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Annotation of 43BSD/etc/named/tools/ns.lookup/src/skip.c, revision 1.1.1.1

1.1       root        1: /*
                      2:  *******************************************************************************
                      3:  *
                      4:  *  skip.c --
                      5:  *
                      6:  *     Routines to skip over portions of a query buffer.
                      7:  *
                      8:  *     Note: this file has been submitted for inclusion in
                      9:  *     BIND resolver library. When this has been done, this file
                     10:  *     is no longer necessary (assuming there haven't been any
                     11:  *     changes).
                     12:  *
                     13:  *     Adapted from 4.3BSD BIND res_debug.c
                     14:  *
                     15:  *     Copyright (c) 1985 Regents of the University of California.
                     16:  *     All rights reserved.  The Berkeley software License Agreement
                     17:  *     specifies the terms and conditions for redistribution.
                     18:  *
                     19:  *******************************************************************************
                     20:  */
                     21: 
                     22: #ifndef lint
                     23: static char sccsid[] = "@(#)skip.c     5.1 (Berkeley) 11/29/85";
                     24: #endif not lint
                     25: 
                     26: #include <sys/types.h>
                     27: #include <netinet/in.h>
                     28: #include <stdio.h>
                     29: #include <arpa/nameser.h>
                     30: 
                     31: char *res_skip_rr();
                     32: 
                     33: 
                     34: /*
                     35:  *******************************************************************************
                     36:  *
                     37:  *  res_skip --
                     38:  *
                     39:  *     Skip the contents of a query.
                     40:  *
                     41:  *     Interpretation of numFieldsToSkip argument:
                     42:  *            res_skip returns pointer to:
                     43:  *     1 ->  start of question records.
                     44:  *     2 ->  start of authoritative answer records.
                     45:  *     3 ->  start of additional records.
                     46:  *     4 ->  first byte after end of additional records.
                     47:  *
                     48:  *   Results:
                     49:  *     (address)       - success operation.
                     50:  *     NULL            - a resource record had an incorrect format.
                     51:  *
                     52:  *******************************************************************************
                     53:  */
                     54: 
                     55: char *
                     56: res_skip(msg, numFieldsToSkip)
                     57:        char *msg;
                     58:        int numFieldsToSkip;
                     59: {
                     60:        register char *cp;
                     61:        register HEADER *hp;
                     62:        register int tmp;
                     63:        register int n;
                     64: 
                     65:        /*
                     66:         * Skip the header fields.
                     67:         */
                     68:        hp = (HEADER *)msg;
                     69:        cp = msg + sizeof(HEADER);
                     70: 
                     71:        /*
                     72:         * skip question records.
                     73:         */
                     74:        if (n = ntohs(hp->qdcount) ) {
                     75:                while (--n >= 0) {
                     76:                        tmp = dn_skip(cp);
                     77:                        if (tmp == -1) return(NULL);
                     78:                        cp += tmp;
                     79:                        cp += sizeof(u_short);  /* type         */
                     80:                        cp += sizeof(u_short);  /* class        */
                     81:                }
                     82:        }
                     83:        if (--numFieldsToSkip <= 0) return(cp);
                     84: 
                     85:        /*
                     86:         * skip authoritative answer records
                     87:         */
                     88:        if (n = ntohs(hp->ancount)) {
                     89:                while (--n >= 0) {
                     90:                        cp = res_skip_rr(cp);
                     91:                        if (cp == NULL) return(NULL);
                     92:                }
                     93:        }
                     94:        if (--numFieldsToSkip == 0) return(cp);
                     95: 
                     96:        /*
                     97:         * skip name server records
                     98:         */
                     99:        if (n = ntohs(hp->nscount)) {
                    100:                while (--n >= 0) {
                    101:                        cp = res_skip_rr(cp);
                    102:                        if (cp == NULL) return(NULL);
                    103:                }
                    104:        }
                    105:        if (--numFieldsToSkip == 0) return(cp);
                    106: 
                    107:        /*
                    108:         * skip additional records
                    109:         */
                    110:        if (n = ntohs(hp->arcount)) {
                    111:                while (--n >= 0) {
                    112:                        cp = res_skip_rr(cp);
                    113:                        if (cp == NULL) return(NULL);
                    114:                }
                    115:        }
                    116: 
                    117:        return(cp);
                    118: }
                    119: 
                    120: 
                    121: /*
                    122:  *******************************************************************************
                    123:  *
                    124:  *  res_skip_rr --
                    125:  *
                    126:  *     Skip over resource record fields.
                    127:  *
                    128:  *   Results:
                    129:  *     (address)       - success operation.
                    130:  *     NULL            - a resource record had an incorrect format.
                    131:  *******************************************************************************
                    132:  */
                    133: 
                    134: char *
                    135: res_skip_rr(cp)
                    136:        char *cp;
                    137: {
                    138:        int tmp;
                    139:        int dlen;
                    140: 
                    141:        if ((tmp = dn_skip(cp)) == -1)
                    142:                return (NULL);                  /* compression error */
                    143:        cp += tmp;
                    144:        cp += sizeof(u_short);  /*      type    */
                    145:        cp += sizeof(u_short);  /*      class   */
                    146:        cp += sizeof(u_long);   /*      ttl     */
                    147:        dlen = getshort(cp);
                    148:        cp += sizeof(u_short);  /*      dlen    */
                    149:        cp += dlen;
                    150:        return (cp);
                    151: }

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