簡(jiǎn)單路由器設(shè)計(jì)與實(shí)現(xiàn)

1、簡(jiǎn)單路由器設(shè)計(jì)與實(shí)現(xiàn)(選做)1.實(shí)驗(yàn)?zāi)康氖煜げ⒄莆章酚善鞯墓ぷ髟?；熟悉Winpcap編程，掌握數(shù)據(jù)包捕獲與發(fā)送的方法；在理解IP協(xié)議、ICMP協(xié)議與路由基本工作原理的基礎(chǔ)上，完成一個(gè)（軟件）路由器基本功能的設(shè)計(jì)與編程實(shí)現(xiàn)。2.實(shí)驗(yàn)環(huán)境 接入局域網(wǎng)的PC機(jī)； 操作系統(tǒng)：Windows xp, Windows 7等； 推薦開(kāi)發(fā)工具：Visual Studio 2010； 推薦編程語(yǔ)言：C+/ Visual C+； 函數(shù)庫(kù)/開(kāi)發(fā)包：Winpcap。3.實(shí)驗(yàn)內(nèi)容(1) 學(xué)習(xí)并掌握winpcap編程：自行完成WinPcap教程中的內(nèi)容，從而掌握winpcap編程。內(nèi)容包括但不限于：a) 獲取設(shè)備列表；

2、b) 打開(kāi)一個(gè)適配器并抓包（分組）；c) 解析分組；d) 發(fā)送分組；學(xué)習(xí)內(nèi)容及源程序參見(jiàn)WinPcap官方教程：/docs/docs_412/html/group_wpcap_tut.html。(2) 利用winpcap開(kāi)發(fā)包實(shí)現(xiàn)簡(jiǎn)單路由程序，該路由程序應(yīng)該至少包括以下功能：a) IP數(shù)據(jù)包捕獲和轉(zhuǎn)發(fā)；b) ARP請(qǐng)求與解析；c) 重新計(jì)算IP數(shù)據(jù)包的頭部校驗(yàn)和；d) 處理IP數(shù)據(jù)包的頭部校驗(yàn)和；處理IP數(shù)據(jù)包的TTL值；e) 靜態(tài)路由表維護(hù)。在下圖所示的完了過(guò)拓?fù)浣Y(jié)構(gòu)中，當(dāng)所開(kāi)發(fā)的路由器程序部署并運(yùn)行在計(jì)算機(jī)C上時(shí)，它將（作為一個(gè)路由器）能夠連通兩個(gè)

3、子網(wǎng)，正確地捕獲、轉(zhuǎn)發(fā)來(lái)自計(jì)算機(jī)A和計(jì)算機(jī)B的分組，使得兩個(gè)子網(wǎng)中的主機(jī)能夠互相訪問(wèn)圖5-1 實(shí)驗(yàn)驗(yàn)證環(huán)境配置示意圖4.實(shí)驗(yàn)方式每位同學(xué)獨(dú)立上機(jī)編程實(shí)驗(yàn)，實(shí)驗(yàn)指導(dǎo)教師現(xiàn)場(chǎng)指導(dǎo)。5.參考內(nèi)容(1) WinPcap簡(jiǎn)介Winpcap (windows packet capture)是windows平臺(tái)下一個(gè)免費(fèi)、公共的網(wǎng)絡(luò)訪問(wèn)系統(tǒng)。開(kāi)發(fā)Winpcap項(xiàng)目的目的在于為win32應(yīng)用程序提供訪問(wèn)網(wǎng)絡(luò)底層的能力。它用于windows系統(tǒng)下的直接的網(wǎng)絡(luò)編程。關(guān)于Winpcap的介紹請(qǐng)參閱Winpcap開(kāi)發(fā)包可以在/上下載，Winpcap的技術(shù)文檔可以從http:/

4、/docs/default.htm下載。附錄中給出了主要函數(shù)的說(shuō)明文檔。(2) Winpcap主要函數(shù)及功能介紹Winpcap部分主要函數(shù)及其功能介紹如下：(1).int pcap_findalldevs_ex(char * source, struct pcap_rmtauth * auth, pcap_if_t * alldevs, char * errbuf)函數(shù)功能:Create a list of network devices that can be opened withpcap_open().參數(shù)說(shuō)明:source:a char* buffer t

5、hat keeps the source localtion, according to the new WinPcap syntax. This source will be examined looking for adapters (local or remote) or pcap files，The strings that must be prepended to the source in order to define if we want local/remote adapters or files is defined in the new Source Specificat

6、ion Syntax .auth:a pointer to a pcap_rmtauth structure. This pointer keeps the information required to authenticate the RPCAP connection to the remote host. This parameter is not meaningful in case of a query to the local host: in that case it can be NULL.alldevs:a struct pcap_if_t pointer, which wi

7、ll be properly allocated inside this function. When the function returns, it is set to point to the first element of the interface list; each element of the list is of type struct pcap_if_t.errbuf: a pointer to a user-allocated buffer (of size PCAP_ERRBUF_SIZE) that will contain the error message (i

8、n case there is one).返回值:0 if everything is fine, -1 if some errors occurred. The list of the devices is returned in the alldevs variable. When the function returns correctly, alldevs cannot be NULL. In other words, this function returns -1 also in case the system does not have any interface to list

9、.(2).void pcap_freealldevs_ex(pcap_if_t * alldevsp)函數(shù)功能：Free an interface list returned by pcap_findalldevs().(3).pcap_t* pcap_open(const char * source, int snaplen, int flags, int read_timeout, struct pcap_rmtauth * auth, char * errbuf)函數(shù)功能:Open a generic source in order to capture / send (WinPcap

10、only) traffic.參數(shù)說(shuō)明:source:zero-terminated string containing the source name to open. The source name has to include the format prefix according to the new Source Specification Syntax and it cannot be NULL.On on Linux systems with 2.2 or later kernels, a device argument of any can be used to capture

11、packets from all interfaces. In order to makes the source syntax easier, please remember that:the adapters returned by the pcap_findalldevs_ex() can be used immediately by the pcap_open()in case the user wants to pass its own source string to the pcap_open(), the pcap_createsrcstr() helps in creatin

12、g the correct source identifier.snaplen:length of the packet that has to be retained. For each packet received by the filter, only the first snaplen bytes are stored in the buffer and passed to the user application. For instance, snaplen equal to 100 means that only the first 100 bytes of each packe

13、t are stored.flags:keeps several flags that can be needed for capturing packets. The allowed flags are defined in the pcap_open() flags .read_timeout:read timeout in milliseconds. The read timeout is used to arrange that the read not necessarily return immediately when a packet is seen, but that it

14、waits for some amount of time to allow more packets to arrive and to read multiple packets from the OS kernel in one operation. Not all platforms support a read timeout; on platforms that dont, the read timeout is ignored.auth:a pointer to a struct pcap_rmtauth that keeps the information required to

15、 authenticate the user on a remote machine. In case this is not a remote capture, this pointer can be set to NULL.errbuf:a pointer to a user-allocated buffer which will contain the error in case this function fails. The pcap_open() and findalldevs() are the only two functions which have this paramet

16、er, since they do not have (yet) a pointer to a pcap_t structure, which reserves space for the error string. Since these functions do not have (yet) a pcap_t pointer (the pcap_t pointer is NULL in case of errors), they need an explicit errbuf variable. errbuf may also be set to warning text when pca

17、p_open_live() succeds; to detect this case the caller should store a zero-length string in errbuf before calling pcap_open_live() and display the warning to the user if errbuf is no longer a zero-length string.返回值: A pointer to a pcap_t which can be used as a parameter to the following calls (pcap_c

18、ompile()and so on) and that specifies an opened WinPcap session. In case of problems, it returns NULL and the errbuf variable keeps the error message.(4). int pcap_next_ex(pcap_t * p, struct pcap_pkthdr * pkt_header, const u_char * pkt_data)函數(shù)功能:Read a packet from an interface or from an offline cap

19、ture.This function is used to retrieve the next available packet, bypassing the callback method traditionally provided by libpcap. pcap_next_ex fills the pkt_header and pkt_data parameters (see pcap_handler() with the pointers to the header and to the data of the next captured packet.返回值:The return

20、value can be:1 if the packet has been read without problems0 if the timeout set with pcap_open_live() has elapsed. In this case pkt_header and pkt_data dont point to a valid packet-1 if an error occurred-2 if EOF was reached reading from an offline capture(5). int pcap_compile(pcap_t * p, struct bpf

21、_program * fp, char * str, int optimize, bpf_u_int32 netmask)函數(shù)功能:Compile a packet filter, converting an high level filtering expression (see Filtering expression syntax) in a program that can be interpreted by the kernel-level filtering engine.(6). int pcap_setfilter(pcap_t * p, struct bpf_program

22、* fp)函數(shù)功能:Associate a filter to a capture. 此函數(shù)是要和函數(shù)pcap_compile()配合使用。(7). int pcap_sendpacket(pcap_t * p, u_char * buf, int size)函數(shù)功能: Send a raw packet.6.實(shí)驗(yàn)步驟6.1 WinPcap開(kāi)發(fā)包安裝與配置下載、安裝WinPcap開(kāi)發(fā)包，配置VisualStudio 2010開(kāi)發(fā)環(huán)境。具體步驟請(qǐng)同學(xué)們參閱網(wǎng)上資料自行完成。6.2 用戶界面設(shè)計(jì)(1).首先打開(kāi)vs2010，新建工程，選擇MFC Application，輸入工程名，點(diǎn)擊OK，圖5-

23、2點(diǎn)擊next，選擇Dialog based,點(diǎn)擊Next跳到最后一個(gè)頁(yè)面選擇.Dlg，點(diǎn)擊finish。圖5-3圖5-4到此為止工程新建完畢，運(yùn)行會(huì)出現(xiàn)以下頁(yè)面，下面就為這個(gè)對(duì)話框拖拽控件。圖5-5首先將對(duì)話框上面的三個(gè)控件刪除，并拖拽相應(yīng)的控件得到如下效果：圖5-6圖5-7其中對(duì)話框可在Resource View打開(kāi)，控件在Toolbox中可以找到，圖5-8其中啟動(dòng)、退出、添加路由、刪除路由為button控件，兩個(gè)空白區(qū)為L(zhǎng)ist Box，日志、路由表、子網(wǎng)掩碼、目的地址、下一跳步為Static Text，三個(gè)輸入IP的控件為IP Address Control，將控件拖拽到相應(yīng)的位置并且

24、在控件的屬性框中修改控件的Caption以及ID。啟動(dòng)ONSTART_BUTTON退出ONSTOP_BUTTON日志IDC_STATIC第一個(gè)空白區(qū)LOGGER_LIST路由表IDC_STATIC第二個(gè)空白區(qū)ROUTER_LIST子網(wǎng)掩碼IDC_STATIC子網(wǎng)掩碼對(duì)應(yīng)的IP輸入?yún)^(qū)IDC_NETMASK目的地址IDC_STATIC目的地址對(duì)應(yīng)的IP輸入?yún)^(qū)IDC_IPADDRESS下一跳步IDC_STATIC下一跳步對(duì)應(yīng)的IP輸入?yún)^(qū)IDC_NEXTHOP添加路由ADD_ROUTER_BUTTON刪除路由DELETE_ROUTER_BUTTON6.3 代碼實(shí)現(xiàn)(1). 事件響應(yīng)函數(shù)及主流程控件添加

25、完成后為Button添加相應(yīng)的單擊事件并修改單擊事件名稱，對(duì)應(yīng)關(guān)系如下：?jiǎn)?dòng)OnStartClickedButton()退出OnBnClickedButton()添加路由OnAddRouterButton()刪除路由OnDeleteRouterButton()VC程序首先執(zhí)行程序初始化函數(shù)OnInitDialog()，在此函數(shù)中我們獲取了MFC窗體指針。當(dāng)我們點(diǎn)擊“啟動(dòng)”按鈕時(shí)，程序會(huì)執(zhí)行OnStartClickedButton()函數(shù)，此函數(shù)流程圖如下圖所示:圖5-9當(dāng)我們點(diǎn)擊結(jié)束按鈕時(shí)程序會(huì)執(zhí)行OnBnClickedButton()，程序自動(dòng)退出。當(dāng)程序退出時(shí)會(huì)觸發(fā)ON_WM_DESTRO

26、Y()消息，從而會(huì)執(zhí)行OnDestroy()函數(shù)，并且程序在執(zhí)行過(guò)程中每隔一段時(shí)間會(huì)執(zhí)行OnTimer()函數(shù)。(2). 主要數(shù)據(jù)結(jié)構(gòu)和函數(shù)聲明首先將程序所用變量以及函數(shù)復(fù)制到VCRouterDlg.cpp文件中：#defineMAX_IF5 / 最大接口數(shù)目#pragma pack(1)typedef struct FrameHeader_t / 幀首部 UCHARDesMAC6; / 目的地址 UCHARSrcMAC6; / 源地址 USHORTFrameType; / 幀類型 FrameHeader_t;typedef struct ARPFrame_t / ARP幀F(xiàn)rameHeade

27、r_tFrameHeader; / 幀首部 WORDHardwareType; / 硬件類型WORDProtocolType; / 協(xié)議類型BYTEHLen; / 硬件地址長(zhǎng)度BYTEPLen; / 協(xié)議地址長(zhǎng)度WORDOperation; / 操作值UCHARSendHa6; / 源MAC地址ULONGSendIP; / 源IP地址UCHARRecvHa6; / 目的MAC地址ULONGRecvIP; / 目的IP地址 ARPFrame_t;typedef struct IPHeader_t / IP首部BYTEVer_HLen; / 版本+頭部長(zhǎng)度BYTETOS; / 服務(wù)類型WORDTo

28、talLen; / 總長(zhǎng)度WORDID; / 標(biāo)識(shí)WORDFlag_Segment; / 標(biāo)志+片偏移BYTETTL; / 生存時(shí)間BYTEProtocol; / 協(xié)議WORDChecksum; / 頭部校驗(yàn)和ULONGSrcIP; / 源IP地址ULONGDstIP; / 目的IP地址 IPHeader_t;typedef struct ICMPHeader_t / ICMP首部BYTE Type; / 類型BYTE Code; / 代碼WORD Checksum; / 校驗(yàn)和WORD Id; / 標(biāo)識(shí)WORD Sequence; / 序列號(hào) ICMPHeader_t;typedef str

29、uct IPFrame_t / IP幀F(xiàn)rameHeader_tFrameHeader; / 幀首部IPHeader_tIPHeader; / IP首部 IPFrame_t;typedef struct ip_t / 網(wǎng)絡(luò)地址ULONGIPAddr; / IP地址ULONGIPMask; / 子網(wǎng)掩碼 ip_t;typedef struct IfInfo_t / 接口信息CStringDeviceName; / 設(shè)備名CStringDescription; / 設(shè)備描述UCHARMACAddr6; / MAC地址CArray ip; / IP地址列表pcap_t*adhandle; / pca

30、p句柄 IfInfo_t;typedef struct SendPacket_t / 發(fā)送數(shù)據(jù)包結(jié)構(gòu)intlen; / 長(zhǎng)度BYTEPktData2000;/ 數(shù)據(jù)緩存ULONGTargetIP; / 目的IP地址UINT_PTRn_mTimer; / 定時(shí)器UINTIfNo; / 接口序號(hào) SendPacket_t;typedef struct RouteTable_t / 路由表結(jié)構(gòu)ULONGMask; / 子網(wǎng)掩碼ULONGDstIP; / 目的地址ULONGNextHop; / 下一跳步UINTIfNo; / 接口序號(hào) RouteTable_t;typedef struct IP_MA

31、C_t / IP-MAC地址映射結(jié)構(gòu)ULONGIPAddr; / IP地址UCHARMACAddr6; / MAC地址 IP_MAC_t;/ 全局變量/*/IfInfo_tIfInfoMAX_IF; / 接口信息數(shù)組intIfCount; / 接口個(gè)數(shù)UINT_PTR TimerCount; / 定時(shí)器個(gè)數(shù)CList SP; / 發(fā)送數(shù)據(jù)包緩存隊(duì)列CList IP_MAC; / IP-MAC地址映射列表CList RouteTable; / 路由表CMyRouterDlg *pDlg ; / 對(duì)話框指針CMutex mMutex(0,0,0); / 互斥/*/ 全局函數(shù)/*/ IP地址轉(zhuǎn)換CS

32、tring IPntoa(ULONG nIPAddr);/ MAC地址轉(zhuǎn)換CString MACntoa(UCHAR *nMACAddr);/ MAC地址比較bool cmpMAC(UCHAR *MAC1, UCHAR *MAC2);/ MAC地址復(fù)制void cpyMAC(UCHAR *MAC1, UCHAR *MAC2);/ MAC地址設(shè)置void setMAC(UCHAR *MAC, UCHAR ch);/ IP地址查詢bool IPLookup(ULONG ipaddr, UCHAR *p);/ 數(shù)據(jù)包捕獲線程UINT Capture(PVOID pParam);/ 獲取本地接口MAC

33、地址線程UINT CaptureLocalARP(PVOID pParam);/ 發(fā)送ARP請(qǐng)求void ARPRequest(pcap_t *adhandle, UCHAR *srcMAC, ULONG srcIP, ULONG targetIP);/ 查詢路由表DWORD RouteLookup(UINT &ifNO, DWORD desIP, CList *routeTable);/ 處理ARP數(shù)據(jù)包void ARPPacketProc(struct pcap_pkthdr *header, const u_char *pkt_data);/ 處理IP數(shù)據(jù)包void IPPacketPr

34、oc(IfInfo_t *pIfInfo, struct pcap_pkthdr *header, const u_char *pkt_data);/ 處理ICMP數(shù)據(jù)包void ICMPPacketProc(IfInfo_t *pIfInfo, BYTE type, BYTE code, const u_char *pkt_data);/ 檢查IP數(shù)據(jù)包頭部校驗(yàn)和是否正確int IsChecksumRight(char * buffer);/ 計(jì)算校驗(yàn)和unsigned short ChecksumCompute(unsigned short *buffer, int size);(3).

35、函數(shù)代碼實(shí)現(xiàn)/ 獲取本地接口MAC地址線程UINT CaptureLocalARP(PVOID pParam)intres;struct pcap_pkthdr*header;const u_char*pkt_data;IfInfo_t*pIfInfo;ARPFrame_t*ARPFrame;CStringDisplayStr;pIfInfo = (IfInfo_t *)pParam;while (true)Sleep(50);res = pcap_next_ex( pIfInfo-adhandle , &header, &pkt_data);/ 超時(shí) if (res = 0) continu

36、e; if (res 0)ARPFrame = (ARPFrame_t *) (pkt_data);/ 得到本接口的MAC地址if (ARPFrame-FrameHeader.FrameType = htons(0x0806) & (ARPFrame-Operation = htons(0x0002) & (ARPFrame-SendIP = pIfInfo-ip0.IPAddr) cpyMAC(pIfInfo-MACAddr, ARPFrame-SendHa);return 0;void setMAC(UCHAR *MAC, UCHAR ch)for (int i=0; i6; i+) MA

37、Ci = ch;return;/ 發(fā)送ARP請(qǐng)求void ARPRequest(pcap_t *adhandle, UCHAR *srcMAC, ULONG srcIP, ULONG targetIP)ARPFrame_tARPFrame;inti;for (i=0; i6; i+)ARPFrame.FrameHeader.DesMACi = 255;ARPFrame.FrameHeader.SrcMACi = srcMACi;ARPFrame.SendHai = srcMACi;ARPFrame.RecvHai = 0;ARPFrame.FrameHeader.FrameType = hto

38、ns(0x0806);ARPFrame.HardwareType = htons(0x0001);ARPFrame.ProtocolType = htons(0x0800);ARPFrame.HLen = 6;ARPFrame.PLen = 4;ARPFrame.Operation = htons(0x0001);ARPFrame.SendIP = srcIP;ARPFrame.RecvIP = targetIP; pcap_sendpacket(adhandle, (u_char *) &ARPFrame, sizeof(ARPFrame_t);void cpyMAC(UCHAR *MAC1

39、, UCHAR *MAC2)for (int i=0; i6; i+) MAC1i=MAC2i;/ 比較兩個(gè)MAC地址是否相同bool cmpMAC(UCHAR *MAC1, UCHAR *MAC2)for (int i=0; iadhandle, &header, &pkt_data); if (res = 1)FrameHeader_t*fh;fh = (FrameHeader_t *) pkt_data;switch (ntohs(fh-FrameType)case 0x0806:ARPFrame_t *ARPf;ARPf = (ARPFrame_t *)pkt_data;/TRACE1

40、(收到ARP包 源IP為：%dn, ARPf-SendIP);/ ARP包，轉(zhuǎn)到ARP包處理函數(shù)ARPPacketProc(header, pkt_data);break;case 0x0800:IPFrame_t *IPf;IPf = (IPFrame_t*) pkt_data;/TRACE1(收到IP包 源IP為：%dn,IPf-IPHeader.SrcIP );/ IP包，轉(zhuǎn)到IP包處理函數(shù)IPPacketProc(pIfInfo, header, pkt_data);break;default: break;else if (res = 0)/ 超時(shí)continue;elseAfxMe

41、ssageBox(pcap_next_ex函數(shù)出錯(cuò)!);return 0;/ 處理ARP數(shù)據(jù)包void ARPPacketProc(struct pcap_pkthdr *header, const u_char *pkt_data)boolflag;ARPFrame_tARPf;IPFrame_t*IPf;SendPacket_tsPacket;POSITIONpos, CurrentPos;IP_MAC_tip_mac;UCHARmacAddr6;ARPf = *(ARPFrame_t *)pkt_data;if (ARPf.Operation = ntohs(0x0002)pDlg-Lo

42、gger.InsertString(-1, 收到ARP響應(yīng)包);pDlg-Logger.InsertString(-1, ( ARP +(IPntoa(ARPf.SendIP)+ - +MACntoa(ARPf.SendHa);/ IPMAC地址映射表中已經(jīng)存在該對(duì)應(yīng)關(guān)系if (IPLookup(ARPf.SendIP, macAddr) pDlg-Logger.InsertString(-1, 該對(duì)應(yīng)關(guān)系已經(jīng)存在于IPMAC地址映射表中);return;elseip_mac.IPAddr = ARPf.SendIP;memcpy(ip_mac.MACAddr, ARPf.SendHa, 6)

43、;/ 將IP-MAC映射關(guān)系存入表中IP_MAC.AddHead(ip_mac);/ 日志輸出信息pDlg-Logger.InsertString(-1, 將該對(duì)應(yīng)關(guān)系存入IPMAC地址映射表中);mMutex.Lock(INFINITE);do/ 查看是否能轉(zhuǎn)發(fā)緩存中的IP數(shù)據(jù)報(bào)flag = false;/ 沒(méi)有需要處理的內(nèi)容if (SP.IsEmpty() break;/ 遍歷轉(zhuǎn)發(fā)緩存區(qū)pos = SP.GetHeadPosition();for (int i=0; i FrameHeader.DesMAC, ARPf.SendHa);for(int t=0; tFrameHeader.S

44、rcMACt = IfInfosPacket.IfNo.MACAddrt;/ 發(fā)送IP數(shù)據(jù)包pcap_sendpacket(IfInfosPacket.IfNo.adhandle, (u_char *) sPacket.PktData, sPacket.len);SP.RemoveAt(CurrentPos);/ 日志輸出信息pDlg-Logger.InsertString(-1, 轉(zhuǎn)發(fā)緩存區(qū)中目的地址是該MAC地址的IP數(shù)據(jù)包);pDlg-Logger.InsertString(-1, ( 發(fā)送IP數(shù)據(jù)包：+IPntoa(IPf-IPHeader.SrcIP) + - + IPntoa(IP

45、f-IPHeader.DstIP) + + MACntoa(IPf-FrameHeader.SrcMAC )+-+MACntoa(IPf-FrameHeader.DesMAC);flag = true;break; while(flag);mMutex.Unlock();/ 查詢IP-MAC映射表bool IPLookup(ULONG ipaddr, UCHAR *p)IP_MAC_tip_mac;POSITIONpos;if (IP_MAC.IsEmpty() return false;pos = IP_MAC.GetHeadPosition(); for (int i = 0; iIP_MAC.GetCount(); i+