BSD 4_3_Net_1 release

[unix-history] / named / tools / nslookup / skip.c

/*
* Copyright (c) 1985 Regents of the University of California.
* All rights reserved.
*
* Redistribution and use in source and binary forms are permitted
* provided that the above copyright notice and this paragraph are
* duplicated in all such forms and that any documentation,
* advertising materials, and other materials related to such
* distribution and use acknowledge that the software was developed
* by the University of California, Berkeley.  The name of the
* University may not be used to endorse or promote products derived
* from this software without specific prior written permission.
* THIS SOFTWARE IS PROVIDED ``AS IS'' AND WITHOUT ANY EXPRESS OR
* IMPLIED WARRANTIES, INCLUDING, WITHOUT LIMITATION, THE IMPLIED
* WARRANTIES OF MERCHANTIBILITY AND FITNESS FOR A PARTICULAR PURPOSE.
*/

#ifndef lint
static char sccsid[] = "@(#)skip.c      5.5 (Berkeley) 6/18/88";
#endif /* not lint */

/*
*******************************************************************************
*
*  skip.c --
*
*      Routines to skip over portions of a query buffer.
*
*      Note: this file has been submitted for inclusion in
*      BIND resolver library. When this has been done, this file
*      is no longer necessary (assuming there haven't been any
*      changes).
*
*      Adapted from 4.3BSD BIND res_debug.c
*
*******************************************************************************
*/

#include <sys/types.h>
#include <netinet/in.h>
#include <stdio.h>
#include <arpa/nameser.h>

char *res_skip_rr();

\f
/*
*******************************************************************************
*
*  res_skip --
*
*      Skip the contents of a query.
*
*      Interpretation of numFieldsToSkip argument:
*            res_skip returns pointer to:
*      1 ->  start of question records.
*      2 ->  start of authoritative answer records.
*      3 ->  start of additional records.
*      4 ->  first byte after end of additional records.
*
*   Results:
*      (address)       - success operation.
*      NULL            - a resource record had an incorrect format.
*
*******************************************************************************
*/

char *
res_skip(msg, numFieldsToSkip, eom)
       char *msg;
       int numFieldsToSkip;
       char *eom;
{
       register char *cp;
       register HEADER *hp;
       register int tmp;
       register int n;

       /*
        * Skip the header fields.
        */
       hp = (HEADER *)msg;
       cp = msg + sizeof(HEADER);

       /*
        * skip question records.
        */
       if (n = ntohs(hp->qdcount) ) {
               while (--n >= 0) {
                       tmp = dn_skipname(cp, eom);
                       if (tmp == -1) return(NULL);
                       cp += tmp;
                       cp += sizeof(u_short);  /* type         */
                       cp += sizeof(u_short);  /* class        */
               }
       }
       if (--numFieldsToSkip <= 0) return(cp);

       /*
        * skip authoritative answer records
        */
       if (n = ntohs(hp->ancount)) {
               while (--n >= 0) {
                       cp = res_skip_rr(cp, eom);
                       if (cp == NULL) return(NULL);
               }
       }
       if (--numFieldsToSkip == 0) return(cp);

       /*
        * skip name server records
        */
       if (n = ntohs(hp->nscount)) {
               while (--n >= 0) {
                       cp = res_skip_rr(cp, eom);
                       if (cp == NULL) return(NULL);
               }
       }
       if (--numFieldsToSkip == 0) return(cp);

       /*
        * skip additional records
        */
       if (n = ntohs(hp->arcount)) {
               while (--n >= 0) {
                       cp = res_skip_rr(cp, eom);
                       if (cp == NULL) return(NULL);
               }
       }

       return(cp);
}

\f
/*
*******************************************************************************
*
*  res_skip_rr --
*
*      Skip over resource record fields.
*
*   Results:
*      (address)       - success operation.
*      NULL            - a resource record had an incorrect format.
*******************************************************************************
*/

char *
res_skip_rr(cp, eom)
       char *cp;
       char *eom;
{
       int tmp;
       int dlen;

       if ((tmp = dn_skipname(cp, eom)) == -1)
               return (NULL);                  /* compression error */
       cp += tmp;
       cp += sizeof(u_short);  /*      type    */
       cp += sizeof(u_short);  /*      class   */
       cp += sizeof(u_long);   /*      ttl     */
       dlen = _getshort(cp);
       cp += sizeof(u_short);  /*      dlen    */
       cp += dlen;
       return (cp);
}