source: MondoRescue/branches/stable/mindi-busybox/networking/nslookup.c@ 821

/* vi: set sw=4 ts=4: */
/*
 * Mini nslookup implementation for busybox
 *
 * Copyright (C) 1999,2000 by Lineo, inc. and John Beppu
 * Copyright (C) 1999,2000,2001 by John Beppu <beppu@codepoet.org>
 *
 * Correct default name server display and explicit name server option
 * added by Ben Zeckel <bzeckel@hmc.edu> June 2001
 *
 * 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 <ctype.h>
#include <errno.h>
#include <stdio.h>
#include <string.h>
#include <stdlib.h>

#include <stdint.h>
#include <netdb.h>
#include <sys/socket.h>
#include <sys/types.h>
#include <netinet/in.h>
#include <resolv.h>
#include <arpa/inet.h>
#include "busybox.h"

/*
 |  I'm only implementing non-interactive mode;
 |  I totally forgot nslookup even had an interactive mode.
 */

/* only works for IPv4 */
static int addr_fprint(char *addr)
{
    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);
    printf("%d.%d.%d.%d", split[0], split[1], split[2], split[3]);
    return 0;
}

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

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

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

    }
    printf("\n");
    return 0;
}

/* print the results as nslookup would */
static struct hostent *hostent_fprint(struct hostent *host, const char *server_host)
{
    if (host) {
        printf("%s     %s\n", server_host, host->h_name);
        addr_list_fprint(host->h_addr_list);
    } else {
        printf("*** Unknown host\n");
    }
    return host;
}

/* 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);
}

/* 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 */
}

/* lookup the default nameserver and display it */
static inline void server_print(void)
{
    struct sockaddr_in def = _res.nsaddr_list[0];
    char *ip = inet_ntoa(def.sin_addr);

    hostent_fprint(gethostbyaddr_wrapper(ip), "Server:");
    printf("\n");
}

/* alter the global _res nameserver structure to use
   an explicit dns server instead of what is in /etc/resolv.h */
static inline void set_default_dns(char *server)
{
    struct in_addr server_in_addr;

    if(inet_aton(server,&server_in_addr))
    {
        _res.nscount = 1;
        _res.nsaddr_list[0].sin_addr = server_in_addr;
    }
}

/* 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;

    /*
    * initialize DNS structure _res used in printing the default
    * name server and in the explicit name server option feature.
    */

    res_init();

    /*
    * We allow 1 or 2 arguments.
    * The first is the name to be looked up and the second is an
    * optional DNS server with which to do the lookup.
    * More than 3 arguments is an error to follow the pattern of the
    * standard nslookup
    */

    if (argc < 2 || *argv[1]=='-' || argc > 3)
        bb_show_usage();
    else if(argc == 3)
        set_default_dns(argv[2]);

    server_print();
    if (is_ip_address(argv[1])) {
        host = gethostbyaddr_wrapper(argv[1]);
    } else {
        host = xgethostbyname(argv[1]);
    }
    hostent_fprint(host, "Name:  ");
    if (host) {
        return EXIT_SUCCESS;
    }
    return EXIT_FAILURE;
}

/* $Id: nslookup.c,v 1.33 2004/10/13 07:25:01 andersen Exp $ */