定量预测方法有哪些:TraceRoute实现原理

   TraceRoute实现原理 http://blog.csdn.net/microtong/archive/2008/11/04/3220450.aspx

本程序实现Windows下tracert的功能，程序使用原始套接字发送ICMP回显请求报文，本接收ICMP超时差错报文，和ICMP回显应答报文，得到每一跳的路由器IP地址和往返时间。

3. //TraceRoute.h
5. #ifndef _ITRACERT_H_
6. #define _ITRACERT_H_
8. #pragma pack(1)
9. //IP数据报头
10. typedef struct
11. {
12. unsigned char hdr_len :4; // length of the header
13. unsigned char version :4; // version of IP
14. unsigned char tos; // type of service
15. unsigned short total_len; // total length of the packet
16. unsigned short identifier; // unique identifier
17. unsigned short frag_and_flags; // flags
18. unsigned char ttl; // time to live
19. unsigned char protocol; // protocol (TCP, UDP etc)
20. unsigned short checksum; // IP checksum
22. unsigned long sourceIP; // source IP address
23. unsigned long destIP; // destination IP address
25. } IP_HEADER;
27. //ICMP数据报头
28. typedef struct
29. {
30. BYTE type; //8位类型
31. BYTE code; //8位代码
32. USHORT cksum; //16位校验和
33. USHORT id; //16位标识符
34. USHORT seq; //16位序列号
36. } ICMP_HEADER;
38. //解码结果
39. typedef struct
40. {
41. USHORT usSeqNo; //包序列号
42. DWORD dwRoundTripTime; //往返时间
43. in_addr dwIPaddr; //对端IP地址
45. } DECODE_RESULT;
47. #pragma pack()
49. //ICMP类型字段
50. const BYTE ICMP_ECHO_REQUEST = 8; //请求回显
51. const BYTE ICMP_ECHO_REPLY = 0; //回显应答
52. const BYTE ICMP_TIMEOUT = 11; //传输超时
54. const DWORD DEF_ICMP_TIMEOUT = 3000; //默认超时时间，单位ms
55. const int DEF_ICMP_DATA_SIZE = 32; //默认ICMP数据部分长度
56. const int MAX_ICMP_PACKET_SIZE = 1024; //最大ICMP数据报的大小
57. const int DEF_MAX_HOP = 30; //最大跳站数
59. USHORT GenerateChecksum(USHORT* pBuf, int iSize);
60. BOOL DecodeIcmpResponse(char* pBuf, int iPacketSize, DECODE_RESULT& stDecodeResult);
62. #endif // _ITRACERT_H_
66. //TraceRoute.cpp
68. /*----------------------------------------------------------
69. 功能说明：该程序简单实现了Windows操作系统的tracert命令功能，
70. 可以输出IP报文从本机出发到达目的主机所经过的路由信息。
71. -----------------------------------------------------------*/
72. #include
73. #include
74. #include
75. #include
76. #include
77. #include "TraceRoute.h"
79. #pragma comment(lib,"ws2_32")
81. using namespace std;
83. int main(int argc, char* argv[])
84. {
85. //检查命令行参数
86. if (argc != 2)
87. {
88. cerr << "/nUsage: itracert ip_or_hostname/n";
89. return -1;
90. }
92. //初始化winsock2环境
93. WSADATA wsa;
94. if (WSAStartup(MAKEWORD(2, 2), &wsa) != 0)
95. {
96. cerr << "/nFailed to initialize the WinSock2 DLL/n"
97. << "error code: " << WSAGetLastError() << endl;
98. return -1;
99. }
101. //将命令行参数转换为IP地址
102. u_long ulDestIP = inet_addr(argv[1]);
103. if (ulDestIP == INADDR_NONE)
104. {
105. //转换不成功时按域名解析
106. hostent* pHostent = gethostbyname(argv[1]);
107. if (pHostent)
108. {
109. ulDestIP = (*(in_addr*)pHostent->h_addr).s_addr;
111. //输出屏幕信息
112. cout << "/nTracing route to " << argv[1]
113. << " [" << inet_ntoa(*(in_addr*)(&ulDestIP)) << "]"
114. << " with a maximum of " << DEF_MAX_HOP << " hops./n" << endl;
115. }
116. else //解析主机名失败
117. {
118. cerr << "/nCould not resolve the host name " << argv[1] << '/n'
119. << "error code: " << WSAGetLastError() << endl;
120. WSACleanup();
121. return -1;
122. }
123. }
124. else
125. {
126. //输出屏幕信息
127. cout << "/nTracing route to " << argv[1]
128. << " with a maximum of " << DEF_MAX_HOP << " hops./n" << endl;
129. }
131. //填充目的Socket地址
132. sockaddr_in destSockAddr;
133. ZeroMemory(&destSockAddr, sizeof(sockaddr_in));
134. destSockAddr.sin_family = AF_INET;
135. destSockAddr.sin_addr.s_addr = ulDestIP;
137. //使用ICMP协议创建Raw Socket
138. SOCKET sockRaw = WSASocket(AF_INET, SOCK_RAW, IPPROTO_ICMP, NULL, 0, WSA_FLAG_OVERLAPPED);
139. if (sockRaw == INVALID_SOCKET)
140. {
141. cerr << "/nFailed to create a raw socket/n"
142. << "error code: " << WSAGetLastError() << endl;
143. WSACleanup();
144. return -1;
145. }
146. //设置端口属性
147. int iTimeout = DEF_ICMP_TIMEOUT;
149. if (setsockopt(sockRaw, SOL_SOCKET, SO_RCVTIMEO, (char*)&iTimeout, sizeof(iTimeout)) == SOCKET_ERROR)
150. {
151. cerr << "/nFailed to set recv timeout/n"
152. << "error code: " << WSAGetLastError() << endl;
153. closesocket(sockRaw);
154. WSACleanup();
155. return -1;
156. }
159. //创建ICMP包发送缓冲区和接收缓冲区
160. char IcmpSendBuf[sizeof(ICMP_HEADER)+DEF_ICMP_DATA_SIZE];
161. memset(IcmpSendBuf, 0, sizeof(IcmpSendBuf));
162. char IcmpRecvBuf[MAX_ICMP_PACKET_SIZE];
163. memset(IcmpRecvBuf, 0, sizeof(IcmpRecvBuf));
165. //填充待发送的ICMP包
166. ICMP_HEADER* pIcmpHeader = (ICMP_HEADER*)IcmpSendBuf;
167. pIcmpHeader->type = ICMP_ECHO_REQUEST;
168. pIcmpHeader->code = 0;
169. pIcmpHeader->id = (USHORT)GetCurrentProcessId();
170. memset(IcmpSendBuf+sizeof(ICMP_HEADER), 'E', DEF_ICMP_DATA_SIZE);
172. //开始探测路由
173. DECODE_RESULT stDecodeResult;
174. BOOL bReachDestHost = FALSE;
175. USHORT usSeqNo = 0;
176. int iTTL = 1;
177. int iMaxHop = DEF_MAX_HOP;
178. while (!bReachDestHost && iMaxHop--)
179. {
180. //设置IP数据报头的ttl字段
181. setsockopt(sockRaw, IPPROTO_IP, IP_TTL, (char*)&iTTL, sizeof(iTTL));
183. //输出当前跳站数作为路由信息序号
184. cout << setw(3) << iTTL << flush;
186. //填充ICMP数据报剩余字段
187. ((ICMP_HEADER*)IcmpSendBuf)->cksum = 0;
188. ((ICMP_HEADER*)IcmpSendBuf)->seq = htons(usSeqNo++);
189. ((ICMP_HEADER*)IcmpSendBuf)->cksum = GenerateChecksum((USHORT*)IcmpSendBuf, sizeof(ICMP_HEADER)+DEF_ICMP_DATA_SIZE);
191. //记录序列号和当前时间
192. stDecodeResult.usSeqNo = ((ICMP_HEADER*)IcmpSendBuf)->seq;
193. stDecodeResult.dwRoundTripTime = GetTickCount();
195. //发送ICMP的EchoRequest数据报
196. if (sendto(sockRaw, IcmpSendBuf, sizeof(IcmpSendBuf), 0,
197. (sockaddr*)&destSockAddr, sizeof(destSockAddr)) == SOCKET_ERROR)
198. {
199. //如果目的主机不可达则直接退出
200. if (WSAGetLastError() == WSAEHOSTUNREACH)
201. cout << '/t' << "Destination host unreachable./n"
202. << "/nTrace complete./n" << endl;
203. closesocket(sockRaw);
204. WSACleanup();
205. return 0;
206. }
208. //接收ICMP的EchoReply数据报
209. //因为收到的可能并非程序所期待的数据报，所以需要循环接收直到收到所要数据或超时
210. sockaddr_in from;
211. int iFromLen = sizeof(from);
212. int iReadDataLen;
213. while (1)
214. {
215. //等待数据到达
216. iReadDataLen = recvfrom(sockRaw, IcmpRecvBuf, MAX_ICMP_PACKET_SIZE,
217. 0, (sockaddr*)&from, &iFromLen);
218. if (iReadDataLen != SOCKET_ERROR) //有数据包到达
219. {
220. //解码得到的数据包，如果解码正确则跳出接收循环发送下一个EchoRequest包
221. if (DecodeIcmpResponse(IcmpRecvBuf, iReadDataLen, stDecodeResult))
222. {
223. if (stDecodeResult.dwIPaddr.s_addr == destSockAddr.sin_addr.s_addr)
224. bReachDestHost = TRUE;
226. cout << '/t' << inet_ntoa(stDecodeResult.dwIPaddr) << endl;
227. break;
228. }
229. }
230. else if (WSAGetLastError() == WSAETIMEDOUT) //接收超时，打印星号
231. {
232. cout << setw(9) << '*' << '/t' << "Request timed out." << endl;
233. break;
234. }
235. else
236. {
237. cerr << "/nFailed to call recvfrom/n"
238. << "error code: " << WSAGetLastError() << endl;
239. closesocket(sockRaw);
240. WSACleanup();
241. return -1;
242. }
243. }
245. //TTL值加1
246. iTTL++;
247. }
248. //输出屏幕信息
249. cout << "/nTrace complete./n" << endl;
251. closesocket(sockRaw);
252. WSACleanup();
253. return 0;
254. }
256. //产生网际校验和
257. USHORT GenerateChecksum(USHORT* pBuf, int iSize)
258. {
259. unsigned long cksum = 0;
260. while (iSize>1)
261. {
262. cksum += *pBuf++;
263. iSize -= sizeof(USHORT);
264. }
265. if (iSize)
266. cksum += *(UCHAR*)pBuf;
268. cksum = (cksum >> 16) + (cksum & 0xffff);
269. cksum += (cksum >> 16);
271. return (USHORT)(~cksum);
272. }
275. //解码得到的数据报
276. BOOL DecodeIcmpResponse(char* pBuf, int iPacketSize, DECODE_RESULT& stDecodeResult)
277. {
278. //检查数据报大小的合法性
279. IP_HEADER* pIpHdr = (IP_HEADER*)pBuf;
280. int iIpHdrLen = pIpHdr->hdr_len * 4;
281. if (iPacketSize < (int)(iIpHdrLen+sizeof(ICMP_HEADER)))
282. return FALSE;
284. //按照ICMP包类型检查id字段和序列号以确定是否是程序应接收的Icmp包
285. ICMP_HEADER* pIcmpHdr = (ICMP_HEADER*)(pBuf+iIpHdrLen);
286. USHORT usID, usSquNo;
287. if (pIcmpHdr->type == ICMP_ECHO_REPLY)
288. {
289. usID = pIcmpHdr->id;
290. usSquNo = pIcmpHdr->seq;
291. }
292. else if(pIcmpHdr->type == ICMP_TIMEOUT)
293. {
294. char* pInnerIpHdr = pBuf+iIpHdrLen+sizeof(ICMP_HEADER); //载荷中的IP头
295. int iInnerIPHdrLen = ((IP_HEADER*)pInnerIpHdr)->hdr_len * 4;//载荷中的IP头长
296. ICMP_HEADER* pInnerIcmpHdr = (ICMP_HEADER*)(pInnerIpHdr+iInnerIPHdrLen);//载荷中的ICMP头
297. usID = pInnerIcmpHdr->id;
298. usSquNo = pInnerIcmpHdr->seq;
299. }
300. else
301. return FALSE;
303. if (usID != (USHORT)GetCurrentProcessId() || usSquNo !=stDecodeResult.usSeqNo)
304. return FALSE;
306. //处理正确收到的ICMP数据报
307. if (pIcmpHdr->type == ICMP_ECHO_REPLY ||
308. pIcmpHdr->type == ICMP_TIMEOUT)
309. {
310. //返回解码结果
311. stDecodeResult.dwIPaddr.s_addr = pIpHdr->sourceIP;
312. stDecodeResult.dwRoundTripTime = GetTickCount()-stDecodeResult.dwRoundTripTime;
314. //打印屏幕信息
315. if (stDecodeResult.dwRoundTripTime)
316. cout << setw(6) << stDecodeResult.dwRoundTripTime << " ms" << flush;
317. else
318. cout << setw(6) << "<1" << " ms" << flush;
320. return TRUE;
321. }
323. return FALSE;
324. }