VC++实现软路由层面的ping

大家都知道ping ,如果是网络层该怎么实现呢，代码实现如下

#include "../common/initsock.h"
#include "../common/protoinfo.h"
#include "../common/comm.h"

#include <stdio.h>


CInitSock theSock;


typedef struct icmp_hdr
{
    unsigned char   icmp_type;		// 消息类型
    unsigned char   icmp_code;		// 代码
    unsigned short  icmp_checksum;	// 校验和
	// 下面是回显头
    unsigned short  icmp_id;		// 用来惟一标识此请求的ID号，通常设置为进程ID
    unsigned short  icmp_sequence;	// 序列号
    unsigned long   icmp_timestamp; // 时间戳
} ICMP_HDR, *PICMP_HDR;


int main()
{
	// 目的IP地址，即要Ping的IP地址
	char szDestIp[] = "10.16.115.178";	// 127.0.0.1

	// 创建原始套节字
	SOCKET sRaw = ::socket(AF_INET, SOCK_RAW, IPPROTO_ICMP);

	// 设置接收超时
	SetTimeout(sRaw, 1000, TRUE);

	// 设置目的地址
	SOCKADDR_IN dest;
	dest.sin_family = AF_INET;
	dest.sin_port = htons(0);
	dest.sin_addr.S_un.S_addr = inet_addr(szDestIp);

	// 创建ICMP封包
	char buff[sizeof(ICMP_HDR) + 32];
	ICMP_HDR* pIcmp = (ICMP_HDR*)buff;
	// 填写ICMP封包数据
	pIcmp->icmp_type = 8;	// 请求一个ICMP回显
	pIcmp->icmp_code = 0;
	pIcmp->icmp_id = (USHORT)::GetCurrentProcessId();
	pIcmp->icmp_checksum = 0;
	pIcmp->icmp_sequence = 0;
	// 填充数据部分，可以为任意
	memset(&buff[sizeof(ICMP_HDR)], 'E', 32);
	
	// 开始发送和接收ICMP封包
	USHORT	nSeq = 0;
	char recvBuf[1024];
	SOCKADDR_IN from;
	int nLen = sizeof(from);
	while(TRUE)
	{
		static int nCount = 0;
		int nRet;
		if(nCount++ == 4)
			break;
		pIcmp->icmp_checksum = 0;
		pIcmp->icmp_timestamp = ::GetTickCount();
		pIcmp->icmp_sequence = nSeq++;
		pIcmp->icmp_checksum = checksum((USHORT*)buff, sizeof(ICMP_HDR) + 32);
		nRet = ::sendto(sRaw, buff, sizeof(ICMP_HDR) + 32, 0, (SOCKADDR *)&dest, sizeof(dest));
		if(nRet == SOCKET_ERROR)
		{
			printf(" sendto() failed: %d \n", ::WSAGetLastError());
			return -1;
		}
		nRet = ::recvfrom(sRaw, recvBuf, 1024, 0, (sockaddr*)&from, &nLen);
		if(nRet == SOCKET_ERROR)
		{
			if(::WSAGetLastError() == WSAETIMEDOUT)
			{
				printf(" timed out\n");
				continue;
			}
			printf(" recvfrom() failed: %d\n", ::WSAGetLastError());
			return -1;
		}

		// 下面开始解析接收到的ICMP封包
		int nTick = ::GetTickCount();
		if(nRet < sizeof(IPHeader) + sizeof(ICMP_HDR))
		{
			printf(" Too few bytes from %s \n", ::inet_ntoa(from.sin_addr));
		}
		// 接收到的数据中包含IP头，IP头大小为20个字节，所以加20得到ICMP头
		ICMP_HDR* pRecvIcmp = (ICMP_HDR*)(recvBuf + 20); // (ICMP_HDR*)(recvBuf + sizeof(IPHeader));
		if(pRecvIcmp->icmp_type != 0)	// 回显
		{
			printf(" nonecho type %d recvd \n", pRecvIcmp->icmp_type);
			return -1;
		}

		if(pRecvIcmp->icmp_id != ::GetCurrentProcessId())
		{
			printf(" someone else's packet! \n");
			return -1;
		}
		
		printf(" %d bytes from %s:", nRet, inet_ntoa(from.sin_addr));
		printf(" icmp_seq = %d. ", pRecvIcmp->icmp_sequence);
		printf(" time: %d ms", nTick - pRecvIcmp->icmp_timestamp);
		printf(" \n");

		::Sleep(1000);
	}

	return 0;
}