开发学院软件开发 VC 透析ICMP协议(4): 应用篇ping(RAW Socket) 阅读

透析ICMP协议(4): 应用篇ping(RAW Socket)

　2006-04-04 11:09:31　来源：WEB开发网　　　

核心提示： /** 程序名: rawping.cpp* 说明:* 主要函数库实现部分*/include <winsock2.h>#include <ws2tcpip.h>#include <iostream.h>#include "rawping.h&qu

/* * 程序名: rawping.cpp * 说明: * 主要函数库实现部分 */ include <winsock2.h> #include <ws2tcpip.h> #include <iostream.h> #include "rawping.h" // 计算ICMP包的校验和的简单算法, 很多地方都有说明, 这里没有必要详细将 // 只是一点要提, 做校验之前, 务必将ICMP包头的checksum字段置为0 USHORT ip_checksum(USHORT* buffer, int size) { unsigned long cksum = 0; // Sum all the words together, adding the final byte if size is odd while (size > 1) { cksum += *buffer++; size -= sizeof(USHORT); } if (size) { cksum += *(UCHAR*)buffer; } // Do a little shuffling cksum = (cksum >> 16) + (cksum & 0xffff); cksum += (cksum >> 16); // Return the bitwise complement of the resulting mishmash return (USHORT)(~cksum); } //初试化RAW Socket, 设置ttl, 初试化dest // 返回值 <0 表失败 int setup_for_ping(char* host, int ttl, SOCKET& sd, sockaddr_in& dest) { // Create the socket sd = WSASocket(AF_INET, SOCK_RAW, IPPROTO_ICMP, 0, 0, 0); if (sd == INVALID_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; } // Initialize the destination host info block memset(&dest, 0, sizeof(dest)); // Turn first passed parameter into an IP address to ping unsigned int addr = inet_addr(host); if (addr != INADDR_NONE) { // It was a dotted quad number, so save result 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) { // Found an address for that host, so save it memcpy(&(dest.sin_addr), hp->h_addr, hp->h_length); dest.sin_family = hp->h_addrtype; } else { // Not a recognized hostname either! cerr << "Failed to resolve " << host << endl; return -1; } } return 0; } //初试化ICMP的包头, 给data部分填充数据, 最后计算整个包的校验和 void init_ping_packet(ICMPHeader* icmp_hdr, int packet_size, int seq_no) { // Set up the packet's fields 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(); // "You're dead meat now, packet!" 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); } // Calculate a checksum on the result icmp_hdr->checksum = ip_checksum((USHORT*)icmp_hdr, packet_size); } // 发送生成的ICMP包 // 返回值 <0 表失败 int send_ping(SOCKET sd, const sockaddr_in& dest, ICMPHeader* send_buf, int packet_size) { // Send the ping packet in send_buf as-is 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; } // 接受ICMP包 // 返回值 <0 表失败 int recv_ping(SOCKET sd, sockaddr_in& source, IPHeader* recv_buf, int packet_size) { // Wait for the ping reply 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; } // 对收到的ICMP解码 // 返回值 -2表忽略, -1 表失败, 0 成功 int decode_reply(IPHeader* reply, int bytes, sockaddr_in* from) { // 跳过IP包头, 找到ICMP的包头 unsigned short header_len = reply->h_len * 4; ICMPHeader* icmphdr = (ICMPHeader*)((char*)reply + header_len); // 包的长度合法, header_len + ICMP_MIN为最小ICMP包的长度 if (bytes < header_len + ICMP_MIN) { cerr << "too few bytes from " << inet_ntoa(from->sin_addr) << endl; return -1; } // 下面的包类型详细参见我的第一部分 "透析ICMP协议(一): 协议原理" else if (icmphdr->type != ICMP_ECHO_REPLY) { //非正常回复 if (icmphdr->type != ICMP_TTL_EXPIRE) { //ttl减为零 if (icmphdr->type == ICMP_DEST_UNREACH) { //主机不可达 cerr << "Destination unreachable" << endl; } else { //非法的ICMP包类型 cerr << "Unknown ICMP packet type " << int(icmphdr->type) << " received" << endl; } return -1; } } else if (icmphdr->id != (USHORT)GetCurrentProcessId()) { //不是本进程发的包, 可能是同机的其它ping进程发的 return -2; } // 指出包传递了多远 // [bugfree]我认为作者这里有问题, 因为有些系统的ttl初值为128如winXP, // 有些为256如我的DNS服务器211.97.168.129, 作者假设为256有点武断, // 可以一起探讨这个问题, 回email:zhangliangsd@hotmail.com int nHops = int(256 - reply->ttl); if (nHops == 192) { // TTL came back 64, so ping was probably to a host on the // LAN -- call it a single hop. nHops = 1; } else if (nHops == 128) { // Probably localhost nHops = 0; } // 所有工作结束,打印信息 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; }