resolv/res_send.c

   1 /*
   2  * ++Copyright++ 1985, 1989, 1993
   3  * -
   4  * Copyright (c) 1985, 1989, 1993
   5  *    The Regents of the University of California.  All rights reserved.
   6  *
   7  * Redistribution and use in source and binary forms, with or without
   8  * modification, are permitted provided that the following conditions
   9  * are met:
  10  * 1. Redistributions of source code must retain the above copyright
  11  *    notice, this list of conditions and the following disclaimer.
  12  * 2. Redistributions in binary form must reproduce the above copyright
  13  *    notice, this list of conditions and the following disclaimer in the
  14  *    documentation and/or other materials provided with the distribution.
  15  * 3. All advertising materials mentioning features or use of this software
  16  *    must display the following acknowledgement:
  17  *      This product includes software developed by the University of
  18  *      California, Berkeley and its contributors.
  19  * 4. Neither the name of the University nor the names of its contributors
  20  *    may be used to endorse or promote products derived from this software
  21  *    without specific prior written permission.
  22  *
  23  * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
  24  * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
  25  * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
  26  * ARE DISCLAIMED.  IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
  27  * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
  28  * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
  29  * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
  30  * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
  31  * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
  32  * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
  33  * SUCH DAMAGE.
  34  * -
  35  * Portions Copyright (c) 1993 by Digital Equipment Corporation.
  36  *
  37  * Permission to use, copy, modify, and distribute this software for any
  38  * purpose with or without fee is hereby granted, provided that the above
  39  * copyright notice and this permission notice appear in all copies, and that
  40  * the name of Digital Equipment Corporation not be used in advertising or
  41  * publicity pertaining to distribution of the document or software without
  42  * specific, written prior permission.
  43  *
  44  * THE SOFTWARE IS PROVIDED "AS IS" AND DIGITAL EQUIPMENT CORP. DISCLAIMS ALL
  45  * WARRANTIES WITH REGARD TO THIS SOFTWARE, INCLUDING ALL IMPLIED WARRANTIES
  46  * OF MERCHANTABILITY AND FITNESS.   IN NO EVENT SHALL DIGITAL EQUIPMENT
  47  * CORPORATION BE LIABLE FOR ANY SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL
  48  * DAMAGES OR ANY DAMAGES WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR
  49  * PROFITS, WHETHER IN AN ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS
  50  * ACTION, ARISING OUT OF OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS
  51  * SOFTWARE.
  52  * -
  53  * --Copyright--
  54  */
  55
  56 #if defined(LIBC_SCCS) && !defined(lint)
  57 static char sccsid[] = "@(#)res_send.c  8.1 (Berkeley) 6/4/93";
  58 static char rcsid[] = "$Id$";
  59 #endif /* LIBC_SCCS and not lint */
  60
  61         /* change this to "0"
  62          * if you talk to a lot
  63          * of multi-homed SunOS
  64          * ("broken") name servers.
  65          */
  66 #define CHECK_SRVR_ADDR 1       /* XXX - should be in options.h */
  67
  68 /*
  69  * Send query to name server and wait for reply.
  70  */
  71
  72 #include <sys/param.h>
  73 #include <sys/time.h>
  74 #include <sys/socket.h>
  75 #include <sys/uio.h>
  76 #include <netinet/in.h>
  77 #include <arpa/nameser.h>
  78 #include <arpa/inet.h>
  79
  80 #include <stdio.h>
  81 #include <netdb.h>
  82 #include <errno.h>
  83 #include <resolv.h>
  84 #if defined(BSD) && (BSD >= 199306)
  85 # include <stdlib.h>
  86 # include <string.h>
  87 # include <unistd.h>
  88 #else
  89 # include "../conf/portability.h"
  90 #endif
  91
  92 #if defined(USE_OPTIONS_H)
  93 # include <../conf/options.h>
  94 #endif
  95
  96 void _res_close __P((void));
  97
  98 static int s = -1;      /* socket used for communications */
  99 static int connected = 0;       /* is the socket connected */
 100 static int vc = 0;      /* is the socket a virtual ciruit? */
 101
 102 #ifndef FD_SET
 103 /* XXX - should be in portability.h */
 104 #define NFDBITS         32
 105 #define FD_SETSIZE      32
 106 #define FD_SET(n, p)    ((p)->fds_bits[(n)/NFDBITS] |= (1 << ((n) % NFDBITS)))
 107 #define FD_CLR(n, p)    ((p)->fds_bits[(n)/NFDBITS] &= ~(1 << ((n) % NFDBITS)))
 108 #define FD_ISSET(n, p)  ((p)->fds_bits[(n)/NFDBITS] & (1 << ((n) % NFDBITS)))
 109 #define FD_ZERO(p)      bzero((char *)(p), sizeof(*(p)))
 110 #endif
 111
 112 /* XXX - this should be done in portability.h */
 113 #if (defined(BSD) && (BSD >= 199103)) || defined(linux)
 114 # define CAN_RECONNECT 1
 115 #else
 116 # define CAN_RECONNECT 0
 117 #endif
 118
 119 #ifndef DEBUG
 120 #   define Dprint(cond, args) /*empty*/
 121 #   define DprintQ(cond, args, query, size) /*empty*/
 122 #   define Aerror(file, string, error, address) /*empty*/
 123 #   define Perror(file, string, error) /*empty*/
 124 #else
 125 #   define Dprint(cond, args) if (cond) {fprintf args;} else {}
 126 #   define DprintQ(cond, args, query, size) if (cond) {\
 127                         fprintf args;\
 128                         __fp_nquery(query, size, stdout);\
 129                 } else {}
 130     static void
 131     Aerror(file, string, error, address)
 132         FILE *file;
 133         char *string;
 134         int error;
 135         struct sockaddr_in address;
 136     {
 137         int save = errno;
 138
 139         if (_res.options & RES_DEBUG) {
 140                 fprintf(file, "res_send: %s ([%s].%u): %s\n",
 141                         string,
 142                         inet_ntoa(address.sin_addr),
 143                         ntohs(address.sin_port),
 144                         strerror(error));
 145         }
 146         errno = save;
 147     }
 148     static void
 149     Perror(file, string, error)
 150         FILE *file;
 151         char *string;
 152         int error;
 153     {
 154         int save = errno;
 155
 156         if (_res.options & RES_DEBUG) {
 157                 fprintf(file, "res_send: %s: %s\n",
 158                         string, strerror(error));
 159         }
 160         errno = save;
 161     }
 162 #endif
 163
 164 static res_send_qhook Qhook = NULL;
 165 static res_send_rhook Rhook = NULL;
 166
 167 void
 168 res_send_setqhook(hook)
 169         res_send_qhook hook;
 170 {
 171
 172         Qhook = hook;
 173 }
 174
 175 void
 176 res_send_setrhook(hook)
 177         res_send_rhook hook;
 178 {
 179
 180         Rhook = hook;
 181 }
 182
 183 /* int
 184  * res_isourserver(ina)
 185  *      looks up "ina" in _res.ns_addr_list[]
 186  * returns:
 187  *      0  : not found
 188  *      >0 : found
 189  * author:
 190  *      paul vixie, 29may94
 191  */
 192 int
 193 res_isourserver(inp)
 194         const struct sockaddr_in *inp;
 195 {
 196         struct sockaddr_in ina;
 197         register int ns, ret;
 198
 199         ina = *inp;
 200         ret = 0;
 201         for (ns = 0;  ns < _res.nscount;  ns++) {
 202                 register const struct sockaddr_in *srv = &_res.nsaddr_list[ns];
 203
 204                 if (srv->sin_family == ina.sin_family &&
 205                     srv->sin_port == ina.sin_port &&
 206                     (srv->sin_addr.s_addr == INADDR_ANY ||
 207                      srv->sin_addr.s_addr == ina.sin_addr.s_addr)) {
 208                         ret++;
 209                         break;
 210                 }
 211         }
 212         return (ret);
 213 }
 214
 215 /* int
 216  * res_nameinquery(name, type, class, buf, eom)
 217  *      look for (name,type,class) in the query section of packet (buf,eom)
 218  * returns:
 219  *      -1 : format error
 220  *      0  : not found
 221  *      >0 : found
 222  * author:
 223  *      paul vixie, 29may94
 224  */
 225 int
 226 res_nameinquery(name, type, class, buf, eom)
 227         const char *name;
 228         register int type, class;
 229         const u_char *buf, *eom;
 230 {
 231         register const u_char *cp = buf + HFIXEDSZ;
 232         int qdcount = ntohs(((HEADER*)buf)->qdcount);
 233
 234         while (qdcount-- > 0) {
 235                 char tname[MAXDNAME+1];
 236                 register int n, ttype, tclass;
 237
 238                 n = dn_expand(buf, eom, cp, tname, sizeof tname);
 239                 if (n < 0)
 240                         return (-1);
 241                 cp += n;
 242                 ttype = _getshort(cp); cp += INT16SZ;
 243                 tclass = _getshort(cp); cp += INT16SZ;
 244                 if (ttype == type &&
 245                     tclass == class &&
 246                     strcasecmp(tname, name) == 0)
 247                         return (1);
 248         }
 249         return (0);
 250 }
 251
 252 /* int
 253  * res_queriesmatch(buf1, eom1, buf2, eom2)
 254  *      is there a 1:1 mapping of (name,type,class)
 255  *      in (buf1,eom1) and (buf2,eom2)?
 256  * returns:
 257  *      -1 : format error
 258  *      0  : not a 1:1 mapping
 259  *      >0 : is a 1:1 mapping
 260  * author:
 261  *      paul vixie, 29may94
 262  */
 263 int
 264 res_queriesmatch(buf1, eom1, buf2, eom2)
 265         const u_char *buf1, *eom1;
 266         const u_char *buf2, *eom2;
 267 {
 268         register const u_char *cp = buf1 + HFIXEDSZ;
 269         int qdcount = ntohs(((HEADER*)buf1)->qdcount);
 270
 271         if (qdcount != ntohs(((HEADER*)buf2)->qdcount))
 272                 return (0);
 273         while (qdcount-- > 0) {
 274                 char tname[MAXDNAME+1];
 275                 register int n, ttype, tclass;
 276
 277                 n = dn_expand(buf1, eom1, cp, tname, sizeof tname);
 278                 if (n < 0)
 279                         return (-1);
 280                 cp += n;
 281                 ttype = _getshort(cp);  cp += INT16SZ;
 282                 tclass = _getshort(cp); cp += INT16SZ;
 283                 if (!res_nameinquery(tname, ttype, tclass, buf2, eom2))
 284                         return (0);
 285         }
 286         return (1);
 287 }
 288
 289 int
 290 res_send(buf, buflen, ans, anssiz)
 291         const u_char *buf;
 292         int buflen;
 293         u_char *ans;
 294         int anssiz;
 295 {
 296         HEADER *hp = (HEADER *) buf;
 297         HEADER *anhp = (HEADER *) ans;
 298         int gotsomewhere, connreset, terrno, try, v_circuit, resplen, ns;
 299         register int n;
 300         u_int badns;    /* XXX NSMAX can't exceed #/bits in this var */
 301
 302         if ((_res.options & RES_INIT) == 0 && res_init() == -1) {
 303                 /* errno should have been set by res_init() in this case. */
 304                 return (-1);
 305         }
 306         DprintQ((_res.options & RES_DEBUG) || (_res.pfcode & RES_PRF_QUERY),
 307                 (stdout, ";; res_send()\n"), buf, buflen);
 308         v_circuit = (_res.options & RES_USEVC) || buflen > PACKETSZ;
 309         gotsomewhere = 0;
 310         connreset = 0;
 311         terrno = ETIMEDOUT;
 312         badns = 0;
 313
 314         /*
 315          * Send request, RETRY times, or until successful
 316          */
 317         for (try = 0; try < _res.retry; try++) {
 318             for (ns = 0; ns < _res.nscount; ns++) {
 319                 struct sockaddr_in *nsap = &_res.nsaddr_list[ns];
 320     same_ns:
 321                 if (badns & (1 << ns)) {
 322                         _res_close();
 323                         goto next_ns;
 324                 }
 325
 326                 if (Qhook) {
 327                         int done = 0, loops = 0;
 328
 329                         do {
 330                                 res_sendhookact act;
 331
 332                                 act = (*Qhook)(&nsap, &buf, &buflen,
 333                                                ans, anssiz, &resplen);
 334                                 switch (act) {
 335                                 case res_goahead:
 336                                         done = 1;
 337                                         break;
 338                                 case res_nextns:
 339                                         _res_close();
 340                                         goto next_ns;
 341                                 case res_done:
 342                                         return (resplen);
 343                                 case res_modified:
 344                                         /* give the hook another try */
 345                                         if (++loops < 42) /*doug adams*/
 346                                                 break;
 347                                         /*FALLTHROUGH*/
 348                                 case res_error:
 349                                         /*FALLTHROUGH*/
 350                                 default:
 351                                         return (-1);
 352                                 }
 353                         } while (!done);
 354                 }
 355
 356                 Dprint(_res.options & RES_DEBUG,
 357                        (stdout, ";; Querying server (# %d) address = %s\n",
 358                         ns + 1, inet_ntoa(nsap->sin_addr)));
 359
 360                 if (v_circuit) {
 361                         int truncated;
 362                         struct iovec iov[2];
 363                         u_short len;
 364                         u_char *cp;
 365
 366                         /*
 367                          * Use virtual circuit;
 368                          * at most one attempt per server.
 369                          */
 370                         try = _res.retry;
 371                         truncated = 0;
 372                         if ((s < 0) || (!vc)) {
 373                                 if (s >= 0)
 374                                         _res_close();
 375
 376                                 s = socket(PF_INET, SOCK_STREAM, 0);
 377                                 if (s < 0) {
 378                                         terrno = errno;
 379                                         Perror(stderr, "socket(vc)", errno);
 380                                         return (-1);
 381                                 }
 382                                 errno = 0;
 383                                 if (connect(s, (struct sockaddr *)nsap,
 384                                             sizeof(struct sockaddr)) < 0) {
 385                                         terrno = errno;
 386                                         Aerror(stderr, "connect/vc",
 387                                                errno, *nsap);
 388                                         badns |= (1 << ns);
 389                                         _res_close();
 390                                         goto next_ns;
 391                                 }
 392                                 vc = 1;
 393                         }
 394                         /*
 395                          * Send length & message
 396                          */
 397                         putshort((u_short)buflen, (u_char*)&len);
 398                         iov[0].iov_base = (caddr_t)&len;
 399                         iov[0].iov_len = INT16SZ;
 400                         iov[1].iov_base = (caddr_t)buf;
 401                         iov[1].iov_len = buflen;
 402                         if (writev(s, iov, 2) != (INT16SZ + buflen)) {
 403                                 terrno = errno;
 404                                 Perror(stderr, "write failed", errno);
 405                                 badns |= (1 << ns);
 406                                 _res_close();
 407                                 goto next_ns;
 408                         }
 409                         /*
 410                          * Receive length & response
 411                          */
 412                         cp = ans;
 413                         len = INT16SZ;
 414                         while ((n = read(s, (char *)cp, (int)len)) > 0) {
 415                                 cp += n;
 416                                 if ((len -= n) <= 0)
 417                                         break;
 418                         }
 419                         if (n <= 0) {
 420                                 terrno = errno;
 421                                 Perror(stderr, "read failed", errno);
 422                                 _res_close();
 423                                 /*
 424                                  * A long running process might get its TCP
 425                                  * connection reset if the remote server was
 426                                  * restarted.  Requery the server instead of
 427                                  * trying a new one.  When there is only one
 428                                  * server, this means that a query might work
 429                                  * instead of failing.  We only allow one reset
 430                                  * per query to prevent looping.
 431                                  */
 432                                 if (terrno == ECONNRESET && !connreset) {
 433                                         connreset = 1;
 434                                         _res_close();
 435                                         goto same_ns;
 436                                 }
 437                                 _res_close();
 438                                 goto next_ns;
 439                         }
 440                         resplen = _getshort(ans);
 441                         if (resplen > anssiz) {
 442                                 Dprint(_res.options & RES_DEBUG,
 443                                        (stdout, ";; response truncated\n")
 444                                        );
 445                                 truncated = 1;
 446                                 len = anssiz;
 447                         } else
 448                                 len = resplen;
 449                         cp = ans;
 450                         while (len != 0 &&
 451                                (n = read(s, (char *)cp, (int)len)) > 0) {
 452                                 cp += n;
 453                                 len -= n;
 454                         }
 455                         if (n <= 0) {
 456                                 terrno = errno;
 457                                 Perror(stderr, "read(vc)", errno);
 458                                 _res_close();
 459                                 goto next_ns;
 460                         }
 461                         if (truncated) {
 462                                 /*
 463                                  * Flush rest of answer
 464                                  * so connection stays in synch.
 465                                  */
 466                                 anhp->tc = 1;
 467                                 len = resplen - anssiz;
 468                                 while (len != 0) {
 469                                         char junk[PACKETSZ];
 470
 471                                         n = (len > sizeof(junk)
 472                                              ? sizeof(junk)
 473                                              : len);
 474                                         if ((n = read(s, junk, n)) > 0)
 475                                                 len -= n;
 476                                         else
 477                                                 break;
 478                                 }
 479                         }
 480                 } else {
 481                         /*
 482                          * Use datagrams.
 483                          */
 484                         struct timeval timeout;
 485                         fd_set dsmask;
 486                         struct sockaddr_in from;
 487                         int fromlen;
 488
 489                         if ((s < 0) || vc) {
 490                                 if (vc)
 491                                         _res_close();
 492                                 s = socket(PF_INET, SOCK_DGRAM, 0);
 493                                 if (s < 0) {
 494 #if !CAN_RECONNECT
 495  bad_dg_sock:
 496 #endif
 497                                         terrno = errno;
 498                                         Perror(stderr, "socket(dg)", errno);
 499                                         return (-1);
 500                                 }
 501                                 connected = 0;
 502                         }
 503                         /*
 504                          * On a 4.3BSD+ machine (client and server,
 505                          * actually), sending to a nameserver datagram
 506                          * port with no nameserver will cause an
 507                          * ICMP port unreachable message to be returned.
 508                          * If our datagram socket is "connected" to the
 509                          * server, we get an ECONNREFUSED error on the next
 510                          * socket operation, and select returns if the
 511                          * error message is received.  We can thus detect
 512                          * the absence of a nameserver without timing out.
 513                          * If we have sent queries to at least two servers,
 514                          * however, we don't want to remain connected,
 515                          * as we wish to receive answers from the first
 516                          * server to respond.
 517                          */
 518                         if (_res.nscount == 1 || (try == 0 && ns == 0)) {
 519                                 /*
 520                                  * Connect only if we are sure we won't
 521                                  * receive a response from another server.
 522                                  */
 523                                 if (!connected) {
 524                                         if (connect(s, (struct sockaddr *)nsap,
 525                                                     sizeof(struct sockaddr)
 526                                                     ) < 0) {
 527                                                 Aerror(stderr,
 528                                                        "connect(dg)",
 529                                                        errno, *nsap);
 530                                                 badns |= (1 << ns);
 531                                                 _res_close();
 532                                                 goto next_ns;
 533                                         }
 534                                         connected = 1;
 535                                 }
 536                                 if (send(s, (char*)buf, buflen, 0) != buflen) {
 537                                         Perror(stderr, "send", errno);
 538                                         badns |= (1 << ns);
 539                                         _res_close();
 540                                         goto next_ns;
 541                                 }
 542                         } else {
 543                                 /*
 544                                  * Disconnect if we want to listen
 545                                  * for responses from more than one server.
 546                                  */
 547                                 if (connected) {
 548 #if CAN_RECONNECT
 549                                         struct sockaddr_in no_addr;
 550
 551                                         no_addr.sin_family = AF_INET;
 552                                         no_addr.sin_addr.s_addr = INADDR_ANY;
 553                                         no_addr.sin_port = 0;
 554                                         (void) connect(s,
 555                                                        (struct sockaddr *)
 556                                                         &no_addr,
 557                                                        sizeof(no_addr));
 558 #else
 559                                         int s1 = socket(PF_INET, SOCK_DGRAM,0);
 560                                         if (s1 < 0)
 561                                                 goto bad_dg_sock;
 562                                         (void) dup2(s1, s);
 563                                         (void) close(s1);
 564                                         Dprint(_res.options & RES_DEBUG,
 565                                                (stdout, ";; new DG socket\n"))
 566 #endif
 567                                         connected = 0;
 568                                         errno = 0;
 569                                 }
 570                                 if (sendto(s, (char*)buf, buflen, 0,
 571                                            (struct sockaddr *)nsap,
 572                                            sizeof(struct sockaddr))
 573                                     != buflen) {
 574                                         Aerror(stderr, "sendto", errno, *nsap);
 575                                         badns |= (1 << ns);
 576                                         _res_close();
 577                                         goto next_ns;
 578                                 }
 579                         }
 580
 581                         /*
 582                          * Wait for reply
 583                          */
 584                         timeout.tv_sec = (_res.retrans << try);
 585                         if (try > 0)
 586                                 timeout.tv_sec /= _res.nscount;
 587                         if ((long) timeout.tv_sec <= 0)
 588                                 timeout.tv_sec = 1;
 589                         timeout.tv_usec = 0;
 590     wait:
 591                         FD_ZERO(&dsmask);
 592                         FD_SET(s, &dsmask);
 593                         n = select(s+1, &dsmask, (fd_set *)NULL,
 594                                    (fd_set *)NULL, &timeout);
 595                         if (n < 0) {
 596                                 Perror(stderr, "select", errno);
 597                                 _res_close();
 598                                 goto next_ns;
 599                         }
 600                         if (n == 0) {
 601                                 /*
 602                                  * timeout
 603                                  */
 604                                 Dprint(_res.options & RES_DEBUG,
 605                                        (stdout, ";; timeout\n"));
 606                                 gotsomewhere = 1;
 607                                 _res_close();
 608                                 goto next_ns;
 609                         }
 610                         errno = 0;
 611                         fromlen = sizeof(struct sockaddr_in);
 612                         resplen = recvfrom(s, (char*)ans, anssiz, 0,
 613                                            (struct sockaddr *)&from, &fromlen);
 614                         if (resplen <= 0) {
 615                                 Perror(stderr, "recvfrom", errno);
 616                                 _res_close();
 617                                 goto next_ns;
 618                         }
 619                         gotsomewhere = 1;
 620                         if (hp->id != anhp->id) {
 621                                 /*
 622                                  * response from old query, ignore it.
 623                                  * XXX - potential security hazard could
 624                                  *       be detected here.
 625                                  */
 626                                 DprintQ((_res.options & RES_DEBUG) ||
 627                                         (_res.pfcode & RES_PRF_REPLY),
 628                                         (stdout, ";; old answer:\n"),
 629                                         ans, resplen);
 630                                 goto wait;
 631                         }
 632 #if CHECK_SRVR_ADDR
 633                         if (!(_res.options & RES_INSECURE1) &&
 634                             !res_isourserver(&from)) {
 635                                 /*
 636                                  * response from wrong server? ignore it.
 637                                  * XXX - potential security hazard could
 638                                  *       be detected here.
 639                                  */
 640                                 DprintQ((_res.options & RES_DEBUG) ||
 641                                         (_res.pfcode & RES_PRF_REPLY),
 642                                         (stdout, ";; not our server:\n"),
 643                                         ans, resplen);
 644                                 goto wait;
 645                         }
 646 #endif
 647                         if (!(_res.options & RES_INSECURE2) &&
 648                             !res_queriesmatch(buf, buf + buflen,
 649                                               ans, ans + anssiz)) {
 650                                 /*
 651                                  * response contains wrong query? ignore it.
 652                                  * XXX - potential security hazard could
 653                                  *       be detected here.
 654                                  */
 655                                 DprintQ((_res.options & RES_DEBUG) ||
 656                                         (_res.pfcode & RES_PRF_REPLY),
 657                                         (stdout, ";; wrong query name:\n"),
 658                                         ans, resplen);
 659                                 goto wait;
 660                         }
 661                         if (anhp->rcode == SERVFAIL ||
 662                             anhp->rcode == NOTIMP ||
 663                             anhp->rcode == REFUSED) {
 664                                 DprintQ(_res.options & RES_DEBUG,
 665                                         (stdout, "server rejected query:\n"),
 666                                         ans, resplen);
 667                                 badns |= (1 << ns);
 668                                 _res_close();
 669                                 /* don't retry if called from dig */
 670                                 if (!_res.pfcode)
 671                                         goto next_ns;
 672                         }
 673                         if (!(_res.options & RES_IGNTC) && anhp->tc) {
 674                                 /*
 675                                  * get rest of answer;
 676                                  * use TCP with same server.
 677                                  */
 678                                 Dprint(_res.options & RES_DEBUG,
 679                                        (stdout, ";; truncated answer\n"));
 680                                 v_circuit = 1;
 681                                 _res_close();
 682                                 goto same_ns;
 683                         }
 684                 } /*if vc/dg*/
 685                 DprintQ((_res.options & RES_DEBUG) ||
 686                         (_res.pfcode & RES_PRF_REPLY),
 687                         (stdout, ";; got answer:\n"),
 688                         ans, resplen);
 689                 /*
 690                  * If using virtual circuits, we assume that the first server
 691                  * is preferred over the rest (i.e. it is on the local
 692                  * machine) and only keep that one open.
 693                  * If we have temporarily opened a virtual circuit,
 694                  * or if we haven't been asked to keep a socket open,
 695                  * close the socket.
 696                  */
 697                 if ((v_circuit && (!(_res.options & RES_USEVC) || ns != 0)) ||
 698                     !(_res.options & RES_STAYOPEN)) {
 699                         _res_close();
 700                 }
 701                 if (Rhook) {
 702                         int done = 0, loops = 0;
 703
 704                         do {
 705                                 res_sendhookact act;
 706
 707                                 act = (*Rhook)(nsap, buf, buflen,
 708                                                ans, anssiz, &resplen);
 709                                 switch (act) {
 710                                 case res_goahead:
 711                                 case res_done:
 712                                         done = 1;
 713                                         break;
 714                                 case res_nextns:
 715                                         _res_close();
 716                                         goto next_ns;
 717                                 case res_modified:
 718                                         /* give the hook another try */
 719                                         if (++loops < 42) /*doug adams*/
 720                                                 break;
 721                                         /*FALLTHROUGH*/
 722                                 case res_error:
 723                                         /*FALLTHROUGH*/
 724                                 default:
 725                                         return (-1);
 726                                 }
 727                         } while (!done);
 728
 729                 }
 730                 return (resplen);
 731     next_ns: ;
 732            } /*foreach ns*/
 733         } /*foreach retry*/
 734         _res_close();
 735         if (!v_circuit)
 736                 if (!gotsomewhere)
 737                         errno = ECONNREFUSED;   /* no nameservers found */
 738                 else
 739                         errno = ETIMEDOUT;      /* no answer obtained */
 740         else
 741                 errno = terrno;
 742         return (-1);
 743 }
 744
 745 /*
 746  * This routine is for closing the socket if a virtual circuit is used and
 747  * the program wants to close it.  This provides support for endhostent()
 748  * which expects to close the socket.
 749  *
 750  * This routine is not expected to be user visible.
 751  */
 752 void
 753 _res_close()
 754 {
 755         if (s >= 0) {
 756                 (void) close(s);
 757                 s = -1;
 758                 connected = 0;
 759                 vc = 0;
 760         }
 761 }