#include <stdio.h>
#include <netdb.h>
#include <sys/types.h>
#include <sys/socket.h>
#include <netinet/in.h>
#include <arpa/inet.h>
#include <string.h>

#define LENGTH4 4
#define LENGTH6 16

void put_addr(char *, int);

main(
    int argc,
    char *argv[])
{
    int i;
    struct hostent *host, *rev;

    if (argc > 1)
    {
        printf("Host:  %s\n", argv[1]);
        printf("IPv4:\n");
        printf("  Forward Lookup:\n");
        if ((host = gethostbyname2(argv[1], AF_INET)))
        {
            printf("    Name:    %s\n",
                   host->h_name);
            printf("    Type:    %-d\n",
                   host->h_addrtype);
            printf("    Length:  %d\n",
                   host->h_length);
            printf("    Alias List:\n");
            for (i=0; host->h_aliases[i] != NULL; i++)
                printf("      %s\n",
                       host->h_aliases[i]);
            printf("    Address List (Reverse Lookup):\n");
            for (i=0; host->h_addr_list[i] != NULL; i++)
            {
                put_addr(host->h_addr_list[i], AF_INET);
                if ((rev = gethostbyaddr(host->h_addr_list[i],
                                         LENGTH4,
                                         AF_INET)) != NULL)
                {
                    printf(" (%s)\n",
                           rev->h_name);
                }
                else
                    printf("\n");
            }
        }
        else
            printf("    %s\n", hstrerror(h_errno));
        printf("IPv6:\n");
        printf("  Forward Lookup:\n");
        if ((host = gethostbyname2(argv[1], AF_INET6)))
        {
            printf("    Name:    %s\n",
                   host->h_name);
            printf("    Type:    %-d\n",
                   host->h_addrtype);
            printf("    Length:  %d\n",
                   host->h_length);
            printf("    Alias List:\n");
            for (i=0; host->h_aliases[i] != NULL; i++)
                printf("      %s\n",
                       host->h_aliases[i]);
            printf("    Address List (Reverse Lookup):\n");
            for (i=0; host->h_addr_list[i] != NULL; i++)
            {
                put_addr(host->h_addr_list[i], AF_INET6);
                if ((rev = gethostbyaddr(host->h_addr_list[i],
                                         LENGTH6,
                                         AF_INET6)) != NULL)
                {
                    printf(" (%s)\n",
                           rev->h_name);
                }
                else
                    printf("\n");
            }
        }
        else
            printf("    %s\n", hstrerror(h_errno));
    }
}

void put_addr(
    char *addr,
    int type)
{
    int i;

    if (type == AF_INET)
    {
        printf("      ");
        for (i=0; i<LENGTH4; i++)
        {
            printf("%d",
                   (unsigned char)addr[i]);
            if (i < LENGTH4 - 1)
                printf(".");
        }
    }
    else if (type == AF_INET6)
    {
        printf("      ");
        for (i=0; i<LENGTH6; i++)
        {
            printf("%02x%02x",
                   (unsigned char)addr[i],
                   (unsigned char)addr[i+1]);
            i++;
            if (i < LENGTH6 - 1)
                printf(":");
        }
    }
}