golang で UPnP をサポートするルーターを検出し、ルーターの外部ポートをローカル PC の転送ポートにマップする / Detects routers that support UPnP and maps the router’s external ports to forward ports on the local PC with golang

下記のパッケージで機能が提供されています：

https://github.com/huin/goupnp
https://gitlab.com/NebulousLabs/go-upnp
https://gitlab.com/NebulousLabs/fastrand

gitlab.com/NebulousLabs/go-upnp は、このままでは
現在の github.com/huin/goupnp とマッチしないので
ローカルの upnp/upnp.go に必要な箇所をコピーして修正して使用しました。

最低限のソースのみ

upnp/upnp.go:

// Package upnp provides a simple and opinionated interface to UPnP-enabled
// routers, allowing users to forward ports and discover their external IP
// address. Specific quirks:
//
// - When attempting to discover UPnP-enabled routers on the network, only the
// first such router is returned. If you have multiple routers, this may cause
// some trouble. But why would you do that?
//
// - Forwarded ports are always symmetric, e.g. the router's port 9980 will be
// mapped to the client's port 9980. This will be unacceptable for some
// purposes, but too bad. Symmetric mappings are the desired behavior 99% of
// the time, and they save a function argument.
//
// - TCP and UDP protocols are forwarded together.
//
// - Ports are forwarded permanently. Some other implementations lease a port
// mapping for a set duration, and then renew it periodically. This is nice,
// because it means mappings won't stick around after they've served their
// purpose. Unfortunately, some routers only support permanent mappings, so this
// package has chosen to support the lowest common denominator. To un-forward a
// port, you must use the Clear function (or do it manually).
//
// Once you've discovered your router, you can retrieve its address by calling
// its Location method. This address can be supplied to Load to connect to the
// router directly, which is much faster than calling Discover.
package upnp

import (
	"context"
	"errors"
	"net/url"
	"time"

	"gitlab.com/NebulousLabs/fastrand"

	"github.com/huin/goupnp"
	"github.com/huin/goupnp/dcps/internetgateway1"
)

// An IGD provides an interface to the most commonly used functions of an
// Internet Gateway Device: discovering the external IP, and forwarding ports.
type IGD struct {
	// This interface is satisfied by the internetgateway1.WANIPConnection1
	// and internetgateway1.WANPPPConnection1 types.
	client interface {
		GetExternalIPAddress() (string, error)
		AddPortMapping(string, uint16, string, uint16, string, bool, string, uint32) error
		GetSpecificPortMappingEntry(string, uint16, string) (uint16, string, bool, string, uint32, error)
		DeletePortMapping(string, uint16, string) error
		GetServiceClient() *goupnp.ServiceClient
	}
}

// ExternalIP returns the router's external IP.
func (d *IGD) ExternalIP() (string, error) {
	return d.client.GetExternalIPAddress()
}

// Forward forwards the specified protcol, port, and adds its description to the
// router's port mapping table.
func (d *IGD) Forward(routerPort uint16, protcol string, destIP string, destPort uint16, desc string) error {
	time.Sleep(time.Millisecond)
	return d.client.AddPortMapping("", routerPort, protcol, destPort, destIP, true, desc, 0)
}

// Clear un-forwards a port, removing it from the router's port mapping table.
func (d *IGD) Clear(port uint16, protcol string) error {
	time.Sleep(time.Millisecond)
	return d.client.DeletePortMapping("", port, protcol)
}

// Discover is deprecated; use DiscoverCtx instead.
func Discover() (*IGD, error) {
	return DiscoverCtx(context.Background())
}

// DiscoverCtx scans the local network for routers and returns the first
// UPnP-enabled router it encounters.  It will try up to 3 times to find a
// router, sleeping a random duration between each attempt.  This is to
// mitigate a race condition with many callers attempting to discover
// simultaneously.
func DiscoverCtx(ctx context.Context) (*IGD, error) {
	// TODO: if more than one client is found, only return those on the same
	// subnet as the user?
	maxTries := 3
	sleepTime := time.Millisecond * time.Duration(fastrand.Intn(5000))
	for try := 0; try < maxTries; try++ {
		pppclients, _, _ := internetgateway1.NewWANPPPConnection1Clients()
		if len(pppclients) > 0 {
			return &IGD{pppclients[0]}, nil
		}
		ipclients, _, _ := internetgateway1.NewWANIPConnection1Clients()
		if len(ipclients) > 0 {
			return &IGD{ipclients[0]}, nil
		}
		select {
		case <-ctx.Done():
			return nil, context.Canceled
		case <-time.After(sleepTime):
		}
		sleepTime *= 2
	}
	return nil, errors.New("no UPnP-enabled gateway found")
}

// Load connects to the router service specified by rawurl. This is much
// faster than Discover. Generally, Load should only be called with values
// returned by the IGD's Location method.
func Load(rawurl string) (*IGD, error) {
	loc, err := url.Parse(rawurl)
	if err != nil {
		return nil, err
	}
	pppclients, _ := internetgateway1.NewWANPPPConnection1ClientsByURL(loc)
	if len(pppclients) > 0 {
		return &IGD{pppclients[0]}, nil
	}
	ipclients, _ := internetgateway1.NewWANIPConnection1ClientsByURL(loc)
	if len(ipclients) > 0 {
		return &IGD{ipclients[0]}, nil
	}
	return nil, errors.New("no UPnP-enabled gateway found at URL " + rawurl)
}

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// Package upnp provides a simple and opinionated interface to UPnP-enabled

// routers, allowing users to forward ports and discover their external IP

// address. Specific quirks:

// - When attempting to discover UPnP-enabled routers on the network, only the

// first such router is returned. If you have multiple routers, this may cause

// some trouble. But why would you do that?

// - Forwarded ports are always symmetric, e.g. the router's port 9980 will be

// mapped to the client's port 9980. This will be unacceptable for some

// purposes, but too bad. Symmetric mappings are the desired behavior 99% of

// the time, and they save a function argument.

// - TCP and UDP protocols are forwarded together.

// - Ports are forwarded permanently. Some other implementations lease a port

// mapping for a set duration, and then renew it periodically. This is nice,

// because it means mappings won't stick around after they've served their

// purpose. Unfortunately, some routers only support permanent mappings, so this

// package has chosen to support the lowest common denominator. To un-forward a

// port, you must use the Clear function (or do it manually).

// Once you've discovered your router, you can retrieve its address by calling

// its Location method. This address can be supplied to Load to connect to the

// router directly, which is much faster than calling Discover.

package upnp

import (

"context"

"errors"

"net/url"

"time"

"gitlab.com/NebulousLabs/fastrand"

"github.com/huin/goupnp"

"github.com/huin/goupnp/dcps/internetgateway1"

)

// An IGD provides an interface to the most commonly used functions of an

// Internet Gateway Device: discovering the external IP, and forwarding ports.

type IGD struct {

// This interface is satisfied by the internetgateway1.WANIPConnection1

// and internetgateway1.WANPPPConnection1 types.

client interface {

GetExternalIPAddress() (string, error)

AddPortMapping(string, uint16, string, uint16, string, bool, string, uint32) error

GetSpecificPortMappingEntry(string, uint16, string) (uint16, string, bool, string, uint32, error)

DeletePortMapping(string, uint16, string) error

GetServiceClient() *goupnp.ServiceClient

}

// ExternalIP returns the router's external IP.

func (d *IGD) ExternalIP() (string, error) {

return d.client.GetExternalIPAddress()

}

// Forward forwards the specified protcol, port, and adds its description to the

// router's port mapping table.

func (d *IGD) Forward(routerPort uint16, protcol string, destIP string, destPort uint16, desc string) error {

time.Sleep(time.Millisecond)

return d.client.AddPortMapping("", routerPort, protcol, destPort, destIP, true, desc, 0)

}

// Clear un-forwards a port, removing it from the router's port mapping table.

func (d *IGD) Clear(port uint16, protcol string) error {

time.Sleep(time.Millisecond)

return d.client.DeletePortMapping("", port, protcol)

}

// Discover is deprecated; use DiscoverCtx instead.

func Discover() (*IGD, error) {

return DiscoverCtx(context.Background())

}

// DiscoverCtx scans the local network for routers and returns the first

// UPnP-enabled router it encounters. It will try up to 3 times to find a

// router, sleeping a random duration between each attempt. This is to

// mitigate a race condition with many callers attempting to discover

// simultaneously.

func DiscoverCtx(ctx context.Context) (*IGD, error) {

// TODO: if more than one client is found, only return those on the same

// subnet as the user?

maxTries := 3

sleepTime := time.Millisecond * time.Duration(fastrand.Intn(5000))

for try := 0; try < maxTries; try++ {

pppclients, _, _ := internetgateway1.NewWANPPPConnection1Clients()

if len(pppclients) > 0 {

return &IGD{pppclients[0]}, nil

}

ipclients, _, _ := internetgateway1.NewWANIPConnection1Clients()

if len(ipclients) > 0 {

return &IGD{ipclients[0]}, nil

}

select {

case <-ctx.Done():

return nil, context.Canceled

case <-time.After(sleepTime):

}

sleepTime *= 2

}

return nil, errors.New("no UPnP-enabled gateway found")

}

// Load connects to the router service specified by rawurl. This is much

// faster than Discover. Generally, Load should only be called with values

// returned by the IGD's Location method.

func Load(rawurl string) (*IGD, error) {

loc, err := url.Parse(rawurl)

if err != nil {

return nil, err

}

pppclients, _ := internetgateway1.NewWANPPPConnection1ClientsByURL(loc)

if len(pppclients) > 0 {

return &IGD{pppclients[0]}, nil

}

ipclients, _ := internetgateway1.NewWANIPConnection1ClientsByURL(loc)

if len(ipclients) > 0 {

return &IGD{ipclients[0]}, nil

}

return nil, errors.New("no UPnP-enabled gateway found at URL " + rawurl)

}

main.go:

package main

import (
	"bufio"
	"fmt"
	"log"
	"os"
	"strings"

	"go-upnp-simple/upnp"
)

func main() {
	localIPv4 := "192.168.1.14"
	var internalPort uint16 = 80
	var externalPort uint16 = 8080
	desc := "go upnp test"

	// UPnPデバイスの検索
	igo, err := upnp.Discover()
	if err != nil {
		log.Println(err)
		return
	}

	// ルーターの外部IPアドレスを取得
	externalIP, err := igo.ExternalIP()
	if err != nil {
		log.Println(err)
		return
	}

	// ポートマッピングを追加 TCP
	err = igo.Forward(externalPort, "TCP", localIPv4, internalPort, desc)
	if err != nil {
		log.Println("error forwarding port", err)
		return
	}
	// ポートマッピングを追加 UDP
	err = igo.Forward(externalPort, "UDP", localIPv4, internalPort, desc)
	if err != nil {
		log.Println("error forwarding port", err)
		return
	}

	log.Printf("From external %s:%d forwarded to local %s:%d\n", externalIP, externalPort, localIPv4, internalPort)

	stringPrompt("Press enter key to exit...")

	// ポートマッピングを削除 TCP
	err = igo.Clear(externalPort, "TCP")
	if err != nil {
		log.Println(err)
	}
	// ポートマッピングを削除 UDP
	err = igo.Clear(externalPort, "UDP")
	if err != nil {
		log.Println(err)
	}
}

// stringPrompt asks for a string value using the label
// https://dev.to/tidalcloud/interactive-cli-prompts-in-go-3bj9
func stringPrompt(label string) string {
	var s string
	r := bufio.NewReader(os.Stdin)
	for {
		fmt.Fprint(os.Stderr, label+" ")
		s, _ = r.ReadString('\n')
		if s != "" {
			break
		}
	}
	return strings.TrimSpace(s)
}

package main

import (

"bufio"

"fmt"

"log"

"os"

"strings"

"go-upnp-simple/upnp"

)

func main() {

localIPv4 := "192.168.1.14"

var internalPort uint16 = 80

var externalPort uint16 = 8080

desc := "go upnp test"

// UPnPデバイスの検索

igo, err := upnp.Discover()

if err != nil {

log.Println(err)

return

}

// ルーターの外部IPアドレスを取得

externalIP, err := igo.ExternalIP()

if err != nil {

log.Println(err)

return

}

// ポートマッピングを追加 TCP

err = igo.Forward(externalPort, "TCP", localIPv4, internalPort, desc)

if err != nil {

log.Println("error forwarding port", err)

return

}

// ポートマッピングを追加 UDP

err = igo.Forward(externalPort, "UDP", localIPv4, internalPort, desc)

if err != nil {

log.Println("error forwarding port", err)

return

}

log.Printf("From external %s:%d forwarded to local %s:%d\n", externalIP, externalPort, localIPv4, internalPort)

stringPrompt("Press enter key to exit...")

// ポートマッピングを削除 TCP

err = igo.Clear(externalPort, "TCP")

if err != nil {

log.Println(err)

}

// ポートマッピングを削除 UDP

err = igo.Clear(externalPort, "UDP")

if err != nil {

log.Println(err)

}

// stringPrompt asks for a string value using the label

// https://dev.to/tidalcloud/interactive-cli-prompts-in-go-3bj9

func stringPrompt(label string) string {

var s string

r := bufio.NewReader(os.Stdin)

for {

fmt.Fprint(os.Stderr, label+" ")

s, _ = r.ReadString('\n')

if s != "" {

break

}

return strings.TrimSpace(s)

}

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