nslookup.c

/*
 * Mini nslookup implementation for busybox
 *
 *
 * Copyright (C) 2000 by Lineo, inc.
 * Written by John Beppu <beppu@lineo.com>
 *
 * This program is free software; you can redistribute it and/or modify
 * it under the terms of the GNU General Public License as published by
 * the Free Software Foundation; either version 2 of the License, or
 * (at your option) any later version.
 *
 * This program is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
 * General Public License for more details.
 *
 * You should have received a copy of the GNU General Public License
 * along with this program; if not, write to the Free Software
 * Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA 02111-1307 USA
 *
 */

#include "internal.h"
#include <ctype.h>
#include <errno.h>
#include <stdio.h>
#include <string.h>

#include <netdb.h>
#include <sys/socket.h>
#include <sys/types.h>
#include <netinet/in.h>

/*
 |  I'm only implementing non-interactive mode;
 |  I totally forgot nslookup even had an interactive mode.
 |
 |  [ TODO ]
 |  + find out how to use non-default name servers
 |  + find out how the real nslookup gets the default name server
 */

static const char nslookup_usage[] =
    "nslookup [HOST]\n\n"
;


/* I have to see how the real nslookup does this.
 * I could dig through /etc/resolv.conf, but is there a
 * better (programatic) way?
 */
static void
server_fprint(FILE *dst)
{
    fprintf(dst, "Server:  %s\n", "something");
    fprintf(dst, "Address:  %s\n\n", "something");
}

/* only works for IPv4 */
static int
addr_fprint(char *addr, FILE *dst)
{
    uint8_t	split[4];
    uint32_t	ip;
    uint32_t	*x = (uint32_t *) addr;

    ip = ntohl(*x);
    split[0] = (ip & 0xff000000) >> 24;
    split[1] = (ip & 0x00ff0000) >> 16;
    split[2] = (ip & 0x0000ff00) >>  8;
    split[3] = (ip & 0x000000ff);
    fprintf (
	dst, "%d.%d.%d.%d", 
	split[0], split[1], split[2], split[3]
    );
    return 0;
}

/* changes a c-string matching the perl regex \d+\.\d+\.\d+\.\d+
 * into a uint32_t
 */
static uint32_t
str_to_addr(const char *addr)
{
    uint32_t	split[4];
    uint32_t	ip;

    sscanf(addr, "%d.%d.%d.%d", 
	    &split[0], &split[1], &split[2], &split[3]);

    /* assuming sscanf worked */
    ip = (split[0] << 24) |
	 (split[1] << 16) |
	 (split[2] << 8)  |
	 (split[3]);

    return htonl(ip);
}

/* takes the NULL-terminated array h_addr_list, and
 * prints its contents appropriately
 */
static int
addr_list_fprint(char **h_addr_list, FILE *dst)
{
    int	    i, j;
    char    *addr_string = (h_addr_list[1]) 
	? "Addresses" 
	: "Address";

    fprintf(dst, "%s:  ", addr_string);
    for (i = 0, j = 0; h_addr_list[i]; i++, j++) {
	addr_fprint(h_addr_list[i], dst);

	/* real nslookup does this */
	if (j == 4) {
	    if (h_addr_list[i+1]) {
		fprintf(dst, "\n          ");
	    }
	    j = 0;
	} else {
	    if (h_addr_list[i+1]) {
		fprintf(dst, ", ");
	    }
	}

    }
    fprintf(dst,"\n");
    return 0;
}

/* gethostbyaddr wrapper */
static struct hostent *
gethostbyaddr_wrapper(const char *address)
{
    struct in_addr  addr;

    addr.s_addr = str_to_addr(address);
    return gethostbyaddr((char *) &addr, 4, AF_INET); /* IPv4 only for now */
}

/* print the results as nslookup would */
static struct hostent *
hostent_fprint(struct hostent *host, FILE *dst)
{
    if (host) {
	fprintf(dst, "Name:    %s\n", host->h_name);
	addr_list_fprint(host->h_addr_list, dst);
    } else {
	fprintf(dst, "*** %s\n", hstrerror(h_errno));
    }
    return host;
}


/* naive function to check whether char *s is an ip address */
static int
is_ip_address(const char *s)
{
    while (*s) {
	if ((isdigit(*s)) || (*s == '.')) { s++; continue; }
	return 0;
    }
    return 1;
}

/* ________________________________________________________________________ */
int
nslookup_main(int argc, char **argv)
{
    struct hostent  *host;

    if (argc < 2) {
	usage(nslookup_usage);
    }

    server_fprint(stdout);
    if (is_ip_address(argv[1])) {
	host = gethostbyaddr_wrapper(argv[1]); 
    } else {
	host = gethostbyname(argv[1]);
    }
    hostent_fprint(host, stdout);
    return 0;
}

/* $Id: nslookup.c,v 1.3 2000/02/07 05:29:42 erik Exp $ */