dns.subproj/res_send.c

   1 /*
   2  * Copyright (c) 1999 Apple Computer, Inc. All rights reserved.
   3  *
   4  * @APPLE_LICENSE_HEADER_START@
   5  *
   6  * Portions Copyright (c) 1999 Apple Computer, Inc.  All Rights
   7  * Reserved.  This file contains Original Code and/or Modifications of
   8  * Original Code as defined in and that are subject to the Apple Public
   9  * Source License Version 1.1 (the "License").  You may not use this file
  10  * except in compliance with the License.  Please obtain a copy of the
  11  * License at http://www.apple.com/publicsource and read it before using
  12  * this file.
  13  *
  14  * The Original Code and all software distributed under the License are
  15  * distributed on an "AS IS" basis, WITHOUT WARRANTY OF ANY KIND, EITHER
  16  * EXPRESS OR IMPLIED, AND APPLE HEREBY DISCLAIMS ALL SUCH WARRANTIES,
  17  * INCLUDING WITHOUT LIMITATION, ANY WARRANTIES OF MERCHANTABILITY,
  18  * FITNESS FOR A PARTICULAR PURPOSE OR NON- INFRINGEMENT.  Please see the
  19  * License for the specific language governing rights and limitations
  20  * under the License.
  21  *
  22  * @APPLE_LICENSE_HEADER_END@
  23  */
  24 /*
  25  * ++Copyright++ 1985, 1989, 1993
  26  * -
  27  * Copyright (c) 1985, 1989, 1993
  28  *    The Regents of the University of California.  All rights reserved.
  29  *
  30  * Redistribution and use in source and binary forms, with or without
  31  * modification, are permitted provided that the following conditions
  32  * are met:
  33  * 1. Redistributions of source code must retain the above copyright
  34  *    notice, this list of conditions and the following disclaimer.
  35  * 2. Redistributions in binary form must reproduce the above copyright
  36  *    notice, this list of conditions and the following disclaimer in the
  37  *    documentation and/or other materials provided with the distribution.
  38  * 3. All advertising materials mentioning features or use of this software
  39  *    must display the following acknowledgement:
  40  *      This product includes software developed by the University of
  41  *      California, Berkeley and its contributors.
  42  * 4. Neither the name of the University nor the names of its contributors
  43  *    may be used to endorse or promote products derived from this software
  44  *    without specific prior written permission.
  45  *
  46  * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
  47  * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
  48  * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
  49  * ARE DISCLAIMED.  IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
  50  * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
  51  * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
  52  * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
  53  * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
  54  * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
  55  * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
  56  * SUCH DAMAGE.
  57  * -
  58  * Portions Copyright (c) 1993 by Digital Equipment Corporation.
  59  *
  60  * Permission to use, copy, modify, and distribute this software for any
  61  * purpose with or without fee is hereby granted, provided that the above
  62  * copyright notice and this permission notice appear in all copies, and that
  63  * the name of Digital Equipment Corporation not be used in advertising or
  64  * publicity pertaining to distribution of the document or software without
  65  * specific, written prior permission.
  66  *
  67  * THE SOFTWARE IS PROVIDED "AS IS" AND DIGITAL EQUIPMENT CORP. DISCLAIMS ALL
  68  * WARRANTIES WITH REGARD TO THIS SOFTWARE, INCLUDING ALL IMPLIED WARRANTIES
  69  * OF MERCHANTABILITY AND FITNESS.   IN NO EVENT SHALL DIGITAL EQUIPMENT
  70  * CORPORATION BE LIABLE FOR ANY SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL
  71  * DAMAGES OR ANY DAMAGES WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR
  72  * PROFITS, WHETHER IN AN ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS
  73  * ACTION, ARISING OUT OF OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS
  74  * SOFTWARE.
  75  * -
  76  * --Copyright--
  77  */
  78
  79 #if defined(LIBC_SCCS) && !defined(lint)
  80 static char sccsid[] = "@(#)res_send.c  8.1 (Berkeley) 6/4/93";
  81 static char rcsid[] = "$Id: res_send.c,v 1.6 2003/02/18 17:29:25 majka Exp $";
  82 #endif /* LIBC_SCCS and not lint */
  83
  84         /* change this to "0"
  85          * if you talk to a lot
  86          * of multi-homed SunOS
  87          * ("broken") name servers.
  88          */
  89 #define CHECK_SRVR_ADDR 1       /* XXX - should be in options.h */
  90
  91 /*
  92  * Send query to name server and wait for reply.
  93  */
  94
  95 #include <sys/param.h>
  96 #include <sys/time.h>
  97 #include <sys/socket.h>
  98 #include <sys/uio.h>
  99 #include <netinet/in.h>
 100 #include <arpa/nameser8_compat.h>
 101 #include <arpa/inet.h>
 102 #include <ifaddrs.h>
 103 #include <net/if.h>
 104
 105 #include <stdio.h>
 106 #include <netdb.h>
 107 #include <errno.h>
 108 #include <resolv8_compat.h>
 109 #if defined(BSD) && (BSD >= 199306)
 110 # include <stdlib.h>
 111 # include <string.h>
 112 # include <unistd.h>
 113 #else
 114 # include "portability.h"
 115 #endif
 116
 117 #if defined(USE_OPTIONS_H)
 118 # include "options.h"
 119 #endif
 120
 121 void _res_close __P((void));
 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 ciruit? */
 126
 127 #ifndef FD_SET
 128 /* XXX - should be in portability.h */
 129 #define NFDBITS         32
 130 #define FD_SETSIZE      32
 131 #define FD_SET(n, p)    ((p)->fds_bits[(n)/NFDBITS] |= (1 << ((n) % NFDBITS)))
 132 #define FD_CLR(n, p)    ((p)->fds_bits[(n)/NFDBITS] &= ~(1 << ((n) % NFDBITS)))
 133 #define FD_ISSET(n, p)  ((p)->fds_bits[(n)/NFDBITS] & (1 << ((n) % NFDBITS)))
 134 #define FD_ZERO(p)      bzero((char *)(p), sizeof(*(p)))
 135 #endif
 136
 137 /* XXX - this should be done in portability.h */
 138 #if (defined(BSD) && (BSD >= 199103)) || defined(linux)
 139 # define CAN_RECONNECT 1
 140 #else
 141 # define CAN_RECONNECT 0
 142 #endif
 143
 144 #ifndef DEBUG
 145 #   define Dprint(cond, args) /*empty*/
 146 #   define DprintQ(cond, args, query, size) /*empty*/
 147 #   define Aerror(file, string, error, address) /*empty*/
 148 #   define Perror(file, string, error) /*empty*/
 149 #else
 150 #   define Dprint(cond, args) if (cond) {fprintf args;} else {}
 151 #   define DprintQ(cond, args, query, size) if (cond) {\
 152                         fprintf args;\
 153                         __fp_nquery(query, size, stdout);\
 154                 } else {}
 155     static void
 156     Aerror(file, string, error, address)
 157         FILE *file;
 158         char *string;
 159         int error;
 160         struct sockaddr_in address;
 161     {
 162         int save = errno;
 163
 164         if (_res.options & RES_DEBUG) {
 165                 fprintf(file, "res_send: %s ([%s].%u): %s\n",
 166                         string,
 167                         inet_ntoa(address.sin_addr),
 168                         ntohs(address.sin_port),
 169                         strerror(error));
 170         }
 171         errno = save;
 172     }
 173     static void
 174     Perror(file, string, error)
 175         FILE *file;
 176         char *string;
 177         int error;
 178     {
 179         int save = errno;
 180
 181         if (_res.options & RES_DEBUG) {
 182                 fprintf(file, "res_send: %s: %s\n",
 183                         string, strerror(error));
 184         }
 185         errno = save;
 186     }
 187 #endif
 188
 189 static res_send_qhook Qhook = NULL;
 190 static res_send_rhook Rhook = NULL;
 191
 192 void
 193 res_send_setqhook(hook)
 194         res_send_qhook hook;
 195 {
 196
 197         Qhook = hook;
 198 }
 199
 200 void
 201 res_send_setrhook(hook)
 202         res_send_rhook hook;
 203 {
 204
 205         Rhook = hook;
 206 }
 207
 208 /* int
 209  * res_isourserver(ina)
 210  *      looks up "ina" in _res.ns_addr_list[]
 211  * returns:
 212  *      0  : not found
 213  *      >0 : found
 214  * author:
 215  *      paul vixie, 29may94
 216  */
 217 int
 218 res_isourserver(inp)
 219         const struct sockaddr_in *inp;
 220 {
 221         struct sockaddr_in ina;
 222         register int ns, ret;
 223
 224         ina = *inp;
 225         ret = 0;
 226         for (ns = 0;  ns < _res.nscount;  ns++) {
 227                 register const struct sockaddr_in *srv = &_res.nsaddr_list[ns];
 228
 229                 if (srv->sin_family == ina.sin_family &&
 230                     srv->sin_port == ina.sin_port &&
 231                     (srv->sin_addr.s_addr == INADDR_ANY ||
 232                      srv->sin_addr.s_addr == ina.sin_addr.s_addr)) {
 233                         ret++;
 234                         break;
 235                 }
 236         }
 237         return (ret);
 238 }
 239
 240 /* int
 241  * res_nameinquery(name, type, class, buf, eom)
 242  *      look for (name,type,class) in the query section of packet (buf,eom)
 243  * returns:
 244  *      -1 : format error
 245  *      0  : not found
 246  *      >0 : found
 247  * author:
 248  *      paul vixie, 29may94
 249  */
 250 int
 251 res_nameinquery(name, type, class, buf, eom)
 252         const char *name;
 253         register int type, class;
 254         const u_char *buf, *eom;
 255 {
 256         register const u_char *cp = buf + HFIXEDSZ;
 257         int qdcount = ntohs(((HEADER*)buf)->qdcount);
 258
 259         while (qdcount-- > 0) {
 260                 char tname[MAXDNAME+1];
 261                 register int n, ttype, tclass;
 262
 263                 n = dn_expand(buf, eom, cp, tname, sizeof tname);
 264                 if (n < 0)
 265                         return (-1);
 266                 cp += n;
 267                 ttype = _getshort(cp); cp += INT16SZ;
 268                 tclass = _getshort(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(buf1, eom1, buf2, eom2)
 290         const u_char *buf1, *eom1;
 291         const u_char *buf2, *eom2;
 292 {
 293         register const u_char *cp = buf1 + HFIXEDSZ;
 294         int qdcount = ntohs(((HEADER*)buf1)->qdcount);
 295
 296         if (qdcount != ntohs(((HEADER*)buf2)->qdcount))
 297                 return (0);
 298         while (qdcount-- > 0) {
 299                 char tname[MAXDNAME+1];
 300                 register int n, ttype, tclass;
 301
 302                 n = dn_expand(buf1, eom1, cp, tname, sizeof tname);
 303                 if (n < 0)
 304                         return (-1);
 305                 cp += n;
 306                 ttype = _getshort(cp);  cp += INT16SZ;
 307                 tclass = _getshort(cp); cp += INT16SZ;
 308                 if (!res_nameinquery(tname, ttype, tclass, buf2, eom2))
 309                         return (0);
 310         }
 311         return (1);
 312 }
 313
 314 /* Returns whether a dns encoded name should be sent to multicast or not */
 315 static int dns_is_local_name(const u_int8_t *name)
 316 {
 317         const u_int8_t *d0 = NULL;              // Top-Level Domain
 318         const u_int8_t *d1 = NULL;              // Second-Level Domain
 319         const u_int8_t *d2 = NULL;              // etc.
 320         const u_int8_t *d3 = NULL;
 321
 322         if (name == NULL) return 0;
 323
 324         while (*name)
 325         {
 326                 d3 = d2;
 327                 d2 = d1;
 328                 d1 = d0;
 329                 d0 = name;
 330                 name += 1 + *name;
 331         }
 332
 333         // "local" domains need to be resolved with multicast
 334         // "local."
 335         if (d0[0] == 5 && strncasecmp((char *)d0+1, "local", 5) == 0) return 1;
 336
 337         // "local.arpa."
 338         if (d1 && d1[0] == 5 && strncasecmp((char *)d1+1, "local", 5) == 0 &&
 339                 d0[0] == 4 && strncasecmp((char *)d0+1, "arpa",  4) == 0) return 1;
 340
 341         // "local.int."
 342         if (d1 && d1[0] == 5 && strncasecmp((char *)d1+1, "local", 5) == 0 &&
 343                 d0[0] == 3 && strncasecmp((char *)d0+1, "int",   3) == 0) return 1;
 344
 345         // The network 169.254/16 is defined to be link-local,
 346         // so lookups in 254.169.in-addr.arpa. also need to be resolved with local multicast
 347         if (d3 && d3[0] == 3 && strncasecmp((char *)d3+1, "254",     3) == 0 &&
 348                 d2 && d2[0] == 3 && strncasecmp((char *)d2+1, "169",     3) == 0 &&
 349                 d1 && d1[0] == 7 && strncasecmp((char *)d1+1, "in-addr", 7) == 0 &&
 350                 d0[0] == 4 && strncasecmp((char *)d0+1, "arpa",    4) == 0) return 1;
 351
 352         return 0;
 353 }
 354
 355 #define DNS_LOCAL_DOMAIN_SERVICE_PORT   5353
 356 #define DNS_HEADER_SIZE 12
 357
 358 #if BYTE_ORDER == BIG_ENDIAN
 359 #define my_htons(x)     (x)
 360 #define my_htonl(x)     (x)
 361 #else
 362 #define my_htons(x)     ((((u_int16_t)x) >> 8) | (((u_int16_t)x) << 8))
 363 #define my_htonl(x)     (((x) >> 24) | (((x) & 0x00FF0000) >> 16) | \
 364                                          (((x) & 0x0000FF00) << 16) | ((x) << 24))
 365 #endif
 366
 367 static const struct sockaddr_in mDNS_addr =
 368 {
 369         sizeof(mDNS_addr),
 370         AF_INET,
 371         my_htons(DNS_LOCAL_DOMAIN_SERVICE_PORT),
 372         {my_htonl(0xE00000FB)}  /* 224.0.0.251 */
 373 };
 374
 375 int
 376 res_send(buf, buflen, ans, anssiz)
 377         const u_char *buf;
 378         int buflen;
 379         u_char *ans;
 380         int anssiz;
 381 {
 382         HEADER *hp = (HEADER *) buf;
 383         HEADER *anhp = (HEADER *) ans;
 384         int gotsomewhere, connreset, terrno, try, v_circuit, resplen, ns;
 385         register int n;
 386         u_int badns;    /* XXX NSMAX can't exceed #/bits in this var */
 387         int multicast;
 388
 389         if ((_res.options & RES_INIT) == 0 && res_init() == -1) {
 390                 /* errno should have been set by res_init() in this case. */
 391                 return (-1);
 392         }
 393         DprintQ((_res.options & RES_DEBUG) || (_res.pfcode & RES_PRF_QUERY),
 394                 (stdout, ";; res_send()\n"), buf, buflen);
 395         v_circuit = (_res.options & RES_USEVC) || buflen > PACKETSZ;
 396         gotsomewhere = 0;
 397         connreset = 0;
 398         terrno = ETIMEDOUT;
 399         badns = 0;
 400
 401         if (dns_is_local_name((u_int8_t*)(buf + DNS_HEADER_SIZE))) {
 402                 multicast = 1;
 403                 v_circuit = 0;
 404         } else {
 405                 multicast = 0;
 406         }
 407
 408
 409         /*
 410          * Send request, RETRY times, or until successful
 411          */
 412         for (try = 0; try < _res.retry; try++) {
 413             for (ns = 0; (multicast == 0 && ns < _res.nscount) ||
 414                         (multicast == 1 && ns < 1) ; ns++) {
 415                 struct sockaddr_in *nsap;
 416                 if (multicast == 0)
 417                         nsap = &_res.nsaddr_list[ns];
 418                 else
 419                         nsap = (struct sockaddr_in*)&mDNS_addr; /* const cast */
 420     same_ns:
 421                 if (badns & (1 << ns)) {
 422                         _res_close();
 423                         goto next_ns;
 424                 }
 425
 426                 if (Qhook) {
 427                         int done = 0, loops = 0;
 428
 429                         do {
 430                                 res_sendhookact act;
 431
 432                                 act = (*Qhook)(&nsap, &buf, &buflen,
 433                                                ans, anssiz, &resplen);
 434                                 switch (act) {
 435                                 case res_goahead:
 436                                         done = 1;
 437                                         break;
 438                                 case res_nextns:
 439                                         _res_close();
 440                                         goto next_ns;
 441                                 case res_done:
 442                                         return (resplen);
 443                                 case res_modified:
 444                                         /* give the hook another try */
 445                                         if (++loops < 42) /*doug adams*/
 446                                                 break;
 447                                         /*FALLTHROUGH*/
 448                                 case res_error:
 449                                         /*FALLTHROUGH*/
 450                                 default:
 451                                         return (-1);
 452                                 }
 453                         } while (!done);
 454                 }
 455
 456                 Dprint(_res.options & RES_DEBUG,
 457                        (stdout, ";; Querying server (# %d) address = %s\n",
 458                         ns + 1, inet_ntoa(nsap->sin_addr)));
 459
 460                 if (v_circuit) {
 461                         int truncated;
 462                         struct iovec iov[2];
 463                         u_short len;
 464                         u_char *cp;
 465
 466                         /*
 467                          * Use virtual circuit;
 468                          * at most one attempt per server.
 469                          */
 470                         try = _res.retry;
 471                         truncated = 0;
 472                         if ((s < 0) || (!vc)) {
 473                                 if (s >= 0)
 474                                         _res_close();
 475
 476                                 s = socket(PF_INET, SOCK_STREAM, 0);
 477                                 if (s < 0) {
 478                                         terrno = errno;
 479                                         Perror(stderr, "socket(vc)", errno);
 480                                         return (-1);
 481                                 }
 482                                 errno = 0;
 483                                 if (connect(s, (struct sockaddr *)nsap,
 484                                             sizeof(struct sockaddr)) < 0) {
 485                                         terrno = errno;
 486                                         Aerror(stderr, "connect/vc",
 487                                                errno, *nsap);
 488                                         badns |= (1 << ns);
 489                                         _res_close();
 490                                         goto next_ns;
 491                                 }
 492                                 vc = 1;
 493                         }
 494                         /*
 495                          * Send length & message
 496                          */
 497                         putshort((u_short)buflen, (u_char*)&len);
 498                         iov[0].iov_base = (caddr_t)&len;
 499                         iov[0].iov_len = INT16SZ;
 500                         iov[1].iov_base = (caddr_t)buf;
 501                         iov[1].iov_len = buflen;
 502                         if (writev(s, iov, 2) != (INT16SZ + buflen)) {
 503                                 terrno = errno;
 504                                 Perror(stderr, "write failed", errno);
 505                                 badns |= (1 << ns);
 506                                 _res_close();
 507                                 goto next_ns;
 508                         }
 509                         /*
 510                          * Receive length & response
 511                          */
 512                         cp = ans;
 513                         len = INT16SZ;
 514                         while ((n = read(s, (char *)cp, (int)len)) > 0) {
 515                                 cp += n;
 516                                 if ((len -= n) <= 0)
 517                                         break;
 518                         }
 519                         if (n <= 0) {
 520                                 terrno = errno;
 521                                 Perror(stderr, "read failed", errno);
 522                                 _res_close();
 523                                 /*
 524                                  * A long running process might get its TCP
 525                                  * connection reset if the remote server was
 526                                  * restarted.  Requery the server instead of
 527                                  * trying a new one.  When there is only one
 528                                  * server, this means that a query might work
 529                                  * instead of failing.  We only allow one reset
 530                                  * per query to prevent looping.
 531                                  */
 532                                 if (terrno == ECONNRESET && !connreset) {
 533                                         connreset = 1;
 534                                         _res_close();
 535                                         goto same_ns;
 536                                 }
 537                                 _res_close();
 538                                 goto next_ns;
 539                         }
 540                         resplen = _getshort(ans);
 541                         if (resplen > anssiz) {
 542                                 Dprint(_res.options & RES_DEBUG,
 543                                        (stdout, ";; response truncated\n")
 544                                        );
 545                                 truncated = 1;
 546                                 len = anssiz;
 547                         } else
 548                                 len = resplen;
 549                         cp = ans;
 550                         while (len != 0 &&
 551                                (n = read(s, (char *)cp, (int)len)) > 0) {
 552                                 cp += n;
 553                                 len -= n;
 554                         }
 555                         if (n <= 0) {
 556                                 terrno = errno;
 557                                 Perror(stderr, "read(vc)", errno);
 558                                 _res_close();
 559                                 goto next_ns;
 560                         }
 561                         if (truncated) {
 562                                 /*
 563                                  * Flush rest of answer
 564                                  * so connection stays in synch.
 565                                  */
 566                                 anhp->tc = 1;
 567                                 len = resplen - anssiz;
 568                                 while (len != 0) {
 569                                         char junk[PACKETSZ];
 570
 571                                         n = (len > sizeof(junk)
 572                                              ? sizeof(junk)
 573                                              : len);
 574                                         if ((n = read(s, junk, n)) > 0)
 575                                                 len -= n;
 576                                         else
 577                                                 break;
 578                                 }
 579                         }
 580                 } else {
 581                         /*
 582                          * Use datagrams.
 583                          */
 584                         struct timeval timeout;
 585                         fd_set dsmask;
 586                         struct sockaddr_in from;
 587                         unsigned int fromlen;
 588
 589                         if ((s < 0) || vc) {
 590                                 if (vc)
 591                                         _res_close();
 592                                 s = socket(PF_INET, SOCK_DGRAM, 0);
 593                                 if (s < 0) {
 594 #if !CAN_RECONNECT
 595  bad_dg_sock:
 596 #endif
 597                                         terrno = errno;
 598                                         Perror(stderr, "socket(dg)", errno);
 599                                         return (-1);
 600                                 }
 601                                 connected = 0;
 602                         }
 603                         /*
 604                          * On a 4.3BSD+ machine (client and server,
 605                          * actually), sending to a nameserver datagram
 606                          * port with no nameserver will cause an
 607                          * ICMP port unreachable message to be returned.
 608                          * If our datagram socket is "connected" to the
 609                          * server, we get an ECONNREFUSED error on the next
 610                          * socket operation, and select returns if the
 611                          * error message is received.  We can thus detect
 612                          * the absence of a nameserver without timing out.
 613                          * If we have sent queries to at least two servers,
 614                          * however, we don't want to remain connected,
 615                          * as we wish to receive answers from the first
 616                          * server to respond.
 617                          */
 618                         if ((_res.nscount == 1 || (try == 0 && ns == 0)) && multicast == 0) {
 619                                 /*
 620                                  * Connect only if we are sure we won't
 621                                  * receive a response from another server.
 622                                  */
 623                                 if (!connected) {
 624                                         if (connect(s, (struct sockaddr *)nsap,
 625                                                     sizeof(struct sockaddr)
 626                                                     ) < 0) {
 627                                                 Aerror(stderr,
 628                                                        "connect(dg)",
 629                                                        errno, *nsap);
 630                                                 badns |= (1 << ns);
 631                                                 _res_close();
 632                                                 goto next_ns;
 633                                         }
 634                                         connected = 1;
 635                                 }
 636                                 if (send(s, (char*)buf, buflen, 0) != buflen) {
 637                                         Perror(stderr, "send", errno);
 638                                         badns |= (1 << ns);
 639                                         _res_close();
 640                                         goto next_ns;
 641                                 }
 642                         } else {
 643                                 /*
 644                                  * Disconnect if we want to listen
 645                                  * for responses from more than one server.
 646                                  */
 647                                 if (connected) {
 648 #if CAN_RECONNECT
 649                                         struct sockaddr_in no_addr;
 650
 651                                         no_addr.sin_family = AF_INET;
 652                                         no_addr.sin_addr.s_addr = INADDR_ANY;
 653                                         no_addr.sin_port = 0;
 654                                         (void) connect(s,
 655                                                        (struct sockaddr *)
 656                                                         &no_addr,
 657                                                        sizeof(no_addr));
 658 #else
 659                                         int s1 = socket(PF_INET, SOCK_DGRAM,0);
 660                                         if (s1 < 0)
 661                                                 goto bad_dg_sock;
 662                                         (void) dup2(s1, s);
 663                                         (void) close(s1);
 664                                         Dprint(_res.options & RES_DEBUG,
 665                                                (stdout, ";; new DG socket\n"))
 666 #endif
 667                                         connected = 0;
 668                                         errno = 0;
 669                                 }
 670
 671                                 if (multicast) {
 672                                         struct ifaddrs* addrs;
 673                                         struct ifaddrs* curAddr;
 674                                         const int twofivefive = 255;
 675
 676                                         // multicast packets with TTL 255
 677                                         if(setsockopt(s, IPPROTO_IP, IP_MULTICAST_TTL, &twofivefive, sizeof(twofivefive))) {
 678                                                 Perror(stderr, "setsocketopt - IP_MULTICAST_TTL", errno);
 679                                                 _res_close();
 680                                                 return (0);
 681                                         }
 682
 683                                         if (getifaddrs(&addrs) != 0)
 684                                         {
 685                                                 Perror(stderr, "getifaddrs", errno);
 686                                                 _res_close();
 687                                                 return (0);
 688                                         }
 689
 690                                         /* multicast should send request on all multicast capable interfaces */
 691                                         for (curAddr = addrs; curAddr != NULL; curAddr = curAddr->ifa_next) {
 692                                                 if ((curAddr->ifa_addr->sa_family) == AF_INET &&
 693                                                         (curAddr->ifa_flags & IFF_MULTICAST) != 0 &&
 694                                                         (curAddr->ifa_flags & IFF_POINTOPOINT) == 0) {
 695                                                         struct in_addr* if_ip_addr = &((struct sockaddr_in*)curAddr->ifa_addr)->sin_addr;
 696
 697                                                         if (setsockopt(s, IPPROTO_IP, IP_MULTICAST_IF,
 698                                                                 if_ip_addr, sizeof(*if_ip_addr)) != 0) {
 699                                                                 freeifaddrs(addrs);
 700                                                                 Perror(stderr, "setsocketopt - IP_MULTICAST_IF", errno);
 701                                                                 _res_close();
 702                                                                 return (0);
 703                                                         }
 704
 705                                                         if (sendto(s, (char*)buf, buflen, 0,
 706                                                                    (struct sockaddr *)nsap, sizeof *nsap) != buflen)
 707                                                         {
 708                                                                 freeifaddrs(addrs);
 709                                                                 Aerror(stderr, "sendto", errno, *nsap);
 710                                                                 _res_close();
 711                                                                 return (0);
 712                                                         }
 713                                                 }
 714                                         }
 715
 716                                         freeifaddrs(addrs);
 717                                 } else {
 718                                         if (sendto(s, (char*)buf, buflen, 0,
 719                                                    (struct sockaddr *)nsap,
 720                                                    sizeof(struct sockaddr))
 721                                                 != buflen) {
 722                                                 Aerror(stderr, "sendto", errno, *nsap);
 723                                                 badns |= (1 << ns);
 724                                                 _res_close();
 725                                                 goto next_ns;
 726                                         }
 727                                 }
 728                         }
 729
 730                         /*
 731                          * Wait for reply
 732                          */
 733                         timeout.tv_sec = (_res.retrans << try);
 734                         if (try > 0)
 735                                 timeout.tv_sec /= _res.nscount;
 736                         if ((long) timeout.tv_sec <= 0 || multicast)
 737                                 timeout.tv_sec = 1;
 738                         timeout.tv_usec = 0;
 739     wait:
 740                         FD_ZERO(&dsmask);
 741                         FD_SET(s, &dsmask);
 742                         n = select(s+1, &dsmask, (fd_set *)NULL,
 743                                    (fd_set *)NULL, &timeout);
 744                         if (n < 0) {
 745                                 Perror(stderr, "select", errno);
 746                                 _res_close();
 747                                 goto next_ns;
 748                         }
 749                         if (n == 0) {
 750                                 /*
 751                                  * timeout
 752                                  */
 753                                 Dprint(_res.options & RES_DEBUG,
 754                                        (stdout, ";; timeout\n"));
 755                                 gotsomewhere = 1;
 756                                 _res_close();
 757                                 goto next_ns;
 758                         }
 759                         errno = 0;
 760                         fromlen = sizeof(struct sockaddr_in);
 761                         resplen = recvfrom(s, (char*)ans, anssiz, 0,
 762                                            (struct sockaddr *)&from, &fromlen);
 763                         if (resplen <= 0) {
 764                                 Perror(stderr, "recvfrom", errno);
 765                                 _res_close();
 766                                 goto next_ns;
 767                         }
 768                         gotsomewhere = 1;
 769                         if (hp->id != anhp->id) {
 770                                 /*
 771                                  * response from old query, ignore it.
 772                                  * XXX - potential security hazard could
 773                                  *       be detected here.
 774                                  */
 775                                 DprintQ((_res.options & RES_DEBUG) ||
 776                                         (_res.pfcode & RES_PRF_REPLY),
 777                                         (stdout, ";; old answer:\n"),
 778                                         ans, resplen);
 779                                 goto wait;
 780                         }
 781 #if CHECK_SRVR_ADDR
 782                         if (!(_res.options & RES_INSECURE1) &&
 783                             multicast == 0 && !res_isourserver(&from)) {
 784                                 /*
 785                                  * response from wrong server? ignore it.
 786                                  * XXX - potential security hazard could
 787                                  *       be detected here.
 788                                  */
 789                                 DprintQ((_res.options & RES_DEBUG) ||
 790                                         (_res.pfcode & RES_PRF_REPLY),
 791                                         (stdout, ";; not our server:\n"),
 792                                         ans, resplen);
 793                                 goto wait;
 794                         }
 795 #endif
 796                         if (!(_res.options & RES_INSECURE2) &&
 797                             !res_queriesmatch(buf, buf + buflen,
 798                                               ans, ans + anssiz)) {
 799                                 /*
 800                                  * response contains wrong query? ignore it.
 801                                  * XXX - potential security hazard could
 802                                  *       be detected here.
 803                                  */
 804                                 DprintQ((_res.options & RES_DEBUG) ||
 805                                         (_res.pfcode & RES_PRF_REPLY),
 806                                         (stdout, ";; wrong query name:\n"),
 807                                         ans, resplen);
 808                                 goto wait;
 809                         }
 810                         if (anhp->rcode == SERVFAIL ||
 811                             anhp->rcode == NOTIMP ||
 812                             anhp->rcode == REFUSED) {
 813                                 DprintQ(_res.options & RES_DEBUG,
 814                                         (stdout, "server rejected query:\n"),
 815                                         ans, resplen);
 816                                 badns |= (1 << ns);
 817                                 _res_close();
 818                                 /* don't retry if called from dig */
 819                                 if (!_res.pfcode)
 820                                         goto next_ns;
 821                         }
 822                         if (!(_res.options & RES_IGNTC) && anhp->tc) {
 823                                 /*
 824                                  * get rest of answer;
 825                                  * use TCP with same server.
 826                                  */
 827                                 Dprint(_res.options & RES_DEBUG,
 828                                        (stdout, ";; truncated answer\n"));
 829                                 v_circuit = 1;
 830                                 _res_close();
 831                                 goto same_ns;
 832                         }
 833                 } /*if vc/dg*/
 834                 DprintQ((_res.options & RES_DEBUG) ||
 835                         (_res.pfcode & RES_PRF_REPLY),
 836                         (stdout, ";; got answer:\n"),
 837                         ans, resplen);
 838                 /*
 839                  * If using virtual circuits, we assume that the first server
 840                  * is preferred over the rest (i.e. it is on the local
 841                  * machine) and only keep that one open.
 842                  * If we have temporarily opened a virtual circuit,
 843                  * or if we haven't been asked to keep a socket open,
 844                  * close the socket.
 845                  */
 846                 if ((v_circuit && (!(_res.options & RES_USEVC) || ns != 0)) ||
 847                     !(_res.options & RES_STAYOPEN)) {
 848                         _res_close();
 849                 }
 850                 if (Rhook) {
 851                         int done = 0, loops = 0;
 852
 853                         do {
 854                                 res_sendhookact act;
 855
 856                                 act = (*Rhook)(nsap, buf, buflen,
 857                                                ans, anssiz, &resplen);
 858                                 switch (act) {
 859                                 case res_goahead:
 860                                 case res_done:
 861                                         done = 1;
 862                                         break;
 863                                 case res_nextns:
 864                                         _res_close();
 865                                         goto next_ns;
 866                                 case res_modified:
 867                                         /* give the hook another try */
 868                                         if (++loops < 42) /*doug adams*/
 869                                                 break;
 870                                         /*FALLTHROUGH*/
 871                                 case res_error:
 872                                         /*FALLTHROUGH*/
 873                                 default:
 874                                         return (-1);
 875                                 }
 876                         } while (!done);
 877
 878                 }
 879                 return (resplen);
 880     next_ns: ;
 881            } /*foreach ns*/
 882         } /*foreach retry*/
 883         _res_close();
 884         if (!v_circuit)
 885                 if (!gotsomewhere)
 886                         errno = ECONNREFUSED;   /* no nameservers found */
 887                 else
 888                         errno = ETIMEDOUT;      /* no answer obtained */
 889         else
 890                 errno = terrno;
 891         return (-1);
 892 }
 893
 894 /*
 895  * This routine is for closing the socket if a virtual circuit is used and
 896  * the program wants to close it.  This provides support for endhostent()
 897  * which expects to close the socket.
 898  *
 899  * This routine is not expected to be user visible.
 900  */
 901 void
 902 _res_close()
 903 {
 904         if (s >= 0) {
 905                 (void) close(s);
 906                 s = -1;
 907                 connected = 0;
 908                 vc = 0;
 909         }
 910 }