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LA77

May 23rd, 2025

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#include <arpa/inet.h>
#include <stdio.h>
#include <string.h>
#include <stdlib.h>
#include <sys/socket.h>
#include <unistd.h>
#include <stdbool.h>
#include <netinet/ip_icmp.h>
unsigned short checksum (void *b, int len) {
unsigned short * buf = b;
unsigned int sum = 0;
unsigned short result;
for(sum = 0; len > 1; len -= 2)
sum += * buf ++;
if(len == 1)
sum += *(unsigned char *) buf ;
sum = (sum >> 16) + (sum & 0xFFFF);
sum += (sum >> 16);
result = ~sum;
return result;
}
int main()
{
char ip[16];
scanf("%s", ip);
// creating a raw socket
int sockfd = socket(AF_INET, SOCK_RAW, IPPROTO_ICMP);
if (sockfd < 0) {
perror("Failed to create socket");
exit(EXIT_FAILURE);
}
// Prepare the ICMP packet
struct icmphdr icmp_packet = {0};
memset(&icmp_packet, 0, sizeof(icmp_packet));
// Structure your packet here (e.g., set type, code, checksum, identifier, sequence number)
icmp_packet.checksum = 0;
icmp_packet.type = ICMP_ECHO;
icmp_packet.code = 0;
icmp_packet.un.echo.id = getpid();
icmp_packet.un.echo.sequence = 1;
icmp_packet.checksum = checksum(&icmp_packet, sizeof(icmp_packet));
// Fill in the destination address
struct sockaddr_in dest_addr = {0};
dest_addr.sin_family = AF_INET;
// Set dest_addr.sin_addr based on input IP
if (inet_pton(AF_INET, ip, &(dest_addr.sin_addr)) <= 0) {
perror("Invalid IP address format");
exit(EXIT_FAILURE);
}
// Send the ICMP packet
int result = sendto(sockfd, &icmp_packet, sizeof(struct icmphdr), 0, (struct sockaddr*)&dest_addr, sizeof(dest_addr));
if (result < 0) {
perror("Failed to send ICMP packet");
// Handle error
} else {
printf("ICMP Echo Request sent successfully.\n");
}
char packet[1500]; // A common MTU size is sufficient for buffer
struct sockaddr_in sourceAddress;
socklen_t sourceLength = sizeof(sourceAddress);
// Receive the packet
ssize_t bytes_received = recvfrom(sockfd, packet, sizeof(packet), 0, (struct
sockaddr*)&sourceAddress, &sourceLength);
if (bytes_received < 0) {
perror("Failed to receive packet");
// Handle error
}
struct iphdr *ip_header = (struct iphdr *)packet;
struct icmphdr *icmp_header = (struct icmphdr *)(packet + (ip_header->ihl * 4));
char src_ip[INET_ADDRSTRLEN], dst_ip[INET_ADDRSTRLEN];
inet_ntop(AF_INET, &(ip_header->saddr), src_ip, INET_ADDRSTRLEN);
inet_ntop(AF_INET, &(ip_header->daddr), dst_ip, INET_ADDRSTRLEN);
printf("Destination Address: %s\n", dst_ip);
printf("Source Address: %s\n", src_ip);
printf("TTL: %d\n", ip_header->ttl);
printf("Protocol: %d\n", ip_header->protocol);
printf("Total Length: %d\n", ntohs(ip_header->tot_len));
printf("Version: %d\n", ip_header->version);
close(sockfd);
return 0;
}

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