1 /* $NetBSD: res_query.c,v 1.7 2006/01/24 17:41:25 christos Exp $ */ 2 3 /* 4 * Copyright (c) 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 36 /* 37 * Portions Copyright (c) 1993 by Digital Equipment Corporation. 38 * 39 * Permission to use, copy, modify, and distribute this software for any 40 * purpose with or without fee is hereby granted, provided that the above 41 * copyright notice and this permission notice appear in all copies, and that 42 * the name of Digital Equipment Corporation not be used in advertising or 43 * publicity pertaining to distribution of the document or software without 44 * specific, written prior permission. 45 * 46 * THE SOFTWARE IS PROVIDED "AS IS" AND DIGITAL EQUIPMENT CORP. DISCLAIMS ALL 47 * WARRANTIES WITH REGARD TO THIS SOFTWARE, INCLUDING ALL IMPLIED WARRANTIES 48 * OF MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL DIGITAL EQUIPMENT 49 * CORPORATION BE LIABLE FOR ANY SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL 50 * DAMAGES OR ANY DAMAGES WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR 51 * PROFITS, WHETHER IN AN ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS 52 * ACTION, ARISING OUT OF OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS 53 * SOFTWARE. 54 */ 55 56 /* 57 * Copyright (c) 2004 by Internet Systems Consortium, Inc. ("ISC") 58 * Portions Copyright (c) 1996-1999 by Internet Software Consortium. 59 * 60 * Permission to use, copy, modify, and distribute this software for any 61 * purpose with or without fee is hereby granted, provided that the above 62 * copyright notice and this permission notice appear in all copies. 63 * 64 * THE SOFTWARE IS PROVIDED "AS IS" AND ISC DISCLAIMS ALL WARRANTIES 65 * WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF 66 * MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL ISC BE LIABLE FOR 67 * ANY SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES 68 * WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS, WHETHER IN AN 69 * ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT 70 * OF OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE. 71 */ 72 73 #define LOG_TAG "resolv" 74 75 #include <arpa/inet.h> 76 #include <arpa/nameser.h> 77 #include <ctype.h> 78 #include <errno.h> 79 #include <netdb.h> 80 #include <netinet/in.h> 81 #include <sys/param.h> 82 #include <stdlib.h> 83 #include <string.h> 84 #include <unistd.h> 85 86 #include <android-base/logging.h> 87 88 #include "res_debug.h" 89 #include "resolv_cache.h" 90 #include "resolv_private.h" 91 92 /* 93 * Formulate a normal query, send, and await answer. 94 * Returned answer is placed in supplied buffer "answer". 95 * Perform preliminary check of answer, returning success only 96 * if no error is indicated and the answer count is nonzero. 97 * Return the size of the response on success, -1 on error. 98 * Error number is left in *herrno. 99 * 100 * Caller must parse answer and determine whether it answers the question. 101 */ 102 int res_nquery(res_state statp, const char* name, // domain name 103 int cl, int type, // class and type of query 104 uint8_t* answer, // buffer to put answer 105 int anslen, // size of answer buffer 106 int* herrno) // legacy and extended h_errno 107 // NETD_RESOLV_H_ERRNO_EXT_* 108 { 109 uint8_t buf[MAXPACKET]; 110 HEADER* hp = (HEADER*) (void*) answer; 111 int n; 112 int rcode = NOERROR; 113 bool retried = false; 114 115 again: 116 hp->rcode = NOERROR; // default 117 118 LOG(DEBUG) << __func__ << ": (" << cl << ", " << type << ")"; 119 120 n = res_nmkquery(QUERY, name, cl, type, /*data=*/nullptr, 0, buf, sizeof(buf), 121 statp->netcontext_flags); 122 if (n > 0 && 123 (statp->netcontext_flags & 124 (NET_CONTEXT_FLAG_USE_DNS_OVER_TLS | NET_CONTEXT_FLAG_USE_EDNS)) && 125 !retried) 126 n = res_nopt(statp, n, buf, sizeof(buf), anslen); 127 if (n <= 0) { 128 LOG(DEBUG) << __func__ << ": mkquery failed"; 129 *herrno = NO_RECOVERY; 130 return n; 131 } 132 n = res_nsend(statp, buf, n, answer, anslen, &rcode, 0); 133 if (n < 0) { 134 // If the query choked with EDNS0, retry without EDNS0 that when the server 135 // has no response, resovler won't retry and do nothing. Even fallback to UDP, 136 // we also has the same symptom if EDNS is enabled. 137 if ((statp->netcontext_flags & 138 (NET_CONTEXT_FLAG_USE_DNS_OVER_TLS | NET_CONTEXT_FLAG_USE_EDNS)) && 139 (statp->_flags & RES_F_EDNS0ERR) && !retried) { 140 LOG(DEBUG) << __func__ << ": retry without EDNS0"; 141 retried = true; 142 goto again; 143 } 144 LOG(DEBUG) << __func__ << ": send error"; 145 146 // Note that rcodes SERVFAIL, NOTIMP, REFUSED may cause res_nquery() to return a general 147 // error code EAI_AGAIN, but mapping the error code from rcode as res_queryN() does for 148 // getaddrinfo(). Different rcodes trigger different behaviors: 149 // 150 // - SERVFAIL, NOTIMP, REFUSED 151 // These result in send_dg() returning 0, causing res_nsend() to try the next 152 // nameserver. After all nameservers failed, res_nsend() returns -ETIMEDOUT, causing 153 // res_nquery() to return EAI_AGAIN here regardless of the rcode from the DNS response. 154 // 155 // - NXDOMAIN, FORMERR 156 // These rcodes may cause res_nsend() to return successfully (i.e. the result is a 157 // positive integer). In this case, res_nquery() returns error number by referring 158 // the rcode from the DNS response. 159 switch (rcode) { 160 case RCODE_TIMEOUT: // Not defined in RFC. 161 // DNS metrics monitors DNS query timeout. 162 *herrno = NETD_RESOLV_H_ERRNO_EXT_TIMEOUT; // extended h_errno. 163 break; 164 default: 165 *herrno = TRY_AGAIN; 166 break; 167 } 168 return n; 169 } 170 171 if (hp->rcode != NOERROR || ntohs(hp->ancount) == 0) { 172 LOG(DEBUG) << __func__ << ": rcode = (" << p_rcode(hp->rcode) 173 << "), counts = an:" << ntohs(hp->ancount) << " ns:" << ntohs(hp->nscount) 174 << " ar:" << ntohs(hp->arcount); 175 176 switch (hp->rcode) { 177 case NXDOMAIN: 178 *herrno = HOST_NOT_FOUND; 179 break; 180 case SERVFAIL: 181 *herrno = TRY_AGAIN; 182 break; 183 case NOERROR: 184 *herrno = NO_DATA; 185 break; 186 case FORMERR: 187 case NOTIMP: 188 case REFUSED: 189 default: 190 *herrno = NO_RECOVERY; 191 break; 192 } 193 return -1; 194 } 195 return n; 196 } 197 198 /* 199 * Formulate a normal query, send, and retrieve answer in supplied buffer. 200 * Return the size of the response on success, -1 on error. 201 * If enabled, implement search rules until answer or unrecoverable failure 202 * is detected. Error code, if any, is left in *herrno. 203 */ 204 int res_nsearch(res_state statp, const char* name, /* domain name */ 205 int cl, int type, /* class and type of query */ 206 uint8_t* answer, /* buffer to put answer */ 207 int anslen, /* size of answer */ 208 int* herrno) /* legacy and extended 209 h_errno NETD_RESOLV_H_ERRNO_EXT_* */ 210 { 211 const char* cp; 212 HEADER* hp = (HEADER*) (void*) answer; 213 uint32_t dots; 214 int ret, saved_herrno; 215 int got_nodata = 0, got_servfail = 0, root_on_list = 0; 216 int tried_as_is = 0; 217 218 errno = 0; 219 *herrno = HOST_NOT_FOUND; /* True if we never query. */ 220 221 dots = 0; 222 for (cp = name; *cp != '\0'; cp++) dots += (*cp == '.'); 223 const bool trailing_dot = (cp > name && *--cp == '.') ? true : false; 224 225 /* 226 * If there are enough dots in the name, let's just give it a 227 * try 'as is'. The threshold can be set with the "ndots" option. 228 * Also, query 'as is', if there is a trailing dot in the name. 229 */ 230 saved_herrno = -1; 231 if (dots >= statp->ndots || trailing_dot) { 232 ret = res_nquerydomain(statp, name, NULL, cl, type, answer, anslen, herrno); 233 if (ret > 0 || trailing_dot) return ret; 234 saved_herrno = *herrno; 235 tried_as_is++; 236 } 237 238 /* 239 * We do at least one level of search if 240 * - there is no dot, or 241 * - there is at least one dot and there is no trailing dot. 242 */ 243 if ((!dots) || (dots && !trailing_dot)) { 244 int done = 0; 245 246 /* Unfortunately we need to load network-specific info 247 * (dns servers, search domains) before 248 * the domain stuff is tried. Will have a better 249 * fix after thread pools are used as this will 250 * be loaded once for the thread instead of each 251 * time a query is tried. 252 */ 253 resolv_populate_res_for_net(statp); 254 255 for (const auto& domain : statp->search_domains) { 256 if (domain == "." || domain == "") ++root_on_list; 257 258 ret = res_nquerydomain(statp, name, domain.c_str(), cl, type, answer, anslen, herrno); 259 if (ret > 0) return ret; 260 261 /* 262 * If no server present, give up. 263 * If name isn't found in this domain, 264 * keep trying higher domains in the search list 265 * (if that's enabled). 266 * On a NO_DATA error, keep trying, otherwise 267 * a wildcard entry of another type could keep us 268 * from finding this entry higher in the domain. 269 * If we get some other error (negative answer or 270 * server failure), then stop searching up, 271 * but try the input name below in case it's 272 * fully-qualified. 273 */ 274 if (errno == ECONNREFUSED) { 275 *herrno = TRY_AGAIN; 276 return -1; 277 } 278 279 switch (*herrno) { 280 case NO_DATA: 281 got_nodata++; 282 break; 283 case HOST_NOT_FOUND: 284 /* keep trying */ 285 break; 286 case TRY_AGAIN: 287 if (hp->rcode == SERVFAIL) { 288 /* try next search element, if any */ 289 got_servfail++; 290 break; 291 } 292 [[fallthrough]]; 293 default: 294 /* anything else implies that we're done */ 295 done++; 296 } 297 } 298 } 299 300 // if we have not already tried the name "as is", do that now. 301 // note that we do this regardless of how many dots were in the 302 // name or whether it ends with a dot. 303 if (!tried_as_is && !root_on_list) { 304 ret = res_nquerydomain(statp, name, NULL, cl, type, answer, anslen, herrno); 305 if (ret > 0) return ret; 306 } 307 308 /* if we got here, we didn't satisfy the search. 309 * if we did an initial full query, return that query's H_ERRNO 310 * (note that we wouldn't be here if that query had succeeded). 311 * else if we ever got a nodata, send that back as the reason. 312 * else send back meaningless H_ERRNO, that being the one from 313 * the last DNSRCH we did. 314 */ 315 if (saved_herrno != -1) 316 *herrno = saved_herrno; 317 else if (got_nodata) 318 *herrno = NO_DATA; 319 else if (got_servfail) 320 *herrno = TRY_AGAIN; 321 return -1; 322 } 323 324 /* 325 * Perform a call on res_query on the concatenation of name and domain, 326 * removing a trailing dot from name if domain is NULL. 327 */ 328 int res_nquerydomain(res_state statp, const char* name, const char* domain, int cl, 329 int type, /* class and type of query */ 330 uint8_t* answer, /* buffer to put answer */ 331 int anslen, /* size of answer */ 332 int* herrno) /* legacy and extended h_errno NETD_RESOLV_H_ERRNO_EXT_* */ 333 { 334 char nbuf[MAXDNAME]; 335 const char* longname = nbuf; 336 int n, d; 337 338 if (domain == NULL) { 339 LOG(DEBUG) << __func__ << ": (null, " << cl << ", " << type << ")"; 340 /* 341 * Check for trailing '.'; 342 * copy without '.' if present. 343 */ 344 n = strlen(name); 345 if (n >= MAXDNAME) { 346 *herrno = NO_RECOVERY; 347 return -1; 348 } 349 n--; 350 if (n >= 0 && name[n] == '.') { 351 strncpy(nbuf, name, (size_t) n); 352 nbuf[n] = '\0'; 353 } else 354 longname = name; 355 } else { 356 LOG(DEBUG) << __func__ << ": (" << cl << ", " << type << ")"; 357 n = strlen(name); 358 d = strlen(domain); 359 if (n + d + 1 >= MAXDNAME) { 360 *herrno = NO_RECOVERY; 361 return -1; 362 } 363 snprintf(nbuf, sizeof(nbuf), "%s.%s", name, domain); 364 } 365 return res_nquery(statp, longname, cl, type, answer, anslen, herrno); 366 } 367