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 1.2.202.1 2002/11/06 17:30:17 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/nameser.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 <resolv.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 extern struct __res_state _res_shadow;
 190
 191 static res_send_qhook Qhook = NULL;
 192 static res_send_rhook Rhook = NULL;
 193
 194 void
 195 res_send_setqhook(hook)
 196         res_send_qhook hook;
 197 {
 198
 199         Qhook = hook;
 200 }
 201
 202 void
 203 res_send_setrhook(hook)
 204         res_send_rhook hook;
 205 {
 206
 207         Rhook = hook;
 208 }
 209
 210 /* int
 211  * res_isourserver(ina)
 212  *      looks up "ina" in _res.ns_addr_list[]
 213  * returns:
 214  *      0  : not found
 215  *      >0 : found
 216  * author:
 217  *      paul vixie, 29may94
 218  */
 219 int
 220 res_isourserver(inp)
 221         const struct sockaddr_in *inp;
 222 {
 223         struct sockaddr_in ina;
 224         register int ns, ret;
 225
 226         ina = *inp;
 227         ret = 0;
 228         for (ns = 0;  ns < _res.nscount;  ns++) {
 229                 register const struct sockaddr_in *srv = &_res.nsaddr_list[ns];
 230
 231                 if (srv->sin_family == ina.sin_family &&
 232                     srv->sin_port == ina.sin_port &&
 233                     (srv->sin_addr.s_addr == INADDR_ANY ||
 234                      srv->sin_addr.s_addr == ina.sin_addr.s_addr)) {
 235                         ret++;
 236                         break;
 237                 }
 238         }
 239         return (ret);
 240 }
 241
 242 /* int
 243  * res_nameinquery(name, type, class, buf, eom)
 244  *      look for (name,type,class) in the query section of packet (buf,eom)
 245  * returns:
 246  *      -1 : format error
 247  *      0  : not found
 248  *      >0 : found
 249  * author:
 250  *      paul vixie, 29may94
 251  */
 252 int
 253 res_nameinquery(name, type, class, buf, eom)
 254         const char *name;
 255         register int type, class;
 256         const u_char *buf, *eom;
 257 {
 258         register const u_char *cp = buf + HFIXEDSZ;
 259         int qdcount = ntohs(((HEADER*)buf)->qdcount);
 260
 261         while (qdcount-- > 0) {
 262                 char tname[MAXDNAME+1];
 263                 register int n, ttype, tclass;
 264
 265                 n = dn_expand(buf, eom, cp, tname, sizeof tname);
 266                 if (n < 0)
 267                         return (-1);
 268                 cp += n;
 269                 ttype = _getshort(cp); cp += INT16SZ;
 270                 tclass = _getshort(cp); cp += INT16SZ;
 271                 if (ttype == type &&
 272                     tclass == class &&
 273                     strcasecmp(tname, name) == 0)
 274                         return (1);
 275         }
 276         return (0);
 277 }
 278
 279 /* int
 280  * res_queriesmatch(buf1, eom1, buf2, eom2)
 281  *      is there a 1:1 mapping of (name,type,class)
 282  *      in (buf1,eom1) and (buf2,eom2)?
 283  * returns:
 284  *      -1 : format error
 285  *      0  : not a 1:1 mapping
 286  *      >0 : is a 1:1 mapping
 287  * author:
 288  *      paul vixie, 29may94
 289  */
 290 int
 291 res_queriesmatch(buf1, eom1, buf2, eom2)
 292         const u_char *buf1, *eom1;
 293         const u_char *buf2, *eom2;
 294 {
 295         register const u_char *cp = buf1 + HFIXEDSZ;
 296         int qdcount = ntohs(((HEADER*)buf1)->qdcount);
 297
 298         if (qdcount != ntohs(((HEADER*)buf2)->qdcount))
 299                 return (0);
 300         while (qdcount-- > 0) {
 301                 char tname[MAXDNAME+1];
 302                 register int n, ttype, tclass;
 303
 304                 n = dn_expand(buf1, eom1, cp, tname, sizeof tname);
 305                 if (n < 0)
 306                         return (-1);
 307                 cp += n;
 308                 ttype = _getshort(cp);  cp += INT16SZ;
 309                 tclass = _getshort(cp); cp += INT16SZ;
 310                 if (!res_nameinquery(tname, ttype, tclass, buf2, eom2))
 311                         return (0);
 312         }
 313         return (1);
 314 }
 315
 316 static int res_using_defaults()
 317 {
 318         int i;
 319
 320         if (_res.nscount != _res_shadow.nscount)
 321                 return 0;
 322
 323         for (i = 0; i < _res.nscount; i++) {
 324                 /* Check that the address and port have not changed */
 325                 if ((_res.nsaddr_list[i].sin_addr.s_addr !=
 326                          _res_shadow.nsaddr_list[i].sin_addr.s_addr) ||
 327                         (_res.nsaddr_list[i].sin_port !=
 328                          _res_shadow.nsaddr_list[i].sin_port)) {
 329                         return 0;
 330                 }
 331         }
 332
 333         return 1;
 334 }
 335
 336 /* Returns whether a dns encoded name should be sent to multicast or not */
 337 static int dns_is_local_name(const u_int8_t *name)
 338 {
 339         const u_int8_t *d0 = NULL;              // Top-Level Domain
 340         const u_int8_t *d1 = NULL;              // Second-Level Domain
 341         const u_int8_t *d2 = NULL;              // etc.
 342         const u_int8_t *d3 = NULL;
 343
 344         while (*name)
 345         {
 346                 d3 = d2;
 347                 d2 = d1;
 348                 d1 = d0;
 349                 d0 = name;
 350                 name += 1 + *name;
 351         }
 352
 353         // "local" domains need to be resolved with multicast
 354         // "local."
 355         if (d0[0] == 5 && strncasecmp((char *)d0+1, "local", 5) == 0) return 1;
 356
 357         // "local.arpa."
 358         if (d1 && d1[0] == 5 && strncasecmp((char *)d1+1, "local", 5) == 0 &&
 359                 d0[0] == 4 && strncasecmp((char *)d0+1, "arpa",  4) == 0) return 1;
 360
 361         // "local.int."
 362         if (d1 && d1[0] == 5 && strncasecmp((char *)d1+1, "local", 5) == 0 &&
 363                 d0[0] == 3 && strncasecmp((char *)d0+1, "int",   3) == 0) return 1;
 364
 365         // The network 169.254/16 is defined to be link-local,
 366         // so lookups in 254.169.in-addr.arpa. also need to be resolved with local multicast
 367         if (d3 && d3[0] == 3 && strncasecmp((char *)d3+1, "254",     3) == 0 &&
 368                 d2 && d2[0] == 3 && strncasecmp((char *)d2+1, "169",     3) == 0 &&
 369                 d1 && d1[0] == 7 && strncasecmp((char *)d1+1, "in-addr", 7) == 0 &&
 370                 d0[0] == 4 && strncasecmp((char *)d0+1, "arpa",    4) == 0) return 1;
 371
 372         return 0;
 373 }
 374
 375 #define DNS_LOCAL_DOMAIN_SERVICE_PORT   5353
 376 #define DNS_HEADER_SIZE 12
 377
 378 #if BYTE_ORDER == BIG_ENDIAN
 379 #define my_htons(x)     (x)
 380 #define my_htonl(x)     (x)
 381 #else
 382 #define my_htons(x)     ((((u_int16_t)x) >> 8) | (((u_int16_t)x) << 8))
 383 #define my_htonl(x)     (((x) >> 24) | (((x) & 0x00FF0000) >> 16) | \
 384                                          (((x) & 0x0000FF00) << 16) | ((x) << 24))
 385 #endif
 386
 387 static const struct sockaddr_in mDNS_addr =
 388 {
 389         sizeof(mDNS_addr),
 390         AF_INET,
 391         my_htons(DNS_LOCAL_DOMAIN_SERVICE_PORT),
 392         {my_htonl(0xE00000FB)}  /* 224.0.0.251 */
 393 };
 394
 395 int
 396 res_send(buf, buflen, ans, anssiz)
 397         const u_char *buf;
 398         int buflen;
 399         u_char *ans;
 400         int anssiz;
 401 {
 402         HEADER *hp = (HEADER *) buf;
 403         HEADER *anhp = (HEADER *) ans;
 404         int gotsomewhere, connreset, terrno, try, v_circuit, resplen, ns;
 405         register int n;
 406         u_int badns;    /* XXX NSMAX can't exceed #/bits in this var */
 407         int multicast;
 408
 409         if ((_res.options & RES_INIT) == 0 && res_init() == -1) {
 410                 /* errno should have been set by res_init() in this case. */
 411                 return (-1);
 412         }
 413         DprintQ((_res.options & RES_DEBUG) || (_res.pfcode & RES_PRF_QUERY),
 414                 (stdout, ";; res_send()\n"), buf, buflen);
 415         v_circuit = (_res.options & RES_USEVC) || buflen > PACKETSZ;
 416         gotsomewhere = 0;
 417         connreset = 0;
 418         terrno = ETIMEDOUT;
 419         badns = 0;
 420
 421         if (res_using_defaults() &&
 422                 dns_is_local_name((u_int8_t*)(buf + DNS_HEADER_SIZE))) {
 423                 multicast = 1;
 424                 v_circuit = 0;
 425         } else {
 426                 multicast = 0;
 427         }
 428
 429
 430         /*
 431          * Send request, RETRY times, or until successful
 432          */
 433         for (try = 0; try < _res.retry; try++) {
 434             for (ns = 0; (multicast == 0 && ns < _res.nscount) ||
 435                         (multicast == 1 && ns < 1) ; ns++) {
 436                 struct sockaddr_in *nsap;
 437                 if (multicast == 0)
 438                         nsap = &_res.nsaddr_list[ns];
 439                 else
 440                         nsap = (struct sockaddr_in*)&mDNS_addr; /* const cast */
 441     same_ns:
 442                 if (badns & (1 << ns)) {
 443                         _res_close();
 444                         goto next_ns;
 445                 }
 446
 447                 if (Qhook) {
 448                         int done = 0, loops = 0;
 449
 450                         do {
 451                                 res_sendhookact act;
 452
 453                                 act = (*Qhook)(&nsap, &buf, &buflen,
 454                                                ans, anssiz, &resplen);
 455                                 switch (act) {
 456                                 case res_goahead:
 457                                         done = 1;
 458                                         break;
 459                                 case res_nextns:
 460                                         _res_close();
 461                                         goto next_ns;
 462                                 case res_done:
 463                                         return (resplen);
 464                                 case res_modified:
 465                                         /* give the hook another try */
 466                                         if (++loops < 42) /*doug adams*/
 467                                                 break;
 468                                         /*FALLTHROUGH*/
 469                                 case res_error:
 470                                         /*FALLTHROUGH*/
 471                                 default:
 472                                         return (-1);
 473                                 }
 474                         } while (!done);
 475                 }
 476
 477                 Dprint(_res.options & RES_DEBUG,
 478                        (stdout, ";; Querying server (# %d) address = %s\n",
 479                         ns + 1, inet_ntoa(nsap->sin_addr)));
 480
 481                 if (v_circuit) {
 482                         int truncated;
 483                         struct iovec iov[2];
 484                         u_short len;
 485                         u_char *cp;
 486
 487                         /*
 488                          * Use virtual circuit;
 489                          * at most one attempt per server.
 490                          */
 491                         try = _res.retry;
 492                         truncated = 0;
 493                         if ((s < 0) || (!vc)) {
 494                                 if (s >= 0)
 495                                         _res_close();
 496
 497                                 s = socket(PF_INET, SOCK_STREAM, 0);
 498                                 if (s < 0) {
 499                                         terrno = errno;
 500                                         Perror(stderr, "socket(vc)", errno);
 501                                         return (-1);
 502                                 }
 503                                 errno = 0;
 504                                 if (connect(s, (struct sockaddr *)nsap,
 505                                             sizeof(struct sockaddr)) < 0) {
 506                                         terrno = errno;
 507                                         Aerror(stderr, "connect/vc",
 508                                                errno, *nsap);
 509                                         badns |= (1 << ns);
 510                                         _res_close();
 511                                         goto next_ns;
 512                                 }
 513                                 vc = 1;
 514                         }
 515                         /*
 516                          * Send length & message
 517                          */
 518                         putshort((u_short)buflen, (u_char*)&len);
 519                         iov[0].iov_base = (caddr_t)&len;
 520                         iov[0].iov_len = INT16SZ;
 521                         iov[1].iov_base = (caddr_t)buf;
 522                         iov[1].iov_len = buflen;
 523                         if (writev(s, iov, 2) != (INT16SZ + buflen)) {
 524                                 terrno = errno;
 525                                 Perror(stderr, "write failed", errno);
 526                                 badns |= (1 << ns);
 527                                 _res_close();
 528                                 goto next_ns;
 529                         }
 530                         /*
 531                          * Receive length & response
 532                          */
 533                         cp = ans;
 534                         len = INT16SZ;
 535                         while ((n = read(s, (char *)cp, (int)len)) > 0) {
 536                                 cp += n;
 537                                 if ((len -= n) <= 0)
 538                                         break;
 539                         }
 540                         if (n <= 0) {
 541                                 terrno = errno;
 542                                 Perror(stderr, "read failed", errno);
 543                                 _res_close();
 544                                 /*
 545                                  * A long running process might get its TCP
 546                                  * connection reset if the remote server was
 547                                  * restarted.  Requery the server instead of
 548                                  * trying a new one.  When there is only one
 549                                  * server, this means that a query might work
 550                                  * instead of failing.  We only allow one reset
 551                                  * per query to prevent looping.
 552                                  */
 553                                 if (terrno == ECONNRESET && !connreset) {
 554                                         connreset = 1;
 555                                         _res_close();
 556                                         goto same_ns;
 557                                 }
 558                                 _res_close();
 559                                 goto next_ns;
 560                         }
 561                         resplen = _getshort(ans);
 562                         if (resplen > anssiz) {
 563                                 Dprint(_res.options & RES_DEBUG,
 564                                        (stdout, ";; response truncated\n")
 565                                        );
 566                                 truncated = 1;
 567                                 len = anssiz;
 568                         } else
 569                                 len = resplen;
 570                         cp = ans;
 571                         while (len != 0 &&
 572                                (n = read(s, (char *)cp, (int)len)) > 0) {
 573                                 cp += n;
 574                                 len -= n;
 575                         }
 576                         if (n <= 0) {
 577                                 terrno = errno;
 578                                 Perror(stderr, "read(vc)", errno);
 579                                 _res_close();
 580                                 goto next_ns;
 581                         }
 582                         if (truncated) {
 583                                 /*
 584                                  * Flush rest of answer
 585                                  * so connection stays in synch.
 586                                  */
 587                                 anhp->tc = 1;
 588                                 len = resplen - anssiz;
 589                                 while (len != 0) {
 590                                         char junk[PACKETSZ];
 591
 592                                         n = (len > sizeof(junk)
 593                                              ? sizeof(junk)
 594                                              : len);
 595                                         if ((n = read(s, junk, n)) > 0)
 596                                                 len -= n;
 597                                         else
 598                                                 break;
 599                                 }
 600                         }
 601                 } else {
 602                         /*
 603                          * Use datagrams.
 604                          */
 605                         struct timeval timeout;
 606                         fd_set dsmask;
 607                         struct sockaddr_in from;
 608                         int fromlen;
 609
 610                         if ((s < 0) || vc) {
 611                                 if (vc)
 612                                         _res_close();
 613                                 s = socket(PF_INET, SOCK_DGRAM, 0);
 614                                 if (s < 0) {
 615 #if !CAN_RECONNECT
 616  bad_dg_sock:
 617 #endif
 618                                         terrno = errno;
 619                                         Perror(stderr, "socket(dg)", errno);
 620                                         return (-1);
 621                                 }
 622                                 connected = 0;
 623                         }
 624                         /*
 625                          * On a 4.3BSD+ machine (client and server,
 626                          * actually), sending to a nameserver datagram
 627                          * port with no nameserver will cause an
 628                          * ICMP port unreachable message to be returned.
 629                          * If our datagram socket is "connected" to the
 630                          * server, we get an ECONNREFUSED error on the next
 631                          * socket operation, and select returns if the
 632                          * error message is received.  We can thus detect
 633                          * the absence of a nameserver without timing out.
 634                          * If we have sent queries to at least two servers,
 635                          * however, we don't want to remain connected,
 636                          * as we wish to receive answers from the first
 637                          * server to respond.
 638                          */
 639                         if ((_res.nscount == 1 || (try == 0 && ns == 0)) && multicast == 0) {
 640                                 /*
 641                                  * Connect only if we are sure we won't
 642                                  * receive a response from another server.
 643                                  */
 644                                 if (!connected) {
 645                                         if (connect(s, (struct sockaddr *)nsap,
 646                                                     sizeof(struct sockaddr)
 647                                                     ) < 0) {
 648                                                 Aerror(stderr,
 649                                                        "connect(dg)",
 650                                                        errno, *nsap);
 651                                                 badns |= (1 << ns);
 652                                                 _res_close();
 653                                                 goto next_ns;
 654                                         }
 655                                         connected = 1;
 656                                 }
 657                                 if (send(s, (char*)buf, buflen, 0) != buflen) {
 658                                         Perror(stderr, "send", errno);
 659                                         badns |= (1 << ns);
 660                                         _res_close();
 661                                         goto next_ns;
 662                                 }
 663                         } else {
 664                                 /*
 665                                  * Disconnect if we want to listen
 666                                  * for responses from more than one server.
 667                                  */
 668                                 if (connected) {
 669 #if CAN_RECONNECT
 670                                         struct sockaddr_in no_addr;
 671
 672                                         no_addr.sin_family = AF_INET;
 673                                         no_addr.sin_addr.s_addr = INADDR_ANY;
 674                                         no_addr.sin_port = 0;
 675                                         (void) connect(s,
 676                                                        (struct sockaddr *)
 677                                                         &no_addr,
 678                                                        sizeof(no_addr));
 679 #else
 680                                         int s1 = socket(PF_INET, SOCK_DGRAM,0);
 681                                         if (s1 < 0)
 682                                                 goto bad_dg_sock;
 683                                         (void) dup2(s1, s);
 684                                         (void) close(s1);
 685                                         Dprint(_res.options & RES_DEBUG,
 686                                                (stdout, ";; new DG socket\n"))
 687 #endif
 688                                         connected = 0;
 689                                         errno = 0;
 690                                 }
 691
 692                                 if (multicast) {
 693                                         struct ifaddrs* addrs;
 694                                         struct ifaddrs* curAddr;
 695                                         const int twofivefive = 255;
 696
 697                                         // multicast packets with TTL 255
 698                                         if(setsockopt(s, IPPROTO_IP, IP_MULTICAST_TTL, &twofivefive, sizeof(twofivefive))) {
 699                                                 Perror(stderr, "setsocketopt - IP_MULTICAST_TTL", errno);
 700                                                 _res_close();
 701                                                 return (0);
 702                                         }
 703
 704                                         if (getifaddrs(&addrs) != 0)
 705                                         {
 706                                                 Perror(stderr, "getifaddrs", errno);
 707                                                 _res_close();
 708                                                 return (0);
 709                                         }
 710
 711                                         /* multicast should send request on all multicast capable interfaces */
 712                                         for (curAddr = addrs; curAddr != NULL; curAddr = curAddr->ifa_next) {
 713                                                 if ((curAddr->ifa_addr->sa_family) == AF_INET &&
 714                                                         (curAddr->ifa_flags & IFF_MULTICAST) != 0 &&
 715                                                         (curAddr->ifa_flags & IFF_POINTOPOINT) == 0) {
 716                                                         struct in_addr* if_ip_addr = &((struct sockaddr_in*)curAddr->ifa_addr)->sin_addr;
 717
 718                                                         if (setsockopt(s, IPPROTO_IP, IP_MULTICAST_IF,
 719                                                                 if_ip_addr, sizeof(*if_ip_addr)) != 0) {
 720                                                                 freeifaddrs(addrs);
 721                                                                 Perror(stderr, "setsocketopt - IP_MULTICAST_IF", errno);
 722                                                                 _res_close();
 723                                                                 return (0);
 724                                                         }
 725
 726                                                         if (sendto(s, (char*)buf, buflen, 0,
 727                                                                    (struct sockaddr *)nsap, sizeof *nsap) != buflen)
 728                                                         {
 729                                                                 freeifaddrs(addrs);
 730                                                                 Aerror(stderr, "sendto", errno, *nsap);
 731                                                                 _res_close();
 732                                                                 return (0);
 733                                                         }
 734                                                 }
 735                                         }
 736
 737                                         freeifaddrs(addrs);
 738                                 } else {
 739                                         if (sendto(s, (char*)buf, buflen, 0,
 740                                                    (struct sockaddr *)nsap,
 741                                                    sizeof(struct sockaddr))
 742                                                 != buflen) {
 743                                                 Aerror(stderr, "sendto", errno, *nsap);
 744                                                 badns |= (1 << ns);
 745                                                 _res_close();
 746                                                 goto next_ns;
 747                                         }
 748                                 }
 749                         }
 750
 751                         /*
 752                          * Wait for reply
 753                          */
 754                         timeout.tv_sec = (_res.retrans << try);
 755                         if (try > 0)
 756                                 timeout.tv_sec /= _res.nscount;
 757                         if ((long) timeout.tv_sec <= 0 || multicast)
 758                                 timeout.tv_sec = 1;
 759                         timeout.tv_usec = 0;
 760     wait:
 761                         FD_ZERO(&dsmask);
 762                         FD_SET(s, &dsmask);
 763                         n = select(s+1, &dsmask, (fd_set *)NULL,
 764                                    (fd_set *)NULL, &timeout);
 765                         if (n < 0) {
 766                                 Perror(stderr, "select", errno);
 767                                 _res_close();
 768                                 goto next_ns;
 769                         }
 770                         if (n == 0) {
 771                                 /*
 772                                  * timeout
 773                                  */
 774                                 Dprint(_res.options & RES_DEBUG,
 775                                        (stdout, ";; timeout\n"));
 776                                 gotsomewhere = 1;
 777                                 _res_close();
 778                                 goto next_ns;
 779                         }
 780                         errno = 0;
 781                         fromlen = sizeof(struct sockaddr_in);
 782                         resplen = recvfrom(s, (char*)ans, anssiz, 0,
 783                                            (struct sockaddr *)&from, &fromlen);
 784                         if (resplen <= 0) {
 785                                 Perror(stderr, "recvfrom", errno);
 786                                 _res_close();
 787                                 goto next_ns;
 788                         }
 789                         gotsomewhere = 1;
 790                         if (hp->id != anhp->id) {
 791                                 /*
 792                                  * response from old query, ignore it.
 793                                  * XXX - potential security hazard could
 794                                  *       be detected here.
 795                                  */
 796                                 DprintQ((_res.options & RES_DEBUG) ||
 797                                         (_res.pfcode & RES_PRF_REPLY),
 798                                         (stdout, ";; old answer:\n"),
 799                                         ans, resplen);
 800                                 goto wait;
 801                         }
 802 #if CHECK_SRVR_ADDR
 803                         if (!(_res.options & RES_INSECURE1) &&
 804                             multicast == 0 && !res_isourserver(&from)) {
 805                                 /*
 806                                  * response from wrong server? ignore it.
 807                                  * XXX - potential security hazard could
 808                                  *       be detected here.
 809                                  */
 810                                 DprintQ((_res.options & RES_DEBUG) ||
 811                                         (_res.pfcode & RES_PRF_REPLY),
 812                                         (stdout, ";; not our server:\n"),
 813                                         ans, resplen);
 814                                 goto wait;
 815                         }
 816 #endif
 817                         if (!(_res.options & RES_INSECURE2) &&
 818                             !res_queriesmatch(buf, buf + buflen,
 819                                               ans, ans + anssiz)) {
 820                                 /*
 821                                  * response contains wrong query? ignore it.
 822                                  * XXX - potential security hazard could
 823                                  *       be detected here.
 824                                  */
 825                                 DprintQ((_res.options & RES_DEBUG) ||
 826                                         (_res.pfcode & RES_PRF_REPLY),
 827                                         (stdout, ";; wrong query name:\n"),
 828                                         ans, resplen);
 829                                 goto wait;
 830                         }
 831                         if (anhp->rcode == SERVFAIL ||
 832                             anhp->rcode == NOTIMP ||
 833                             anhp->rcode == REFUSED) {
 834                                 DprintQ(_res.options & RES_DEBUG,
 835                                         (stdout, "server rejected query:\n"),
 836                                         ans, resplen);
 837                                 badns |= (1 << ns);
 838                                 _res_close();
 839                                 /* don't retry if called from dig */
 840                                 if (!_res.pfcode)
 841                                         goto next_ns;
 842                         }
 843                         if (!(_res.options & RES_IGNTC) && anhp->tc) {
 844                                 /*
 845                                  * get rest of answer;
 846                                  * use TCP with same server.
 847                                  */
 848                                 Dprint(_res.options & RES_DEBUG,
 849                                        (stdout, ";; truncated answer\n"));
 850                                 v_circuit = 1;
 851                                 _res_close();
 852                                 goto same_ns;
 853                         }
 854                 } /*if vc/dg*/
 855                 DprintQ((_res.options & RES_DEBUG) ||
 856                         (_res.pfcode & RES_PRF_REPLY),
 857                         (stdout, ";; got answer:\n"),
 858                         ans, resplen);
 859                 /*
 860                  * If using virtual circuits, we assume that the first server
 861                  * is preferred over the rest (i.e. it is on the local
 862                  * machine) and only keep that one open.
 863                  * If we have temporarily opened a virtual circuit,
 864                  * or if we haven't been asked to keep a socket open,
 865                  * close the socket.
 866                  */
 867                 if ((v_circuit && (!(_res.options & RES_USEVC) || ns != 0)) ||
 868                     !(_res.options & RES_STAYOPEN)) {
 869                         _res_close();
 870                 }
 871                 if (Rhook) {
 872                         int done = 0, loops = 0;
 873
 874                         do {
 875                                 res_sendhookact act;
 876
 877                                 act = (*Rhook)(nsap, buf, buflen,
 878                                                ans, anssiz, &resplen);
 879                                 switch (act) {
 880                                 case res_goahead:
 881                                 case res_done:
 882                                         done = 1;
 883                                         break;
 884                                 case res_nextns:
 885                                         _res_close();
 886                                         goto next_ns;
 887                                 case res_modified:
 888                                         /* give the hook another try */
 889                                         if (++loops < 42) /*doug adams*/
 890                                                 break;
 891                                         /*FALLTHROUGH*/
 892                                 case res_error:
 893                                         /*FALLTHROUGH*/
 894                                 default:
 895                                         return (-1);
 896                                 }
 897                         } while (!done);
 898
 899                 }
 900                 return (resplen);
 901     next_ns: ;
 902            } /*foreach ns*/
 903         } /*foreach retry*/
 904         _res_close();
 905         if (!v_circuit)
 906                 if (!gotsomewhere)
 907                         errno = ECONNREFUSED;   /* no nameservers found */
 908                 else
 909                         errno = ETIMEDOUT;      /* no answer obtained */
 910         else
 911                 errno = terrno;
 912         return (-1);
 913 }
 914
 915 /*
 916  * This routine is for closing the socket if a virtual circuit is used and
 917  * the program wants to close it.  This provides support for endhostent()
 918  * which expects to close the socket.
 919  *
 920  * This routine is not expected to be user visible.
 921  */
 922 void
 923 _res_close()
 924 {
 925         if (s >= 0) {
 926                 (void) close(s);
 927                 s = -1;
 928                 connected = 0;
 929                 vc = 0;
 930         }
 931 }