Limit the additional processing for large RDATA sets

When answering queries, don't add data to the additional section if
the answer has more than 13 names in the RDATA.  This limits the
number of lookups into the database(s) during a single client query,
reducing query processing load.

Also, don't append any additional data to type=ANY queries. The
answer to ANY is already big enough.

(cherry picked from commit a1982cf1bb)

bin/tests/system/additional/tests.sh

@@ -279,7 +279,7 @@ n=$((n + 1))
 echo_i "testing with 'minimal-any no;' ($n)"
 ret=0
 $DIG $DIGOPTS -t ANY www.rt.example @10.53.0.1 >dig.out.$n || ret=1
-grep "ANSWER: 3, AUTHORITY: 2, ADDITIONAL: 2" dig.out.$n >/dev/null || ret=1
+grep "ANSWER: 3, AUTHORITY: 2, ADDITIONAL: 1" dig.out.$n >/dev/null || ret=1
 if [ $ret -eq 1 ]; then
   echo_i "failed"
   status=$((status + 1))

lib/dns/include/dns/rdataset.h

@@ -54,6 +54,8 @@
 #include <dns/rdatastruct.h>
 #include <dns/types.h>
 
+#define DNS_RDATASET_MAXADDITIONAL 13
+
 ISC_LANG_BEGINDECLS
 
 typedef enum {
@@ -454,7 +456,8 @@ dns_rdataset_towirepartial(dns_rdataset_t   *rdataset,
 isc_result_t
 dns_rdataset_additionaldata(dns_rdataset_t	    *rdataset,
 			    const dns_name_t	    *owner_name,
-			    dns_additionaldatafunc_t add, void *arg);
+			    dns_additionaldatafunc_t add, void *arg,
+			    size_t limit);
 /*%<
  * For each rdata in rdataset, call 'add' for each name and type in the
  * rdata which is subject to additional section processing.
@@ -473,10 +476,15 @@ dns_rdataset_additionaldata(dns_rdataset_t	    *rdataset,
  *\li	If a call to dns_rdata_additionaldata() is not successful, the
  *	result returned will be the result of dns_rdataset_additionaldata().
  *
+ *\li	If 'limit' is non-zero and the number of the rdatasets is larger
+ *	than 'limit', no additional data will be processed.
+ *
  * Returns:
  *
  *\li	#ISC_R_SUCCESS
  *
+ *\li	#DNS_R_TOOMANYRECORDS in case rdataset count is larger than 'limit'
+ *
  *\li	Any error that dns_rdata_additionaldata() can return.
  */
 

lib/dns/rbtdb.c

@@ -10332,7 +10332,7 @@ no_glue:
 	idx = hash_32(hash, rbtversion->glue_table_bits);
 
 	(void)dns_rdataset_additionaldata(rdataset, dns_rootname,
-					  glue_nsdname_cb, &ctx);
+					  glue_nsdname_cb, &ctx, 0);
 
 	cur = isc_mem_get(rbtdb->common.mctx, sizeof(*cur));
 

lib/dns/rdataset.c

@@ -577,7 +577,8 @@ dns_rdataset_towire(dns_rdataset_t *rdataset, const dns_name_t *owner_name,
 isc_result_t
 dns_rdataset_additionaldata(dns_rdataset_t *rdataset,
 			    const dns_name_t *owner_name,
-			    dns_additionaldatafunc_t add, void *arg) {
+			    dns_additionaldatafunc_t add, void *arg,
+			    size_t limit) {
 	dns_rdata_t rdata = DNS_RDATA_INIT;
 	isc_result_t result;
 
@@ -589,6 +590,10 @@ dns_rdataset_additionaldata(dns_rdataset_t *rdataset,
 	REQUIRE(DNS_RDATASET_VALID(rdataset));
 	REQUIRE((rdataset->attributes & DNS_RDATASETATTR_QUESTION) == 0);
 
+	if (limit != 0 && dns_rdataset_count(rdataset) > limit) {
+		return DNS_R_TOOMANYRECORDS;
+	}
+
 	result = dns_rdataset_first(rdataset);
 	if (result != ISC_R_SUCCESS) {
 		return result;

lib/dns/resolver.c

@@ -8961,7 +8961,7 @@ rctx_answer_any(respctx_t *rctx) {
 		rdataset->trust = rctx->trust;
 
 		(void)dns_rdataset_additionaldata(rdataset, rctx->aname,
-						  check_related, rctx);
+						  check_related, rctx, 0);
 	}
 
 	return ISC_R_SUCCESS;
@@ -9009,7 +9009,7 @@ rctx_answer_match(respctx_t *rctx) {
 	rctx->ardataset->attributes |= DNS_RDATASETATTR_CACHE;
 	rctx->ardataset->trust = rctx->trust;
 	(void)dns_rdataset_additionaldata(rctx->ardataset, rctx->aname,
-					  check_related, rctx);
+					  check_related, rctx, 0);
 
 	for (sigrdataset = ISC_LIST_HEAD(rctx->aname->list);
 	     sigrdataset != NULL;
@@ -9216,7 +9216,7 @@ rctx_authority_positive(respctx_t *rctx) {
 					 */
 					(void)dns_rdataset_additionaldata(
 						rdataset, name, check_related,
-						rctx);
+						rctx, 0);
 					done = true;
 				}
 			}
@@ -9723,8 +9723,12 @@ rctx_referral(respctx_t *rctx) {
 	 */
 	INSIST(rctx->ns_rdataset != NULL);
 	FCTX_ATTR_SET(fctx, FCTX_ATTR_GLUING);
+
+	/*
+	 * Mark the glue records in the additional section to be cached.
+	 */
 	(void)dns_rdataset_additionaldata(rctx->ns_rdataset, rctx->ns_name,
-					  check_related, rctx);
+					  check_related, rctx, 0);
 #if CHECK_FOR_GLUE_IN_ANSWER
 	/*
 	 * Look in the answer section for "glue" that is incorrectly
@@ -9736,8 +9740,9 @@ rctx_referral(respctx_t *rctx) {
 	if (rctx->glue_in_answer &&
 	    (fctx->type == dns_rdatatype_aaaa || fctx->type == dns_rdatatype_a))
 	{
-		(void)dns_rdataset_additionaldata(
-			rctx->ns_rdataset, rctx->ns_name, check_answer, fctx);
+		(void)dns_rdataset_additionaldata(rctx->ns_rdataset,
+						  rctx->ns_name, check_answer,
+						  fctx, 0);
 	}
 #endif /* if CHECK_FOR_GLUE_IN_ANSWER */
 	FCTX_ATTR_CLR(fctx, FCTX_ATTR_GLUING);
@@ -9839,7 +9844,7 @@ again:
 			if (CHASE(rdataset)) {
 				rdataset->attributes &= ~DNS_RDATASETATTR_CHASE;
 				(void)dns_rdataset_additionaldata(
-					rdataset, name, check_related, rctx);
+					rdataset, name, check_related, rctx, 0);
 				rescan = true;
 			}
 		}

lib/ns/query.c

@@ -2098,7 +2098,8 @@ addname:
 	if (trdataset != NULL && dns_rdatatype_followadditional(type)) {
 		if (client->additionaldepth++ < client->view->max_restarts) {
 			eresult = dns_rdataset_additionaldata(
-				trdataset, fname, query_additional_cb, qctx);
+				trdataset, fname, query_additional_cb, qctx,
+				DNS_RDATASET_MAXADDITIONAL);
 		}
 		client->additionaldepth--;
 	}
@@ -2198,7 +2199,7 @@ regular:
 	 * We don't care if dns_rdataset_additionaldata() fails.
 	 */
 	(void)dns_rdataset_additionaldata(rdataset, name, query_additional_cb,
-					  qctx);
+					  qctx, DNS_RDATASET_MAXADDITIONAL);
 	CTRACE(ISC_LOG_DEBUG(3), "query_additional: done");
 }
 
@@ -2224,7 +2225,8 @@ query_addrrset(query_ctx_t *qctx, dns_name_t **namep,
 	 * To the current response for 'client', add the answer RRset
 	 * '*rdatasetp' and an optional signature set '*sigrdatasetp', with
 	 * owner name '*namep', to section 'section', unless they are
-	 * already there.  Also add any pertinent additional data.
+	 * already there.  Also add any pertinent additional data, unless
+	 * the query was for type ANY.
 	 *
 	 * If 'dbuf' is not NULL, then '*namep' is the name whose data is
 	 * stored in 'dbuf'.  In this case, query_addrrset() guarantees that
@@ -2279,7 +2281,9 @@ query_addrrset(query_ctx_t *qctx, dns_name_t **namep,
 	 */
 	query_addtoname(mname, rdataset);
 	query_setorder(qctx, mname, rdataset);
-	query_additional(qctx, mname, rdataset);
+	if (qctx->qtype != dns_rdatatype_any) {
+		query_additional(qctx, mname, rdataset);
+	}
 
 	/*
 	 * Note: we only add SIGs if we've added the type they cover, so