最近看了一篇文章覺得非常好：

?https://www.zhihu.com/question/21546408/answer/2303205686

為了加深印象，特寫了一個程序來模擬一下其中的傳輸

傳送門:github

因為代碼和現實的一些差異，可能顯得有些地方設計的有些丑陋了，有想法的可以多提提意見~

首先是主機層?

package modelimport "fmt"//主機 type Computer struct {Ip string//ipMac string//mac地址SubnetMask string//子網掩碼DefaultGateway string//默認網關Arp map[string]string//arp 用于緩存ip到mac的關系ExchangeBoard *ExchangeBoard//所屬的交換機Port int//所屬的交換機的端口MsgCh chan Message //監聽消息MsgList []Message//消息存儲下來 } func (c *Computer)IsSubnet(ip string)bool{return isIpSubNet(c.Ip,ip,c.SubnetMask) } func (c *Computer)NewMessage(ip,msg string)Message{mac:=""if c.IsSubnet(ip){//同一個子網走正常ipmac=c.Arp[ip]}else{mac=c.Arp[c.DefaultGateway]//不是同一個子網走默認網關}return Message{Head: MessageHead{FromMac: c.Mac,ToMac: mac,FromIp: c.Ip,ToIp: ip,FromPort: c.Port,},Body: msg,} } func (c *Computer)SendMessage(message Message){//只知道目標ipc.ExchangeBoard.SendMessage(message)//通過交換機發送消息 } func (c *Computer)Wait(){go func() {for{select {case v:=<-c.MsgCh:if v.Head.ToMac==""{//第一次，不知道我的mac，需要通過ip驗證if v.Head.ToIp==c.Ip{if v.Head.IsArpReq{//arp請求c.Arp[v.Head.FromIp]=v.Head.FromMac//更新自己的arp表message:=Message{Head: MessageHead{FromMac: c.Mac,ToMac: v.Head.FromMac,FromIp: c.Ip,ToIp: v.Head.FromIp,IsArpRes: true,FromPort: c.Port,},}c.MsgList=append(c.MsgList,v)//不確定要不要發送c.ExchangeBoard.SendMessage(message)//通過交換機響應}}} else if v.Head.ToMac==c.Mac{//收到消息，確實是自己的macif v.Head.IsArpRes{wait=truec.Arp[v.Head.FromIp]=v.Head.FromMac//只更新自己的arp表即可}else{fmt.Println(fmt.Sprintf("[%s]電腦收到[%s]的消息啦：%s",c.Mac,v.Head.FromMac,v.Body))//正常請求，接收即可c.MsgList=append(c.MsgList,v)}}}}}() }

然后是交換機：

?

package modelimport ("fmt""time" )//交換機 type ExchangeBoard struct {MacPort map[string]int//mac與端口映射表PortList PortSenderM//所有的端口 端口后可能是電腦，也可能是交換機//ExchangeBoardPortM ExchangeBoardPortM//交換機與別的交換機連接的端口，比如A的端口上是B 就是A.ExchangeBoardPortM= [B]1Router *Router//路由器Port int //交換機與路由器連接的端口 } func NewExchangeBoard()*ExchangeBoard{return &ExchangeBoard{MacPort: map[string]int{},PortList: PortSenderM{},} } func (e *ExchangeBoard)NewMessage(ip,msg string)Message{//交換機本身沒有自己的初始消息return Message{} } func (exchangeBoard *ExchangeBoard)SetSender(portSenderM PortSenderM){for k,v:=range portSenderM{exchangeBoard.PortList[k]=v} } func (exchangeBoard *ExchangeBoard)GetSender(port int)Sender{return exchangeBoard.PortList[port] } var wait bool func (e *ExchangeBoard)SendMessage(message Message){e.MacPort[message.Head.FromMac]=message.Head.FromPort//更新mac與端口映射表，每次都更新，防止機器換端口if message.Head.ToMac==""{//目標mac為空，發送廣播message.Head.IsArpReq=truefor k,v:=range e.PortList{if k==message.Head.FromPort && !message.Head.IsFromRouter{//發送方端口不對其發送消息 且不是從路由器來的消息continue}e.commonSendMessage(v,message)}//這一段主要是為了解決同一個交換機下的機器不用通過路由器廣播，如果同交換機下找不到，再走路由器time.Sleep(1*time.Second)if wait{wait=falsereturn}if !message.Head.IsFromRouter{message.Head.ToMac=e.Router.PortMacM[e.Port].Mace.Router.SendMessage(message)//給路由器也發}}else{//有macif port,ok:=e.MacPort[message.Head.ToMac];ok{if port==-1{e.Router.SendMessage(message)}else{e.commonSendMessage(e.PortList[port],message)}}else{//廣播，更新mac地址表，不存在了fmt.Println("?")}} } //給指定端口機器發送消息 func (e *ExchangeBoard)commonSendMessage(v interface{},message Message){switch v.(type) {case *Computer:v.(*Computer).MsgCh<-message//case *ExchangeBoard:// message.Head.FromPort=v.(*ExchangeBoard).ExchangeBoardPortM[e]//交換機的的fromport需要替換// v.(*ExchangeBoard).SendMessage(message)} }

然后是路由器：

?

package modelimport ("strings" )//路由器 type Router struct {IpPort IpPort//ip網段與端口映射表 路由表 分為靜態和動態Arp map[string]string//arp 用于緩存ip到mac的關系PortExchangeBoardM PortExchangeBoardM //路由器端口列表PortMacM PortMacM//保存端口和mac,ip的關系 初始化就有 } type NextPort struct {Next *Router//下一跳Port int//端口 } type MacAndIp struct {Mac stringIp string }func (r *Router)SendMessage(message Message){if message.Head.IsArpReq || message.Head.IsArpRes{r.Arp[message.Head.FromIp]=message.Head.FromMac}port:=r.GetPortFromIp(message.Head.ToIp)//根據路由表找到ip對應的端口message.Head.FromMac=r.PortMacM[port].Mac//來源mac置為路由器發送端口的macmessage.Head.ToMac=r.Arp[message.Head.ToIp]//需要根據arp得到ip對應的macmessage.Head.IsFromRouter=truemessage.Head.FromPort=-1//-1代表在交換機上 路由器沒有插在正常的lan口上，而是wan口，這里用-1表示r.PortExchangeBoardM[port].SendMessage(message)//向指定端口發送消息 }func (r *Router)GetPortFromIp(ip string)int{for k,v:=range r.IpPort{ipList:=strings.Split(k,"/")if len(ipList)==0{panic("error")}if isIpSubNet(ip,ipList[0],SubNetM[ipList[1]]){if v.Next!=nil{return v.Next.GetPortFromIp(ip)}return v.Port}}panic("數據不可達") }

還有一些其他的方法先不展示了，直接初始化各個設備，插上設備：

package mainimport ("mac-ip/model""time" ) var exchangeBoard1,exchangeBoard2,exchangeBoard3 *model.ExchangeBoard var senderM1=model.PortSenderM{0:&model.Computer{Ip: "192.168.0.1",Mac: "AAAA",SubnetMask: "255.255.255.0",DefaultGateway: "192.168.0.254",ExchangeBoard:exchangeBoard1,Port: 0,},1:&model.Computer{Ip: "192.168.0.2",Mac: "BBBB",SubnetMask: "255.255.255.0",DefaultGateway: "192.168.0.254",ExchangeBoard: exchangeBoard1,Port: 1,}, } var senderM2=model.PortSenderM{0:&model.Computer{Ip: "192.168.1.1",Mac: "CCCC",SubnetMask: "255.255.255.0",DefaultGateway: "192.168.1.254",ExchangeBoard: exchangeBoard2,Port: 0,},1:&model.Computer{Ip: "192.168.1.2",Mac: "DDDD",SubnetMask: "255.255.255.0",DefaultGateway: "192.168.1.254",ExchangeBoard: exchangeBoard2,Port: 1,}} var senderM3=model.PortSenderM{0:&model.Computer{Ip: "192.168.2.1",Mac: "EEEE",SubnetMask: "255.255.255.0",DefaultGateway: "192.168.2.254",ExchangeBoard: exchangeBoard3,Port: 0,},1:&model.Computer{Ip: "192.168.2.2",Mac: "FFFF",SubnetMask: "255.255.255.0",DefaultGateway: "192.168.2.254",ExchangeBoard: exchangeBoard3,Port: 1,}} var router=&model.Router{IpPort: model.IpPort{"192.168.0.0/24":&model.NextPort{Next: nil,Port: 0,},"192.168.1.0/24":&model.NextPort{Next: nil,Port: 1,},},Arp: map[string]string{},PortExchangeBoardM: nil,PortMacM: model.PortMacM{0:model.MacAndIp{Mac: "ABAB",Ip: "192.168.0.254",},1:model.MacAndIp{Mac: "CDCD",Ip: "192.168.1.254",},}, } func init(){exchangeBoard1,exchangeBoard2,exchangeBoard3=model.NewExchangeBoard(),model.NewExchangeBoard(),model.NewExchangeBoard()exchangeBoard1.SetSender(senderM1)exchangeBoard2.SetSender(senderM2)exchangeBoard3.SetSender(senderM3)router.PortExchangeBoardM=model.PortExchangeBoardM{0:exchangeBoard1,1:exchangeBoard2,}exchangeBoard1.Router=routerexchangeBoard1.Port=0exchangeBoard2.Router=routerexchangeBoard2.Port=1initComputer(exchangeBoard1,exchangeBoard2,exchangeBoard3)wait(exchangeBoard1,exchangeBoard2,exchangeBoard3)//監聽消息 } func main(){computer,_,computer3,_:=exchangeBoard1.GetSender(0),exchangeBoard1.GetSender(1),exchangeBoard2.GetSender(0),exchangeBoard3.GetSender(0)computer.SendMessage(computer.NewMessage("192.168.0.2","arp"))computer.SendMessage(computer.NewMessage("192.168.1.1","arp"))//computer.SendMessage(computer.NewMessage("192.168.2.1","arp"))time.Sleep(1*time.Second)computer.SendMessage(computer.NewMessage("192.168.0.2","hello"))//computer.SendMessage(computer.NewMessage("192.168.0.2","hello2"))//computer2.SendMessage(computer2.NewMessage("192.168.0.1","hello2"))computer.SendMessage(computer.NewMessage("192.168.1.1","hello3"))computer3.SendMessage(computer3.NewMessage("192.168.0.1","hello4"))for{} } func wait(ExchangeBoardList ...*model.ExchangeBoard){for i,_:=range ExchangeBoardList{go func(i int) {for _,v:=range ExchangeBoardList[i].PortList{if _,ok:=v.(*model.Computer);ok{v.(*model.Computer).Wait()}}}(i)} } func initComputer(exchangeBoardList ...*model.ExchangeBoard){for _,exchangeBoard:=range exchangeBoardList{for _,v:=range exchangeBoard.PortList{if computer,ok:=v.(*model.Computer);ok{computer.ExchangeBoard=exchangeBoardcomputer.MsgCh=make(chan model.Message,20)computer.Arp=map[string]string{}}}} }

?

跑起來：

沒毛病

目錄結構是這樣的：

總結

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