dns

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Alternative (more granular) approach to a DNS library

Less is more.

Complete and usable DNS library. All Resource Records are supported, including the DNSSEC types. It follows a lean and mean philosophy. If there is stuff you should know as a DNS programmer there isn't a convenience function for it. Server side and client side programming is supported, i.e. you can build servers and resolvers with it.

We try to keep the "master" branch as sane as possible and at the bleeding edge of standards, avoiding breaking changes wherever reasonable. We support the last two versions of Go.

Goals

  • KISS;
  • Fast;
  • Small API. If it's easy to code in Go, don't make a function for it.

Users

A not-so-up-to-date-list-that-may-be-actually-current:

Send pull request if you want to be listed here.

Features

  • UDP/TCP queries, IPv4 and IPv6
  • RFC 1035 zone file parsing ($INCLUDE, $ORIGIN, $TTL and $GENERATE (for all record types) are supported
  • Fast
  • Server side programming (mimicking the net/http package)
  • Client side programming
  • DNSSEC: signing, validating and key generation for DSA, RSA, ECDSA and Ed25519
  • EDNS0, NSID, Cookies
  • AXFR/IXFR
  • TSIG, SIG(0)
  • DNS over TLS (DoT): encrypted connection between client and server over TCP
  • DNS name compression

Have fun!

Miek Gieben - 2010-2012 - miek@miek.nl DNS Authors 2012-

Building

Building is done with the go tool. If you have setup your GOPATH correctly, the following should work:

go get github.com/miekg/dns
go build github.com/miekg/dns

Examples

A short "how to use the API" is at the beginning of doc.go (this also will show when you call godoc github.com/miekg/dns).

Example programs can be found in the github.com/miekg/exdns repository.

Supported RFCs

all of them

  • 103{4,5} - DNS standard
  • 1348 - NSAP record (removed the record)
  • 1982 - Serial Arithmetic
  • 1876 - LOC record
  • 1995 - IXFR
  • 1996 - DNS notify
  • 2136 - DNS Update (dynamic updates)
  • 2181 - RRset definition - there is no RRset type though, just []RR
  • 2537 - RSAMD5 DNS keys
  • 2065 - DNSSEC (updated in later RFCs)
  • 2671 - EDNS record
  • 2782 - SRV record
  • 2845 - TSIG record
  • 2915 - NAPTR record
  • 2929 - DNS IANA Considerations
  • 3110 - RSASHA1 DNS keys
  • 3225 - DO bit (DNSSEC OK)
  • 340{1,2,3} - NAPTR record
  • 3445 - Limiting the scope of (DNS)KEY
  • 3597 - Unknown RRs
  • 403{3,4,5} - DNSSEC + validation functions
  • 4255 - SSHFP record
  • 4343 - Case insensitivity
  • 4408 - SPF record
  • 4509 - SHA256 Hash in DS
  • 4592 - Wildcards in the DNS
  • 4635 - HMAC SHA TSIG
  • 4701 - DHCID
  • 4892 - id.server
  • 5001 - NSID
  • 5155 - NSEC3 record
  • 5205 - HIP record
  • 5702 - SHA2 in the DNS
  • 5936 - AXFR
  • 5966 - TCP implementation recommendations
  • 6605 - ECDSA
  • 6725 - IANA Registry Update
  • 6742 - ILNP DNS
  • 6840 - Clarifications and Implementation Notes for DNS Security
  • 6844 - CAA record
  • 6891 - EDNS0 update
  • 6895 - DNS IANA considerations
  • 6944 - DNSSEC DNSKEY Algorithm Status
  • 6975 - Algorithm Understanding in DNSSEC
  • 7043 - EUI48/EUI64 records
  • 7314 - DNS (EDNS) EXPIRE Option
  • 7477 - CSYNC RR
  • 7828 - edns-tcp-keepalive EDNS0 Option
  • 7553 - URI record
  • 7858 - DNS over TLS: Initiation and Performance Considerations
  • 7871 - EDNS0 Client Subnet
  • 7873 - Domain Name System (DNS) Cookies
  • 8080 - EdDSA for DNSSEC
  • 8499 - DNS Terminology

Loosely Based Upon

Documentation

Overview

Package dns implements a full featured interface to the Domain Name System. Both server- and client-side programming is supported. The package allows complete control over what is sent out to the DNS. The API follows the less-is-more principle, by presenting a small, clean interface.

It supports (asynchronous) querying/replying, incoming/outgoing zone transfers, TSIG, EDNS0, dynamic updates, notifies and DNSSEC validation/signing.

Note that domain names MUST be fully qualified before sending them, unqualified names in a message will result in a packing failure.

Resource records are native types. They are not stored in wire format. Basic usage pattern for creating a new resource record: 

r := new(dns.MX)
r.Hdr = dns.RR_Header{Name: "miek.nl.", Rrtype: dns.TypeMX, Class: dns.ClassINET, Ttl: 3600}
r.Preference = 10
r.Mx = "mx.miek.nl."

Or directly from a string: 

mx, err := dns.NewRR("miek.nl. 3600 IN MX 10 mx.miek.nl.")

Or when the default origin (.) and TTL (3600) and class (IN) suit you: 

mx, err := dns.NewRR("miek.nl MX 10 mx.miek.nl")

Or even: 

mx, err := dns.NewRR("$ORIGIN nl.\nmiek 1H IN MX 10 mx.miek")

In the DNS messages are exchanged, these messages contain resource records (sets). Use pattern for creating a message: 

m := new(dns.Msg)
m.SetQuestion("miek.nl.", dns.TypeMX)

Or when not certain if the domain name is fully qualified: 

m.SetQuestion(dns.Fqdn("miek.nl"), dns.TypeMX)

The message m is now a message with the question section set to ask the MX records for the miek.nl. zone.

The following is slightly more verbose, but more flexible: 

m1 := new(dns.Msg)
m1.Id = dns.Id()
m1.RecursionDesired = true
m1.Question = make([]dns.Question, 1)
m1.Question[0] = dns.Question{"miek.nl.", dns.TypeMX, dns.ClassINET}

After creating a message it can be sent. Basic use pattern for synchronous querying the DNS at a server configured on 127.0.0.1 and port 53: 

c := new(dns.Client)
in, rtt, err := c.Exchange(m1, "127.0.0.1:53")

Suppressing multiple outstanding queries (with the same question, type and class) is as easy as setting: 

c.SingleInflight = true

More advanced options are available using a net.Dialer and the corresponding API. For example it is possible to set a timeout, or to specify a source IP address and port to use for the connection: 

c := new(dns.Client)
laddr := net.UDPAddr{
	IP: net.ParseIP("[::1]"),
	Port: 12345,
	Zone: "",
}
c.Dialer := &net.Dialer{
	Timeout: 200 * time.Millisecond,
	LocalAddr: &laddr,
}
in, rtt, err := c.Exchange(m1, "8.8.8.8:53")

If these "advanced" features are not needed, a simple UDP query can be sent, with: 

in, err := dns.Exchange(m1, "127.0.0.1:53")

When this functions returns you will get dns message. A dns message consists out of four sections. The question section: in.Question, the answer section: in.Answer, the authority section: in.Ns and the additional section: in.Extra.

Each of these sections (except the Question section) contain a []RR. Basic use pattern for accessing the rdata of a TXT RR as the first RR in the Answer section: 

if t, ok := in.Answer[0].(*dns.TXT); ok {
	// do something with t.Txt
}

Domain Name and TXT Character String Representations

Both domain names and TXT character strings are converted to presentation form both when unpacked and when converted to strings.

For TXT character strings, tabs, carriage returns and line feeds will be converted to \t, \r and \n respectively. Back slashes and quotations marks will be escaped. Bytes below 32 and above 127 will be converted to \DDD form.

For domain names, in addition to the above rules brackets, periods, spaces, semicolons and the at symbol are escaped.

DNSSEC

DNSSEC (DNS Security Extension) adds a layer of security to the DNS. It uses public key cryptography to sign resource records. The public keys are stored in DNSKEY records and the signatures in RRSIG records.

Requesting DNSSEC information for a zone is done by adding the DO (DNSSEC OK) bit to a request. 

m := new(dns.Msg)
m.SetEdns0(4096, true)

Signature generation, signature verification and key generation are all supported.

DYNAMIC UPDATES

Dynamic updates reuses the DNS message format, but renames three of the sections. Question is Zone, Answer is Prerequisite, Authority is Update, only the Additional is not renamed. See RFC 2136 for the gory details.

You can set a rather complex set of rules for the existence of absence of certain resource records or names in a zone to specify if resource records should be added or removed. The table from RFC 2136 supplemented with the Go DNS function shows which functions exist to specify the prerequisites. 

3.2.4 - Table Of Metavalues Used In Prerequisite Section

 CLASS    TYPE     RDATA    Meaning                    Function
 --------------------------------------------------------------
 ANY      ANY      empty    Name is in use             dns.NameUsed
 ANY      rrset    empty    RRset exists (value indep) dns.RRsetUsed
 NONE     ANY      empty    Name is not in use         dns.NameNotUsed
 NONE     rrset    empty    RRset does not exist       dns.RRsetNotUsed
 zone     rrset    rr       RRset exists (value dep)   dns.Used

The prerequisite section can also be left empty. If you have decided on the prerequisites you can tell what RRs should be added or deleted. The next table shows the options you have and what functions to call. 

3.4.2.6 - Table Of Metavalues Used In Update Section

 CLASS    TYPE     RDATA    Meaning                     Function
 ---------------------------------------------------------------
 ANY      ANY      empty    Delete all RRsets from name dns.RemoveName
 ANY      rrset    empty    Delete an RRset             dns.RemoveRRset
 NONE     rrset    rr       Delete an RR from RRset     dns.Remove
 zone     rrset    rr       Add to an RRset             dns.Insert

TRANSACTION SIGNATURE

An TSIG or transaction signature adds a HMAC TSIG record to each message sent. The supported algorithms include: HmacMD5, HmacSHA1, HmacSHA256 and HmacSHA512.

Basic use pattern when querying with a TSIG name "axfr." (note that these key names must be fully qualified - as they are domain names) and the base64 secret "so6ZGir4GPAqINNh9U5c3A==":

If an incoming message contains a TSIG record it MUST be the last record in the additional section (RFC2845 3.2). This means that you should make the call to SetTsig last, right before executing the query. If you make any changes to the RRset after calling SetTsig() the signature will be incorrect. 

c := new(dns.Client)
c.TsigSecret = map[string]string{"axfr.": "so6ZGir4GPAqINNh9U5c3A=="}
m := new(dns.Msg)
m.SetQuestion("miek.nl.", dns.TypeMX)
m.SetTsig("axfr.", dns.HmacMD5, 300, time.Now().Unix())
...
// When sending the TSIG RR is calculated and filled in before sending

When requesting an zone transfer (almost all TSIG usage is when requesting zone transfers), with TSIG, this is the basic use pattern. In this example we request an AXFR for miek.nl. with TSIG key named "axfr." and secret "so6ZGir4GPAqINNh9U5c3A==" and using the server 176.58.119.54: 

t := new(dns.Transfer)
m := new(dns.Msg)
t.TsigSecret = map[string]string{"axfr.": "so6ZGir4GPAqINNh9U5c3A=="}
m.SetAxfr("miek.nl.")
m.SetTsig("axfr.", dns.HmacMD5, 300, time.Now().Unix())
c, err := t.In(m, "176.58.119.54:53")
for r := range c { ... }

You can now read the records from the transfer as they come in. Each envelope is checked with TSIG. If something is not correct an error is returned.

Basic use pattern validating and replying to a message that has TSIG set. 

server := &dns.Server{Addr: ":53", Net: "udp"}
server.TsigSecret = map[string]string{"axfr.": "so6ZGir4GPAqINNh9U5c3A=="}
go server.ListenAndServe()
dns.HandleFunc(".", handleRequest)

func handleRequest(w dns.ResponseWriter, r *dns.Msg) {
	m := new(dns.Msg)
	m.SetReply(r)
	if r.IsTsig() != nil {
		if w.TsigStatus() == nil {
			// *Msg r has an TSIG record and it was validated
			m.SetTsig("axfr.", dns.HmacMD5, 300, time.Now().Unix())
		} else {
			// *Msg r has an TSIG records and it was not valided
		}
	}
	w.WriteMsg(m)
}

PRIVATE RRS

RFC 6895 sets aside a range of type codes for private use. This range is 65,280 - 65,534 (0xFF00 - 0xFFFE). When experimenting with new Resource Records these can be used, before requesting an official type code from IANA.

See https://miek.nl/2014/September/21/idn-and-private-rr-in-go-dns/ for more information.

EDNS0

EDNS0 is an extension mechanism for the DNS defined in RFC 2671 and updated by RFC 6891. It defines an new RR type, the OPT RR, which is then completely abused.

Basic use pattern for creating an (empty) OPT RR: 

o := new(dns.OPT)
o.Hdr.Name = "." // MUST be the root zone, per definition.
o.Hdr.Rrtype = dns.TypeOPT

The rdata of an OPT RR consists out of a slice of EDNS0 (RFC 6891) interfaces. Currently only a few have been standardized: EDNS0_NSID (RFC 5001) and EDNS0_SUBNET (draft-vandergaast-edns-client-subnet-02). Note that these options may be combined in an OPT RR. Basic use pattern for a server to check if (and which) options are set: 

// o is a dns.OPT
for _, s := range o.Option {
	switch e := s.(type) {
	case *dns.EDNS0_NSID:
		// do stuff with e.Nsid
	case *dns.EDNS0_SUBNET:
		// access e.Family, e.Address, etc.
	}
}

SIG(0)

From RFC 2931: 

SIG(0) provides protection for DNS transactions and requests ....
... protection for glue records, DNS requests, protection for message headers
on requests and responses, and protection of the overall integrity of a response.

It works like TSIG, except that SIG(0) uses public key cryptography, instead of the shared secret approach in TSIG. Supported algorithms: DSA, ECDSAP256SHA256, ECDSAP384SHA384, RSASHA1, RSASHA256 and RSASHA512.

Signing subsequent messages in multi-message sessions is not implemented.

Index

Examples

Constants

View Source 
const (

	// DefaultMsgSize is the standard default for messages larger than 512 bytes.
	DefaultMsgSize = 4096
	// MinMsgSize is the minimal size of a DNS packet.
	MinMsgSize = 512
	// MaxMsgSize is the largest possible DNS packet.
	MaxMsgSize = 65535
)
View Source 
const (
	RSAMD5 uint8
	DH
	DSA

	RSASHA1
	DSANSEC3SHA1
	RSASHA1NSEC3SHA1
	RSASHA256

	RSASHA512

	ECCGOST
	ECDSAP256SHA256
	ECDSAP384SHA384
	ED25519
	ED448
	INDIRECT   uint8 = 252
	PRIVATEDNS uint8 = 253 // Private (experimental keys)
	PRIVATEOID uint8 = 254
)

DNSSEC encryption algorithm codes.

View Source 
const (
	SHA1   uint8 // RFC 4034
	SHA256       // RFC 4509
	GOST94       // RFC 5933
	SHA384       // Experimental
	SHA512       // Experimental
)

DNSSEC hashing algorithm codes.

View Source 
const (
	SEP    = 1
	REVOKE = 1 << 7
	ZONE   = 1 << 8
)

DNSKEY flag values.

View Source 
const (
	EDNS0LLQ          = 0x1    // long lived queries: http://tools.ietf.org/html/draft-sekar-dns-llq-01
	EDNS0UL           = 0x2    // update lease draft: http://files.dns-sd.org/draft-sekar-dns-ul.txt
	EDNS0NSID         = 0x3    // nsid (See RFC 5001)
	EDNS0DAU          = 0x5    // DNSSEC Algorithm Understood
	EDNS0DHU          = 0x6    // DS Hash Understood
	EDNS0N3U          = 0x7    // NSEC3 Hash Understood
	EDNS0SUBNET       = 0x8    // client-subnet (See RFC 7871)
	EDNS0EXPIRE       = 0x9    // EDNS0 expire
	EDNS0COOKIE       = 0xa    // EDNS0 Cookie
	EDNS0TCPKEEPALIVE = 0xb    // EDNS0 tcp keep alive (See RFC 7828)
	EDNS0PADDING      = 0xc    // EDNS0 padding (See RFC 7830)
	EDNS0LOCALSTART   = 0xFDE9 // Beginning of range reserved for local/experimental use (See RFC 6891)
	EDNS0LOCALEND     = 0xFFFE // End of range reserved for local/experimental use (See RFC 6891)

)

EDNS0 Option codes.

View Source 
const (
	HmacMD5    = "hmac-md5.sig-alg.reg.int."
	HmacSHA1   = "hmac-sha1."
	HmacSHA256 = "hmac-sha256."
	HmacSHA512 = "hmac-sha512."
)

HMAC hashing codes. These are transmitted as domain names.

View Source 
const (
	TypeNone       uint16 = 0
	TypeA          uint16 = 1
	TypeNS         uint16 = 2
	TypeMD         uint16 = 3
	TypeMF         uint16 = 4
	TypeCNAME      uint16 = 5
	TypeSOA        uint16 = 6
	TypeMB         uint16 = 7
	TypeMG         uint16 = 8
	TypeMR         uint16 = 9
	TypeNULL       uint16 = 10
	TypePTR        uint16 = 12
	TypeHINFO      uint16 = 13
	TypeMINFO      uint16 = 14
	TypeMX         uint16 = 15
	TypeTXT        uint16 = 16
	TypeRP         uint16 = 17
	TypeAFSDB      uint16 = 18
	TypeX25        uint16 = 19
	TypeISDN       uint16 = 20
	TypeRT         uint16 = 21
	TypeNSAPPTR    uint16 = 23
	TypeSIG        uint16 = 24
	TypeKEY        uint16 = 25
	TypePX         uint16 = 26
	TypeGPOS       uint16 = 27
	TypeAAAA       uint16 = 28
	TypeLOC        uint16 = 29
	TypeNXT        uint16 = 30
	TypeEID        uint16 = 31
	TypeNIMLOC     uint16 = 32
	TypeSRV        uint16 = 33
	TypeATMA       uint16 = 34
	TypeNAPTR      uint16 = 35
	TypeKX         uint16 = 36
	TypeCERT       uint16 = 37
	TypeDNAME      uint16 = 39
	TypeOPT        uint16 = 41 // EDNS
	TypeDS         uint16 = 43
	TypeSSHFP      uint16 = 44
	TypeRRSIG      uint16 = 46
	TypeNSEC       uint16 = 47
	TypeDNSKEY     uint16 = 48
	TypeDHCID      uint16 = 49
	TypeNSEC3      uint16 = 50
	TypeNSEC3PARAM uint16 = 51
	TypeTLSA       uint16 = 52
	TypeSMIMEA     uint16 = 53
	TypeHIP        uint16 = 55
	TypeNINFO      uint16 = 56
	TypeRKEY       uint16 = 57
	TypeTALINK     uint16 = 58
	TypeCDS        uint16 = 59
	TypeCDNSKEY    uint16 = 60
	TypeOPENPGPKEY uint16 = 61
	TypeCSYNC      uint16 = 62
	TypeSPF        uint16 = 99
	TypeUINFO      uint16 = 100
	TypeUID        uint16 = 101
	TypeGID        uint16 = 102
	TypeUNSPEC     uint16 = 103
	TypeNID        uint16 = 104
	TypeL32        uint16 = 105
	TypeL64        uint16 = 106
	TypeLP         uint16 = 107
	TypeEUI48      uint16 = 108
	TypeEUI64      uint16 = 109
	TypeURI        uint16 = 256
	TypeCAA        uint16 = 257
	TypeAVC        uint16 = 258

	TypeTKEY uint16 = 249
	TypeTSIG uint16 = 250

	// valid Question.Qtype only
	TypeIXFR  uint16 = 251
	TypeAXFR  uint16 = 252
	TypeMAILB uint16 = 253
	TypeMAILA uint16 = 254
	TypeANY   uint16 = 255

	TypeTA       uint16 = 32768
	TypeDLV      uint16 = 32769
	TypeReserved uint16 = 65535

	// valid Question.Qclass
	ClassINET   = 1
	ClassCSNET  = 2
	ClassCHAOS  = 3
	ClassHESIOD = 4
	ClassNONE   = 254
	ClassANY    = 255

	// Message Response Codes, see https://www.iana.org/assignments/dns-parameters/dns-parameters.xhtml
	RcodeSuccess        = 0  // NoError   - No Error                          [DNS]
	RcodeFormatError    = 1  // FormErr   - Format Error                      [DNS]
	RcodeServerFailure  = 2  // ServFail  - Server Failure                    [DNS]
	RcodeNameError      = 3  // NXDomain  - Non-Existent Domain               [DNS]
	RcodeNotImplemented = 4  // NotImp    - Not Implemented                   [DNS]
	RcodeRefused        = 5  // Refused   - Query Refused                     [DNS]
	RcodeYXDomain       = 6  // YXDomain  - Name Exists when it should not    [DNS Update]
	RcodeYXRrset        = 7  // YXRRSet   - RR Set Exists when it should not  [DNS Update]
	RcodeNXRrset        = 8  // NXRRSet   - RR Set that should exist does not [DNS Update]
	RcodeNotAuth        = 9  // NotAuth   - Server Not Authoritative for zone [DNS Update]
	RcodeNotZone        = 10 // NotZone   - Name not contained in zone        [DNS Update/TSIG]
	RcodeBadSig         = 16 // BADSIG    - TSIG Signature Failure            [TSIG]
	RcodeBadVers        = 16 // BADVERS   - Bad OPT Version                   [EDNS0]
	RcodeBadKey         = 17 // BADKEY    - Key not recognized                [TSIG]
	RcodeBadTime        = 18 // BADTIME   - Signature out of time window      [TSIG]
	RcodeBadMode        = 19 // BADMODE   - Bad TKEY Mode                     [TKEY]
	RcodeBadName        = 20 // BADNAME   - Duplicate key name                [TKEY]
	RcodeBadAlg         = 21 // BADALG    - Algorithm not supported           [TKEY]
	RcodeBadTrunc       = 22 // BADTRUNC  - Bad Truncation                    [TSIG]
	RcodeBadCookie      = 23 // BADCOOKIE - Bad/missing Server Cookie         [DNS Cookies]

	// Message Opcodes. There is no 3.
	OpcodeQuery  = 0
	OpcodeIQuery = 1
	OpcodeStatus = 2
	OpcodeNotify = 4
	OpcodeUpdate = 5
)

Wire constants and supported types.

View Source 
const (
	LOC_EQUATOR       = 1 << 31 // RFC 1876, Section 2.
	LOC_PRIMEMERIDIAN = 1 << 31 // RFC 1876, Section 2.
	LOC_HOURS         = 60 * 1000
	LOC_DEGREES       = 60 * LOC_HOURS
	LOC_ALTITUDEBASE  = 100000
)

Various constants used in the LOC RR, See RFC 1887.

View Source 
const (
	CertPKIX = 1 + iota
	CertSPKI
	CertPGP
	CertIPIX
	CertISPKI
	CertIPGP
	CertACPKIX
	CertIACPKIX
	CertURI = 253
	CertOID = 254
)

Different Certificate Types, see RFC 4398, Section 2.1

Variables

View Source 
var (
	ErrAlg           error = &Error{err: "bad algorithm"}                  // ErrAlg indicates an error with the (DNSSEC) algorithm.
	ErrAuth          error = &Error{err: "bad authentication"}             // ErrAuth indicates an error in the TSIG authentication.
	ErrBuf           error = &Error{err: "buffer size too small"}          // ErrBuf indicates that the buffer used is too small for the message.
	ErrConnEmpty     error = &Error{err: "conn has no connection"}         // ErrConnEmpty indicates a connection is being used before it is initialized.
	ErrExtendedRcode error = &Error{err: "bad extended rcode"}             // ErrExtendedRcode ...
	ErrFqdn          error = &Error{err: "domain must be fully qualified"} // ErrFqdn indicates that a domain name does not have a closing dot.
	ErrId            error = &Error{err: "id mismatch"}                    // ErrId indicates there is a mismatch with the message's ID.
	ErrKeyAlg        error = &Error{err: "bad key algorithm"}              // ErrKeyAlg indicates that the algorithm in the key is not valid.
	ErrKey           error = &Error{err: "bad key"}
	ErrKeySize       error = &Error{err: "bad key size"}
	ErrLongDomain    error = &Error{err: fmt.Sprintf("domain name exceeded %d wire-format octets", maxDomainNameWireOctets)}
	ErrNoSig         error = &Error{err: "no signature found"}
	ErrPrivKey       error = &Error{err: "bad private key"}
	ErrRcode         error = &Error{err: "bad rcode"}
	ErrRdata         error = &Error{err: "bad rdata"}
	ErrRRset         error = &Error{err: "bad rrset"}
	ErrSecret        error = &Error{err: "no secrets defined"}
	ErrShortRead     error = &Error{err: "short read"}
	ErrSig           error = &Error{err: "bad signature"} // ErrSig indicates that a signature can not be cryptographically validated.
	ErrSoa           error = &Error{err: "no SOA"}        // ErrSOA indicates that no SOA RR was seen when doing zone transfers.
	ErrTime          error = &Error{err: "bad time"}      // ErrTime indicates a timing error in TSIG authentication.
)

Errors defined in this package.

View Source 
var AlgorithmToHash = map[uint8]crypto.Hash{
	RSAMD5:           crypto.MD5,
	DSA:              crypto.SHA1,
	RSASHA1:          crypto.SHA1,
	RSASHA1NSEC3SHA1: crypto.SHA1,
	RSASHA256:        crypto.SHA256,
	ECDSAP256SHA256:  crypto.SHA256,
	ECDSAP384SHA384:  crypto.SHA384,
	RSASHA512:        crypto.SHA512,
	ED25519:          crypto.Hash(0),
}

AlgorithmToHash is a map of algorithm crypto hash IDs to crypto.Hash's.

View Source 
var AlgorithmToString = map[uint8]string{
	RSAMD5:           "RSAMD5",
	DH:               "DH",
	DSA:              "DSA",
	RSASHA1:          "RSASHA1",
	DSANSEC3SHA1:     "DSA-NSEC3-SHA1",
	RSASHA1NSEC3SHA1: "RSASHA1-NSEC3-SHA1",
	RSASHA256:        "RSASHA256",
	RSASHA512:        "RSASHA512",
	ECCGOST:          "ECC-GOST",
	ECDSAP256SHA256:  "ECDSAP256SHA256",
	ECDSAP384SHA384:  "ECDSAP384SHA384",
	ED25519:          "ED25519",
	ED448:            "ED448",
	INDIRECT:         "INDIRECT",
	PRIVATEDNS:       "PRIVATEDNS",
	PRIVATEOID:       "PRIVATEOID",
}

AlgorithmToString is a map of algorithm IDs to algorithm names.

View Source 
var CertTypeToString = map[uint16]string{
	CertPKIX:    "PKIX",
	CertSPKI:    "SPKI",
	CertPGP:     "PGP",
	CertIPIX:    "IPIX",
	CertISPKI:   "ISPKI",
	CertIPGP:    "IPGP",
	CertACPKIX:  "ACPKIX",
	CertIACPKIX: "IACPKIX",
	CertURI:     "URI",
	CertOID:     "OID",
}

CertTypeToString converts the Cert Type to its string representation. See RFC 4398 and RFC 6944.

View Source 
var ClassToString = map[uint16]string{
	ClassINET:   "IN",
	ClassCSNET:  "CS",
	ClassCHAOS:  "CH",
	ClassHESIOD: "HS",
	ClassNONE:   "NONE",
	ClassANY:    "ANY",
}

ClassToString is a maps Classes to strings for each CLASS wire type.

View Source 
var DefaultServeMux = NewServeMux()

DefaultServeMux is the default ServeMux used by Serve.

View Source 
var HashToString = map[uint8]string{
	SHA1:   "SHA1",
	SHA256: "SHA256",
	GOST94: "GOST94",
	SHA384: "SHA384",
	SHA512: "SHA512",
}

HashToString is a map of hash IDs to names.

View Source 
var Id = id

Id by default, returns a 16 bits random number to be used as a message id. The random provided should be good enough. This being a variable the function can be reassigned to a custom function. For instance, to make it return a static value: 

dns.Id = func() uint16 { return 3 }
View Source 
var OpcodeToString = map[int]string{
	OpcodeQuery:  "QUERY",
	OpcodeIQuery: "IQUERY",
	OpcodeStatus: "STATUS",
	OpcodeNotify: "NOTIFY",
	OpcodeUpdate: "UPDATE",
}

OpcodeToString maps Opcodes to strings.

View Source 
var RcodeToString = map[int]string{
	RcodeSuccess:        "NOERROR",
	RcodeFormatError:    "FORMERR",
	RcodeServerFailure:  "SERVFAIL",
	RcodeNameError:      "NXDOMAIN",
	RcodeNotImplemented: "NOTIMP",
	RcodeRefused:        "REFUSED",
	RcodeYXDomain:       "YXDOMAIN",
	RcodeYXRrset:        "YXRRSET",
	RcodeNXRrset:        "NXRRSET",
	RcodeNotAuth:        "NOTAUTH",
	RcodeNotZone:        "NOTZONE",
	RcodeBadSig:         "BADSIG",

	RcodeBadKey:    "BADKEY",
	RcodeBadTime:   "BADTIME",
	RcodeBadMode:   "BADMODE",
	RcodeBadName:   "BADNAME",
	RcodeBadAlg:    "BADALG",
	RcodeBadTrunc:  "BADTRUNC",
	RcodeBadCookie: "BADCOOKIE",
}

RcodeToString maps Rcodes to strings.

View Source 
var StringToAlgorithm = reverseInt8(AlgorithmToString)

StringToAlgorithm is the reverse of AlgorithmToString.

View Source 
var StringToCertType = reverseInt16(CertTypeToString)

StringToCertType is the reverseof CertTypeToString.

View Source 
var StringToClass = reverseInt16(ClassToString)

StringToClass is the reverse of ClassToString, needed for string parsing.

View Source 
var StringToHash = reverseInt8(HashToString)

StringToHash is a map of names to hash IDs.

View Source 
var StringToOpcode = reverseInt(OpcodeToString)

StringToOpcode is a map of opcodes to strings.

View Source 
var StringToRcode = reverseInt(RcodeToString)

StringToRcode is a map of rcodes to strings.

View Source 
var StringToType = reverseInt16(TypeToString)

StringToType is the reverse of TypeToString, needed for string parsing.

View Source 
var TypeToRR = map[uint16]func() RR{
	TypeA:          func() RR { return new(A) },
	TypeAAAA:       func() RR { return new(AAAA) },
	TypeAFSDB:      func() RR { return new(AFSDB) },
	TypeANY:        func() RR { return new(ANY) },
	TypeAVC:        func() RR { return new(AVC) },
	TypeCAA:        func() RR { return new(CAA) },
	TypeCDNSKEY:    func() RR { return new(CDNSKEY) },
	TypeCDS:        func() RR { return new(CDS) },
	TypeCERT:       func() RR { return new(CERT) },
	TypeCNAME:      func() RR { return new(CNAME) },
	TypeCSYNC:      func() RR { return new(CSYNC) },
	TypeDHCID:      func() RR { return new(DHCID) },
	TypeDLV:        func() RR { return new(DLV) },
	TypeDNAME:      func() RR { return new(DNAME) },
	TypeDNSKEY:     func() RR { return new(DNSKEY) },
	TypeDS:         func() RR { return new(DS) },
	TypeEID:        func() RR { return new(EID) },
	TypeEUI48:      func() RR { return new(EUI48) },
	TypeEUI64:      func() RR { return new(EUI64) },
	TypeGID:        func() RR { return new(GID) },
	TypeGPOS:       func() RR { return new(GPOS) },
	TypeHINFO:      func() RR { return new(HINFO) },
	TypeHIP:        func() RR { return new(HIP) },
	TypeKEY:        func() RR { return new(KEY) },
	TypeKX:         func() RR { return new(KX) },
	TypeL32:        func() RR { return new(L32) },
	TypeL64:        func() RR { return new(L64) },
	TypeLOC:        func() RR { return new(LOC) },
	TypeLP:         func() RR { return new(LP) },
	TypeMB:         func() RR { return new(MB) },
	TypeMD:         func() RR { return new(MD) },
	TypeMF:         func() RR { return new(MF) },
	TypeMG:         func() RR { return new(MG) },
	TypeMINFO:      func() RR { return new(MINFO) },
	TypeMR:         func() RR { return new(MR) },
	TypeMX:         func() RR { return new(MX) },
	TypeNAPTR:      func() RR { return new(NAPTR) },
	TypeNID:        func() RR { return new(NID) },
	TypeNIMLOC:     func() RR { return new(NIMLOC) },
	TypeNINFO:      func() RR { return new(NINFO) },
	TypeNS:         func() RR { return new(NS) },
	TypeNSAPPTR:    func() RR { return new(NSAPPTR) },
	TypeNSEC:       func() RR { return new(NSEC) },
	TypeNSEC3:      func() RR { return new(NSEC3) },
	TypeNSEC3PARAM: func() RR { return new(NSEC3PARAM) },
	TypeNULL:       func() RR { return new(NULL) },
	TypeOPENPGPKEY: func() RR { return new(OPENPGPKEY) },
	TypeOPT:        func() RR { return new(OPT) },
	TypePTR:        func() RR { return new(PTR) },
	TypePX:         func() RR { return new(PX) },
	TypeRKEY:       func() RR { return new(RKEY) },
	TypeRP:         func() RR { return new(RP) },
	TypeRRSIG:      func() RR { return new(RRSIG) },
	TypeRT:         func() RR { return new(RT) },
	TypeSIG:        func() RR { return new(SIG) },
	TypeSMIMEA:     func() RR { return new(SMIMEA) },
	TypeSOA:        func() RR { return new(SOA) },
	TypeSPF:        func() RR { return new(SPF) },
	TypeSRV:        func() RR { return new(SRV) },
	TypeSSHFP:      func() RR { return new(SSHFP) },
	TypeTA:         func() RR { return new(TA) },
	TypeTALINK:     func() RR { return new(TALINK) },
	TypeTKEY:       func() RR { return new(TKEY) },
	TypeTLSA:       func() RR { return new(TLSA) },
	TypeTSIG:       func() RR { return new(TSIG) },
	TypeTXT:        func() RR { return new(TXT) },
	TypeUID:        func() RR { return new(UID) },
	TypeUINFO:      func() RR { return new(UINFO) },
	TypeURI:        func() RR { return new(URI) },
	TypeX25:        func() RR { return new(X25) },
}

TypeToRR is a map of constructors for each RR type.

View Source 
var TypeToString = map[uint16]string{
	TypeA:          "A",
	TypeAAAA:       "AAAA",
	TypeAFSDB:      "AFSDB",
	TypeANY:        "ANY",
	TypeATMA:       "ATMA",
	TypeAVC:        "AVC",
	TypeAXFR:       "AXFR",
	TypeCAA:        "CAA",
	TypeCDNSKEY:    "CDNSKEY",
	TypeCDS:        "CDS",
	TypeCERT:       "CERT",
	TypeCNAME:      "CNAME",
	TypeCSYNC:      "CSYNC",
	TypeDHCID:      "DHCID",
	TypeDLV:        "DLV",
	TypeDNAME:      "DNAME",
	TypeDNSKEY:     "DNSKEY",
	TypeDS:         "DS",
	TypeEID:        "EID",
	TypeEUI48:      "EUI48",
	TypeEUI64:      "EUI64",
	TypeGID:        "GID",
	TypeGPOS:       "GPOS",
	TypeHINFO:      "HINFO",
	TypeHIP:        "HIP",
	TypeISDN:       "ISDN",
	TypeIXFR:       "IXFR",
	TypeKEY:        "KEY",
	TypeKX:         "KX",
	TypeL32:        "L32",
	TypeL64:        "L64",
	TypeLOC:        "LOC",
	TypeLP:         "LP",
	TypeMAILA:      "MAILA",
	TypeMAILB:      "MAILB",
	TypeMB:         "MB",
	TypeMD:         "MD",
	TypeMF:         "MF",
	TypeMG:         "MG",
	TypeMINFO:      "MINFO",
	TypeMR:         "MR",
	TypeMX:         "MX",
	TypeNAPTR:      "NAPTR",
	TypeNID:        "NID",
	TypeNIMLOC:     "NIMLOC",
	TypeNINFO:      "NINFO",
	TypeNS:         "NS",
	TypeNSEC:       "NSEC",
	TypeNSEC3:      "NSEC3",
	TypeNSEC3PARAM: "NSEC3PARAM",
	TypeNULL:       "NULL",
	TypeNXT:        "NXT",
	TypeNone:       "None",
	TypeOPENPGPKEY: "OPENPGPKEY",
	TypeOPT:        "OPT",
	TypePTR:        "PTR",
	TypePX:         "PX",
	TypeRKEY:       "RKEY",
	TypeRP:         "RP",
	TypeRRSIG:      "RRSIG",
	TypeRT:         "RT",
	TypeReserved:   "Reserved",
	TypeSIG:        "SIG",
	TypeSMIMEA:     "SMIMEA",
	TypeSOA:        "SOA",
	TypeSPF:        "SPF",
	TypeSRV:        "SRV",
	TypeSSHFP:      "SSHFP",
	TypeTA:         "TA",
	TypeTALINK:     "TALINK",
	TypeTKEY:       "TKEY",
	TypeTLSA:       "TLSA",
	TypeTSIG:       "TSIG",
	TypeTXT:        "TXT",
	TypeUID:        "UID",
	TypeUINFO:      "UINFO",
	TypeUNSPEC:     "UNSPEC",
	TypeURI:        "URI",
	TypeX25:        "X25",
	TypeNSAPPTR:    "NSAP-PTR",
}

TypeToString is a map of strings for each RR type.

View Source 
var Version = V{1, 1, 12}

Version is current version of this library.

Functions

func ActivateAndServe 

func ActivateAndServe(l net.Listener, p net.PacketConn, handler Handler) error

ActivateAndServe activates a server with a listener from systemd, l and p should not both be non-nil. If both l and p are not nil only p will be used. Invoke handler for incoming queries.

func CertificateToDANE 

func CertificateToDANE(selector, matchingType uint8, cert *x509.Certificate) (string, error)

CertificateToDANE converts a certificate to a hex string as used in the TLSA or SMIMEA records.

func CompareDomainName 

func CompareDomainName(s1, s2 string) (n int)

CompareDomainName compares the names s1 and s2 and returns how many labels they have in common starting from the *right*. The comparison stops at the first inequality. The names are downcased before the comparison.

www.miek.nl. and miek.nl. have two labels in common: miek and nl www.miek.nl. and www.bla.nl. have one label in common: nl

s1 and s2 must be syntactically valid domain names.

func CountLabel 

func CountLabel(s string) (labels int)

CountLabel counts the the number of labels in the string s. s must be a syntactically valid domain name.

func Field 

func Field(r RR, i int) string

Field returns the rdata field i as a string. Fields are indexed starting from 1. RR types that holds slice data, for instance the NSEC type bitmap will return a single string where the types are concatenated using a space. Accessing non existing fields will cause a panic.

func Fqdn 

func Fqdn(s string) string

Fqdn return the fully qualified domain name from s. If s is already fully qualified, it behaves as the identity function.

func Handle 

func Handle(pattern string, handler Handler)

Handle registers the handler with the given pattern in the DefaultServeMux. The documentation for ServeMux explains how patterns are matched.

func HandleFailed 

func HandleFailed(w ResponseWriter, r *Msg)

HandleFailed returns a HandlerFunc that returns SERVFAIL for every request it gets.

func HandleFunc 

func HandleFunc(pattern string, handler func(ResponseWriter, *Msg))

HandleFunc registers the handler function with the given pattern in the DefaultServeMux.

func HandleRemove 

func HandleRemove(pattern string)

HandleRemove deregisters the handle with the given pattern in the DefaultServeMux.

func HashName 

func HashName(label string, ha uint8, iter uint16, salt string) string

HashName hashes a string (label) according to RFC 5155. It returns the hashed string in uppercase.

func IsDomainName 

func IsDomainName(s string) (labels int, ok bool)

IsDomainName checks if s is a valid domain name, it returns the number of labels and true, when a domain name is valid. Note that non fully qualified domain name is considered valid, in this case the last label is counted in the number of labels. When false is returned the number of labels is not defined. Also note that this function is extremely liberal; almost any string is a valid domain name as the DNS is 8 bit protocol. It checks if each label fits in 63 characters and that the entire name will fit into the 255 octet wire format limit.

func IsDuplicate added in v1.0.11 

func IsDuplicate(r1, r2 RR) bool

IsDuplicate checks of r1 and r2 are duplicates of each other, excluding the TTL. So this means the header data is equal *and* the RDATA is the same. Return true is so, otherwise false. It's is a protocol violation to have identical RRs in a message.

func IsFqdn 

func IsFqdn(s string) bool

IsFqdn checks if a domain name is fully qualified.

func IsMsg 

func IsMsg(buf []byte) error

IsMsg sanity checks buf and returns an error if it isn't a valid DNS packet. The checking is performed on the binary payload.

func IsRRset 

func IsRRset(rrset []RR) bool

IsRRset checks if a set of RRs is a valid RRset as defined by RFC 2181. This means the RRs need to have the same type, name, and class. Returns true if the RR set is valid, otherwise false.

func IsSubDomain 

func IsSubDomain(parent, child string) bool

IsSubDomain checks if child is indeed a child of the parent. If child and parent are the same domain true is returned as well.

func Len 

func Len(r RR) int

Len returns the length (in octets) of the uncompressed RR in wire format.

func ListenAndServe 

func ListenAndServe(addr string, network string, handler Handler) error

ListenAndServe Starts a server on address and network specified Invoke handler for incoming queries.

func ListenAndServeTLS 

func ListenAndServeTLS(addr, certFile, keyFile string, handler Handler) error

ListenAndServeTLS acts like http.ListenAndServeTLS, more information in http://golang.org/pkg/net/http/#ListenAndServeTLS

func NextLabel 

func NextLabel(s string, offset int) (i int, end bool)

NextLabel returns the index of the start of the next label in the string s starting at offset. The bool end is true when the end of the string has been reached. Also see PrevLabel.

func NumField 

func NumField(r RR) int

NumField returns the number of rdata fields r has.

func PackDomainName 

func PackDomainName(s string, msg []byte, off int, compression map[string]int, compress bool) (off1 int, err error)

PackDomainName packs a domain name s into msg[off:]. If compression is wanted compress must be true and the compression map needs to hold a mapping between domain names and offsets pointing into msg.

func PackRR 

func PackRR(rr RR, msg []byte, off int, compression map[string]int, compress bool) (off1 int, err error)

PackRR packs a resource record rr into msg[off:]. See PackDomainName for documentation about the compression.

func ParseZone deprecated 

func ParseZone(r io.Reader, origin, file string) chan *Token

ParseZone reads a RFC 1035 style zonefile from r. It returns *Tokens on the returned channel, each consisting of either a parsed RR and optional comment or a nil RR and an error. The channel is closed by ParseZone when the end of r is reached.

The string file is used in error reporting and to resolve relative $INCLUDE directives. The string origin is used as the initial origin, as if the file would start with an $ORIGIN directive.

The directives $INCLUDE, $ORIGIN, $TTL and $GENERATE are all supported.

Basic usage pattern when reading from a string (z) containing the zone data: 

	for x := range dns.ParseZone(strings.NewReader(z), "", "") {
		if x.Error != nil {
                 // log.Println(x.Error)
             } else {
                 // Do something with x.RR
             }
	}

Comments specified after an RR (and on the same line!) are returned too: 

foo. IN A 10.0.0.1 ; this is a comment

The text "; this is comment" is returned in Token.Comment. Comments inside the RR are returned concatenated along with the RR. Comments on a line by themselves are discarded.

To prevent memory leaks it is important to always fully drain the returned channel. If an error occurs, it will always be the last Token sent on the channel.

Deprecated: New users should prefer the ZoneParser API.

func PrevLabel 

func PrevLabel(s string, n int) (i int, start bool)

PrevLabel returns the index of the label when starting from the right and jumping n labels to the left. The bool start is true when the start of the string has been overshot. Also see NextLabel.

func PrivateHandle 

func PrivateHandle(rtypestr string, rtype uint16, generator func() PrivateRdata)

PrivateHandle registers a private resource record type. It requires string and numeric representation of private RR type and generator function as argument.

Example 
package main

import (
	"errors"
	"fmt"
	"log"
	"net"

	"github.com/miekg/dns"
)

const TypeAPAIR = 0x0F99

type APAIR struct {
	addr [2]net.IP
}

func NewAPAIR() dns.PrivateRdata { return new(APAIR) }

func (rd *APAIR) String() string { return rd.addr[0].String() + " " + rd.addr[1].String() }
func (rd *APAIR) Parse(txt []string) error {
	if len(txt) != 2 {
		return errors.New("two addresses required for APAIR")
	}
	for i, s := range txt {
		ip := net.ParseIP(s)
		if ip == nil {
			return errors.New("invalid IP in APAIR text representation")
		}
		rd.addr[i] = ip
	}
	return nil
}

func (rd *APAIR) Pack(buf []byte) (int, error) {
	b := append([]byte(rd.addr[0]), []byte(rd.addr[1])...)
	n := copy(buf, b)
	if n != len(b) {
		return n, dns.ErrBuf
	}
	return n, nil
}

func (rd *APAIR) Unpack(buf []byte) (int, error) {
	ln := net.IPv4len * 2
	if len(buf) != ln {
		return 0, errors.New("invalid length of APAIR rdata")
	}
	cp := make([]byte, ln)
	copy(cp, buf)

	rd.addr[0] = net.IP(cp[:3])
	rd.addr[1] = net.IP(cp[4:])

	return len(buf), nil
}

func (rd *APAIR) Copy(dest dns.PrivateRdata) error {
	cp := make([]byte, rd.Len())
	_, err := rd.Pack(cp)
	if err != nil {
		return err
	}

	d := dest.(*APAIR)
	d.addr[0] = net.IP(cp[:3])
	d.addr[1] = net.IP(cp[4:])
	return nil
}

func (rd *APAIR) Len() int {
	return net.IPv4len * 2
}

func main() {
	dns.PrivateHandle("APAIR", TypeAPAIR, NewAPAIR)
	defer dns.PrivateHandleRemove(TypeAPAIR)

	rr, err := dns.NewRR("miek.nl. APAIR (1.2.3.4    1.2.3.5)")
	if err != nil {
		log.Fatal("could not parse APAIR record: ", err)
	}
	fmt.Println(rr)
	

Output:

func PrivateHandleRemove 

func PrivateHandleRemove(rtype uint16)

PrivateHandleRemove removes definitions required to support private RR type.

func ReverseAddr 

func ReverseAddr(addr string) (arpa string, err error)

ReverseAddr returns the in-addr.arpa. or ip6.arpa. hostname of the IP address suitable for reverse DNS (PTR) record lookups or an error if it fails to parse the IP address.

func SMIMEAName 

func SMIMEAName(email, domain string) (string, error)

SMIMEAName returns the ownername of a SMIMEA resource record as per the format specified in RFC 'draft-ietf-dane-smime-12' Section 2 and 3

func Split 

func Split(s string) []int

Split splits a name s into its label indexes. www.miek.nl. returns []int{0, 4, 9}, www.miek.nl also returns []int{0, 4, 9}. The root name (.) returns nil. Also see SplitDomainName. s must be a syntactically valid domain name.

func SplitDomainName 

func SplitDomainName(s string) (labels []string)

SplitDomainName splits a name string into it's labels. www.miek.nl. returns []string{"www", "miek", "nl"} .www.miek.nl. returns []string{"", "www", "miek", "nl"}, The root label (.) returns nil. Note that using strings.Split(s) will work in most cases, but does not handle escaped dots (\.) for instance. s must be a syntactically valid domain name, see IsDomainName.

func StringToTime 

func StringToTime(s string) (uint32, error)

StringToTime translates the RRSIG's incep. and expir. times from string values like "20110403154150" to an 32 bit integer. It takes serial arithmetic (RFC 1982) into account.

func TLSAName 

func TLSAName(name, service, network string) (string, error)

TLSAName returns the ownername of a TLSA resource record as per the rules specified in RFC 6698, Section 3.

func TimeToString 

func TimeToString(t uint32) string

TimeToString translates the RRSIG's incep. and expir. times to the string representation used when printing the record. It takes serial arithmetic (RFC 1982) into account.

func TsigGenerate 

func TsigGenerate(m *Msg, secret, requestMAC string, timersOnly bool) ([]byte, string, error)

TsigGenerate fills out the TSIG record attached to the message. The message should contain a "stub" TSIG RR with the algorithm, key name (owner name of the RR), time fudge (defaults to 300 seconds) and the current time The TSIG MAC is saved in that Tsig RR. When TsigGenerate is called for the first time requestMAC is set to the empty string and timersOnly is false. If something goes wrong an error is returned, otherwise it is nil.

func TsigVerify 

func TsigVerify(msg []byte, secret, requestMAC string, timersOnly bool) error

TsigVerify verifies the TSIG on a message. If the signature does not validate err contains the error, otherwise it is nil.

func UnpackDomainName 

func UnpackDomainName(msg []byte, off int) (string, int, error)

UnpackDomainName unpacks a domain name into a string. It returns the name, the new offset into msg and any error that occurred.

When an error is encountered, the unpacked name will be discarded and len(msg) will be returned as the offset.

func WriteToSessionUDP 

func WriteToSessionUDP(conn *net.UDPConn, b []byte, session *SessionUDP) (int, error)

WriteToSessionUDP acts just like net.UDPConn.WriteTo(), but uses a *SessionUDP instead of a net.Addr.

Types

type A 

type A struct {
	Hdr RR_Header
	A   net.IP `dns:"a"`
}

A RR. See RFC 1035.

func (*A) Header 

func (rr *A) Header() *RR_Header

func (*A) String 

func (rr *A) String() string

type AAAA 

type AAAA struct {
	Hdr  RR_Header
	AAAA net.IP `dns:"aaaa"`
}

AAAA RR. See RFC 3596.

func (*AAAA) Header 

func (rr *AAAA) Header() *RR_Header

func (*AAAA) String 

func (rr *AAAA) String() string

type AFSDB 

type AFSDB struct {
	Hdr      RR_Header
	Subtype  uint16
	Hostname string `dns:"domain-name"`
}

AFSDB RR. See RFC 1183.

func (*AFSDB) Header 

func (rr *AFSDB) Header() *RR_Header

func (*AFSDB) String 

func (rr *AFSDB) String() string

type ANY 

type ANY struct {
	Hdr RR_Header
}

ANY is a wildcard record. See RFC 1035, Section 3.2.3. ANY is named "*" there.

func (*ANY) Header 

func (rr *ANY) Header() *RR_Header

func (*ANY) String 

func (rr *ANY) String() string

type AVC 

type AVC struct {
	Hdr RR_Header
	Txt []string `dns:"txt"`
}

AVC RR. See https://www.iana.org/assignments/dns-parameters/AVC/avc-completed-template.

func (*AVC) Header 

func (rr *AVC) Header() *RR_Header

func (*AVC) String 

func (rr *AVC) String() string

type CAA 

type CAA struct {
	Hdr   RR_Header
	Flag  uint8
	Tag   string
	Value string `dns:"octet"`
}

CAA RR. See RFC 6844.

func (*CAA) Header 

func (rr *CAA) Header() *RR_Header

func (*CAA) String 

func (rr *CAA) String() string

type CDNSKEY 

type CDNSKEY struct {
	DNSKEY
}

CDNSKEY RR. See RFC 7344.

func (*CDNSKEY) Header 

func (rr *CDNSKEY) Header() *RR_Header

type CDS 

type CDS struct{ DS }

CDS RR. See RFC 7344.

func (*CDS) Header 

func (rr *CDS) Header() *RR_Header

type CERT 

type CERT struct {
	Hdr         RR_Header
	Type        uint16
	KeyTag      uint16
	Algorithm   uint8
	Certificate string `dns:"base64"`
}

CERT RR. See RFC 4398.

func (*CERT) Header 

func (rr *CERT) Header() *RR_Header

func (*CERT) String 

func (rr *CERT) String() string

type CNAME 

type CNAME struct {
	Hdr    RR_Header
	Target string `dns:"cdomain-name"`
}

CNAME RR. See RFC 1034.

func (*CNAME) Header 

func (rr *CNAME) Header() *RR_Header

func (*CNAME) String 

func (rr *CNAME) String() string

type CSYNC 

type CSYNC struct {
	Hdr        RR_Header
	Serial     uint32
	Flags      uint16
	TypeBitMap []uint16 `dns:"nsec"`
}

CSYNC RR. See RFC 7477.

func (*CSYNC) Header 

func (rr *CSYNC) Header() *RR_Header

func (*CSYNC) String 

func (rr *CSYNC) String() string

type Class 

type Class uint16

Class is a DNS class.

func (Class) String 

func (c Class) String() string

String returns the string representation for the class c.

type Client 

type Client struct {
	Net       string      // if "tcp" or "tcp-tls" (DNS over TLS) a TCP query will be initiated, otherwise an UDP one (default is "" for UDP)
	UDPSize   uint16      // minimum receive buffer for UDP messages
	TLSConfig *tls.Config // TLS connection configuration
	Dialer    *net.Dialer // a net.Dialer used to set local address, timeouts and more
	// Timeout is a cumulative timeout for dial, write and read, defaults to 0 (disabled) - overrides DialTimeout, ReadTimeout,
	// WriteTimeout when non-zero. Can be overridden with net.Dialer.Timeout (see Client.ExchangeWithDialer and
	// Client.Dialer) or context.Context.Deadline (see the deprecated ExchangeContext)
	Timeout        time.Duration
	DialTimeout    time.Duration     // net.DialTimeout, defaults to 2 seconds, or net.Dialer.Timeout if expiring earlier - overridden by Timeout when that value is non-zero
	ReadTimeout    time.Duration     // net.Conn.SetReadTimeout value for connections, defaults to 2 seconds - overridden by Timeout when that value is non-zero
	WriteTimeout   time.Duration     // net.Conn.SetWriteTimeout value for connections, defaults to 2 seconds - overridden by Timeout when that value is non-zero
	TsigSecret     map[string]string // secret(s) for Tsig map[<zonename>]<base64 secret>, zonename must be in canonical form (lowercase, fqdn, see RFC 4034 Section 6.2)
	SingleInflight bool              // if true suppress multiple outstanding queries for the same Qname, Qtype and Qclass
	// contains filtered or unexported fields
}

A Client defines parameters for a DNS client.

func (*Client) Dial 

func (c *Client) Dial(address string) (conn *Conn, err error)

Dial connects to the address on the named network.

func (*Client) Exchange 

func (c *Client) Exchange(m *Msg, address string) (r *Msg, rtt time.Duration, err error)

Exchange performs a synchronous query. It sends the message m to the address contained in a and waits for a reply. Basic use pattern with a *dns.Client: 

c := new(dns.Client)
in, rtt, err := c.Exchange(message, "127.0.0.1:53")

Exchange does not retry a failed query, nor will it fall back to TCP in case of truncation. It is up to the caller to create a message that allows for larger responses to be returned. Specifically this means adding an EDNS0 OPT RR that will advertise a larger buffer, see SetEdns0. Messages without an OPT RR will fallback to the historic limit of 512 bytes To specify a local address or a timeout, the caller has to set the `Client.Dialer` attribute appropriately

func (*Client) ExchangeContext 

func (c *Client) ExchangeContext(ctx context.Context, m *Msg, a string) (r *Msg, rtt time.Duration, err error)

ExchangeContext acts like Exchange, but honors the deadline on the provided context, if present. If there is both a context deadline and a configured timeout on the client, the earliest of the two takes effect.

type ClientConfig 

type ClientConfig struct {
	Servers  []string // servers to use
	Search   []string // suffixes to append to local name
	Port     string   // what port to use
	Ndots    int      // number of dots in name to trigger absolute lookup
	Timeout  int      // seconds before giving up on packet
	Attempts int      // lost packets before giving up on server, not used in the package dns
}

ClientConfig wraps the contents of the /etc/resolv.conf file.

func ClientConfigFromFile 

func ClientConfigFromFile(resolvconf string) (*ClientConfig, error)

ClientConfigFromFile parses a resolv.conf(5) like file and returns a *ClientConfig.

func ClientConfigFromReader 

func ClientConfigFromReader(resolvconf io.Reader) (*ClientConfig, error)

ClientConfigFromReader works like ClientConfigFromFile but takes an io.Reader as argument

func (*ClientConfig) NameList 

func (c *ClientConfig) NameList(name string) []string

NameList returns all of the names that should be queried based on the config. It is based off of go's net/dns name building, but it does not check the length of the resulting names.

type Conn 

type Conn struct {
	net.Conn                     // a net.Conn holding the connection
	UDPSize    uint16            // minimum receive buffer for UDP messages
	TsigSecret map[string]string // secret(s) for Tsig map[<zonename>]<base64 secret>, zonename must be in canonical form (lowercase, fqdn, see RFC 4034 Section 6.2)
	// contains filtered or unexported fields
}

A Conn represents a connection to a DNS server.

func Dial 

func Dial(network, address string) (conn *Conn, err error)

Dial connects to the address on the named network.

func DialTimeout 

func DialTimeout(network, address string, timeout time.Duration) (conn *Conn, err error)

DialTimeout acts like Dial but takes a timeout.

func DialTimeoutWithTLS 

func DialTimeoutWithTLS(network, address string, tlsConfig *tls.Config, timeout time.Duration) (conn *Conn, err error)

DialTimeoutWithTLS acts like DialWithTLS but takes a timeout.

func DialWithTLS 

func DialWithTLS(network, address string, tlsConfig *tls.Config) (conn *Conn, err error)

DialWithTLS connects to the address on the named network with TLS.

func (*Conn) Read 

func (co *Conn) Read(p []byte) (n int, err error)

Read implements the net.Conn read method.

func (*Conn) ReadMsg 

func (co *Conn) ReadMsg() (*Msg, error)

ReadMsg reads a message from the connection co. If the received message contains a TSIG record the transaction signature is verified. This method always tries to return the message, however if an error is returned there are no guarantees that the returned message is a valid representation of the packet read.

func (*Conn) ReadMsgHeader 

func (co *Conn) ReadMsgHeader(hdr *Header) ([]byte, error)

ReadMsgHeader reads a DNS message, parses and populates hdr (when hdr is not nil). Returns message as a byte slice to be parsed with Msg.Unpack later on. Note that error handling on the message body is not possible as only the header is parsed.

func (*Conn) Write 

func (co *Conn) Write(p []byte) (n int, err error)

Write implements the net.Conn Write method.

func (*Conn) WriteMsg 

func (co *Conn) WriteMsg(m *Msg) (err error)

WriteMsg sends a message through the connection co. If the message m contains a TSIG record the transaction signature is calculated.

type ConnectionStater added in v1.0.11 

type ConnectionStater interface {
	ConnectionState() *tls.ConnectionState
}

A ConnectionStater interface is used by a DNS Handler to access TLS connection state when available.

type DHCID 

type DHCID struct {
	Hdr    RR_Header
	Digest string `dns:"base64"`
}

DHCID RR. See RFC 4701.

func (*DHCID) Header 

func (rr *DHCID) Header() *RR_Header

func (*DHCID) String 

func (rr *DHCID) String() string

type DLV 

type DLV struct{ DS }

DLV RR. See RFC 4431.

func (*DLV) Header 

func (rr *DLV) Header() *RR_Header

type DNAME 

type DNAME struct {
	Hdr    RR_Header
	Target string `dns:"domain-name"`
}

DNAME RR. See RFC 2672.

func (*DNAME) Header 

func (rr *DNAME) Header() *RR_Header

func (*DNAME) String 

func (rr *DNAME) String() string

type DNSKEY 

type DNSKEY struct {
	Hdr       RR_Header
	Flags     uint16
	Protocol  uint8
	Algorithm uint8
	PublicKey string `dns:"base64"`
}

DNSKEY RR. See RFC 4034 and RFC 3755.

func (*DNSKEY) Generate 

func (k *DNSKEY) Generate(bits int) (crypto.PrivateKey, error)

Generate generates a DNSKEY of the given bit size. The public part is put inside the DNSKEY record. The Algorithm in the key must be set as this will define what kind of DNSKEY will be generated. The ECDSA algorithms imply a fixed keysize, in that case bits should be set to the size of the algorithm.

func (*DNSKEY) Header 

func (rr *DNSKEY) Header() *RR_Header

func (*DNSKEY) KeyTag 

func (k *DNSKEY) KeyTag() uint16

KeyTag calculates the keytag (or key-id) of the DNSKEY.

func (*DNSKEY) NewPrivateKey 

func (k *DNSKEY) NewPrivateKey(s string) (crypto.PrivateKey, error)

NewPrivateKey returns a PrivateKey by parsing the string s. s should be in the same form of the BIND private key files.

func (*DNSKEY) PrivateKeyString 

func (r *DNSKEY) PrivateKeyString(p crypto.PrivateKey) string

PrivateKeyString converts a PrivateKey to a string. This string has the same format as the private-key-file of BIND9 (Private-key-format: v1.3). It needs some info from the key (the algorithm), so its a method of the DNSKEY It supports rsa.PrivateKey, ecdsa.PrivateKey and dsa.PrivateKey

func (*DNSKEY) ReadPrivateKey 

func (k *DNSKEY) ReadPrivateKey(q io.Reader, file string) (crypto.PrivateKey, error)

ReadPrivateKey reads a private key from the io.Reader q. The string file is only used in error reporting. The public key must be known, because some cryptographic algorithms embed the public inside the privatekey.

func (*DNSKEY) String 

func (rr *DNSKEY) String() string

func (*DNSKEY) ToCDNSKEY 

func (k *DNSKEY) ToCDNSKEY() *CDNSKEY

ToCDNSKEY converts a DNSKEY record to a CDNSKEY record.

func (*DNSKEY) ToDS 

func (k *DNSKEY) ToDS(h uint8) *DS

ToDS converts a DNSKEY record to a DS record.

type DS 

type DS struct {
	Hdr        RR_Header
	KeyTag     uint16
	Algorithm  uint8
	DigestType uint8
	Digest     string `dns:"hex"`
}

DS RR. See RFC 4034 and RFC 3658.

Example

Retrieve the DNSKEY records of a zone and convert them to DS records for SHA1, SHA256 and SHA384. 

package main

import (
	"fmt"

	"github.com/miekg/dns"
)

func main() {
	config, _ := dns.ClientConfigFromFile("/etc/resolv.conf")
	c := new(dns.Client)
	m := new(dns.Msg)
	zone := "miek.nl"
	m.SetQuestion(dns.Fqdn(zone), dns.TypeDNSKEY)
	m.SetEdns0(4096, true)
	r, _, err := c.Exchange(m, config.Servers[0]+":"+config.Port)
	if err != nil {
		return
	}
	if r.Rcode != dns.RcodeSuccess {
		return
	}
	for _, k := range r.Answer {
		if key, ok := k.(*dns.DNSKEY); ok {
			for _, alg := range []uint8{dns.SHA1, dns.SHA256, dns.SHA384} {
				fmt.Printf("%s; %d\n", key.ToDS(alg).String(), key.Flags)
			}
		}
	}
}

Output:

func (*DS) Header 

func (rr *DS) Header() *RR_Header

func (*DS) String 

func (rr *DS) String() string

func (*DS) ToCDS 

func (d *DS) ToCDS() *CDS

ToCDS converts a DS record to a CDS record.

type DecorateReader 

type DecorateReader func(Reader) Reader

DecorateReader is a decorator hook for extending or supplanting the functionality of a Reader. Implementations should never return a nil Reader.

type DecorateWriter 

type DecorateWriter func(Writer) Writer

DecorateWriter is a decorator hook for extending or supplanting the functionality of a Writer. Implementations should never return a nil Writer.

Example 
// instrument raw DNS message writing
wf := DecorateWriter(func(w Writer) Writer {
	return &ExampleFrameLengthWriter{w}
})

// simple UDP server
pc, err := net.ListenPacket("udp", ":0")
if err != nil {
	fmt.Println(err.Error())
	return
}
server := &Server{
	PacketConn:     pc,
	DecorateWriter: wf,
	ReadTimeout:    time.Hour, WriteTimeout: time.Hour,
}

waitLock := sync.Mutex{}
waitLock.Lock()
server.NotifyStartedFunc = waitLock.Unlock
defer server.Shutdown()

go func() {
	server.ActivateAndServe()
	pc.Close()
}()

waitLock.Lock()

HandleFunc("miek.nl.", HelloServer)

c := new(Client)
m := new(Msg)
m.SetQuestion("miek.nl.", TypeTXT)
_, _, err = c.Exchange(m, pc.LocalAddr().String())
if err != nil {
	fmt.Println("failed to exchange", err.Error())
	return
}

Output:

writing raw DNS message of length 56

type EDNS0 

type EDNS0 interface {
	// Option returns the option code for the option.
	Option() uint16

	// String returns the string representation of the option.
	String() string
	// contains filtered or unexported methods
}

EDNS0 defines an EDNS0 Option. An OPT RR can have multiple options appended to it. 

type EDNS0_COOKIE struct {
	Code   uint16 // Always EDNS0COOKIE
	Cookie string // Hex-encoded cookie data
}

The EDNS0_COOKIE option is used to add a DNS Cookie to a message. 

o := new(dns.OPT)
o.Hdr.Name = "."
o.Hdr.Rrtype = dns.TypeOPT
e := new(dns.EDNS0_COOKIE)
e.Code = dns.EDNS0COOKIE
e.Cookie = "24a5ac.."
o.Option = append(o.Option, e)

The Cookie field consists out of a client cookie (RFC 7873 Section 4), that is always 8 bytes. It may then optionally be followed by the server cookie. The server cookie is of variable length, 8 to a maximum of 32 bytes. In other words: 

cCookie := o.Cookie[:16]
sCookie := o.Cookie[16:]

There is no guarantee that the Cookie string has a specific length.

func (*EDNS0_COOKIE) Option 

func (e *EDNS0_COOKIE) Option() uint16

Option implements the EDNS0 interface.

func (*EDNS0_COOKIE) String 

func (e *EDNS0_COOKIE) String() string

type EDNS0_DAU 

type EDNS0_DAU struct {
	Code    uint16 // Always EDNS0DAU
	AlgCode []uint8
}

EDNS0_DUA implements the EDNS0 "DNSSEC Algorithm Understood" option. See RFC 6975.

func (*EDNS0_DAU) Option 

func (e *EDNS0_DAU) Option() uint16

Option implements the EDNS0 interface.

func (*EDNS0_DAU) String 

func (e *EDNS0_DAU) String() string

type EDNS0_DHU 

type EDNS0_DHU struct {
	Code    uint16 // Always EDNS0DHU
	AlgCode []uint8
}

EDNS0_DHU implements the EDNS0 "DS Hash Understood" option. See RFC 6975.

func (*EDNS0_DHU) Option 

func (e *EDNS0_DHU) Option() uint16

Option implements the EDNS0 interface.

func (*EDNS0_DHU) String 

func (e *EDNS0_DHU) String() string

type EDNS0_EXPIRE 

type EDNS0_EXPIRE struct {
	Code   uint16 // Always EDNS0EXPIRE
	Expire uint32
}

EDNS0_EXPIRE implementes the EDNS0 option as described in RFC 7314.

func (*EDNS0_EXPIRE) Option 

func (e *EDNS0_EXPIRE) Option() uint16

Option implements the EDNS0 interface.

func (*EDNS0_EXPIRE) String 

func (e *EDNS0_EXPIRE) String() string

type EDNS0_LLQ 

type EDNS0_LLQ struct {
	Code      uint16 // Always EDNS0LLQ
	Version   uint16
	Opcode    uint16
	Error     uint16
	Id        uint64
	LeaseLife uint32
}

EDNS0_LLQ stands for Long Lived Queries: http://tools.ietf.org/html/draft-sekar-dns-llq-01 Implemented for completeness, as the EDNS0 type code is assigned.

func (*EDNS0_LLQ) Option 

func (e *EDNS0_LLQ) Option() uint16

Option implements the EDNS0 interface.

func (*EDNS0_LLQ) String 

func (e *EDNS0_LLQ) String() string

type EDNS0_LOCAL 

type EDNS0_LOCAL struct {
	Code uint16
	Data []byte
}

The EDNS0_LOCAL option is used for local/experimental purposes. The option code is recommended to be within the range [EDNS0LOCALSTART, EDNS0LOCALEND] (RFC6891), although any unassigned code can actually be used. The content of the option is made available in Data, unaltered. Basic use pattern for creating a local option: 

o := new(dns.OPT)
o.Hdr.Name = "."
o.Hdr.Rrtype = dns.TypeOPT
e := new(dns.EDNS0_LOCAL)
e.Code = dns.EDNS0LOCALSTART
e.Data = []byte{72, 82, 74}
o.Option = append(o.Option, e)

func (*EDNS0_LOCAL) Option 

func (e *EDNS0_LOCAL) Option() uint16

Option implements the EDNS0 interface.

func (*EDNS0_LOCAL) String 

func (e *EDNS0_LOCAL) String() string

type EDNS0_N3U 

type EDNS0_N3U struct {
	Code    uint16 // Always EDNS0N3U
	AlgCode []uint8
}

EDNS0_N3U implements the EDNS0 "NSEC3 Hash Understood" option. See RFC 6975.

func (*EDNS0_N3U) Option 

func (e *EDNS0_N3U) Option() uint16

Option implements the EDNS0 interface.

func (*EDNS0_N3U) String 

func (e *EDNS0_N3U) String() string

type EDNS0_NSID 

type EDNS0_NSID struct {
	Code uint16 // Always EDNS0NSID
	Nsid string // This string needs to be hex encoded
}

EDNS0_NSID option is used to retrieve a nameserver identifier. When sending a request Nsid must be set to the empty string The identifier is an opaque string encoded as hex. Basic use pattern for creating an nsid option: 

o := new(dns.OPT)
o.Hdr.Name = "."
o.Hdr.Rrtype = dns.TypeOPT
e := new(dns.EDNS0_NSID)
e.Code = dns.EDNS0NSID
e.Nsid = "AA"
o.Option = append(o.Option, e)

func (*EDNS0_NSID) Option 

func (e *EDNS0_NSID) Option() uint16

Option implements the EDNS0 interface.

func (*EDNS0_NSID) String 

func (e *EDNS0_NSID) String() string

type EDNS0_PADDING 

type EDNS0_PADDING struct {
	Padding []byte
}

EDNS0_PADDING option is used to add padding to a request/response. The default value of padding SHOULD be 0x0 but other values MAY be used, for instance if compression is applied before encryption which may break signatures.

func (*EDNS0_PADDING) Option 

func (e *EDNS0_PADDING) Option() uint16

Option implements the EDNS0 interface.

func (*EDNS0_PADDING) String 

func (e *EDNS0_PADDING) String() string

type EDNS0_SUBNET 

type EDNS0_SUBNET struct {
	Code          uint16 // Always EDNS0SUBNET
	Family        uint16 // 1 for IP, 2 for IP6
	SourceNetmask uint8
	SourceScope   uint8
	Address       net.IP
}

EDNS0_SUBNET is the subnet option that is used to give the remote nameserver an idea of where the client lives. See RFC 7871. It can then give back a different answer depending on the location or network topology. Basic use pattern for creating an subnet option: 

o := new(dns.OPT)
o.Hdr.Name = "."
o.Hdr.Rrtype = dns.TypeOPT
e := new(dns.EDNS0_SUBNET)
e.Code = dns.EDNS0SUBNET
e.Family = 1	// 1 for IPv4 source address, 2 for IPv6
e.SourceNetmask = 32	// 32 for IPV4, 128 for IPv6
e.SourceScope = 0
e.Address = net.ParseIP("127.0.0.1").To4()	// for IPv4
// e.Address = net.ParseIP("2001:7b8:32a::2")	// for IPV6
o.Option = append(o.Option, e)

This code will parse all the available bits when unpacking (up to optlen). When packing it will apply SourceNetmask. If you need more advanced logic, patches welcome and good luck.

func (*EDNS0_SUBNET) Option 

func (e *EDNS0_SUBNET) Option() uint16

Option implements the EDNS0 interface.

func (*EDNS0_SUBNET) String 

func (e *EDNS0_SUBNET) String() (s string)

type EDNS0_TCP_KEEPALIVE 

type EDNS0_TCP_KEEPALIVE struct {
	Code    uint16 // Always EDNSTCPKEEPALIVE
	Length  uint16 // the value 0 if the TIMEOUT is omitted, the value 2 if it is present;
	Timeout uint16 // an idle timeout value for the TCP connection, specified in units of 100 milliseconds, encoded in network byte order.
}

EDNS0_TCP_KEEPALIVE is an EDNS0 option that instructs the server to keep the TCP connection alive. See RFC 7828.

func (*EDNS0_TCP_KEEPALIVE) Option 

func (e *EDNS0_TCP_KEEPALIVE) Option() uint16

Option implements the EDNS0 interface.

func (*EDNS0_TCP_KEEPALIVE) String 

func (e *EDNS0_TCP_KEEPALIVE) String() (s string)

type EDNS0_UL 

type EDNS0_UL struct {
	Code  uint16 // Always EDNS0UL
	Lease uint32
}

The EDNS0_UL (Update Lease) (draft RFC) option is used to tell the server to set an expiration on an update RR. This is helpful for clients that cannot clean up after themselves. This is a draft RFC and more information can be found at http://files.dns-sd.org/draft-sekar-dns-ul.txt 

o := new(dns.OPT)
o.Hdr.Name = "."
o.Hdr.Rrtype = dns.TypeOPT
e := new(dns.EDNS0_UL)
e.Code = dns.EDNS0UL
e.Lease = 120 // in seconds
o.Option = append(o.Option, e)

func (*EDNS0_UL) Option 

func (e *EDNS0_UL) Option() uint16

Option implements the EDNS0 interface.

func (*EDNS0_UL) String 

func (e *EDNS0_UL) String() string

type EID 

type EID struct {
	Hdr      RR_Header
	Endpoint string `dns:"hex"`
}

EID RR. See http://ana-3.lcs.mit.edu/~jnc/nimrod/dns.txt.

func (*EID) Header 

func (rr *EID) Header() *RR_Header

func (*EID) String 

func (rr *EID) String() string

type EUI48 

type EUI48 struct {
	Hdr     RR_Header
	Address uint64 `dns:"uint48"`
}

EUI48 RR. See RFC 7043.

func (*EUI48) Header 

func (rr *EUI48) Header() *RR_Header

func (*EUI48) String 

func (rr *EUI48) String() string

type EUI64 

type EUI64 struct {
	Hdr     RR_Header
	Address uint64
}

EUI64 RR. See RFC 7043.

func (*EUI64) Header 

func (rr *EUI64) Header() *RR_Header

func (*EUI64) String 

func (rr *EUI64) String() string

type Envelope 

type Envelope struct {
	RR    []RR  // The set of RRs in the answer section of the xfr reply message.
	Error error // If something went wrong, this contains the error.
}

Envelope is used when doing a zone transfer with a remote server.

type Error 

type Error struct {
	// contains filtered or unexported fields
}

Error represents a DNS error.

func (*Error) Error 

func (e *Error) Error() string

type GID 

type GID struct {
	Hdr RR_Header
	Gid uint32
}

GID RR. Deprecated, IANA-Reserved.

func (*GID) Header 

func (rr *GID) Header() *RR_Header

func (*GID) String 

func (rr *GID) String() string

type GPOS 

type GPOS struct {
	Hdr       RR_Header
	Longitude string
	Latitude  string
	Altitude  string
}

GPOS RR. See RFC 1712.

func (*GPOS) Header 

func (rr *GPOS) Header() *RR_Header

func (*GPOS) String 

func (rr *GPOS) String() string

type HINFO 

type HINFO struct {
	Hdr RR_Header
	Cpu string
	Os  string
}

HINFO RR. See RFC 1034.

func (*HINFO) Header 

func (rr *HINFO) Header() *RR_Header

func (*HINFO) String 

func (rr *HINFO) String() string

type HIP 

type HIP struct {
	Hdr                RR_Header
	HitLength          uint8
	PublicKeyAlgorithm uint8
	PublicKeyLength    uint16
	Hit                string   `dns:"size-hex:HitLength"`
	PublicKey          string   `dns:"size-base64:PublicKeyLength"`
	RendezvousServers  []string `dns:"domain-name"`
}

HIP RR. See RFC 8005.

func (*HIP) Header 

func (rr *HIP) Header() *RR_Header

func (*HIP) String 

func (rr *HIP) String() string

type Handler 

type Handler interface {
	ServeDNS(w ResponseWriter, r *Msg)
}

Handler is implemented by any value that implements ServeDNS.

type HandlerFunc 

type HandlerFunc func(ResponseWriter, *Msg)

The HandlerFunc type is an adapter to allow the use of ordinary functions as DNS handlers. If f is a function with the appropriate signature, HandlerFunc(f) is a Handler object that calls f.

func (HandlerFunc) ServeDNS 

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

ServeDNS calls f(w, r). 

type Header struct {
	Id                                 uint16
	Bits                               uint16
	Qdcount, Ancount, Nscount, Arcount uint16
}

Header is the wire format for the DNS packet header.

type KEY 

type KEY struct {
	DNSKEY
}

KEY RR. See RFC RFC 2535.

func (*KEY) Header 

func (rr *KEY) Header() *RR_Header

type KX 

type KX struct {
	Hdr        RR_Header
	Preference uint16
	Exchanger  string `dns:"domain-name"`
}

KX RR. See RFC 2230.

func (*KX) Header 

func (rr *KX) Header() *RR_Header

func (*KX) String 

func (rr *KX) String() string

type L32 

type L32 struct {
	Hdr        RR_Header
	Preference uint16
	Locator32  net.IP `dns:"a"`
}

L32 RR, See RFC 6742.

func (*L32) Header 

func (rr *L32) Header() *RR_Header

func (*L32) String 

func (rr *L32) String() string

type L64 

type L64 struct {
	Hdr        RR_Header
	Preference uint16
	Locator64  uint64
}

L64 RR, See RFC 6742.

func (*L64) Header 

func (rr *L64) Header() *RR_Header

func (*L64) String 

func (rr *L64) String() string

type LOC 

type LOC struct {
	Hdr       RR_Header
	Version   uint8
	Size      uint8
	HorizPre  uint8
	VertPre   uint8
	Latitude  uint32
	Longitude uint32
	Altitude  uint32
}

LOC RR. See RFC RFC 1876.

func (*LOC) Header 

func (rr *LOC) Header() *RR_Header

func (*LOC) String 

func (rr *LOC) String() string

type LP 

type LP struct {
	Hdr        RR_Header
	Preference uint16
	Fqdn       string `dns:"domain-name"`
}

LP RR. See RFC 6742.

func (*LP) Header 

func (rr *LP) Header() *RR_Header

func (*LP) String 

func (rr *LP) String() string

type MB 

type MB struct {
	Hdr RR_Header
	Mb  string `dns:"cdomain-name"`
}

MB RR. See RFC 1035.

func (*MB) Header 

func (rr *MB) Header() *RR_Header

func (*MB) String 

func (rr *MB) String() string

type MD 

type MD struct {
	Hdr RR_Header
	Md  string `dns:"cdomain-name"`
}

MD RR. See RFC 1035.

func (*MD) Header 

func (rr *MD) Header() *RR_Header

func (*MD) String 

func (rr *MD) String() string

type MF 

type MF struct {
	Hdr RR_Header
	Mf  string `dns:"cdomain-name"`
}

MF RR. See RFC 1035.

func (*MF) Header 

func (rr *MF) Header() *RR_Header

func (*MF) String 

func (rr *MF) String() string

type MG 

type MG struct {
	Hdr RR_Header
	Mg  string `dns:"cdomain-name"`
}

MG RR. See RFC 1035.

func (*MG) Header 

func (rr *MG) Header() *RR_Header

func (*MG) String 

func (rr *MG) String() string

type MINFO 

type MINFO struct {
	Hdr   RR_Header
	Rmail string `dns:"cdomain-name"`
	Email string `dns:"cdomain-name"`
}

MINFO RR. See RFC 1035.

func (*MINFO) Header 

func (rr *MINFO) Header() *RR_Header

func (*MINFO) String 

func (rr *MINFO) String() string

type MR 

type MR struct {
	Hdr RR_Header
	Mr  string `dns:"cdomain-name"`
}

MR RR. See RFC 1035.

func (*MR) Header 

func (rr *MR) Header() *RR_Header

func (*MR) String 

func (rr *MR) String() string

type MX 

type MX struct {
	Hdr        RR_Header
	Preference uint16
	Mx         string `dns:"cdomain-name"`
}

MX RR. See RFC 1035.

Example

Retrieve the MX records for miek.nl. 

package main

import (
	"fmt"

	"github.com/miekg/dns"
)

func main() {
	config, _ := dns.ClientConfigFromFile("/etc/resolv.conf")
	c := new(dns.Client)
	m := new(dns.Msg)
	m.SetQuestion("miek.nl.", dns.TypeMX)
	m.RecursionDesired = true
	r, _, err := c.Exchange(m, config.Servers[0]+":"+config.Port)
	if err != nil {
		return
	}
	if r.Rcode != dns.RcodeSuccess {
		return
	}
	for _, a := range r.Answer {
		if mx, ok := a.(*dns.MX); ok {
			fmt.Printf("%s\n", mx.String())
		}
	}
}

Output:

func (*MX) Header 

func (rr *MX) Header() *RR_Header

func (*MX) String 

func (rr *MX) String() string

type Msg 

type Msg struct {
	MsgHdr
	Compress bool       `json:"-"` // If true, the message will be compressed when converted to wire format.
	Question []Question // Holds the RR(s) of the question section.
	Answer   []RR       // Holds the RR(s) of the answer section.
	Ns       []RR       // Holds the RR(s) of the authority section.
	Extra    []RR       // Holds the RR(s) of the additional section.
}

Msg contains the layout of a DNS message.

func Exchange 

func Exchange(m *Msg, a string) (r *Msg, err error)

Exchange performs a synchronous UDP query. It sends the message m to the address contained in a and waits for a reply. Exchange does not retry a failed query, nor will it fall back to TCP in case of truncation. See client.Exchange for more information on setting larger buffer sizes.

func ExchangeConn 

func ExchangeConn(c net.Conn, m *Msg) (r *Msg, err error)

ExchangeConn performs a synchronous query. It sends the message m via the connection c and waits for a reply. The connection c is not closed by ExchangeConn. Deprecated: This function is going away, but can easily be mimicked: 

co := &dns.Conn{Conn: c} // c is your net.Conn
co.WriteMsg(m)
in, _  := co.ReadMsg()
co.Close()

func ExchangeContext 

func ExchangeContext(ctx context.Context, m *Msg, a string) (r *Msg, err error)

ExchangeContext performs a synchronous UDP query, like Exchange. It additionally obeys deadlines from the passed Context.

func (*Msg) Copy 

func (dns *Msg) Copy() *Msg

Copy returns a new *Msg which is a deep-copy of dns.

func (*Msg) CopyTo 

func (dns *Msg) CopyTo(r1 *Msg) *Msg

CopyTo copies the contents to the provided message using a deep-copy and returns the copy.

func (*Msg) Insert 

func (u *Msg) Insert(rr []RR)

Insert creates a dynamic update packet that adds an complete RRset, see RFC 2136 section 2.5.1.

func (*Msg) IsEdns0 

func (dns *Msg) IsEdns0() *OPT

IsEdns0 checks if the message has a EDNS0 (OPT) record, any EDNS0 record in the additional section will do. It returns the OPT record found or nil.

func (*Msg) IsTsig 

func (dns *Msg) IsTsig() *TSIG

IsTsig checks if the message has a TSIG record as the last record in the additional section. It returns the TSIG record found or nil.

func (*Msg) Len 

func (dns *Msg) Len() int

Len returns the message length when in (un)compressed wire format. If dns.Compress is true compression it is taken into account. Len() is provided to be a faster way to get the size of the resulting packet, than packing it, measuring the size and discarding the buffer.

func (*Msg) NameNotUsed 

func (u *Msg) NameNotUsed(rr []RR)

NameNotUsed sets the RRs in the prereq section to "Name is in not use" RRs. RFC 2136 section 2.4.5.

func (*Msg) NameUsed 

func (u *Msg) NameUsed(rr []RR)

NameUsed sets the RRs in the prereq section to "Name is in use" RRs. RFC 2136 section 2.4.4.

func (*Msg) Pack 

func (dns *Msg) Pack() (msg []byte, err error)

Pack packs a Msg: it is converted to to wire format. If the dns.Compress is true the message will be in compressed wire format.

func (*Msg) PackBuffer 

func (dns *Msg) PackBuffer(buf []byte) (msg []byte, err error)

PackBuffer packs a Msg, using the given buffer buf. If buf is too small a new buffer is allocated.

func (*Msg) RRsetNotUsed 

func (u *Msg) RRsetNotUsed(rr []RR)

RRsetNotUsed sets the RRs in the prereq section to "RRset does not exist" RRs. RFC 2136 section 2.4.3.

func (*Msg) RRsetUsed 

func (u *Msg) RRsetUsed(rr []RR)

RRsetUsed sets the RRs in the prereq section to "RRset exists (value independent -- no rdata)" RRs. RFC 2136 section 2.4.1.

func (*Msg) Remove 

func (u *Msg) Remove(rr []RR)

Remove creates a dynamic update packet deletes RR from a RRSset, see RFC 2136 section 2.5.4

func (*Msg) RemoveName 

func (u *Msg) RemoveName(rr []RR)

RemoveName creates a dynamic update packet that deletes all RRsets of a name, see RFC 2136 section 2.5.3

func (*Msg) RemoveRRset 

func (u *Msg) RemoveRRset(rr []RR)

RemoveRRset creates a dynamic update packet that deletes an RRset, see RFC 2136 section 2.5.2.

func (*Msg) SetAxfr 

func (dns *Msg) SetAxfr(z string) *Msg

SetAxfr creates message for requesting an AXFR.

func (*Msg) SetEdns0 

func (dns *Msg) SetEdns0(udpsize uint16, do bool) *Msg

SetEdns0 appends a EDNS0 OPT RR to the message. TSIG should always the last RR in a message.

func (*Msg) SetIxfr 

func (dns *Msg) SetIxfr(z string, serial uint32, ns, mbox string) *Msg

SetIxfr creates message for requesting an IXFR.

func (*Msg) SetNotify 

func (dns *Msg) SetNotify(z string) *Msg

SetNotify creates a notify message, it sets the Question section, generates an Id and sets the Authoritative (AA) bit to true.

func (*Msg) SetQuestion 

func (dns *Msg) SetQuestion(z string, t uint16) *Msg

SetQuestion creates a question message, it sets the Question section, generates an Id and sets the RecursionDesired (RD) bit to true.

func (*Msg) SetRcode 

func (dns *Msg) SetRcode(request *Msg, rcode int) *Msg

SetRcode creates an error message suitable for the request.

func (*Msg) SetRcodeFormatError 

func (dns *Msg) SetRcodeFormatError(request *Msg) *Msg

SetRcodeFormatError creates a message with FormError set.

func (*Msg) SetReply 

func (dns *Msg) SetReply(request *Msg) *Msg

SetReply creates a reply message from a request message.

func (*Msg) SetTsig 

func (dns *Msg) SetTsig(z, algo string, fudge uint16, timesigned int64) *Msg

SetTsig appends a TSIG RR to the message. This is only a skeleton TSIG RR that is added as the last RR in the additional section. The Tsig is calculated when the message is being send.

func (*Msg) SetUpdate 

func (dns *Msg) SetUpdate(z string) *Msg

SetUpdate makes the message a dynamic update message. It sets the ZONE section to: z, TypeSOA, ClassINET.

func (*Msg) String 

func (dns *Msg) String() string

Convert a complete message to a string with dig-like output.

func (*Msg) Truncate added in v1.1.9 

func (dns *Msg) Truncate(size int)

Truncate ensures the reply message will fit into the requested buffer size by removing records that exceed the requested size.

It will first check if the reply fits without compression and then with compression. If it won't fit with compression, Truncate then walks the record adding as many records as possible without exceeding the requested buffer size.

The TC bit will be set if any answer records were excluded from the message. This indicates to that the client should retry over TCP.

The appropriate buffer size can be retrieved from the requests OPT record, if present, and is transport specific otherwise. dns.MinMsgSize should be used for UDP requests without an OPT record, and dns.MaxMsgSize for TCP requests without an OPT record.

func (*Msg) Unpack 

func (dns *Msg) Unpack(msg []byte) (err error)

Unpack unpacks a binary message to a Msg structure.

func (*Msg) Used 

func (u *Msg) Used(rr []RR)

Used sets the RRs in the prereq section to "RRset exists (value dependent -- with rdata)" RRs. RFC 2136 section 2.4.2.

type MsgAcceptAction added in v1.1.1 

type MsgAcceptAction int

MsgAcceptAction represents the action to be taken. 

const (
	MsgAccept MsgAcceptAction = iota // Accept the message
	MsgReject                        // Reject the message with a RcodeFormatError
	MsgIgnore                        // Ignore the error and send nothing back.
)

type MsgAcceptFunc added in v1.1.1 

type MsgAcceptFunc func(dh Header) MsgAcceptAction

MsgAcceptFunc is used early in the server code to accept or reject a message with RcodeFormatError. It returns a MsgAcceptAction to indicate what should happen with the message. 

var DefaultMsgAcceptFunc MsgAcceptFunc = defaultMsgAcceptFunc

DefaultMsgAcceptFunc checks the request and will reject if:

* isn't a request (don't respond in that case). * opcode isn't OpcodeQuery or OpcodeNotify * Zero bit isn't zero * has more than 1 question in the question section * has more than 1 RR in the Answer section * has more than 0 RRs in the Authority section * has more than 2 RRs in the Additional section

type MsgHdr 

type MsgHdr struct {
	Id                 uint16
	Response           bool
	Opcode             int
	Authoritative      bool
	Truncated          bool
	RecursionDesired   bool
	RecursionAvailable bool
	Zero               bool
	AuthenticatedData  bool
	CheckingDisabled   bool
	Rcode              int
}

MsgHdr is a a manually-unpacked version of (id, bits).

func (*MsgHdr) String 

func (h *MsgHdr) String() string

Convert a MsgHdr to a string, with dig-like headers:

;; opcode: QUERY, status: NOERROR, id: 48404

;; flags: qr aa rd ra;

type NAPTR 

type NAPTR struct {
	Hdr         RR_Header
	Order       uint16
	Preference  uint16
	Flags       string
	Service     string
	Regexp      string
	Replacement string `dns:"domain-name"`
}

NAPTR RR. See RFC 2915.

func (*NAPTR) Header 

func (rr *NAPTR) Header() *RR_Header

func (*NAPTR) String 

func (rr *NAPTR) String() string

type NID 

type NID struct {
	Hdr        RR_Header
	Preference uint16
	NodeID     uint64
}

NID RR. See RFC RFC 6742.

func (*NID) Header 

func (rr *NID) Header() *RR_Header

func (*NID) String 

func (rr *NID) String() string

type NIMLOC 

type NIMLOC struct {
	Hdr     RR_Header
	Locator string `dns:"hex"`
}

NIMLOC RR. See http://ana-3.lcs.mit.edu/~jnc/nimrod/dns.txt.

func (*NIMLOC) Header 

func (rr *NIMLOC) Header() *RR_Header

func (*NIMLOC) String 

func (rr *NIMLOC) String() string

type NINFO 

type NINFO struct {
	Hdr    RR_Header
	ZSData []string `dns:"txt"`
}

NINFO RR. See https://www.iana.org/assignments/dns-parameters/NINFO/ninfo-completed-template.

func (*NINFO) Header 

func (rr *NINFO) Header() *RR_Header

func (*NINFO) String 

func (rr *NINFO) String() string

type NS 

type NS struct {
	Hdr RR_Header
	Ns  string `dns:"cdomain-name"`
}

NS RR. See RFC 1035.

func (*NS) Header 

func (rr *NS) Header() *RR_Header

func (*NS) String 

func (rr *NS) String() string

type NSAPPTR 

type NSAPPTR struct {
	Hdr RR_Header
	Ptr string `dns:"domain-name"`
}

NSAPPTR RR. See RFC 1348.

func (*NSAPPTR) Header 

func (rr *NSAPPTR) Header() *RR_Header

func (*NSAPPTR) String 

func (rr *NSAPPTR) String() string

type NSEC 

type NSEC struct {
	Hdr        RR_Header
	NextDomain string   `dns:"domain-name"`
	TypeBitMap []uint16 `dns:"nsec"`
}

NSEC RR. See RFC 4034 and RFC 3755.

func (*NSEC) Header 

func (rr *NSEC) Header() *RR_Header

func (*NSEC) String 

func (rr *NSEC) String() string

type NSEC3 

type NSEC3 struct {
	Hdr        RR_Header
	Hash       uint8
	Flags      uint8
	Iterations uint16
	SaltLength uint8
	Salt       string `dns:"size-hex:SaltLength"`
	HashLength uint8
	NextDomain string   `dns:"size-base32:HashLength"`
	TypeBitMap []uint16 `dns:"nsec"`
}

NSEC3 RR. See RFC 5155.

func (*NSEC3) Cover 

func (rr *NSEC3) Cover(name string) bool

Cover returns true if a name is covered by the NSEC3 record

func (*NSEC3) Header 

func (rr *NSEC3) Header() *RR_Header

func (*NSEC3) Match 

func (rr *NSEC3) Match(name string) bool

Match returns true if a name matches the NSEC3 record

func (*NSEC3) String 

func (rr *NSEC3) String() string

type NSEC3PARAM 

type NSEC3PARAM struct {
	Hdr        RR_Header
	Hash       uint8
	Flags      uint8
	Iterations uint16
	SaltLength uint8
	Salt       string `dns:"size-hex:SaltLength"`
}

NSEC3PARAM RR. See RFC 5155.

func (*NSEC3PARAM) Header 

func (rr *NSEC3PARAM) Header() *RR_Header

func (*NSEC3PARAM) String 

func (rr *NSEC3PARAM) String() string

type NULL added in v1.1.3 

type NULL struct {
	Hdr  RR_Header
	Data string `dns:"any"`
}

NULL RR. See RFC 1035.

func (*NULL) Header added in v1.1.3 

func (rr *NULL) Header() *RR_Header

func (*NULL) String added in v1.1.3 

func (rr *NULL) String() string

type Name 

type Name string

Name is a DNS domain name.

func (Name) String 

func (n Name) String() string

String returns the string representation for the name n.

type OPENPGPKEY 

type OPENPGPKEY struct {
	Hdr       RR_Header
	PublicKey string `dns:"base64"`
}

OPENPGPKEY RR. See RFC 7929.

func (*OPENPGPKEY) Header 

func (rr *OPENPGPKEY) Header() *RR_Header

func (*OPENPGPKEY) String 

func (rr *OPENPGPKEY) String() string

type OPT 

type OPT struct {
	Hdr    RR_Header
	Option []EDNS0 `dns:"opt"`
}

OPT is the EDNS0 RR appended to messages to convey extra (meta) information. See RFC 6891.

func (*OPT) Do 

func (rr *OPT) Do() bool

Do returns the value of the DO (DNSSEC OK) bit.

func (*OPT) ExtendedRcode 

func (rr *OPT) ExtendedRcode() int

ExtendedRcode returns the EDNS extended RCODE field (the upper 8 bits of the TTL).

func (*OPT) Header 

func (rr *OPT) Header() *RR_Header

func (*OPT) SetDo 

func (rr *OPT) SetDo(do ...bool)

SetDo sets the DO (DNSSEC OK) bit. If we pass an argument, set the DO bit to that value. It is possible to pass 2 or more arguments. Any arguments after the 1st is silently ignored.

func (*OPT) SetExtendedRcode 

func (rr *OPT) SetExtendedRcode(v uint16)

SetExtendedRcode sets the EDNS extended RCODE field.

If the RCODE is not an extended RCODE, will reset the extended RCODE field to 0.

func (*OPT) SetUDPSize 

func (rr *OPT) SetUDPSize(size uint16)

SetUDPSize sets the UDP buffer size.

func (*OPT) SetVersion 

func (rr *OPT) SetVersion(v uint8)

SetVersion sets the version of EDNS. This is usually zero.

func (*OPT) String 

func (rr *OPT) String() string

func (*OPT) UDPSize 

func (rr *OPT) UDPSize() uint16

UDPSize returns the UDP buffer size.

func (*OPT) Version 

func (rr *OPT) Version() uint8

Version returns the EDNS version used. Only zero is defined.

type PTR 

type PTR struct {
	Hdr RR_Header
	Ptr string `dns:"cdomain-name"`
}

PTR RR. See RFC 1035.

func (*PTR) Header 

func (rr *PTR) Header() *RR_Header

func (*PTR) String 

func (rr *PTR) String() string

type PX 

type PX struct {
	Hdr        RR_Header
	Preference uint16
	Map822     string `dns:"domain-name"`
	Mapx400    string `dns:"domain-name"`
}

PX RR. See RFC 2163.

func (*PX) Header 

func (rr *PX) Header() *RR_Header

func (*PX) String 

func (rr *PX) String() string

type ParseError 

type ParseError struct {
	// contains filtered or unexported fields
}

ParseError is a parsing error. It contains the parse error and the location in the io.Reader where the error occurred.

func (*ParseError) Error 

func (e *ParseError) Error() (s string)

type PrivateRR 

type PrivateRR struct {
	Hdr  RR_Header
	Data PrivateRdata
	// contains filtered or unexported fields
}

PrivateRR represents an RR that uses a PrivateRdata user-defined type. It mocks normal RRs and implements dns.RR interface.

func (*PrivateRR) Header 

func (r *PrivateRR) Header() *RR_Header

Header return the RR header of r.

func (*PrivateRR) String 

func (r *PrivateRR) String() string

type PrivateRdata 

type PrivateRdata interface {
	// String returns the text presentaton of the Rdata of the Private RR.
	String() string
	// Parse parses the Rdata of the private RR.
	Parse([]string) error
	// Pack is used when packing a private RR into a buffer.
	Pack([]byte) (int, error)
	// Unpack is used when unpacking a private RR from a buffer.
	// TODO(miek): diff. signature than Pack, see edns0.go for instance.
	Unpack([]byte) (int, error)
	// Copy copies the Rdata into the PrivateRdata argument.
	Copy(PrivateRdata) error
	// Len returns the length in octets of the Rdata.
	Len() int
}

PrivateRdata is an interface used for implementing "Private Use" RR types, see RFC 6895. This allows one to experiment with new RR types, without requesting an official type code. Also see dns.PrivateHandle and dns.PrivateHandleRemove.

type Question 

type Question struct {
	Name   string `dns:"cdomain-name"` // "cdomain-name" specifies encoding (and may be compressed)
	Qtype  uint16
	Qclass uint16
}

Question holds a DNS question. There can be multiple questions in the question section of a message. Usually there is just one.

func (*Question) String 

func (q *Question) String() (s string)

type RFC3597 

type RFC3597 struct {
	Hdr   RR_Header
	Rdata string `dns:"hex"`
}

RFC3597 represents an unknown/generic RR. See RFC 3597.

func (*RFC3597) Header 

func (rr *RFC3597) Header() *RR_Header

func (*RFC3597) String 

func (rr *RFC3597) String() string

func (*RFC3597) ToRFC3597 

func (rr *RFC3597) ToRFC3597(r RR) error

ToRFC3597 converts a known RR to the unknown RR representation from RFC 3597.

type RKEY 

type RKEY struct {
	Hdr       RR_Header
	Flags     uint16
	Protocol  uint8
	Algorithm uint8
	PublicKey string `dns:"base64"`
}

RKEY RR. See https://www.iana.org/assignments/dns-parameters/RKEY/rkey-completed-template.

func (*RKEY) Header 

func (rr *RKEY) Header() *RR_Header

func (*RKEY) String 

func (rr *RKEY) String() string

type RP 

type RP struct {
	Hdr  RR_Header
	Mbox string `dns:"domain-name"`
	Txt  string `dns:"domain-name"`
}

RP RR. See RFC 1138, Section 2.2.

func (*RP) Header 

func (rr *RP) Header() *RR_Header

func (*RP) String 

func (rr *RP) String() string

type RR 

type RR interface {
	// Header returns the header of an resource record. The header contains
	// everything up to the rdata.
	Header() *RR_Header
	// String returns the text representation of the resource record.
	String() string
	// contains filtered or unexported methods
}

An RR represents a resource record.

func Copy 

func Copy(r RR) RR

Copy returns a new RR which is a deep-copy of r.

func Dedup 

func Dedup(rrs []RR, m map[string]RR) []RR

Dedup removes identical RRs from rrs. It preserves the original ordering. The lowest TTL of any duplicates is used in the remaining one. Dedup modifies rrs. m is used to store the RRs temporary. If it is nil a new map will be allocated.

func NewRR 

func NewRR(s string) (RR, error)

NewRR reads the RR contained in the string s. Only the first RR is returned. If s contains no records, NewRR will return nil with no error.

The class defaults to IN and TTL defaults to 3600. The full zone file syntax like $TTL, $ORIGIN, etc. is supported.

All fields of the returned RR are set, except RR.Header().Rdlength which is set to 0.

func ReadRR 

func ReadRR(r io.Reader, file string) (RR, error)

ReadRR reads the RR contained in r.

The string file is used in error reporting and to resolve relative $INCLUDE directives.

See NewRR for more documentation.

func UnpackRR 

func UnpackRR(msg []byte, off int) (rr RR, off1 int, err error)

UnpackRR unpacks msg[off:] into an RR.

func UnpackRRWithHeader 

func UnpackRRWithHeader(h RR_Header, msg []byte, off int) (rr RR, off1 int, err error)

UnpackRRWithHeader unpacks the record type specific payload given an existing RR_Header.

type RRSIG 

type RRSIG struct {
	Hdr         RR_Header
	TypeCovered uint16
	Algorithm   uint8
	Labels      uint8
	OrigTtl     uint32
	Expiration  uint32
	Inception   uint32
	KeyTag      uint16
	SignerName  string `dns:"domain-name"`
	Signature   string `dns:"base64"`
}

RRSIG RR. See RFC 4034 and RFC 3755.

func (*RRSIG) Header 

func (rr *RRSIG) Header() *RR_Header

func (*RRSIG) Sign 

func (rr *RRSIG) Sign(k crypto.Signer, rrset []RR) error

Sign signs an RRSet. The signature needs to be filled in with the values: Inception, Expiration, KeyTag, SignerName and Algorithm. The rest is copied from the RRset. Sign returns a non-nill error when the signing went OK. There is no check if RRSet is a proper (RFC 2181) RRSet. If OrigTTL is non zero, it is used as-is, otherwise the TTL of the RRset is used as the OrigTTL.

func (*RRSIG) String 

func (rr *RRSIG) String() string

func (*RRSIG) ValidityPeriod 

func (rr *RRSIG) ValidityPeriod(t time.Time) bool

ValidityPeriod uses RFC1982 serial arithmetic to calculate if a signature period is valid. If t is the zero time, the current time is taken other t is. Returns true if the signature is valid at the given time, otherwise returns false.

func (*RRSIG) Verify 

func (rr *RRSIG) Verify(k *DNSKEY, rrset []RR) error

Verify validates an RRSet with the signature and key. This is only the cryptographic test, the signature validity period must be checked separately. This function copies the rdata of some RRs (to lowercase domain names) for the validation to work.

type RR_Header 

type RR_Header struct {
	Name     string `dns:"cdomain-name"`
	Rrtype   uint16
	Class    uint16
	Ttl      uint32
	Rdlength uint16 // Length of data after header.
}

RR_Header is the header all DNS resource records share.

func (*RR_Header) Header 

func (h *RR_Header) Header() *RR_Header

Header returns itself. This is here to make RR_Header implements the RR interface.

func (*RR_Header) String 

func (h *RR_Header) String() string

type RT 

type RT struct {
	Hdr        RR_Header
	Preference uint16
	Host       string `dns:"domain-name"` // RFC 3597 prohibits compressing records not defined in RFC 1035.
}

RT RR. See RFC 1183, Section 3.3.

func (*RT) Header 

func (rr *RT) Header() *RR_Header

func (*RT) String 

func (rr *RT) String() string

type Reader 

type Reader interface {
	// ReadTCP reads a raw message from a TCP connection. Implementations may alter
	// connection properties, for example the read-deadline.
	ReadTCP(conn net.Conn, timeout time.Duration) ([]byte, error)
	// ReadUDP reads a raw message from a UDP connection. Implementations may alter
	// connection properties, for example the read-deadline.
	ReadUDP(conn *net.UDPConn, timeout time.Duration) ([]byte, *SessionUDP, error)
}

Reader reads raw DNS messages; each call to ReadTCP or ReadUDP should return an entire message.

type ResponseWriter 

type ResponseWriter interface {
	// LocalAddr returns the net.Addr of the server
	LocalAddr() net.Addr
	// RemoteAddr returns the net.Addr of the client that sent the current request.
	RemoteAddr() net.Addr
	// WriteMsg writes a reply back to the client.
	WriteMsg(*Msg) error
	// Write writes a raw buffer back to the client.
	Write([]byte) (int, error)
	// Close closes the connection.
	Close() error
	// TsigStatus returns the status of the Tsig.
	TsigStatus() error
	// TsigTimersOnly sets the tsig timers only boolean.
	TsigTimersOnly(bool)
	// Hijack lets the caller take over the connection.
	// After a call to Hijack(), the DNS package will not do anything with the connection.
	Hijack()
}

A ResponseWriter interface is used by an DNS handler to construct an DNS response.

type SIG 

type SIG struct {
	RRSIG
}

SIG RR. See RFC 2535. The SIG RR is identical to RRSIG and nowadays only used for SIG(0), See RFC 2931.

func (*SIG) Header 

func (rr *SIG) Header() *RR_Header

func (*SIG) Sign 

func (rr *SIG) Sign(k crypto.Signer, m *Msg) ([]byte, error)

Sign signs a dns.Msg. It fills the signature with the appropriate data. The SIG record should have the SignerName, KeyTag, Algorithm, Inception and Expiration set.

func (*SIG) Verify 

func (rr *SIG) Verify(k *KEY, buf []byte) error

Verify validates the message buf using the key k. It's assumed that buf is a valid message from which rr was unpacked.

type SMIMEA 

type SMIMEA struct {
	Hdr          RR_Header
	Usage        uint8
	Selector     uint8
	MatchingType uint8
	Certificate  string `dns:"hex"`
}

SMIMEA RR. See RFC 8162.

func (*SMIMEA) Header 

func (rr *SMIMEA) Header() *RR_Header

func (*SMIMEA) Sign 

func (r *SMIMEA) Sign(usage, selector, matchingType int, cert *x509.Certificate) (err error)

Sign creates a SMIMEA record from an SSL certificate.

func (*SMIMEA) String 

func (rr *SMIMEA) String() string

func (*SMIMEA) Verify 

func (r *SMIMEA) Verify(cert *x509.Certificate) error

Verify verifies a SMIMEA record against an SSL certificate. If it is OK a nil error is returned.

type SOA 

type SOA struct {
	Hdr     RR_Header
	Ns      string `dns:"cdomain-name"`
	Mbox    string `dns:"cdomain-name"`
	Serial  uint32
	Refresh uint32
	Retry   uint32
	Expire  uint32
	Minttl  uint32
}

SOA RR. See RFC 1035.

func (*SOA) Header 

func (rr *SOA) Header() *RR_Header

func (*SOA) String 

func (rr *SOA) String() string

type SPF 

type SPF struct {
	Hdr RR_Header
	Txt []string `dns:"txt"`
}

SPF RR. See RFC 4408, Section 3.1.1.

func (*SPF) Header 

func (rr *SPF) Header() *RR_Header

func (*SPF) String 

func (rr *SPF) String() string

type SRV 

type SRV struct {
	Hdr      RR_Header
	Priority uint16
	Weight   uint16
	Port     uint16
	Target   string `dns:"domain-name"`
}

SRV RR. See RFC 2782.

func (*SRV) Header 

func (rr *SRV) Header() *RR_Header

func (*SRV) String 

func (rr *SRV) String() string

type SSHFP 

type SSHFP struct {
	Hdr         RR_Header
	Algorithm   uint8
	Type        uint8
	FingerPrint string `dns:"hex"`
}

SSHFP RR. See RFC RFC 4255.

func (*SSHFP) Header 

func (rr *SSHFP) Header() *RR_Header

func (*SSHFP) String 

func (rr *SSHFP) String() string

type ServeMux 

type ServeMux struct {
	// contains filtered or unexported fields
}

ServeMux is an DNS request multiplexer. It matches the zone name of each incoming request against a list of registered patterns add calls the handler for the pattern that most closely matches the zone name.

ServeMux is DNSSEC aware, meaning that queries for the DS record are redirected to the parent zone (if that is also registered), otherwise the child gets the query.

ServeMux is also safe for concurrent access from multiple goroutines.

The zero ServeMux is empty and ready for use.

func NewServeMux 

func NewServeMux() *ServeMux

NewServeMux allocates and returns a new ServeMux.

func (*ServeMux) Handle 

func (mux *ServeMux) Handle(pattern string, handler Handler)

Handle adds a handler to the ServeMux for pattern.

func (*ServeMux) HandleFunc 

func (mux *ServeMux) HandleFunc(pattern string, handler func(ResponseWriter, *Msg))

HandleFunc adds a handler function to the ServeMux for pattern.

func (*ServeMux) HandleRemove 

func (mux *ServeMux) HandleRemove(pattern string)

HandleRemove deregisters the handler specific for pattern from the ServeMux.

func (*ServeMux) ServeDNS 

func (mux *ServeMux) ServeDNS(w ResponseWriter, req *Msg)

ServeDNS dispatches the request to the handler whose pattern most closely matches the request message.

ServeDNS is DNSSEC aware, meaning that queries for the DS record are redirected to the parent zone (if that is also registered), otherwise the child gets the query.

If no handler is found, or there is no question, a standard SERVFAIL message is returned

type Server 

type Server struct {
	// Address to listen on, ":dns" if empty.
	Addr string
	// if "tcp" or "tcp-tls" (DNS over TLS) it will invoke a TCP listener, otherwise an UDP one
	Net string
	// TCP Listener to use, this is to aid in systemd's socket activation.
	Listener net.Listener
	// TLS connection configuration
	TLSConfig *tls.Config
	// UDP "Listener" to use, this is to aid in systemd's socket activation.
	PacketConn net.PacketConn
	// Handler to invoke, dns.DefaultServeMux if nil.
	Handler Handler
	// Default buffer size to use to read incoming UDP messages. If not set
	// it defaults to MinMsgSize (512 B).
	UDPSize int
	// The net.Conn.SetReadTimeout value for new connections, defaults to 2 * time.Second.
	ReadTimeout time.Duration
	// The net.Conn.SetWriteTimeout value for new connections, defaults to 2 * time.Second.
	WriteTimeout time.Duration
	// TCP idle timeout for multiple queries, if nil, defaults to 8 * time.Second (RFC 5966).
	IdleTimeout func() time.Duration
	// Secret(s) for Tsig map[<zonename>]<base64 secret>. The zonename must be in canonical form (lowercase, fqdn, see RFC 4034 Section 6.2).
	TsigSecret map[string]string
	// If NotifyStartedFunc is set it is called once the server has started listening.
	NotifyStartedFunc func()
	// DecorateReader is optional, allows customization of the process that reads raw DNS messages.
	DecorateReader DecorateReader
	// DecorateWriter is optional, allows customization of the process that writes raw DNS messages.
	DecorateWriter DecorateWriter
	// Maximum number of TCP queries before we close the socket. Default is maxTCPQueries (unlimited if -1).
	MaxTCPQueries int
	// Whether to set the SO_REUSEPORT socket option, allowing multiple listeners to be bound to a single address.
	// It is only supported on go1.11+ and when using ListenAndServe.
	ReusePort bool
	// AcceptMsgFunc will check the incoming message and will reject it early in the process.
	// By default DefaultMsgAcceptFunc will be used.
	MsgAcceptFunc MsgAcceptFunc
	// contains filtered or unexported fields
}

A Server defines parameters for running an DNS server.

func (*Server) ActivateAndServe 

func (srv *Server) ActivateAndServe() error

ActivateAndServe starts a nameserver with the PacketConn or Listener configured in *Server. Its main use is to start a server from systemd.

func (*Server) ListenAndServe 

func (srv *Server) ListenAndServe() error

ListenAndServe starts a nameserver on the configured address in *Server.

func (*Server) Shutdown 

func (srv *Server) Shutdown() error

Shutdown shuts down a server. After a call to Shutdown, ListenAndServe and ActivateAndServe will return.

func (*Server) ShutdownContext added in v1.0.11 

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

ShutdownContext shuts down a server. After a call to ShutdownContext, ListenAndServe and ActivateAndServe will return.

A context.Context may be passed to limit how long to wait for connections to terminate.

type SessionUDP 

type SessionUDP struct {
	// contains filtered or unexported fields
}

SessionUDP holds the remote address and the associated out-of-band data.

func ReadFromSessionUDP 

func ReadFromSessionUDP(conn *net.UDPConn, b []byte) (int, *SessionUDP, error)

ReadFromSessionUDP acts just like net.UDPConn.ReadFrom(), but returns a session object instead of a net.UDPAddr.

func (*SessionUDP) RemoteAddr 

func (s *SessionUDP) RemoteAddr() net.Addr

RemoteAddr returns the remote network address.

type TA 

type TA struct {
	Hdr        RR_Header
	KeyTag     uint16
	Algorithm  uint8
	DigestType uint8
	Digest     string `dns:"hex"`
}

TA RR. See http://www.watson.org/~weiler/INI1999-19.pdf.

func (*TA) Header 

func (rr *TA) Header() *RR_Header

func (*TA) String 

func (rr *TA) String() string
type TALINK struct {
	Hdr          RR_Header
	PreviousName string `dns:"domain-name"`
	NextName     string `dns:"domain-name"`
}

TALINK RR. See https://www.iana.org/assignments/dns-parameters/TALINK/talink-completed-template.

func (*TALINK) Header 

func (rr *TALINK) Header() *RR_Header

func (*TALINK) String 

func (rr *TALINK) String() string

type TKEY 

type TKEY struct {
	Hdr        RR_Header
	Algorithm  string `dns:"domain-name"`
	Inception  uint32
	Expiration uint32
	Mode       uint16
	Error      uint16
	KeySize    uint16
	Key        string `dns:"size-hex:KeySize"`
	OtherLen   uint16
	OtherData  string `dns:"size-hex:OtherLen"`
}

TKEY RR. See RFC 2930.

func (*TKEY) Header 

func (rr *TKEY) Header() *RR_Header

func (*TKEY) String 

func (rr *TKEY) String() string

TKEY has no official presentation format, but this will suffice.

type TLSA 

type TLSA struct {
	Hdr          RR_Header
	Usage        uint8
	Selector     uint8
	MatchingType uint8
	Certificate  string `dns:"hex"`
}

TLSA RR. See RFC 6698.

func (*TLSA) Header 

func (rr *TLSA) Header() *RR_Header

func (*TLSA) Sign 

func (r *TLSA) Sign(usage, selector, matchingType int, cert *x509.Certificate) (err error)

Sign creates a TLSA record from an SSL certificate.

func (*TLSA) String 

func (rr *TLSA) String() string

func (*TLSA) Verify 

func (r *TLSA) Verify(cert *x509.Certificate) error

Verify verifies a TLSA record against an SSL certificate. If it is OK a nil error is returned.

type TSIG 

type TSIG struct {
	Hdr        RR_Header
	Algorithm  string `dns:"domain-name"`
	TimeSigned uint64 `dns:"uint48"`
	Fudge      uint16
	MACSize    uint16
	MAC        string `dns:"size-hex:MACSize"`
	OrigId     uint16
	Error      uint16
	OtherLen   uint16
	OtherData  string `dns:"size-hex:OtherLen"`
}

TSIG is the RR the holds the transaction signature of a message. See RFC 2845 and RFC 4635.

func (*TSIG) Header 

func (rr *TSIG) Header() *RR_Header

func (*TSIG) String 

func (rr *TSIG) String() string

type TXT 

type TXT struct {
	Hdr RR_Header
	Txt []string `dns:"txt"`
}

TXT RR. See RFC 1035.

func (*TXT) Header 

func (rr *TXT) Header() *RR_Header

func (*TXT) String 

func (rr *TXT) String() string

type Token 

type Token struct {
	// The scanned resource record when error is not nil.
	RR
	// When an error occurred, this has the error specifics.
	Error *ParseError
	// A potential comment positioned after the RR and on the same line.
	Comment string
}

Token holds the token that are returned when a zone file is parsed.

type Transfer 

type Transfer struct {
	*Conn
	DialTimeout  time.Duration     // net.DialTimeout, defaults to 2 seconds
	ReadTimeout  time.Duration     // net.Conn.SetReadTimeout value for connections, defaults to 2 seconds
	WriteTimeout time.Duration     // net.Conn.SetWriteTimeout value for connections, defaults to 2 seconds
	TsigSecret   map[string]string // Secret(s) for Tsig map[<zonename>]<base64 secret>, zonename must be in canonical form (lowercase, fqdn, see RFC 4034 Section 6.2)
	// contains filtered or unexported fields
}

A Transfer defines parameters that are used during a zone transfer.

func (*Transfer) In 

func (t *Transfer) In(q *Msg, a string) (env chan *Envelope, err error)

In performs an incoming transfer with the server in a. If you would like to set the source IP, or some other attribute of a Dialer for a Transfer, you can do so by specifying the attributes in the Transfer.Conn: 

d := net.Dialer{LocalAddr: transfer_source}
con, err := d.Dial("tcp", master)
dnscon := &dns.Conn{Conn:con}
transfer = &dns.Transfer{Conn: dnscon}
channel, err := transfer.In(message, master)

func (*Transfer) Out 

func (t *Transfer) Out(w ResponseWriter, q *Msg, ch chan *Envelope) error

Out performs an outgoing transfer with the client connecting in w. Basic use pattern: 

ch := make(chan *dns.Envelope)
tr := new(dns.Transfer)
go tr.Out(w, r, ch)
ch <- &dns.Envelope{RR: []dns.RR{soa, rr1, rr2, rr3, soa}}
close(ch)
w.Hijack()
// w.Close() // Client closes connection

The server is responsible for sending the correct sequence of RRs through the channel ch.

func (*Transfer) ReadMsg 

func (t *Transfer) ReadMsg() (*Msg, error)

ReadMsg reads a message from the transfer connection t.

func (*Transfer) WriteMsg 

func (t *Transfer) WriteMsg(m *Msg) (err error)

WriteMsg writes a message through the transfer connection t.

type Type 

type Type uint16

Type is a DNS type.

func (Type) String 

func (t Type) String() string

String returns the string representation for the type t.

type UID 

type UID struct {
	Hdr RR_Header
	Uid uint32
}

UID RR. Deprecated, IANA-Reserved.

func (*UID) Header 

func (rr *UID) Header() *RR_Header

func (*UID) String 

func (rr *UID) String() string

type UINFO 

type UINFO struct {
	Hdr   RR_Header
	Uinfo string
}

UINFO RR. Deprecated, IANA-Reserved.

func (*UINFO) Header 

func (rr *UINFO) Header() *RR_Header

func (*UINFO) String 

func (rr *UINFO) String() string

type URI 

type URI struct {
	Hdr      RR_Header
	Priority uint16
	Weight   uint16
	Target   string `dns:"octet"`
}

URI RR. See RFC 7553.

func (*URI) Header 

func (rr *URI) Header() *RR_Header

func (*URI) String 

func (rr *URI) String() string

type V 

type V struct {
	Major, Minor, Patch int
}

V holds the version of this library.

func (V) String 

func (v V) String() string

type Writer 

type Writer interface {
	io.Writer
}

Writer writes raw DNS messages; each call to Write should send an entire message.

type X25 

type X25 struct {
	Hdr         RR_Header
	PSDNAddress string
}

X25 RR. See RFC 1183, Section 3.1.

func (*X25) Header 

func (rr *X25) Header() *RR_Header

func (*X25) String 

func (rr *X25) String() string

type ZoneParser added in v1.1.1 

type ZoneParser struct {
	// contains filtered or unexported fields
}

ZoneParser is a parser for an RFC 1035 style zonefile.

Each parsed RR in the zone is returned sequentially from Next. An optional comment can be retrieved with Comment.

The directives $INCLUDE, $ORIGIN, $TTL and $GENERATE are all supported. Although $INCLUDE is disabled by default.

Basic usage pattern when reading from a string (z) containing the zone data: 

zp := NewZoneParser(strings.NewReader(z), "", "")

for rr, ok := zp.Next(); ok; rr, ok = zp.Next() {
	// Do something with rr
}

if err := zp.Err(); err != nil {
	// log.Println(err)
}

Comments specified after an RR (and on the same line!) are returned too: 

foo. IN A 10.0.0.1 ; this is a comment

The text "; this is comment" is returned from Comment. Comments inside the RR are returned concatenated along with the RR. Comments on a line by themselves are discarded.

func NewZoneParser added in v1.1.1 

func NewZoneParser(r io.Reader, origin, file string) *ZoneParser

NewZoneParser returns an RFC 1035 style zonefile parser that reads from r.

The string file is used in error reporting and to resolve relative $INCLUDE directives. The string origin is used as the initial origin, as if the file would start with an $ORIGIN directive.

func (*ZoneParser) Comment added in v1.1.1 

func (zp *ZoneParser) Comment() string

Comment returns an optional text comment that occurred alongside the RR.

func (*ZoneParser) Err added in v1.1.1 

func (zp *ZoneParser) Err() error

Err returns the first non-EOF error that was encountered by the ZoneParser.

func (*ZoneParser) Next added in v1.1.1 

func (zp *ZoneParser) Next() (RR, bool)

Next advances the parser to the next RR in the zonefile and returns the (RR, true). It will return (nil, false) when the parsing stops, either by reaching the end of the input or an error. After Next returns (nil, false), the Err method will return any error that occurred during parsing.

func (*ZoneParser) SetDefaultTTL added in v1.1.1 

func (zp *ZoneParser) SetDefaultTTL(ttl uint32)

SetDefaultTTL sets the parsers default TTL to ttl.

func (*ZoneParser) SetIncludeAllowed added in v1.1.1 

func (zp *ZoneParser) SetIncludeAllowed(v bool)

SetIncludeAllowed controls whether $INCLUDE directives are allowed. $INCLUDE directives are not supported by default.

The $INCLUDE directive will open and read from a user controlled file on the system. Even if the file is not a valid zonefile, the contents of the file may be revealed in error messages, such as: 

/etc/passwd: dns: not a TTL: "root:x:0:0:root:/root:/bin/bash" at line: 1:31
/etc/shadow: dns: not a TTL: "root:$6$<redacted>::0:99999:7:::" at line: 1:125

Source Files

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Directories

Path Synopsis
Package dnsutil contains higher-level methods useful with the dns package.
 Package dnsutil contains higher-level methods useful with the dns package.

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