github.com/miekg/dns

import "github.com/miekg/dns"

import "github.com/miekg/dns/dnsutil"

package main

import (
    "fmt"
    "github.com/miekg/dns"
)

func main() {
    // Create a new DNS message
    m := new(dns.Msg)
    m.SetQuestion(dns.Fqdn("example.com"), dns.TypeA)
    m.RecursionDesired = true

    // Send the query
    c := new(dns.Client)
    in, rtt, err := c.Exchange(m, "8.8.8.8:53")
    if err != nil {
        panic(err)
    }

    // Process answers
    for _, ans := range in.Answer {
        if a, ok := ans.(*dns.A); ok {
            fmt.Printf("A record: %s\n", a.A)
        }
    }
}

package main

import (
    "github.com/miekg/dns"
    "log"
    "net"
)

func handleRequest(w dns.ResponseWriter, r *dns.Msg) {
    m := new(dns.Msg)
    m.SetReply(r)
    m.Authoritative = true

    // Add answer
    rr := &dns.A{
        Hdr: dns.RR_Header{
            Name:   r.Question[0].Name,
            Rrtype: dns.TypeA,
            Class:  dns.ClassINET,
            Ttl:    3600,
        },
        A: net.ParseIP("192.0.2.1"),
    }
    m.Answer = append(m.Answer, rr)

    w.WriteMsg(m)
}

func main() {
    dns.HandleFunc(".", handleRequest)
    server := &dns.Server{Addr: ":53", Net: "udp"}
    log.Fatal(server.ListenAndServe())
}

// Msg represents a DNS message
type Msg struct {
    Id                 uint16
    Response           bool
    Opcode             int
    Authoritative      bool
    Truncated          bool
    RecursionDesired   bool
    RecursionAvailable bool
    Zero               bool
    AuthenticatedData  bool
    CheckingDisabled   bool
    Rcode              int
    Compress           bool
    Question           []Question
    Answer             []RR
    Ns                 []RR
    Extra              []RR
}

func (dns *Msg) Pack() ([]byte, error)
func (dns *Msg) PackBuffer(buf []byte) ([]byte, error)
func (dns *Msg) Unpack(msg []byte) error
func (dns *Msg) SetQuestion(z string, t uint16) *Msg
func (dns *Msg) SetReply(request *Msg) *Msg
func (dns *Msg) SetEdns0(udpsize uint16, do bool) *Msg
func (dns *Msg) IsTsig() *TSIG
func (dns *Msg) IsEdns0() *OPT
func (dns *Msg) Copy() *Msg
func (dns *Msg) String() string
func (dns *Msg) Len() int

// Question represents a DNS question
type Question struct {
    Name   string
    Qtype  uint16
    Qclass uint16
}

// Message ID generation
func Id() uint16

// Client performs DNS queries
type Client struct {
    Net           string
    UDPSize       uint16
    TLSConfig     *tls.Config
    Dialer        *net.Dialer
    Timeout       time.Duration
    DialTimeout   time.Duration
    ReadTimeout   time.Duration
    WriteTimeout  time.Duration
    TsigSecret    map[string]string
    TsigProvider  TsigProvider
    SingleInflight bool
}

func (c *Client) Exchange(m *Msg, address string) (r *Msg, rtt time.Duration, err error)
func (c *Client) ExchangeContext(ctx context.Context, m *Msg, address string) (r *Msg, rtt time.Duration, err error)
func (c *Client) Dial(address string) (conn *Conn, err error)
func (c *Client) DialContext(ctx context.Context, address string) (conn *Conn, err error)

// Simple query functions
func Exchange(m *Msg, address string) (r *Msg, err error)
func ExchangeContext(ctx context.Context, m *Msg, address string) (r *Msg, err error)

// Connection functions
func Dial(network, address string) (*Conn, error)
func DialTimeout(network, address string, timeout time.Duration) (*Conn, error)
func DialWithTLS(network, address string, tlsConfig *tls.Config) (*Conn, error)
func DialTimeoutWithTLS(network, address string, tlsConfig *tls.Config, timeout time.Duration) (*Conn, error)

// Server defines parameters for running a DNS server
type Server struct {
    Addr            string
    Net             string
    TLSConfig       *tls.Config
    Handler         Handler
    UDPSize         uint16
    MaxTCPQueries   int
    ReusePort       bool
    ReuseAddr       bool
    TsigSecret      map[string]string
    TsigProvider    TsigProvider
    MsgAcceptFunc   MsgAcceptFunc
    NotifyStartedFunc func()
}

func (srv *Server) ListenAndServe() error
func (srv *Server) ActivateAndServe() error
func (srv *Server) Shutdown() error
func (srv *Server) ShutdownContext(ctx context.Context) error

// Handler interface for DNS request handlers
type Handler interface {
    ServeDNS(w ResponseWriter, r *Msg)
}

// HandlerFunc adapter
type HandlerFunc func(ResponseWriter, *Msg)
func (f HandlerFunc) ServeDNS(w ResponseWriter, r *Msg)

// ResponseWriter interface for writing responses
type ResponseWriter interface {
    LocalAddr() net.Addr
    RemoteAddr() net.Addr
    WriteMsg(*Msg) error
    Write([]byte) (int, error)
    Close() error
    TsigStatus() error
    TsigTimersOnly(bool)
    Hijack()
}

// ServeMux multiplexes DNS requests
type ServeMux struct{}
func NewServeMux() *ServeMux
func (mux *ServeMux) Handle(pattern string, handler Handler)
func (mux *ServeMux) HandleFunc(pattern string, handler func(ResponseWriter, *Msg))
func (mux *ServeMux) HandleRemove(pattern string)
func (mux *ServeMux) ServeDNS(w ResponseWriter, r *Msg)

// Package-level convenience functions
func Handle(pattern string, handler Handler)
func HandleFunc(pattern string, handler func(ResponseWriter, *Msg))
func HandleRemove(pattern string)
func ListenAndServe(addr string, network string, handler Handler) error
func ListenAndServeTLS(addr, certFile, keyFile string, handler Handler) error

// RR is the base interface for all resource records
type RR interface {
    Header() *RR_Header
    String() string
}

// RR_Header is the common header for all resource records
type RR_Header struct {
    Name     string
    Rrtype   uint16
    Class    uint16
    Ttl      uint32
    Rdlength uint16
}

func (h *RR_Header) Header() *RR_Header

// Common RR creation functions
func NewRR(s string) (RR, error)
func Copy(r RR) RR

// DNSKEY represents a DNSSEC public key
type DNSKEY struct {
    Hdr       RR_Header
    Flags     uint16
    Protocol  uint8
    Algorithm uint8
    PublicKey string
}

func (k *DNSKEY) KeyTag() uint16
func (k *DNSKEY) ToDS(h uint8) *DS
func (k *DNSKEY) ToCDNSKEY() *CDNSKEY
func (k *DNSKEY) NewPrivateKey(s string) (crypto.PrivateKey, error)

// DS represents a delegation signer record
type DS struct {
    Hdr        RR_Header
    KeyTag     uint16
    Algorithm  uint8
    DigestType uint8
    Digest     string
}

func (ds *DS) ToCDS() *CDS

// RRSIG represents a resource record signature
type RRSIG struct {
    Hdr         RR_Header
    TypeCovered uint16
    Algorithm   uint8
    Labels      uint8
    OrigTtl     uint32
    Expiration  uint32
    Inception   uint32
    KeyTag      uint16
    SignerName  string
    Signature   string
}

func (rr *RRSIG) Sign(k crypto.Signer, rrset []RR) error
func (rr *RRSIG) Verify(k *DNSKEY, rrset []RR) error
func (rr *RRSIG) ValidityPeriod(t time.Time) bool

// ZoneParser parses RFC 1035 style zone files
type ZoneParser struct{}

func NewZoneParser(r io.Reader, origin, file string) *ZoneParser
func (zp *ZoneParser) Next() (RR, bool)
func (zp *ZoneParser) Err() error
func (zp *ZoneParser) Comment() string
func (zp *ZoneParser) SetDefaultTTL(ttl uint32)
func (zp *ZoneParser) SetIncludeAllowed(v bool)
func (zp *ZoneParser) SetIncludeFS(fs fs.FS)

// Parse single RR from string
func NewRR(s string) (RR, error)
func ReadRR(r io.Reader, file string) (RR, error)

// Transfer handles zone transfers
type Transfer struct {
    *Conn
    DialTimeout  time.Duration
    ReadTimeout  time.Duration
    WriteTimeout time.Duration
    TsigSecret   map[string]string
    TsigProvider TsigProvider
    TLS          *tls.Config
}

func (t *Transfer) In(m *Msg, a string) (env chan *Envelope, err error)
func (t *Transfer) Out(w ResponseWriter, q *Msg, ch chan *Envelope) error

// Envelope wraps zone transfer records
type Envelope struct {
    RR    []RR
    Error error
}

// TSIG algorithms
const (
    HmacSHA1   = "hmac-sha1."
    HmacSHA224 = "hmac-sha224."
    HmacSHA256 = "hmac-sha256."
    HmacSHA384 = "hmac-sha384."
    HmacSHA512 = "hmac-sha512."
)

// TSIG represents a transaction signature record
type TSIG struct {
    Hdr        RR_Header
    Algorithm  string
    TimeSigned uint64
    Fudge      uint16
    MACSize    uint16
    MAC        string
    OrigId     uint16
    Error      uint16
    OtherLen   uint16
    OtherData  string
}

// TsigProvider allows custom TSIG implementations
type TsigProvider interface {
    Generate(msg []byte, t *TSIG) ([]byte, error)
    Verify(msg []byte, t *TSIG) error
}

// TSIG functions
func TsigGenerate(m *Msg, secret, requestMAC string, timersOnly bool) ([]byte, string, error)
func TsigGenerateWithProvider(m *Msg, provider TsigProvider, requestMAC string, timersOnly bool) ([]byte, string, error)
func TsigVerify(msg []byte, secret, requestMAC string, timersOnly bool) error
func TsigVerifyWithProvider(msg []byte, provider TsigProvider, requestMAC string, timersOnly bool) error

// Msg TSIG methods
func (dns *Msg) SetTsig(z, algo string, fudge uint16, timeSigned int64) *Msg
func (dns *Msg) IsTsig() *TSIG

// OPT represents an EDNS0 pseudo-record
type OPT struct {
    Hdr    RR_Header
    Option []EDNS0
}

func (rr *OPT) Do() bool
func (rr *OPT) SetDo(do bool)
func (rr *OPT) Version() uint8
func (rr *OPT) SetVersion(v uint8)
func (rr *OPT) ExtendedRcode() int
func (rr *OPT) SetExtendedRcode(v uint8)
func (rr *OPT) UDPSize() uint16
func (rr *OPT) SetUDPSize(size uint16)

// EDNS0 option interface
type EDNS0 interface {
    Option() uint16
    pack() ([]byte, error)
    unpack([]byte) error
    String() string
    copy() EDNS0
}

// Msg EDNS0 methods
func (dns *Msg) SetEdns0(udpsize uint16, do bool) *Msg
func (dns *Msg) IsEdns0() *OPT

// Msg methods for dynamic updates
func (dns *Msg) SetUpdate(z string) *Msg
func (dns *Msg) NameUsed(rr []RR)
func (dns *Msg) NameNotUsed(rr []RR)
func (dns *Msg) Used(rr []RR)
func (dns *Msg) RRsetUsed(rr []RR)
func (dns *Msg) RRsetNotUsed(rr []RR)
func (dns *Msg) Insert(rr []RR)
func (dns *Msg) RemoveRRset(rr []RR)
func (dns *Msg) RemoveName(rr []RR)
func (dns *Msg) Remove(rr []RR)

// Domain name operations
func Fqdn(s string) string
func IsFqdn(s string) bool
func CanonicalName(s string) string
func IsDomainName(s string) (labels int, ok bool)
func IsSubDomain(parent, child string) bool
func SplitDomainName(s string) []string
func CountLabel(s string) int
func Split(s string) []int
func CompareDomainName(s1, s2 string) int
func ReverseAddr(addr string) (arpa string, err error)

// Type and class operations
func TypeToString(t uint16) string
func StringToType(s string) (uint16, bool)
func ClassToString(c uint16) string
func StringToClass(s string) (uint16, bool)

// RR utilities
func Copy(r RR) RR
func IsDuplicate(r1, r2 RR) bool
func IsRRset(rrset []RR) bool

const (
    DefaultMsgSize = 4096  // Standard default for messages larger than 512 bytes
    MinMsgSize     = 512   // Minimal size of a DNS packet
    MaxMsgSize     = 65535 // Largest possible DNS packet
)

const (
    ClassINET   = 1   // Internet
    ClassCSNET  = 2   // CSNET (obsolete)
    ClassCHAOS  = 3   // Chaos
    ClassHESIOD = 4   // Hesiod
    ClassNONE   = 254 // None
    ClassANY    = 255 // Any
)

const (
    OpcodeQuery  = 0 // Standard query
    OpcodeIQuery = 1 // Inverse query (obsolete)
    OpcodeStatus = 2 // Server status request
    OpcodeNotify = 4 // Notify
    OpcodeUpdate = 5 // Dynamic update
)

const (
    RcodeSuccess                   = 0  // NOERROR - No error
    RcodeFormatError              = 1  // FORMERR - Format error
    RcodeServerFailure            = 2  // SERVFAIL - Server failure
    RcodeNameError                = 3  // NXDOMAIN - Non-existent domain
    RcodeNotImplemented           = 4  // NOTIMP - Not implemented
    RcodeRefused                  = 5  // REFUSED - Query refused
    RcodeYXDomain                 = 6  // YXDOMAIN - Name exists when it should not
    RcodeYXRrset                  = 7  // YXRRSET - RR set exists when it should not
    RcodeNXRrset                  = 8  // NXRRSET - RR set that should exist does not
    RcodeNotAuth                  = 9  // NOTAUTH - Server not authoritative
    RcodeNotZone                  = 10 // NOTZONE - Name not contained in zone
    RcodeStatefulTypeNotImplemented = 11 // DSOTYPENI - DSO-type not implemented
    RcodeBadSig                   = 16 // BADSIG - TSIG signature failure
    RcodeBadKey                   = 17 // BADKEY - Key not recognized
    RcodeBadTime                  = 18 // BADTIME - Signature out of time window
    RcodeBadMode                  = 19 // BADMODE - Bad TKEY mode
    RcodeBadName                  = 20 // BADNAME - Duplicate key name
    RcodeBadAlg                   = 21 // BADALG - Algorithm not supported
    RcodeBadTrunc                 = 22 // BADTRUNC - Bad truncation
    RcodeBadCookie                = 23 // BADCOOKIE - Bad/missing server cookie
)

import "github.com/miekg/dns/dnsutil"

// AddOrigin adds origin to relative domain names
func AddOrigin(s, origin string) string

// TrimDomainName trims origin from absolute domain names
// Returns @ for zone apex
func TrimDomainName(s, origin string) string

TypeA, TypeNS, TypeMD, TypeMF, TypeCNAME, TypeSOA, TypeMB, TypeMG,
TypeMR, TypeNULL, TypePTR, TypeHINFO, TypeMINFO, TypeMX, TypeTXT,
TypeRP, TypeAFSDB, TypeX25, TypeISDN, TypeRT, TypeNSAPPTR, TypeSIG,
TypeKEY, TypePX, TypeGPOS, TypeAAAA, TypeLOC, TypeNXT, TypeEID,
TypeNIMLOC, TypeSRV, TypeATMA, TypeNAPTR, TypeKX, TypeCERT, TypeDNAME,
TypeOPT, TypeAPL, TypeDS, TypeSSHFP, TypeIPSECKEY, TypeRRSIG, TypeNSEC,
TypeDNSKEY, TypeDHCID, TypeNSEC3, TypeNSEC3PARAM, TypeTLSA, TypeSMIMEA,
TypeHIP, TypeNINFO, TypeRKEY, TypeTALINK, TypeCDS, TypeCDNSKEY,
TypeOPENPGPKEY, TypeCSYNC, TypeZONEMD, TypeSVCB, TypeHTTPS, TypeSPF,
TypeUINFO, TypeUID, TypeGID, TypeUNSPEC, TypeNID, TypeL32, TypeL64,
TypeLP, TypeEUI48, TypeEUI64, TypeNXNAME, TypeURI, TypeCAA, TypeAVC,
TypeAMTRELAY, TypeRESINFO, TypeTKEY, TypeTSIG, TypeIXFR, TypeAXFR,
TypeMAILB, TypeMAILA, TypeANY, TypeTA, TypeDLV, TypeReserved

var (
    ErrAlg          error // Unsupported algorithm
    ErrAuth         error // Authentication failed
    ErrBuf          error // Buffer size too small
    ErrConnEmpty    error // Connection is nil or not initialized
    ErrExtendedRcode error // Extended rcode error
    ErrFqdn         error // Domain must be fully qualified
    ErrId           error // Message ID mismatch
    ErrKey          error // Key error
    ErrKeyAlg       error // Unsupported key algorithm
    ErrKeySize      error // Invalid key size
    ErrLongDomain   error // Domain name too long
    ErrNoSig        error // No signature found
    ErrPrivKey      error // Private key error
    ErrRcode        error // Response code error
    ErrRdata        error // Bad rdata
    ErrRRset        error // RRset error
    ErrSecret       error // Secret key error
    ErrShortRead    error // Short read from connection
    ErrSig          error // Signature error
    ErrSoa          error // SOA record error
    ErrTime         error // Time error
)

// Id generates a 16-bit random identifier for DNS messages
// Can be reassigned for testing or custom ID generation
var Id func() uint16

var Version struct {
    Major int
    Minor int
    Patch int
}