299 lines
9.3 KiB
C
299 lines
9.3 KiB
C
/*
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* Asterisk -- An open source telephony toolkit.
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*
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* Copyright (C) 1999 - 2006 Thorsten Lockert
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*
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* Written by Thorsten Lockert <tholo@trollphone.org>
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*
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* Funding provided by Troll Phone Networks AS
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*
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* See http://www.asterisk.org for more information about
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* the Asterisk project. Please do not directly contact
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* any of the maintainers of this project for assistance;
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* the project provides a web site, mailing lists and IRC
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* channels for your use.
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*
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* This program is free software, distributed under the terms of
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* the GNU General Public License Version 2. See the LICENSE file
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* at the top of the source tree.
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*/
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/*! \file
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*
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* \brief DNS Support for Asterisk
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*
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* \author Thorsten Lockert <tholo@trollphone.org>
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*
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* \par Reference
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* - DNR SRV records http://www.ietf.org/rfc/rfc2782.txt
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*
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*/
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#include "asterisk.h"
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ASTERISK_FILE_VERSION(__FILE__, "$Revision$")
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#include "asterisk/network.h"
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#include <arpa/nameser.h> /* res_* functions */
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#include <resolv.h>
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#include "asterisk/channel.h"
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#include "asterisk/dns.h"
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#include "asterisk/endian.h"
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#define MAX_SIZE 4096
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#ifdef __PDP_ENDIAN
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#if __BYTE_ORDER == __PDP_ENDIAN
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#define DETERMINED_BYTE_ORDER __LITTLE_ENDIAN
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#endif
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#endif
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#if __BYTE_ORDER == __BIG_ENDIAN
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#define DETERMINED_BYTE_ORDER __BIG_ENDIAN
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#endif
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#if __BYTE_ORDER == __LITTLE_ENDIAN
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#define DETERMINED_BYTE_ORDER __LITTLE_ENDIAN
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#endif
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/* The dns_HEADER structure definition below originated
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in the arpa/nameser.h header file distributed with ISC
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BIND, which contains the following copyright and license
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notices:
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* ++Copyright++ 1983, 1989, 1993
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* -
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* Copyright (c) 1983, 1989, 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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* 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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* --Copyright--
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*/
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typedef struct {
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unsigned id:16; /*!< query identification number */
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#if DETERMINED_BYTE_ORDER == __BIG_ENDIAN
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/* fields in third byte */
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unsigned qr:1; /*!< response flag */
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unsigned opcode:4; /*!< purpose of message */
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unsigned aa:1; /*!< authoritive answer */
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unsigned tc:1; /*!< truncated message */
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unsigned rd:1; /*!< recursion desired */
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/* fields in fourth byte */
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unsigned ra:1; /*!< recursion available */
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unsigned unused:1; /*!< unused bits (MBZ as of 4.9.3a3) */
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unsigned ad:1; /*!< authentic data from named */
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unsigned cd:1; /*!< checking disabled by resolver */
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unsigned rcode:4; /*!< response code */
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#endif
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#if DETERMINED_BYTE_ORDER == __LITTLE_ENDIAN
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/* fields in third byte */
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unsigned rd:1; /*!< recursion desired */
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unsigned tc:1; /*!< truncated message */
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unsigned aa:1; /*!< authoritive answer */
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unsigned opcode:4; /*!< purpose of message */
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unsigned qr:1; /*!< response flag */
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/* fields in fourth byte */
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unsigned rcode:4; /*!< response code */
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unsigned cd:1; /*!< checking disabled by resolver */
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unsigned ad:1; /*!< authentic data from named */
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unsigned unused:1; /*!< unused bits (MBZ as of 4.9.3a3) */
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unsigned ra:1; /*!< recursion available */
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#endif
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/* remaining bytes */
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unsigned qdcount:16; /*!< number of question entries */
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unsigned ancount:16; /*!< number of answer entries */
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unsigned nscount:16; /*!< number of authority entries */
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unsigned arcount:16; /*!< number of resource entries */
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} dns_HEADER;
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struct dn_answer {
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unsigned short rtype;
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unsigned short class;
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unsigned int ttl;
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unsigned short size;
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} __attribute__((__packed__));
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static int skip_name(unsigned char *s, int len)
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{
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int x = 0;
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while (x < len) {
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if (*s == '\0') {
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s++;
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x++;
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break;
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}
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if ((*s & 0xc0) == 0xc0) {
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s += 2;
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x += 2;
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break;
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}
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x += *s + 1;
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s += *s + 1;
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}
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if (x >= len)
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return -1;
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return x;
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}
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/*! \brief Parse DNS lookup result, call callback */
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static int dns_parse_answer(void *context,
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int class, int type, unsigned char *answer, int len,
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int (*callback)(void *context, unsigned char *answer, int len, unsigned char *fullanswer))
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{
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unsigned char *fullanswer = answer;
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struct dn_answer *ans;
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dns_HEADER *h;
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int ret = 0;
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int res;
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int x;
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h = (dns_HEADER *)answer;
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answer += sizeof(dns_HEADER);
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len -= sizeof(dns_HEADER);
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for (x = 0; x < ntohs(h->qdcount); x++) {
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if ((res = skip_name(answer, len)) < 0) {
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ast_log(LOG_WARNING, "Couldn't skip over name\n");
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return -1;
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}
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answer += res + 4; /* Skip name and QCODE / QCLASS */
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len -= res + 4;
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if (len < 0) {
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ast_log(LOG_WARNING, "Strange query size\n");
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return -1;
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}
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}
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for (x = 0; x < ntohs(h->ancount); x++) {
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if ((res = skip_name(answer, len)) < 0) {
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ast_log(LOG_WARNING, "Failed skipping name\n");
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return -1;
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}
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answer += res;
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len -= res;
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ans = (struct dn_answer *)answer;
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answer += sizeof(struct dn_answer);
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len -= sizeof(struct dn_answer);
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if (len < 0) {
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ast_log(LOG_WARNING, "Strange result size\n");
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return -1;
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}
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if (len < 0) {
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ast_log(LOG_WARNING, "Length exceeds frame\n");
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return -1;
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}
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if (ntohs(ans->class) == class && ntohs(ans->rtype) == type) {
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if (callback) {
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if ((res = callback(context, answer, ntohs(ans->size), fullanswer)) < 0) {
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ast_log(LOG_WARNING, "Failed to parse result\n");
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return -1;
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}
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ret = 1;
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}
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}
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answer += ntohs(ans->size);
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len -= ntohs(ans->size);
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}
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return ret;
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}
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#ifndef HAVE_RES_NINIT
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AST_MUTEX_DEFINE_STATIC(res_lock);
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#endif
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/*! \brief Lookup record in DNS
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\note Asterisk DNS is synchronus at this time. This means that if your DNS does
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not work properly, Asterisk might not start properly or a channel may lock.
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*/
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int ast_search_dns(void *context,
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const char *dname, int class, int type,
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int (*callback)(void *context, unsigned char *answer, int len, unsigned char *fullanswer))
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{
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#ifdef HAVE_RES_NINIT
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struct __res_state dnsstate;
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#endif
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unsigned char answer[MAX_SIZE];
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int res, ret = -1;
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#ifdef HAVE_RES_NINIT
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memset(&dnsstate, 0, sizeof(dnsstate));
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res_ninit(&dnsstate);
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res = res_nsearch(&dnsstate, dname, class, type, answer, sizeof(answer));
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#else
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ast_mutex_lock(&res_lock);
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res_init();
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res = res_search(dname, class, type, answer, sizeof(answer));
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#endif
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if (res > 0) {
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if ((res = dns_parse_answer(context, class, type, answer, res, callback)) < 0) {
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ast_log(LOG_WARNING, "DNS Parse error for %s\n", dname);
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ret = -1;
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} else if (res == 0) {
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ast_debug(1, "No matches found in DNS for %s\n", dname);
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ret = 0;
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} else
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ret = 1;
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}
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#ifdef HAVE_RES_NINIT
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#ifdef HAVE_RES_NDESTROY
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res_ndestroy(&dnsstate);
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#else
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res_nclose(&dnsstate);
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#endif
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#else
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#ifdef HAVE_RES_CLOSE
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res_close();
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#endif
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ast_mutex_unlock(&res_lock);
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#endif
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return ret;
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}
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