dns.subproj/res_send.c

   1 /*
   2  * Copyright (c) 1999 Apple Computer, Inc. All rights reserved.
   3  *
   4  * @APPLE_LICENSE_HEADER_START@
   5  *
   6  * Copyright (c) 1999-2003 Apple Computer, Inc.  All Rights Reserved.
   7  *
   8  * This file contains Original Code and/or Modifications of Original Code
   9  * as defined in and that are subject to the Apple Public Source License
  10  * Version 2.0 (the 'License'). You may not use this file except in
  11  * compliance with the License. Please obtain a copy of the License at
  12  * http://www.opensource.apple.com/apsl/ and read it before using this
  13  * file.
  14  *
  15  * The Original Code and all software distributed under the License are
  16  * distributed on an 'AS IS' basis, WITHOUT WARRANTY OF ANY KIND, EITHER
  17  * EXPRESS OR IMPLIED, AND APPLE HEREBY DISCLAIMS ALL SUCH WARRANTIES,
  18  * INCLUDING WITHOUT LIMITATION, ANY WARRANTIES OF MERCHANTABILITY,
  19  * FITNESS FOR A PARTICULAR PURPOSE, QUIET ENJOYMENT OR NON-INFRINGEMENT.
  20  * Please see the License for the specific language governing rights and
  21  * limitations under the License.
  22  *
  23  * @APPLE_LICENSE_HEADER_END@
  24  */
  25 /*
  26  * ++Copyright++ 1985, 1989, 1993
  27  * -
  28  * Copyright (c) 1985, 1989, 1993
  29  *    The Regents of the University of California.  All rights reserved.
  30  *
  31  * Redistribution and use in source and binary forms, with or without
  32  * modification, are permitted provided that the following conditions
  33  * are met:
  34  * 1. Redistributions of source code must retain the above copyright
  35  *    notice, this list of conditions and the following disclaimer.
  36  * 2. Redistributions in binary form must reproduce the above copyright
  37  *    notice, this list of conditions and the following disclaimer in the
  38  *    documentation and/or other materials provided with the distribution.
  39  * 3. All advertising materials mentioning features or use of this software
  40  *    must display the following acknowledgement:
  41  *      This product includes software developed by the University of
  42  *      California, Berkeley and its contributors.
  43  * 4. Neither the name of the University nor the names of its contributors
  44  *    may be used to endorse or promote products derived from this software
  45  *    without specific prior written permission.
  46  *
  47  * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
  48  * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
  49  * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
  50  * ARE DISCLAIMED.  IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
  51  * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
  52  * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
  53  * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
  54  * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
  55  * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
  56  * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
  57  * SUCH DAMAGE.
  58  * -
  59  * Portions Copyright (c) 1993 by Digital Equipment Corporation.
  60  *
  61  * Permission to use, copy, modify, and distribute this software for any
  62  * purpose with or without fee is hereby granted, provided that the above
  63  * copyright notice and this permission notice appear in all copies, and that
  64  * the name of Digital Equipment Corporation not be used in advertising or
  65  * publicity pertaining to distribution of the document or software without
  66  * specific, written prior permission.
  67  *
  68  * THE SOFTWARE IS PROVIDED "AS IS" AND DIGITAL EQUIPMENT CORP. DISCLAIMS ALL
  69  * WARRANTIES WITH REGARD TO THIS SOFTWARE, INCLUDING ALL IMPLIED WARRANTIES
  70  * OF MERCHANTABILITY AND FITNESS.   IN NO EVENT SHALL DIGITAL EQUIPMENT
  71  * CORPORATION BE LIABLE FOR ANY SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL
  72  * DAMAGES OR ANY DAMAGES WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR
  73  * PROFITS, WHETHER IN AN ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS
  74  * ACTION, ARISING OUT OF OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS
  75  * SOFTWARE.
  76  * -
  77  * --Copyright--
  78  */
  79
  80 #if defined(LIBC_SCCS) && !defined(lint)
  81 static char sccsid[] = "@(#)res_send.c  8.1 (Berkeley) 6/4/93";
  82 static char rcsid[] = "$Id: res_send.c,v 1.6 2003/02/18 17:29:25 majka Exp $";
  83 #endif /* LIBC_SCCS and not lint */
  84
  85         /* change this to "0"
  86          * if you talk to a lot
  87          * of multi-homed SunOS
  88          * ("broken") name servers.
  89          */
  90 #define CHECK_SRVR_ADDR 1       /* XXX - should be in options.h */
  91
  92 /*
  93  * Send query to name server and wait for reply.
  94  */
  95
  96 #include <sys/param.h>
  97 #include <sys/time.h>
  98 #include <sys/socket.h>
  99 #include <sys/uio.h>
 100 #include <netinet/in.h>
 101 #include <arpa/nameser8_compat.h>
 102 #include <arpa/inet.h>
 103 #include <ifaddrs.h>
 104 #include <net/if.h>
 105
 106 #include <stdio.h>
 107 #include <netdb.h>
 108 #include <errno.h>
 109 #include <resolv8_compat.h>
 110 #if defined(BSD) && (BSD >= 199306)
 111 # include <stdlib.h>
 112 # include <string.h>
 113 # include <unistd.h>
 114 #else
 115 # include "portability.h"
 116 #endif
 117
 118 #if defined(USE_OPTIONS_H)
 119 # include "options.h"
 120 #endif
 121
 122 void _res_close __P((void));
 123
 124 static int s = -1;      /* socket used for communications */
 125 static int connected = 0;       /* is the socket connected */
 126 static int vc = 0;      /* is the socket a virtual ciruit? */
 127
 128 #ifndef FD_SET
 129 /* XXX - should be in portability.h */
 130 #define NFDBITS         32
 131 #define FD_SETSIZE      32
 132 #define FD_SET(n, p)    ((p)->fds_bits[(n)/NFDBITS] |= (1 << ((n) % NFDBITS)))
 133 #define FD_CLR(n, p)    ((p)->fds_bits[(n)/NFDBITS] &= ~(1 << ((n) % NFDBITS)))
 134 #define FD_ISSET(n, p)  ((p)->fds_bits[(n)/NFDBITS] & (1 << ((n) % NFDBITS)))
 135 #define FD_ZERO(p)      bzero((char *)(p), sizeof(*(p)))
 136 #endif
 137
 138 /* XXX - this should be done in portability.h */
 139 #if (defined(BSD) && (BSD >= 199103)) || defined(linux)
 140 # define CAN_RECONNECT 1
 141 #else
 142 # define CAN_RECONNECT 0
 143 #endif
 144
 145 #ifndef DEBUG
 146 #   define Dprint(cond, args) /*empty*/
 147 #   define DprintQ(cond, args, query, size) /*empty*/
 148 #   define Aerror(file, string, error, address) /*empty*/
 149 #   define Perror(file, string, error) /*empty*/
 150 #else
 151 #   define Dprint(cond, args) if (cond) {fprintf args;} else {}
 152 #   define DprintQ(cond, args, query, size) if (cond) {\
 153                         fprintf args;\
 154                         __fp_nquery(query, size, stdout);\
 155                 } else {}
 156     static void
 157     Aerror(file, string, error, address)
 158         FILE *file;
 159         char *string;
 160         int error;
 161         struct sockaddr_in address;
 162     {
 163         int save = errno;
 164
 165         if (_res.options & RES_DEBUG) {
 166                 fprintf(file, "res_send: %s ([%s].%u): %s\n",
 167                         string,
 168                         inet_ntoa(address.sin_addr),
 169                         ntohs(address.sin_port),
 170                         strerror(error));
 171         }
 172         errno = save;
 173     }
 174     static void
 175     Perror(file, string, error)
 176         FILE *file;
 177         char *string;
 178         int error;
 179     {
 180         int save = errno;
 181
 182         if (_res.options & RES_DEBUG) {
 183                 fprintf(file, "res_send: %s: %s\n",
 184                         string, strerror(error));
 185         }
 186         errno = save;
 187     }
 188 #endif
 189
 190 static res_send_qhook Qhook = NULL;
 191 static res_send_rhook Rhook = NULL;
 192
 193 void
 194 res_send_setqhook(hook)
 195         res_send_qhook hook;
 196 {
 197
 198         Qhook = hook;
 199 }
 200
 201 void
 202 res_send_setrhook(hook)
 203         res_send_rhook hook;
 204 {
 205
 206         Rhook = hook;
 207 }
 208
 209 /* int
 210  * res_isourserver(ina)
 211  *      looks up "ina" in _res.ns_addr_list[]
 212  * returns:
 213  *      0  : not found
 214  *      >0 : found
 215  * author:
 216  *      paul vixie, 29may94
 217  */
 218 int
 219 res_isourserver(inp)
 220         const struct sockaddr_in *inp;
 221 {
 222         struct sockaddr_in ina;
 223         register int ns, ret;
 224
 225         ina = *inp;
 226         ret = 0;
 227         for (ns = 0;  ns < _res.nscount;  ns++) {
 228                 register const struct sockaddr_in *srv = &_res.nsaddr_list[ns];
 229
 230                 if (srv->sin_family == ina.sin_family &&
 231                     srv->sin_port == ina.sin_port &&
 232                     (srv->sin_addr.s_addr == INADDR_ANY ||
 233                      srv->sin_addr.s_addr == ina.sin_addr.s_addr)) {
 234                         ret++;
 235                         break;
 236                 }
 237         }
 238         return (ret);
 239 }
 240
 241 /* int
 242  * res_nameinquery(name, type, class, buf, eom)
 243  *      look for (name,type,class) in the query section of packet (buf,eom)
 244  * returns:
 245  *      -1 : format error
 246  *      0  : not found
 247  *      >0 : found
 248  * author:
 249  *      paul vixie, 29may94
 250  */
 251 int
 252 res_nameinquery(name, type, class, buf, eom)
 253         const char *name;
 254         register int type, class;
 255         const u_char *buf, *eom;
 256 {
 257         register const u_char *cp = buf + HFIXEDSZ;
 258         int qdcount = ntohs(((HEADER*)buf)->qdcount);
 259
 260         while (qdcount-- > 0) {
 261                 char tname[MAXDNAME+1];
 262                 register int n, ttype, tclass;
 263
 264                 n = dn_expand(buf, eom, cp, tname, sizeof tname);
 265                 if (n < 0)
 266                         return (-1);
 267                 cp += n;
 268                 ttype = _getshort(cp); cp += INT16SZ;
 269                 tclass = _getshort(cp); cp += INT16SZ;
 270                 if (ttype == type &&
 271                     tclass == class &&
 272                     strcasecmp(tname, name) == 0)
 273                         return (1);
 274         }
 275         return (0);
 276 }
 277
 278 /* int
 279  * res_queriesmatch(buf1, eom1, buf2, eom2)
 280  *      is there a 1:1 mapping of (name,type,class)
 281  *      in (buf1,eom1) and (buf2,eom2)?
 282  * returns:
 283  *      -1 : format error
 284  *      0  : not a 1:1 mapping
 285  *      >0 : is a 1:1 mapping
 286  * author:
 287  *      paul vixie, 29may94
 288  */
 289 int
 290 res_queriesmatch(buf1, eom1, buf2, eom2)
 291         const u_char *buf1, *eom1;
 292         const u_char *buf2, *eom2;
 293 {
 294         register const u_char *cp = buf1 + HFIXEDSZ;
 295         int qdcount = ntohs(((HEADER*)buf1)->qdcount);
 296
 297         if (qdcount != ntohs(((HEADER*)buf2)->qdcount))
 298                 return (0);
 299         while (qdcount-- > 0) {
 300                 char tname[MAXDNAME+1];
 301                 register int n, ttype, tclass;
 302
 303                 n = dn_expand(buf1, eom1, cp, tname, sizeof tname);
 304                 if (n < 0)
 305                         return (-1);
 306                 cp += n;
 307                 ttype = _getshort(cp);  cp += INT16SZ;
 308                 tclass = _getshort(cp); cp += INT16SZ;
 309                 if (!res_nameinquery(tname, ttype, tclass, buf2, eom2))
 310                         return (0);
 311         }
 312         return (1);
 313 }
 314
 315 /* Returns whether a dns encoded name should be sent to multicast or not */
 316 static int dns_is_local_name(const u_int8_t *name)
 317 {
 318         const u_int8_t *d0 = NULL;              // Top-Level Domain
 319         const u_int8_t *d1 = NULL;              // Second-Level Domain
 320         const u_int8_t *d2 = NULL;              // etc.
 321         const u_int8_t *d3 = NULL;
 322
 323         if (name == NULL) return 0;
 324
 325         while (*name)
 326         {
 327                 d3 = d2;
 328                 d2 = d1;
 329                 d1 = d0;
 330                 d0 = name;
 331                 name += 1 + *name;
 332         }
 333
 334         // "local" domains need to be resolved with multicast
 335         // "local."
 336         if (d0[0] == 5 && strncasecmp((char *)d0+1, "local", 5) == 0) return 1;
 337
 338         // "local.arpa."
 339         if (d1 && d1[0] == 5 && strncasecmp((char *)d1+1, "local", 5) == 0 &&
 340                 d0[0] == 4 && strncasecmp((char *)d0+1, "arpa",  4) == 0) return 1;
 341
 342         // "local.int."
 343         if (d1 && d1[0] == 5 && strncasecmp((char *)d1+1, "local", 5) == 0 &&
 344                 d0[0] == 3 && strncasecmp((char *)d0+1, "int",   3) == 0) return 1;
 345
 346         // The network 169.254/16 is defined to be link-local,
 347         // so lookups in 254.169.in-addr.arpa. also need to be resolved with local multicast
 348         if (d3 && d3[0] == 3 && strncasecmp((char *)d3+1, "254",     3) == 0 &&
 349                 d2 && d2[0] == 3 && strncasecmp((char *)d2+1, "169",     3) == 0 &&
 350                 d1 && d1[0] == 7 && strncasecmp((char *)d1+1, "in-addr", 7) == 0 &&
 351                 d0[0] == 4 && strncasecmp((char *)d0+1, "arpa",    4) == 0) return 1;
 352
 353         return 0;
 354 }
 355
 356 #define DNS_LOCAL_DOMAIN_SERVICE_PORT   5353
 357 #define DNS_HEADER_SIZE 12
 358
 359 #if BYTE_ORDER == BIG_ENDIAN
 360 #define my_htons(x)     (x)
 361 #define my_htonl(x)     (x)
 362 #else
 363 #define my_htons(x)     ((((u_int16_t)x) >> 8) | (((u_int16_t)x) << 8))
 364 #define my_htonl(x)     (((x) >> 24) | (((x) & 0x00FF0000) >> 16) | \
 365                                          (((x) & 0x0000FF00) << 16) | ((x) << 24))
 366 #endif
 367
 368 static const struct sockaddr_in mDNS_addr =
 369 {
 370         sizeof(mDNS_addr),
 371         AF_INET,
 372         my_htons(DNS_LOCAL_DOMAIN_SERVICE_PORT),
 373         {my_htonl(0xE00000FB)}  /* 224.0.0.251 */
 374 };
 375
 376 int
 377 res_send(buf, buflen, ans, anssiz)
 378         const u_char *buf;
 379         int buflen;
 380         u_char *ans;
 381         int anssiz;
 382 {
 383         HEADER *hp = (HEADER *) buf;
 384         HEADER *anhp = (HEADER *) ans;
 385         int gotsomewhere, connreset, terrno, try, v_circuit, resplen, ns;
 386         register int n;
 387         u_int badns;    /* XXX NSMAX can't exceed #/bits in this var */
 388         int multicast;
 389
 390         if ((_res.options & RES_INIT) == 0 && res_init() == -1) {
 391                 /* errno should have been set by res_init() in this case. */
 392                 return (-1);
 393         }
 394         DprintQ((_res.options & RES_DEBUG) || (_res.pfcode & RES_PRF_QUERY),
 395                 (stdout, ";; res_send()\n"), buf, buflen);
 396         v_circuit = (_res.options & RES_USEVC) || buflen > PACKETSZ;
 397         gotsomewhere = 0;
 398         connreset = 0;
 399         terrno = ETIMEDOUT;
 400         badns = 0;
 401
 402         if (dns_is_local_name((u_int8_t*)(buf + DNS_HEADER_SIZE))) {
 403                 multicast = 1;
 404                 v_circuit = 0;
 405         } else {
 406                 multicast = 0;
 407         }
 408
 409
 410         /*
 411          * Send request, RETRY times, or until successful
 412          */
 413         for (try = 0; try < _res.retry; try++) {
 414             for (ns = 0; (multicast == 0 && ns < _res.nscount) ||
 415                         (multicast == 1 && ns < 1) ; ns++) {
 416                 struct sockaddr_in *nsap;
 417                 if (multicast == 0)
 418                         nsap = &_res.nsaddr_list[ns];
 419                 else
 420                         nsap = (struct sockaddr_in*)&mDNS_addr; /* const cast */
 421     same_ns:
 422                 if (badns & (1 << ns)) {
 423                         _res_close();
 424                         goto next_ns;
 425                 }
 426
 427                 if (Qhook) {
 428                         int done = 0, loops = 0;
 429
 430                         do {
 431                                 res_sendhookact act;
 432
 433                                 act = (*Qhook)(&nsap, &buf, &buflen,
 434                                                ans, anssiz, &resplen);
 435                                 switch (act) {
 436                                 case res_goahead:
 437                                         done = 1;
 438                                         break;
 439                                 case res_nextns:
 440                                         _res_close();
 441                                         goto next_ns;
 442                                 case res_done:
 443                                         return (resplen);
 444                                 case res_modified:
 445                                         /* give the hook another try */
 446                                         if (++loops < 42) /*doug adams*/
 447                                                 break;
 448                                         /*FALLTHROUGH*/
 449                                 case res_error:
 450                                         /*FALLTHROUGH*/
 451                                 default:
 452                                         return (-1);
 453                                 }
 454                         } while (!done);
 455                 }
 456
 457                 Dprint(_res.options & RES_DEBUG,
 458                        (stdout, ";; Querying server (# %d) address = %s\n",
 459                         ns + 1, inet_ntoa(nsap->sin_addr)));
 460
 461                 if (v_circuit) {
 462                         int truncated;
 463                         struct iovec iov[2];
 464                         u_short len;
 465                         u_char *cp;
 466
 467                         /*
 468                          * Use virtual circuit;
 469                          * at most one attempt per server.
 470                          */
 471                         try = _res.retry;
 472                         truncated = 0;
 473                         if ((s < 0) || (!vc)) {
 474                                 if (s >= 0)
 475                                         _res_close();
 476
 477                                 s = socket(PF_INET, SOCK_STREAM, 0);
 478                                 if (s < 0) {
 479                                         terrno = errno;
 480                                         Perror(stderr, "socket(vc)", errno);
 481                                         return (-1);
 482                                 }
 483                                 errno = 0;
 484                                 if (connect(s, (struct sockaddr *)nsap,
 485                                             sizeof(struct sockaddr)) < 0) {
 486                                         terrno = errno;
 487                                         Aerror(stderr, "connect/vc",
 488                                                errno, *nsap);
 489                                         badns |= (1 << ns);
 490                                         _res_close();
 491                                         goto next_ns;
 492                                 }
 493                                 vc = 1;
 494                         }
 495                         /*
 496                          * Send length & message
 497                          */
 498                         putshort((u_short)buflen, (u_char*)&len);
 499                         iov[0].iov_base = (caddr_t)&len;
 500                         iov[0].iov_len = INT16SZ;
 501                         iov[1].iov_base = (caddr_t)buf;
 502                         iov[1].iov_len = buflen;
 503                         if (writev(s, iov, 2) != (INT16SZ + buflen)) {
 504                                 terrno = errno;
 505                                 Perror(stderr, "write failed", errno);
 506                                 badns |= (1 << ns);
 507                                 _res_close();
 508                                 goto next_ns;
 509                         }
 510                         /*
 511                          * Receive length & response
 512                          */
 513                         cp = ans;
 514                         len = INT16SZ;
 515                         while ((n = read(s, (char *)cp, (int)len)) > 0) {
 516                                 cp += n;
 517                                 if ((len -= n) <= 0)
 518                                         break;
 519                         }
 520                         if (n <= 0) {
 521                                 terrno = errno;
 522                                 Perror(stderr, "read failed", errno);
 523                                 _res_close();
 524                                 /*
 525                                  * A long running process might get its TCP
 526                                  * connection reset if the remote server was
 527                                  * restarted.  Requery the server instead of
 528                                  * trying a new one.  When there is only one
 529                                  * server, this means that a query might work
 530                                  * instead of failing.  We only allow one reset
 531                                  * per query to prevent looping.
 532                                  */
 533                                 if (terrno == ECONNRESET && !connreset) {
 534                                         connreset = 1;
 535                                         _res_close();
 536                                         goto same_ns;
 537                                 }
 538                                 _res_close();
 539                                 goto next_ns;
 540                         }
 541                         resplen = _getshort(ans);
 542                         if (resplen > anssiz) {
 543                                 Dprint(_res.options & RES_DEBUG,
 544                                        (stdout, ";; response truncated\n")
 545                                        );
 546                                 truncated = 1;
 547                                 len = anssiz;
 548                         } else
 549                                 len = resplen;
 550                         cp = ans;
 551                         while (len != 0 &&
 552                                (n = read(s, (char *)cp, (int)len)) > 0) {
 553                                 cp += n;
 554                                 len -= n;
 555                         }
 556                         if (n <= 0) {
 557                                 terrno = errno;
 558                                 Perror(stderr, "read(vc)", errno);
 559                                 _res_close();
 560                                 goto next_ns;
 561                         }
 562                         if (truncated) {
 563                                 /*
 564                                  * Flush rest of answer
 565                                  * so connection stays in synch.
 566                                  */
 567                                 anhp->tc = 1;
 568                                 len = resplen - anssiz;
 569                                 while (len != 0) {
 570                                         char junk[PACKETSZ];
 571
 572                                         n = (len > sizeof(junk)
 573                                              ? sizeof(junk)
 574                                              : len);
 575                                         if ((n = read(s, junk, n)) > 0)
 576                                                 len -= n;
 577                                         else
 578                                                 break;
 579                                 }
 580                         }
 581                 } else {
 582                         /*
 583                          * Use datagrams.
 584                          */
 585                         struct timeval timeout;
 586                         fd_set dsmask;
 587                         struct sockaddr_in from;
 588                         int fromlen;
 589
 590                         if ((s < 0) || vc) {
 591                                 if (vc)
 592                                         _res_close();
 593                                 s = socket(PF_INET, SOCK_DGRAM, 0);
 594                                 if (s < 0) {
 595 #if !CAN_RECONNECT
 596  bad_dg_sock:
 597 #endif
 598                                         terrno = errno;
 599                                         Perror(stderr, "socket(dg)", errno);
 600                                         return (-1);
 601                                 }
 602                                 connected = 0;
 603                         }
 604                         /*
 605                          * On a 4.3BSD+ machine (client and server,
 606                          * actually), sending to a nameserver datagram
 607                          * port with no nameserver will cause an
 608                          * ICMP port unreachable message to be returned.
 609                          * If our datagram socket is "connected" to the
 610                          * server, we get an ECONNREFUSED error on the next
 611                          * socket operation, and select returns if the
 612                          * error message is received.  We can thus detect
 613                          * the absence of a nameserver without timing out.
 614                          * If we have sent queries to at least two servers,
 615                          * however, we don't want to remain connected,
 616                          * as we wish to receive answers from the first
 617                          * server to respond.
 618                          */
 619                         if ((_res.nscount == 1 || (try == 0 && ns == 0)) && multicast == 0) {
 620                                 /*
 621                                  * Connect only if we are sure we won't
 622                                  * receive a response from another server.
 623                                  */
 624                                 if (!connected) {
 625                                         if (connect(s, (struct sockaddr *)nsap,
 626                                                     sizeof(struct sockaddr)
 627                                                     ) < 0) {
 628                                                 Aerror(stderr,
 629                                                        "connect(dg)",
 630                                                        errno, *nsap);
 631                                                 badns |= (1 << ns);
 632                                                 _res_close();
 633                                                 goto next_ns;
 634                                         }
 635                                         connected = 1;
 636                                 }
 637                                 if (send(s, (char*)buf, buflen, 0) != buflen) {
 638                                         Perror(stderr, "send", errno);
 639                                         badns |= (1 << ns);
 640                                         _res_close();
 641                                         goto next_ns;
 642                                 }
 643                         } else {
 644                                 /*
 645                                  * Disconnect if we want to listen
 646                                  * for responses from more than one server.
 647                                  */
 648                                 if (connected) {
 649 #if CAN_RECONNECT
 650                                         struct sockaddr_in no_addr;
 651
 652                                         no_addr.sin_family = AF_INET;
 653                                         no_addr.sin_addr.s_addr = INADDR_ANY;
 654                                         no_addr.sin_port = 0;
 655                                         (void) connect(s,
 656                                                        (struct sockaddr *)
 657                                                         &no_addr,
 658                                                        sizeof(no_addr));
 659 #else
 660                                         int s1 = socket(PF_INET, SOCK_DGRAM,0);
 661                                         if (s1 < 0)
 662                                                 goto bad_dg_sock;
 663                                         (void) dup2(s1, s);
 664                                         (void) close(s1);
 665                                         Dprint(_res.options & RES_DEBUG,
 666                                                (stdout, ";; new DG socket\n"))
 667 #endif
 668                                         connected = 0;
 669                                         errno = 0;
 670                                 }
 671
 672                                 if (multicast) {
 673                                         struct ifaddrs* addrs;
 674                                         struct ifaddrs* curAddr;
 675                                         const int twofivefive = 255;
 676
 677                                         // multicast packets with TTL 255
 678                                         if(setsockopt(s, IPPROTO_IP, IP_MULTICAST_TTL, &twofivefive, sizeof(twofivefive))) {
 679                                                 Perror(stderr, "setsocketopt - IP_MULTICAST_TTL", errno);
 680                                                 _res_close();
 681                                                 return (0);
 682                                         }
 683
 684                                         if (getifaddrs(&addrs) != 0)
 685                                         {
 686                                                 Perror(stderr, "getifaddrs", errno);
 687                                                 _res_close();
 688                                                 return (0);
 689                                         }
 690
 691                                         /* multicast should send request on all multicast capable interfaces */
 692                                         for (curAddr = addrs; curAddr != NULL; curAddr = curAddr->ifa_next) {
 693                                                 if ((curAddr->ifa_addr->sa_family) == AF_INET &&
 694                                                         (curAddr->ifa_flags & IFF_MULTICAST) != 0 &&
 695                                                         (curAddr->ifa_flags & IFF_POINTOPOINT) == 0) {
 696                                                         struct in_addr* if_ip_addr = &((struct sockaddr_in*)curAddr->ifa_addr)->sin_addr;
 697
 698                                                         if (setsockopt(s, IPPROTO_IP, IP_MULTICAST_IF,
 699                                                                 if_ip_addr, sizeof(*if_ip_addr)) != 0) {
 700                                                                 freeifaddrs(addrs);
 701                                                                 Perror(stderr, "setsocketopt - IP_MULTICAST_IF", errno);
 702                                                                 _res_close();
 703                                                                 return (0);
 704                                                         }
 705
 706                                                         if (sendto(s, (char*)buf, buflen, 0,
 707                                                                    (struct sockaddr *)nsap, sizeof *nsap) != buflen)
 708                                                         {
 709                                                                 freeifaddrs(addrs);
 710                                                                 Aerror(stderr, "sendto", errno, *nsap);
 711                                                                 _res_close();
 712                                                                 return (0);
 713                                                         }
 714                                                 }
 715                                         }
 716
 717                                         freeifaddrs(addrs);
 718                                 } else {
 719                                         if (sendto(s, (char*)buf, buflen, 0,
 720                                                    (struct sockaddr *)nsap,
 721                                                    sizeof(struct sockaddr))
 722                                                 != buflen) {
 723                                                 Aerror(stderr, "sendto", errno, *nsap);
 724                                                 badns |= (1 << ns);
 725                                                 _res_close();
 726                                                 goto next_ns;
 727                                         }
 728                                 }
 729                         }
 730
 731                         /*
 732                          * Wait for reply
 733                          */
 734                         timeout.tv_sec = (_res.retrans << try);
 735                         if (try > 0)
 736                                 timeout.tv_sec /= _res.nscount;
 737                         if ((long) timeout.tv_sec <= 0 || multicast)
 738                                 timeout.tv_sec = 1;
 739                         timeout.tv_usec = 0;
 740     wait:
 741                         FD_ZERO(&dsmask);
 742                         FD_SET(s, &dsmask);
 743                         n = select(s+1, &dsmask, (fd_set *)NULL,
 744                                    (fd_set *)NULL, &timeout);
 745                         if (n < 0) {
 746                                 Perror(stderr, "select", errno);
 747                                 _res_close();
 748                                 goto next_ns;
 749                         }
 750                         if (n == 0) {
 751                                 /*
 752                                  * timeout
 753                                  */
 754                                 Dprint(_res.options & RES_DEBUG,
 755                                        (stdout, ";; timeout\n"));
 756                                 gotsomewhere = 1;
 757                                 _res_close();
 758                                 goto next_ns;
 759                         }
 760                         errno = 0;
 761                         fromlen = sizeof(struct sockaddr_in);
 762                         resplen = recvfrom(s, (char*)ans, anssiz, 0,
 763                                            (struct sockaddr *)&from, &fromlen);
 764                         if (resplen <= 0) {
 765                                 Perror(stderr, "recvfrom", errno);
 766                                 _res_close();
 767                                 goto next_ns;
 768                         }
 769                         gotsomewhere = 1;
 770                         if (hp->id != anhp->id) {
 771                                 /*
 772                                  * response from old query, ignore it.
 773                                  * XXX - potential security hazard could
 774                                  *       be detected here.
 775                                  */
 776                                 DprintQ((_res.options & RES_DEBUG) ||
 777                                         (_res.pfcode & RES_PRF_REPLY),
 778                                         (stdout, ";; old answer:\n"),
 779                                         ans, resplen);
 780                                 goto wait;
 781                         }
 782 #if CHECK_SRVR_ADDR
 783                         if (!(_res.options & RES_INSECURE1) &&
 784                             multicast == 0 && !res_isourserver(&from)) {
 785                                 /*
 786                                  * response from wrong server? ignore it.
 787                                  * XXX - potential security hazard could
 788                                  *       be detected here.
 789                                  */
 790                                 DprintQ((_res.options & RES_DEBUG) ||
 791                                         (_res.pfcode & RES_PRF_REPLY),
 792                                         (stdout, ";; not our server:\n"),
 793                                         ans, resplen);
 794                                 goto wait;
 795                         }
 796 #endif
 797                         if (!(_res.options & RES_INSECURE2) &&
 798                             !res_queriesmatch(buf, buf + buflen,
 799                                               ans, ans + anssiz)) {
 800                                 /*
 801                                  * response contains wrong query? ignore it.
 802                                  * XXX - potential security hazard could
 803                                  *       be detected here.
 804                                  */
 805                                 DprintQ((_res.options & RES_DEBUG) ||
 806                                         (_res.pfcode & RES_PRF_REPLY),
 807                                         (stdout, ";; wrong query name:\n"),
 808                                         ans, resplen);
 809                                 goto wait;
 810                         }
 811                         if (anhp->rcode == SERVFAIL ||
 812                             anhp->rcode == NOTIMP ||
 813                             anhp->rcode == REFUSED) {
 814                                 DprintQ(_res.options & RES_DEBUG,
 815                                         (stdout, "server rejected query:\n"),
 816                                         ans, resplen);
 817                                 badns |= (1 << ns);
 818                                 _res_close();
 819                                 /* don't retry if called from dig */
 820                                 if (!_res.pfcode)
 821                                         goto next_ns;
 822                         }
 823                         if (!(_res.options & RES_IGNTC) && anhp->tc) {
 824                                 /*
 825                                  * get rest of answer;
 826                                  * use TCP with same server.
 827                                  */
 828                                 Dprint(_res.options & RES_DEBUG,
 829                                        (stdout, ";; truncated answer\n"));
 830                                 v_circuit = 1;
 831                                 _res_close();
 832                                 goto same_ns;
 833                         }
 834                 } /*if vc/dg*/
 835                 DprintQ((_res.options & RES_DEBUG) ||
 836                         (_res.pfcode & RES_PRF_REPLY),
 837                         (stdout, ";; got answer:\n"),
 838                         ans, resplen);
 839                 /*
 840                  * If using virtual circuits, we assume that the first server
 841                  * is preferred over the rest (i.e. it is on the local
 842                  * machine) and only keep that one open.
 843                  * If we have temporarily opened a virtual circuit,
 844                  * or if we haven't been asked to keep a socket open,
 845                  * close the socket.
 846                  */
 847                 if ((v_circuit && (!(_res.options & RES_USEVC) || ns != 0)) ||
 848                     !(_res.options & RES_STAYOPEN)) {
 849                         _res_close();
 850                 }
 851                 if (Rhook) {
 852                         int done = 0, loops = 0;
 853
 854                         do {
 855                                 res_sendhookact act;
 856
 857                                 act = (*Rhook)(nsap, buf, buflen,
 858                                                ans, anssiz, &resplen);
 859                                 switch (act) {
 860                                 case res_goahead:
 861                                 case res_done:
 862                                         done = 1;
 863                                         break;
 864                                 case res_nextns:
 865                                         _res_close();
 866                                         goto next_ns;
 867                                 case res_modified:
 868                                         /* give the hook another try */
 869                                         if (++loops < 42) /*doug adams*/
 870                                                 break;
 871                                         /*FALLTHROUGH*/
 872                                 case res_error:
 873                                         /*FALLTHROUGH*/
 874                                 default:
 875                                         return (-1);
 876                                 }
 877                         } while (!done);
 878
 879                 }
 880                 return (resplen);
 881     next_ns: ;
 882            } /*foreach ns*/
 883         } /*foreach retry*/
 884         _res_close();
 885         if (!v_circuit)
 886                 if (!gotsomewhere)
 887                         errno = ECONNREFUSED;   /* no nameservers found */
 888                 else
 889                         errno = ETIMEDOUT;      /* no answer obtained */
 890         else
 891                 errno = terrno;
 892         return (-1);
 893 }
 894
 895 /*
 896  * This routine is for closing the socket if a virtual circuit is used and
 897  * the program wants to close it.  This provides support for endhostent()
 898  * which expects to close the socket.
 899  *
 900  * This routine is not expected to be user visible.
 901  */
 902 void
 903 _res_close()
 904 {
 905         if (s >= 0) {
 906                 (void) close(s);
 907                 s = -1;
 908                 connected = 0;
 909                 vc = 0;
 910         }
 911 }