lib/libc/net/gethostbydns.c

   1 /*
   2  * ++Copyright++ 1985, 1988, 1993
   3  * -
   4  * Copyright (c) 1985, 1988, 1993
   5  *      The Regents of the University of California.  All rights reserved.
   6  *
   7  * Redistribution and use in source and binary forms, with or without
   8  * modification, are permitted provided that the following conditions
   9  * are met:
  10  * 1. Redistributions of source code must retain the above copyright
  11  *    notice, this list of conditions and the following disclaimer.
  12  * 2. Redistributions in binary form must reproduce the above copyright
  13  *    notice, this list of conditions and the following disclaimer in the
  14  *    documentation and/or other materials provided with the distribution.
  15  * 3. All advertising materials mentioning features or use of this software
  16  *    must display the following acknowledgement:
  17  *      This product includes software developed by the University of
  18  *      California, Berkeley and its contributors.
  19  * 4. Neither the name of the University nor the names of its contributors
  20  *    may be used to endorse or promote products derived from this software
  21  *    without specific prior written permission.
  22  *
  23  * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
  24  * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
  25  * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
  26  * ARE DISCLAIMED.  IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
  27  * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
  28  * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
  29  * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
  30  * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
  31  * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
  32  * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
  33  * SUCH DAMAGE.
  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  * --Copyright--
  54  */
  55
  56 #if defined(LIBC_SCCS) && !defined(lint)
  57 static char sccsid[] = "@(#)gethostnamadr.c     8.1 (Berkeley) 6/4/93";
  58 static char fromrcsid[] = "From: Id: gethnamaddr.c,v 8.23 1998/04/07 04:59:46 vixie Exp $";
  59 static char rcsid[] = "$FreeBSD: src/lib/libc/net/gethostbydns.c,v 1.27.2.5 2002/11/02 18:54:57 ume Exp $";
  60 #endif /* LIBC_SCCS and not lint */
  61
  62 #include <sys/types.h>
  63 #include <sys/param.h>
  64 #include <sys/socket.h>
  65 #include <netinet/in.h>
  66 #include <arpa/inet.h>
  67 #include <arpa/nameser.h>
  68
  69 #include <stdio.h>
  70 #include <stdlib.h>
  71 #include <unistd.h>
  72 #include <string.h>
  73 #include <netdb.h>
  74 #include <resolv.h>
  75 #include <ctype.h>
  76 #include <errno.h>
  77 #include <syslog.h>
  78
  79 #include "res_config.h"
  80
  81 #define SPRINTF(x) ((size_t)sprintf x)
  82
  83 #define MAXALIASES      35
  84 #define MAXADDRS        35
  85
  86 static const char AskedForGot[] =
  87                 "gethostby*.gethostanswer: asked for \"%s\", got \"%s\"";
  88
  89 static char *h_addr_ptrs[MAXADDRS + 1];
  90
  91 static struct hostent host;
  92 static char *host_aliases[MAXALIASES];
  93 static char hostbuf[8*1024];
  94 static u_char host_addr[16];    /* IPv4 or IPv6 */
  95
  96 #ifdef RESOLVSORT
  97 static void addrsort __P((char **, int));
  98 #endif
  99
 100 #define MAXPACKET       (64*1024)
 101
 102 typedef union {
 103     HEADER hdr;
 104     u_char buf[MAXPACKET];
 105 } querybuf;
 106
 107 typedef union {
 108     int32_t al;
 109     char ac;
 110 } align;
 111
 112 extern int h_errno;
 113 int _dns_ttl_;
 114
 115 #ifdef DEBUG
 116 static void
 117 dprintf(msg, num)
 118         char *msg;
 119         int num;
 120 {
 121         if (_res.options & RES_DEBUG) {
 122                 int save = errno;
 123
 124                 printf(msg, num);
 125                 errno = save;
 126         }
 127 }
 128 #else
 129 # define dprintf(msg, num) /*nada*/
 130 #endif
 131
 132 #define BOUNDED_INCR(x) \
 133         do { \
 134                 cp += x; \
 135                 if (cp > eom) { \
 136                         h_errno = NO_RECOVERY; \
 137                         return (NULL); \
 138                 } \
 139         } while (0)
 140
 141 #define BOUNDS_CHECK(ptr, count) \
 142         do { \
 143                 if ((ptr) + (count) > eom) { \
 144                         h_errno = NO_RECOVERY; \
 145                         return (NULL); \
 146                 } \
 147         } while (0)
 148
 149 static struct hostent *
 150 gethostanswer(answer, anslen, qname, qtype)
 151         const querybuf *answer;
 152         int anslen;
 153         const char *qname;
 154         int qtype;
 155 {
 156         register const HEADER *hp;
 157         register const u_char *cp;
 158         register int n;
 159         const u_char *eom, *erdata;
 160         char *bp, **ap, **hap;
 161         int type, class, buflen, ancount, qdcount;
 162         int haveanswer, had_error;
 163         int toobig = 0;
 164         char tbuf[MAXDNAME];
 165         const char *tname;
 166         int (*name_ok) __P((const char *));
 167
 168         tname = qname;
 169         host.h_name = NULL;
 170         eom = answer->buf + anslen;
 171         switch (qtype) {
 172         case T_A:
 173         case T_AAAA:
 174                 name_ok = res_hnok;
 175                 break;
 176         case T_PTR:
 177                 name_ok = res_dnok;
 178                 break;
 179         default:
 180                 h_errno = NO_RECOVERY;
 181                 return (NULL);  /* XXX should be abort(); */
 182         }
 183         /*
 184          * find first satisfactory answer
 185          */
 186         hp = &answer->hdr;
 187         ancount = ntohs(hp->ancount);
 188         qdcount = ntohs(hp->qdcount);
 189         bp = hostbuf;
 190         buflen = sizeof hostbuf;
 191         cp = answer->buf;
 192         BOUNDED_INCR(HFIXEDSZ);
 193         if (qdcount != 1) {
 194                 h_errno = NO_RECOVERY;
 195                 return (NULL);
 196         }
 197         n = dn_expand(answer->buf, eom, cp, bp, buflen);
 198         if ((n < 0) || !(*name_ok)(bp)) {
 199                 h_errno = NO_RECOVERY;
 200                 return (NULL);
 201         }
 202         BOUNDED_INCR(n + QFIXEDSZ);
 203         if (qtype == T_A || qtype == T_AAAA) {
 204                 /* res_send() has already verified that the query name is the
 205                  * same as the one we sent; this just gets the expanded name
 206                  * (i.e., with the succeeding search-domain tacked on).
 207                  */
 208                 n = strlen(bp) + 1;             /* for the \0 */
 209                 if (n >= MAXHOSTNAMELEN) {
 210                         h_errno = NO_RECOVERY;
 211                         return (NULL);
 212                 }
 213                 host.h_name = bp;
 214                 bp += n;
 215                 buflen -= n;
 216                 /* The qname can be abbreviated, but h_name is now absolute. */
 217                 qname = host.h_name;
 218         }
 219         ap = host_aliases;
 220         *ap = NULL;
 221         host.h_aliases = host_aliases;
 222         hap = h_addr_ptrs;
 223         *hap = NULL;
 224         host.h_addr_list = h_addr_ptrs;
 225         haveanswer = 0;
 226         had_error = 0;
 227         _dns_ttl_ = -1;
 228         while (ancount-- > 0 && cp < eom && !had_error) {
 229                 n = dn_expand(answer->buf, eom, cp, bp, buflen);
 230                 if ((n < 0) || !(*name_ok)(bp)) {
 231                         had_error++;
 232                         continue;
 233                 }
 234                 cp += n;                        /* name */
 235                 BOUNDS_CHECK(cp, 3 * INT16SZ + INT32SZ);
 236                 type = _getshort(cp);
 237                 cp += INT16SZ;                  /* type */
 238                 class = _getshort(cp);
 239                 cp += INT16SZ;                  /* class */
 240                 if (qtype == T_A  && type == T_A)
 241                         _dns_ttl_ = _getlong(cp);
 242                 cp += INT32SZ;                  /* TTL */
 243                 n = _getshort(cp);
 244                 cp += INT16SZ;                  /* len */
 245                 BOUNDS_CHECK(cp, n);
 246                 erdata = cp + n;
 247                 if (class != C_IN) {
 248                         /* XXX - debug? syslog? */
 249                         cp += n;
 250                         continue;               /* XXX - had_error++ ? */
 251                 }
 252                 if ((qtype == T_A || qtype == T_AAAA) && type == T_CNAME) {
 253                         if (ap >= &host_aliases[MAXALIASES-1])
 254                                 continue;
 255                         n = dn_expand(answer->buf, eom, cp, tbuf, sizeof tbuf);
 256                         if ((n < 0) || !(*name_ok)(tbuf)) {
 257                                 had_error++;
 258                                 continue;
 259                         }
 260                         cp += n;
 261                         if (cp != erdata) {
 262                                 h_errno = NO_RECOVERY;
 263                                 return (NULL);
 264                         }
 265                         /* Store alias. */
 266                         *ap++ = bp;
 267                         n = strlen(bp) + 1;     /* for the \0 */
 268                         if (n >= MAXHOSTNAMELEN) {
 269                                 had_error++;
 270                                 continue;
 271                         }
 272                         bp += n;
 273                         buflen -= n;
 274                         /* Get canonical name. */
 275                         n = strlen(tbuf) + 1;   /* for the \0 */
 276                         if (n > buflen || n >= MAXHOSTNAMELEN) {
 277                                 had_error++;
 278                                 continue;
 279                         }
 280                         strcpy(bp, tbuf);
 281                         host.h_name = bp;
 282                         bp += n;
 283                         buflen -= n;
 284                         continue;
 285                 }
 286                 if (qtype == T_PTR && type == T_CNAME) {
 287                         n = dn_expand(answer->buf, eom, cp, tbuf, sizeof tbuf);
 288                         if (n < 0 || !res_dnok(tbuf)) {
 289                                 had_error++;
 290                                 continue;
 291                         }
 292                         cp += n;
 293                         if (cp != erdata) {
 294                                 h_errno = NO_RECOVERY;
 295                                 return (NULL);
 296                         }
 297                         /* Get canonical name. */
 298                         n = strlen(tbuf) + 1;   /* for the \0 */
 299                         if (n > buflen || n >= MAXHOSTNAMELEN) {
 300                                 had_error++;
 301                                 continue;
 302                         }
 303                         strcpy(bp, tbuf);
 304                         tname = bp;
 305                         bp += n;
 306                         buflen -= n;
 307                         continue;
 308                 }
 309                 if (type != qtype) {
 310                         if (type != T_SIG)
 311                                 syslog(LOG_NOTICE|LOG_AUTH,
 312         "gethostby*.gethostanswer: asked for \"%s %s %s\", got type \"%s\"",
 313                                        qname, p_class(C_IN), p_type(qtype),
 314                                        p_type(type));
 315                         cp += n;
 316                         continue;               /* XXX - had_error++ ? */
 317                 }
 318                 switch (type) {
 319                 case T_PTR:
 320                         if (strcasecmp(tname, bp) != 0) {
 321                                 syslog(LOG_NOTICE|LOG_AUTH,
 322                                        AskedForGot, qname, bp);
 323                                 cp += n;
 324                                 continue;       /* XXX - had_error++ ? */
 325                         }
 326                         n = dn_expand(answer->buf, eom, cp, bp, buflen);
 327                         if ((n < 0) || !res_hnok(bp)) {
 328                                 had_error++;
 329                                 break;
 330                         }
 331 #if MULTI_PTRS_ARE_ALIASES
 332                         cp += n;
 333                         if (cp != erdata) {
 334                                 h_errno = NO_RECOVERY;
 335                                 return (NULL);
 336                         }
 337                         if (!haveanswer)
 338                                 host.h_name = bp;
 339                         else if (ap < &host_aliases[MAXALIASES-1])
 340                                 *ap++ = bp;
 341                         else
 342                                 n = -1;
 343                         if (n != -1) {
 344                                 n = strlen(bp) + 1;     /* for the \0 */
 345                                 if (n >= MAXHOSTNAMELEN) {
 346                                         had_error++;
 347                                         break;
 348                                 }
 349                                 bp += n;
 350                                 buflen -= n;
 351                         }
 352                         break;
 353 #else
 354                         host.h_name = bp;
 355                         if (_res.options & RES_USE_INET6) {
 356                                 n = strlen(bp) + 1;     /* for the \0 */
 357                                 if (n >= MAXHOSTNAMELEN) {
 358                                         had_error++;
 359                                         break;
 360                                 }
 361                                 bp += n;
 362                                 buflen -= n;
 363                                 _map_v4v6_hostent(&host, &bp, &buflen);
 364                         }
 365                         h_errno = NETDB_SUCCESS;
 366                         return (&host);
 367 #endif
 368                 case T_A:
 369                 case T_AAAA:
 370                         if (strcasecmp(host.h_name, bp) != 0) {
 371                                 syslog(LOG_NOTICE|LOG_AUTH,
 372                                        AskedForGot, host.h_name, bp);
 373                                 cp += n;
 374                                 continue;       /* XXX - had_error++ ? */
 375                         }
 376                         if (n != host.h_length) {
 377                                 cp += n;
 378                                 continue;
 379                         }
 380                         if (!haveanswer) {
 381                                 register int nn;
 382
 383                                 host.h_name = bp;
 384                                 nn = strlen(bp) + 1;    /* for the \0 */
 385                                 bp += nn;
 386                                 buflen -= nn;
 387                         }
 388
 389                         buflen -= sizeof(align) - ((u_long)bp % sizeof(align));
 390                         bp += sizeof(align) - ((u_long)bp % sizeof(align));
 391
 392                         if (bp + n >= &hostbuf[sizeof hostbuf]) {
 393                                 dprintf("size (%d) too big\n", n);
 394                                 had_error++;
 395                                 continue;
 396                         }
 397                         if (hap >= &h_addr_ptrs[MAXADDRS-1]) {
 398                                 if (!toobig++)
 399                                         dprintf("Too many addresses (%d)\n",
 400                                                 MAXADDRS);
 401                                 cp += n;
 402                                 continue;
 403                         }
 404                         bcopy(cp, *hap++ = bp, n);
 405                         bp += n;
 406                         buflen -= n;
 407                         cp += n;
 408                         if (cp != erdata) {
 409                                 h_errno = NO_RECOVERY;
 410                                 return (NULL);
 411                         }
 412                         break;
 413                 default:
 414                         dprintf("Impossible condition (type=%d)\n", type);
 415                         h_errno = NO_RECOVERY;
 416                         return (NULL);
 417                         /* BIND has abort() here, too risky on bad data */
 418                 }
 419                 if (!had_error)
 420                         haveanswer++;
 421         }
 422         if (haveanswer) {
 423                 *ap = NULL;
 424                 *hap = NULL;
 425 # if defined(RESOLVSORT)
 426                 /*
 427                  * Note: we sort even if host can take only one address
 428                  * in its return structures - should give it the "best"
 429                  * address in that case, not some random one
 430                  */
 431                 if (_res.nsort && haveanswer > 1 && qtype == T_A)
 432                         addrsort(h_addr_ptrs, haveanswer);
 433 # endif /*RESOLVSORT*/
 434                 if (!host.h_name) {
 435                         n = strlen(qname) + 1;  /* for the \0 */
 436                         if (n > buflen || n >= MAXHOSTNAMELEN)
 437                                 goto no_recovery;
 438                         strcpy(bp, qname);
 439                         host.h_name = bp;
 440                         bp += n;
 441                         buflen -= n;
 442                 }
 443                 if (_res.options & RES_USE_INET6)
 444                         _map_v4v6_hostent(&host, &bp, &buflen);
 445                 h_errno = NETDB_SUCCESS;
 446                 return (&host);
 447         }
 448  no_recovery:
 449         h_errno = NO_RECOVERY;
 450         return (NULL);
 451 }
 452
 453 struct hostent *
 454 __dns_getanswer(answer, anslen, qname, qtype)
 455         const char *answer;
 456         int anslen;
 457         const char *qname;
 458         int qtype;
 459 {
 460         switch(qtype) {
 461         case T_AAAA:
 462                 host.h_addrtype = AF_INET6;
 463                 host.h_length = IN6ADDRSZ;
 464                 break;
 465         case T_A:
 466         default:
 467                 host.h_addrtype = AF_INET;
 468                 host.h_length = INADDRSZ;
 469                 break;
 470         }
 471
 472         return(gethostanswer((const querybuf *)answer, anslen, qname, qtype));
 473 }
 474
 475 struct hostent *
 476 _gethostbydnsname(name, af)
 477         const char *name;
 478         int af;
 479 {
 480         querybuf *buf;
 481         register const char *cp;
 482         char *bp;
 483         int n, size, type, len;
 484         struct hostent *hp;
 485
 486         if ((_res.options & RES_INIT) == 0 && res_init() == -1) {
 487                 h_errno = NETDB_INTERNAL;
 488                 return (NULL);
 489         }
 490
 491         switch (af) {
 492         case AF_INET:
 493                 size = INADDRSZ;
 494                 type = T_A;
 495                 break;
 496         case AF_INET6:
 497                 size = IN6ADDRSZ;
 498                 type = T_AAAA;
 499                 break;
 500         default:
 501                 h_errno = NETDB_INTERNAL;
 502                 errno = EAFNOSUPPORT;
 503                 return (NULL);
 504         }
 505
 506         host.h_addrtype = af;
 507         host.h_length = size;
 508
 509         /*
 510          * if there aren't any dots, it could be a user-level alias.
 511          * this is also done in res_query() since we are not the only
 512          * function that looks up host names.
 513          */
 514         if (!strchr(name, '.') && (cp = __hostalias(name)))
 515                 name = cp;
 516
 517         /*
 518          * disallow names consisting only of digits/dots, unless
 519          * they end in a dot.
 520          */
 521         if (isdigit((unsigned char)name[0]))
 522                 for (cp = name;; ++cp) {
 523                         if (!*cp) {
 524                                 if (*--cp == '.')
 525                                         break;
 526                                 /*
 527                                  * All-numeric, no dot at the end.
 528                                  * Fake up a hostent as if we'd actually
 529                                  * done a lookup.
 530                                  */
 531                                 if (inet_pton(af, name, host_addr) <= 0) {
 532                                         h_errno = HOST_NOT_FOUND;
 533                                         return (NULL);
 534                                 }
 535                                 strncpy(hostbuf, name, MAXDNAME);
 536                                 hostbuf[MAXDNAME] = '\0';
 537                                 bp = hostbuf + MAXDNAME;
 538                                 len = sizeof hostbuf - MAXDNAME;
 539                                 host.h_name = hostbuf;
 540                                 host.h_aliases = host_aliases;
 541                                 host_aliases[0] = NULL;
 542                                 h_addr_ptrs[0] = (char *)host_addr;
 543                                 h_addr_ptrs[1] = NULL;
 544                                 host.h_addr_list = h_addr_ptrs;
 545                                 if (_res.options & RES_USE_INET6)
 546                                         _map_v4v6_hostent(&host, &bp, &len);
 547                                 h_errno = NETDB_SUCCESS;
 548                                 return (&host);
 549                         }
 550                         if (!isdigit((unsigned char)*cp) && *cp != '.')
 551                                 break;
 552                 }
 553         if ((isxdigit((unsigned char)name[0]) && strchr(name, ':') != NULL) ||
 554             name[0] == ':')
 555                 for (cp = name;; ++cp) {
 556                         if (!*cp) {
 557                                 if (*--cp == '.')
 558                                         break;
 559                                 /*
 560                                  * All-IPv6-legal, no dot at the end.
 561                                  * Fake up a hostent as if we'd actually
 562                                  * done a lookup.
 563                                  */
 564                                 if (inet_pton(af, name, host_addr) <= 0) {
 565                                         h_errno = HOST_NOT_FOUND;
 566                                         return (NULL);
 567                                 }
 568                                 strncpy(hostbuf, name, MAXDNAME);
 569                                 hostbuf[MAXDNAME] = '\0';
 570                                 bp = hostbuf + MAXDNAME;
 571                                 len = sizeof hostbuf - MAXDNAME;
 572                                 host.h_name = hostbuf;
 573                                 host.h_aliases = host_aliases;
 574                                 host_aliases[0] = NULL;
 575                                 h_addr_ptrs[0] = (char *)host_addr;
 576                                 h_addr_ptrs[1] = NULL;
 577                                 host.h_addr_list = h_addr_ptrs;
 578                                 h_errno = NETDB_SUCCESS;
 579                                 return (&host);
 580                         }
 581                         if (!isxdigit((unsigned char)*cp) && *cp != ':' && *cp != '.')
 582                                 break;
 583                 }
 584
 585         if ((buf = malloc(sizeof(*buf))) == NULL) {
 586                 h_errno = NETDB_INTERNAL;
 587                 return (NULL);
 588         }
 589         n = res_search(name, C_IN, type, buf->buf, sizeof(buf->buf));
 590         if (n < 0) {
 591                 free(buf);
 592                 dprintf("res_search failed (%d)\n", n);
 593                 return (NULL);
 594         } else if (n > sizeof(buf->buf)) {
 595                 free(buf);
 596                 dprintf("static buffer is too small (%d)\n", n);
 597                 return (NULL);
 598         }
 599         hp = gethostanswer(buf, n, name, type);
 600         free(buf);
 601         return (hp);
 602 }
 603
 604 struct hostent *
 605 _gethostbydnsaddr(addr, len, af)
 606         const char *addr;       /* XXX should have been def'd as u_char! */
 607         int len, af;
 608 {
 609         const u_char *uaddr = (const u_char *)addr;
 610         static const u_char mapped[] = { 0,0, 0,0, 0,0, 0,0, 0,0, 0xff,0xff };
 611         static const u_char tunnelled[] = { 0,0, 0,0, 0,0, 0,0, 0,0, 0,0 };
 612         int n, size;
 613         querybuf *buf;
 614         register struct hostent *hp;
 615         char qbuf[MAXDNAME+1], *qp;
 616 #ifdef SUNSECURITY
 617         register struct hostent *rhp;
 618         char **haddr;
 619         u_long old_options;
 620         char hname2[MAXDNAME+1];
 621 #endif /*SUNSECURITY*/
 622
 623         if ((_res.options & RES_INIT) == 0 && res_init() == -1) {
 624                 h_errno = NETDB_INTERNAL;
 625                 return (NULL);
 626         }
 627         if (af == AF_INET6 && len == IN6ADDRSZ &&
 628             (!bcmp(uaddr, mapped, sizeof mapped) ||
 629              !bcmp(uaddr, tunnelled, sizeof tunnelled))) {
 630                 /* Unmap. */
 631                 addr += sizeof mapped;
 632                 uaddr += sizeof mapped;
 633                 af = AF_INET;
 634                 len = INADDRSZ;
 635         }
 636         switch (af) {
 637         case AF_INET:
 638                 size = INADDRSZ;
 639                 break;
 640         case AF_INET6:
 641                 size = IN6ADDRSZ;
 642                 break;
 643         default:
 644                 errno = EAFNOSUPPORT;
 645                 h_errno = NETDB_INTERNAL;
 646                 return (NULL);
 647         }
 648         if (size != len) {
 649                 errno = EINVAL;
 650                 h_errno = NETDB_INTERNAL;
 651                 return (NULL);
 652         }
 653         switch (af) {
 654         case AF_INET:
 655                 (void) sprintf(qbuf, "%u.%u.%u.%u.in-addr.arpa",
 656                                (uaddr[3] & 0xff),
 657                                (uaddr[2] & 0xff),
 658                                (uaddr[1] & 0xff),
 659                                (uaddr[0] & 0xff));
 660                 break;
 661         case AF_INET6:
 662                 qp = qbuf;
 663                 for (n = IN6ADDRSZ - 1; n >= 0; n--) {
 664                         qp += SPRINTF((qp, "%x.%x.",
 665                                        uaddr[n] & 0xf,
 666                                        (uaddr[n] >> 4) & 0xf));
 667                 }
 668                 strlcat(qbuf, "ip6.arpa", sizeof(qbuf));
 669                 break;
 670         default:
 671                 abort();
 672         }
 673         if ((buf = malloc(sizeof(*buf))) == NULL) {
 674                 h_errno = NETDB_INTERNAL;
 675                 return (NULL);
 676         }
 677         n = res_query(qbuf, C_IN, T_PTR, (u_char *)buf->buf, sizeof buf->buf);
 678         if (n < 0 && af == AF_INET6) {
 679                 *qp = '\0';
 680                 strlcat(qbuf, "ip6.int", sizeof(qbuf));
 681                 n = res_query(qbuf, C_IN, T_PTR, (u_char *)buf->buf,
 682                               sizeof buf->buf);
 683         }
 684         if (n < 0) {
 685                 free(buf);
 686                 dprintf("res_query failed (%d)\n", n);
 687                 return (NULL);
 688         }
 689         if (n > sizeof buf->buf) {
 690                 free(buf);
 691                 dprintf("static buffer is too small (%d)\n", n);
 692                 return (NULL);
 693         }
 694         if (!(hp = gethostanswer(buf, n, qbuf, T_PTR))) {
 695                 free(buf);
 696                 return (NULL);  /* h_errno was set by gethostanswer() */
 697         }
 698         free(buf);
 699 #ifdef SUNSECURITY
 700         if (af == AF_INET) {
 701             /*
 702              * turn off search as the name should be absolute,
 703              * 'localhost' should be matched by defnames
 704              */
 705             strncpy(hname2, hp->h_name, MAXDNAME);
 706             hname2[MAXDNAME] = '\0';
 707             old_options = _res.options;
 708             _res.options &= ~RES_DNSRCH;
 709             _res.options |= RES_DEFNAMES;
 710             if (!(rhp = gethostbyname(hname2))) {
 711                 syslog(LOG_NOTICE|LOG_AUTH,
 712                        "gethostbyaddr: No A record for %s (verifying [%s])",
 713                        hname2, inet_ntoa(*((struct in_addr *)addr)));
 714                 _res.options = old_options;
 715                 h_errno = HOST_NOT_FOUND;
 716                 return (NULL);
 717             }
 718             _res.options = old_options;
 719             for (haddr = rhp->h_addr_list; *haddr; haddr++)
 720                 if (!memcmp(*haddr, addr, INADDRSZ))
 721                         break;
 722             if (!*haddr) {
 723                 syslog(LOG_NOTICE|LOG_AUTH,
 724                        "gethostbyaddr: A record of %s != PTR record [%s]",
 725                        hname2, inet_ntoa(*((struct in_addr *)addr)));
 726                 h_errno = HOST_NOT_FOUND;
 727                 return (NULL);
 728             }
 729         }
 730 #endif /*SUNSECURITY*/
 731         hp->h_addrtype = af;
 732         hp->h_length = len;
 733         bcopy(addr, host_addr, len);
 734         h_addr_ptrs[0] = (char *)host_addr;
 735         h_addr_ptrs[1] = NULL;
 736         if (af == AF_INET && (_res.options & RES_USE_INET6)) {
 737                 _map_v4v6_address((char*)host_addr, (char*)host_addr);
 738                 hp->h_addrtype = AF_INET6;
 739                 hp->h_length = IN6ADDRSZ;
 740         }
 741         h_errno = NETDB_SUCCESS;
 742         return (hp);
 743 }
 744
 745 #ifdef RESOLVSORT
 746 static void
 747 addrsort(ap, num)
 748         char **ap;
 749         int num;
 750 {
 751         int i, j;
 752         char **p;
 753         short aval[MAXADDRS];
 754         int needsort = 0;
 755
 756         p = ap;
 757         for (i = 0; i < num; i++, p++) {
 758             for (j = 0 ; (unsigned)j < _res.nsort; j++)
 759                 if (_res.sort_list[j].addr.s_addr ==
 760                     (((struct in_addr *)(*p))->s_addr & _res.sort_list[j].mask))
 761                         break;
 762             aval[i] = j;
 763             if (needsort == 0 && i > 0 && j < aval[i-1])
 764                 needsort = i;
 765         }
 766         if (!needsort)
 767             return;
 768
 769         while (needsort < num) {
 770             for (j = needsort - 1; j >= 0; j--) {
 771                 if (aval[j] > aval[j+1]) {
 772                     char *hp;
 773
 774                     i = aval[j];
 775                     aval[j] = aval[j+1];
 776                     aval[j+1] = i;
 777
 778                     hp = ap[j];
 779                     ap[j] = ap[j+1];
 780                     ap[j+1] = hp;
 781
 782                 } else
 783                     break;
 784             }
 785             needsort++;
 786         }
 787 }
 788 #endif
 789 void
 790 _sethostdnsent(stayopen)
 791         int stayopen;
 792 {
 793         if ((_res.options & RES_INIT) == 0 && res_init() == -1)
 794                 return;
 795         if (stayopen)
 796                 _res.options |= RES_STAYOPEN | RES_USEVC;
 797 }
 798
 799 void
 800 _endhostdnsent()
 801 {
 802         _res.options &= ~(RES_STAYOPEN | RES_USEVC);
 803         res_close();
 804 }