lib/dns/ncache.c

	ncache.c revision 6e49e91bd08778d7eae45a2229dcf41ed97cc636
/*
 * Copyright (C) 1999, 2000  Internet Software Consortium.
 *
 * Permission to use, copy, modify, and distribute this software for any
 * purpose with or without fee is hereby granted, provided that the above
 * copyright notice and this permission notice appear in all copies.
 *
 * THE SOFTWARE IS PROVIDED "AS IS" AND INTERNET SOFTWARE CONSORTIUM DISCLAIMS
 * ALL WARRANTIES WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES
 * OF MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL INTERNET SOFTWARE
 * CONSORTIUM BE LIABLE FOR ANY SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL
 * DAMAGES OR ANY DAMAGES WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR
 * PROFITS, WHETHER IN AN ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS
 * ACTION, ARISING OUT OF OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS
 * SOFTWARE.
 */

#include <config.h>

#include <isc/assertions.h>
#include <isc/region.h>
#include <isc/buffer.h>

#include <dns/types.h>
#include <dns/ncache.h>
#include <dns/name.h>
#include <dns/compress.h>
#include <dns/message.h>
#include <dns/db.h>
#include <dns/rdata.h>
#include <dns/rdataset.h>
#include <dns/rdatalist.h>

/*
 * The format of an ncache rdata is a sequence of one or more records of
 * the following format:
 *
 *  owner name
 *  type
 *  rdata count
 *      rdata length            These two occur 'rdata count'
 *      rdata               times.
 *
 */

static inline isc_result_t
copy_rdataset(dns_rdataset_t *rdataset, isc_buffer_t *buffer) {
    isc_result_t result;
    unsigned int count;
    isc_region_t ar, r;
    dns_rdata_t rdata;

    /*
     * Copy the rdataset count to the buffer.
     */
    isc_buffer_availableregion(buffer, &ar);
    if (ar.length < 2)
        return (ISC_R_NOSPACE);
    count = dns_rdataset_count(rdataset);
    INSIST(count <= 65535);
    isc_buffer_putuint16(buffer, (isc_uint16_t)count);

    result = dns_rdataset_first(rdataset);
    while (result == ISC_R_SUCCESS) {
        dns_rdataset_current(rdataset, &rdata);
        dns_rdata_toregion(&rdata, &r);
        INSIST(r.length <= 65535);
        isc_buffer_availableregion(buffer, &ar);
        if (ar.length < 2)
            return (ISC_R_NOSPACE);
        /*
         * Copy the rdata length to the buffer.
         */
        isc_buffer_putuint16(buffer, (isc_uint16_t)r.length);
        /*
         * Copy the rdata to the buffer.
         */
        result = isc_buffer_copyregion(buffer, &r);
        if (result != ISC_R_SUCCESS)
            return (result);
        result = dns_rdataset_next(rdataset);
    }
    if (result != ISC_R_NOMORE)
        return (result);

    return (ISC_R_SUCCESS);
}

isc_result_t
dns_ncache_add(dns_message_t *message, dns_db_t *cache, dns_dbnode_t *node,
           dns_rdatatype_t covers, isc_stdtime_t now,
           dns_rdataset_t *addedrdataset)
{
    isc_result_t result;
    isc_buffer_t buffer;
    isc_region_t r;
    dns_rdataset_t *rdataset;
    dns_rdatatype_t type;
    dns_name_t *name;
    dns_ttl_t ttl;
    dns_trust_t trust;
    dns_rdata_t rdata;
    dns_rdataset_t ncrdataset;
    dns_rdatalist_t ncrdatalist;
    unsigned char data[4096];

    /*
     * Convert the authority data from 'message' into a negative cache
     * rdataset, and store it in 'cache' at 'node'.
     */

    REQUIRE(message != NULL);

    /*
     * We assume that all data in the authority section has been
     * validated by the caller.
     */

    /*
     * First, build an ncache rdata in buffer.
     */
    ttl = 0xffffffff;
    trust = 0xffff;
    isc_buffer_init(&buffer, data, sizeof(data));
    result = dns_message_firstname(message, DNS_SECTION_AUTHORITY);
    while (result == ISC_R_SUCCESS) {
        name = NULL;
        dns_message_currentname(message, DNS_SECTION_AUTHORITY,
                    &name);
        if ((name->attributes & DNS_NAMEATTR_NCACHE) != 0) {
            for (rdataset = ISC_LIST_HEAD(name->list);
                 rdataset != NULL;
                 rdataset = ISC_LIST_NEXT(rdataset, link)) {
                if ((rdataset->attributes &
                     DNS_RDATASETATTR_NCACHE) == 0)
                    continue;
                type = rdataset->type;
                if (type == dns_rdatatype_sig)
                    type = rdataset->covers;
                if (type == dns_rdatatype_soa ||
                    type == dns_rdatatype_nxt) {
                    if (ttl > rdataset->ttl)
                        ttl = rdataset->ttl;
                    if (trust > rdataset->trust)
                        trust = rdataset->trust;
                    /*
                     * Copy the owner name to the buffer.
                     */
                    dns_name_toregion(name, &r);
                    result = isc_buffer_copyregion(&buffer,
                                       &r);
                    if (result != ISC_R_SUCCESS)
                        return (result);
                    /*
                     * Copy the type to the buffer.
                     */
                    isc_buffer_availableregion(&buffer, &r);
                    if (r.length < 2)
                        return (ISC_R_NOSPACE);
                    isc_buffer_putuint16(&buffer,
                                 rdataset->type);
                    /*
                     * Copy the rdataset into the buffer.
                     */
                    result = copy_rdataset(rdataset,
                                   &buffer);
                    if (result != ISC_R_SUCCESS)
                        return (result);
                }
            }
        }
        result = dns_message_nextname(message, DNS_SECTION_AUTHORITY);
    }
    if (result != ISC_R_NOMORE)
        return (result);

    if (trust == 0xffff) {
        /*
         * We didn't find any authority data from which to create a
         * negative cache rdataset.  In particular, we have no SOA.
         *
         * We trust that the caller wants negative caching, so this
         * means we have a "type 3 nxdomain" or "type 3 nodata"
         * response (see RFC 2308 for details).
         *
         * We will now build a suitable negative cache rdataset that
         * will cause zero bytes to be emitted when converted to
         * wire format.
         */

        /*
         * The ownername must exist, but it doesn't matter what value
         * it has.  We use the root name.
         */
        dns_name_toregion(dns_rootname, &r);
        result = isc_buffer_copyregion(&buffer, &r);
        if (result != ISC_R_SUCCESS)
            return (result);
        /*
         * Copy the type and a zero rdata count to the buffer.
         */
        isc_buffer_availableregion(&buffer, &r);
        if (r.length < 4)
            return (ISC_R_NOSPACE);
        isc_buffer_putuint16(&buffer, 0);
        isc_buffer_putuint16(&buffer, 0);
        /*
         * RFC 2308, section 5, says that negative answers without
         * SOAs should not be cached.
         */
        ttl = 0;
        /*
         * Set trust.
         */
        if ((message->flags & DNS_MESSAGEFLAG_AA) != 0 &&
            message->counts[DNS_SECTION_ANSWER] == 0) {
            /*
             * The response has aa set and we haven't followed
             * any CNAME or DNAME chains.
             */
            trust = dns_trust_authauthority;
        } else
            trust = dns_trust_additional;
    }

    /*
     * Now add it to the cache.
     */
    INSIST(trust != 0xffff);
    dns_rdata_init(&rdata);
    isc_buffer_usedregion(&buffer, &r);
    rdata.data = r.base;
    rdata.length = r.length;
    rdata.rdclass = dns_db_class(cache);
    rdata.type = 0;

    ncrdatalist.rdclass = rdata.rdclass;
    ncrdatalist.type = 0;
    ncrdatalist.covers = covers;
    ncrdatalist.ttl = ttl;
    ISC_LIST_INIT(ncrdatalist.rdata);
    ISC_LINK_INIT(&ncrdatalist, link);

    ISC_LIST_APPEND(ncrdatalist.rdata, &rdata, link);

    dns_rdataset_init(&ncrdataset);
    dns_rdatalist_tordataset(&ncrdatalist, &ncrdataset);
    ncrdataset.trust = trust;

    return (dns_db_addrdataset(cache, node, NULL, now, &ncrdataset,
                   0, addedrdataset));
}

isc_result_t
dns_ncache_towire(dns_rdataset_t *rdataset, dns_compress_t *cctx,
          isc_buffer_t *target, unsigned int *countp)
{
    dns_rdata_t rdata;
    isc_result_t result;
    isc_region_t remaining, tremaining;
    isc_buffer_t source, savedbuffer, rdlen;
    dns_name_t name;
    dns_rdatatype_t type;
    unsigned int i, rcount, count;

    /*
     * Convert the negative caching rdataset 'rdataset' to wire format,
     * compressing names as specified in 'cctx', and storing the result in
     * 'target'.
     */

    REQUIRE(rdataset != NULL);
    REQUIRE(rdataset->type == 0);

    result = dns_rdataset_first(rdataset);
    if (result != ISC_R_SUCCESS)
        return (result);
    dns_rdataset_current(rdataset, &rdata);
    INSIST(dns_rdataset_next(rdataset) == ISC_R_NOMORE);
    isc_buffer_init(&source, rdata.data, rdata.length);
    isc_buffer_add(&source, rdata.length);

    if (dns_compress_getedns(cctx) >= 1)
        dns_compress_setmethods(cctx, DNS_COMPRESS_GLOBAL);
    else
        dns_compress_setmethods(cctx, DNS_COMPRESS_GLOBAL14);

    savedbuffer = *target;

    count = 0;
    do {
        dns_name_init(&name, NULL);
        isc_buffer_remainingregion(&source, &remaining);
        dns_name_fromregion(&name, &remaining);
        INSIST(remaining.length >= name.length);
        isc_buffer_forward(&source, name.length);
        remaining.length -= name.length;

        INSIST(remaining.length >= 4);
        type = isc_buffer_getuint16(&source);
        rcount = isc_buffer_getuint16(&source);

        for (i = 0; i < rcount; i++) {
            /*
             * Get the length of this rdata and set up an
             * rdata structure for it.
             */
            isc_buffer_remainingregion(&source, &remaining);
            INSIST(remaining.length >= 2);
            dns_rdata_init(&rdata);
            rdata.length = isc_buffer_getuint16(&source);
            isc_buffer_remainingregion(&source, &remaining);
            rdata.data = remaining.base;
            rdata.type = type;
            rdata.rdclass = rdataset->rdclass;
            INSIST(remaining.length >= rdata.length);
            isc_buffer_forward(&source, rdata.length);

            /*
             * Write the name.
             */
            result = dns_name_towire(&name, cctx, target);
            if (result != ISC_R_SUCCESS)
                goto rollback;

            /*
             * See if we have space for type, class, ttl, and
             * rdata length.  Write the type, class, and ttl.
             */
            isc_buffer_remainingregion(target, &tremaining);
            if (tremaining.length < 10) {
                result = ISC_R_NOSPACE;
                goto rollback;
            }
            isc_buffer_putuint16(target, type);
            isc_buffer_putuint16(target, rdataset->rdclass);
            isc_buffer_putuint32(target, rdataset->ttl);

            /*
             * Save space for rdata length.
             */
            rdlen = *target;
            isc_buffer_add(target, 2);

            /*
             * Write the rdata.
             */
            result = dns_rdata_towire(&rdata, cctx, target);
            if (result != ISC_R_SUCCESS)
                goto rollback;

            /*
             * Set the rdata length field to the compressed
             * length.
             */
            INSIST((target->used >= rdlen.used + 2) &&
                   (target->used - rdlen.used - 2 < 65536));
            isc_buffer_putuint16(&rdlen,
                         (isc_uint16_t)(target->used -
                                rdlen.used - 2));

            count++;
        }
        isc_buffer_remainingregion(&source, &remaining);
    } while (remaining.length > 0);

    *countp = count;

    return (ISC_R_SUCCESS);

 rollback:
    INSIST(savedbuffer.used < 65536);
    dns_compress_rollback(cctx, (isc_uint16_t)savedbuffer.used);
    *countp = 0;
    *target = savedbuffer;

    return (result);
}