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 <errno.h>
  82 #include <resolv.h>
  83 #if defined(BSD) && (BSD >= 199306)
  84 # include <stdlib.h>
  85 # include <string.h>
  86 #else
  87 # include "../conf/portability.h"
  88 #endif
  89
  90 #if defined(USE_OPTIONS_H)
  91 # include <../conf/options.h>
  92 #endif
  93
  94 void _res_close __P((void));
  95
  96 static int s = -1;      /* socket used for communications */
  97 static int connected = 0;       /* is the socket connected */
  98 static int vc = 0;      /* is the socket a virtual ciruit? */
  99
 100 #ifndef FD_SET
 101 /* XXX - should be in portability.h */
 102 #define NFDBITS         32
 103 #define FD_SETSIZE      32
 104 #define FD_SET(n, p)    ((p)->fds_bits[(n)/NFDBITS] |= (1 << ((n) % NFDBITS)))
 105 #define FD_CLR(n, p)    ((p)->fds_bits[(n)/NFDBITS] &= ~(1 << ((n) % NFDBITS)))
 106 #define FD_ISSET(n, p)  ((p)->fds_bits[(n)/NFDBITS] & (1 << ((n) % NFDBITS)))
 107 #define FD_ZERO(p)      bzero((char *)(p), sizeof(*(p)))
 108 #endif
 109
 110 #ifndef DEBUG
 111 #   define Dprint(cond, args) /*empty*/
 112 #   define DprintQ(cond, args, query) /*empty*/
 113 #   define Aerror(file, string, error, address) /*empty*/
 114 #   define Perror(file, string, error) /*empty*/
 115 #else
 116 #   define Dprint(cond, args) if (cond) {fprintf args;} else {}
 117 #   define DprintQ(cond, args, query) if (cond) {\
 118                         fprintf args;\
 119                         __p_query(query);\
 120                 } else {}
 121     static void
 122     Aerror(file, string, error, address)
 123         FILE *file;
 124         char *string;
 125         int error;
 126         struct sockaddr_in address;
 127     {
 128         int save = errno;
 129
 130         if (_res.options & RES_DEBUG) {
 131                 fprintf(file, "res_send: %s ([%s].%d): %s\n",
 132                         string,
 133                         inet_ntoa(address.sin_addr),
 134                         address.sin_port,
 135                         strerror(error));
 136         }
 137         errno = save;
 138     }
 139     static void
 140     Perror(file, string, error)
 141         FILE *file;
 142         char *string;
 143         int error;
 144     {
 145         int save = errno;
 146
 147         if (_res.options & RES_DEBUG) {
 148                 fprintf(file, "res_send: %s: %s\n",
 149                         string, strerror(error));
 150         }
 151         errno = save;
 152     }
 153 #endif
 154
 155 static res_send_qhook Qhook = NULL;
 156 static res_send_rhook Rhook = NULL;
 157
 158 void
 159 res_send_setqhook(hook)
 160         res_send_qhook hook;
 161 {
 162         Qhook = hook;
 163 }
 164
 165 void
 166 res_send_setrhook(hook)
 167         res_send_rhook hook;
 168 {
 169         Rhook = hook;
 170 }
 171
 172 /* int
 173  * our_server(ina)
 174  *      looks up "ina" in _res.ns_addr_list[]
 175  * returns:
 176  *      0  : not found
 177  *      >0 : found
 178  * author:
 179  *      paul vixie, 29may94
 180  */
 181 static int
 182 our_server(inp)
 183         const struct sockaddr_in *inp;
 184 {
 185         struct sockaddr_in ina;
 186         register int ns, ret;
 187
 188         ina = *inp;
 189         ret = 0;
 190         for (ns = 0;  ns < _res.nscount;  ns++) {
 191                 register const struct sockaddr_in *srv = &_res.nsaddr_list[ns];
 192
 193                 if (srv->sin_family == ina.sin_family &&
 194                     srv->sin_port == ina.sin_port &&
 195                     (srv->sin_addr.s_addr == INADDR_ANY ||
 196                      srv->sin_addr.s_addr == ina.sin_addr.s_addr)) {
 197                         ret++;
 198                         break;
 199                 }
 200         }
 201         return (ret);
 202 }
 203
 204 /* int
 205  * name_in_query(name, type, class, buf, eom)
 206  *      look for (name,type,class) in the query section of packet (buf,eom)
 207  * returns:
 208  *      -1 : format error
 209  *      0  : not found
 210  *      >0 : found
 211  */
 212 static int
 213 name_in_query(name, type, class, buf, eom)
 214         const char *name;
 215         register int type, class;
 216         const u_char *buf, *eom;
 217 {
 218         register const u_char *cp = buf + HFIXEDSZ;
 219         int qdcount = ntohs(((HEADER*)buf)->qdcount);
 220
 221         while (qdcount-- > 0) {
 222                 char tname[MAXDNAME+1];
 223                 register int n, ttype, tclass;
 224
 225                 n = dn_expand(buf, eom, cp, tname, sizeof tname);
 226                 if (n < 0)
 227                         return (-1);
 228                 cp += n;
 229                 ttype = _getshort(cp);  cp += INT16SZ;
 230                 tclass = _getshort(cp); cp += INT16SZ;
 231                 if (ttype == type &&
 232                     tclass == class &&
 233                     strcasecmp(tname, name) == 0)
 234                         return (1);
 235         }
 236         return (0);
 237 }
 238
 239 /* int
 240  * queries_match(buf1, eom1, buf2, eom2)
 241  *      is there a 1:1 mapping of (name,type,class)
 242  *      in (buf1,eom1) and (buf2,eom2)?
 243  * returns:
 244  *      -1 : format error
 245  *      0  : not a 1:1 mapping
 246  *      >0 : is a 1:1 mapping
 247  */
 248 static int
 249 queries_match(buf1, eom1, buf2, eom2)
 250         const u_char *buf1, *eom1;
 251         const u_char *buf2, *eom2;
 252 {
 253         register const u_char *cp = buf1 + HFIXEDSZ;
 254         int qdcount = ntohs(((HEADER*)buf1)->qdcount);
 255
 256         if (qdcount != ntohs(((HEADER*)buf2)->qdcount))
 257                 return (0);
 258         while (qdcount-- > 0) {
 259                 char tname[MAXDNAME+1];
 260                 register int n, ttype, tclass;
 261
 262                 n = dn_expand(buf1, eom1, cp, tname, sizeof tname);
 263                 if (n < 0)
 264                         return (-1);
 265                 cp += n;
 266                 ttype = _getshort(cp);  cp += INT16SZ;
 267                 tclass = _getshort(cp); cp += INT16SZ;
 268                 if (!name_in_query(tname, ttype, tclass, buf2, eom2))
 269                         return (0);
 270         }
 271         return (1);
 272 }
 273
 274 int
 275 res_send(buf, buflen, ans, anssiz)
 276         const u_char    *buf;
 277         int             buflen;
 278         u_char          *ans;
 279         int             anssiz;
 280 {
 281         HEADER          *hp = (HEADER *) buf;
 282         HEADER          *anhp = (HEADER *) ans;
 283         int             gotsomewhere = 0,
 284                         connreset = 0,
 285                         terrno = ETIMEDOUT;
 286
 287         register int    n;
 288         int             try, v_circuit, resplen, ns;
 289         u_int           badns;  /* XXX NSMAX can't exceed #/bits in this var */
 290
 291         DprintQ((_res.options & RES_DEBUG) || (_res.pfcode & RES_PRF_QUERY),
 292                 (stdout, ";; res_send()\n"), buf);
 293         if (!(_res.options & RES_INIT)) {
 294                 if (res_init() == -1)
 295                         return (-1);
 296         }
 297         v_circuit = (_res.options & RES_USEVC) || buflen > PACKETSZ;
 298         badns = 0;
 299
 300         /*
 301          * Send request, RETRY times, or until successful
 302          */
 303         for (try = 0; try < _res.retry; try++) {
 304             for (ns = 0; ns < _res.nscount; ns++) {
 305                 struct sockaddr_in *nsap = &_res.nsaddr_list[ns];
 306     same_ns:
 307                 if (badns & (1<<ns)) {
 308                         _res_close();
 309                         goto next_ns;
 310                 }
 311
 312                 if (Qhook) {
 313                         int done = 0, loops = 0;
 314
 315                         do {
 316                                 res_sendhookact act;
 317
 318                                 act = (*Qhook)(&nsap,
 319                                                &buf,
 320                                                &buflen,
 321                                                ans,
 322                                                anssiz,
 323                                                &resplen);
 324                                 switch (act) {
 325                                 case res_goahead:
 326                                         done = 1;
 327                                         break;
 328                                 case res_nextns:
 329                                         _res_close();
 330                                         goto next_ns;
 331                                 case res_done:
 332                                         return (resplen);
 333                                 case res_modified:
 334                                         /* give the hook another try */
 335                                         if (++loops < 42) /*doug adams*/
 336                                                 break;
 337                                         /*FALLTHROUGH*/
 338                                 case res_error:
 339                                         /*FALLTHROUGH*/
 340                                 default:
 341                                         return (-1);
 342                                 }
 343                         } while (!done);
 344                 }
 345
 346                 Dprint(_res.options & RES_DEBUG,
 347                        (stdout, ";; Querying server (# %d) address = %s\n",
 348                         ns+1, inet_ntoa(nsap->sin_addr)));
 349
 350                 if (v_circuit) {
 351                         int             truncated;
 352                         struct iovec    iov[2];
 353                         u_short         len;
 354                         u_char          *cp;
 355
 356                         /*
 357                          * Use virtual circuit;
 358                          * at most one attempt per server.
 359                          */
 360                         try = _res.retry;
 361                         truncated = 0;
 362                         if ((s < 0) || (!vc)) {
 363                                 if (s >= 0)
 364                                         _res_close();
 365
 366                                 s = socket(AF_INET, SOCK_STREAM, PF_UNSPEC);
 367                                 if (s < 0) {
 368                                         terrno = errno;
 369                                         Perror(stderr, "socket(vc)", errno);
 370                                         return (-1);
 371                                 }
 372                                 if (connect(s,
 373                                             (struct sockaddr *)nsap,
 374                                             sizeof(struct sockaddr))
 375                                     < 0) {
 376                                         terrno = errno;
 377                                         Aerror(stderr, "connect/vc",
 378                                                errno, *nsap);
 379                                         badns |= (1<<ns);
 380                                         _res_close();
 381                                         goto next_ns;
 382                                 }
 383                                 vc = 1;
 384                         }
 385                         /*
 386                          * Send length & message
 387                          */
 388                         putshort((u_short)buflen, (u_char*)&len);
 389                         iov[0].iov_base = (caddr_t)&len;
 390                         iov[0].iov_len = INT16SZ;
 391                         iov[1].iov_base = (caddr_t)buf;
 392                         iov[1].iov_len = buflen;
 393                         if (writev(s, iov, 2) != (INT16SZ + buflen)) {
 394                                 terrno = errno;
 395                                 Perror(stderr, "write failed", errno);
 396                                 badns |= (1<<ns);
 397                                 _res_close();
 398                                 goto next_ns;
 399                         }
 400                         /*
 401                          * Receive length & response
 402                          */
 403                         cp = ans;
 404                         len = INT16SZ;
 405                         while ((n = read(s, (char *)cp, (int)len)) > 0) {
 406                                 cp += n;
 407                                 if ((len -= n) <= 0)
 408                                         break;
 409                         }
 410                         if (n <= 0) {
 411                                 terrno = errno;
 412                                 Perror(stderr, "read failed", errno);
 413                                 _res_close();
 414                                 /*
 415                                  * A long running process might get its TCP
 416                                  * connection reset if the remote server was
 417                                  * restarted.  Requery the server instead of
 418                                  * trying a new one.  When there is only one
 419                                  * server, this means that a query might work
 420                                  * instead of failing.  We only allow one reset
 421                                  * per query to prevent looping.
 422                                  */
 423                                 if (terrno == ECONNRESET && !connreset) {
 424                                         connreset = 1;
 425                                         _res_close();
 426                                         goto same_ns;
 427                                 }
 428                                 _res_close();
 429                                 goto next_ns;
 430                         }
 431                         resplen = _getshort(ans);
 432                         if (resplen > anssiz) {
 433                                 Dprint(_res.options & RES_DEBUG,
 434                                        (stdout, ";; response truncated\n")
 435                                        );
 436                                 truncated = 1;
 437                                 len = anssiz;
 438                         } else
 439                                 len = resplen;
 440                         cp = ans;
 441                         while (len != 0 &&
 442                                (n = read(s, (char *)cp, (int)len)) > 0
 443                                ) {
 444                                 cp += n;
 445                                 len -= n;
 446                         }
 447                         if (n <= 0) {
 448                                 terrno = errno;
 449                                 Perror(stderr, "read(vc)", errno);
 450                                 _res_close();
 451                                 goto next_ns;
 452                         }
 453                         if (truncated) {
 454                                 /*
 455                                  * Flush rest of answer
 456                                  * so connection stays in synch.
 457                                  */
 458                                 anhp->tc = 1;
 459                                 len = resplen - anssiz;
 460                                 while (len != 0) {
 461                                         char junk[512];
 462
 463                                         n = (len > sizeof(junk)
 464                                              ? sizeof(junk)
 465                                              : len);
 466                                         if ((n = read(s, junk, n)) > 0)
 467                                                 len -= n;
 468                                         else
 469                                                 break;
 470                                 }
 471                         }
 472                 } else {
 473                         /*
 474                          * Use datagrams.
 475                          */
 476                         struct timeval  timeout;
 477                         fd_set          dsmask;
 478                         struct sockaddr_in from;
 479                         int             fromlen;
 480
 481                         if ((s < 0) || vc) {
 482                                 if (vc)
 483                                         _res_close();
 484                                 s = socket(AF_INET, SOCK_DGRAM, PF_UNSPEC);
 485                                 if (s < 0) {
 486  bad_dg_sock:                           terrno = errno;
 487                                         Perror(stderr, "socket(dg)", errno);
 488                                         return (-1);
 489                                 }
 490                                 connected = 0;
 491                         }
 492                         /*
 493                          * On a 4.3BSD+ machine (client and server,
 494                          * actually), sending to a nameserver datagram
 495                          * port with no nameserver will cause an
 496                          * ICMP port unreachable message to be returned.
 497                          * If our datagram socket is "connected" to the
 498                          * server, we get an ECONNREFUSED error on the next
 499                          * socket operation, and select returns if the
 500                          * error message is received.  We can thus detect
 501                          * the absence of a nameserver without timing out.
 502                          * If we have sent queries to at least two servers,
 503                          * however, we don't want to remain connected,
 504                          * as we wish to receive answers from the first
 505                          * server to respond.
 506                          */
 507                         if (_res.nscount == 1 || (try == 0 && ns == 0)) {
 508                                 /*
 509                                  * Connect only if we are sure we won't
 510                                  * receive a response from another server.
 511                                  */
 512                                 if (!connected) {
 513                                         if (connect(s,
 514                                                     (struct sockaddr *)nsap,
 515                                                     sizeof(struct sockaddr)
 516                                                     ) < 0
 517                                             ) {
 518                                                 Aerror(stderr,
 519                                                        "connect(dg)",
 520                                                        errno, *nsap);
 521                                                 badns |= (1<<ns);
 522                                                 _res_close();
 523                                                 goto next_ns;
 524                                         }
 525                                         connected = 1;
 526                                 }
 527                                 if (send(s, buf, buflen, 0) != buflen) {
 528                                         Perror(stderr, "send", errno);
 529                                         badns |= (1<<ns);
 530                                         _res_close();
 531                                         goto next_ns;
 532                                 }
 533                         } else {
 534                                 /*
 535                                  * Disconnect if we want to listen
 536                                  * for responses from more than one server.
 537                                  */
 538                                 if (connected) {
 539 #if defined(BSD) && (BSD >= 199103)
 540                                         struct sockaddr_in no_addr;
 541
 542                                         no_addr.sin_family = AF_INET;
 543                                         no_addr.sin_addr.s_addr = INADDR_ANY;
 544                                         no_addr.sin_port = 0;
 545                                         (void) connect(s,
 546                                                        (struct sockaddr *)
 547                                                         &no_addr,
 548                                                        sizeof(no_addr));
 549 #else
 550                                         int s1 = socket(AF_INET, SOCK_DGRAM,
 551                                                         PF_UNSPEC);
 552                                         if (s1 < 0)
 553                                                 goto bad_dg_sock;
 554                                         (void) dup2(s1, s);
 555                                         (void) close(s1);
 556                                         Dprint(_res.options & RES_DEBUG,
 557                                                (stdout, ";; new DG socket\n"))
 558 #endif
 559                                         connected = 0;
 560                                         errno = 0;
 561                                 }
 562                                 if (sendto(s, buf, buflen, 0,
 563                                            (struct sockaddr *)nsap,
 564                                            sizeof(struct sockaddr))
 565                                     != buflen) {
 566                                         Aerror(stderr, "sendto", errno, *nsap);
 567                                         badns |= (1<<ns);
 568                                         _res_close();
 569                                         goto next_ns;
 570                                 }
 571                         }
 572
 573                         /*
 574                          * Wait for reply
 575                          */
 576                         timeout.tv_sec = (_res.retrans << try);
 577                         if (try > 0)
 578                                 timeout.tv_sec /= _res.nscount;
 579                         if ((long) timeout.tv_sec <= 0)
 580                                 timeout.tv_sec = 1;
 581                         timeout.tv_usec = 0;
 582     wait:
 583                         FD_ZERO(&dsmask);
 584                         FD_SET(s, &dsmask);
 585                         n = select(s+1, &dsmask, (fd_set *)NULL,
 586                                    (fd_set *)NULL, &timeout);
 587                         if (n < 0) {
 588                                 Perror(stderr, "select", errno);
 589                                 _res_close();
 590                                 goto next_ns;
 591                         }
 592                         if (n == 0) {
 593                                 /*
 594                                  * timeout
 595                                  */
 596                                 Dprint(_res.options & RES_DEBUG,
 597                                        (stdout, ";; timeout\n")
 598                                        );
 599                                 gotsomewhere = 1;
 600                                 _res_close();
 601                                 goto next_ns;
 602                         }
 603                         fromlen = sizeof(struct sockaddr_in);
 604                         resplen = recvfrom(s, ans, anssiz, 0,
 605                                            (struct sockaddr *)&from, &fromlen);
 606                         if (resplen <= 0) {
 607                                 Perror(stderr, "recvfrom", errno);
 608                                 _res_close();
 609                                 goto next_ns;
 610                         }
 611                         gotsomewhere = 1;
 612                         if (hp->id != anhp->id) {
 613                                 /*
 614                                  * response from old query, ignore it.
 615                                  * XXX - potential security hazard could
 616                                  *       be detected here.
 617                                  */
 618                                 DprintQ((_res.options & RES_DEBUG) ||
 619                                         (_res.pfcode & RES_PRF_REPLY),
 620                                         (stdout, ";; old answer:\n"),
 621                                         ans);
 622                                 goto wait;
 623                         }
 624 #if CHECK_SRVR_ADDR
 625                         if (!(_res.options & RES_INSECURE1) &&
 626                             !our_server(&from)) {
 627                                 /*
 628                                  * response from wrong server? ignore it.
 629                                  * XXX - potential security hazard could
 630                                  *       be detected here.
 631                                  */
 632                                 DprintQ((_res.options & RES_DEBUG) ||
 633                                         (_res.pfcode & RES_PRF_REPLY),
 634                                         (stdout, ";; not our server:\n"),
 635                                         ans);
 636                                 goto wait;
 637                         }
 638 #endif
 639                         if (!(_res.options & RES_INSECURE2) &&
 640                             !queries_match(buf, buf + buflen,
 641                                            ans, ans + anssiz)) {
 642                                 /*
 643                                  * response contains wrong query? ignore it.
 644                                  * XXX - potential security hazard could
 645                                  *       be detected here.
 646                                  */
 647                                 DprintQ((_res.options & RES_DEBUG) ||
 648                                         (_res.pfcode & RES_PRF_REPLY),
 649                                         (stdout, ";; wrong query name:\n"),
 650                                         ans);
 651                                 goto wait;
 652                         }
 653                         if (anhp->rcode == SERVFAIL ||
 654                             anhp->rcode == NOTIMP ||
 655                             anhp->rcode == REFUSED) {
 656                                 DprintQ(_res.options & RES_DEBUG,
 657                                         (stdout, "server rejected query:\n"),
 658                                         ans);
 659                                 badns |= (1<<ns);
 660                                 _res_close();
 661                                 goto next_ns;
 662                         }
 663                         if (!(_res.options & RES_IGNTC) && anhp->tc) {
 664                                 /*
 665                                  * get rest of answer;
 666                                  * use TCP with same server.
 667                                  */
 668                                 Dprint(_res.options & RES_DEBUG,
 669                                        (stdout, ";; truncated answer\n")
 670                                        );
 671                                 v_circuit = 1;
 672                                 _res_close();
 673                                 goto same_ns;
 674                         }
 675                 } /*if vc/dg*/
 676                 DprintQ((_res.options & RES_DEBUG) ||
 677                         (_res.pfcode & RES_PRF_REPLY),
 678                         (stdout, ";; got answer:\n"),
 679                         ans);
 680                 /*
 681                  * If using virtual circuits, we assume that the first server
 682                  * is preferred over the rest (i.e. it is on the local
 683                  * machine) and only keep that one open.
 684                  * If we have temporarily opened a virtual circuit,
 685                  * or if we haven't been asked to keep a socket open,
 686                  * close the socket.
 687                  */
 688                 if ((v_circuit && (!(_res.options & RES_USEVC) || ns != 0)) ||
 689                     !(_res.options & RES_STAYOPEN)) {
 690                         _res_close();
 691                 }
 692                 if (Rhook) {
 693                         int done = 0, loops = 0;
 694
 695                         do {
 696                                 res_sendhookact act;
 697
 698                                 act = (*Rhook)(nsap,
 699                                                buf,
 700                                                buflen,
 701                                                ans,
 702                                                anssiz,
 703                                                &resplen);
 704                                 switch (act) {
 705                                 case res_goahead:
 706                                 case res_done:
 707                                         done = 1;
 708                                         break;
 709                                 case res_nextns:
 710                                         _res_close();
 711                                         goto next_ns;
 712                                 case res_modified:
 713                                         /* give the hook another try */
 714                                         if (++loops < 42) /*doug adams*/
 715                                                 break;
 716                                         /*FALLTHROUGH*/
 717                                 case res_error:
 718                                         /*FALLTHROUGH*/
 719                                 default:
 720                                         return (-1);
 721                                 }
 722                         } while (!done);
 723
 724                 }
 725                 return (resplen);
 726     next_ns: ;
 727            } /*foreach ns*/
 728         } /*foreach retry*/
 729         _res_close();
 730         if (!v_circuit) {
 731                 if (!gotsomewhere)
 732                         errno = ECONNREFUSED;   /* no nameservers found */
 733                 else
 734                         errno = ETIMEDOUT;      /* no answer obtained */
 735         } else {
 736                 errno = terrno;
 737         }
 738         return (-1);
 739 }
 740
 741 /*
 742  * This routine is for closing the socket if a virtual circuit is used and
 743  * the program wants to close it.  This provides support for endhostent()
 744  * which expects to close the socket.
 745  *
 746  * This routine is not expected to be user visible.
 747  */
 748 void
 749 _res_close()
 750 {
 751         if (s >= 0) {
 752                 (void) close(s);
 753                 s = -1;
 754                 connected = 0;
 755                 vc = 0;
 756         }
 757 }