1 /* 2 * @(#)res_query.c 8.1 (Berkeley) 6/4/93 3 * $Id: res_query.c,v 1.8.672.2 2008/04/03 10:49:22 marka Exp $ 4 */ 5 6 /* 7 * Copyright (c) 1988, 1993 8 * The Regents of the University of California. All rights reserved. 9 * 10 * Redistribution and use in source and binary forms, with or without 11 * modification, are permitted provided that the following conditions 12 * are met: 13 * 1. Redistributions of source code must retain the above copyright 14 * notice, this list of conditions and the following disclaimer. 15 * 2. Redistributions in binary form must reproduce the above copyright 16 * notice, this list of conditions and the following disclaimer in the 17 * documentation and/or other materials provided with the distribution. 18 * 3. Neither the name of the University nor the names of its contributors 19 * may be used to endorse or promote products derived from this software 20 * without specific prior written permission. 21 * 22 * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND 23 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE 24 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE 25 * ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE 26 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL 27 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS 28 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) 29 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT 30 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY 31 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF 32 * SUCH DAMAGE. 33 */ 34 35 /* 36 * Portions Copyright (c) 1993 by Digital Equipment Corporation. 37 * 38 * Permission to use, copy, modify, and distribute this software for any 39 * purpose with or without fee is hereby granted, provided that the above 40 * copyright notice and this permission notice appear in all copies, and that 41 * the name of Digital Equipment Corporation not be used in advertising or 42 * publicity pertaining to distribution of the document or software without 43 * specific, written prior permission. 44 * 45 * THE SOFTWARE IS PROVIDED "AS IS" AND DIGITAL EQUIPMENT CORP. DISCLAIMS ALL 46 * WARRANTIES WITH REGARD TO THIS SOFTWARE, INCLUDING ALL IMPLIED WARRANTIES 47 * OF MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL DIGITAL EQUIPMENT 48 * CORPORATION BE LIABLE FOR ANY SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL 49 * DAMAGES OR ANY DAMAGES WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR 50 * PROFITS, WHETHER IN AN ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS 51 * ACTION, ARISING OUT OF OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS 52 * SOFTWARE. 53 */ 54 55 /* 56 * Copyright (c) 2004 by Internet Systems Consortium, Inc. ("ISC") 57 * Portions Copyright (c) 1996-1999 by Internet Software Consortium. 58 * 59 * Permission to use, copy, modify, and distribute this software for any 60 * purpose with or without fee is hereby granted, provided that the above 61 * copyright notice and this permission notice appear in all copies. 62 * 63 * THE SOFTWARE IS PROVIDED "AS IS" AND ISC DISCLAIMS ALL WARRANTIES 64 * WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF 65 * MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL ISC BE LIABLE FOR 66 * ANY SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES 67 * WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS, WHETHER IN AN 68 * ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT 69 * OF OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE. 70 */ 71 72 #include "port_before.h" 73 #include <sys/types.h> 74 #include <sys/param.h> 75 #include <netinet/in.h> 76 #include <arpa/inet.h> 77 #include <arpa/nameser.h> 78 #include <ctype.h> 79 #include <errno.h> 80 #include <netdb.h> 81 #include <resolv.h> 82 #include <stdio.h> 83 #include <stdlib.h> 84 #include <string.h> 85 #include "port_after.h" 86 87 /* Options. Leave them on. */ 88 #define DEBUG 89 90 #if PACKETSZ > 1024 91 #define MAXPACKET PACKETSZ 92 #else 93 #define MAXPACKET 1024 94 #endif 95 96 /*% 97 * Formulate a normal query, send, and await answer. 98 * Returned answer is placed in supplied buffer "answer". 99 * Perform preliminary check of answer, returning success only 100 * if no error is indicated and the answer count is nonzero. 101 * Return the size of the response on success, -1 on error. 102 * Error number is left in H_ERRNO. 103 * 104 * Caller must parse answer and determine whether it answers the question. 105 */ 106 int 107 res_nquery(res_state statp, 108 const char *name, /*%< domain name */ 109 int class, int type, /*%< class and type of query */ 110 u_char *answer, /*%< buffer to put answer */ 111 int anslen) /*%< size of answer buffer */ 112 { 113 u_char buf[MAXPACKET]; 114 HEADER *hp = (HEADER *) answer; 115 u_int oflags; 116 u_char *rdata; 117 int n; 118 119 oflags = statp->_flags; 120 121 again: 122 hp->rcode = NOERROR; /*%< default */ 123 #ifdef DEBUG 124 if (statp->options & RES_DEBUG) 125 printf(";; res_query(%s, %d, %d)\n", name, class, type); 126 #endif 127 128 n = res_nmkquery(statp, QUERY, name, class, type, NULL, 0, NULL, 129 buf, sizeof(buf)); 130 #ifdef RES_USE_EDNS0 131 if (n > 0 && (statp->_flags & RES_F_EDNS0ERR) == 0 && 132 (statp->options & (RES_USE_EDNS0|RES_USE_DNSSEC|RES_NSID))) { 133 n = res_nopt(statp, n, buf, sizeof(buf), anslen); 134 rdata = &buf[n]; 135 if (n > 0 && (statp->options & RES_NSID) != 0U) { 136 n = res_nopt_rdata(statp, n, buf, sizeof(buf), rdata, 137 NS_OPT_NSID, 0, NULL); 138 } 139 } 140 #endif 141 if (n <= 0) { 142 #ifdef DEBUG 143 if (statp->options & RES_DEBUG) 144 printf(";; res_query: mkquery failed\n"); 145 #endif 146 RES_SET_H_ERRNO(statp, NO_RECOVERY); 147 return (n); 148 } 149 150 n = res_nsend(statp, buf, n, answer, anslen); 151 if (n < 0) { 152 #ifdef RES_USE_EDNS0 153 /* if the query choked with EDNS0, retry without EDNS0 */ 154 if ((statp->options & (RES_USE_EDNS0|RES_USE_DNSSEC)) != 0U && 155 ((oflags ^ statp->_flags) & RES_F_EDNS0ERR) != 0) { 156 statp->_flags |= RES_F_EDNS0ERR; 157 if (statp->options & RES_DEBUG) 158 printf(";; res_nquery: retry without EDNS0\n"); 159 goto again; 160 } 161 #endif 162 #ifdef DEBUG 163 if (statp->options & RES_DEBUG) 164 printf(";; res_query: send error\n"); 165 #endif 166 RES_SET_H_ERRNO(statp, TRY_AGAIN); 167 return (n); 168 } 169 170 if (hp->rcode != NOERROR || ntohs(hp->ancount) == 0) { 171 #ifdef DEBUG 172 if (statp->options & RES_DEBUG) 173 printf(";; rcode = (%s), counts = an:%d ns:%d ar:%d\n", 174 p_rcode(hp->rcode), 175 ntohs(hp->ancount), 176 ntohs(hp->nscount), 177 ntohs(hp->arcount)); 178 #endif 179 switch (hp->rcode) { 180 case NXDOMAIN: 181 RES_SET_H_ERRNO(statp, HOST_NOT_FOUND); 182 break; 183 case SERVFAIL: 184 RES_SET_H_ERRNO(statp, TRY_AGAIN); 185 break; 186 case NOERROR: 187 RES_SET_H_ERRNO(statp, NO_DATA); 188 break; 189 case FORMERR: 190 case NOTIMP: 191 case REFUSED: 192 default: 193 RES_SET_H_ERRNO(statp, NO_RECOVERY); 194 break; 195 } 196 return (-1); 197 } 198 return (n); 199 } 200 201 /*% 202 * Formulate a normal query, send, and retrieve answer in supplied buffer. 203 * Return the size of the response on success, -1 on error. 204 * If enabled, implement search rules until answer or unrecoverable failure 205 * is detected. Error code, if any, is left in H_ERRNO. 206 */ 207 int 208 res_nsearch(res_state statp, 209 const char *name, /*%< domain name */ 210 int class, int type, /*%< class and type of query */ 211 u_char *answer, /*%< buffer to put answer */ 212 int anslen) /*%< size of answer */ 213 { 214 const char *cp, * const *domain; 215 HEADER *hp = (HEADER *) answer; 216 char tmp[NS_MAXDNAME]; 217 u_int dots; 218 int trailing_dot, ret, saved_herrno; 219 int got_nodata = 0, got_servfail = 0, root_on_list = 0; 220 int tried_as_is = 0; 221 int searched = 0; 222 223 errno = 0; 224 RES_SET_H_ERRNO(statp, HOST_NOT_FOUND); /*%< True if we never query. */ 225 dots = 0; 226 for (cp = name; *cp != '\0'; cp++) 227 dots += (*cp == '.'); 228 trailing_dot = 0; 229 if (cp > name && *--cp == '.') 230 trailing_dot++; 231 232 /* If there aren't any dots, it could be a user-level alias. */ 233 if (!dots && (cp = res_hostalias(statp, name, tmp, sizeof tmp))!= NULL) 234 return (res_nquery(statp, cp, class, type, answer, anslen)); 235 236 /* 237 * If there are enough dots in the name, let's just give it a 238 * try 'as is'. The threshold can be set with the "ndots" option. 239 * Also, query 'as is', if there is a trailing dot in the name. 240 */ 241 saved_herrno = -1; 242 if (dots >= statp->ndots || trailing_dot) { 243 ret = res_nquerydomain(statp, name, NULL, class, type, 244 answer, anslen); 245 if (ret > 0 || trailing_dot) 246 return (ret); 247 saved_herrno = statp->res_h_errno; 248 tried_as_is++; 249 } 250 251 /* 252 * We do at least one level of search if 253 * - there is no dot and RES_DEFNAME is set, or 254 * - there is at least one dot, there is no trailing dot, 255 * and RES_DNSRCH is set. 256 */ 257 if ((!dots && (statp->options & RES_DEFNAMES) != 0U) || 258 (dots && !trailing_dot && (statp->options & RES_DNSRCH) != 0U)) { 259 int done = 0; 260 261 for (domain = (const char * const *)statp->dnsrch; 262 *domain && !done; 263 domain++) { 264 searched = 1; 265 266 if (domain[0][0] == '\0' || 267 (domain[0][0] == '.' && domain[0][1] == '\0')) 268 root_on_list++; 269 270 ret = res_nquerydomain(statp, name, *domain, 271 class, type, 272 answer, anslen); 273 if (ret > 0) 274 return (ret); 275 276 /* 277 * If no server present, give up. 278 * If name isn't found in this domain, 279 * keep trying higher domains in the search list 280 * (if that's enabled). 281 * On a NO_DATA error, keep trying, otherwise 282 * a wildcard entry of another type could keep us 283 * from finding this entry higher in the domain. 284 * If we get some other error (negative answer or 285 * server failure), then stop searching up, 286 * but try the input name below in case it's 287 * fully-qualified. 288 */ 289 if (errno == ECONNREFUSED) { 290 RES_SET_H_ERRNO(statp, TRY_AGAIN); 291 return (-1); 292 } 293 294 switch (statp->res_h_errno) { 295 case NO_DATA: 296 got_nodata++; 297 /* FALLTHROUGH */ 298 case HOST_NOT_FOUND: 299 /* keep trying */ 300 break; 301 case TRY_AGAIN: 302 if (hp->rcode == SERVFAIL) { 303 /* try next search element, if any */ 304 got_servfail++; 305 break; 306 } 307 /* FALLTHROUGH */ 308 default: 309 /* anything else implies that we're done */ 310 done++; 311 } 312 313 /* if we got here for some reason other than DNSRCH, 314 * we only wanted one iteration of the loop, so stop. 315 */ 316 if ((statp->options & RES_DNSRCH) == 0U) 317 done++; 318 } 319 } 320 321 /* 322 * If the query has not already been tried as is then try it 323 * unless RES_NOTLDQUERY is set and there were no dots. 324 */ 325 if ((dots || !searched || (statp->options & RES_NOTLDQUERY) == 0U) && 326 !(tried_as_is || root_on_list)) { 327 ret = res_nquerydomain(statp, name, NULL, class, type, 328 answer, anslen); 329 if (ret > 0) 330 return (ret); 331 } 332 333 /* if we got here, we didn't satisfy the search. 334 * if we did an initial full query, return that query's H_ERRNO 335 * (note that we wouldn't be here if that query had succeeded). 336 * else if we ever got a nodata, send that back as the reason. 337 * else send back meaningless H_ERRNO, that being the one from 338 * the last DNSRCH we did. 339 */ 340 if (saved_herrno != -1) 341 RES_SET_H_ERRNO(statp, saved_herrno); 342 else if (got_nodata) 343 RES_SET_H_ERRNO(statp, NO_DATA); 344 else if (got_servfail) 345 RES_SET_H_ERRNO(statp, TRY_AGAIN); 346 return (-1); 347 } 348 349 /*% 350 * Perform a call on res_query on the concatenation of name and domain, 351 * removing a trailing dot from name if domain is NULL. 352 */ 353 int 354 res_nquerydomain(res_state statp, 355 const char *name, 356 const char *domain, 357 int class, int type, /*%< class and type of query */ 358 u_char *answer, /*%< buffer to put answer */ 359 int anslen) /*%< size of answer */ 360 { 361 char nbuf[MAXDNAME]; 362 const char *longname = nbuf; 363 int n, d; 364 365 #ifdef DEBUG 366 if (statp->options & RES_DEBUG) 367 printf(";; res_nquerydomain(%s, %s, %d, %d)\n", 368 name, domain?domain:"<Nil>", class, type); 369 #endif 370 if (domain == NULL) { 371 /* 372 * Check for trailing '.'; 373 * copy without '.' if present. 374 */ 375 n = strlen(name); 376 if (n >= MAXDNAME) { 377 RES_SET_H_ERRNO(statp, NO_RECOVERY); 378 return (-1); 379 } 380 n--; 381 if (n >= 0 && name[n] == '.') { 382 strncpy(nbuf, name, n); 383 nbuf[n] = '\0'; 384 } else 385 longname = name; 386 } else { 387 n = strlen(name); 388 d = strlen(domain); 389 if (n + d + 1 >= MAXDNAME) { 390 RES_SET_H_ERRNO(statp, NO_RECOVERY); 391 return (-1); 392 } 393 sprintf(nbuf, "%s.%s", name, domain); 394 } 395 return (res_nquery(statp, longname, class, type, answer, anslen)); 396 } 397 398 const char * 399 res_hostalias(const res_state statp, const char *name, char *dst, size_t siz) { 400 char *file, *cp1, *cp2; 401 char buf[BUFSIZ]; 402 FILE *fp; 403 404 if (statp->options & RES_NOALIASES) 405 return (NULL); 406 file = getenv("HOSTALIASES"); 407 if (file == NULL || (fp = fopen(file, "r")) == NULL) 408 return (NULL); 409 setbuf(fp, NULL); 410 buf[sizeof(buf) - 1] = '\0'; 411 while (fgets(buf, sizeof(buf), fp)) { 412 for (cp1 = buf; *cp1 && !isspace((unsigned char)*cp1); ++cp1) 413 ; 414 if (!*cp1) 415 break; 416 *cp1 = '\0'; 417 if (ns_samename(buf, name) == 1) { 418 while (isspace((unsigned char)*++cp1)) 419 ; 420 if (!*cp1) 421 break; 422 for (cp2 = cp1 + 1; *cp2 && 423 !isspace((unsigned char)*cp2); ++cp2) 424 ; 425 *cp2 = '\0'; 426 strncpy(dst, cp1, siz - 1); 427 dst[siz - 1] = '\0'; 428 fclose(fp); 429 return (dst); 430 } 431 } 432 fclose(fp); 433 return (NULL); 434 } 435 436 /*! \file */ 437