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. All advertising materials mentioning features or use of this software
  14  *    must display the following acknowledgement:
  15  *      This product includes software developed by the University of
  16  *      California, Berkeley and its contributors.
  17  * 4. Neither the name of the University nor the names of its contributors
  18  *    may be used to endorse or promote products derived from this software
  19  *    without specific prior written permission.
  20  *
  21  * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
  22  * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
  23  * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
  24  * ARE DISCLAIMED.  IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
  25  * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
  26  * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
  27  * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
  28  * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
  29  * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
  30  * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
  31  * SUCH DAMAGE.
  32  *
  33  * @(#)res_send.c       8.1 (Berkeley) 6/4/93
  34  * $From: Id: res_send.c,v 8.20 1998/04/06 23:27:51 halley Exp $
  35  * $FreeBSD: src/lib/libc/net/res_send.c,v 1.31.2.9 2002/04/11 17:30:24 ume Exp $
  36  * $DragonFly: src/lib/libc/net/res_send.c,v 1.3 2003/11/12 20:21:24 eirikn Exp $
  37  */
  38
  39 /*
  40  * Portions Copyright (c) 1993 by Digital Equipment Corporation.
  41  *
  42  * Permission to use, copy, modify, and distribute this software for any
  43  * purpose with or without fee is hereby granted, provided that the above
  44  * copyright notice and this permission notice appear in all copies, and that
  45  * the name of Digital Equipment Corporation not be used in advertising or
  46  * publicity pertaining to distribution of the document or software without
  47  * specific, written prior permission.
  48  *
  49  * THE SOFTWARE IS PROVIDED "AS IS" AND DIGITAL EQUIPMENT CORP. DISCLAIMS ALL
  50  * WARRANTIES WITH REGARD TO THIS SOFTWARE, INCLUDING ALL IMPLIED WARRANTIES
  51  * OF MERCHANTABILITY AND FITNESS.   IN NO EVENT SHALL DIGITAL EQUIPMENT
  52  * CORPORATION BE LIABLE FOR ANY SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL
  53  * DAMAGES OR ANY DAMAGES WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR
  54  * PROFITS, WHETHER IN AN ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS
  55  * ACTION, ARISING OUT OF OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS
  56  * SOFTWARE.
  57  */
  58
  59 /*
  60  * Portions Copyright (c) 1996 by Internet Software Consortium.
  61  *
  62  * Permission to use, copy, modify, and distribute this software for any
  63  * purpose with or without fee is hereby granted, provided that the above
  64  * copyright notice and this permission notice appear in all copies.
  65  *
  66  * THE SOFTWARE IS PROVIDED "AS IS" AND INTERNET SOFTWARE CONSORTIUM DISCLAIMS
  67  * ALL WARRANTIES WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES
  68  * OF MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL INTERNET SOFTWARE
  69  * CONSORTIUM BE LIABLE FOR ANY SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL
  70  * DAMAGES OR ANY DAMAGES WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR
  71  * PROFITS, WHETHER IN AN ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS
  72  * ACTION, ARISING OUT OF OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS
  73  * SOFTWARE.
  74  */
  75
  76 /*
  77  * Send query to name server and wait for reply.
  78  */
  79
  80 #include <sys/types.h>
  81 #include <sys/event.h>
  82 #include <sys/param.h>
  83 #include <sys/time.h>
  84 #include <sys/socket.h>
  85 #include <sys/uio.h>
  86
  87 #include <netinet/in.h>
  88 #include <arpa/nameser.h>
  89 #include <arpa/inet.h>
  90
  91 #include <errno.h>
  92 #include <netdb.h>
  93 #include <resolv.h>
  94 #include <stdio.h>
  95 #include <stdlib.h>
  96 #include <string.h>
  97 #include <unistd.h>
  98
  99 #include "res_config.h"
 100
 101 static int s = -1;              /* socket used for communications */
 102 static int connected = 0;       /* is the socket connected */
 103 static int vc = 0;              /* is the socket a virtual circuit? */
 104 static int af = 0;              /* address family of socket */
 105 static res_send_qhook Qhook = NULL;
 106 static res_send_rhook Rhook = NULL;
 107
 108
 109 #define CAN_RECONNECT 1
 110
 111 #ifndef DEBUG
 112 #   define Dprint(cond, args) /*empty*/
 113 #   define DprintQ(cond, args, query, size) /*empty*/
 114 #   define Aerror(file, string, error, address) /*empty*/
 115 #   define Perror(file, string, error) /*empty*/
 116 #else
 117 #   define Dprint(cond, args) if (cond) {fprintf args;} else {}
 118 #   define DprintQ(cond, args, query, size) if (cond) {\
 119                         fprintf args;\
 120                         __fp_nquery(query, size, stdout);\
 121                 } else {}
 122 static char abuf[NI_MAXHOST];
 123 static char pbuf[NI_MAXSERV];
 124 static void Aerror (FILE *, char *, int, struct sockaddr *);
 125 static void Perror (FILE *, char *, int);
 126
 127     static void
 128     Aerror(file, string, error, address)
 129         FILE *file;
 130         char *string;
 131         int error;
 132         struct sockaddr *address;
 133     {
 134         int save = errno;
 135
 136         if (_res.options & RES_DEBUG) {
 137                 if (getnameinfo(address, address->sa_len, abuf, sizeof(abuf),
 138                     pbuf, sizeof(pbuf),
 139                     NI_NUMERICHOST|NI_NUMERICSERV|NI_WITHSCOPEID) != 0) {
 140                         strncpy(abuf, "?", sizeof(abuf));
 141                         strncpy(pbuf, "?", sizeof(pbuf));
 142                 }
 143                 fprintf(file, "res_send: %s ([%s].%s): %s\n",
 144                         string, abuf, pbuf, strerror(error));
 145         }
 146         errno = save;
 147     }
 148     static void
 149     Perror(file, string, error)
 150         FILE *file;
 151         char *string;
 152         int error;
 153     {
 154         int save = errno;
 155
 156         if (_res.options & RES_DEBUG) {
 157                 fprintf(file, "res_send: %s: %s\n",
 158                         string, strerror(error));
 159         }
 160         errno = save;
 161     }
 162 #endif
 163
 164 void
 165 res_send_setqhook(hook)
 166         res_send_qhook hook;
 167 {
 168
 169         Qhook = hook;
 170 }
 171
 172 void
 173 res_send_setrhook(hook)
 174         res_send_rhook hook;
 175 {
 176
 177         Rhook = hook;
 178 }
 179
 180 static struct sockaddr * get_nsaddr (size_t);
 181
 182 /*
 183  * pick appropriate nsaddr_list for use.  see res_init() for initialization.
 184  */
 185 static struct sockaddr *
 186 get_nsaddr(n)
 187         size_t n;
 188 {
 189
 190         if (!_res.nsaddr_list[n].sin_family) {
 191                 /*
 192                  * - _res_ext.nsaddr_list[n] holds an address that is larger
 193                  *   than struct sockaddr, and
 194                  * - user code did not update _res.nsaddr_list[n].
 195                  */
 196                 return (struct sockaddr *)&_res_ext.nsaddr_list[n];
 197         } else {
 198                 /*
 199                  * - user code updated _res.nsaddr_list[n], or
 200                  * - _res.nsaddr_list[n] has the same content as
 201                  *   _res_ext.nsaddr_list[n].
 202                  */
 203                 return (struct sockaddr *)&_res.nsaddr_list[n];
 204         }
 205 }
 206
 207 /* int
 208  * res_isourserver(ina)
 209  *      looks up "ina" in _res.ns_addr_list[]
 210  * returns:
 211  *      0  : not found
 212  *      >0 : found
 213  * author:
 214  *      paul vixie, 29may94
 215  */
 216 int
 217 res_isourserver(inp)
 218         const struct sockaddr_in *inp;
 219 {
 220         const struct sockaddr_in6 *in6p = (const struct sockaddr_in6 *)inp;
 221         const struct sockaddr_in6 *srv6;
 222         const struct sockaddr_in *srv;
 223         int ns, ret;
 224
 225         ret = 0;
 226         switch (inp->sin_family) {
 227         case AF_INET6:
 228                 for (ns = 0; ns < _res.nscount; ns++) {
 229                         srv6 = (struct sockaddr_in6 *)get_nsaddr(ns);
 230                         if (srv6->sin6_family == in6p->sin6_family &&
 231                             srv6->sin6_port == in6p->sin6_port &&
 232                             srv6->sin6_scope_id == in6p->sin6_scope_id &&
 233                             (IN6_IS_ADDR_UNSPECIFIED(&srv6->sin6_addr) ||
 234                              IN6_ARE_ADDR_EQUAL(&srv6->sin6_addr,
 235                                  &in6p->sin6_addr))) {
 236                                 ret++;
 237                                 break;
 238                         }
 239                 }
 240                 break;
 241         case AF_INET:
 242                 for (ns = 0; ns < _res.nscount; ns++) {
 243                         srv = (struct sockaddr_in *)get_nsaddr(ns);
 244                         if (srv->sin_family == inp->sin_family &&
 245                             srv->sin_port == inp->sin_port &&
 246                             (srv->sin_addr.s_addr == INADDR_ANY ||
 247                              srv->sin_addr.s_addr == inp->sin_addr.s_addr)) {
 248                                 ret++;
 249                                 break;
 250                         }
 251                 }
 252                 break;
 253         }
 254         return (ret);
 255 }
 256
 257 /* int
 258  * res_nameinquery(name, type, class, buf, eom)
 259  *      look for (name,type,class) in the query section of packet (buf,eom)
 260  * requires:
 261  *      buf + HFIXEDSZ <= eom
 262  * returns:
 263  *      -1 : format error
 264  *      0  : not found
 265  *      >0 : found
 266  * author:
 267  *      paul vixie, 29may94
 268  */
 269 int
 270 res_nameinquery(name, type, class, buf, eom)
 271         const char *name;
 272         int type, class;
 273         const u_char *buf, *eom;
 274 {
 275         const u_char *cp = buf + HFIXEDSZ;
 276         int qdcount = ntohs(((HEADER*)buf)->qdcount);
 277
 278         while (qdcount-- > 0) {
 279                 char tname[MAXDNAME+1];
 280                 int n, ttype, tclass;
 281
 282                 n = dn_expand(buf, eom, cp, tname, sizeof tname);
 283                 if (n < 0)
 284                         return (-1);
 285                 cp += n;
 286                 if (cp + 2 * INT16SZ > eom)
 287                         return (-1);
 288                 ttype = ns_get16(cp); cp += INT16SZ;
 289                 tclass = ns_get16(cp); cp += INT16SZ;
 290                 if (ttype == type &&
 291                     tclass == class &&
 292                     strcasecmp(tname, name) == 0)
 293                         return (1);
 294         }
 295         return (0);
 296 }
 297
 298 /* int
 299  * res_queriesmatch(buf1, eom1, buf2, eom2)
 300  *      is there a 1:1 mapping of (name,type,class)
 301  *      in (buf1,eom1) and (buf2,eom2)?
 302  * returns:
 303  *      -1 : format error
 304  *      0  : not a 1:1 mapping
 305  *      >0 : is a 1:1 mapping
 306  * author:
 307  *      paul vixie, 29may94
 308  */
 309 int
 310 res_queriesmatch(buf1, eom1, buf2, eom2)
 311         const u_char *buf1, *eom1;
 312         const u_char *buf2, *eom2;
 313 {
 314         const u_char *cp = buf1 + HFIXEDSZ;
 315         int qdcount = ntohs(((HEADER*)buf1)->qdcount);
 316
 317         if (buf1 + HFIXEDSZ > eom1 || buf2 + HFIXEDSZ > eom2)
 318                 return (-1);
 319
 320         /*
 321          * Only header section present in replies to
 322          * dynamic update packets.
 323          */
 324         if ( (((HEADER *)buf1)->opcode == ns_o_update) &&
 325              (((HEADER *)buf2)->opcode == ns_o_update) )
 326                 return (1);
 327
 328         if (qdcount != ntohs(((HEADER*)buf2)->qdcount))
 329                 return (0);
 330         while (qdcount-- > 0) {
 331                 char tname[MAXDNAME+1];
 332                 int n, ttype, tclass;
 333
 334                 n = dn_expand(buf1, eom1, cp, tname, sizeof tname);
 335                 if (n < 0)
 336                         return (-1);
 337                 cp += n;
 338                 if (cp + 2 * INT16SZ > eom1)
 339                         return (-1);
 340                 ttype = ns_get16(cp);   cp += INT16SZ;
 341                 tclass = ns_get16(cp); cp += INT16SZ;
 342                 if (!res_nameinquery(tname, ttype, tclass, buf2, eom2))
 343                         return (0);
 344         }
 345         return (1);
 346 }
 347
 348 int
 349 res_send(buf, buflen, ans, anssiz)
 350         const u_char *buf;
 351         int buflen;
 352         u_char *ans;
 353         int anssiz;
 354 {
 355         HEADER *hp = (HEADER *) buf;
 356         HEADER *anhp = (HEADER *) ans;
 357         int gotsomewhere, connreset, terrno, try, v_circuit, resplen, ns, n;
 358         int kq;
 359         u_int badns;    /* XXX NSMAX can't exceed #/bits in this variable */
 360
 361         if ((_res.options & RES_INIT) == 0 && res_init() == -1) {
 362                 /* errno should have been set by res_init() in this case. */
 363                 return (-1);
 364         }
 365         if (anssiz < HFIXEDSZ) {
 366                 errno = EINVAL;
 367                 return (-1);
 368         }
 369         DprintQ((_res.options & RES_DEBUG) || (_res.pfcode & RES_PRF_QUERY),
 370                 (stdout, ";; res_send()\n"), buf, buflen);
 371         v_circuit = (_res.options & RES_USEVC) || buflen > PACKETSZ;
 372         gotsomewhere = 0;
 373         connreset = 0;
 374         terrno = ETIMEDOUT;
 375         badns = 0;
 376
 377         if ((kq = kqueue()) < 0) {
 378                 Perror(stderr, "kqueue", errno);
 379                 return (-1);
 380         }
 381
 382         /*
 383          * Send request, RETRY times, or until successful
 384          */
 385         for (try = 0; try < _res.retry; try++) {
 386             for (ns = 0; ns < _res.nscount; ns++) {
 387                 struct sockaddr *nsap = get_nsaddr(ns);
 388                 socklen_t salen;
 389
 390                 if (nsap->sa_len)
 391                         salen = nsap->sa_len;
 392                 else if (nsap->sa_family == AF_INET6)
 393                         salen = sizeof(struct sockaddr_in6);
 394                 else if (nsap->sa_family == AF_INET)
 395                         salen = sizeof(struct sockaddr_in);
 396                 else
 397                         salen = 0;      /*unknown, die on connect*/
 398
 399     same_ns:
 400                 if (badns & (1 << ns)) {
 401                         res_close();
 402                         goto next_ns;
 403                 }
 404
 405                 if (Qhook) {
 406                         int done = 0, loops = 0;
 407
 408                         do {
 409                                 res_sendhookact act;
 410
 411                                 act = (*Qhook)((struct sockaddr_in **)&nsap,
 412                                                &buf, &buflen,
 413                                                ans, anssiz, &resplen);
 414                                 switch (act) {
 415                                 case res_goahead:
 416                                         done = 1;
 417                                         break;
 418                                 case res_nextns:
 419                                         res_close();
 420                                         goto next_ns;
 421                                 case res_done:
 422                                         _close(kq);
 423                                         return (resplen);
 424                                 case res_modified:
 425                                         /* give the hook another try */
 426                                         if (++loops < 42) /*doug adams*/
 427                                                 break;
 428                                         /*FALLTHROUGH*/
 429                                 case res_error:
 430                                         /*FALLTHROUGH*/
 431                                 default:
 432                                         _close(kq);
 433                                         return (-1);
 434                                 }
 435                         } while (!done);
 436                 }
 437
 438                 Dprint((_res.options & RES_DEBUG) &&
 439                        getnameinfo(nsap, salen, abuf, sizeof(abuf),
 440                            NULL, 0, NI_NUMERICHOST | NI_WITHSCOPEID) == 0,
 441                        (stdout, ";; Querying server (# %d) address = %s\n",
 442                         ns + 1, abuf));
 443
 444                 if (v_circuit) {
 445                         int truncated;
 446                         struct iovec iov[2];
 447                         u_short len;
 448                         u_char *cp;
 449
 450                         /*
 451                          * Use virtual circuit;
 452                          * at most one attempt per server.
 453                          */
 454                         try = _res.retry;
 455                         truncated = 0;
 456                         if (s < 0 || !vc || hp->opcode == ns_o_update ||
 457                             af != nsap->sa_family) {
 458                                 if (s >= 0)
 459                                         res_close();
 460
 461                                 af = nsap->sa_family;
 462                                 s = socket(af, SOCK_STREAM, 0);
 463                                 if (s < 0) {
 464                                         terrno = errno;
 465                                         Perror(stderr, "socket(vc)", errno);
 466                                         badns |= (1 << ns);
 467                                         res_close();
 468                                         goto next_ns;
 469                                 }
 470                                 errno = 0;
 471                                 if (connect(s, nsap, salen) < 0) {
 472                                         terrno = errno;
 473                                         Aerror(stderr, "connect/vc",
 474                                                errno, nsap);
 475                                         badns |= (1 << ns);
 476                                         res_close();
 477                                         goto next_ns;
 478                                 }
 479                                 vc = 1;
 480                         }
 481                         /*
 482                          * Send length & message
 483                          */
 484                         putshort((u_short)buflen, (u_char*)&len);
 485                         iov[0].iov_base = (caddr_t)&len;
 486                         iov[0].iov_len = INT16SZ;
 487                         iov[1].iov_base = (caddr_t)buf;
 488                         iov[1].iov_len = buflen;
 489                         if (writev(s, iov, 2) != (INT16SZ + buflen)) {
 490                                 terrno = errno;
 491                                 Perror(stderr, "write failed", errno);
 492                                 badns |= (1 << ns);
 493                                 res_close();
 494                                 goto next_ns;
 495                         }
 496                         /*
 497                          * Receive length & response
 498                          */
 499 read_len:
 500                         cp = ans;
 501                         len = INT16SZ;
 502                         while ((n = _read(s, (char *)cp, (int)len)) > 0) {
 503                                 cp += n;
 504                                 if ((len -= n) <= 0)
 505                                         break;
 506                         }
 507                         if (n <= 0) {
 508                                 terrno = errno;
 509                                 Perror(stderr, "read failed", errno);
 510                                 res_close();
 511                                 /*
 512                                  * A long running process might get its TCP
 513                                  * connection reset if the remote server was
 514                                  * restarted.  Requery the server instead of
 515                                  * trying a new one.  When there is only one
 516                                  * server, this means that a query might work
 517                                  * instead of failing.  We only allow one reset
 518                                  * per query to prevent looping.
 519                                  */
 520                                 if (terrno == ECONNRESET && !connreset) {
 521                                         connreset = 1;
 522                                         res_close();
 523                                         goto same_ns;
 524                                 }
 525                                 res_close();
 526                                 goto next_ns;
 527                         }
 528                         resplen = ns_get16(ans);
 529                         if (resplen > anssiz) {
 530                                 Dprint(_res.options & RES_DEBUG,
 531                                        (stdout, ";; response truncated\n")
 532                                        );
 533                                 truncated = 1;
 534                                 len = anssiz;
 535                         } else
 536                                 len = resplen;
 537                         if (len < HFIXEDSZ) {
 538                                 /*
 539                                  * Undersized message.
 540                                  */
 541                                 Dprint(_res.options & RES_DEBUG,
 542                                        (stdout, ";; undersized: %d\n", len));
 543                                 terrno = EMSGSIZE;
 544                                 badns |= (1 << ns);
 545                                 res_close();
 546                                 goto next_ns;
 547                         }
 548                         cp = ans;
 549                         while (len != 0 &&
 550                                (n = _read(s, (char *)cp, (int)len)) > 0) {
 551                                 cp += n;
 552                                 len -= n;
 553                         }
 554                         if (n <= 0) {
 555                                 terrno = errno;
 556                                 Perror(stderr, "read(vc)", errno);
 557                                 res_close();
 558                                 goto next_ns;
 559                         }
 560                         if (truncated) {
 561                                 /*
 562                                  * Flush rest of answer
 563                                  * so connection stays in synch.
 564                                  */
 565                                 anhp->tc = 1;
 566                                 len = resplen - anssiz;
 567                                 while (len != 0) {
 568                                         char junk[PACKETSZ];
 569
 570                                         n = (len > sizeof(junk)
 571                                              ? sizeof(junk)
 572                                              : len);
 573                                         if ((n = _read(s, junk, n)) > 0)
 574                                                 len -= n;
 575                                         else
 576                                                 break;
 577                                 }
 578                         }
 579                         /*
 580                          * The calling applicating has bailed out of
 581                          * a previous call and failed to arrange to have
 582                          * the circuit closed or the server has got
 583                          * itself confused. Anyway drop the packet and
 584                          * wait for the correct one.
 585                          */
 586                         if (hp->id != anhp->id) {
 587                                 DprintQ((_res.options & RES_DEBUG) ||
 588                                         (_res.pfcode & RES_PRF_REPLY),
 589                                         (stdout, ";; old answer (unexpected):\n"),
 590                                         ans, (resplen>anssiz)?anssiz:resplen);
 591                                 goto read_len;
 592                         }
 593                 } else {
 594                         /*
 595                          * Use datagrams.
 596                          */
 597                         struct kevent kv;
 598                         struct timespec ts;
 599                         struct timeval timeout, ctv;
 600                         struct sockaddr_storage from;
 601                         int fromlen;
 602
 603                         if (s < 0 || vc || af != nsap->sa_family) {
 604                                 if (vc)
 605                                         res_close();
 606                                 af = nsap->sa_family;
 607                                 s = socket(af, SOCK_DGRAM, 0);
 608                                 if (s < 0) {
 609 #ifndef CAN_RECONNECT
 610  bad_dg_sock:
 611 #endif
 612                                         terrno = errno;
 613                                         Perror(stderr, "socket(dg)", errno);
 614                                         badns |= (1 << ns);
 615                                         res_close();
 616                                         goto next_ns;
 617                                 }
 618                                 connected = 0;
 619                         }
 620 #ifndef CANNOT_CONNECT_DGRAM
 621                         /*
 622                          * On a 4.3BSD+ machine (client and server,
 623                          * actually), sending to a nameserver datagram
 624                          * port with no nameserver will cause an
 625                          * ICMP port unreachable message to be returned.
 626                          * If our datagram socket is "connected" to the
 627                          * server, we get an ECONNREFUSED error on the next
 628                          * socket operation, and select returns if the
 629                          * error message is received.  We can thus detect
 630                          * the absence of a nameserver without timing out.
 631                          * If we have sent queries to at least two servers,
 632                          * however, we don't want to remain connected,
 633                          * as we wish to receive answers from the first
 634                          * server to respond.
 635                          *
 636                          * When the option "insecure1" is specified, we'd
 637                          * rather expect to see responses from an "unknown"
 638                          * address.  In order to let the kernel accept such
 639                          * responses, do not connect the socket here.
 640                          * XXX: or do we need an explicit option to disable
 641                          * connecting?
 642                          */
 643                         if (!(_res.options & RES_INSECURE1) &&
 644                             (_res.nscount == 1 || (try == 0 && ns == 0))) {
 645                                 /*
 646                                  * Connect only if we are sure we won't
 647                                  * receive a response from another server.
 648                                  */
 649                                 if (!connected) {
 650                                         if (connect(s, nsap, salen) < 0) {
 651                                                 Aerror(stderr,
 652                                                        "connect(dg)",
 653                                                        errno, nsap);
 654                                                 badns |= (1 << ns);
 655                                                 res_close();
 656                                                 goto next_ns;
 657                                         }
 658                                         connected = 1;
 659                                 }
 660                                 if (send(s, (char*)buf, buflen, 0) != buflen) {
 661                                         Perror(stderr, "send", errno);
 662                                         badns |= (1 << ns);
 663                                         res_close();
 664                                         goto next_ns;
 665                                 }
 666                         } else {
 667                                 /*
 668                                  * Disconnect if we want to listen
 669                                  * for responses from more than one server.
 670                                  */
 671                                 if (connected) {
 672 #ifdef CAN_RECONNECT
 673                                         /* XXX: any errornous address */
 674                                         struct sockaddr_in no_addr;
 675
 676                                         no_addr.sin_family = AF_INET;
 677                                         no_addr.sin_addr.s_addr = INADDR_ANY;
 678                                         no_addr.sin_port = 0;
 679                                         (void) connect(s,
 680                                                        (struct sockaddr *)
 681                                                         &no_addr,
 682                                                        sizeof no_addr);
 683 #else
 684                                         int s1 = socket(af, SOCK_DGRAM,0);
 685                                         if (s1 < 0)
 686                                                 goto bad_dg_sock;
 687                                         (void)dup2(s1, s);
 688                                         (void)_close(s1);
 689                                         Dprint(_res.options & RES_DEBUG,
 690                                                 (stdout, ";; new DG socket\n"))
 691 #endif /* CAN_RECONNECT */
 692                                         connected = 0;
 693                                         errno = 0;
 694                                 }
 695 #endif /* !CANNOT_CONNECT_DGRAM */
 696                                 if (sendto(s, (char*)buf, buflen, 0,
 697                                            nsap, salen) != buflen) {
 698                                         Aerror(stderr, "sendto", errno, nsap);
 699                                         badns |= (1 << ns);
 700                                         res_close();
 701                                         goto next_ns;
 702                                 }
 703 #ifndef CANNOT_CONNECT_DGRAM
 704                         }
 705 #endif /* !CANNOT_CONNECT_DGRAM */
 706
 707                         /*
 708                          * Wait for reply
 709                          */
 710
 711                         timeout.tv_sec = (_res.retrans << try);
 712                         if (try > 0)
 713                                 timeout.tv_sec /= _res.nscount;
 714                         if ((long) timeout.tv_sec <= 0)
 715                                 timeout.tv_sec = 1;
 716                         timeout.tv_usec = 0;
 717                         TIMEVAL_TO_TIMESPEC(&timeout, &ts);
 718                         (void) gettimeofday(&ctv, NULL);
 719                         timeradd(&timeout, &ctv, &timeout);
 720     wait:
 721                         if (s < 0) {
 722                                 Perror(stderr, "s out-of-bounds", EMFILE);
 723                                 res_close();
 724                                 goto next_ns;
 725                         }
 726
 727                         EV_SET(&kv, s, EVFILT_READ, EV_ADD | EV_ONESHOT, 0,0,0);
 728
 729                         n = kevent(kq, &kv, 1, &kv, 1, &ts);
 730                         if (n < 0) {
 731                                 if (errno == EINTR) {
 732                                         (void) gettimeofday(&ctv, NULL);
 733                                         if (timercmp(&ctv, &timeout, <)) {
 734                                                 timersub(&timeout, &ctv, &ctv);
 735                                                 TIMEVAL_TO_TIMESPEC(&ctv, &ts);
 736                                                 goto wait;
 737                                         }
 738                                 }
 739                                 Perror(stderr, "kevent", errno);
 740                                 res_close();
 741                                 goto next_ns;
 742                         }
 743
 744                         if (n == 0) {
 745                                 /*
 746                                  * timeout
 747                                  */
 748                                 Dprint(_res.options & RES_DEBUG,
 749                                        (stdout, ";; timeout\n"));
 750                                 gotsomewhere = 1;
 751                                 res_close();
 752                                 goto next_ns;
 753                         }
 754                         errno = 0;
 755                         fromlen = sizeof(from);
 756                         resplen = recvfrom(s, (char*)ans, anssiz, 0,
 757                                            (struct sockaddr *)&from, &fromlen);
 758                         if (resplen <= 0) {
 759                                 Perror(stderr, "recvfrom", errno);
 760                                 res_close();
 761                                 goto next_ns;
 762                         }
 763                         gotsomewhere = 1;
 764                         if (resplen < HFIXEDSZ) {
 765                                 /*
 766                                  * Undersized message.
 767                                  */
 768                                 Dprint(_res.options & RES_DEBUG,
 769                                        (stdout, ";; undersized: %d\n",
 770                                         resplen));
 771                                 terrno = EMSGSIZE;
 772                                 badns |= (1 << ns);
 773                                 res_close();
 774                                 goto next_ns;
 775                         }
 776                         if (hp->id != anhp->id) {
 777                                 /*
 778                                  * response from old query, ignore it.
 779                                  * XXX - potential security hazard could
 780                                  *       be detected here.
 781                                  */
 782                                 DprintQ((_res.options & RES_DEBUG) ||
 783                                         (_res.pfcode & RES_PRF_REPLY),
 784                                         (stdout, ";; old answer:\n"),
 785                                         ans, (resplen>anssiz)?anssiz:resplen);
 786                                 goto wait;
 787                         }
 788 #ifdef CHECK_SRVR_ADDR
 789                         if (!(_res.options & RES_INSECURE1) &&
 790                             !res_isourserver((struct sockaddr_in *)&from)) {
 791                                 /*
 792                                  * response from wrong server? 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, ";; not our server:\n"),
 799                                         ans, (resplen>anssiz)?anssiz:resplen);
 800                                 goto wait;
 801                         }
 802 #endif
 803                         if (!(_res.options & RES_INSECURE2) &&
 804                             !res_queriesmatch(buf, buf + buflen,
 805                                               ans, ans + anssiz)) {
 806                                 /*
 807                                  * response contains wrong query? ignore it.
 808                                  * XXX - potential security hazard could
 809                                  *       be detected here.
 810                                  */
 811                                 DprintQ((_res.options & RES_DEBUG) ||
 812                                         (_res.pfcode & RES_PRF_REPLY),
 813                                         (stdout, ";; wrong query name:\n"),
 814                                         ans, (resplen>anssiz)?anssiz:resplen);
 815                                 goto wait;
 816                         }
 817                         if (anhp->rcode == SERVFAIL ||
 818                             anhp->rcode == NOTIMP ||
 819                             anhp->rcode == REFUSED) {
 820                                 DprintQ(_res.options & RES_DEBUG,
 821                                         (stdout, "server rejected query:\n"),
 822                                         ans, (resplen>anssiz)?anssiz:resplen);
 823                                 badns |= (1 << ns);
 824                                 res_close();
 825                                 /* don't retry if called from dig */
 826                                 if (!_res.pfcode)
 827                                         goto next_ns;
 828                         }
 829                         if (!(_res.options & RES_IGNTC) && anhp->tc) {
 830                                 /*
 831                                  * get rest of answer;
 832                                  * use TCP with same server.
 833                                  */
 834                                 Dprint(_res.options & RES_DEBUG,
 835                                        (stdout, ";; truncated answer\n"));
 836                                 v_circuit = 1;
 837                                 res_close();
 838                                 goto same_ns;
 839                         }
 840                 } /*if vc/dg*/
 841                 Dprint((_res.options & RES_DEBUG) ||
 842                        ((_res.pfcode & RES_PRF_REPLY) &&
 843                         (_res.pfcode & RES_PRF_HEAD1)),
 844                        (stdout, ";; got answer:\n"));
 845                 DprintQ((_res.options & RES_DEBUG) ||
 846                         (_res.pfcode & RES_PRF_REPLY),
 847                         (stdout, ""),
 848                         ans, (resplen>anssiz)?anssiz:resplen);
 849                 /*
 850                  * If using virtual circuits, we assume that the first server
 851                  * is preferred over the rest (i.e. it is on the local
 852                  * machine) and only keep that one open.
 853                  * If we have temporarily opened a virtual circuit,
 854                  * or if we haven't been asked to keep a socket open,
 855                  * close the socket.
 856                  */
 857                 if ((v_circuit && (!(_res.options & RES_USEVC) || ns != 0)) ||
 858                     !(_res.options & RES_STAYOPEN)) {
 859                         res_close();
 860                 }
 861                 if (Rhook) {
 862                         int done = 0, loops = 0;
 863
 864                         do {
 865                                 res_sendhookact act;
 866
 867                                 act = (*Rhook)((struct sockaddr_in *)nsap,
 868                                                buf, buflen,
 869                                                ans, anssiz, &resplen);
 870                                 switch (act) {
 871                                 case res_goahead:
 872                                 case res_done:
 873                                         done = 1;
 874                                         break;
 875                                 case res_nextns:
 876                                         res_close();
 877                                         goto next_ns;
 878                                 case res_modified:
 879                                         /* give the hook another try */
 880                                         if (++loops < 42) /*doug adams*/
 881                                                 break;
 882                                         /*FALLTHROUGH*/
 883                                 case res_error:
 884                                         /*FALLTHROUGH*/
 885                                 default:
 886                                         _close(kq);
 887                                         return (-1);
 888                                 }
 889                         } while (!done);
 890
 891                 }
 892                 _close(kq);
 893                 return (resplen);
 894     next_ns: ;
 895            } /*foreach ns*/
 896         } /*foreach retry*/
 897         res_close();
 898         _close(kq);
 899         if (!v_circuit) {
 900                 if (!gotsomewhere)
 901                         errno = ECONNREFUSED;   /* no nameservers found */
 902                 else
 903                         errno = ETIMEDOUT;      /* no answer obtained */
 904         } else
 905                 errno = terrno;
 906         return (-1);
 907 }
 908
 909 /*
 910  * This routine is for closing the socket if a virtual circuit is used and
 911  * the program wants to close it.  This provides support for endhostent()
 912  * which expects to close the socket.
 913  *
 914  * This routine is not expected to be user visible.
 915  */
 916 void
 917 res_close()
 918 {
 919         if (s >= 0) {
 920                 (void)_close(s);
 921                 s = -1;
 922                 connected = 0;
 923                 vc = 0;
 924                 af = 0;
 925         }
 926 }
 927
 928 /*
 929  * Weak aliases for applications that use certain private entry points,
 930  * and fail to include <resolv.h>.
 931  */
 932 #undef res_close
 933 __weak_reference(__res_close, _res_close);
 934 #undef res_send
 935 __weak_reference(__res_send, res_send);