nat

Documentation

Index

• Constants
• Variables
• type Mapping
• type NAT
  • func DiscoverNAT(ctx context.Context) (*NAT, error)
  • func (nat *NAT) Close() error
  • func (nat *NAT) Mappings() []Mapping
  • func (nat *NAT) NewMapping(protocol string, port int) (Mapping, error)

Constants

const CacheTime = time.Second * 15

CacheTime is the time a mapping will cache an external address for

const MappingDuration = time.Second * 60

MappingDuration is a default port mapping duration. Port mappings are renewed every (MappingDuration / 3)

Variables

var ErrNoMapping = errors.New("mapping not established")

ErrNoMapping signals no mapping exists for an address

Types

type Mapping

type Mapping interface {
	// NAT returns the NAT object this Mapping belongs to.
	NAT() *NAT

	// Protocol returns the protocol of this port mapping. This is either
	// "tcp" or "udp" as no other protocols are likely to be NAT-supported.
	Protocol() string

	// InternalPort returns the internal device port. Mapping will continue to
	// try to map InternalPort() to an external facing port.
	InternalPort() int

	// ExternalPort returns the external facing port. If the mapping is not
	// established, port will be 0
	ExternalPort() int

	// ExternalAddr returns the external facing address. If the mapping is not
	// established, addr will be nil, and and ErrNoMapping will be returned.
	ExternalAddr() (addr net.Addr, err error)

	// Close closes the port mapping
	Close() error
}

Mapping represents a port mapping in a NAT.

type NAT

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

NAT is an object that manages address port mappings in NATs (Network Address Translators). It is a long-running service that will periodically renew port mappings, and keep an up-to-date list of all the external addresses.

func DiscoverNAT

func DiscoverNAT(ctx context.Context) (*NAT, error)

DiscoverNAT looks for a NAT device in the network and returns an object that can manage port mappings.

func (*NAT) Close

func (nat *NAT) Close() error

Close shuts down all port mappings. NAT can no longer be used.

func (*NAT) Mappings

func (nat *NAT) Mappings() []Mapping

Mappings returns a slice of all NAT mappings

func (*NAT) NewMapping

func (nat *NAT) NewMapping(protocol string, port int) (Mapping, error)

NewMapping attempts to construct a mapping on protocol and internal port It will also periodically renew the mapping until the returned Mapping -- or its parent NAT -- is Closed.

May not succeed, and mappings may change over time; NAT devices may not respect our port requests, and even lie. Clients should not store the mapped results, but rather always poll our object for the latest mappings.