[821] | 1 | /* vi: set sw=4 ts=4: */
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| 2 | /*
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| 3 | * Mini nslookup implementation for busybox
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| 4 | *
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| 5 | * Copyright (C) 1999,2000 by Lineo, inc. and John Beppu
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| 6 | * Copyright (C) 1999,2000,2001 by John Beppu <beppu@codepoet.org>
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| 7 | *
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| 8 | * Correct default name server display and explicit name server option
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| 9 | * added by Ben Zeckel <bzeckel@hmc.edu> June 2001
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| 10 | *
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[1770] | 11 | * Licensed under GPLv2 or later, see file LICENSE in this tarball for details.
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[821] | 12 | */
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| 13 |
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| 14 | #include <resolv.h>
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[1770] | 15 | #include "libbb.h"
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[821] | 16 |
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| 17 | /*
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[1770] | 18 | * I'm only implementing non-interactive mode;
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| 19 | * I totally forgot nslookup even had an interactive mode.
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[821] | 20 | */
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| 21 |
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[1770] | 22 | /* Examples of 'standard' nslookup output
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| 23 | * $ nslookup yahoo.com
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| 24 | * Server: 128.193.0.10
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| 25 | * Address: 128.193.0.10#53
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| 26 | *
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| 27 | * Non-authoritative answer:
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| 28 | * Name: yahoo.com
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| 29 | * Address: 216.109.112.135
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| 30 | * Name: yahoo.com
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| 31 | * Address: 66.94.234.13
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| 32 | *
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| 33 | * $ nslookup 204.152.191.37
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| 34 | * Server: 128.193.4.20
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| 35 | * Address: 128.193.4.20#53
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| 36 | *
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| 37 | * Non-authoritative answer:
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| 38 | * 37.191.152.204.in-addr.arpa canonical name = 37.32-27.191.152.204.in-addr.arpa.
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| 39 | * 37.32-27.191.152.204.in-addr.arpa name = zeus-pub2.kernel.org.
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| 40 | *
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| 41 | * Authoritative answers can be found from:
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| 42 | * 32-27.191.152.204.in-addr.arpa nameserver = ns1.kernel.org.
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| 43 | * 32-27.191.152.204.in-addr.arpa nameserver = ns2.kernel.org.
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| 44 | * 32-27.191.152.204.in-addr.arpa nameserver = ns3.kernel.org.
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| 45 | * ns1.kernel.org internet address = 140.211.167.34
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| 46 | * ns2.kernel.org internet address = 204.152.191.4
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| 47 | * ns3.kernel.org internet address = 204.152.191.36
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| 48 | */
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| 49 |
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| 50 | static int print_host(const char *hostname, const char *header)
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[821] | 51 | {
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[1770] | 52 | /* We can't use xhost2sockaddr() - we want to get ALL addresses,
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| 53 | * not just one */
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[821] | 54 |
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[1770] | 55 | struct addrinfo *result = NULL;
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| 56 | int rc;
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| 57 | struct addrinfo hint;
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[821] | 58 |
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[1770] | 59 | memset(&hint, 0 , sizeof(hint));
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| 60 | /* hint.ai_family = AF_UNSPEC; - zero anyway */
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| 61 | /* Needed. Or else we will get each address thrice (or more)
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| 62 | * for each possible socket type (tcp,udp,raw...): */
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| 63 | hint.ai_socktype = SOCK_STREAM;
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| 64 | // hint.ai_flags = AI_CANONNAME;
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| 65 | rc = getaddrinfo(hostname, NULL /*service*/, &hint, &result);
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[821] | 66 |
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[1770] | 67 | if (!rc) {
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| 68 | struct addrinfo *cur = result;
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| 69 | unsigned cnt = 0;
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[821] | 70 |
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[1770] | 71 | printf("%-10s %s\n", header, hostname);
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| 72 | // printf("%s\n", cur->ai_canonname); ?
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| 73 | while (cur) {
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| 74 | char *dotted, *revhost;
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| 75 | dotted = xmalloc_sockaddr2dotted_noport(cur->ai_addr);
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| 76 | revhost = xmalloc_sockaddr2hostonly_noport(cur->ai_addr);
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| 77 |
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| 78 | printf("Address %u: %s%c", ++cnt, dotted, revhost ? ' ' : '\n');
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| 79 | if (revhost) {
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| 80 | puts(revhost);
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| 81 | if (ENABLE_FEATURE_CLEAN_UP)
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| 82 | free(revhost);
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[821] | 83 | }
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[1770] | 84 | if (ENABLE_FEATURE_CLEAN_UP)
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| 85 | free(dotted);
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| 86 | cur = cur->ai_next;
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[821] | 87 | }
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| 88 | } else {
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[1770] | 89 | #if ENABLE_VERBOSE_RESOLUTION_ERRORS
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| 90 | bb_error_msg("can't resolve '%s': %s", hostname, gai_strerror(rc));
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| 91 | #else
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| 92 | bb_error_msg("can't resolve '%s'", hostname);
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| 93 | #endif
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[821] | 94 | }
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[1770] | 95 | if (ENABLE_FEATURE_CLEAN_UP)
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| 96 | freeaddrinfo(result);
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| 97 | return (rc != 0);
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[821] | 98 | }
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| 99 |
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| 100 | /* lookup the default nameserver and display it */
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[1770] | 101 | static void server_print(void)
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[821] | 102 | {
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[1770] | 103 | char *server;
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[821] | 104 |
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[1770] | 105 | server = xmalloc_sockaddr2dotted_noport((struct sockaddr*)&_res.nsaddr_list[0]);
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| 106 | /* I honestly don't know what to do if DNS server has _IPv6 address_.
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| 107 | * Probably it is listed in
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| 108 | * _res._u._ext_.nsaddrs[MAXNS] (of type "struct sockaddr_in6*" each)
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| 109 | * but how to find out whether resolver uses
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| 110 | * _res.nsaddr_list[] or _res._u._ext_.nsaddrs[], or both?
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| 111 | * Looks like classic design from hell, BIND-grade. Hard to surpass. */
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| 112 | print_host(server, "Server:");
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| 113 | if (ENABLE_FEATURE_CLEAN_UP)
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| 114 | free(server);
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| 115 | puts("");
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[821] | 116 | }
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| 117 |
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| 118 | /* alter the global _res nameserver structure to use
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| 119 | an explicit dns server instead of what is in /etc/resolv.h */
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[1770] | 120 | static void set_default_dns(char *server)
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[821] | 121 | {
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| 122 | struct in_addr server_in_addr;
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| 123 |
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[1770] | 124 | if (inet_pton(AF_INET, server, &server_in_addr) > 0) {
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[821] | 125 | _res.nscount = 1;
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| 126 | _res.nsaddr_list[0].sin_addr = server_in_addr;
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| 127 | }
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| 128 | }
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| 129 |
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[1770] | 130 | int nslookup_main(int argc, char **argv);
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[821] | 131 | int nslookup_main(int argc, char **argv)
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| 132 | {
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[1770] | 133 | /* We allow 1 or 2 arguments.
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| 134 | * The first is the name to be looked up and the second is an
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| 135 | * optional DNS server with which to do the lookup.
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| 136 | * More than 3 arguments is an error to follow the pattern of the
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| 137 | * standard nslookup */
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[821] | 138 |
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[1770] | 139 | if (argc < 2 || *argv[1] == '-' || argc > 3)
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| 140 | bb_show_usage();
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[821] | 141 |
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[1770] | 142 | /* initialize DNS structure _res used in printing the default
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| 143 | * name server and in the explicit name server option feature. */
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[821] | 144 | res_init();
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[1770] | 145 | /* rfc2133 says this enables IPv6 lookups */
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| 146 | /* (but it also says "may be enabled in /etc/resolv.conf|) */
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| 147 | /*_res.options |= RES_USE_INET6;*/
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[821] | 148 |
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[1770] | 149 | if (argc == 3)
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[821] | 150 | set_default_dns(argv[2]);
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| 151 |
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| 152 | server_print();
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[1770] | 153 | return print_host(argv[1], "Name:");
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[821] | 154 | }
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