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3 * Portions Copyright (C) 1996-2001, 2003 Internet Software Consortium.
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50 * Permission to use, copy, modify, and distribute this software for any
51 * purpose with or without fee is hereby granted, provided that the above
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58 * WARRANTIES WITH REGARD TO THIS SOFTWARE, INCLUDING ALL IMPLIED WARRANTIES
59 * OF MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL DIGITAL EQUIPMENT
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67 #if defined(LIBC_SCCS) && !defined(lint)
68 static const char sccsid[] = "@(#)res_query.c 8.1 (Berkeley) 6/4/93";
69 static const char rcsid[] = "$Id: res_query.c,v 1.11 2008/11/14 02:36:51 marka Exp $";
70 #endif /* LIBC_SCCS and not lint */
71 #include <sys/cdefs.h>
72 __FBSDID("$FreeBSD$");
74 #include "port_before.h"
75 #include <sys/param.h>
76 #include <netinet/in.h>
77 #include <arpa/inet.h>
78 #include <arpa/nameser.h>
87 #include "port_after.h"
89 /* Options. Leave them on. */
95 #define MAXPACKET PACKETSZ
97 #define MAXPACKET 1024
101 * Formulate a normal query, send, and await answer.
102 * Returned answer is placed in supplied buffer "answer".
103 * Perform preliminary check of answer, returning success only
104 * if no error is indicated and the answer count is nonzero.
105 * Return the size of the response on success, -1 on error.
106 * Error number is left in H_ERRNO.
108 * Caller must parse answer and determine whether it answers the question.
111 res_nquery(res_state statp,
112 const char *name, /*%< domain name */
113 int class, int type, /*%< class and type of query */
114 u_char *answer, /*%< buffer to put answer */
115 int anslen) /*%< size of answer buffer */
117 u_char buf[MAXPACKET];
118 HEADER *hp = (HEADER *) answer;
123 oflags = statp->_flags;
126 hp->rcode = NOERROR; /*%< default */
128 if (statp->options & RES_DEBUG)
129 printf(";; res_query(%s, %d, %d)\n", name, class, type);
132 n = res_nmkquery(statp, QUERY, name, class, type, NULL, 0, NULL,
135 if (n > 0 && (statp->_flags & RES_F_EDNS0ERR) == 0 &&
136 (statp->options & (RES_USE_EDNS0|RES_USE_DNSSEC|RES_NSID))) {
137 n = res_nopt(statp, n, buf, sizeof(buf), anslen);
139 if (n > 0 && (statp->options & RES_NSID) != 0U) {
140 n = res_nopt_rdata(statp, n, buf, sizeof(buf), rdata,
141 NS_OPT_NSID, 0, NULL);
147 if (statp->options & RES_DEBUG)
148 printf(";; res_query: mkquery failed\n");
150 RES_SET_H_ERRNO(statp, NO_RECOVERY);
154 n = res_nsend(statp, buf, n, answer, anslen);
157 /* if the query choked with EDNS0, retry without EDNS0 */
158 if ((statp->options & (RES_USE_EDNS0|RES_USE_DNSSEC)) != 0U &&
159 ((oflags ^ statp->_flags) & RES_F_EDNS0ERR) != 0) {
160 statp->_flags |= RES_F_EDNS0ERR;
161 if (statp->options & RES_DEBUG)
162 printf(";; res_nquery: retry without EDNS0\n");
167 if (statp->options & RES_DEBUG)
168 printf(";; res_query: send error\n");
170 RES_SET_H_ERRNO(statp, TRY_AGAIN);
174 if (hp->rcode != NOERROR || ntohs(hp->ancount) == 0) {
176 if (statp->options & RES_DEBUG)
177 printf(";; rcode = (%s), counts = an:%d ns:%d ar:%d\n",
185 RES_SET_H_ERRNO(statp, HOST_NOT_FOUND);
188 RES_SET_H_ERRNO(statp, TRY_AGAIN);
191 RES_SET_H_ERRNO(statp, NO_DATA);
197 RES_SET_H_ERRNO(statp, NO_RECOVERY);
206 * Formulate a normal query, send, and retrieve answer in supplied buffer.
207 * Return the size of the response on success, -1 on error.
208 * If enabled, implement search rules until answer or unrecoverable failure
209 * is detected. Error code, if any, is left in H_ERRNO.
212 res_nsearch(res_state statp,
213 const char *name, /*%< domain name */
214 int class, int type, /*%< class and type of query */
215 u_char *answer, /*%< buffer to put answer */
216 int anslen) /*%< size of answer */
218 const char *cp, * const *domain;
219 HEADER *hp = (HEADER *) answer;
220 char tmp[NS_MAXDNAME];
222 int trailing_dot, ret, saved_herrno;
223 int got_nodata = 0, got_servfail = 0, root_on_list = 0;
228 RES_SET_H_ERRNO(statp, HOST_NOT_FOUND); /*%< True if we never query. */
230 for (cp = name; *cp != '\0'; cp++)
231 dots += (*cp == '.');
233 if (cp > name && *--cp == '.')
236 /* If there aren't any dots, it could be a user-level alias. */
237 if (!dots && (cp = res_hostalias(statp, name, tmp, sizeof tmp))!= NULL)
238 return (res_nquery(statp, cp, class, type, answer, anslen));
241 * If there are enough dots in the name, let's just give it a
242 * try 'as is'. The threshold can be set with the "ndots" option.
243 * Also, query 'as is', if there is a trailing dot in the name.
246 if (dots >= statp->ndots || trailing_dot) {
247 ret = res_nquerydomain(statp, name, NULL, class, type,
249 if (ret > 0 || trailing_dot)
251 if (errno == ECONNREFUSED) {
252 RES_SET_H_ERRNO(statp, TRY_AGAIN);
255 switch (statp->res_h_errno) {
260 if (hp->rcode == SERVFAIL)
266 saved_herrno = statp->res_h_errno;
271 * We do at least one level of search if
272 * - there is no dot and RES_DEFNAME is set, or
273 * - there is at least one dot, there is no trailing dot,
274 * and RES_DNSRCH is set.
276 if ((!dots && (statp->options & RES_DEFNAMES) != 0U) ||
277 (dots && !trailing_dot && (statp->options & RES_DNSRCH) != 0U)) {
280 for (domain = (const char * const *)statp->dnsrch;
285 if (domain[0][0] == '\0' ||
286 (domain[0][0] == '.' && domain[0][1] == '\0'))
289 if (root_on_list && tried_as_is)
292 ret = res_nquerydomain(statp, name, *domain,
299 * If no server present, give up.
300 * If name isn't found in this domain,
301 * keep trying higher domains in the search list
302 * (if that's enabled).
303 * On a NO_DATA error, keep trying, otherwise
304 * a wildcard entry of another type could keep us
305 * from finding this entry higher in the domain.
306 * If we get some other error (negative answer or
307 * server failure), then stop searching up,
308 * but try the input name below in case it's
311 if (errno == ECONNREFUSED) {
312 RES_SET_H_ERRNO(statp, TRY_AGAIN);
316 switch (statp->res_h_errno) {
325 * This can occur due to a server failure
326 * (that is, all listed servers have failed),
327 * or all listed servers have timed out.
328 * ((HEADER *)answer)->rcode may not be set
329 * to SERVFAIL in the case of a timeout.
331 * Either way we must return TRY_AGAIN in
332 * order to avoid non-deterministic
334 * For example, loaded name servers or races
335 * against network startup/validation (dhcp,
336 * ppp, etc) can cause the search to timeout
337 * on one search element, e.g. 'fu.bar.com',
338 * and return a definitive failure on the
339 * next search element, e.g. 'fu.'.
342 if (hp->rcode == SERVFAIL) {
343 /* try next search element, if any */
348 /* anything else implies that we're done */
352 /* if we got here for some reason other than DNSRCH,
353 * we only wanted one iteration of the loop, so stop.
355 if ((statp->options & RES_DNSRCH) == 0U)
360 switch (statp->res_h_errno) {
365 if (hp->rcode == SERVFAIL)
373 * If the query has not already been tried as is then try it
374 * unless RES_NOTLDQUERY is set and there were no dots.
376 if ((dots || !searched || (statp->options & RES_NOTLDQUERY) == 0U) &&
377 !(tried_as_is || root_on_list)) {
378 ret = res_nquerydomain(statp, name, NULL, class, type,
384 /* if we got here, we didn't satisfy the search.
385 * if we did an initial full query, return that query's H_ERRNO
386 * (note that we wouldn't be here if that query had succeeded).
387 * else if we ever got a nodata, send that back as the reason.
388 * else send back meaningless H_ERRNO, that being the one from
389 * the last DNSRCH we did.
392 if (saved_herrno != -1)
393 RES_SET_H_ERRNO(statp, saved_herrno);
395 RES_SET_H_ERRNO(statp, NO_DATA);
396 else if (got_servfail)
397 RES_SET_H_ERRNO(statp, TRY_AGAIN);
402 * Perform a call on res_query on the concatenation of name and domain,
403 * removing a trailing dot from name if domain is NULL.
406 res_nquerydomain(res_state statp,
409 int class, int type, /*%< class and type of query */
410 u_char *answer, /*%< buffer to put answer */
411 int anslen) /*%< size of answer */
414 const char *longname = nbuf;
418 if (statp->options & RES_DEBUG)
419 printf(";; res_nquerydomain(%s, %s, %d, %d)\n",
420 name, domain?domain:"<Nil>", class, type);
422 if (domain == NULL) {
424 * Check for trailing '.';
425 * copy without '.' if present.
429 RES_SET_H_ERRNO(statp, NO_RECOVERY);
433 if (n >= 0 && name[n] == '.') {
434 strncpy(nbuf, name, n);
441 if (n + d + 1 >= MAXDNAME) {
442 RES_SET_H_ERRNO(statp, NO_RECOVERY);
445 sprintf(nbuf, "%s.%s", name, domain);
447 return (res_nquery(statp, longname, class, type, answer, anslen));
451 res_hostalias(const res_state statp, const char *name, char *dst, size_t siz) {
452 char *file, *cp1, *cp2;
456 if (statp->options & RES_NOALIASES)
460 file = getenv("HOSTALIASES");
461 if (file == NULL || (fp = fopen(file, "re")) == NULL)
464 buf[sizeof(buf) - 1] = '\0';
465 while (fgets(buf, sizeof(buf), fp)) {
466 for (cp1 = buf; *cp1 && !isspace((unsigned char)*cp1); ++cp1)
471 if (ns_samename(buf, name) == 1) {
472 while (isspace((unsigned char)*++cp1))
476 for (cp2 = cp1 + 1; *cp2 &&
477 !isspace((unsigned char)*cp2); ++cp2)
480 strncpy(dst, cp1, siz - 1);