1/* $NetBSD: res_query.c,v 1.16 2015/02/24 17:56:20 christos Exp $ */ 2 3/* 4 * Portions Copyright (C) 2004, 2005, 2008 Internet Systems Consortium, Inc. ("ISC") 5 * Portions Copyright (C) 1996-2001, 2003 Internet Software Consortium. 6 * 7 * Permission to use, copy, modify, and/or distribute this software for any 8 * purpose with or without fee is hereby granted, provided that the above 9 * copyright notice and this permission notice appear in all copies. 10 * 11 * THE SOFTWARE IS PROVIDED "AS IS" AND ISC DISCLAIMS ALL WARRANTIES WITH 12 * REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF MERCHANTABILITY 13 * AND FITNESS. IN NO EVENT SHALL ISC BE LIABLE FOR ANY SPECIAL, DIRECT, 14 * INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES WHATSOEVER RESULTING FROM 15 * LOSS OF USE, DATA OR PROFITS, WHETHER IN AN ACTION OF CONTRACT, NEGLIGENCE 16 * OR OTHER TORTIOUS ACTION, ARISING OUT OF OR IN CONNECTION WITH THE USE OR 17 * PERFORMANCE OF THIS SOFTWARE. 18 */ 19 20/* 21 * Copyright (c) 1988, 1993 22 * The Regents of the University of California. All rights reserved. 23 * 24 * Redistribution and use in source and binary forms, with or without 25 * modification, are permitted provided that the following conditions 26 * are met: 27 * 1. Redistributions of source code must retain the above copyright 28 * notice, this list of conditions and the following disclaimer. 29 * 2. Redistributions in binary form must reproduce the above copyright 30 * notice, this list of conditions and the following disclaimer in the 31 * documentation and/or other materials provided with the distribution. 32 * 3. Neither the name of the University nor the names of its contributors 33 * may be used to endorse or promote products derived from this software 34 * without specific prior written permission. 35 * 36 * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND 37 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE 38 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE 39 * ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE 40 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL 41 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS 42 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) 43 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT 44 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY 45 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF 46 * SUCH DAMAGE. 47 */ 48 49/* 50 * Portions Copyright (c) 1993 by Digital Equipment Corporation. 51 * 52 * Permission to use, copy, modify, and distribute this software for any 53 * purpose with or without fee is hereby granted, provided that the above 54 * copyright notice and this permission notice appear in all copies, and that 55 * the name of Digital Equipment Corporation not be used in advertising or 56 * publicity pertaining to distribution of the document or software without 57 * specific, written prior permission. 58 * 59 * THE SOFTWARE IS PROVIDED "AS IS" AND DIGITAL EQUIPMENT CORP. DISCLAIMS ALL 60 * WARRANTIES WITH REGARD TO THIS SOFTWARE, INCLUDING ALL IMPLIED WARRANTIES 61 * OF MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL DIGITAL EQUIPMENT 62 * CORPORATION BE LIABLE FOR ANY SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL 63 * DAMAGES OR ANY DAMAGES WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR 64 * PROFITS, WHETHER IN AN ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS 65 * ACTION, ARISING OUT OF OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS 66 * SOFTWARE. 67 */ 68 69#if defined(LIBC_SCCS) && !defined(lint) 70static const char sccsid[] = "@(#)res_query.c 8.1 (Berkeley) 6/4/93"; 71static const char rcsid[] = "$Id: res_query.c,v 1.11 2008/11/14 02:36:51 marka Exp $"; 72#endif /* LIBC_SCCS and not lint */ 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 "port_after.h" 88 89/* Options. Leave them on. */ 90//#define DEBUG 91 92#if PACKETSZ > 1024 93#define MAXPACKET PACKETSZ 94#else 95#define MAXPACKET 1024 96#endif 97 98/*% 99 * Formulate a normal query, send, and await answer. 100 * Returned answer is placed in supplied buffer "answer". 101 * Perform preliminary check of answer, returning success only 102 * if no error is indicated and the answer count is nonzero. 103 * Return the size of the response on success, -1 on error. 104 * Error number is left in H_ERRNO. 105 * 106 * Caller must parse answer and determine whether it answers the question. 107 */ 108int 109res_nquery(res_state statp, 110 const char *name, /*%< domain name */ 111 int class, int type, /*%< class and type of query */ 112 u_char *answer, /*%< buffer to put answer */ 113 int anslen) /*%< size of answer buffer */ 114{ 115 u_char buf[MAXPACKET]; 116 HEADER *hp = (HEADER *)(void *)answer; 117 u_int oflags; 118 u_char *rdata; 119 int n; 120 121 oflags = statp->_flags; 122 123again: 124 hp->rcode = NOERROR; /*%< default */ 125#ifdef DEBUG 126 if (statp->options & RES_DEBUG) 127 printf(";; res_query(%s, %d, %d)\n", name, class, type); 128#endif 129 130 n = res_nmkquery(statp, QUERY, name, class, type, NULL, 0, NULL, 131 buf, (int)sizeof(buf)); 132#ifdef RES_USE_EDNS0 133 if (n > 0 && (statp->_flags & RES_F_EDNS0ERR) == 0 && 134 (statp->options & (RES_USE_EDNS0|RES_USE_DNSSEC|RES_NSID)) != 0U) { 135 n = res_nopt(statp, n, buf, (int)sizeof(buf), anslen); 136 rdata = &buf[n]; 137 if (n > 0 && (statp->options & RES_NSID) != 0U) { 138 n = res_nopt_rdata(statp, n, buf, (int)sizeof(buf), 139 rdata, NS_OPT_NSID, 0, NULL); 140 } 141 } 142#endif 143 if (n <= 0) { 144#ifdef DEBUG 145 if (statp->options & RES_DEBUG) 146 printf(";; res_query: mkquery failed\n"); 147#endif 148 RES_SET_H_ERRNO(statp, NO_RECOVERY); 149 return (n); 150 } 151 152 n = res_nsend(statp, buf, n, answer, anslen); 153 if (n < 0) { 154#ifdef RES_USE_EDNS0 155 /* if the query choked with EDNS0, retry without EDNS0 */ 156 if ((statp->options & (RES_USE_EDNS0|RES_USE_DNSSEC)) != 0U && 157 ((oflags ^ statp->_flags) & RES_F_EDNS0ERR) != 0) { 158 statp->_flags |= RES_F_EDNS0ERR; 159 if (statp->options & RES_DEBUG) 160 printf(";; res_nquery: retry without EDNS0\n"); 161 goto again; 162 } 163#endif 164#ifdef DEBUG 165 if (statp->options & RES_DEBUG) 166 printf(";; res_query: send error\n"); 167#endif 168 RES_SET_H_ERRNO(statp, TRY_AGAIN); 169 return (n); 170 } 171 172 if (hp->rcode != NOERROR || ntohs(hp->ancount) == 0) { 173#ifdef DEBUG 174 if (statp->options & RES_DEBUG) 175 printf(";; rcode = (%s), counts = an:%d ns:%d ar:%d\n", 176 p_rcode(hp->rcode), 177 ntohs(hp->ancount), 178 ntohs(hp->nscount), 179 ntohs(hp->arcount)); 180#endif 181 switch (hp->rcode) { 182 case NXDOMAIN: 183 RES_SET_H_ERRNO(statp, HOST_NOT_FOUND); 184 break; 185 case SERVFAIL: 186 RES_SET_H_ERRNO(statp, TRY_AGAIN); 187 break; 188 case NOERROR: 189 RES_SET_H_ERRNO(statp, NO_DATA); 190 break; 191 case FORMERR: 192 case NOTIMP: 193 case REFUSED: 194 default: 195 RES_SET_H_ERRNO(statp, NO_RECOVERY); 196 break; 197 } 198 return (-1); 199 } 200 return (n); 201} 202 203/*% 204 * Formulate a normal query, send, and retrieve answer in supplied buffer. 205 * Return the size of the response on success, -1 on error. 206 * If enabled, implement search rules until answer or unrecoverable failure 207 * is detected. Error code, if any, is left in H_ERRNO. 208 */ 209int 210res_nsearch(res_state statp, 211 const char *name, /*%< domain name */ 212 int class, int type, /*%< class and type of query */ 213 u_char *answer, /*%< buffer to put answer */ 214 int anslen) /*%< size of answer */ 215{ 216 const char *cp, * const *domain; 217 HEADER *hp = (HEADER *)(void *)answer; 218 char tmp[NS_MAXDNAME]; 219 u_int dots; 220 int trailing_dot, ret, saved_herrno; 221 int got_nodata = 0, got_servfail = 0, root_on_list = 0; 222 int tried_as_is = 0; 223 int searched = 0; 224 225 errno = 0; 226 RES_SET_H_ERRNO(statp, HOST_NOT_FOUND); /*%< True if we never query. */ 227 dots = 0; 228 for (cp = name; *cp != '\0'; cp++) 229 dots += (*cp == '.'); 230 trailing_dot = 0; 231 if (cp > name && *--cp == '.') 232 trailing_dot++; 233 234 /* If there aren't any dots, it could be a user-level alias. */ 235 if (!dots && (cp = res_hostalias(statp, name, tmp, sizeof tmp))!= NULL) 236 return (res_nquery(statp, cp, class, type, answer, anslen)); 237 238 /* 239 * If there are enough dots in the name, let's just give it a 240 * try 'as is'. The threshold can be set with the "ndots" option. 241 * Also, query 'as is', if there is a trailing dot in the name. 242 */ 243 saved_herrno = -1; 244 if (dots >= statp->ndots || trailing_dot) { 245 ret = res_nquerydomain(statp, name, NULL, class, type, 246 answer, anslen); 247 if (ret > 0 || trailing_dot) 248 return (ret); 249 saved_herrno = statp->res_h_errno; 250 tried_as_is++; 251 } 252 253 /* 254 * We do at least one level of search if 255 * - there is no dot and RES_DEFNAME is set, or 256 * - there is at least one dot, there is no trailing dot, 257 * and RES_DNSRCH is set. 258 */ 259 if ((!dots && (statp->options & RES_DEFNAMES) != 0U) || 260 (dots && !trailing_dot && (statp->options & RES_DNSRCH) != 0U)) { 261 int done = 0; 262 263 for (domain = (const char * const *)statp->dnsrch; 264 *domain && !done; 265 domain++) { 266 searched = 1; 267 268 if (domain[0][0] == '\0' || 269 (domain[0][0] == '.' && domain[0][1] == '\0')) 270 root_on_list++; 271 272 ret = res_nquerydomain(statp, name, *domain, 273 class, type, 274 answer, anslen); 275 if (ret > 0) 276 return (ret); 277 278 /* 279 * If no server present, give up. 280 * If name isn't found in this domain, 281 * keep trying higher domains in the search list 282 * (if that's enabled). 283 * On a NO_DATA error, keep trying, otherwise 284 * a wildcard entry of another type could keep us 285 * from finding this entry higher in the domain. 286 * If we get some other error (negative answer or 287 * server failure), then stop searching up, 288 * but try the input name below in case it's 289 * fully-qualified. 290 */ 291 if (errno == ECONNREFUSED) { 292 RES_SET_H_ERRNO(statp, TRY_AGAIN); 293 return (-1); 294 } 295 296 switch (statp->res_h_errno) { 297 case NO_DATA: 298 got_nodata++; 299 /* FALLTHROUGH */ 300 case HOST_NOT_FOUND: 301 /* keep trying */ 302 break; 303 case TRY_AGAIN: 304 if (hp->rcode == SERVFAIL) { 305 /* try next search element, if any */ 306 got_servfail++; 307 break; 308 } 309 /* FALLTHROUGH */ 310 default: 311 /* anything else implies that we're done */ 312 done++; 313 } 314 315 /* if we got here for some reason other than DNSRCH, 316 * we only wanted one iteration of the loop, so stop. 317 */ 318 if ((statp->options & RES_DNSRCH) == 0U) 319 done++; 320 } 321 } 322 323 /* 324 * If the query has not already been tried as is then try it 325 * unless RES_NOTLDQUERY is set and there were no dots. 326 */ 327 if ((dots || !searched || (statp->options & RES_NOTLDQUERY) == 0U) && 328 !(tried_as_is || root_on_list)) { 329 ret = res_nquerydomain(statp, name, NULL, class, type, 330 answer, anslen); 331 if (ret > 0) 332 return (ret); 333 } 334 335 /* if we got here, we didn't satisfy the search. 336 * if we did an initial full query, return that query's H_ERRNO 337 * (note that we wouldn't be here if that query had succeeded). 338 * else if we ever got a nodata, send that back as the reason. 339 * else send back meaningless H_ERRNO, that being the one from 340 * the last DNSRCH we did. 341 */ 342 if (saved_herrno != -1) 343 RES_SET_H_ERRNO(statp, saved_herrno); 344 else if (got_nodata) 345 RES_SET_H_ERRNO(statp, NO_DATA); 346 else if (got_servfail) 347 RES_SET_H_ERRNO(statp, TRY_AGAIN); 348 return (-1); 349} 350 351/*% 352 * Perform a call on res_query on the concatenation of name and domain, 353 * removing a trailing dot from name if domain is NULL. 354 */ 355int 356res_nquerydomain(res_state statp, 357 const char *name, 358 const char *domain, 359 int class, int type, /*%< class and type of query */ 360 u_char *answer, /*%< buffer to put answer */ 361 int anslen) /*%< size of answer */ 362{ 363 char nbuf[MAXDNAME]; 364 const char *longname = nbuf; 365 size_t n, d; 366 367#ifdef DEBUG 368 if (statp->options & RES_DEBUG) 369 printf(";; res_nquerydomain(%s, %s, %d, %d)\n", 370 name, domain?domain:"<Nil>", class, type); 371#endif 372 if (domain == NULL) { 373 /* 374 * Check for trailing '.'; 375 * copy without '.' if present. 376 */ 377 n = strlen(name); 378 if (n >= MAXDNAME) { 379 RES_SET_H_ERRNO(statp, NO_RECOVERY); 380 return (-1); 381 } 382 if (n && name[--n] == '.') { 383 strncpy(nbuf, name, n); 384 nbuf[n] = '\0'; 385 } else 386 longname = name; 387 } else { 388 n = strlen(name); 389 d = strlen(domain); 390 if (n + d + 1 >= MAXDNAME) { 391 RES_SET_H_ERRNO(statp, NO_RECOVERY); 392 return (-1); 393 } 394 sprintf(nbuf, "%s.%s", name, domain); 395 } 396 return (res_nquery(statp, longname, class, type, answer, anslen)); 397} 398 399const char * 400res_hostalias(const res_state statp, const char *name, char *dst, size_t siz) { 401 char *file, *cp1, *cp2; 402 char buf[BUFSIZ]; 403 FILE *fp; 404 405 if (statp->options & RES_NOALIASES) 406 return (NULL); 407 408 file = getenv("HOSTALIASES"); 409 if (file == NULL || (fp = fopen(file, "re")) == NULL) 410 return (NULL); 411 buf[sizeof(buf) - 1] = '\0'; 412 while (fgets(buf, (int)sizeof(buf), fp)) { 413 for (cp1 = buf; *cp1 && !isspace((unsigned char)*cp1); ++cp1) 414 ; 415 if (!*cp1) 416 break; 417 *cp1 = '\0'; 418 if (ns_samename(buf, name) == 1) { 419 while (isspace((unsigned char)*++cp1)) 420 ; 421 if (!*cp1) 422 break; 423 for (cp2 = cp1 + 1; *cp2 && 424 !isspace((unsigned char)*cp2); ++cp2) 425 ; 426 *cp2 = '\0'; 427 strncpy(dst, cp1, siz - 1); 428 dst[siz - 1] = '\0'; 429 fclose(fp); 430 return (dst); 431 } 432 } 433 fclose(fp); 434 return (NULL); 435} 436 437/*! \file */ 438