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#include <stdio.h>
#include <errno.h>
#include <netinet/ip.h>
#include <arpa/inet.h>
#include <strings.h>
#include <string.h>
#include <stdlib.h>
#include <netinet/ip_icmp.h>
#include <assert.h>
#define MAX_TTL 30
#define MESSAGES_PER_TTL 3
void print_as_bytes (unsigned char* buff, ssize_t length)
{
for (ssize_t i = 0; i < length; i++, buff++)
printf ("%.2x ", *buff);
}
struct sockaddr_in get_sockaddr_from_ip(char *ip) {
struct sockaddr_in sock;
bzero(&sock, sizeof(sock));
sock.sin_family = AF_INET;
if (!inet_pton(AF_INET, ip, &sock.sin_addr)) {
fprintf(stderr, "Given ip is invalid: %s\n", ip);
exit(EXIT_FAILURE);
}
return sock;
}
int create_raw_icmp_socket() {
int sockfd = socket(AF_INET, SOCK_RAW, IPPROTO_ICMP);
if (sockfd < 0) {
fprintf(stderr, "socket error: %s\n", strerror(errno));
exit(EXIT_FAILURE);
}
return sockfd;
}
uint16_t compute_icmp_checksum (const void *buff, int length)
{
uint32_t sum;
const uint16_t* ptr = buff;
assert (length % 2 == 0);
for (sum = 0; length > 0; length -= 2)
sum += *ptr++;
sum = (sum >> 16) + (sum & 0xffff);
return (uint16_t)(~(sum + (sum >> 16)));
}
struct icmp create_icmp_header() {
static uint16_t pid = 0;
static uint16_t seq = 0;
struct icmp header;
header.icmp_type = ICMP_ECHO;
header.icmp_code = 0;
header.icmp_id = ++pid;
header.icmp_seq = ++seq;
header.icmp_cksum = 0;
header.icmp_cksum = compute_icmp_checksum(
(uint16_t*)&header, sizeof(header));
return header;
}
void send_icmp_packet(int sockfd, struct sockaddr_in *destination, int ttl) {
struct icmp header = create_icmp_header();
setsockopt(sockfd, IPPROTO_IP, IP_TTL, &ttl, sizeof(int));
printf("%ld %d\n", destination->sin_addr.s_addr, sockfd);
ssize_t bytes_sent = sendto(
sockfd,
&header,
sizeof(header),
0,
(struct sockaddr*)destination,
sizeof(*destination)
);
if (bytes_sent == -1) {
fprintf(stderr, "Error while sending ICMP packet: %s\n", strerror(errno));
exit(EXIT_FAILURE);
}
fprintf(stdout, "Bytes sent: %ld\n", bytes_sent);
}
int traceroute(struct sockaddr_in *destination) {
int sockfd = create_raw_icmp_socket();
struct sockaddr_in sender;
socklen_t sender_len = sizeof(sender);
uint8_t buffer[IP_MAXPACKET];
for (int ttl = 1; ttl <= MAX_TTL; ++ttl) {
send_icmp_packet(sockfd, destination, ttl);
}
}
int main(int argc, char * argv[]) {
if (argc < 2) {
fprintf(stderr, "Usage:\n\t%s [host ip]\n", argv[0]);
return 1;
}
struct sockaddr_in destination = get_sockaddr_from_ip(argv[1]);
traceroute(&destination);
}
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