[ICMP] Minor Project

icmp.c

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

int main() {

  libnet_t *l;  /* libnet context */
  char errbuf[LIBNET_ERRBUF_SIZE], ip_addr_str[16], *payload;
  u_int32_t ip_addr;
  u_int16_t id, seq;
  FILE *fp;
  fp = fopen("base64.txt","r");
  payload = (char *) malloc (sizeof(char *)*100);
  fscanf(fp, "%s", payload);
  puts(payload);
//  char payload[] = "libnet :D";
  int bytes_written;

  l = libnet_init(LIBNET_RAW4, NULL, errbuf);
  if ( l == NULL ) {
    fprintf(stderr, "libnet_init() failed: %s\n", errbuf);
    exit(EXIT_FAILURE);
  }

  /* Generating a random id */

  libnet_seed_prand (l);
  id = (u_int16_t)libnet_get_prand(LIBNET_PR16);

  /* Getting destination IP address */

  printf("Destination IP address: ");
  scanf("%15s",ip_addr_str);

  ip_addr = libnet_name2addr4(l, ip_addr_str,\
                  LIBNET_DONT_RESOLVE);

  if ( ip_addr == -1 ) {
    fprintf(stderr, "Error converting IP address.\n");
    libnet_destroy(l);
    exit(EXIT_FAILURE);
  }

  /* Building ICMP header */

  seq = 1;

  if (libnet_build_icmpv4_echo(ICMP_ECHO, 0, 0, id, seq,\
        (u_int8_t*)payload,sizeof(payload), l, 0) == -1)
  {
    fprintf(stderr, "Error building ICMP header: %s\n",\
        libnet_geterror(l));
    libnet_destroy(l);
    exit(EXIT_FAILURE);
  }

  /* Building IP header */

  if (libnet_autobuild_ipv4(LIBNET_IPV4_H +\
        LIBNET_ICMPV4_ECHO_H + sizeof(payload),\
        IPPROTO_ICMP, ip_addr, l) == -1 )
  {
    fprintf(stderr, "Error building IP header: %s\n",\
        libnet_geterror(l));
    libnet_destroy(l);
    exit(EXIT_FAILURE);
  }

  /* Writing packet */

  bytes_written = libnet_write(l);
  if ( bytes_written != -1 )
    printf("%d bytes written.\n", bytes_written);
  else
    fprintf(stderr, "Error writing packet: %s\n",\
        libnet_geterror(l));

  libnet_destroy(l);
  fclose(fp);
  return 0;
}