需要测试外网的联通性，想到了用ping。网上下载了ping的源代码，调试下整理如下：
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; //消息类型
47 BYTE i_code; //代码 /* type sub code */
48 USHORT i_cksum; //校验和
49 USHORT i_id; //ID号
50 USHORT i_seq; //序列号
51 ULONG timestamp; //时间戳 /* This is not the std header, but we reserve space for time */
52 }IcmpHeader; //ICMP报文 包括报头和数据
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 为了使用发送接收超时设置(即设置SO_RCVTIMEO, SO_SNDTIMEO)，
89 // 必须将标志位设为WSA_FLAG_OVERLAPPED !
90 */
91 sockRaw = WSASocket (AF_INET, SOCK_RAW, IPPROTO_ICMP, NULL, 0,WSA_FLAG_OVERLAPPED); //建立一个原始套接字
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; //设置接收超时时间
101 bread = setsockopt(sockRaw,SOL_SOCKET,SO_RCVTIMEO,(char*)&timeout, sizeof(timeout)); //RECVTIMEO是接收超时时间
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; //设置发送超时时间
109 bread = setsockopt(sockRaw,SOL_SOCKET,SO_SNDTIMEO,(char*)&timeout, sizeof(timeout)); //SNDTIMEO是发送超时时间
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)); //目标地址清零
116
117 hp = gethostbyname("www.baidu.com"); //通过域名或者主机名获取IP地址
118 if (!hp) //失败返回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)) //既不是域名也不是点分十进制的IP地址
128 {
129 ExitProcess(STATUS_FAILED);
130 }
131
132 if (hp != NULL) //获取的是域名
133 memcpy(&(dest.sin_addr),hp->h_addr,hp->h_length); //从hostent得到的对方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不是一定只能填AF_INET吗？
139 else
140 dest.sin_family = AF_INET;
141
142 dest_ip = inet_ntoa(dest.sin_addr); //目标IP地址
143
144 datasize = DEF_PACKET_SIZE; //ICMP包数据大小设定为32
145
146 datasize += sizeof(IcmpHeader); //另外加上ICMP包的包头 其实包头占12个字节
147
148 icmp_data = (char *)xmalloc(MAX_PACKET);//发送icmp_data数据包内存
149 recvbuf = (char *)xmalloc(MAX_PACKET); //存放接收到的数据
150
151 if (!icmp_data) //分配内存
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(); //时间戳
167
168 ((IcmpHeader*)icmp_data)->i_seq = seq_no++; //ICMP的序列号
169 ((IcmpHeader*)icmp_data)->i_cksum = checksum((USHORT*)icmp_data, datasize); //icmp校验位
170
171 //下面这个函数的问题是 发送数据只是ICMP数据包，而接收到的数据时包含ip头的 也就是发送和接收不对等
172 //问题是sockRaw 设定了协议为 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) //发送时间超时
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; //接收到的数据就是原始的IP数据报
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的校验
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要求收到包的主机回复此ICMP包
284 icmp_hdr->i_code = 0;
285 icmp_hdr->i_id = (USHORT)GetCurrentProcessId(); //id填当前进程的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)); //填充了一些废物
294 }
我下到代码的时候，第91行创建原始套接字的地方原本是被屏蔽的第92行，区别在与创建套接字时赋予的标志位不一样。
WSASocket函数的定义如下：
SOCKET WSASocket ( int af, int type, int protocol, LPWSAPROTOCOL_INFO lpProtocolInfo, GROUP g, DWORD dwFlags );
af：[in]一个地址族规范。目前仅支持AF_INET格式，亦即ARPA Internet地址格式。
type：新套接口的类型描述。
protocol：套接口使用的特定协议，如果调用者不愿指定协议则定为0。
lpProtocolInfo：一个指向PROTOCOL_INFO结构的指针，该结构定义所创建套接口的特性。如果本参数非零，则前三个参数（af, type, protocol）被忽略。
g：保留给未来使用的套接口组。套接口组的标识符。
iFlags：套接口属性描述。
具体详细介绍看微软官方介绍文档：https://msdn.microsoft.com/en-us/library/ms742212(VS.85).aspx
时间： 2024-11-07 04:26:10