busybox/networking/nslookup.c

/* 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.
 *
 * This applet is the only user of res_init(). Without it,
 * you may avoid pulling in _res global from libc.
 */

/* 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);
		// puts(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;
	struct sockaddr *sa;

#if ENABLE_FEATURE_IPV6
	sa = (struct sockaddr*)_res._u._ext.nsaddrs[0];
	if (!sa)
#endif
		sa = (struct sockaddr*)&_res.nsaddr_list[0];
	server = xmalloc_sockaddr2dotted_noport(sa);

	print_host(server, "Server:");
	if (ENABLE_FEATURE_CLEAN_UP)
		free(server);
	bb_putchar('\n');
}

/* alter the global _res nameserver structure to use
   an explicit dns server instead of what is in /etc/resolv.conf */
static void set_default_dns(const char *server)
{
	len_and_sockaddr *lsa;

	/* NB: this works even with, say, "[::1]:5353"! :) */
	lsa = xhost2sockaddr(server, 53);

	if (lsa->u.sa.sa_family == AF_INET) {
		_res.nscount = 1;
		/* struct copy */
		_res.nsaddr_list[0] = lsa->u.sin;
	}
#if ENABLE_FEATURE_IPV6
	/* Hoped libc can cope with IPv4 address there too.
	 * No such luck, glibc 2.4 segfaults even with IPv6,
	 * maybe I misunderstand how to make glibc use IPv6 addr?
	 * (uclibc 0.9.31+ should work) */
	if (lsa->u.sa.sa_family == AF_INET6) {
		// glibc neither SEGVs nor sends any dgrams with this
		// (strace shows no socket ops):
		//_res.nscount = 0;
		_res._u._ext.nscount = 1;
		/* store a pointer to part of malloc'ed lsa */
		_res._u._ext.nsaddrs[0] = &lsa->u.sin6;
		/* must not free(lsa)! */
	}
#endif
}

int nslookup_main(int argc, char **argv) MAIN_EXTERNALLY_VISIBLE;
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 (!argv[1] || argv[1][0] == '-' || 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 (argv[2])
		set_default_dns(argv[2]);

	server_print();
	return print_host(argv[1], "Name:");
}
1	niro	532	/* 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 tarball for details.
12			*/
13
14			#include <resolv.h>
15	niro	816	#include "libbb.h"
16	niro	532
17			/*
18	niro	816	* I'm only implementing non-interactive mode;
19			* I totally forgot nslookup even had an interactive mode.
20			*
21			* This applet is the only user of res_init(). Without it,
22			* you may avoid pulling in _res global from libc.
23	niro	532	*/
24
25			/* Examples of 'standard' nslookup output
26			* $ nslookup yahoo.com
27			* Server: 128.193.0.10
28			* Address: 128.193.0.10#53
29			*
30			* Non-authoritative answer:
31			* Name: yahoo.com
32			* Address: 216.109.112.135
33			* Name: yahoo.com
34			* Address: 66.94.234.13
35			*
36			* $ nslookup 204.152.191.37
37			* Server: 128.193.4.20
38			* Address: 128.193.4.20#53
39			*
40			* Non-authoritative answer:
41			* 37.191.152.204.in-addr.arpa canonical name = 37.32-27.191.152.204.in-addr.arpa.
42			* 37.32-27.191.152.204.in-addr.arpa name = zeus-pub2.kernel.org.
43			*
44			* Authoritative answers can be found from:
45			* 32-27.191.152.204.in-addr.arpa nameserver = ns1.kernel.org.
46			* 32-27.191.152.204.in-addr.arpa nameserver = ns2.kernel.org.
47			* 32-27.191.152.204.in-addr.arpa nameserver = ns3.kernel.org.
48			* ns1.kernel.org internet address = 140.211.167.34
49			* ns2.kernel.org internet address = 204.152.191.4
50			* ns3.kernel.org internet address = 204.152.191.36
51			*/
52
53			static int print_host(const char hostname, const char header)
54			{
55	niro	816	/* We can't use xhost2sockaddr() - we want to get ALL addresses,
56			* not just one */
57	niro	532	struct addrinfo *result = NULL;
58			int rc;
59			struct addrinfo hint;
60
61			memset(&hint, 0 , sizeof(hint));
62			/* hint.ai_family = AF_UNSPEC; - zero anyway */
63			/* Needed. Or else we will get each address thrice (or more)
64			* for each possible socket type (tcp,udp,raw...): */
65			hint.ai_socktype = SOCK_STREAM;
66			// hint.ai_flags = AI_CANONNAME;
67			rc = getaddrinfo(hostname, NULL /service/, &hint, &result);
68	niro	816
69	niro	532	if (!rc) {
70			struct addrinfo *cur = result;
71	niro	816	unsigned cnt = 0;
72
73			printf("%-10s %s\n", header, hostname);
74			// puts(cur->ai_canonname); ?
75	niro	532	while (cur) {
76	niro	816	char dotted, revhost;
77			dotted = xmalloc_sockaddr2dotted_noport(cur->ai_addr);
78			revhost = xmalloc_sockaddr2hostonly_noport(cur->ai_addr);
79
80			printf("Address %u: %s%c", ++cnt, dotted, revhost ? ' ' : '\n');
81			if (revhost) {
82			puts(revhost);
83			if (ENABLE_FEATURE_CLEAN_UP)
84			free(revhost);
85			}
86			if (ENABLE_FEATURE_CLEAN_UP)
87			free(dotted);
88	niro	532	cur = cur->ai_next;
89			}
90			} else {
91	niro	816	#if ENABLE_VERBOSE_RESOLUTION_ERRORS
92			bb_error_msg("can't resolve '%s': %s", hostname, gai_strerror(rc));
93			#else
94			bb_error_msg("can't resolve '%s'", hostname);
95			#endif
96	niro	532	}
97	niro	816	if (ENABLE_FEATURE_CLEAN_UP)
98			freeaddrinfo(result);
99	niro	532	return (rc != 0);
100			}
101
102	niro	816	/* lookup the default nameserver and display it */
103			static void server_print(void)
104			{
105			char *server;
106	niro	984	struct sockaddr *sa;
107	niro	532
108	niro	984	#if ENABLE_FEATURE_IPV6
109			sa = (struct sockaddr*)_res._u._ext.nsaddrs[0];
110			if (!sa)
111			#endif
112			sa = (struct sockaddr*)&_res.nsaddr_list[0];
113			server = xmalloc_sockaddr2dotted_noport(sa);
114
115	niro	816	print_host(server, "Server:");
116			if (ENABLE_FEATURE_CLEAN_UP)
117			free(server);
118			bb_putchar('\n');
119			}
120
121	niro	532	/* alter the global _res nameserver structure to use
122	niro	816	an explicit dns server instead of what is in /etc/resolv.conf */
123	niro	984	static void set_default_dns(const char *server)
124	niro	532	{
125	niro	984	len_and_sockaddr *lsa;
126	niro	532
127	niro	984	/* NB: this works even with, say, "[::1]:5353"! :) */
128			lsa = xhost2sockaddr(server, 53);
129
130			if (lsa->u.sa.sa_family == AF_INET) {
131	niro	532	_res.nscount = 1;
132	niro	984	/* struct copy */
133			_res.nsaddr_list[0] = lsa->u.sin;
134	niro	532	}
135	niro	984	#if ENABLE_FEATURE_IPV6
136			/* Hoped libc can cope with IPv4 address there too.
137			* No such luck, glibc 2.4 segfaults even with IPv6,
138			* maybe I misunderstand how to make glibc use IPv6 addr?
139			* (uclibc 0.9.31+ should work) */
140			if (lsa->u.sa.sa_family == AF_INET6) {
141			// glibc neither SEGVs nor sends any dgrams with this
142			// (strace shows no socket ops):
143			//_res.nscount = 0;
144			_res._u._ext.nscount = 1;
145			/* store a pointer to part of malloc'ed lsa */
146			_res._u._ext.nsaddrs[0] = &lsa->u.sin6;
147			/* must not free(lsa)! */
148			}
149			#endif
150	niro	532	}
151
152	niro	816	int nslookup_main(int argc, char **argv) MAIN_EXTERNALLY_VISIBLE;
153	niro	532	int nslookup_main(int argc, char **argv)
154			{
155	niro	816	/* We allow 1 or 2 arguments.
156			* The first is the name to be looked up and the second is an
157			* optional DNS server with which to do the lookup.
158			* More than 3 arguments is an error to follow the pattern of the
159			* standard nslookup */
160			if (!argv[1] \|\| argv[1][0] == '-' \|\| argc > 3)
161			bb_show_usage();
162	niro	532
163	niro	816	/* initialize DNS structure _res used in printing the default
164			* name server and in the explicit name server option feature. */
165	niro	532	res_init();
166	niro	816	/* rfc2133 says this enables IPv6 lookups */
167			/* (but it also says "may be enabled in /etc/resolv.conf") */
168			/_res.options \|= RES_USE_INET6;/
169	niro	532
170	niro	816	if (argv[2])
171	niro	532	set_default_dns(argv[2]);
172
173			server_print();
174	niro	816	return print_host(argv[1], "Name:");
175	niro	532	}