完成ping的功能,能够方便的设置与ping指令相关的参数

一、任务概述及需求分析○1编写一个网络应用程序。

○2基本要求：完成ping的功能，能够方便的设置与ping指令相关的参数（至少两项参数：-n count和-l size）；不限实现的方式和语言。

说明：最低要求在给的例程中进行修改，更高级要求为做出图形化界面○3扩展要求：实现trace route的功能二、ICMP协议分析ICMP是（Internet Control Message Protocol）Internet控制报文协议。

它是TCP/IP协议族的一个子协议，用于在IP主机、路由器之间传递控制消息。

控制消息是指网络通不通、主机是否可达、路由是否可用等网络本身的消息。

这些控制消息虽然并不传输用户数据，但是对于用户数据的传递起着重要的作用。

图2-1 ICMP在协议框架中的位置图2-2 ICMP协议帧格式报文类型分为两类：○1差错报告Error-Reporting：报告路由器或目的站点处理一个ip分组时可能遇到的一些问题○2测试查询Query：帮助主机或管理员从某一个路由器或主机获得一些特定的信息图2-3 ICMP报文类型及作用三、代码框架及流程图图3-1 程序流程图图3-2 代码框架四、重要函数分析○1IP报头格式struct IPHeader {BYTE h_len:4; // Length of the header in dwordsBYTE version:4; // Version of IPBYTE tos; // Type of serviceUSHORT total_len; // Length of the packet in dwordsUSHORT USHORT ident; // unique identifierUSHORT flags; // FlagsBYTE ttl; // Time to liveBYTE proto; // Protocol number (TCP, UDP etc)USHORT checksum; // IP checksumULONG source_ip;ULONG dest_ip; };○2ICMP报头格式struct ICMPHeader {BYTE type; // ICMP packet typeBYTE code; // Type sub codeUSHORT checksum;USHORT id;USHORT seq;ULONG timestamp; // not part of ICMP };○3Raw SocketSOCKET sd;sd=WSASocket(AF_INET,SOCK_RAW,IPPROTO_ICMP,0,0,0); setsockopt(sd, IPPROTO_IP, IP_TTL, (const char*)&ttl, sizeof(ttl)) ;RawSocket的作用主要在三个方面:1.通过raw socket来接受发向本机的ICMP,IGMP协议包,或者用来发送这些协议包.2.接受发向本机的但TCP/IP栈不能够处理的IP包.3.用来发送一些自己制定源地址特殊作用的IP包(自己写IP 头,TCP头等)○4Struct of addressstruct sockaddr_in{u_short sin_family;u_short sin_port;struct in_addr sin_addr;char sin_zero[8];}struct in_addr{union {struct { u_char s_b1,s_b2,s_b3,s_b4; } S_un_b;struct { u_short s_w1,s_w2; } S_un_w;u_long S_addr;}S_un; }○5Set addresssockaddr_in dest, source;dest.sin_family = AF_INET;dest.sin_addr.s_addr = inet_addr(host);○6Initial Send_buf && Calculate checksumallocate_buffers(send_buf, recv_buf, packet_size)Sizeof(ICMPHeader)<=Packet_size <=MAX_DATA_SIZE icmp_hdr->type = ICMP_ECHO_REQUEST;icmp_hdr->code = 0;icmp_hdr->checksum = 0;icmp_hdr->id = (USHORT)GetCurrentProcessId();icmp_hdr->seq = seq_no;icmp_hdr->timestamp = GetTickCount();const unsigned long int deadmeat = 0xDEADBEEF;char*datapart=(char*)icmp_hdr + sizeof(ICMPHeader);int bytes_left = packet_size - sizeof(ICMPHeader);while (bytes_left > 0) {memcpy(datapart,&deadmeat,min(int(sizeof(deadme at)), bytes_left));bytes_left -= sizeof(deadmeat);datapart += sizeof(deadmeat);}USHORT ip_checksum(USHORT* buffer, int size){unsigned long cksum = 0;while (size > 1) {cksum += *buffer++;size -= sizeof(USHORT);}if (size) {cksum += *(UCHAR*)buffer;}cksum = (cksum >> 16) + (cksum & 0xffff);cksum += (cksum >> 16);return (USHORT)(~cksum);}○7Send _tosend_buf = icmp_hdr;sendto(sd, (char*)send_buf, packet_size, 0, (sockaddr*)&dest, sizeof(dest));○8recvfromrecvfrom(sd, (char*)recv_buf,packet_size + sizeof(IPHeader), 0,(sockaddr*)&source, &fromlen);五、代码实现结果(截图)1.Ping清水河畔论坛202.115.22.221，能探测到此主机。

2.Ping本机回送地址。

3.Ping一台主机，探测超时。

六、总结及心得体会通过这次生产实习，我不但加深了对SOCKET的原始套接字RAW编程的理解，同时也对IP和ICMP协议有了进一步的认识。

这次设计的主要难点，在于数据包的发送接收，TTL的计算，以及超时的判断。

通过手动实践，对Ping 程序的流程有了深层理解。

七、附录：程序清单1.cpp:#include <winsock2.h>#include <iostream.h>#include "rawping.h"#define DEFAULT_PACKET_SIZE 32#define DEFAULT_TTL 30#define MAX_PING_DATA_SIZE 1024#define MAX_PING_PACKET_SIZE(MAX_PING_DA TA_SIZE + sizeof(IPHeader))int allocate_buffers(ICMPHeader*& send_buf, IPHeader*& recv_buf,int packet_size);int main(int argc, char* argv[]){int seq_no = 0;ICMPHeader* send_buf = 0;IPHeader* recv_buf = 0;if (argc < 2) {cerr << "usage: " << argv[0] << " <host> [data_size] [ttl]" <<endl;cerr << "\tdata_size can be up to " << MAX_PING_DA TA_SIZE <<" bytes. Default is " << DEFAULT_PACKET_SIZE << "." << endl;cerr << "\tttl should be 255 or lower. Default is " <<DEFAULT_TTL << "." << endl;return 1;}int packet_size = DEFAULT_PACKET_SIZE;int ttl = DEFAULT_TTL;if (argc > 2) {int temp = atoi(argv[2]);if (temp != 0) { packet_size = temp;}if (argc > 3) {temp = atoi(argv[3]);if ((temp >= 0) && (temp <= 255)) {ttl = temp;}}}packet_size = max(sizeof(ICMPHeader),min(MAX_PING_DATA_SIZE,(unsigned int)packet_size));// Start Winsock upWSAData wsaData;if (WSAStartup(MAKEWORD(2, 1), &wsaData) != 0) {cerr << "Failed to find Winsock 2.1 or better." << endl;return 1;}// Set up for pingingSOCKET sd;sockaddr_in dest, source;if (setup_for_ping(argv[1], ttl, sd, dest) < 0) { goto cleanup;}if (allocate_buffers(send_buf, recv_buf, packet_size) < 0) { goto cleanup;}init_ping_packet(send_buf, packet_size, seq_no);// Send the ping and receive the replyif (send_ping(sd, dest, send_buf, packet_size) >= 0) { while (1) {if (recv_ping(sd, source, recv_buf, MAX_PING_PACKET_SIZE) <0) {unsigned short header_len = recv_buf->h_len * 4;ICMPHeader* icmphdr = (ICMPHeader*)((char*)recv_buf + header_len);if (icmphdr->seq != seq_no) {cerr << "bad sequence number!" << endl;continue;}else {break;}}if (decode_reply(recv_buf, packet_size, &source) != -2) {break;}}}cleanup:delete[]send_buf;delete[]recv_buf;WSACleanup();return 0;}/////////////allocate_buffers ////////////int allocate_buffers(ICMPHeader*& send_buf, IPHeader*& recv_buf,int packet_size){// First the send buffersend_buf = (ICMPHeader*)new char[packet_size];if (send_buf == 0) {cerr << "Failed to allocate output buffer." << endl;return -1;}// And then the receive bufferrecv_buf=(IPHeader*)new char[MAX_PING_PACKET_SIZE];if (recv_buf == 0) {cerr << "Failed to allocate output buffer." << endl;return -1;}return 0;}rawping.cpp:#include <winsock2.h>#include <ws2tcpip.h>#include <iostream.h>#include "rawping.h"#include "ip_checksum.h"/////////setup_for_ping ///////////////int setup_for_ping(char* host, int ttl, SOCKET& sd, sockaddr_in& dest){// Create the socketsd =WSASocket(AF_INET, SOCK_RAW, IPPROTO_ICMP, 0, 0, 0);if (sd == INV ALID_SOCKET) {cerr << "Failed to create raw socket: " << WSAGetLastError() <<endl;return -1;}if (setsockopt(sd, IPPROTO_IP, IP_TTL, (const char*)&ttl, sizeof(ttl)) == SOCKET_ERROR){cerr << "TTL setsockopt failed: " << WSAGetLastError() << endl;return -1;}memset(&dest, 0, sizeof(dest));unsigned int addr = inet_addr(host);if (addr != INADDR_NONE) {dest.sin_addr.s_addr = addr;dest.sin_family = AF_INET;}else {// Not in dotted quad form, so try and look it up hostent* hp = gethostbyname(host);if (hp != 0) {memcpy(&(dest.sin_addr),hp->h_addr, hp->h_length); dest.sin_family = hp->h_addrtype;}else {cerr << "Failed to resolve " << host << endl;return -1;}}return 0;}///////////init_ping_packet ////////////////void init_ping_packet(ICMPHeader* icmp_hdr, int packet_size, int seq_no){// Set up the packet's fieldsicmp_hdr->type = ICMP_ECHO_REQUEST;icmp_hdr->code = 0;icmp_hdr->checksum = 0;icmp_hdr->id = (USHORT)GetCurrentProcessId();icmp_hdr->seq = seq_no;icmp_hdr->timestamp = GetTickCount();const unsigned long int deadmeat = 0xDEADBEEF;char* datapart =(char*)icmp_hdr + sizeof(ICMPHeader);int bytes_left = packet_size - sizeof(ICMPHeader); while (bytes_left > 0) {memcpy(datapart, &deadmeat, min(int(sizeof(deadmeat)), bytes_left));bytes_left -= sizeof(deadmeat);datapart += sizeof(deadmeat);}icmp_hdr->checksum =ip_checksum((USHORT*)icmp_hdr, packet_size);}//////// send_ping //////////////int send_ping(SOCKET sd, const sockaddr_in& dest, ICMPHeader* send_buf,int packet_size){cout << "Sending " << packet_size << " bytes to " << inet_ntoa(dest.sin_addr) << "..." << flush;int bwrote = sendto(sd, (char*)send_buf, packet_size, 0, (sockaddr*)&dest, sizeof(dest));if (bwrote == SOCKET_ERROR) {cerr << "send failed: " << WSAGetLastError() << endl;return -1;}else if (bwrote < packet_size) {cout << "sent " << bwrote << " bytes..." << flush;}return 0;}////////recv_ping /////////////int recv_ping(SOCKET sd, sockaddr_in& source, IPHeader* recv_buf, int packet_size){int fromlen = sizeof(source);int bread =recvfrom(sd, (char*)recv_buf,packet_size + sizeof(IPHeader), 0,(sockaddr*)&source, &fromlen);if (bread == SOCKET_ERROR) {cerr << "read failed: ";if (WSAGetLastError() == WSAEMSGSIZE) {cerr << "buffer too small" << endl;}else {cerr << "error #" << WSAGetLastError() << endl;}return -1;}return 0;}////////////decode_reply //////////////int decode_reply(IPHeader* reply, int bytes, sockaddr_in* from){ unsigned short header_len = reply->h_len * 4;ICMPHeader* icmphdr =(ICMPHeader*)((char*)reply + header_len);if (bytes < header_len + ICMP_MIN) {cerr << "too few bytes from " << inet_ntoa(from->sin_addr) << endl;return -1;}else if (icmphdr->type != ICMP_ECHO_REPL Y) { if (icmphdr->type != ICMP_TTL_EXPIRE) {if (icmphdr->type == ICMP_DEST_UNREACH) {cerr << "Destination unreachable" << endl;}else {cerr << "Unknown ICMP packet type " << int(icmphdr->type) <<" received" << endl;}return -1;}}Else if(icmphdr->id != (USHORT)GetCurrentProcessId()) {return -2;}int nHops = int(256 - reply->ttl);if (nHops == 192) {nHops = 1;}else if (nHops == 128) {nHops = 0;}cout << endl << bytes << " bytes from " <<inet_ntoa(from->sin_addr) << ", icmp_seq " <<icmphdr->seq << ", ";if (icmphdr->type == ICMP_TTL_EXPIRE) {cout << "TTL expired." << endl;}else {cout << nHops << " hop" << (nHops == 1 ? "" : "s");cout << ", time: " << (GetTickCount() - icmphdr->timestamp) << " ms." << endl;}return 0;}rawping.h:#define WIN32_LEAN_AND_MEAN#include <winsock2.h>#define ICMP_ECHO_REPL Y 0#define ICMP_DEST_UNREACH 3#define ICMP_TTL_EXPIRE 11#define ICMP_ECHO_REQUEST 8#define ICMP_MIN 8#ifdef _MSC_VER#pragma pack(1)#endif// The IP headerstruct IPHeader {BYTE h_len:4; // Length of the header in dwordsBYTE version:4; // Version of IPBYTE tos; // Type of serviceUSHORT total_len; // Length of the packet in dwordsUSHORT ident; // unique identifierUSHORT flags; // FlagsBYTE ttl; // Time to liveBYTE proto; // Protocol number (TCP, UDP etc)USHORT checksum; // IP checksumULONG source_ip;ULONG dest_ip;};// ICMP headerstruct ICMPHeader {BYTE type; // ICMP packet typeBYTE code; // Type sub codeUSHORT checksum;USHORT id;USHORT seq;ULONG timestamp;};#ifdef _MSC_VER#pragma pack()#endifextern int setup_for_ping(char* host, int ttl, SOCKET& sd, sockaddr_in& dest); extern int send_ping(SOCKET sd,const sockaddr_in&dest,ICMPHeader* send_buf, int packet_size);extern int recv_ping(SOCKET sd, sockaddr_in& source, IPHeader* recv_buf,int packet_size);extern int decode_reply(IPHeader* reply, int bytes, sockaddr_in* from);extern void init_ping_packet(ICMPHeader* icmp_hdr, int packet_size, int seq_no);ip_checksum.cpp:#define WIN32_LEAN_AND_MEAN#include <windows.h>USHORT ip_checksum(USHORT* buffer, int size){unsigned long cksum = 0;while (size > 1) {cksum += *buffer++;size -= sizeof(USHORT);}if (size) {cksum += *(UCHAR*)buffer;}cksum = (cksum >> 16) + (cksum & 0xffff);cksum += (cksum >> 16);return (USHORT)(~cksum);}ip_checksum.h:extern USHORT ip_checksum(USHORT* buffer, int size);。