Derek解读Bytom源码-P2P网络 upnp端口映射-白红宇

作者：Derek

简介

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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}复制代码

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 := "
    
     \r\n" +		"
     
     
      " + strconv.Itoa(externalPort)	message += "
     
     
      " + protocol + "
     "	message += "
     
      " + strconv.Itoa(internalPort) + "
     " +		"
     
      " + n.ourIP + "
     " +		"
     
      1
     
     
      "	message += description +		"
     
     
      " + strconv.Itoa(timeout) +		"
     
    "	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}复制代码

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 := "
    
     \r\n" +		"
     
     
      " + strconv.Itoa(externalPort) +		"
     
     
      " + protocol + "
     " +		"
    "	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}复制代码

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 := "
    
     \r\n" +		"
    "	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}复制代码