dns.subproj/res_send.c

   1 /*
   2  * Copyright (c) 1999 Apple Computer, Inc. All rights reserved.
   3  *
   4  * @APPLE_LICENSE_HEADER_START@
   5  *
   6  * Portions Copyright (c) 1999 Apple Computer, Inc.  All Rights
   7  * Reserved.  This file contains Original Code and/or Modifications of
   8  * Original Code as defined in and that are subject to the Apple Public
   9  * Source License Version 1.1 (the "License").  You may not use this file
  10  * except in compliance with the License.  Please obtain a copy of the
  11  * License at http://www.apple.com/publicsource and read it before using
  12  * this file.
  13  *
  14  * The Original Code and all software distributed under the License are
  15  * distributed on an "AS IS" basis, WITHOUT WARRANTY OF ANY KIND, EITHER
  16  * EXPRESS OR IMPLIED, AND APPLE HEREBY DISCLAIMS ALL SUCH WARRANTIES,
  17  * INCLUDING WITHOUT LIMITATION, ANY WARRANTIES OF MERCHANTABILITY,
  18  * FITNESS FOR A PARTICULAR PURPOSE OR NON- INFRINGEMENT.  Please see the
  19  * License for the specific language governing rights and limitations
  20  * under the License.
  21  *
  22  * @APPLE_LICENSE_HEADER_END@
  23  */
  24 /*
  25  * ++Copyright++ 1985, 1989, 1993
  26  * -
  27  * Copyright (c) 1985, 1989, 1993
  28  *    The Regents of the University of California.  All rights reserved.
  29  *
  30  * Redistribution and use in source and binary forms, with or without
  31  * modification, are permitted provided that the following conditions
  32  * are met:
  33  * 1. Redistributions of source code must retain the above copyright
  34  *    notice, this list of conditions and the following disclaimer.
  35  * 2. Redistributions in binary form must reproduce the above copyright
  36  *    notice, this list of conditions and the following disclaimer in the
  37  *    documentation and/or other materials provided with the distribution.
  38  * 3. All advertising materials mentioning features or use of this software
  39  *    must display the following acknowledgement:
  40  *      This product includes software developed by the University of
  41  *      California, Berkeley and its contributors.
  42  * 4. Neither the name of the University nor the names of its contributors
  43  *    may be used to endorse or promote products derived from this software
  44  *    without specific prior written permission.
  45  *
  46  * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
  47  * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
  48  * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
  49  * ARE DISCLAIMED.  IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
  50  * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
  51  * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
  52  * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
  53  * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
  54  * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
  55  * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
  56  * SUCH DAMAGE.
  57  * -
  58  * Portions Copyright (c) 1993 by Digital Equipment Corporation.
  59  *
  60  * Permission to use, copy, modify, and distribute this software for any
  61  * purpose with or without fee is hereby granted, provided that the above
  62  * copyright notice and this permission notice appear in all copies, and that
  63  * the name of Digital Equipment Corporation not be used in advertising or
  64  * publicity pertaining to distribution of the document or software without
  65  * specific, written prior permission.
  66  *
  67  * THE SOFTWARE IS PROVIDED "AS IS" AND DIGITAL EQUIPMENT CORP. DISCLAIMS ALL
  68  * WARRANTIES WITH REGARD TO THIS SOFTWARE, INCLUDING ALL IMPLIED WARRANTIES
  69  * OF MERCHANTABILITY AND FITNESS.   IN NO EVENT SHALL DIGITAL EQUIPMENT
  70  * CORPORATION BE LIABLE FOR ANY SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL
  71  * DAMAGES OR ANY DAMAGES WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR
  72  * PROFITS, WHETHER IN AN ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS
  73  * ACTION, ARISING OUT OF OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS
  74  * SOFTWARE.
  75  * -
  76  * --Copyright--
  77  */
  78
  79 #if defined(LIBC_SCCS) && !defined(lint)
  80 static char sccsid[] = "@(#)res_send.c  8.1 (Berkeley) 6/4/93";
  81 static char rcsid[] = "$Id: res_send.c,v 1.2 1999/10/14 21:56:45 wsanchez Exp $";
  82 #endif /* LIBC_SCCS and not lint */
  83
  84         /* change this to "0"
  85          * if you talk to a lot
  86          * of multi-homed SunOS
  87          * ("broken") name servers.
  88          */
  89 #define CHECK_SRVR_ADDR 1       /* XXX - should be in options.h */
  90
  91 /*
  92  * Send query to name server and wait for reply.
  93  */
  94
  95 #include <sys/param.h>
  96 #include <sys/time.h>
  97 #include <sys/socket.h>
  98 #include <sys/uio.h>
  99 #include <netinet/in.h>
 100 #include <arpa/nameser.h>
 101 #include <arpa/inet.h>
 102
 103 #include <stdio.h>
 104 #include <netdb.h>
 105 #include <errno.h>
 106 #include <resolv.h>
 107 #if defined(BSD) && (BSD >= 199306)
 108 # include <stdlib.h>
 109 # include <string.h>
 110 # include <unistd.h>
 111 #else
 112 # include "portability.h"
 113 #endif
 114
 115 #if defined(USE_OPTIONS_H)
 116 # include "options.h"
 117 #endif
 118
 119 void _res_close __P((void));
 120
 121 static int s = -1;      /* socket used for communications */
 122 static int connected = 0;       /* is the socket connected */
 123 static int vc = 0;      /* is the socket a virtual ciruit? */
 124
 125 #ifndef FD_SET
 126 /* XXX - should be in portability.h */
 127 #define NFDBITS         32
 128 #define FD_SETSIZE      32
 129 #define FD_SET(n, p)    ((p)->fds_bits[(n)/NFDBITS] |= (1 << ((n) % NFDBITS)))
 130 #define FD_CLR(n, p)    ((p)->fds_bits[(n)/NFDBITS] &= ~(1 << ((n) % NFDBITS)))
 131 #define FD_ISSET(n, p)  ((p)->fds_bits[(n)/NFDBITS] & (1 << ((n) % NFDBITS)))
 132 #define FD_ZERO(p)      bzero((char *)(p), sizeof(*(p)))
 133 #endif
 134
 135 /* XXX - this should be done in portability.h */
 136 #if (defined(BSD) && (BSD >= 199103)) || defined(linux)
 137 # define CAN_RECONNECT 1
 138 #else
 139 # define CAN_RECONNECT 0
 140 #endif
 141
 142 #ifndef DEBUG
 143 #   define Dprint(cond, args) /*empty*/
 144 #   define DprintQ(cond, args, query, size) /*empty*/
 145 #   define Aerror(file, string, error, address) /*empty*/
 146 #   define Perror(file, string, error) /*empty*/
 147 #else
 148 #   define Dprint(cond, args) if (cond) {fprintf args;} else {}
 149 #   define DprintQ(cond, args, query, size) if (cond) {\
 150                         fprintf args;\
 151                         __fp_nquery(query, size, stdout);\
 152                 } else {}
 153     static void
 154     Aerror(file, string, error, address)
 155         FILE *file;
 156         char *string;
 157         int error;
 158         struct sockaddr_in address;
 159     {
 160         int save = errno;
 161
 162         if (_res.options & RES_DEBUG) {
 163                 fprintf(file, "res_send: %s ([%s].%u): %s\n",
 164                         string,
 165                         inet_ntoa(address.sin_addr),
 166                         ntohs(address.sin_port),
 167                         strerror(error));
 168         }
 169         errno = save;
 170     }
 171     static void
 172     Perror(file, string, error)
 173         FILE *file;
 174         char *string;
 175         int error;
 176     {
 177         int save = errno;
 178
 179         if (_res.options & RES_DEBUG) {
 180                 fprintf(file, "res_send: %s: %s\n",
 181                         string, strerror(error));
 182         }
 183         errno = save;
 184     }
 185 #endif
 186
 187 static res_send_qhook Qhook = NULL;
 188 static res_send_rhook Rhook = NULL;
 189
 190 void
 191 res_send_setqhook(hook)
 192         res_send_qhook hook;
 193 {
 194
 195         Qhook = hook;
 196 }
 197
 198 void
 199 res_send_setrhook(hook)
 200         res_send_rhook hook;
 201 {
 202
 203         Rhook = hook;
 204 }
 205
 206 /* int
 207  * res_isourserver(ina)
 208  *      looks up "ina" in _res.ns_addr_list[]
 209  * returns:
 210  *      0  : not found
 211  *      >0 : found
 212  * author:
 213  *      paul vixie, 29may94
 214  */
 215 int
 216 res_isourserver(inp)
 217         const struct sockaddr_in *inp;
 218 {
 219         struct sockaddr_in ina;
 220         register int ns, ret;
 221
 222         ina = *inp;
 223         ret = 0;
 224         for (ns = 0;  ns < _res.nscount;  ns++) {
 225                 register const struct sockaddr_in *srv = &_res.nsaddr_list[ns];
 226
 227                 if (srv->sin_family == ina.sin_family &&
 228                     srv->sin_port == ina.sin_port &&
 229                     (srv->sin_addr.s_addr == INADDR_ANY ||
 230                      srv->sin_addr.s_addr == ina.sin_addr.s_addr)) {
 231                         ret++;
 232                         break;
 233                 }
 234         }
 235         return (ret);
 236 }
 237
 238 /* int
 239  * res_nameinquery(name, type, class, buf, eom)
 240  *      look for (name,type,class) in the query section of packet (buf,eom)
 241  * returns:
 242  *      -1 : format error
 243  *      0  : not found
 244  *      >0 : found
 245  * author:
 246  *      paul vixie, 29may94
 247  */
 248 int
 249 res_nameinquery(name, type, class, buf, eom)
 250         const char *name;
 251         register int type, class;
 252         const u_char *buf, *eom;
 253 {
 254         register const u_char *cp = buf + HFIXEDSZ;
 255         int qdcount = ntohs(((HEADER*)buf)->qdcount);
 256
 257         while (qdcount-- > 0) {
 258                 char tname[MAXDNAME+1];
 259                 register int n, ttype, tclass;
 260
 261                 n = dn_expand(buf, eom, cp, tname, sizeof tname);
 262                 if (n < 0)
 263                         return (-1);
 264                 cp += n;
 265                 ttype = _getshort(cp); cp += INT16SZ;
 266                 tclass = _getshort(cp); cp += INT16SZ;
 267                 if (ttype == type &&
 268                     tclass == class &&
 269                     strcasecmp(tname, name) == 0)
 270                         return (1);
 271         }
 272         return (0);
 273 }
 274
 275 /* int
 276  * res_queriesmatch(buf1, eom1, buf2, eom2)
 277  *      is there a 1:1 mapping of (name,type,class)
 278  *      in (buf1,eom1) and (buf2,eom2)?
 279  * returns:
 280  *      -1 : format error
 281  *      0  : not a 1:1 mapping
 282  *      >0 : is a 1:1 mapping
 283  * author:
 284  *      paul vixie, 29may94
 285  */
 286 int
 287 res_queriesmatch(buf1, eom1, buf2, eom2)
 288         const u_char *buf1, *eom1;
 289         const u_char *buf2, *eom2;
 290 {
 291         register const u_char *cp = buf1 + HFIXEDSZ;
 292         int qdcount = ntohs(((HEADER*)buf1)->qdcount);
 293
 294         if (qdcount != ntohs(((HEADER*)buf2)->qdcount))
 295                 return (0);
 296         while (qdcount-- > 0) {
 297                 char tname[MAXDNAME+1];
 298                 register int n, ttype, tclass;
 299
 300                 n = dn_expand(buf1, eom1, cp, tname, sizeof tname);
 301                 if (n < 0)
 302                         return (-1);
 303                 cp += n;
 304                 ttype = _getshort(cp);  cp += INT16SZ;
 305                 tclass = _getshort(cp); cp += INT16SZ;
 306                 if (!res_nameinquery(tname, ttype, tclass, buf2, eom2))
 307                         return (0);
 308         }
 309         return (1);
 310 }
 311
 312 int
 313 res_send(buf, buflen, ans, anssiz)
 314         const u_char *buf;
 315         int buflen;
 316         u_char *ans;
 317         int anssiz;
 318 {
 319         HEADER *hp = (HEADER *) buf;
 320         HEADER *anhp = (HEADER *) ans;
 321         int gotsomewhere, connreset, terrno, try, v_circuit, resplen, ns;
 322         register int n;
 323         u_int badns;    /* XXX NSMAX can't exceed #/bits in this var */
 324
 325         if ((_res.options & RES_INIT) == 0 && res_init() == -1) {
 326                 /* errno should have been set by res_init() in this case. */
 327                 return (-1);
 328         }
 329         DprintQ((_res.options & RES_DEBUG) || (_res.pfcode & RES_PRF_QUERY),
 330                 (stdout, ";; res_send()\n"), buf, buflen);
 331         v_circuit = (_res.options & RES_USEVC) || buflen > PACKETSZ;
 332         gotsomewhere = 0;
 333         connreset = 0;
 334         terrno = ETIMEDOUT;
 335         badns = 0;
 336
 337         /*
 338          * Send request, RETRY times, or until successful
 339          */
 340         for (try = 0; try < _res.retry; try++) {
 341             for (ns = 0; ns < _res.nscount; ns++) {
 342                 struct sockaddr_in *nsap = &_res.nsaddr_list[ns];
 343     same_ns:
 344                 if (badns & (1 << ns)) {
 345                         _res_close();
 346                         goto next_ns;
 347                 }
 348
 349                 if (Qhook) {
 350                         int done = 0, loops = 0;
 351
 352                         do {
 353                                 res_sendhookact act;
 354
 355                                 act = (*Qhook)(&nsap, &buf, &buflen,
 356                                                ans, anssiz, &resplen);
 357                                 switch (act) {
 358                                 case res_goahead:
 359                                         done = 1;
 360                                         break;
 361                                 case res_nextns:
 362                                         _res_close();
 363                                         goto next_ns;
 364                                 case res_done:
 365                                         return (resplen);
 366                                 case res_modified:
 367                                         /* give the hook another try */
 368                                         if (++loops < 42) /*doug adams*/
 369                                                 break;
 370                                         /*FALLTHROUGH*/
 371                                 case res_error:
 372                                         /*FALLTHROUGH*/
 373                                 default:
 374                                         return (-1);
 375                                 }
 376                         } while (!done);
 377                 }
 378
 379                 Dprint(_res.options & RES_DEBUG,
 380                        (stdout, ";; Querying server (# %d) address = %s\n",
 381                         ns + 1, inet_ntoa(nsap->sin_addr)));
 382
 383                 if (v_circuit) {
 384                         int truncated;
 385                         struct iovec iov[2];
 386                         u_short len;
 387                         u_char *cp;
 388
 389                         /*
 390                          * Use virtual circuit;
 391                          * at most one attempt per server.
 392                          */
 393                         try = _res.retry;
 394                         truncated = 0;
 395                         if ((s < 0) || (!vc)) {
 396                                 if (s >= 0)
 397                                         _res_close();
 398
 399                                 s = socket(PF_INET, SOCK_STREAM, 0);
 400                                 if (s < 0) {
 401                                         terrno = errno;
 402                                         Perror(stderr, "socket(vc)", errno);
 403                                         return (-1);
 404                                 }
 405                                 errno = 0;
 406                                 if (connect(s, (struct sockaddr *)nsap,
 407                                             sizeof(struct sockaddr)) < 0) {
 408                                         terrno = errno;
 409                                         Aerror(stderr, "connect/vc",
 410                                                errno, *nsap);
 411                                         badns |= (1 << ns);
 412                                         _res_close();
 413                                         goto next_ns;
 414                                 }
 415                                 vc = 1;
 416                         }
 417                         /*
 418                          * Send length & message
 419                          */
 420                         putshort((u_short)buflen, (u_char*)&len);
 421                         iov[0].iov_base = (caddr_t)&len;
 422                         iov[0].iov_len = INT16SZ;
 423                         iov[1].iov_base = (caddr_t)buf;
 424                         iov[1].iov_len = buflen;
 425                         if (writev(s, iov, 2) != (INT16SZ + buflen)) {
 426                                 terrno = errno;
 427                                 Perror(stderr, "write failed", errno);
 428                                 badns |= (1 << ns);
 429                                 _res_close();
 430                                 goto next_ns;
 431                         }
 432                         /*
 433                          * Receive length & response
 434                          */
 435                         cp = ans;
 436                         len = INT16SZ;
 437                         while ((n = read(s, (char *)cp, (int)len)) > 0) {
 438                                 cp += n;
 439                                 if ((len -= n) <= 0)
 440                                         break;
 441                         }
 442                         if (n <= 0) {
 443                                 terrno = errno;
 444                                 Perror(stderr, "read failed", errno);
 445                                 _res_close();
 446                                 /*
 447                                  * A long running process might get its TCP
 448                                  * connection reset if the remote server was
 449                                  * restarted.  Requery the server instead of
 450                                  * trying a new one.  When there is only one
 451                                  * server, this means that a query might work
 452                                  * instead of failing.  We only allow one reset
 453                                  * per query to prevent looping.
 454                                  */
 455                                 if (terrno == ECONNRESET && !connreset) {
 456                                         connreset = 1;
 457                                         _res_close();
 458                                         goto same_ns;
 459                                 }
 460                                 _res_close();
 461                                 goto next_ns;
 462                         }
 463                         resplen = _getshort(ans);
 464                         if (resplen > anssiz) {
 465                                 Dprint(_res.options & RES_DEBUG,
 466                                        (stdout, ";; response truncated\n")
 467                                        );
 468                                 truncated = 1;
 469                                 len = anssiz;
 470                         } else
 471                                 len = resplen;
 472                         cp = ans;
 473                         while (len != 0 &&
 474                                (n = read(s, (char *)cp, (int)len)) > 0) {
 475                                 cp += n;
 476                                 len -= n;
 477                         }
 478                         if (n <= 0) {
 479                                 terrno = errno;
 480                                 Perror(stderr, "read(vc)", errno);
 481                                 _res_close();
 482                                 goto next_ns;
 483                         }
 484                         if (truncated) {
 485                                 /*
 486                                  * Flush rest of answer
 487                                  * so connection stays in synch.
 488                                  */
 489                                 anhp->tc = 1;
 490                                 len = resplen - anssiz;
 491                                 while (len != 0) {
 492                                         char junk[PACKETSZ];
 493
 494                                         n = (len > sizeof(junk)
 495                                              ? sizeof(junk)
 496                                              : len);
 497                                         if ((n = read(s, junk, n)) > 0)
 498                                                 len -= n;
 499                                         else
 500                                                 break;
 501                                 }
 502                         }
 503                 } else {
 504                         /*
 505                          * Use datagrams.
 506                          */
 507                         struct timeval timeout;
 508                         fd_set dsmask;
 509                         struct sockaddr_in from;
 510                         int fromlen;
 511
 512                         if ((s < 0) || vc) {
 513                                 if (vc)
 514                                         _res_close();
 515                                 s = socket(PF_INET, SOCK_DGRAM, 0);
 516                                 if (s < 0) {
 517 #if !CAN_RECONNECT
 518  bad_dg_sock:
 519 #endif
 520                                         terrno = errno;
 521                                         Perror(stderr, "socket(dg)", errno);
 522                                         return (-1);
 523                                 }
 524                                 connected = 0;
 525                         }
 526                         /*
 527                          * On a 4.3BSD+ machine (client and server,
 528                          * actually), sending to a nameserver datagram
 529                          * port with no nameserver will cause an
 530                          * ICMP port unreachable message to be returned.
 531                          * If our datagram socket is "connected" to the
 532                          * server, we get an ECONNREFUSED error on the next
 533                          * socket operation, and select returns if the
 534                          * error message is received.  We can thus detect
 535                          * the absence of a nameserver without timing out.
 536                          * If we have sent queries to at least two servers,
 537                          * however, we don't want to remain connected,
 538                          * as we wish to receive answers from the first
 539                          * server to respond.
 540                          */
 541                         if (_res.nscount == 1 || (try == 0 && ns == 0)) {
 542                                 /*
 543                                  * Connect only if we are sure we won't
 544                                  * receive a response from another server.
 545                                  */
 546                                 if (!connected) {
 547                                         if (connect(s, (struct sockaddr *)nsap,
 548                                                     sizeof(struct sockaddr)
 549                                                     ) < 0) {
 550                                                 Aerror(stderr,
 551                                                        "connect(dg)",
 552                                                        errno, *nsap);
 553                                                 badns |= (1 << ns);
 554                                                 _res_close();
 555                                                 goto next_ns;
 556                                         }
 557                                         connected = 1;
 558                                 }
 559                                 if (send(s, (char*)buf, buflen, 0) != buflen) {
 560                                         Perror(stderr, "send", errno);
 561                                         badns |= (1 << ns);
 562                                         _res_close();
 563                                         goto next_ns;
 564                                 }
 565                         } else {
 566                                 /*
 567                                  * Disconnect if we want to listen
 568                                  * for responses from more than one server.
 569                                  */
 570                                 if (connected) {
 571 #if CAN_RECONNECT
 572                                         struct sockaddr_in no_addr;
 573
 574                                         no_addr.sin_family = AF_INET;
 575                                         no_addr.sin_addr.s_addr = INADDR_ANY;
 576                                         no_addr.sin_port = 0;
 577                                         (void) connect(s,
 578                                                        (struct sockaddr *)
 579                                                         &no_addr,
 580                                                        sizeof(no_addr));
 581 #else
 582                                         int s1 = socket(PF_INET, SOCK_DGRAM,0);
 583                                         if (s1 < 0)
 584                                                 goto bad_dg_sock;
 585                                         (void) dup2(s1, s);
 586                                         (void) close(s1);
 587                                         Dprint(_res.options & RES_DEBUG,
 588                                                (stdout, ";; new DG socket\n"))
 589 #endif
 590                                         connected = 0;
 591                                         errno = 0;
 592                                 }
 593                                 if (sendto(s, (char*)buf, buflen, 0,
 594                                            (struct sockaddr *)nsap,
 595                                            sizeof(struct sockaddr))
 596                                     != buflen) {
 597                                         Aerror(stderr, "sendto", errno, *nsap);
 598                                         badns |= (1 << ns);
 599                                         _res_close();
 600                                         goto next_ns;
 601                                 }
 602                         }
 603
 604                         /*
 605                          * Wait for reply
 606                          */
 607                         timeout.tv_sec = (_res.retrans << try);
 608                         if (try > 0)
 609                                 timeout.tv_sec /= _res.nscount;
 610                         if ((long) timeout.tv_sec <= 0)
 611                                 timeout.tv_sec = 1;
 612                         timeout.tv_usec = 0;
 613     wait:
 614                         FD_ZERO(&dsmask);
 615                         FD_SET(s, &dsmask);
 616                         n = select(s+1, &dsmask, (fd_set *)NULL,
 617                                    (fd_set *)NULL, &timeout);
 618                         if (n < 0) {
 619                                 Perror(stderr, "select", errno);
 620                                 _res_close();
 621                                 goto next_ns;
 622                         }
 623                         if (n == 0) {
 624                                 /*
 625                                  * timeout
 626                                  */
 627                                 Dprint(_res.options & RES_DEBUG,
 628                                        (stdout, ";; timeout\n"));
 629                                 gotsomewhere = 1;
 630                                 _res_close();
 631                                 goto next_ns;
 632                         }
 633                         errno = 0;
 634                         fromlen = sizeof(struct sockaddr_in);
 635                         resplen = recvfrom(s, (char*)ans, anssiz, 0,
 636                                            (struct sockaddr *)&from, &fromlen);
 637                         if (resplen <= 0) {
 638                                 Perror(stderr, "recvfrom", errno);
 639                                 _res_close();
 640                                 goto next_ns;
 641                         }
 642                         gotsomewhere = 1;
 643                         if (hp->id != anhp->id) {
 644                                 /*
 645                                  * response from old query, ignore it.
 646                                  * XXX - potential security hazard could
 647                                  *       be detected here.
 648                                  */
 649                                 DprintQ((_res.options & RES_DEBUG) ||
 650                                         (_res.pfcode & RES_PRF_REPLY),
 651                                         (stdout, ";; old answer:\n"),
 652                                         ans, resplen);
 653                                 goto wait;
 654                         }
 655 #if CHECK_SRVR_ADDR
 656                         if (!(_res.options & RES_INSECURE1) &&
 657                             !res_isourserver(&from)) {
 658                                 /*
 659                                  * response from wrong server? ignore it.
 660                                  * XXX - potential security hazard could
 661                                  *       be detected here.
 662                                  */
 663                                 DprintQ((_res.options & RES_DEBUG) ||
 664                                         (_res.pfcode & RES_PRF_REPLY),
 665                                         (stdout, ";; not our server:\n"),
 666                                         ans, resplen);
 667                                 goto wait;
 668                         }
 669 #endif
 670                         if (!(_res.options & RES_INSECURE2) &&
 671                             !res_queriesmatch(buf, buf + buflen,
 672                                               ans, ans + anssiz)) {
 673                                 /*
 674                                  * response contains wrong query? ignore it.
 675                                  * XXX - potential security hazard could
 676                                  *       be detected here.
 677                                  */
 678                                 DprintQ((_res.options & RES_DEBUG) ||
 679                                         (_res.pfcode & RES_PRF_REPLY),
 680                                         (stdout, ";; wrong query name:\n"),
 681                                         ans, resplen);
 682                                 goto wait;
 683                         }
 684                         if (anhp->rcode == SERVFAIL ||
 685                             anhp->rcode == NOTIMP ||
 686                             anhp->rcode == REFUSED) {
 687                                 DprintQ(_res.options & RES_DEBUG,
 688                                         (stdout, "server rejected query:\n"),
 689                                         ans, resplen);
 690                                 badns |= (1 << ns);
 691                                 _res_close();
 692                                 /* don't retry if called from dig */
 693                                 if (!_res.pfcode)
 694                                         goto next_ns;
 695                         }
 696                         if (!(_res.options & RES_IGNTC) && anhp->tc) {
 697                                 /*
 698                                  * get rest of answer;
 699                                  * use TCP with same server.
 700                                  */
 701                                 Dprint(_res.options & RES_DEBUG,
 702                                        (stdout, ";; truncated answer\n"));
 703                                 v_circuit = 1;
 704                                 _res_close();
 705                                 goto same_ns;
 706                         }
 707                 } /*if vc/dg*/
 708                 DprintQ((_res.options & RES_DEBUG) ||
 709                         (_res.pfcode & RES_PRF_REPLY),
 710                         (stdout, ";; got answer:\n"),
 711                         ans, resplen);
 712                 /*
 713                  * If using virtual circuits, we assume that the first server
 714                  * is preferred over the rest (i.e. it is on the local
 715                  * machine) and only keep that one open.
 716                  * If we have temporarily opened a virtual circuit,
 717                  * or if we haven't been asked to keep a socket open,
 718                  * close the socket.
 719                  */
 720                 if ((v_circuit && (!(_res.options & RES_USEVC) || ns != 0)) ||
 721                     !(_res.options & RES_STAYOPEN)) {
 722                         _res_close();
 723                 }
 724                 if (Rhook) {
 725                         int done = 0, loops = 0;
 726
 727                         do {
 728                                 res_sendhookact act;
 729
 730                                 act = (*Rhook)(nsap, buf, buflen,
 731                                                ans, anssiz, &resplen);
 732                                 switch (act) {
 733                                 case res_goahead:
 734                                 case res_done:
 735                                         done = 1;
 736                                         break;
 737                                 case res_nextns:
 738                                         _res_close();
 739                                         goto next_ns;
 740                                 case res_modified:
 741                                         /* give the hook another try */
 742                                         if (++loops < 42) /*doug adams*/
 743                                                 break;
 744                                         /*FALLTHROUGH*/
 745                                 case res_error:
 746                                         /*FALLTHROUGH*/
 747                                 default:
 748                                         return (-1);
 749                                 }
 750                         } while (!done);
 751
 752                 }
 753                 return (resplen);
 754     next_ns: ;
 755            } /*foreach ns*/
 756         } /*foreach retry*/
 757         _res_close();
 758         if (!v_circuit)
 759                 if (!gotsomewhere)
 760                         errno = ECONNREFUSED;   /* no nameservers found */
 761                 else
 762                         errno = ETIMEDOUT;      /* no answer obtained */
 763         else
 764                 errno = terrno;
 765         return (-1);
 766 }
 767
 768 /*
 769  * This routine is for closing the socket if a virtual circuit is used and
 770  * the program wants to close it.  This provides support for endhostent()
 771  * which expects to close the socket.
 772  *
 773  * This routine is not expected to be user visible.
 774  */
 775 void
 776 _res_close()
 777 {
 778         if (s >= 0) {
 779                 (void) close(s);
 780                 s = -1;
 781                 connected = 0;
 782                 vc = 0;
 783         }
 784 }