clarify dns_rdataslab_fromrdataset()

there are now two functions for creating an rdataslab from an
rdataset: dns_rdataslab_fromrdataset() creates a full slab (including
space for a slab header), and dns_rdataslab_raw_fromrdataset() creates
a raw slab.

lib/dns/include/dns/rdataslab.h

@@ -173,11 +173,17 @@ extern dns_rdatasetmethods_t dns_rdataslab_rdatasetmethods;
 
 isc_result_t
 dns_rdataslab_fromrdataset(dns_rdataset_t *rdataset, isc_mem_t *mctx,
-			   isc_region_t *region, unsigned int reservelen,
-			   uint32_t limit);
+			   isc_region_t *region, uint32_t limit);
+isc_result_t
+dns_rdataslab_raw_fromrdataset(dns_rdataset_t *rdataset, isc_mem_t *mctx,
+			       isc_region_t *region, uint32_t limit);
 /*%<
- * Slabify a rdataset.  The slab area will be allocated and returned
- * in 'region'.
+ * Allocate space for a slab to hold the data in rdataset, and copy the
+ * data into it.  The resulting slab will be returned in 'region'.
+ *
+ * The dns_rdataslab_raw_fromrdataset() function allocates and fills only
+ * the memory needed for a raw slab. dns_rdataslab_fromrdataset() also
+ * allocates space for a dns_slabheader object.
  *
  * Requires:
  *\li	'rdataset' is valid.

lib/dns/qpcache.c

@@ -3090,12 +3090,13 @@ addnoqname(isc_mem_t *mctx, dns_slabheader_t *newheader, uint32_t maxrrperset,
 	result = dns_rdataset_getnoqname(rdataset, &name, &neg, &negsig);
 	RUNTIME_CHECK(result == ISC_R_SUCCESS);
 
-	result = dns_rdataslab_fromrdataset(&neg, mctx, &r1, 0, maxrrperset);
+	result = dns_rdataslab_raw_fromrdataset(&neg, mctx, &r1, maxrrperset);
 	if (result != ISC_R_SUCCESS) {
 		goto cleanup;
 	}
 
-	result = dns_rdataslab_fromrdataset(&negsig, mctx, &r2, 0, maxrrperset);
+	result = dns_rdataslab_raw_fromrdataset(&negsig, mctx, &r2,
+						maxrrperset);
 	if (result != ISC_R_SUCCESS) {
 		goto cleanup;
 	}
@@ -3129,12 +3130,13 @@ addclosest(isc_mem_t *mctx, dns_slabheader_t *newheader, uint32_t maxrrperset,
 	result = dns_rdataset_getclosest(rdataset, &name, &neg, &negsig);
 	RUNTIME_CHECK(result == ISC_R_SUCCESS);
 
-	result = dns_rdataslab_fromrdataset(&neg, mctx, &r1, 0, maxrrperset);
+	result = dns_rdataslab_raw_fromrdataset(&neg, mctx, &r1, maxrrperset);
 	if (result != ISC_R_SUCCESS) {
 		goto cleanup;
 	}
 
-	result = dns_rdataslab_fromrdataset(&negsig, mctx, &r2, 0, maxrrperset);
+	result = dns_rdataslab_raw_fromrdataset(&negsig, mctx, &r2,
+						maxrrperset);
 	if (result != ISC_R_SUCCESS) {
 		goto cleanup;
 	}
@@ -3184,8 +3186,7 @@ qpcache_addrdataset(dns_db_t *db, dns_dbnode_t *node, dns_dbversion_t *version,
 	REQUIRE(version == NULL);
 
 	result = dns_rdataslab_fromrdataset(rdataset, qpdb->common.mctx,
-					    &region, sizeof(dns_slabheader_t),
-					    qpdb->maxrrperset);
+					    &region, qpdb->maxrrperset);
 	if (result != ISC_R_SUCCESS) {
 		if (result == DNS_R_TOOMANYRECORDS) {
 			dns__db_logtoomanyrecords((dns_db_t *)qpdb,

lib/dns/qpzone.c

@@ -2241,8 +2241,7 @@ loading_addrdataset(void *arg, const dns_name_t *name,
 
 	loading_addnode(loadctx, name, rdataset->type, rdataset->covers, &node);
 	result = dns_rdataslab_fromrdataset(rdataset, qpdb->common.mctx,
-					    &region, sizeof(dns_slabheader_t),
-					    qpdb->maxrrperset);
+					    &region, qpdb->maxrrperset);
 	if (result != ISC_R_SUCCESS) {
 		if (result == DNS_R_TOOMANYRECORDS) {
 			dns__db_logtoomanyrecords((dns_db_t *)qpdb, name,
@@ -4724,8 +4723,7 @@ qpzone_addrdataset(dns_db_t *db, dns_dbnode_t *dbnode,
 		 rdataset->covers != dns_rdatatype_nsec3));
 
 	result = dns_rdataslab_fromrdataset(rdataset, qpdb->common.mctx,
-					    &region, sizeof(dns_slabheader_t),
-					    qpdb->maxrrperset);
+					    &region, qpdb->maxrrperset);
 	if (result != ISC_R_SUCCESS) {
 		if (result == DNS_R_TOOMANYRECORDS) {
 			dns__db_logtoomanyrecords((dns_db_t *)qpdb, &node->name,
@@ -4854,8 +4852,7 @@ qpzone_subtractrdataset(dns_db_t *db, dns_dbnode_t *dbnode,
 
 	dns_name_copy(&node->name, nodename);
 	result = dns_rdataslab_fromrdataset(rdataset, qpdb->common.mctx,
-					    &region, sizeof(dns_slabheader_t),
-					    0);
+					    &region, 0);
 	if (result != ISC_R_SUCCESS) {
 		return result;
 	}

lib/dns/rdataslab.c

@@ -47,7 +47,7 @@
  * The rdataslab structure allows iteration to occur in both load order
  * and DNSSEC order.  The structure is as follows:
  *
- *	header		(reservelen bytes)
+ *	header		(dns_slabheader_t)
  *	record count	(2 bytes)
  *	offset table	(4 x record count bytes in load order)
  *	data records
@@ -56,6 +56,8 @@
  *		meta data	(1 byte for RRSIG's)
  *		data		(data length bytes)
  *
+ * A "raw" rdataslab is the same but without the header.
+ *
  * DNSSEC order traversal is performed by walking the data records.
  *
  * The order is stored with record to allow for efficient reconstruction
@@ -118,10 +120,9 @@ compare_rdata(const void *p1, const void *p2) {
 	return dns_rdata_compare(p1, p2);
 }
 
-isc_result_t
-dns_rdataslab_fromrdataset(dns_rdataset_t *rdataset, isc_mem_t *mctx,
-			   isc_region_t *region, unsigned int reservelen,
-			   uint32_t maxrrperset) {
+static isc_result_t
+makeslab(dns_rdataset_t *rdataset, isc_mem_t *mctx, isc_region_t *region,
+	 uint32_t maxrrperset, bool raw) {
 	/*
 	 * Use &removed as a sentinel pointer for duplicate
 	 * rdata as rdata.data == NULL is valid.
@@ -129,6 +130,7 @@ dns_rdataslab_fromrdataset(dns_rdataset_t *rdataset, isc_mem_t *mctx,
 	static unsigned char removed;
 	dns_rdata_t *rdata = NULL;
 	unsigned char *rawbuf = NULL;
+	unsigned int headerlen = raw ? 0 : sizeof(dns_slabheader_t);
 	unsigned int buflen;
 	isc_result_t result;
 	unsigned int nitems;
@@ -136,7 +138,7 @@ dns_rdataslab_fromrdataset(dns_rdataset_t *rdataset, isc_mem_t *mctx,
 	unsigned int length;
 	unsigned int i;
 
-	buflen = reservelen + 2;
+	buflen = headerlen + 2;
 
 	nitems = dns_rdataset_count(rdataset);
 
@@ -151,7 +153,7 @@ dns_rdataslab_fromrdataset(dns_rdataset_t *rdataset, isc_mem_t *mctx,
 		rawbuf = isc_mem_get(mctx, buflen);
 		region->base = rawbuf;
 		region->length = buflen;
-		rawbuf += reservelen;
+		rawbuf += headerlen;
 		*rawbuf++ = 0;
 		*rawbuf = 0;
 		return ISC_R_SUCCESS;
@@ -231,6 +233,7 @@ dns_rdataslab_fromrdataset(dns_rdataset_t *rdataset, isc_mem_t *mctx,
 	 * Don't forget the last item!
 	 */
 	buflen += (2 + rdata[i - 1].length);
+
 	/*
 	 * Provide space to store the per RR meta data.
 	 */
@@ -259,7 +262,7 @@ dns_rdataslab_fromrdataset(dns_rdataset_t *rdataset, isc_mem_t *mctx,
 	region->base = rawbuf;
 	region->length = buflen;
 
-	rawbuf += reservelen;
+	rawbuf += headerlen;
 
 	put_uint16(rawbuf, nitems);
 
@@ -272,6 +275,7 @@ dns_rdataslab_fromrdataset(dns_rdataset_t *rdataset, isc_mem_t *mctx,
 			length++;
 		}
 		INSIST(length <= 0xffff);
+
 		put_uint16(rawbuf, length);
 
 		/*
@@ -295,6 +299,18 @@ free_rdatas:
 	return result;
 }
 
+isc_result_t
+dns_rdataslab_fromrdataset(dns_rdataset_t *rdataset, isc_mem_t *mctx,
+			   isc_region_t *region, uint32_t maxrrperset) {
+	return makeslab(rdataset, mctx, region, maxrrperset, false);
+}
+
+isc_result_t
+dns_rdataslab_raw_fromrdataset(dns_rdataset_t *rdataset, isc_mem_t *mctx,
+			       isc_region_t *region, uint32_t maxrrperset) {
+	return makeslab(rdataset, mctx, region, maxrrperset, true);
+}
+
 unsigned int
 dns_rdataslab_sizeraw(unsigned char *slab) {
 	REQUIRE(slab != NULL);