void ip_print (struct iphdr * ip)
{
    printf ("ver:      %hu\n"
	    "ihl:      %hu\n"
	    "tos:      ",
	    ip->version, ip->ihl, ip->tos);
    print_bin (ip->tos);
    printf (" bin\n");
    printf ("tot_len:  %u\n"
	    "id:       %u\n"
	    "frag_off: %d\n"
	    "ttl:      %hu\n"
	    "protocol: %hu\n"
	    "check:    %u\n",
	    ip->tot_len,
	    ip->id, 
	    ip->frag_off,
	    ip->ttl,
	    ip->protocol,
	    ip->check
    );
    printf ("saddr:    %s (%lu)\n", inet_ntoa(ip->saddr), ip->saddr);
    printf ("daddr:    %s (%lu)\n", inet_ntoa(ip->daddr), ip->daddr);
}