The Tor Browser: other-licenses/android/res_send.c@6474c204b198 (annotated)

other-licenses/android/res_send.c@6474c204b198 (annotated)

other-licenses/android/res_send.c

Wed, 31 Dec 2014 06:09:35 +0100

author: Michael Schloh von Bennewitz <michael@schloh.com>
date: Wed, 31 Dec 2014 06:09:35 +0100
changeset 0: 6474c204b198
permissions: -rw-r--r--

Cloned upstream origin tor-browser at tor-browser-31.3.0esr-4.5-1-build1
revision ID fc1c9ff7c1b2defdbc039f12214767608f46423f for hacking purpose.

 /*	$NetBSD: res_send.c,v 1.9 2006/01/24 17:41:25 christos Exp $	*/
 /*
  * Copyright 2008  Android Open Source Project (source port randomization)
  * Copyright (c) 1985, 1989, 1993
  *    The Regents of the University of California.  All rights reserved.
  *
  * Redistribution and use in source and binary forms, with or without
  * modification, are permitted provided that the following conditions
  * are met:
  * 1. Redistributions of source code must retain the above copyright
  *    notice, this list of conditions and the following disclaimer.
  * 2. Redistributions in binary form must reproduce the above copyright
  *    notice, this list of conditions and the following disclaimer in the
  *    documentation and/or other materials provided with the distribution.
  * 3. All advertising materials mentioning features or use of this software
  *    must display the following acknowledgement:
  * 	This product includes software developed by the University of
  * 	California, Berkeley and its contributors.
  * 4. Neither the name of the University nor the names of its contributors
  *    may be used to endorse or promote products derived from this software
  *    without specific prior written permission.
  *
  * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
  * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
  * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
  * ARE DISCLAIMED.  IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
  * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
  * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
  * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
  * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
  * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
  * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
  * SUCH DAMAGE.
  */
 /*
  * Portions Copyright (c) 1993 by Digital Equipment Corporation.
  *
  * Permission to use, copy, modify, and distribute this software for any
  * purpose with or without fee is hereby granted, provided that the above
  * copyright notice and this permission notice appear in all copies, and that
  * the name of Digital Equipment Corporation not be used in advertising or
  * publicity pertaining to distribution of the document or software without
  * specific, written prior permission.
  *
  * THE SOFTWARE IS PROVIDED "AS IS" AND DIGITAL EQUIPMENT CORP. DISCLAIMS ALL
  * WARRANTIES WITH REGARD TO THIS SOFTWARE, INCLUDING ALL IMPLIED WARRANTIES
  * OF MERCHANTABILITY AND FITNESS.   IN NO EVENT SHALL DIGITAL EQUIPMENT
  * CORPORATION BE LIABLE FOR ANY SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL
  * DAMAGES OR ANY DAMAGES WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR
  * PROFITS, WHETHER IN AN ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS
  * ACTION, ARISING OUT OF OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS
  * SOFTWARE.
  */
 /*
  * Copyright (c) 2004 by Internet Systems Consortium, Inc. ("ISC")
  * Portions Copyright (c) 1996-1999 by Internet Software Consortium.
  *
  * Permission to use, copy, modify, and distribute this software for any
  * purpose with or without fee is hereby granted, provided that the above
  * copyright notice and this permission notice appear in all copies.
  *
  * THE SOFTWARE IS PROVIDED "AS IS" AND ISC DISCLAIMS ALL WARRANTIES
  * WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF
  * MERCHANTABILITY AND FITNESS.  IN NO EVENT SHALL ISC BE LIABLE FOR
  * ANY SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES
  * WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS, WHETHER IN AN
  * ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT
  * OF OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE.
  */
 /*
  * This version of this file is derived from Android 2.3 "Gingerbread",
  * which contains uncredited changes by Android/Google developers.  It has
  * been modified in 2011 for use in the Android build of Mozilla Firefox by
  * Mozilla contributors (including Michael Edwards <m.k.edwards@gmail.com>,
  * and Steve Workman <sjhworkman@gmail.com>).
  * These changes are offered under the same license as the original NetBSD
  * file, whose copyright and license are unchanged above.
  */
 #define ANDROID_CHANGES 1
 #define MOZILLA_NECKO_EXCLUDE_CODE 1
 #include <sys/cdefs.h>
 #if defined(LIBC_SCCS) && !defined(lint)
 #ifdef notdef
 static const char sccsid[] = "@(#)res_send.c	8.1 (Berkeley) 6/4/93";
 static const char rcsid[] = "Id: res_send.c,v 1.5.2.2.4.5 2004/08/10 02:19:56 marka Exp";
 #else
 __RCSID("$NetBSD: res_send.c,v 1.9 2006/01/24 17:41:25 christos Exp $");
 #endif
 #endif /* LIBC_SCCS and not lint */
 /* Set to 0 to not use the small/simple/limited DNS cache
  * Cache implemented higher up in Gecko */
 #define  USE_RESOLV_CACHE  0
 /*
  * Send query to name server and wait for reply.
  */
 #include <sys/types.h>
 #include <sys/param.h>
 #include <sys/time.h>
 #include <sys/socket.h>
 #include <sys/uio.h>
 #include <netinet/in.h>
 #include "arpa_nameser.h"
 #include <arpa/inet.h>
 #include <errno.h>
 #include <netdb.h>
 #ifdef ANDROID_CHANGES
 #include "resolv_private.h"
 #else
 #include <resolv.h>
 #endif
 #include <signal.h>
 #include <stdio.h>
 #include <stdlib.h>
 #include <string.h>
 #include <unistd.h>
 #include "eventlib.h"
 #if USE_RESOLV_CACHE
 #  include <resolv_cache.h>
 #endif
 #ifndef DE_CONST
 #define DE_CONST(c,v)   v = ((c) ? \
     strchr((const void *)(c), *(const char *)(const void *)(c)) : NULL)
 #endif
 /* Options.  Leave them on. */
 #ifndef DEBUG
 #define DEBUG
 #endif
 #include "res_debug.h"
 #include "res_private.h"
 #define EXT(res) ((res)->_u._ext)
 static const int highestFD = FD_SETSIZE - 1;
 /* Forward. */
 static int		get_salen __P((const struct sockaddr *));
 static struct sockaddr * get_nsaddr __P((res_state, size_t));
 static int		send_vc(res_state, const u_char *, int,
 				u_char *, int, int *, int);
 static int		send_dg(res_state, const u_char *, int,
 				u_char *, int, int *, int,
 				int *, int *);
 static void		Aerror(const res_state, FILE *, const char *, int,
 			       const struct sockaddr *, int);
 static void		Perror(const res_state, FILE *, const char *, int);
 static int		sock_eq(struct sockaddr *, struct sockaddr *);
 #ifdef NEED_PSELECT
 static int		pselect(int, void *, void *, void *,
 				struct timespec *,
 				const sigset_t *);
 #endif
 void res_pquery(const res_state, const u_char *, int, FILE *);
 /* BIONIC-BEGIN: implement source port randomization */
 typedef union {
     struct sockaddr      sa;
     struct sockaddr_in   sin;
     struct sockaddr_in6  sin6;
 } _sockaddr_union;
 static int
 random_bind( int  s, int  family )
 {
     _sockaddr_union  u;
     int              j;
     socklen_t        slen;
     /* clear all, this also sets the IP4/6 address to 'any' */
     memset( &u, 0, sizeof u );
     switch (family) {
         case AF_INET:
             u.sin.sin_family = family;
             slen             = sizeof u.sin;
             break;
         case AF_INET6:
             u.sin6.sin6_family = family;
             slen               = sizeof u.sin6;
             break;
         default:
             errno = EPROTO;
             return -1;
     }
     /* first try to bind to a random source port a few times */
     for (j = 0; j < 10; j++) {
         /* find a random port between 1025 .. 65534 */
         int  port = 1025 + (res_randomid() % (65535-1025));
         if (family == AF_INET)
             u.sin.sin_port = htons(port);
         else
             u.sin6.sin6_port = htons(port);
         if ( !bind( s, &u.sa, slen ) )
             return 0;
     }
     /* nothing after 10 tries, our network table is probably busy */
     /* let the system decide which port is best */
     if (family == AF_INET)
         u.sin.sin_port = 0;
     else
         u.sin6.sin6_port = 0;
     return bind( s, &u.sa, slen );
 }
 /* BIONIC-END */
 static const int niflags = NI_NUMERICHOST | NI_NUMERICSERV;
 /* Public. */
 /* int
  * res_isourserver(ina)
  *	looks up "ina" in _res.ns_addr_list[]
  * returns:
  *	0  : not found
  *	>0 : found
  * author:
  *	paul vixie, 29may94
  */
 int
 res_ourserver_p(const res_state statp, const struct sockaddr *sa) {
 	const struct sockaddr_in *inp, *srv;
 	const struct sockaddr_in6 *in6p, *srv6;
 	int ns;
 	switch (sa->sa_family) {
 	case AF_INET:
 		inp = (const struct sockaddr_in *)(const void *)sa;
 		for (ns = 0;  ns < statp->nscount;  ns++) {
 			srv = (struct sockaddr_in *)(void *)get_nsaddr(statp, (size_t)ns);
 			if (srv->sin_family == inp->sin_family &&
 			    srv->sin_port == inp->sin_port &&
 			    (srv->sin_addr.s_addr == INADDR_ANY ||
 			     srv->sin_addr.s_addr == inp->sin_addr.s_addr))
 				return (1);
 		}
 		break;
 	case AF_INET6:
 		if (EXT(statp).ext == NULL)
 			break;
 		in6p = (const struct sockaddr_in6 *)(const void *)sa;
 		for (ns = 0;  ns < statp->nscount;  ns++) {
 			srv6 = (struct sockaddr_in6 *)(void *)get_nsaddr(statp, (size_t)ns);
 			if (srv6->sin6_family == in6p->sin6_family &&
 			    srv6->sin6_port == in6p->sin6_port &&
 #ifdef HAVE_SIN6_SCOPE_ID
 			    (srv6->sin6_scope_id == 0 ||
 			     srv6->sin6_scope_id == in6p->sin6_scope_id) &&
 #endif
 			    (IN6_IS_ADDR_UNSPECIFIED(&srv6->sin6_addr) ||
 			     IN6_ARE_ADDR_EQUAL(&srv6->sin6_addr, &in6p->sin6_addr)))
 				return (1);
 		}
 		break;
 	default:
 		break;
 	}
 	return (0);
 }
 /* int
  * res_nameinquery(name, type, class, buf, eom)
  *	look for (name,type,class) in the query section of packet (buf,eom)
  * requires:
  *	buf + HFIXEDSZ <= eom
  * returns:
  *	-1 : format error
  *	0  : not found
  *	>0 : found
  * author:
  *	paul vixie, 29may94
  */
 int
 res_nameinquery(const char *name, int type, int class,
 		const u_char *buf, const u_char *eom)
 {
 	const u_char *cp = buf + HFIXEDSZ;
 	int qdcount = ntohs(((const HEADER*)(const void *)buf)->qdcount);
 	while (qdcount-- > 0) {
 		char tname[MAXDNAME+1];
 		int n, ttype, tclass;
 		n = dn_expand(buf, eom, cp, tname, sizeof tname);
 		if (n < 0)
 			return (-1);
 		cp += n;
 		if (cp + 2 * INT16SZ > eom)
 			return (-1);
 		ttype = ns_get16(cp); cp += INT16SZ;
 		tclass = ns_get16(cp); cp += INT16SZ;
 		if (ttype == type && tclass == class &&
 		    ns_samename(tname, name) == 1)
 			return (1);
 	}
 	return (0);
 }
 /* int
  * res_queriesmatch(buf1, eom1, buf2, eom2)
  *	is there a 1:1 mapping of (name,type,class)
  *	in (buf1,eom1) and (buf2,eom2)?
  * returns:
  *	-1 : format error
  *	0  : not a 1:1 mapping
  *	>0 : is a 1:1 mapping
  * author:
  *	paul vixie, 29may94
  */
 int
 res_queriesmatch(const u_char *buf1, const u_char *eom1,
 		 const u_char *buf2, const u_char *eom2)
 {
 	const u_char *cp = buf1 + HFIXEDSZ;
 	int qdcount = ntohs(((const HEADER*)(const void *)buf1)->qdcount);
 	if (buf1 + HFIXEDSZ > eom1 || buf2 + HFIXEDSZ > eom2)
 		return (-1);
 	/*
 	 * Only header section present in replies to
 	 * dynamic update packets.
 	 */
 	if ((((const HEADER *)(const void *)buf1)->opcode == ns_o_update) &&
 	    (((const HEADER *)(const void *)buf2)->opcode == ns_o_update))
 		return (1);
 	if (qdcount != ntohs(((const HEADER*)(const void *)buf2)->qdcount))
 		return (0);
 	while (qdcount-- > 0) {
 		char tname[MAXDNAME+1];
 		int n, ttype, tclass;
 		n = dn_expand(buf1, eom1, cp, tname, sizeof tname);
 		if (n < 0)
 			return (-1);
 		cp += n;
 		if (cp + 2 * INT16SZ > eom1)
 			return (-1);
 		ttype = ns_get16(cp);	cp += INT16SZ;
 		tclass = ns_get16(cp); cp += INT16SZ;
 		if (!res_nameinquery(tname, ttype, tclass, buf2, eom2))
 			return (0);
 	}
 	return (1);
 }
 int
 res_nsend(res_state statp,
 	  const u_char *buf, int buflen, u_char *ans, int anssiz)
 {
 	int gotsomewhere, terrno, try, v_circuit, resplen, ns, n;
 	char abuf[NI_MAXHOST];
 #if USE_RESOLV_CACHE
         struct resolv_cache*  cache;
         ResolvCacheStatus     cache_status = RESOLV_CACHE_UNSUPPORTED;
 #endif
 	if (statp->nscount == 0) {
 		errno = ESRCH;
 		return (-1);
 	}
 	if (anssiz < HFIXEDSZ) {
 		errno = EINVAL;
 		return (-1);
 	}
 	DprintQ((statp->options & RES_DEBUG) || (statp->pfcode & RES_PRF_QUERY),
 		(stdout, ";; res_send()\n"), buf, buflen);
 	v_circuit = (statp->options & RES_USEVC) || buflen > PACKETSZ;
 	gotsomewhere = 0;
 	terrno = ETIMEDOUT;
 #if USE_RESOLV_CACHE
         cache = __get_res_cache();
         if (cache != NULL) {
             int  anslen = 0;
             cache_status = _resolv_cache_lookup(
                                 cache, buf, buflen,
                                 ans, anssiz, &anslen);
             if (cache_status == RESOLV_CACHE_FOUND) {
                 return anslen;
             }
         }
 #endif
 	/*
 	 * If the ns_addr_list in the resolver context has changed, then
 	 * invalidate our cached copy and the associated timing data.
 	 */
 	if (EXT(statp).nscount != 0) {
 		int needclose = 0;
 		struct sockaddr_storage peer;
 		socklen_t peerlen;
 		if (EXT(statp).nscount != statp->nscount)
 			needclose++;
 		else
 			for (ns = 0; ns < statp->nscount; ns++) {
 				if (statp->nsaddr_list[ns].sin_family &&
 				    !sock_eq((struct sockaddr *)(void *)&statp->nsaddr_list[ns],
 					     (struct sockaddr *)(void *)&EXT(statp).ext->nsaddrs[ns])) {
 					needclose++;
 					break;
 				}
 				if (EXT(statp).nssocks[ns] == -1)
 					continue;
 				peerlen = sizeof(peer);
 				if (getsockname(EXT(statp).nssocks[ns],
 				    (struct sockaddr *)(void *)&peer, &peerlen) < 0) {
 					needclose++;
 					break;
 				}
 				if (!sock_eq((struct sockaddr *)(void *)&peer,
 				    get_nsaddr(statp, (size_t)ns))) {
 					needclose++;
 					break;
 				}
 			}
 		if (needclose) {
 			res_nclose(statp);
 			EXT(statp).nscount = 0;
 		}
 	}
 	/*
 	 * Maybe initialize our private copy of the ns_addr_list.
 	 */
 	if (EXT(statp).nscount == 0) {
 		for (ns = 0; ns < statp->nscount; ns++) {
 			EXT(statp).nstimes[ns] = RES_MAXTIME;
 			EXT(statp).nssocks[ns] = -1;
 			if (!statp->nsaddr_list[ns].sin_family)
 				continue;
 			EXT(statp).ext->nsaddrs[ns].sin =
 				 statp->nsaddr_list[ns];
 		}
 		EXT(statp).nscount = statp->nscount;
 	}
 	/*
 	 * Some resolvers want to even out the load on their nameservers.
 	 * Note that RES_BLAST overrides RES_ROTATE.
 	 */
 	if ((statp->options & RES_ROTATE) != 0U &&
 	    (statp->options & RES_BLAST) == 0U) {
 		union res_sockaddr_union inu;
 		struct sockaddr_in ina;
 		int lastns = statp->nscount - 1;
 		int fd;
 		u_int16_t nstime;
 		if (EXT(statp).ext != NULL)
 			inu = EXT(statp).ext->nsaddrs[0];
 		ina = statp->nsaddr_list[0];
 		fd = EXT(statp).nssocks[0];
 		nstime = EXT(statp).nstimes[0];
 		for (ns = 0; ns < lastns; ns++) {
 			if (EXT(statp).ext != NULL)
                                 EXT(statp).ext->nsaddrs[ns] =
 					EXT(statp).ext->nsaddrs[ns + 1];
 			statp->nsaddr_list[ns] = statp->nsaddr_list[ns + 1];
 			EXT(statp).nssocks[ns] = EXT(statp).nssocks[ns + 1];
 			EXT(statp).nstimes[ns] = EXT(statp).nstimes[ns + 1];
 		}
 		if (EXT(statp).ext != NULL)
 			EXT(statp).ext->nsaddrs[lastns] = inu;
 		statp->nsaddr_list[lastns] = ina;
 		EXT(statp).nssocks[lastns] = fd;
 		EXT(statp).nstimes[lastns] = nstime;
 	}
 	/*
 	 * Send request, RETRY times, or until successful.
 	 */
 	for (try = 0; try < statp->retry; try++) {
 	    for (ns = 0; ns < statp->nscount; ns++) {
 		struct sockaddr *nsap;
 		int nsaplen;
 		nsap = get_nsaddr(statp, (size_t)ns);
 		nsaplen = get_salen(nsap);
 		statp->_flags &= ~RES_F_LASTMASK;
 		statp->_flags |= (ns << RES_F_LASTSHIFT);
  same_ns:
 		if (statp->qhook) {
 			int done = 0, loops = 0;
 			do {
 				res_sendhookact act;
 				act = (*statp->qhook)(&nsap, &buf, &buflen,
 						      ans, anssiz, &resplen);
 				switch (act) {
 				case res_goahead:
 					done = 1;
 					break;
 				case res_nextns:
 					res_nclose(statp);
 					goto next_ns;
 				case res_done:
 					return (resplen);
 				case res_modified:
 					/* give the hook another try */
 					if (++loops < 42) /*doug adams*/
 						break;
 					/*FALLTHROUGH*/
 				case res_error:
 					/*FALLTHROUGH*/
 				default:
 					goto fail;
 				}
 			} while (!done);
 		}
 		Dprint(((statp->options & RES_DEBUG) &&
 			getnameinfo(nsap, (socklen_t)nsaplen, abuf, sizeof(abuf),
 				    NULL, 0, niflags) == 0),
 		       (stdout, ";; Querying server (# %d) address = %s\n",
 			ns + 1, abuf));
 		if (v_circuit) {
 			/* Use VC; at most one attempt per server. */
 			try = statp->retry;
 			n = send_vc(statp, buf, buflen, ans, anssiz, &terrno,
 				    ns);
 			if (n < 0)
 				goto fail;
 			if (n == 0)
 				goto next_ns;
 			resplen = n;
 		} else {
 			/* Use datagrams. */
 			n = send_dg(statp, buf, buflen, ans, anssiz, &terrno,
 				    ns, &v_circuit, &gotsomewhere);
 			if (n < 0)
 				goto fail;
 			if (n == 0)
 				goto next_ns;
 			if (v_circuit)
 				goto same_ns;
 			resplen = n;
 		}
 		Dprint((statp->options & RES_DEBUG) ||
 		       ((statp->pfcode & RES_PRF_REPLY) &&
 			(statp->pfcode & RES_PRF_HEAD1)),
 		       (stdout, ";; got answer:\n"));
 		DprintQ((statp->options & RES_DEBUG) ||
 			(statp->pfcode & RES_PRF_REPLY),
 			(stdout, "%s", ""),
 			ans, (resplen > anssiz) ? anssiz : resplen);
 #if USE_RESOLV_CACHE
                 if (cache_status == RESOLV_CACHE_NOTFOUND) {
                     _resolv_cache_add(cache, buf, buflen,
                                       ans, resplen);
                 }
 #endif
 		/*
 		 * If we have temporarily opened a virtual circuit,
 		 * or if we haven't been asked to keep a socket open,
 		 * close the socket.
 		 */
 		if ((v_circuit && (statp->options & RES_USEVC) == 0U) ||
 		    (statp->options & RES_STAYOPEN) == 0U) {
 			res_nclose(statp);
 		}
 		if (statp->rhook) {
 			int done = 0, loops = 0;
 			do {
 				res_sendhookact act;
 				act = (*statp->rhook)(nsap, buf, buflen,
 						      ans, anssiz, &resplen);
 				switch (act) {
 				case res_goahead:
 				case res_done:
 					done = 1;
 					break;
 				case res_nextns:
 					res_nclose(statp);
 					goto next_ns;
 				case res_modified:
 					/* give the hook another try */
 					if (++loops < 42) /*doug adams*/
 						break;
 					/*FALLTHROUGH*/
 				case res_error:
 					/*FALLTHROUGH*/
 				default:
 					goto fail;
 				}
 			} while (!done);
 		}
 		return (resplen);
  next_ns: ;
 	   } /*foreach ns*/
 	} /*foreach retry*/
 	res_nclose(statp);
 	if (!v_circuit) {
 		if (!gotsomewhere)
 			errno = ECONNREFUSED;	/* no nameservers found */
 		else
 			errno = ETIMEDOUT;	/* no answer obtained */
 	} else
 		errno = terrno;
 	return (-1);
  fail:
 	res_nclose(statp);
 	return (-1);
 }
 /* Private */
 static int
 get_salen(sa)
 	const struct sockaddr *sa;
 {
 #ifdef HAVE_SA_LEN
 	/* There are people do not set sa_len.  Be forgiving to them. */
 	if (sa->sa_len)
 		return (sa->sa_len);
 #endif
 	if (sa->sa_family == AF_INET)
 		return (sizeof(struct sockaddr_in));
 	else if (sa->sa_family == AF_INET6)
 		return (sizeof(struct sockaddr_in6));
 	else
 		return (0);	/* unknown, die on connect */
 }
 /*
  * pick appropriate nsaddr_list for use.  see res_init() for initialization.
  */
 static struct sockaddr *
 get_nsaddr(statp, n)
 	res_state statp;
 	size_t n;
 {
 	if (!statp->nsaddr_list[n].sin_family && EXT(statp).ext) {
 		/*
 		 * - EXT(statp).ext->nsaddrs[n] holds an address that is larger
 		 *   than struct sockaddr, and
 		 * - user code did not update statp->nsaddr_list[n].
 		 */
 		return (struct sockaddr *)(void *)&EXT(statp).ext->nsaddrs[n];
 	} else {
 		/*
 		 * - user code updated statp->nsaddr_list[n], or
 		 * - statp->nsaddr_list[n] has the same content as
 		 *   EXT(statp).ext->nsaddrs[n].
 		 */
 		return (struct sockaddr *)(void *)&statp->nsaddr_list[n];
 	}
 }
 static int
 send_vc(res_state statp,
 	const u_char *buf, int buflen, u_char *ans, int anssiz,
 	int *terrno, int ns)
 {
 	const HEADER *hp = (const HEADER *)(const void *)buf;
 	HEADER *anhp = (HEADER *)(void *)ans;
 	struct sockaddr *nsap;
 	int nsaplen;
 	int truncating, connreset, resplen, n;
 	struct iovec iov[2];
 	u_short len;
 	u_char *cp;
 	void *tmp;
 	nsap = get_nsaddr(statp, (size_t)ns);
 	nsaplen = get_salen(nsap);
 	connreset = 0;
  same_ns:
 	truncating = 0;
 	/* Are we still talking to whom we want to talk to? */
 	if (statp->_vcsock >= 0 && (statp->_flags & RES_F_VC) != 0) {
 		struct sockaddr_storage peer;
 		socklen_t size = sizeof peer;
 		if (getpeername(statp->_vcsock,
 				(struct sockaddr *)(void *)&peer, &size) < 0 ||
 		    !sock_eq((struct sockaddr *)(void *)&peer, nsap)) {
 			res_nclose(statp);
 			statp->_flags &= ~RES_F_VC;
 		}
 	}
 	if (statp->_vcsock < 0 || (statp->_flags & RES_F_VC) == 0) {
 		if (statp->_vcsock >= 0)
 			res_nclose(statp);
 		statp->_vcsock = socket(nsap->sa_family, SOCK_STREAM, 0);
 		if (statp->_vcsock > highestFD) {
 			res_nclose(statp);
 			errno = ENOTSOCK;
 		}
 		if (statp->_vcsock < 0) {
 			switch (errno) {
 			case EPROTONOSUPPORT:
 #ifdef EPFNOSUPPORT
 			case EPFNOSUPPORT:
 #endif
 			case EAFNOSUPPORT:
 				Perror(statp, stderr, "socket(vc)", errno);
 				return (0);
 			default:
 				*terrno = errno;
 				Perror(statp, stderr, "socket(vc)", errno);
 				return (-1);
 			}
 		}
 		errno = 0;
 		if (random_bind(statp->_vcsock,nsap->sa_family) < 0) {
 			*terrno = errno;
 			Aerror(statp, stderr, "bind/vc", errno, nsap,
 			    nsaplen);
 			res_nclose(statp);
 			return (0);
 		}
 		if (connect(statp->_vcsock, nsap, (socklen_t)nsaplen) < 0) {
 			*terrno = errno;
 			Aerror(statp, stderr, "connect/vc", errno, nsap,
 			    nsaplen);
 			res_nclose(statp);
 			return (0);
 		}
 		statp->_flags |= RES_F_VC;
 	}
 	/*
 	 * Send length & message
 	 */
 	ns_put16((u_short)buflen, (u_char*)(void *)&len);
 	iov[0] = evConsIovec(&len, INT16SZ);
 	DE_CONST(buf, tmp);
 	iov[1] = evConsIovec(tmp, (size_t)buflen);
 	if (writev(statp->_vcsock, iov, 2) != (INT16SZ + buflen)) {
 		*terrno = errno;
 		Perror(statp, stderr, "write failed", errno);
 		res_nclose(statp);
 		return (0);
 	}
 	/*
 	 * Receive length & response
 	 */
  read_len:
 	cp = ans;
 	len = INT16SZ;
 	while ((n = read(statp->_vcsock, (char *)cp, (size_t)len)) > 0) {
 		cp += n;
 		if ((len -= n) == 0)
 			break;
 	}
 	if (n <= 0) {
 		*terrno = errno;
 		Perror(statp, stderr, "read failed", errno);
 	  res_nclose(statp);
 		/*
 		 * A long running process might get its TCP
 		 * connection reset if the remote server was
 		 * restarted.  Requery the server instead of
 		 * trying a new one.  When there is only one
 		 * server, this means that a query might work
 		 * instead of failing.  We only allow one reset
 		 * per query to prevent looping.
 		 */
 		if (*terrno == ECONNRESET && !connreset) {
 			connreset = 1;
 			res_nclose(statp);
 			goto same_ns;
 		}
 		res_nclose(statp);
 		return (0);
 	}
 	resplen = ns_get16(ans);
 	if (resplen > anssiz) {
 		Dprint(statp->options & RES_DEBUG,
 		       (stdout, ";; response truncated\n")
 		       );
 		truncating = 1;
 		len = anssiz;
 	} else
 		len = resplen;
 	if (len < HFIXEDSZ) {
 		/*
 		 * Undersized message.
 		 */
 		Dprint(statp->options & RES_DEBUG,
 		       (stdout, ";; undersized: %d\n", len));
 		*terrno = EMSGSIZE;
 		res_nclose(statp);
 		return (0);
 	}
 	cp = ans;
 	while (len != 0 && (n = read(statp->_vcsock, (char *)cp, (size_t)len)) > 0){
 		cp += n;
 		len -= n;
 	}
 	if (n <= 0) {
 		*terrno = errno;
 		Perror(statp, stderr, "read(vc)", errno);
 		res_nclose(statp);
 		return (0);
 	}
 	if (truncating) {
 		/*
 		 * Flush rest of answer so connection stays in synch.
 		 */
 		anhp->tc = 1;
 		len = resplen - anssiz;
 		while (len != 0) {
 			char junk[PACKETSZ];
 			n = read(statp->_vcsock, junk,
 				 (len > sizeof junk) ? sizeof junk : len);
 			if (n > 0)
 				len -= n;
 			else
 				break;
 		}
 	}
 	/*
 	 * If the calling applicating has bailed out of
 	 * a previous call and failed to arrange to have
 	 * the circuit closed or the server has got
 	 * itself confused, then drop the packet and
 	 * wait for the correct one.
 	 */
 	if (hp->id != anhp->id) {
 		DprintQ((statp->options & RES_DEBUG) ||
 			(statp->pfcode & RES_PRF_REPLY),
 			(stdout, ";; old answer (unexpected):\n"),
 			ans, (resplen > anssiz) ? anssiz: resplen);
 		goto read_len;
 	}
 	/*
 	 * All is well, or the error is fatal.  Signal that the
 	 * next nameserver ought not be tried.
 	 */
 	return (resplen);
 }
 static int
 send_dg(res_state statp,
 	const u_char *buf, int buflen, u_char *ans, int anssiz,
 	int *terrno, int ns, int *v_circuit, int *gotsomewhere)
 {
 	const HEADER *hp = (const HEADER *)(const void *)buf;
 	HEADER *anhp = (HEADER *)(void *)ans;
 	const struct sockaddr *nsap;
 	int nsaplen;
 	struct timespec now, timeout, finish;
 	fd_set dsmask;
 	struct sockaddr_storage from;
 	socklen_t fromlen;
 	int resplen, seconds, n, s;
 	nsap = get_nsaddr(statp, (size_t)ns);
 	nsaplen = get_salen(nsap);
 	if (EXT(statp).nssocks[ns] == -1) {
 		EXT(statp).nssocks[ns] = socket(nsap->sa_family, SOCK_DGRAM, 0);
 		if (EXT(statp).nssocks[ns] > highestFD) {
 			res_nclose(statp);
 			errno = ENOTSOCK;
 		}
 		if (EXT(statp).nssocks[ns] < 0) {
 			switch (errno) {
 			case EPROTONOSUPPORT:
 #ifdef EPFNOSUPPORT
 			case EPFNOSUPPORT:
 #endif
 			case EAFNOSUPPORT:
 				Perror(statp, stderr, "socket(dg)", errno);
 				return (0);
 			default:
 				*terrno = errno;
 				Perror(statp, stderr, "socket(dg)", errno);
 				return (-1);
 			}
 		}
 #ifndef CANNOT_CONNECT_DGRAM
 		/*
 		 * On a 4.3BSD+ machine (client and server,
 		 * actually), sending to a nameserver datagram
 		 * port with no nameserver will cause an
 		 * ICMP port unreachable message to be returned.
 		 * If our datagram socket is "connected" to the
 		 * server, we get an ECONNREFUSED error on the next
 		 * socket operation, and select returns if the
 		 * error message is received.  We can thus detect
 		 * the absence of a nameserver without timing out.
 		 */
 		if (random_bind(EXT(statp).nssocks[ns], nsap->sa_family) < 0) {
 			Aerror(statp, stderr, "bind(dg)", errno, nsap,
 			    nsaplen);
 			res_nclose(statp);
 			return (0);
 		}
 		if (connect(EXT(statp).nssocks[ns], nsap, (socklen_t)nsaplen) < 0) {
 			Aerror(statp, stderr, "connect(dg)", errno, nsap,
 			    nsaplen);
 			res_nclose(statp);
 			return (0);
 		}
 #endif /* !CANNOT_CONNECT_DGRAM */
 		Dprint(statp->options & RES_DEBUG,
 		       (stdout, ";; new DG socket\n"))
 	}
 	s = EXT(statp).nssocks[ns];
 #ifndef CANNOT_CONNECT_DGRAM
 	if (send(s, (const char*)buf, (size_t)buflen, 0) != buflen) {
 		Perror(statp, stderr, "send", errno);
 		res_nclose(statp);
 		return (0);
 	}
 #else /* !CANNOT_CONNECT_DGRAM */
 	if (sendto(s, (const char*)buf, buflen, 0, nsap, nsaplen) != buflen)
 	{
 		Aerror(statp, stderr, "sendto", errno, nsap, nsaplen);
 		res_nclose(statp);
 		return (0);
 	}
 #endif /* !CANNOT_CONNECT_DGRAM */
 	/*
 	 * Wait for reply.
 	 */
 	seconds = (statp->retrans << ns);
 	if (ns > 0)
 		seconds /= statp->nscount;
 	if (seconds <= 0)
 		seconds = 1;
 	now = evNowTime();
 	timeout = evConsTime((long)seconds, 0L);
 	finish = evAddTime(now, timeout);
 	goto nonow;
  wait:
 	now = evNowTime();
  nonow:
 	FD_ZERO(&dsmask);
 	FD_SET(s, &dsmask);
 	if (evCmpTime(finish, now) > 0)
 		timeout = evSubTime(finish, now);
 	else
 		timeout = evConsTime(0L, 0L);
 	n = pselect(s + 1, &dsmask, NULL, NULL, &timeout, NULL);
 	if (n == 0) {
 		Dprint(statp->options & RES_DEBUG, (stdout, ";; timeout\n"));
 		*gotsomewhere = 1;
 		return (0);
 	}
 	if (n < 0) {
 		if (errno == EINTR)
 			goto wait;
 		Perror(statp, stderr, "select", errno);
 		res_nclose(statp);
 		return (0);
 	}
 	errno = 0;
 	fromlen = sizeof(from);
 	resplen = recvfrom(s, (char*)ans, (size_t)anssiz,0,
 			   (struct sockaddr *)(void *)&from, &fromlen);
 	if (resplen <= 0) {
 		Perror(statp, stderr, "recvfrom", errno);
 		res_nclose(statp);
 		return (0);
 	}
 	*gotsomewhere = 1;
 	if (resplen < HFIXEDSZ) {
 		/*
 		 * Undersized message.
 		 */
 		Dprint(statp->options & RES_DEBUG,
 		       (stdout, ";; undersized: %d\n",
 			resplen));
 		*terrno = EMSGSIZE;
 		res_nclose(statp);
 		return (0);
 	}
 	if (hp->id != anhp->id) {
 		/*
 		 * response from old query, ignore it.
 		 * XXX - potential security hazard could
 		 *	 be detected here.
 		 */
 		DprintQ((statp->options & RES_DEBUG) ||
 			(statp->pfcode & RES_PRF_REPLY),
 			(stdout, ";; old answer:\n"),
 			ans, (resplen > anssiz) ? anssiz : resplen);
 		goto wait;
 	}
 	if (!(statp->options & RES_INSECURE1) &&
 	    !res_ourserver_p(statp, (struct sockaddr *)(void *)&from)) {
 		/*
 		 * response from wrong server? ignore it.
 		 * XXX - potential security hazard could
 		 *	 be detected here.
 		 */
 		DprintQ((statp->options & RES_DEBUG) ||
 			(statp->pfcode & RES_PRF_REPLY),
 			(stdout, ";; not our server:\n"),
 			ans, (resplen > anssiz) ? anssiz : resplen);
 		goto wait;
 	}
 #ifdef RES_USE_EDNS0
 	if (anhp->rcode == FORMERR && (statp->options & RES_USE_EDNS0) != 0U) {
 		/*
 		 * Do not retry if the server do not understand EDNS0.
 		 * The case has to be captured here, as FORMERR packet do not
 		 * carry query section, hence res_queriesmatch() returns 0.
 		 */
 		DprintQ(statp->options & RES_DEBUG,
 			(stdout, "server rejected query with EDNS0:\n"),
 			ans, (resplen > anssiz) ? anssiz : resplen);
 		/* record the error */
 		statp->_flags |= RES_F_EDNS0ERR;
 		res_nclose(statp);
 		return (0);
 	}
 #endif
 	if (!(statp->options & RES_INSECURE2) &&
 	    !res_queriesmatch(buf, buf + buflen,
 			      ans, ans + anssiz)) {
 		/*
 		 * response contains wrong query? ignore it.
 		 * XXX - potential security hazard could
 		 *	 be detected here.
 		 */
 		DprintQ((statp->options & RES_DEBUG) ||
 			(statp->pfcode & RES_PRF_REPLY),
 			(stdout, ";; wrong query name:\n"),
 			ans, (resplen > anssiz) ? anssiz : resplen);
 		goto wait;
 	}
 	if (anhp->rcode == SERVFAIL ||
 	    anhp->rcode == NOTIMP ||
 	    anhp->rcode == REFUSED) {
 		DprintQ(statp->options & RES_DEBUG,
 			(stdout, "server rejected query:\n"),
 			ans, (resplen > anssiz) ? anssiz : resplen);
 		res_nclose(statp);
 		/* don't retry if called from dig */
 		if (!statp->pfcode)
 			return (0);
 	}
 	if (!(statp->options & RES_IGNTC) && anhp->tc) {
 		/*
 		 * To get the rest of answer,
 		 * use TCP with same server.
 		 */
 		Dprint(statp->options & RES_DEBUG,
 		       (stdout, ";; truncated answer\n"));
 		*v_circuit = 1;
 		res_nclose(statp);
 		return (1);
 	}
 	/*
 	 * All is well, or the error is fatal.  Signal that the
 	 * next nameserver ought not be tried.
 	 */
 	return (resplen);
 }
 static void
 Aerror(const res_state statp, FILE *file, const char *string, int error,
        const struct sockaddr *address, int alen)
 {
 	int save = errno;
 	char hbuf[NI_MAXHOST];
 	char sbuf[NI_MAXSERV];
 	alen = alen;
 	if ((statp->options & RES_DEBUG) != 0U) {
 		if (getnameinfo(address, (socklen_t)alen, hbuf, sizeof(hbuf),
 		    sbuf, sizeof(sbuf), niflags)) {
 			strncpy(hbuf, "?", sizeof(hbuf) - 1);
 			hbuf[sizeof(hbuf) - 1] = '\0';
 			strncpy(sbuf, "?", sizeof(sbuf) - 1);
 			sbuf[sizeof(sbuf) - 1] = '\0';
 		}
 		fprintf(file, "res_send: %s ([%s].%s): %s\n",
 			string, hbuf, sbuf, strerror(error));
 	}
 	errno = save;
 }
 static void
 Perror(const res_state statp, FILE *file, const char *string, int error) {
 	int save = errno;
 	if ((statp->options & RES_DEBUG) != 0U)
 		fprintf(file, "res_send: %s: %s\n",
 			string, strerror(error));
 	errno = save;
 }
 static int
 sock_eq(struct sockaddr *a, struct sockaddr *b) {
 	struct sockaddr_in *a4, *b4;
 	struct sockaddr_in6 *a6, *b6;
 	if (a->sa_family != b->sa_family)
 		return 0;
 	switch (a->sa_family) {
 	case AF_INET:
 		a4 = (struct sockaddr_in *)(void *)a;
 		b4 = (struct sockaddr_in *)(void *)b;
 		return a4->sin_port == b4->sin_port &&
 		    a4->sin_addr.s_addr == b4->sin_addr.s_addr;
 	case AF_INET6:
 		a6 = (struct sockaddr_in6 *)(void *)a;
 		b6 = (struct sockaddr_in6 *)(void *)b;
 		return a6->sin6_port == b6->sin6_port &&
 #ifdef HAVE_SIN6_SCOPE_ID
 		    a6->sin6_scope_id == b6->sin6_scope_id &&
 #endif
 		    IN6_ARE_ADDR_EQUAL(&a6->sin6_addr, &b6->sin6_addr);
 	default:
 		return 0;
 	}
 }
 #ifdef NEED_PSELECT
 /* XXX needs to move to the porting library. */
 static int
 pselect(int nfds, void *rfds, void *wfds, void *efds,
 	struct timespec *tsp, const sigset_t *sigmask)
 {
 	struct timeval tv, *tvp;
 	sigset_t sigs;
 	int n;
 	if (tsp) {
 		tvp = &tv;
 		tv = evTimeVal(*tsp);
 	} else
 		tvp = NULL;
 	if (sigmask)
 		sigprocmask(SIG_SETMASK, sigmask, &sigs);
 	n = select(nfds, rfds, wfds, efds, tvp);
 	if (sigmask)
 		sigprocmask(SIG_SETMASK, &sigs, NULL);
 	if (tsp)
 		*tsp = evTimeSpec(tv);
 	return (n);
 }
 #endif

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