res_query.c

   1 /*
   2  * Copyright (c) 1988, 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) 1996-1999 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 const char sccsid[] = "@(#)res_query.c   8.1 (Berkeley) 6/4/93";
  73 static const char rcsid[] = "$Id: res_query.c,v 1.1 2006/03/01 19:01:38 majka Exp $";
  74 #endif /* LIBC_SCCS and not lint */
  75
  76 #ifndef __APPLE__
  77 #include "port_before.h"
  78 #endif
  79 #include <sys/types.h>
  80 #include <sys/param.h>
  81 #include <netinet/in.h>
  82 #include <arpa/inet.h>
  83 #include <arpa/nameser.h>
  84 #include <ctype.h>
  85 #include <errno.h>
  86 #include <netdb.h>
  87 #include <resolv.h>
  88 #include <stdio.h>
  89 #include <stdlib.h>
  90 #include <string.h>
  91 #include "res_private.h"
  92 #include <dns_sd.h>
  93 #include <sys/event.h>
  94 #include <sys/time.h>
  95 #include <time.h>
  96 #include <unistd.h>
  97 #include <notify.h>
  98 #include <pthread.h>
  99 #ifndef __APPLE__
 100 #include "port_after.h"
 101 #endif
 102
 103 /* interrupt mechanism is implemented in res_send.c */
 104 extern int interrupt_pipe_enabled;
 105 extern pthread_key_t interrupt_pipe_key;
 106
 107 /* Options.  Leave them on. */
 108 #define DEBUG
 109
 110 #if PACKETSZ > 1024
 111 #define MAXPACKET       PACKETSZ
 112 #else
 113 #define MAXPACKET       1024
 114 #endif
 115
 116 #define BILLION 1000000000
 117
 118 /* length of a reverse DNS IPv6 address query name, e.g. "9.4.a.f.c.e.e.f.e.e.1.5.4.1.4.0.0.0.0.0.0.0.0.0.0.0.0.0.0.8.e.f.ip6.arpa" */
 119 #define IPv6_REVERSE_LEN 72
 120
 121 /* index of the trailing char that must be "8", "9", "A", "a", "b", or "B" */
 122 #define IPv6_REVERSE_LINK_LOCAL_TRAILING_CHAR 58
 123
 124 /* index of low-order nibble of embedded scope id */
 125 #define IPv6_REVERSE_LINK_LOCAL_SCOPE_ID_LOW 48
 126
 127 const static uint8_t hexval[128] =
 128 {
 129         0,  0,  0,  0,  0,  0,  0,  0,  0,  0,  0,  0,  0,  0,  0,  0,          /*  0 - 15 */
 130         0,  0,  0,  0,  0,  0,  0,  0,  0,  0,  0,  0,  0,  0,  0,  0,          /* 16 - 31 */
 131         0,  0,  0,  0,  0,  0,  0,  0,  0,  0,  0,  0,  0,  0,  0,  0,          /* 32 - 47 */
 132         0,  1,  2,  3,  4,  5,  6,  7,  8,  9,  0,  0,  0,  0,  0,  0,          /* 48 - 63 */
 133         0, 10, 11, 12, 13, 14, 15,  0,  0,  0,  0,  0,  0,  0,  0,  0,          /* 64 - 79 */
 134         0,  0,  0,  0,  0,  0,  0,  0,  0,  0,  0,  0,  0,  0,  0,  0,          /* 80 - 95 */
 135         0, 10, 11, 12, 13, 14, 15,  0,  0,  0,  0,  0,  0,  0,  0,  0,          /* 96 - 111 */
 136         0,  0,  0,  0,  0,  0,  0,  0,  0,  0,  0,  0,  0,  0,  0,  0           /* 112 - 127 */
 137 };
 138
 139 struct res_query_context
 140 {
 141         u_char *answer;
 142         size_t anslen;
 143         size_t ansmaxlen;
 144         uint16_t lastanstype;
 145         uint32_t ifnum;
 146         uint32_t res_flags;
 147         DNSServiceFlags flags;
 148         DNSServiceErrorType error;
 149 };
 150
 151 static void
 152 res_query_callback(DNSServiceRef sdRef, DNSServiceFlags flags, uint32_t ifIndex, DNSServiceErrorType errorCode, const char *fullname, uint16_t rrtype, uint16_t rrclass, uint16_t rdlen, const void *rdata, uint32_t ttl, void *ctx)
 153 {
 154         struct res_query_context *context;
 155         int n;
 156         size_t buflen;
 157         u_char *dnlist[2], *cp;
 158         HEADER *ans;
 159         struct in6_addr a6;
 160
 161         context = (struct res_query_context *)ctx;
 162
 163         context->flags = flags;
 164         context->error = errorCode;
 165
 166         if (errorCode != kDNSServiceErr_NoError)
 167         {
 168                 if (context->res_flags & RES_DEBUG) printf(";; res_query_mDNSResponder callback [%s %hu %hu]: error %u\n", fullname, rrtype, rrclass, errorCode);
 169                 return;
 170         }
 171
 172         buflen = context->ansmaxlen - context->anslen;
 173         if (buflen < NS_HFIXEDSZ)
 174         {
 175                 if (context->res_flags & RES_DEBUG) printf(";; res_query_mDNSResponder callback [%s %hu %hu]: malformed reply\n", fullname, rrtype, rrclass);
 176                 return;
 177         }
 178
 179         dnlist[0] = context->answer + NS_HFIXEDSZ;
 180         dnlist[1] = NULL;
 181
 182         cp = context->answer + context->anslen;
 183
 184         n = dn_comp((char *)fullname, cp, buflen, dnlist, &dnlist[1]);
 185         if (n < 0)
 186         {
 187                 if (context->res_flags & RES_DEBUG) printf(";; res_query_mDNSResponder callback [%s %hu %hu]: name mismatch\n", fullname, rrtype, rrclass);
 188                 return;
 189         }
 190
 191         /*
 192          * Check that there is enough space in the buffer for the resource name (n),
 193          * the resource record data (rdlen) and the resource record header (10).
 194          */
 195         if (buflen < n + rdlen + 10)
 196         {
 197                 if (context->res_flags & RES_DEBUG) printf(";; res_query_mDNSResponder callback [%s %hu %hu]: insufficient buffer space for reply\n", fullname, rrtype, rrclass);
 198                 return;
 199         }
 200
 201         if (context->res_flags & RES_DEBUG) printf(";; res_query_mDNSResponder callback for %s %hu %hu\n", fullname, rrtype, rrclass);
 202
 203         cp += n;
 204         buflen -= n;
 205
 206         putshort(rrtype, cp);
 207         cp += sizeof(uint16_t);
 208
 209         putshort(rrclass, cp);
 210         cp += sizeof(uint16_t);
 211
 212         putlong(ttl, cp);
 213         cp += sizeof(uint32_t);
 214
 215         putshort(rdlen, cp);
 216         cp += sizeof(uint16_t);
 217
 218         memcpy(cp, rdata, rdlen);
 219         cp += rdlen;
 220
 221         ans = (HEADER *)context->answer;
 222         ans->ancount = htons(ntohs(ans->ancount) + 1);
 223
 224         context->anslen = (size_t)(cp - context->answer);
 225
 226         context->lastanstype = rrtype;
 227
 228         /*
 229          * Save the interface number for the first AAAA record for link-local addresses.
 230          * It's used by getaddrinfo to set the scope id.
 231          */
 232         if ((context->ifnum == 0) && (rrtype == ns_t_aaaa))
 233         {
 234                 memset(&a6, 0, sizeof(struct in6_addr));
 235                 memcpy(&a6, rdata, sizeof(struct in6_addr));
 236                 if (IN6_IS_ADDR_LINKLOCAL(&a6)) context->ifnum = ifIndex;
 237         }
 238 }
 239
 240 static void
 241 h_errno_for_dnssd_err(DNSServiceErrorType dnssd_err, int *h_errno_err)
 242 {
 243         switch (dnssd_err)
 244         {
 245                 case kDNSServiceErr_NoError:
 246                         *h_errno_err = NETDB_SUCCESS;
 247                         break;
 248                 case kDNSServiceErr_Unknown:
 249                         *h_errno_err = NO_RECOVERY;
 250                         break;
 251                 case kDNSServiceErr_NoSuchRecord:
 252                         *h_errno_err = NO_DATA;
 253                         break;
 254                 case kDNSServiceErr_NoSuchName:
 255                         *h_errno_err = HOST_NOT_FOUND;
 256                         break;
 257                 case kDNSServiceErr_NoMemory:
 258                 default:
 259                         *h_errno_err = NETDB_INTERNAL;
 260                         break;
 261         }
 262 }
 263
 264 static int
 265 _is_rev_link_local(const char *name)
 266 {
 267         int len, i;
 268
 269         if (name == NULL) return 0;
 270
 271         len = strlen(name);
 272         if (len == 0) return 0;
 273
 274         /* check for trailing '.' */
 275         if (name[len - 1] == '.') len--;
 276
 277         if (len != IPv6_REVERSE_LEN) return 0;
 278
 279         i = IPv6_REVERSE_LINK_LOCAL_TRAILING_CHAR;
 280         if ((name[i] != '8') && (name[i] != '9') && (name[i] != 'A') && (name[i] != 'a') && (name[i] != 'B') && (name[i] != 'b')) return 0;
 281
 282         i = IPv6_REVERSE_LINK_LOCAL_TRAILING_CHAR + 1;
 283         if (strncasecmp(name + i, ".e.f.ip6.arpa", 13)) return 0;
 284
 285         for (i = 0; i < IPv6_REVERSE_LINK_LOCAL_TRAILING_CHAR; i += 2)
 286         {
 287                 if (name[i] < '0') return 0;
 288                 if ((name[i] > '9') && (name[i] < 'A')) return 0;
 289                 if ((name[i] > 'F') && (name[i] < 'a')) return 0;
 290                 if (name[i] > 'f') return 0;
 291                 if (name[i + 1] != '.') return 0;
 292         }
 293
 294         return 1;
 295 }
 296
 297 int
 298 res_query_mDNSResponder(res_state statp, const char *name, int class, int type, u_char *answer, int anslen, struct sockaddr *from, uint32_t *fromlen)
 299 {
 300         DNSServiceRef sdRef;
 301         DNSServiceErrorType result;
 302         struct res_query_context context;
 303         int i, kq, n, wait, cancelled, notify_token, status;
 304         struct kevent mevent, ievent, event;
 305         struct timeval ctv;
 306         struct timespec now, finish, timeout;
 307         HEADER *ans;
 308         uint32_t iface;
 309         uint16_t nibble;
 310         char *qname, *notify_name;
 311         int *interrupt_pipe;
 312         uint64_t exit_requested;
 313
 314         interrupt_pipe = NULL;
 315         result = 0;
 316         kq = -1;
 317         ans = (HEADER *)answer;
 318         cancelled = 0;
 319         ans->rcode = 0;
 320
 321         memset(&context, 0, sizeof(struct res_query_context));
 322
 323         /* Build a dummy DNS header with question for the answer */
 324         context.res_flags = statp->options;
 325         context.answer = answer;
 326         context.ansmaxlen = anslen;
 327         context.anslen = res_nmkquery(statp, ns_o_query, name, class, type, NULL, 0, NULL, answer, anslen);
 328         if (context.anslen <= 0) return 0;
 329
 330         /* Mark DNS packet as a response */
 331         ans->qr = 1;
 332         ans->qr = htons(ans->qr);
 333
 334         /* Pull out Scope ID in link-local reverse queries */
 335         qname = (char *)name;
 336         iface = 0;
 337         if (_is_rev_link_local(name))
 338         {
 339                 /* _is_rev_link_local rejects chars > 127 so it's safe to index into hexval */
 340                 i = IPv6_REVERSE_LINK_LOCAL_SCOPE_ID_LOW;
 341                 nibble = hexval[(uint32_t)name[i]];
 342                 iface = nibble;
 343
 344                 i += 2;
 345                 nibble = hexval[(uint32_t)name[i]];
 346                 iface += (nibble << 4);
 347
 348                 i += 2;
 349                 nibble = hexval[(uint32_t)name[i]];
 350                 iface += (nibble << 8);
 351
 352                 i += 2;
 353                 nibble = hexval[(uint32_t)name[i]];
 354                 iface += (nibble << 12);
 355
 356                 if (iface != 0)
 357                 {
 358                         qname = strdup(name);
 359                         if (qname == NULL)
 360                         {
 361                                 h_errno = NO_RECOVERY;
 362                                 errno = ENOMEM;
 363                                 return -1;
 364                         }
 365
 366                         i = IPv6_REVERSE_LINK_LOCAL_SCOPE_ID_LOW;
 367                         qname[i] = '0';
 368                         qname[i + 2] = '0';
 369                         qname[i + 4] = '0';
 370                         qname[i + 6] = '0';
 371                 }
 372         }
 373
 374         if (statp->options & RES_DEBUG) printf(";; res_query_mDNSResponder\n");
 375
 376         result = DNSServiceQueryRecord(&sdRef, kDNSServiceFlagsReturnIntermediates, iface, qname, type, class, res_query_callback, &context);
 377         if (iface != 0) free(qname);
 378
 379         if (result != 0) return 0;
 380
 381         /* Use a kqueue to wait for a response from mDNSResponder */
 382         kq = kqueue();
 383
 384         /* determine the maximum time to wait for a result */
 385         gettimeofday(&ctv, NULL);
 386
 387         /* N.B. statp->retrans is actually the total timeount in seconds */
 388         timeout.tv_sec = statp->retrans;
 389         timeout.tv_nsec = 0;
 390
 391         finish.tv_sec = ctv.tv_sec + statp->retrans;
 392         finish.tv_nsec = ctv.tv_usec * 1000;
 393
 394         /* add mdns reply FD to kqueue */
 395         EV_SET(&mevent, DNSServiceRefSockFD(sdRef), EVFILT_READ, EV_ADD, 0, 0, 0);
 396         n = kevent(kq, &mevent, 1, NULL, 0, NULL);
 397         if (n != 0) return 0;
 398
 399         /* add interrupt pipe to kqueue if interrupt is enabled */
 400         if (interrupt_pipe_enabled != 0)
 401         {
 402                 interrupt_pipe = pthread_getspecific(interrupt_pipe_key);
 403                 if (interrupt_pipe != NULL)
 404                 {
 405                         if (interrupt_pipe[0] >= 0)
 406                         {
 407                                 EV_SET(&ievent, interrupt_pipe[0], EVFILT_READ, EV_ADD, 0, 0, (void *)name);
 408                                 /* allow this to fail silently (should never happen, but it would only break interrupts */
 409                                 n = kevent(kq, &ievent, 1, NULL, 0, NULL);
 410                         }
 411                 }
 412         }
 413
 414         /*
 415          * Get notification token
 416          * we use a self-notification token to allow a caller
 417          * to signal the thread doing this DNS query to quit.
 418          */
 419         notify_name = NULL;
 420         notify_token = -1;
 421
 422         asprintf(&notify_name, "self.thread.%lu", (unsigned long)pthread_self());
 423         if (notify_name != NULL)
 424         {
 425                 status = notify_register_plain(notify_name, &notify_token);
 426                 free(notify_name);
 427         }
 428
 429         wait = 1;
 430         while (wait == 1)
 431         {
 432                 memset(&event, 0, sizeof(struct kevent));
 433                 n = kevent(kq, NULL, 0, &event, 1, &timeout);
 434
 435                 if (notify_token != -1)
 436                 {
 437                         exit_requested = 0;
 438                         status = notify_get_state(notify_token, &exit_requested);
 439                         if (exit_requested == ThreadStateExitRequested)
 440                         {
 441                                 /* interrupted */
 442                                 if (statp->options & RES_DEBUG) printf(";; cancelled\n");
 443                                 cancelled = 1;
 444                                 break;
 445                         }
 446                 }
 447
 448                 if (n < 0)
 449                 {
 450                         if (errno == EINTR) goto keep_waiting;
 451                         h_errno = NO_RECOVERY;
 452                         wait = 0;
 453                 }
 454                 else if ((n == 0) && (ans->ancount == 0))
 455                 {
 456                         h_errno = TRY_AGAIN;
 457                         wait = 0;
 458                 }
 459                 else if (event.udata == (void *)name)
 460                 {
 461                         /* interrupted */
 462                         if (statp->options & RES_DEBUG) printf(";; cancelled\n");
 463                         cancelled = 1;
 464                         break;
 465                 }
 466                 else
 467                 {
 468                         result = DNSServiceProcessResult(sdRef);
 469                         if ((result != 0) || (context.error != 0))
 470                         {
 471                                 if (result == 0) result = context.error;
 472                                 h_errno_for_dnssd_err(result, &h_errno);
 473                                 wait = 0;
 474                         }
 475
 476                         if ((ans->ancount > 0) && ((context.flags & kDNSServiceFlagsMoreComing) == 0) && ((context.lastanstype != ns_t_cname) || (type == ns_t_cname))) wait = 0;
 477                 }
 478
 479         keep_waiting:
 480
 481                 if (wait == 1)
 482                 {
 483                         /* calculate remaining timeout */
 484                         gettimeofday(&ctv, NULL);
 485
 486                         now.tv_sec = ctv.tv_sec;
 487                         now.tv_nsec = ctv.tv_usec * 1000;
 488
 489                         timeout.tv_sec = finish.tv_sec - now.tv_sec;
 490                         if (finish.tv_nsec >= now.tv_nsec)
 491                         {
 492                                 timeout.tv_nsec = finish.tv_nsec - now.tv_nsec;
 493                         }
 494                         else
 495                         {
 496                                 timeout.tv_nsec = BILLION - now.tv_nsec + finish.tv_nsec;
 497                                 timeout.tv_sec--;
 498                         }
 499                 }
 500         }
 501
 502         if (notify_token != -1) notify_cancel(notify_token);
 503         DNSServiceRefDeallocate(sdRef);
 504         close(kq);
 505
 506         if ((ans->ancount == 0) || (cancelled == 1)) context.anslen = -1;
 507
 508         if ((from != NULL) && (fromlen != NULL) && (context.ifnum != 0))
 509         {
 510                 ((struct sockaddr_in6 *)from)->sin6_len = sizeof(struct sockaddr_in6);
 511                 ((struct sockaddr_in6 *)from)->sin6_family = AF_INET6;
 512                 ((struct sockaddr_in6 *)from)->sin6_addr.__u6_addr.__u6_addr8[15] = 1;
 513                 ((struct sockaddr_in6 *)from)->sin6_scope_id = context.ifnum;
 514                 *fromlen = sizeof(struct sockaddr_in6);
 515         }
 516
 517         return context.anslen;
 518 }
 519
 520 static int
 521 res_soa_minimum(const u_char *msg, int len)
 522 {
 523         ns_msg handle;
 524         const u_char *eom;
 525         uint32_t i;
 526         int32_t b;
 527         int min, soa_min;
 528
 529         eom = msg + len;
 530
 531         handle._msg = msg;
 532         handle._eom = eom;
 533
 534         if (msg + NS_INT16SZ > eom) return -1;
 535         NS_GET16(handle._id, msg);
 536
 537         if (msg + NS_INT16SZ > eom) return -1;
 538         NS_GET16(handle._flags, msg);
 539
 540         for (i = 0; i < ns_s_max; i++)
 541         {
 542                 if (msg + NS_INT16SZ > eom) return -1;
 543                 NS_GET16(handle._counts[i], msg);
 544         }
 545
 546         if (handle._counts[ns_s_ns] == 0) return -1;
 547
 548         /* Skip forward to nameserver section */
 549         for (i = 0; i < ns_s_ns; i++)
 550         {
 551                 if (handle._counts[i] == 0) handle._sections[i] = NULL;
 552                 else
 553                 {
 554                         b = ns_skiprr(msg, eom, (ns_sect)i, handle._counts[i]);
 555                         if (b < 0) return -1;
 556
 557                         handle._sections[i] = msg;
 558                         msg += b;
 559                 }
 560         }
 561
 562         min = -1;
 563         for (i = 0; i < handle._counts[ns_s_ns]; i++)
 564         {
 565                 b = ns_skiprr(msg, eom, ns_s_ns, 1);
 566                 if (b < 0) return -1;
 567
 568                 memcpy(&soa_min, msg + b - sizeof(int32_t), sizeof(int32_t));
 569                 soa_min = ntohl(soa_min);
 570                 if ((i == 0) || (soa_min < min)) min = soa_min;
 571                 msg += b;
 572         }
 573
 574         return min;
 575 }
 576
 577 /*
 578  * Formulate a normal query, send, and await answer.
 579  * Returned answer is placed in supplied buffer "answer".
 580  * Perform preliminary check of answer, returning success only
 581  * if no error is indicated and the answer count is nonzero.
 582  * Return the size of the response on success, -1 on error.
 583  * Error number is left in H_ERRNO.
 584  *
 585  * Caller must parse answer and determine whether it answers the question.
 586  */
 587 __attribute__((__visibility__("hidden"))) int
 588 res_nquery_soa_min(res_state statp, const char *name, int class, int type, u_char *answer, int anslen, struct sockaddr *from, int *fromlen, int *min)
 589 {
 590         u_char buf[MAXPACKET];
 591         HEADER *hp = (HEADER *) answer;
 592         int n;
 593         u_int oflags;
 594
 595         if (min != NULL) *min = -1;
 596
 597         oflags = statp->_flags;
 598
 599 again:
 600         __h_errno_set(statp, 0);
 601         hp->rcode = ns_r_noerror;       /* default */
 602
 603 #ifdef DEBUG
 604         if (statp->options & RES_DEBUG) printf(";; res_query(%s, %d, %d)\n", name, class, type);
 605 #endif
 606
 607         n = res_nmkquery(statp, ns_o_query, name, class, type, NULL, 0, NULL, buf, sizeof(buf));
 608 #ifdef RES_USE_EDNS0
 609         if (n > 0 && (statp->_flags & RES_F_EDNS0ERR) == 0 && (statp->options & (RES_USE_EDNS0|RES_USE_DNSSEC)) != 0)
 610                 n = res_nopt(statp, n, buf, sizeof(buf), anslen);
 611 #endif
 612         if (n <= 0)
 613         {
 614 #ifdef DEBUG
 615                 if (statp->options & RES_DEBUG) printf(";; res_query: mkquery failed\n");
 616 #endif
 617                 __h_errno_set(statp, NO_RECOVERY);
 618                 return (n);
 619         }
 620
 621         n = res_nsend_2(statp, buf, n, answer, anslen, from, fromlen);
 622         if (n < 0)
 623         {
 624 #ifdef RES_USE_EDNS0
 625                 /* if the query choked with EDNS0, retry without EDNS0 */
 626                 if ((statp->options & (RES_USE_EDNS0|RES_USE_DNSSEC)) != 0 && ((oflags ^ statp->_flags) & RES_F_EDNS0ERR) != 0)
 627                 {
 628                         statp->_flags |= RES_F_EDNS0ERR;
 629                         if (statp->options & RES_DEBUG) printf(";; res_nquery: retry without EDNS0\n");
 630                         goto again;
 631                 }
 632 #endif
 633 #ifdef DEBUG
 634                 if (statp->options & RES_DEBUG) printf(";; res_query: send error\n");
 635 #endif
 636                 __h_errno_set(statp, TRY_AGAIN);
 637                 return (n);
 638         }
 639
 640         if ((hp->rcode == ns_r_nxdomain) || ((hp->rcode == ns_r_noerror) && (ntohs(hp->ancount) == 0)))
 641         {
 642                 if (min != NULL)
 643                 {
 644                         *min = res_soa_minimum(answer, anslen);
 645                         if (statp->options & RES_DEBUG) printf(";; res_nquery: SOA minimum TTL = %d\n", *min);
 646                 }
 647         }
 648
 649         if (hp->rcode != ns_r_noerror || ntohs(hp->ancount) == 0)
 650         {
 651 #ifdef DEBUG
 652                 if (statp->options & RES_DEBUG) printf(";; rcode = %d, ancount=%d\n", hp->rcode, ntohs(hp->ancount));
 653 #endif
 654                 switch (hp->rcode)
 655                 {
 656                         case ns_r_nxdomain:
 657                                 __h_errno_set(statp, HOST_NOT_FOUND);
 658                                 break;
 659                         case ns_r_servfail:
 660                                 __h_errno_set(statp, TRY_AGAIN);
 661                                 break;
 662                         case ns_r_noerror:
 663                                 __h_errno_set(statp, NO_DATA);
 664                                 break;
 665                         case ns_r_formerr:
 666                         case ns_r_notimpl:
 667                         case ns_r_refused:
 668                         default:
 669                                 __h_errno_set(statp, NO_RECOVERY);
 670                                 break;
 671                 }
 672
 673                 return (-1);
 674         }
 675
 676         return (n);
 677 }
 678
 679 __attribute__((__visibility__("hidden")))
 680 int
 681 res_nquery_2(res_state statp, const char *name, int class, int type, u_char *answer, int anslen, struct sockaddr *from, int *fromlen)
 682 {
 683         int unused = 0;
 684
 685         return res_nquery_soa_min(statp, name, class, type, answer, anslen, from, fromlen, &unused);
 686 }
 687
 688 int
 689 res_nquery(res_state statp, const char *name, int class, int type, u_char *answer, int anslen)
 690 {
 691         struct sockaddr_storage f;
 692         int l;
 693
 694         l = sizeof(struct sockaddr_storage);
 695
 696         return res_nquery_2(statp, name, class, type, answer, anslen, (struct sockaddr *)&f, &l);
 697 }
 698
 699 /*
 700  * Perform a call on res_query on the concatenation of name and domain,
 701  * removing a trailing dot from name if domain is NULL.
 702  */
 703 __attribute__((__visibility__("hidden")))
 704 int
 705 res_nquerydomain_2(res_state statp, const char *name, const char *domain, int class, int type, u_char *answer, int anslen, struct sockaddr *from, int *fromlen)
 706 {
 707         char nbuf[NS_MAXDNAME];
 708         const char *longname = nbuf;
 709         int n, d;
 710
 711 #ifdef DEBUG
 712         if (statp->options & RES_DEBUG) printf(";; res_nquerydomain(%s, %s, %d, %d)\n", name, domain?domain:"<Nil>", class, type);
 713 #endif
 714         if (domain == NULL)
 715         {
 716                 /*
 717                  * Check for trailing '.';
 718                  * copy without '.' if present.
 719                  */
 720                 n = strlen(name);
 721                 if (n >= NS_MAXDNAME)
 722                 {
 723                         __h_errno_set(statp, NO_RECOVERY);
 724                         return (-1);
 725                 }
 726
 727                 n--;
 728                 if (n >= 0 && name[n] == '.')
 729                 {
 730                         strncpy(nbuf, name, n);
 731                         nbuf[n] = '\0';
 732                 }
 733                 else
 734                 {
 735                         longname = name;
 736                 }
 737         }
 738         else
 739         {
 740                 n = strlen(name);
 741                 d = strlen(domain);
 742                 if (n + d + 1 >= NS_MAXDNAME)
 743                 {
 744                         __h_errno_set(statp, NO_RECOVERY);
 745                         return (-1);
 746                 }
 747
 748                 sprintf(nbuf, "%s.%s", name, domain);
 749         }
 750
 751         return (res_nquery_2(statp, longname, class, type, answer, anslen, from, fromlen));
 752 }
 753
 754 int
 755 res_nquerydomain(res_state statp, const char *name, const char *domain, int class, int type, u_char *answer, int anslen)
 756 {
 757         struct sockaddr_storage f;
 758         int l;
 759
 760         l = sizeof(struct sockaddr_storage);
 761
 762         return res_nquerydomain_2(statp, name, domain, class, type, answer, anslen, (struct sockaddr *)&f, &l);
 763 }
 764
 765 /*
 766  * Formulate a normal query, send, and retrieve answer in supplied buffer.
 767  * Return the size of the response on success, -1 on error.
 768  * If enabled, implement search rules until answer or unrecoverable failure
 769  * is detected.  Error code, if any, is left in H_ERRNO.
 770  */
 771 __attribute__((__visibility__("hidden")))
 772 int
 773 res_nsearch_2(res_state statp, const char *name, int class, int type, u_char *answer, int anslen, struct sockaddr *from, int *fromlen)
 774 {
 775         const char *cp, * const *domain;
 776         HEADER *hp = (HEADER *) answer;
 777         char tmp[NS_MAXDNAME];
 778         u_int dots;
 779         int trailing_dot, ret, saved_herrno;
 780         int got_nodata = 0, got_servfail = 0, root_on_list = 0;
 781         int tried_as_is = 0;
 782         int searched = 0;
 783
 784         errno = 0;
 785         __h_errno_set(statp, HOST_NOT_FOUND);  /* True if we never query. */
 786
 787         dots = 0;
 788         for (cp = name; *cp != '\0'; cp++) dots += (*cp == '.');
 789
 790         trailing_dot = 0;
 791         if (cp > name && *--cp == '.') trailing_dot++;
 792
 793         /* If there aren't any dots, it could be a user-level alias. */
 794         if (!dots && (cp = res_hostalias(statp, name, tmp, sizeof tmp))!= NULL)
 795                 return (res_nquery(statp, cp, class, type, answer, anslen));
 796
 797         /*
 798          * If there are enough dots in the name, let's just give it a
 799          * try 'as is'. The threshold can be set with the "ndots" option.
 800          * Also, query 'as is', if there is a trailing dot in the name.
 801          */
 802         saved_herrno = -1;
 803         if (dots >= statp->ndots || trailing_dot)
 804         {
 805                 ret = res_nquerydomain_2(statp, name, NULL, class, type, answer, anslen, from, fromlen);
 806                 if (ret > 0 || trailing_dot) return (ret);
 807                 saved_herrno = h_errno;
 808                 tried_as_is++;
 809         }
 810
 811         /*
 812          * We do at least one level of search if
 813          *      - there is no dot and RES_DEFNAME is set, or
 814          *      - there is at least one dot, there is no trailing dot,
 815          *        and RES_DNSRCH is set.
 816          */
 817         if ((!dots && (statp->options & RES_DEFNAMES) != 0) || (dots && !trailing_dot && (statp->options & RES_DNSRCH) != 0))
 818         {
 819                 int done = 0;
 820
 821                 for (domain = (const char * const *)statp->dnsrch; *domain && !done; domain++)
 822                 {
 823                         searched = 1;
 824
 825                         if (domain[0][0] == '\0' || (domain[0][0] == '.' && domain[0][1] == '\0')) root_on_list++;
 826
 827                         ret = res_nquerydomain_2(statp, name, *domain, class, type, answer, anslen, from, fromlen);
 828                         if (ret > 0) return (ret);
 829
 830                         /*
 831                          * If no server present, give up.
 832                          * If name isn't found in this domain,
 833                          * keep trying higher domains in the search list
 834                          * (if that's enabled).
 835                          * On a NO_DATA error, keep trying, otherwise
 836                          * a wildcard entry of another type could keep us
 837                          * from finding this entry higher in the domain.
 838                          * If we get some other error (negative answer or
 839                          * server failure), then stop searching up,
 840                          * but try the input name below in case it's
 841                          * fully-qualified.
 842                          */
 843                         if (errno == ECONNREFUSED)
 844                         {
 845                                 __h_errno_set(statp, TRY_AGAIN);
 846                                 return (-1);
 847                         }
 848
 849                         switch (statp->res_h_errno)
 850                         {
 851                                 case NO_DATA:
 852                                         got_nodata++;
 853                                         /* FALLTHROUGH */
 854                                 case HOST_NOT_FOUND:
 855                                         /* keep trying */
 856                                         break;
 857                                 case TRY_AGAIN:
 858                                         if (hp->rcode == ns_r_refused)
 859                                         {
 860                                                 /* try next search element, if any */
 861                                                 got_servfail++;
 862                                                 break;
 863                                         }
 864                                         /* FALLTHROUGH */
 865                                 default:
 866                                         /* anything else implies that we're done */
 867                                         done++;
 868                         }
 869
 870                         /* if we got here for some reason other than DNSRCH,
 871                          * we only wanted one iteration of the loop, so stop.
 872                          */
 873                         if ((statp->options & RES_DNSRCH) == 0) done++;
 874                 }
 875         }
 876
 877         /*
 878          * If the query has not already been tried as is then try it
 879          * unless RES_NOTLDQUERY is set and there were no dots.
 880          */
 881         if ((dots || !searched || (statp->options & RES_NOTLDQUERY) == 0) && !(tried_as_is || root_on_list))
 882         {
 883                 ret = res_nquerydomain_2(statp, name, NULL, class, type, answer, anslen, from, fromlen);
 884                 if (ret > 0) return (ret);
 885         }
 886
 887         /* if we got here, we didn't satisfy the search.
 888          * if we did an initial full query, return that query's H_ERRNO
 889          * (note that we wouldn't be here if that query had succeeded).
 890          * else if we ever got a nodata, send that back as the reason.
 891          * else send back meaningless H_ERRNO, that being the one from
 892          * the last DNSRCH we did.
 893          */
 894         if (saved_herrno != -1)
 895                 __h_errno_set(statp, saved_herrno);
 896         else if (got_nodata)
 897                 __h_errno_set(statp, NO_DATA);
 898         else if (got_servfail)
 899                 __h_errno_set(statp, TRY_AGAIN);
 900         return (-1);
 901 }
 902
 903 __attribute__((__visibility__("hidden")))
 904 int
 905 __res_nsearch_list_2(res_state statp, const char *name, int class, int type, u_char *answer, int anslen, struct sockaddr *from, int *fromlen, int nsearch, char **search)
 906 {
 907         const char *cp, *domain;
 908         HEADER *hp = (HEADER *) answer;
 909         char tmp[NS_MAXDNAME];
 910         u_int dots;
 911         int trailing_dot, ret, saved_herrno, i;
 912         int got_nodata = 0, got_servfail = 0, root_on_list = 0;
 913         int tried_as_is = 0;
 914         int searched = 0;
 915
 916         errno = 0;
 917         __h_errno_set(statp, HOST_NOT_FOUND);  /* True if we never query. */
 918
 919         dots = 0;
 920         for (cp = name; *cp != '\0'; cp++) dots += (*cp == '.');
 921
 922         trailing_dot = 0;
 923         if (cp > name && *--cp == '.') trailing_dot++;
 924
 925         /* If there aren't any dots, it could be a user-level alias. */
 926         if (!dots && (cp = res_hostalias(statp, name, tmp, sizeof tmp)) != NULL)
 927                 return (res_nquery(statp, cp, class, type, answer, anslen));
 928
 929         /*
 930          * If there are enough dots in the name, let's just give it a
 931          * try 'as is'. The threshold can be set with the "ndots" option.
 932          * Also, query 'as is', if there is a trailing dot in the name.
 933          */
 934         saved_herrno = -1;
 935         if (dots >= statp->ndots || trailing_dot)
 936         {
 937                 ret = res_nquerydomain(statp, name, NULL, class, type, answer, anslen);
 938                 if (ret > 0 || trailing_dot) return ret;
 939                 saved_herrno = h_errno;
 940                 tried_as_is++;
 941         }
 942
 943         /*
 944          * We do at least one level of search if
 945          *      - there is no dot and RES_DEFNAME is set, or
 946          *      - there is at least one dot, there is no trailing dot,
 947          *        and RES_DNSRCH is set.
 948          */
 949         if ((!dots && (statp->options & RES_DEFNAMES) != 0) || (dots && !trailing_dot && (statp->options & RES_DNSRCH) != 0))
 950         {
 951                 int done = 0;
 952
 953                 for (i = 0; i < nsearch; i++)
 954                 {
 955                         domain = search[i];
 956                         searched = 1;
 957
 958                         if (domain[0] == '\0' || (domain[0] == '.' && domain[1] == '\0')) root_on_list++;
 959
 960                         ret = res_nquerydomain_2(statp, name, domain, class, type, answer, anslen, from, fromlen);
 961                         if (ret > 0) return ret;
 962
 963                         /*
 964                          * If no server present, give up.
 965                          * If name isn't found in this domain,
 966                          * keep trying higher domains in the search list
 967                          * (if that's enabled).
 968                          * On a NO_DATA error, keep trying, otherwise
 969                          * a wildcard entry of another type could keep us
 970                          * from finding this entry higher in the domain.
 971                          * If we get some other error (negative answer or
 972                                                                                    * server failure), then stop searching up,
 973                          * but try the input name below in case it's
 974                          * fully-qualified.
 975                          */
 976                         if (errno == ECONNREFUSED)
 977                         {
 978                                 __h_errno_set(statp, TRY_AGAIN);
 979                                 return -1;
 980                         }
 981
 982                         switch (statp->res_h_errno)
 983                         {
 984                                 case NO_DATA:
 985                                         got_nodata++;
 986                                         /* FALLTHROUGH */
 987                                 case HOST_NOT_FOUND:
 988                                         /* keep trying */
 989                                         break;
 990                                 case TRY_AGAIN:
 991                                         if (hp->rcode == ns_r_refused)
 992                                         {
 993                                                 /* try next search element, if any */
 994                                                 got_servfail++;
 995                                                 break;
 996                                         }
 997                                         /* FALLTHROUGH */
 998                                 default:
 999                                         /* anything else implies that we're done */
1000                                         done++;
1001                         }
1002
1003                         /*
1004                          * if we got here for some reason other than DNSRCH,
1005                          * we only wanted one iteration of the loop, so stop.
1006                          */
1007                         if ((statp->options & RES_DNSRCH) == 0) done++;
1008                 }
1009         }
1010
1011         /*
1012          * If the query has not already been tried as is then try it
1013          * unless RES_NOTLDQUERY is set and there were no dots.
1014          */
1015         if ((dots || !searched || (statp->options & RES_NOTLDQUERY) == 0) && !(tried_as_is || root_on_list))
1016         {
1017                 ret = res_nquerydomain_2(statp, name, NULL, class, type, answer, anslen, from, fromlen);
1018                 if (ret > 0) return ret;
1019         }
1020
1021         /*
1022          * we got here, we didn't satisfy the search.
1023          * if we did an initial full query, return that query's H_ERRNO
1024          * (note that we wouldn't be here if that query had succeeded).
1025          * else if we ever got a nodata, send that back as the reason.
1026          * else send back meaningless H_ERRNO, that being the one from
1027          * the last DNSRCH we did.
1028          */
1029         if (saved_herrno != -1) __h_errno_set(statp, saved_herrno);
1030         else if (got_nodata) __h_errno_set(statp, NO_DATA);
1031         else if (got_servfail) __h_errno_set(statp, TRY_AGAIN);
1032         return -1;
1033 }
1034
1035 int
1036 res_nsearch(res_state statp, const char *name, int class, int type, u_char *answer, int anslen)
1037 {
1038         struct sockaddr_storage f;
1039         int l;
1040
1041         l = sizeof(struct sockaddr_storage);
1042
1043         return res_nsearch_2(statp, name, class, type, answer, anslen, (struct sockaddr *)&f, &l);
1044 }
1045
1046 const char *
1047 res_hostalias(const res_state statp, const char *name, char *dst, size_t siz)
1048 {
1049         char *file, *cp1, *cp2;
1050         char buf[BUFSIZ];
1051         FILE *fp;
1052
1053         if (statp->options & RES_NOALIASES) return (NULL);
1054
1055         file = getenv("HOSTALIASES");
1056         if (file == NULL || (fp = fopen(file, "r")) == NULL) return (NULL);
1057
1058         setbuf(fp, NULL);
1059         buf[sizeof(buf) - 1] = '\0';
1060         while (fgets(buf, sizeof(buf), fp))
1061         {
1062                 for (cp1 = buf; *cp1 && !isspace((unsigned char)*cp1); ++cp1) ;
1063
1064                 if (!*cp1) break;
1065                 *cp1 = '\0';
1066
1067                 if (ns_samename(buf, name) == 1)
1068                 {
1069                         while (isspace((unsigned char)*++cp1)) ;
1070
1071                         if (!*cp1) break;
1072
1073                         for (cp2 = cp1 + 1; *cp2 && !isspace((unsigned char)*cp2); ++cp2) ;
1074
1075                         *cp2 = '\0';
1076                         strncpy(dst, cp1, siz - 1);
1077                         dst[siz - 1] = '\0';
1078                         fclose(fp);
1079                         return (dst);
1080                 }
1081         }
1082
1083         fclose(fp);
1084         return (NULL);
1085 }