Windows ping源碼

     須要測試外網的聯通性，想到了用ping。網上下載了ping的源代碼，調試下整理以下：

  1 /******************************************************************************\ 
  2 * ping.c - Simple ping utility using SOCK_RAW 
  3 * 
  4 * This is a part of the Microsoft Source Code Samples. 
  5 * Copyright 1996-1997 Microsoft Corporation. 
  6 * All rights reserved. 
  7 * This source code is only intended as a supplement to 
  8 * Microsoft Development Tools and/or WinHelp documentation. 
  9 * See these sources for detailed information regarding the 
 10 * Microsoft samples programs. 
 11 \******************************************************************************/ 
 12 
 13 #pragma pack(4) 
 14 
 15 #define WIN32_LEAN_AND_MEAN 
 16 #include <winsock2.h> 
 17 #include <stdio.h> 
 18 #include <stdlib.h> 
 19 #pragma comment(lib,"ws2_32.lib")
 20 
 21 #define ICMP_ECHO 8 
 22 #define ICMP_ECHOREPLY 0 
 23 
 24 #define ICMP_MIN 8                                           // minimum 8 byte icmp packet (just header) 
 25 
 26 /* The IP header */ 
 27 typedef struct iphdr 
 28 { 
 29     unsigned int h_len:4; // length of the header 
 30     unsigned int version:4; // Version of IP 
 31     unsigned char tos; // Type of service 
 32     unsigned short total_len; // total length of the packet 
 33     unsigned short ident; // unique identifier 
 34     unsigned short frag_and_flags; // flags 
 35     unsigned char ttl; 
 36     unsigned char proto; // protocol (TCP, UDP etc) 
 37     unsigned short checksum; // IP checksum 
 38     unsigned int sourceIP; 
 39     unsigned int destIP; 
 40 }IpHeader; 
 41 
 42 // 
 43 // ICMP header 
 44 // 
 45 typedef struct _ihdr { 
 46     BYTE i_type;     //消息類型
 47     BYTE i_code;     //代碼  /* type sub code */ 
 48     USHORT i_cksum;  //校驗和
 49     USHORT i_id;     //ID號
 50     USHORT i_seq;    //序列號
 51     ULONG timestamp; //時間戳  /* This is not the std header, but we reserve space for time */ 
 52 }IcmpHeader;         //ICMP報文  包括報頭和數據
 53 
 54 #define STATUS_FAILED 0xFFFF 
 55 #define DEF_PACKET_SIZE 32 
 56 #define MAX_PACKET 1024 
 57 
 58 #define xmalloc(s) HeapAlloc(GetProcessHeap(),HEAP_ZERO_MEMORY,(s)) 
 59 #define xfree(p) HeapFree (GetProcessHeap(),0,(p)) 
 60 
 61 void fill_icmp_data(char *, int); 
 62 USHORT checksum(USHORT *, int); 
 63 void decode_resp(char *,int ,struct sockaddr_in *);
 64 
 65 int main(int argc, char **argv)
 66 { 
 67     WSADATA wsaData; 
 68     SOCKET sockRaw; 
 69     struct sockaddr_in dest; 
 70     struct hostent * hp; 
 71     int bread,datasize; 
 72     int timeout = 1000; 
 73     char *dest_ip; 
 74     char *icmp_data; 
 75     char *recvbuf; 
 76     unsigned int addr=0; 
 77     USHORT seq_no = 0; 
 78     struct sockaddr_in from;
 79     int fromlen = sizeof(from);
 80 
 81     if (WSAStartup(MAKEWORD(2,1),&wsaData) != 0)
 82     { 
 83         fprintf(stderr,"WSAStartup failed: %d\n",GetLastError()); 
 84         ExitProcess(STATUS_FAILED); 
 85     }
 86 
 87     /*
 88     爲了使用發送接收超時設置(即設置SO_RCVTIMEO, SO_SNDTIMEO)， 
 89 //    必須將標誌位設爲WSA_FLAG_OVERLAPPED ! 
 90     */
 91     sockRaw = WSASocket (AF_INET, SOCK_RAW, IPPROTO_ICMP, NULL, 0,WSA_FLAG_OVERLAPPED);                    //創建一個原始套接字
 92     //sockRaw = WSASocket (AF_INET, SOCK_RAW, IPPROTO_ICMP, NULL, 0,0);
 93 
 94     if (sockRaw == INVALID_SOCKET) 
 95     { 
 96         fprintf(stderr,"WSASocket() failed: %d\n",WSAGetLastError()); 
 97         ExitProcess(STATUS_FAILED); 
 98     } 
 99 
100     timeout = 1000;   //設置接收超時時間
101     bread = setsockopt(sockRaw,SOL_SOCKET,SO_RCVTIMEO,(char*)&timeout, sizeof(timeout)); //RECVTIMEO是接收超時時間
102     if(bread == SOCKET_ERROR) 
103     { 
104         fprintf(stderr,"failed to set recv timeout: %d\n",WSAGetLastError()); 
105         ExitProcess(STATUS_FAILED); 
106     } 
107                                                                                                         
108     timeout = 1000;   //設置發送超時時間
109     bread = setsockopt(sockRaw,SOL_SOCKET,SO_SNDTIMEO,(char*)&timeout, sizeof(timeout)); //SNDTIMEO是發送超時時間 
110     if(bread == SOCKET_ERROR) 
111     { 
112         fprintf(stderr,"failed to set send timeout: %d\n",WSAGetLastError()); 
113         ExitProcess(STATUS_FAILED); 
114     } 
115     memset(&dest,0,sizeof(dest));            //目標地址清零
116 
117     hp = gethostbyname("www.baidu.com");      //經過域名或者主機名獲取IP地址
118     if (!hp)  //失敗返回NULL
119     {
120          ExitProcess(STATUS_FAILED);
121     }
122     else
123     {
124          addr = inet_addr("14.215.177.37");    //www.baidu.com的ip地址
125     }
126 
127     if ((!hp) && (addr == INADDR_NONE))        //既不是域名也不是點分十進制的IP地址 
128     { 
129         ExitProcess(STATUS_FAILED);
130     }
131 
132     if (hp != NULL)                           //獲取的是域名
133         memcpy(&(dest.sin_addr),hp->h_addr,hp->h_length);   //從hostent獲得的對方ip地址
134     else 
135         dest.sin_addr.s_addr = addr; 
136 
137     if (hp) 
138         dest.sin_family = hp->h_addrtype;    //sin_family不是必定只能填AF_INET嗎？
139     else 
140         dest.sin_family = AF_INET; 
141 
142     dest_ip = inet_ntoa(dest.sin_addr);        //目標IP地址
143 
144     datasize = DEF_PACKET_SIZE;             //ICMP包數據大小設定爲32
145 
146     datasize += sizeof(IcmpHeader);         //另外加上ICMP包的包頭 其實包頭佔12個字節
147 
148     icmp_data = (char *)xmalloc(MAX_PACKET);//發送icmp_data數據包內存
149     recvbuf = (char *)xmalloc(MAX_PACKET);  //存放接收到的數據
150 
151     if (!icmp_data)                         //分配內存
152     {
153         ExitProcess(STATUS_FAILED); 
154     }
155 
156     memset(icmp_data,0,MAX_PACKET); 
157     fill_icmp_data(icmp_data,datasize);         //只填充了ICMP包
158 
159     fprintf(stdout,"\nPinging %s ....\n\n",dest_ip); 
160 
161     while(1)
162     {   
163         int bwrote; 
164 
165         ((IcmpHeader*)icmp_data)->i_cksum = 0; 
166         ((IcmpHeader*)icmp_data)->timestamp = GetTickCount(); //時間戳
167 
168         ((IcmpHeader*)icmp_data)->i_seq = seq_no++;           //ICMP的序列號
169         ((IcmpHeader*)icmp_data)->i_cksum = checksum((USHORT*)icmp_data, datasize);   //icmp校驗位  
170 
171         //下面這個函數的問題是 發送數據只是ICMP數據包，而接收到的數據時包含ip頭的 也就是發送和接收不對等
172         //問題是sockRaw 設定了協議爲 IPPROTO_ICMP
173         bwrote = sendto(sockRaw,icmp_data,datasize,0,(struct sockaddr*)&dest, sizeof(dest)); 
174         if (bwrote == SOCKET_ERROR)
175         {   
176             if (WSAGetLastError() == WSAETIMEDOUT)     //發送時間超時
177             { 
178                 printf("timed out\n"); 
179                 continue; 
180             } 
181 
182             fprintf(stderr,"sendto failed: %d\n",WSAGetLastError()); 
183             ExitProcess(STATUS_FAILED); 
184         }
185 
186         if (bwrote < datasize ) 
187         { 
188             fprintf(stdout,"Wrote %d bytes\n",bwrote); 
189         } 
190 
191         bread = recvfrom(sockRaw,recvbuf,MAX_PACKET,0,(struct sockaddr*)&from, &fromlen); 
192         if (bread == SOCKET_ERROR)
193         {
194             if (WSAGetLastError() == WSAETIMEDOUT)
195             {
196                 printf("timed out\n");
197                 continue;
198             }
199             fprintf(stderr,"recvfrom failed: %d\n",WSAGetLastError()); 
200             ExitProcess(STATUS_FAILED); 
201         }
202         decode_resp(recvbuf,bread,&from); 
203 
204         Sleep(1000);
205     }
206 
207     WSACleanup(); 
208     system("pause");
209 
210     return 0; 
211 } 
212 
213 /* 
214 The response is an IP packet. We must decode the IP header to locate 
215 the ICMP data 
216 */ 
217 void decode_resp(char *buf, int bytes,struct sockaddr_in *from) 
218 { 
219     IpHeader *iphdr; 
220     IcmpHeader *icmphdr; 
221     unsigned short iphdrlen; 
222 
223     iphdr = (IpHeader *)buf;      //接收到的數據就是原始的IP數據報
224 
225     iphdrlen = iphdr->h_len * 4 ; // number of 32-bit words *4 = bytes 
226 
227     if (bytes < iphdrlen + ICMP_MIN) 
228     { 
229         printf("Too few bytes from %s\n",inet_ntoa(from->sin_addr)); 
230     } 
231 
232     icmphdr = (IcmpHeader*)(buf + iphdrlen); 
233 
234     if(icmphdr->i_type == 3)
235     {
236         printf("network unreachable -- Response from %s.\n",inet_ntoa(from->sin_addr));
237         return ;
238     }
239 
240     if (icmphdr->i_id != (USHORT)GetCurrentProcessId())
241     { 
242         fprintf(stderr,"someone else's packet!\n"); 
243         return ; 
244     }
245     printf("%d bytes from %s:",bytes, inet_ntoa(from->sin_addr)); 
246     printf(" icmp_seq = %d ",icmphdr->i_seq); 
247     printf(" time: %d ms ",GetTickCount()-icmphdr->timestamp); 
248     printf(" ttl: %d",iphdr->ttl);
249     printf("\n"); 
250 } 
251 
252 //完成ICMP的校驗
253 USHORT checksum(USHORT *buffer, int size) 
254 { 
255     unsigned long cksum=0; 
256 
257     while(size >1) 
258     { 
259         cksum+=*buffer++; 
260         size -=sizeof(USHORT); 
261     } 
262 
263     if(size ) 
264     { 
265         cksum += *(UCHAR*)buffer; 
266     } 
267 
268     cksum = (cksum >> 16) + (cksum & 0xffff); 
269     cksum += (cksum >>16); 
270     return (USHORT)(~cksum); 
271 }
272 
273 /* 
274 Helper function to fill in various stuff in our ICMP request. 
275 */ 
276 void fill_icmp_data(char * icmp_data, int datasize){ 
277 
278     IcmpHeader *icmp_hdr; 
279     char *datapart; 
280 
281     icmp_hdr = (IcmpHeader*)icmp_data; 
282 
283     icmp_hdr->i_type = ICMP_ECHO;                   //ICMP_ECHO要求收到包的主機回覆此ICMP包
284     icmp_hdr->i_code = 0; 
285     icmp_hdr->i_id = (USHORT)GetCurrentProcessId(); //id填當前進程的id
286     icmp_hdr->i_cksum = 0; 
287     icmp_hdr->i_seq = 0; 
288 
289     datapart = icmp_data + sizeof(IcmpHeader); 
290     // 
291     // Place some junk in the buffer. 
292     // 
293     memset(datapart,'E', datasize - sizeof(IcmpHeader));  //填充了一些廢物
294 } 

       我下到代碼的時候，第91行建立原始套接字的地方本來是被屏蔽的第92行，區別在與建立套接字時賦予的標誌位不同。

       WSASocket函數的定義以下：

SOCKET WSASocket (
　　int af, 
　　int type, 
　　int protocol, 
　　LPWSAPROTOCOL_INFO lpProtocolInfo, 
　　GROUP g, 
　　DWORD dwFlags 
　　);

        af：[in]一個地址族規範。目前僅支持AF_INET格式，亦即ARPA Internet地址格式。

        type：新套接口的類型描述。

        protocol：套接口使用的特定協議，若是調用者不肯指定協議則定爲0。

        lpProtocolInfo：一個指向PROTOCOL_INFO結構的指針，該結構定義所建立套接口的特性。若是本參數非零，則前三個參數（af, type, protocol）被忽略。

        g：保留給將來使用的套接口組。套接口組的標識符。

        iFlags：套接口屬性描述。

       具體詳細介紹看微軟官方介紹文檔：https://msdn.microsoft.com/en-us/library/ms742212(VS.85).aspx