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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//config:config NSLOOKUP
14//config: bool "nslookup"
15//config: default y
16//config: help
17//config: nslookup is a tool to query Internet name servers.
18
19//applet:IF_NSLOOKUP(APPLET(nslookup, BB_DIR_USR_BIN, BB_SUID_DROP))
20
21//kbuild:lib-$(CONFIG_NSLOOKUP) += nslookup.o
22
23//usage:#define nslookup_trivial_usage
24//usage: "[HOST] [SERVER]"
25//usage:#define nslookup_full_usage "\n\n"
26//usage: "Query the nameserver for the IP address of the given HOST\n"
27//usage: "optionally using a specified DNS server"
28//usage:
29//usage:#define nslookup_example_usage
30//usage: "$ nslookup localhost\n"
31//usage: "Server: default\n"
32//usage: "Address: default\n"
33//usage: "\n"
34//usage: "Name: debian\n"
35//usage: "Address: 127.0.0.1\n"
36
37#include <resolv.h>
38#include "libbb.h"
39
40#ifdef ANDROID
41# include <netinet/in.h>
42# if ENABLE_FEATURE_IPV6
43# include <netinet/in6.h>
44# endif
45# define ANDROID_CHANGES
46# ifdef BIONIC_L
47# include <arpa/nameser.h>
48# include <dns/include/resolv_private.h>
49# include <dns/resolv/res_private.h>
50# else
51# include <arpa_nameser.h>
52# include <private/resolv_private.h>
53# include <netbsd/resolv/res_private.h>
54# endif
55
56static struct __res_state res_st;
57struct __res_state * __res_state(void)
58{
59 return &res_st;
60}
61#endif
62
63#define EXT(res) ((&res)->_u._ext)
64
65/*
66 * I'm only implementing non-interactive mode;
67 * I totally forgot nslookup even had an interactive mode.
68 *
69 * This applet is the only user of res_init(). Without it,
70 * you may avoid pulling in _res global from libc.
71 */
72
73/* Examples of 'standard' nslookup output
74 * $ nslookup yahoo.com
75 * Server: 128.193.0.10
76 * Address: 128.193.0.10#53
77 *
78 * Non-authoritative answer:
79 * Name: yahoo.com
80 * Address: 216.109.112.135
81 * Name: yahoo.com
82 * Address: 66.94.234.13
83 *
84 * $ nslookup 204.152.191.37
85 * Server: 128.193.4.20
86 * Address: 128.193.4.20#53
87 *
88 * Non-authoritative answer:
89 * 37.191.152.204.in-addr.arpa canonical name = 37.32-27.191.152.204.in-addr.arpa.
90 * 37.32-27.191.152.204.in-addr.arpa name = zeus-pub2.kernel.org.
91 *
92 * Authoritative answers can be found from:
93 * 32-27.191.152.204.in-addr.arpa nameserver = ns1.kernel.org.
94 * 32-27.191.152.204.in-addr.arpa nameserver = ns2.kernel.org.
95 * 32-27.191.152.204.in-addr.arpa nameserver = ns3.kernel.org.
96 * ns1.kernel.org internet address = 140.211.167.34
97 * ns2.kernel.org internet address = 204.152.191.4
98 * ns3.kernel.org internet address = 204.152.191.36
99 */
100
101static int print_host(const char *hostname, const char *header)
102{
103 /* We can't use xhost2sockaddr() - we want to get ALL addresses,
104 * not just one */
105 struct addrinfo *result = NULL;
106 int rc;
107 struct addrinfo hint;
108
109 memset(&hint, 0 , sizeof(hint));
110 /* hint.ai_family = AF_UNSPEC; - zero anyway */
111 /* Needed. Or else we will get each address thrice (or more)
112 * for each possible socket type (tcp,udp,raw...): */
113 hint.ai_socktype = SOCK_STREAM;
114 // hint.ai_flags = AI_CANONNAME;
115 rc = getaddrinfo(hostname, NULL /*service*/, &hint, &result);
116
117 if (rc == 0) {
118 struct addrinfo *cur = result;
119 unsigned cnt = 0;
120
121 printf("%-10s %s\n", header, hostname);
122 // puts(cur->ai_canonname); ?
123 while (cur) {
124 char *dotted, *revhost;
125 dotted = xmalloc_sockaddr2dotted_noport(cur->ai_addr);
126 revhost = xmalloc_sockaddr2hostonly_noport(cur->ai_addr);
127
128 printf("Address %u: %s%c", ++cnt, dotted, revhost ? ' ' : '\n');
129 if (revhost) {
130 puts(revhost);
131 if (ENABLE_FEATURE_CLEAN_UP)
132 free(revhost);
133 }
134 if (ENABLE_FEATURE_CLEAN_UP)
135 free(dotted);
136 cur = cur->ai_next;
137 }
138 } else {
139#if ENABLE_VERBOSE_RESOLUTION_ERRORS
140 bb_error_msg("can't resolve '%s': %s", hostname, gai_strerror(rc));
141#else
142 bb_error_msg("can't resolve '%s'", hostname);
143#endif
144 }
145 if (ENABLE_FEATURE_CLEAN_UP && result)
146 freeaddrinfo(result);
147 return (rc != 0);
148}
149
150/* lookup the default nameserver and display it */
151static void server_print(void)
152{
153 char *server;
154 struct sockaddr *sa = NULL;
155
156#if ENABLE_FEATURE_IPV6
157# ifdef ANDROID
158 if (EXT(_res).ext)
159 sa = (struct sockaddr*) &EXT(_res).ext->nsaddrs[0];
160# else
161 sa = (struct sockaddr*)_res._u._ext.nsaddrs[0];
162# endif
163
164 if (!sa)
165#endif
166 sa = (struct sockaddr*) &_res.nsaddr_list[0];
167 server = xmalloc_sockaddr2dotted_noport(sa);
168
169 print_host(server, "Server:");
170 if (ENABLE_FEATURE_CLEAN_UP)
171 free(server);
172 bb_putchar('\n');
173}
174
175/* alter the global _res nameserver structure to use
176 an explicit dns server instead of what is in /etc/resolv.conf */
177static void set_default_dns(const char *server)
178{
179 len_and_sockaddr *lsa;
180
181 if (!server)
182 return;
183
184 /* NB: this works even with, say, "[::1]:53"! :) */
185 lsa = xhost2sockaddr(server, 53);
186
187 if (lsa->u.sa.sa_family == AF_INET) {
188 _res.nscount = 1;
189 /* struct copy */
190 _res.nsaddr_list[0] = lsa->u.sin;
191 }
192
193#if ENABLE_FEATURE_IPV6
194 /* Hoped libc can cope with IPv4 address there too.
195 * No such luck, glibc 2.4 segfaults even with IPv6,
196 * maybe I misunderstand how to make glibc use IPv6 addr?
197 * (uclibc 0.9.31+ should work) */
198 if (lsa->u.sa.sa_family == AF_INET6) {
199 // glibc neither SEGVs nor sends any dgrams with this
200 // (strace shows no socket ops):
201 //_res.nscount = 0;
202 #ifdef ANDROID
203 if (EXT(_res).ext) {
204 EXT(_res).nscount = 1;
205 memcpy(&EXT(_res).ext->nsaddrs[0].sin6, &lsa->u.sin6,
206 sizeof(struct sockaddr_in6));
207 }
208 #else
209 /* store a pointer to part of malloc'ed lsa */
210 _res._u._ext.nscount = 1;
211 _res._u._ext.nsaddrs[0] = &lsa->u.sin6;
212 /* must not free(lsa)! */
213 #endif
214 }
215#endif
216}
217
218int nslookup_main(int argc, char **argv) MAIN_EXTERNALLY_VISIBLE;
219int nslookup_main(int argc, char **argv)
220{
221 /* We allow 1 or 2 arguments.
222 * The first is the name to be looked up and the second is an
223 * optional DNS server with which to do the lookup.
224 * More than 3 arguments is an error to follow the pattern of the
225 * standard nslookup */
226 if (!argv[1] || argv[1][0] == '-' || argc > 3)
227 bb_show_usage();
228
229 /* initialize DNS structure _res used in printing the default
230 * name server and in the explicit name server option feature. */
231 res_init();
232
233#ifdef ANDROID
234 res_ninit(&_res);
235#endif
236
237 /* rfc2133 says this enables IPv6 lookups */
238 /* (but it also says "may be enabled in /etc/resolv.conf") */
239 /*_res.options |= RES_USE_INET6;*/
240
241 set_default_dns(argv[2]);
242
243 server_print();
244
245 /* getaddrinfo and friends are free to request a resolver
246 * reinitialization. Just in case, set_default_dns() again
247 * after getaddrinfo (in server_print). This reportedly helps
248 * with bug 675 "nslookup does not properly use second argument"
249 * at least on Debian Wheezy and Openwrt AA (eglibc based).
250 */
251 set_default_dns(argv[2]);
252
253 return print_host(argv[1], "Name:");
254}
255
generated by cgit at 2024-05-15 01:45:22 (GMT)