#include <stdio.h> // fread,
#include <stdlib.h>

/*
 * The number of bytes in an ethernet (MAC) address.
 */
#define	ETHER_ADDR_LEN		6

/*
 * The number of bytes in the type field.
 */
#define	ETHER_TYPE_LEN		2

/*
 * The number of bytes in the trailing CRC field.
 */
#define	ETHER_CRC_LEN		4


/*
 * Structure of Ethernet header.
 */
struct	ether_header {
	u_char	ether_dhost[ETHER_ADDR_LEN]; // 6 bytes
	u_char	ether_shost[ETHER_ADDR_LEN]; // 6 bytes
    int   ether_optional;                // 4 bytes
	u_short	ether_len_packet;            // 2 bytes
};



int main(int argc, const char *argv[])
{

    struct ether_header eth_header;

    printf("Sizeof struct eth_header: %d bytes\n", sizeof(struct ether_header));
    printf("Sizeof struct eth_header.ether_dhost: %d bytes\n", sizeof( ((struct ether_header*)0)->ether_dhost ));
    printf("Sizeof struct eth_header.ether_shost: %d bytes\n", sizeof( ((struct ether_header*)0)->ether_shost ));
    printf("Sizeof struct eth_header.ether_optional: %d bytes\n", sizeof( ((struct ether_header*)0)->ether_optional ));
    printf("Sizeof struct eth_header.ether_len_packet: %d bytes\n", sizeof( ((struct ether_header*)0)->ether_len_packet ));
    return 0;
}

/*

bezrukov@Jdanovsk:~/$ ./TTT
Sizeof struct eth_header: 20 bytes
Sizeof struct eth_header.ether_dhost: 6 bytes
Sizeof struct eth_header.ether_shost: 6 bytes
Sizeof struct eth_header.ether_optional: 4 bytes
Sizeof struct eth_header.ether_len_packet: 2 bytes

*/