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/* 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 source tree.
*/
//config:config NSLOOKUP
//config: bool "nslookup (4.5 kb)"
//config: default y
//config: help
//config: nslookup is a tool to query Internet name servers.
//applet:IF_NSLOOKUP(APPLET(nslookup, BB_DIR_USR_BIN, BB_SUID_DROP))
//kbuild:lib-$(CONFIG_NSLOOKUP) += nslookup.o
//usage:#define nslookup_trivial_usage
//usage: "[HOST] [SERVER]"
//usage:#define nslookup_full_usage "\n\n"
//usage: "Query the nameserver for the IP address of the given HOST\n"
//usage: "optionally using a specified DNS server"
//usage:
//usage:#define nslookup_example_usage
//usage: "$ nslookup localhost\n"
//usage: "Server: default\n"
//usage: "Address: default\n"
//usage: "\n"
//usage: "Name: debian\n"
//usage: "Address: 127.0.0.1\n"
#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 == 0) {
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 && result)
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;
if (!server)
return;
/* 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;*/
set_default_dns(argv[2]);
server_print();
/* getaddrinfo and friends are free to request a resolver
* reinitialization. Just in case, set_default_dns() again
* after getaddrinfo (in server_print). This reportedly helps
* with bug 675 "nslookup does not properly use second argument"
* at least on Debian Wheezy and Openwrt AA (eglibc based).
*/
set_default_dns(argv[2]);
return print_host(argv[1], "Name:");
}
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