dnsmessage

Documentation

Overview

Package dnsmessage provides a mostly RFC 1035 compliant implementation of DNS message packing and unpacking.

This implementation is designed to minimize heap allocations and avoid unnecessary packing and unpacking as much as possible.

Index

• Constants
• Variables
• type AAAAResource
• type AResource
• type CNAMEResource
• type Class
• type Header
• type MXResource
• type Message
  • func (m *Message) Pack() ([]byte, error)
  • func (m *Message) Unpack(msg []byte) error
• type NSResource
• type OpCode
• type PTRResource
• type Parser
  • func (p *Parser) Additional() (Resource, error)
  • func (p *Parser) AdditionalHeader() (ResourceHeader, error)
  • func (p *Parser) AllAdditionals() ([]Resource, error)
  • func (p *Parser) AllAnswers() ([]Resource, error)
  • func (p *Parser) AllAuthorities() ([]Resource, error)
  • func (p *Parser) AllQuestions() ([]Question, error)
  • func (p *Parser) Answer() (Resource, error)
  • func (p *Parser) AnswerHeader() (ResourceHeader, error)
  • func (p *Parser) Authority() (Resource, error)
  • func (p *Parser) AuthorityHeader() (ResourceHeader, error)
  • func (p *Parser) Question() (Question, error)
  • func (p *Parser) SkipAdditional() error
  • func (p *Parser) SkipAllAdditionals() error
  • func (p *Parser) SkipAllAnswers() error
  • func (p *Parser) SkipAllAuthorities() error
  • func (p *Parser) SkipAllQuestions() error
  • func (p *Parser) SkipAnswer() error
  • func (p *Parser) SkipAuthority() error
  • func (p *Parser) SkipQuestion() error
  • func (p *Parser) Start(msg []byte) (Header, error)
• type Question
• type RCode
• type Resource
• type ResourceHeader
  • func (h *ResourceHeader) Header() *ResourceHeader
• type SOAResource
• type SRVResource
• type TXTResource
• type Type

Constants

const (
	// ResourceHeader.Type and Question.Type
	TypeA     Type = 1
	TypeNS    Type = 2
	TypeCNAME Type = 5
	TypeSOA   Type = 6
	TypePTR   Type = 12
	TypeMX    Type = 15
	TypeTXT   Type = 16
	TypeAAAA  Type = 28
	TypeSRV   Type = 33

	// Question.Type
	TypeWKS   Type = 11
	TypeHINFO Type = 13
	TypeMINFO Type = 14
	TypeAXFR  Type = 252
	TypeALL   Type = 255

	// ResourceHeader.Class and Question.Class
	ClassINET   Class = 1
	ClassCSNET  Class = 2
	ClassCHAOS  Class = 3
	ClassHESIOD Class = 4

	// Question.Class
	ClassANY Class = 255

	// Message.Rcode
	RCodeSuccess        RCode = 0
	RCodeFormatError    RCode = 1
	RCodeServerFailure  RCode = 2
	RCodeNameError      RCode = 3
	RCodeNotImplemented RCode = 4
	RCodeRefused        RCode = 5
)

Wire constants.

Variables

var (
	// ErrNotStarted indicates that the prerequisite information isn't
	// available yet because the previous records haven't been appropriately
	// parsed or skipped.
	ErrNotStarted = errors.New("parsing of this type isn't available yet")

	// ErrSectionDone indicated that all records in the section have been
	// parsed.
	ErrSectionDone = errors.New("parsing of this section has completed")
)

Types

type AAAAResource

type AAAAResource struct {
	ResourceHeader

	AAAA [16]byte
}

An AAAAResource is an AAAA Resource record.

type AResource

type AResource struct {
	ResourceHeader

	A [4]byte
}

An AResource is an A Resource record.

type CNAMEResource

type CNAMEResource struct {
	ResourceHeader

	CNAME string
}

A CNAMEResource is a CNAME Resource record.

type Class

type Class uint16

A Class is a type of network.

type Header

type Header struct {
	ID                 uint16
	Response           bool
	OpCode             OpCode
	Authoritative      bool
	Truncated          bool
	RecursionDesired   bool
	RecursionAvailable bool
	RCode              RCode
}

Header is a representation of a DNS message header.

type MXResource

type MXResource struct {
	ResourceHeader

	Pref uint16
	MX   string
}

An MXResource is an MX Resource record.

type Message

type Message struct {
	Header
	Questions   []Question
	Answers     []Resource
	Authorities []Resource
	Additionals []Resource
}

Message is a representation of a DNS message.

func (*Message) Pack

func (m *Message) Pack() ([]byte, error)

Pack packs a full Message.

func (*Message) Unpack

func (m *Message) Unpack(msg []byte) error

Unpack parses a full Message.

type NSResource

type NSResource struct {
	ResourceHeader

	NS string
}

An NSResource is an NS Resource record.

type OpCode

type OpCode uint16

An OpCode is a DNS operation code.

type PTRResource

type PTRResource struct {
	ResourceHeader

	PTR string
}

A PTRResource is a PTR Resource record.

type Parser

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

A Parser allows incrementally parsing a DNS message.

When parsing is started, the Header is parsed. Next, each Question can be either parsed or skipped. Alternatively, all Questions can be skipped at once. When all Questions have been parsed, attempting to parse Questions will return (nil, nil) and attempting to skip Questions will return (true, nil). After all Questions have been either parsed or skipped, all Answers, Authorities and Additionals can be either parsed or skipped in the same way, and each type of Resource must be fully parsed or skipped before proceeding to the next type of Resource.

Note that there is no requirement to fully skip or parse the message.

func (*Parser) Additional

func (p *Parser) Additional() (Resource, error)

Additional parses a single Additional Resource.

func (*Parser) AdditionalHeader

func (p *Parser) AdditionalHeader() (ResourceHeader, error)

AdditionalHeader parses a single Additional ResourceHeader.

func (*Parser) AllAdditionals

func (p *Parser) AllAdditionals() ([]Resource, error)

AllAdditionals parses all Additional Resources.

func (*Parser) AllAnswers

func (p *Parser) AllAnswers() ([]Resource, error)

AllAnswers parses all Answer Resources.

func (*Parser) AllAuthorities

func (p *Parser) AllAuthorities() ([]Resource, error)

AllAuthorities parses all Authority Resources.

func (*Parser) AllQuestions

func (p *Parser) AllQuestions() ([]Question, error)

AllQuestions parses all Questions.

func (*Parser) Answer

func (p *Parser) Answer() (Resource, error)

Answer parses a single Answer Resource.

func (*Parser) AnswerHeader

func (p *Parser) AnswerHeader() (ResourceHeader, error)

AnswerHeader parses a single Answer ResourceHeader.

func (*Parser) Authority

func (p *Parser) Authority() (Resource, error)

Authority parses a single Authority Resource.

func (*Parser) AuthorityHeader

func (p *Parser) AuthorityHeader() (ResourceHeader, error)

AuthorityHeader parses a single Authority ResourceHeader.

func (*Parser) Question

func (p *Parser) Question() (Question, error)

Question parses a single Question.

func (*Parser) SkipAdditional

func (p *Parser) SkipAdditional() error

SkipAdditional skips a single Additional Resource.

func (*Parser) SkipAllAdditionals

func (p *Parser) SkipAllAdditionals() error

SkipAllAdditionals skips all Additional Resources.

func (*Parser) SkipAllAnswers

func (p *Parser) SkipAllAnswers() error

SkipAllAnswers skips all Answer Resources.

func (*Parser) SkipAllAuthorities

func (p *Parser) SkipAllAuthorities() error

SkipAllAuthorities skips all Authority Resources.

func (*Parser) SkipAllQuestions

func (p *Parser) SkipAllQuestions() error

SkipAllQuestions skips all Questions.

func (*Parser) SkipAnswer

func (p *Parser) SkipAnswer() error

SkipAnswer skips a single Answer Resource.

func (*Parser) SkipAuthority

func (p *Parser) SkipAuthority() error

SkipAuthority skips a single Authority Resource.

func (*Parser) SkipQuestion

func (p *Parser) SkipQuestion() error

SkipQuestion skips a single Question.

func (*Parser) Start

func (p *Parser) Start(msg []byte) (Header, error)

Start parses the header and enables the parsing of Questions.

type Question

type Question struct {
	Name  string
	Type  Type
	Class Class
}

A Question is a DNS query.

type RCode

type RCode uint16

An RCode is a DNS response status code.

type Resource

type Resource interface {
	// Header return's the Resource's ResourceHeader.
	Header() *ResourceHeader
	// contains filtered or unexported methods
}

A Resource is a DNS resource record.

type ResourceHeader

type ResourceHeader struct {
	// Name is the domain name for which this resource record pertains.
	Name string

	// Type is the type of DNS resource record.
	//
	// This field will be set automatically during packing.
	Type Type

	// Class is the class of network to which this DNS resource record
	// pertains.
	Class Class

	// TTL is the length of time (measured in seconds) which this resource
	// record is valid for (time to live). All Resources in a set should
	// have the same TTL (RFC 2181 Section 5.2).
	TTL uint32

	// Length is the length of data in the resource record after the header.
	//
	// This field will be set automatically during packing.
	Length uint16
}

An ResourceHeader is the header of a DNS resource record. There are many types of DNS resource records, but they all share the same header.

func (*ResourceHeader) Header

func (h *ResourceHeader) Header() *ResourceHeader

Header implements Resource.Header.

type SOAResource

type SOAResource struct {
	ResourceHeader

	NS      string
	MBox    string
	Serial  uint32
	Refresh uint32
	Retry   uint32
	Expire  uint32

	// MinTTL the is the default TTL of Resources records which did not
	// contain a TTL value and the TTL of negative responses. (RFC 2308
	// Section 4)
	MinTTL uint32
}

An SOAResource is an SOA Resource record.

type SRVResource

type SRVResource struct {
	ResourceHeader

	Priority uint16
	Weight   uint16
	Port     uint16
	Target   string // Not compressed as per RFC 2782.
}

An SRVResource is an SRV Resource record.

type TXTResource

type TXTResource struct {
	ResourceHeader

	Txt string // Not a domain name.
}

A TXTResource is a TXT Resource record.

type Type

type Type uint16

A Type is a type of DNS request and response.