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res_send.c

/*
 * 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.
 * 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.
 */

/*
 * 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 INTERNET SOFTWARE CONSORTIUM DISCLAIMS
 * ALL WARRANTIES WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES
 * OF MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL INTERNET SOFTWARE
 * CONSORTIUM 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[] = "$BINDId: res_send.c,v 8.38 2000/03/30 20:16:51 vixie Exp $";
#endif /* LIBC_SCCS and not lint */

/*
 * 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>
#ifdef _LIBC
#include <sys/poll.h>
#endif

#include <netinet/in.h>
#include <arpa/nameser.h>
#include <arpa/inet.h>
#include <sys/ioctl.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>

#if PACKETSZ > 65536
#define MAXPACKET       PACKETSZ
#else
#define MAXPACKET       65536
#endif

#ifndef _LIBC
#include <isc/eventlib.h>
#else

/* From ev_streams.c.  */

static inline struct iovec
evConsIovec(void *buf, size_t cnt) {
      struct iovec ret;

      memset(&ret, 0xf5, sizeof ret);
      ret.iov_base = buf;
      ret.iov_len = cnt;
      return (ret);
}

/* From ev_timers.c.  */

#define BILLION 1000000000

static inline struct timespec
evTimeSpec(struct timeval tv) {
        struct timespec ts;

        ts.tv_sec = tv.tv_sec;
        ts.tv_nsec = tv.tv_usec * 1000;
        return (ts);
}

static inline struct timespec
evConsTime(time_t sec, long nsec) {
      struct timespec x;

      x.tv_sec = sec;
      x.tv_nsec = nsec;
      return (x);
}

static inline struct timespec
evAddTime(struct timespec addend1, struct timespec addend2) {
      struct timespec x;

      x.tv_sec = addend1.tv_sec + addend2.tv_sec;
      x.tv_nsec = addend1.tv_nsec + addend2.tv_nsec;
      if (x.tv_nsec >= BILLION) {
            x.tv_sec++;
            x.tv_nsec -= BILLION;
      }
      return (x);
}

static inline struct timespec
evSubTime(struct timespec minuend, struct timespec subtrahend) {
      struct timespec x;

      x.tv_sec = minuend.tv_sec - subtrahend.tv_sec;
      if (minuend.tv_nsec >= subtrahend.tv_nsec)
            x.tv_nsec = minuend.tv_nsec - subtrahend.tv_nsec;
      else {
            x.tv_nsec = BILLION - subtrahend.tv_nsec + minuend.tv_nsec;
            x.tv_sec--;
      }
      return (x);
}

static inline int
evCmpTime(struct timespec a, struct timespec b) {
      long x = a.tv_sec - b.tv_sec;

      if (x == 0L)
            x = a.tv_nsec - b.tv_nsec;
      return (x < 0L ? (-1) : x > 0L ? (1) : (0));
}

static inline struct timespec
evNowTime() {
      struct timeval now;

      if (gettimeofday(&now, NULL) < 0)
            return (evConsTime(0, 0));
      return (evTimeSpec(now));
}

#endif

/* Options.  Leave them on. */
/* #undef DEBUG */
#include "res_debug.h"

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

#ifndef _LIBC
static const int highestFD = FD_SETSIZE - 1;
#endif

/* Forward. */

static int        send_vc(res_state, const u_char *, int,
                        u_char **, int *, int *, int, u_char **);
static int        send_dg(res_state, const u_char *, int,
                        u_char **, int *, int *, int,
                        int *, int *, u_char **);
#ifdef DEBUG
static void       Aerror(const res_state, FILE *, const char *, int,
                         struct sockaddr_in);
static void       Perror(const res_state, FILE *, const char *, int);
#endif
#ifdef _LIBC
static int        sock_eq(struct sockaddr_in6 *, struct sockaddr_in6 *);
#else
static int        sock_eq(struct sockaddr_in *, struct sockaddr_in *);
#endif
#ifdef NEED_PSELECT
static int        pselect(int, void *, void *, void *,
                        struct timespec *,
                        const sigset_t *);
#endif

/* Reachover. */

#ifdef _LIBC
static void convaddr4to6(struct sockaddr_in6 *sa);
#endif
void res_pquery(const res_state, const u_char *, int, FILE *);

/* Public. */

/* int
 * res_isourserver(ina)
 *    looks up "ina" in _res.ns_addr_list[]
 * returns:
 *    0  : not found
 *    >0 : found
 * author:
 *    paul vixie, 29may94
 */
int
#ifdef _LIBC
res_ourserver_p(const res_state statp, const struct sockaddr_in6 *inp)
#else
res_ourserver_p(const res_state statp, const struct sockaddr_in *inp)
#endif
{
      int ns;

#ifdef _LIBC
        if (inp->sin6_family == AF_INET) {
            struct sockaddr_in *in4p = (struct sockaddr_in *) inp;
          in_port_t port = in4p->sin_port;
          in_addr_t addr = in4p->sin_addr.s_addr;

            for (ns = 0;  ns < MAXNS;  ns++) {
                const struct sockaddr_in *srv =
                (struct sockaddr_in *)EXT(statp).nsaddrs[ns];

                if ((srv != NULL) && (srv->sin_family == AF_INET) &&
                    (srv->sin_port == port) &&
                    (srv->sin_addr.s_addr == INADDR_ANY ||
                     srv->sin_addr.s_addr == addr))
                    return (1);
            }
        } else if (inp->sin6_family == AF_INET6) {
            for (ns = 0;  ns < MAXNS;  ns++) {
                const struct sockaddr_in6 *srv = EXT(statp).nsaddrs[ns];
                if ((srv != NULL) && (srv->sin6_family == AF_INET6) &&
                    (srv->sin6_port == inp->sin6_port) &&
                    !(memcmp(&srv->sin6_addr, &in6addr_any,
                             sizeof (struct in6_addr)) &&
                      memcmp(&srv->sin6_addr, &inp->sin6_addr,
                             sizeof (struct in6_addr))))
                    return (1);
            }
        }
#else
      struct sockaddr_in ina = *inp;
      for (ns = 0; ns < statp->nscount; ns++) {
            const struct sockaddr_in *srv = &statp->nsaddr_list[ns];

            if (srv->sin_family == ina.sin_family &&
                srv->sin_port == ina.sin_port &&
                (srv->sin_addr.s_addr == INADDR_ANY ||
                 srv->sin_addr.s_addr == ina.sin_addr.s_addr))
                  return (1);
      }
#endif
      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(((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);
}

/* 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(((HEADER*)buf1)->qdcount);

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

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

      if (qdcount != ntohs(((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
__libc_res_nsend(res_state statp, const u_char *buf, int buflen,
             u_char *ans, int anssiz, u_char **ansp)
{
      int gotsomewhere, terrno, try, v_circuit, resplen, ns, n;

      if (statp->nscount == 0) {
            __set_errno (ESRCH);
            return (-1);
      }

      if (anssiz < HFIXEDSZ) {
            __set_errno (EINVAL);
            return (-1);
      }

      if ((statp->qhook || statp->rhook) && anssiz < MAXPACKET && ansp) {
            u_char *buf = malloc (MAXPACKET);
            if (buf == NULL)
                  return (-1);
            memcpy (buf, ans, HFIXEDSZ);
            *ansp = buf;
            ans = buf;
            anssiz = MAXPACKET;
      }

      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 the ns_addr_list in the resolver context has changed, then
       * invalidate our cached copy and the associated timing data.
       */
      if (EXT(statp).nsinit) {
            int needclose = 0;

            if (EXT(statp).nscount != statp->nscount)
                  needclose++;
            else
#ifdef _LIBC
                  for (ns = 0; ns < MAXNS; ns++) {
                        unsigned int map = EXT(statp).nsmap[ns];
                        if (map < MAXNS
                            && !sock_eq((struct sockaddr_in6 *)
                                    &statp->nsaddr_list[map],
                                    EXT(statp).nsaddrs[ns]))
#else
                  for (ns = 0; ns < statp->nscount; ns++) {
                        if (!sock_eq(&statp->nsaddr_list[ns],
                                   &EXT(statp).nsaddrs[ns]))
#endif
                        {
                              needclose++;
                              break;
                        }
                  }
            if (needclose)
                  res_nclose(statp);
      }

      /*
       * Maybe initialize our private copy of the ns_addr_list.
       */
      if (EXT(statp).nsinit == 0) {
#ifdef _LIBC
            unsigned char map[MAXNS];

            memset (map, MAXNS, sizeof (map));
            for (n = 0; n < MAXNS; n++) {
                  ns = EXT(statp).nsmap[n];
                  if (ns < statp->nscount)
                        map[ns] = n;
                  else if (ns < MAXNS) {
                        free(EXT(statp).nsaddrs[n]);
                        EXT(statp).nsaddrs[n] = NULL;
                        EXT(statp).nsmap[n] = MAXNS;
                  }
            }
            n = statp->nscount;
            if (statp->nscount > EXT(statp).nscount)
                  for (n = EXT(statp).nscount, ns = 0;
                       n < statp->nscount; n++) {
                        while (ns < MAXNS
                               && EXT(statp).nsmap[ns] != MAXNS)
                              ns++;
                        if (ns == MAXNS)
                              break;
                        EXT(statp).nsmap[ns] = n;
                        map[n] = ns++;
                  }
            EXT(statp).nscount = n;
            for (ns = 0; ns < EXT(statp).nscount; ns++) {
                  n = map[ns];
                  if (EXT(statp).nsaddrs[n] == NULL)
                        EXT(statp).nsaddrs[n] =
                            malloc(sizeof (struct sockaddr_in6));
                  if (EXT(statp).nsaddrs[n] != NULL) {
                        memcpy(EXT(statp).nsaddrs[n],
                               &statp->nsaddr_list[ns],
                               sizeof (struct sockaddr_in));
                        EXT(statp).nssocks[n] = -1;
                        n++;
                  }
            }
#else
            for (ns = 0; ns < statp->nscount; ns++) {
                  EXT(statp).nsaddrs[ns] = statp->nsaddr_list[ns];
                  EXT(statp).nssocks[ns] = -1;
            }
            EXT(statp).nscount = ns;
#endif
            EXT(statp).nsinit = 1;
      }

      /*
       * Some resolvers want to even out the load on their nameservers.
       * Note that RES_BLAST overrides RES_ROTATE.
       */
      if ((statp->options & RES_ROTATE) != 0 &&
          (statp->options & RES_BLAST) == 0) {
#ifdef _LIBC
            struct sockaddr_in6 *ina;
            unsigned int map;

            n = 0;
            while (n < MAXNS && EXT(statp).nsmap[n] == MAXNS)
                  n++;
            if (n < MAXNS) {
                  ina = EXT(statp).nsaddrs[n];
                  map = EXT(statp).nsmap[n];
                  for (;;) {
                        ns = n + 1;
                        while (ns < MAXNS
                               && EXT(statp).nsmap[ns] == MAXNS)
                              ns++;
                        if (ns == MAXNS)
                              break;
                        EXT(statp).nsaddrs[n] = EXT(statp).nsaddrs[ns];
                        EXT(statp).nsmap[n] = EXT(statp).nsmap[ns];
                        n = ns;
                  }
                  EXT(statp).nsaddrs[n] = ina;
                  EXT(statp).nsmap[n] = map;
            }
#else
            struct sockaddr_in ina;
            int lastns = statp->nscount - 1;

            ina = statp->nsaddr_list[0];
            for (ns = 0; ns < lastns; ns++)
                  statp->nsaddr_list[ns] = statp->nsaddr_list[ns + 1];
            statp->nsaddr_list[lastns] = ina;
#endif
      }

      /*
       * Send request, RETRY times, or until successful.
       */
      for (try = 0; try < statp->retry; try++) {
#ifdef _LIBC
          for (ns = 0; ns < MAXNS; ns++)
#else
          for (ns = 0; ns < statp->nscount; ns++)
#endif
          {
#ifdef _LIBC
            struct sockaddr_in6 *nsap = EXT(statp).nsaddrs[ns];

            if (nsap == NULL)
                  goto next_ns;
#else
            struct sockaddr_in *nsap = &statp->nsaddr_list[ns];
#endif
 same_ns:
            if (statp->qhook) {
                  int done = 0, loops = 0;

                  do {
                        res_sendhookact act;

#ifdef _LIBC
                        act = (*statp->qhook)((struct sockaddr_in **)
                                          &nsap, &buf, &buflen,
                                          ans, anssiz, &resplen);
#else
                        act = (*statp->qhook)(&nsap, &buf, &buflen,
                                          ans, anssiz, &resplen);
#endif
                        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:
                              return (-1);
                        }
                  } while (!done);
            }

            Dprint(statp->options & RES_DEBUG,
                   (stdout, ";; Querying server (# %d) address = %s\n",
                  ns + 1, inet_ntoa(nsap->sin_addr)));

            if (v_circuit) {
                  /* Use VC; at most one attempt per server. */
                  try = statp->retry;
                  n = send_vc(statp, buf, buflen, &ans, &anssiz, &terrno,
                            ns, ansp);
                  if (n < 0)
                        return (-1);
                  if (n == 0)
                        goto next_ns;
                  resplen = n;
            } else {
                  /* Use datagrams. */
                  n = send_dg(statp, buf, buflen, &ans, &anssiz, &terrno,
                            ns, &v_circuit, &gotsomewhere, ansp);
                  if (n < 0)
                        return (-1);
                  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, ""),
                  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) == 0) ||
                (statp->options & RES_STAYOPEN) == 0) {
                  res_nclose(statp);
            }
            if (statp->rhook) {
                  int done = 0, loops = 0;

                  do {
                        res_sendhookact act;

#ifdef _LIBC
                        act = (*statp->rhook)((struct sockaddr_in *)
                                          nsap, buf, buflen,
                                          ans, anssiz, &resplen);
#else
                        act = (*statp->rhook)(nsap, buf, buflen,
                                          ans, anssiz, &resplen);
#endif
                        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:
                              return (-1);
                        }
                  } while (!done);

            }
            return (resplen);
 next_ns: ;
         } /*foreach ns*/
      } /*foreach retry*/
      res_nclose(statp);
      if (!v_circuit) {
            if (!gotsomewhere)
                  __set_errno (ECONNREFUSED);   /* no nameservers found */
            else
                  __set_errno (ETIMEDOUT);      /* no answer obtained */
      } else
            __set_errno (terrno);
      return (-1);
}

int
res_nsend(res_state statp,
        const u_char *buf, int buflen, u_char *ans, int anssiz)
{
      return __libc_res_nsend(statp, buf, buflen, ans, anssiz, NULL);
}

/* Private */

static int
send_vc(res_state statp,
      const u_char *buf, int buflen, u_char **ansp, int *anssizp,
      int *terrno, int ns, u_char **anscp)
{
      const HEADER *hp = (HEADER *) buf;
      u_char *ans = *ansp;
      int anssiz = *anssizp;
      HEADER *anhp = (HEADER *) ans;
#ifdef _LIBC
      struct sockaddr_in6 *nsap = EXT(statp).nsaddrs[ns];
#else
      struct sockaddr_in *nsap = &statp->nsaddr_list[ns];
#endif
      int truncating, connreset, resplen, n;
      struct iovec iov[2];
      u_short len;
      u_char *cp;

      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) {
#ifdef _LIBC
            struct sockaddr_in6 peer;
#else
            struct sockaddr_in peer;
#endif
            int size = sizeof peer;

            if (getpeername(statp->_vcsock,
                        (struct sockaddr *)&peer, &size) < 0 ||
                !sock_eq(&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);

#ifdef _LIBC
            statp->_vcsock = socket(nsap->sin6_family, SOCK_STREAM, 0);
#else
            statp->_vcsock = socket(PF_INET, SOCK_STREAM, 0);
            if (statp->_vcsock > highestFD) {
                  res_nclose(statp);
                  __set_errno (ENOTSOCK);
            }
#endif
            if (statp->_vcsock < 0) {
                  *terrno = errno;
                  Perror(statp, stderr, "socket(vc)", errno);
                  return (-1);
            }
            __set_errno (0);
            if (connect(statp->_vcsock, (struct sockaddr *)nsap,
                      sizeof *nsap) < 0) {
                  *terrno = errno;
                  Aerror(statp, stderr, "connect/vc", errno, *nsap);
                  res_nclose(statp);
                  return (0);
            }
            statp->_flags |= RES_F_VC;
      }

      /*
       * Send length & message
       */
      putshort((u_short)buflen, (u_char*)&len);
      iov[0] = evConsIovec(&len, INT16SZ);
      iov[1] = evConsIovec((void*)buf, 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) {
            if (anscp) {
                  ans = malloc (MAXPACKET);
                  if (ans == NULL) {
                        *terrno = ENOMEM;
                        res_nclose(statp);
                        return (0);
                  }
                  anssiz = MAXPACKET;
                  *anssizp = MAXPACKET;
                  *ansp = ans;
                  *anscp = ans;
                  anhp = (HEADER *) ans;
                  len = resplen;
            } else {
                  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,
      const u_char *buf, int buflen, u_char **ansp, int *anssizp,
      int *terrno, int ns, int *v_circuit, int *gotsomewhere, u_char **anscp)
{
      const HEADER *hp = (HEADER *) buf;
      u_char *ans = *ansp;
      int anssiz = *anssizp;
      HEADER *anhp = (HEADER *) ans;
#ifdef _LIBC
      struct sockaddr_in6 *nsap = EXT(statp).nsaddrs[ns];
#else
      const struct sockaddr_in *nsap = &statp->nsaddr_list[ns];
#endif
      struct timespec now, timeout, finish;
#ifdef _LIBC
      struct pollfd pfd[1];
        int ptimeout;
      struct sockaddr_in6 from;
      static int socket_pf = 0;
#else
      fd_set dsmask;
      struct sockaddr_in from;
#endif
      int fromlen, resplen, seconds, n, s;

      if (EXT(statp).nssocks[ns] == -1) {
#ifdef _LIBC
            /* only try IPv6 if IPv6 NS and if not failed before */
            if ((EXT(statp).nscount6 > 0) && (socket_pf != PF_INET)) {
                  EXT(statp).nssocks[ns] =
                      socket(PF_INET6, SOCK_DGRAM, 0);
                  socket_pf = EXT(statp).nssocks[ns] < 0 ? PF_INET
                                                         : PF_INET6;
            }
            if (EXT(statp).nssocks[ns] < 0)
                  EXT(statp).nssocks[ns] = socket(PF_INET, SOCK_DGRAM, 0);
#else
            EXT(statp).nssocks[ns] = socket(PF_INET, SOCK_DGRAM, 0);
            if (EXT(statp).nssocks[ns] > highestFD) {
                  res_nclose(statp);
                  __set_errno (ENOTSOCK);
            }
#endif
            if (EXT(statp).nssocks[ns] < 0) {
                  *terrno = errno;
                  Perror(statp, stderr, "socket(dg)", errno);
                  return (-1);
            }
#ifndef CANNOT_CONNECT_DGRAM
#ifdef _LIBC
            /* If IPv6 socket and nsap is IPv4, make it IPv4-mapped */
            if ((socket_pf == PF_INET6) && (nsap->sin6_family == AF_INET))
                  convaddr4to6(nsap);
#endif
            /*
             * 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 (connect(EXT(statp).nssocks[ns], (struct sockaddr *)nsap,
                      sizeof *nsap) < 0) {
                  Aerror(statp, stderr, "connect(dg)", errno, *nsap);
                  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, (char*)buf, buflen, 0) != buflen) {
            Perror(statp, stderr, "send", errno);
            res_nclose(statp);
            return (0);
      }
#else /* !CANNOT_CONNECT_DGRAM */
#ifdef _LIBC
      /* If IPv6 socket and nsap is IPv4, make it IPv4-mapped */
      if ((socket_pf == PF_INET6) && (nsap->sin6_family == AF_INET))
            convaddr4to6(nsap);
#endif
      if (sendto(s, (char*)buf, buflen, 0,
               (struct sockaddr *)nsap, sizeof *nsap) != buflen)
      {
            Aerror(statp, stderr, "sendto", errno, *nsap);
            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(seconds, 0);
      finish = evAddTime(now, timeout);
 wait:
#ifdef _LIBC
        /* Convert struct timespec in milliseconds.  */
      ptimeout = timeout.tv_sec * 1000 + timeout.tv_nsec / 1000000;

      pfd[0].fd = s;
      pfd[0].events = POLLIN;
      n = __poll (pfd, 1, ptimeout);
#else
      FD_ZERO(&dsmask);
      FD_SET(s, &dsmask);
      n = pselect(s + 1, &dsmask, NULL, NULL, &timeout, NULL);
#endif
      if (n == 0) {
            Dprint(statp->options & RES_DEBUG, (stdout, ";; timeout\n"));
            *gotsomewhere = 1;
            return (0);
      }
      if (n < 0) {
            if (errno == EINTR) {
                  now = evNowTime();
                  if (evCmpTime(finish, now) > 0) {
                        timeout = evSubTime(finish, now);
                        goto wait;
                  }
            }
            Perror(statp, stderr, "select", errno);
            res_nclose(statp);
            return (0);
      }
      __set_errno (0);
#ifdef _LIBC
      fromlen = sizeof(struct sockaddr_in6);
#else
      fromlen = sizeof(struct sockaddr_in);
#endif
      if (anssiz < MAXPACKET
          && anscp
          && (ioctl (s, FIONREAD, &resplen) < 0
            || anssiz < resplen)) {
            ans = malloc (MAXPACKET);
            if (ans == NULL)
                  ans = *ansp;
            else {
                  anssiz = MAXPACKET;
                  *anssizp = MAXPACKET;
                  *ansp = ans;
                  *anscp = ans;
                  anhp = (HEADER *) ans;
            }
      }
      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, &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;
      }
      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);
}

#ifdef DEBUG
static void
Aerror(const res_state statp, FILE *file, const char *string, int error,
       struct sockaddr_in address)
{
      int save = errno;

      if ((statp->options & RES_DEBUG) != 0) {
            char tmp[sizeof "255.255.255.255"];

            fprintf(file, "res_send: %s ([%s].%u): %s\n",
                  string,
                  inet_ntop(address.sin_family, &address.sin_addr,
                          tmp, sizeof tmp),
                  ntohs(address.sin_port),
                  strerror(error));
      }
      __set_errno (save);
}

static void
Perror(const res_state statp, FILE *file, const char *string, int error) {
      int save = errno;

      if ((statp->options & RES_DEBUG) != 0)
            fprintf(file, "res_send: %s: %s\n",
                  string, strerror(error));
      __set_errno (save);
}
#endif

static int
#ifdef _LIBC
sock_eq(struct sockaddr_in6 *a1, struct sockaddr_in6 *a2) {
      if (a1->sin6_family == a2->sin6_family) {
            if (a1->sin6_family == AF_INET)
                  return ((((struct sockaddr_in *)a1)->sin_port ==
                         ((struct sockaddr_in *)a2)->sin_port) &&
                        (((struct sockaddr_in *)a1)->sin_addr.s_addr ==
                         ((struct sockaddr_in *)a2)->sin_addr.s_addr));
            else
                  return ((a1->sin6_port == a2->sin6_port) &&
                        !memcmp(&a1->sin6_addr, &a2->sin6_addr,
                              sizeof (struct in6_addr)));
      }
      if (a1->sin6_family == AF_INET) {
            struct sockaddr_in6 *sap = a1;
            a1 = a2;
            a2 = sap;
      } /* assumes that AF_INET and AF_INET6 are the only possibilities */
      return ((a1->sin6_port == ((struct sockaddr_in *)a2)->sin_port) &&
            IN6_IS_ADDR_V4MAPPED(&a1->sin6_addr) &&
            (a1->sin6_addr.s6_addr32[3] ==
             ((struct sockaddr_in *)a2)->sin_addr.s_addr));
}
#else
sock_eq(struct sockaddr_in *a1, struct sockaddr_in *a2) {
      return ((a1->sin_family == a2->sin_family) &&
            (a1->sin_port == a2->sin_port) &&
            (a1->sin_addr.s_addr == a2->sin_addr.s_addr));
}
#endif

#ifdef _LIBC
/*
 * Converts IPv4 family, address and port to
 * IPv6 family, IPv4-mapped IPv6 address and port.
 */
static void
convaddr4to6(struct sockaddr_in6 *sa)
{
    struct sockaddr_in *sa4p = (struct sockaddr_in *) sa;
    in_port_t port = sa4p->sin_port;
    in_addr_t addr = sa4p->sin_addr.s_addr;

    sa->sin6_family = AF_INET6;
    sa->sin6_port = port;
    sa->sin6_addr.s6_addr32[0] = 0;
    sa->sin6_addr.s6_addr32[1] = 0;
    sa->sin6_addr.s6_addr32[2] = htonl(0xFFFF);
    sa->sin6_addr.s6_addr32[3] = addr;
}
#endif

#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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