TunTap Device receiving ping - c

Question

I am trying to get familiar with tuntap devices. I have read the following article:
https://backreference.org/2010/03/26/tuntap-interface-tutorial/
but somehow the code from the article doesn't work.
I have this code:
#include <sys/socket.h> //well get our socket
#include <sys/ioctl.h> //thats our input output control
#include <sys/time.h>
#include <fcntl.h>
#include <asm/types.h> //these are data types liked signed unsingend
#include <math.h>
#include <string.h>
#include <stdio.h>
#include <stdlib.h>
#include <unistd.h> //read write close and stuff
#include <signal.h> //different signals
#include <linux/if_packet.h> //interface for packets
#include <linux/if_ether.h> //interface or ethernet frames
#include <linux/if_arp.h> //interface for arp
#include <linux/if.h>
#include <linux/if_tun.h>
#include <arpa/inet.h>
int tun_alloc(char *dev, int flags) {
struct ifreq ifr;
int fd, err;
char *clonedev = "/dev/net/tun";
/* Arguments taken by the function:
*
* char *dev: the name of an interface (or '\0'). MUST have enough
* space to hold the interface name if '\0' is passed
* int flags: interface flags (eg, IFF_TUN etc.)
*/
/* open the clone device */
if( (fd = open(clonedev, O_RDWR)) < 0 ) {
return fd;
}
/* preparation of the struct ifr, of type "struct ifreq" */
memset(&ifr, 0, sizeof(ifr));
ifr.ifr_flags = flags; /* IFF_TUN or IFF_TAP, plus maybe IFF_NO_PI */
if (*dev) {
/* if a device name was specified, put it in the structure; otherwise,
* the kernel will try to allocate the "next" device of the
* specified type */
strncpy(ifr.ifr_name, dev, IFNAMSIZ);
}
/* try to create the device */
if( (err = ioctl(fd, TUNSETIFF, (void *) &ifr)) < 0 ) {
close(fd);
return err;
}
/* if the operation was successful, write back the name of the
* interface to the variable "dev", so the caller can know
* it. Note that the caller MUST reserve space in *dev (see calling
* code below) */
strcpy(dev, ifr.ifr_name);
/* this is the special file descriptor that the caller will use to talk
* with the virtual interface */
return fd;
}
int main(void){
unsigned int seconds = 1;
char tap_name[IFNAMSIZ];
strcpy(tap_name, "tun0");
printf("%s\n", tap_name);
int tap_fd = tun_alloc(tap_name, IFF_TUN);
void *buffer = (void *)(malloc(3000));
printf("%s\n", tap_name);
if(tap_fd < 0){
perror("Allocating interface");
exit(1);
}
int nread;
while(1){
nread = read(tap_fd, buffer, sizeof(buffer));
if (nread < 0){
perror("Nread: ");
close(tap_fd);
free(buffer);
exit(1);
}
printf("Read %d Bytes from devies %s \n", nread, tap_name);
sleep(seconds);
}
}
I executed this program on one terminal and pinged the interface from another terminal.
But when I ping the interface from the command line (ping 192.168.0.24, I have assigned that IP to the interface), on the terminal of the program there's always written "read 8 Bytes from interface", although the number of bytes should vary when I ping the interface. Does anyone see the mistake?