dns

package
v0.2.8 Latest Latest
Warning

This package is not in the latest version of its module.

 Go to latest Published: Apr 10, 2026 License: CC0-1.0 Imports: 7 Imported by: 0

Documentation

Overview

Package dns deals with encoding and decoding DNS wire format.

Index

Constants

View Source 
const (
	// https://tools.ietf.org/html/rfc1035#section-3.2.2
	RRTypeA     = 1
	RRTypeNS    = 2
	RRTypeCNAME = 5
	RRTypeNULL  = 10
	RRTypeMX    = 15
	RRTypeTXT   = 16
	RRTypeAAAA  = 28
	RRTypeSRV   = 33
	RRTypeCAA   = 257
	// https://tools.ietf.org/html/rfc6891#section-6.1.1
	RRTypeOPT = 41

	// https://tools.ietf.org/html/rfc1035#section-3.2.4
	ClassIN = 1

	// https://tools.ietf.org/html/rfc1035#section-4.1.1
	RcodeNoError        = 0 // a.k.a. NOERROR
	RcodeFormatError    = 1 // a.k.a. FORMERR
	RcodeServerFailure  = 2 // a.k.a. SERVFAIL
	RcodeNameError      = 3 // a.k.a. NXDOMAIN
	RcodeNotImplemented = 4 // a.k.a. NOTIMPL
	// https://tools.ietf.org/html/rfc6891#section-9
	ExtendedRcodeBadVers = 16 // a.k.a. BADVERS
)

Variables

View Source 
var (
	// ErrZeroLengthLabel is the error returned for names that contain a
	// zero-length label, like "example..com".
	ErrZeroLengthLabel = errors.New("name contains a zero-length label")

	// ErrLabelTooLong is the error returned for labels that are longer than
	// 63 octets.
	ErrLabelTooLong = errors.New("name contains a label longer than 63 octets")

	// ErrNameTooLong is the error returned for names whose encoded
	// representation is longer than 255 octets.
	ErrNameTooLong = errors.New("name is longer than 255 octets")

	// ErrReservedLabelType is the error returned when reading a label type
	// prefix whose two most significant bits are not 00 or 11.
	ErrReservedLabelType = errors.New("reserved label type")

	// ErrTooManyPointers is the error returned when reading a compressed
	// name that has too many compression pointers.
	ErrTooManyPointers = errors.New("too many compression pointers")

	// ErrTrailingBytes is the error returned when bytes remain in the parse
	// buffer after parsing a message.
	ErrTrailingBytes = errors.New("trailing bytes after message")

	// ErrIntegerOverflow is the error returned when trying to encode an
	// integer greater than 65535 into a 16-bit field.
	ErrIntegerOverflow = errors.New("integer overflow")
)

Functions

func DecodeRDataA added in v0.2.4 

func DecodeRDataA(chunks [][]byte) ([]byte, error)

DecodeRDataA decodes multiple A record RDATA chunks back to the original payload.

func DecodeRDataAAAA added in v0.2.4 

func DecodeRDataAAAA(chunks [][]byte) ([]byte, error)

DecodeRDataAAAA decodes multiple AAAA record RDATA chunks back to the original payload.

func DecodeRDataCAA added in v0.2.8 

func DecodeRDataCAA(p []byte) ([]byte, error)

DecodeRDataCAA decodes CAA RDATA and returns the value portion. https://datatracker.ietf.org/doc/html/rfc8659

func DecodeRDataCNAME added in v0.2.4 

func DecodeRDataCNAME(data []byte, domain Name) ([]byte, error)

DecodeRDataCNAME decodes CNAME RDATA back to the original payload.

func DecodeRDataMX added in v0.2.4 

func DecodeRDataMX(data []byte, domain Name) ([]byte, error)

DecodeRDataMX decodes MX RDATA back to the original payload.

func DecodeRDataNS added in v0.2.4 

func DecodeRDataNS(data []byte, domain Name) ([]byte, error)

DecodeRDataNS decodes NS RDATA back to the original payload.

func DecodeRDataNULL added in v0.2.8 

func DecodeRDataNULL(p []byte) ([]byte, error)

DecodeRDataNULL decodes NULL RDATA as a raw byte slice. https://tools.ietf.org/html/rfc1035#section-3.3.10

func DecodeRDataSRV added in v0.2.4 

func DecodeRDataSRV(data []byte, domain Name) ([]byte, error)

DecodeRDataSRV decodes SRV RDATA back to the original payload.

func DecodeRDataTXT 

func DecodeRDataTXT(p []byte) ([]byte, error)

DecodeRDataTXT decodes TXT-DATA (as found in the RDATA for a resource record with TYPE=TXT) as a raw byte slice, by concatenating all the <character-string>s it contains.

https://tools.ietf.org/html/rfc1035#section-3.3.14

func EncodeRDataA added in v0.2.4 

func EncodeRDataA(p []byte) [][]byte

EncodeRDataA encodes a payload as multiple A record RDATA chunks (4 bytes each).

func EncodeRDataAAAA added in v0.2.4 

func EncodeRDataAAAA(p []byte) [][]byte

EncodeRDataAAAA encodes a payload as multiple AAAA record RDATA chunks (16 bytes each).

func EncodeRDataCAA added in v0.2.8 

func EncodeRDataCAA(p []byte) []byte

EncodeRDataCAA encodes a slice of bytes as CAA RDATA using a fixed "issue" tag so the payload lives entirely in the value portion. https://datatracker.ietf.org/doc/html/rfc8659

func EncodeRDataCNAME added in v0.2.4 

func EncodeRDataCNAME(p []byte, domain Name) ([]byte, error)

EncodeRDataCNAME encodes a payload as CNAME RDATA. https://tools.ietf.org/html/rfc1035#section-3.3.1

func EncodeRDataMX added in v0.2.4 

func EncodeRDataMX(p []byte, domain Name) ([]byte, error)

EncodeRDataMX encodes a payload as MX RDATA: [preference:2][exchange:name]. https://tools.ietf.org/html/rfc1035#section-3.3.9

func EncodeRDataNS added in v0.2.4 

func EncodeRDataNS(p []byte, domain Name) ([]byte, error)

EncodeRDataNS encodes a payload as NS RDATA (identical format to CNAME). https://tools.ietf.org/html/rfc1035#section-3.3.11

func EncodeRDataNULL added in v0.2.8 

func EncodeRDataNULL(p []byte) []byte

EncodeRDataNULL encodes a slice of bytes as NULL RDATA. https://tools.ietf.org/html/rfc1035#section-3.3.10

func EncodeRDataSRV added in v0.2.4 

func EncodeRDataSRV(p []byte, domain Name) ([]byte, error)

EncodeRDataSRV encodes a payload as SRV RDATA: [priority:2][weight:2][port:2][target:name]. https://tools.ietf.org/html/rfc2782

func EncodeRDataTXT 

func EncodeRDataTXT(p []byte) []byte

EncodeRDataTXT encodes a slice of bytes as TXT-DATA, as appropriate for the RDATA of a resource record with TYPE=TXT. No length restriction is enforced here; that must be checked at a higher level.

https://tools.ietf.org/html/rfc1035#section-3.3.14

func ParseRecordType added in v0.2.4 

func ParseRecordType(s string) (uint16, error)

ParseRecordType converts a record type string ("txt", "cname", "a", etc.) to the corresponding RR type constant. Returns an error for unknown types.

Types

type Message 

type Message struct {
	ID    uint16
	Flags uint16

	Question   []Question
	Answer     []RR
	Authority  []RR
	Additional []RR
}

Message represents a DNS message.

https://tools.ietf.org/html/rfc1035#section-4.1

func MessageFromWireFormat 

func MessageFromWireFormat(buf []byte) (Message, error)

MessageFromWireFormat parses a message from buf and returns a Message object. It returns ErrTrailingBytes if there are bytes remaining in buf after parsing is done.

func (*Message) Opcode 

func (message *Message) Opcode() uint16

Opcode extracts the OPCODE part of the Flags field.

https://tools.ietf.org/html/rfc1035#section-4.1.1

func (*Message) Rcode 

func (message *Message) Rcode() uint16

Rcode extracts the RCODE part of the Flags field.

https://tools.ietf.org/html/rfc1035#section-4.1.1

func (*Message) WireFormat 

func (message *Message) WireFormat() ([]byte, error)

WireFormat encodes a Message as a slice of bytes in DNS wire format. It returns ErrIntegerOverflow if the number of entries in any section, or the length of the data in any resource record, does not fit in 16 bits.

type Name 

type Name [][]byte

Name represents a domain name, a sequence of labels each of which is 63 octets or less in length.

https://tools.ietf.org/html/rfc1035#section-3.1

func NameFromWireFormat added in v0.2.4 

func NameFromWireFormat(data []byte) (Name, error)

NameFromWireFormat parses an uncompressed DNS name from raw bytes. It does not handle compression pointers.

func NewName 

func NewName(labels [][]byte) (Name, error)

NewName returns a Name from a slice of labels, after checking the labels for validity. Does not include a zero-length label at the end of the slice.

func ParseName 

func ParseName(s string) (Name, error)

ParseName returns a new Name from a string of labels separated by dots, after checking the name for validity. A single dot at the end of the string is ignored.

func (Name) String 

func (name Name) String() string

String returns a reversible string representation of name. Labels are separated by dots, and any bytes in a label that are outside the set [0-9A-Za-z-] are replaced with a \xXX hex escape sequence.

func (Name) TrimSuffix 

func (name Name) TrimSuffix(suffix Name) (Name, bool)

TrimSuffix returns a Name with the given suffix removed, if it was present. The second return value indicates whether the suffix was present. If the suffix was not present, the first return value is nil.

func (Name) WireFormat added in v0.2.4 

func (name Name) WireFormat() []byte

WireFormat serializes a Name to uncompressed DNS wire format: a sequence of length-prefixed labels followed by a zero-length root label.

type Question 

type Question struct {
	Name  Name
	Type  uint16
	Class uint16
}

Question represents an entry in the question section of a message.

https://tools.ietf.org/html/rfc1035#section-4.1.2

type RR 

type RR struct {
	Name  Name
	Type  uint16
	Class uint16
	TTL   uint32
	Data  []byte
}

RR represents a resource record.

https://tools.ietf.org/html/rfc1035#section-4.1.3

Source Files

View all Source files

Jump to

Keyboard shortcuts

? : This menu
/ : Search site
f or F : Jump to
y or Y : Canonical URL
go.dev uses cookies from Google to deliver and enhance the quality of its services and to analyze traffic. Learn more.