Windows ping源码

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：

 /******************************************************************************\
 * ping.c - Simple ping utility using SOCK_RAW
 *
 * This is a part of the Microsoft Source Code Samples.
 * Copyright 1996-1997 Microsoft Corporation.
 * All rights reserved.
 * This source code is only intended as a supplement to
 * Microsoft Development Tools and/or WinHelp documentation.
 * See these sources for detailed information regarding the
 * Microsoft samples programs.
 \******************************************************************************/ 

 #pragma pack(4) 

 #define WIN32_LEAN_AND_MEAN
 #include <winsock2.h>
 #include <stdio.h>
 #include <stdlib.h>
 #pragma comment(lib,"ws2_32.lib")

 #define ICMP_ECHO 8
 #define ICMP_ECHOREPLY 0 

 #define ICMP_MIN 8                                           // minimum 8 byte icmp packet (just header) 

 /* The IP header */
 typedef struct iphdr
 {
     unsigned int h_len:; // length of the header
     unsigned int version:; // Version of IP
     unsigned char tos; // Type of service
     unsigned short total_len; // total length of the packet
     unsigned short ident; // unique identifier
     unsigned short frag_and_flags; // flags
     unsigned char ttl;
     unsigned char proto; // protocol (TCP, UDP etc)
     unsigned short checksum; // IP checksum
     unsigned int sourceIP;
     unsigned int destIP;
 }IpHeader; 

 //
 // ICMP header
 //
 typedef struct _ihdr {
     BYTE i_type;     //消息类型
     BYTE i_code;     //代码  /* type sub code */
     USHORT i_cksum;  //校验和
     USHORT i_id;     //ID号
     USHORT i_seq;    //序列号
     ULONG timestamp; //时间戳  /* This is not the std header, but we reserve space for time */
 }IcmpHeader;         //ICMP报文  包括报头和数据

 #define STATUS_FAILED 0xFFFF
 #define DEF_PACKET_SIZE 32
 #define MAX_PACKET 1024 

 #define xmalloc(s) HeapAlloc(GetProcessHeap(),HEAP_ZERO_MEMORY,(s))
 #define xfree(p) HeapFree (GetProcessHeap(),0,(p)) 

 void fill_icmp_data(char *, int);
 USHORT checksum(USHORT *, int);
 void decode_resp(char *,int ,struct sockaddr_in *);

 int main(int argc, char **argv)
 {
     WSADATA wsaData;
     SOCKET sockRaw;
     struct sockaddr_in dest;
     struct hostent * hp;
     int bread,datasize;
     int timeout = ;
     char *dest_ip;
     char *icmp_data;
     char *recvbuf;
     unsigned int addr=;
     USHORT seq_no = ;
     struct sockaddr_in from;
     int fromlen = sizeof(from);

     if (WSAStartup(MAKEWORD(,),&wsaData) != )
     {
         fprintf(stderr,"WSAStartup failed: %d\n",GetLastError());
         ExitProcess(STATUS_FAILED);
     }

     /*
     为了使用发送接收超时设置(即设置SO_RCVTIMEO, SO_SNDTIMEO)，
 //    必须将标志位设为WSA_FLAG_OVERLAPPED !
     */
     sockRaw = WSASocket (AF_INET, SOCK_RAW, IPPROTO_ICMP, NULL, ,WSA_FLAG_OVERLAPPED);                    //建立一个原始套接字
     //sockRaw = WSASocket (AF_INET, SOCK_RAW, IPPROTO_ICMP, NULL, 0,0);

     if (sockRaw == INVALID_SOCKET)
     {
         fprintf(stderr,"WSASocket() failed: %d\n",WSAGetLastError());
         ExitProcess(STATUS_FAILED);
     } 

     timeout = ;   //设置接收超时时间
     bread = setsockopt(sockRaw,SOL_SOCKET,SO_RCVTIMEO,(char*)&timeout, sizeof(timeout)); //RECVTIMEO是接收超时时间
     if(bread == SOCKET_ERROR)
     {
         fprintf(stderr,"failed to set recv timeout: %d\n",WSAGetLastError());
         ExitProcess(STATUS_FAILED);
     } 

     timeout = ;   //设置发送超时时间
     bread = setsockopt(sockRaw,SOL_SOCKET,SO_SNDTIMEO,(char*)&timeout, sizeof(timeout)); //SNDTIMEO是发送超时时间
     if(bread == SOCKET_ERROR)
     {
         fprintf(stderr,"failed to set send timeout: %d\n",WSAGetLastError());
         ExitProcess(STATUS_FAILED);
     }
     memset(&dest,,sizeof(dest));            //目标地址清零

     hp = gethostbyname("www.baidu.com");      //通过域名或者主机名获取IP地址
     if (!hp)  //失败返回NULL
     {
          ExitProcess(STATUS_FAILED);
     }
     else
     {
          addr = inet_addr("14.215.177.37");    //www.baidu.com的ip地址
     }

     if ((!hp) && (addr == INADDR_NONE))        //既不是域名也不是点分十进制的IP地址
     {
         ExitProcess(STATUS_FAILED);
     }

     if (hp != NULL)                           //获取的是域名
         memcpy(&(dest.sin_addr),hp->h_addr,hp->h_length);   //从hostent得到的对方ip地址
     else
         dest.sin_addr.s_addr = addr; 

     if (hp)
         dest.sin_family = hp->h_addrtype;    //sin_family不是一定只能填AF_INET吗？
     else
         dest.sin_family = AF_INET; 

     dest_ip = inet_ntoa(dest.sin_addr);        //目标IP地址

     datasize = DEF_PACKET_SIZE;             //ICMP包数据大小设定为32

     datasize += sizeof(IcmpHeader);         //另外加上ICMP包的包头 其实包头占12个字节

     icmp_data = (char *)xmalloc(MAX_PACKET);//发送icmp_data数据包内存
     recvbuf = (char *)xmalloc(MAX_PACKET);  //存放接收到的数据

     if (!icmp_data)                         //分配内存
     {
         ExitProcess(STATUS_FAILED);
     }

     memset(icmp_data,,MAX_PACKET);
     fill_icmp_data(icmp_data,datasize);         //只填充了ICMP包

     fprintf(stdout,"\nPinging %s ....\n\n",dest_ip); 

     while()
     {
         int bwrote; 

         ((IcmpHeader*)icmp_data)->i_cksum = ;
         ((IcmpHeader*)icmp_data)->timestamp = GetTickCount(); //时间戳

         ((IcmpHeader*)icmp_data)->i_seq = seq_no++;           //ICMP的序列号
         ((IcmpHeader*)icmp_data)->i_cksum = checksum((USHORT*)icmp_data, datasize);   //icmp校验位  

         //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
         //问题是sockRaw 设定了协议为 IPPROTO_ICMP
         bwrote = sendto(sockRaw,icmp_data,datasize,,(struct sockaddr*)&dest, sizeof(dest));
         if (bwrote == SOCKET_ERROR)
         {
             if (WSAGetLastError() == WSAETIMEDOUT)     //发送时间超时
             {
                 printf("timed out\n");
                 continue;
             } 

             fprintf(stderr,"sendto failed: %d\n",WSAGetLastError());
             ExitProcess(STATUS_FAILED);
         }

         if (bwrote < datasize )
         {
             fprintf(stdout,"Wrote %d bytes\n",bwrote);
         } 

         bread = recvfrom(sockRaw,recvbuf,MAX_PACKET,,(struct sockaddr*)&from, &fromlen);
         if (bread == SOCKET_ERROR)
         {
             if (WSAGetLastError() == WSAETIMEDOUT)
             {
                 printf("timed out\n");
                 continue;
             }
             fprintf(stderr,"recvfrom failed: %d\n",WSAGetLastError());
             ExitProcess(STATUS_FAILED);
         }
         decode_resp(recvbuf,bread,&from); 

         Sleep();
     }

     WSACleanup();
     system("pause");

     return ;
 } 

 /*
 The response is an IP packet. We must decode the IP header to locate
 the ICMP data
 */
 void decode_resp(char *buf, int bytes,struct sockaddr_in *from)
 {
     IpHeader *iphdr;
     IcmpHeader *icmphdr;
     unsigned short iphdrlen; 

     iphdr = (IpHeader *)buf;      //接收到的数据就是原始的IP数据报

     iphdrlen = iphdr->h_len *  ; // number of 32-bit words *4 = bytes 

     if (bytes < iphdrlen + ICMP_MIN)
     {
         printf("Too few bytes from %s\n",inet_ntoa(from->sin_addr));
     } 

     icmphdr = (IcmpHeader*)(buf + iphdrlen); 

     if(icmphdr->i_type == )
     {
         printf("network unreachable -- Response from %s.\n",inet_ntoa(from->sin_addr));
         return ;
     }

     if (icmphdr->i_id != (USHORT)GetCurrentProcessId())
     {
         fprintf(stderr,"someone else's packet!\n");
         return ;
     }
     printf("%d bytes from %s:",bytes, inet_ntoa(from->sin_addr));
     printf(" icmp_seq = %d ",icmphdr->i_seq);
     printf(" time: %d ms ",GetTickCount()-icmphdr->timestamp);
     printf(" ttl: %d",iphdr->ttl);
     printf("\n");
 } 

 //完成ICMP的校验
 USHORT checksum(USHORT *buffer, int size)
 {
     unsigned long cksum=; 

     while(size >)
     {
         cksum+=*buffer++;
         size -=sizeof(USHORT);
     } 

     if(size )
     {
         cksum += *(UCHAR*)buffer;
     } 

     cksum = (cksum >> ) + (cksum & 0xffff);
     cksum += (cksum >>);
     return (USHORT)(~cksum);
 }

 /*
 Helper function to fill in various stuff in our ICMP request.
 */
 void fill_icmp_data(char * icmp_data, int datasize){ 

     IcmpHeader *icmp_hdr;
     char *datapart; 

     icmp_hdr = (IcmpHeader*)icmp_data; 

     icmp_hdr->i_type = ICMP_ECHO;                   //ICMP_ECHO要求收到包的主机回复此ICMP包
     icmp_hdr->i_code = ;
     icmp_hdr->i_id = (USHORT)GetCurrentProcessId(); //id填当前进程的id
     icmp_hdr->i_cksum = ;
     icmp_hdr->i_seq = ; 

     datapart = icmp_data + sizeof(IcmpHeader);
     //
     // Place some junk in the buffer.
     //
     memset(datapart,'E', datasize - sizeof(IcmpHeader));  //填充了一些废物
 } 

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