source: branches/3.2/mindi-busybox/networking/nslookup.c @ 3232

Last change on this file since 3232 was 3232, checked in by bruno, 6 years ago
  • Update mindi-busybox to 1.21.1
File size: 5.5 KB
Line 
1/* vi: set sw=4 ts=4: */
2/*
3 * Mini nslookup implementation for busybox
4 *
5 * Copyright (C) 1999,2000 by Lineo, inc. and John Beppu
6 * Copyright (C) 1999,2000,2001 by John Beppu <beppu@codepoet.org>
7 *
8 * Correct default name server display and explicit name server option
9 * added by Ben Zeckel <bzeckel@hmc.edu> June 2001
10 *
11 * Licensed under GPLv2 or later, see file LICENSE in this source tree.
12 */
13
14//usage:#define nslookup_trivial_usage
15//usage:       "[HOST] [SERVER]"
16//usage:#define nslookup_full_usage "\n\n"
17//usage:       "Query the nameserver for the IP address of the given HOST\n"
18//usage:       "optionally using a specified DNS server"
19//usage:
20//usage:#define nslookup_example_usage
21//usage:       "$ nslookup localhost\n"
22//usage:       "Server:     default\n"
23//usage:       "Address:    default\n"
24//usage:       "\n"
25//usage:       "Name:       debian\n"
26//usage:       "Address:    127.0.0.1\n"
27
28#include <resolv.h>
29#include "libbb.h"
30
31/*
32 * I'm only implementing non-interactive mode;
33 * I totally forgot nslookup even had an interactive mode.
34 *
35 * This applet is the only user of res_init(). Without it,
36 * you may avoid pulling in _res global from libc.
37 */
38
39/* Examples of 'standard' nslookup output
40 * $ nslookup yahoo.com
41 * Server:         128.193.0.10
42 * Address:        128.193.0.10#53
43 *
44 * Non-authoritative answer:
45 * Name:   yahoo.com
46 * Address: 216.109.112.135
47 * Name:   yahoo.com
48 * Address: 66.94.234.13
49 *
50 * $ nslookup 204.152.191.37
51 * Server:         128.193.4.20
52 * Address:        128.193.4.20#53
53 *
54 * Non-authoritative answer:
55 * 37.191.152.204.in-addr.arpa     canonical name = 37.32-27.191.152.204.in-addr.arpa.
56 * 37.32-27.191.152.204.in-addr.arpa       name = zeus-pub2.kernel.org.
57 *
58 * Authoritative answers can be found from:
59 * 32-27.191.152.204.in-addr.arpa  nameserver = ns1.kernel.org.
60 * 32-27.191.152.204.in-addr.arpa  nameserver = ns2.kernel.org.
61 * 32-27.191.152.204.in-addr.arpa  nameserver = ns3.kernel.org.
62 * ns1.kernel.org  internet address = 140.211.167.34
63 * ns2.kernel.org  internet address = 204.152.191.4
64 * ns3.kernel.org  internet address = 204.152.191.36
65 */
66
67static int print_host(const char *hostname, const char *header)
68{
69    /* We can't use xhost2sockaddr() - we want to get ALL addresses,
70     * not just one */
71    struct addrinfo *result = NULL;
72    int rc;
73    struct addrinfo hint;
74
75    memset(&hint, 0 , sizeof(hint));
76    /* hint.ai_family = AF_UNSPEC; - zero anyway */
77    /* Needed. Or else we will get each address thrice (or more)
78     * for each possible socket type (tcp,udp,raw...): */
79    hint.ai_socktype = SOCK_STREAM;
80    // hint.ai_flags = AI_CANONNAME;
81    rc = getaddrinfo(hostname, NULL /*service*/, &hint, &result);
82
83    if (rc == 0) {
84        struct addrinfo *cur = result;
85        unsigned cnt = 0;
86
87        printf("%-10s %s\n", header, hostname);
88        // puts(cur->ai_canonname); ?
89        while (cur) {
90            char *dotted, *revhost;
91            dotted = xmalloc_sockaddr2dotted_noport(cur->ai_addr);
92            revhost = xmalloc_sockaddr2hostonly_noport(cur->ai_addr);
93
94            printf("Address %u: %s%c", ++cnt, dotted, revhost ? ' ' : '\n');
95            if (revhost) {
96                puts(revhost);
97                if (ENABLE_FEATURE_CLEAN_UP)
98                    free(revhost);
99            }
100            if (ENABLE_FEATURE_CLEAN_UP)
101                free(dotted);
102            cur = cur->ai_next;
103        }
104    } else {
105#if ENABLE_VERBOSE_RESOLUTION_ERRORS
106        bb_error_msg("can't resolve '%s': %s", hostname, gai_strerror(rc));
107#else
108        bb_error_msg("can't resolve '%s'", hostname);
109#endif
110    }
111    if (ENABLE_FEATURE_CLEAN_UP && result)
112        freeaddrinfo(result);
113    return (rc != 0);
114}
115
116/* lookup the default nameserver and display it */
117static void server_print(void)
118{
119    char *server;
120    struct sockaddr *sa;
121
122#if ENABLE_FEATURE_IPV6
123    sa = (struct sockaddr*)_res._u._ext.nsaddrs[0];
124    if (!sa)
125#endif
126        sa = (struct sockaddr*)&_res.nsaddr_list[0];
127    server = xmalloc_sockaddr2dotted_noport(sa);
128
129    print_host(server, "Server:");
130    if (ENABLE_FEATURE_CLEAN_UP)
131        free(server);
132    bb_putchar('\n');
133}
134
135/* alter the global _res nameserver structure to use
136   an explicit dns server instead of what is in /etc/resolv.conf */
137static void set_default_dns(const char *server)
138{
139    len_and_sockaddr *lsa;
140
141    /* NB: this works even with, say, "[::1]:5353"! :) */
142    lsa = xhost2sockaddr(server, 53);
143
144    if (lsa->u.sa.sa_family == AF_INET) {
145        _res.nscount = 1;
146        /* struct copy */
147        _res.nsaddr_list[0] = lsa->u.sin;
148    }
149#if ENABLE_FEATURE_IPV6
150    /* Hoped libc can cope with IPv4 address there too.
151     * No such luck, glibc 2.4 segfaults even with IPv6,
152     * maybe I misunderstand how to make glibc use IPv6 addr?
153     * (uclibc 0.9.31+ should work) */
154    if (lsa->u.sa.sa_family == AF_INET6) {
155        // glibc neither SEGVs nor sends any dgrams with this
156        // (strace shows no socket ops):
157        //_res.nscount = 0;
158        _res._u._ext.nscount = 1;
159        /* store a pointer to part of malloc'ed lsa */
160        _res._u._ext.nsaddrs[0] = &lsa->u.sin6;
161        /* must not free(lsa)! */
162    }
163#endif
164}
165
166int nslookup_main(int argc, char **argv) MAIN_EXTERNALLY_VISIBLE;
167int nslookup_main(int argc, char **argv)
168{
169    /* We allow 1 or 2 arguments.
170     * The first is the name to be looked up and the second is an
171     * optional DNS server with which to do the lookup.
172     * More than 3 arguments is an error to follow the pattern of the
173     * standard nslookup */
174    if (!argv[1] || argv[1][0] == '-' || argc > 3)
175        bb_show_usage();
176
177    /* initialize DNS structure _res used in printing the default
178     * name server and in the explicit name server option feature. */
179    res_init();
180    /* rfc2133 says this enables IPv6 lookups */
181    /* (but it also says "may be enabled in /etc/resolv.conf") */
182    /*_res.options |= RES_USE_INET6;*/
183
184    if (argv[2])
185        set_default_dns(argv[2]);
186
187    server_print();
188    return print_host(argv[1], "Name:");
189}
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