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  * 4. Neither the name of the University nor the names of its contributors
  16  *    may be used to endorse or promote products derived from this software
  17  *    without specific prior written permission.
  18  *
  19  * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
  20  * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
  21  * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
  22  * ARE DISCLAIMED.  IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
  23  * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
  24  * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
  25  * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
  26  * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
  27  * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
  28  * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
  29  * SUCH DAMAGE.
  30  * -
  31  * Portions Copyright (c) 1993 by Digital Equipment Corporation.
  32  *
  33  * Permission to use, copy, modify, and distribute this software for any
  34  * purpose with or without fee is hereby granted, provided that the above
  35  * copyright notice and this permission notice appear in all copies, and that
  36  * the name of Digital Equipment Corporation not be used in advertising or
  37  * publicity pertaining to distribution of the document or software without
  38  * specific, written prior permission.
  39  *
  40  * THE SOFTWARE IS PROVIDED "AS IS" AND DIGITAL EQUIPMENT CORP. DISCLAIMS ALL
  41  * WARRANTIES WITH REGARD TO THIS SOFTWARE, INCLUDING ALL IMPLIED WARRANTIES
  42  * OF MERCHANTABILITY AND FITNESS.   IN NO EVENT SHALL DIGITAL EQUIPMENT
  43  * CORPORATION BE LIABLE FOR ANY SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL
  44  * DAMAGES OR ANY DAMAGES WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR
  45  * PROFITS, WHETHER IN AN ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS
  46  * ACTION, ARISING OUT OF OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS
  47  * SOFTWARE.
  48  * -
  49  * --Copyright--
  50  */
  51
  52 #if defined(LIBC_SCCS) && !defined(lint)
  53 static char sccsid[] = "@(#)res_send.c  8.1 (Berkeley) 6/4/93";
  54 static char rcsid[] = "$Id$";
  55 #endif /* LIBC_SCCS and not lint */
  56
  57         /* change this to "0"
  58          * if you talk to a lot
  59          * of multi-homed SunOS
  60          * ("broken") name servers.
  61          */
  62 #define CHECK_SRVR_ADDR 1       /* XXX - should be in options.h */
  63
  64 /*
  65  * Send query to name server and wait for reply.
  66  */
  67
  68 #include <sys/types.h>
  69 #include <sys/param.h>
  70 #include <sys/poll.h>
  71 #include <sys/time.h>
  72 #include <sys/socket.h>
  73 #include <sys/uio.h>
  74 #include <netinet/in.h>
  75 #include <arpa/nameser.h>
  76 #include <arpa/inet.h>
  77
  78 #include <stdio.h>
  79 #include <netdb.h>
  80 #include <errno.h>
  81 #include <resolv.h>
  82 #if defined(BSD) && (BSD >= 199306)
  83 # include <stdlib.h>
  84 # include <string.h>
  85 # include <unistd.h>
  86 #else
  87 # include "../conf/portability.h"
  88 #endif
  89
  90 #include <bits/libc-lock.h>
  91
  92 /* Lock to protect the connection use.  */
  93 __libc_lock_define_initialized (static, lock)
  94
  95 static void res_close_internal (void);
  96
  97 #if defined(USE_OPTIONS_H)
  98 # include <../conf/options.h>
  99 #endif
 100
 101 static int s = -1;      /* socket used for communications */
 102 static int connected = 0;       /* is the socket connected */
 103 static int vc = 0;      /* is the socket a virtual circuit? */
 104
 105 /* XXX - this should be done in portability.h */
 106 #if (defined(BSD) && (BSD >= 199103)) || defined(linux)
 107 # define CAN_RECONNECT 1
 108 #else
 109 # define CAN_RECONNECT 0
 110 #endif
 111
 112 #ifndef DEBUG
 113 #   define Dprint(cond, args) /*empty*/
 114 #   define DprintQ(cond, args, query, size) /*empty*/
 115 #   define Aerror(file, string, error, address) /*empty*/
 116 #   define Perror(file, string, error) /*empty*/
 117 #else
 118 #   define Dprint(cond, args) if (cond) {fprintf args;} else {}
 119 #   define DprintQ(cond, args, query, size) if (cond) {\
 120                         fprintf args;\
 121                         __fp_nquery(query, size, stdout);\
 122                 } else {}
 123     static void
 124     Aerror(file, string, error, address)
 125         FILE *file;
 126         char *string;
 127         int error;
 128         struct sockaddr_in address;
 129     {
 130         int save = errno;
 131
 132         if (_res.options & RES_DEBUG) {
 133                 fprintf(file, "res_send: %s ([%s].%u): %s\n",
 134                         string,
 135                         inet_ntoa(address.sin_addr),
 136                         ntohs(address.sin_port),
 137                         strerror(error));
 138         }
 139         __set_errno (save);
 140     }
 141     static void
 142     Perror(file, string, error)
 143         FILE *file;
 144         char *string;
 145         int error;
 146     {
 147         int save = errno;
 148
 149         if (_res.options & RES_DEBUG) {
 150                 fprintf(file, "res_send: %s: %s\n",
 151                         string, strerror(error));
 152         }
 153         __set_errno (save);
 154     }
 155 #endif
 156
 157 static res_send_qhook Qhook = NULL;
 158 static res_send_rhook Rhook = NULL;
 159
 160 void
 161 res_send_setqhook(hook)
 162         res_send_qhook hook;
 163 {
 164
 165         Qhook = hook;
 166 }
 167
 168 void
 169 res_send_setrhook(hook)
 170         res_send_rhook hook;
 171 {
 172
 173         Rhook = hook;
 174 }
 175
 176 /* int
 177  * res_isourserver(ina)
 178  *      looks up "ina" in _res.ns_addr_list[]
 179  * returns:
 180  *      0  : not found
 181  *      >0 : found
 182  * author:
 183  *      paul vixie, 29may94
 184  */
 185 int
 186 res_isourserver(inp)
 187         const struct sockaddr_in *inp;
 188 {
 189         struct sockaddr_in ina;
 190         register int ns, ret;
 191
 192         ina = *inp;
 193         ret = 0;
 194         for (ns = 0;  ns < _res.nscount;  ns++) {
 195                 register const struct sockaddr_in *srv = &_res.nsaddr_list[ns];
 196
 197                 if (srv->sin_family == ina.sin_family &&
 198                     srv->sin_port == ina.sin_port &&
 199                     (srv->sin_addr.s_addr == INADDR_ANY ||
 200                      srv->sin_addr.s_addr == ina.sin_addr.s_addr)) {
 201                         ret++;
 202                         break;
 203                 }
 204         }
 205         return (ret);
 206 }
 207
 208 /* int
 209  * res_nameinquery(name, type, class, buf, eom)
 210  *      look for (name,type,class) in the query section of packet (buf,eom)
 211  * requires:
 212  *      buf + HFIXESDZ <= eom
 213  * returns:
 214  *      -1 : format error
 215  *      0  : not found
 216  *      >0 : found
 217  * author:
 218  *      paul vixie, 29may94
 219  */
 220 int
 221 res_nameinquery(name, type, class, buf, eom)
 222         const char *name;
 223         register int type, class;
 224         const u_char *buf, *eom;
 225 {
 226         register const u_char *cp = buf + HFIXEDSZ;
 227         int qdcount = ntohs(((HEADER*)buf)->qdcount);
 228
 229         while (qdcount-- > 0) {
 230                 char tname[MAXDNAME+1];
 231                 register int n, ttype, tclass;
 232
 233                 n = dn_expand(buf, eom, cp, tname, sizeof tname);
 234                 if (n < 0)
 235                         return (-1);
 236                 cp += n;
 237                 if (cp + 2 * INT16SZ > eom)
 238                         return (-1);
 239                 ttype = _getshort(cp); cp += INT16SZ;
 240                 tclass = _getshort(cp); cp += INT16SZ;
 241                 if (ttype == type &&
 242                     tclass == class &&
 243                     strcasecmp(tname, name) == 0)
 244                         return (1);
 245         }
 246         return (0);
 247 }
 248
 249 /* int
 250  * res_queriesmatch(buf1, eom1, buf2, eom2)
 251  *      is there a 1:1 mapping of (name,type,class)
 252  *      in (buf1,eom1) and (buf2,eom2)?
 253  * returns:
 254  *      -1 : format error
 255  *      0  : not a 1:1 mapping
 256  *      >0 : is a 1:1 mapping
 257  * author:
 258  *      paul vixie, 29may94
 259  */
 260 int
 261 res_queriesmatch(buf1, eom1, buf2, eom2)
 262         const u_char *buf1, *eom1;
 263         const u_char *buf2, *eom2;
 264 {
 265         register const u_char *cp = buf1 + HFIXEDSZ;
 266         int qdcount = ntohs(((HEADER*)buf1)->qdcount);
 267
 268         if (buf1 + HFIXEDSZ > eom1 || buf2 + HFIXEDSZ > eom2)
 269                 return (-1);
 270
 271         if (qdcount != ntohs(((HEADER*)buf2)->qdcount))
 272                 return (0);
 273         while (qdcount-- > 0) {
 274                 char tname[MAXDNAME+1];
 275                 register int n, ttype, tclass;
 276
 277                 n = dn_expand(buf1, eom1, cp, tname, sizeof tname);
 278                 if (n < 0)
 279                         return (-1);
 280                 cp += n;
 281                 if (cp + 2 * INT16SZ > eom1)
 282                         return (-1);
 283                 ttype = _getshort(cp);  cp += INT16SZ;
 284                 tclass = _getshort(cp); cp += INT16SZ;
 285                 if (!res_nameinquery(tname, ttype, tclass, buf2, eom2))
 286                         return (0);
 287         }
 288         return (1);
 289 }
 290
 291 int
 292 res_send(buf, buflen, ans, anssiz)
 293         const u_char *buf;
 294         int buflen;
 295         u_char *ans;
 296         int anssiz;
 297 {
 298         HEADER *hp = (HEADER *) buf;
 299         HEADER *anhp = (HEADER *) ans;
 300         int gotsomewhere, connreset, terrno, try, v_circuit, resplen, ns;
 301         register int n;
 302         u_int badns;    /* XXX NSMAX can't exceed #/bits in this var */
 303         int result = -1;
 304
 305         if ((_res.options & RES_INIT) == 0 && res_init() == -1) {
 306                 /* errno should have been set by res_init() in this case. */
 307                 return (-1);
 308         }
 309         if (anssiz < HFIXEDSZ) {
 310                 __set_errno (EINVAL);
 311                 return (-1);
 312         }
 313         DprintQ((_res.options & RES_DEBUG) || (_res.pfcode & RES_PRF_QUERY),
 314                 (stdout, ";; res_send()\n"), buf, buflen);
 315         v_circuit = (_res.options & RES_USEVC) || buflen > PACKETSZ;
 316         gotsomewhere = 0;
 317         connreset = 0;
 318         terrno = ETIMEDOUT;
 319         badns = 0;
 320
 321         __libc_lock_lock (lock);
 322
 323         /*
 324          * Send request, RETRY times, or until successful
 325          */
 326         for (try = 0; try < _res.retry; try++) {
 327             for (ns = 0; ns < _res.nscount; ns++) {
 328                 struct sockaddr_in *nsap = &_res.nsaddr_list[ns];
 329     same_ns:
 330                 if (badns & (1 << ns)) {
 331                         res_close_internal();
 332                         goto next_ns;
 333                 }
 334
 335                 if (Qhook) {
 336                         int done = 0, loops = 0;
 337
 338                         do {
 339                                 res_sendhookact act;
 340
 341                                 act = (*Qhook)(&nsap, &buf, &buflen,
 342                                                ans, anssiz, &resplen);
 343                                 switch (act) {
 344                                 case res_goahead:
 345                                         done = 1;
 346                                         break;
 347                                 case res_nextns:
 348                                         res_close_internal();
 349                                         goto next_ns;
 350                                 case res_done:
 351                                         result = resplen;
 352                                         goto and_out;
 353                                 case res_modified:
 354                                         /* give the hook another try */
 355                                         if (++loops < 42) /*doug adams*/
 356                                                 break;
 357                                         /*FALLTHROUGH*/
 358                                 case res_error:
 359                                         /*FALLTHROUGH*/
 360                                 default:
 361                                         goto and_out;
 362                                 }
 363                         } while (!done);
 364                 }
 365
 366                 Dprint(_res.options & RES_DEBUG,
 367                        (stdout, ";; Querying server (# %d) address = %s\n",
 368                         ns + 1, inet_ntoa(nsap->sin_addr)));
 369
 370                 if (v_circuit) {
 371                         int truncated;
 372                         struct iovec iov[2];
 373                         u_short len;
 374                         u_char *cp;
 375
 376                         /*
 377                          * Use virtual circuit;
 378                          * at most one attempt per server.
 379                          */
 380                         try = _res.retry;
 381                         truncated = 0;
 382                         if ((s < 0) || (!vc)) {
 383                                 if (s >= 0)
 384                                         res_close_internal();
 385
 386                                 s = socket(PF_INET, SOCK_STREAM, 0);
 387                                 if (s < 0) {
 388                                         terrno = errno;
 389                                         Perror(stderr, "socket(vc)", errno);
 390                                         goto and_out;
 391                                 }
 392                                 __set_errno (0);
 393                                 if (connect(s, (struct sockaddr *)nsap,
 394                                             sizeof(struct sockaddr)) < 0) {
 395                                         terrno = errno;
 396                                         Aerror(stderr, "connect/vc",
 397                                                errno, *nsap);
 398                                         badns |= (1 << ns);
 399                                         res_close_internal();
 400                                         goto next_ns;
 401                                 }
 402                                 vc = 1;
 403                         }
 404                         /*
 405                          * Send length & message
 406                          */
 407                         putshort((u_short)buflen, (u_char*)&len);
 408                         iov[0].iov_base = (caddr_t)&len;
 409                         iov[0].iov_len = INT16SZ;
 410                         iov[1].iov_base = (caddr_t)buf;
 411                         iov[1].iov_len = buflen;
 412                         if (writev(s, iov, 2) != (INT16SZ + buflen)) {
 413                                 terrno = errno;
 414                                 Perror(stderr, "write failed", errno);
 415                                 badns |= (1 << ns);
 416                                 res_close_internal();
 417                                 goto next_ns;
 418                         }
 419                         /*
 420                          * Receive length & response
 421                          */
 422 read_len:
 423                         cp = ans;
 424                         len = INT16SZ;
 425                         while ((n = read(s, (char *)cp, (int)len)) > 0) {
 426                                 cp += n;
 427                                 if ((len -= n) <= 0)
 428                                         break;
 429                         }
 430                         if (n <= 0) {
 431                                 terrno = errno;
 432                                 Perror(stderr, "read failed", errno);
 433                                 res_close_internal();
 434                                 /*
 435                                  * A long running process might get its TCP
 436                                  * connection reset if the remote server was
 437                                  * restarted.  Requery the server instead of
 438                                  * trying a new one.  When there is only one
 439                                  * server, this means that a query might work
 440                                  * instead of failing.  We only allow one reset
 441                                  * per query to prevent looping.
 442                                  */
 443                                 if (terrno == ECONNRESET && !connreset) {
 444                                         connreset = 1;
 445                                         res_close_internal();
 446                                         goto same_ns;
 447                                 }
 448                                 res_close_internal();
 449                                 goto next_ns;
 450                         }
 451                         resplen = _getshort(ans);
 452                         if (resplen > anssiz) {
 453                                 Dprint(_res.options & RES_DEBUG,
 454                                        (stdout, ";; response truncated\n")
 455                                        );
 456                                 truncated = 1;
 457                                 len = anssiz;
 458                         } else
 459                                 len = resplen;
 460                         if (len < HFIXEDSZ) {
 461                                 /*
 462                                  * Undersized message.
 463                                  */
 464                                 Dprint(_res.options & RES_DEBUG,
 465                                        (stdout, ";; undersized: %d\n", len));
 466                                 terrno = EMSGSIZE;
 467                                 badns |= (1 << ns);
 468                                 res_close_internal();
 469                                 goto next_ns;
 470                         }
 471                         cp = ans;
 472                         while (len != 0 &&
 473                                (n = read(s, (char *)cp, (int)len)) > 0) {
 474                                 cp += n;
 475                                 len -= n;
 476                         }
 477                         if (n <= 0) {
 478                                 terrno = errno;
 479                                 Perror(stderr, "read(vc)", errno);
 480                                 res_close_internal();
 481                                 goto next_ns;
 482                         }
 483                         if (truncated) {
 484                                 /*
 485                                  * Flush rest of answer
 486                                  * so connection stays in synch.
 487                                  */
 488                                 anhp->tc = 1;
 489                                 len = resplen - anssiz;
 490                                 while (len != 0) {
 491                                         char junk[PACKETSZ];
 492
 493                                         n = ((size_t) len > sizeof(junk)
 494                                              ? sizeof(junk)
 495                                              : len);
 496                                         if ((n = read(s, junk, n)) > 0)
 497                                                 len -= n;
 498                                         else
 499                                                 break;
 500                                 }
 501                         }
 502                         /*
 503                          * The calling applicating has bailed out of
 504                          * a previous call and failed to arrange to have
 505                          * the circuit closed or the server has got
 506                          * itself confused. Anyway drop the packet and
 507                          * wait for the correct one.
 508                          */
 509                         if (hp->id != anhp->id) {
 510                                 DprintQ((_res.options & RES_DEBUG) ||
 511                                         (_res.pfcode & RES_PRF_REPLY),
 512                                         (stdout, ";; old answer (unexpected):\n"),
 513                                         ans, (resplen>anssiz)?anssiz:resplen);
 514                                 goto read_len;
 515                         }
 516                 } else {
 517                         /*
 518                          * Use datagrams.
 519                          */
 520                         int timeout;
 521                         struct pollfd pfd[1];
 522                         struct sockaddr_in from;
 523                         socklen_t fromlen;
 524                         time_t curtime;
 525                         time_t endtime;
 526
 527                         if ((s < 0) || vc) {
 528                                 if (vc)
 529                                         res_close_internal();
 530                                 s = socket(PF_INET, SOCK_DGRAM, 0);
 531                                 if (s < 0) {
 532 #if !CAN_RECONNECT
 533  bad_dg_sock:
 534 #endif
 535                                         terrno = errno;
 536                                         Perror(stderr, "socket(dg)", errno);
 537                                         goto and_out;
 538                                 }
 539                                 connected = 0;
 540                         }
 541                         /*
 542                          * On a 4.3BSD+ machine (client and server,
 543                          * actually), sending to a nameserver datagram
 544                          * port with no nameserver will cause an
 545                          * ICMP port unreachable message to be returned.
 546                          * If our datagram socket is "connected" to the
 547                          * server, we get an ECONNREFUSED error on the next
 548                          * socket operation, and select returns if the
 549                          * error message is received.  We can thus detect
 550                          * the absence of a nameserver without timing out.
 551                          * If we have sent queries to at least two servers,
 552                          * however, we don't want to remain connected,
 553                          * as we wish to receive answers from the first
 554                          * server to respond.
 555                          */
 556                         if (_res.nscount == 1 || (try == 0 && ns == 0)) {
 557                                 /*
 558                                  * Connect only if we are sure we won't
 559                                  * receive a response from another server.
 560                                  */
 561                                 if (!connected) {
 562                                         if (connect(s, (struct sockaddr *)nsap,
 563                                                     sizeof(struct sockaddr)
 564                                                     ) < 0) {
 565                                                 Aerror(stderr,
 566                                                        "connect(dg)",
 567                                                        errno, *nsap);
 568                                                 badns |= (1 << ns);
 569                                                 res_close_internal();
 570                                                 goto next_ns;
 571                                         }
 572                                         connected = 1;
 573                                 }
 574                                 if (send(s, (char*)buf, buflen, 0) != buflen) {
 575                                         Perror(stderr, "send", errno);
 576                                         badns |= (1 << ns);
 577                                         res_close_internal();
 578                                         goto next_ns;
 579                                 }
 580                         } else {
 581                                 /*
 582                                  * Disconnect if we want to listen
 583                                  * for responses from more than one server.
 584                                  */
 585                                 if (connected) {
 586 #if CAN_RECONNECT
 587                                         struct sockaddr_in no_addr;
 588
 589                                         no_addr.sin_family = AF_INET;
 590                                         no_addr.sin_addr.s_addr = INADDR_ANY;
 591                                         no_addr.sin_port = 0;
 592                                         (void) connect(s,
 593                                                        (struct sockaddr *)
 594                                                         &no_addr,
 595                                                        sizeof(no_addr));
 596 #else
 597                                         int s1 = socket(PF_INET, SOCK_DGRAM,0);
 598                                         if (s1 < 0)
 599                                                 goto bad_dg_sock;
 600                                         (void) dup2(s1, s);
 601                                         (void) close(s1);
 602                                         Dprint(_res.options & RES_DEBUG,
 603                                                (stdout, ";; new DG socket\n"))
 604 #endif
 605                                         connected = 0;
 606                                         __set_errno (0);
 607                                 }
 608                                 if (sendto(s, (char*)buf, buflen, 0,
 609                                            (struct sockaddr *)nsap,
 610                                            sizeof(struct sockaddr))
 611                                     != buflen) {
 612                                         Aerror(stderr, "sendto", errno, *nsap);
 613                                         badns |= (1 << ns);
 614                                         res_close_internal();
 615                                         goto next_ns;
 616                                 }
 617                         }
 618
 619                         /*
 620                          * Wait for reply
 621                          */
 622                         curtime = time (NULL);
 623                         if (try > 0)
 624                                 endtime = (_res.retrans << try) / _res.nscount;
 625                         else {
 626                                 endtime = _res.retrans;
 627                                 if (endtime <= 0)
 628                                         endtime = 1;
 629                         }
 630                         endtime += curtime;
 631     wait:
 632                         timeout = MAX (endtime - curtime, 0) * 1000;
 633 #if 0
 634                         if (s < 0 || s >= FD_SETSIZE) {
 635                                 Perror(stderr, "s out-of-bounds", EMFILE);
 636                                 res_close_internal();
 637                                 goto next_ns;
 638                         }
 639 #endif
 640                         pfd[0].fd = s;
 641                         pfd[0].events = POLLIN;
 642                         n = __poll(pfd, 1, timeout);
 643                         if (n < 0) {
 644                                 if (errno == EINTR) {
 645                                         curtime = time (NULL);
 646                                         goto wait;
 647                                 }
 648                                 Perror(stderr, "poll", errno);
 649                                 res_close_internal();
 650                                 goto next_ns;
 651                         }
 652                         if (n == 0) {
 653                                 /*
 654                                  * timeout
 655                                  */
 656                                 Dprint(_res.options & RES_DEBUG,
 657                                        (stdout, ";; timeout\n"));
 658                                 gotsomewhere = 1;
 659                                 res_close_internal();
 660                                 goto next_ns;
 661                         }
 662                         __set_errno (0);
 663                         fromlen = sizeof(struct sockaddr_in);
 664                         resplen = recvfrom(s, (char*)ans, anssiz, 0,
 665                                            (struct sockaddr *)&from, &fromlen);
 666                         if (resplen <= 0) {
 667                                 Perror(stderr, "recvfrom", errno);
 668                                 res_close_internal();
 669                                 goto next_ns;
 670                         }
 671                         gotsomewhere = 1;
 672                         if (resplen < HFIXEDSZ) {
 673                                 /*
 674                                  * Undersized message.
 675                                  */
 676                                 Dprint(_res.options & RES_DEBUG,
 677                                        (stdout, ";; undersized: %d\n",
 678                                         resplen));
 679                                 terrno = EMSGSIZE;
 680                                 badns |= (1 << ns);
 681                                 res_close_internal();
 682                                 goto next_ns;
 683                         }
 684                         if (hp->id != anhp->id) {
 685                                 /*
 686                                  * response from old query, ignore it.
 687                                  * XXX - potential security hazard could
 688                                  *       be detected here.
 689                                  */
 690                                 DprintQ((_res.options & RES_DEBUG) ||
 691                                         (_res.pfcode & RES_PRF_REPLY),
 692                                         (stdout, ";; old answer:\n"),
 693                                         ans, (resplen>anssiz)?anssiz:resplen);
 694                                 curtime = time (NULL);
 695                                 goto wait;
 696                         }
 697 #if CHECK_SRVR_ADDR
 698                         if (!(_res.options & RES_INSECURE1) &&
 699                             !res_isourserver(&from)) {
 700                                 /*
 701                                  * response from wrong server? ignore it.
 702                                  * XXX - potential security hazard could
 703                                  *       be detected here.
 704                                  */
 705                                 DprintQ((_res.options & RES_DEBUG) ||
 706                                         (_res.pfcode & RES_PRF_REPLY),
 707                                         (stdout, ";; not our server:\n"),
 708                                         ans, (resplen>anssiz)?anssiz:resplen);
 709                                 curtime = time (NULL);
 710                                 goto wait;
 711                         }
 712 #endif
 713                         if (!(_res.options & RES_INSECURE2) &&
 714                             !res_queriesmatch(buf, buf + buflen,
 715                                               ans, ans + anssiz)) {
 716                                 /*
 717                                  * response contains wrong query? ignore it.
 718                                  * XXX - potential security hazard could
 719                                  *       be detected here.
 720                                  */
 721                                 DprintQ((_res.options & RES_DEBUG) ||
 722                                         (_res.pfcode & RES_PRF_REPLY),
 723                                         (stdout, ";; wrong query name:\n"),
 724                                         ans, (resplen>anssiz)?anssiz:resplen);
 725                                 curtime = time (NULL);
 726                                 goto wait;
 727                         }
 728                         if (anhp->rcode == SERVFAIL ||
 729                             anhp->rcode == NOTIMP ||
 730                             anhp->rcode == REFUSED) {
 731                                 DprintQ(_res.options & RES_DEBUG,
 732                                         (stdout, "server rejected query:\n"),
 733                                         ans, (resplen>anssiz)?anssiz:resplen);
 734                                 badns |= (1 << ns);
 735                                 res_close_internal();
 736                                 /* don't retry if called from dig */
 737                                 if (!_res.pfcode)
 738                                         goto next_ns;
 739                         }
 740                         if (!(_res.options & RES_IGNTC) && anhp->tc) {
 741                                 /*
 742                                  * get rest of answer;
 743                                  * use TCP with same server.
 744                                  */
 745                                 Dprint(_res.options & RES_DEBUG,
 746                                        (stdout, ";; truncated answer\n"));
 747                                 v_circuit = 1;
 748                                 res_close_internal();
 749                                 goto same_ns;
 750                         }
 751                 } /*if vc/dg*/
 752                 Dprint((_res.options & RES_DEBUG) ||
 753                        ((_res.pfcode & RES_PRF_REPLY) &&
 754                         (_res.pfcode & RES_PRF_HEAD1)),
 755                        (stdout, ";; got answer:\n"));
 756                 DprintQ((_res.options & RES_DEBUG) ||
 757                         (_res.pfcode & RES_PRF_REPLY),
 758                         (stdout, ""),
 759                         ans, (resplen>anssiz)?anssiz:resplen);
 760                 /*
 761                  * If using virtual circuits, we assume that the first server
 762                  * is preferred over the rest (i.e. it is on the local
 763                  * machine) and only keep that one open.
 764                  * If we have temporarily opened a virtual circuit,
 765                  * or if we haven't been asked to keep a socket open,
 766                  * close the socket.
 767                  */
 768                 if ((v_circuit && (!(_res.options & RES_USEVC) || ns != 0)) ||
 769                     !(_res.options & RES_STAYOPEN)) {
 770                         res_close_internal();
 771                 }
 772                 if (Rhook) {
 773                         int done = 0, loops = 0;
 774
 775                         do {
 776                                 res_sendhookact act;
 777
 778                                 act = (*Rhook)(nsap, buf, buflen,
 779                                                ans, anssiz, &resplen);
 780                                 switch (act) {
 781                                 case res_goahead:
 782                                 case res_done:
 783                                         done = 1;
 784                                         break;
 785                                 case res_nextns:
 786                                         res_close_internal();
 787                                         goto next_ns;
 788                                 case res_modified:
 789                                         /* give the hook another try */
 790                                         if (++loops < 42) /*doug adams*/
 791                                                 break;
 792                                         /*FALLTHROUGH*/
 793                                 case res_error:
 794                                         /*FALLTHROUGH*/
 795                                 default:
 796                                         goto and_out;
 797                                 }
 798                         } while (!done);
 799
 800                 }
 801                 result = resplen;
 802                 goto and_out;
 803     next_ns: ;
 804            } /*foreach ns*/
 805         } /*foreach retry*/
 806         res_close_internal();
 807         if (!v_circuit) {
 808                 if (!gotsomewhere)
 809                         __set_errno (ECONNREFUSED); /* no nameservers found */
 810                 else
 811                         __set_errno (ETIMEDOUT);    /* no answer obtained */
 812         } else
 813                 __set_errno (terrno);
 814
 815  and_out:
 816         __libc_lock_unlock (lock);
 817
 818         return result;
 819 }
 820
 821 /*
 822  * This routine is for closing the socket if a virtual circuit is used and
 823  * the program wants to close it.  This provides support for endhostent()
 824  * which expects to close the socket.
 825  *
 826  * This routine is not expected to be user visible.
 827  */
 828 static void
 829 res_close_internal()
 830 {
 831         if (s >= 0) {
 832                 (void) close(s);
 833                 s = -1;
 834                 connected = 0;
 835                 vc = 0;
 836         }
 837 }
 838
 839 void
 840 res_close ()
 841 {
 842         __libc_lock_lock (lock);
 843         res_close_internal ();
 844         __libc_lock_unlock (lock);
 845 }
 846
 847 #ifdef ultrix
 848 /* ultrix 4.0 had some icky packaging in its libc.a.  alias for it here.
 849  * there is more gunk of this kind over in res_debug.c.
 850  */
 851
 852 void
 853 _res_close()
 854 {
 855         res_close();
 856 }
 857
 858 #undef res_send
 859 int
 860 res_send(buf, buflen, ans, anssiz)
 861         const u_char *buf;
 862         int buflen;
 863         u_char *ans;
 864         int anssiz;
 865 {
 866         return (__res_send(buf, buflen, ans, anssiz));
 867 }
 868 #endif /* Ultrix 4.0 hackery */