StdLib/BsdSocketLib/res_send.c

   1 /*
   2  * Copyright (c) 1985, 1989, 1993
   3  *    The Regents of the University of California.  All rights reserved.
   4  *
   5  * Portions copyright (c) 1999, 2000
   6  * Intel Corporation.
   7  * All rights reserved.
   8  *
   9  * Redistribution and use in source and binary forms, with or without
  10  * modification, are permitted provided that the following conditions
  11  * are met:
  12  *
  13  * 1. Redistributions of source code must retain the above copyright
  14  *    notice, this list of conditions and the following disclaimer.
  15  *
  16  * 2. Redistributions in binary form must reproduce the above copyright
  17  *    notice, this list of conditions and the following disclaimer in the
  18  *    documentation and/or other materials provided with the distribution.
  19  *
  20  * 3. All advertising materials mentioning features or use of this software
  21  *    must display the following acknowledgement:
  22  *
  23  *    This product includes software developed by the University of
  24  *    California, Berkeley, Intel Corporation, and its contributors.
  25  *
  26  * 4. Neither the name of University, Intel Corporation, or their respective
  27  *    contributors may be used to endorse or promote products derived from
  28  *    this software without specific prior written permission.
  29  *
  30  * THIS SOFTWARE IS PROVIDED BY THE REGENTS, INTEL CORPORATION AND
  31  * CONTRIBUTORS ``AS IS'' AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING,
  32  * BUT NOT LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS
  33  * FOR A PARTICULAR PURPOSE ARE DISCLAIMED.  IN NO EVENT SHALL THE REGENTS,
  34  * INTEL CORPORATION OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT,
  35  * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT
  36  * NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
  37  * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
  38  * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
  39  * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF
  40  * THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
  41  *
  42  */
  43
  44 /*
  45  * Portions Copyright (c) 1993 by Digital Equipment Corporation.
  46  *
  47  * Permission to use, copy, modify, and distribute this software for any
  48  * purpose with or without fee is hereby granted, provided that the above
  49  * copyright notice and this permission notice appear in all copies, and that
  50  * the name of Digital Equipment Corporation not be used in advertising or
  51  * publicity pertaining to distribution of the document or software without
  52  * specific, written prior permission.
  53  *
  54  * THE SOFTWARE IS PROVIDED "AS IS" AND DIGITAL EQUIPMENT CORP. DISCLAIMS ALL
  55  * WARRANTIES WITH REGARD TO THIS SOFTWARE, INCLUDING ALL IMPLIED WARRANTIES
  56  * OF MERCHANTABILITY AND FITNESS.   IN NO EVENT SHALL DIGITAL EQUIPMENT
  57  * CORPORATION BE LIABLE FOR ANY SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL
  58  * DAMAGES OR ANY DAMAGES WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR
  59  * PROFITS, WHETHER IN AN ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS
  60  * ACTION, ARISING OUT OF OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS
  61  * SOFTWARE.
  62  */
  63
  64 /*
  65  * Portions Copyright (c) 1996 by Internet Software Consortium.
  66  *
  67  * Permission to use, copy, modify, and distribute this software for any
  68  * purpose with or without fee is hereby granted, provided that the above
  69  * copyright notice and this permission notice appear in all copies.
  70  *
  71  * THE SOFTWARE IS PROVIDED "AS IS" AND INTERNET SOFTWARE CONSORTIUM DISCLAIMS
  72  * ALL WARRANTIES WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES
  73  * OF MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL INTERNET SOFTWARE
  74  * CONSORTIUM BE LIABLE FOR ANY SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL
  75  * DAMAGES OR ANY DAMAGES WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR
  76  * PROFITS, WHETHER IN AN ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS
  77  * ACTION, ARISING OUT OF OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS
  78  * SOFTWARE.
  79  */
  80
  81 #if defined(LIBC_SCCS) && !defined(lint)
  82 static char sccsid[] = "@(#)res_send.c  8.1 (Berkeley) 6/4/93";
  83 static char orig_rcsid[] = "From: Id: res_send.c,v 8.20 1998/04/06 23:27:51 halley Exp $";
  84 static char rcsid[] = "$Id: res_send.c,v 1.1.1.1 2003/11/19 01:51:39 kyu3 Exp $";
  85 #endif /* LIBC_SCCS and not lint */
  86
  87 /*
  88  * Send query to name server and wait for reply.
  89  */
  90
  91 #include <sys/types.h>
  92 #include <sys/param.h>
  93 #include <sys/select.h>
  94 #include <sys/socket.h>
  95 #include <sys/time.h>
  96 #include <sys/uio.h>
  97
  98 #include <netinet/in.h>
  99 #include <arpa/nameser.h>
 100 #include <arpa/inet.h>
 101
 102 #include <errno.h>
 103 #include <netdb.h>
 104 #include <resolv.h>
 105 #include <stdio.h>
 106 #include <stdlib.h>
 107 #include <string.h>
 108 #include <unistd.h>
 109
 110 #include "res_config.h"
 111
 112 #ifndef _ORG_FREEBSD_
 113 #define NOPOLL
 114 #endif
 115
 116 #ifdef NOPOLL           /* libc_r doesn't wrap poll yet() */
 117 #else
 118 #include <poll.h>
 119 static int use_poll = 1;    /* adapt to poll() syscall availability */
 120                 /* 0 = not present, 1 = try it, 2 = exists */
 121 #endif
 122
 123 static int s = -1;      /* socket used for communications */
 124 static int connected = 0;   /* is the socket connected */
 125 static int vc = 0;      /* is the socket a virtual circuit? */
 126 static res_send_qhook Qhook = NULL;
 127 static res_send_rhook Rhook = NULL;
 128
 129
 130 #define CAN_RECONNECT 1
 131
 132 #ifndef DEBUG
 133 #   define Dprint(cond, args) /*empty*/
 134 #   define DprintQ(cond, args, query, size) /*empty*/
 135 #   define Aerror(file, string, error, address) /*empty*/
 136 #   define Perror(file, string, error) /*empty*/
 137 #else
 138 #   define Dprint(cond, args) if (cond) {fprintf args;} else {}
 139 #   define DprintQ(cond, args, query, size) if (cond) {\
 140             fprintf args;\
 141             __fp_nquery(query, size, stdout);\
 142         } else {}
 143
 144 static void
 145 Aerror(
 146     FILE *file,
 147     char *string,
 148     int error,
 149     struct sockaddr_in address
 150     )
 151 {
 152     int save = errno;
 153
 154     if (_res.options & RES_DEBUG) {
 155         fprintf(file, "res_send: %s ([%s].%u): %s\n",
 156             string,
 157             inet_ntoa(address.sin_addr),
 158             ntohs(address.sin_port),
 159             strerror(error));
 160     }
 161     errno = save;
 162 }
 163
 164
 165 static void
 166 Perror(
 167     FILE *file,
 168     char *string,
 169     int error
 170     )
 171 {
 172     int save = errno;
 173
 174     if (_res.options & RES_DEBUG) {
 175         fprintf(file, "res_send: %s: %s\n",
 176             string, strerror(error));
 177     }
 178     errno = save;
 179 }
 180 #endif
 181
 182 void
 183 res_send_setqhook(
 184     res_send_qhook hook
 185     )
 186 {
 187
 188     Qhook = hook;
 189 }
 190
 191 void
 192 res_send_setrhook(
 193     res_send_rhook hook
 194     )
 195 {
 196
 197     Rhook = hook;
 198 }
 199
 200 /* int
 201  * res_isourserver(ina)
 202  *  looks up "ina" in _res.ns_addr_list[]
 203  * returns:
 204  *  0  : not found
 205  *  >0 : found
 206  * author:
 207  *  paul vixie, 29may94
 208  */
 209 int
 210 res_isourserver(
 211     const struct sockaddr_in *inp
 212     )
 213 {
 214     struct sockaddr_in ina;
 215     int ns, ret;
 216
 217     ina = *inp;
 218     ret = 0;
 219     for (ns = 0;  ns < _res.nscount;  ns++) {
 220         const struct sockaddr_in *srv = &_res.nsaddr_list[ns];
 221
 222         if (srv->sin_family == ina.sin_family &&
 223             srv->sin_port == ina.sin_port &&
 224             (srv->sin_addr.s_addr == INADDR_ANY ||
 225              srv->sin_addr.s_addr == ina.sin_addr.s_addr)) {
 226             ret++;
 227             break;
 228         }
 229     }
 230     return (ret);
 231 }
 232
 233 /* int
 234  * res_nameinquery(name, type, class, buf, eom)
 235  *  look for (name,type,class) in the query section of packet (buf,eom)
 236  * requires:
 237  *  buf + HFIXEDSZ <= eom
 238  * returns:
 239  *  -1 : format error
 240  *  0  : not found
 241  *  >0 : found
 242  * author:
 243  *  paul vixie, 29may94
 244  */
 245 int
 246 res_nameinquery(
 247     const char *name,
 248     int type,
 249     int class,
 250     const u_char *buf,
 251     const u_char *eom
 252     )
 253 {
 254     const u_char *cp = buf + HFIXEDSZ;
 255     int qdcount = ntohs(((HEADER*)buf)->qdcount);
 256
 257     while (qdcount-- > 0) {
 258         char tname[MAXDNAME+1];
 259         int n, ttype, tclass;
 260
 261         n = dn_expand(buf, eom, cp, tname, sizeof tname);
 262         if (n < 0)
 263             return (-1);
 264         cp += n;
 265         if (cp + 2 * INT16SZ > eom)
 266             return (-1);
 267         ttype = ns_get16(cp); cp += INT16SZ;
 268         tclass = ns_get16(cp); cp += INT16SZ;
 269         if (ttype == type &&
 270             tclass == class &&
 271             strcasecmp(tname, name) == 0)
 272             return (1);
 273     }
 274     return (0);
 275 }
 276
 277 /* int
 278  * res_queriesmatch(buf1, eom1, buf2, eom2)
 279  *  is there a 1:1 mapping of (name,type,class)
 280  *  in (buf1,eom1) and (buf2,eom2)?
 281  * returns:
 282  *  -1 : format error
 283  *  0  : not a 1:1 mapping
 284  *  >0 : is a 1:1 mapping
 285  * author:
 286  *  paul vixie, 29may94
 287  */
 288 int
 289 res_queriesmatch(
 290     const u_char *buf1,
 291     const u_char *eom1,
 292     const u_char *buf2,
 293     const u_char *eom2
 294     )
 295 {
 296     const u_char *cp = buf1 + HFIXEDSZ;
 297     int qdcount = ntohs(((HEADER*)buf1)->qdcount);
 298
 299     if (buf1 + HFIXEDSZ > eom1 || buf2 + HFIXEDSZ > eom2)
 300         return (-1);
 301
 302     /*
 303      * Only header section present in replies to
 304      * dynamic update packets.
 305      */
 306     if ( (((HEADER *)buf1)->opcode == ns_o_update) &&
 307          (((HEADER *)buf2)->opcode == ns_o_update) )
 308         return (1);
 309
 310     if (qdcount != ntohs(((HEADER*)buf2)->qdcount))
 311         return (0);
 312     while (qdcount-- > 0) {
 313         char tname[MAXDNAME+1];
 314         int n, ttype, tclass;
 315
 316         n = dn_expand(buf1, eom1, cp, tname, sizeof tname);
 317         if (n < 0)
 318             return (-1);
 319         cp += n;
 320         if (cp + 2 * INT16SZ > eom1)
 321             return (-1);
 322         ttype = ns_get16(cp);   cp += INT16SZ;
 323         tclass = ns_get16(cp); cp += INT16SZ;
 324         if (!res_nameinquery(tname, ttype, tclass, buf2, eom2))
 325             return (0);
 326     }
 327     return (1);
 328 }
 329
 330 int
 331 res_send(
 332     const u_char *buf,
 333     int buflen,
 334     u_char *ans,
 335     int anssiz
 336     )
 337 {
 338     HEADER *hp = (HEADER *) buf;
 339     HEADER *anhp = (HEADER *) ans;
 340     int gotsomewhere, connreset, terrno, try, v_circuit, resplen, ns;
 341     ssize_t n;
 342     u_int32_t badns;    /* XXX NSMAX can't exceed #/bits in this variable */
 343
 344     if ((_res.options & RES_INIT) == 0 && res_init() == -1) {
 345         /* errno should have been set by res_init() in this case. */
 346         return (-1);
 347     }
 348     if (anssiz < HFIXEDSZ) {
 349         errno = EINVAL;
 350         return (-1);
 351     }
 352     DprintQ((_res.options & RES_DEBUG) || (_res.pfcode & RES_PRF_QUERY),
 353         (stdout, ";; res_send()\n"), buf, buflen);
 354     v_circuit = (_res.options & RES_USEVC) || buflen > PACKETSZ;
 355     gotsomewhere = 0;
 356     connreset = 0;
 357     terrno = ETIMEDOUT;
 358     badns = 0;
 359
 360     /*
 361      * Send request, RETRY times, or until successful
 362      */
 363     for (try = 0; try < _res.retry; try++) {
 364         for (ns = 0; ns < _res.nscount; ns++) {
 365         struct sockaddr_in *nsap = &_res.nsaddr_list[ns];
 366     same_ns:
 367         if (badns & (1 << ns)) {
 368             res_close();
 369             goto next_ns;
 370         }
 371
 372         if (Qhook) {
 373             int done = 0, loops = 0;
 374
 375             do {
 376                 res_sendhookact act;
 377
 378                 act = (*Qhook)(&nsap, &buf, &buflen,
 379                            ans, anssiz, &resplen);
 380                 switch (act) {
 381                 case res_goahead:
 382                     done = 1;
 383                     break;
 384                 case res_nextns:
 385                     res_close();
 386                     goto next_ns;
 387                 case res_done:
 388                     return (resplen);
 389                 case res_modified:
 390                     /* give the hook another try */
 391                     if (++loops < 42) /*doug adams*/
 392                         break;
 393                     /*FALLTHROUGH*/
 394                 case res_error:
 395                     /*FALLTHROUGH*/
 396                 default:
 397                     return (-1);
 398                 }
 399             } while (!done);
 400         }
 401
 402         Dprint(_res.options & RES_DEBUG,
 403                (stdout, ";; Querying server (# %d) address = %s\n",
 404             ns + 1, inet_ntoa(nsap->sin_addr)));
 405
 406         if (v_circuit) {
 407             int truncated;
 408             struct iovec iov[2];
 409             u_short len;
 410             u_char *cp;
 411
 412             /*
 413              * Use virtual circuit;
 414              * at most one attempt per server.
 415              */
 416             try = _res.retry;
 417             truncated = 0;
 418             if (s < 0 || !vc || hp->opcode == ns_o_update) {
 419                 if (s >= 0)
 420                     res_close();
 421
 422                 s = socket(PF_INET, SOCK_STREAM, 0);
 423                 if (s < 0) {
 424                     terrno = errno;
 425                     Perror(stderr, "socket(vc)", errno);
 426                     return (-1);
 427                 }
 428                 errno = 0;
 429                 nsap->sin_len = sizeof ( *nsap );
 430                 if (connect(s, (struct sockaddr *)nsap,
 431                         sizeof *nsap) < 0) {
 432                     terrno = errno;
 433                     Aerror(stderr, "connect/vc",
 434                            errno, *nsap);
 435                     badns |= (1 << ns);
 436                     res_close();
 437                     goto next_ns;
 438                 }
 439                 vc = 1;
 440             }
 441             /*
 442              * Send length & message
 443              */
 444             putshort((u_short)buflen, (u_char*)&len);
 445             iov[0].iov_base = (caddr_t)&len;
 446             iov[0].iov_len = INT16SZ;
 447             iov[1].iov_base = (caddr_t)buf;
 448             iov[1].iov_len = buflen;
 449             if (writev(s, iov, 2) != (INT16SZ + buflen)) {
 450                 terrno = errno;
 451                 Perror(stderr, "write failed", errno);
 452                 badns |= (1 << ns);
 453                 res_close();
 454                 goto next_ns;
 455             }
 456             /*
 457              * Receive length & response
 458              */
 459 read_len:
 460             cp = ans;
 461             len = INT16SZ;
 462             while ((n = read(s, (char *)cp, (int)len)) > 0) {
 463                 cp += n;
 464                 len = (u_short)( len - n );
 465                 if (len <= 0)
 466                     break;
 467             }
 468             if (n <= 0) {
 469                 terrno = errno;
 470                 Perror(stderr, "read failed", errno);
 471                 res_close();
 472                 /*
 473                  * A long running process might get its TCP
 474                  * connection reset if the remote server was
 475                  * restarted.  Requery the server instead of
 476                  * trying a new one.  When there is only one
 477                  * server, this means that a query might work
 478                  * instead of failing.  We only allow one reset
 479                  * per query to prevent looping.
 480                  */
 481                 if (terrno == ECONNRESET && !connreset) {
 482                     connreset = 1;
 483                     res_close();
 484                     goto same_ns;
 485                 }
 486                 res_close();
 487                 goto next_ns;
 488             }
 489             resplen = ns_get16(ans);
 490             if (resplen > anssiz) {
 491                 Dprint(_res.options & RES_DEBUG,
 492                        (stdout, ";; response truncated\n")
 493                        );
 494                 truncated = 1;
 495                 len = (ushort)anssiz;
 496             } else
 497                 len = (ushort)resplen;
 498             if (len < HFIXEDSZ) {
 499                 /*
 500                  * Undersized message.
 501                  */
 502                 Dprint(_res.options & RES_DEBUG,
 503                        (stdout, ";; undersized: %d\n", len));
 504                 terrno = EMSGSIZE;
 505                 badns |= (1 << ns);
 506                 res_close();
 507                 goto next_ns;
 508             }
 509             cp = ans;
 510             while (len != 0 &&
 511                    (n = read(s, (char *)cp, (int)len)) > 0) {
 512                 cp += n;
 513                 len = (u_short)( len - n );
 514             }
 515             if (n <= 0) {
 516                 terrno = errno;
 517                 Perror(stderr, "read(vc)", errno);
 518                 res_close();
 519                 goto next_ns;
 520             }
 521             if (truncated) {
 522                 /*
 523                  * Flush rest of answer
 524                  * so connection stays in synch.
 525                  */
 526                 anhp->tc = 1;
 527                 len = (ushort)( resplen - anssiz );
 528                 while (len != 0) {
 529                     char junk[PACKETSZ];
 530
 531                     n = (len > sizeof(junk)
 532                          ? sizeof(junk)
 533                          : len);
 534                     if ((n = read(s, junk, n)) > 0)
 535                         len = (u_short)( len - n );
 536                     else
 537                         break;
 538                 }
 539             }
 540             /*
 541              * The calling applicating has bailed out of
 542              * a previous call and failed to arrange to have
 543              * the circuit closed or the server has got
 544              * itself confused. Anyway drop the packet and
 545              * wait for the correct one.
 546              */
 547             if (hp->id != anhp->id) {
 548                 DprintQ((_res.options & RES_DEBUG) ||
 549                     (_res.pfcode & RES_PRF_REPLY),
 550                     (stdout, ";; old answer (unexpected):\n"),
 551                     ans, (resplen>anssiz)?anssiz:resplen);
 552                 goto read_len;
 553             }
 554         } else {
 555             /*
 556              * Use datagrams.
 557              */
 558 #ifndef NOPOLL
 559             struct pollfd pfd;
 560             int msec;
 561 #endif
 562             struct timeval timeout;
 563             fd_set dsmask, *dsmaskp;
 564             int dsmasklen;
 565             struct sockaddr_in from;
 566             int fromlen;
 567
 568             if ((s < 0) || vc) {
 569                 if (vc)
 570                     res_close();
 571                 s = socket(PF_INET, SOCK_DGRAM, 0);
 572                 if (s < 0) {
 573 #ifndef CAN_RECONNECT
 574  bad_dg_sock:
 575 #endif
 576                     terrno = errno;
 577                     Perror(stderr, "socket(dg)", errno);
 578                     return (-1);
 579                 }
 580                 connected = 0;
 581             }
 582 #ifndef CANNOT_CONNECT_DGRAM
 583             /*
 584              * On a 4.3BSD+ machine (client and server,
 585              * actually), sending to a nameserver datagram
 586              * port with no nameserver will cause an
 587              * ICMP port unreachable message to be returned.
 588              * If our datagram socket is "connected" to the
 589              * server, we get an ECONNREFUSED error on the next
 590              * socket operation, and select returns if the
 591              * error message is received.  We can thus detect
 592              * the absence of a nameserver without timing out.
 593              * If we have sent queries to at least two servers,
 594              * however, we don't want to remain connected,
 595              * as we wish to receive answers from the first
 596              * server to respond.
 597              */
 598             if (_res.nscount == 1 || (try == 0 && ns == 0)) {
 599                 /*
 600                  * Connect only if we are sure we won't
 601                  * receive a response from another server.
 602                  */
 603                 if (!connected) {
 604                     nsap->sin_len = sizeof ( *nsap );
 605                     if (connect(s, (struct sockaddr *)nsap,
 606                             sizeof *nsap
 607                             ) < 0) {
 608                         Aerror(stderr,
 609                                "connect(dg)",
 610                                errno, *nsap);
 611                         badns |= (1 << ns);
 612                         res_close();
 613                         goto next_ns;
 614                     }
 615                     connected = 1;
 616                 }
 617                 if (send(s, (char*)buf, buflen, 0) != buflen) {
 618                     Perror(stderr, "send", errno);
 619                     badns |= (1 << ns);
 620                     res_close();
 621                     goto next_ns;
 622                 }
 623             } else {
 624                 /*
 625                  * Disconnect if we want to listen
 626                  * for responses from more than one server.
 627                  */
 628                 if (connected) {
 629 #ifdef CAN_RECONNECT
 630                     struct sockaddr_in no_addr;
 631
 632                     no_addr.sin_family = AF_INET;
 633                     no_addr.sin_addr.s_addr = INADDR_ANY;
 634                     no_addr.sin_port = 0;
 635                     (void) connect(s,
 636                                (struct sockaddr *)
 637                                 &no_addr,
 638                                sizeof no_addr);
 639 #else
 640                     int s1 = socket(PF_INET, SOCK_DGRAM,0);
 641                     if (s1 < 0)
 642                         goto bad_dg_sock;
 643                     (void) dup2(s1, s);
 644                     (void) close(s1);
 645                     Dprint(_res.options & RES_DEBUG,
 646                         (stdout, ";; new DG socket\n"))
 647 #endif /* CAN_RECONNECT */
 648                     connected = 0;
 649                     errno = 0;
 650                 }
 651 #endif /* !CANNOT_CONNECT_DGRAM */
 652                 if (sendto(s, (char*)buf, buflen, 0,
 653                        (struct sockaddr *)nsap,
 654                        sizeof *nsap)
 655                     != buflen) {
 656                     Aerror(stderr, "sendto", errno, *nsap);
 657                     badns |= (1 << ns);
 658                     res_close();
 659                     goto next_ns;
 660                 }
 661 #ifndef CANNOT_CONNECT_DGRAM
 662             }
 663 #endif /* !CANNOT_CONNECT_DGRAM */
 664
 665             /*
 666              * Wait for reply
 667              */
 668 #ifndef NOPOLL
 669     othersyscall:
 670             if (use_poll) {
 671                 msec = (_res.retrans << try) * 1000;
 672                 if (try > 0)
 673                     msec /= _res.nscount;
 674                 if (msec <= 0)
 675                     msec = 1000;
 676             } else {
 677 #endif
 678                 timeout.tv_sec = (_res.retrans << try);
 679                 if (try > 0)
 680                     timeout.tv_sec /= _res.nscount;
 681                 if ((long) timeout.tv_sec <= 0)
 682                     timeout.tv_sec = 1;
 683                 timeout.tv_usec = 0;
 684 #ifndef NOPOLL
 685             }
 686 #endif
 687     wait:
 688             if (s < 0) {
 689                 Perror(stderr, "s out-of-bounds", EMFILE);
 690                 res_close();
 691                 goto next_ns;
 692             }
 693 #ifndef NOPOLL
 694             if (use_poll) {
 695                 struct sigaction sa, osa;
 696                 int sigsys_installed = 0;
 697
 698                 pfd.fd = s;
 699                 pfd.events = POLLIN;
 700                 if (use_poll == 1) {
 701                     bzero(&sa, sizeof(sa));
 702                     sa.sa_handler = SIG_IGN;
 703                     if (sigaction(SIGSYS, &sa, &osa) >= 0)
 704                         sigsys_installed = 1;
 705                 }
 706                 n = poll(&pfd, 1, msec);
 707                 if (sigsys_installed == 1) {
 708                     int oerrno = errno;
 709                     sigaction(SIGSYS, &osa, NULL);
 710                     errno = oerrno;
 711                 }
 712                 /* XXX why does nosys() return EINVAL? */
 713                 if (n < 0 && (errno == ENOSYS ||
 714                     errno == EINVAL)) {
 715                     use_poll = 0;
 716                     goto othersyscall;
 717                 } else if (use_poll == 1)
 718                     use_poll = 2;
 719                 if (n < 0) {
 720                     if (errno == EINTR)
 721                         goto wait;
 722                     Perror(stderr, "poll", errno);
 723                     res_close();
 724                     goto next_ns;
 725                 }
 726             } else {
 727 #endif
 728                 dsmasklen = howmany(s + 1, NFDBITS) *
 729                         sizeof(fd_mask);
 730                 if (dsmasklen > sizeof(fd_set)) {
 731                     dsmaskp = (fd_set *)malloc(dsmasklen);
 732                     if (dsmaskp == NULL) {
 733                         res_close();
 734                         goto next_ns;
 735                     }
 736                 } else
 737                     dsmaskp = &dsmask;
 738                 /* only zero what we need */
 739                 memset((char *)dsmaskp, 0, dsmasklen);
 740                 FD_SET(s, dsmaskp);
 741                 n = select(s + 1, dsmaskp, (fd_set *)NULL,
 742                        (fd_set *)NULL, &timeout);
 743                 if (dsmaskp != &dsmask)
 744                     free(dsmaskp);
 745                 if (n < 0) {
 746                     if (errno == EINTR)
 747                         goto wait;
 748                     Perror(stderr, "select", errno);
 749                     res_close();
 750                     goto next_ns;
 751                 }
 752 #ifndef NOPOLL
 753             }
 754 #endif
 755
 756             if (n == 0) {
 757                 /*
 758                  * timeout
 759                  */
 760                 Dprint(_res.options & RES_DEBUG,
 761                        (stdout, ";; timeout\n"));
 762                 gotsomewhere = 1;
 763                 res_close();
 764                 goto next_ns;
 765             }
 766             errno = 0;
 767             fromlen = sizeof(struct sockaddr_in);
 768             resplen = (int)recvfrom(s, (char*)ans, anssiz, 0,
 769                        (struct sockaddr *)&from, (socklen_t *)&fromlen);
 770             if (resplen <= 0) {
 771                 Perror(stderr, "recvfrom", errno);
 772                 res_close();
 773                 goto next_ns;
 774             }
 775             gotsomewhere = 1;
 776             if (resplen < HFIXEDSZ) {
 777                 /*
 778                  * Undersized message.
 779                  */
 780                 Dprint(_res.options & RES_DEBUG,
 781                        (stdout, ";; undersized: %d\n",
 782                     resplen));
 783                 terrno = EMSGSIZE;
 784                 badns |= (1 << ns);
 785                 res_close();
 786                 goto next_ns;
 787             }
 788             if (hp->id != anhp->id) {
 789                 /*
 790                  * response from old query, ignore it.
 791                  * XXX - potential security hazard could
 792                  *   be detected here.
 793                  */
 794                 DprintQ((_res.options & RES_DEBUG) ||
 795                     (_res.pfcode & RES_PRF_REPLY),
 796                     (stdout, ";; old answer:\n"),
 797                     ans, (resplen>anssiz)?anssiz:resplen);
 798                 goto wait;
 799             }
 800 #ifdef CHECK_SRVR_ADDR
 801             if (!(_res.options & RES_INSECURE1) &&
 802                 !res_isourserver(&from)) {
 803                 /*
 804                  * response from wrong server? ignore it.
 805                  * XXX - potential security hazard could
 806                  *   be detected here.
 807                  */
 808                 DprintQ((_res.options & RES_DEBUG) ||
 809                     (_res.pfcode & RES_PRF_REPLY),
 810                     (stdout, ";; not our server:\n"),
 811                     ans, (resplen>anssiz)?anssiz:resplen);
 812                 goto wait;
 813             }
 814 #endif
 815             if (!(_res.options & RES_INSECURE2) &&
 816                 !res_queriesmatch(buf, buf + buflen,
 817                           ans, ans + anssiz)) {
 818                 /*
 819                  * response contains wrong query? ignore it.
 820                  * XXX - potential security hazard could
 821                  *   be detected here.
 822                  */
 823                 DprintQ((_res.options & RES_DEBUG) ||
 824                     (_res.pfcode & RES_PRF_REPLY),
 825                     (stdout, ";; wrong query name:\n"),
 826                     ans, (resplen>anssiz)?anssiz:resplen);
 827                 goto wait;
 828             }
 829             if (anhp->rcode == SERVFAIL ||
 830                 anhp->rcode == NOTIMP ||
 831                 anhp->rcode == REFUSED) {
 832                 DprintQ(_res.options & RES_DEBUG,
 833                     (stdout, "server rejected query:\n"),
 834                     ans, (resplen>anssiz)?anssiz:resplen);
 835                 badns |= (1 << ns);
 836                 res_close();
 837                 /* don't retry if called from dig */
 838                 if (!_res.pfcode)
 839                     goto next_ns;
 840             }
 841             if (!(_res.options & RES_IGNTC) && anhp->tc) {
 842                 /*
 843                  * get rest of answer;
 844                  * use TCP with same server.
 845                  */
 846                 Dprint(_res.options & RES_DEBUG,
 847                        (stdout, ";; truncated answer\n"));
 848                 v_circuit = 1;
 849                 res_close();
 850                 goto same_ns;
 851             }
 852         } /*if vc/dg*/
 853         Dprint((_res.options & RES_DEBUG) ||
 854                ((_res.pfcode & RES_PRF_REPLY) &&
 855             (_res.pfcode & RES_PRF_HEAD1)),
 856                (stdout, ";; got answer:\n"));
 857         if((_res.options & RES_DEBUG) ||
 858             (_res.pfcode & RES_PRF_REPLY)) {
 859             __fp_nquery(ans, (resplen>anssiz)?anssiz:resplen, stdout);
 860         }
 861         /*
 862          * If using virtual circuits, we assume that the first server
 863          * is preferred over the rest (i.e. it is on the local
 864          * machine) and only keep that one open.
 865          * If we have temporarily opened a virtual circuit,
 866          * or if we haven't been asked to keep a socket open,
 867          * close the socket.
 868          */
 869         if ((v_circuit && (!(_res.options & RES_USEVC) || ns != 0)) ||
 870             !(_res.options & RES_STAYOPEN)) {
 871             res_close();
 872         }
 873         if (Rhook) {
 874             int done = 0, loops = 0;
 875
 876             do {
 877                 res_sendhookact act;
 878
 879                 act = (*Rhook)(nsap, buf, buflen,
 880                            ans, anssiz, &resplen);
 881                 switch (act) {
 882                 case res_goahead:
 883                 case res_done:
 884                     done = 1;
 885                     break;
 886                 case res_nextns:
 887                     res_close();
 888                     goto next_ns;
 889                 case res_modified:
 890                     /* give the hook another try */
 891                     if (++loops < 42) /*doug adams*/
 892                         break;
 893                     /*FALLTHROUGH*/
 894                 case res_error:
 895                     /*FALLTHROUGH*/
 896                 default:
 897                     return (-1);
 898                 }
 899             } while (!done);
 900
 901         }
 902         return (resplen);
 903     next_ns: ;
 904        } /*foreach ns*/
 905     } /*foreach retry*/
 906     res_close();
 907     if (!v_circuit) {
 908         if (!gotsomewhere)
 909             errno = ECONNREFUSED;   /* no nameservers found */
 910         else
 911             errno = ETIMEDOUT;  /* no answer obtained */
 912     } else
 913         errno = terrno;
 914     return (-1);
 915 }
 916
 917 /*
 918  * This routine is for closing the socket if a virtual circuit is used and
 919  * the program wants to close it.  This provides support for endhostent()
 920  * which expects to close the socket.
 921  *
 922  * This routine is not expected to be user visible.
 923  */
 924 void
 925 res_close()
 926 {
 927     if (s >= 0) {
 928         (void) close(s);
 929         s = -1;
 930         connected = 0;
 931         vc = 0;
 932     }
 933 }