// Package nat provides access to common port mapping protocols.
package nat
import (
"errors"
"fmt"
"net"
"strings"
"sync"
"time"
"github.com/ethereum/go-ethereum/logger"
"github.com/jackpal/go-nat-pmp"
)
var log = logger.NewLogger("P2P NAT")
// An implementation of nat.Interface can map local ports to ports
// accessible from the Internet.
type Interface interface {
// These methods manage a mapping between a port on the local
// machine to a port that can be connected to from the internet.
//
// protocol is "UDP" or "TCP". Some implementations allow setting
// a display name for the mapping. The mapping may be removed by
// the gateway when its lifetime ends.
AddMapping(protocol string, extport, intport int, name string, lifetime time.Duration) error
DeleteMapping(protocol string, extport, intport int) error
// This method should return the external (Internet-facing)
// address of the gateway device.
ExternalIP() (net.IP, error)
// Should return name of the method. This is used for logging.
String() string
}
// Parse parses a NAT interface description.
// The following formats are currently accepted.
// Note that mechanism names are not case-sensitive.
//
// "" or "none" return nil
// "extip:77.12.33.4" will assume the local machine is reachable on the given IP
// "any" uses the first auto-detected mechanism
// "upnp" uses the Universal Plug and Play protocol
// "pmp" uses NAT-PMP with an auto-detected gateway address
// "pmp:192.168.0.1" uses NAT-PMP with the given gateway address
func Parse(spec string) (Interface, error) {
var (
parts = strings.SplitN(spec, ":", 2)
mech = strings.ToLower(parts[0])
ip net.IP
)
if len(parts) > 1 {
ip = net.ParseIP(parts[1])
if ip == nil {
return nil, errors.New("invalid IP address")
}
}
switch mech {
case "", "none", "off":
return nil, nil
case "any", "auto", "on":
return Any(), nil
case "extip", "ip":
if ip == nil {
return nil, errors.New("missing IP address")
}
return ExtIP(ip), nil
case "upnp":
return UPnP(), nil
case "pmp", "natpmp", "nat-pmp":
return PMP(ip), nil
default:
return nil, fmt.Errorf("unknown mechanism %q", parts[0])
}
}
const (
mapTimeout = 20 * time.Minute
mapUpdateInterval = 15 * time.Minute
)
// Map adds a port mapping on m and keeps it alive until c is closed.
// This function is typically invoked in its own goroutine.
func Map(m Interface, c chan struct{}, protocol string, extport, intport int, name string) {
refresh := time.NewTimer(mapUpdateInterval)
defer func() {
refresh.Stop()
log.Debugf("Deleting port mapping: %s %d -> %d (%s) using %s\n", protocol, extport, intport, name, m)
m.DeleteMapping(protocol, extport, intport)
}()
log.Debugf("add mapping: %s %d -> %d (%s) using %s\n", protocol, extport, intport, name, m)
if err := m.AddMapping(protocol, intport, extport, name, mapTimeout); err != nil {
log.Errorf("mapping error: %v\n", err)
}
for {
select {
case _, ok := <-c:
if !ok {
return
}
case <-refresh.C:
log.DebugDetailf("refresh mapping: %s %d -> %d (%s) using %s\n", protocol, extport, intport, name, m)
if err := m.AddMapping(protocol, intport, extport, name, mapTimeout); err != nil {
log.Errorf("mapping error: %v\n", err)
}
refresh.Reset(mapUpdateInterval)
}
}
}
// ExtIP assumes that the local machine is reachable on the given
// external IP address, and that any required ports were mapped manually.
// Mapping operations will not return an error but won't actually do anything.
func ExtIP(ip net.IP) Interface {
if ip == nil {
panic("IP must not be nil")
}
return extIP(ip)
}
type extIP net.IP
func (n extIP) ExternalIP() (net.IP, error) { return net.IP(n), nil }
func (n extIP) String() string { return fmt.Sprintf("ExtIP(%v)", net.IP(n)) }
// These do nothing.
func (extIP) AddMapping(string, int, int, string, time.Duration) error { return nil }
func (extIP) DeleteMapping(string, int, int) error { return nil }
// Any returns a port mapper that tries to discover any supported
// mechanism on the local network.
func Any() Interface {
// TODO: attempt to discover whether the local machine has an
// Internet-class address. Return ExtIP in this case.
return startautodisc("UPnP or NAT-PMP", func() Interface {
found := make(chan Interface, 2)
go func() { found <- discoverUPnP() }()
go func() { found <- discoverPMP() }()
for i := 0; i < cap(found); i++ {
if c := <-found; c != nil {
return c
}
}
return nil
})
}
// UPnP returns a port mapper that uses UPnP. It will attempt to
// discover the address of your router using UDP broadcasts.
func UPnP() Interface {
return startautodisc("UPnP", discoverUPnP)
}
// PMP returns a port mapper that uses NAT-PMP. The provided gateway
// address should be the IP of your router. If the given gateway
// address is nil, PMP will attempt to auto-discover the router.
func PMP(gateway net.IP) Interface {
if gateway != nil {
return &pmp{gw: gateway, c: natpmp.NewClient(gateway)}
}
return startautodisc("NAT-PMP", discoverPMP)
}
// autodisc represents a port mapping mechanism that is still being
// auto-discovered. Calls to the Interface methods on this type will
// wait until the discovery is done and then call the method on the
// discovered mechanism.
//
// This type is useful because discovery can take a while but we
// want return an Interface value from UPnP, PMP and Auto immediately.
type autodisc struct {
what string
done <-chan Interface
mu sync.Mutex
found Interface
}
func startautodisc(what string, doit func() Interface) Interface {
// TODO: monitor network configuration and rerun doit when it changes.
done := make(chan Interface)
ad := &autodisc{what: what, done: done}
go func() { done <- doit(); close(done) }()
return ad
}
func (n *autodisc) AddMapping(protocol string, extport, intport int, name string, lifetime time.Duration) error {
if err := n.wait(); err != nil {
return err
}
return n.found.AddMapping(protocol, extport, intport, name, lifetime)
}
func (n *autodisc) DeleteMapping(protocol string, extport, intport int) error {
if err := n.wait(); err != nil {
return err
}
return n.found.DeleteMapping(protocol, extport, intport)
}
func (n *autodisc) ExternalIP() (net.IP, error) {
if err := n.wait(); err != nil {
return nil, err
}
return n.found.ExternalIP()
}
func (n *autodisc) String() string {
n.mu.Lock()
defer n.mu.Unlock()
if n.found == nil {
return n.what
} else {
return n.found.String()
}
}
func (n *autodisc) wait() error {
n.mu.Lock()
found := n.found
n.mu.Unlock()
if found != nil {
// already discovered
return nil
}
if found = <-n.done; found == nil {
return errors.New("no devices discovered")
}
n.mu.Lock()
n.found = found
n.mu.Unlock()
return nil
}
