client

Documentation

Overview

Package client implements DNS client wrappers

Index

• Constants
• func HasIPv6Support() bool
• func NewDefaultClient(udpSize uint16) *dns.Client
• func Unwrap(c Client) *dns.Client
• type Auto
  • func NewAutoClient(udp, tcp Client, exp time.Duration) (*Auto, error)
  • func (c *Auto) ExchangeContext(ctx context.Context, req *dns.Msg, server string) (*dns.Msg, time.Duration, error)
  • func (c *Auto) SetDefaults() error
• type Client
• type ExchangeFunc
  • func (fn ExchangeFunc) ExchangeContext(ctx context.Context, req *dns.Msg, server string) (*dns.Msg, time.Duration, error)
• type NoAAAA
  • func NewNoAAAA(c Client) *NoAAAA
  • func (c NoAAAA) ExchangeContext(ctx context.Context, req *dns.Msg, server string) (*dns.Msg, time.Duration, error)
  • func (c NoAAAA) Unwrap() *dns.Client
• type SingleFlight
  • func NewSingleFlight(c Client, exp time.Duration) *SingleFlight
  • func (sfc *SingleFlight) ExchangeContext(ctx context.Context, req *dns.Msg, server string) (*dns.Msg, time.Duration, error)
  • func (*SingleFlight) RequestKey(req *dns.Msg, server string) string
  • func (sfc *SingleFlight) Unwrap() *dns.Client
• type Unwrapper

Constants

const (
	// DefaultSingleFlightExpiration tells how long will we cache
	// the result after an exchange
	DefaultSingleFlightExpiration = 1 * time.Second
)

Functions

func HasIPv6Support

func HasIPv6Support() bool

HasIPv6Support tells if the system supports IPv6 or not. This doesn't guarantee connections will be successful.

func NewDefaultClient

func NewDefaultClient(udpSize uint16) *dns.Client

NewDefaultClient allocate a default dns.Client in the same manner as dns.ExchangeContext(), plain UDP.

func Unwrap

func Unwrap(c Client) *dns.Client

Unwrap uses the Unwrapper interface to find the underlying *dns.Client

Types

type Auto

type Auto struct {
	UDP Client
	TCP Client
	TLS Client
	// contains filtered or unexported fields
}

Auto is a client that allows different networks based on the server's prefix. * udp:// for UDP-only * tcp:// for TCP-only * tls:// for TCP+TLS * and without prefix for TCP-fallback

func NewAutoClient

func NewAutoClient(udp, tcp Client, exp time.Duration) (*Auto, error)

NewAutoClient allocates a new Auto client. If changes to fields are done manually after this call, or manually assembling the Auto struct, it is required to call Auto.SetDefaults.

NewAutoClient allows specifying a custom expiration value for SingleFlight, but when Auto is assembled manually or `exp == 0`, DefaultSingleFlightExpiration will be used.

func (*Auto) ExchangeContext

func (c *Auto) ExchangeContext(ctx context.Context, req *dns.Msg,
	server string) (*dns.Msg, time.Duration, error)

ExchangeContext uses different exchange networks based on the prefix of the server string.

func (*Auto) SetDefaults

func (c *Auto) SetDefaults() error

SetDefaults fills the configuration gaps

type Client

type Client interface {
	ExchangeContext(context.Context, *dns.Msg, string) (*dns.Msg, time.Duration, error)
}

A Client makes a request to a server

type ExchangeFunc

type ExchangeFunc func(context.Context, *dns.Msg, string) (*dns.Msg, time.Duration, error)

ExchangeFunc is a function that implements the Client interface

func (ExchangeFunc) ExchangeContext

func (fn ExchangeFunc) ExchangeContext(ctx context.Context, req *dns.Msg,
	server string) (*dns.Msg, time.Duration, error)

ExchangeContext implements the Client interface

type NoAAAA

type NoAAAA struct {
	Client
}

NoAAAA is a dns.Client middleware to remove AAAA entries from all responses

func NewNoAAAA

func NewNoAAAA(c Client) *NoAAAA

NewNoAAAA creates a Client middleware that filters out all AAAA entries

func (NoAAAA) ExchangeContext

func (c NoAAAA) ExchangeContext(ctx context.Context, req *dns.Msg,
	server string) (*dns.Msg, time.Duration, error)

ExchangeContext calls the next client in the chain if it's not an AAAA, and discards all AAAA entries on the response.

func (NoAAAA) Unwrap

func (c NoAAAA) Unwrap() *dns.Client

type SingleFlight

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

SingleFlight wraps a Client to minimize redundant queries

func NewSingleFlight

func NewSingleFlight(c Client, exp time.Duration) *SingleFlight

NewSingleFlight creates a SingleFlight Client around another. if no Client is specified, the default udp dns.Client will be used. if exp is positive, the result will be cached that long. if exp is negative, the result will expire immediately if exp is zero, DefaultSingleFlightExpiration will be used

func (*SingleFlight) ExchangeContext

func (sfc *SingleFlight) ExchangeContext(ctx context.Context, req *dns.Msg,
	server string) (*dns.Msg, time.Duration, error)

ExchangeContext makes a DNS query to a server, minimizing duplications.

func (*SingleFlight) RequestKey

func (*SingleFlight) RequestKey(req *dns.Msg, server string) string

RequestKey serializes a DNS request to act as temporary cache key

func (*SingleFlight) Unwrap

func (sfc *SingleFlight) Unwrap() *dns.Client

Unwrap returns the underlying *dns.Client

type Unwrapper

type Unwrapper interface {
	Unwrap() *dns.Client
}

An Unwrapper can tell what's the underlying *dns.Client