Derek解读Bytom源码-P2P网络 upnp端口映射

作者：Derek

简介

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

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

本章介绍bytom代码P2P网络中upnp端口映射

作者使用MacOS操作系统，其他平台也大同小异

Golang Version: 1.8

UPNP介绍

UPNP（Universal Plug and Play）通用即插即用。UPNP端口映射将一个外部端口映射到一个内网ip:port。从而实现p2p网络从外网能够穿透网关访问到内网的bytomd节点。

UPNP协议

SSDP（Simple Service Discovery Protocol 简单服务发现协议）
GENA（Generic Event Notification Architecture 通用事件通知结构）
SOAP（Simple Object Access Protocol 简单对象访问协议）
XML（Extensible Markup Language 可扩张标记语言）

UPNP代码

** p2p/upnp/upnp.go **

发现网络中支持UPNP功能的设备

从网络中发现支持UPNP功能的设备，并得到该设备的location和url等相关信息

type upnpNAT struct {
	serviceURL string // 设备的描述文件URL，用于得到该设备的描述信息
	ourIP      string // 节点本地ip地址
	urnDomain  string // 设备类型
}

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"

	// 多播请求：M-SEARCH SSDP协议定义的发现请求。
	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发送一条多播请求
		_, err = socket.WriteToUDP(message, ssdp)
		if err != nil {
			return
		}
		// 如果从网络中发现UPNP设备则会从239.255.255.250:1900收到响应消息
		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
			// 获得设备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
			}
			// 获得设备的描述url和设备类型
			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设备发送一条http post请求，将内部网络ip:port和外部网络ip:port做映射

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
}

删除端口映射

向upnp设备发送一条http post请求，将内部网络ip:port和外部网络ip:port删除映射关系

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
}

获取映射后的公网地址

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
}