source: MondoRescue/branches/2.2.5/mindi-busybox/networking/nslookup.c@ 1765

/* 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
 *
 * Licensed under GPLv2 or later, see file LICENSE in this tarball for details.
 */

#include <resolv.h>
#include "libbb.h"

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

/* Examples of 'standard' nslookup output
 * $ nslookup yahoo.com
 * Server:         128.193.0.10
 * Address:        128.193.0.10#53
 *
 * Non-authoritative answer:
 * Name:   yahoo.com
 * Address: 216.109.112.135
 * Name:   yahoo.com
 * Address: 66.94.234.13
 *
 * $ nslookup 204.152.191.37
 * Server:         128.193.4.20
 * Address:        128.193.4.20#53
 *
 * Non-authoritative answer:
 * 37.191.152.204.in-addr.arpa     canonical name = 37.32-27.191.152.204.in-addr.arpa.
 * 37.32-27.191.152.204.in-addr.arpa       name = zeus-pub2.kernel.org.
 *
 * Authoritative answers can be found from:
 * 32-27.191.152.204.in-addr.arpa  nameserver = ns1.kernel.org.
 * 32-27.191.152.204.in-addr.arpa  nameserver = ns2.kernel.org.
 * 32-27.191.152.204.in-addr.arpa  nameserver = ns3.kernel.org.
 * ns1.kernel.org  internet address = 140.211.167.34
 * ns2.kernel.org  internet address = 204.152.191.4
 * ns3.kernel.org  internet address = 204.152.191.36
 */

static int print_host(const char *hostname, const char *header)
{
    /* We can't use xhost2sockaddr() - we want to get ALL addresses,
     * not just one */

    struct addrinfo *result = NULL;
    int rc;
    struct addrinfo hint;

    memset(&hint, 0 , sizeof(hint));
    /* hint.ai_family = AF_UNSPEC; - zero anyway */
    /* Needed. Or else we will get each address thrice (or more)
     * for each possible socket type (tcp,udp,raw...): */
    hint.ai_socktype = SOCK_STREAM;
    // hint.ai_flags = AI_CANONNAME;
    rc = getaddrinfo(hostname, NULL /*service*/, &hint, &result);

    if (!rc) {
        struct addrinfo *cur = result;
        unsigned cnt = 0;

        printf("%-10s %s\n", header, hostname);
        // printf("%s\n", cur->ai_canonname); ?
        while (cur) {
            char *dotted, *revhost;
            dotted = xmalloc_sockaddr2dotted_noport(cur->ai_addr);
            revhost = xmalloc_sockaddr2hostonly_noport(cur->ai_addr);

            printf("Address %u: %s%c", ++cnt, dotted, revhost ? ' ' : '\n');
            if (revhost) {
                puts(revhost);
                if (ENABLE_FEATURE_CLEAN_UP)
                    free(revhost);
            }
            if (ENABLE_FEATURE_CLEAN_UP)
                free(dotted);
            cur = cur->ai_next;
        }
    } else {
#if ENABLE_VERBOSE_RESOLUTION_ERRORS
        bb_error_msg("can't resolve '%s': %s", hostname, gai_strerror(rc));
#else
        bb_error_msg("can't resolve '%s'", hostname);
#endif
    }
    if (ENABLE_FEATURE_CLEAN_UP)
        freeaddrinfo(result);
    return (rc != 0);
}

/* lookup the default nameserver and display it */
static void server_print(void)
{
    char *server;

    server = xmalloc_sockaddr2dotted_noport((struct sockaddr*)&_res.nsaddr_list[0]);
    /* I honestly don't know what to do if DNS server has _IPv6 address_.
     * Probably it is listed in
     * _res._u._ext_.nsaddrs[MAXNS] (of type "struct sockaddr_in6*" each)
     * but how to find out whether resolver uses
     * _res.nsaddr_list[] or _res._u._ext_.nsaddrs[], or both?
     * Looks like classic design from hell, BIND-grade. Hard to surpass. */
    print_host(server, "Server:");
    if (ENABLE_FEATURE_CLEAN_UP)
        free(server);
    puts("");
}

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

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

int nslookup_main(int argc, char **argv);
int nslookup_main(int argc, char **argv)
{
    /* 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();

    /* initialize DNS structure _res used in printing the default
     * name server and in the explicit name server option feature. */
    res_init();
    /* rfc2133 says this enables IPv6 lookups */
    /* (but it also says "may be enabled in /etc/resolv.conf|) */
    /*_res.options |= RES_USE_INET6;*/

    if (argc == 3)
        set_default_dns(argv[2]);

    server_print();
    return print_host(argv[1], "Name:");
}