dns

package
v0.9.8 Latest Latest
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 Go to latest Published: Dec 19, 2019 License: GPL-3.0 Imports: 11 Imported by: 0

Documentation

Index

Constants

View Source 
const (
	Query    = 0
	Response = 1
)

Message types

View Source 
const (
	QTypeA    uint16 = 1  //ipv4
	QTypeAAAA uint16 = 28 ///ipv6
)

Query types

View Source 
const ClassINET uint16 = 1

ClassINET .

View Source 
const HeaderLen = 12

HeaderLen is the length of dns msg header.

View Source 
const LongTTL = 50 * 365 * 24 * 3600

LongTTL is 50 years duration in seconds, used for none-expired items.

View Source 
const UDPMaxLen = 512

UDPMaxLen is the max size of udp dns request. https://tools.ietf.org/html/rfc1035#section-4.2.1 Messages carried by UDP are restricted to 512 bytes (not counting the IP or UDP headers). Longer messages are truncated and the TC bit is set in the header.

Variables

This section is empty.

Functions

func MarshalDomain added in v0.6.5 

func MarshalDomain(domain string) []byte

MarshalDomain marshals domain string struct to []byte.

func UnmarshalHeader added in v0.6.5 

func UnmarshalHeader(b []byte, h *Header) error

UnmarshalHeader unmarshals []bytes to Header.

Types

type Cache added in v0.6.5 

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

Cache is the struct of cache.

func NewCache added in v0.6.5 

func NewCache() (c *Cache)

NewCache returns a new cache.

func (*Cache) Get added in v0.6.5 

func (c *Cache) Get(k string) (v []byte)

Get an item from cache.

func (*Cache) Len added in v0.6.5 

func (c *Cache) Len() int

Len returns the length of cache.

func (*Cache) Put added in v0.6.5 

func (c *Cache) Put(k string, v []byte, ttl int)

Put an item into cache, invalid after ttl seconds.

type Client added in v0.6.5 

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

Client is a dns client struct.

func NewClient added in v0.6.5 

func NewClient(proxy proxy.Proxy, config *Config) (*Client, error)

NewClient returns a new dns client.

func (*Client) AddHandler added in v0.6.5 

func (c *Client) AddHandler(h HandleFunc)

AddHandler adds a custom handler to handle the resolved result (A and AAAA).

func (*Client) AddRecord added in v0.6.5 

func (c *Client) AddRecord(record string) error

AddRecord adds custom record to dns cache, format: www.example.com/1.2.3.4 or www.example.com/2606:2800:220:1:248:1893:25c8:1946

func (*Client) Exchange added in v0.6.5 

func (c *Client) Exchange(reqBytes []byte, clientAddr string, preferTCP bool) ([]byte, error)

Exchange handles request message and returns response message. reqBytes = reqLen + reqMsg

func (*Client) GenResponse added in v0.6.5 

func (c *Client) GenResponse(domain string, ip string) (*Message, error)

GenResponse generates a dns response message for the given domain and ip address.

func (*Client) GetServers added in v0.6.6 

func (c *Client) GetServers(domain string) []string

GetServers gets upstream dns servers for the given domain

func (*Client) SetServers added in v0.6.7 

func (c *Client) SetServers(domain string, servers ...string)

SetServers sets upstream dns servers for the given domain.

type Config added in v0.6.6 

type Config struct {
	Servers   []string
	Timeout   int
	MaxTTL    int
	MinTTL    int
	Records   []string
	AlwaysTCP bool
}

Config for dns.

type HandleFunc added in v0.6.5 

type HandleFunc func(Domain, ip string) error

HandleFunc function handles the dns TypeA or TypeAAAA answer. 

type Header struct {
	ID      uint16
	Bits    uint16
	QDCOUNT uint16
	ANCOUNT uint16
	NSCOUNT uint16
	ARCOUNT uint16
}

Header format https://tools.ietf.org/html/rfc1035#section-4.1.1 The header contains the following fields: 

                                1  1  1  1  1  1
  0  1  2  3  4  5  6  7  8  9  0  1  2  3  4  5
+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+
|                      ID                       |
+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+
|QR|   Opcode  |AA|TC|RD|RA|   Z    |   RCODE   |
+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+
|                    QDCOUNT                    |
+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+
|                    ANCOUNT                    |
+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+
|                    NSCOUNT                    |
+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+
|                    ARCOUNT                    |
+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+

func (*Header) Marshal added in v0.6.5 

func (h *Header) Marshal() ([]byte, error)

Marshal marshals header struct to []byte.

func (*Header) SetAncount added in v0.6.5 

func (h *Header) SetAncount(ancount int)

SetAncount sets answers count.

func (*Header) SetMsgType added in v0.6.5 

func (h *Header) SetMsgType(qr int)

SetMsgType sets the message type.

func (*Header) SetQdcount added in v0.6.5 

func (h *Header) SetQdcount(qdcount int)

SetQdcount sets query count, most dns servers only support 1 query per request.

func (*Header) SetTC added in v0.6.5 

func (h *Header) SetTC(tc int)

SetTC sets the tc flag.

type Message added in v0.6.5 

type Message struct {
	Header
	// most dns implementation only support 1 question
	Question   *Question
	Answers    []*RR
	Authority  []*RR
	Additional []*RR
	// contains filtered or unexported fields
}

Message format https://tools.ietf.org/html/rfc1035#section-4.1 All communications inside of the domain protocol are carried in a single format called a message. The top level format of message is divided into 5 sections (some of which are empty in certain cases) shown below: 

+---------------------+
|        Header       |
+---------------------+
|       Question      | the question for the name server
+---------------------+
|        Answer       | RRs answering the question
+---------------------+
|      Authority      | RRs pointing toward an authority
+---------------------+
|      Additional     | RRs holding additional information

func NewMessage added in v0.6.5 

func NewMessage(id uint16, msgType int) *Message

NewMessage returns a new message.

func UnmarshalMessage added in v0.6.5 

func UnmarshalMessage(b []byte) (*Message, error)

UnmarshalMessage unmarshals []bytes to Message.

func (*Message) AddAnswer added in v0.6.5 

func (m *Message) AddAnswer(rr *RR) error

AddAnswer adds an answer to dns message.

func (*Message) Marshal added in v0.6.5 

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

Marshal marshals message struct to []byte.

func (*Message) SetQuestion added in v0.6.5 

func (m *Message) SetQuestion(q *Question) error

SetQuestion sets a question to dns message.

func (*Message) UnmarshalDomain added in v0.6.5 

func (m *Message) UnmarshalDomain(b []byte) (string, int, error)

UnmarshalDomain gets domain from bytes.

func (*Message) UnmarshalDomainPoint added in v0.6.5 

func (m *Message) UnmarshalDomainPoint(offset int) (string, error)

UnmarshalDomainPoint gets domain from offset point.

func (*Message) UnmarshalQuestion added in v0.6.5 

func (m *Message) UnmarshalQuestion(b []byte, q *Question) (n int, err error)

UnmarshalQuestion unmarshals []bytes to Question.

func (*Message) UnmarshalRR added in v0.6.5 

func (m *Message) UnmarshalRR(start int, rr *RR) (n int, err error)

UnmarshalRR unmarshals []bytes to RR.

type Question 

type Question struct {
	QNAME  string
	QTYPE  uint16
	QCLASS uint16
}

Question format https://tools.ietf.org/html/rfc1035#section-4.1.2 The question section is used to carry the "question" in most queries, i.e., the parameters that define what is being asked. The section contains QDCOUNT (usually 1) entries, each of the following format: 

                                1  1  1  1  1  1
  0  1  2  3  4  5  6  7  8  9  0  1  2  3  4  5
+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+
|                                               |
/                     QNAME                     /
/                                               /
+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+
|                     QTYPE                     |
+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+
|                     QCLASS                    |
+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+

func NewQuestion added in v0.6.5 

func NewQuestion(qtype uint16, domain string) *Question

NewQuestion returns a new dns question.

func (*Question) Marshal added in v0.6.5 

func (q *Question) Marshal() ([]byte, error)

Marshal marshals Question struct to []byte.

type RR 

type RR struct {
	NAME     string
	TYPE     uint16
	CLASS    uint16
	TTL      uint32
	RDLENGTH uint16
	RDATA    []byte

	IP string
}

RR format https://tools.ietf.org/html/rfc1035#section-3.2.1 https://tools.ietf.org/html/rfc1035#section-4.1.3 The answer, authority, and additional sections all share the same format: a variable number of resource records, where the number of records is specified in the corresponding count field in the header. Each resource record has the following format: 

                                1  1  1  1  1  1
  0  1  2  3  4  5  6  7  8  9  0  1  2  3  4  5
+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+
|                                               |
/                                               /
/                      NAME                     /
|                                               |
+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+
|                      TYPE                     |
+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+
|                     CLASS                     |
+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+
|                      TTL                      |
|                                               |
+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+
|                   RDLENGTH                    |
+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--|
/                     RDATA                     /
/                                               /
+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+

func NewRR added in v0.6.5 

func NewRR() *RR

NewRR returns a new dns rr.

func (*RR) Marshal added in v0.6.5 

func (rr *RR) Marshal() ([]byte, error)

Marshal marshals RR struct to []byte.

type Server added in v0.6.5 

type Server struct {

	// Client is used to communicate with upstream dns servers
	*Client
	// contains filtered or unexported fields
}

Server is a dns server struct.

func NewServer added in v0.6.5 

func NewServer(addr string, p proxy.Proxy, config *Config) (*Server, error)

NewServer returns a new dns server.

func (*Server) ListenAndServeTCP added in v0.6.5 

func (s *Server) ListenAndServeTCP(wg *sync.WaitGroup)

ListenAndServeTCP listen and serves on tcp port.

func (*Server) ListenAndServeUDP added in v0.6.5 

func (s *Server) ListenAndServeUDP(wg *sync.WaitGroup)

ListenAndServeUDP listen and serves on udp port.

func (*Server) ServeTCP added in v0.6.5 

func (s *Server) ServeTCP(c net.Conn)

ServeTCP serves a tcp connection.

func (*Server) Start added in v0.6.7 

func (s *Server) Start()

Start starts the dns forwarding server. We use WaitGroup here to ensure both udp and tcp serer are completly running, so we can start any other services later, since they may rely on dns service.

Source Files

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