, label_type)) => match label_type {
+                // 域名未压缩
+                DNS_LABEL_TYPE::Normal(size) => {
+                    total_size += 1 + size;
+                    if name.len() > 0 {
+                        name.push('.');
+                    }
+
+                    let (left, _) = label_decode(inner_input, size, &mut name)?;
+                    input = left;
+                }
+                // 域名压缩
+                DNS_LABEL_TYPE::Pointer(_position) => {
+                    total_size += 2;
+                    if name.len() > 0 {
+                        name.push('.');
+                    }
+
+                    let label = match labels.get(_position) {
+                        Some(label) => label,
+                        _ => {
+                            return Err(Err::Failure(Error::new(inner_input, ErrorKind::Fail)));
+                        }
+                    };
+                    name.push_str(label);
+                    let n = labels.set(position, total_size, &name);
+                    return Ok((inner_input, (n, total_size)));
+                }
+                // 域名未压缩
+                DNS_LABEL_TYPE::End => {
+                    total_size += 1;
+                    name.push('.');
+
+                    let n = labels.set(position, total_size, &name);
+                    return Ok((inner_input, (n, total_size)));
+                }
+                DNS_LABEL_TYPE::Other => {
+                    return Err(Err::Failure(Error::new(inner_input, ErrorKind::Fail)));
+                }
+            },
+            _ => {
+                return Err(Err::Failure(Error::new(input, ErrorKind::Fail)));
+            }
+        }
+    }
+}
+
+/******************************************************************************
+ * TEST
+ ******************************************************************************/
+
+/*
+fn main() -> io::Result<()> {
+    // dig @1.1.1.1 A www.kpn.com
+    let id = 52749u16;
+    let query_flags = 0b0_0000_0010_000_0000u16;
+    let counts = [0u8, 1u8, 0u8, 0u8, 0u8, 0u8, 0u8, 0u8];
+    // let qname = [0b00000011u8, b'w', b'w', b'w', 0b00000011u8, b'k', b'p', b'n', 0b00000011u8, b'c', b'o', b'm', 0b00000000u8];
+    let qname = [0b00000011u8, b'k', b'p', b'n', 0b00000011u8, b'c', b'o', b'm', 0b00000000u8];
+    // let qname = [0b00001010u8, b'q', b'u', b'a', b't', b'e', b'r', b'n', b'i', b'o', b'n', 0b00000101u8, b's', b'p', b'a', b'c', b'e', 0b00000000u8];
+    let qtype = 48u16;
+    let qclass = 1u16;
+    let mut query_msg = vec![];
+    query_msg.extend_from_slice(&id.to_be_bytes());
+    query_msg.extend_from_slice(&query_flags.to_be_bytes());
+    query_msg.extend_from_slice(&counts);
+    query_msg.extend_from_slice(&qname);
+    query_msg.extend_from_slice(&qtype.to_be_bytes());
+    query_msg.extend_from_slice(&qclass.to_be_bytes());
+    let socket = UdpSocket::bind("0.0.0.0:34254").expect("Failed to open UDP connection.");
+    socket.connect(("1.1.1.1", 53)).expect("Failed to connect to server.");
+    socket.send(&query_msg).expect("Failed to send query to server.");
+    let mut buf = [0; 512];
+    let input = match socket.recv(&mut buf) {
+        Ok(received) => {
+            // println!("received {} bytes {:?}\n", received, &buf[..received]);
+            &buf[..received]
+        },
+        Err(_e) => {
+            // println!("recv function failed: {:?}\n", e);
+            return Ok(());
+        },
+    };
+    match DNS_MESSAGE::decode(input) {
+        Ok((_rest, message)) => {
+            println!("{}", message);
+            Ok(())
+        },
+        Err(err) => {
+            println!("err:{:?}\n", err);
+            Ok(())
+        },
+
+    }
+}
+*/
+
+#[cfg(test)]
+mod tests {
+    use super::character_string_decode;
+    use super::dname_decode;
+    use super::label_decode;
+    use super::DNS_HDR_OPCODE;
+    use super::DNS_HDR_QR;
+    use super::DNS_HDR_RCODE;
+    use super::DNS_HEADER;
+    use super::DNS_LABEL_TABLE;
+    use super::DNS_MESSAGE;
+    use super::DNS_QCLASS;
+    use super::DNS_QTYPE;
+    use super::DNS_QUESTION_SECTION;
+    use super::DNS_RR_DATA;
+    use super::DNS_RR_HDR;
+    use super::DNS_RR_SECTION;
+
+    const LAST_SLICE: &'static [u8] = &[];
+
+    /**************************************************************************
+     * test util
+     **************************************************************************/
+
+    #[test]
+    fn test_character_string_decode() {
+        let input = [0b00000101u8, b'h', b'i', b'!', b'!', 0b11000000u8];
+        let result = character_string_decode(&input);
+        assert_eq!(
+            result,
+            Ok((&[][..], &[b'h', b'i', b'!', b'!', 0b11000000u8][..]))
+        );
+
+        let input = [0b00000101u8, 0b11000000u8];
+        let result = character_string_decode(&input);
+        assert_eq!(result, Err(nom::Err::Incomplete(nom::Needed::new(4))));
+    }
+
+    #[test]
+    fn test_label_table() {
+        let mut table = DNS_LABEL_TABLE::new();
+        table.set(30, 16, "www.example.com.");
+
+        assert_eq!(table.get(29), None);
+        assert_eq!(table.get(30), Some("www.example.com."));
+        assert_eq!(table.get(31), None);
+        assert_eq!(table.get(32), None);
+        assert_eq!(table.get(33), None);
+        assert_eq!(table.get(34), Some("example.com."));
+        assert_eq!(table.get(35), None);
+        assert_eq!(table.get(36), None);
+        assert_eq!(table.get(37), None);
+        assert_eq!(table.get(38), None);
+        assert_eq!(table.get(39), None);
+        assert_eq!(table.get(40), None);
+        assert_eq!(table.get(41), None);
+        assert_eq!(table.get(42), Some("com."));
+        assert_eq!(table.get(43), None);
+    }
+
+    #[test]
+    fn test_label_decode() {
+        /*
+         * [letter] -> OK
+         * [digit]  -> OK
+         * [-]      -> OK
+         * [other]  -> Err
+         */
+
+        let buf1 = &[b'a']; // OK
+        let buf2 = &[b'1']; // OK
+        let buf3 = &[b'-']; // OK
+        let buf4 = &[b'_']; // OK
+        let buf5 = &[b'+']; // Err
+
+        let mut str = String::new();
+        let ret = label_decode(buf1, 1, &mut str);
+        assert_eq!(str, "a");
+        assert_eq!(ret, Ok((LAST_SLICE, "OK")));
+
+        let mut str = String::new();
+        let ret = label_decode(buf2, 1, &mut str);
+        assert_eq!(str, "1");
+        assert_eq!(ret, Ok((LAST_SLICE, "OK")));
+
+        let mut str = String::new();
+        let ret = label_decode(buf3, 1, &mut str);
+        assert_eq!(str, "-");
+        assert_eq!(ret, Ok((LAST_SLICE, "OK")));
+
+        let mut str = String::new();
+        let ret = label_decode(buf4, 1, &mut str);
+        assert_eq!(str, "_");
+        assert_eq!(ret, Ok((LAST_SLICE, "OK")));
+
+        let mut str = String::new();
+        let ret = label_decode(buf5, 1, &mut str);
+        assert_eq!(str, "");
+        assert_ne!(ret, Ok((LAST_SLICE, "OK")));
+    }
+
+    #[test]
+    fn test_dname_decode() {
+        let mut table = DNS_LABEL_TABLE::new();
+
+        // uncompress name: www.example.com
+        let input1 = [
+            0x03, // uncompress and lable length 3
+            0x77, 0x77, 0x77, // www
+            0x07, // lable length 7
+            0x65, 0x78, 0x61, 0x6d, 0x70, 0x6c, 0x65, // example
+            0x03, // lable length 3
+            0x63, 0x6f, 0x6d, // com
+            0x00, // label length 0
+        ];
+
+        let result = dname_decode(&input1, &mut table, 10);
+        assert_eq!(result, Ok((LAST_SLICE, ("www.example.com.", 17))));
+        assert_eq!(table.get(10), Some("www.example.com."));
+
+        // NOTE: second_msg_position >= first_msg_position + data_length
+
+        // compress name: www.example.com
+        let input2 = [0b11000000u8, 0b00001010u8]; // Pointer to 10
+        let result = dname_decode(&input2, &mut table, 50);
+        assert_eq!(result, Ok((LAST_SLICE, ("www.example.com.", 2))));
+        assert_eq!(table.get(50), Some("www.example.com."));
+    }
+
+    /**************************************************************************
+     * test decode query
+     **************************************************************************/
+
+    #[test]
+    fn test_query_a_decode() {
+        /*
+         * dig www.baidu.com
+         *
+         * Domain Name System (query)
+         *     Transaction ID: 0xa59a
+         *     Flags: 0x0120 Standard query
+         *         0... .... .... .... = Response: Message is a query
+         *         .000 0... .... .... = Opcode: Standard query (0)
+         *         .... ..0. .... .... = Truncated: Message is not truncated
+         *         .... ...1 .... .... = Recursion desired: Do query recursively
+         *         .... .... .0.. .... = Z: reserved (0)
+         *         .... .... ..1. .... = AD bit: Set
+         *         .... .... ...0 .... = Non-authenticated data: Unacceptable
+         *     Questions: 1
+         *     Answer RRs: 0
+         *     Authority RRs: 0
+         *     Additional RRs: 1
+         *     Queries
+         *         www.baidu.com: type A, class IN
+         *             Name: www.baidu.com
+         *             [Name Length: 13]
+         *             [Label Count: 3]
+         *             Type: A (Host Address) (1)
+         *             Class: IN (0x0001)
+         *     Additional records
+         *         <Root>: type OPT
+         *             Name: <Root>
+         *             Type: OPT (41)
+         *             UDP payload size: 4096
+         *             Higher bits in extended RCODE: 0x00
+         *             EDNS0 version: 0
+         *             Z: 0x0000
+         *                 0... .... .... .... = DO bit: Cannot handle DNSSEC security RRs
+         *                 .000 0000 0000 0000 = Reserved: 0x0000
+         *             Data length: 0
+         */
+        let bytes = [
+            0xa5, 0x9a, /* Transaction ID: 0xa59a */
+            0x01, 0x20, /* Flags: 0x0120 Standard query */
+            0x00, 0x01, /* Questions: 1 */
+            0x00, 0x00, /* Answer RRs: 0 */
+            0x00, 0x00, /* Authority RRs: 0 */
+            0x00, 0x01, /* Additional RRs: 1 */
+            0x03, 0x77, 0x77, 0x77, 0x05, 0x62, 0x61, 0x69, 0x64, 0x75, 0x03, 0x63, 0x6f, 0x6d,
+            0x00, /* Name: www.baidu.com */
+            0x00, 0x01, /* Type: A (Host Address) (1) */
+            0x00, 0x01, /* Type: A (Host Address) (1) */
+            0x00, /* Name: <Root> */
+            0x00, 0x29, /* Type: OPT (41) */
+            0x10, 0x00, /* UDP payload size: 4096 */
+            0x00, /* Higher bits in extended RCODE: 0x00 */
+            0x00, /* EDNS0 version: 0 */
+            0x00, 0x00, /* Z: 0x0000 */
+            0x00, 0x00, /* Data length: 0 */
+        ];
+
+        let expectation = DNS_MESSAGE {
+            header: DNS_HEADER {
+                id: 0xa59a,
+                qr: DNS_HDR_QR::Query,
+                op_code: DNS_HDR_OPCODE::Query,
+                aa: false,
+                tc: false,
+                rd: true,
+                ra: false,
+                ad: true,
+                cd: false,
+                r_code: DNS_HDR_RCODE::NoError,
+                qd_count: 1,
+                an_count: 0,
+                ns_count: 0,
+                ar_count: 1,
+            },
+            labels: DNS_LABEL_TABLE {
+                labels: vec![
+                    ((12, 15), "www.baidu.com.".to_string()),
+                    ((31, 1), ".".to_string()),
+                ],
+            },
+            qd: vec![DNS_QUESTION_SECTION {
+                qname: "www.baidu.com.".to_string(),
+                qtype: DNS_QTYPE::A,
+                qclass: DNS_QCLASS::Internet,
+                size: 19,
+            }],
+            an: vec![],
+            ns: vec![],
+            ar: vec![
+                (DNS_RR_SECTION {
+                    hdr: DNS_RR_HDR {
+                        qname: ".".to_string(),
+                        rr_type: DNS_QTYPE::OPT,
+                        rr_class: DNS_QCLASS::Other(4096),
+                        ttl: 0,
+                        rd_length: 0,
+                        size: 11,
+                    },
+                    data: DNS_RR_DATA::Other {
+                        qtype: DNS_QTYPE::OPT,
+                        data: vec![],
+                    },
+                }),
+            ],
+        };
+
+        assert_eq!(DNS_MESSAGE::decode(&bytes), Ok((LAST_SLICE, expectation)));
+
+        match DNS_MESSAGE::decode(&bytes) {
+            Ok((left, message)) => {
+                println!("{:?}; left {:?}", message, left);
+            }
+            Err(err) => {
+                println!("{:?}\n", err);
+            }
+        }
+        // assert_eq!(0, 1);
+    }
+
+    #[test]
+    fn test_query_aaaa_decode() {
+        /*
+         * dig www.baidu.com aaaa
+         *
+         * Domain Name System (query)
+         *     Transaction ID: 0xf086
+         *     Flags: 0x0120 Standard query
+         *         0... .... .... .... = Response: Message is a query
+         *         .000 0... .... .... = Opcode: Standard query (0)
+         *         .... ..0. .... .... = Truncated: Message is not truncated
+         *         .... ...1 .... .... = Recursion desired: Do query recursively
+         *         .... .... .0.. .... = Z: reserved (0)
+         *         .... .... ..1. .... = AD bit: Set
+         *         .... .... ...0 .... = Non-authenticated data: Unacceptable
+         *     Questions: 1
+         *     Answer RRs: 0
+         *     Authority RRs: 0
+         *     Additional RRs: 1
+         *     Queries
+         *         www.baidu.com: type AAAA, class IN
+         *             Name: www.baidu.com
+         *             [Name Length: 13]
+         *             [Label Count: 3]
+         *             Type: AAAA (IPv6 Address) (28)
+         *             Class: IN (0x0001)
+         *     Additional records
+         *         <Root>: type OPT
+         *             Name: <Root>
+         *             Type: OPT (41)
+         *             UDP payload size: 4096
+         *             Higher bits in extended RCODE: 0x00
+         *             EDNS0 version: 0
+         *             Z: 0x0000
+         *                 0... .... .... .... = DO bit: Cannot handle DNSSEC security RRs
+         *                 .000 0000 0000 0000 = Reserved: 0x0000
+         *             Data length: 0
+         */
+
+        let bytes = [
+            0xf0, 0x86, /* Transaction ID: 0xf086 */
+            0x01, 0x20, /* Flags: 0x0120 Standard query */
+            0x00, 0x01, /* Questions: 1 */
+            0x00, 0x00, /* Answer RRs: 0 */
+            0x00, 0x00, /* Authority RRs: 0 */
+            0x00, 0x01, /* Additional RRs: 1 */
+            0x03, 0x77, 0x77, 0x77, 0x05, 0x62, 0x61, 0x69, 0x64, 0x75, 0x03, 0x63, 0x6f, 0x6d,
+            0x00, /* Name: www.baidu.com */
+            0x00, 0x1c, /* Type: AAAA (IPv6 Address) (28) */
+            0x00, 0x01, /* Class: IN (0x0001) */
+            0x00, /* Name: <Root> */
+            0x00, 0x29, /* Type: OPT (41) */
+            0x10, 0x00, /* UDP payload size: 4096 */
+            0x00, /* Higher bits in extended RCODE: 0x00 */
+            0x00, /* EDNS0 version: 0 */
+            0x00, 0x00, /* Z: 0x0000 */
+            0x00, 0x00, /* Data length: 0 */
+        ];
+
+        let expectation = DNS_MESSAGE {
+            header: DNS_HEADER {
+                id: 0xf086,
+                qr: DNS_HDR_QR::Query,
+                op_code: DNS_HDR_OPCODE::Query,
+                aa: false,
+                tc: false,
+                rd: true,
+                ra: false,
+                ad: true,
+                cd: false,
+                r_code: DNS_HDR_RCODE::NoError,
+                qd_count: 1,
+                an_count: 0,
+                ns_count: 0,
+                ar_count: 1,
+            },
+            labels: DNS_LABEL_TABLE {
+                labels: vec![
+                    ((12, 15), "www.baidu.com.".to_string()),
+                    ((31, 1), ".".to_string()),
+                ],
+            },
+            qd: vec![DNS_QUESTION_SECTION {
+                qname: "www.baidu.com.".to_string(),
+                qtype: DNS_QTYPE::AAAA,
+                qclass: DNS_QCLASS::Internet,
+                size: 19,
+            }],
+            an: vec![],
+            ns: vec![],
+            ar: vec![
+                (DNS_RR_SECTION {
+                    hdr: DNS_RR_HDR {
+                        qname: ".".to_string(),
+                        rr_type: DNS_QTYPE::OPT,
+                        rr_class: DNS_QCLASS::Other(4096),
+                        ttl: 0,
+                        rd_length: 0,
+                        size: 11,
+                    },
+                    data: DNS_RR_DATA::Other {
+                        qtype: DNS_QTYPE::OPT,
+                        data: vec![],
+                    },
+                }),
+            ],
+        };
+
+        assert_eq!(DNS_MESSAGE::decode(&bytes), Ok((LAST_SLICE, expectation)));
+
+        match DNS_MESSAGE::decode(&bytes) {
+            Ok((left, message)) => {
+                println!("{:?}; left {:?}", message, left);
+            }
+            Err(err) => {
+                println!("{:?}\n", err);
+            }
+        }
+        // assert_eq!(0, 1);
+    }
+
+    #[test]
+    fn test_query_cname_decode() {
+        /*
+         * dig www.baidu.com cname
+         *
+         * Domain Name System (query)
+         *     Transaction ID: 0x61a5
+         *     Flags: 0x0120 Standard query
+         *         0... .... .... .... = Response: Message is a query
+         *         .000 0... .... .... = Opcode: Standard query (0)
+         *         .... ..0. .... .... = Truncated: Message is not truncated
+         *         .... ...1 .... .... = Recursion desired: Do query recursively
+         *         .... .... .0.. .... = Z: reserved (0)
+         *         .... .... ..1. .... = AD bit: Set
+         *         .... .... ...0 .... = Non-authenticated data: Unacceptable
+         *     Questions: 1
+         *     Answer RRs: 0
+         *     Authority RRs: 0
+         *     Additional RRs: 1
+         *     Queries
+         *         www.baidu.com: type CNAME, class IN
+         *             Name: www.baidu.com
+         *             [Name Length: 13]
+         *             [Label Count: 3]
+         *             Type: CNAME (Canonical NAME for an alias) (5)
+         *             Class: IN (0x0001)
+         *     Additional records
+         *         <Root>: type OPT
+         *             Name: <Root>
+         *             Type: OPT (41)
+         *             UDP payload size: 4096
+         *             Higher bits in extended RCODE: 0x00
+         *             EDNS0 version: 0
+         *             Z: 0x0000
+         *                 0... .... .... .... = DO bit: Cannot handle DNSSEC security RRs
+         *                 .000 0000 0000 0000 = Reserved: 0x0000
+         *             Data length: 0
+         */
+
+        let bytes = [
+            0x61, 0xa5, /* Transaction ID: 0x61a5 */
+            0x01, 0x20, /* Flags: 0x0120 Standard query */
+            0x00, 0x01, /* Questions: 1 */
+            0x00, 0x00, /* Answer RRs: 0 */
+            0x00, 0x00, /* Authority RRs: 0 */
+            0x00, 0x01, /* Additional RRs: 1 */
+            0x03, 0x77, 0x77, 0x77, 0x05, 0x62, 0x61, 0x69, 0x64, 0x75, 0x03, 0x63, 0x6f, 0x6d,
+            0x00, /* Name: www.baidu.com */
+            0x00, 0x05, /* Type: CNAME (Canonical NAME for an alias) (5) */
+            0x00, 0x01, /* Class: IN (0x0001) */
+            0x00, /* Name: <Root> */
+            0x00, 0x29, /* Type: OPT (41) */
+            0x10, 0x00, /* UDP payload size: 4096 */
+            0x00, /* Higher bits in extended RCODE: 0x00 */
+            0x00, /* EDNS0 version: 0 */
+            0x00, 0x00, /* Z: 0x0000 */
+            0x00, 0x00, /* Data length: 0 */
+        ];
+
+        let expectation = DNS_MESSAGE {
+            header: DNS_HEADER {
+                id: 0x61a5,
+                qr: DNS_HDR_QR::Query,
+                op_code: DNS_HDR_OPCODE::Query,
+                aa: false,
+                tc: false,
+                rd: true,
+                ra: false,
+                ad: true,
+                cd: false,
+                r_code: DNS_HDR_RCODE::NoError,
+                qd_count: 1,
+                an_count: 0,
+                ns_count: 0,
+                ar_count: 1,
+            },
+            labels: DNS_LABEL_TABLE {
+                labels: vec![
+                    ((12, 15), "www.baidu.com.".to_string()),
+                    ((31, 1), ".".to_string()),
+                ],
+            },
+            qd: vec![DNS_QUESTION_SECTION {
+                qname: "www.baidu.com.".to_string(),
+                qtype: DNS_QTYPE::CNAME,
+                qclass: DNS_QCLASS::Internet,
+                size: 19,
+            }],
+            an: vec![],
+            ns: vec![],
+            ar: vec![
+                (DNS_RR_SECTION {
+                    hdr: DNS_RR_HDR {
+                        qname: ".".to_string(),
+                        rr_type: DNS_QTYPE::OPT,
+                        rr_class: DNS_QCLASS::Other(4096),
+                        ttl: 0,
+                        rd_length: 0,
+                        size: 11,
+                    },
+                    data: DNS_RR_DATA::Other {
+                        qtype: DNS_QTYPE::OPT,
+                        data: vec![],
+                    },
+                }),
+            ],
+        };
+
+        assert_eq!(DNS_MESSAGE::decode(&bytes), Ok((LAST_SLICE, expectation)));
+
+        match DNS_MESSAGE::decode(&bytes) {
+            Ok((left, message)) => {
+                println!("{:?}; left {:?}", message, left);
+            }
+            Err(err) => {
+                println!("{:?}\n", err);
+            }
+        }
+        // assert_eq!(0, 1);
+    }
+
+    // TODO
+    #[test]
+    fn test_query_hinfo_decode() {}
+
+    #[test]
+    fn test_query_mx_decode() {
+        /*
+         * dig 163.com mx
+         *
+         * Domain Name System (query)
+         *     Transaction ID: 0xd35c
+         *     Flags: 0x0120 Standard query
+         *         0... .... .... .... = Response: Message is a query
+         *         .000 0... .... .... = Opcode: Standard query (0)
+         *         .... ..0. .... .... = Truncated: Message is not truncated
+         *         .... ...1 .... .... = Recursion desired: Do query recursively
+         *         .... .... .0.. .... = Z: reserved (0)
+         *         .... .... ..1. .... = AD bit: Set
+         *         .... .... ...0 .... = Non-authenticated data: Unacceptable
+         *     Questions: 1
+         *     Answer RRs: 0
+         *     Authority RRs: 0
+         *     Additional RRs: 1
+         *     Queries
+         *         163.com: type MX, class IN
+         *             Name: 163.com
+         *             [Name Length: 7]
+         *             [Label Count: 2]
+         *             Type: MX (Mail eXchange) (15)
+         *             Class: IN (0x0001)
+         *     Additional records
+         *         <Root>: type OPT
+         *             Name: <Root>
+         *             Type: OPT (41)
+         *             UDP payload size: 4096
+         *             Higher bits in extended RCODE: 0x00
+         *             EDNS0 version: 0
+         *             Z: 0x0000
+         *                 0... .... .... .... = DO bit: Cannot handle DNSSEC security RRs
+         *                 .000 0000 0000 0000 = Reserved: 0x0000
+         *             Data length: 0
+         */
+
+        let bytes = [
+            0xd3, 0x5c, /* Transaction ID: 0xd35c */
+            0x01, 0x20, /* Flags: 0x0120 Standard query */
+            0x00, 0x01, /* Questions: 1 */
+            0x00, 0x00, /* Answer RRs: 0 */
+            0x00, 0x00, /* Authority RRs: 0 */
+            0x00, 0x01, /* Additional RRs: 1 */
+            0x03, 0x31, 0x36, 0x33, 0x03, 0x63, 0x6f, 0x6d, 0x00, /* Name: 163.com */
+            0x00, 0x0f, /* Type: MX (Mail eXchange) (15) */
+            0x00, 0x01, /* Class: IN (0x0001) */
+            0x00, /* Name: <Root> */
+            0x00, 0x29, /* Type: OPT (41) */
+            0x10, 0x00, /* UDP payload size: 4096 */
+            0x00, /* Higher bits in extended RCODE: 0x00 */
+            0x00, /* EDNS0 version: 0 */
+            0x00, 0x00, /* Z: 0x0000 */
+            0x00, 0x00, /* Data length: 0 */
+        ];
+
+        let expectation = DNS_MESSAGE {
+            header: DNS_HEADER {
+                id: 0xd35c,
+                qr: DNS_HDR_QR::Query,
+                op_code: DNS_HDR_OPCODE::Query,
+                aa: false,
+                tc: false,
+                rd: true,
+                ra: false,
+                ad: true,
+                cd: false,
+                r_code: DNS_HDR_RCODE::NoError,
+                qd_count: 1,
+                an_count: 0,
+                ns_count: 0,
+                ar_count: 1,
+            },
+            labels: DNS_LABEL_TABLE {
+                labels: vec![
+                    ((12, 9), "163.com.".to_string()),
+                    ((25, 1), ".".to_string()),
+                ],
+            },
+            qd: vec![DNS_QUESTION_SECTION {
+                qname: "163.com.".to_string(),
+                qtype: DNS_QTYPE::MX,
+                qclass: DNS_QCLASS::Internet,
+                size: 13,
+            }],
+            an: vec![],
+            ns: vec![],
+            ar: vec![
+                (DNS_RR_SECTION {
+                    hdr: DNS_RR_HDR {
+                        qname: ".".to_string(),
+                        rr_type: DNS_QTYPE::OPT,
+                        rr_class: DNS_QCLASS::Other(4096),
+                        ttl: 0,
+                        rd_length: 0,
+                        size: 11,
+                    },
+                    data: DNS_RR_DATA::Other {
+                        qtype: DNS_QTYPE::OPT,
+                        data: vec![],
+                    },
+                }),
+            ],
+        };
+
+        assert_eq!(DNS_MESSAGE::decode(&bytes), Ok((LAST_SLICE, expectation)));
+
+        match DNS_MESSAGE::decode(&bytes) {
+            Ok((left, message)) => {
+                println!("{:?}; left {:?}", message, left);
+            }
+            Err(err) => {
+                println!("{:?}\n", err);
+            }
+        }
+        // assert_eq!(0, 1);
+    }
+
+    // TODO
+    #[test]
+    fn test_query_nx_decode() {}
+
+    // TODO
+    #[test]
+    fn test_query_ptr_decode() {}
+
+    #[test]
+    fn test_query_soa_decode() {
+        /*
+         * dig www.baidu.com soa
+         *
+         * Domain Name System (query)
+         *     Transaction ID: 0xb613
+         *     Flags: 0x0120 Standard query
+         *         0... .... .... .... = Response: Message is a query
+         *         .000 0... .... .... = Opcode: Standard query (0)
+         *         .... ..0. .... .... = Truncated: Message is not truncated
+         *         .... ...1 .... .... = Recursion desired: Do query recursively
+         *         .... .... .0.. .... = Z: reserved (0)
+         *         .... .... ..1. .... = AD bit: Set
+         *         .... .... ...0 .... = Non-authenticated data: Unacceptable
+         *     Questions: 1
+         *     Answer RRs: 0
+         *     Authority RRs: 0
+         *     Additional RRs: 1
+         *     Queries
+         *         www.baidu.com: type SOA, class IN
+         *             Name: www.baidu.com
+         *             [Name Length: 13]
+         *             [Label Count: 3]
+         *             Type: SOA (Start Of a zone of Authority) (6)
+         *             Class: IN (0x0001)
+         *     Additional records
+         *         <Root>: type OPT
+         *             Name: <Root>
+         *             Type: OPT (41)
+         *             UDP payload size: 4096
+         *             Higher bits in extended RCODE: 0x00
+         *             EDNS0 version: 0
+         *             Z: 0x0000
+         *                 0... .... .... .... = DO bit: Cannot handle DNSSEC security RRs
+         *                 .000 0000 0000 0000 = Reserved: 0x0000
+         *             Data length: 0
+         */
+
+        let bytes = [
+            0xb6, 0x13, /* Transaction ID: 0xb613 */
+            0x01, 0x20, /* Flags: 0x0120 Standard query */
+            0x00, 0x01, /* Questions: 1 */
+            0x00, 0x00, /* Answer RRs: 0 */
+            0x00, 0x00, /* Authority RRs: 0 */
+            0x00, 0x01, /* Additional RRs: 1 */
+            0x03, 0x77, 0x77, 0x77, 0x05, 0x62, 0x61, 0x69, 0x64, 0x75, 0x03, 0x63, 0x6f, 0x6d,
+            0x00, /* Name: www.baidu.com */
+            0x00, 0x06, /* Type: SOA (Start Of a zone of Authority) (6) */
+            0x00, 0x01, /* Class: IN (0x0001) */
+            0x00, /* Name: <Root> */
+            0x00, 0x29, /* Type: OPT (41) */
+            0x10, 0x00, /* UDP payload size: 4096 */
+            0x00, /* Higher bits in extended RCODE: 0x00 */
+            0x00, /* EDNS0 version: 0 */
+            0x00, 0x00, /* Z: 0x0000 */
+            0x00, 0x00, /* Data length: 0 */
+        ];
+
+        let expectation = DNS_MESSAGE {
+            header: DNS_HEADER {
+                id: 0xb613,
+                qr: DNS_HDR_QR::Query,
+                op_code: DNS_HDR_OPCODE::Query,
+                aa: false,
+                tc: false,
+                rd: true,
+                ra: false,
+                ad: true,
+                cd: false,
+                r_code: DNS_HDR_RCODE::NoError,
+                qd_count: 1,
+                an_count: 0,
+                ns_count: 0,
+                ar_count: 1,
+            },
+            labels: DNS_LABEL_TABLE {
+                labels: vec![
+                    ((12, 15), "www.baidu.com.".to_string()),
+                    ((31, 1), ".".to_string()),
+                ],
+            },
+            qd: vec![DNS_QUESTION_SECTION {
+                qname: "www.baidu.com.".to_string(),
+                qtype: DNS_QTYPE::SOA,
+                qclass: DNS_QCLASS::Internet,
+                size: 19,
+            }],
+            an: vec![],
+            ns: vec![],
+            ar: vec![
+                (DNS_RR_SECTION {
+                    hdr: DNS_RR_HDR {
+                        qname: ".".to_string(),
+                        rr_type: DNS_QTYPE::OPT,
+                        rr_class: DNS_QCLASS::Other(4096),
+                        ttl: 0,
+                        rd_length: 0,
+                        size: 11,
+                    },
+                    data: DNS_RR_DATA::Other {
+                        qtype: DNS_QTYPE::OPT,
+                        data: vec![],
+                    },
+                }),
+            ],
+        };
+
+        assert_eq!(DNS_MESSAGE::decode(&bytes), Ok((LAST_SLICE, expectation)));
+
+        match DNS_MESSAGE::decode(&bytes) {
+            Ok((left, message)) => {
+                println!("{:?}; left {:?}", message, left);
+            }
+            Err(err) => {
+                println!("{:?}\n", err);
+            }
+        }
+        // assert_eq!(0, 1);
+    }
+
+    #[test]
+    fn test_query_txt_decode() {
+        /*
+         * dig baidu.com txt
+         *
+         * Domain Name System (query)
+         *     Transaction ID: 0x6721
+         *     Flags: 0x0120 Standard query
+         *         0... .... .... .... = Response: Message is a query
+         *         .000 0... .... .... = Opcode: Standard query (0)
+         *         .... ..0. .... .... = Truncated: Message is not truncated
+         *         .... ...1 .... .... = Recursion desired: Do query recursively
+         *         .... .... .0.. .... = Z: reserved (0)
+         *         .... .... ..1. .... = AD bit: Set
+         *         .... .... ...0 .... = Non-authenticated data: Unacceptable
+         *     Questions: 1
+         *     Answer RRs: 0
+         *     Authority RRs: 0
+         *     Additional RRs: 1
+         *     Queries
+         *         baidu.com: type TXT, class IN
+         *             Name: baidu.com
+         *             [Name Length: 9]
+         *             [Label Count: 2]
+         *             Type: TXT (Text strings) (16)
+         *             Class: IN (0x0001)
+         *     Additional records
+         *         <Root>: type OPT
+         *             Name: <Root>
+         *             Type: OPT (41)
+         *             UDP payload size: 4096
+         *             Higher bits in extended RCODE: 0x00
+         *             EDNS0 version: 0
+         *             Z: 0x0000
+         *                 0... .... .... .... = DO bit: Cannot handle DNSSEC security RRs
+         *                 .000 0000 0000 0000 = Reserved: 0x0000
+         *             Data length: 0
+         */
+        let bytes = [
+            0x67, 0x21, /* Transaction ID: 0x6721 */
+            0x01, 0x20, /* Flags: 0x0120 Standard query */
+            0x00, 0x01, /* Questions: 1 */
+            0x00, 0x00, /* Answer RRs: 0 */
+            0x00, 0x00, /* Authority RRs: 0 */
+            0x00, 0x01, /* Additional RRs: 1 */
+            /* Queries */
+            0x05, 0x62, 0x61, 0x69, 0x64, 0x75, 0x03, 0x63, 0x6f, 0x6d,
+            0x00, /* Name: baidu.com */
+            0x00, 0x10, /* Type: TXT (Text strings) (16) */
+            0x00, 0x01, /* Class: IN (0x0001) */
+            /* Additional records */
+            0x00, /* Name: <Root> */
+            0x00, 0x29, /* Type: OPT (41) */
+            0x10, 0x00, /* UDP payload size: 4096 */
+            0x00, /* Higher bits in extended RCODE: 0x00 */
+            0x00, /* EDNS0 version: 0 */
+            0x00, 0x00, /* Z: 0x0000 */
+            0x00, 0x00, /* Data length: 0 */
+        ];
+
+        let expectation = DNS_MESSAGE {
+            header: DNS_HEADER {
+                id: 0x6721,
+                qr: DNS_HDR_QR::Query,
+                op_code: DNS_HDR_OPCODE::Query,
+                aa: false,
+                tc: false,
+                rd: true,
+                ra: false,
+                ad: true,
+                cd: false,
+                r_code: DNS_HDR_RCODE::NoError,
+                qd_count: 1,
+                an_count: 0,
+                ns_count: 0,
+                ar_count: 1,
+            },
+            labels: DNS_LABEL_TABLE {
+                labels: vec![
+                    ((12, 11), "baidu.com.".to_string()),
+                    ((27, 1), ".".to_string()),
+                ],
+            },
+            qd: vec![DNS_QUESTION_SECTION {
+                qname: "baidu.com.".to_string(),
+                qtype: DNS_QTYPE::TXT,
+                qclass: DNS_QCLASS::Internet,
+                size: 15,
+            }],
+            an: vec![],
+            ns: vec![],
+            ar: vec![
+                (DNS_RR_SECTION {
+                    hdr: DNS_RR_HDR {
+                        qname: ".".to_string(),
+                        rr_type: DNS_QTYPE::OPT,
+                        rr_class: DNS_QCLASS::Other(4096),
+                        ttl: 0,
+                        rd_length: 0,
+                        size: 11,
+                    },
+                    data: DNS_RR_DATA::Other {
+                        qtype: DNS_QTYPE::OPT,
+                        data: vec![],
+                    },
+                }),
+            ],
+        };
+
+        assert_eq!(DNS_MESSAGE::decode(&bytes), Ok((LAST_SLICE, expectation)));
+
+        match DNS_MESSAGE::decode(&bytes) {
+            Ok((left, message)) => {
+                println!("{:?}; left {:?}", message, left);
+            }
+            Err(err) => {
+                println!("{:?}\n", err);
+            }
+        }
+        // assert_eq!(0, 1);
+    }
+
+    // TODO
+    #[test]
+    fn test_query_other_decode() {}
+
+    /**************************************************************************
+     * test decode answer
+     **************************************************************************/
+
+    #[test]
+    fn test_answer_a_decode() {
+        // test in test_answer_txt_decode
+    }
+
+    #[test]
+    fn test_answer_aaaa_decode() {
+        // test in test_answer_txt_decode
+    }
+
+    #[test]
+    fn test_answer_ns_decode() {
+        // test in test_answer_txt_decode
+    }
+
+    // TODO
+    #[test]
+    fn test_answer_hinfo_decode() {}
+
+    #[test]
+    fn test_answer_mx_decode() {
+        /*
+         * Domain Name System (response)
+         *     Transaction ID: 0xd35c
+         *     Flags: 0x8180 Standard query response, No error
+         *         1... .... .... .... = Response: Message is a response
+         *         .000 0... .... .... = Opcode: Standard query (0)
+         *         .... .0.. .... .... = Authoritative: Server is not an authority for domain
+         *         .... ..0. .... .... = Truncated: Message is not truncated
+         *         .... ...1 .... .... = Recursion desired: Do query recursively
+         *         .... .... 1... .... = Recursion available: Server can do recursive queries
+         *         .... .... .0.. .... = Z: reserved (0)
+         *         .... .... ..0. .... = Answer authenticated: Answer/authority portion was not authenticated by the server
+         *         .... .... ...0 .... = Non-authenticated data: Unacceptable
+         *         .... .... .... 0000 = Reply code: No error (0)
+         *     Questions: 1
+         *     Answer RRs: 4
+         *     Authority RRs: 7
+         *     Additional RRs: 13
+         *     Queries
+         *         163.com: type MX, class IN
+         *             Name: 163.com
+         *             [Name Length: 7]
+         *             [Label Count: 2]
+         *             Type: MX (Mail eXchange) (15)
+         *             Class: IN (0x0001)
+         *     Answers
+         *         163.com: type MX, class IN, preference 10, mx 163mx02.mxmail.netease.com
+         *             Name: 163.com
+         *             Type: MX (Mail eXchange) (15)
+         *             Class: IN (0x0001)
+         *             Time to live: 12492 (3 hours, 28 minutes, 12 seconds)
+         *             Data length: 27
+         *             Preference: 10
+         *             Mail Exchange: 163mx02.mxmail.netease.com
+         *         163.com: type MX, class IN, preference 50, mx 163mx00.mxmail.netease.com
+         *             Name: 163.com
+         *             Type: MX (Mail eXchange) (15)
+         *             Class: IN (0x0001)
+         *             Time to live: 12492 (3 hours, 28 minutes, 12 seconds)
+         *             Data length: 12
+         *             Preference: 50
+         *             Mail Exchange: 163mx00.mxmail.netease.com
+         *         163.com: type MX, class IN, preference 10, mx 163mx03.mxmail.netease.com
+         *             Name: 163.com
+         *             Type: MX (Mail eXchange) (15)
+         *             Class: IN (0x0001)
+         *             Time to live: 12492 (3 hours, 28 minutes, 12 seconds)
+         *             Data length: 12
+         *             Preference: 10
+         *             Mail Exchange: 163mx03.mxmail.netease.com
+         *         163.com: type MX, class IN, preference 10, mx 163mx01.mxmail.netease.com
+         *             Name: 163.com
+         *             Type: MX (Mail eXchange) (15)
+         *             Class: IN (0x0001)
+         *             Time to live: 12492 (3 hours, 28 minutes, 12 seconds)
+         *             Data length: 12
+         *             Preference: 10
+         *             Mail Exchange: 163mx01.mxmail.netease.com
+         *     Authoritative nameservers
+         *         163.com: type NS, class IN, ns ns5.nease.net
+         *             Name: 163.com
+         *             Type: NS (authoritative Name Server) (2)
+         *             Class: IN (0x0001)
+         *             Time to live: 34967 (9 hours, 42 minutes, 47 seconds)
+         *             Data length: 15
+         *             Name Server: ns5.nease.net
+         *         163.com: type NS, class IN, ns ns3.nease.net
+         *             Name: 163.com
+         *             Type: NS (authoritative Name Server) (2)
+         *             Class: IN (0x0001)
+         *             Time to live: 34967 (9 hours, 42 minutes, 47 seconds)
+         *             Data length: 6
+         *             Name Server: ns3.nease.net
+         *         163.com: type NS, class IN, ns ns1.nease.net
+         *             Name: 163.com
+         *             Type: NS (authoritative Name Server) (2)
+         *             Class: IN (0x0001)
+         *             Time to live: 34967 (9 hours, 42 minutes, 47 seconds)
+         *             Data length: 6
+         *             Name Server: ns1.nease.net
+         *         163.com: type NS, class IN, ns ns8.166.com
+         *             Name: 163.com
+         *             Type: NS (authoritative Name Server) (2)
+         *             Class: IN (0x0001)
+         *             Time to live: 34967 (9 hours, 42 minutes, 47 seconds)
+         *             Data length: 10
+         *             Name Server: ns8.166.com
+         *         163.com: type NS, class IN, ns ns4.nease.net
+         *             Name: 163.com
+         *             Type: NS (authoritative Name Server) (2)
+         *             Class: IN (0x0001)
+         *             Time to live: 34967 (9 hours, 42 minutes, 47 seconds)
+         *             Data length: 6
+         *             Name Server: ns4.nease.net
+         *         163.com: type NS, class IN, ns ns2.166.com
+         *             Name: 163.com
+         *             Type: NS (authoritative Name Server) (2)
+         *             Class: IN (0x0001)
+         *             Time to live: 34967 (9 hours, 42 minutes, 47 seconds)
+         *             Data length: 6
+         *             Name Server: ns2.166.com
+         *         163.com: type NS, class IN, ns ns6.nease.net
+         *             Name: 163.com
+         *             Type: NS (authoritative Name Server) (2)
+         *             Class: IN (0x0001)
+         *             Time to live: 34967 (9 hours, 42 minutes, 47 seconds)
+         *             Data length: 6
+         *             Name Server: ns6.nease.net
+         *     Additional records
+         *         163mx03.mxmail.netease.com: type A, class IN, addr 220.181.12.119
+         *             Name: 163mx03.mxmail.netease.com
+         *             Type: A (Host Address) (1)
+         *             Class: IN (0x0001)
+         *             Time to live: 442 (7 minutes, 22 seconds)
+         *             Data length: 4
+         *             Address: 220.181.12.119
+         *         163mx01.mxmail.netease.com: type A, class IN, addr 220.181.12.117
+         *             Name: 163mx01.mxmail.netease.com
+         *             Type: A (Host Address) (1)
+         *             Class: IN (0x0001)
+         *             Time to live: 442 (7 minutes, 22 seconds)
+         *             Data length: 4
+         *             Address: 220.181.12.117
+         *         163mx02.mxmail.netease.com: type A, class IN, addr 220.181.12.118
+         *             Name: 163mx02.mxmail.netease.com
+         *             Type: A (Host Address) (1)
+         *             Class: IN (0x0001)
+         *             Time to live: 442 (7 minutes, 22 seconds)
+         *             Data length: 4
+         *             Address: 220.181.12.118
+         *         163mx00.mxmail.netease.com: type A, class IN, addr 220.181.12.180
+         *             Name: 163mx00.mxmail.netease.com
+         *             Type: A (Host Address) (1)
+         *             Class: IN (0x0001)
+         *             Time to live: 442 (7 minutes, 22 seconds)
+         *             Data length: 4
+         *             Address: 220.181.12.180
+         *         ns6.nease.net: type A, class IN, addr 54.228.156.72
+         *             Name: ns6.nease.net
+         *             Type: A (Host Address) (1)
+         *             Class: IN (0x0001)
+         *             Time to live: 5583 (1 hour, 33 minutes, 3 seconds)
+         *             Data length: 4
+         *             Address: 54.228.156.72
+         *         ns1.nease.net: type A, class IN, addr 42.186.35.222
+         *             Name: ns1.nease.net
+         *             Type: A (Host Address) (1)
+         *             Class: IN (0x0001)
+         *             Time to live: 32644 (9 hours, 4 minutes, 4 seconds)
+         *             Data length: 4
+         *             Address: 42.186.35.222
+         *         ns4.nease.net: type A, class IN, addr 103.72.16.81
+         *             Name: ns4.nease.net
+         *             Type: A (Host Address) (1)
+         *             Class: IN (0x0001)
+         *             Time to live: 51974 (14 hours, 26 minutes, 14 seconds)
+         *             Data length: 4
+         *             Address: 103.72.16.81
+         *         ns3.nease.net: type A, class IN, addr 220.181.36.234
+         *             Name: ns3.nease.net
+         *             Type: A (Host Address) (1)
+         *             Class: IN (0x0001)
+         *             Time to live: 41374 (11 hours, 29 minutes, 34 seconds)
+         *             Data length: 4
+         *             Address: 220.181.36.234
+         *         ns2.166.com: type A, class IN, addr 103.71.201.3
+         *             Name: ns2.166.com
+         *             Type: A (Host Address) (1)
+         *             Class: IN (0x0001)
+         *             Time to live: 73500 (20 hours, 25 minutes)
+         *             Data length: 4
+         *             Address: 103.71.201.3
+         *         ns5.nease.net: type A, class IN, addr 121.195.179.18
+         *             Name: ns5.nease.net
+         *             Type: A (Host Address) (1)
+         *             Class: IN (0x0001)
+         *             Time to live: 34614 (9 hours, 36 minutes, 54 seconds)
+         *             Data length: 4
+         *             Address: 121.195.179.18
+         *         ns8.166.com: type A, class IN, addr 18.182.82.158
+         *             Name: ns8.166.com
+         *             Type: A (Host Address) (1)
+         *             Class: IN (0x0001)
+         *             Time to live: 64949 (18 hours, 2 minutes, 29 seconds)
+         *             Data length: 4
+         *             Address: 18.182.82.158
+         *         ns8.166.com: type A, class IN, addr 44.228.163.69
+         *             Name: ns8.166.com
+         *             Type: A (Host Address) (1)
+         *             Class: IN (0x0001)
+         *             Time to live: 64949 (18 hours, 2 minutes, 29 seconds)
+         *             Data length: 4
+         *             Address: 44.228.163.69
+         *         <Root>: type OPT
+         *             Name: <Root>
+         *             Type: OPT (41)
+         *             UDP payload size: 4096
+         *             Higher bits in extended RCODE: 0x00
+         *             EDNS0 version: 0
+         *             Z: 0x0000
+         *                 0... .... .... .... = DO bit: Cannot handle DNSSEC security RRs
+         *                 .000 0000 0000 0000 = Reserved: 0x0000
+         *             Data length: 0
+         */
+
+        let bytes = [
+            0xd3, 0x5c, 0x81, 0x80, 0x00, 0x01, 0x00, 0x04, 0x00, 0x07, 0x00, 0x0d, 0x03, 0x31,
+            0x36, 0x33, 0x03, 0x63, 0x6f, 0x6d, 0x00, 0x00, 0x0f, 0x00, 0x01, 0xc0, 0x0c, 0x00,
+            0x0f, 0x00, 0x01, 0x00, 0x00, 0x30, 0xcc, 0x00, 0x1b, 0x00, 0x0a, 0x07, 0x31, 0x36,
+            0x33, 0x6d, 0x78, 0x30, 0x32, 0x06, 0x6d, 0x78, 0x6d, 0x61, 0x69, 0x6c, 0x07, 0x6e,
+            0x65, 0x74, 0x65, 0x61, 0x73, 0x65, 0xc0, 0x10, 0xc0, 0x0c, 0x00, 0x0f, 0x00, 0x01,
+            0x00, 0x00, 0x30, 0xcc, 0x00, 0x0c, 0x00, 0x32, 0x07, 0x31, 0x36, 0x33, 0x6d, 0x78,
+            0x30, 0x30, 0xc0, 0x2f, 0xc0, 0x0c, 0x00, 0x0f, 0x00, 0x01, 0x00, 0x00, 0x30, 0xcc,
+            0x00, 0x0c, 0x00, 0x0a, 0x07, 0x31, 0x36, 0x33, 0x6d, 0x78, 0x30, 0x33, 0xc0, 0x2f,
+            0xc0, 0x0c, 0x00, 0x0f, 0x00, 0x01, 0x00, 0x00, 0x30, 0xcc, 0x00, 0x0c, 0x00, 0x0a,
+            0x07, 0x31, 0x36, 0x33, 0x6d, 0x78, 0x30, 0x31, 0xc0, 0x2f, 0xc0, 0x0c, 0x00, 0x02,
+            0x00, 0x01, 0x00, 0x00, 0x88, 0x97, 0x00, 0x0f, 0x03, 0x6e, 0x73, 0x35, 0x05, 0x6e,
+            0x65, 0x61, 0x73, 0x65, 0x03, 0x6e, 0x65, 0x74, 0x00, 0xc0, 0x0c, 0x00, 0x02, 0x00,
+            0x01, 0x00, 0x00, 0x88, 0x97, 0x00, 0x06, 0x03, 0x6e, 0x73, 0x33, 0xc0, 0x98, 0xc0,
+            0x0c, 0x00, 0x02, 0x00, 0x01, 0x00, 0x00, 0x88, 0x97, 0x00, 0x06, 0x03, 0x6e, 0x73,
+            0x31, 0xc0, 0x98, 0xc0, 0x0c, 0x00, 0x02, 0x00, 0x01, 0x00, 0x00, 0x88, 0x97, 0x00,
+            0x0a, 0x03, 0x6e, 0x73, 0x38, 0x03, 0x31, 0x36, 0x36, 0xc0, 0x10, 0xc0, 0x0c, 0x00,
+            0x02, 0x00, 0x01, 0x00, 0x00, 0x88, 0x97, 0x00, 0x06, 0x03, 0x6e, 0x73, 0x34, 0xc0,
+            0x98, 0xc0, 0x0c, 0x00, 0x02, 0x00, 0x01, 0x00, 0x00, 0x88, 0x97, 0x00, 0x06, 0x03,
+            0x6e, 0x73, 0x32, 0xc0, 0xd7, 0xc0, 0x0c, 0x00, 0x02, 0x00, 0x01, 0x00, 0x00, 0x88,
+            0x97, 0x00, 0x06, 0x03, 0x6e, 0x73, 0x36, 0xc0, 0x98, 0xc0, 0x66, 0x00, 0x01, 0x00,
+            0x01, 0x00, 0x00, 0x01, 0xba, 0x00, 0x04, 0xdc, 0xb5, 0x0c, 0x77, 0xc0, 0x7e, 0x00,
+            0x01, 0x00, 0x01, 0x00, 0x00, 0x01, 0xba, 0x00, 0x04, 0xdc, 0xb5, 0x0c, 0x75, 0xc0,
+            0x27, 0x00, 0x01, 0x00, 0x01, 0x00, 0x00, 0x01, 0xba, 0x00, 0x04, 0xdc, 0xb5, 0x0c,
+            0x76, 0xc0, 0x4e, 0x00, 0x01, 0x00, 0x01, 0x00, 0x00, 0x01, 0xba, 0x00, 0x04, 0xdc,
+            0xb5, 0x0c, 0xb4, 0xc1, 0x0d, 0x00, 0x01, 0x00, 0x01, 0x00, 0x00, 0x15, 0xcf, 0x00,
+            0x04, 0x36, 0xe4, 0x9c, 0x48, 0xc0, 0xc1, 0x00, 0x01, 0x00, 0x01, 0x00, 0x00, 0x7f,
+            0x84, 0x00, 0x04, 0x2a, 0xba, 0x23, 0xde, 0xc0, 0xe9, 0x00, 0x01, 0x00, 0x01, 0x00,
+            0x00, 0xcb, 0x06, 0x00, 0x04, 0x67, 0x48, 0x10, 0x51, 0xc0, 0xaf, 0x00, 0x01, 0x00,
+            0x01, 0x00, 0x00, 0xa1, 0x9e, 0x00, 0x04, 0xdc, 0xb5, 0x24, 0xea, 0xc0, 0xfb, 0x00,
+            0x01, 0x00, 0x01, 0x00, 0x01, 0x1f, 0x1c, 0x00, 0x04, 0x67, 0x47, 0xc9, 0x03, 0xc0,
+            0x94, 0x00, 0x01, 0x00, 0x01, 0x00, 0x00, 0x87, 0x36, 0x00, 0x04, 0x79, 0xc3, 0xb3,
+            0x12, 0xc0, 0xd3, 0x00, 0x01, 0x00, 0x01, 0x00, 0x00, 0xfd, 0xb5, 0x00, 0x04, 0x12,
+            0xb6, 0x52, 0x9e, 0xc0, 0xd3, 0x00, 0x01, 0x00, 0x01, 0x00, 0x00, 0xfd, 0xb5, 0x00,
+            0x04, 0x2c, 0xe4, 0xa3, 0x45, 0x00, 0x00, 0x29, 0x10, 0x00, 0x00, 0x00, 0x00, 0x00,
+            0x00, 0x00,
+        ];
+
+        let expectation = DNS_MESSAGE {
+            header: DNS_HEADER {
+                id: 0xd35c,
+                qr: DNS_HDR_QR::Response,
+                op_code: DNS_HDR_OPCODE::Query,
+                aa: false,
+                tc: false,
+                rd: true,
+                ra: true,
+                ad: false,
+                cd: false,
+                r_code: DNS_HDR_RCODE::NoError,
+                qd_count: 1,
+                an_count: 4,
+                ns_count: 7,
+                ar_count: 13,
+            },
+            labels: DNS_LABEL_TABLE {
+                labels: vec![
+                    ((12, 9), "163.com.".to_string()),
+                    ((25, 2), "163.com.".to_string()),
+                    ((39, 25), "163mx02.mxmail.netease.com.".to_string()),
+                    ((64, 2), "163.com.".to_string()),
+                    ((78, 10), "163mx00.mxmail.netease.com.".to_string()),
+                    ((88, 2), "163.com.".to_string()),
+                    ((102, 10), "163mx03.mxmail.netease.com.".to_string()),
+                    ((112, 2), "163.com.".to_string()),
+                    ((126, 10), "163mx01.mxmail.netease.com.".to_string()),
+                    ((136, 2), "163.com.".to_string()),
+                    ((148, 15), "ns5.nease.net.".to_string()),
+                    ((163, 2), "163.com.".to_string()),
+                    ((175, 6), "ns3.nease.net.".to_string()),
+                    ((181, 2), "163.com.".to_string()),
+                    ((193, 6), "ns1.nease.net.".to_string()),
+                    ((199, 2), "163.com.".to_string()),
+                    ((211, 10), "ns8.166.com.".to_string()),
+                    ((221, 2), "163.com.".to_string()),
+                    ((233, 6), "ns4.nease.net.".to_string()),
+                    ((239, 2), "163.com.".to_string()),
+                    ((251, 6), "ns2.166.com.".to_string()),
+                    ((257, 2), "163.com.".to_string()),
+                    ((269, 6), "ns6.nease.net.".to_string()),
+                    ((275, 2), "163mx03.mxmail.netease.com.".to_string()),
+                    ((291, 2), "163mx01.mxmail.netease.com.".to_string()),
+                    ((307, 2), "163mx02.mxmail.netease.com.".to_string()),
+                    ((323, 2), "163mx00.mxmail.netease.com.".to_string()),
+                    ((339, 2), "ns6.nease.net.".to_string()),
+                    ((355, 2), "ns1.nease.net.".to_string()),
+                    ((371, 2), "ns4.nease.net.".to_string()),
+                    ((387, 2), "ns3.nease.net.".to_string()),
+                    ((403, 2), "ns2.166.com.".to_string()),
+                    ((419, 2), "ns5.nease.net.".to_string()),
+                    ((435, 2), "ns8.166.com.".to_string()),
+                    ((451, 2), "ns8.166.com.".to_string()),
+                    ((467, 1), ".".to_string()),
+                ],
+            },
+            qd: vec![DNS_QUESTION_SECTION {
+                qname: "163.com.".to_string(),
+                qtype: DNS_QTYPE::MX,
+                qclass: DNS_QCLASS::Internet,
+                size: 13,
+            }],
+            an: vec![
+                (DNS_RR_SECTION {
+                    hdr: DNS_RR_HDR {
+                        qname: "163.com.".to_string(),
+                        rr_type: DNS_QTYPE::MX,
+                        rr_class: DNS_QCLASS::Internet,
+                        ttl: 12492,
+                        rd_length: 27,
+                        size: 12,
+                    },
+                    data: DNS_RR_DATA::MX {
+                        preference: 10,
+                        exchange: "163mx02.mxmail.netease.com.".to_string(),
+                    },
+                }),
+                (DNS_RR_SECTION {
+                    hdr: DNS_RR_HDR {
+                        qname: "163.com.".to_string(),
+                        rr_type: DNS_QTYPE::MX,
+                        rr_class: DNS_QCLASS::Internet,
+                        ttl: 12492,
+                        rd_length: 12,
+                        size: 12,
+                    },
+                    data: DNS_RR_DATA::MX {
+                        preference: 50,
+                        exchange: "163mx00.mxmail.netease.com.".to_string(),
+                    },
+                }),
+                (DNS_RR_SECTION {
+                    hdr: DNS_RR_HDR {
+                        qname: "163.com.".to_string(),
+                        rr_type: DNS_QTYPE::MX,
+                        rr_class: DNS_QCLASS::Internet,
+                        ttl: 12492,
+                        rd_length: 12,
+                        size: 12,
+                    },
+                    data: DNS_RR_DATA::MX {
+                        preference: 10,
+                        exchange: "163mx03.mxmail.netease.com.".to_string(),
+                    },
+                }),
+                (DNS_RR_SECTION {
+                    hdr: DNS_RR_HDR {
+                        qname: "163.com.".to_string(),
+                        rr_type: DNS_QTYPE::MX,
+                        rr_class: DNS_QCLASS::Internet,
+                        ttl: 12492,
+                        rd_length: 12,
+                        size: 12,
+                    },
+                    data: DNS_RR_DATA::MX {
+                        preference: 10,
+                        exchange: "163mx01.mxmail.netease.com.".to_string(),
+                    },
+                }),
+            ],
+            ns: vec![
+                (DNS_RR_SECTION {
+                    hdr: DNS_RR_HDR {
+                        qname: "163.com.".to_string(),
+                        rr_type: DNS_QTYPE::NS,
+                        rr_class: DNS_QCLASS::Internet,
+                        ttl: 34967,
+                        rd_length: 15,
+                        size: 12,
+                    },
+                    data: DNS_RR_DATA::NS {
+                        nsdname: "ns5.nease.net.".to_string(),
+                    },
+                }),
+                (DNS_RR_SECTION {
+                    hdr: DNS_RR_HDR {
+                        qname: "163.com.".to_string(),
+                        rr_type: DNS_QTYPE::NS,
+                        rr_class: DNS_QCLASS::Internet,
+                        ttl: 34967,
+                        rd_length: 6,
+                        size: 12,
+                    },
+                    data: DNS_RR_DATA::NS {
+                        nsdname: "ns3.nease.net.".to_string(),
+                    },
+                }),
+                (DNS_RR_SECTION {
+                    hdr: DNS_RR_HDR {
+                        qname: "163.com.".to_string(),
+                        rr_type: DNS_QTYPE::NS,
+                        rr_class: DNS_QCLASS::Internet,
+                        ttl: 34967,
+                        rd_length: 6,
+                        size: 12,
+                    },
+                    data: DNS_RR_DATA::NS {
+                        nsdname: "ns1.nease.net.".to_string(),
+                    },
+                }),
+                (DNS_RR_SECTION {
+                    hdr: DNS_RR_HDR {
+                        qname: "163.com.".to_string(),
+                        rr_type: DNS_QTYPE::NS,
+                        rr_class: DNS_QCLASS::Internet,
+                        ttl: 34967,
+                        rd_length: 10,
+                        size: 12,
+                    },
+                    data: DNS_RR_DATA::NS {
+                        nsdname: "ns8.166.com.".to_string(),
+                    },
+                }),
+                (DNS_RR_SECTION {
+                    hdr: DNS_RR_HDR {
+                        qname: "163.com.".to_string(),
+                        rr_type: DNS_QTYPE::NS,
+                        rr_class: DNS_QCLASS::Internet,
+                        ttl: 34967,
+                        rd_length: 6,
+                        size: 12,
+                    },
+                    data: DNS_RR_DATA::NS {
+                        nsdname: "ns4.nease.net.".to_string(),
+                    },
+                }),
+                (DNS_RR_SECTION {
+                    hdr: DNS_RR_HDR {
+                        qname: "163.com.".to_string(),
+                        rr_type: DNS_QTYPE::NS,
+                        rr_class: DNS_QCLASS::Internet,
+                        ttl: 34967,
+                        rd_length: 6,
+                        size: 12,
+                    },
+                    data: DNS_RR_DATA::NS {
+                        nsdname: "ns2.166.com.".to_string(),
+                    },
+                }),
+                (DNS_RR_SECTION {
+                    hdr: DNS_RR_HDR {
+                        qname: "163.com.".to_string(),
+                        rr_type: DNS_QTYPE::NS,
+                        rr_class: DNS_QCLASS::Internet,
+                        ttl: 34967,
+                        rd_length: 6,
+                        size: 12,
+                    },
+                    data: DNS_RR_DATA::NS {
+                        nsdname: "ns6.nease.net.".to_string(),
+                    },
+                }),
+            ],
+            ar: vec![
+                (DNS_RR_SECTION {
+                    hdr: DNS_RR_HDR {
+                        qname: "163mx03.mxmail.netease.com.".to_string(),
+                        rr_type: DNS_QTYPE::A,
+                        rr_class: DNS_QCLASS::Internet,
+                        ttl: 442,
+                        rd_length: 4,
+                        size: 12,
+                    },
+                    data: DNS_RR_DATA::A {
+                        address: "220.181.12.119".to_string(),
+                    },
+                }),
+                (DNS_RR_SECTION {
+                    hdr: DNS_RR_HDR {
+                        qname: "163mx01.mxmail.netease.com.".to_string(),
+                        rr_type: DNS_QTYPE::A,
+                        rr_class: DNS_QCLASS::Internet,
+                        ttl: 442,
+                        rd_length: 4,
+                        size: 12,
+                    },
+                    data: DNS_RR_DATA::A {
+                        address: "220.181.12.117".to_string(),
+                    },
+                }),
+                (DNS_RR_SECTION {
+                    hdr: DNS_RR_HDR {
+                        qname: "163mx02.mxmail.netease.com.".to_string(),
+                        rr_type: DNS_QTYPE::A,
+                        rr_class: DNS_QCLASS::Internet,
+                        ttl: 442,
+                        rd_length: 4,
+                        size: 12,
+                    },
+                    data: DNS_RR_DATA::A {
+                        address: "220.181.12.118".to_string(),
+                    },
+                }),
+                (DNS_RR_SECTION {
+                    hdr: DNS_RR_HDR {
+                        qname: "163mx00.mxmail.netease.com.".to_string(),
+                        rr_type: DNS_QTYPE::A,
+                        rr_class: DNS_QCLASS::Internet,
+                        ttl: 442,
+                        rd_length: 4,
+                        size: 12,
+                    },
+                    data: DNS_RR_DATA::A {
+                        address: "220.181.12.180".to_string(),
+                    },
+                }),
+                (DNS_RR_SECTION {
+                    hdr: DNS_RR_HDR {
+                        qname: "ns6.nease.net.".to_string(),
+                        rr_type: DNS_QTYPE::A,
+                        rr_class: DNS_QCLASS::Internet,
+                        ttl: 5583,
+                        rd_length: 4,
+                        size: 12,
+                    },
+                    data: DNS_RR_DATA::A {
+                        address: "54.228.156.72".to_string(),
+                    },
+                }),
+                (DNS_RR_SECTION {
+                    hdr: DNS_RR_HDR {
+                        qname: "ns1.nease.net.".to_string(),
+                        rr_type: DNS_QTYPE::A,
+                        rr_class: DNS_QCLASS::Internet,
+                        ttl: 32644,
+                        rd_length: 4,
+                        size: 12,
+                    },
+                    data: DNS_RR_DATA::A {
+                        address: "42.186.35.222".to_string(),
+                    },
+                }),
+                (DNS_RR_SECTION {
+                    hdr: DNS_RR_HDR {
+                        qname: "ns4.nease.net.".to_string(),
+                        rr_type: DNS_QTYPE::A,
+                        rr_class: DNS_QCLASS::Internet,
+                        ttl: 51974,
+                        rd_length: 4,
+                        size: 12,
+                    },
+                    data: DNS_RR_DATA::A {
+                        address: "103.72.16.81".to_string(),
+                    },
+                }),
+                (DNS_RR_SECTION {
+                    hdr: DNS_RR_HDR {
+                        qname: "ns3.nease.net.".to_string(),
+                        rr_type: DNS_QTYPE::A,
+                        rr_class: DNS_QCLASS::Internet,
+                        ttl: 41374,
+                        rd_length: 4,
+                        size: 12,
+                    },
+                    data: DNS_RR_DATA::A {
+                        address: "220.181.36.234".to_string(),
+                    },
+                }),
+                (DNS_RR_SECTION {
+                    hdr: DNS_RR_HDR {
+                        qname: "ns2.166.com.".to_string(),
+                        rr_type: DNS_QTYPE::A,
+                        rr_class: DNS_QCLASS::Internet,
+                        ttl: 73500,
+                        rd_length: 4,
+                        size: 12,
+                    },
+                    data: DNS_RR_DATA::A {
+                        address: "103.71.201.3".to_string(),
+                    },
+                }),
+                (DNS_RR_SECTION {
+                    hdr: DNS_RR_HDR {
+                        qname: "ns5.nease.net.".to_string(),
+                        rr_type: DNS_QTYPE::A,
+                        rr_class: DNS_QCLASS::Internet,
+                        ttl: 34614,
+                        rd_length: 4,
+                        size: 12,
+                    },
+                    data: DNS_RR_DATA::A {
+                        address: "121.195.179.18".to_string(),
+                    },
+                }),
+                (DNS_RR_SECTION {
+                    hdr: DNS_RR_HDR {
+                        qname: "ns8.166.com.".to_string(),
+                        rr_type: DNS_QTYPE::A,
+                        rr_class: DNS_QCLASS::Internet,
+                        ttl: 64949,
+                        rd_length: 4,
+                        size: 12,
+                    },
+                    data: DNS_RR_DATA::A {
+                        address: "18.182.82.158".to_string(),
+                    },
+                }),
+                (DNS_RR_SECTION {
+                    hdr: DNS_RR_HDR {
+                        qname: "ns8.166.com.".to_string(),
+                        rr_type: DNS_QTYPE::A,
+                        rr_class: DNS_QCLASS::Internet,
+                        ttl: 64949,
+                        rd_length: 4,
+                        size: 12,
+                    },
+                    data: DNS_RR_DATA::A {
+                        address: "44.228.163.69".to_string(),
+                    },
+                }),
+                (DNS_RR_SECTION {
+                    hdr: DNS_RR_HDR {
+                        qname: ".".to_string(),
+                        rr_type: DNS_QTYPE::OPT,
+                        rr_class: DNS_QCLASS::Other(4096),
+                        ttl: 0,
+                        rd_length: 0,
+                        size: 11,
+                    },
+                    data: DNS_RR_DATA::Other {
+                        qtype: DNS_QTYPE::OPT,
+                        data: vec![],
+                    },
+                }),
+            ],
+        };
+
+        assert_eq!(DNS_MESSAGE::decode(&bytes), Ok((LAST_SLICE, expectation)));
+
+        match DNS_MESSAGE::decode(&bytes) {
+            Ok((left, message)) => {
+                println!("{:?}; left {:?}", message, left);
+            }
+            Err(err) => {
+                println!("{:?}\n", err);
+            }
+        }
+        // assert_eq!(0, 1);
+    }
+
+    // TODO
+    #[test]
+    fn dns_answer_nx() {}
+
+    // TODO
+    #[test]
+    fn test_answer_ptr_decode() {}
+
+    #[test]
+    fn test_answer_cname_decode() {
+        // test in test_answer_soa_decode
+    }
+
+    #[test]
+    fn test_answer_soa_decode() {
+        /*
+         * Domain Name System (response)
+         *     Transaction ID: 0xb613
+         *     Flags: 0x8180 Standard query response, No error
+         *         1... .... .... .... = Response: Message is a response
+         *         .000 0... .... .... = Opcode: Standard query (0)
+         *         .... .0.. .... .... = Authoritative: Server is not an authority for domain
+         *         .... ..0. .... .... = Truncated: Message is not truncated
+         *         .... ...1 .... .... = Recursion desired: Do query recursively
+         *         .... .... 1... .... = Recursion available: Server can do recursive queries
+         *         .... .... .0.. .... = Z: reserved (0)
+         *         .... .... ..0. .... = Answer authenticated: Answer/authority portion was not authenticated by the server
+         *         .... .... ...0 .... = Non-authenticated data: Unacceptable
+         *         .... .... .... 0000 = Reply code: No error (0)
+         *     Questions: 1
+         *     Answer RRs: 1
+         *     Authority RRs: 1
+         *     Additional RRs: 1
+         *     Queries
+         *         www.baidu.com: type SOA, class IN
+         *             Name: www.baidu.com
+         *             [Name Length: 13]
+         *             [Label Count: 3]
+         *             Type: SOA (Start Of a zone of Authority) (6)
+         *             Class: IN (0x0001)
+         *     Answers
+         *         www.baidu.com: type CNAME, class IN, cname www.a.shifen.com
+         *             Name: www.baidu.com
+         *             Type: CNAME (Canonical NAME for an alias) (5)
+         *             Class: IN (0x0001)
+         *             Time to live: 221 (3 minutes, 41 seconds)
+         *             Data length: 15
+         *             CNAME: www.a.shifen.com
+         *     Authoritative nameservers
+         *         a.shifen.com: type SOA, class IN, mname ns1.a.shifen.com
+         *             Name: a.shifen.com
+         *             Type: SOA (Start Of a zone of Authority) (6)
+         *             Class: IN (0x0001)
+         *             Time to live: 296 (4 minutes, 56 seconds)
+         *             Data length: 45
+         *             Primary name server: ns1.a.shifen.com
+         *             Responsible authority's mailbox: baidu_dns_master.baidu.com
+         *             Serial Number: 2211240019
+         *             Refresh Interval: 5 (5 seconds)
+         *             Retry Interval: 5 (5 seconds)
+         *             Expire limit: 2592000 (30 days)
+         *             Minimum TTL: 3600 (1 hour)
+         *     Additional records
+         *         <Root>: type OPT
+         *             Name: <Root>
+         *             Type: OPT (41)
+         *             UDP payload size: 4096
+         *             Higher bits in extended RCODE: 0x00
+         *             EDNS0 version: 0
+         *             Z: 0x0000
+         *                 0... .... .... .... = DO bit: Cannot handle DNSSEC security RRs
+         *                 .000 0000 0000 0000 = Reserved: 0x0000
+         *             Data length: 0
+         *     [Request In: 14]
+         *     [Time: 0.075849000 seconds]
+         */
+
+        let bytes = [
+            0xb6, 0x13, /* Transaction ID: 0xb613 */
+            0x81, 0x80, /* Flags: 0x8180 Standard query response, No error */
+            0x00, 0x01, /* Questions: 1 */
+            0x00, 0x01, /* Answer RRs: 1 */
+            0x00, 0x01, /* Authority RRs: 1 */
+            0x00, 0x01, /* Additional RRs: 1 */
+            /* Queries */
+            0x03, 0x77, 0x77, 0x77, 0x05, 0x62, 0x61, 0x69, 0x64, 0x75, 0x03, 0x63, 0x6f, 0x6d,
+            0x00, /* Name: www.baidu.com */
+            0x00, 0x06, /* Type: SOA (Start Of a zone of Authority) (6) */
+            0x00, 0x01, /* Class: IN (0x0001) */
+            /* Answers */
+            0xc0, 0x0c, /*  Name: www.baidu.com */
+            0x00, 0x05, /* Type: CNAME (Canonical NAME for an alias) (5) */
+            0x00, 0x01, /* Class: IN (0x0001) */
+            0x00, 0x00, 0x00, 0xdd, /* Time to live: 221 (3 minutes, 41 seconds) */
+            0x00, 0x0f, /*  Data length: 15 */
+            0x03, 0x77, 0x77, 0x77, 0x01, 0x61, 0x06, 0x73, 0x68, 0x69, 0x66, 0x65, 0x6e, 0xc0,
+            0x16, /* CNAME: www.a.shifen.com */
+            /* Authoritative nameservers */
+            0xc0, 0x2f, /* Name: a.shifen.com */
+            0x00, 0x06, /*  Type: SOA (Start Of a zone of Authority) (6) */
+            0x00, 0x01, /* Class: IN (0x0001) */
+            0x00, 0x00, 0x01, 0x28, /* Time to live: 296 (4 minutes, 56 seconds) */
+            0x00, 0x2d, /*  Data length: 45 */
+            0x03, 0x6e, 0x73, 0x31, 0xc0, 0x2f, /* Primary name server: ns1.a.shifen.com */
+            0x10, 0x62, 0x61, 0x69, 0x64, 0x75, 0x5f, 0x64, 0x6e, 0x73, 0x5f, 0x6d, 0x61, 0x73,
+            0x74, 0x65, 0x72, 0xc0,
+            0x10, /* Responsible authority's mailbox: baidu_dns_master.baidu.com */
+            0x83, 0xcc, 0xd8, 0x53, /* Serial Number: 2211240019 */
+            0x00, 0x00, 0x00, 0x05, /* Refresh Interval: 5 (5 seconds) */
+            0x00, 0x00, 0x00, 0x05, /* Retry Interval: 5 (5 seconds) */
+            0x00, 0x27, 0x8d, 0x00, /* Expire limit: 2592000 (30 days) */
+            0x00, 0x00, 0x0e, 0x10, /* Minimum TTL: 3600 (1 hour) */
+            /*  Additional records */
+            0x00, /* Name: <Root> */
+            0x00, 0x29, /* Type: OPT (41) */
+            0x10, 0x00, /* UDP payload size: 4096 */
+            0x00, /* Higher bits in extended RCODE: 0x00 */
+            0x00, /* EDNS0 version: 0 */
+            0x00, 0x00, /* Z: 0x0000 */
+            0x00, 0x00, /* Data length: 0 */
+        ];
+
+        let expectation = DNS_MESSAGE {
+            header: DNS_HEADER {
+                id: 0xb613,
+                qr: DNS_HDR_QR::Response,
+                op_code: DNS_HDR_OPCODE::Query,
+                aa: false,
+                tc: false,
+                rd: true,
+                ra: true,
+                ad: false,
+                cd: false,
+                r_code: DNS_HDR_RCODE::NoError,
+                qd_count: 1,
+                an_count: 1,
+                ns_count: 1,
+                ar_count: 1,
+            },
+            labels: DNS_LABEL_TABLE {
+                labels: vec![
+                    ((12, 15), "www.baidu.com.".to_string()),
+                    ((31, 2), "www.baidu.com.".to_string()),
+                    ((43, 15), "www.a.shifen.com.".to_string()),
+                    ((58, 2), "a.shifen.com.".to_string()),
+                    ((70, 6), "ns1.a.shifen.com.".to_string()),
+                    ((76, 19), "baidu_dns_master.baidu.com.".to_string()),
+                    ((115, 1), ".".to_string()),
+                ],
+            },
+            qd: vec![DNS_QUESTION_SECTION {
+                qname: "www.baidu.com.".to_string(),
+                qtype: DNS_QTYPE::SOA,
+                qclass: DNS_QCLASS::Internet,
+                size: 19,
+            }],
+            an: vec![
+                (DNS_RR_SECTION {
+                    hdr: DNS_RR_HDR {
+                        qname: "www.baidu.com.".to_string(),
+                        rr_type: DNS_QTYPE::CNAME,
+                        rr_class: DNS_QCLASS::Internet,
+                        ttl: 221,
+                        rd_length: 15,
+                        size: 12,
+                    },
+                    data: DNS_RR_DATA::CNAME {
+                        cname: "www.a.shifen.com.".to_string(),
+                    },
+                }),
+            ],
+            ns: vec![
+                (DNS_RR_SECTION {
+                    hdr: DNS_RR_HDR {
+                        qname: "a.shifen.com.".to_string(),
+                        rr_type: DNS_QTYPE::SOA,
+                        rr_class: DNS_QCLASS::Internet,
+                        ttl: 296,
+                        rd_length: 45,
+                        size: 12,
+                    },
+                    data: DNS_RR_DATA::SOA {
+                        mname: "ns1.a.shifen.com.".to_string(),
+                        rname: "baidu_dns_master.baidu.com.".to_string(),
+                        serial: 2211240019,
+                        refresh: 5,
+                        retry: 5,
+                        expire: 2592000,
+                        minimum: 3600,
+                    },
+                }),
+            ],
+            ar: vec![
+                (DNS_RR_SECTION {
+                    hdr: DNS_RR_HDR {
+                        qname: ".".to_string(),
+                        rr_type: DNS_QTYPE::OPT,
+                        rr_class: DNS_QCLASS::Other(4096),
+                        ttl: 0,
+                        rd_length: 0,
+                        size: 11,
+                    },
+                    data: DNS_RR_DATA::Other {
+                        qtype: DNS_QTYPE::OPT,
+                        data: vec![],
+                    },
+                }),
+            ],
+        };
+
+        assert_eq!(DNS_MESSAGE::decode(&bytes), Ok((LAST_SLICE, expectation)));
+
+        match DNS_MESSAGE::decode(&bytes) {
+            Ok((left, message)) => {
+                println!("{:?}; left {:?}", message, left);
+            }
+            Err(err) => {
+                println!("{:?}\n", err);
+            }
+        }
+        // assert_eq!(0, 1);
+    }
+
+    #[test]
+    fn test_answer_txt_decode() {
+        /*
+         * Domain Name System (response)
+         *     Transaction ID: 0x6721
+         *     Flags: 0x8180 Standard query response, No error
+         *         1... .... .... .... = Response: Message is a response
+         *         .000 0... .... .... = Opcode: Standard query (0)
+         *         .... .0.. .... .... = Authoritative: Server is not an authority for domain
+         *         .... ..0. .... .... = Truncated: Message is not truncated
+         *         .... ...1 .... .... = Recursion desired: Do query recursively
+         *         .... .... 1... .... = Recursion available: Server can do recursive queries
+         *         .... .... .0.. .... = Z: reserved (0)
+         *         .... .... ..0. .... = Answer authenticated: Answer/authority portion was not authenticated by the server
+         *         .... .... ...0 .... = Non-authenticated data: Unacceptable
+         *         .... .... .... 0000 = Reply code: No error (0)
+         *     Questions: 1
+         *     Answer RRs: 3
+         *     Authority RRs: 5
+         *     Additional RRs: 10
+         *     Queries
+         *         baidu.com: type TXT, class IN
+         *             Name: baidu.com
+         *             [Name Length: 9]
+         *             [Label Count: 2]
+         *             Type: TXT (Text strings) (16)
+         *             Class: IN (0x0001)
+         *     Answers
+         *         baidu.com: type TXT, class IN
+         *             Name: baidu.com
+         *             Type: TXT (Text strings) (16)
+         *             Class: IN (0x0001)
+         *             Time to live: 7200 (2 hours)
+         *             Data length: 75
+         *             TXT Length: 74
+         *             TXT: _globalsign-domain-verification=qjb28W2jJSrWj04NHpB0CvgK9tle5JkOq-EcyWBgnE
+         *         baidu.com: type TXT, class IN
+         *             Name: baidu.com
+         *             Type: TXT (Text strings) (16)
+         *             Class: IN (0x0001)
+         *             Time to live: 7200 (2 hours)
+         *             Data length: 69
+         *             TXT Length: 68
+         *             TXT: google-site-verification=GHb98-6msqyx_qqjGl5eRatD3QTHyVB6-xQ3gJB5UwM
+         *         baidu.com: type TXT, class IN
+         *             Name: baidu.com
+         *             Type: TXT (Text strings) (16)
+         *             Class: IN (0x0001)
+         *             Time to live: 7200 (2 hours)
+         *             Data length: 113
+         *             TXT Length: 112
+         *             TXT: v=spf1 include:spf1.baidu.com include:spf2.baidu.com include:spf3.baidu.com include:spf4.baidu.com a mx ptr -all
+         *     Authoritative nameservers
+         *         baidu.com: type NS, class IN, ns ns7.baidu.com
+         *             Name: baidu.com
+         *             Type: NS (authoritative Name Server) (2)
+         *             Class: IN (0x0001)
+         *             Time to live: 53898 (14 hours, 58 minutes, 18 seconds)
+         *             Data length: 6
+         *             Name Server: ns7.baidu.com
+         *         baidu.com: type NS, class IN, ns dns.baidu.com
+         *             Name: baidu.com
+         *             Type: NS (authoritative Name Server) (2)
+         *             Class: IN (0x0001)
+         *             Time to live: 53898 (14 hours, 58 minutes, 18 seconds)
+         *             Data length: 6
+         *             Name Server: dns.baidu.com
+         *         baidu.com: type NS, class IN, ns ns3.baidu.com
+         *             Name: baidu.com
+         *             Type: NS (authoritative Name Server) (2)
+         *             Class: IN (0x0001)
+         *             Time to live: 53898 (14 hours, 58 minutes, 18 seconds)
+         *             Data length: 6
+         *             Name Server: ns3.baidu.com
+         *         baidu.com: type NS, class IN, ns ns2.baidu.com
+         *             Name: baidu.com
+         *             Type: NS (authoritative Name Server) (2)
+         *             Class: IN (0x0001)
+         *             Time to live: 53898 (14 hours, 58 minutes, 18 seconds)
+         *             Data length: 6
+         *             Name Server: ns2.baidu.com
+         *         baidu.com: type NS, class IN, ns ns4.baidu.com
+         *             Name: baidu.com
+         *             Type: NS (authoritative Name Server) (2)
+         *             Class: IN (0x0001)
+         *             Time to live: 53898 (14 hours, 58 minutes, 18 seconds)
+         *             Data length: 6
+         *             Name Server: ns4.baidu.com
+         *     Additional records
+         *         ns3.baidu.com: type A, class IN, addr 36.152.45.193
+         *             Name: ns3.baidu.com
+         *             Type: A (Host Address) (1)
+         *             Class: IN (0x0001)
+         *             Time to live: 25922 (7 hours, 12 minutes, 2 seconds)
+         *             Data length: 4
+         *             Address: 36.152.45.193
+         *         ns3.baidu.com: type A, class IN, addr 112.80.248.64
+         *             Name: ns3.baidu.com
+         *             Type: A (Host Address) (1)
+         *             Class: IN (0x0001)
+         *             Time to live: 25922 (7 hours, 12 minutes, 2 seconds)
+         *             Data length: 4
+         *             Address: 112.80.248.64
+         *         ns2.baidu.com: type A, class IN, addr 220.181.33.31
+         *             Name: ns2.baidu.com
+         *             Type: A (Host Address) (1)
+         *             Class: IN (0x0001)
+         *             Time to live: 23967 (6 hours, 39 minutes, 27 seconds)
+         *             Data length: 4
+         *             Address: 220.181.33.31
+         *         ns7.baidu.com: type A, class IN, addr 180.76.76.92
+         *             Name: ns7.baidu.com
+         *             Type: A (Host Address) (1)
+         *             Class: IN (0x0001)
+         *             Time to live: 50794 (14 hours, 6 minutes, 34 seconds)
+         *             Data length: 4
+         *             Address: 180.76.76.92
+         *         ns4.baidu.com: type A, class IN, addr 14.215.178.80
+         *             Name: ns4.baidu.com
+         *             Type: A (Host Address) (1)
+         *             Class: IN (0x0001)
+         *             Time to live: 58399 (16 hours, 13 minutes, 19 seconds)
+         *             Data length: 4
+         *             Address: 14.215.178.80
+         *         ns4.baidu.com: type A, class IN, addr 111.45.3.226
+         *             Name: ns4.baidu.com
+         *             Type: A (Host Address) (1)
+         *             Class: IN (0x0001)
+         *             Time to live: 58399 (16 hours, 13 minutes, 19 seconds)
+         *             Data length: 4
+         *             Address: 111.45.3.226
+         *         dns.baidu.com: type A, class IN, addr 110.242.68.134
+         *             Name: dns.baidu.com
+         *             Type: A (Host Address) (1)
+         *             Class: IN (0x0001)
+         *             Time to live: 114889 (1 day, 7 hours, 54 minutes, 49 seconds)
+         *             Data length: 4
+         *             Address: 110.242.68.134
+         *         ns7.baidu.com: type AAAA, class IN, addr 240e:940:603:4:0:ff:b01b:589a
+         *             Name: ns7.baidu.com
+         *             Type: AAAA (IPv6 Address) (28)
+         *             Class: IN (0x0001)
+         *             Time to live: 80536 (22 hours, 22 minutes, 16 seconds)
+         *             Data length: 16
+         *             AAAA Address: 240e:940:603:4:0:ff:b01b:589a
+         *         ns7.baidu.com: type AAAA, class IN, addr 240e:bf:b801:1002:0:ff:b024:26de
+         *             Name: ns7.baidu.com
+         *             Type: AAAA (IPv6 Address) (28)
+         *             Class: IN (0x0001)
+         *             Time to live: 80536 (22 hours, 22 minutes, 16 seconds)
+         *             Data length: 16
+         *             AAAA Address: 240e:bf:b801:1002:0:ff:b024:26de
+         *         <Root>: type OPT
+         *             Name: <Root>
+         *             Type: OPT (41)
+         *             UDP payload size: 4096
+         *             Higher bits in extended RCODE: 0x00
+         *             EDNS0 version: 0
+         *             Z: 0x0000
+         *                 0... .... .... .... = DO bit: Cannot handle DNSSEC security RRs
+         *                 .000 0000 0000 0000 = Reserved: 0x0000
+         *             Data length: 0
+         */
+
+        let bytes = [
+            0x67, 0x21, 0x81, 0x80, 0x00, 0x01, 0x00, 0x03, 0x00, 0x05, 0x00, 0x0a, 0x05, 0x62,
+            0x61, 0x69, 0x64, 0x75, 0x03, 0x63, 0x6f, 0x6d, 0x00, 0x00, 0x10, 0x00, 0x01, 0xc0,
+            0x0c, 0x00, 0x10, 0x00, 0x01, 0x00, 0x00, 0x1c, 0x20, 0x00, 0x4b, 0x4a, 0x5f, 0x67,
+            0x6c, 0x6f, 0x62, 0x61, 0x6c, 0x73, 0x69, 0x67, 0x6e, 0x2d, 0x64, 0x6f, 0x6d, 0x61,
+            0x69, 0x6e, 0x2d, 0x76, 0x65, 0x72, 0x69, 0x66, 0x69, 0x63, 0x61, 0x74, 0x69, 0x6f,
+            0x6e, 0x3d, 0x71, 0x6a, 0x62, 0x32, 0x38, 0x57, 0x32, 0x6a, 0x4a, 0x53, 0x72, 0x57,
+            0x6a, 0x30, 0x34, 0x4e, 0x48, 0x70, 0x42, 0x30, 0x43, 0x76, 0x67, 0x4b, 0x39, 0x74,
+            0x6c, 0x65, 0x35, 0x4a, 0x6b, 0x4f, 0x71, 0x2d, 0x45, 0x63, 0x79, 0x57, 0x42, 0x67,
+            0x6e, 0x45, 0xc0, 0x0c, 0x00, 0x10, 0x00, 0x01, 0x00, 0x00, 0x1c, 0x20, 0x00, 0x45,
+            0x44, 0x67, 0x6f, 0x6f, 0x67, 0x6c, 0x65, 0x2d, 0x73, 0x69, 0x74, 0x65, 0x2d, 0x76,
+            0x65, 0x72, 0x69, 0x66, 0x69, 0x63, 0x61, 0x74, 0x69, 0x6f, 0x6e, 0x3d, 0x47, 0x48,
+            0x62, 0x39, 0x38, 0x2d, 0x36, 0x6d, 0x73, 0x71, 0x79, 0x78, 0x5f, 0x71, 0x71, 0x6a,
+            0x47, 0x6c, 0x35, 0x65, 0x52, 0x61, 0x74, 0x44, 0x33, 0x51, 0x54, 0x48, 0x79, 0x56,
+            0x42, 0x36, 0x2d, 0x78, 0x51, 0x33, 0x67, 0x4a, 0x42, 0x35, 0x55, 0x77, 0x4d, 0xc0,
+            0x0c, 0x00, 0x10, 0x00, 0x01, 0x00, 0x00, 0x1c, 0x20, 0x00, 0x71, 0x70, 0x76, 0x3d,
+            0x73, 0x70, 0x66, 0x31, 0x20, 0x69, 0x6e, 0x63, 0x6c, 0x75, 0x64, 0x65, 0x3a, 0x73,
+            0x70, 0x66, 0x31, 0x2e, 0x62, 0x61, 0x69, 0x64, 0x75, 0x2e, 0x63, 0x6f, 0x6d, 0x20,
+            0x69, 0x6e, 0x63, 0x6c, 0x75, 0x64, 0x65, 0x3a, 0x73, 0x70, 0x66, 0x32, 0x2e, 0x62,
+            0x61, 0x69, 0x64, 0x75, 0x2e, 0x63, 0x6f, 0x6d, 0x20, 0x69, 0x6e, 0x63, 0x6c, 0x75,
+            0x64, 0x65, 0x3a, 0x73, 0x70, 0x66, 0x33, 0x2e, 0x62, 0x61, 0x69, 0x64, 0x75, 0x2e,
+            0x63, 0x6f, 0x6d, 0x20, 0x69, 0x6e, 0x63, 0x6c, 0x75, 0x64, 0x65, 0x3a, 0x73, 0x70,
+            0x66, 0x34, 0x2e, 0x62, 0x61, 0x69, 0x64, 0x75, 0x2e, 0x63, 0x6f, 0x6d, 0x20, 0x61,
+            0x20, 0x6d, 0x78, 0x20, 0x70, 0x74, 0x72, 0x20, 0x2d, 0x61, 0x6c, 0x6c, 0xc0, 0x0c,
+            0x00, 0x02, 0x00, 0x01, 0x00, 0x00, 0xd2, 0x8a, 0x00, 0x06, 0x03, 0x6e, 0x73, 0x37,
+            0xc0, 0x0c, 0xc0, 0x0c, 0x00, 0x02, 0x00, 0x01, 0x00, 0x00, 0xd2, 0x8a, 0x00, 0x06,
+            0x03, 0x64, 0x6e, 0x73, 0xc0, 0x0c, 0xc0, 0x0c, 0x00, 0x02, 0x00, 0x01, 0x00, 0x00,
+            0xd2, 0x8a, 0x00, 0x06, 0x03, 0x6e, 0x73, 0x33, 0xc0, 0x0c, 0xc0, 0x0c, 0x00, 0x02,
+            0x00, 0x01, 0x00, 0x00, 0xd2, 0x8a, 0x00, 0x06, 0x03, 0x6e, 0x73, 0x32, 0xc0, 0x0c,
+            0xc0, 0x0c, 0x00, 0x02, 0x00, 0x01, 0x00, 0x00, 0xd2, 0x8a, 0x00, 0x06, 0x03, 0x6e,
+            0x73, 0x34, 0xc0, 0x0c, 0xc1, 0x70, 0x00, 0x01, 0x00, 0x01, 0x00, 0x00, 0x65, 0x42,
+            0x00, 0x04, 0x24, 0x98, 0x2d, 0xc1, 0xc1, 0x70, 0x00, 0x01, 0x00, 0x01, 0x00, 0x00,
+            0x65, 0x42, 0x00, 0x04, 0x70, 0x50, 0xf8, 0x40, 0xc1, 0x82, 0x00, 0x01, 0x00, 0x01,
+            0x00, 0x00, 0x5d, 0x9f, 0x00, 0x04, 0xdc, 0xb5, 0x21, 0x1f, 0xc1, 0x4c, 0x00, 0x01,
+            0x00, 0x01, 0x00, 0x00, 0xc6, 0x6a, 0x00, 0x04, 0xb4, 0x4c, 0x4c, 0x5c, 0xc1, 0x94,
+            0x00, 0x01, 0x00, 0x01, 0x00, 0x00, 0xe4, 0x1f, 0x00, 0x04, 0x0e, 0xd7, 0xb2, 0x50,
+            0xc1, 0x94, 0x00, 0x01, 0x00, 0x01, 0x00, 0x00, 0xe4, 0x1f, 0x00, 0x04, 0x6f, 0x2d,
+            0x03, 0xe2, 0xc1, 0x5e, 0x00, 0x01, 0x00, 0x01, 0x00, 0x01, 0xc0, 0xc9, 0x00, 0x04,
+            0x6e, 0xf2, 0x44, 0x86, 0xc1, 0x4c, 0x00, 0x1c, 0x00, 0x01, 0x00, 0x01, 0x3a, 0x98,
+            0x00, 0x10, 0x24, 0x0e, 0x09, 0x40, 0x06, 0x03, 0x00, 0x04, 0x00, 0x00, 0x00, 0xff,
+            0xb0, 0x1b, 0x58, 0x9a, 0xc1, 0x4c, 0x00, 0x1c, 0x00, 0x01, 0x00, 0x01, 0x3a, 0x98,
+            0x00, 0x10, 0x24, 0x0e, 0x00, 0xbf, 0xb8, 0x01, 0x10, 0x02, 0x00, 0x00, 0x00, 0xff,
+            0xb0, 0x24, 0x26, 0xde, 0x00, 0x00, 0x29, 0x10, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00,
+            0x00,
+        ];
+
+        let expectation = DNS_MESSAGE {
+            header: DNS_HEADER {
+                id: 0x6721,
+                qr: DNS_HDR_QR::Response,
+                op_code: DNS_HDR_OPCODE::Query,
+                aa: false,
+                tc: false,
+                rd: true,
+                ra: true,
+                ad: false,
+                cd: false,
+                r_code: DNS_HDR_RCODE::NoError,
+                qd_count: 1,
+                an_count: 3,
+                ns_count: 5,
+                ar_count: 10,
+            },
+            labels: DNS_LABEL_TABLE {
+                labels: vec![
+                    ((12, 11), "baidu.com.".to_string()),
+                    ((27, 2), "baidu.com.".to_string()),
+                    ((114, 2), "baidu.com.".to_string()),
+                    ((195, 2), "baidu.com.".to_string()),
+                    ((320, 2), "baidu.com.".to_string()),
+                    ((332, 6), "ns7.baidu.com.".to_string()),
+                    ((338, 2), "baidu.com.".to_string()),
+                    ((350, 6), "dns.baidu.com.".to_string()),
+                    ((356, 2), "baidu.com.".to_string()),
+                    ((368, 6), "ns3.baidu.com.".to_string()),
+                    ((374, 2), "baidu.com.".to_string()),
+                    ((386, 6), "ns2.baidu.com.".to_string()),
+                    ((392, 2), "baidu.com.".to_string()),
+                    ((404, 6), "ns4.baidu.com.".to_string()),
+                    ((410, 2), "ns3.baidu.com.".to_string()),
+                    ((426, 2), "ns3.baidu.com.".to_string()),
+                    ((442, 2), "ns2.baidu.com.".to_string()),
+                    ((458, 2), "ns7.baidu.com.".to_string()),
+                    ((474, 2), "ns4.baidu.com.".to_string()),
+                    ((490, 2), "ns4.baidu.com.".to_string()),
+                    ((506, 2), "dns.baidu.com.".to_string()),
+                    ((522, 2), "ns7.baidu.com.".to_string()),
+                    ((550, 2), "ns7.baidu.com.".to_string()),
+                    ((578, 1), ".".to_string()),
+                ]
+            },
+            qd: vec![
+                DNS_QUESTION_SECTION {
+                    qname: "baidu.com.".to_string(),
+                    qtype: DNS_QTYPE::TXT,
+                    qclass: DNS_QCLASS::Internet,
+                    size: 15
+                }
+            ],
+            an: vec![
+                (DNS_RR_SECTION {
+                    hdr: DNS_RR_HDR {
+                        qname: "baidu.com.".to_string(),
+                        rr_type: DNS_QTYPE::TXT,
+                        rr_class: DNS_QCLASS::Internet,
+                        ttl: 7200,
+                        rd_length: 75,
+                        size: 12
+                    },
+                    data:DNS_RR_DATA::TXT{ txtdata:vec!["_globalsign-domain-verification=qjb28W2jJSrWj04NHpB0CvgK9tle5JkOq-EcyWBgnE".to_string()]},}
+                ),
+                (DNS_RR_SECTION {
+                    hdr: DNS_RR_HDR {
+                        qname: "baidu.com.".to_string(),
+                        rr_type: DNS_QTYPE::TXT,
+                        rr_class: DNS_QCLASS::Internet,
+                        ttl: 7200,
+                        rd_length: 69,
+                        size: 12
+                    },
+                    data:DNS_RR_DATA::TXT{ txtdata:vec!["google-site-verification=GHb98-6msqyx_qqjGl5eRatD3QTHyVB6-xQ3gJB5UwM".to_string()]},}
+                ),
+                (DNS_RR_SECTION {
+                    hdr: DNS_RR_HDR {
+                        qname: "baidu.com.".to_string(),
+                        rr_type: DNS_QTYPE::TXT,
+                        rr_class: DNS_QCLASS::Internet,
+                        ttl: 7200,
+                        rd_length: 113,
+                        size: 12
+                    },
+                    data:  DNS_RR_DATA::TXT{ txtdata:vec!["v=spf1 include:spf1.baidu.com include:spf2.baidu.com include:spf3.baidu.com include:spf4.baidu.com a mx ptr -all".to_string()]}, }
+                )],
+            ns: vec![
+                (DNS_RR_SECTION {
+                    hdr: DNS_RR_HDR {
+                        qname: "baidu.com.".to_string(),
+                        rr_type: DNS_QTYPE::NS,
+                        rr_class: DNS_QCLASS::Internet,
+                        ttl: 53898,
+                        rd_length: 6,
+                        size: 12
+                    },
+                    data:   DNS_RR_DATA::NS{nsdname: "ns7.baidu.com.".to_string()},}
+                ),
+                (DNS_RR_SECTION {
+                    hdr: DNS_RR_HDR {
+                        qname: "baidu.com.".to_string(),
+                        rr_type: DNS_QTYPE::NS,
+                        rr_class: DNS_QCLASS::Internet,
+                        ttl: 53898,
+                        rd_length: 6,
+                        size: 12
+                    },
+                    data:  DNS_RR_DATA::NS{nsdname: "dns.baidu.com.".to_string()},}
+                ),
+                (DNS_RR_SECTION {
+                    hdr: DNS_RR_HDR {
+                        qname: "baidu.com.".to_string(),
+                        rr_type: DNS_QTYPE::NS,
+                        rr_class: DNS_QCLASS::Internet,
+                        ttl: 53898,
+                        rd_length: 6,
+                        size: 12
+                     },
+                     data:  DNS_RR_DATA::NS{nsdname: "ns3.baidu.com.".to_string()},}
+                ),
+                (DNS_RR_SECTION {
+                    hdr: DNS_RR_HDR {
+                        qname: "baidu.com.".to_string(),
+                        rr_type: DNS_QTYPE::NS,
+                        rr_class:  DNS_QCLASS::Internet,
+                        ttl: 53898,
+                        rd_length: 6,
+                        size: 12
+                     },
+                     data:  DNS_RR_DATA:: NS{ nsdname: "ns2.baidu.com.".to_string()},}
+                ),
+                (DNS_RR_SECTION {
+                    hdr: DNS_RR_HDR {
+                        qname: "baidu.com.".to_string(),
+                        rr_type: DNS_QTYPE::NS,
+                        rr_class: DNS_QCLASS::Internet,
+                        ttl: 53898,
+                        rd_length: 6,
+                        size: 12
+                    },
+                    data: DNS_RR_DATA::NS{nsdname: "ns4.baidu.com.".to_string()},}
+                )
+                ],
+            ar: vec![
+                (DNS_RR_SECTION {
+                    hdr: DNS_RR_HDR {
+                        qname: "ns3.baidu.com.".to_string(),
+                        rr_type: DNS_QTYPE::A,
+                        rr_class: DNS_QCLASS::Internet,
+                        ttl: 25922,
+                        rd_length: 4,
+                        size: 12
+                    },
+                    data: DNS_RR_DATA::A{address: "36.152.45.193".to_string()},
+                }
+                ),
+                (DNS_RR_SECTION {
+                    hdr: DNS_RR_HDR {
+                        qname: "ns3.baidu.com.".to_string(),
+                        rr_type: DNS_QTYPE::A,
+                        rr_class: DNS_QCLASS::Internet,
+                        ttl: 25922,
+                        rd_length: 4,
+                        size: 12
+                    },
+                    data: DNS_RR_DATA::A{address: "112.80.248.64".to_string()},
+                }
+                ),
+                (
+                    DNS_RR_SECTION {
+                        hdr: DNS_RR_HDR {
+                        qname: "ns2.baidu.com.".to_string(),
+                        rr_type: DNS_QTYPE::A,
+                        rr_class: DNS_QCLASS::Internet,
+                        ttl: 23967,
+                        rd_length: 4,
+                        size: 12
+                    },
+                    data: DNS_RR_DATA::A{address: "220.181.33.31".to_string()},
+                }
+                ),
+                (
+                    DNS_RR_SECTION {
+                        hdr: DNS_RR_HDR {
+                        qname: "ns7.baidu.com.".to_string(),
+                        rr_type: DNS_QTYPE::A,
+                        rr_class: DNS_QCLASS::Internet,
+                        ttl: 50794,
+                        rd_length: 4,
+                        size: 12
+                    },
+                  data:  DNS_RR_DATA::A{address: "180.76.76.92".to_string()},
+                }
+                ),
+                (
+                    DNS_RR_SECTION {
+                        hdr: DNS_RR_HDR {
+                        qname: "ns4.baidu.com.".to_string(),
+                        rr_type: DNS_QTYPE::A,
+                        rr_class: DNS_QCLASS::Internet,
+                        ttl: 58399,
+                        rd_length: 4,
+                        size: 12
+                    },
+                    data:DNS_RR_DATA::A{address: "14.215.178.80".to_string()},
+                }
+                ),
+                (
+                    DNS_RR_SECTION {
+                        hdr: DNS_RR_HDR {
+                        qname: "ns4.baidu.com.".to_string(),
+                        rr_type: DNS_QTYPE::A,
+                        rr_class: DNS_QCLASS::Internet,
+                        ttl: 58399,
+                        rd_length: 4,
+                        size: 12
+                    },
+                    data:DNS_RR_DATA::A{address: "111.45.3.226".to_string()},}
+                ),
+                (
+                    DNS_RR_SECTION {
+                        hdr: DNS_RR_HDR {
+                        qname: "dns.baidu.com.".to_string(),
+                        rr_type: DNS_QTYPE::A,
+                        rr_class: DNS_QCLASS::Internet,
+                        ttl: 114889,
+                        rd_length: 4,
+                        size: 12
+                    },
+                    data: DNS_RR_DATA::A{address: "110.242.68.134".to_string()},}
+                ),
+                (DNS_RR_SECTION {
+                    hdr: DNS_RR_HDR {
+                        qname: "ns7.baidu.com.".to_string(),
+                        rr_type: DNS_QTYPE::AAAA,
+                        rr_class: DNS_QCLASS::Internet,
+                        ttl: 80536,
+                        rd_length: 16,
+                        size: 12
+                    },
+                    data: DNS_RR_DATA::AAAA{ address : "240E:0940:0603:0004:0000:00FF:B01B:589A".to_string()},}
+                ),
+                (DNS_RR_SECTION {
+                    hdr: DNS_RR_HDR {
+                        qname: "ns7.baidu.com.".to_string(),
+                        rr_type: DNS_QTYPE::AAAA,
+                        rr_class: DNS_QCLASS::Internet,
+                        ttl: 80536,
+                        rd_length: 16,
+                        size: 12
+                    },
+                    data: DNS_RR_DATA::AAAA{ address: "240E:00BF:B801:1002:0000:00FF:B024:26DE".to_string()},}
+                ),
+                (DNS_RR_SECTION {
+                    hdr: DNS_RR_HDR {
+                        qname: ".".to_string(),
+                        rr_type: DNS_QTYPE::OPT,
+                        rr_class: DNS_QCLASS::Other(4096),
+                        ttl: 0,
+                        rd_length: 0,
+                        size: 11
+                    },
+                    data:DNS_RR_DATA::Other{ qtype: DNS_QTYPE::OPT,data:vec![]},}
+                )
+            ]
+        };
+
+        assert_eq!(DNS_MESSAGE::decode(&bytes), Ok((LAST_SLICE, expectation)));
+
+        match DNS_MESSAGE::decode(&bytes) {
+            Ok((left, message)) => {
+                println!("{:?}; left {:?}", message, left);
+            }
+            Err(err) => {
+                println!("{:?}\n", err);
+            }
+        }
+        // assert_eq!(0, 1);
+    }
+
+    // TODO
+    #[test]
+    fn test_answer_other_decode() {}
+}
diff --git a/src/protocol/mod.rs b/src/protocol/mod.rs
index cff0932..3427b8b 100644
--- a/src/protocol/mod.rs
+++ b/src/protocol/mod.rs
@@ -3,4 +3,5 @@ pub mod ip;
 pub mod ipv4;
 pub mod ipv6;
 pub mod udp;
-pub mod tcp;
\ No newline at end of file
+pub mod tcp;
+pub mod dns;
\ No newline at end of file