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