| /* $NetBSD: res_query.c,v 1.7 2006/01/24 17:41:25 christos Exp $ */ |
| |
| /* |
| * Copyright (c) 1988, 1993 |
| * The Regents of the University of California. All rights reserved. |
| * |
| * Redistribution and use in source and binary forms, with or without |
| * modification, are permitted provided that the following conditions |
| * are met: |
| * 1. Redistributions of source code must retain the above copyright |
| * notice, this list of conditions and the following disclaimer. |
| * 2. Redistributions in binary form must reproduce the above copyright |
| * notice, this list of conditions and the following disclaimer in the |
| * documentation and/or other materials provided with the distribution. |
| * 3. All advertising materials mentioning features or use of this software |
| * must display the following acknowledgement: |
| * This product includes software developed by the University of |
| * California, Berkeley and its contributors. |
| * 4. Neither the name of the University nor the names of its contributors |
| * may be used to endorse or promote products derived from this software |
| * without specific prior written permission. |
| * |
| * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND |
| * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE |
| * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE |
| * ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE |
| * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL |
| * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS |
| * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) |
| * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT |
| * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY |
| * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF |
| * SUCH DAMAGE. |
| */ |
| |
| /* |
| * Portions Copyright (c) 1993 by Digital Equipment Corporation. |
| * |
| * Permission to use, copy, modify, and distribute this software for any |
| * purpose with or without fee is hereby granted, provided that the above |
| * copyright notice and this permission notice appear in all copies, and that |
| * the name of Digital Equipment Corporation not be used in advertising or |
| * publicity pertaining to distribution of the document or software without |
| * specific, written prior permission. |
| * |
| * THE SOFTWARE IS PROVIDED "AS IS" AND DIGITAL EQUIPMENT CORP. DISCLAIMS ALL |
| * WARRANTIES WITH REGARD TO THIS SOFTWARE, INCLUDING ALL IMPLIED WARRANTIES |
| * OF MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL DIGITAL EQUIPMENT |
| * CORPORATION BE LIABLE FOR ANY SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL |
| * DAMAGES OR ANY DAMAGES WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR |
| * PROFITS, WHETHER IN AN ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS |
| * ACTION, ARISING OUT OF OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS |
| * SOFTWARE. |
| */ |
| |
| /* |
| * Copyright (c) 2004 by Internet Systems Consortium, Inc. ("ISC") |
| * Portions Copyright (c) 1996-1999 by Internet Software Consortium. |
| * |
| * Permission to use, copy, modify, and distribute this software for any |
| * purpose with or without fee is hereby granted, provided that the above |
| * copyright notice and this permission notice appear in all copies. |
| * |
| * THE SOFTWARE IS PROVIDED "AS IS" AND ISC DISCLAIMS ALL WARRANTIES |
| * WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF |
| * MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL ISC BE LIABLE FOR |
| * ANY SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES |
| * WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS, WHETHER IN AN |
| * ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT |
| * OF OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE. |
| */ |
| |
| #define LOG_TAG "resolv" |
| |
| #include <arpa/inet.h> |
| #include <arpa/nameser.h> |
| #include <ctype.h> |
| #include <errno.h> |
| #include <netdb.h> |
| #include <netinet/in.h> |
| #include <sys/param.h> |
| #include <stdlib.h> |
| #include <string.h> |
| #include <unistd.h> |
| |
| #include <android-base/logging.h> |
| |
| #include "res_debug.h" |
| #include "resolv_cache.h" |
| #include "resolv_private.h" |
| |
| /* |
| * Formulate a normal query, send, and await answer. |
| * Returned answer is placed in supplied buffer "answer". |
| * Perform preliminary check of answer, returning success only |
| * if no error is indicated and the answer count is nonzero. |
| * Return the size of the response on success, -1 on error. |
| * Error number is left in *herrno. |
| * |
| * Caller must parse answer and determine whether it answers the question. |
| */ |
| int res_nquery(res_state statp, const char* name, // domain name |
| int cl, int type, // class and type of query |
| uint8_t* answer, // buffer to put answer |
| int anslen, // size of answer buffer |
| int* herrno) // legacy and extended h_errno |
| // NETD_RESOLV_H_ERRNO_EXT_* |
| { |
| uint8_t buf[MAXPACKET]; |
| HEADER* hp = (HEADER*) (void*) answer; |
| int n; |
| int rcode = NOERROR; |
| bool retried = false; |
| |
| again: |
| hp->rcode = NOERROR; // default |
| |
| LOG(DEBUG) << __func__ << ": (" << cl << ", " << type << ")"; |
| |
| n = res_nmkquery(QUERY, name, cl, type, /*data=*/nullptr, 0, buf, sizeof(buf), |
| statp->netcontext_flags); |
| if (n > 0 && |
| (statp->netcontext_flags & |
| (NET_CONTEXT_FLAG_USE_DNS_OVER_TLS | NET_CONTEXT_FLAG_USE_EDNS)) && |
| !retried) |
| n = res_nopt(statp, n, buf, sizeof(buf), anslen); |
| if (n <= 0) { |
| LOG(DEBUG) << __func__ << ": mkquery failed"; |
| *herrno = NO_RECOVERY; |
| return n; |
| } |
| n = res_nsend(statp, buf, n, answer, anslen, &rcode, 0); |
| if (n < 0) { |
| // If the query choked with EDNS0, retry without EDNS0 that when the server |
| // has no response, resovler won't retry and do nothing. Even fallback to UDP, |
| // we also has the same symptom if EDNS is enabled. |
| if ((statp->netcontext_flags & |
| (NET_CONTEXT_FLAG_USE_DNS_OVER_TLS | NET_CONTEXT_FLAG_USE_EDNS)) && |
| (statp->_flags & RES_F_EDNS0ERR) && !retried) { |
| LOG(DEBUG) << __func__ << ": retry without EDNS0"; |
| retried = true; |
| goto again; |
| } |
| LOG(DEBUG) << __func__ << ": send error"; |
| |
| // Note that rcodes SERVFAIL, NOTIMP, REFUSED may cause res_nquery() to return a general |
| // error code EAI_AGAIN, but mapping the error code from rcode as res_queryN() does for |
| // getaddrinfo(). Different rcodes trigger different behaviors: |
| // |
| // - SERVFAIL, NOTIMP, REFUSED |
| // These result in send_dg() returning 0, causing res_nsend() to try the next |
| // nameserver. After all nameservers failed, res_nsend() returns -ETIMEDOUT, causing |
| // res_nquery() to return EAI_AGAIN here regardless of the rcode from the DNS response. |
| // |
| // - NXDOMAIN, FORMERR |
| // These rcodes may cause res_nsend() to return successfully (i.e. the result is a |
| // positive integer). In this case, res_nquery() returns error number by referring |
| // the rcode from the DNS response. |
| switch (rcode) { |
| case RCODE_TIMEOUT: // Not defined in RFC. |
| // DNS metrics monitors DNS query timeout. |
| *herrno = NETD_RESOLV_H_ERRNO_EXT_TIMEOUT; // extended h_errno. |
| break; |
| default: |
| *herrno = TRY_AGAIN; |
| break; |
| } |
| return n; |
| } |
| |
| if (hp->rcode != NOERROR || ntohs(hp->ancount) == 0) { |
| LOG(DEBUG) << __func__ << ": rcode = (" << p_rcode(hp->rcode) |
| << "), counts = an:" << ntohs(hp->ancount) << " ns:" << ntohs(hp->nscount) |
| << " ar:" << ntohs(hp->arcount); |
| |
| switch (hp->rcode) { |
| case NXDOMAIN: |
| *herrno = HOST_NOT_FOUND; |
| break; |
| case SERVFAIL: |
| *herrno = TRY_AGAIN; |
| break; |
| case NOERROR: |
| *herrno = NO_DATA; |
| break; |
| case FORMERR: |
| case NOTIMP: |
| case REFUSED: |
| default: |
| *herrno = NO_RECOVERY; |
| break; |
| } |
| return -1; |
| } |
| return n; |
| } |
| |
| /* |
| * Formulate a normal query, send, and retrieve answer in supplied buffer. |
| * Return the size of the response on success, -1 on error. |
| * If enabled, implement search rules until answer or unrecoverable failure |
| * is detected. Error code, if any, is left in *herrno. |
| */ |
| int res_nsearch(res_state statp, const char* name, /* domain name */ |
| int cl, int type, /* class and type of query */ |
| uint8_t* answer, /* buffer to put answer */ |
| int anslen, /* size of answer */ |
| int* herrno) /* legacy and extended |
| h_errno NETD_RESOLV_H_ERRNO_EXT_* */ |
| { |
| const char* cp; |
| HEADER* hp = (HEADER*) (void*) answer; |
| uint32_t dots; |
| int ret, saved_herrno; |
| int got_nodata = 0, got_servfail = 0, root_on_list = 0; |
| int tried_as_is = 0; |
| |
| errno = 0; |
| *herrno = HOST_NOT_FOUND; /* True if we never query. */ |
| |
| dots = 0; |
| for (cp = name; *cp != '\0'; cp++) dots += (*cp == '.'); |
| const bool trailing_dot = (cp > name && *--cp == '.') ? true : false; |
| |
| /* |
| * If there are enough dots in the name, let's just give it a |
| * try 'as is'. The threshold can be set with the "ndots" option. |
| * Also, query 'as is', if there is a trailing dot in the name. |
| */ |
| saved_herrno = -1; |
| if (dots >= statp->ndots || trailing_dot) { |
| ret = res_nquerydomain(statp, name, NULL, cl, type, answer, anslen, herrno); |
| if (ret > 0 || trailing_dot) return ret; |
| saved_herrno = *herrno; |
| tried_as_is++; |
| } |
| |
| /* |
| * We do at least one level of search if |
| * - there is no dot, or |
| * - there is at least one dot and there is no trailing dot. |
| */ |
| if ((!dots) || (dots && !trailing_dot)) { |
| int done = 0; |
| |
| /* Unfortunately we need to load network-specific info |
| * (dns servers, search domains) before |
| * the domain stuff is tried. Will have a better |
| * fix after thread pools are used as this will |
| * be loaded once for the thread instead of each |
| * time a query is tried. |
| */ |
| resolv_populate_res_for_net(statp); |
| |
| for (const auto& domain : statp->search_domains) { |
| if (domain == "." || domain == "") ++root_on_list; |
| |
| ret = res_nquerydomain(statp, name, domain.c_str(), cl, type, answer, anslen, herrno); |
| if (ret > 0) return ret; |
| |
| /* |
| * If no server present, give up. |
| * If name isn't found in this domain, |
| * keep trying higher domains in the search list |
| * (if that's enabled). |
| * On a NO_DATA error, keep trying, otherwise |
| * a wildcard entry of another type could keep us |
| * from finding this entry higher in the domain. |
| * If we get some other error (negative answer or |
| * server failure), then stop searching up, |
| * but try the input name below in case it's |
| * fully-qualified. |
| */ |
| if (errno == ECONNREFUSED) { |
| *herrno = TRY_AGAIN; |
| return -1; |
| } |
| |
| switch (*herrno) { |
| case NO_DATA: |
| got_nodata++; |
| break; |
| case HOST_NOT_FOUND: |
| /* keep trying */ |
| break; |
| case TRY_AGAIN: |
| if (hp->rcode == SERVFAIL) { |
| /* try next search element, if any */ |
| got_servfail++; |
| break; |
| } |
| [[fallthrough]]; |
| default: |
| /* anything else implies that we're done */ |
| done++; |
| } |
| } |
| } |
| |
| // if we have not already tried the name "as is", do that now. |
| // note that we do this regardless of how many dots were in the |
| // name or whether it ends with a dot. |
| if (!tried_as_is && !root_on_list) { |
| ret = res_nquerydomain(statp, name, NULL, cl, type, answer, anslen, herrno); |
| if (ret > 0) return ret; |
| } |
| |
| /* if we got here, we didn't satisfy the search. |
| * if we did an initial full query, return that query's H_ERRNO |
| * (note that we wouldn't be here if that query had succeeded). |
| * else if we ever got a nodata, send that back as the reason. |
| * else send back meaningless H_ERRNO, that being the one from |
| * the last DNSRCH we did. |
| */ |
| if (saved_herrno != -1) |
| *herrno = saved_herrno; |
| else if (got_nodata) |
| *herrno = NO_DATA; |
| else if (got_servfail) |
| *herrno = TRY_AGAIN; |
| return -1; |
| } |
| |
| /* |
| * Perform a call on res_query on the concatenation of name and domain, |
| * removing a trailing dot from name if domain is NULL. |
| */ |
| int res_nquerydomain(res_state statp, const char* name, const char* domain, int cl, |
| int type, /* class and type of query */ |
| uint8_t* answer, /* buffer to put answer */ |
| int anslen, /* size of answer */ |
| int* herrno) /* legacy and extended h_errno NETD_RESOLV_H_ERRNO_EXT_* */ |
| { |
| char nbuf[MAXDNAME]; |
| const char* longname = nbuf; |
| int n, d; |
| |
| if (domain == NULL) { |
| LOG(DEBUG) << __func__ << ": (null, " << cl << ", " << type << ")"; |
| /* |
| * Check for trailing '.'; |
| * copy without '.' if present. |
| */ |
| n = strlen(name); |
| if (n >= MAXDNAME) { |
| *herrno = NO_RECOVERY; |
| return -1; |
| } |
| n--; |
| if (n >= 0 && name[n] == '.') { |
| strncpy(nbuf, name, (size_t) n); |
| nbuf[n] = '\0'; |
| } else |
| longname = name; |
| } else { |
| LOG(DEBUG) << __func__ << ": (" << cl << ", " << type << ")"; |
| n = strlen(name); |
| d = strlen(domain); |
| if (n + d + 1 >= MAXDNAME) { |
| *herrno = NO_RECOVERY; |
| return -1; |
| } |
| snprintf(nbuf, sizeof(nbuf), "%s.%s", name, domain); |
| } |
| return res_nquery(statp, longname, cl, type, answer, anslen, herrno); |
| } |
