xref: /freebsd/lib/libc/net/gethostbydns.c (revision 5521ff5a4d1929056e7ffc982fac3341ca54df7c)
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 #if PACKETSZ > 1024
102 #define	MAXPACKET	PACKETSZ
103 #else
104 #define	MAXPACKET	1024
105 #endif
106 
107 typedef union {
108     HEADER hdr;
109     u_char buf[MAXPACKET];
110 } querybuf;
111 
112 typedef union {
113     int32_t al;
114     char ac;
115 } align;
116 
117 extern int h_errno;
118 int _dns_ttl_;
119 
120 #ifdef DEBUG
121 static void
122 dprintf(msg, num)
123 	char *msg;
124 	int num;
125 {
126 	if (_res.options & RES_DEBUG) {
127 		int save = errno;
128 
129 		printf(msg, num);
130 		errno = save;
131 	}
132 }
133 #else
134 # define dprintf(msg, num) /*nada*/
135 #endif
136 
137 #define BOUNDED_INCR(x) \
138 	do { \
139 		cp += x; \
140 		if (cp > eom) { \
141 			h_errno = NO_RECOVERY; \
142 			return (NULL); \
143 		} \
144 	} while (0)
145 
146 #define BOUNDS_CHECK(ptr, count) \
147 	do { \
148 		if ((ptr) + (count) > eom) { \
149 			h_errno = NO_RECOVERY; \
150 			return (NULL); \
151 		} \
152 	} while (0)
153 
154 static struct hostent *
155 gethostanswer(answer, anslen, qname, qtype)
156 	const querybuf *answer;
157 	int anslen;
158 	const char *qname;
159 	int qtype;
160 {
161 	register const HEADER *hp;
162 	register const u_char *cp;
163 	register int n;
164 	const u_char *eom, *erdata;
165 	char *bp, **ap, **hap;
166 	int type, class, buflen, ancount, qdcount;
167 	int haveanswer, had_error;
168 	int toobig = 0;
169 	char tbuf[MAXDNAME];
170 	const char *tname;
171 	int (*name_ok) __P((const char *));
172 
173 	tname = qname;
174 	host.h_name = NULL;
175 	eom = answer->buf + anslen;
176 	switch (qtype) {
177 	case T_A:
178 	case T_AAAA:
179 		name_ok = res_hnok;
180 		break;
181 	case T_PTR:
182 		name_ok = res_dnok;
183 		break;
184 	default:
185 		h_errno = NO_RECOVERY;
186 		return (NULL);	/* XXX should be abort(); */
187 	}
188 	/*
189 	 * find first satisfactory answer
190 	 */
191 	hp = &answer->hdr;
192 	ancount = ntohs(hp->ancount);
193 	qdcount = ntohs(hp->qdcount);
194 	bp = hostbuf;
195 	buflen = sizeof hostbuf;
196 	cp = answer->buf;
197 	BOUNDED_INCR(HFIXEDSZ);
198 	if (qdcount != 1) {
199 		h_errno = NO_RECOVERY;
200 		return (NULL);
201 	}
202 	n = dn_expand(answer->buf, eom, cp, bp, buflen);
203 	if ((n < 0) || !(*name_ok)(bp)) {
204 		h_errno = NO_RECOVERY;
205 		return (NULL);
206 	}
207 	BOUNDED_INCR(n + QFIXEDSZ);
208 	if (qtype == T_A || qtype == T_AAAA) {
209 		/* res_send() has already verified that the query name is the
210 		 * same as the one we sent; this just gets the expanded name
211 		 * (i.e., with the succeeding search-domain tacked on).
212 		 */
213 		n = strlen(bp) + 1;		/* for the \0 */
214 		if (n >= MAXHOSTNAMELEN) {
215 			h_errno = NO_RECOVERY;
216 			return (NULL);
217 		}
218 		host.h_name = bp;
219 		bp += n;
220 		buflen -= n;
221 		/* The qname can be abbreviated, but h_name is now absolute. */
222 		qname = host.h_name;
223 	}
224 	ap = host_aliases;
225 	*ap = NULL;
226 	host.h_aliases = host_aliases;
227 	hap = h_addr_ptrs;
228 	*hap = NULL;
229 	host.h_addr_list = h_addr_ptrs;
230 	haveanswer = 0;
231 	had_error = 0;
232 	_dns_ttl_ = -1;
233 	while (ancount-- > 0 && cp < eom && !had_error) {
234 		n = dn_expand(answer->buf, eom, cp, bp, buflen);
235 		if ((n < 0) || !(*name_ok)(bp)) {
236 			had_error++;
237 			continue;
238 		}
239 		cp += n;			/* name */
240 		BOUNDS_CHECK(cp, 3 * INT16SZ + INT32SZ);
241 		type = _getshort(cp);
242  		cp += INT16SZ;			/* type */
243 		class = _getshort(cp);
244  		cp += INT16SZ;			/* class */
245 		if (qtype == T_A  && type == T_A)
246 			_dns_ttl_ = _getlong(cp);
247 		cp += INT32SZ;			/* TTL */
248 		n = _getshort(cp);
249 		cp += INT16SZ;			/* len */
250 		BOUNDS_CHECK(cp, n);
251 		erdata = cp + n;
252 		if (class != C_IN) {
253 			/* XXX - debug? syslog? */
254 			cp += n;
255 			continue;		/* XXX - had_error++ ? */
256 		}
257 		if ((qtype == T_A || qtype == T_AAAA) && type == T_CNAME) {
258 			if (ap >= &host_aliases[MAXALIASES-1])
259 				continue;
260 			n = dn_expand(answer->buf, eom, cp, tbuf, sizeof tbuf);
261 			if ((n < 0) || !(*name_ok)(tbuf)) {
262 				had_error++;
263 				continue;
264 			}
265 			cp += n;
266 			if (cp != erdata) {
267 				h_errno = NO_RECOVERY;
268 				return (NULL);
269 			}
270 			/* Store alias. */
271 			*ap++ = bp;
272 			n = strlen(bp) + 1;	/* for the \0 */
273 			if (n >= MAXHOSTNAMELEN) {
274 				had_error++;
275 				continue;
276 			}
277 			bp += n;
278 			buflen -= n;
279 			/* Get canonical name. */
280 			n = strlen(tbuf) + 1;	/* for the \0 */
281 			if (n > buflen || n >= MAXHOSTNAMELEN) {
282 				had_error++;
283 				continue;
284 			}
285 			strcpy(bp, tbuf);
286 			host.h_name = bp;
287 			bp += n;
288 			buflen -= n;
289 			continue;
290 		}
291 		if (qtype == T_PTR && type == T_CNAME) {
292 			n = dn_expand(answer->buf, eom, cp, tbuf, sizeof tbuf);
293 			if (n < 0 || !res_dnok(tbuf)) {
294 				had_error++;
295 				continue;
296 			}
297 			cp += n;
298 			if (cp != erdata) {
299 				h_errno = NO_RECOVERY;
300 				return (NULL);
301 			}
302 			/* Get canonical name. */
303 			n = strlen(tbuf) + 1;	/* for the \0 */
304 			if (n > buflen || n >= MAXHOSTNAMELEN) {
305 				had_error++;
306 				continue;
307 			}
308 			strcpy(bp, tbuf);
309 			tname = bp;
310 			bp += n;
311 			buflen -= n;
312 			continue;
313 		}
314 		if (type != qtype) {
315 			if (type != T_SIG)
316 				syslog(LOG_NOTICE|LOG_AUTH,
317 	"gethostby*.gethostanswer: asked for \"%s %s %s\", got type \"%s\"",
318 				       qname, p_class(C_IN), p_type(qtype),
319 				       p_type(type));
320 			cp += n;
321 			continue;		/* XXX - had_error++ ? */
322 		}
323 		switch (type) {
324 		case T_PTR:
325 			if (strcasecmp(tname, bp) != 0) {
326 				syslog(LOG_NOTICE|LOG_AUTH,
327 				       AskedForGot, qname, bp);
328 				cp += n;
329 				continue;	/* XXX - had_error++ ? */
330 			}
331 			n = dn_expand(answer->buf, eom, cp, bp, buflen);
332 			if ((n < 0) || !res_hnok(bp)) {
333 				had_error++;
334 				break;
335 			}
336 #if MULTI_PTRS_ARE_ALIASES
337 			cp += n;
338 			if (cp != erdata) {
339 				h_errno = NO_RECOVERY;
340 				return (NULL);
341 			}
342 			if (!haveanswer)
343 				host.h_name = bp;
344 			else if (ap < &host_aliases[MAXALIASES-1])
345 				*ap++ = bp;
346 			else
347 				n = -1;
348 			if (n != -1) {
349 				n = strlen(bp) + 1;	/* for the \0 */
350 				if (n >= MAXHOSTNAMELEN) {
351 					had_error++;
352 					break;
353 				}
354 				bp += n;
355 				buflen -= n;
356 			}
357 			break;
358 #else
359 			host.h_name = bp;
360 			if (_res.options & RES_USE_INET6) {
361 				n = strlen(bp) + 1;	/* for the \0 */
362 				if (n >= MAXHOSTNAMELEN) {
363 					had_error++;
364 					break;
365 				}
366 				bp += n;
367 				buflen -= n;
368 				_map_v4v6_hostent(&host, &bp, &buflen);
369 			}
370 			h_errno = NETDB_SUCCESS;
371 			return (&host);
372 #endif
373 		case T_A:
374 		case T_AAAA:
375 			if (strcasecmp(host.h_name, bp) != 0) {
376 				syslog(LOG_NOTICE|LOG_AUTH,
377 				       AskedForGot, host.h_name, bp);
378 				cp += n;
379 				continue;	/* XXX - had_error++ ? */
380 			}
381 			if (n != host.h_length) {
382 				cp += n;
383 				continue;
384 			}
385 			if (!haveanswer) {
386 				register int nn;
387 
388 				host.h_name = bp;
389 				nn = strlen(bp) + 1;	/* for the \0 */
390 				bp += nn;
391 				buflen -= nn;
392 			}
393 
394 			bp += sizeof(align) - ((u_long)bp % sizeof(align));
395 
396 			if (bp + n >= &hostbuf[sizeof hostbuf]) {
397 				dprintf("size (%d) too big\n", n);
398 				had_error++;
399 				continue;
400 			}
401 			if (hap >= &h_addr_ptrs[MAXADDRS-1]) {
402 				if (!toobig++)
403 					dprintf("Too many addresses (%d)\n",
404 						MAXADDRS);
405 				cp += n;
406 				continue;
407 			}
408 			bcopy(cp, *hap++ = bp, n);
409 			bp += n;
410 			buflen -= n;
411 			cp += n;
412 			if (cp != erdata) {
413 				h_errno = NO_RECOVERY;
414 				return (NULL);
415 			}
416 			break;
417 		default:
418 			dprintf("Impossible condition (type=%d)\n", type);
419 			h_errno = NO_RECOVERY;
420 			return (NULL);
421 			/* BIND has abort() here, too risky on bad data */
422 		}
423 		if (!had_error)
424 			haveanswer++;
425 	}
426 	if (haveanswer) {
427 		*ap = NULL;
428 		*hap = NULL;
429 # if defined(RESOLVSORT)
430 		/*
431 		 * Note: we sort even if host can take only one address
432 		 * in its return structures - should give it the "best"
433 		 * address in that case, not some random one
434 		 */
435 		if (_res.nsort && haveanswer > 1 && qtype == T_A)
436 			addrsort(h_addr_ptrs, haveanswer);
437 # endif /*RESOLVSORT*/
438 		if (!host.h_name) {
439 			n = strlen(qname) + 1;	/* for the \0 */
440 			if (n > buflen || n >= MAXHOSTNAMELEN)
441 				goto no_recovery;
442 			strcpy(bp, qname);
443 			host.h_name = bp;
444 			bp += n;
445 			buflen -= n;
446 		}
447 		if (_res.options & RES_USE_INET6)
448 			_map_v4v6_hostent(&host, &bp, &buflen);
449 		h_errno = NETDB_SUCCESS;
450 		return (&host);
451 	}
452  no_recovery:
453 	h_errno = NO_RECOVERY;
454 	return (NULL);
455 }
456 
457 struct hostent *
458 __dns_getanswer(answer, anslen, qname, qtype)
459 	const char *answer;
460 	int anslen;
461 	const char *qname;
462 	int qtype;
463 {
464 	switch(qtype) {
465 	case T_AAAA:
466 		host.h_addrtype = AF_INET6;
467 		host.h_length = IN6ADDRSZ;
468 		break;
469 	case T_A:
470 	default:
471 		host.h_addrtype = AF_INET;
472 		host.h_length = INADDRSZ;
473 		break;
474 	}
475 
476 	return(gethostanswer((const querybuf *)answer, anslen, qname, qtype));
477 }
478 
479 int
480 _dns_gethostbyname(void *rval, void *cb_data, va_list ap)
481 {
482 	const char *name;
483 	int af;
484 	querybuf buf;
485 	register const char *cp;
486 	char *bp;
487 	int n, size, type, len;
488 
489 	name = va_arg(ap, const char *);
490 	af = va_arg(ap, int);
491 	*(struct hostent **)rval = NULL;
492 
493 	if ((_res.options & RES_INIT) == 0 && res_init() == -1) {
494 		h_errno = NETDB_INTERNAL;
495 		return NS_UNAVAIL;
496 	}
497 
498 	switch (af) {
499 	case AF_INET:
500 		size = INADDRSZ;
501 		type = T_A;
502 		break;
503 	case AF_INET6:
504 		size = IN6ADDRSZ;
505 		type = T_AAAA;
506 		break;
507 	default:
508 		h_errno = NETDB_INTERNAL;
509 		errno = EAFNOSUPPORT;
510 		return NS_UNAVAIL;
511 	}
512 
513 	host.h_addrtype = af;
514 	host.h_length = size;
515 
516 	/*
517 	 * if there aren't any dots, it could be a user-level alias.
518 	 * this is also done in res_query() since we are not the only
519 	 * function that looks up host names.
520 	 */
521 	if (!strchr(name, '.') && (cp = __hostalias(name)))
522 		name = cp;
523 
524 	/*
525 	 * disallow names consisting only of digits/dots, unless
526 	 * they end in a dot.
527 	 */
528 	if (isdigit((unsigned char)name[0]))
529 		for (cp = name;; ++cp) {
530 			if (!*cp) {
531 				if (*--cp == '.')
532 					break;
533 				/*
534 				 * All-numeric, no dot at the end.
535 				 * Fake up a hostent as if we'd actually
536 				 * done a lookup.
537 				 */
538 				if (inet_pton(af, name, host_addr) <= 0) {
539 					h_errno = HOST_NOT_FOUND;
540 					return NS_NOTFOUND;
541 				}
542 				strncpy(hostbuf, name, MAXDNAME);
543 				hostbuf[MAXDNAME] = '\0';
544 				bp = hostbuf + MAXDNAME;
545 				len = sizeof hostbuf - MAXDNAME;
546 				host.h_name = hostbuf;
547 				host.h_aliases = host_aliases;
548 				host_aliases[0] = NULL;
549 				h_addr_ptrs[0] = (char *)host_addr;
550 				h_addr_ptrs[1] = NULL;
551 				host.h_addr_list = h_addr_ptrs;
552 				if (_res.options & RES_USE_INET6)
553 					_map_v4v6_hostent(&host, &bp, &len);
554 				h_errno = NETDB_SUCCESS;
555 				*(struct hostent **)rval = &host;
556 				return NS_SUCCESS;
557 			}
558 			if (!isdigit((unsigned char)*cp) && *cp != '.')
559 				break;
560 		}
561 	if ((isxdigit((unsigned char)name[0]) && strchr(name, ':') != NULL) ||
562 	    name[0] == ':')
563 		for (cp = name;; ++cp) {
564 			if (!*cp) {
565 				if (*--cp == '.')
566 					break;
567 				/*
568 				 * All-IPv6-legal, no dot at the end.
569 				 * Fake up a hostent as if we'd actually
570 				 * done a lookup.
571 				 */
572 				if (inet_pton(af, name, host_addr) <= 0) {
573 					h_errno = HOST_NOT_FOUND;
574 					return NS_NOTFOUND;
575 				}
576 				strncpy(hostbuf, name, MAXDNAME);
577 				hostbuf[MAXDNAME] = '\0';
578 				bp = hostbuf + MAXDNAME;
579 				len = sizeof hostbuf - MAXDNAME;
580 				host.h_name = hostbuf;
581 				host.h_aliases = host_aliases;
582 				host_aliases[0] = NULL;
583 				h_addr_ptrs[0] = (char *)host_addr;
584 				h_addr_ptrs[1] = NULL;
585 				host.h_addr_list = h_addr_ptrs;
586 				h_errno = NETDB_SUCCESS;
587 				*(struct hostent **)rval = &host;
588 				return NS_SUCCESS;
589 			}
590 			if (!isxdigit((unsigned char)*cp) && *cp != ':' && *cp != '.')
591 				break;
592 		}
593 
594 	if ((n = res_search(name, C_IN, type, buf.buf, sizeof(buf))) < 0) {
595 		dprintf("res_search failed (%d)\n", n);
596 		return NS_UNAVAIL;
597 	}
598 	*(struct hostent **)rval = gethostanswer(&buf, n, name, type);
599 	return (*(struct hostent **)rval != NULL) ? NS_SUCCESS : NS_NOTFOUND;
600 }
601 
602 int
603 _dns_gethostbyaddr(void *rval, void *cb_data, va_list ap)
604 {
605 	const char *addr;	/* XXX should have been def'd as u_char! */
606 	int len, af;
607 	const u_char *uaddr;
608 	static const u_char mapped[] = { 0,0, 0,0, 0,0, 0,0, 0,0, 0xff,0xff };
609 	static const u_char tunnelled[] = { 0,0, 0,0, 0,0, 0,0, 0,0, 0,0 };
610 	int n, size;
611 	querybuf buf;
612 	register struct hostent *hp;
613 	char qbuf[MAXDNAME+1], *qp;
614 #ifdef SUNSECURITY
615 	register struct hostent *rhp;
616 	char **haddr;
617 	u_long old_options;
618 	char hname2[MAXDNAME+1];
619 #endif /*SUNSECURITY*/
620 
621 	addr = va_arg(ap, const char *);
622 	uaddr = (const u_char *)addr;
623 	len = va_arg(ap, int);
624 	af = va_arg(ap, int);
625 
626 	*(struct hostent **)rval = NULL;
627 
628 	if ((_res.options & RES_INIT) == 0 && res_init() == -1) {
629 		h_errno = NETDB_INTERNAL;
630 		return NS_UNAVAIL;
631 	}
632 	if (af == AF_INET6 && len == IN6ADDRSZ &&
633 	    (!bcmp(uaddr, mapped, sizeof mapped) ||
634 	     !bcmp(uaddr, tunnelled, sizeof tunnelled))) {
635 		/* Unmap. */
636 		addr += sizeof mapped;
637 		uaddr += sizeof mapped;
638 		af = AF_INET;
639 		len = INADDRSZ;
640 	}
641 	switch (af) {
642 	case AF_INET:
643 		size = INADDRSZ;
644 		break;
645 	case AF_INET6:
646 		size = IN6ADDRSZ;
647 		break;
648 	default:
649 		errno = EAFNOSUPPORT;
650 		h_errno = NETDB_INTERNAL;
651 		return NS_UNAVAIL;
652 	}
653 	if (size != len) {
654 		errno = EINVAL;
655 		h_errno = NETDB_INTERNAL;
656 		return NS_UNAVAIL;
657 	}
658 	switch (af) {
659 	case AF_INET:
660 		(void) sprintf(qbuf, "%u.%u.%u.%u.in-addr.arpa",
661 			       (uaddr[3] & 0xff),
662 			       (uaddr[2] & 0xff),
663 			       (uaddr[1] & 0xff),
664 			       (uaddr[0] & 0xff));
665 		break;
666 	case AF_INET6:
667 		qp = qbuf;
668 		for (n = IN6ADDRSZ - 1; n >= 0; n--) {
669 			qp += SPRINTF((qp, "%x.%x.",
670 				       uaddr[n] & 0xf,
671 				       (uaddr[n] >> 4) & 0xf));
672 		}
673 		strcpy(qp, "ip6.int");
674 		break;
675 	default:
676 		abort();
677 	}
678 	n = res_query(qbuf, C_IN, T_PTR, (u_char *)buf.buf, sizeof buf.buf);
679 	if (n < 0) {
680 		dprintf("res_query failed (%d)\n", n);
681 		return NS_UNAVAIL;
682 	}
683 	if (n > sizeof buf.buf) {
684 		dprintf("static buffer is too small (%d)\n", n);
685 		return NS_UNAVAIL;
686 	}
687 	if (!(hp = gethostanswer(&buf, n, qbuf, T_PTR)))
688 		return NS_NOTFOUND;   /* h_errno was set by gethostanswer() */
689 #ifdef SUNSECURITY
690 	if (af == AF_INET) {
691 	    /*
692 	     * turn off search as the name should be absolute,
693 	     * 'localhost' should be matched by defnames
694 	     */
695 	    strncpy(hname2, hp->h_name, MAXDNAME);
696 	    hname2[MAXDNAME] = '\0';
697 	    old_options = _res.options;
698 	    _res.options &= ~RES_DNSRCH;
699 	    _res.options |= RES_DEFNAMES;
700 	    if (!(rhp = gethostbyname(hname2))) {
701 		syslog(LOG_NOTICE|LOG_AUTH,
702 		       "gethostbyaddr: No A record for %s (verifying [%s])",
703 		       hname2, inet_ntoa(*((struct in_addr *)addr)));
704 		_res.options = old_options;
705 		h_errno = HOST_NOT_FOUND;
706 		return NS_NOTFOUND;
707 	    }
708 	    _res.options = old_options;
709 	    for (haddr = rhp->h_addr_list; *haddr; haddr++)
710 		if (!memcmp(*haddr, addr, INADDRSZ))
711 			break;
712 	    if (!*haddr) {
713 		syslog(LOG_NOTICE|LOG_AUTH,
714 		       "gethostbyaddr: A record of %s != PTR record [%s]",
715 		       hname2, inet_ntoa(*((struct in_addr *)addr)));
716 		h_errno = HOST_NOT_FOUND;
717 		return NS_NOTFOUND;
718 	    }
719 	}
720 #endif /*SUNSECURITY*/
721 	hp->h_addrtype = af;
722 	hp->h_length = len;
723 	bcopy(addr, host_addr, len);
724 	h_addr_ptrs[0] = (char *)host_addr;
725 	h_addr_ptrs[1] = NULL;
726 	if (af == AF_INET && (_res.options & RES_USE_INET6)) {
727 		_map_v4v6_address((char*)host_addr, (char*)host_addr);
728 		hp->h_addrtype = AF_INET6;
729 		hp->h_length = IN6ADDRSZ;
730 	}
731 	h_errno = NETDB_SUCCESS;
732 	*(struct hostent **)rval = hp;
733 	return (hp != NULL) ? NS_SUCCESS : NS_NOTFOUND;
734 }
735 
736 #ifdef RESOLVSORT
737 static void
738 addrsort(ap, num)
739 	char **ap;
740 	int num;
741 {
742 	int i, j;
743 	char **p;
744 	short aval[MAXADDRS];
745 	int needsort = 0;
746 
747 	p = ap;
748 	for (i = 0; i < num; i++, p++) {
749 	    for (j = 0 ; (unsigned)j < _res.nsort; j++)
750 		if (_res.sort_list[j].addr.s_addr ==
751 		    (((struct in_addr *)(*p))->s_addr & _res.sort_list[j].mask))
752 			break;
753 	    aval[i] = j;
754 	    if (needsort == 0 && i > 0 && j < aval[i-1])
755 		needsort = i;
756 	}
757 	if (!needsort)
758 	    return;
759 
760 	while (needsort < num) {
761 	    for (j = needsort - 1; j >= 0; j--) {
762 		if (aval[j] > aval[j+1]) {
763 		    char *hp;
764 
765 		    i = aval[j];
766 		    aval[j] = aval[j+1];
767 		    aval[j+1] = i;
768 
769 		    hp = ap[j];
770 		    ap[j] = ap[j+1];
771 		    ap[j+1] = hp;
772 
773 		} else
774 		    break;
775 	    }
776 	    needsort++;
777 	}
778 }
779 #endif
780 void
781 _sethostdnsent(stayopen)
782 	int stayopen;
783 {
784 	if ((_res.options & RES_INIT) == 0 && res_init() == -1)
785 		return;
786 	if (stayopen)
787 		_res.options |= RES_STAYOPEN | RES_USEVC;
788 }
789 
790 void
791 _endhostdnsent()
792 {
793 	_res.options &= ~(RES_STAYOPEN | RES_USEVC);
794 	res_close();
795 }
796