Linux network advanced programming-analysis of data packets at each layer

We stole a picture online

We use raw sockets to verify the authenticity of this picture [I know it is true]

#include <iostream>
#include <netinet/in.h>
#include <sys/socket.h>
#include <netinet/ether.h>
#include <unistd.h>
#include <string.h>
#include <string>
#include <stdio.h>


static int32_t Debug = 1;

using namespace std;

int32_t main(int32_t argc, const char *argv[])
{
    unsigned char buf[1519]; // 1518 + 1
	int sock_raw_fd = socket(PF_PACKET, SOCK_RAW, htons(ETH_P_ALL));
	string line(50, '-');
	while(1) {// 解析协议  这些协议的字段我在网络篇都介绍了
        cout << line << endl;
		unsigned char src_mac[18] = "";
		unsigned char dst_mac[18] = "";
		recvfrom(sock_raw_fd, buf, sizeof(buf), 0, NULL, NULL);
		//"%x:%x:%x:%x:%x:%x"
		sprintf((char*)dst_mac, "%02x:%02x:%02x:%02x:%02x:%02x",  // MAC
			buf[0],buf[1],buf[2],buf[3],buf[4],buf[5]);
	
		sprintf((char*)src_mac, "%02x:%02x:%02x:%02x:%02x:%02x",
			buf[6],buf[7],buf[8],buf[9],buf[10],buf[11]);
        
        printf(" MAC : src_mac: %s => dst_mac: %s\n", src_mac, dst_mac);
        if(buf[12] == 0x08 && buf[13] == 0x00){ // IP
            printf("IP packet \n");
            unsigned char src_ip[17] = "";
		    unsigned char dst_ip[17] = "";
            sprintf((char*)src_ip, "%d.%d.%d.%d", buf[26],buf[27],buf[28],buf[29]);
            sprintf((char*)dst_ip, "%d.%d.%d.%d", buf[30],buf[31],buf[32],buf[33]);

             printf(" IP : src_ip: %s => dst_ip: %s\n", src_ip, dst_ip);
            if(buf[23] == 6){
                printf("TCP packet\n");
            }else if(buf[23] == 17){
                printf("UDP packet\n");
            }
            
        }else if(buf[12] == 0x08 && buf[13] == 0x06){
            printf("ARP packet\n");
        }else if(buf[12] == 0x80 && buf[13] == 0x35){
            printf("RARP packet\n");
        }
	    cout << line << endl;
        memset(buf, 0, sizeof(buf));
	}


	return 0;
}

Effect: [ Execute program must add sudo (execute with root authority) ]

Here should be the interaction information between my remote terminal shell and the virtual machine

Ubuntu information in the virtual machine

Local host information

Verified successfully