contrib/bind/lib/resolv/res_send.c

   1 /*
   2  * Copyright (c) 1985, 1989, 1993
   3  *    The Regents of the University of California.  All rights reserved.
   4  *
   5  * Redistribution and use in source and binary forms, with or without
   6  * modification, are permitted provided that the following conditions
   7  * are met:
   8  * 1. Redistributions of source code must retain the above copyright
   9  *    notice, this list of conditions and the following disclaimer.
  10  * 2. Redistributions in binary form must reproduce the above copyright
  11  *    notice, this list of conditions and the following disclaimer in the
  12  *    documentation and/or other materials provided with the distribution.
  13  * 3. All advertising materials mentioning features or use of this software
  14  *    must display the following acknowledgement:
  15  *      This product includes software developed by the University of
  16  *      California, Berkeley and its contributors.
  17  * 4. Neither the name of the University nor the names of its contributors
  18  *    may be used to endorse or promote products derived from this software
  19  *    without specific prior written permission.
  20  *
  21  * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
  22  * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
  23  * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
  24  * ARE DISCLAIMED.  IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
  25  * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
  26  * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
  27  * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
  28  * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
  29  * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
  30  * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
  31  * SUCH DAMAGE.
  32  */
  33
  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
  54 /*
  55  * Portions Copyright (c) 1996 by Internet Software Consortium.
  56  *
  57  * Permission to use, copy, modify, and distribute this software for any
  58  * purpose with or without fee is hereby granted, provided that the above
  59  * copyright notice and this permission notice appear in all copies.
  60  *
  61  * THE SOFTWARE IS PROVIDED "AS IS" AND INTERNET SOFTWARE CONSORTIUM DISCLAIMS
  62  * ALL WARRANTIES WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES
  63  * OF MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL INTERNET SOFTWARE
  64  * CONSORTIUM BE LIABLE FOR ANY SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL
  65  * DAMAGES OR ANY DAMAGES WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR
  66  * PROFITS, WHETHER IN AN ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS
  67  * ACTION, ARISING OUT OF OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS
  68  * SOFTWARE.
  69  */
  70
  71 #if defined(LIBC_SCCS) && !defined(lint)
  72 static char sccsid[] = "@(#)res_send.c  8.1 (Berkeley) 6/4/93";
  73 static char rcsid[] = "$Id: res_send.c,v 8.20 1998/04/06 23:27:51 halley Exp $";
  74 #endif /* LIBC_SCCS and not lint */
  75
  76 /*
  77  * Send query to name server and wait for reply.
  78  */
  79
  80 #include "port_before.h"
  81 #include "fd_setsize.h"
  82
  83 #include <sys/types.h>
  84 #include <sys/param.h>
  85 #include <sys/time.h>
  86 #include <sys/socket.h>
  87 #include <sys/uio.h>
  88
  89 #include <netinet/in.h>
  90 #include <arpa/nameser.h>
  91 #include <arpa/inet.h>
  92
  93 #include <errno.h>
  94 #include <netdb.h>
  95 #include <resolv.h>
  96 #include <stdio.h>
  97 #include <stdlib.h>
  98 #include <string.h>
  99 #include <unistd.h>
 100
 101 #include "port_after.h"
 102
 103 /* Options.  Leave them on. */
 104 #define DEBUG
 105 #define CHECK_SRVR_ADDR
 106
 107 static int s = -1;              /* socket used for communications */
 108 static int connected = 0;       /* is the socket connected */
 109 static int vc = 0;              /* is the socket a virtual circuit? */
 110 static res_send_qhook Qhook = NULL;
 111 static res_send_rhook Rhook = NULL;
 112
 113
 114 #ifndef DEBUG
 115 #   define Dprint(cond, args) /*empty*/
 116 #   define DprintQ(cond, args, query, size) /*empty*/
 117 #   define Aerror(file, string, error, address) /*empty*/
 118 #   define Perror(file, string, error) /*empty*/
 119 #else
 120 #   define Dprint(cond, args) if (cond) {fprintf args;} else {}
 121 #   define DprintQ(cond, args, query, size) if (cond) {\
 122                         fprintf args;\
 123                         __fp_nquery(query, size, stdout);\
 124                 } else {}
 125     static void
 126     Aerror(file, string, error, address)
 127         FILE *file;
 128         char *string;
 129         int error;
 130         struct sockaddr_in address;
 131     {
 132         int save = errno;
 133
 134         if (_res.options & RES_DEBUG) {
 135                 fprintf(file, "res_send: %s ([%s].%u): %s\n",
 136                         string,
 137                         inet_ntoa(address.sin_addr),
 138                         ntohs(address.sin_port),
 139                         strerror(error));
 140         }
 141         errno = save;
 142     }
 143     static void
 144     Perror(file, string, error)
 145         FILE *file;
 146         char *string;
 147         int error;
 148     {
 149         int save = errno;
 150
 151         if (_res.options & RES_DEBUG) {
 152                 fprintf(file, "res_send: %s: %s\n",
 153                         string, strerror(error));
 154         }
 155         errno = save;
 156     }
 157 #endif
 158
 159 void
 160 res_send_setqhook(res_send_qhook hook) {
 161         Qhook = hook;
 162 }
 163
 164 void
 165 res_send_setrhook(res_send_rhook hook) {
 166         Rhook = hook;
 167 }
 168
 169 /* int
 170  * res_isourserver(ina)
 171  *      looks up "ina" in _res.ns_addr_list[]
 172  * returns:
 173  *      0  : not found
 174  *      >0 : found
 175  * author:
 176  *      paul vixie, 29may94
 177  */
 178 int
 179 res_isourserver(const struct sockaddr_in *inp) {
 180         struct sockaddr_in ina;
 181         int ns, ret;
 182
 183         ina = *inp;
 184         ret = 0;
 185         for (ns = 0;  ns < _res.nscount;  ns++) {
 186                 const struct sockaddr_in *srv = &_res.nsaddr_list[ns];
 187
 188                 if (srv->sin_family == ina.sin_family &&
 189                     srv->sin_port == ina.sin_port &&
 190                     (srv->sin_addr.s_addr == INADDR_ANY ||
 191                      srv->sin_addr.s_addr == ina.sin_addr.s_addr)) {
 192                         ret++;
 193                         break;
 194                 }
 195         }
 196         return (ret);
 197 }
 198
 199 /* int
 200  * res_nameinquery(name, type, class, buf, eom)
 201  *      look for (name,type,class) in the query section of packet (buf,eom)
 202  * requires:
 203  *      buf + HFIXEDSZ <= eom
 204  * returns:
 205  *      -1 : format error
 206  *      0  : not found
 207  *      >0 : found
 208  * author:
 209  *      paul vixie, 29may94
 210  */
 211 int
 212 res_nameinquery(const char *name, int type, int class,
 213                 const u_char *buf, const u_char *eom)
 214 {
 215         const u_char *cp = buf + HFIXEDSZ;
 216         int qdcount = ntohs(((HEADER*)buf)->qdcount);
 217
 218         while (qdcount-- > 0) {
 219                 char tname[MAXDNAME+1];
 220                 int n, ttype, tclass;
 221
 222                 n = dn_expand(buf, eom, cp, tname, sizeof tname);
 223                 if (n < 0)
 224                         return (-1);
 225                 cp += n;
 226                 if (cp + 2 * INT16SZ > eom)
 227                         return (-1);
 228                 ttype = ns_get16(cp); cp += INT16SZ;
 229                 tclass = ns_get16(cp); cp += INT16SZ;
 230                 if (ttype == type &&
 231                     tclass == class &&
 232                     strcasecmp(tname, name) == 0)
 233                         return (1);
 234         }
 235         return (0);
 236 }
 237
 238 /* int
 239  * res_queriesmatch(buf1, eom1, buf2, eom2)
 240  *      is there a 1:1 mapping of (name,type,class)
 241  *      in (buf1,eom1) and (buf2,eom2)?
 242  * returns:
 243  *      -1 : format error
 244  *      0  : not a 1:1 mapping
 245  *      >0 : is a 1:1 mapping
 246  * author:
 247  *      paul vixie, 29may94
 248  */
 249 int
 250 res_queriesmatch(const u_char *buf1, const u_char *eom1,
 251                  const u_char *buf2, const u_char *eom2)
 252 {
 253         const u_char *cp = buf1 + HFIXEDSZ;
 254         int qdcount = ntohs(((HEADER*)buf1)->qdcount);
 255
 256         if (buf1 + HFIXEDSZ > eom1 || buf2 + HFIXEDSZ > eom2)
 257                 return (-1);
 258
 259         /*
 260          * Only header section present in replies to
 261          * dynamic update packets.
 262          */
 263         if ( (((HEADER *)buf1)->opcode == ns_o_update) &&
 264              (((HEADER *)buf2)->opcode == ns_o_update) )
 265                 return (1);
 266
 267         if (qdcount != ntohs(((HEADER*)buf2)->qdcount))
 268                 return (0);
 269         while (qdcount-- > 0) {
 270                 char tname[MAXDNAME+1];
 271                 int n, ttype, tclass;
 272
 273                 n = dn_expand(buf1, eom1, cp, tname, sizeof tname);
 274                 if (n < 0)
 275                         return (-1);
 276                 cp += n;
 277                 if (cp + 2 * INT16SZ > eom1)
 278                         return (-1);
 279                 ttype = ns_get16(cp);   cp += INT16SZ;
 280                 tclass = ns_get16(cp); cp += INT16SZ;
 281                 if (!res_nameinquery(tname, ttype, tclass, buf2, eom2))
 282                         return (0);
 283         }
 284         return (1);
 285 }
 286
 287 int
 288 res_send(const u_char *buf, int buflen, u_char *ans, int anssiz) {
 289         HEADER *hp = (HEADER *) buf;
 290         HEADER *anhp = (HEADER *) ans;
 291         int gotsomewhere, connreset, terrno, try, v_circuit, resplen, ns, n;
 292         u_int badns;    /* XXX NSMAX can't exceed #/bits in this variable */
 293
 294         if ((_res.options & RES_INIT) == 0 && res_init() == -1) {
 295                 /* errno should have been set by res_init() in this case. */
 296                 return (-1);
 297         }
 298         if (anssiz < HFIXEDSZ) {
 299                 errno = EINVAL;
 300                 return (-1);
 301         }
 302         DprintQ((_res.options & RES_DEBUG) || (_res.pfcode & RES_PRF_QUERY),
 303                 (stdout, ";; res_send()\n"), buf, buflen);
 304         v_circuit = (_res.options & RES_USEVC) || buflen > PACKETSZ;
 305         gotsomewhere = 0;
 306         connreset = 0;
 307         terrno = ETIMEDOUT;
 308         badns = 0;
 309
 310         /*
 311          * Send request, RETRY times, or until successful
 312          */
 313         for (try = 0; try < _res.retry; try++) {
 314             for (ns = 0; ns < _res.nscount; ns++) {
 315                 struct sockaddr_in *nsap = &_res.nsaddr_list[ns];
 316  same_ns:
 317                 if (badns & (1 << ns)) {
 318                         res_close();
 319                         goto next_ns;
 320                 }
 321
 322                 if (Qhook) {
 323                         int done = 0, loops = 0;
 324
 325                         do {
 326                                 res_sendhookact act;
 327
 328                                 act = (*Qhook)(&nsap, &buf, &buflen,
 329                                                ans, anssiz, &resplen);
 330                                 switch (act) {
 331                                 case res_goahead:
 332                                         done = 1;
 333                                         break;
 334                                 case res_nextns:
 335                                         res_close();
 336                                         goto next_ns;
 337                                 case res_done:
 338                                         return (resplen);
 339                                 case res_modified:
 340                                         /* give the hook another try */
 341                                         if (++loops < 42) /*doug adams*/
 342                                                 break;
 343                                         /*FALLTHROUGH*/
 344                                 case res_error:
 345                                         /*FALLTHROUGH*/
 346                                 default:
 347                                         return (-1);
 348                                 }
 349                         } while (!done);
 350                 }
 351
 352                 Dprint(_res.options & RES_DEBUG,
 353                        (stdout, ";; Querying server (# %d) address = %s\n",
 354                         ns + 1, inet_ntoa(nsap->sin_addr)));
 355
 356                 if (v_circuit) {
 357                         int truncated;
 358                         struct iovec iov[2];
 359                         u_short len;
 360                         u_char *cp;
 361
 362                         /*
 363                          * Use virtual circuit;
 364                          * at most one attempt per server.
 365                          */
 366                         try = _res.retry;
 367                         truncated = 0;
 368                         if (s < 0 || !vc || hp->opcode == ns_o_update) {
 369                                 if (s >= 0)
 370                                         res_close();
 371
 372                                 s = socket(PF_INET, SOCK_STREAM, 0);
 373                                 if (s < 0) {
 374                                         terrno = errno;
 375                                         Perror(stderr, "socket(vc)", errno);
 376                                         return (-1);
 377                                 }
 378                                 errno = 0;
 379                                 if (connect(s, (struct sockaddr *)nsap,
 380                                             sizeof *nsap) < 0) {
 381                                         terrno = errno;
 382                                         Aerror(stderr, "connect/vc",
 383                                                errno, *nsap);
 384                                         badns |= (1 << ns);
 385                                         res_close();
 386                                         goto next_ns;
 387                                 }
 388                                 vc = 1;
 389                         }
 390                         /*
 391                          * Send length & message
 392                          */
 393                         putshort((u_short)buflen, (u_char*)&len);
 394                         iov[0].iov_base = (caddr_t)&len;
 395                         iov[0].iov_len = INT16SZ;
 396                         iov[1].iov_base = (caddr_t)buf;
 397                         iov[1].iov_len = buflen;
 398                         if (writev(s, iov, 2) != (INT16SZ + buflen)) {
 399                                 terrno = errno;
 400                                 Perror(stderr, "write failed", errno);
 401                                 badns |= (1 << ns);
 402                                 res_close();
 403                                 goto next_ns;
 404                         }
 405                         /*
 406                          * Receive length & response
 407                          */
 408  read_len:
 409                         cp = ans;
 410                         len = INT16SZ;
 411                         while ((n = read(s, (char *)cp, (int)len)) > 0) {
 412                                 cp += n;
 413                                 if ((len -= n) <= 0)
 414                                         break;
 415                         }
 416                         if (n <= 0) {
 417                                 terrno = errno;
 418                                 Perror(stderr, "read failed", errno);
 419                                 res_close();
 420                                 /*
 421                                  * A long running process might get its TCP
 422                                  * connection reset if the remote server was
 423                                  * restarted.  Requery the server instead of
 424                                  * trying a new one.  When there is only one
 425                                  * server, this means that a query might work
 426                                  * instead of failing.  We only allow one reset
 427                                  * per query to prevent looping.
 428                                  */
 429                                 if (terrno == ECONNRESET && !connreset) {
 430                                         connreset = 1;
 431                                         res_close();
 432                                         goto same_ns;
 433                                 }
 434                                 res_close();
 435                                 goto next_ns;
 436                         }
 437                         resplen = ns_get16(ans);
 438                         if (resplen > anssiz) {
 439                                 Dprint(_res.options & RES_DEBUG,
 440                                        (stdout, ";; response truncated\n")
 441                                        );
 442                                 truncated = 1;
 443                                 len = anssiz;
 444                         } else
 445                                 len = resplen;
 446                         if (len < HFIXEDSZ) {
 447                                 /*
 448                                  * Undersized message.
 449                                  */
 450                                 Dprint(_res.options & RES_DEBUG,
 451                                        (stdout, ";; undersized: %d\n", len));
 452                                 terrno = EMSGSIZE;
 453                                 badns |= (1 << ns);
 454                                 res_close();
 455                                 goto next_ns;
 456                         }
 457                         cp = ans;
 458                         while (len != 0 &&
 459                                (n = read(s, (char *)cp, (int)len)) > 0) {
 460                                 cp += n;
 461                                 len -= n;
 462                         }
 463                         if (n <= 0) {
 464                                 terrno = errno;
 465                                 Perror(stderr, "read(vc)", errno);
 466                                 res_close();
 467                                 goto next_ns;
 468                         }
 469                         if (truncated) {
 470                                 /*
 471                                  * Flush rest of answer
 472                                  * so connection stays in synch.
 473                                  */
 474                                 anhp->tc = 1;
 475                                 len = resplen - anssiz;
 476                                 while (len != 0) {
 477                                         char junk[PACKETSZ];
 478
 479                                         n = (len > sizeof(junk)
 480                                              ? sizeof(junk)
 481                                              : len);
 482                                         if ((n = read(s, junk, n)) > 0)
 483                                                 len -= n;
 484                                         else
 485                                                 break;
 486                                 }
 487                         }
 488                         /*
 489                          * The calling applicating has bailed out of
 490                          * a previous call and failed to arrange to have
 491                          * the circuit closed or the server has got
 492                          * itself confused. Anyway drop the packet and
 493                          * wait for the correct one.
 494                          */
 495                         if (hp->id != anhp->id) {
 496                                 DprintQ((_res.options & RES_DEBUG) ||
 497                                         (_res.pfcode & RES_PRF_REPLY),
 498                                         (stdout, ";; old answer (unexpected):\n"),
 499                                         ans, (resplen>anssiz)?anssiz:resplen);
 500                                 goto read_len;
 501                         }
 502                 } else {
 503                         /*
 504                          * Use datagrams.
 505                          */
 506                         struct timeval timeout;
 507                         fd_set dsmask;
 508                         struct sockaddr_in from;
 509                         int fromlen;
 510
 511                         if ((s < 0) || vc) {
 512                                 if (vc)
 513                                         res_close();
 514                                 s = socket(PF_INET, SOCK_DGRAM, 0);
 515                                 if (s < 0) {
 516 #ifndef CAN_RECONNECT
 517  bad_dg_sock:
 518 #endif
 519                                         terrno = errno;
 520                                         Perror(stderr, "socket(dg)", errno);
 521                                         return (-1);
 522                                 }
 523                                 connected = 0;
 524                         }
 525 #ifndef CANNOT_CONNECT_DGRAM
 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 *nsap
 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 #ifdef 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 /* CAN_RECONNECT */
 590                                         connected = 0;
 591                                         errno = 0;
 592                                 }
 593 #endif /* !CANNOT_CONNECT_DGRAM */
 594                                 if (sendto(s, (char*)buf, buflen, 0,
 595                                            (struct sockaddr *)nsap,
 596                                            sizeof *nsap)
 597                                     != buflen) {
 598                                         Aerror(stderr, "sendto", errno, *nsap);
 599                                         badns |= (1 << ns);
 600                                         res_close();
 601                                         goto next_ns;
 602                                 }
 603 #ifndef CANNOT_CONNECT_DGRAM
 604                         }
 605 #endif /* !CANNOT_CONNECT_DGRAM */
 606
 607                         /*
 608                          * Wait for reply
 609                          */
 610                         timeout.tv_sec = (_res.retrans << try);
 611                         if (try > 0)
 612                                 timeout.tv_sec /= _res.nscount;
 613                         if ((long) timeout.tv_sec <= 0)
 614                                 timeout.tv_sec = 1;
 615                         timeout.tv_usec = 0;
 616  wait:
 617                         if (s < 0 || s >= FD_SETSIZE) {
 618                                 Perror(stderr, "s out-of-bounds", EMFILE);
 619                                 res_close();
 620                                 goto next_ns;
 621                         }
 622                         FD_ZERO(&dsmask);
 623                         FD_SET(s, &dsmask);
 624                         n = select(s+1, &dsmask, (fd_set *)NULL,
 625                                    (fd_set *)NULL, &timeout);
 626                         if (n < 0) {
 627                                 if (errno == EINTR)
 628                                         goto wait;
 629                                 Perror(stderr, "select", errno);
 630                                 res_close();
 631                                 goto next_ns;
 632                         }
 633                         if (n == 0) {
 634                                 /*
 635                                  * timeout
 636                                  */
 637                                 Dprint(_res.options & RES_DEBUG,
 638                                        (stdout, ";; timeout\n"));
 639                                 gotsomewhere = 1;
 640                                 res_close();
 641                                 goto next_ns;
 642                         }
 643                         errno = 0;
 644                         fromlen = sizeof(struct sockaddr_in);
 645                         resplen = recvfrom(s, (char*)ans, anssiz, 0,
 646                                            (struct sockaddr *)&from, &fromlen);
 647                         if (resplen <= 0) {
 648                                 Perror(stderr, "recvfrom", errno);
 649                                 res_close();
 650                                 goto next_ns;
 651                         }
 652                         gotsomewhere = 1;
 653                         if (resplen < HFIXEDSZ) {
 654                                 /*
 655                                  * Undersized message.
 656                                  */
 657                                 Dprint(_res.options & RES_DEBUG,
 658                                        (stdout, ";; undersized: %d\n",
 659                                         resplen));
 660                                 terrno = EMSGSIZE;
 661                                 badns |= (1 << ns);
 662                                 res_close();
 663                                 goto next_ns;
 664                         }
 665                         if (hp->id != anhp->id) {
 666                                 /*
 667                                  * response from old query, ignore it.
 668                                  * XXX - potential security hazard could
 669                                  *       be detected here.
 670                                  */
 671                                 DprintQ((_res.options & RES_DEBUG) ||
 672                                         (_res.pfcode & RES_PRF_REPLY),
 673                                         (stdout, ";; old answer:\n"),
 674                                         ans, (resplen>anssiz)?anssiz:resplen);
 675                                 goto wait;
 676                         }
 677 #ifdef CHECK_SRVR_ADDR
 678                         if (!(_res.options & RES_INSECURE1) &&
 679                             !res_isourserver(&from)) {
 680                                 /*
 681                                  * response from wrong server? ignore it.
 682                                  * XXX - potential security hazard could
 683                                  *       be detected here.
 684                                  */
 685                                 DprintQ((_res.options & RES_DEBUG) ||
 686                                         (_res.pfcode & RES_PRF_REPLY),
 687                                         (stdout, ";; not our server:\n"),
 688                                         ans, (resplen>anssiz)?anssiz:resplen);
 689                                 goto wait;
 690                         }
 691 #endif
 692                         if (!(_res.options & RES_INSECURE2) &&
 693                             !res_queriesmatch(buf, buf + buflen,
 694                                               ans, ans + anssiz)) {
 695                                 /*
 696                                  * response contains wrong query? ignore it.
 697                                  * XXX - potential security hazard could
 698                                  *       be detected here.
 699                                  */
 700                                 DprintQ((_res.options & RES_DEBUG) ||
 701                                         (_res.pfcode & RES_PRF_REPLY),
 702                                         (stdout, ";; wrong query name:\n"),
 703                                         ans, (resplen>anssiz)?anssiz:resplen);
 704                                 goto wait;
 705                         }
 706                         if (anhp->rcode == SERVFAIL ||
 707                             anhp->rcode == NOTIMP ||
 708                             anhp->rcode == REFUSED) {
 709                                 DprintQ(_res.options & RES_DEBUG,
 710                                         (stdout, "server rejected query:\n"),
 711                                         ans, (resplen>anssiz)?anssiz:resplen);
 712                                 badns |= (1 << ns);
 713                                 res_close();
 714                                 /* don't retry if called from dig */
 715                                 if (!_res.pfcode)
 716                                         goto next_ns;
 717                         }
 718                         if (!(_res.options & RES_IGNTC) && anhp->tc) {
 719                                 /*
 720                                  * get rest of answer;
 721                                  * use TCP with same server.
 722                                  */
 723                                 Dprint(_res.options & RES_DEBUG,
 724                                        (stdout, ";; truncated answer\n"));
 725                                 v_circuit = 1;
 726                                 res_close();
 727                                 goto same_ns;
 728                         }
 729                 } /*if vc/dg*/
 730                 Dprint((_res.options & RES_DEBUG) ||
 731                        ((_res.pfcode & RES_PRF_REPLY) &&
 732                         (_res.pfcode & RES_PRF_HEAD1)),
 733                        (stdout, ";; got answer:\n"));
 734                 DprintQ((_res.options & RES_DEBUG) ||
 735                         (_res.pfcode & RES_PRF_REPLY),
 736                         (stdout, ""),
 737                         ans, (resplen>anssiz)?anssiz:resplen);
 738                 /*
 739                  * If using virtual circuits, we assume that the first server
 740                  * is preferred over the rest (i.e. it is on the local
 741                  * machine) and only keep that one open.
 742                  * If we have temporarily opened a virtual circuit,
 743                  * or if we haven't been asked to keep a socket open,
 744                  * close the socket.
 745                  */
 746                 if ((v_circuit && (!(_res.options & RES_USEVC) || ns != 0)) ||
 747                     !(_res.options & RES_STAYOPEN)) {
 748                         res_close();
 749                 }
 750                 if (Rhook) {
 751                         int done = 0, loops = 0;
 752
 753                         do {
 754                                 res_sendhookact act;
 755
 756                                 act = (*Rhook)(nsap, buf, buflen,
 757                                                ans, anssiz, &resplen);
 758                                 switch (act) {
 759                                 case res_goahead:
 760                                 case res_done:
 761                                         done = 1;
 762                                         break;
 763                                 case res_nextns:
 764                                         res_close();
 765                                         goto next_ns;
 766                                 case res_modified:
 767                                         /* give the hook another try */
 768                                         if (++loops < 42) /*doug adams*/
 769                                                 break;
 770                                         /*FALLTHROUGH*/
 771                                 case res_error:
 772                                         /*FALLTHROUGH*/
 773                                 default:
 774                                         return (-1);
 775                                 }
 776                         } while (!done);
 777
 778                 }
 779                 return (resplen);
 780  next_ns: ;
 781            } /*foreach ns*/
 782         } /*foreach retry*/
 783         res_close();
 784         if (!v_circuit) {
 785                 if (!gotsomewhere)
 786                         errno = ECONNREFUSED;   /* no nameservers found */
 787                 else
 788                         errno = ETIMEDOUT;      /* no answer obtained */
 789         } else
 790                 errno = terrno;
 791         return (-1);
 792 }
 793
 794 /*
 795  * This routine is for closing the socket if a virtual circuit is used and
 796  * the program wants to close it.  This provides support for endhostent()
 797  * which expects to close the socket.
 798  *
 799  * This routine is not expected to be user visible.
 800  */
 801 void
 802 res_close() {
 803         if (s >= 0) {
 804                 (void) close(s);
 805                 s = -1;
 806                 connected = 0;
 807                 vc = 0;
 808         }
 809 }