实验 ICMP协议实践ping解析

1、计算机网络实验上机指导书专业 班级 学号 姓名 沈阳工程学院信息工程系实验2ICMP协议实践-ping解析一 实验目的掌握ICMP原理，利用其实现网络主机状态测试。二 实验内容 利用ICMP协议原理编程实现PING命令，测试目标主机是否可到达。并了解Ping实现原理。三 实验前的准备l 了解ICMP原理及相关概念。l 掌握相关软件编程知识。四 实验要求及实验软硬件环境【基本要求】l 设计程序完成PING命令。l 完成此项实验，完成实验报告。【实验组织方式】l 个人实验【实验条件】l 局域网环境下微机两台，编程软件。五 实验步骤.了解ICMP原理以及网络编程（1）源程序：Windows/ Pin

2、g.h/#pragma pack(1)#define ICMP_ECHOREPLY0#define ICMP_ECHOREQ8/ IP Header - RFC 791typedef struct tagIPHDRu_char VIHL;/ Version and IHLu_charTOS;/ Type Of ServiceshortTotLen;/ Total LengthshortID;/ IdentificationshortFlagOff;/ Flags and Fragment Offsetu_charTTL;/ Time To Liveu_charProtocol;/ Protoc

3、olu_shortChecksum;/ Checksumstructin_addr iaSrc;/ Internet Address - Sourcestructin_addr iaDst;/ Internet Address - DestinationIPHDR, *PIPHDR;/ ICMP Header - RFC 792typedef struct tagICMPHDRu_charType;/ Typeu_charCode;/ Codeu_shortChecksum;/ Checksumu_shortID;/ Identificationu_shortSeq;/ Sequencecha

4、rData;/ DataICMPHDR, *PICMPHDR;#define REQ_DATASIZE 32/ Echo Request Data size/ ICMP Echo Requesttypedef struct tagECHOREQUESTICMPHDR icmpHdr;DWORDdwTime;charcDataREQ_DATASIZE;ECHOREQUEST, *PECHOREQUEST;/ ICMP Echo Replytypedef struct tagECHOREPLYIPHDRipHdr;ECHOREQUESTechoRequest;char cFiller256;ECH

5、OREPLY, *PECHOREPLY;#pragma pack()/ PING.C - Ping program using ICMP and RAW Sockets/#include #include #include #include ping.h/ Internal Functionsvoid Ping(LPCSTR pstrHost);void ReportError(LPCSTR pstrFrom);int WaitForEchoReply(SOCKET s);u_short in_cksum(u_short *addr, int len);/ ICMP Echo Request/

6、Reply functionsintSendEchoRequest(SOCKET, LPSOCKADDR_IN);DWORDRecvEchoReply(SOCKET, LPSOCKADDR_IN, u_char *);/ main()void main(int argc, char *argv) WSADATA wsaData; WORD wVersionRequested = MAKEWORD(1,1); int nRet;/ Check arguments if (argc != 2) fprintf(stderr,nUsage: ping hostnamen);return; / Ini

7、t WinSock nRet = WSAStartup(wVersionRequested, &wsaData); if (nRet) fprintf(stderr,nError initializing WinSockn);return; / Check versionif (wsaData.wVersion != wVersionRequested)fprintf(stderr,nWinSock version not supportedn);return;/ Go do the pingPing(argv1);/ Free WinSock WSACleanup();/ Ping()/ C

8、alls SendEchoRequest() and/ RecvEchoReply() and prints resultsvoid Ping(LPCSTR pstrHost)SOCKET rawSocket;LPHOSTENT lpHost;struct sockaddr_in saDest;struct sockaddr_in saSrc;DWORD dwTimeSent;DWORD dwElapsed;u_char cTTL;int nLoop;int nRet;/ Create a Raw socketrawSocket = socket(AF_INET, SOCK_RAW, IPPR

9、OTO_ICMP);if (rawSocket = SOCKET_ERROR) ReportError(socket();return;/ Lookup hostlpHost = gethostbyname(pstrHost);if (lpHost = NULL)fprintf(stderr,nHost not found: %sn, pstrHost);return;/ Setup destination socket addresssaDest.sin_addr.s_addr = *(u_long FAR *) (lpHost-h_addr);saDest.sin_family = AF_

10、INET;saDest.sin_port = 0;/ Tell the user what were doingprintf(nPinging %s %s with %d bytes of data:n,pstrHost,inet_ntoa(saDest.sin_addr),REQ_DATASIZE);/ Ping multiple timesfor (nLoop = 0; nLoop 4; nLoop+)/ Send ICMP echo requestSendEchoRequest(rawSocket, &saDest);/ Use select() to wait for data to

11、be receivednRet = WaitForEchoReply(rawSocket);if (nRet = SOCKET_ERROR)ReportError(select();break;if (!nRet)printf(nTimeOut);break;/ Receive replydwTimeSent = RecvEchoReply(rawSocket, &saSrc, &cTTL);/ Calculate elapsed timedwElapsed = GetTickCount() - dwTimeSent;printf(nReply from: %s: bytes=%d time=

12、%ldms TTL=%d, inet_ntoa(saSrc.sin_addr), REQ_DATASIZE, dwElapsed, cTTL);printf(n);nRet = closesocket(rawSocket);if (nRet = SOCKET_ERROR)ReportError(closesocket();/ SendEchoRequest()/ Fill in echo request header/ and send to destinationint SendEchoRequest(SOCKET s,LPSOCKADDR_IN lpstToAddr) static ECH

13、OREQUEST echoReq;static nId = 1;static nSeq = 1;int nRet;/ Fill in echo requestechoReq.icmpHdr.Type= ICMP_ECHOREQ;echoReq.icmpHdr.Code= 0;echoReq.icmpHdr.Checksum= 0;echoReq.icmpHdr.ID= nId+;echoReq.icmpHdr.Seq= nSeq+;/ Fill in some data to sendfor (nRet = 0; nRet 1 ) sum += *w+;nleft -= 2;/* mop up

14、 an odd byte, if necessary */if( nleft = 1 ) u_shortu = 0;*(u_char *)(&u) = *(u_char *)w ;sum += u;/* * add back carry outs from top 16 bits to low 16 bits */sum = (sum 16) + (sum & 0xffff);/* add hi 16 to low 16 */sum += (sum 16);/* add carry */answer = sum;/* truncate to 16 bits */return (answer);

15、实验结果如图6-1所示。图6-1 ping程序运行结果（2）LINUX /*简单的ping程序*/#include #include #include #include #include #include #include #include #include #include #include #include #define PACKET_SIZE 4096#define MAX_WAIT_TIME 5#define MAX_NO_PACKETS 3char sendpacketPACKET_SIZE;char recvpacketPACKET_SIZE;int sockfd,datalen

16、=56;int nsend=0,nreceived=0;struct sockaddr_in dest_addr;pid_t pid;struct sockaddr_in from;struct timeval tvrecv;void statistics(int signo);unsigned short cal_chksum(unsigned short *addr,int len);int pack(int pack_no);void send_packet(void);void recv_packet(void);int unpack(char *buf,int len);void t

17、v_sub(struct timeval *out,struct timeval *in);void statistics(int signo) printf(n-PING statistics-n); printf(%d packets transmitted, %d received , %d lostn,nsend,nreceived, (nsend-nreceived)/nsend*100); close(sockfd); exit(1);/*校验和算法*/unsigned short cal_chksum(unsigned short *addr,int len) int nleft

18、=len; int sum=0; unsigned short *w=addr; unsigned short answer=0;/*把ICMP报头二进制数据以2字节为单位累加起来*/ while(nleft1) sum+=*w+; nleft-=2; /*若ICMP报头为奇数个字节，会剩下最后一字节。把最后一个字节视为一个2字节数据的高字节，这个2字节数据的低字节为0，继续累加*/ if( nleft=1) *(unsigned char *)(&answer)=*(unsigned char *)w; sum+=answer; sum=(sum16)+(sum&0xffff); sum+=

19、(sum16); answer=sum; return answer;/*设置ICMP报头*/int pack(int pack_no) int i,packsize; struct icmp *icmp; struct timeval *tval; icmp=(struct icmp*)sendpacket; icmp-icmp_type=ICMP_ECHO; icmp-icmp_code=0; icmp-icmp_cksum=0; icmp-icmp_seq=pack_no; icmp-icmp_id=pid; packsize=8+datalen; tval= (struct timev

20、al *)icmp-icmp_data; gettimeofday(tval,NULL); /*记录发送时间*/ icmp-icmp_cksum=cal_chksum( (unsigned short *)icmp,packsize); /*校验算法*/ return packsize;/*发送三个ICMP报文*/void send_packet() int packetsize; while( nsendMAX_NO_PACKETS) nsend+; packetsize=pack(nsend); /*设置ICMP报头*/ if( sendto(sockfd,sendpacket,packe

21、tsize,0, (struct sockaddr *)&dest_addr,sizeof(dest_addr) )0 ) perror(sendto error); continue; sleep(1); /*每隔一秒发送一个ICMP报文*/ /*接收所有ICMP报文*/void recv_packet() int n,fromlen; extern int errno; signal(SIGALRM,statistics); fromlen=sizeof(from); while( nreceivednsend) alarm(MAX_WAIT_TIME); if( (n=recvfrom(

22、sockfd,recvpacket,sizeof(recvpacket),0, (struct sockaddr *)&from,&fromlen) ip_hl2; /*求ip报头长度,即ip报头的长度标志乘4*/ icmp=(struct icmp *)(buf+iphdrlen); /*越过ip报头,指向ICMP报头*/ len-=iphdrlen; /*ICMP报头及ICMP数据报的总长度*/ if( lenicmp_type=ICMP_ECHOREPLY) & (icmp-icmp_id=pid) ) tvsend=(struct timeval *)icmp-icmp_data; tv_sub(&tvrecv,tvsend); /*接收和发送的时间差*/ rtt=tvrecv.tv_sec*1000+tvrecv.tv_usec/1000; /*以毫秒为单位计算rtt*/ /*显示相关信息*/ printf(%d byte from %s: icmp_seq=%u ttl=%d rtt=%.3f msn, len, inet_ntoa(from.sin_addr), icmp-icm