lib/libcr/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
  34 /*
  35  * Portions Copyright (c) 1993 by Digital Equipment Corporation.
  36  *
  37  * Permission to use, copy, modify, and distribute this software for any
  38  * purpose with or without fee is hereby granted, provided that the above
  39  * copyright notice and this permission notice appear in all copies, and that
  40  * the name of Digital Equipment Corporation not be used in advertising or
  41  * publicity pertaining to distribution of the document or software without
  42  * specific, written prior permission.
  43  *
  44  * THE SOFTWARE IS PROVIDED "AS IS" AND DIGITAL EQUIPMENT CORP. DISCLAIMS ALL
  45  * WARRANTIES WITH REGARD TO THIS SOFTWARE, INCLUDING ALL IMPLIED WARRANTIES
  46  * OF MERCHANTABILITY AND FITNESS.   IN NO EVENT SHALL DIGITAL EQUIPMENT
  47  * CORPORATION BE LIABLE FOR ANY SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL
  48  * DAMAGES OR ANY DAMAGES WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR
  49  * PROFITS, WHETHER IN AN ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS
  50  * ACTION, ARISING OUT OF OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS
  51  * SOFTWARE.
  52  */
  53
  54 /*
  55  * Portions Copyright (c) 1996 by Internet Software Consortium.
  56  *
  57  * Permission to use, copy, modify, and distribute this software for any
  58  * purpose with or without fee is hereby granted, provided that the above
  59  * copyright notice and this permission notice appear in all copies.
  60  *
  61  * THE SOFTWARE IS PROVIDED "AS IS" AND INTERNET SOFTWARE CONSORTIUM DISCLAIMS
  62  * ALL WARRANTIES WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES
  63  * OF MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL INTERNET SOFTWARE
  64  * CONSORTIUM BE LIABLE FOR ANY SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL
  65  * DAMAGES OR ANY DAMAGES WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR
  66  * PROFITS, WHETHER IN AN ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS
  67  * ACTION, ARISING OUT OF OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS
  68  * SOFTWARE.
  69  */
  70
  71 #if defined(LIBC_SCCS) && !defined(lint)
  72 static char sccsid[] = "@(#)res_send.c  8.1 (Berkeley) 6/4/93";
  73 static char orig_rcsid[] = "From: Id: res_send.c,v 8.20 1998/04/06 23:27:51 halley Exp $";
  74 static char rcsid[] = "$FreeBSD: src/lib/libc/net/res_send.c,v 1.31.2.9 2002/04/11 17:30:24 ume Exp $";
  75 #endif /* LIBC_SCCS and not lint */
  76
  77 /*
  78  * Send query to name server and wait for reply.
  79  */
  80
  81 #include <sys/types.h>
  82 #include <sys/event.h>
  83 #include <sys/param.h>
  84 #include <sys/time.h>
  85 #include <sys/socket.h>
  86 #include <sys/uio.h>
  87
  88 #include <netinet/in.h>
  89 #include <arpa/nameser.h>
  90 #include <arpa/inet.h>
  91
  92 #include <errno.h>
  93 #include <netdb.h>
  94 #include <resolv.h>
  95 #include <stdio.h>
  96 #include <stdlib.h>
  97 #include <string.h>
  98 #include <unistd.h>
  99
 100 #include "res_config.h"
 101
 102 static int s = -1;              /* socket used for communications */
 103 static int connected = 0;       /* is the socket connected */
 104 static int vc = 0;              /* is the socket a virtual circuit? */
 105 static int af = 0;              /* address family of socket */
 106 static res_send_qhook Qhook = NULL;
 107 static res_send_rhook Rhook = NULL;
 108
 109
 110 #define CAN_RECONNECT 1
 111
 112 #ifndef DEBUG
 113 #   define Dprint(cond, args) /*empty*/
 114 #   define DprintQ(cond, args, query, size) /*empty*/
 115 #   define Aerror(file, string, error, address) /*empty*/
 116 #   define Perror(file, string, error) /*empty*/
 117 #else
 118 #   define Dprint(cond, args) if (cond) {fprintf args;} else {}
 119 #   define DprintQ(cond, args, query, size) if (cond) {\
 120                         fprintf args;\
 121                         __fp_nquery(query, size, stdout);\
 122                 } else {}
 123 static char abuf[NI_MAXHOST];
 124 static char pbuf[NI_MAXSERV];
 125 static void Aerror __P((FILE *, char *, int, struct sockaddr *));
 126 static void Perror __P((FILE *, char *, int));
 127
 128     static void
 129     Aerror(file, string, error, address)
 130         FILE *file;
 131         char *string;
 132         int error;
 133         struct sockaddr *address;
 134     {
 135         int save = errno;
 136
 137         if (_res.options & RES_DEBUG) {
 138                 if (getnameinfo(address, address->sa_len, abuf, sizeof(abuf),
 139                     pbuf, sizeof(pbuf),
 140                     NI_NUMERICHOST|NI_NUMERICSERV|NI_WITHSCOPEID) != 0) {
 141                         strncpy(abuf, "?", sizeof(abuf));
 142                         strncpy(pbuf, "?", sizeof(pbuf));
 143                 }
 144                 fprintf(file, "res_send: %s ([%s].%s): %s\n",
 145                         string, abuf, pbuf, strerror(error));
 146         }
 147         errno = save;
 148     }
 149     static void
 150     Perror(file, string, error)
 151         FILE *file;
 152         char *string;
 153         int error;
 154     {
 155         int save = errno;
 156
 157         if (_res.options & RES_DEBUG) {
 158                 fprintf(file, "res_send: %s: %s\n",
 159                         string, strerror(error));
 160         }
 161         errno = save;
 162     }
 163 #endif
 164
 165 void
 166 res_send_setqhook(hook)
 167         res_send_qhook hook;
 168 {
 169
 170         Qhook = hook;
 171 }
 172
 173 void
 174 res_send_setrhook(hook)
 175         res_send_rhook hook;
 176 {
 177
 178         Rhook = hook;
 179 }
 180
 181 static struct sockaddr * get_nsaddr __P((size_t));
 182
 183 /*
 184  * pick appropriate nsaddr_list for use.  see res_init() for initialization.
 185  */
 186 static struct sockaddr *
 187 get_nsaddr(n)
 188         size_t n;
 189 {
 190
 191         if (!_res.nsaddr_list[n].sin_family) {
 192                 /*
 193                  * - _res_ext.nsaddr_list[n] holds an address that is larger
 194                  *   than struct sockaddr, and
 195                  * - user code did not update _res.nsaddr_list[n].
 196                  */
 197                 return (struct sockaddr *)&_res_ext.nsaddr_list[n];
 198         } else {
 199                 /*
 200                  * - user code updated _res.nsaddr_list[n], or
 201                  * - _res.nsaddr_list[n] has the same content as
 202                  *   _res_ext.nsaddr_list[n].
 203                  */
 204                 return (struct sockaddr *)&_res.nsaddr_list[n];
 205         }
 206 }
 207
 208 /* int
 209  * res_isourserver(ina)
 210  *      looks up "ina" in _res.ns_addr_list[]
 211  * returns:
 212  *      0  : not found
 213  *      >0 : found
 214  * author:
 215  *      paul vixie, 29may94
 216  */
 217 int
 218 res_isourserver(inp)
 219         const struct sockaddr_in *inp;
 220 {
 221         const struct sockaddr_in6 *in6p = (const struct sockaddr_in6 *)inp;
 222         const struct sockaddr_in6 *srv6;
 223         const struct sockaddr_in *srv;
 224         int ns, ret;
 225
 226         ret = 0;
 227         switch (inp->sin_family) {
 228         case AF_INET6:
 229                 for (ns = 0; ns < _res.nscount; ns++) {
 230                         srv6 = (struct sockaddr_in6 *)get_nsaddr(ns);
 231                         if (srv6->sin6_family == in6p->sin6_family &&
 232                             srv6->sin6_port == in6p->sin6_port &&
 233                             srv6->sin6_scope_id == in6p->sin6_scope_id &&
 234                             (IN6_IS_ADDR_UNSPECIFIED(&srv6->sin6_addr) ||
 235                              IN6_ARE_ADDR_EQUAL(&srv6->sin6_addr,
 236                                  &in6p->sin6_addr))) {
 237                                 ret++;
 238                                 break;
 239                         }
 240                 }
 241                 break;
 242         case AF_INET:
 243                 for (ns = 0; ns < _res.nscount; ns++) {
 244                         srv = (struct sockaddr_in *)get_nsaddr(ns);
 245                         if (srv->sin_family == inp->sin_family &&
 246                             srv->sin_port == inp->sin_port &&
 247                             (srv->sin_addr.s_addr == INADDR_ANY ||
 248                              srv->sin_addr.s_addr == inp->sin_addr.s_addr)) {
 249                                 ret++;
 250                                 break;
 251                         }
 252                 }
 253                 break;
 254         }
 255         return (ret);
 256 }
 257
 258 /* int
 259  * res_nameinquery(name, type, class, buf, eom)
 260  *      look for (name,type,class) in the query section of packet (buf,eom)
 261  * requires:
 262  *      buf + HFIXEDSZ <= eom
 263  * returns:
 264  *      -1 : format error
 265  *      0  : not found
 266  *      >0 : found
 267  * author:
 268  *      paul vixie, 29may94
 269  */
 270 int
 271 res_nameinquery(name, type, class, buf, eom)
 272         const char *name;
 273         int type, class;
 274         const u_char *buf, *eom;
 275 {
 276         const u_char *cp = buf + HFIXEDSZ;
 277         int qdcount = ntohs(((HEADER*)buf)->qdcount);
 278
 279         while (qdcount-- > 0) {
 280                 char tname[MAXDNAME+1];
 281                 int n, ttype, tclass;
 282
 283                 n = dn_expand(buf, eom, cp, tname, sizeof tname);
 284                 if (n < 0)
 285                         return (-1);
 286                 cp += n;
 287                 if (cp + 2 * INT16SZ > eom)
 288                         return (-1);
 289                 ttype = ns_get16(cp); cp += INT16SZ;
 290                 tclass = ns_get16(cp); cp += INT16SZ;
 291                 if (ttype == type &&
 292                     tclass == class &&
 293                     strcasecmp(tname, name) == 0)
 294                         return (1);
 295         }
 296         return (0);
 297 }
 298
 299 /* int
 300  * res_queriesmatch(buf1, eom1, buf2, eom2)
 301  *      is there a 1:1 mapping of (name,type,class)
 302  *      in (buf1,eom1) and (buf2,eom2)?
 303  * returns:
 304  *      -1 : format error
 305  *      0  : not a 1:1 mapping
 306  *      >0 : is a 1:1 mapping
 307  * author:
 308  *      paul vixie, 29may94
 309  */
 310 int
 311 res_queriesmatch(buf1, eom1, buf2, eom2)
 312         const u_char *buf1, *eom1;
 313         const u_char *buf2, *eom2;
 314 {
 315         const u_char *cp = buf1 + HFIXEDSZ;
 316         int qdcount = ntohs(((HEADER*)buf1)->qdcount);
 317
 318         if (buf1 + HFIXEDSZ > eom1 || buf2 + HFIXEDSZ > eom2)
 319                 return (-1);
 320
 321         /*
 322          * Only header section present in replies to
 323          * dynamic update packets.
 324          */
 325         if ( (((HEADER *)buf1)->opcode == ns_o_update) &&
 326              (((HEADER *)buf2)->opcode == ns_o_update) )
 327                 return (1);
 328
 329         if (qdcount != ntohs(((HEADER*)buf2)->qdcount))
 330                 return (0);
 331         while (qdcount-- > 0) {
 332                 char tname[MAXDNAME+1];
 333                 int n, ttype, tclass;
 334
 335                 n = dn_expand(buf1, eom1, cp, tname, sizeof tname);
 336                 if (n < 0)
 337                         return (-1);
 338                 cp += n;
 339                 if (cp + 2 * INT16SZ > eom1)
 340                         return (-1);
 341                 ttype = ns_get16(cp);   cp += INT16SZ;
 342                 tclass = ns_get16(cp); cp += INT16SZ;
 343                 if (!res_nameinquery(tname, ttype, tclass, buf2, eom2))
 344                         return (0);
 345         }
 346         return (1);
 347 }
 348
 349 int
 350 res_send(buf, buflen, ans, anssiz)
 351         const u_char *buf;
 352         int buflen;
 353         u_char *ans;
 354         int anssiz;
 355 {
 356         HEADER *hp = (HEADER *) buf;
 357         HEADER *anhp = (HEADER *) ans;
 358         int gotsomewhere, connreset, terrno, try, v_circuit, resplen, ns, n;
 359         int kq;
 360         u_int badns;    /* XXX NSMAX can't exceed #/bits in this variable */
 361
 362         if ((_res.options & RES_INIT) == 0 && res_init() == -1) {
 363                 /* errno should have been set by res_init() in this case. */
 364                 return (-1);
 365         }
 366         if (anssiz < HFIXEDSZ) {
 367                 errno = EINVAL;
 368                 return (-1);
 369         }
 370         DprintQ((_res.options & RES_DEBUG) || (_res.pfcode & RES_PRF_QUERY),
 371                 (stdout, ";; res_send()\n"), buf, buflen);
 372         v_circuit = (_res.options & RES_USEVC) || buflen > PACKETSZ;
 373         gotsomewhere = 0;
 374         connreset = 0;
 375         terrno = ETIMEDOUT;
 376         badns = 0;
 377
 378         if ((kq = kqueue()) < 0) {
 379                 Perror(stderr, "kqueue", errno);
 380                 return (-1);
 381         }
 382
 383         /*
 384          * Send request, RETRY times, or until successful
 385          */
 386         for (try = 0; try < _res.retry; try++) {
 387             for (ns = 0; ns < _res.nscount; ns++) {
 388                 struct sockaddr *nsap = get_nsaddr(ns);
 389                 socklen_t salen;
 390
 391                 if (nsap->sa_len)
 392                         salen = nsap->sa_len;
 393                 else if (nsap->sa_family == AF_INET6)
 394                         salen = sizeof(struct sockaddr_in6);
 395                 else if (nsap->sa_family == AF_INET)
 396                         salen = sizeof(struct sockaddr_in);
 397                 else
 398                         salen = 0;      /*unknown, die on connect*/
 399
 400     same_ns:
 401                 if (badns & (1 << ns)) {
 402                         res_close();
 403                         goto next_ns;
 404                 }
 405
 406                 if (Qhook) {
 407                         int done = 0, loops = 0;
 408
 409                         do {
 410                                 res_sendhookact act;
 411
 412                                 act = (*Qhook)((struct sockaddr_in **)&nsap,
 413                                                &buf, &buflen,
 414                                                ans, anssiz, &resplen);
 415                                 switch (act) {
 416                                 case res_goahead:
 417                                         done = 1;
 418                                         break;
 419                                 case res_nextns:
 420                                         res_close();
 421                                         goto next_ns;
 422                                 case res_done:
 423                                         _close(kq);
 424                                         return (resplen);
 425                                 case res_modified:
 426                                         /* give the hook another try */
 427                                         if (++loops < 42) /*doug adams*/
 428                                                 break;
 429                                         /*FALLTHROUGH*/
 430                                 case res_error:
 431                                         /*FALLTHROUGH*/
 432                                 default:
 433                                         _close(kq);
 434                                         return (-1);
 435                                 }
 436                         } while (!done);
 437                 }
 438
 439                 Dprint((_res.options & RES_DEBUG) &&
 440                        getnameinfo(nsap, salen, abuf, sizeof(abuf),
 441                            NULL, 0, NI_NUMERICHOST | NI_WITHSCOPEID) == 0,
 442                        (stdout, ";; Querying server (# %d) address = %s\n",
 443                         ns + 1, abuf));
 444
 445                 if (v_circuit) {
 446                         int truncated;
 447                         struct iovec iov[2];
 448                         u_short len;
 449                         u_char *cp;
 450
 451                         /*
 452                          * Use virtual circuit;
 453                          * at most one attempt per server.
 454                          */
 455                         try = _res.retry;
 456                         truncated = 0;
 457                         if (s < 0 || !vc || hp->opcode == ns_o_update ||
 458                             af != nsap->sa_family) {
 459                                 if (s >= 0)
 460                                         res_close();
 461
 462                                 af = nsap->sa_family;
 463                                 s = socket(af, SOCK_STREAM, 0);
 464                                 if (s < 0) {
 465                                         terrno = errno;
 466                                         Perror(stderr, "socket(vc)", errno);
 467                                         badns |= (1 << ns);
 468                                         res_close();
 469                                         goto next_ns;
 470                                 }
 471                                 errno = 0;
 472                                 if (connect(s, nsap, salen) < 0) {
 473                                         terrno = errno;
 474                                         Aerror(stderr, "connect/vc",
 475                                                errno, nsap);
 476                                         badns |= (1 << ns);
 477                                         res_close();
 478                                         goto next_ns;
 479                                 }
 480                                 vc = 1;
 481                         }
 482                         /*
 483                          * Send length & message
 484                          */
 485                         putshort((u_short)buflen, (u_char*)&len);
 486                         iov[0].iov_base = (caddr_t)&len;
 487                         iov[0].iov_len = INT16SZ;
 488                         iov[1].iov_base = (caddr_t)buf;
 489                         iov[1].iov_len = buflen;
 490                         if (writev(s, iov, 2) != (INT16SZ + buflen)) {
 491                                 terrno = errno;
 492                                 Perror(stderr, "write failed", errno);
 493                                 badns |= (1 << ns);
 494                                 res_close();
 495                                 goto next_ns;
 496                         }
 497                         /*
 498                          * Receive length & response
 499                          */
 500 read_len:
 501                         cp = ans;
 502                         len = INT16SZ;
 503                         while ((n = _read(s, (char *)cp, (int)len)) > 0) {
 504                                 cp += n;
 505                                 if ((len -= n) <= 0)
 506                                         break;
 507                         }
 508                         if (n <= 0) {
 509                                 terrno = errno;
 510                                 Perror(stderr, "read failed", errno);
 511                                 res_close();
 512                                 /*
 513                                  * A long running process might get its TCP
 514                                  * connection reset if the remote server was
 515                                  * restarted.  Requery the server instead of
 516                                  * trying a new one.  When there is only one
 517                                  * server, this means that a query might work
 518                                  * instead of failing.  We only allow one reset
 519                                  * per query to prevent looping.
 520                                  */
 521                                 if (terrno == ECONNRESET && !connreset) {
 522                                         connreset = 1;
 523                                         res_close();
 524                                         goto same_ns;
 525                                 }
 526                                 res_close();
 527                                 goto next_ns;
 528                         }
 529                         resplen = ns_get16(ans);
 530                         if (resplen > anssiz) {
 531                                 Dprint(_res.options & RES_DEBUG,
 532                                        (stdout, ";; response truncated\n")
 533                                        );
 534                                 truncated = 1;
 535                                 len = anssiz;
 536                         } else
 537                                 len = resplen;
 538                         if (len < HFIXEDSZ) {
 539                                 /*
 540                                  * Undersized message.
 541                                  */
 542                                 Dprint(_res.options & RES_DEBUG,
 543                                        (stdout, ";; undersized: %d\n", len));
 544                                 terrno = EMSGSIZE;
 545                                 badns |= (1 << ns);
 546                                 res_close();
 547                                 goto next_ns;
 548                         }
 549                         cp = ans;
 550                         while (len != 0 &&
 551                                (n = _read(s, (char *)cp, (int)len)) > 0) {
 552                                 cp += n;
 553                                 len -= n;
 554                         }
 555                         if (n <= 0) {
 556                                 terrno = errno;
 557                                 Perror(stderr, "read(vc)", errno);
 558                                 res_close();
 559                                 goto next_ns;
 560                         }
 561                         if (truncated) {
 562                                 /*
 563                                  * Flush rest of answer
 564                                  * so connection stays in synch.
 565                                  */
 566                                 anhp->tc = 1;
 567                                 len = resplen - anssiz;
 568                                 while (len != 0) {
 569                                         char junk[PACKETSZ];
 570
 571                                         n = (len > sizeof(junk)
 572                                              ? sizeof(junk)
 573                                              : len);
 574                                         if ((n = _read(s, junk, n)) > 0)
 575                                                 len -= n;
 576                                         else
 577                                                 break;
 578                                 }
 579                         }
 580                         /*
 581                          * The calling applicating has bailed out of
 582                          * a previous call and failed to arrange to have
 583                          * the circuit closed or the server has got
 584                          * itself confused. Anyway drop the packet and
 585                          * wait for the correct one.
 586                          */
 587                         if (hp->id != anhp->id) {
 588                                 DprintQ((_res.options & RES_DEBUG) ||
 589                                         (_res.pfcode & RES_PRF_REPLY),
 590                                         (stdout, ";; old answer (unexpected):\n"),
 591                                         ans, (resplen>anssiz)?anssiz:resplen);
 592                                 goto read_len;
 593                         }
 594                 } else {
 595                         /*
 596                          * Use datagrams.
 597                          */
 598                         struct kevent kv;
 599                         struct timespec ts;
 600                         struct timeval timeout, ctv;
 601                         struct sockaddr_storage from;
 602                         int fromlen;
 603
 604                         if (s < 0 || vc || af != nsap->sa_family) {
 605                                 if (vc)
 606                                         res_close();
 607                                 af = nsap->sa_family;
 608                                 s = socket(af, SOCK_DGRAM, 0);
 609                                 if (s < 0) {
 610 #ifndef CAN_RECONNECT
 611  bad_dg_sock:
 612 #endif
 613                                         terrno = errno;
 614                                         Perror(stderr, "socket(dg)", errno);
 615                                         badns |= (1 << ns);
 616                                         res_close();
 617                                         goto next_ns;
 618                                 }
 619                                 connected = 0;
 620                         }
 621 #ifndef CANNOT_CONNECT_DGRAM
 622                         /*
 623                          * On a 4.3BSD+ machine (client and server,
 624                          * actually), sending to a nameserver datagram
 625                          * port with no nameserver will cause an
 626                          * ICMP port unreachable message to be returned.
 627                          * If our datagram socket is "connected" to the
 628                          * server, we get an ECONNREFUSED error on the next
 629                          * socket operation, and select returns if the
 630                          * error message is received.  We can thus detect
 631                          * the absence of a nameserver without timing out.
 632                          * If we have sent queries to at least two servers,
 633                          * however, we don't want to remain connected,
 634                          * as we wish to receive answers from the first
 635                          * server to respond.
 636                          *
 637                          * When the option "insecure1" is specified, we'd
 638                          * rather expect to see responses from an "unknown"
 639                          * address.  In order to let the kernel accept such
 640                          * responses, do not connect the socket here.
 641                          * XXX: or do we need an explicit option to disable
 642                          * connecting?
 643                          */
 644                         if (!(_res.options & RES_INSECURE1) &&
 645                             (_res.nscount == 1 || (try == 0 && ns == 0))) {
 646                                 /*
 647                                  * Connect only if we are sure we won't
 648                                  * receive a response from another server.
 649                                  */
 650                                 if (!connected) {
 651                                         if (connect(s, nsap, salen) < 0) {
 652                                                 Aerror(stderr,
 653                                                        "connect(dg)",
 654                                                        errno, nsap);
 655                                                 badns |= (1 << ns);
 656                                                 res_close();
 657                                                 goto next_ns;
 658                                         }
 659                                         connected = 1;
 660                                 }
 661                                 if (send(s, (char*)buf, buflen, 0) != buflen) {
 662                                         Perror(stderr, "send", errno);
 663                                         badns |= (1 << ns);
 664                                         res_close();
 665                                         goto next_ns;
 666                                 }
 667                         } else {
 668                                 /*
 669                                  * Disconnect if we want to listen
 670                                  * for responses from more than one server.
 671                                  */
 672                                 if (connected) {
 673 #ifdef CAN_RECONNECT
 674                                         /* XXX: any errornous address */
 675                                         struct sockaddr_in no_addr;
 676
 677                                         no_addr.sin_family = AF_INET;
 678                                         no_addr.sin_addr.s_addr = INADDR_ANY;
 679                                         no_addr.sin_port = 0;
 680                                         (void) connect(s,
 681                                                        (struct sockaddr *)
 682                                                         &no_addr,
 683                                                        sizeof no_addr);
 684 #else
 685                                         int s1 = socket(af, SOCK_DGRAM,0);
 686                                         if (s1 < 0)
 687                                                 goto bad_dg_sock;
 688                                         (void)dup2(s1, s);
 689                                         (void)_close(s1);
 690                                         Dprint(_res.options & RES_DEBUG,
 691                                                 (stdout, ";; new DG socket\n"))
 692 #endif /* CAN_RECONNECT */
 693                                         connected = 0;
 694                                         errno = 0;
 695                                 }
 696 #endif /* !CANNOT_CONNECT_DGRAM */
 697                                 if (sendto(s, (char*)buf, buflen, 0,
 698                                            nsap, salen) != buflen) {
 699                                         Aerror(stderr, "sendto", errno, nsap);
 700                                         badns |= (1 << ns);
 701                                         res_close();
 702                                         goto next_ns;
 703                                 }
 704 #ifndef CANNOT_CONNECT_DGRAM
 705                         }
 706 #endif /* !CANNOT_CONNECT_DGRAM */
 707
 708                         /*
 709                          * Wait for reply
 710                          */
 711
 712                         timeout.tv_sec = (_res.retrans << try);
 713                         if (try > 0)
 714                                 timeout.tv_sec /= _res.nscount;
 715                         if ((long) timeout.tv_sec <= 0)
 716                                 timeout.tv_sec = 1;
 717                         timeout.tv_usec = 0;
 718                         TIMEVAL_TO_TIMESPEC(&timeout, &ts);
 719                         (void) gettimeofday(&ctv, NULL);
 720                         timeradd(&timeout, &ctv, &timeout);
 721     wait:
 722                         if (s < 0) {
 723                                 Perror(stderr, "s out-of-bounds", EMFILE);
 724                                 res_close();
 725                                 goto next_ns;
 726                         }
 727
 728                         EV_SET(&kv, s, EVFILT_READ, EV_ADD | EV_ONESHOT, 0,0,0);
 729
 730                         n = kevent(kq, &kv, 1, &kv, 1, &ts);
 731                         if (n < 0) {
 732                                 if (errno == EINTR) {
 733                                         (void) gettimeofday(&ctv, NULL);
 734                                         if (timercmp(&ctv, &timeout, <)) {
 735                                                 timersub(&timeout, &ctv, &ctv);
 736                                                 TIMEVAL_TO_TIMESPEC(&ctv, &ts);
 737                                                 goto wait;
 738                                         }
 739                                 }
 740                                 Perror(stderr, "kevent", errno);
 741                                 res_close();
 742                                 goto next_ns;
 743                         }
 744
 745                         if (n == 0) {
 746                                 /*
 747                                  * timeout
 748                                  */
 749                                 Dprint(_res.options & RES_DEBUG,
 750                                        (stdout, ";; timeout\n"));
 751                                 gotsomewhere = 1;
 752                                 res_close();
 753                                 goto next_ns;
 754                         }
 755                         errno = 0;
 756                         fromlen = sizeof(from);
 757                         resplen = recvfrom(s, (char*)ans, anssiz, 0,
 758                                            (struct sockaddr *)&from, &fromlen);
 759                         if (resplen <= 0) {
 760                                 Perror(stderr, "recvfrom", errno);
 761                                 res_close();
 762                                 goto next_ns;
 763                         }
 764                         gotsomewhere = 1;
 765                         if (resplen < HFIXEDSZ) {
 766                                 /*
 767                                  * Undersized message.
 768                                  */
 769                                 Dprint(_res.options & RES_DEBUG,
 770                                        (stdout, ";; undersized: %d\n",
 771                                         resplen));
 772                                 terrno = EMSGSIZE;
 773                                 badns |= (1 << ns);
 774                                 res_close();
 775                                 goto next_ns;
 776                         }
 777                         if (hp->id != anhp->id) {
 778                                 /*
 779                                  * response from old query, ignore it.
 780                                  * XXX - potential security hazard could
 781                                  *       be detected here.
 782                                  */
 783                                 DprintQ((_res.options & RES_DEBUG) ||
 784                                         (_res.pfcode & RES_PRF_REPLY),
 785                                         (stdout, ";; old answer:\n"),
 786                                         ans, (resplen>anssiz)?anssiz:resplen);
 787                                 goto wait;
 788                         }
 789 #ifdef CHECK_SRVR_ADDR
 790                         if (!(_res.options & RES_INSECURE1) &&
 791                             !res_isourserver((struct sockaddr_in *)&from)) {
 792                                 /*
 793                                  * response from wrong server? ignore it.
 794                                  * XXX - potential security hazard could
 795                                  *       be detected here.
 796                                  */
 797                                 DprintQ((_res.options & RES_DEBUG) ||
 798                                         (_res.pfcode & RES_PRF_REPLY),
 799                                         (stdout, ";; not our server:\n"),
 800                                         ans, (resplen>anssiz)?anssiz:resplen);
 801                                 goto wait;
 802                         }
 803 #endif
 804                         if (!(_res.options & RES_INSECURE2) &&
 805                             !res_queriesmatch(buf, buf + buflen,
 806                                               ans, ans + anssiz)) {
 807                                 /*
 808                                  * response contains wrong query? ignore it.
 809                                  * XXX - potential security hazard could
 810                                  *       be detected here.
 811                                  */
 812                                 DprintQ((_res.options & RES_DEBUG) ||
 813                                         (_res.pfcode & RES_PRF_REPLY),
 814                                         (stdout, ";; wrong query name:\n"),
 815                                         ans, (resplen>anssiz)?anssiz:resplen);
 816                                 goto wait;
 817                         }
 818                         if (anhp->rcode == SERVFAIL ||
 819                             anhp->rcode == NOTIMP ||
 820                             anhp->rcode == REFUSED) {
 821                                 DprintQ(_res.options & RES_DEBUG,
 822                                         (stdout, "server rejected query:\n"),
 823                                         ans, (resplen>anssiz)?anssiz:resplen);
 824                                 badns |= (1 << ns);
 825                                 res_close();
 826                                 /* don't retry if called from dig */
 827                                 if (!_res.pfcode)
 828                                         goto next_ns;
 829                         }
 830                         if (!(_res.options & RES_IGNTC) && anhp->tc) {
 831                                 /*
 832                                  * get rest of answer;
 833                                  * use TCP with same server.
 834                                  */
 835                                 Dprint(_res.options & RES_DEBUG,
 836                                        (stdout, ";; truncated answer\n"));
 837                                 v_circuit = 1;
 838                                 res_close();
 839                                 goto same_ns;
 840                         }
 841                 } /*if vc/dg*/
 842                 Dprint((_res.options & RES_DEBUG) ||
 843                        ((_res.pfcode & RES_PRF_REPLY) &&
 844                         (_res.pfcode & RES_PRF_HEAD1)),
 845                        (stdout, ";; got answer:\n"));
 846                 DprintQ((_res.options & RES_DEBUG) ||
 847                         (_res.pfcode & RES_PRF_REPLY),
 848                         (stdout, ""),
 849                         ans, (resplen>anssiz)?anssiz:resplen);
 850                 /*
 851                  * If using virtual circuits, we assume that the first server
 852                  * is preferred over the rest (i.e. it is on the local
 853                  * machine) and only keep that one open.
 854                  * If we have temporarily opened a virtual circuit,
 855                  * or if we haven't been asked to keep a socket open,
 856                  * close the socket.
 857                  */
 858                 if ((v_circuit && (!(_res.options & RES_USEVC) || ns != 0)) ||
 859                     !(_res.options & RES_STAYOPEN)) {
 860                         res_close();
 861                 }
 862                 if (Rhook) {
 863                         int done = 0, loops = 0;
 864
 865                         do {
 866                                 res_sendhookact act;
 867
 868                                 act = (*Rhook)((struct sockaddr_in *)nsap,
 869                                                buf, buflen,
 870                                                ans, anssiz, &resplen);
 871                                 switch (act) {
 872                                 case res_goahead:
 873                                 case res_done:
 874                                         done = 1;
 875                                         break;
 876                                 case res_nextns:
 877                                         res_close();
 878                                         goto next_ns;
 879                                 case res_modified:
 880                                         /* give the hook another try */
 881                                         if (++loops < 42) /*doug adams*/
 882                                                 break;
 883                                         /*FALLTHROUGH*/
 884                                 case res_error:
 885                                         /*FALLTHROUGH*/
 886                                 default:
 887                                         _close(kq);
 888                                         return (-1);
 889                                 }
 890                         } while (!done);
 891
 892                 }
 893                 _close(kq);
 894                 return (resplen);
 895     next_ns: ;
 896            } /*foreach ns*/
 897         } /*foreach retry*/
 898         res_close();
 899         _close(kq);
 900         if (!v_circuit) {
 901                 if (!gotsomewhere)
 902                         errno = ECONNREFUSED;   /* no nameservers found */
 903                 else
 904                         errno = ETIMEDOUT;      /* no answer obtained */
 905         } else
 906                 errno = terrno;
 907         return (-1);
 908 }
 909
 910 /*
 911  * This routine is for closing the socket if a virtual circuit is used and
 912  * the program wants to close it.  This provides support for endhostent()
 913  * which expects to close the socket.
 914  *
 915  * This routine is not expected to be user visible.
 916  */
 917 void
 918 res_close()
 919 {
 920         if (s >= 0) {
 921                 (void)_close(s);
 922                 s = -1;
 923                 connected = 0;
 924                 vc = 0;
 925                 af = 0;
 926         }
 927 }
 928
 929 /*
 930  * Weak aliases for applications that use certain private entry points,
 931  * and fail to include <resolv.h>.
 932  */
 933 #undef res_close
 934 __weak_reference(__res_close, _res_close);
 935 #undef res_send
 936 __weak_reference(__res_send, res_send);