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/types.h>
  73 #include <sys/param.h>
  74 #include <sys/time.h>
  75 #include <sys/socket.h>
  76 #include <sys/uio.h>
  77 #include <netinet/in.h>
  78 #include <arpa/nameser.h>
  79 #include <arpa/inet.h>
  80
  81 #include <stdio.h>
  82 #include <netdb.h>
  83 #include <errno.h>
  84 #include <resolv.h>
  85 #if defined(BSD) && (BSD >= 199306)
  86 # include <stdlib.h>
  87 # include <string.h>
  88 # include <unistd.h>
  89 #else
  90 # include "../conf/portability.h"
  91 #endif
  92
  93 #if defined(USE_OPTIONS_H)
  94 # include <../conf/options.h>
  95 #endif
  96
  97 void _res_close __P((void));
  98
  99 static int s = -1;      /* socket used for communications */
 100 static int connected = 0;       /* is the socket connected */
 101 static int vc = 0;      /* is the socket a virtual ciruit? */
 102
 103 #ifndef FD_SET
 104 /* XXX - should be in portability.h */
 105 #define NFDBITS         32
 106 #define FD_SETSIZE      32
 107 #define FD_SET(n, p)    ((p)->fds_bits[(n)/NFDBITS] |= (1 << ((n) % NFDBITS)))
 108 #define FD_CLR(n, p)    ((p)->fds_bits[(n)/NFDBITS] &= ~(1 << ((n) % NFDBITS)))
 109 #define FD_ISSET(n, p)  ((p)->fds_bits[(n)/NFDBITS] & (1 << ((n) % NFDBITS)))
 110 #define FD_ZERO(p)      bzero((char *)(p), sizeof(*(p)))
 111 #endif
 112
 113 /* XXX - this should be done in portability.h */
 114 #if (defined(BSD) && (BSD >= 199103)) || defined(linux)
 115 # define CAN_RECONNECT 1
 116 #else
 117 # define CAN_RECONNECT 0
 118 #endif
 119
 120 #ifndef DEBUG
 121 #   define Dprint(cond, args) /*empty*/
 122 #   define DprintQ(cond, args, query, size) /*empty*/
 123 #   define Aerror(file, string, error, address) /*empty*/
 124 #   define Perror(file, string, error) /*empty*/
 125 #else
 126 #   define Dprint(cond, args) if (cond) {fprintf args;} else {}
 127 #   define DprintQ(cond, args, query, size) if (cond) {\
 128                         fprintf args;\
 129                         __fp_nquery(query, size, stdout);\
 130                 } else {}
 131     static void
 132     Aerror(file, string, error, address)
 133         FILE *file;
 134         char *string;
 135         int error;
 136         struct sockaddr_in address;
 137     {
 138         int save = errno;
 139
 140         if (_res.options & RES_DEBUG) {
 141                 fprintf(file, "res_send: %s ([%s].%u): %s\n",
 142                         string,
 143                         inet_ntoa(address.sin_addr),
 144                         ntohs(address.sin_port),
 145                         strerror(error));
 146         }
 147         errno = save;
 148     }
 149     static void
 150     Perror(file, string, error)
 151         FILE *file;
 152         char *string;
 153         int error;
 154     {
 155         int save = errno;
 156
 157         if (_res.options & RES_DEBUG) {
 158                 fprintf(file, "res_send: %s: %s\n",
 159                         string, strerror(error));
 160         }
 161         errno = save;
 162     }
 163 #endif
 164
 165 static res_send_qhook Qhook = NULL;
 166 static res_send_rhook Rhook = NULL;
 167
 168 void
 169 res_send_setqhook(hook)
 170         res_send_qhook hook;
 171 {
 172
 173         Qhook = hook;
 174 }
 175
 176 void
 177 res_send_setrhook(hook)
 178         res_send_rhook hook;
 179 {
 180
 181         Rhook = hook;
 182 }
 183
 184 /* int
 185  * res_isourserver(ina)
 186  *      looks up "ina" in _res.ns_addr_list[]
 187  * returns:
 188  *      0  : not found
 189  *      >0 : found
 190  * author:
 191  *      paul vixie, 29may94
 192  */
 193 int
 194 res_isourserver(inp)
 195         const struct sockaddr_in *inp;
 196 {
 197         struct sockaddr_in ina;
 198         register int ns, ret;
 199
 200         ina = *inp;
 201         ret = 0;
 202         for (ns = 0;  ns < _res.nscount;  ns++) {
 203                 register const struct sockaddr_in *srv = &_res.nsaddr_list[ns];
 204
 205                 if (srv->sin_family == ina.sin_family &&
 206                     srv->sin_port == ina.sin_port &&
 207                     (srv->sin_addr.s_addr == INADDR_ANY ||
 208                      srv->sin_addr.s_addr == ina.sin_addr.s_addr)) {
 209                         ret++;
 210                         break;
 211                 }
 212         }
 213         return (ret);
 214 }
 215
 216 /* int
 217  * res_nameinquery(name, type, class, buf, eom)
 218  *      look for (name,type,class) in the query section of packet (buf,eom)
 219  * returns:
 220  *      -1 : format error
 221  *      0  : not found
 222  *      >0 : found
 223  * author:
 224  *      paul vixie, 29may94
 225  */
 226 int
 227 res_nameinquery(name, type, class, buf, eom)
 228         const char *name;
 229         register int type, class;
 230         const u_char *buf, *eom;
 231 {
 232         register const u_char *cp = buf + HFIXEDSZ;
 233         int qdcount = ntohs(((HEADER*)buf)->qdcount);
 234
 235         while (qdcount-- > 0) {
 236                 char tname[MAXDNAME+1];
 237                 register int n, ttype, tclass;
 238
 239                 n = dn_expand(buf, eom, cp, tname, sizeof tname);
 240                 if (n < 0)
 241                         return (-1);
 242                 cp += n;
 243                 ttype = _getshort(cp); cp += INT16SZ;
 244                 tclass = _getshort(cp); cp += INT16SZ;
 245                 if (ttype == type &&
 246                     tclass == class &&
 247                     strcasecmp(tname, name) == 0)
 248                         return (1);
 249         }
 250         return (0);
 251 }
 252
 253 /* int
 254  * res_queriesmatch(buf1, eom1, buf2, eom2)
 255  *      is there a 1:1 mapping of (name,type,class)
 256  *      in (buf1,eom1) and (buf2,eom2)?
 257  * returns:
 258  *      -1 : format error
 259  *      0  : not a 1:1 mapping
 260  *      >0 : is a 1:1 mapping
 261  * author:
 262  *      paul vixie, 29may94
 263  */
 264 int
 265 res_queriesmatch(buf1, eom1, buf2, eom2)
 266         const u_char *buf1, *eom1;
 267         const u_char *buf2, *eom2;
 268 {
 269         register const u_char *cp = buf1 + HFIXEDSZ;
 270         int qdcount = ntohs(((HEADER*)buf1)->qdcount);
 271
 272         if (qdcount != ntohs(((HEADER*)buf2)->qdcount))
 273                 return (0);
 274         while (qdcount-- > 0) {
 275                 char tname[MAXDNAME+1];
 276                 register int n, ttype, tclass;
 277
 278                 n = dn_expand(buf1, eom1, cp, tname, sizeof tname);
 279                 if (n < 0)
 280                         return (-1);
 281                 cp += n;
 282                 ttype = _getshort(cp);  cp += INT16SZ;
 283                 tclass = _getshort(cp); cp += INT16SZ;
 284                 if (!res_nameinquery(tname, ttype, tclass, buf2, eom2))
 285                         return (0);
 286         }
 287         return (1);
 288 }
 289
 290 int
 291 res_send(buf, buflen, ans, anssiz)
 292         const u_char *buf;
 293         int buflen;
 294         u_char *ans;
 295         int anssiz;
 296 {
 297         HEADER *hp = (HEADER *) buf;
 298         HEADER *anhp = (HEADER *) ans;
 299         int gotsomewhere, connreset, terrno, try, v_circuit, resplen, ns;
 300         register int n;
 301         u_int badns;    /* XXX NSMAX can't exceed #/bits in this var */
 302
 303         if ((_res.options & RES_INIT) == 0 && res_init() == -1) {
 304                 /* errno should have been set by res_init() in this case. */
 305                 return (-1);
 306         }
 307         DprintQ((_res.options & RES_DEBUG) || (_res.pfcode & RES_PRF_QUERY),
 308                 (stdout, ";; res_send()\n"), buf, buflen);
 309         v_circuit = (_res.options & RES_USEVC) || buflen > PACKETSZ;
 310         gotsomewhere = 0;
 311         connreset = 0;
 312         terrno = ETIMEDOUT;
 313         badns = 0;
 314
 315         /*
 316          * Send request, RETRY times, or until successful
 317          */
 318         for (try = 0; try < _res.retry; try++) {
 319             for (ns = 0; ns < _res.nscount; ns++) {
 320                 struct sockaddr_in *nsap = &_res.nsaddr_list[ns];
 321     same_ns:
 322                 if (badns & (1 << ns)) {
 323                         _res_close();
 324                         goto next_ns;
 325                 }
 326
 327                 if (Qhook) {
 328                         int done = 0, loops = 0;
 329
 330                         do {
 331                                 res_sendhookact act;
 332
 333                                 act = (*Qhook)(&nsap, &buf, &buflen,
 334                                                ans, anssiz, &resplen);
 335                                 switch (act) {
 336                                 case res_goahead:
 337                                         done = 1;
 338                                         break;
 339                                 case res_nextns:
 340                                         _res_close();
 341                                         goto next_ns;
 342                                 case res_done:
 343                                         return (resplen);
 344                                 case res_modified:
 345                                         /* give the hook another try */
 346                                         if (++loops < 42) /*doug adams*/
 347                                                 break;
 348                                         /*FALLTHROUGH*/
 349                                 case res_error:
 350                                         /*FALLTHROUGH*/
 351                                 default:
 352                                         return (-1);
 353                                 }
 354                         } while (!done);
 355                 }
 356
 357                 Dprint(_res.options & RES_DEBUG,
 358                        (stdout, ";; Querying server (# %d) address = %s\n",
 359                         ns + 1, inet_ntoa(nsap->sin_addr)));
 360
 361                 if (v_circuit) {
 362                         int truncated;
 363                         struct iovec iov[2];
 364                         u_short len;
 365                         u_char *cp;
 366
 367                         /*
 368                          * Use virtual circuit;
 369                          * at most one attempt per server.
 370                          */
 371                         try = _res.retry;
 372                         truncated = 0;
 373                         if ((s < 0) || (!vc)) {
 374                                 if (s >= 0)
 375                                         _res_close();
 376
 377                                 s = socket(PF_INET, SOCK_STREAM, 0);
 378                                 if (s < 0) {
 379                                         terrno = errno;
 380                                         Perror(stderr, "socket(vc)", errno);
 381                                         return (-1);
 382                                 }
 383                                 errno = 0;
 384                                 if (connect(s, (struct sockaddr *)nsap,
 385                                             sizeof(struct sockaddr)) < 0) {
 386                                         terrno = errno;
 387                                         Aerror(stderr, "connect/vc",
 388                                                errno, *nsap);
 389                                         badns |= (1 << ns);
 390                                         _res_close();
 391                                         goto next_ns;
 392                                 }
 393                                 vc = 1;
 394                         }
 395                         /*
 396                          * Send length & message
 397                          */
 398                         putshort((u_short)buflen, (u_char*)&len);
 399                         iov[0].iov_base = (caddr_t)&len;
 400                         iov[0].iov_len = INT16SZ;
 401                         iov[1].iov_base = (caddr_t)buf;
 402                         iov[1].iov_len = buflen;
 403                         if (writev(s, iov, 2) != (INT16SZ + buflen)) {
 404                                 terrno = errno;
 405                                 Perror(stderr, "write failed", errno);
 406                                 badns |= (1 << ns);
 407                                 _res_close();
 408                                 goto next_ns;
 409                         }
 410                         /*
 411                          * Receive length & response
 412                          */
 413 read_len:
 414                         cp = ans;
 415                         len = INT16SZ;
 416                         while ((n = read(s, (char *)cp, (int)len)) > 0) {
 417                                 cp += n;
 418                                 if ((len -= n) <= 0)
 419                                         break;
 420                         }
 421                         if (n <= 0) {
 422                                 terrno = errno;
 423                                 Perror(stderr, "read failed", errno);
 424                                 _res_close();
 425                                 /*
 426                                  * A long running process might get its TCP
 427                                  * connection reset if the remote server was
 428                                  * restarted.  Requery the server instead of
 429                                  * trying a new one.  When there is only one
 430                                  * server, this means that a query might work
 431                                  * instead of failing.  We only allow one reset
 432                                  * per query to prevent looping.
 433                                  */
 434                                 if (terrno == ECONNRESET && !connreset) {
 435                                         connreset = 1;
 436                                         _res_close();
 437                                         goto same_ns;
 438                                 }
 439                                 _res_close();
 440                                 goto next_ns;
 441                         }
 442                         resplen = _getshort(ans);
 443                         if (resplen > anssiz) {
 444                                 Dprint(_res.options & RES_DEBUG,
 445                                        (stdout, ";; response truncated\n")
 446                                        );
 447                                 truncated = 1;
 448                                 len = anssiz;
 449                         } else
 450                                 len = resplen;
 451                         cp = ans;
 452                         while (len != 0 &&
 453                                (n = read(s, (char *)cp, (int)len)) > 0) {
 454                                 cp += n;
 455                                 len -= n;
 456                         }
 457                         if (n <= 0) {
 458                                 terrno = errno;
 459                                 Perror(stderr, "read(vc)", errno);
 460                                 _res_close();
 461                                 goto next_ns;
 462                         }
 463                         if (truncated) {
 464                                 /*
 465                                  * Flush rest of answer
 466                                  * so connection stays in synch.
 467                                  */
 468                                 anhp->tc = 1;
 469                                 len = resplen - anssiz;
 470                                 while (len != 0) {
 471                                         char junk[PACKETSZ];
 472
 473                                         n = (len > sizeof(junk)
 474                                              ? sizeof(junk)
 475                                              : len);
 476                                         if ((n = read(s, junk, n)) > 0)
 477                                                 len -= n;
 478                                         else
 479                                                 break;
 480                                 }
 481                         }
 482                         /*
 483                          * The calling applicating has bailed out of
 484                          * a previous call and failed to arrange to have
 485                          * the circuit closed or the server has got
 486                          * itself confused. Anyway drop the packet and
 487                          * wait for the correct one.
 488                          */
 489                         if (hp->id != anhp->id) {
 490                                 DprintQ((_res.options & RES_DEBUG) ||
 491                                         (_res.pfcode & RES_PRF_REPLY),
 492                                         (stdout, ";; old answer (unexpected):\n"),
 493                                         ans, (resplen>anssiz)?anssiz:resplen);
 494                                 goto read_len;
 495                         }
 496                 } else {
 497                         /*
 498                          * Use datagrams.
 499                          */
 500                         struct timeval timeout;
 501                         fd_set dsmask;
 502                         struct sockaddr_in from;
 503                         size_t fromlen;
 504
 505                         if ((s < 0) || vc) {
 506                                 if (vc)
 507                                         _res_close();
 508                                 s = socket(PF_INET, SOCK_DGRAM, 0);
 509                                 if (s < 0) {
 510 #if !CAN_RECONNECT
 511  bad_dg_sock:
 512 #endif
 513                                         terrno = errno;
 514                                         Perror(stderr, "socket(dg)", errno);
 515                                         return (-1);
 516                                 }
 517                                 connected = 0;
 518                         }
 519                         /*
 520                          * On a 4.3BSD+ machine (client and server,
 521                          * actually), sending to a nameserver datagram
 522                          * port with no nameserver will cause an
 523                          * ICMP port unreachable message to be returned.
 524                          * If our datagram socket is "connected" to the
 525                          * server, we get an ECONNREFUSED error on the next
 526                          * socket operation, and select returns if the
 527                          * error message is received.  We can thus detect
 528                          * the absence of a nameserver without timing out.
 529                          * If we have sent queries to at least two servers,
 530                          * however, we don't want to remain connected,
 531                          * as we wish to receive answers from the first
 532                          * server to respond.
 533                          */
 534                         if (_res.nscount == 1 || (try == 0 && ns == 0)) {
 535                                 /*
 536                                  * Connect only if we are sure we won't
 537                                  * receive a response from another server.
 538                                  */
 539                                 if (!connected) {
 540                                         if (connect(s, (struct sockaddr *)nsap,
 541                                                     sizeof(struct sockaddr)
 542                                                     ) < 0) {
 543                                                 Aerror(stderr,
 544                                                        "connect(dg)",
 545                                                        errno, *nsap);
 546                                                 badns |= (1 << ns);
 547                                                 _res_close();
 548                                                 goto next_ns;
 549                                         }
 550                                         connected = 1;
 551                                 }
 552                                 if (send(s, (char*)buf, buflen, 0) != buflen) {
 553                                         Perror(stderr, "send", errno);
 554                                         badns |= (1 << ns);
 555                                         _res_close();
 556                                         goto next_ns;
 557                                 }
 558                         } else {
 559                                 /*
 560                                  * Disconnect if we want to listen
 561                                  * for responses from more than one server.
 562                                  */
 563                                 if (connected) {
 564 #if CAN_RECONNECT
 565                                         struct sockaddr_in no_addr;
 566
 567                                         no_addr.sin_family = AF_INET;
 568                                         no_addr.sin_addr.s_addr = INADDR_ANY;
 569                                         no_addr.sin_port = 0;
 570                                         (void) connect(s,
 571                                                        (struct sockaddr *)
 572                                                         &no_addr,
 573                                                        sizeof(no_addr));
 574 #else
 575                                         int s1 = socket(PF_INET, SOCK_DGRAM,0);
 576                                         if (s1 < 0)
 577                                                 goto bad_dg_sock;
 578                                         (void) dup2(s1, s);
 579                                         (void) close(s1);
 580                                         Dprint(_res.options & RES_DEBUG,
 581                                                (stdout, ";; new DG socket\n"))
 582 #endif
 583                                         connected = 0;
 584                                         errno = 0;
 585                                 }
 586                                 if (sendto(s, (char*)buf, buflen, 0,
 587                                            (struct sockaddr *)nsap,
 588                                            sizeof(struct sockaddr))
 589                                     != buflen) {
 590                                         Aerror(stderr, "sendto", errno, *nsap);
 591                                         badns |= (1 << ns);
 592                                         _res_close();
 593                                         goto next_ns;
 594                                 }
 595                         }
 596
 597                         /*
 598                          * Wait for reply
 599                          */
 600                         timeout.tv_sec = (_res.retrans << try);
 601                         if (try > 0)
 602                                 timeout.tv_sec /= _res.nscount;
 603                         if ((long) timeout.tv_sec <= 0)
 604                                 timeout.tv_sec = 1;
 605                         timeout.tv_usec = 0;
 606     wait:
 607                         FD_ZERO(&dsmask);
 608                         FD_SET(s, &dsmask);
 609                         n = select(s+1, &dsmask, (fd_set *)NULL,
 610                                    (fd_set *)NULL, &timeout);
 611                         if (n < 0) {
 612                                 if (errno == EINTR)
 613                                         goto wait;
 614                                 Perror(stderr, "select", errno);
 615                                 _res_close();
 616                                 goto next_ns;
 617                         }
 618                         if (n == 0) {
 619                                 /*
 620                                  * timeout
 621                                  */
 622                                 Dprint(_res.options & RES_DEBUG,
 623                                        (stdout, ";; timeout\n"));
 624                                 gotsomewhere = 1;
 625                                 _res_close();
 626                                 goto next_ns;
 627                         }
 628                         errno = 0;
 629                         fromlen = sizeof(struct sockaddr_in);
 630                         resplen = recvfrom(s, (char*)ans, anssiz, 0,
 631                                            (struct sockaddr *)&from, &fromlen);
 632                         if (resplen <= 0) {
 633                                 Perror(stderr, "recvfrom", errno);
 634                                 _res_close();
 635                                 goto next_ns;
 636                         }
 637                         gotsomewhere = 1;
 638                         if (hp->id != anhp->id) {
 639                                 /*
 640                                  * response from old query, ignore it.
 641                                  * XXX - potential security hazard could
 642                                  *       be detected here.
 643                                  */
 644                                 DprintQ((_res.options & RES_DEBUG) ||
 645                                         (_res.pfcode & RES_PRF_REPLY),
 646                                         (stdout, ";; old answer:\n"),
 647                                         ans, (resplen>anssiz)?anssiz:resplen);
 648                                 goto wait;
 649                         }
 650 #if CHECK_SRVR_ADDR
 651                         if (!(_res.options & RES_INSECURE1) &&
 652                             !res_isourserver(&from)) {
 653                                 /*
 654                                  * response from wrong server? ignore it.
 655                                  * XXX - potential security hazard could
 656                                  *       be detected here.
 657                                  */
 658                                 DprintQ((_res.options & RES_DEBUG) ||
 659                                         (_res.pfcode & RES_PRF_REPLY),
 660                                         (stdout, ";; not our server:\n"),
 661                                         ans, (resplen>anssiz)?anssiz:resplen);
 662                                 goto wait;
 663                         }
 664 #endif
 665                         if (!(_res.options & RES_INSECURE2) &&
 666                             !res_queriesmatch(buf, buf + buflen,
 667                                               ans, ans + anssiz)) {
 668                                 /*
 669                                  * response contains wrong query? ignore it.
 670                                  * XXX - potential security hazard could
 671                                  *       be detected here.
 672                                  */
 673                                 DprintQ((_res.options & RES_DEBUG) ||
 674                                         (_res.pfcode & RES_PRF_REPLY),
 675                                         (stdout, ";; wrong query name:\n"),
 676                                         ans, (resplen>anssiz)?anssiz:resplen);
 677                                 goto wait;
 678                         }
 679                         if (anhp->rcode == SERVFAIL ||
 680                             anhp->rcode == NOTIMP ||
 681                             anhp->rcode == REFUSED) {
 682                                 DprintQ(_res.options & RES_DEBUG,
 683                                         (stdout, "server rejected query:\n"),
 684                                         ans, (resplen>anssiz)?anssiz:resplen);
 685                                 badns |= (1 << ns);
 686                                 _res_close();
 687                                 /* don't retry if called from dig */
 688                                 if (!_res.pfcode)
 689                                         goto next_ns;
 690                         }
 691                         if (!(_res.options & RES_IGNTC) && anhp->tc) {
 692                                 /*
 693                                  * get rest of answer;
 694                                  * use TCP with same server.
 695                                  */
 696                                 Dprint(_res.options & RES_DEBUG,
 697                                        (stdout, ";; truncated answer\n"));
 698                                 v_circuit = 1;
 699                                 _res_close();
 700                                 goto same_ns;
 701                         }
 702                 } /*if vc/dg*/
 703                 Dprint((_res.options & RES_DEBUG) ||
 704                        ((_res.pfcode & RES_PRF_REPLY) &&
 705                         (_res.pfcode & RES_PRF_HEAD1)),
 706                        (stdout, ";; got answer:\n"));
 707                 DprintQ((_res.options & RES_DEBUG) ||
 708                         (_res.pfcode & RES_PRF_REPLY),
 709                         (stdout, ""),
 710                         ans, (resplen>anssiz)?anssiz:resplen);
 711                 /*
 712                  * If using virtual circuits, we assume that the first server
 713                  * is preferred over the rest (i.e. it is on the local
 714                  * machine) and only keep that one open.
 715                  * If we have temporarily opened a virtual circuit,
 716                  * or if we haven't been asked to keep a socket open,
 717                  * close the socket.
 718                  */
 719                 if ((v_circuit && (!(_res.options & RES_USEVC) || ns != 0)) ||
 720                     !(_res.options & RES_STAYOPEN)) {
 721                         _res_close();
 722                 }
 723                 if (Rhook) {
 724                         int done = 0, loops = 0;
 725
 726                         do {
 727                                 res_sendhookact act;
 728
 729                                 act = (*Rhook)(nsap, buf, buflen,
 730                                                ans, anssiz, &resplen);
 731                                 switch (act) {
 732                                 case res_goahead:
 733                                 case res_done:
 734                                         done = 1;
 735                                         break;
 736                                 case res_nextns:
 737                                         _res_close();
 738                                         goto next_ns;
 739                                 case res_modified:
 740                                         /* give the hook another try */
 741                                         if (++loops < 42) /*doug adams*/
 742                                                 break;
 743                                         /*FALLTHROUGH*/
 744                                 case res_error:
 745                                         /*FALLTHROUGH*/
 746                                 default:
 747                                         return (-1);
 748                                 }
 749                         } while (!done);
 750
 751                 }
 752                 return (resplen);
 753     next_ns: ;
 754            } /*foreach ns*/
 755         } /*foreach retry*/
 756         _res_close();
 757         if (!v_circuit)
 758                 if (!gotsomewhere)
 759                         errno = ECONNREFUSED;   /* no nameservers found */
 760                 else
 761                         errno = ETIMEDOUT;      /* no answer obtained */
 762         else
 763                 errno = terrno;
 764         return (-1);
 765 }
 766
 767 /*
 768  * This routine is for closing the socket if a virtual circuit is used and
 769  * the program wants to close it.  This provides support for endhostent()
 770  * which expects to close the socket.
 771  *
 772  * This routine is not expected to be user visible.
 773  */
 774 void
 775 _res_close()
 776 {
 777         if (s >= 0) {
 778                 (void) close(s);
 779                 s = -1;
 780                 connected = 0;
 781                 vc = 0;
 782         }
 783 }