lib/libc/net/res_send.c

   1 /*
   2  * Copyright (c) 1985, 1989, 1993
   3  *    The Regents of the University of California.  All rights reserved.
   4  *
   5  * Redistribution and use in source and binary forms, with or without
   6  * modification, are permitted provided that the following conditions
   7  * are met:
   8  * 1. Redistributions of source code must retain the above copyright
   9  *    notice, this list of conditions and the following disclaimer.
  10  * 2. Redistributions in binary form must reproduce the above copyright
  11  *    notice, this list of conditions and the following disclaimer in the
  12  *    documentation and/or other materials provided with the distribution.
  13  * 3. Neither the name of the University nor the names of its contributors
  14  *    may be used to endorse or promote products derived from this software
  15  *    without specific prior written permission.
  16  *
  17  * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
  18  * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
  19  * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
  20  * ARE DISCLAIMED.  IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
  21  * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
  22  * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
  23  * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
  24  * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
  25  * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
  26  * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
  27  * SUCH DAMAGE.
  28  *
  29  * @(#)res_send.c       8.1 (Berkeley) 6/4/93
  30  * $From: Id: res_send.c,v 8.20 1998/04/06 23:27:51 halley Exp $
  31  * $FreeBSD: src/lib/libc/net/res_send.c,v 1.31.2.9 2002/04/11 17:30:24 ume Exp $
  32  * $DragonFly: src/lib/libc/net/res_send.c,v 1.6 2005/11/13 02:04:47 swildner Exp $
  33  */
  34
  35 /*
  36  * Portions Copyright (c) 1993 by Digital Equipment Corporation.
  37  *
  38  * Permission to use, copy, modify, and distribute this software for any
  39  * purpose with or without fee is hereby granted, provided that the above
  40  * copyright notice and this permission notice appear in all copies, and that
  41  * the name of Digital Equipment Corporation not be used in advertising or
  42  * publicity pertaining to distribution of the document or software without
  43  * specific, written prior permission.
  44  *
  45  * THE SOFTWARE IS PROVIDED "AS IS" AND DIGITAL EQUIPMENT CORP. DISCLAIMS ALL
  46  * WARRANTIES WITH REGARD TO THIS SOFTWARE, INCLUDING ALL IMPLIED WARRANTIES
  47  * OF MERCHANTABILITY AND FITNESS.   IN NO EVENT SHALL DIGITAL EQUIPMENT
  48  * CORPORATION BE LIABLE FOR ANY SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL
  49  * DAMAGES OR ANY DAMAGES WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR
  50  * PROFITS, WHETHER IN AN ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS
  51  * ACTION, ARISING OUT OF OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS
  52  * SOFTWARE.
  53  */
  54
  55 /*
  56  * Portions Copyright (c) 1996 by Internet Software Consortium.
  57  *
  58  * Permission to use, copy, modify, and distribute this software for any
  59  * purpose with or without fee is hereby granted, provided that the above
  60  * copyright notice and this permission notice appear in all copies.
  61  *
  62  * THE SOFTWARE IS PROVIDED "AS IS" AND INTERNET SOFTWARE CONSORTIUM DISCLAIMS
  63  * ALL WARRANTIES WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES
  64  * OF MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL INTERNET SOFTWARE
  65  * CONSORTIUM BE LIABLE FOR ANY SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL
  66  * DAMAGES OR ANY DAMAGES WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR
  67  * PROFITS, WHETHER IN AN ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS
  68  * ACTION, ARISING OUT OF OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS
  69  * SOFTWARE.
  70  */
  71
  72 /*
  73  * Send query to name server and wait for reply.
  74  */
  75
  76 #include "namespace.h"
  77 #include <sys/types.h>
  78 #include <sys/event.h>
  79 #include <sys/param.h>
  80 #include <sys/time.h>
  81 #include <sys/socket.h>
  82 #include <sys/uio.h>
  83
  84 #include <netinet/in.h>
  85 #include <arpa/nameser.h>
  86 #include <arpa/inet.h>
  87
  88 #include <errno.h>
  89 #include <netdb.h>
  90 #include <resolv.h>
  91 #include <stdio.h>
  92 #include <stdlib.h>
  93 #include <string.h>
  94 #include <unistd.h>
  95 #include "un-namespace.h"
  96
  97 #include "res_config.h"
  98
  99 static int s = -1;              /* socket used for communications */
 100 static int connected = 0;       /* is the socket connected */
 101 static int vc = 0;              /* is the socket a virtual circuit? */
 102 static int af = 0;              /* address family of socket */
 103 static res_send_qhook Qhook = NULL;
 104 static res_send_rhook Rhook = NULL;
 105
 106
 107 #define CAN_RECONNECT 1
 108
 109 #ifndef DEBUG
 110 #   define Dprint(cond, args) /*empty*/
 111 #   define DprintQ(cond, args, query, size) /*empty*/
 112 #   define Aerror(file, string, error, address) /*empty*/
 113 #   define Perror(file, string, error) /*empty*/
 114 #else
 115 #   define Dprint(cond, args) if (cond) {fprintf args;} else {}
 116 #   define DprintQ(cond, args, query, size) if (cond) {\
 117                         fprintf args;\
 118                         __fp_nquery(query, size, stdout);\
 119                 } else {}
 120 static char abuf[NI_MAXHOST];
 121 static char pbuf[NI_MAXSERV];
 122 static void Aerror (FILE *, char *, int, struct sockaddr *);
 123 static void Perror (FILE *, char *, int);
 124
 125 static void
 126 Aerror(FILE *file, char *string, int error, struct sockaddr *address)
 127 {
 128         int save = errno;
 129
 130         if (_res.options & RES_DEBUG) {
 131                 if (getnameinfo(address, address->sa_len, abuf, sizeof(abuf),
 132                     pbuf, sizeof(pbuf),
 133                     NI_NUMERICHOST|NI_NUMERICSERV|NI_WITHSCOPEID) != 0) {
 134                         strncpy(abuf, "?", sizeof(abuf));
 135                         strncpy(pbuf, "?", sizeof(pbuf));
 136                 }
 137                 fprintf(file, "res_send: %s ([%s].%s): %s\n",
 138                         string, abuf, pbuf, strerror(error));
 139         }
 140         errno = save;
 141 }
 142
 143 static void
 144 Perror(FILE *file, char *string, int error)
 145 {
 146         int save = errno;
 147
 148         if (_res.options & RES_DEBUG) {
 149                 fprintf(file, "res_send: %s: %s\n",
 150                         string, strerror(error));
 151         }
 152         errno = save;
 153 }
 154 #endif
 155
 156 void
 157 res_send_setqhook(res_send_qhook hook)
 158 {
 159
 160         Qhook = hook;
 161 }
 162
 163 void
 164 res_send_setrhook(res_send_rhook hook)
 165 {
 166
 167         Rhook = hook;
 168 }
 169
 170 static struct sockaddr * get_nsaddr (size_t);
 171
 172 /*
 173  * pick appropriate nsaddr_list for use.  see res_init() for initialization.
 174  */
 175 static struct sockaddr *
 176 get_nsaddr(size_t n)
 177 {
 178
 179         if (!_res.nsaddr_list[n].sin_family) {
 180                 /*
 181                  * - _res_ext.nsaddr_list[n] holds an address that is larger
 182                  *   than struct sockaddr, and
 183                  * - user code did not update _res.nsaddr_list[n].
 184                  */
 185                 return (struct sockaddr *)&_res_ext.nsaddr_list[n];
 186         } else {
 187                 /*
 188                  * - user code updated _res.nsaddr_list[n], or
 189                  * - _res.nsaddr_list[n] has the same content as
 190                  *   _res_ext.nsaddr_list[n].
 191                  */
 192                 return (struct sockaddr *)&_res.nsaddr_list[n];
 193         }
 194 }
 195
 196 /* int
 197  * res_isourserver(ina)
 198  *      looks up "ina" in _res.ns_addr_list[]
 199  * returns:
 200  *      0  : not found
 201  *      >0 : found
 202  * author:
 203  *      paul vixie, 29may94
 204  */
 205 int
 206 res_isourserver(const struct sockaddr_in *inp)
 207 {
 208         const struct sockaddr_in6 *in6p = (const struct sockaddr_in6 *)inp;
 209         const struct sockaddr_in6 *srv6;
 210         const struct sockaddr_in *srv;
 211         int ns, ret;
 212
 213         ret = 0;
 214         switch (inp->sin_family) {
 215         case AF_INET6:
 216                 for (ns = 0; ns < _res.nscount; ns++) {
 217                         srv6 = (struct sockaddr_in6 *)get_nsaddr(ns);
 218                         if (srv6->sin6_family == in6p->sin6_family &&
 219                             srv6->sin6_port == in6p->sin6_port &&
 220                             srv6->sin6_scope_id == in6p->sin6_scope_id &&
 221                             (IN6_IS_ADDR_UNSPECIFIED(&srv6->sin6_addr) ||
 222                              IN6_ARE_ADDR_EQUAL(&srv6->sin6_addr,
 223                                  &in6p->sin6_addr))) {
 224                                 ret++;
 225                                 break;
 226                         }
 227                 }
 228                 break;
 229         case AF_INET:
 230                 for (ns = 0; ns < _res.nscount; ns++) {
 231                         srv = (struct sockaddr_in *)get_nsaddr(ns);
 232                         if (srv->sin_family == inp->sin_family &&
 233                             srv->sin_port == inp->sin_port &&
 234                             (srv->sin_addr.s_addr == INADDR_ANY ||
 235                              srv->sin_addr.s_addr == inp->sin_addr.s_addr)) {
 236                                 ret++;
 237                                 break;
 238                         }
 239                 }
 240                 break;
 241         }
 242         return (ret);
 243 }
 244
 245 /* int
 246  * res_nameinquery(name, type, class, buf, eom)
 247  *      look for (name,type,class) in the query section of packet (buf,eom)
 248  * requires:
 249  *      buf + HFIXEDSZ <= eom
 250  * returns:
 251  *      -1 : format error
 252  *      0  : not found
 253  *      >0 : found
 254  * author:
 255  *      paul vixie, 29may94
 256  */
 257 int
 258 res_nameinquery(const char *name, int type, int class, const u_char *buf,
 259                 const u_char *eom)
 260 {
 261         const u_char *cp = buf + HFIXEDSZ;
 262         int qdcount = ntohs(((HEADER*)buf)->qdcount);
 263
 264         while (qdcount-- > 0) {
 265                 char tname[MAXDNAME+1];
 266                 int n, ttype, tclass;
 267
 268                 n = dn_expand(buf, eom, cp, tname, sizeof tname);
 269                 if (n < 0)
 270                         return (-1);
 271                 cp += n;
 272                 if (cp + 2 * INT16SZ > eom)
 273                         return (-1);
 274                 ttype = ns_get16(cp); cp += INT16SZ;
 275                 tclass = ns_get16(cp); cp += INT16SZ;
 276                 if (ttype == type &&
 277                     tclass == class &&
 278                     strcasecmp(tname, name) == 0)
 279                         return (1);
 280         }
 281         return (0);
 282 }
 283
 284 /* int
 285  * res_queriesmatch(buf1, eom1, buf2, eom2)
 286  *      is there a 1:1 mapping of (name,type,class)
 287  *      in (buf1,eom1) and (buf2,eom2)?
 288  * returns:
 289  *      -1 : format error
 290  *      0  : not a 1:1 mapping
 291  *      >0 : is a 1:1 mapping
 292  * author:
 293  *      paul vixie, 29may94
 294  */
 295 int
 296 res_queriesmatch(const u_char *buf1, const u_char *eom1,
 297                  const u_char *buf2, const u_char *eom2)
 298 {
 299         const u_char *cp = buf1 + HFIXEDSZ;
 300         int qdcount = ntohs(((HEADER*)buf1)->qdcount);
 301
 302         if (buf1 + HFIXEDSZ > eom1 || buf2 + HFIXEDSZ > eom2)
 303                 return (-1);
 304
 305         /*
 306          * Only header section present in replies to
 307          * dynamic update packets.
 308          */
 309         if ( (((HEADER *)buf1)->opcode == ns_o_update) &&
 310              (((HEADER *)buf2)->opcode == ns_o_update) )
 311                 return (1);
 312
 313         if (qdcount != ntohs(((HEADER*)buf2)->qdcount))
 314                 return (0);
 315         while (qdcount-- > 0) {
 316                 char tname[MAXDNAME+1];
 317                 int n, ttype, tclass;
 318
 319                 n = dn_expand(buf1, eom1, cp, tname, sizeof tname);
 320                 if (n < 0)
 321                         return (-1);
 322                 cp += n;
 323                 if (cp + 2 * INT16SZ > eom1)
 324                         return (-1);
 325                 ttype = ns_get16(cp);   cp += INT16SZ;
 326                 tclass = ns_get16(cp); cp += INT16SZ;
 327                 if (!res_nameinquery(tname, ttype, tclass, buf2, eom2))
 328                         return (0);
 329         }
 330         return (1);
 331 }
 332
 333 int
 334 res_send(const u_char *buf, int buflen, u_char *ans, int anssiz)
 335 {
 336         HEADER *hp = (HEADER *) buf;
 337         HEADER *anhp = (HEADER *) ans;
 338         int gotsomewhere, connreset, terrno, try, v_circuit, resplen, ns, n;
 339         int kq;
 340         u_int badns;    /* XXX NSMAX can't exceed #/bits in this variable */
 341
 342         if ((_res.options & RES_INIT) == 0 && res_init() == -1) {
 343                 /* errno should have been set by res_init() in this case. */
 344                 return (-1);
 345         }
 346         if (anssiz < HFIXEDSZ) {
 347                 errno = EINVAL;
 348                 return (-1);
 349         }
 350         DprintQ((_res.options & RES_DEBUG) || (_res.pfcode & RES_PRF_QUERY),
 351                 (stdout, ";; res_send()\n"), buf, buflen);
 352         v_circuit = (_res.options & RES_USEVC) || buflen > PACKETSZ;
 353         gotsomewhere = 0;
 354         connreset = 0;
 355         terrno = ETIMEDOUT;
 356         badns = 0;
 357
 358         if ((kq = kqueue()) < 0) {
 359                 Perror(stderr, "kqueue", errno);
 360                 return (-1);
 361         }
 362
 363         /*
 364          * Send request, RETRY times, or until successful
 365          */
 366         for (try = 0; try < _res.retry; try++) {
 367             for (ns = 0; ns < _res.nscount; ns++) {
 368                 struct sockaddr *nsap = get_nsaddr(ns);
 369                 socklen_t salen;
 370
 371                 if (nsap->sa_len)
 372                         salen = nsap->sa_len;
 373                 else if (nsap->sa_family == AF_INET6)
 374                         salen = sizeof(struct sockaddr_in6);
 375                 else if (nsap->sa_family == AF_INET)
 376                         salen = sizeof(struct sockaddr_in);
 377                 else
 378                         salen = 0;      /*unknown, die on connect*/
 379
 380     same_ns:
 381                 if (badns & (1 << ns)) {
 382                         res_close();
 383                         goto next_ns;
 384                 }
 385
 386                 if (Qhook) {
 387                         int done = 0, loops = 0;
 388
 389                         do {
 390                                 res_sendhookact act;
 391
 392                                 act = (*Qhook)((struct sockaddr_in **)&nsap,
 393                                                &buf, &buflen,
 394                                                ans, anssiz, &resplen);
 395                                 switch (act) {
 396                                 case res_goahead:
 397                                         done = 1;
 398                                         break;
 399                                 case res_nextns:
 400                                         res_close();
 401                                         goto next_ns;
 402                                 case res_done:
 403                                         _close(kq);
 404                                         return (resplen);
 405                                 case res_modified:
 406                                         /* give the hook another try */
 407                                         if (++loops < 42) /*doug adams*/
 408                                                 break;
 409                                         /*FALLTHROUGH*/
 410                                 case res_error:
 411                                         /*FALLTHROUGH*/
 412                                 default:
 413                                         _close(kq);
 414                                         return (-1);
 415                                 }
 416                         } while (!done);
 417                 }
 418
 419                 Dprint((_res.options & RES_DEBUG) &&
 420                        getnameinfo(nsap, salen, abuf, sizeof(abuf),
 421                            NULL, 0, NI_NUMERICHOST | NI_WITHSCOPEID) == 0,
 422                        (stdout, ";; Querying server (# %d) address = %s\n",
 423                         ns + 1, abuf));
 424
 425                 if (v_circuit) {
 426                         int truncated;
 427                         struct iovec iov[2];
 428                         u_short len;
 429                         u_char *cp;
 430
 431                         /*
 432                          * Use virtual circuit;
 433                          * at most one attempt per server.
 434                          */
 435                         try = _res.retry;
 436                         truncated = 0;
 437                         if (s < 0 || !vc || hp->opcode == ns_o_update ||
 438                             af != nsap->sa_family) {
 439                                 if (s >= 0)
 440                                         res_close();
 441
 442                                 af = nsap->sa_family;
 443                                 s = _socket(af, SOCK_STREAM, 0);
 444                                 if (s < 0) {
 445                                         terrno = errno;
 446                                         Perror(stderr, "socket(vc)", errno);
 447                                         badns |= (1 << ns);
 448                                         res_close();
 449                                         goto next_ns;
 450                                 }
 451                                 errno = 0;
 452                                 if (_connect(s, nsap, salen) < 0) {
 453                                         terrno = errno;
 454                                         Aerror(stderr, "connect/vc",
 455                                                errno, nsap);
 456                                         badns |= (1 << ns);
 457                                         res_close();
 458                                         goto next_ns;
 459                                 }
 460                                 vc = 1;
 461                         }
 462                         /*
 463                          * Send length & message
 464                          */
 465                         putshort((u_short)buflen, (u_char*)&len);
 466                         iov[0].iov_base = (caddr_t)&len;
 467                         iov[0].iov_len = INT16SZ;
 468                         iov[1].iov_base = (caddr_t)buf;
 469                         iov[1].iov_len = buflen;
 470                         if (_writev(s, iov, 2) != (INT16SZ + buflen)) {
 471                                 terrno = errno;
 472                                 Perror(stderr, "write failed", errno);
 473                                 badns |= (1 << ns);
 474                                 res_close();
 475                                 goto next_ns;
 476                         }
 477                         /*
 478                          * Receive length & response
 479                          */
 480 read_len:
 481                         cp = ans;
 482                         len = INT16SZ;
 483                         while ((n = _read(s, (char *)cp, (int)len)) > 0) {
 484                                 cp += n;
 485                                 if ((len -= n) <= 0)
 486                                         break;
 487                         }
 488                         if (n <= 0) {
 489                                 terrno = errno;
 490                                 Perror(stderr, "read failed", errno);
 491                                 res_close();
 492                                 /*
 493                                  * A long running process might get its TCP
 494                                  * connection reset if the remote server was
 495                                  * restarted.  Requery the server instead of
 496                                  * trying a new one.  When there is only one
 497                                  * server, this means that a query might work
 498                                  * instead of failing.  We only allow one reset
 499                                  * per query to prevent looping.
 500                                  */
 501                                 if (terrno == ECONNRESET && !connreset) {
 502                                         connreset = 1;
 503                                         res_close();
 504                                         goto same_ns;
 505                                 }
 506                                 res_close();
 507                                 goto next_ns;
 508                         }
 509                         resplen = ns_get16(ans);
 510                         if (resplen > anssiz) {
 511                                 Dprint(_res.options & RES_DEBUG,
 512                                        (stdout, ";; response truncated\n")
 513                                        );
 514                                 truncated = 1;
 515                                 len = anssiz;
 516                         } else
 517                                 len = resplen;
 518                         if (len < HFIXEDSZ) {
 519                                 /*
 520                                  * Undersized message.
 521                                  */
 522                                 Dprint(_res.options & RES_DEBUG,
 523                                        (stdout, ";; undersized: %d\n", len));
 524                                 terrno = EMSGSIZE;
 525                                 badns |= (1 << ns);
 526                                 res_close();
 527                                 goto next_ns;
 528                         }
 529                         cp = ans;
 530                         while (len != 0 &&
 531                                (n = _read(s, (char *)cp, (int)len)) > 0) {
 532                                 cp += n;
 533                                 len -= n;
 534                         }
 535                         if (n <= 0) {
 536                                 terrno = errno;
 537                                 Perror(stderr, "read(vc)", errno);
 538                                 res_close();
 539                                 goto next_ns;
 540                         }
 541                         if (truncated) {
 542                                 /*
 543                                  * Flush rest of answer
 544                                  * so connection stays in synch.
 545                                  */
 546                                 anhp->tc = 1;
 547                                 len = resplen - anssiz;
 548                                 while (len != 0) {
 549                                         char junk[PACKETSZ];
 550
 551                                         n = (len > sizeof(junk)
 552                                              ? sizeof(junk)
 553                                              : len);
 554                                         if ((n = _read(s, junk, n)) > 0)
 555                                                 len -= n;
 556                                         else
 557                                                 break;
 558                                 }
 559                         }
 560                         /*
 561                          * The calling applicating has bailed out of
 562                          * a previous call and failed to arrange to have
 563                          * the circuit closed or the server has got
 564                          * itself confused. Anyway drop the packet and
 565                          * wait for the correct one.
 566                          */
 567                         if (hp->id != anhp->id) {
 568                                 DprintQ((_res.options & RES_DEBUG) ||
 569                                         (_res.pfcode & RES_PRF_REPLY),
 570                                         (stdout, ";; old answer (unexpected):\n"),
 571                                         ans, (resplen>anssiz)?anssiz:resplen);
 572                                 goto read_len;
 573                         }
 574                 } else {
 575                         /*
 576                          * Use datagrams.
 577                          */
 578                         struct kevent kv;
 579                         struct timespec ts;
 580                         struct timeval timeout, ctv;
 581                         struct sockaddr_storage from;
 582                         int fromlen;
 583
 584                         if (s < 0 || vc || af != nsap->sa_family) {
 585                                 if (vc)
 586                                         res_close();
 587                                 af = nsap->sa_family;
 588                                 s = _socket(af, SOCK_DGRAM, 0);
 589                                 if (s < 0) {
 590 #ifndef CAN_RECONNECT
 591  bad_dg_sock:
 592 #endif
 593                                         terrno = errno;
 594                                         Perror(stderr, "socket(dg)", errno);
 595                                         badns |= (1 << ns);
 596                                         res_close();
 597                                         goto next_ns;
 598                                 }
 599                                 connected = 0;
 600                         }
 601 #ifndef CANNOT_CONNECT_DGRAM
 602                         /*
 603                          * On a 4.3BSD+ machine (client and server,
 604                          * actually), sending to a nameserver datagram
 605                          * port with no nameserver will cause an
 606                          * ICMP port unreachable message to be returned.
 607                          * If our datagram socket is "connected" to the
 608                          * server, we get an ECONNREFUSED error on the next
 609                          * socket operation, and select returns if the
 610                          * error message is received.  We can thus detect
 611                          * the absence of a nameserver without timing out.
 612                          * If we have sent queries to at least two servers,
 613                          * however, we don't want to remain connected,
 614                          * as we wish to receive answers from the first
 615                          * server to respond.
 616                          *
 617                          * When the option "insecure1" is specified, we'd
 618                          * rather expect to see responses from an "unknown"
 619                          * address.  In order to let the kernel accept such
 620                          * responses, do not connect the socket here.
 621                          * XXX: or do we need an explicit option to disable
 622                          * connecting?
 623                          */
 624                         if (!(_res.options & RES_INSECURE1) &&
 625                             (_res.nscount == 1 || (try == 0 && ns == 0))) {
 626                                 /*
 627                                  * Connect only if we are sure we won't
 628                                  * receive a response from another server.
 629                                  */
 630                                 if (!connected) {
 631                                         if (_connect(s, nsap, salen) < 0) {
 632                                                 Aerror(stderr,
 633                                                        "connect(dg)",
 634                                                        errno, nsap);
 635                                                 badns |= (1 << ns);
 636                                                 res_close();
 637                                                 goto next_ns;
 638                                         }
 639                                         connected = 1;
 640                                 }
 641                                 if (send(s, (char*)buf, buflen, 0) != buflen) {
 642                                         Perror(stderr, "send", errno);
 643                                         badns |= (1 << ns);
 644                                         res_close();
 645                                         goto next_ns;
 646                                 }
 647                         } else {
 648                                 /*
 649                                  * Disconnect if we want to listen
 650                                  * for responses from more than one server.
 651                                  */
 652                                 if (connected) {
 653 #ifdef CAN_RECONNECT
 654                                         /* XXX: any errornous address */
 655                                         struct sockaddr_in no_addr;
 656
 657                                         no_addr.sin_family = AF_INET;
 658                                         no_addr.sin_addr.s_addr = INADDR_ANY;
 659                                         no_addr.sin_port = 0;
 660                                         _connect(s,
 661                                                  (struct sockaddr *)&no_addr,
 662                                                  sizeof(no_addr));
 663 #else
 664                                         int s1 = _socket(af, SOCK_DGRAM,0);
 665                                         if (s1 < 0)
 666                                                 goto bad_dg_sock;
 667                                         _dup2(s1, s);
 668                                         _close(s1);
 669                                         Dprint(_res.options & RES_DEBUG,
 670                                                 (stdout, ";; new DG socket\n"))
 671 #endif /* CAN_RECONNECT */
 672                                         connected = 0;
 673                                         errno = 0;
 674                                 }
 675 #endif /* !CANNOT_CONNECT_DGRAM */
 676                                 if (_sendto(s, (char*)buf, buflen, 0,
 677                                            nsap, salen) != buflen) {
 678                                         Aerror(stderr, "sendto", errno, nsap);
 679                                         badns |= (1 << ns);
 680                                         res_close();
 681                                         goto next_ns;
 682                                 }
 683 #ifndef CANNOT_CONNECT_DGRAM
 684                         }
 685 #endif /* !CANNOT_CONNECT_DGRAM */
 686
 687                         /*
 688                          * Wait for reply
 689                          */
 690
 691                         timeout.tv_sec = (_res.retrans << try);
 692                         if (try > 0)
 693                                 timeout.tv_sec /= _res.nscount;
 694                         if ((long) timeout.tv_sec <= 0)
 695                                 timeout.tv_sec = 1;
 696                         timeout.tv_usec = 0;
 697                         TIMEVAL_TO_TIMESPEC(&timeout, &ts);
 698                         gettimeofday(&ctv, NULL);
 699                         timeradd(&timeout, &ctv, &timeout);
 700     wait:
 701                         if (s < 0) {
 702                                 Perror(stderr, "s out-of-bounds", EMFILE);
 703                                 res_close();
 704                                 goto next_ns;
 705                         }
 706
 707                         EV_SET(&kv, s, EVFILT_READ, EV_ADD | EV_ONESHOT, 0,0,0);
 708
 709                         n = _kevent(kq, &kv, 1, &kv, 1, &ts);
 710                         if (n < 0) {
 711                                 if (errno == EINTR) {
 712                                         gettimeofday(&ctv, NULL);
 713                                         if (timercmp(&ctv, &timeout, <)) {
 714                                                 timersub(&timeout, &ctv, &ctv);
 715                                                 TIMEVAL_TO_TIMESPEC(&ctv, &ts);
 716                                                 goto wait;
 717                                         }
 718                                 }
 719                                 Perror(stderr, "kevent", errno);
 720                                 res_close();
 721                                 goto next_ns;
 722                         }
 723
 724                         if (n == 0) {
 725                                 /*
 726                                  * timeout
 727                                  */
 728                                 Dprint(_res.options & RES_DEBUG,
 729                                        (stdout, ";; timeout\n"));
 730                                 gotsomewhere = 1;
 731                                 res_close();
 732                                 goto next_ns;
 733                         }
 734                         errno = 0;
 735                         fromlen = sizeof(from);
 736                         resplen = _recvfrom(s, (char*)ans, anssiz, 0,
 737                                            (struct sockaddr *)&from, &fromlen);
 738                         if (resplen <= 0) {
 739                                 Perror(stderr, "recvfrom", errno);
 740                                 res_close();
 741                                 goto next_ns;
 742                         }
 743                         gotsomewhere = 1;
 744                         if (resplen < HFIXEDSZ) {
 745                                 /*
 746                                  * Undersized message.
 747                                  */
 748                                 Dprint(_res.options & RES_DEBUG,
 749                                        (stdout, ";; undersized: %d\n",
 750                                         resplen));
 751                                 terrno = EMSGSIZE;
 752                                 badns |= (1 << ns);
 753                                 res_close();
 754                                 goto next_ns;
 755                         }
 756                         if (hp->id != anhp->id) {
 757                                 /*
 758                                  * response from old query, ignore it.
 759                                  * XXX - potential security hazard could
 760                                  *       be detected here.
 761                                  */
 762                                 DprintQ((_res.options & RES_DEBUG) ||
 763                                         (_res.pfcode & RES_PRF_REPLY),
 764                                         (stdout, ";; old answer:\n"),
 765                                         ans, (resplen>anssiz)?anssiz:resplen);
 766                                 goto wait;
 767                         }
 768 #ifdef CHECK_SRVR_ADDR
 769                         if (!(_res.options & RES_INSECURE1) &&
 770                             !res_isourserver((struct sockaddr_in *)&from)) {
 771                                 /*
 772                                  * response from wrong server? 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, ";; not our server:\n"),
 779                                         ans, (resplen>anssiz)?anssiz:resplen);
 780                                 goto wait;
 781                         }
 782 #endif
 783                         if (!(_res.options & RES_INSECURE2) &&
 784                             !res_queriesmatch(buf, buf + buflen,
 785                                               ans, ans + anssiz)) {
 786                                 /*
 787                                  * response contains wrong query? ignore it.
 788                                  * XXX - potential security hazard could
 789                                  *       be detected here.
 790                                  */
 791                                 DprintQ((_res.options & RES_DEBUG) ||
 792                                         (_res.pfcode & RES_PRF_REPLY),
 793                                         (stdout, ";; wrong query name:\n"),
 794                                         ans, (resplen>anssiz)?anssiz:resplen);
 795                                 goto wait;
 796                         }
 797                         if (anhp->rcode == SERVFAIL ||
 798                             anhp->rcode == NOTIMP ||
 799                             anhp->rcode == REFUSED) {
 800                                 DprintQ(_res.options & RES_DEBUG,
 801                                         (stdout, "server rejected query:\n"),
 802                                         ans, (resplen>anssiz)?anssiz:resplen);
 803                                 badns |= (1 << ns);
 804                                 res_close();
 805                                 /* don't retry if called from dig */
 806                                 if (!_res.pfcode)
 807                                         goto next_ns;
 808                         }
 809                         if (!(_res.options & RES_IGNTC) && anhp->tc) {
 810                                 /*
 811                                  * get rest of answer;
 812                                  * use TCP with same server.
 813                                  */
 814                                 Dprint(_res.options & RES_DEBUG,
 815                                        (stdout, ";; truncated answer\n"));
 816                                 v_circuit = 1;
 817                                 res_close();
 818                                 goto same_ns;
 819                         }
 820                 } /*if vc/dg*/
 821                 Dprint((_res.options & RES_DEBUG) ||
 822                        ((_res.pfcode & RES_PRF_REPLY) &&
 823                         (_res.pfcode & RES_PRF_HEAD1)),
 824                        (stdout, ";; got answer:\n"));
 825                 DprintQ((_res.options & RES_DEBUG) ||
 826                         (_res.pfcode & RES_PRF_REPLY),
 827                         (stdout, ""),
 828                         ans, (resplen>anssiz)?anssiz:resplen);
 829                 /*
 830                  * If using virtual circuits, we assume that the first server
 831                  * is preferred over the rest (i.e. it is on the local
 832                  * machine) and only keep that one open.
 833                  * If we have temporarily opened a virtual circuit,
 834                  * or if we haven't been asked to keep a socket open,
 835                  * close the socket.
 836                  */
 837                 if ((v_circuit && (!(_res.options & RES_USEVC) || ns != 0)) ||
 838                     !(_res.options & RES_STAYOPEN)) {
 839                         res_close();
 840                 }
 841                 if (Rhook) {
 842                         int done = 0, loops = 0;
 843
 844                         do {
 845                                 res_sendhookact act;
 846
 847                                 act = (*Rhook)((struct sockaddr_in *)nsap,
 848                                                buf, buflen,
 849                                                ans, anssiz, &resplen);
 850                                 switch (act) {
 851                                 case res_goahead:
 852                                 case res_done:
 853                                         done = 1;
 854                                         break;
 855                                 case res_nextns:
 856                                         res_close();
 857                                         goto next_ns;
 858                                 case res_modified:
 859                                         /* give the hook another try */
 860                                         if (++loops < 42) /*doug adams*/
 861                                                 break;
 862                                         /*FALLTHROUGH*/
 863                                 case res_error:
 864                                         /*FALLTHROUGH*/
 865                                 default:
 866                                         _close(kq);
 867                                         return (-1);
 868                                 }
 869                         } while (!done);
 870
 871                 }
 872                 _close(kq);
 873                 return (resplen);
 874     next_ns: ;
 875            } /*foreach ns*/
 876         } /*foreach retry*/
 877         res_close();
 878         _close(kq);
 879         if (!v_circuit) {
 880                 if (!gotsomewhere)
 881                         errno = ECONNREFUSED;   /* no nameservers found */
 882                 else
 883                         errno = ETIMEDOUT;      /* no answer obtained */
 884         } else
 885                 errno = terrno;
 886         return (-1);
 887 }
 888
 889 /*
 890  * This routine is for closing the socket if a virtual circuit is used and
 891  * the program wants to close it.  This provides support for endhostent()
 892  * which expects to close the socket.
 893  *
 894  * This routine is not expected to be user visible.
 895  */
 896 void
 897 res_close(void)
 898 {
 899         if (s >= 0) {
 900                 _close(s);
 901                 s = -1;
 902                 connected = 0;
 903                 vc = 0;
 904                 af = 0;
 905         }
 906 }
 907
 908 /*
 909  * Weak aliases for applications that use certain private entry points,
 910  * and fail to include <resolv.h>.
 911  */
 912 #undef res_close
 913 __weak_reference(__res_close, _res_close);
 914 #undef res_send
 915 __weak_reference(__res_send, res_send);