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 tarball for details. 12 */ 13 14#include <resolv.h> 15#include "libbb.h" 16 17/* 18 * I'm only implementing non-interactive mode; 19 * I totally forgot nslookup even had an interactive mode. 20 */ 21 22/* Examples of 'standard' nslookup output 23 * $ nslookup yahoo.com 24 * Server: 128.193.0.10 25 * Address: 128.193.0.10#53 26 * 27 * Non-authoritative answer: 28 * Name: yahoo.com 29 * Address: 216.109.112.135 30 * Name: yahoo.com 31 * Address: 66.94.234.13 32 * 33 * $ nslookup 204.152.191.37 34 * Server: 128.193.4.20 35 * Address: 128.193.4.20#53 36 * 37 * Non-authoritative answer: 38 * 37.191.152.204.in-addr.arpa canonical name = 37.32-27.191.152.204.in-addr.arpa. 39 * 37.32-27.191.152.204.in-addr.arpa name = zeus-pub2.kernel.org. 40 * 41 * Authoritative answers can be found from: 42 * 32-27.191.152.204.in-addr.arpa nameserver = ns1.kernel.org. 43 * 32-27.191.152.204.in-addr.arpa nameserver = ns2.kernel.org. 44 * 32-27.191.152.204.in-addr.arpa nameserver = ns3.kernel.org. 45 * ns1.kernel.org internet address = 140.211.167.34 46 * ns2.kernel.org internet address = 204.152.191.4 47 * ns3.kernel.org internet address = 204.152.191.36 48 */ 49 50static int print_host(const char *hostname, const char *header) 51{ 52 /* We can't use xhost2sockaddr() - we want to get ALL addresses, 53 * not just one */ 54 55 struct addrinfo *result = NULL; 56 int rc; 57 struct addrinfo hint; 58 59 memset(&hint, 0 , sizeof(hint)); 60 /* hint.ai_family = AF_UNSPEC; - zero anyway */ 61 /* Needed. Or else we will get each address thrice (or more) 62 * for each possible socket type (tcp,udp,raw...): */ 63 hint.ai_socktype = SOCK_STREAM; 64 // hint.ai_flags = AI_CANONNAME; 65 rc = getaddrinfo(hostname, NULL /*service*/, &hint, &result); 66 67 if (!rc) { 68 struct addrinfo *cur = result; 69 unsigned cnt = 0; 70 71 printf("%-10s %s\n", header, hostname); 72 // printf("%s\n", cur->ai_canonname); ? 73 while (cur) { 74 char *dotted, *revhost; 75 dotted = xmalloc_sockaddr2dotted_noport(cur->ai_addr); 76 revhost = xmalloc_sockaddr2hostonly_noport(cur->ai_addr); 77 78 printf("Address %u: %s%c", ++cnt, dotted, revhost ? ' ' : '\n'); 79 if (revhost) { 80 puts(revhost); 81 if (ENABLE_FEATURE_CLEAN_UP) 82 free(revhost); 83 } 84 if (ENABLE_FEATURE_CLEAN_UP) 85 free(dotted); 86 cur = cur->ai_next; 87 } 88 } else { 89#if ENABLE_VERBOSE_RESOLUTION_ERRORS 90 bb_error_msg("can't resolve '%s': %s", hostname, gai_strerror(rc)); 91#else 92 bb_error_msg("can't resolve '%s'", hostname); 93#endif 94 } 95 if (ENABLE_FEATURE_CLEAN_UP) 96 freeaddrinfo(result); 97 return (rc != 0); 98} 99 100/* lookup the default nameserver and display it */ 101static void server_print(void) 102{ 103 char *server; 104 105 server = xmalloc_sockaddr2dotted_noport((struct sockaddr*)&_res.nsaddr_list[0]); 106 /* I honestly don't know what to do if DNS server has _IPv6 address_. 107 * Probably it is listed in 108 * _res._u._ext_.nsaddrs[MAXNS] (of type "struct sockaddr_in6*" each) 109 * but how to find out whether resolver uses 110 * _res.nsaddr_list[] or _res._u._ext_.nsaddrs[], or both? 111 * Looks like classic design from hell, BIND-grade. Hard to surpass. */ 112 print_host(server, "Server:"); 113 if (ENABLE_FEATURE_CLEAN_UP) 114 free(server); 115 puts(""); 116} 117 118/* alter the global _res nameserver structure to use 119 an explicit dns server instead of what is in /etc/resolv.h */ 120static void set_default_dns(char *server) 121{ 122 struct in_addr server_in_addr; 123 124 if (inet_pton(AF_INET, server, &server_in_addr) > 0) { 125 _res.nscount = 1; 126 _res.nsaddr_list[0].sin_addr = server_in_addr; 127 } 128} 129 130int nslookup_main(int argc, char **argv); 131int nslookup_main(int argc, char **argv) 132{ 133 /* We allow 1 or 2 arguments. 134 * The first is the name to be looked up and the second is an 135 * optional DNS server with which to do the lookup. 136 * More than 3 arguments is an error to follow the pattern of the 137 * standard nslookup */ 138 139 if (argc < 2 || *argv[1] == '-' || argc > 3) 140 bb_show_usage(); 141 142 /* initialize DNS structure _res used in printing the default 143 * name server and in the explicit name server option feature. */ 144 res_init(); 145 /* rfc2133 says this enables IPv6 lookups */ 146 /* (but it also says "may be enabled in /etc/resolv.conf|) */ 147 /*_res.options |= RES_USE_INET6;*/ 148 149 if (argc == 3) 150 set_default_dns(argv[2]); 151 152 server_print(); 153 return print_host(argv[1], "Name:"); 154} 155