| /* 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" |
| //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:"); |
| } |