283 lines
8.3 KiB
C
283 lines
8.3 KiB
C
/*
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* Copyright (c) 1988 Regents of the University of California.
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* 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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#if defined(LIBC_SCCS) && !defined(lint)
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/*static char sccsid[] = "from: @(#)res_query.c 5.11 (Berkeley) 3/6/91";*/
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static char rcsid[] = "$Id: res_query.c,v 1.2 1993/08/01 18:39:20 mycroft Exp $";
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#endif /* LIBC_SCCS and not lint */
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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 <arpa/nameser.h>
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#include <netdb.h>
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#include <resolv.h>
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#include <stdio.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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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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* Caller must parse answer and determine whether it answers the question.
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*/
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res_query(name, class, type, answer, anslen)
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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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char buf[MAXPACKET];
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HEADER *hp;
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int n;
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if ((_res.options & RES_INIT) == 0 && res_init() == -1)
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return (-1);
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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, (char *)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, (char *)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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hp = (HEADER *) answer;
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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 number is left in h_errno.
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* Only useful for queries in the same name hierarchy as the local host
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* (not, for example, for host address-to-name lookups in domain in-addr.arpa).
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*/
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res_search(name, class, type, answer, anslen)
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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 char *cp, **domain;
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int n, ret, got_nodata = 0;
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char *__hostalias();
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if ((_res.options & RES_INIT) == 0 && res_init() == -1)
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return (-1);
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errno = 0;
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h_errno = HOST_NOT_FOUND; /* default, if we never query */
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for (cp = name, n = 0; *cp; cp++)
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if (*cp == '.')
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n++;
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if (n == 0 && (cp = __hostalias(name)))
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return (res_query(cp, class, type, answer, anslen));
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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 ((n == 0 && _res.options & RES_DEFNAMES) ||
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(n != 0 && *--cp != '.' && _res.options & RES_DNSRCH))
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for (domain = _res.dnsrch; *domain; 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 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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if (h_errno == NO_DATA)
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got_nodata++;
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if ((h_errno != HOST_NOT_FOUND && h_errno != NO_DATA) ||
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(_res.options & RES_DNSRCH) == 0)
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break;
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}
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/*
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* If the search/default failed, try the name as fully-qualified,
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* but only if it contained at least one dot (even trailing).
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* This is purely a heuristic; we assume that any reasonable query
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* about a top-level domain (for servers, SOA, etc) will not use
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* res_search.
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*/
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if (n && (ret = res_querydomain(name, (char *)NULL, class, type,
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answer, anslen)) > 0)
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return (ret);
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if (got_nodata)
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h_errno = NO_DATA;
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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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res_querydomain(name, domain, class, type, answer, anslen)
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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[2*MAXDNAME+2];
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char *longname = nbuf;
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int n;
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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, 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 (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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(void)sprintf(nbuf, "%.*s.%.*s",
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MAXDNAME, name, MAXDNAME, domain);
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return (res_query(longname, class, type, answer, anslen));
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}
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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 *C1, *C2;
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FILE *fp;
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char *file, *getenv(), *strcpy(), *strncpy();
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char buf[BUFSIZ];
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static char abuf[MAXDNAME];
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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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buf[sizeof(buf) - 1] = '\0';
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while (fgets(buf, sizeof(buf), fp)) {
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for (C1 = buf; *C1 && !isspace(*C1); ++C1);
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if (!*C1)
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break;
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*C1 = '\0';
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if (!strcasecmp(buf, name)) {
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while (isspace(*++C1));
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if (!*C1)
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break;
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for (C2 = C1 + 1; *C2 && !isspace(*C2); ++C2);
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abuf[sizeof(abuf) - 1] = *C2 = '\0';
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(void)strncpy(abuf, C1, 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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