source: rtems-libbsd/freebsd/lib/libc/resolv/res_send.c

#include <machine/rtems-bsd-user-space.h>

/*-
 * SPDX-License-Identifier: (ISC AND BSD-3-Clause)
 *
 * Portions Copyright (C) 2004-2009  Internet Systems Consortium, Inc. ("ISC")
 * Portions Copyright (C) 1996-2003  Internet Software Consortium.
 *
 * Permission to use, copy, modify, and/or 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.
 */

/*
 * 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. 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.
 */

#if defined(LIBC_SCCS) && !defined(lint)
static const char sccsid[] = "@(#)res_send.c    8.1 (Berkeley) 6/4/93";
static const char rcsid[] = "$Id: res_send.c,v 1.22 2009/01/22 23:49:23 tbox Exp $";
#endif /* LIBC_SCCS and not lint */
#include <sys/cdefs.h>
__FBSDID("$FreeBSD$");

/*! \file
 * \brief
 * Send query to name server and wait for reply.
 */

#include "port_before.h"
#if !defined(USE_KQUEUE) && !defined(USE_POLL)
#include "fd_setsize.h"
#endif

#include "namespace.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>
#include <resolv.h>
#include <signal.h>
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <unistd.h>

#include <isc/eventlib.h>

#include "port_after.h"

#ifdef USE_KQUEUE
#include <sys/event.h>
#else
#ifdef USE_POLL
#ifdef HAVE_STROPTS_H
#include <stropts.h>
#endif
#include <poll.h>
#endif /* USE_POLL */
#endif

#include "un-namespace.h"

/* Options.  Leave them on. */
#ifndef DEBUG
#define DEBUG
#endif
#include "res_debug.h"
#include "res_private.h"

#define EXT(res) ((res)->_u._ext)

#if !defined(USE_POLL) && !defined(USE_KQUEUE)
static const int highestFD = FD_SETSIZE - 1;
#endif

/* Forward. */

static int              get_salen(const struct sockaddr *);
static struct sockaddr * get_nsaddr(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,
#ifdef USE_KQUEUE
                                int kq,
#endif
                                const u_char *, int,
                                u_char *, int, 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 *);
#if defined(NEED_PSELECT) && !defined(USE_POLL) && !defined(USE_KQUEUE)
static int              pselect(int, void *, void *, void *,
                                struct timespec *,
                                const sigset_t *);
#endif
void res_pquery(const res_state, const u_char *, int, FILE *);

static const int niflags = NI_NUMERICHOST | NI_NUMERICSERV;

/* Public. */

/*%
 *      looks up "ina" in _res.ns_addr_list[]
 *
 * returns:
 *\li   0  : not found
 *\li   >0 : found
 *
 * author:
 *\li   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 *)sa;
                for (ns = 0;  ns < statp->nscount;  ns++) {
                        srv = (struct sockaddr_in *)get_nsaddr(statp, 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 *)sa;
                for (ns = 0;  ns < statp->nscount;  ns++) {
                        srv6 = (struct sockaddr_in6 *)get_nsaddr(statp, 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);
}

/*%
 *      look for (name,type,class) in the query section of packet (buf,eom)
 *
 * requires:
 *\li   buf + HFIXEDSZ <= eom
 *
 * returns:
 *\li   -1 : format error
 *\li   0  : not found
 *\li   >0 : found
 *
 * author:
 *\li   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*)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);
}

/*%
 *      is there a 1:1 mapping of (name,type,class)
 *      in (buf1,eom1) and (buf2,eom2)?
 *
 * returns:
 *\li   -1 : format error
 *\li   0  : not a 1:1 mapping
 *\li   >0 : is a 1:1 mapping
 *
 * author:
 *\li   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*)buf1)->qdcount);

        if (buf1 + HFIXEDSZ > eom1 || buf2 + HFIXEDSZ > eom2)
                return (-1);

        /*
         * Only header section present in replies to
         * dynamic update packets.
         */
        if ((((const HEADER *)buf1)->opcode == ns_o_update) &&
            (((const HEADER *)buf2)->opcode == ns_o_update))
                return (1);

        if (qdcount != ntohs(((const HEADER*)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, tries, v_circuit, resplen, ns, n;
#ifdef USE_KQUEUE
        int kq;
#endif
        char abuf[NI_MAXHOST];

        /* No name servers or res_init() failure */
        if (statp->nscount == 0 || EXT(statp).ext == NULL) {
                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;

#ifdef USE_KQUEUE
        if ((kq = kqueue()) < 0) {
                Perror(statp, stderr, "kqueue", errno);
                return (-1);
        }
#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;
                ISC_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 *)&statp->nsaddr_list[ns],
                                             (struct sockaddr *)&EXT(statp).ext->nsaddrs[ns])) {
                                        needclose++;
                                        break;
                                }

                                if (EXT(statp).nssocks[ns] == -1)
                                        continue;
                                peerlen = sizeof(peer);
                                if (_getpeername(EXT(statp).nssocks[ns],
                                    (struct sockaddr *)&peer, &peerlen) < 0) {
                                        needclose++;
                                        break;
                                }
                                if (!sock_eq((struct sockaddr *)&peer,
                                    get_nsaddr(statp, 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 (tries = 0; tries < statp->retry; tries++) {
            for (ns = 0; ns < statp->nscount; ns++) {
                struct sockaddr *nsap;
                int nsaplen;
                nsap = get_nsaddr(statp, 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:
#ifdef USE_KQUEUE
                                        _close(kq);
#endif
                                        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, 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. */
                        tries = 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,
#ifdef USE_KQUEUE
                                    kq,
#endif
                                    buf, buflen, ans, anssiz, &terrno,
                                    ns, tries, &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 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);

                }
#ifdef USE_KQUEUE
                _close(kq);
#endif
                return (resplen);
 next_ns: ;
           } /*foreach ns*/
        } /*foreach retry*/
        res_nclose(statp);
#ifdef USE_KQUEUE
        _close(kq);
#endif
        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);
#ifdef USE_KQUEUE
        _close(kq);
#endif
        return (-1);
}

/* Private */

static int
get_salen(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(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 *) buf;
        HEADER *anhp = (HEADER *) ans;
        struct sockaddr *nsap;
        int nsaplen;
        int truncating, connreset, resplen, n;
        struct iovec iov[2];
        u_short len;
        u_char *cp;
        void *tmp;
#ifdef SO_NOSIGPIPE
        int on = 1;
#endif

        nsap = get_nsaddr(statp, 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;
                ISC_SOCKLEN_T size = sizeof peer;

                if (_getpeername(statp->_vcsock,
                                (struct sockaddr *)&peer, &size) < 0 ||
                    !sock_eq((struct sockaddr *)&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 |
                    SOCK_CLOEXEC, 0);
#if !defined(USE_POLL) && !defined(USE_KQUEUE)
                if (statp->_vcsock > highestFD) {
                        res_nclose(statp);
                        errno = ENOTSOCK;
                }
#endif
                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);
                        }
                }
#ifdef SO_NOSIGPIPE
                /*
                 * Disable generation of SIGPIPE when writing to a closed
                 * socket.  Write should return -1 and set errno to EPIPE
                 * instead.
                 *
                 * Push on even if setsockopt(SO_NOSIGPIPE) fails.
                 */
                (void)_setsockopt(statp->_vcsock, SOL_SOCKET, SO_NOSIGPIPE, &on,
                                 sizeof(on));
#endif
                errno = 0;
                if (_connect(statp->_vcsock, nsap, 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*)&len);
        iov[0] = evConsIovec(&len, INT16SZ);
        DE_CONST(buf, tmp);
        iov[1] = evConsIovec(tmp, 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, (int)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, (int)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,
#ifdef USE_KQUEUE
        int kq,
#endif
        const u_char *buf, int buflen, u_char *ans,
        int anssiz, int *terrno, int ns, int tries, int *v_circuit,
        int *gotsomewhere)
{
        const HEADER *hp = (const HEADER *) buf;
        HEADER *anhp = (HEADER *) ans;
        const struct sockaddr *nsap;
        int nsaplen;
        struct timespec now, timeout, finish;
        struct sockaddr_storage from;
        ISC_SOCKLEN_T fromlen;
        int resplen, seconds, n, s;
#ifdef USE_KQUEUE
        struct kevent kv;
#else
#ifdef USE_POLL
        int     polltimeout;
        struct pollfd   pollfd;
#else
        fd_set dsmask;
#endif
#endif

        nsap = get_nsaddr(statp, ns);
        nsaplen = get_salen(nsap);
        if (EXT(statp).nssocks[ns] == -1) {
                EXT(statp).nssocks[ns] = _socket(nsap->sa_family,
                    SOCK_DGRAM | SOCK_CLOEXEC, 0);
#if !defined(USE_POLL) && !defined(USE_KQUEUE)
                if (EXT(statp).nssocks[ns] > highestFD) {
                        res_nclose(statp);
                        errno = ENOTSOCK;
                }
#endif
                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.
                 *
                 * When the option "insecure1" is specified, we'd
                 * rather expect to see responses from an "unknown"
                 * address.  In order to let the kernel accept such
                 * responses, do not connect the socket here.
                 * XXX: or do we need an explicit option to disable
                 * connecting?
                 */
                if (!(statp->options & RES_INSECURE1) &&
                    _connect(EXT(statp).nssocks[ns], nsap, 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 (statp->options & RES_INSECURE1) {
                if (_sendto(s,
                    (const char*)buf, buflen, 0, nsap, nsaplen) != buflen) {
                        Aerror(statp, stderr, "sendto", errno, nsap, nsaplen);
                        res_nclose(statp);
                        return (0);
                }
        } else if (send(s, (const char*)buf, 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 << tries);
        if (ns > 0)
                seconds /= statp->nscount;
        if (seconds <= 0)
                seconds = 1;
        now = evNowTime();
        timeout = evConsTime(seconds, 0);
        finish = evAddTime(now, timeout);
        goto nonow;
 wait:
        now = evNowTime();
 nonow:
#ifndef USE_POLL
        if (evCmpTime(finish, now) > 0)
                timeout = evSubTime(finish, now);
        else
                timeout = evConsTime(0, 0);
#ifdef USE_KQUEUE
        EV_SET(&kv, s, EVFILT_READ, EV_ADD | EV_ONESHOT, 0, 0, 0);
        n = _kevent(kq, &kv, 1, &kv, 1, &timeout);
#else
        FD_ZERO(&dsmask);
        FD_SET(s, &dsmask);
        n = pselect(s + 1, &dsmask, NULL, NULL, &timeout, NULL);
#endif
#else
        timeout = evSubTime(finish, now);
        if (timeout.tv_sec < 0)
                timeout = evConsTime(0, 0);
        polltimeout = 1000*timeout.tv_sec +
                timeout.tv_nsec/1000000;
        pollfd.fd = s;
        pollfd.events = POLLRDNORM;
        n = _poll(&pollfd, 1, polltimeout);
#endif /* USE_POLL */

        if (n == 0) {
                Dprint(statp->options & RES_DEBUG, (stdout, ";; timeout\n"));
                *gotsomewhere = 1;
                return (0);
        }
        if (n < 0) {
                if (errno == EINTR)
                        goto wait;
#ifdef USE_KQUEUE
                Perror(statp, stderr, "kevent", errno);
#else
#ifndef USE_POLL
                Perror(statp, stderr, "select", errno);
#else
                Perror(statp, stderr, "poll", errno);
#endif /* USE_POLL */
#endif
                res_nclose(statp);
                return (0);
        }
#ifdef USE_KQUEUE
        if (kv.ident != s)
                goto wait;
#endif
        errno = 0;
        fromlen = sizeof(from);
        resplen = _recvfrom(s, (char*)ans, anssiz,0,
                           (struct sockaddr *)&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 *)&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];

        if ((statp->options & RES_DEBUG) != 0U) {
                if (getnameinfo(address, 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 *)a;
                b4 = (struct sockaddr_in *)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 *)a;
                b6 = (struct sockaddr_in6 *)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;
        }
}

#if defined(NEED_PSELECT) && !defined(USE_POLL) && !defined(USE_KQUEUE)
/* 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