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Code Issues Releases Wiki Activity

Decouple database and node lifetimes by adding node-specific vtables

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All databases in the codebase follow the same structure: a database is
an associative container from DNS names to nodes, and each node is an
associative container from RR types to RR data.

Each database implementation (qpzone, qpcache, sdlz, builtin, dyndb) has
its own corresponding node type (qpznode, qpcnode, etc). However, some
code needs to work with nodes generically regardless of their specific
type - for example, to acquire locks, manage references, or
register/unregister slabs from the heap.

Currently, these generic node operations are implemented as methods in
the database vtable, which creates problematic coupling between database
and node lifetimes. If a node outlives its parent database, the node
destructor will destroy all RR data, and each RR data destructor will
try to unregister from heaps by calling a virtual function from the
database vtable. Since the database was already freed, this causes a
crash.

This commit breaks the coupling by standardizing the layout of all
database nodes, adding a dedicated vtable for node operations, and
moving node-specific methods from the database vtable to the node
vtable.
This commit is contained in:
Alessio Podda
2025-06-05 11:51:29 +02:00
committed by Evan Hunt
parent 4a8f77e483
commit ae6a34cbda
43 changed files with 564 additions and 589 deletions
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63
lib/dns/sdlz.c
View File

@@ -105,11 +105,11 @@ struct dns_sdlz_db {
struct dns_sdlzlookup {
/* Unlocked */
unsigned int magic;
DBNODE_FIELDS;
dns_sdlz_db_t *sdlz;
ISC_LIST(dns_rdatalist_t) lists;
ISC_LIST(isc_buffer_t) buffers;
dns_name_t name;
ISC_LINK(dns_sdlzlookup_t) link;
dns_rdatacallbacks_t callbacks;
@@ -187,8 +187,18 @@ static void
list_tordataset(dns_rdatalist_t *rdatalist, dns_db_t *db, dns_dbnode_t *node,
dns_rdataset_t *rdataset);
/*
* Node methods forward declarations
*/
static void
detachnode(dns_db_t *db, dns_dbnode_t **targetp DNS__DB_FLARG);
sdlznode_attachnode(dns_dbnode_t *source, dns_dbnode_t **targetp DNS__DB_FLARG);
static void
sdlznode_detachnode(dns_dbnode_t **targetp DNS__DB_FLARG);
static dns_dbnode_methods_t sdlznode_methods = (dns_dbnode_methods_t){
.attachnode = sdlznode_attachnode,
.detachnode = sdlznode_detachnode,
};
static void
dbiterator_destroy(dns_dbiterator_t **iteratorp DNS__DB_FLARG);
@@ -248,8 +258,7 @@ static void
rdatasetiter_destroy(dns_rdatasetiter_t **iteratorp DNS__DB_FLARG) {
sdlz_rdatasetiter_t *sdlziterator = (sdlz_rdatasetiter_t *)(*iteratorp);
detachnode(sdlziterator->common.db,
&sdlziterator->common.node DNS__DB_FLARG_PASS);
sdlznode_detachnode(&sdlziterator->common.node DNS__DB_FLARG_PASS);
isc_mem_put(sdlziterator->common.db->mctx, sdlziterator,
sizeof(sdlz_rdatasetiter_t));
*iteratorp = NULL;
@@ -396,6 +405,7 @@ createnode(dns_sdlz_db_t *sdlz, dns_sdlznode_t **nodep) {
node = isc_mem_get(sdlz->common.mctx, sizeof(dns_sdlznode_t));
node->methods = &sdlznode_methods;
node->sdlz = NULL;
dns_db_attach((dns_db_t *)sdlz, (dns_db_t **)&node->sdlz);
ISC_LIST_INIT(node->lists);
@@ -622,16 +632,11 @@ findnode(dns_db_t *db, const dns_name_t *name, bool create,
}
static void
attachnode(dns_db_t *db, dns_dbnode_t *source,
dns_dbnode_t **targetp DNS__DB_FLARG) {
dns_sdlz_db_t *sdlz = (dns_sdlz_db_t *)db;
sdlznode_attachnode(dns_dbnode_t *source,
dns_dbnode_t **targetp DNS__DB_FLARG) {
dns_sdlznode_t *node = (dns_sdlznode_t *)source;
uint_fast32_t refs;
REQUIRE(VALID_SDLZDB(sdlz));
UNUSED(sdlz);
refs = isc_refcount_increment(&node->references);
#if DNS_DB_NODETRACE
fprintf(stderr, "incr:node:%s:%s:%u:%p->references = %" PRIuFAST32 "\n",
@@ -644,16 +649,12 @@ attachnode(dns_db_t *db, dns_dbnode_t *source,
}
static void
detachnode(dns_db_t *db, dns_dbnode_t **targetp DNS__DB_FLARG) {
dns_sdlz_db_t *sdlz = (dns_sdlz_db_t *)db;
sdlznode_detachnode(dns_dbnode_t **targetp DNS__DB_FLARG) {
dns_sdlznode_t *node;
uint_fast32_t refs;
REQUIRE(VALID_SDLZDB(sdlz));
REQUIRE(targetp != NULL && *targetp != NULL);
UNUSED(sdlz);
node = (dns_sdlznode_t *)(*targetp);
*targetp = NULL;
@@ -878,7 +879,7 @@ findext(dns_db_t *db, const dns_name_t *name, dns_dbversion_t *version,
* and try again.
*/
if (i < nlabels) {
detachnode(db, &node DNS__DB_FLARG_PASS);
sdlznode_detachnode(&node DNS__DB_FLARG_PASS);
node = NULL;
continue;
}
@@ -928,7 +929,7 @@ findext(dns_db_t *db, const dns_name_t *name, dns_dbversion_t *version,
if (nodep != NULL) {
*nodep = node;
} else if (node != NULL) {
detachnode(db, &node DNS__DB_FLARG_PASS);
sdlznode_detachnode(&node DNS__DB_FLARG_PASS);
}
return result;
@@ -964,7 +965,8 @@ allrdatasets(dns_db_t *db, dns_dbnode_t *node, dns_dbversion_t *version,
iterator->common.methods = &rdatasetiter_methods;
iterator->common.db = db;
iterator->common.node = NULL;
attachnode(db, node, &iterator->common.node DNS__DB_FLARG_PASS);
sdlznode_attachnode((dns_dbnode_t *)node,
&iterator->common.node DNS__DB_FLARG_PASS);
iterator->common.version = version;
iterator->common.options = options;
iterator->common.now = now;
@@ -1157,8 +1159,6 @@ static dns_dbmethods_t sdlzdb_methods = {
.closeversion = closeversion,
.findnode = findnode,
.find = find,
.attachnode = attachnode,
.detachnode = detachnode,
.createiterator = createiterator,
.findrdataset = findrdataset,
.allrdatasets = allrdatasets,
@@ -1265,8 +1265,8 @@ dbiterator_current(dns_dbiterator_t *iterator, dns_dbnode_t **nodep,
dns_name_t *name DNS__DB_FLARG) {
sdlz_dbiterator_t *sdlziter = (sdlz_dbiterator_t *)iterator;
attachnode(iterator->db, (dns_dbnode_t *)sdlziter->current,
nodep DNS__DB_FLARG_PASS);
sdlznode_attachnode((dns_dbnode_t *)sdlziter->current,
nodep DNS__DB_FLARG_PASS);
if (name != NULL) {
dns_name_copy(&sdlziter->current->name, name);
return ISC_R_SUCCESS;
@@ -1295,21 +1295,16 @@ dbiterator_origin(dns_dbiterator_t *iterator, dns_name_t *name) {
static void
disassociate(dns_rdataset_t *rdataset DNS__DB_FLARG) {
dns_dbnode_t *node = rdataset->rdlist.node;
dns_sdlznode_t *sdlznode = (dns_sdlznode_t *)node;
dns_db_t *db = (dns_db_t *)sdlznode->sdlz;
detachnode(db, &node DNS__DB_FLARG_PASS);
sdlznode_detachnode(&node DNS__DB_FLARG_PASS);
dns_rdatalist_disassociate(rdataset DNS__DB_FLARG_PASS);
}
static void
rdataset_clone(dns_rdataset_t *source, dns_rdataset_t *target DNS__DB_FLARG) {
dns_dbnode_t *node = source->rdlist.node;
dns_sdlznode_t *sdlznode = (dns_sdlznode_t *)node;
dns_db_t *db = (dns_db_t *)sdlznode->sdlz;
dns_rdatalist_clone(source, target DNS__DB_FLARG_PASS);
attachnode(db, node, &target->rdlist.node DNS__DB_FLARG_PASS);
sdlznode_attachnode(node, &target->rdlist.node DNS__DB_FLARG_PASS);
}
static dns_rdatasetmethods_t rdataset_methods = {
@@ -1324,8 +1319,8 @@ static dns_rdatasetmethods_t rdataset_methods = {
};
static void
list_tordataset(dns_rdatalist_t *rdatalist, dns_db_t *db, dns_dbnode_t *node,
dns_rdataset_t *rdataset) {
list_tordataset(dns_rdatalist_t *rdatalist, dns_db_t *db ISC_ATTR_UNUSED,
dns_dbnode_t *node, dns_rdataset_t *rdataset) {
/*
* The sdlz rdataset is an rdatalist, but additionally holds
* a database node reference.
@@ -1333,7 +1328,7 @@ list_tordataset(dns_rdatalist_t *rdatalist, dns_db_t *db, dns_dbnode_t *node,
dns_rdatalist_tordataset(rdatalist, rdataset);
rdataset->methods = &rdataset_methods;
dns_db_attachnode(db, node, &rdataset->rdlist.node);
dns_db_attachnode(node, &rdataset->rdlist.node);
}
/*