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
  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 $";
  74 #endif /* LIBC_SCCS and not lint */
  75 #include <sys/cdefs.h>
  76 __FBSDID("$FreeBSD$");
  77
  78 /*
  79  * Send query to name server and wait for reply.
  80  */
  81
  82 #include "namespace.h"
  83 #include <sys/types.h>
  84 #include <sys/event.h>
  85 #include <sys/param.h>
  86 #include <sys/time.h>
  87 #include <sys/socket.h>
  88 #include <sys/uio.h>
  89
  90 #include <netinet/in.h>
  91 #include <arpa/nameser.h>
  92 #include <arpa/inet.h>
  93
  94 #include <errno.h>
  95 #include <netdb.h>
  96 #include <resolv.h>
  97 #include <stdio.h>
  98 #include <stdlib.h>
  99 #include <string.h>
 100 #include <unistd.h>
 101 #include "un-namespace.h"
 102
 103 #include "res_config.h"
 104 #include "res_send_private.h"
 105
 106
 107 #define s               ___res_send_private()->s
 108 #define connected       ___res_send_private()->connected
 109 #define vc              ___res_send_private()->vc
 110 #define af              ___res_send_private()->af
 111 #define Qhook           ___res_send_private()->Qhook
 112 #define Rhook           ___res_send_private()->Rhook
 113
 114 #define CAN_RECONNECT 1
 115
 116 #ifndef DEBUG
 117 #   define Dprint(cond, args) /*empty*/
 118 #   define DprintQ(cond, args, query, size) /*empty*/
 119 #   define Aerror(file, string, error, address) /*empty*/
 120 #   define Perror(file, string, error) /*empty*/
 121 #else
 122 #   define Dprint(cond, args) if (cond) {fprintf args;} else {}
 123 #   define DprintQ(cond, args, query, size) if (cond) {\
 124                         fprintf args;\
 125                         __fp_nquery(query, size, stdout);\
 126                 } else {}
 127 static void Aerror(FILE *, char *, int, struct sockaddr *);
 128 static void Perror(FILE *, char *, int);
 129
 130     static void
 131     Aerror(file, string, error, address)
 132         FILE *file;
 133         char *string;
 134         int error;
 135         struct sockaddr *address;
 136     {
 137         int save = errno;
 138
 139         if (_res.options & RES_DEBUG) {
 140                 char abuf[NI_MAXHOST];
 141                 char pbuf[NI_MAXSERV];
 142
 143                 if (getnameinfo(address, address->sa_len, abuf, sizeof(abuf),
 144                     pbuf, sizeof(pbuf), NI_NUMERICHOST|NI_NUMERICSERV) != 0) {
 145                         strncpy(abuf, "?", sizeof(abuf));
 146                         strncpy(pbuf, "?", sizeof(pbuf));
 147                 }
 148                 fprintf(file, "res_send: %s ([%s].%s): %s\n",
 149                         string, abuf, pbuf, strerror(error));
 150         }
 151         errno = save;
 152     }
 153     static void
 154     Perror(file, string, error)
 155         FILE *file;
 156         char *string;
 157         int error;
 158     {
 159         int save = errno;
 160
 161         if (_res.options & RES_DEBUG) {
 162                 fprintf(file, "res_send: %s: %s\n",
 163                         string, strerror(error));
 164         }
 165         errno = save;
 166     }
 167 #endif
 168
 169 void
 170 res_send_setqhook(hook)
 171         res_send_qhook hook;
 172 {
 173
 174         Qhook = hook;
 175 }
 176
 177 void
 178 res_send_setrhook(hook)
 179         res_send_rhook hook;
 180 {
 181
 182         Rhook = hook;
 183 }
 184
 185 static struct sockaddr * get_nsaddr(size_t);
 186
 187 /*
 188  * pick appropriate nsaddr_list for use.  see res_init() for initialization.
 189  */
 190 static struct sockaddr *
 191 get_nsaddr(n)
 192         size_t n;
 193 {
 194
 195         if (!_res.nsaddr_list[n].sin_family) {
 196                 /*
 197                  * - _res_ext.nsaddr_list[n] holds an address that is larger
 198                  *   than struct sockaddr, and
 199                  * - user code did not update _res.nsaddr_list[n].
 200                  */
 201                 return (struct sockaddr *)&_res_ext.nsaddr_list[n];
 202         } else {
 203                 /*
 204                  * - user code updated _res.nsaddr_list[n], or
 205                  * - _res.nsaddr_list[n] has the same content as
 206                  *   _res_ext.nsaddr_list[n].
 207                  */
 208                 return (struct sockaddr *)&_res.nsaddr_list[n];
 209         }
 210 }
 211
 212 /* int
 213  * res_isourserver(ina)
 214  *      looks up "ina" in _res.ns_addr_list[]
 215  * returns:
 216  *      0  : not found
 217  *      >0 : found
 218  * author:
 219  *      paul vixie, 29may94
 220  */
 221 int
 222 res_isourserver(inp)
 223         const struct sockaddr_in *inp;
 224 {
 225         const struct sockaddr_in6 *in6p = (const struct sockaddr_in6 *)inp;
 226         const struct sockaddr_in6 *srv6;
 227         const struct sockaddr_in *srv;
 228         int ns, ret;
 229
 230         ret = 0;
 231         switch (inp->sin_family) {
 232         case AF_INET6:
 233                 for (ns = 0; ns < _res.nscount; ns++) {
 234                         srv6 = (struct sockaddr_in6 *)get_nsaddr(ns);
 235                         if (srv6->sin6_family == in6p->sin6_family &&
 236                             srv6->sin6_port == in6p->sin6_port &&
 237                             srv6->sin6_scope_id == in6p->sin6_scope_id &&
 238                             (IN6_IS_ADDR_UNSPECIFIED(&srv6->sin6_addr) ||
 239                              IN6_ARE_ADDR_EQUAL(&srv6->sin6_addr,
 240                                  &in6p->sin6_addr))) {
 241                                 ret++;
 242                                 break;
 243                         }
 244                 }
 245                 break;
 246         case AF_INET:
 247                 for (ns = 0; ns < _res.nscount; ns++) {
 248                         srv = (struct sockaddr_in *)get_nsaddr(ns);
 249                         if (srv->sin_family == inp->sin_family &&
 250                             srv->sin_port == inp->sin_port &&
 251                             (srv->sin_addr.s_addr == INADDR_ANY ||
 252                              srv->sin_addr.s_addr == inp->sin_addr.s_addr)) {
 253                                 ret++;
 254                                 break;
 255                         }
 256                 }
 257                 break;
 258         }
 259         return (ret);
 260 }
 261
 262 /* int
 263  * res_nameinquery(name, type, class, buf, eom)
 264  *      look for (name,type,class) in the query section of packet (buf,eom)
 265  * requires:
 266  *      buf + HFIXEDSZ <= eom
 267  * returns:
 268  *      -1 : format error
 269  *      0  : not found
 270  *      >0 : found
 271  * author:
 272  *      paul vixie, 29may94
 273  */
 274 int
 275 res_nameinquery(name, type, class, buf, eom)
 276         const char *name;
 277         int type, class;
 278         const u_char *buf, *eom;
 279 {
 280         const u_char *cp = buf + HFIXEDSZ;
 281         int qdcount = ntohs(((HEADER*)buf)->qdcount);
 282
 283         while (qdcount-- > 0) {
 284                 char tname[MAXDNAME+1];
 285                 int n, ttype, tclass;
 286
 287                 n = dn_expand(buf, eom, cp, tname, sizeof tname);
 288                 if (n < 0)
 289                         return (-1);
 290                 cp += n;
 291                 if (cp + 2 * INT16SZ > eom)
 292                         return (-1);
 293                 ttype = ns_get16(cp); cp += INT16SZ;
 294                 tclass = ns_get16(cp); cp += INT16SZ;
 295                 if (ttype == type &&
 296                     tclass == class &&
 297                     strcasecmp(tname, name) == 0)
 298                         return (1);
 299         }
 300         return (0);
 301 }
 302
 303 /* int
 304  * res_queriesmatch(buf1, eom1, buf2, eom2)
 305  *      is there a 1:1 mapping of (name,type,class)
 306  *      in (buf1,eom1) and (buf2,eom2)?
 307  * returns:
 308  *      -1 : format error
 309  *      0  : not a 1:1 mapping
 310  *      >0 : is a 1:1 mapping
 311  * author:
 312  *      paul vixie, 29may94
 313  */
 314 int
 315 res_queriesmatch(buf1, eom1, buf2, eom2)
 316         const u_char *buf1, *eom1;
 317         const u_char *buf2, *eom2;
 318 {
 319         const u_char *cp = buf1 + HFIXEDSZ;
 320         int qdcount = ntohs(((HEADER*)buf1)->qdcount);
 321
 322         if (buf1 + HFIXEDSZ > eom1 || buf2 + HFIXEDSZ > eom2)
 323                 return (-1);
 324
 325         /*
 326          * Only header section present in replies to
 327          * dynamic update packets.
 328          */
 329         if ( (((HEADER *)buf1)->opcode == ns_o_update) &&
 330              (((HEADER *)buf2)->opcode == ns_o_update) )
 331                 return (1);
 332
 333         if (qdcount != ntohs(((HEADER*)buf2)->qdcount))
 334                 return (0);
 335         while (qdcount-- > 0) {
 336                 char tname[MAXDNAME+1];
 337                 int n, ttype, tclass;
 338
 339                 n = dn_expand(buf1, eom1, cp, tname, sizeof tname);
 340                 if (n < 0)
 341                         return (-1);
 342                 cp += n;
 343                 if (cp + 2 * INT16SZ > eom1)
 344                         return (-1);
 345                 ttype = ns_get16(cp);   cp += INT16SZ;
 346                 tclass = ns_get16(cp); cp += INT16SZ;
 347                 if (!res_nameinquery(tname, ttype, tclass, buf2, eom2))
 348                         return (0);
 349         }
 350         return (1);
 351 }
 352
 353 int
 354 res_send(buf, buflen, ans, anssiz)
 355         const u_char *buf;
 356         int buflen;
 357         u_char *ans;
 358         int anssiz;
 359 {
 360         HEADER *hp = (HEADER *) buf;
 361         HEADER *anhp = (HEADER *) ans;
 362         int gotsomewhere, connreset, terrno, try, v_circuit, resplen, ns, n;
 363         int kq;
 364         u_int badns;    /* XXX NSMAX can't exceed #/bits in this variable */
 365
 366         if ((_res.options & RES_INIT) == 0 && res_init() == -1) {
 367                 /* errno should have been set by res_init() in this case. */
 368                 return (-1);
 369         }
 370         if (anssiz < HFIXEDSZ) {
 371                 errno = EINVAL;
 372                 return (-1);
 373         }
 374         DprintQ((_res.options & RES_DEBUG) || (_res.pfcode & RES_PRF_QUERY),
 375                 (stdout, ";; res_send()\n"), buf, buflen);
 376         v_circuit = (_res.options & RES_USEVC) || buflen > PACKETSZ;
 377         gotsomewhere = 0;
 378         connreset = 0;
 379         terrno = ETIMEDOUT;
 380         badns = 0;
 381
 382         if ((kq = kqueue()) < 0) {
 383                 Perror(stderr, "kqueue", errno);
 384                 return (-1);
 385         }
 386
 387         /*
 388          * Send request, RETRY times, or until successful
 389          */
 390         for (try = 0; try < _res.retry; try++) {
 391             for (ns = 0; ns < _res.nscount; ns++) {
 392                 char abuf[NI_MAXHOST];
 393                 struct sockaddr *nsap = get_nsaddr(ns);
 394                 socklen_t salen;
 395
 396                 if (nsap->sa_len)
 397                         salen = nsap->sa_len;
 398                 else if (nsap->sa_family == AF_INET6)
 399                         salen = sizeof(struct sockaddr_in6);
 400                 else if (nsap->sa_family == AF_INET)
 401                         salen = sizeof(struct sockaddr_in);
 402                 else
 403                         salen = 0;      /*unknown, die on connect*/
 404
 405     same_ns:
 406                 if (badns & (1 << ns)) {
 407                         res_close();
 408                         goto next_ns;
 409                 }
 410
 411                 if (Qhook) {
 412                         int done = 0, loops = 0;
 413
 414                         do {
 415                                 res_sendhookact act;
 416
 417                                 act = (*Qhook)(&nsap,
 418                                                &buf, &buflen,
 419                                                ans, anssiz, &resplen);
 420                                 switch (act) {
 421                                 case res_goahead:
 422                                         done = 1;
 423                                         break;
 424                                 case res_nextns:
 425                                         res_close();
 426                                         goto next_ns;
 427                                 case res_done:
 428                                         _close(kq);
 429                                         return (resplen);
 430                                 case res_modified:
 431                                         /* give the hook another try */
 432                                         if (++loops < 42) /*doug adams*/
 433                                                 break;
 434                                         /*FALLTHROUGH*/
 435                                 case res_error:
 436                                         /*FALLTHROUGH*/
 437                                 default:
 438                                         _close(kq);
 439                                         return (-1);
 440                                 }
 441                         } while (!done);
 442                 }
 443
 444                 Dprint((_res.options & RES_DEBUG) &&
 445                        getnameinfo(nsap, salen, abuf, sizeof(abuf),
 446                            NULL, 0, NI_NUMERICHOST) == 0,
 447                        (stdout, ";; Querying server (# %d) address = %s\n",
 448                         ns + 1, abuf));
 449
 450                 if (v_circuit) {
 451                         int truncated;
 452                         struct iovec iov[2];
 453                         u_short len;
 454                         u_char *cp;
 455
 456                         /*
 457                          * Use virtual circuit;
 458                          * at most one attempt per server.
 459                          */
 460                         try = _res.retry;
 461                         truncated = 0;
 462                         if (s < 0 || !vc || hp->opcode == ns_o_update ||
 463                             af != nsap->sa_family) {
 464                                 if (s >= 0)
 465                                         res_close();
 466
 467                                 af = nsap->sa_family;
 468                                 s = _socket(af, SOCK_STREAM, 0);
 469                                 if (s < 0) {
 470                                         terrno = errno;
 471                                         Perror(stderr, "socket(vc)", errno);
 472                                         badns |= (1 << ns);
 473                                         res_close();
 474                                         goto next_ns;
 475                                 }
 476                                 errno = 0;
 477                                 if (_connect(s, nsap, salen) < 0) {
 478                                         terrno = errno;
 479                                         Aerror(stderr, "connect/vc",
 480                                                errno, nsap);
 481                                         badns |= (1 << ns);
 482                                         res_close();
 483                                         goto next_ns;
 484                                 }
 485                                 vc = 1;
 486                         }
 487                         /*
 488                          * Send length & message
 489                          */
 490                         putshort((u_short)buflen, (u_char*)&len);
 491                         iov[0].iov_base = (caddr_t)&len;
 492                         iov[0].iov_len = INT16SZ;
 493                         iov[1].iov_base = (caddr_t)buf;
 494                         iov[1].iov_len = buflen;
 495                         if (_writev(s, iov, 2) != (INT16SZ + buflen)) {
 496                                 terrno = errno;
 497                                 Perror(stderr, "write failed", errno);
 498                                 badns |= (1 << ns);
 499                                 res_close();
 500                                 goto next_ns;
 501                         }
 502                         /*
 503                          * Receive length & response
 504                          */
 505 read_len:
 506                         cp = ans;
 507                         len = INT16SZ;
 508                         while ((n = _read(s, (char *)cp, (int)len)) > 0) {
 509                                 cp += n;
 510                                 if ((len -= n) <= 0)
 511                                         break;
 512                         }
 513                         if (n <= 0) {
 514                                 terrno = errno;
 515                                 Perror(stderr, "read failed", errno);
 516                                 res_close();
 517                                 /*
 518                                  * A long running process might get its TCP
 519                                  * connection reset if the remote server was
 520                                  * restarted.  Requery the server instead of
 521                                  * trying a new one.  When there is only one
 522                                  * server, this means that a query might work
 523                                  * instead of failing.  We only allow one reset
 524                                  * per query to prevent looping.
 525                                  */
 526                                 if (terrno == ECONNRESET && !connreset) {
 527                                         connreset = 1;
 528                                         res_close();
 529                                         goto same_ns;
 530                                 }
 531                                 res_close();
 532                                 goto next_ns;
 533                         }
 534                         resplen = ns_get16(ans);
 535                         if (resplen > anssiz) {
 536                                 Dprint(_res.options & RES_DEBUG,
 537                                        (stdout, ";; response truncated\n")
 538                                        );
 539                                 truncated = 1;
 540                                 len = anssiz;
 541                         } else
 542                                 len = resplen;
 543                         if (len < HFIXEDSZ) {
 544                                 /*
 545                                  * Undersized message.
 546                                  */
 547                                 Dprint(_res.options & RES_DEBUG,
 548                                        (stdout, ";; undersized: %d\n", len));
 549                                 terrno = EMSGSIZE;
 550                                 badns |= (1 << ns);
 551                                 res_close();
 552                                 goto next_ns;
 553                         }
 554                         cp = ans;
 555                         while (len != 0 &&
 556                                (n = _read(s, (char *)cp, (int)len)) > 0) {
 557                                 cp += n;
 558                                 len -= n;
 559                         }
 560                         if (n <= 0) {
 561                                 terrno = errno;
 562                                 Perror(stderr, "read(vc)", errno);
 563                                 res_close();
 564                                 goto next_ns;
 565                         }
 566                         if (truncated) {
 567                                 /*
 568                                  * Flush rest of answer
 569                                  * so connection stays in synch.
 570                                  */
 571                                 anhp->tc = 1;
 572                                 len = resplen - anssiz;
 573                                 while (len != 0) {
 574                                         char junk[PACKETSZ];
 575
 576                                         n = (len > sizeof(junk)
 577                                              ? sizeof(junk)
 578                                              : len);
 579                                         if ((n = _read(s, junk, n)) > 0)
 580                                                 len -= n;
 581                                         else
 582                                                 break;
 583                                 }
 584                         }
 585                         /*
 586                          * The calling applicating has bailed out of
 587                          * a previous call and failed to arrange to have
 588                          * the circuit closed or the server has got
 589                          * itself confused. Anyway drop the packet and
 590                          * wait for the correct one.
 591                          */
 592                         if (hp->id != anhp->id) {
 593                                 DprintQ((_res.options & RES_DEBUG) ||
 594                                         (_res.pfcode & RES_PRF_REPLY),
 595                                         (stdout, ";; old answer (unexpected):\n"),
 596                                         ans, (resplen>anssiz)?anssiz:resplen);
 597                                 goto read_len;
 598                         }
 599                 } else {
 600                         /*
 601                          * Use datagrams.
 602                          */
 603                         struct kevent kv;
 604                         struct timespec ts;
 605                         struct timeval timeout, ctv;
 606                         struct sockaddr_storage from;
 607                         socklen_t fromlen;
 608
 609                         if (s < 0 || vc || af != nsap->sa_family) {
 610                                 if (vc)
 611                                         res_close();
 612                                 af = nsap->sa_family;
 613                                 s = _socket(af, SOCK_DGRAM, 0);
 614                                 if (s < 0) {
 615 #ifndef CAN_RECONNECT
 616  bad_dg_sock:
 617 #endif
 618                                         terrno = errno;
 619                                         Perror(stderr, "socket(dg)", errno);
 620                                         badns |= (1 << ns);
 621                                         res_close();
 622                                         goto next_ns;
 623                                 }
 624                                 connected = 0;
 625                         }
 626 #ifndef CANNOT_CONNECT_DGRAM
 627                         /*
 628                          * On a 4.3BSD+ machine (client and server,
 629                          * actually), sending to a nameserver datagram
 630                          * port with no nameserver will cause an
 631                          * ICMP port unreachable message to be returned.
 632                          * If our datagram socket is "connected" to the
 633                          * server, we get an ECONNREFUSED error on the next
 634                          * socket operation, and select returns if the
 635                          * error message is received.  We can thus detect
 636                          * the absence of a nameserver without timing out.
 637                          * If we have sent queries to at least two servers,
 638                          * however, we don't want to remain connected,
 639                          * as we wish to receive answers from the first
 640                          * server to respond.
 641                          *
 642                          * When the option "insecure1" is specified, we'd
 643                          * rather expect to see responses from an "unknown"
 644                          * address.  In order to let the kernel accept such
 645                          * responses, do not connect the socket here.
 646                          * XXX: or do we need an explicit option to disable
 647                          * connecting?
 648                          */
 649                         if (!(_res.options & RES_INSECURE1) &&
 650                             (_res.nscount == 1 || (try == 0 && ns == 0))) {
 651                                 /*
 652                                  * Connect only if we are sure we won't
 653                                  * receive a response from another server.
 654                                  */
 655                                 if (!connected) {
 656                                         if (_connect(s, nsap, salen) < 0) {
 657                                                 Aerror(stderr,
 658                                                        "connect(dg)",
 659                                                        errno, nsap);
 660                                                 badns |= (1 << ns);
 661                                                 res_close();
 662                                                 goto next_ns;
 663                                         }
 664                                         connected = 1;
 665                                 }
 666                                 if (send(s, (char*)buf, buflen, 0) != buflen) {
 667                                         Perror(stderr, "send", errno);
 668                                         badns |= (1 << ns);
 669                                         res_close();
 670                                         goto next_ns;
 671                                 }
 672                         } else {
 673                                 /*
 674                                  * Disconnect if we want to listen
 675                                  * for responses from more than one server.
 676                                  */
 677                                 if (connected) {
 678 #ifdef CAN_RECONNECT
 679                                         /* XXX: any errornous address */
 680                                         struct sockaddr_in no_addr;
 681
 682                                         no_addr.sin_family = AF_INET;
 683                                         no_addr.sin_addr.s_addr = INADDR_ANY;
 684                                         no_addr.sin_port = 0;
 685                                         (void) _connect(s,
 686                                                        (struct sockaddr *)
 687                                                         &no_addr,
 688                                                        sizeof no_addr);
 689 #else
 690                                         int s1 = _socket(af, SOCK_DGRAM,0);
 691                                         if (s1 < 0)
 692                                                 goto bad_dg_sock;
 693                                         (void)_dup2(s1, s);
 694                                         (void)_close(s1);
 695                                         Dprint(_res.options & RES_DEBUG,
 696                                                 (stdout, ";; new DG socket\n"))
 697 #endif /* CAN_RECONNECT */
 698                                         connected = 0;
 699                                         errno = 0;
 700                                 }
 701 #endif /* !CANNOT_CONNECT_DGRAM */
 702                                 if (_sendto(s, (char*)buf, buflen, 0,
 703                                            nsap, salen) != buflen) {
 704                                         Aerror(stderr, "sendto", errno, nsap);
 705                                         badns |= (1 << ns);
 706                                         res_close();
 707                                         goto next_ns;
 708                                 }
 709 #ifndef CANNOT_CONNECT_DGRAM
 710                         }
 711 #endif /* !CANNOT_CONNECT_DGRAM */
 712
 713                         /*
 714                          * Wait for reply
 715                          */
 716
 717                         timeout.tv_sec = (_res.retrans << try);
 718                         if (try > 0)
 719                                 timeout.tv_sec /= _res.nscount;
 720                         if ((long) timeout.tv_sec <= 0)
 721                                 timeout.tv_sec = 1;
 722                         timeout.tv_usec = 0;
 723                         TIMEVAL_TO_TIMESPEC(&timeout, &ts);
 724                         (void) gettimeofday(&ctv, NULL);
 725                         timeradd(&timeout, &ctv, &timeout);
 726     wait:
 727                         if (s < 0) {
 728                                 Perror(stderr, "s out-of-bounds", EMFILE);
 729                                 res_close();
 730                                 goto next_ns;
 731                         }
 732
 733                         EV_SET(&kv, s, EVFILT_READ, EV_ADD | EV_ONESHOT, 0,0,0);
 734
 735                         n = _kevent(kq, &kv, 1, &kv, 1, &ts);
 736                         if (n < 0) {
 737                                 if (errno == EINTR) {
 738                                         (void) gettimeofday(&ctv, NULL);
 739                                         if (timercmp(&ctv, &timeout, <)) {
 740                                                 timersub(&timeout, &ctv, &ctv);
 741                                                 TIMEVAL_TO_TIMESPEC(&ctv, &ts);
 742                                                 goto wait;
 743                                         }
 744                                 }
 745                                 Perror(stderr, "kevent", errno);
 746                                 res_close();
 747                                 goto next_ns;
 748                         }
 749
 750                         if (n == 0) {
 751                                 /*
 752                                  * timeout
 753                                  */
 754                                 Dprint(_res.options & RES_DEBUG,
 755                                        (stdout, ";; timeout\n"));
 756                                 gotsomewhere = 1;
 757                                 res_close();
 758                                 goto next_ns;
 759                         }
 760                         errno = 0;
 761                         fromlen = sizeof(from);
 762                         resplen = _recvfrom(s, (char*)ans, anssiz, 0,
 763                                            (struct sockaddr *)&from, &fromlen);
 764                         if (resplen <= 0) {
 765                                 Perror(stderr, "recvfrom", errno);
 766                                 res_close();
 767                                 goto next_ns;
 768                         }
 769                         gotsomewhere = 1;
 770                         if (resplen < HFIXEDSZ) {
 771                                 /*
 772                                  * Undersized message.
 773                                  */
 774                                 Dprint(_res.options & RES_DEBUG,
 775                                        (stdout, ";; undersized: %d\n",
 776                                         resplen));
 777                                 terrno = EMSGSIZE;
 778                                 badns |= (1 << ns);
 779                                 res_close();
 780                                 goto next_ns;
 781                         }
 782                         if (hp->id != anhp->id) {
 783                                 /*
 784                                  * response from old query, ignore it.
 785                                  * XXX - potential security hazard could
 786                                  *       be detected here.
 787                                  */
 788                                 DprintQ((_res.options & RES_DEBUG) ||
 789                                         (_res.pfcode & RES_PRF_REPLY),
 790                                         (stdout, ";; old answer:\n"),
 791                                         ans, (resplen>anssiz)?anssiz:resplen);
 792                                 goto wait;
 793                         }
 794 #ifdef CHECK_SRVR_ADDR
 795                         if (!(_res.options & RES_INSECURE1) &&
 796                             !res_isourserver((struct sockaddr_in *)&from)) {
 797                                 /*
 798                                  * response from wrong server? ignore it.
 799                                  * XXX - potential security hazard could
 800                                  *       be detected here.
 801                                  */
 802                                 DprintQ((_res.options & RES_DEBUG) ||
 803                                         (_res.pfcode & RES_PRF_REPLY),
 804                                         (stdout, ";; not our server:\n"),
 805                                         ans, (resplen>anssiz)?anssiz:resplen);
 806                                 goto wait;
 807                         }
 808 #endif
 809                         if (!(_res.options & RES_INSECURE2) &&
 810                             !res_queriesmatch(buf, buf + buflen,
 811                                               ans, ans + anssiz)) {
 812                                 /*
 813                                  * response contains wrong query? ignore it.
 814                                  * XXX - potential security hazard could
 815                                  *       be detected here.
 816                                  */
 817                                 DprintQ((_res.options & RES_DEBUG) ||
 818                                         (_res.pfcode & RES_PRF_REPLY),
 819                                         (stdout, ";; wrong query name:\n"),
 820                                         ans, (resplen>anssiz)?anssiz:resplen);
 821                                 goto wait;
 822                         }
 823                         if (anhp->rcode == SERVFAIL ||
 824                             anhp->rcode == NOTIMP ||
 825                             anhp->rcode == REFUSED) {
 826                                 DprintQ(_res.options & RES_DEBUG,
 827                                         (stdout, "server rejected query:\n"),
 828                                         ans, (resplen>anssiz)?anssiz:resplen);
 829                                 badns |= (1 << ns);
 830                                 res_close();
 831                                 /* don't retry if called from dig */
 832                                 if (!_res.pfcode)
 833                                         goto next_ns;
 834                         }
 835                         if (!(_res.options & RES_IGNTC) && anhp->tc) {
 836                                 /*
 837                                  * get rest of answer;
 838                                  * use TCP with same server.
 839                                  */
 840                                 Dprint(_res.options & RES_DEBUG,
 841                                        (stdout, ";; truncated answer\n"));
 842                                 v_circuit = 1;
 843                                 res_close();
 844                                 goto same_ns;
 845                         }
 846                 } /*if vc/dg*/
 847                 Dprint((_res.options & RES_DEBUG) ||
 848                        ((_res.pfcode & RES_PRF_REPLY) &&
 849                         (_res.pfcode & RES_PRF_HEAD1)),
 850                        (stdout, ";; got answer:\n"));
 851                 DprintQ((_res.options & RES_DEBUG) ||
 852                         (_res.pfcode & RES_PRF_REPLY),
 853                         (stdout, "%.*s", 0, ""),
 854                         ans, (resplen>anssiz)?anssiz:resplen);
 855                 /*
 856                  * If using virtual circuits, we assume that the first server
 857                  * is preferred over the rest (i.e. it is on the local
 858                  * machine) and only keep that one open.
 859                  * If we have temporarily opened a virtual circuit,
 860                  * or if we haven't been asked to keep a socket open,
 861                  * close the socket.
 862                  */
 863                 if ((v_circuit && (!(_res.options & RES_USEVC) || ns != 0)) ||
 864                     !(_res.options & RES_STAYOPEN)) {
 865                         res_close();
 866                 }
 867                 if (Rhook) {
 868                         int done = 0, loops = 0;
 869
 870                         do {
 871                                 res_sendhookact act;
 872
 873                                 act = (*Rhook)(nsap,
 874                                                buf, buflen,
 875                                                ans, anssiz, &resplen);
 876                                 switch (act) {
 877                                 case res_goahead:
 878                                 case res_done:
 879                                         done = 1;
 880                                         break;
 881                                 case res_nextns:
 882                                         res_close();
 883                                         goto next_ns;
 884                                 case res_modified:
 885                                         /* give the hook another try */
 886                                         if (++loops < 42) /*doug adams*/
 887                                                 break;
 888                                         /*FALLTHROUGH*/
 889                                 case res_error:
 890                                         /*FALLTHROUGH*/
 891                                 default:
 892                                         _close(kq);
 893                                         return (-1);
 894                                 }
 895                         } while (!done);
 896
 897                 }
 898                 _close(kq);
 899                 return (resplen);
 900     next_ns: ;
 901            } /*foreach ns*/
 902         } /*foreach retry*/
 903         res_close();
 904         _close(kq);
 905         if (!v_circuit) {
 906                 if (!gotsomewhere)
 907                         errno = ECONNREFUSED;   /* no nameservers found */
 908                 else
 909                         errno = ETIMEDOUT;      /* no answer obtained */
 910         } else
 911                 errno = terrno;
 912         return (-1);
 913 }
 914
 915 /*
 916  * This routine is for closing the socket if a virtual circuit is used and
 917  * the program wants to close it.  This provides support for endhostent()
 918  * which expects to close the socket.
 919  *
 920  * This routine is not expected to be user visible.
 921  */
 922 void
 923 res_close()
 924 {
 925         if (s >= 0) {
 926                 (void)_close(s);
 927                 s = -1;
 928                 connected = 0;
 929                 vc = 0;
 930                 af = 0;
 931         }
 932 }
 933
 934 /*
 935  * Weak aliases for applications that use certain private entry points,
 936  * and fail to include <resolv.h>.
 937  */
 938 #undef res_close
 939 __weak_reference(__res_close, _res_close);
 940 #undef res_send
 941 __weak_reference(__res_send, res_send);