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Diffstat (limited to 'networking/nslookup.c')
-rw-r--r-- | networking/nslookup.c | 155 |
1 files changed, 155 insertions, 0 deletions
diff --git a/networking/nslookup.c b/networking/nslookup.c new file mode 100644 index 0000000..73ccb0d --- /dev/null +++ b/networking/nslookup.c @@ -0,0 +1,155 @@ +/* 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 tarball for details. + */ + +#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) { + 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) + freeaddrinfo(result); + return (rc != 0); +} + +/* lookup the default nameserver and display it */ +static void server_print(void) +{ + char *server; + + server = xmalloc_sockaddr2dotted_noport((struct sockaddr*)&_res.nsaddr_list[0]); + /* I honestly don't know what to do if DNS server has _IPv6 address_. + * Probably it is listed in + * _res._u._ext_.nsaddrs[MAXNS] (of type "struct sockaddr_in6*" each) + * but how to find out whether resolver uses + * _res.nsaddr_list[] or _res._u._ext_.nsaddrs[], or both? + * Looks like classic design from hell, BIND-grade. Hard to surpass. */ + 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(char *server) +{ + struct in_addr server_in_addr; + + if (inet_pton(AF_INET, server, &server_in_addr) > 0) { + _res.nscount = 1; + _res.nsaddr_list[0].sin_addr = server_in_addr; + } +} + +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;*/ + + if (argv[2]) + set_default_dns(argv[2]); + + server_print(); + return print_host(argv[1], "Name:"); +} |