388 lines
11 KiB
C
388 lines
11 KiB
C
/*
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* ++Copyright++ 1988, 1993
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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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* 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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#if defined(LIBC_SCCS) && !defined(lint)
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static char sccsid[] = "@(#)res_query.c 8.1 (Berkeley) 6/4/93";
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static char orig_rcsid = "From: Id: res_query.c,v 8.9 1996/09/22 00:13:28 vixie Exp";
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static char rcsid[] = "$Id$";
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#endif /* LIBC_SCCS and not lint */
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#include <sys/types.h>
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#include <sys/param.h>
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#include <netinet/in.h>
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#include <arpa/inet.h>
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#include "res_config.h"
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#include <arpa/nameser.h>
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#include <stdio.h>
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#include <netdb.h>
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#include <resolv.h>
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#include <ctype.h>
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#include <errno.h>
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#include <stdlib.h>
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#include <string.h>
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#if PACKETSZ > 1024
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#define MAXPACKET PACKETSZ
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#else
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#define MAXPACKET 1024
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#endif
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const char *hostalias __P((const char *));
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int h_errno;
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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 h_errno.
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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
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res_query(name, class, type, answer, anslen)
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const char *name; /* domain name */
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int class, type; /* class and type of query */
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u_char *answer; /* buffer to put answer */
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int anslen; /* size of answer buffer */
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{
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u_char buf[MAXPACKET];
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register HEADER *hp = (HEADER *) answer;
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int n;
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hp->rcode = NOERROR; /* default */
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if ((_res.options & RES_INIT) == 0 && res_init() == -1) {
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h_errno = NETDB_INTERNAL;
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return (-1);
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}
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#ifdef DEBUG
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if (_res.options & RES_DEBUG)
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printf(";; res_query(%s, %d, %d)\n", name, class, type);
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#endif
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n = res_mkquery(QUERY, name, class, type, NULL, 0, NULL,
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buf, sizeof(buf));
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if (n <= 0) {
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#ifdef DEBUG
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if (_res.options & RES_DEBUG)
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printf(";; res_query: mkquery failed\n");
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#endif
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h_errno = NO_RECOVERY;
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return (n);
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}
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n = res_send(buf, n, answer, anslen);
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if (n < 0) {
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#ifdef DEBUG
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if (_res.options & RES_DEBUG)
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printf(";; res_query: send error\n");
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#endif
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h_errno = TRY_AGAIN;
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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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#ifdef DEBUG
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if (_res.options & RES_DEBUG)
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printf(";; rcode = %d, ancount=%d\n", hp->rcode,
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ntohs(hp->ancount));
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#endif
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switch (hp->rcode) {
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case NXDOMAIN:
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h_errno = HOST_NOT_FOUND;
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break;
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case SERVFAIL:
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h_errno = TRY_AGAIN;
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break;
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case NOERROR:
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h_errno = 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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h_errno = 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 h_errno.
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*/
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int
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res_search(name, class, type, answer, anslen)
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const char *name; /* domain name */
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int class, type; /* class and type of query */
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u_char *answer; /* buffer to put answer */
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int anslen; /* size of answer */
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{
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register const char *cp, * const *domain;
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HEADER *hp = (HEADER *) answer;
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u_int dots;
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int trailing_dot, ret, saved_herrno;
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int got_nodata = 0, got_servfail = 0, tried_as_is = 0;
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if ((_res.options & RES_INIT) == 0 && res_init() == -1) {
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h_errno = NETDB_INTERNAL;
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return (-1);
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}
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errno = 0;
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h_errno = HOST_NOT_FOUND; /* default, if we never query */
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dots = 0;
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for (cp = name; *cp; cp++)
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dots += (*cp == '.');
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trailing_dot = 0;
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if (cp > name && *--cp == '.')
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trailing_dot++;
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/*
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* if there aren't any dots, it could be a user-level alias
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*/
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if (!dots && (cp = __hostalias(name)) != NULL)
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return (res_query(cp, class, type, answer, anslen));
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/*
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* If there are dots in the name already, let's just give it a try
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* 'as is'. The threshold can be set with the "ndots" option.
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*/
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saved_herrno = -1;
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if (dots >= _res.ndots) {
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ret = res_querydomain(name, NULL, class, type, answer, anslen);
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if (ret > 0)
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return (ret);
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saved_herrno = h_errno;
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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 and RES_DEFNAME is set, or
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* - there is at least one dot, there is no trailing dot,
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* and RES_DNSRCH is set.
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*/
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if ((!dots && (_res.options & RES_DEFNAMES)) ||
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(dots && !trailing_dot && (_res.options & RES_DNSRCH))) {
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int done = 0;
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for (domain = (const char * const *)_res.dnsrch;
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*domain && !done;
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domain++) {
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ret = res_querydomain(name, *domain, class, type,
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answer, anslen);
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if (ret > 0)
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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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h_errno = TRY_AGAIN;
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return (-1);
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}
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switch (h_errno) {
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case NO_DATA:
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got_nodata++;
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/* FALLTHROUGH */
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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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/* if we got here for some reason other than DNSRCH,
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* we only wanted one iteration of the loop, so stop.
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*/
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if (!(_res.options & RES_DNSRCH))
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done++;
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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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*/
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if (!tried_as_is) {
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ret = res_querydomain(name, NULL, class, type, answer, anslen);
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if (ret > 0)
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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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h_errno = saved_herrno;
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else if (got_nodata)
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h_errno = NO_DATA;
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else if (got_servfail)
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h_errno = 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
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res_querydomain(name, domain, class, type, answer, anslen)
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const char *name, *domain;
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int class, type; /* class and type of query */
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u_char *answer; /* buffer to put answer */
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int anslen; /* size of answer */
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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;
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if ((_res.options & RES_INIT) == 0 && res_init() == -1) {
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h_errno = NETDB_INTERNAL;
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return (-1);
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}
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#ifdef DEBUG
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if (_res.options & RES_DEBUG)
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printf(";; res_querydomain(%s, %s, %d, %d)\n",
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name, domain?domain:"<Nil>", class, type);
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#endif
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if (domain == NULL) {
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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) - 1;
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if (n != (0 - 1) && name[n] == '.' && n < sizeof(nbuf) - 1) {
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bcopy(name, nbuf, 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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sprintf(nbuf, "%.*s.%.*s", MAXDNAME, name, MAXDNAME, domain);
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return (res_query(longname, class, type, answer, anslen));
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}
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const char *
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hostalias(name)
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register const char *name;
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{
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register char *cp1, *cp2;
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FILE *fp;
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char *file;
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char buf[BUFSIZ];
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static char abuf[MAXDNAME];
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if (_res.options & RES_NOALIASES)
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return (NULL);
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file = getenv("HOSTALIASES");
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if (file == NULL || (fp = fopen(file, "r")) == NULL)
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return (NULL);
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setbuf(fp, NULL);
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buf[sizeof(buf) - 1] = '\0';
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while (fgets(buf, sizeof(buf), fp)) {
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for (cp1 = buf; *cp1 && !isspace(*cp1); ++cp1)
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;
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if (!*cp1)
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break;
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*cp1 = '\0';
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if (!strcasecmp(buf, name)) {
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while (isspace(*++cp1))
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;
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if (!*cp1)
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break;
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for (cp2 = cp1 + 1; *cp2 && !isspace(*cp2); ++cp2)
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;
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abuf[sizeof(abuf) - 1] = *cp2 = '\0';
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strncpy(abuf, cp1, sizeof(abuf) - 1);
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fclose(fp);
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return (abuf);
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}
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}
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fclose(fp);
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return (NULL);
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}
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