* 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.
+ * 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.
+ * 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
{
/* We can't use xhost2sockaddr() - we want to get ALL addresses,
* not just one */
-
struct addrinfo *result = NULL;
int rc;
struct addrinfo hint;
// hint.ai_flags = AI_CANONNAME;
rc = getaddrinfo(hostname, NULL /*service*/, &hint, &result);
- if (!rc) {
+ if (rc == 0) {
struct addrinfo *cur = result;
unsigned cnt = 0;
bb_error_msg("can't resolve '%s'", hostname);
#endif
}
- if (ENABLE_FEATURE_CLEAN_UP)
+ if (ENABLE_FEATURE_CLEAN_UP && result)
freeaddrinfo(result);
return (rc != 0);
}
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);
- 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);
}
/* alter the global _res nameserver structure to use
- an explicit dns server instead of what is in /etc/resolv.h */
-static void set_default_dns(char *server)
+ an explicit dns server instead of what is in /etc/resolv.conf */
+static void set_default_dns(const char *server)
{
- struct in_addr server_in_addr;
+ len_and_sockaddr *lsa;
+
+ if (!server)
+ return;
- if (inet_pton(AF_INET, server, &server_in_addr) > 0) {
+ /* NB: this works even with, say, "[::1]:5353"! :) */
+ lsa = xhost2sockaddr(server, 53);
+
+ if (lsa->u.sa.sa_family == AF_INET) {
_res.nscount = 1;
- _res.nsaddr_list[0].sin_addr = server_in_addr;
+ /* 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;
* 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 (argc < 2 || *argv[1] == '-' || argc > 3)
+ 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|) */
+ /* (but it also says "may be enabled in /etc/resolv.conf") */
/*_res.options |= RES_USE_INET6;*/
- if (argc == 3)
- set_default_dns(argv[2]);
+ 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:");
}
projects / platform / upstream / busybox.git / blobdiff