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      1 /*	$NetBSD: res_send.c,v 1.9 2006/01/24 17:41:25 christos Exp $	*/
      2 
      3 /*
      4  * Copyright 2008  Android Open Source Project (source port randomization)
      5  * Copyright (c) 1985, 1989, 1993
      6  *    The Regents of the University of California.  All rights reserved.
      7  *
      8  * Redistribution and use in source and binary forms, with or without
      9  * modification, are permitted provided that the following conditions
     10  * are met:
     11  * 1. Redistributions of source code must retain the above copyright
     12  *    notice, this list of conditions and the following disclaimer.
     13  * 2. Redistributions in binary form must reproduce the above copyright
     14  *    notice, this list of conditions and the following disclaimer in the
     15  *    documentation and/or other materials provided with the distribution.
     16  * 3. All advertising materials mentioning features or use of this software
     17  *    must display the following acknowledgement:
     18  * 	This product includes software developed by the University of
     19  * 	California, Berkeley and its contributors.
     20  * 4. Neither the name of the University nor the names of its contributors
     21  *    may be used to endorse or promote products derived from this software
     22  *    without specific prior written permission.
     23  *
     24  * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
     25  * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
     26  * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
     27  * ARE DISCLAIMED.  IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
     28  * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
     29  * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
     30  * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
     31  * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
     32  * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
     33  * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
     34  * SUCH DAMAGE.
     35  */
     36 
     37 /*
     38  * Portions Copyright (c) 1993 by Digital Equipment Corporation.
     39  *
     40  * Permission to use, copy, modify, and distribute this software for any
     41  * purpose with or without fee is hereby granted, provided that the above
     42  * copyright notice and this permission notice appear in all copies, and that
     43  * the name of Digital Equipment Corporation not be used in advertising or
     44  * publicity pertaining to distribution of the document or software without
     45  * specific, written prior permission.
     46  *
     47  * THE SOFTWARE IS PROVIDED "AS IS" AND DIGITAL EQUIPMENT CORP. DISCLAIMS ALL
     48  * WARRANTIES WITH REGARD TO THIS SOFTWARE, INCLUDING ALL IMPLIED WARRANTIES
     49  * OF MERCHANTABILITY AND FITNESS.   IN NO EVENT SHALL DIGITAL EQUIPMENT
     50  * CORPORATION BE LIABLE FOR ANY SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL
     51  * DAMAGES OR ANY DAMAGES WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR
     52  * PROFITS, WHETHER IN AN ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS
     53  * ACTION, ARISING OUT OF OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS
     54  * SOFTWARE.
     55  */
     56 
     57 /*
     58  * Copyright (c) 2004 by Internet Systems Consortium, Inc. ("ISC")
     59  * Portions Copyright (c) 1996-1999 by Internet Software Consortium.
     60  *
     61  * Permission to use, copy, modify, and distribute this software for any
     62  * purpose with or without fee is hereby granted, provided that the above
     63  * copyright notice and this permission notice appear in all copies.
     64  *
     65  * THE SOFTWARE IS PROVIDED "AS IS" AND ISC DISCLAIMS ALL WARRANTIES
     66  * WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF
     67  * MERCHANTABILITY AND FITNESS.  IN NO EVENT SHALL ISC BE LIABLE FOR
     68  * ANY SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES
     69  * WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS, WHETHER IN AN
     70  * ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT
     71  * OF OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE.
     72  */
     73 
     74 #include <sys/cdefs.h>
     75 #if defined(LIBC_SCCS) && !defined(lint)
     76 #ifdef notdef
     77 static const char sccsid[] = "@(#)res_send.c	8.1 (Berkeley) 6/4/93";
     78 static const char rcsid[] = "Id: res_send.c,v 1.5.2.2.4.5 2004/08/10 02:19:56 marka Exp";
     79 #else
     80 __RCSID("$NetBSD: res_send.c,v 1.9 2006/01/24 17:41:25 christos Exp $");
     81 #endif
     82 #endif /* LIBC_SCCS and not lint */
     83 
     84 /*
     85  * Send query to name server and wait for reply.
     86  */
     87 
     88 #include <sys/types.h>
     89 #include <sys/param.h>
     90 #include <sys/time.h>
     91 #include <sys/socket.h>
     92 #include <sys/uio.h>
     93 
     94 #include <netinet/in.h>
     95 #include <arpa/nameser.h>
     96 #include <arpa/inet.h>
     97 
     98 #include <errno.h>
     99 #include <fcntl.h>
    100 #include <netdb.h>
    101 #ifdef ANDROID_CHANGES
    102 #include "resolv_netid.h"
    103 #include "resolv_private.h"
    104 #else
    105 #include <resolv.h>
    106 #endif
    107 #include <signal.h>
    108 #include <stdio.h>
    109 #include <stdlib.h>
    110 #include <string.h>
    111 #include <time.h>
    112 #include <unistd.h>
    113 
    114 #include <isc/eventlib.h>
    115 
    116 #include <resolv_cache.h>
    117 
    118 #include "private/libc_logging.h"
    119 
    120 #ifndef DE_CONST
    121 #define DE_CONST(c,v)   v = ((c) ? \
    122     strchr((const void *)(c), *(const char *)(const void *)(c)) : NULL)
    123 #endif
    124 
    125 /* Options.  Leave them on. */
    126 #ifndef DEBUG
    127 #define DEBUG
    128 #endif
    129 #include "res_debug.h"
    130 #include "res_private.h"
    131 #include "resolv_stats.h"
    132 
    133 #define EXT(res) ((res)->_u._ext)
    134 #define DBG 0
    135 
    136 static const int highestFD = FD_SETSIZE - 1;
    137 
    138 /* Forward. */
    139 
    140 static int		get_salen __P((const struct sockaddr *));
    141 static struct sockaddr * get_nsaddr __P((res_state, size_t));
    142 static int		send_vc(res_state, const u_char *, int,
    143 				u_char *, int, int *, int,
    144 				time_t *, int *, int *);
    145 static int		send_dg(res_state, const u_char *, int,
    146 				u_char *, int, int *, int,
    147 				int *, int *,
    148 				time_t *, int *, int *);
    149 static void		Aerror(const res_state, FILE *, const char *, int,
    150 			       const struct sockaddr *, int);
    151 static void		Perror(const res_state, FILE *, const char *, int);
    152 static int		sock_eq(struct sockaddr *, struct sockaddr *);
    153 #ifdef NEED_PSELECT
    154 static int		pselect(int, void *, void *, void *,
    155 				struct timespec *,
    156 				const sigset_t *);
    157 #endif
    158 void res_pquery(const res_state, const u_char *, int, FILE *);
    159 static int connect_with_timeout(int sock, const struct sockaddr *nsap,
    160 			socklen_t salen, int sec);
    161 static int retrying_select(const int sock, fd_set *readset, fd_set *writeset,
    162 			const struct timespec *finish);
    163 
    164 /* BIONIC-BEGIN: implement source port randomization */
    165 typedef union {
    166     struct sockaddr      sa;
    167     struct sockaddr_in   sin;
    168     struct sockaddr_in6  sin6;
    169 } _sockaddr_union;
    170 
    171 static int
    172 random_bind( int  s, int  family )
    173 {
    174     _sockaddr_union  u;
    175     int              j;
    176     socklen_t        slen;
    177 
    178     /* clear all, this also sets the IP4/6 address to 'any' */
    179     memset( &u, 0, sizeof u );
    180 
    181     switch (family) {
    182         case AF_INET:
    183             u.sin.sin_family = family;
    184             slen             = sizeof u.sin;
    185             break;
    186         case AF_INET6:
    187             u.sin6.sin6_family = family;
    188             slen               = sizeof u.sin6;
    189             break;
    190         default:
    191             errno = EPROTO;
    192             return -1;
    193     }
    194 
    195     /* first try to bind to a random source port a few times */
    196     for (j = 0; j < 10; j++) {
    197         /* find a random port between 1025 .. 65534 */
    198         int  port = 1025 + (res_randomid() % (65535-1025));
    199         if (family == AF_INET)
    200             u.sin.sin_port = htons(port);
    201         else
    202             u.sin6.sin6_port = htons(port);
    203 
    204         if ( !bind( s, &u.sa, slen ) )
    205             return 0;
    206     }
    207 
    208     /* nothing after 10 tries, our network table is probably busy */
    209     /* let the system decide which port is best */
    210     if (family == AF_INET)
    211         u.sin.sin_port = 0;
    212     else
    213         u.sin6.sin6_port = 0;
    214 
    215     return bind( s, &u.sa, slen );
    216 }
    217 /* BIONIC-END */
    218 
    219 static const int niflags = NI_NUMERICHOST | NI_NUMERICSERV;
    220 
    221 /* Public. */
    222 
    223 /* int
    224  * res_isourserver(ina)
    225  *	looks up "ina" in _res.ns_addr_list[]
    226  * returns:
    227  *	0  : not found
    228  *	>0 : found
    229  * author:
    230  *	paul vixie, 29may94
    231  */
    232 __LIBC_HIDDEN__ int
    233 res_ourserver_p(const res_state statp, const struct sockaddr *sa) {
    234 	const struct sockaddr_in *inp, *srv;
    235 	const struct sockaddr_in6 *in6p, *srv6;
    236 	int ns;
    237 
    238 	switch (sa->sa_family) {
    239 	case AF_INET:
    240 		inp = (const struct sockaddr_in *)(const void *)sa;
    241 		for (ns = 0;  ns < statp->nscount;  ns++) {
    242 			srv = (struct sockaddr_in *)(void *)get_nsaddr(statp, (size_t)ns);
    243 			if (srv->sin_family == inp->sin_family &&
    244 			    srv->sin_port == inp->sin_port &&
    245 			    (srv->sin_addr.s_addr == INADDR_ANY ||
    246 			     srv->sin_addr.s_addr == inp->sin_addr.s_addr))
    247 				return (1);
    248 		}
    249 		break;
    250 	case AF_INET6:
    251 		if (EXT(statp).ext == NULL)
    252 			break;
    253 		in6p = (const struct sockaddr_in6 *)(const void *)sa;
    254 		for (ns = 0;  ns < statp->nscount;  ns++) {
    255 			srv6 = (struct sockaddr_in6 *)(void *)get_nsaddr(statp, (size_t)ns);
    256 			if (srv6->sin6_family == in6p->sin6_family &&
    257 			    srv6->sin6_port == in6p->sin6_port &&
    258 #ifdef HAVE_SIN6_SCOPE_ID
    259 			    (srv6->sin6_scope_id == 0 ||
    260 			     srv6->sin6_scope_id == in6p->sin6_scope_id) &&
    261 #endif
    262 			    (IN6_IS_ADDR_UNSPECIFIED(&srv6->sin6_addr) ||
    263 			     IN6_ARE_ADDR_EQUAL(&srv6->sin6_addr, &in6p->sin6_addr)))
    264 				return (1);
    265 		}
    266 		break;
    267 	default:
    268 		break;
    269 	}
    270 	return (0);
    271 }
    272 
    273 /* int
    274  * res_nameinquery(name, type, class, buf, eom)
    275  *	look for (name,type,class) in the query section of packet (buf,eom)
    276  * requires:
    277  *	buf + HFIXEDSZ <= eom
    278  * returns:
    279  *	-1 : format error
    280  *	0  : not found
    281  *	>0 : found
    282  * author:
    283  *	paul vixie, 29may94
    284  */
    285 int
    286 res_nameinquery(const char *name, int type, int class,
    287 		const u_char *buf, const u_char *eom)
    288 {
    289 	const u_char *cp = buf + HFIXEDSZ;
    290 	int qdcount = ntohs(((const HEADER*)(const void *)buf)->qdcount);
    291 
    292 	while (qdcount-- > 0) {
    293 		char tname[MAXDNAME+1];
    294 		int n, ttype, tclass;
    295 
    296 		n = dn_expand(buf, eom, cp, tname, sizeof tname);
    297 		if (n < 0)
    298 			return (-1);
    299 		cp += n;
    300 		if (cp + 2 * INT16SZ > eom)
    301 			return (-1);
    302 		ttype = ns_get16(cp); cp += INT16SZ;
    303 		tclass = ns_get16(cp); cp += INT16SZ;
    304 		if (ttype == type && tclass == class &&
    305 		    ns_samename(tname, name) == 1)
    306 			return (1);
    307 	}
    308 	return (0);
    309 }
    310 
    311 /* int
    312  * res_queriesmatch(buf1, eom1, buf2, eom2)
    313  *	is there a 1:1 mapping of (name,type,class)
    314  *	in (buf1,eom1) and (buf2,eom2)?
    315  * returns:
    316  *	-1 : format error
    317  *	0  : not a 1:1 mapping
    318  *	>0 : is a 1:1 mapping
    319  * author:
    320  *	paul vixie, 29may94
    321  */
    322 int
    323 res_queriesmatch(const u_char *buf1, const u_char *eom1,
    324 		 const u_char *buf2, const u_char *eom2)
    325 {
    326 	const u_char *cp = buf1 + HFIXEDSZ;
    327 	int qdcount = ntohs(((const HEADER*)(const void *)buf1)->qdcount);
    328 
    329 	if (buf1 + HFIXEDSZ > eom1 || buf2 + HFIXEDSZ > eom2)
    330 		return (-1);
    331 
    332 	/*
    333 	 * Only header section present in replies to
    334 	 * dynamic update packets.
    335 	 */
    336 	if ((((const HEADER *)(const void *)buf1)->opcode == ns_o_update) &&
    337 	    (((const HEADER *)(const void *)buf2)->opcode == ns_o_update))
    338 		return (1);
    339 
    340 	if (qdcount != ntohs(((const HEADER*)(const void *)buf2)->qdcount))
    341 		return (0);
    342 	while (qdcount-- > 0) {
    343 		char tname[MAXDNAME+1];
    344 		int n, ttype, tclass;
    345 
    346 		n = dn_expand(buf1, eom1, cp, tname, sizeof tname);
    347 		if (n < 0)
    348 			return (-1);
    349 		cp += n;
    350 		if (cp + 2 * INT16SZ > eom1)
    351 			return (-1);
    352 		ttype = ns_get16(cp);	cp += INT16SZ;
    353 		tclass = ns_get16(cp); cp += INT16SZ;
    354 		if (!res_nameinquery(tname, ttype, tclass, buf2, eom2))
    355 			return (0);
    356 	}
    357 	return (1);
    358 }
    359 
    360 int
    361 res_nsend(res_state statp,
    362 	  const u_char *buf, int buflen, u_char *ans, int anssiz)
    363 {
    364 	int gotsomewhere, terrno, try, v_circuit, resplen, ns, n;
    365 	char abuf[NI_MAXHOST];
    366 	ResolvCacheStatus     cache_status = RESOLV_CACHE_UNSUPPORTED;
    367 
    368 	if (anssiz < HFIXEDSZ) {
    369 		errno = EINVAL;
    370 		return (-1);
    371 	}
    372 	DprintQ((statp->options & RES_DEBUG) || (statp->pfcode & RES_PRF_QUERY),
    373 		(stdout, ";; res_send()\n"), buf, buflen);
    374 	v_circuit = (statp->options & RES_USEVC) || buflen > PACKETSZ;
    375 	gotsomewhere = 0;
    376 	terrno = ETIMEDOUT;
    377 
    378 	int  anslen = 0;
    379 	cache_status = _resolv_cache_lookup(
    380 			statp->netid, buf, buflen,
    381 			ans, anssiz, &anslen);
    382 
    383 	if (cache_status == RESOLV_CACHE_FOUND) {
    384 		return anslen;
    385 	} else if (cache_status != RESOLV_CACHE_UNSUPPORTED) {
    386 		// had a cache miss for a known network, so populate the thread private
    387 		// data so the normal resolve path can do its thing
    388 		_resolv_populate_res_for_net(statp);
    389 	}
    390 	if (statp->nscount == 0) {
    391 		// We have no nameservers configured, so there's no point trying.
    392 		// Tell the cache the query failed, or any retries and anyone else asking the same
    393 		// question will block for PENDING_REQUEST_TIMEOUT seconds instead of failing fast.
    394 		_resolv_cache_query_failed(statp->netid, buf, buflen);
    395 		errno = ESRCH;
    396 		return (-1);
    397 	}
    398 
    399 	/*
    400 	 * If the ns_addr_list in the resolver context has changed, then
    401 	 * invalidate our cached copy and the associated timing data.
    402 	 */
    403 	if (EXT(statp).nscount != 0) {
    404 		int needclose = 0;
    405 		struct sockaddr_storage peer;
    406 		socklen_t peerlen;
    407 
    408 		if (EXT(statp).nscount != statp->nscount) {
    409 			needclose++;
    410 		} else {
    411 			for (ns = 0; ns < statp->nscount; ns++) {
    412 				if (statp->nsaddr_list[ns].sin_family &&
    413 				    !sock_eq((struct sockaddr *)(void *)&statp->nsaddr_list[ns],
    414 					     (struct sockaddr *)(void *)&EXT(statp).ext->nsaddrs[ns])) {
    415 					needclose++;
    416 					break;
    417 				}
    418 
    419 				if (EXT(statp).nssocks[ns] == -1)
    420 					continue;
    421 				peerlen = sizeof(peer);
    422 				if (getpeername(EXT(statp).nssocks[ns],
    423 				    (struct sockaddr *)(void *)&peer, &peerlen) < 0) {
    424 					needclose++;
    425 					break;
    426 				}
    427 				if (!sock_eq((struct sockaddr *)(void *)&peer,
    428 				    get_nsaddr(statp, (size_t)ns))) {
    429 					needclose++;
    430 					break;
    431 				}
    432 			}
    433 		}
    434 		if (needclose) {
    435 			res_nclose(statp);
    436 			EXT(statp).nscount = 0;
    437 		}
    438 	}
    439 
    440 	/*
    441 	 * Maybe initialize our private copy of the ns_addr_list.
    442 	 */
    443 	if (EXT(statp).nscount == 0) {
    444 		for (ns = 0; ns < statp->nscount; ns++) {
    445 			EXT(statp).nstimes[ns] = RES_MAXTIME;
    446 			EXT(statp).nssocks[ns] = -1;
    447 			if (!statp->nsaddr_list[ns].sin_family)
    448 				continue;
    449 			EXT(statp).ext->nsaddrs[ns].sin =
    450 				 statp->nsaddr_list[ns];
    451 		}
    452 		EXT(statp).nscount = statp->nscount;
    453 	}
    454 
    455 	/*
    456 	 * Some resolvers want to even out the load on their nameservers.
    457 	 * Note that RES_BLAST overrides RES_ROTATE.
    458 	 */
    459 	if ((statp->options & RES_ROTATE) != 0U &&
    460 	    (statp->options & RES_BLAST) == 0U) {
    461 		union res_sockaddr_union inu;
    462 		struct sockaddr_in ina;
    463 		int lastns = statp->nscount - 1;
    464 		int fd;
    465 		u_int16_t nstime;
    466 
    467 		if (EXT(statp).ext != NULL)
    468 			inu = EXT(statp).ext->nsaddrs[0];
    469 		ina = statp->nsaddr_list[0];
    470 		fd = EXT(statp).nssocks[0];
    471 		nstime = EXT(statp).nstimes[0];
    472 		for (ns = 0; ns < lastns; ns++) {
    473 			if (EXT(statp).ext != NULL)
    474 				EXT(statp).ext->nsaddrs[ns] =
    475 					EXT(statp).ext->nsaddrs[ns + 1];
    476 			statp->nsaddr_list[ns] = statp->nsaddr_list[ns + 1];
    477 			EXT(statp).nssocks[ns] = EXT(statp).nssocks[ns + 1];
    478 			EXT(statp).nstimes[ns] = EXT(statp).nstimes[ns + 1];
    479 		}
    480 		if (EXT(statp).ext != NULL)
    481 			EXT(statp).ext->nsaddrs[lastns] = inu;
    482 		statp->nsaddr_list[lastns] = ina;
    483 		EXT(statp).nssocks[lastns] = fd;
    484 		EXT(statp).nstimes[lastns] = nstime;
    485 	}
    486 
    487 	/*
    488 	 * Send request, RETRY times, or until successful.
    489 	 */
    490 	for (try = 0; try < statp->retry; try++) {
    491 	    struct __res_stats stats[MAXNS];
    492 	    struct __res_params params;
    493 	    int revision_id = _resolv_cache_get_resolver_stats(statp->netid, &params, stats);
    494 	    bool usable_servers[MAXNS];
    495 	    android_net_res_stats_get_usable_servers(&params, stats, statp->nscount,
    496 		    usable_servers);
    497 
    498 	    for (ns = 0; ns < statp->nscount; ns++) {
    499 		if (!usable_servers[ns]) continue;
    500 		struct sockaddr *nsap;
    501 		int nsaplen;
    502 		time_t now = 0;
    503 		int rcode = RCODE_INTERNAL_ERROR;
    504 		int delay = 0;
    505 		nsap = get_nsaddr(statp, (size_t)ns);
    506 		nsaplen = get_salen(nsap);
    507 		statp->_flags &= ~RES_F_LASTMASK;
    508 		statp->_flags |= (ns << RES_F_LASTSHIFT);
    509 
    510  same_ns:
    511 		if (statp->qhook) {
    512 			int done = 0, loops = 0;
    513 
    514 			do {
    515 				res_sendhookact act;
    516 
    517 				act = (*statp->qhook)(&nsap, &buf, &buflen,
    518 						      ans, anssiz, &resplen);
    519 				switch (act) {
    520 				case res_goahead:
    521 					done = 1;
    522 					break;
    523 				case res_nextns:
    524 					res_nclose(statp);
    525 					goto next_ns;
    526 				case res_done:
    527 					return (resplen);
    528 				case res_modified:
    529 					/* give the hook another try */
    530 					if (++loops < 42) /*doug adams*/
    531 						break;
    532 					/*FALLTHROUGH*/
    533 				case res_error:
    534 					/*FALLTHROUGH*/
    535 				default:
    536 					goto fail;
    537 				}
    538 			} while (!done);
    539 		}
    540 
    541 		Dprint(((statp->options & RES_DEBUG) &&
    542 			getnameinfo(nsap, (socklen_t)nsaplen, abuf, sizeof(abuf),
    543 				NULL, 0, niflags) == 0),
    544 				(stdout, ";; Querying server (# %d) address = %s\n",
    545 				ns + 1, abuf));
    546 
    547 
    548 		if (v_circuit) {
    549 			/* Use VC; at most one attempt per server. */
    550 			try = statp->retry;
    551 
    552 			n = send_vc(statp, buf, buflen, ans, anssiz, &terrno,
    553 				    ns, &now, &rcode, &delay);
    554 
    555 			/*
    556 			 * Only record stats the first time we try a query. This ensures that
    557 			 * queries that deterministically fail (e.g., a name that always returns
    558 			 * SERVFAIL or times out) do not unduly affect the stats.
    559 			 */
    560 			if (try == 0) {
    561 				struct __res_sample sample;
    562 				_res_stats_set_sample(&sample, now, rcode, delay);
    563 				_resolv_cache_add_resolver_stats_sample(statp->netid, revision_id,
    564 					ns, &sample, params.max_samples);
    565 			}
    566 
    567 			if (DBG) {
    568 				__libc_format_log(ANDROID_LOG_DEBUG, "libc",
    569 					"used send_vc %d\n", n);
    570 			}
    571 
    572 			if (n < 0)
    573 				goto fail;
    574 			if (n == 0)
    575 				goto next_ns;
    576 			resplen = n;
    577 		} else {
    578 			/* Use datagrams. */
    579 			if (DBG) {
    580 				__libc_format_log(ANDROID_LOG_DEBUG, "libc", "using send_dg\n");
    581 			}
    582 
    583 			n = send_dg(statp, buf, buflen, ans, anssiz, &terrno,
    584 				    ns, &v_circuit, &gotsomewhere, &now, &rcode, &delay);
    585 
    586 			/* Only record stats the first time we try a query. See above. */
    587 			if (try == 0) {
    588 				struct __res_sample sample;
    589 				_res_stats_set_sample(&sample, now, rcode, delay);
    590 				_resolv_cache_add_resolver_stats_sample(statp->netid, revision_id,
    591 					ns, &sample, params.max_samples);
    592 			}
    593 
    594 			if (DBG) {
    595 				__libc_format_log(ANDROID_LOG_DEBUG, "libc", "used send_dg %d\n",n);
    596 			}
    597 
    598 			if (n < 0)
    599 				goto fail;
    600 			if (n == 0)
    601 				goto next_ns;
    602 			if (DBG) {
    603 				__libc_format_log(ANDROID_LOG_DEBUG, "libc", "time=%ld\n",
    604 						  time(NULL));
    605 			}
    606 			if (v_circuit)
    607 				goto same_ns;
    608 			resplen = n;
    609 		}
    610 
    611 		Dprint((statp->options & RES_DEBUG) ||
    612 		       ((statp->pfcode & RES_PRF_REPLY) &&
    613 			(statp->pfcode & RES_PRF_HEAD1)),
    614 		       (stdout, ";; got answer:\n"));
    615 
    616 		DprintQ((statp->options & RES_DEBUG) ||
    617 			(statp->pfcode & RES_PRF_REPLY),
    618 			(stdout, "%s", ""),
    619 			ans, (resplen > anssiz) ? anssiz : resplen);
    620 
    621 		if (cache_status == RESOLV_CACHE_NOTFOUND) {
    622 		    _resolv_cache_add(statp->netid, buf, buflen,
    623 				      ans, resplen);
    624 		}
    625 		/*
    626 		 * If we have temporarily opened a virtual circuit,
    627 		 * or if we haven't been asked to keep a socket open,
    628 		 * close the socket.
    629 		 */
    630 		if ((v_circuit && (statp->options & RES_USEVC) == 0U) ||
    631 		    (statp->options & RES_STAYOPEN) == 0U) {
    632 			res_nclose(statp);
    633 		}
    634 		if (statp->rhook) {
    635 			int done = 0, loops = 0;
    636 
    637 			do {
    638 				res_sendhookact act;
    639 
    640 				act = (*statp->rhook)(nsap, buf, buflen,
    641 						      ans, anssiz, &resplen);
    642 				switch (act) {
    643 				case res_goahead:
    644 				case res_done:
    645 					done = 1;
    646 					break;
    647 				case res_nextns:
    648 					res_nclose(statp);
    649 					goto next_ns;
    650 				case res_modified:
    651 					/* give the hook another try */
    652 					if (++loops < 42) /*doug adams*/
    653 						break;
    654 					/*FALLTHROUGH*/
    655 				case res_error:
    656 					/*FALLTHROUGH*/
    657 				default:
    658 					goto fail;
    659 				}
    660 			} while (!done);
    661 
    662 		}
    663 		return (resplen);
    664  next_ns: ;
    665 	   } /*foreach ns*/
    666 	} /*foreach retry*/
    667 	res_nclose(statp);
    668 	if (!v_circuit) {
    669 		if (!gotsomewhere)
    670 			errno = ECONNREFUSED;	/* no nameservers found */
    671 		else
    672 			errno = ETIMEDOUT;	/* no answer obtained */
    673 	} else
    674 		errno = terrno;
    675 
    676 	_resolv_cache_query_failed(statp->netid, buf, buflen);
    677 
    678 	return (-1);
    679  fail:
    680 
    681 	_resolv_cache_query_failed(statp->netid, buf, buflen);
    682 	res_nclose(statp);
    683 	return (-1);
    684 }
    685 
    686 /* Private */
    687 
    688 static int
    689 get_salen(sa)
    690 	const struct sockaddr *sa;
    691 {
    692 
    693 #ifdef HAVE_SA_LEN
    694 	/* There are people do not set sa_len.  Be forgiving to them. */
    695 	if (sa->sa_len)
    696 		return (sa->sa_len);
    697 #endif
    698 
    699 	if (sa->sa_family == AF_INET)
    700 		return (sizeof(struct sockaddr_in));
    701 	else if (sa->sa_family == AF_INET6)
    702 		return (sizeof(struct sockaddr_in6));
    703 	else
    704 		return (0);	/* unknown, die on connect */
    705 }
    706 
    707 /*
    708  * pick appropriate nsaddr_list for use.  see res_init() for initialization.
    709  */
    710 static struct sockaddr *
    711 get_nsaddr(statp, n)
    712 	res_state statp;
    713 	size_t n;
    714 {
    715 
    716 	if (!statp->nsaddr_list[n].sin_family && EXT(statp).ext) {
    717 		/*
    718 		 * - EXT(statp).ext->nsaddrs[n] holds an address that is larger
    719 		 *   than struct sockaddr, and
    720 		 * - user code did not update statp->nsaddr_list[n].
    721 		 */
    722 		return (struct sockaddr *)(void *)&EXT(statp).ext->nsaddrs[n];
    723 	} else {
    724 		/*
    725 		 * - user code updated statp->nsaddr_list[n], or
    726 		 * - statp->nsaddr_list[n] has the same content as
    727 		 *   EXT(statp).ext->nsaddrs[n].
    728 		 */
    729 		return (struct sockaddr *)(void *)&statp->nsaddr_list[n];
    730 	}
    731 }
    732 
    733 static int get_timeout(const res_state statp, const int ns)
    734 {
    735 	int timeout = (statp->retrans << ns);
    736 	if (ns > 0) {
    737 		timeout /= statp->nscount;
    738 	}
    739 	if (timeout <= 0) {
    740 		timeout = 1;
    741 	}
    742 	if (DBG) {
    743 		__libc_format_log(ANDROID_LOG_DEBUG, "libc", "using timeout of %d sec\n", timeout);
    744 	}
    745 
    746 	return timeout;
    747 }
    748 
    749 static int
    750 send_vc(res_state statp,
    751 	const u_char *buf, int buflen, u_char *ans, int anssiz,
    752 	int *terrno, int ns, time_t* at, int* rcode, int* delay)
    753 {
    754 	*at = time(NULL);
    755 	*rcode = RCODE_INTERNAL_ERROR;
    756 	*delay = 0;
    757 	const HEADER *hp = (const HEADER *)(const void *)buf;
    758 	HEADER *anhp = (HEADER *)(void *)ans;
    759 	struct sockaddr *nsap;
    760 	int nsaplen;
    761 	int truncating, connreset, resplen, n;
    762 	struct iovec iov[2];
    763 	u_short len;
    764 	u_char *cp;
    765 	void *tmp;
    766 
    767 	if (DBG) {
    768 		__libc_format_log(ANDROID_LOG_DEBUG, "libc", "using send_vc\n");
    769 	}
    770 
    771 	nsap = get_nsaddr(statp, (size_t)ns);
    772 	nsaplen = get_salen(nsap);
    773 
    774 	connreset = 0;
    775  same_ns:
    776 	truncating = 0;
    777 
    778 	struct timespec now = evNowTime();
    779 
    780 	/* Are we still talking to whom we want to talk to? */
    781 	if (statp->_vcsock >= 0 && (statp->_flags & RES_F_VC) != 0) {
    782 		struct sockaddr_storage peer;
    783 		socklen_t size = sizeof peer;
    784 		unsigned old_mark;
    785 		socklen_t mark_size = sizeof(old_mark);
    786 		if (getpeername(statp->_vcsock,
    787 				(struct sockaddr *)(void *)&peer, &size) < 0 ||
    788 		    !sock_eq((struct sockaddr *)(void *)&peer, nsap) ||
    789 			getsockopt(statp->_vcsock, SOL_SOCKET, SO_MARK, &old_mark, &mark_size) < 0 ||
    790 			old_mark != statp->_mark) {
    791 			res_nclose(statp);
    792 			statp->_flags &= ~RES_F_VC;
    793 		}
    794 	}
    795 
    796 	if (statp->_vcsock < 0 || (statp->_flags & RES_F_VC) == 0) {
    797 		if (statp->_vcsock >= 0)
    798 			res_nclose(statp);
    799 
    800 		statp->_vcsock = socket(nsap->sa_family, SOCK_STREAM | SOCK_CLOEXEC, 0);
    801 		if (statp->_vcsock > highestFD) {
    802 			res_nclose(statp);
    803 			errno = ENOTSOCK;
    804 		}
    805 		if (statp->_vcsock < 0) {
    806 			switch (errno) {
    807 			case EPROTONOSUPPORT:
    808 #ifdef EPFNOSUPPORT
    809 			case EPFNOSUPPORT:
    810 #endif
    811 			case EAFNOSUPPORT:
    812 				Perror(statp, stderr, "socket(vc)", errno);
    813 				return (0);
    814 			default:
    815 				*terrno = errno;
    816 				Perror(statp, stderr, "socket(vc)", errno);
    817 				return (-1);
    818 			}
    819 		}
    820 		if (statp->_mark != MARK_UNSET) {
    821 			if (setsockopt(statp->_vcsock, SOL_SOCKET,
    822 				    SO_MARK, &statp->_mark, sizeof(statp->_mark)) < 0) {
    823 				*terrno = errno;
    824 				Perror(statp, stderr, "setsockopt", errno);
    825 				return -1;
    826 			}
    827 		}
    828 		errno = 0;
    829 		if (random_bind(statp->_vcsock,nsap->sa_family) < 0) {
    830 			*terrno = errno;
    831 			Aerror(statp, stderr, "bind/vc", errno, nsap,
    832 			    nsaplen);
    833 			res_nclose(statp);
    834 			return (0);
    835 		}
    836 		if (connect_with_timeout(statp->_vcsock, nsap, (socklen_t)nsaplen,
    837 				get_timeout(statp, ns)) < 0) {
    838 			*terrno = errno;
    839 			Aerror(statp, stderr, "connect/vc", errno, nsap,
    840 			    nsaplen);
    841 			res_nclose(statp);
    842 			/*
    843 			 * The way connect_with_timeout() is implemented prevents us from reliably
    844 			 * determining whether this was really a timeout or e.g. ECONNREFUSED. Since
    845 			 * currently both cases are handled in the same way, there is no need to
    846 			 * change this (yet). If we ever need to reliably distinguish between these
    847 			 * cases, both connect_with_timeout() and retrying_select() need to be
    848 			 * modified, though.
    849 			 */
    850 			*rcode = RCODE_TIMEOUT;
    851 			return (0);
    852 		}
    853 		statp->_flags |= RES_F_VC;
    854 	}
    855 
    856 	/*
    857 	 * Send length & message
    858 	 */
    859 	ns_put16((u_short)buflen, (u_char*)(void *)&len);
    860 	iov[0] = evConsIovec(&len, INT16SZ);
    861 	DE_CONST(buf, tmp);
    862 	iov[1] = evConsIovec(tmp, (size_t)buflen);
    863 	if (writev(statp->_vcsock, iov, 2) != (INT16SZ + buflen)) {
    864 		*terrno = errno;
    865 		Perror(statp, stderr, "write failed", errno);
    866 		res_nclose(statp);
    867 		return (0);
    868 	}
    869 	/*
    870 	 * Receive length & response
    871 	 */
    872  read_len:
    873 	cp = ans;
    874 	len = INT16SZ;
    875 	while ((n = read(statp->_vcsock, (char *)cp, (size_t)len)) > 0) {
    876 		cp += n;
    877 		if ((len -= n) == 0)
    878 			break;
    879 	}
    880 	if (n <= 0) {
    881 		*terrno = errno;
    882 		Perror(statp, stderr, "read failed", errno);
    883 		res_nclose(statp);
    884 		/*
    885 		 * A long running process might get its TCP
    886 		 * connection reset if the remote server was
    887 		 * restarted.  Requery the server instead of
    888 		 * trying a new one.  When there is only one
    889 		 * server, this means that a query might work
    890 		 * instead of failing.  We only allow one reset
    891 		 * per query to prevent looping.
    892 		 */
    893 		if (*terrno == ECONNRESET && !connreset) {
    894 			connreset = 1;
    895 			res_nclose(statp);
    896 			goto same_ns;
    897 		}
    898 		res_nclose(statp);
    899 		return (0);
    900 	}
    901 	resplen = ns_get16(ans);
    902 	if (resplen > anssiz) {
    903 		Dprint(statp->options & RES_DEBUG,
    904 		       (stdout, ";; response truncated\n")
    905 		       );
    906 		truncating = 1;
    907 		len = anssiz;
    908 	} else
    909 		len = resplen;
    910 	if (len < HFIXEDSZ) {
    911 		/*
    912 		 * Undersized message.
    913 		 */
    914 		Dprint(statp->options & RES_DEBUG,
    915 		       (stdout, ";; undersized: %d\n", len));
    916 		*terrno = EMSGSIZE;
    917 		res_nclose(statp);
    918 		return (0);
    919 	}
    920 	cp = ans;
    921 	while (len != 0 && (n = read(statp->_vcsock, (char *)cp, (size_t)len)) > 0){
    922 		cp += n;
    923 		len -= n;
    924 	}
    925 	if (n <= 0) {
    926 		*terrno = errno;
    927 		Perror(statp, stderr, "read(vc)", errno);
    928 		res_nclose(statp);
    929 		return (0);
    930 	}
    931 
    932 	if (truncating) {
    933 		/*
    934 		 * Flush rest of answer so connection stays in synch.
    935 		 */
    936 		anhp->tc = 1;
    937 		len = resplen - anssiz;
    938 		while (len != 0) {
    939 			char junk[PACKETSZ];
    940 
    941 			n = read(statp->_vcsock, junk,
    942 				 (len > sizeof junk) ? sizeof junk : len);
    943 			if (n > 0)
    944 				len -= n;
    945 			else
    946 				break;
    947 		}
    948 	}
    949 	/*
    950 	 * If the calling applicating has bailed out of
    951 	 * a previous call and failed to arrange to have
    952 	 * the circuit closed or the server has got
    953 	 * itself confused, then drop the packet and
    954 	 * wait for the correct one.
    955 	 */
    956 	if (hp->id != anhp->id) {
    957 		DprintQ((statp->options & RES_DEBUG) ||
    958 			(statp->pfcode & RES_PRF_REPLY),
    959 			(stdout, ";; old answer (unexpected):\n"),
    960 			ans, (resplen > anssiz) ? anssiz: resplen);
    961 		goto read_len;
    962 	}
    963 
    964 	/*
    965 	 * All is well, or the error is fatal.  Signal that the
    966 	 * next nameserver ought not be tried.
    967 	 */
    968 	if (resplen > 0) {
    969 	    struct timespec done = evNowTime();
    970 	    *delay = _res_stats_calculate_rtt(&done, &now);
    971 	    *rcode = anhp->rcode;
    972 	}
    973 	return (resplen);
    974 }
    975 
    976 /* return -1 on error (errno set), 0 on success */
    977 static int
    978 connect_with_timeout(int sock, const struct sockaddr *nsap, socklen_t salen, int sec)
    979 {
    980 	int res, origflags;
    981 	fd_set rset, wset;
    982 	struct timespec now, timeout, finish;
    983 
    984 	origflags = fcntl(sock, F_GETFL, 0);
    985 	fcntl(sock, F_SETFL, origflags | O_NONBLOCK);
    986 
    987 	res = __connect(sock, nsap, salen);
    988 	if (res < 0 && errno != EINPROGRESS) {
    989 		res = -1;
    990 		goto done;
    991 	}
    992 	if (res != 0) {
    993 		now = evNowTime();
    994 		timeout = evConsTime((long)sec, 0L);
    995 		finish = evAddTime(now, timeout);
    996 		if (DBG) {
    997 			__libc_format_log(ANDROID_LOG_DEBUG, "libc", "  %d send_vc\n", sock);
    998 		}
    999 
   1000 		res = retrying_select(sock, &rset, &wset, &finish);
   1001 		if (res <= 0) {
   1002 			res = -1;
   1003 		}
   1004 	}
   1005 done:
   1006 	fcntl(sock, F_SETFL, origflags);
   1007 	if (DBG) {
   1008 		__libc_format_log(ANDROID_LOG_DEBUG, "libc",
   1009 			"  %d connect_with_timeout returning %d\n", sock, res);
   1010 	}
   1011 	return res;
   1012 }
   1013 
   1014 static int
   1015 retrying_select(const int sock, fd_set *readset, fd_set *writeset, const struct timespec *finish)
   1016 {
   1017 	struct timespec now, timeout;
   1018 	int n, error;
   1019 	socklen_t len;
   1020 
   1021 
   1022 retry:
   1023 	if (DBG) {
   1024 		__libc_format_log(ANDROID_LOG_DEBUG, "libc", "  %d retrying_select\n", sock);
   1025 	}
   1026 
   1027 	now = evNowTime();
   1028 	if (readset) {
   1029 		FD_ZERO(readset);
   1030 		FD_SET(sock, readset);
   1031 	}
   1032 	if (writeset) {
   1033 		FD_ZERO(writeset);
   1034 		FD_SET(sock, writeset);
   1035 	}
   1036 	if (evCmpTime(*finish, now) > 0)
   1037 		timeout = evSubTime(*finish, now);
   1038 	else
   1039 		timeout = evConsTime(0L, 0L);
   1040 
   1041 	n = pselect(sock + 1, readset, writeset, NULL, &timeout, NULL);
   1042 	if (n == 0) {
   1043 		if (DBG) {
   1044 			__libc_format_log(ANDROID_LOG_DEBUG, " libc",
   1045 				"  %d retrying_select timeout\n", sock);
   1046 		}
   1047 		errno = ETIMEDOUT;
   1048 		return 0;
   1049 	}
   1050 	if (n < 0) {
   1051 		if (errno == EINTR)
   1052 			goto retry;
   1053 		if (DBG) {
   1054 			__libc_format_log(ANDROID_LOG_DEBUG, "libc",
   1055 				"  %d retrying_select got error %d\n",sock, n);
   1056 		}
   1057 		return n;
   1058 	}
   1059 	if ((readset && FD_ISSET(sock, readset)) || (writeset && FD_ISSET(sock, writeset))) {
   1060 		len = sizeof(error);
   1061 		if (getsockopt(sock, SOL_SOCKET, SO_ERROR, &error, &len) < 0 || error) {
   1062 			errno = error;
   1063 			if (DBG) {
   1064 				__libc_format_log(ANDROID_LOG_DEBUG, "libc",
   1065 					"  %d retrying_select dot error2 %d\n", sock, errno);
   1066 			}
   1067 
   1068 			return -1;
   1069 		}
   1070 	}
   1071 	if (DBG) {
   1072 		__libc_format_log(ANDROID_LOG_DEBUG, "libc",
   1073 			"  %d retrying_select returning %d\n",sock, n);
   1074 	}
   1075 
   1076 	return n;
   1077 }
   1078 
   1079 static int
   1080 send_dg(res_state statp,
   1081 	const u_char *buf, int buflen, u_char *ans, int anssiz,
   1082 	int *terrno, int ns, int *v_circuit, int *gotsomewhere,
   1083 	time_t *at, int *rcode, int* delay)
   1084 {
   1085 	*at = time(NULL);
   1086 	*rcode = RCODE_INTERNAL_ERROR;
   1087 	*delay = 0;
   1088 	const HEADER *hp = (const HEADER *)(const void *)buf;
   1089 	HEADER *anhp = (HEADER *)(void *)ans;
   1090 	const struct sockaddr *nsap;
   1091 	int nsaplen;
   1092 	struct timespec now, timeout, finish, done;
   1093 	fd_set dsmask;
   1094 	struct sockaddr_storage from;
   1095 	socklen_t fromlen;
   1096 	int resplen, seconds, n, s;
   1097 
   1098 	nsap = get_nsaddr(statp, (size_t)ns);
   1099 	nsaplen = get_salen(nsap);
   1100 	if (EXT(statp).nssocks[ns] == -1) {
   1101 		EXT(statp).nssocks[ns] = socket(nsap->sa_family, SOCK_DGRAM | SOCK_CLOEXEC, 0);
   1102 		if (EXT(statp).nssocks[ns] > highestFD) {
   1103 			res_nclose(statp);
   1104 			errno = ENOTSOCK;
   1105 		}
   1106 		if (EXT(statp).nssocks[ns] < 0) {
   1107 			switch (errno) {
   1108 			case EPROTONOSUPPORT:
   1109 #ifdef EPFNOSUPPORT
   1110 			case EPFNOSUPPORT:
   1111 #endif
   1112 			case EAFNOSUPPORT:
   1113 				Perror(statp, stderr, "socket(dg)", errno);
   1114 				return (0);
   1115 			default:
   1116 				*terrno = errno;
   1117 				Perror(statp, stderr, "socket(dg)", errno);
   1118 				return (-1);
   1119 			}
   1120 		}
   1121 
   1122 		if (statp->_mark != MARK_UNSET) {
   1123 			if (setsockopt(EXT(statp).nssocks[ns], SOL_SOCKET,
   1124 					SO_MARK, &(statp->_mark), sizeof(statp->_mark)) < 0) {
   1125 				res_nclose(statp);
   1126 				return -1;
   1127 			}
   1128 		}
   1129 #ifndef CANNOT_CONNECT_DGRAM
   1130 		/*
   1131 		 * On a 4.3BSD+ machine (client and server,
   1132 		 * actually), sending to a nameserver datagram
   1133 		 * port with no nameserver will cause an
   1134 		 * ICMP port unreachable message to be returned.
   1135 		 * If our datagram socket is "connected" to the
   1136 		 * server, we get an ECONNREFUSED error on the next
   1137 		 * socket operation, and select returns if the
   1138 		 * error message is received.  We can thus detect
   1139 		 * the absence of a nameserver without timing out.
   1140 		 */
   1141 		if (random_bind(EXT(statp).nssocks[ns], nsap->sa_family) < 0) {
   1142 			Aerror(statp, stderr, "bind(dg)", errno, nsap,
   1143 			    nsaplen);
   1144 			res_nclose(statp);
   1145 			return (0);
   1146 		}
   1147 		if (__connect(EXT(statp).nssocks[ns], nsap, (socklen_t)nsaplen) < 0) {
   1148 			Aerror(statp, stderr, "connect(dg)", errno, nsap,
   1149 			    nsaplen);
   1150 			res_nclose(statp);
   1151 			return (0);
   1152 		}
   1153 #endif /* !CANNOT_CONNECT_DGRAM */
   1154 		Dprint(statp->options & RES_DEBUG,
   1155 		       (stdout, ";; new DG socket\n"))
   1156 
   1157 	}
   1158 	s = EXT(statp).nssocks[ns];
   1159 #ifndef CANNOT_CONNECT_DGRAM
   1160 	if (send(s, (const char*)buf, (size_t)buflen, 0) != buflen) {
   1161 		Perror(statp, stderr, "send", errno);
   1162 		res_nclose(statp);
   1163 		return (0);
   1164 	}
   1165 #else /* !CANNOT_CONNECT_DGRAM */
   1166 	if (sendto(s, (const char*)buf, buflen, 0, nsap, nsaplen) != buflen)
   1167 	{
   1168 		Aerror(statp, stderr, "sendto", errno, nsap, nsaplen);
   1169 		res_nclose(statp);
   1170 		return (0);
   1171 	}
   1172 #endif /* !CANNOT_CONNECT_DGRAM */
   1173 
   1174 	/*
   1175 	 * Wait for reply.
   1176 	 */
   1177 	seconds = get_timeout(statp, ns);
   1178 	now = evNowTime();
   1179 	timeout = evConsTime((long)seconds, 0L);
   1180 	finish = evAddTime(now, timeout);
   1181 retry:
   1182 	n = retrying_select(s, &dsmask, NULL, &finish);
   1183 
   1184 	if (n == 0) {
   1185 		*rcode = RCODE_TIMEOUT;
   1186 		Dprint(statp->options & RES_DEBUG, (stdout, ";; timeout\n"));
   1187 		*gotsomewhere = 1;
   1188 		return (0);
   1189 	}
   1190 	if (n < 0) {
   1191 		Perror(statp, stderr, "select", errno);
   1192 		res_nclose(statp);
   1193 		return (0);
   1194 	}
   1195 	errno = 0;
   1196 	fromlen = sizeof(from);
   1197 	resplen = recvfrom(s, (char*)ans, (size_t)anssiz,0,
   1198 			   (struct sockaddr *)(void *)&from, &fromlen);
   1199 	if (resplen <= 0) {
   1200 		Perror(statp, stderr, "recvfrom", errno);
   1201 		res_nclose(statp);
   1202 		return (0);
   1203 	}
   1204 	*gotsomewhere = 1;
   1205 	if (resplen < HFIXEDSZ) {
   1206 		/*
   1207 		 * Undersized message.
   1208 		 */
   1209 		Dprint(statp->options & RES_DEBUG,
   1210 		       (stdout, ";; undersized: %d\n",
   1211 			resplen));
   1212 		*terrno = EMSGSIZE;
   1213 		res_nclose(statp);
   1214 		return (0);
   1215 	}
   1216 	if (hp->id != anhp->id) {
   1217 		/*
   1218 		 * response from old query, ignore it.
   1219 		 * XXX - potential security hazard could
   1220 		 *	 be detected here.
   1221 		 */
   1222 #ifdef ANDROID_CHANGES
   1223 		__libc_android_log_event_uid(BIONIC_EVENT_RESOLVER_OLD_RESPONSE);
   1224 #endif
   1225 		DprintQ((statp->options & RES_DEBUG) ||
   1226 			(statp->pfcode & RES_PRF_REPLY),
   1227 			(stdout, ";; old answer:\n"),
   1228 			ans, (resplen > anssiz) ? anssiz : resplen);
   1229 		goto retry;
   1230 	}
   1231 	if (!(statp->options & RES_INSECURE1) &&
   1232 	    !res_ourserver_p(statp, (struct sockaddr *)(void *)&from)) {
   1233 		/*
   1234 		 * response from wrong server? ignore it.
   1235 		 * XXX - potential security hazard could
   1236 		 *	 be detected here.
   1237 		 */
   1238 #ifdef ANDROID_CHANGES
   1239 		__libc_android_log_event_uid(BIONIC_EVENT_RESOLVER_WRONG_SERVER);
   1240 #endif
   1241 		DprintQ((statp->options & RES_DEBUG) ||
   1242 			(statp->pfcode & RES_PRF_REPLY),
   1243 			(stdout, ";; not our server:\n"),
   1244 			ans, (resplen > anssiz) ? anssiz : resplen);
   1245 		goto retry;
   1246 	}
   1247 #ifdef RES_USE_EDNS0
   1248 	if (anhp->rcode == FORMERR && (statp->options & RES_USE_EDNS0) != 0U) {
   1249 		/*
   1250 		 * Do not retry if the server do not understand EDNS0.
   1251 		 * The case has to be captured here, as FORMERR packet do not
   1252 		 * carry query section, hence res_queriesmatch() returns 0.
   1253 		 */
   1254 		DprintQ(statp->options & RES_DEBUG,
   1255 			(stdout, "server rejected query with EDNS0:\n"),
   1256 			ans, (resplen > anssiz) ? anssiz : resplen);
   1257 		/* record the error */
   1258 		statp->_flags |= RES_F_EDNS0ERR;
   1259 		res_nclose(statp);
   1260 		return (0);
   1261 	}
   1262 #endif
   1263 	if (!(statp->options & RES_INSECURE2) &&
   1264 	    !res_queriesmatch(buf, buf + buflen,
   1265 			      ans, ans + anssiz)) {
   1266 		/*
   1267 		 * response contains wrong query? ignore it.
   1268 		 * XXX - potential security hazard could
   1269 		 *	 be detected here.
   1270 		 */
   1271 #ifdef ANDROID_CHANGES
   1272 		__libc_android_log_event_uid(BIONIC_EVENT_RESOLVER_WRONG_QUERY);
   1273 #endif
   1274 		DprintQ((statp->options & RES_DEBUG) ||
   1275 			(statp->pfcode & RES_PRF_REPLY),
   1276 			(stdout, ";; wrong query name:\n"),
   1277 			ans, (resplen > anssiz) ? anssiz : resplen);
   1278 		goto retry;;
   1279 	}
   1280 	done = evNowTime();
   1281 	*delay = _res_stats_calculate_rtt(&done, &now);
   1282 	if (anhp->rcode == SERVFAIL ||
   1283 	    anhp->rcode == NOTIMP ||
   1284 	    anhp->rcode == REFUSED) {
   1285 		DprintQ(statp->options & RES_DEBUG,
   1286 			(stdout, "server rejected query:\n"),
   1287 			ans, (resplen > anssiz) ? anssiz : resplen);
   1288 		res_nclose(statp);
   1289 		/* don't retry if called from dig */
   1290 		if (!statp->pfcode) {
   1291 			*rcode = anhp->rcode;
   1292 			return (0);
   1293 		}
   1294 	}
   1295 	if (!(statp->options & RES_IGNTC) && anhp->tc) {
   1296 		/*
   1297 		 * To get the rest of answer,
   1298 		 * use TCP with same server.
   1299 		 */
   1300 		Dprint(statp->options & RES_DEBUG,
   1301 		       (stdout, ";; truncated answer\n"));
   1302 		*v_circuit = 1;
   1303 		res_nclose(statp);
   1304 		return (1);
   1305 	}
   1306 	/*
   1307 	 * All is well, or the error is fatal.  Signal that the
   1308 	 * next nameserver ought not be tried.
   1309 	 */
   1310 	if (resplen > 0) {
   1311 		*rcode = anhp->rcode;
   1312 	}
   1313 	return (resplen);
   1314 }
   1315 
   1316 static void
   1317 Aerror(const res_state statp, FILE *file, const char *string, int error,
   1318        const struct sockaddr *address, int alen)
   1319 {
   1320 	int save = errno;
   1321 	char hbuf[NI_MAXHOST];
   1322 	char sbuf[NI_MAXSERV];
   1323 
   1324 	if ((statp->options & RES_DEBUG) != 0U) {
   1325 		if (getnameinfo(address, (socklen_t)alen, hbuf, sizeof(hbuf),
   1326 		    sbuf, sizeof(sbuf), niflags)) {
   1327 			strncpy(hbuf, "?", sizeof(hbuf) - 1);
   1328 			hbuf[sizeof(hbuf) - 1] = '\0';
   1329 			strncpy(sbuf, "?", sizeof(sbuf) - 1);
   1330 			sbuf[sizeof(sbuf) - 1] = '\0';
   1331 		}
   1332 		fprintf(file, "res_send: %s ([%s].%s): %s\n",
   1333 			string, hbuf, sbuf, strerror(error));
   1334 	}
   1335 	errno = save;
   1336 }
   1337 
   1338 static void
   1339 Perror(const res_state statp, FILE *file, const char *string, int error) {
   1340 	int save = errno;
   1341 
   1342 	if ((statp->options & RES_DEBUG) != 0U)
   1343 		fprintf(file, "res_send: %s: %s\n",
   1344 			string, strerror(error));
   1345 	errno = save;
   1346 }
   1347 
   1348 static int
   1349 sock_eq(struct sockaddr *a, struct sockaddr *b) {
   1350 	struct sockaddr_in *a4, *b4;
   1351 	struct sockaddr_in6 *a6, *b6;
   1352 
   1353 	if (a->sa_family != b->sa_family)
   1354 		return 0;
   1355 	switch (a->sa_family) {
   1356 	case AF_INET:
   1357 		a4 = (struct sockaddr_in *)(void *)a;
   1358 		b4 = (struct sockaddr_in *)(void *)b;
   1359 		return a4->sin_port == b4->sin_port &&
   1360 		    a4->sin_addr.s_addr == b4->sin_addr.s_addr;
   1361 	case AF_INET6:
   1362 		a6 = (struct sockaddr_in6 *)(void *)a;
   1363 		b6 = (struct sockaddr_in6 *)(void *)b;
   1364 		return a6->sin6_port == b6->sin6_port &&
   1365 #ifdef HAVE_SIN6_SCOPE_ID
   1366 		    a6->sin6_scope_id == b6->sin6_scope_id &&
   1367 #endif
   1368 		    IN6_ARE_ADDR_EQUAL(&a6->sin6_addr, &b6->sin6_addr);
   1369 	default:
   1370 		return 0;
   1371 	}
   1372 }
   1373 
   1374 #ifdef NEED_PSELECT
   1375 /* XXX needs to move to the porting library. */
   1376 static int
   1377 pselect(int nfds, void *rfds, void *wfds, void *efds,
   1378 	struct timespec *tsp, const sigset_t *sigmask)
   1379 {
   1380 	struct timeval tv, *tvp;
   1381 	sigset_t sigs;
   1382 	int n;
   1383 
   1384 	if (tsp) {
   1385 		tvp = &tv;
   1386 		tv = evTimeVal(*tsp);
   1387 	} else
   1388 		tvp = NULL;
   1389 	if (sigmask)
   1390 		sigprocmask(SIG_SETMASK, sigmask, &sigs);
   1391 	n = select(nfds, rfds, wfds, efds, tvp);
   1392 	if (sigmask)
   1393 		sigprocmask(SIG_SETMASK, &sigs, NULL);
   1394 	if (tsp)
   1395 		*tsp = evTimeSpec(tv);
   1396 	return (n);
   1397 }
   1398 #endif
   1399