/* 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. */ //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:"); }