lib/dns/rdata.c

/*
 * Copyright (C) 1998-2017  Internet Systems Consortium, Inc. ("ISC")
 *
 * This Source Code Form is subject to the terms of the Mozilla Public
 * License, v. 2.0. If a copy of the MPL was not distributed with this
 * file, You can obtain one at http://mozilla.org/MPL/2.0/.
 */

/* $Id$ */

/*! \file */

#include <config.h>
#include <ctype.h>

#include <isc/base64.h>
#include <isc/hex.h>
#include <isc/lex.h>
#include <isc/mem.h>
#include <isc/parseint.h>
#include <isc/print.h>
#include <isc/string.h>
#include <isc/stdlib.h>
#include <isc/util.h>

#include <dns/callbacks.h>
#include <dns/cert.h>
#include <dns/compress.h>
#include <dns/dsdigest.h>
#include <dns/enumtype.h>
#include <dns/keyflags.h>
#include <dns/keyvalues.h>
#include <dns/message.h>
#include <dns/rcode.h>
#include <dns/rdata.h>
#include <dns/rdataclass.h>
#include <dns/rdatastruct.h>
#include <dns/rdatatype.h>
#include <dns/result.h>
#include <dns/secalg.h>
#include <dns/secproto.h>
#include <dns/time.h>
#include <dns/ttl.h>

#define RETERR(x) \
    do { \
        isc_result_t _r = (x); \
        if (_r != ISC_R_SUCCESS) \
            return (_r); \
    } while (0)

#define RETTOK(x) \
    do { \
        isc_result_t _r = (x); \
        if (_r != ISC_R_SUCCESS) { \
            isc_lex_ungettoken(lexer, &token); \
            return (_r); \
        } \
    } while (0)

#define CHECK(op)                       \
    do { result = (op);                 \
        if (result != ISC_R_SUCCESS) goto cleanup;  \
    } while (0)

#define CHECKTOK(op)                        \
    do { result = (op);                 \
        if (result != ISC_R_SUCCESS) {          \
            isc_lex_ungettoken(lexer, &token);  \
            goto cleanup;               \
        }                       \
    } while (0)

#define DNS_AS_STR(t) ((t).value.as_textregion.base)

#define ARGS_FROMTEXT   int rdclass, dns_rdatatype_t type, \
            isc_lex_t *lexer, dns_name_t *origin, \
            unsigned int options, isc_buffer_t *target, \
            dns_rdatacallbacks_t *callbacks

#define ARGS_TOTEXT dns_rdata_t *rdata, dns_rdata_textctx_t *tctx, \
            isc_buffer_t *target

#define ARGS_FROMWIRE   int rdclass, dns_rdatatype_t type, \
            isc_buffer_t *source, dns_decompress_t *dctx, \
            unsigned int options, isc_buffer_t *target

#define ARGS_TOWIRE dns_rdata_t *rdata, dns_compress_t *cctx, \
            isc_buffer_t *target

#define ARGS_COMPARE    const dns_rdata_t *rdata1, const dns_rdata_t *rdata2

#define ARGS_FROMSTRUCT int rdclass, dns_rdatatype_t type, \
            void *source, isc_buffer_t *target

#define ARGS_TOSTRUCT   dns_rdata_t *rdata, void *target, isc_mem_t *mctx

#define ARGS_FREESTRUCT void *source

#define ARGS_ADDLDATA   dns_rdata_t *rdata, dns_additionaldatafunc_t add, \
            void *arg

#define ARGS_DIGEST dns_rdata_t *rdata, dns_digestfunc_t digest, void *arg

#define ARGS_CHECKOWNER dns_name_t *name, dns_rdataclass_t rdclass, \
            dns_rdatatype_t type, isc_boolean_t wildcard

#define ARGS_CHECKNAMES dns_rdata_t *rdata, dns_name_t *owner, dns_name_t *bad


/*%
 * Context structure for the totext_ functions.
 * Contains formatting options for rdata-to-text
 * conversion.
 */
typedef struct dns_rdata_textctx {
    dns_name_t *origin; /*%< Current origin, or NULL. */
    unsigned int flags; /*%< DNS_STYLEFLAG_*  */
    unsigned int width; /*%< Width of rdata column. */
    const char *linebreak;  /*%< Line break string. */
} dns_rdata_textctx_t;

static isc_result_t
txt_totext(isc_region_t *source, isc_boolean_t quote, isc_buffer_t *target);

static isc_result_t
txt_fromtext(isc_textregion_t *source, isc_buffer_t *target);

static isc_result_t
txt_fromwire(isc_buffer_t *source, isc_buffer_t *target);

static isc_result_t
multitxt_totext(isc_region_t *source, isc_buffer_t *target);

static isc_result_t
multitxt_fromtext(isc_textregion_t *source, isc_buffer_t *target);

static isc_boolean_t
name_prefix(dns_name_t *name, dns_name_t *origin, dns_name_t *target);

static unsigned int
name_length(dns_name_t *name);

static isc_result_t
str_totext(const char *source, isc_buffer_t *target);

static isc_result_t
inet_totext(int af, isc_region_t *src, isc_buffer_t *target);

static isc_boolean_t
buffer_empty(isc_buffer_t *source);

static void
buffer_fromregion(isc_buffer_t *buffer, isc_region_t *region);

static isc_result_t
uint32_tobuffer(isc_uint32_t, isc_buffer_t *target);

static isc_result_t
uint16_tobuffer(isc_uint32_t, isc_buffer_t *target);

static isc_result_t
uint8_tobuffer(isc_uint32_t, isc_buffer_t *target);

static isc_result_t
name_tobuffer(dns_name_t *name, isc_buffer_t *target);

static isc_uint32_t
uint32_fromregion(isc_region_t *region);

static isc_uint16_t
uint16_fromregion(isc_region_t *region);

static isc_uint8_t
uint8_fromregion(isc_region_t *region);

static isc_uint8_t
uint8_consume_fromregion(isc_region_t *region);

static isc_result_t
mem_tobuffer(isc_buffer_t *target, void *base, unsigned int length);

static int
hexvalue(char value);

static int
decvalue(char value);

static isc_result_t
btoa_totext(unsigned char *inbuf, int inbuflen, isc_buffer_t *target);

static isc_result_t
atob_tobuffer(isc_lex_t *lexer, isc_buffer_t *target);

static void
default_fromtext_callback(dns_rdatacallbacks_t *callbacks, const char *, ...)
     ISC_FORMAT_PRINTF(2, 3);

static void
fromtext_error(void (*callback)(dns_rdatacallbacks_t *, const char *, ...),
           dns_rdatacallbacks_t *callbacks, const char *name,
           unsigned long line, isc_token_t *token, isc_result_t result);

static void
fromtext_warneof(isc_lex_t *lexer, dns_rdatacallbacks_t *callbacks);

static isc_result_t
rdata_totext(dns_rdata_t *rdata, dns_rdata_textctx_t *tctx,
         isc_buffer_t *target);

static void
warn_badname(dns_name_t *name, isc_lex_t *lexer,
         dns_rdatacallbacks_t *callbacks);

static void
warn_badmx(isc_token_t *token, isc_lex_t *lexer,
       dns_rdatacallbacks_t *callbacks);

static isc_uint16_t
uint16_consume_fromregion(isc_region_t *region);

static isc_result_t
unknown_totext(dns_rdata_t *rdata, dns_rdata_textctx_t *tctx,
           isc_buffer_t *target);

static inline isc_result_t
generic_fromtext_key(ARGS_FROMTEXT);

static inline isc_result_t
generic_totext_key(ARGS_TOTEXT);

static inline isc_result_t
generic_fromwire_key(ARGS_FROMWIRE);

static inline isc_result_t
generic_fromstruct_key(ARGS_FROMSTRUCT);

static inline isc_result_t
generic_tostruct_key(ARGS_TOSTRUCT);

static inline void
generic_freestruct_key(ARGS_FREESTRUCT);

static isc_result_t
generic_fromtext_txt(ARGS_FROMTEXT);

static isc_result_t
generic_totext_txt(ARGS_TOTEXT);

static isc_result_t
generic_fromwire_txt(ARGS_FROMWIRE);

static isc_result_t
generic_fromstruct_txt(ARGS_FROMSTRUCT);

static isc_result_t
generic_tostruct_txt(ARGS_TOSTRUCT);

static void
generic_freestruct_txt(ARGS_FREESTRUCT);

static isc_result_t
generic_txt_first(dns_rdata_txt_t *txt);

static isc_result_t
generic_txt_next(dns_rdata_txt_t *txt);

static isc_result_t
generic_txt_current(dns_rdata_txt_t *txt, dns_rdata_txt_string_t *string);

static isc_result_t
generic_totext_ds(ARGS_TOTEXT);

static isc_result_t
generic_tostruct_ds(ARGS_TOSTRUCT);

static isc_result_t
generic_fromtext_ds(ARGS_FROMTEXT);

static isc_result_t
generic_fromwire_ds(ARGS_FROMWIRE);

static isc_result_t
generic_fromstruct_ds(ARGS_FROMSTRUCT);

static isc_result_t
generic_fromtext_tlsa(ARGS_FROMTEXT);

static isc_result_t
generic_totext_tlsa(ARGS_TOTEXT);

static isc_result_t
generic_fromwire_tlsa(ARGS_FROMWIRE);

static isc_result_t
generic_fromstruct_tlsa(ARGS_FROMSTRUCT);

static isc_result_t
generic_tostruct_tlsa(ARGS_TOSTRUCT);

static void
generic_freestruct_tlsa(ARGS_FREESTRUCT);

/*% INT16 Size */
#define NS_INT16SZ  2
/*% IPv6 Address Size */
#define NS_LOCATORSZ    8

/*
 * Active Diretory gc._msdcs.<forest> prefix.
 */
static unsigned char gc_msdcs_data[]  = "\002gc\006_msdcs";
static unsigned char gc_msdcs_offset [] = { 0, 3 };

static dns_name_t const gc_msdcs =
    DNS_NAME_INITNONABSOLUTE(gc_msdcs_data, gc_msdcs_offset);

/*%
 *  convert presentation level address to network order binary form.
 * \return
 *  1 if `src' is a valid [RFC1884 2.2] address, else 0.
 * \note
 *  (1) does not touch `dst' unless it's returning 1.
 */
static inline int
locator_pton(const char *src, unsigned char *dst) {
    static const char xdigits_l[] = "0123456789abcdef",
              xdigits_u[] = "0123456789ABCDEF";
    unsigned char tmp[NS_LOCATORSZ];
    unsigned char *tp = tmp, *endp;
    const char *xdigits;
    int ch, seen_xdigits;
    unsigned int val;

    memset(tp, '\0', NS_LOCATORSZ);
    endp = tp + NS_LOCATORSZ;
    seen_xdigits = 0;
    val = 0;
    while ((ch = *src++) != '\0') {
        const char *pch;

        pch = strchr((xdigits = xdigits_l), ch);
        if (pch == NULL)
            pch = strchr((xdigits = xdigits_u), ch);
        if (pch != NULL) {
            val <<= 4;
            val |= (pch - xdigits);
            if (++seen_xdigits > 4)
                return (0);
            continue;
        }
        if (ch == ':') {
            if (!seen_xdigits)
                return (0);
            if (tp + NS_INT16SZ > endp)
                return (0);
            *tp++ = (unsigned char) (val >> 8) & 0xff;
            *tp++ = (unsigned char) val & 0xff;
            seen_xdigits = 0;
            val = 0;
            continue;
        }
        return (0);
    }
    if (seen_xdigits) {
        if (tp + NS_INT16SZ > endp)
            return (0);
        *tp++ = (unsigned char) (val >> 8) & 0xff;
        *tp++ = (unsigned char) val & 0xff;
    }
    if (tp != endp)
        return (0);
    memmove(dst, tmp, NS_LOCATORSZ);
    return (1);
}

static inline int
getquad(const void *src, struct in_addr *dst,
    isc_lex_t *lexer, dns_rdatacallbacks_t *callbacks)
{
    int result;
    struct in_addr tmp;

    result = inet_aton(src, dst);
    if (result == 1 && callbacks != NULL &&
        inet_pton(AF_INET, src, &tmp) != 1) {
        const char *name = isc_lex_getsourcename(lexer);
        if (name == NULL)
            name = "UNKNOWN";
        (*callbacks->warn)(callbacks, "%s:%lu: \"%s\" "
                   "is not a decimal dotted quad", name,
                   isc_lex_getsourceline(lexer), src);
    }
    return (result);
}

static inline isc_result_t
name_duporclone(dns_name_t *source, isc_mem_t *mctx, dns_name_t *target) {

    if (mctx != NULL)
        return (dns_name_dup(source, mctx, target));
    dns_name_clone(source, target);
    return (ISC_R_SUCCESS);
}

static inline void *
mem_maybedup(isc_mem_t *mctx, void *source, size_t length) {
    void *copy;

    if (mctx == NULL)
        return (source);
    copy = isc_mem_allocate(mctx, length);
    if (copy != NULL)
        memmove(copy, source, length);

    return (copy);
}

static inline isc_result_t
typemap_fromtext(isc_lex_t *lexer, isc_buffer_t *target,
         isc_boolean_t allow_empty)
{
    isc_token_t token;
    unsigned char bm[8*1024]; /* 64k bits */
    dns_rdatatype_t covered, max_used;
    int octet;
    unsigned int max_octet, newend, end;
    int window;
    isc_boolean_t first = ISC_TRUE;

    max_used = 0;
    bm[0] = 0;
    end = 0;

    do {
        RETERR(isc_lex_getmastertoken(lexer, &token,
                          isc_tokentype_string, ISC_TRUE));
        if (token.type != isc_tokentype_string)
            break;
        RETTOK(dns_rdatatype_fromtext(&covered,
                          &token.value.as_textregion));
        if (covered > max_used) {
            newend = covered / 8;
            if (newend > end) {
                memset(&bm[end + 1], 0, newend - end);
                end = newend;
            }
            max_used = covered;
        }
        bm[covered/8] |= (0x80>>(covered%8));
        first = ISC_FALSE;
    } while (1);
    isc_lex_ungettoken(lexer, &token);
    if (!allow_empty && first)
        return (DNS_R_FORMERR);

    for (window = 0; window < 256 ; window++) {
        if (max_used < window * 256)
            break;

        max_octet = max_used - (window * 256);
        if (max_octet >= 256)
            max_octet = 31;
        else
            max_octet /= 8;

        /*
         * Find if we have a type in this window.
         */
        for (octet = max_octet; octet >= 0; octet--) {
            if (bm[window * 32 + octet] != 0)
                break;
        }
        if (octet < 0)
            continue;
        RETERR(uint8_tobuffer(window, target));
        RETERR(uint8_tobuffer(octet + 1, target));
        RETERR(mem_tobuffer(target, &bm[window * 32], octet + 1));
    }
    return (ISC_R_SUCCESS);
}

static inline isc_result_t
typemap_totext(isc_region_t *sr, dns_rdata_textctx_t *tctx,
           isc_buffer_t *target)
{
    unsigned int i, j, k;
    unsigned int window, len;
    isc_boolean_t first = ISC_FALSE;

    for (i = 0; i < sr->length; i += len) {
        if (tctx != NULL &&
            (tctx->flags & DNS_STYLEFLAG_MULTILINE) != 0) {
            RETERR(str_totext(tctx->linebreak, target));
            first = ISC_TRUE;
        }
        INSIST(i + 2 <= sr->length);
        window = sr->base[i];
        len = sr->base[i + 1];
        INSIST(len > 0 && len <= 32);
        i += 2;
        INSIST(i + len <= sr->length);
        for (j = 0; j < len; j++) {
            dns_rdatatype_t t;
            if (sr->base[i + j] == 0)
                continue;
            for (k = 0; k < 8; k++) {
                if ((sr->base[i + j] & (0x80 >> k)) == 0)
                    continue;
                t = window * 256 + j * 8 + k;
                if (!first)
                    RETERR(str_totext(" ", target));
                first = ISC_FALSE;
                if (dns_rdatatype_isknown(t)) {
                    RETERR(dns_rdatatype_totext(t, target));
                } else {
                    char buf[sizeof("TYPE65535")];
                    snprintf(buf, sizeof(buf), "TYPE%u", t);
                    RETERR(str_totext(buf, target));
                }
            }
        }
    }
    return (ISC_R_SUCCESS);
}

static isc_result_t
typemap_test(isc_region_t *sr, isc_boolean_t allow_empty) {
    unsigned int window, lastwindow = 0;
    unsigned int len;
    isc_boolean_t first = ISC_TRUE;
    unsigned int i;

    for (i = 0; i < sr->length; i += len) {
        /*
         * Check for overflow.
         */
        if (i + 2 > sr->length)
            RETERR(DNS_R_FORMERR);
        window = sr->base[i];
        len = sr->base[i + 1];
        i += 2;
        /*
         * Check that bitmap windows are in the correct order.
         */
        if (!first && window <= lastwindow)
            RETERR(DNS_R_FORMERR);
        /*
         * Check for legal lengths.
         */
        if (len < 1 || len > 32)
            RETERR(DNS_R_FORMERR);
        /*
         * Check for overflow.
         */
        if (i + len > sr->length)
            RETERR(DNS_R_FORMERR);
        /*
         * The last octet of the bitmap must be non zero.
         */
        if (sr->base[i + len - 1] == 0)
            RETERR(DNS_R_FORMERR);
        lastwindow = window;
        first = ISC_FALSE;
    }
    if (i != sr->length)
        return (DNS_R_EXTRADATA);
    if (!allow_empty && first)
        RETERR(DNS_R_FORMERR);
    return (ISC_R_SUCCESS);
}

static const char hexdigits[] = "0123456789abcdef";
static const char decdigits[] = "0123456789";

#include "code.h"

#define META 0x0001
#define RESERVED 0x0002

/***
 *** Initialization
 ***/

void
dns_rdata_init(dns_rdata_t *rdata) {

    REQUIRE(rdata != NULL);

    rdata->data = NULL;
    rdata->length = 0;
    rdata->rdclass = 0;
    rdata->type = 0;
    rdata->flags = 0;
    ISC_LINK_INIT(rdata, link);
    /* ISC_LIST_INIT(rdata->list); */
}

void
dns_rdata_reset(dns_rdata_t *rdata) {

    REQUIRE(rdata != NULL);

    REQUIRE(!ISC_LINK_LINKED(rdata, link));
    REQUIRE(DNS_RDATA_VALIDFLAGS(rdata));

    rdata->data = NULL;
    rdata->length = 0;
    rdata->rdclass = 0;
    rdata->type = 0;
    rdata->flags = 0;
}

/***
 ***
 ***/

void
dns_rdata_clone(const dns_rdata_t *src, dns_rdata_t *target) {

    REQUIRE(src != NULL);
    REQUIRE(target != NULL);

    REQUIRE(DNS_RDATA_INITIALIZED(target));

    REQUIRE(DNS_RDATA_VALIDFLAGS(src));
    REQUIRE(DNS_RDATA_VALIDFLAGS(target));

    target->data = src->data;
    target->length = src->length;
    target->rdclass = src->rdclass;
    target->type = src->type;
    target->flags = src->flags;
}


/***
 *** Comparisons
 ***/

int
dns_rdata_compare(const dns_rdata_t *rdata1, const dns_rdata_t *rdata2) {
    int result = 0;
    isc_boolean_t use_default = ISC_FALSE;

    REQUIRE(rdata1 != NULL);
    REQUIRE(rdata2 != NULL);
    REQUIRE(rdata1->length == 0 || rdata1->data != NULL);
    REQUIRE(rdata2->length == 0 || rdata2->data != NULL);
    REQUIRE(DNS_RDATA_VALIDFLAGS(rdata1));
    REQUIRE(DNS_RDATA_VALIDFLAGS(rdata2));

    if (rdata1->rdclass != rdata2->rdclass)
        return (rdata1->rdclass < rdata2->rdclass ? -1 : 1);

    if (rdata1->type != rdata2->type)
        return (rdata1->type < rdata2->type ? -1 : 1);

    COMPARESWITCH

    if (use_default) {
        isc_region_t r1;
        isc_region_t r2;

        dns_rdata_toregion(rdata1, &r1);
        dns_rdata_toregion(rdata2, &r2);
        result = isc_region_compare(&r1, &r2);
    }
    return (result);
}

int
dns_rdata_casecompare(const dns_rdata_t *rdata1, const dns_rdata_t *rdata2) {
    int result = 0;
    isc_boolean_t use_default = ISC_FALSE;

    REQUIRE(rdata1 != NULL);
    REQUIRE(rdata2 != NULL);
    REQUIRE(rdata1->length == 0 || rdata1->data != NULL);
    REQUIRE(rdata2->length == 0 || rdata2->data != NULL);
    REQUIRE(DNS_RDATA_VALIDFLAGS(rdata1));
    REQUIRE(DNS_RDATA_VALIDFLAGS(rdata2));

    if (rdata1->rdclass != rdata2->rdclass)
        return (rdata1->rdclass < rdata2->rdclass ? -1 : 1);

    if (rdata1->type != rdata2->type)
        return (rdata1->type < rdata2->type ? -1 : 1);

    CASECOMPARESWITCH

    if (use_default) {
        isc_region_t r1;
        isc_region_t r2;

        dns_rdata_toregion(rdata1, &r1);
        dns_rdata_toregion(rdata2, &r2);
        result = isc_region_compare(&r1, &r2);
    }
    return (result);
}

/***
 *** Conversions
 ***/

void
dns_rdata_fromregion(dns_rdata_t *rdata, dns_rdataclass_t rdclass,
             dns_rdatatype_t type, isc_region_t *r)
{

    REQUIRE(rdata != NULL);
    REQUIRE(DNS_RDATA_INITIALIZED(rdata));
    REQUIRE(r != NULL);

    REQUIRE(DNS_RDATA_VALIDFLAGS(rdata));

    rdata->data = r->base;
    rdata->length = r->length;
    rdata->rdclass = rdclass;
    rdata->type = type;
    rdata->flags = 0;
}

void
dns_rdata_toregion(const dns_rdata_t *rdata, isc_region_t *r) {

    REQUIRE(rdata != NULL);
    REQUIRE(r != NULL);
    REQUIRE(DNS_RDATA_VALIDFLAGS(rdata));

    r->base = rdata->data;
    r->length = rdata->length;
}

isc_result_t
dns_rdata_fromwire(dns_rdata_t *rdata, dns_rdataclass_t rdclass,
           dns_rdatatype_t type, isc_buffer_t *source,
           dns_decompress_t *dctx, unsigned int options,
           isc_buffer_t *target)
{
    isc_result_t result = ISC_R_NOTIMPLEMENTED;
    isc_region_t region;
    isc_buffer_t ss;
    isc_buffer_t st;
    isc_boolean_t use_default = ISC_FALSE;
    isc_uint32_t activelength;
    unsigned int length;

    REQUIRE(dctx != NULL);
    if (rdata != NULL) {
        REQUIRE(DNS_RDATA_INITIALIZED(rdata));
        REQUIRE(DNS_RDATA_VALIDFLAGS(rdata));
    }
    REQUIRE(source != NULL);
    REQUIRE(target != NULL);

    if (type == 0)
        return (DNS_R_FORMERR);

    ss = *source;
    st = *target;

    activelength = isc_buffer_activelength(source);
    INSIST(activelength < 65536);

    FROMWIRESWITCH

    if (use_default) {
        if (activelength > isc_buffer_availablelength(target))
            result = ISC_R_NOSPACE;
        else {
            isc_buffer_putmem(target, isc_buffer_current(source),
                      activelength);
            isc_buffer_forward(source, activelength);
            result = ISC_R_SUCCESS;
        }
    }

    /*
     * Reject any rdata that expands out to more than DNS_RDATA_MAXLENGTH
     * as we cannot transmit it.
     */
    length = isc_buffer_usedlength(target) - isc_buffer_usedlength(&st);
    if (result == ISC_R_SUCCESS && length > DNS_RDATA_MAXLENGTH)
        result = DNS_R_FORMERR;

    /*
     * We should have consumed all of our buffer.
     */
    if (result == ISC_R_SUCCESS && !buffer_empty(source))
        result = DNS_R_EXTRADATA;

    if (rdata != NULL && result == ISC_R_SUCCESS) {
        region.base = isc_buffer_used(&st);
        region.length = length;
        dns_rdata_fromregion(rdata, rdclass, type, &region);
    }

    if (result != ISC_R_SUCCESS) {
        *source = ss;
        *target = st;
    }
    return (result);
}

isc_result_t
dns_rdata_towire(dns_rdata_t *rdata, dns_compress_t *cctx,
         isc_buffer_t *target)
{
    isc_result_t result = ISC_R_NOTIMPLEMENTED;
    isc_boolean_t use_default = ISC_FALSE;
    isc_region_t tr;
    isc_buffer_t st;

    REQUIRE(rdata != NULL);
    REQUIRE(DNS_RDATA_VALIDFLAGS(rdata));

    /*
     * Some DynDNS meta-RRs have empty rdata.
     */
    if ((rdata->flags & DNS_RDATA_UPDATE) != 0) {
        INSIST(rdata->length == 0);
        return (ISC_R_SUCCESS);
    }

    st = *target;

    TOWIRESWITCH

    if (use_default) {
        isc_buffer_availableregion(target, &tr);
        if (tr.length < rdata->length)
            return (ISC_R_NOSPACE);
        memmove(tr.base, rdata->data, rdata->length);
        isc_buffer_add(target, rdata->length);
        return (ISC_R_SUCCESS);
    }
    if (result != ISC_R_SUCCESS) {
        *target = st;
        INSIST(target->used < 65536);
        dns_compress_rollback(cctx, (isc_uint16_t)target->used);
    }
    return (result);
}

/*
 * If the binary data in 'src' is valid uncompressed wire format
 * rdata of class 'rdclass' and type 'type', return ISC_R_SUCCESS
 * and copy the validated rdata to 'dest'.  Otherwise return an error.
 */
static isc_result_t
rdata_validate(isc_buffer_t *src, isc_buffer_t *dest, dns_rdataclass_t rdclass,
        dns_rdatatype_t type)
{
    dns_decompress_t dctx;
    isc_result_t result;

    dns_decompress_init(&dctx, -1, DNS_DECOMPRESS_NONE);
    isc_buffer_setactive(src, isc_buffer_usedlength(src));
    result = dns_rdata_fromwire(NULL, rdclass, type, src, &dctx, 0, dest);
    dns_decompress_invalidate(&dctx);

    return (result);
}

static isc_result_t
unknown_fromtext(dns_rdataclass_t rdclass, dns_rdatatype_t type,
         isc_lex_t *lexer, isc_mem_t *mctx, isc_buffer_t *target)
{
    isc_result_t result;
    isc_buffer_t *buf = NULL;
    isc_token_t token;

    if (type == 0 || dns_rdatatype_ismeta(type))
        return (DNS_R_METATYPE);

    RETERR(isc_lex_getmastertoken(lexer, &token, isc_tokentype_number,
                    ISC_FALSE));
    if (token.value.as_ulong > 65535U)
        return (ISC_R_RANGE);
    result = isc_buffer_allocate(mctx, &buf, token.value.as_ulong);
    if (result != ISC_R_SUCCESS)
        return (result);

    result = isc_hex_tobuffer(lexer, buf,
                  (unsigned int)token.value.as_ulong);
    if (result != ISC_R_SUCCESS)
           goto failure;
    if (isc_buffer_usedlength(buf) != token.value.as_ulong) {
        result = ISC_R_UNEXPECTEDEND;
        goto failure;
    }

    if (dns_rdatatype_isknown(type)) {
        result = rdata_validate(buf, target, rdclass, type);
    } else {
        isc_region_t r;
        isc_buffer_usedregion(buf, &r);
        result = isc_buffer_copyregion(target, &r);
    }
    if (result != ISC_R_SUCCESS)
        goto failure;

    isc_buffer_free(&buf);
    return (ISC_R_SUCCESS);

 failure:
    isc_buffer_free(&buf);
    return (result);
}

isc_result_t
dns_rdata_fromtext(dns_rdata_t *rdata, dns_rdataclass_t rdclass,
           dns_rdatatype_t type, isc_lex_t *lexer,
           dns_name_t *origin, unsigned int options, isc_mem_t *mctx,
           isc_buffer_t *target, dns_rdatacallbacks_t *callbacks)
{
    isc_result_t result = ISC_R_NOTIMPLEMENTED;
    isc_region_t region;
    isc_buffer_t st;
    isc_token_t token;
    unsigned int lexoptions = ISC_LEXOPT_EOL | ISC_LEXOPT_EOF |
                  ISC_LEXOPT_DNSMULTILINE | ISC_LEXOPT_ESCAPE;
    char *name;
    unsigned long line;
    void (*callback)(dns_rdatacallbacks_t *, const char *, ...);
    isc_result_t tresult;
    unsigned int length;
    isc_boolean_t unknown;

    REQUIRE(origin == NULL || dns_name_isabsolute(origin) == ISC_TRUE);
    if (rdata != NULL) {
        REQUIRE(DNS_RDATA_INITIALIZED(rdata));
        REQUIRE(DNS_RDATA_VALIDFLAGS(rdata));
    }
    if (callbacks != NULL) {
        REQUIRE(callbacks->warn != NULL);
        REQUIRE(callbacks->error != NULL);
    }

    st = *target;

    if (callbacks != NULL)
        callback = callbacks->error;
    else
        callback = default_fromtext_callback;

    result = isc_lex_getmastertoken(lexer, &token, isc_tokentype_qstring,
                    ISC_FALSE);
    if (result != ISC_R_SUCCESS) {
        name = isc_lex_getsourcename(lexer);
        line = isc_lex_getsourceline(lexer);
        fromtext_error(callback, callbacks, name, line, NULL, result);
        return (result);
    }

    unknown = ISC_FALSE;
    if (token.type == isc_tokentype_string &&
        strcmp(DNS_AS_STR(token), "\\#") == 0) {
        /*
         * If this is a TXT record '\#' could be a escaped '#'.
         * Look to see if the next token is a number and if so
         * treat it as a unknown record format.
         */
        if (type == dns_rdatatype_txt) {
            result = isc_lex_getmastertoken(lexer, &token,
                            isc_tokentype_number,
                            ISC_FALSE);
            if (result == ISC_R_SUCCESS)
                isc_lex_ungettoken(lexer, &token);
        }

        if (result == ISC_R_SUCCESS) {
            unknown = ISC_TRUE;
            result = unknown_fromtext(rdclass, type, lexer,
                          mctx, target);
        } else
            options |= DNS_RDATA_UNKNOWNESCAPE;
    } else
        isc_lex_ungettoken(lexer, &token);

    if (!unknown)
        FROMTEXTSWITCH

    /*
     * Consume to end of line / file.
     * If not at end of line initially set error code.
     * Call callback via fromtext_error once if there was an error.
     */
    do {
        name = isc_lex_getsourcename(lexer);
        line = isc_lex_getsourceline(lexer);
        tresult = isc_lex_gettoken(lexer, lexoptions, &token);
        if (tresult != ISC_R_SUCCESS) {
            if (result == ISC_R_SUCCESS)
                result = tresult;
            if (callback != NULL)
                fromtext_error(callback, callbacks, name,
                           line, NULL, result);
            break;
        } else if (token.type != isc_tokentype_eol &&
               token.type != isc_tokentype_eof) {
            if (result == ISC_R_SUCCESS)
                result = DNS_R_EXTRATOKEN;
            if (callback != NULL) {
                fromtext_error(callback, callbacks, name,
                           line, &token, result);
                callback = NULL;
            }
        } else if (result != ISC_R_SUCCESS && callback != NULL) {
            fromtext_error(callback, callbacks, name, line,
                       &token, result);
            break;
        } else {
            if (token.type == isc_tokentype_eof)
                fromtext_warneof(lexer, callbacks);
            break;
        }
    } while (1);

    length = isc_buffer_usedlength(target) - isc_buffer_usedlength(&st);
    if (result == ISC_R_SUCCESS && length > DNS_RDATA_MAXLENGTH)
        result = ISC_R_NOSPACE;

    if (rdata != NULL && result == ISC_R_SUCCESS) {
        region.base = isc_buffer_used(&st);
        region.length = length;
        dns_rdata_fromregion(rdata, rdclass, type, &region);
    }
    if (result != ISC_R_SUCCESS) {
        *target = st;
    }
    return (result);
}

static isc_result_t
unknown_totext(dns_rdata_t *rdata, dns_rdata_textctx_t *tctx,
           isc_buffer_t *target)
{
    isc_result_t result;
    char buf[sizeof("65535")];
    isc_region_t sr;

    strlcpy(buf, "\\# ", sizeof(buf));
    result = str_totext(buf, target);
    if (result != ISC_R_SUCCESS)
        return (result);

    dns_rdata_toregion(rdata, &sr);
    INSIST(sr.length < 65536);
    snprintf(buf, sizeof(buf), "%u", sr.length);
    result = str_totext(buf, target);
    if (result != ISC_R_SUCCESS)
        return (result);

    if (sr.length != 0U) {
        if ((tctx->flags & DNS_STYLEFLAG_MULTILINE) != 0)
            result = str_totext(" ( ", target);
        else
            result = str_totext(" ", target);

        if (result != ISC_R_SUCCESS)
            return (result);

        if (tctx->width == 0) /* No splitting */
            result = isc_hex_totext(&sr, 0, "", target);
        else
            result = isc_hex_totext(&sr, tctx->width - 2,
                        tctx->linebreak,
                        target);
        if (result == ISC_R_SUCCESS &&
            (tctx->flags & DNS_STYLEFLAG_MULTILINE) != 0)
            result = str_totext(" )", target);
    }
    return (result);
}

static isc_result_t
rdata_totext(dns_rdata_t *rdata, dns_rdata_textctx_t *tctx,
         isc_buffer_t *target)
{
    isc_result_t result = ISC_R_NOTIMPLEMENTED;
    isc_boolean_t use_default = ISC_FALSE;
    unsigned int cur;

    REQUIRE(rdata != NULL);
    REQUIRE(tctx->origin == NULL ||
        dns_name_isabsolute(tctx->origin) == ISC_TRUE);

    /*
     * Some DynDNS meta-RRs have empty rdata.
     */
    if ((rdata->flags & DNS_RDATA_UPDATE) != 0) {
        INSIST(rdata->length == 0);
        return (ISC_R_SUCCESS);
    }

    if ((tctx->flags & DNS_STYLEFLAG_UNKNOWNFORMAT) != 0)
        return (unknown_totext(rdata, tctx, target));

    cur = isc_buffer_usedlength(target);

    TOTEXTSWITCH

    if (use_default || (result == ISC_R_NOTIMPLEMENTED)) {
        unsigned int u = isc_buffer_usedlength(target);

        INSIST(u >= cur);
        isc_buffer_subtract(target, u - cur);
        result = unknown_totext(rdata, tctx, target);
    }

    return (result);
}

isc_result_t
dns_rdata_totext(dns_rdata_t *rdata, dns_name_t *origin, isc_buffer_t *target)
{
    dns_rdata_textctx_t tctx;

    REQUIRE(DNS_RDATA_VALIDFLAGS(rdata));

    /*
     * Set up formatting options for single-line output.
     */
    tctx.origin = origin;
    tctx.flags = 0;
    tctx.width = 60;
    tctx.linebreak = " ";
    return (rdata_totext(rdata, &tctx, target));
}

isc_result_t
dns_rdata_tofmttext(dns_rdata_t *rdata, dns_name_t *origin,
            unsigned int flags, unsigned int width,
            unsigned int split_width, const char *linebreak,
            isc_buffer_t *target)
{
    dns_rdata_textctx_t tctx;

    REQUIRE(DNS_RDATA_VALIDFLAGS(rdata));

    /*
     * Set up formatting options for formatted output.
     */
    tctx.origin = origin;
    tctx.flags = flags;
    if (split_width == 0xffffffff)
        tctx.width = width;
    else
        tctx.width = split_width;

    if ((flags & DNS_STYLEFLAG_MULTILINE) != 0)
        tctx.linebreak = linebreak;
    else {
        if (split_width == 0xffffffff)
            tctx.width = 60; /* Used for hex word length only. */
        tctx.linebreak = " ";
    }
    return (rdata_totext(rdata, &tctx, target));
}

isc_result_t
dns_rdata_fromstruct(dns_rdata_t *rdata, dns_rdataclass_t rdclass,
             dns_rdatatype_t type, void *source,
             isc_buffer_t *target)
{
    isc_result_t result = ISC_R_NOTIMPLEMENTED;
    isc_buffer_t st;
    isc_region_t region;
    isc_boolean_t use_default = ISC_FALSE;
    unsigned int length;

    REQUIRE(source != NULL);
    if (rdata != NULL) {
        REQUIRE(DNS_RDATA_INITIALIZED(rdata));
        REQUIRE(DNS_RDATA_VALIDFLAGS(rdata));
    }

    st = *target;

    FROMSTRUCTSWITCH

    if (use_default)
        (void)NULL;

    length = isc_buffer_usedlength(target) - isc_buffer_usedlength(&st);
    if (result == ISC_R_SUCCESS && length > DNS_RDATA_MAXLENGTH)
        result = ISC_R_NOSPACE;

    if (rdata != NULL && result == ISC_R_SUCCESS) {
        region.base = isc_buffer_used(&st);
        region.length = length;
        dns_rdata_fromregion(rdata, rdclass, type, &region);
    }
    if (result != ISC_R_SUCCESS)
        *target = st;
    return (result);
}

isc_result_t
dns_rdata_tostruct(dns_rdata_t *rdata, void *target, isc_mem_t *mctx) {
    isc_result_t result = ISC_R_NOTIMPLEMENTED;
    isc_boolean_t use_default = ISC_FALSE;

    REQUIRE(rdata != NULL);
    REQUIRE(DNS_RDATA_VALIDFLAGS(rdata));

    TOSTRUCTSWITCH

    if (use_default)
        (void)NULL;

    return (result);
}

void
dns_rdata_freestruct(void *source) {
    dns_rdatacommon_t *common = source;
    REQUIRE(source != NULL);

    FREESTRUCTSWITCH
}

isc_result_t
dns_rdata_additionaldata(dns_rdata_t *rdata, dns_additionaldatafunc_t add,
             void *arg)
{
    isc_result_t result = ISC_R_NOTIMPLEMENTED;
    isc_boolean_t use_default = ISC_FALSE;

    /*
     * Call 'add' for each name and type from 'rdata' which is subject to
     * additional section processing.
     */

    REQUIRE(rdata != NULL);
    REQUIRE(add != NULL);
    REQUIRE(DNS_RDATA_VALIDFLAGS(rdata));

    ADDITIONALDATASWITCH

    /* No additional processing for unknown types */
    if (use_default)
        result = ISC_R_SUCCESS;

    return (result);
}

isc_result_t
dns_rdata_digest(dns_rdata_t *rdata, dns_digestfunc_t digest, void *arg) {
    isc_result_t result = ISC_R_NOTIMPLEMENTED;
    isc_boolean_t use_default = ISC_FALSE;
    isc_region_t r;

    /*
     * Send 'rdata' in DNSSEC canonical form to 'digest'.
     */

    REQUIRE(rdata != NULL);
    REQUIRE(digest != NULL);
    REQUIRE(DNS_RDATA_VALIDFLAGS(rdata));

    DIGESTSWITCH

    if (use_default) {
        dns_rdata_toregion(rdata, &r);
        result = (digest)(arg, &r);
    }

    return (result);
}

isc_boolean_t
dns_rdata_checkowner(dns_name_t *name, dns_rdataclass_t rdclass,
             dns_rdatatype_t type, isc_boolean_t wildcard)
{
    isc_boolean_t result;

    CHECKOWNERSWITCH
    return (result);
}

isc_boolean_t
dns_rdata_checknames(dns_rdata_t *rdata, dns_name_t *owner, dns_name_t *bad)
{
    isc_boolean_t result;

    CHECKNAMESSWITCH
    return (result);
}

unsigned int
dns_rdatatype_attributes(dns_rdatatype_t type)
{
    RDATATYPE_ATTRIBUTE_SW
    if (type >= (dns_rdatatype_t)128 && type < (dns_rdatatype_t)255)
        return (DNS_RDATATYPEATTR_UNKNOWN | DNS_RDATATYPEATTR_META);
    return (DNS_RDATATYPEATTR_UNKNOWN);
}

isc_result_t
dns_rdatatype_fromtext(dns_rdatatype_t *typep, isc_textregion_t *source) {
    unsigned int hash;
    unsigned int n;
    unsigned char a, b;

    n = source->length;

    if (n == 0)
        return (DNS_R_UNKNOWN);

    a = tolower((unsigned char)source->base[0]);
    b = tolower((unsigned char)source->base[n - 1]);

    hash = ((a + n) * b) % 256;

    /*
     * This switch block is inlined via \#define, and will use "return"
     * to return a result to the caller if it is a valid (known)
     * rdatatype name.
     */
    RDATATYPE_FROMTEXT_SW(hash, source->base, n, typep);

    if (source->length > 4 && source->length < (4 + sizeof("65000")) &&
        strncasecmp("type", source->base, 4) == 0) {
        char buf[sizeof("65000")];
        char *endp;
        unsigned int val;

        /*
         * source->base is not required to be NUL terminated.
         * Copy up to remaining bytes and NUL terminate.
         */
        snprintf(buf, sizeof(buf), "%.*s",
             (int)(source->length - 4), source->base + 4);
        val = strtoul(buf, &endp, 10);
        if (*endp == '\0' && val <= 0xffff) {
            *typep = (dns_rdatatype_t)val;
            return (ISC_R_SUCCESS);
        }
    }

    return (DNS_R_UNKNOWN);
}

isc_result_t
dns_rdatatype_totext(dns_rdatatype_t type, isc_buffer_t *target) {
    RDATATYPE_TOTEXT_SW

    return (dns_rdatatype_tounknowntext(type, target));
}

isc_result_t
dns_rdatatype_tounknowntext(dns_rdatatype_t type, isc_buffer_t *target) {
    char buf[sizeof("TYPE65535")];

    snprintf(buf, sizeof(buf), "TYPE%u", type);
    return (str_totext(buf, target));
}

void
dns_rdatatype_format(dns_rdatatype_t rdtype,
             char *array, unsigned int size)
{
    isc_result_t result;
    isc_buffer_t buf;

    if (size == 0U)
        return;

    isc_buffer_init(&buf, array, size);
    result = dns_rdatatype_totext(rdtype, &buf);
    /*
     * Null terminate.
     */
    if (result == ISC_R_SUCCESS) {
        if (isc_buffer_availablelength(&buf) >= 1)
            isc_buffer_putuint8(&buf, 0);
        else
            result = ISC_R_NOSPACE;
    }
    if (result != ISC_R_SUCCESS)
        strlcpy(array, "<unknown>", size);
}

/*
 * Private function.
 */

static unsigned int
name_length(dns_name_t *name) {
    return (name->length);
}

static isc_result_t
txt_totext(isc_region_t *source, isc_boolean_t quote, isc_buffer_t *target) {
    unsigned int tl;
    unsigned int n;
    unsigned char *sp;
    char *tp;
    isc_region_t region;

    isc_buffer_availableregion(target, &region);
    sp = source->base;
    tp = (char *)region.base;
    tl = region.length;

    n = *sp++;

    REQUIRE(n + 1 <= source->length);
    if (n == 0U)
        REQUIRE(quote == ISC_TRUE);

    if (quote) {
        if (tl < 1)
            return (ISC_R_NOSPACE);
        *tp++ = '"';
        tl--;
    }
    while (n--) {
        /*
         * \DDD space (0x20) if not quoting.
         */
        if (*sp < (quote ? 0x20 : 0x21) || *sp >= 0x7f) {
            if (tl < 4)
                return (ISC_R_NOSPACE);
            *tp++ = 0x5c;
            *tp++ = 0x30 + ((*sp / 100) % 10);
            *tp++ = 0x30 + ((*sp / 10) % 10);
            *tp++ = 0x30 + (*sp % 10);
            sp++;
            tl -= 4;
            continue;
        }
        /*
         * Escape double quote and backslash.  If we are not
         * enclosing the string in double quotes also escape
         * at sign and semicolon.
         */
        if (*sp == 0x22 || *sp == 0x5c ||
            (!quote && (*sp == 0x40 || *sp == 0x3b))) {
            if (tl < 2)
                return (ISC_R_NOSPACE);
            *tp++ = '\\';
            tl--;
        }
        if (tl < 1)
            return (ISC_R_NOSPACE);
        *tp++ = *sp++;
        tl--;
    }
    if (quote) {
        if (tl < 1)
            return (ISC_R_NOSPACE);
        *tp++ = '"';
        tl--;
    }
    isc_buffer_add(target, (unsigned int)(tp - (char *)region.base));
    isc_region_consume(source, *source->base + 1);
    return (ISC_R_SUCCESS);
}

static isc_result_t
txt_fromtext(isc_textregion_t *source, isc_buffer_t *target) {
    isc_region_t tregion;
    isc_boolean_t escape;
    unsigned int n, nrem;
    char *s;
    unsigned char *t;
    int d;
    int c;

    isc_buffer_availableregion(target, &tregion);
    s = source->base;
    n = source->length;
    t = tregion.base;
    nrem = tregion.length;
    escape = ISC_FALSE;
    if (nrem < 1)
        return (ISC_R_NOSPACE);
    /*
     * Length byte.
     */
    nrem--;
    t++;
    /*
     * Maximum text string length.
     */
    if (nrem > 255)
        nrem = 255;
    while (n-- != 0) {
        c = (*s++) & 0xff;
        if (escape && (d = decvalue((char)c)) != -1) {
            c = d;
            if (n == 0)
                return (DNS_R_SYNTAX);
            n--;
            if ((d = decvalue(*s++)) != -1)
                c = c * 10 + d;
            else
                return (DNS_R_SYNTAX);
            if (n == 0)
                return (DNS_R_SYNTAX);
            n--;
            if ((d = decvalue(*s++)) != -1)
                c = c * 10 + d;
            else
                return (DNS_R_SYNTAX);
            if (c > 255)
                return (DNS_R_SYNTAX);
        } else if (!escape && c == '\\') {
            escape = ISC_TRUE;
            continue;
        }
        escape = ISC_FALSE;
        if (nrem == 0)
            return ((tregion.length <= 256U) ?
                ISC_R_NOSPACE : DNS_R_SYNTAX);
        *t++ = c;
        nrem--;
    }
    if (escape)
        return (DNS_R_SYNTAX);
    *tregion.base = (unsigned char)(t - tregion.base - 1);
    isc_buffer_add(target, *tregion.base + 1);
    return (ISC_R_SUCCESS);
}

static isc_result_t
txt_fromwire(isc_buffer_t *source, isc_buffer_t *target) {
    unsigned int n;
    isc_region_t sregion;
    isc_region_t tregion;

    isc_buffer_activeregion(source, &sregion);
    if (sregion.length == 0)
        return (ISC_R_UNEXPECTEDEND);
    n = *sregion.base + 1;
    if (n > sregion.length)
        return (ISC_R_UNEXPECTEDEND);

    isc_buffer_availableregion(target, &tregion);
    if (n > tregion.length)
        return (ISC_R_NOSPACE);

    if (tregion.base != sregion.base)
        memmove(tregion.base, sregion.base, n);
    isc_buffer_forward(source, n);
    isc_buffer_add(target, n);
    return (ISC_R_SUCCESS);
}

/*
 * Conversion of TXT-like rdata fields without length limits.
 */
static isc_result_t
multitxt_totext(isc_region_t *source, isc_buffer_t *target) {
    unsigned int tl;
    unsigned int n0, n;
    unsigned char *sp;
    char *tp;
    isc_region_t region;

    isc_buffer_availableregion(target, &region);
    sp = source->base;
    tp = (char *)region.base;
    tl = region.length;

    if (tl < 1)
        return (ISC_R_NOSPACE);
    *tp++ = '"';
    tl--;
    do {
        n = source->length;
        n0 = source->length - 1;

        while (n--) {
            if (*sp < 0x20 || *sp >= 0x7f) {
                if (tl < 4)
                    return (ISC_R_NOSPACE);
                *tp++ = 0x5c;
                *tp++ = 0x30 + ((*sp / 100) % 10);
                *tp++ = 0x30 + ((*sp / 10) % 10);
                *tp++ = 0x30 + (*sp % 10);
                sp++;
                tl -= 4;
                continue;
            }
            /* double quote, backslash */
            if (*sp == 0x22 || *sp == 0x5c) {
                if (tl < 2)
                    return (ISC_R_NOSPACE);
                *tp++ = '\\';
                tl--;
            }
            if (tl < 1)
                return (ISC_R_NOSPACE);
            *tp++ = *sp++;
            tl--;
        }
        isc_region_consume(source, n0 + 1);
    } while (source->length != 0);
    if (tl < 1)
        return (ISC_R_NOSPACE);
    *tp++ = '"';
    tl--;
    isc_buffer_add(target, (unsigned int)(tp - (char *)region.base));
    return (ISC_R_SUCCESS);
}

static isc_result_t
multitxt_fromtext(isc_textregion_t *source, isc_buffer_t *target) {
    isc_region_t tregion;
    isc_boolean_t escape;
    unsigned int n, nrem;
    char *s;
    unsigned char *t0, *t;
    int d;
    int c;

    s = source->base;
    n = source->length;
    escape = ISC_FALSE;

    do {
        isc_buffer_availableregion(target, &tregion);
        t0 = t = tregion.base;
        nrem = tregion.length;
        if (nrem < 1)
            return (ISC_R_NOSPACE);

        while (n != 0) {
            --n;
            c = (*s++) & 0xff;
            if (escape && (d = decvalue((char)c)) != -1) {
                c = d;
                if (n == 0)
                    return (DNS_R_SYNTAX);
                n--;
                if ((d = decvalue(*s++)) != -1)
                    c = c * 10 + d;
                else
                    return (DNS_R_SYNTAX);
                if (n == 0)
                    return (DNS_R_SYNTAX);
                n--;
                if ((d = decvalue(*s++)) != -1)
                    c = c * 10 + d;
                else
                    return (DNS_R_SYNTAX);
                if (c > 255)
                    return (DNS_R_SYNTAX);
            } else if (!escape && c == '\\') {
                escape = ISC_TRUE;
                continue;
            }
            escape = ISC_FALSE;
            *t++ = c;
            nrem--;
            if (nrem == 0)
                break;
        }
        if (escape)
            return (DNS_R_SYNTAX);

        isc_buffer_add(target, (unsigned int)(t - t0));
    } while (n != 0);
    return (ISC_R_SUCCESS);
}

static isc_boolean_t
name_prefix(dns_name_t *name, dns_name_t *origin, dns_name_t *target) {
    int l1, l2;

    if (origin == NULL)
        goto return_false;

    if (dns_name_compare(origin, dns_rootname) == 0)
        goto return_false;

    if (!dns_name_issubdomain(name, origin))
        goto return_false;

    l1 = dns_name_countlabels(name);
    l2 = dns_name_countlabels(origin);

    if (l1 == l2)
        goto return_false;

    /* Master files should be case preserving. */
    dns_name_getlabelsequence(name, l1 - l2, l2, target);
    if (!dns_name_caseequal(origin, target))
        goto return_false;

    dns_name_getlabelsequence(name, 0, l1 - l2, target);
    return (ISC_TRUE);

return_false:
    *target = *name;
    return (ISC_FALSE);
}

static isc_result_t
str_totext(const char *source, isc_buffer_t *target) {
    unsigned int l;
    isc_region_t region;

    isc_buffer_availableregion(target, &region);
    l = strlen(source);

    if (l > region.length)
        return (ISC_R_NOSPACE);

    memmove(region.base, source, l);
    isc_buffer_add(target, l);
    return (ISC_R_SUCCESS);
}

static isc_result_t
inet_totext(int af, isc_region_t *src, isc_buffer_t *target) {
    char tmpbuf[64];

    /* Note - inet_ntop doesn't do size checking on its input. */
    if (inet_ntop(af, src->base, tmpbuf, sizeof(tmpbuf)) == NULL)
        return (ISC_R_NOSPACE);
    if (strlen(tmpbuf) > isc_buffer_availablelength(target))
        return (ISC_R_NOSPACE);
    isc_buffer_putstr(target, tmpbuf);
    return (ISC_R_SUCCESS);
}

static isc_boolean_t
buffer_empty(isc_buffer_t *source) {
    return((source->current == source->active) ? ISC_TRUE : ISC_FALSE);
}

static void
buffer_fromregion(isc_buffer_t *buffer, isc_region_t *region) {
    isc_buffer_init(buffer, region->base, region->length);
    isc_buffer_add(buffer, region->length);
    isc_buffer_setactive(buffer, region->length);
}

static isc_result_t
uint32_tobuffer(isc_uint32_t value, isc_buffer_t *target) {
    isc_region_t region;

    isc_buffer_availableregion(target, &region);
    if (region.length < 4)
        return (ISC_R_NOSPACE);
    isc_buffer_putuint32(target, value);
    return (ISC_R_SUCCESS);
}

static isc_result_t
uint16_tobuffer(isc_uint32_t value, isc_buffer_t *target) {
    isc_region_t region;

    if (value > 0xffff)
        return (ISC_R_RANGE);
    isc_buffer_availableregion(target, &region);
    if (region.length < 2)
        return (ISC_R_NOSPACE);
    isc_buffer_putuint16(target, (isc_uint16_t)value);
    return (ISC_R_SUCCESS);
}

static isc_result_t
uint8_tobuffer(isc_uint32_t value, isc_buffer_t *target) {
    isc_region_t region;

    if (value > 0xff)
        return (ISC_R_RANGE);
    isc_buffer_availableregion(target, &region);
    if (region.length < 1)
        return (ISC_R_NOSPACE);
    isc_buffer_putuint8(target, (isc_uint8_t)value);
    return (ISC_R_SUCCESS);
}

static isc_result_t
name_tobuffer(dns_name_t *name, isc_buffer_t *target) {
    isc_region_t r;
    dns_name_toregion(name, &r);
    return (isc_buffer_copyregion(target, &r));
}

static isc_uint32_t
uint32_fromregion(isc_region_t *region) {
    isc_uint32_t value;

    REQUIRE(region->length >= 4);
    value = (isc_uint32_t)region->base[0] << 24;
    value |= (isc_uint32_t)region->base[1] << 16;
    value |= (isc_uint32_t)region->base[2] << 8;
    value |= (isc_uint32_t)region->base[3];
    return(value);
}

static isc_uint16_t
uint16_consume_fromregion(isc_region_t *region) {
    isc_uint16_t r = uint16_fromregion(region);

    isc_region_consume(region, 2);
    return r;
}

static isc_uint16_t
uint16_fromregion(isc_region_t *region) {

    REQUIRE(region->length >= 2);

    return ((region->base[0] << 8) | region->base[1]);
}

static isc_uint8_t
uint8_fromregion(isc_region_t *region) {

    REQUIRE(region->length >= 1);

    return (region->base[0]);
}

static isc_uint8_t
uint8_consume_fromregion(isc_region_t *region) {
    isc_uint8_t r = uint8_fromregion(region);

    isc_region_consume(region, 1);
    return r;
}

static isc_result_t
mem_tobuffer(isc_buffer_t *target, void *base, unsigned int length) {
    isc_region_t tr;

    if (length == 0U)
        return (ISC_R_SUCCESS);

    isc_buffer_availableregion(target, &tr);
    if (length > tr.length)
        return (ISC_R_NOSPACE);
    if (tr.base != base)
        memmove(tr.base, base, length);
    isc_buffer_add(target, length);
    return (ISC_R_SUCCESS);
}

static int
hexvalue(char value) {
    const char *s;
    unsigned char c;

    c = (unsigned char)value;

    if (!isascii(c))
        return (-1);
    if (isupper(c))
        c = tolower(c);
    if ((s = strchr(hexdigits, c)) == NULL)
        return (-1);
    return (int)(s - hexdigits);
}

static int
decvalue(char value) {
    const char *s;

    /*
     * isascii() is valid for full range of int values, no need to
     * mask or cast.
     */
    if (!isascii(value))
        return (-1);
    if ((s = strchr(decdigits, value)) == NULL)
        return (-1);
    return (int)(s - decdigits);
}

static const char atob_digits[86] =
    "!\"#$%&'()*+,-./0123456789:;<=>?@ABCDEFGHIJKLMNOPQRSTUVWXYZ[\\]^_`" \
    "abcdefghijklmnopqrstu";
/*
 * Subroutines to convert between 8 bit binary bytes and printable ASCII.
 * Computes the number of bytes, and three kinds of simple checksums.
 * Incoming bytes are collected into 32-bit words, then printed in base 85:
 *  exp(85,5) > exp(2,32)
 * The ASCII characters used are between '!' and 'u';
 * 'z' encodes 32-bit zero; 'x' is used to mark the end of encoded data.
 *
 * Originally by Paul Rutter (philabs!per) and Joe Orost (petsd!joe) for
 * the atob/btoa programs, released with the compress program, in mod.sources.
 * Modified by Mike Schwartz 8/19/86 for use in BIND.
 * Modified to be re-entrant 3/2/99.
 */


struct state {
    isc_int32_t Ceor;
    isc_int32_t Csum;
    isc_int32_t Crot;
    isc_int32_t word;
    isc_int32_t bcount;
};

#define Ceor state->Ceor
#define Csum state->Csum
#define Crot state->Crot
#define word state->word
#define bcount state->bcount

#define times85(x)  ((((((x<<2)+x)<<2)+x)<<2)+x)

static isc_result_t byte_atob(int c, isc_buffer_t *target,
                  struct state *state);
static isc_result_t putbyte(int c, isc_buffer_t *, struct state *state);
static isc_result_t byte_btoa(int c, isc_buffer_t *, struct state *state);

/*
 * Decode ASCII-encoded byte c into binary representation and
 * place into *bufp, advancing bufp.
 */
static isc_result_t
byte_atob(int c, isc_buffer_t *target, struct state *state) {
    const char *s;
    if (c == 'z') {
        if (bcount != 0)
            return(DNS_R_SYNTAX);
        else {
            RETERR(putbyte(0, target, state));
            RETERR(putbyte(0, target, state));
            RETERR(putbyte(0, target, state));
            RETERR(putbyte(0, target, state));
        }
    } else if ((s = strchr(atob_digits, c)) != NULL) {
        if (bcount == 0) {
            word = (isc_int32_t)(s - atob_digits);
            ++bcount;
        } else if (bcount < 4) {
            word = times85(word);
            word += (isc_int32_t)(s - atob_digits);
            ++bcount;
        } else {
            word = times85(word);
            word += (isc_int32_t)(s - atob_digits);
            RETERR(putbyte((word >> 24) & 0xff, target, state));
            RETERR(putbyte((word >> 16) & 0xff, target, state));
            RETERR(putbyte((word >> 8) & 0xff, target, state));
            RETERR(putbyte(word & 0xff, target, state));
            word = 0;
            bcount = 0;
        }
    } else
        return(DNS_R_SYNTAX);
    return(ISC_R_SUCCESS);
}

/*
 * Compute checksum info and place c into target.
 */
static isc_result_t
putbyte(int c, isc_buffer_t *target, struct state *state) {
    isc_region_t tr;

    Ceor ^= c;
    Csum += c;
    Csum += 1;
    if ((Crot & 0x80000000)) {
        Crot <<= 1;
        Crot += 1;
    } else {
        Crot <<= 1;
    }
    Crot += c;
    isc_buffer_availableregion(target, &tr);
    if (tr.length < 1)
        return (ISC_R_NOSPACE);
    tr.base[0] = c;
    isc_buffer_add(target, 1);
    return (ISC_R_SUCCESS);
}

/*
 * Read the ASCII-encoded data from inbuf, of length inbuflen, and convert
 * it into T_UNSPEC (binary data) in outbuf, not to exceed outbuflen bytes;
 * outbuflen must be divisible by 4.  (Note: this is because outbuf is filled
 * in 4 bytes at a time.  If the actual data doesn't end on an even 4-byte
 * boundary, there will be no problem...it will be padded with 0 bytes, and
 * numbytes will indicate the correct number of bytes.  The main point is
 * that since the buffer is filled in 4 bytes at a time, even if there is
 * not a full 4 bytes of data at the end, there has to be room to 0-pad the
 * data, so the buffer must be of size divisible by 4).  Place the number of
 * output bytes in numbytes, and return a failure/success status.
 */

static isc_result_t
atob_tobuffer(isc_lex_t *lexer, isc_buffer_t *target) {
    long oeor, osum, orot;
    struct state statebuf, *state= &statebuf;
    isc_token_t token;
    char c;
    char *e;

    Ceor = Csum = Crot = word = bcount = 0;

    RETERR(isc_lex_getmastertoken(lexer, &token, isc_tokentype_string,
                      ISC_FALSE));
    while (token.value.as_textregion.length != 0) {
        if ((c = token.value.as_textregion.base[0]) == 'x') {
            break;
        } else
            RETERR(byte_atob(c, target, state));
        isc_textregion_consume(&token.value.as_textregion, 1);
    }

    /*
     * Number of bytes.
     */
    RETERR(isc_lex_getmastertoken(lexer, &token, isc_tokentype_number,
                      ISC_FALSE));
    if ((token.value.as_ulong % 4) != 0U) {
        unsigned long padding = 4 - (token.value.as_ulong % 4);
        if (isc_buffer_usedlength(target) < padding)
            return (DNS_R_SYNTAX);
        isc_buffer_subtract(target, padding);
    }

    /*
     * Checksum.
     */
    RETERR(isc_lex_getmastertoken(lexer, &token, isc_tokentype_string,
                      ISC_FALSE));
    oeor = strtol(DNS_AS_STR(token), &e, 16);
    if (*e != 0)
        return (DNS_R_SYNTAX);

    /*
     * Checksum.
     */
    RETERR(isc_lex_getmastertoken(lexer, &token, isc_tokentype_string,
                      ISC_FALSE));
    osum = strtol(DNS_AS_STR(token), &e, 16);
    if (*e != 0)
        return (DNS_R_SYNTAX);

    /*
     * Checksum.
     */
    RETERR(isc_lex_getmastertoken(lexer, &token, isc_tokentype_string,
                      ISC_FALSE));
    orot = strtol(DNS_AS_STR(token), &e, 16);
    if (*e != 0)
        return (DNS_R_SYNTAX);

    if ((oeor != Ceor) || (osum != Csum) || (orot != Crot))
        return(DNS_R_BADCKSUM);
    return (ISC_R_SUCCESS);
}

/*
 * Encode binary byte c into ASCII representation and place into *bufp,
 * advancing bufp.
 */
static isc_result_t
byte_btoa(int c, isc_buffer_t *target, struct state *state) {
    isc_region_t tr;

    isc_buffer_availableregion(target, &tr);
    Ceor ^= c;
    Csum += c;
    Csum += 1;
    if ((Crot & 0x80000000)) {
        Crot <<= 1;
        Crot += 1;
    } else {
        Crot <<= 1;
    }
    Crot += c;

    word <<= 8;
    word |= c;
    if (bcount == 3) {
        if (word == 0) {
            if (tr.length < 1)
                return (ISC_R_NOSPACE);
            tr.base[0] = 'z';
            isc_buffer_add(target, 1);
        } else {
            register int tmp = 0;
            register isc_int32_t tmpword = word;

            if (tmpword < 0) {
               /*
                * Because some don't support u_long.
                */
            tmp = 32;
            tmpword -= (isc_int32_t)(85 * 85 * 85 * 85 * 32);
            }
            if (tmpword < 0) {
            tmp = 64;
            tmpword -= (isc_int32_t)(85 * 85 * 85 * 85 * 32);
            }
            if (tr.length < 5)
                return (ISC_R_NOSPACE);
            tr.base[0] = atob_digits[(tmpword /
                          (isc_int32_t)(85 * 85 * 85 * 85))
                        + tmp];
            tmpword %= (isc_int32_t)(85 * 85 * 85 * 85);
            tr.base[1] = atob_digits[tmpword / (85 * 85 * 85)];
            tmpword %= (85 * 85 * 85);
            tr.base[2] = atob_digits[tmpword / (85 * 85)];
            tmpword %= (85 * 85);
            tr.base[3] = atob_digits[tmpword / 85];
            tmpword %= 85;
            tr.base[4] = atob_digits[tmpword];
            isc_buffer_add(target, 5);
        }
        bcount = 0;
    } else {
        bcount += 1;
    }
    return (ISC_R_SUCCESS);
}


/*
 * Encode the binary data from inbuf, of length inbuflen, into a
 * target.  Return success/failure status
 */
static isc_result_t
btoa_totext(unsigned char *inbuf, int inbuflen, isc_buffer_t *target) {
    int inc;
    struct state statebuf, *state = &statebuf;
    char buf[sizeof("x 2000000000 ffffffff ffffffff ffffffff")];

    Ceor = Csum = Crot = word = bcount = 0;
    for (inc = 0; inc < inbuflen; inbuf++, inc++)
        RETERR(byte_btoa(*inbuf, target, state));

    while (bcount != 0)
        RETERR(byte_btoa(0, target, state));

    /*
     * Put byte count and checksum information at end of buffer,
     * delimited by 'x'
     */
    snprintf(buf, sizeof(buf), "x %d %x %x %x", inbuflen, Ceor, Csum, Crot);
    return (str_totext(buf, target));
}


static void
default_fromtext_callback(dns_rdatacallbacks_t *callbacks, const char *fmt,
              ...)
{
    va_list ap;

    UNUSED(callbacks);

    va_start(ap, fmt);
    vfprintf(stderr, fmt, ap);
    va_end(ap);
    fprintf(stderr, "\n");
}

static void
fromtext_warneof(isc_lex_t *lexer, dns_rdatacallbacks_t *callbacks) {
    if (isc_lex_isfile(lexer) && callbacks != NULL) {
        const char *name = isc_lex_getsourcename(lexer);
        if (name == NULL)
            name = "UNKNOWN";
        (*callbacks->warn)(callbacks,
                   "%s:%lu: file does not end with newline",
                   name, isc_lex_getsourceline(lexer));
    }
}

static void
warn_badmx(isc_token_t *token, isc_lex_t *lexer,
       dns_rdatacallbacks_t *callbacks)
{
    const char *file;
    unsigned long line;

    if (lexer != NULL) {
        file = isc_lex_getsourcename(lexer);
        line = isc_lex_getsourceline(lexer);
        (*callbacks->warn)(callbacks, "%s:%u: warning: '%s': %s",
                   file, line, DNS_AS_STR(*token),
                   dns_result_totext(DNS_R_MXISADDRESS));
    }
}

static void
warn_badname(dns_name_t *name, isc_lex_t *lexer,
         dns_rdatacallbacks_t *callbacks)
{
    const char *file;
    unsigned long line;
    char namebuf[DNS_NAME_FORMATSIZE];

    if (lexer != NULL) {
        file = isc_lex_getsourcename(lexer);
        line = isc_lex_getsourceline(lexer);
        dns_name_format(name, namebuf, sizeof(namebuf));
        (*callbacks->warn)(callbacks, "%s:%u: warning: %s: %s",
                   file, line, namebuf,
                   dns_result_totext(DNS_R_BADNAME));
    }
}

static void
fromtext_error(void (*callback)(dns_rdatacallbacks_t *, const char *, ...),
           dns_rdatacallbacks_t *callbacks, const char *name,
           unsigned long line, isc_token_t *token, isc_result_t result)
{
    if (name == NULL)
        name = "UNKNOWN";

    if (token != NULL) {
        switch (token->type) {
        case isc_tokentype_eol:
            (*callback)(callbacks, "%s: %s:%lu: near eol: %s",
                    "dns_rdata_fromtext", name, line,
                    dns_result_totext(result));
            break;
        case isc_tokentype_eof:
            (*callback)(callbacks, "%s: %s:%lu: near eof: %s",
                    "dns_rdata_fromtext", name, line,
                    dns_result_totext(result));
            break;
        case isc_tokentype_number:
            (*callback)(callbacks, "%s: %s:%lu: near %lu: %s",
                    "dns_rdata_fromtext", name, line,
                    token->value.as_ulong,
                    dns_result_totext(result));
            break;
        case isc_tokentype_string:
        case isc_tokentype_qstring:
            (*callback)(callbacks, "%s: %s:%lu: near '%s': %s",
                    "dns_rdata_fromtext", name, line,
                    DNS_AS_STR(*token),
                    dns_result_totext(result));
            break;
        default:
            (*callback)(callbacks, "%s: %s:%lu: %s",
                    "dns_rdata_fromtext", name, line,
                    dns_result_totext(result));
            break;
        }
    } else {
        (*callback)(callbacks, "dns_rdata_fromtext: %s:%lu: %s",
                name, line, dns_result_totext(result));
    }
}

dns_rdatatype_t
dns_rdata_covers(dns_rdata_t *rdata) {
    if (rdata->type == dns_rdatatype_rrsig)
        return (covers_rrsig(rdata));
    return (covers_sig(rdata));
}

isc_boolean_t
dns_rdatatype_ismeta(dns_rdatatype_t type) {
    if ((dns_rdatatype_attributes(type) & DNS_RDATATYPEATTR_META) != 0)
        return (ISC_TRUE);
    return (ISC_FALSE);
}

isc_boolean_t
dns_rdatatype_issingleton(dns_rdatatype_t type) {
    if ((dns_rdatatype_attributes(type) & DNS_RDATATYPEATTR_SINGLETON)
        != 0)
        return (ISC_TRUE);
    return (ISC_FALSE);
}

isc_boolean_t
dns_rdatatype_notquestion(dns_rdatatype_t type) {
    if ((dns_rdatatype_attributes(type) & DNS_RDATATYPEATTR_NOTQUESTION)
        != 0)
        return (ISC_TRUE);
    return (ISC_FALSE);
}

isc_boolean_t
dns_rdatatype_questiononly(dns_rdatatype_t type) {
    if ((dns_rdatatype_attributes(type) & DNS_RDATATYPEATTR_QUESTIONONLY)
        != 0)
        return (ISC_TRUE);
    return (ISC_FALSE);
}

isc_boolean_t
dns_rdatatype_atparent(dns_rdatatype_t type) {
    if ((dns_rdatatype_attributes(type) & DNS_RDATATYPEATTR_ATPARENT) != 0)
        return (ISC_TRUE);
    return (ISC_FALSE);
}

isc_boolean_t
dns_rdataclass_ismeta(dns_rdataclass_t rdclass) {

    if (rdclass == dns_rdataclass_reserved0
        || rdclass == dns_rdataclass_none
        || rdclass == dns_rdataclass_any)
        return (ISC_TRUE);

    return (ISC_FALSE);  /* Assume it is not a meta class. */
}

isc_boolean_t
dns_rdatatype_isdnssec(dns_rdatatype_t type) {
    if ((dns_rdatatype_attributes(type) & DNS_RDATATYPEATTR_DNSSEC) != 0)
        return (ISC_TRUE);
    return (ISC_FALSE);
}

isc_boolean_t
dns_rdatatype_iszonecutauth(dns_rdatatype_t type) {
    if ((dns_rdatatype_attributes(type)
         & (DNS_RDATATYPEATTR_DNSSEC | DNS_RDATATYPEATTR_ZONECUTAUTH))
        != 0)
        return (ISC_TRUE);
    return (ISC_FALSE);
}

isc_boolean_t
dns_rdatatype_isknown(dns_rdatatype_t type) {
    if ((dns_rdatatype_attributes(type) & DNS_RDATATYPEATTR_UNKNOWN)
        == 0)
        return (ISC_TRUE);
    return (ISC_FALSE);
}

void
dns_rdata_exists(dns_rdata_t *rdata, dns_rdatatype_t type) {

    REQUIRE(rdata != NULL);
    REQUIRE(DNS_RDATA_INITIALIZED(rdata));

    rdata->data = NULL;
    rdata->length = 0;
    rdata->flags = DNS_RDATA_UPDATE;
    rdata->type = type;
    rdata->rdclass = dns_rdataclass_any;
}

void
dns_rdata_notexist(dns_rdata_t *rdata, dns_rdatatype_t type) {

    REQUIRE(rdata != NULL);
    REQUIRE(DNS_RDATA_INITIALIZED(rdata));

    rdata->data = NULL;
    rdata->length = 0;
    rdata->flags = DNS_RDATA_UPDATE;
    rdata->type = type;
    rdata->rdclass = dns_rdataclass_none;
}

void
dns_rdata_deleterrset(dns_rdata_t *rdata, dns_rdatatype_t type) {

    REQUIRE(rdata != NULL);
    REQUIRE(DNS_RDATA_INITIALIZED(rdata));

    rdata->data = NULL;
    rdata->length = 0;
    rdata->flags = DNS_RDATA_UPDATE;
    rdata->type = type;
    rdata->rdclass = dns_rdataclass_any;
}

void
dns_rdata_makedelete(dns_rdata_t *rdata) {
    REQUIRE(rdata != NULL);

    rdata->rdclass = dns_rdataclass_none;
}

const char *
dns_rdata_updateop(dns_rdata_t *rdata, dns_section_t section) {

    REQUIRE(rdata != NULL);
    REQUIRE(DNS_RDATA_INITIALIZED(rdata));

    switch (section) {
    case DNS_SECTION_PREREQUISITE:
        switch (rdata->rdclass) {
        case dns_rdataclass_none:
            switch (rdata->type) {
            case dns_rdatatype_any:
                return ("domain doesn't exist");
            default:
                return ("rrset doesn't exist");
            }
        case dns_rdataclass_any:
            switch (rdata->type) {
            case dns_rdatatype_any:
                return ("domain exists");
            default:
                return ("rrset exists (value independent)");
            }
        default:
            return ("rrset exists (value dependent)");
        }
    case DNS_SECTION_UPDATE:
        switch (rdata->rdclass) {
        case dns_rdataclass_none:
            return ("delete");
        case dns_rdataclass_any:
            switch (rdata->type) {
            case dns_rdatatype_any:
                return ("delete all rrsets");
            default:
                return ("delete rrset");
            }
        default:
            return ("add");
        }
    }
    return ("invalid");
}