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