1 /* vi: set sw=4 ts=4: */
3 * Mini nslookup implementation for busybox
5 * Copyright (C) 1999,2000 by Lineo, inc. and John Beppu
6 * Copyright (C) 1999,2000,2001 by John Beppu <beppu@codepoet.org>
8 * Correct default name server display and explicit name server option
9 * added by Ben Zeckel <bzeckel@hmc.edu> June 2001
11 * Licensed under GPLv2 or later, see file LICENSE in this source tree.
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"
20 //usage:#define nslookup_example_usage
21 //usage: "$ nslookup localhost\n"
22 //usage: "Server: default\n"
23 //usage: "Address: default\n"
25 //usage: "Name: debian\n"
26 //usage: "Address: 127.0.0.1\n"
32 * I'm only implementing non-interactive mode;
33 * I totally forgot nslookup even had an interactive mode.
35 * This applet is the only user of res_init(). Without it,
36 * you may avoid pulling in _res global from libc.
39 /* Examples of 'standard' nslookup output
40 * $ nslookup yahoo.com
41 * Server: 128.193.0.10
42 * Address: 128.193.0.10#53
44 * Non-authoritative answer:
46 * Address: 216.109.112.135
48 * Address: 66.94.234.13
50 * $ nslookup 204.152.191.37
51 * Server: 128.193.4.20
52 * Address: 128.193.4.20#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.
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
67 static int print_host(const char *hostname, const char *header)
69 /* We can't use xhost2sockaddr() - we want to get ALL addresses,
71 struct addrinfo *result = NULL;
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);
84 struct addrinfo *cur = result;
87 printf("%-10s %s\n", header, hostname);
88 // puts(cur->ai_canonname); ?
90 char *dotted, *revhost;
91 dotted = xmalloc_sockaddr2dotted_noport(cur->ai_addr);
92 revhost = xmalloc_sockaddr2hostonly_noport(cur->ai_addr);
94 printf("Address %u: %s%c", ++cnt, dotted, revhost ? ' ' : '\n');
97 if (ENABLE_FEATURE_CLEAN_UP)
100 if (ENABLE_FEATURE_CLEAN_UP)
105 #if ENABLE_VERBOSE_RESOLUTION_ERRORS
106 bb_error_msg("can't resolve '%s': %s", hostname, gai_strerror(rc));
108 bb_error_msg("can't resolve '%s'", hostname);
111 if (ENABLE_FEATURE_CLEAN_UP && result)
112 freeaddrinfo(result);
116 /* lookup the default nameserver and display it */
117 static void server_print(void)
122 #if ENABLE_FEATURE_IPV6
123 sa = (struct sockaddr*)_res._u._ext.nsaddrs[0];
126 sa = (struct sockaddr*)&_res.nsaddr_list[0];
127 server = xmalloc_sockaddr2dotted_noport(sa);
129 print_host(server, "Server:");
130 if (ENABLE_FEATURE_CLEAN_UP)
135 /* alter the global _res nameserver structure to use
136 an explicit dns server instead of what is in /etc/resolv.conf */
137 static void set_default_dns(const char *server)
139 len_and_sockaddr *lsa;
141 /* NB: this works even with, say, "[::1]:5353"! :) */
142 lsa = xhost2sockaddr(server, 53);
144 if (lsa->u.sa.sa_family == AF_INET) {
147 _res.nsaddr_list[0] = lsa->u.sin;
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):
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)! */
166 int nslookup_main(int argc, char **argv) MAIN_EXTERNALLY_VISIBLE;
167 int nslookup_main(int argc, char **argv)
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)
177 /* initialize DNS structure _res used in printing the default
178 * name server and in the explicit name server option feature. */
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;*/
185 set_default_dns(argv[2]);
188 return print_host(argv[1], "Name:");