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:4; // length of the header 
    unsigned int version:4; // 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 = 1000; 
    char *dest_ip; 
    char *icmp_data; 
    char *recvbuf; 
    unsigned int addr=0; 
    USHORT seq_no = 0; 
    struct sockaddr_in from;
    int fromlen = sizeof(from);

    if (WSAStartup(MAKEWORD(2,1),&wsaData) != 0)
    { 
        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, 0,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 = 1000;   //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 = 1000;   //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,0,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,0,MAX_PACKET); 
    fill_icmp_data(icmp_data,datasize);         //只填充了ICMP包

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

    while(1)
    {   
        int bwrote; 

        ((IcmpHeader*)icmp_data)->i_cksum = 0; 
        ((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,0,(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,0,(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(1000);
    }

    WSACleanup(); 
    system("pause");

    return 0; 
} 

/* 
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 * 4 ; // 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 == 3)
    {
        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=0; 

    while(size >1) 
    { 
        cksum+=*buffer++; 
        size -=sizeof(USHORT); 
    } 

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

    cksum = (cksum >> 16) + (cksum & 0xffff); 
    cksum += (cksum >>16); 
    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 = 0; 
    icmp_hdr->i_id = (USHORT)GetCurrentProcessId(); //id填当前进程的id
    icmp_hdr->i_cksum = 0; 
    icmp_hdr->i_seq = 0; 

    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