Adding upstream version 1:9.16.44.upstream/1%9.16.44upstream

Signed-off-by: Daniel Baumann <daniel.baumann@progress-linux.org>

1 files changed, 1005 insertions, 0 deletions

diff --git a/lib/dns/rdataslab.c b/lib/dns/rdataslab.c
new file mode 100644
index 0000000..2783c1c
--- /dev/null
+++ b/lib/dns/rdataslab.c
@@ -0,0 +1,1005 @@
+/*
+ * Copyright (C) Internet Systems Consortium, Inc. ("ISC")
+ *
+ * SPDX-License-Identifier: MPL-2.0
+ *
+ * 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 https://mozilla.org/MPL/2.0/.
+ *
+ * See the COPYRIGHT file distributed with this work for additional
+ * information regarding copyright ownership.
+ */
+
+/*! \file */
+
+#include <stdbool.h>
+#include <stdlib.h>
+
+#include <isc/mem.h>
+#include <isc/region.h>
+#include <isc/string.h> /* Required for HP/UX (and others?) */
+#include <isc/util.h>
+
+#include <dns/rdata.h>
+#include <dns/rdataset.h>
+#include <dns/rdataslab.h>
+#include <dns/result.h>
+
+/*
+ * The rdataslab structure allows iteration to occur in both load order
+ * and DNSSEC order.  The structure is as follows:
+ *
+ *	header		(reservelen bytes)
+ *	record count	(2 bytes)
+ *	offset table	(4 x record count bytes in load order)
+ *	data records
+ *		data length	(2 bytes)
+ *		order		(2 bytes)
+ *		meta data	(1 byte for RRSIG's)
+ *		data		(data length bytes)
+ *
+ * If DNS_RDATASET_FIXED is defined to be zero (0) the format of a
+ * rdataslab is as follows:
+ *
+ *	header		(reservelen bytes)
+ *	record count	(2 bytes)
+ *	data records
+ *		data length	(2 bytes)
+ *		meta data	(1 byte for RRSIG's)
+ *		data		(data length bytes)
+ *
+ * Offsets are from the end of the header.
+ *
+ * Load order traversal is performed by walking the offset table to find
+ * the start of the record (DNS_RDATASET_FIXED = 1).
+ *
+ * DNSSEC order traversal is performed by walking the data records.
+ *
+ * The order is stored with record to allow for efficient reconstruction
+ * of the offset table following a merge or subtraction.
+ *
+ * The iterator methods in rbtdb support both load order and DNSSEC order
+ * iteration.
+ *
+ * WARNING:
+ *	rbtdb.c directly interacts with the slab's raw structures.  If the
+ *	structure changes then rbtdb.c also needs to be updated to reflect
+ *	the changes.  See the areas tagged with "RDATASLAB".
+ */
+
+struct xrdata {
+	dns_rdata_t rdata;
+	unsigned int order;
+};
+
+/*% Note: the "const void *" are just to make qsort happy.  */
+static int
+compare_rdata(const void *p1, const void *p2) {
+	const struct xrdata *x1 = p1;
+	const struct xrdata *x2 = p2;
+	return (dns_rdata_compare(&x1->rdata, &x2->rdata));
+}
+
+#if DNS_RDATASET_FIXED
+static void
+fillin_offsets(unsigned char *offsetbase, unsigned int *offsettable,
+	       unsigned length) {
+	unsigned int i, j;
+	unsigned char *raw;
+
+	for (i = 0, j = 0; i < length; i++) {
+		if (offsettable[i] == 0) {
+			continue;
+		}
+
+		/*
+		 * Fill in offset table.
+		 */
+		raw = &offsetbase[j * 4 + 2];
+		*raw++ = (offsettable[i] & 0xff000000) >> 24;
+		*raw++ = (offsettable[i] & 0xff0000) >> 16;
+		*raw++ = (offsettable[i] & 0xff00) >> 8;
+		*raw = offsettable[i] & 0xff;
+
+		/*
+		 * Fill in table index.
+		 */
+		raw = offsetbase + offsettable[i] + 2;
+		*raw++ = (j & 0xff00) >> 8;
+		*raw = j++ & 0xff;
+	}
+}
+#endif /* if DNS_RDATASET_FIXED */
+
+isc_result_t
+dns_rdataslab_fromrdataset(dns_rdataset_t *rdataset, isc_mem_t *mctx,
+			   isc_region_t *region, unsigned int reservelen) {
+	/*
+	 * Use &removed as a sentinel pointer for duplicate
+	 * rdata as rdata.data == NULL is valid.
+	 */
+	static unsigned char removed;
+	struct xrdata *x;
+	unsigned char *rawbuf;
+#if DNS_RDATASET_FIXED
+	unsigned char *offsetbase;
+#endif /* if DNS_RDATASET_FIXED */
+	unsigned int buflen;
+	isc_result_t result;
+	unsigned int nitems;
+	unsigned int nalloc;
+	unsigned int i;
+#if DNS_RDATASET_FIXED
+	unsigned int *offsettable;
+#endif /* if DNS_RDATASET_FIXED */
+	unsigned int length;
+
+	buflen = reservelen + 2;
+
+	nitems = dns_rdataset_count(rdataset);
+
+	/*
+	 * If there are no rdata then we can just need to allocate a header
+	 * with zero a record count.
+	 */
+	if (nitems == 0) {
+		if (rdataset->type != 0) {
+			return (ISC_R_FAILURE);
+		}
+		rawbuf = isc_mem_get(mctx, buflen);
+		region->base = rawbuf;
+		region->length = buflen;
+		rawbuf += reservelen;
+		*rawbuf++ = 0;
+		*rawbuf = 0;
+		return (ISC_R_SUCCESS);
+	}
+
+	if (nitems > 0xffff) {
+		return (ISC_R_NOSPACE);
+	}
+
+	/*
+	 * Remember the original number of items.
+	 */
+	nalloc = nitems;
+	x = isc_mem_get(mctx, nalloc * sizeof(struct xrdata));
+
+	/*
+	 * Save all of the rdata members into an array.
+	 */
+	result = dns_rdataset_first(rdataset);
+	if (result != ISC_R_SUCCESS && result != ISC_R_NOMORE) {
+		goto free_rdatas;
+	}
+	for (i = 0; i < nalloc && result == ISC_R_SUCCESS; i++) {
+		INSIST(result == ISC_R_SUCCESS);
+		dns_rdata_init(&x[i].rdata);
+		dns_rdataset_current(rdataset, &x[i].rdata);
+		INSIST(x[i].rdata.data != &removed);
+#if DNS_RDATASET_FIXED
+		x[i].order = i;
+#endif /* if DNS_RDATASET_FIXED */
+		result = dns_rdataset_next(rdataset);
+	}
+	if (i != nalloc || result != ISC_R_NOMORE) {
+		/*
+		 * Somehow we iterated over fewer rdatas than
+		 * dns_rdataset_count() said there were or there
+		 * were more items than dns_rdataset_count said
+		 * there were.
+		 */
+		result = ISC_R_FAILURE;
+		goto free_rdatas;
+	}
+
+	/*
+	 * Put into DNSSEC order.
+	 */
+	if (nalloc > 1U) {
+		qsort(x, nalloc, sizeof(struct xrdata), compare_rdata);
+	}
+
+	/*
+	 * Remove duplicates and compute the total storage required.
+	 *
+	 * If an rdata is not a duplicate, accumulate the storage size
+	 * required for the rdata.  We do not store the class, type, etc,
+	 * just the rdata, so our overhead is 2 bytes for the number of
+	 * records, and 8 for each rdata, (length(2), offset(4) and order(2))
+	 * and then the rdata itself.
+	 */
+	for (i = 1; i < nalloc; i++) {
+		if (compare_rdata(&x[i - 1].rdata, &x[i].rdata) == 0) {
+			x[i - 1].rdata.data = &removed;
+#if DNS_RDATASET_FIXED
+			/*
+			 * Preserve the least order so A, B, A -> A, B
+			 * after duplicate removal.
+			 */
+			if (x[i - 1].order < x[i].order) {
+				x[i].order = x[i - 1].order;
+			}
+#endif /* if DNS_RDATASET_FIXED */
+			nitems--;
+		} else {
+#if DNS_RDATASET_FIXED
+			buflen += (8 + x[i - 1].rdata.length);
+#else  /* if DNS_RDATASET_FIXED */
+			buflen += (2 + x[i - 1].rdata.length);
+#endif /* if DNS_RDATASET_FIXED */
+			/*
+			 * Provide space to store the per RR meta data.
+			 */
+			if (rdataset->type == dns_rdatatype_rrsig) {
+				buflen++;
+			}
+		}
+	}
+
+	/*
+	 * Don't forget the last item!
+	 */
+#if DNS_RDATASET_FIXED
+	buflen += (8 + x[i - 1].rdata.length);
+#else  /* if DNS_RDATASET_FIXED */
+	buflen += (2 + x[i - 1].rdata.length);
+#endif /* if DNS_RDATASET_FIXED */
+	/*
+	 * Provide space to store the per RR meta data.
+	 */
+	if (rdataset->type == dns_rdatatype_rrsig) {
+		buflen++;
+	}
+
+	/*
+	 * Ensure that singleton types are actually singletons.
+	 */
+	if (nitems > 1 && dns_rdatatype_issingleton(rdataset->type)) {
+		/*
+		 * We have a singleton type, but there's more than one
+		 * RR in the rdataset.
+		 */
+		result = DNS_R_SINGLETON;
+		goto free_rdatas;
+	}
+
+	/*
+	 * Allocate the memory, set up a buffer, start copying in
+	 * data.
+	 */
+	rawbuf = isc_mem_get(mctx, buflen);
+
+#if DNS_RDATASET_FIXED
+	/* Allocate temporary offset table. */
+	offsettable = isc_mem_get(mctx, nalloc * sizeof(unsigned int));
+	memset(offsettable, 0, nalloc * sizeof(unsigned int));
+#endif /* if DNS_RDATASET_FIXED */
+
+	region->base = rawbuf;
+	region->length = buflen;
+
+	memset(rawbuf, 0, buflen);
+	rawbuf += reservelen;
+
+#if DNS_RDATASET_FIXED
+	offsetbase = rawbuf;
+#endif /* if DNS_RDATASET_FIXED */
+
+	*rawbuf++ = (nitems & 0xff00) >> 8;
+	*rawbuf++ = (nitems & 0x00ff);
+
+#if DNS_RDATASET_FIXED
+	/* Skip load order table.  Filled in later. */
+	rawbuf += nitems * 4;
+#endif /* if DNS_RDATASET_FIXED */
+
+	for (i = 0; i < nalloc; i++) {
+		if (x[i].rdata.data == &removed) {
+			continue;
+		}
+#if DNS_RDATASET_FIXED
+		offsettable[x[i].order] = rawbuf - offsetbase;
+#endif /* if DNS_RDATASET_FIXED */
+		length = x[i].rdata.length;
+		if (rdataset->type == dns_rdatatype_rrsig) {
+			length++;
+		}
+		INSIST(length <= 0xffff);
+		*rawbuf++ = (length & 0xff00) >> 8;
+		*rawbuf++ = (length & 0x00ff);
+#if DNS_RDATASET_FIXED
+		rawbuf += 2; /* filled in later */
+#endif			     /* if DNS_RDATASET_FIXED */
+		/*
+		 * Store the per RR meta data.
+		 */
+		if (rdataset->type == dns_rdatatype_rrsig) {
+			*rawbuf++ = (x[i].rdata.flags & DNS_RDATA_OFFLINE)
+					    ? DNS_RDATASLAB_OFFLINE
+					    : 0;
+		}
+		memmove(rawbuf, x[i].rdata.data, x[i].rdata.length);
+		rawbuf += x[i].rdata.length;
+	}
+
+#if DNS_RDATASET_FIXED
+	fillin_offsets(offsetbase, offsettable, nalloc);
+	isc_mem_put(mctx, offsettable, nalloc * sizeof(unsigned int));
+#endif /* if DNS_RDATASET_FIXED */
+
+	result = ISC_R_SUCCESS;
+
+free_rdatas:
+	isc_mem_put(mctx, x, nalloc * sizeof(struct xrdata));
+	return (result);
+}
+
+unsigned int
+dns_rdataslab_size(unsigned char *slab, unsigned int reservelen) {
+	unsigned int count, length;
+	unsigned char *current;
+
+	REQUIRE(slab != NULL);
+
+	current = slab + reservelen;
+	count = *current++ * 256;
+	count += *current++;
+#if DNS_RDATASET_FIXED
+	current += (4 * count);
+#endif /* if DNS_RDATASET_FIXED */
+	while (count > 0) {
+		count--;
+		length = *current++ * 256;
+		length += *current++;
+#if DNS_RDATASET_FIXED
+		current += length + 2;
+#else  /* if DNS_RDATASET_FIXED */
+		current += length;
+#endif /* if DNS_RDATASET_FIXED */
+	}
+
+	return ((unsigned int)(current - slab));
+}
+
+unsigned int
+dns_rdataslab_rdatasize(unsigned char *slab, unsigned int reservelen) {
+	unsigned int count, length, rdatalen = 0;
+	unsigned char *current;
+
+	REQUIRE(slab != NULL);
+
+	current = slab + reservelen;
+	count = *current++ * 256;
+	count += *current++;
+#if DNS_RDATASET_FIXED
+	current += (4 * count);
+#endif /* if DNS_RDATASET_FIXED */
+	while (count > 0) {
+		count--;
+		length = *current++ * 256;
+		length += *current++;
+		rdatalen += length;
+#if DNS_RDATASET_FIXED
+		current += length + 2;
+#else  /* if DNS_RDATASET_FIXED */
+		current += length;
+#endif /* if DNS_RDATASET_FIXED */
+	}
+
+	return (rdatalen);
+}
+
+unsigned int
+dns_rdataslab_count(unsigned char *slab, unsigned int reservelen) {
+	unsigned int count;
+	unsigned char *current;
+
+	REQUIRE(slab != NULL);
+
+	current = slab + reservelen;
+	count = *current++ * 256;
+	count += *current++;
+	return (count);
+}
+
+/*
+ * Make the dns_rdata_t 'rdata' refer to the slab item
+ * beginning at '*current', which is part of a slab of type
+ * 'type' and class 'rdclass', and advance '*current' to
+ * point to the next item in the slab.
+ */
+static void
+rdata_from_slab(unsigned char **current, dns_rdataclass_t rdclass,
+		dns_rdatatype_t type, dns_rdata_t *rdata) {
+	unsigned char *tcurrent = *current;
+	isc_region_t region;
+	unsigned int length;
+	bool offline = false;
+
+	length = *tcurrent++ * 256;
+	length += *tcurrent++;
+
+	if (type == dns_rdatatype_rrsig) {
+		if ((*tcurrent & DNS_RDATASLAB_OFFLINE) != 0) {
+			offline = true;
+		}
+		length--;
+		tcurrent++;
+	}
+	region.length = length;
+#if DNS_RDATASET_FIXED
+	tcurrent += 2;
+#endif /* if DNS_RDATASET_FIXED */
+	region.base = tcurrent;
+	tcurrent += region.length;
+	dns_rdata_fromregion(rdata, rdclass, type, &region);
+	if (offline) {
+		rdata->flags |= DNS_RDATA_OFFLINE;
+	}
+	*current = tcurrent;
+}
+
+/*
+ * Return true iff 'slab' (slab data of type 'type' and class 'rdclass')
+ * contains an rdata identical to 'rdata'.  This does case insensitive
+ * comparisons per DNSSEC.
+ */
+static bool
+rdata_in_slab(unsigned char *slab, unsigned int reservelen,
+	      dns_rdataclass_t rdclass, dns_rdatatype_t type,
+	      dns_rdata_t *rdata) {
+	unsigned int count, i;
+	unsigned char *current;
+	dns_rdata_t trdata = DNS_RDATA_INIT;
+	int n;
+
+	current = slab + reservelen;
+	count = *current++ * 256;
+	count += *current++;
+
+#if DNS_RDATASET_FIXED
+	current += (4 * count);
+#endif /* if DNS_RDATASET_FIXED */
+
+	for (i = 0; i < count; i++) {
+		rdata_from_slab(&current, rdclass, type, &trdata);
+
+		n = dns_rdata_compare(&trdata, rdata);
+		if (n == 0) {
+			return (true);
+		}
+		if (n > 0) { /* In DNSSEC order. */
+			break;
+		}
+		dns_rdata_reset(&trdata);
+	}
+	return (false);
+}
+
+isc_result_t
+dns_rdataslab_merge(unsigned char *oslab, unsigned char *nslab,
+		    unsigned int reservelen, isc_mem_t *mctx,
+		    dns_rdataclass_t rdclass, dns_rdatatype_t type,
+		    unsigned int flags, unsigned char **tslabp) {
+	unsigned char *ocurrent, *ostart, *ncurrent, *tstart, *tcurrent, *data;
+	unsigned int ocount, ncount, count, olength, tlength, tcount, length;
+	dns_rdata_t ordata = DNS_RDATA_INIT;
+	dns_rdata_t nrdata = DNS_RDATA_INIT;
+	bool added_something = false;
+	unsigned int oadded = 0;
+	unsigned int nadded = 0;
+	unsigned int nncount = 0;
+#if DNS_RDATASET_FIXED
+	unsigned int oncount;
+	unsigned int norder = 0;
+	unsigned int oorder = 0;
+	unsigned char *offsetbase;
+	unsigned int *offsettable;
+#endif /* if DNS_RDATASET_FIXED */
+
+	/*
+	 * XXX  Need parameter to allow "delete rdatasets in nslab" merge,
+	 * or perhaps another merge routine for this purpose.
+	 */
+
+	REQUIRE(tslabp != NULL && *tslabp == NULL);
+	REQUIRE(oslab != NULL && nslab != NULL);
+
+	ocurrent = oslab + reservelen;
+	ocount = *ocurrent++ * 256;
+	ocount += *ocurrent++;
+#if DNS_RDATASET_FIXED
+	ocurrent += (4 * ocount);
+#endif /* if DNS_RDATASET_FIXED */
+	ostart = ocurrent;
+	ncurrent = nslab + reservelen;
+	ncount = *ncurrent++ * 256;
+	ncount += *ncurrent++;
+#if DNS_RDATASET_FIXED
+	ncurrent += (4 * ncount);
+#endif /* if DNS_RDATASET_FIXED */
+	INSIST(ocount > 0 && ncount > 0);
+
+#if DNS_RDATASET_FIXED
+	oncount = ncount;
+#endif /* if DNS_RDATASET_FIXED */
+
+	/*
+	 * Yes, this is inefficient!
+	 */
+
+	/*
+	 * Figure out the length of the old slab's data.
+	 */
+	olength = 0;
+	for (count = 0; count < ocount; count++) {
+		length = *ocurrent++ * 256;
+		length += *ocurrent++;
+#if DNS_RDATASET_FIXED
+		olength += length + 8;
+		ocurrent += length + 2;
+#else  /* if DNS_RDATASET_FIXED */
+		olength += length + 2;
+		ocurrent += length;
+#endif /* if DNS_RDATASET_FIXED */
+	}
+
+	/*
+	 * Start figuring out the target length and count.
+	 */
+	tlength = reservelen + 2 + olength;
+	tcount = ocount;
+
+	/*
+	 * Add in the length of rdata in the new slab that aren't in
+	 * the old slab.
+	 */
+	do {
+		dns_rdata_init(&nrdata);
+		rdata_from_slab(&ncurrent, rdclass, type, &nrdata);
+		if (!rdata_in_slab(oslab, reservelen, rdclass, type, &nrdata)) {
+			/*
+			 * This rdata isn't in the old slab.
+			 */
+#if DNS_RDATASET_FIXED
+			tlength += nrdata.length + 8;
+#else  /* if DNS_RDATASET_FIXED */
+			tlength += nrdata.length + 2;
+#endif /* if DNS_RDATASET_FIXED */
+			if (type == dns_rdatatype_rrsig) {
+				tlength++;
+			}
+			tcount++;
+			nncount++;
+			added_something = true;
+		}
+		ncount--;
+	} while (ncount > 0);
+	ncount = nncount;
+
+	if (((flags & DNS_RDATASLAB_EXACT) != 0) && (tcount != ncount + ocount))
+	{
+		return (DNS_R_NOTEXACT);
+	}
+
+	if (!added_something && (flags & DNS_RDATASLAB_FORCE) == 0) {
+		return (DNS_R_UNCHANGED);
+	}
+
+	/*
+	 * Ensure that singleton types are actually singletons.
+	 */
+	if (tcount > 1 && dns_rdatatype_issingleton(type)) {
+		/*
+		 * We have a singleton type, but there's more than one
+		 * RR in the rdataset.
+		 */
+		return (DNS_R_SINGLETON);
+	}
+
+	if (tcount > 0xffff) {
+		return (ISC_R_NOSPACE);
+	}
+
+	/*
+	 * Copy the reserved area from the new slab.
+	 */
+	tstart = isc_mem_get(mctx, tlength);
+	memmove(tstart, nslab, reservelen);
+	tcurrent = tstart + reservelen;
+#if DNS_RDATASET_FIXED
+	offsetbase = tcurrent;
+#endif /* if DNS_RDATASET_FIXED */
+
+	/*
+	 * Write the new count.
+	 */
+	*tcurrent++ = (tcount & 0xff00) >> 8;
+	*tcurrent++ = (tcount & 0x00ff);
+
+#if DNS_RDATASET_FIXED
+	/*
+	 * Skip offset table.
+	 */
+	tcurrent += (tcount * 4);
+
+	offsettable = isc_mem_get(mctx,
+				  (ocount + oncount) * sizeof(unsigned int));
+	memset(offsettable, 0, (ocount + oncount) * sizeof(unsigned int));
+#endif /* if DNS_RDATASET_FIXED */
+
+	/*
+	 * Merge the two slabs.
+	 */
+	ocurrent = ostart;
+	INSIST(ocount != 0);
+#if DNS_RDATASET_FIXED
+	oorder = ocurrent[2] * 256 + ocurrent[3];
+	INSIST(oorder < ocount);
+#endif /* if DNS_RDATASET_FIXED */
+	rdata_from_slab(&ocurrent, rdclass, type, &ordata);
+
+	ncurrent = nslab + reservelen + 2;
+#if DNS_RDATASET_FIXED
+	ncurrent += (4 * oncount);
+#endif /* if DNS_RDATASET_FIXED */
+
+	if (ncount > 0) {
+		do {
+			dns_rdata_reset(&nrdata);
+#if DNS_RDATASET_FIXED
+			norder = ncurrent[2] * 256 + ncurrent[3];
+
+			INSIST(norder < oncount);
+#endif /* if DNS_RDATASET_FIXED */
+			rdata_from_slab(&ncurrent, rdclass, type, &nrdata);
+		} while (rdata_in_slab(oslab, reservelen, rdclass, type,
+				       &nrdata));
+	}
+
+	while (oadded < ocount || nadded < ncount) {
+		bool fromold;
+		if (oadded == ocount) {
+			fromold = false;
+		} else if (nadded == ncount) {
+			fromold = true;
+		} else {
+			fromold = (dns_rdata_compare(&ordata, &nrdata) < 0);
+		}
+		if (fromold) {
+#if DNS_RDATASET_FIXED
+			offsettable[oorder] = tcurrent - offsetbase;
+#endif /* if DNS_RDATASET_FIXED */
+			length = ordata.length;
+			data = ordata.data;
+			if (type == dns_rdatatype_rrsig) {
+				length++;
+				data--;
+			}
+			*tcurrent++ = (length & 0xff00) >> 8;
+			*tcurrent++ = (length & 0x00ff);
+#if DNS_RDATASET_FIXED
+			tcurrent += 2; /* fill in later */
+#endif				       /* if DNS_RDATASET_FIXED */
+			memmove(tcurrent, data, length);
+			tcurrent += length;
+			oadded++;
+			if (oadded < ocount) {
+				dns_rdata_reset(&ordata);
+#if DNS_RDATASET_FIXED
+				oorder = ocurrent[2] * 256 + ocurrent[3];
+				INSIST(oorder < ocount);
+#endif /* if DNS_RDATASET_FIXED */
+				rdata_from_slab(&ocurrent, rdclass, type,
+						&ordata);
+			}
+		} else {
+#if DNS_RDATASET_FIXED
+			offsettable[ocount + norder] = tcurrent - offsetbase;
+#endif /* if DNS_RDATASET_FIXED */
+			length = nrdata.length;
+			data = nrdata.data;
+			if (type == dns_rdatatype_rrsig) {
+				length++;
+				data--;
+			}
+			*tcurrent++ = (length & 0xff00) >> 8;
+			*tcurrent++ = (length & 0x00ff);
+#if DNS_RDATASET_FIXED
+			tcurrent += 2; /* fill in later */
+#endif				       /* if DNS_RDATASET_FIXED */
+			memmove(tcurrent, data, length);
+			tcurrent += length;
+			nadded++;
+			if (nadded < ncount) {
+				do {
+					dns_rdata_reset(&nrdata);
+#if DNS_RDATASET_FIXED
+					norder = ncurrent[2] * 256 +
+						 ncurrent[3];
+					INSIST(norder < oncount);
+#endif /* if DNS_RDATASET_FIXED */
+					rdata_from_slab(&ncurrent, rdclass,
+							type, &nrdata);
+				} while (rdata_in_slab(oslab, reservelen,
+						       rdclass, type, &nrdata));
+			}
+		}
+	}
+
+#if DNS_RDATASET_FIXED
+	fillin_offsets(offsetbase, offsettable, ocount + oncount);
+
+	isc_mem_put(mctx, offsettable,
+		    (ocount + oncount) * sizeof(unsigned int));
+#endif /* if DNS_RDATASET_FIXED */
+
+	INSIST(tcurrent == tstart + tlength);
+
+	*tslabp = tstart;
+
+	return (ISC_R_SUCCESS);
+}
+
+isc_result_t
+dns_rdataslab_subtract(unsigned char *mslab, unsigned char *sslab,
+		       unsigned int reservelen, isc_mem_t *mctx,
+		       dns_rdataclass_t rdclass, dns_rdatatype_t type,
+		       unsigned int flags, unsigned char **tslabp) {
+	unsigned char *mcurrent, *sstart, *scurrent, *tstart, *tcurrent;
+	unsigned int mcount, scount, rcount, count, tlength, tcount, i;
+	dns_rdata_t srdata = DNS_RDATA_INIT;
+	dns_rdata_t mrdata = DNS_RDATA_INIT;
+#if DNS_RDATASET_FIXED
+	unsigned char *offsetbase;
+	unsigned int *offsettable;
+	unsigned int order;
+#endif /* if DNS_RDATASET_FIXED */
+
+	REQUIRE(tslabp != NULL && *tslabp == NULL);
+	REQUIRE(mslab != NULL && sslab != NULL);
+
+	mcurrent = mslab + reservelen;
+	mcount = *mcurrent++ * 256;
+	mcount += *mcurrent++;
+	scurrent = sslab + reservelen;
+	scount = *scurrent++ * 256;
+	scount += *scurrent++;
+	INSIST(mcount > 0 && scount > 0);
+
+	/*
+	 * Yes, this is inefficient!
+	 */
+
+	/*
+	 * Start figuring out the target length and count.
+	 */
+	tlength = reservelen + 2;
+	tcount = 0;
+	rcount = 0;
+
+#if DNS_RDATASET_FIXED
+	mcurrent += 4 * mcount;
+	scurrent += 4 * scount;
+#endif /* if DNS_RDATASET_FIXED */
+	sstart = scurrent;
+
+	/*
+	 * Add in the length of rdata in the mslab that aren't in
+	 * the sslab.
+	 */
+	for (i = 0; i < mcount; i++) {
+		unsigned char *mrdatabegin = mcurrent;
+		rdata_from_slab(&mcurrent, rdclass, type, &mrdata);
+		scurrent = sstart;
+		for (count = 0; count < scount; count++) {
+			dns_rdata_reset(&srdata);
+			rdata_from_slab(&scurrent, rdclass, type, &srdata);
+			if (dns_rdata_compare(&mrdata, &srdata) == 0) {
+				break;
+			}
+		}
+		if (count == scount) {
+			/*
+			 * This rdata isn't in the sslab, and thus isn't
+			 * being subtracted.
+			 */
+			tlength += (unsigned int)(mcurrent - mrdatabegin);
+			tcount++;
+		} else {
+			rcount++;
+		}
+		dns_rdata_reset(&mrdata);
+	}
+
+#if DNS_RDATASET_FIXED
+	tlength += (4 * tcount);
+#endif /* if DNS_RDATASET_FIXED */
+
+	/*
+	 * Check that all the records originally existed.  The numeric
+	 * check only works as rdataslabs do not contain duplicates.
+	 */
+	if (((flags & DNS_RDATASLAB_EXACT) != 0) && (rcount != scount)) {
+		return (DNS_R_NOTEXACT);
+	}
+
+	/*
+	 * Don't continue if the new rdataslab would be empty.
+	 */
+	if (tcount == 0) {
+		return (DNS_R_NXRRSET);
+	}
+
+	/*
+	 * If nothing is going to change, we can stop.
+	 */
+	if (rcount == 0) {
+		return (DNS_R_UNCHANGED);
+	}
+
+	/*
+	 * Copy the reserved area from the mslab.
+	 */
+	tstart = isc_mem_get(mctx, tlength);
+	memmove(tstart, mslab, reservelen);
+	tcurrent = tstart + reservelen;
+#if DNS_RDATASET_FIXED
+	offsetbase = tcurrent;
+
+	offsettable = isc_mem_get(mctx, mcount * sizeof(unsigned int));
+	memset(offsettable, 0, mcount * sizeof(unsigned int));
+#endif /* if DNS_RDATASET_FIXED */
+
+	/*
+	 * Write the new count.
+	 */
+	*tcurrent++ = (tcount & 0xff00) >> 8;
+	*tcurrent++ = (tcount & 0x00ff);
+
+#if DNS_RDATASET_FIXED
+	tcurrent += (4 * tcount);
+#endif /* if DNS_RDATASET_FIXED */
+
+	/*
+	 * Copy the parts of mslab not in sslab.
+	 */
+	mcurrent = mslab + reservelen;
+	mcount = *mcurrent++ * 256;
+	mcount += *mcurrent++;
+#if DNS_RDATASET_FIXED
+	mcurrent += (4 * mcount);
+#endif /* if DNS_RDATASET_FIXED */
+	for (i = 0; i < mcount; i++) {
+		unsigned char *mrdatabegin = mcurrent;
+#if DNS_RDATASET_FIXED
+		order = mcurrent[2] * 256 + mcurrent[3];
+		INSIST(order < mcount);
+#endif /* if DNS_RDATASET_FIXED */
+		rdata_from_slab(&mcurrent, rdclass, type, &mrdata);
+		scurrent = sstart;
+		for (count = 0; count < scount; count++) {
+			dns_rdata_reset(&srdata);
+			rdata_from_slab(&scurrent, rdclass, type, &srdata);
+			if (dns_rdata_compare(&mrdata, &srdata) == 0) {
+				break;
+			}
+		}
+		if (count == scount) {
+			/*
+			 * This rdata isn't in the sslab, and thus should be
+			 * copied to the tslab.
+			 */
+			unsigned int length;
+			length = (unsigned int)(mcurrent - mrdatabegin);
+#if DNS_RDATASET_FIXED
+			offsettable[order] = tcurrent - offsetbase;
+#endif /* if DNS_RDATASET_FIXED */
+			memmove(tcurrent, mrdatabegin, length);
+			tcurrent += length;
+		}
+		dns_rdata_reset(&mrdata);
+	}
+
+#if DNS_RDATASET_FIXED
+	fillin_offsets(offsetbase, offsettable, mcount);
+
+	isc_mem_put(mctx, offsettable, mcount * sizeof(unsigned int));
+#endif /* if DNS_RDATASET_FIXED */
+
+	INSIST(tcurrent == tstart + tlength);
+
+	*tslabp = tstart;
+
+	return (ISC_R_SUCCESS);
+}
+
+bool
+dns_rdataslab_equal(unsigned char *slab1, unsigned char *slab2,
+		    unsigned int reservelen) {
+	unsigned char *current1, *current2;
+	unsigned int count1, count2;
+	unsigned int length1, length2;
+
+	current1 = slab1 + reservelen;
+	count1 = *current1++ * 256;
+	count1 += *current1++;
+
+	current2 = slab2 + reservelen;
+	count2 = *current2++ * 256;
+	count2 += *current2++;
+
+	if (count1 != count2) {
+		return (false);
+	}
+
+#if DNS_RDATASET_FIXED
+	current1 += (4 * count1);
+	current2 += (4 * count2);
+#endif /* if DNS_RDATASET_FIXED */
+
+	while (count1 > 0) {
+		length1 = *current1++ * 256;
+		length1 += *current1++;
+
+		length2 = *current2++ * 256;
+		length2 += *current2++;
+
+#if DNS_RDATASET_FIXED
+		current1 += 2;
+		current2 += 2;
+#endif /* if DNS_RDATASET_FIXED */
+
+		if (length1 != length2 ||
+		    memcmp(current1, current2, length1) != 0)
+		{
+			return (false);
+		}
+
+		current1 += length1;
+		current2 += length1;
+
+		count1--;
+	}
+	return (true);
+}
+
+bool
+dns_rdataslab_equalx(unsigned char *slab1, unsigned char *slab2,
+		     unsigned int reservelen, dns_rdataclass_t rdclass,
+		     dns_rdatatype_t type) {
+	unsigned char *current1, *current2;
+	unsigned int count1, count2;
+	dns_rdata_t rdata1 = DNS_RDATA_INIT;
+	dns_rdata_t rdata2 = DNS_RDATA_INIT;
+
+	current1 = slab1 + reservelen;
+	count1 = *current1++ * 256;
+	count1 += *current1++;
+
+	current2 = slab2 + reservelen;
+	count2 = *current2++ * 256;
+	count2 += *current2++;
+
+	if (count1 != count2) {
+		return (false);
+	}
+
+#if DNS_RDATASET_FIXED
+	current1 += (4 * count1);
+	current2 += (4 * count2);
+#endif /* if DNS_RDATASET_FIXED */
+
+	while (count1-- > 0) {
+		rdata_from_slab(&current1, rdclass, type, &rdata1);
+		rdata_from_slab(&current2, rdclass, type, &rdata2);
+		if (dns_rdata_compare(&rdata1, &rdata2) != 0) {
+			return (false);
+		}
+		dns_rdata_reset(&rdata1);
+		dns_rdata_reset(&rdata2);
+	}
+	return (true);
+}