#include <sys/socket.h>
#include <sys/types.h>
#include <netinet/ip.h>
#include <netinet/ip_icmp.h>
#include <string.h>

#include "exam.h"
char buffer[1024];

/*校验码的计算*/
unsigned short cksum(unsigned char *data, int len)
{
    int sum=0;
    int odd = len & 0x01;
    unsigned short *value = (unsigned short*)data; 
    while( len & 0xfffe)
    {
       sum += *(unsigned short*)data;
       data += 2;
       len -=2;
    }
    if(odd)
    {
       unsigned short tmp = ((*data)<<8)&0xff00;
       sum += tmp;
    }
    sum = (sum >>16) + (sum & 0xffff);
    sum += (sum >>16) ;       
    return ~sum; 
}

int main()
{
    int s;
    int ret = 0; 
    int on = 1; 
    struct icmp * icmp; 
    struct ip * ip = (struct ip *)buffer; 
    struct sockaddr_in addr;

    s = socket(AF_INET, SOCK_RAW, 1); //使用原始套接字
    failure("socket", s, -1); 
    memset(buffer, '\0', 1024);

    addr.sin_family = AF_INET;
    addr.sin_addr.s_addr = inet_addr("119.75.213.51"); //百度的ip，目的是伪造IP地址给百度发数据包

    ret = setsockopt(s, IPPROTO_IP, IP_HDRINCL, &on, sizeof(on)); //自己构造ip头的选项
    failure("setsockopt", ret, -1);

    /*ip头的信息*/
    ip->ip_hl = 5; ip->ip_v = 4; ip->ip_tos = 0; ip->ip_len = htons(32); 
    ip->ip_id = 0; ip->ip_off = 0; 
    ip->ip_ttl = 56; ip->ip_p = 1; ip->ip_sum = 0;  
    ip->ip_src.s_addr = inet_addr("192.168.205.199"); //这是伪造的ip，本机的ip当然不是这个啦 
    ip->ip_dst.s_addr = inet_addr("119.75.213.51");

    /*icmp头信息*/
    icmp = (struct icmp*)(buffer+20); 
    icmp->icmp_type = ICMP_ECHO; icmp->icmp_code=0; icmp->icmp_cksum =0;
    icmp->icmp_id = 1234; icmp->icmp_seq = 8080;
    icmp->icmp_cksum = cksum((char*)icmp, 12);

    /*发送*/
    ret = sendto(s, buffer, 32, 0, (struct sockaddr*)&addr, sizeof(addr));
    failure("send", ret, -1);

    return 0;
}

#ifndef EXAM_H
#define EXAM_H

#include <stdio.h>
#include <stdlib.h>

#define failure(msg, ret, error_code) \
{              \
    if(ret == error_code)       \
    {             \
       perror(msg);        \
       exit(EXIT_FAILURE);      \
    }             \
}

#define success(msg, ret, success_code)\
{              \
    if(ret != success_code)      \
    {             \
       perror(msg);        \
       exit(EXIT_FAILURE);      \
    }             \
}

#endif