189 lines
5.1 KiB
C
189 lines
5.1 KiB
C
/*
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* Copyright (c) 1985 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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#ifndef lint
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/*static char sccsid[] = "from: @(#)skip.c 5.12 (Berkeley) 3/21/91";*/
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static char rcsid[] = "$Id: skip.c,v 1.2 1993/08/01 17:58:07 mycroft Exp $";
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#endif /* not lint */
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/*
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*******************************************************************************
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*
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* skip.c --
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*
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* Routines to skip over portions of a query buffer.
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*
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* Note: this file has been submitted for inclusion in
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* BIND resolver library. When this has been done, this file
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* is no longer necessary (assuming there haven't been any
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* changes).
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*
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* Adapted from 4.3BSD BIND res_debug.c
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*
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*******************************************************************************
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*/
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#include <sys/param.h>
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#include <netinet/in.h>
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#include <arpa/nameser.h>
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#include <resolv.h>
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#include <stdio.h>
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char *res_skip_rr();
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/*
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*******************************************************************************
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*
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* res_skip --
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*
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* Skip the contents of a query.
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*
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* Interpretation of numFieldsToSkip argument:
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* res_skip returns pointer to:
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* 1 -> start of question records.
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* 2 -> start of authoritative answer records.
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* 3 -> start of additional records.
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* 4 -> first byte after end of additional records.
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*
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* Results:
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* (address) - success operation.
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* NULL - a resource record had an incorrect format.
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*
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*******************************************************************************
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*/
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char *
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res_skip(msg, numFieldsToSkip, eom)
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char *msg;
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int numFieldsToSkip;
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char *eom;
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{
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register char *cp;
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register HEADER *hp;
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register int tmp;
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register int n;
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/*
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* Skip the header fields.
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*/
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hp = (HEADER *)msg;
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cp = msg + sizeof(HEADER);
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/*
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* skip question records.
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*/
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if (n = ntohs(hp->qdcount) ) {
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while (--n >= 0 && cp < eom) {
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tmp = dn_skipname((u_char *)cp, (u_char *)eom);
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if (tmp == -1) return(NULL);
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cp += tmp;
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cp += sizeof(u_short); /* type */
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cp += sizeof(u_short); /* class */
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}
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}
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if (--numFieldsToSkip <= 0) return(cp);
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/*
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* skip authoritative answer records
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*/
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if (n = ntohs(hp->ancount)) {
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while (--n >= 0 && cp < eom) {
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cp = res_skip_rr(cp, eom);
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if (cp == NULL) return(NULL);
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}
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}
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if (--numFieldsToSkip == 0) return(cp);
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/*
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* skip name server records
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*/
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if (n = ntohs(hp->nscount)) {
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while (--n >= 0 && cp < eom) {
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cp = res_skip_rr(cp, eom);
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if (cp == NULL) return(NULL);
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}
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}
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if (--numFieldsToSkip == 0) return(cp);
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/*
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* skip additional records
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*/
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if (n = ntohs(hp->arcount)) {
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while (--n >= 0 && cp < eom) {
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cp = res_skip_rr(cp, eom);
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if (cp == NULL) return(NULL);
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}
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}
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return(cp);
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}
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/*
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*******************************************************************************
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*
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* res_skip_rr --
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*
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* Skip over resource record fields.
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*
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* Results:
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* (address) - success operation.
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* NULL - a resource record had an incorrect format.
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*******************************************************************************
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*/
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char *
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res_skip_rr(cp, eom)
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char *cp;
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char *eom;
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{
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int tmp;
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int dlen;
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if ((tmp = dn_skipname((u_char *)cp, (u_char *)eom)) == -1)
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return (NULL); /* compression error */
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cp += tmp;
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if ((cp + RRFIXEDSZ) > eom)
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return (NULL);
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cp += sizeof(u_short); /* type */
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cp += sizeof(u_short); /* class */
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cp += sizeof(u_long); /* ttl */
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dlen = _getshort(cp);
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cp += sizeof(u_short); /* dlen */
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cp += dlen;
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if (cp > eom)
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return (NULL);
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return (cp);
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}
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