Derek解讀Bytom源碼-P2P網絡 upnp端口映射

做者：Derek

簡介

Github地址：https://github.com/Bytom/bytom

Gitee地址：https://gitee.com/BytomBlockchain/bytom

本章介紹bytom代碼P2P網絡中upnp端口映射

做者使用MacOS操做系統，其餘平臺也大同小異

Golang Version: 1.8

UPNP介紹

UPNP（Universal Plug and Play）通用即插即用。UPNP端口映射將一個外部端口映射到一個內網ip:port。從而實現p2p網絡從外網可以穿透網關訪問到內網的bytomd節點。

UPNP協議

SSDP（Simple Service Discovery Protocol 簡單服務發現協議） GENA（Generic Event Notification Architecture 通用事件通知結構） SOAP（Simple Object Access Protocol 簡單對象訪問協議） XML（Extensible Markup Language 可擴張標記語言）

UPNP代碼

** p2p/upnp/upnp.go **

發現網絡中支持UPNP功能的設備

從網絡中發現支持UPNP功能的設備，並獲得該設備的location和url等相關信息

type upnpNAT struct {
	serviceURL string // 設備的描述文件URL，用於獲得該設備的描述信息
	ourIP      string // 節點本地ip地址
	urnDomain  string // 設備類型
}

func Discover() (nat NAT, err error) {
	ssdp, err := net.ResolveUDPAddr("udp4", "239.255.255.250:1900")
	if err != nil {
		return
	}
	conn, err := net.ListenPacket("udp4", ":0")
	if err != nil {
		return
	}
	socket := conn.(*net.UDPConn)
	defer socket.Close()

	err = socket.SetDeadline(time.Now().Add(3 * time.Second))
	if err != nil {
		return
	}

	st := "InternetGatewayDevice:1"

	// 多播請求：M-SEARCH SSDP協議定義的發現請求。
	buf := bytes.NewBufferString(
		"M-SEARCH * HTTP/1.1\r\n" +
			"HOST: 239.255.255.250:1900\r\n" +
			"ST: ssdp:all\r\n" +
			"MAN: \"ssdp:discover\"\r\n" +
			"MX: 2\r\n\r\n")
	message := buf.Bytes()
	answerBytes := make([]byte, 1024)
	for i := 0; i < 3; i++ {
		// 向239.255.255.250:1900發送一條多播請求
		_, err = socket.WriteToUDP(message, ssdp)
		if err != nil {
			return
		}
		// 若是從網絡中發現UPNP設備則會從239.255.255.250:1900收到響應消息
		var n int
		n, _, err = socket.ReadFromUDP(answerBytes)
		for {
			n, _, err = socket.ReadFromUDP(answerBytes)
			if err != nil {
				break
			}
			answer := string(answerBytes[0:n])
			if strings.Index(answer, st) < 0 {
				continue
			}
			// HTTP header field names are case-insensitive.
			// http://www.w3.org/Protocols/rfc2616/rfc2616-sec4.html#sec4.2
			// 得到設備location
			locString := "\r\nlocation:"
			answer = strings.ToLower(answer)
			locIndex := strings.Index(answer, locString)
			if locIndex < 0 {
				continue
			}
			loc := answer[locIndex+len(locString):]
			endIndex := strings.Index(loc, "\r\n")
			if endIndex < 0 {
				continue
			}
			// 得到設備的描述url和設備類型
			locURL := strings.TrimSpace(loc[0:endIndex])
			var serviceURL, urnDomain string
			serviceURL, urnDomain, err = getServiceURL(locURL)
			if err != nil {
				return
			}
			var ourIP net.IP
			ourIP, err = localIPv4()
			if err != nil {
				return
			}
			nat = &upnpNAT{serviceURL: serviceURL, ourIP: ourIP.String(), urnDomain: urnDomain}
			return
		}
	}
	err = errors.New("UPnP port discovery failed.")
	return
}

添加端口映射

向upnp設備發送一條http post請求，將內部網絡ip:port和外部網絡ip:port作映射

func (n *upnpNAT) AddPortMapping(protocol string, externalPort, internalPort int, description string, timeout int) (mappedExternalPort int, err error) {
	// A single concatenation would break ARM compilation.
	message := "<u:AddPortMapping xmlns:u=\"urn:" + n.urnDomain + ":service:WANIPConnection:1\">\r\n" +
		"<NewRemoteHost></NewRemoteHost><NewExternalPort>" + strconv.Itoa(externalPort)
	message += "</NewExternalPort><NewProtocol>" + protocol + "</NewProtocol>"
	message += "<NewInternalPort>" + strconv.Itoa(internalPort) + "</NewInternalPort>" +
		"<NewInternalClient>" + n.ourIP + "</NewInternalClient>" +
		"<NewEnabled>1</NewEnabled><NewPortMappingDescription>"
	message += description +
		"</NewPortMappingDescription><NewLeaseDuration>" + strconv.Itoa(timeout) +
		"</NewLeaseDuration></u:AddPortMapping>"

	var response *http.Response
	response, err = soapRequest(n.serviceURL, "AddPortMapping", message, n.urnDomain)
	if response != nil {
		defer response.Body.Close()
	}
	if err != nil {
		return
	}

	// TODO: check response to see if the port was forwarded
	// log.Println(message, response)
	// JAE:
	// body, err := ioutil.ReadAll(response.Body)
	// fmt.Println(string(body), err)
	mappedExternalPort = externalPort
	_ = response
	return
}

刪除端口映射

向upnp設備發送一條http post請求，將內部網絡ip:port和外部網絡ip:port刪除映射關係

func (n *upnpNAT) DeletePortMapping(protocol string, externalPort, internalPort int) (err error) {

	message := "<u:DeletePortMapping xmlns:u=\"urn:" + n.urnDomain + ":service:WANIPConnection:1\">\r\n" +
		"<NewRemoteHost></NewRemoteHost><NewExternalPort>" + strconv.Itoa(externalPort) +
		"</NewExternalPort><NewProtocol>" + protocol + "</NewProtocol>" +
		"</u:DeletePortMapping>"

	var response *http.Response
	response, err = soapRequest(n.serviceURL, "DeletePortMapping", message, n.urnDomain)
	if response != nil {
		defer response.Body.Close()
	}
	if err != nil {
		return
	}

	// TODO: check response to see if the port was deleted
	// log.Println(message, response)
	_ = response
	return
}

獲取映射後的公網地址

func (n *upnpNAT) GetExternalAddress() (addr net.IP, err error) {
	info, err := n.getExternalIPAddress()
	if err != nil {
		return
	}
	addr = net.ParseIP(info.externalIpAddress)
	return
}

func (n *upnpNAT) getExternalIPAddress() (info statusInfo, err error) {

	message := "<u:GetExternalIPAddress xmlns:u=\"urn:" + n.urnDomain + ":service:WANIPConnection:1\">\r\n" +
		"</u:GetExternalIPAddress>"

	var response *http.Response
	response, err = soapRequest(n.serviceURL, "GetExternalIPAddress", message, n.urnDomain)
	if response != nil {
		defer response.Body.Close()
	}
	if err != nil {
		return
	}
	var envelope Envelope
	data, err := ioutil.ReadAll(response.Body)
	reader := bytes.NewReader(data)
	xml.NewDecoder(reader).Decode(&envelope)

	info = statusInfo{envelope.Soap.ExternalIP.IPAddress}

	if err != nil {
		return
	}

	return
}