xref: /freebsd/lib/libc/net/gethostbydns.c (revision b52b9d56d4e96089873a75f9e29062eec19fabba)
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 $";
59 #endif /* LIBC_SCCS and not lint */
60 #include <sys/cdefs.h>
61 __FBSDID("$FreeBSD$");
62 
63 #include <sys/types.h>
64 #include <sys/param.h>
65 #include <sys/socket.h>
66 #include <netinet/in.h>
67 #include <arpa/inet.h>
68 #include <arpa/nameser.h>
69 
70 #include <stdio.h>
71 #include <unistd.h>
72 #include <string.h>
73 #include <netdb.h>
74 #include <resolv.h>
75 #include <ctype.h>
76 #include <errno.h>
77 #include <syslog.h>
78 #include <stdarg.h>
79 #include <nsswitch.h>
80 
81 #include "res_config.h"
82 
83 #define SPRINTF(x) ((size_t)sprintf x)
84 
85 #define	MAXALIASES	35
86 #define	MAXADDRS	35
87 
88 static const char AskedForGot[] =
89 		"gethostby*.gethostanswer: asked for \"%s\", got \"%s\"";
90 
91 static char *h_addr_ptrs[MAXADDRS + 1];
92 
93 static struct hostent host;
94 static char *host_aliases[MAXALIASES];
95 static char hostbuf[8*1024];
96 static u_char host_addr[16];	/* IPv4 or IPv6 */
97 
98 #ifdef RESOLVSORT
99 static void addrsort(char **, int);
100 #endif
101 
102 #ifdef DEBUG
103 static void dprintf(char *, int) __printflike(1, 0);
104 #endif
105 
106 #if PACKETSZ > 1024
107 #define	MAXPACKET	PACKETSZ
108 #else
109 #define	MAXPACKET	1024
110 #endif
111 
112 typedef union {
113     HEADER hdr;
114     u_char buf[MAXPACKET];
115 } querybuf;
116 
117 typedef union {
118     int32_t al;
119     char ac;
120 } align;
121 
122 extern int h_errno;
123 int _dns_ttl_;
124 
125 #ifdef DEBUG
126 static void
127 dprintf(msg, num)
128 	char *msg;
129 	int num;
130 {
131 	if (_res.options & RES_DEBUG) {
132 		int save = errno;
133 
134 		printf(msg, num);
135 		errno = save;
136 	}
137 }
138 #else
139 # define dprintf(msg, num) /*nada*/
140 #endif
141 
142 #define BOUNDED_INCR(x) \
143 	do { \
144 		cp += x; \
145 		if (cp > eom) { \
146 			h_errno = NO_RECOVERY; \
147 			return (NULL); \
148 		} \
149 	} while (0)
150 
151 #define BOUNDS_CHECK(ptr, count) \
152 	do { \
153 		if ((ptr) + (count) > eom) { \
154 			h_errno = NO_RECOVERY; \
155 			return (NULL); \
156 		} \
157 	} while (0)
158 
159 static struct hostent *
160 gethostanswer(answer, anslen, qname, qtype)
161 	const querybuf *answer;
162 	int anslen;
163 	const char *qname;
164 	int qtype;
165 {
166 	const HEADER *hp;
167 	const u_char *cp;
168 	int n;
169 	const u_char *eom, *erdata;
170 	char *bp, *ep, **ap, **hap;
171 	int type, class, ancount, qdcount;
172 	int haveanswer, had_error;
173 	int toobig = 0;
174 	char tbuf[MAXDNAME];
175 	const char *tname;
176 	int (*name_ok)(const char *);
177 
178 	tname = qname;
179 	host.h_name = NULL;
180 	eom = answer->buf + anslen;
181 	switch (qtype) {
182 	case T_A:
183 	case T_AAAA:
184 		name_ok = res_hnok;
185 		break;
186 	case T_PTR:
187 		name_ok = res_dnok;
188 		break;
189 	default:
190 		h_errno = NO_RECOVERY;
191 		return (NULL);	/* XXX should be abort(); */
192 	}
193 	/*
194 	 * find first satisfactory answer
195 	 */
196 	hp = &answer->hdr;
197 	ancount = ntohs(hp->ancount);
198 	qdcount = ntohs(hp->qdcount);
199 	bp = hostbuf;
200 	ep = hostbuf + sizeof hostbuf;
201 	cp = answer->buf;
202 	BOUNDED_INCR(HFIXEDSZ);
203 	if (qdcount != 1) {
204 		h_errno = NO_RECOVERY;
205 		return (NULL);
206 	}
207 	n = dn_expand(answer->buf, eom, cp, bp, ep - bp);
208 	if ((n < 0) || !(*name_ok)(bp)) {
209 		h_errno = NO_RECOVERY;
210 		return (NULL);
211 	}
212 	BOUNDED_INCR(n + QFIXEDSZ);
213 	if (qtype == T_A || qtype == T_AAAA) {
214 		/* res_send() has already verified that the query name is the
215 		 * same as the one we sent; this just gets the expanded name
216 		 * (i.e., with the succeeding search-domain tacked on).
217 		 */
218 		n = strlen(bp) + 1;		/* for the \0 */
219 		if (n >= MAXHOSTNAMELEN) {
220 			h_errno = NO_RECOVERY;
221 			return (NULL);
222 		}
223 		host.h_name = bp;
224 		bp += 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, ep - bp);
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 			/* Get canonical name. */
283 			n = strlen(tbuf) + 1;	/* for the \0 */
284 			if (n > ep - bp || n >= MAXHOSTNAMELEN) {
285 				had_error++;
286 				continue;
287 			}
288 			strcpy(bp, tbuf);
289 			host.h_name = bp;
290 			bp += n;
291 			continue;
292 		}
293 		if (qtype == T_PTR && type == T_CNAME) {
294 			n = dn_expand(answer->buf, eom, cp, tbuf, sizeof tbuf);
295 			if (n < 0 || !res_dnok(tbuf)) {
296 				had_error++;
297 				continue;
298 			}
299 			cp += n;
300 			if (cp != erdata) {
301 				h_errno = NO_RECOVERY;
302 				return (NULL);
303 			}
304 			/* Get canonical name. */
305 			n = strlen(tbuf) + 1;	/* for the \0 */
306 			if (n > ep - bp || n >= MAXHOSTNAMELEN) {
307 				had_error++;
308 				continue;
309 			}
310 			strcpy(bp, tbuf);
311 			tname = bp;
312 			bp += n;
313 			continue;
314 		}
315 		if (type != qtype) {
316 			if (type != T_SIG)
317 				syslog(LOG_NOTICE|LOG_AUTH,
318 	"gethostby*.gethostanswer: asked for \"%s %s %s\", got type \"%s\"",
319 				       qname, p_class(C_IN), p_type(qtype),
320 				       p_type(type));
321 			cp += n;
322 			continue;		/* XXX - had_error++ ? */
323 		}
324 		switch (type) {
325 		case T_PTR:
326 			if (strcasecmp(tname, bp) != 0) {
327 				syslog(LOG_NOTICE|LOG_AUTH,
328 				       AskedForGot, qname, bp);
329 				cp += n;
330 				continue;	/* XXX - had_error++ ? */
331 			}
332 			n = dn_expand(answer->buf, eom, cp, bp, ep - bp);
333 			if ((n < 0) || !res_hnok(bp)) {
334 				had_error++;
335 				break;
336 			}
337 #if MULTI_PTRS_ARE_ALIASES
338 			cp += n;
339 			if (cp != erdata) {
340 				h_errno = NO_RECOVERY;
341 				return (NULL);
342 			}
343 			if (!haveanswer)
344 				host.h_name = bp;
345 			else if (ap < &host_aliases[MAXALIASES-1])
346 				*ap++ = bp;
347 			else
348 				n = -1;
349 			if (n != -1) {
350 				n = strlen(bp) + 1;	/* for the \0 */
351 				if (n >= MAXHOSTNAMELEN) {
352 					had_error++;
353 					break;
354 				}
355 				bp += 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 				_map_v4v6_hostent(&host, &bp, &ep);
368 			}
369 			h_errno = NETDB_SUCCESS;
370 			return (&host);
371 #endif
372 		case T_A:
373 		case T_AAAA:
374 			if (strcasecmp(host.h_name, bp) != 0) {
375 				syslog(LOG_NOTICE|LOG_AUTH,
376 				       AskedForGot, host.h_name, bp);
377 				cp += n;
378 				continue;	/* XXX - had_error++ ? */
379 			}
380 			if (n != host.h_length) {
381 				cp += n;
382 				continue;
383 			}
384 			if (!haveanswer) {
385 				int nn;
386 
387 				host.h_name = bp;
388 				nn = strlen(bp) + 1;	/* for the \0 */
389 				bp += nn;
390 			}
391 
392 			bp += sizeof(align) - ((u_long)bp % sizeof(align));
393 
394 			if (bp + n >= ep) {
395 				dprintf("size (%d) too big\n", n);
396 				had_error++;
397 				continue;
398 			}
399 			if (hap >= &h_addr_ptrs[MAXADDRS-1]) {
400 				if (!toobig++)
401 					dprintf("Too many addresses (%d)\n",
402 						MAXADDRS);
403 				cp += n;
404 				continue;
405 			}
406 			bcopy(cp, *hap++ = bp, n);
407 			bp += n;
408 			cp += n;
409 			if (cp != erdata) {
410 				h_errno = NO_RECOVERY;
411 				return (NULL);
412 			}
413 			break;
414 		default:
415 			dprintf("Impossible condition (type=%d)\n", type);
416 			h_errno = NO_RECOVERY;
417 			return (NULL);
418 			/* BIND has abort() here, too risky on bad data */
419 		}
420 		if (!had_error)
421 			haveanswer++;
422 	}
423 	if (haveanswer) {
424 		*ap = NULL;
425 		*hap = NULL;
426 # if defined(RESOLVSORT)
427 		/*
428 		 * Note: we sort even if host can take only one address
429 		 * in its return structures - should give it the "best"
430 		 * address in that case, not some random one
431 		 */
432 		if (_res.nsort && haveanswer > 1 && qtype == T_A)
433 			addrsort(h_addr_ptrs, haveanswer);
434 # endif /*RESOLVSORT*/
435 		if (!host.h_name) {
436 			n = strlen(qname) + 1;	/* for the \0 */
437 			if (n > ep - bp || n >= MAXHOSTNAMELEN)
438 				goto no_recovery;
439 			strcpy(bp, qname);
440 			host.h_name = bp;
441 			bp += n;
442 		}
443 		if (_res.options & RES_USE_INET6)
444 			_map_v4v6_hostent(&host, &bp, &ep);
445 		h_errno = NETDB_SUCCESS;
446 		return (&host);
447 	}
448  no_recovery:
449 	h_errno = NO_RECOVERY;
450 	return (NULL);
451 }
452 
453 struct hostent *
454 __dns_getanswer(answer, anslen, qname, qtype)
455 	const char *answer;
456 	int anslen;
457 	const char *qname;
458 	int qtype;
459 {
460 	switch(qtype) {
461 	case T_AAAA:
462 		host.h_addrtype = AF_INET6;
463 		host.h_length = IN6ADDRSZ;
464 		break;
465 	case T_A:
466 	default:
467 		host.h_addrtype = AF_INET;
468 		host.h_length = INADDRSZ;
469 		break;
470 	}
471 
472 	return(gethostanswer((const querybuf *)answer, anslen, qname, qtype));
473 }
474 
475 int
476 _dns_gethostbyname(void *rval, void *cb_data, va_list ap)
477 {
478 	const char *name;
479 	int af;
480 	querybuf buf;
481 	const char *cp;
482 	char *bp, *ep;
483 	int n, size, type, len;
484 
485 	name = va_arg(ap, const char *);
486 	af = va_arg(ap, int);
487 	*(struct hostent **)rval = NULL;
488 
489 	if ((_res.options & RES_INIT) == 0 && res_init() == -1) {
490 		h_errno = NETDB_INTERNAL;
491 		return NS_UNAVAIL;
492 	}
493 
494 	switch (af) {
495 	case AF_INET:
496 		size = INADDRSZ;
497 		type = T_A;
498 		break;
499 	case AF_INET6:
500 		size = IN6ADDRSZ;
501 		type = T_AAAA;
502 		break;
503 	default:
504 		h_errno = NETDB_INTERNAL;
505 		errno = EAFNOSUPPORT;
506 		return NS_UNAVAIL;
507 	}
508 
509 	host.h_addrtype = af;
510 	host.h_length = size;
511 
512 	/*
513 	 * if there aren't any dots, it could be a user-level alias.
514 	 * this is also done in res_query() since we are not the only
515 	 * function that looks up host names.
516 	 */
517 	if (!strchr(name, '.') && (cp = __hostalias(name)))
518 		name = cp;
519 
520 	/*
521 	 * disallow names consisting only of digits/dots, unless
522 	 * they end in a dot.
523 	 */
524 	if (isdigit((unsigned char)name[0]))
525 		for (cp = name;; ++cp) {
526 			if (!*cp) {
527 				if (*--cp == '.')
528 					break;
529 				/*
530 				 * All-numeric, no dot at the end.
531 				 * Fake up a hostent as if we'd actually
532 				 * done a lookup.
533 				 */
534 				if (inet_pton(af, name, host_addr) <= 0) {
535 					h_errno = HOST_NOT_FOUND;
536 					return NS_NOTFOUND;
537 				}
538 				strncpy(hostbuf, name, MAXDNAME);
539 				hostbuf[MAXDNAME] = '\0';
540 				bp = hostbuf + MAXDNAME;
541 				ep = hostbuf + sizeof hostbuf;
542 				host.h_name = hostbuf;
543 				host.h_aliases = host_aliases;
544 				host_aliases[0] = NULL;
545 				h_addr_ptrs[0] = (char *)host_addr;
546 				h_addr_ptrs[1] = NULL;
547 				host.h_addr_list = h_addr_ptrs;
548 				if (_res.options & RES_USE_INET6)
549 					_map_v4v6_hostent(&host, &bp, &ep);
550 				h_errno = NETDB_SUCCESS;
551 				*(struct hostent **)rval = &host;
552 				return NS_SUCCESS;
553 			}
554 			if (!isdigit((unsigned char)*cp) && *cp != '.')
555 				break;
556 		}
557 	if ((isxdigit((unsigned char)name[0]) && strchr(name, ':') != NULL) ||
558 	    name[0] == ':')
559 		for (cp = name;; ++cp) {
560 			if (!*cp) {
561 				if (*--cp == '.')
562 					break;
563 				/*
564 				 * All-IPv6-legal, no dot at the end.
565 				 * Fake up a hostent as if we'd actually
566 				 * done a lookup.
567 				 */
568 				if (inet_pton(af, name, host_addr) <= 0) {
569 					h_errno = HOST_NOT_FOUND;
570 					return NS_NOTFOUND;
571 				}
572 				strncpy(hostbuf, name, MAXDNAME);
573 				hostbuf[MAXDNAME] = '\0';
574 				bp = hostbuf + MAXDNAME;
575 				len = sizeof hostbuf - MAXDNAME;
576 				host.h_name = hostbuf;
577 				host.h_aliases = host_aliases;
578 				host_aliases[0] = NULL;
579 				h_addr_ptrs[0] = (char *)host_addr;
580 				h_addr_ptrs[1] = NULL;
581 				host.h_addr_list = h_addr_ptrs;
582 				h_errno = NETDB_SUCCESS;
583 				*(struct hostent **)rval = &host;
584 				return NS_SUCCESS;
585 			}
586 			if (!isxdigit((unsigned char)*cp) && *cp != ':' && *cp != '.')
587 				break;
588 		}
589 
590 	if ((n = res_search(name, C_IN, type, buf.buf, sizeof(buf))) < 0) {
591 		dprintf("res_search failed (%d)\n", n);
592 		return NS_UNAVAIL;
593 	}
594 	*(struct hostent **)rval = gethostanswer(&buf, n, name, type);
595 	return (*(struct hostent **)rval != NULL) ? NS_SUCCESS : NS_NOTFOUND;
596 }
597 
598 int
599 _dns_gethostbyaddr(void *rval, void *cb_data, va_list ap)
600 {
601 	const char *addr;	/* XXX should have been def'd as u_char! */
602 	int len, af;
603 	const u_char *uaddr;
604 	static const u_char mapped[] = { 0,0, 0,0, 0,0, 0,0, 0,0, 0xff,0xff };
605 	static const u_char tunnelled[] = { 0,0, 0,0, 0,0, 0,0, 0,0, 0,0 };
606 	int n, size;
607 	querybuf buf;
608 	struct hostent *hp;
609 	char qbuf[MAXDNAME+1], *qp;
610 #ifdef SUNSECURITY
611 	struct hostent *rhp;
612 	char **haddr;
613 	u_long old_options;
614 	char hname2[MAXDNAME+1];
615 #endif /*SUNSECURITY*/
616 
617 	addr = va_arg(ap, const char *);
618 	uaddr = (const u_char *)addr;
619 	len = va_arg(ap, int);
620 	af = va_arg(ap, int);
621 
622 	*(struct hostent **)rval = NULL;
623 
624 	if ((_res.options & RES_INIT) == 0 && res_init() == -1) {
625 		h_errno = NETDB_INTERNAL;
626 		return NS_UNAVAIL;
627 	}
628 	if (af == AF_INET6 && len == IN6ADDRSZ &&
629 	    (!bcmp(uaddr, mapped, sizeof mapped) ||
630 	     !bcmp(uaddr, tunnelled, sizeof tunnelled))) {
631 		/* Unmap. */
632 		addr += sizeof mapped;
633 		uaddr += sizeof mapped;
634 		af = AF_INET;
635 		len = INADDRSZ;
636 	}
637 	switch (af) {
638 	case AF_INET:
639 		size = INADDRSZ;
640 		break;
641 	case AF_INET6:
642 		size = IN6ADDRSZ;
643 		break;
644 	default:
645 		errno = EAFNOSUPPORT;
646 		h_errno = NETDB_INTERNAL;
647 		return NS_UNAVAIL;
648 	}
649 	if (size != len) {
650 		errno = EINVAL;
651 		h_errno = NETDB_INTERNAL;
652 		return NS_UNAVAIL;
653 	}
654 	switch (af) {
655 	case AF_INET:
656 		(void) sprintf(qbuf, "%u.%u.%u.%u.in-addr.arpa",
657 			       (uaddr[3] & 0xff),
658 			       (uaddr[2] & 0xff),
659 			       (uaddr[1] & 0xff),
660 			       (uaddr[0] & 0xff));
661 		break;
662 	case AF_INET6:
663 		qp = qbuf;
664 		for (n = IN6ADDRSZ - 1; n >= 0; n--) {
665 			qp += SPRINTF((qp, "%x.%x.",
666 				       uaddr[n] & 0xf,
667 				       (uaddr[n] >> 4) & 0xf));
668 		}
669 		strcpy(qp, "ip6.int");
670 		break;
671 	default:
672 		abort();
673 	}
674 	n = res_query(qbuf, C_IN, T_PTR, (u_char *)buf.buf, sizeof buf.buf);
675 	if (n < 0) {
676 		dprintf("res_query failed (%d)\n", n);
677 		return NS_UNAVAIL;
678 	}
679 	if (n > sizeof buf.buf) {
680 		dprintf("static buffer is too small (%d)\n", n);
681 		return NS_UNAVAIL;
682 	}
683 	if (!(hp = gethostanswer(&buf, n, qbuf, T_PTR)))
684 		return NS_NOTFOUND;   /* h_errno was set by gethostanswer() */
685 #ifdef SUNSECURITY
686 	if (af == AF_INET) {
687 	    /*
688 	     * turn off search as the name should be absolute,
689 	     * 'localhost' should be matched by defnames
690 	     */
691 	    strncpy(hname2, hp->h_name, MAXDNAME);
692 	    hname2[MAXDNAME] = '\0';
693 	    old_options = _res.options;
694 	    _res.options &= ~RES_DNSRCH;
695 	    _res.options |= RES_DEFNAMES;
696 	    if (!(rhp = gethostbyname(hname2))) {
697 		syslog(LOG_NOTICE|LOG_AUTH,
698 		       "gethostbyaddr: No A record for %s (verifying [%s])",
699 		       hname2, inet_ntoa(*((struct in_addr *)addr)));
700 		_res.options = old_options;
701 		h_errno = HOST_NOT_FOUND;
702 		return NS_NOTFOUND;
703 	    }
704 	    _res.options = old_options;
705 	    for (haddr = rhp->h_addr_list; *haddr; haddr++)
706 		if (!memcmp(*haddr, addr, INADDRSZ))
707 			break;
708 	    if (!*haddr) {
709 		syslog(LOG_NOTICE|LOG_AUTH,
710 		       "gethostbyaddr: A record of %s != PTR record [%s]",
711 		       hname2, inet_ntoa(*((struct in_addr *)addr)));
712 		h_errno = HOST_NOT_FOUND;
713 		return NS_NOTFOUND;
714 	    }
715 	}
716 #endif /*SUNSECURITY*/
717 	hp->h_addrtype = af;
718 	hp->h_length = len;
719 	bcopy(addr, host_addr, len);
720 	h_addr_ptrs[0] = (char *)host_addr;
721 	h_addr_ptrs[1] = NULL;
722 	if (af == AF_INET && (_res.options & RES_USE_INET6)) {
723 		_map_v4v6_address((char*)host_addr, (char*)host_addr);
724 		hp->h_addrtype = AF_INET6;
725 		hp->h_length = IN6ADDRSZ;
726 	}
727 	h_errno = NETDB_SUCCESS;
728 	*(struct hostent **)rval = hp;
729 	return (hp != NULL) ? NS_SUCCESS : NS_NOTFOUND;
730 }
731 
732 #ifdef RESOLVSORT
733 static void
734 addrsort(ap, num)
735 	char **ap;
736 	int num;
737 {
738 	int i, j;
739 	char **p;
740 	short aval[MAXADDRS];
741 	int needsort = 0;
742 
743 	p = ap;
744 	for (i = 0; i < num; i++, p++) {
745 	    for (j = 0 ; (unsigned)j < _res.nsort; j++)
746 		if (_res.sort_list[j].addr.s_addr ==
747 		    (((struct in_addr *)(*p))->s_addr & _res.sort_list[j].mask))
748 			break;
749 	    aval[i] = j;
750 	    if (needsort == 0 && i > 0 && j < aval[i-1])
751 		needsort = i;
752 	}
753 	if (!needsort)
754 	    return;
755 
756 	while (needsort < num) {
757 	    for (j = needsort - 1; j >= 0; j--) {
758 		if (aval[j] > aval[j+1]) {
759 		    char *hp;
760 
761 		    i = aval[j];
762 		    aval[j] = aval[j+1];
763 		    aval[j+1] = i;
764 
765 		    hp = ap[j];
766 		    ap[j] = ap[j+1];
767 		    ap[j+1] = hp;
768 
769 		} else
770 		    break;
771 	    }
772 	    needsort++;
773 	}
774 }
775 #endif
776 void
777 _sethostdnsent(stayopen)
778 	int stayopen;
779 {
780 	if ((_res.options & RES_INIT) == 0 && res_init() == -1)
781 		return;
782 	if (stayopen)
783 		_res.options |= RES_STAYOPEN | RES_USEVC;
784 }
785 
786 void
787 _endhostdnsent()
788 {
789 	_res.options &= ~(RES_STAYOPEN | RES_USEVC);
790 	res_close();
791 }
792