VERSION: Disable GIT_SNAPSHOT for the 4.17.9 release.

[Samba.git] / source4 / dns_server / dnsserver_common.c

/*
   Unix SMB/CIFS implementation.

   DNS server utils

   Copyright (C) 2010 Kai Blin
   Copyright (C) 2014 Stefan Metzmacher
   Copyright (C) 2015 Andrew Bartlett

   This program is free software; you can redistribute it and/or modify
   it under the terms of the GNU General Public License as published by
   the Free Software Foundation; either version 3 of the License, or
   (at your option) any later version.

   This program is distributed in the hope that it will be useful,
   but WITHOUT ANY WARRANTY; without even the implied warranty of
   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
   GNU General Public License for more details.

   You should have received a copy of the GNU General Public License
   along with this program.  If not, see <http://www.gnu.org/licenses/>.
*/

#include "includes.h"
#include "libcli/util/ntstatus.h"
#include "libcli/util/werror.h"
#include "librpc/ndr/libndr.h"
#include "librpc/gen_ndr/ndr_dns.h"
#include "librpc/gen_ndr/ndr_dnsp.h"
#include <ldb.h>
#include "dsdb/samdb/samdb.h"
#include "dsdb/common/util.h"
#include "dns_server/dnsserver_common.h"
#include "rpc_server/dnsserver/dnsserver.h"
#include "lib/util/dlinklist.h"
#include "system/network.h"

#undef DBGC_CLASS
#define DBGC_CLASS DBGC_DNS

#undef strncasecmp

uint8_t werr_to_dns_err(WERROR werr)
{
        if (W_ERROR_EQUAL(WERR_OK, werr)) {
                return DNS_RCODE_OK;
        } else if (W_ERROR_EQUAL(DNS_ERR(FORMAT_ERROR), werr)) {
                return DNS_RCODE_FORMERR;
        } else if (W_ERROR_EQUAL(DNS_ERR(SERVER_FAILURE), werr)) {
                return DNS_RCODE_SERVFAIL;
        } else if (W_ERROR_EQUAL(DNS_ERR(NAME_ERROR), werr)) {
                return DNS_RCODE_NXDOMAIN;
        } else if (W_ERROR_EQUAL(WERR_DNS_ERROR_NAME_DOES_NOT_EXIST, werr)) {
                return DNS_RCODE_NXDOMAIN;
        } else if (W_ERROR_EQUAL(DNS_ERR(NOT_IMPLEMENTED), werr)) {
                return DNS_RCODE_NOTIMP;
        } else if (W_ERROR_EQUAL(DNS_ERR(REFUSED), werr)) {
                return DNS_RCODE_REFUSED;
        } else if (W_ERROR_EQUAL(DNS_ERR(YXDOMAIN), werr)) {
                return DNS_RCODE_YXDOMAIN;
        } else if (W_ERROR_EQUAL(DNS_ERR(YXRRSET), werr)) {
                return DNS_RCODE_YXRRSET;
        } else if (W_ERROR_EQUAL(DNS_ERR(NXRRSET), werr)) {
                return DNS_RCODE_NXRRSET;
        } else if (W_ERROR_EQUAL(DNS_ERR(NOTAUTH), werr)) {
                return DNS_RCODE_NOTAUTH;
        } else if (W_ERROR_EQUAL(DNS_ERR(NOTZONE), werr)) {
                return DNS_RCODE_NOTZONE;
        } else if (W_ERROR_EQUAL(DNS_ERR(BADKEY), werr)) {
                return DNS_RCODE_BADKEY;
        }
        DEBUG(5, ("No mapping exists for %s\n", win_errstr(werr)));
        return DNS_RCODE_SERVFAIL;
}

WERROR dns_common_extract(struct ldb_context *samdb,
                          const struct ldb_message_element *el,
                          TALLOC_CTX *mem_ctx,
                          struct dnsp_DnssrvRpcRecord **records,
                          uint16_t *num_records)
{
        uint16_t ri;
        struct dnsp_DnssrvRpcRecord *recs;

        *records = NULL;
        *num_records = 0;

        recs = talloc_zero_array(mem_ctx, struct dnsp_DnssrvRpcRecord,
                                 el->num_values);
        if (recs == NULL) {
                return WERR_NOT_ENOUGH_MEMORY;
        }
        for (ri = 0; ri < el->num_values; ri++) {
                bool am_rodc;
                int ret;
                const char *dnsHostName = NULL;
                struct ldb_val *v = &el->values[ri];
                enum ndr_err_code ndr_err;
                ndr_err = ndr_pull_struct_blob(v, recs, &recs[ri],
                                (ndr_pull_flags_fn_t)ndr_pull_dnsp_DnssrvRpcRecord);
                if (!NDR_ERR_CODE_IS_SUCCESS(ndr_err)) {
                        TALLOC_FREE(recs);
                        DEBUG(0, ("Failed to grab dnsp_DnssrvRpcRecord\n"));
                        return DNS_ERR(SERVER_FAILURE);
                }

                /*
                 * In AD, except on an RODC (where we should list a random RWDC,
                 * we should over-stamp the MNAME with our own hostname
                 */
                if (recs[ri].wType != DNS_TYPE_SOA) {
                        continue;
                }

                ret = samdb_rodc(samdb, &am_rodc);
                if (ret != LDB_SUCCESS) {
                        DEBUG(0, ("Failed to confirm we are not an RODC: %s\n",
                                  ldb_errstring(samdb)));
                        return DNS_ERR(SERVER_FAILURE);
                }

                if (am_rodc) {
                        continue;
                }

                ret = samdb_dns_host_name(samdb, &dnsHostName);
                if (ret != LDB_SUCCESS || dnsHostName == NULL) {
                        DEBUG(0, ("Failed to get dnsHostName from rootDSE"));
                        return DNS_ERR(SERVER_FAILURE);
                }

                recs[ri].data.soa.mname = talloc_strdup(recs, dnsHostName);
        }

        *records = recs;
        *num_records = el->num_values;
        return WERR_OK;
}

/*
 * Lookup a DNS record, performing an exact match.
 * i.e. DNS wild card records are not considered.
 */
WERROR dns_common_lookup(struct ldb_context *samdb,
                         TALLOC_CTX *mem_ctx,
                         struct ldb_dn *dn,
                         struct dnsp_DnssrvRpcRecord **records,
                         uint16_t *num_records,
                         bool *tombstoned)
{
        const struct timeval start = timeval_current();
        static const char * const attrs[] = {
                "dnsRecord",
                "dNSTombstoned",
                NULL
        };
        int ret;
        WERROR werr = WERR_OK;
        struct ldb_message *msg = NULL;
        struct ldb_message_element *el;

        *records = NULL;
        *num_records = 0;

        if (tombstoned != NULL) {
                *tombstoned = false;
                ret = dsdb_search_one(samdb, mem_ctx, &msg, dn,
                        LDB_SCOPE_BASE, attrs, 0,
                        "(objectClass=dnsNode)");
        } else {
                ret = dsdb_search_one(samdb, mem_ctx, &msg, dn,
                        LDB_SCOPE_BASE, attrs, 0,
                        "(&(objectClass=dnsNode)(!(dNSTombstoned=TRUE)))");
        }
        if (ret == LDB_ERR_NO_SUCH_OBJECT) {
                werr = WERR_DNS_ERROR_NAME_DOES_NOT_EXIST;
                goto exit;
        }
        if (ret != LDB_SUCCESS) {
                /* TODO: we need to check if there's a glue record we need to
                 * create a referral to */
                werr = DNS_ERR(NAME_ERROR);
                goto exit;
        }

        if (tombstoned != NULL) {
                *tombstoned = ldb_msg_find_attr_as_bool(msg,
                                        "dNSTombstoned", false);
        }

        el = ldb_msg_find_element(msg, "dnsRecord");
        if (el == NULL) {
                TALLOC_FREE(msg);
                /*
                 * records produced by older Samba releases
                 * keep dnsNode objects without dnsRecord and
                 * without setting dNSTombstoned=TRUE.
                 *
                 * We just pretend they're tombstones.
                 */
                if (tombstoned != NULL) {
                        struct dnsp_DnssrvRpcRecord *recs;
                        recs = talloc_array(mem_ctx,
                                            struct dnsp_DnssrvRpcRecord,
                                            1);
                        if (recs == NULL) {
                                werr = WERR_NOT_ENOUGH_MEMORY;
                                goto exit;
                        }
                        recs[0] = (struct dnsp_DnssrvRpcRecord) {
                                .wType = DNS_TYPE_TOMBSTONE,
                                /*
                                 * A value of timestamp != 0
                                 * indicated that the object was already
                                 * a tombstone, this will be used
                                 * in dns_common_replace()
                                 */
                                .data.EntombedTime = 1,
                        };

                        *tombstoned = true;
                        *records = recs;
                        *num_records = 1;
                        werr = WERR_OK;
                        goto exit;
                } else {
                        /*
                         * Because we are not looking for a tombstone
                         * in this codepath, we just pretend it does
                         * not exist at all.
                         */
                        werr = WERR_DNS_ERROR_NAME_DOES_NOT_EXIST;
                        goto exit;
                }
        }

        werr = dns_common_extract(samdb, el, mem_ctx, records, num_records);
        TALLOC_FREE(msg);
        if (!W_ERROR_IS_OK(werr)) {
                goto exit;
        }

        werr = WERR_OK;
exit:
        DNS_COMMON_LOG_OPERATION(
                win_errstr(werr),
                &start,
                NULL,
                dn == NULL ? NULL : ldb_dn_get_linearized(dn),
                NULL);
        return werr;
}

/*
 * Build an ldb_parse_tree node for an equality check
 *
 * Note: name is assumed to have been validated by dns_name_check
 *       so will be zero terminated and of a reasonable size.
 */
static struct ldb_parse_tree *build_equality_operation(
        TALLOC_CTX *mem_ctx,
        bool add_asterix,     /* prepend an '*' to the name          */
        const uint8_t *name,  /* the value being matched             */
        const char *attr,     /* the attribute to check name against */
        size_t size)          /* length of name                      */
{

        struct ldb_parse_tree *el = NULL;  /* Equality node being built */
        struct ldb_val *value = NULL;      /* Value the attr will be compared
                                              with */
        size_t length = 0;                 /* calculated length of the value
                                              including option '*' prefix and
                                              '\0' string terminator */

        el = talloc(mem_ctx, struct ldb_parse_tree);
        if (el == NULL) {
                DBG_ERR("Unable to allocate ldb_parse_tree\n");
                return NULL;
        }

        el->operation = LDB_OP_EQUALITY;
        el->u.equality.attr = talloc_strdup(mem_ctx, attr);
        value = &el->u.equality.value;
        length = (add_asterix) ? size + 2 : size + 1;
        value->data = talloc_zero_array(el, uint8_t, length);
        if (value->data == NULL) {
                DBG_ERR("Unable to allocate value->data\n");
                TALLOC_FREE(el);
                return NULL;
        }

        value->length = length;
        if (add_asterix) {
                value->data[0] = '*';
                if (name != NULL) {
                        memcpy(&value->data[1], name, size);
                }
        } else if (name != NULL) {
                memcpy(value->data, name, size);
        }
        return el;
}

/*
 * Determine the number of levels in name
 * essentially the number of '.'s in the name + 1
 *
 * name is assumed to have been validated by dns_name_check
 */
static unsigned int number_of_labels(const struct ldb_val *name) {
        int x  = 0;
        unsigned int labels = 1;
        for (x = 0; x < name->length; x++) {
                if (name->data[x] == '.') {
                        labels++;
                }
        }
        return labels;
}
/*
 * Build a query that matches the target name, and any possible
 * DNS wild card entries
 *
 * Builds a parse tree equivalent to the example query.
 *
 * x.y.z -> (|(name=x.y.z)(name=\2a.y.z)(name=\2a.z)(name=\2a))
 *
 * The attribute 'name' is used as this is what the LDB index is on
 * (the RDN, being 'dc' in this use case, does not have an index in
 * the AD schema).
 *
 * Returns NULL if unable to build the query.
 *
 * The first component of the DN is assumed to be the name being looked up
 * and also that it has been validated by dns_name_check
 *
 */
#define BASE "(&(objectClass=dnsNode)(!(dNSTombstoned=TRUE))(|(a=b)(c=d)))"
static struct ldb_parse_tree *build_wildcard_query(
        TALLOC_CTX *mem_ctx,
        struct ldb_dn *dn)
{
        const struct ldb_val *name = NULL;            /* The DNS name being
                                                         queried */
        const char *attr = "name";                    /* The attribute name */
        struct ldb_parse_tree *query = NULL;          /* The constructed query
                                                         parse tree*/
        struct ldb_parse_tree *wildcard_query = NULL; /* The parse tree for the
                                                         name and wild card
                                                         entries */
        int labels = 0;         /* The number of labels in the name */

        name = ldb_dn_get_rdn_val(dn);
        if (name == NULL) {
                DBG_ERR("Unable to get domain name value\n");
                return NULL;
        }
        labels = number_of_labels(name);

        query = ldb_parse_tree(mem_ctx, BASE);
        if (query == NULL) {
                DBG_ERR("Unable to parse query %s\n", BASE);
                return NULL;
        }

        /*
         * The 3rd element of BASE is a place holder which is replaced with
         * the actual wild card query
         */
        wildcard_query = query->u.list.elements[2];
        TALLOC_FREE(wildcard_query->u.list.elements);

        wildcard_query->u.list.num_elements = labels + 1;
        wildcard_query->u.list.elements = talloc_array(
                wildcard_query,
                struct ldb_parse_tree *,
                labels + 1);
        /*
         * Build the wild card query
         */
        {
                int x = 0;   /* current character in the name               */
                int l = 0;   /* current equality operator index in elements */
                struct ldb_parse_tree *el = NULL; /* Equality operator being
                                                     built */
                bool add_asterix = true;  /* prepend an '*' to the value    */
                for (l = 0, x = 0; l < labels && x < name->length; l++) {
                        unsigned int size = name->length - x;
                        add_asterix = (name->data[x] == '.');
                        el = build_equality_operation(
                                mem_ctx,
                                add_asterix,
                                &name->data[x],
                                attr,
                                size);
                        if (el == NULL) {
                                return NULL;  /* Reason will have been logged */
                        }
                        wildcard_query->u.list.elements[l] = el;

                        /* skip to the start of the next label */
                        x++;
                        for (;x < name->length && name->data[x] != '.'; x++);
                }

                /* Add the base level "*" only query */
                el = build_equality_operation(mem_ctx, true, NULL, attr, 0);
                if (el == NULL) {
                        TALLOC_FREE(query);
                        return NULL;  /* Reason will have been logged */
                }
                wildcard_query->u.list.elements[l] = el;
        }
        return query;
}

/*
 * Scan the list of records matching a dns wildcard query and return the
 * best match.
 *
 * The best match is either an exact name match, or the longest wild card
 * entry returned
 *
 * i.e. name = a.b.c candidates *.b.c, *.c,        - *.b.c would be selected
 *      name = a.b.c candidates a.b.c, *.b.c, *.c  - a.b.c would be selected
 */
static struct ldb_message *get_best_match(struct ldb_dn *dn,
                                          struct ldb_result *result)
{
        int matched = 0;    /* Index of the current best match in result */
        size_t length = 0;  /* The length of the current candidate       */
        const struct ldb_val *target = NULL;    /* value we're looking for */
        const struct ldb_val *candidate = NULL; /* current candidate value */
        int x = 0;

        target = ldb_dn_get_rdn_val(dn);
        for(x = 0; x < result->count; x++) {
                candidate = ldb_dn_get_rdn_val(result->msgs[x]->dn);
                if (strncasecmp((char *) target->data,
                                (char *) candidate->data,
                                target->length) == 0) {
                        /* Exact match stop searching and return */
                        return result->msgs[x];
                }
                if (candidate->length > length) {
                        matched = x;
                        length  = candidate->length;
                }
        }
        return result->msgs[matched];
}

/*
 * Look up a DNS entry, if an exact match does not exist, return the
 * closest matching DNS wildcard entry if available
 *
 * Returns: LDB_ERR_NO_SUCH_OBJECT     If no matching record exists
 *          LDB_ERR_OPERATIONS_ERROR   If the query fails
 *          LDB_SUCCESS                If a matching record was retrieved
 *
 */
static int dns_wildcard_lookup(struct ldb_context *samdb,
                               TALLOC_CTX *mem_ctx,
                               struct ldb_dn *dn,
                               struct ldb_message **msg)
{
        static const char * const attrs[] = {
                "dnsRecord",
                "dNSTombstoned",
                NULL
        };
        struct ldb_dn *parent = NULL;     /* The parent dn                    */
        struct ldb_result *result = NULL; /* Results of the search            */
        int ret;                          /* Return code                      */
        struct ldb_parse_tree *query = NULL; /* The query to run              */
        struct ldb_request *request = NULL;  /* LDB request for the query op  */
        struct ldb_message *match = NULL;    /* the best matching DNS record  */
        TALLOC_CTX *frame = talloc_stackframe();

        parent = ldb_dn_get_parent(frame, dn);
        if (parent == NULL) {
                DBG_ERR("Unable to extract parent from dn\n");
                TALLOC_FREE(frame);
                return LDB_ERR_OPERATIONS_ERROR;
        }

        query = build_wildcard_query(frame, dn);
        if (query == NULL) {
                TALLOC_FREE(frame);
                return LDB_ERR_OPERATIONS_ERROR;
        }

        result = talloc_zero(mem_ctx, struct ldb_result);
        if (result == NULL) {
                TALLOC_FREE(frame);
                DBG_ERR("Unable to allocate ldb_result\n");
                return LDB_ERR_OPERATIONS_ERROR;
        }

        ret = ldb_build_search_req_ex(&request,
                                      samdb,
                                      frame,
                                      parent,
                                      LDB_SCOPE_SUBTREE,
                                      query,
                                      attrs,
                                      NULL,
                                      result,
                                      ldb_search_default_callback,
                                      NULL);
        if (ret != LDB_SUCCESS) {
                TALLOC_FREE(frame);
                DBG_ERR("ldb_build_search_req_ex returned %d\n", ret);
                return ret;
        }

        ret = ldb_request(samdb, request);
        if (ret != LDB_SUCCESS) {
                TALLOC_FREE(frame);
                return ret;
        }

        ret = ldb_wait(request->handle, LDB_WAIT_ALL);
        if (ret != LDB_SUCCESS) {
                TALLOC_FREE(frame);
                return ret;
        }

        if (result->count == 0) {
                TALLOC_FREE(frame);
                return LDB_ERR_NO_SUCH_OBJECT;
        }

        match = get_best_match(dn, result);
        if (match == NULL) {
                TALLOC_FREE(frame);
                return LDB_ERR_OPERATIONS_ERROR;
        }

        *msg = talloc_move(mem_ctx, &match);
        TALLOC_FREE(frame);
        return LDB_SUCCESS;
}

/*
 * Lookup a DNS record, will match DNS wild card records if an exact match
 * is not found.
 */
WERROR dns_common_wildcard_lookup(struct ldb_context *samdb,
                                  TALLOC_CTX *mem_ctx,
                                  struct ldb_dn *dn,
                                  struct dnsp_DnssrvRpcRecord **records,
                                  uint16_t *num_records)
{
        const struct timeval start = timeval_current();
        int ret;
        WERROR werr = WERR_OK;
        struct ldb_message *msg = NULL;
        struct ldb_message_element *el = NULL;
        const struct ldb_val *name = NULL;

        *records = NULL;
        *num_records = 0;

        name = ldb_dn_get_rdn_val(dn);
        if (name == NULL) {
                werr = DNS_ERR(NAME_ERROR);
                goto exit;
        }

        /* Don't look for a wildcard for @ */
        if (name->length == 1 && name->data[0] == '@') {
                werr = dns_common_lookup(samdb,
                                         mem_ctx,
                                         dn,
                                         records,
                                         num_records,
                                         NULL);
                goto exit;
        }

        werr =  dns_name_check(
                        mem_ctx,
                        strlen((const char*)name->data),
                        (const char*) name->data);
        if (!W_ERROR_IS_OK(werr)) {
                goto exit;
        }

        /*
         * Do a point search first, then fall back to a wildcard
         * lookup if it does not exist
         */
        werr = dns_common_lookup(samdb,
                                 mem_ctx,
                                 dn,
                                 records,
                                 num_records,
                                 NULL);
        if (!W_ERROR_EQUAL(werr, WERR_DNS_ERROR_NAME_DOES_NOT_EXIST)) {
                goto exit;
        }

        ret = dns_wildcard_lookup(samdb, mem_ctx, dn, &msg);
        if (ret == LDB_ERR_OPERATIONS_ERROR) {
                werr = DNS_ERR(SERVER_FAILURE);
                goto exit;
        }
        if (ret != LDB_SUCCESS) {
                werr = DNS_ERR(NAME_ERROR);
                goto exit;
        }

        el = ldb_msg_find_element(msg, "dnsRecord");
        if (el == NULL) {
                werr = WERR_DNS_ERROR_NAME_DOES_NOT_EXIST;
                goto exit;
        }

        werr = dns_common_extract(samdb, el, mem_ctx, records, num_records);
        TALLOC_FREE(msg);
        if (!W_ERROR_IS_OK(werr)) {
                goto exit;
        }

        werr = WERR_OK;
exit:
        DNS_COMMON_LOG_OPERATION(
                win_errstr(werr),
                &start,
                NULL,
                dn == NULL ? NULL : ldb_dn_get_linearized(dn),
                NULL);
        return werr;
}

static int rec_cmp(const struct dnsp_DnssrvRpcRecord *r1,
                   const struct dnsp_DnssrvRpcRecord *r2)
{
        if (r1->wType != r2->wType) {
                /*
                 * The records are sorted with higher types first,
                 * which puts tombstones (type 0) last.
                 */
                return r2->wType - r1->wType;
        }
        /*
         * Then we need to sort from the oldest to newest timestamp.
         *
         * Note that dwTimeStamp == 0 (never expiring) records come first,
         * then the ones whose expiry is soonest.
         */
        return r1->dwTimeStamp - r2->dwTimeStamp;
}

/*
 * Check for valid DNS names. These are names which:
 *   - are non-empty
 *   - do not start with a dot
 *   - do not have any empty labels
 *   - have no more than 127 labels
 *   - are no longer than 253 characters
 *   - none of the labels exceed 63 characters
 */
WERROR dns_name_check(TALLOC_CTX *mem_ctx, size_t len, const char *name)
{
        size_t i;
        unsigned int labels    = 0;
        unsigned int label_len = 0;

        if (len == 0) {
                return WERR_DS_INVALID_DN_SYNTAX;
        }

        if (len > 1 && name[0] == '.') {
                return WERR_DS_INVALID_DN_SYNTAX;
        }

        if ((len - 1) > DNS_MAX_DOMAIN_LENGTH) {
                return WERR_DS_INVALID_DN_SYNTAX;
        }

        for (i = 0; i < len - 1; i++) {
                if (name[i] == '.' && name[i+1] == '.') {
                        return WERR_DS_INVALID_DN_SYNTAX;
                }
                if (name[i] == '.') {
                        labels++;
                        if (labels > DNS_MAX_LABELS) {
                                return WERR_DS_INVALID_DN_SYNTAX;
                        }
                        label_len = 0;
                } else {
                        label_len++;
                        if (label_len > DNS_MAX_LABEL_LENGTH) {
                                return WERR_DS_INVALID_DN_SYNTAX;
                        }
                }
        }

        return WERR_OK;
}

static WERROR check_name_list(TALLOC_CTX *mem_ctx, uint16_t rec_count,
                              struct dnsp_DnssrvRpcRecord *records)
{
        WERROR werr;
        uint16_t i;
        size_t len;
        struct dnsp_DnssrvRpcRecord record;

        werr = WERR_OK;
        for (i = 0; i < rec_count; i++) {
                record = records[i];

                switch (record.wType) {

                case DNS_TYPE_NS:
                        len = strlen(record.data.ns);
                        werr = dns_name_check(mem_ctx, len, record.data.ns);
                        break;
                case DNS_TYPE_CNAME:
                        len = strlen(record.data.cname);
                        werr = dns_name_check(mem_ctx, len, record.data.cname);
                        break;
                case DNS_TYPE_SOA:
                        len = strlen(record.data.soa.mname);
                        werr = dns_name_check(mem_ctx, len, record.data.soa.mname);
                        if (!W_ERROR_IS_OK(werr)) {
                                break;
                        }
                        len = strlen(record.data.soa.rname);
                        werr = dns_name_check(mem_ctx, len, record.data.soa.rname);
                        break;
                case DNS_TYPE_PTR:
                        len = strlen(record.data.ptr);
                        werr = dns_name_check(mem_ctx, len, record.data.ptr);
                        break;
                case DNS_TYPE_MX:
                        len = strlen(record.data.mx.nameTarget);
                        werr = dns_name_check(mem_ctx, len, record.data.mx.nameTarget);
                        break;
                case DNS_TYPE_SRV:
                        len = strlen(record.data.srv.nameTarget);
                        werr = dns_name_check(mem_ctx, len,
                                              record.data.srv.nameTarget);
                        break;
                /*
                 * In the default case, the record doesn't have a DN, so it
                 * must be ok.
                 */
                default:
                        break;
                }

                if (!W_ERROR_IS_OK(werr)) {
                        return werr;
                }
        }

        return WERR_OK;
}

bool dns_name_is_static(struct dnsp_DnssrvRpcRecord *records,
                        uint16_t rec_count)
{
        int i = 0;
        for (i = 0; i < rec_count; i++) {
                if (records[i].wType == DNS_TYPE_TOMBSTONE) {
                        continue;
                }

                if (records[i].wType == DNS_TYPE_SOA ||
                    records[i].dwTimeStamp == 0) {
                        return true;
                }
        }
        return false;
}

/*
 * Helper function to copy a dnsp_ip4_array struct to an IP4_ARRAY struct.
 * The new structure and it's data are allocated on the supplied talloc context
 */
static struct IP4_ARRAY *copy_ip4_array(TALLOC_CTX *ctx,
                                        const char *name,
                                        struct dnsp_ip4_array array)
{

        struct IP4_ARRAY *ip4_array = NULL;
        unsigned int i;

        ip4_array = talloc_zero(ctx, struct IP4_ARRAY);
        if (ip4_array == NULL) {
                DBG_ERR("Out of memory copying property [%s]\n", name);
                return NULL;
        }

        ip4_array->AddrCount = array.addrCount;
        if (ip4_array->AddrCount == 0) {
                return ip4_array;
        }

        ip4_array->AddrArray =
            talloc_array(ip4_array, uint32_t, ip4_array->AddrCount);
        if (ip4_array->AddrArray == NULL) {
                TALLOC_FREE(ip4_array);
                DBG_ERR("Out of memory copying property [%s] values\n", name);
                return NULL;
        }

        for (i = 0; i < ip4_array->AddrCount; i++) {
                ip4_array->AddrArray[i] = array.addrArray[i];
        }

        return ip4_array;
}

bool dns_zoneinfo_load_zone_property(struct dnsserver_zoneinfo *zoneinfo,
                                     struct dnsp_DnsProperty *prop)
{
        switch (prop->id) {
        case DSPROPERTY_ZONE_TYPE:
                zoneinfo->dwZoneType = prop->data.zone_type;
                break;
        case DSPROPERTY_ZONE_ALLOW_UPDATE:
                zoneinfo->fAllowUpdate = prop->data.allow_update_flag;
                break;
        case DSPROPERTY_ZONE_NOREFRESH_INTERVAL:
                zoneinfo->dwNoRefreshInterval = prop->data.norefresh_hours;
                break;
        case DSPROPERTY_ZONE_REFRESH_INTERVAL:
                zoneinfo->dwRefreshInterval = prop->data.refresh_hours;
                break;
        case DSPROPERTY_ZONE_AGING_STATE:
                zoneinfo->fAging = prop->data.aging_enabled;
                break;
        case DSPROPERTY_ZONE_SCAVENGING_SERVERS:
                zoneinfo->aipScavengeServers = copy_ip4_array(
                    zoneinfo, "ZONE_SCAVENGING_SERVERS", prop->data.servers);
                if (zoneinfo->aipScavengeServers == NULL) {
                        return false;
                }
                break;
        case DSPROPERTY_ZONE_AGING_ENABLED_TIME:
                zoneinfo->dwAvailForScavengeTime =
                    prop->data.next_scavenging_cycle_hours;
                break;
        case DSPROPERTY_ZONE_MASTER_SERVERS:
                zoneinfo->aipLocalMasters = copy_ip4_array(
                    zoneinfo, "ZONE_MASTER_SERVERS", prop->data.master_servers);
                if (zoneinfo->aipLocalMasters == NULL) {
                        return false;
                }
                break;
        case DSPROPERTY_ZONE_EMPTY:
        case DSPROPERTY_ZONE_SECURE_TIME:
        case DSPROPERTY_ZONE_DELETED_FROM_HOSTNAME:
        case DSPROPERTY_ZONE_AUTO_NS_SERVERS:
        case DSPROPERTY_ZONE_DCPROMO_CONVERT:
        case DSPROPERTY_ZONE_SCAVENGING_SERVERS_DA:
        case DSPROPERTY_ZONE_MASTER_SERVERS_DA:
        case DSPROPERTY_ZONE_NS_SERVERS_DA:
        case DSPROPERTY_ZONE_NODE_DBFLAGS:
                break;
        }
        return true;
}
WERROR dns_get_zone_properties(struct ldb_context *samdb,
                               TALLOC_CTX *mem_ctx,
                               struct ldb_dn *zone_dn,
                               struct dnsserver_zoneinfo *zoneinfo)
{

        int ret, i;
        struct dnsp_DnsProperty *prop = NULL;
        struct ldb_message_element *element = NULL;
        const char *const attrs[] = {"dNSProperty", NULL};
        struct ldb_result *res = NULL;
        enum ndr_err_code err;

        ret = ldb_search(samdb,
                         mem_ctx,
                         &res,
                         zone_dn,
                         LDB_SCOPE_BASE,
                         attrs,
                         "(objectClass=dnsZone)");
        if (ret != LDB_SUCCESS) {
                DBG_ERR("dnsserver: Failed to find DNS zone: %s\n",
                        ldb_dn_get_linearized(zone_dn));
                return DNS_ERR(SERVER_FAILURE);
        }

        element = ldb_msg_find_element(res->msgs[0], "dNSProperty");
        if (element == NULL) {
                return DNS_ERR(NOTZONE);
        }

        for (i = 0; i < element->num_values; i++) {
                bool valid_property;
                prop = talloc_zero(mem_ctx, struct dnsp_DnsProperty);
                if (prop == NULL) {
                        return WERR_NOT_ENOUGH_MEMORY;
                }
                err = ndr_pull_struct_blob(
                    &(element->values[i]),
                    mem_ctx,
                    prop,
                    (ndr_pull_flags_fn_t)ndr_pull_dnsp_DnsProperty);
                if (!NDR_ERR_CODE_IS_SUCCESS(err)) {
                        /*
                         * If we can't pull it, then there is no valid
                         * data to load into the zone, so ignore this
                         * as Micosoft does.  Windows can load an
                         * invalid property with a zero length into
                         * the dnsProperty attribute.
                         */
                        continue;
                }

                valid_property =
                    dns_zoneinfo_load_zone_property(zoneinfo, prop);
                if (!valid_property) {
                        return DNS_ERR(SERVER_FAILURE);
                }
        }

        return WERR_OK;
}

WERROR dns_common_replace(struct ldb_context *samdb,
                          TALLOC_CTX *mem_ctx,
                          struct ldb_dn *dn,
                          bool needs_add,
                          uint32_t serial,
                          struct dnsp_DnssrvRpcRecord *records,
                          uint16_t rec_count)
{
        const struct timeval start = timeval_current();
        struct ldb_message_element *el;
        uint16_t i;
        int ret;
        WERROR werr;
        struct ldb_message *msg = NULL;
        bool was_tombstoned = false;
        bool become_tombstoned = false;
        struct ldb_dn *zone_dn = NULL;
        struct dnsserver_zoneinfo *zoneinfo = NULL;
        uint32_t t;

        msg = ldb_msg_new(mem_ctx);
        W_ERROR_HAVE_NO_MEMORY(msg);

        msg->dn = dn;

        zone_dn = ldb_dn_copy(mem_ctx, dn);
        if (zone_dn == NULL) {
                werr = WERR_NOT_ENOUGH_MEMORY;
                goto exit;
        }
        if (!ldb_dn_remove_child_components(zone_dn, 1)) {
                werr = DNS_ERR(SERVER_FAILURE);
                goto exit;
        }
        zoneinfo = talloc(mem_ctx, struct dnsserver_zoneinfo);
        if (zoneinfo == NULL) {
                werr = WERR_NOT_ENOUGH_MEMORY;
                goto exit;
        }
        werr = dns_get_zone_properties(samdb, mem_ctx, zone_dn, zoneinfo);
        if (W_ERROR_EQUAL(DNS_ERR(NOTZONE), werr)) {
                /*
                 * We only got zoneinfo for aging so if we didn't find any
                 * properties then just disable aging and keep going.
                 */
                zoneinfo->fAging = 0;
        } else if (!W_ERROR_IS_OK(werr)) {
                goto exit;
        }

        werr = check_name_list(mem_ctx, rec_count, records);
        if (!W_ERROR_IS_OK(werr)) {
                goto exit;
        }

        ret = ldb_msg_add_empty(msg, "dnsRecord", LDB_FLAG_MOD_REPLACE, &el);
        if (ret != LDB_SUCCESS) {
                werr = DNS_ERR(SERVER_FAILURE);
                goto exit;
        }

        /*
         * we have at least one value,
         * which might be used for the tombstone marker
         */
        el->values = talloc_zero_array(el, struct ldb_val, MAX(1, rec_count));
        if (el->values == NULL) {
                werr = WERR_NOT_ENOUGH_MEMORY;
                goto exit;
        }

        if (rec_count > 1) {
                /*
                 * We store a sorted list with the high wType values first
                 * that's what windows does. It also simplifies the
                 * filtering of DNS_TYPE_TOMBSTONE records
                 */
                TYPESAFE_QSORT(records, rec_count, rec_cmp);
        }

        for (i = 0; i < rec_count; i++) {
                struct ldb_val *v = &el->values[el->num_values];
                enum ndr_err_code ndr_err;

                if (records[i].wType == DNS_TYPE_TOMBSTONE) {
                        /*
                         * There are two things that could be going on here.
                         *
                         * 1. We use a tombstone with EntombedTime == 0 for
                         * passing deletion messages through the stack, and
                         * this is the place we filter them out to perform
                         * that deletion.
                         *
                         * 2. This node is tombstoned, with no records except
                         * for a single tombstone, and it is just waiting to
                         * disappear. In this case, unless the caller has
                         * added a record, rec_count should be 1, and
                         * el->num_values will end up at 0, and we will make
                         * no changes. But if the caller has added a record,
                         * we need to un-tombstone the node.
                         *
                         * It is not possible to add an explicit tombstone
                         * record.
                         */
                        if (records[i].data.EntombedTime != 0) {
                                was_tombstoned = true;
                        }
                        continue;
                }

                if (zoneinfo->fAging == 1 && records[i].dwTimeStamp != 0) {
                        t = unix_to_dns_timestamp(time(NULL));
                        if (t - records[i].dwTimeStamp >
                            zoneinfo->dwNoRefreshInterval) {
                                records[i].dwTimeStamp = t;
                        }
                }

                records[i].dwSerial = serial;
                ndr_err = ndr_push_struct_blob(v, el->values, &records[i],
                                (ndr_push_flags_fn_t)ndr_push_dnsp_DnssrvRpcRecord);
                if (!NDR_ERR_CODE_IS_SUCCESS(ndr_err)) {
                        DEBUG(0, ("Failed to push dnsp_DnssrvRpcRecord\n"));
                        werr = DNS_ERR(SERVER_FAILURE);
                        goto exit;
                }
                el->num_values++;
        }

        if (needs_add) {
                /*
                 * This is a new dnsNode, which simplifies everything as we
                 * know there is nothing to delete or change. We add the
                 * records and get out.
                 */
                if (el->num_values == 0) {
                        werr = WERR_OK;
                        goto exit;
                }

                ret = ldb_msg_add_string(msg, "objectClass", "dnsNode");
                if (ret != LDB_SUCCESS) {
                        werr = DNS_ERR(SERVER_FAILURE);
                        goto exit;
                }

                ret = ldb_add(samdb, msg);
                if (ret != LDB_SUCCESS) {
                        werr = DNS_ERR(SERVER_FAILURE);
                        goto exit;
                }

                werr = WERR_OK;
                goto exit;
        }

        if (el->num_values == 0) {
                /*
                 * We get here if there are no records or all the records were
                 * tombstones.
                 */
                struct dnsp_DnssrvRpcRecord tbs;
                struct ldb_val *v = &el->values[el->num_values];
                enum ndr_err_code ndr_err;
                struct timeval tv;

                if (was_tombstoned) {
                        /*
                         * This is already a tombstoned object.
                         * Just leave it instead of updating the time stamp.
                         */
                        werr = WERR_OK;
                        goto exit;
                }

                tv = timeval_current();
                tbs = (struct dnsp_DnssrvRpcRecord) {
                        .wType = DNS_TYPE_TOMBSTONE,
                        .dwSerial = serial,
                        .data.EntombedTime = timeval_to_nttime(&tv),
                };

                ndr_err = ndr_push_struct_blob(v, el->values, &tbs,
                                (ndr_push_flags_fn_t)ndr_push_dnsp_DnssrvRpcRecord);
                if (!NDR_ERR_CODE_IS_SUCCESS(ndr_err)) {
                        DEBUG(0, ("Failed to push dnsp_DnssrvRpcRecord\n"));
                        werr = DNS_ERR(SERVER_FAILURE);
                        goto exit;
                }
                el->num_values++;

                become_tombstoned = true;
        }

        if (was_tombstoned || become_tombstoned) {
                ret = ldb_msg_append_fmt(msg, LDB_FLAG_MOD_REPLACE,
                                         "dNSTombstoned", "%s",
                                         become_tombstoned ? "TRUE" : "FALSE");
                if (ret != LDB_SUCCESS) {
                        werr = DNS_ERR(SERVER_FAILURE);
                        goto exit;
                }
        }

        ret = ldb_modify(samdb, msg);
        if (ret != LDB_SUCCESS) {
                NTSTATUS nt = dsdb_ldb_err_to_ntstatus(ret);
                werr = ntstatus_to_werror(nt);
                goto exit;
        }

        werr = WERR_OK;
exit:
        talloc_free(msg);
        DNS_COMMON_LOG_OPERATION(
                win_errstr(werr),
                &start,
                NULL,
                dn == NULL ? NULL : ldb_dn_get_linearized(dn),
                NULL);
        return werr;
}

bool dns_name_match(const char *zone, const char *name, size_t *host_part_len)
{
        size_t zl = strlen(zone);
        size_t nl = strlen(name);
        ssize_t zi, ni;
        static const size_t fixup = 'a' - 'A';

        if (zl > nl) {
                return false;
        }

        for (zi = zl, ni = nl; zi >= 0; zi--, ni--) {
                char zc = zone[zi];
                char nc = name[ni];

                /* convert to lower case */
                if (zc >= 'A' && zc <= 'Z') {
                        zc += fixup;
                }
                if (nc >= 'A' && nc <= 'Z') {
                        nc += fixup;
                }

                if (zc != nc) {
                        return false;
                }
        }

        if (ni >= 0) {
                if (name[ni] != '.') {
                        return false;
                }

                ni--;
        }

        *host_part_len = ni+1;

        return true;
}

WERROR dns_common_name2dn(struct ldb_context *samdb,
                          struct dns_server_zone *zones,
                          TALLOC_CTX *mem_ctx,
                          const char *name,
                          struct ldb_dn **_dn)
{
        struct ldb_dn *base;
        struct ldb_dn *dn;
        const struct dns_server_zone *z;
        size_t host_part_len = 0;
        struct ldb_val host_part;
        WERROR werr;
        bool ok;
        const char *casefold = NULL;

        if (name == NULL) {
                return DNS_ERR(FORMAT_ERROR);
        }

        if (strcmp(name, "") == 0) {
                base = ldb_get_default_basedn(samdb);
                dn = ldb_dn_copy(mem_ctx, base);
                ok = ldb_dn_add_child_fmt(dn,
                                          "DC=@,DC=RootDNSServers,CN=MicrosoftDNS,CN=System");
                if (ok == false) {
                        TALLOC_FREE(dn);
                        return WERR_NOT_ENOUGH_MEMORY;
                }

                *_dn = dn;
                return WERR_OK;
        }

        /* Check non-empty names */
        werr = dns_name_check(mem_ctx, strlen(name), name);
        if (!W_ERROR_IS_OK(werr)) {
                return werr;
        }

        for (z = zones; z != NULL; z = z->next) {
                bool match;

                match = dns_name_match(z->name, name, &host_part_len);
                if (match) {
                        break;
                }
        }

        if (z == NULL) {
                return DNS_ERR(NAME_ERROR);
        }

        if (host_part_len == 0) {
                dn = ldb_dn_copy(mem_ctx, z->dn);
                ok = ldb_dn_add_child_fmt(dn, "DC=@");
                if (! ok) {
                        TALLOC_FREE(dn);
                        return WERR_NOT_ENOUGH_MEMORY;
                }
                *_dn = dn;
                return WERR_OK;
        }

        dn = ldb_dn_copy(mem_ctx, z->dn);
        if (dn == NULL) {
                TALLOC_FREE(dn);
                return WERR_NOT_ENOUGH_MEMORY;
        }

        host_part = data_blob_const(name, host_part_len);

        ok = ldb_dn_add_child_val(dn, "DC", host_part);

        if (ok == false) {
                TALLOC_FREE(dn);
                return WERR_NOT_ENOUGH_MEMORY;
        }

        /*
         * Check the new DN here for validity, so as to catch errors
         * early
         */
        ok = ldb_dn_validate(dn);
        if (ok == false) {
                TALLOC_FREE(dn);
                return DNS_ERR(NAME_ERROR);
        }

        /*
         * The value from this check is saved in the DN, and doing
         * this here allows an easy return here.
         */
        casefold = ldb_dn_get_casefold(dn);
        if (casefold == NULL) {
                TALLOC_FREE(dn);
                return DNS_ERR(NAME_ERROR);
        }

        *_dn = dn;
        return WERR_OK;
}


/*
  see if two dns records match
 */


bool dns_record_match(struct dnsp_DnssrvRpcRecord *rec1,
                      struct dnsp_DnssrvRpcRecord *rec2)
{
        int i;
        struct in6_addr rec1_in_addr6;
        struct in6_addr rec2_in_addr6;

        if (rec1->wType != rec2->wType) {
                return false;
        }

        /* see if the data matches */
        switch (rec1->wType) {
        case DNS_TYPE_A:
                return strcmp(rec1->data.ipv4, rec2->data.ipv4) == 0;
        case DNS_TYPE_AAAA: {
                int ret;

                ret = inet_pton(AF_INET6, rec1->data.ipv6, &rec1_in_addr6);
                if (ret != 1) {
                        return false;
                }
                ret = inet_pton(AF_INET6, rec2->data.ipv6, &rec2_in_addr6);
                if (ret != 1) {
                        return false;
                }

                return memcmp(&rec1_in_addr6, &rec2_in_addr6, sizeof(rec1_in_addr6)) == 0;
        }
        case DNS_TYPE_CNAME:
                return samba_dns_name_equal(rec1->data.cname,
                                            rec2->data.cname);
        case DNS_TYPE_TXT:
                if (rec1->data.txt.count != rec2->data.txt.count) {
                        return false;
                }
                for (i = 0; i < rec1->data.txt.count; i++) {
                        if (strcmp(rec1->data.txt.str[i], rec2->data.txt.str[i]) != 0) {
                                return false;
                        }
                }
                return true;
        case DNS_TYPE_PTR:
                return samba_dns_name_equal(rec1->data.ptr, rec2->data.ptr);
        case DNS_TYPE_NS:
                return samba_dns_name_equal(rec1->data.ns, rec2->data.ns);

        case DNS_TYPE_SRV:
                return rec1->data.srv.wPriority == rec2->data.srv.wPriority &&
                        rec1->data.srv.wWeight  == rec2->data.srv.wWeight &&
                        rec1->data.srv.wPort    == rec2->data.srv.wPort &&
                        samba_dns_name_equal(rec1->data.srv.nameTarget,
                                             rec2->data.srv.nameTarget);

        case DNS_TYPE_MX:
                return rec1->data.mx.wPriority == rec2->data.mx.wPriority &&
                        samba_dns_name_equal(rec1->data.mx.nameTarget,
                                             rec2->data.mx.nameTarget);

        case DNS_TYPE_SOA:
                return samba_dns_name_equal(rec1->data.soa.mname,
                                            rec2->data.soa.mname) &&
                        samba_dns_name_equal(rec1->data.soa.rname,
                                             rec2->data.soa.rname) &&
                        rec1->data.soa.serial == rec2->data.soa.serial &&
                        rec1->data.soa.refresh == rec2->data.soa.refresh &&
                        rec1->data.soa.retry == rec2->data.soa.retry &&
                        rec1->data.soa.expire == rec2->data.soa.expire &&
                        rec1->data.soa.minimum == rec2->data.soa.minimum;
        case DNS_TYPE_TOMBSTONE:
                return true;
        default:
                break;
        }

        return false;
}


static int dns_common_sort_zones(struct ldb_message **m1, struct ldb_message **m2)
{
        const char *n1, *n2;
        size_t l1, l2;

        n1 = ldb_msg_find_attr_as_string(*m1, "name", NULL);
        n2 = ldb_msg_find_attr_as_string(*m2, "name", NULL);
        if (n1 == NULL || n2 == NULL) {
                if (n1 != NULL) {
                        return -1;
                } else if (n2 != NULL) {
                        return 1;
                } else {
                        return 0;
                }
        }
        l1 = strlen(n1);
        l2 = strlen(n2);

        /* If the string lengths are not equal just sort by length */
        if (l1 != l2) {
                /* If m1 is the larger zone name, return it first */
                return l2 - l1;
        }

        /*TODO: We need to compare DNs here, we want the DomainDNSZones first */
        return 0;
}

NTSTATUS dns_common_zones(struct ldb_context *samdb,
                          TALLOC_CTX *mem_ctx,
                          struct ldb_dn *base_dn,
                          struct dns_server_zone **zones_ret)
{
        const struct timeval start = timeval_current();
        int ret;
        static const char * const attrs[] = { "name", NULL};
        struct ldb_result *res;
        int i;
        struct dns_server_zone *new_list = NULL;
        TALLOC_CTX *frame = talloc_stackframe();
        NTSTATUS result = NT_STATUS_OK;

        if (base_dn) {
                /* This search will work against windows */
                ret = dsdb_search(samdb, frame, &res,
                                  base_dn, LDB_SCOPE_SUBTREE,
                                  attrs, 0, "(objectClass=dnsZone)");
        } else {
                /* TODO: this search does not work against windows */
                ret = dsdb_search(samdb, frame, &res, NULL,
                                  LDB_SCOPE_SUBTREE,
                                  attrs,
                                  DSDB_SEARCH_SEARCH_ALL_PARTITIONS,
                                  "(objectClass=dnsZone)");
        }
        if (ret != LDB_SUCCESS) {
                TALLOC_FREE(frame);
                result = NT_STATUS_INTERNAL_DB_CORRUPTION;
                goto exit;
        }

        TYPESAFE_QSORT(res->msgs, res->count, dns_common_sort_zones);

        for (i=0; i < res->count; i++) {
                struct dns_server_zone *z;

                z = talloc_zero(mem_ctx, struct dns_server_zone);
                if (z == NULL) {
                        TALLOC_FREE(frame);
                        result = NT_STATUS_NO_MEMORY;
                        goto exit;
                }

                z->name = ldb_msg_find_attr_as_string(res->msgs[i], "name", NULL);
                talloc_steal(z, z->name);
                z->dn = talloc_move(z, &res->msgs[i]->dn);
                /*
                 * Ignore the RootDNSServers zone and zones that we don't support yet
                 * RootDNSServers should never be returned (Windows DNS server don't)
                 * ..TrustAnchors should never be returned as is, (Windows returns
                 * TrustAnchors) and for the moment we don't support DNSSEC so we'd better
                 * not return this zone.
                 */
                if ((strcmp(z->name, "RootDNSServers") == 0) ||
                    (strcmp(z->name, "..TrustAnchors") == 0))
                {
                        DEBUG(10, ("Ignoring zone %s\n", z->name));
                        talloc_free(z);
                        continue;
                }
                DLIST_ADD_END(new_list, z);
        }

        *zones_ret = new_list;
        TALLOC_FREE(frame);
        result = NT_STATUS_OK;
exit:
        DNS_COMMON_LOG_OPERATION(
                nt_errstr(result),
                &start,
                NULL,
                base_dn == NULL ? NULL : ldb_dn_get_linearized(base_dn),
                NULL);
        return result;
}

/*
  see if two DNS names are the same
 */
bool samba_dns_name_equal(const char *name1, const char *name2)
{
        size_t len1 = strlen(name1);
        size_t len2 = strlen(name2);

        if (len1 > 0 && name1[len1 - 1] == '.') {
                len1--;
        }
        if (len2 > 0 && name2[len2 - 1] == '.') {
                len2--;
        }
        if (len1 != len2) {
                return false;
        }
        return strncasecmp(name1, name2, len1) == 0;
}


/*
 * Convert unix time to a DNS timestamp
 * uint32 hours in the NTTIME epoch
 *
 * This uses unix_to_nt_time() which can return special flag NTTIMEs like
 * UINT64_MAX (0xFFF...) or NTTIME_MAX (0x7FF...), which will convert to
 * distant future timestamps; or 0 as a flag value, meaning a 1601 timestamp,
 * which is used to indicate a record does not expire.
 *
 * As we don't generally check for these special values in NTTIME conversions,
 * we also don't check here, but for the benefit of people encountering these
 * timestamps and searching for their origin, here is a list:
 *
 **  TIME_T_MAX
 *
 * Even if time_t is 32 bit, this will become NTTIME_MAX (a.k.a INT64_MAX,
 * 0x7fffffffffffffff) in 100ns units. That translates to 256204778 hours
 * since 1601, which converts back to 9223372008000000000 or
 * 0x7ffffff9481f1000. It will present as 30828-09-14 02:00:00, around 48
 * minutes earlier than NTTIME_MAX.
 *
 **  0, the start of the unix epoch, 1970-01-01 00:00:00
 *
 * This is converted into 0 in the Windows epoch, 1601-01-01 00:00:00 which is
 * clearly the same whether you count in 100ns units or hours. In DNS record
 * timestamps this is a flag meaning the record will never expire.
 *
 **  (time_t)-1, such as what *might* mean 1969-12-31 23:59:59
 *
 * This becomes (NTTIME)-1ULL a.k.a. UINT64_MAX, 0xffffffffffffffff thence
 * 512409557 in hours since 1601. That in turn is 0xfffffffaf2028800 or
 * 18446744052000000000 in NTTIME (rounded to the hour), which might be
 * presented as -21709551616 or -0x50dfd7800, because NTITME is not completely
 * dedicated to being unsigned. If it gets shown as a year, it will be around
 * 60055.
 *
 **  Other negative time_t values (e.g. 1969-05-29).
 *
 * The meaning of these is somewhat undefined, but in any case they will
 * translate perfectly well into the same dates in NTTIME.
 *
 **  Notes
 *
 * There are dns timestamps that exceed the range of NTTIME (up to 488356 AD),
 * but it is not possible for this function to produce them.
 *
 * It is plausible that it was at midnight on 1601-01-01, in London, that
 * Shakespeare wrote:
 *
 *  The time is out of joint. O cursed spite
 *  That ever I was born to set it right!
 *
 * and this is why we have this epoch and time zone.
 */
uint32_t unix_to_dns_timestamp(time_t t)
{
        NTTIME nt;
        unix_to_nt_time(&nt, t);
        nt /= NTTIME_TO_HOURS;
        return (uint32_t) nt;
}

/*
 * Convert a DNS timestamp into NTTIME.
 *
 * Because DNS timestamps cover a longer time period than NTTIME, and these
 * would wrap to an arbitrary NTTIME, we saturate at NTTIME_MAX and return an
 * error in this case.
 */
NTSTATUS dns_timestamp_to_nt_time(NTTIME *_nt, uint32_t t)
{
        NTTIME nt = t;
        if (nt > NTTIME_MAX / NTTIME_TO_HOURS) {
                *_nt = NTTIME_MAX;
                return NT_STATUS_INTEGER_OVERFLOW;
        }
        *_nt = nt * NTTIME_TO_HOURS;
        return NT_STATUS_OK;
}