xref: /freebsd/lib/libc/net/name6.c (revision 87569f75a91f298c52a71823c04d41cf53c88889)
1 /*	$KAME: name6.c,v 1.25 2000/06/26 16:44:40 itojun Exp $	*/
2 
3 /*
4  * Copyright (C) 1995, 1996, 1997, 1998, and 1999 WIDE Project.
5  * 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. Neither the name of the project nor the names of its contributors
16  *    may be used to endorse or promote products derived from this software
17  *    without specific prior written permission.
18  *
19  * THIS SOFTWARE IS PROVIDED BY THE PROJECT AND CONTRIBUTORS ``AS IS'' AND
20  * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
21  * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
22  * ARE DISCLAIMED.  IN NO EVENT SHALL THE PROJECT OR CONTRIBUTORS BE LIABLE
23  * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
24  * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
25  * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
26  * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
27  * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
28  * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
29  * SUCH DAMAGE.
30  */
31 /*
32  * ++Copyright++ 1985, 1988, 1993
33  * -
34  * Copyright (c) 1985, 1988, 1993
35  *    The Regents of the University of California.  All rights reserved.
36  *
37  * Redistribution and use in source and binary forms, with or without
38  * modification, are permitted provided that the following conditions
39  * are met:
40  * 1. Redistributions of source code must retain the above copyright
41  *    notice, this list of conditions and the following disclaimer.
42  * 2. Redistributions in binary form must reproduce the above copyright
43  *    notice, this list of conditions and the following disclaimer in the
44  *    documentation and/or other materials provided with the distribution.
45  * 3. All advertising materials mentioning features or use of this software
46  *    must display the following acknowledgement:
47  * 	This product includes software developed by the University of
48  * 	California, Berkeley and its contributors.
49  * 4. Neither the name of the University nor the names of its contributors
50  *    may be used to endorse or promote products derived from this software
51  *    without specific prior written permission.
52  *
53  * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
54  * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
55  * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
56  * ARE DISCLAIMED.  IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
57  * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
58  * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
59  * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
60  * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
61  * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
62  * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
63  * SUCH DAMAGE.
64  * -
65  * Portions Copyright (c) 1993 by Digital Equipment Corporation.
66  *
67  * Permission to use, copy, modify, and distribute this software for any
68  * purpose with or without fee is hereby granted, provided that the above
69  * copyright notice and this permission notice appear in all copies, and that
70  * the name of Digital Equipment Corporation not be used in advertising or
71  * publicity pertaining to distribution of the document or software without
72  * specific, written prior permission.
73  *
74  * THE SOFTWARE IS PROVIDED "AS IS" AND DIGITAL EQUIPMENT CORP. DISCLAIMS ALL
75  * WARRANTIES WITH REGARD TO THIS SOFTWARE, INCLUDING ALL IMPLIED WARRANTIES
76  * OF MERCHANTABILITY AND FITNESS.   IN NO EVENT SHALL DIGITAL EQUIPMENT
77  * CORPORATION BE LIABLE FOR ANY SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL
78  * DAMAGES OR ANY DAMAGES WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR
79  * PROFITS, WHETHER IN AN ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS
80  * ACTION, ARISING OUT OF OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS
81  * SOFTWARE.
82  * -
83  * --Copyright--
84  */
85 
86 /*
87  *	Atsushi Onoe <onoe@sm.sony.co.jp>
88  */
89 
90 #include <sys/cdefs.h>
91 __FBSDID("$FreeBSD$");
92 
93 #include "namespace.h"
94 #ifdef ICMPNL
95 #include "reentrant.h"
96 #endif
97 #include <sys/param.h>
98 #include <sys/socket.h>
99 #include <sys/time.h>
100 #include <sys/queue.h>
101 #include <netinet/in.h>
102 #ifdef INET6
103 #include <net/if.h>
104 #include <net/if_var.h>
105 #include <sys/sysctl.h>
106 #include <sys/ioctl.h>
107 #include <netinet6/in6_var.h>	/* XXX */
108 #endif
109 
110 #include <arpa/inet.h>
111 #include <arpa/nameser.h>
112 
113 #include <errno.h>
114 #include <netdb.h>
115 #include <resolv.h>
116 #include <stdio.h>
117 #include <stdlib.h>
118 #include <string.h>
119 #include <stdarg.h>
120 #include <nsswitch.h>
121 #include <unistd.h>
122 #include "un-namespace.h"
123 #include "netdb_private.h"
124 #include "res_config.h"
125 
126 #ifndef _PATH_HOSTS
127 #define	_PATH_HOSTS	"/etc/hosts"
128 #endif
129 
130 #ifndef MAXALIASES
131 #define	MAXALIASES	10
132 #endif
133 #ifndef	MAXADDRS
134 #define	MAXADDRS	20
135 #endif
136 #ifndef MAXDNAME
137 #define	MAXDNAME	1025
138 #endif
139 
140 #ifdef INET6
141 #define	ADDRLEN(af)	((af) == AF_INET6 ? sizeof(struct in6_addr) : \
142 					    sizeof(struct in_addr))
143 #else
144 #define	ADDRLEN(af)	sizeof(struct in_addr)
145 #endif
146 
147 #define	MAPADDR(ab, ina) \
148 do {									\
149 	memcpy(&(ab)->map_inaddr, ina, sizeof(struct in_addr));		\
150 	memset((ab)->map_zero, 0, sizeof((ab)->map_zero));		\
151 	memset((ab)->map_one, 0xff, sizeof((ab)->map_one));		\
152 } while (0)
153 #define	MAPADDRENABLED(flags) \
154 	(((flags) & AI_V4MAPPED) || \
155 	 (((flags) & AI_V4MAPPED_CFG) && _mapped_addr_enabled()))
156 
157 union inx_addr {
158 	struct in_addr	in_addr;
159 #ifdef INET6
160 	struct in6_addr	in6_addr;
161 #endif
162 	struct {
163 		u_char	mau_zero[10];
164 		u_char	mau_one[2];
165 		struct in_addr mau_inaddr;
166 	}		map_addr_un;
167 #define	map_zero	map_addr_un.mau_zero
168 #define	map_one		map_addr_un.mau_one
169 #define	map_inaddr	map_addr_un.mau_inaddr
170 };
171 
172 struct policyqueue {
173 	TAILQ_ENTRY(policyqueue) pc_entry;
174 #ifdef INET6
175 	struct in6_addrpolicy pc_policy;
176 #endif
177 };
178 TAILQ_HEAD(policyhead, policyqueue);
179 
180 #define AIO_SRCFLAG_DEPRECATED	0x1
181 
182 struct hp_order {
183 	union {
184 		struct sockaddr_storage aiou_ss;
185 		struct sockaddr aiou_sa;
186 	} aio_src_un;
187 #define aio_srcsa aio_src_un.aiou_sa
188 	u_int32_t aio_srcflag;
189 	int aio_srcscope;
190 	int aio_dstscope;
191 	struct policyqueue *aio_srcpolicy;
192 	struct policyqueue *aio_dstpolicy;
193 	union {
194 		struct sockaddr_storage aiou_ss;
195 		struct sockaddr aiou_sa;
196 	} aio_un;
197 #define aio_sa aio_un.aiou_sa
198 	int aio_matchlen;
199 	char *aio_h_addr;
200 };
201 
202 static struct	 hostent *_hpcopy(struct hostent *hp, int *errp);
203 static struct	 hostent *_hpaddr(int af, const char *name, void *addr, int *errp);
204 static struct	 hostent *_hpmerge(struct hostent *hp1, struct hostent *hp2, int *errp);
205 #ifdef INET6
206 static struct	 hostent *_hpmapv6(struct hostent *hp, int *errp);
207 #endif
208 static struct	 hostent *_hpsort(struct hostent *hp);
209 static struct	 hostent *_ghbyname(const char *name, int af, int flags, int *errp);
210 static char	*_hgetword(char **pp);
211 static int	 _mapped_addr_enabled(void);
212 
213 static struct	 hostent *_hpreorder(struct hostent *hp);
214 static int	 get_addrselectpolicy(struct policyhead *);
215 static void	 free_addrselectpolicy(struct policyhead *);
216 static struct	 policyqueue *match_addrselectpolicy(struct sockaddr *,
217 	struct policyhead *);
218 static void	 set_source(struct hp_order *, struct policyhead *);
219 static int	 matchlen(struct sockaddr *, struct sockaddr *);
220 static int	 comp_dst(const void *, const void *);
221 static int	 gai_addr2scopetype(struct sockaddr *);
222 
223 static FILE	*_files_open(int *errp);
224 static int	 _files_ghbyname(void *, void *, va_list);
225 static int	 _files_ghbyaddr(void *, void *, va_list);
226 #ifdef YP
227 static int	 _nis_ghbyname(void *, void *, va_list);
228 static int	 _nis_ghbyaddr(void *, void *, va_list);
229 #endif
230 static int	 _dns_ghbyname(void *, void *, va_list);
231 static int	 _dns_ghbyaddr(void *, void *, va_list);
232 static void	 _dns_shent(int stayopen) __unused;
233 static void	 _dns_ehent(void) __unused;
234 #ifdef ICMPNL
235 static int	 _icmp_ghbyaddr(void *, void *, va_list);
236 #endif /* ICMPNL */
237 
238 #ifdef ICMPNL
239 static mutex_t _getipnodeby_thread_lock = MUTEX_INITIALIZER;
240 #define THREAD_LOCK()	mutex_lock(&_getipnodeby_thread_lock);
241 #define THREAD_UNLOCK()	mutex_unlock(&_getipnodeby_thread_lock);
242 #endif
243 
244 /* Host lookup order if nsswitch.conf is broken or nonexistant */
245 static const ns_src default_src[] = {
246 	{ NSSRC_FILES, NS_SUCCESS },
247 	{ NSSRC_DNS, NS_SUCCESS },
248 #ifdef ICMPNL
249 #define NSSRC_ICMP "icmp"
250 	{ NSSRC_ICMP, NS_SUCCESS },
251 #endif
252 	{ 0 }
253 };
254 
255 /*
256  * Check if kernel supports mapped address.
257  *	implementation dependent
258  */
259 #ifdef __KAME__
260 #include <sys/sysctl.h>
261 #endif /* __KAME__ */
262 
263 static int
264 _mapped_addr_enabled(void)
265 {
266 	/* implementation dependent check */
267 #if defined(__KAME__) && defined(IPV6CTL_MAPPED_ADDR)
268 	int mib[4];
269 	size_t len;
270 	int val;
271 
272 	mib[0] = CTL_NET;
273 	mib[1] = PF_INET6;
274 	mib[2] = IPPROTO_IPV6;
275 	mib[3] = IPV6CTL_MAPPED_ADDR;
276 	len = sizeof(val);
277 	if (sysctl(mib, 4, &val, &len, 0, 0) == 0 && val != 0)
278 		return 1;
279 #endif /* __KAME__ && IPV6CTL_MAPPED_ADDR */
280 	return 0;
281 }
282 
283 /*
284  * Functions defined in RFC2553
285  *	getipnodebyname, getipnodebyaddr, freehostent
286  */
287 
288 static struct hostent *
289 _ghbyname(const char *name, int af, int flags, int *errp)
290 {
291 	struct hostent *hp;
292 	int rval;
293 
294 	static const ns_dtab dtab[] = {
295 		NS_FILES_CB(_files_ghbyname, NULL)
296 		{ NSSRC_DNS, _dns_ghbyname, NULL },
297 		NS_NIS_CB(_nis_ghbyname, NULL)
298 		{ 0 }
299 	};
300 
301 	if (flags & AI_ADDRCONFIG) {
302 		int s;
303 
304 		if ((s = _socket(af, SOCK_DGRAM, 0)) < 0)
305 			return NULL;
306 		/*
307 		 * TODO:
308 		 * Note that implementation dependent test for address
309 		 * configuration should be done everytime called
310 		 * (or apropriate interval),
311 		 * because addresses will be dynamically assigned or deleted.
312 		 */
313 		_close(s);
314 	}
315 
316 	rval = _nsdispatch(&hp, dtab, NSDB_HOSTS, "ghbyname", default_src,
317 			  name, af, errp);
318 	return (rval == NS_SUCCESS) ? hp : NULL;
319 }
320 
321 struct hostent *
322 getipnodebyname(const char *name, int af, int flags, int *errp)
323 {
324 	struct hostent *hp;
325 	union inx_addr addrbuf;
326 
327 	switch (af) {
328 	case AF_INET:
329 #ifdef INET6
330 	case AF_INET6:
331 #endif
332 		break;
333 	default:
334 		*errp = NO_RECOVERY;
335 		return NULL;
336 	}
337 
338 #ifdef INET6
339 	/* special case for literal address */
340 	if (inet_pton(AF_INET6, name, &addrbuf) == 1) {
341 		if (af != AF_INET6) {
342 			*errp = HOST_NOT_FOUND;
343 			return NULL;
344 		}
345 		return _hpaddr(af, name, &addrbuf, errp);
346 	}
347 #endif
348 	if (inet_aton(name, (struct in_addr *)&addrbuf) == 1) {
349 		if (af != AF_INET) {
350 			if (MAPADDRENABLED(flags)) {
351 				MAPADDR(&addrbuf, &addrbuf.in_addr);
352 			} else {
353 				*errp = HOST_NOT_FOUND;
354 				return NULL;
355 			}
356 		}
357 		return _hpaddr(af, name, &addrbuf, errp);
358 	}
359 
360 	*errp = HOST_NOT_FOUND;
361 	hp = _ghbyname(name, af, flags, errp);
362 
363 #ifdef INET6
364 	if (af == AF_INET6 && ((flags & AI_ALL) || hp == NULL) &&
365 	    MAPADDRENABLED(flags)) {
366 		struct hostent *hp2 = _ghbyname(name, AF_INET, flags, errp);
367 		if (hp == NULL)
368 			hp = _hpmapv6(hp2, errp);
369 		else {
370 			if (hp2 && strcmp(hp->h_name, hp2->h_name) != 0) {
371 				freehostent(hp2);
372 				hp2 = NULL;
373 			}
374 			hp = _hpmerge(hp, hp2, errp);
375 		}
376 	}
377 #endif
378 	return _hpreorder(_hpsort(hp));
379 }
380 
381 struct hostent *
382 getipnodebyaddr(const void *src, size_t len, int af, int *errp)
383 {
384 	struct hostent *hp;
385 	int rval;
386 #ifdef INET6
387 	struct in6_addr addrbuf;
388 #else
389 	struct in_addr addrbuf;
390 #endif
391 
392 	static const ns_dtab dtab[] = {
393 		NS_FILES_CB(_files_ghbyaddr, NULL)
394 		{ NSSRC_DNS, _dns_ghbyaddr, NULL },
395 		NS_NIS_CB(_nis_ghbyaddr, NULL)
396 #ifdef ICMPNL
397 		{ NSSRC_ICMP, _icmp_ghbyaddr, NULL },
398 #endif
399 		{ 0 }
400 	};
401 
402 	*errp = HOST_NOT_FOUND;
403 
404 	switch (af) {
405 	case AF_INET:
406 		if (len != sizeof(struct in_addr)) {
407 			*errp = NO_RECOVERY;
408 			return NULL;
409 		}
410 		if ((long)src & ~(sizeof(struct in_addr) - 1)) {
411 			memcpy(&addrbuf, src, len);
412 			src = &addrbuf;
413 		}
414 		if (((struct in_addr *)src)->s_addr == 0)
415 			return NULL;
416 		break;
417 #ifdef INET6
418 	case AF_INET6:
419 		if (len != sizeof(struct in6_addr)) {
420 			*errp = NO_RECOVERY;
421 			return NULL;
422 		}
423 		if ((long)src & ~(sizeof(struct in6_addr) / 2 - 1)) {	/*XXX*/
424 			memcpy(&addrbuf, src, len);
425 			src = &addrbuf;
426 		}
427 		if (IN6_IS_ADDR_UNSPECIFIED((struct in6_addr *)src))
428 			return NULL;
429 		if (IN6_IS_ADDR_V4MAPPED((struct in6_addr *)src)
430 		||  IN6_IS_ADDR_V4COMPAT((struct in6_addr *)src)) {
431 			src = (char *)src +
432 			    (sizeof(struct in6_addr) - sizeof(struct in_addr));
433 			af = AF_INET;
434 			len = sizeof(struct in_addr);
435 		}
436 		break;
437 #endif
438 	default:
439 		*errp = NO_RECOVERY;
440 		return NULL;
441 	}
442 
443 	rval = _nsdispatch(&hp, dtab, NSDB_HOSTS, "ghbyaddr", default_src,
444 			  src, len, af, errp);
445 	return (rval == NS_SUCCESS) ? hp : NULL;
446 }
447 
448 void
449 freehostent(struct hostent *ptr)
450 {
451 	free(ptr);
452 }
453 
454 /*
455  * Private utility functions
456  */
457 
458 /*
459  * _hpcopy: allocate and copy hostent structure
460  */
461 static struct hostent *
462 _hpcopy(struct hostent *hp, int *errp)
463 {
464 	struct hostent *nhp;
465 	char *cp, **pp;
466 	int size, addrsize;
467 	int nalias = 0, naddr = 0;
468 	int al_off;
469 	int i;
470 
471 	if (hp == NULL)
472 		return hp;
473 
474 	/* count size to be allocated */
475 	size = sizeof(struct hostent);
476 	if (hp->h_name != NULL)
477 		size += strlen(hp->h_name) + 1;
478 	if ((pp = hp->h_aliases) != NULL) {
479 		for (i = 0; *pp != NULL; i++, pp++) {
480 			if (**pp != '\0') {
481 				size += strlen(*pp) + 1;
482 				nalias++;
483 			}
484 		}
485 	}
486 	/* adjust alignment */
487 	size = ALIGN(size);
488 	al_off = size;
489 	size += sizeof(char *) * (nalias + 1);
490 	addrsize = ALIGN(hp->h_length);
491 	if ((pp = hp->h_addr_list) != NULL) {
492 		while (*pp++ != NULL)
493 			naddr++;
494 	}
495 	size += addrsize * naddr;
496 	size += sizeof(char *) * (naddr + 1);
497 
498 	/* copy */
499 	if ((nhp = (struct hostent *)malloc(size)) == NULL) {
500 		*errp = TRY_AGAIN;
501 		return NULL;
502 	}
503 	cp = (char *)&nhp[1];
504 	if (hp->h_name != NULL) {
505 		nhp->h_name = cp;
506 		strcpy(cp, hp->h_name);
507 		cp += strlen(cp) + 1;
508 	} else
509 		nhp->h_name = NULL;
510 	nhp->h_aliases = (char **)((char *)nhp + al_off);
511 	if ((pp = hp->h_aliases) != NULL) {
512 		for (i = 0; *pp != NULL; pp++) {
513 			if (**pp != '\0') {
514 				nhp->h_aliases[i++] = cp;
515 				strcpy(cp, *pp);
516 				cp += strlen(cp) + 1;
517 			}
518 		}
519 	}
520 	nhp->h_aliases[nalias] = NULL;
521 	cp = (char *)&nhp->h_aliases[nalias + 1];
522 	nhp->h_addrtype = hp->h_addrtype;
523 	nhp->h_length = hp->h_length;
524 	nhp->h_addr_list = (char **)cp;
525 	if ((pp = hp->h_addr_list) != NULL) {
526 		cp = (char *)&nhp->h_addr_list[naddr + 1];
527 		for (i = 0; *pp != NULL; pp++) {
528 			nhp->h_addr_list[i++] = cp;
529 			memcpy(cp, *pp, hp->h_length);
530 			cp += addrsize;
531 		}
532 	}
533 	nhp->h_addr_list[naddr] = NULL;
534 	return nhp;
535 }
536 
537 /*
538  * _hpaddr: construct hostent structure with one address
539  */
540 static struct hostent *
541 _hpaddr(int af, const char *name, void *addr, int *errp)
542 {
543 	struct hostent *hp, hpbuf;
544 	char *addrs[2];
545 
546 	hp = &hpbuf;
547 	hp->h_name = (char *)name;
548 	hp->h_aliases = NULL;
549 	hp->h_addrtype = af;
550 	hp->h_length = ADDRLEN(af);
551 	hp->h_addr_list = addrs;
552 	addrs[0] = (char *)addr;
553 	addrs[1] = NULL;
554 	return _hpcopy(hp, errp);
555 }
556 
557 /*
558  * _hpmerge: merge 2 hostent structure, arguments will be freed
559  */
560 static struct hostent *
561 _hpmerge(struct hostent *hp1, struct hostent *hp2, int *errp)
562 {
563 	int i, j;
564 	int naddr, nalias;
565 	char **pp;
566 	struct hostent *hp, hpbuf;
567 	char *aliases[MAXALIASES + 1], *addrs[MAXADDRS + 1];
568 	union inx_addr addrbuf[MAXADDRS];
569 
570 	if (hp1 == NULL)
571 		return hp2;
572 	if (hp2 == NULL)
573 		return hp1;
574 
575 #define	HP(i)	(i == 1 ? hp1 : hp2)
576 	hp = &hpbuf;
577 	hp->h_name = (hp1->h_name != NULL ? hp1->h_name : hp2->h_name);
578 	hp->h_aliases = aliases;
579 	nalias = 0;
580 	for (i = 1; i <= 2; i++) {
581 		if ((pp = HP(i)->h_aliases) == NULL)
582 			continue;
583 		for (; nalias < MAXALIASES && *pp != NULL; pp++) {
584 			/* check duplicates */
585 			for (j = 0; j < nalias; j++)
586 				if (strcasecmp(*pp, aliases[j]) == 0)
587 					break;
588 			if (j == nalias)
589 				aliases[nalias++] = *pp;
590 		}
591 	}
592 	aliases[nalias] = NULL;
593 #ifdef INET6
594 	if (hp1->h_length != hp2->h_length) {
595 		hp->h_addrtype = AF_INET6;
596 		hp->h_length = sizeof(struct in6_addr);
597 	} else {
598 #endif
599 		hp->h_addrtype = hp1->h_addrtype;
600 		hp->h_length = hp1->h_length;
601 #ifdef INET6
602 	}
603 #endif
604 	hp->h_addr_list = addrs;
605 	naddr = 0;
606 	for (i = 1; i <= 2; i++) {
607 		if ((pp = HP(i)->h_addr_list) == NULL)
608 			continue;
609 		if (HP(i)->h_length == hp->h_length) {
610 			while (naddr < MAXADDRS && *pp != NULL)
611 				addrs[naddr++] = *pp++;
612 		} else {
613 			/* copy IPv4 addr as mapped IPv6 addr */
614 			while (naddr < MAXADDRS && *pp != NULL) {
615 				MAPADDR(&addrbuf[naddr], *pp++);
616 				addrs[naddr] = (char *)&addrbuf[naddr];
617 				naddr++;
618 			}
619 		}
620 	}
621 	addrs[naddr] = NULL;
622 	hp = _hpcopy(hp, errp);
623 	freehostent(hp1);
624 	freehostent(hp2);
625 	return hp;
626 }
627 
628 /*
629  * _hpmapv6: convert IPv4 hostent into IPv4-mapped IPv6 addresses
630  */
631 #ifdef INET6
632 static struct hostent *
633 _hpmapv6(struct hostent *hp, int *errp)
634 {
635 	struct hostent *hp6;
636 
637 	if (hp == NULL)
638 		return NULL;
639 	if (hp->h_addrtype == AF_INET6)
640 		return hp;
641 
642 	/* make dummy hostent to convert IPv6 address */
643 	if ((hp6 = (struct hostent *)malloc(sizeof(struct hostent))) == NULL) {
644 		*errp = TRY_AGAIN;
645 		return NULL;
646 	}
647 	hp6->h_name = NULL;
648 	hp6->h_aliases = NULL;
649 	hp6->h_addrtype = AF_INET6;
650 	hp6->h_length = sizeof(struct in6_addr);
651 	hp6->h_addr_list = NULL;
652 	return _hpmerge(hp6, hp, errp);
653 }
654 #endif
655 
656 /*
657  * _hpsort: sort address by sortlist
658  */
659 static struct hostent *
660 _hpsort(struct hostent *hp)
661 {
662 	int i, j, n;
663 	u_char *ap, *sp, *mp, **pp;
664 	char t;
665 	char order[MAXADDRS];
666 	int nsort = _res.nsort;
667 
668 	if (hp == NULL || hp->h_addr_list[1] == NULL || nsort == 0)
669 		return hp;
670 	for (i = 0; (ap = (u_char *)hp->h_addr_list[i]); i++) {
671 		for (j = 0; j < nsort; j++) {
672 #ifdef INET6
673 			if (_res_ext.sort_list[j].af != hp->h_addrtype)
674 				continue;
675 			sp = (u_char *)&_res_ext.sort_list[j].addr;
676 			mp = (u_char *)&_res_ext.sort_list[j].mask;
677 #else
678 			sp = (u_char *)&_res.sort_list[j].addr;
679 			mp = (u_char *)&_res.sort_list[j].mask;
680 #endif
681 			for (n = 0; n < hp->h_length; n++) {
682 				if ((ap[n] & mp[n]) != sp[n])
683 					break;
684 			}
685 			if (n == hp->h_length)
686 				break;
687 		}
688 		order[i] = j;
689 	}
690 	n = i;
691 	pp = (u_char **)hp->h_addr_list;
692 	for (i = 0; i < n - 1; i++) {
693 		for (j = i + 1; j < n; j++) {
694 			if (order[i] > order[j]) {
695 				ap = pp[i];
696 				pp[i] = pp[j];
697 				pp[j] = ap;
698 				t = order[i];
699 				order[i] = order[j];
700 				order[j] = t;
701 			}
702 		}
703 	}
704 	return hp;
705 }
706 
707 static char *
708 _hgetword(char **pp)
709 {
710 	char c, *p, *ret;
711 	const char *sp;
712 	static const char sep[] = "# \t\n";
713 
714 	ret = NULL;
715 	for (p = *pp; (c = *p) != '\0'; p++) {
716 		for (sp = sep; *sp != '\0'; sp++) {
717 			if (c == *sp)
718 				break;
719 		}
720 		if (c == '#')
721 			p[1] = '\0';	/* ignore rest of line */
722 		if (ret == NULL) {
723 			if (*sp == '\0')
724 				ret = p;
725 		} else {
726 			if (*sp != '\0') {
727 				*p++ = '\0';
728 				break;
729 			}
730 		}
731 	}
732 	*pp = p;
733 	if (ret == NULL || *ret == '\0')
734 		return NULL;
735 	return ret;
736 }
737 
738 /*
739  * _hpreorder: sort address by default address selection
740  */
741 static struct hostent *
742 _hpreorder(struct hostent *hp)
743 {
744 	struct hp_order *aio;
745 	int i, n;
746 	char *ap;
747 	struct sockaddr *sa;
748 	struct policyhead policyhead;
749 
750 	if (hp == NULL)
751 		return hp;
752 
753 	switch (hp->h_addrtype) {
754 	case AF_INET:
755 #ifdef INET6
756 	case AF_INET6:
757 #endif
758 		break;
759 	default:
760 		free_addrselectpolicy(&policyhead);
761 		return hp;
762 	}
763 
764 	/* count the number of addrinfo elements for sorting. */
765 	for (n = 0; hp->h_addr_list[n] != NULL; n++)
766 		;
767 
768 	/*
769 	 * If the number is small enough, we can skip the reordering process.
770 	 */
771 	if (n <= 1)
772 		return hp;
773 
774 	/* allocate a temporary array for sort and initialization of it. */
775 	if ((aio = malloc(sizeof(*aio) * n)) == NULL)
776 		return hp;	/* give up reordering */
777 	memset(aio, 0, sizeof(*aio) * n);
778 
779 	/* retrieve address selection policy from the kernel */
780 	TAILQ_INIT(&policyhead);
781 	if (!get_addrselectpolicy(&policyhead)) {
782 		/* no policy is installed into kernel, we don't sort. */
783 		free(aio);
784 		return hp;
785 	}
786 
787 	for (i = 0; i < n; i++) {
788 		ap = hp->h_addr_list[i];
789 		aio[i].aio_h_addr = ap;
790 		sa = &aio[i].aio_sa;
791 		switch (hp->h_addrtype) {
792 		case AF_INET:
793 			sa->sa_family = AF_INET;
794 			sa->sa_len = sizeof(struct sockaddr_in);
795 			memcpy(&((struct sockaddr_in *)sa)->sin_addr, ap,
796 			    sizeof(struct in_addr));
797 			break;
798 #ifdef INET6
799 		case AF_INET6:
800 			if (IN6_IS_ADDR_V4MAPPED((struct in6_addr *)ap)) {
801 				sa->sa_family = AF_INET;
802 				sa->sa_len = sizeof(struct sockaddr_in);
803 				memcpy(&((struct sockaddr_in *)sa)->sin_addr,
804 				    &ap[12], sizeof(struct in_addr));
805 			} else {
806 				sa->sa_family = AF_INET6;
807 				sa->sa_len = sizeof(struct sockaddr_in6);
808 				memcpy(&((struct sockaddr_in6 *)sa)->sin6_addr,
809 				    ap, sizeof(struct in6_addr));
810 			}
811 			break;
812 #endif
813 		}
814 		aio[i].aio_dstscope = gai_addr2scopetype(sa);
815 		aio[i].aio_dstpolicy = match_addrselectpolicy(sa, &policyhead);
816 		set_source(&aio[i], &policyhead);
817 	}
818 
819 	/* perform sorting. */
820 	qsort(aio, n, sizeof(*aio), comp_dst);
821 
822 	/* reorder the h_addr_list. */
823 	for (i = 0; i < n; i++)
824 		hp->h_addr_list[i] = aio[i].aio_h_addr;
825 
826 	/* cleanup and return */
827 	free(aio);
828 	free_addrselectpolicy(&policyhead);
829 	return hp;
830 }
831 
832 static int
833 get_addrselectpolicy(head)
834 	struct policyhead *head;
835 {
836 #ifdef INET6
837 	int mib[] = { CTL_NET, PF_INET6, IPPROTO_IPV6, IPV6CTL_ADDRCTLPOLICY };
838 	size_t l;
839 	char *buf;
840 	struct in6_addrpolicy *pol, *ep;
841 
842 	if (sysctl(mib, sizeof(mib) / sizeof(mib[0]), NULL, &l, NULL, 0) < 0)
843 		return (0);
844 	if ((buf = malloc(l)) == NULL)
845 		return (0);
846 	if (sysctl(mib, sizeof(mib) / sizeof(mib[0]), buf, &l, NULL, 0) < 0) {
847 		free(buf);
848 		return (0);
849 	}
850 
851 	ep = (struct in6_addrpolicy *)(buf + l);
852 	for (pol = (struct in6_addrpolicy *)buf; pol + 1 <= ep; pol++) {
853 		struct policyqueue *new;
854 
855 		if ((new = malloc(sizeof(*new))) == NULL) {
856 			free_addrselectpolicy(head); /* make the list empty */
857 			break;
858 		}
859 		new->pc_policy = *pol;
860 		TAILQ_INSERT_TAIL(head, new, pc_entry);
861 	}
862 
863 	free(buf);
864 	return (1);
865 #else
866 	return (0);
867 #endif
868 }
869 
870 static void
871 free_addrselectpolicy(head)
872 	struct policyhead *head;
873 {
874 	struct policyqueue *ent, *nent;
875 
876 	for (ent = TAILQ_FIRST(head); ent; ent = nent) {
877 		nent = TAILQ_NEXT(ent, pc_entry);
878 		TAILQ_REMOVE(head, ent, pc_entry);
879 		free(ent);
880 	}
881 }
882 
883 static struct policyqueue *
884 match_addrselectpolicy(addr, head)
885 	struct sockaddr *addr;
886 	struct policyhead *head;
887 {
888 #ifdef INET6
889 	struct policyqueue *ent, *bestent = NULL;
890 	struct in6_addrpolicy *pol;
891 	int matchlen, bestmatchlen = -1;
892 	u_char *mp, *ep, *k, *p, m;
893 	struct sockaddr_in6 key;
894 
895 	switch(addr->sa_family) {
896 	case AF_INET6:
897 		key = *(struct sockaddr_in6 *)addr;
898 		break;
899 	case AF_INET:
900 		/* convert the address into IPv4-mapped IPv6 address. */
901 		memset(&key, 0, sizeof(key));
902 		key.sin6_family = AF_INET6;
903 		key.sin6_len = sizeof(key);
904 		key.sin6_addr.s6_addr[10] = 0xff;
905 		key.sin6_addr.s6_addr[11] = 0xff;
906 		memcpy(&key.sin6_addr.s6_addr[12],
907 		       &((struct sockaddr_in *)addr)->sin_addr, 4);
908 		break;
909 	default:
910 		return(NULL);
911 	}
912 
913 	for (ent = TAILQ_FIRST(head); ent; ent = TAILQ_NEXT(ent, pc_entry)) {
914 		pol = &ent->pc_policy;
915 		matchlen = 0;
916 
917 		mp = (u_char *)&pol->addrmask.sin6_addr;
918 		ep = mp + 16;	/* XXX: scope field? */
919 		k = (u_char *)&key.sin6_addr;
920 		p = (u_char *)&pol->addr.sin6_addr;
921 		for (; mp < ep && *mp; mp++, k++, p++) {
922 			m = *mp;
923 			if ((*k & m) != *p)
924 				goto next; /* not match */
925 			if (m == 0xff) /* short cut for a typical case */
926 				matchlen += 8;
927 			else {
928 				while (m >= 0x80) {
929 					matchlen++;
930 					m <<= 1;
931 				}
932 			}
933 		}
934 
935 		/* matched.  check if this is better than the current best. */
936 		if (matchlen > bestmatchlen) {
937 			bestent = ent;
938 			bestmatchlen = matchlen;
939 		}
940 
941 	  next:
942 		continue;
943 	}
944 
945 	return(bestent);
946 #else
947 	return(NULL);
948 #endif
949 
950 }
951 
952 static void
953 set_source(aio, ph)
954 	struct hp_order *aio;
955 	struct policyhead *ph;
956 {
957 	struct sockaddr_storage ss = aio->aio_un.aiou_ss;
958 	socklen_t srclen;
959 	int s;
960 
961 	/* set unspec ("no source is available"), just in case */
962 	aio->aio_srcsa.sa_family = AF_UNSPEC;
963 	aio->aio_srcscope = -1;
964 
965 	switch(ss.ss_family) {
966 	case AF_INET:
967 		((struct sockaddr_in *)&ss)->sin_port = htons(1);
968 		break;
969 #ifdef INET6
970 	case AF_INET6:
971 		((struct sockaddr_in6 *)&ss)->sin6_port = htons(1);
972 		break;
973 #endif
974 	default:		/* ignore unsupported AFs explicitly */
975 		return;
976 	}
977 
978 	/* open a socket to get the source address for the given dst */
979 	if ((s = _socket(ss.ss_family, SOCK_DGRAM, IPPROTO_UDP)) < 0)
980 		return;		/* give up */
981 	if (_connect(s, (struct sockaddr *)&ss, ss.ss_len) < 0)
982 		goto cleanup;
983 	srclen = ss.ss_len;
984 	if (_getsockname(s, &aio->aio_srcsa, &srclen) < 0) {
985 		aio->aio_srcsa.sa_family = AF_UNSPEC;
986 		goto cleanup;
987 	}
988 	aio->aio_srcscope = gai_addr2scopetype(&aio->aio_srcsa);
989 	aio->aio_srcpolicy = match_addrselectpolicy(&aio->aio_srcsa, ph);
990 	aio->aio_matchlen = matchlen(&aio->aio_srcsa, (struct sockaddr *)&ss);
991 #ifdef INET6
992 	if (ss.ss_family == AF_INET6) {
993 		struct in6_ifreq ifr6;
994 		u_int32_t flags6;
995 
996 		/* XXX: interface name should not be hardcoded */
997 		strncpy(ifr6.ifr_name, "lo0", sizeof(ifr6.ifr_name));
998 		memset(&ifr6, 0, sizeof(ifr6));
999 		memcpy(&ifr6.ifr_addr, &ss, ss.ss_len);
1000 		if (_ioctl(s, SIOCGIFAFLAG_IN6, &ifr6) == 0) {
1001 			flags6 = ifr6.ifr_ifru.ifru_flags6;
1002 			if ((flags6 & IN6_IFF_DEPRECATED))
1003 				aio->aio_srcflag |= AIO_SRCFLAG_DEPRECATED;
1004 		}
1005 	}
1006 #endif
1007 
1008   cleanup:
1009 	_close(s);
1010 	return;
1011 }
1012 
1013 static int
1014 matchlen(src, dst)
1015 	struct sockaddr *src, *dst;
1016 {
1017 	int match = 0;
1018 	u_char *s, *d;
1019 	u_char *lim, r;
1020 	int addrlen;
1021 
1022 	switch (src->sa_family) {
1023 #ifdef INET6
1024 	case AF_INET6:
1025 		s = (u_char *)&((struct sockaddr_in6 *)src)->sin6_addr;
1026 		d = (u_char *)&((struct sockaddr_in6 *)dst)->sin6_addr;
1027 		addrlen = sizeof(struct in6_addr);
1028 		lim = s + addrlen;
1029 		break;
1030 #endif
1031 	case AF_INET:
1032 		s = (u_char *)&((struct sockaddr_in *)src)->sin_addr;
1033 		d = (u_char *)&((struct sockaddr_in *)dst)->sin_addr;
1034 		addrlen = sizeof(struct in_addr);
1035 		lim = s + addrlen;
1036 		break;
1037 	default:
1038 		return(0);
1039 	}
1040 
1041 	while (s < lim)
1042 		if ((r = (*d++ ^ *s++)) != 0) {
1043 			while (r < addrlen * 8) {
1044 				match++;
1045 				r <<= 1;
1046 			}
1047 			break;
1048 		} else
1049 			match += 8;
1050 	return(match);
1051 }
1052 
1053 static int
1054 comp_dst(arg1, arg2)
1055 	const void *arg1, *arg2;
1056 {
1057 	const struct hp_order *dst1 = arg1, *dst2 = arg2;
1058 
1059 	/*
1060 	 * Rule 1: Avoid unusable destinations.
1061 	 * XXX: we currently do not consider if an appropriate route exists.
1062 	 */
1063 	if (dst1->aio_srcsa.sa_family != AF_UNSPEC &&
1064 	    dst2->aio_srcsa.sa_family == AF_UNSPEC) {
1065 		return(-1);
1066 	}
1067 	if (dst1->aio_srcsa.sa_family == AF_UNSPEC &&
1068 	    dst2->aio_srcsa.sa_family != AF_UNSPEC) {
1069 		return(1);
1070 	}
1071 
1072 	/* Rule 2: Prefer matching scope. */
1073 	if (dst1->aio_dstscope == dst1->aio_srcscope &&
1074 	    dst2->aio_dstscope != dst2->aio_srcscope) {
1075 		return(-1);
1076 	}
1077 	if (dst1->aio_dstscope != dst1->aio_srcscope &&
1078 	    dst2->aio_dstscope == dst2->aio_srcscope) {
1079 		return(1);
1080 	}
1081 
1082 	/* Rule 3: Avoid deprecated addresses. */
1083 	if (dst1->aio_srcsa.sa_family != AF_UNSPEC &&
1084 	    dst2->aio_srcsa.sa_family != AF_UNSPEC) {
1085 		if (!(dst1->aio_srcflag & AIO_SRCFLAG_DEPRECATED) &&
1086 		    (dst2->aio_srcflag & AIO_SRCFLAG_DEPRECATED)) {
1087 			return(-1);
1088 		}
1089 		if ((dst1->aio_srcflag & AIO_SRCFLAG_DEPRECATED) &&
1090 		    !(dst2->aio_srcflag & AIO_SRCFLAG_DEPRECATED)) {
1091 			return(1);
1092 		}
1093 	}
1094 
1095 	/* Rule 4: Prefer home addresses. */
1096 	/* XXX: not implemented yet */
1097 
1098 	/* Rule 5: Prefer matching label. */
1099 #ifdef INET6
1100 	if (dst1->aio_srcpolicy && dst1->aio_dstpolicy &&
1101 	    dst1->aio_srcpolicy->pc_policy.label ==
1102 	    dst1->aio_dstpolicy->pc_policy.label &&
1103 	    (dst2->aio_srcpolicy == NULL || dst2->aio_dstpolicy == NULL ||
1104 	     dst2->aio_srcpolicy->pc_policy.label !=
1105 	     dst2->aio_dstpolicy->pc_policy.label)) {
1106 		return(-1);
1107 	}
1108 	if (dst2->aio_srcpolicy && dst2->aio_dstpolicy &&
1109 	    dst2->aio_srcpolicy->pc_policy.label ==
1110 	    dst2->aio_dstpolicy->pc_policy.label &&
1111 	    (dst1->aio_srcpolicy == NULL || dst1->aio_dstpolicy == NULL ||
1112 	     dst1->aio_srcpolicy->pc_policy.label !=
1113 	     dst1->aio_dstpolicy->pc_policy.label)) {
1114 		return(1);
1115 	}
1116 #endif
1117 
1118 	/* Rule 6: Prefer higher precedence. */
1119 #ifdef INET6
1120 	if (dst1->aio_dstpolicy &&
1121 	    (dst2->aio_dstpolicy == NULL ||
1122 	     dst1->aio_dstpolicy->pc_policy.preced >
1123 	     dst2->aio_dstpolicy->pc_policy.preced)) {
1124 		return(-1);
1125 	}
1126 	if (dst2->aio_dstpolicy &&
1127 	    (dst1->aio_dstpolicy == NULL ||
1128 	     dst2->aio_dstpolicy->pc_policy.preced >
1129 	     dst1->aio_dstpolicy->pc_policy.preced)) {
1130 		return(1);
1131 	}
1132 #endif
1133 
1134 	/* Rule 7: Prefer native transport. */
1135 	/* XXX: not implemented yet */
1136 
1137 	/* Rule 8: Prefer smaller scope. */
1138 	if (dst1->aio_dstscope >= 0 &&
1139 	    dst1->aio_dstscope < dst2->aio_dstscope) {
1140 		return(-1);
1141 	}
1142 	if (dst2->aio_dstscope >= 0 &&
1143 	    dst2->aio_dstscope < dst1->aio_dstscope) {
1144 		return(1);
1145 	}
1146 
1147 	/*
1148 	 * Rule 9: Use longest matching prefix.
1149 	 * We compare the match length in a same AF only.
1150 	 */
1151 	if (dst1->aio_sa.sa_family == dst2->aio_sa.sa_family) {
1152 		if (dst1->aio_matchlen > dst2->aio_matchlen) {
1153 			return(-1);
1154 		}
1155 		if (dst1->aio_matchlen < dst2->aio_matchlen) {
1156 			return(1);
1157 		}
1158 	}
1159 
1160 	/* Rule 10: Otherwise, leave the order unchanged. */
1161 	return(-1);
1162 }
1163 
1164 /*
1165  * Copy from scope.c.
1166  * XXX: we should standardize the functions and link them as standard
1167  * library.
1168  */
1169 static int
1170 gai_addr2scopetype(sa)
1171 	struct sockaddr *sa;
1172 {
1173 #ifdef INET6
1174 	struct sockaddr_in6 *sa6;
1175 #endif
1176 	struct sockaddr_in *sa4;
1177 
1178 	switch(sa->sa_family) {
1179 #ifdef INET6
1180 	case AF_INET6:
1181 		sa6 = (struct sockaddr_in6 *)sa;
1182 		if (IN6_IS_ADDR_MULTICAST(&sa6->sin6_addr)) {
1183 			/* just use the scope field of the multicast address */
1184 			return(sa6->sin6_addr.s6_addr[2] & 0x0f);
1185 		}
1186 		/*
1187 		 * Unicast addresses: map scope type to corresponding scope
1188 		 * value defined for multcast addresses.
1189 		 * XXX: hardcoded scope type values are bad...
1190 		 */
1191 		if (IN6_IS_ADDR_LOOPBACK(&sa6->sin6_addr))
1192 			return(1); /* node local scope */
1193 		if (IN6_IS_ADDR_LINKLOCAL(&sa6->sin6_addr))
1194 			return(2); /* link-local scope */
1195 		if (IN6_IS_ADDR_SITELOCAL(&sa6->sin6_addr))
1196 			return(5); /* site-local scope */
1197 		return(14);	/* global scope */
1198 		break;
1199 #endif
1200 	case AF_INET:
1201 		/*
1202 		 * IPv4 pseudo scoping according to RFC 3484.
1203 		 */
1204 		sa4 = (struct sockaddr_in *)sa;
1205 		/* IPv4 autoconfiguration addresses have link-local scope. */
1206 		if (((u_char *)&sa4->sin_addr)[0] == 169 &&
1207 		    ((u_char *)&sa4->sin_addr)[1] == 254)
1208 			return(2);
1209 		/* Private addresses have site-local scope. */
1210 		if (((u_char *)&sa4->sin_addr)[0] == 10 ||
1211 		    (((u_char *)&sa4->sin_addr)[0] == 172 &&
1212 		     (((u_char *)&sa4->sin_addr)[1] & 0xf0) == 16) ||
1213 		    (((u_char *)&sa4->sin_addr)[0] == 192 &&
1214 		     ((u_char *)&sa4->sin_addr)[1] == 168))
1215 			return(14);	/* XXX: It should be 5 unless NAT */
1216 		/* Loopback addresses have link-local scope. */
1217 		if (((u_char *)&sa4->sin_addr)[0] == 127)
1218 			return(2);
1219 		return(14);
1220 		break;
1221 	default:
1222 		errno = EAFNOSUPPORT; /* is this a good error? */
1223 		return(-1);
1224 	}
1225 }
1226 
1227 /*
1228  * FILES (/etc/hosts)
1229  */
1230 
1231 static FILE *
1232 _files_open(int *errp)
1233 {
1234 	FILE *fp;
1235 	fp = fopen(_PATH_HOSTS, "r");
1236 	if (fp == NULL)
1237 		*errp = NO_RECOVERY;
1238 	return fp;
1239 }
1240 
1241 static int
1242 _files_ghbyname(void *rval, void *cb_data, va_list ap)
1243 {
1244 	const char *name;
1245 	int af;
1246 	int *errp;
1247 	int match, nalias;
1248 	char *p, *line, *addrstr, *cname;
1249 	FILE *fp;
1250 	struct hostent *rethp, *hp, hpbuf;
1251 	char *aliases[MAXALIASES + 1], *addrs[2];
1252 	union inx_addr addrbuf;
1253 	char buf[BUFSIZ];
1254 
1255 	name = va_arg(ap, const char *);
1256 	af = va_arg(ap, int);
1257 	errp = va_arg(ap, int *);
1258 
1259 	*(struct hostent **)rval = NULL;
1260 
1261 	if ((fp = _files_open(errp)) == NULL)
1262 		return NS_UNAVAIL;
1263 	rethp = hp = NULL;
1264 
1265 	while (fgets(buf, sizeof(buf), fp)) {
1266 		line = buf;
1267 		if ((addrstr = _hgetword(&line)) == NULL
1268 		||  (cname = _hgetword(&line)) == NULL)
1269 			continue;
1270 		match = (strcasecmp(cname, name) == 0);
1271 		nalias = 0;
1272 		while ((p = _hgetword(&line)) != NULL) {
1273 			if (!match)
1274 				match = (strcasecmp(p, name) == 0);
1275 			if (nalias < MAXALIASES)
1276 				aliases[nalias++] = p;
1277 		}
1278 		if (!match)
1279 			continue;
1280 		switch (af) {
1281 		case AF_INET:
1282 			if (inet_aton(addrstr, (struct in_addr *)&addrbuf)
1283 			    != 1) {
1284 				*errp = NO_DATA;	/* name found */
1285 				continue;
1286 			}
1287 			break;
1288 #ifdef INET6
1289 		case AF_INET6:
1290 			if (inet_pton(af, addrstr, &addrbuf) != 1) {
1291 				*errp = NO_DATA;	/* name found */
1292 				continue;
1293 			}
1294 			break;
1295 #endif
1296 		}
1297 		hp = &hpbuf;
1298 		hp->h_name = cname;
1299 		hp->h_aliases = aliases;
1300 		aliases[nalias] = NULL;
1301 		hp->h_addrtype = af;
1302 		hp->h_length = ADDRLEN(af);
1303 		hp->h_addr_list = addrs;
1304 		addrs[0] = (char *)&addrbuf;
1305 		addrs[1] = NULL;
1306 		hp = _hpcopy(hp, errp);
1307 		rethp = _hpmerge(rethp, hp, errp);
1308 	}
1309 	fclose(fp);
1310 	*(struct hostent **)rval = rethp;
1311 	return (rethp != NULL) ? NS_SUCCESS : NS_NOTFOUND;
1312 }
1313 
1314 static int
1315 _files_ghbyaddr(void *rval, void *cb_data, va_list ap)
1316 {
1317 	const void *addr;
1318 	int addrlen;
1319 	int af;
1320 	int *errp;
1321 	int nalias;
1322 	char *p, *line;
1323 	FILE *fp;
1324 	struct hostent *hp, hpbuf;
1325 	char *aliases[MAXALIASES + 1], *addrs[2];
1326 	union inx_addr addrbuf;
1327 	char buf[BUFSIZ];
1328 
1329 	addr = va_arg(ap, const void *);
1330 	addrlen = va_arg(ap, int);
1331 	af = va_arg(ap, int);
1332 	errp = va_arg(ap, int *);
1333 
1334 	*(struct hostent**)rval = NULL;
1335 
1336 	if ((fp = _files_open(errp)) == NULL)
1337 		return NS_UNAVAIL;
1338 	hp = NULL;
1339 	while (fgets(buf, sizeof(buf), fp)) {
1340 		line = buf;
1341 		if ((p = _hgetword(&line)) == NULL
1342 		||  (af == AF_INET
1343 		     ? inet_aton(p, (struct in_addr *)&addrbuf)
1344 		     : inet_pton(af, p, &addrbuf)) != 1
1345 		||  memcmp(addr, &addrbuf, addrlen) != 0
1346 		||  (p = _hgetword(&line)) == NULL)
1347 			continue;
1348 		hp = &hpbuf;
1349 		hp->h_name = p;
1350 		hp->h_aliases = aliases;
1351 		nalias = 0;
1352 		while ((p = _hgetword(&line)) != NULL) {
1353 			if (nalias < MAXALIASES)
1354 				aliases[nalias++] = p;
1355 		}
1356 		aliases[nalias] = NULL;
1357 		hp->h_addrtype = af;
1358 		hp->h_length = addrlen;
1359 		hp->h_addr_list = addrs;
1360 		addrs[0] = (char *)&addrbuf;
1361 		addrs[1] = NULL;
1362 		hp = _hpcopy(hp, errp);
1363 		break;
1364 	}
1365 	fclose(fp);
1366 	*(struct hostent **)rval = hp;
1367 	return (hp != NULL) ? NS_SUCCESS : NS_NOTFOUND;
1368 }
1369 
1370 #ifdef YP
1371 /*
1372  * NIS
1373  *
1374  * XXX actually a hack.
1375  */
1376 static int
1377 _nis_ghbyname(void *rval, void *cb_data, va_list ap)
1378 {
1379 	const char *name;
1380 	int af;
1381 	int *errp;
1382 	struct hostent *hp = NULL;
1383 
1384 	name = va_arg(ap, const char *);
1385 	af = va_arg(ap, int);
1386 	errp = va_arg(ap, int *);
1387 
1388 	hp = _gethostbynisname(name, af);
1389 	if (hp != NULL)
1390 		hp = _hpcopy(hp, errp);
1391 
1392 	*(struct hostent **)rval = hp;
1393 	return (hp != NULL) ? NS_SUCCESS : NS_NOTFOUND;
1394 }
1395 
1396 static int
1397 _nis_ghbyaddr(void *rval, void *cb_data, va_list ap)
1398 {
1399 	const void *addr;
1400 	int addrlen;
1401 	int af;
1402 	int *errp;
1403 	struct hostent *hp = NULL;
1404 
1405 	addr = va_arg(ap, const void *);
1406 	addrlen = va_arg(ap, int);
1407 	af = va_arg(ap, int);
1408 
1409 	hp = _gethostbynisaddr(addr, addrlen, af);
1410 	if (hp != NULL)
1411 		hp = _hpcopy(hp, errp);
1412 	*(struct hostent **)rval = hp;
1413 	return (hp != NULL) ? NS_SUCCESS : NS_NOTFOUND;
1414 }
1415 #endif
1416 
1417 #define	MAXPACKET	(64*1024)
1418 
1419 typedef union {
1420 	HEADER hdr;
1421 	u_char buf[MAXPACKET];
1422 } querybuf;
1423 
1424 static struct hostent *getanswer(const querybuf *, int, const char *, int,
1425 	    struct hostent *, int *);
1426 
1427 /*
1428  * we don't need to take care about sorting, nor IPv4 mapped address here.
1429  */
1430 static struct hostent *
1431 getanswer(answer, anslen, qname, qtype, template, errp)
1432 	const querybuf *answer;
1433 	int anslen;
1434 	const char *qname;
1435 	int qtype;
1436 	struct hostent *template;
1437 	int *errp;
1438 {
1439 	const HEADER *hp;
1440 	const u_char *cp;
1441 	int n;
1442 	const u_char *eom, *erdata;
1443 	char *bp, *ep, **ap, **hap;
1444 	int type, class, ancount, qdcount;
1445 	int haveanswer, had_error;
1446 	char tbuf[MAXDNAME];
1447 	const char *tname;
1448 	int (*name_ok)(const char *);
1449 	static char *h_addr_ptrs[MAXADDRS + 1];
1450 	static char *host_aliases[MAXALIASES];
1451 	static char hostbuf[8*1024];
1452 
1453 #define BOUNDED_INCR(x) \
1454 	do { \
1455 		cp += x; \
1456 		if (cp > eom) { \
1457 			*errp = NO_RECOVERY; \
1458 			return (NULL); \
1459 		} \
1460 	} while (0)
1461 
1462 #define BOUNDS_CHECK(ptr, count) \
1463 	do { \
1464 		if ((ptr) + (count) > eom) { \
1465 			*errp = NO_RECOVERY; \
1466 			return (NULL); \
1467 		} \
1468 	} while (0)
1469 
1470 /* XXX do {} while (0) cannot be put here */
1471 #define DNS_ASSERT(x) \
1472 	{				\
1473 		if (!(x)) {		\
1474 			cp += n;	\
1475 			continue;	\
1476 		}			\
1477 	}
1478 
1479 /* XXX do {} while (0) cannot be put here */
1480 #define DNS_FATAL(x) \
1481 	{				\
1482 		if (!(x)) {		\
1483 			had_error++;	\
1484 			continue;	\
1485 		}			\
1486 	}
1487 
1488 	tname = qname;
1489 	template->h_name = NULL;
1490 	eom = answer->buf + anslen;
1491 	switch (qtype) {
1492 	case T_A:
1493 	case T_AAAA:
1494 		name_ok = res_hnok;
1495 		break;
1496 	case T_PTR:
1497 		name_ok = res_dnok;
1498 		break;
1499 	default:
1500 		return (NULL);	/* XXX should be abort(); */
1501 	}
1502 	/*
1503 	 * find first satisfactory answer
1504 	 */
1505 	hp = &answer->hdr;
1506 	ancount = ntohs(hp->ancount);
1507 	qdcount = ntohs(hp->qdcount);
1508 	bp = hostbuf;
1509 	ep = hostbuf + sizeof hostbuf;
1510 	cp = answer->buf;
1511 	BOUNDED_INCR(HFIXEDSZ);
1512 	if (qdcount != 1) {
1513 		*errp = NO_RECOVERY;
1514 		return (NULL);
1515 	}
1516 	n = dn_expand(answer->buf, eom, cp, bp, ep - bp);
1517 	if ((n < 0) || !(*name_ok)(bp)) {
1518 		*errp = NO_RECOVERY;
1519 		return (NULL);
1520 	}
1521 	BOUNDED_INCR(n + QFIXEDSZ);
1522 	if (qtype == T_A || qtype == T_AAAA) {
1523 		/* res_send() has already verified that the query name is the
1524 		 * same as the one we sent; this just gets the expanded name
1525 		 * (i.e., with the succeeding search-domain tacked on).
1526 		 */
1527 		n = strlen(bp) + 1;		/* for the \0 */
1528 		if (n >= MAXHOSTNAMELEN) {
1529 			*errp = NO_RECOVERY;
1530 			return (NULL);
1531 		}
1532 		template->h_name = bp;
1533 		bp += n;
1534 		/* The qname can be abbreviated, but h_name is now absolute. */
1535 		qname = template->h_name;
1536 	}
1537 	ap = host_aliases;
1538 	*ap = NULL;
1539 	template->h_aliases = host_aliases;
1540 	hap = h_addr_ptrs;
1541 	*hap = NULL;
1542 	template->h_addr_list = h_addr_ptrs;
1543 	haveanswer = 0;
1544 	had_error = 0;
1545 	while (ancount-- > 0 && cp < eom && !had_error) {
1546 		n = dn_expand(answer->buf, eom, cp, bp, ep - bp);
1547 		DNS_FATAL(n >= 0);
1548 		DNS_FATAL((*name_ok)(bp));
1549 		cp += n;			/* name */
1550 		BOUNDS_CHECK(cp, 3 * INT16SZ + INT32SZ);
1551 		type = _getshort(cp);
1552  		cp += INT16SZ;			/* type */
1553 		class = _getshort(cp);
1554  		cp += INT16SZ + INT32SZ;	/* class, TTL */
1555 		n = _getshort(cp);
1556 		cp += INT16SZ;			/* len */
1557 		BOUNDS_CHECK(cp, n);
1558 		erdata = cp + n;
1559 		DNS_ASSERT(class == C_IN);
1560 		if ((qtype == T_A || qtype == T_AAAA) && type == T_CNAME) {
1561 			if (ap >= &host_aliases[MAXALIASES-1])
1562 				continue;
1563 			n = dn_expand(answer->buf, eom, cp, tbuf, sizeof tbuf);
1564 			DNS_FATAL(n >= 0);
1565 			DNS_FATAL((*name_ok)(tbuf));
1566 			cp += n;
1567 			if (cp != erdata) {
1568 				*errp = NO_RECOVERY;
1569 				return (NULL);
1570 			}
1571 			/* Store alias. */
1572 			*ap++ = bp;
1573 			n = strlen(bp) + 1;	/* for the \0 */
1574 			DNS_FATAL(n < MAXHOSTNAMELEN);
1575 			bp += n;
1576 			/* Get canonical name. */
1577 			n = strlen(tbuf) + 1;	/* for the \0 */
1578 			DNS_FATAL(n <= ep - bp);
1579 			DNS_FATAL(n < MAXHOSTNAMELEN);
1580 			strcpy(bp, tbuf);
1581 			template->h_name = bp;
1582 			bp += n;
1583 			continue;
1584 		}
1585 		if (qtype == T_PTR && type == T_CNAME) {
1586 			n = dn_expand(answer->buf, eom, cp, tbuf, sizeof tbuf);
1587 			if (n < 0 || !res_dnok(tbuf)) {
1588 				had_error++;
1589 				continue;
1590 			}
1591 			cp += n;
1592 			if (cp != erdata) {
1593 				*errp = NO_RECOVERY;
1594 				return (NULL);
1595 			}
1596 			/* Get canonical name. */
1597 			n = strlen(tbuf) + 1;	/* for the \0 */
1598 			if (n > ep - bp || n >= MAXHOSTNAMELEN) {
1599 				had_error++;
1600 				continue;
1601 			}
1602 			strcpy(bp, tbuf);
1603 			tname = bp;
1604 			bp += n;
1605 			continue;
1606 		}
1607 		DNS_ASSERT(type == qtype);
1608 		switch (type) {
1609 		case T_PTR:
1610 			DNS_ASSERT(strcasecmp(tname, bp) == 0);
1611 			n = dn_expand(answer->buf, eom, cp, bp, ep - bp);
1612 			DNS_FATAL(n >= 0);
1613 			DNS_FATAL(res_hnok(bp));
1614 #if MULTI_PTRS_ARE_ALIASES
1615 			cp += n;
1616 			if (cp != erdata) {
1617 				*errp = NO_RECOVERY;
1618 				return (NULL);
1619 			}
1620 			if (!haveanswer)
1621 				template->h_name = bp;
1622 			else if (ap < &host_aliases[MAXALIASES-1])
1623 				*ap++ = bp;
1624 			else
1625 				n = -1;
1626 			if (n != -1) {
1627 				n = strlen(bp) + 1;	/* for the \0 */
1628 				if (n >= MAXHOSTNAMELEN) {
1629 					had_error++;
1630 					break;
1631 				}
1632 				bp += n;
1633 			}
1634 			break;
1635 #else
1636 			template->h_name = bp;
1637 			*errp = NETDB_SUCCESS;
1638 			return (template);
1639 #endif
1640 		case T_A:
1641 		case T_AAAA:
1642 			DNS_ASSERT(strcasecmp(template->h_name, bp) == 0);
1643 			DNS_ASSERT(n == template->h_length);
1644 			if (!haveanswer) {
1645 				int nn;
1646 
1647 				template->h_name = bp;
1648 				nn = strlen(bp) + 1;	/* for the \0 */
1649 				bp += nn;
1650 			}
1651 			bp = (char *)ALIGN(bp);
1652 
1653 			DNS_FATAL(bp + n < ep);
1654 			DNS_ASSERT(hap < &h_addr_ptrs[MAXADDRS-1]);
1655 #ifdef FILTER_V4MAPPED
1656 			if (type == T_AAAA) {
1657 				struct in6_addr in6;
1658 				memcpy(&in6, cp, sizeof(in6));
1659 				DNS_ASSERT(IN6_IS_ADDR_V4MAPPED(&in6) == 0);
1660 			}
1661 #endif
1662 			bcopy(cp, *hap++ = bp, n);
1663 			bp += n;
1664 			cp += n;
1665 			if (cp != erdata) {
1666 				*errp = NO_RECOVERY;
1667 				return (NULL);
1668 			}
1669 			break;
1670 		default:
1671 			abort();
1672 		}
1673 		if (!had_error)
1674 			haveanswer++;
1675 	}
1676 	if (haveanswer) {
1677 		*ap = NULL;
1678 		*hap = NULL;
1679 		if (!template->h_name) {
1680 			n = strlen(qname) + 1;	/* for the \0 */
1681 			if (n > ep - bp || n >= MAXHOSTNAMELEN)
1682 				goto no_recovery;
1683 			strcpy(bp, qname);
1684 			template->h_name = bp;
1685 			bp += n;
1686 		}
1687 		*errp = NETDB_SUCCESS;
1688 		return (template);
1689 	}
1690  no_recovery:
1691 	*errp = NO_RECOVERY;
1692 	return (NULL);
1693 
1694 #undef BOUNDED_INCR
1695 #undef BOUNDS_CHECK
1696 #undef DNS_ASSERT
1697 #undef DNS_FATAL
1698 }
1699 
1700 static int
1701 _dns_ghbyname(void *rval, void *cb_data, va_list ap)
1702 {
1703 	const char *name;
1704 	int af;
1705 	int *errp;
1706 	int n;
1707 	struct hostent *hp;
1708 	int qtype;
1709 	struct hostent hbuf;
1710 	querybuf *buf;
1711 
1712 	name = va_arg(ap, const char *);
1713 	af = va_arg(ap, int);
1714 	errp = va_arg(ap, int *);
1715 
1716 	if ((_res.options & RES_INIT) == 0) {
1717 		if (res_init() < 0) {
1718 			*errp = h_errno;
1719 			return NS_UNAVAIL;
1720 		}
1721 	}
1722 	memset(&hbuf, 0, sizeof(hbuf));
1723 	hbuf.h_addrtype = af;
1724 	hbuf.h_length = ADDRLEN(af);
1725 
1726 	switch (af) {
1727 #ifdef INET6
1728 	case AF_INET6:
1729 		qtype = T_AAAA;
1730 		break;
1731 #endif
1732 	case AF_INET:
1733 		qtype = T_A;
1734 		break;
1735 	default:
1736 		*errp = NO_RECOVERY;
1737 		return NS_NOTFOUND;
1738 	}
1739 	buf = malloc(sizeof(*buf));
1740 	if (buf == NULL) {
1741 		*errp = NETDB_INTERNAL;
1742 		return NS_UNAVAIL;
1743 	}
1744 	n = res_search(name, C_IN, qtype, buf->buf, sizeof(buf->buf));
1745 	if (n < 0) {
1746 		free(buf);
1747 		*errp = h_errno;
1748 		return NS_UNAVAIL;
1749 	}
1750 	hp = getanswer(buf, n, name, qtype, &hbuf, errp);
1751 	free(buf);
1752 	if (!hp) {
1753 		*errp = NO_RECOVERY;
1754 		return NS_NOTFOUND;
1755 	}
1756 	*(struct hostent **)rval = _hpcopy(&hbuf, errp);
1757 	if (*(struct hostent **)rval != NULL)
1758 		return NS_SUCCESS;
1759 	else if (*errp == TRY_AGAIN)
1760 		return NS_TRYAGAIN;
1761 	else
1762 		return NS_NOTFOUND;
1763 }
1764 
1765 static int
1766 _dns_ghbyaddr(void *rval, void *cb_data, va_list ap)
1767 {
1768 	const void *addr;
1769 	int addrlen;
1770 	int af;
1771 	int *errp;
1772 	int n;
1773 	int err;
1774 	struct hostent *hp;
1775 	u_char c, *cp;
1776 	char *bp;
1777 	struct hostent hbuf;
1778 #ifdef INET6
1779 	static const char hex[] = "0123456789abcdef";
1780 #endif
1781 	querybuf *buf;
1782 	char qbuf[MAXDNAME+1];
1783 	char *hlist[2];
1784 	char *tld6[] = { "ip6.arpa", NULL };
1785 	char *tld4[] = { "in-addr.arpa", NULL };
1786 	char **tld;
1787 
1788 	addr = va_arg(ap, const void *);
1789 	addrlen = va_arg(ap, int);
1790 	af = va_arg(ap, int);
1791 	errp = va_arg(ap, int *);
1792 
1793 	*(struct hostent **)rval = NULL;
1794 
1795 #ifdef INET6
1796 	/* XXX */
1797 	if (af == AF_INET6 && IN6_IS_ADDR_LINKLOCAL((struct in6_addr *)addr))
1798 		return NS_NOTFOUND;
1799 #endif
1800 
1801 	switch (af) {
1802 #ifdef INET6
1803 	case AF_INET6:
1804 		tld = tld6;
1805 		break;
1806 #endif
1807 	case AF_INET:
1808 		tld = tld4;
1809 		break;
1810 	default:
1811 		return NS_NOTFOUND;
1812 	}
1813 
1814 	if ((_res.options & RES_INIT) == 0) {
1815 		if (res_init() < 0) {
1816 			*errp = h_errno;
1817 			return NS_UNAVAIL;
1818 		}
1819 	}
1820 	memset(&hbuf, 0, sizeof(hbuf));
1821 	hbuf.h_name = NULL;
1822 	hbuf.h_addrtype = af;
1823 	hbuf.h_length = addrlen;
1824 
1825 	buf = malloc(sizeof(*buf));
1826 	if (buf == NULL) {
1827 		*errp = NETDB_INTERNAL;
1828 		return NS_UNAVAIL;
1829 	}
1830 	err = NS_SUCCESS;
1831 	for (/* nothing */; *tld; tld++) {
1832 		/*
1833 		 * XXX assumes that MAXDNAME is big enough - error checks
1834 		 * has been made by callers
1835 		 */
1836 		n = 0;
1837 		bp = qbuf;
1838 		cp = (u_char *)addr+addrlen-1;
1839 		switch (af) {
1840 #ifdef INET6
1841 		case AF_INET6:
1842 			for (; n < addrlen; n++, cp--) {
1843 				c = *cp;
1844 				*bp++ = hex[c & 0xf];
1845 				*bp++ = '.';
1846 				*bp++ = hex[c >> 4];
1847 				*bp++ = '.';
1848 			}
1849 			strcpy(bp, *tld);
1850 			break;
1851 #endif
1852 		case AF_INET:
1853 			for (; n < addrlen; n++, cp--) {
1854 				c = *cp;
1855 				if (c >= 100)
1856 					*bp++ = '0' + c / 100;
1857 				if (c >= 10)
1858 					*bp++ = '0' + (c % 100) / 10;
1859 				*bp++ = '0' + c % 10;
1860 				*bp++ = '.';
1861 			}
1862 			strcpy(bp, *tld);
1863 			break;
1864 		}
1865 
1866 		n = res_query(qbuf, C_IN, T_PTR, buf->buf, sizeof buf->buf);
1867 		if (n < 0) {
1868 			*errp = h_errno;
1869 			err = NS_UNAVAIL;
1870 			continue;
1871 		} else if (n > sizeof(buf->buf)) {
1872 #if 0
1873 			errno = ERANGE; /* XXX is it OK to set errno here? */
1874 #endif
1875 			*errp = NETDB_INTERNAL;
1876 			err = NS_UNAVAIL;
1877 			continue;
1878 		}
1879 		hp = getanswer(buf, n, qbuf, T_PTR, &hbuf, errp);
1880 		if (!hp) {
1881 			err = NS_NOTFOUND;
1882 			continue;
1883 		}
1884 		free(buf);
1885 		hbuf.h_addrtype = af;
1886 		hbuf.h_length = addrlen;
1887 		hbuf.h_addr_list = hlist;
1888 		hlist[0] = (char *)addr;
1889 		hlist[1] = NULL;
1890 		*(struct hostent **)rval = _hpcopy(&hbuf, errp);
1891 		return NS_SUCCESS;
1892 	}
1893 	free(buf);
1894 	return err;
1895 }
1896 
1897 static void
1898 _dns_shent(int stayopen)
1899 {
1900 	if ((_res.options & RES_INIT) == 0) {
1901 		if (res_init() < 0)
1902 			return;
1903 	}
1904 	if (stayopen)
1905 		_res.options |= RES_STAYOPEN | RES_USEVC;
1906 }
1907 
1908 static void
1909 _dns_ehent(void)
1910 {
1911 	_res.options &= ~(RES_STAYOPEN | RES_USEVC);
1912 	res_close();
1913 }
1914 
1915 #ifdef ICMPNL
1916 
1917 /*
1918  * experimental:
1919  *	draft-ietf-ipngwg-icmp-namelookups-02.txt
1920  *	ifindex is assumed to be encoded in addr.
1921  */
1922 #include <sys/uio.h>
1923 #include <netinet/ip6.h>
1924 #include <netinet/icmp6.h>
1925 
1926 struct _icmp_host_cache {
1927 	struct _icmp_host_cache *hc_next;
1928 	int hc_ifindex;
1929 	struct in6_addr hc_addr;
1930 	char *hc_name;
1931 };
1932 
1933 static char *
1934 _icmp_fqdn_query(const struct in6_addr *addr, int ifindex)
1935 {
1936 	int s;
1937 	struct icmp6_filter filter;
1938 	struct msghdr msg;
1939 	struct cmsghdr *cmsg;
1940 	struct in6_pktinfo *pkt;
1941 	char cbuf[256];
1942 	char buf[1024];
1943 	int cc;
1944 	struct icmp6_fqdn_query *fq;
1945 	struct icmp6_fqdn_reply *fr;
1946 	struct _icmp_host_cache *hc;
1947 	struct sockaddr_in6 sin6;
1948 	struct iovec iov;
1949 	fd_set s_fds, fds;
1950 	struct timeval tout;
1951 	int len;
1952 	char *name;
1953 	static struct _icmp_host_cache *hc_head;
1954 
1955 	THREAD_LOCK();
1956 	for (hc = hc_head; hc; hc = hc->hc_next) {
1957 		if (hc->hc_ifindex == ifindex
1958 		&&  IN6_ARE_ADDR_EQUAL(&hc->hc_addr, addr)) {
1959 			THREAD_UNLOCK();
1960 			return hc->hc_name;	/* XXX: never freed */
1961 		}
1962 	}
1963 	THREAD_UNLOCK();
1964 
1965 	ICMP6_FILTER_SETBLOCKALL(&filter);
1966 	ICMP6_FILTER_SETPASS(ICMP6_FQDN_REPLY, &filter);
1967 
1968 	FD_ZERO(&s_fds);
1969 	tout.tv_sec = 0;
1970 	tout.tv_usec = 200000;	/*XXX: 200ms*/
1971 
1972 	fq = (struct icmp6_fqdn_query *)buf;
1973 	fq->icmp6_fqdn_type = ICMP6_FQDN_QUERY;
1974 	fq->icmp6_fqdn_code = 0;
1975 	fq->icmp6_fqdn_cksum = 0;
1976 	fq->icmp6_fqdn_id = (u_short)getpid();
1977 	fq->icmp6_fqdn_unused = 0;
1978 	fq->icmp6_fqdn_cookie[0] = 0;
1979 	fq->icmp6_fqdn_cookie[1] = 0;
1980 
1981 	memset(&sin6, 0, sizeof(sin6));
1982 	sin6.sin6_family = AF_INET6;
1983 	sin6.sin6_addr = *addr;
1984 
1985 	memset(&msg, 0, sizeof(msg));
1986 	msg.msg_name = (caddr_t)&sin6;
1987 	msg.msg_namelen = sizeof(sin6);
1988 	msg.msg_iov = &iov;
1989 	msg.msg_iovlen = 1;
1990 	msg.msg_control = NULL;
1991 	msg.msg_controllen = 0;
1992 	iov.iov_base = (caddr_t)buf;
1993 	iov.iov_len = sizeof(struct icmp6_fqdn_query);
1994 
1995 	if (ifindex) {
1996 		msg.msg_control = cbuf;
1997 		msg.msg_controllen = sizeof(cbuf);
1998 		cmsg = CMSG_FIRSTHDR(&msg);
1999 		cmsg->cmsg_len = CMSG_LEN(sizeof(struct in6_pktinfo));
2000 		cmsg->cmsg_level = IPPROTO_IPV6;
2001 		cmsg->cmsg_type = IPV6_PKTINFO;
2002 		pkt = (struct in6_pktinfo *)&cmsg[1];
2003 		memset(&pkt->ipi6_addr, 0, sizeof(struct in6_addr));
2004 		pkt->ipi6_ifindex = ifindex;
2005 		cmsg = CMSG_NXTHDR(&msg, cmsg);
2006 		msg.msg_controllen = (char *)cmsg - cbuf;
2007 	}
2008 
2009 	if ((s = _socket(PF_INET6, SOCK_RAW, IPPROTO_ICMPV6)) < 0)
2010 		return NULL;
2011 	(void)_setsockopt(s, IPPROTO_ICMPV6, ICMP6_FILTER,
2012 			 (char *)&filter, sizeof(filter));
2013 	cc = _sendmsg(s, &msg, 0);
2014 	if (cc < 0) {
2015 		_close(s);
2016 		return NULL;
2017 	}
2018 	FD_SET(s, &s_fds);
2019 	for (;;) {
2020 		fds = s_fds;
2021 		if (_select(s + 1, &fds, NULL, NULL, &tout) <= 0) {
2022 			_close(s);
2023 			return NULL;
2024 		}
2025 		len = sizeof(sin6);
2026 		cc = _recvfrom(s, buf, sizeof(buf), 0,
2027 			      (struct sockaddr *)&sin6, &len);
2028 		if (cc <= 0) {
2029 			_close(s);
2030 			return NULL;
2031 		}
2032 		if (cc < sizeof(struct ip6_hdr) + sizeof(struct icmp6_hdr))
2033 			continue;
2034 		if (!IN6_ARE_ADDR_EQUAL(addr, &sin6.sin6_addr))
2035 			continue;
2036 		fr = (struct icmp6_fqdn_reply *)(buf + sizeof(struct ip6_hdr));
2037 		if (fr->icmp6_fqdn_type == ICMP6_FQDN_REPLY)
2038 			break;
2039 	}
2040 	_close(s);
2041 	if (fr->icmp6_fqdn_cookie[1] != 0) {
2042 		/* rfc1788 type */
2043 		name = buf + sizeof(struct ip6_hdr) + sizeof(struct icmp6_hdr) + 4;
2044 		len = (buf + cc) - name;
2045 	} else {
2046 		len = fr->icmp6_fqdn_namelen;
2047 		name = fr->icmp6_fqdn_name;
2048 	}
2049 	if (len <= 0)
2050 		return NULL;
2051 	name[len] = 0;
2052 
2053 	if ((hc = (struct _icmp_host_cache *)malloc(sizeof(*hc))) == NULL)
2054 		return NULL;
2055 	/* XXX: limit number of cached entries */
2056 	hc->hc_ifindex = ifindex;
2057 	hc->hc_addr = *addr;
2058 	hc->hc_name = strdup(name);
2059 	THREAD_LOCK();
2060 	hc->hc_next = hc_head;
2061 	hc_head = hc;
2062 	THREAD_UNLOCK();
2063 	return hc->hc_name;
2064 }
2065 
2066 static struct hostent *
2067 _icmp_ghbyaddr(const void *addr, int addrlen, int af, int *errp)
2068 {
2069 	char *hname;
2070 	int ifindex;
2071 	struct in6_addr addr6;
2072 
2073 	if (af != AF_INET6) {
2074 		/*
2075 		 * Note: rfc1788 defines Who Are You for IPv4,
2076 		 * but no one implements it.
2077 		 */
2078 		return NULL;
2079 	}
2080 
2081 	memcpy(&addr6, addr, addrlen);
2082 	ifindex = (addr6.s6_addr[2] << 8) | addr6.s6_addr[3];
2083 	addr6.s6_addr[2] = addr6.s6_addr[3] = 0;
2084 
2085 	if (!IN6_IS_ADDR_LINKLOCAL(&addr6))
2086 		return NULL;	/*XXX*/
2087 
2088 	if ((hname = _icmp_fqdn_query(&addr6, ifindex)) == NULL)
2089 		return NULL;
2090 	return _hpaddr(af, hname, &addr6, errp);
2091 }
2092 #endif /* ICMPNL */
2093