xref: /freebsd/lib/libc/net/getaddrinfo.c (revision 313376588638950ba1e93c403dd8c97bc52fd3a2)
1 /*	$KAME: getaddrinfo.c,v 1.15 2000/07/09 04:37:24 itojun Exp $	*/
2 
3 /*
4  * Copyright (C) 1995, 1996, 1997, and 1998 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 /*
33  * "#ifdef FAITH" part is local hack for supporting IPv4-v6 translator.
34  *
35  * Issues to be discussed:
36  * - Return values.  There are nonstandard return values defined and used
37  *   in the source code.  This is because RFC2553 is silent about which error
38  *   code must be returned for which situation.
39  * - freeaddrinfo(NULL).  RFC2553 is silent about it.  XNET 5.2 says it is
40  *   invalid.  current code - SEGV on freeaddrinfo(NULL)
41  *
42  * Note:
43  * - The code filters out AFs that are not supported by the kernel,
44  *   when globbing NULL hostname (to loopback, or wildcard).  Is it the right
45  *   thing to do?  What is the relationship with post-RFC2553 AI_ADDRCONFIG
46  *   in ai_flags?
47  * - (post-2553) semantics of AI_ADDRCONFIG itself is too vague.
48  *   (1) what should we do against numeric hostname (2) what should we do
49  *   against NULL hostname (3) what is AI_ADDRCONFIG itself.  AF not ready?
50  *   non-loopback address configured?  global address configured?
51  *
52  * OS specific notes for freebsd4:
53  * - FreeBSD supported $GAI.  The code does not.
54  */
55 
56 #include <sys/cdefs.h>
57 __FBSDID("$FreeBSD$");
58 
59 #include "namespace.h"
60 #include <sys/types.h>
61 #include <sys/param.h>
62 #include <sys/socket.h>
63 #include <net/if.h>
64 #include <netinet/in.h>
65 #include <net/if_types.h>
66 #include <ifaddrs.h>
67 #include <sys/queue.h>
68 #ifdef INET6
69 #include <net/if_var.h>
70 #include <sys/sysctl.h>
71 #include <sys/ioctl.h>
72 #include <netinet6/in6_var.h>
73 #include <netinet6/nd6.h>
74 #endif
75 #include <arpa/inet.h>
76 #include <arpa/nameser.h>
77 #include <rpc/rpc.h>
78 #include <rpcsvc/yp_prot.h>
79 #include <rpcsvc/ypclnt.h>
80 #include <netdb.h>
81 #include <resolv.h>
82 #include <string.h>
83 #include <stdlib.h>
84 #include <stddef.h>
85 #include <ctype.h>
86 #include <unistd.h>
87 #include <stdio.h>
88 #include <errno.h>
89 
90 #include "res_config.h"
91 
92 #ifdef DEBUG
93 #include <syslog.h>
94 #endif
95 
96 #include <stdarg.h>
97 #include <nsswitch.h>
98 #include "un-namespace.h"
99 #include "libc_private.h"
100 #ifdef NS_CACHING
101 #include "nscache.h"
102 #endif
103 
104 #if defined(__KAME__) && defined(INET6)
105 # define FAITH
106 #endif
107 
108 #define ANY 0
109 #define YES 1
110 #define NO  0
111 
112 static const char in_addrany[] = { 0, 0, 0, 0 };
113 static const char in_loopback[] = { 127, 0, 0, 1 };
114 #ifdef INET6
115 static const char in6_addrany[] = {
116 	0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0
117 };
118 static const char in6_loopback[] = {
119 	0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 1
120 };
121 #endif
122 
123 struct policyqueue {
124 	TAILQ_ENTRY(policyqueue) pc_entry;
125 #ifdef INET6
126 	struct in6_addrpolicy pc_policy;
127 #endif
128 };
129 TAILQ_HEAD(policyhead, policyqueue);
130 
131 static const struct afd {
132 	int a_af;
133 	int a_addrlen;
134 	socklen_t a_socklen;
135 	int a_off;
136 	const char *a_addrany;
137 	const char *a_loopback;
138 	int a_scoped;
139 } afdl [] = {
140 #ifdef INET6
141 #define	N_INET6 0
142 	{PF_INET6, sizeof(struct in6_addr),
143 	 sizeof(struct sockaddr_in6),
144 	 offsetof(struct sockaddr_in6, sin6_addr),
145 	 in6_addrany, in6_loopback, 1},
146 #define	N_INET 1
147 #else
148 #define	N_INET 0
149 #endif
150 	{PF_INET, sizeof(struct in_addr),
151 	 sizeof(struct sockaddr_in),
152 	 offsetof(struct sockaddr_in, sin_addr),
153 	 in_addrany, in_loopback, 0},
154 	{0, 0, 0, 0, NULL, NULL, 0},
155 };
156 
157 struct explore {
158 	int e_af;
159 	int e_socktype;
160 	int e_protocol;
161 	int e_wild;
162 #define WILD_AF(ex)		((ex)->e_wild & 0x01)
163 #define WILD_SOCKTYPE(ex)	((ex)->e_wild & 0x02)
164 #define WILD_PROTOCOL(ex)	((ex)->e_wild & 0x04)
165 };
166 
167 static const struct explore explore[] = {
168 #if 0
169 	{ PF_LOCAL, ANY, ANY, 0x01 },
170 #endif
171 #ifdef INET6
172 	{ PF_INET6, SOCK_DGRAM, IPPROTO_UDP, 0x07 },
173 	{ PF_INET6, SOCK_STREAM, IPPROTO_TCP, 0x07 },
174 	{ PF_INET6, SOCK_STREAM, IPPROTO_SCTP, 0x03 },
175 	{ PF_INET6, SOCK_SEQPACKET, IPPROTO_SCTP, 0x07 },
176 	{ PF_INET6, SOCK_DGRAM, IPPROTO_UDPLITE, 0x03 },
177 	{ PF_INET6, SOCK_RAW, ANY, 0x05 },
178 #endif
179 	{ PF_INET, SOCK_DGRAM, IPPROTO_UDP, 0x07 },
180 	{ PF_INET, SOCK_STREAM, IPPROTO_TCP, 0x07 },
181 	{ PF_INET, SOCK_STREAM, IPPROTO_SCTP, 0x03 },
182 	{ PF_INET, SOCK_SEQPACKET, IPPROTO_SCTP, 0x07 },
183 	{ PF_INET, SOCK_DGRAM, IPPROTO_UDPLITE, 0x03 },
184 	{ PF_INET, SOCK_RAW, ANY, 0x05 },
185 	{ -1, 0, 0, 0 },
186 };
187 
188 #ifdef INET6
189 #define PTON_MAX	16
190 #else
191 #define PTON_MAX	4
192 #endif
193 
194 #define AIO_SRCFLAG_DEPRECATED	0x1
195 
196 struct ai_order {
197 	union {
198 		struct sockaddr_storage aiou_ss;
199 		struct sockaddr aiou_sa;
200 	} aio_src_un;
201 #define aio_srcsa aio_src_un.aiou_sa
202 	u_int32_t aio_srcflag;
203 	int aio_srcscope;
204 	int aio_dstscope;
205 	struct policyqueue *aio_srcpolicy;
206 	struct policyqueue *aio_dstpolicy;
207 	struct addrinfo *aio_ai;
208 	int aio_matchlen;
209 };
210 
211 static const ns_src default_dns_files[] = {
212 	{ NSSRC_FILES, 	NS_SUCCESS },
213 	{ NSSRC_DNS, 	NS_SUCCESS },
214 	{ 0 }
215 };
216 
217 struct res_target {
218 	struct res_target *next;
219 	const char *name;	/* domain name */
220 	int qclass, qtype;	/* class and type of query */
221 	u_char *answer;		/* buffer to put answer */
222 	int anslen;		/* size of answer buffer */
223 	int n;			/* result length */
224 };
225 
226 #define MAXPACKET	(64*1024)
227 
228 typedef union {
229 	HEADER hdr;
230 	u_char buf[MAXPACKET];
231 } querybuf;
232 
233 static int str2number(const char *, int *);
234 static int explore_copy(const struct addrinfo *, const struct addrinfo *,
235 	struct addrinfo **);
236 static int explore_null(const struct addrinfo *,
237 	const char *, struct addrinfo **);
238 static int explore_numeric(const struct addrinfo *, const char *,
239 	const char *, struct addrinfo **, const char *);
240 static int explore_numeric_scope(const struct addrinfo *, const char *,
241 	const char *, struct addrinfo **);
242 static int get_canonname(const struct addrinfo *,
243 	struct addrinfo *, const char *);
244 static struct addrinfo *get_ai(const struct addrinfo *,
245 	const struct afd *, const char *);
246 static struct addrinfo *copy_ai(const struct addrinfo *);
247 static int get_portmatch(const struct addrinfo *, const char *);
248 static int get_port(struct addrinfo *, const char *, int);
249 static const struct afd *find_afd(int);
250 static int addrconfig(struct addrinfo *);
251 #ifdef INET6
252 static int is_ifdisabled(char *);
253 #endif
254 static void set_source(struct ai_order *, struct policyhead *);
255 static int comp_dst(const void *, const void *);
256 #ifdef INET6
257 static int ip6_str2scopeid(char *, struct sockaddr_in6 *, u_int32_t *);
258 #endif
259 static int gai_addr2scopetype(struct sockaddr *);
260 
261 static int explore_fqdn(const struct addrinfo *, const char *,
262 	const char *, struct addrinfo **);
263 
264 static int reorder(struct addrinfo *);
265 static int get_addrselectpolicy(struct policyhead *);
266 static void free_addrselectpolicy(struct policyhead *);
267 static struct policyqueue *match_addrselectpolicy(struct sockaddr *,
268 	struct policyhead *);
269 static int matchlen(struct sockaddr *, struct sockaddr *);
270 
271 static struct addrinfo *getanswer(const querybuf *, int, const char *, int,
272 	const struct addrinfo *, res_state);
273 #if defined(RESOLVSORT)
274 static int addr4sort(struct addrinfo *, res_state);
275 #endif
276 static int _dns_getaddrinfo(void *, void *, va_list);
277 static void _sethtent(FILE **);
278 static void _endhtent(FILE **);
279 static struct addrinfo *_gethtent(FILE **, const char *,
280 	const struct addrinfo *);
281 static int _files_getaddrinfo(void *, void *, va_list);
282 #ifdef YP
283 static struct addrinfo *_yphostent(char *, const struct addrinfo *);
284 static int _yp_getaddrinfo(void *, void *, va_list);
285 #endif
286 #ifdef NS_CACHING
287 static int addrinfo_id_func(char *, size_t *, va_list, void *);
288 static int addrinfo_marshal_func(char *, size_t *, void *, va_list, void *);
289 static int addrinfo_unmarshal_func(char *, size_t, void *, va_list, void *);
290 #endif
291 
292 static int res_queryN(const char *, struct res_target *, res_state);
293 static int res_searchN(const char *, struct res_target *, res_state);
294 static int res_querydomainN(const char *, const char *,
295 	struct res_target *, res_state);
296 
297 /* XXX macros that make external reference is BAD. */
298 
299 #define GET_AI(ai, afd, addr) \
300 do { \
301 	/* external reference: pai, error, and label free */ \
302 	(ai) = get_ai(pai, (afd), (addr)); \
303 	if ((ai) == NULL) { \
304 		error = EAI_MEMORY; \
305 		goto free; \
306 	} \
307 } while (/*CONSTCOND*/0)
308 
309 #define GET_PORT(ai, serv) \
310 do { \
311 	/* external reference: error and label free */ \
312 	error = get_port((ai), (serv), 0); \
313 	if (error != 0) \
314 		goto free; \
315 } while (/*CONSTCOND*/0)
316 
317 #define GET_CANONNAME(ai, str) \
318 do { \
319 	/* external reference: pai, error and label free */ \
320 	error = get_canonname(pai, (ai), (str)); \
321 	if (error != 0) \
322 		goto free; \
323 } while (/*CONSTCOND*/0)
324 
325 #define ERR(err) \
326 do { \
327 	/* external reference: error, and label bad */ \
328 	error = (err); \
329 	goto bad; \
330 	/*NOTREACHED*/ \
331 } while (/*CONSTCOND*/0)
332 
333 #define MATCH_FAMILY(x, y, w) \
334 	((x) == (y) || (/*CONSTCOND*/(w) && ((x) == PF_UNSPEC || (y) == PF_UNSPEC)))
335 #define MATCH(x, y, w) \
336 	((x) == (y) || (/*CONSTCOND*/(w) && ((x) == ANY || (y) == ANY)))
337 
338 void
339 freeaddrinfo(struct addrinfo *ai)
340 {
341 	struct addrinfo *next;
342 
343 	do {
344 		next = ai->ai_next;
345 		if (ai->ai_canonname)
346 			free(ai->ai_canonname);
347 		/* no need to free(ai->ai_addr) */
348 		free(ai);
349 		ai = next;
350 	} while (ai);
351 }
352 
353 static int
354 str2number(const char *p, int *portp)
355 {
356 	char *ep;
357 	unsigned long v;
358 
359 	if (*p == '\0')
360 		return -1;
361 	ep = NULL;
362 	errno = 0;
363 	v = strtoul(p, &ep, 10);
364 	if (errno == 0 && ep && *ep == '\0' && v <= UINT_MAX) {
365 		*portp = v;
366 		return 0;
367 	} else
368 		return -1;
369 }
370 
371 int
372 getaddrinfo(const char *hostname, const char *servname,
373     const struct addrinfo *hints, struct addrinfo **res)
374 {
375 	struct addrinfo sentinel;
376 	struct addrinfo *cur;
377 	int error = 0;
378 	struct addrinfo ai, ai0, *afai;
379 	struct addrinfo *pai;
380 	const struct afd *afd;
381 	const struct explore *ex;
382 	struct addrinfo *afailist[sizeof(afdl)/sizeof(afdl[0])];
383 	struct addrinfo *afai_unspec;
384 	int found;
385 	int numeric = 0;
386 
387 	/* ensure we return NULL on errors */
388 	*res = NULL;
389 
390 	memset(&ai, 0, sizeof(ai));
391 
392 	memset(afailist, 0, sizeof(afailist));
393 	afai_unspec = NULL;
394 
395 	memset(&sentinel, 0, sizeof(sentinel));
396 	cur = &sentinel;
397 	pai = &ai;
398 	pai->ai_flags = 0;
399 	pai->ai_family = PF_UNSPEC;
400 	pai->ai_socktype = ANY;
401 	pai->ai_protocol = ANY;
402 	pai->ai_addrlen = 0;
403 	pai->ai_canonname = NULL;
404 	pai->ai_addr = NULL;
405 	pai->ai_next = NULL;
406 
407 	if (hostname == NULL && servname == NULL)
408 		return EAI_NONAME;
409 	if (hints) {
410 		/* error check for hints */
411 		if (hints->ai_addrlen || hints->ai_canonname ||
412 		    hints->ai_addr || hints->ai_next)
413 			ERR(EAI_BADHINTS); /* xxx */
414 		if (hints->ai_flags & ~AI_MASK)
415 			ERR(EAI_BADFLAGS);
416 		switch (hints->ai_family) {
417 		case PF_UNSPEC:
418 		case PF_INET:
419 #ifdef INET6
420 		case PF_INET6:
421 #endif
422 			break;
423 		default:
424 			ERR(EAI_FAMILY);
425 		}
426 		memcpy(pai, hints, sizeof(*pai));
427 
428 		/*
429 		 * if both socktype/protocol are specified, check if they
430 		 * are meaningful combination.
431 		 */
432 		if (pai->ai_socktype != ANY && pai->ai_protocol != ANY) {
433 			for (ex = explore; ex->e_af >= 0; ex++) {
434 				if (!MATCH_FAMILY(pai->ai_family, ex->e_af,
435 				    WILD_AF(ex)))
436 					continue;
437 				if (!MATCH(pai->ai_socktype, ex->e_socktype,
438 				    WILD_SOCKTYPE(ex)))
439 					continue;
440 				if (!MATCH(pai->ai_protocol, ex->e_protocol,
441 				    WILD_PROTOCOL(ex)))
442 					continue;
443 
444 				/* matched */
445 				break;
446 			}
447 
448 			if (ex->e_af < 0)
449 				ERR(EAI_BADHINTS);
450 		}
451 	}
452 
453 	/*
454 	 * check for special cases.  (1) numeric servname is disallowed if
455 	 * socktype/protocol are left unspecified. (2) servname is disallowed
456 	 * for raw and other inet{,6} sockets.
457 	 */
458 	if (MATCH_FAMILY(pai->ai_family, PF_INET, 1)
459 #ifdef PF_INET6
460 	    || MATCH_FAMILY(pai->ai_family, PF_INET6, 1)
461 #endif
462 	    ) {
463 		ai0 = *pai;	/* backup *pai */
464 
465 		if (pai->ai_family == PF_UNSPEC) {
466 #ifdef PF_INET6
467 			pai->ai_family = PF_INET6;
468 #else
469 			pai->ai_family = PF_INET;
470 #endif
471 		}
472 		error = get_portmatch(pai, servname);
473 		if (error)
474 			goto bad;
475 
476 		*pai = ai0;
477 	}
478 
479 	ai0 = *pai;
480 
481 	/*
482 	 * NULL hostname, or numeric hostname.
483 	 * If numeric representation of AF1 can be interpreted as FQDN
484 	 * representation of AF2, we need to think again about the code below.
485 	 */
486 	found = 0;
487 	for (afd = afdl; afd->a_af; afd++) {
488 		*pai = ai0;
489 
490 		if (!MATCH_FAMILY(pai->ai_family, afd->a_af, 1))
491 			continue;
492 
493 		if (pai->ai_family == PF_UNSPEC)
494 			pai->ai_family = afd->a_af;
495 
496 		if (hostname == NULL) {
497 			error = explore_null(pai, servname,
498 			    &afailist[afd - afdl]);
499 
500 			/*
501 			 * Errors from explore_null should be unexpected and
502 			 * be caught to avoid returning an incomplete result.
503 			 */
504 			if (error != 0)
505 				goto bad;
506 		} else {
507 			error = explore_numeric_scope(pai, hostname, servname,
508 			    &afailist[afd - afdl]);
509 
510 			/*
511 			 * explore_numeric_scope returns an error for address
512 			 * families that do not match that of hostname.
513 			 * Thus we should not catch the error at this moment.
514 			 */
515 		}
516 
517 		if (!error && afailist[afd - afdl])
518 			found++;
519 	}
520 	if (found) {
521 		numeric = 1;
522 		goto globcopy;
523 	}
524 
525 	if (hostname == NULL)
526 		ERR(EAI_NONAME);	/* used to be EAI_NODATA */
527 	if (pai->ai_flags & AI_NUMERICHOST)
528 		ERR(EAI_NONAME);
529 
530 	if ((pai->ai_flags & AI_ADDRCONFIG) != 0 && !addrconfig(&ai0))
531 		ERR(EAI_FAIL);
532 
533 	/*
534 	 * hostname as alphabetical name.
535 	 */
536 	*pai = ai0;
537 	error = explore_fqdn(pai, hostname, servname, &afai_unspec);
538 
539 globcopy:
540 	for (ex = explore; ex->e_af >= 0; ex++) {
541 		*pai = ai0;
542 
543 		if (!MATCH_FAMILY(pai->ai_family, ex->e_af, WILD_AF(ex)))
544 			continue;
545 		if (!MATCH(pai->ai_socktype, ex->e_socktype,
546 		    WILD_SOCKTYPE(ex)))
547 			continue;
548 		if (!MATCH(pai->ai_protocol, ex->e_protocol,
549 		    WILD_PROTOCOL(ex)))
550 			continue;
551 
552 		if (pai->ai_family == PF_UNSPEC)
553 			pai->ai_family = ex->e_af;
554 		if (pai->ai_socktype == ANY && ex->e_socktype != ANY)
555 			pai->ai_socktype = ex->e_socktype;
556 		if (pai->ai_protocol == ANY && ex->e_protocol != ANY)
557 			pai->ai_protocol = ex->e_protocol;
558 
559 		/*
560 		 * if the servname does not match socktype/protocol, ignore it.
561 		 */
562 		if (get_portmatch(pai, servname) != 0)
563 			continue;
564 
565 		if (afai_unspec)
566 			afai = afai_unspec;
567 		else {
568 			if ((afd = find_afd(pai->ai_family)) == NULL)
569 				continue;
570 			/* XXX assumes that afd points inside afdl[] */
571 			afai = afailist[afd - afdl];
572 		}
573 		if (!afai)
574 			continue;
575 
576 		error = explore_copy(pai, afai, &cur->ai_next);
577 		if (error != 0)
578 			goto bad;
579 
580 		while (cur && cur->ai_next)
581 			cur = cur->ai_next;
582 	}
583 
584 	/*
585 	 * ensure we return either:
586 	 * - error == 0, non-NULL *res
587 	 * - error != 0, NULL *res
588 	 */
589 	if (error == 0) {
590 		if (sentinel.ai_next) {
591 			/*
592 			 * If the returned entry is for an active connection,
593 			 * and the given name is not numeric, reorder the
594 			 * list, so that the application would try the list
595 			 * in the most efficient order.  Since the head entry
596 			 * of the original list may contain ai_canonname and
597 			 * that entry may be moved elsewhere in the new list,
598 			 * we keep the pointer and will  restore it in the new
599 			 * head entry.  (Note that RFC3493 requires the head
600 			 * entry store it when requested by the caller).
601 			 */
602 			if (hints == NULL || !(hints->ai_flags & AI_PASSIVE)) {
603 				if (!numeric) {
604 					char *canonname;
605 
606 					canonname =
607 					    sentinel.ai_next->ai_canonname;
608 					sentinel.ai_next->ai_canonname = NULL;
609 					(void)reorder(&sentinel);
610 					if (sentinel.ai_next->ai_canonname ==
611 					    NULL) {
612 						sentinel.ai_next->ai_canonname
613 						    = canonname;
614 					} else if (canonname != NULL)
615 						free(canonname);
616 				}
617 			}
618 			*res = sentinel.ai_next;
619 		} else
620 			error = EAI_FAIL;
621 	}
622 
623 bad:
624 	if (afai_unspec)
625 		freeaddrinfo(afai_unspec);
626 	for (afd = afdl; afd->a_af; afd++) {
627 		if (afailist[afd - afdl])
628 			freeaddrinfo(afailist[afd - afdl]);
629 	}
630 	if (!*res)
631 		if (sentinel.ai_next)
632 			freeaddrinfo(sentinel.ai_next);
633 
634 	return (error);
635 }
636 
637 static int
638 reorder(struct addrinfo *sentinel)
639 {
640 	struct addrinfo *ai, **aip;
641 	struct ai_order *aio;
642 	int i, n;
643 	struct policyhead policyhead;
644 
645 	/* count the number of addrinfo elements for sorting. */
646 	for (n = 0, ai = sentinel->ai_next; ai != NULL; ai = ai->ai_next, n++)
647 		;
648 
649 	/*
650 	 * If the number is small enough, we can skip the reordering process.
651 	 */
652 	if (n <= 1)
653 		return(n);
654 
655 	/* allocate a temporary array for sort and initialization of it. */
656 	if ((aio = malloc(sizeof(*aio) * n)) == NULL)
657 		return(n);	/* give up reordering */
658 	memset(aio, 0, sizeof(*aio) * n);
659 
660 	/* retrieve address selection policy from the kernel */
661 	TAILQ_INIT(&policyhead);
662 	if (!get_addrselectpolicy(&policyhead)) {
663 		/* no policy is installed into kernel, we don't sort. */
664 		free(aio);
665 		return (n);
666 	}
667 
668 	for (i = 0, ai = sentinel->ai_next; i < n; ai = ai->ai_next, i++) {
669 		aio[i].aio_ai = ai;
670 		aio[i].aio_dstscope = gai_addr2scopetype(ai->ai_addr);
671 		aio[i].aio_dstpolicy = match_addrselectpolicy(ai->ai_addr,
672 							      &policyhead);
673 		set_source(&aio[i], &policyhead);
674 	}
675 
676 	/* perform sorting. */
677 	qsort(aio, n, sizeof(*aio), comp_dst);
678 
679 	/* reorder the addrinfo chain. */
680 	for (i = 0, aip = &sentinel->ai_next; i < n; i++) {
681 		*aip = aio[i].aio_ai;
682 		aip = &aio[i].aio_ai->ai_next;
683 	}
684 	*aip = NULL;
685 
686 	/* cleanup and return */
687 	free(aio);
688 	free_addrselectpolicy(&policyhead);
689 	return(n);
690 }
691 
692 static int
693 get_addrselectpolicy(struct policyhead *head)
694 {
695 #ifdef INET6
696 	int mib[] = { CTL_NET, PF_INET6, IPPROTO_IPV6, IPV6CTL_ADDRCTLPOLICY };
697 	size_t l;
698 	char *buf;
699 	struct in6_addrpolicy *pol, *ep;
700 
701 	if (sysctl(mib, sizeof(mib) / sizeof(mib[0]), NULL, &l, NULL, 0) < 0)
702 		return (0);
703 	if (l == 0)
704 		return (0);
705 	if ((buf = malloc(l)) == NULL)
706 		return (0);
707 	if (sysctl(mib, sizeof(mib) / sizeof(mib[0]), buf, &l, NULL, 0) < 0) {
708 		free(buf);
709 		return (0);
710 	}
711 
712 	ep = (struct in6_addrpolicy *)(buf + l);
713 	for (pol = (struct in6_addrpolicy *)buf; pol + 1 <= ep; pol++) {
714 		struct policyqueue *new;
715 
716 		if ((new = malloc(sizeof(*new))) == NULL) {
717 			free_addrselectpolicy(head); /* make the list empty */
718 			break;
719 		}
720 		new->pc_policy = *pol;
721 		TAILQ_INSERT_TAIL(head, new, pc_entry);
722 	}
723 
724 	free(buf);
725 	return (1);
726 #else
727 	return (0);
728 #endif
729 }
730 
731 static void
732 free_addrselectpolicy(struct policyhead *head)
733 {
734 	struct policyqueue *ent, *nent;
735 
736 	for (ent = TAILQ_FIRST(head); ent; ent = nent) {
737 		nent = TAILQ_NEXT(ent, pc_entry);
738 		TAILQ_REMOVE(head, ent, pc_entry);
739 		free(ent);
740 	}
741 }
742 
743 static struct policyqueue *
744 match_addrselectpolicy(struct sockaddr *addr, struct policyhead *head)
745 {
746 #ifdef INET6
747 	struct policyqueue *ent, *bestent = NULL;
748 	struct in6_addrpolicy *pol;
749 	int matchlen, bestmatchlen = -1;
750 	u_char *mp, *ep, *k, *p, m;
751 	struct sockaddr_in6 key;
752 
753 	switch(addr->sa_family) {
754 	case AF_INET6:
755 		key = *(struct sockaddr_in6 *)addr;
756 		break;
757 	case AF_INET:
758 		/* convert the address into IPv4-mapped IPv6 address. */
759 		memset(&key, 0, sizeof(key));
760 		key.sin6_family = AF_INET6;
761 		key.sin6_len = sizeof(key);
762 		key.sin6_addr.s6_addr[10] = 0xff;
763 		key.sin6_addr.s6_addr[11] = 0xff;
764 		memcpy(&key.sin6_addr.s6_addr[12],
765 		       &((struct sockaddr_in *)addr)->sin_addr, 4);
766 		break;
767 	default:
768 		return(NULL);
769 	}
770 
771 	for (ent = TAILQ_FIRST(head); ent; ent = TAILQ_NEXT(ent, pc_entry)) {
772 		pol = &ent->pc_policy;
773 		matchlen = 0;
774 
775 		mp = (u_char *)&pol->addrmask.sin6_addr;
776 		ep = mp + 16;	/* XXX: scope field? */
777 		k = (u_char *)&key.sin6_addr;
778 		p = (u_char *)&pol->addr.sin6_addr;
779 		for (; mp < ep && *mp; mp++, k++, p++) {
780 			m = *mp;
781 			if ((*k & m) != *p)
782 				goto next; /* not match */
783 			if (m == 0xff) /* short cut for a typical case */
784 				matchlen += 8;
785 			else {
786 				while (m >= 0x80) {
787 					matchlen++;
788 					m <<= 1;
789 				}
790 			}
791 		}
792 
793 		/* matched.  check if this is better than the current best. */
794 		if (matchlen > bestmatchlen) {
795 			bestent = ent;
796 			bestmatchlen = matchlen;
797 		}
798 
799 	  next:
800 		continue;
801 	}
802 
803 	return(bestent);
804 #else
805 	return(NULL);
806 #endif
807 
808 }
809 
810 static void
811 set_source(struct ai_order *aio, struct policyhead *ph)
812 {
813 	struct addrinfo ai = *aio->aio_ai;
814 	struct sockaddr_storage ss;
815 	socklen_t srclen;
816 	int s;
817 
818 	/* set unspec ("no source is available"), just in case */
819 	aio->aio_srcsa.sa_family = AF_UNSPEC;
820 	aio->aio_srcscope = -1;
821 
822 	switch(ai.ai_family) {
823 	case AF_INET:
824 #ifdef INET6
825 	case AF_INET6:
826 #endif
827 		break;
828 	default:		/* ignore unsupported AFs explicitly */
829 		return;
830 	}
831 
832 	/* XXX: make a dummy addrinfo to call connect() */
833 	ai.ai_socktype = SOCK_DGRAM;
834 	ai.ai_protocol = IPPROTO_UDP; /* is UDP too specific? */
835 	ai.ai_next = NULL;
836 	memset(&ss, 0, sizeof(ss));
837 	memcpy(&ss, ai.ai_addr, ai.ai_addrlen);
838 	ai.ai_addr = (struct sockaddr *)&ss;
839 	get_port(&ai, "1", 0);
840 
841 	/* open a socket to get the source address for the given dst */
842 	if ((s = _socket(ai.ai_family, ai.ai_socktype | SOCK_CLOEXEC,
843 	    ai.ai_protocol)) < 0)
844 		return;		/* give up */
845 	if (_connect(s, ai.ai_addr, ai.ai_addrlen) < 0)
846 		goto cleanup;
847 	srclen = ai.ai_addrlen;
848 	if (_getsockname(s, &aio->aio_srcsa, &srclen) < 0) {
849 		aio->aio_srcsa.sa_family = AF_UNSPEC;
850 		goto cleanup;
851 	}
852 	aio->aio_srcscope = gai_addr2scopetype(&aio->aio_srcsa);
853 	aio->aio_srcpolicy = match_addrselectpolicy(&aio->aio_srcsa, ph);
854 	aio->aio_matchlen = matchlen(&aio->aio_srcsa, aio->aio_ai->ai_addr);
855 #ifdef INET6
856 	if (ai.ai_family == AF_INET6) {
857 		struct in6_ifreq ifr6;
858 		u_int32_t flags6;
859 
860 		memset(&ifr6, 0, sizeof(ifr6));
861 		memcpy(&ifr6.ifr_addr, ai.ai_addr, ai.ai_addrlen);
862 		if (_ioctl(s, SIOCGIFAFLAG_IN6, &ifr6) == 0) {
863 			flags6 = ifr6.ifr_ifru.ifru_flags6;
864 			if ((flags6 & IN6_IFF_DEPRECATED))
865 				aio->aio_srcflag |= AIO_SRCFLAG_DEPRECATED;
866 		}
867 	}
868 #endif
869 
870   cleanup:
871 	_close(s);
872 	return;
873 }
874 
875 static int
876 matchlen(struct sockaddr *src, struct sockaddr *dst)
877 {
878 	int match = 0;
879 	u_char *s, *d;
880 	u_char *lim, r;
881 	int addrlen;
882 
883 	switch (src->sa_family) {
884 #ifdef INET6
885 	case AF_INET6:
886 		s = (u_char *)&((struct sockaddr_in6 *)src)->sin6_addr;
887 		d = (u_char *)&((struct sockaddr_in6 *)dst)->sin6_addr;
888 		addrlen = sizeof(struct in6_addr);
889 		lim = s + addrlen;
890 		break;
891 #endif
892 	case AF_INET:
893 		s = (u_char *)&((struct sockaddr_in *)src)->sin_addr;
894 		d = (u_char *)&((struct sockaddr_in *)dst)->sin_addr;
895 		addrlen = sizeof(struct in_addr);
896 		lim = s + addrlen;
897 		break;
898 	default:
899 		return(0);
900 	}
901 
902 	while (s < lim)
903 		if ((r = (*d++ ^ *s++)) != 0) {
904 			while (r < addrlen * 8) {
905 				match++;
906 				r <<= 1;
907 			}
908 			break;
909 		} else
910 			match += 8;
911 	return(match);
912 }
913 
914 static int
915 comp_dst(const void *arg1, const void *arg2)
916 {
917 	const struct ai_order *dst1 = arg1, *dst2 = arg2;
918 
919 	/*
920 	 * Rule 1: Avoid unusable destinations.
921 	 * XXX: we currently do not consider if an appropriate route exists.
922 	 */
923 	if (dst1->aio_srcsa.sa_family != AF_UNSPEC &&
924 	    dst2->aio_srcsa.sa_family == AF_UNSPEC) {
925 		return(-1);
926 	}
927 	if (dst1->aio_srcsa.sa_family == AF_UNSPEC &&
928 	    dst2->aio_srcsa.sa_family != AF_UNSPEC) {
929 		return(1);
930 	}
931 
932 	/* Rule 2: Prefer matching scope. */
933 	if (dst1->aio_dstscope == dst1->aio_srcscope &&
934 	    dst2->aio_dstscope != dst2->aio_srcscope) {
935 		return(-1);
936 	}
937 	if (dst1->aio_dstscope != dst1->aio_srcscope &&
938 	    dst2->aio_dstscope == dst2->aio_srcscope) {
939 		return(1);
940 	}
941 
942 	/* Rule 3: Avoid deprecated addresses. */
943 	if (dst1->aio_srcsa.sa_family != AF_UNSPEC &&
944 	    dst2->aio_srcsa.sa_family != AF_UNSPEC) {
945 		if (!(dst1->aio_srcflag & AIO_SRCFLAG_DEPRECATED) &&
946 		    (dst2->aio_srcflag & AIO_SRCFLAG_DEPRECATED)) {
947 			return(-1);
948 		}
949 		if ((dst1->aio_srcflag & AIO_SRCFLAG_DEPRECATED) &&
950 		    !(dst2->aio_srcflag & AIO_SRCFLAG_DEPRECATED)) {
951 			return(1);
952 		}
953 	}
954 
955 	/* Rule 4: Prefer home addresses. */
956 	/* XXX: not implemented yet */
957 
958 	/* Rule 5: Prefer matching label. */
959 #ifdef INET6
960 	if (dst1->aio_srcpolicy && dst1->aio_dstpolicy &&
961 	    dst1->aio_srcpolicy->pc_policy.label ==
962 	    dst1->aio_dstpolicy->pc_policy.label &&
963 	    (dst2->aio_srcpolicy == NULL || dst2->aio_dstpolicy == NULL ||
964 	     dst2->aio_srcpolicy->pc_policy.label !=
965 	     dst2->aio_dstpolicy->pc_policy.label)) {
966 		return(-1);
967 	}
968 	if (dst2->aio_srcpolicy && dst2->aio_dstpolicy &&
969 	    dst2->aio_srcpolicy->pc_policy.label ==
970 	    dst2->aio_dstpolicy->pc_policy.label &&
971 	    (dst1->aio_srcpolicy == NULL || dst1->aio_dstpolicy == NULL ||
972 	     dst1->aio_srcpolicy->pc_policy.label !=
973 	     dst1->aio_dstpolicy->pc_policy.label)) {
974 		return(1);
975 	}
976 #endif
977 
978 	/* Rule 6: Prefer higher precedence. */
979 #ifdef INET6
980 	if (dst1->aio_dstpolicy &&
981 	    (dst2->aio_dstpolicy == NULL ||
982 	     dst1->aio_dstpolicy->pc_policy.preced >
983 	     dst2->aio_dstpolicy->pc_policy.preced)) {
984 		return(-1);
985 	}
986 	if (dst2->aio_dstpolicy &&
987 	    (dst1->aio_dstpolicy == NULL ||
988 	     dst2->aio_dstpolicy->pc_policy.preced >
989 	     dst1->aio_dstpolicy->pc_policy.preced)) {
990 		return(1);
991 	}
992 #endif
993 
994 	/* Rule 7: Prefer native transport. */
995 	/* XXX: not implemented yet */
996 
997 	/* Rule 8: Prefer smaller scope. */
998 	if (dst1->aio_dstscope >= 0 &&
999 	    dst1->aio_dstscope < dst2->aio_dstscope) {
1000 		return(-1);
1001 	}
1002 	if (dst2->aio_dstscope >= 0 &&
1003 	    dst2->aio_dstscope < dst1->aio_dstscope) {
1004 		return(1);
1005 	}
1006 
1007 	/*
1008 	 * Rule 9: Use longest matching prefix.
1009 	 * We compare the match length in a same AF only.
1010 	 */
1011 	if (dst1->aio_ai->ai_addr->sa_family ==
1012 	    dst2->aio_ai->ai_addr->sa_family &&
1013 	    dst1->aio_ai->ai_addr->sa_family != AF_INET) {
1014 		if (dst1->aio_matchlen > dst2->aio_matchlen) {
1015 			return(-1);
1016 		}
1017 		if (dst1->aio_matchlen < dst2->aio_matchlen) {
1018 			return(1);
1019 		}
1020 	}
1021 
1022 	/* Rule 10: Otherwise, leave the order unchanged. */
1023 	return(-1);
1024 }
1025 
1026 /*
1027  * Copy from scope.c.
1028  * XXX: we should standardize the functions and link them as standard
1029  * library.
1030  */
1031 static int
1032 gai_addr2scopetype(struct sockaddr *sa)
1033 {
1034 #ifdef INET6
1035 	struct sockaddr_in6 *sa6;
1036 #endif
1037 	struct sockaddr_in *sa4;
1038 
1039 	switch(sa->sa_family) {
1040 #ifdef INET6
1041 	case AF_INET6:
1042 		sa6 = (struct sockaddr_in6 *)sa;
1043 		if (IN6_IS_ADDR_MULTICAST(&sa6->sin6_addr)) {
1044 			/* just use the scope field of the multicast address */
1045 			return(sa6->sin6_addr.s6_addr[2] & 0x0f);
1046 		}
1047 		/*
1048 		 * Unicast addresses: map scope type to corresponding scope
1049 		 * value defined for multcast addresses.
1050 		 * XXX: hardcoded scope type values are bad...
1051 		 */
1052 		if (IN6_IS_ADDR_LOOPBACK(&sa6->sin6_addr))
1053 			return(1); /* node local scope */
1054 		if (IN6_IS_ADDR_LINKLOCAL(&sa6->sin6_addr))
1055 			return(2); /* link-local scope */
1056 		if (IN6_IS_ADDR_SITELOCAL(&sa6->sin6_addr))
1057 			return(5); /* site-local scope */
1058 		return(14);	/* global scope */
1059 		break;
1060 #endif
1061 	case AF_INET:
1062 		/*
1063 		 * IPv4 pseudo scoping according to RFC 3484.
1064 		 */
1065 		sa4 = (struct sockaddr_in *)sa;
1066 		/* IPv4 autoconfiguration addresses have link-local scope. */
1067 		if (((u_char *)&sa4->sin_addr)[0] == 169 &&
1068 		    ((u_char *)&sa4->sin_addr)[1] == 254)
1069 			return(2);
1070 		/* Private addresses have site-local scope. */
1071 		if (((u_char *)&sa4->sin_addr)[0] == 10 ||
1072 		    (((u_char *)&sa4->sin_addr)[0] == 172 &&
1073 		     (((u_char *)&sa4->sin_addr)[1] & 0xf0) == 16) ||
1074 		    (((u_char *)&sa4->sin_addr)[0] == 192 &&
1075 		     ((u_char *)&sa4->sin_addr)[1] == 168))
1076 			return(14);	/* XXX: It should be 5 unless NAT */
1077 		/* Loopback addresses have link-local scope. */
1078 		if (((u_char *)&sa4->sin_addr)[0] == 127)
1079 			return(2);
1080 		return(14);
1081 		break;
1082 	default:
1083 		errno = EAFNOSUPPORT; /* is this a good error? */
1084 		return(-1);
1085 	}
1086 }
1087 
1088 static int
1089 explore_copy(const struct addrinfo *pai, const struct addrinfo *src0,
1090     struct addrinfo **res)
1091 {
1092 	int error;
1093 	struct addrinfo sentinel, *cur;
1094 	const struct addrinfo *src;
1095 
1096 	error = 0;
1097 	sentinel.ai_next = NULL;
1098 	cur = &sentinel;
1099 
1100 	for (src = src0; src != NULL; src = src->ai_next) {
1101 		if (src->ai_family != pai->ai_family)
1102 			continue;
1103 
1104 		cur->ai_next = copy_ai(src);
1105 		if (!cur->ai_next) {
1106 			error = EAI_MEMORY;
1107 			goto fail;
1108 		}
1109 
1110 		cur->ai_next->ai_socktype = pai->ai_socktype;
1111 		cur->ai_next->ai_protocol = pai->ai_protocol;
1112 		cur = cur->ai_next;
1113 	}
1114 
1115 	*res = sentinel.ai_next;
1116 	return 0;
1117 
1118 fail:
1119 	freeaddrinfo(sentinel.ai_next);
1120 	return error;
1121 }
1122 
1123 /*
1124  * hostname == NULL.
1125  * passive socket -> anyaddr (0.0.0.0 or ::)
1126  * non-passive socket -> localhost (127.0.0.1 or ::1)
1127  */
1128 static int
1129 explore_null(const struct addrinfo *pai, const char *servname,
1130     struct addrinfo **res)
1131 {
1132 	int s;
1133 	const struct afd *afd;
1134 	struct addrinfo *ai;
1135 	int error;
1136 
1137 	*res = NULL;
1138 	ai = NULL;
1139 
1140 	/*
1141 	 * filter out AFs that are not supported by the kernel
1142 	 * XXX errno?
1143 	 */
1144 	s = _socket(pai->ai_family, SOCK_DGRAM | SOCK_CLOEXEC, 0);
1145 	if (s < 0) {
1146 		if (errno != EMFILE)
1147 			return 0;
1148 	} else
1149 		_close(s);
1150 
1151 	afd = find_afd(pai->ai_family);
1152 	if (afd == NULL)
1153 		return 0;
1154 
1155 	if (pai->ai_flags & AI_PASSIVE) {
1156 		GET_AI(ai, afd, afd->a_addrany);
1157 		GET_PORT(ai, servname);
1158 	} else {
1159 		GET_AI(ai, afd, afd->a_loopback);
1160 		GET_PORT(ai, servname);
1161 	}
1162 
1163 	*res = ai;
1164 	return 0;
1165 
1166 free:
1167 	if (ai != NULL)
1168 		freeaddrinfo(ai);
1169 	return error;
1170 }
1171 
1172 /*
1173  * numeric hostname
1174  */
1175 static int
1176 explore_numeric(const struct addrinfo *pai, const char *hostname,
1177     const char *servname, struct addrinfo **res, const char *canonname)
1178 {
1179 	const struct afd *afd;
1180 	struct addrinfo *ai;
1181 	int error;
1182 	char pton[PTON_MAX];
1183 
1184 	*res = NULL;
1185 	ai = NULL;
1186 
1187 	afd = find_afd(pai->ai_family);
1188 	if (afd == NULL)
1189 		return 0;
1190 
1191 	switch (afd->a_af) {
1192 	case AF_INET:
1193 		/*
1194 		 * RFC3493 requires getaddrinfo() to accept AF_INET formats
1195 		 * that are accepted by inet_addr() and its family.  The
1196 		 * accepted forms includes the "classful" one, which inet_pton
1197 		 * does not accept.  So we need to separate the case for
1198 		 * AF_INET.
1199 		 */
1200 		if (inet_aton(hostname, (struct in_addr *)pton) != 1)
1201 			return 0;
1202 		break;
1203 	default:
1204 		if (inet_pton(afd->a_af, hostname, pton) != 1)
1205 			return 0;
1206 		break;
1207 	}
1208 
1209 	if (pai->ai_family == afd->a_af) {
1210 		GET_AI(ai, afd, pton);
1211 		GET_PORT(ai, servname);
1212 		if ((pai->ai_flags & AI_CANONNAME)) {
1213 			/*
1214 			 * Set the numeric address itself as the canonical
1215 			 * name, based on a clarification in RFC3493.
1216 			 */
1217 			GET_CANONNAME(ai, canonname);
1218 		}
1219 	} else {
1220 		/*
1221 		 * XXX: This should not happen since we already matched the AF
1222 		 * by find_afd.
1223 		 */
1224 		ERR(EAI_FAMILY);
1225 	}
1226 
1227 	*res = ai;
1228 	return 0;
1229 
1230 free:
1231 bad:
1232 	if (ai != NULL)
1233 		freeaddrinfo(ai);
1234 	return error;
1235 }
1236 
1237 /*
1238  * numeric hostname with scope
1239  */
1240 static int
1241 explore_numeric_scope(const struct addrinfo *pai, const char *hostname,
1242     const char *servname, struct addrinfo **res)
1243 {
1244 #if !defined(SCOPE_DELIMITER) || !defined(INET6)
1245 	return explore_numeric(pai, hostname, servname, res, hostname);
1246 #else
1247 	const struct afd *afd;
1248 	struct addrinfo *cur;
1249 	int error;
1250 	char *cp, *hostname2 = NULL, *scope, *addr;
1251 	struct sockaddr_in6 *sin6;
1252 
1253 	afd = find_afd(pai->ai_family);
1254 	if (afd == NULL)
1255 		return 0;
1256 
1257 	if (!afd->a_scoped)
1258 		return explore_numeric(pai, hostname, servname, res, hostname);
1259 
1260 	cp = strchr(hostname, SCOPE_DELIMITER);
1261 	if (cp == NULL)
1262 		return explore_numeric(pai, hostname, servname, res, hostname);
1263 
1264 	/*
1265 	 * Handle special case of <scoped_address><delimiter><scope id>
1266 	 */
1267 	hostname2 = strdup(hostname);
1268 	if (hostname2 == NULL)
1269 		return EAI_MEMORY;
1270 	/* terminate at the delimiter */
1271 	hostname2[cp - hostname] = '\0';
1272 	addr = hostname2;
1273 	scope = cp + 1;
1274 
1275 	error = explore_numeric(pai, addr, servname, res, hostname);
1276 	if (error == 0) {
1277 		u_int32_t scopeid;
1278 
1279 		for (cur = *res; cur; cur = cur->ai_next) {
1280 			if (cur->ai_family != AF_INET6)
1281 				continue;
1282 			sin6 = (struct sockaddr_in6 *)(void *)cur->ai_addr;
1283 			if (ip6_str2scopeid(scope, sin6, &scopeid) == -1) {
1284 				free(hostname2);
1285 				freeaddrinfo(*res);
1286 				*res = NULL;
1287 				return(EAI_NONAME); /* XXX: is return OK? */
1288 			}
1289 			sin6->sin6_scope_id = scopeid;
1290 		}
1291 	}
1292 
1293 	free(hostname2);
1294 
1295 	if (error && *res) {
1296 		freeaddrinfo(*res);
1297 		*res = NULL;
1298 	}
1299 	return error;
1300 #endif
1301 }
1302 
1303 static int
1304 get_canonname(const struct addrinfo *pai, struct addrinfo *ai, const char *str)
1305 {
1306 	if ((pai->ai_flags & AI_CANONNAME) != 0) {
1307 		ai->ai_canonname = strdup(str);
1308 		if (ai->ai_canonname == NULL)
1309 			return EAI_MEMORY;
1310 	}
1311 	return 0;
1312 }
1313 
1314 static struct addrinfo *
1315 get_ai(const struct addrinfo *pai, const struct afd *afd, const char *addr)
1316 {
1317 	char *p;
1318 	struct addrinfo *ai;
1319 #ifdef FAITH
1320 	struct in6_addr faith_prefix;
1321 	char *fp_str;
1322 	int translate = 0;
1323 #endif
1324 
1325 #ifdef FAITH
1326 	/*
1327 	 * Transfrom an IPv4 addr into a special IPv6 addr format for
1328 	 * IPv6->IPv4 translation gateway. (only TCP is supported now)
1329 	 *
1330 	 * +-----------------------------------+------------+
1331 	 * | faith prefix part (12 bytes)      | embedded   |
1332 	 * |                                   | IPv4 addr part (4 bytes)
1333 	 * +-----------------------------------+------------+
1334 	 *
1335 	 * faith prefix part is specified as ascii IPv6 addr format
1336 	 * in environmental variable GAI.
1337 	 * For FAITH to work correctly, routing to faith prefix must be
1338 	 * setup toward a machine where a FAITH daemon operates.
1339 	 * Also, the machine must enable some mechanizm
1340 	 * (e.g. faith interface hack) to divert those packet with
1341 	 * faith prefixed destination addr to user-land FAITH daemon.
1342 	 */
1343 	fp_str = getenv("GAI");
1344 	if (fp_str && inet_pton(AF_INET6, fp_str, &faith_prefix) == 1 &&
1345 	    afd->a_af == AF_INET && pai->ai_socktype == SOCK_STREAM) {
1346 		u_int32_t v4a;
1347 		u_int8_t v4a_top;
1348 
1349 		memcpy(&v4a, addr, sizeof v4a);
1350 		v4a_top = v4a >> IN_CLASSA_NSHIFT;
1351 		if (!IN_MULTICAST(v4a) && !IN_EXPERIMENTAL(v4a) &&
1352 		    v4a_top != 0 && v4a != IN_LOOPBACKNET) {
1353 			afd = &afdl[N_INET6];
1354 			memcpy(&faith_prefix.s6_addr[12], addr,
1355 			       sizeof(struct in_addr));
1356 			translate = 1;
1357 		}
1358 	}
1359 #endif
1360 
1361 	ai = (struct addrinfo *)malloc(sizeof(struct addrinfo)
1362 		+ (afd->a_socklen));
1363 	if (ai == NULL)
1364 		return NULL;
1365 
1366 	memcpy(ai, pai, sizeof(struct addrinfo));
1367 	ai->ai_addr = (struct sockaddr *)(void *)(ai + 1);
1368 	memset(ai->ai_addr, 0, (size_t)afd->a_socklen);
1369 	ai->ai_addr->sa_len = afd->a_socklen;
1370 	ai->ai_addrlen = afd->a_socklen;
1371 	ai->ai_addr->sa_family = ai->ai_family = afd->a_af;
1372 	p = (char *)(void *)(ai->ai_addr);
1373 #ifdef FAITH
1374 	if (translate == 1)
1375 		memcpy(p + afd->a_off, &faith_prefix, (size_t)afd->a_addrlen);
1376 	else
1377 #endif
1378 	memcpy(p + afd->a_off, addr, (size_t)afd->a_addrlen);
1379 	return ai;
1380 }
1381 
1382 /* XXX need to malloc() the same way we do from other functions! */
1383 static struct addrinfo *
1384 copy_ai(const struct addrinfo *pai)
1385 {
1386 	struct addrinfo *ai;
1387 	size_t l;
1388 
1389 	l = sizeof(*ai) + pai->ai_addrlen;
1390 	if ((ai = (struct addrinfo *)malloc(l)) == NULL)
1391 		return NULL;
1392 	memset(ai, 0, l);
1393 	memcpy(ai, pai, sizeof(*ai));
1394 	ai->ai_addr = (struct sockaddr *)(void *)(ai + 1);
1395 	memcpy(ai->ai_addr, pai->ai_addr, pai->ai_addrlen);
1396 
1397 	if (pai->ai_canonname) {
1398 		l = strlen(pai->ai_canonname) + 1;
1399 		if ((ai->ai_canonname = malloc(l)) == NULL) {
1400 			free(ai);
1401 			return NULL;
1402 		}
1403 		strlcpy(ai->ai_canonname, pai->ai_canonname, l);
1404 	} else {
1405 		/* just to make sure */
1406 		ai->ai_canonname = NULL;
1407 	}
1408 
1409 	ai->ai_next = NULL;
1410 
1411 	return ai;
1412 }
1413 
1414 static int
1415 get_portmatch(const struct addrinfo *ai, const char *servname)
1416 {
1417 
1418 	/* get_port does not touch first argument when matchonly == 1. */
1419 	/* LINTED const cast */
1420 	return get_port((struct addrinfo *)ai, servname, 1);
1421 }
1422 
1423 static int
1424 get_port(struct addrinfo *ai, const char *servname, int matchonly)
1425 {
1426 	const char *proto;
1427 	struct servent *sp;
1428 	int port, error;
1429 	int allownumeric;
1430 
1431 	if (servname == NULL)
1432 		return 0;
1433 	switch (ai->ai_family) {
1434 	case AF_INET:
1435 #ifdef AF_INET6
1436 	case AF_INET6:
1437 #endif
1438 		break;
1439 	default:
1440 		return 0;
1441 	}
1442 
1443 	switch (ai->ai_socktype) {
1444 	case SOCK_RAW:
1445 		return EAI_SERVICE;
1446 	case SOCK_DGRAM:
1447 	case SOCK_STREAM:
1448 	case SOCK_SEQPACKET:
1449 		allownumeric = 1;
1450 		break;
1451 	case ANY:
1452 		switch (ai->ai_family) {
1453 		case AF_INET:
1454 #ifdef AF_INET6
1455 		case AF_INET6:
1456 #endif
1457 			allownumeric = 1;
1458 			break;
1459 		default:
1460 			allownumeric = 0;
1461 			break;
1462 		}
1463 		break;
1464 	default:
1465 		return EAI_SOCKTYPE;
1466 	}
1467 
1468 	error = str2number(servname, &port);
1469 	if (error == 0) {
1470 		if (!allownumeric)
1471 			return EAI_SERVICE;
1472 		if (port < 0 || port > 65535)
1473 			return EAI_SERVICE;
1474 		port = htons(port);
1475 	} else {
1476 		if (ai->ai_flags & AI_NUMERICSERV)
1477 			return EAI_NONAME;
1478 
1479 		switch (ai->ai_protocol) {
1480 		case IPPROTO_UDP:
1481 			proto = "udp";
1482 			break;
1483 		case IPPROTO_TCP:
1484 			proto = "tcp";
1485 			break;
1486 		case IPPROTO_SCTP:
1487 			proto = "sctp";
1488 			break;
1489 		case IPPROTO_UDPLITE:
1490 			proto = "udplite";
1491 			break;
1492 		default:
1493 			proto = NULL;
1494 			break;
1495 		}
1496 
1497 		if ((sp = getservbyname(servname, proto)) == NULL)
1498 			return EAI_SERVICE;
1499 		port = sp->s_port;
1500 	}
1501 
1502 	if (!matchonly) {
1503 		switch (ai->ai_family) {
1504 		case AF_INET:
1505 			((struct sockaddr_in *)(void *)
1506 			    ai->ai_addr)->sin_port = port;
1507 			break;
1508 #ifdef INET6
1509 		case AF_INET6:
1510 			((struct sockaddr_in6 *)(void *)
1511 			    ai->ai_addr)->sin6_port = port;
1512 			break;
1513 #endif
1514 		}
1515 	}
1516 
1517 	return 0;
1518 }
1519 
1520 static const struct afd *
1521 find_afd(int af)
1522 {
1523 	const struct afd *afd;
1524 
1525 	if (af == PF_UNSPEC)
1526 		return NULL;
1527 	for (afd = afdl; afd->a_af; afd++) {
1528 		if (afd->a_af == af)
1529 			return afd;
1530 	}
1531 	return NULL;
1532 }
1533 
1534 /*
1535  * RFC 3493: AI_ADDRCONFIG check.  Determines which address families are
1536  * configured on the local system and correlates with pai->ai_family value.
1537  * If an address family is not configured on the system, it will not be
1538  * queried for.  For this purpose, loopback addresses are not considered
1539  * configured addresses.
1540  *
1541  * XXX PF_UNSPEC -> PF_INET6 + PF_INET mapping needs to be in sync with
1542  * _dns_getaddrinfo.
1543  */
1544 static int
1545 addrconfig(struct addrinfo *pai)
1546 {
1547 	struct ifaddrs *ifaddrs, *ifa;
1548 	struct sockaddr_in *sin;
1549 #ifdef INET6
1550 	struct sockaddr_in6 *sin6;
1551 #endif
1552 	int seen_inet = 0, seen_inet6 = 0;
1553 
1554 	if (getifaddrs(&ifaddrs) != 0)
1555 		return (0);
1556 
1557 	for (ifa = ifaddrs; ifa != NULL; ifa = ifa->ifa_next) {
1558 		if (ifa->ifa_addr == NULL || (ifa->ifa_flags & IFF_UP) == 0)
1559 			continue;
1560 		switch (ifa->ifa_addr->sa_family) {
1561 		case AF_INET:
1562 			if (seen_inet)
1563 				continue;
1564 			sin = (struct sockaddr_in *)(ifa->ifa_addr);
1565 			if (IN_LOOPBACK(htonl(sin->sin_addr.s_addr)))
1566 				continue;
1567 			seen_inet = 1;
1568 			break;
1569 #ifdef INET6
1570 		case AF_INET6:
1571 			if (seen_inet6)
1572 				continue;
1573 			sin6 = (struct sockaddr_in6 *)(ifa->ifa_addr);
1574 			if (IN6_IS_ADDR_LOOPBACK(&sin6->sin6_addr))
1575 				continue;
1576 			if ((ifa->ifa_flags & IFT_LOOP) != 0 &&
1577 			    IN6_IS_ADDR_LINKLOCAL(&sin6->sin6_addr))
1578 				continue;
1579 			if (is_ifdisabled(ifa->ifa_name))
1580 				continue;
1581 			seen_inet6 = 1;
1582 			break;
1583 #endif
1584 		}
1585 	}
1586 	freeifaddrs(ifaddrs);
1587 
1588 	switch(pai->ai_family) {
1589 	case AF_INET6:
1590 		return (seen_inet6);
1591 	case AF_INET:
1592 		return (seen_inet);
1593 	case AF_UNSPEC:
1594 		if (seen_inet == seen_inet6)
1595 			return (seen_inet);
1596 		pai->ai_family = seen_inet ? AF_INET : AF_INET6;
1597 		return (1);
1598 	}
1599 	return (1);
1600 }
1601 
1602 #ifdef INET6
1603 static int
1604 is_ifdisabled(char *name)
1605 {
1606 	struct in6_ndireq nd;
1607 	int fd;
1608 
1609 	if ((fd = _socket(AF_INET6, SOCK_DGRAM | SOCK_CLOEXEC, 0)) < 0)
1610 		return (-1);
1611 	memset(&nd, 0, sizeof(nd));
1612 	strlcpy(nd.ifname, name, sizeof(nd.ifname));
1613 	if (_ioctl(fd, SIOCGIFINFO_IN6, &nd) < 0) {
1614 		_close(fd);
1615 		return (-1);
1616 	}
1617 	_close(fd);
1618 	return ((nd.ndi.flags & ND6_IFF_IFDISABLED) != 0);
1619 }
1620 
1621 /* convert a string to a scope identifier. XXX: IPv6 specific */
1622 static int
1623 ip6_str2scopeid(char *scope, struct sockaddr_in6 *sin6, u_int32_t *scopeid)
1624 {
1625 	u_long lscopeid;
1626 	struct in6_addr *a6;
1627 	char *ep;
1628 
1629 	a6 = &sin6->sin6_addr;
1630 
1631 	/* empty scopeid portion is invalid */
1632 	if (*scope == '\0')
1633 		return -1;
1634 
1635 	if (IN6_IS_ADDR_LINKLOCAL(a6) || IN6_IS_ADDR_MC_LINKLOCAL(a6) ||
1636 	    IN6_IS_ADDR_MC_NODELOCAL(a6)) {
1637 		/*
1638 		 * We currently assume a one-to-one mapping between links
1639 		 * and interfaces, so we simply use interface indices for
1640 		 * like-local scopes.
1641 		 */
1642 		*scopeid = if_nametoindex(scope);
1643 		if (*scopeid == 0)
1644 			goto trynumeric;
1645 		return 0;
1646 	}
1647 
1648 	/* still unclear about literal, allow numeric only - placeholder */
1649 	if (IN6_IS_ADDR_SITELOCAL(a6) || IN6_IS_ADDR_MC_SITELOCAL(a6))
1650 		goto trynumeric;
1651 	if (IN6_IS_ADDR_MC_ORGLOCAL(a6))
1652 		goto trynumeric;
1653 	else
1654 		goto trynumeric;	/* global */
1655 
1656 	/* try to convert to a numeric id as a last resort */
1657   trynumeric:
1658 	errno = 0;
1659 	lscopeid = strtoul(scope, &ep, 10);
1660 	*scopeid = (u_int32_t)(lscopeid & 0xffffffffUL);
1661 	if (errno == 0 && ep && *ep == '\0' && *scopeid == lscopeid)
1662 		return 0;
1663 	else
1664 		return -1;
1665 }
1666 #endif
1667 
1668 
1669 #ifdef NS_CACHING
1670 static int
1671 addrinfo_id_func(char *buffer, size_t *buffer_size, va_list ap,
1672     void *cache_mdata)
1673 {
1674 	res_state statp;
1675 	u_long res_options;
1676 
1677 	const int op_id = 0;	/* identifies the getaddrinfo for the cache */
1678 	char *hostname;
1679 	struct addrinfo *hints;
1680 
1681 	char *p;
1682 	int ai_flags, ai_family, ai_socktype, ai_protocol;
1683 	size_t desired_size, size;
1684 
1685 	statp = __res_state();
1686 	res_options = statp->options & (RES_RECURSE | RES_DEFNAMES |
1687 	    RES_DNSRCH | RES_NOALIASES | RES_USE_INET6);
1688 
1689 	hostname = va_arg(ap, char *);
1690 	hints = va_arg(ap, struct addrinfo *);
1691 
1692 	desired_size = sizeof(res_options) + sizeof(int) + sizeof(int) * 4;
1693 	if (hostname != NULL) {
1694 		size = strlen(hostname);
1695 		desired_size += size + 1;
1696 	} else
1697 		size = 0;
1698 
1699 	if (desired_size > *buffer_size) {
1700 		*buffer_size = desired_size;
1701 		return (NS_RETURN);
1702 	}
1703 
1704 	if (hints == NULL)
1705 		ai_flags = ai_family = ai_socktype = ai_protocol = 0;
1706 	else {
1707 		ai_flags = hints->ai_flags;
1708 		ai_family = hints->ai_family;
1709 		ai_socktype = hints->ai_socktype;
1710 		ai_protocol = hints->ai_protocol;
1711 	}
1712 
1713 	p = buffer;
1714 	memcpy(p, &res_options, sizeof(res_options));
1715 	p += sizeof(res_options);
1716 
1717 	memcpy(p, &op_id, sizeof(int));
1718 	p += sizeof(int);
1719 
1720 	memcpy(p, &ai_flags, sizeof(int));
1721 	p += sizeof(int);
1722 
1723 	memcpy(p, &ai_family, sizeof(int));
1724 	p += sizeof(int);
1725 
1726 	memcpy(p, &ai_socktype, sizeof(int));
1727 	p += sizeof(int);
1728 
1729 	memcpy(p, &ai_protocol, sizeof(int));
1730 	p += sizeof(int);
1731 
1732 	if (hostname != NULL)
1733 		memcpy(p, hostname, size);
1734 
1735 	*buffer_size = desired_size;
1736 	return (NS_SUCCESS);
1737 }
1738 
1739 static int
1740 addrinfo_marshal_func(char *buffer, size_t *buffer_size, void *retval,
1741     va_list ap, void *cache_mdata)
1742 {
1743 	struct addrinfo	*ai, *cai;
1744 	char *p;
1745 	size_t desired_size, size, ai_size;
1746 
1747 	ai = *((struct addrinfo **)retval);
1748 
1749 	desired_size = sizeof(size_t);
1750 	ai_size = 0;
1751 	for (cai = ai; cai != NULL; cai = cai->ai_next) {
1752 		desired_size += sizeof(struct addrinfo) + cai->ai_addrlen;
1753 		if (cai->ai_canonname != NULL)
1754 			desired_size += sizeof(size_t) +
1755 			    strlen(cai->ai_canonname);
1756 		++ai_size;
1757 	}
1758 
1759 	if (desired_size > *buffer_size) {
1760 		/* this assignment is here for future use */
1761 		errno = ERANGE;
1762 		*buffer_size = desired_size;
1763 		return (NS_RETURN);
1764 	}
1765 
1766 	memset(buffer, 0, desired_size);
1767 	p = buffer;
1768 
1769 	memcpy(p, &ai_size, sizeof(size_t));
1770 	p += sizeof(size_t);
1771 	for (cai = ai; cai != NULL; cai = cai->ai_next) {
1772 		memcpy(p, cai, sizeof(struct addrinfo));
1773 		p += sizeof(struct addrinfo);
1774 
1775 		memcpy(p, cai->ai_addr, cai->ai_addrlen);
1776 		p += cai->ai_addrlen;
1777 
1778 		if (cai->ai_canonname != NULL) {
1779 			size = strlen(cai->ai_canonname);
1780 			memcpy(p, &size, sizeof(size_t));
1781 			p += sizeof(size_t);
1782 
1783 			memcpy(p, cai->ai_canonname, size);
1784 			p += size;
1785 		}
1786 	}
1787 
1788 	return (NS_SUCCESS);
1789 }
1790 
1791 static int
1792 addrinfo_unmarshal_func(char *buffer, size_t buffer_size, void *retval,
1793     va_list ap, void *cache_mdata)
1794 {
1795 	struct addrinfo	new_ai, *result, *sentinel, *lasts;
1796 
1797 	char *p;
1798 	size_t ai_size, ai_i, size;
1799 
1800 	p = buffer;
1801 	memcpy(&ai_size, p, sizeof(size_t));
1802 	p += sizeof(size_t);
1803 
1804 	result = NULL;
1805 	lasts = NULL;
1806 	for (ai_i = 0; ai_i < ai_size; ++ai_i) {
1807 		memcpy(&new_ai, p, sizeof(struct addrinfo));
1808 		p += sizeof(struct addrinfo);
1809 		size = new_ai.ai_addrlen + sizeof(struct addrinfo) +
1810 			_ALIGNBYTES;
1811 
1812 		sentinel = (struct addrinfo *)malloc(size);
1813 		memset(sentinel, 0, size);
1814 
1815 		memcpy(sentinel, &new_ai, sizeof(struct addrinfo));
1816 		sentinel->ai_addr = (struct sockaddr *)_ALIGN((char *)sentinel +
1817 		    sizeof(struct addrinfo));
1818 
1819 		memcpy(sentinel->ai_addr, p, new_ai.ai_addrlen);
1820 		p += new_ai.ai_addrlen;
1821 
1822 		if (new_ai.ai_canonname != NULL) {
1823 			memcpy(&size, p, sizeof(size_t));
1824 			p += sizeof(size_t);
1825 
1826 			sentinel->ai_canonname = (char *)malloc(size + 1);
1827 			memset(sentinel->ai_canonname, 0, size + 1);
1828 
1829 			memcpy(sentinel->ai_canonname, p, size);
1830 			p += size;
1831 		}
1832 
1833 		if (result == NULL) {
1834 			result = sentinel;
1835 			lasts = sentinel;
1836 		} else {
1837 			lasts->ai_next = sentinel;
1838 			lasts = sentinel;
1839 		}
1840 	}
1841 
1842 	*((struct addrinfo **)retval) = result;
1843 	return (NS_SUCCESS);
1844 }
1845 #endif /* NS_CACHING */
1846 
1847 /*
1848  * FQDN hostname, DNS lookup
1849  */
1850 static int
1851 explore_fqdn(const struct addrinfo *pai, const char *hostname,
1852     const char *servname, struct addrinfo **res)
1853 {
1854 	struct addrinfo *result;
1855 	struct addrinfo *cur;
1856 	int error = 0;
1857 
1858 #ifdef NS_CACHING
1859 	static const nss_cache_info cache_info =
1860 	NS_COMMON_CACHE_INFO_INITIALIZER(
1861 		hosts, NULL, addrinfo_id_func, addrinfo_marshal_func,
1862 		addrinfo_unmarshal_func);
1863 #endif
1864 	static const ns_dtab dtab[] = {
1865 		NS_FILES_CB(_files_getaddrinfo, NULL)
1866 		{ NSSRC_DNS, _dns_getaddrinfo, NULL },	/* force -DHESIOD */
1867 		NS_NIS_CB(_yp_getaddrinfo, NULL)
1868 #ifdef NS_CACHING
1869 		NS_CACHE_CB(&cache_info)
1870 #endif
1871 		{ 0 }
1872 	};
1873 
1874 	result = NULL;
1875 
1876 	/*
1877 	 * if the servname does not match socktype/protocol, ignore it.
1878 	 */
1879 	if (get_portmatch(pai, servname) != 0)
1880 		return 0;
1881 
1882 	switch (_nsdispatch(&result, dtab, NSDB_HOSTS, "getaddrinfo",
1883 			default_dns_files, hostname, pai)) {
1884 	case NS_TRYAGAIN:
1885 		error = EAI_AGAIN;
1886 		goto free;
1887 	case NS_UNAVAIL:
1888 		error = EAI_FAIL;
1889 		goto free;
1890 	case NS_NOTFOUND:
1891 		error = EAI_NONAME;
1892 		goto free;
1893 	case NS_SUCCESS:
1894 		error = 0;
1895 		for (cur = result; cur; cur = cur->ai_next) {
1896 			GET_PORT(cur, servname);
1897 			/* canonname should be filled already */
1898 		}
1899 		break;
1900 	}
1901 
1902 	*res = result;
1903 
1904 	return 0;
1905 
1906 free:
1907 	if (result)
1908 		freeaddrinfo(result);
1909 	return error;
1910 }
1911 
1912 #ifdef DEBUG
1913 static const char AskedForGot[] =
1914 	"gethostby*.getanswer: asked for \"%s\", got \"%s\"";
1915 #endif
1916 
1917 static struct addrinfo *
1918 getanswer(const querybuf *answer, int anslen, const char *qname, int qtype,
1919     const struct addrinfo *pai, res_state res)
1920 {
1921 	struct addrinfo sentinel, *cur;
1922 	struct addrinfo ai;
1923 	const struct afd *afd;
1924 	char *canonname;
1925 	const HEADER *hp;
1926 	const u_char *cp;
1927 	int n;
1928 	const u_char *eom;
1929 	char *bp, *ep;
1930 	int type, class, ancount, qdcount;
1931 	int haveanswer, had_error;
1932 	char tbuf[MAXDNAME];
1933 	int (*name_ok)(const char *);
1934 	char hostbuf[8*1024];
1935 
1936 	memset(&sentinel, 0, sizeof(sentinel));
1937 	cur = &sentinel;
1938 
1939 	canonname = NULL;
1940 	eom = answer->buf + anslen;
1941 	switch (qtype) {
1942 	case T_A:
1943 	case T_AAAA:
1944 	case T_ANY:	/*use T_ANY only for T_A/T_AAAA lookup*/
1945 		name_ok = res_hnok;
1946 		break;
1947 	default:
1948 		return (NULL);	/* XXX should be abort(); */
1949 	}
1950 	/*
1951 	 * find first satisfactory answer
1952 	 */
1953 	hp = &answer->hdr;
1954 	ancount = ntohs(hp->ancount);
1955 	qdcount = ntohs(hp->qdcount);
1956 	bp = hostbuf;
1957 	ep = hostbuf + sizeof hostbuf;
1958 	cp = answer->buf + HFIXEDSZ;
1959 	if (qdcount != 1) {
1960 		RES_SET_H_ERRNO(res, NO_RECOVERY);
1961 		return (NULL);
1962 	}
1963 	n = dn_expand(answer->buf, eom, cp, bp, ep - bp);
1964 	if ((n < 0) || !(*name_ok)(bp)) {
1965 		RES_SET_H_ERRNO(res, NO_RECOVERY);
1966 		return (NULL);
1967 	}
1968 	cp += n + QFIXEDSZ;
1969 	if (qtype == T_A || qtype == T_AAAA || qtype == T_ANY) {
1970 		/* res_send() has already verified that the query name is the
1971 		 * same as the one we sent; this just gets the expanded name
1972 		 * (i.e., with the succeeding search-domain tacked on).
1973 		 */
1974 		n = strlen(bp) + 1;		/* for the \0 */
1975 		if (n >= MAXHOSTNAMELEN) {
1976 			RES_SET_H_ERRNO(res, NO_RECOVERY);
1977 			return (NULL);
1978 		}
1979 		canonname = bp;
1980 		bp += n;
1981 		/* The qname can be abbreviated, but h_name is now absolute. */
1982 		qname = canonname;
1983 	}
1984 	haveanswer = 0;
1985 	had_error = 0;
1986 	while (ancount-- > 0 && cp < eom && !had_error) {
1987 		n = dn_expand(answer->buf, eom, cp, bp, ep - bp);
1988 		if ((n < 0) || !(*name_ok)(bp)) {
1989 			had_error++;
1990 			continue;
1991 		}
1992 		cp += n;			/* name */
1993 		type = _getshort(cp);
1994  		cp += INT16SZ;			/* type */
1995 		class = _getshort(cp);
1996  		cp += INT16SZ + INT32SZ;	/* class, TTL */
1997 		n = _getshort(cp);
1998 		cp += INT16SZ;			/* len */
1999 		if (class != C_IN) {
2000 			/* XXX - debug? syslog? */
2001 			cp += n;
2002 			continue;		/* XXX - had_error++ ? */
2003 		}
2004 		if ((qtype == T_A || qtype == T_AAAA || qtype == T_ANY) &&
2005 		    type == T_CNAME) {
2006 			n = dn_expand(answer->buf, eom, cp, tbuf, sizeof tbuf);
2007 			if ((n < 0) || !(*name_ok)(tbuf)) {
2008 				had_error++;
2009 				continue;
2010 			}
2011 			cp += n;
2012 			/* Get canonical name. */
2013 			n = strlen(tbuf) + 1;	/* for the \0 */
2014 			if (n > ep - bp || n >= MAXHOSTNAMELEN) {
2015 				had_error++;
2016 				continue;
2017 			}
2018 			strlcpy(bp, tbuf, ep - bp);
2019 			canonname = bp;
2020 			bp += n;
2021 			continue;
2022 		}
2023 		if (qtype == T_ANY) {
2024 			if (!(type == T_A || type == T_AAAA)) {
2025 				cp += n;
2026 				continue;
2027 			}
2028 		} else if (type != qtype) {
2029 #ifdef DEBUG
2030 			if (type != T_KEY && type != T_SIG &&
2031 			    type != ns_t_dname)
2032 				syslog(LOG_NOTICE|LOG_AUTH,
2033 	       "gethostby*.getanswer: asked for \"%s %s %s\", got type \"%s\"",
2034 				       qname, p_class(C_IN), p_type(qtype),
2035 				       p_type(type));
2036 #endif
2037 			cp += n;
2038 			continue;		/* XXX - had_error++ ? */
2039 		}
2040 		switch (type) {
2041 		case T_A:
2042 		case T_AAAA:
2043 			if (strcasecmp(canonname, bp) != 0) {
2044 #ifdef DEBUG
2045 				syslog(LOG_NOTICE|LOG_AUTH,
2046 				       AskedForGot, canonname, bp);
2047 #endif
2048 				cp += n;
2049 				continue;	/* XXX - had_error++ ? */
2050 			}
2051 			if (type == T_A && n != INADDRSZ) {
2052 				cp += n;
2053 				continue;
2054 			}
2055 			if (type == T_AAAA && n != IN6ADDRSZ) {
2056 				cp += n;
2057 				continue;
2058 			}
2059 #ifdef FILTER_V4MAPPED
2060 			if (type == T_AAAA) {
2061 				struct in6_addr in6;
2062 				memcpy(&in6, cp, sizeof(in6));
2063 				if (IN6_IS_ADDR_V4MAPPED(&in6)) {
2064 					cp += n;
2065 					continue;
2066 				}
2067 			}
2068 #endif
2069 			if (!haveanswer) {
2070 				int nn;
2071 
2072 				canonname = bp;
2073 				nn = strlen(bp) + 1;	/* for the \0 */
2074 				bp += nn;
2075 			}
2076 
2077 			/* don't overwrite pai */
2078 			ai = *pai;
2079 			ai.ai_family = (type == T_A) ? AF_INET : AF_INET6;
2080 			afd = find_afd(ai.ai_family);
2081 			if (afd == NULL) {
2082 				cp += n;
2083 				continue;
2084 			}
2085 			cur->ai_next = get_ai(&ai, afd, (const char *)cp);
2086 			if (cur->ai_next == NULL)
2087 				had_error++;
2088 			while (cur && cur->ai_next)
2089 				cur = cur->ai_next;
2090 			cp += n;
2091 			break;
2092 		default:
2093 			abort();
2094 		}
2095 		if (!had_error)
2096 			haveanswer++;
2097 	}
2098 	if (haveanswer) {
2099 #if defined(RESOLVSORT)
2100 		/*
2101 		 * We support only IPv4 address for backward
2102 		 * compatibility against gethostbyname(3).
2103 		 */
2104 		if (res->nsort && qtype == T_A) {
2105 			if (addr4sort(&sentinel, res) < 0) {
2106 				freeaddrinfo(sentinel.ai_next);
2107 				RES_SET_H_ERRNO(res, NO_RECOVERY);
2108 				return NULL;
2109 			}
2110 		}
2111 #endif /*RESOLVSORT*/
2112 		if (!canonname)
2113 			(void)get_canonname(pai, sentinel.ai_next, qname);
2114 		else
2115 			(void)get_canonname(pai, sentinel.ai_next, canonname);
2116 		RES_SET_H_ERRNO(res, NETDB_SUCCESS);
2117 		return sentinel.ai_next;
2118 	}
2119 
2120 	RES_SET_H_ERRNO(res, NO_RECOVERY);
2121 	return NULL;
2122 }
2123 
2124 #ifdef RESOLVSORT
2125 struct addr_ptr {
2126 	struct addrinfo *ai;
2127 	int aval;
2128 };
2129 
2130 static int
2131 addr4sort(struct addrinfo *sentinel, res_state res)
2132 {
2133 	struct addrinfo *ai;
2134 	struct addr_ptr *addrs, addr;
2135 	struct sockaddr_in *sin;
2136 	int naddrs, i, j;
2137 	int needsort = 0;
2138 
2139 	if (!sentinel)
2140 		return -1;
2141 	naddrs = 0;
2142 	for (ai = sentinel->ai_next; ai; ai = ai->ai_next)
2143 		naddrs++;
2144 	if (naddrs < 2)
2145 		return 0;		/* We don't need sorting. */
2146 	if ((addrs = malloc(sizeof(struct addr_ptr) * naddrs)) == NULL)
2147 		return -1;
2148 	i = 0;
2149 	for (ai = sentinel->ai_next; ai; ai = ai->ai_next) {
2150 		sin = (struct sockaddr_in *)ai->ai_addr;
2151 		for (j = 0; (unsigned)j < res->nsort; j++) {
2152 			if (res->sort_list[j].addr.s_addr ==
2153 			    (sin->sin_addr.s_addr & res->sort_list[j].mask))
2154 				break;
2155 		}
2156 		addrs[i].ai = ai;
2157 		addrs[i].aval = j;
2158 		if (needsort == 0 && i > 0 && j < addrs[i - 1].aval)
2159 			needsort = i;
2160 		i++;
2161 	}
2162 	if (!needsort) {
2163 		free(addrs);
2164 		return 0;
2165 	}
2166 
2167 	while (needsort < naddrs) {
2168 		for (j = needsort - 1; j >= 0; j--) {
2169 			if (addrs[j].aval > addrs[j+1].aval) {
2170 				addr = addrs[j];
2171 				addrs[j] = addrs[j + 1];
2172 				addrs[j + 1] = addr;
2173 			} else
2174 				break;
2175 		}
2176 		needsort++;
2177 	}
2178 
2179 	ai = sentinel;
2180 	for (i = 0; i < naddrs; ++i) {
2181 		ai->ai_next = addrs[i].ai;
2182 		ai = ai->ai_next;
2183 	}
2184 	ai->ai_next = NULL;
2185 	free(addrs);
2186 	return 0;
2187 }
2188 #endif /*RESOLVSORT*/
2189 
2190 /*ARGSUSED*/
2191 static int
2192 _dns_getaddrinfo(void *rv, void *cb_data, va_list ap)
2193 {
2194 	struct addrinfo *ai;
2195 	querybuf *buf, *buf2;
2196 	const char *hostname;
2197 	const struct addrinfo *pai;
2198 	struct addrinfo sentinel, *cur;
2199 	struct res_target q, q2;
2200 	res_state res;
2201 
2202 	hostname = va_arg(ap, char *);
2203 	pai = va_arg(ap, const struct addrinfo *);
2204 
2205 	memset(&q, 0, sizeof(q));
2206 	memset(&q2, 0, sizeof(q2));
2207 	memset(&sentinel, 0, sizeof(sentinel));
2208 	cur = &sentinel;
2209 
2210 	buf = malloc(sizeof(*buf));
2211 	if (!buf) {
2212 		RES_SET_H_ERRNO(res, NETDB_INTERNAL);
2213 		return NS_NOTFOUND;
2214 	}
2215 	buf2 = malloc(sizeof(*buf2));
2216 	if (!buf2) {
2217 		free(buf);
2218 		RES_SET_H_ERRNO(res, NETDB_INTERNAL);
2219 		return NS_NOTFOUND;
2220 	}
2221 
2222 	switch (pai->ai_family) {
2223 	case AF_UNSPEC:
2224 		q.name = hostname;
2225 		q.qclass = C_IN;
2226 		q.qtype = T_A;
2227 		q.answer = buf->buf;
2228 		q.anslen = sizeof(buf->buf);
2229 		q.next = &q2;
2230 		q2.name = hostname;
2231 		q2.qclass = C_IN;
2232 		q2.qtype = T_AAAA;
2233 		q2.answer = buf2->buf;
2234 		q2.anslen = sizeof(buf2->buf);
2235 		break;
2236 	case AF_INET:
2237 		q.name = hostname;
2238 		q.qclass = C_IN;
2239 		q.qtype = T_A;
2240 		q.answer = buf->buf;
2241 		q.anslen = sizeof(buf->buf);
2242 		break;
2243 	case AF_INET6:
2244 		q.name = hostname;
2245 		q.qclass = C_IN;
2246 		q.qtype = T_AAAA;
2247 		q.answer = buf->buf;
2248 		q.anslen = sizeof(buf->buf);
2249 		break;
2250 	default:
2251 		free(buf);
2252 		free(buf2);
2253 		return NS_UNAVAIL;
2254 	}
2255 
2256 	res = __res_state();
2257 	if ((res->options & RES_INIT) == 0 && res_ninit(res) == -1) {
2258 		RES_SET_H_ERRNO(res, NETDB_INTERNAL);
2259 		free(buf);
2260 		free(buf2);
2261 		return NS_NOTFOUND;
2262 	}
2263 
2264 	if (res_searchN(hostname, &q, res) < 0) {
2265 		free(buf);
2266 		free(buf2);
2267 		return NS_NOTFOUND;
2268 	}
2269 	/* prefer IPv6 */
2270 	if (q.next) {
2271 		ai = getanswer(buf2, q2.n, q2.name, q2.qtype, pai, res);
2272 		if (ai) {
2273 			cur->ai_next = ai;
2274 			while (cur && cur->ai_next)
2275 				cur = cur->ai_next;
2276 		}
2277 	}
2278 	ai = getanswer(buf, q.n, q.name, q.qtype, pai, res);
2279 	if (ai)
2280 		cur->ai_next = ai;
2281 	free(buf);
2282 	free(buf2);
2283 	if (sentinel.ai_next == NULL)
2284 		switch (res->res_h_errno) {
2285 		case HOST_NOT_FOUND:
2286 			return NS_NOTFOUND;
2287 		case TRY_AGAIN:
2288 			return NS_TRYAGAIN;
2289 		default:
2290 			return NS_UNAVAIL;
2291 		}
2292 	*((struct addrinfo **)rv) = sentinel.ai_next;
2293 	return NS_SUCCESS;
2294 }
2295 
2296 static void
2297 _sethtent(FILE **hostf)
2298 {
2299 	if (!*hostf)
2300 		*hostf = fopen(_PATH_HOSTS, "re");
2301 	else
2302 		rewind(*hostf);
2303 }
2304 
2305 static void
2306 _endhtent(FILE **hostf)
2307 {
2308 	if (*hostf) {
2309 		(void) fclose(*hostf);
2310 		*hostf = NULL;
2311 	}
2312 }
2313 
2314 static struct addrinfo *
2315 _gethtent(FILE **hostf, const char *name, const struct addrinfo *pai)
2316 {
2317 	char *p;
2318 	char *cp, *tname, *cname;
2319 	struct addrinfo hints, *res0, *res;
2320 	int error;
2321 	const char *addr;
2322 	char hostbuf[8*1024];
2323 
2324 	if (!*hostf && !(*hostf = fopen(_PATH_HOSTS, "re")))
2325 		return (NULL);
2326 again:
2327 	if (!(p = fgets(hostbuf, sizeof hostbuf, *hostf)))
2328 		return (NULL);
2329 	if (*p == '#')
2330 		goto again;
2331 	cp = strpbrk(p, "#\n");
2332 	if (cp != NULL)
2333 		*cp = '\0';
2334 	if (!(cp = strpbrk(p, " \t")))
2335 		goto again;
2336 	*cp++ = '\0';
2337 	addr = p;
2338 	cname = NULL;
2339 	/* if this is not something we're looking for, skip it. */
2340 	while (cp && *cp) {
2341 		if (*cp == ' ' || *cp == '\t') {
2342 			cp++;
2343 			continue;
2344 		}
2345 		tname = cp;
2346 		if (cname == NULL)
2347 			cname = cp;
2348 		if ((cp = strpbrk(cp, " \t")) != NULL)
2349 			*cp++ = '\0';
2350 		if (strcasecmp(name, tname) == 0)
2351 			goto found;
2352 	}
2353 	goto again;
2354 
2355 found:
2356 	/* we should not glob socktype/protocol here */
2357 	memset(&hints, 0, sizeof(hints));
2358 	hints.ai_family = pai->ai_family;
2359 	hints.ai_socktype = SOCK_DGRAM;
2360 	hints.ai_protocol = 0;
2361 	hints.ai_flags = AI_NUMERICHOST;
2362 	error = getaddrinfo(addr, "0", &hints, &res0);
2363 	if (error)
2364 		goto again;
2365 #ifdef FILTER_V4MAPPED
2366 	/* XXX should check all items in the chain */
2367 	if (res0->ai_family == AF_INET6 &&
2368 	    IN6_IS_ADDR_V4MAPPED(&((struct sockaddr_in6 *)res0->ai_addr)->sin6_addr)) {
2369 		freeaddrinfo(res0);
2370 		goto again;
2371 	}
2372 #endif
2373 	for (res = res0; res; res = res->ai_next) {
2374 		/* cover it up */
2375 		res->ai_flags = pai->ai_flags;
2376 		res->ai_socktype = pai->ai_socktype;
2377 		res->ai_protocol = pai->ai_protocol;
2378 
2379 		if (pai->ai_flags & AI_CANONNAME) {
2380 			if (get_canonname(pai, res, cname) != 0) {
2381 				freeaddrinfo(res0);
2382 				goto again;
2383 			}
2384 		}
2385 	}
2386 	return res0;
2387 }
2388 
2389 /*ARGSUSED*/
2390 static int
2391 _files_getaddrinfo(void *rv, void *cb_data, va_list ap)
2392 {
2393 	const char *name;
2394 	const struct addrinfo *pai;
2395 	struct addrinfo sentinel, *cur;
2396 	struct addrinfo *p;
2397 	FILE *hostf = NULL;
2398 
2399 	name = va_arg(ap, char *);
2400 	pai = va_arg(ap, struct addrinfo *);
2401 
2402 	memset(&sentinel, 0, sizeof(sentinel));
2403 	cur = &sentinel;
2404 
2405 	_sethtent(&hostf);
2406 	while ((p = _gethtent(&hostf, name, pai)) != NULL) {
2407 		cur->ai_next = p;
2408 		while (cur && cur->ai_next)
2409 			cur = cur->ai_next;
2410 	}
2411 	_endhtent(&hostf);
2412 
2413 	*((struct addrinfo **)rv) = sentinel.ai_next;
2414 	if (sentinel.ai_next == NULL)
2415 		return NS_NOTFOUND;
2416 	return NS_SUCCESS;
2417 }
2418 
2419 #ifdef YP
2420 /*ARGSUSED*/
2421 static struct addrinfo *
2422 _yphostent(char *line, const struct addrinfo *pai)
2423 {
2424 	struct addrinfo sentinel, *cur;
2425 	struct addrinfo hints, *res, *res0;
2426 	int error;
2427 	char *p = line;
2428 	const char *addr, *canonname;
2429 	char *nextline;
2430 	char *cp;
2431 
2432 	addr = canonname = NULL;
2433 
2434 	memset(&sentinel, 0, sizeof(sentinel));
2435 	cur = &sentinel;
2436 
2437 nextline:
2438 	/* terminate line */
2439 	cp = strchr(p, '\n');
2440 	if (cp) {
2441 		*cp++ = '\0';
2442 		nextline = cp;
2443 	} else
2444 		nextline = NULL;
2445 
2446 	cp = strpbrk(p, " \t");
2447 	if (cp == NULL) {
2448 		if (canonname == NULL)
2449 			return (NULL);
2450 		else
2451 			goto done;
2452 	}
2453 	*cp++ = '\0';
2454 
2455 	addr = p;
2456 
2457 	while (cp && *cp) {
2458 		if (*cp == ' ' || *cp == '\t') {
2459 			cp++;
2460 			continue;
2461 		}
2462 		if (!canonname)
2463 			canonname = cp;
2464 		if ((cp = strpbrk(cp, " \t")) != NULL)
2465 			*cp++ = '\0';
2466 	}
2467 
2468 	hints = *pai;
2469 	hints.ai_flags = AI_NUMERICHOST;
2470 	error = getaddrinfo(addr, NULL, &hints, &res0);
2471 	if (error == 0) {
2472 		for (res = res0; res; res = res->ai_next) {
2473 			/* cover it up */
2474 			res->ai_flags = pai->ai_flags;
2475 
2476 			if (pai->ai_flags & AI_CANONNAME)
2477 				(void)get_canonname(pai, res, canonname);
2478 		}
2479 	} else
2480 		res0 = NULL;
2481 	if (res0) {
2482 		cur->ai_next = res0;
2483 		while (cur && cur->ai_next)
2484 			cur = cur->ai_next;
2485 	}
2486 
2487 	if (nextline) {
2488 		p = nextline;
2489 		goto nextline;
2490 	}
2491 
2492 done:
2493 	return sentinel.ai_next;
2494 }
2495 
2496 /*ARGSUSED*/
2497 static int
2498 _yp_getaddrinfo(void *rv, void *cb_data, va_list ap)
2499 {
2500 	struct addrinfo sentinel, *cur;
2501 	struct addrinfo *ai = NULL;
2502 	char *ypbuf;
2503 	int ypbuflen, r;
2504 	const char *name;
2505 	const struct addrinfo *pai;
2506 	char *ypdomain;
2507 
2508 	if (_yp_check(&ypdomain) == 0)
2509 		return NS_UNAVAIL;
2510 
2511 	name = va_arg(ap, char *);
2512 	pai = va_arg(ap, const struct addrinfo *);
2513 
2514 	memset(&sentinel, 0, sizeof(sentinel));
2515 	cur = &sentinel;
2516 
2517 	/* hosts.byname is only for IPv4 (Solaris8) */
2518 	if (pai->ai_family == PF_UNSPEC || pai->ai_family == PF_INET) {
2519 		r = yp_match(ypdomain, "hosts.byname", name,
2520 			(int)strlen(name), &ypbuf, &ypbuflen);
2521 		if (r == 0) {
2522 			struct addrinfo ai4;
2523 
2524 			ai4 = *pai;
2525 			ai4.ai_family = AF_INET;
2526 			ai = _yphostent(ypbuf, &ai4);
2527 			if (ai) {
2528 				cur->ai_next = ai;
2529 				while (cur && cur->ai_next)
2530 					cur = cur->ai_next;
2531 			}
2532 			free(ypbuf);
2533 		}
2534 	}
2535 
2536 	/* ipnodes.byname can hold both IPv4/v6 */
2537 	r = yp_match(ypdomain, "ipnodes.byname", name,
2538 		(int)strlen(name), &ypbuf, &ypbuflen);
2539 	if (r == 0) {
2540 		ai = _yphostent(ypbuf, pai);
2541 		if (ai)
2542 			cur->ai_next = ai;
2543 		free(ypbuf);
2544 	}
2545 
2546 	if (sentinel.ai_next == NULL) {
2547 		RES_SET_H_ERRNO(__res_state(), HOST_NOT_FOUND);
2548 		return NS_NOTFOUND;
2549 	}
2550 	*((struct addrinfo **)rv) = sentinel.ai_next;
2551 	return NS_SUCCESS;
2552 }
2553 #endif
2554 
2555 /* resolver logic */
2556 
2557 /*
2558  * Formulate a normal query, send, and await answer.
2559  * Returned answer is placed in supplied buffer "answer".
2560  * Perform preliminary check of answer, returning success only
2561  * if no error is indicated and the answer count is nonzero.
2562  * Return the size of the response on success, -1 on error.
2563  * Error number is left in h_errno.
2564  *
2565  * Caller must parse answer and determine whether it answers the question.
2566  */
2567 static int
2568 res_queryN(const char *name, struct res_target *target, res_state res)
2569 {
2570 	u_char *buf;
2571 	HEADER *hp;
2572 	int n;
2573 	u_int oflags;
2574 	struct res_target *t;
2575 	int rcode;
2576 	int ancount;
2577 
2578 	rcode = NOERROR;
2579 	ancount = 0;
2580 
2581 	buf = malloc(MAXPACKET);
2582 	if (!buf) {
2583 		RES_SET_H_ERRNO(res, NETDB_INTERNAL);
2584 		return -1;
2585 	}
2586 
2587 	for (t = target; t; t = t->next) {
2588 		int class, type;
2589 		u_char *answer;
2590 		int anslen;
2591 
2592 		hp = (HEADER *)(void *)t->answer;
2593 
2594 		/* make it easier... */
2595 		class = t->qclass;
2596 		type = t->qtype;
2597 		answer = t->answer;
2598 		anslen = t->anslen;
2599 
2600 		oflags = res->_flags;
2601 
2602 again:
2603 		hp->rcode = NOERROR;	/* default */
2604 
2605 #ifdef DEBUG
2606 		if (res->options & RES_DEBUG)
2607 			printf(";; res_query(%s, %d, %d)\n", name, class, type);
2608 #endif
2609 
2610 		n = res_nmkquery(res, QUERY, name, class, type, NULL, 0, NULL,
2611 		    buf, MAXPACKET);
2612 		if (n > 0 && (res->_flags & RES_F_EDNS0ERR) == 0 &&
2613 		    (res->options & (RES_USE_EDNS0|RES_USE_DNSSEC)) != 0U)
2614 			n = res_nopt(res, n, buf, MAXPACKET, anslen);
2615 		if (n <= 0) {
2616 #ifdef DEBUG
2617 			if (res->options & RES_DEBUG)
2618 				printf(";; res_query: mkquery failed\n");
2619 #endif
2620 			free(buf);
2621 			RES_SET_H_ERRNO(res, NO_RECOVERY);
2622 			return (n);
2623 		}
2624 		n = res_nsend(res, buf, n, answer, anslen);
2625 		if (n < 0) {
2626 			/*
2627 			 * if the query choked with EDNS0, retry
2628 			 * without EDNS0
2629 			 */
2630 			if ((res->options & (RES_USE_EDNS0|RES_USE_DNSSEC))
2631 			    != 0U &&
2632 			    ((oflags ^ res->_flags) & RES_F_EDNS0ERR) != 0) {
2633 				res->_flags |= RES_F_EDNS0ERR;
2634 				if (res->options & RES_DEBUG)
2635 					printf(";; res_nquery: retry without EDNS0\n");
2636 				goto again;
2637 			}
2638 			rcode = hp->rcode;	/* record most recent error */
2639 #ifdef DEBUG
2640 			if (res->options & RES_DEBUG)
2641 				printf(";; res_query: send error\n");
2642 #endif
2643 			continue;
2644 		}
2645 
2646 		if (n > anslen)
2647 			hp->rcode = FORMERR; /* XXX not very informative */
2648 		if (hp->rcode != NOERROR || ntohs(hp->ancount) == 0) {
2649 			rcode = hp->rcode;	/* record most recent error */
2650 #ifdef DEBUG
2651 			if (res->options & RES_DEBUG)
2652 				printf(";; rcode = %u, ancount=%u\n", hp->rcode,
2653 				    ntohs(hp->ancount));
2654 #endif
2655 			continue;
2656 		}
2657 
2658 		ancount += ntohs(hp->ancount);
2659 
2660 		t->n = n;
2661 	}
2662 
2663 	free(buf);
2664 
2665 	if (ancount == 0) {
2666 		switch (rcode) {
2667 		case NXDOMAIN:
2668 			RES_SET_H_ERRNO(res, HOST_NOT_FOUND);
2669 			break;
2670 		case SERVFAIL:
2671 			RES_SET_H_ERRNO(res, TRY_AGAIN);
2672 			break;
2673 		case NOERROR:
2674 			RES_SET_H_ERRNO(res, NO_DATA);
2675 			break;
2676 		case FORMERR:
2677 		case NOTIMP:
2678 		case REFUSED:
2679 		default:
2680 			RES_SET_H_ERRNO(res, NO_RECOVERY);
2681 			break;
2682 		}
2683 		return (-1);
2684 	}
2685 	return (ancount);
2686 }
2687 
2688 /*
2689  * Formulate a normal query, send, and retrieve answer in supplied buffer.
2690  * Return the size of the response on success, -1 on error.
2691  * If enabled, implement search rules until answer or unrecoverable failure
2692  * is detected.  Error code, if any, is left in h_errno.
2693  */
2694 static int
2695 res_searchN(const char *name, struct res_target *target, res_state res)
2696 {
2697 	const char *cp, * const *domain;
2698 	HEADER *hp = (HEADER *)(void *)target->answer;	/*XXX*/
2699 	u_int dots;
2700 	int trailing_dot, ret, saved_herrno;
2701 	int got_nodata = 0, got_servfail = 0, root_on_list = 0;
2702 	int tried_as_is = 0;
2703 	int searched = 0;
2704 	char abuf[MAXDNAME];
2705 
2706 	errno = 0;
2707 	RES_SET_H_ERRNO(res, HOST_NOT_FOUND); /* default, if we never query */
2708 	dots = 0;
2709 	for (cp = name; *cp; cp++)
2710 		dots += (*cp == '.');
2711 	trailing_dot = 0;
2712 	if (cp > name && *--cp == '.')
2713 		trailing_dot++;
2714 
2715 	/*
2716 	 * if there aren't any dots, it could be a user-level alias
2717 	 */
2718 	if (!dots &&
2719 	    (cp = res_hostalias(res, name, abuf, sizeof(abuf))) != NULL)
2720 		return (res_queryN(cp, target, res));
2721 
2722 	/*
2723 	 * If there are enough dots in the name, let's just give it a
2724 	 * try 'as is'. The threshold can be set with the "ndots" option.
2725 	 * Also, query 'as is', if there is a trailing dot in the name.
2726 	 */
2727 	saved_herrno = -1;
2728 	if (dots >= res->ndots || trailing_dot) {
2729 		ret = res_querydomainN(name, NULL, target, res);
2730 		if (ret > 0 || trailing_dot)
2731 			return (ret);
2732 		if (errno == ECONNREFUSED) {
2733 			RES_SET_H_ERRNO(res, TRY_AGAIN);
2734 			return (-1);
2735 		}
2736 		switch (res->res_h_errno) {
2737 		case NO_DATA:
2738 		case HOST_NOT_FOUND:
2739 			break;
2740 		case TRY_AGAIN:
2741 			if (hp->rcode == SERVFAIL)
2742 				break;
2743 			/* FALLTHROUGH */
2744 		default:
2745 			return (-1);
2746 		}
2747 		saved_herrno = res->res_h_errno;
2748 		tried_as_is++;
2749 	}
2750 
2751 	/*
2752 	 * We do at least one level of search if
2753 	 *	- there is no dot and RES_DEFNAME is set, or
2754 	 *	- there is at least one dot, there is no trailing dot,
2755 	 *	  and RES_DNSRCH is set.
2756 	 */
2757 	if ((!dots && (res->options & RES_DEFNAMES)) ||
2758 	    (dots && !trailing_dot && (res->options & RES_DNSRCH))) {
2759 		int done = 0;
2760 
2761 		for (domain = (const char * const *)res->dnsrch;
2762 		   *domain && !done;
2763 		   domain++) {
2764 			searched = 1;
2765 
2766 			if (domain[0][0] == '\0' ||
2767 			    (domain[0][0] == '.' && domain[0][1] == '\0'))
2768 				root_on_list++;
2769 
2770 			if (root_on_list && tried_as_is)
2771 				continue;
2772 
2773 			ret = res_querydomainN(name, *domain, target, res);
2774 			if (ret > 0)
2775 				return (ret);
2776 
2777 			/*
2778 			 * If no server present, give up.
2779 			 * If name isn't found in this domain,
2780 			 * keep trying higher domains in the search list
2781 			 * (if that's enabled).
2782 			 * On a NO_DATA error, keep trying, otherwise
2783 			 * a wildcard entry of another type could keep us
2784 			 * from finding this entry higher in the domain.
2785 			 * If we get some other error (negative answer or
2786 			 * server failure), then stop searching up,
2787 			 * but try the input name below in case it's
2788 			 * fully-qualified.
2789 			 */
2790 			if (errno == ECONNREFUSED) {
2791 				RES_SET_H_ERRNO(res, TRY_AGAIN);
2792 				return (-1);
2793 			}
2794 
2795 			switch (res->res_h_errno) {
2796 			case NO_DATA:
2797 				got_nodata++;
2798 				/* FALLTHROUGH */
2799 			case HOST_NOT_FOUND:
2800 				/* keep trying */
2801 				break;
2802 			case TRY_AGAIN:
2803 				got_servfail++;
2804 				if (hp->rcode == SERVFAIL) {
2805 					/* try next search element, if any */
2806 					break;
2807 				}
2808 				/* FALLTHROUGH */
2809 			default:
2810 				/* anything else implies that we're done */
2811 				done++;
2812 			}
2813 			/*
2814 			 * if we got here for some reason other than DNSRCH,
2815 			 * we only wanted one iteration of the loop, so stop.
2816 			 */
2817 			if (!(res->options & RES_DNSRCH))
2818 			        done++;
2819 		}
2820 	}
2821 
2822 	switch (res->res_h_errno) {
2823 	case NO_DATA:
2824 	case HOST_NOT_FOUND:
2825 		break;
2826 	case TRY_AGAIN:
2827 		if (hp->rcode == SERVFAIL)
2828 			break;
2829 		/* FALLTHROUGH */
2830 	default:
2831 		goto giveup;
2832 	}
2833 
2834 	/*
2835 	 * If the query has not already been tried as is then try it
2836 	 * unless RES_NOTLDQUERY is set and there were no dots.
2837 	 */
2838 	if ((dots || !searched || !(res->options & RES_NOTLDQUERY)) &&
2839 	    !(tried_as_is || root_on_list)) {
2840 		ret = res_querydomainN(name, NULL, target, res);
2841 		if (ret > 0)
2842 			return (ret);
2843 	}
2844 
2845 	/*
2846 	 * if we got here, we didn't satisfy the search.
2847 	 * if we did an initial full query, return that query's h_errno
2848 	 * (note that we wouldn't be here if that query had succeeded).
2849 	 * else if we ever got a nodata, send that back as the reason.
2850 	 * else send back meaningless h_errno, that being the one from
2851 	 * the last DNSRCH we did.
2852 	 */
2853 giveup:
2854 	if (saved_herrno != -1)
2855 		RES_SET_H_ERRNO(res, saved_herrno);
2856 	else if (got_nodata)
2857 		RES_SET_H_ERRNO(res, NO_DATA);
2858 	else if (got_servfail)
2859 		RES_SET_H_ERRNO(res, TRY_AGAIN);
2860 	return (-1);
2861 }
2862 
2863 /*
2864  * Perform a call on res_query on the concatenation of name and domain,
2865  * removing a trailing dot from name if domain is NULL.
2866  */
2867 static int
2868 res_querydomainN(const char *name, const char *domain,
2869     struct res_target *target, res_state res)
2870 {
2871 	char nbuf[MAXDNAME];
2872 	const char *longname = nbuf;
2873 	size_t n, d;
2874 
2875 #ifdef DEBUG
2876 	if (res->options & RES_DEBUG)
2877 		printf(";; res_querydomain(%s, %s)\n",
2878 			name, domain?domain:"<Nil>");
2879 #endif
2880 	if (domain == NULL) {
2881 		/*
2882 		 * Check for trailing '.';
2883 		 * copy without '.' if present.
2884 		 */
2885 		n = strlen(name);
2886 		if (n >= MAXDNAME) {
2887 			RES_SET_H_ERRNO(res, NO_RECOVERY);
2888 			return (-1);
2889 		}
2890 		if (n > 0 && name[--n] == '.') {
2891 			strncpy(nbuf, name, n);
2892 			nbuf[n] = '\0';
2893 		} else
2894 			longname = name;
2895 	} else {
2896 		n = strlen(name);
2897 		d = strlen(domain);
2898 		if (n + d + 1 >= MAXDNAME) {
2899 			RES_SET_H_ERRNO(res, NO_RECOVERY);
2900 			return (-1);
2901 		}
2902 		snprintf(nbuf, sizeof(nbuf), "%s.%s", name, domain);
2903 	}
2904 	return (res_queryN(longname, target, res));
2905 }
2906