status-go/vendor/github.com/libp2p/go-nat/nat.go

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2019-06-09 07:24:20 +00:00
// Package nat implements NAT handling facilities
package nat
import (
"context"
"errors"
"math"
"math/rand"
"net"
"time"
)
var ErrNoExternalAddress = errors.New("no external address")
var ErrNoInternalAddress = errors.New("no internal address")
var ErrNoNATFound = errors.New("no NAT found")
// protocol is either "udp" or "tcp"
type NAT interface {
// Type returns the kind of NAT port mapping service that is used
Type() string
// GetDeviceAddress returns the internal address of the gateway device.
GetDeviceAddress() (addr net.IP, err error)
// GetExternalAddress returns the external address of the gateway device.
GetExternalAddress() (addr net.IP, err error)
// GetInternalAddress returns the address of the local host.
GetInternalAddress() (addr net.IP, err error)
// AddPortMapping maps a port on the local host to an external port.
AddPortMapping(protocol string, internalPort int, description string, timeout time.Duration) (mappedExternalPort int, err error)
// DeletePortMapping removes a port mapping.
DeletePortMapping(protocol string, internalPort int) (err error)
}
// DiscoverNATs returns all NATs discovered in the network.
func DiscoverNATs(ctx context.Context) <-chan NAT {
nats := make(chan NAT)
go func() {
defer close(nats)
upnpIg1 := discoverUPNP_IG1(ctx)
upnpIg2 := discoverUPNP_IG2(ctx)
natpmp := discoverNATPMP(ctx)
upnpGenIGDev := discoverUPNP_GenIGDev(ctx)
for upnpIg1 != nil || upnpIg2 != nil || natpmp != nil || upnpGenIGDev != nil {
var (
nat NAT
ok bool
)
select {
case nat, ok = <-upnpIg1:
if !ok {
upnpIg1 = nil
}
case nat, ok = <-upnpIg2:
if !ok {
upnpIg2 = nil
}
case nat, ok = <-upnpGenIGDev:
if !ok {
upnpGenIGDev = nil
}
case nat, ok = <-natpmp:
if !ok {
natpmp = nil
}
case <-ctx.Done():
// timeout.
return
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}
if ok {
select {
case nats <- nat:
case <-ctx.Done():
return
}
}
}
}()
return nats
}
// DiscoverGateway attempts to find a gateway device.
func DiscoverGateway() (NAT, error) {
ctx, cancel := context.WithTimeout(context.Background(), 10*time.Second)
defer cancel()
var nats []NAT
for nat := range DiscoverNATs(ctx) {
nats = append(nats, nat)
}
switch len(nats) {
case 0:
return nil, ErrNoNATFound
case 1:
return nats[0], nil
}
gw, _ := getDefaultGateway()
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bestNAT := nats[0]
natGw, _ := bestNAT.GetDeviceAddress()
bestNATIsGw := gw != nil && natGw.Equal(gw)
// 1. Prefer gateways discovered _last_. This is an OK heuristic for
// discovering the most-upstream (furthest) NAT.
// 2. Prefer gateways that actually match our known gateway address.
// Some relays like to claim to be NATs even if they aren't.
for _, nat := range nats[1:] {
natGw, _ := nat.GetDeviceAddress()
natIsGw := gw != nil && natGw.Equal(gw)
if bestNATIsGw && !natIsGw {
continue
}
bestNATIsGw = natIsGw
bestNAT = nat
}
return bestNAT, nil
}
func randomPort() int {
rand.Seed(time.Now().UnixNano())
return rand.Intn(math.MaxUint16-10000) + 10000
}