res_query.c revision 270838
1/* 2 * Portions Copyright (C) 2004, 2005, 2008 Internet Systems Consortium, Inc. ("ISC") 3 * Portions Copyright (C) 1996-2001, 2003 Internet Software Consortium. 4 * 5 * Permission to use, copy, modify, and/or distribute this software for any 6 * purpose with or without fee is hereby granted, provided that the above 7 * copyright notice and this permission notice appear in all copies. 8 * 9 * THE SOFTWARE IS PROVIDED "AS IS" AND ISC DISCLAIMS ALL WARRANTIES WITH 10 * REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF MERCHANTABILITY 11 * AND FITNESS. IN NO EVENT SHALL ISC BE LIABLE FOR ANY SPECIAL, DIRECT, 12 * INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES WHATSOEVER RESULTING FROM 13 * LOSS OF USE, DATA OR PROFITS, WHETHER IN AN ACTION OF CONTRACT, NEGLIGENCE 14 * OR OTHER TORTIOUS ACTION, ARISING OUT OF OR IN CONNECTION WITH THE USE OR 15 * PERFORMANCE OF THIS SOFTWARE. 16 */ 17 18/* 19 * Copyright (c) 1988, 1993 20 * The Regents of the University of California. All rights reserved. 21 * 22 * Redistribution and use in source and binary forms, with or without 23 * modification, are permitted provided that the following conditions 24 * are met: 25 * 1. Redistributions of source code must retain the above copyright 26 * notice, this list of conditions and the following disclaimer. 27 * 2. Redistributions in binary form must reproduce the above copyright 28 * notice, this list of conditions and the following disclaimer in the 29 * documentation and/or other materials provided with the distribution. 30 * 4. Neither the name of the University nor the names of its contributors 31 * may be used to endorse or promote products derived from this software 32 * without specific prior written permission. 33 * 34 * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND 35 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE 36 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE 37 * ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE 38 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL 39 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS 40 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) 41 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT 42 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY 43 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF 44 * SUCH DAMAGE. 45 */ 46 47/* 48 * Portions Copyright (c) 1993 by Digital Equipment Corporation. 49 * 50 * Permission to use, copy, modify, and distribute this software for any 51 * purpose with or without fee is hereby granted, provided that the above 52 * copyright notice and this permission notice appear in all copies, and that 53 * the name of Digital Equipment Corporation not be used in advertising or 54 * publicity pertaining to distribution of the document or software without 55 * specific, written prior permission. 56 * 57 * THE SOFTWARE IS PROVIDED "AS IS" AND DIGITAL EQUIPMENT CORP. DISCLAIMS ALL 58 * WARRANTIES WITH REGARD TO THIS SOFTWARE, INCLUDING ALL IMPLIED WARRANTIES 59 * OF MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL DIGITAL EQUIPMENT 60 * CORPORATION BE LIABLE FOR ANY SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL 61 * DAMAGES OR ANY DAMAGES WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR 62 * PROFITS, WHETHER IN AN ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS 63 * ACTION, ARISING OUT OF OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS 64 * SOFTWARE. 65 */ 66 67#if defined(LIBC_SCCS) && !defined(lint) 68static const char sccsid[] = "@(#)res_query.c 8.1 (Berkeley) 6/4/93"; 69static const char rcsid[] = "$Id: res_query.c,v 1.11 2008/11/14 02:36:51 marka Exp $"; 70#endif /* LIBC_SCCS and not lint */ 71#include <sys/cdefs.h> 72__FBSDID("$FreeBSD: stable/10/lib/libc/resolv/res_query.c 270838 2014-08-30 10:16:25Z ume $"); 73 74#include "port_before.h" 75#include <sys/types.h> 76#include <sys/param.h> 77#include <netinet/in.h> 78#include <arpa/inet.h> 79#include <arpa/nameser.h> 80#include <ctype.h> 81#include <errno.h> 82#include <netdb.h> 83#include <resolv.h> 84#include <stdio.h> 85#include <stdlib.h> 86#include <string.h> 87#include <unistd.h> 88#include "port_after.h" 89 90/* Options. Leave them on. */ 91#define DEBUG 92 93#if PACKETSZ > 1024 94#define MAXPACKET PACKETSZ 95#else 96#define MAXPACKET 1024 97#endif 98 99/*% 100 * Formulate a normal query, send, and await answer. 101 * Returned answer is placed in supplied buffer "answer". 102 * Perform preliminary check of answer, returning success only 103 * if no error is indicated and the answer count is nonzero. 104 * Return the size of the response on success, -1 on error. 105 * Error number is left in H_ERRNO. 106 * 107 * Caller must parse answer and determine whether it answers the question. 108 */ 109int 110res_nquery(res_state statp, 111 const char *name, /*%< domain name */ 112 int class, int type, /*%< class and type of query */ 113 u_char *answer, /*%< buffer to put answer */ 114 int anslen) /*%< size of answer buffer */ 115{ 116 u_char buf[MAXPACKET]; 117 HEADER *hp = (HEADER *) answer; 118 u_int oflags; 119 u_char *rdata; 120 int n; 121 122 oflags = statp->_flags; 123 124again: 125 hp->rcode = NOERROR; /*%< default */ 126#ifdef DEBUG 127 if (statp->options & RES_DEBUG) 128 printf(";; res_query(%s, %d, %d)\n", name, class, type); 129#endif 130 131 n = res_nmkquery(statp, QUERY, name, class, type, NULL, 0, NULL, 132 buf, sizeof(buf)); 133#ifdef RES_USE_EDNS0 134 if (n > 0 && (statp->_flags & RES_F_EDNS0ERR) == 0 && 135 (statp->options & (RES_USE_EDNS0|RES_USE_DNSSEC|RES_NSID))) { 136 n = res_nopt(statp, n, buf, sizeof(buf), anslen); 137 rdata = &buf[n]; 138 if (n > 0 && (statp->options & RES_NSID) != 0U) { 139 n = res_nopt_rdata(statp, n, buf, sizeof(buf), rdata, 140 NS_OPT_NSID, 0, NULL); 141 } 142 } 143#endif 144 if (n <= 0) { 145#ifdef DEBUG 146 if (statp->options & RES_DEBUG) 147 printf(";; res_query: mkquery failed\n"); 148#endif 149 RES_SET_H_ERRNO(statp, NO_RECOVERY); 150 return (n); 151 } 152 153 n = res_nsend(statp, buf, n, answer, anslen); 154 if (n < 0) { 155#ifdef RES_USE_EDNS0 156 /* if the query choked with EDNS0, retry without EDNS0 */ 157 if ((statp->options & (RES_USE_EDNS0|RES_USE_DNSSEC)) != 0U && 158 ((oflags ^ statp->_flags) & RES_F_EDNS0ERR) != 0) { 159 statp->_flags |= RES_F_EDNS0ERR; 160 if (statp->options & RES_DEBUG) 161 printf(";; res_nquery: retry without EDNS0\n"); 162 goto again; 163 } 164#endif 165#ifdef DEBUG 166 if (statp->options & RES_DEBUG) 167 printf(";; res_query: send error\n"); 168#endif 169 RES_SET_H_ERRNO(statp, TRY_AGAIN); 170 return (n); 171 } 172 173 if (hp->rcode != NOERROR || ntohs(hp->ancount) == 0) { 174#ifdef DEBUG 175 if (statp->options & RES_DEBUG) 176 printf(";; rcode = (%s), counts = an:%d ns:%d ar:%d\n", 177 p_rcode(hp->rcode), 178 ntohs(hp->ancount), 179 ntohs(hp->nscount), 180 ntohs(hp->arcount)); 181#endif 182 switch (hp->rcode) { 183 case NXDOMAIN: 184 RES_SET_H_ERRNO(statp, HOST_NOT_FOUND); 185 break; 186 case SERVFAIL: 187 RES_SET_H_ERRNO(statp, TRY_AGAIN); 188 break; 189 case NOERROR: 190 RES_SET_H_ERRNO(statp, NO_DATA); 191 break; 192 case FORMERR: 193 case NOTIMP: 194 case REFUSED: 195 default: 196 RES_SET_H_ERRNO(statp, NO_RECOVERY); 197 break; 198 } 199 return (-1); 200 } 201 return (n); 202} 203 204/*% 205 * Formulate a normal query, send, and retrieve answer in supplied buffer. 206 * Return the size of the response on success, -1 on error. 207 * If enabled, implement search rules until answer or unrecoverable failure 208 * is detected. Error code, if any, is left in H_ERRNO. 209 */ 210int 211res_nsearch(res_state statp, 212 const char *name, /*%< domain name */ 213 int class, int type, /*%< class and type of query */ 214 u_char *answer, /*%< buffer to put answer */ 215 int anslen) /*%< size of answer */ 216{ 217 const char *cp, * const *domain; 218 HEADER *hp = (HEADER *) answer; 219 char tmp[NS_MAXDNAME]; 220 u_int dots; 221 int trailing_dot, ret, saved_herrno; 222 int got_nodata = 0, got_servfail = 0, root_on_list = 0; 223 int tried_as_is = 0; 224 int searched = 0; 225 226 errno = 0; 227 RES_SET_H_ERRNO(statp, HOST_NOT_FOUND); /*%< True if we never query. */ 228 dots = 0; 229 for (cp = name; *cp != '\0'; cp++) 230 dots += (*cp == '.'); 231 trailing_dot = 0; 232 if (cp > name && *--cp == '.') 233 trailing_dot++; 234 235 /* If there aren't any dots, it could be a user-level alias. */ 236 if (!dots && (cp = res_hostalias(statp, name, tmp, sizeof tmp))!= NULL) 237 return (res_nquery(statp, cp, class, type, answer, anslen)); 238 239 /* 240 * If there are enough dots in the name, let's just give it a 241 * try 'as is'. The threshold can be set with the "ndots" option. 242 * Also, query 'as is', if there is a trailing dot in the name. 243 */ 244 saved_herrno = -1; 245 if (dots >= statp->ndots || trailing_dot) { 246 ret = res_nquerydomain(statp, name, NULL, class, type, 247 answer, anslen); 248 if (ret > 0 || trailing_dot) 249 return (ret); 250 if (errno == ECONNREFUSED) { 251 RES_SET_H_ERRNO(statp, TRY_AGAIN); 252 return (-1); 253 } 254 switch (statp->res_h_errno) { 255 case NO_DATA: 256 case HOST_NOT_FOUND: 257 break; 258 case TRY_AGAIN: 259 if (hp->rcode == SERVFAIL) 260 break; 261 /* FALLTHROUGH */ 262 default: 263 return (-1); 264 } 265 saved_herrno = statp->res_h_errno; 266 tried_as_is++; 267 } 268 269 /* 270 * We do at least one level of search if 271 * - there is no dot and RES_DEFNAME is set, or 272 * - there is at least one dot, there is no trailing dot, 273 * and RES_DNSRCH is set. 274 */ 275 if ((!dots && (statp->options & RES_DEFNAMES) != 0U) || 276 (dots && !trailing_dot && (statp->options & RES_DNSRCH) != 0U)) { 277 int done = 0; 278 279 for (domain = (const char * const *)statp->dnsrch; 280 *domain && !done; 281 domain++) { 282 searched = 1; 283 284 if (domain[0][0] == '\0' || 285 (domain[0][0] == '.' && domain[0][1] == '\0')) 286 root_on_list++; 287 288 if (root_on_list && tried_as_is) 289 continue; 290 291 ret = res_nquerydomain(statp, name, *domain, 292 class, type, 293 answer, anslen); 294 if (ret > 0) 295 return (ret); 296 297 /* 298 * If no server present, give up. 299 * If name isn't found in this domain, 300 * keep trying higher domains in the search list 301 * (if that's enabled). 302 * On a NO_DATA error, keep trying, otherwise 303 * a wildcard entry of another type could keep us 304 * from finding this entry higher in the domain. 305 * If we get some other error (negative answer or 306 * server failure), then stop searching up, 307 * but try the input name below in case it's 308 * fully-qualified. 309 */ 310 if (errno == ECONNREFUSED) { 311 RES_SET_H_ERRNO(statp, TRY_AGAIN); 312 return (-1); 313 } 314 315 switch (statp->res_h_errno) { 316 case NO_DATA: 317 got_nodata++; 318 /* FALLTHROUGH */ 319 case HOST_NOT_FOUND: 320 /* keep trying */ 321 break; 322 case TRY_AGAIN: 323 /* 324 * This can occur due to a server failure 325 * (that is, all listed servers have failed), 326 * or all listed servers have timed out. 327 * ((HEADER *)answer)->rcode may not be set 328 * to SERVFAIL in the case of a timeout. 329 * 330 * Either way we must return TRY_AGAIN in 331 * order to avoid non-deterministic 332 * return codes. 333 * For example, loaded name servers or races 334 * against network startup/validation (dhcp, 335 * ppp, etc) can cause the search to timeout 336 * on one search element, e.g. 'fu.bar.com', 337 * and return a definitive failure on the 338 * next search element, e.g. 'fu.'. 339 */ 340 got_servfail++; 341 if (hp->rcode == SERVFAIL) { 342 /* try next search element, if any */ 343 break; 344 } 345 /* FALLTHROUGH */ 346 default: 347 /* anything else implies that we're done */ 348 done++; 349 } 350 351 /* if we got here for some reason other than DNSRCH, 352 * we only wanted one iteration of the loop, so stop. 353 */ 354 if ((statp->options & RES_DNSRCH) == 0U) 355 done++; 356 } 357 } 358 359 switch (statp->res_h_errno) { 360 case NO_DATA: 361 case HOST_NOT_FOUND: 362 break; 363 case TRY_AGAIN: 364 if (hp->rcode == SERVFAIL) 365 break; 366 /* FALLTHROUGH */ 367 default: 368 goto giveup; 369 } 370 371 /* 372 * If the query has not already been tried as is then try it 373 * unless RES_NOTLDQUERY is set and there were no dots. 374 */ 375 if ((dots || !searched || (statp->options & RES_NOTLDQUERY) == 0U) && 376 !(tried_as_is || root_on_list)) { 377 ret = res_nquerydomain(statp, name, NULL, class, type, 378 answer, anslen); 379 if (ret > 0) 380 return (ret); 381 } 382 383 /* if we got here, we didn't satisfy the search. 384 * if we did an initial full query, return that query's H_ERRNO 385 * (note that we wouldn't be here if that query had succeeded). 386 * else if we ever got a nodata, send that back as the reason. 387 * else send back meaningless H_ERRNO, that being the one from 388 * the last DNSRCH we did. 389 */ 390giveup: 391 if (saved_herrno != -1) 392 RES_SET_H_ERRNO(statp, saved_herrno); 393 else if (got_nodata) 394 RES_SET_H_ERRNO(statp, NO_DATA); 395 else if (got_servfail) 396 RES_SET_H_ERRNO(statp, TRY_AGAIN); 397 return (-1); 398} 399 400/*% 401 * Perform a call on res_query on the concatenation of name and domain, 402 * removing a trailing dot from name if domain is NULL. 403 */ 404int 405res_nquerydomain(res_state statp, 406 const char *name, 407 const char *domain, 408 int class, int type, /*%< class and type of query */ 409 u_char *answer, /*%< buffer to put answer */ 410 int anslen) /*%< size of answer */ 411{ 412 char nbuf[MAXDNAME]; 413 const char *longname = nbuf; 414 int n, d; 415 416#ifdef DEBUG 417 if (statp->options & RES_DEBUG) 418 printf(";; res_nquerydomain(%s, %s, %d, %d)\n", 419 name, domain?domain:"<Nil>", class, type); 420#endif 421 if (domain == NULL) { 422 /* 423 * Check for trailing '.'; 424 * copy without '.' if present. 425 */ 426 n = strlen(name); 427 if (n >= MAXDNAME) { 428 RES_SET_H_ERRNO(statp, NO_RECOVERY); 429 return (-1); 430 } 431 n--; 432 if (n >= 0 && name[n] == '.') { 433 strncpy(nbuf, name, n); 434 nbuf[n] = '\0'; 435 } else 436 longname = name; 437 } else { 438 n = strlen(name); 439 d = strlen(domain); 440 if (n + d + 1 >= MAXDNAME) { 441 RES_SET_H_ERRNO(statp, NO_RECOVERY); 442 return (-1); 443 } 444 sprintf(nbuf, "%s.%s", name, domain); 445 } 446 return (res_nquery(statp, longname, class, type, answer, anslen)); 447} 448 449const char * 450res_hostalias(const res_state statp, const char *name, char *dst, size_t siz) { 451 char *file, *cp1, *cp2; 452 char buf[BUFSIZ]; 453 FILE *fp; 454 455 if (statp->options & RES_NOALIASES) 456 return (NULL); 457 if (issetugid()) 458 return (NULL); 459 file = getenv("HOSTALIASES"); 460 if (file == NULL || (fp = fopen(file, "re")) == NULL) 461 return (NULL); 462 setbuf(fp, NULL); 463 buf[sizeof(buf) - 1] = '\0'; 464 while (fgets(buf, sizeof(buf), fp)) { 465 for (cp1 = buf; *cp1 && !isspace((unsigned char)*cp1); ++cp1) 466 ; 467 if (!*cp1) 468 break; 469 *cp1 = '\0'; 470 if (ns_samename(buf, name) == 1) { 471 while (isspace((unsigned char)*++cp1)) 472 ; 473 if (!*cp1) 474 break; 475 for (cp2 = cp1 + 1; *cp2 && 476 !isspace((unsigned char)*cp2); ++cp2) 477 ; 478 *cp2 = '\0'; 479 strncpy(dst, cp1, siz - 1); 480 dst[siz - 1] = '\0'; 481 fclose(fp); 482 return (dst); 483 } 484 } 485 fclose(fp); 486 return (NULL); 487} 488 489/*! \file */ 490