2 * SPDX-License-Identifier: (ISC AND BSD-3-Clause)
4 * Portions Copyright (C) 2004, 2005, 2008 Internet Systems Consortium, Inc. ("ISC")
5 * Portions Copyright (C) 1996-2001, 2003 Internet Software Consortium.
7 * Permission to use, copy, modify, and/or distribute this software for any
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15 * LOSS OF USE, DATA OR PROFITS, WHETHER IN AN ACTION OF CONTRACT, NEGLIGENCE
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17 * PERFORMANCE OF THIS SOFTWARE.
21 * Copyright (c) 1988, 1993
22 * The Regents of the University of California. All rights reserved.
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25 * modification, are permitted provided that the following conditions
27 * 1. Redistributions of source code must retain the above copyright
28 * notice, this list of conditions and the following disclaimer.
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50 * Portions Copyright (c) 1993 by Digital Equipment Corporation.
52 * Permission to use, copy, modify, and distribute this software for any
53 * purpose with or without fee is hereby granted, provided that the above
54 * copyright notice and this permission notice appear in all copies, and that
55 * the name of Digital Equipment Corporation not be used in advertising or
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59 * THE SOFTWARE IS PROVIDED "AS IS" AND DIGITAL EQUIPMENT CORP. DISCLAIMS ALL
60 * WARRANTIES WITH REGARD TO THIS SOFTWARE, INCLUDING ALL IMPLIED WARRANTIES
61 * OF MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL DIGITAL EQUIPMENT
62 * CORPORATION BE LIABLE FOR ANY SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL
63 * DAMAGES OR ANY DAMAGES WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR
64 * PROFITS, WHETHER IN AN ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS
65 * ACTION, ARISING OUT OF OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS
69 #if defined(LIBC_SCCS) && !defined(lint)
70 static const char sccsid[] = "@(#)res_query.c 8.1 (Berkeley) 6/4/93";
71 static const char rcsid[] = "$Id: res_query.c,v 1.11 2008/11/14 02:36:51 marka Exp $";
72 #endif /* LIBC_SCCS and not lint */
73 #include <sys/cdefs.h>
74 __FBSDID("$FreeBSD$");
76 #include "port_before.h"
77 #include <sys/param.h>
78 #include <netinet/in.h>
79 #include <arpa/inet.h>
80 #include <arpa/nameser.h>
89 #include "port_after.h"
91 /* Options. Leave them on. */
97 #define MAXPACKET PACKETSZ
99 #define MAXPACKET 1024
103 * Formulate a normal query, send, and await answer.
104 * Returned answer is placed in supplied buffer "answer".
105 * Perform preliminary check of answer, returning success only
106 * if no error is indicated and the answer count is nonzero.
107 * Return the size of the response on success, -1 on error.
108 * Error number is left in H_ERRNO.
110 * Caller must parse answer and determine whether it answers the question.
113 res_nquery(res_state statp,
114 const char *name, /*%< domain name */
115 int class, int type, /*%< class and type of query */
116 u_char *answer, /*%< buffer to put answer */
117 int anslen) /*%< size of answer buffer */
119 u_char buf[MAXPACKET];
120 HEADER *hp = (HEADER *) answer;
125 oflags = statp->_flags;
128 hp->rcode = NOERROR; /*%< default */
130 if (statp->options & RES_DEBUG)
131 printf(";; res_query(%s, %d, %d)\n", name, class, type);
134 n = res_nmkquery(statp, QUERY, name, class, type, NULL, 0, NULL,
137 if (n > 0 && (statp->_flags & RES_F_EDNS0ERR) == 0 &&
138 (statp->options & (RES_USE_EDNS0|RES_USE_DNSSEC|RES_NSID))) {
139 n = res_nopt(statp, n, buf, sizeof(buf), anslen);
140 if (n > 0 && (statp->options & RES_NSID) != 0U) {
142 n = res_nopt_rdata(statp, n, buf, sizeof(buf), rdata,
143 NS_OPT_NSID, 0, NULL);
149 if (statp->options & RES_DEBUG)
150 printf(";; res_query: mkquery failed\n");
152 RES_SET_H_ERRNO(statp, NO_RECOVERY);
156 n = res_nsend(statp, buf, n, answer, anslen);
159 /* if the query choked with EDNS0, retry without EDNS0 */
160 if ((statp->options & (RES_USE_EDNS0|RES_USE_DNSSEC)) != 0U &&
161 ((oflags ^ statp->_flags) & RES_F_EDNS0ERR) != 0) {
162 statp->_flags |= RES_F_EDNS0ERR;
163 if (statp->options & RES_DEBUG)
164 printf(";; res_nquery: retry without EDNS0\n");
169 if (statp->options & RES_DEBUG)
170 printf(";; res_query: send error\n");
172 RES_SET_H_ERRNO(statp, TRY_AGAIN);
176 if (hp->rcode != NOERROR || ntohs(hp->ancount) == 0) {
178 if (statp->options & RES_DEBUG)
179 printf(";; rcode = (%s), counts = an:%d ns:%d ar:%d\n",
187 RES_SET_H_ERRNO(statp, HOST_NOT_FOUND);
190 RES_SET_H_ERRNO(statp, TRY_AGAIN);
193 RES_SET_H_ERRNO(statp, NO_DATA);
199 RES_SET_H_ERRNO(statp, NO_RECOVERY);
208 * Formulate a normal query, send, and retrieve answer in supplied buffer.
209 * Return the size of the response on success, -1 on error.
210 * If enabled, implement search rules until answer or unrecoverable failure
211 * is detected. Error code, if any, is left in H_ERRNO.
214 res_nsearch(res_state statp,
215 const char *name, /*%< domain name */
216 int class, int type, /*%< class and type of query */
217 u_char *answer, /*%< buffer to put answer */
218 int anslen) /*%< size of answer */
220 const char *cp, * const *domain;
221 HEADER *hp = (HEADER *) answer;
222 char tmp[NS_MAXDNAME];
224 int trailing_dot, ret, saved_herrno;
225 int got_nodata = 0, got_servfail = 0, root_on_list = 0;
230 RES_SET_H_ERRNO(statp, HOST_NOT_FOUND); /*%< True if we never query. */
232 for (cp = name; *cp != '\0'; cp++)
233 dots += (*cp == '.');
235 if (cp > name && *--cp == '.')
238 /* If there aren't any dots, it could be a user-level alias. */
239 if (!dots && (cp = res_hostalias(statp, name, tmp, sizeof tmp))!= NULL)
240 return (res_nquery(statp, cp, class, type, answer, anslen));
243 * If there are enough dots in the name, let's just give it a
244 * try 'as is'. The threshold can be set with the "ndots" option.
245 * Also, query 'as is', if there is a trailing dot in the name.
248 if (dots >= statp->ndots || trailing_dot) {
249 ret = res_nquerydomain(statp, name, NULL, class, type,
251 if (ret > 0 || trailing_dot)
253 if (errno == ECONNREFUSED) {
254 RES_SET_H_ERRNO(statp, TRY_AGAIN);
257 switch (statp->res_h_errno) {
262 if (hp->rcode == SERVFAIL)
268 saved_herrno = statp->res_h_errno;
273 * We do at least one level of search if
274 * - there is no dot and RES_DEFNAME is set, or
275 * - there is at least one dot, there is no trailing dot,
276 * and RES_DNSRCH is set.
278 if ((!dots && (statp->options & RES_DEFNAMES) != 0U) ||
279 (dots && !trailing_dot && (statp->options & RES_DNSRCH) != 0U)) {
282 for (domain = (const char * const *)statp->dnsrch;
287 if (domain[0][0] == '\0' ||
288 (domain[0][0] == '.' && domain[0][1] == '\0'))
291 if (root_on_list && tried_as_is)
294 ret = res_nquerydomain(statp, name, *domain,
301 * If no server present, give up.
302 * If name isn't found in this domain,
303 * keep trying higher domains in the search list
304 * (if that's enabled).
305 * On a NO_DATA error, keep trying, otherwise
306 * a wildcard entry of another type could keep us
307 * from finding this entry higher in the domain.
308 * If we get some other error (negative answer or
309 * server failure), then stop searching up,
310 * but try the input name below in case it's
313 if (errno == ECONNREFUSED) {
314 RES_SET_H_ERRNO(statp, TRY_AGAIN);
318 switch (statp->res_h_errno) {
327 * This can occur due to a server failure
328 * (that is, all listed servers have failed),
329 * or all listed servers have timed out.
330 * ((HEADER *)answer)->rcode may not be set
331 * to SERVFAIL in the case of a timeout.
333 * Either way we must return TRY_AGAIN in
334 * order to avoid non-deterministic
336 * For example, loaded name servers or races
337 * against network startup/validation (dhcp,
338 * ppp, etc) can cause the search to timeout
339 * on one search element, e.g. 'fu.bar.com',
340 * and return a definitive failure on the
341 * next search element, e.g. 'fu.'.
344 if (hp->rcode == SERVFAIL) {
345 /* try next search element, if any */
350 /* anything else implies that we're done */
354 /* if we got here for some reason other than DNSRCH,
355 * we only wanted one iteration of the loop, so stop.
357 if ((statp->options & RES_DNSRCH) == 0U)
362 switch (statp->res_h_errno) {
367 if (hp->rcode == SERVFAIL)
375 * If the query has not already been tried as is then try it
376 * unless RES_NOTLDQUERY is set and there were no dots.
378 if ((dots || !searched || (statp->options & RES_NOTLDQUERY) == 0U) &&
379 !(tried_as_is || root_on_list)) {
380 ret = res_nquerydomain(statp, name, NULL, class, type,
386 /* if we got here, we didn't satisfy the search.
387 * if we did an initial full query, return that query's H_ERRNO
388 * (note that we wouldn't be here if that query had succeeded).
389 * else if we ever got a nodata, send that back as the reason.
390 * else send back meaningless H_ERRNO, that being the one from
391 * the last DNSRCH we did.
394 if (saved_herrno != -1)
395 RES_SET_H_ERRNO(statp, saved_herrno);
397 RES_SET_H_ERRNO(statp, NO_DATA);
398 else if (got_servfail)
399 RES_SET_H_ERRNO(statp, TRY_AGAIN);
404 * Perform a call on res_query on the concatenation of name and domain,
405 * removing a trailing dot from name if domain is NULL.
408 res_nquerydomain(res_state statp,
411 int class, int type, /*%< class and type of query */
412 u_char *answer, /*%< buffer to put answer */
413 int anslen) /*%< size of answer */
416 const char *longname = nbuf;
420 if (statp->options & RES_DEBUG)
421 printf(";; res_nquerydomain(%s, %s, %d, %d)\n",
422 name, domain?domain:"<Nil>", class, type);
424 if (domain == NULL) {
426 * Check for trailing '.';
427 * copy without '.' if present.
431 RES_SET_H_ERRNO(statp, NO_RECOVERY);
435 if (n >= 0 && name[n] == '.') {
436 strncpy(nbuf, name, n);
443 if (n + d + 1 >= MAXDNAME) {
444 RES_SET_H_ERRNO(statp, NO_RECOVERY);
447 sprintf(nbuf, "%s.%s", name, domain);
449 return (res_nquery(statp, longname, class, type, answer, anslen));
453 res_hostalias(const res_state statp, const char *name, char *dst, size_t siz) {
454 char *file, *cp1, *cp2;
458 if (statp->options & RES_NOALIASES)
462 file = getenv("HOSTALIASES");
463 if (file == NULL || (fp = fopen(file, "re")) == NULL)
466 buf[sizeof(buf) - 1] = '\0';
467 while (fgets(buf, sizeof(buf), fp)) {
468 for (cp1 = buf; *cp1 && !isspace((unsigned char)*cp1); ++cp1)
473 if (ns_samename(buf, name) == 1) {
474 while (isspace((unsigned char)*++cp1))
478 for (cp2 = cp1 + 1; *cp2 &&
479 !isspace((unsigned char)*cp2); ++cp2)
482 strncpy(dst, cp1, siz - 1);