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