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 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" 19//usage: 20//usage:#define nslookup_example_usage 21//usage: "$ nslookup localhost\n" 22//usage: "Server: default\n" 23//usage: "Address: default\n" 24//usage: "\n" 25//usage: "Name: debian\n" 26//usage: "Address: 127.0.0.1\n" 27 28#include <resolv.h> 29#include "libbb.h" 30 31/* 32 * I'm only implementing non-interactive mode; 33 * I totally forgot nslookup even had an interactive mode. 34 * 35 * This applet is the only user of res_init(). Without it, 36 * you may avoid pulling in _res global from libc. 37 */ 38 39/* Examples of 'standard' nslookup output 40 * $ nslookup yahoo.com 41 * Server: 128.193.0.10 42 * Address: 128.193.0.10#53 43 * 44 * Non-authoritative answer: 45 * Name: yahoo.com 46 * Address: 216.109.112.135 47 * Name: yahoo.com 48 * Address: 66.94.234.13 49 * 50 * $ nslookup 204.152.191.37 51 * Server: 128.193.4.20 52 * Address: 128.193.4.20#53 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. 57 * 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 65 */ 66 67static int print_host(const char *hostname, const char *header) 68{ 69 /* We can't use xhost2sockaddr() - we want to get ALL addresses, 70 * not just one */ 71 struct addrinfo *result = NULL; 72 int rc; 73 struct addrinfo hint; 74 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); 82 83 if (rc == 0) { 84 struct addrinfo *cur = result; 85 unsigned cnt = 0; 86 87 printf("%-10s %s\n", header, hostname); 88 // puts(cur->ai_canonname); ? 89 while (cur) { 90 char *dotted, *revhost; 91 dotted = xmalloc_sockaddr2dotted_noport(cur->ai_addr); 92 revhost = xmalloc_sockaddr2hostonly_noport(cur->ai_addr); 93 94 printf("Address %u: %s%c", ++cnt, dotted, revhost ? ' ' : '\n'); 95 if (revhost) { 96 puts(revhost); 97 if (ENABLE_FEATURE_CLEAN_UP) 98 free(revhost); 99 } 100 if (ENABLE_FEATURE_CLEAN_UP) 101 free(dotted); 102 cur = cur->ai_next; 103 } 104 } else { 105#if ENABLE_VERBOSE_RESOLUTION_ERRORS 106 bb_error_msg("can't resolve '%s': %s", hostname, gai_strerror(rc)); 107#else 108 bb_error_msg("can't resolve '%s'", hostname); 109#endif 110 } 111 if (ENABLE_FEATURE_CLEAN_UP && result) 112 freeaddrinfo(result); 113 return (rc != 0); 114} 115 116/* lookup the default nameserver and display it */ 117static void server_print(void) 118{ 119 char *server; 120 struct sockaddr *sa; 121 122#if ENABLE_FEATURE_IPV6 123 sa = (struct sockaddr*)_res._u._ext.nsaddrs[0]; 124 if (!sa) 125#endif 126 sa = (struct sockaddr*)&_res.nsaddr_list[0]; 127 server = xmalloc_sockaddr2dotted_noport(sa); 128 129 print_host(server, "Server:"); 130 if (ENABLE_FEATURE_CLEAN_UP) 131 free(server); 132 bb_putchar('\n'); 133} 134 135/* alter the global _res nameserver structure to use 136 an explicit dns server instead of what is in /etc/resolv.conf */ 137static void set_default_dns(const char *server) 138{ 139 len_and_sockaddr *lsa; 140 141 /* NB: this works even with, say, "[::1]:5353"! :) */ 142 lsa = xhost2sockaddr(server, 53); 143 144 if (lsa->u.sa.sa_family == AF_INET) { 145 _res.nscount = 1; 146 /* struct copy */ 147 _res.nsaddr_list[0] = lsa->u.sin; 148 } 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): 157 //_res.nscount = 0; 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)! */ 162 } 163#endif 164} 165 166int nslookup_main(int argc, char **argv) MAIN_EXTERNALLY_VISIBLE; 167int nslookup_main(int argc, char **argv) 168{ 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) 175 bb_show_usage(); 176 177 /* initialize DNS structure _res used in printing the default 178 * name server and in the explicit name server option feature. */ 179 res_init(); 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;*/ 183 184 if (argv[2]) 185 set_default_dns(argv[2]); 186 187 server_print(); 188 return print_host(argv[1], "Name:"); 189} 190