xref: /freebsd/lib/libc/net/gethostbydns.c (revision 3becbb252c733d3d09172a34d7d00d27f84d0e86)
1 /*
2  * ++Copyright++ 1985, 1988, 1993
3  * -
4  * Copyright (c) 1985, 1988, 1993
5  *	The Regents of the University of California.  All rights reserved.
6  *
7  * Redistribution and use in source and binary forms, with or without
8  * modification, are permitted provided that the following conditions
9  * are met:
10  * 1. Redistributions of source code must retain the above copyright
11  *    notice, this list of conditions and the following disclaimer.
12  * 2. Redistributions in binary form must reproduce the above copyright
13  *    notice, this list of conditions and the following disclaimer in the
14  *    documentation and/or other materials provided with the distribution.
15  * 3. All advertising materials mentioning features or use of this software
16  *    must display the following acknowledgement:
17  *	This product includes software developed by the University of
18  *	California, Berkeley and its contributors.
19  * 4. Neither the name of the University nor the names of its contributors
20  *    may be used to endorse or promote products derived from this software
21  *    without specific prior written permission.
22  *
23  * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
24  * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
25  * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
26  * ARE DISCLAIMED.  IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
27  * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
28  * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
29  * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
30  * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
31  * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
32  * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
33  * SUCH DAMAGE.
34  * -
35  * Portions Copyright (c) 1993 by Digital Equipment Corporation.
36  *
37  * Permission to use, copy, modify, and distribute this software for any
38  * purpose with or without fee is hereby granted, provided that the above
39  * copyright notice and this permission notice appear in all copies, and that
40  * the name of Digital Equipment Corporation not be used in advertising or
41  * publicity pertaining to distribution of the document or software without
42  * specific, written prior permission.
43  *
44  * THE SOFTWARE IS PROVIDED "AS IS" AND DIGITAL EQUIPMENT CORP. DISCLAIMS ALL
45  * WARRANTIES WITH REGARD TO THIS SOFTWARE, INCLUDING ALL IMPLIED WARRANTIES
46  * OF MERCHANTABILITY AND FITNESS.   IN NO EVENT SHALL DIGITAL EQUIPMENT
47  * CORPORATION BE LIABLE FOR ANY SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL
48  * DAMAGES OR ANY DAMAGES WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR
49  * PROFITS, WHETHER IN AN ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS
50  * ACTION, ARISING OUT OF OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS
51  * SOFTWARE.
52  * -
53  * --Copyright--
54  */
55 
56 #if defined(LIBC_SCCS) && !defined(lint)
57 static char sccsid[] = "@(#)gethostnamadr.c	8.1 (Berkeley) 6/4/93";
58 static char fromrcsid[] = "From: Id: gethnamaddr.c,v 8.23 1998/04/07 04:59:46 vixie Exp $";
59 static char rcsid[] = "$FreeBSD$";
60 #endif /* LIBC_SCCS and not lint */
61 
62 #include <sys/types.h>
63 #include <sys/param.h>
64 #include <sys/socket.h>
65 #include <netinet/in.h>
66 #include <arpa/inet.h>
67 #include <arpa/nameser.h>
68 
69 #include <stdio.h>
70 #include <unistd.h>
71 #include <string.h>
72 #include <netdb.h>
73 #include <resolv.h>
74 #include <ctype.h>
75 #include <errno.h>
76 #include <syslog.h>
77 #include <stdarg.h>
78 #include <nsswitch.h>
79 
80 #include "res_config.h"
81 
82 #define SPRINTF(x) ((size_t)sprintf x)
83 
84 #define	MAXALIASES	35
85 #define	MAXADDRS	35
86 
87 static const char AskedForGot[] =
88 		"gethostby*.gethostanswer: asked for \"%s\", got \"%s\"";
89 
90 static char *h_addr_ptrs[MAXADDRS + 1];
91 
92 static struct hostent host;
93 static char *host_aliases[MAXALIASES];
94 static char hostbuf[8*1024];
95 static u_char host_addr[16];	/* IPv4 or IPv6 */
96 
97 #ifdef RESOLVSORT
98 static void addrsort __P((char **, int));
99 #endif
100 
101 #ifdef DEBUG
102 static void dprintf(char *, int) __printflike(1, 0);
103 #endif
104 
105 #if PACKETSZ > 1024
106 #define	MAXPACKET	PACKETSZ
107 #else
108 #define	MAXPACKET	1024
109 #endif
110 
111 typedef union {
112     HEADER hdr;
113     u_char buf[MAXPACKET];
114 } querybuf;
115 
116 typedef union {
117     int32_t al;
118     char ac;
119 } align;
120 
121 extern int h_errno;
122 int _dns_ttl_;
123 
124 #ifdef DEBUG
125 static void
126 dprintf(msg, num)
127 	char *msg;
128 	int num;
129 {
130 	if (_res.options & RES_DEBUG) {
131 		int save = errno;
132 
133 		printf(msg, num);
134 		errno = save;
135 	}
136 }
137 #else
138 # define dprintf(msg, num) /*nada*/
139 #endif
140 
141 #define BOUNDED_INCR(x) \
142 	do { \
143 		cp += x; \
144 		if (cp > eom) { \
145 			h_errno = NO_RECOVERY; \
146 			return (NULL); \
147 		} \
148 	} while (0)
149 
150 #define BOUNDS_CHECK(ptr, count) \
151 	do { \
152 		if ((ptr) + (count) > eom) { \
153 			h_errno = NO_RECOVERY; \
154 			return (NULL); \
155 		} \
156 	} while (0)
157 
158 static struct hostent *
159 gethostanswer(answer, anslen, qname, qtype)
160 	const querybuf *answer;
161 	int anslen;
162 	const char *qname;
163 	int qtype;
164 {
165 	register const HEADER *hp;
166 	register const u_char *cp;
167 	register int n;
168 	const u_char *eom, *erdata;
169 	char *bp, **ap, **hap;
170 	int type, class, buflen, ancount, qdcount;
171 	int haveanswer, had_error;
172 	int toobig = 0;
173 	char tbuf[MAXDNAME];
174 	const char *tname;
175 	int (*name_ok) __P((const char *));
176 
177 	tname = qname;
178 	host.h_name = NULL;
179 	eom = answer->buf + anslen;
180 	switch (qtype) {
181 	case T_A:
182 	case T_AAAA:
183 		name_ok = res_hnok;
184 		break;
185 	case T_PTR:
186 		name_ok = res_dnok;
187 		break;
188 	default:
189 		h_errno = NO_RECOVERY;
190 		return (NULL);	/* XXX should be abort(); */
191 	}
192 	/*
193 	 * find first satisfactory answer
194 	 */
195 	hp = &answer->hdr;
196 	ancount = ntohs(hp->ancount);
197 	qdcount = ntohs(hp->qdcount);
198 	bp = hostbuf;
199 	buflen = sizeof hostbuf;
200 	cp = answer->buf;
201 	BOUNDED_INCR(HFIXEDSZ);
202 	if (qdcount != 1) {
203 		h_errno = NO_RECOVERY;
204 		return (NULL);
205 	}
206 	n = dn_expand(answer->buf, eom, cp, bp, buflen);
207 	if ((n < 0) || !(*name_ok)(bp)) {
208 		h_errno = NO_RECOVERY;
209 		return (NULL);
210 	}
211 	BOUNDED_INCR(n + QFIXEDSZ);
212 	if (qtype == T_A || qtype == T_AAAA) {
213 		/* res_send() has already verified that the query name is the
214 		 * same as the one we sent; this just gets the expanded name
215 		 * (i.e., with the succeeding search-domain tacked on).
216 		 */
217 		n = strlen(bp) + 1;		/* for the \0 */
218 		if (n >= MAXHOSTNAMELEN) {
219 			h_errno = NO_RECOVERY;
220 			return (NULL);
221 		}
222 		host.h_name = bp;
223 		bp += n;
224 		buflen -= n;
225 		/* The qname can be abbreviated, but h_name is now absolute. */
226 		qname = host.h_name;
227 	}
228 	ap = host_aliases;
229 	*ap = NULL;
230 	host.h_aliases = host_aliases;
231 	hap = h_addr_ptrs;
232 	*hap = NULL;
233 	host.h_addr_list = h_addr_ptrs;
234 	haveanswer = 0;
235 	had_error = 0;
236 	_dns_ttl_ = -1;
237 	while (ancount-- > 0 && cp < eom && !had_error) {
238 		n = dn_expand(answer->buf, eom, cp, bp, buflen);
239 		if ((n < 0) || !(*name_ok)(bp)) {
240 			had_error++;
241 			continue;
242 		}
243 		cp += n;			/* name */
244 		BOUNDS_CHECK(cp, 3 * INT16SZ + INT32SZ);
245 		type = _getshort(cp);
246  		cp += INT16SZ;			/* type */
247 		class = _getshort(cp);
248  		cp += INT16SZ;			/* class */
249 		if (qtype == T_A  && type == T_A)
250 			_dns_ttl_ = _getlong(cp);
251 		cp += INT32SZ;			/* TTL */
252 		n = _getshort(cp);
253 		cp += INT16SZ;			/* len */
254 		BOUNDS_CHECK(cp, n);
255 		erdata = cp + n;
256 		if (class != C_IN) {
257 			/* XXX - debug? syslog? */
258 			cp += n;
259 			continue;		/* XXX - had_error++ ? */
260 		}
261 		if ((qtype == T_A || qtype == T_AAAA) && type == T_CNAME) {
262 			if (ap >= &host_aliases[MAXALIASES-1])
263 				continue;
264 			n = dn_expand(answer->buf, eom, cp, tbuf, sizeof tbuf);
265 			if ((n < 0) || !(*name_ok)(tbuf)) {
266 				had_error++;
267 				continue;
268 			}
269 			cp += n;
270 			if (cp != erdata) {
271 				h_errno = NO_RECOVERY;
272 				return (NULL);
273 			}
274 			/* Store alias. */
275 			*ap++ = bp;
276 			n = strlen(bp) + 1;	/* for the \0 */
277 			if (n >= MAXHOSTNAMELEN) {
278 				had_error++;
279 				continue;
280 			}
281 			bp += n;
282 			buflen -= n;
283 			/* Get canonical name. */
284 			n = strlen(tbuf) + 1;	/* for the \0 */
285 			if (n > buflen || n >= MAXHOSTNAMELEN) {
286 				had_error++;
287 				continue;
288 			}
289 			strcpy(bp, tbuf);
290 			host.h_name = bp;
291 			bp += n;
292 			buflen -= n;
293 			continue;
294 		}
295 		if (qtype == T_PTR && type == T_CNAME) {
296 			n = dn_expand(answer->buf, eom, cp, tbuf, sizeof tbuf);
297 			if (n < 0 || !res_dnok(tbuf)) {
298 				had_error++;
299 				continue;
300 			}
301 			cp += n;
302 			if (cp != erdata) {
303 				h_errno = NO_RECOVERY;
304 				return (NULL);
305 			}
306 			/* Get canonical name. */
307 			n = strlen(tbuf) + 1;	/* for the \0 */
308 			if (n > buflen || n >= MAXHOSTNAMELEN) {
309 				had_error++;
310 				continue;
311 			}
312 			strcpy(bp, tbuf);
313 			tname = bp;
314 			bp += n;
315 			buflen -= n;
316 			continue;
317 		}
318 		if (type != qtype) {
319 			if (type != T_SIG)
320 				syslog(LOG_NOTICE|LOG_AUTH,
321 	"gethostby*.gethostanswer: asked for \"%s %s %s\", got type \"%s\"",
322 				       qname, p_class(C_IN), p_type(qtype),
323 				       p_type(type));
324 			cp += n;
325 			continue;		/* XXX - had_error++ ? */
326 		}
327 		switch (type) {
328 		case T_PTR:
329 			if (strcasecmp(tname, bp) != 0) {
330 				syslog(LOG_NOTICE|LOG_AUTH,
331 				       AskedForGot, qname, bp);
332 				cp += n;
333 				continue;	/* XXX - had_error++ ? */
334 			}
335 			n = dn_expand(answer->buf, eom, cp, bp, buflen);
336 			if ((n < 0) || !res_hnok(bp)) {
337 				had_error++;
338 				break;
339 			}
340 #if MULTI_PTRS_ARE_ALIASES
341 			cp += n;
342 			if (cp != erdata) {
343 				h_errno = NO_RECOVERY;
344 				return (NULL);
345 			}
346 			if (!haveanswer)
347 				host.h_name = bp;
348 			else if (ap < &host_aliases[MAXALIASES-1])
349 				*ap++ = bp;
350 			else
351 				n = -1;
352 			if (n != -1) {
353 				n = strlen(bp) + 1;	/* for the \0 */
354 				if (n >= MAXHOSTNAMELEN) {
355 					had_error++;
356 					break;
357 				}
358 				bp += n;
359 				buflen -= n;
360 			}
361 			break;
362 #else
363 			host.h_name = bp;
364 			if (_res.options & RES_USE_INET6) {
365 				n = strlen(bp) + 1;	/* for the \0 */
366 				if (n >= MAXHOSTNAMELEN) {
367 					had_error++;
368 					break;
369 				}
370 				bp += n;
371 				buflen -= n;
372 				_map_v4v6_hostent(&host, &bp, &buflen);
373 			}
374 			h_errno = NETDB_SUCCESS;
375 			return (&host);
376 #endif
377 		case T_A:
378 		case T_AAAA:
379 			if (strcasecmp(host.h_name, bp) != 0) {
380 				syslog(LOG_NOTICE|LOG_AUTH,
381 				       AskedForGot, host.h_name, bp);
382 				cp += n;
383 				continue;	/* XXX - had_error++ ? */
384 			}
385 			if (n != host.h_length) {
386 				cp += n;
387 				continue;
388 			}
389 			if (!haveanswer) {
390 				register int nn;
391 
392 				host.h_name = bp;
393 				nn = strlen(bp) + 1;	/* for the \0 */
394 				bp += nn;
395 				buflen -= nn;
396 			}
397 
398 			bp += sizeof(align) - ((u_long)bp % sizeof(align));
399 
400 			if (bp + n >= &hostbuf[sizeof hostbuf]) {
401 				dprintf("size (%d) too big\n", n);
402 				had_error++;
403 				continue;
404 			}
405 			if (hap >= &h_addr_ptrs[MAXADDRS-1]) {
406 				if (!toobig++)
407 					dprintf("Too many addresses (%d)\n",
408 						MAXADDRS);
409 				cp += n;
410 				continue;
411 			}
412 			bcopy(cp, *hap++ = bp, n);
413 			bp += n;
414 			buflen -= n;
415 			cp += n;
416 			if (cp != erdata) {
417 				h_errno = NO_RECOVERY;
418 				return (NULL);
419 			}
420 			break;
421 		default:
422 			dprintf("Impossible condition (type=%d)\n", type);
423 			h_errno = NO_RECOVERY;
424 			return (NULL);
425 			/* BIND has abort() here, too risky on bad data */
426 		}
427 		if (!had_error)
428 			haveanswer++;
429 	}
430 	if (haveanswer) {
431 		*ap = NULL;
432 		*hap = NULL;
433 # if defined(RESOLVSORT)
434 		/*
435 		 * Note: we sort even if host can take only one address
436 		 * in its return structures - should give it the "best"
437 		 * address in that case, not some random one
438 		 */
439 		if (_res.nsort && haveanswer > 1 && qtype == T_A)
440 			addrsort(h_addr_ptrs, haveanswer);
441 # endif /*RESOLVSORT*/
442 		if (!host.h_name) {
443 			n = strlen(qname) + 1;	/* for the \0 */
444 			if (n > buflen || n >= MAXHOSTNAMELEN)
445 				goto no_recovery;
446 			strcpy(bp, qname);
447 			host.h_name = bp;
448 			bp += n;
449 			buflen -= n;
450 		}
451 		if (_res.options & RES_USE_INET6)
452 			_map_v4v6_hostent(&host, &bp, &buflen);
453 		h_errno = NETDB_SUCCESS;
454 		return (&host);
455 	}
456  no_recovery:
457 	h_errno = NO_RECOVERY;
458 	return (NULL);
459 }
460 
461 struct hostent *
462 __dns_getanswer(answer, anslen, qname, qtype)
463 	const char *answer;
464 	int anslen;
465 	const char *qname;
466 	int qtype;
467 {
468 	switch(qtype) {
469 	case T_AAAA:
470 		host.h_addrtype = AF_INET6;
471 		host.h_length = IN6ADDRSZ;
472 		break;
473 	case T_A:
474 	default:
475 		host.h_addrtype = AF_INET;
476 		host.h_length = INADDRSZ;
477 		break;
478 	}
479 
480 	return(gethostanswer((const querybuf *)answer, anslen, qname, qtype));
481 }
482 
483 int
484 _dns_gethostbyname(void *rval, void *cb_data, va_list ap)
485 {
486 	const char *name;
487 	int af;
488 	querybuf buf;
489 	register const char *cp;
490 	char *bp;
491 	int n, size, type, len;
492 
493 	name = va_arg(ap, const char *);
494 	af = va_arg(ap, int);
495 	*(struct hostent **)rval = NULL;
496 
497 	if ((_res.options & RES_INIT) == 0 && res_init() == -1) {
498 		h_errno = NETDB_INTERNAL;
499 		return NS_UNAVAIL;
500 	}
501 
502 	switch (af) {
503 	case AF_INET:
504 		size = INADDRSZ;
505 		type = T_A;
506 		break;
507 	case AF_INET6:
508 		size = IN6ADDRSZ;
509 		type = T_AAAA;
510 		break;
511 	default:
512 		h_errno = NETDB_INTERNAL;
513 		errno = EAFNOSUPPORT;
514 		return NS_UNAVAIL;
515 	}
516 
517 	host.h_addrtype = af;
518 	host.h_length = size;
519 
520 	/*
521 	 * if there aren't any dots, it could be a user-level alias.
522 	 * this is also done in res_query() since we are not the only
523 	 * function that looks up host names.
524 	 */
525 	if (!strchr(name, '.') && (cp = __hostalias(name)))
526 		name = cp;
527 
528 	/*
529 	 * disallow names consisting only of digits/dots, unless
530 	 * they end in a dot.
531 	 */
532 	if (isdigit((unsigned char)name[0]))
533 		for (cp = name;; ++cp) {
534 			if (!*cp) {
535 				if (*--cp == '.')
536 					break;
537 				/*
538 				 * All-numeric, no dot at the end.
539 				 * Fake up a hostent as if we'd actually
540 				 * done a lookup.
541 				 */
542 				if (inet_pton(af, name, host_addr) <= 0) {
543 					h_errno = HOST_NOT_FOUND;
544 					return NS_NOTFOUND;
545 				}
546 				strncpy(hostbuf, name, MAXDNAME);
547 				hostbuf[MAXDNAME] = '\0';
548 				bp = hostbuf + MAXDNAME;
549 				len = sizeof hostbuf - MAXDNAME;
550 				host.h_name = hostbuf;
551 				host.h_aliases = host_aliases;
552 				host_aliases[0] = NULL;
553 				h_addr_ptrs[0] = (char *)host_addr;
554 				h_addr_ptrs[1] = NULL;
555 				host.h_addr_list = h_addr_ptrs;
556 				if (_res.options & RES_USE_INET6)
557 					_map_v4v6_hostent(&host, &bp, &len);
558 				h_errno = NETDB_SUCCESS;
559 				*(struct hostent **)rval = &host;
560 				return NS_SUCCESS;
561 			}
562 			if (!isdigit((unsigned char)*cp) && *cp != '.')
563 				break;
564 		}
565 	if ((isxdigit((unsigned char)name[0]) && strchr(name, ':') != NULL) ||
566 	    name[0] == ':')
567 		for (cp = name;; ++cp) {
568 			if (!*cp) {
569 				if (*--cp == '.')
570 					break;
571 				/*
572 				 * All-IPv6-legal, no dot at the end.
573 				 * Fake up a hostent as if we'd actually
574 				 * done a lookup.
575 				 */
576 				if (inet_pton(af, name, host_addr) <= 0) {
577 					h_errno = HOST_NOT_FOUND;
578 					return NS_NOTFOUND;
579 				}
580 				strncpy(hostbuf, name, MAXDNAME);
581 				hostbuf[MAXDNAME] = '\0';
582 				bp = hostbuf + MAXDNAME;
583 				len = sizeof hostbuf - MAXDNAME;
584 				host.h_name = hostbuf;
585 				host.h_aliases = host_aliases;
586 				host_aliases[0] = NULL;
587 				h_addr_ptrs[0] = (char *)host_addr;
588 				h_addr_ptrs[1] = NULL;
589 				host.h_addr_list = h_addr_ptrs;
590 				h_errno = NETDB_SUCCESS;
591 				*(struct hostent **)rval = &host;
592 				return NS_SUCCESS;
593 			}
594 			if (!isxdigit((unsigned char)*cp) && *cp != ':' && *cp != '.')
595 				break;
596 		}
597 
598 	if ((n = res_search(name, C_IN, type, buf.buf, sizeof(buf))) < 0) {
599 		dprintf("res_search failed (%d)\n", n);
600 		return NS_UNAVAIL;
601 	}
602 	*(struct hostent **)rval = gethostanswer(&buf, n, name, type);
603 	return (*(struct hostent **)rval != NULL) ? NS_SUCCESS : NS_NOTFOUND;
604 }
605 
606 int
607 _dns_gethostbyaddr(void *rval, void *cb_data, va_list ap)
608 {
609 	const char *addr;	/* XXX should have been def'd as u_char! */
610 	int len, af;
611 	const u_char *uaddr;
612 	static const u_char mapped[] = { 0,0, 0,0, 0,0, 0,0, 0,0, 0xff,0xff };
613 	static const u_char tunnelled[] = { 0,0, 0,0, 0,0, 0,0, 0,0, 0,0 };
614 	int n, size;
615 	querybuf buf;
616 	register struct hostent *hp;
617 	char qbuf[MAXDNAME+1], *qp;
618 #ifdef SUNSECURITY
619 	register struct hostent *rhp;
620 	char **haddr;
621 	u_long old_options;
622 	char hname2[MAXDNAME+1];
623 #endif /*SUNSECURITY*/
624 
625 	addr = va_arg(ap, const char *);
626 	uaddr = (const u_char *)addr;
627 	len = va_arg(ap, int);
628 	af = va_arg(ap, int);
629 
630 	*(struct hostent **)rval = NULL;
631 
632 	if ((_res.options & RES_INIT) == 0 && res_init() == -1) {
633 		h_errno = NETDB_INTERNAL;
634 		return NS_UNAVAIL;
635 	}
636 	if (af == AF_INET6 && len == IN6ADDRSZ &&
637 	    (!bcmp(uaddr, mapped, sizeof mapped) ||
638 	     !bcmp(uaddr, tunnelled, sizeof tunnelled))) {
639 		/* Unmap. */
640 		addr += sizeof mapped;
641 		uaddr += sizeof mapped;
642 		af = AF_INET;
643 		len = INADDRSZ;
644 	}
645 	switch (af) {
646 	case AF_INET:
647 		size = INADDRSZ;
648 		break;
649 	case AF_INET6:
650 		size = IN6ADDRSZ;
651 		break;
652 	default:
653 		errno = EAFNOSUPPORT;
654 		h_errno = NETDB_INTERNAL;
655 		return NS_UNAVAIL;
656 	}
657 	if (size != len) {
658 		errno = EINVAL;
659 		h_errno = NETDB_INTERNAL;
660 		return NS_UNAVAIL;
661 	}
662 	switch (af) {
663 	case AF_INET:
664 		(void) sprintf(qbuf, "%u.%u.%u.%u.in-addr.arpa",
665 			       (uaddr[3] & 0xff),
666 			       (uaddr[2] & 0xff),
667 			       (uaddr[1] & 0xff),
668 			       (uaddr[0] & 0xff));
669 		break;
670 	case AF_INET6:
671 		qp = qbuf;
672 		for (n = IN6ADDRSZ - 1; n >= 0; n--) {
673 			qp += SPRINTF((qp, "%x.%x.",
674 				       uaddr[n] & 0xf,
675 				       (uaddr[n] >> 4) & 0xf));
676 		}
677 		strcpy(qp, "ip6.int");
678 		break;
679 	default:
680 		abort();
681 	}
682 	n = res_query(qbuf, C_IN, T_PTR, (u_char *)buf.buf, sizeof buf.buf);
683 	if (n < 0) {
684 		dprintf("res_query failed (%d)\n", n);
685 		return NS_UNAVAIL;
686 	}
687 	if (n > sizeof buf.buf) {
688 		dprintf("static buffer is too small (%d)\n", n);
689 		return NS_UNAVAIL;
690 	}
691 	if (!(hp = gethostanswer(&buf, n, qbuf, T_PTR)))
692 		return NS_NOTFOUND;   /* h_errno was set by gethostanswer() */
693 #ifdef SUNSECURITY
694 	if (af == AF_INET) {
695 	    /*
696 	     * turn off search as the name should be absolute,
697 	     * 'localhost' should be matched by defnames
698 	     */
699 	    strncpy(hname2, hp->h_name, MAXDNAME);
700 	    hname2[MAXDNAME] = '\0';
701 	    old_options = _res.options;
702 	    _res.options &= ~RES_DNSRCH;
703 	    _res.options |= RES_DEFNAMES;
704 	    if (!(rhp = gethostbyname(hname2))) {
705 		syslog(LOG_NOTICE|LOG_AUTH,
706 		       "gethostbyaddr: No A record for %s (verifying [%s])",
707 		       hname2, inet_ntoa(*((struct in_addr *)addr)));
708 		_res.options = old_options;
709 		h_errno = HOST_NOT_FOUND;
710 		return NS_NOTFOUND;
711 	    }
712 	    _res.options = old_options;
713 	    for (haddr = rhp->h_addr_list; *haddr; haddr++)
714 		if (!memcmp(*haddr, addr, INADDRSZ))
715 			break;
716 	    if (!*haddr) {
717 		syslog(LOG_NOTICE|LOG_AUTH,
718 		       "gethostbyaddr: A record of %s != PTR record [%s]",
719 		       hname2, inet_ntoa(*((struct in_addr *)addr)));
720 		h_errno = HOST_NOT_FOUND;
721 		return NS_NOTFOUND;
722 	    }
723 	}
724 #endif /*SUNSECURITY*/
725 	hp->h_addrtype = af;
726 	hp->h_length = len;
727 	bcopy(addr, host_addr, len);
728 	h_addr_ptrs[0] = (char *)host_addr;
729 	h_addr_ptrs[1] = NULL;
730 	if (af == AF_INET && (_res.options & RES_USE_INET6)) {
731 		_map_v4v6_address((char*)host_addr, (char*)host_addr);
732 		hp->h_addrtype = AF_INET6;
733 		hp->h_length = IN6ADDRSZ;
734 	}
735 	h_errno = NETDB_SUCCESS;
736 	*(struct hostent **)rval = hp;
737 	return (hp != NULL) ? NS_SUCCESS : NS_NOTFOUND;
738 }
739 
740 #ifdef RESOLVSORT
741 static void
742 addrsort(ap, num)
743 	char **ap;
744 	int num;
745 {
746 	int i, j;
747 	char **p;
748 	short aval[MAXADDRS];
749 	int needsort = 0;
750 
751 	p = ap;
752 	for (i = 0; i < num; i++, p++) {
753 	    for (j = 0 ; (unsigned)j < _res.nsort; j++)
754 		if (_res.sort_list[j].addr.s_addr ==
755 		    (((struct in_addr *)(*p))->s_addr & _res.sort_list[j].mask))
756 			break;
757 	    aval[i] = j;
758 	    if (needsort == 0 && i > 0 && j < aval[i-1])
759 		needsort = i;
760 	}
761 	if (!needsort)
762 	    return;
763 
764 	while (needsort < num) {
765 	    for (j = needsort - 1; j >= 0; j--) {
766 		if (aval[j] > aval[j+1]) {
767 		    char *hp;
768 
769 		    i = aval[j];
770 		    aval[j] = aval[j+1];
771 		    aval[j+1] = i;
772 
773 		    hp = ap[j];
774 		    ap[j] = ap[j+1];
775 		    ap[j+1] = hp;
776 
777 		} else
778 		    break;
779 	    }
780 	    needsort++;
781 	}
782 }
783 #endif
784 void
785 _sethostdnsent(stayopen)
786 	int stayopen;
787 {
788 	if ((_res.options & RES_INIT) == 0 && res_init() == -1)
789 		return;
790 	if (stayopen)
791 		_res.options |= RES_STAYOPEN | RES_USEVC;
792 }
793 
794 void
795 _endhostdnsent()
796 {
797 	_res.options &= ~(RES_STAYOPEN | RES_USEVC);
798 	res_close();
799 }
800