From: Evan Hunt <each@isc.org>
Date: Sat, 8 Feb 2025 05:06:34 +0000 (-0800)
Subject: initialize header in dns_rdataslab_fromrdataset()
X-Git-Tag: ondrej/lock-free-qpzone-reads-v1~47^2~4
X-Git-Url: http://git.ipfire.org/cgi-bin/gitweb.cgi?a=commitdiff_plain;h=82edec67a58afc837bf6b7ff62737faf931102e5;p=thirdparty%2Fbind9.git

initialize header in dns_rdataslab_fromrdataset()

when dns_rdataslab_fromrdataset() is run, in addition to
allocating space for a slab header, it also partially
initializes it, setting the type match rdataset->type and
rdataset->covers, the trust to rdataset->trust, and the TTL to
rdataset->ttl.
---

diff --git a/lib/dns/include/dns/rdataslab.h b/lib/dns/include/dns/rdataslab.h
index 82f2a426b18..b2886871097 100644
--- a/lib/dns/include/dns/rdataslab.h
+++ b/lib/dns/include/dns/rdataslab.h
@@ -183,7 +183,11 @@ dns_rdataslab_raw_fromrdataset(dns_rdataset_t *rdataset, isc_mem_t *mctx,
  *
  * 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.
+ * allocates space for a dns_slabheader object, and partially initializes
+ * it, setting the type, trust, and TTL fields to match rdataset->type,
+ * rdataset->covers, rdataset->trust, and rdataset->ttl.  (Note that the
+ * last field needs to be overridden when used in the cache database,
+ * since cache headers use an expire time instead of a TTL.)
  *
  * Requires:
  *\li	'rdataset' is valid.
diff --git a/lib/dns/qpcache.c b/lib/dns/qpcache.c
index b25bf45b6e1..78c5476535c 100644
--- a/lib/dns/qpcache.c
+++ b/lib/dns/qpcache.c
@@ -3201,18 +3201,20 @@ qpcache_addrdataset(dns_db_t *db, dns_dbnode_t *node, dns_dbversion_t *version,
 	dns_rdataset_getownercase(rdataset, name);
 
 	newheader = (dns_slabheader_t *)region.base;
-	*newheader = (dns_slabheader_t){
-		.type = DNS_TYPEPAIR_VALUE(rdataset->type, rdataset->covers),
-		.trust = rdataset->trust,
-		.last_used = now,
-		.node = (dns_dbnode_t *)qpnode,
-	};
-
 	dns_slabheader_reset(newheader, db, node);
+
+	newheader->last_used = now;
+
+	/*
+	 * By default, dns_rdataslab_fromrdataset() sets newheader->ttl
+	 * to the rdataset TTL. In the case of the cache, that's wrong;
+	 * we need it to be set to the expire time instead.
+	 */
 	setttl(newheader, rdataset->ttl + now);
 	if (rdataset->ttl == 0U) {
 		DNS_SLABHEADER_SETATTR(newheader, DNS_SLABHEADERATTR_ZEROTTL);
 	}
+
 	atomic_init(&newheader->count,
 		    atomic_fetch_add_relaxed(&init_count, 1));
 	if ((rdataset->attributes & DNS_RDATASETATTR_PREFETCH) != 0) {
diff --git a/lib/dns/qpzone.c b/lib/dns/qpzone.c
index db5f6a0727e..8b3d67c705d 100644
--- a/lib/dns/qpzone.c
+++ b/lib/dns/qpzone.c
@@ -2252,16 +2252,13 @@ loading_addrdataset(void *arg, const dns_name_t *name,
 	}
 
 	newheader = (dns_slabheader_t *)region.base;
-	*newheader = (dns_slabheader_t){
-		.type = DNS_TYPEPAIR_VALUE(rdataset->type, rdataset->covers),
-		.ttl = rdataset->ttl,
-		.trust = rdataset->trust,
-		.node = (dns_dbnode_t *)node,
-		.serial = 1,
-		.count = 1,
-	};
-
 	dns_slabheader_reset(newheader, (dns_db_t *)qpdb, (dns_dbnode_t *)node);
+
+	newheader->ttl = rdataset->ttl;
+	newheader->trust = rdataset->trust;
+	newheader->serial = 1;
+	newheader->count = 1;
+
 	dns_slabheader_setownercase(newheader, name);
 
 	if ((rdataset->attributes & DNS_RDATASETATTR_RESIGN) != 0) {
@@ -4737,17 +4734,12 @@ qpzone_addrdataset(dns_db_t *db, dns_dbnode_t *dbnode,
 	dns_rdataset_getownercase(rdataset, name);
 
 	newheader = (dns_slabheader_t *)region.base;
-	*newheader = (dns_slabheader_t){
-		.type = DNS_TYPEPAIR_VALUE(rdataset->type, rdataset->covers),
-		.trust = rdataset->trust,
-		.node = (dns_dbnode_t *)node,
-	};
-
 	dns_slabheader_reset(newheader, db, (dns_dbnode_t *)node);
 	newheader->ttl = rdataset->ttl;
 	if (rdataset->ttl == 0U) {
 		DNS_SLABHEADER_SETATTR(newheader, DNS_SLABHEADERATTR_ZEROTTL);
 	}
+
 	atomic_init(&newheader->count,
 		    atomic_fetch_add_relaxed(&init_count, 1));
 
@@ -4860,26 +4852,16 @@ qpzone_subtractrdataset(dns_db_t *db, dns_dbnode_t *dbnode,
 	newheader = (dns_slabheader_t *)region.base;
 	dns_slabheader_reset(newheader, db, (dns_dbnode_t *)node);
 	newheader->ttl = rdataset->ttl;
-	newheader->type = DNS_TYPEPAIR_VALUE(rdataset->type, rdataset->covers);
 	atomic_init(&newheader->attributes, 0);
 	newheader->serial = version->serial;
-	newheader->trust = 0;
-	newheader->noqname = NULL;
-	newheader->closest = NULL;
 	atomic_init(&newheader->count,
 		    atomic_fetch_add_relaxed(&init_count, 1));
-	newheader->last_used = 0;
-	newheader->node = (dns_dbnode_t *)node;
-	newheader->db = (dns_db_t *)qpdb;
 	if ((rdataset->attributes & DNS_RDATASETATTR_RESIGN) != 0) {
 		DNS_SLABHEADER_SETATTR(newheader, DNS_SLABHEADERATTR_RESIGN);
 		newheader->resign =
 			(isc_stdtime_t)(dns_time64_from32(rdataset->resign) >>
 					1);
 		newheader->resign_lsb = rdataset->resign & 0x1;
-	} else {
-		newheader->resign = 0;
-		newheader->resign_lsb = 0;
 	}
 
 	nlock = &qpdb->buckets[node->locknum].lock;
diff --git a/lib/dns/rdataslab.c b/lib/dns/rdataslab.c
index 14305914051..c316fe5dd6c 100644
--- a/lib/dns/rdataslab.c
+++ b/lib/dns/rdataslab.c
@@ -302,7 +302,22 @@ free_rdatas:
 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 result;
+
+	result = makeslab(rdataset, mctx, region, maxrrperset, false);
+	if (result == ISC_R_SUCCESS) {
+		dns_slabheader_t *new = (dns_slabheader_t *)region->base;
+
+		*new = (dns_slabheader_t){
+			.type = DNS_TYPEPAIR_VALUE(rdataset->type,
+						   rdataset->covers),
+			.trust = rdataset->trust,
+			.ttl = rdataset->ttl,
+			.link = ISC_LINK_INITIALIZER,
+		};
+	}
+
+	return result;
 }
 
 isc_result_t